JP2006287165A - Pressure sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor in which damping is reduced by keeping sensitivity almost constant, and to provide a method for manufacturing it. <P>SOLUTION: The pressure sensor 10 comprises a vibration plate 11a vibrates corresponding to variation of sound pressure by sound wave, a back plate 12 arranged while facing the vibration plate 11a through a gap 16, an electrode 17 provided on a semiconductor substrate 11, and an electrode 18 provided on the back plate 12. The back plate 12 comprises a plurality of through-holes 15. The through-hole 15 is constituted by a rectangular opening 15a formed on the lower surface of the back plate 12, a rectangular opening 15b formed on the upper surface of the back plate 12, and four tapered inner wall surfaces 15c spreading from the lower surface toward the upper surface. The opening 15a is set based on forms of a plurality of temporary openings 20 temporarily arranged like mesh so as to have a specified opening rate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pressure sensor that operates by detecting a change in capacitance, and a method for manufacturing the same.

  As a conventional pressure sensor, one shown in FIG. 5 is known. 5A is a cross-sectional view of a conventional pressure sensor, FIG. 5B is a top view of a back plate according to the conventional pressure sensor, and FIGS. 5C to 5F are explanatory views of through holes. It is.

  The conventional pressure sensor 1 shown in FIG. 5 (a) is disposed opposite to the diaphragm 2a through a gap 6 and a semiconductor substrate 2 including a diaphragm 2a that vibrates in response to a change in sound pressure due to sound waves. A back plate 3, an insulating film 4 provided between the semiconductor substrate 2 and the back plate 3, an electrode 7 provided on the semiconductor substrate 2, and an electrode 8 provided on the back plate 3, The back plate 3 is provided with a plurality of through holes 5 (see, for example, Patent Document 1).

  As shown in FIG. 5B, the plurality of through holes 5 are formed in a mesh shape on the back plate 3, and allow the air in the gap 6 to enter and exit to reduce damping. Each of the plurality of through holes 5 is formed by anisotropic etching of an alkaline solution, and is formed in a square opening formed on the surface of the back plate 3 on the diaphragm 2a side (hereinafter referred to as “lower surface”). 5a, a square-shaped opening 5b formed on the surface opposite to the surface on the diaphragm 2a side (hereinafter referred to as “upper surface”), and four tapered inner wall surfaces 5c that spread from the lower surface toward the upper surface. It consists of Hereinafter, one set constituting the through hole 5 is referred to as a square unit.

  The conventional pressure sensor has a uniform arrangement in which square units are arranged at equal intervals, and by allowing the air in the gap 6 to enter and exit isotropically, the displacement of the diaphragm 2a is prevented from being biased and directivity is prevented. The sound is converted into an electrical signal based on the amount of change in capacitance between the diaphragm 2a and the back plate 3 that is generated when the diaphragm 2a vibrates in response to sound waves. It has become.

Incidentally, it is known that the sensitivity of a conventional pressure sensor is inversely proportional to the distance between the diaphragm 2a and the back plate 3 (hereinafter referred to as “gap length”) (for example, see Non-Patent Document 1). In order to sufficiently increase the sensitivity, it is necessary to reduce the gap length. However, as the gap length is reduced, the effect of damping in the high band becomes conspicuous and the sensitivity in the high band decreases. According to Non-Patent Document 1, if the viscous resistance due to air in the gap that causes dumping is _RG , the viscous resistance _RG does not include the area of the back plate 3 (the area of the opening 5a is included. The same applies hereinafter). It is known that it is proportional to the function B (A) of the following equation using the aperture ratio A of the opening 5a formed in the back plate 3 as a parameter. The function B (A) is a monotone decreasing function of the aperture ratio A.

  Therefore, in the conventional pressure sensor, the damping is reduced by reducing the area of the back plate 3 or increasing the opening ratio of the through holes 5 formed in the back plate 3.

JP 2002-27595 A (page 3-4, FIG. 1) A review of silicon microphones, P.A. R. Scheper, et al. , Sensors and Actuators A44 (1994), pp. 1-11

  However, the conventional pressure sensor has a problem that the sensitivity decreases when the damping is reduced. This will be specifically described below.

  First, the suitability of reducing the damping by reducing the area of the back plate 3 will be described. The area of the back plate 3 is closely related to the sensitivity of the pressure sensor as described below.

