Amit: Well I have been conducting some research work on Ga implanted Silicon system and I know why you are seeing this problem. This may be caused due to two factors: * If you are using HF-HNO3-DI that you had mixed more than 40 min (this time is dependant on the concentration/ratio of etchants) prior to etching you tend to see these brownish stain. Try to mix your etchant just before you are going to etch. * Check the ratio of HF-HNO3-DI of your etchant, you may be in the staining regions (refer tot he ternary diagram). Also if you can email me a brief write-up as to what you are doing and what you are trying to achieve may be I can suggest some receipes. Are you using either DC bias or UV activation while etching. Regards Jayant ********************************************************** Jayant Neogi Director: Research and Development NORSAM Technologies (http://www.norsam.com) Portland, Oregon Ph# (503) 807-3367 (work) ************************************************************ ---------- > From: Amit Shiwalkar> To: MEMS@ISI.EDU > Subject: Help on Si-Etch Phenomenon. > Date: Friday, August 21, 1998 6:56 AM > > Hello, > I have done some etching ( isotropic ) on Si with HNO3 (63%)& > HF(49.3%) mixture and using DI H20 as diluent. On certain occasions it was > observed that there were blackish-brown marks ( like charring ) on the > wafer. This wafer was P-type. Also if the etching was done using glacial > ascetic acid as diluent then on no ocassion were these brown marks > observed. Also these marks were not consistently observed even in the H2O > diluent recipe. > I would appreciate if anybody could give me any references or > suggestions about the cause of this phenomenon. Classic recipe handbooks > like Ghandhi, Donovan & Burger etc. do not mention any such phenomenon. > Note that even in the case of glacial ascetic acid as the diluent, > some places(where water droplets were retained) were charred in the step > where etching was stopped by a dip in DI water. > > Thanking you all in advance > > Regards > Amit Shiwalkar > > &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& && > Amit Shiwalkar Dept. Of Bio-Medical Engineering. > 3,Vasant, IIT Bombay. > Carter Road, Powai, Bombay-400076 > Khar, > Bombay(Mumbai)-400052 > INDIA. > > > Email: amits@cc.iitb.ernet.in > > " Reality Is a Figment of IMAGINATION " > ----------- Amit Shiwalkar > > @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @@ > >