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We performed an extensive study of light induced degradation experiments in PERC solar cells made of Boron doped Cz Silicon material from several experimental crystals. Strong LeTID (Light and Elevated Temperature Induced Degradation) amplitudes were found in cells originating from the top and tail part of the crystals. A statistical analysis reveals a strong correlation to the bulk concentration of Aluminium in cells originating from wafers close to the tail. Close to the top, the LeTID effect is strongly enhanced whenever Oxygen precipitation occurs in the cell process.

Four industrial-scale n-type Czochralski silicon crystals were grown with different impurity contents, i.e. metallics, phosphorus and oxygen. Horizontal slices were obtained from the top and middle of the crystals and were characterized in terms of lifetime and both defect and impurity distribution. The slabs characterization was performed both under as-grown conditions and after 2-step oxidation. Solar cells were fabricated from neighboring wafers with n-PASHA process and the overall efficiency determined. The crystal grown under low oxygen incorporation conditions has shown higher average as-grown lifetimes compared to the other crystals. The addition of lower phosphorus concentration to the melt resulted in an improvement of the lifetime of the crystal while the use of low grade feedstock has mainly affected the quality at the middle of the corresponding crystal. However, the major difference between top and middle heights was still the interstitial oxygen concentration for all crystals under investigation. The distribution of the interstitial oxygen concentration has not shown significant fluctuations through the samples radial direction. In addition, significant void fluctuations were found through the slabs radial direction, and demonstrate possible variations in the vacancy incorporation at the solidification interface during crystal growth. After heat treatment, large fluctuations of the lifetime were found through the samples radial direction, and are mainly associated to the local fluctuations of the oxygen precipitate density. However, these variations were suppressed in the crystal of lower oxygen incorporation. Solar cells performance degradation was mainly correlated with oxygen precipitation during their fabrication. It was also demonstrated that their efficiency is largely affected by the formation of detrimental striations of high periodicity. Their formation was thus associated to fluctuations of the vacancy concentration due to transient growth and their interaction with oxygen during crystal cooling. These oxygen nuclei may grow during solar cells processing and become even more detrimental to their performance.

We report on the bulk lifetime improvement in Czochralski (CZ) silicon wafers of solar cells by pre-rapid thermal processing (RTP). The commercially available n-type CZ silicon wafers with the thickness of 180 µm were used. Silicon wafers were subjected to pre-RTP followed by the three-step thermal annealing: the first was oxidation at 900 °C for 60 min, the second was isothermal annealing at 1050 °C for 30 min in a nitrogen atmosphere, and the third was oxidation at 900 °C for 10 min, which corresponded to the typical processes of a fully ion-implanted passivated emitters, rear totally diffused silicon solar cell. We investigated the impact of pre-RTP condition on the oxygen precipitation in CZ silicon wafer. A pre-rapid thermal oxidation (RTO) at 1050 °C for 30 sec suppressed the oxygen precipitation during the above three-step annealing, resulting in the lifetime improvement.We report on the bulk lifetime improvement in Czochralski (CZ) silicon wafers of solar cells by pre-rapid thermal processing (RTP). The commercially available n-type CZ silicon wafers with the thickness of 180 µm were used. Silicon wafers were subjected to pre-RTP followed by the three-step thermal annealing: the first was oxidation at 900 °C for 60 min, the second was isothermal annealing at 1050 °C for 30 min in a nitrogen atmosphere, and the third was oxidation at 900 °C for 10 min, which corresponded to the typical processes of a fully ion-implanted passivated emitters, rear totally diffused silicon solar cell. We investigated the impact of pre-RTP condition on the oxygen precipitation in CZ silicon wafer. A pre-rapid thermal oxidation (RTO) at 1050 °C for 30 sec suppressed the oxygen precipitation during the above three-step annealing, resulting in the lifetime improvement.

