JP5000626B2 - Physical quantity sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a physical quantity sensor such as an acceleration sensor formed using MEMS (Micro ElectroMechanical System) technology.

  For example, in an acceleration sensor formed using an SOI substrate, a movable portion that is displaced by acceleration is provided on one substrate, a detection portion that measures the displacement of the movable portion, and the like.

  In the following patent document, in order to enable detection of acceleration in the height direction, the film thicknesses (lengths in the height direction) of the movable electrode itself and the fixed electrode itself constituting the detection unit are made different. (For example, see FIG. 2 of Patent Document 1 and FIG. 3 of Patent Document 2).

  In these patent documents, the electrode widths of the movable electrode and the fixed electrode are made different, and the film thicknesses of the movable electrode and the fixed electrode are made different using an etching rate difference or the like.

However, if the width of one electrode is made larger than the other, the area where the detection part is formed is increased, and the sensor cannot be reduced in size. In addition, if the difference in electrode width is small, the difference in film thickness of the electrode itself becomes small, and the detection accuracy cannot be improved. Moreover, as in the patent document, in the manufacturing method using the difference in the etching rate and the like by changing the electrode width between the movable electrode and the fixed electrode, for example, the accuracy of the release process from FIG. 12B to FIG. Seems to be very difficult. That is, it is presumed that the manufacturing method disclosed in the patent document cannot manufacture a movable electrode and a fixed electrode having a desired shape with high accuracy.
JP 2006-266873 A JP 2003-014778 A

  Therefore, the present invention is to solve the above-described conventional problems, and in particular, an object of the present invention is to provide a physical quantity sensor capable of improving detection accuracy with a simpler configuration than the conventional one and a method for manufacturing the same. .

The physical quantity sensor of the present invention is
A movable part supported so as to be movable in the height direction, and a first detection part and a second detection part for detecting a displacement of the movable part based on a capacitance change,
Each of the first detection unit and the second detection unit includes a movable electrode and a fixed electrode arranged alternately in a plane, the movable electrode is formed integrally with the movable unit, and the fixed electrode is the movable electrode. It is formed separately from the electrode,
The first movable electrode that constitutes the first detection unit is in relation to the first fixed electrode that constitutes the first detection unit, and the second fixed electrode that constitutes the second detection unit is the second detection. Both of the second movable electrodes constituting the part are warped downward or upward.

  Accordingly, in the present invention, in the physical quantity sensor having a structure in which the movable part moves in the height direction, it is possible to stably obtain high detection accuracy with a simpler configuration than in the past. In addition, in the present invention, all electrode widths can be formed narrow, which can contribute to downsizing of the sensor.

  In the present invention, each of the first movable electrode and the second fixed electrode may be formed with a stress applying film for applying a tensile stress or a compressive stress to each electrode. preferable. Accordingly, the first movable electrode and the second fixed electrode can be warped in a desired direction easily and appropriately.

The physical quantity sensor of the present invention is
A movable part supported so as to be movable in the height direction, and a first detection part and a second detection part for detecting a displacement of the movable part based on a capacitance change,
Each of the first detection unit and the second detection unit includes a movable electrode and a fixed electrode arranged alternately in a plane, the movable electrode is formed integrally with the movable unit, and the fixed electrode is the movable electrode. It is formed separately from the electrode,
The first movable electrode that constitutes the first detection unit protrudes in the height direction from the first fixed electrode that constitutes the first detection unit, and the second fixed electrode that constitutes the second detection unit includes The protruding films protruding in the height direction from the second movable electrode constituting the second detection unit are formed so as to overlap each other.

  Accordingly, in the present invention, in the physical quantity sensor having a structure in which the movable part moves in the height direction, it is possible to stably obtain high detection accuracy with a simpler configuration than in the past. In addition, in the present invention, all electrode widths can be formed narrow, which can contribute to downsizing of the sensor.

According to the present invention, a movable part supported so as to be movable up and down, and a movable electrode and a fixed electrode for detecting displacement of the movable part based on a change in electrostatic capacitance are alternately arranged in a plane. In the manufacturing method of the physical quantity sensor comprising the first detection unit and the second detection unit,
Forming a stress applying film on the first substrate,
Leaving the stress applying film with respect to the movable electrode constituting the first detector and the fixed electrode constituting the second detector;
The first substrate in a state where the second substrate is bonded to the lower surface via an insulating layer is etched to move the movable portion, the detection portion, and the anchor portions of the movable portion and the fixed electrode from the first substrate. Forming a step;
The movable electrode constituting the first detection unit is formed by leaving the insulating layer between the anchor unit and the second substrate, and removing the insulating layer located between the movable unit and each detection unit and the second substrate. And a step of bending the fixed electrodes constituting the second detection unit downward or upward by tensile stress or compressive stress from the stress applying film,
It is characterized by having.

