Wafer Prep for Oxidizing Wafers (from TP Ma's Group)

This procedure applies to the case where the Si wafer has never been oxidized before.  For example, it is appropriate for forming steam oxides.



0)  Talk to someone in T.P.'s group to set up a time to use their ovens under their 

      supervision and get permission to use their clean beakers, boats, and tweezers.

1)  Rinse wafers in acetone with ultrasound for 180s.

2)  Rinse in running DI water for 60s.

3)  Rinse in methanol with ultrasound for 60s.

4)  Rinse in DI water for 120s.

5)  Soak in BOE for 30s.  Do NOT use a glass beaker to contain HF!

6)  Rinse in running DI water for 120s.

7)  Transfer wafers to beaker prefilled with fresh methanol.  This beaker may now be 

      carried to the furnace loading area and the wafer may be oxidized.

Wafer Prep for Photoresist

A wafer holder is convenient for when processing multiple wafers.  In this case, use 225mL of fluid.



1)	Use N2 to blow any junk out of sample holder.  Close sample holder.

2)	Ultrasound in 50 mL Acetone bath for 20s

3)	Ultrasound in 50 mL Methanol bath for 20s

4)	DI rinse under running water for 60s

5)	Remove from beaker bottom and N2 dry.

Wafer Prep for Electron-beam Resist

Do NOT use water with an e-beam resist!



1)	Use N2 to blow any junk out of sample holder.  Close sample holder.

2)	Ultrasound in 50 mL Acetone for 20s

3)	Ultrasound in 50 mL Methanol for 20s

4)	Remove from beaker bottom and N2 Dry.

Spinning/Baking Bilayer MMA(8.5)-MAA EL10/PMMA A3 950k (310-390nm total thickness on 2" wafer)

While the spin curves suggest that the MMA layer should be ~360nm thick and the PMMA layer ~180nm thick, our estimate is that the PMMA is ~105nm and the MMA is ~250nm thick



0)  Use "Silicon Wafer Preparation for Electron-beam Resist" recipe



Bottom Layer: MMA (8.5) MAA EL10

	

1)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 5000 rpm.

2)  With clean pipette cover entire wafer with MMA.

3)  Spin 60s @ 5000 RPM  

4)  Bake 60s @ 170C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Cool off



2nd Layer: PMMA A3 950



6)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 1500 rpm.

7)  With clean pipette cover entire wafer with PMMA.

8)  Spin 60s @ 1500 RPM 

9)  Bake 30 min @ 170C (Keep covered with petri dish)

10) Cool off

Spinning/Baking Single Layer PMMA A4 950k (180-190nm thick on 2" wafer)

While the spin curves suggest that the PMMA layer should be ~280nm thick, our estimate is that the PMMA is ~180-190nm



0) Use "Silicon Wafer Preparation for Electron-beam Resist" recipe

1) Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 2000 rpm.

2) With clean pipette cover entire wafer with PMMA.

3) Spin 60s @ 2000 RPM

4) Bake 30min @ 170C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5) Cool off

Spinning/Baking Single Layer PMMA A4 950k (180-190nm thick on 2" wafer--different bake time seems to have no effect)

While the spin curves suggest that the PMMA layer should be ~280nm thick, our estimate is that the PMMA is ~180-190nm.  The only difference between this and the previous recipe is the bake time.  There was no 

apparent effect.  We bake longer in the hope of hardening the resist more for bridge structures.



0) Use "Silicon Wafer Preparation for Electron-beam Resist" recipe

1) Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 2000 rpm.

2) With clean pipette cover entire wafer with PMMA.

3) Spin 60s @ 2000 RPM

4) Bake 3min @ 170C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5) Cool off

Spinning/Baking Single Layer PMMA A6 950k (370-390nm thick on 2" wafer)

While the spin curves suggest that the PMMA layer should be ~450nm thick, our estimate is that the PMMA is ~370-390nm



0) Use "Silicon Wafer Preparation for Electron-beam Resist" recipe

1) Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 3000 rpm.

2) With clean pipette cover entire wafer with PMMA.

3) Spin 60s @ 3000 RPM

4) Bake 3min @ 170C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5) Cool off

Spinning/Baking Bilayer MMA(8.5)-MAA EL13/PMMA A3 950k (650nm total thickness on 2" wafer)

While the spin curves suggest that the MMA layer should be ~650nm thick and the PMMA layer ~120nm thick, our estimate is that the PMMA is ~70nm and the MMA is ~580nm thick



0)  Use "Silicon Wafer Preparation for Electron-beam Resist" recipe



Bottom Layer: MMA (8.5) MAA EL13

	

1)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 5000 rpm.

2)  With clean pipette cover entire wafer with MMA.

3)  Spin 60s @ 5000 RPM  

4)  Bake 60s @ 170C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Cool off



2nd Layer: PMMA A3 950



6)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 4000 rpm.

