JP4134384B2 - Manufacturing method of semiconductor dynamic quantity sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, acceleration, a method for manufacturing the semiconductor dynamic quantity sensor for detecting a physical quantity of the yaw rate and the like.
[0002]
[Prior art]
Conventionally, this type of semiconductor dynamic quantity sensor is disclosed in Japanese Patent Laid-Open No. 9-212102. In this structure, a beam structure having a movable electrode is supported on a substrate by a first anchor portion, and a fixed electrode is fixed on the substrate by a second anchor portion. The mechanical quantity is detected based on the change in capacitance between the movable electrode and the fixed electrode.
[0003]
[Problems to be solved by the invention]
As a result of further studies by the present inventors on the above-described mechanical quantity sensor, it has been found that there are the following problems. That is, in the above-described mechanical quantity sensor, for example, after the sacrificial layer etching when forming the beam structure and the fixed electrode, if the beam structure is deformed in the vertical direction of the substrate due to internal stress, the movable electrode and the fixed electrode are completely formed. Since they do not face each other, the capacitance between the movable electrode and the fixed electrode is reduced, and the detection accuracy is lowered. Further, when the beam structure is deformed and comes into contact with the substrate, the mechanical quantity cannot be detected by being fixed or rubbed.
[0004]
The present invention aims to solve the above-mentioned problems.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, in the invention according to claim 1, a substrate, a beam structure supported by a first anchor portion so as to be displaced by a mechanical quantity on the substrate, and having a movable electrode, A deformation electrode that is disposed to face the movable electrode of the beam structure and is fixed on the substrate by a second anchor portion, and that suppresses deformation of the beam structure due to internal stress. A method of manufacturing a semiconductor dynamic quantity sensor in which a suppression film is formed on a surface of the beam structure on the substrate side, the step of forming the deformation suppression film on a first semiconductor substrate, Forming a sacrificial layer thin film on the deformation suppressing film; forming an opening in the sacrificial layer thin film and the deformation suppressing film; and configuring the first and second anchor portions at least in the opening Form a film A step of forming a thin film for bonding on the entire surface of the first semiconductor substrate on the side where the thin film for sacrificial layer is formed, and planarizing the surface; and for the flattened bonding Bonding the thin film and the second semiconductor substrate, and forming a groove for defining the beam structure and the fixed electrode in the first semiconductor substrate and the deformation suppressing film after the bonding; Etching the sacrificial layer thin film through a groove for defining the beam structure and the fixed electrode, and forming the beam structure and the fixed electrode on the first semiconductor substrate. It is characterized by that. According to this manufacturing method, it is possible to manufacture a semiconductor dynamic quantity sensor in which a deformation suppressing film that suppresses deformation of the beam structure due to internal stress is formed on the surface of the beam structure on the substrate side. In this semiconductor dynamic quantity sensor, since the deformation of the beam structure is suppressed by the deformation suppression film, it is possible to prevent a decrease in detection accuracy due to the deformation of the beam structure.
[0006]
In this case, when the beam structure is deformed in the direction opposite to the substrate, a film having tensile stress is used as the deformation suppressing film, and when the beam structure is deformed in the direction of the substrate, compressive stress is used as the deformation suppressing film. A film having the following can be used .
[0008]
A silicon nitride film can be used as the above-described deformation suppression film.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a plan view of an acceleration sensor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA in FIG.
1 and 2, a beam structure 2 made of single crystal silicon (single crystal semiconductor material) is disposed on the upper surface of a substrate 1. The beam structure 2 is constructed by four anchor portions (first anchor portions) 3 a, 3 b, 3 c, 3 d protruding from the substrate 1 side, and is disposed at a position spaced apart from the substrate 1 by a predetermined distance. ing.
[0010]
Anchor portions 3a to 3d are made of a polysilicon thin film. A beam portion 4 is constructed between the anchor portion 3a and the anchor portion 3b, and a beam portion 5 is constructed between the anchor portion 3c and the anchor portion 3d.
In addition, a rectangular mass portion (mass portion) 6 is installed between the beam portion 4 and the beam portion 5, and the mass portion 6 is provided with a through hole 6 a penetrating vertically. Yes. Furthermore, four movable electrodes 7a, 7b, 7c, and 7d protrude from one side surface (the left side surface in FIG. 1) of the mass portion 6. Further, four movable electrodes 8a, 8b, 8c, and 8d protrude from the other side surface (the right side surface in FIG. 1) of the mass portion 6. The movable electrodes 7a to 7d and 8a to 8d have a comb-like shape extending in parallel at equal intervals.
[0011]
First fixed electrodes 9a, 9b, 9c, 9d and second fixed electrodes 11a, 11b, 11c, 11d are fixed to the upper surface of the substrate 1. The first fixed electrodes 9a to 9d are fixed by anchor portions (second anchor portions) 10a, 10b, 10c, and 10d that protrude from the substrate 1 side, and are positioned at a predetermined interval on the upper surface of the substrate 1. It arrange | positions and opposes one side surface of each movable electrode 7a-7d of the beam structure 2. FIG. The second fixed electrodes 11a to 11d are supported by anchor portions 12a, 12b, 12c, and 12d protruding from the substrate 1, and are arranged on the upper surface of the substrate 1 at positions spaced apart from each other by a beam structure. The movable electrode 7a to 7d of the body 2 is opposed to the other side surface.
[0012]
Similarly, the first fixed electrodes 13a, 13b, 13c, 13d and the second fixed electrodes 15a, 15b, 15c, 15d are fixed to the upper surface of the substrate 1. The first fixed electrodes 13a to 13d are supported by anchor portions 14a, 14b, 14c, and 14d that protrude from the substrate 1 side, and are arranged on the upper surface of the substrate 1 at positions spaced apart from each other by the beam structure 2. Of the movable electrodes 8a to 8d. The second fixed electrodes 15a to 15d are supported by anchor portions 16a, 16b, 16c, and 16d protruding from the substrate 1, and are arranged on the upper surface of the substrate 1 at positions spaced apart from each other by a beam structure. It faces one side surface of each movable electrode 8a to 8d of the body 2.
[0013]
As shown in FIG. 2, the substrate 1 has a polysilicon thin film 42, a silicon oxide film (first insulating thin film) 43, a nitride film (second insulating thin film) 44, polysilicon on a silicon substrate 41. A thin film 45 and a silicon nitride film (third insulating thin film) 46 are stacked. The polysilicon thin film 45 is a conductive thin film doped with impurities such as phosphorus.
[0014]
Further, as shown in FIG. 1, four wiring patterns 22, 23, 24, and 25 are formed by the conductive thin film made of the polysilicon thin film 45 described above. The wiring patterns 22 to 25 are wirings of the fixed electrodes 9a to 9d, 11a to 11d, 13a to 13d, and 15a to 15d, respectively, have a strip shape and extend in an L shape. Further, a lower electrode is formed in the region facing the beam structure 2 on the upper surface portion of the substrate 1 by the conductive thin film.
[0015]
Furthermore, electrode extraction portions 27a, 27b, 27c, and 27d are formed on the upper surface of the substrate 1. These electrode extraction portions 27 to 27 d are supported by anchor portions 28 a, 28 b, 28 c and 28 d that protrude from the substrate 1. And the electrode extraction part 27a is electrically connected with the wiring pattern 22 via the anchor part 28a. Similarly, the electrode extraction portions 27b, 27c, and 27d are electrically connected to the wiring patterns 23, 24, and 25 via the anchor portions 28b, 28c, and 28d, respectively. Note that metal electrodes (bonding pads) 34, 35a, 35b, 35c, and 35d made of an aluminum thin film as electrode portions are provided above the anchor portion 3a and on the upper surfaces of the electrode extraction portions 27a, 27b, 27c, and 27d, respectively. ing.
[0016]
In the configuration described above, the first capacitor is provided between the movable electrodes 7a to 7d and the first fixed electrodes 9a to 9d of the beam structure 2, and the movable electrodes 7a to 7d of the beam structure 2 are connected to the second electrodes. A second capacitor is formed between the fixed electrodes 11a to 11d. Similarly, a first capacitor is provided between the movable electrodes 8a to 8d of the beam structure 2 and the first fixed electrodes 13a to 13d, and the movable electrodes 8a to 8d and the second fixed electrode of the beam structure 2 are also provided. A second capacitor is formed between 15a to 15d.
