JP2000022171A - Semiconductor dynamic quantity sensor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation of detection accuracy, etc., caused by deformation of a beam structure. SOLUTION: This dynamic quantity sensor has a beam structure 2 with a movable electrode supported on a substrate 1. A fixed electrode is fixed on the substrate 1. If the beam structure 2 is displaced by a dynamic quantity such as acceleration, etc., the dynamic quantity is detected on the basis of the change in electrostatic capacitance between the movable electrode and the fixed electrode. In this case, a silicon nitride film 47 is formed on the bottom surface of the beam structure 2 as a displacement inhibiting film for inhibiting the deformation of the beam structure 2 caused by internal stress.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor dynamic quantity sensor for detecting dynamic quantities such as acceleration and yaw rate, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as this kind of semiconductor dynamic quantity sensor, there is one disclosed in Japanese Patent Application Laid-Open No. 9-211022. According to this method, a beam structure having a movable electrode is supported on a substrate by a first anchor, and a fixed electrode is fixed on the substrate by a second anchor. When the displacement is caused, the dynamic quantity is detected based on the change in the capacitance between the movable electrode and the fixed electrode.

[0003]

As a result of further studies by the present inventors on the above-mentioned mechanical quantity sensor, it has been found that there are the following problems. That is, in the above-described physical quantity sensor, for example, when the beam structure is deformed in the vertical direction of the substrate due to internal stress after etching the sacrificial layer when forming the beam structure and the fixed electrode, the movable electrode and the fixed electrode are completely Since the electrodes no longer face each other, the capacitance between the movable electrode and the fixed electrode decreases, and the detection accuracy decreases. In addition, when the beam structure is deformed and comes into contact with the substrate, the beam is fixed or rubbed, so that the physical quantity cannot be detected.

[0004] It is an object of the present invention to solve the above problems.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a deformation suppressing film for suppressing deformation of a beam structure due to internal stress is provided on a substrate side of the beam structure. It is characterized by being formed on the surface. As described above, since the deformation of the beam structure is suppressed by the deformation suppressing film, it is possible to prevent the detection accuracy from being lowered due to the deformation of the beam structure.

In this case, when the beam structure is deformed in the direction opposite to the substrate, a film having a tensile stress is used as the deformation suppressing film. When the beam structure is deformed in the direction of the substrate, the deformation suppressing film is used. Can be used as a film having a compressive stress. Further, even when the deformation suppressing film is formed on the surface of the beam structure opposite to the substrate as in the invention according to the second aspect, the same effect as the invention according to the first aspect can be obtained. .

In this case, when the beam structure is deformed in the direction opposite to the substrate, a film having a compressive stress is used as the deformation suppressing film. When the beam structure is deformed in the direction of the substrate, the deformation suppressing film is used. Can be used as a film having a tensile stress. The semiconductor physical quantity sensor according to claim 1 can be manufactured using the manufacturing method according to claim 3, and the semiconductor physical quantity sensor according to claim 2 is
It can be manufactured using the manufacturing method according to the fourth aspect.

Note that a silicon nitride film can be used as the deformation suppressing film.

[0009]

FIG. 1 is a plan view of an acceleration sensor according to an embodiment of the present invention. FIG. 2 is a sectional view taken along line AA in FIG. 1 and 2
In FIG. 1, a beam structure 2 made of single crystal silicon (single crystal semiconductor material) is arranged on the upper surface of a substrate 1. The beam structure 2 is bridged by four anchor portions (first anchor portions) 3a, 3b, 3c, and 3d protruding from the substrate 1 side, and is disposed at a predetermined interval on the upper surface of the substrate 1. ing.