  According to said manufacturing method, the said movable electrode which comprises the said 1st detection part, and the said fixed electrode which comprises the said 2nd detection part can be bent easily and appropriately. Further, in the present invention, since all electrode widths can be formed narrow, the downsizing of the sensor can be promoted.

According to the present invention, a movable part supported so as to be movable up and down, and a movable electrode and a fixed electrode for detecting displacement of the movable part based on a change in electrostatic capacitance are alternately arranged in a plane. In the manufacturing method of the physical quantity sensor comprising the first detection unit and the second detection unit,
Forming a protruding film on the first substrate,
Leaving the protruding film with respect to the movable electrode constituting the first detector and the fixed electrode constituting the second detector;
The first substrate in a state where the second substrate is bonded to the lower surface via an insulating layer is etched to move the movable portion, the detection portion, and the anchor portions of the movable portion and the fixed electrode from the first substrate. Forming a step;
Leaving the insulating layer between the anchor portion and the second substrate, and removing the insulating layer located between the movable portion and each detecting portion and the second substrate;
It is characterized by having.

  According to said manufacturing method, the height of a movable electrode and a fixed electrode can be varied by a simple method. Further, in the present invention, since all electrode widths can be formed narrow, the downsizing of the sensor can be promoted.

  In the present invention, in a physical quantity sensor having a structure in which the movable portion moves in the height direction, high detection accuracy can be stably obtained with a simpler configuration than in the past. Further, in the present invention, all the electrode widths can be formed narrow, thereby contributing to the downsizing of the sensor.

  FIG. 1A is a plan view of the acceleration sensor according to the present embodiment, and FIG. 1B is a cross-sectional view of the acceleration sensor 1 of FIG. 2 is a partially enlarged plan view in which a portion II in FIG. 1 is enlarged, and FIG. 3 is a partially enlarged plan view in which a portion III in FIG. 1 is enlarged.

The acceleration sensor 1 is formed using, for example, an SOI (Silicon on Insulator) substrate 2. The SOI substrate 2 is formed in a laminated structure of a first substrate 3, a second substrate (support substrate) 4, and an insulating layer 5 interposed between the first substrate 3 and the second substrate 4. The first substrate 3 and the second substrate 4 are made of silicon, and the insulating layer 5 is made of SiO ₂ .

  As shown in FIG. 1, a movable portion 41 is provided on the first substrate 3. The movable portion 41 is integrally formed with a right mass portion 41A on the X1 side and a left mass portion 41B on the X2 side with respect to the center line O1, and a connecting portion 41C is provided between the right mass portion 41A and the left mass portion 41B. It is integrally formed. The center line O1 is located at the connecting portion 41C.

  Anchor portions 42 and 42 are provided at positions adjacent to the Y1 side and the Y2 side of the connecting portion 41C of the movable portion 41. Further, a U-shaped right link portion 43A is provided outside the right mass portion 41A of the movable portion 41, and a left link portion 43B is provided outside the left mass portion 41B. The anchor portions 42, 42, the right link portion 43 </ b> A, and the left link portion 43 </ b> B are formed separately from the first substrate 3 together with the movable portion 41.

  As shown in FIG. 1, two end portions on the X2 side of the right link portion 43A are rotatably connected to the anchor portions 42 and 42 via hinge portions 44A and 44A, respectively. Two end portions on the X1 side of 43B are rotatably connected to the anchor portions 42 and 42 via hinge portions 44B and 44B, respectively. Further, two end portions on the X2 side of the right link portion 43A and two end portions on the X1 side of the left link portion 43B are connected to each other by connecting hinge portions 45 and 45 so as to be rotatable. The end portion on the X1 side of the right mass portion 41A of the movable portion 41 and the right link portion 43A are rotatably connected via hinge portions 46A and 46A, and the end portion on the X2 side of the left mass portion 41B. The left link portion 43B is rotatably connected via hinge portions 46B and 46B.

  The hinge portions 44A, 44B, 45, 46A, and 46B are formed, for example, in a columnar shape or a prismatic shape, and can be elastically twisted and deformed so that they are not twisted by an elastic force when no external force is applied. Restore.

  As shown in FIG. 1B, an insulating layer 5 is interposed between the anchor portions 42 and 42 and the second substrate 4, and the anchor portions 42 and 42 are fixedly supported on the second substrate 4. .

