JPS61248481A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To avoid an excessive etching by a method wherein an etching stopper layer is formed beforehand as a foundation of a semi-insulating polycrystalline silicon layer using the material whose etching rate is different from that of the semi-insulating polycrystalline silicon such as silicon dioxide. CONSTITUTION:An insulation layer 12 is formed on a silicon substrate 11 and a strain detecting silicon semiconductor 13 is formed on the layer 12. A silicon dioxide layer 18 is formed over the whole surface and the parts of the layer 18 corresponding to the electrode fitting positions 19 of the silicon semiconductor layer 13 are left by etching. Then a semi-insulating polycrystalline silicon layer 16 is formed over the whole surface of the substrate 11. A resist layer 21 is formed and the semi-insulating polycrystalline silicon layer 16 is etched with the layer 21 as a mask to leave a surface protection film 14 with contact holes 17. When the etching stopper layers 20 are exposed by etching, the etching rate changes. Therefore, the etching can be discontinued before the etching is progressed to the silicon semiconductor 13. Then the resist layer 21 and the stopper layers 20 are successively removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides, for example, a semiconductor that constitutes a strain sensing element is protected with a semi-insulating polycrystalline silicon layer, and then a terminal is connected from the semiconductor through this layer. The present invention relates to a method of manufacturing a semiconductor device such as a semiconductor strain detection device, in which the depth direction of etching of the semi-insulating polycrystalline silicon layer is accurately controlled during derivation.

[Background Art] Conventionally, silicon dioxide has often been used as a material for surface protective films of semiconductor devices. However, in recent years, it has become known that semi-insulating polycrystalline silicon is more suitable as a protective film material than silicon dioxide depending on the type of semiconductor device.

By the way, recently 5OI (3i1i
A type of structure has been proposed, in which a silicon dioxide film formed by CVD is used as a surface protective film. However, if a temperature change occurs under the operating conditions of a semiconductor strain detector,
Because the coefficient of thermal expansion of silicon dioxide is significantly different from that of the strain-sensing silicon semiconductor on the silicon substrate or insulating layer, thermal strain occurs on the surface of the silicon dioxide protective film, and this strain causes strain-sensing silicon semiconductors. In addition to this, it has been found that this also interferes with the normal operation of semiconductor strain detectors.

Therefore, the present inventors proposed that the surface protective film be made of semi-insulating polycrystalline silicon, which has a coefficient of thermal expansion close to that of a silicon substrate or a strain-detecting silicon semiconductor.

However, when semi-insulating polycrystalline silicon is simply used as the material for the surface protective film, a problem arises when forming contact holes 17 in semi-insulating polycrystalline silicon layer 16 by etching, as shown in FIG. That's what I found out. That is, since there is no suitable etching solution that can provide a high selection ratio between the semi-insulating polycrystalline silicon layer 16 and the silicon semiconductor 13, it is difficult to judge the end point of etching, and as a result, the silicon semiconductor 13 and the silicon substrate 11 are There is a high possibility that the hole will be drilled to the bottom, resulting in the situation shown in Figures 3(B) and 3(C). In particular, when the etching reaches the silicon substrate 11 as shown in FIG. 3(C), leakage current occurs through the silicon substrate 11, making it impossible to obtain the required performance as a semiconductor strain detector.

[Problems to be Solved by the Invention] This invention has been made in view of the above points, and by clarifying the end point of etching the semi-insulating polycrystalline silicon layer, excessive etching can be prevented. The present invention aims to provide a method for manufacturing a semiconductor device.

[Means for Solving the Problems and Their Effects] That is, in the method of manufacturing a semiconductor device according to the present invention, first, an etching stopper layer is formed in advance as a base for a semi-insulating polycrystalline silicon layer. The polycrystalline silicon layer is formed of a material having a different etching rate, such as silicon dioxide.

Then, a semi-insulating polycrystalline silicon layer is formed on this stopper layer, and in this state, this semi-insulating polycrystalline silicon layer is etched. In this etching process, the end point of etching can be clearly known due to the difference in etching speed between the semi-insulating polycrystalline silicon layer and the stopper layer, so there is no need to etch more than necessary as in the conventional method. . Note that the stopper layer is removed after the etching so that it does not remain in the semiconductor device.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Here, a method for manufacturing a semiconductor strain detector will be explained with reference to FIG. In addition to the protective film, the present invention can also be carried out when manufacturing any semiconductor device having a layer of semi-insulating polycrystalline silicon.

First, as shown in FIG.
is a thin film layer made of single crystal, polycrystal, or amorphous silicon, and is formed by CVD or vacuum evaporation.

