Pattern Transfer of 3-dimensional Fine Structures to the Si Substrate with expanding the Vertical Dimensions Using the Reactive Ion Etching

在这项研究中，我们的目标是开发一种将三维结构从抗蚀剂掩模转移到硅衬底的图形转移技术，并扩展其垂直尺寸。这一关键技术将用于制造需要比抗蚀剂厚度更深的垂直尺寸的微透镜和微机械等。利用光栅束扫描的电子束光刻和不同掩模图案的倍增曝光，在抗蚀剂层上形成多能级阶梯结构。利用抗蚀剂掩模和衬底之间的刻蚀选择性，利用反应离子刻蚀技术进行图形转移。结果表明，利用SF6气体的反应离子刻蚀可以将多能级台阶的抗蚀剂截面转移到硅衬底上，并将其垂直尺寸扩大约5倍，而图形转移则使抗蚀剂截面形状发生变形。RIE的各向同性降低了阶跃宽度为1μm时转移图案的质量，RIE将90%的CHF_3气体与10%的SF_6混合后，改善了这些问题，但垂直尺寸的扩展程度有所降低。还提出了通过改变RIE工艺中的射频偏置电压来控制扩展图案转移的程度。

In this research, we aimed at developing a pattern transfer technique of 3-dimensional structures from a resist mask to a Si substrate with expanding their vertical dimensions. This key technique will be useful for fabricating a microlens and a micromachine etc. which need deeper vertical dimension than the resist thickness. Multi-level step structures were formed to a resist layer using the electron beam lithography with raster beam scan and multiplying exposures of different mask patterns. The pattern transfer was performed using the reactive ion etching utilizing the etching selectivity between the resist mask and the substrate.It is demonstrated that resist cross sections of multi-level steps can be transferred to Si substrates with expanding their vertical dimensions about 5 times by the RIE using SF_6 gas, while the cross sectional shapes were deformed by the pattern transfer. The isotropic nature of RIE degraded the quality of transferred patterns when their step widths were as fine as 1μm. These problems were improved by RIE with mixing CHF_3 (90%) gas to SF_6 (10%), whereas the degree of expanding the vertical dimension was decreased. It is also presented that the degree of expanded pattern transfer is controllable by changing the RF bias voltage at RIE process.