Development of an I-Line Negative Resist Process for High Resolution
Surface Acoustic Wave (SAW) devices require the formation of dense line and space structures referred to as inter- digital transducers (IDTs). Precise dimension control of these features is essential to the performance of the device. Design requirements for SAW applications are becoming more aggressive such that standard process capability is restrictive. Therefore, a new process development effort was initiated to enable a simple, yet lower cost process, which can precisely and repeatedly define the IDT structures with critical dimensions anywhere from 1um to as low as 300nm. Such a process capability is beneficial not only in SAW manufacturing, but could easily be used in other wafer fabrication environments. This paper discusses the process development effort to establish a fine line liftoff process using a negative tone resist for a SAW filter application. Discussion is focused on the process optimization sequence required to enable a robust process which can define features as small as
300nm using existing 365nm stepper technology.
Keywords: High Resolution, Liftoff, Process Development, Process Capability