Local Stress-strain Structure in CVD Diamond Observed by Raman Peak-shift Mapping
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Local Stress-strain Structure in CVD Diamond Observed by Raman Peak-shift Mapping
Yukako Kato1, Hitoshi Umezawa1, Tokuyuki Teraji2, Shin-ichi Shikata1 1 Diamond Research Laboratory, Advanced Industrial Science and Technology, Tsukuba 3058568, Japan 2 National Institute for Material Science, Tsukuba 305-0047, Japan
ABSTRACT Semiconductor epitaxial CVD single crystal diamond is considered a potential material for power devices because of its unique characteristics. In the discussion on the relationship between crystal quality and device performance, the atomic purity and defect concentration have been considered; however, the information on the local stress-strain distribution in a single crystal is not sufficient. In this paper, the local stress-strain distribution of the epitaxial CVD single crystal diamond is quantitatively examined using the birefringence and cathodoluminescence images and the Raman peak-shift map. From the Raman peak-shift map, the local stress-strain is estimated and the stress is found to range from -67 MPa to +160 MPa in the observed area. INTRODUCTION Semiconductor diamond has attracted considerable attention as a power device material that is able to perform with a high breakdown characteristic and high carrier mobility. Because of its material properties, it is expected that a diamond power device can perform in a hightemperature and high-voltage environment. The Baliga's figure of merit (BFOM) is used for the comparison of power device material properties. The BFOM of diamond, when normalized to Si, is 44000. This value is much higher than the BFOM of SiC, which is 640 [1]. Recently, Umezawa et al. reported the development of a diamond Schottky barrier diode with high temperature characteristics [2-3]. For the practical application of a diamond power device, it should be examined for its stability behavior at high performance. One of the factors that affect stability behavior is the presence of crystal defects. The relationship between defects and device properties has been discussed by several research groups. They have suggested that a highquality crystal with flat surface and low defect density is required [4-6]. In this paper, we focus on the local stress-strain in the epitaxial layer because the amount of local stress-strain is related to the electrical and thermal carrier mobility. The local stress-strain in the epitaxial layer is mapped using confocal Raman microscopy. Raman spectroscopy is the most powerful method for mapping the local stress-strain. Chen et al. and Habka et al. have already discussed the local stress in a polycrystalline CVD diamond [7-8] but no data have been reported for epitaxial single-crystal CVD diamond used for device applications.
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EXPERIMENT The analyzed sample is an epitaxial CVD single crystal diamond (001) on the Ib-type HPHT single crystal diamond. The sample size is about 3 mm × 3 mm. The thickness of the epitaxial layer and substrate are 25 ȝm and 0.5 mm, respectively. In order to compare the experimental data, the Ti/Au crossed-line marker i
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