Michael L. Kerbaugh

Wafer line productivity optimization in a multi-technology multi-part-number fabricator

Successful semiconductor manufacturing is driven by wafer-level productivity. Increasing profits by reducing manufacturing cost is a matter of optimizing the factors contributing to wafer productivity. The major wafer productivity components are chips per wafer (CPW), wafer process or fabricator yield (WPY) and wafer final test (WFT) or functional yield. CPW is the count of product chips fitting within the useable wafer surface, and is dependent upon the chip size, dicing channel (kerf) space, and wafer-field size. WPY yield is the percentage of wafers successfully exiting the line; losses include scrap for broken wafers and failed-wafer specifications. WFT yield is the percent of chips that meet all final parametric functional electrical test specifications. Thus, the total wafer level productivity (GCPW) is described by GCPW=CPW/spl middot/WPY/spl middot/WFT. IBMs Vermont fabricator is one of the few in the industry that manufactures DRAMs, SRAMs, microprocessors, ASICs, custom logic, mixed signal, and foundry products, all on the same production floor. The product portfolio spans 12 base technologies across four photolithographic generations from 0.8 /spl mu/m to 0.225 /spl mu/m, with development of 0.18 /spl mu/m. This also encompasses 40 major process flows and over 4000 active part numbers. Such staggering complexity has motivated IBM to consider all possible optimization of these productivity components. This paper describes some of the techniques that have been deployed to achieve this goal.

Silicon Oxynitride As A Barrier Layer In A 3-Layer Photoresist System

A plasma-enhanced chemically vapor deposited (PECVD) silicon oxynitride (Si-O-N) was used in a 3-layer resist system in combination with a 0.42 na lens to provide device process developers with a means for extending photolithography down to 0.5 pm feature size. This delayed the need for using more expensive lithography alternatives. In this paper, the procedures used for forming the 3-layer structure are outlined. Typical plasma deposition conditions are cited. Results from the comparison among Si-N-0 films of differing composition are described in terms of refractive index, stress, and pinhole densities for varying ratios of S:N:O. Etch rates and their ratios pertinent to transferring the image into base resist are reported. Lift-off profiles were obtained and a pol*mide was used for a base which remains soluble in common solvents after being baked at 200oC. Scanning electron micrographs (SEMs) of sub-micron image profiles are shown and linewidth measurement data are presented to show linewidth precision and constant bias into the 0.7 μm range. The latter demonstrates the adequacy of this technique for sub-micron device development.