JPS63122278A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To make an etching depth for the formation of a diaphragm part small and to manufacture a semiconductor pressure sensor which is improved in characteristics of zero point unbalance, inclination, and hysteresis, by making a semiconductor substrate thin by the lapping of its rear before the formation of the diaphragm part. CONSTITUTION:After the whole rear of a silicon plate is lapped to thickness D so that D/A becomes about 1/2, position alignment to a surface pattern is performed by the use of a two-surface mask aligner so that respective etching- proof film masks 11 are formed. Next while these masks 11 are used, etching is performed to form a diaphragm part 10 of thickness C. When thickness A of the silicon plate 1 and D, the one after the back lapping, are 500 mum and 250 mum, respectively, for example, an etching depth E for the formation of the diaphragm part 10 of 30 mum in thickness C becomes 220 mum, which is a half or less as small as the etching depth of 470 mum in a conventional method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for forming a gauge resistance layer of a second conductivity type on one surface of a semiconductor substrate of a first conductivity type, and forming a gauge resistance layer of a second conductivity type on the other surface of the semiconductor substrate. The present invention relates to a method of manufacturing a semiconductor pressure sensor that converts pressure into an electrical signal, in which a diaphragm portion is formed by etching to reduce the thickness of a substrate from a region facing the substrate.

[Conventional technology]

The conventional method for manufacturing a semiconductor pressure sensor is shown in Fig. 2(a) to
It is performed in the process shown in (C), and first, as shown in Figure (a), n
An oxide film 2 is formed on both the front and back sides of a silicon plate 1, a double-sided mask aligner is used to align the front scribe line 6 and the back marker B, and a pattern of the oxide film 2 is formed by photolithography. The back surface marker 8 is formed by etching the back surface of the silicon plate 1 with a fluoro-nitric acid-based etching solution to form a recess so that it does not disappear during the next wafer process. The p-type gauge resistor 3 is made by normal wafer process.
, M membrane 4. Ni film 5. A plurality of pad portions 7 etc. are formed,
Furthermore, an etching-resistant film mask 11 is formed on the back surface to form a diaphragm 10. As shown in FIG.

[Problem that the invention seeks to solve]

However, recently, the diameter of silicon plates has become larger, and as a result, the thickness of silicon plates has become thicker to prevent cracking during wafer processing. A is about 500n, and the thickness of the diaphragm part C is 30n to increase the sensor sensitivity.
- To make it -, the etching depth B is 470n,
As the etching time becomes longer, it becomes difficult to control the thickness of the diaphragm part 10, which deteriorates the accuracy of the thickness of the diaphragm part 10 and the flatness of the surface, resulting in variations in sensitivity, unbalance of the zero point, tilt, and hysteresis. The impact on other characteristics will be greater. There is a limit to reducing the thickness A in terms of strength, and heat treatment in the wafer process.

It becomes difficult to prevent damage during multiple processes such as etching. Forming a large number of diaphragm parts on one silicon plate is desirable from the viewpoint of cost reduction, but the above-mentioned reasons prevent the diameter from increasing.

It is an object of the present invention to solve the above-mentioned problems so as to eliminate the need for deep etching and therefore to improve the accuracy of the thickness of the diaphragm.
An object of the present invention is to provide a semiconductor pressure sensor that has improved surface flatness and can therefore easily use a large-diameter silicon plate.

[Means for solving problems]

In order to achieve the above object, the method of the present invention includes forming a gauge resistance layer of a second conductivity type on one surface of a semiconductor substrate of a first conductivity type, and forming a gauge resistance layer of a second conductivity type on the other surface of the semiconductor substrate. When forming a diaphragm part by etching to reduce the thickness of the substrate starting from the region, the other side of the semiconductor substrate is entirely polished to a predetermined thickness before etching after forming the gauge resistance layer. It is something.

[Effect]

As mentioned above, polishing the entire surface of the substrate in advance to reduce its thickness reduces the amount of etching required to form the diaphragm, thereby increasing the accuracy of the thickness of the diaphragm.
The diaphragm surface can be flattened.

〔Example〕

FIGS. 1(a) to 1(e) show steps of an embodiment of the present invention, and parts common to those in FIG. 2 are given the same reference numerals.

In this case, an oxide film 2 is formed on the surface of an n-type silicon plate 1 having a thickness of A, and then a normal wafer process is performed to form the oxide film 2 shown in FIG. 1a.
3. P-type gauge resistor as shown in l. Aj film 4, dust film 5. In order to form a plurality of scribe lines 61 pad portions 7, etc., these patterns are formed by photolithography from the front side, and pattern alignment on both the front and back sides is not performed. After polishing the entire surface of the silicon plate from the back side to a thickness D such that /A becomes approximately 〃, use a double-sided mask aligner, such as Union Optical Co., Ltd.
Using type PEM-5, etching-resistant film masks 11 are formed by aligning with the pattern on the surface.Next, etching is performed using these masks 11, and the thickness is adjusted as shown in Fig. 1 (C1). For example, if the thickness A of the silicon plate 1 forming the diaphragm part 10 of C is 500n and the thickness D after backlapping is 250n, the thickness C is 3
The etching depth E for forming the 0μ diaphragm portion 10 is 220n, which is less than half of the etching depth B of 470-n in the conventional method shown in FIG.

〔Effect of the invention〕

According to the present invention, by thinning the semiconductor substrate by polishing the back surface before forming the diaphragm part, the etching depth for forming the diaphragm part is reduced, and the thickness of the diaphragm part can be reduced.

Improved surface flatness, less variation in sensitivity,
A semiconductor pressure sensor with improved zero point imbalance, tilt, hysteresis characteristics, etc. can be manufactured. Moreover, since a thin substrate is not used from the beginning and polishing is performed after the heat treatment process, etching process, and other wafer processes are completed, there is no risk of cracking even if a large diameter substrate is used (the present invention can be implemented extremely easily). So the effect is big.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view sequentially showing the steps of an embodiment of the present invention, and FIG. 2 is a sectional view sequentially showing the conventional manufacturing process. 1: n-type silicon plate, 3: gauge resistor, 11: mask,
10: Diaphragm part.

Claims (1)

[Claims] 1) A gauge resistance layer of a second conductivity type is formed on one surface of a semiconductor substrate of a first conductivity type, and etching is performed to reduce the thickness of the substrate from a region facing the gauge resistance layer on the other surface of the semiconductor substrate. A method for manufacturing a semiconductor pressure sensor, characterized in that when forming a diaphragm part, after forming a gauge resistance layer and before etching, the other surface of the semiconductor substrate is entirely polished to give the substrate a predetermined thickness.