Patent Grant
8121315
1. Field of the Invention
The present invention relates to a semiconductor condenser microphone chip.
2. Description of the Related Art
A condenser microphone chip is a capacitor composed of a diaphragm and a backplate. Currently, in most reports and patents a double-membrane capacitor structure which is manufactured by forming a diaphragm and a backplate on a silicon wafer by micromachining is adopted. Few efforts are made to the development of single-membrane silicon condenser microphone. A single-membrane silicon condenser microphone is reported in “Fabrication of Silicon Condenser Microphone Using Single Wafer Technology”, Journal of microelectromechanical systems, VOL. 1. No. 3, 1992, p 147-154. In the single-membrane silicon condenser microphone, a capacitor structure is formed by an edge portion of a diaphragm and a silicon substrate with the silicon substrate serving as a backplate and with a large hole at a center of the backplate serving as a sound hole. However, the single-membrane silicon condenser microphone is disadvantageous because an edge of the diaphragm is connected to a peripheral portion. When a sound wave is applied to the diaphragm, a maximum vibration occurs at a center portion of the diaphragm, and a small vibration is generated at the edge portion of the diaphragm. Because the center portion of the diaphragm is directly opposite to the sound hole of the backplate, mechanical sensitivity in the region with maximum amplitude is not used, so that the mechanical sensitivity of the diaphragm contributes less to sensitivity of the microphone.
In order that a diaphragm has good vibration performance, a residual stress in the diaphragm can be reduced. In the Publication titled Sensor and Actuators A. 31, 1992, 90-96, a material with tensile stress and a material with compressive stress are used to make a low-stress composite membranes for a microphone. In U.S. Pat. No. 6,622,368B1 in which silicon nitride/polysilicon/silicon nitride composite membrane structure is disclosed, the low-stress composite membrane is used as a diaphragm of a microphone. In the Publication “Sensor and Actuators A. 31, 1992, 149-152” and U.S. Pat. No. 6,012,335, a monocrystalline silicon diaphragm is made by doping monocrystalline silicon with boron. In the Publication “A High Sensitivity Polysilicon Diaphragm Condenser Microphone”, 1998 MEMS Conference, Heideberg Germany January 25-29, it is reported that a diaphragm is made with low-stress polysilicon. However, requirements for a growing process of a membrane is strict and it is difficult to assure uniformity of the membrane if vibration performance of the diaphragm is improved only by making a material of low residual stress.
In addition, the methods for releasing residual stress in a diaphragm with various structures have been known in the art. In the Publication U.S. Pat. Nos. 5,452,268 and 5,146,435, Chinese Patent Publication No. 1787693A, and a literature (The 11th International Conference on Solid-State Sensors and Actuators, Munich Germany, Jun. 10-14, 2001), mechanical sensitivity of a diaphragm is improved by releasing residual stress in the diaphragm by using a cantilever structure. Since stress in the diaphragm is concentrated at an edge of the diaphragm due to the cantilever structure and the beam structure is often too soft, an adhesion problem is apt to occur. In U.S. Pat. No. 6,535,460 B2, a free diaphragm structure is disclosed. With the free diaphragm structure, a microphone with a diaphragm of residual stress of zero can be obtained, but a process required for preparing the structure is complicated.
A rigid backplate is a premise for a microphone having good frequency characteristic and low noise. Currently, methods for making a rigid backplate comprises: employing a thick gold layer as a backplate in U.S. Pat. No. 6,012,335; employing a composite metal membrane as a backplate, which increases thickness of the backplate while decreasing stress in the backplate, in U.S. Pat. No. 6,677,176 B2; employing a monocrystalline silicon layer in a SOI silicon wafer as a backplate in U.S. Pat. No. 6,140,689; employing electrochemical corrosion to make a low-stress thick monocrystalline silicon backplate in U.S. Pat. No. 6,667,189 B1; and making a particular structure to increase strength of a backplate in U.S. Pat. No. 6,532,460 B2. However, most of the above processes are complicated and are high in manufacturing cost.
After a soft diaphragm and a rigid backplate are obtained, it is also necessary to solve the problem that the diaphragm is attached or adhered to the backplate. Up to now, there have been many methods. An effective method is to make attachment or adhesion preventing protrusions, but it is necessary to increase a number of processing steps and thus cost.
In U.S. Pat. No. 5,870,482, a cantilever beam type diaphragm is described. A cantilever beam is fixed at an end, and constitutes a capacitor at an edge portion of a free end with a backplate. With the above configuration, mechanical sensitivity makes great contribution to microphone sensitivity, but structure of the diaphragm is complicated. In addition, because of the cantilever structure having 3 DOF (Dimension of Freedom), it is difficult to assure pose and reliability of the diaphragm. In U.S. Pat. Application Publication No. 2006/0093170 A1, a single membrane structure in which outer cantilever beams are distributed at equal intervals is disclosed. An edge portion of a diaphragm and the backplate form a capacitor. The cantilever beams improve contribution of mechanical sensitivity to microphone sensitivity, but can not enable the diaphragm to translate. In addition, with the above configuration, it is difficult to assure yield and reliability.
It is an object of the present invention to provide a condenser microphone chip having a curved beam which can alleviate at least a part of the above problems.
It is another object of the present invention to provide a condenser microphone chip having a curved beam which can effectively release residual stress in a diaphragm, prevent attachment or adhesion of the diaphragm to a backplate, and improve the reliability of condenser microphone chip.
According to an aspect of the invention, there is provided a condenser microphone chip comprising: a substrate; a diaphragm spaced from the substrate; and a curved beam connected with the diaphragm to anchor the diaphragm to the substrate.
With the above configuration, residual stress in the diaphragm of the condenser microphone chip can be released by the curved beam. The soft curved beam serves as a spring so as to assure easy vibration of the diaphragm.
The curved beam may extend in one of a substantial “S” shape, a shape of a substantial arc, and a substantial helical shape.
According to an aspect of the invention, the curved beam includes one curved beam disposed at a substantial center portion of the diaphragm. Alternatively, the curved beam may include at least one pair of curved beams arranged at substantially equal intervals and substantially symmetrical about a center of the diaphragm.
According to an aspect of the invention, the curved beam is arranged in the diaphragm.
In the case that the curved beam is arranged in the diaphragm, the diaphragm can be prevented from being attached to the backplate during manufacturing. Moreover, the entire diaphragm can uniformly vibrate and mechanical sensitivity of the diaphragm can be fully utilized.
Preferably, the condenser microphone chip further comprises a curved beam connecting part having a shape of a substantially circular plate, wherein the curved beam is arranged in the diaphragm, and wherein each curved beam includes a plurality of sub beams, each of the plurality of sub beams including a first sub beam portion extending in a substantially radial direction of the curved beam connecting part from a circumference of the curved beam connecting part; a second sub beam portion extending in a substantially circumferential direction of the curved beam connecting part or around the curved beam connecting part from an end of the first sub beam portion away from the circumference of the curved beam connecting part and having a shape of a substantial arc; and a third sub beam portion extending in the radial direction from an end of the second sub beam portion away from the first sub beam portion and connected to the diaphragm.
