Reduction of oxide charge and interface-trap density in MOS capacitors with ITO gates

The electrical properties of MOS capacitors with an indium tin oxide (ITO) gate are studied in terms of the number density of the fixed oxide charge and of the interface traps N/sub f/ and N/sub it/, respectively. Both depend on the deposition conditions of ITO and the subsequent annealing procedures. The fixed oxide charge and the interface-trap density are minimized by depositing at a substrate temperature of 240 degrees C at low power conditions and in an oxygen-rich ambient. Under these conditions, as-deposited ITO films are electrically conductive. The most effective annealing procedure consists of a two-step anneal: a 45-s rapid thermal anneal at 950 degrees C in N/sub 2/, followed by a 30 min anneal in N/sub 2//20% H/sub 2/ at 450 degrees C. Typical values obtained for N/sub it/ and N/sub f/ are 4.2*10/sup 10/ cm/sup -2/ and 2.8*10/sup 10/ cm/sup -2/, respectively. These values are further reduced to 1.9*10/sup 10/ cm/sup -2/ and >