JP2006003100A - Piezoresistance type pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve detection sensitivity without having to enlarge the region of diaphragm formation in a piezoresistance type pressure sensor. <P>SOLUTION: In the piezoresistance type pressure sensor using a semiconductor substrate, parts of a supporting frame are protruded from the vicinities of the centers of the sides of a diaphragm 3 to the center of the diaphragm as protrusion parts 10. By providing the protrusion parts 10, stress concentration positions are formed in the vicinities of the tips of the protrusion parts 10. Piezoresistance type pressure detecting parts 4a and 4b made of piezoresistors (diffused resistors) are arranged at the stress concentration positions. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoresistive pressure sensor configured by arranging a piezoresistor on a semiconductor substrate, and more particularly, to a piezoresistive type in which detection sensitivity is improved without increasing the area of a diaphragm formation region in the semiconductor substrate. The present invention relates to a pressure sensor.

  In recent years, sensors for detecting various physical quantities have been manufactured by applying semiconductor device manufacturing technology. Pressure sensors are also manufactured as piezoresistive pressure sensors based on semiconductor device manufacturing technology. It has come to be.

  FIG. 6A is a top view showing the principle of this type of piezoresistive pressure sensor, and FIG. 6B is a cross-sectional view taken along the two-dot chain line in FIG. 6A. In this piezoresistive pressure sensor 20, for example, a semiconductor substrate made of silicon is used, and a hollow portion 2 is provided in a partial region of the semiconductor substrate from the back side of the semiconductor substrate, and the thickness of the semiconductor substrate is reduced in that region. Thus, the diaphragm 3 is formed. The diaphragm 3 is also called a membrane. In FIG. 6A, the area of the diaphragm 3 is indicated by hatching composed of unidirectional diagonal lines. A region thicker than the diaphragm 3 located around the hollow portion 2 in the semiconductor substrate functions as a support frame 1 for the diaphragm 3. The diaphragm 3 is generally formed as a region having a square or rectangular planar shape or a circular region. The diaphragm 3 is a region that shows a minute deformation according to the pressure difference when a pressure difference is generated between the one surface and the other surface of the semiconductor substrate, and stress accompanying this deformation is generated. At the position, a diffusion resistance (piezoresistance) whose resistance value changes according to the stress is formed on the surface of the semiconductor substrate including the diaphragm 3. This diffusion resistance is provided by, for example, ion implantation with respect to the semiconductor substrate, and constitutes the piezoresistive pressure detector 4. The pressure detection unit 4 made of a piezoresistor is provided in an elongated shape, and a wiring pattern (not shown) is connected to both ends in the longitudinal direction so that the resistance value can be measured. The shape of the piezoresistor is not limited to a linear one, but may be U-shaped or U-shaped so that the resistance between both ends can be measured.

  In this sensor, a pressure difference between both sides of the diaphragm 3 can be detected by detecting a resistance change in the pressure detector 4. The upper surface of the diaphragm 3 and the support frame 1 including the pressure detection unit 4, that is, the entire surface on the surface side of the semiconductor substrate is covered with a protective film 5.

  In order to improve the detection sensitivity, generally, diffusion resistors are provided along two opposing sides of the substantially rectangular diaphragm 3, or diffusion resistors are provided along each side of the substantially rectangular diaphragm 3, respectively. An electrical bridge connection has been made. In the illustrated example, the pressure detector 4 provided along a pair of opposing two sides of the diaphragm 3 has a longitudinal direction parallel to the extending direction of the corresponding side, and another pair of opposing two sides. The pressure detection unit 4 arranged in the vicinity has its longitudinal direction orthogonal to the extending direction of the corresponding side. Since the stress sensitivity characteristic in the pressure detector 4 varies depending on the direction of current flow in the piezoresistor and the direction in which the stress is applied, the two pairs of pressure detectors 4 arranged in the diaphragm 3 are connected in a Wheatstone bridge. Thus, the pressure can be measured accurately with high sensitivity.

