Formation Of Thermal Double Donors Research Articles

Development of the conductivity type inversion caused by thermal double donors’ formation in p-type high-resistivity silicon

The formation of thermal double donors (TDDs) during the iso-thermal annealing at 450 °C in low-oxygen and high-resistivity silicon was quantitatively investigated, and the oxygen related power parameter for low-oxygen and high-resistivity silicon was obtained. Excessive TDDs formed in the p-type high-resistivity silicon during the device manufacturing process will invert the conductivity to n-type. A quantitative relationship between the critical wafer start resistivity and oxygen concentration in p-type high-resistivity silicon was obtained. The p-type conductivity can be maintained after the device fabrication by controlling the resistivity below the critical resistivity corresponding to the oxygen concentration in p-type high-resistivity silicon.

Processing‐induced near‐interfacial thermal donor generation in (100)Si/Si‐oxycarbide insulator structures revealed by electron spin resonance

AbstractLow temperature electron spin resonance (ESR) study of Cz‐(100)Si/insulator structures with organosilicate films of low dielectric constant κ grown at 300 °C using plasma‐enhanced chemical vapor deposition (PECVD) reveals, after subjection to UV‐irradiation assisted thermal curing at 430 °C to remove organics, the observation of the NL8 ESR spectrum. This indicates the generation in the c‐Si substrate of singly ionized thermal double donor (TDD) defects with a core contained of oxygen atoms. The generation is found to be highly non uniform, which is concluded to be the result of interfacial stress acting as the major driving component in the enhancement of TDD formation during thermal treatment. This suggests substantial stress being involved with PECVD organosilicate low‐κ glasses. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Near-interfacial thermal donor generation during processing of (100)Si/low-κ Si-oxycarbide insulator structures revealed by electron spin resonance

A low-temperature multifrequency electron spin resonance (ESR) study has been carried out on Cz-(110)Si/insulator structures with organosilicate films of low dielectric constant κ grown at 300 °C using the plasma-enhanced chemical vapor deposition method (PECVD). After subjection to a short-term UV-irradiation-assisted thermal curing treatment at 430 °C to remove the organic component from the low-κ film and obtain optimal porosity, the NL8 ESR spectrum of C2v symmetry is observed, characterized by g1 (//[100] = 1.999 83(8), g2(//[011] = 1.992 74(8), g3 = (//[]) = 2.001 15(8). Based on previous insight, this reveals the generation in the c-Si substrate of singly ionized thermal double donor (TDD) defects with a core containing oxygen atoms. Remarkably, the generation is found to be highly nonuniform, and the defect density depth profile shows an exponential-like decay (decay length ∼3.8 μm) from the oxide/Si interface inward the Si substrate, thus exposing the defect formation as an interface-administered effect. Upon analysis, the strain induced by interfacial stress in the c-Si beneath the interface is suggested as the major driving component in the enhancement of TDD formation during thermal treatment, suggesting that substantial stress is involved with PECVD organosilicate low-κ glasses. The result represents a different and affirmative illustration of the influence of strain on TDD formation. Based on the principal g values, the observed TDD is closest to the NL81 type, the one formed first in bulk c-Si through oxygen agglomeration during short-term thermal treatment.

Interstitial oxygen behavior for thermal double donor formation in germanium: Infrared absorption studies

The kinetics of the reduction of interstitial oxygen (Oi) due to the formation of thermal double donors (TDDs) upon heat treatment in an oxygen-rich Ge crystal were investigated at various temperatures. Specimens were prepared from a Ge crystal with oxygen at a concentration of 4–5 × 1017 cm−3 grown by a new Czochralski method and were heat-treated in the temperature range 300–500 °C. Shrinkage of a dissolved oxygen absorption peak at 855 cm−1 and simultaneous development of a thermal double donor peak at 780 cm−1 were observed by infrared absorption spectroscopy at room temperature. The formation of TDDs was also detected electrically. Reduction of dissolved oxygen concentration upon the heat treatments was kinetically analyzed. The activation energy of the reduction of Oi concentration was evaluated to be 1.7 and 2.0 eV in the early and prolonged stages of the heat treatment, respectively, close to that of Oi diffusion. From the results, TDD development process was indicated to be the merge reaction of Oi-Oi to form oxygen dimers (Odimer) in the early stage of the heat treatment and further enlargement of Odimer to TDDs by absorbing Oi in the prolonged stage of the heat treatment in accordance with the On-2NN model.

Enhanced Formation of Thermal Donors in Germanium Doped Czochralski Silicon Pretreated by Rapid Thermal Annealing

The thermal donor formation at 425oC - 450oC in Ge doped Czochralski (GCZ) silicon having about 1016 cm-3 Ge content pretreated by rapid thermal annealing (RTA) and conventional furnace annealing (CFA) has been investigated using low-temperature infrared spectroscopy (LT-IR). The measurements prove that lightly Ge doping can enhance the formation of thermal double donors in the initial stage of the low temperature annealing after RTA process. Ge induced additional grown-in oxygen precipitates during silicon ingot growth and the abundant self-interstitials during RTA may be the reason for the enhancement. However, after extending the annealing time at the low temperatures, the thermal donor concentration in the GCZ silicon is lower than that in the conventional CZ silicon. In final, the mechanism is also discussed.

