Investigation of aluminum gate CMP in a novel alkaline solution

Beyond 45 nm, due to the superior CMP performance requirements with the metal gate of aluminum in the advanced CMOS process, a novel alkaline slurry for an aluminum gate CMP with poly-amine alkali slurry is investigated. The aluminum gate CMP under alkaline conditions has two steps:stock polishing and fine polishing. A controllable removal rate, the uniformity of aluminum gate and low corrosion are the key challenges for the alkaline polishing slurry of the aluminum gate CMP. This work utilizes the complexation-soluble function of FA/O Ⅱ and the preference adsorption mechanism of FA/O Ⅰ nonionic surfactant to improve the uniformity of the surface chemistry function with the electrochemical corrosion research, such as OCP-TIME curves, Tafel curves and AC impedance. The result is that the stock polishing slurry (with SiO₂ abrasive) contains 1 wt.% H₂O₂ ,0.5 wt.% FA/O Ⅱ and 1.0 wt.% FA/O Ⅰ nonionic surfactant. For a fine polishing process, 1.5 wt.% H₂O₂ , 0.4 wt.% FA/O Ⅱ and 2.0 wt.% FA/O Ⅰ nonionic surfactant are added. The polishing experiments show that the removal rates are 3000±50 Å/min and 1600±60 Å/min, respectively. The surface roughnesses are 2.05±0.128 nm and 1.59±0.081 nm, respectively. A combination of the functions of FA/O Ⅱ and FA/O Ⅰ nonionic surfactant obtains a controllable removal rate and a better surface roughness in alkaline solution.     

铝栅碱性CMP的析氢腐蚀北大核心

采用碱性抛光液对铝栅进行化学机械抛光(CMP),在pH值大于8.3时会发生析氢反应,表面产生氢气泡,在铝栅表面留下大量蚀坑缺陷,降低平坦化效果,严重影响芯片器件性能的完整性和可靠性。对铝栅在碱性介质CMP条件下的析氢反应机理及控制理论进行了深入探究。通过接触角实验和静态腐蚀实验,并结合金相显微镜观察静态腐蚀后表面状态,发现抛光液中加入FA/O I非离子型表面活性剂可有效抑制碱性环境中铝栅CMP析氢腐蚀。通过实验得出,当碱性抛光液中FA/O I非离子型表面活性剂的体积分数为1.5%时,抛光液的表面张力最小,接触角最小,抑制析氢腐蚀效果最好。