Woongjin Energy Co., Ltd., Daejeon 305-509, Korea(Received November 13, 2014)(Revised November 27, 2014)(Accepted December 5, 2014)Abstract Recent studies have shown methods of improving solar cell efficiency. Especially on single crystalline siliconwafer which is high-efficiency solar cell material that has been widely studied. Interstitial oxygen (Oi) is the main impurityin the Czochralski (Cz) growing method, and excess of this can form precipitates during cell fabrication. We havedemonstrated the effect of Oi impurity and oxygen precipitation concentration of the wafer on Cz-silicon solar cell efficiency.The result showed a decrease in cell efficiency as Oi and oxygen precipitation increase. Moreover, we have found that thecritical point of [Oi] to bring higher cell efficiency is at 14.5 ppma in non-existent Bulk Micro Defect (BMD).Key wordsSolar cells, Efficiency, Czochralski silicon, Oxygen precipitation, BMD

The swirl defect is observed in both n-type Czochralski (Cz) and non-contact crucible (NOC) Si wafers. It is postulated to be the outcome of oxygen precipitation during crystal growth and/or post-growth high temperature processes, specifically processes involving temperatures in the range of 800°C–1000°C. This defect is characterized by low lifetime ring-like regions that decrease the device performance. We employ a technique based on temperature- and injection-dependent photoluminescence imaging (TIDPLI) to characterize the swirl defect. We compare the calculated fingerprints of the defects responsible for the swirl pattern observed in both Cz and NOC-Si wafers to determine whether the swirls are caused by the same defect. We find significantly different defect fingerprints for the swirl defects in n-type Cz and NOC-Si. The Shockley-Read-Hall (SRH) description of the Cz-Si defects differ not much from the SRH description of intentionally grown oxygen precipitates, whereas the SRH parameters for the NOC-Si defects differ significantly. Identifying the limiting defect, allows us to suggest methods for its annihilation. We then successfully apply a rapid thermal annealing treatment to dissolve swirl defects in Cz-Si samples and homogenize the lifetime.

Oxygen precipitation (OP) behaviors were investigated for Czochralski (Cz) silicon wafers, which were coated with silicon nitride (SiNx) films or not, subjected to two-step anneal of 800C/4 h+1000°C/16 h following rapid thermal processing (RTP) at different temperatures ranging from 1150 to 1250C for 50 s. It was found that OP in the Cz silicon wafers coated with SiNx films was stronger in each case. This was because that nitrogen atoms diffused into bulk of Cz silicon wafer from the surface coated SiNx film during the high temperature RTP. Furthermore, it was proved that the RTP lamp irradiation facilitated the in-diffusion of nitrogen atoms, which was most likely due to that the ultraviolet light enhanced the breakage of silicon-nitrogen bonds.

In this paper, the influence of the rapid thermal annealing of single crystalline Cz-Si wafers on the evolution of the concentration of interstitial oxygen as well as oxygen in precipitated oxide phase was investigated by infrared spectroscopy. The wafers were preliminary furnace annealed to create the precipitate seeds. The concentration of interstitial oxygen was shows to decrease considerably as a result of annealing during up to 40 min together with the growth of the concentration of precipitated oxygen. This effect depended on the purity and defect structure of initial wafers. The kinetic model was developed to account for the observed effects based on the modification of the solubility level for interstitial oxygen induced by defects as well as its diffusivity. Obtained results of simulation agree well with the experimental data.

Low temperature boron and phosphorous diffusion gettering (BDG and PDG) of iron in Czochralski-grown silicon were experimentally studied. Differences and similarities between the gettering techniques were clarified by using intentionally iron contaminated wafers emphasizing especially the effect of oxygen. Experiments showed that the surprisingly high gettering effects of BDG could be explained by B-Si precipitates. Oxygen precipitation was seen to decrease minority carrier diffusion length after long gettering at low temperatures in both BDG and PDG. In the case of BDG oxygen precipitation affected more as a higher thermal budget was needed to obtain similar sheet resistance to that of PDG. According to experiments the efficiency of BDG can not be concluded from the sheet resistance, whereas the efficiency of PDG can. This has practical influences in a process control environment.

