JP2008045911A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor which can be used even under high-pressure environments, by preventing the separation between a semiconductor substrate and a support substrate and preventing damages to a diaphragm. <P>SOLUTION: In the cross section along the thickness direction N of the semiconductor substrate 11, inner surfaces 13a, 13b of a cavity section 13 of the semiconductor substrate 11 and a surface 12a of the support substrate 12 that adjoins an angle θ, respectively. The angles θ form an acute angle so that they face each other, directed toward the inside S of the cavity section 13. In the present embodiment, for example, the inner surfaces 13a, 13b form a tapered shape, in which the angle θ gradually decreases from a direction along the thickness direction N of the semiconductor substrate 11 in a direction along the surface 12a of the support substrate 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure sensor using a substrate made of a semiconductor.

  As a small and high-precision pressure sensor, for example, a diaphragm made by thinning a part of a semiconductor substrate such as a silicon wafer is formed, and a pressure sensitive element such as a strain gauge is arranged on the diaphragm to change the pressure sensitive element. 2. Description of the Related Art A semiconductor pressure sensor that detects a pressure applied to a diaphragm by measurement is known.

  Such a semiconductor pressure sensor is obtained by bonding a semiconductor substrate having a diaphragm to a supporting substrate (pedestal) such as glass. However, when the semiconductor substrate and the supporting substrate are easily peeled off and a strong pressure is applied to the diaphragm depending on the use environment. There is a problem that the pressure sensor is easily damaged.

In response to the problem of peeling between the semiconductor substrate and the support substrate due to excessive pressure, for example, in the invention described in Patent Document 1, the boundary portion between the side surface of the concave portion of the semiconductor substrate and the top surface forming the diaphragm portion is rounded. In addition, a semiconductor pressure sensor is described in which the angle of the joint between the side surface of the recess and the support substrate (pedestal) is 80 ° or more.
JP 2001-343299 A

  However, in the semiconductor pressure sensor having the structure described in Patent Document 1, the effect of suppressing the stress applied to the joint portion between the semiconductor substrate and the support substrate is limited, and the breakdown pressure of the joint portion is limited to about 10 MPa. . For this reason, the environment in which the semiconductor pressure sensor can be used is limited, and a semiconductor pressure sensor that can withstand pressure detection under a higher pressure environment is desired.

  The present invention has been devised in view of the above circumstances, and provides a semiconductor pressure sensor that can be used even in a high-pressure environment by preventing separation between a semiconductor substrate and a support substrate and damage to a diaphragm portion. With the goal.

According to a first aspect of the present invention, there is provided a semiconductor pressure sensor according to the first aspect of the present invention, wherein a concave portion is formed from one surface of the semiconductor substrate toward the other surface, and a portion of the semiconductor substrate is thinned, and the diaphragm portion is disposed on the diaphragm portion. A pressure sensor, a support substrate bonded to one surface of the semiconductor substrate, and an opening penetrating the support substrate toward the recess,
In a cross section along the thickness direction of the semiconductor substrate, an angle between an inner surface of the recess and one surface of the support substrate bonded to one surface of the semiconductor substrate forms an acute angle toward the inner side of the recess. It is characterized by.
A semiconductor pressure sensor according to a second aspect of the present invention is the semiconductor pressure sensor according to the first aspect, wherein the concave portions are opposed to each other between inner surfaces facing each other between one surface of the semiconductor substrate and a top surface of the concave portion forming the diaphragm portion. It is characterized in that it has a shape that maximizes the width.
According to a third aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, the angle of the inner surface of the concave portion with respect to the one surface of the support substrate gradually decreases as the inner surface of the concave portion approaches the other surface of the semiconductor substrate. To do.
A semiconductor pressure sensor according to a fourth aspect of the present invention is the semiconductor pressure sensor according to the first aspect, wherein the support substrate is a glass substrate.

