JPH01258471A - Manufacture of mos type semiconductor device - Google Patents

Abstract

PURPOSE:To enable an etching residue of a polysilicon to be oxidized without making the surface of a gate electrode formed of a polysilicon film oxidized by a method wherein a treatment, where the surface of the gate electrode is covered with an oxidation resistant coating, is performed before an oxidizing process of the polisilicon film is executed. CONSTITUTION:An element isolating region 2 of a thick polysilicon film is formed on a silicon substrate 1, and a diffusion layer 3 is formed through an ion implantation. Then, a gate oxide film 4, a polysilicon film 5, a silicon nitride film 6, and a resist film 7 are formed. The silicon nitride film 6 and the polysilicon film 5 are selectively removed to form a gate electrode pattern. Next, the resist film 7 is removed and the silicon nitride film 6 is made to grow, which is subjected to an anisotropic etching so as to leave the silicon nitride film 6 on the upper face and the side wall of a gate electrode formed of the polysilicon film 5 unremoved. Next, an etching residue of the polysilicon film 5 on the step of a ridge or the like of the element isolating region 2 left unremoved after the etching is made to be an insulator by oxidizing through a thermal oxidation method so as to prevent the residue from causing a short circuit between the polysilicon layers.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a MOS type semiconductor device.

2. Description of the Related Art In recent years, MOS type semiconductor devices have come into widespread use due to the demand for low power consumption. On the other hand, as the degree of integration of integrated circuits increases, it is required to reduce the dimensions of semiconductor devices, but as the gate length of MOS type semiconductor devices is shortened, a so-called short channel effect occurs, and the size of semiconductor devices increases. It is known that the threshold voltage drops significantly, and it has become important to control the dimensions of the gate electrode.

A conventional method for manufacturing a MOS type semiconductor device will be described below. 2(a) and 2(b) are cross-sectional views of a part of a conventional method for manufacturing a MOS type semiconductor device, in which 11 is a silicon substrate, 12 is an element isolation region, 13 is a diffusion layer, 1
4 is a gate oxide film, 15 is a polysilicon film, 17 is a resist film, and 18 is an oxidized polysilicon film.

First, an element isolation region 12 made of a thick oxide film is formed on a silicon substrate 11 using a known technique. Next, ions are implanted into the silicon substrate 11 to form a diffusion layer 13 for setting a threshold voltage. After this, a gate oxide 1[4 is grown, and a polysilicon film 15 that will become a gate electrode is grown thereon. Next, phosphorus is vapor-phase diffused into the polysilicon film 15 at a high concentration to form a low resistance film. Furthermore, after selectively removing the phosphorized polysilicon film, a resist film 17 is formed into a desired resist pattern using light exposure technology, electron beam exposure technology, X-ray exposure technology, or ion beam exposure technology. Using the pattern as a mask, polysilicon film 15 is selectively removed by dry etching to form a gate electrode. The state at this time is shown in FIG. 2 fa).

Next, the resist film 17 is removed, and as shown in FIG. 2(b), the polysilicon film that could not be completely removed due to the steps at the edges of the element isolation region 12! To prevent the etch residue of 215 from causing an electrical short circuit between the same polysilicon layers,
Polysilicon W using thermal oxidation method:! The etched residue of No. 15 is oxidized to form an insulator. At the same time, the side walls and surface of the gate electrode made of polysilicon are also oxidized. Furthermore, at this time, the oxidation invades the gate oxide film 14 in the gate mff1 portion, and the polysilicon film 15 is lifted up, resulting in a shape called a gate bird's beak in which the thickness of the gate oxide #9 increases at both ends 19 of the gate electrode. A significant channel length reduction may occur.

Problems to be Solved by the Invention However, in the conventional manufacturing method described above, the surface of the gate electrode made of polysilicon film 15 is oxidized and becomes an insulator, so the effective dimensions of the conductive gate electrode become thin. Furthermore, the gate bird's beak shape changes the channel length of the MOS type semiconductor device. In particular, there was a problem in that the electrical resistance value of the gate electrode increased because the polysilicon film 15 became thinner due to oxidation. Therefore, it is necessary to control oxidation with high precision, but the polysilicon film 15 in which phosphorus is diffused at a high concentration has a significantly faster oxidation rate than the silicon substrate 11 due to the accelerated oxidation phenomenon, so the process is difficult. 11! If the control becomes rough and the control accuracy is impaired, variations will occur in the characteristics of the MOS type semiconductor device.

The present invention solves the above-mentioned conventional problems.
M that can reduce the etching residue of polysilicon to Mt without changing the dimensions of the gate electrode of type semiconductor #7Al.
It is an object of the present invention to provide a method for manufacturing an OS type semiconductor device.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a MOS type semiconductor device of the present invention includes coating the surface of a gate electrode made of a polysilicon film with an oxidation-resistant film before the oxidation process of the polysilicon film. This is a process that covers the area.

