Performance of a new silicon-coated disk material: disk manufacturing control and device production experience

As the common metal contaminants requirements in ion implanters approach the ⩽E10 cm² range, the selection of proper material for critical beam strike areas has become a major factor in the design of new assemblies and new systems. The fundamental requirement of virtual elimination of surface Al, Fe, Cr, Cu, Zn, etc. represents only one aspect of this task with other vital criteria being surface finish, particle generation, wear under high dose or long term use and manufacturing control. In the process of evaluating and selecting a coating to fulfil all of the basic requirements for high-current and high energy implanter disks, we evaluated several materials and coating techniques. These coatings are identified and evaluation results presented with emphasis on coating elemental purity, smoothness, adhesion, wear qualities, cost-effectiveness and performance in implanter manufacturing. The coating technique selected is unique in its finish and overall performance. The coating is deposited under vacuum in a tightly controlled environment using 99.999% pure Si with all other potential contamination sources (i.e., spray gun, cathode, etc.) eliminated. The amorphous structure of this silicon coating ensures excellent adhesion, conformance to the substrate surface, and a low wear and particle generation rate. For manufacturing evaluation, glow discharge mass spectrometry (GDMS), inductively coupled plasma mass spectrometry (ICPMS), atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM) were used directly on the disk material and total reflection X-ray fluorescence (TXRF) and secondary ion mass spectrometry (SIMS) were used on wafers implanted on the disks. To evaluate the coating performance in a production environment, several alpha and beta disks were used and an Eaten customer at a beta site corroborates the results presented here