WO2007052800A1

WO2007052800A1 - Semiconductor pressure sensor

Info

Publication number: WO2007052800A1
Application number: PCT/JP2006/322127
Authority: WO
Inventors: Masaru Igaki; Hideaki Shikata
Original assignee: Rohm Co., Ltd.
Priority date: 2005-11-07
Filing date: 2006-11-07
Publication date: 2007-05-10
Also published as: TW200732642A

Abstract

It is possible to provide a low-cost semiconductor pressure sensor of a simple structure capable of easily controlling, for example, the thickness of its diaphragm portion, and having a high yield, a low dependence on temperature, and a high sensitivity. The semiconductor pressure sensor comprises a Schottky barrier diode (10) consisting of a barrier film (1), an electrode film (2), and an n-type semiconductor substrate (3), and a base (4). In the Schottky barrier diode (10), the barrier film (1) formed of a metal is brought into contact with the n-type semiconductor substrate (3), so that a depletion layer is formed in the contact area on the side of the n-type semiconductor substrate (3) and a Schottky barrier is generated. This Schottky junction portion is included in the diaphragm portion (5) in the n-type semiconductor substrate (3) and functions as a pressure sensing area.

Description

Specification

Semiconductor pressure sensor technology

[0001] The present invention relates to a semiconductor pressure sensor used for sensing pressure.

Background art

[0002] In recent years, a technology called micromachining, which produces ultra-small machines (micromachines) that physically move by taking advantage of the semiconductor microfabrication technology used in the manufacture of semiconductor integrated circuits, has attracted attention. The development of semiconductor sensors such as semiconductor pressure sensors is advancing using this micromachining. Semiconductor pressure sensors are widely used in automobiles, home appliances, industrial measuring instruments, and so on.

In the semiconductor pressure sensor, a silicon diaphragm type pressure sensor is mainly used.

In this pressure sensor, boron is selectively diffused into silicon to form a diffusion resistor, and the pressure is detected using the piezoresistance effect of the diffusion resistor. FIG. 28 shows the structure of a conventional piezoresistive effect type semiconductor pressure sensor, in which (a) shows a longitudinal sectional structure and (b) shows a planar structure (see, for example, Patent Documents 1 and 2).

[0004] The semiconductor chip 50 in FIG. 28 is made of silicon (Si) and has a substantially flat plate shape. The semiconductor chip 50 is formed with a truncated cone-shaped opening hole in the center so that the taper 53 is formed, leaving the pedestal 52, and the semiconductor chip 50 has a thinned diameter W in the center. A diaphragm portion (elastic portion) 54 is formed. A diffusion resistor 51 having a piezo effect is formed on the upper surface of the diaphragm portion 54.

When the pressure is detected by this semiconductor pressure sensor, the pressure is introduced from the lower part of the semiconductor chip 50 toward the diaphragm portion 54. Due to this pressure, uneven deformation occurs in the diaphragm portion 54, and the diffusion resistor 51 expands and contracts (distorts) due to the uneven deformation, and the interatomic distance of the silicon crystal changes, and the resistance value of the diffusion resistor 51 changes. The so-called piezo effect is used to detect the pressure of the resistance changing force.

Patent Document 1: JP-A-6-163941

Patent Document 2: JP-A-5-340828 Disclosure of the invention

Problems to be solved by the invention

[0006] In the above conventional semiconductor pressure sensor, the piezoresistive effect is small, but the resistance change due to temperature change is also large in silicon. Therefore, a system is adopted in which four diffusion resistors 51 are bridge-coupled to extract signals. Used. In addition, the thickness t of the diaphragm portion 54 is usually a thin film of about 20 m or less so as to be sensitively unevenly deformed by the pressure difference between the upper and lower sides, and alkali etching or the like is performed to form the diaphragm portion 54. Because it is difficult to control to a certain degree of accuracy, the yield is low and the cost is high.

[0007] Furthermore, it is necessary to provide an external resistor in order to compensate for the deviation of the zero point due to the temperature change, the compensation of the deviation of the output sensing, and the adjustment of the difference in the output sensitivity that causes the variation in the thickness of the diaphragm portion. For these reasons, the number of manufacturing processes has increased, leading to increased lead times and costs.

Meanwhile, the sensitivity S of the semiconductor pressure sensor is expressed as S = AX (WZt) ² . Where A is a proportionality constant. Therefore, in order to improve the sensitivity S, the thickness t of the diaphragm portion 54 is made as thin as possible, and the diameter W of the diaphragm portion 54 needs to be made as large as possible.

However, when the thickness t of the diaphragm portion 54 is further reduced, as described above, it becomes more difficult to control to a certain accuracy, and there is a limit to reducing the thickness. In recent years, the demand for miniaturization of semiconductor pressure sensors has become stronger, and it is virtually impossible to increase the diameter W. As described above, it is not easy to improve the sensitivity of semiconductor pressure sensors.

[0010] The present invention was created to solve the above-described problems, and has a simple configuration, easy control of the thickness of the diaphragm portion, etc., high yield, low cost, and temperature dependence. It aims to provide a low and high sensitivity semiconductor pressure sensor.

Means for solving the problem

[0011] In order to achieve the above object, the invention according to claim 1 (semiconductor pressure sensor according to the first configuration) is a semiconductor pressure sensor that detects a pressure by distortion of a diaphragm, and the diaphragm includes A semiconductor pressure sensor including a Schottky junction. [0012] The invention according to claim 2 is the semiconductor pressure sensor according to claim 1, wherein the Schottky junction is formed by bringing a barrier film into contact with a semiconductor.

[0013] Further, in the invention of claim 3, the electrode formed on the semiconductor, the barrier film, and the semiconductor constitute a Schottky noria diode. It is a semiconductor pressure sensor.

[0014] The invention according to claim 4 is characterized in that a forward current is passed between the electrode and the barrier film, and the pressure is detected by a change in the resistance value of the Schottky junction. Term

3. The semiconductor pressure sensor according to 3.

[0015] The invention according to claim 5 is characterized in that the electrode is formed so as to surround the periphery of the barrier film. This is a semiconductor pressure sensor.

[0016] The invention according to claim 6 is the semiconductor pressure sensor according to claim 5, wherein the barrier film is formed in a central portion of the semiconductor.

