Patent Application
20190084825
Embodiments described herein relate generally to a connection structure between a plug and a silicon germanium layer, a manufacturing method thereof, and a sensor.
As a semiconductor material other than silicon, silicon germanium is known. A micro-electromechanical systems (HEMS) device is an example of a device that employs a layer containing silicon germanium.
In general, according to one embodiment, a connection structure is disclosed. The connection structure includes a plug having conductivity, a first insulating film, and an electrode. The first insulating film covers a side surface of the plug. The electrode is provided on an upper surface of the plug, and includes a polycrystalline silicon germanium layer and an amorphous silicon germanium layer. The polycrystalline silicon germanium layer is in contact with at least part of the upper surface of the plug without an intervention the amorphous silicon germanium layer.
According to another embodiment, a method of manufacturing a connection structure is disclosed. An intermediate insulating film, and an upper insulating film are sequentially formed on a lower insulating film. A first through hole is formed in the lower insulating film, the intermediate insulating film and the upper insulating film. A plug is formed in the first through hole. An amorphous silicon germanium layer is formed on the upper insulating film and the plug. A second through hole is formed in the amorphous silicon germanium layer such that the second through hole is communicated with the first plug. A polycrystalline silicon germanium layer is formed on the plug and the amorphous silicon germanium layer such that the polycrystalline silicon germanium layer tills the second through hole.
According to yet another embodiment, a sensor is disclosed. The sensor includes a variable capacitance element, a circuit, a plug having conductivity, an insulating film, and a connection structure. The variable capacitance element includes a first electrode and a second electrode. The circuit senses a predetermined physical property by detecting a variation of capacitance between the first electrode and the second electrode. The plug connects the circuit and the variable capacitance element each other. The insulating film covers a side surface of the plug. The connection structure connects the first electrode and the plug each other, and includes a connection structure of an embodiment.
Embodiments will be described hereinafter with reference to the accompanying drawings. The drawings are schematic and conceptual, and the dimensions, the proportions, etc., of each of the drawings are not necessarily the same as those in reality. Further, in the drawings, the same reference symbols denote the same or corresponding portions, and overlapping explanations thereof will be made as necessary. In addition, as used in the description and the appended claims, what is expressed by a singular form shall include the meaning of “more than one.”
In
A method of forming the aluminum interconnection includes a process of forming an aluminum film on the interlayer insulating film 11, a process of forming a resist pattern on the aluminum film, a process of etching the aluminum film by reactive ion etching process (RIE) using the resist pattern as a mask. The interconnection 12 may employ a stuck structure of an aluminum interconnection and a barrier metal film. The barrier metal film is, for example, a titanium film, or a stacked film of a nitride titanium film and a titanium film. The titanium film is stacked on the nitride titanium film. The interconnection 12 may be a copper interconnection. The copper interconnection is formed by using, for example, a damascene process. The plug 20 is provided on the interconnection 12.
The plug 20 is electrically connected to the interconnection 12. The side surface of the plug 20 is covered with an interlayer insulating film (lower insulating film) 21 and an interlayer insulating film (upper insulating film) 21. More specifically, the side surface of the upper portion side of the plug 20 is covered with the interlayer insulating film 22, and the side surface of the other side (lower portion side) of the interlayer insulating film 22 is covered with the interlayer insulating film 21. The interlayer insulating film 21 and the interlayer insulating film 22 are insulating films of different type, and for example, the interlayer insulating film 21 is a silicon oxide film, and the interlayer insulating film 22 is a silicon nitride film or a silicon carbide film. The upper surface of the plug 20 is not covered with the interlayer insulating film 21 nor the interlayer insulating film 22.
The electrode 24 is provided on the upper surface of the plug 20. The electrode 24 includes a polycrystalline silicon germanium layer 25 and an amorphous silicon germanium layer 26. The amorphous silicon germanium layer 26 is provide under the polycrystalline silicon germanium layer 25. The polycrystalline silicon germanium layer 25 may contain dopants.
The ratio of silicon and germanium (Si/Ge ratio) of the polycrystalline silicon germanium layer 25 is in a range from 25/75 to 35/65, for example. The Si/Ge ratio of the amorphous silicon germanium layer 26 is also in the range from 25/75 to 35/65, for example. The Si/Ge ratio of the polycrystalline silicon germanium layer 25 may be same as or may be different from the Si/Ge ratio of the amorphous silicon germanium layer 26.
In the present embodiment, the polycrystalline silicon germanium layer 25 is directly in contact with an entire upper surface of the plug 20. The area of the lower surface of the polycrystalline silicon germanium layer 25 is greater than the area of the upper surface of the plug 20. The amorphous silicon germanium layer 26 does not overlap with the upper surface of the plug 20.
The resistivity of the amorphous silicon germanium layer is greater than the resistivity of the polycrystalline silicon germanium layer. For example, the resistivity of the amorphous silicon germanium having about 100 nm thickness is 1.00×10 Ω·cm, and the resistivity of the polycrystalline silicon germanium having about 5 to 20 μm thickness is 3.38×10−3 Ω·cm.
