Properties: Heated KOH is widely used for bulk etching of silicon. Potassium, as an alkali metal ion, will destroy device performance. Thus, controlling the use of potassium in the lab is extremely important. KOH may be used ONLY at wbgeneral. If your process flow requires silicon wafers that have been processed through KOH to be subsequently processed in any clean or semiclean equipment, you must perform the KOH clean-up procedure. (Your process flow up to this point must have carefully excluded all other possible metal contaminants.) I. Post KOH etch wafer clean-up (to remove KOH contaminants). The following information pertains ONLY to Si wafers that have not been exposed to any metals. The KOH etch must have been done in a nonmetal contaminated quartz beaker. After etching.... A. Full 4" wafers 1. DO NOT RINSE THE WAFERS IN THE DUMP RINSER At: wbsilicide Heat fresh: 5:1:1 H2O:H2O2:HCl to 70C Tweezers: KOH etch Load: the wafers in a silicide cassette Place the cassette directly in the H2O:H2O2:HCl solution Clean: 20 minutes Dump Rinse: standard 6 times Rinse/Spin Dry: standard 2. The Si wafers may then be transferred to a diffusion cassette using post-wbnonmetal tweezers or a special pair of tweezers dedicated to this purpose. Continue with a standard pre-diffusion clean at wbdiff. After the pre-diffusion clean, the wafers may be processed in any tylan furnace. 3. CLEAN the wbsilicide HCl HOT POT, cassette, and handle. Aspirate: the KOH contaminated HCl mixture Rinse : the hot pot THOROUGHLY with DI water Mix : 1:1:1 H20:H2O2:HCL DO NOT HEAT Clean: 20 minutes Dump rinse: the handle and boat; standard 6 times Aspirate : the HCl solution Rinse : the hot pot THOROUGHLY with DI water Refill: with fresh chemicals (5:1:1 DI H2O:H2O2:HCl) B. Wafer pieces After etching in designated KOH (nonmetal) quartzware 1. Use wbgeneral. Use clean gloves. Do NOT touch any work surfaces or any equipment used in the wetbench, especially with the clean gloves. 2. Use a clean quartz beaker and a clean quartz or teflon wafer holder. "Clean" means never used for KOH etching and/or never used with any other contaminating source. Do NOT put the beaker on the barewetbench deck. The outside surface of the clean quartz beaker should be sandblasted with "post KOH HCl clean ONLY". 3. Heat: 5:1:1 H2O:H2O2:HCl to 70C Tweezers: KOH etch Load: the wafers in a quartz or teflon holder Clean: 20 minutes Rinse and dump: 6 times 4. The Si wafers may then be transferred to a pre-diffusion clean boat and beaker. Use post-wbnonmetal tweezers or a special pair of tweezers dedicated to this purpose. Continue with a standard pre-diffusion clean. After the pre-diffusion clean, the wafers may be processed in any tylan furnace. 5. Store the HCl cleaning beaker and wafer holder away from wbgeneral. II. Clean up of KOH labware Totally immerse all labware in a solution of 5:1:1 H2O:H2O2:HCl so all areas are thoroughly cleaned.