EBL Fabrication Protocol

EBL Fabrication Protocol

EBL Fabrication Protocol

Joshua Sadar, Xiangbing Jiao, Ching-wei Tsao

Outline

  1. Chip Preparation
  2. Resist Spin-coating

III. Exposure

  1. Development
  2. Metal Evaporation

 

  1. Chip Preparation
  2. Use silicon chip of appropriate size
  3. Clean chip (front and back) with acetone. Flush thoroughly with isopropanol to avoid  acetone residue.
  4. Dry wafer with N2.

 

  1. Resist Spin-coating (to be done in PSF 303)

Note:   If employing a double-layer procedure, follow the same procedure for both layers. When spin-coating SU8, turn off the light and use the yellow light during whole procedure.

  1. Use sterilized pipettes to get desired amount of resist. This makes the resist to be sealed in the pipettes and prevents its evaporation. Put the each pipette in a plastic cup. Get rid of first few drops before depositing resist on chip surface.
  2. Deposit a few drops (enough to cover) on wafer surface
  3. Spin 10s @ 840 RPM / 40s @ 4020 RPM (recipe 1 on controller)
  4. Bake 10min at 180C
  5. Wipe spinner and hot plate using acetone after spin-coating.

 

III. Exposure – JEOL EBL writer (consult operating manual for full directions on use)

  • Log book entry
  • Note: If the A1/A2 Current reaches 300uA (emmission), the tool requires service.
  • Unload cassette
    1. Verify Status: Stage Init (LED on), Position Init (LED (red light) on), Vi Button is OFF (Gate valve is closed), ALL direction arrows are blinking.
    2. Unhinge SEC Door (rotate door counter-clock-wise)
    3. Press VENT to vent the loading chamber
    4. Press VENT again after door opens automatically to stop venting
    5. Lock CASSETTE FLAP
    6. Elevate transfer rails
    7. Release CASSETTE LOCK
    8. Pull out cassette from the rail
    9. Unlock CASSETTE FLAP
    10. Remove cassette
  • Sample placement
    1. Place Cassette #1 upside-down, onto the circular Teflon platform located on the manual alignment fixture.
    2. Removed the backing plate of the exposure aperture (A, B, C or D) by rotating the locking tab.
    3. Place the sample into the exposure aperture with the PMMA coated side, facing DOWN.
    4. Secure the backing plate onto the exposure aperture.
    5. Blow off the entire cassette with dry Nitrogen Gas located in the rear of the laboratory.
  • Load cassette
  1. Insert cassette (Teflon side DOWN) (substrate facing up)
  2. Lock CASSETTE FLAP
  3. Push cassette back to SEC chamber
  4. Engage CASSETTE LOCK
  5. Unlock CASSETTE FLAP
  6. Lower transfer rails
  7. Close and Hinge the SEC Door and the SEC chamber is going to pump down automatically.
  8.  

While waiting for the S.E.C. vacuum pressure to equalize with the Exposure column, there are a number of computer operations that can be done. Typically, ~30 minutes

3a. If necessary, use alignment cameras to zero sample theta and record coordinates of P-mark

  1. Use N2 gun to clean cassette surface. Load cassette into exchange chamber and start pump
  2. While exchange chamber is pumping, perform basic tool calibration for desired current level

 

