SEMICONDUCTOR APPLICATIONS

CCH Do and Do* Titanium

Introduction

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 Formation

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Figure 1. Illustration of particle generation mechanism

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.

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Figure 2. Comparison of nodule formation at the target periphery between standard (bottom) and Praxair MRC modified (top) target designs.
Due to the shape of the magnetic field, such regions exist on the periphery of the target, where the magnetic field is not as strong. Praxair MRC has developed target modifications that increase the strength of the magnetic field on the periphery resulting in a dramatic reduction in particle formation. In Figure 2 the reduction of nodules is clearly observed. Note the high density of nodules formed on a standard TEL RMX 10 Ti target used for TiN deposition (left). The modified Praxair MRC target shows the elimination of nodules (right)

With the modified target design, the end of life rise in particle generation typically seen during TiN deposition is significantly reduced, Figure 3.

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Figure 3. Comparison of particle generation (particles >0.3m m) between the Praxair MRC modified design (DoBLVD) and a standard (Do) TEL RMX 10 Ti target.

Do* Finish

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.

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Figure 4. Titanium Do* target surface quality mirrors the as-sputtered target structure.

Summary

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

    • Ultra fine grain of <15m m
    • Controlled Texture
    • Design modifications (e.g. TEL, RMX, G-series AMAT and Durasource designs....)
    • Do* surface improvements

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.

 

   
 

CCH Process
CCH Do Aluminum Alloys
CCH Do and Do* Ti
Co and Ni
Ta and Cu

Thin Films Application Lab
Bonding Technology
Novellus Inova™ Tool
Endura™ & Centura™ Systems
RE-Al PLUS": Sputter Targets
Technical Papers  
  1. Reduction of TiN Nodule Density Through Optimization of Cathode and Process Variables
  2. Effect of Oxygen Content on Particle Generation in TiN Reactive Sputtering
  3. Link From Titanium Target Orientation to Titanium/Titanium Nitride/Aluminum Thin Film Orientations
  4. Technical Papers Available in PDF