Reactive ion etching of TiN, TiAlN, CrN and TiCN Films in CF 4 /O 2 and CHF 3 /O 2 Plasmas
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0890-Y08-13.1
Reactive ion etching of TiN, TiAlN, CrN and TiCN Films in CF4/O2 and CHF3/O2 Plasmas P.W. Leech1, G.K. Reeves2 and A.S. Holland2 1 CSIRO Manufacturing and Infrastructure Technology, Clayton, 3169, Victoria, Australia. 2 RMIT University, School of Computer Systems and Electrical Eng., Melbourne, Australia.
Abstract The reactive ion etching of a range of hard coatings (TiN, TiCN, CrN and TiAlN) has been examined as a function of rf power, flow rate and pressure. The films were deposited by filtered arc deposition (TiN, TiAlN and CrN) or low energy electron beam (TiCN) on polished disc substrates of M2 tool steel. The flat surfaces were lithographically patterned with a grating structure (~1 µm pitch). The TiN and TiCN layers have shown significantly higher etch rates (100-250 nm/min) than the CrN and TiAlN (~5 nm/min) coatings. These regimes of higher and low etch rate were identified as ion-enhanced chemical etching and physical sputtering, respectively. In CF4/O2 plasma, the etch rate of the TiN and TiCN layers increased with rf power, flow rate and pressure which were parameters known to enhance the density of active fluorine species. The etch rates of TiN and TiCN layers were higher in CF4/O2 plasma than in CHF3/O2 gases in which polymer deposition was produced at pressure > 35 mTorr. 1. Introduction Hot embossing has become a key process in the replication of nano- and microscale structures. Advantages of this technique including the low cost, biochemical compatability and ease of processing have resulted in many potential applications in chemical and biomedical science [1]. A critical component in hot embossing has been the mold insert which comprised the primary microstructure for replication. Methods of fabrication of the insert have included the copying of an original structure by the electroplating of a Ni shim or the etching of the pattern into silicon or glass [1]. However, the nickel shims have shown susceptibility to damage from contaminant particles during embossing while the inherently low ductility of silicon and glass inserts has resulted in fracture of fine features under load. An alternative method of fabrication described in this paper is the etching of a microstructure into a hard coating. TiN films have been widely applied to the surface of tools and mechanical parts to prevent wear [2]. Thin films of TiN have also been used in integrated circuits as a gate electrode and as a migration barrier between Al and Si in multilevel metallisations. In these microelectronic applications, both fluorocarbon [3,4] and chlorine [5,6] based plasmas have been used in the etching of patterns into TiN films. Etched features down to 30 nm have been reported in TiN using a C2F6 plasma [7] which has a relatively low fluorine concentration compared with CF4 and SF6 gases. In this paper, we have compared for the first time the etch characteristics of a series of current PVD coatings (TiN, TiCN, CrN and TiAlN) in CF4/O2 and CHF3/O2 plasmas. These coatings were selected as representing a wide range of c
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