不锈钢基板表面粗糙度对水膜吸附夹持的影响

目的从水膜吸附的功能研究出发,对不锈钢基板表面进行不同粗糙度处理,并测量不同基板对蓝宝石晶片的吸附力以及切向摩擦力的影响,从而得出粗糙度对水膜吸附效果的影响规律。方法通过砂纸打磨、研磨、抛光等方法,得到不同平均粗糙度(Sa=633.4、332.6、116.2、64.5、41.4nm)的不锈钢基板。利用接触角计对液滴在基板表面形成的静态接触角进行拍摄,得出不同粗糙度不锈钢表面的润湿性能。开发设计高精度的多维力测量平台,测量蓝宝石晶片在不同粗糙度不锈钢基板上润湿后的吸附力和切向摩擦力,并与未润湿的基板得到的测量结果进行对比研究,得出粗糙度对吸附力和摩擦系数的影响规律。结果5种粗糙度的不锈钢基板的静态接触角均小于90°,属于亲水性材料。水膜吸附条件下,吸附力大小随粗糙度的增加而减小;接触角大小随粗糙度的增加而增大,且吸附力的减小率和接触角的增大率趋势相似;摩擦系数随粗糙度的增大而增大。基板表面粗糙度较大时,水膜提供一定的粘滞力,使水膜吸附条件下比无水膜时的切向摩擦力更大;当粗糙度较小时,水膜更多的是润滑作用,此时比无水膜时的切向摩擦力要小得多。结论基板表面粗糙度较小时,基板能提供较大的吸附力,而摩擦力不如无水膜时的大;基板粗糙度较大时,吸附力相对较弱,但是摩擦力比无水膜的更大。在选择不锈钢基板作为水膜吸附夹持基板时,在保证足够吸附力的条件下,可以适当提高基板的表面粗糙度,抵抗晶片抛光过程中受到抛光垫的摩擦力。

Effect of Surface Roughness of Stainless-steel Substrate on Water-film Adhesion

The work aims to treat the surface of the stainless-steel substrate to different roughness from the functional study of water film adhesion and measure the effect of different substrates on adhesion force and tangential friction force of sapphire wafer, so as to obtain the effect laws of roughness on the adhesion effect of the water film. Stainless-steel substrates with different roughness (Sa=633.4, 332.6, 116.2, 64.5, 41.4 nm) were obtained by sanding, grinding, polishing. The contact angle meter was used to photograph the static contact angle formed by the droplets on the surface of the substrate and then obtain the wetting properties of the stainless-steel surfaces with different roughness. A high-precision multi-dimensional force measurement platform was developed and designed to measure the adsorption force and tangential force of the sapphire wafer after wetting, and compare the measurement results with that of the unwetted substrate. Finally, the effect of roughness on adsorption coefficient and friction coefficient was obtained. The static contact angles of the five stainless steel substrates with different roughness were all less than 90°, which were all hydrophilic. Under the adsorption condition of water film, the adsorption force decreased with the increase of roughness, the contact angle increased with the increase of roughness, and the decrease rate of adsorption force was similar to the increase rate of contact angle. The coefficient of friction increased as the roughness increased. When the roughness of the substrate was large, the water film could provide certain adhesion which made the tangential force of friction under adsorption of water film larger than that of unwetted film. When the surface roughness of the substrate was small, the water film was more likely used for lubrication, so the tangential force of friction was much smaller than that of unwetted film. When the substrate roughness is smaller, the substrate can provide more adsorption, but the friction is not as large as that of unwetted film. When the substrate roughness is larger, the adsorption is relative weak, but the friction is larger than that of the unwetted film. When the stainless-steel substrate is selected as the water film adsorption substrate, under the condition of ensuring sufficient adsorption force, the surface roughness of the substrate can be appropriately increased to resist the frictional force of the polishing pad during the wafer polishing process.