JPS6158257A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the part around electrode 3 from swelling up by a method wherein an electrode layer to be the first electrode is formed on a substrate through the intermediary of an oxide film and after isotropically etching the electrode utilizing specific pattern to retract it from the end of mask, the surface of electrode is oxidized to be coated with the second electrode. CONSTITUTION:An Si substrate 101 is coated with a gate oxide film 102 wherein a polycrystalline Si electrode layer 103 is deposited while a resist mask 104 with specified shape is provided to etch the electrode layer 103 utilizing the mask 104 leaving the layer 113 only below the mask 104. Next the end of layer 113 is isotropically etched utilizing the mask 104 as it is to be formed into a specified dimension of the first electrode 3. Later the mask 104 is removed to oxide the exposed part of electrode 3 so that the oxide film formed on the side may combine with a film 12 slightly thined by preceding etching process. Finally the overall surface of electrode 3 and the film 12 is coated with the second electrode layer 5. Through these procedure, any withstand voltage may be prevented from deteriorating due to electric field concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and is particularly used for forming gate electrodes, wiring electrodes, etc. of a semiconductor device.

[Technical background of the invention and its problems]

Semiconductor devices having a superimposed structure on gate electrodes, wiring electrodes, etc. have been manufactured using conventional methods.

That is, FIGS. 1(a) to (C) and FIG. 2(a)
As shown in succession in (C), first, a gate oxide film (10
2) Form an electrode M (103) made of polysilicon or the like thereon (FIG. 1(a)), then form a resist mask (104) on the electrode layer (103) (FIG. 1(b)); This electrode layer (103) is etched to form a first electrode layer (103).
13) (FIG. (c)). Note that this etching also slightly etches the gate oxide film (102).

Next, using the first electrode layer (113) as a mask, the gate oxide film (102) is removed by etching (see FIG.
a)) The purpose of this etching is to temporarily remove the gate oxide film, but at this time, the gate oxide film under the first electrode is also etched, leaving a gate oxide film as shown in the figure (
112) Next, the exposed portion of the silicon substrate (101) is oxidized to form a second gate oxide film (112) (Figure (b)), and then a polysilicon second electrode (105) is formed. ) is formed (Figure (C)).

When the second gate oxide film (112) is formed after etching the gate oxide film (102), the peripheral portion of the first electrode is pushed up. As shown in FIG. 2(C), a portion of the second electrode that is formed as a primary layer digs into the lower part of the first electrode.

As the periphery of the first electrode is lifted, the potential of the diffusion layer formed below the first electrode becomes deeper in the armpit, forming a potential pocket.

For example, in a device such as a COD that transfers charge sequentially, this potential pocket causes charge transfer failure, and the digging of the second electrode below the first electrode causes electric field concentration. This may lead to deterioration in voltage resistance.

[Purpose of the invention]

The present invention improves the manufacturing method of the conventional semiconductor device so as to prevent lifting around the electrodes.

[Summary of the invention]

The method for manufacturing a semiconductor device according to the present invention includes forming an electrode layer by photolithography, etching the electrode layer isotropically using the photoetching mask to retreat from the periphery of the mask, and then removing the mask. , and then oxidizing the electrode surface.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained in order of steps with reference to FIG. 1. It should be noted that the steps shown in FIGS. 1A to 1C are the same as those of the conventional process, so the explanation thereof will be omitted. Further, in each figure, members that are the same as those in the conventional system are designated by the same reference numerals, and explanations thereof will be omitted.

FIG. 1(d) shows that the first electrode layer (113) is isotropically etched while leaving the mask (104) used for forming the first electrode layer shown in FIG. 1(b). electrode layer (
3) is formed. This etching is performed on the first electrode layer (1
This is achieved by chemical dry etching using Freon, for example, so that the end of the mask (104) is set back to a predetermined distance from the end face of the mask (104).

Next, the mask (104) is removed and the first electrode layer (
The surface of the silicon substrate (101) is oxidized (FIG. (e)), and the gate oxide film (2) is etched to expose the surface of the silicon substrate (101) (FIG. (f)).

Next, heating is applied to form a new gate oxide film (12) (Figure (g)), and a second electrode layer (5) is deposited (Figure (h)).

〔Effect of the invention〕

According to this invention, after forming the first electrode, it is isotropically etched to oxidize the surrounding area (Fig. This prevents the oxide film from being etched. As a result, the first electrode is formed by a silicon oxide film that grows on the lower surface of the conventional 1 electrode (polysilicon) layer at a much faster rate than silicon single crystal, and a silicon oxide film that grows on the exposed surface of the silicon single crystal substrate. The raised periphery of the layer has been completely improved. Therefore, it is possible to prevent potential pockets from being generated below the first electrode layer, and since the second electrode layer does not dig into the bottom of the first electrode layer, it is possible to prevent breakdown voltage deterioration due to electric field concentration. It has a remarkable effect.

Next, the present invention has the advantage that it can be easily put into practical use to the extent that the extension of the manufacturing process can be almost ignored.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an electrode forming process in manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a part of an electrode forming process in manufacturing a conventional semiconductor device.

Claims (1)

[Claims] A step of forming an electrode film on a semiconductor substrate via an electrical insulating layer, a step of photo-etching the electrode film to form an electrode layer, and isotropically etching the electrode layer using the photo-etching mask. A method for manufacturing a semiconductor device, including a step of subsequently removing a mask, and a step of oxidizing the surface of the electrode layer.