Polyimide-Damage-Free, CMOS-Compatible Removal of Polymer Residues from Deep Reactive Ion Etching Passivation

A method for removal of passivation polymer residues from deep reactive ion-etching (DRIE) has been systematically investigated in this study. The method combines dry oxygen plasma ashing and conventional photoresist wet stripping. Samples were carefully examined by x-ray photoelectron spectroscopy (XPS), energy-dispersive x-ray spectroscopy (EDX), and study of surface morphology. XPS and EDX analysis showed that the polymer residues consisted mainly of C-O, CFx (x = 1, 2, 3), and C-CF bonds. Optimized oxygen plasma ashing effectively removes most of the fluorocarbon content, except some nano-residues. Subsequent conventional wet stripping in organic solvents could eliminate these stubborn nanoparticles while dissolving the underlying photoresist. Excellent removal is apparent from scanning electron microscopy images. The fluorine content determined by EDX analysis showed that the residues were completely removed. The metal layers, oxide insulator layers, and the polyimide insulators function well after this critical surface treatment. The excellent results show this is an outstanding method for removal of DRIE passivation polymer residues for MEMS fabrication.

[1]  N. D. Theodore,et al.  Integration and electrical characterization of photosensitive polyimide , 2001 .

[2]  T. Mayer,et al.  Removal of Fluorocarbon Residues on CF 4 / H 2 Reactive‐Ion‐Etched Silicon Surfaces Using a Hydrogen Plasma , 1991 .

[3]  F. Marty,et al.  Advanced etching of silicon based on deep reactive ion etching for silicon high aspect ratio microstructures and three-dimensional micro- and nanostructures , 2005, Microelectron. J..

[4]  E. Collart,et al.  Ion‐induced etching of organic polymers in argon and oxygen radio‐frequency plasmas , 1994 .

[5]  Nancy R. Sottos,et al.  Interfacial adhesion of photodefinable polyimide films on passivated silicon , 2014 .

[6]  M. Ueda,et al.  Recent Progress of Photosensitive Polyimides , 2008 .

[7]  M. Schmidt,et al.  Characterization of a Time Multiplexed Inductively Coupled Plasma Etcher , 1999 .

[8]  Stephen J. Fonash,et al.  An Overview of Dry Etching Damage and Contamination Effects , 1990 .

[9]  Hyeongtag Jeon,et al.  Characteristics of the post-etch polymer residues formed at the via hole and polymer removal using a semi-aqueous stripper , 2006 .

[10]  Ying Wang,et al.  Understanding of Via‐Etch‐Induced Polymer Formation and Its Removal , 1997 .

[11]  G. Oehrlein,et al.  Formation of a silicon‐carbide layer during CF4/H2 dry etching of Si , 1985 .

[12]  J. M. Noworolski,et al.  Silicon fusion bonding and deep reactive ion etching: a new technology for microstructures , 1996 .

[13]  N. Fujiwara,et al.  Analysis of Fluorocarbon Deposition during SiO2 Etching , 1996 .

[14]  The effect of polyimide passivation on the electromigration of Cu multilayer interconnections , 2001 .

[15]  H. Hayashi,et al.  Mechanism of C4F8 dissociation in parallel-plate-type plasma , 1999 .

[16]  F. Ayazi,et al.  Micro-gravity capacitive silicon-on-insulator accelerometers , 2005 .

[17]  Didier Leonard,et al.  Silver localization on polyimide using microcontact printing and electroless metallization , 2014 .

[18]  M. Gao,et al.  Patterning amorphous fluoropolymer films by reactive ion milling , 1997 .