[0017] Further, in the invention according to claim 7 (semiconductor pressure sensor according to the second configuration), a plurality of the Schottky junctions are arranged in a distributed manner. A semiconductor pressure sensor according to item 1.

[0018] The invention according to claim 8 is the semiconductor pressure sensor according to claim 7, wherein the Schottky junction portion constitutes a Wheatstone bridge circuit.

[0019] Further, the invention according to claim 9 includes a pad electrode connected to the anode side or the force sword side of the Schottky noria diode, and the force according to claim 7 or claim 8, The semiconductor pressure sensor according to item 1.

The invention's effect

[0020] In the semiconductor pressure sensor according to the first configuration of the present invention, a completely new configuration, that is, contact between a metal and a semiconductor, is not used for detecting pressure, unlike the prior art using a diffusion resistor having a piezo effect. Since the Schottky junction generated by the above is used, high sensitivity can be achieved. Further, since the forward characteristics of the Schottky noria diode having the Schottky junction are used for pressure detection, the temperature dependence is low, and a sensor can be obtained. In addition, when a pedestal is provided as a configuration of the semiconductor pressure sensor, there is a hole for introducing pressure. The formed pedestal is joined to a thinly polished diaphragm so that it can be elastically deformed. Therefore, it is not necessary to control the thickness of the diaphragm by etching. In addition, since it is not necessary to provide a sensitivity compensation circuit or the like, it can be manufactured at a high yield and at a low cost, and a highly accurate sensor can be configured.

[0021] Further, in the semiconductor pressure sensor according to the second configuration of the present invention, a shot junction is used for the pressure sensing portion, and a plurality of Schottky junctions are formed dispersed in the diaphragm! /, Therefore, it is possible to reduce the influence of the asymmetry of the stress distribution caused by the uneven deflection of the diaphragm. Furthermore, by using a plurality of Schottky junctions, the sensitivity can be further improved as compared with the case of using a single Schottky junction, and high sensitivity can be maintained even if the thickness of the diaphragm is increased.

Brief Description of Drawings

FIG. 1 is a diagram showing a structure of a first semiconductor pressure sensor of the present invention.

FIG. 2 is a view showing a structure of a second semiconductor pressure sensor of the present invention.

[FIG. 3] FIG. 3 is a graph showing the forward current vs. forward voltage characteristics for each element temperature of the semiconductor pressure sensor.

FIG. 4 is a graph showing a pressure-output voltage change characteristic of a semiconductor pressure sensor.

[FIG. 5] FIG. 5 is a graph showing forward current vs. forward voltage characteristics for each element temperature of a semiconductor pressure sensor.

FIG. 6 is a graph showing a pressure-output voltage change characteristic of a semiconductor pressure sensor.

[FIG. 7] FIG. 7 is a diagram showing a forward current vs. forward voltage characteristic for each element temperature of a semiconductor pressure sensor.

FIG. 8 is a graph showing a pressure-output voltage change characteristic of a semiconductor pressure sensor.

FIG. 9 is a diagram showing the structure of a can-type pressure sensor using the first semiconductor pressure sensor.

FIG. 10 is a diagram showing a structure of a can-type pressure sensor using a Schottky noria diode element portion of the first semiconductor pressure sensor.

[Fig. 11] Fig. 11 shows the structure of a can type pressure sensor using a second semiconductor pressure sensor. FIG.

FIG. 12 is a diagram showing a structure of a can type pressure sensor using a Schottky noria diode element portion of a second semiconductor pressure sensor.

FIG. 13 is a plan view showing the structure of a third semiconductor pressure sensor of the present invention.

FIG. 14 is a side view showing the structure of a third semiconductor pressure sensor of the present invention.

FIG. 15 is a diagram showing a connection configuration of Schottky noria diodes in a third semiconductor pressure sensor.

FIG. 16 is a diagram showing a connection configuration in which the Schottky noria diode in FIG. 15 is replaced with the value of the internal resistance.

FIG. 17 is a diagram showing the types of stress acting on the Schottky noria diode on the third semiconductor pressure sensor.

FIG. 18 is a diagram showing forward current vs. forward voltage characteristics of one Schottky barrier diode.

FIG. 19 is a diagram showing forward current-forward voltage characteristics according to temperature of a Schottky noria diode.

FIG. 20 is a diagram showing forward current Kerr temperature variation characteristics of a semiconductor pressure sensor.

FIG. 21 is a diagram showing a structure of a semiconductor pressure sensor using one Schottky barrier diode.

FIG. 22 is a diagram showing the characteristics of the diaphragm thickness and output voltage of a semiconductor pressure sensor.

FIG. 23 is a graph showing the pressure output voltage change characteristic of the semiconductor pressure sensor.

FIG. 24 is a diagram showing a structure of a third semiconductor pressure sensor having a pedestal portion.

FIG. 25 is a view showing a structure of a third semiconductor pressure sensor having no pedestal portion.

FIG. 26 is a diagram comparing the sensitivities of a third semiconductor pressure sensor having no pedestal portion and a third semiconductor pressure sensor having a pedestal portion.

FIG. 27 is a view showing a pressure sensor of a mold type structure using a third semiconductor pressure sensor having no pedestal portion. FIG. 28 is a diagram showing a conventional diffusion resistance type semiconductor pressure sensor, explanation of reference numerals

1 Barrier film

2 Electrode membrane

3 n-type semiconductor substrate

4 pedestal

5 Diaphragm part

6 opening

10 Schottky barrier diode

11 Barrier film

12 Electrode membrane

13 n-type semiconductor substrate

14 pedestal

15 Diaphragm part

16 opening

20 Schottky barrier diode

32, 42 Support base

33, 45 Lead pin

31, 41 Pressure inlet pipe

34, 35, 43 Pressure inlet

44 Resin mold

46 Hollow part

61 Barrier film

62

63 Barrier film

64 Turtle

65 Barrier film 67 Barrier film

68 electrodes

69 '-72 wiring

73 '-76 pad electrode

77 Semiconductor substrate

78 Diaphragm area

80 Schottky barrier diode

81 pedestal

82 pedestal

83 Bonding layer

91 Pressure inlet pipe

92 Pressure inlet

93 Resin mold

94 Hollow part

96 lead wire

97 Lead pin

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the structure of a first semiconductor pressure sensor according to the present invention, FIG. 1 ( _a ) shows a planar structure, and FIG. 1 (b) shows a longitudinal section.

