This Small Business Innovation Research (SBIR) Phase II project aims to develop a single wafer processing clean tool for semiconductor wafer cleaning at all stages of wafer processing. The method relies on using acoustically controlled micro-cavitation to remove on-wafer particles. This is a chemical-free cleaning method, using ultra-pure water as the only processing fluid. During cleaning the particles will be counted as they get removed. The cleaning is deemed complete when there remain no more particles to be removed. The wafer will then be rinsed and dried in the same tool. This project is expected to provide a one-at-a-time wafer cleaning method with all the four functionalities of cleaning, inspection, rinsing and drying accomplished in a single setting.
The broader/commercial impacts of this project will be the potential to provide a complete environmentally-friendly solution to the wafer cleaning predicament. Cleanliness is a critical requirement in semiconductor manufacturing that directly impact the chip yields. Among all processing steps in semiconductor manufacturing, approximately one in every five processing steps is wafer cleaning. Perfect wafer cleaning is a significant, yet unsolved, problem in semiconductor industry, and the need is becoming more urgent as the technology moves towards sub-50nm design nodes. In this project, a wafer-cleaning tool will be developed to address this market need. This tool will also be useful in precision cleaning needed in the cleaning of lithography masks, Microelectromechanical Systems (MEMS), solar cells, flat panel displays, and hard disk drives (HDDs).
We began this project with the ambitious goal of developing a much needed Clean Tool of wide applicability at all stages of wafer processing in semiconductor manufacturing: A single wafer processing Clean Tool to implement a unified approach to wafer cleaning with the following three distinct features: I. Clean wafers using only UPW with ACIM coupled acoustics—no chemicals! II. Monitor particulates being removed as cleaning proceeds and so implement "endpoint" cleaning—cleaning wafers until all particles are removed. III. Rinse and dry wafers without causing watermarks. We were successfully able to accomplish the above objectives. The outcomes are listed below: Our technical objective during the SBIR Phase II was to develop an ACIM Clean Tool™—A unified wafer cleaning system—that measures up to the following performance requirements: • Clean 300mm wafers one at a time • Use UPW (ultra pure water) as the cleaning medium; no chemicals • Accomplish cleaning unto endpoint—all unwanted particles removed • Provide end-of-cleaning record of total particles removed • Clean, Rinse and Dry the wafer in the same setting • Process one wafer in 3 minutes Cleanliness is next to "Godliness" in IC manufacturing. On-wafer particulates kill IC chip yield by causing shorts, opens, layer flaws and other defects. The critical size—the largest tolerable particulate size—is less than half the smallest feature size in a given IC generation, the technology node. The importance of cleaning and surface conditioning, is underscored by the fact that about 20% of the 500 to 800 steps it takes to manufacture an integrated circuit are wafer cleaning operations. Current cleaning methods are not able to remove 100% of the on-wafer particles of critical size. In this SBIR project, we have successfully develop a new-to-the-world, wafer cleaning tool.