Diffusion doping with gold is shown to reduce the microhardness of silicon single crystals. Oxygen precipitation suppresses this process because diffusing interstitial gold atoms, Aui, interact with oxygen and become captured by growing precipitates.

Oxygen precipitation in heavily phosphorous (P)-doped Czochralski silicon (CZ-Si) subjected to the ramping or two-step anneals was investigated. It was revealed that the grown-in oxygen precipitates exerted significant effect on oxygen precipitation behaviors and then resulted in distinctive oxygen precipitation for the wafers form various positions of the ingot. Moreover, it was found that both the seed and tang-end wafers processed significantly intense nucleation at 650 oC without the influence of grown-in oxygen precipitates. It was considered that the heavily P-doping introduced phosphorus related precipitation at 650 oC. When the annealing temperature increased, the capability for nucleation of oxygen precipitation by heavily P-doping would be gradually weakened but the one by oxygen clustering became pronounced. In this case, it was understandable that the tang-end wafer processed higher density of oxygen precipitates than the seed-end wafer at around 750 oC, while a lower one at 1000 oC.

Oxygen precipitation in heavily phosphorus-doped (P-doped) Czochralski (CZ) silicon subjected to single-step annealing at high temperatures in the range of 1050–1150 °C has been investigated. It was indicated that in the heavily P-doped CZ silicon there were more grown-in oxygen precipitates, thus promoting the generation of induced defects and accelerating the Ostwald ripening of oxygen precipitates during the high temperature annealing, in comparison with the control lightly P-doped CZ silicon with comparable initial oxygen concentration and thermal history. Moreover, it was found that, during the annealing at 1050 °C, oxygen precipitation in the outer region about 2.5 cm in width was noticeably retarded with respect to that in the inner region across the heavily P-doped CZ silicon wafer. The mechanism for the enhanced formation of grown-in oxygen precipitates and the retardation of oxygen precipitation at high temperature, as mentioned above, has been tentatively explained.

The effects of two-step rapid thermal processing (RTP) sequentially in different ambients on the formation of denuded zone (DZ) and oxygen precipitation in the Czochralski (CZ) silicon wafers have been investigated. With the first-step RTP in Ar ambient, no obvious DZ but a high density of bulk micro-defects (BMDs) were formed in the sample with the second-step RTP in N2 ambient, while the BMD density in the sample with the second-step RTP in O2 ambient was remarkably low. With the first-step RTP in N2 ambient, a high density of BMDs and a width of DZ could be formed in either of the samples with the second-step RTP in Ar or O2 ambient, but the DZ width in the two samples differed to a certain extent. With the first-step RTP in O2 ambient, the two samples with the second-step RTP in Ar and N2 ambients respectively possessed reasonably comparable DZ width and BMD density. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Czochralski silicon (Cz Si) crystals with germanium (Ge) doping are considered to be of potential application for integrated devices. In this presentation, the influence of Ge doping of Cz Si crystals on oxygen precipitate thermal stability has been discussed. Compared with the conventional Cz Si, oxygen precipitates in Ge-doped Cz (GCz) Si was proposed to be poorer stable thermally during high temperature anneals, which is ascribed to the formation of smaller precipitates. Meanwhile, the oxygen precipitation was promoted in GCz Si wafers that received a high temperature pre-anneal treatment, which has been considered to be associated with the assumption of Ge-related complexes by the intended Ge doping.

