Gate Oxide Integrity Improvement Research Articles

GOI Improvement in 65nm Sacrificial Oxide Free Process Integration

GOI (Gate Oxide Integrity) improvement in 65nm SAC OX (Sacrificial Oxide) free process integration was studied in this paper. After studying the effects of various processes in STI (Shallow Trench Isolation) module with SAC OX free scheme on GOI, it was found that the dominant process that could degrade GOI was the STI HDP (High Density Plasma) gap fill process. STI HDP gap fill process could cause Si damage on AA corners, also named as AA clipping, which will result in irregular corners and hence a thinner gate oxide formation at imperfect AA corners. This was observed by a TEM (transmission electron microscopy) study. In SAC OX free scheme, the exposed AA Si corners that were damaged during the HDP process did not get consumed and repaired while they would have gotten in the scheme with SAC OX and hence degraded GOI. By optimizing the STI gap fill processes and hardware configuration, the AA clipping can be greatly reduced and GOI can be improved to the required level.

Improvement of Gate Oxide Integrity in Low Temperature Poly Silicon TFT

AbstractThe electrical characteristics of SiH4-based PECVD gate oxide have been investigated with respect to gate oxide integrity (GOI) and its reliability. It was found that the GOI of poly-Si TFT integrated on glass substrate strongly depended on the charge trapping and deep level interface states generation under Fowler-Nordheim stress (FNS). By applying elevated temperature postanneal without vacuum break after the gate oxide deposition, highly reliable gate oxide was obtained. Under FNS, ID-VG curve showed severe shift and degradation of subthreshold slope, which were reduced by adopting post-annealed gate oxide. Besides, the TFT with post-annealed gate oxide showed around 10 times higher charge to breakdown than that of as-deposited gate oxide. Charge to breakdown of MOS capacitors were also studied. By applying post-annealed gate oxide, charge to breakdown drastically improved, which could be explained by reduced charge trapping under FNS.

Influence of oxygen and nitrogen on point defect aggregation in silicon single crystals

Oxygen- and nitrogen-doped floating zone (FZ) crystals were investigated with regard to radial oxygen precipitation, D-defect formation and gate oxide integrity (GOI) behavior as a function of the nitrogen content. It is shown that the inactivation of the nitrogen-enhanced D-defect suppression and GOI improvement is not a result of the reduction of the N-pair concentration due to nitrogen-oxygen interaction. Instead, it is suggested that the diffusivity of vacancies, Si interstitials and nitrogen is reduced due to interaction with oxygen. This leads to a considerable decrease in the nitrogen- enhanced recombination between vacancies and interstitials, which was previously proposed to explain the simultaneous suppression of vacancy- and Si interstitial-type defects by nitrogen doping. The radial oxygen precipitation behavior is explained by applying the formula of Vanhellemont and Claeys (J. Appl. Phys., 62 (9) (1987) 3960; 71 (2) (1992) 1073) for the critical radius of oxygen precipitates which accounts for the influence of vacancies and self- interstitials. A qualitative picture of the radial variation of the vacancy and interstitial concentrations is derived assuming that D-defect formation occurs before the onset of oxygen precipitation.