The first semiconductor pressure sensor includes a barrier film 1, an electrode film 2, for example, a Schottky noria diode element 10 made of an n-type semiconductor substrate 3 and a pedestal 4. In the present invention, unlike the prior art, a Schottky junction generated by contact between a metal and a semiconductor is used as a pressure detection means with a completely new configuration. In the Schottky noria diode element 10, when the noria film 1 made of metal is brought into contact with the n-type semiconductor substrate 3, a depletion layer is formed on the contact surface on the n-type semiconductor substrate 3 side, and the Schottky barrier Occurs.

This Schottky junction partial force is included in diaphragm portion 5 (shaded portion in the figure) in n-type semiconductor substrate 3 and serves as a pressure sensing region. In order to generate a Schottky junction, the NORA film 1 has a work function that is larger than the work function of the n-type semiconductor substrate 3. It is necessary to select materials for the film 1 and the n-type semiconductor substrate 3. For example, the barrier film 1 is used a composite film of a metal such as Noriametaru and A1 such P _t, the n-type semiconductor substrate 3 such as a silicon substrate with an n-type non-pure product doped is used. In addition to Pt, there are Ti, Mo, W, Al, V, Pd, Au, etc. as materials for the barrier metal.

[0027] The pedestal 4 is made of a silicon substrate or the like, and is pierced in a taper shape around the position where the Schottky junction between the barrier film 1 and the n-type semiconductor substrate 3 is arranged to form the opening 6. The pedestal 4 and the Schottky noria diode element 10 are joined. The shape of the opening 6 is a square shape in accordance with the shape of the noria film 1. The electrode film 2 as a force sword electrode and the noria film 1 as an anode electrode are electrically connected, and a forward current is supplied from a constant current source to extract a forward voltage.

When pressure is introduced from the opening 6 in the pedestal 4, the diaphragm 5 of the Schottky barrier diode element 10 is distorted, and a Schottky junction between the noria film 1 and the n-type semiconductor substrate 3. Since distortion also occurs, the resistance of the n-type semiconductor substrate 3 changes and the forward voltage changes, and the relationship between the introduced pressure and the change of the forward voltage can be detected.

[0029] The dimensions of the semiconductor pressure sensor in Fig. 1 are, for example, W1 is 1.7 mm, W2 is 3.4 mm, W3 force is 0 μm, and W4 is 260 μm. Can be formed on the sensor. Further, as the Schottky Noria diode element 10, a p-type semiconductor substrate may be used instead of the n-type semiconductor substrate 3. In this case, the work function force of the p-type semiconductor substrate is larger than the work function of the S barrier film. The material is selected so that a Schottky junction is formed.

Next, a method for manufacturing the semiconductor pressure sensor will be described below. First, the method for forming the Schottky Noria diode element 10 is described. On the n-type semiconductor substrate (first conductive semiconductor substrate) 3, the thickness is 3.33 to 4.07 ^ m, and the resistivity is 0.63 to 0.77. An epitaxial layer of Ω'cm is grown, and a thermal oxide film is grown at 9500 A. The thermal oxide film is selectively removed by photoresist technology and hydrofluoric acid etching, and PoCl diffusion is performed at 1050 ° C for 120 minutes to form a force sword region electrode. Phosphorus can be supplied by implanting phosphorus ions in addition to PoCl.

Next, a CVD film containing phosphorus appropriate for gettering mobile ions is deposited, and 1000 Flatten by heat treatment at ° C for 30 minutes. Of course, phosphorus may not be included. The CVD and thermal oxide films are selectively removed again by the photoresist technique and etching with hydrofluoric acid. Pt, Ti, Mo, W, Al, V, Pd, Au, etc., which are Schottky barrier metals, are deposited by sputtering or vapor deposition and heat-treated at an appropriate temperature to form silicide. On the barrier metal, an appropriate metal layer serving as a diffusion layer is disposed on the barrier metal, and an A1 layer having a top thickness of 24 to 26 kA is provided to form the noria film 1 serving as an anode electrode. The force sword electrode film 2 is also formed of the same metal as the anode barrier film 1 in the same manner as described above. However, since the force sword region has a very high impurity concentration, no Schottky barrier is formed and an ohmic contact is formed.

[0032] A 8000A silicon nitride film is deposited thereon under reduced pressure at all times or with a plasma CVD machine, and the regions of the barrier film 1 and the electrode film 2 and the periphery of the device are selectively removed by photolithography and dry etching. Polishing from the back while protecting the surface with tape, etc., so as not to damage the surface. Finishing was 2000.

[0033] Next will be described the method of forming the base portion 4, 1 X 10 ¹⁸ cm_ ³ below B, P, As, 8000 A silicon nitride to silicon wafer (100) plane containing the n-type impurity such as Sb A film is deposited, and a region corresponding to the upper area of the opening 6 is selectively removed by photolithography and dry etching. The surface pattern is protected with tape or the like and polished from the back surface to a thickness of 200 to 300 m. Immerse in a 24wt% KOH aqueous solution and etch until opening 6 is formed.

[0034] Finally, when the Schottky noria diode element 10 and the pedestal 4 are joined using a thermosetting high-strength tape and heated at 180 to 200 ° C, the semiconductor pressure sensor of FIG. Complete. The bonding may be a high-strength adhesive or bonding using SOI technology.

FIG. 2 shows a structural example of a second semiconductor pressure sensor according to the present invention, FIG. 2 (a) shows a planar structure, and FIG. 2 (b) shows a longitudinal section. A barrier film 11 as an anode electrode is formed on the n-type semiconductor substrate 13 in the center portion, and an electrode film 12 as a force sword electrode is provided so as to surround the noria film 11. The diaphragm portion 15 in the n-type semiconductor substrate 13 corresponds to a region where the n-type semiconductor substrate 13 and the barrier film 11 are in a Schottky junction, as indicated by the oblique lines in the figure. As the size of the semiconductor pressure sensor in FIG. 2, for example, an n-type semiconductor The size of the substrate 13 is 1.6 mm square both vertically and horizontally, and the thickness of the n-type semiconductor substrate 13 and the height of the pedestal 14 are 50 μm and 260 μm, respectively, similar to W3 and W4 in FIG. can do. The operation and manufacturing method are the same as those of the semiconductor pressure sensor of FIG.