For that reason, the structure in which the amorphous silicon germanium layer 26 is directly in contact with the entire upper surface of the plug 20, and the polycrystalline silicon germanium layer 25 is indirectly in contact with the entire upper surface of the plug through the amorphous silicon germanium layer 26 (connection structure of a comparative example) has a high contact resistance between the plug 20 and the electrode 24. The contact resistance of the connection structure of the comparative example is, for example, 5.1 KΩ.
On the other hand, the connection structure according to the present embodiment is directly in contact with the entire upper surface of the plug, so that the contact resistance between the plug 20 and the electrode 24 is low. For example, the contact resistance is 17 Ω. Hereafter, the connection structure of the present embodiment will be further described in accordance with manufacturing processes thereof.
First, as shown
Subsequently, as shown
A forming method of the plug includes, for example, a process of depositing a tungsten film to be processed into the plug 20 on the entire surface such that the tungsten film fill the through hole, a process of planarizing the surface of the tungsten film and the surface of the interlayer insulating film 22 by CMP process. The upper surface of the plug 20 and the upper surface of the interlayer insulating film 2 form a flat surface.
It is noted that a conductive film other than the tungsten film may be used. For example, a copper film may be used. In this case, for example, the plug (copper) 20 is formed in the through hole after the bottom surface and the side surface of the through hole is covered with a barrier metal film. Consequently, the side surface of the plug 20 is indirectly covered with interlayer insulating films 21 and 22 through the barrier metal film. The barrier metal film is, for example, a stacked film of a titanium nitride film and a titanium film. The titanium nitride film is arranged between the side surface of the plug 20 and the titanium film.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
The polycrystalline silicon germanium layer 25 and the amorphous silicon germanium layer 26 are formed by CVD process, but the conditions (e.g., pressure or source gas) of the CVD process to form the polycrystalline silicon germanium layer 25 are different from the conditions (e.g., pressure or source gas) of the CVD process to form the amorphous silicon germanium layer 26, so that both the polycrystalline and amorphous silicon germanium layers 25 and 26 can be formed by CVD process.
Subsequently, as shown in
After that, the insulating film (sacrifice film) 23 is removed by dry process using hydrogen fluoride gas (HF gas), thereby obtaining the connection. structure that is shown in
A modification example of the present embodiment is illustrated in
The present embodiment is different from the first embodiment in that a barrier metal film (conductive film) 27 is employed. The barrier metal film 27 covers the entire upper surface of the plug. In the present embodiment, the polycrystalline silicon germanium layer 25 is indirectly in contact with the entire surface of the plug through the barrier metal film 27.
Hereafter, the connection structure according to the present embodiment will be further explained in accordance with a manufacturing method of the connection structure.
After the process shown in
Subsequently, as shown in
A method of forming the interlayer insulating film 23 having the through hole 31 includes, for example, a process of forming an insulating film to be processed into the interlayer insulating film 23 on the interlayer insulating film 22 and the barrier metal film 27, a process of forming the through hole 31 by patterning the insulating film by using photolithography process and etching process.
Subsequently, as shown in
The upper surface of the plug is covered by the barrier metal film 27, so that damage of the upper surface of the plug caused by the etching process (etching damage) is reduced. Thereby suppressing increase of contact resistance between the plug 20 and the electrode 24 due to the etching damage.
In addition, even if a seam (not shown) communicated with the upper surface of the plug 20, or a void (not shown) in the plug is generated, the increase of contact resistance between the plug 20 and the electrode 24 due to the seam or the void is suppressed since the surface of the plug is covered with the barrier metal film 27.
After the process shown in
As a modification of the present embodiment, the interlayer insulating film 23 may be remained similarly to the modification. of the first embodiment.
The present embodiment is different from the first embodiment in that the polycrystalline silicon germanium layer 25 is not directly in contact with the entire upper surface of the plug 20 but is directly in contact with a part of the upper surface of the plug 20. More particularly, the polycrystalline silicon germanium layer 25 is in contact with a central portion of the upper surface of the plug 20. The amorphous silicon germanium layer 26 is directly in contact with the other portion the upper surface of the plug 20. From the point of reducing the contact resistance, the contact area between the polycrystalline silicon germanium layer 25 and the plug 20 is preferably greater than the contact area between the amorphous silicon germanium layer 26 and the plug 20.
In order to obtain the connection structure of the third embodiment, for example, in the process of
As a modification of the present embodiment, the interlayer insulating film 23 may be remained similarly to the modification of the first embodiment.
In the present embodiment, the side surface of the upper side of the plug 25 is covered with an interlayer insulating film (upper portion insulating film) 23, the side surface of the lower side lower than the upper side of the plug is covered with an interlayer insulating film (lower portion insulating film) 21, and the side surface between the side surface of lower side and the side surface of upper side of the plug 20 is covered with an interlayer insulating film (intermediate insulating film) 22. That is, although the side surface of the plug 20 in the first to third embodiments is covered with the interlayer insulating film 21 and the interlayer insulating film 22, the side surface of the plug 20 is further covered with the interlayer insulating film 23 in the present embodiment.
