Impact of Rapid Thermal Oxidation at Ultrahigh-Temperatures on Oxygen Precipitation Behavior in Czochralski-Silicon Crystals III

Abstract

This paper describes the annihilation behavior of void defects in Czochralski silicon wafers during ultrahigh-temperature rapid thermal oxidation (RTO) at temperatures over 1300 • C. Our results clearly demonstrate that ultrahigh-temperature RTO can provide not only the control of oxygen precipitation nuclei, but also annihilation of void defects. It is estimated from point defect calculations that the Ci/Ci eq ratio still remains supersaturated because of the oxidation of the Si surface even though the type of the dominant point defect changes from interstitial Si to vacancies during ultrahigh-temperature RTO. Oxygen precipitates (OPs) in a Czochralski silicon (Cz-Si) wafer can degrade the performance of semiconductor devices if they are in the active region of the Si wafer, i.e., the surface layer. On the other hand, they can improve device fabrication yield through their ability to enhance impurity gettering and through mechanical strengthening, both of which are important characteristics for semiconductor device fabrication.1,2 Thus, the OPs must be controlled in an appropriate manner depending on the structure of the intended semiconductor devices and the production process employed. More precise and uniform control of OPs in Si wafers will be a significant factor for future advanced semiconductor devices. To understand this very important issue, we previously investigated the re-formation effect of OP nuclei using ultrahigh-temperature rapid thermal oxidation (RTO), at over 1300• C, and achieved wide and precise controllability of new OP nuclei.3 This technique also demonstrated a remarkable ability to eliminate heterogeneity effects such as OP nuclei or related defects in the grown crystal. Ultrahigh-temperature annealing using rapid thermal processing (RTP) has significant advantages in terms of excellent temperature uniformity in the radial direction of the Si wafer as compared to the Cz-Si crystal growth process.As mentioned above, ultrahigh-temperature RTO showed a remarkable ability to control the effects of the OP nuclei. The behavior of OP nuclei in Cz-Si crystals is strongly related to point defects such as vacancies and Si interstitials. 4 Vacancies promote the formation of OP nuclei because these nuclei are formed as a complex between oxygen atoms and vacancies. It is generally known that annealing in an oxygen atmosphere is not a practical way to increase vacancy concentration because Si interstitials are dominant in the Si wafer due to the injection of Si interstitials from the oxidized surface. However, as we previously reported, 3 the behavior of OP nuclei can be controlled by changing the dominant point defects from Si interstitials to vacancies depending on the difference of each thermal equilibrium concentration at ultrahigh temperatures, even though the oxidation atmosphere is used for RTP. Furthermore, in the case of ultrahigh-temperature RTO, it is expected that Si interstitials also exist at high concentration due to the Si surface oxidation even though the dominant point defects are ...

Point Defect Reaction in Silicon Wafers by Rapid Thermal Processing at More Than 1300°C Using an Oxidation Ambient

“…2 Araki et al reported unique results for the RTP technique above 1300 • C using a pure oxygen ambient. [5][6][7] This technique not only effectively annihilates void defects in the wafers but also generates and leaves excess V in spite of oxidation, leading to wafers with the DZ-IG structure. Furthermore, Maeda et al explained this feature as a characteristic state of point defects in the wafers using a numerical simulation.…”

Near‐Surface Defect Control by Vacancy Injecting/Out‐Diffusing Rapid Thermal Annealing

“…The inclusion of a pre‐step at temperatures >1210 °C in an Ar/O 2 ambient before nitriding is useful as the wafer can further homogenize and increase the BMD‐denuded zone, as small grown‐in BMDs (≤12 nm) are dissolved near the surface and in the bulk. This dissolution of BMD nuclei starts lower in temperature as described by Sudo et al and Araki et al, respectively …”

“…This dissolution of BMD nuclei starts lower in temperature as described by Sudo et al [17,18] and Araki et al, respectively. [14,15]…”

“…Recently, the oxygen precipitation behavior and defect annihilation of grown-in voids were studied above 1300 C by Araki et al [14,15] They found that even under these oxidizing ambient the BMD formation occurred and in parallel void formation was possible. The complex interplay of interstitial supersaturation and in parallel oxygen precipitate nuclei formation by vacancies was simulated and the needed thermal conditions for nucleation and void dissolution were simulated by Sudo and co-workers.…”