  The sensitivity of the pressure sensor is determined by the amount of change in capacitance that occurs when the diaphragm 2a is displaced. Further, the displacement of the diaphragm 2a is large in the central part of the diaphragm 2a and small in the peripheral part, so that the electrostatic capacity in the central part contributes to the sensitivity, but the electrostatic capacity in the peripheral part becomes a parasitic capacitance and decreases the sensitivity. . For this reason, if the area of the back plate 3 facing the diaphragm 2a is too small, the capacitance contributing to the sensitivity decreases, and if it is too large, the parasitic capacitance increases. Therefore, based on the optimum value for obtaining the maximum sensitivity. The area of the back plate 3 is determined. Therefore, it is not preferable to reduce the area of the back plate 3 in order to reduce the damping because the sensitivity decreases in proportion to the area of the back plate 3.

  Next, the suitability of reducing the damping by increasing the aperture ratio of the through hole 5 formed in the back plate 3 will be described with reference to FIGS. As shown in FIGS. 5C and 5D, the dimension a is the length of one side of the opening 4a, the dimension b is the length obtained by projecting the tapered portion on the upper surface of the back plate, and the dimension c is the frame portion. The length of one side, w is the width of the square unit, and w = a + 2b + 2c.

  First, in order to increase the aperture ratio without changing the width w of the square unit, it is necessary to reduce the dimension b or c and increase the dimension a. Here, the dimension b is a length determined by the taper portion manufactured by the anisotropic etching of the alkaline solution as described above. As shown in FIG. 5C, this etching is performed on the silicon (100) surface. Therefore, when the thickness of the back plate is t, the dimension b = t / tan 55 °, and the dimension b is determined by the thickness of the back plate 3.

  Therefore, to reduce the dimension b, the back plate 3 may be thinned, but it is not preferable to make the back plate 3 thin because the strength of the back plate 3 is reduced. Similarly, reducing the dimension c to make the frame portion thinner is not preferable because the strength of the back plate 3 is reduced.

  As described above, since it is not preferable to change the dimensions b and c, as shown in FIGS. 5E and 5F, the aperture ratio can be increased by increasing only the dimension a without changing the dimensions b and c. In this case, when the dimension a is multiplied by n, the width w of the square unit becomes w = na + 2b + 2c, and the area of the square unit increases. Therefore, the entire area of the back plate 3 is increased. Increasing the area of the back plate 3 beyond the optimum value increases the parasitic capacitance as described above, and decreases the sensitivity. Therefore, it is not preferable to increase the dimension a.

  As described above, in the conventional pressure sensor, if the area of the back plate 3 is reduced or the aperture ratio of the through hole 5 formed in the back plate 3 is increased in order to reduce damping, the sensitivity is lowered. There was a problem that.

  The present invention has been made to solve such a problem, and provides a pressure sensor capable of reducing damping while maintaining sensitivity almost constant, and a method of manufacturing the same.

  The pressure sensor of the present invention includes a vibrating electrode plate that vibrates according to an applied pressure, and a fixed electrode plate that is disposed to face the vibrating electrode plate at a predetermined interval, and the fixed electrode plate includes: A first surface facing the vibration electrode plate; a second surface parallel to the first surface; and a through hole penetrating from the first surface to the second surface; And the second surface has first and second openings of the through hole, respectively, and the through hole extends from the first opening toward the second opening. The first opening has a tapered inner wall surface, and the shape of the first opening is set based on the shapes of a plurality of temporary openings temporarily arranged in a mesh pattern on the fixed electrode plate so as to have a predetermined opening ratio. It has the composition which is.

  With this configuration, the pressure sensor of the present invention is set based on the shapes of the plurality of temporary openings temporarily arranged in a mesh pattern on the fixed electrode plate so that the shape of the first opening has a predetermined opening ratio. Therefore, damping can be reduced while maintaining the sensitivity almost constant.

  In the pressure sensor of the present invention, the first opening has a shape including at least two temporary openings, and the temporary opening has a substantially square shape. Yes.

  With this configuration, the pressure sensor of the present invention can be applied with the conventional manufacturing process for forming the opening, and does not require new equipment investment. Therefore, the opening ratio is increased without increasing the manufacturing cost and the damping is performed. Can be reduced.

  In the pressure sensor of the present invention, the first opening has a configuration in which substantially the same substantially rectangular shape is repeated.

