Application of neural-network potential based on trainable descriptor to crystallographically complex lattice defects in silicon

Atomic hydrogen can neutralize the dangling bonds associated with lattice defects in silicon wafers; and therefore has found important applications in manufacturing of several silicon devices. The electron cyclotron resonance (ECR) hydrogenation technique was used for passivation of structural defects produced by low-energy Si implantation in silicon wafers. Schottky-diode I/V measurements were used to study the effect of hydrogenation in defect compensation in the samples. Remarkable (more than 90%) recovery towards the I/V characteristics of the undamaged sample was observed in case of moderately damaged n-type samples. Although ECR hydrogenation (at 490/spl deg/C substrate temperature during the process) produced noticeable improvements in the case of highly damaged n-type samples, many defects were still left uncompensated in these samples. The effect of the hydrogenation process was less prominent in the case of p-type samples. Explanations for the observed results are given.

Probing of structural defects in silicon by the perturbed γγ angular correlation (PAC) technique is demonstrated between 77 K and 1300 K. The behaviour of radioactive111 In probe atoms implanted at 295 K, is monitored during isochronal annealing in n-type, p-type and intrinsic Si. Trapping of defects, produced by the111In implantation itself or by postirradiation is studied in P-doped crystals (1016/cm3-1017/cm3).

A theoretical and experimental study is carried out on the behaviour of the Li donor impurity in the Si lattice with vacancy‐like (V) radiation‐induced defects. The electronic and geometrical structure of the cluster Si4H12 + Li4 simulating the V + Li4 complex in Si is calculated by the discrete variational Xα‐method. It is found that the cubic tetrahedral configuration of the complex is geometrically stable where the 8t2 state near the edge of the valence band is completely populated. The principal possibility of passivation of the V‐type defects by Li atoms is checked experimentally on n‐ and p‐Si samples with a Li concentration of ≈ 1017 cm−3 irradiated by reactor neutrons at fluences of 1.6 × 1015, 4 × 1015, and 3.4 × 1016 cm−3. The temperature dependences of the conductivity, Hall constant, and mobility are measured. It is shown that at high Li atom concentrations considerably in excess of the concentration of the dopant and radiation‐induced defects the electrical characteristics of the irradiated Si restore to the original level which is in agreement with the calculations on the passivation of the Li atoms by the V‐states in Si.

Various characteristic lattice defects in silicon have been recorded by some of the main X-ray topographic methods (Bragg and Laue case, scanning- and fixed-crystal techniques, single and double diffraction, hard and soft radiation), with the same specimens used for all methods. The comparison of the results allows some general statements on the qualification (advantages and disadvantages) of each method for detecting and investigating different kinds of lattice defects.

ABSTRACTThe structural characterization of the oxygen related lattice defects formed under different thermal cycling conditions is discussed. The present understanding on the nature of rod-like defects and oxide precipitates is reviewed. Attention is given to the whole lattice defect spectrum which is induced by the oxygen precipitation. The influence of carbon and dopants on the defects is discussed.

A technique for realizing electrically erasable photonics devices using micro-heaters for localized annealing of lattice defects in silicon is presented. The lattice defects have previously been introduced by ion implantation in order to cause a refractive index change. This technique can be used to fabricate electrically erasable on-chip directional couplers (DCs) and Mach-Zehnder Interferometer (MZI) switches. These devices can be used for wafer scale testing of photonics circuits, allowing testing of individual optical components in a complex photonic integrated circuit, or components for programmable optical circuits, whilst inducing negligible additional optical loss when erased electrically. In this paper, we report the designs and experimental results of fully, rapidly annealing of these devices.

Subsurface lattice defects in silicon induced by ion implantation were studied by the use of the photo-acoustic displacement (PAD) method based on the sensitive measurements of the surface displacement due to the absorption of laser-light energy. A definite correlation between PAD and displaced atoms density (DAD) was found because PAD reflects the change in thermal conductivity associated with the net amount of displaced atoms in the crystal lattice beneath the surface. According to the linear dependence of 1/PAD on DAD, defects below a DAD of 1014/cm2 (corresponding to implant doses of 2×1011, 8×1010, and 6×1010 ions/cm2 for 100 keV B+, P+, and As+, respectively) were concluded to be point defects. After the DAD reached 1014/cm2, the PAD showed a gentle increase, and this can be attributed to the growth of point-defect clusters. A marked dependence of the PAD on the DAD was not observed beyond a DAD of 1016/cm2. In this region, the presence of an amorphous layer was observed by cross-sectional transmission electron microscopy. Annealing behavior due to low-temperature heating was studied by the change in temperature dependence curves of the PAD, and the results reflected the characteristics of the defects described above.

