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We present a study on the electrochemical behavior of magnesium hydroxide (MgOH+) reduction on a tungsten (W) cathode in molten chloride salt (MgCl2-KCl-NaCl) across the temperature range of 475-525℃. MgOH+, which forms within the salt upon exposure to moisture, is a leading cause of corrosion. Corrosion is a major barrier to deployment of chloride salts across a number of applications, including concentrating solar power plants and nuclear power plants. While pre-purification protocols have been developed to ensure MgOH+ is removed from molten chloride salts prior to deployment, MgOH+ forms in-situ during operation of chloride-salt based plants. Thus, methods for continuous purification during plant operation are needed. Continuous electrochemical purification via electrolysis using a Mg anode and W cathode has been proposed, but little has been done to assess scalability. Here, we assess fundamental properties of electrochemical removal of MgOH+ to enable future scale up of this method.

Two-side Surface Photovoltage (TS-SPV) based on measuring SPV from both wafer sides is proposed as novel approach for silicon surface contamination monitoring. TS-SPV is applied to investigate the process of diffusion of implanted iron in lightly doped p-type silicon during Rapid Thermal Anneal (RTA). Good correlation was found for iron distribution vs. RTA conditions in the temperature range from 375 to 1100oC. The portion of electrically active interstitial iron measured by TS-SPV was studied as function of RTA time and temperature conditions. Low thermal budget RTA combined with TS-SPV is proven to be effective to monitor iron contamination and to identify the contamination sources character and location.

One major source of metals contamination during high temperature processing are metals pre-deposited on the wafers surface before thermal treatment and metals cross- contamination from other wafers and/or furnace components. This study investigates the mechanism of metals transfer via gas phase vs. temperature and oxygen gas flow conditions. We also investigated the cross-contamination from Silicon Carbide (SiC) components at elevated temperatures. Cross-contamination from SiC can be explained as (a) metal diffusion from the direct contact area between silicon wafer and SiC (MDD - Metals Direct Diffusion) and (b) metal desorption from the SiC surface and re-adsorption on the silicon wafer surface from the gas phase (MAG - Metals Adsorption from Gas Phase). Both MDD and MAG contamination components are driven by SiC surface metal contamination. Using high resolution Surface Photo- Voltage (SPV) iron mapping we investigated the character of iron cross-contamination. Iron diffusion and desorption activation energies were experimentally determined.

Two-side Surface Photovoltage (TS-SPV) based on measuring SPV from both wafer sides is proposed as novel approach for silicon surface contamination monitoring. TS-SPV is applied to investigate the process of diffusion of implanted iron in lightly doped p-type silicon during Rapid Thermal Anneal (RTA). Good correlation was found for iron distribution vs. RTA conditions in the temperature range from 375 to 1100oC. The portion of electrically active interstitial iron measured by TS-SPV was studied as function of RTA time and temperature conditions. Low thermal budget RTA combined with TS-SPV is proven to be effective to monitor iron contamination and to identify the contamination sources character and location.

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Photoluminescence (PL) was proposed as non-destructive technique for highly doped silicon material characterization. PL intensity had been observed to decrease for intentionally metal contaminated areas. PL studies were applied to iron contaminated silicon wafers after the thermal treatment at 1150 and 1250oC to validate the PL technique for the quantitative evaluation of bulk iron in silicon. Iron contamination ranged from 109 cm-3 to 1012 cm-3. For lightly doped p-type and n-type silicon a good correlation was found between PCD lifetime, SPV diffusion length (DL) and iron readings and PL intensity readings. PCD, SPV and PL high- resolution mapping was applied to build the point-to-point correlation. PL was shown to be sensitive to iron contamination at concentrations exceeding 1010cm-3 as calibrated by SPV using lightly doped p-type silicon. PL may be used as high-resolution non-destructive technique to track down the metal contamination sources in wafers processing.