  With this configuration, the pressure sensor of the present invention can arbitrarily combine substantially the same substantially rectangular openings, and can set a desired opening ratio.

  Further, in the pressure sensor of the present invention, the first opening has a configuration in which different substantially rectangular shapes are repeated.

  With this configuration, the pressure sensor of the present invention can arbitrarily combine mutually different substantially rectangular openings, and can set a desired opening ratio.

  Furthermore, the pressure sensor of the present invention has a configuration in which at least one of the vibration electrode plate and the fixed electrode plate is made of single crystal silicon and is formed by anisotropic etching of an alkaline solution.

  With this configuration, the pressure sensor of the present invention can be applied with the conventional manufacturing process for forming the opening, and does not require new equipment investment. Therefore, the opening ratio is increased without increasing the manufacturing cost and the damping is performed. Can be reduced.

  The method for manufacturing a pressure sensor according to the present invention includes a step of forming a vibrating electrode plate, and a fixed electrode plate having a first surface facing the vibrating electrode plate and a second surface parallel to the first surface. Forming a predetermined distance from the vibrating electrode plate; first and second openings formed in the first and second surfaces; and the second opening from the first opening. Forming a through hole having a plurality of tapered inner wall surfaces extending toward the portion by wet etching, and a plurality of temporary openings temporarily arranged in a mesh form on the fixed electrode plate so as to have a predetermined opening ratio And a step of setting the shape of the first opening based on the shape of the first opening.

  With this configuration, the pressure sensor manufacturing method of the present invention is based on the shapes of the plurality of temporary openings temporarily arranged in a mesh pattern on the fixed electrode plate so that the shape of the first opening has a predetermined opening ratio. Therefore, the damping can be reduced while maintaining the sensitivity almost constant.

In the pressure sensor manufacturing method of the present invention, a plurality of the fixed electrode plates are collectively formed on the same wafer, and the first opening is formed in a different shape for each fixed electrode plate. It has a configuration.

  With this configuration, the pressure sensor manufacturing method of the present invention can simultaneously produce a plurality of fixed electrode plates having different aperture ratios on the same wafer, so that pressure sensors having various frequency characteristics can be simultaneously produced. Can be produced.

  The present invention can provide a pressure sensor having an effect of reducing damping while maintaining sensitivity almost constant, and a method for manufacturing the same.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the structure of the pressure sensor of this Embodiment is demonstrated using FIG. FIG. 1A is a cross-sectional view of the pressure sensor of the present embodiment, FIG. 1B is a top view conceptually showing a back plate according to the pressure sensor of the present embodiment, and FIG. These are figures which show the temporary opening part temporarily arrange | positioned at the backplate which concerns on the pressure sensor of this Embodiment. 1A is a cross-sectional view taken along line AA in FIG.

  As shown in FIG. 1A, the pressure sensor 10 of the present embodiment is opposed to the diaphragm 11a through the semiconductor substrate 11 including the diaphragm 11a that vibrates according to the applied pressure, and the gap portion 16. The arranged back plate 12, the insulating film 13 provided between the semiconductor substrate 11 and the back plate 12, the electrode 17 provided on the semiconductor substrate 11, the electrode 18 provided on the back plate 12, The back plate 12 is provided with a plurality of through holes 15.

  The semiconductor substrate 11 and the back plate 12 are made of, for example, a single crystal silicon semiconductor. The insulating film 13 is made of, for example, a silicon oxide film, and the electrodes 17 and 18 are made of, for example, an aluminum film. The diaphragm 11a constitutes a vibrating electrode plate of the present invention. The back plate 12 constitutes the fixed electrode plate of the present invention.

  The through hole 15 provided in the back plate 12 is configured as shown in FIG. In FIG. 1B, the through hole 15 is opposite to the rectangular opening 15a formed on the diaphragm 11a side surface (hereinafter referred to as "lower surface") of the back plate 12 and the diaphragm 11a side surface. It is composed of a rectangular opening 15b formed on the side surface (hereinafter referred to as “upper surface”) and four tapered inner wall surfaces 15c extending from the lower surface toward the upper surface. Hereinafter, one set constituting the through hole 15 is referred to as a rectangular unit.

  As shown in FIG. 1C, the openings 15a are set based on the shapes of a plurality of temporary openings 20 temporarily arranged in a mesh shape so as to have a predetermined opening ratio. Here, as an example, the one in which the opening 15a is set based on the same configuration as the square unit (see FIG. 5B) by anisotropic etching of an alkaline solution shown in the above-described conventional example. Show.

