JPS60154575A - Manufacturing method of semiconductor pressure sensing element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention is applicable to industrial measurement, automobiles, and medical treatments.

The present invention relates to a method of manufacturing a semiconductor pressure detection element used in a pressure sensor for general use such as home appliances.

[Prior art]

2. Description of the Related Art In recent years, with the development of semiconductor manufacturing technology, pressure sensors have been developed that use a semiconductor pressure detection element made of silicon in the shape of a diaphragm as a pressure receiving part. This pressure sensor utilizes the fact that when pressure is applied to a semiconductor with a crystal structure, strain is generated in the crystal, and its piezoresistance changes.The pressure/electrical signal conversion is directly performed by the semiconductor pressure sensing element itself, and is mechanically Since there are no moving parts, there is no characteristic deterioration due to mechanical wear, and this has attracted widespread attention.

The semiconductor pressure sensing element is conventionally manufactured by chemically etching or electrolytically etching a silicon wafer. That is, the former is a method in which a mask of metal, resist, etc. is applied to the surface that will become the diaphragm, and then the semiconductor substrate is dissolved by the chemical action of chemicals. On the other hand, the latter method involves providing a resistive layer on a semiconductor substrate and melting the semiconductor substrate using the principle of electrolysis.

However, in the conventional manufacturing method of this type of semiconductor pressure sensing element, the former requires controlling the etching liquid such as temperature, concentration, stirring conditions, etc., and controlling the time to adjust the depth of etching. For this reason, there are many process control elements, making it difficult to control the process to obtain a diaphragm with an accurate thickness. In the latter case, the first
As shown in the figure, since the resistive layer 2 is provided on the semiconductor substrate 1, the etched portion 4 not covered with the mask 3 is exposed to the resistive layer 2.
Since the current decreases when the current is close to , there is an advantage that process control can be easily performed using this current.

On the other hand, when the etched portion 4 approaches the resistive layer 2, the current is concentrated at the end portion 4a, so that an acute notch is formed at the end portion 4a or the central portion 4b is left thick. As a result, stress concentrates on the acute notch, resulting in a disadvantage in that the withstand pressure of the diaphragm formed by the etched portion 4 is reduced.

[Summary of the invention]

The present invention has been made in consideration of these circumstances.
With an extremely simple configuration in which a resistive layer and a mask are provided on a semiconductor substrate, a part of the semiconductor substrate is electrolytically etched, and this etched portion is further chemically etched, a semiconductor pressure sensing element with a high withstand voltage can be manufactured with simple process control. The present invention provides a method for manufacturing a semiconductor pressure sensing element.

Hereinafter, the configuration and the like will be explained in detail with reference to illustrated embodiments.

〔Example〕

2 to 5 are cross-sectional views for explaining the method of manufacturing a semiconductor pressure sensing element according to the present invention. In these figures, 1 is a semiconductor substrate such as a silicon wafer, and p-type is more piezoelectric than n-type. Since the resistance coefficient is large, an n-type semiconductor is used and formed into a plate shape. First, as shown in FIG. 2, a resistive layer 2 having a relatively higher resistance than the semiconductor substrate 1 is provided on the upper surface of the semiconductor substrate 1. This resistance layer 2 is a p-type resistance layer, and can be provided by diffusion of impurities in a semiconductor or by epitaxial growth. Next, as shown in FIG. 3, a mask 3 is provided on the back surface of the semiconductor substrate 1 to cover the non-etched portion of the back surface. This mask 3 can be made of, for example, a conductive metal such as platinum PT or an alloy, or a combination of this metal and a resist film. 5 is a mask that covers the surface of the semiconductor substrate 1, and in addition to the conductive metal 1, a chemical-resistant material having corrosion resistance against chemicals can be used.

