JPH0548085A - Manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To easily obtain a semiconductor device with high breakdown strength and reliability together with a low on-voltage by forming a resist mask in which the thickness of the corner of a cathode electrode contact hole is thinner and then performing etching process when opening the contact hole for a gate electrode. CONSTITUTION:A photoresist film is formed by coating a photoresist liquid by a fast rotation application method, and a window 21 is opened at the position where the contact hole for a gate electrode is opened, and a resist mask 20 in which a corner 15a of a cathode electrode contact hole 15 is thinner is formed. Since the window 21 for the gate electrode contact hole is smaller than the gate diffusion window 11, even at a corner 11a of the window, the resist mask 20 is thinner. After the resist mask 20 is formed, dry etching is performed and a gate electrode contact hole 17 is opened. As a result, at the corners 15a and 11a of the window 15, level differences 25 and 26 are provided respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art One of useful semiconductor devices is an electrostatic induction thyristor. FIG. 6 shows a main part configuration of a conventional surface gate type electrostatic induction thyristor. In the electrostatic induction thyristor 50 of FIG. 6, the cathode region 52 is located on the surface of the semiconductor substrate 51 on one side, and the gate region 53 for controlling the current flowing through the cathode region 52 is located between the gate regions 53. And the semiconductor substrate 51
An anode region 54 is provided on the other side, and a high specific resistance region (base region) 55 is provided between the cathode region 52 and the anode region 54. The cathode electrode 62 is in contact with the cathode region 52, and the gate electrode 63 is in contact with the gate region 53 through the oxide film (insulating film) 65.

However, the electrostatic induction thyristor 5 described above is used.
0 is an MTF (Median Time to Failur) when the oxide film (field oxide film) 65 is thickened to increase the breakdown voltage.
e) has the drawback of being short. This is because the corner area 62a of the cathode electrode 62 has an electrode coverage ratio of 30%.
As a result, the electrode resistance is increased, the on-voltage characteristics are deteriorated, the current density is increased, the MTF is shortened, and a failure occurs.

The reason why the electrode coverage ratio is small in the corner portion 62a is that the step difference of the cathode electrode contact hole 68 becomes large when the oxide film 65 is thick. If the contact hole 68 is tapered, the electrode coverage ratio is increased. However, if the contact hole 68 is tapered to improve the electrode coverage ratio, this time, the miniaturization for lowering the on-voltage of the thyristor itself does not proceed and the low reduction is achieved. Another problem arises in that the on-voltage cannot be achieved and is not practical.

[0005]

In view of the above circumstances, an object of the present invention is to provide a method capable of easily obtaining a semiconductor device having a high breakdown voltage, a long MTF and a low on-voltage.

[0006]

In order to solve the above problems, in the method of manufacturing a semiconductor device of the present invention, a cathode region and a gate region for controlling a current flowing through the cathode region are provided in a surface portion on one side of the semiconductor substrate. In order to obtain a semiconductor device in which the surface of the semiconductor substrate one side is covered with an oxide film and the cathode electrode and the gate electrode penetrate the oxide film and are in contact with the respective regions, for example, As shown in FIG. 2, the semiconductor substrate 1 in which the cathode region 2, the gate region 3 and the oxide film 8 are formed, and the cathode electrode contact hole 15 is opened in the oxide film 8 is prepared in advance, For example, as shown in FIG. 3, a resist solution is applied on the corner 15a of the contact hole 15 for the cathode electrode so that the thickness is thin. Strike film is formed, then the window 21 of the contact hole forming a gate electrode on the resist film
To form a resist mask 20, and then, for example, as shown in FIG. 4, etching treatment is performed to open a gate electrode contact hole 17, and thereafter, the cathode electrode and the gate electrode are formed. There is.

The semiconductor device manufactured by the present invention is as follows:
Examples include static induction thyristors, static induction transistors, and IC configurations, but the invention is not limited to these, and is effective for various semiconductor devices as long as the gist of the invention is not impaired. When the semiconductor device has a transistor structure, the cathode is often referred to as the source.

In the present invention, one of the essential points in the structure is to form a resist film by coating so that the thickness at the corner of the contact hole for the cathode electrode becomes thin. This is, for example, a photolithography process. At 700, a photoresist solution with a viscosity of 30 centipoise is used.
It can be realized by applying high-speed spin coating at 0 to 8000 times / minute to form a photoresist film. Conventionally, the viscosity is usually 30
Sentipoise photoresist solution is 3000-8000
Spin application at 1 / min. Further, the subsequent etching treatment is anisotropic etching (dry etching).

