Patent Application
20240317578
The present invention relates to MEMS devices and manufacturing methods of the MEMS devices.
MEMS devices, which are manufactured by using microelectromechanical systems (MEMS) technology, are known. A MEMS device is formed by joining, to a first substrate, a second substrate, the first substrate including a MEMS structure, for example, such as a resonator.
For example, Japanese Unexamined Patent Application Publication No. 2010-541244 discloses a microelectronic assembly as an example of MEMS devices.
In the microelectronic assembly disclosed in Japanese Unexamined Patent Application Publication No. 2010-541244, a microelectronic element (a first substrate) and a substrate (a second substrate) are spaced from each other. The first substrate and the second substrate each include a conductive post made of gold. The end portion of each conductive post is coated with other material which forms a relatively low-melting alloy with gold. The first and second substrates are joined with the conductive posts interposed therebetween through a metal eutectic reaction between each conductive post and the coating material.
In the microelectronic assembly disclosed in Japanese Unexamined Patent Application Publication No. 2010-541244, a spacer structure made of metal, such as copper, is disposed between the first and second substrates during a process performed to join the conductive post provided for the first substrate to the conductive post provided for the second substrate. This makes variations in interval between the first and second substrates smaller.
The spacer structure disposed between the first and second substrates has conductivity. The first and second substrates could be unintentionally electrically coupled through the spacer structure. In this case, the microelectronic assembly includes unwanted wiring. The unwanted wiring could form a stray capacitance with at least one of the first and second substrates, and the stray capacitance could deteriorate the electric characteristics of the microelectronic assembly. Furthermore, the unwanted wiring could increase the power consumption of the microelectronic assembly.
Example embodiments of the present invention provide MEMS devices in each of which stray capacitances and an increase in power consumption are prevented.
A MEMS device according to an example embodiment of the present invention includes a first substrate including a MEMS structure, a second substrate facing the first substrate with an interval therebetween in a facing direction, a first joint portion including a eutectic layer including as a main material, a eutectic alloy including a plurality of types of metal, provided between the first substrate and the second substrate and surrounding the MEMS structure as viewed in the facing direction, and being joined to the first substrate and the second substrate, a conductive contact layer between the first substrate and the second substrate, directly or indirectly in contact with the first substrate and directly or indirectly in contact with the second substrate, and that does not melt at a temperature at which the plurality of types of metal undergo a metal eutectic reaction, and a first insulating layer on the contact layer and electrically insulated.
According to example embodiments of the present invention, it is possible to prevent stray capacitances and an increase in power consumption.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
A MEMS device according to an example embodiment of the present invention includes a first substrate including a MEMS structure, a second substrate facing the first substrate with an interval therebetween in a facing direction, a first joint portion that includes a eutectic layer including as a main material, a eutectic alloy including a plurality of types of metal, provided between the first substrate and the second substrate and surrounding the MEMS structure as viewed in the facing direction, and that is joined to the first substrate and the second substrate, a conductive contact layer, that is provided between the first substrate and the second substrate, that is directly or indirectly in contact with the first substrate and is directly or indirectly in contact with the second substrate, and that does not melt at a temperature at which the plurality of types of metal undergo a metal eutectic reaction, and a first insulating layer that is provided on the contact layer and is electrically insulated.
According to this configuration, the first substrate, the second substrate, and the first joint portion define a space for the MEMS structure to vibrate.
According to this configuration, the distance between the first and second substrates can be controlled so as to be equal or substantially equal to the height of the contact layer by the contact layer coming into contact with the first and second substrates in a manufacturing process of the MEMS device.
An unintended electrical coupling between the first and second substrates through the contact layer creates unwanted wiring in the MEMS device. In this case, a stray capacitance could be generated, for example, between the unwanted wiring and a via conductor or an electrode pad provided in the second substrate. The stray capacitance could deteriorate the electric characteristics of the MEMS device. Furthermore, the unwanted wiring could increase the power consumption of the MEMS device.
According to the above-described configuration, the first insulating layer prevents electrical coupling between the first and second substrates through the contact layer. It is therefore possible to prevent stray capacitance and increase in power consumption described above.
In the MEMS device, the length of the first joint portion in the facing direction may be greater than or equal to the length of the contact layer in the facing direction.
According to this configuration, the length of the first joint portion in the facing direction is greater than or equal to the length of the contact layer in the facing direction. This allows for application of a high load to the first joint portion in the manufacturing process of the MEMS device.
The MEMS device may further include a second joint portion that includes a eutectic layer including as a main material, the eutectic alloy including the plurality of types of metal, that is positioned inside the first joint portion as viewed in the facing direction between the first substrate and the second substrate, and that is joined to the first substrate and the second substrate.
According to this configuration, the second joint portion is positioned inside the first joint portion as viewed in the facing direction. The second joint portion is positioned closer to the MEMS structure than in the configuration in which the second joint portion is positioned outside the first joint portion as viewed in the facing direction. Therefore, the second joint portion and the MEMS structure can be electrically coupled with shorter wiring.
In the MEMS device, the second joint portion may include at least a portion of materials of the first substrate and the second substrate.
According to this configuration, the material included in the second joint portion diffuses into at least one of the first substrate and the second substrate. This allows the second joint portion to maintain ohmic contact with at least one of the first substrate and the second substrate. Therefore, when the second joint portion is used as wiring, the second joint portion and at least one of the first substrate and the second substrate can be electrically coupled with a high degree of reliability.
In the MEMS device, the first insulating layer may be embedded in at least one of the first substrate and the second substrate.
According to this configuration, the contact surface of the first insulating layer with the contact layer can be flush with the first or second substrate in which the first insulating layer is embedded. Therefore, the control of the interval between the first and second substrates by the contact layer can be easily performed with high accuracy.
The MEMS device may further include a second insulating layer that is on the first joint portion and is electrically insulated, the second insulating layer may be provided at the same position or substantially the same position in the facing direction as the first insulating layer.
If an insulating layer is provided only on the contact layer, among the contact layer and the first joint portion, there could be a height difference between the first joint portion and the contact layer equivalent to the height of the insulating layer in the manufacturing process of the MEMS device. According to this configuration, the insulating layers are provided on both of the first joint portion and the contact layer. This can make the height difference between the first joint portion and the contact layer smaller in the manufacturing process of the MEMS device. Therefore, the control of the interval between the first and second substrates by the formation of the contact layer can be easily performed with high accuracy.
In the MEMS device, the first insulating layer and the second insulating layer may be embedded in at least one of the first substrate and the second substrate.
According to this configuration, the contact surface between the second insulating layer and the first joint portion and the contact surface between the first insulating layer and the contact layer can be flush with the first or second substrate in which the insulating layers are embedded. Therefore, the control of the interval between the first and second substrates by the contact layer can be easily performed with high accuracy.
In the MEMS device, a cavity may be provided in an interface between the first insulating layer and the contact layer.
If no cavity is provided in the interface between the first insulating layer and the contact layer, the first insulating layer and the contact layer are in contact over a large area. The contact layer is therefore more likely to be crushed and deformed by the first insulating layer at high temperature under high load in the manufacturing process of the MEMS device. According to this configuration, however, the cavity is provided in the interface between the first insulating layer and the contact layer, so that the first insulating layer and the contact layer are in contact over a small area. Therefore, the contact layer is less likely to be deformed at high temperature under high load in the manufacturing process of the MEMS device.
In the MEMS device, the contact layer may include a portion of the plurality of types of metal included in the first joint portion.
