Pre-bond megasonic cleaning with improved process control

Abstract

A pre-bond cleaning process was developed utilizing a unique, radially uniform, large area proximity type Megasonic transducer. In prior work this new cleaning method was investigated for PRE (particle removal efficiency) as well as particle neutrality. These tests yielded higher values than those achieved with the processes of record. Subsequently, this process was integrated into an industrial volume low temperature fusion bonding process and enabled higher bonding yields. In the above process flow the process fluid was dispensed to fill the gap between the Megasonic transducer surface and the substrate using an atmospheric free flow stream applied to the substrate. Current work describes development, testing and operational verification of a process fluid management device used in conjunction with the wide area proximity Megasonic transducer. The goals of this development were reduction of process fluid amount required, increase the operating substrate rotation speed, and provide better control of process fluid parameters. The design criteria and process flow as well as test results demonstrating the benefits of the new system are presented.