ELECTRICAL-CONDUCTIVITY MEASUREMENT IN LIQUEFIED HYDROGEN-CHLORIDE

A measurement technology for trace impurities in hydrogen chloride (HC I) was developed in relation to future ultra-large scale integration ( ULSI). We developed an electrical conductivity measurement system for analyzing liquified HCl with an in-line high pressure cell. The detect ion limit of this measurement system is 1.0 X 10(-11) S/cm, and the ex ternal leak rate of the cell is below 1. 5 X 10(-11) Torr - liter/s. T he apparent temperature coefficient of the electrical conductivity is negative in the range from - 12 to 20-degrees-C at constant pressure, which is caused by a decrease of the density of HCI with increasing te mperature. The real temperature coefficient of the electrical conducti vity is positive at constant density We observed differences in the el ectrical conductivity of HCI at different lapsed times after filling a nd between different gas sources. An electrical conductivity of 5.5 X 10(-10) S/cm was obtained by repeated liquifaction of HCl at a pressur e of 41 kg/cm2 and 15-degrees-C.