Analysis of Radioactive Impurities in Alumina and Silica Used for Electronic Materials

The electric, electronic, mechanical and thermal characteristics of high density electronic devices can be affected by the physico-chemical characteristics of base materials as well as by trace impurities. It is well known that soft errors caused by trace -emitting impurities are one cause of the faulty operation of electronic devices. This phenomenon was initially reported in May[1] in the 1970s. Recently, a number of studies concentrating on the solving and preventing of soft errors have progressed in the military and airplane industries, as high precision electronic devices such as VLSI, DRAM, SRAM, are rapidly developing[2-6]. Neutron activation analysis(NAA) is known to be a useful technique for the determination of metallic elements in insoluble materials such as alumina and silica, due to its capabilities of nondestructive and absolute analyzable characteristics of a high sensitivity for most metallic elements[7-9]. Various conducting elements such as Na, Mg, Fe, Cu and Ti may decrease the conductance of alumina, and soft errors can occur as a result of -emitting elements such as U and Th. For these reasons, high purity alumina is required for use in electronic device materials. Alumina is also used in a ball form in industries that produce fine powders. The produced powder can be contaminated by metallic impurities in alumina balls due to their abrasion; therefore, strict quality control is required. The aim of this work is the development of simple, accurate and sensitive NAA procedures for the determination of trace and ultra-trace metallic elements, particularly U and Th, in high purity silica and alumina materials. In order to achieve this aim, optimum NAA procedures were investigated, and a low background counting system was set up using a nitrogen purging system.