JPH03211832A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a clean semiconductor surface, by performing, in order, a first process exposing a semiconductor substrate to gas containing fluorine atoms, a second process dipping it in aqueous ammonia, and a third process drying the semiconductor substrate on which the aqueous ammonia attaches. CONSTITUTION:In a first process exposing a semiconductor substrate to gas containing fluorine atoms, a natural oxide film on the surface is eliminated, but the fluorine atoms are left on the surface. In a second process dipping the substrate in aqueous ammonia, the remaining fluorine atoms react with ammonia atoms, and compounds such as NH4, F, NH2, F are produced, which dissolve in liquid phase. In a third process drying the substrate on which aqueous ammonia attaches, the aqueous ammonia is evaporated, and a clean semiconductor surface is obtained. Thereby a semiconductor substrate wherein a natural oxide film and fluonine atoms are not present can be obtained.

Description

[Detailed Description of the Invention] [Summary] This method relates to a method for manufacturing a semiconductor device, and in particular to a method for forming a clean surface of a semiconductor substrate. A first step of exposing the formed semiconductor substrate to a gas containing fluorine atoms, a second step of immersing the semiconductor substrate in ammonia water, and a third step of drying the semiconductor substrate to which the ammonia water has adhered. The first step and the second step.

A semiconductor device manufacturing method is configured in which the third step is performed in this order.

Further, the semiconductor device manufacturing method described above includes a step of washing the semiconductor substrate with water between the second step and the third step.

Further, after the drying process, annealing is performed to remove remaining ammonia components.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a clean surface of a semiconductor substrate.

[Conventional technology]

The technology for removing the natural oxide film on silicon wafers involves pre-treatment for epitaxial growth, pre-treatment for contact formation,
This will be an important technology in future ULSI manufacturing. In the process of removing the natural oxide film to obtain a clean silicon surface, lower temperatures are desired.

Recently, research has been conducted on methods using fluorine-based gases such as HF, but this method has the problem that fluorine atoms remain on the silicon surface after removing the native oxide film, and these fluorine atoms are difficult to remove. It was happening. For example, if a fluorine-based gas is used in pretreatment for contact formation, fluorine atoms remaining on the silicon surface may make the contact characteristics unstable. cause deterioration.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for removing fluorine atoms remaining after cleaning a silicon surface using a fluorine-based gas at a low temperature.

[Failure to solve the problem]

The above problem consists of two steps: a first step in which a semiconductor substrate with an oxide film formed on its surface is exposed to a gas containing fluorine atoms; a second step in which the semiconductor substrate is immersed in ammonia water; The problem is solved by a semiconductor device manufacturing method that includes a third step of drying the semiconductor substrate, and performs the first step, the second step, and the third step in this order.

Further, the problem is solved by the above method for manufacturing a semiconductor device, which includes a step of washing the semiconductor substrate with water between the second step and the third step.

Further, the problem is solved by a semiconductor device manufacturing method that performs annealing to remove remaining ammonia components after the third step of drying the semiconductor substrate to which ammonia water has adhered.

[Effect]

In the first step of exposing the semiconductor substrate to a gas containing fluorine atoms, the natural oxide film on the surface is removed.

At that time, fluorine atoms remain on the surface. In the second step, the semiconductor substrate is immersed in ammonia water.

Ammonia reacts with residual fluorine atoms.

Compounds such as NH, F, and NH2F are generated, and these compounds are desorbed into the liquid phase.

After that, in the third step of drying the semiconductor substrate to which the ammonia water has adhered, the ammonia water evaporates.

A clean semiconductor surface is obtained.

Furthermore, if a step of washing the semiconductor substrate with water is added between the second and third steps, almost all that adheres to the surface of the semiconductor substrate is water, and the third step of heating the semiconductor substrate is
In the process, the moisture evaporates and a clean semiconductor surface is obtained.

Furthermore, even if the Yoshiba ammonia component remains on the surface of the semiconductor substrate after the above-mentioned drying process.

If annealing is performed to remove it, an extremely clean semiconductor surface can be obtained.

(Example〕 Example I A silicon substrate with a contact window completed.

Introduced into the HF treatment tank and added 5% to 3% HF gas diluted with nitrogen.
exposed for minutes.

Next, the silicon substrate was taken out from the HF treatment tank 2 and immediately immersed in 0.1% ammonia water for 30 seconds.

Next, it was dried with a spin dryer.

FIG. 1 shows the results of analyzing the surface of the silicon substrate in this state by X-ray photoelectron spectroscopy (XPS). Figure 1 shows the relationship between the number of photoelectrons and the binding energy, F'+*
indicates the number of photoelectrons emitted from the Is state of a fluorine atom. As seen in this figure, there is a peak due to fluorine atoms before immersion in ammonia water, but no peak due to fluorine atoms is observed after immersion in ammonia water.

When the buffer ground was subtracted, it was found that the number of photoelectrons due to fluorine atoms after immersion in ammonia water was less than one tenth of that before immersion in ammonia water.

After drying with a spin dryer, tungsten silicide was immediately deposited on this silicon substrate by the CVD method.

Contacts formed in this way have unstable properties,
No deterioration was observed.

In addition, in order to completely remove the remaining ammonia component from the silicon substrate surface, after drying with a spin dryer,
It may be placed in a heat treatment furnace and heat treated at a temperature 2, for example, 500''C or less, which does not affect the already formed element portions.

Example■ A silicon substrate with a contact window completed.

Introduced into the HF treatment tank and added 5% to 3% HF gas diluted with nitrogen.
exposed for minutes.

Next, the silicon substrate is removed from the HF treatment tank and immediately
．． It was immersed in 1% ammonia water for 30 seconds.

Next, it was washed with running water for 10 minutes.

Next, it was dried with a spin dryer.

In this case, as in Example I, X-ray photoelectron spectroscopy (xps
), no peak due to fluorine atoms was observed.

Note that as the gas containing fluorine atoms in the first step, hydrogen fluoride (HF) or fluorine gas (F2) diluted with an inert gas may be used, and H and O may also be mixed. good.

〔Effect of the invention〕

As explained above, according to the present invention, a natural oxide film on the surface of a semiconductor substrate can be removed and fluorine atoms can be prevented from remaining, thereby providing a clean surface.

For example, when the present invention is applied to pre-treatment for contact formation, improvement and stabilization of contact characteristics can be achieved.

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[Brief explanation of drawings]

Figure 1 shows the results of XPs analysis of the silicon substrate surface. electric thousand Satoshi (αLL,)

Claims (1)

[Scope of Claims] [1] A first step of exposing a semiconductor substrate on which an oxide film is formed to a gas containing fluorine atoms; a second step of immersing the semiconductor substrate in ammonia water; A method for manufacturing a semiconductor device, comprising: a third step of drying the semiconductor substrate to which water has adhered; and performing the first step, the second step, and the third step in this order. [2] The method for manufacturing a semiconductor device according to claim 1, further comprising a step of washing the semiconductor substrate with water between the second step and the third step. [3] A method for manufacturing a semiconductor device, which comprises performing annealing to remove remaining ammonia components after the step according to claim 1 or the step according to claim 2.