Gas utilization in remote plasma cleaning and stripping applications

Abstract

Nitrogen trifluoride (NF3) is a likely candidate to replace perfluorocompounds (PFCs) in stripping and reactor cleaning applications. In this article, the performance of NF3 for the etching of silicon, silicon dioxide (SiO2), and silicon nitride (Si3N4) is compared with that of CF4, C2F6, and C3F8. The performance measures emphasized in this article are the dissociation efficiency of the parent molecule in the discharge, the etch rate, and the gas utilization. The destruction efficiency of NF3 in the discharge as determined by mass spectrometry is typically 100%. The maximum destruction of the PFC gases for the parameters used in this investigation is approximately 75% for CF4, and can approach 100% for C2F6 and C3F8. The removal rates for NF3 obtained at optimum settings of O2 addition and microwave power are significantly higher than those for PFC gases. The gas utilization, which describes the degree of conversion of the parent molecules into etch products and is defined in this article, is also higher for NF3 than for the other gases investigated.

Rf discharge dissociative mode in NF3and SiH4

“…The NF 3 and its radicals possess the following bond dissociation energies: NF 2 [53]), N-F, 2.6 eV [54]. However, the probability of direct splitting the NF 3 molecules with the energy, say, 4 eV, is very small because of the shorttime electron-molecule interaction during which heavy atoms (radicals) have no time to get the momentum required for flying off.…”

Nitrogen Trifluoride-Based Fluoride- Volatility Separations Process: Initial Studies

“…A potential alternative fluorinating reagent nitrogen trifluoride (NF 3 ) is currently used on an industrial scale to etch and clean microelectronic devices (Golja et al 1985;Golja et al 1983;Langan 1998;Kastenmeier 2000). Nitrogen trifluoride is not corrosive and does not react with moisture, acids, or bases at room temperature, is thermally stable to relatively high temperatures, and also is insensitive to shock to pressures above 100,000 psi (Anderson et al 1977).…”

Applying RF current harmonics for end-point detection during etching multi-layered substrates and cleaning discharge chambers with NF3 discharge

“…However, plasma cleaning began later to be widely applied in various technological processes: degassing the surfaces of discharge vessels, cleaning silicon wafers from carbon impurities, removing impurities from the electrodes 035 and walls of technological vessels which had formed during deposition of semiconducting and polymer materials, cleaning plane items and other devices from lubricants, grease removal and preparation of surfaces for dying, removal of metallic impurities from the surfaces of ceramic insulators, restoration of metallic archaeological artefacts, etc. [12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”