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The present invention provides a low dielectric constant copper diffusion barrier film composed, at least in part, of boron-doped silicon carbide suitable for use in a semiconductor device and methods for fabricating such a film. The copper diffusion barrier maintains a stable dielectric constant of

The present invention provides a low dielectric constant copper diffusion barrier film composed, at least in part, of boron-doped silicon carbide suitable for use in a semiconductor device and methods for fabricating such a film. The copper diffusion barrier maintains a stable dielectric constant of less than 4.5 in the presence of atmospheric moisture.

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It is claimed: 1. A method of forming a copper diffusion barrier film in a semiconductor device, comprising a copper interconnect, the method comprising: forming a copper diffusion barrier film on the copper interconnect, the copper diffusion barrier film comprising a layer of a nitrogen-free boron

It is claimed: 1. A method of forming a copper diffusion barrier film in a semiconductor device, comprising a copper interconnect, the method comprising: forming a copper diffusion barrier film on the copper interconnect, the copper diffusion barrier film comprising a layer of a nitrogen-free boron-doped silicon carbide and a layer of an oxygen-doped silicon carbide forming a stack, wherein forming the copper diffusion barrier film comprises forming the layer of nitrogen-free boron-doped silicon carbide adjacent the copper interconnect and forming the layer of oxygen-doped silicon carbide not in a direct contact with the copper interconnect. 2. The method of claim 1, wherein forming the copper diffusion barrier film comprises forming the nitrogen-free boron-doped silicon carbide layer adjacent the copper interconnect; forming a nitrogen-doped silicon carbide layer and forming the oxygen-doped silicon carbide layer, wherein the nitrogen-free boron-doped silicon carbide layer, the nitrogen-doped silicon carbide layer and the oxygen-doped silicon carbide layer are compositionally distinct layers. 3. The method of claim 1, wherein the copper diffusion barrier film maintains an effective dielectric constant of less than about 4.5 in the presence of atmospheric moisture. 4. The method of claim 1, wherein the copper diffusion barrier film is formed by PECVD. 5. The method of claim 4, wherein the PECVD uses an organosilicon precursor and a boron precursor to form the nitrogen-free boron-doped silicon carbide layer. 6. The method of claim 5, wherein the organosilicon precursor is selected from the group consisting of tetramethylsilane, ethynyltrimethylsilane, vinylphenylmethylsilane, phenyldimethylsilane, tri-iso-propylsilane, 3-(trimethylsilyl)cyclopentene, vinylphenyldimethylsilane and vinyldimethylsilane. 7. The method of claim 6, wherein the PECVD uses an organosilicon precursor selected from the group consisting of ethynyltrimethylsilane, vinylphenylmethylsilane, phenyldimethylsilane, tri-iso-propylsilane, 3-(trimethylsilyl)cyclopentene, vinylphenyldimethylsilane and vinyldimethylsilane. 8. The method of claim 6, wherein the PECVD uses an organosilicon precursor selected from the group consisting of ethynyltrimethylsilane, vinylphenylmethylsilane and phenyldimethylsilane. 9. The method of claim 6, wherein the PECVD uses a boron precursor selected from the group consisting of diborane, trimethylborate, dimethylamine borane, triethylamine borane and nido-pentaborane. 10. The method of claim 6, wherein the PECVD uses diborane as the boron precursor. 11. A method of forming a copper diffusion barrier film in a semiconductor device, comprising a copper interconnect, the method comprising: forming a copper diffusion barrier film on the copper interconnect, the copper diffusion barrier film comprising a layer of a nitrogen-free boron-doped silicon carbide and a layer of an oxygen-doped silicon carbide forming a stack, wherein forming the copper diffusion barrier film comprises forming the layer of nitrogen-free boron-doped silicon carbide adjacent the copper interconnect; forming a nitrogen-doped silicon carbide layer and forming the oxygen-doped silicon carbide layer, wherein the nitrogen-free boron-doped silicon carbide layer, the nitrogen-doped silicon carbide layer and the oxygen-doped silicon carbide layer are compositionally distinct layers. 12. The method of claim 11, wherein the copper diffusion barrier film maintains an effective dielectric constant of less than about 4.5 in the presence of atmospheric moisture. 13. The method of claim 11, wherein the copper diffusion barrier film is formed by PECVD. 14. The method of claim 13, wherein the PECVD uses an organosilicon precursor and a boron precursor to form the nitrogen-free boron-doped silicon carbide layer. 15. The method of claim 14, wherein the organosilicon precursor is selected from the group consisting of tetramethylsilane, ethynyltrimethylsilane, vinylphenylmethylsilane, phenyldimethylsilane, tri-iso-propylsilane, 3-(trimethylsilyl)cyclopentene, vinylphenyldimethylsilane and vinyldimethylsilane. 16. The method of claim 13, wherein the PECVD uses an organosilicon precursor selected from the group consisting of ethynyltrimethylsilane, vinylphenylmethylsilane, phenyldimethylsilane, tri-iso-propylsilane, 3-(trimethylsilyl)cyclopentene, vinylphenyldimethylsilane and vinyldimethylsilane. 17. The method of claim 13, wherein the PECVD uses ethynyltrimethylsilane as an organosilicon precursor. 18. The method of claim 15, wherein the PECVD uses a boron precursor selected from the group consisting of diborane, trimethylborate, dimethylamine borane, triethylamine borane and nido-pentaborane. 19. The method of claim 15, wherein the PECVD uses diborane as the boron precursor. 20. The method of claim 19, wherein forming the nitrogen-free boron-doped silicon carbide layer comprises providing diborane and an inert gas as a 5%/95% mixture into a PECVD process chamber. 21. The method of claim 11, further comprising removing metal oxide from the metal interconnect prior to forming the copper diffusion barrier film.