本論文探究銅電化學機械研磨(ECMP)形成機制在奈米半導體積體電路製程之研究。本研究皆採用無研磨粒子(abrasive particle)的電化學機械研磨製程，減低奈米級積體電路因為研磨粒子造成之刮傷而形成斷路。在此研究中，利用高解析穿透式電子顯微鏡(HRTEM) 與X射線光電子能譜分析儀(XPS)探討薄膜鈍化層微結構及表面成長機制，並利用電化學阻抗儀(EIS)與動態電壓(Potentiodynamic)極化曲線進行電化學性質之研究。另一方面探討經電化學機械研磨的銅平坦化效能(PE)之變化，及其在奈米半導體積體電路製程之研究。
本論文依研究主題可區分為三大部分。第一部份，研究在電化學拋光(electropolishing)期間，磷酸(H3PO4)電解液中銅離子濃度對銅移除率(removal rate)的影響，而且銅移除率會隨電解液中銅離子濃度的增加而減少。發現在動態電壓極化曲線中，溶解電流密度(Id)隨電解液中銅離子濃度的增加而減少。在實際和理論銅移除率之間的差異明顯存在，可能是在銅表面上形成薄膜鈍化層時氧化還原反應的能源消耗。隨著電解液裡銅離子濃度增加，經電化學拋光的銅薄膜表面，其薄膜鈍化層的厚度也增加。利用HRTEM來探討薄膜鈍化層微結構並確認薄膜鈍化層的厚度增加是由於電解液中銅離子濃度的增加。從XPS分析此薄膜鈍化層有三個氧化物型態，為Cu2O、 Cu(OH)2及 CuO，而薄膜鈍化層的厚度增加明顯與CuO/Cu2O的強度比例增加有關。因此，電解液中銅離子濃度的增加所產生的CuO薄膜鈍化層的厚度增加，對銅溶解速率減緩。
第二部份，研究在銅電化學機械拋光處理、電化學拋光處理及化學機械研磨處理(CMP)期間，電解液中銅離子濃度對銅移除率的影響。發現在銅電化學機械拋光處理的銅移除率影響最大，而且銅移除率會隨電解液中銅離子濃度的增加而減少。減少的銅移除率比率分別為45.8% (ECMP) 、9.55% (electropolishing)及 5.71% (CMP)。而先前第一部份已探討在電化學拋光期間，電解液中銅離子濃度對銅移除率的影響。在銅電化學機械拋光處理期間，於動態電壓極化曲線中，溶解電流密度(Id)隨電解液中銅離子濃度的增加而減少。EIS分析資料後提出一模擬等效電路圖，發現在銅溶解速率期間，表面含有擴散層使薄膜鈍化層的阻抗(Rp)明顯增加。從XPS分析知，此薄膜鈍化層的阻抗增加明顯與二價銅中CuO的強度比例增加有關。因此，電解液中銅離子濃度的增加所產生的CuO薄膜鈍化層的厚度增加，銅溶解速率減緩造成移除率下降。使用45 μm寬的銅特徵圖案，在含銅離子濃度的電解液中研磨後，銅薄膜平坦化效能評估值達25.7%，顯示銅離子濃度及電壓可控制薄膜鈍化層之成長及平坦化效能。
最後一部分，研究在銅電化學機械拋光處理期間，電解液中電壓、研磨時的下壓力及旋轉速度對銅移除率的影響。發現電壓的影響最大，其次是下壓力及旋轉速度，而且銅移除率會隨電壓、下壓力及旋轉速度的增加而增加。EIS分析資料後提出一模擬等效電路圖，發現在銅溶解速率期間，表面含有擴散層使薄膜鈍化層的阻抗隨電壓增加而明顯增加，而隨下壓力及旋轉速度增加而下降。電荷轉移延遲時間(charge-transfer time-delay) 隨電壓、下壓力及旋轉速度的增加而減少，表示銅溶解速率變快。從XPS分析此薄膜鈍化層知，此薄膜鈍化層的阻抗增加明顯與Cu2O與二價銅的強度比例增加有關。在低電壓時，銅溶解速率低，Cu2O成長慢，而高電壓時，銅溶解速率較高，Cu2O成長較快，再加上機械力移除銅氧化物後，銅移除率又再隨電壓增加而增加。

This dissertation explores nano-scale copper (Cu) electrochemical mechanical planarization (ECMP) mechanism on damascene process for semiconductor integrated circuits. ECMP process has no abrasive particle because the broken circuits are formed by scratches due to abrasive particles in nano-scale semiconductor integrated circuits. We have investigated the microstructures and growth mechanism of passive film on the Cu surface by high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the samples were investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve. In addition, we have evaluated the planarization efficiency (PE) after ECMP processing in the in the semiconductor integrated circuits.
