Specific features in the generation and motion of dislocations in silicon single crystals doped with nitrogen

The specific features in the generation and motion of dislocations are investigated in Si: N single crystals grown by the Czochralski method. The motion of dislocation loops is analyzed by the four-point bending technique in the temperature range 500–800°C. The dislocation loops are preliminarily introduced into the samples with the use of a Knoopp indenter at room temperature. It is found that doping with nitrogen leads to a considerable increase in the critical stress of the onset of dislocation motion from surface sources (indentations) and in the stress of the generation of dislocations from internal sources. The velocity of dislocation motion in Si: N crystals is less than that in undoped crystals (under comparable loads). The hardening effect of nitrogen is explained by the fact that nitrogen promotes the decomposition of a solid solution of oxygen in silicon during postcrystallization cooling.     

Dynamic properties of dislocations in silicon wafers heat-treated at low temperatures

The specific features of the dislocation motion in dislocation-free silicon wafers (single crystals are grown by the Czochralski method) heat-treated at 450 and 650°C have been investigated. It is found that the low-temperature treatment of silicon wafers with an oxygen content of (7–8)×10¹⁷ cm^?3 substantially affects the dynamic properties of dislocations generated into silicon wafers during their four-point bending and brings about an increase in the starting stresses of the onset of the dislocation motion. A characteristic spatial inhomogeneity is observed in the generation and propagation of dislocations from indentations upon the bending of heat-treated wafers. The reasons for the regularities revealed are discussed.     

Dislocation generation in heat-treated nitrogen-doped silicon wafers when applying external loads

The features of generation and motion of dislocations in nitrogen-doped dislocation-free silicon wafers after their multistage thermal treatments are investigated. It is established that doping with nitrogen leads to a substantial increase in stresses of the onset of plastic deformation from the external and internal heterogeneous sources in heat-treated wafers. The motion velocity of dislocations in nitrogen-doped silicon wafers is lower than in undoped wafers. The strengthening effect of nitrogen is apparently caused by its activating effect on the decomposition process of a supersaturated solid solution of oxygen during heat treatment.     

Diffuse x-ray scattering study of the formation of microdefects in heat-treated dislocation-free large-diameter silicon wafers

Diffuse x-ray scattering (DXS) is used to study the formation of microdefects (MDs) in heat-treated dislocation-free large-diameter silicon wafers with vacancies. The DXS method is shown to be efficient for investigating MDs in silicon single crystals. Specific defects, such as impurity clouds, are found to form in the silicon wafers during low-temperature annealing at 450°C. These defects are oxygen-rich regions in the solid solution with diffuse coherent interfaces. In the following stages of decomposition of the supersaturated solid solution, oxide precipitates form inside these regions and the impurity clouds disappear. As a result of the decomposition of the supersaturated solid solution of oxygen, interstitial MDs form in the silicon wafers during multistep heat treatment. These MDs lie in the {110} planes and have nonspherical displacement fields. The volume density and size of MDs forming in the silicon wafers at various stages of the decomposition are determined.     

应力预释放对单晶硅片的压痕位错滑移的影响

单晶硅片的压痕位错在一定温度下的滑移距离反映了硅片的机械强度. 压痕位错的滑移是受压痕的残余应力驱动的, 因此研究残余应力与位错滑移之间的关系具有重要的意义. 本文首先采用共聚焦显微拉曼术研究了单晶硅片压痕的残余应力经过300或500 ℃ 热处理后的预释放, 然后研究了上述应力预释放对压痕位错在后续较高温度(700–900 ℃)热处理过程中滑移的影响. 在未经应力预释放的情况下, 压痕位错在700–900 ℃热处理2 h后即可滑移至最大距离. 当经过上述预应力释放后, 位错在900 ℃热处理2 h后仍能达到上述最大距离, 但位错滑移速度明显降低; 而在700和800 ℃时热处理2 h后的滑移距离变小, 其减小幅度在预热处理温度为500 ℃时更为显著. 然而, 进一步的研究表明: 即使经过预应力释放, 只要足够地延长700和800 ℃ 的热处理时间, 位错滑移的最大距离几乎与未经预应力释放情形时的一样. 根据以上结果, 可以认为在压痕的残余应力大于位错在某一温度滑移所需临界应力的前提下, 压痕位错在某一温度滑移的最大距离与应力大小无关, 不过达到最大距离所需的时间随应力的减小而显著增长.     