  On the other hand, the movable portion 41, the right link portion 43 </ b> A, and the left link portion 43 </ b> B are separated from the surfaces of the second substrate 4 and the insulating layer 5. Therefore, when the right link portion 43A rotates, for example, counterclockwise using the hinge portion 44A as a fulcrum, the left link portion 43B rotates clockwise using the hinge portion 44B as a fulcrum. Thereby, the movable part 41 can be moved in the Z1 direction. Conversely, the first movable portion 41 can move in the Z2 direction by rotating the hinge portion 44A and the hinge portion 44B in the opposite direction.

  In addition, when an external force in the height direction (Z direction) is not acting, each hinge part is restored to a state where it is not torsionally deformed, so that the movable part 41 is in a neutral position where it does not move in the Z1 direction and the Z2 direction. is there.

  As shown in an enlarged view in FIG. 2, a plurality of first movable electrodes 47a that extend linearly in the Y2 direction from the side portion on the Y1 side are integrally formed on the right mass portion 41A of the movable portion 41. Similarly, a plurality of first movable electrodes 47a linearly extending in the Y1 direction from the side portion on the Y2 side are integrally formed on the right mass portion 41A.

  3, the left mass portion 41B of the movable portion 41 is integrally formed with a plurality of second movable electrodes 47b that linearly extend in the Y2 direction from the side portion on the Y1 side. Similarly, a plurality of second movable electrodes 47b extending linearly from the side portion on the Y2 side toward the Y1 direction are integrally formed on the left mass portion 41B.

  As shown in FIG. 1, a right fixed portion 51 and a left fixed portion 53 are formed inside the movable portion 41 separately from the movable portion 41. The right fixing part 51 is located on the right side of the center line O1, and the left fixing part 53 is located on the left side of the center line O1. The right fixed portion 51 is integrally formed with a square anchor portion 52 at a position approaching the center line O1, and the left fixed portion 53 is integrally formed with a square anchor portion 54 at a position approaching the center line O1. Is formed.

  As shown in FIG. 1B, the anchor portion 52 and the anchor portion 54 are fixedly supported on the second substrate 4 via the insulating layer 5. The right fixing part 51 and the left fixing part 53 are apart from the second substrate 4 and the insulating layer 5 except for the anchor parts 52 and 54.

  As shown in FIG. 2, the right fixed portion 51 is integrally formed with a plurality of first fixed electrodes 51a extending in both the Y1 direction and the Y2 direction. The 1st detection part 55 is comprised by the 1st movable electrode 47a and the 1st fixed electrode 51a which are shown in FIG.

  Further, as shown in FIG. 3, the left fixed portion 53 is integrally formed with a plurality of second fixed electrodes 53a extending in both the Y1 direction and the Y2 direction. The second movable electrode 47b and the second fixed electrode 53a shown in FIG.

The characteristic part of this embodiment is demonstrated.
FIG. 4 shows the first movable electrode 47a and the first fixed electrode 51a that constitute the first detection unit 55 in the present embodiment, and the second movable electrode 47b and the second fixed electrode 53a that constitute the second detection unit 56 in the lateral direction. FIG. 4 is a side view seen from the X direction (viewed from the X direction shown in FIGS. 2 and 3).

  FIG. 4A is a diagram of an initial state, that is, a state in which an external force in the height direction (Z direction) is not applied to the movable portion 41.

  As shown in FIG. 4A, a stress applying film 58 is formed on the upper surfaces of the first movable electrode 47a and the second fixed electrode 53a. In the embodiment of FIG. 4, compressive stress is applied from the stress applying film 58 to the first movable electrode 47a and the second fixed electrode 53a, and the first movable electrode 47a and the second fixed electrode 53a are directed upward (Z1 direction). It is warped. In the following description, the upper surfaces 47d and 53d of the first movable electrode 47a and the second fixed electrode 53a refer to the upper surface of the stress applying film 58 unless otherwise specified.

  On the other hand, the first fixed electrode 51a and the second movable electrode 47b extend in parallel to the Y1-Y2 direction orthogonal to the height direction (Z1-Z2 direction).

  As shown in FIG. 4A, in the initial state, the lower surface 47c1 of the first movable electrode 47a on the support end 47a1 side coincides with the lower surface 51c of the first fixed electrode 51a. The upper surface 47d1 on the support end 47a1 side is higher than the upper surface 51d of the first fixed electrode 51a by the thickness of the stress applying film 58.

  On the other hand, the lower surface 47c2 on the free end 47a2 side of the first movable electrode 47a is positioned higher than the lower surface 51c of the first fixed electrode 51a, and the upper surface 47d2 on the free end 47a2 side is the first fixed electrode 51a. And a position higher than the upper surface 47d1 on the support end 47a1 side.

