應用具有局部快速加熱能力的模仁的微米成形技術的開發

Abstract

近年來，高分子材料的微成形技術變的越來越重要。相較於其他的成形技術，熱壓成形具有材料流動率低、流動距離短的性質，適合用來成形微結構和光學元件。然而，由於材料和模仁彼此熱膨脹係數的差異，當加工到冷卻保壓階段，材料的收縮會對模仁產生挾持的力量，導致成形品微結構有脫模破壞問題產生，限制了熱壓技術在大面積化和高深寬比結構成形上的應用。為此，本研究進一步改良本實驗室所開發的可局部快速加熱的微模仁，期望能使上述微熱壓的瓶頸得以突破。我們嘗試以P type 矽晶圓作為模仁，並佈植磷離子於晶片表面上，當施加電力於佈植的通道上，可使模仁本身具有加熱的功能，以適時控制成形材料的溫度分佈，藉此降低材料在成形過程中的收縮應力。 實驗結果顯示，熱壓成形在成形深寬比三以上的微結構，脫模皆會產生微結構斷裂、傾倒或模仁毀損等不同程度的破壞。在冷卻保壓階段，施加適當的功率在模仁表面可以有效的降低模仁和材料間的熱收縮應力，解決脫模破壞的問題，對材料收縮不均勻的缺陷亦有相當程度的改善。

Polymer micromolding technique are becoming increasingly important in recent years. Compared with other molding technique, hot embossing is favorable for molding microstructures and optical devices because of its low flow rate and low material flow character. However, due to the differences of thermal expansion coefficient between polymer and mold insert, shrinking of polymer in the cooling stage may lead the mold cavities to press the microstructure from both sides. This force will cause the demolding destruction of microstructures and limit the application of molding larger surface areas and higher aspect ratio microstructures on hot embossing technique. Therefore, this study improve the mold insert with rapid heating-function which our laboratory develop and use it to surmount the limit on micro-hot-embossing. We try to use P type silicon wafer as mold insert and implant phosphorous ion into the surface of silicon wafer to make mold insert have heating function. With the heating function, we can decrease the thermal stress of polymer in molding process. Experiment results demonstrate that the microstructure will produce these defects with creak, slant, damage in the mold insert at demolding when the microstructure by hot embossing has filled with up to 3 times of aspect ratio. Applying appropriate heating power to the surface of mold insert can decrease the thermal stress effectively in the cooling stage to solve the problem of demolding and can improve non-uniform shrinkage of polymer.