  Although such a piezoresistive pressure sensor has a problem that it is easily affected by temperature, this problem can be easily solved by providing a simple temperature compensation circuit, and a normal semiconductor device manufacturing process is used. In addition, it has the advantage that high sensitivity, small size, and low cost can be easily achieved by applying the current semiconductor microfabrication technology.

  For piezoresistive pressure sensors, further efforts are being made to improve detection sensitivity. For example, in Patent Document 1, as shown in FIGS. 7A to 7D, a thick film region 7 having a relatively large film thickness and a thin film region 6 having a relatively small film thickness are provided in the diaphragm. A structure is disclosed in which stress is concentrated on the piezoresistive pressure detector 4 by disposing the piezoresistive pressure detector 4 in the thick film region 7. Although the thickness of the semiconductor substrate in the thick film region 7 is thicker than that in the thin film region 6, it is sufficiently thinner than the thickness of the semiconductor substrate in the portion of the support frame around the diaphragm.

  FIGS. 7A to 7D each correspond to an embodiment in which the shape of the thick film region 7 is made different, and only the diaphragm portion is shown. The hatched portion is the thick film region 7, and the non-hatched portion is the thin film region 6. In the case shown in FIG. 7A, a thick film region 7 is formed in a substantially square shape at the center portion of the diaphragm, and each of the center portion of each side of the square thick film region 7 and the outer periphery of the diaphragm is formed. The central part of each side is connected by the thick film region 7. In FIG. 7B, the thick film region 7 is formed in a cross shape so as to connect the central portions of the opposing sides of the outer periphery of the diaphragm. In FIG. 7C, the thick film region 7 is formed in a single character so as to connect the central portions of a pair of opposing sides on the outer periphery of the diaphragm. In FIG. 7D, a thick film region 7 is formed from the center of a pair of opposing sides on the outer periphery of the diaphragm toward the center of the diaphragm.

In addition, in a piezoresistive pressure sensor, a trapezoidal (mesa-type) protrusion may be provided in the central region on the back side of the diaphragm in order to improve detection linearity. The mesa-shaped projecting portion can be provided in the shape of a quadrangular pyramid by applying anisotropic etching to the silicon semiconductor substrate during the formation of the diaphragm. At this time, as shown in FIG. There is a problem in that the corner drop portions 9 are formed at the four corners, and the shape is not a strict quadrangular pyramid shape. In FIG. 8, in the mesa portion 8 composed of the inclined surface 8a and the top surface 8b, a corner drop portion 9 occurs at a portion that becomes a ridge line between the adjacent inclined surfaces 8a. Therefore, in Patent Document 2, an etching mask 31 as shown in FIG. 9 is used as an etching mask when anisotropic etching is performed on a silicon semiconductor substrate, and a mesa portion is formed in an octagonal truncated pyramid shape. It is disclosed. In FIG. 9, an opening 32 is formed in the etching mask 31.
JP 2002-71492 A Japanese Patent Laid-Open No. 7-209121

In the standard piezoresistive pressure sensor 20 using the diaphragm having a substantially square planar shape shown in FIGS. 6A and 6B and having no mesa portion in the diaphragm, one side of the diaphragm 3 is used. It is known that the maximum stress generated in the diaphragm 3 is proportional to (h / a) ² where h is the length of and the thickness of the diaphragm 3 is a. From this equation, it can be seen that in order to increase the maximum stress and improve the detection sensitivity, the length h of one side of the diaphragm should be increased or the thickness a should be decreased. In order to reduce the size of the pressure sensor, the length h of one side cannot be increased. Therefore, in order to improve the detection sensitivity of the pressure sensor without increasing the formation area of the diaphragm 3, It is necessary to reduce the thickness a of the diaphragm 3. However, when the thickness a of the diaphragm 3 is reduced, the mechanical strength of the diaphragm 3 is lowered.

  Even when the thick film region and the thin film region are provided in the diaphragm as shown in FIGS. 7A to 7D, if the proportion of the thin film region 7 in the diaphragm is increased in order to promote stress concentration. The mechanical strength of the diaphragm 3 itself is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoresistive pressure sensor capable of improving detection sensitivity without increasing the diaphragm formation region or reducing the thickness of the diaphragm.

