I want to know about the plasma mechanism at the time of plasma etching of crystalline silicon wafers with atomic hydrogen plasma etching. In ICP-PECVD system only atomic hydrogen can etched crystalline silicon wafer. But I didn't know the plasma mechanism. Please tell me about the mechanism.
Please find attached paper for understanding the chemical kinetics for the reaction of H atom with SiHx radicals and related unimolecular decomposition process.
Crystalline silicon? When you are talking about plasma-surface interaction then you are talking about the top few monolayers. Surface contamination and native oxide are key -- at least for the initial phase.
We looked at the reduction of native oxide and removal of fluorocarbon films in a hydrogen discharge. (Delfino, et al., J.Appl.Phys. 71 (2), 15 Jan 1992) There are energy thresholds for the native oxide removal, and the formation of a hydrogen-passivation layer on the surface. Basically we were motivated by the Hf-dip, HF-vapor passivation of 111-Si and tried with hydrogen-plasma. In your ICP you would expect to be below the ion-threshold for native oxide removal, but with a small bit of dc-bias you would be able to remove the native oxide.
As for bulk removal I expect it would be via surface formation of silane under ion bombardment. Mostly the incoming H will reform with H on the surface; this abstraction is usually thought to increase the surface crystallinity, but wit sufficient ion energy there should be pathways to get to SiH4. The time-scale between successive H-ion and H2-Vib-excited collisions with a particular atomic site on the surface is so log in comparison to the surface relaxation time that most events will not result in etching.
Also note that in your Hydrogen discharge there are going to be H+, H2+, *and* H3+ ions. For moderate power density H3+ is the dominant species. In our work we used ECR plasma at very low pressure to get significant H+ fractional-flux.
Hello,
Did you tried RF plasma downstream, with low pressure, and a recipe with forming gas? You could try HDRF tool, like Odyssey from Plasma-Therm, with a recipe able to provide high flow of radicals H* , and/or OH or HF (that depend on additive gas), and with no ions.
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