Low-temperature Preannealing Research Articles

High-Performance Ge p-n Photodiode Achieved With Preannealing and Excimer Laser Annealing

A germanium (Ge) n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /p shallow junction photodiode fabricated by a combination of low-temperature preannealing and excimer laser annealing of the phosphorus-implanted p-type Ge is demonstrated. The Ge photodiode shows a high responsivity of 0.48 A/W at the 1.55-μm wavelength and an extremely low leakage current density of 1 pA/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at room temperature, over two orders of magnitude lower than that of diodes formed by the rapid thermal annealing process. In addition, the reverse leakage current is close to the theoretical limitation of Ge diodes dominated by the ideal carrier diffusion model. The well-controlled dopant profile of the Ge shallow junction should be beneficial for improving the performance of the diodes, which may also be used in making the source and drain of scaled Ge nMOSFET.

Germanium n+/p Shallow Junction With Record Rectification Ratio Formed by Low-Temperature Preannealing and Excimer Laser Annealing

A germanium n + /p shallow junction formed by a combination of low-temperature preannealing (LTPA) and excimer laser annealing at a low fluence of 150 mJ/cm 2 for phosphorus-implanted germanium is demonstrated. The LTPA step plays a critical role in annihilating the implantation damages and significantly suppressing phosphorus diffusion during laser annealing process, resulting in a very small dopant diffusion length with high activation level of phosphorus. A well-behaved Ge n + /p shallow junction diode with a record rectification ratio of ~10 7 and low leakage current density of 8.3 × 10 -5 A/cm 2 is achieved, which is greatly beneficial to the scaled Ge MOSFET technology.

Solid-phase crystallization kinetics and grain structure during thermal annealing of a-Si:H grown by chemical vapor deposition

Abstract Solid-phase crystallization kinetics are examined during thermal annealing of as-deposited hydrogenated amorphous silicon (a-Si:H) thin films deposited by hot-wire chemical vapor deposition (HWCVD) and plasma-enhanced chemical vapor deposition (PECVD). The influence of deposition temperature of HWCVD material on crystallization is also considered. Real-time observation of the crystallization process using in situ transmission electron microscope heating allowed tracking of the crystalline volume fraction and grain number density by image-processing methods. Beyond an initial incubation period, roughly constant grain nucleation rate and growth velocity are observed. Extrapolation from early stages of crystallization allows estimation of the final average grain sizes. PECVD material shows a much lower nucleation rate than does HWCVD material under the same annealing conditions, whereas the grain growth velocities are comparable, leading to dramatically larger grain sizes in PECVD material. X-ray diffraction line widths from PECVD material are broader compared to HWCVD material. The diffraction line broadening is primarily determined by intragranular defect structure, rather than grain size. Low-temperature preannealing reduced the final XRD line widths of HWCVD material, indicating an influence on defect structure or density. Lattice contraction during crystallization of HWCVD material is observed to be independent of the initial hydrogen content.

Effect of Low Temperature Pre-Annealing on the Thermal Stability and Mechanical Properties of Ni-Zr-Al-Hf-Nb Bulk Metallic Glass

Effect of Low Temperature Pre-Annealing on the Thermal Stability and Mechanical Properties of Ni-Zr-Al-Hf-Nb Bulk Metallic Glass

Characteristics of heavily doped p+∕n ultrashallow junction prepared by plasma doping and laser annealing

High quality p+∕n ultrashallow junctions were fabricated by high dose plasma doping and two step annealing involving low-temperature furnace annealing and excimer laser annealing. Without a preamorphization process, laser annealing is effective in terms of activation and annealing. Meanwhile, the junction depth can be controlled by the low-temperature annealing process prior to the laser annealing. By combining low-temperature preannealing and laser annealing, ultrashallow (junction depth ∼22nm), low sheet resistance (∼275Ω∕sq.), and a defect-free p+∕n junction can be obtained without preamorphization.

Deep Levels in Oxygenated n-Type High-Resistivity FZ Silicon before and after a Low-Temperature Hydrogenation Step

The behavior of oxygen in oxygen-doped high-resistivity (HR) n-type float-zone (FZ) silicon has been studied using a combination of analytical techniques. In the as-doped material, a large number of deep levels have been observed with deep-level transient spectroscopy. The corresponding parameters (concentration, activation energy, and trap signature) are given, and the possible identity is discussed in view of the presence of oxygen and other impurities in the material. In addition, the impact of a low-temperature hydrogen-plasma preannealing on the formation of oxygen thermal donors (OTDs) and other oxygen-related shallow thermal donors (STDs) at 450°C is described. It is shown that the introduction rate of OTDs in oxygenated HR FZ silicon is much smaller than in Czochralski silicon. In fact, for short anneals at 450°C following a plasma treatment, the STDs are the ones which have been predominantly created near the surface of the samples. © 2003 The Electrochemical Society. All rights reserved.

Effect of low-temperature preannealing on laser-annealed p+/n ultrashallow junctions

The effect of low-temperature preannealing on ultrashallow p+/n junctions was examined. An ultrashallow junction was formed by means of B2H6 plasma doping at an energy of 500 V. The junction was activated by low-temperature (300–500 °C) annealing, followed by laser annealing. Compared with control samples which were not preannealed, low-temperature preannealing significantly improves junction characteristics, resulting in a reduction in junction depth and a lower leakage current density. A cross-sectional transmission-electron-microscopy analysis confirmed the lower defect density, which explains the lower leakage current. By optimizing the process conditions, excellent electrical characteristics of the p+/n junction, i.e., a junction depth of 28 nm and a sheet resistance of 250 Ω/sq, can be obtained.

