Ultrathin Gate Dielectric Growth at Reduced Pressure

Abstract

The Growth of ultrathin oxides in N2O ambient has been a subject of extensive research for submicron CMOS technology. Oxides grown in N2O tend to have a higher charge-to-breakdown, less charge trapping under constant current stress, and less interface state generation under current stress and radiation than conventional oxides grown in oxygen [1,2]. In addition the penetration of boron through N2O oxides is significantly less than through conventional thermal oxides [3]. The improved characteristics of N2O are due to an interfacial pileup of nitrogen atoms [1-3]. Thus the growth of thermal oxides in N2O provides a method for obtaining many of the more favorable aspects of reoxidized-nitrided silicon dioxides, with a much simpler process.

Growth characterization of rapid thermal oxides

“…2͑b͒, 3͑b͒, and 4͑b͔͒. This was similarly observed by other groups 14,19,20,22,26 and has been shown to be flow related, and hence dependent on pressure. Furthermore, the values of b obtained from the variable power law fittings range from 0.43 to 0.68, which is close to 0.5.…”

“…For O 2 RTO the mean thickness uniformity obtained is better than 2%. 19,22,26,27 McIntosh et al attributed the phenomenon to a relatively stagnant gas flow at the wafer's center. This suggests that the growth characteristics are parabolic like.…”

“…Furthermore, the values of b obtained from the variable power law fittings range from 0.43 to 0.68, which is close to 0.5. 22 Tobin et al found that the peak N concentration incorporated in oxides that had been annealed in furnace oxidized N 2 O decreased with the flow rate. Indeed, while the variable power law provides a better fit at 100 Torr, especially below 1025°C ͓Fig.…”

“…Indeed, while the variable power law provides a better fit at 100 Torr, especially below 1025°C ͓Fig. 22 It has also been shown that a low oxidant flow rate coupled with a high wafer rotation speed will give the best uniformity. 5͑a͒͑ii͔͒.…”

Nitric Oxide Rapid Thermal Nitridation of Thin Gate Oxides

“…The N 2 0 process is limited in two areas. First, the oxide growth rate is significantly lower than for 02, resulting in a higher thermal-budget process [10]. Second, the incorporation of nitrogen is limited to moderately low levels, approximately 1.7 atomic percent for a 40 A film [11].…”