近年來，Solid-liquid interdiffusion (SLID) bonding 或稱作Transient
liquid phase (TLP) bonding 被視為是晶圓對接(Wafer bonding)或是3D IC 堆疊
中的新興科技，透過兩種不同熔點的金屬進行接合的動作，製程中採用比低熔點金
屬還高的製程溫度，使低熔點金屬在對接過程中保持液態，可以增加高熔點金屬在
低熔點金屬中的擴散速率，大幅降低接合所需時間，是SLID bonding 的重要優點
之一。近期更有作者在SLID bonding 技術中引進熱梯度(thermal gradient)的概
念，結果顯示一旦導入溫度梯度，接合時間將可以比傳統製程快上3-10 倍。
加上為了因應人工智慧(Artificial Intelligence, AI)世代的來臨與高效能
運算(High Performance Computing, HPC)晶片的需求逐漸增溫，傳統導電材料像
是銅與鎢金屬在10 奈米以下製程無法再順利微縮，加上電性不良與填洞(Gapfill)
能力不佳等問題，讓電晶體效能無法有效發揮，成為先進製程上的阻礙。然而全球
最大半導體設備商:應用材料於2018 年6 月的新聞稿表示，透過“鈷”金屬當作新
的導電材料，使導線擁有更低的功耗、增加導電性與提升晶片效能，可望一舉突破
限制，為未來個位數奈米節點製程注入一線生機，繼續延續摩爾定律。
有鑑於此本研究試片一共分為4 個系列，分別為系列1-鈷(冷)/焊錫/銅(熱)、
系列2-銅(冷)/焊錫/鈷(熱)非對稱結構與對照組系列3-鈷(冷)/焊錫/鈷(熱)、系
列4-銅(冷)/焊錫/銅(熱)對稱結構。我們將各系列試片連同特殊載具一同放置在
260°C 的加熱板上，並在試片上端擺放鋁製散熱鰭片，研究鈷和銅元素在溫度梯度
環境下的擴散行為、擴散元素對界面生成相種類與表面形貌的影響以及相關的動力
學機制探討。
研究結果顯示，在靠近鈷端界面的焊錫中銅濃度多寡將大大影響(Co,Cu)Sn3 相
的生成與否，銅濃度較低鈷端界面生成相為:(Co,Cu)Sn3 與(Cu,Co)6Sn5 兩項共存；
銅濃度較高則鈷端界面僅有(Cu,Co)6Sn5 存在。非常有趣的是，如果鈷端界面僅有
一相(Cu,Co)6Sn5 存在，在生成一定厚度之後會有大量(Cu,Co)6Sn5 脫離界面的特別
現象，在鈷端界面形成鈷/(Cu,Co)6Sn5/焊錫/(Cu,Co)6Sn5/焊錫的分層結果；然而鈷
端界面一但有(Co,Cu)Sn3 的生成，即使只有非常的少量，(Cu,Co)6Sn5 就可以完整附
著在其上，所以我們可以得知，鈷端(Cu,Co)6Sn5 的分層、脫離界面與否，跟是否
生成(Co,Cu)Sn3 有直接的關係。
最讓人意外的是，在本研究系列2 中，鈷基板擺放於熱端，在時間20 分鐘後，
竟讓在溫度梯度條件下熱端所生成的(Cu,Co)6Sn5 厚度持續大於冷端，與文獻中銅
原子會受溫度梯度驅使往冷端擴散造成冷端IMC 厚度較厚的結果截然不同。由此可
見，鈷基板擺放於熱端或冷端，對於(Cu,Co)6Sn5 的生成厚度有著重大的影響，也
顯示鈷基板具有吸引銅原子擴散的驅動力。