[0017]
Here, the movable electrodes 7a to 7d (8a to 8d) are located at the centers of the fixed electrodes 9a to 9d (13a to 13d) and 11a to 11d (15a to 15d) on both sides, and are static between the movable electrode and the fixed electrode. Capacitances C1 and C2 are equal. The voltage V1 is between the movable electrodes 7a to 7d (8a to 8d) and the fixed electrodes 9a to 9d (13a to 13d), and the movable electrodes 7a to 7d (8a to 8d) and the fixed electrodes 11a to 11d (15a to 15d). ) Is applied with the voltage V2.
[0018]
When acceleration is not generated, V1 = V2, and the movable electrodes 7a to 7d (8a to 8d) are attracted by the same electrostatic force from the fixed electrodes 9a to 9d (13a to 13d) and 11a to 11d (15a to 15d). It has been.
When the acceleration acts in a direction parallel to the substrate surface and the movable electrodes 7a to 7d (8a to 8d) are displaced, the distance between the movable electrode and the fixed electrode changes, and the capacitances C1 and C2 are not equal. At this time, for example, if the movable electrodes 7a to 7d (8a to 8d) are displaced to the fixed electrodes 9a to 9d (13a to 13d) side so that the electrostatic forces are equal, the voltage V1 decreases and the voltage V2 increases. Thereby, the movable electrodes 7a to 7d (8a to 8d) are pulled toward the fixed electrodes 11a to 11d (15a to 15d) by electrostatic force. If the movable electrodes 7a to 7d (8a to 8d) return to the center position and the capacitances C1 and C2 are equal, the acceleration and the electrostatic force are equally balanced, and the magnitude of the acceleration is obtained from the voltages V1 and V2 at this time. be able to.
[0019]
In this way, in the first capacitor and the second capacitor, the voltage of the fixed electrode forming the first and second capacitors is controlled so that the movable electrode is not displaced with respect to the displacement due to the action of the mechanical quantity. The acceleration is detected by the change in voltage.
The above-described acceleration sensor basically has the same configuration as that shown in Japanese Patent Laid-Open No. 9-212102, but in this embodiment, as shown in FIG. A warp control film 47 as a deformation suppression film that suppresses deformation of the beam structure 2 due to internal stress is formed on the back surface, that is, the surface on the substrate 1 side.
[0020]
The warp control film 47 uses a film having a tensile stress when the beam structure 2 warps upward with respect to the substrate 1, and conversely when the beam structure 2 warps toward the substrate 1. A film having compressive stress is used. Here, the warp control film 47 needs to be a film that does not disappear at the time of sacrifice layer etching in the manufacturing process described later. For example, a silicon nitride film can be used. This silicon nitride film has a tensile stress when formed by the LP-CVD method, and has a compressive stress when formed by the plasma CVD method. Therefore, depending on the direction of the warp of the beam structure 2, the film forming method and the film forming conditions Decide.
[0021]
Next, a method for manufacturing the acceleration sensor described above will be described with reference to a process diagram using an AA cross section in FIG.
First, in the process shown in FIG. 3, a single crystal silicon substrate (first semiconductor substrate) 40 is prepared, and a warpage control film 47, specifically, an HF-resistant silicon nitride film is formed on the silicon substrate 40 by a CVD method. Form a film. Thereafter, an alignment groove 40a is formed by trench etching.
[0022]
Next, in the step shown in FIG. 4, a silicon oxide film 51 as a sacrificial layer thin film is formed on the warpage control film 47 by the CVD method, and the groove 40a is buried.
Next, in the step shown in FIG. 5, a part of the silicon oxide film 51 is etched to form a recess 51a. The recess 51a is formed to provide a protrusion for reducing the adhesion area when the beam structure 2 adheres to the substrate due to surface tension or the like in a sacrificial layer etching step described later. Thereafter, a silicon nitride film 46 serving as an etching stopper at the time of sacrifice layer etching is formed. Then, an opening 52 is formed in the anchor portion formation region by dry etching or the like through photolithography with respect to the stacked body of the silicon nitride film 46, the silicon oxide film 51, and the warpage control film 47. The opening 52 is for connecting the beam structure 2 and the substrate 1.
[0023]
Next, in the process shown in FIG. 6, a polysilicon thin film 45 is formed on the silicon nitride film 46 including the opening 52 as a film constituting the anchor portion to a thickness of about 0.5 to 2 μm. Impurities are introduced during film formation to form a conductive thin film. Further, the polysilicon thin film 45 is patterned through photolithography to form the polysilicon thin film 45 in a predetermined region on the silicon nitride film 46 including the opening 52. Thereafter, a nitride film 44 is formed on the polysilicon thin film 45.
