Semiconductor device having reinforced low-k insulating film and its manufacture method

Abstract

A semiconductor device manufacture method has the steps of: (a) coating a low dielectric constant low-level insulating film above a semiconductor substrate formed with a plurality of semiconductor elements; (b) processing the low-level insulating film to increase a mechanical strength of the low-level insulating film; (c) coating a low dielectric constant high-level insulating film above the low-level insulating film; and (d) forming a buried wiring including a wiring pattern in the high-level insulating film and a via conductor in the low-level insulating film. The low-level insulating film and high-level insulating film are made from the same material. The process of increasing the mechanical strength includes an ultraviolet ray irradiation process or a hydrogen plasma applying process.

1 . A semiconductor device comprising:
 a semiconductor substrate having a plurality of semiconductor elements;   a buried wiring formed above said semiconductor substrate and including a via conductor for connection to a conductor in a lower layer and a wiring pattern connected to the via conductor; and   an interlayer insulating film surrounding a periphery of said buried wiring and including a low-level insulating film surrounding the via conductor and a high-level insulating film surrounding the wiring pattern, said low-level insulating film and said high-level insulating film being made from a same starting material, and said low-level insulating film having a higher mechanical strength than a mechanical strength of said high-level insulating film.   
     
     
         2 . The semiconductor device according to  claim 1 , further comprising a middle-level insulating film made of material functioning as an etch stopper and disposed between said low-level insulating film and said high-level insulating film. 
     
     
         3 . The semiconductor device according to  claim 2 , wherein said middle-level insulating film is made of SiC. 
     
     
         4 . The semiconductor device according to  claim 1 , wherein said low-level insulating film and said high-level insulating film are made of a porous insulating film. 
     
     
         5 . The semiconductor device according to  claim 4 , wherein said porous insulating film is made of porous silica. 
     
     
         6 . The semiconductor device according to  claim 5 , wherein said low-level insulating film has a Young's modulus higher by 1 GPa or more, than a Young's modulus of said high-level insulating film. 
     
     
         7 . The semiconductor device according to  claim 1 , wherein said buried wiring has a lamination of a barrier layer and a copper layer. 
     
     
         8 . The semiconductor device according to  claim 7 , further comprising an insulating copper diffusion preventive film formed under said low-level insulating film. 
     
     
         9 . A method of manufacturing a semiconductor device comprising the steps of:
 (a) coating a low-level insulating film above a semiconductor substrate formed with a plurality of semiconductor elements;   (b) processing said low-level insulating film to increase a mechanical strength;   (c) coating a high-level insulating film above said low-level insulating film; and   (d) forming a buried wiring including a wiring pattern in said high-level insulating film and a via conductor in said low-level insulating film.   
     
     
         10 . The method of manufacturing a semiconductor device according to claim  9 , wherein said step (b) induces cross-linking reactions in said low-level insulating film. 
     
     
         11 . The method of manufacturing a semiconductor device according to  claim 9 , wherein said step (b) includes irradiating ultraviolet rays. 
     
     
         12 . The method of manufacturing a semiconductor device according to  claim 11 , wherein said ultraviolet rays contain a component having a wavelength in a range of 200 nm to 300 nm. 
     
     
         13 . The method of manufacturing a semiconductor device according to  claim 9 , wherein said step (b) includes processing by hydrogen plasma. 
     
     
         14 . The method of manufacturing a semiconductor device according to  claim 9 , wherein said steps (a) and (c) coat a same starting material for a porous insulating material. 
     
     
         15 . The method of manufacturing a semiconductor device according to  claim 14 , wherein said porous insulating material is porous silica. 
     
     
         16 . The method of manufacturing a semiconductor device according to  claim 15 , wherein said steps (a) and (c) include a step of baking the coated film at a plurality of gradually rising baking temperatures. 
     
     
         17 . The method of manufacturing a semiconductor device according to claim  16 , wherein said step (b) is performed by heating the semiconductor substrate at a temperature equal to or higher than a highest one of said plurality of baking temperatures. 
     
     
         18 . The method of manufacturing a semiconductor device according to  claim 9 , further comprising the step of:
 (e) forming a middle-level insulating film functioning as an etch stopper on said low-level insulating film, between said steps (b) and (c),   wherein said step (d) includes the step of forming a via hole through said high-level insulating film to said low-level insulating film and the step of forming a wiring pattern trench at least in said high-level insulating film by using said middle-level insulating film as an etch stopper.   
     
     
         19 . The method of manufacturing a semiconductor device according to  claim 9 , further comprising the step of:
 (f) after said step (d), forming an insulating copper diffusion preventive film on said high-level insulating film, said insulating copper diffusion preventive film covering said buried wiring.