JPS63308390A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To make it possible to obtain good breakdown strength characteristics and good temperature characteristics by a method wherein a part to correspond to a recessed part is doped with an impurity to form a P-type conductivity type part and an n-type conductivity type part is removed by etching. CONSTITUTION:A part A to correspond to a recessed part 21 of an n-type substrate 1 is doped with a P-type impurity, an N-type epitaxial layer is formed on the side of one surface of the substrate and a mask consisting of an Si nitride (SiN) film is provided on the side of the other surface of the substrate. Then, an alkali etching is performed to the depth to reach the recessed part 21 from the other surface side of the substrate, an inverse bias voltage E is applied to the P/N junction part between the substrate 1 and a diaphragm 2, an alkali etching is performed, the diaphragm 2 and the substrate 1 are formed and a P-type layer only is etched in an inversely biased state. Moreover, a semiconductor process for forming a piezo-resistance gauge 3 and lead wires 31 is executed. Thereby, a semiconductor pressure sensor; which has good breakdown strength characteristics and good temperature characteristics, is suitable for mass production and is low in cost; can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a 9J manufacturing method for a semiconductor pressure sensor.

More specifically, the present invention relates to a method of manufacturing a semiconductor pressure sensor in which a diaphragm and a support substrate are integrally formed using an etching process.

(Prior Art) FIG. 4 is a diagram illustrating the configuration of a conventional example that has been commonly used.

In the figure, 1 is a substrate made of a semiconductor.

A diaphragm 2 is attached to the substrate 1 and receives the measurement pressure P. 21 is a recessed portion forming a diaphragm main body portion 22 in the diaphragm 2 . 3 is the diaphragm main body part 2
This is a piezoresistance gauge installed at 2.

In the above configuration, when a measurement pressure P is applied to the diaphragm main body portion 22, distortion occurs, and an output corresponding to the measurement pressure P is obtained from the piezoresistance gauge 3.

(Problems to be Solved by the Invention) In such a conventional arrangement, the recess 21 is
The diaphragm 2 provided with the diaphragm 2 is assembled by joining.

In this case, a bonding technique is required to attach the diaphragm 2 to the substrate 1, and issues such as bonding strength and temperature expansion coefficient differences arise, which greatly affects the characteristics of the device.

The present invention solves these problems.

An object of the present invention is to provide an inexpensive semiconductor pressure sensor that has good pressure resistance and temperature characteristics, is suitable for mass production, and is inexpensive.

(Means for Solving the Problems) In order to achieve this object, the present invention provides a semiconductor pressure sensor having a diaphragm, in which a portion of an n-type conductive silicon substrate corresponding to a recessed portion forming the diaphragm is A P-type conduction type portion is formed by doping with impurities. Next, the epitaxial layer having the n-type conductivity type is laminated on the silicon substrate. Thereafter, a reverse bias voltage is applied between the impurity doped portion and the silicon substrate portion, and between the doped portion and the epitaxial layer, and the recessed portion is removed by anisotropic etching to form a semiconductor pressure sensor. This method employs a semiconductor pressure sensor manufacturing method.

(Function) In the above configuration, when measurement pressure is applied to the diaphragm, distortion occurs, and an output corresponding to the measurement pressure is obtained from the piezoresistive gauge.

In this case, a semiconductor pressure sensor integrated with a substrate and a diaphragm is formed by doping impurities to form a P-type conductivity type portion in a portion corresponding to the recessed portion and removing the N-type conductivity type portion by etching. Obtainable.

Hereinafter, a detailed explanation will be given based on examples.

(Example) FIG. 1 is a manufacturing process diagram of an embodiment of the present invention.

In the figure, the same symbols as in FIG. 4 indicate the same functions.

Hereinafter, only the differences from FIG. 4 will be explained.

(1) A portion A corresponding to the recess 21 of the n-type blade l is doped with a P-type impurity as shown in FIG. 1(a). In this case, boron is doped.

In addition to the portions corresponding to the recesses 21, the band-like portions 23 extend beyond the recesses 21, as shown in FIG. 1(b). This is to enable the corresponding portion A to be electrically conductive through the strip portion 23.

(2) On one side of the n-shaped blade plate, as shown in Figure 1 (C),
Forming an epitaxial layer (3) As shown in Figure 1(d), apply a silicon nitride (SiN) film mask to the other side of the n-type blade plate.The silicon nitride film (SiN) is etched with an alkaline anisotropic etching solution. The etch rate is 2A'/mi+1 or less compared to the etch rate, and there is sufficient masking ability.

(4) As shown in FIG. 1<e>, alkali etching is performed from the other side of the n-type blade plate to a depth that reaches the recess 21.