[0024]
Next, in the step shown in FIG. 7, a silicon oxide film 43 is formed on the nitride film 44, and a polysilicon thin film 42 as a thin film for bonding is formed on the silicon oxide film 43. Thereafter, as shown in FIG. 8, the surface of the polysilicon thin film 42 is flattened by mechanical polishing or the like for bonding.
Next, in the step shown in FIG. 9, a single crystal silicon substrate (second semiconductor substrate) 41 different from the silicon substrate 40 is prepared, and the surface of the polysilicon thin film 42 and the silicon substrate 41 are bonded together. Then, the silicon substrates 40 and 41 are turned upside down, and the silicon substrate 40 side is polished by mechanical polishing or the like to form a thin film. That is, the silicon substrate 40 is polished to a desired thickness. At this time, if polishing is performed to the depth of the alignment groove 40a formed in the silicon substrate 40, the layer of the silicon oxide film 51 appears (exposes), so that the hardness in the polishing changes and the polishing end point is easily detected. can do. The silicon oxide film 51 formed in the alignment groove 40a is used as an alignment mark in the following film formation and trench etching steps.
[0025]
Next, in the step shown in FIG. 10, in order to use the silicon substrate 40 as an electrode, impurities are introduced into the silicon substrate 40 by phosphorus diffusion or the like. Then, after a silicon oxide film 54 is formed as an interlayer insulating film, holes are formed by photolithography at locations that become contact portions of the electrodes, and aluminum electrodes 34 (35a to 35d) are formed and formed by photolithography.
[0026]
Next, in the step shown in FIG. 11, the beam structure 2 is formed through photolithography of the pattern of the beam structure 2. That is, the trench 55 for defining the beam structure 2 and the fixed electrodes 9a to 9d, 11a to 11d, 13a to 13d, and 15a to 15d is formed in the silicon substrate 40 by trench etching. At this time, the warpage control film 47 in the groove 55 is also removed by the etching. As a mask used for etching, a soft mask such as a photoresist or a hard mask such as an oxide film can be used. In this embodiment, the silicon oxide film 54 used for the interlayer insulating film is used as a mask material. It is used as.
[0027]
Finally, in the step shown in FIG. 12, the silicon oxide film 51 is removed by etching with an HF-based etchant to make the silicon substrate 40 a movable structure. The beam structure 2 and the fixed electrodes 9a to 9d, 11a are formed on the silicon substrate 40. To 11d, 13a to 13d, and 15a to 15d. At that time, a sublimation agent such as rose dichlorobenzene is used in order to prevent the movable part from adhering to the substrate in the drying step after etching. Further, the silicon oxide film 54 used as a mask material is also removed during the sacrifice layer etching.
[0028]
In this way, an acceleration sensor using a bonded substrate can be formed.
In the above-described embodiment, after forming the aluminum electrode 34 (35a to 35d), the groove 55 for defining the beam structure and the fixed electrode is formed in the silicon substrate 40, and sacrifice is performed through the groove 55. Since the silicon oxide film 51 as the layer thin film is removed by etching, the degree of freedom in setting the width of the groove 55 can be increased, and the restriction in the structural design of the acceleration sensor can be reduced. Can do.
[0029]
The mass part (mass part) 6 may be square, or a plurality of movable electrodes extending from the mass part 6 may be provided.
(Second Embodiment)
In the first embodiment described above, the warp control film 47 is formed on the lower surface of the beam structure 2, but as shown in FIG. 13, the upper surface (front surface) of the beam structure 2, that is, the substrate 1 and The warpage control film 47 may be formed on the opposite surface. In this case, contrary to the first embodiment, when the beam structure 2 warps upward with respect to the substrate 1, a film having compressive stress is used as the warpage control film 47, and conversely the substrate 1 In the case of warping toward the surface, a film having tensile stress is used as the warpage control film 47. 13 shows the AA cross section in FIG. 1, as in FIG.
[0030]
Next, a method for manufacturing the acceleration sensor according to the second embodiment will be described. With respect to the manufacturing method of the first embodiment, the steps from FIG. 3 to FIG. 9 are performed without forming the warp control film 47 in the step of FIG. 3 to obtain the structure shown in FIG.