The anchor portions 3a to 3d are made of a polysilicon thin film. A beam 4 is provided between the anchors 3a and 3b, and a beam 5 is provided between the anchors 3c and 3d. Also,
A rectangular mass part (mass part) 6 is provided between the beam part 4 and the beam part 5, and the mass part 6 is provided with a through hole 6a penetrating vertically. Further, the mass part 6
From one side (left side in FIG. 1)
One movable electrode 7a, 7b, 7c, 7d protrudes.
Further, four movable electrodes 8a, 8b, 8c, 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 shape extending in parallel at equal intervals.

On the upper surface of the substrate 1, first fixed electrodes 9a, 9
b, 9c, 9d and second fixed electrodes 11a, 11b,
11c and 11d are fixed. First fixed electrode 9a
9a to 9d are fixed by anchor portions (second anchor portions) 10a, 10b, 10c, and 10d protruding from the substrate 1 side, and are arranged on the upper surface of the substrate 1 at positions spaced apart from each other by a predetermined distance. 2 and one side surface of each of the movable electrodes 7a to 7d. In addition, the second fixed electrodes 11a to 11a
d denotes anchor portions 12a and 12 protruding from the substrate 1 side.
b, 12c, and 12d, are arranged at predetermined intervals on the upper surface of the substrate 1, and face the other side surface of each of the movable electrodes 7a to 7d of the beam structure 2.

Similarly, first fixed electrodes 13a, 13b, 13c, 13d and second fixed electrodes 15a, 15b, 15c, 15d are fixed on the upper surface of the substrate 1. The first fixed electrodes 13a to 13d are supported by anchor portions 14a, 14b, 14c, and 14d protruding from the substrate 1 side. Of the movable electrodes 8a to 8d. Also, the second fixed electrodes 15a to 15
d is an anchor portion 16a, 16 protruding from the substrate 1 side.
b, 16c, and 16d, are arranged on the upper surface of the substrate 1 at predetermined intervals, and face one side surface of each of the movable electrodes 8a to 8d of the beam structure 2.

As shown in FIG. 2, a substrate 1 has a polysilicon thin film 42, a silicon oxide film (first insulating thin film) 43, and a nitride film (second insulating thin film) 44 on a silicon substrate 41. , A polysilicon thin film 45, and a silicon nitride film (third insulating thin film) 46. The polysilicon thin film 45 is a conductive thin film doped with an impurity such as phosphorus.

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 fixed electrodes 9a to 9 respectively.
d, 11a to 11d, 13a to 13d and 15a to 1
This is a 5d wiring, and has a band shape and is extended in an L-shape. A lower electrode is formed of the conductive thin film in a region facing the beam structure 2 on the upper surface of the substrate 1.

Further, on the upper surface of the substrate 1, an electrode extraction portion 2 is provided.
7a, 27b, 27c and 27d are formed. These electrode extraction portions 27 to 27d are supported by anchor portions 28a, 28b, 28c, 28d protruding from the substrate 1. The electrode extraction portion 27a is connected to the anchor portion 28.
It is electrically connected to the wiring pattern 22 via a. Similarly, the electrode extraction portions 27b, 27c, 27d are electrically connected to the wiring patterns 23, 24, 25 via anchor portions 28b, 28c, 28d, respectively.
In addition, above the anchor part 3a, the electrode extraction parts 27a, 27
Metal electrodes (bonding pads) 34, 3 made of an aluminum thin film as electrode portions are provided on the upper surfaces of b, 27c, 27d.
5a, 35b, 35c, and 35d are provided, respectively.

In the above configuration, the first capacitor is provided between the movable electrodes 7a to 7d of the beam structure 2 and the first fixed electrodes 9a to 9d, and the movable electrode 7a of the beam structure 2 is provided.
To 7d and the second fixed electrodes 11a to 11d
Are formed. Similarly, the 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 electrode 8a to 8d of the beam structure 2 is connected to the second fixed electrode. A second capacitor is formed between 15a to 15d.