According to an aspect of the invention, the curved beam may comprise three sub beams.
The second sub beam portions of the plurality of the sub beams of the curved beam may extend toward an identical circumferential direction from the ends of the first sub beam portions away from the circumference of the curved beam connecting part.
The plurality of the sub beams of the curved beam may have a substantially identical shape. In addition, the plurality of the sub beams of the curved beam may be arranged at substantially equal intervals around the circumference of the curved beam connecting part.
According to an aspect of the invention, the condenser microphone chip further comprises: an auxiliary beam including a first portion configured by forming an opening in the diaphragm at a predetermined distance from an edge of the diaphragm, the first portion having two ends connected with the diaphragm; and a second portion extending from the first portion away from the diaphragm, the second portion being fixed to the substrate at an end of the second portion away from the first portion.
According to another aspect of the invention, the condenser microphone chip further comprises: an auxiliary beam including a first elongated portion configured by forming an opening in the diaphragm substantially parallel to an edge of the diaphragm at a predetermined distance from the edge, the first portion having two ends connected with the diaphragm; and a second elongated portion extending away from the diaphragm from a substantially middle portion of the first portion, the second portion being fixed to the substrate at an end of the second portion away from the first portion, and the first portion and the second portion being formed in a “T” shape together.
According to an aspect of the invention, the condenser microphone chip further comprises: a curved beam support which is fixed to the substrate and to which an end of the curved beam of the curved beam is connected; and a diaphragm side electrode which is attached to the end of the curved beam connected to the curved beam support so as to be electrically connected with the diaphragm.
According to another aspect of the invention, the condenser microphone chip further comprises: an auxiliary beam support fixed to the substrate, the end of the second portion of the auxiliary beam being fixed to the substrate by connecting to the auxiliary beam support; and a diaphragm side electrode which is attached to the end of the second portion of the auxiliary beam connected to the auxiliary beam support so as to be electrically connected with the diaphragm.
The above curved beam is applicable to a double-membrane condenser microphone chip, a single-membrane condenser microphone chip, and other condenser microphone chips.
In a condenser microphone chip according to the present invention, the substrate serves as the backplate, the substrate may have a large hole, that is, a sound hole, at a center portion thereof, and the diaphragm covers the sound hole. A plurality of small holes are disposed in the diaphragm outside a region of the diaphragm directly opposite to the sound hole. The plurality of small holes cooperate with the sound hole of the backplate to release a sacrificial layer between the diaphragm and the backplate during manufacturing and can improve frequency response characteristic of the condenser microphone chip.
In a condenser microphone chip according to the present invention, a diaphragm is fixedly attached to a substrate with a curved beam arranged within the diaphragm. With this configuration, residual stress in the diaphragm can effectively be released, and the diaphragm can be prevented from being attached to a backplate and be improved in reliability. In addition, the backplate has a large stiffness since the substrate servers as the backplate. Therefore, the condenser microphone chip according to the present invention is simple in structure, low in process difficulty and cost, and high in reliability.
In a condenser microphone chip according to the present invention, a curved beam is arranged within the diaphragm. The curved beam can well release residual stress of the diaphragm. In addition, the curved beam serves as a spring to connect and support the diaphragm, so that the diaphragm can vibrate well. Furthermore, the curved beam can uniformly support the diaphragm when the curved beam is arranged in the diaphragm. As a result, this arrangement can effectively prevent attachment of the diaphragm to the backplate due to electrostatic force, van de waals force and capillary force during the manufacturing process, thereby improving reliability of the condenser microphone chip.
According to further aspect of the present invention, there is provided a condenser microphone chip comprising: a substrate; a backplate connected with the substrate; a diaphragm spaced from the backplate, for example, by a predetermined distance; and a curved beam connected with the diaphragm to anchor the diaphragm to the substrate.
The curved beam may extend in one of a substantial “S” shape, a shape of a substantial arc, and a substantial helical shape.
According to an aspect of the present invention, the curved beam includes one curved beam disposed at a substantial center portion of the diaphragm.
According to an aspect of the present invention, the curved beam includes at least one pair of curved beams arranged at substantially equal intervals and substantially symmetrical about a center of the diaphragm.
According to another aspect of the present invention, the curved beam is arranged in the diaphragm.
According to an aspect of the invention, the condenser microphone chip further comprises: a curved beam connecting part having a shape of a substantially circular plate, wherein the curved beam is arranged in the diaphragm, and wherein each curved beam includes a plurality of sub beams, each of the plurality of sub beams including a first sub beam portion extending in a substantially radial direction from a circumference of the curved beam connecting part; a second sub beam portion extending in a substantially circumferential direction from an end of the first sub beam portion away from the circumference of the curved beam connecting part and having a shape of a substantial arc; and a third sub beam portion extending in the radial direction from an end of the second sub beam portion away from the first sub beam portion and connected to the diaphragm.
According to an aspect of the present invention, each curved beam comprises three sub beams.
According to another aspect of the present invention, the second sub beam portions of the plurality of the sub beams of the curved beam extend toward an identical circumferential direction from the ends of the first sub beam portions away from the circumference of the curved beam connecting part.
The plurality of the sub beams of the curved beam may have a substantially identical shape. In addition, the plurality of the sub beams of the curved beam are arranged at substantially equal intervals around the circumference of the curved beam connecting part.
According to an aspect of the present invention, the condenser microphone chip further comprises: an auxiliary beam including a first portion configured by forming an opening in the diaphragm at a predetermined distance from an edge of the diaphragm, the first portion having two ends connected with the diaphragm; and a second portion extending from the first portion away from the diaphragm, an end of the second portion away from the first portion being fixed to the substrate.
With the above configuration, when sound wave acts on the diaphragm, the diaphragm transmits a force applied to the diaphragm to the curved beam and the auxiliary beam so that the curved beam and the auxiliary beam deform. Since deformation mainly occurs at the curved beam and the auxiliary beam, the diaphragm vibrates back and forth in a direction perpendicular to a surface of the diaphragm, and the vibration is of translation all over the diaphragm. As a result, an amount of displacement of the diaphragm is converted into a change in capacitance to achieve a function of a sensor.
According to an aspect of the present invention, the condenser microphone chip further comprises: an auxiliary beam including a first elongated portion configured by forming an opening in the diaphragm substantially parallel to an edge of the diaphragm at a predetermined distance from the edge, the first portion having two ends connected with the diaphragm; and a second elongated portion extending away from the diaphragm from a substantially middle portion of the first portion, an end of the second portion away from the first portion being fixed to the substrate, and the first portion and the second portion being formed in a “T” shape together.
With the above configuration, the curved beam and the auxiliary beam may be uniformly arranged within and outside the diaphragm, respectively. Therefore, stress is uniformly distributed in the diaphragm, and vibration amplitude is substantially uniform all over the diaphragm. Attachment of the diaphragm to the backplate can be effectively prevented while sensitivity is ensured.