单晶硅片中的位错在快速热处理过程中的滑移

研究了单晶硅片中维氏压痕诱生的位错在不同气氛下高温快速热处理中的滑移行为.研究表明: 在快速热处理时, 位错在压痕残余应力的弛豫过程中能发生快速滑移; 当快速热处理温度高于1100℃时, 在氮气氛下处理的硅片比在氩气氛下处理的硅片有更小的位错滑移距离. 我们认为这是由于氮气氛下的高温快速热处理在压痕处注入的氮原子钉扎了位错, 增加了位错的临界滑移应力, 从而在相当程度上抑制了位错的滑移. 可以推断氮气氛下的高温快速热处理注入的氮原子增强了硅片的机械强度. 关键词： 快速热处理 位错滑移 机械性能 单晶硅     

Influence of rapid thermal annealing on the specific features of defect generation in silicon wafers during the formation of effective internal getters

The specific features of the defect generation in silicon wafers subjected to a rapid thermal annealing during the formation of an internal getter have been investigated using optical microscopy and transmission electron microscopy. It has been established that rapid thermal annealing leads to a significant intensification of the decomposition of a supersaturated solid solution of oxygen in silicon, especially in the central region of the wafer. This intensification is responsible for the appearance of characteristic differences in sizes, densities, and morphological features of the microdefects generated in the samples subjected to a rapid thermal annealing as compared to the samples after a conventional heat treatment. The results obtained have demonstrated that the use of rapid thermal annealing has undoubted advantages in the formation of effective internal getters in silicon wafers.     

The influence of the implantation temperature on the generation of dislocations in antimony-implanted and annealed silicon

We report the first observation of non-equilibrium redistribution effects during laser treatment of a binary system having equilibrium segregation coefficient, k₀, much greater than unity. Polycrystalline aluminium samples implanted with 30 keV Sb⁺ ions to a dose of 1.7 × 10¹⁷ ions/cm² were irradiated with single pulses (7 ns FWHM) from a Nd: glass laser operating in TEM₀₀ mode. The peak energy density (at the centre of the laser spot) varied from 2.0 to 5.7 J/cm². A detailed liquid phase diffusion analysis, explicitly incorporating rapid melt front motion and interfacial segregation, is performed to fit the Sb depth profiles measured with a nuclear microprobe. An effective distribution coefficient k = 1 (as compared to equilibrium value of k₀～7) is obtained in agreement with the theoretical limiting value for large melt front velocities.     

Radiation breakdown in silicon wafers

Radiation breakdown in silicon slabs is observed and studied as revealed in anomalous behavior of the dose characteristics of their radiation defects when the radiative intensity is varied. A theory is constructed for reversible radiation breakdown due to the bistability which develops in a gas of radiation vacancies when the gas can be regarded as quasi-two-dimensional. In order to explain the exponential saturation of the dose characteristics as the irradiation intensity is increased, scenarios are proposed in which different forms of the constituent radiation defects develop. Some parameters of the bistable gas of primary vacancies are estimated, including diffusion coefficients, dimensions of inhomogeneity regions, and the rate of movement of the stratification line. On the whole, satisfactory agreement with experiment is obtained. Discrepancies between the diffusion coefficient for neutral vacancies obtained here and in the literature are attributed to the role of interband recombination accompanying radiation defect formation during electron bombardment. Zh. éksp. Teor. Fiz. 114, 1067–1078 (September 1998)     

Specific features and mechanisms of photoluminescence of nanostructured silicon carbide films grown on silicon in vacuum

The light-emitting properties of cubic silicon carbide films grown by vacuum vapor phase epitaxy on Si(100) and Si(111) substrates under conditions of decreased growth temperatures (T _gr ∼ 900–700°C) have been discussed. Structural investigations have revealed a nanocrystalline structure and, simultaneously, a homogeneity of the phase composition of the grown 3C-SiC films. Photoluminescence spectra of these structures under excitation of the electronic subsystem by a helium-cadmium laser (λ_excit = 325 nm) are characterized by a rather intense luminescence band with the maximum shifted toward the ultraviolet (∼3 eV) region of the spectral range. It has been found that the integral curve of photoluminescence at low temperatures of measurements is split into a set of Lorentzian components. The correlation between these components and the specific features of the crystal structure of the grown silicon carbide layers has been analyzed.     

