Nanoimprint Processes

Nanoimprint

Si/SiO2 Mold: Cavity

Substrate: Si/SiO2(500nm)

  1. Spin on 115nm of PMMA resist
    1. Dispense PMMA 950 C2 on wafer
    2. Spin at 2500 rpm at 1250 rpm/s for 60s
    3. Bake at 180C for 2 minutes
  2. Expose pattern in ebeam writer
    1. The critical dose of PMMA is approximately 300 uC/cm2
  3. Develop pattern in 2:1 IPA:Water for 1 minute
  4. Process mold in RIE180 using the recipe LVC Quartz Mold
    1. Etch SiO2:PMMA
    2. Remove residual PMMA
    3. Coat with anti-sticking layer

Si/SiO2 Mold: Protrusion

Substrate: Si/SiO2(500nm)

  1. Spin on 115nm of PMMA resist
    1. Dispense PMMA 950 C2 on wafer
    2. Spin at 2500 rpm at 1250 rpm/s for 60s
    3. Bake at 180C for 2 minutes
  2. Expose pattern in ebeam writer
    1. The critical dose of PMMA is approximately 300 uC/cm2
  3. Develop pattern in 2:1 IPA:Water for 1 minute
    • *Caution* Pattern will continue to develop beyond 1 minute
  4. Deposit 10 nm of Cr in ebeam evaporator
  5. Lift-off
    1. Immerse in acetone
    2. Ultrasonic agitation with heat for 30 minutes
    3. Rinse with fresh acetone while removing sample from bath
      • If acetone dries, a lot of Cr particulate will stick on sample surface
    4. Rinse with IPA
    5. N2 Dry
  6. Process mold in RIE180 using the recipe LVC SiO2:Cr
  7. Remove Cr in CEP 200
    1. Immerse in CEP 200 for 3 minute
  8. Apply anti-sticking layer

Imprint: mr-I 7000R

Substrate: Si/SiO2(500nm)

  1. Spin on mr-I 7000R resist
    1. Dehydration and cool to room temperature immediately before coating
    2. Select mr-I resist based on desired thickness
      • mr-I 7010R is approximately 100 ± 15 nm
      • mr-I 7020R is approximately 200 ± 15 nm
      • mr-I 7030R is approximately 300 ± 20 nm
    3. Spin at 3000 rpm at 1250 rpm/s for 30s
    4. Bake at 100C for 1 minute
  2. Place mold on sample
  3. Place sample and mold on a 3 inch wafer
  4. Place the wafer inside the nanoimprint instrument
  5. Imprint with the following conditions
  6. Pump Time [s] 120
    Temperature [C] 90
    Pressure [psi] 500
    Duration [s] 60

The datasheet recommends imprinting at 120-140 °C and 290-580 psi for 60-240 seconds. The recipe described showed no flow boundary defects.

Imprint: HSQ

Substrate: Si/SiO2(500nm)

  1. Spin on HSQ resist
    1. Select HSQ resist based on desired thickness
      • HSQ 2% is approximately 35 nm
      • HSQ 4% is approximately 73 nm
      • HSQ 6% is approximately 110 nm
    2. Spin at 3000 rpm at 1250 rpm/s for 60s
    3. Bake at 90C for 1 minute
  2. Place mold on sample
  3. Place sample and mold on a 3 inch wafer
  4. Place the wafer inside the nanoimprint instrument
  5. Imprint with the following conditions
  6. Pump Time [s] 120
    Temperature [C] 0
    Pressure [psi] 500
    Duration [s] 60

HSQ can be imprinted at room temperatures, but it requires significant amount of pressure. This recipe uses the maximum pressure the instrument is capable of producing.

Imprint: PMMA

Substrate: Si/SiO2(500nm)

  1. Spin on PMMA resist
    1. Select PMMA resist based on the desired thickness
    2. Spin at 3000 rpm at 1250 rpm/s for 60s
    3. Bake at 180C for 2 minute
  2. Place mold on sample
  3. Place sample and mold on a 3 inch wafer
  4. Place the wafer inside the nanoimprint instrument
  5. Imprint with the following conditions
  6. Pump Time [s] 120
    Temperature [C] 150
    Pressure [psi] 500
    Duration [s] 60

Nanoimprint was initially developed using PMMA. PMMA is cheap, stable and commonly available in any nanofabrication facility.