Photolithography Protocol (GCA stepper)

Photolithography Protocol (GCA stepper)

Photolithography Protocol (GCA stepper)
Draft 3.0

Outline
I. Chip Preparation
II. Spin Coating
III. Exposure
IV. Development
V. Metal Evaporation
VI. Lift-off

I. Chip Preparation
1. Use 3” or 4” Silicon Wafer or cleave wafer using a wafer scriber.
2. Clean wafer (front and back) with acetone. Flush thoroughly with isopropanol (IPA) to avoid
acetone residue.
3. Dry wafer with N2 gently.

II. Spin Coating (Cee coater is required. Consult operating manual for full directions on use)
1. Attach appropriate size chuck for the substrate to be coated. For sample smaller than 2’’, use the small chuck. For 3’’ or larger wafer, use the large chucks that requires an attachment screw to hold it on the spindle.

2. Install a catch tray for excess resist spin-off.
3. Adjust the pins on the hotplate for your samples size.

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4. Log in the system using password “RECIPE”. Select “Run Thermal Process”. Pre-heat the hot plate by running recipe “100C 60S”. Once the hotplate temperature has been reached, continue to the next step
5. Select “Run Spin Process”. Select recipe “4000RPM 40S”.
6. Place substrate on the chuck; if it a round wafer, use the centering device before hitting the Vacuum “Hold” button
7. Press the “Center” button on the screen to observe if the sample is centered
8. Once the wafer stops the slow speed spin for centering, dispense HMDS on the wafer. Close the lid and press “Start Process” button. Once the sample is completely stopped, hit the “OK” button
9. Select “Run Thermal Process”. Hit “Run Process” button and place wafer on hotplate. Once the bake process is complete, hit “OK” button.
10. Repeat step 6-9 for LOR3A and AZ3312.
11. Clean the spin coat bowl and hot plate.

III. Exposure – GCA 8500 Stepper (consult operating manual for full directions on use)
1. Illumination check
a. Log in the system. Type “[10,6]”. Enter password “QING”
b. Type “CHUCK” to change the chuck size to 100mm.
c. Type “LOAD” to move stage to loading position. Load a 4’’ wafer (provided by CSSER) on the chuck. DO NOT HIT THE OBJECTIVES WHEN LOADING THE CHUCK


d. Type in command “UNIF”. Select item 3 to check ad mechanically peak the UC intensity on the MAXIMUS illumination assembly.


e. The system will proceed to request stage initiation by pressing “RESET” and “MAN”, “S/C”, “MAN” to start the stage and move to the UV detector.


f. When pressing the “RESET” button, wait until the red LEDs on the wafer handler flash on and off before continuing with the “MAN’, “S/C, “MAN” buttons. Also, press the buttons for at least one second or they may not properly register the selection.

g. Flip the manual shutter switch to ON position. The switch is located in the rack below the console keyboard. Then type “C’ on the keyboard to continue.


h. Check the screen display above the operator console for peak bulb intensity and record this number.
2. Exposing wafer
a. Type in command “LOAD” to move the stage to loading position. Replace the testing wafer with your wafer if it’s 4’’. If your wafer isn’t 4’’, change the chuck to desired size.
b. Type in command “CHUCK” and change the chuck size.
c. Load the reticle to holder box. Make sure the bar code is in the right position
d. Type in command “INVENTORY” to verify the reticle is correctly loaded
e. Type in “EX **”. (** is the recipe name. Select recipe according to photoresist) Select the floor number of reticle
f. The system will proceed to request stage initiation by pressing “RESET” and “MAN”, “S/C”, “MAN” to start the stage and move to the UV detector
g. Tune the chuck stage position to align the wafer with marker
h. Make sure the wafer is properly aligned. Press the EXP button to expose wafer
i. After exposure, press ctrl+C and type in “A” to stop the process. Unload the wafer
j. Type in “RMSRET” to return the reticle to reticle box.
k. Type “L O” to log out the system
l. Close the door of stepper. DO NOT LEAVE THE DOOR OPEN, OR SYSTEM ACCURACY WOULD BE AFFECTED DUE TO TEMPERATURE INSTABILITY

IV. Development
1. Put on PPE (chemical gown, face shield, and chemical gloves)
2. Transport CD-26 developer and large (>4” diameter) beaker to base hood
3. Pour into beaker enough developer to completely cover wafer
4. Immerse chip in developer for 60s. Use gentle stirring motion
5. Rinse chip with DI water for 30s to stop reaction
6. Dry chip with N2

V. Metal Evaporation (Lesker #3 PVD)
1. Run chamber vent recipe
2. Clean chamber
a. Wipe door gasket area with IPA on cleanroom wipe
b. Vacuum chamber interior. DO NOT MAKE CONTACT WITH FILAMENT
c. Replace plastic window cover if necessary
3. Load Au and Cr crucibles in chamber
4. Load sample in chamber
a. Unload platen from top of chamber. Lift up slightly, then pull out.
b. Fix sample as close to center of platen as possible
c. Return platen to position in chamber
5. Run pump-down recipe – wait for pressure to reach 3×10-6 Torr (about 3 hours)
6. Deposit Cr
a. Rotate crucible holder to Cr source
b. Turn on e-beam HV
c. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is ~1Å/s
d. Deposit 50 Å of Cr (5 nm)
e. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS
DAMAGE TO THE CRUCIBLE MAY OCCUR.
f. Turn off e-beam HV
7. Deposit Au
a. Rotate crucible holder to Au source
b. Turn on e-beam HV
c. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is 1-2Å/s
d. Deposit 550 Å of Au (55 nm)
e. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS
DAMAGE TO THE CRUCIBLE MAY OCCUR.
f. Turn off e-beam HV
8. Wait 5-10 minutes for sources and sample to cool
9. Run chamber vent recipe
10. Unload Cr and Au crucibles
11. Unload sample; replace platen
12. Clean chamber
a. Wipe door gasket area with IPA on cleanroom wipe
b. Vacuum chamber interior. DO NOT MAKE CONTACT WITH FILAMENT
c. Replace plastic window cover
13. Run pump-down recipe
14. Deposit Al (per CSSER regulations)
a. Rotate crucible holder to Al source
b. Turn on e-beam HV
c. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is 2-3Å/s
d. Deposit 2000 Å of Au (200 nm)
e. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS
DAMAGE TO THE CRUCIBLE MAY OCCUR.
f. Turn off e-beam HV
VI. Lift-off
1. Select a glass container sufficient in size to hold the substrate
2. Fill container with Remover-PG to a sufficient level to cover the substrate
3. On a hotplate, heat the Remover-PG to 80 ⁰C.
4. Soak the substrate until the resist and deposited metal film have completely
lifted-off from the substrate. The time depends on metal area and thickness, and can range from tens of minutes to a few hours.
5. Remove the substrate from the Remover-PG, and rinse with isopropanol, then
blow dry with nitrogen.