Creating Snow flake structures using EBL Date:January 2011 by:Lejmarc Snowball Principle Investigator:Dr. William Knowlton for:Nanoscale Materials and Device Group

Wafer SiO 2 wafer with a 500 nm (5000 Å) oxide thickness Nanospec to verify oxide thickness 0-10 Ohms or 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 180°C 60% PMMA 495 C4 – Recipe 3000RPM: ≈ 90nm thickness ◦ 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 180°C 100% PMMA 495 C4 – Recipe 2000RPM: ≈ 300nm thickness ◦ 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 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 180°C 40% PMMA 495 C4 – Recipe 3000RPM: ≈ 45nm thickness ◦ 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