Mathematical prediction of dry etch results have been difficult, if not impossible, over the years due to the complexity inherent in plasma processing. With device requirements tightening combined with the high cost of running test masks, it becomes even more important for process engineers to have some means by which to model accurately this increasingly complex activity. In this paper, a correlation between a novel, plasma chrome etch model and empirical data will be presented. Practical effects of chrome loading are also discussed. From the empirical data side, studies on the photomask chrome etch process using e-beam resists were carried out following strict design of experiments (DOE) format. Photomask chrome etch processes with different resists (ZEP and positive CAR) were investigated using a Unaxis VLR 770 ICP etcher and an AMAT Tetra etcher. A Toshiba EBM-3500B (50KeV) was used for the pattern writing on positive CAR resist. A KLA-Tencor P12-EX profiler, Leica LWM 250 UV CD optical measurement system, and a KLA-Tencor 8250XP-R CD SEM were used for metrology and product characterization. Significant etch performance differences were shown on these etchers irrespective of the resist type used. A special measurable number was defined and found to have a linear relationship with etch movement on both AMAT and VLR etchers.
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