dear kamlesh,

               I agree with Mr sinha.if you have facility you can use thermal
oxide in place of PECVD or LPCVD.We use the following recipe for BHF
(30gm NH4OH in 45 ml of DI water)-after filtering one ninth of filtered solution
we add HFto it.

I hope this may work.


On Tue, 16 Sep 2008 kamlesh_engg@iitb.ac.in wrote :
>hi
>i am doing BHF etch on silicon dioxide deposited on silicon wafer.
>i am using 5:1 BHF etchant
>etch rate 120 nm/min
>i want to etch 1 micron deeep channel with 200 micron width. there are
>multiple channels in parallel each seprated by 6 micron. so i diped my
>sample in BHF for 8.33 min
>but after the etch no channels was formed and everything is etched away.
>can anyone tell me what could be the problem ???

with regrads

Jaibir Sharma
Reasearch Scholar(PhD)
Electrical Department,
IIT Madras,
Chennai - 36
INDIA

Phone:044-22575444(off)
      09445311513(home)