Here, the movable electrodes 7a to 7d (8a to 8d)
d) is the fixed electrodes 9a to 9d (13a to 13d) on both sides.
And 11a-11d (15a-15d),
The capacitances C1 and C2 between the movable electrode and the fixed electrode are equal.
The movable electrodes 7a to 7d (8a to 8d) and the fixed electrodes 9
The voltage V1 is applied between the movable electrodes 7a to 7d (8a to 8d) and the fixed electrodes 11a to 11d between a to 9d (13a to 13d).
The voltage V2 is applied between (15a to 15d).

When no acceleration occurs, V1 = V
The movable electrodes 7a to 7d (8a to 8d) are fixed electrodes 9a to 9d (13a to 13d) and 11a to 11d.
(15a to 15d) with the same electrostatic force. And the acceleration acts in a direction parallel to the substrate surface,
When 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, C
2 will not be equal. At this time, assuming that the movable electrodes 7a to 7d (8a to 8d) are displaced toward the fixed electrodes 9a to 9d (13a to 13d) so that the electrostatic forces are equal, the voltage V1 decreases and the voltage V2 increases. As a result, the fixed electrodes 11a to 11d (15a to 15d)
The movable electrodes 7a to 7d (8a to 8d) are drawn on the d) side. When the movable electrodes 7a to 7d (8a to 8d) return to the center position and the capacitances C1 and C2 become equal, the acceleration and the electrostatic force are equally balanced, and the voltages V1 and V2 at this time are balanced.
The magnitude of the acceleration can be obtained from the equation.

As described above, in the first capacitor and the second capacitor, the displacement caused by the action of the mechanical quantity is
The voltage of the fixed electrode forming the first and second capacitors is controlled so that the movable electrode is not displaced, and the acceleration is detected based on the change in the voltage. The above-described acceleration sensor has basically the same configuration as that described in Japanese Patent Application Laid-Open No. 9-211022, but in the present embodiment, as shown in FIG. On the (back surface), that is, on the surface on the substrate 1 side, a warpage control film 47 as a deformation suppressing film for suppressing the beam structure 2 from being deformed by internal stress is formed.

When the beam structure 2 warps upward with respect to the substrate 1, a film having a tensile stress is used as the warpage control film 47. In such a case, a film having a compressive stress is used. Here, the warpage control film 47 needs to be a film that does not disappear during etching of a sacrificial layer in a manufacturing process described later, and for example, a silicon nitride film can be used. Since 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, the film forming method and the film forming conditions depend on the warping direction of the beam structure 2. Decide.

Next, a method of manufacturing the above-described acceleration sensor will be described with reference to a process diagram using the AA cross section in FIG. First, in the step shown in FIG. 3, a single-crystal silicon substrate (first semiconductor substrate) 40 is prepared, and a warpage control film 47, specifically, a 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.

Next, in a step shown in FIG. 4, a silicon oxide film 51 as a thin film for a sacrificial layer is formed on the warp control film 47.
Is formed 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 concave portion 51a. This recess 51a
Is a beam structure 2 in a sacrificial layer etching step described later.
Is formed in order to provide a projection for reducing the adhesion area when is adhered to the substrate due to surface tension or the like. Thereafter, a silicon nitride film 46 serving as an etching stopper at the time of etching the sacrificial layer is formed. Then, an opening 52 is formed in the anchor portion forming region of the stacked body of the silicon nitride film 46, the silicon oxide film 51, and the warpage control film 47 by dry etching or the like via photolithography. This opening 52
Is for connecting the beam structure 2 and the substrate 1.

Next, in the step shown in FIG.
A polysilicon thin film 45 having a thickness of about 0.5 to 2 μm is formed as a film constituting an anchor portion on the silicon nitride film 46 including the silicon oxide film 46, and impurities are introduced during the formation to form a conductive thin film. And Further, the polysilicon thin film 45 is patterned through photolithography to form a 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.

