Regrowth Process

Adopted from Patterning substrates for MBE growth – 130205 by VDD Written by NTS 09/23/2014. Modified by NTS 141106

Note: Read Regrowth Processing Notes before running process

Note: GaAs (100) substrates must be cleaved into quarters and in sample holders to begin

Note: Line all surfaces dipper (and sample corner) will touch with LASE Paper Kimwipes. To line surfaces, place LASE kimwipes on top of clean room kimwipes

Note: Make an Al sample boat with lid for each step of the process. Keep samples covered

Deposit SiNx Hard Mask

1. Use wafer tweezers #1 for this step

2. Refer to PECVD procedure

3. Clean PECVD chamber

   1. Wipe out PECVD chamber and heat up

   2. O2 clean chamber for 30 minutes with O2cln250 (takes 42 minutes total)

4. Prime PECVD

   1. Place Si backing wafer on chuck

   2. Run Prime: Recipe AMC_SIN 10 minutes (takes 20 minutes total)

5. Deposit SiNx onto both sides of GaAs samples

   1. Run AMC_SIN for 15 minutes

   2. Open chamber and flip substrates to deposit on back sides

   3. Run AMC_SIN for 30 minutes

6. Remove substrates from PECVD and clean chamber

   1. Run O2 clean for 10 minutes

Lithography

1. Use wafer tweezers #2 for this step

2. Refer to Photolithograpy – MJB4 procedure

3. Remove AZ 5209E PR from fridge so it warms up to room temperature

4. Solvent clean

   1. Acetone – 3 min

   2. IPA– 3 min

   3. DI cascade rinse – 3 min

   4. N2 blow dry

5. Dehydration bake

   1. 150 C oven – 5 min

6. Spin on PR

   1. AZ 5209E

   2. 5k rpm

   3. 30 sec

7. Pre-exposure bake

   1. 90 C oven – 6 min

8. Align and Expose

   1. MJB4 contact aligner

   2. Place sample on stage Epi up

      1. Keep track of which SiNx side/color is up and down, esp for QI qtr

   3. Pay attention to wafer flat and position

   4. Align sample so that we etch along (11-0) AKA (1-10) (bar over middle number).

      1. Etch Parallel to Major, perp to minor flat

      2. Take your time to align mask

      3. Use underlining the UTexas text across the sample and multiple zoom levels

   5. Expose– 16 sec

9. Develop

   1. AZ 726 MIF or MF-26A – 15 sec

   2. DI rinse – 2 min

   3. N2 blow dry

10. Inspect wafer using optical microscope to confirm that features have resolved

Etch SiN, Remove PR

1. Use wafer tweezers #3 for this step

2. Prepare acid hood work area

3. Etch SiN (create openings in hard mask to match the pattern in the PR)

   1. BOE – 60 sec

   2. DI cascade rinse – 5 min

   3. N2 blow dry

4. Solvent clean to remove PR

   1. Acetone #1 to strip resist – 3 min

   2. Acetone #2 to clean -3 min

   3. IPA – 3 min

   4. DI – 3 min

   5. Switch to tweezer #4 after DI rinse

   6. N2 blow dry

Etch GaAs

1. Use wafer tweezers #4 for this step

2. Prepare GaAs etch solution – H2SO4 : H2O2 : H2O (1:8:1)

3. Etch GaAs (create V-grooves in substrate)

   1. H2SO4 Solution – 10 sec

   2. DI cascade rinse – 5 min

   3. N2 blow dry

4. Etch SiN (remove rest of hard mask)

   1. BOE – 60 sec

   2. DI cascade rinse – 5 min

   3. N2 blow dry

   4. At the end of this step, we’re left with only patterned GaAs, no more mask

Preparation to load into MBE

1. Use wafer tweezers #5 for this step

2. Solvent clean

   1. Acetone – 3 min

   2. IPA– 3 min

   3. DI cascade rinse – 3 min

   4. N2 blow dry

3. Put sample into desiccator to dehydrate, instead of cleanroom oven

4. Surface prep

   1. Oxidize wafer surface in UV Ozone – 30 min

5. Prep HCl : H2O (1:10) solution in the MBE lab

6. Unload the wafers from the UV Ozone system, take them to the MBE lab

7. Etch the surface oxide

   1. HCl solution – 1 min

   2. DI – 1 min

   3. N2 dry

8. Mount onto MBE wafer carrier and load into the MBE chamber

In MBE Buffer Chamber

• Clean with Atomic H