JP2013124947A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor capable of easily measuring thickness of a diaphragm after forming the diaphragm.SOLUTION: The semiconductor pressure sensor having a diaphragm 50 composed of a semiconductor and capable of detecting pressure applied to the diaphragm 50 includes a resistor part formed from the upper surface up to the lower surface of the diaphragm 50 and a plurality of electrodes respectively electrically connected to the resistor part and exposed to the outside.

Description

  The present invention relates to a semiconductor pressure sensor that detects a pressure applied to a diaphragm.

  A semiconductor pressure sensor is known in which a Wheatstone bridge is constituted by four gauge resistors and wirings formed by performing impurity diffusion on the surface of a single crystal silicon substrate, and pressure is detected using the piezoelectric effect of the gauge resistor. . A semiconductor pressure sensor using a gauge resistor has a diaphragm (thin plate portion) formed by etching on the surface opposite to the surface on which the gauge resistor is formed. When the diaphragm is deformed by receiving pressure and the gauge resistance is deformed, the output signal of the bridge circuit varies, and pressure variation is detected (see Patent Document 1).

  Since such a semiconductor pressure sensor is manufactured from a large-diameter wafer, several thousand chips are manufactured from one wafer. Since the wafer size is large, the diaphragm thickness varies due to etching when forming the diaphragm and variations in the initial wafer thickness. This variation in the diaphragm thickness results in a variation in pressure sensitivity, which greatly affects the accuracy of sensor chip completion. Sensitivity due to this variation is corrected in the signal processing circuit and adjusted so that there is no variation between the sensor chips.

Japanese Patent Laid-Open No. 9-288026

  However, in order to adjust the variation in pressure sensitivity, it is necessary to measure the thickness by optical means and to check the output by applying pressure, and therefore it takes a long time to calculate the correction coefficient.

  In view of the above problems, an object of the present invention is to provide a semiconductor pressure sensor that can easily measure the thickness of the diaphragm after the diaphragm is formed.

  In order to achieve the above object, a first aspect of the present invention is a semiconductor pressure sensor having a diaphragm made of a semiconductor and detecting a pressure applied to the diaphragm, which is formed from the upper surface to the lower surface of the diaphragm. And a plurality of electrodes electrically connected to the resistor portions and exposed to the outside. The semiconductor pressure sensor is characterized in that:

  In the semiconductor pressure sensor according to the first aspect of the present invention, the diaphragm is formed to have a gap below by selectively etching the semiconductor substrate, and four gauge resistors are formed on the upper surface. The four gauge resistors can form a Wheatstone bridge.

  In the semiconductor pressure sensor according to the first aspect of the present invention, an electrode layer disposed below the diaphragm so as to have a gap between the diaphragm and the electrode layer positioned below the electrode layer And a semiconductor substrate supporting the electrode layer, and the pressure can be detected based on the capacitance of the diaphragm and the electrode layer.

  Further, in the semiconductor pressure sensor according to the first aspect of the present invention, the resistance portion can be formed over the entire area of the diaphragm.

  The semiconductor pressure sensor according to the first aspect of the present invention may further include a pedestal that seals the gap to a vacuum by being bonded to the lower surface of the semiconductor substrate.

  In the semiconductor pressure sensor according to the first aspect of the present invention, the semiconductor pressure sensor further includes a pedestal joined to the lower surface of the semiconductor and having a through hole, and the air gap can be set to atmospheric pressure by the through hole. .

  In the semiconductor pressure sensor according to the first aspect of the present invention, an integrated circuit for amplifying a detection signal can be provided around the diaphragm.

  In the semiconductor pressure sensor according to the first aspect of the present invention, the integrated circuit can output a detection signal corrected using a correction coefficient calculated based on a resistance value of the resistance unit. .

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductor pressure sensor which can measure the thickness of a diaphragm easily after diaphragm formation can be provided.