The temperature at which the plurality of types of metal undergo a metal eutectic reaction is lower than the melting point of each of the plurality of types of metal. The plurality of types of metal included in the first joint portion undergo a metal eutectic reaction at a temperature lower than the melting point of each of the plurality of types of metal in the manufacturing process of the MEMS device. Herein, according to this configuration, the contact layer includes a portion of the same plurality of types of metal as the first joint portion. The melting point of the metal included in the contact layer is therefore higher than the temperature at which the plurality of types of metal included in the first joint portion undergo a metal eutectic reaction in the manufacturing process of the MEMS device. This means that the contact layer can be chemically stabilized in a high-temperature and high-load condition where the metals undergo a metal eutectic reaction. It is therefore possible to reduce deformation of the contact layer in the manufacturing process of the MEMS device, thus making the variations in interval between the first and second substrates smaller.
According to this configuration, the contact layer includes a portion of the same plurality of types of metal as the first joint portion. Therefore, even if the metal included in the contact layer is mixed into the first joint portion in the manufacturing process of the MEMS device, its influence on the first joint portion can be made smaller.
In the MEMS device, the contact layer may be positioned inside the first joint portion as viewed in the facing direction.
According to this configuration, the contact layer is positioned inside the first joint portion as viewed in the facing direction. The MEMS device can be reduced in size compared to a configuration in which the contact layer is positioned outside the first joint portion as viewed in the facing direction.
In the MEMS device, the MEMS structure may include a fixed portion fixed to the first substrate, and a moving portion flexible relative to the first substrate, and the contact layer may be in contact with the fixed portion as viewed in the facing direction.
According to this configuration, the contact layer is in contact with the MEMS structure. The second substrate therefore does not need to include a region for the contact layer to come into contact with, other than the MEMS structure. This can reduce the size of the MEMS device.
According to this configuration, the contact layer is in contact with the fixed portion of the MEMS structure. The contact layer therefore cannot inhibit the vibration of the MEMS structure.
In the MEMS device, the region surrounded by the first joint portion may be rotationally symmetric as viewed in the facing direction, and, as viewed in the facing direction, the distance between the center of rotational symmetry of the region surrounded by the first joint portion and the contact layer may be shorter than the distance between the first joint portion and the contact layer.
When the first joint portion is distant from the center of rotational symmetry of the region surrounded by the first joint portion as viewed in the facing direction, the first and second substrates are more likely to bend at the center.
According to this configuration, the contact layer is positioned close to the center of rotational symmetry of the region surrounded by the first joint portion as viewed in the facing direction. This can prevent the first and second substrates from bending at the center.
In the MEMS device, the contact layer may surround the MEMS structure as viewed in the facing direction.
According to this configuration, the contact layer surrounds the MEMS structure as viewed in the facing direction. The contact layer thus has a large area as viewed in the facing direction. Furthermore, the distances between the first joint portion and the contact layer at all locations can be equal or substantially equal. Therefore, the control of the interval between the first and second substrates by the contact layer can be easily performed with high accuracy.
In the MEMS device, the distance between the first joint portion and the contact layer may be, for example, less than or equal to about 1 mm and greater than or equal to about 0 mm as viewed in the facing direction.
When the first joint portion is distant from the contact layer as viewed in the facing direction, the load on the first joint portion, which is in liquid form and has a fluidity under high load in the manufacturing process of the MEMS device, could be excessively high in some localities. According to this configuration, the distance between the first joint portion and the contact layer is, for example, less than or equal to about 1 mm as viewed in the facing direction. This can reduce the application of local excessive load on the first joint portion as described above.
In the MEMS device, the area of the contact layer may be, for example, greater than or equal to about 8% of the area of the first joint portion and may be less than or equal to the area of the first substrate excluding a region overlapping the first joint portion as viewed in the facing direction.
When the area of the contact layer is small as viewed in the facing direction, excessively high load on the contact layers could deform the contact layer at high temperature under high load in the manufacturing process of the MEMS device. According to this configuration, the area of the contact layer as viewed in the facing direction is, for example, greater than or equal to about 8% of the area of the first joint portion. Therefore, in the manufacturing process of the MEMS device, the load on the contact layer is less likely to excessively increase at high temperature under high load.
A method of manufacturing a MEMS device according to an example embodiment of the present invention includes a first metal layer formation step of forming on a major surface of a first substrate including a MEMS structure, a first metal layer that includes a first type of metal and surrounds the MEMS structure, a second metal layer formation step of forming in a region corresponding to the first metal layer on a major surface of a second substrate, a second metal layer including a second type of metal that is able to undergo a metal eutectic reaction with the first type of metal, an insulating layer formation step of forming on at least one of the major surface of the first substrate and the major surface of the second substrate, an insulating layer that is electrically insulated, a contact layer formation step of forming on the insulating layer formed on at least one of the major surface of the first substrate and the major surface of the second substrate or in a region corresponding to the insulating layer on the major surface of the first substrate or the major surface of the second substrate, a contact layer that is conductive and does not melt at a temperature at which the first type of metal and the second type of metal undergo a metal eutectic reaction, and a joint step of, after executing the first metal layer formation step, the second metal layer formation step, the insulating layer formation step, and the contact layer formation step, arranging the major surface of the first substrate and the major surface of the second substrate opposite to each other in the facing direction and bringing the first substrate and the second substrate close to each other until the contact layer comes into contact with the major surface of the first substrate and the major surface of the second substrate directly or with the insulating layer interposed therebetween to cause the first metal layer and the second metal layer to undergo a metal eutectic reaction.
According to this manufacturing method, the interval between the first and second substrates can be controlled so as to be equal or substantially equal to the total height of the contact layer and the insulating layer by the contact layer coming into contact with the major surface of the first substrate and the major surface of the second substrate directly or with the insulating layer interposed therebetween in the joint step.
An unintended electrical coupling between the first and second substrates through the contact layer creates unwanted wiring in the MEMS device. In this case, stray capacitance is generated, for example, between the unwanted wiring and a via conductor or an electrode pad provided in the second substrate. The stray capacitance deteriorates the electric characteristics of the MEMS device. Furthermore, the unwanted wiring increases the power consumption of the MEMS device.
According to this manufacturing method, the insulating layer prevents electrical coupling between the first and second substrates through the contact layer. It is therefore possible to prevent the generation of stray capacitance or the increase in power consumption described above.
In the method of manufacturing a MEMS device, the total length of the first metal layer and the second metal layer in the facing direction may be greater than the total length of the contact layer and the insulating layer in the facing direction.
According to this manufacturing method, the total length of the first and second metal layers in the facing direction is greater than the total length of the contact layer and the insulating layer in the facing direction. This allows for application of a high load to the first metal layer and the second metal layer in the joint step.
In the method of manufacturing a MEMS device, in the first metal layer formation step, a third metal layer including the first type of metal may be formed inside the first metal layer on the major surface of the first substrate, in the second metal layer formation step, a fourth metal layer including the second type of metal may be formed in a region corresponding to the third metal layer on the major surface of the second substrate, and, in the joint step, the third metal layer and the fourth metal layer may undergo a metal eutectic reaction.
According to this manufacturing method, the third metal layer is formed inside the first metal layer as viewed in the facing direction. Therefore, the third metal layer can be formed closer to the MEMS structure than that in the manufacturing method in which the third metal layer is formed outside the first metal layer as viewed in the facing direction. The third metal layer and the MEMS structure can therefore be electrically coupled with short wiring.
In the method of manufacturing a MEMS device, at least one of the third metal layer and the fourth metal layer may include at least a portion of materials included in the first substrate or the second substrate that is adjacent to the at least one of the third metal layer and the fourth metal layer.
According to this manufacturing method, the third and fourth metal layers include at least a portion of the same materials as those of the first and second substrates. In the process of the metal eutectic reaction between the first type of metal and the second type of metal in the joint step, the materials included in the third and fourth metal layers diffuse into the first substrate and the second substrate. This allows the third and fourth metal layers to maintain ohmic contact with the first and second substrates.
