JPH0686045U - Semiconductor pressure sensor - Google Patents

Abstract

(57) [Summary] [Purpose] The stress in each part of the gauge part can be made almost equal and maximum output can be obtained. [Structure] Two gauges 3a of differential pressure detection gauges (piezoresistive elements) 3A and 3B arranged in two radii and tangential directions near the outer periphery of the diaphragm 2 are divided into four minute line segments 30a to 30a. 30d are separated and divided, and these line segments 30a to 30d are arranged on the substantially same radius R from the center 0 of the diaphragm portion 2. And these line segments 3a-3d are connected by the connection part 3b.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a semiconductor pressure sensor that detects a differential pressure or pressure.

[0002]

[Prior art]

 Conventionally, as this type of semiconductor pressure sensor, one using a Si (silicon) semiconductor diaphragm is known. This Si diaphragm type semiconductor pressure sensor forms a gauge acting as a piezoresistive region on the surface of a substrate made of a semiconductor crystal (hereinafter referred to as a semiconductor substrate) by an impurity diffusion or ion implantation technique, and also by vapor deposition of Al or the like. It is configured by forming a lead and removing a part of the back surface by etching to form a thin portion with a thickness of about 20 μm to 50 μm, that is, a diaphragm portion, and applies a measurement pressure to the front and back surfaces of the diaphragm portion, respectively. When the diaphragm is deformed, the specific resistance of the gauge changes, and the output voltage accompanying the resistance change at this time is detected to measure the differential pressure or pressure.

2 and 3 are a plan view and a cross-sectional view showing a conventional example of such a semiconductor pressure sensor. The semiconductor substrate 1 is made of n-type single crystal Si of (100) plane, and its back surface is formed by etching. It is equipped with a thin disk-shaped pressure sensitive diaphragm part 2 which is sensitive to differential pressure or pressure by removing the central part, and which acts as a piezo region on the surface side of this diaphragm part 2 to detect differential pressure or pressure. Pressure detecting gauges 3 (3A, 3B) are provided and electrostatically bonded onto the back plate 4. The back plate 4 is formed of Pyrex glass, ceramics, or the like having a thermal expansion coefficient similar to that of the semiconductor substrate 1, and the back plate 4 has a recessed portion 5 formed on the back surface of the semiconductor substrate 1 in the center thereof. A through hole 6 for guiding one of the pressures P1 and P2 (P1) to be measured is formed on the back surface side.

The differential pressure detecting gauge 3 is located near the peripheral portion where the radial and circumferential stresses generated in the diaphragm portion 2 when the differential pressure or the pressure is applied are maximized on the surface of the pressure sensitive diaphragm portion 2. Four are formed by the diffusion or ion implantation method, and by connecting to the Wheelstone bridge, the differential pressure signals of the pressures P1 and P2 to be measured applied to the front and back surfaces of the diaphragm part 2 are output differentially. To do. Maximum measured differential pressure or pressure is 140 kgf / cm² , 420 Kgf / cm² It is a degree. Further, of the four differential pressure detection gauges 3, the two radial differential pressure detection gauges 3A form a folded-back gauge, so that the low concentration (10¹⁹ Pieces / cm³ ) Has a predetermined sheet resistance, and the two gauge parts 3a, 3a parallel to the <110> crystal axis direction having the maximum piezoresistance coefficient in the crystal plane orientation (100) and the gauge parts 3a, 3a. It is composed of a connecting portion 3b that connects one end to each other and two lead-out portions 3c and 3c that are connected to the other ends of the gauge portions 3a and 3a, respectively. The connecting portion 3b and the lead-out portions 3c and 3c are the gauge portion. In order to eliminate these effects on 3a and 3a, high concentrations (10^{twenty one} Pieces / cm³ ) Conductivity type (p⁺ (Type) semiconductor material region is formed. On the other hand, the two tangential direction differential pressure detection gauges 3B do not form a turnback gauge, and the low concentration (10¹⁹ Pieces / cm³ ) Has a predetermined sheet resistance and is connected to one gauge part 3a parallel to the crystal axis direction of <110> that has the maximum piezoresistive coefficient in the crystal plane orientation (100) and the end part of the gauge part 3a. High concentration (10 ^{twenty one} Pieces / cm³ ) Conductivity type (p⁺ (Type) two lead-out portions 3c, 3c forming a semiconductor material region.