It is a typical top view explaining the basic composition of the semiconductor pressure sensor concerning a 1st embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is a typical top view explaining the basic composition of the modification of the semiconductor pressure sensor concerning a 1st embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is a typical top view explaining the basic composition of the modification of the semiconductor pressure sensor concerning a 1st embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is a typical top view explaining the basic composition of the modification of the semiconductor pressure sensor concerning a 1st embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is typical sectional drawing explaining the modification of the semiconductor pressure sensor which concerns on 1st Embodiment. It is a typical top view explaining the basic composition of the semiconductor pressure sensor concerning a 2nd embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is a typical top view explaining the basic composition of the modification of the semiconductor pressure sensor concerning a 2nd embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is a typical top view explaining the basic composition of the modification of the semiconductor pressure sensor concerning a 2nd embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is a typical top view explaining the basic composition of the modification of the semiconductor pressure sensor concerning a 2nd embodiment. (B) is typical sectional drawing seen from the AA direction of (a). It is typical sectional drawing explaining the modification of the semiconductor pressure sensor which concerns on 2nd Embodiment. It is a typical top view explaining the semiconductor pressure sensor concerning other embodiments of the present invention.

  Next, first and second embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the cross-sectional view and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

(First embodiment)
The semiconductor pressure sensor according to the first embodiment of the present invention has a diaphragm (thin plate portion) 50 made of a semiconductor and is applied to the diaphragm 50 as shown in FIGS. Is a semiconductor element for detecting The diaphragm 50 is made of silicon (Si), and is formed thinner than other portions by selectively etching the lower surface of the rectangular flat semiconductor substrate 10.

  The semiconductor pressure sensor according to the first embodiment includes a resistance portion 5 formed from the upper surface to the lower surface of the diaphragm 50, and four electrodes 31, 32, which are electrically connected to the resistance portion 5 and exposed to the outside. 33, 34. The resistance unit 5 is made of an n-type semiconductor. The resistance unit 5 and the electrodes 31 to 34 are electrically connected to the upper surface of the semiconductor substrate 10 by diffusion wirings 30 formed by selectively diffusing high-concentration p-type impurities, respectively.

  The resistance portion 5 has a thickness measured by measuring a resistance value via the electrodes 31 to 34. The upper surface and the lower surface of the resistance portion 5 form the upper surface and the lower surface of the diaphragm 50, respectively, and the thickness of the resistance portion 5 is equal to the thickness of the diaphragm 50. A protective film 6 that protects the resistor unit 5 and the semiconductor substrate 10 is formed on the upper surfaces of the resistor unit 5 and the semiconductor substrate 10. The protective film 6 is formed except for the positions of the electrodes 31 to 34 and the input / output terminals.

  In the semiconductor pressure sensor according to the first embodiment, the electrodes 31 to 34 exposed to the outside are brought into contact with the probes, respectively, and the resistance value of the resistance unit 5 is measured by a processing device connected to the probes. The processing device can calculate the thickness of the resistance unit 5 and the diaphragm 50 from the resistance value of the resistance unit 5 and calculate a correction coefficient for pressure detection. The correction coefficient can be calculated based on the shape of the resistance unit and the resistance value stored in advance in the processing apparatus.

  For example, the shape and resistance value of the resistance portion stored in advance can be data before completion of the formation of the diaphragm 50 by etching. The processing device calculates a correction coefficient for pressure detection from the resistance value of the resistance unit 5 after the formation of the diaphragm 50 based on the shape and resistance value of the resistance unit stored in advance. The processing apparatus can relatively compare the thicknesses of the diaphragms 50 by using the data of the resistance part 5 of another semiconductor pressure sensor as the data of the resistance part stored in advance.

  Diaphragm 50 is generally square in plan pattern. On the upper surface of the diaphragm 50, four gauge resistors 4a, 4b, 4c, and 4d are formed near the midpoints of the four sides of the diaphragm 50, respectively. The gauge resistors 4a to 4d are connected to each other by a diffusion wiring 20 formed on the upper surface of the semiconductor substrate 10, and constitute a Wheatstone bridge.

  The semiconductor substrate 10 is made of a low concentration n-type semiconductor. The four gauge resistors 4 a to 4 d are formed on the upper surface of the semiconductor substrate 10 by selectively diffusing p-type impurities. The four gauge resistors 4a to 4d have the same resistance value when the diaphragm 50 is not stressed. The diffusion wiring 20 is formed on the upper surface of the semiconductor substrate 10 by selectively diffusing high-concentration p-type impurities.