In the case of the semiconductor pressure sensor of FIG. 1, since the barrier film 1 and the electrode film 2 are provided side by side on the n-type semiconductor substrate 3, the sensor area becomes large and the shape becomes rectangular, which will be described later. When packaged, it cannot fit in a compact. On the other hand, as shown in FIG. 2, by forming the electrode film 12 so as to surround the noria film 11, the sensor area can be made smaller than in FIG. 1, and the diaphragm portion 15 can be provided in the central portion. The sensor shape can be formed in a square shape.

[0037] Further, in order to increase the sensitivity of the sensor, even when the area of the diaphragm 15 is increased, the four sides can be evenly expanded, and the area of the opening 16 is also a region close to the area of the n-type semiconductor substrate 13. Therefore, even if the area is smaller than that of the semiconductor pressure sensor of FIG. 1, a semiconductor pressure sensor having the same accuracy and sensitivity can be configured, and the size can be reduced. Further, when the sensor has a square shape and the diaphragm portion 15 is provided in the central portion, the pressure introduced from the opening portion 16 is equally applied to the diaphragm portion 15 and the accuracy of pressure measurement is improved.

FIG. 3 shows the characteristics of forward current and forward output voltage in the semiconductor pressure sensor of the present invention.

[0039] As the Noria film, a composite metal film in which Pt was used as a Schottky barrier metal and an A1 film was formed thereon was used. The solid line indicates the case where the element temperature of the semiconductor pressure sensor is 25 ° C, the broken line indicates the case where the temperature is 25 ° C, and the alternate long and short dash line indicates the case where the temperature is 75 ° C. As the forward current IF is increased, the output voltage VF also increases.At the first rise, the characteristics are different.The forward current IF is around 1000 mA. Draw different traces!

Thus, it can be seen that the temperature dependence in the high current density region is very small. By operating the semiconductor pressure sensor in the high current density region, accurate measurements can be performed regardless of temperature changes. For example, the fluctuation at the same forward current value was measured with reference to the output voltage VF (752mV) at an element temperature of 25 ° C when the forward current IF = 1000mA. As a result, the rate of change was + 0.6% at -25 ° C (VF = 756.2mV), and at 0.5 ° C, it was -0.5% (VF = 748.2mV). . When the element temperature changed to -25 ° C, 25 ° C, and 75 ° C, the forward current IF value with the smallest change rate of the output voltage VF was the reference value. In the example of Fig. 3, the reference was IF = 1000mA. Assuming that the operating point is the intersection point with the curve with a device temperature of 25 ° C, the operating range that can be used as a sensor is the range of approximately ± 5 mV (shaded area) around this operating point.

[0041] FIG. 4 shows changes in output voltage with respect to changes in pressure when pressure is actually introduced. In the high current density region shown in Fig. 3 where the temperature dependence is very small, the change in output voltage when pressure is applied to the diaphragm (Schottky junction) of the semiconductor pressure sensor of the present invention and the pressure is changed. Show. Forward current in high-density current region IF = 100 OmA, constant forward current is constant with a constant current source, and output voltage change AVF under pressure when the output voltage under atmospheric pressure is the standard. Shown in Even if the element temperature changes to 25 ° C, 25 ° C, and 75 ° C, there is no significant difference in the AVF-pressure curve.

By the way, by reducing the junction area between the barrier metal of the barrier film 1 and the n-type semiconductor substrate 3, the temperature dependence of the forward output voltage is small! / The region has a small forward current! Can be shifted. Practical drive forward constant current is often less than 10mA.

FIG. 5 shows the forward current and the forward output voltage in the semiconductor pressure sensor when the same barrier metal Pt as in FIG. 3 is used and the junction area between the noria metal and the n-type semiconductor substrate 3 is smaller than that in FIG. The characteristics are shown. As the barrier film, a composite metal film in which an A1 film was formed on a Schottky barrier metal Pt was used. The solid line shows the case where the element temperature of the semiconductor pressure sensor is 0 ° C, the broken line shows the case at 25 ° C, and the alternate long and short dash line shows the case at 40 ° C. As the forward current IF increases, the output voltage VF also increases.At the first rise, the characteristics are different, but the curves are almost the same when the forward current IF is around 2 mA. Draws almost the same trajectory even at different temperatures. The operating point is the intersection of the forward current IF = 2mA and the curve with the reference element temperature of 25 ° C. The range of approximately ± 5mV (shaded area) that can be used as a sensor is centered on this operating point. It becomes an area. Based on the output voltage VF (686mV) at an element temperature of 25 ° C at IF = 2mA, the variation in the same forward current was measured, and the change rate at 0 ° C was + 0.5% (VF = 690mV ), 0.88% at 40 ° C (VF = 680mV) Very low temperature dependence!

FIG. 6 shows a change in output voltage with respect to a change in pressure when pressure is actually introduced into the semiconductor pressure sensor having the characteristics shown in FIG. The forward current in the high-density current region is IF = 2 mA, the forward current is constant with a constant current source, and the output voltage change AVF under pressure when the output voltage under atmospheric pressure is the standard. Shown in Element temperature is 0. Even when changing to C, 25 ° C and 40 ° C, there is no significant difference in the AVF-pressure curve. In addition, two curves for each element temperature of 0 ° C, 25 ° C, and 40 ° C are drawn, indicating the range of variation at each temperature.

[0045] FIG. 7 shows the forward current and forward output in the semiconductor pressure sensor when Ti is used for the barrier metal under the same conditions as in FIG. 5 where the junction area between the barrier metal and the n-type semiconductor substrate 3 is the same as in FIG. The voltage characteristics are shown. As the barrier film, a composite metal film in which an A1 film was formed on Schottky barrier metal Ti was used. As in Fig. 5, the solid line shows the case where the element temperature of the semiconductor pressure sensor is 0 ° C, the broken line shows the case of 25 ° C, and the alternate long and short dash line shows the case of 40 ° C. As the forward current IF is increased, the output voltage VF also increases.At the first rise, the characteristics are different, but the curves are almost the same when the forward current IF is around 2 mA. Draws almost the same trajectory even at different temperatures. The operating point is the intersection of the forward current IF = 2 mA and the reference element temperature 25 ° C curve, and the operating range in which approximately ± 5 mV centered around this operating point (shaded area) can be used as a sensor. It becomes. The operating point is the point at which the rate of change of the output voltage VF is the smallest when the element temperature changes to 0 ° C, 25 ° C, and 40 ° C. The output voltage VF at an element temperature of 25 ° C at IF = 2mA Based on (633mV) as a reference, the variation in the same forward current value was measured. As a result, the rate of change was + 0.32% (VF = 635mV) at 0 ° C, and 0.32% (VF = 631mV at 40 ° C). ) Was obtained with very little temperature dependence.

