- 學位論文
各種不同中間氧化層對晶圓接合性質之影響
Effect of various interfacial SiO2 layer on the properties of wafer direct bonding
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摘要
本研究之目標，為利用日益成熟之晶圓接合技術，將具有自生氧化層(Native Oxide)或成長不同厚度氧化層(Thermal Oxide)之矽晶圓利用化學法晶圓直接接合，或電漿表面活化接合兩種方式接合，分別接合成為各種不同中間氧化層的矽晶圓對，並討論不同中間氧化層厚度與接合強度的關係，且探討矽晶圓對接合界面之物理和化學性質。 研究之另一目標，比較各種不同中間氧化層厚度的矽晶圓對，經過刀刃法(Crack Opening Method)後熱癒合(Thermal Healing)的情況，以了解不同中間氧化層厚度與熱癒合行為的關係，以達到最佳接合結果和條件。 利用紅外線照相術(IR)、光學顯微鏡(OM)和場發射掃描式電子顯微鏡(SEM)觀察矽晶圓對的接合形貌，發現電漿表面活化處理過的矽晶圓對，較化學法清洗處理過的矽晶圓對，除有較佳的接合形貌之外，其拉伸強度(Tensile Strength)和界面能(Surface Energy)也較強，且隨中間氧化層厚度的增厚，矽晶圓對的界面能也隨之增強，可能是經電漿表面活化過的矽晶圓表面，氫氧基(-OH)數量增加，兩矽晶圓彼此之間能以較多的凡得瓦爾鍵或氫鍵鍵結接合，隨熱處理溫度增加，氧與矽原子形成較多siloxane (Si-O-Si)的化學鍵結，使接合表面以較多共價鍵展現較強之界面能。 對於中間只有較薄自生氧化層厚度(~36Å)的矽晶圓對，其熱癒合的產生除要在高溫(1273K以上)，熱癒合的時間也需要較長，才能達到熱癒合的效果。而對於具有較厚中間氧化層(≧1000Å)的接合矽晶圓對，只有973K熱癒合溫度和時間45分鐘，就可產生熱癒合且得到高界面能，證實了中間氧化層對熱癒合行為的重要性。本晶圓接合研究結果，用來評估晶圓接合製程和配合的中間氧化層厚度，達到較佳接合性質，以期更廣泛地應用於微機電系統和積體電路上。
並列摘要
The technology of wafer direct bonding has been employed in present study to bond several types of silicon bonded wafer pairs with various interfacial SiO2 layers, such as: a silicon wafer with a surface native oxide layer bonded to another silicon wafer with a native oxide layer, a silicon wafer with a native oxide bonded to a thermally oxidized silicon wafer, or a thermally oxidized silicon wafer bonded to another thermally oxidized silicon wafer. Those wafers were cleaned by chemical solution with/without activation process by oxygen plasma treatment prior to wafer direct bonding. The bonding qualities and the cross-sectional microstructures of those bonded wafer pairs were examined with the infrared (IR) photography, optical microscope (OM), field emission scanning electron microscope (FESEM), and the crack opening method for bonding surface energy evaluation. From these results, the bonded wafer pairs with plasma surface activation demonstrated better bonding qualities than those with chemical solution cleaning process only. Moreover, the boned wafer pairs with thicker interfacial SiO2 layer have greater bonding strengths. It is suggested that the increase of hydroxyl groups (-OH) with plasma activation process induces higher van der Waals attraction forces or hydrogen bond between the surfaces of two bonded wafers. The second aim of this study is to examine the relationship of thermal healing properties for recovering the surface energy of previously de-bonded wafer pairs by crack opening method versus various thicknesses of interfacial SiO2 layers. An optimal process option for the bonded wafer pairs with thickness of interfacial SiO2 layers is suggested from this study. The temperature and the time for effectively thermal healing process in a bonded wafer pairs with a thin interfacial SiO2 layer (~36Å) have to be higher (~1273K) and longer (~90min). On the other hand, the temperature and time for effectively thermal healing process in a bonded wafer pairs with a relatively thick interfacial SiO2 layer (~1000Å) were found to be lower (~973K) and shorter (~45min), respectively. From the present investigation, the significant of interfacial SiO2 layer in the wafer bonding process as well as the thermal healing behavior was observed. Furthermore, the bonded wafer pairs with an appropriate interfacial SiO2 layer demonstrate a great potential on the constructions and applications in MEMS, micro-sensors and micro-pumps, etc.
參考文獻
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