Development of Evaluation methods for mechanical properties in micro-sized components for MEMS devices

首先，利用SU-8光致抗蚀剂制成的微米级弯曲试件进行弯曲试验，以明确微米级聚合物的弯曲性能。利用数码显微镜对激光切割板材悬臂式弯曲试件的弹塑性变形进行了原位观察。使用我们开发的用于微电子机械系统(MEMS)的微尺寸材料的机械试验机对这些悬臂梁施加载荷。尽管SU-8通常是脆性材料，但微尺度SU-8试件在弯曲载荷条件下的载荷-位移曲线显示出明显的延性。最大载荷后，试件根部附近出现剪切带状变形，加载过程中塑性变形区扩大。其次，利用环氧型光致抗蚀剂SU-8进行了微尺寸弯曲试验，以阐明工艺条件、紫外线曝光、后烘烤和热固化条件对弯曲性能的影响。根据第一年的结果，设计了用于微尺寸弯曲试件的光掩模。大多数微尺度SU-8试件的荷载-位移曲线都表现出极高的延性，所有试件均为梁根部破坏。SU-8试件的杨氏模量、屈服点和抗弯强度随暴露剂量和热养护剂量的增加而显著增加。结果表明，微米光致抗蚀剂的弯曲性能受紫外线照射和热固化的影响很大。

Firstly, bending tests were developed using micro-sized bending specimens made of SU-8 photo resist to clarify the bending properties of a micro-sized polymer. A digital microscope was used for the in situ observation of elastic and plastic deformation of cantilever type bend specimens, which had been cut from sheets using a laser cutting system. Loads were applied to these cantilevers using a mechanical testing machine, which was developed by us for micro-sized materials for Micro-electro mechanical systems (MEMS). Load-displacement curve under bending load conditions in micro-sized SU-8 specimens clearly shows ductile manner, although SU-8 is usually brittle material. Shear band like deformation was appeared near root of the specimens after maximum load, and then this plastic deformation area was expanded during loading. The ductile behavior in a micro-sized SU-8 may be caused by regional shear band deformation near the root.Secondly, micro-sized bending tests were performed using epoxy type photo-resist, SU-8, to clarify effects of a processing condition, UV exposure, Post baking and heat curing conditions on bending properties. Form the results in the first year, photo-masks for micro-sized bending specimens were planed. Load-displacement curves of most microsized SU-8 specimens show in an extremely ductile manner and all the specimens were failed by root of the beam. Young's modulus, Yield point and bending strength of SU-8 specimens remarkably increase with increasing exposure dose and heat curing. All the results clarify that bending properties of microsized photoresist are strongly affected by UV exposure and heat curing.