Redistribution Of Boron Atoms Research Articles

Annealing of ultrashallow p+/n junction by 248 nm excimer laser and rapid thermal processing with different preamorphization depths

Ultrashallow p+/n junctions formed by B+-ion implantation and annealed by spike rapid thermal annealing (RTA) or laser annealing were studied. The effect of the preamorphizing depth on the redistribution of boron atoms after annealing has also been investigated. Our results show that for ultrashallow junctions formed by ultra-low-energy ion implantation and spike RTA, the depth of the preamorphizing implant has very little impact on the junction depth. By optimizing the laser fluence and preamorphization depth, a highly activated, ultrashallow, and abrupt junction can be obtained using a 248 nm excimer laser. The secondary-ion-mass spectrometry results clearly indicate that a step-like profile with a junction depth of 370 Å (for a B+ implant at 1 keV) can be formed with a single-pulse laser irradiation at 0.5 J/cm2.

High Energy Implantation of Boron in 4H-SiC

ABSTRACTThe high energy implantation of boron into n-type Silicon Carbide epitaxial layers of the polytype 4H was investigated for various sample temperatures during implantation and different doping concentrations. Depth profiling using secondary ion mass spectrometry was applied to determine the boron distribution in the as-implanted epilayers and the re-distribution of boron atoms during a half hour heat treatment at a temperature of 1700 °C. The SIMS boron profiles are compared to numerical Monte Carlo calculations using the program TRIM96 and to electrical profiling by scanning capacitance microscopy.In general we found that boron is moving towards the implantation damage already during the implantation of a profile with four different energies. The defect enhanced diffusion of boron is more pronounced during the high temperature anneal, where a higher concentration of boron diffusing towards the sample surface was observed. Into the bulk of the epilayer the boron diffusion is on a lower level and shows an exponential decay with a length of up to 5 Pm. An out-diffusion of boron during the post implantation anneal was not observed at implantation temperatures up to 500 °C.Electrical profiling using scanning capacitance microscopy revealed that complicated layer structures with several pn-junctions can occur due to the re-distribution of boron during post implantation anneal.

Boron Gettering by Fluorine in Ion Implanted Silicon

ABSTRACTSi was implanted with fluorine and boron ions. Boron gettering by fluorine was studied. By varying the implantation energy of F+ ions, three types of samples were made in which Rp(F)<Rp(B), Rp(F)∼Rp(B) and Rp(F)>Rp(B). There are three special regions in which the redistribution of Boron atoms during annealing differ. The first one is the near surface region in which the Boron concentration exceeds the value of Boron solid solubility at the annealing temperature. In this region, B atoms are intensively redistributed and have two peaks of concentration. The positions of these peaks coincide with the position of the peaks on the fluorine concentration profile. In the second specific region, the boron concentration is less than the value of solid solubility in Si and higher than the value of the intrinsic carrier concentration in Si at the annealing temperature. In this region, the B concentration was identical in all samples, and it exponentially decreased to the value of 5×108 cm−3. The slope of the boron concentration in the third region dictates the depth of p-n junction. A possible mechanism of boron gettering by fluorine is discussed.

Characterization of TiN/TiSi2 bilayer for application to ULSI

The properties of TiN/TiSi2 bilayer formed by rapid thermal annealing (RTA) in an NH3 ambient after the titanium film is deposited on the silicon substrate is investigated. It is found that the formation of TiN/TiSi2 bilayer depends on the RTA temperature and a competitive reaction for the TiN/TiSi2 bilayer occurs at 600°C. Both the TiN and TiSi2 layers represent titanium-rich films at 600°C anneal. The TiN layer has a stable structure at 700°C anneal while the TiSi2 layer has C49 and C54 phase. Both the TiN and TiSi2 layers have stable structures and stoichiometries at 800°C anneal. When the TiN/TiSi2 bilayer is formed, the redistribution of boron atoms within the TiSi2 layer gets active as the anneal temperature is increased. According to secondary ion mass spectroscopy analysis, boron atoms pile up within the TiN layer and at the TiSi2−Si interface. The electrical properties for n+ and p+ contacts are investigated. The n+ contact resistance increases slightly with increasing annealing temperature but the p+ contact resistance decreases. The leakage current indicates degradation of the contact at high annealing temperature for both n+ and p+ junctions.

The development of normalized and tempered A1-B treated 1 1/4Cr-1/2Mo steel plate

Strength and toughness of normalized and tempered 1 1/4Cr-1/2Mo steel plate decrease to a certain extent after stress relief annealing during fabrication. The addition of Al and small amounts of B increases the hardenability of 1 1/4Cr-1/2Mo steel for normalizing treatments and improves the strength and toughness so that enlargement of stress relief annealing condition up to 720°C × 50 h (temper parameter 21.5 × 103) is possible for plate thicknesses of 200 mm. The increase of hardenability during normalizing by a very slight amount of total boron is due to the redistribution of boron atoms during slow cooling. Such behavior of boron atoms is explained by the Gibbs absorption equation.