Wet etching of hydrogenated amorphous carbon films

Amorphous hydrogenated carbon films (a-C,H) have found many applications in microelectronics, micro-machining and sensors, as a dielectric material, s tructural layers, sacrificial layers and masks for etching in alkaline solu tions. The possibility of deposition at low temperature (< 100 degreesC) is another interesting characteristic of this film for production of micro-de vices using post-processing technology, in this work, a-C:H films were depo sited on silicon by a RF reactive magnetron sputtering system, using methan e as the discharge gas. Films that were 1 mum thick with a stress of 2 MPa presented a roughness of 1.55 nm, These films were submitted to a wet etchi ng process in aqueous solutions of KOH (27 wt.% at 80 degreesC). After 43 h of wet etching, a slight increase in the roughness to 1.60 nm was observed , Under these conditions, the etching rate was 4.3 x 10(-2) nm min(-1), sig nificantly smaller than that of other traditional materials used in micro-m achines, as for example SiO2, which in the same solution has an etching rat e of approximately 250 nm min(-1). These results indicate that a-C:H film i s a promising material for use in post-processing technology. (C) 2001 Else vier Science B.V. All rights reserved.