Abstract
In this study, we report a 9wt% PSG film for increasing the etch selectivity to poly gate by changing the sputtering gas from Argon to Helium to avoid the film haze and other issues. Due to the change of new sputtering gas, a new recipe has been developed to fine tune key film properties, including within wafer thickness non-uniformity (WIW NU%) and phosphor concentration uniform-ity in three dimensions. In order to get desired profile after etch process, it is very crucial to control the profile of initial layer and bulk PSG film phosphor doping concentration. Therefore, a new concept which is called "PH3 flow ramp up" has been developed and implemented. Other key concern of integration, i.e., how to control "flower pattern" shape is also discussed in this paper.
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