  The temporary opening 20 shown in FIG. 1C includes a square opening 20 a virtually formed on the lower surface of the back plate 12 and a square shape virtually formed on the upper surface of the back plate 12. The opening 20b and four tapered inner wall surfaces 20c that virtually expand from the lower surface to the upper surface are arranged in the vertical direction and the horizontal direction. For example, the opening 20a has an opening ratio of 5%. The area is determined. Then, by combining two openings 20a of two temporary openings 20 adjacent in the vertical direction without changing the unit width (horizontal direction in the drawing), a rectangular shape as shown in FIG. An opening 15a is configured.

  In addition, the aperture ratio in FIG.1 (c) means the ratio of the total area of the some opening part 20a with respect to the area of the backplate 12. FIG. Similarly, the aperture ratio in FIG. 1B refers to the ratio of the total area of the plurality of rectangular openings 15 a to the area of the back plate 12. Here, the area of the back plate 12 refers to the area obtained by removing the area where the four insulating films 13 are in contact with the back plate 12 from the area of the bottom surface of the back plate 12.

  Next, the rectangular unit shown in FIG. 1B will be described in detail with reference to FIG. 2A is a detailed top view of the rectangular unit, FIG. 2B is a cross-sectional view of the rectangular unit, and FIGS. 2C to 2E are diagrams illustrating arrangement examples of the rectangular unit. is there.

  As shown in FIG. 2A, the rectangular unit has openings 15a and 15b and a tapered inner wall surface 15c. In FIG. 2A, the dimension a is the length of one side of the opening 15a, the dimension b is the length of the taper portion projected onto the upper surface of the back plate 12, the dimension c is the length of one side of the frame portion, and w is a rectangle. Width of the unit, w = a + 2b + 2c. Therefore, the vertical dimension of the opening 15a is (w + a), and the horizontal dimension is a. As specific examples of dimensions, when the thickness of the back plate 12 is about 50 μm, a = about 5-30 μm, b = about 35 μm, c = about 5-10 μm, and w = about 85-120 μm are preferable. .

  Accordingly, in order to obtain a desired aperture ratio, the number of square units is N in the vertical direction × M in the horizontal direction, and the vertical dimension ((N−1) w + a) and the horizontal dimension ((M−1) w + a) are penetrated. A hole can be arranged (N and M are integers of 1 or more). However, at least one of N and M is preferably 1 in order to maintain the strength of the back plate 12.

  As a structure which provides a through-hole in the backplate 12, it is not limited to what was shown by FIG.1 (b). For example, as shown in FIG. 2 (c), a rectangular unit 21 composed of 2 units in the vertical direction and one unit in the horizontal direction may be arranged to be repeatedly expanded in the vertical and horizontal directions. Further, as shown in FIG. 2 (d), it is composed of a rectangular unit 21 composed of 2 units in the vertical direction × 1 unit in the horizontal direction and a square unit composed of 1 unit in the vertical direction × 2 units in the horizontal direction. The rectangular units 22 may be arranged as a set and repeatedly deployed in the vertical and horizontal directions. Furthermore, as shown in FIG. 2 (e), it is composed of a rectangular unit 23 composed of 3 units in the vertical direction × 1 unit in the horizontal direction, and a square unit composed of 1 unit in the vertical direction × 2 units in the horizontal direction. The rectangular unit 22 and the two square units 24 may be arranged as a set and repeatedly expanded in the vertical and horizontal directions.

  In addition, since the structure of the through hole 15 in the back plate 12 according to the present embodiment is an arrangement for connecting the square units, the square units are selected and connected, and the connected ones are arranged. Various methods other than those illustrated are conceivable. Moreover, since various through holes can be provided, the pressure sensor 10 of the present embodiment can freely set the aperture ratio.

  Moreover, as shown in FIG. 1B and FIG. 2C, when the same rectangular unit is arranged and the directions of the rectangular openings are the same direction, the air enters and exits the gap 16. Since direction dependency may occur in the ease of handling, as shown in FIGS. 2D and 2E, the gap 16 is based on a plurality of combinations having different directions and lengths of the openings. It is preferable to arrange the air so that the air enters and exits isotropically.