Diffusion Coefficient of Hydrogen in Silicon at an Intermediate Temperature

The hydrogen diffusion coefficient in silicon (Si) in an intermediate temperature region (429–800 °C) is obtained using an enhanced formation of thermal double donors (TDDs), which is a phenomenon caused by in-grown hydrogen. An as-grown Czochralski (CZ) Si ingot contains hydrogen as a low-concentration impurity. Although present in a very low quantity, it is possible to observe an enhanced TDD formation due to in-grown hydrogen as a variation of the resistance of the specimen using a high-resistance ingot (>500 Ω cm). The hydrogen diffusion coefficient obtained using the depth profile of TDDs, which are generated under the influence of the depth profile of the in-grown hydrogen, shows a value close to that given by Van Wieringen and Warmoltz (VWW) [Physica 22 (1956) 849]. Furthermore, it is found that the activation energy of hydrogen diffusion in the intermediate temperature region is almost the same as that obtained by VWW. This result indicates that the hydrogen diffusion coefficient can be expressed by an equation given by VWW at an intermediate temperature region.

"New Donors" in Czochralski Grown Silicon Annealed at T≥ 600°C under Compressive Stress

Effects of compressive stress on oxygen agglomeration processes in Czochralski grown silicon heat treated at T= 450OC, used as a reference temperature, and T= 600OC to 800OC are investigated in some detail. Compressive stresses of about P= 1 GPa lead to enhanced formation of Thermal Double Donors in materials annealed over a temperature range of T= 450OC – 600OC. It has been shown that the formation of thermal donors at T= 450OC under normal conditions and compressive stress is accompanied with loss of substitutional boron. In contrast, the concentration of the shallow acceptor states of substitutional boron in silicon annealed under stress at T≥ 600OC remains constant. An enhancement effect of thermal donor formation is gradually weakened at T≥ 700OC. The oxygen diffusivity sensitive to mechanical stress is believed to be responsible for the observed effects in heat-treated silicon.

Calibration Factor for Determination of Interstitial Oxygen Concentration in Germanium by Infrared Absorption

Intensities of infrared absorption due to asymmetric stretching vibrations of interstitial oxygen atoms in Ge crystals enriched with 16O and 18O isotopes have been compared with oxygen concentrations determined by means of secondary ion mass spectrometry (SIMS). For Ge samples with oxygen content less than 5⋅1017 cm-3 a good correlation has been found between the values of oxygen concentration and values of absorption coefficient in maximum of the absorption band at 855.6 cm-1 with a proportionality coefficient CO = 0.95.1017 сm-2. It is argued that kinetics of oxygen-related thermal double donor formation and oxygen loss upon heat-treatments of Ge crystals at 350 оС cannot be described properly with the application of calibration coefficient CO = 5.1016 cm-2, which is widely used for the determination of oxygen concentration in Ge crystals.

Stress-induced changes of thermal donor formation in heat-treated Czochralski-grown silicon

Formation processes of oxygen-related thermal donors in Czochralski-grown silicon annealed at T=450°C under high hydrostatic pressures at P⩾1GPa are studied by means of electrical and optical measurements. As for heat treatment of materials at atmospheric pressure, the formation of thermal double donors (TDDs) takes also place in Czochralski-grown silicon subjected to compressive stresses during heat treatment. However, their formation rate turned out to be much larger than that observed under normal conditions, even in carbon-rich materials. This strongly enhanced formation of thermal donors is believed to be due to increasing diffusivity of oxygen under pressures. In addition to the TDDs, other shallow and deep thermal donors are also making their appearance in silicon heat treated under high pressures.

Interstitial oxygen loss and the formation of thermal double donors in Si

The combination of first-principles total energy calculations and a general kinetic model, which takes into account all processes of association, dissociation, and restructuring, is used to study the kinetics of thermal double donors (TDDs) in silicon over the temperature range of 300–650 °C. A strong correlation is found between the formation rate of TDDs and the loss rate of interstitial oxygen atoms. Also, a close agreement with experiments is obtained. It is found that TDDs grow via consecutive reactions where fast diffusing oxygen dimers and all TDDs capture interstitial oxygen atoms.

Infrared vibrational bands related to the thermal donors in silicon

Two groups of infrared (IR) localized vibrational bands in the regions 975–1015 and 724–748 cm−1 have been correlated with the well-known IR electronic bands due to the thermal double donors (TDs) and with the TD concentration from resistivity measurements. The two groups are suggested to be due to two different vibrational modes of oxygen atoms in a TD core. The vibrational bands at 975, 988, 999, and 1006 cm−1 are correlated to TD1, TD2, TD3, and TDs≥TD4, respectively, while the band at 1012 cm−1 correlates to the NL10 center. A calibration coefficient for the TD-related vibrational bands was determined. This calibration coefficient can be used to estimate the sizes of the TD-related centers, assuming that the calibration coefficient for interstitial oxygen is applicable on the oxygen atoms of these centers. This results in that all of the TD-related bands originates from centers of 1–2 oxygen atoms, suggesting these bands to be due to the vibrations of oxygen atoms in a TD core. The different positions of the TD-related bands could be explained by differently strained environments caused by different oxygen clusters. It is suggested that these clusters will develop into larger oxygen precipitates, which at the end of TD formation appear in the spectrum with a broad IR band at about 1060 cm−1. The early stages of the TD formation at temperatures below about 450 °C are closely related to a transformation process of preexisting clusters related to the 1012 cm−1 band. This explains the formation of the early TDs at low temperatures, when the interstitial oxygen concentration is nearly constant.

Effect of Carbon on Thermal Double Donor Formation in Silicon

Effect of Carbon on Thermal Double Donor Formation in Silicon