Then, in the step shown in Fig. 4, sodium hydroxide Na'O
The electrode connected to the negative side of the DC power source is placed in an electrolytic solution such as an aqueous solution of H to apply negative electricity, and the semiconductor substrate 1 with the mask 3 connected to the positive side of the DC power source is immersed in the liquid. Electrolytic etching is performed on the etching portion 4, which is a part of the back surface of the substrate 1. The process control of this electrolytic etching can be performed using an etching current. That is, as shown in FIG. 6, which shows the relationship between the etching current I and the time T, the etching current decreases as the etched portion 4 approaches the resistive layer 2, so the etching current I decreases to a predetermined current 1c. The electrolytic etching is finished at a time Tc.

Thereafter, the semiconductor substrate 1 is further immersed in an etching solution such as acid, and the etched portion 4 is chemically etched. This fifth
Process control in the chemical etching process shown in the figure is performed by time management.

In the method for manufacturing the semiconductor pressure sensing element constructed in this way, the resistive layer 2 is provided on the semiconductor substrate 1, and the conductive mask 3 is connected to a DC power source for electrolytic etching. This layer can be used as an etching stop layer and processed to leave a diaphragm shape.This is because the resistance layer 2 has a higher resistance than the semiconductor substrate 1 and is less likely to be electrolyzed.
As the etching current approaches the resistive layer 2, the etching current decreases, so that the etching current can be used as a process control element to easily control the process.

Furthermore, since this etched portion 4 is chemically etched after electrolytic etching, as shown in FIG. 7 by the chain line in FIG. The notch can be processed into a rounded curved surface.

This is because chemical etching is performed uniformly on the same material, and chemicals are less likely to be supplied to sharp corners than to other smooth surfaces. In addition, in chemical etching, since the semiconductor substrate 1 with lower resistance melts faster, the thick part of the central part 4b left in the electrolytic etching process is melted faster than the resistive layer 2, and the thickness is reduced to approximately It can be modified to be even.

Here, since etching has already been carried out in the previous electrolytic etching process, the amount of etching is small, so that the process can be controlled only by time management without requiring the management of the etching solution.

Therefore, by controlling the etching current and the chemical etching time, the end portion 4 of the etching portion 4 that becomes the diaphragm can be
a can be formed into a rounded curved surface.

In the above embodiment, an example was explained in which a p-type resistor Ii2 was provided on an n-type semiconductor substrate 1, but the present invention is not limited to this. Of course, the resistance layer 2 may also be provided.

〔Effect of the invention〕

As explained above, according to the present invention, after electrolytically etching a resistive layer on a semiconductor substrate, the etched portion is further chemically etched. The curved surface shape can be corrected by the etching liquid level, and the semiconductor pressure sensing element can be processed by controlling the process by controlling the etching current and time.

Therefore, since it is possible to prevent stress from concentrating on the end portions as in the conventional case, there is an effect that a semiconductor pressure sensing element with high proof strength can be manufactured with simple process control.

As a result, since the thickness of the element can be made thinner, it is also possible to increase the output with respect to the measured pressure.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor substrate for explaining a conventional method for manufacturing a semiconductor pressure sensing element, and FIGS. 2 to 5 are semiconductor substrates for explaining a method for manufacturing a semiconductor pressure sensing element according to the present invention. FIG. Figure 6 shows the etching current 2 in the electrolytic etching process.
Fig. 7 is an enlarged cross-sectional view showing the end of the cutting part of Fig. 7 showing the time 6'' relationship. 1... Semiconductor substrate, 2... Resistance layer, 3...
・Mask, 4...Etched part, 4a...End part. Patent applicant: Yamatake Honeywell Co., Ltd. Agent: Masaki Yamakawa (and 2 others) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A semiconductor substrate is provided with a resistive layer having a relatively higher resistance on the upper surface of the semiconductor substrate, and a mask is provided on the back surface of the semiconductor substrate to cover the non-etched portion, and after a part of the back surface of the semiconductor substrate is electrolytically etched, this etching is further performed. 1. A method of manufacturing a semiconductor pressure sensing element, comprising chemically etching a portion thereof.