The piezoresistive coefficient of the differential pressure detection gauge 3 decreases as the doping amount of impurities into the semiconductor substrate 1 increases for both p-type and n-type. Therefore, the impurity concentration is set low in order to increase the rate of change of the specific resistance of the differential pressure detection gauge 3 to increase the sensitivity to pressure and obtain a large output voltage. Further, the piezoresistance coefficient differs between p-type and n-type, and the p-type is larger. Therefore, it is general to provide a p-type resistance layer on an n-type semiconductor.

The output voltage of the differential pressure detection gauge 3 varies depending on the shape and thickness of the diaphragm portion 2, the formation position of the differential pressure detection gauge 3, the orientation of the gauge itself, and the like. For example, regarding the orientation, when a gauge is provided on Si with a crystal plane orientation (001), the direction in which the piezoresistive coefficient becomes maximum is the <110> crystal axis direction, so differential pressure detection is performed in this direction. It is desirable to form a working gauge 3. However, regarding the tangential differential pressure detecting gauge 3B, since it is formed in one elongated strip, as shown in FIG. 2, the radius R from the center 0 of the diaphragm portion 2 to the center of the gauge portion is , The radius R1 to the end of the gauge portion is different (R1> R), and therefore the stress applied to the gauge portion 3a is different at the positions of the radius R1 and R. The radial pressure difference detecting gauge 3A is also the same as the tangential gauge 3B because the distance from the center 0 to each end is different.

FIG. 4 is a diagram showing the stress distribution of the differential pressure detecting gauge 3 in the tangential direction, where σr is the radial stress and σθ is the circumferential stress. As is clear from this figure, the stress applied to the center of the gauge section and the stress applied to the end of the gauge section are different, and the stress distribution is broad. The output voltage is proportional to the stress difference | σr−σθ |, and the smaller the stress distribution spreads, the larger the output.

In FIG. 1, 7a and 7b are leads made of aluminum formed by vapor deposition, and one ends of these leads 7a and 7b are connected to the lead-out portions 3c and 3c, respectively. Reference numeral 8 is a terminal portion for extracting the differential pressure signal, and 9 is a power source terminal portion for detecting the differential pressure.

[0009]

[Problems to be solved by the device]

 In the above-described conventional semiconductor pressure sensor, the differential pressure detection gauge 3 is formed in alignment with the crystal axis direction (<110>) that maximizes the piezoresistance coefficient in the crystal plane orientation (001) so as to be sensitive to pressure. . However, since the radius R from the center 0 of the diaphragm part 2 to the center of the gauge part of the differential pressure detection gauge 3 and the radius R1 to the end of the gauge part are different (R1> R), the stress is distributed over a wide range. However, there was an inconvenience that the maximum output could not be obtained.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to make stresses in respective portions of a gauge portion substantially equal to obtain a maximum output. Another object of the present invention is to provide a semiconductor pressure sensor that can be used.

[0011]

[Means for Solving the Problems]

 In order to solve the above-mentioned object, the present invention forms a thin portion by forming a concave portion on the back surface of a substrate made of a semiconductor crystal, and a pair of piezoresistors is formed on the main surface of the thin portion in the radial direction and the tangential direction, respectively. In a semiconductor pressure sensor provided with an element, each of the piezoresistive elements is divided into a plurality of minute line segments, and these line segments are arranged on substantially the same radius with the thin portion as the center.

[0012]

[Action]

 A plurality of minute line segments forming the piezoresistive element generate an output signal in response to stress. The stresses applied to these line segments are almost equal because they are arranged on the same radius centered on the thin portion, so that almost equal output signals can be generated and, as a result, maximum output can be obtained. it can.

