新型抑制剂对铜膜CMP后碟形坑与蚀坑的影响

Effect of new inhibitors on dishing and erosion of copper film after CMP

为了控制铜膜(Cu)表面在化学机械平坦化(CMP)过程中产生碟形坑、腐蚀坑等缺陷,提出了将3-巯基-1,2,4-三氮唑(TAT)作为CMP抛光液中的抑制剂,研究了在抛光液低pH值条件下不同TAT浓度对Cu去除速率(RR)及静态腐蚀速率(SER)的影响,还研究了TAT对铜膜CMP后碟形坑和蚀坑的控制效果,并分析了其机理。铜膜去除速率和静态腐蚀速率实验结果显示:在抛光液低pH值条件下,随着TAT浓度的升高,Cu的去除速率和静态腐蚀速率均出现大幅下降,TAT能够起到抑制Cu去除速率的作用。碟形坑和蚀坑深度实验结果显示:采用加入TAT的抛光液抛光后,铜布线宽度/间距(L/S)为100μm/100μm的碟形坑深度由355 nm降为77 nm,L/S为9μm/1μm的蚀坑深度由172 nm降为81 nm,TAT能够有效控制抛光后碟形坑和蚀坑的深度。其控制机理为TAT能够与Cu形成一层钝化膜并吸附在铜膜表面阻碍其进一步的化学反应,并在机械作用下使得铜膜表面凸出和凹陷处产生较大的去除速率差,最终减小抛光后碟形坑和蚀坑的深度。

In order to control the surface defects of copper film(Cu)such as dishing and erosion produced in the process of chemical mechanical polishing(CMP),1H-1,2,4-Triazole-3-thiol(TAT)was proposed as an inhibitor in CMP slurry.The effects of different TAT concentrations on the Cu removal rate(RR)and static erosion rate(SER)at low slurry pH were studied.The effects of TAT on the dishing and erosion of copper film after CMP were studied and the mechanism was analyzed.The experimental results show that under the condition of low pH,the RR and SER of Cu decreases significantly with the increase of TAT concentration in the slurry,indicating that TAT can effectively inhibit the Cu removal rate.The experimental results of dishing and erosion depth show that after polishing with the slurry added to TAT,the depth of dishing and erosion with different copper wiring line width/spacing(L/S)are significantly reduced,so the inhibitor TAT can effectively reduce the depth of the dishing and erosion after polishing.It is believed that TAT can form a passivation film with Cu and adsorb on the surface of copper to hinder the further chemical reaction,and make a large difference in the removal rate on the surface of Cu under mechanical treatment,and finally reduce the depth of dishing and erosion after the polishment.