IP Library › Granted Patent US 7,166,538
Granted Patent B2
US 7,166,538 · App. 10/465,648 · Granted Jan 23, 2007

Method for fabricating semiconductor device

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Quick Facts
Patent No.
US 7,166,538
App. No.
10/465,648
Granted
Jan 23, 2007
Kind
B2
Abstract

After forming a gate insulating film on a semiconductor substrate, a silicon film is deposited on the gate insulating film, and a high-melting point metal film is deposited on the silicon film. After forming a hard mask made of a silicon oxide film or a silicon nitride film on the high-melting point metal film, the high-melting point metal film is dry etched by using the hard mask as a mask. After removing a residue or a natural oxide film present on the silicon film through dry etching, the silicon film is dry etched by using the hard mask as a mask. The residue or the natural oxide film is removed while suppressing excessive etching of the silicon film.

Claims (23)

1. A method for fabricating a semiconductor device comprising the steps of:

forming a gate insulating film on a semiconductor substrate;

depositing a silicon film on said gate insulating film;

depositing a high-melting point metal film on said silicon film;

forming a hard mask made of a silicon oxide film or a silicon nitride film on said high-melting point metal film;

dry etching said high-melting point metal film with said hard mask used as a mask;

removing a residue or a natural oxide film present on said silicon film through dry etching; and

dry etching said silicon film with said hard mask used as a mask,

wherein the silicon film before the step of removing a residue or a natural oxide film is a polysilicon film, and

the step of removing a residue or a natural oxide film is performed using a mixed gas in which a gas including chlorine and an HBr gas are mixed together while suppressing a difference between an etching rate in a grain boundary of the polysilicon film and an etching rate in the other portion of the polysilicon film and a formation of a groove in the grain boundary of the polysilicon film.

2. The method for fabricating a semiconductor device of claim 1 , wherein the silicon film includes a group V impurity and a concentration of the group V impurity is higher than a solubility limit in the silicon film.

3. The method for fabricating a semiconductor device of claim 2 , wherein the group V impurity is deposited in the grain boundary in the silicon film.

4. A method for fabricating a semiconductor device comprising the steps of:

forming a gate insulating film on a semiconductor substrate;

depositing a silicon film on said gate insulating film;

depositing a high-melting point metal film on said silicon film;

forming a hard mask made of a silicon oxide film or a silicon nitride film on said high-melting point metal film;

dry etching said high-melting point metal film with said hard mask used as a mask;

removing a residue or a natural oxide film present on said silicon film through dry etching; and

dry etching said silicon film with said hard mask used as a mask,

wherein said silicon film is an amorphous silicon film, and

the step of removing a residue or a natural oxide film deposited on the gate insulating film is carried out while keeping said silicon film in amorphous condition.

5. The method for fabricating a semiconductor device of claim 4 , wherein each of the step of depositing a high-melting point metal film, the step of forming a hard mask and the step of removing a residue or a natural oxide film is carried out at a temperature at which the amorphous silicon film is not crystallized, the temperature being less than 550° C.