7)  With clean pipette cover entire wafer with PMMA.

8)  Spin 60s @ 4000 RPM 

9)  Bake 30 min @ 170C (Keep covered with petri dish)

10) Cool off

Spinning/Baking Bilayer MMA(8.5)-MAA EL15/PMMA A3 950k (~1300nm total thickness on 2" wafer)

0)  Use "Silicon Wafer Preparation for Electron-beam Resist" recipe


Bottom Layer: MMA (8.5) MAA EL15

	

1)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 1500 rpm.

2)  With clean pipette cover entire wafer with MMA.

3)  Spin 60s @ 1500 RPM  

4)  Bake 60s @ 170C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Cool off


2nd Layer: PMMA A3 950


6)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 4000 rpm.

7)  With clean pipette cover entire wafer with PMMA.

8)  Spin 60s @ 4000 RPM 

9)  Bake 30 min @ 170C (Keep covered with petri dish)

10) Cool off

Spinning/Baking/Developing Bilayer LOR 20B/PMMA A6 950k (~2400nm total thickness on 2" wafer)

0)  Use "Silicon Wafer Preparation for Electron-beam Resist" recipe


Bottom Layer: LOR 20B
	

1)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 3200 rpm.

2)  With clean pipette cover entire wafer with LOR.

3)  Spin 60s @ 3200 RPM  

4)  Bake 180s @ 150C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Cool off


2nd Layer: PMMA A6 950k


6)  Center clean wafer on spinner (most easily done at low speed), set time for 45s and speed to 3500 rpm.

7)  With clean pipette cover entire wafer with PMMA.

8)  Spin 45s @ 3500 RPM 

9)  Bake 10 min @ 180C (Keep covered with petri dish)

10) Cool off

11) Develop in MIBK:IPA 1:3 for 90 sec

12) Soak in IPA for 30 sec

13) Develop in LDD-26W for 45s.

14) Dip in DI for 15 sec

15) Rinse in DI

16) Blow dry N2

Spinning/Baking/Developing Bilayer LOR 5A/PMMA A6 950k (~1000nm total thickness on 2" wafer)

0)  Use "Silicon Wafer Preparation for Electron-beam Resist" recipe


Bottom Layer: LOR 5A
	

1)  Center clean wafer on spinner (most easily done at low speed), set time for 60s and speed to 2000 rpm.

2)  With clean pipette cover entire wafer with LOR.

3)  Spin 60s @ 2000 RPM  

4)  Bake 180s @ 150C (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Cool off


2nd Layer: PMMA A6 950k


6)  Center clean wafer on spinner (most easily done at low speed), set time for 45s and speed to 1500 rpm.

7)  With clean pipette cover entire wafer with PMMA.

8)  Spin 45s @ 1500 RPM 

9)  Bake 1 min @ 180C (Keep covered with petri dish)

10) Cool off

11) Develop in MIBK:IPA 1:3 for 90 sec

12) Soak in IPA for 30 sec

13) Develop in LDD-26W for 45s.

14) Dip in DI for 15 sec

15) Rinse in DI

16) Blow dry N2

Developing E-beam Resist without Ultrasound

1) Waste MIBK and IPA that is remaining in small containers

2) Write down MIBK & fume hood info on the calendar.  MIBK should be at 25C ± 0.5C.

3) Pour MIBK:IPA (1:3) solution into MIBK container

4) Pour IPA into IPA container

5) Develop MIBK for 48s (always moving sample, holding onto it with tweezers)

6) Remove sample and fling off MIBK with "whip" motion

7) Put in IPA for 10s

8) Remove with "whip" motion

9) Blow dry

Developing E-beam Resist with Ultrasound

Using ultrasound is supposed to reduce development time by as much as a factor of 3x from a dip develop, it is also supposed to improve the resolution of the features. 



1) Waste MIBK and IPA that is remaining in small containers

2) Write down MIBK & fume hood info on the calendar.  MIBK should be at 25C ± 0.5C.

3) Pour MIBK:IPA (1:3) solution into MIBK container

4) Pour IPA into IPA container

5) Place MIBK container in sonic bath and turn on sonicator

5) Develop sample in MIBK for 20s (always moving sample, holding onto it with tweezers)

6) Remove sample and fling off MIBK with "whip" motion

7) Put in IPA for 10s

8) Remove with "whip" motion

9) Blow dry

Spinning/Baking/Developing AZ5218E (Used as a negative resist)

0) Use "Silicon Wafer Preparation for Photoresist" recipe

1)  Center clean wafer on spinner (most easily done at low speed), set time for 45s and speed to 3500 rpm.

2)  With clean pipette cover entire wafer with AZ5218E photoresist.

3)  Spin wafer @ 3500 rpm for 45s.