  One end of the gauge resistor 4 a is connected to the power supply terminal 21, and the other end is connected to the output terminal 23. One end of the gauge resistor 4 b is connected to the output terminal 23, and the other end is connected to the ground terminal 22. One end of the gauge resistor 4 c is connected to the output terminal 24, and the other end is connected to the power supply terminal 21. One end of the gauge resistor 4 d is connected to the ground terminal 22 and the other end is connected to the output terminal 24. The gauge resistors 4a to 4d, the power supply terminal 21, the ground terminal 22, and the output terminals 23 and 24 may be electrically connected not by the diffusion wiring 20 but by a metal thin film or the like.

  When pressure is applied to the pressure sensor according to the first embodiment, the diaphragm 50 bends and the gauge resistors 4a to 4d are distorted, thereby changing the resistance values of the gauge resistors 4a to 4d. Therefore, the output voltage between the output terminals 23 and 24 with respect to the input voltage between the power supply terminal 21 and the ground terminal 22 changes, and the pressure is detected from the change in the output voltage.

  According to the semiconductor pressure sensor according to the first embodiment, after the diaphragm is formed, the thickness of the diaphragm can be easily measured by measuring the resistance value of the resistance portion, and the variation in the thickness of the diaphragm is taken into consideration. The correction coefficient for the detected pressure can be calculated.

-Modification-
Hereinafter, modifications of the semiconductor pressure sensor according to the first embodiment will be described. The configurations not described in the following modification examples are substantially the same as those in the first embodiment described above, and thus redundant description is omitted.

  In the semiconductor pressure sensor according to the first modification of the first embodiment, as shown in FIGS. 2A and 2B, the resistance portion for calculating the correction coefficient used for pressure detection is the entire area of the semiconductor substrate 11. Formed. In the semiconductor pressure sensor according to the first modification of the first embodiment, since the diaphragm 50 is formed by selectively etching the semiconductor substrate 11 doped with n-type impurities, the entire area of the diaphragm 50 is Thus, a resistance portion is formed. The electrodes 31 to 34 are directly electrically connected to the diaphragm 50 and do not require diffusion wiring. The diaphragm 50 has a thickness measured by measuring a resistance value through the electrodes 31 to 34.

  The four gauge resistors 4a to 4d are respectively formed on upper portions of diffusion regions 42a to 42d formed by diffusing high-concentration n-type impurities on the upper surface of the semiconductor substrate 11. The four diffusion regions 42a to 42d form pn junctions with the four gauge resistors 4a to 4d and the diffusion wiring 20, respectively.

  In the semiconductor pressure sensor according to the second modification of the first embodiment, the resistance portion 51 is formed over the entire area of the diaphragm 50 as shown in FIGS. The entire area of the diaphragm 50 of the semiconductor substrate 10 is doped with a p-type impurity, thereby forming a resistance portion 51. The resistance part 51 and the electrodes 31 to 34 are electrically connected to each other by the diffusion wiring 30.

  The four gauge resistors 4a to 4d are respectively formed on upper portions of diffusion regions 41a to 41d formed by diffusing high-concentration n-type impurities on the upper surface of the semiconductor substrate 10. The four diffusion regions 41a to 41d form pn junctions with the four gauge resistors 4a to 4d and the diffusion wiring 20, respectively.

  The semiconductor pressure sensor according to the third modification of the first embodiment includes a pedestal 15 bonded to the lower surface of the semiconductor substrate 11 as shown in FIGS. The space below is sealed in a vacuum. The base 15 is made of, for example, a glass substrate. The semiconductor pressure sensor according to the third modification of the first embodiment can detect an absolute pressure using an absolute vacuum as a reference pressure. Other configurations of the semiconductor pressure sensor according to the third modification of the first embodiment are the same as those of the first modification.

  As shown in FIG. 5, the semiconductor pressure sensor according to the fourth modification of the first embodiment includes a pedestal 151 bonded to the lower surface of the semiconductor substrate and having a through hole 150. The base 151 is made of, for example, a glass substrate. Since the pedestal 151 has a through-hole, the space below the diaphragm 50 is at atmospheric pressure. According to the semiconductor pressure sensor according to the fourth modification of the first embodiment, the rigidity of the sensor chip is increased, and the influence of the stress applied to the entire sensor chip can be reduced.

