Study of plasma etching impact on chemoepitaxy directed self-assembly

Directed self-assembly (DSA) of block copolymers is one of the most promising solutions investigated to obtain small and dense patterns for the sub-10 nm nodes. One of the most important aspects of the DSA technology is the orientation control of the block copolymer, which is determined by surface properties and different guiding techniques. Regarding the Arkema-CEA (ACE) chemoepitaxy process, one of the critical parameters is the preservation of the neutral layer’s properties during hydrofluoric acid wet etching, especially regarding its adherence to the titanium nitride (TiN) hard mask. In this paper, the different etching steps involved in the ACE integration flow are evaluated. Their effects on the surface properties of the TiN hard mask and on the adherence of the neutral layer are investigated by x-ray photoelectron spectroscopy and contact angle measurements. Finally, the results obtained are used to optimize the different etching steps, thus demonstrating the chemoepitaxy of a polystyrene-b-poly(methyl methacrylate) block copolymer with 32 nm pitch without alignment defects on a 100 μm2 surface.