Ion Implanted p+/n 4H-SiC Junctions: effect of the Heating Rate during Post Implantation Annealing
TL;DR: In this paper, structural, morphological and electrical characteristics of Al-implanted p+/n 4H-SiC diodes are compared for the same implantation process and post implantation annealing with identical stationary and cooling cycles but different heating velocity.
Abstract: Structural, morphological and electrical characteristics of Al-implanted p+/n 4H-SiC diodes are compared for the same implantation process and post implantation annealing with identical stationary and cooling cycles but different heating velocity. Al+ ions were implanted at 400°C, with energies in the range 250-350 keV and total fluence of 1.2×1015 cm−2. Post implantation annealing processes were done at 1600°C for 30 min with a constant heating velocity in the range 7 – 40°C/sec and an abrupt cooling cycle. Gas in the annealing ambient was high purity Ar. The Al depth profile of annealed and as implanted samples were equal except for concentrations below 10E17 cm−3 where the former profiles showed a diffusion tail. With the increase of the heating velocity of the post implantation annealing process, sheet resistance of the Al implanted layer and diode leakage currents decrease while the surface roughness increases.
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TL;DR: In this article, the x-ray diffraction and rocking curve of both virgin and processed 4H-SiC samples have been analyzed to obtain the sample crystal quality up to about 3 μm depth from the wafer surface.
Abstract: Semi-insulating 4H-SiC ⟨0001⟩ wafers have been phosphorus ion implanted at 500°C to obtain phosphorus box depth profiles with dopant concentration from 5 × 1019 cm−3 to 8 × 1020 cm−3. These samples have been annealed by microwave and conventional inductively heated systems in the temperature range 1700°C to 2050°C. Resistivity, Hall electron density, and Hall mobility of the phosphorus-implanted and annealed 4H-SiC layers have been measured in the temperature range from room temperature to 450°C. The high-resolution x-ray diffraction and rocking curve of both virgin and processed 4H-SiC samples have been analyzed to obtain the sample crystal quality up to about 3 μm depth from the wafer surface. For both increasing implanted phosphorus concentration and increasing post-implantation annealing temperature the implanted material resistivity decreases to an asymptotic value of about 1.5 × 10−3 Ω cm. Increasing the implanted phosphorus concentration and post-implantation annealing temperature beyond 4 × 1020 cm−3 and 2000°C, respectively, does not bring any apparent benefit with respect to the minimum obtainable resistivity. Sheet resistance and sheet electron density increase with increasing measurement temperature. Electron density saturates at 1.5 × 1020 cm−3 for implanted phosphorus plateau values ≥4 × 1020 cm−3, irrespective of the post-implantation annealing method. Implantation produces an increase of the lattice parameter in the bulk 4H-SiC underneath the phosphorus-implanted layer. Microwave and conventional annealing produce a further increase of the lattice parameter in such a depth region and an equivalent recovered lattice in the phosphorus-implanted layers.
18 citations
TL;DR: In this paper, two kinds of p+n layers have been implemented, aiming at studying the influence of the junction elaborated by the ion implantation process (and subsequent annealing) on the device characteristics.
Abstract: This paper presents a study of 4H-SiC UV photodetectors based on p+n thin junctions. Two kinds of p+ layers have been implemented, aiming at studying the influence of the junction elaborated by the ion implantation process (and the subsequent annealing) on the device characteristics. Aluminum and Boron dopants have been introduced by beam line and by plasma ion implantation, respectively. Dark currents are lower with Al-implanted diodes (2 pA/cm2 @ - 5 V). Accordingly to simulation results concerning the influence of the junction thickness and doping, plasma B-implanted diodes give rise to the best sensitivity values (1.5x10-1 A/W @ 330 nm).
7 citations
Dissertation•
25 Mar 2015
TL;DR: This work is embargoed by the author and will not be publicly available until January 1, 2016.
Abstract: This work is embargoed by the author and will not be publicly available until January 1, 2016.
4 citations
Cites background from "Ion Implanted p+/n 4H-SiC Junctions..."
...A cap film on the implanted SiC wafer during the very high temperature post implant annealing helps to preserve the surface morphology [10]and a very high annealing ramping rate provides favorable electrical properties to the implanted SiC [11], [12]....
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TL;DR: In this article, the surface morphology and electrical activation of P+ implanted 4H-SiC were investigated with respect to annealing treatments that differ only for the heating rate.
Abstract: The surface morphology and the electrical activation of P+ implanted 4H-SiC were investigated with respect to annealing treatments that differ only for the heating rate. P+ implantation was carried out in lightly doped n-type epitaxial layers. The implantation temperature was 300 °C. The computed P profile was 250 nm thick with a concentration of 1×1020 cm-3. Two samples underwent annealing at 1400 °C in argon with different constant ramp up rates equal to 0.05° C/s and 40 °C/s. A third sample underwent an incoherent light Rapid Thermal Annealing (RTA) at 1100 °C in argon before the annealing at 1400 °C with the lower ramp rate. The ramp up of the RTA process is a few hundred degrees per second. Atomic Force Microscopy (AFM) micrographs pointed out that the surface roughness of the samples annealed at 1400 °C increases with increasing heating rate and that the critical temperature for surface roughening is above 1100 °C. Independently on the annealing cycle, Scanning Capacitance Microscopy (SCM) measurements showed that the P profiles are uniform over the implantation thickness and have plateau concentration around 9×1018 cm-3 in all the implanted samples. The fraction of P atoms activated as donors is 13% of the total implanted fluence.
