Hard Materials Create Unique Challenges for Grinding

As we develop new grinding processes at Axus Technology, we generally encounter three types of materials; silicon, compound semiconductor substrates, and very hard materials.  The nature of silicon and compound semiconductor substrates makes these processes relatively simple to control.  In these cases, the grind wheel matrix and diamond abrasive are substantially harder than the substrate, resulting in high grinding removal rates, relatively low grind wheel wear, and good TTV and surface finish results.

Hard materialsHowever, Sapphire and SiC, as examples of very hard substrate materials, present more difficult challenges.  With material hardness that nears that of the grinding wheel abrasive, the grind process is generally much slower, with exceptionally high wear rates for the grind wheels, making TTV and surface finish more difficult to control.  Axus Technology has been working with end-users and our process consumables partners in recent years to further refine the grind wheel formulations and to develop effective process techniques for these materials on a wide range of process tools.

In a typical application for both sapphire and SiC, subsequent device processing may require a substantial improvement in the surface quality, in some cases requiring surface roughness as low as 1nm Ra.  With incoming material that starts with a surface roughness as high as 1,000nm Ra, this presents a challenge in both process performance and efficiency.  A two-step grind process, using coarse and fine grind wheels, can reduce roughness to less than 100nm, with TTV under 3µm.  Where a very high quality surface is required, a subsequent polish step is applied to achieve low nm results.  The polishing process has the additional benefit of reducing or removing subsurface damage and stress that can result from the grinding process.  For grinding and polishing, Axus Technology has developed efficient processes for SiC and sapphire that have substantially reduced overall process time and cost - in certain cases improving throughput by three or four times the original process.

And, while the grinding process for most materials does not vary much based on the model of grinder being used, hard materials grinding does highlight the differences in performance between grinding tools.  For users working with hard substrates, Axus Technology has a range of process solutions that we can apply to your product in our foundry and development lab, as well as the consumables and tool sets that will deliver effective process results in your own facility.  If you have a surface processing requirement for SiC, sapphire, or other hard materials, the Axus process and engineering team is ready to help.