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CVD Growth of Silicon Carbide for High Frequency Applications
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2001. , 35 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 708
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
URN: urn:nbn:se:liu:diva-15070ISBN: 91-7373-081-5 (print)OAI: oai:DiVA.org:liu-15070DiVA: diva2:37759
Public defence
2001-09-07, Planck, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2014-10-08Bibliographically approved
List of papers
1. Nitrogen doping of epitaxial Silicon Carbide
Open this publication in new window or tab >>Nitrogen doping of epitaxial Silicon Carbide
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2002 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 236, no 1-3, 101-112 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
ScienceDirect, 2002
Keyword
A1. Doping, A3. Hot wall epitaxy, B2. Superconducting materials
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15068 (URN)10.1016/S0022-0248(01)02198-4 (DOI)
Note
The status of this article on the day of the defence was: Submitted and the title of the article was "Nitrogen doping of Silicon Carbide: Effect of Process Parameters"Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2017-12-11Bibliographically approved
2. Aluminum doping of epitaxial Silicon Carbide
Open this publication in new window or tab >>Aluminum doping of epitaxial Silicon Carbide
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2003 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 253, no 1-4, 340-350 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
ScienceDirect, 2003
Keyword
A1. Doping; A1. Growth models; A3. Chemical vapor deposition processes; A3. Hot wall epitaxy; B2. Semiconducting silicon carbide
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15055 (URN)10.1016/S0022-0248(03)01045-5 (DOI)
Note
The status of the article on the defence day was: Submitted and the original title was "Aluminum doping of Silicon Carbide: Effect of Process Parameters".Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2017-12-11Bibliographically approved
3. Growth and characterisation 4H-SiC MESFET structures grown by Hot-Wall CVD
Open this publication in new window or tab >>Growth and characterisation 4H-SiC MESFET structures grown by Hot-Wall CVD
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2001 (English)In: Proc. of the MRS 2000 Fall Meeting, 2001, H2.3.2- p.Conference paper, Published paper (Refereed)
Abstract [en]

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.

Keyword
Hot-Wall CVD, MESFET, Silicon carbide, SEM, SIMS
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15062 (URN)
Conference
MRS 2000 Fall Meeting
Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2016-08-31Bibliographically approved
4. Determination of nitrogen doping concentration in doped 4H-SiC epilayers by low temperature photoluminescence
Open this publication in new window or tab >>Determination of nitrogen doping concentration in doped 4H-SiC epilayers by low temperature photoluminescence
2005 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 72, no 2-3, 254-257 p.Article in journal (Refereed) Published
Abstract [en]

A complete calibration of nitrogen concentration in doped 4H-SiC material is presented. This is done in the very large range of doping available today, i.e. from low 1014 to 1019 cm-3. The samples are 4H-SiC films fabricated by hot-wall chemical vapour deposition. Low temperature photoluminescence is used as the experimental tool. For doping concentrations less than 8 × 1017 cm-3 comparison between the intensity of various luminescence lines is used, whereas for doping higher than 3 × 1018 cm-3 the energy position of an observed broad band allows the determination of the doping level.

National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15063 (URN)10.1238/Physica.Regular.072a00254 (DOI)
Note
On the day of the defence the status of article IV was: Submitted to Applied Physics Letter.Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2017-12-11Bibliographically approved
5. Investigation of the temperature profile in a hot-wall SiC chemical vapour deposition reactor
Open this publication in new window or tab >>Investigation of the temperature profile in a hot-wall SiC chemical vapour deposition reactor
2002 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 235, no 1-4, 352-364 p.Article in journal (Refereed) Published
Abstract [en]

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 <!--[if !vml]--><!--[endif]-->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.

Place, publisher, year, edition, pages
ScienceDirect, 2002
Keyword
A1. Computer simulation, A1. Heat transfer, A3. Chemical, vapor deposition, A3. Hot-wall epitaxy, B2. Semiconducting silicon carbide
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15064 (URN)10.1016/S0022-0248(01)01831-0 (DOI)
Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2017-12-11Bibliographically approved
6. Growth of high quality AlN Epitaxial Films by Hot-Wall Chemical Vapour Deposition
Open this publication in new window or tab >>Growth of high quality AlN Epitaxial Films by Hot-Wall Chemical Vapour Deposition
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1998 (English)In: Proceedings of the International Conference on Silicon Carbide, III-Nitrides and Related Materials, 1997, 1998, Vol. 264-268, 1133-1136 p.Conference paper, Published paper (Refereed)
Abstract [en]

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.

 

Keyword
Hot-Wall CVD, Thin Film, XRD, TEM, Infrared reflectance
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15065 (URN)
Conference
International Conference on Silicon Carbide, III-Nitrides and Related Materials, 1997
Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2013-06-12Bibliographically approved
7. Infrared Reflectance of Extremely Thin AlN Epi Films Deposited on SiC Substrates
Open this publication in new window or tab >>Infrared Reflectance of Extremely Thin AlN Epi Films Deposited on SiC Substrates
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1998 (English)In: Materials Science Forum Vols. 264-268, 1998, Vol. 264-268, 649-652 p.Conference paper, Published paper (Refereed)
Abstract [en]

The room temperature reflectance of thin (£ 1000Å) AlN epi-films deposited on n type 6H SiC has been measure. These epi-films are too thin to produce interference fringes, from which epi-films thickness is often extracted, within the measured spectral region. However, features from the AlN reststrahl reflectance band can be clearly seen for AlN epi-films as thin as 250Å. Thicknesses are extracted from the measured spectra by comparing them directly to calculated spectra with the epi-film thickness being the only fitting parameter. The accuracy of these thickness determinations is confirmed by comparing them to thickness measured on samples studied by cross sectional TEM.

Keyword
Epi-film Thickness, Reflectance, TEM
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15066 (URN)
Conference
Conference on Silicon Carbide, III-Nitrides and Related Materials, 1997
Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2016-08-31Bibliographically approved

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