Hasan Sharifi, Even though the rated film thickness is 5 um, the SU-8 materials can definitely stretch to greater film thicknesses, especially considering what you are trying to do. At lower spin speeds (such as 1000 RPM), it is about 7.5 um. At 500 rpm, this thickness gets even greater. In addition, since you are filling a gap, a large amount of material will pour into that gap during the spinning process. By the end of the spin coat process, if you choose your parameters correctly, the resist can have the gap completely filled (at least, prior to the soft bake). Your biggest problem will show up during the soft bake. SU-8 2005 has a fairly low solids content (I don't know exactly, but it is definitely less than 50%). So, if your trench is full prior to soft bake, it will be, at best, about half full after soft bake. Since your trench width is 150 um, you actually could get away with a thicker version of SU-8, which will have a higher solids content. The only thing to bear in mind is that the film thickness above the surface of your wafer will be higher, as well. In either case, you need to be aware of the fact that, when spin coating substrates with trenches as you describe, there's a pretty big risk that your coat surface will be non-uniform, and not just because of the thickness shrink during soft bake. Since your trenches will break up the smooth flow of material across the surface of the substrate, you may end up with "shadows" on the edge- ward side of the trenches, where the resist layer is thinner. One final bit of advice. The glass transition temperature of SU-8 is 55 C. The soft bake is a two step process at 65 C and 95C. If you hold the bake longer at 95C, the material will reflow somewhat, allowing more material to "pour" from the wafer surface into the trench, especially with thicker layers of SU-8. Best Regards, Chad Brubaker EV Group invent * innovate * implement Technology - Tel: (602) 437-9492, Fax: (602)437-9435 e-mail: C.Brubaker@EVGroup.com, www.EVGroup.com This message and any attachments contain confidential or privileged information, which is intended for the named addressee(s) only. If you have received it in error, please notify the sender immediately and then delete this e-mail. Please note that unauthorized review, copying, disclosing, distributing or otherwise making use of the information is strictly prohibited. -----Original Message----- From: mems-talk-bounces+c.brubaker=evgroup.com@memsnet.org [mailto:mems-talk- bounces+c.brubaker=evgroup.com@memsnet.org] On Behalf Of hsharifi@purdue.edu Sent: Monday, November 24, 2003 10:17 AM To: mems-talk@memsnet.org Subject: [mems-talk] SU-8 2005 Hi all, I want to use SU-8 2005 in order to fill a gap inside of my si wafer. The dimension of the gap is: L=3mm, W=150 um, and Hieght= 550 um. I have a condition for 5um thickness from microchem but my thickness is abour 550 um. I think I should use SU-8 2005 b/c the gap is too samll. I appreciate if any body has the condition (soft bake times, exposure time , ..) for this high thickness. Best regards, Hasan Sharifi Purdue University _______________________________________________ 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.memsnet.org/