  1. Conversion of .GDS to .J51 (Convert .GDS pattern design to .J51 format that the tool uses to generate the e-beam writing.)
    1. L-clk JEOL Icon (Opens EBX window)
    2. L-clk JBX Filer
    3. Select CAD DATA List
    4. Double-clk “……/user/stm” (The PATH to the Source File)
    5. Highlight “FILEn.gds”
    6. R-clk “FILEn.gds”/INFORMATION
    7. L-clk FILE INFORMATION
    8. Select SCREEN and then OK
    9. R-clk “FILEn.gds”
    10. L-clk CONV
    11. Enter TOP STRUCTURE (Reference INFORMATION window, Case Sensitive, ALL CAPITAL words are recommended)
    12. Enter UP-LT, LOW-RT (Reference INFORMATION window, eg. X1,Y1,X2,Y2)
    13. Enter LAYER NUMBER (Reference INFORMATION window, eg. nn/0)
    14. L-clk ADD NEW LAYER and then OK
    15. Rename OUTPUT FILE, for consistency use “FILEn. j51”
    16. Select OUTPUT UNIT (Use higher numbers for fine features to maintain perpendicular write/beam angle to the substrate (smaller write areas))
    17. Press OK
  2. Creation of .PCHK file (.PCHK is file format for display )
    1. L-clk JEOL Icon
    2. L-clk JBX Filer (Opens JBX Filer window)
    3. Select CAD DATA List
    4. Double-clk “……/user/j51” (The path to the .j51 Source File)
    5. Highlight and R-clk “FILEn.j51”
    6. L-clk Convert to Graphical Data and then OK
    7. L-clk REFRESH Button to update the list of files
    8. Highlight and R-clk “FILEn.pchk”
    9. L-clk DISPLAY DATA and L-clk DISPLAY and OK
  3.              This opens Graphical Display, having a BLACK and GREEN appearance. Within this graphical display, use the COMMAND BLOCK to verify design. Make measurement(s) to determine that the proper SCALE attributes have been employed during the                       conversion.
    1. L-clk DRAW to DISPLAY pattern
    2. L-clk END and FILE/END and then YES to return to JBX Filer
  4. Conversion of J51 to .PTD and .PTN
    1. highlight correct .j51 file
    2. R-clk and select READ(data)
    3. Set the directory to desired path for .ptd and .ptn file to go
    4. Set the EOS mode to 7, your resize, if any, and the scan step to “1” and OK
    5. If this is a re-write an duplication window will open, just select “overwrite” and the existing file will be overwritten.
  1. Creation of .SDF SCHEDULE file
  2. L-clk FILE MANAGER/HOME FOLDER
  1. Double-clk “…../job/user” and double-clk “FILEn.sdf”

It will open a TEXT EDITOR, the following information need to be edited

MAGAZIN  ‘  ‘         (Do not alter)

#1               (Cassette #, Do not alter unless using another cassette)

%2B(%2A=5x5mm)  (Location of sample within the multi-piece cassette)

JDF  ‘FILEn’, 1           (Modify with your FILEn. Do not specify .EXT)

EOS 7, U50-100pA           (Modify with your MODE and CONDITION FILE)

GLMDET  M               (Global Mark Detection: Manual or Automatic)

WFR3M  9

OFFSET  (0,0)       (Sample center relationship to the Aperture center)

END  1            (Do not alter unless using a different cassette, refer to “#1”)

  1. L-clk FILE/SAVE AS to save file to “……/Job/User/”
  2. Name file “FILEn.sdf” and OK and FILE/CLOSE to close TEXT EDITOR
  3. Creating .JDF JOBDECK file
  4. L-clk FILE MANAGER/HOME FOLDER
  5. Double-clk “…../job/user” and double-clk “*FILEn*.jdf”

It will open a TEXT EDITOR, the following information need to be edited

JOB ‘FILEn’, 2.0(ALL capital letters/No spaces/No .Ext, refers to 2 in. work piece)

GLMPOS P=(-X,0),Q=(X,0)            (coordinate of the P alignment mark – from Design)

GLMP 4.0, 1500,0,0;(P mark width=4um, Length=1500um, Only for Auto-Align)

GLMQRS 4.0, 1500,0,0;     (QRS widths=4um, Length=1500um, Only for Auto-Align)

PATH

ARRAY  (0,1,0) / (0,1,0)      (Start, Array Size, Pitch)

ASSIGN  P(1)→ (*,*)            (UNKNOWN)

PEND

LAYER  1

P(1)  ‘FILEn’  (0,0)    (Offset of Design center to ABSOLUTE ORIGIN)

