A case study of pad dual profile issues encountered at pad etch

The paper is to present report regarding the pad dual profile issues encountered in the production line. The pad dual profile is observed for thick passivation layer at the wafer edge. The defect caused the pad open area to be distorted. The location is at the wafer edge. Engineering simulation was performed to simulate the pad dual profile and understand the root cause. There were many factors contributing to the pad dual profile. The most significant is the thermal factor. The other factors were photoresist thickness, processing time, radio frequency (r. f.) power, gas ratio, passivation layer thickness and the wafer cooling efficiency. The split run was performed by varying the backside helium flow and varying the photoresist thickness. It is perceived that the backside helium cooling is the main contributor to cause the pad dual profile. The backside helium flow split has the highest severity impact on the result. The processing chamber which has dual backside helium cooling is used to perform the simulation. The wafer map for the edge zone which is flowing with low flow matches the defect area location.