Study of Negative Charge Accumulation Mechanism and Removal Method on the Wafer Surface in Via Photo Development Process

Influence of the wafer surface charging effect on the precision of measuring ADI features during photo development process using CD-SEM was reported. An initial mechanism has been proposed that the surface charge generation may be related to previous hard mark opening and via photo development, but the essential generation mechanism has not been clarified clearly. In this paper we will report some further studies for the mechanism analysis and removal of the generated surface charge. By measuring the wafer surface potential with partition check, we found that deionized water (DIW) used in via photo development process would induce to negative charge accumulation on the wafer surface. Based on this mechanism, a functional rinse containing surfactant molecules was used after DIW rinse to absorb the surface charge and take it away. Finally, the removal approaches of the generated surface charge was discussed by optimizing the dispense time and spin speed of functional rinse.