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A Cleaning for Silicon Thin-Film Deposition Chamber Disclosure Number: IPCOM000224795D
Publication Date: 2013-Jan-03
Document File: 2 page(s) / 46K

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It is know that remote plasma generator is capable of decomposing NF3 to generate F radicals with 97% and more dissociation efficiency.  NF3 with remote plasma generator (MKS, Astron-i, 6kw, maximum flow rate: 3slm) enables to etch silicon at 10 micron/ minute.  F2 combined with remote plasma generator also leads to etching silicon at mostly same etching rate of NF3 if same number of fluorine radicals was provided.  To further etching rate in NF3 remote plasma process, an additive is considered and injected at location either before or after remote plasma generator. 

Addition of NO into NF3 remote plasma greatly contributes etching of silicon thin film with acceptable etching speed and improving uniformity.  Dry cleaning process developed can replace wet cleaning that is labor intensive and take many steps to be done.  This process improves on cost reduction and eventually throughput and uptime.

In the experiments an operational pressure set at 3Torr and chamber to put sample is kept at 200oC.  An RF power applied in the plasma region is automatically tuned and not being variable.  In the screening process, addition of nitric oxide (NO) at downstream of remote plasma is effective to increasing 1.3 times silicon etching rate compared with sole NF3.  This phenomenon is reproducible even if F2 was used instead of NF3.  On the other hand etching rate is declined if NF3 and NO are introduced into remote plasma generator at the same time.  In addition silicon is uniformly etched by NF3 and NO but NF3 alone result in heterogeneous etching.  Etching rate linearly increases as a function of increase of NF3 and NO flow rate.  FTIR revealed the formation of FNO in the exhaust and it may play an important role to increase etching rate and uniformity.  One possibility is that FNO led to lengthen the life time of fluorine radicals otherwise FNO reacts with N radicals to avoid forming NF3 through reversible reaction of F and N radicals. 

The disclosed process improves on increasing etching rate of silicon in NF3 (or F2) remote plasma cleaning process.  The disclosed process also greatly improves uniformity after cleaning.  The disclosed process eventually contributes to increase throughput and uptime in silicon thin-film deposition process and reduce defects of solar cell modules.

Undesired silicon compounds left in the cha...