  Here, the arrangement in which air enters and exits the gap 16 isotropically refers to an arrangement as shown in FIG. 3, for example. In FIG. 3, a rectangular unit 21 composed of 2 square units × 1 lateral unit, a rectangular unit 22 composed of 1 vertical unit × 2 horizontal units, and a square shape. By the combination with the unit 24, the opening is formed in the left and right and up and down directions.

  In the present invention, it is assumed that the aperture ratio is changed with an area substantially equal to the area of the back plate set so that the sensitivity is maximized. Therefore, the range in which the aperture ratio is changed is set so that the sensitivity is not affected by the change in the aperture ratio.

  For example, the area of the back plate is 99% (opening ratio 1%) in the temporary arrangement state shown in FIG. 1C, and the area of the back plate is 95 after the through holes are joined as shown in FIG. % (Aperture ratio 5%), 0.95 / 0.99 = 0.96, resulting in a 4% reduction in sensitivity. However, when the pressure sensor 10 of the present embodiment is applied to a silicon microphone, A sensitivity drop of about 5% has no effect. Therefore, when applied to a silicon microphone, after determining the number and arrangement of the through holes so that the sensitivity is maximized when the square temporary openings shown in FIG. The square openings may be combined to form a rectangular opening as shown in FIG.

  Further, for example, the area of the back plate is 90% (opening ratio 10%) in the temporarily arranged state shown in FIG. 1C, and the area of the back plate in the state after the through holes shown in FIG. Is 70% (aperture ratio 30%), 0.7 / 0.9 = 0.78, resulting in a sensitivity reduction of 22%. In such a case, after setting the optimal back plate area with an aperture ratio of 30% when the square openings shown in FIG. 1C are temporarily arranged, the back plate area is 68%, for example. If the square openings are combined so that the opening ratio is about 32% to form a rectangular opening as shown in FIG. 1B, 0.68 / 0.7 = 0.97. The decrease in sensitivity can be suppressed to 3%.

  As described above, since the opening 15a according to the pressure sensor 10 of the present embodiment is set based on the shape of the plurality of square-shaped temporary openings 20, the temporary pressure sensor 10 of the present embodiment It becomes easy to calculate the aperture ratio when the opening 20 is temporarily arranged, and to recalculate the aperture ratio by performing temporary arrangement again.

  Note that the terms “rectangular shape” and “square shape” used in the above description of the configuration do not mean a complete rectangle or a complete square.

  Next, the manufacturing method of the pressure sensor 10 of this Embodiment is demonstrated using FIG. FIG. 4 is an explanatory diagram of the manufacturing process of the pressure sensor 10 of the present embodiment. In addition, the material, film thickness, manufacturing method, and the like described below are examples, and are not limited to these.

  First, as shown in FIG. 4A, an insulating film 13 containing powder silicon oxide as a main component and containing boron or phosphorus in a high concentration is formed on a semiconductor substrate 11 on which a diaphragm of the pressure sensor 10 is formed to a desired thickness. Sedimentation. For example, the insulating film 13 having a thickness of about 3 to 15 μm is deposited on the semiconductor substrate 11 having a thickness of 300 μm or more by chemical vapor deposition. Here, the insulating film 13 may be deposited on the back plate 12 formed of a semiconductor substrate instead of the semiconductor substrate 11.

  Next, as shown in FIG. 4B, the semiconductor substrate 11 and the back plate 12 are overlapped with each other through the insulating film 13 and heat-treated to be bonded. Then, the back plate 12 is ground and polished so that the thickness of the back plate 12 is about 50 μm, for example. In the following description, the semiconductor substrate 11 and the back plate 12 bonded together are referred to as a silicon wafer. Further, the surface on the back plate 12 side of the silicon wafer is referred to as the front surface, and the surface on the semiconductor substrate 11 side is referred to as the back surface.

  Subsequently, as shown in FIG. 4C, an oxide film 14 is grown on the front and back surfaces of the silicon wafer, for example, by heat treatment, and the oxide film 14 is processed by a photolithography technique to form an etching mask.

  The pattern of the etching mask formed here is adjacent based on the shape of a plurality of temporary openings 20 temporarily arranged in a mesh shape so as to have a predetermined opening ratio, for example, as shown in FIG. Two openings 20a of the two temporary openings 20 are joined to form a rectangular opening 15a pattern as shown in FIG.

  Subsequently, as shown in FIG. 4D, the diaphragm 11a and the back plate 12 are etched by etching with an alkaline solution, for example, TMAH (tetramethylammonium hydroxide) using the etching mask formed of the oxide film 14. And a through hole 15 is formed.