According to an aspect of the present invention, the condenser microphone chip further comprises: a curved beam support which is fixed to the substrate and to which the curved beam is connected at an end of the curved beam; and a diaphragm side electrode which is attached to the end of the curved beam connected to the curved beam support so as to be electrically connected with the diaphragm.
According to an aspect of the present invention, the condenser microphone chip further comprises: an auxiliary beam support fixed to the substrate, the end of the second portion of the auxiliary beam being fixed to the substrate by connecting to the auxiliary beam support; and a diaphragm side electrode which is attached to the end of the second portion of the auxiliary beam connected to the auxiliary beam support so as to be electrically connected with the diaphragm.
According to an aspect of the present invention, the substrate has a through hole, and the backplate has a suspended region opposite to the through hole of the substrate.
With the above configuration, a center portion of the backplate may be suspended and a portion of the backplate layer surrounding the center portion may be supported by the substrate, to increase stiffness of the backplate.
The suspended region may have a plurality of sound holes. In addition, the condenser microphone chip may further comprise a dielectric layer disposed between the substrate and the backplate. The dielectric layer may have an slit generally aligned with and identical with an opening of the through hole opened at a side of the dielectric layer.
According to an aspect of the present invention, the condenser microphone chip further comprises an opening located at a center of the suspended region.
According to an aspect of the present invention, the condenser microphone chip further comprises a reinforcing rib connected with the backplate for reinforcing the stiffness of the backplate.
According to another aspect of the present invention, the condenser microphone chip further comprises a reinforcing rib connected with the backplate and extending from a position outside the suspended region to the suspended region or toward a center of the suspended region for reinforcing the stiffness of the backplate.
With the above configuration, the stiffness of the backplate is further increased by providing the reinforcing rib at the suspended region. Since only a portion of the backplate is suspended and the reinforcing rib is disposed at the suspended region, it is easier to obtain a rigid backplate. Therefore, difficulty in process and cost are reduced and rate of finished products is increased.
Preferably, the diaphragm has an opening located corresponding to the reinforcing rib; and the reinforcing rib protrudes from the backplate into the opening of the diaphragm with a slit formed between the reinforcing rib and an edge of the opening.
According to an aspect of the present invention, the reinforcing rib comprises four reinforcing ribs arranged at substantially equal intervals and substantially symmetrical about a center of the suspended region.
According to an aspect of the present invention, the reinforcing rib comprises a dielectric strip located in the same layer as the curved beam support, and a conductive strip fixed to the dielectric strip and located in the same layer as the diaphragm.
According to another aspect of the present invention, the condenser microphone chip further comprises a supporting member supported between the diaphragm and the suspended region, wherein a predetermined region of the suspended region around the supporting member has a stiffness lower than that of the other region of the suspended region.
The supporting member may be positioned at a center portion of the suspended region.
Preferably, the predetermined region of the suspended region comprises: an opening formed at a center portion of the suspended region, a backplate beam connecting part located at a center portion of the opening, and a plurality of backplate beams connected between the backplate beam connecting part and an edge of the opening.
With the above configuration, when sound wave acts on the diaphragm, the diaphragm transmits a force applied to the diaphragm to the backplate beam and the curved beam so that the backplate beam and the curved beam deform. Since deformation mainly occurs at the backplate beam and the curved beam, the diaphragm vibrates in a direction perpendicular to a surface of the diaphragm, and motion of translation is generated all over the diaphragm. As a result, an amount of displacement of the vibration of the diaphragm is converted into a change in capacitance to achieve a function of a sensor.
The plurality of backplate beams may comprise four backplate beams arranged at substantially equal intervals and substantially symmetrical about a center of the suspended region.
According to an aspect of the present invention, the supporting member is supported between the diaphragm and the backplate beam connecting part of the suspended region.
With the above configuration, when the diaphragm vibrates, stress is uniformly distributed in the diaphragm of the condenser microphone chip and probability of attachment of the diaphragm to the backplate is effectively reduced so that rate of finished products is increased. In addition, the diaphragm has good vibration characteristics due to the curved beam, the auxiliary beam and the backplate beam.
According to an aspect of the present invention, the condenser microphone chip further comprises a reinforcing rib connected with the backplate for reinforcing a stiffness of a region of the backplate except the predetermined region of the suspended region.
According to another aspect of the present invention, the condenser microphone chip further comprises a reinforcing rib connected with the backplate and extending from a position outside the suspended region to the suspended region or toward a center of the suspended region for reinforcing a stiffness of a region of the backplate except the predetermined region of the suspended region.
In the above condenser microphone chip having the predetermined region of the suspended region, the diaphragm has an opening located corresponding to the reinforcing rib; and the reinforcing rib protrudes from the backplate into the opening of the diaphragm with a slit formed between the reinforcing rib and an edge of the opening.
According to an aspect of the invention, a plurality of small holes are disposed in an edge portion of the diaphragm. The plurality of small holes cooperate with the sound holes of the suspended region of the backplate to release a sacrificial layer between the diaphragm and the backplate during manufacturing process and can improve frequency response characteristics of the condenser microphone chip.
According to a further aspect of the present invention, there is provided a condenser microphone chip comprising: a substrate having a through hole; a backplate connected with the substrate and having a suspended region opposite to the through hole of the substrate; a diaphragm spaced from the backplate, for example, by a predetermined distance; and a supporting member supported between the diaphragm and the suspended region, wherein a predetermined region of the suspended region around the supporting member has a stiffness lower than that of the other region of the suspended region.
According to an aspect of the present invention, the condenser microphone chip further comprises a curved beam connected with the diaphragm to anchor the diaphragm to the substrate.
The curved beam may extend in one of a substantial “S” shape, a shape of a substantial arc, and a substantial helical shape.
According to another aspect of the present invention, the curved beam includes at least one pair of curved beams arranged at substantially equal intervals and substantially symmetrical about a center of the diaphragm.
The curved beam may be arranged in the diaphragm.
According to an aspect of the invention, the condenser microphone chip further comprises: an auxiliary beam including a first portion configured by forming an opening in the diaphragm at a predetermined distance from an edge of the diaphragm, the first portion having two ends connected with the diaphragm; and a second portion extending from the first portion away from the diaphragm, the second portion being fixed to the substrate at an end of the second portion away from the first portion.
According to another aspect of the present invention, the condenser microphone chip further comprises: an auxiliary beam including a first elongated portion configured by forming an opening in the diaphragm substantially parallel to an edge of the diaphragm at a predetermined distance from the edge, the first portion having two ends connected with the diaphragm; and a second elongated portion extending away from the diaphragm from a substantially middle portion of the first portion, the second portion being fixed at an end of the second portion away from the first portion to the substrate, and the first portion and the second portion being formed in a “T” shape together.
According to an aspect of the present invention, the condenser microphone chip further comprises: a curved beam support which is fixed to the substrate and connected with an end of the curved beam; and a diaphragm side electrode which is attached to the end of the curved beam connected to the curved beam support so as to be electrically connected with the diaphragm.
