What are Extraction Technologies?
Extraction technologies, for this article's purposes, refer to the removal of unwanted contaminants from gas or air stream(s). The contaminants can interfere with the production of devices through molecular contamination contained in ambient air or impurities in the high purity gas streams, which can cause device defects in the end product. This is achieved through filtration and purification. Contaminants present in the exhaust stream can be dangerous to life and health and/or the local environment. Contaminants in the exhaust stream can be removed through filtration and/or through central or point of use abatement systems.
Airborne molecular contamination can be present in a cleanroom. These contaminants can be delivered to the cleanroom through the makeup air system, cleanroom personnel, and/or chemicals used in the cleanroom. Makeup air systems can draw in contaminants from sources such as idling vehicles found near air intake grills or other ambient environmental contaminants. Recirculation air systems can distribute these contaminants throughout the cleanroom. Organic amines and ammonia can poison chemically amplified photoresists, also known as deep UV photoresists. These compounds are present in the cleanroom from sources such as a worker’s breath. Volatile organic compounds (VOC’s) can condense on wafer surfaces, causing wafer and optic hazing, corrosion of metal surfaces, or deterioration of device gates. The use of chemically treated filtration media on the inlet of air handling equipment can reduce the concentration of these contaminants within the cleanroom envelope.
Before getting into gas filtration and purification, one needs to look at the gas(es) involved, their respective flow rates, process gas quality requirements, and gas source sizes and quality. Higher purity gases are available from gas suppliers but not in container sizes practical for manufacturing. The high flow rate demands push the size of the gas sources that manufacturers use into bulk sources such as tube trailers, bulk tanks, gas generators and/or air separation plants. These sources, typically, do not have the purities that the process requires for an acceptable yield level. However, not all processes require the same high purity requirements. Evaluation of process requirements will decide what purification and filtration approach is practical for each gas system.
Typical bulk gas purification is done on argon, carbon dioxide, hydrogen, or nitrogen gas distribution systems to name a few of the common gas systems. Moisture is a common impurity targeted for removal. Other impurities that can be removed depend on the source gas but may include oxygen, carbon monoxide, carbon dioxide, hydrogen, and/or nitrogen. However, gases like ammonia and hydrogen chloride may need to be purified close to their point of use due to potential recontamination concerns. Gas purification can be done for the entire gas distribution system through bulk gas purifiers, a specific group of tools through smaller bulk gas purifiers or large point of use purifiers, or at each gas location through point of use purifiers and filters. Bulk gas purifiers can be single use or automatically regenerated on site. Point of use purifiers are single-use canisters/cartridges that may be returned to the manufacturer to be regenerated or properly discarded.
Post processing extraction removes contaminants that are harmful to people and/or the environment. Additional constituents that can be removed are vapors and particulate materials that can condense in exhaust ducts that can cause lines to clog. Water cooled traps can filter out particulates and condensable vapors that can cause particles or solids that can clog pump forelines and point of use abatement systems. Point of use and/or central scrubbers can remove post processing contaminants from the exhaust stream. Central scrubbers can be wet systems, VOC thermal systems, VOC concentrator systems, VOC regenerative systems. Point of use abatement systems can be a wet system, thermal/wet system, dry resin system, plasma system, or a plasma wet system. The right system can remove hydride gases, flammable gases, solvent fumes and vapors, ammonia, halogen, mineral acid gases, and/or PFC gases to name the common contaminants that can be removed from the exhaust stream. The system most effective on removing contaminant(s) from the exhaust stream will depend on the targeted contaminant(s). The need for point of use and/or central scrubbers are dependent on local codes, regulations, and/or air permit requirements. Consult your local air permit district for local regulations and air permit requirements. Contact a code consultant that is knowledgeable with your local codes.
Whether you need molecular contamination removal, gas purification, and/or exhaust treatment system(s), CSI can help you find the right solution for your needs. You can learn more about our Wet and Dry systems.