| 摘要 |
PURPOSE:To improve the detection sensitivity (counting rate) to radiation by a method wherein a substrate bias voltage, which is applied to bias terminals on the substrate of a dynamic random access memory, is adjusted. CONSTITUTION:A fixed voltage is applied to each circuit other than a DRAM 1 by a positive voltage regulator 21 and at the same time, a variable resistance of a power circuit for the DRAM is carried out a controlled operation, whereby a supply voltage (VCC-VSS) subjected to voltage control is applied to the DRAM 1. On the other hand, the variable resistor of a substrate bias voltage circuit for the DRAM is adjusted, whereby a substrate bias voltage (VBB-BSS) subjected to voltage adjustment is applied to the DRAM 1. By such an adjustment using each voltage, the substrate bias voltage is adjusted conforming to a remarkably high point of a counting rate, whereby the detection sensitivity of alpha rays can be improved and at the same time, variation in the sensitivities between the DRAMs can be easily adjusted. |