  As shown in FIG. 4A, in the initial state, the lower surface 53c1 of the second fixed electrode 53a on the support end 53a1 side coincides with the lower surface 47c of the second movable electrode 47b. The upper surface 53d1 on the support end 53a1 side is higher than the upper surface 47d of the second movable electrode 47b by the thickness of the stress applying film 58.

  On the other hand, the lower surface 53c2 on the free end 53a2 side of the second fixed electrode 53a is positioned higher than the lower surface 47c of the second movable electrode 47b, and the upper surface 53d2 on the free end 53a2 side is the second movable electrode 47b. And a position higher than the upper surface 53d1 on the support end 47a1 side.

  Here, in FIG. 4 (a), the opposing region between the first movable electrode 47a and the first fixed electrode 51a of the first detector 55, and the second movable electrode 47b and the second fixed electrode 53a of the second detector 56 are shown. The opposite area is indicated by hatching.

  For example, it is assumed that the movable unit 41 has moved upward (Z1 direction). This state is shown in FIG. FIG. 5A shows a change in capacitance of the first detection unit 55, and FIG. 5B shows a change in capacitance of the second detection unit 56.

  As shown in FIG. 4B, when the movable part 41 moves upward, the first movable electrode 47a constituting the first detection part 55 moves upward. As a result, as shown by the oblique lines in FIG. 4B, the facing area between the first movable electrode 47a and the first fixed electrode 51a is reduced compared to the initial state of FIG. 4A. Therefore, as shown in FIG. 5A, the capacitance of the first detection unit 55 decreases from the initial state.

  On the other hand, as shown in FIG. 4B, when the movable part 41 moves upward, the second movable electrode 47b constituting the second detection part 56 moves upward. At this time, as indicated by the hatched lines in FIG. 4B, the facing area between the second movable electrode 47b and the second fixed electrode 53a increases slightly from the initial state of FIG. Therefore, as shown in FIG. 5B, the capacitance of the first detection unit 55 becomes substantially constant after increasing slightly from the initial state.

  Further, when the movable unit 41 moves downward, as shown in FIG. 5A, the capacitance of the first detection unit 55 becomes substantially constant after slightly increasing from the initial state. Moreover, as shown in FIG.5 (b), the electrostatic capacitance of the 2nd detection part 56 reduces from an initial state.

  FIG. 5C shows the differential capacitance change of the capacitance change of the first detection unit 55 and the capacitance change of the second detection unit 56. Based on this differential output, the moving distance and moving direction of the movable portion 41 can be known.

  In the embodiment of FIG. 4, the first movable electrode 47a constituting the first detection unit 55 and the second fixed electrode 53a constituting the second detection unit 56 are warped upward, but as shown in FIG. It may be warped.

  As shown in FIG. 6A, a stress applying film 59 is formed on the upper surfaces of the first movable electrode 47a and the second fixed electrode 53a. In the embodiment of FIG. 6, tensile stress is applied from the stress applying film 59 to the first movable electrode 47a and the second fixed electrode 53a, and the first movable electrode 47a and the second fixed electrode 53a are moved downward (Z2 direction). It is warped. In the following description, the upper surfaces 47d and 53d of the first movable electrode 47a and the second fixed electrode 53a refer to the upper surface of the stress applying film 59 unless otherwise specified.

  On the other hand, the first fixed electrode 51a and the second movable electrode 47b extend in parallel to the Y1-Y2 direction orthogonal to the height direction (Z1-Z2 direction).

  As shown in FIG. 6A, in the initial state, the lower surface 47c1 of the first movable electrode 47a on the support end 47a1 side coincides with the lower surface 51c of the first fixed electrode 51a. The upper surface 47d1 on the support end 47a1 side is higher than the upper surface 51d of the first fixed electrode 51a by the thickness of the stress applying film 59.

  On the other hand, the lower surface 47c2 on the free end 47a2 side of the first movable electrode 47a is at a lower position than the lower surface 51c of the first fixed electrode 51a, and the upper surface 47d2 on the free end 47a2 side is the first fixed electrode 51a. The upper surface 51d is lower than the upper surface 51d and is lower than the upper surface 47d1 on the support end 47a1 side. Depending on the amount of warpage, the upper surface 47d2 on the free end 47a2 side may be approximately the same height as the upper surface 51d of the first fixed electrode 51a.

  As shown in FIG. 6A, in the initial state, the lower surface 53c1 of the second fixed electrode 53a on the support end 53a1 side coincides with the lower surface 47c of the second movable electrode 47b. The upper surface 53d1 on the support end 53a1 side is higher than the upper surface 47d of the second movable electrode 47b by the thickness of the stress applying film 59.