  The piezoresistive pressure sensor of the present invention includes a diaphragm, a support frame that supports the diaphragm on the outer periphery of the diaphragm and is formed relatively thicker than the diaphragm, and is distorted by deformation of the diaphragm caused by pressure applied to the diaphragm. A piezoresistive pressure sensor including a piezoresistive pressure detector that detects pressure as an electric quantity is characterized in that a part of the support frame forms a protruding portion that protrudes toward the diaphragm.

  In the present invention, it is preferable that the piezoresistive pressure detector is provided corresponding to the protrusion. In that case, (1) the piezoresistive pressure detector may be formed on the diaphragm and in the vicinity of the protruding portion, or (2) the piezoresistive pressure detecting portion protrudes from the diaphragm. It may be formed so as to straddle the part, or (3) at least a part of the formation region of the piezoresistive pressure detection part may be arranged at the position of the protruding part.

  The shape of the diaphragm is not particularly limited, and may be a square or rectangular planar shape or a circular shape. In the case of using a square or rectangular planar diaphragm, it is preferable that the protruding portion protrudes from the central portion of at least one side of the diaphragm, and further, the protruding portion respectively protrudes from the central portion of each side of the diaphragm. It is preferable that the piezoresistive pressure detection unit is arranged so as to protrude.

  The shape of the protrusion is not particularly limited, but the protrusion length of the protrusion toward the center of the diaphragm is Y, the width of the protrusion in the direction perpendicular to the protrusion length is X, and the length of the side of the diaphragm Where h is the thickness of the diaphragm and a is the area where a / h is 0.03 or less, X is preferably 0.15 h or less, Y is preferably 0.1 h or less, and X is 0.05 h or less. , Y is more preferably 0.1 h or less.

  In the present invention, the diaphragm has the first uniform thickness, and the support frame including the protrusions is provided at the second uniform thickness at least in the peripheral region of the diaphragm. It is preferable.

  According to the present invention, in the piezoresistive pressure sensor, by projecting the support frame from the side of the diaphragm toward the center of the diaphragm, the thickness of the diaphragm is kept substantially constant, and the strength of the diaphragm is maintained. Stress can be concentrated around the part. By disposing the piezoresistive pressure detector in such a stress concentration region, it is possible to improve detection sensitivity and output linearity without increasing the diaphragm formation region.

  Reference is now made to the drawings for preferred embodiments of the invention. Each of the embodiments and examples described below is a preferable specific example of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these forms.

  1A and 1B are a top view and a plan view, respectively, showing the structure of a piezoresistive pressure sensor according to an embodiment of the present invention.

  The illustrated piezoresistive pressure sensor 20 uses a semiconductor substrate made of, for example, silicon. The hollow portion 2 is formed from the back side of the semiconductor substrate, and the semiconductor substrate on the upper surface of the hollow portion 2 is a diaphragm. It is set to be 3. The portion surrounding the diaphragm 3 is configured as a support frame 1 for the diaphragm 3 because the semiconductor substrate is thicker than the area of the diaphragm 3 so as not to be the hollow portion 2. The support frame 1 has a uniform thickness at least in a region surrounding the diaphragm 3. Although not shown here, a protective film is formed on the entire surface of the semiconductor substrate including the area of the diaphragm 3 and the support frame 1.