Hereafter, the connection structure of the present embodiment will be further explained in accordance with a manufacturing method of the connection structure.
After the process shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
After that, a hard mask (not shown) is formed on the polycrystalline silicon germanium layer 25, and then the polycrystalline silicon germanium layer 25 and the amorphous silicon germanium layer 26 are sequentially etched by using the hard mask as a mask, thereby obtaining the connection structure that is shown in
The present embodiment is different from the fourth embodiment in that the interlayer insulating film 23 is arranged inner side of the interlayer insulating film 22 when viewed from above the plug 20. Consequently, the area of the interlayer insulating film 23 is smaller than the area of the interlayer insulating film 21.
The connection structure of the present embodiment is obtained, for example, by employing a process in which the outer portion of the interlayer insulating film (sacrifice film) 23 is removed and the inner portion of the film 23 is remained after the process shown in
The present embodiment is different from the fifth embodiment in that a barrier metal film 27 is provided, which covers the entire upper surface of the plug 20. That is, in the present embodiment, the barrier metal film 27 in the second embodiment is applied to the fifth embodiment.
The connection structure of the present embodiment is obtained in the following manner. In the process of
The acceleration sensor of the present embodiment includes a substrate 1 including a CMOS integrated circuit, a multilevel interconnection layer 2 provided on the substrate 1, a MEMS device 3 provided on the multilevel interconnection layer 2. The MEMS device 3 is electrically connected to the substrate 1 through the multilevel interconnection layer 2.
The substrate I includes a silicon substrate 101, an isolation region 102 provide in the silicon substrate 101, and transistors 103 constituting in the CMOS integrated circuit. The transistor 103 includes source/drain regions 104 and a gate portion (gate insulating film, gate electrode).
The multilevel interconnection layer 2 includes plugs 20 and 106, interconnections 12 and 107, and interlayer insulating films 11, 21 and 22. The interlayer insulating film 11 has a structure in which insulating films (not shown) are stacked, however the structure is omitted for simplicity of the drawing. The interconnection and the plug in the uppermost layer of the multilevel interconnection layer 2 are denoted by reference numerals 12 and 20, respectively. The interconnection layer and plug arranged lower than the uppermost layer are denoted by reference numerals 107 and 106, respectively.
The MEMS device 3 includes a MEMS capacitor 3a, and a pad portion 3b.
The connection structure between the fixed plug 111 and the plug 20 is simply illustrated in
The fixed electrode 111 and the movable electrode 112 are arranged such that the comb-shaped portion of the fixed electrode 111 and the comb-shaped portion of the movable electrode 112 are engaged with each other and are spaced apart from each other by a gap. A pair of the fixed electrode and the movable electrode 12 form two capacitors. The difference between the capacitances of the two capacitors change in accordance with a change in acceleration. The CMOS integrated circuit is configured to detect the difference of capacitances between the two capacitor and to compute the acceleration based on the detection result.
The movable electrode 112 is connected to a first anchor portion 114 through a spring portion 113. The second anchor portion 115 is provided outside the first anchor portion 114. A ceiling portion (cap layer) 116 illustrated in
The pad portion 3b includes an electrode 121 connected to the plug 20, a pad electrode 122 provided on the electrode 121, and a solder ball 123 provided on the pad electrode 122. A connection structure of the first electrode 112 and the plug 20 also employs the connection structure described in the first embodiment, which comprises the electrode 24 and the plug 20.
The connection structure between the electrode 121 and the plug 20 is simply depicted in
Noted that, reference numerals 124 and 125 denote insulating films. The insulating film 124 is, for example, a silicon nitride film having about 1 to 5 μm thickness.
First, as shown in
Subsequently, as shown in
Note that, in the following figures (after
Subsequently, as shown in.
Note that, the amorphous silicon germanium layer 26 in the through hole 31 has the shape shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Thereafter performing well-known processes, and thus obtaining the acceleration sensor shown in
Noted that, in the present embodiment, the connection structure of the first embodiment is applied. to the MEMS device, but any of the connection structures of the second to sixth embodiments may be applied to the MEMS device.
Further, the present embodiment describes the acceleration sensor which detects acceleration based on the capacitance between the fixed electrode and the movable electrode of the MEMS capacitor, however the present embodiment is applicable to other sensor which detects other physical quantity based on the capacitance of the MEMS capacitor, for example a gyro sensor which detects angular velocity, or a pressure sensor which detects pressure. Still further, the connection structure according to the present embodiment is also applicable to devices other than the MEMS device.
Furthermore, the effect of the embodiment described above may be obtained even an electrode structure other than the above mentioned connection structure of the embodiments described above as long as the electrode structure in which the polycrystalline silicon germanium layer is in contact with at least part of the upper surface of the plug without intervention of the amorphous silicon germanium layer.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-178170 | Sep 2017 | JP | national |
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-178170, filed Sep. 15, 2017, the entire contents of which are incorporated herein by reference.