The effect of the prior conventional furnace anneal at 1250 °C with different cooling rates on oxygen precipitation in Czochralski silicon during the subsequent low–high two-step heat treatment was investigated. In comparison with oxygen precipitation in the as-received sample, that in the samples with the prior 1250 °C anneal with fast or slow cooling rate was significantly enhanced. It is believed that the prior 1250 °C anneal with fast cooling rate introduced a considerable amount of vacancies, thus enhancing oxygen precipitation in the subsequent anneal; while, that with slow cooling rate substantially removed the silicon interstitials generated during the formation of grow-in oxygen precipitates, thus eliminating the retard effect on oxygen precipitation in the subsequent anneal.

Oxygen precipitation within the magic denuded zone (MDZ) founded by rapid thermal processing in Czochralski silicon (CZ-Si) wafers is investigated. After the standard MDZ process, the CZ-Si wafers are further subjected to two specific oxygen precipitation annealing, respectively. It is found that the MDZs in CZ-Si wafers shrunk notably because oxygen precipitation occurs within the MDZs. However, a width of substantial DZ still remains within the wafer. Therefore, it is believed that the outer region of the MDZs, which corresponds to the oxygen denuded zone formed in the course of rapid thermal process and high temperature annealing, is a substantial defect-free zone which acts as the active area for semiconductor devices.

The formation of a denuded zone (DZ) and the bulk-microdefects (BMDs) region within conventional and nitrogen-doped Czochralski (NCZ) silicon subjected to ramping anneals has been investigated. It was found that the terminal temperature of the ramping anneal should be high enough to create a DZ while the starting temperature should be low enough to generate desirable high density of BMDs. Comparatively speaking, with the same heat treatment, the NCZ silicon possesses higher density of BMDs and a narrower DZ than CZ silicon. Moreover, for NCZ silicon, the ramping anneal can initiate at relatively higher temperature to generate an appropriately high density of BMDs. Of importance is that the ramping anneal with a final isothermal anneal at an elevated temperature such as 1150 °C can effectively create a substantial DZ, where there were no defects generated in the subsequent heat treatment significantly enabling oxygen precipitation.

The effect of rapid thermal processing (RTP) on the oxygen precipitation occurring at 1050 °C in a Czochralski (CZ) silicon wafer has been investigated. It has been proved that the RTP-induced vacancies only enhance the early stage oxygen precipitation at 1050 °C in terms of the precipitation rate. Furthermore, it is somewhat unexpected that after a lengthy 1050 °C anneal the oxygen precipitates generated in the CZ silicon wafer with prior RTP treatment had considerably lower density and larger sizes in comparison with those generated in the CZ silicon wafer without prior RTP treatment. The reason for this is that the prior RTP treatment will dissolve some of the grown-in oxygen precipitates, thus making the RTP-treated wafer possess fewer nuclei contributing to oxygen precipitation in the subsequent 1050 °C anneal. Moreover, the numbers of resulting precipitated oxygen atoms due to a lengthy 1050 °C anneal were nearly the same in the CZ silicon wafers with and without prior RTP treatment. Additionally, it has been illustrated that the high temperature RTP has superior capability to dissolve the existing oxygen precipitates. It is worthwhile to point out that, when addressing the effect of RTP on the oxygen precipitation behaviour during the subsequent anneal, two functions arising from the RTP treatment, that is, the injection of vacancies into the silicon wafer and the dissolution of grown-in oxygen precipitates existing in the silicon wafer, should be taken into account.

In this paper, through the investigation of the effect of rapid thermal processing (RTP) at different temperatures on oxygen precipitation in Czochralski (CZ) silicon wafers subjected to two-step (low?high) anneal and one-step high-temperature anneal, the enhancement role played by vacancies in oxygen precipitation occurring at low temperature and high temperature have been revealed. For the two-step anneal, the RTP-introduced vacancies significantly facilitate the formation of oxygen precipitate nuclei during the low-temperature anneal and, therefore, enhance oxygen precipitation during the subsequent high-temperature anneal. Regarding the one-step high-temperature anneal, the RTP-induced vacancies that later combine with oxygen atoms to become the O2V species significantly enhance the early stage oxygen precipitation in terms of the precipitation rate, however, the RTP-induced vacancies do not increase the amount of precipitated oxygen atoms in the CZ silicon wafer subjected to a prolonged high-temperature anneal. Due to the fact that for the CZ wafer with prior RTP the one-step high-temperature anneal produces much lower density bulk microdefects than the two-step (low?high) anneal, it is believed that the low-temperature anneal is a must for the 'magic denuded zone' process.

