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- Danielsson, Örjan, et al.
(författare)
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Investigation of the temperature profile in a hot-wall SiC chemical vapour deposition reactor
- 2002
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Ingår i: Journal of Crystal Growth. - : ScienceDirect. - 0022-0248 .- 1873-5002. ; 235:1-4, s. 352-364
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Tidskriftsartikel (refereegranskat)abstract
- The chemical vapor deposition (CVD) technique is widely used to grow epitaxial layers of silicon carbide. To meet the demands for high quality epitaxial layers, which have good morphology and a minimum variation of the doping and thickness, a good knowledge of the CVD process is essential. The present work uses a simulation tool to investigate several parameters influencing the heating of a hot-wall CVD reactor. The simulations are set up as 2D axisymmetric problems and validation is made in a 2D horizontal hot-wall CVD reactor. By applying the knowledge achieved from the simulations, the temperature profile is optimized to give as large area as possible with homogeneous temperature. New susceptor and coil designs are tested. A very good agreement between the simulated and the measured results is obtained. The new design has a temperature variation of less than 0.5% over more than 70% of the total susceptor length at an operating temperature of 1650°C. In addition, the power input needed to reach the operating temperature is decreased by 15% compared to the original design. 3D simulations are performed to show that the changes made in the 2D case give similar results for the real 3D case.
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| 4. |
- Forsberg, Urban, 1971-, et al.
(författare)
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Aluminum doping of epitaxial Silicon Carbide
- 2003
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Ingår i: Journal of Crystal Growth. - : ScienceDirect. - 0022-0248 .- 1873-5002. ; 253:1-4, s. 340-350
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Tidskriftsartikel (refereegranskat)abstract
- Intentional doping of aluminum in 4H and 6H SiC has been performed using a hot-wall CVD reactor. The dependence of aluminum incorporation on temperature, pressure, C/Si ratio, growth rate, and TMA flow has been investigated. The aluminum incorporation showed to be polarity dependent. The high aluminum incorporation on the Si-face is closely related to the carbon coverage on the SiC surface. Changes in process parameters changes the effective C/Si ratio close to the SiC surface. Increased growth rate and C/Si ratio increases the aluminum incorporation on the Si-face. Diffusion limited incorporation occurs at high growth rate. Reduced pressure increases the effective C/Si ratio, and at low growth rate, the aluminum incorporation increases initially, levels off at a critical pressure, and continues to decrease below the critical pressure. The aluminum incorporation showed to be constant in a temperature range of 50°C. The highest atomic concentration of aluminum observed in this study was 3×1017 and 8×1018 cm−3 in Si and C-face, respectively.
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| 5. |
- Forsberg, Urban, 1971-
(författare)
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CVD Growth of Silicon Carbide for High Frequency Applications
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Silicon Carbide (SiC) is an important wide band gap semiconductor with outstanding electronic properties. With figures of merit far better than silicon, SiC is believed to replace and outcompete silicon in many applications using high frequencies, high voltage and high temperatures. With the introduction of seeded sublimation technique, a realisation of substrates with large diameter and high quality became possible. Recent progress in the bulk growth using high temperature chemical vapour deposition (HTCVD) has shown excellent results with high purity substrates with semi insulating (SI) properties. The availability of high quality SI substrates allows the fabrication of microwave devices with low rf losses such as the Metal Schottky Field Effect Transistor (MESFET). With the introduction of the hot-wall CVD technique, thick low doped n-type epitaxial layers have been grown for high power devices (> 4 kV) such as the PiN diode.The main contribution of the present work relates to the investigation of growth of MESFET structures. The goal has been to demonstrate the ability to grow MESFET structures using the hot-wall CVD technique. The challenge with abrupt interfaces and controlled doping has been investigated. A comprehensive investigation has been made on how nitrogen and aluminum dopant atoms incorporate into the SiC lattice using the hot-wall CVD technique. Fundamental research of MESFET structures has been combined with growth of device structures for both Swedish and European groups as well as industries. The research has been focused towards the understanding of dopant incorporation, characterization of doped epitaxial layers, the growth of device structures, the modelling of temperature distribution in a hot-wall susceptor and the development of growth systems for future up scaling.In paper 1 we present how the nitrogen dopant is incorporated into the SiC lattice. The influence of several different growth parameters on the nitrogen incorporation is presented. Equilibrium thermodynamical calculations have been performed to give a further insight into the incorporation mechanism. The investigation shows that the N2 molecule itself does not contribute directly to the nitrogen incorporation, however, molecules like the HCN and HNC are more likely.In paper 2 the incorporation of the aluminum dopant into the SiC lattice is investigated in a similar way as the nitrogen incorporation in paper 1. The results show that the aluminum incorporation in SiC is mainly controlled by the carbon coverage on the SiC surface. The investigation shows that it is difficult to obtain high aluminum doping on carbon face whereas the silicon face is sensitive to changes of the growth parameters. High growth rate resulted in a diffusion controlled incorporation.In Paper 3 we present the results from the growth of MESFET structures as well as characterization of the structures and final device properties. Knowledge taken from paper 1 and 2 was used to improve the abruptness of the grown structures.Paper 4 presents the results obtained by low temperature photoluminescence (LTPL) on separately grown 4H-SiC epitaxial layers. Doping calibration curves for nitrogen in the doping range from 1⋅1014 to 2⋅1019 cm-3 are presented. A discussion concerning the Mott transition is also presented.Paper 5 presents the results of the use of simulation to investigate the heating of a hot-wall CVD reactor. New susceptor and coil design are tested. The simulation has been verified with experimental heating tests which show excellent agreement. The new design has a temperature variation of less than 0.5 % over more than 70% of the total susceptor length in addition to a decreased power input of 15 %.In the final two papers, paper 6 and 7, we present work of growth of AlN on SiC. Thin films were grown and characterized with different techniques concerning crystal quality and thickness. The use of infrared reflectance and the features of the AlN reststrahl reflectance band allowed us to determine the thickness of AlN films as thin as 250 Å.
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| 6. |
- Forsberg, Urban, 1971-, et al.
(författare)
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Growth and characterisation 4H-SiC MESFET structures grown by Hot-Wall CVD
- 2001
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Ingår i: Proc. of the MRS 2000 Fall Meeting. ; , s. H2.3.2-
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Konferensbidrag (refereegranskat)abstract
- Metal semiconductor field effect transistor structures have been grown in a hot-wall CVD reactor. Using trimethylaluminium and nitrogen, p- and n-type epitaxial layers were grown on semi insulating substrates. A comprehensive characterization study of thickness and doping of these multi structures has been performed by using scanning electron microscopy , secondary ion mass spectrometry, capacitance-voltage and low temperature photoluminescence. Optimisation of growth parameters has resulted in very abrupt doping profiles. The grown metal semiconductor field effect transistor structures have been processed and parts of the transistor properties are presented.
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| 7. |
- Forsberg, Urban, 1971-, et al.
(författare)
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Growth of high quality AlN Epitaxial Films by Hot-Wall Chemical Vapour Deposition
- 1998
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Ingår i: Proceedings of the International Conference on Silicon Carbide, III-Nitrides and Related Materials, 1997. ; , s. 1133-1136
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Konferensbidrag (refereegranskat)abstract
- Epitaxial films of high quality AlN have been grown on SiC substrates at 1200 °C and 1450 °C, using a hot-wall CVD reactor. The thickness of the epitaxial layers were measured using room temperature infrared reflectance. To verify the crystal quality, X-ray diffraction (XRD) rocking curves of the ALN 0002 peak were measured. A 250 Å thick film grown at 1450°C had a full width half maximum (FWHM) of 42 arcsec, whereas a 1000 Å thick film grown at 1200 °C had a FWHM of 100 arcsec. A TEM image of the sample grown at the lower temperature showed thickness of around 950 Å, thereby verifying the infrared reflectance measurements. We conclude that the higher temperature the better the crystal quality we obtain.
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| 8. |
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| 9. |
- Forsberg, Urban, 1971-, et al.
(författare)
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Nitrogen doping of epitaxial Silicon Carbide
- 2002
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Ingår i: Journal of Crystal Growth. - : ScienceDirect. - 0022-0248 .- 1873-5002. ; 236:1-3, s. 101-112
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Tidskriftsartikel (refereegranskat)abstract
- Intentional doping with nitrogen of 4H- and 6H-SiC has been performed using a hot-wall CVD reactor. The nitrogen doping dependence on the temperature, pressure, C/Si ratio, growth rate and nitrogen flow has been investigated. The nitrogen incorporation for C-face material showed to be C/Si ratio independent, whereas the doping decreased with increasing C/Si ratio for the Si-face material in accordance with the “site-competition” model. The nitrogen incorporation was constant in a temperature “window” of 75°C on Si-face material indicating a mass transport limited incorporation. Increasing the growth rate resulted in a decrease of nitrogen incorporation on Si-face but an increase on C-face material. Finally, a comparison between previously published results on cold-wall CVD-grown material and the present hot-wall-grown material is presented.
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| 10. |
- Gunnarsson, Svante, 1959-, et al.
(författare)
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Reflections about reflections
- 2023
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Ingår i: Proceedings of the 19th CDIO International Conference. - : NTNU SEED. - 9788230361863 ; , s. 56-66
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Konferensbidrag (refereegranskat)abstract
- A case study of the use of reflections within the Applied physics and electrical engineering program at Linköping University is presented. Reflections have been used for several years and they are done at four stages in the program, in terms of reflections at the end of the Introductory course in year one, design-implement experiences in year three and five, and a reflection document that is the last component of the Master’s thesis. In the first three stages a project model is used to support the planning and execution of the project, and in the project model the project work ends with a reflection. In the reflection document connected to the Master’s thesis the student reflects upon both the thesis work itself and the entire education program, according to the sections and subsections of the CDIO Syllabus. The paper describes how the reflections are integrated in the program. Experiences from student perspective are collected in a small-scale study via interviews with students from year one and year five.
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