Refractive Micro-Optics Fabrication With A 1-D Binary Phase Grating Mask Applicable To Moems Processing

We present a new photomask technology capable of forming a continuous rotationally symmetric microstructure in thick photoresist. This technique eliminates many of the drawbacks of grayscale and halftone masking technology. A binary phase grating of pi phase depth on a transparent quartz mask plate is fabricated in PMMA resist using an e-beam direct writing technique. When the phase mask is used in the stepper, an analog intensity profile is created on the wafer. The period is constrained, allowing for control of the zero-order in the stepper. The duty cycle of the phase gratings can be varied in such a way to provide the proper analog intensity profile for a wide range of micro-optics on the photoresist. The design, analysis, and fabrication procedures of this technique are discussed. This processing technique can be applied to many MOEMS devices that require refractive elements for optical processing. The method greatly simplifies the device process, reducing the cost and improving the device yield. © 2005 Society of Photo-Optical Instrumentation Engineers