(Second Embodiment)
As shown in FIGS. 6A and 6B, the semiconductor pressure sensor according to the second embodiment of the present invention includes an SOI substrate 100, an insulating film 61 formed on the upper surface of the SOI substrate 100, and an insulating film. A diaphragm (thin plate portion) 12 is provided so as to have a gap between the membrane 61. The semiconductor pressure sensor according to the second embodiment is a capacitance type and detects the pressure applied to the diaphragm 12.

  The SOI substrate 100 includes an SOI layer (electrode layer) 101, an insulating layer 102, and a support substrate (semiconductor substrate) 103 in order from the upper layer. The SOI substrate 100 has a gap by removing the support substrate 103 and the insulating layer 102 so that the planar pattern is circular. The SOI layer 101 has a through-hole penetrating from the upper surface to the lower surface at the center of a circle which is a pattern from which the support substrate 103 and the insulating layer 102 are removed.

  The insulating film 61 formed on the upper surface of the SOI layer 101 has convex portions formed on the upper surface along a circumference that is a pattern from which the support substrate 103 and the insulating layer 102 are removed. The diaphragm 12 is arranged with a predetermined gap from the SOI layer 101 and the insulating film 61 in a circular plane pattern by the convex portions of the insulating film 61. The support substrate 103 supports the diaphragm 12, the SOI layer, and the like.

  The diaphragm 12 is made of silicon (Si). In the diaphragm 12, a resistance portion 52 is formed from the upper surface to the lower surface at the center of a circle that is a pattern having a gap between the SOI layer 101 and the insulating film 61. The resistance portion 52 is formed by diffusing n-type impurities.

  The semiconductor pressure sensor according to the second embodiment includes four electrodes 31, 32, 33, and 34 that are electrically connected to the resistance portion 52 and exposed to the outside. The electrodes 31 to 34 are provided around the diaphragm, and are electrically connected to the resistance portion 52 by the diffusion wiring 30 formed by selectively diffusing high-concentration p-type impurities on the upper surface of the diaphragm 12. It is connected.

  The resistance portion 52 has a thickness measured by measuring a resistance value via the electrodes 31 to 34. The upper surface and the lower surface of the resistance portion 52 form the upper surface and the lower surface of the diaphragm 12, respectively. The thickness of the resistance portion 52 is equal to the thickness of the diaphragm 12.

  In the semiconductor pressure sensor according to the second embodiment, the electrodes 31 to 34 exposed to the outside are brought into contact with the probes, respectively, and the resistance value of the resistance unit 52 is measured by a processing device connected to the probes. The processing device can calculate the thickness of the resistance part 52 and the diaphragm 12 from the resistance value of the resistance part 52 and calculate a correction coefficient for pressure detection. The correction coefficient can be calculated based on the shape of the resistance unit and the resistance value stored in advance in the processing apparatus.

  The processing device calculates a correction coefficient for pressure detection from the resistance value of the resistance portion 52 after the formation of the diaphragm 12 is completed based on the shape and resistance value of the resistance portion stored in advance. The processing apparatus can relatively compare the thicknesses of the diaphragms 12 by using the data of the resistance part 52 of another semiconductor pressure sensor as the data of the resistance part stored in advance.

  The semiconductor pressure sensor according to the second embodiment includes electrode pads 25 and 26 around the diaphragm 12. The electrode pad 25 is electrically connected to the diaphragm 12, and the electrode pad 26 is electrically connected to the SOI layer 101.

  When pressure is applied to the pressure sensor according to the second embodiment, the diaphragm 12 bends and the distance between the diaphragm 12 and the SOI layer 101 changes, so that the capacitances of the diaphragm 12 and the SOI layer 101 change. As described above, the pressure sensor according to the second embodiment detects the pressure based on the change in the capacitance via the electrode pads 25 and 26.

  According to the semiconductor pressure sensor according to the second embodiment, after the diaphragm is formed, the thickness of the diaphragm can be easily measured by measuring the resistance value of the resistance portion, and the variation in the thickness of the diaphragm is taken into consideration. The correction coefficient for the detected pressure can be calculated.

-Modification-
Hereinafter, modifications of the semiconductor pressure sensor according to the second embodiment will be described. The configurations not described in the following modification examples are substantially the same as those in the second embodiment described above, and thus redundant description is omitted.

  In the semiconductor pressure sensor according to the first modification of the second embodiment, the resistance portion 53 is formed over the entire area of the diaphragm 12 as shown in FIGS.

