Laser Annealing of P and Al Implanted 4H-SiC Epitaxial Layers.

Cristiano Calabretta,Francesco La Via,Andrea Castiello,Lorenzo Torrisi,Lucia Calcagno,Massimo Zimbone,Alessandro Pecora,Simona Boninelli,Marta Agati,Guglielmo Fortunato

doi:10.3390/ma12203362

Cristiano Calabretta, Francesco La Via + Show 8 more

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https://doi.org/10.3390/ma12203362

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Abstract

This work describes the development of a new method for ion implantation induced crystal damage recovery using multiple XeCl (308 nm) laser pulses with a duration of 30 ns. Experimental activity was carried on single phosphorus (P) as well as double phosphorus and aluminum (Al) implanted 4H-SiC epitaxial layers. Samples were then characterized through micro-Raman spectroscopy, Photoluminescence (PL) and Transmission Electron Microscopy (TEM) and results were compared with those coming from P implanted thermally annealed samples at 1650–1700–1750 °C for 1 h as well as P and Al implanted samples annealed at 1650 °C for 30 min. The activity outcome shows that laser annealing allows to achieve full crystal recovery in the energy density range between 0.50 and 0.60 J/cm2. Moreover, laser treated crystal shows an almost stress-free lattice with respect to thermally annealed samples that are characterized by high point and extended defects concentration. Laser annealing process, instead, allows to strongly reduce carbon vacancy (VC) concentration in the implanted area and to avoid intra-bandgap carrier recombination centres. Implanted area was almost preserved, except for some surface oxidation processes due to oxygen leakage inside the testing chamber. However, the results of this experimental activity gives way to laser annealing process viability for damage recovery and dopant activation inside the implanted area.

Highlights

4H-SiC popularity, due to its favourable properties for high-temperature and high-power applications, has recently grown and its expansion in semiconductor devices, and in MOSFET technology, has begun
Thermal annealing is involved in VC generation under standard thermal equilibrium processes so that new non equilibrium methods based on short time annealing duration are required
A comprehensive description of thermal annealing dynamics is provided by transient model activation [1], which states that the initial activation speed for both donor and acceptor impurities is extremely high and decrease rapidly with time

Summary

Introduction

4H-SiC popularity, due to its favourable properties for high-temperature and high-power applications, has recently grown and its expansion in semiconductor devices, and in MOSFET technology, has begun. The realization of MOSFET selected doped areas, such as the source and body regions, are achieved through ion implantation. Low diffusivity of mostly used dopants in SiC requires the use of multi-ion implantation with different energies and doses to achieve. The realization of MOSFET’s n-type source region occurs through phosphorus ion implantation, while the p-type body region is obtained using Al. The realization of MOSFET’s n-type source region occurs through phosphorus ion implantation, while the p-type body region is obtained using Al The use of these processes involves the generation of a considerable implantation defectiveness, which is only partially recovered by conventional thermal treatments. Rapid thermal annealing systems, are able to obtain high dopant incorporation eluding the usual impurity deactivation due to solid solubility lowering during cooling ramps. Laser annealing technique counts on ramps as high as 109 K/s and allows to obtain much higher temperatures than conventional processes

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