|
Advanced semiconductor devices can suffer from a plethora ofdefects, some of which are attributable to the processes used for their manufacture and others which are inherent to the materials used to fabricate the device. As the level of integration in these devices continues to become more sophisticated, so too must the detection techniques and ultimately the control of such defects. One possible method to reduce defects is to monitor and control the purity of chemicals utilized to fabricate advanced devices. This paper will specifically deal with one such chemical, photoresist. The manufacture ofphotoresist chemicals has advanced significantly over the past 5-10 years. The once relatively crude "refmery-like" resist production facilities have been replaced with ultraclean facilities which are constructed and operated in a similar manner as advanced device fabs today. The driving force behind this transformation is to increase wafer yield by limiting defects on product wafers which are caused by particulate contamination in the resist material. Specific particles come in many flavors such as inactive dirt or dust particles to active metallic impurities containing elements such as sodium, calcium or iron. Likewise, there are many new techniques utilized to control specific particulates (e.g. ion exchange for metallic impurities). However, in general, to remove generic particulate contamination, filtration or ultrafiltration has been the mechanism of choice for many years and will probably continue to be so in the foreseeable future. In order to continually improve the efficiency ofthe filtration process, the ability to evaluate new filtration materials and techniques must be acquired. In addition, developing models which allow scaling from pilot systems to large production systems without repeating process optimization is critical in order to deliver leading edge products t the market quickly and efficiently. This study was primarily concerned with developing a technique to evaluate filter systems in an efficient manner. In addition to generating empirical data, mathematical models were utilized to understand the filtration process and to use for future scale up purposes. Additionally, new or improved filtration devices must be studied to determine the effects on the photoresist chemical using advanced analytical techniques. It is with the above information that the photoresist manufacturer will be able to continually drive particulate contamination levels lower and lower in the future.
|