In the method of manufacturing a MEMS device, the insulating layer formed in the insulating layer formation step may include a first insulating layer overlapping the first metal layer and the second metal layer as viewed in the facing direction when the major surface of the first substrate and the major surface of the second substrate are arranged opposite to each other in the facing direction in the joint step, and a second insulating layer overlapping the contact layer as viewed in the facing direction when the major surface of the first substrate and the major surface of the second substrate are arranged opposite to each other in the facing direction in the joint step, when the insulating layer is formed on the major surface of the first substrate, the first metal layer may be formed on the major surface of the first substrate with the first insulating layer interposed therebetween in the first metal layer formation step, when the insulating layer is formed on the major surface of the second substrate, the second metal layer may be formed on the major surface of the second substrate with the first insulating layer interposed therebetween in the second metal layer formation step, and, in the contact layer formation step, the contact layer may be formed on the second insulating layer formed on at least one of the major surface of the first substrate and the major surface of the second substrate or in a region corresponding to the second insulating layer on the major surface of the first substrate or the major surface of the second substrate.
According to this manufacturing method, insulating layers are formed both at the position corresponding to the first and second metal layers and at the position corresponding to the contact layer. This can make the height difference between these positions smaller. Therefore, the control of the interval between the first and second substrates by the formation of the contact layer can be easily performed with high accuracy.
The method of manufacturing a MEMS device according to an example embodiment of the present invention may further include a recess formation step of forming a recess in the major surface of the first substrate or the major surface of the second substrate,
According to this manufacturing method, the insulating layers can be formed so as not to protrude from the major surface of the first substrate and the major surface of the second substrate. For example, the insulating layers can be formed so as to be flush with the major surface of the first substrate and the major surface of the second substrate. Therefore, the control of the interval between the first and second substrates by the formation of the contact layer can be easily performed with high accuracy.
In the method of manufacturing a MEMS device, the contact layer may include one of the first type of metal and the second type of metal.
The temperature at which the plurality of types of metal undergo a metal eutectic reaction is lower than the melting point of each of the plurality of types of metal. The first type of metal included in the first metal layer and the second type of metal included in the second metal layer undergo a metal eutectic reaction at a temperature lower than the melting points of the first and second types of metal. According to this manufacturing method, the contact layer includes one of the first type of metal and the second type of metal. In the joint step, the melting point of the metal included in the contact layer is therefore higher than the temperature at which the metal eutectic reaction occurs. This means that the contact layer can be chemically stabilized in a high-temperature and high-load condition where the metals undergo a metal eutectic reaction. It is therefore possible to reduce deformation of the contact layer in the joint step, thus making variations in interval between the first and second substrates smaller.
According to the above-described manufacturing method, the contact layer includes one of the first type of metal and the second type of metal. In the case where the contact layer includes the first type of metal, even if the metal included in the contact layer is mixed into the first metal layer in the joint step, its influence on the first metal layer can be made smaller. In the case where the contact layer includes the second type of metal, even if the metal included in the contact layer is mixed into the second metal layer in the joint step, its influence on the second metal layer can be made smaller.
As illustrated in
In the following description, the direction in which the first substrate 20 and the second substrate 30 are stacked on each other with the first joint portion 40, the contact layers 51, and the insulating layers 52 interposed therebetween is referred to as a facing direction 100. In the following description, for convenience of explanation, the side of the MEMS device 10 in which the second substrate 30 is provided is referred to as an upper side, and the side in which the first substrate 20 is provided is referred to as a lower side.
As illustrated in
The first substrate 20 includes a lower layer 21, an upper layer 22, and an insulating layer 23. The main material of each of the lower layer 21 and the upper layer 22 is, for example, silicon (Si). That is, for example, the lower layer 21 and the upper layer 22 include silicon. The term “main material” refers to a material whose proportion is the largest among the materials included in a particular portion (the lower layer 21, for example). The insulating layer 23 includes an insulator that is electrically insulated. For example, the insulating layer 23 includes silicon dioxide (SiO2) in the first example embodiment. The insulating layer 23 is sandwiched between the lower layer 21 and the upper layer 22 and is joined to the lower layer 21 and the upper layer 22. That is, the lower layer 21 and the upper layer 22 are joined with the insulating layer 23 interposed therebetween. In the first example embodiment, therefore, the first substrate 20 is, for example, an SOI (silicon-on-insulator) substrate. The first substrate 20 is not limited to an SOI substrate. For example, the lower layer 21 and the upper layer 22 may include a piezoelectric monocrystal material (LT, LN, or the like), such as LN (LiNbO3) or a LT (LiTaO3) instead of silicon. For example, the insulating layer 23 may include an insulator (SiO2, for example) other than silicon dioxide.
A recess is provided in the lower layer 21 and the insulating layer 23. The upper portion of the recess is covered with the upper layer 22. An air gap 24 is thus provided in the first substrate 20.
The upper layer 22 includes a MEMS structure 25. The upper layer 22 and the MEMS structure 25 are integrally provided. In the first example embodiment, the MEMS structure 25 is a structure including a fixed portion fixed to the upper layer 22 of the first substrate 20 and a moving portion that is coupled to the fixed portion and resonates relative to the fixed portion. The moving portion is a resonator (a MEMS resonator manufactured using a MEMS technology). The MEMS structure 25 faces the air gap 24 and a later-described air gap 70. In other words, the MEMS structure 25 is at the position overlapping the spaces 24 and 70 as viewed in the facing direction 100. Between the fixed portion and the moving portion, a not-illustrated gap is provided. The MEMS structure 25 (to be specific, the moving portion of the MEMS structure 25) is able to vibrate in a space including the air gaps 24 and 70 and the gap. The air gaps 24 and 70 communicate with each other (not illustrated). The air gaps 24 and 70 define a closed space while communicating with each other.
In addition to silicon, the MEMS structure 25 includes a piezoelectric thin film or a metal layer, which is not illustrated in
The resonator can be of various types of resonators that are publicly known (for example, a resonator using an out-of-plane bending vibration mode, a resonator using a thickness expansion mode, and a resonator using a Lamb wave vibration mode). The MEMS structure 25 is not limited to the resonator and may be, for example, an acceleration sensor or a strain sensor statically driven.
The second substrate 30 is disposed opposite to the first substrate 20 in the facing direction 100 above the first substrate 20. The second substrate 30 is spaced away from the first substrate 20 in the facing direction 100. The main material of the second substrate 30 is, for example, silicon. That is, the second substrate 30 includes, for example, silicon. The main material of the second substrate 30 may be other than silicon, for example, glass.
In the first substrate 20 and the second substrate 30, a via conductor and an electrode pad, which are not illustrated in the drawings, can be provided. The via conductor is formed by, for example, filling a through-hole, a recess, or a closed space formed in a conductive substrate with an insulating material. The method of forming the via conductor is not limited to the above method. The via conductor may be formed by, for example, filling a through-hole, a recess, or a closed space formed in a substrate with a conductive paste. The electrode pad is formed by, for example, a semiconductor process. The method of forming the electrode pad is not limited to a semiconductor process and may be formed by, for example, printing or the like.
The first joint portion 40 is disposed between the first substrate 20 and the second substrate 30. The lower end portion of the first joint portion 40 is joined to a major surface 20A (the upper surface of the upper layer 22 of the first substrate 20) of the first substrate 20. The upper end portion of the first joint portion 40 is joined to a major surface 30A (the lower surface of the second substrate 30) of the second substrate 30.
As illustrated in
As illustrated in
The first metal layer 41 is joined to the major surface 20A of the first substrate 20. The second metal layer 42 is joined to the major surface 30A of the second substrate 30.
