Impacts of HF etching on ultra-thin core gate oxide integrity in dual gate oxide CMOS technology

In this paper, we investigate the effects of HF etching on the integrity of ultra-thin oxides in dual gate oxide (DGO) CMOS technologies. We found that both the HF concentration in the etching solution and the over etching (OE) time are important parameters that greatly affect the device performance and reliability. Our results indicate that, with a proper over etching period, using a concentrated HF solution results in better ultra-thin gate oxides in terms of reduced defect density, improved device performance and reliability, compared to using diluted HF solution. It is also found for the first time that negative-bias-temperature instability (NBTI) immunity for PMOSFETs is improved by using concentrated HF solutions.