The effect of ultrahigh temperature rapid thermal oxidation (RTO) on the behavior of oxygen precipitates in Czochralski silicon (Cz-Si) wafers was investigated using infrared (IR) tomography. Dense oxygen precipitate nuclei were formed in the bulk of the Cz-Si wafers when the treatment temperature was increased to 1350 • C. Furthermore, when ultrahigh-temperature RTO was combined with cooling rates of over 50 • C/s, the density of the oxygen precipitate along the radial direction exhibited significant uniformity. It is assumed that the tendency to form oxygen precipitates in Cz-Si wafers during RTO critically depends upon increasing the concentrations of vacancies that form under ultrahigh-temperature conditions and an oxygen atmosphere. Our results clearly indicate that highly dense oxygen precipitate nuclei can uniformly form along the radial direction of the Si wafer during rapid cooling after RTO at temperatures above 1350 • C.Oxygen precipitates in Czochralski silicon (Cz-Si) wafers, which effectively act as getter sites of impurities, are one of the most important characteristics that enable the fabrication of consistently stable devices. 1,2 However, they are also responsible for decreasing the mechanical strength of Cz-Si wafers if the size and density are not appropriately established. 3 For this reason, strict and highly accurate control of oxygen precipitates over the entire span of a Cz-Si wafer is necessary in order to develop advanced semiconductor devices. In particular, for semiconductor devices that require complicated structural enhancements such as scaling and three-dimensional chip integration, new technology for controlling oxygen precipitates will gain more significance, specifically because endurance against the stress induced in Si wafers during device fabrication is becoming increasingly crucial. [4][5][6] The behavior of oxygen precipitates in Cz-Si crystals is closely related to point defects such as vacancies and interstitial Si atoms. [7][8][9] Vacancies promote the formation of oxygen precipitates because their nucleus is formed as a complex between oxygen atoms (O) and vacancies (Va); for instance, in the form of O 2 Va. Therefore, controlling point defects during Cz-Si crystal growth has been extensively studied. 7-9 Maeda et al. 7 investigated the relation between the density of oxygen precipitate nuclei and the cooling rate used during CzSi crystal growth at approximately 1100 • C. Their results indicated the importance of vacancy survival by void aggregation during the cooling process, which results in the formation of oxygen precipitate nuclei. V/G (i.e., the ratio of the rate of crystal growth (V) to the axis temperature gradient (G) in the neighborhood of the growth interface) is suggested to be the key parameter that determines the excess number of point defects that form during Cz-Si crystal growth. 8 It has previously been reported that a whole defect-free domain can be formed in a Cz-Si crystal by appropriately structuring the hot zone in pulling furnace so that the distr...

To clarify the point defect reaction in silicon wafers under rapid thermal processing (RTP) at more than 1300 • C using an oxidation ambient, the vacancy (V) concentration induced in the wafers by RTP was investigated at various oxygen partial pressures. The V concentration was estimated by evaluating the density of oxygen precipitates after thermal treatment. The degree of supersaturation of interstitial silicon (I) was determined using the estimated V concentration, resulting in the equation (C I −C I eq )/C I eq = A(T)(dX O /dt) 0.4 . Here, (C I −C I eq )/C I eq denotes the supersaturation of I, A(T) denotes a coefficient depending on temperature T, and dX O /dt denotes the growth rate of the oxide film. Furthermore, the same relationship was confirmed for the oxidation-enhanced diffusion (OED) of dopants (900-1150 • C) and oxidation-induced stacking fault (OSF) growth (1100-1240 • C). As the Arrhenius plots of A(T) for RTP, OED, and OSF can be represented by a single line, it was determined that A(T) = 1.84 × 10 −9 exp(2.51 eV/k B T) (h/μm) 0.4 in the range 900-1350 • C.

