Smif Microenvironment In Semiconductor Production Effect On Wafer Yield Improvement Study

With the semiconductor engineering technical coming into nanometer generation, the requirement of extra clean production environment has became strictly critical, the challenge for how to well control the polluted particle and reduce its impact to wafer yield must be resolved. SMIF (Standard mechanical interface system) is now the main stream in 8’inch wafer transferring device, and it has developed into Front Opening Unit Pod (FOUP). SMIF has three components:SMIF Pod, SMIF Arm and SMIF-Enclosure. This design makes the wafer production process isolated into a mini-environment, which can obviously reduce particle and increase wafer yield.Anyhow, SMIF itself also will cause particle by its mechanical movement and material out gassing. The main purpose of this research is to study the airflow’s effects on SMIF carrier module and to study the problem caused on the transferring process of wafer cassette. By studying the possible factors one by one, we can get the best precise mechanical parameter and then to control well the cleanliness of the SMIF mini-environment and reduce the pollute rate on chips by the means of amend the device parameter and change the material of wafer lock from PC to PEEK. The summary of this thesis:1. The material of the wafer lock in POD is the key point to anti-pollution and the material made of PEEK can get the better quality than PC. It’s also the main pollution source when wafer lock touches the wafer edge while SMIF load/unload.2. Airflow and wind pressure are the main factors to affect the mini-environment. Through the verification of the experiments, they affirm that can control the cleanness level in a certain way and reduce the rate of abnormal production by adjusting the SMIF parameter from 0.5m/s and 300kPa to 0.4m/s and 360kPa. Which also could reduce the failure rate of the chip production from 6%～10% to 0.1% such brilliant figure.3. SMIF Pod’s out gassing will cause particle, and we can distinctly improve the yield gap between POD edge & POD center by increase POD recycle time, in this way the yield gap can be reduced from 3.5% to 1%.