JPH06207873A - Semiconductor pressure sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable execution of accurate position alignment of a diaphragm of a small diameter with a piezo-resistance region in a semiconductor pressure sensor provided with two diaphragms being different in dimensions. CONSTITUTION:A diaphragm 6 for sensing a differential pressure is formed in a semiconductor substrate 2 by electrolytic etching of the semiconductor substrate 2 itself, and the large-thickness part of the semiconductor substrate 2 corresponding to a recessed part 20 provided on the side of a backplate 1 to which the semiconductor substrate 2 is joined and fixed is used as a diaphragm 7 for sensing a static pressure. The thickness of the diaphragm 7 for sensing the static pressure is equal to the thickness (t) of the semiconductor substrate 2. Therefore the diaphragm diameter (d) can be larger than the one obtained in the case when the diaphragm for sensing the static pressure is formed by forming the semiconductor substrate 2 to be thin, and thereby position alignment of the diaphragm 7 with a gage 9 for detecting the static pressure is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor for detecting a differential pressure or pressure and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor pressure sensor of this type, one using a Si (silicon) semiconductor diaphragm is known. In this Si diaphragm type semiconductor pressure sensor, a gauge that acts as a piezoresistive region is formed on the surface of a semiconductor substrate made of Si single crystal by an impurity diffusion or ion implantation technique, and leads are formed by vapor deposition of Al and the back surface is formed. Is formed by forming a strain-flexing portion having a thickness of about 20 μm to 50 μm, that is, a diaphragm by removing a part of it by etching. When pressure to be measured is applied to the front and back surfaces of the diaphragm, the diaphragm is deformed. Along with this, the specific resistance of the gauge changes, and the output voltage due to the resistance change at this time is detected to measure the differential pressure or pressure. Recently, in order to prevent the zero point change of the sensor caused by temperature or static pressure, the static pressure and temperature are detected, and the differential pressure or pressure signal is corrected by these detection signals to increase the differential pressure or pressure. A multi-function type semiconductor pressure sensor capable of measuring with high accuracy is known (eg, Japanese Patent Laid-Open No. 4-113).
No. 239).

FIGS. 3 and 4 show a conventional example of such a multi-function type semiconductor pressure sensor, in which 1 is a back plate, which is a Pyrex glass having a thermal expansion coefficient similar to that of the semiconductor substrate 2. A pressure introducing hole 3 is formed of ceramics or the like and penetrates the upper and lower surfaces, and the semiconductor substrate 2 is electrostatically bonded to the upper surface. The semiconductor substrate 2 is made of (100) -faced n-type single crystal Si and has a disk-shaped differential pressure-sensitive diaphragm 6 in which a thin portion is formed because of the recesses 4 and 5 provided on the back side. A pressure diaphragm 7 is formed, and both diaphragms 6 and 7 are formed.
On the front surface side, there are provided four differential pressure detection gauges 8 for detecting a differential pressure or pressure and a static pressure detection gauge 9 for detecting a static pressure. One concave portion 4 provided on the back surface side of the semiconductor substrate 2 communicates with the pressure introducing hole 3 and one side P1 of the measured pressure is introduced. The other recessed portion 5 provided on the back surface side forms a reference pressure chamber 11 by being sealed by the back plate 1, and is maintained in vacuum or atmospheric pressure. The recesses 4 and 5 are formed by electrolytic etching. The differential pressure detection gauge 8 is formed by an impurity diffusion or ion implantation technique and acts as a piezoresistive region (piezoresistive element).
By forming a wheelstone bridge with the leads 10 formed by vapor deposition of the above, differential pressure signals of pressures P1 and P2 to be measured applied to the front and back surfaces of the diaphragm 5 are differentially output. Measuring differential pressure or pressure is maximum ^{140Kgf / cm 2, 420Kgf / cm} 2 approximately, respectively. The static pressure detection gauge 9 is also the differential pressure detection gauge 8
In the same manner as described above, it acts as a piezoresistive region by being formed by impurity diffusion or ion implantation technology,
The static pressure P3 change in the reference pressure chamber 11 is detected by being connected to the wheel stone bridge by a lead (not shown) formed by vapor deposition of Al or the like. The orientation of these gauges 8 and 9 affects the output voltage when the bridge is constructed. When the gauges 8 and 9 are provided on Si having a crystal plane orientation (100), the direction in which the piezoresistive coefficient becomes maximum is the <110> crystal axis direction, and therefore the gauges 8 and 9 may be formed in this direction. desirable. 12 is an epitaxial layer.