FIG. 8 shows changes in output voltage with respect to changes in pressure when pressure is actually introduced into the semiconductor pressure sensor having the characteristics shown in FIG. The forward current in the high-density current region is IF = 2 mA, the forward current is constant with a constant current source, and the output voltage change AVF under pressure when the output voltage under atmospheric pressure is the standard. Shown in Element temperature is 0. Even when changing to C, 25 ° C and 40 ° C, there is no significant difference in the AVF-pressure curve. Two curves for each element temperature of 0 ° C, 25 ° C, and 40 ° C are drawn at each temperature. The range of variation is shown.

[0047] As described above, by changing the type of noria metal used in the semiconductor pressure sensor and the junction area between the noria metal and the semiconductor, it is adapted to the temperature range, driving forward constant current, detection pressure range, etc. to be used. be able to.

Next, FIG. 9 shows a pressure sensor unit of the can type using the first semiconductor pressure sensor of FIG. A first semiconductor pressure sensor is attached to a pressure introduction pipe 31 through which a pressure is introduced via a support base 32. The support base 32 is made of silicon, glass, or the like in order to improve the adhesion with the first semiconductor pressure sensor. Further, the pressure introduction hole 35 of the support base 32 is formed to be substantially the same as the size of the diaphragm portion 5 of the first semiconductor pressure sensor, and converts the diameter of the pressure introduction hole 34 of the pressure introduction pipe 31. Have a role. Fix it to the base or board with the lead bin 33.

FIG. 10 shows a structure in which the base 4 of the first semiconductor pressure sensor is removed and the Schottky barrier diode element 10 is directly attached to the support base 32, which is higher than the unit of FIG. The height can be lowered.

[0050] In any of the cases shown in Figs. 9 and 10, the diaphragm portion 5 of the semiconductor pressure sensor in Fig. 1 is biased to one side connecting to the central portion of the element, and the element shape is rectangular. In the case of a knocker, the placement position is biased from the center to one side, and it cannot be made compact.

[0051] FIG. 11 shows a pressure sensor unit of a mold type using the second semiconductor pressure sensor of FIG. A second semiconductor pressure sensor is mounted on a support base 42 made of glass or the like, which is formed in a pressure introduction pipe 41 into which pressure is introduced. The second semiconductor pressure sensor has a square shape and is provided with a diaphragm portion 15 as a pressure sensing portion in the center portion. In addition, since the size of the opening 16 can be appropriately formed, it can be formed compactly with good consistency with the pressure introducing hole 43 of the pressure introducing pipe 41. The second semiconductor pressure sensor and the support base 42 are covered with a resin mold 44 except for the hollow portion 46, and are fixed to the base and the substrate by lead pins 45. The reason why the hollow portion 46 is provided is that if the entire sensor interior is filled with the resin mold 44, the diaphragm portion 15 will not be elastically deformed and pressure measurement will not be possible. [0052] FIG. 12 shows that the Schottky noria diode element 20 is directly attached on the support base 42 by anodic bonding without forming the base portion 14 of the second semiconductor pressure sensor, and the hollow portion is formed by the resin mold 44. Covered except for 46. As a result, the size can be made smaller than the type shown in FIG.

[0053] Next, a third semiconductor pressure sensor of the present invention will be described. 13 and 14 show the structure of a third semiconductor pressure sensor according to the present invention, FIG. 13 shows a plan view, and FIG. 14 shows a side view.

The third semiconductor pressure sensor is formed by dispersing a plurality of Schottky noria diodes on an n-type or p-type semiconductor substrate 77. Dl, D2, D3, and D4 indicate Schottky noria diodes, and each Schottky noria diode includes a barrier film, an electrode, and a semiconductor substrate.

[0055] The Schottky Noria diode D1 includes the Noria film 61, the electrode 62, and the semiconductor substrate 77, and the Schottky Noria diode D2 includes the Noria film 63, the electrode 64, and the semiconductor substrate 77, and the Schottky barrier diode D3 is The Schottky barrier diode D4 includes the noria film 67, the electrode 68, and the semiconductor substrate 77. The Schottky barrier diode D4 includes the noria film 65, the electrode 66, and the semiconductor substrate 77. As can be seen from the figure, each electrode 62, 64, 66, 68 is formed in a semicircular shape so as to surround the noria film. In each Schottky noria diode, when the barrier films 61, 63, 65, 67 made of metal and the semiconductor substrate 77 are brought into contact with each other, a depletion layer is formed on the contact surface on the semiconductor substrate 77 side, and a Schottky barrier is generated. To do.

[0056] As described above, each Schottky junction formed by contacting each of the barrier films 61, 63, 65, 67 and the semiconductor substrate 77 is a diaphragm region 78 in the semiconductor substrate 77 (indicated by a dotted line in the figure). It is included in the (enclosed area) and becomes an area for sensing pressure. As will be described later, a portion other than the diaphragm region 78 may be provided with a pedestal as shown in FIG. 24, for example. Further, without forming the pedestal portion, it may be directly joined to the pressure introducing pipe 91 having an inner diameter suitable for the diaphragm region 78 as shown in FIG.

[0057] In order to generate a Schottky junction, when an n-type semiconductor substrate is used as the semiconductor substrate 77, the work function of each barrier film 61, 63, 65, 67 is the work function of the n-type semiconductor substrate 77. Choose a material for each noria film and n-type semiconductor substrate 77 so that it is larger than the number. There is a need. For example, the barrier film is a composite film of a noria metal such as Pt and a metal such as A1, and the n-type semiconductor substrate 77 is a silicon substrate doped with an n-type impurity. In addition to Pt, there are Ti, Mo, W, Al, V, Pd, Au, etc. as materials for forming noria metal. In this case, each barrier film is on the anode (positive electrode) side, and each of the electrodes 62, 64, 66, and 68 is on the force sword (negative electrode) side.