By this etching treatment, a step is formed at the corner of the contact hole for the cathode electrode, and the step is usually appropriate in the range of about 30 to 50% of the oxide film thickness, but not limited to this. The shape of the step is not limited to a staircase shape, but may be a slightly rounded shape.

[0010]

In the method of manufacturing a semiconductor device according to the present invention, when the contact hole for the gate electrode is opened, a resist mask whose thickness is thin at the corner of the contact hole for the cathode electrode is formed and etching is performed. Due to the difference in etching characteristics between the oxide film and the resist film, a small step is formed at the corner of the contact hole for the cathode electrode. Therefore, even if the thickness of the oxide film (field oxide film) is increased to increase the breakdown voltage, the electrode coverage at the corner of the cathode electrode is improved and the current density is reduced.
MTF becomes longer. In addition, as shown in FIG. 7, unlike the case where the taper T is provided, even if the step 25 is provided, the contact hole 15 for the cathode electrode is only slightly increased, which does not hinder the miniaturization and increases the integration degree. Therefore, there is no problem in lowering the on-voltage (improvement of the on-voltage).

The present invention is also easy to implement. The step of the corner of the contact hole for the gate electrode is extremely small,
There is no need for a special resist mask, and there is no need for alignment because the resist solution is applied at high speed when forming the resist mask for opening the contact hole for the gate electrode. This is because it is realized and no other special processing is added.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. In this embodiment, an electrostatic induction thyristor is manufactured using the example method of the present invention. First, as shown in FIG. 1, the oxide film 8 of the semiconductor substrate 1 whose surface is covered with the oxide film 8 and whose anode region 4 is provided on the back surface side.
To the gate diffusion window 11 using photolithography technology
And an impurity is introduced by an ion implantation method, a thermal diffusion method or the like to form an impurity diffusion region G. The anode region 4 may be formed together when the gate region is formed, or may be formed first by an epitaxial growth method.

Subsequently, as shown in FIG. 2, a gate region 3 in which impurities are diffused to a desired depth is obtained and a window 11 is formed.
Form a thermal oxide film 9 that is slightly thinner than the oxide film 8,
Further, a hole (cathode diffusion window) 15 which also serves as a contact hole for a cathode electrode is opened in the oxide film 8 by using a photolithography technique, and impurities are introduced by an ion implantation method, a thermal diffusion method or the like to form the cathode region 2. .. Normally, an extremely thin oxide film is formed in the hole 15, and thereafter, light etching for selectively removing the oxide film is performed to form the contact hole 15 for the cathode electrode.

Next, a photoresist film is formed by applying a photoresist solution at a high speed, and a window 21 is opened at a position where a contact hole for a gate electrode is to be opened.
As can be seen from the above, the resist mask 20 is thin at the corner 15a of the cathode electrode contact hole 15.
To form. Since the window 21 for the contact hole for the gate electrode is smaller than the upper gate diffusion window 11, the thickness of the resist mask 20 is thin even at the corner 11a of the window.

After forming the resist mask 20, dry etching is performed to open a contact hole 17 for a gate electrode as shown in FIG. The corners 15a of the window 15 and the corners 11a of the window have steps 25 and 26, respectively. Further, in the contact hole 17 for the gate electrode, the window 21 was smaller than the gate diffusion window 11, so that the thermal oxide film 9 was formed.
A part of is left and another step 27 is formed.

Thereafter, as shown in FIG. 5, a cathode electrode 31 and a gate electrode 32 are formed of a conductive material such as aluminum at the positions of both contact holes 15 and 17. Figure 5
As can be seen from the above, even if the oxide film (field oxide film) 9 is thick, the corner portion 31a of the cathode electrode 31 has the step 25, so that it is in an appropriate electrode coverage state. Of course, even at the corner portion 32a of the gate electrode 32, the steps 26, 2
Since there is 7, it is in an appropriate electrode coverage state.

The cathode electrode 31 and the gate electrode 32
The number of steps in the contact hole can be increased by forming a windowless resist mask having a thin thickness at the corners of the step and performing dry etching in the same manner as the resist mask 20 before formation. However, it goes without saying that the number of steps increases, so it is preferable to omit it if it is not necessary.

