Accurate Theoretical Arsenic Diffusion Profiles in Silicon from Processing Data

Nishimatsu

1978

264

Grain growth phenomena of heavily phosphorus-implanted polycrystalline silicon films owing to high temperature annealing are investigated by transmission electron microscope. Phosphorus doping in excess of 4 • 1020 cm -~ is found to enhance grain growth. This growth is broken down into primary and secondary recrystallization. Isochronal annealing reveals the activation energies for these as 2.4 and 1.0 eV, respectively. The driving force of the primary recrystallization is found to be the interface energy. Therefore, the elementary process behind the primary, recrystallization is attributed to silicon diffusion across the grain boundary region.

Section: Discussionmentioning

confidence: 68%

Grain Growth Mechanism of Heavily Phosphorus‐Implanted Polycrystalline Silicon

Nishimatsu

1978

264

“…1, As ions should As ion implantation distribute within 0.1 #m from the gate oxide-silicon substrate interface. In addition, As ions have a diffusion coefficient as low as 3 >< 10-3 #m/hrl/2 at 1000~ (8); these e x p e r i m e n t a l conditions do not cause As ions to diffuse into silicon substrate. Therefore, the implanted ions can be measured in terms of surface states (Qss).…”

Section: Mos Capacitor Fabrication and Capacitance-voltagementioning

confidence: 99%

Arsenic Ion Channeling through Single Crystal Silicon

Nishimatsu

Hashimoto

1980

The main mechanism of anomalous tail generation in arsenic ion implanted layers is examined using silicon gate MOS capacitance flatband voltage and MOSFET threshold voltage measurements. Primarily, this approach measures the quantity of arsenic ions incorporated in silicon substrates as functions of polycrystalline silicon grain size. This method can measure ion amounts as low as 1011 cm -~ in the substrate. Only samples with large grains which extend across the polycrystalline silicon layer show flatband and threshold voltage shifts. Therefore, the mechanism of anomalous tail generation is attributed to arsenic ion channeling through single crystal silicon. Variations in the implant angle, as well as formation of a surface amorphous layer, are not sufficient to prevent channeling.High dose arsenic ion implantation technology has attracted attention recently for the fabrication of high packing density MOS LSI source and drain regions (1, 2), due to its precise control and flexible application. Nevertheless, designers continue to ask for higher packing density LSI's. Therefore, it is necessary to fabricate even better-controlled source and drain regions than ever.In order to control precisely the arsenic profile in these regions, it is imperative to control the initial arsenic profile, as well as diffusion conditions such as temperature, time, and ambient. However, arsenic ion implantation into single crystal silicon has been reported to generate an anomalous tail in deep substrate regions which exceeds the main peak profile (3, 4). This phenomenon has been observed using the neutron activation analysis. The possible causes were attributed to channeling (3), and to anomalous diffusion (4) through single crystal silicon. The concentration of the anomalous tail was reported to be less than 1017 cm -8, which is almost too low a concentration to be detected by conventional analyses other than neutron activation analysis. Therefore, in order fully to investigate and identify this phenomenon, it was necessary to develop a new method which enables the determination of anomalous profiles in impurity implanted silicon layers. This paper describes a highly sophisticated, yet simple method to determine the cause of anomalous arsenic profile in silicon. This new method utilizes conventional silicon gate MOS LSI technology (5), combined with controlled polycrystalline silicon grain growth phenomenon (6). Fundamental ConceptIn order to determine whether the arsenic incorporation mechanism is anomalous diffusion or channeling, polycrystalline silicon (poly-Si) gate MOS capacitor (MOS C) was used. The crystalline state of poly-Si can be controlled by impurity doping and annealing (6). Therefore, arsenic ions can be implanted through a gate, with the crystalline state between small grain poly-and single crystal. A schematic representation of the MOS C is shown in Fig. 1. If ion channeling takes place in the poly-Si layer with large crystals which extend across the thickness, some fractions of the implanted ions would reach the sub...

“…The heavier the ion dose, the deeper the carrier profile becomes. The dose dependence of carrier profile can be explained in terms of concentration dependent arsenic diffusion coefficient in silicon (14). The peak carrier concentration remained at about 2 X 102~ cm-Z, regardless of ion dose.…”

Section: Resultsmentioning

confidence: 95%

“…Taking a 0.2 #m depth junction for example, ~ 20 the lowest resistivity achievable by arsenic ion im-eplantation and high temperature annealing is around tf) 35 ~/E]. These limitations are determined by the contribution of temperature dependent solid solubility 10 (8), as well as the concentration dependent arsenic diffusion coefficient in silicon (14).…”

Section: Resultsmentioning

confidence: 99%

“…nique (9). 'E Junction diode :fabrication and leakage current meau ~urements.--An n+-p junction diode with 1 mm ~ area 1019 was fabricated by conventional silicon gate MOS LSI c 0 processing technologies (14). A 1 #m thick oxide layer ",= was thermally grown on a p-type, (100) oriented 10 a-cm silicon wafer.…”

Section: Carrier and Defect Pro~le Measurements--carriermentioning

confidence: 99%

See 1 more Smart Citation

Arsenic Ion‐Implanted Shallow Junction

Hashimoto

1980

Shallow junction formation technology by arsenic ion implantation is evaluated from the viewpoint of practical application to the coming VLSI's. Carrier profile, residual defect profile, and electrical characteristics are examined as functions of acceleration energy, dose, annealing conditions, and surface oxide thickness. The carrier profile is determined mainly by both arsenic ion amount in the substrate layer and annealing conditions. The residual defect profile is determined by implantation energy and surface oxide thickness. It is necessary to implant arsenic ions shallower than the resulting carrier profile, to obtain arsenic ion‐implanted junctions with acceptable electrical characteristics. A junction diode, with junction depth as shallow as 0.16 μm is fabricated according to this principle, and is ascertained to have acceptable electrical characteristics.