[0004]

When two diaphragms 6 and 7 having different sizes and measurement ranges are formed on one semiconductor substrate 2, both diaphragms 6 and 7 are formed by electrolytic etching utilizing the difference in impurity concentration. Then, if the thicknesses h of both diaphragms are the same, it is possible to accurately control the thicknesses of both diaphragms by one etching. However, the diameter D of the differential pressure detection diaphragm 6
Is 2.5 mm, for example, the static pressure detection diaphragm 7 must withstand a pressure difference of several hundreds of times that of the differential pressure detection diaphragm 6. Therefore, if the wall thickness is the same, the outer diameter d of the diaphragm 7 is It must be significantly smaller than the diaphragm 6. For example, the thickness h of the two diaphragms 6 and 7 are both 25 μm, and the measured differential pressure is 1 Kgf / cm.
² , and the maximum static pressure Ps is 420 Kgf / cm ² , the diameter d of the diaphragm 7 can be calculated by the following equation. d ≦ h · (σt · / K · Ps) ^1/2 ≦ 0.025 / (90 / 0.38 × 4.2) ^1/2 = 0.187 mm, where σt is the fracture stress of Si and K is proportional It is a constant. As will be clear from now on, the diameter d of the static pressure sensitive diaphragm 7
Is much smaller than the differential pressure sensitive diaphragm 6,
Therefore, when the static pressure detection gauge 9 is formed, the diaphragm 7
There is a problem that it is difficult to align the static pressure detection gauge 9 and the static pressure detection gauge 9 with high accuracy.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to adjust the pressure of a semiconductor and a diaphragm with high accuracy. It is to provide a sensor and a manufacturing method thereof.

[0006]

In order to solve the above-mentioned problems, a semiconductor pressure sensor according to the present invention comprises a semiconductor substrate made of single crystal bonded and fixed on a back plate, and bonded to the back plate of the semiconductor substrate. A first diaphragm is formed by forming a recess in a part of the surface, and a first piezoresistive element is provided on the upper surface side of the diaphragm.
A recess is formed in a part of the surface of the back plate to be joined to the semiconductor substrate, spaced apart from the substrate-side recess, and a thick portion of the semiconductor substrate corresponding to the recess is used as a second diaphragm, and the upper surface side of this diaphragm is formed. The second piezoresistive element is provided in the. A method of manufacturing a semiconductor pressure sensor according to the present invention is the semiconductor pressure sensor described above, wherein a recess on the semiconductor substrate side is formed by etching, and a back plate side of the semiconductor substrate is formed by polishing. .

[0007]

In the present invention, the thick portion of the semiconductor substrate corresponding to the recess of the back plate forms the second diaphragm. This second diaphragm has a thickness equal to that of the semiconductor substrate itself, and therefore has a larger diameter than in the case where a recess is provided on the semiconductor substrate side. Since the recess of the back plate has a large diameter, the diaphragm and the static pressure detecting gauge can be aligned with high accuracy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor pressure sensor and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings. 1 is a plan view showing an embodiment of a semiconductor pressure sensor according to the present invention, and FIG. 2 is a sectional view of the sensor. In the figure, the same components as those in FIGS. 3 and 4 are designated by the same reference numerals. Further, the thickness and size of each part in the drawing are exaggerated for ease of understanding, and are different from actual dimensions. In these figures, the semiconductor substrate 2 according to the present embodiment is shown.
A differential pressure sensing diaphragm (first diaphragm) 6 is formed by forming a recess 4 on the back surface side of the differential pressure sensing diaphragm 4 and four differential pressure detections acting on the front surface side of the differential pressure sensing diaphragm 6 as piezoresistive regions. Forming a gauge 8 for diffusion by an ion implantation method,
A concave portion 20 is formed on the bonding surface of the back plate 1 with the semiconductor substrate 2.
Is formed by polishing to be separated from the concave portion 4 of the semiconductor substrate 2, and the thick portion of the semiconductor substrate 2 corresponding to the concave portion 4 is used as a static pressure sensitive diaphragm (second diaphragm) 7.
A static pressure detecting gauge 9 is provided on the surface of the static pressure sensitive diaphragm 7 by a diffusion or ion implantation method.