According to another aspect of the present invention, the condenser microphone chip further comprises: an auxiliary beam support fixed to the substrate, the end of the second portion of the auxiliary beam being fixed to the substrate by connecting to the auxiliary beam support; and a diaphragm side electrode which is attached to the end of the second portion of the auxiliary beam connected to the auxiliary beam support so as to be electrically connected with the diaphragm.
According to an aspect of the present invention, the condenser microphone chip further comprises: a curved beam connecting part having a shape of a substantially circular plate, wherein the curved beam is arranged in the diaphragm, and wherein each curved beam includes a plurality of sub beams, each of the plurality of sub beams including a first sub beam portion extending in a substantially radial direction from a circumference of the curved beam connecting part; a second sub beam portion extending in a substantially circumferential direction from an end of the first sub beam portion away from the circumference of the curved beam connecting part and having a shape of a substantial arc; and a third sub beam portion extending in the radial direction from an end of the second sub beam portion away from the first sub beam portion and connected to the diaphragm.
According to an aspect of the present invention, each curved beam comprises three sub beams.
According to an aspect of the present invention, the second sub beam portions of the plurality of the sub beams of the curved beam extend toward an identical circumferential direction from the ends of the first sub beam portions away from the circumference of the curved beam connecting part.
The plurality of the sub beams of the curved beam may have a substantially identical shape. In addition, the plurality of the sub beams of the curved beam may be arranged at substantially equal intervals around the circumference of the curved beam connecting part.
The suspended region may have a plurality of sound holes. In addition, the condenser microphone chip may further comprise a dielectric layer disposed between the substrate and the backplate. The dielectric layer may have an opening generally aligned with and identical with an opening of the through hole opened at a side of the dielectric layer.
According to an aspect of the present invention, the condenser microphone chip may further comprise: a reinforcing rib connected with the backplate for reinforcing a stiffness of a region of the backplate except the predetermined region of the suspended region.
According to another aspect of the present invention, the condenser microphone chip further comprises: a reinforcing rib connected with the backplate and extending from a position outside the suspended region to the suspended region or toward a center of the suspended region for reinforcing a stiffness of a region of the backplate except the predetermined region of the suspended region.
According to an aspect of the present invention, the diaphragm has an opening located corresponding to the reinforcing rib; and the reinforcing rib protrudes from the backplate into the opening of the diaphragm with a slit formed between the reinforcing rib and an edge of the opening.
According to an aspect of the present invention, the reinforcing rib comprises four reinforcing ribs arranged at substantially equal intervals and substantially symmetrical about a center of the suspended region.
According to an aspect of the present invention, the reinforcing rib comprises a dielectric strip located in the same layer as the curved beam support, and a conductive strip fixed to the dielectric strip and located in the same layer as the diaphragm.
According to an aspect of the present invention, the supporting member is positioned at a center portion of the suspended region.
According to an aspect of the present invention, the predetermined region of the suspended region comprises: an opening formed at a center portion of the suspended region, a backplate beam connecting part located at a center portion of the opening, and a plurality of backplate beams connected between the backplate beam connecting part and an edge of the opening. The backplate beam connecting part may have one of a square shape, a circular shape, and a polygonal shape. In addition, the opening may have one of a square shape, a circular shape, and a polygonal shape.
According to an aspect of the present invention, the plurality of backplate beams comprise four backplate beams arranged at substantially equal intervals and substantially symmetrical about a center of the suspended region.
According to another aspect of the present invention, the supporting member is supported between the diaphragm and the backplate beam connecting part of the suspended region.
These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawing.
Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.
The first embodiment according to the present invention will be described hereinafter with reference to
Referring to
The substrate 21 may have a through hole as a sound hole 33 at a center portion thereof. The substrate 21 may be a conductor material or a semiconductor material such as silicon. The sound hole 33 at the center portion of the substrate 21 of silicon material may be formed by bulk silicon etching, or the sound hole 33 may be formed into a back cavity having a post shape by dry etching. The curved beam may be located outside the sound hole 33, and a portion of the diaphragm 26 and a corresponding portion of the substrate 21 constitute a capacitor, and a projection of the portion of the diaphragm 20 on the surface of the substrate 21 is located outside an opening of the sound hole 33 on a side of the diaphragm 20.
In the illustrated examples, the diaphragm 26 is formed in a circular shape by a separating groove 50. However, the diaphragm 26 may have any appropriate shapes such as a square shape, a rectangular shape, and a polygonal shape. In addition, the sound hole 33 has a truncated prism shape in the illustrated examples, but it may have any other appropriate shapes.
In an example of the present invention, the curved beam 27 includes a plurality of sub beams, each of the plurality of sub beams has an end attached to the same curved beam support 24 fixed to the substrate 21.
In an example of the present invention, the curved beam 27 comprises one curved beam 27 disposed at a substantial center portion of the diaphragm 26. In this case, the sound hole 33 may have therein one or two beams passing through a substantial center of the sound hole 33 and extending between an edge of the sound hole 33, and the two beams intersect or are perpendicular to each other. The curved beam 27 is supported on the one or two beams by the curved beam support. Alternatively, the curved beam 27 includes at least one pair of curved beams 27 arranged at substantially equal intervals and substantially symmetrical about a center of the diaphragm 26.
The condenser microphone chip according to the present invention may further comprise a curved beam connecting part 29 which is fixed to or on the curved beam support 24 and to which the curved beam 27 is connected. In the illustrated examples, the curved beam 27, the diaphragm 26 and the curved beam connecting part 29 are integrally formed.
The curved beam 27 may be arranged in the diaphragm 26. The curved beam 27 is disposed in the diaphragm 26 in
In an example of the present invention, the curved beam connecting part 29 has a shape of a substantially circular plate. The curved beam 27 is arranged in the diaphragm 26. The curved beam 27 each includes a plurality of sub beams, each of the plurality of sub beams including a first sub beam portion extending in a substantially radial direction (or radially) from a circumference of the curved beam connecting part 29; a second sub beam portion extending in a substantially circumferential direction (or around the circumference) from an end of the first sub beam portion away from the circumference of the curved beam connecting part 29 and having a shape of a substantial arc; and a third sub beam portion extending in the radial direction (or radially) from an end of the second sub beam portion away from the first sub beam portion and connected to the diaphragm 26.
The second sub beam portions of the plurality of the sub beams of the curved beam 27 may extend toward an identical circumferential direction from the ends of the first sub beam portions away from the circumference of the curved beam connecting part 29. However, the second sub beam portions of the plurality of the sub beams of the curved beam 27 may extend toward opposite circumferential directions from the ends of the first sub beam portions away from the circumference of the curved beam connecting part 29. For example, in a case that the curved beam 27 comprises four or six sub beams, the second sub beam portions of the adjacent two sub beams of the curved beam 27 may extend toward two circumferential directions toward or away from each other from the ends of the respective first sub beam portions away from the circumference of the curved beam connecting part 29, and the first sub beam portions of the curved beam 27 may be correspondingly positioned. In addition, the plurality of the sub beams of the curved beam 27 may have a substantially identical shape or different shapes. The plurality of the sub beams of the curved beam 27 may be arranged at substantially equal intervals around the circumference of the curved beam connecting part 29.