  The diaphragm 3 has a rectangular or square planar shape, but unlike the one shown in FIGS. 6A and 6B, the support frame 1 is located at the center of the diaphragm 3 at substantially the center of each side of the diaphragm 3. As the shape of the diaphragm 3 itself, the central part of each side recedes toward the center. In the protruding portion 10 toward the center of the diaphragm 3, the thickness of the support frame 1 is the same as the thickness of the support frame 1 in the region other than the protruding portion 10 that surrounds the diaphragm 3. Such a protruding portion 10 can be provided by preventing the region corresponding to the protruding portion 10 from being etched away when the hollow portion 2 is formed on the back side of the semiconductor substrate by etching or the like. In the illustrated example, the protruding shape of the protruding portion 10 toward the center of the diaphragm 3 is a rectangular shape, the protruding length (the length of the protruding portion 10 extending from the side of the diaphragm 3 toward the center) is Y, and the protruding width ( The length of the side of the diaphragm 3 where the protruding portion 10 is formed is represented by X. Note that the side of the diaphragm 3 refers to the side as a square or a rectangle because the diaphragm 3 is a square or a rectangle when the protruding portion 10 is not provided. Although depending on the application and the measurement range of pressure, the length of one side of the diaphragm 3 is, for example, about 100 to 400 μm, and the thickness is, for example, about 1 to 10 μm.

  The protruding portion 10 in the support frame 1 is for concentrating stress on a region in the vicinity of the protruding portion 10 while keeping the thickness of the diaphragm 3 substantially constant and maintaining the strength of the diaphragm 3. Therefore, pressure detection portions 4a and 4b made of piezoresistance (diffusion resistance) are provided on the surface of the semiconductor substrate at a position where stress will concentrate corresponding to the formation region of the protrusion 10. The pressure detection unit 4a is provided corresponding to each of the protrusions 10 of the support frame from the left side and the right side of the diaphragm 3 toward the diaphragm, and the pressure detection unit 4b is formed from the upper side and the lower side of the diaphragm 3 in the drawing. Are provided corresponding to the protrusions 10 of the support frame toward the front. These pressure detectors 4a and 4b are for detecting pressure as an electric signal by being distorted by deformation of the diaphragm 3, and are connected by Wheatstone bridge by a circuit pattern (not shown).

  In the piezoresistive pressure sensor described above, a part of the support frame 1 is projected as the projecting portion 10 in the direction of the diaphragm 3 so that stress is concentrated in the region where the projecting portion 10 is formed. By disposing the resistance-type pressure detection unit, it is possible to improve the pressure detection sensitivity without increasing the diaphragm formation region with respect to the semiconductor substrate.

  Next, the manufacturing process of such a piezoresistive pressure sensor will be described with reference to FIGS. A semiconductor substrate 30 made of silicon or the like is prepared, and the piezoresistive pressure detector 4 is formed on the surface of the semiconductor substrate 30 by ion implantation and heat treatment, as shown in FIG. Next, as shown in FIG. 2B, the silicon at the position of the hollow portion 2 is removed from the back surface of the semiconductor substrate 30 by anisotropic wet etching or RIE (Reactive Ion Etching). Part 2 is formed. At that time, as a matter of course, the support frame 1 including the protruding portion 10 is not removed by etching. Thereafter, a piezoresistive pressure sensor is completed by providing a wiring pattern (not shown) and a protective film (not shown).

  In the above description, the protruding portions of the support frame 1 are provided corresponding to all four sides of the square or rectangular diaphragm, but the present invention is not limited to this. If at least one projecting portion for concentrating stress is provided and the piezoresistive pressure detecting unit is provided corresponding to the projecting portion, in other words, in a region where stress is concentrated by the projecting portion, The goal is achieved. In this case, when there are a plurality of piezoresistive pressure detectors disposed in the vicinity of the diaphragm, it is sufficient that at least one of them corresponds to the protruding portion.

  The shape of the protruding portion of the support frame is not limited to a rectangle, and the support frame can protrude in the center direction of the diaphragm, for example, in a semicircular shape or a bow shape. Further, the planar shape of the diaphragm itself is not limited to the above-described one. For example, in a circular or elliptical diaphragm, a projecting portion toward the center of the diaphragm may be provided at one or more locations on the circumference.

  Pressure detector 4a. Also for 4b, U-shaped or U-shaped piezoresistors can be used in addition to linear piezoresistors (diffusion resistors).

