The Mechanism Study of Rounded AA Damage Defect after POLY Loop

AA damage is a common defect caused by particle residue, charge accumulation, abnormal etch and so on. In the actual production process, on different products such as logical and CMOS, it is found that the AA damage with the same characteristics can be observed after POLY loop to show regular circular and annular distribution, but impact wafer cannot find the regularity. In this paper, for the same form AA damage defect occurring after the POLY Loop, according to the impact wafer condition, and the information such as the condition of the front film, the etch condition and the pretreatment mode are deeply investigated, and the reasons for the AA damage defect are obtained: insufficient etch selection ratio, high vacuum cavity operation in the front layer and the influence of particle. The experimental results show that the generation of this type of AA damage can be effectively improved by prohibiting the operation of high vacuum cavity, adopting the pretreatment of removing particle and selecting the high selection ratio when the process is established.