Abstract
Surface activated bonding is a three-dimensional wafer stacking technology utilized in the semiconductor field. In this process wafer surfaces are activated by argon atoms irradiated from a fast atom beam source, allowing bonding to take place is at room temperature and low pressure. However, fast atom beam sources present an issue wherein carbon agglomerates, responsible for bonding defects, are discharged alongside the argon atoms. Therefore, it becomes necessary to replace the carbon electrode before these aggregates released. However, quantitatively measuring the ideal time for replacement has been challenging. To address this concern we developed and validated a quantitative in-process measurement method for monitoring discharged carbon agglomerates. This method involves illuminatinge the wafer surface, capturing dark-field images of carbon agglomerates, and performing image processing to quantify measure the amount of discharged carbon agglomerates discharged. In order to establish a reliable relationship between the size of carbon aggregates (maximum Feret diameter) and the corresponding maximum Feret diameter in the dark-field image, we conduct an investigation. The results of the measurement indicated a significant increase in the number of discharged carbon agglomerates after 150 irradiations. Moreover, the largest number of carbon agglomerates was detected in the area between 5 and 7 pixels. These results suggest that the formation of carbon agglomerates occurs through exfolitation, particularly when the irradiation is temporarily interrrupted before the 150th irradiation.