Next, in the step shown in FIG.
4, a silicon oxide film 43 is formed on the silicon oxide film 43, and a polysilicon thin film 42 as a bonding thin film is formed on the silicon oxide film 43. Thereafter, as shown in FIG. For this purpose, the surface of the polysilicon thin film 42 is flattened by mechanical polishing or the like. 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 a polysilicon thin film 42 is prepared.
And the silicon substrate 41 are bonded together. And
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 reduce the thickness.
That is, the silicon substrate 40 is polished to a desired thickness.
At this time, if the polishing is performed to the depth of the alignment groove 40a formed in the silicon substrate 40, the silicon oxide film 51 is formed.
Appears (exposed), the hardness in polishing changes, and the end point of polishing can be easily detected. In addition,
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.

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 the silicon oxide film 54 is formed as an interlayer insulating film, holes are formed by photolithography at locations to be contact portions of the electrodes, and aluminum electrodes 34 (35a to 35d) are formed and formed by photolithography.

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 beam structure 2 and the fixed electrodes 9a to 9d, 11a to 11d, and 13a to 13
d, a groove 55 for defining 15a to 15d is formed by trench etching. At this time, the warp control film 47 in the groove 55 is also removed by the etching. In addition,
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 the present embodiment, the silicon oxide film 54 used for the interlayer insulating film is used as a mask material. ing.

Finally, in the step shown in FIG.
The silicon oxide film 51 is removed by etching with a system etchant to make the silicon substrate 40 movable, and the beam structure 2 and the fixed electrodes 9a to 9d, 1
1a to 11d, 13a to 13d, and 15a to 15d are formed. At that time, a sublimating agent such as balazichlorobenzene is used in order to prevent the movable portion from sticking to the substrate in the drying step after the etching. Also, when etching the sacrificial layer,
The silicon oxide film 54 used as the mask material is also removed.

In this manner, an acceleration sensor using the bonded substrate can be formed. In the above embodiment, the aluminum electrode 34 (35a to 35a) is used.
After forming d), a groove 55 for defining the beam structure and the fixed electrode is formed in the silicon substrate 40, and the groove 55 is formed.
, The silicon oxide film 51 serving as the sacrificial layer thin film is removed by etching, so that the degree of freedom in setting the width of the groove 55 can be increased, and restrictions in designing the structure of the acceleration sensor. Can be reduced.

The mass part (mass part) 6 may be a square, and 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. However, as shown in FIG. ), That is, the warpage control film 47 is formed on the surface opposite to the substrate 1.
May be formed. In this case, contrary to the first embodiment, when the beam structure 2 warps upward with respect to the substrate 1, a film having a compressive stress is used as the warpage control film 47. If you warp towards
As the warpage control film 47, a film having a tensile stress is used. FIG. 13 shows a cross section taken along the line AA in FIG. 1, as in FIG.

Next, a method of manufacturing the acceleration sensor according to the second embodiment will be described. 3 to 9 are performed without forming the warpage control film 47 in the process of FIG. 3 in the manufacturing method of the first embodiment, and the structure shown in FIG. 14 is obtained. Then, in the step shown in FIG. 15, in order to use the silicon substrate 40 as an electrode, an impurity is introduced into the silicon substrate 40 by phosphorus diffusion or the like, and then a silicon nitride film is formed as a warpage control film 47 by a CVD method. Then, a hole is formed by photolithography at a location to be a contact part of the electrode, and the aluminum electrode 34 (35a to
35d) is formed by film formation and photolithography.

Next, in the step shown in FIG. 16, the beam structure 2 and the fixed electrodes 9a to 9d, 1
A groove 55 for defining 1a to 11d, 13a to 13d, and 15a to 15d is formed by trench etching. Finally, in the step shown in FIG. 17, the silicon oxide film 51 is removed by etching with an HF-based etchant, so that the silicon substrate 40 has a movable structure.
0, the beam structure 2 and the fixed electrodes 9a to 9d, 11a to 1
1d, 13a to 13d and 15a to 15d are formed.