The main materials of the first metal layer 41 and the second metal layer 42 are, for example, aluminum (Al), gold (Au), indium (In), tin (Sn), germanium (Ge), or the like, provided that the main material of the first metal layer 41 and the main material of the second metal layer 42 are able to undergo a metal eutectic reaction. In the first example embodiment, the main material of the first metal layer 41 is, for example, aluminum while the main material of the second metal layer 42 is, for example, germanium. In the first example embodiment, the first metal layer 41 and the second metal layer 42 include small amounts of copper (Cu) and titanium (Ti), for example.
The eutectic layer 43 is positioned between the first metal layer 41 and the second metal layer 42. The eutectic layer 43 is undergoing a metal eutectic reaction with the first metal layer 41 and the second metal layer 42. The main material of the eutectic layer 43 is a eutectic alloy of metal included in the first metal layer 41 and metal included in the second metal layer 42. In the first example embodiment, the main material of the eutectic layer 43 is, for example, a eutectic alloy of aluminum as the main material of the first metal layer 41 and germanium as the main material of the second metal layer 42. That is, in the first example embodiment, for example, aluminum and germanium correspond to a plurality of types of metal.
The contact layers 51 are arranged between the first substrate 20 and the second substrate 30. The lower end portions of the contact layers 51 are in contact with the major surface 20A of the first substrate 20. The upper end portions of the contact layers 51 are laid on the respective insulating layers 52.
As illustrated in
As illustrated in
The contact layers 51 do not melt at a temperature at which the plural types of metal of the eutectic alloy as the main material of the eutectic layer 43 of the first joint portion 40 undergo a metal eutectic reaction. In other words, the melting point of the material of the contact layers 51 is higher than the temperature at which the plural types of metal of the eutectic alloy as the main material of the eutectic layer 43 of the first joint potion 40 undergo a metal eutectic reaction. The contact layers 51 are made of a conductive material. In the first example embodiment, the contact layers 51 include a portion of the same plural types of metal as those included in the eutectic alloy as the main material of the eutectic layer 43 of the first joint portion 40. In the first example embodiment, the contact layers 51 include a portion of the same two metals (for example, aluminum and germanium) as those included in the eutectic alloy of the eutectic layer 43. That is, the contact layers 51 include either aluminum or germanium, for example. The contact layers 51 do not include a eutectic alloy. When the portion of the plural types of metal include plural types of metal, the portion of the plural types of metal include plural types of metal that are not able to undergo a eutectic reaction with each other.
The contact layers 51 may only include a portion (for example, only one of aluminum and germanium in the first example embodiment) of the same plural types of metal as those included in the eutectic alloy of the eutectic layer 43 or may include a material other than the plural types of metal, for example, tin.
In the first example embodiment, the contact layers 51 include as the main material, a portion of the same plural types of metal (for example, aluminum and germanium) as those included in the eutectic alloy of the eutectic layer 43. However, the contact layers 51 may include a material other than the plural types of metal as the main material provided that the contact layers 51 include a portion of the same plural types of metal as those included in the eutectic alloy of the eutectic layer 43. For example, when the first metal layer 41 includes gold, the second metal layer 42 includes indium, and the eutectic layer 43 includes a eutectic alloy of gold and indium, the contact layers 51 may include gold or indium as the main material.
The insulating layers 52 are made of an insulator that is electrically insulated. For example, in the first example embodiment, the insulating layers 52 include silicon dioxide (SiO2) The insulating layers 52 are interposed between the respective contact layers 51 and the second substrate 30. The contact layers 51 and the first substrate 20 are electrically insulated from the second substrate 30.
As described above, the insulating layers 52 are positioned above the contact layers 51. The insulating layers 52 may be positioned below the contact layers 51. In this case, the lower end portions of the insulating layers 52 are in contact with the major surface 20A of the first substrate 20. That is, the contact layers 51 are in contact with the first substrate 20 with the insulating layers 52 interposed therebetween. The upper end portions of the contact layers 51 are in contact with the major surface 30A of the second substrate 30. In this case, the contact layers 51 are indirectly in contact with the first substrate 20 and are directly in contact with the second substrate 30.
In addition, the insulating layers 52 may be positioned both above and below the contact layers 51. In other words, two insulating layers 52 may sandwich each contact layer 51 in the facing direction 100. In this case, the lower end portion of one of the two insulating layers 52 is in contact with the major surface 20A of the first substrate 20. That is, the contact layer 51 is in contact with the first substrate 20 with the one insulating layer 52 interposed therebetween. The upper end portion of the other insulating layer 52 is in contact with the major surface 30A of the second substrate 30. That is, the contact layer 51 is in contact with the second substrate 30 with the other insulating layer 52 interposed therebetween. That is, in this case, the contact layer 51 is indirectly in contact with the first substrate 20 and is indirectly in contact with the second substrate 30.
Each insulating layer 52 may be positioned between two contact layers 51 in the facing direction 100. In other words, each insulating layer 52 may be sandwiched by two contact layers 51 in the facing direction 100. In this case, the lower end portion of one of the two contact layers 51 is in contact with the major surface 20A of the first substrate 20. The upper end portion of the other contact layer 51 is in contact with the major surface 30A of the second substrate 30. That is, in this case, one of the two contact layers 51 is directly in contact with the first substrate 20 while the other contact layer 51 is directly in contact with the second substrate 30.
The length of each contact layer 51 and each insulating layer 52 in the facing direction 100 is equal to or substantially equal to the length of the first joint portion 40 in the facing direction 100. The length of the first joint portion 40 in the facing direction 100 may be greater than the total length of each contact layer 51 and each insulating layer 52 in the facing direction 100. For example, when the interval between the first substrate 20 and the second substrate 30 varies due to warpage of at least one of the first substrate 20 and the second substrate 30, the length of the first joint portion 40 in the facing direction 100 can be greater than the total length of each contact layer 51 and each insulating layer 52 in the facing direction 100. For example, when at least one of the upper and lower end portions of the first joint portion 40 is embedded in the first substrate 20 or the second substrate 30, the length of the first joint portion 40 in the facing direction 100 can be greater than the total length of each contact layer 51 and each insulating layer 52 in the facing direction 100.
As illustrated in
As illustrated in
As illustrated in
The third metal layer 61 is joined to the major surface 20A of the first substrate 20. The fourth metal layer 62 is joined to the major surface 30A of the second substrate 30.
The main materials of the third metal layer 61 and the fourth metal layer 62 are, for example, aluminum (Al), gold (Au), indium (In), tin (Sn), germanium (Ge), or the like, provided that the main material of the third metal layer 61 and the main material of the fourth metal layer 62 are able to undergo a metal eutectic reaction. In the first example embodiment, the main material of the third metal layer 61 is the same as the main material of the first metal layer 41, and the main material of the fourth metal layer 62 is the same as the main material of the second metal layer 42. Specifically, for example, the main material of the third metal layer 61 is aluminum, and the main material of the fourth metal layer 62 is germanium. In the first example embodiment, the third metal layer 61 and the fourth metal layer 62 include, for example, small amounts of copper (Cu) and titanium (Ti). The main material of the third metal layer 61 may be different from the main material of the first metal layer 41. The main material of the fourth metal layer 62 may be different from the main material of the second metal layer 42.
The second joint portion 60 includes at least a portion of the same materials as those included the first substrate 20 and the second substrate 30. In the first example embodiment, for example, the third metal layer 61 includes silicon, which is the material included in the upper layer 22 of the first substrate 20, and the fourth metal layer 62 includes silicon, which is the material included in the second substrate 30.
When the first substrate 20 includes a first material and the second substrate 30 includes a second material that is different from the first material, the third metal layer 61 may include the first material while the fourth metal layer 62 include the second material. Furthermore, only one of the third metal layer 61 and the fourth metal layer 62 may include at least one of the first material and the second material, regardless of whether the first and second materials are the same.