(5) As shown in FIG. 1(f), apply a reverse bias voltage E to the P/N junction between the substrate 1 and the diaphragm 2,
Alkali etching is performed to form the diaphragm 2 and the substrate 1. Under reverse bias conditions, only the P-type layer is etched.

(6) As shown in FIG. 1(g), a semiconductor process is performed to form the lead wire 31 of the piezoresistive gauge 3.

Note that even in the case of anisotropic etching using alkali etching, as shown in FIG. 2, the etching is initially performed in a square shape, but it can eventually be etched in a circular shape.

As a result (1) Since the substrate 1 and the diaphragm 2 are integrally formed, it is not necessary to bond the substrate 1 and the diaphragm 2, and the problem of instability due to bonding is eliminated.

(2) Since the substrate 1 and the diaphragm 2 are made of the same silicon, there is no temperature fluctuation at the zero point due to a difference in thermal expansion coefficients.

(3) The position, thickness, and shape of the silicon diaphragm 2 can be accurately controlled by anisotropic etching that applies a reverse bias voltage.

(4) Since each wafer can be processed, it is suitable for mass production.

(5) The diaphragm can be easily formed using normal semiconductor process technology.

(6) Since no machining is used to process the silicon diaphragm, its breaking strength is high.

(7) Since the main body portion of the diaphragm 2 is composed of an n-epitaxial layer, it can be made extremely thin.
Devices for low pressure ranges such as differential pressure gauges can be easily made.

FIG. 1 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, a piezo resistance gauge 3 and a lead wire 3 are used.
The diaphragm 2 is subjected to alkali etching after the semiconductor process for forming the diaphragm 1 is completed.

In this case, the P+ terminal 32 for reverse bias during etching
It is necessary to set up

(Effects of the Invention) As explained above, the present invention provides a semiconductor pressure sensor having a diaphragm, in which a portion of a silicon substrate of an n-type conductivity type corresponding to a concave portion forming a diaphragm is doped with an impurity to conduct a p-type semiconductor pressure sensor. form the conductive part of.

Next, an epitaxial layer of the n-type conductivity is deposited on the silicon substrate. after that,! 1'i
the impurity doped portion and the silicon substrate portion;
A method for manufacturing a semiconductor pressure sensor is adopted in which a reverse bias voltage is applied between the doped portion and the epitaxial layer and the recessed portion is removed by anisotropic etching to form a semiconductor pressure sensor. A semiconductor pressure sensor with an integrated diaphragm can be obtained.

As a result, (1) there is no longer a problem of instability due to bonding, which occurs when the substrate and diaphragm are separate bodies; (2
) Since the substrate and diaphragm are made of the same silicon, there is no temperature fluctuation at the zero point due to differences in thermal expansion coefficients. (3)
The position, thickness, and shape of the silicon diaphragm can be precisely controlled by anisotropic etching that applies a reverse bias voltage. (4) Since each wafer can be processed, it is suitable for mass production.

(5) The diaphragm can be easily formed using normal semiconductor process technology. (6) No machining is used to process the silicon diaphragm, so
It has high breaking strength. (7) Since the main body portion of the diaphragm is composed of an epitaxial layer of the first conductivity type, it can be made extremely thin, and devices for low pressure ranges such as differential pressure gauges can be easily manufactured. (8) Circular diaphragms can be manufactured even with anisotropic etching.

Therefore, according to the present invention, it is possible to realize an inexpensive semiconductor pressure sensor that has good pressure resistance characteristics and temperature characteristics, is suitable for mass production, and is inexpensive.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of one embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of Fig. 1, Fig. 3 is an explanatory diagram of the configuration of another embodiment of the invention, and Fig. 4 is a conventionally commonly used FIG. 2 is an explanatory diagram of a conventional one-row configuration. l...Substrate, 2...Diaphragm, 21...Recess, 22...Diaphragm body, 3...Piezoresistance game Figure 1, Figure 2, Figure 3, Figure 7At, Figure

Claims (1)

[Claims] In a semiconductor pressure sensor having a diaphragm, an impurity is doped into a portion of a silicon substrate of an n-type conductivity type corresponding to a recessed portion forming the diaphragm to form a p-type conductivity type portion. Next, the epitaxial layer having the n-type conductivity type is laminated on the silicon substrate. Thereafter, a reverse bias voltage is applied between the impurity doped portion and the silicon substrate portion, and between the doped portion and the epitaxial layer, and the recessed portion is removed by anisotropic etching to form a semiconductor pressure sensor. A method for manufacturing a semiconductor pressure sensor.