Improved Reliability of Electron Devices Through Optimized Coverage of Surface Topography

Improper coverage of surface topography can lead to a variety of reliability and yield problems in electron devices. The nature of coverage defects and failure mechanisms is discussed, and techniques for improving the reliability by chemical tapering processes and/or optimized film deposition methods are reviewed and classified. Specific examples of experimental conditions are given for obtaining tapered edges of delineated films by chemical and by fusion techniques. Means for achieving improved step coverage by deposited films are also outlined. Several examples of applications to device processing are presented in the experimental part of the paper. A novel electrical process control method utilizing noise measurements in a selected frequency range is demonstrated to be an extremely sensitive tool for rapidly determining variations in the cross-sectional area of conductor films. Experimental results are given to illustrate the applicability of the new method for evaluating taper angles from 3 to 90°.