Growth Principle And Prevention Of Crystal Defect On DUV Mask

With the Moore law development of semiconductor manufacturing, larger wafer size, more narrow line width, higher precision, more efficiency and lower cost are the most critical factors that semiconductor industry is continuing pursued. The repeated use of the mask in photolithography process which can easily grow tiny crystal particles on the surface of mask, these particles would be transferred to graphics defect on the wafer during the exposure, and it can cause wafer yield than before. Especially since the usage of 193nm developer, the low yield increase due to the surface crystal defect, which is a big challenge to litho engineer, so it’s an urgent project to study surface crystal defect formation mechanism and prevention solution.The crystal defect element analysis shows that the defect element is NH4+, SO42-, Cl- etc. From the paper and related document, the crystal defect formed under 193nm exposure light source, the infinitesimal NH4+, SO42- which permeate or adhere to the mask or NH4+, Cl- from the usage circumstance, which generate crystal object with acid and alkali chemical reaction. The occurrence and frequency of crystal defects on the mask surface is relate to the raw materials, production process and cleaning process; And wafer size, exposure wavelength, lithography process parameters, mask storage environment even habits are closely related. The wafer size increasing, exposure wavelength shorter, lithography pattern is more and more intensive is the mainstream development of semiconductor and trends. Therefore, solution of crystal defects on mask surface emphasis on improvement of mask production process, using environment and the usage mode.In the dissertation, through the way that mask cleaning process change from the traditional acid, alkali cleaning process to clear without acid and alkali process, in order to reduce the mask surface chemical ion adhesion. We proposed solution is that change mask usage and storage environment to ultra pure dry air, and applied "Queue and Queue-Time" function to control the time that mask leave stepper and protective equipment which can improve the effect of protection of ultra pure dry air. This solution can not only obviously improve lithography area environment and effect of stabilization, and also significantly reduce maintenance cost. Base on the principle of mask crystal defect formation and growth characteristics to optimize the inspection method and frequency of 193 nm exposure light source mask, which can maintain the quality of the mask and at the same time it can reduce defect detection equipment needs. With the wafer exposure technology and wafer graph defect detection, the development of alternative mask crystal defect detection which has the quick detection speed, high efficiency and timely effect, and also greatly reduce the cost of mask defect detection equipment, furthermore it can reduce mask crystal defects on wafer product yield, and lay a good foundation to continuous improvement of mask qualityThe research is focused on the crystal defect on 193 nm exposure light source mask. The defect growth mechanism is found, and combining the actual production in semiconductor industry, at the end a solution to solve the defects is proposed which is fit to wafer manufactory in the consideration of improving effect and implementation cost.