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
In the piezoresistive pressure sensor shown in FIGS. 1A and 1B described above, the shape of the diaphragm 3 (when no protrusion is provided) is a square, the length of the side is h, and the diaphragm 3 Assuming that the thickness of the semiconductor substrate at a is a, if a / h is sufficiently small, the maximum stress generated in the piezoresistive pressure sensor when a pressure difference occurs between both surfaces of the diaphragm 3 is the protrusion 10. Is generated near the boundary between the diaphragm 3 and the diaphragm 3. In the first embodiment, each of the pressure detection units 4a and 4b is configured such that a part or all of the region as a single pressure detection unit is formed in a diaphragm region adjacent to the protruding portion 10. ing. Specifically, with respect to a pair of opposing sides of the diaphragm 3, each of the pressure detection units 4 a extending in a direction orthogonal to the extending direction of the sides straddles the protruding portion 10 made of the support frame and the diaphragm 3. Is formed. Further, with respect to the other pair of opposing sides of the diaphragm 3, the pressure detection unit 4 b extending in a direction parallel to the extending direction of those sides is in the vicinity of the tip of the protruding portion 10 and inside the diaphragm 3. Formed in position.

  By adopting such a configuration, the thickness of the semiconductor substrate in the region of the diaphragm 3 is substantially uniform, so that the detection sensitivity is improved without increasing the diaphragm formation region while preventing the strength from being lowered. be able to.

  Here, in the piezoresistive pressure sensor having the structure shown in FIGS. 1A and 1B and using a square diaphragm having a side length of 100 μm and a thickness of 1.5 μm, a supporting frame The detection sensitivity was compared between the case where no protrusion was provided and the case where it was provided. When the protrusion 10 of the support frame is provided, the protrusion 10 has a rectangular shape as shown in FIGS. 1A and 1B, the width X is 10 μm, and the length Y is 5 μm. As a result, when the protrusion was provided, the pressure detection sensitivity was improved by 30% compared to the case where the protrusion was not provided.

Example 2
3A and 3B show the piezoresistive pressure sensor 20 according to the second embodiment of the present invention. The piezoresistive pressure sensor of the second embodiment has the same structure as the pressure sensor of the first embodiment, but the formation positions of the pressure detection units 4a and 4b are slightly different.

  In the piezoresistive pressure sensor shown in FIGS. 1A and 1B described above, the shape of the diaphragm 3 (when no protrusion is provided) is a square, the length of the side is h, and the diaphragm 3 Assuming that the thickness of the semiconductor substrate in a is a, if a / h is increased, the maximum stress generated in the piezoresistive pressure sensor when a pressure difference occurs between both surfaces of the diaphragm 3 is generated. Shifts from a position on the diaphragm 3 to a position on the protrusion 10 of the support frame. Therefore, in the piezoresistive pressure sensor 20 shown in FIGS. 3A and 3B, each of the piezoresistive pressure detectors 4a and 4b is a part of one pressure detector or All the regions are arranged in the region of the protrusion 10. Specifically, with respect to a pair of opposing sides of the diaphragm 3, each of the pressure detectors 4 a extending in a direction orthogonal to the extending direction of the sides is formed so as to straddle the protruding portion 10 and the diaphragm 3. Yes. In addition, with respect to the other pair of opposing sides of the diaphragm 3, the pressure detection unit 4 b extending in a direction parallel to the extending direction of those sides is also formed so as to straddle the protruding portion 10 and the diaphragm 3. .

  By adopting such a configuration, the thickness of the semiconductor substrate in the region of the diaphragm 3 is substantially uniform, so that the detection sensitivity is improved without increasing the diaphragm formation region while preventing the strength from being lowered. be able to. This piezoresistive pressure sensor can also be manufactured by the manufacturing method described above with reference to FIGS.

  Here, in the piezoresistive pressure sensor having the structure shown in FIGS. 3A and 3B and using a square diaphragm having a side length of 100 μm and a thickness of 1.5 μm, a supporting frame The detection sensitivity was compared between the case where no protrusion was provided and the case where it was provided. When the protrusion 10 of the support frame is provided, the protrusion 10 has a rectangular shape as shown in FIGS. 1A and 1B, the width X is 10 μm, and the length Y is 5 μm. As a result, when the protrusion was provided, the pressure detection sensitivity was improved by 20% compared to the case where the protrusion was not provided.

