Transcript Creating “Snow flake” structures using EBL on SiO2 substrate

Creating Snow flake structures
using EBL
Date: January 2011
by: Lejmarc Snowball
Principle Investigator: Dr. William Knowlton
for: Nanoscale Materials and Device Group
Wafer
SiO2 wafer with a
500 nm (5000 Å)
oxide thickness
 Nanospec to verify
oxide thickness
 0-10 Ohms or 0-100
Ohms

Spin On (electrodes)
Wafer should be cleaned at wet bench
with AIM protocol
 Prior to spin-on wafer oxide thickness
should be verified with the nanospec
 Pre-heat sample for approximately 90
seconds on hot plate @ 180°C
 60% PMMA 495 C4 – Recipe 8 @
3000RPM: ≈ 90nm thickness

◦ Bake @ 180°C on hot plate for 5 minutes
◦ Nanospec to verify film thickness
EBL (electrodes)

Set apertures to 30um (micro meters)
◦ Defining and Blanking aperture in the 30 um
position
Beam current 8pA (Pico amps)
 Run file: Snowlong_Chara.RF6

◦ Area Dosage 260
Development (electrodes)
MIBK/ IPA 1:3
 1 minute developing

◦ 30 sec agitation
◦ 30 sec still
Etching (electrodes)

Buffered Oxide Etchant (BOE)
◦ Spray the surface of the sample with
Deionized water and allow a layer of water to
remain on the surface of sample before
submerging it into the etchant
◦ 1 minute etch (Buffered Oxide Etchant 7:1)
 Agitation total time
 Etches ~80 nm
Physical Vapor Deposition
(electrodes)

Sputter
◦
◦
◦
◦
◦
50 Watts on both Axial and Flex Guns
Deposition pressure: 8 mTorr,
Argon gas flow rate 25.5 Sccm
Cr – 7min 30 sec (Axial Gun)
Au – 4 min (Flex Gun)
 ~ 100 nm total deposition thickness
Lift Off (electrodes)

Sonication w/ Acetone
◦ Sonicate until sample is clean there is no
designated time
◦ Clean w/ AIM (Acetone, IPA, Methanol) wash
Spin On (Pads)
Wafer should be cleaned at wet bench
with AIM protocol
 Prior to spin-on wafer oxide thickness
should be verified with the nanospec
 Pre-heat sample for approximately 90
seconds on hot plate @ 180°C
 100% PMMA 495 C4 – Recipe 8 @
2000RPM: ≈ 300nm thickness

◦ Bake @ 180°C on hot plate for 7:30 minutes
◦ Nanospec to verify film thickness
EBL (Pads)

Apertures set to 50 um (micro meters)
◦ Defining aperture in the open position
◦ Blanking aperture in the 50 um position


Beam current 100 pA (Pico amps)
Run file: Snowlong_AL100_Pads.RF6
◦ Area Dosage 280
◦ From the end of the scratch
◦ To find the alignment mark move the stage on the delta xy





Move -0.2 in the x-axis
Center the alignment mark
Move -0.1 in the x and -0.1 in the y
Center the structure preferably using crosshairs for added precision
Move -0.06 in the y direction to get the beam off of the pattern
 This is for the first two structures out of four at that particular scratch
 NPGS will show a scanned version of the structures and for fine alignment use the delta xy
 For the next two structures




From the end of the scratch
Move -0.2 in the x-axis
Center the alignment mark
Move -0.3 in the x and 0.1 in the y
 NPGS will show a scanned version of the structures and for fine alignment use the delta xy
Development (Pads)
MIBK/ IPA 1:3
 1 minute developing

◦ 30 sec agitation
◦ 30 sec still
Physical Vapor Deposition (PVD) for
Pads

Sputter Al Pads:
◦
◦
◦
◦
50 Watts on both Axial and Flex Guns
Deposition pressure: 8 mTorr,
Argon gas flow rate: 25.5 Sccm
Al – 25minutes
 ~ ?nm deposition thickness

Sputter Cr/Au Pads:
◦ 50 Watts, 8 mTorr, 25.5 Sccms
◦ 6:15 -> 25nm Cr
◦ 5:30 -> 75nm Au
Lift Off (Pads)

Sonication w/ Acetone
◦ Sonicate until sample is clean there is no
designated time
◦ Clean w/ AIM (Acetone, IPA, Methanol) wash
Spin-On (Windows)
Wafer should be cleaned at wet bench with
AIM protocol
 Prior to spin-on wafer oxide thickness
should be verified with the nanospec
 Pre-heat sample for approximately :90
seconds on hot plate @ 180°C
 40% PMMA 495 C4 – Recipe 8 @ 3000RPM:
≈ 45nm thickness

◦ Bake @ 180°C on hot plate for 5 minutes
◦ Nanospec to verify film thickness
Exposure (Windows)

Expose with Beam current ~8pA
Develop(Windows)

Develop for 30 seconds
◦ With hand agitation

Rinse with water and blow dry
AFM (Windows)

3 um scan of windows and create/update
Traveler