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Fabrication of flexible microelectrodes using Cold HV sputtering

O. BERKH1,* , A. INBERG1, B. SOROKOV2, N. FISHELSON1, R. OFEK ALMOG1, L. BURSTEIN3, Y. SHACHAM-DIAMAND1

Affiliation

  1. Tel Aviv University, Department of Physical Electronics, Ramat Aviv 69978, Israel
  2. a Thin Films Ltd., P.O.BOX 302, Nesher 36602, Haifa, Israel
  3. Tel Aviv University, Wolfson Applied Materials Research Center, Ramat Aviv 69978, Israel

Abstract

Flexible biocompatible microelectrodes are highly required for bio- and medical applications. Reliability of microelectrodes is associated with adhesion of metallic electrodes to polymeric flexible substrate. Therefore studying the fabrication process of microelectrodes based on different methods of metallization is of great interest. In the present work we showed the feasibility of microelectrode fabrication on polyimide substrate using its metallization by the method of Cold HV sputtering. The fabrication process includes formation of 0.1-0.5 µm Pd layer on polyimide substrate, photolithography defining the electrodes, deposition of about 1.0-1.5 µm gold layer on Pd electrodes by electroplating, removal of photoresist and Pd layer from the area unprotected by Au. Polyimide samples with deposited Pd layer were studied by SEM and XPS methods. Scaly structure of Pd layers explains their high electrical resistance (specific resistance of 20-200 μΩ·cm) and limits the Pd films application as interconnects. Along with this, Pd layers are characterized by very good adhesion to polyimide (metallized samples successfully passed Scotch peeling test and allowed numerous folding without adhesion disturbance) which provide a good advance as a seed layers for electroplating. Excellent Pd adhesion to polyimide was shown to be associated with Pd/polyimide chemical interaction..

Keywords

Microelectrode, Cold HV sputtering, polyimide, Adhesion, Electroplating, SEM, XPS.

Submitted at: April 5, 2010
Accepted at: May 26, 2010

Citation

O. BERKH, A. INBERG, B. SOROKOV, N. FISHELSON, R. OFEK ALMOG, L. BURSTEIN, Y. SHACHAM-DIAMAND, Fabrication of flexible microelectrodes using Cold HV sputtering, Journal of Optoelectronics and Advanced Materials Vol. 12, Iss. 5, pp. 1176-1182 (2010)