Next, as shown in FIG. 1B, silicon dioxide WA 18 is formed on the insulating layer 12 including the silicon semiconductor 13. Then, as shown in FIG. Then, as shown in FIG. 1C, this silicon dioxide layer 18 is etched to leave only the portion corresponding to the position 19 for attaching the silicon semiconductor electrode. The portion left here is the stopper layer 20.

Next, as shown in FIG. 1 (D), a semi-insulating polycrystalline silicon layer 16 is formed over the entire substrate 11.
lycrystalline 3i1icon:5I
PO3 (chemical formula 3ixOy) is formed by a CVD method using reactions such as SiH++N20→5ixty and SiH++CO2→5iXOV.

The electrical properties of the semi-insulating polycrystalline silicon thus produced are
The mechanical properties change continuously between silicon and silicon dioxide depending on the amount of oxygen added, but in this case, it is necessary to have the resistance required for a surface protective film of a semiconductor strain detector and the coefficient of thermal expansion to be as low as possible. The layer is formed to be similar to the silicon semiconductor 13 (the insulating layer 12 can also be formed of semi-insulating polycrystalline silicon similar to this).

In this way, the semi-insulating polycrystalline silicon layer 16 is formed.
A resist layer 21 is formed as shown in FIG. 1(E). This resist 1121 is used as a mask when etching a contact hole in the semi-insulating polycrystalline silicon layer 16, so the opening 22 is formed in the stopper layer 20 as shown in the figure.
match the position of

Then, using this resist layer 21 as a mask, as shown in FIG.
), the semi-insulating polycrystalline silicon layer 16 is etched to leave the surface protective film 14 having contact holes 17. At this time, since the etching speed changes when the etching reaches the stopper 17120, it becomes easy to know that the etching of the semi-insulating polycrystalline silicon layer 16 has ended, and as a result, the etching reaches the silicon semiconductor 13. It becomes possible to stop etching at a stage where it has not progressed.

After forming the surface protective film 14 of semi-insulating polycrystalline silicon in this way, the resist layer 21 and the stopper layer 20 are removed in order as shown in FIG. is removed using dilute hydrofluoric acid or the like. Then, by attaching electrodes to the contact holes 17 of the surface protection film 14, a semiconductor strain detector as shown in FIG. 2 is manufactured.

Note that if the semi-insulating polycrystalline silicon layer 16 is formed while the entire silicon dioxide layer 18 remains, the silicon dioxide mia in the portion other than the contact hole 17 cannot be removed. If the silicon dioxide layer 1& remains in this way, thermal strain will occur in the semiconductor strain detector as described above, and there will be no point in replacing the surface protection film 14 with semi-insulating polycrystalline silicon.

In addition, in the above embodiment, 5 is used as semi-insulating polycrystalline silicon.
Although it has been explained that ixty is used, the same effect can be obtained using semi-insulating polycrystalline silicon in which oxygen atoms are replaced with nitrogen atoms.

[Effects of the Invention] As described above, in the method for manufacturing a semiconductor device according to the present invention, an etching stopper layer is formed in advance under a semi-insulating polycrystalline silicon layer, and in that state, an etching stopper layer is formed under a semi-insulating polycrystalline silicon layer. etching the polycrystalline silicon layer. Therefore, due to the presence of the stopper layer, it is possible to easily know the end point of etching, and as a result, excessive etching can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a process for explaining a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a completed diagram of the semiconductor device, and FIG. 3 is a diagram of the semiconductor device which is the basis of the present invention FIG. 3 is a diagram for explaining a manufacturing method. 11... Silicon substrate, 12... Insulating layer, 13...
・Silicon semiconductor, 14... Surface protective film, 15...
Electrode, 16... Semi-insulating polycrystalline silicon layer, 17...
・Contact hole, 18... silicon dioxide layer, 1
9... Electrode mounting position, 20... Stopper layer, 21
...Resist layer, 22...Opening. Applicant's agent Patent attorney Takehiko Suzue No. 1 N-(N″ P+-”-P+”-

Claims (2)

[Claims] (1) A step of partially providing a stopper layer made of a material whose etching speed is different from that of semi-insulating polycrystalline silicon on the semiconductor made of silicon, and the semiconductor made of silicon including the top of the stopper layer. forming a semi-insulating polycrystalline silicon layer on the stopper layer; etching a portion of the semi-insulating polycrystalline silicon layer corresponding to the stopper layer until the stopper layer is exposed; 1. A method for manufacturing a semiconductor device, comprising the step of removing. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the material constituting the stopper layer is silicon dioxide.