Predicting oxide reliability from in line process statistical reliability control

This paper demonstrates the applicability of the building in reliability approach by using a combination of experimental design techniques and test structures to relate in line SPC parameters to reliability. The experimental design techniques used to demonstrate the links between SPC and reliability were Taguchi and Response Surface Methodology Central Composite Face Centred Design. Of primary interest was modelling the intrinsic distribution and the secondary objective was modelling the total distribution to understand the causes of the extrinsic component of the total distribution. The Taguchi experiment was used initially as a screening experiment to select the SPC parameters which had the most critical effect on the intrinsic and extrinsic oxide reliability. Once these parameters were selected Central Composite Face Centred Design was used to generate another experiment with which to model the results. The results from this experiment indicate that the intrinsic reliability of the oxide could be predicted from in line process control parameters with 95% confidence. The extrinsic contribution to the reliability distribution was investigated by analysing the total distribution and modelling the results. In this instance it was possible to model the results with 99.5% confidence. In both cases models and response surfaces have been generated which are different for the 2 distributions analysed. The models were generated with the untransformed data and are highly quadratic. The paper introduces the concept of Statistical Reliability Control (SRC) and indicates that by using Statistical Reliability Control it is possible to monitor and predict the reliability of the gate oxide process on line in real time