  For example, when TMAH at 80 ° C. is used, the etching rate is about 20 to 25 μm / hour, and the thickness of the semiconductor substrate 11 is 300 μm or more. Therefore, the etching time is about 15 to 18 hours. The alkaline solution used for etching is not limited to TMAH, and for example, a potassium hydroxide solution, an EDP (ethylenediamine pyrocatechol) solution, or the like may be used.

  Subsequently, as shown in FIG. 4E, the gap 16 is obtained by etching the insulating film 13 with hydrofluoric acid using the back plate 12 as an etching mask. Then, a metal film is deposited from the back plate 12 side to form electrodes 17 and 18.

  In addition, although the explanatory view of the manufacturing process of the pressure sensor 10 of the present embodiment shown in FIG. 4 shows the process of manufacturing one pressure sensor 10 in order to simplify the description, It is good also as a process of manufacturing the pressure sensor 10. In the manufacturing process shown in FIG. 4C, pressure sensors having various frequency characteristics are produced by simultaneously producing a plurality of back plates having different aperture ratios by using an etching mask formed of the oxide film 14. It can be produced at the same time.

  Further, the manufacturing method for forming the through hole 15 is not limited to the anisotropic etching of the alkaline solution described above, and dry etching can be used. It is preferable to form by etching.

According to the literature (A Silicon condenser microphone using bond and etch-back technology, J. Bergqvist, et al., Sensors and Actuators A45 (1994), pp. 115-124) when the viscous resistance and R _H, the viscous resistance R _H when the cross section of the through-hole of the straight shape rather than the tapered shape is represented by the formula (2), known to be responsible for dumping similarly to the above-mentioned R _G It has been.

  Here, μ is the viscosity of air, t is the thickness of the back plate, A is the area of the back plate (not including the area of the through holes), n is the hole density of the back plate, and r is the through hole of the back plate. The radius is shown.

On the other hand, the viscous resistance _{RH in} the case where the cross-section of the through hole is a taper shape is expressed by Expression (3).

Next, R _H (R _H1 ) of the tapered through hole shown in FIG. 5C is calculated, and as a through hole having the same aperture ratio and produced by dry etching, FIG. c) Assuming that the distance a shown in FIG. 1 is one side and a through-hole having a straight cross-section, calculating R _H (R _H2 ) of this through-hole, and taking the ratio of R _H1 and R _H2 Equation (4) is obtained. Here, the distance a in FIG. 5C is 10 μm, and the thickness t of the back plate in FIG. 5D is 50 μm.

  Therefore, in a tapered through hole made by anisotropic etching of an alkaline solution, the viscous resistance can be reduced to about 5% compared to a straight through hole made by dry etching and having a uniform cross section. Therefore, it is preferable to form the through hole 15 by anisotropic etching of an alkaline solution rather than dry etching.

  As described above, according to the pressure sensor 10 of the present embodiment, the shape of the opening 15a is the shape of the plurality of temporary openings 20 temporarily arranged in a mesh pattern on the fixed electrode plate so as to have a predetermined opening ratio. Therefore, the damping can be reduced while maintaining the sensitivity almost constant.

  Further, according to the pressure sensor 10 of the present embodiment, the manufacturing process for forming the opening 15a can apply a conventional manufacturing process, and does not require new equipment investment, thus increasing the manufacturing cost. Without increasing the aperture ratio, the damping can be reduced.

  Further, according to the pressure sensor 10 of the present embodiment, as shown in FIG. 1B and FIG. 2C, substantially the same substantially rectangular openings can be arbitrarily combined, The aperture ratio can be easily set, and damping can be reduced while maintaining the sensitivity almost constant.

  Further, according to the pressure sensor 10 of the present embodiment, as shown in FIGS. 2D and 2E, different substantially rectangular openings can be arbitrarily combined, so that a desired opening ratio can be obtained. It can be set easily, and damping can be reduced while maintaining the sensitivity almost constant.

  Further, according to the pressure sensor 10 of the present embodiment, the air enters and exits the gap portion 16 isotropically as shown in FIG. 3 while maintaining the sensitivity almost constant and reducing the damping. An opening can be arranged in

  In the above-described embodiment, the example in which the opening 15a is formed in a rectangular shape has been described. However, the present invention is not limited to this, and the same may be achieved by forming a polygon other than a rectangle. An effect is obtained.

