NUMERICAL-ANALYSIS OF THE PRESSURE-DEPENDENCE OF THE ETCH RATE IN AN AL ETCHING REACTOR EQUIPPED WITH A HELICON SOURCE

The pressure dependence of the etch rate in an Al etching reactor has been studied with the goal of developing a method of numerically simul ating the etching process. Experimentally, the etch rate was measured at pressures between 3 and 100 mTorr and reached a maximum at about 10 mTorr, whereas the calculated etch rate, which took the etching react ion between Al and Cl-2 on an Al surface into account, increased with pressure. To explain the experimental data, the residence time tau(0) Of the inhibitor adsorbed on the Al surface and time-averaged surface coverage were included in the calculations. In the low-pressure region below 10 mTorr, the etch rate increased with an increase in pressure, due to the increased Cl-2 flux on the Al surface. On the other hand, in the high-pressure region over 10 mTorr, the etch rate decreased whe n the effect of the inhibitor became stronger; this was explained by d eveloping an improved model. Consideration of the inhibitor adsorbed o n the Al surface is important, where the increase of tau(0) with press ure is necessary to precisely simulate the correlation between the etc h rate and pressure. (C) 1998 American Vacuum Society.