In an example of the present invention, the condenser microphone chip may further comprise an auxiliary beam 28. The auxiliary beam 28 includes: a first portion configured by forming an opening in the diaphragm 26 at a predetermined distance from an edge of the diaphragm 26, the first portion having two ends connected with the diaphragm 26; and a second portion extending from the first portion away from the diaphragm 26, the second portion being fixed at an end of the second portion away from the first portion to the substrate 21, for example, by an auxiliary beam support 25 fixed to the substrate 21.
In another example of the present invention, the auxiliary beam 28 includes a first elongated portion configured by forming an opening in the diaphragm 26 substantially parallel to the edge of the diaphragm 26 at a predetermined distance from the edge, the first portion having two ends connected with the diaphragm 26; and a second elongated portion extending away from the diaphragm 26 from a substantially middle portion of the first portion, the second portion being fixed to the substrate 21 at an end of the second portion away from the first portion, for example, by the auxiliary beam support 25, and the first portion and the second portion being formed in a “T” shape together, as shown in
The dielectric layer 25′ comprises the curved beam support 24, the auxiliary beam support 25 and a surrounding dielectric layer 25′c, as shown in
In the illustrated examples, a through hole is disposed on a side of the ring-shaped surrounding dielectric layer 25′c above the surrounding dielectric layer 25′c to serve as a backplate side electrode hole 37. A metal electrode as a backplate side electrode 31 is fixed to the surface (an upper surface in
The conductive layer 60 comprises the diaphragm 26, the curved beam 27, the auxiliary beam 28, the curved beam connecting part 29, the auxiliary beam connecting part 30 and a surrounding conductive layer 30′, as shown in
In the illustrated examples, the edge of the diaphragm 26 is connected to the auxiliary beam connecting part 30 through the auxiliary beam 28, and the auxiliary beam connecting part 30 is fixed on a surface (an upper surface in
In the illustrated examples, the diaphragm 26 covers the opening of the sound hole 33 on the side of the diaphragm 26 and has an area larger than that of the opening of the sound hole 33. A portion of the diaphragm 26 and a corresponding portion of the substrate 21 constitute a capacitor, and a projection of the portion of the diaphragm 26 on the surface of the substrate 21 is located outside the opening of the sound hole 33 on the side of the diaphragm 26. A plurality of small holes 38 are disposed in the aforesaid portion of the diaphragm 26. The metal electrode as the diaphragm side electrode 32 is fixed on the surface (the upper surface in
In the examples shown in
In an example of the present invention, the end of the curved beam 27 is connected to the curved beam support 24, and the diaphragm side electrode 32 is attached to the end of the curved beam 27 connected to the curved beam support 24 so as to be electrically connected with the diaphragm 26. Alternatively, the diaphragm side electrode 32 may be disposed at the curved beam connecting part 29, or may be electrically connected with the diaphragm 26 in other manners.
In the illustrated examples, the auxiliary beam connecting part 30 is connected to the auxiliary beam support 25, and the end of the second portion of the auxiliary beam 28 is coupled to the auxiliary beam connecting part 30.
In an example of the present invention, the diaphragm side electrode 32 may be attached to the end of the second portion of the auxiliary beam 28 connected to the auxiliary beam support 25 so as to be electrically connected with the diaphragm 26, or the diaphragm side electrode 32 may be attached to the auxiliary beam connecting part 30 connected to the auxiliary beam support 25 so as to be electrically connected with the diaphragm 26.
In the illustrated examples, the substrate 21 and the diaphragm 26 form a plate type capacitor with an air gap of 2-5 μm therebetween. When sound wave acts on the diaphragm 26, the diaphragm 26 transmits a force applied to the diaphragm to the curved beam 27 and the auxiliary beam 28 so that the curved beam and the auxiliary beam deform. Since deformation mainly occurs at the curved beam 27 and the auxiliary beam 28, the diaphragm 26 easily vibrates in a direction perpendicular to a surface of the diaphragm. As a result, an amount of displacement of the diaphragm is converted into a change in capacitance to achieve a function of a sensor. Since the diaphragm 26 almost translates when the diaphragm 26 vibrates due to the sound wave, mechanical sensitivity of the diaphragm 26 can be sufficiently used. Since the present invention employs the curved beams disposed in the diaphragm so that the vibration all over the diaphragm 26 is substantially of translation, the diaphragm 26 is not easily attached to the substrate 21 as compared with the prior arts with identical sensitivity. Therefore, the curved beams disposed in the diaphragm improve rate of finished products and reliability of the chip to a great extent.
The second embodiment according to the present invention will be described hereinafter with reference to
Referring to
In the illustrated examples, the conductive layer 23 is attached to or fixed on the dielectric layer 22 and comprises the backplate 23a, a lead wire 23b for the electrode, a support partition 23c and a surround layer 23d. The backplate 23a is disposed at an middle region of the conductive layer 23 and has a center region as a suspended region 23e directly opposite an opening (an upper opening in
In the illustrated examples, the diaphragm 26 is formed in a circular shape by a separating groove 50. Apparently, the diaphragm 26 may have any other appropriate shapes such as a square shape, a rectangular shape, and a polygonal shape. In addition, the sound hole 33 has a truncated prism shape in the illustrated examples, but it may have any other appropriate shapes.
The curved beam may extend in one of a substantial “S” shape, a shape of a substantial arc, and a substantial helical shape.
In an example of the present invention, the curved beam 27 comprises one curved beam 27 disposed at a substantial center portion of the diaphragm 26. In this case, the sound hole 33 may have therein one or two beams passing through a substantial center of the sound hole 33 and extending between an edge of the sound hole 33, and the two beams intersect or are perpendicular to each other. The curved beam 27 is supported on the one or two beams by the curved beam support. Alternatively, the curved beam 27 includes at least one pair of curved beams 27 arranged at substantially equal intervals and substantially symmetrical about a center of the diaphragm 26.
The condenser microphone chip according to the present invention may further comprise a curved beam connecting part 29 which is fixed to a curved beam support 24 (to be described in detail later) and to which the curved beam 27 is connected. In the illustrated examples, the curved beam 27, the diaphragm 26 and the curved beam connecting part 29 are integrally formed. In addition, the curved beam may be formed within the diaphragm 26.
In an example of the present invention, the curved beam connecting part 29 of the condenser microphone chip has a shape of a substantially circular plate. The curved beam 27 is arranged in the diaphragm 26. The curved beam 27 includes a plurality of sub beams, each of the plurality of sub beams including a first sub beam portion extending in a substantially radial direction (or radially) from a circumference of the curved beam connecting part 29; a second sub beam portion extending in a substantially circumferential direction (or around the circumference) from an end of the first sub beam portion away from the circumference of the curved beam connecting part 29 and having a shape of a substantial arc; and a third sub beam portion extending in the radial direction (or radially) from an end of the second sub beam portion away from the first sub beam portion and connected to the diaphragm 26.