In the electrostatic induction thyristor of FIG. 5, an n ⁺ type cathode region 2 and a p ⁺ type gate region 3 for controlling on / off of a current flowing through the cathode region 2 are formed on the surface portion of the semiconductor substrate 1 on one side. 3 is provided such that the cathode region 2 is located between the cathode region 2 and the anode region 4, and the p ⁺ -type anode region 4 is provided on the other side of the semiconductor substrate 1, and the n ⁻ -type high specific resistance is provided between the cathode region 2 and the anode region 4. Area (base area) 5
Has become. The cathode electrode 31 is in contact with the cathode region 2 and the gate electrode 32 is in contact with the gate region 3 through the oxide film (insulating film) 8.

The present invention is not limited to the above embodiment. For example, another embodiment is one in which the conductivity types n and p are inverted in the drawing.

[0020]

As described above, according to the manufacturing method of the present invention, it is possible to obtain a semiconductor device having a high breakdown voltage, a long MTF and a low on-voltage, and moreover, it is easy to carry out the present invention. Is very useful.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a state before and after a gate diffusion window forming step in an example.

2A and 2B are cross-sectional views for illustrating a state before and after a step of forming a contact hole for a cathode electrode in an example.

FIG. 3 is a cross-sectional view for explaining a state before and after a resist mask forming step in an example.

FIG. 4 is a cross-sectional view for explaining a state before and after a gate electrode contact hole forming step in an example.

FIG. 5 is a cross-sectional view showing a configuration of a main part of an electrostatic induction thyristor obtained in an example.

FIG. 6 is a cross-sectional view showing a configuration of a main part of a conventional electrostatic induction thyristor.

FIG. 7 is a partial cross-sectional view showing a structure around a gate electrode contact hole in an example.

[Description of References] 1 semiconductor substrate 2 cathode region 3 gate region 8 oxide film 15 contact hole for cathode electrode 17 contact hole for gate electrode 20 resist mask 31 cathode electrode 32 gate electrode

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[Procedure amendment]

[Submission date] November 9, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

In the present invention, one of the essential points in the structure is to form a resist film by coating so that the thickness at the corner of the contact hole for the cathode electrode becomes thin. This is, for example, a photolithography process. At 700, a photoresist solution with a viscosity of 30 centipoise is used.
It can be realized by applying high-speed spin coating at 0 to 8000 times / minute to form a photoresist film. Conventionally, the viscosity is usually 30
Centipoise of photoresist solution is from 3,000 to 6,000
Spin application at 1 / min. Further, the subsequent etching treatment is anisotropic etching (dry etching).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

[0010]

In the method of manufacturing a semiconductor device according to the present invention, when the contact hole for the gate electrode is opened, a resist mask whose thickness is thin at the corner of the contact hole for the cathode electrode is formed and etching is performed. Due to the difference in etching characteristics between the oxide film and the resist film, a small step is formed at the corner of the contact hole for the cathode electrode. Therefore, even if the thickness of the oxide film (field oxide film) is increased to increase the breakdown voltage, the electrode coverage at the corner of the cathode electrode is improved, the current density is lowered, and the MTF is increased. In addition, as shown in FIG. 7, unlike the case where the taper T is provided, even if the step 25 is provided, the contact hole 15 for the cathode electrode is only slightly increased, which does not hinder the miniaturization and increases the integration degree. Therefore, there is no problem in lowering the on-voltage (improvement of the on-voltage).

Claims (1)

[Claims] 1. A cathode region and a gate region for controlling a current flowing through the cathode region are provided on a surface portion of the semiconductor substrate one side, and the surface of the semiconductor substrate one side is covered with an oxide film. In a method of manufacturing a semiconductor device in which a cathode electrode and a gate electrode penetrate through the oxide film and are in contact with respective regions, the cathode region, the gate region, and the oxide film are formed, and the oxide film contacts the cathode electrode. A semiconductor substrate in which holes are opened is prepared in advance, and a resist solution is applied onto the semiconductor substrate so that the thickness becomes thin at the corners of the cathode electrode contact hole to form a resist film, and then,
A window for forming a contact hole for a gate electrode is formed in the resist film to form a resist mask, an etching process is performed to open the contact hole for a gate electrode, and then the cathode electrode and the gate electrode are formed. A method of manufacturing a semiconductor device, comprising: