The study on the effect of multi-level exposure technique to fabricate air bearing surface microstructure

Many photolithography and etching steps for a fabrication of an Air Bearing Surface (ABS) structure which is responsible for the aerodynamic behavior of a read/write head make a significant impact to HDDs overall cost. To reduce a cost/time consuming, the ABS can be fabricated by a technique called "multi-level exposure". This technique focuses on the exposure by changing the TV light intensity after moving the stage to a new position until all positions are completely exposed. The exposed wafer is then developed and etched in a single step to form 3 levels of the ABS structure. The relation between the remaining photoresist (PR) film thickness and the singleand the double-exposure dose can be calculated by using the exponential equations with 95.8% and 91.5% correlation, respectively.