4)  Soft bake @ 90C for 180s (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Let cool for at least 60s (Keep covered with petri dish)

6)  Blow off any junk that may be on mask.

7)  Check HTG power at 405nm

8)  Pattern expose for 4s.  Assume a dose of ~6.45mW/cm2 (Dose ~ 25.8mJ/cm2) 

9)  Bake @ 110C for 150s (Keep covered with petri dish)

10) Let cool for 60s (Keep covered with petri dish)

11) Flood expose for 60s (this will invert the resist).  Line up on table using electrical tape "x".

12) Develop in 1:1 Microposit Developer:DI for 68s.

Spinning/Baking/Developing S1813

0) Use "Silicon Wafer Preparation for Photoresist" recipe

1)  Center clean wafer on spinner (most easily done at low speed), set time for 45s and speed to 4000 rpm.

2)  With clean pipette cover entire wafer with S1813 photoresist.

3)  Spin wafer @ 4000 rpm for 45s.

4)  Soft bake @ 90C for 180s (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Let cool for at least 60s (Keep covered with petri dish)

6)  Blow off any junk that may be on mask.

7)  Check HTG power at 405nm

8)  Pattern expose for 13s.  Assume a dose of ~6.45mW/cm2 (Dose ~ 83.9mJ/cm2) 

9)  Bake @ 110C for 150s (Keep covered with petri dish)

10) Let cool for 60s (Keep covered with petri dish)

11) Develop in 1:1 Microposit Developer:DI for 75s.



2

Spinning/Baking/Developing Bilayer of LOR 5A/S1813

0) Use "Silicon Wafer Preparation for Photoresist" recipe

1)  Center clean wafer on spinner (most easily done at low speed), set time for 45s and speed to 6000 rpm.

2)  With clean pipette cover entire wafer with LOR 5A photoresist.

3)  Spin wafer @ 6000 rpm for 45s.

4)  Soft bake @ 150C for 120s (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

5)  Let cool for at least 60s (Keep covered with petri dish)

6)  Blow off any junk that may be on mask.

7)  Center clean wafer on spinner (most easily done at low speed), set time for 45s and speed to 4100 rpm.

8)  With clean pipette cover entire wafer with S1813 photoresist.

9)  Spin wafer @ 4100 rpm for 45s.

10) Soft bake @ 90C for 180s (Keep covered with petri dish propped up on slides to allow ventilation while keeping out dust)

11) Let cool for at least 60s (Keep covered with petri dish)

12) Blow off any junk that may be on mask.

13) Check HTG power at 405nm

14) Pattern expose for 13s.  Assume a dose of ~6.45mW/cm2 (Dose ~ 83.9mJ/cm2) 

15) Bake @ 110C for 150s (Keep covered with petri dish)

16) Let cool for 60s (Keep covered with petri dish)

17) Develop in LDD-26W for 70s.

Wet Etching Ta

1)  Soak in ACE with ultrasound for 20 seconds; 

2)  Soak in MET with ultrasound for 20 seconds; 

3)  Rinse in running DI for 1 minute;

4)  Blow dry wafer with N2; 

5)  Spin dry wafer for 45 seconds;

6)  Spin Shipley 1813 photoresist at 4100 rpm for 45 seconds (thickness≈1200nm).

7)  Bake on hotplate at 90 ˚C for 180 seconds. 

8)  Expose in HTG contact mask aligner for 16 seconds (4.87 mW/cm2) with ABSORBER mask.

9)  Develop in 100 ml of (1 : 1 = H2O : Microposit Developer) for 90 seconds. 

10) Soak in DI bath immediately to stop the development.

11) Rinse in running DI for 1 minute.

12) Bake on hotplate at 110 ˚C for 10 minutes. 

13) Etch in 52 ml of (3 : 1=Kepro etch solution (FeC13, HCl) : HF), etch rate is about 5.5 nm/sec, endpoint determined by inspection.

14) Soak in DI bath immediately to stop the etching.

15) Rinse in running DI for 1 minute.

16) Blow dry wafer with N2.

17) Spin dry wafer for 45 seconds.

18) Strip the photoresist:

19) Soak in ACE/PH with ultrasonic agitation for 20 seconds; 

20) Soak in ACE with ultrasonic agitation for 20 seconds;

21) Soak in MET with ultrasonic agitation for 20 seconds; 

22) Rinse in running DI for 1 minute;

23) Blow dry wafer with N2; 

24) Spin dry wafer for 45 seconds;

Wet Etching Nb

1)  Soak in ACE with ultrasound for 20 seconds; 

2)  Soak in MET with ultrasound for 20 seconds; 

3)  Rinse in running DI for 1 minute;

4)  Blow dry wafer with N2; 

5)  Spin dry wafer for 45 seconds;

6)  Spin Shipley 1813 photoresist at 4100 rpm for 45 seconds (thickness≈1200nm).

