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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal>Hi Russ,<o:p></o:p></p><p class=MsoNormal>PDMS mold fabrication is pretty straightforward. Mask material depends on how deep into the silicon wafer they want to etch. You’ll want a tool that can run the Bosch process with C4F8 and SF6. We have two at Cornell NanoScale Facility. A photoresist mask with 1-2 um of resist should yield you up to 50 um of etch depth. Beyond that you’d want to use a silicon oxide mask as it has higher selectivity and can allow you to etch through a wafer.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><ol style='margin-top:0in' start=1 type=1><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo1'>Coat, bake, expose and develop resist pattern<o:p></o:p></li><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo1'>Perform an oxygen descum plasma process to clean resist residue from open areas.<o:p></o:p></li><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo1'>Deep silicon etch process – number of loops depends on etch rate - dependent on open silicon area, for PDMS molds the wafer is mostly bare silicon, so open areas will etch slower. Also depends on the tool. Some of the work I’ve done in this area has me yield a 20 um deep feature in about 30 minutes of etch time per wafer.<o:p></o:p></li><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo1'>Wet strip photoresist<o:p></o:p></li><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo1'>Coat with hydrophobic coating like FOTS or the PDMS will permanently bond to the mold and not release.<o:p></o:p></li></ol><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>We do this process regularly at CNF. If you don’t have the tools or resources, we could possibly do it as a remote process for you.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Best Regards,<o:p></o:p></p><p class=MsoNormal>Tom Pennell<o:p></o:p></p><p class=MsoNormal>Cornell NanoScale Facility<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> labnetwork <labnetwork-bounces@mtl.mit.edu> <b>On Behalf Of </b>vsoares@inesc-mn.pt<br><b>Sent:</b> Thursday, September 4, 2025 9:10 AM<br><b>To:</b> 'Russ Renzas' <rrenzas@unr.edu>; 'Lab Network' <labnetwork@mtl.mit.edu><br><b>Subject:</b> Re: [labnetwork] PDMS mold process?<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span lang=EN-ZW>Hi</span><span lang=PT> Russ,<o:p></o:p></span></p><p class=MsoNormal><span lang=PT><o:p> </o:p></span></p><p class=MsoNormal>We make PDMS molds in our lab but we have banned it from the cleanroom. It tends to stick everywhere and since it’s transparent, you often don’t notice it until it’s too late. We have had pieces sticking on the bottom of wafers.<o:p></o:p></p><p class=MsoNormal>So now the molds are made outside the cleanroom inside a laminar flow hood.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span lang=PT>Melhores Cumprimentos/ Best Regards<o:p></o:p></span></p><p class=MsoNormal><span lang=PT><o:p> </o:p></span></p><p class=MsoNormal><span lang=PT>Virginia Soares<o:p></o:p></span></p><p class=MsoNormal><span lang=PT><o:p> </o:p></span></p><p class=MsoNormal><span lang=PT><img width=40 height=35 style='width:.4166in;height:.3666in' id="Picture_x0020_1" src="cid:image002.png@01DC1DA0.A75C01F0"></span><span lang=PT>INESC-MN<o:p></o:p></span></p><p class=MsoNormal><span lang=PT>Rua Alves Redol,9<o:p></o:p></span></p><p class=MsoNormal><span lang=PT>1000-029 LISBON<o:p></o:p></span></p><p class=MsoNormal><span lang=PT>PORTUGAL<o:p></o:p></span></p><p class=MsoNormal><span lang=PT>Tel: +3513100237<o:p></o:p></span></p><p class=MsoNormal><span lang=PT><a href="https://inesc-mn.pt">https://inesc-mn.pt</a><o:p></o:p></span></p></div><p class=MsoNormal><span lang=PT><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>> <b>On Behalf Of </b>Russ Renzas<br><b>Sent:</b> 4 de setembro de 2025 01:22<br><b>To:</b> Lab Network (<a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a>) <<a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a>><br><b>Subject:</b> [labnetwork] PDMS mold process?<o:p></o:p></p></div></div><p class=MsoNormal><span lang=PT><o:p> </o:p></span></p><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'>Is anyone familiar with PDMS (or other material) mold fabrication? Any procedures or gotchas to worry about? <o:p></o:p></span></p></div><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'>Bio faculty member asking if we can make molds in our fab. I only know how to make semiconductor, photonic, and quantum devices. <o:p></o:p></span></p></div><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'>Thanks!<o:p></o:p></span></p></div><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'>Russ<o:p></o:p></span></p></div><div id=ms-outlook-mobile-body-separator-line><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'><o:p> </o:p></span></p></div></div><div id=ms-outlook-mobile-signature><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'>Russ Renzas<o:p></o:p></span></p></div><div><p class=MsoNormal><span lang=PT style='font-size:12.0pt;font-family:"Aptos",sans-serif'>University of Nevada, Reno<o:p></o:p></span></p></div></div></div></body></html>