[0058] On the other hand, a p-type semiconductor substrate may be used instead of the n-type semiconductor substrate as the semiconductor substrate 77. In this case, the material is made larger than the work function of the work function force barrier film of the p-type semiconductor substrate. To form a Schottky junction. In this case, each noria membrane is on the force sword (negative electrode) side, and each electrode is on the anode (positive electrode) side.

Each electrode 62, 64, 66, 68 is manufactured by forming an n + diffusion layer or a P + diffusion layer having a very high impurity concentration on the semiconductor substrate 77. When the n-type semiconductor substrate 77 is used, the electrodes 62, 64, 66, and 68 are formed of n + diffusion layers.

In this example, it is assumed that the n-type semiconductor substrate 77 is used, and the electrodes 62, 64, 66, and 68 are configured by n + diffusion layers. In this case, the electrodes 62, 64, 66, 68 as the force sword electrodes and the barrier films 61, 63, 65, 67 as the corresponding anode electrodes are electrically connected to allow a forward current to flow.

[0061] Pad electrodes 73 and 75 are provided as input terminals for connecting a constant current source or the like in order to flow a forward current to each of the Schottky barrier diodes D1 to D4. The node electrode 73 is connected to the noria films 61 and 65 by the wiring 69. The pad electrode 75 is connected to the electrodes 64 and 68 by the wiring 71. In addition, pad electrodes 74 and 76 are provided as output terminals so that forward voltage changes can be taken out when a forward current is passed through each Schottky noria diode. The nod electrode 74 is connected to the electrode 62 and the barrier film 63 by the wiring 70. The pad electrode 76 is connected to the electrode 66 and the barrier film 67 by the wiring 72. The selfish wires 69, 70, 71, 72 and the nod electrodes 73, 74, 75, 76 are each formed of A1 (anoromium).

The size of the semiconductor pressure sensor configured as described above can be, for example, a square shape having a length L of 1.5 mm, and can be formed into a relatively small pressure sensor.

[0063] When pressure is applied to the diaphragm region 78, the diaphragm region 78 is distorted. This distortion causes distortion at each Schottky junction between each barrier film 61, 63, 65, 67 and the n-type semiconductor substrate 77, so that the resistance of each Schottky junction changes and the forward current is changed. The pressure changes, and the pressure can be detected from the relationship between the introduced pressure and the forward voltage change.

By the way, the semiconductor pressure sensor of the present invention has a configuration in which a plurality of the Schottky junctions are arranged in the diaphragm region 78 in a distributed manner. By doing so, as described later, the sensitivity can be made larger than that of a semiconductor pressure sensor having one Schottky junction.

For example, FIG. 17 schematically shows a state in which a Schottky Noria diode force is formed corresponding to the configuration of FIG. 13, and when the pressure is introduced, the diaphragm is distorted. Tensile stress acts on the Schottky junction diodes corresponding to the Schottky diodes D2 and D3 formed near the center of the diaphragm, and the Schottky noria diodes D1 and D4 formed around the diaphragm Compressive stress acts on the corresponding Schottky joint.

A relationship as shown in FIG. 18 exists between the forward current IF and the forward output voltage VF of the Schottky barrier diode. Here, it is assumed that the magnitudes of the compressive stress and the tensile stress are almost the same. When the pressure is not applied and the Schottky junction is not distorted, the initial characteristics indicated by the solid line (initial) are shown, but when the Schottky junction shrinks due to the compressive stress. Indicates the characteristic indicated by the broken line. When compared with the specified forward current, VF is smaller by AVF than the initial value.

[0067] On the other hand, when the Schottky joint is stretched by the action of tensile stress, it shows the characteristics represented by the alternate long and short dash line, and when compared with the same forward current as in the case of compressive stress, VF is higher than the initial value. AVF only grows. If these two Schottky diodes are connected in series in the forward direction, a fluctuation range of 2 Δν can be obtained at the connection point.

[0068] Therefore, when two Schottky barrier diodes are formed in a diaphragm, the sensitivity is doubled by disposing one in the range where tensile stress works and the other in the range where compressive stress works. be able to. In addition, the diaphragm stagnation is not uniform and uneven, but the effect of the unevenness can be reduced by distributing the Schottky junctions. And stable output characteristics can be obtained. By applying the above principle and increasing the number of Schottky junctions to be distributed, sensitivity can be further increased and the effect of stress unevenness can be reduced.

[0069] On the other hand, in a semiconductor pressure sensor using a Schottky noria diode, the wafer (semiconductor substrate 77) is ground to a thickness smaller than that of a normal diode element, so that the semiconductor substrate 77 is cracked or chipped. The probability of doing is high. For example, when the semiconductor pressure sensor is being transported or installed, the diaphragm composed of the semiconductor substrate 77 is broken, or if the pressure is measured many times, the diaphragm may be fatigued.

However, when the thickness of the semiconductor substrate 77 is increased in order to prevent the diaphragm from being cracked or chipped, there is a problem that the sensitivity is lowered. However, as in the present invention, by distributing the Schottky junctions in the diaphragm, it becomes possible to increase the sensitivity more than twice as much as the semiconductor pressure sensor with one Schottky junction. Even if the thickness of the semiconductor substrate 77 is increased, the sensitivity can be maintained high, and the occurrence of diaphragm cracks and chipping can be suppressed.

The semiconductor pressure sensor shown in FIG. 13 is obtained by increasing the number of Schottky junctions to be distributed and arranging four Schottky junctions in a diaphragm.

In FIG. 13, the force represented by D1 to D4 for each of the four Schottky barrier diodes having a Schottky junction is equivalent to the circuit of FIG. 15 if expressed as an electric circuit. The power supply voltage (operating current) is input with the pad electrode 73 serving as the input terminal as the positive electrode and the pad electrode 75 serving as the negative electrode, and the output voltage is taken out between the pad electrode 74 and the pad electrode 76 serving as the output terminals.