[0013]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is a plan view showing an embodiment of a semiconductor pressure sensor according to the present invention. The same components as those in FIGS. 2 and 3 are designated by the same reference numerals, and the description thereof will be omitted. In the present embodiment, a plurality of gauge portions 3a, for example, four minute gauge portions 3a of the differential pressure detection gauges (piezoresistive elements) 3A and 3B, which are arranged near the outer periphery of the diaphragm portion 2 are provided in the radial direction and the tangential direction. Each of the line segments 30a to 30d is separated and divided, and these line segments 30a to 30d are arranged on the substantially same half radius R from the center 0 of the diaphragm portion 2, and these line segments are connected by the connecting portion 3b. It is a thing. When the differential pressure detection gauges 3A and 3B are provided on the crystal plane orientation (001) Si, the directions of the line segments 30a to 30d are the directions in which the piezoresistance coefficient is the maximum, that is, the crystal axis direction of <110> Match. It is desirable that the lengths of the line segments 30a to 30d are substantially equal, but the lengths of the line segments 30a to 30d are not limited to this, and the total length of the line segments 30a to 30d is the same as that of the conventional gauge shown in FIG. The length may be approximately equal to the length. The other structures are the same as those of the conventional semiconductor pressure sensor shown in FIGS. 2 and 3.

In the semiconductor pressure sensor having such a configuration, the four line segments 30a to 30d forming the gauge portion 3a of each of the differential pressure detecting gauges 3A and 3B have resistances corresponding to the stresses generated. The values change and each produces an output signal. In this case, assuming that the lengths of the line segments 30a to 30d are all equal, the stress applied to the line segments 30a to 30d is that these line segments are arranged on the substantially same radius R from the center 0 of the diaphragm portion 2. All yield equal and therefore equal output signals, resulting in maximum output as a pressure sensor on radius R.

Although the above embodiment has shown an example in which the gauge portion 3a is divided into four minute line segments 30a to 30d, the present invention is not limited to this, but two, three It is possible to divide into an appropriate number such as four or more. In the above-mentioned embodiment, the semiconductor substrate 1 is made of n-type silicon and the piezoresistive region, that is, the gate portion 3a is made of p-type silicon. However, this method uses a piezoresistor made of p-type silicon. However, the linearity of the pressure-resistance is better than that of the n-type, the (001) plane where the piezoresistance coefficient is maximum, and the output in both the forward and reverse directions with good symmetry in the <110> crystal axis direction can be taken out. However, the present invention is not limited to this, and it goes without saying that an n-type piezoelectric region may be formed on a p-type substrate.

[0016]

[Effect of device]

 As described above, in the semiconductor pressure sensor according to the present invention, each of the piezoresistive elements arranged near the outer periphery of the thin portion forming the diaphragm is divided into a plurality of line segments, and these line segments are divided into the thin wall portions. Since they are arranged on substantially the same radius centered on the part, the stress applied to each line segment can be made equal. Therefore, the stress distribution does not spread, the maximum output can be obtained, and the detection sensitivity of the sensor can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a semiconductor pressure sensor according to the present invention.

FIG. 2 is a plan view showing a conventional example of a semiconductor pressure sensor.

FIG. 3 is a sectional view of the sensor.

FIG. 4 is a diagram showing a stress distribution in a gauge section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Diaphragm part (thin part) 3A Radial differential pressure detection gauge 3B Tangent direction differential pressure detection gauge 3a Gauge part 3b Connecting part 3c Lead-out part 4 Back plate 5 Recessed part 30a-30d Line segment

Claims (1)

[Scope of utility model registration request] 1. A semiconductor device comprising a substrate made of a semiconductor crystal, a recess formed on a back surface of the substrate to form a thin portion, and a main surface of the thin portion provided with a pair of piezoresistive elements in a radial direction and a tangential direction, respectively. In the sensor, a semiconductor pressure sensor characterized in that each of the piezoresistive elements is divided into a plurality of minute line segments, and these line segments are arranged on substantially the same radius centered on the thin portion.