Example 3
4A and 4B show a piezoresistive pressure sensor 20 according to a third embodiment of the present invention. As in the pressure sensor of the second embodiment, each of the piezoresistive pressure detectors 4a and 4b is a part of a piezoresistive pressure sensor according to the third embodiment. All the regions are arranged in the region of the protrusion 10. However, unlike the second embodiment, in the piezoresistive pressure sensor of the third embodiment, with respect to a pair of opposing sides of the diaphragm 3, a pressure detection unit 4a extending in a direction orthogonal to the extending direction of those sides. Is formed so as to straddle the protruding portion 10 and the main body portion of the support frame 1 other than the protruding portion 10. Further, with respect to the other pair of opposing sides of the diaphragm 3, the pressure detection unit 4 b extending in a direction parallel to the extending direction of those sides is formed at a position in the protruding portion 10.

  By adopting such a configuration, the thickness of the semiconductor substrate in the region of the diaphragm 3 is substantially uniform, so that the detection sensitivity is improved without increasing the diaphragm formation region while preventing the strength from being lowered. be able to. This piezoresistive pressure sensor can also be manufactured by the manufacturing method described above with reference to FIGS.

  Here, in the piezoresistive pressure sensor having the structure shown in FIGS. 4A and 4B and using a square diaphragm having a side length of 100 μm and a thickness of 1.5 μm, a supporting frame The detection sensitivity was compared between the case where no protrusion was provided and the case where it was provided. When the protrusion 10 of the support frame is provided, the protrusion 10 has a rectangular shape as shown in FIGS. 1A and 1B, the width X is 10 μm, and the length Y is 5 μm. As a result, when the protrusion was provided, the pressure detection sensitivity was improved by 20% compared to the case where the protrusion was not provided.

Example 4
In the piezoresistive pressure sensor shown in the first embodiment, when the length of the diaphragm side is h and the thickness is a, the width of the protrusion 10 of the support frame 1 in a region where a / h is 0.03 or less. x, the protrusion length y, and the degree of stress concentration due to the protrusion 10 were examined based on simulation. FIG. 5 shows that when a / h = 0.03 (= 3/100), the maximum stress generated in the diaphragm 3 is compared with the case where the protrusion 10 is not provided when the protrusion 10 is provided. The ratio of how many times the maximum stress increases. Here, the width x and the length y of the protrusion 10 are expressed with the length h of the side of the diaphragm as a unit. As is apparent from the graph of FIG. 5, the width x of the protrusion 10 is 0.15 h or less and the length y is 0.1 h or less, compared with the case where a part of the support frame is not protruded. A maximum stress of 0 to 2.0 times occurs. In particular, by setting the width x of the protrusion 10 to 0.05 h or less and the length y to 0.1 h or less, a stress that is 1.4 to 2.0 times that of the case where no protrusion is provided is generated. . If a / h is further smaller than 0.03, it is considered that the stress concentration due to the provision of the protruding portion 10 extending from the support frame 1 toward the center of the diaphragm 3 becomes more remarkable.

  Even when the shape of the diaphragm is a rectangle, when a / h is 0.03 or less, when the length of the side of the projection provided for a side is h, the width x of the projection is It is preferable that the length y is 0.15 h or less, the width x is 0.05 h or less, and the length y is 0.1 h or less.

  When the shape of the protrusion is semicircular or bowed, the width of the protrusion at the side of the diaphragm 3 when the protrusion is not provided is the width x, and the position of the side is Assuming that the maximum protruding length of the protruding portion protruding in the center direction of the diaphragm is the length y, when the a / h is 0.03 or less, the width x is 0.15 h or less and the length y is 0. Preferably, the width x is 0.05 h or less, and the length y is 0.1 h or less.

