表面粗糙度對奈米級封裝的效應研究

Abstract

為了奈米元件的封裝以及減少製造上的複雜性，本研究探討紫外光固化膠在奈米元件封裝時受表面粗糙度的影響。 紫外光固化膠在接受足夠強度與劑量的紫外光照射後，會產生光化學上的固化反應，接合兩異質表面。這樣的方式完全不必用到任何的加熱程序，十分適合應用在對溫度敏感的材料或製程上。而利用表面粗糙度的改變，增加紫外光固化膠的接合面積來使接合強度增加，可以有效的縮小封裝尺寸。 首先矽晶圓以光阻塗佈加上活性離子蝕刻改變表面粗糙度，改變前後的表面粗糙度經過量測分別為0.4nm與12.4nm。接下來利用活性離子蝕刻挖出微孔穴，接合的尺寸分別為2μm與4μm。另外將Pyrex 7740玻璃旋塗上紫外光固化膠後，經由足夠的紫外光照射與矽晶圓進行接合，進行切割後評估接合的密封性與強度。 經過泡水與拉伸測試，發現增加接合面的粗糙度，可以降低約3至8％水氣的洩漏，而接合強度也能增加約35至43％，達到縮小封裝尺寸，增加接合強度，以及室溫製程的效果，證實改變表面粗糙度對紫外光固化膠式封裝方法有明顯之功效。另外，利用未拋光的矽晶片背面進行實驗，表面粗糙度為0.6μm，在進行黃光製程時會產生殘留光阻造成元件製作失敗，發現過高的表面粗糙度不適合與製程整合。

In order to package the nano devices and resolve the process complexity of fabrications, this research investigates the surface roughness effects on UV curable adhesive for nanopackaging. The UV curable adhesive is cured through UV light exposure without any additional heating, suitable for packaging the devices with temperature sensitive materials or processes. On the other hand, the addition of surface roughness increases bonding area of UV curable adhesive and enhances bonding strength. The packaging size can be reduced effectively. At first, the surface roughness of Si wafer is modified by photoresist spin and RIE etching. The Ra before and after modification are 0.4nm and 12.4nm respectively. Then shells are fabricated by RIE etching and the bonding width is 2μm and 4μm. Finally UV curable adhesive is spun on Pyrex7740 and cured through UV light exposure to bond to Si wafers. The packaging hermeticity and strength are evaluated. The addition of surface roughness reduces leakage from 3％ to 8％ and enhances bonding strength from 35％ to 43％. The surface roughness effects on UV curable adhesive for nonopackaging are achieved by the results of decreasing packaging size, increasing bonding strength, and under room temperature process. In addition, the backside of Si wafers is unpolished and used to experiment. The Ra 0.6μm generates residual photoresist and results in fabrication failure during lithography process. Such high surface roughness is unsuitable to integrate in fabrication processes.