Double‐layer resist method to improve descum result when removing negative photoresist

A novel double‐layer resist method was presented in this work to decrease the negative photoresist scum. Positive photoresist was chosen as the bottom layer resist and negative photoresist as the top layer resist. This work studied the effect of viscosity and thickness of bottom layer resist on the mean number of scum. The experiment shows that the low viscosity positive photoresist AZ703, with the spin speed of 3000 r/min and the thickness of 1.10 um, had prominent effect on the removal of photoresist. To minimise the area of the top layer contact with substrate and further reduce the scum, 8 µm was selected as the optimal retracting distance d of the bottom layer resist.