Surface Deposition of Ionic Contaminants on Silicon Wafers in a Cleanroom Environment

Abstract

The adsorption and desorption behaviors of ionic micro-contaminants on the silicon wafers in a cleanroom environment were investigated in this study. The experimental measurements showed that the surface density of ionic contaminants was significantly affected by both the exposure time and the properties of contaminants. The rate parameters of a kinetic model for surface deposition were determined by numerical optimization of fitting the experimental data on surface and ambient concentrations of airborne molecular contaminants (AMCs). Subsequently, the time-dependent deposition velocity and sticking coefficient of ionic species were obtained. The results showed that F , Cl , NO 3 , SO 2 4 , Na + , NH + 4 , K + , and Mg 2+ were the major ionic microcontamination species on the wafer surfaces, with the adsorption rate constant and the sticking coefficient of K + ion being larger than those of other ionic contaminants.After the determination of sticking coefficients, the allowable wafer exposure durations and the maximum ambient concentrations of ionic species were exemplified based on the guideline recommended by the International Technology Roadmap for Semiconductors (ITRS).

Analysis of Relationship between Inorganic Gases and Fine Particles in Cleanroom Environment

“…The deposition rates of ionic contaminants on silicon wafer and their adsorption/desorption behaviors on the silicon wafer were reported in our prior study (Lin et al, 2009). Inorganic gases could lead to harmful precipitates and result in irreversible damage to process wafers (MacDonald et al, 1993;Saiki et al, 1995).…”

“…The samplers were operated at a constant flow rate of 10 L/min and 24 hours sampling time to determine possible components of the hazing contaminants onto the wafer surface (Lin et al, 2009). A total of 10 samples was used for the average species concentrations at the photo and etch areas, respectively, in this study.…”

“…The sampling time of 24 hours for the DDS is required because the chemical compositions of the wafer contaminants can be analyzed only after long time exposure (Lin et al, 2009). However, sampling bias due to the reaction of residual NH 3 with the acidic particulate species in the downstream filter pack is possible during long sampling time.…”

Metal Corrosion of Al-Si-Cu Pattern Wafer Due to Chloride Ion Contaminants

“…The Cl -concentration was on-line monitored by the multi-sampling real-time monitor (IMS, Ion Mobility Spectrometer, 815910-20-100b, Saes, USA) for 6 months. The IMS method has been proven to be a useful technique for determining trace ionic concentrations with detailed description of the sampling and analysis procedure referred to our prior study (Lin et al, 2008;Lin et al, 2009). The real time monitoring instrument of IMS took one data point for every 5 minutes located in each process area.…”

Wafer Container Monitoring Concerning Airborne Molecular Contaminations along a 300 mm Power Semiconductor Production Flow

“…An additional issue within a 300 mm wafer facility is the fact, that all silicon substrates are transported in closed wafer containers (FOUPs). Gaseous contaminations, which are coming out of the processes, can directly attack the critical layers on the chips [3]. Therefore, new container management concepts have to be developed.…”