Reduction in microloading by high-gas-flow-rate electron cyclotron resonance plasma etching

• Published in: Japanese Journal of Applied Physics Vol. 34; no. 5A; pp. 2489 - 2494
• Main Authors: KOFUJI, N, TSUJIMOTO, K, KUMIHASHI, T, TACHI, S
• Format: Journal Article
• Language: English
• Published: Tokyo Japanese journal of applied physics 1995
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Microelectronic fabrication (materials and surfaces technology); Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Parasitic behavior; Neutral gas; Electron cyclotron resonance; Microelectronic fabrication; Reactive ion etching; Reduction; Pumping; Gas flow; Manufacturing process; Plasma etching; Low pressure; High speed; Ion emission
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.34.2489

High-gas-flow-rate electron cyclotron resonance plasma etching was employed to reduce microloading in Si etching with Cl
2
at low pressure. Microloading estimated with a conventional etching system increases with decrease in pressure from 5 to 0.5 mTorr. The increase in microloading is attributed to the increase in the ratio of ion flux to reacting neutrals. The ion/neutral ratio was found to be as large as 6.4 at 0.5 mTorr. This large ratio was caused by both the decrease in reacting neutral density and the increase in reaction products. The high gas flow rate with a high effective pumping speed of 2000 l/s reduces the reaction products, increases the reacting neutrals and reduces the ion/neutral ratio to 0.65. As the result, the microloading is reduced. The relative etch rate at an aspect ratio of 7 increases from 0.65 at 136 l/s to 1.00 at 2000 l/s. Thus high-gas-flow-rate-etching solved the problem of large microloading which is not suppressed even with high density plasma and low gas pressure.