The second sub beam portions of the plurality of the sub beams of the curved beam 27 may extend toward an identical circumferential direction from the ends of the first sub beam portions away from the circumference of the curved beam connecting part 29. However, the second sub beam portions of the plurality of the sub beams of the curved beam 27 may extend toward opposite circumferential directions from the ends of the first sub beam portions away from the circumference of the curved beam connecting part 29. For example, in a case that the curved beam 27 comprises four or six sub beams, the second sub beam portions of the adjacent two sub beams of the curved beam 27 may extend toward two circumferential directions toward or away from each other from the ends of the respective first sub beam portions away from the circumference of the curved beam connecting part 29, and the first sub beam portions of the curved beam 27 may be correspondingly positioned. In addition, the plurality of the sub beams of the curved beam 27 may have a substantially identical shape or different shapes. The plurality of the sub beams of the curved beam 27 may be arranged at substantially equal intervals around the circumference of the curved beam connecting part 29.
In an example of the present invention, the condenser microphone chip may further comprise an auxiliary beam 28. The auxiliary beam 28 includes: a first portion configured by forming an opening in the diaphragm 26 at a predetermined distance from an edge of the diaphragm 26, the first portion having two ends connected with the diaphragm 26; and a second portion extending from the first portion away from the diaphragm 26, the second portion being fixed at an end of the second portion away from the first portion to the substrate 21, for example, by an auxiliary beam support 25 fixed to the substrate 21.
In another example of the present invention, the auxiliary beam 28 includes a first elongated portion configured by forming an opening in the diaphragm 26 substantially parallel to the edge of the diaphragm 26 at a predetermined distance from the edge, the first portion having two ends connected with the diaphragm 26; and a second elongated portion extending away from the diaphragm from a substantially middle portion of the first portion, the second portion being fixed at an end of the second portion away from the first portion to the substrate 21, for example, by the auxiliary beam support 25, and the first portion and the second portion being formed in a “T” shape together. The second elongated portion of the auxiliary beam may be attached to an auxiliary beam connecting part 30 connected with the auxiliary beam support 25.
In the illustrated examples, the curved beam support 24 and the auxiliary beam support 25 are fixedly attached to the conductive layer 23. Specifically, the curved beam support 24 is fixedly attached to the support partition 23c. The curved beam connecting part 29 is fixed on the curved beam support 24, while the auxiliary beam support 25 is fixed on the surrounding layer 23d. A through hole 37 is disposed on a side of the auxiliary beam support 25 so that a projection of an edge of the through hole 37 on the conductive layer 23 is outside an edge of the lead wire 23b. The backplate side electrode 31 is disposed to a surface (an upper surface in
The diaphragm 26 and the backplate 23a may substantially correspond in shape to each other and be directly opposite to each other in a direction perpendicular to a surface of the diaphragm. The diaphragm 26 is located within the auxiliary beam connecting part 30, and may be connected to the curved beam connecting part 29 and the auxiliary beam connecting part 30 through the curved beam 27 and the auxiliary beam 28, respectively. The curved beam 27 and the auxiliary beam 28 can be formed in many shapes.
In the illustrated examples, the curved beam 27 and the auxiliary beam 28 extend in a “T” shape. The beams extending in the “T” shape can well release stress in the diaphragm in a limited space. There is a gap of 2-4 μm between the diaphragm 26 and the backplate 23a. A plurality of small holes 38 are disposed in a portion of the diaphragm 26 outside a range of a projection of an opening of the sound hole 33, which projection is on a surface of the diaphragm 26 and which opening is on a side of the diaphragm 26. The curved beam connecting part 29, the auxiliary beam connecting part 30, the curved beam 27, the auxiliary beam 28, and diaphragm 26 may be formed of conductive material, or may be made of be an n type semiconductor layer or a p type semiconductor layer formed by doping polysilicon with phosphor or boron.
In an example of the present invention, the condenser microphone chip further comprises a diaphragm side electrode 32 which is attached to an end of the curved beam 27 connected to the curved beam support 24 so as to be electrically connected with the diaphragm 26. Alternatively, the diaphragm side electrode 32 may be disposed at the curved beam connecting part 29 or electrically connected with the diaphragm 26 in other appropriate manners.
In an example of the preset invention, the diaphragm side electrode 32 may be attached to the auxiliary beam connecting part 30 connected to the auxiliary beam support 25 so as to be electrically connected with the diaphragm 26.
In an example of the present invention, the condenser microphone chip further comprises an opening 39 formed in the suspended region 23e. The suspended region sound holes 34 are not formed in a region of the suspended region 23e where the opening 39, a backplate beam connecting part 23g (to be described in detail later), and a plurality of backplate beams 23f (to be described in detail later) are formed. The opening 39 of the suspended region 23e may be located at a center of the suspended region 23, and may be square, circular, or polygonal, as shown in
In an example of the present invention, the condenser microphone chip further comprises a reinforcing rib connected with the backplate 23a for reinforcing stiffness of the backplate 23a. In the illustrated examples, since a part of the backplate 23a forms the suspended region 23e, the reinforcing rib is mainly used to increase stiffness of the suspended region 23e of the backplate 23a. The reinforcing rib may be disposed at the suspended region 23e of the backplate 23a without number of process steps increased.
In an example of the preset invention, the reinforcing rib is connected with the backplate 23a and extends from a position outside the suspended region 23e to the suspended region 23e or toward a center of the suspended region 23e.
In the illustrated examples, the reinforcing rib extends to a vicinity of the center of the suspended region 23e. Apparently, the reinforcing rib may extend across the suspended region 23e from a position to another position outside the suspended region 23e.
In an example of the present invention, the diaphragm 26 has an opening located to correspond to the reinforcing rib; and the reinforcing rib protrudes from the backplate 23a into the opening of the diaphragm 26 with a slit 42 formed between the reinforcing rib and an edge of the opening.
The reinforcing rib may comprise four reinforcing ribs arranged at substantially equal intervals and substantially symmetrical about the center of the suspended region 23e, as shown in
The reinforcing rib comprises a dielectric strip 40 located in the same layer as the curved beam support 24, and a conductive strip 41 fixed to the dielectric strip 40 and located in the same layer as the diaphragm 26. Alternatively, the reinforcing rib may comprise only the dielectric strip 40.
In addition, the reinforcing rib may be formed on a side of the suspended region 23e near the substrate 21. Furthermore, the reinforcing rib may be formed of the dielectric layer 22 or a separate material. In this case, the diaphragm 26 does not necessarily have the opening positioned to correspond to the reinforcing rib.