The effect of rapid thermal process (RTP) on the oxygen precipitation and on the denuded zone (DZ) formation in nitrogen-doped Czochralski (NCZ) silicon wafers has been investigated. The DZ can be formed at the surface of NCZ wafers subjected to RTP annealing. However, the oxygen precipitation and bulk microdefects in NCZ silicon are changed by RTP preannealing, which is a result of N-N bonds broken during RTP treatment.

The warpage of conventional Czochralski (CZ) and nitrogen-doped Czochralski silicon (NCZ) wafers with similar oxygen concentration were investigated. In the experiments, a two-step annealing process was taken to generate oxygen precipitates. After the elevated temperature annealing, no obvious warpage in both the CZ and NCZ silicon wafers was found, even'if nitrogen was found to enhance oxygen precipitation and the stronger internal stresses were detected at the edge and center of an annealed wafer. It is considered that oxygen precipitates with relatively smaller sizes were successful in preventing the warpage of the silicon wafers, which is mainly dependent on thermal stress, because the oxygen precipitates can pin dislocations.

The carrier concentration profiles in p-type Czochralski (CZ) silicon (Si) wafers respectively subjected to one-step high temperature and three-step high-low-high annealing followed by a prolonged 450°C annealing have been investigated by spreading resistance profile (SRP). It is found that the carrier concentration profile in the p-type CZ Si wafer subjected to three-step annealing is characteristic of a PNP bipolar structure, while, that in the wafer subjected to one-step annealing is just characteristic of a PN junction. It is suggested that the formation of the PNP bipolar structure is due to the denuded zone formation and bulk oxygen precipitation.

The effect of heat treatment conditions and point defects on oxygen precipitation was investigated with various grown-in defect region wafers. The behavior of oxygen precipitation depends on the nucleation temperature and the type and the concentration of point defects. The peak temperature of nucleation for oxygen precipitation is 687–734°C in vacancy-rich, oxidation-induced stacking fault ring, interstitial Si-rich and interstitial pure regions. In vacancy-pure region, the peak temperature of nucleation is about 870°C. The vacancy plays an important role in increasing the peak temperature of nucleation for oxygen precipitation.

Flash lamp annealing of moderately B-doped CZ silicon wafers for 20 ms with a normalized irradiance of about 0.9 was used to efficiently suppress oxygen precipitation during subsequent thermal processing. In this way, the minority carrier lifetime measured at high injection level by microwave-detected photo-conductance decay (μ-PCD) was increased from about 30 microseconds to about 300 microseconds after a thermal process consisting of 780 °C 3 h + 1000 °C 16 h. The grown-in oxide precipitate nuclei were shrunken to a subcritical size during the flash lamp anneal which prevents further growth during subsequent thermal processing.

The behavior of oxygen precipitation was investigated in radial direction using Si wafers with different generation area of vacancy-related defects. Oxygen precipitation is more enhanced in vacancy-rich region than in interstitial-rich region. The behavior of oxygen precipitation in the radial direction is strongly dependent on the size of vacancy-rich region which is related to crystal growth condition. Anomalous oxygen precipitation occurred in the marginal vacancy-rich region and the inner edge of interstitial rich region. In the marginal interstitial-rich region, however, oxygen precipitation is suppressed to nearly zero.