  In the semiconductor pressure sensor according to the second modification of the second embodiment, as shown in FIGS. 8A and 8B, the diaphragm 13 is made of a silicon substrate doped with an n-type impurity. Thus, a resistance portion is formed in the entire area 13.

  As shown in FIGS. 9A and 9B, the semiconductor pressure sensor according to the third modification of the second embodiment includes a pedestal 16 bonded to the lower surface of the support substrate 103, so that the diaphragm 12 The space below is sealed in a vacuum. The pedestal 16 is made of, for example, a glass substrate. The semiconductor pressure sensor according to the third modification of the second embodiment can detect an absolute pressure using an absolute vacuum as a reference pressure. Other configurations of the semiconductor pressure sensor according to the third modification of the second embodiment are the same as those of the first modification.

  As shown in FIG. 10, the semiconductor pressure sensor according to the fourth modification of the second embodiment includes a pedestal 161 bonded to the lower surface of the support substrate 103 and having a through hole 160. The pedestal 161 is made of, for example, a glass substrate. Since the pedestal 161 has a through-hole, the space below the diaphragm 12 is at atmospheric pressure. According to the semiconductor pressure sensor according to the fourth modification of the second embodiment, the rigidity of the sensor chip is increased, and the influence of the stress applied to the entire sensor chip can be reduced.

(Other embodiments)
As described above, the present invention has been described according to the first and second embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first and second embodiments, an integrated circuit that amplifies the detection signal of the semiconductor pressure sensor may be provided around the diaphragm of the semiconductor pressure sensor. For example, a semiconductor pressure sensor according to another embodiment of the present invention includes an integrated circuit 8 that amplifies a detection signal around a diaphragm 50 as shown in FIG. The electrodes 71 to 74 are electrically connected to the resistance unit 5, respectively. Terminals 75 to 79 are used for input / output of the semiconductor pressure sensor. The integrated circuit 8 stores a correction coefficient calculated based on the resistance value of the resistance unit 5, the shape and resistance value of the predetermined resistance unit, and outputs a detection signal corrected using the correction coefficient. May be.

  In addition to the above, the present invention naturally includes various embodiments not described here, such as configurations applying the first and second embodiments. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

4a, 4b, 4c, 4d ... Gauge resistor 5, 51, 52, 53 ... Resistor 8 ... Integrated circuit 10, 11 ... Semiconductor substrate 12, 13, 50 ... Diaphragm 15, 16, 151, 161 ... Base 31-34 71-74 ... Electrode 101 ... SOI layer (electrode layer)
103 ... Support substrate (semiconductor substrate)
150, 160 ... through hole

Claims (8)

A semiconductor pressure sensor having a diaphragm made of a semiconductor and detecting a pressure applied to the diaphragm,
A resistance portion formed from the upper surface to the lower surface of the diaphragm;
A semiconductor pressure sensor, comprising: a plurality of electrodes electrically connected to the resistance portion and exposed to the outside. The diaphragm is formed to have a gap below by selectively etching the semiconductor substrate, and four gauge resistors are formed on the upper surface,
The semiconductor pressure sensor according to claim 1, wherein the four gauge resistors constitute a Wheatstone bridge. An electrode layer disposed below the diaphragm so as to have a gap between the diaphragm and the diaphragm;
A semiconductor substrate that is positioned below the electrode layer and supports the electrode layer;
The semiconductor pressure sensor according to claim 1, wherein the pressure is detected based on capacitance of the diaphragm and the electrode layer.   The semiconductor pressure sensor according to claim 1, wherein the resistance portion is formed over the entire area of the diaphragm.   The semiconductor pressure sensor according to claim 2, further comprising a pedestal for sealing the gap to a vacuum by being bonded to a lower surface of the semiconductor substrate. A pedestal joined to the lower surface of the semiconductor and having a through hole;
The semiconductor pressure sensor according to claim 2, wherein the air gap is set to atmospheric pressure by the through hole.   The semiconductor pressure sensor according to claim 1, further comprising an integrated circuit that amplifies a detection signal around the diaphragm.   The semiconductor pressure sensor according to claim 7, wherein the integrated circuit outputs a detection signal corrected using a correction coefficient calculated based on a resistance value of the resistance unit.

Images