In the illustrated examples, the backplate 23a and the diaphragm 26 form a plate type capacitor. When sound wave acts on the diaphragm 26, the diaphragm 26 transmits a force applied to the diaphragm to the curved beam 27 and the auxiliary beam 28 so that the curved beam and the auxiliary beam deform. Since deformation mainly occurs at the curved beam 27 and the auxiliary beam 28, the diaphragm easily vibrates in the direction perpendicular to the surface of the diaphragm. As a result, an amount of displacement of the diaphragm 26 is converted into a change in capacitance to achieve a function of a sensor. Since the vibration all over the diaphragm 26 is generally of translation, the diaphragm 26 is not easily attached to the substrate 21 as compared with that of the prior art with the same sensitivity. Therefore, rate of finished products and reliability of the chip are improved to a great extent. With a configuration in which a part of the backplate 23a is suspended, stiffness of the suspended structure is increased, and the chip can be made smaller in the case that the backplate has identical size.
The third embodiment according to the present invention will be described hereinafter with reference to
Referring to
With the above configuration, the supporting member 24′ can prevent the diaphragm 26 from being attached to the backplate 23a, and at the same time resistance to vibration of the diaphragm 26 due to the supporting member 24′ can be minimized.
In the illustrated examples, only one supporting member 24′ is shown, but a plurality of supporting member 24′ can be used and arranged at substantially equal intervals and substantially symmetrical about a center of the suspended region 23e. In addition, the suspended region 23e may comprise a plurality of suspended region sound holes 34. The backplate may be suspended only at a center region thereof, as shown in
The substrate 21 may be made of semiconductor material such as silicon. The sound hole 33 at the center portion of the substrate 21 of silicon material may be formed by bulk silicon etching, or the sound hole 33 may be formed into a back cavity having a post shape by dry etching. The dielectric layer 22 is fixed to a surface (an upper surface in
In an example of the present invention, the condenser microphone chip may further comprise a curved beam 27 connected with the diaphragm 26 to anchor the diaphragm 26 to the substrate 21. The curved beam 27 may extend in one of a substantial “S” shape, a shape of a substantial arc, and a substantial helical shape. Apparently, the curved beam 27 may extend in any other appropriate curved shapes. The curved beam 27 may be formed within the diaphragm 26.
In an example of the present invention, the curved beam 27 includes at least one pair of curved beams 27 arranged at substantially equal intervals and substantially symmetrical about a center of the diaphragm 26.
In an example of the present invention, the condenser microphone chip further comprises a curved beam connecting part 29 with which the curved beam 27 is connected at an end thereof and which is attached to a curved beam support 24 fixed to the substrate 21.
In an example of the present invention, the curved beam connecting part 29 of the condenser microphone chip has a shape of a substantially circular plate. The curved beam 27 is arranged in the diaphragm 26. The curved beam 27 includes a plurality of sub beams, each of the plurality of sub beams including a first sub beam portion extending in a substantially radial direction (or radially) from a circumference of the curved beam connecting part 29; a second sub beam portion extending in a substantially circumferential direction (or around the circumference) from an end of the first sub beam portion away from the circumference of the curved beam connecting part 29 and having a shape of a substantial arc; and a third sub beam portion extending in the radial direction (or radially) from an end of the second sub beam portion away from the first sub beam portion and connected to the diaphragm 26.
The second sub beam portions of the plurality of the sub beams of the curved beam 27 may extend toward an identical circumferential direction from the ends of the first sub beam portions away from the circumference of the curved beam connecting part 29. However, the second sub beam portions of the plurality of the sub beams of the curved beam 27 may extend toward opposite circumferential directions from the ends of the first sub beam portions away from the circumference of the curved beam connecting part 29. For example, in a case that the curved beam 27 comprises four or six sub beams, the second sub beam portions of the adjacent two sub beams of the curved beam 27 may extend toward two circumferential directions toward or away from each other from the ends of the respective first sub beam portions away from the circumference of the curved beam connecting part 29, and the first sub beam portions of the curved beam 27 may be correspondingly positioned. In addition, the plurality of the sub beams of the curved beam 27 may have a substantially identical shape or different shapes. The plurality of the sub beams of the curved beam 27 may be arranged at substantially equal intervals around the circumference of the curved beam connecting part 29.
In an example of the present invention, the condenser microphone chip may further comprise an auxiliary beam 28. The auxiliary beam 28 includes: a first portion configured by forming an opening in the diaphragm 26 at a predetermined distance from an edge of the diaphragm 26, the first portion having two ends connected with the diaphragm 26; and a second portion extending from the first portion away from the diaphragm 26, the second portion being fixed at an end of the second portion away from the first portion to the substrate 21, for example, by an auxiliary beam support 25. The auxiliary beam support 25 is fixedly disposed on the conductive layer 23 as shown in
In another example of the present invention, the auxiliary beam 28 includes a first elongated portion configured by forming an opening in the diaphragm 26 substantially parallel to the edge of the diaphragm 26 at a predetermined distance from the edge, the first portion having two ends connected with the diaphragm 26; and a second elongated portion extending away from the diaphragm 26 from a substantially middle portion of the first portion, the second portion being fixed at an end of the second portion away from the first portion to the substrate 21, for example, by the auxiliary beam support 25, and the first portion and the second portion being formed in a “T” shape together, as shown in
In an example of the present invention, the condenser microphone chip further comprises a diaphragm side electrode 32 which is attached to the end of the curved beam 27 connected to the curved beam support 24 so as to be electrically connected with the diaphragm 26. Alternatively, the diaphragm side electrode 32 may be attached to the end of the second portion of the auxiliary beam 28 connected with the auxiliary beam support 25 or to the auxiliary beam connecting part 30 so as to be electrically connected with the diaphragm 26.
In an example of the present invention, the condenser microphone chip further comprises a reinforcing rib connected with the backplate 23a for reinforcing stiffness of a region of the backplate 23a except the predetermined region of the suspended region 23e. The reinforcing rib may be disposed at the suspended region 23e of the backplate 23a without number of process steps increased.
In another example of the preset invention, the reinforcing rib is connected with the backplate 23a and extends from a position outside the suspended region 23e to the suspended region 23e or toward a center of the suspended region 23e.
In an example of the present invention, the diaphragm 26 has an opening located to correspond to the reinforcing rib; and the reinforcing rib protrudes from the backplate 23a into the opening of the diaphragm 26 with a slit 42 formed between the reinforcing rib and an edge of the opening.
The reinforcing rib may comprise four reinforcing ribs arranged at substantially equal intervals and substantially symmetrical about the center of the suspended region 23e.
The reinforcing rib may comprises a dielectric strip 40 located in the same layer as the curved beam support 24, and a conductive strip 41 fixed to the dielectric strip 40 and located in the same layer as the diaphragm 26, as shown in
The supporting member 24′ may be supported between the diaphragm 26 and the suspended region 23e at the center portion of the suspended region 23e.
In an example of the present invention, the predetermined low-stiffness region of the suspended region comprises: an opening formed at the center portion of the suspended region 23e, a backplate beam connecting part 23g located at a center portion of the opening, and a plurality of backplate beams 23f connected between the backplate beam connecting part 23g and an edge of the opening. The backplate beam connecting part 23g may have a square shape, a circular shape, a polygonal shape, or any other appropriate shapes. In addition, the opening may have a square shape, a circular shape, a polygonal shape, or any other appropriate shapes. The backplate beam 23f may be a straightline-shaped beam.
