The invention relates to a method of forming a titanium silicide film serving as an electrode or an an interconnection involved in a semiconductor device.
In the prior art, polysilicon films doped with phosphorus have often been used as electrodes and interconnections in fabrication processes of semiconductor integrated circuits including MOS field effect transistors. A resistance of the gate electrode or the interconnection comprising the polysilicon film doped with phosphorus provides a limitation to an improvement in a high speed performance of the MOS field effect transistor.
To solve the above problem and permit a further improvement in a high speed performance of the MOS field effect transistor, in place of the phosphorus doped polysilicon film, a polycide structure comprising a polysilicon and a high melting point metal silicide has been on the use. Particularly, a titanium silicide film has a smaller resistivity in various high melting point metal silicide films. A titanium silicide film serving as the gate electrode is suitable in a self-alignment process for reductions of resistances of source and drain diffusion regions in the MOS field effect transistor. For the above reasons, the titanium silicide film is attractive as an electrode and an interconnection.
In the formation of the interconnection comprising the titanium silicide film, an inter-layer insulator comprising a phospho-silicate glass film or a boron phospho-silicate glass film is deposited on a titanium silicide film by a vapor phase growth for subsequent heat treatment at a temperature in the range of from 750.degree. C. to 900.degree. C. of the inter-layer insulator to cause a reflow of the phospho-silicate glass film or the boron phospho-silicate glass film. The heat treatment is carried out by annealing for at least a time in the range of from 5 to 10 minutes.
The heat treatment at the temperature of 750.degree. C. to 900.degree. C. for the time of 5 to 10 minutes may cause a cohesion reaction of the titanium silicide in the electrode or the interconnection layer. The cohesion reaction of the titanium silicide may cause a disconnection of the titanium silicide layer constituting the electrode or the interconnection.
To prevent the disconnection of the titanium silicide layer constituting the electrode or the interconnection, the titanium layer is required to have a thickness of at least 100 nanometers. Notwithstanding, a reduction of the thickness of the titanium layer constituting the electrode or the interconnection is necessarily required for a further scaling down of the MOS field effect transistors in order to achieve a further improvement in the density of the integration of the semiconductor integrated circuits.
In the above-viewpoints, it is required to develop a novel method of forming a titanium silicide film underlying an insulation film of silicate glass including phosphorus with suppression of any cohesion reaction.