JPS63117468A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the breakage of a gate insulating film and to reduce the rate of rejects during a process to form a gate electrode by a plasma etching method in such a way that the gate electrode is formed while it is electrically conducted to a semiconductor substrate through a discharge electrode. CONSTITUTION:By a plasma etching method by making use of photoresist as a mask, a gate electrode 6 and a discharge electrode 7, which is connected to this gate electrode 6 and is connected to a semiconductor substrate 1 through an opening 4, are formed. In succession, the gate electrode 6 and the discharge electrode 7 are cut by a wet etching method by making use of the photoresist as the mask and are then separated so as to insulate them from each other. Because the gate electrode 6 is formed in such a way that it is electrically conducted to the semiconductor substrate 1 through the discharge electrode 7, no electric charge is accumulated in the gate electrode 6 during the plasma etching process. As a result, it is possible to prevent the breakage of a gate insulating film 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a MOS type semiconductor device including a step of forming a gate electrode using a plasma etching method.

[Conventional technology]

Conventionally, in the manufacturing method of this type of semiconductor device, when forming the gate electrode of a semiconductor element, a web I etching method or a dry etching method is used, but the wet etching method has the disadvantage of poor controllability of pattern dimensions. For some reason, recent dry etching methods are used in the formation of highly integrated semiconductor devices, while plasma etching methods, which cause less side etching and have an excellent selectivity between the gate electrode material and the gate insulating film, are preferred. It is often used.

[Problem that the invention seeks to solve]

In the conventional semiconductor device manufacturing method described above, the gate electrode is formed by plasma etching, so that charge is accumulated in the gate electrode during etching, and this charge is transferred to the gate insulating film as soon as the etching process is completed. The drawback is that it often flows through the semiconductor substrate and destroys the gate insulating film, resulting in poor characteristics. This phenomenon often occurs in highly integrated semiconductor devices where the film thickness of the gate insulating film is less than 500 nm.

An object of the present invention is to provide a method for manufacturing a semiconductor device that can prevent breakdown of a gate insulating film and reduce the defect rate.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes forming a gate insulating film and a field insulating film following the gate insulating film on a semiconductor substrate, and then opening a part of the field insulating film close to the gate insulating film. forming an opening reaching the semiconductor substrate; forming an electrode layer on each surface of the gate insulating film, the field insulating film, and the opening;
selectively etching the electrode layer by a plasma etching method to form a gate electrode and a discharge electrode portion connected to the gate electrode and connected to the semiconductor substrate via the opening; and a step of cutting and insulating the discharge electrode portion.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(d) are cross-sectional views of a semiconductor device shown in the order of manufacturing steps for explaining one embodiment of the present invention.

First, as shown in FIG. 1(a), an L is placed on a semiconductor substrate 1.
After forming an oxide gate insulating film 2 and a field insulating film 3 following this gate insulating film 2 by the OCO3 method, a part of the field insulating film 3 adjacent to the gate insulating film 2 is
Using photoresist as a mask, an opening 4 is formed by plasma etching until the semiconductor substrate 1 is reached.

Next, as shown in FIG. 1(b), the gate insulating film 2. An electrode layer 5 of polycrystalline silicon is formed on each surface of the field insulating film 3 and the opening 4 by CVD.

Next, as shown in FIG. 1(c), the gate electrode 6 is etched by plasma etching using a photoresist as a mask.
A discharge electrode portion 7 is formed to be connected to the gate electrode 6 and to the semiconductor substrate 1 via the opening 4.

Subsequently, as shown in FIG. 1(d), the gate electrode 6 and the discharge electrode portion 7 are cut and separated by a wet etching method using a photoresist as a mask to electrically insulate them.

According to this method, the gate electrode 6 is formed to be electrically connected to the semiconductor substrate 1 through the discharge electrode portion 7, so that no charge is accumulated in the gate electrode 6 during plasma etching, and breakdown of the gate insulating film 1 can be prevented. Can be done.

Note that in FIG. 1, the opening 4 is the field insulating film 3.
Although a part of the opening is made thinner to make it easier to open, the opening may be made without making it thinner.

FIG. 2 is a characteristic diagram showing the frequency distribution of the breakdown electric field strength for the gate insulating film 3.

As shown in FIG. 2, the breakdown electric field strength of the gate insulating film 3 according to this example is not low, and is 0,7~0,
The distribution is concentrated in a narrow range of 9 MV/cm, whereas the conventional example has a large distribution starting from a low range, which shows that the effect of this example is large.

FIG. 3 is a characteristic diagram showing the relationship between defective rate and yield of semiconductor devices.

As shown in FIG. 3, according to this embodiment, even if the yield remains the same, the defective rate is significantly reduced.

〔Effect of the invention〕

As explained above, in the present invention, when forming the gate electrode by plasma etching, the gate electrode is formed while being electrically connected to the semiconductor substrate through the discharge electrode portion, thereby making it possible to prevent damage to the gate insulating film. This has the effect of reducing the defective rate.

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are cross-sectional views of a semiconductor device shown in the order of manufacturing steps to explain one embodiment of the present invention, and FIG. 2 is a characteristic showing the frequency distribution of breakdown electric field strength with respect to the gate insulating film. 3 are characteristic diagrams showing the relationship between defective rate and yield of semiconductor devices. 1... Semiconductor substrate, 2... Gate insulating film, 3...
field insulating film, 4... opening, 5... electrode layer,
6... Gate electrode, 7... Discharge electrode part, 8... Cutting part. 10,000 eyes

Claims (1)

[Claims] After forming a gate insulating film and a field insulating film following the gate insulating film on a semiconductor substrate, a part of the field insulating film close to the gate insulating film is opened to form an opening that reaches the semiconductor substrate. a step of forming an electrode layer on each surface of the gate insulating film, the field insulating film and the opening, and selectively etching the electrode layer by a plasma etching method to connect the gate electrode to the gate electrode. and a step of forming a discharge electrode portion connected to the semiconductor substrate through the opening, and a step of cutting and insulating the gate electrode and the discharge electrode portion. Method.