  According to the present invention, the inner surface of the concave portion on one surface of the semiconductor substrate forms an acute angle so as to face each other on the one surface of the support substrate, so that the inner surface of the concave portion is added to the portion in contact with the one surface of the support substrate. The pressure in the concave portion is dispersed, and a part of the pressure acts in the direction of pressing the semiconductor substrate toward the support substrate. Therefore, even if a strong pressure is applied to the inside of the recess through the opening, the force that presses the semiconductor substrate toward the support substrate acts at the portion where the inner surface of the recess contacts the support substrate, so that the semiconductor substrate peels off from the support substrate. Can be effectively prevented.

  Hereinafter, an embodiment of a semiconductor pressure sensor according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a semiconductor pressure sensor of the present invention. The semiconductor pressure sensor 10 of the present invention has a semiconductor substrate 11 and a support substrate 12. The semiconductor substrate 11 is bonded to the one surface 12a of the support substrate 12 at one surface 11a.

  A recess 13 is formed in the semiconductor substrate 11 from the one surface 11a toward the other surface 11b. A region where the semiconductor substrate 11 is thinned by the formation of the concave portion 13 is a diaphragm portion 14. The diaphragm portion 14 in which the semiconductor substrate 11 is thinned is bent by the pressure fluctuation inside the recess 13.

  A pressure sensitive element 15 is disposed on the other surface 11 b side of the semiconductor substrate 11. The pressure sensitive element 15 detects the pressure in the recess 13 by changing the output signal according to the degree of curvature of the diaphragm portion 14.

  In the cross section along the thickness direction N of the semiconductor substrate 11, the inner side surfaces 13 a and 13 b of the recess 13 of the semiconductor substrate 11 and the one surface 12 a of the support substrate 12 are in contact with each other at an angle θ. An acute angle is formed so as to face each other toward S. For example, in the present embodiment, the inner side surfaces 13 a and 13 b are tapered so that the angle θ gradually decreases from the direction along the thickness direction N of the semiconductor substrate 11 toward the direction along the one surface 12 a of the support substrate 12. Is made.

  The support substrate 12 is bonded to the one surface 12 a of the semiconductor substrate 11 and closes the open end side of the recess 13. An opening 16 penetrating between the one surface 12 a and the other surface 12 b is formed in the support substrate 12 toward the recess 13. By this opening 16, the inner side S of the recess 13 is connected to the outside air.

  According to the semiconductor pressure sensor 10 of the present invention having such a configuration, when the external pressure connected to the opening 16 of the support substrate 12 increases, the internal pressure of the inside S of the recess 13 also increases through the opening 16. Then, the diaphragm portion 14 in which a part of the semiconductor substrate 11 is thinned is curved toward the other surface 12b side of the semiconductor substrate 11 as indicated by a dotted line F in FIG. When the diaphragm portion 14 is bent, the output signal of the pressure-sensitive element 15 disposed in the vicinity of the diaphragm portion 14 changes according to the degree of bending of the diaphragm portion 14. By detecting the change in the output signal of the pressure-sensitive element 15, the pressure inside the recess 13, that is, the external pressure connected to the recess 13 through the opening 16 can be detected.

  When the pressure on the inner side S of the recess 13 is increased, the pressure applied to the top surface 13c, which is the inner wall of the recess 13 on the diaphragm 14 side, acts in a direction in which the semiconductor substrate 11 and the support substrate 12 are peeled off. However, in the semiconductor pressure sensor 10 of the present invention, the inner side surfaces 13 a and 13 b of the recess 13 on the one surface 11 a side of the semiconductor substrate 11 form an acute angle so as to face each other with respect to the one surface 12 a of the support substrate 12. Thus, as shown in FIG. 1B, the pressure P of the recess 13 applied to the portion where the inner side surfaces 13a and 13b of the recess 13 are in contact with the one surface 12a of the support substrate 12 is divided into two components in the x direction and the y direction. be able to.

  The x-direction component of the pressure P does not act in the direction in which the semiconductor substrate 11 and the support substrate 12 are peeled off, and the y-direction component of the pressure P is in the direction in which the semiconductor substrate 11 is pressed toward the support substrate 12. Works. Therefore, even if a strong pressure is applied to the inner side S of the recess 13 through the opening 16, a force is exerted to press the semiconductor substrate 11 toward the support substrate 12 at the portion where the inner side surfaces 13 a and 13 b of the recess 13 are in contact with the support substrate 12. Therefore, it can prevent effectively that the semiconductor substrate 11 peels from the support substrate 12. FIG.

  The semiconductor substrate 11 may be composed of, for example, a silicon wafer. Moreover, the support substrate 13 should just be formed from the glass substrate etc., for example. For the bonding between the semiconductor substrate 11 and the support substrate 13, various bonding methods such as anodic bonding and bonding with an adhesive layer can be used.

  As the pressure sensitive element 15, various pressure detecting elements such as a strain gauge sensor can be used. Moreover, the installation location of the pressure-sensitive element 15 protrudes on the other surface 11b of the semiconductor substrate 11, for example, besides being embedded in the other surface 11b of the semiconductor substrate 11 in the vicinity of the diaphragm portion 14 as in the above-described embodiment. As long as it is a position where the bending of the diaphragm portion 14 can be detected, such as forming in such a manner, it may be installed at any position.

  As shown in FIG. 1, it is preferable that the intersecting portion between the top surface 13c of the recess 13 and the inner side surfaces 13a and 13b has a tapered shape. Thereby, by dispersing the pressure applied to the diaphragm portion 14, even when a strong pressure is applied to the inner side S of the recess 13, it is possible to prevent the diaphragm portion 14 having a thin strength of the semiconductor substrate 11 from being damaged.

  As shown in FIG. 1, the inner side S of the recess 13 has a width t1 between the inner side surfaces 13a and 13b facing each other between the one surface 11a of the semiconductor substrate 11 and the top surface 13c of the recess 13 forming the diaphragm portion 14. Preferably it is maximized. That is, the recess 13 may be formed in a shape such that the width t1 between the inner side surfaces 13a and 13b in the middle of the recess 13 is greater than the width t2 of the one surface 11a and the width t3 of the top surface 13a. Thereby, it is possible to prevent an excessive pressure from being applied to a portion where the inner side surfaces 13 a and 13 b of the recess 13 intersect with the top surface 13 c and the one surface 12 a of the support substrate 12, thereby improving the pressure resistance of the recess 13.

  The angle θ formed by the inner side surfaces 13a and 13b of the recess 13 and the one surface 12a of the support substrate 12 may be an acute angle, but may preferably be set in a range of 60 ° to 89 °. When the angle θ is 60 ° or less, the stress relaxation effect between the semiconductor substrate 11 and the support substrate 12 is almost saturated. Further, as the angle θ becomes smaller, the concave portion 13 spreads and the semiconductor substrate 11 becomes larger. For these reasons, the angle θ is preferably set in the range of 60 ° to 89 °.

  The shape of the concave portion in the semiconductor pressure sensor of the present invention is not limited to a tapered shape in which a portion where the support substrate and the top surface and the inner surface are in contact with each other is curved as viewed from the cross section as in the above-described embodiment. For example, in the semiconductor pressure sensor 20 shown in FIG. 2, the inner surfaces 23a and 23b of the recess 23 of the semiconductor substrate 21 are refracted in the middle to form a substantially hexagonal shape, and the inner surfaces 23a and 23b are supported. A portion in contact with one surface 22a of the substrate 22 is an inclined surface in which the angle θ forms an acute angle.

  Further, for example, in the semiconductor pressure sensor 30 shown in FIG. 3, a cross section in which the inner side surfaces 33 a and 33 b of the recess 33 of the semiconductor substrate 31 are curved toward the middle forms a barrel shape, and the inner side surfaces 33 a and 33 b A portion in contact with the one surface 32a of the support substrate 32 forms a taper where the angle θ gradually decreases. Even with such a configuration, it is possible to increase the pressure resistance of the recess 33 and to distribute the pressure acting in the direction in which the semiconductor substrate 31 and the support substrate 32 are peeled off.