Then, in the step shown in FIG. 15, in order to use the silicon substrate 40 as an electrode, after introducing impurities into the silicon substrate 40 by phosphorus diffusion or the like, a silicon nitride film is formed as a warp control film 47 by the CVD method. And a hole is formed in the place used as the contact part of an electrode by photolithography, and the aluminum electrode 34 (35a-35d) is formed into a film and formed by photolithography.
[0031]
Next, in the step shown in FIG. 16, a groove 55 for defining the beam structure 2 and the fixed electrodes 9a to 9d, 11a to 11d, 13a to 13d, and 15a to 15d is formed in the silicon substrate 40 by trench etching.
Finally, in the process shown in FIG. 17, the silicon oxide film 51 is removed by etching with an HF-based etchant to make the silicon substrate 40 a movable structure, and the beam structure 2 and the fixed electrodes 9a to 9d, 11a are formed on the silicon substrate 40. To 11d, 13a to 13d, and 15a to 15d.
[0032]
In this way, an acceleration sensor using a bonded substrate can be formed.
The present invention is not limited to the acceleration sensor described above, and can be applied to a semiconductor dynamic quantity sensor that detects a dynamic quantity such as a yaw rate.
[Brief description of the drawings]
FIG. 1 is a plan view of an acceleration sensor according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a cross section AA in FIG. 1;
FIG. 3 is a diagram showing a manufacturing process of the acceleration sensor according to the first embodiment of the present invention.
4 is a process diagram showing a process that follows the process of FIG. 3. FIG.
FIG. 5 is a process diagram illustrating a process following the process in FIG. 4;
6 is a process diagram showing a process that follows the process shown in FIG. 5. FIG.
FIG. 7 is a process diagram illustrating a process following the process in FIG. 6;
FIG. 8 is a process diagram illustrating a process continued from FIG. 7;
FIG. 9 is a process diagram illustrating a process continued from FIG. 8;
FIG. 10 is a process diagram illustrating a process following the process in FIG. 9;
FIG. 11 is a process diagram illustrating a process continued from FIG. 10;
FIG. 12 is a process diagram illustrating a process continued from FIG. 11;
FIG. 13 is a cross-sectional view showing a second embodiment of the present invention.
FIG. 14 is a diagram showing a manufacturing process of the acceleration sensor according to the second embodiment of the present invention.
FIG. 15 is a process diagram illustrating a process continued from FIG. 14;
FIG. 16 is a process diagram illustrating a process following the process in FIG. 15;
FIG. 17 is a process diagram illustrating a process continued from FIG. 16;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Beam structure, 3a-3d ... 1st anchor part, 7a-7d, 8a-8d ... Movable electrode, 9a-9d, 11a-11d, 13a-13d, 15a-15d ... Fixed electrode, 10a-10d, 12a-12d, 14a-14d, 16a-16d ... 2nd anchor part, 47 ... Warpage control film | membrane as a deformation | transformation suppression film | membrane.

Claims (1)

A substrate,
A beam structure supported by a first anchor portion so as to be displaced by a mechanical quantity on the substrate, and having a movable electrode;
A fixed electrode disposed opposite to the movable electrode of the beam structure and fixed on the substrate by a second anchor portion;
A method of manufacturing a semiconductor dynamic quantity sensor in which a deformation suppressing film that suppresses deformation of the beam structure due to internal stress is formed on a surface of the beam structure on the substrate side ,
Forming the deformation suppressing film on the first semiconductor substrate;
Forming a sacrificial layer thin film on the deformation suppressing film;
Forming an opening in the sacrificial layer thin film and the deformation suppressing film, and forming a film constituting the first and second anchor portions at least in the opening;
Forming a thin film for bonding on the entire surface of the first semiconductor substrate on the side where the thin film for sacrificial layer is formed, and planarizing the surface;
Bonding the planarized thin film for bonding and the second semiconductor substrate;
After the bonding, forming a groove for defining the beam structure and the fixed electrode in the first semiconductor substrate and the deformation suppressing film ;
Etching the sacrificial layer thin film through a groove for defining the beam structure and the fixed electrode, and forming the beam structure and the fixed electrode on the first semiconductor substrate. A method for manufacturing a semiconductor dynamic quantity sensor.

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