The eutectic layer 63 is positioned between the third metal layer 61 and the fourth metal layer 62. The eutectic layer 63 undergoes a metal eutectic reaction individually with the third metal layer 61 and the fourth metal layer 62. The eutectic layer 63 includes as the main material, the eutectic alloy of metal included in the third metal layer 61 and metal included in the fourth metal layer 62. In the first example embodiment, for example, the eutectic layer 63 includes as the main material, a eutectic alloy of aluminum, which is the main material of the third metal layer 61, and germanium, which is the main material of the fourth metal layer 62.
As illustrated in
As illustrated in
According to the first example embodiment, the first substrate 20, the second substrate 30, and the first joint portion 40 define a space for the MEMS structure 25 to vibrate.
According to the first example embodiment, the contact layers 51 and the insulating layers 52 come into contact with the first substrate 20 and the second substrate 30 in the manufacturing process of the MEMS device 10, so that the interval between the first substrate 20 and the second substrate 30 can be controlled so as to be equal or substantially equal to the height of each contact layer 51 and each insulating layer 52.
An unintended electrical coupling between the first substrate 20 and the second substrate 30 through the contact layer 51 creates unwanted wiring in the MEMS device 10. In this case, a stray capacitance could be generated, for example, between the unwanted wiring and a via conductor or an electrode pad formed in the second substrate 30. The stray capacitance could deteriorate the electric characteristics of the MEMS device 10. Furthermore, the unwanted wiring could increase the power consumption of the MEMS device 10.
According to the first example embodiment, the insulating layers 52 prevent the first substrate 20 and the second substrate 30 from being electrically coupled to each other through the contact layers 51. It is therefore possible to prevent the formation of stray capacitance and the increase in power consumption described above.
According to the first example embodiment, the length of the first joint portion 40 in the facing direction 100 is greater than or equal to the length of the contact layers 51 in the facing direction 100. This allows for application of high load to the first metal layer 41 and the second metal layer 42 of the first joint portion 40 in the manufacturing process of the MEMS device 10.
According to the first example embodiment, the second joint portion 60 is positioned inside the first joint portion 40 as viewed in the facing direction 100. The second joint portion 60 is therefore closer to the MEMS structure 25 than that in a configuration where the second joint portion 60 is positioned outside the first joint portion 40 as viewed in the facing direction 100. The second joint portion 60 and the MEMS structure 25 can therefore be electrically coupled with short wiring.
According to the first example embodiment, the second joint portion 60 includes at least a portion of the same materials as those included in the first substrate 20 and the second substrate 30. In the manufacturing process of the MEMS device 10, when the plural types of metal undergo a metal eutectic reaction to form a eutectic alloy, the materials included in the second joint portion 60 diffuse into the first substrate 20 and the second substrate 30. This allows the second joint portion 60 to maintain ohmic contact with at least one of the first substrate 20 and the second substrate 30. Therefore, when the second joint portion 60 is used as wiring, the second joint portion 60 and at least one of the first substrate 20 and the second substrate 30 can be electrically coupled with a high degree of reliability.
The temperature at which plural types of metal undergo a metal eutectic reaction is lower than the melting point of each of the plural types of metal. The plural types of metal included in the first joint portion 40 undergo a metal eutectic reaction at a temperature lower than the melting point of each of the plural types of metal in the manufacturing process of the MEMS device 10. Herein, according to the first example embodiment, the contact layers 51 include a portion of the same plural types of metal as the first joint portion 40. The melting point of the metal included in the contact layers 51 is therefore higher than the temperature at which the plural types of metal included in the first joint portion 40 undergo a metal eutectic reaction in the manufacturing process of the MEMS device 10. This means that the contact layers 51 can be chemically stabilized in a high-temperature and high-load condition where the metals undergo a metal eutectic reaction. It is therefore possible to reduce deformation of the contact layers 51 in the manufacturing process of the MEMS device 10, thus making variations in interval between the first substrate 20 and the second substrate 30 smaller.
According to the first example embodiment, the contact layers 51 include a portion of the same plural types of metal as the first joint portion 40. Therefore, even if the metal included in the contact layers 51 is mixed into the first joint portion 40 in the manufacturing process of the MEMS device 10, its influence on the first joint portion 40 can be reduced.
When the first joint portion 40 is distant from the contact layers 51 as viewed in the facing direction 100, the load on the first joint portion 40, which is in liquid form and has a fluidity under high load in the manufacturing process of the MEMS device 10, could be excessively high in some locations. According to the first example embodiment, the distance between the first joint portion 40 and the contact layers 51 as viewed in the facing direction 100 is, for example, less than or equal to about 1 mm. This can reduce the application of local excessive load to the first joint portion 40 described above.
When the total area of the contact layers 51 is small as viewed in the facing direction 100, an excessively high load on the contact layers 51 at high temperature under high load in the manufacturing process of the MEMS device 10 could deform the contact layers 51. According to the first example embodiment, the total area of the contact layers 51 as viewed in the facing direction 100 is, for example, greater than or equal to about 8% of the area of the first joint portion 40. Therefore, in the manufacturing process of the MEMS device 10, the load on the contact layers 51 is less likely to excessively increase at high temperature under high load.
According to the first example embodiment, the contact layers 51 include a portion of the same plural types of metal as those included in the eutectic alloy that is the main material of the eutectic layer 43 of the first joint portion 40. However, the contact layers 51 do not need to include the plural types of metal.
Hereinafter, an example of the manufacturing method of the MEMS device 10 according to the first example embodiment will be described with reference to
The MEMS device 10 is manufactured by singulation of a multilayer body into plural pieces. The multilayer body integrally includes a plurality of MEMS devices 10 that are arrayed.
First, the first metal layer formation step is executed. In the first metal layer formation step, the first substrate 20 is prepared as illustrated in
On the major surface 20A of the first substrate 20, the first metal layer 41 and the third metal layer 61 are formed. As described above, in the first example embodiment, the main materials of the first metal layer 41 and the third metal layer 61 are, for example, aluminum. Aluminum is an example of a first type of metal. The first type of metal is able to undergo a metal eutectic reaction with a later-described second type of metal. The first type of metal may be other than aluminum, provided with the first type of metal is able to undergo a metal eutectic reaction with the second type of metal. For example, the first type of metal may be gold, indium, tin, germanium, or the like.
The third metal layer 61 includes silicon, which is the material included the upper layer 22 of the first substrate 20 adjacent to the third metal layer 61.
The third metal layer 61 is formed at a position different from the MEMS structure 25. The first metal layer 41 is ring-shaped as viewed in the facing direction 100. The first metal layer 41 is formed so as to surround the MEMS structure 25 and the third metal layer 61 as viewed in the facing direction 100. That is, the third metal layer 61 is formed inside the first metal layer 41 on the major surface 20A.
The first metal layer 41 and the third metal layer 61 are formed by, for example, a semiconductor process. The method of forming the first metal layer 41 and the third metal layer 61 is not limited to a semiconductor process and may be, for example, printing or the like.
Next, the contact layer formation step is executed. In the contact layer formation step, the contact layers 51 are formed on the major surface 20A of the first substrate 20 as illustrated in
In this manufacturing method, four contact layers 51 are formed outside the first metal layer 41 as viewed in the facing direction 100. The four contact layers 51 are formed near the respective four vertices of the first metal layer 41 having a rectangular or substantially rectangular shape as viewed in the facing direction 100.
The contact layers 51 are formed by, for example, a semiconductor process. The method of forming the contact layers 51 is not limited to a semiconductor process and may be, for example, printing or the like.
