Hard error dose distributions of gate oxide arrays in the laboratory and space environments

Hard errors or "stuck bits" observed in a single memory can occur over a broad range of macroscopically measured doses. It is shown here that a major contributing factor to this is the microscopic variation of deposited dose across the large array of gate oxides composing the memory. In addition, processing variations also contribute to the spreading of hard error doses. A statistical model of these factors is presented and compared to Co-60 data. Comparisons are then made between the hard error dose distribution for Co-60 and that expected in the heart of the proton belts. It is shown that even though the average hard error dose in the proton belts is greater, the onset hard error dose can be less. Thus, the relations between the onset dose for hard errors in the two environments should be thoroughly understood before qualifying parts for space applications.