GENERATION OF MICRO-ICE JET AND SELECTIVE REMOVAL PROCESS OF RESINOID INSULATOR FILM FOR MULTIPLAYER SEMICONDUCTORS

本课题介绍了用于半导体树脂隔离膜通孔加工的微冰射流加工装置（IJM）的研制，该装置可实现微冰的间歇爆破。IJM工艺类似于磨料射流加工（AJM），并选择性地去除比纯水微冰更软的材料。IJM采用细冰粉，在-150℃或以下的低温条件下生产。首先，利用PIV（粒子图像测速）系统测量了喷嘴的喷射模式和注入速度分布。根据实测的喷雾模式和水滴临界冻结时间的计算值，设计了IJM装置冰室的尺寸。然后，对IJM工艺的爆破特性和可行性进行了研究。当喷嘴喷出的冰射流聚焦在工件上时，可以加工出小孔或槽。爆破后的微冰是融化的，对生产过程的环境没有影响。铝、铜、硅和树脂板用冰喷流喷射。硬度相近的铝和铜没有加工。但由于残余应力的作用，表面粗糙度增大，爆破区域中心增大。硅（单晶片）比微冰更硬，没有经过机械加工，对表面没有影响。比微冰更软的树脂被移除。然后，我们在硅片上制作树脂类隔离膜，并重叠金属掩膜。冰喷喷在面具上。只除去树脂隔离膜，将口罩的相同图案转录到隔离膜上。演示了选择性去除过程。

This project describes the development of the micro-ice jet machining (IJM) device for the via fabrication on the resin isolation film of semiconductors, which is capable of intermittent blasting of micro-ice. The IJM process is similar to an abrasive jet machining (AJM), and selectively removes softer materials than the micro ice of pure water. IJM uses fine ice powders, which are produced under the low temperature condition of -150 ℃ or below. First, the spray pattern from the nozzle and the injected velocity distribution were measured using PIV (Particle Image Velocimetry) system. The size of ice chamber for IJM device was designed on the basis of measured spray pattern and calculated value of critical freezing time of water drop. Then, we investigated the blasting characteristics and the possibility of the IJM process. As the ice jet stream from the nozzle is focused onto the workpiece, small holes or slots can be machined. The blasted micro-ice is melted and has no influence upon the environment of production processes. Al, Cu, Si and resin plates were blasted with ice jet stream. Al and Cu, which have similar hardness, were not machined. The surface roughness, however, increased and its center of blasted area rises due to the residual stress. Si (single crystal wafer), which is harder than micro-ice, was not machined and has no influence on the surface. Resin, which is softer than the micro-ice, was removed. Then, we made a resinoid isolation film on the silicon wafer and a metal mask was overlapped. Ice jet was blasted on the mask. Only the resin isolation film was removed, and the same pattern of the mask was transcribed onto the film. The selective removal process was demonstrated.