ISOLATION RATIO AND PARTICLE PERFORMANCE-MEASUREMENT OF A SMIF SYSTEM

This paper discusses the performance evaluation of a SMIF (Standard Me chanical Interface) system. A two-chamber experimental system is used with one chamber providing the test atmosphere of the cleanroom and th e other providing the test atmosphere of the minienvironment. The clea nroom atmosphere can be varied by adjusting the amount of particles in jected into the chamber. Particle concentration ranges from 1,000/ft(- 3) to 10 million/ft(3) can be created in the chamber to simulate diffe rent cleanroom conditions. The atmosphere of the second chamber is mai ntained at Class 1 or better equivalent by means of a self-powered ult ra-low penetration air (ULPA) filter blower unit. By means of this sys tem, the ability of the SMIF system to isolate the contaminants in the cleanroom atmosphere from the minienvironment atmosphere was measured . In addition, the particles added to the wafer during wafer cassette handling by the SMIF-Arm were also measured by a wafer scanner The res ults indicate that the SMIF system tested is capable of providing extr emely high isolation ratios in terms of its ability to isolate the cle anroom atmosphere from the atmosphere of the minienvironment. Isolatio n ratios in excess of 1 million to I or better have been measured. The measured particle per wafer per pass (PWP) numbers were generally aro und 0.02 or less for most wafers, with the average at 0.0118.