2 citations
TL;DR: In this article, a review study on the relevance of the heating ramp on the annealing of ion implanted SiC is presented, focusing on the heating rate and results that highlight the importance of the ramp on morphological, structural and electrical properties of implanted 4H- and 6H-SiC.
Abstract: With the aim to set a starting point for future investigations on the relevance of the heating ramp on the annealing of ion implanted SiC, a review study is presented here. This study focuses on the heating rate of different annealing setups and presents results that highlight the relevance of the heating ramp on the morphological, structural and electrical properties of ion implanted 4H- and 6H-SiC. The post-implantation annealing results of hot and room temperature implanted SiC are so different that their presentation is kept distinct.
2 citations
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TL;DR: In this paper, the development of optimized processes for p-type doping of SiC by ion implantation and subsequent annealing is a remaining challenge to SiC-device technology.
101 citations
TL;DR: In this paper, a flash-lamp annealing was used for activation and crystal recovery of highly aluminum-implanted 6H-SiC wafers, and the free hole concentration was remarkably increased at high acceptor atom concentrations (⩾5×1020 cm−3).
Abstract: Flash-lamp annealing was used for activation and crystal recovery of highly aluminum-implanted 6H-SiC wafers. In comparison with conventional furnace annealing, the free hole concentration can be remarkably increased at high acceptor atom concentrations (⩾5×1020 cm−3). The lowest resistivity measured at room temperature was 0.01 Ω cm. In this case, the layers are characterized by metallic conduction with weak dependence of the hole concentration on the temperature. This effect is caused by freezing-in of the enhanced solubility of aluminum in SiC at the extraordinary high temperature of about 2000 °C during the light-flash.
65 citations
TL;DR: In this paper, multiple energy N and Al ion implantations were performed into bulk semi-insulating 4H-SiC at various doses to obtain uniform implant concentrations in the range 1×1018-1×1020 cm−3 to a depth of 1.0 μm.
Abstract: Multiple energy N (at 500 °C) and Al (at 800 °C) ion implantations were performed into bulk semi-insulating 4H–SiC at various doses to obtain uniform implant concentrations in the range 1×1018–1×1020 cm−3 to a depth of 1.0 μm. Implant anneals were performed at 1400, 1500, and 1600 °C for 15 min. For both N and Al implants, the carrier concentration measured at room temperature for implant concentrations ⩽1019 cm−3 is limited by carrier ionization energies, whereas for the 1020 cm−3 implant, the carrier concentration is also limited by factors such as the solubility limit of the implanted nitrogen and residual implant damage. Lattice quality of the as-implanted and annealed material was evaluated by Rutherford backscattering spectroscopy measurements. Residual lattice damage was observed in the implanted material even after high temperature annealing. Atomic force microscopy revealed increasing deterioration in surface morphology (due to the evaporation of Si containing species) with increasing annealing t...
59 citations
TL;DR: In this paper, the influence of thermal conditions during solid phase epitaxial regrowth (SPER) on the electrical activation level of boron in preamorphized silicon, both with respect to heating ramp rates and the use of low temperature preanneals, was investigated.
Abstract: We investigate the influence of thermal conditions during solid phase epitaxial regrowth (SPER) on the electrical activation level of boron in preamorphized silicon, both with respect to heating ramp rates and the use of low temperature preanneals. Enhancement of electrically active boron concentration by 36% is observed for activation with the fastest ramp rate (487°C∕s) compared to the slowest one (1°C∕s). An important clustering pathway occurs within the amorphous silicon phase (during low temperature preanneal) prior to completion of the SPER process. In these junctions boron deactivation during isochronal post-annealing is almost independent on the maximum boron activation level.
33 citations
TL;DR: In this paper, the electrical behavior of implanted Al and B near implant-tail region in 4H-SiC (0001) after high-temperature annealing has been investigated.
Abstract: Electrical behavior of implanted Al and B near implant-tail region in 4H–SiC (0001) after high-temperature annealing has been investigated. Depth profiles of Al and B acceptors determined by capacitance-voltage characteristics are compared with those of Al and B atoms measured by secondary-ion-mass spectrometry. For Al+ (aluminum-ion) implantation, slight in-diffusion of Al implants occurred in the initial stage of annealing at 1700°C. The profile of the Al-acceptor concentration in a “box-profile” region as well as an “implant-tail” region is in good agreement with that of the Al-atom concentration, indicating that nearly all of the implanted Al atoms, including the in-diffused Al atoms, work as Al acceptors. Several electrically deep centers were formed by Al+ implantation. For B+ (boron-ion) implantation, significant out- and in-diffusion of B implants occurred in the initial stage of annealing at 1700°C. A high density of B-related D centers exists near the tail region. In the tail region, the sum of B-acceptor concentration and D-center concentration corresponds to the B-atom concentration. C+ (carbon-ion) coimplantation with a ten times higher dose than B+ effectively suppressed the B diffusion, but additional deep centers were introduced by C+ coimplantation.
33 citations