JPS6362329A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent any defective characteristics from occuring by a method wherein semiconductor elements are cleaned up by alkali and diluted fluoric acid cleaning process and then vacuumized lamp anneal baking process is additionally performed. CONSTITUTION:Semiconductor elements are cleaned up by alkali cleaning process using mixed solution of ammonia, hydrogen peroxide and pure water to be etched using diluted fluoric acid for removing a natural oxide film and heavy metal. Furtheremore, any attached dirt is removed using diluted fluoric acid to be incinerated by anneal baking process in a vacuumized in-tube annealing device not to form an oxide film. Through these procedures, after resetting to room temperature to release the vacuumized atmosphere, an Si substrate is not oxidized enabling polysilicon to be grown later.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of cleaning before growing polysilicon using polysilicon CVD technology using SiH4 gas.

[Conventional technology]

Conventional polysilicon growth pretreatment methods include alkaline cleaning with a mixture of ammonia, hydrogen peroxide, and pure water;
There is acid cleaning using a mixture of sulfuric acid and hydrogen peroxide, and diluted acid cleaning with hydrofluoric acid and pure water for the purpose of removing natural oxide films.

[Problem that the invention seeks to solve]

The conventional cleaning techniques mentioned above have both advantages and disadvantages. In the case of acid cleaning, it is easy to remove heavy metal contamination, but it is necessary to control the mixing ratio of the liquid, the degree of fatigue, etc., and it is difficult to maintain as a mass-produced cleaning device. difficult. Although the alkaline cleaning method is suitable for mass production, it is difficult to remove heavy metals, leaving residue at the interface between the silicon (Si) substrate and polysilicon of the semiconductor device, and subsequent heat treatment causes characteristic defects such as leakage defects. After acid cleaning and alkali cleaning, a natural oxide film remains, so that even if impurities are diffused after polysilicon growth, they are difficult to diffuse into the Si substrate. When etching is performed using hydrofluoric acid and diluted hydrofluoric acid in pure water for the purpose of removing the natural oxide film, heavy metals are removed, but dust contained in the solution tends to adhere to the Si substrate itself because it is activated. If dust remains, it changes the film thickness and quality of the polysilicon film, and becomes a factor in the occurrence of characteristic defects due to subsequent impurity diffusion.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to relate to a method for manufacturing a semiconductor device, which allows for good cleaning and prevents the occurrence of characteristic defects.

[Means for solving problems]

The structure of the present invention is that in the pre-growth treatment process for polysilicon on a semiconductor element, after the semiconductor element is cleaned by alkaline cleaning, which is a mixture of ammonia, hydrogen peroxide, and pure water, natural oxide films are removed and heavy metals are removed. Therefore, the tube was etched using diluted hydrofluoric acid diluted with pure water, and then the attached dust was removed using diluted hydrofluoric acid, and annealing was performed in a lamp annealing device that evacuated the inside of the tube to prevent the formation of an oxide film. It is characterized by burning away garbage.

[Effect]

In contrast to the above-mentioned conventional polysilicon growth pretreatment method, the present invention does not affect the characteristics of semiconductor devices before polysilicon growth, reduces heavy metal contamination, minimizes natural oxide film, and is highly suitable for mass production. The present invention provides a cleaning method that burns off dust attached to the Si substrate and prevents the Si substrate from being oxidized by the heat treatment at this time.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a process diagram sequentially showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. In the figure, polysilicon pretreatment involves performing alkaline cleaning 1 using a mixture of ammonia, warm hydrogen oxide, and pure water in order to remove heavy metals and organic dirt deposited in previous steps. However, although this process can remove dirt, it is less effective in removing heavy metals and has the effect of adhering aluminum and the like.

Therefore, a step for removing heavy metals is required in the next step, and furthermore, a natural oxide film of about 20X is formed, which affects product characteristics. Therefore, etching 2 is performed using diluted hydrofluoric acid such that the ratio of hydrofluoric acid to pure water is 1:30. However, although heavy metals and natural oxide films can be removed, the Si substrate is activated, so dust is removed from the Si substrate during etching and water washing.
It will stick to the board. If this dust is left as it is and polysilicon is grown, unevenness in the polysilicon film thickness will occur.
Furthermore, film quality is involved, which affects product characteristics. death ·
Therefore, a process for removing dust is required before polysilicon growth, and a process that can remove dust without forming a natural oxide film is burning off dust by lamp annealing. The inside of the tube into which the 8i substrate is placed in the lamp annealing device is evacuated, heated from room temperature to about 700° C., and Bake 3 is performed.

If the temperature is returned to room temperature and the vacuum is released, the Si substrate will not be oxidized. After that, polysilicon growth 4 is performed.

〔Effect of the invention〕

As explained above, according to the present invention, alkaline cleaning,
By adding a vacuum lamp annealing bake after cleaning with diluted hydrofluoric acid, it is possible to achieve excellent mass productivity and avoid problems in improving product characteristics.

In the above embodiments, polysilicon is used, but it can also be applied to polysilicon doped with impurities.
The present invention can be similarly applied to oxide film growth, nitride film growth, etc. grown on an i-substrate.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. 1... Alkaline cleaning step, 2... Diluted hydrofluoric acid etching step, 3... Baking step, 4.
...Polysilicon growth process.ゝ；fー′

Claims (1)

[Claims] In a semiconductor manufacturing method that performs a pre-growth treatment for polysilicon on a semiconductor element, the semiconductor element is washed with an alkali solution of ammonia, hydrogen peroxide, and pure water, and then the native oxide film is removed with diluted hydrofluoric acid, and A method for manufacturing a semiconductor device, characterized by baking using lamp annealing in a vacuumed tube.