1950°C Post Implantation Annealing of Al⁺Implanted 4H-SiC: Relevance of the Annealing Time

Abstract

Previous studies have shown that the electrical activation of a given implanted Al concentration in 4H-SiC increases with the increasing of the post implantation annealing temperature up to 1950-2100 • C and different annealing times in the range 0.5-5 min. This study shows that, at 1950 • C, the electrical activation of Al implanted in 4H-SiC increases with the increase of the annealing time up to attain saturation for annealing times longer than 22 min. Samples were obtained from the same Al implanted HPSI 4H-SiC wafer with an implanted Al concentration lower than the Al solubility limit in 4H-SiC at the annealing temperature of 1950 • C. The annealing time was varied in the range 5-40 min.

Phosphorous and Aluminum Implantation for MOSFET Manufacturing: Revisiting Implantation Dose Rate and Subsequent Surface Morphology

“…All curves show a negative temperature coefficient at low temperatures, which is more pronounced for the Al implantations. In agreement with previous reports [10], the resistivity decreases with increasing annealing time or annealing temperature. Despite the large differences in dose rate -20 to 70 times larger in Sample C than in Samples A and B -very similar resistivity values between the samples are observed for both the dopants.…”

(Invited) Thermal Stability of 1×1020cm-3Al+Implanted 4H-SiC after Electrical Activation at Temperature ≥ 1850°C

“…The thermal activation energy of the sample annealed 1500 °C/240 min is (115 + 3) meV. The temperature dependence of R sh is mostly dominated by the temperature dependence of the Al acceptor partial ionization as shown in [10]. In such a case the thermal activation of the Arrhenius plots can be used for a rough estimation of the Al electrical activation in the layer by using the dependence of the dopant ionization energy on the dopant density [11]: 23% for 115 meV and 69% for 77 meV.…”

(Invited) Al+ Ion Implanted 4H-SiC: Electrical Activation versus Annealing Time

“…3(a-d), 4(a-d) and 5(a-d), a remark is necessary. In the case of the 0.5-1×10 20 cm -3 Al implanted wafer [13], the plateau of the Al depth profile was not flat. This prevents to obtain the implanted Al material resistivity and drift carrier density per unit volume from a simple multiplication of the implanted layer thickness times the measured sheet resistance and times the measured Hall coefficient (once corrected by the Hall factor), respectively.…”

“…3(a-d), 4(a-d), and 5(a-d) compare the temperature dependences of the sheet resistance (resistivity), of the drift holes density (per unit area or per unit volume), and of the drift holes mobility, respectively, in Al + ion implanted 4H-SiC layers for equal Al implanted concentrations and equal annealing temperature but different annealing times. The data come from [13,14]. Holes density and holes mobility are defined "drift" because they have been corrected for the Hall factor.…”

“…The results for two annealing temperatures, 1600°C and 1950°C, and two annealing times in the range 5 min -5 h per each temperature, are shown in these figures. The used 4H-SiC substrates were either High Purity Semi Insulating 8° off-axis <0001> (HPSI) [13] or n-type homo epitaxial substrates 4° off-axis <0001> (EPI) [14]. The authors think that this is licit because, in their experience, no significant difference was evident between HPSI and EPI substrates, neither between 8° and 4° off-axis <0001>, for identical study of ion implantation and post implantation annealing.…”