In the illustrated examples, the backplate 23a is formed in a shape of a frame, and a center of the center opening of the backplate 23a is aligned with a center of an opening of the back cavity or sound hole 33 on a side of the backplate 23a. A region of backplate 23a is the suspended region 23e, and a projection of the region of the backplate 23a on the substrate 21 is within the opening of the sound hole 33. The other region of the backplate 23a is fixed on the dielectric layer 22, and a projection of the other region of the backplate 23a on the substrate 21 is outside the opening of the back cavity 33.
The plurality of backplate beams 23f may comprise four backplate beams 23f arranged at substantially equal intervals and substantially symmetrical about the center of the suspended region 23e. The supporting member 24′ is supported at the center portion of the suspended region 23e between the diaphragm 26 and the backplate beam connecting part 23g of the suspended region 23e.
The conductive layer 23 comprises the backplate 23a, a lead wire 23b, the backplate beam connecting part 23g, a surround layer 23d, and backplate beams 23f, as shown in
Referring to
The auxiliary beam support 25 is fixed on the surrounding layer 23d, and a through hole 37 is disposed on a side of the auxiliary beam support 25 so that a projection of an edge of the through hole 37 on the conductive layer 23 is outside an edge of the lead wire 23b. The backplate side electrode 31 is disposed on an upper surface of the lead wire 23b in the through hole 37. The supporting member 24′ and the auxiliary beam support 25 are insulator formed of silicon oxide such as LTO, PSG, and TEOS or other materials.
In the illustrated examples, the diaphragm 26 and the backplate 23a may be substantially identical in shape with each other and be aligned with each other in a direction perpendicular to a surface of the diaphragm. The diaphragm 26 is located within the auxiliary beam connecting part 30, and may be connected at a center portion of the diaphragm without a hole to an upper end of the supporting member 24′. The edge of the diaphragm 26 is connected to the auxiliary beam connecting part 30 through the auxiliary beam 28, and the auxiliary beam 28 may be configured in many structures. In the illustrated examples, the auxiliary beam 28 extends in a “T” shape. The beams extending in the “T” shape can accomplish a good stress releasing effect in a limited space. There is a gap of 2-4 μm between the diaphragm 26 and the backplate 23a. A plurality of small holes 38 are disposed in a portion of the diaphragm 26 outside a range of a projection of the opening of the sound hole 33, which projection is on a surface of the diaphragm 26 and which opening is on a side of the diaphragm 26. The auxiliary beam connecting part 30, the auxiliary beam 28, and diaphragm 26 may be formed of conductive material, or may be made of be an n type semiconductor layer or a p type semiconductor layer formed by doping polysilicon with phosphor or boron. The diaphragm side electrode 32 is disposed on a side on the auxiliary beam connecting part 30.
In the illustrated examples, the backplate 23a and the diaphragm 26 form a plate type capacitor. When sound wave acts on the diaphragm 26, the diaphragm 26 transmits a force applied to the diaphragm to the auxiliary beam 28 and the backplate beam 23f so that the auxiliary beam 28 and the backplate beam 23f deform. Since deformation mainly occurs at the auxiliary beam 28 and the backplate beam 23f, the diaphragm easily vibrates in the direction perpendicular to the surface of the diaphragm. As a result, an amount of displacement of the vibration of the diaphragm is converted into a change in capacitance to achieve a function of a sensor. The vibration all over the diaphragm 26 is generally of translation. Therefore, the diaphragm 26 is not easily attached to the substrate 21 in the case of identical sensitivity. Therefore, rate of finished products of the chip is improved to a great extent. With a configuration in which a part of the backplate 23a is suspended, stiffness of the suspended structure is increased, and the chip can be made smaller with the same size of the backplate.
A method for manufacturing a condenser microphone chip according to the present invention will be described hereinafter.
The condenser microphone chips are made by MEMS (Micro-electro-mechanical system) in many ways such as the following specific one.
The condenser microphone chip according to the first embodiment of the present invention, as shown in
1. A low resistance silicon wafer with a first side and a second side polished is selected as a substrate 21. Silicon nitride films of a thickness of 3000 Å grow on the two sides of the silicon wafer by low pressure chemical vapor deposition (LPCVD) process, respectively.
2. The silicon nitride film on the first side of the silicon wafer is removed by reactive ion etching, and the silicon nitride film on the second side of the silicon wafer is partially etched by the reactive ion etching. The etched region is to serve as a window for corroding the silicon wafer.
3. A layer of silicon oxide such as PSG, LTO, and TEOS of a thickness of 3 μm grows on the first side as a sacrificial layer and a supporting layer.
4. Low stress polysilicon layers of a thickness of 1 μm further grow on the first side and the second side of the silicon wafer by LPCVD process, so that n type or p type polysilicon layers are formed by injection or diffusion.
5. A pattern design for the polysilicon layer on the first side is etched by reactive ion etching to form a diaphragm, beams, and the like.
6. The layer of silicon oxide such as PSG, LTO, and TEOS is corroded to be perforated by HF solution to form a backplate side electrode hole.
7. A metal electrode is made on the first side of the silicon wafer by sputtering, evaporation, or plating.
8. The polysilicon layer on the second side of the silicon wafer is firstly removed by washing the silicon wafer with potassium hydroxide (KOH) and then the substrate is corroded up to the layer of silicon oxide such as PSG, LTO, and TEOS to form a sound hole by bulk silicon etching while the first side of the silicon wafer is protected.
9. The layer of silicon oxide such as PSG, LTO, and TEOS under the diaphragm is corroded to be removed by HF solution through small holes located in a portion of the diaphragm outside the sound hole and the sound hole. Size of beam connecting parts is far larger than that between the small holes, so that beam supports beneath the beam connecting parts can be formed by appropriately controlling time of the corrosion.
Furthermore, a manufacturing process for the condenser microphone chip according to the second embodiment of the present invention, as shown in
The following steps are added prior to growing the silicon nitride films in the above step 1:
a. Dielectric layers of silicon dioxide of a thickness of 3000 Å are formed on the two sides of the silicon wafer by thermal oxidation.
b. The dielectric layer of silicon dioxide on the first side is removed while the first side of the silicon wafer is protected.
The following steps are added between the steps 2 and 3:
c. Low stress polysilicon layers of a thickness of 2 μm further grow on the first side and the second side of the silicon wafer by LPCVD process, so that n type or p type polysilicon layers are formed by injection or diffusion.
d. A pattern design for the polysilicon layer on the first side is etched by reactive ion etching.
Finally, a manufacturing process for the condenser microphone chip according to the third embodiment of the present invention, as shown in
It will be understood that the present invention may be embodied in other specific forms without departing from the spirit or principle thereof. The present examples and the embodiments, therefore, are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein.
For example, some of the above features, structures and components in the above embodiments and examples may be combined to form various embodiments and examples, unless the combination is impracticable. Therefore, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
In addition, the use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.
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| 2007 1 0064610 | Mar 2007 | CN | national |
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