Method of film deposition on substrate surface and substrate produced by the method

Abstract

A method of film deposition is disclosed, which eliminates the conventional problem that a coating film having a component concentration gradient in the thickness direction and thus having a boundary with a compositional gradient or a coating film in which two or more components coexist as a mixture thereof cannot be stably obtained by sputtering. In the method, two planar cathodes are closely arranged as a pair, and a voltage is applied thereto while alternately inverting the polarities thereof so that when a target A bonded to one of the cathodes is used as a negative electrode, then a target B bonded to the other cathode and differing to the target A in component is used as a positive electrode. The targets A and B are simultaneously bombarded with positive ions while passing a substrate in front of the targets so as to cross the cathodes. Thus, a coating film having a boundary with a compositional gradient in the thickness direction or a coating film having a two-layer structure composed of a layer of ingredient A and a layer of ingredient B is deposited by sputtering through one-direction conveyance.

What is claimed is:  
     
         1 . A method of film deposition on a substrate surface which comprises closely arranging a pair of cathodes in a vacuum apparatus in which an atmosphere having a reduced pressure can be prepared, applying a voltage thereto while alternately inverting the polarities thereof so that when one of the cathodes is used as a negative or positive electrode, then the other cathode is used as a positive or negative electrode, respectively, to generate glow discharges on targets respectively disposed on the two cathodes, and simultaneously bombarding the targets with positive ions resulting from the glow discharges to thereby sputter a coating film comprising the materials of the targets on a surface of a substrate, 
 wherein the material of the target disposed on one of the cathodes differs from that of the target disposed on the other cathode and the film deposited on the substrate surface comprises both of the target materials.    
     
     
         2 . The method of film deposition on a substrate surface of  claim 1 , wherein the cathodes as a pair are planar cathodes arranged so that the longer sides of one of the cathodes are parallel to those of the other, and the substrate is passed in front of the cathodes in such a manner as to cross the cathodes in a direction perpendicular to the direction of the longer sides of the cathodes, whereby the coating film deposited has a concentration gradient in the thickness direction with respect to the concentration of each of the different target materials.  
     
     
         3 . The method of film deposition on a substrate surface of  claim 1 , wherein the two cathodes are arranged so that one is surrounded by the other, whereby the different target materials in the coating film deposited are present as a mixture of both.  
     
     
         4 . The method of film deposition on a substrate surface of  claim 1 ,  2  or  3 , wherein the target materials each is a metal.  
     
     
         5 . The method of film deposition on a substrate surface of  claim 1 ,  2  or  3 , wherein the target materials each is an electroconductive metal oxide.  
     
     
         6 . A substrate with reflective coating which comprises a transparent substrate and formed thereon two coating layers comprising a silicon dioxide film and a titanium dioxide film which have been deposited by the method of  claim 4  or  5  so that the two-layer coating has a compositional gradient around the boundary between the layers.