  On the other hand, the lower surface 53c2 on the free end 53a2 side of the second fixed electrode 53a is lower than the lower surface 47c of the second movable electrode 47b, and the upper surface 53d2 on the free end 53a2 side is the second movable electrode 47b. And a position lower than the upper surface 53d1 on the support end 47a1 side. Depending on the amount of warpage, the upper surface 53d2 on the free end 53a2 side may be approximately the same height as the upper surface 47d of the second movable electrode 47b.

  Here, in FIG. 6A, the opposing region between the first movable electrode 47a and the first fixed electrode 51a of the first detection unit 55, and the second movable electrode 47b and the second fixed electrode 53a of the second detection unit 56 are shown. The area opposite to is indicated by hatching.

  Here, for example, it is assumed that the movable portion 41 has moved downward (Z2 direction). This state is shown in FIG. FIG. 7A shows a change in capacitance of the first detection unit 55, and FIG. 7B shows a change in capacitance of the second detection unit 56.

  As shown in FIG. 6B, when the movable portion 41 moves downward, the first movable electrode 47a constituting the first detection portion 55 moves downward. As a result, as indicated by the oblique lines in FIG. 6B, the facing area between the first movable electrode 47a and the first fixed electrode 51a is reduced compared to the initial state of FIG. Therefore, as shown in FIG. 7A, the capacitance of the first detection unit 55 decreases due to the downward movement from the initial state.

  On the other hand, as shown in FIG. 6B, when the movable part 41 moves downward, the second movable electrode 47b constituting the second detection part 56 moves downward. At this time, as indicated by the hatched lines in FIG. 6B, the facing area between the second movable electrode 47b and the second fixed electrode 53a becomes substantially constant after slightly increasing from the initial state of FIG. 6A. Accordingly, as shown in FIG. 7B, the capacitance of the first detection unit 55 becomes substantially constant after increasing slightly from the initial state.

  When the movable part 41 moves upward, as shown in FIG. 7A, the capacitance of the first detection part 55 becomes substantially constant after slightly increasing from the initial state. Moreover, as shown in FIG.7 (b), the electrostatic capacitance of the 2nd detection part 56 reduces from an initial state.

  FIG. 7C shows the differential capacitance change of the capacitance change of the first detection unit 55 and the capacitance change of the second detection unit 56. Based on this differential output, the moving distance and moving direction of the movable portion 41 can be known.

  Although not shown, the stress applying films 58 and 59 may be provided on the lower surface of the first movable electrode 47a and the lower surface of the second fixed electrode 53a.

  As described above, in the present embodiment, the stress applying films 58 and 59 are formed so as to overlap the first movable electrode 47a and the second fixed electrode 53a, and the first movable electrode 47a and the second fixed electrode 53a are moved upward. Or by making it curve downward, a high detection accuracy can be stably obtained with a simpler structure than in the past. In addition, in the present embodiment, all electrode widths can be formed to be equally thin, thereby contributing to downsizing of the sensor.

Next, the stress applying films 58 and 59 will be described. First, the material may be either conductive or insulating. When the stress applying films 58 and 59 are formed of metal, for example, gold (Au), aluminum (Al), chromium (Cr), tungsten (W), nickel (Ni), tantalum (Ta), germanium (Ge), Examples include copper (Cu) and titanium (Ti). Moreover, when forming the stress provision films | membranes 58 and 59 with an alloy, an aluminum copper alloy (AlCu) and an aluminum scandium copper alloy (AlScCu) can be illustrated. Further, when the stress applying films 58 and 59 are formed of an insulator, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), silicon oxynitride (SiON), and Pyrex (registered trademark) glass can be exemplified.

  For example, in the case of film formation by the CVD method, the film stress of the stress applying films 58 and 59 can be controlled by adjusting general film formation conditions such as gas pressure and flow rate during film formation.

FIG. 8 is a graph showing the relationship between pressure and film stress when a Si ₃ N ₄ film is formed by the CVD method.

  As shown in FIG. 8, it was found that when the pressure was greatly increased, tensile stress was obtained. This is because the gas desorption reaction is promoted by atoms radicalized by heat or plasma, but under a high pressure condition, non-radical H atoms remain as N—H bonds, and this bonding force causes tension. This is probably because the stress increases.

On the other hand, as shown in FIG. 8, it was found that when the pressure was lowered, a compressive stress was generated. This is presumably because the density of the pure Si ₃ N ₄ film becomes dense by sharing N.

