What are the effects of localized discharge in reactive ion etching?

[brad sue]

HI,
I have some questions on localized discharge in reactive ion etching. I just start studying etching ... it is a bit confusing.

Please can someone explain me this sentence?
"bromine containing plasmas have the tendency to form localized discharges. Localized discharges are particularly undesirable in reactive ion etching, since they will result in poor etch uniformity."

My questions are:
1- can you please give me some reference about localized discharge OR tell me what they are?
2- why localized discharges are bad for etching uniformity?

Thank you

 

[Navin A S]

!Localized discharges are areas of intense electrical activity that can form in the plasma during the etching process. These discharges can cause arcing or sparking, which can damage the substrate or cause hot spots that cause uneven etching. Bromine plasmas are particularly prone to forming localized discharges, due to the higher ionization energy of bromine compared to other etching gases. The high ionization energy makes it harder to maintain a uniform plasma across the substrate, which leads to the formation of localized discharges. References: 1. J. G. Eden, "The Fundamentals of Reactive Ion Etching," Journal of Vacuum Science and Technology A 4, 1265 (1986). 2. P. E. Blamire, "Reactive-Ion Etching," in Handbook of Microlithography, Micromachining, and Microfabrication, Volume I, edited by P. Rai-Choudhury (SPIE Press, Bellingham, WA, 1997).