Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-11-22
2002-09-10
Meeks, Timothy (Department: 1762)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S660000, C438S685000, C438S770000, C427S255270, C427S255400, C427S372200
Reexamination Certificate
active
06448178
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heat treatment method for heat treating and depositing a thin film used for a gate electrode and wiring of a semi-conductor device.
BACKGROUND OF THE INVENTION
In a semi-conductor device such as an LSI, a polycide layer having a polysilicon layer and a tungsten silicide layer given low resistance by doping impurities such as, for example, phosphorous, is widely used as a material for a gate electrode and wiring in order to lower resistance of the gate electrode and the wiring. The tungsten silicide layer as an upper layer of polycide structure is generally deposited by a CVD method using WF
6
/SiCl
2
H
2
/Ar as reactive gas. Thus when the tungsten silicide layer is deposited on the polysilicon layer, a deposition temperature, a reactive gas pressure, a gas flow rate, a gas flow rate ratio and so on are controlled to obtain required thin film properties of the tungsten silicide layer.
Since recent rapid development of microprocessing technology results in a requirement for further reducing the resistance of the gate electrode and the wiring, it has been tried so far to reduce the resistance of the tungsten silicide thin film by applying various conditions of the reactive gas (WF
6
/SiCl
2
H
2
/Ar). However if only an adjustment of compositions of the thin film by changing the conditions of the reactive gas is performed, the reduction of the resistance of the thin film encounters a limitation. Therefore it is difficult to reduce the resistance by the conventional method corresponding to the microprocessing and thin film thickness reduction that will further progress.
DISCLOSURE OF THE INVENTION
The present invention is to solve the above-mentioned problems and has an object to provide a heat treatment method for heat treating and depositing a thin film that ensures to realize lowering of resistance of the thin film and enables to correspond to the lowering of the resistance that will further progress from now on.
This invention is the heat treatment method for heat treating a thin film including a metallic silicide layer containing an element of Group V of the Periodic table comprising a heating step to heat the thin film to a predetermined temperature, a keeping step to keep the thin film at the predetermined temperature and a cooling step to cool the thin film from the predetermined temperature, wherein the thin film is heated in an atmosphere of gas which is oxidizing gas or contains oxidizing gas at least in the heating step.
The present invention is the heat treatment method for heating the thin film, wherein the thin film is provided on a silicon substrate.
The present invention is the heat treatment method for heating the thin film, wherein the thin film further has a polysilicon layer provided on the silicon substrate side and containing an element of Group V of the Periodic table.
The present invention is the heat treatment method for heating the thin film, wherein the thin film is kept and cooled in an inert gas atmosphere in the temperature keeping step and the cooling step, respectively.
The present invention is the heat treatment method for heating the thin film, wherein the thin film has a metallic silicide layer containing phosphorous atoms.
The present invention is the heat treatment method, wherein the oxidizing gas is oxygen gas and the gas containing the oxidizing gas is mixed gas comprising oxygen gas and inert gas.
The present invention is the heat treatment method for heating the thin film, wherein the thin film is heated to a temperature of 950° C. to 1100° C. in the heating step.
The present invention is a deposition method for depositing a thin film having a metallic silicide layer containing an element of Group V of the Periodic table comprising a step to depositing a thin film having the metallic silicide layer containing an element of Group V of the Periodic table, the heating step to heat the thin film to the predetermined temperature, the temperature keeping step to keep the thin film at the predetermined temperature and the cooling step to cool the thin film from the predetermined temperature, wherein the thin film is heated in an atmosphere of gas which is oxidizing gas or contains oxidizing gas at least in the heating step.
The present invention is the deposition method for depositing the thin film, wherein the thin film is provided on the silicon substrate.
The present invention is the deposition method for depositing the thin film, wherein the thin film further has the polysilicon layer provided on the silicon substrate side and containing an element of Group V of the Periodic table.
The present invention is the deposition method for depositing the thin film, wherein the thin film is kept at the predetermined temperature and cooled in the inert gas atmosphere in the temperature keeping step and the cooling step, respectively.
The present invention is the deposition method for depositing the thin film, wherein the metallic silicide layer of the thin film includes phosphorous atoms.
The present invention is the deposition method for depositing the thin film, wherein the oxidizing gas is oxygen gas, and the gas including oxidizing gas is the mixed gas comprising oxygen gas and inert gas.
The present invention is the deposition method for depositing the thin film, wherein the thin film is heated to a temperature of 950° C. to 1100° C. in the heating step.
We studied a conventional heat treatment method in various ways in order to solve a problem that a film deposition step provides a limitation to the lowering the resistance of the film. As a result we reached a conclusion that inert gas such as nitrogen gas which is used for adjusting properties of the thin film in the conventional heat treatment method is the cause of providing the limitation to the lowering the resistance. In other words, since the heat treatment of the thin film is performed in the inert gas atmosphere, one of the causes is considered to be a phenomenon that impurities such as the phosphorous atoms contained in the thin film and contributing to the lowering the resistance thermally disperse in the thin film during the heat treatment and escape from the thin film, and an effect of reducing the resistance by adding the impurities that should have been essentially obtained during the film deposition is obstructed. Thus we obtained information that we can prevent the impurities such as the phosphorous atoms from escaping from the thin film by performing the heat treatment of the thin film in a specified gas atmosphere, and realize the further lowering of the resistance of the thin film.
The thin film to be subjected to the heat treatment in the present invention is one having the metallic silicide layer containing an element of Group V of the Periodic table. The resistance of the metallic silicide layer was reduced by adding the element of Group V of the Periodic table, and it has been so far deposited in a known method. The elements of Group V of the Periodic table including phosphorous, arsenic, antimony, and bismuth have been widely used so far as a dopant of the thin film. And the thin film in the present invention is that containing at least the metallic silicide layer. Therefore the thin film in the present invention may be one made from the metallic silicide layer only, or one made from the polysilicon layer overlaid by the metallic silicide layer. The metallic silicides include, for example, tungsten silicide, titanium silicide, cobalt silicide and molybdenum silicide.
The thin film to be subjected to the heat treatment in the present invention is one having a polysilicon layer and a metallic silicide layer containing the element of Group V of the Periodic table. The polysilicon layer and the metallic silicide layer of this thin film contain an element of Group V. Both of these layers can be continuously deposited by same deposition equipment, or the polysilicon layer and the metallic silicide layer can be individually deposited by different deposition equipment. In either deposition method, an addition of the element of G
Matsudo Masahiko
Suzuki Kenji
Meeks Timothy
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
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