Electron Beam Lithography Processes

Single Resist Process

PMMA

  1. Prepare a Si substrate
  2. Spin on PMMA 950 A
  3. Bake on a hotplate at 180 °C for 2 minutes
  4. Expose patterns at a dose of 100 through 900 [uC/cm2] at steps of 100 [uC/cm2]
    • The critical dose for PMMA is approximately 350 [uC/cm2]
  5. Develop by immersion in IPA:Water (2:1) for 1 minute
  6. Blow dry with nitrogen/li>

PMMA is a high resolution positive tone photoresist. It costs approximately $0.75 per milliliter and remains stable for many years.

HSQ

  1. Prepare a Si substrate
  2. Spin on HSQ
    • Refer to the Dow Corning XR-1541 data sheet to select the proper concentration and spin speed for a desired thickness
  3. Bake on a hotplate at 90 °C for 1 minutes
  4. Expose patterns at a dose of 500 through 1300 [uC/cm2] at steps of 100 [uC/cm2]
    • The critical dose for HSQ is approximately 700 [uC/cm2]
  5. Develop by immersion in TMAH 25% for 1 minute
  6. Blow dry with nitrogen

HSQ is a high resolution (sub 10 nm) negative tone resist. It costs approximately $5.25 per milliliter and has a short shelf-life of 6 months. The maximum thickness for HSQ is approximately 180 nm.

PHOST

  1. Prepare a Si substrate
  2. Spin on PHOST
  3. Bake on a hotplate at 170 °C for 2 minutes
  4. Expose patterns at a dose of 6000 through 15000 [uC/cm2] at steps of 1000 [uC/cm2]
    • The critical dose for PHOST is approximately 10000 [uC/cm2]
  5. Develop by immersion in PGMEA for 1 minute
  6. Blow dry with nitrogen

PHOST is a low resolution negative tone resist. PHOST resist is not sold commercially, but can be prepared in the lab.