JPH0795600B2 - Method for manufacturing semiconductor pressure sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor pressure sensor in which a diaphragm portion where a gauge resistor is arranged is formed by using a stop etching method.

[Conventional technology]

The semiconductor pressure sensor forms a thin diaphragm portion on a semiconductor wafer and detects the pressure by utilizing the resistance value change of a gauge resistance provided in the diaphragm portion when the diaphragm portion is deformed by the pressure. 2 (a) to 2 (c) show an example of a conventional diaphragm forming process, in which a P layer 2 as a stopper layer is formed on an N-type silicon substrate 1 by an epitaxial method.
Then, the N-layer 3 is laminated, and the P-type gauge resistance layer 4 is formed on the N-layer 3. First, rough processing is performed by dry etching or the like up to the vicinity of the stopper layer 2 to form the recess 5 (FIG. A). . Then, after forming a mask 6 on the surface of the substrate 1 as shown in FIG. B, stop etching up to the stopper layer 2 is performed by electrochemical etching (FIG. C).

[Problems to be solved by the invention]

When the diaphragm portion is formed by the above method, there is a large variation in the recesses 5 in the wafer or between the wafers in the rough processing shown in FIG. 2 (a), and the recesses 5 after the finishing processing shown in FIG. 2 (c). There is a problem that the depth and shape of the pressure sensor also vary greatly, and thus the characteristics of the pressure sensor also vary widely.

FIG. 3 (a) is a relationship between the diameter D of the diaphragm portion 7 after finishing of the semiconductor pressure sensor manufactured by the above method and the sensitivity, and FIG. 3 (b) is D and the sensor output nonlinearity. It can be seen that there is a large variation in characteristics.

An object of the present invention is to provide a method for manufacturing a semiconductor pressure sensor, which can reduce variations in thickness and shape of a diaphragm portion in which a gauge resistance is formed to reduce variations in characteristics.

[Means for solving problems]

In order to achieve the above-mentioned object, the method of the present invention is a semiconductor on the side opposite to the surface on which the gauge resistance is arranged, when the diaphragm portion where a plurality of gauge resistances is arranged is formed up to the stopper layer by the stop etching method. After processing from the substrate surface and forming a recess having a bottom part wider than the gauge resistance arrangement area up to the area above the stopper layer where the diaphragm deformation effect due to pressure does not reach, the area connecting the gauge resistance and the gauge resistance is surrounded. It is assumed that the mask is covered with a mask having an opening only on the outer periphery, and etching is performed from the mask opening to the stopper layer surface by a stop etching method.

[Action]

Stop etching is performed only in the depth direction of the limited diaphragm portion region by forming a mask having an opening only on the outer periphery with a region connecting the gauge resistor and the gauge resistor as the outer periphery after rough processing. Therefore, variations in the shape and thickness of the gauge resistance formation region are reduced.

〔Example〕

1 (a) and 1 (b) show the steps of one embodiment of the present invention, and the same parts as those in FIG. 2 are designated by the same reference numerals. As shown in FIG. 2 (a), rough processing is performed by dry etching from one surface of the N-type silicon substrate 1 in which the P epitaxial layer 2 and the N ^- epitaxial layer 3 are laminated on the other surface. The area is larger than the arrangement area of the gauge resistor 4. However, the bottom surface 51 is arranged so that the distance from the interface with the stopper P layer 2 is as small as possible. Then, as shown in FIG. 1A, a resist mask 6 having an opening 61 is formed only above the area where the gauge resistor 4 is arranged. Then, when stop etching is performed by electrochemical etching using the substrate 1 as an anode and the etch station as a cathode, only the lower portion of the mask opening 61 is etched as shown in FIG. Etching stops. As a result, the thickness of the gauge resistance arrangement region 7 of the diaphragm is accurately maintained at the sum of the thicknesses of the P layer 2 and the N ⁻ layer 3, and its shape is almost determined by the size of the mask opening 61, so there is no variation. Very small This variation becomes smaller as the bottom surface 51 of the recess 5 closer to the stopper layer 2 becomes closer to the stopper layer 2. However, when the thickness of that portion becomes smaller than 50 μm, the diaphragm deformation effect due to pressure extends to this portion, which is unavoidable. I have to.

4 (a) shows the relationship between the sensitivity and the diameter D of the diaphragm portion 7, and FIG. 4 (b) shows the relationship between the output nonlinearity and D,
Compared to FIGS. 3A and 3B, variations in sensitivity and non-linearity are extremely small. Further, as can be seen from FIG. 4 (a), the value of sensitivity can be arbitrarily controlled by adjusting the size of the opening 61 of the mask 6. Although not shown, variations in sensitivity, non-linearity, slope of the zero-point temperature characteristic, bending, etc. are also small.

Although dry etching is adopted as the rough processing method in the above-described embodiments, a wet etching method may be used. Although electrochemical etching is adopted as a stop etching method for finishing, a chemical etching method using a difference in impurity concentration may be used.

〔The invention's effect〕

According to the present invention, when a diaphragm of a semiconductor pressure sensor is formed, a concave portion having a bottom portion wider than an arrangement region of a gauge resistor in which the gauge resistor is arranged is formed by roughing, and a region connecting the gauge resistor and the gauge resistor is formed. The outer periphery is covered with a mask having an opening only on the outer periphery, and stop etching is performed from the opening to the stopper layer to form a concave shape. Since the variation can be reduced, the variation in the characteristic value of the pressure sensor is also reduced. Further, as a result, the correlation between the size of the diaphragm and the sensitivity has been clarified, and the sensitivity value can be arbitrarily controlled by adjusting the mask size.

[Brief description of drawings]

1 (a) and 1 (b) show a part of the manufacturing process of one embodiment of the present invention, (a) is a roughing process, (b) is a cross-sectional view showing a finishing process, and FIG. 2 (a). (C) shows a part of conventional manufacturing process, (a) is roughing, (b) is preparation for finishing, (c) is a sectional view showing finishing, FIG. 3 (a),
FIG. 4B is a diagram showing the relationship between the sensitivity and output nonlinearity of the pressure sensor manufactured by the conventional method and the diameter of the diaphragm portion, and FIGS. 4A and 4B are manufactured by the embodiment of the present invention. It is a figure which respectively shows the relationship of the sensitivity of a pressure sensor and output nonlinearity, and the diameter of a diaphragm part. 1: N-type Si substrate, 2: Stopper P layer, 3: N ^- layer, 4: Gauge resistance, 5: Recess, 6: Mask, 7: Diaphragm part.

Claims (1)

[Claims] 1. When forming a diaphragm portion in which a plurality of gauge resistors are arranged up to a stopper layer by a stop etching method, processing is carried out from the surface of a semiconductor substrate opposite to the surface where the gauge resistors are arranged, and the gauge resistors are arranged. After forming a concave portion having a bottom portion wider than the region up to the region above the stopper layer where the diaphragm deformation effect due to pressure does not reach, the region connecting the gauge resistance and the gauge resistance is the outer circumference, and the opening is formed only on the outer circumference. A method for manufacturing a semiconductor pressure sensor, which comprises covering with a mask and etching from a mask opening to a stopper layer surface by a stop etching method.