  FIG. 9 is a diagram of a movable electrode and a fixed electrode having a comb-like structure showing another embodiment. FIG. 9 is a cross-sectional view when each electrode is cut in the height direction (Z1-Z2 direction) along the X1-X2 direction shown in FIGS. 3 and 4. However, for the sake of clarity, the hatched lines are not shown on the fixed electrode side. FIG. 10 is a side view of the first detection unit 55 viewed from the side surface direction, for example.

  9 and 10, a protruding film (lifting film) 60 is formed on the upper surface of the first movable electrode 47 a of the first detection unit 55 and the upper surface of the second fixed electrode 53 a of the second detection unit 56. The film stress of the protruding film 60 is approximately 0 (MPa). Therefore, the first movable electrode 47a and the second fixed electrode 53a are not warped as shown in FIGS. 4 and 6, but extend in parallel in the horizontal direction. As described above, the film stress can be set to 0 (MPa) by adjusting the pressure at the time of film formation by, for example, the CVD method as shown in FIG.

  In the embodiment shown in FIGS. 9 and 10, in the initial state (the state in which no acceleration is applied), the lower surfaces of the first movable electrode 47a, the first fixed electrode 51a, the second movable electrode 47b, and the second fixed electrode 53a are It is the same position (reference position indicated by a dotted line). The first movable electrode 47a and the second fixed electrode 53a are higher than the first fixed electrode 51a and the second movable electrode 47b by the thickness of the protruding film 60.

  As shown in FIG. 9A, when the movable electrodes 47a and 47b move downward, the opposing area of the first movable electrode 47a and the first fixed electrode 51a does not change in the first detection unit 55. The capacitance does not change. On the other hand, in the 2nd detection part 56, since the opposing area of the 2nd movable electrode 47b and the 2nd fixed electrode 53a reduces, an electrostatic capacitance reduces.

  Next, as shown in FIG. 9B, when the movable electrodes 47a and 47b move upward, in the first detector 55, the facing area between the first movable electrode 47a and the first fixed electrode 51a decreases. As a result, the capacitance decreases. On the other hand, in the 2nd detection part 56, since the opposing area of the 2nd movable electrode 47b and the 2nd fixed electrode 53a does not change, an electrostatic capacitance does not change.

  Then, by obtaining the differential output of the capacitances of the first detection unit 55 and the second detection unit 56, the moving distance and moving direction of the movable unit 41 can be known.

  The protruding film 60 may be formed on the lower surface of the first movable electrode 47a and the lower surface of the second fixed electrode 53a.

  As described above, in the present embodiment, the protruding film 60 is formed so as to overlap the first movable electrode 47a and the second fixed electrode 53a, so that high detection accuracy can be stably obtained with a simpler configuration than in the past. I can do it. In addition, in the present embodiment, all electrode widths can be formed to be equally thin, thereby contributing to downsizing of the sensor.

  11 to 18 are cross-sectional views showing a method of manufacturing an electrode having a comb-like structure in the acceleration sensor according to this embodiment.

First, in the step shown in FIG. 11, the first substrate 3 made of silicon, the second substrate 4 made of silicon, and the SiO ₂ interposed between the first substrate 3 and the second substrate 4 are formed. An SOI substrate 2 including an insulating layer 5 is prepared.

  Subsequently, a stress applying film 59 is formed on the entire upper surface 3 a of the first substrate 3. At this time, when the stress applying film 59 is formed by, for example, the CVD method, the film stress is controlled by adjusting the pressure as shown in FIG. For example, in this embodiment, the pressure during film formation is adjusted so that the film stress of the stress applying film 59 becomes a tensile stress.

  Next, in a step shown in FIG. 12, a resist pattern 70 having a first movable electrode shape and a second fixed electrode shape is formed on the upper surface 59a of the stress applying film 59.

  Next, in the process of FIG. 13, the stress applying film 59 not covered with the resist pattern 70 is removed by, for example, RIE (reactive ion etching).

Next, in the process of FIG. 14, the resist pattern 70 is removed.
Next, in the process of FIG. 15, the detection patterns 55 and 56, the movable part 41, the anchor parts 42, 52 and 54, the right link part 43A, the left link part 43B, and the resist pattern 71 in the shape of each hinge part are formed on the first substrate. 3 and on the stress applying film 59.

  Subsequently, in the process of FIG. 16, the first substrate 3 not covered with the resist pattern 71 is removed by using deep RIE (Deep RIE). Thereby, the detection parts 55 and 56, the movable part 41, the anchor parts 42, 52, and 54, the right link part 43A, the left link part 43B, and each hinge part can be formed. 16 to 18 illustrate the first movable electrode 47a and the first fixed electrode 51a of the first detection unit 55.