The study of the optical behavior of oxygen in silicon is presented, based on infrared absorption measurements performed at liquid helium temperature. A total of six groups of silicon wafers characterized by different initial concentrations of interstitial oxygen from similar to 2 x 10(17) to similar to 10(18) atoms cm(-3) were analysed. The experimental conditions were chosen so as to distinguish the contributions from interstitial and precipitated oxygen, while the thermal treatment of the samples was studied in order to cause the growth of the grown-in precipitates. The relative concentrations of platelet and spheroid precipitates grown after the thermal treatment of the wafers are discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

The structures of Ge–O complexes in germanium-doped Czochralski (CZ) silicon wafers have been investigated by means of density functional theory (DFT). The calculations present the fact that the Ge–O complexes can be formed with the absence of vacancy during low-temperature thermal cycles so that they can enhance oxygen precipitation. Furthermore, the total energy of different Ge–O complexes is calculated, and then optimized and stable structure of Ge–O complexes is suggested.

Two-step and three-step anneals were applied systematically to a set of commercial Czochralski silicon wafers. The microdefects generated during the anneals were decorated with Wright etchant and investigated by optical microscopy. The types of microdefect generated were observed to vary with the time and temperatures of the nucleation anneal. The observations provide very useful information relevant to the control of microdefects in Czochralski silicon to improve the gettering efficiency.

Quantitative measurements of the oxygen precipitate rate as a function of annealing were made in Czochralski-grown silicon wafers that contained different initial concentrations of oxygen. All wafers were annealed at 1000 °C for 15 min to ensure that the initial cluster-size distributions were identical in all samples of the same composition prior to the multi-step annealing treatments used for the precipitation studies. The experimental data are compared with numerical predictions for time-dependent nucleation within the classical theory of nucleation. Quantitative agreement is obtained between the measured and calculated densities of oxygen precipitates for nucleation temperatures greater than 600 °C, but only over a narrow range of oxygen composition. Below 600 °C, the measured density for all samples is orders of magnitude larger than is predicted from the model. Further, the measured data show an anomalously small temperature dependence for the induction time for nucleation that does not scale with the diffusion coefficient, as expected from the classical theory of nucleation. Fundamentally, the classical theory of nucleation cannot explain the time-dependent nucleation of oxygen precipitates for temperatures below 650 °C. A possible reason is given.

Microscopic and spectroscopic photoluminescence (PL) mapping was performed on a region including intra-grain defects in multicrystalline silicon wafers in the temperature range between 15 and 300 K, and the temperature dependence of PL spectra from the region was studied. We confirmed that the origin of deep-level emission with an intensity maximum at 0.78 eV at room temperature was different from that of dislocation-related lines at low temperature. We believe that the 0.78 eV emission is associated with oxygen precipitation, and that the intra-grain defects are dislocation clusters decorated with not only heavy-metal but also oxygen impurities.

The thermal warpage of nitrogen-doped Czochralski (NCZ) silicon wafers affected by preannealing was investigated. After preannealing at 1000 °C for 6 h, the warpage of the NCZ silicon wafers was suppressed during subsequently thermal warping tests, while the silicon wafers grown under an argon ambient (ACZ) showed an increase in warpage. Nitrogen was considered to be very effective to increase the mechanical strength of silicon wafers because of the formation of nitrogen-oxygen clusters with smaller sizes. After preannealing at 1000 °C for 16 h, both ACZ and NCZ silicon wafers showed a large increase of warpage due to the large amount of oxygen precipitation.

Dependence of mechanical strength of Czochralski silicon (CZ-Si) wafers on the temperature of oxygen precipitation annealing has been studied both experimentally and theoretically. Thermal stress was applied to CZ-Si wafers after oxygen precipitation annealing at 1100°C or 1000°C after preannealing at 800°C. The warpages and the densities of slip dislocations in the wafers annealed at 1100°C are much higher than those in the wafers annealed at 1000°C, nevertheless each precipitate density is almost equal. Transmission electron microscopy observations of the 1100°C samples showed that both platelet and polyhedral precipitates were generated, but very few of these precipitates actually generated punched-out dislocations. In contrast, in the 1000°C samples, only platelet precipitates were generated, many of which generated punched-out dislocations. Further studies showed that slip dislocations formed only from platelets which did not punch out dislocations, i.e., slip dislocations formed only in the 1100°C samples. The mechanism of the generation of slip dislocation by oxide precipitates is discussed with calculated results of the system energy change due to slip dislocation generation.