  In the above-described embodiment, the opening 15a has been described by taking as an example the configuration in which the opening 15a is set based on the shape of the plurality of square-shaped temporary openings 20, but the present invention is not limited thereto. Instead, the temporary opening may be formed in a shape other than a square shape. However, since the square-shaped opening has a conventionally used shape, and the aperture ratio can be easily calculated, it is preferable that the temporary opening be square.

(A) Cross-sectional view of the pressure sensor of the present embodiment (b) Top view conceptually showing the back plate according to the pressure sensor of the present embodiment (c) On the back plate of the pressure sensor according to the present embodiment The figure which shows the temporary opening part temporarily arranged (A) Detailed top view of the rectangular unit according to the pressure sensor of the present embodiment (b) Sectional view of the rectangular unit according to the pressure sensor of the present embodiment (c) Rectangle according to the pressure sensor of the present embodiment (D) The figure which shows the example of arrangement | positioning of the rectangular unit which concerns on the pressure sensor of this Embodiment (e) The figure which shows the example of arrangement | positioning of the rectangular unit which concerns on the pressure sensor of this Embodiment The figure which shows the example of arrangement | positioning in which the entrance / exit of the air of a space | gap part isotropically performed in the pressure sensor of this Embodiment. Explanatory drawing of the manufacturing process which concerns on the pressure sensor of this Embodiment (A) Cross-sectional view of a conventional pressure sensor (b) Top view of a back plate according to a conventional pressure sensor (c) Illustration of a through hole according to a conventional pressure sensor (d) Depth of a through hole according to a conventional pressure sensor Sectional drawing (e) Explanatory drawing of the through-hole which concerns on the conventional pressure sensor (f) Sectional drawing of the through-hole which concerns on the conventional pressure sensor

Explanation of symbols

10 Pressure sensor 11 Semiconductor substrate 11a Vibration plate (vibration electrode plate)
12 Back plate (fixed electrode plate)
DESCRIPTION OF SYMBOLS 13 Insulating film 14 Oxide film 15 Through-hole 15a Rectangular opening part 15b Rectangular opening part 15c Tapered inner wall 16 Gap part 17, 18 Electrode 20 Temporary opening part 20a Square-shaped opening part 20b Square-shaped opening part 20c Tapered inner wall 21, 22, 23 Rectangular unit 24 Square unit

Claims (7)

A vibration electrode plate that vibrates in accordance with an applied pressure; and a fixed electrode plate that is disposed to face the vibration electrode plate at a predetermined interval, the fixed electrode plate facing the vibration electrode plate. 1 surface, a second surface parallel to the first surface, and a through hole penetrating from the first surface to the second surface, wherein the first and second surfaces are Each having a first opening and a second opening of the through hole, and the through hole has a plurality of tapered inner wall surfaces extending from the first opening toward the second opening. The shape of the first opening is set based on the shape of a plurality of temporary openings temporarily arranged in a mesh pattern on the fixed electrode plate so as to have a predetermined opening ratio. Sensor. 2. The pressure sensor according to claim 1, wherein the first opening has a shape including at least two temporary openings, and the temporary opening has a substantially square shape. The pressure sensor according to claim 1 or 2, wherein the first opening is formed by repeating substantially the same substantially rectangular shape. 3. The pressure sensor according to claim 1, wherein the first opening is formed by repeating substantially different rectangular shapes. 5. At least one of the vibrating electrode plate and the fixed electrode plate is made of single crystal silicon, and is formed by anisotropic etching of an alkaline solution. The pressure sensor described in 1. Forming a vibrating electrode plate, and a fixed electrode plate having a first surface facing the vibrating electrode plate and a second surface parallel to the first surface at a predetermined interval from the vibrating electrode plate. Forming the first and second openings formed on the first and second surfaces, respectively, and a plurality of tapered shapes extending from the first opening toward the second opening. A step of forming a through hole having an inner wall surface by wet etching, and the first opening based on the shape of a plurality of temporary openings temporarily arranged in a mesh form on the fixed electrode plate so as to have a predetermined opening ratio. And a step of setting the shape of the part. The pressure according to claim 6, wherein a plurality of the fixed electrode plates are collectively formed on the same wafer, and the first openings are formed in different shapes for each of the fixed electrode plates. Sensor manufacturing method.

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