Specific features of luminescence of oxygen-deficient centres in nanostructured silicon dioxide

Specific features of radiative and non-radiative relaxations of oxygen-deficient centres (ODC's) in nanostructured silicon dioxide were studied using optically stimulated electron emission and time-resolved photoluminescence. It was found that modifications of oxygen-deficient centres in the form of surface analogues can exist in nanostructured samples prepared by thermal decomposition of polysilazane in air. Photoluminescence of these centres was efficiently excited in the optical absorption bands of surface $E_{\mathrm{s}}^{\prime }$-centres and silicon clusters $\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/tbnd"></mglyph>}\mathrm{SiSiSi}\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/tbnd"></mglyph>}$ and could be associated with the intercentre energy transfer during their nonradiative relaxation. Specific features of thermally induced changes in the luminescence characteristics of the defects due to transformation of the structure of silica samples from amorphous to partially crystalline modification were established from analysis of the spectral composition and the decay kinetics of the photoluminescence.     

On the magnetic properties of dislocations in silicon

The anisotropy of a group of equidistant lines in the EPR spectrum of plastically deformed Si can be described as line splitting in a nearly axial crystal field, the axis being parallel to the Burgers vector of the dislocations. We suppose that the spins of the unpaired electrons in the core of the 60° dislocations are coupled along limited segments giving rise to superparamagnetic resonance.     

Specific features of morphology and the structure of nanocrystalline cubic silicon carbide films grown on a silicon surface

Physics of the Solid State - The composition, surface morphology, and crystal structure of nanocrystalline cubic silicon carbide films grown on a silicon surface through chemical conversion from...     

Passivation of dislocations in silicon by hydrogenation

Multicrystalline silicon wafers containing dislocations have been investigated before and after hydrogenation, after external gettering by phosphorus diffusion and also after the two treatments.

It was found that the two treatments are complementary, and improve drastically the wafers.

As gettering by phosphorus is able to remove fast diffusers it is concluded that interaction of hydrogen with segregated oxygen atoms could explain the passivation of dislocations.     

Nanopolishing of silicon wafers using ultrafine-dispersed diamonds

In the present study, two new methods are proposed for the polishing of silicon wafers using ultrafine-dispersed diamonds (UDDs). The first proposed polishing method uses a polishing tool with an ultrafine abrasive material made through the electrophoretic deposition of UDDs onto a brass rod. Dry polishing tests showed that the surface roughness of the silicon wafer was reduced from R_a=107 to 4 nm after polishing for 30 min. The second method uses a new polishing pad with self-generating porosity. By polishing with the new pad in combination with the polycrystalline UDD in a water suspension, it is possible to achieve the specified surface roughness of the silicon wafer much faster than when using a conventional pad made of foamed polyurethane. The tests showed that the surface roughness of the silicon wafer was reduced from R_a=107 to 2 nm after polishing for 90 min.     

ESR studies of thermally oxidized silicon wafers

We have performed ESR measurements on oxidized (111) silicon wafers and found two ESR centers. One, the previously known P_b center,was found to be a two level interface trap by corona bias studies. The other one, previously known as “damaged silicon” center was found to be a silicon center, probably related to the oxide growth process.     

Interaction between oxygen and dislocations in p-type silicon

The interaction between dislocations and impurities in silicon has been the subject of many studies over several years; nevertheless, many questions mainly relevant to the electronic states of complex defects containing impurities and dislocations are still unclear. In oxygen precipitated and plastically deformed p-type silicon deep levels were detected by deep level transient spectroscopy (DLTS). The comparison between differently treated samples allowed us to clarify the influence of oxygen on the defective states. One of the most prominent DLTS peaks usually observed in plastically deformed silicon was found to change substantially as a function of O precipitation. In particular, O precipitation increased the thermal stability of the peak, and also changed the capture and emission processes at the deep level. PACS 78.55.-m; 78.55.Ap; 71.55.-i; 71.55.Cn