[0073] As shown in FIG. 15, D1 to D4 form a Wheatstone bridge circuit. If the internal resistances of the Schottky barrier diodes D1 to D4 are represented by R1 to R4, they are equivalent to the circuit of FIG. become. When a forward operating current is applied between the input terminals IN 1 (pad electrode 73) and IN2 (pad electrode 75), if the Schottky junction of the Schottky noria diode is distorted, R1 ~ Force that changes R4 The voltage difference generated by the change of R1 to R4 is taken out from the output terminal, that is, between OUT2 (pad electrode 74) and OUT1 (pad electrode 76). For example, Schottky barrier diodes D1 to D4 having the same configuration are used, and Rl = R2 = R3 = R4 = R and all internal resistances are made equal. In the state where the Schottky junction is not distorted, that is, in the initial state, the voltage difference between OUT 1 and OUT 2 of the Wheatstone bridge circuit is 0 and the equilibrium state is obtained. Next, when pressure is applied to the diaphragm region 78 of the semiconductor substrate 77 to cause stagnation, the resistance values of R1 to R4 change.

As shown in FIG. 17, tensile stress is applied to D2 and D3 formed at the center of the diaphragm region 78, and compressive stress is applied to Dl and D4 formed at the peripheral portion of the diaphragm region 78. Therefore, if the strain caused by the compressive stress and the strain caused by the tensile stress are the same, a voltage difference S of 2 ΔVF is generated at the connection point of the two Schottky barrier diodes as shown in Fig. 18. Therefore, OUT1 in Figure 16 has a maximum voltage fluctuation of 2 AVF, while OUT2 has a maximum voltage fluctuation of +2 AVF, so the maximum voltage difference between the output terminals OUT1 and OUT2 is 4 AVF. The sensitivity is up to 4 times that of sensing pressure with a key barrier diode.

FIG. 19 shows characteristics of forward current density (10 ⁵ AZm ² ) and forward output voltage (mV) of one Schottky noria diode in the semiconductor pressure sensor of the present invention. As the barrier film, Pt was used as a Schottky barrier metal, and a composite metal film with an A1 film formed thereon was used. The curves for the semiconductor pressure sensor element temperature of -25 ° C, 25 ° C, and 75 ° C are shown. As the forward current iF increases, the output voltage VF also increases. At the first rise, the force has different characteristics. The forward current density iF is 1.35 ~: L 4 (10 ⁵ AZm Near the middle point of ² ), the curves are almost the same, and even if the element temperatures are different, the traces are almost the same. When the element temperature is changed, the VF-iF curves intersect and the matching area is called the zero cross point.

It can be seen that the zero cross point is a high current density region with very little temperature dependence. By operating the semiconductor pressure sensor in a high current density region, it is possible to perform accurate measurement regardless of temperature changes. If the operating current is determined with the vicinity of the zero cross point as the operating point, and the operating current is supplied by a constant current source, the sensor operates accurately without being affected by temperature changes.

FIG. 20 shows a conventional diffusion resistance type semiconductor pressure sensor and a Schottky junction type semiconductor. The comparison of the output voltage fluctuation by the temperature change with a pressure sensor is shown. The graph of Fig. 19 shows the fluctuation of the output voltage per 1 ° C with reference to the output voltage VF at the element temperature of 25 ° C. With the conventional diffused resistor type, the output voltage variation per 1 ° C is about 0.25% on average regardless of where the operating current is changed, whereas with the Schottky junction type, If the operating current is set near the zero cross point shown in the figure, the output voltage fluctuation per 1 ° C can be suppressed to 0.03% or less, and a semiconductor pressure sensor with extremely low temperature dependence must be formed. Can do. Therefore, there is no need to add a temperature correction circuit or the like as in the prior art.

FIG. 22 shows the relationship between the diaphragm thickness m) of the semiconductor pressure sensor and the magnitude of the output voltage. As shown in Fig. 13, a semiconductor pressure sensor consisting of four Schottky barrier diodes and a Wheatstone bridge circuit is denoted by X2, and as shown in Fig. 21, a comparative semiconductor pressure sensor consisting of one Schottky barrier diode is XI. Represented by The comparative semiconductor pressure sensor shown in FIG. 21 uses the same material as that shown in FIG. 13 and forms only one Schottky barrier diode 80 to form a pedestal 81. As can be seen from Fig. 22, the sensitivity difference between X2 and XI varies depending on the diaphragm thickness. When the diaphragm thickness is about 50 μm or less, the sensitivity of X2 is about 4 times the sensitivity of XI. I can read that I'm talking.

[0080] Figure 23 shows the change in output voltage with respect to the change in pressure when pressure is actually introduced. The vertical axis indicates the change in output voltage Δν under pressure when the output voltage under atmospheric pressure is used as a reference. In the Schottky junction type semiconductor pressure sensor, the forward current at the zero cross point is set as the operating current, the forward current is made constant by the constant current source, Pt is used as the Schottky barrier metal as the NORA film, On top of this, a composite metal film in which an A1 film was formed was used. The third semiconductor pressure sensor using four Schottky diodes of the present invention is represented by the Y3 curve, and the comparative semiconductor pressure sensor using one Schottky barrier diode is represented by the Y2 curve. The semiconductor pressure sensor is shown by the Y 1 curve. Y3 has a diaphragm thickness of 50 μm, Y2 has a diaphragm thickness of 50 μm, and Y1 has a diaphragm thickness of 20 / zm. The linearity of Y3 was ± 0.35% FS, Y2 was ± 0.59% FS, and Y3 force S ± 0.6% FS. Thus, even when the diaphragm thickness is 50 m, the Y3 semiconductor pressure sensor of the present invention shows the highest sensitivity and the best linearity. It has become a thing.

[0081] Next, when pressure is applied to the diaphragm of the third semiconductor pressure sensor, a pedestal 82 is often provided as shown in FIG. 24, but without providing a pedestal as shown in FIG. A structure in which a semiconductor pressure sensor is mounted on the pressure introducing pipe can be employed. The height of the element can be made lower than when a pedestal is provided.

[0082] Normally, the pedestal portion 82 uses a silicon substrate or the like to form a tapered cut-out opening, and the pedestal portion 82 and the third semiconductor pressure sensor include a thermosetting resin or the like. It is joined by a joining layer 83 which also has a force. However, if the structure has the pedestal portion 82, it is necessary to bond the semiconductor pressure sensor to the semiconductor pressure sensor via the bonding layer 83 after forming the pedestal portion. There was a drawback of increasing. However, if the pedestal is not provided as shown in FIG. 25 and is directly joined onto the pressure introducing pipe 91 as shown in FIG. 27, the above problem is solved.