Next, the second metal layer formation step is executed. In the second metal layer formation step, the second substrate 30 is prepared as illustrated in
On the major surface 30A of the second substrate 30, the second metal layer 42 and the fourth metal layer 62 are formed. As described above, in the first example embodiment, the main materials of the second metal layer 42 and the fourth metal layer 62 are, for example, germanium. Germanium is an example of the second type of metal. The second type of metal is able to undergo a metal eutectic reaction with the first type of metal. The second type of metal may be other than germanium, provided that the second type of metal is able to undergo a metal eutectic reaction with the first type of metal. For example, the second type of metal may be aluminum, gold, indium, tin, or the like.
The fourth metal layer 62 includes, for example, silicon, which is the material included in the second substrate 30 adjacent to the fourth metal layer 62.
The second metal layer 42 is formed in a region that corresponds to the first metal layer 41 when the second substrate 30 is disposed opposite to the first substrate 20 in the joint step described later. That is, the second metal layer 42 has the same size and the same shape (or substantially the same size and substantially the same shape) as the first metal layer 41 as viewed in the facing direction 100.
The fourth metal layer 62 is formed in a region that corresponds to the third metal layer 61 when the second substrate 30 is disposed opposite to the first substrate 20 in the joint step described later. That is, the fourth metal layer 62 has the same size and the same shape (or substantially the same size and substantially the same shape) as the third metal layer 61 as viewed in the facing direction 100.
The second metal layer 42 and the fourth metal layer 62 are formed by, for example, a semiconductor process. The method of forming the second metal layer 42 and the fourth metal layer 62 is not limited to a semiconductor process and may be, for example, printing or the like.
Next, the insulating layer formation step is executed. In the insulating layer formation step, the insulating layers 52 are formed on the major surface 30A of the second substrate 30 as illustrated in
The insulating layers 52 are formed in regions that correspond to the contact layers 51 when the second substrate 30 is disposed opposite to the first substrate 20 in the later-described joint step. That is, the insulating layers 52 have the same sizes and the same shapes (or substantially the same sizes and substantially the same shapes) as the respective contact layers 51 as viewed in the facing direction 100.
The insulating layers 52 are formed by, for example, a semiconductor process.
The sum of length L4 (see
In this manufacturing method, the contact layers 51 are formed on the major surface 20A of the first substrate 20, and the insulating layers 52 are formed on the major surface 30A of the second substrate 30. However, the present invention is not limited to such a method.
For example, the insulating layers 52 may be formed on the major surface 20A of the first substrate 20 while the contact layers 51 are formed on the major surface 30A of the second substrate 30. In this case, the contact layers 51 are formed in regions that correspond to the respective insulating layers 52 when the second substrate 30 is disposed opposite to the first substrate 20 in the joint step.
Furthermore, for example, the contact layers 51 and the insulating layers 52 may be formed on the major surface 20A of the first substrate 20 together. In this case, the insulating layers 52 are formed on the major surface 20A of the first substrate 20 in the insulating layer formation step. Then the contact layer formation step is executed. In the contact layer formation step, the contact layers 51 are laid on the insulating layers 52. The contact layers 51 are thus formed on the major surface 20A of the first substrate 20 with the insulating layers 52 interposed therebetween.
Still furthermore, for example, the contact layers 51 and the insulating layers 52 may be formed on the major surface 30A of the second substrate 30 together. In this case, the insulating layers 52 are formed on the major surface 30A of the second substrate 30 in the insulating layer formation step. Then the contact layer formation step is executed. In the contact layer formation step, the contact layers 51 are laid on the insulating layers 52. The contact layers 51 are thus formed on the major surface 30A of the second substrate 30 with the insulating layers 52 interposed therebetween.
Still furthermore, for example, the insulating layers 52 may be formed on the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30 in the insulating layer formation step. In this case, the contact layers 51 are laid on the insulating layers 52 formed on the major surface 20A or the insulating layers 52 formed on the major surface 30A in the contact layer formation step.
Thus, the contact layers 51 can be formed on the major surface 20A of the first substrate 20 or the major surface 30A of the second substrate 30.
The contact layers 51 in this manufacturing method include one of the first type of metal (for example, aluminum in this manufacturing method) and the second type of metal (for example, germanium in this manufacturing method) but do not need to include any one of the first type of metal and the second type of metal.
Next, the joint step is executed. In the joint step, the first substrate 20 illustrated in
Next, loads of, for example, greater than or equal to about 10 MPa are applied to the first substrate 20 and the second substrate 30 under a predetermined temperature. The direction of the load applied to the first substrate 20 is the direction toward the second substrate 30. The direction of the load applied to the second substrate 30 is a direction toward the first substrate 20.
A predetermined temperature is, for example, higher than or equal to about 200° C. The predetermined temperature is set not lower than a temperature at which the main materials (for example, aluminum in the first example embodiment) of the first metal layer 41 and the third metal layer 61 are able to undergo a metal eutectic reaction with the main materials (for example, germanium in the first example embodiment) of the second metal layer 42 and the fourth metal layer 62, respectively. The predetermined temperature is set to a temperature lower than the melting points of the main materials (for example, aluminum in the first example embodiment) of the first metal layer 41 and the third metal layer 61 and lower than the melting points of the main materials (for example, germanium in the first example embodiment) of the second metal layer 42 and the fourth metal layer 62.
By the loads being applied to the first substrate 20 and the second substrate 30, the first substrate 20 and the second substrate 30 come close to each other, and the first metal layer 41 comes into contact with the second metal layer 42 while the third metal layer 61 comes into contact with the fourth metal layer 62. The contact layers 51 are not yet in contact with the insulating layers 52 at this time. This is because the sum of the lengths L1 and L2 is greater than the sum of the lengths L3 and L4.
Furthermore, in a situation where the first metal layer 41 and the third metal layer 61 are in contact with the second metal layer 42 and the fourth metal layer 62, respectively, when the contact layers 51 come close to the insulating layers 52, diffusion occurs.
That is, in the interface between the first metal layer 41 and the second metal layer 42, the main material (for example, aluminum in the first example embodiment) of the first metal layer 41 and the main material (for example, germanium in the first example embodiment) of the second metal layer 42 diffuse into each other to undergo a metal eutectic reaction. The eutectic layer 43, which includes as the main material the eutectic alloy of the main materials of the first metal layer 41 and the second metal layer 42, is thus formed between the first metal layer 41 and the second metal layer 42.
In the interface between the third metal layer 61 and the fourth metal layer 62, the main material (for example, aluminum in the first example embodiment) of the third metal layer 61 and the main material (for example, germanium in the first example embodiment) of the fourth metal layer 62 diffuse into each other to undergo a metal eutectic reaction. The eutectic layer 63, which includes as the main material the eutectic alloy of the main materials of the third metal layer 61 and the fourth metal layer 62, is thus formed between the third metal layer 61 and the fourth metal layer 62.
When the contact layers 51 come into contact with the insulating layers 52, in other words, when the contact layers 51 come into contact with the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30 directly or with the insulating layers 52 interposed therebetween, the change in relative position of the first substrate 20 to the second substrate 30 due to the application of the loads stops. The positions of the first metal layer 41, the second metal layer 42, the third metal layer 61, and the fourth metal layer 62 are thus fixed, so that the diffusion and metal eutectic reaction cannot occur anymore. Thus, as illustrated in
Next, the grinding step is executed. In the grinding step, the surface of the second substrate 30 opposite to the major surface 30A is ground and removed. When the second substrate 30 includes a through-silicon via, the through-silicon via can thus be exposed.
Next, the electrode formation step is executed. In the electrode formation step, the through-silicon via exposed in the grinding step is subjected to patterning of a metal thin film of, for example, gold, aluminum, or the like by a publicly-known process. An electrode pad is thus formed in the second substrate 30.
Next, the singulation step is executed. In the singulation step, the multilayer body is cut into plural MEMS devices 10. Cutting the multilayer body uses, for example, a dicing saw, a guillotine cutter, a laser, or the like.
