Preferential Etching Technique Research Articles

Some features of a microdefect revealing in single-crystal silicon by the preferential etching technique

Some features of a microdefect revealing in single-crystal silicon by the preferential etching technique

Delineation of Microdefects in Silicon Substrates by Chromium-Free Preferential Etching Solutions and Laser Scattering Tomography

Chromium-free preferential etching techniques in combination with light optical microscopy were compared with the non-destructive Laser Scattering Tomography (LST) for the evaluation of crystal defect densities in Czochralski substrates grown under different conditions. Dichromate containing etching solutions (original Secco etch and dilute Secco etch) were included into the study as reference. The chromium-free etching solutions with high etch rates comprised mixtures of nitric, hydrofluoric and acetic acid with water (JEITA 1, MEMC). Those with low etch rates consisted of mixtures of nitric and acetic or propanoic acid with hydrogen peroxide which form peracetic or perpropanoic acid (Organic Peracid Etches). OPE solutions provide improved discrimination of different types of defects and work also on highly doped substrates. As a general result, it turned out that the defect densities determined by the preferential etching solutions applied were significantly higher than those evaluated by LST. Relatively close to the LST defect densities are those determined by original Secco etch for larger etch pits.

Some features of a microdefect revealing in single-crystal silicon by the preferential etching technique

Abstract Poorly known features of a microdefect (MD) delineation in dislocation-free single-crystal silicon by the defect-contrast (DC) etching technique were studied experimentally using DC-solutions of the HF–CrO 3 –H 2 O and HF–K 2 Cr 2 O 7 –H 2 O systems. The dependences of shape and size of an individual MD-trace on the etchant type, etch time (etch depth), and microdefect type have been demonstrated. Taking into account of these dependences allows one to improve selectivity and sensitivity of the technique. Compositions of the most effective DC-etchants were noted.

Delineation of Crystalline Defects in Semiconductor Substrates and Thin Films by Chemical Etching Techniques

Successful implementation of novel materials like SOI and sSOI into the mass production of advanced devices requires monitoring of their crystal quality and defect densities. Preferential etching techniques in combination with light optical microscopy are still the workhorse for a quick and simple evaluation of defect types and area densities.Classical etching recipes applied to SOI and sSOI substrates reveal certain limitations and the most common recipes are based on toxic Cr(VI). Therefore there is a need for alternative Cr-free recipes with adequate or superior performance for application to SOI and sSOI. We discuss some basic aspects of preferential etching and present two different types of novel Cr-free preferential etching chemistries which are suitable for the application on SOI. Organic peracid etches consist of hydrofluoric acid, an organic acid and hydrogen peroxide which reacts with the organic acid forming the corresponding organic peracid which then acts as the oxidizing agent. These etch solutions have very low removal rates (0.4 -1.5 nm/min at 25{degree sign}C), are very defect sensitive and are suitable for the application on SOI films as well as on CZ bulk material where they reveal vacancy agglomerates (D defects, COPs) with high sensitivity.

High-sensitivity Defect Evaluation by a New Preferential Etching Technique for Highly As-doped Si Crystals

A high-sensitivity preferential etching technique is presented to evaluate crystal defects in a highly As-doped silicon crystal with a resistivity lower than 0.01 Ω· cm. For highly doped n-type Si, a conventional preferential etching technique, such as Secco etching, Wright etching or Dash etching becomes less useful because of a significant decrease in defect detection sensitivity. The new method is quite sensitive to dislocations, stacking faults and oxygen precipitates in highly As-doped crystals with a surface of either (111) or (100). In this method, copper is first decorated at the defect site, then the defect is preferentially etched by a dilute alkaline solution. The technique thus offers us a sensitive and Cr-free method, attractive from an environmental aspect. A correlation between the laser scattering method is also obtained for the oxygen precipitate density.

EBIC investigation of defects in SOI materials using a Schottky diode and buried oxide capacitor

Silicon-on-insulator (SOI) is a promising technology for the fabrication of ultra large scale integration circuits as thin silicon layers of good crystalline quality are now available which permit substantial enhancements of device performance. However, the fabrication of ultra thin films suitable for CMOS applications often reveals some crystal defects which must be characterised to understand their consequences on device performances. Such defects were already extensively studied from a crystal point of view using preferential etching techniques. In this work, the non-destructive electron beam induced conductivity (EBIC) technique was successfully used to study dislocations and stacking faults in SOI films obtained by direct bonding. The presence of a buried oxide in the SOI structure prevented any direct current path between the collection junction formed on the active layer and the back ohmic contact. It is shown that collection using a Schottky junction in series with the buried oxide capacitor yields a differentiation of the EBIC signal. The latter may be digitally integrated to retrieve the image with a substantially improved signal over noise ( S/N) ratio. The variation of the EBIC signal as a function of the scanning rate was also investigated. This technique permitted the observation of stacking faults and dislocations in the active layer simultaneously with defects in the buried oxide and/or at the silicon-oxide interface.

Lattice Defects in High Quality As-Grown CZ Silicon, Studied with Ligth Scattering and Preferential Etching Techniques

Lattice Defects in High Quality As-Grown CZ Silicon, Studied with Ligth Scattering and Preferential Etching Techniques

Recognition of D defects in silicon single crystals by preferential etching and effect on gate oxide integrity

A method for revealing point defects in silicon single crystals has been investigated. D or A defects could be revealed by a preferential etching technique using Secco's etchant. Wedge-shaped flow patterns and etch pits were recognised in the D and A regions, respectively. The flow patterns were so characteristic that the D region could be distinguished very easily.

High characteristic temperature of 1·3 µm crescent buried heterostructure laser diodes

Two-step liquid phase epitaxy and preferential etching technique have been used to fabricate 1·3 µm InGaAsP/InP buried crescent laser. The p-n-p-n thristor-like structure is used as the blocking layers. The leakage current is very small even at high temperatures. The characteristic temperatureT 0 at room temperature is as high as 79 K. This value is higher than those ever reported.

Nitrogen effect on oxygen precipitation in Czochralski silicon

The nitrogen effect on enhancement of oxygen precipitation in Czochralski-grown silicon wafers has been investigated by means of a preferential chemical etching technique and secondary ion mass spectroscopy. The precipitate enhancement is evident in an oxygen out-diffused region in which oxygen precipitation does not normally occur. Incorporation of the nitrogen atoms in substitutional sites to generate very stable microdefects in Czochralski-grown silicon crystals can explain the nitrogen effect on oxygen precipitation.

The Gravitational Field of a 111 Tetrahedron

Advances in crystal growth technology together with advances in preferential etching techniques may make it possible to produce a nearly perfect single crystal of silicon in the form of a 111 tetrahedron. The density homogeneity of such an artifact together with the high precision to which its centre of mass could be located with respect to its faces would suggest its use as an attracting mass in experiments to determine the gravitational constant G. In this paper a closed-form expression for the gravitational field of a 111 tetrahedron is derived.

Epitaxial integrated d E1 − d E2 silicon detectors

Epitaxial integrated d E 1 − d E 2 silicon detectors have been developed by using the multilayer epitaxial crystal growth technique combined with the chemical preferential etching technique. These detectors are useful for eliminating events affected by channeling and blocking effects in the identification of heavy ions using multiple detector telescope systems. Characteristics of d E detectors of the integrated d E 1 − d E 2 type are confirmed to as good as those of integrated E − d E detectors.