We investigated the effect of hydrogen annealing in the temperature range from 850 to 1200°C on oxygen precipitation and gate oxide integrity in Czochralski Si wafers. The bulk microdefect density of dynamic random access memory thermal simulation wafers showed a strong dependence on the ramp-up rate conditions of hydrogen annealing. The gate oxide integrity improved after hydrogen annealing at temperatures above 1000°C. However, for better stability of the gate oxide integrity after the heat-treatment, higher temperature annealing is necessary. We observed that the effect of hydrogen annealing was limited to the near surface, because the gate oxide integrity of hydrogen-annealed wafers degraded to that for nonannealed wafers after repolishing.

The influence of native point defect concentration on oxygen precipitation processes in Si O i system has been investigated. The supersaturation degree of native point defects in the bulk of the silicon wafers was varied by changing the conditions of the preliminary oxidation. It has been shown supersaturation of a certain type of native point defect can retard the oxygen precipitation process and change the picture of defect formation.

We have studied internal gettering efficiency of iron in silicon by Deep Level Transient Spectroscopy (DLTS) and standard lifetime – methods (SPV, PCD). Conventional high–low–high anneals were performed to produce a series of wafers with varying denuded zone (DZ) width and oxygen precipitation density. The wafers were intentionally iron contaminated to a level of about 3–5 ∗ 1013 cm−3. After contamination the wafers were annealed at 900 ◦ C and then slowly cooled to 850, 800, 750, 700 or 600 ◦ C. After cooling the remaining interstitial iron concentration was measured by SPV, -PCD and DLTS. The experimental results are compared with simulations. Our results indicate that with this contamination level, the gettering is effective only at temperatures below 750 ◦ C when iron is supersaturated over a factor of twenty. For temperatures above 750 ◦ C the gettering is limited by iron precipitation in the bulk.

During the last decade, the 300 mm silicon wafer has been optimized and one is studying the move to 450 mm crystals and wafers. The ever increasing silicon crystal diameter leads to two important trends with respect to substrate characteristics: the interstitial oxygen concentration decreases while the size of grown in voids (COP’s) in vacancy-rich crystals is increasing. The first effect is due to the large melt in which movements have to be controlled and partly suppressed by the use of magnetic fields. This magnetic confinement leads to a more uniform dopant incorporation but at the same time to a more limited transport of oxygen from the quartz crucible to the melt and the growing crystal. The reduced interstitial oxygen concentration and the lower thermal budget of modern device processing leads to strongly reduced oxygen precipitation and thus internal gettering capacity. The increasing COP size (accompanied by a decreasing density) is caused by the decreasing pulling rate and thermal gradient that have to be used in order to avoid dislocation formation. The slower cooling of the crystal leads to a decreased void nucleation rate and at the same time to an increased thermal budget for void growth as well as a larger number of vacancies available per void.

Gold diffusion in usual Czochralski (Cz) grown Si and in Cz Si doped with nitrogen during growth has been studied. The results presented can be explained under the assumption that the substitutional Aus concentration in the Cz Si samples is effected by the competition between the generation of self-interstitials and their annihilation at some defects. It is found that the Aus concentration after diffusion at 750 °C in Cz Si doped with nitrogen is always less than that in usual Cz Si independent of the thermal history of the wafers. A decrease in the Aus concentration in nitrogen doped crystals can be explained under the assumptions that nitrogen or nitrogen related centers stimulate oxygen precipitation or vacancy annihilation.