Next, in a step shown in FIG. 17, the resist pattern 71 is removed.
Next, in the process shown in FIG. 18, the detecting portions 55 and 56, the movable portion 41, the right link portion 43 </ b> A, the left link portion 43 </ b> B, and the insulating layer 5 between each hinge portion and the second substrate 4 are wetted. It is removed in an isotropic etching process by etching or dry etching. Note that a large number of micro holes leading to the insulating layer 5 are formed in the first substrate 3 before the step of removing the insulating layer 5 at locations where the insulating layer 5 is difficult to remove because of the large area. Thus, the insulating layer 5 can be removed by isotropic etching.

  In this step, the insulating layer 5 under the anchor portions 42, 52, and 54 is left, and the anchor portions 42, 52, and 54 are fixedly supported on the second substrate 4.

  As shown in FIG. 18, by removing the insulating layer 5, tensile stress is applied from the stress applying film 59 to the first movable electrode 47a and the second fixed electrode 53a, and the first movable electrode 47a and the second fixed electrode 53a. Is warped downward (see also FIG. 6).

  If the film stress is adjusted to be a compressive stress when forming the stress applying film of FIG. 11, the first movable electrode 47a and the second fixed electrode 53a are warped upward in the process of FIG. (See also FIG. 4).

  Further, if the film is formed so that the film stress becomes substantially 0 (MPa) in the process of FIG. 11, the film can be formed as the protruding film (raised film) described in FIG.

  According to the above manufacturing method, the first movable electrode 47a and the second fixed electrode 53a can be warped in a predetermined direction easily and appropriately. The amount of warpage can also be easily adjusted by adjusting the conditions during film formation. Or according to the manufacturing method of this embodiment, the height of a movable electrode and a fixed electrode can be varied by a simple method. Moreover, in this embodiment, since all the electrode widths can be formed thinly, size reduction of a sensor can be promoted.

  In the manufacturing method described above, the SOI substrate 2 is used. However, for example, the first substrate 3 and the second substrate 4 are prepared separately, and the first substrate 3 and the second substrate 4 are connected to the insulating layer in a later step. You may make it join via 5. In such a case, it is possible to form a stress applying film or a protruding film on the lower surface of the first substrate 3 (the surface facing the second substrate 4).

  Further, in the above, the stress applying film and the protruding film may be formed so as to overlap not only the electrode but also the movable part. Thereby, the mass of a movable part can be enlarged more effectively.

In the above configuration, the first movable electrode 47a of the first detection unit 55 and the second fixed electrode 53a of the second detection unit 56 are warped in the height direction, while the first fixed electrode of the first detection unit 55 51a and the second movable electrode 47b of the second detector 56 extend in the horizontal direction. However, the first fixed electrode 51a of the first detection unit 55 and the second movable electrode 47b of the second detection unit 56 may be slightly warped in the height direction, or the first movable portion of the first detection unit 55 is movable. The electrode 47a and the second fixed electrode 53a of the second detector 56 may be warped in the opposite direction. In the present embodiment, the first movable electrode 47a of the first detection unit 55 is relative to the first fixed electrode 51a (with respect to the reference when the extending direction of the first fixed electrode 51a is used as a reference), and The second fixed electrode 53a of the second detector 56 is either downward or upward with respect to the second movable electrode 47b (when the extension direction of the second movable electrode 47b is used as a reference). It only has to be warped.
This embodiment can be applied not only to an acceleration sensor but also to an angular velocity sensor or the like.

