From pethe at stanford.edu Tue Jun 1 12:22:16 2004 From: pethe at stanford.edu (Abhijit Pethe) Date: Tue, 1 Jun 2004 12:22:16 -0700 Subject: Ques: Develop Resist on thin metal films Message-ID: <000801c4480d$bffe1110$296440ab@flash> Hi, Has anyone seen the developer attack thin metal films on the developer track? My process involves deposition of thin Pt/Al film in the Innotec. Pt: 300A Al: 700A Base Pressure: 3e-7 I did a bake in the Yes oven followed by 1mm 3612 resist followed by exposure. When I put the wafers through the standard developer track LDD26W (Prog. 3), I notice metal peeling from those wafers. During the develop program I did notice some reaction on the wafers. Has anyone seen this before? I would appreciate any help on this topic. Thanks Abhijit Abhijit Jayant Pethe PhD Candidate Department of Electrical Engineering Stanford University, CA Phone :(O)(650)-725-3608; (C) (650)-387-6435 e-mail: pethe at stanford.edu -------------- next part -------------- An HTML attachment was scrubbed... URL: From afflannery at comcast.net Tue Jun 1 15:53:53 2004 From: afflannery at comcast.net (Anthony Flannery) Date: Tue, 1 Jun 2004 15:53:53 -0700 Subject: Ques: Develop Resist on thin metal films In-Reply-To: <000801c4480d$bffe1110$296440ab@flash> Message-ID: <000001c4482b$50778420$1401a8c0@Ibscus3> Yep, You have learned the painful lesson of a galvanic reaction. The etching of Al in contact with Pt is so violent in LDD26W it generates gas and blows out the sidewalls of your resist. This is caused by the work function difference between the two metals. The Pt "biases" the Al and drives its etching. Short answer - you can't do it. Long answer - it will be very difficult. If you can completely isolate the Pt from the developer you can possible pattern them on the same wafer with the same resist, but the Pt must be COMPLETELY isolated (nothing around the edge). If they have to be in contact and exposed, it may be possible to find a developer chemistry that does not attack the Al, but it probably won't be with this resist. You will have to experiment with other resists - I would suggest switching to a negative resist. Good luck. I've always thought there is a very very good paper waiting to be written on using galvanic interaction to selectively control etching in MEMS. Maybe for my next PhD :) Tony Flannery -----Original Message----- From: Abhijit Pethe [mailto:pethe at stanford.edu] Sent: Tuesday, June 01, 2004 12:22 PM To: svgdev at snf.stanford.edu Cc: innotec at snf.stanford.edu Subject: Ques: Develop Resist on thin metal films Hi, Has anyone seen the developer attack thin metal films on the developer track? My process involves deposition of thin Pt/Al film in the Innotec. Pt: 300A Al: 700A Base Pressure: 3e-7 I did a bake in the Yes oven followed by 1mm 3612 resist followed by exposure. When I put the wafers through the standard developer track LDD26W (Prog. 3), I notice metal peeling from those wafers. During the develop program I did notice some reaction on the wafers. Has anyone seen this before? I would appreciate any help on this topic. Thanks Abhijit Abhijit Jayant Pethe PhD Candidate Department of Electrical Engineering Stanford University, CA Phone :(O)(650)-725-3608; (C) (650)-387-6435 e-mail: pethe at stanford.edu -------------- next part -------------- An HTML attachment was scrubbed... URL: From rajesh at t-ram.com Tue Jun 1 16:00:30 2004 From: rajesh at t-ram.com (Rajesh Gupta) Date: Tue, 1 Jun 2004 16:00:30 -0700 Subject: Ques: Develop Resist on thin metal films Message-ID: <40F9C31A3EE27D459370EFA2DD3194EA01247FBF@exchange1.t-ram.com> Hello Try bi-layer resist. (develop the top layer; etch the second in an oxygen plasma) Rajesh -----Original Message----- From: Anthony Flannery [mailto:afflannery at comcast.net] Sent: Tuesday, June 01, 2004 3:54 PM To: 'Abhijit Pethe'; svgdev at snf.stanford.edu Cc: innotec at snf.stanford.edu Subject: RE: Ques: Develop Resist on thin metal films Yep, You have learned the painful lesson of a galvanic reaction. The etching of Al in contact with Pt is so violent in LDD26W it generates gas and blows out the sidewalls of your resist. This is caused by the work function difference between the two metals. The Pt "biases" the Al and drives its etching. Short answer - you can't do it. Long answer - it will be very difficult. If you can completely isolate the Pt from the developer you can possible pattern them on the same wafer with the same resist, but the Pt must be COMPLETELY isolated (nothing around the edge). If they have to be in contact and exposed, it may be possible to find a developer chemistry that does not attack the Al, but it probably won't be with this resist. You will have to experiment with other resists - I would suggest switching to a negative resist. Good luck. I've always thought there is a very very good paper waiting to be written on using galvanic interaction to selectively control etching in MEMS. Maybe for my next PhD :) Tony Flannery -----Original Message----- From: Abhijit Pethe [mailto:pethe at stanford.edu] Sent: Tuesday, June 01, 2004 12:22 PM To: svgdev at snf.stanford.edu Cc: innotec at snf.stanford.edu Subject: Ques: Develop Resist on thin metal films Hi, Has anyone seen the developer attack thin metal films on the developer track? My process involves deposition of thin Pt/Al film in the Innotec. Pt: 300A Al: 700A Base Pressure: 3e-7 I did a bake in the Yes oven followed by 1mm 3612 resist followed by exposure. When I put the wafers through the standard developer track LDD26W (Prog. 3), I notice metal peeling from those wafers. During the develop program I did notice some reaction on the wafers. Has anyone seen this before? I would appreciate any help on this topic. Thanks Abhijit Abhijit Jayant Pethe PhD Candidate Department of Electrical Engineering Stanford University, CA Phone :(O)(650)-725-3608; (C) (650)-387-6435 e-mail: pethe at stanford.edu -------------- next part -------------- An HTML attachment was scrubbed... URL: