Defect Etching Research Articles

An Etch for Delineation of Defects in Silicon

An investigation of the system shows that preferential etching of crystal defects on silicon surfaces is very sensitive to the concentration ratio of to . This leads to development of a new etch consisting of one part by volume of and one part of 49% . This etch can delineate a wide variety of crystal defects with sharp definition. The shape of dislocation etch pits is uniquely determined by the orientation of wafer surfaces and dislocation lines.

A New Defect Etch for Polycrystalline Silicon

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Solid phase epitaxy of silicon on gallium phosphide

Epitaxial silicon films have been grown on gallium phosphide by molecular beam and solid phase epitaxy or combinations of both methods. During molecular beam epitaxial growth Ga segregates on top of the Si films, which can be considerably reduced by solid phase epitaxy but not completely suppressed. The cause of segregation is investigated using Rutherford backscattering, defect etching, and scanning electron microscopic inspection. We conclude that imperfections in the epitaxial layer act as diffusion pipes for atoms.

The precipitation of oxygen in silicon

The precipitation of oxygen in silicon has been studied over a wide temperature range, using a number of experimental methods including: kinetic rate data from infra red absorption in the 9 μm band at 4.2 K, Particle densities by optical scattering between 1.5-3.0 μm (large precipitates), chemical etching of defects (medium precipitates) and small angle neutron scattering (small precipitates). From the Ham theory of diffusion limited precipitation, a direct relation between the kinetic time constants and the equilibrium numbers and sizes of particles is predicted - which is confirmed by the results. This places emphasis on the need for precise diffusion data over a wide range. This has been explored by extending the above work with classical oxygen in-diffusion measurements up to 1250°C and stress dichroism in the range 350ȁ400°C, from which a value of D is obtained over 12 orders of magnitude with a single activation energy ȲE = 2.50 ± 0.15 eV. Recent results throw some light on the basic diffusion mechanism and the role of supersaturation and other impurities in the nucleation stage of this process.

Precipitation of tellurium in (Hg, Cd)Te alloys

The precipitation of tellurium in alloys of Hg1−xCdxTe with x = 0.2 to 0.3 prepared under conditions of excess tellurium by the solid state recrystallization method have been studied using chemical defect etching and transmission eloctron microscopy. Precipitation of tellurium occurred during the quench from the recrystallization anneal. During the initial part of the quench, precipitation occurred as a result of nucleation of precipitates on pre-existing dislocations. This precipitation resulted in the formation of dislocation helices with precipitates in the interior of the helix loops. Both monoclinic and trigonal phases of tellurium were found in these precipitate defects, as well as the twinned matrix phase. Later in the quench, an additional nucleation mechanism, either homogeneous or heterogeneous on an impurity occurs resulting in the formation of complex defects in the bulk. During a subsequent post-anneal at temperatures of approximately 300°C, the tellurium precipitates dissolve, and interstitial perfect and faulted dislocation loops are formed. Both the precipitation process and the subsequent post-annealing result in considerable multiplication of dislocations.

Etch characteristics and defect structure in sputtered zinc oxide films

Sputtered zinc oxide films are used in the fabrication of acoustical and optical microelectronic devices. The ZnO deposits as a fine grain C-axis oriented polycrystalline film on amorphous substrates with piezoelectric and electro-optic properties approaching single crystal material. Different sputtering techniques have yielded different levels of performance particularly with respect to surface acoustic wave, SAW, and guided optical wave, GOW, propagation characteristics. Etching studies have shown that rapid etch rates are associated with lower velocities and higher propagation losses whereas slow etch rates yield films with near single crystal velocities and low propagation losses. In this investigation partially etched ZnO films were examined using a scanning electron microscope to determine the microstructural changes. This has led to a more detailed understanding of the defect structure of the films, the nature of the etch process and its relation to the etch characteristics of single crystal ZnO.

EBIC characterization of electrically active defects in (Hg,Cd)Te

A comparison of low temperature electron beam induced current imaging in the scanning electron microscope and surface defect etch studies has identified subgrain boundaries and isolated dislocations as electrically active recombination centers in p-type solid state recrystallized (Hg1−X,CdX)Te with X=0.3. The ‘‘spotty’’ appearance of these images is attributed to enhanced recombination at Te-rich precipitates decorating dislocations in the subgrain boundaries.

