硅片RCA清洗

The RCA clean is a standard set of wafer cleaning steps which needs to be performed before high temp processing steps ( oxidation , diffusion , CVD ) of silicon wafers in semiconductor manufacturing. RCA cleaning includes RCA-1 and RCA-2 cleaning procedures. RCA-1 involves removal of organic contaminants, while RCA-2 involves removal of metallic contaminants Werner Kern developed the basic procedure in 1965 while working for RCA, the Radio Corporation of America [1] It involves the following : 1. Removal of the organic contaminants (Organic Clean) 2. Removal of thin oxide layer (Oxide Strip) 3. Removal of ionic contamination (Ionic Clean) The wafers are prepared by soaking them in DI water . The first step (called SC-1, where SC stands for Standard Clean ) is performed with a 1:1:5 solution of NH 4OH + H 2O2 + H 2O at 75 or 80 degrees (Celsius) [1] typically for 10 minutes. This treatment results in the formation of a thin silicon dioxide layer (about 10 Angstrom) on the silicon surface, along with a certain degree of metallic contamination (notably Iron) that shall be removed in subsequent steps. This is followed by transferring the wafers into a DI water bath The second step is a short immersion in a 1:50 solution of HF + H 2O at 25 degrees Celsius, in order to remove the thin oxide layer and some fraction of ionic contaminants [1]. The third and last step (called SC-2) is performed with a 1:1:6 solution of HCl + H2O2 + H 2O at 75 or 80 degrees Celsius. This treatment effectively removes the remaining traces of metallic (ionic) contaminants [1]. AdditionsIn his book, “Handbook of Semiconductor Wafer Cleaning Technology“ [2], Werner Kern writes that the first step in the ex situ cleaning process is ultrasonically degrease in trichloroethylene , acetone and methanol . RCA cleaning (also known as SC1/SC2 etching) submits silicon wafers to oxidation by NH 3:H2O2:H2O mixtures, oxide removal in diluted HF, further oxidation by HCl:H 2O2:H2O mixtures, and final etching in diluted HF. RCA-1 Silicon Wafer Cleaning Process name: RCA01 Mark Bachman Fall 1999 OverviewThe famous RCA- 1 clean (sometimes called “ standard clean -1” , SC-1), developed by Werner Kern at RCA laboratories in the late 1960’ s, is a procedure for removing organic residue and films from silicon wafers. The decontamination works based on sequential oxidative desorption and complexing with H2O2-NH4OH-H2O (RCA1). A second RCA-2 clean (SC-2) is often used H2O2-HCl-H2O to further clean the surface. RCA-1 clean is used to remove organic residues from silicon wafers. In the process, it oxidizes the silicon and leaves a thin oxide on the surface of the wafer which should be removed is a pure silicon surface is desired. This is a level-1 process and requires basic INRF safety certification. The use of dangerous chemicals requires that the user may not perform the process alone. Time neededThis process takes 30 minutes to complete in total. Materials neededo Ammonium hydroxide o Hydrogen peroxide o Pyrex bath containers o Hot plate PreparationSetup time for this process is about 5 minutes. This process takes about 20 minutes to complete. The general recipe is for RCA-1 cleanser is: 5 parts water (H2O), 1 part 27% ammonium hydroxide (NH4OH), 1 part 30% hydrogen peroxide (H2O2). 325 ml DI water 65 ml NH4OH (27%) 65 ml H2O2 (30%) Procedure [RCA-1]Put 325 ml DI water in a Pyrex beaker, add 65 ml NH4OH (27%) and then heat to 70 ±5° C on hot plate. Remove from hot plate and add 65 ml H2O2 (30%). Solution will bubble vigorously after 1 – 2 minutes, indicating that it is ready for use. Soak the silicon wafer in the solution for 15 minutes. When finished, transfer the wafer to a container with overflowing DI water from a tap to rinse and remove the solution. After several water changes, remove the wafer under flowing water. (Still water surface can contain organic residue that will redeposit on the wafer surface when removing wafer.) Clean upTo dispose of the RCA-1 solution, dilute with cold water, let cool and sit for 10 minutes, then pour down the drain with plenty of cold water to flush. Old RCA cleaning solution cannot be used since it loses its effectiveness in 24 hours at room temperature (30 minutes at 70° C). Rinse all labware three times in clean water. Safety and emergencyAll safety and procedural regulations must be followed. Review the INRF standard operating procedures for fire, chemical spill, and chemical exposure. Use of RCA requires at least one other person in the clean room (buddy system). RCA clean should be performed in a laminar flow bench, using nitrile gloves and eye protection. Hydrogen peroxide is an explosive chemical. Never leave the RCA process unattended. Do not store the hydrogen peroxide near the hotplate or any other source of heat. Any small spills should be wiped up immediately with wipes. Dispose the wipes in the corrosive waste container. In case of exposure to skin or eyes, flush immediately with water for 15 minutes. Remove all clothing that are exposed and flush with water. Report to INRF staff or report to EH&S. Seek medical attention to ensure that the burns are minimal. In case of large spill, follow the INRF Standard Operating Procedure for chemical spills.