According to this manufacturing method, the contact layers 51 come into contact with the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30 directly or with the insulating layers 52 interposed therebetween in the joint step, so that the interval between the first substrate 20 and the second substrate 30 can be controlled so as to be equal or substantially equal to the total height of each contact layer 51 and each insulating layer 52.
An unintended electrical coupling between the first substrate 20 and the second substrate 30 through the contact layer 51 creates unwanted wiring in the MEMS device 10. In this case, a stray capacitance could be generated, for example, between the unwanted wiring and a via conductor or an electrode pad formed in the second substrate 30. The stray capacitance could deteriorate the electric characteristics of the MEMS device 10. In addition, the unwanted wiring could increase the power consumption of the MEMS device 10.
According to this manufacturing method, the insulating layers 52 prevent electrical coupling between the first substrate 20 and the second substrate 30 through the contact layers 51. It is therefore possible to prevent the formation of stray capacitance and an increase in power consumption described above.
According to this manufacturing method, the sum L1+L2 of the lengths of the first metal layer 41 and the second metal layer 42 in the facing direction 100 is greater than the sum L3+L4 of the lengths of the contact layers 51 and the insulating layers 52 in the facing direction 100. This allows for application of a high load to the first metal layer 41 and the second metal layer 42 in the joint step.
According to this manufacturing method, the third metal layer 61 is formed inside the first metal layer 41 as viewed in the facing direction 100. Therefore, the third metal layer 61 can be formed closer to the MEMS structure 25 than in the manufacturing method in which the third metal layer 61 is formed outside the first metal layer 41 as viewed in the facing direction 100. The third metal layer 61 and the MEMS structure 25 can therefore be electrically coupled with short wiring.
According to this manufacturing method, the third metal layer 61 and the fourth metal layer 62 include at least a portion of the same materials as those included in the first substrate 20 and the second substrate 30. In the process of the metal eutectic reaction between the first type of metal and the second type of metal in the joint step, the materials included in the third metal layer 61 and the fourth metal layer 62 diffuse into the first substrate 20 and the second substrate 30. This allows the third metal layer 61 and the fourth metal layer 62 to maintain ohmic contact with the first substrate 20 and the second substrate 30.
The temperature at which plural types of metal undergo a metal eutectic reaction is lower than the melting point of each of the plural types of metal. The first type of metal included in the first metal layer 41 and the second type of metal included in the second metal layer 42 undergo a metal eutectic reaction at a temperature lower than the melting points of the first and second types of metal. According to this manufacturing method, the contact layers 51 include one of the first type of metal and the second type of metal. In the joint step, therefore, the melting point of the metal included in the contact layers 51 is higher than the temperature at which the metal eutectic reaction occurs. This means that the contact layers 51 can be chemically stabilized in a high-temperature and high-load condition where the metals undergo a metal eutectic reaction. It is therefore possible to reduce deformation of the contact layers 51 in the joint step, thus making variations in interval between the first substrate 20 and the second substrate 30 smaller.
According to this manufacturing method, the contact layers 51 include one of the first type of metal and the second type of metal. In the case where the contact layers 51 include the first type of metal, even if the metal included in the contact layers 51 is mixed into the first metal layer 41 in the joint step, its influence on the first metal layer 41 can be made smaller. In the case where the contact layers 51 include the second type of metal, even if the metal included in the contact layers 51 is mixed into the second metal layer 42 in the joint step, its influence on the second metal layer 42 can be made smaller.
According to the aforementioned manufacturing method, the third metal layer 61 includes silicon, which is the material constituting the first substrate 20 adjacent to the third metal layer 61, and the fourth metal layer 62 includes silicon, which is the material constituting the second substrate 30 adjacent to the fourth metal layer 62. However, only one of the third metal layer 61 and the fourth metal layer 62 may include the same material (for example, silicon in the first example embodiment) as that included in the substrate adjacent thereto.
The order of the steps of the above-described manufacturing method is not limited to the above-described order. For example, the second metal layer formation step and the insulating layer formation step may be executed before the first metal layer formation step and the contact layer formation step.
The MEMS device 10A includes the insulating layer 44. The insulating layer 44 is an example of a second insulating layer.
In the second example embodiment, the insulating layer 44 is positioned between the second metal layer 42 and the major surface 30A of the second substrate 30. That is, the insulating layer 44 is provided on the second metal layer 42. In other words, the insulating layer 44 is provided on the major surface 30A of the second substrate 30. In the second example embodiment, the insulating layer 44 is at the same or substantially the same position in the facing direction 100 as the insulating layers 52. The insulating layer 44 may be at or substantially at the same position in the facing direction 100 as the insulating layers 52. The insulating layer 44 may be at a position different from the insulating layers 52 in the facing direction 100. For example, the insulating layer 44 may be provided on the major surface 30A while the insulating layers 52 are provided on the major surface 20A.
The insulating layer 44 is made of an insulator that is electrically insulated. In the second example embodiment, for example, the insulating layer 44 is made of the same material (for example, silicon dioxide (SiO2)) as the insulating layers 52. The first substrate 20 and the second substrate 30 are thus electrically insulated from each other. The insulating layer 44 may be made of a material different from the insulating layers 52.
The insulating layer 44 is positioned between the second metal layer 42 and the major surface 30A of the second substrate 30 as described above. However, the position of the insulating layer 44 in the facing direction 100 is not limited to between the second metal layer 42 and the major surface 30A of the second substrate 30. For example, the insulating layer 44 may be positioned between the first metal layer 41 and the major surface 20A of the first substrate 20. That is, the insulating layer 44 may be at a position different from the insulating layers 52 in the facing direction 100. Furthermore, for example, the insulating layer 44 may be positioned between the second metal layer 42 and the major surface 30A of the second substrate 30, and may be also positioned between the first metal layer 41 and the major surface 20A of the first substrate 20.
If insulating layers are provided only on the contact layers 51, among the contact layers 51 and the first joint portion 40, there could be a height difference between the first joint portion 40 and the contact layers 51 equivalent to the height of the insulating layers in the manufacturing process of the MEMS device 10. According to the second example embodiment, insulating layers are provided on both of the first joint portion 40 and the contact layers 51. This can make the height difference between the first joint portion 40 and the contact layers 51 smaller in the manufacturing process of the MEMS device 10. Therefore, the control of the interval between the first substrate 20 and the second substrate 30 by the formation of the contact layers 51 can be easily performed with high accuracy.
In an example of a method of manufacturing the MEMS device 10A according to the second example embodiment, the insulating layers 44 and 52 are formed on the major surface 30A of the second substrate 30 in the insulating layer formation step.
The insulating layer 44 is formed in a region that corresponds to the first metal layer 41 and the second metal layer 42 when the major surface 30A of the second substrate 30 is disposed opposite to the major surface 20A of the first substrate 20 in the facing direction 100 in the joint step. The insulating layer 44 thus overlaps the first metal layer 41 and the second metal layer 42 as viewed in the facing direction 100 when the major surface 30A of the second substrate 30 is disposed opposite to the major surface 20A of the first substrate 20 in the facing direction 100 in the joint step.
The insulating layers 52 are formed in regions that correspond to the respective contact layers 51 when the major surface 30A of the second substrate 30 is disposed opposite to the major surface 20A of the first substrate 20 in the facing direction 100 in the joint step. The insulating layers 52 thus overlap the contact layers 51 as viewed in the facing direction 100 when the major surface 30A of the second substrate 30 is disposed opposite to the major surface 20A of the first substrate 20 in the facing direction 100 in the joint step. The insulating layers 52 are an example of the first insulating layer.
When the insulating layer 44 is formed on the major surface 30A of the second substrate 30 as in this manufacturing example, the second metal layer 42 is formed on the major surface 30A of the second substrate 30 with the insulating layer 44 interposed therebetween in the second metal layer formation step.
