Wet chemical cleaning and conditioning of wafer surfaces is a critical process step in most, if not all, semiconductor device fabrication schemes.
Many multi-chamber single-wafer cleaning tools employ ozonated water (DI-O3) for their wafer cleaning recipes. Typically, these tools have up to a dozen individual single wafer chambers and these chambers operate in an intermittent fashion. The tool generally maintains a continuous flow of DI-O3 to each chamber, routing the flow to drain when the cleaning protocol is not operating. This leads to large quantities of DI-O3 being wasted with concomitant operating cost and environmental penalties for unused DI-O3 production and disposal.
The LIQUOZON PrimO3 Ozonated Water Reclaim System provides a cost-effective solution. This system directs the DI-O3 from the cleaning chamber bypass flow to the LIQUOZON production and delivery system in the sub-fab. There, the DI-O3 flow is topped up with UPW, re-ozonated to maintain the desired ozone concentration, then boosted to a stable pressure suitable to act as the feed stream to the cleaning tool. The LIQUOZON PrimO3 accepts return DI-O3 flow rates between 0 and 40 lpm at variable ozone concentration setpoints. It can supply the specified DI-O3 stream at flows of up to 40 lpm.
Environmental engineers currently do not have an independent method to verify the claims made by scrubber manufacturers upon installation or during operation. Dynamic process gas flow can change scrubber efficiencies, making it difficult to detect efficiency changes when they occur. With aqueous scrubbers, the ability to obtain real-time HF or HCl measurements is a challenge for the environmental engineer. Although FTIR instruments can measure HF and HCl directly, measuring HF at low levels in a wet stream has been difficult in the past.
Designed to monitor real-time emissions streams for abatement efficiency, the easily transportable MKS MultiGas 2030 Continuous Gas Analyzer can accurately monitor PFCs and their by-products at low levels without drift. The high resolution FTIR based measurement technology can also differentiate between overlapping spectra such as water and HF, even in saturated aqueous scrubber streams. In tests conducted on an aqueous scrubber at a semiconductor fab in the US, the 2030 monitored HF concentrations near 0.4 ppm with variations of only 30 to 40 ppb. The spike in the sample was due to a water droplet entering the heated sampling line and vaporizing. The 2030 can distinguish HF from water in the spectra, proving that 2% absolute water does not affect the analytical results.
Several process steps in the semiconductor industry require de-ionized (DI) water with precisely defined conductivity.
The DI-SOLVER CO2 is used in single substrate cleaning tools for rinsing steps to prevent ESD effects and/or corrosion by creating UPW (ultrapure water) with precisely defined conductivity. It is a compact system for tool integration, providing conductive DI-CO2 water (carbonated ultra-pure water) with closed loop controlled conductivity. The conductivity is kept at a constant value under changing flow conditions by control of the CO2 concentration in the DI-CO2 water.
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