[0083] In addition, by forming the diaphragm region, that is, the semiconductor pressure sensor, the force pedestal portion 82 that improves the sensitivity as the thickness of the semiconductor substrate 77 is reduced is not formed, so that the pressure introduction side is not formed. The surface of the semiconductor substrate 77 can be prevented from being covered with the bonding layer 83, and the sensitivity can be prevented from being deteriorated even a little.

FIG. 27 shows an example in which a semiconductor pressure sensor not provided with a pedestal portion is provided on the pressure introduction pipe 91. A third semiconductor pressure sensor is mounted on the upper end of the pressure introducing pipe 91 into which pressure is introduced. When pressure is introduced from the pressure introduction hole 92 formed in the pressure introduction pipe 91, the semiconductor substrate in the third semiconductor pressure sensor stagnates and the output voltage changes. Remove from lead pin 97.

In addition, the semiconductor pressure sensor is covered with a resin mold 93 except for the hollow portion 94, and is fixed to a base or a substrate by a lid bin 97. The reason why the hollow portion 94 is provided is that if the sensor is entirely filled with the resin mold 93, the diaphragm region of the semiconductor pressure sensor will not be elastically deformed and pressure measurement will not be possible. Because.

By the way, FIG. 26 compares the sensitivity of a semiconductor pressure sensor having a pedestal portion and the sensitivity of a semiconductor pressure sensor having a pedestal portion. When there is no pedestal as shown in Fig. 27, When the semiconductor pressure sensor is arranged directly on the pressure introduction pipe 91 and there is a pedestal, the structure of Fig. 27 is used, and the semiconductor pressure sensor having the structure of Fig. 24 is used, and the area of the diaphragm area to which pressure is applied is Configured to be equal. As a result, as shown in Fig. 26, the sensitivity characteristics with or without the pedestal were equal to or better than those with the pedestal.

Next, a method for manufacturing the semiconductor pressure sensor shown in FIGS. 13, 14, and 25 of the present invention will be described below. First, a method for forming Schottky Noria diodes D1 to D4 in a semiconductor pressure sensor is described. For example, a thickness of 3.33 to 4.07 ^ m, on an n-type semiconductor substrate (first conductivity type semiconductor substrate) 77, Grow an epitaxial layer with a resistivity of 0.63 to 0.77 Ω'cm and grow a thermal oxide film at 9500 A. The thermal oxide film is selectively removed by photoresist technology and etching with hydrofluoric acid, PoCl diffusion is performed at 1050 ° C for 120 minutes, and each electrode 62, 64, 66, 68 as a force sword region is formed on a semiconductor substrate Form inside 77. Phosphorus can be supplied by implanting phosphorus ions in addition to PoCl.

Next, a CVD film containing phosphorus appropriate for gettering mobile ions is deposited and flattened by heat treatment at 1000 ° C. for 30 minutes. Of course, phosphorus may not be included. The CVD and thermal oxide films are selectively removed again by the photoresist technique and etching with hydrofluoric acid. Pt, Ti, Mo, W, Al, V, Pd, Au, etc., which are Schottky barrier metals, are deposited by sputtering or vapor deposition and heat-treated at an appropriate temperature to form silicide. Barrier films 61, 63, 65, 67 that serve as anode electrodes by providing several layers of appropriate metal layers that serve as diffusion layers on the barrier metal, and an A1 layer having a top thickness of 24 to 26 kA. Form.

[0089] On the force sword region of each electrode 62, 64, 66, 68, wirings 69 to 72 by A1 are patterned, but the force sword region becomes an n + diffusion layer with a very high impurity concentration. Therefore, a Schottky barrier is not formed at the junction with the wirings 69 to 72, and an ohmic contact is made. Then, pad electrodes 73 to 76 are formed by A1 at corresponding portions of the wirings 69 to 72.

[0090] A 8000A silicon nitride film is deposited thereon under reduced pressure at all times or by a plasma CVD machine, and barrier films 61, 63, 65, 67 and electrodes 62, 64, 66, 68 are formed by photolithography and dry etching. The region and the element periphery are selectively removed. Tape etc. so as not to damage the surface Polish from the back while protecting with a thickness of 20-120 μm. Finishing was 2000 finish.

[0091] Next, including the method of forming the base portion is described in a case having a base portion 82 as shown in FIG. 24, 1 X 10 ¹⁸ cm_ ³ below B, P, As, an n-type impurity such as Sb A silicon nitride film of 8000A is deposited on the (100) plane silicon wafer, and a region corresponding to the upper area of the opening is selectively removed by photolithography and dry etching. Protect the surface pattern with tape, etc., and polish it from the back surface to a thickness of 200 to 300 μm. Immerse in 24wt% KOH aqueous solution and etch until an opening is formed.

[0092] When the semiconductor substrate 77 on which the Schottky diodes D1 to D4 are formed and the pedestal portion 82 are joined by applying a heat of 180 to 200 ° C using the joining layer 83 made of thermosetting resin, 24 semiconductor pressure sensors are completed. The bonding layer 83 may be a high-strength adhesive or a bonding layer using SOI technology.

Claims

The scope of the claims

[1] A semiconductor pressure sensor that detects pressure based on diaphragm distortion,

A semiconductor pressure sensor, wherein the diaphragm includes a Schottky junction.

[2] The semiconductor pressure sensor according to [1], wherein the Schottky junction is formed by bringing a Noria film into contact with a semiconductor.

3. The semiconductor pressure sensor according to claim 2, wherein the electrode formed on the semiconductor, the barrier film, and the semiconductor constitute a Schottky barrier diode.

4. The semiconductor pressure sensor according to claim 3, wherein a forward current is passed between the electrode and the barrier film, and the pressure is detected by a change in resistance value of the Schottky junction.

[5] The semiconductor pressure sensor according to any one of [3] and [4], wherein the electrode is formed so as to surround the periphery of the noria film.

6. The semiconductor pressure sensor according to claim 5, wherein the barrier film is formed at a central portion of the semiconductor.

[7] The semiconductor pressure sensor according to any one of claims 1 to 4, wherein a plurality of Schottky junctions are dispersedly arranged.

8. The semiconductor pressure sensor according to claim 7, wherein the Schottky junction constitutes a Wheatstone bridge circuit.

9. The semiconductor pressure sensor according to claim 7, further comprising a pad electrode connected to the anode side or the force sword side of the Schottky noria diode.