Error Budget of Wafer Bonding Alignment System Based on Vision¹

Accurate wafer alignment is the key to achieving wafer bonding accuracy. High-precision wafer alignment systems typically use vision to locate the aligned Mark on two wafers, and use complex mechanisms to perform multiple composite movements to achieve functionality, making the coupling effect of multiple types of errors more complex and challenging the error budget of wafer alignment systems. This paper proposes an error budgeting method for such vision based multibody precision systems. This method takes the homogeneous transformation matrix (HTM) method as the core to model the system error and establish two types of error transfer chains. For the error chain involving visual measurement, an analysis method based on geometrical optics is proposed to consider the influence of the position and orientation errors of the optical path components. Then organize the possible error sources in the system and model the parameters of each error based on actual test results. Combined with the process flow, customize the error model for each link. Finally, perform Monte Carlo simulation. Using the aforementioned method to budget errors for a certain configuration of wafer alignment system, main error sources were identified, and accuracy indicators were proposed based on the alignment accuracy requirements of ± 200 nm. The rationality of the error budget conclusion in this study has been verified through experiments on the construction machine.