KR19980057114A - Dielectric film formation method of flash memory device - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Semiconductor device manufacturing method

2. The technical problem to be solved by the invention

In the conventional method of forming a dielectric film of a polysilicon film thermal oxidation method, abnormal oxidation occurs due to a non-uniform distribution of impurities in the polysilicon film, and the dielectric film of a chemical vapor deposition method is formed by undercut by longitudinal wet etching so that the characteristics of the device There was a problem that deteriorated.

3. Summary of Solution to Invention

The present invention is to provide a dielectric film forming method of a flash memory device to form a spacer amorphous polysilicon film, and thermally oxidizes it.

4. Important uses of the invention

Flash memory devices, particularly for the manufacture of stacked gate type flash memory devices.

Description

Dielectric film formation method of flash memory device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a dielectric film during a manufacturing process of a stacked gate flash memory device having a selection gate which is one of flash EEPROMs.

Hereinafter, the prior art and its problems will be described in detail with reference to FIG. 1.

First, as shown in FIG. 1, the active region and the device isolation region are formed on the silicon substrate 10, and then the gate oxide layer 11 is grown, and a predetermined deposition process, a photo and etching process, and a magnetic layer are formed thereon. Self-aligned etching is used to form an oxide-nitride-oxide (ONO) film 13 and a control gate 14, which are dielectric films made of a floating gate 12, an oxide film, and a nitride film.

Subsequently, after the dielectric film 15 is formed through thermal oxidation of the polysilicon film, the polysilicon film 16 is deposited on the entire structure. Thereafter, the selection gate is formed using a photolithography and an etching process.

The ONO film 13 is grown by thermal oxidation of a polysilicon film for forming a floating gate. In consideration of dielectric properties, it is impossible to inject sufficient impurities into the polysilicon film to prevent excessive growth. This is because thermal oxidation is actively performed at the sites where the impurity doping concentration is large.

As a result, when forming the dielectric layer 25 through thermal oxidation of the polysilicon film after self-alignment etching, as shown in FIG. 2, a part of the polysilicon film for forming the floating gate does not grow to the required thickness, and an abnormally shaped oxidation site is formed. Cause (A). This phenomenon occurs because, as mentioned above, sufficient impurity doping is not performed on the polysilicon film, resulting in uneven distribution of impurities. Reference numeral 20 denotes a silicon substrate, 21 a gate oxide film, 22 a floating gate, 23 an ONO film, and 24 a control gate.

In addition, when a high temperature chemical vapor deposition method is used without using a thermal oxidation method as shown in FIG. 3, an undercut may be formed under the spacer nitride layer 36a and the spacer oxide layer 35 during the wet etching of the gate industry. There is a problem that caused the change in the program characteristics of the flash memory device and increase the leakage current. This is because the chemical vapor deposition type oxide film has a faster etching rate than the gate oxide film 31 which is a thermal oxide film. Reference numeral 30 denotes a silicon substrate, 31 a gate oxide film, 32 a floating gate, 33 an ONO film, 34 a control gate, and 36 a nitride film pattern.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dielectric film forming method of a flash memory device in which a spacer amorphous polysilicon film is formed and monoxide is formed.

1 is a cross-sectional view of a dielectric film and a flash memory device formed according to the prior art;

2 and 3 are cross-sectional views for explaining the problem of the dielectric film formed according to the prior art,

4 is a cross-sectional view of a dielectric film and a flash memory device formed in accordance with one embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10, 20, 30, 40: silicon substrate 11, 21, 31, 41: gate oxide film

12, 22, 32, 42: floating gate 13, 23, 33, 43: ONO film

14, 24, 34, 44: control gate 15, 25: dielectric film

16, 47: select gate 35, 45: spacer oxide film

36, 46: nitride film pattern 36a, 46a: spacer nitride film

A: abnormally shaped oxidation sites

In order to achieve the above object, the present invention forms a gate insulating film on a semiconductor substrate, and forming a floating gate, a first dielectric film and a control gate thereon, an amorphous polysilicon film formed on the entire structure, and Forming an amorphous polysilicon film spacer on the sidewalls of the floating gate, the first dielectric film, and the control gate by thermal etching, and thermally oxidizing the amorphous polysilicon film spacer to form a second dielectric film.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 4, first, a gate oxide layer 41 is formed on a silicon substrate 40 and a process for forming a conventional stacked gate type flash memory device is performed. The silicon film is sequentially self-etched to form the floating gate 42, the ONO film 43, and the control gate 44.

Subsequently, an amorphous polysilicon film is deposited on the entire structure, and the entire surface is etched to form an amorphous polysilicon film spacer, and then thermally oxidized to form the dielectric film 45. In this case, the etching of the amorphous polysilicon film is performed in such a manner that the etching selectivity of the amorphous polysilicon film with respect to the oxide film is high in order to protect the gate oxide film.

Subsequently, a nitride film is deposited on the entire structure and anisotropically etched using a photoresist pattern covering one bonding layer and one side of the gate to form the nitride film pattern 46 and the spacer nitride film 46a, and then the selection gate 47. To form.

Thereafter, the subsequent process is performed.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is possible in the art to which various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

As described above, according to the present invention, a second dielectric layer is formed using a method of thermally oxidizing an amorphous polysilicon layer spacer when fabricating a flash memory device having a stacked structure, and thus, a conventional polysilicon layer thermal oxidation method or an oxide film deposition method using chemical vapor deposition. Thereby, there is an effect of preventing the characteristic oxidation due to abnormal oxidation or undercut generated when forming the second dielectric layer, thereby improving the reliability and manufacturing yield of the flash memory device can be expected.

Claims (1)

Forming a gate insulating film on the semiconductor substrate, forming a floating gate, a first dielectric layer, and a control gate on the semiconductor substrate, forming an amorphous polysilicon layer on the entire structure, and etching the entire surface to etch the floating gate and the first dielectric layer And forming an amorphous polysilicon film spacer on the sidewall of the control gate, and thermally oxidizing the amorphous polysilicon film spacer to form a second dielectric film.