Method of manufacturing a semiconductor device

Abstract

A method of performing irradiation of laser light is given as a method of crystallizing a semiconductor film. However, if laser light is irradiated to a semiconductor film, the semiconductor film is instantaneously melted and expands locally. The temperature gradient between a substrate and the semiconductor film is precipitous, distortions may develop in the semiconductor film. Thus, the film quality of the crystalline semiconductor film obtained will drop in some cases. With the present invention, distortions of the semiconductor film are reduced by heating the semiconductor film using a heat treatment process after performing crystallization of the semiconductor film using laser light. Compared to the localized heating due to the irradiation of laser light, the heat treatment process is performed over the entire substrate and semiconductor film. Therefore, it is possible to reduce distortions formed in the semiconductor film and to increase the physical properties of the semiconductor film.

1 . A method of manufacturing a semiconductor device comprising the steps of:
 irradiating a semiconductor film over a substrate with laser light to increase crystallinity of the semiconductor film, the semiconductor film comprising crystalline silicon;   performing a heat treatment to heat the semiconductor film at a temperature equal to or greater than 500° C. after irradiating the semiconductor film with the laser light; and   patterning the semiconductor film into at least one island shape semiconductor layer after the heat treatment.   
     
     
         2 . The method according to  claim 1 , wherein the heat treatment is performed in a nitrogen atmosphere. 
     
     
         3 . The method according to  claim 1 , wherein the heat treatment is performed in an inert gas. 
     
     
         4 . The method according to  claim 1 , wherein the irradiation with the laser light is performed in a reduced pressure atmosphere. 
     
     
         5 . The method according to  claim 1 , wherein the irradiation with the laser light is performed in a nitrogen atmosphere. 
     
     
         6 . The method according to  claim 1 , wherein the irradiation with the laser light is performed in an inert gas. 
     
     
         7 . The method according to  claim 1 , wherein the semiconductor film is formed over the substrate by deposition. 
     
     
         8 . The method according to  claim 1 , further comprising:
 a step of depositing a semiconductor film comprising amorphous silicon; and   a step of heating the semiconductor film comprising amorphous silicon for crystallization.   
       heating the semiconductor film comprising crystalline silicon is formed by heating the semiconductor film for crystallization. 
     
     
         9 . The method according to  claim 1 , wherein the laser light is a pulsed excimer laser light. 
     
     
         10 . The method according to  claim 1 , wherein the semiconductor device is an active matrix display device. 
     
     
         11 . The method according to  claim 1 , wherein the heat treatment is performed in order to reduce distortion in the semiconductor film, the distortion caused by the irradiation of the laser light. 
     
     
         12 . A method of manufacturing a semiconductor device comprising the steps of:
 irradiating a semiconductor film over a substrate with laser light in a reduced pressure atmosphere to increase crystallinity of the semiconductor film, the semiconductor film comprising crystalline silicon;   performing a heat treatment to heat the semiconductor film at a temperature equal to or greater than 500° C. in a nitrogen atmosphere after irradiating the semiconductor film with the laser light; and   patterning the semiconductor film into at least one island shape semiconductor layer after the heat treatment.   
     
     
         13 . The method according to  claim 12 , wherein the semiconductor film is formed over the substrate by deposition. 
     
     
         14 . The method according to  claim 12 , further comprising:
 a step of depositing a semiconductor film comprising amorphous silicon; and   a step of heating the semiconductor film comprising amorphous silicon for crystallization.   
     
     
         15 . The method according to  claim 12 , wherein the laser light is a pulsed excimer laser light. 
     
     
         16 . The method according to  claim 12 , wherein the semiconductor device is an active matrix display device. 
     
     
         17 . The method according to  claim 12 , wherein the heat treatment is performed in order to reduce distortion in the semiconductor film, the distortion caused by the irradiation of the laser light. 
     
     
         18 . A method of manufacturing a semiconductor device comprising the steps of:
 irradiating a semiconductor film over a substrate with laser light to increase crystallinity of the semiconductor film, the semiconductor film comprising crystalline silicon;   performing a heat treatment to heat the semiconductor film at a temperature equal to or greater than 500° C. after irradiating the semiconductor film with the laser light;   patterning the semiconductor film into at least one island shape semiconductor layer after the heat treatment;   forming a gate insulating film over the island shape semiconductor layer; and   forming a gate electrode over the gate insulating film.   
     
     
         19 . The method according to  claim 18 , wherein the heat treatment is performed in a nitrogen atmosphere. 
     
     
         20 . The method according to  claim 18 , wherein the heat treatment is performed in an inert gas. 
     
     
         21 . The method according to  claim 18 , wherein the irradiation with the laser light is performed in a reduced pressure atmosphere. 
     
     
         22 . The method according to  claim 18 , wherein the irradiation with the laser light is performed in a nitrogen atmosphere. 
     
     
         23 . The method according to  claim 18 , wherein the irradiation with the laser light is performed in an inert gas. 
     
     
         24 . The method according to  claim 18 , wherein the semiconductor film is formed over the substrate by deposition. 
     
     
         25 . The method according to  claim 18 , further comprising:
 a step of depositing a semiconductor film comprising amorphous silicon; and   a step of heating the semiconductor film comprising amorphous silicon for crystallization.   
     
     
         26 . The method according to  claim 18 , wherein the laser light is a pulsed excimer laser light. 
     
     
         27 . The method according to  claim 18 , wherein the semiconductor device is an active matrix display device. 
     
     
         28 . The method according to  claim 18 , wherein the heat treatment is performed in order to reduce distortion in the semiconductor film, the distortion caused by the irradiation of the laser light.