应用X射线光刻的微针阵列及掩模板补偿

Microneedle array and mask compensation based on X-ray lithography

提出了一种聚甲基丙烯酸甲酯(PMMA)微针的微细加工工艺,该工艺基于PCT技术,结合X射线以及光刻掩模制作三维微结构。通过移动LIGA掩模板曝光来加工微立体PMMA结构,其加工形状取决于X光光刻掩模板吸收体的形状。实验显示,最终的结构形状并非完全与掩模板上吸收体的形状一致。如果不对X光光刻掩模板的吸收体形状进行补偿,即会使被加工的微结构侧面变形,从而影响微针的性能。分析了微针阵列侧面变形的原因,认为这种变形是由于显影时间与曝光量之间的非线性关系导致结构形状与曝光量分布不完全一致造成的。利用PCT方法制作的PMMA微针其长度为100～750μm,直径为30～150μm,针尖的直径最小可达100nm。通过对LIGA掩模板上的吸收体图形进行适当的补偿,使吸收体图形从中空的双直角三角形变为中空的半椭圆图形,增强了带沟道的微注射针阵列的强度。

A new microfabrication technology based on PMMA（polymethylmethacrylate）microneedles was presented by using the PCT technology with X-ray and lithographic mask. By moving lithographic mask, three-dimensional PMMA microstructures could be made,and the fabricated shape was directly dependent on the absorber pattern on X-ray mask. From the experiment, the final microstructure was not the same as the absorber pattern on X-ray mask. Experiments show that if there is no compensation for mask design, the shapes of sloped side-wall on the exposed structures will be deformed, which affects the performance of microneedles. The main reason of the deformed shapes of sloped side-wall was analyzed in this paper,and results show that it comes from nonlinear relationship between developing time and exposure energy. Based on the PCT method of fabricating PMMA microneedles, the length of the microneedle is 100-- 750μm, and the diameter is 30-- 150μm, which means that the minimum of the microneedle＇s diameter is 100 nm. Based on the compensation of the mask pattern, the strength of microneedle with the channels has been improved by changing the mask pattern from a hollow double right-triangular pattern to a hollow double semi-elliptic pattern.