內連接是半導體晶片中非常重要的元件，其功用是將晶片中的其他元件連接在一起以傳遞訊號。內連接在半導體晶圓製造的後段製程中以大馬士革工藝製造。在大馬士革製程中，最重要的一個步驟是以物理氣相沉積或濺鍍將均勻的銅晶種層沉積到內連接的溝槽中。銅晶種層需要非常均勻以利於接下來的電鍍。然而，隨著半導體先進製程的發展，晶片和內連接的尺度越縮越小，沉積均勻的銅晶種層已成為半導體製程中很大的挑戰。
這篇論文討論了濺鍍參數，包括入射能量、入射角度、沉積率、和基材溫度以增進銅晶種層的品質。此研究也討論了不同的材料性質和阻障層材料以改善銅晶種層的均勻性。由分子動力學模擬可得知，在製程中給予系統額外能量，如增加入射能和基板溫度會使溝槽兩翼的原子往溝槽的壁面頂部擴散，造成遮蔽效應增加而使均勻性變差。降低沉積率可以增強奧斯瓦爾德熟化使壁面頂部的原子往溝槽兩翼移動，進而減少遮蔽效應而增加均勻性。調整入射的角度能改善溝槽各個部份的均勻性。
由勢能和材料結構所造成的不同擴散勢壘是影響銅晶種層在不同材料表面沉積和成長最重要的參數。當溝槽兩翼的擴散勢壘較高而溝槽壁面的擴散勢壘較低時，原子會傾向於由溝槽壁面頂部流向溝槽兩翼，使遮蔽效應減少而增加均勻性。不同的阻障層材料中，合金比例所造成的不同擴散勢壘是影響銅晶種層成長結果的最大因素。當阻障層材料的內聚能越大時，基材受到入射銅衝擊而進入晶種層的原子會減少，合金比例也會因此降低。較低的合金比例可以減少銅晶種層受到合金基材原子勢能吸引力所增加的擴散勢壘，進而增進銅晶種層的擴散能力。這讓壁面頂部的銅原子往溝槽兩翼移動，減少遮蔽效應而增加均勻性。
整體來說，內連接溝槽兩翼和壁面頂部的原子移動趨勢是決定銅晶種層均勻性最重要的因素。若溝槽壁面頂部的原子傾向於往溝槽兩翼擴散，遮蔽效應會降低，更多的銅原子會沉積在溝槽的底部和壁面使的均勻性增加。此研究所討論的濺鍍參數和材料性質中，不同的材料表面對銅晶種層的影響最大。溝槽壁面方向擴散勢壘低的材料表面可以成長出均勻性非常好的銅晶種層。
這篇論文以分子動力學模擬提供了銅晶種層薄膜成長機制和製程參數與阻障層材料的相關研究。本論文也提出了銅晶種層濺鍍參數與材料性質的趨勢圖，可以做為半導體導線金屬化製程的參考。

Interconnect, a significant element in integrated circuit (IC) as it connects individual components of the circuit into a functioning whole. It is manufactured at the back end of line of the IC fabrication by a series of process known as Damascene process. One of the most significant step in Damascene process is the physical vapor deposition or sputtering of the copper seed layer. To form a void-free interconnect, a thin and uniform copper seed layer must be deposited as a basis for electroplating. However, the shrinking size of advanced IC manufacturing has made the uniform deposition of copper seed layer more challenging than ever.
In this thesis, process parameters of sputtering including incident energy, incident angle, deposition rate and substrate temperature are studied. Moreover, different Liner/Barrier materials and properties including the crystal planes are studied to enhance the quality of copper seed layer. It is found that giving additional energy to the atoms during sputtering process increases their diffusivity, leading atoms at the wing to flow into the trench and mainly accumulates at the top sidewall. This increases the step coverage but results in poorer uniformity and larger alloy percentage. In addition, it is shown that by decreasing the deposition rate, Ostwald ripening effect begins to dominant and increases the uniformity. Moreover, altering the incident angle could also improve the uniformity.
Surface diffusion barrier energy caused by the potential energy and lattice structure is the dominant factor of different crystal planes. It is shown that a lower diffusion barrier energy at the sidewall direction of the trench with a larger diffusion barrier energy at the wing direction of the trench allows the atoms at the top sidewall to flow to the wing, while stopping atoms to flow the other way round. This decreases the necking and leads to a better uniformity. For different liner materials, alloy percentage of the copper seed layer is the dominant factor. With a greater cohesive energy, the alloy percentage decreases which reduce the additional diffusion barrier energy from the alloy atoms. This leads the atoms at top sidewall to flow to the wing, therefore increases the necking and uniformity.
It is concluded that the diffusion trend of atoms at the wing and top sidewall is the decisive factor in the feature of copper seed layer. If the atoms tend to flow from the top sidewall to the wing rather than the other round, necking would increase. Atoms depositing into the trench would thus increase and lead to a better uniformity. Among the sputtering process parameters and material properties discussed in this study, surface diffusion barrier energy of different crystal planes is the most influence factor which leads to a nearly perfect necking and uniformity.
This thesis provides an insight to various mechanisms of copper seed layer thin film growth with different process parameters and material properties by molecular dynamics simulation. Valuable trend charts are developed for tuning recipe of copper seed layer deposition for advanced interconnect metallization process.

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