Abstract

Ion implantation is a commonly used process step in 4H-SiC device manufacturing to implement precise concentrations of dopant atoms in selected areas and depths. This paper reports on vanadium (V) implantation into 4H-SiC(0001) and how the crystal lattice, with preferential directions, channels, for the ions, will influence the final dopant distribution. Concentration versus depth profiles of V-ions, intentionally and unintentionally channelled, has been recorded by secondary ion mass spectrometry. Ion implantations have been performed between 50 and 300 keV at various impact angles and fluence at room temperature as well as at elevated temperatures. Before ion implantation, the samples were aligned utilizing the blocking pattern of 100 keV backscattered protons. In addition to the aligned implantations, our standard beam line for ion implantation has been used for implantations in a ‘random’ direction using the wafer miscut angle of 4°. The electronic stopping has been determined from these ‘random’ cases and the values have been used in 3D simulations to predict preferential crystallographic directions using SIIMPL, a Monte Carlo simulation code based on the binary collision approximation. The results show that, independent of the used impact angle there is always a probability that the vanadium ions will be steered into the [000-1] and the family of 〈11-2-3〉 crystal directions and therefore penetrate deep into the sample, resulting in unwanted ‘spikes’. If the implantation is performed at elevated temperatures, a larger degree of dechanneling is present due to increased thermal vibrations and the penetration depth of vanadium is slightly reduced.

Highlights

  • We present experimental results supported by MC-BCA simulations for intentional and unintentional ion channeling during implantations of 51V+-ions at energies between 50 and 300 keV in 4H-SiC at room temperature (RT) as well as at elevated temperatures

  • The electronic stopping, Se, has been determined to 6E0.45 eV/, which is used in simulations of V in 4H-SiC

  • Experimental secondary ion mass spectrometry (SIMS) profiles, show a change between the dominant channeling direction from [000-1] to 〈11-2-3〉 as the tilt angle is increasing from 0° to 17°

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Summary

Introduction

Ion implantation is today a well-established technique for introduction of dopants into 4H-SiC since, (i) diffusion of. The so called channeling may considerably increase the ion penetration depth in crystalline material compared to an amorphous target This phenomenon may occur if the direction of the incident ion beam is nearly in parallel to major crystallographic axes or planes. As implantation direction in 4HSiC (hexagonal silicon carbide), a 4° off-axis from the [0001] towards the [11,12,13,14,15,16,17,18,19,20] direction is often used as a ‘random’ direction, taking advantage of the standard miscut angle of SiC wafers This results in more or less Gaussian shaped dopant versus depth profiles, where the depth is determined by the energy, the used ions and the target atoms. Experimental data in combination with simulations show that a fully non-channeling direction is hard to find and independent of the used impinging ion direction, a certain amount of ions will be steered, into [0001] and 〈11-23〉 channels and travel to substantial depth

Experimental
Simulations
Crystal structure and beam alignment
Electronic stopping and ‘random’ implantation directions
Aligned implantation directions
Hot implantations
Summary
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