7)  Bake on hotplate at 90 ˚C for 180 seconds. 

8)  Expose in HTG contact mask aligner for 16 seconds (4.87 mW/cm2) with ABSORBER mask.

9)  Develop in 100 ml of (1 : 1 = H2O : Microposit Developer) for 90 seconds. 

10) Soak in DI bath immediately to stop the development.

11) Rinse in running DI for 1 minute.

12) Bake on hotplate at 110 ˚C for 10 minutes. 

13) Etch in 30 ml of (1 : 1: 1 = HNO3: HF: H2O), etch rate is about 50 nm/sec, endpoint determined by inspection.

14) Soak in DI bath immediately to stop the etching.

15) Rinse in running DI for 1 minute.

16) Blow dry wafer with N2.

17) Spin dry wafer for 45 seconds.

18) Strip the photoresist:

19) Soak in ACE/PH with ultrasonic agitation for 20 seconds; 

20) Soak in ACE with ultrasonic agitation for 20 seconds;

21) Soak in MET with ultrasonic agitation for 20 seconds; 

22) Rinse in running DI for 1 minute;

23) Blow dry wafer with N2; 

24) Spin dry wafer for 45 seconds;

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Wet Etching Al

1)  Soak in ACE with ultrasonic agitation for 20 seconds;

2)  Soak in MET with ultrasonic agitation for 20 seconds;

3)  Rinse in running DI for 1 minute;

4)  Blow dry wafer with N2; 

5)  Spin dry wafer for 45 seconds;

6)  Spin Shipley 1813 photoresist at 4000 rpm for 45 seconds (thickness≈1.25 m).

7)  Bake on hotplate at 90 ˚C for 180 seconds.

8)  Expose in HTG contact mask aligner for 16 seconds (4.87 mW/cm2) with TRAP mask.

9)  Develop in 100 ml of (1 : 1 = H2O : Microposit Developer) for 70 seconds.

10) Soak in DI bath immediately to stop the development.

11) Rinse in running DI for 1 minute.

12) Bake on hotplate at 110 ˚C for 10 minutes.

13) Etch in 75 ml of (8 : 4 : 1 : 1 = H3PO4 : CH3COOH : HNO3 : H2O) (white bottle, acid cabinet) at 45 ˚C, rate ≈ 3.7 nm/s, endpoint determined by inspection.

14) Soak in DI bath immediately to stop the etching.

15) Rinse in running DI for 1 minute.

16) Blow dry wafer with N2.

17) Spin dry wafer for 45 seconds.

18) Test the result of this etch with the Dektak to make sure the tunnel barrier has been etched through.

Wet Etching (Aqua Regia) Au

This recipe is used for cleaning parts in deposition systems that have been coated with Au.  This is NOT for wafer cleaning!



1)  Soak in ACE with ultrasound for 20 seconds; 

2)  Soak in MET with ultrasound for 20 seconds; 

3)  Rinse in running DI for 1 minute;

4)  Blow dry with N2; 

5)  Etch in  (3 : 4 = HNO3: HCl), endpoint determined by inspection.

6) Soak in DI bath immediately to stop the etching.

7) Rinse in running DI for 1 minute.

8) Blow dry with N2.



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Lift-off with Photoresist


1)  Soak in ACE with ultrasonic agitation for 20 seconds; 
2)  Soak in MET with ultrasonic agitation for 20 seconds; 

3)  Rinse in running DI for 1 minute;

4)  Blow dry wafer with N2; 

5)  Spin dry wafer for 45 seconds;

6)  Spin Hoechst-Celanese AZ5218E photoresist at 3500 rpm for 45 seconds (thickness≈1.6 m).

7)  Bake on hotplate at 90 ˚C for 180 seconds. 

8)  Expose in HTG contact mask aligner for 5.5 seconds (4.87 mW/cm2) with CONTACT mask.

9)  Bake on hotplate at exactly 110 ˚C for 150 seconds.

10) Blanket expose the wafer in HTG contact mask aligner for 65 seconds.

11) Develop in 100 ml of (1 : 1 = H2O : Microposit Developer) for 65 seconds. 

12) Soak in DI bath immediately to stop the development.

13) Rinse in running DI for 1 minute.

14) Spin dry wafer for 45 seconds.

15) Deposit material

16) Soak in ACE/PH for at least 30 minutes to gently remove the material-coated photoresist; 

17) Soak in ACE with ultrasonic agitation for 20 seconds;

18) Soak in MET with ultrasonic agitation for 20 seconds; 

19) Rinse in running DI for 1 minute;

20) Blow dry wafer with N2; 

21) Spin dry wafer for 45 seconds;



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Contact Luigi Frunzio (432-4268)