Predictive Analysis of Microcircuits’ Radiation Hardness in the Fabrication Process. II. Selection of Test Objects and the Statistical Processing of the Obtained Results

The requirements on the radiation hardness (RH) of mass produced products must be confirmed for each wafer lot. The core manufacturing process (CMP) must be controlled to ensure the accuracy and stability of all the declared product parameters, including RH. The development of a monitoring and statistical control system for the CMP is based on the data obtained during the radiation-oriented characterization (ROC) of the CMP or during preliminary tests during the product development process. At each stage of manufacturing, appropriate test structures (TSs) are used to predict an estimate of the radiation hardness of the product. Based on the results of an analysis of engineering practice and the published data, a set of TSs for monitoring the technological process using the example of 250-nm SOI CMOS technology, which meets the requirements for radiation hardness, is proposed in this study. Statistical processing of the data from monitoring production batches of wafers is aimed at checking the degree of deviation of the current batch from the base group, which is selected as the reference. However, as the sample size is only 3 pieces, it is proposed to evaluate the homogeneity of production batches using nonparametric statistical evaluation criteria. The considered approach makes it possible to guarantee radiation hardness due to the controllability and stability of the CMP, which helps to minimize technical and economic costs and the volume of radiation tests.