B. C. Dems, F. Rodriguez, C. M. Solbrig, Y.M.N. Namaste, S. K. Obendorf
May 27, 2013
The need for nanometer-sized features in integrated circuits calls for the use of dry-etching techniques using glow-discharge plasmas. The reactive ion etching (RIE) mode in which there is a large difference in potential between the gas phase and the solid surface yields particularly desirable, straight-walled etched structures. The design of processes and materials for RIE requires a knowledge of the effects of operating variables on various parameters. In the present work, the parameter emphasized is the etch rate. A novel aspect of the apparatus used incorporates a laser interferometer for in situ measurements of etch rate. Some observations on operating variables are: i. Chamber pressure is more critical when a fluoride-oxygen plasma is used than when oxygen alone is used. This is due to polymer deposition that occurs with the former along with etching. 2. The etch rate in the oxygen/RIE mode is almost the arithmetic sum of the oxygen/plasma mode together with the nitrogen/RIE mode except at low incident power levels where etch rate with oxygen/RIE is much greater than the sum of the other two. 3. Aromatic polymers etch more slowly than aliphatic polymers. 4. The oxygen/RIE rate of polyvinylchloride, PVC, decreases on addition of a compatible organotin compound. A 1:1 mixture of PVC with a tin compound etches at i/10 the rate of PVC alone.