9 July 1986 A Method For Generating Sloped Contact Holes Using A Cantilever Resist Structure
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Reliable coverage of contact holes in the 0.8 to 1.25 micron range with sputtered metals requires sloping of the contact sidewalls. Conventional single layer resist and fluorocarbon based oxide etch techniques produce sidewalls close to 90 degrees. With mild alteration to the C2F6/CHF3 oxide etch chemistry to produce a highly selective oxide etch and separation of the printed resist openings from the substrate by a spacer layer of 1.5 to 3.5 microns in thickness a sloped contact can be etched into the dielectric. To generate the separation a cantilevered resist structure has been produced by modifying the sestertius multilayer resist process. The sestertius resist process is a "two and one-half" layer process, using PMMA as the bottom planarizing layer, a thin anti-reflective coating layer to block intermixing and to eliminate the effect of reflected light on patterning, and novolak resist as the top imaging layer. The undercut cantilever structure is produced by over exposing and over developing the PMMA. Controlled contact slopes between 60 and 90 degrees can be generated reliably. The degree of variation in contact angles over different topography is dependent on the percent variation of total spacer thickness. For typical MOS topography a variation in angle of less than 10 degrees is observed. The process has excellent repeatability and process control. Sputtered aluminum sidewall coverage is improved from the 10 to 25 percent range to the 45 to 65 percent range.
© (1986) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Vic Marriott, Vic Marriott, Barry Jucha, Barry Jucha, } "A Method For Generating Sloped Contact Holes Using A Cantilever Resist Structure", Proc. SPIE 0631, Advances in Resist Technology and Processing III, (9 July 1986); doi: 10.1117/12.963653; https://doi.org/10.1117/12.963653

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