| Popis: |
Introduction Since silicon carbide (SiC) is a very hard substrate and is stable both chemically and physically, wafer processing is costly and takes a lot of time. Particularly, in the chemical mechanical polishing (CMP) process, which is the final wafering process, significant improvement in performance such as surface quality and productivity is required for high volume commercial production. At Fujimi, we have developed a high removal rate slurry of over 1.5 μm per hour on the Si-face under neutral pH and conventional CMP processing conditions. We have also proven that the slurry had a nice behavior in removal rate performance based on Prenston equation, that is, removal rate was proportional to the pressure and velocity of substrate. Furthermore, our testing result has shown great surface morphology such as no scratches and no latent scratches beneath the surface. Low surface roughness was achieved under 0.1nm of RMS at 10x10μm area. Fujimi has introduced this new SiC slurry at the Advanced Industrial Science and Technology (AIST) as a suitable stock polishing slurry to remove surface damage coming from previous grinding or lapping steps. We have demonstrated the benefit of a two-step CMP process which applies a stock step using the higher removal rate slurry followed by a fine step using our Colloidal silica type slurry. As a result, the combination process could realize to produce the SiC epi-ready wafer with fine quality surface in shorter process time than conventional process [1]. Results and Discussion In this study, we will discuss our SiC slurry development technologies. At Fujimi, we can control the size and shape of the abrasive grains. Utilizing our expertise in chemical and additive formulation, we can modify our slurries to meet our customers’ various performance criteria. In Figure 1, it shows a test result example in which the removal rate of the Si-Face was improved. These improved performances depended on the type of additive used in the slurry. Test was performed using substrates of 4-inch 4H-N SiC (4°off) Si-face substrates with exactly the same polishing process and pad condition for all slurries. Slurry A was a result of high speed conventional slurry used by AIST [1] as a reference slurry. Slurry B was a newly developed slurry with improved abrasive grains dispersion. Slurry C was also a newly developed slurry focusing on the improvement of oxidation efficiency. As a result, it was possible to achieve a polishing removal rate over 2 um / hour as well as maintain low surface roughness at the same time. [1] S. Hirano et al., Journal of the Japan Society for Abrasive Technology, 60, (2016)353 Figure 1 |
