高精度石英全息透镜的MEMS工艺制作

通过微电子机械技术(MEMS)在抛光的熔融石英基材表面制作了平面精度达到0.4μm的超大单片面积的全息透镜。采用了分辨率达到0.2μm的步进投影式拼接光刻,适合石英基材的专用等离子耦合刻蚀(ICP)干法刻蚀技术,特殊的物理清洗方法,以及相关的多项辅助工艺。透镜理想面形横截面曲线为分段抛物线,每一片由23个柱状结构单元周期横向排列构成,采用等深度不等宽度的4台阶结构拟合,单元宽度约为2.966mm。在4in(10.16cm)圆片上,获得了单片尺寸为68mm×68mm的方形透镜。采用接触式台阶仪,扫描电子显微镜(SEM),高倍光学显微镜等方法进行不同阶段检测。结果显示:台阶平面精度为0.4μm,垂直精度为30nm,有非常好的立墙陡直度和刻蚀均匀性。此工艺方案可实现小规模批量生产,成本适中,可以直接用于制作6in(15.24cm)以上同等级要求的石英透镜,经适当改进也可用于蓝宝石等基底材料的制作。

MEMS manufacture process of high precision quartz hologram lens

An over-sized monolithic holographic lens with a micron plane precision of 0.4μm is fabricated on a quartz substrate well polished by Micro-electro-mechanical system(MEMs) process. Some improved methods are used in this series process, such as the stepper projection exposure with a resolution of 0.2μm and the stitching method, the improved ICP(Inductively Coupled Plasma)dry etching technology for a quartz, the physical cleaning method designed especially and a lot of other supporting processes. The ideal surface shape curve of cross section for the hologram lens is a piecewise parabola. A single lens is horizontally arrayed by 23 column cell structures with a width about 2.966 mm. Because of the difficulty in practice, the 4-step structure with an equal depth and an unequal width is used to fit it. At last, single piece square hologram lenses with the area more than 68 mm×68 mm are obtained at a 4 in(10.16 cm)circle piece. The step profiler, scanning electron microscope, high-powered and resolution optical microscope are used to measure lens accuracy at different stages. The results indicate that the lens has a plane precision of 0.4μm, vertical precision of 30 nm, and shows a good vertical wall shape and etching uniformity. This process technology can be used for small batch production, and the cost is moderate. It is suitable for processing the same grade lenses with the size of 6 in(15.24 cm), and also for processing the sapphire substrates.