Next, a method for forming a recess in a semiconductor substrate constituting such a semiconductor pressure sensor will be exemplified. As shown in FIG. 4A, first, the pressure sensitive element 52 is formed on the other surface 51b of the semiconductor substrate 51 such as a silicon wafer. Next, as shown in FIG. 4B, a diaphragm portion is formed from one surface 51a of the semiconductor substrate 51 by alternately performing plasma etching using SF ₆ gas and forming a protective film using C ₄ F ₈ gas. . At this time, the etching hole 53 is formed from the one surface 51a of the semiconductor substrate 51 toward the other surface 51b by gradually reducing the protective film formation time by the C ₄ F ₈ gas with respect to the plasma etching time by the SF ₆ gas. Increase the width W.

When the etching of the semiconductor substrate 51 reaches the middle of the thickness direction N of the semiconductor substrate, this time, the protective film formation time is increased stepwise by the C ₄ F ₈ gas with respect to the plasma etching time by the SF ₆ gas. As a result, as shown in FIG. 4C, the width W of the etching hole 53 is reduced toward the other surface 51 b of the semiconductor substrate 51. As described above, when the etching with SF ₆ gas plasma and the formation of the protective film with C ₄ F ₈ gas plasma are alternately performed, the respective processing times are changed stepwise so that the inner side surfaces 54a and 54b facing each other. It is possible to obtain the concave portion 54 having an inner surface shape in which the width W of each other changes in the thickness direction N of the semiconductor substrate.

  In addition, the formation of the concave portion 54 forms a diaphragm portion 56 in which the semiconductor substrate 51 is thinned. Thereafter, a support substrate having an opening formed in advance is bonded to one surface 51 a of the semiconductor substrate 51, thereby forming an acute angle so that the inner side surfaces 54 a and 54 b and one surface of the support substrate face each other toward the inside of the recess 54. The recessed portion 54 can be formed.

In addition to the above-described embodiment, for example, a thick film resist having a thickness of about several tens of μm is prepared as a mask material at the time of diaphragm etching, and the formation of such a recess is intentionally performed using SF ₆ + O ₂ gas or the like. Etching in the width direction of the semiconductor substrate by performing an etching by a non-Bosch process for forming a concave portion having a shape as shown in FIG. 3, for example, by doping to an arbitrary depth in the thickness direction of the semiconductor substrate A method such as changing the rate midway may be used.

It is sectional drawing which shows an example of the semiconductor pressure sensor which concerns on this invention. It is sectional drawing which shows another example of the semiconductor pressure sensor which concerns on this invention. It is sectional drawing which shows another example of the semiconductor pressure sensor which concerns on this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor pressure sensor which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor pressure sensor, 11 Semiconductor substrate, 12 Support substrate, 13 Recessed part, 13a, 13b Inner side surface (recessed part), 14 Diaphragm part, 15 Pressure sensitive element, 16 Opening.

Claims (4)

Semiconductor substrate, diaphragm portion having concave portion arranged from one surface of semiconductor substrate toward other surface, and thinned region in part of semiconductor substrate, pressure-sensitive element arranged in diaphragm portion, and semiconductor A semiconductor pressure sensor comprising at least a support substrate bonded to one surface of the substrate and having an opening penetrating toward the recess,
The semiconductor substrate is characterized in that an angle θ formed by an inner surface of the recess and one surface of the support substrate bonded to one surface of the semiconductor substrate is an acute angle in a cross section along the thickness direction thereof. Pressure sensor.   2. The semiconductor pressure sensor according to claim 1, wherein the recess has a shape in which a width between inner side surfaces facing each other in the intermediate region is maximized.   2. The semiconductor pressure sensor according to claim 1, wherein an end portion of the semiconductor composed of an inner surface of the concave portion and one surface of the support substrate has a tapered shape when viewed from a cross-sectional direction thereof. The semiconductor pressure sensor according to claim 1, wherein the support substrate is a glass-based member.

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