Ultralow dielectric constant layer with controlled biaxial stress

Abstract

A method for forming a ultralow dielectric constant layer with controlled biaxial stress is described incorporating the steps of forming a layer containing Si, C, O and H by one of PECVD and spin-on coating and curing the film in an environment containing very low concentrations of oxygen and water each less than 10 ppm. A material is also described by using the method with a dielectric constant of not more than 2.8. The invention overcomes the problem of forming films with low biaxial stress less than 46 MPa.

1 . A method for fabricating an ultralow dielectric constant film containing elements of Si, C, O and H, and having low and controllable biaxial stress comprising the steps of:
 forming a film on a substrate by a process selected from the group consisting of plasma enhanced chemical vapor deposition (PECVD) and spin-on process; and   curing said film in an environment containing a concentration of oxygen in the range from 0 to 10 ppm.   
     
     
         2 . The method of  claim 1  wherein said step of curing includes using an energy source selected from the group consisting of thermal, electron beam, plasma, UV, DUV and laser. 
     
     
         3 . The method of  claim 1  wherein said O 2  concentration does not exceed 8 parts per million (ppm). 
     
     
         4 . The method of  claim 2  wherein said films are exposed a second time to one of said energy sources in an environment containing a concentration of water in the range from 0 to 10 ppm. 
     
     
         5 . The method of  claim 1  wherein said biaxial stress of said film does not exceed 46 MPa. 
     
     
         6 . The method of  claim 1  wherein said biaxial stress of said film does not exceed the stress of the as-deposited, uncured film by more than 5 MPa. 
     
     
         7 . The method of  claim 1  wherein said curing is done by heating said films at temperatures not lower than 300 C for a period of not less than 0.25 hours. 
     
     
         8 . The method of  claim 1  wherein said step of curing includes using an energy source selected from the group consisting of an electron beam, plasma, UV, DUV (deep UV) or laser, while said film is maintained at temperatures not lower than 300 C. 
     
     
         9 . The method of  claim 1  wherein said ultralow k film has a dielectric constant of not more than about 2.8. 
     
     
         10 . The method of  claim 1  wherein said ultralow k film has a dielectric constant in the range from about 1.5 to about 2.8. 
     
     
         11 . The method of  claim 1  wherein said ultralow k film comprises about 5 to about 40 atomic percent of Si; about 5 to about 45 atomic percent of C; about 0 to about 50 atomic percent of O; and about 10 to about 55 atomic percent of H. 
     
     
         12 . A method for fabricating an ultralow dielectric constant film containing elements of Si, C, O and H, and exhibiting low and controllable biaxial stress:
 forming said film on a substrate by a process selected from the group consisting of plasma enhanced chemical vapor deposition (PECVD) and a spin-coating process;   allowing the as-deposited film and the substrate on which it is formed to cool down in a non oxidizing environment containing controlled very low concentrations of oxygen and in the range from 0 to 10 ppm, before said as-deposited film is exposed to ambient atmosphere, and   curing said as-deposited film in an environment containing controlled very low concentrations of oxygen and water each in the range from 0 to 10 ppm.   
     
     
         13 . The method of  claim 12  wherein the said curing is performed using an energy source from the group comprising at least one of thermal, electron beam, plasma, UV, DUV and laser. 
     
     
         14 . The method of  claim 12  wherein said curing further includes exposing said film a second time to one or more energy sources from the group comprising thermal, electron beam, plasma, UV, DUV or laser, in an environment containing controlled very low concentrations of oxygen or water each in the range from 0 to 10 ppm. 
     
     
         15 . The method of  claim 12  wherein said curing is done by heating said deposited film at temperatures not lower than 300 C for a period of not less 0.25 hours. 
     
     
         16 . The method of  claim 12  wherein said film is UV or e-beam treated, and then allowed to cool down to room temperature in the same environment. 
     
     
         17 . A curing tool wherein an ultralow dielectric constant film containing elements of Si, C, O and H is cured, the said curing being performed using an energy source from the group comprising thermal, electron beam, plasma, UV, DUV and laser in an environment containing controlled very low concentrations of oxygen water each in the range from 0 to 100 ppm, resulting in a film with low and controllable biaxial stress. 
     
     
         18 . The tool of  claim 17  wherein said films are optionally exposed a second time to one or more energy sources from the group comprising thermal, electron beam, plasma, UV, DUV and laser, in an environment containing controlled very low concentrations of oxygen water each in the range from 0 to 10 ppm. 
     
     
         19 . The tool of  claim 17  wherein said curing is done by heating the said deposited films at temperatures not lower than 300 C for a period of not less 0.25 hours. 
     
     
         20 . The tool of  claim 17  wherein said curing is performed using an energy source from the group comprising electron beam, plasma, UV, DUV (deep UV) or laser, while the said deposited films are kept at temperatures not lower than 300 C. 
     
     
         21 . An integrated PECVD-Cure tool for fabricating an ultralow dielectric constant film containing elements of Si, C, O and H, and exhibiting low and controllable biaxial stress, in which the following processing steps are performed:
 depositing said film on a substrate using plasma enhanced chemical vapor deposition (PECVD);   transferring said substrate between process areas in the tool in a non-oxidizing environment containing controlled very low concentrations of oxygen in the range from 0 to 100 ppm.   curing the deposited film in an environment containing controlled very low concentrations of oxygen or water each in the range from 0 to 100 ppm;   allowing said substrate to cool down in a non oxidizing environment containing controlled very low concentrations of oxygen or water each in the range from 0 to 10 ppm, before it is exposed to ambient atmosphere.   
     
     
         22 . The tool of  claim 21  wherein the environment is a non-oxidizing (no oxygen) hydrocarbon ambient with double bond groups and with the oxygen level less than 10 ppm to passivate the reactive site after curing and to reduce the SiCOH and porous SiCOH film oxidation. 
     
     
         23 . The tool of  claim 22  wherein said hydrocarbon ambient double bond groups include ethylene or 1,3 butadiene.