The Solid-liquid interdiffusion (SLID) bonding, also known as transient liquid phase (TLP) bonding, is a very promising technology for direct wafer bonding or three-dimensional integrated circuit (3D IC) stacking in recent years. The SLID bonding process was conducted by bonding two different metals; one has low melting point, yet the other has higher melting point. Firstly, the process took place at a temperature higher than the low melting point metal; thus the interdiffusion occurred between solid and liquid phases during the bonding process. Secondly, after reaching the solubility limit, the intermetallic compound (IMC) phases with a high melting point were formed. As a result, the bonding joint can withstand the high temperature environment which is one of the advandages of SLID bonding. Instead of using isothermal bonding process, some studies proposed to superimpose a temperature gradient across the joint during the bonding process to shorten the bonding period, which is 3-10 times faster than the traditional process. In addition, for the forthcoming artificial intelligence era and high requirement of high performance computing chips, using Cu as local interconnects are suffering in term of gapfill, resistance and reliability problems, which limit the performance of the chips. Thus, Applied Materials company launches new technology - using Co for metallization instead of Cu. In this study, we investigate the diffusion behavior of Co and Cu in Pb-free solder
joints under a temperature gradient to understand the interfacial reaction and phase evolution of intermetallic compounds during the bonding process. We designed four series of samples, there were asymmetrical structures of series1-Co(cold)/SnAg/Cu(hot), series2-Cu(cold)/SnAg/Co(hot) and symmetrical structures of series3-Co(cold)/SnAg/Co(hot) and series4-Cu(cold)/SnAg/Cu(hot) as control group. In order to establish a temperature gradient across the solder layer, the Al heat sink was placed on the sample during reflowing
the samples at 260℃ on a hot plate for different durations. The results showed that the concentration of Cu would determine the phase of the IMC at the Co side. For regions with relatively low Cu concentration, (Cu,Co)6Sn5 and (Co,Cu)Sn3 coexisted. On the contrary,
for the regions with relatively high Cu concentration, only (Cu,Co)6Sn5 appeared at the Co/solder interface, suggesting that the interfacial reaction between Co and solder was very sensitive to the Cu concentration near the interface. Interestingly, if only one phase
(Cu,Co)6Sn5 was formed at the Co/solder interface, a lot amount of (Cu,Co)6Sn5 would detached from the Co interface and dissolved into the solder. In addition, it is surprised to find that the thickness of (Cu,Co)6Sn5 at the hot end was thicker than the cold end in the sample of series2 after 20 min, which was inconsistent with the result in the traditional Cu/Solder/Cu symmetrical structure, implying that the Co substrate played a significant role on the growth of the interfacial
IMC.

摘要................................................................I
ABSTRACT..........................................................III
致謝................................................................V
目錄...............................................................VII
表格目錄............................................................IX
圖目錄..............................................................X
第一章簡介..........................................................1
第二章文獻回顧.......................................................3
2.1 熱遷移..........................................................3
2.1.1 熱遷移原理....................................................3
2.1.2 在覆晶封裝技術中焦耳熱誘發溫度梯度..............................6
2.1.3 銲錫中的熱遷移................................................11
2.1.4 金屬墊層(UBM, Under Bump Metallurgy)的熱遷移..................21
2.2 焊錫與金屬的界面反應(等溫熱處理).................................30
2.2.1 焊錫/銅的界面反應.............................................30
2.2.2 焊錫/鈷的界面反應.............................................36
2.2.3 鈷/錫/銅的界面反應............................................44
第三章實驗步驟......................................................49
3.1 試片製備.......................................................49
3.2 熱遷移實驗設置與分析.............................................49
3.3 ANSYSWORKBENCH 溫度梯度模擬.....................................50
第四章結果與討論.....................................................54
4.1 三明治結構中的溫度分佈...........................................54
4.2 溫度梯度下焊錫和金屬的界面反應....................................59
4.2.1 系列1-鈷(冷)/焊錫/銅(熱).......................................59
4.2.2 系列2-銅(冷)/焊錫/鈷(熱).......................................67
4.2.3 系列3-鈷(冷)/焊錫/鈷(熱).......................................74
4.2.4 系列4-銅(冷)/焊錫/銅(熱).......................................82
4.3 綜合討論........................................................88
4.3.1 在非對稱結構中CoSn3 的成長情形..................................88
4.3.2 溫度梯度下介金屬化合物成長機制探討(S1 vs. S4)....................93
第五章結論..........................................................101
第六章未來工作......................................................103
參考文獻............................................................104

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