New method for lifetime evaluation of gate oxide damaged by plasma processing

A quantitative model is proposed, clarifying the relationship between the charge-to-breakdown with constant current injection (Q/sub bd/) and the time-to-breakdown with constant-voltage stress (t/sub bd/) for gate oxides damaged by plasma processing. By including the dependence of Q/sub bd/ on the stress current density, one can predict the t/sub bd/ by means of counting the fraction of the lifetime expenditure; J/spl Delta/t/Q/sub bd/(J), where J is the current density at each period (/spl Delta/t) under constant-voltage stressing, until the sum of the ratio is unity. The results show good agreement for the oxides of MOS capacitors with different gate areas. This method is useful for projection of the oxide lifetime.<
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