Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2003-02-28
2004-09-14
Ghyka, Alexander (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S758000, C438S787000
Reexamination Certificate
active
06790793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device in which the semiconductor devices are processed in a state of charging a plurality of substrates on a boat.
2. Description of the Related Art
When a reactive gas, such as SiH
2
Cl
2
(DCS: dichlorosilane) and NH3 gas, for instance, is supplied into a brand-new semiconductor device manufacturing apparatus which has been just delivered to a user to form a Si
3
N
4
film on a wafer, a detected amount of Fe contamination on the wafer comes to 10 to 30 times of the permissible value (10×10
10
atoms/cm
2
). This is due to initial metal contamination. The source of the initial metal contamination is due to a residue containing Fe, which comes from corrosion on the surface of metal parts of a furnace port of the apparatus or remains in a supply system. Yield of the semiconductor device which is produced with a wafer exposed to a contamination amount over the permissible value comes to remarkably low. Therefore, it is necessary to suppress the amount of contamination below the permissible value. It has been known from practical experience that repeated deposition decreases the initial metal contamination gradually. Accordingly, a method of repeating the deposition 30 to 40 times until the amount of the metal contamination reaches equal to or less than the permissible value has been adopted generally in order to decrease the initial metal contamination.
However, the above-described method to repeat the deposition requires to continue the deposition repeatedly for three to four weeks from start of the method till the amount of metal contamination reaches equal to or below the permissible value. Thus, it is difficult to decrease the metal contamination in a short time, and the semiconductor device manufacturing apparatus cannot be used during that time for manufacturing semiconductor device. Therefore, various methods to decrease the metal contamination at the furnace port have been proposed.
In a patent document 1, in order to prevent generation of metal impurities by the surface of metal parts (manifold) being exposed to NH
3
in a heat treatment apparatus using NH
3
, a method to form an oxide film on the surface of metal parts is proposed. In order to form the oxide film, O
2
is supplied from an O
2
gas supply port and the heat treatment is carried out in an O
2
gas atmosphere.
In a patent document 2, a method is disclosed in that a passivation treatment (forming of a chromium oxide film) is applied to a metal substance (SUS flange) in a CVD apparatus so that the metal substance changes to be inactive to a corrosive gas and a reducing gas, and a coating film is formed further thereon to prevent the metal contamination.
o
In order to form a chromium oxide film, the surface of the metal parts made of SUS is smoothed by electropolishing and the like and then the SUS part is washed with heated deionized water. The film deposited on the chromium oxide film is a CVD film. As the sort of film (raw materials), a Poly-Si film (SiH
4
/N
2
), a Si
3
N
4
film (DCS/NH
3
/N
2
), a SiC film (SiH
4
/CH
4
/N
2
), and a SiO
2
film (TEOS/N
2
) can be used. The thickness of the coating film is about 100 nm.
In a patent document 3, a method of coating metal parts with a chromic oxide film to suppress corrosion and metal contamination on the metal parts in an oxidation apparatus and a CVD apparatus is disclosed. In order to apply coating, a slurry is coated on a metal surface, then a porous film is formed by heating, which is impregnated with an aqueous solution of chromium acid anhydride while being heated. This combination of impregnation of chromium acid and heat treatment is repeated. Incidentally, there is also a description that a cycle purge is carried out after a wafer is loaded and before it is treated. The timing of the cycle purge is after the wafer loading and before the wafer treatment.
In a patent document 4, a method is disclosed in that in a CVD apparatus depositing a SiN film, the inside of a reaction tube is coated with the same film as the film to be deposited in order to prevent contamination by impurities of heavy metals and the like generated from a reaction tube, not from metal members. When coating, a reactive gas is supplied in an amount equal to or more than the amount supplied during the deposition. The thickness of the coating film is equal to or more than 0.8 &mgr;m, or equal to or more than 1 &mgr;m.
In a patent document 5, in a CVD apparatus, a method of covering at least exposed portions of a flange portion and a lid body (metal members) in the inside of a reaction tube with an adherent layer (ceramics, quartz glass, SiC, and so on) of non-metal material is disclosed. The kinds of film (raw materials) deposited by the CVD apparatus is SiO
2
(SiH
4
/O
2
), and Si(DCS/H
2
).
The patent document 1: Japanese Patent Laid-open No. Hei 11-26441
The patent document 2: Japanese Patent Laid-open No. Hei 11-345772
The patent document 3: Japanese Patent Laid-open No. 2002-222807
The patent document 4: Japanese Patent Laid-open No. Hei 9-246256
The patent document 5: Japanese Patent Laid-open No. Hei 2-174225
However, in all of the inventions in the above-described patent documents 1 to 5, since the methods of decreasing the metal contamination are complicated and not enough in lowering a metal contamination level, there is room for improvement. That is, there are the following disadvantages respectively in (1) the method of decreasing the metal contamination by growing an oxide film as described in the patent document 1 and 2, (2) the method of decreasing the metal contamination by cycle purge as described in the patent document 2, and (3) the method of decreasing the metal contamination by coating as described in the patent document 2 to 5.
(1) In the method of decreasing the metal contamination by growing an oxide film, the invention described in the patent document 1 requires a new O
2
gas supply port, which makes the structure complicated, and the invention described in the patent document 2 requires polishing and washing of the SUS parts, which makes the steps complicated.
(2) In the method of decreasing the metal contamination by cycle purge, in the invention described in the patent document 3, the cycle purge is performed after the wafer load and before the wafer processing (deposition), which takes too much time till the deposition starts.
(3) In the method of reducing the metal contamination by coating, the invention described in the patent document 2 required the coating on the chromium oxide film. The coating film has a similar composition to the kind of film deposited in the CVD process, but not the same composition, which makes the steps complicated. Further, in the invention described in the patent document 3, the coating film is a chromium oxide film and in order to form the chromium oxide film, slurry is applied and heated, and then, an aqueous solution of chromium acid anhydride is impregnated and heat-treated. Repetition of the chromium impregnation and the heat-treatment is required, which makes the steps complicated. In the invention described in the patent document 4, the same film as the deposited film is applied on the inside surface of the reaction tube by coating, but since the number of the coating is only one time, reduction of the metal contamination is not enough. Furthermore, since a reactive gas in an amount equal to or more than that at the time of deposition is supplied to perform the coating without loading wafers in the inside of the reaction tube, the film more than required is formed in the inside of the reaction tube, which causes fears of generating particles due to peeling-off of the film. Further, the invention described in the patent document 5 requires to coat with a non-metal film different from the kind of film used for deposition, which makes the steps complicated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for manufacturing a semiconductor device, whi
Mizuno Norikazu
Nishino Yutaka
Suzaki Ken-ichi
Ghyka Alexander
Hitachi Kokusai Electric Inc.
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