The method of silicon doping by thermal neutron transmutation (producing phosphorus atoms) is compared to the conventional method. Both the electronic and atomic lattice defects are considered. From accurate radioactive and electrical measurements, the numbers of carriers and phosphorus atoms are measured separately in order to derive the concentration of electronic defects. Diffusion profiles of gallium are determined by activation analysis as well as ion microprobe before and after neutron doping, which gives the influence of the doping on the concentration of the atomic defects responsible for diffusion. No difference between the methods of doping can be detected within the range of experimental errors.

Lattice defects in silicon rapidly solidified from the melt

The recombination activity of oxygen precipitation related lattice defects in p- and n-type silicon is studied with photoluminescence (PL) and microwave absorption (MWA) techniques. A direct correlation is observed between the amount of precipitated oxygen and the extended defect density on one hand and the minority carrier lifetime and PL activity on the other hand. The PL analyses show as dominant features in the spectra the Dl and D2 lines. The relative amplitude of the D-lines in the different samples is investigated as a function of the oxygen content, defect density and excitation level. The results are correlated with those of complementary techniques and are interrelated on the basis of Shockley-Read-Hall (SRH) theory.

We have developed a new photodisplacement microscope system for practical use that achieves high-sensitivity simultaneous real-time imaging of surface and subsurface structures from a single space-frequency multiplexed interferogram. In this system a linear region of photothermal displacement is excited on the sample surface for subsurface imaging by a line-focused intensity-modulated laser beam. Surface information such as reflectivity and topography along with the displacement is detected with a charge-coupled device sensor-based parallel heterodyne interferometer. Surface and subsurface information components are space-frequency multiplexed into the sensor signal as orthogonal functions based on a frequency-optimized undersampling scheme, allowing each to be discretely reproduced by using a real-time Fourier analysis technique. Preliminary experiments demonstrate that this system is effective, simultaneously imaging reflectivity, topography, and photodisplacement for the detection of subsurface lattice defects in silicon, at a remarkable speed of only 0.26 s/256x256 pixel area. This new microscope is promising for nondestructive hybrid surface and subsurface inspection and other applications.

Some results of preliminary observations of dislocations and loops in differently doped Silicon slices are reported. Local melting of Silicon by means of the electron beam, has shown that the loops are due to impurity concentration.

Structure and thermal behavior of lattice defects in silicon induced by excimer laser irradiation, which is expected to be adopted as a new extrinsic gettering technique, were examined by transmission electron microscopy. Stacking fault tetrahedra and a peculiar type of dislocations which appeared in a V-shape were found in a melted and regrown layer of an as-irradiated sample. After subsequent heat treatment, slip dislocations were generated from the traces of laser beam shot and the stacking fault tetrahedra were mostly transformed into the V-shaped dislocations. These V-shaped dislocations were proved to be thermally stable and were expected to work as effective extrinsic gettering centers.

A parallel photodisplacement technique that achieves real-time imaging of subsurface structures is presented. In this technique, a linear region of photothermal displacement is excited by a line-focused intensity-modulated laser beam and detected with a parallel heterodyne interferometer using a charge-coupled device linear image sensor as a detector. Because of integration and sampling effects of the sensor, the interference light is spatiotemporally multiplexed. To extract the spatially resolved photodisplacement component from the sensor signal, a scheme of phase-shifting light integration combined with a Fourier analysis technique is developed for parallel interferometry. The frequencies of several control signals, including the heterodyne beat signal, modulation signal, and sensor gate signal, are optimized so as to eliminate undesirable components, allowing only the displacement component to be extracted. Two-dimensional subsurface lattice defects in silicon are clearly imaged at a remarkable speed of only 0.26s for an area of 256×256pixels. Thus, the proposed technique allows for real-time imaging more than 10 000 times faster than conventional photoacoustic microscopy.

Observation of Lattice Defects in Silicon by Scanning Electron Microscopy Utilizing Beam Induced Current Generated in Schottky Barriers