Develop wafers

• Some resists need a post exposure bake. 3612 resist should be baked at 115C on a hotplate for 60 seconds after exposure and before develop for 1 um or smaller features.
• Use your own designated beakers to develop your wafers.

• Transfer all lithography chemicals with the stainless steel solvent cart. No chemicals may be carried in the lab.
• Most lithography chemicals (including personal resist bottles with the yellow labels) are stored in the two yellow cabinets behind the furnaces. Some (i.e. Polyimides) are stored in the refrigerator or freezer behind the ion implanter.
• Completely fill out the Blue Hazardous Labels (one for each beaker or container that does not have a yellow personal label on it - even water must have one) and keep it with the container. If you are working at the lithosolv or wbmiscres benches you may check that the MSDS sheet for the chemical you are using is there. If the MSDS sheet for the product is there, you may list the product name instead of the percentage of every chemical in the product. This option ONLY at these two benches because there is an MSDS book at the bench. Other benches in the lab require the complete list of all chemicals in the product.
• Make sure any open containers are at least 6 inches back from the front of the exhaust hood to prevent fumes from getting in the lithography room.
• Never bring an open container out from under the exhaust hood unless it is covered with foil.
• Beakers should not be stored at the wetbenches because beakers for general use at the wetbenches are gold contaminated and other lab members may use your beakers and not read your labels.
• Label your beakers with the contamination level and your name and store them in your personal storage box.

Solvent developers

• Solvent developers should be used at the solvent bench only (lithosolv). Solvents such as Acetone, Methanol, Isopropyl Alcohol and Chlorobenzene are only used at the solvent bench.
• Chlorobenzene can not be poured down the solvent drain or in the solvent collection carboy. It must be collected in a separate gallon solvent bottle with a hazardous waste tag on it.
• Solvent based resist strippers such as Shipley's 1165 should not be used in the lithography area (1165 should be used at the GaAs solvent bench ONLY, see Robin for training at that bench. 1165 MUST be collected as hazardous waste and sent out for disposal).
  • Beaker develop in your own personal beaker for the time listed on the webpages.
  • Use a wide shallow beaker with about 1/2 inch of developer in it.
  • Lower the wafer into the beaker and move the beaker for a little agitation. When the time is up remove the wafer.
  • Some solvent developers require a solvent rinse solution
  • After develop or rinsing place the wafer face up on cleanroom paper and blow the top dry. Turn the wafer over (but do not lay it face down on the paper - partcles may get on your wafer) and blow the backside dry.
  • Inspect your wafers for proper exposure (check for underexposure, over exposure, misalignment, bad contact - contact printers only, and proper focus - projection or steppers only). If you see a little scuming (i.e. your wafer is slightly under exposed) you may be able to save the wafer by developing for a little longer, rinse and inspect again. If this happens increase your exposure on the next wafer, develop and inspect it before proceeding with the rest of them.

Acid or base developers

• Acid or base developers should be used at the wbmiscres bench. This bench is for developing wafers only. No resist strip chemicals should be used in the lithography area (i.e. no sulfuric acid, EMT130 or PRS1000).
  • Beaker develop in your own personal beaker for the time listed on the webpages (see svgdev programs for standard times).
  • Use a wide shallow beaker with about 1/2 inch of developer in it.
  • You could just develop for the same time listed for the svgdev programs.
  • Lower the wafer into the beaker and move the beaker for a little agitation. When the time is up remove the wafer.
  • Rinse your wafers either with the DI water gun or in your own personal beaker of DI water.
  • After rinsing place the wafer face up on cleanroom paper and blow the top dry. Turn the wafer over (but do not lay it face down on the paper - partcles may get on your wafer) and blow the backside dry.
  • Inspect your wafers for proper exposure (check for underexposure, over exposure, misalignment, bad contact - contact printers only, and proper focus - projection or steppers only). If you see a little scuming (i.e. your wafer is slightly under exposed) you may be able to save the wafer by developing for a little longer, rinse and inspect again. If this happens increase your exposure on the next wafer, develop and inspect it before proceeding with the rest of them.
  • TMAH based developers are weak bases and can be dumped down the acid base drain (wbmiscres is an acid base wetbench).

Bake resist

• You could use a hotplate bake or an oven bake. Check the webpages to see what bake temperature and time to use (you could just mimic the procedure used for the svgcoat system for coating and baking information). 3612 is baked after develop for 1 minute at 110C on a hot plate. You could instead bake it at 110C in the oven for 25 minutes. When you coat both sides of the wafers you must use the oven for the second coat.
• NEVER put resist side down on a hotplate.

Clean up

• Always dispose of solvent contaminated items properly. Never bring solvent contaminated items out from under an exhaust hood unless they are in a closed plastic bag (your glove can be used for small items). If you glove is contaminated (i.e. with photoresist) turn it inside out to prevent fumes during the transfer. Transfer the sealed bag under the hood of the lithosolv bench and place the black bucket under the hood. Open the black bucket under the hood and place the sealed bag in it. Replace the lid and clamp tightly then transfer the black bucket back under the solvent bench. When the black bucket is full, place it under the hood and seal its bag with a tie-wrap and transfer the sealed bag to the large white barrel (remove the clamp and the lid and place the sealed bag inside, replace the lid and secure the clamp).
• All of the lab air is 80% recirculated so any fumes released into the air will stay in the lab for a long time. Notify the staff immediately if you smell solvents. Evacuate the area and press the red button in the gowning room if the smell is strong (doing this supplies the office area with non-recirculated air, but the lab still remains 80% recirculated).