Method of forming dielectric film and dielectric film

Abstract

A first interlayer insulating film ( 3 ) having low dielectric constant is formed on an underlying insulating film ( 2 ) and a second interlayer insulating film ( 4 ) is formed on the first interlayer insulating film ( 3 ). Subsequently, a photoresist ( 5 ) having a pattern with openings above regions in which copper wirings are to be formed is formed on the second interlayer insulating film ( 4 ). Using the photoresist ( 5 ) as an etching mask, the second interlayer insulating film ( 4 ) and the first interlayer insulating film ( 3 ) are etched, to form a recess ( 6 ). Next, an ashing process using oxygen gas plasma ( 7 ) is performed, to remove the photoresist ( 5 ). This ashing process is performed under a plasma forming condition that the RF power is 300 W, the chamber pressure is 30 Pa, the oxygen flow is 100 sccm and the substrate temperature is 25 ° C. That provides a method of forming a dielectric film and a structure thereof, which allows suppression of a rise in dielectric constant of an interlayer insulating film, which is caused by a change of Si—C n H 2n+1 bond into Si—OH bond in the film.

What is claimed is:  
     
         1 . A method of forming a dielectric film, comprising the steps of: 
 (a) forming an insulating film including Si—C n H 2n+1  bond;    (b) forming a resist selectively on a main surface of said insulating film;    (c) removing said insulating film not covered with said resist to form a recess in said main surface of said insulating film; and    (d) performing an ashing process using gas plasma under a condition that said Si—C n H 2n+1  bond should not be changed to Si—OH bond to remove said resist.    
     
     
         2 . The method of forming a dielectric film according to  claim 1 , wherein 
 said Si—C n H 2n+1  bond is changed to Si—H bond in said ashing process under said condition in said step (d).    
     
     
         3 . The method of forming a dielectric film according to  claim 1 , wherein 
 said condition is that oxygen gas plasma is used, the temperature is 25° C. or lower and the chamber pressure ranges from 4 to 70 Pa.    
     
     
         4 . The method of forming a dielectric film according to  claim 1 , wherein 
 said condition is that oxygen gas plasma is used, the temperature is 100° C. or lower and the chamber pressure ranges from 4 to 13.3 Pa.    
     
     
         5 . The method of forming a dielectric film according to  claim 1 , wherein 
 said ashing process is performed by using hydrogen gas plasma or ammonia gas plasma in said step (d).    
     
     
         6 . The method of forming a dielectric film according to  claim 1 , further comprising the step of: 
 (e) filling the inside of said recess with a metal film, wherein said step (e) is executed after said step (d).    
     
     
         7 . The method of forming a dielectric film according to  claim 1 , wherein 
 said insulating film is formed on an underlying layer in said step (a), and    said recess is so formed as not to reach said underlying layer in said step (c).    
     
     
         8 . A dielectric film, comprising: 
 an insulating film including Si—C n H 2n+1  bond;    a recess formed selectively in a main surface of said insulating film; and    a surface protective layer including Si—H bond, being formed in a surface of said insulating film in an inner wall of said recess.    
     
     
         9 . The dielectric film according to  claim 8 , further comprising: 
 a metal film for filling the inside of said recess.    
     
     
         10 . The dielectric film according to  claim 8 , wherein 
 said insulating film is formed on an underlying layer, and    said recess is so formed, extending from said main surface of said insulating film, as not to reach said underlying layer.