(A), (b) is the top view and sectional drawing of the piezoresistive type pressure sensor of one Embodiment of this invention, respectively. (A), (b) is sectional drawing which shows sequentially the manufacturing process of the piezoresistive type pressure sensor shown in FIG. (A), (b) is the top view and sectional drawing of the piezoresistive type pressure sensor of Example 2, respectively. (A), (b) is the top view and sectional drawing of the piezoresistive type pressure sensor of Example 3, respectively. It is a graph which shows the relationship between the shape of the protruded support frame, and the maximum stress which generate | occur | produces in a piezoresistive type pressure sensor. (A), (b) is the top view and sectional drawing of the conventional piezoresistive type pressure sensor, respectively. (A)-(d) are all the top views of the piezoresistive type pressure sensor disclosed by Unexamined-Japanese-Patent No. 2002-71492. It is a figure which shows the angle drop in a mesa part in the conventional piezoresistive type pressure sensor which has a mesa part. It is a top view which shows the etching mask used in order to manufacture the piezoresistive type pressure sensor which has a mesa part disclosed by Unexamined-Japanese-Patent No. 7-209121.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support frame 2 Hollow part 3 Diaphragm 4, 4a, 4b Piezoresistive type pressure detection part 5 Protective film 6 Thin film area 7 Thick film area 8 Mesa part 9 Corner drop part 10 Protrusion part 20 Piezoresistive type pressure sensor 30 Semiconductor substrate 31 Etching Mask 32 opening

Claims (12)

A diaphragm, a support frame that supports the diaphragm on the outer periphery of the diaphragm, and is formed relatively thicker than the diaphragm; and the pressure is converted into an electric quantity by being distorted by deformation of the diaphragm caused by pressure applied to the diaphragm. In a piezoresistive pressure sensor equipped with a piezoresistive pressure detector that detects as
A piezoresistive pressure sensor characterized in that a part of the support frame forms a protruding portion protruding toward the diaphragm.   2. The piezoresistive pressure sensor according to claim 1, wherein at least one piezoresistive pressure detector is provided corresponding to the protrusion. 3.   3. The piezoresistive pressure sensor according to claim 1, wherein the diaphragm has a square or rectangular planar shape, and the protruding portion protrudes from a central portion of at least one side of the diaphragm. The diaphragm has a square or rectangular planar shape, and the protrusions protrude from the center of each side of the diaphragm,
2. The piezoresistive pressure sensor according to claim 1, wherein the piezoresistive pressure detector is disposed for each of the protrusions.   The protrusion length of the protrusion toward the center of the diaphragm is Y, the width of the protrusion in the direction orthogonal to the protrusion length is X, the side length of the diaphragm is h, and the thickness of the diaphragm is 5. The piezoresistive pressure sensor according to claim 1, wherein as a, a / h is 0.03 or less, X is 0.15 h or less, and Y is 0.1 h or less. .   The piezoresistive pressure sensor according to claim 5, wherein X is 0.05 h or less and Y is 0.1 h or less.   The piezoresistive pressure sensor according to any one of claims 1 to 6, wherein at least one of the piezoresistive pressure detection units is formed at a position on the diaphragm and in the vicinity of the protrusion.   The piezoresistive pressure sensor according to any one of claims 1 to 6, wherein at least one of the piezoresistive pressure detectors is formed so as to straddle the diaphragm and the protrusion.   The piezoresistive pressure sensor according to any one of claims 1 to 6, wherein at least a part of a formation region of at least one of the piezoresistive pressure detectors is disposed at the position of the protrusion.   10. The piezoresistive pressure sensor according to claim 1, wherein the support frame including the protruding portion and the diaphragm are formed of a semiconductor substrate. 11.   The piezoresistive pressure detector is formed on one main surface of the semiconductor substrate, a hollow portion is formed on the other main surface of the semiconductor substrate, and a peripheral edge of the hollow portion is configured as the support frame. The piezoresistive pressure sensor according to claim 10, wherein an upper surface of the part is configured as the diaphragm.   The diaphragm has a first uniform thickness, and the support frame is provided with a second uniform thickness including the protrusions at least in a peripheral region of the diaphragm. The piezoresistive pressure sensor according to any one of Items 11 to 11.

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