Cw laser crystallization of glow discharge a-Si:H on glass substrates

Glow discharge hydrogenated amorphous Si films were crystallized using a cw Ar laser. The properties of the crystallized films were studied by optical and electron microscopy, electrical measurements and elastic recoil detection (ERD) analysis. In addition, a preferential plasma etching technique was used to determine the degree of crystallization. Large (>3 μm) high quality crystallites were induced above a threshold laser power of 100 W/cm by an explosive crystallization process. This was accompanied by the formation of bubbles and ejection of material from the crystallization centers. The sheet resistivity decreased by five to six orders of magnitude. Some 50–90% of the hydrogen remained in the films after laser annealing. A simple model shows that solid state diffusion accounts for the final hydrogen distribution in the laser annealed films. The use of this material for the fabrication of devices on glass substrates is discussed.

A novel buried grid device fabrication technology

A new buried grid fabrication technology based upon preferential etching and planar epitaxial refill techniques is described. This technology produces buried grids with a rectangular cross-section. The resulting improvement in the aspect ratio of the channel between the grids allows the fabrication of large area, high voltage, vertical channel field effect transistors and field controlled thyristors with very high blocking gains.

The morphology and composition of an immature C 3S paste

The morphology of a one month old hydrated C 3S paste has been studied using the scanning electron microscope (SEM) and preferential etching techniques. The C/S ratios of the calcium silicate hydrates (CSH) have been determined using the SEM with an energy dispersive spectrometer. The hydrate rims covering the partially hydrated C 3S grains were found to consist of two layers; an outer porous product with an acicular morphology having a C/S ratio of 1.6 ± 0.1 and an inner product with a C/S ratio of 1.90 ± 0.05. A region of increased C/S ratio in the C 3S core at the C 3S-CSH interface is attributed to a depletion of SiO 2 resulting from the diffusion of Si 4+ ions into the hydrate.

Optical bends and rings fabricated by preferential etching

We have applied the preferential etching technique to the fabrication of optical bends and rings. Nearly perfect smooth waveguide walls formed by crystalline planes can still be obtained in the curved section. Applications of such preferentially etched optical bends and rings in integrated optics are discussed.

A thin-film prism as a beam separator for multimode guided waves in integrated optics

We discuss a new application of a thin-film prism as a beam separator for multimode guided waves in integrated optics. For each mode of propagation, the angle of deflection by the thin-film prism is different and each deflected beam can be processed subsequently. Deflection angles for different modes can be predicted by using the concept of effective index of refraction. The thickness and index of refraction of the guiding film are determined simultaneously by measuring the coupling angles of the laser beam and a simple graphical method. Calculated and observed angles of deflection are in good agreement. The thin-film prism is made by using preferential etching technique in order to obtain linear, well defined, tapered edges. Furthermore, silicon is used as the base material for possible future integration of optical and electronic components.

Integral heat-sink IMPATT diodes fabricated using p+etch stop

The problems in batch fabrication of integral heat-sink IMPATT diodes are greatly simplified through a newly developed preferential etching technique. Devices fabricated utilizing the new technique have thermal resistance (θ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">jc</inf> ) values of 17-20°C/W for an active area of 2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Multilayer vapor-phase epitaxial silicon millimeter-wave IMPATT diodes

A new procedure has been developed for fabricating small-area silicon avalanche diodes directly on a plated copper heat sink. The process incorporates multilayer vapor-phase epitaxially grown silicon and a preferential electrochemical etching technique to fabricate thin uniform silicon films; 6 µ thick films on 2-cm diameter wafers have been obtained reproducibly with little difficulty. Inverted mesa diodes 30-40 µ in diameter have been formed by etching through the unmasked area of the thinned silicon wafer. Implementation of this technology has resulted in single drift region p+-n-n+diodes that generate over ¼ W CW power with 6-percent efficiency at 60 GHz.

The precision manufacture and registration of masks for vacuum evaporation

An apparatus is described which enables a set of six masks to be repeatedly registered with a substrate in a high-vacuum environment with an accuracy to ±1 μm. Details are given of the mask manufacture, which involves preferential etching techniques to produce high definition patterns. An analysis is made of the registration errors to be expected.