Extremely rapid outdiffusion of n-type impurities in InP

During sealed ampoule annealing at 550 °C, an unexpected, deep diffuson front was observed in n-type InP crystals using defect etching and cathodoluminescence (CL) imaging. The diffusivities of the fronts were determined to be 1–5×10−8 cm2 s−1 which is approximately two orders of magnitude greater than that of the rapidly diffusing Zn impurity. By measuring the changes in the CL intensity and the photoluminescence linewidth to determine the changes in carrier concentration, the diffusion fronts were shown to be caused by the outdiffusion of the dopants. Although outdiffusion of Cr and Fe, affecting an ∼1 μm surface region during thermal annealing at 550 °C for 30 min, has previously been reported for InP, we believe this is the first reported observation of rapid outdiffusion of n-type impurities that can affect InP crystals to a substantial depth (∼200 μm) for similar annealing conditions.

Evaluation of misfit dislocations in planar, zinc-diffused In 0.53Ga 0.47As pin photodiodes

Misfit dislocations in planar, zinc-diffused In 0.53Ga 0.47As PIN photodiodes were analyzed using defect etching, cathode-luminescence, and electron-beam-induced current (EBIC). It was found that the misfit dislocations in wafers grown by liquid-phase epitaxy are present only in the InP buffer layer and they act as non-radiative recombination centers. These dislocations also affect the p-n junction since the misfit stress locally increases the diffusion depth by 80–400 Å. EBIC examination of the photodiodes under reverse bias shows that the misfit dislocations do not cause localized breakdown of the p-n junction.

Defect evaluation of Si MBE film

Crystalline defects in (100) and (111) Si MBE films were evaluated by various chemical etching techniques. Although the defects and defect patterns in an MBE film were similar to those observed in a CVD film, they were generated by different mechanisms because of the vast difference in the growth conditions of the two epitaxial techniques. Furthermore, (111) Si MBE films contained a unique defect pattern which has not been observed in CVD films. In this paper, defect etch patterns in a Si MBE film are described in terms of the cause of the defects.

A Quantitative Study of the Relationship Between Interfacial Carbon and Line Dislocation Density in Silicon Molecular Beam Epitaxy

Silicon layers grown by molecular beam epitaxy on (100) silicon substrates were depth‐profiled for carbon and oxygen by secondary ion mass spectrometry (SIMS). The same epitaxial layers were subjected to a defect etch to reveal dislocation density. A strong correlation is found between the carbon concentration at the substrate‐epitaxy interface and the line dislocation density of the epitaxial layer. Layers with interfacial carbon concentration ≈1021cm−3 exhibit line dislocation densities ⩾107cm−2, while layers with interfacial carbon concentration ⩽1019cm−3 (⩽0.01 monolayer carbon) have line dislocation densities ⩽104cm−2. In contrast, no correlation is found between interfacial oxygen (as revealed by SIMS) and the line dislocation density of the epitaxial layers.

Patterned silicon molecular beam epitaxy with submicron lateral resolution

Patterned epitaxial silicon films are grown on silicon substrates by molecular beam deposition (MBE) through an oxide masking layer. Epitaxial patterns faithfully reproduce the oxide mask, which is fabricated by conventional photolithographic processes. Resolution is determined solely by the mask, and linewidths below 1 μ are demonstrated. Sample morphology and crystallinity are examined by scanning and transmission electron microscopy, and Nomarski interference contrast microscopy in conjunction with chemical defect etching. These techniques confirm that patterned films are epitaxial and free of observable defects. A chemical liftoff step dissolves the oxide mask and leaves an elevated silicon pattern. Patterned film growth requires no modification to the MBE apparatus.

Methods for Defect Evaluation of Thin Oriented Silicon Epitaxial Layers Using a Wet Chemical Etch

Wet chemical defect etch diagnostic methods for <100> oriented silicon have been developed which have been used to evaluate epitaxial layers as thin as 4000Å.

