Low dielectric constant insulating film and method of forming the same

Abstract

The present invention relates to a method of forming a low dielectric constant insulating film. Its constitution has the steps of: (a) forming an insulating film containing Si—CH 3 bond in the skeleton of Si—O—Si on a substrate; (b) irradiating ultraviolet ray to the insulating film in reduced-pressure atmosphere to break CH 3 groups from Si—CH 3 bond in the insulating film; and (c) ejecting the broken CH 3 groups from the insulating film.

1 . A method of forming a low dielectric constant insulating film, comprising the steps of: 
 (a) forming an insulating film, which contains Si—CH n  (n=1, 2, 3) bond in Si—O—Si or another silica skeleton, on a substrate;    (b) irradiating ultraviolet ray to said insulating film in reduced-pressure atmosphere or reduced-pressure atmosphere mainly containing inert gas and nitrogen to break CH n  groups from Si—CH n  bond in said insulating film; and    (c) ejecting said broken CH n  groups from said insulating film.    
     
     
         2 . The method of forming the low dielectric constant insulating film according to  claim 1 , wherein 
 the wavelength of said ultraviolet ray is 120 nm or more.    
     
     
         3 . The method of forming the low dielectric constant insulating film according to  claim 1 , wherein 
 the step of said (c) is performed after the step of said (b).    
     
     
         4 . The method of forming the low dielectric constant insulating film according to  claim 3 , wherein 
 the step of said (b) and the step of said (c) are performed simultaneously by irradiating ultraviolet ray on said insulating film in the reduced-pressure atmosphere while heating said substrate.    
     
     
         5 . The method of forming the low dielectric constant insulating film according to  claim 1 , wherein the steps of said (a) to said (c) are performed repeatedly.  
     
     
         6 . The method of forming the low dielectric constant insulating film according to  claim 1 , wherein 
 the step of said (a) is a step of applying electric power to deposition gas, which contains an organic compound having Si—CH 3  bond and siloxane bond or an another organic compound having Si—CH 3  bond and oxidizing gas, to generate plasma so that reaction is caused to form a CVD insulating film containing said Si—CH n  bond on said substrate.    
     
     
         7 . The method of forming the low dielectric constant insulating film according to  claim 6 , wherein 
 the organic compound having said Si—CH 3  bond and siloxane bond is any one of    hexamethyldisiloxane (HMDSO: (CH 3 ) 3 Si—O—Si(CH 3 ) 3 ),                                            
     
     
         8 . The method of forming the low dielectric constant insulating film according to  claim 6 , wherein another organic compound having said Si—CH 3  bond is any one of 
 dimethyldimethoxysilane (Si(CH 3 ) 2 OCH 3 ) 2 ),    tetramethylsilane (Si(CH 3 ) 4 ),    trimethylsilane (SiH(CH 3 ) 3 ),    dimethylsilane (SiH 2 (CH 3 ) 2 ) and    monomethylsilane (SiH 3  (CH 3 )).    
     
     
         9 . The method of forming the low dielectric constant insulating film according to  claim 6 , wherein 
 said oxidizing gas is at least one of H 2 O, N 2 O, CH 3 OH, C 2 H 5 OH, H 2 O 2  and O 2 .    
     
     
         10 . The method of forming the low dielectric constant insulating film according to  claim 6 , wherein 
 said deposition gas contains C x  H y  F z  (x is a positive integer, y is 0 or a positive integer, z is 0 or a positive integer, and y and z do not become 0 at the same time) in addition to the organic compound having siloxane bond and the oxidizing gas.    
     
     
         11 . The method of forming the low dielectric constant insulating film according to  claim 10 , wherein said C x  H y  F z  is C 4 F 8  and C 2 F 4 .  
     
     
         12 . The method of forming the low dielectric constant insulating film according to  claim 1 , wherein 
 the step of said (a) is a step of coating organic SOG having Si—CH 3  bond and siloxane bond on said substrate to form a coated insulating film containing Si—CH n  (n=1, 2, 3) bond.    
     
     
         13 . The method of forming the low dielectric constant insulating film according to  claim 12 , wherein 
 said organic SOG having siloxane bond is alkylsilsesquioxane polymer (MSQ).    
     
     
         14 . A low dielectric constant insulating film characterized in having a low dielectric constant and sufficient mechanical strength on the basis of an initial insulating film being non-porous or porous and having Si—CH 3  bond with respect to the silica skeleton of Si—O—Si, or Si—O other than Si—O—Si, wherein CH 3  group in said initial insulating film is broken by ultraviolet irradiation in reduced-pressure atmosphere and said CH 3  group is ejected from said initial insulating film by heat treatment.