The Influence of Low Temperature Pre-Annealing on the Defect Removal and the Reduction of Junction Depth in Excimer Laser Annealing

AbstractThe influence of low temperature pre-annealing on p+/n ultra-shallow junction was investigated. An ultra-shallow junction was formed by means of B2H6 plasma doping at an energy of 500V. The activation was performed by excimer laser annealing. To study the low temperature annealing prior to laser annealing, furnace annealing at 300°C∼500°C for 5min was performed. Compared with control samples with no pre-annealing, the low temperature preannealing significantly improves junction characteristics, resulting in a reduction of junction depth and a lower leakage current density. A cross-sectional transmission electron microscopy analysis confirmed the lower defect density, which explains the lower leakage current. By optimizing the process conditions, excellent electrical characteristics of the p+/n ultra-shallow junction such as a junction depth of 28nm and a sheet resistance of 250Δ/sq. can be obtained.

Evidence for the effect of carbon on oxygen precipitation in Czochralski silicon crystal

This article reports some new experimental evidence for the effect of carbon on oxygen precipitation in a high carbon content Czochralski silicon (H[C] Cz-Si) crystal. The oxygen precipitation occurring at an intermediate temperature of 950 °C has been especially investigated. In such case, the carbon atoms slightly participate in oxygen precipitation with 1200 °C preannealing, while the carbon atoms actively participate in oxygen precipitation with low temperature preannealing. The experiments show that the 1230 cm−1 absorption band in the Fourier transmission infrared spectrum definitely originates from the oxygen precipitates involving insignificant carbon reduction; on the other hand, the oxygen precipitates involving significant carbon reduction are surely irrelevant to the 1230 cm−1 absorption band. According to the correlation of the change in oxygen and carbon concentrations during oxygen precipitation, it is plausible that there is a critical precipitate size which distinguishes the carbon behavior in oxygen precipitation, that is, the carbon atoms actively participate in oxygen precipitation when the precipitates are smaller than the critical size; whereas, the carbon atoms are only slightly involved in oxygen precipitation when the precipitates are larger than the critical size.

Effects of low temperature preannealing on ion-implant assisted intermixing of Si1−xGex/Si quantum wells

Using photoluminescence we have studied the effect of a low temperature ‘‘preanneal’’ stage on the intermixing of 3 nm Si0.7Ge0.3/Si quantum wells, implanted with silicon ions having energies up to 1 MeV and then exposed to rapid thermal annealing at 850 °C for 300 s. We find that an unwanted quantum well band gap increase in unimplanted samples after rapid thermal annealing can be reduced substantially from ∼30 to ∼5 meV due to the removal of grown-in defects by preannealing at 630 °C for 24 h. Preannealed samples that were implanted and rapid thermal annealed showed at least the same band gap increase (up to 70 meV in these samples) observed for nonpreannealed samples. These results are understood in terms of significantly different activation energies for defect diffusion and quantum well intermixing and a nonlinear dependence of the energy shifts on defect concentrations.

Improved Characteristics of p+-n Junctions formed by Excimer Laser Annealing with Low Temperature Pre-Annealing

P+-n diodes with shallow junctions less than 50 nm deep were formed utilizing single pulse excimer laser annealing. The diode characteristics and the crystallinity near the junctions was investigated and it was found that the characteristics were improved by annealing the sample at 600° C for 1 h prior to excimer laser annealing. A low leakage current density of ≤10 nA/cm2 under reverse bias and ideal I–V curves of 60 mV/dec. over 7 decades under forward bias were obtained. The average leakage current and the device to device leakage current fluctuation were both reduced when the pre-annealing was used. The crystallinity near the junction was investigated by cross sectional transmission electron microscopy (TEM).

Low temperature preannealing for carbon removal from Si surface in GaAs-on-Si molecular beam epitaxial growth

Using Auger electron spectroscopy, quadrupole mass-spectroscopy of the desorption process, X-ray diffraction and transmission electron microscopy of molecular beam epitaxial (MBE) grown films, we compared the commonly used pregrowth thermal treatments (in the range 300 < T < 1200°C) in vacuum with a new low temperature annealing procedure in hydrogen for Si (100) substrates tilted 0°, 4° and 9° towards [011]. We showed that carbon on the Si surface suppresses the epitaxial growth of GaAs and determines the evaporation process on the Si surface. We concluded that a protective oxide layer prevented carbide formation more effectively than a hydrogen terminated layer. Using the proposed preparation technique, 1.5 μm thick MBE GaAs films on Si with a rocking curve FWHM of 10 arc min for as-grown films and 6 arc min for 20 min 850°C annealed films were produced.

Rapid thermal annealing of high dose arsenic-implanted silicon

A model for rapid thermal annealing of high dose arsenic-implanted silicon layers is proposed. The kinetics of arsenic clustering was taken into account. Assuming that all arsenic is initially electrically active, the clustering rate is found to be enhanced during the early stage of annealing in comparison with results reported for conventional furnace tempering [1]. An influence of a low temperature preannealing on the diffusion behaviour of arsenic has not been observed.

Impact of high temperature processing on bulk defects in czochralski silicon

The near-surface and bulk behaviour of lattice defects introduced during high temperature processing steps is examined for respectively dry and wet oxidations, oxidations in a chlorine containing atmosphere and inert annealings. The depth and radial distribution of the defects is investigated with optical microscopy and high voltage electron microscopy. The influence of the interstitial oxygen concentration and of the application of a low temperature preannealing is studied in detail. The defect kinetics is discussed in terms of an interstitial growth model.