Furthermore, the present invention includes a step of growing an oxidation-resistant film on a polysilicon film, and a step of growing the oxidation-resistant film on a polysilicon film, and applying the oxidation-resistant film and polysilicon film to a predetermined gate electrode. This method consists of the steps of forming a pattern, and further forming a FA-resistant film on the oxidation-resistant film, and then etching the oxidation-resistant film into a desired shape.

Effect According to the above structure, by covering the surface portion of the gate electrode made of polysilicon with an oxidation-resistant film, the surface portion of the gate electrode is not oxidized, the gate dimensions are not reduced due to oxidation, and the polysilicon film is Etch residue can be oxidized.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIGS. 1(a) to 1(d) show M in an embodiment of the present invention.
In FIG. 1, which shows a cross-sectional view of a part of the method for manufacturing an OS type semiconductor device, 1 is a silicon substrate, 2 is an element isolation region, 3 is a diffusion layer, 4 is a gate oxide film, 5 is a polysilicon film, and 6 is a silicon substrate. is an oxidation-resistant film, and the silicon nitride film 7 is a resist film.

``First, an element isolation region 2 of a thick oxide film is formed on a silicon substrate 1 using a known technique. Next, ions are implanted into the silicon substrate 1 to form a diffusion layer 3 for setting the threshold voltage.
form. Thereafter, a gate oxide film 4 is grown, and a polysilicon film 5 that will become a gate electrode is grown thereon.

Next, phosphorus is vapor-phase diffused into the polysilicon film 5 to a high degree of i1 to form a low resistance film. Next, after selectively removing the polysilicon sacrificial material that has been turned into phosphor glass, the silicon nitride layer 6 is heated using a well-known C.
It is grown to a thickness of 0.1 μm using the VD method. Furthermore, the resist film 7 is formed into a desired resist pattern using light exposure technology, electron beam exposure technology, X-ray exposure technology, or ion beam exposure technology, and using this resist pattern as a mask, the silicon nitride film 6 and polysilicon WA5 is selectively removed by dry etching to form a gate electrode pattern. The state at this time is shown in FIG. 1(a).

Next, the resist film 7 is removed and, as shown in FIG. 1(b), a silicon nitride pattern 6 is grown to a thickness of 0.1 μm by CVD. Next, as shown in FIG. 1C, the silicon nitride film 6 is anisotropically etched to leave the silicon nitride film 6 on the upper surface and sidewalls of the gate electrode made of the polysilicon film 5. Furthermore, in FIG. 1(d), the remaining polysilicon film 5 that could not be removed due to the steps at the edges of the element isolation region 2 is prevented from causing an electrical short circuit between the polysilicon layers. Next, the etch residue on the polysilicon film 5 is oxidized using a thermal oxidation method to form an insulator. Thereafter, a MOS type semiconductor device can be formed using a known technique.

In this example, silicon nitride was used as the oxidation-resistant film covering the surface of the gate electrode made of polysilicon film, but any oxidation-resistant film such as silicon carbide or aluminum oxide would be effective. It goes without saying that there is.

As described above, according to this embodiment, by covering the surface and sidewalls of the gate electrode made of polysilicon with the acid-resistant film, the surface of the gate electrode is not oxidized and the gate electrode of the MOS type semiconductor device is protected from oxidation. without changing the electrical resistance value.
Furthermore, since the gate does not have a bird's beak shape,
The gate length does not decrease, and the etch residue can be oxidized to form an insulator.

Effects of the Invention According to the method for manufacturing a MOS type semiconductor device of the present invention, the etched residue of the polysilicon film can be oxidized without oxidizing the surface portion of the gate electrode made of the polysilicon film. It is possible to provide a manufacturing method in which the electrical resistance value of the gate electrode does not change, and is particularly excellent in the formation of ultrafine semiconductor devices of highly integrated circuits.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) show MO in one embodiment of the present invention.
FIGS. 2(a) and 2(b) are cross-sectional views illustrating steps in a conventional method for manufacturing an S-type semiconductor device. FIGS. 1... Silicon substrate, 2... Element isolation region, 3...
・Diffusion layer, 4... Gate acid film, 5... Polysilicon film, 6... Silicon nitride layer (oxidation resistant film), 7
...Resist film. Agent Yoshihiro Morimoto Figure 1 Part 1 Cause 1 Part 2 Figure 2/9 tQ

Claims (1)

[Claims] 1. A method for manufacturing a MOS semiconductor device, in which the surface of a gate electrode made of a polysilicon film of the MOS semiconductor device is covered with an oxidation-resistant film, and then thermally oxidized. 2. The step of covering the surface of the gate electrode with an oxidation-resistant film is a step of growing the oxidation-resistant film on the polysilicon film, and forming the oxidation-resistant film and the polysilicon film into a predetermined gate electrode pattern. and a step of further forming an oxidation-resistant film on the oxidation-resistant film and then etching the oxidation-resistant film into a desired shape.
A method of manufacturing the described MOS type semiconductor device.