First, 250 K-Ohm cm seems like an unrealistically high value. I've seen silicon up to 12 KOhm-cm, and have used material up to 6KOhm-cm. Looking at the web site, they don't actually seem to produce this value - it might just be the theoretical resistivity of pure silicon with no dopants that they are quoting. There are other suppliers of high-resistivity silicon, for example wacker and topsil. Next, I've heard (but can't say for sure) that if you grow a thermal oxide, the resistivity will never be higher than a few thousand ohm-cm when your done, no matter how good it was to start. Any thermal treatment will diffuse some impurities into the wafer, depending on the time and temperature of the treatment. If you need to end up with 2000 ohm-cm, your probably fine. If you need to end up with 6000 ohm-cm, you will need to be careful about your thermal processing and may have problems. If you need 250000 ohm-cm, your probably out of luck. David Nemeth Senior Process Engineer Sophia Wireless, Inc. 14225-C Sullyfield Circle Chantilly, VA Ph: (703) 961-9573 x206 Fax:(703) 961-9576 -----Original Message----- From: mems-talk-admin@memsnet.org [mailto:mems-talk-admin@memsnet.org]On Behalf Of Fred Hussain Sent: Monday, May 20, 2002 6:47 AM To: mems-talk@memsnet.org Subject: [mems-talk] Highest resistivity silicon? Dear all, I am looking for silicon substrates which can be machined using conventional MEMS type processes, but at the same time are highly insulating. I've found a web page with silicon of 250Kohm-cm resistivity - http://www.tydex.ru/materials/materials2/Si.html. Does anybody: have any experience of working with such materials? know of any issues, for example the stability of the resistivity with temperature? micromachined it without any major issues? know of any suppliers? Thanking you in advance. Regards, Fred. -------------------------------------------- Dr Fred Hussain The Technology Partnership plc Melbourn Science Park Cambridge Road Melbourn Royston Hertfordshire SG8 6EE Tel: 01763 262626 Fax: 01763 261582 www.ttpgroup.com --------------------------------------------- _______________________________________________ mems-talk@memsnet.org mailing list: to unsubscribe or change your list options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk Hosted by the MEMS Exchange, providers of MEMS processing services. Visit us at http://www.mems-exchange.org/