CONDUCTIVITY INSTRUMENTS MEASUREMENTS RESISTIVITY SEMICONDUCTORS STANDARDS

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Abstract

Microelectronics ultrapure water (UPW*) requirements continue to grow more and more demanding as line widths of circuits are narrowed. This trend is reflected in periodic updates to the International Technology Roadmap for Semiconductors (ITRS). Conductivity/resistivity measurement has marginal sensitivity to detect trace ionic impurities at levels that affect product yields in semiconductor manufacturing. As a result, resistivity measuring equipment is challenged by semiconductor facilities experts to achieve higher accuracy of resistivity calibration and measurement. This is an update on recent improvements in these areas. Because the goal of the measurement is to know water purity, not its actual resistivity at temperature, temperature effects must be compensated very accurately to obtain the resistivity value referenced to 25oC, regardless of the water temperature. The resistivity of UPW is accepted as 18.18 Mohm-cm at 25.0oC and is well documented at other temperatures as shown in Table A (1). This precise data enables accurate temperature compensation, provided appropriate algorithms and very precise resistivity and temperature measuring devices are used. Temperature measurement and compensation accuracy is critical because the temperature coefficient of UPW resistivity is 5.3% per oC at 25oC and more than 7% per oC in cold UPW.

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