Properties of Atmospheric and High Pressure Oxide Capacitors with Laser‐Recrystallized Polysilicon Electrodes

Abstract

A study concerning the effects of cw laser recrystallization of polysilicon electrodes on the integrity of the underlying oxide and the interface properties has been carried out. Thicknesses of the oxides used in this study ranged from 300 to 1100Å. There was no significant change in the breakdown field strength, in the I‐V characteristics, or in the minority carrier generation lifetime of the oxides due to laser annealing. A slight undesirable shift of the C‐V curves was observed as a result of laser processing, but was eliminated with a subsequent thermal anneal at 900°C or higher in ambient. SEM examination of the recrystallized polysilicon surface morphology revealed that large, smooth grains were formed, with no undesirable effects on the oxide integrity. However, for laser powers above the threshold for melting of the silicon substrate, degradation of the electrical and structural properties was observed. This result was difficult to avoid for the case of thin oxides (≤ 300Å), due to the narrow laser processing window. Therefore, it is concluded that cw laser recrystallization does not adversely affect the properties of the oxide layer, the starting substrate, or the interface, if it is carried out at a laser power within the useful laser processing window.