ELECTRICAL PROPERTIES OF DIFFUSED ZINC ON SIO2-SI MOS STRUCTURES

Studies have been made on the C-V characteristics of SiO2-Si MOS structures under various oxidation temperature, heat treatment, and zinc doping conditions. Diffused zinc is expected to have three major effects on the characteristics of SiO2-Si MOS structures. Firstly, zinc behaves as negatively charged ion in SiO2 layer which will compensate a positively charged ion such as a sodium ion. Secondly, zinc atoms behave as acceptor-like surface states at the SiO2-Si interface which may also compensate donor-like surface states at the interface. These two effects will cause the C-V curves to shift toward the positive-voltage direction. Thirdly, zinc atoms behave as shallow acceptors in the semiconductor substrate. These acceptors will change the background doping of the substrate which in turn causes a change of the normalized minimum capacitance. The above three effects have indeed been observed experimentally in both n-type and p-type silicon samples. C-V measurements of zinc diffused samples after 3 months room-temperature aging in air show that there are virtually no changes in comparison with those measured immediately after device fabrication. © 1969.