When the insulating layer 44 is formed on the major surface 20A of the first substrate 20 unlike in this manufacturing example, the first metal layer 41 is formed on the major surface 20A of the first substrate 20 with the insulating layer 44 interposed therebetween in the first metal layer formation step. Furthermore, when the insulating layer 44 is formed on both of the major surfaces 20A and 30A, the first metal layer 41 is formed on the major surface 20A of the first substrate 20 with one of the insulating layers 44 interposed therebetween in the first metal layer formation step, and the second metal layer 42 is formed on the major surface 30A of the second substrate 30 with the other insulating layer 44 interposed therebetween in the second metal layer formation step.
The contact layers 51 are formed in the same or substantially the same manner as in the manufacturing method of the MEMS device 10 according to the first example embodiment.
The insulating layer 44 and the insulating layers 52 may be formed in separate steps. For example, the insulating layer 44 and the insulating layers 52 are formed in separate steps when the insulating layer 44 is made of a material different from the insulating layers 52. Furthermore, for example, the insulating layer 44 and the insulating layers 52 are formed in separate steps when the insulating layer 44 is formed at a position different from the insulating layers 52 (for example, when the insulating layer 44 is formed on the major surface 30A of the second substrate 30 while the insulating layers 52 are formed on the major surface 20A of the first substrate 20).
According to this manufacturing method, the insulating layers are formed both at the position corresponding to the first metal layer 41 and the second metal layer 42 and at the positions corresponding to the contact layers 51. This can make the height difference between these positions smaller. Therefore, the control of the interval between the first substrate 20 and the second substrate 30 by the formation of the contact layers 51 can be easily performed with high accuracy.
In the MEMS device 10B, recesses 31 are formed in the major surface 30A of the second substrate 30. The recesses 31 are formed in regions corresponding to the insulating layers 44 and 52. In the recesses 31, the insulating layers 44 and 52 are embedded. That is, the insulating layers 44 and 52 are embedded in the second substrate 30.
The insulating layers 44 and 52 may be embedded in the first substrate 20. In this case, the recesses 31 are formed in the major surface 20A of the first substrate 20. Either the insulating layer 44 or the insulating layers 52 may be embedded in the first substrate 20 while the other is embedded in the second substrate 30. In this case, the recesses 31 are formed in the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30. The insulating layers 44 and 52 may be embedded in both of the first substrate 20 and the second substrate 30.
In the MEMS device 10 according to the first example embodiment not including the insulating layers 52, the insulating layer 44 may be embedded. In this case, the insulating layer 44 is embedded in at least one of the first substrate 20 and the second substrate 30.
According to the third example embodiment, the contact surfaces between the insulating layers 52 and the contact layers 51 can be flush with the first and second substrates 20 and 30 with the insulating layers 52 embedded. Therefore, the control of the interval between the first substrate 20 and the second substrate 30 by the contact layers 51 can be easily performed with high accuracy.
According to the third example embodiment, the contact surface between the insulating layer 44 and the first joint portion 40 and the contact surfaces between the insulating layers 52 and the contact layers 51 can be flush with the first and second substrates 20 and 30 with the insulating layers embedded. Therefore, the control of the interval between the first substrate 20 and the second substrate 30 by the contact layers 51 can be easily performed with high accuracy.
In an example of a manufacturing method of the MEMS device 10B according to the third example embodiment, a recess formation step is executed before the insulating layer formation step.
In the recess formation step, the recesses 31 are formed in regions of the major surface 30A of the second substrate 30 where the insulating layers 44 and 52 are to be formed.
In the insulating layer formation step executed after the recess formation step, the recesses 31 are filled with paste made of the materials (silicon dioxide, for example) of the insulating layers 44 and 52.
Then the second metal layer formation step is executed. The second metal layer 42 is formed on the major surface 30A of the second substrate 30 with the insulating layer 44 interposed therebetween.
In the case of forming the insulating layers 44 and 52 on the first substrate 20, in the recess formation step, the recesses are formed in regions of the major surface 20A of the first substrate 20 where the insulating layers 44 and 52 are to be formed. In the case of forming the insulating layers 44 and 52 on the first substrate 20 and the second substrate 30, in the recess formation step, the recesses are formed in regions of the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30 where the insulating layers 44 and 52 are to be formed. That is, the recesses are formed in at least one of the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30.
According to this manufacturing method, the insulating layers 44 and 52 can be formed so as not to protrude from the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30. For example, the insulating layers 44 and 52 can be formed so as to be flush with the major surface 20A of the first substrate 20 and the major surface 30A of the second substrate 30. Therefore, the control of the interval between the first substrate 20 and the second substrate 30 by the formation of the contact layers 51 can be easily performed with high accuracy.
As illustrated in
For example, the MEMS device 10C illustrated in
Furthermore, for example, the MEMS device 10D illustrated in
Still furthermore, for example, the MEMS device 10E illustrated in
According to the configuration illustrated in
As illustrated in
According to the fifth example, the contact layers 51E are positioned inside the first joint portion 40 as viewed in the facing direction 100. Therefore, the MEMS device 10 can be reduced in size compared to a configuration in which the contact layers 51E are positioned outside the first joint portion 40 as viewed in the facing direction 100.
As illustrated in
For example, the MEMS device 10G illustrated in
Furthermore, for example, the MEMS device 10H illustrated in
Still furthermore, for example, the MEMS device 10I illustrated in
MEMS devices may include plural MEMS structures 25. As illustrated in
As illustrated in
As illustrated in
As illustrated in
In
As illustrated in
In
When the center C of rotational symmetry of the region surrounded by the first joint portion 40 is distant from the first joint portion as viewed in the facing direction 100, the first and second substrates 20 and 30 are more likely to bend at the center C.
According to the seventh example embodiment, the contact layers 51 are positioned near the center C of rotational symmetry in the region surrounded by the first joint portion 40 as viewed in the facing direction 100. This can prevent the first substrate 20 and the second substrate 30 from bending at the center C.
In the example explained with
As illustrated in
According to the eighth example embodiment, the contact layer 51 is in contact with the MEMS structure 25. The second substrate 30, therefore, does not need to include a region for the contact layer 51 to come into contact with, other than the MEMS structure 25. This can reduce the MEMS device 10M in size.
According to the eighth example embodiment, the contact layer 51 is joined to the fixed portion 25A of the MEMS structure 25. Therefore, the contact layer 51 cannot inhibit the vibration of the MEMS structure 25.
In the MEMS device 10 according to the first example embodiment, as illustrated in
For example, as illustrated in
The number, shape, position, and size of the cavities 54 are not limited to the number, shape, position, and size illustrated in
When the cavities 54 are not provided in the interface 53 between the insulating layer 52 and the contact layer 51, the insulating layer 52 and contact layer 51 of the second joint portion 50 are in contact over a large area. In this case, the contact layer 51 is more likely to be crushed and deformed by the insulating layer 52 at high temperature under high load in the manufacturing process of the MEMS device 10. According to the ninth example embodiment, the cavities 54 are provided in the interface 53 between the insulating layer 52 and the contact layer 51, so that the insulating layer 52 and the contact layer 51 are in contact over a small area. The contact layer 51 is therefore less likely to be deformed at high temperature under high load in the manufacturing process of the MEMS device 10.
By properly combining any of the example embodiments of the present invention, the advantageous effects thereof can be achieved.
While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-209531 | Dec 2021 | JP | national |
This application claims the benefit of priority to Japanese Patent Application No. 2021-209531 filed on Dec. 23, 2021 and is a Continuation application of PCT Application No. PCT/JP2022/044772 filed on Dec. 5, 2022. The entire contents of each application are hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/044772 | Dec 2022 | WO |
| Child | 18735274 | US |