EOS  7  ‘U50_100pA’          (Mode and Condition File)

SHOT  A,4     (A utomatic, Pitch)

RESIST  350, 3        (2% PMMA)

END

  1. L-clk FILE/SAVE AS to save file to “……/Job/User/”
  2. Name file “FILEn.jdf” and OK and FILE/CLOSE to close TEXT EDITOR
  3. Creating .MGN MAGAZINE file (.MGN Compiles all FILES and DATA into a MACHINE usable form to EXECUTE an Exposure Session.)
  4. L-clk FILE MANAGER/HOME FOLDER
  5. L-clk File/Open Terminal
  6. Type: “schd FILEn”
  7. Type: “EXIT”
  8. Verify .MGN with ARRAY CHECK to verify their ARRAY declaration. The BLUE box define the limits of the pattern and the number is the field number.
  9. L-clk ANALYSIS icon on the EBX Menu.
  • ACHK icon
  1. ZOOM IN (use L-clk&Drag to define a ZOOM area)
  2. Transfer cassette from SEC to Exposure column
  • Press Step-Up button (Red LED in the level of the first cassette Green LED will appear)
  1. Press Vi Button to open gate valve
  2. Press Transfer Button
  3. Press Vi Button to close gate valve
  4. Setup gun current
  5. L-clk JOEL ICON
  6. L-clk CALIB ICON
  • L-clk EOSSET
  1. L-clk SELECT CONDITION FILE
  2. L-clk SELECT EOS MODE 7 Note: Modes 3 and 4 uses 4th lens, Modes 7 and 8 uses 5th
  3. Select desired condition file and OK
  4. EDIT PARAMETER
  5. Check RESTOR EXECUTION and DEMAG boxes
  6. L-clk RUN
  7. L-clk SAVE & CANCEL
  8. Current Saturation(This step adjust the actual current to deigned current amplitude)
  9. L-clk CURRNT
  10. L-clk SUB-PROGRAM EXECUTION. (This moves the stage to the Faraday Cup where the current can me measured and changed.
  1. L-clk LOCAL
  2. L-clk SUB-PROGRAM EXECUTION (Enables manual console controls
  3. Press 2/3 Lens Button  (LED on)  This button MUST be pushed first, this keeps the 2nd and 3rd lenses moving in tandem as to not totally misalign the beam from lenses 4 and 5.)
  • Press 2nd Lens Button (LED on)
  1. Press G_AL Button (LED on)
  2. Press BLK Button (LED off)
  3. Adjust HORIZ Controls (find the PEAK VALUE for the current: X-Atten and Y-Level)

Note: DO NOT adjust the x- and y- knobs, these should be left at zero, if they are not zero please adjust back.

  • Adjust FOCUS: COURSE & FINE knobs (to the desired current value (eg. 50pA, 100pA, 500pA). This is the same current value that you selected in EOSSET.
  1. Press BLK Button (LED on)
  • Press G-AL Button (LED off)
  1. Press 5th Lens Button (LED on)
  2. Perform focus adjustment (This step adjusts the stage to a focused level)
  3. L-clk STGCOM
  4. L-clk EDIT PARAMETER
  5. L-clk SELECT (Opens Selection Menu)
  6. Double-clk MESH MARK

Note: Turning OFF the room lights will make it easier to view the screen.

  1. Press SEI Button (if nothing is visible, reduce the MAG)
  2. Press SPD Button (LED on, to adjust scan rate, Use COARSE [Left] Button, as necessary)


Adjust   BRIGHTNESS and CONTRAST knobs     (for optimal screen image)

Press   MAG Button     (LED on, Enables magnification UP or DOWN with arrows)

Note: The MAG value represented by the two numbers reads n1x10n2, e.g. the lowest MAG number is 13, which the user reads at 1×103 or 1e3 or 1000, all the way up to 78 or 7e8 or 700,000,000.

