Projection (Stepper) Lithography

Projection (Stepper) Lithography

 

 

 

 

 

 

 

 

 

We have two GCA i-line wafer steppers that use masks compatible with both systems. System Features are:

  • 5” x 5” x .09” mask size; special mask alignment marks available
  • 15 mm x 15 mm maximum die size
  • 1 cm x 1 cm pieces up to 4 inch wafers with custom wafer holders
  • Autofocus system
  • Resolution of ~ 500 nm (6300 system) and ~ 400 nm (Autostep 200)
  • Alignment accuracy of ~ 250 nm using manual alignment
  • Alignment accuracy of ~ 150 nm using automatic alignment
  • Positive and negative high resolution resists and processes available
  • Automatic leveling and mask aperturing on Autostep 200 system

 

Established Processes

 

Recipes for projection lithography are developed for flat silicon wafers. Exposure times and focus offsets may change depending on substrate type and surface topography. In general, an exposure time and projection lens focus variation is done to determine best focus. Also, for projection lithography using a monochromatic source, a resist post exposure bake (PEB) is needed to wash out standing wave effects in the resist sidewalls. Contrast enhancement materials (CEMs) are available to increase the process tolerance window and improve resolution. We also have some experience with RELACS for narrowing trench widths. Positive and negative resists are available.

 

Technical and educational staff services are possible through the generosity of the National Science Foundation through support via the NNIN.