低溫晶圓接合之結構特性研究

近年來在電子產業蓬勃發展之下，其晶片功能也日益增大，電子相關產品逐漸走向高傳輸速度、小面積與低成本方向，造成傳統2D平面構裝面臨著極大的挑戰，因此，近年來推出3D堆疊構裝技術，用以解決上述之需求。本研究將探討兩晶圓堆疊接合後，並且同時維持高強度，藉以省去多餘之製程成本。本研究成功地利用擴散接合技術完成矽晶圓-矽晶圓間低溫接合之目的，首先在晶圓試片依序濺鍍阻障層鉻薄膜(防止銅的擴散)及銅薄膜做為接合層。在熱壓接合前先將試片進行酸性處理以去除表面氧化層，使其表面達活化之效果，並在真空低溫條件下進行銅-銅活性擴散接合。接合界面利用OM與SEM觀察其接合微結構，EPMA確認擴散反應，最後利用附著力測試及耐候實驗觀察其接合強度與品質。研究結果顯示，利用化學處理能有效地去除銅表面原生之氧化物，進而促使銅-銅間相互擴散，當接合溫度於250℃持溫一小時，接合界面已有擴散反應，其接合強度亦隨著溫度的提升而增加，當接合溫度於350℃持溫一小時，其接合強度已達10Mpa。

關鍵字

3D堆疊構裝；晶圓接合；熱壓接合；表面活性接合；銅金屬；鉻金屬

並列摘要

Currently, the increase in development of electronic industry, minimization, multi-functions and low cost of an electronic product is the significant challenge to the semiconductor industry in two-dimensional integrated circuits (2DICs). As a result, three-dimensional integrated circuits (3DICs) have been proposed as promising solution to all of the issues. In this study, we focus on the silicon-silicon bonding with high tensile strength. Meanwhile, the demands of low cost and simplified manufacturing process are also investigated. The silicon-silicon bonding was achieved completely by using the diffusion bonding technique. The experimental steps show as follows: firstly, Cr thin films were deposited on silicon substrate as barrier layer to prevent the Cu diffusion. Then, the bonding layers were prepared by sputtering of Cu target. Prior to thermal-compression bonding, the silicon substrates were dipped in acidic solution to remove any native oxide existing on the Cu surface. The surface-activated bonding process for Cu-Cu was performed in the vacuum system under low temperature. The microstructure of the bonding interface was observed by OM and SEM; in addition, the diffusion process was confirmed by EPMA. Finally, the strength and quality of the bonding structure were identified by durability test and adhesion test. The result show that wet pretreatment could effectively remove the native Cu oxide, which led to easy diffusion of Cu atoms into the other Cu layer. Higher bonding temperature helps to improve the mechanical strength, the maximum tensile strength of the layer can reach 10 Mpa at 350℃1hr.

並列關鍵字

Three-dimensional staking technology ； Wafer bonding ； Thermal-compression bonding ； Surface-activated bonding ； Copper(Cu) ； Chromium(Cr)

參考文獻

[20]蘇珍誼，電漿活化及退火處理對直接接合矽晶圓對接合性質之影響，碩士論文，國立清華大學材料科學與工程研究所，新竹，2004。

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低溫晶圓接合之結構特性研究

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