Time evolution of dislocation formation in ion implanted silicon

Annealing of crystal damage from ion implantation may result in dislocation formation. Here we study the nucleation, growth, and annihilation of such dislocations during rapid thermal anneals of Si, Ge, As, and In implanted Si. The dislocation formation process is observed for single or multiple damage profiles, as well as in amorphous-crystal transition regions. Dislocations initially nucleate in all these cases, even if they eventually annihilate during further annealing. It is also shown that for C implants in Si not only do dislocations not remain after annealing, but they do not even nucleate

Improvement of device characteristics by multiple step implants or introducing a C gettering layer

Ion implantation is used for realization of the collector in vertical bipolar transistors in a BiCMOS process. Secondary defects, remaining after annealing the implant damage, can give rise to an increased leakage current and to collector-emitter shorts. Two methods are proposed to avoid dislocation formation. First, by using multiple step implants, and second, by application of a carbon gettering layer. Experimental results show that these schemes can lower leakage currents, and moreover dramatically increase device yield. However, the carbon profile needs a further optimization with respect to the quality of the collector-substrate junction

Dislocation formation in silicon implanted at different temperatures

The formation of pre-amorphization damage, i.e. dislocations formed by the agglomeration of silicon interstitials, requires a minimum amount of implant damage. The amount of damage can be altered by changing the implant temperature or current density, which can influence dislocation formation. We studied this using cross-sectional transmission electron microscopy for boron and indium implants at kiloelectronvolt and megaelectronvolt energies respectively. Dislocation formation for boron implants, where only simple cascade densities are generated, does not depend on implant temperature or current density. For 1 MeV indium implants, where the implant damage consists mainly of amorphous zones, an increase in critical dose for dislocation formation by a factor of approximately 3 is observed if the implant temperature is raised. This is attributed to the interaction of point defects with the amorphous zones during the elevated temperature implant. Implants of 150 keV indium at room temperature result in complete amorphization before the critical amount of crystal damage is reached. Here, end-of-range loops (EOR-loops) from after annealing. Increasing the implant temperature suppresses amorphization, and pre-amorphization damage is observed if a critical amount of crystal damage has been generated. EOR-loop formation results from the agglomeration of silicon interstitials from the amorphous-crystalline transition region. If the number of interstitials in this region is lowered by carrying out the implant at low temperature, EOR-loop formation can be suppressed. This is shown by comparing amorphizing germanium implants done at room and liquid nitrogen temperatures

Identification and impact of excess soil potassium on crop and livestock nutrition

Several soils have been identified in the Intermountain West which contain excessive amounts of extractable potassium (K). A "normal" ammonium acetate extractable potassium level may be from 200 to 500 parts per million (ppm), while the high potassium soils contain 1,000 to over 7,000 ppm. Initial observation of crops grown on these soils continually showed poor crop yield, general chlorosis and failure to respond to fertilizer additions. While not widely reported in the literature, these soils have been identified at sites in Idaho, Montana, Oregon, Utah and Wyoming. Their discovery suggests a need to further explore the distribution and origin of high extractable K soils. We may also be able to define steps to improve crop and livestock productivity on the sites. This paper presents what we know about excess-K soils and outlines current efforts to determine their origin, chemistry and impacts on crops and livestock

Growth and properties of W-B-N diffusion barriers deposited by chemical vapor deposition

The authors have used chemical vapor deposition to grow ternary tungsten-based diffusion barriers to determine if they exhibit properties similar to those of sputter-deposited ternaries. A range of different W-B-N compositions in a band of compositions roughly between 20 and 40% W were produced. The deposition temperature was low, 350 C, and the precursors used are well accepted by the industry. Deposition rates are high for a diffusion barrier application. Resistivities range from 200 to 20,000 {micro}{Omega}-cm, the films with the best barrier properties having {approximately}1,000 {micro}{Omega}-cm resistivities. Adhesion to oxides is sufficient to allow these films to be used as the adhesion layer in a tungsten chemical mechanical polishing plug application. The films are x-ray amorphous as-deposited and have crystallization temperatures of up to 900 C. Barrier performance against Cu has been tested using diode test structures. A composition of W{sub .23}B{sub .49}N{sub .28} was able to prevent diode failure up to a 700 C, 30 minute anneal. These materials, deposited by CVD, display properties similar to those deposited by physical deposition techniques

Erbium ion implantation doping of opto-electronic materials operating at 1.5 mu m

Soda-lime silicate and Al/sub 2/O/sub 3/ waveguide films, LiNbO/sub 3/ single crystal, as well as crystal Si are doped with erbium by ion implantation. All materials show luminescence at 1.5 mu m, characteristic for Er, with lifetimes up to 12 m