LAM 9400/Processes/LNF Poly
|About this Process|
|Gases Used||HBr, He|
LNF_Poly can be used for etching Si, Polysilicon and GaAs. This process is fairly sensitive to the amount of open area of the wafer; the open area is the primary way to control the amount of sidewall passivation. This process is also used as the routine qualification for the LAM 9400.
- 5 min etch, Si wafer with SPR 955 mask, 22% open area
- Si: 181 nm/min
- SPR 955 (0.9): 27 nm/min (6.7:1)
- SiO2 (6" SiO2 wafer): 15 nm/min
In general increasing the Si open area will slow the etch and increase the amount of passivation. The resist etch rate is also very dependent on the amount of open area. A piece on a SiO2 carrier vs a piece on a Si carrier will have drastically different resist etch rates (55 nm/min for SiO2 vs 24 nm/min for Si).
|Pressure||5 mTorr||30 mTorr|
|TCP Power||300 W||600 W|
|Bias Power||100 W||90 W|
|Cl2 Flow||60 sccm||0 sccm|
|HBr Flow||0 sccm||100 sccm|
|He Flow||0 sccm||100 sccm|
This etch can produce very vertical sidewall profiles, although trenches smaller then ~1µm will develop micro trenches as the etch progresses.
The sidewall passivation in this process is a SiOBr compound, and changing the amount of open area of Si is the main way to change the amount of passivation. With almost no exposed silicon the sidewall passivation will be very thin and the etch will be faster.
With a very high amount of open area the etch will be very over passivated.
To remove the photoresist a ~20 sec dip in 100:1 HF is necessary before nanostrip or piranah.