Cr in matrix
Process note from jimkruger:
Exposed chromium film on substrates processed in the matrix can be eroded in the plasma. Typically, Cr is etched in chlorine/oxygen plasma at elevated substrate temperatures because Cr has a volatile oxychloride. Chromium oxide is not volatile, however. Although the matrix does not have a chlorine source, the hypothesis is that there may be residual fluorines, possibly from the lubricating fluid in the pump, which can react to form oxyfluorides of chromium, which are also volatile. jimkruger observed that 3 1/2 minutes of matrix plasma seems to be sufficient to remove 200 A of Cr under resist.