Hi everybody,

I'm student at a German University and my current job is to set up a SF6 RIE
process for etching nanostructures.
As I am completely new to this topic, I could really need some advices.
The target should be to optimize parameters to meet the following requirements:

1. In most cases we don't want to etch deep. Therefore the etch rate shouldn't
be too high. i.e. about 100 nm/min would be useable, 1um/min would scare me.
2. we want ansiotropic walls. (90° would be perfect, but I think you allready
guessed that)
3. Damages are to be kept as low as possible. (-->avoid sputtering)
4. material would be (100) n-Si for now. Masking is done with SP2510 photoresist
(seems to work fine).

Now I have a lot of questions (or in other words: no clear idea of what I'm
doing) :
  1.. We started with SF6/Ar in a ratio of 1sccm SF6 to 7sccm Ar. Is this one a
good choice for our task? For now it seems we're sputtering too much, cause
etching deepth much depends on HF-Bias. Didn't have the opportunity to
  I read a lot about SF6/O2 processes. What are the adventages/disadventages of
using Ar <--> O2? What about pure SF6?
  Avaible gases: SF6 up to 52 sccm, 02 up to 99sccm, CF4 up to 84 sccm, Ar up to
145 sccm and BCl3 (that we don't want to use at this time)
  2.. We have the following parameters that want to be optimized: gas flows,
ratio of the gas mixture, pressure, ICP power, HF power and process time.
  First of all I could need some hints for parameters to start with. On the
other hand I'm really interested in how changes on these parameters may effect
my process. So what happens i.e. if I lower pressure? which parameters have much
influence on etch rates, which doesn't have? On what do I have to keep my eyes
on while maniputaling these parameters?
  3.. Let's imagine I have my start values, and now I want to optimize the
process. any hints with which parameter I should start? Are there any common
tactics for process optimizing? (for example: "Start increasing the pressure
until.. then try to find the ICP power where....." until I reach the finetuning
part.)
  4.. We found that we had some kind of dust in our etching chamber after our
first few tests. I read a bit about some people who use o2 plasmas to clean
their chambers after/before every etching. We didn't have to do this for any of
our other processes before. maybe someone can help me here with tips on cleaning
frequency/time/power.

On all these topics I could need sources where to find some useable info, or
even better some hints from your own experiences. If there is anything else I
didn't ask, but seems to you to be usefull for me to know, just let me know.
With my current knowledge I could use nearly every piece of information
concerning my task I could get.
Thanks a lot for your help.

Greetings
Markus