Post‐Epitaxial Polysilicon and Si3 N 4 Gettering in Silicon

Substantial improvement of the quality of silicon epitaxial films by post‐epitaxial polysilicon back‐side gettering has been observed. This improvement is displayed by the reduction of defect counts revealed by the Wright etch and anodic etch and the increase of carrier lifetime characterized by the improved MOS retention time. Correlation between the defect etch pit counts and the retention time of MOS devices fabricated is reported.

INVESTIGATION OF THE DEFECTS IN SILICON SINGLE CRYSTALS GROWN BY FLOATING-ZONE METHOD IN THE ATMOSPHERE CONTAINING HYDROGEN

Defects in dislocation-free silicon single crystals grown by floating-zone method in the atmosphere containing Ar-H2 or H2 were investigated by means of chemical etching and X-ray projection topography. It has been found that anomalous etch pits and defect density are closely related to the hydrogen content. (Change of the defect density with hydrogen content shows a maximum at approximately 10% hydrogen for ay-grown crystals. After annealing at high temperatures, the defect density in the inner part of the crystal is found to be more than that at the surface and also more than that in as-grown state when hydrogen content is greater than 25% in the atmosphere.) Defects in annealed crystals grown in the pure hydrogen atmosphere have been observed. The relationship between some defects showing in topographs and etch patterns was found. Effect of annealing on wafer with these defects was also observed. Finally, clustering and precipitating of hydrogen have been discussed. Dislocation loops formed at precipitate-matrix interface were described. The process of motion and interaction of the loops as well as the forming of multi-centre loops at high temperatures were also discussed briefly.

Substrate effects on performance of InP MOSFETs

InP MOSFET devices with a SiO2 dielectric layer have been fabricated on p-type and SI substrates. Surface mobilities in the range 250 to 750 cm2 V−1 s−1 have been routinely obtained from all substrates except those from one crystal of Fe-doped SI InP. Defect etching studies have revealed large prismatic dislocation loops in this crystal. A correlation between these observations is proposed.

Transmission Cathodoluminescence

The application of transmission cathodoluminescence (TCL) in evaluating the quality of luminescing materials is reviewed. This scanning electron microscope technique is particularly useful in imaging localized nonuniformities, such as dislocations and inclusions, in semiconductors. Understanding and analyzing such material defects are of practical importance since they greatly affect device performance and lifetime. After a detailed description of TCL, the advantages of this technique in comparison to defect etching, cathodoluminescence imaging, and electron beam-induced current (EBIC) is presented. Since TCL is simple to perform, this technique can be used to evaluate and monitor material growth and device processing procedures. Although TCL may be applied to any luminescing material, this paper demonstrates its usefulness for the GaAs/GaAlAs and InP/InGaAsP materials systems which provide most sources and detectors for optical communication.

Shallow defect etching of GaAs using AB solution under laser illumination

A defect etch procedure for GaAs 〈100〉 oriented surfaces was developed. I and Buiocchi etch, used under laser (λ = 6328 å) illumination. A comparison of etch patterns obtained with the original AB etch under white light illumination, and those obtained with the procedure developed shows that, in addition to some practical advantages, the latter allows good contrast patterns to be revealed with a tenfold reduction of the etch depth (0.2–0.5 μm), while retaining all the interesting features of the Abrahams and Buiocchi solution. The procedure should therefore be of particular value in the study of thin GaAs epitaxial layers.

Picosecond Dynamics of Laser Annealing

ABSTRACTWe report simultaneous measurements of time resolved reflection and transmission of low intensity 1.06 μm, 35 ps pulses subsequent to excitation of 50 KeV, 1016 cm−2 boron implanted silicon by 0.53 μm 35 ps pulses of varying energy densities. The samples are examined by optical and scanning electron microscopy in conjunction with defect etching. These data are discussed from the point of view of both the thermal melting model and plasma model.

The Detection of Structural Defects in Indium Phosphide by Electrochemical Etching

Two new etching procedures for are described; one for damage removal with retention of surface flatness, and the other for high resolution defect delineation. A comparison of the defect etching with transmission x‐ray topography is given. Studies of wafers from Sn, S, and Fe‐doped ingots are reported. The new procedures have revealed a variety of defects.