In manufacturing the differential pressure-sensitive diaphragm 6, a noble metal film such as Pt or Au is formed on the surface of the semiconductor substrate 2 by vapor deposition or the like, and the noble metal film is used as an anode in an electrolytic solution such as hydrogen fluoride. The recess 4 may be formed by dipping 2 and performing electrolytic etching or anisotropic etching in a KOH solution.

In such a structure, if the thickness t of the semiconductor substrate 2 is 250 μm, the thickness h of the static pressure-sensitive diaphragm 7 is equal to the plate thickness t of the semiconductor substrate 2, so the diameter d of the static pressure sensitive diaphragm 7 is , 1.87 from the above equation
mm, the diameter of the diaphragm can be made larger than that of the static pressure sensitive diaphragm of the conventional semiconductor pressure sensor shown in FIGS. Therefore, the static pressure sensing diaphragm 7 and the static pressure detecting sensor 9 can be easily aligned with each other, and the diaphragm 7 can be provided at a predetermined position with high accuracy. Further, the thickness of the semiconductor substrate 2 can be polished and can be formed with high precision.

The formation of the differential pressure detecting gauge 8, the static pressure detecting gauge 9, the leads 10, etc. is not directly related to the present invention and is well known in the art, and therefore its explanation is omitted here.

[0012]

As described above, according to the semiconductor pressure sensor and the method of manufacturing the same according to the present invention, in the semiconductor pressure sensor having two diaphragms having different sizes and measurement ranges, the first diaphragm is provided on the semiconductor substrate. Since the second diaphragm is formed by electrolytic etching of itself, and the second diaphragm is formed by the thick portion of the semiconductor substrate corresponding to the recessed portion provided on the back plate side where the semiconductor substrate is bonded and fixed, the thickness of the second diaphragm is equal to that of the semiconductor. The thickness of the diaphragm is equal to the thickness of the substrate. Therefore, the diameter of the diaphragm can be increased as compared with the case where the semiconductor substrate is formed thin to form the second diaphragm. Therefore, the diaphragm and the piezoresistive element can be easily aligned with each other with high accuracy, and the performance of the sensor can be improved. Further, since the recess of the back plate has a large diameter, it can be polished and formed with high accuracy.

[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 sectional view of the sensor.

FIG. 3 is a cross-sectional view showing a conventional example of a semiconductor pressure sensor.

FIG. 4 is a plan view of a sensor.

[Explanation of symbols]

 1 Back Plate 2 Semiconductor Substrate 4, 5 Recessed 6 Differential Pressure Sensitive Diaphragm 7 Static Pressure Sensitive Diaphragm 8 Differential Pressure Detection Gauge 9 Static Pressure Detection Gauge 10 Lead 20 Recessed

Claims (2)

[Claims] 1. A semiconductor substrate made of a single crystal bonded and fixed onto a back plate is provided, and a recess is formed in a part of a surface of the semiconductor substrate to be bonded with the back plate to form a first diaphragm, A first piezoresistive element is provided on the upper surface side of the diaphragm, and a recess is formed in a part of the surface of the back plate to be joined with the semiconductor substrate, spaced apart from the substrate-side recess, and the meat of the semiconductor substrate corresponding to this recess is formed. A semiconductor pressure sensor characterized in that a thick portion is used as a second diaphragm, and a second piezoresistive element is provided on an upper surface side of the diaphragm. 2. The semiconductor pressure sensor according to claim 1, wherein the recess on the semiconductor substrate side is formed by etching, and the back plate side of the semiconductor substrate is formed by polishing. Method.