CCH Do and Do* Titanium
Particle reduction during the reactive deposition of TiN is key to high yields in today’s IC wafer fabs. To meet this need, Praxair MRC has developed its CCH Do technology to the production of high purity titanium (4N5 and 5N) sputtering targets. CCH (Controlled Consistent High performance) technology utilizes thermomechanical processing and the degree of deformation and thermal treatments have been carefully optimized. Based on this fundamental CCH process technology, Praxair MRC has now developed the CCH Do microstructure where the grain size has been reduced to < 15 microns with a controlled texture. Our titanium targets are "tuned" for optimal performance for specific cathodes. This has been proven across all of today’s sequential and cluster tool sputtering platforms.
Particle generation is very sensitive to uniformity of sputter rates in different target sections, which in-turn are dependent on crystallographic orientation. A fine grain structure leads to uniform sputter rates and minimization of particle nucleation and growth. Past Praxair MRC investigations have shown that particle generation from the target results from the nucleation and growth of nodules of redeposited material at the target’s peripheral regions. This nucleation of nodules occurs when the rate of re-deposition exceeds the erosion rate during sputtering. Particles are generated when these highly stressed nodule fracture, Figure 1.
With the modified target design, the end of life rise in particle generation typically seen during TiN deposition is significantly reduced, Figure 3.
Any defect, macroscopic or microscopic, on the target surface can act as a nucleation site for a TiN nodule. A standard finish leaves scratches on the surface, which can act as a nucleation site. The solution to this problem is to fabricate targets with a non-deformed surface layer. Praxair MRC has developed proprietary surface modification processes, which have been effective in eliminating surface defects. Targets treated with these processes have a superior surface finish. The material on the target surface is not mechanically damaged and the surface finish is similar to a ‘sputtered finish’ resulting in reduced burn-in times.
In IC wafer production, titanium targets made with Praxair MRC’s CCH Do technology offers key attributes for higher yield and lower cost of ownership. These targets exhibit
All of these Praxair MRC enhancements are key to successful deposition of Ti and TiN films with a minimum number of particles while maintaining high uniformity and long life.