Robert W. Grant

Etching of Thermal Oxides in Low Pressure Anhydrous HF / CH 3 OH Gas Mixture at Elevated Temperature

Etching of thermal oxides in HF/CH 3 OH gas mixture at the pressure from 100 to 500 Torr and wafer temperatures from 25 to 120 o C is studied using a commercial cluster tool compatible reactor. Pressure and temperature are selected to control condensation of reactants on the etched surfaces, and hence, the thermal oxide etch rate. Using this etching mode, controlled etching of thermal oxides at rates up to 200 A/min was achieved without any water vapor intentionally added to the input gases

Reduced Pressure Etching of Thermal Oxides in Anhydrous HF / Alcoholic Gas Mixtures

Reduced pressure etching of thermal oxide in anhydrous HF gas with three different alcoholic solvent vapors is studied. Thermal oxide etch rates as functions of temperature, pressure, time, and HF partial pressure are presented for methanol, ethanol-water azeotrope (95.6% ethanol, 4.4% water), and 2-propanol (isopropyl alcohol). The etch rates are interpreted in terms of alcohol vapor pressure, HF ionization, and reaction product desorption. The efficient desorption of reaction products compared to vapor HF/H 2 O is believed to be responsible for both the wider process window for alcoholic solvents and the alleviation of the solid residue formation problem. Among the alcoholic solvents studied, methanol has the best potential while 2-propanol can also be useful in selected applications

In-Situ Chemical Concentration control cor Wafer Wet Cleaning

The continuously increasing integration of todays advanced semiconductors requires increasingly tight process control in the IC manufacturing steps. This paper demonstrates the use of conductivity sensors to monitor and control the chemical concentrations of RCA cleaning and HF etching solutions. Electrodeless conductivity sensors were used to monitor and regulate the concentration of these process chemicals. A linear relationship between the conductivity of the solution and the chemical concentration was obtained within the range studied. A chemical monitoring and concentration scheme (ICE-1™) was developed. Different concentrations of RCA and HF solutions were investigated. Results show that these techniques are suitable for monitoring and controlling the concentration of chemicals in the process tanks for better process control. These techniques provide a lower cost of ownership of the process due to longer bath lives and the use of dilute chemicals.