Profile control processes based on contact types in silicon wafer DSP manufacturing management

Abstract

To reduce the manufacturing cost of integrated circuits, the size of the silicon wafer has become larger, with the diameter increasing from 200 to 450 mm. The large diameter silicon wafer poses challenges to the manufacturing process, as its surface profile is more difficult to control and the planarization process is harder to optimize in mass production. Based on different types of contact, gap adjustment and convex pad dressing methods were proposed in this paper to control the pressure distribution on the wafer, which further influenced the wafer profile. Pressure distributions with different gap values and different pad profiles were explained with contact mechanics and verified by simulations. The simulation results show that a negative gap value and a convex pad profile contribute to the improvement of the pressure uniformity on the wafer. Both methods were then applied in the double-sided planarization (DSP) process of 300 mm silicon wafers. The results from the test run of the DSP process show that wafer flatness is improved with a negative gap value. This indicates that gap adjustment is an effective approach for wafer profile control. In the subsequent mass production of the DSP process, silicon wafers with a global flatness of 120 nm and a site flatness of 21.7 nm were obtained.