Intentional and unintentional channeling during implantation of ⁵¹V ions into 4H-SiC

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.

Intentional and Unintentional Channeling during Implantation of p-Dopants in 4H-SiC

“…4 by a red line for the 3D-images, or a dotted red line for the 2D-images. In the simulations 1.5×10 7 ions have been simulated, thermal vibrations for RT have been used and, to include the build-up of damage, a dose of 5×10 14 cm -2 have been utilized. A small impact area of 1×1 nm 2 has been used to readily identify the preferred crystallographic directions for channeling.…”

“…However, even for implantations 4° off from the [000-1] direction, some ions will be steered into crystal channels and these ions will contribute to a deep tail in the dopant distribution [7]. In SiC, the channeled ions may come to rest significantly deeper than the projected range of an amorphous target [4][5][6][7][8][9]. The degree of channeling varies with atomic number of implanted ions as well as the energies used.…”

Efficacy of Ion Implantation in Zinc Oxide for Optoelectronic Applications: A Review

“…The orientation of the crystal plane and temperature of the lattice atoms are also important parameters in the case of single crystals. The crystal orientation affects the ion dispersion during the implantation via the channeling effect. − When the motion of an ion is along the atomic rows, the ion moves through the open space of the atomic rows. Initially, the ions bounce from row to row, forming an oscillatory motion with a wavelength of some hundreds of Å.…”

Depth Profiling of Ion-Implanted 4H–SiC Using Confocal Raman Spectroscopy

“…On one hand, the smaller angle of incidence θ for the 50L× lens (Table 2) reduced the refraction influence. The length of the laser beam waist, which is also called the depth of focus ω [11], is shown in Table 2 and Figure 6b. ω is usually defined as Equation 1.…”

“…The most relevant method for rather thin implanted 4H-SiC layers with high doping concentrations is secondary ion mass spectroscopy (SIMS) depth profiling. However, this gives only the "chemical" depth profile of the implanted species [11]. Unfortunately, though, especially in 4H-SiC (compared to e.g., Si), the electrically active doping concentration and, thus, the carrier concentration profile might differ significantly from the chemically implanted concentrations.…”