Removal of low concentrations of acid gases: issues and solutions

Abstract

Part per billion concentrations of acid gases such as SO x and NO x have been detected in both high purity gases and CDA lines. These contaminants can have deleterious effects on a number of high purity applications such as the optics found in lithography equipment steppers, scanners, and inspection tools. In addition, acidic gases have also been shown to reduce the life of masks and reticles, decrease fuel cell output due to catalyst poisoning, and cause hard disk drive crashes due to surface contamination and corrosion. Consequently, acid gas control in these applications has become a critical part of the required filtration system. SO x concentrations are typically used as the baseline for acid gas filter exposure guidelines and performance testing. However, this approach has been shown to provide poor filter life predictions, which has been attributed to the presence of other acidic and organic contaminants that compete with SO x for the available adsorption sites. Equally important, the type of sorbents and methods used to control acid gases can significantly affect the ability to remove SO x . In this work we will compare the performance of various sorbents, structures, and methods for the removal of SO x and NO x .

Air shield system to reduce lens contamination in optical lithography based on turbulence simulation

“…Because airborne molecular contamination during the lithographic process is the biggest problem causing lens contamination, 2 the sensitivity of the lithographic process to airborne molecular contamination is recognized as one of the most challenging issues affecting the next generation of submicron geometries 3 – 6 …”

“…Because airborne molecular contamination during the lithographic process is the biggest problem causing lens contamination, 2 the sensitivity of the lithographic process to airborne molecular contamination is recognized as one of the most challenging issues affecting the next generation of submicron geometries. [3][4][5][6] During the early 2000s, an argon fluoride light source with a short wavelength of 193 nm and a high energy of 148 kcal∕mol was developed. 7 However, as the power of the light source was increased, more types of contaminants were activated.…”

High-Magnification SEM Micrograph of Siloxanes

“…HMDS is well known as a versatile silylation reagent with the ability to block or protect Si─H, N─H, and O─H bonds. HMDS is converted into trimethylsilanol (TMS) and ammonia by the process of hydrolysis in aqueous mediums, as in the equation ((CH 3 ) 3 Si) 2 NH + 2H 2 O ⇌ 2(CH 3 ) 3 SiOH + NH 3 or directly to hexamethyldisiloxane (HMDSO), and ammonia in an aqueous medium, as equation [5] (…”

An investigation of perfluoroalkylamine contamination control

“…Over the years, the AMC contaminants of greatest concern in photolithography applications have changed dramatically. Since the early 1990s the focus of AMC filtration has ranged from ammonia (NH3), 1,2 n-methyl-2-pyrrolidinone (NMP), 3,4 amines, 5 sulfur dioxide (SO2) 6 and acid gases in general, 7 to siloxanes (HMDS, HMDSO, and TMS). 8,9 The issues associated with these contaminants have ranged from photoresist issues (e.g.…”