The fused silica glass is needed in the electronics and micro manufacturing industry. The thickness requirement is 0.02 ~ 0.2mm, which is difficult to be achieved by traditional machining. In this paper, a new thinning technology is proposed. Through the combination of chemical mechanical polishing (CMP and chemical etching, ultra-thin fused silica glass with diameter of 50 mm, thickness of 0.05 mm and Ra<1 nm can be prepared. It was also found that the fused silica glass could be thinned uniformly and efficiently by high-speed rotation and adding active agent in the chemical etching process.
To investigate the distribution characteristics of subsurface damage in fused silica, three different machining methods - cutting, grinding and lapping were adopted. The method of combination of step-by-step polishing and wet etching were applied to expose the subsurface damage and their distribution characteristics in horizontal and vertical directions were analyzed and compared. Experiment results showed that the numbers of subsurface cracks induced by different processes have similar exponential distribution in depth, although their maximum depths were varied with machining methods. Most of the cracks, more than 90%, distribute within half of the maximum crack depth, while only a few cracks extend deeper and contribute the maximum SSD depth. The ratio of SSD depth to Rz for lapping, slicing and grinding based on our work are about 1.4, 1.8 and 2.8, respectively. The present results indicate a nonlinear correlation between SSD depth and Rz.
To inspect the treatment effect of high power plasma on fused silica, inductively coupled plasma with power of 36kW at atmospheric pressure , CF4 as working gas, was applied to carry out the etching experiments of fused silica, in which the effect of CF4 flow rate on material remove rate, surface roughness and surface profile were investigated. The experimental results showed that the material remove mechanism of fused silica treated by high power inductively coupled plasma was a result of the comprehensive effect of melting and evaporation at high temperature, chemical etching and bombardment of high energy ions. The fused silica remove rate reached 0.208g/min with the CF4 flow rate of 2.8L/min. The surfaces of fused silica samples became rougher with the increased CF4 flow rate, as the subsurface micro-cracks were opened and formed etching pits by the plasma etching. The surface global profile was affected seriously by the distance between outer plasma flame and samples while the local profile was dominated by etching pits.
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