The suppression of oxygen precipitation in Czochralski silicon (Cz-Si) using the ultrahigh-temperature rapid thermal oxidation (ultrahigh-temperature RTO) technique was investigated by infrared (IR) tomography. The oxygen precipitate nuclei generated during crystal growth were completely dissolved, and the formation of new nuclei due to ultrahigh-temperature RTO was also restrained by controlled slowing of the cooling rate. The ultrahigh-temperature RTO technique is demonstrated to effectively control the oxygen precipitate nucleus formation to yield either uniformly distributed precipitates or completely suppressed precipitation. Our results indicate the flexible and precise control of oxygen precipitation nucleus using ultrahigh-temperature RTO technique is beneficial for device fabrication. Oxygen precipitates in Czochralski Silicon (Cz-Si) wafers effectively act as getter sites for heavy metal impurities in semiconductor devices, 1,2 and they also increase the mechanical strength of the wafer by precipitation hardening.3 Both these roles are important for stable device manufacturing, but oxygen precipitates are also responsible for decreasing the mechanical strength of the wafers if their size and density are not appropriately controlled. 4 In addition, when oxygen precipitates remain in the device formation region, they can result in failure due to current leakage. 5 For this reason, oxygen precipitation must sometimes be suppressed depending on the kind, structure, and process conditions of a semiconductor device. In particular, because of current advances in device structures such as scaling and threedimensional chip integration, precise control of oxygen precipitation will become more significant as the stress induced in Si wafers during device fabrication becomes increasingly crucial.6-8 Therefore, an effective method that can be used for either promoting or suppressing oxygen precipitation in Cz-Si crystals is needed.Many studies have been performed on methods for achieving such precise control of oxygen precipitation. However, maintaining the stability of the growing crystal both in the pulling and radial directions still remains difficult. Thus, both local and widespread nonuniformity often exists in the grown crystal. 9,10 To address this very important problem, we have proposed rapid thermal oxidation (RTO) at ultrahigh temperature (ultrahigh-temperature RTO).11 Our results obviously demonstrated that the oxygen precipitates generated during the crystal growth were dissipated entirely, and dense oxygen precipitate nuclei were formed uniformly in the radial direction during RTO at temperatures over 1350• C. We believed that the newly formed oxygen precipitates in the wafers that had been subjected to ultrahigh-temperature RTO were closely related to preserved vacancies. In particular, each oxygen precipitate nucleus is thought to consist of an oxygen-vacancy complex (for example, O 2 V). 12Ultrahigh-temperature annealing using rapid thermal processing (RTP) has great advantages in terms of uniformit...

A new control technique for achieving compatibility between crystal quality and gettering ability for heavy metal impurities was demonstrated for a nitrogen-doped Czochralski silicon wafer with a diameter of 300 mm via ultra-high temperature rapid thermal oxidation (UHT-RTO) processing. We have found that the DZ-IG structure with surface denuded zone and the wafer bulk with dense oxygen precipitates were formed by the control of vacancies in UHT-RTO process at temperature exceeding 1300 °C. It was also confirmed that most of the void defects were annihilated from the sub-surface of the wafer due to the interstitial Si atoms that were generated at the SiO2/Si interface. These results indicated that vacancies corresponded to dominant species, despite numerous interstitial silicon injections. We have explained these prominent features by the degree of super-saturation for the interstitial silicon due to oxidation and the precise thermal properties of the vacancy and interstitial silicon.

Coupled theoretical and computational work is presented aimed at understanding and modelling stimulated Raman backscattering (SRBS) relevant to laser-plasma interactions in large-scale, homogeneous plasmas. With the aid of a new code for simulating and studying the nonlinear coupling in space-time of a large number of modes, and an Eulerian Vlasov-Maxwell code for studying the evolution of large amplitude electron plasma waves, we report results and their interpretations to elucidate the following five observed, nonlinear phenomena associated with SRBS: coupling of SRBS to Langmuir decay instabilities (LDIs); effect of ion-acoustic damping on SRBS; cascading of LDI; stimulated Raman scattering cascades; and stimulated electron acoustic wave scattering (SEAS).