Godin:Protocols/Lift-Off Resist

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Safety Safety goggles Nitrile gloves Lab coat Fume hood Materials Part 1: Microscope Slide Cleaning 8 microscope slides Acetone Isopropanol Ethanol Microscope slide holder 3 300 mL bottles Godin:Protocols/Sonicator Tweezers Part 2: Pattern Photoresist TMAH Toluene Acetone Ethanol Distilled water in small dish Shipley S1813 Photoresist 2 hot plates Magnetic stirrer, 2 cm Aluminum foil Scotch tape 300 mL beaker Glass dish Spill tray 1 ml pipette and rubber bulb Precision pipette for >= 1 mL Positive photomask Godin:Protocols/Spin coater Godin:Protocols/Mask aligner Part 3: Deposit Metallic Film Thermal deposition system Part 4: Remove Resist Etching solution in 300 mL beaker Spill dish Description Lift-off is a technique used to pattern metallic films using photolithography. In this procedure, Shipley S1813 photoresist is used in conjunction with toluene to create micro-sized features on glass slides. A positive mask is used, so as to expose the glass where electrodes are to be placed. Silver is then deposited, followed by an etching step to lift-off the surrounding photoresist. The silver is then electrochemically altered to form silver chloride electrodes. Microscope Slide Cleaning 5 min sonicate Acetone / IPA / EtOH + N2 dry Cleaning the microscope slides is an essential first step to the lift-off process. Start by inserting 8 microscope slides in the microscope slide holder, and filling it with acetone. Place the slide holder in the sonicator for 5 minutes, then pour the used acetone into a 300 mL bottle for future use. Repeat this step for isopropanol (IPA) and ethanol (EtOH). Once complete, enter the clean room. Use the tweezers to remove each slide, and blow dry with high-purity nitrogen. Visually inspect each slide. Do not touch the ethanol with your gloves, as the latter will slowly dissolve and taint your slides. If any impurities remain, dip the slides in ethanol and dry them. If any are irreparably scratched or damaged, discard. Pattern Photoresist Setup This step shall be completed completely within the clean room, so use appropriate gowning. Wrap a hot plate with aluminum foil, and cover with glass top also wrapped in aluminum foil. Place on counter. Place a 2nd hotplate in the fume hood, also covered in aluminum foil. Place glass dishes in the spill tray, and place within the fume hood. Fill the 1st glass dish with toluene, the 2nd with distilled water. Fill a beaker with 185 mL of distilled water, then use the precision pipette to add 15 mL of TMAH to the beaker, and place on the hot plate in the fume hood. Add a stirring stick, and mix at 400 RPM. Wrap the top of the spin coater with aluminum foil, and make sure it is clean. Turn on the power, vacuum and nitrogen feed. Turn on the ventilation switch, and open the shutter leading to the mask aligner, making sure to reach a flow level of 0.2. Turn on the mask aligner main power, and then the lamp. Set timer to 16 seconds. Place your photomask ink-side down under the glass filter using tape. Make sure the glass is securely in place by applying the vacuum. Also, place a silicon wafer as a target, and vacuum it down securely in place. Your coated slides will later be placed on the silicon wafer. Use an unclean glass slide (practice one) to determine correct positioning of the mask/slide, so as to have it centered. We want illumination to be uniform on the sample. Make sure the mask can be lifted all the way without hitting the 4 corner clamps. This may take some adjustment. Once satisfied, delineate the slide's position with tape. It will serve as a guide later on. 10 min 110°C TMAH Toluene Acetone Ethanol Distilled water in small dish Shipley S1813 Photoresist 2 hot plates Magnetic stirrer, 2 cm Aluminum foil Scotch tape 300 mL beaker 2 Glass dishes Spill tray 1 ml pipette and rubber bulb Precision pipette for >= 1 mL Positive photomask Godin:Protocols/Spin coater Godin:Protocols/Mask aligner