The main focus of this dissertation can be divided into three parts. First, the dependence of Cu removal rate during Cu electropolishing on Cu ion concentration in 85wt% H3PO4 is investigated. With increasing Cu ion concentration in the electrolyte, results show that the Cu removal rate significantly decreases, because more Cu ions in the electrolyte facilitate the formation of a surface passive film. The dissolution current density (Id) increases with increasing Cu ion concentrations in the potentiodynamic curves of the Cu films during electropolishing. The discrepancy between the removal rate in reality and in theory may be due to the additional energy consumption of forming passive films on the Cu surface. It is found that thickness of the passive film on the Cu surface after Cu electropolishing in electrolytes with increasing Cu ion concentration. Microstructures and crystallography of the passive film are examined by HRTEM, which confirms the increase of the passive film thickness due to the high Cu ion concentration in a H3PO4 electrolyte. Three types of Cu oxide are detected using XPS, namely Cu2O, Cu(OH)2, and CuO. The increase of passive film thickness is related to the intensity ratio of CuO/Cu2O obviously. Therefore, the increase of CuO passive film thickness due to the increase of Cu ion concentration in a H3PO4 electrolyte reduces Cu dissolution rate.
Then, the dependence of Cu removal rate on Cu ion concentration during ECMP, electropolishing, and chemical mechanical polishing (CMP) in an 85wt% H3PO4 electrolyte is investigated. ECMP rate is the highest in all polishing, and the percentage of the ratio of the decrease of the Cu removal rate to maximum of the Cu removal rate for ECMP, electropolishing, and CMP are 45.8%, 9.55% and 5.71%. The dependence of Cu removal rate on Cu ion concentration during electropolishing has been discussed in previous section. Id decreased when the Cu ion concentration is increased in current-voltage curves during ECMP in electrolytes with various Cu ion concentrations. Simulation results from the proposed equivalent circuit diagram that are matched with the impedance data and the resistance of the passive layer (Rp) increases obviously. From XPS analysis, the increase of passive film thickness is related to the intensity ratio of CuO/Cu(II) obviously. Therefore, the increase of CuO passive film thickness reduces Cu dissolution rate and removal rate. PE values of the Cu films with feature size of 45 μm in the 85 wt% H3PO4 electrolyte with Cu ion concentrations reach 25.7%, because Cu ion concentrations and potentials can control the growth of the passive film and PE.
Finally, the dependence of Cu removal rate on potential, down-force and rotation speed during ECMP in an 85wt% H3PO4 electrolyte is investigated. The factor of the potential is the more influence than down-force and rotation speed. With increasing potential, down-force and rotation speed, results show that the Cu removal rate increases. Simulation results from the proposed equivalent circuit diagram that are matched with the impedance data and Rp increases obviously with increasing potential, Rp decreases with increasing down-force and rotation speed. The charge-transfer time-delay decrease with increasing potential, down-force and rotation speed, indicating that the Cu dissolution rate becomes quick. From XPS analysis, the increase of passive film thickness is related to the intensity ratio of Cu2O /Cu(II) obviously. Cu2O grows slowly and Cu dissolves low at low potential; Cu2O grows quickly and Cu dissolves fast at high potential. Cu2O passive film is removed by mechanic force, and then Cu removal rate increases with increasing potentials.

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