9a. If necessary, find coordinate marks for manual alignment or calibrate mark detection for auto-alignment

  1. Expose the design, following instructions for manual mark detection if necessary. For PMMA, proper dosage

depends on the resist(s) being used and should be determined by a dose test. For SU8, dose should be 3.5 μC/cm2.

  1. Unload cassette from exposure chamber
  2. Vent exchange chamber, remove cassette, and remove sample from cassette
  3. Use N2 gun to clean cassette surface. Load cassette into exchange chamber and start pump
  4. Log off computer

 

  1. Development (to be done in PSF 303)
  2. For PMMA Resist
  3. Prepare plastic cups and graduated cylinder
  4. Retrieve MIBK from lab refrigerator
  5. Prepare 1:3 MIBK:IPA development solution in plastic beaker
  6. Prepare IPA rinse in plastic beaker
  7. Immerse chip in developer solution for 90s. Use gentle stirring motion
  8. Immerse chip in IPA rinse for 30s to stop reaction. Use gentle stirring motion. Dry chip with N2

 

  1. For SU8 Resist
  2. Make sure the light is turned off. Use yellow light instead.
  3. Set the hot plate’s temperature to be 75 °C. Put the chip on hot plate for 2 minutes to perform post exposure baking (PEB). After PEB, the pattern should be visible.
  4. Immerse chip in SU8 developer for 1 min. No need to stir.
  5. Rinse the chip using IPA for 30s. Dry the chip with N2.
  6. Ramp on hotplate from RT to 180°C, bake at 180°C for 5 min, ramp down to RT.
  7. Wipe hot plate surface using acetone after baking.

 

  1. Metal Evaporation (Lesker #3 PVD)

Note: For SU8 resist, there is no need to do metal evaporation.

  1. Run chamber vent recipe
  2. Clean chamber
  3. Wipe door gasket area with IPA on cleanroom wipe
  4. Vacuum chamber interior. DO NOT MAKE CONTACT WITH FILAMENT
  5. Replace plastic window cover if necessary
  6. Load Au and Cr crucibles in chamber
  7. Load sample in chamber
  8. Unload platen from top of chamber. Lift up slightly, then pull out.
  9. Fix sample as close to center of platen as possible
  10. Return platen to position in chamber
  11. Run pump-down recipe – wait for pressure to reach 3×10-6 Torr.
  12. Deposit Cr
  13. Rotate crucible holder to Cr source
  14. Turn on e-beam HV
  15. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is ~1Å/s
  16. Deposit 50 Å of Cr (5 nm)
  17. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS

DAMAGE TO THE CRUCIBLE MAY OCCUR.

  1. Turn off e-beam HV
  2. Deposit Au
  3. Rotate crucible holder to Au source
  4. Turn on e-beam HV
  5. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is 1-2Å/s
  6. Deposit 550 Å of Au (55 nm)
  7. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS

DAMAGE TO THE CRUCIBLE MAY OCCUR.

  1. Turn off e-beam HV
  2. Deposit Al (per CSSER regulations)
  3. Rotate crucible holder to Al source
  4. Turn on e-beam HV
  5. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is 2-3Å/s
  6. Deposit 2000 Å of Au (200 nm)
  7. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS

DAMAGE TO THE CRUCIBLE MAY OCCUR.

  1. Turn off e-beam HV
  2. Wait 5-10 minutes for sources and sample to cool
  3. Run chamber vent recipe
  4. Unload Cr and Au crucibles
  5. Unload sample; replace platen
  6. Clean chamber
  7. Wipe door gasket area with IPA on cleanroom wipe
  8. Vacuum chamber interior. DO NOT MAKE CONTACT WITH FILAMENT
  9. Replace plastic window cover
  10. Run pump-down recipe
  11. Lift-off
  12. Select a glass container sufficient in size to hold the substrate
  13. Fill container with Acetone to a sufficient level to cover the substrate
  14. On a hotplate, heat the acetone to 70 ⁰C.
  15. 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.

  1. Remove the substrate from acetone, and rinse with IPA, then blow dry with nitrogen.