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Analysis of Breakdown in New Stepgate Structures with Graded LDD


Roji Marjorie S, Govindacharyalu PA, Lal Kishore K


Vol. 17  No. 4  pp. 106-114


A new stepped gate structure with a graded LDD is presented. This graded LDD helps to spread the electric field throughout the LDD region and thereby obtain a high breakdown voltage of 68 V. Efforts were made to obtain the optimum structure from the breakdown point of view by determining the number of LDD implantations needed, the optimum LDD dose and the optimum device length. A 2D analysis was carried out on the various parameters such as the horizontal and vertical electric field patterns, the impact generation profiles, generation recombination, impact generation before and after breakdown, the carrier concentration, electron and whole current densities and the conduction current densities of the structure. A mathematical analysis was also carried out which established that the breakdown phenomenon is not only by the ionization integral but the shape of the field contours also contribute to the breakdown region and breakdown occurs in the middle of the wedge shaped neutral region.


Stepped gate, breakdown voltage, LDMOS, LDD, carrier.