Thus, an acceleration sensor using the bonded substrate can be formed. The present invention is not limited to the acceleration sensor described above, but 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 sectional view showing an AA section in FIG. 1;

FIG. 3 is a diagram illustrating a manufacturing process of the acceleration sensor according to the first embodiment of the present invention.

FIG. 4 is a process diagram showing a process following FIG. 3;

FIG. 5 is a process chart showing a step following FIG. 4;

FIG. 6 is a process chart showing a step following FIG. 5;

FIG. 7 is a process chart showing a step following FIG. 6;

FIG. 8 is a process chart showing a step following FIG. 7;

FIG. 9 is a process chart showing a step following FIG. 8;

FIG. 10 is a process drawing showing a step following FIG. 9;

FIG. 11 is a process diagram showing a process following FIG. 10;

FIG. 12 is a process chart showing a step following FIG. 11;

FIG. 13 is a sectional view showing a second embodiment of the present invention.

FIG. 14 is a diagram illustrating a manufacturing process of the acceleration sensor according to the second embodiment of the present invention.

FIG. 15 is a process chart showing a step following FIG. 14;

FIG. 16 is a process chart showing a step following FIG. 15;

FIG. 17 is a process chart showing a step following FIG. 16;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Beam structure, 3a-3d ... 1st anchor part, 7a-7d, 8a-8d ... Movable electrode, 9a-9d,
11a-11d, 13a-13d, 15a-15d ... fixed electrodes, 10a-10d, 12a-12d, 14a-1
4d, 16a to 16d: second anchor portion, 47: warpage control film as a deformation suppressing film.

Claims (4)

[Claims] 1. A substrate, a beam structure supported by a first anchor unit so as to be displaced on the substrate by a mechanical amount, and having a movable electrode, and a beam structure facing the movable electrode of the beam structure. And a fixed electrode fixed on the substrate by a second anchor unit, wherein the deformation suppressing film for suppressing deformation of the beam structure due to internal stress is provided on the beam. A semiconductor dynamic quantity sensor formed on a surface of the structure on the substrate side. 2. A substrate, a beam structure supported by a first anchor portion to be displaced on the substrate by a mechanical amount, and having a movable electrode, and a beam structure facing the movable electrode of the beam structure. And a fixed electrode fixed on the substrate by a second anchor unit, wherein the deformation suppressing film for suppressing deformation of the beam structure due to internal stress is provided on the beam. A semiconductor dynamic quantity sensor formed on a surface of a structure opposite to the substrate. 3. The method of manufacturing a semiconductor physical quantity sensor according to claim 1, wherein the step of forming the deformation suppressing film on a first semiconductor substrate; and a sacrificial layer 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 in at least the opening; A step of forming a bonding thin film on the entire surface of the first semiconductor substrate on which the sacrificial layer thin film is formed, and flattening a surface thereof; Bonding the semiconductor substrate with the second semiconductor substrate; and forming a groove for defining the beam structure and the fixed electrode in the first semiconductor substrate after the bonding. Through the grooves to define the electrodes The thin film for the sacrificial layer is removed by etching, the first
Forming the beam structure and the fixed electrode on the semiconductor substrate according to (1). 4. A method for manufacturing a semiconductor physical quantity sensor according to claim 2, wherein a step of forming a thin film for a sacrificial layer on a first semiconductor substrate; and forming an opening in the thin film for a sacrificial layer. Forming a film constituting the first and second anchor portions at least in the openings thereof; and bonding the entire surface of the first semiconductor substrate on the side where the sacrificial layer thin film is formed. Forming a bonding thin film and flattening the surface thereof; bonding the flattened bonding thin film to a second semiconductor substrate; and after bonding, the first semiconductor substrate. Forming the deformation suppressing film on the surface of the substrate, and forming grooves for defining the beam structure and the fixed electrode in the deformation suppressing film and the first semiconductor substrate; and forming the beam structure and the fixing. Through the groove to define the electrode The sacrificial layer thin film is removed by etching,
Forming the beam structure and the fixed electrode on the semiconductor substrate according to (1).