FIG. 1A is a plan view of the acceleration sensor according to the present embodiment, and FIG. 1B is a cross-sectional view of the acceleration sensor 1 of FIG. , FIG. 1 is a partially enlarged plan view in which a portion II in FIG. 1 is enlarged; FIG. 1 is a partially enlarged plan view in which a portion III in FIG. 1 is enlarged; The side view which looked at the 1st movable electrode and the 1st fixed electrode which constitute the 1st detection part in this embodiment from the side direction, and the 2nd movable electrode and the 2nd fixed electrode which constitute the 2nd detection part, (A) is a graph showing the capacitance change of the first detection unit in the form of FIG. 4, (b) is a graph showing the capacitance change of the second detection unit in the form of FIG. 4, (c) ) Is the differential capacitance graph, The side surface which looked at the 1st movable electrode and the 1st fixed electrode which constitute the 1st detection part in the embodiment different from Drawing 4, the 2nd movable electrode which constitutes the 2nd detection part, and the 2nd fixed electrode from the side direction. Figure, (A) is a graph showing the capacitance change of the first detection unit in the form of FIG. 6, (b) is a graph showing the capacitance change of the second detection unit in the form of FIG. 6, (c) ) Is the differential capacitance graph, A graph showing the relationship between pressure and film stress when a Si ₃ N ₄ film is formed by a CVD method; Sectional drawing of the movable electrode and fixed electrode of a comb-tooth structure which show another embodiment, The side view which looked at the 1st detection part in the embodiment of Drawing 9 from the side direction, Among the acceleration sensors of the present embodiment, a process diagram (cross-sectional view) showing a method of manufacturing a comb-shaped electrode structure, in particular, Process drawing (cross-sectional view) performed after FIG. Process drawing (cross-sectional view) performed after FIG. Process drawing (cross-sectional view) performed after FIG. Process drawing (cross-sectional view) performed after FIG. Process drawing (cross-sectional view) performed after FIG. Process drawing (cross-sectional view) performed after FIG. Process drawing (cross-sectional view) performed after FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Acceleration sensor 2 SOI substrate 3 1st board | substrate 4 2nd board | substrate 5 Insulating layer 41 Movable part 42,52,54 Anchor part 47a 1st movable electrode 47b 2nd movable electrode 51a 1st fixed electrode 53a 2nd fixed electrode 55 1st Detection unit 56 Second detection unit 58, 59 Stress applying film 60 Protruding film (lifting film)
70, 71 resist pattern

Claims (5)

A movable part supported so as to be movable in the height direction, and a first detection part and a second detection part for detecting a displacement of the movable part based on a capacitance change,
Each of the first detection unit and the second detection unit includes a movable electrode and a fixed electrode arranged alternately in a plane, the movable electrode is formed integrally with the movable unit, and the fixed electrode is the movable electrode. It is formed separately from the electrode,
The first movable electrode that constitutes the first detection unit is in relation to the first fixed electrode that constitutes the first detection unit, and the second fixed electrode that constitutes the second detection unit is the second detection. A physical quantity sensor characterized in that it is warped downward or upward with respect to the second movable electrode constituting the part.   2. The physical quantity sensor according to claim 1, wherein a stress applying film for applying a tensile stress or a compressive stress to each electrode is formed on the first movable electrode and the second fixed electrode, respectively. . A movable part supported so as to be movable in the height direction, and a first detection part and a second detection part for detecting a displacement of the movable part based on a capacitance change,
Each of the first detection unit and the second detection unit includes a movable electrode and a fixed electrode arranged alternately in a plane, the movable electrode is formed integrally with the movable unit, and the fixed electrode is the movable electrode. It is formed separately from the electrode,
The first movable electrode that constitutes the first detection unit protrudes in the height direction from the first fixed electrode that constitutes the first detection unit, and the second fixed electrode that constitutes the second detection unit includes A physical quantity sensor characterized in that projecting films projecting in a height direction from the second movable electrode constituting the second detection unit are formed to overlap each other. A first detection unit and a first detection unit configured by a movable unit supported so as to be movable up and down, and a movable electrode and a fixed electrode that are alternately arranged in a plane in order to detect displacement of the movable unit based on a change in capacitance. In the manufacturing method of the physical quantity sensor comprising two detection units,
Forming a stress applying film on the first substrate,
Leaving the stress applying film with respect to the movable electrode constituting the first detector and the fixed electrode constituting the second detector;
The first substrate in a state where the second substrate is bonded to the lower surface via an insulating layer is etched to move the movable portion, the detection portion, and the anchor portions of the movable portion and the fixed electrode from the first substrate. Forming a step;
The movable electrode constituting the first detection unit is formed by leaving the insulating layer between the anchor unit and the second substrate, and removing the insulating layer located between the movable unit and each detection unit and the second substrate. And a step of bending the fixed electrodes constituting the second detection unit downward or upward by tensile stress or compressive stress from the stress applying film,
A method of manufacturing a physical quantity sensor, comprising: A first detection unit and a first detection unit configured by a movable unit supported so as to be movable up and down, and a movable electrode and a fixed electrode that are alternately arranged in a plane in order to detect displacement of the movable unit based on a change in capacitance. In the manufacturing method of the physical quantity sensor comprising two detection units,
Forming a protruding film on the first substrate,
Leaving the protruding film with respect to the movable electrode constituting the first detector and the fixed electrode constituting the second detector;
The first substrate in a state where the second substrate is bonded to the lower surface via an insulating layer is etched to move the movable portion, the detection portion, and the anchor portions of the movable portion and the fixed electrode from the first substrate. Forming a step;
Leaving the insulating layer between the anchor portion and the second substrate, and removing the insulating layer located between the movable portion and each detecting portion and the second substrate;
A method of manufacturing a physical quantity sensor, comprising:

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