含添加剂的各向异性腐蚀液中实现小掩膜下高硅尖的腐蚀

Microfabrication High Silicon Tips under Small Masks in Anisotropic Solutions by Adding Various Additives

各向异性KOH溶液腐蚀硅尖具有简单、易于实现、成本低廉、(100)晶面腐蚀速率均匀等优点。然而在40%KOH溶液中削角速率和(100)晶面的腐蚀速率之比约为1.6～1.9,并且该比值随着KOH浓度的减小而增大。如此高的削角速率会给AFM探针的制作带来技术上的困难。而对腐蚀场发射器件和隧道式传感器的硅尖阵列来说,高的削角速率会减少单位面积内的硅尖数量。本文通过在氢氧化钾(KOH)或者四甲基氢氧化胺(TMAH)溶液中添加适当的添加剂(如异丙醇(IPA)、1,5戊二醇或碘)降低了削角速率,在较小直径的掩膜下腐蚀出高硅尖。实验结果还表明:在TMAH基腐蚀液中每个硅尖的八个快腐蚀面的削角速率几乎相等,硅尖直径偏差较KOH溶液中腐蚀的硅尖直径偏差更小,因此成品率得到了提高。

Etching silicon tips in anisotropic KOH solution has the advantages of simple, easy to handle,low cost and homogeneous etching rate of （100） crystal plane on a whole wafer. Unfortunately the ratio of undercutting rate to etching rate of （100） crystal plane in 40 % KOH solution is about 1.6-1.9 and increases with decreasing the concentration of solution. This characteristic of etching processes will bring about some technical difficulties in fabricating AFM probe and reduces the realizable number of silicon tip per unit area for field emission electron devices and some tunneling-based sensors. In this paper, we have etched high silicon tips in KOH or TMAH solutions by adding various additives, such as isopropyl alcohol （IPA）, 1,5-pentanediol and 12. The results of experiments show that the height of tips can be heighten greatly by adding above additives and the uniformity of etching in TMAH-based solution is better than that etched in KOH-based solution. It will be help to realize silicon tips with high performance.