成果報告書詳細
管理番号20160000000692
タイトル*平成27年度中間年報 SIP(戦略的イノベーション創造プログラム)/次世代パワーエレクトロニクス 将来のパワーエレクトロニクスを支える基盤研究開発 ダイヤモンドパワーデバイス用ウエハの研究開発
公開日2016/8/5
報告書年度2015 - 2015
委託先名国立研究開発法人産業技術総合研究所 国立大学法人千葉大学 国立大学法人大阪大学
プロジェクト番号P14029
部署名IoT推進部
和文要約
英文要約Title: Cross-ministerial Strategic Innovation Promotion Program / Next Generation Power Electronics / Fundamental Research and Development Project for Future Power Electronics / Development of Diamond Wafer for Diamond Power Electronic Device (FY2014-FY2016) FY2015 Annual Report

1. Development of low defect single crystal diamond wafer of 2inch
Development of large and low defect diamond wafer is important for realizing future diamond power electric devices. In this fiscal year, we conducted homo-epitaxial growth of single crystal diamond layers by using the pulse microwave (PW) plasma, which was introduced last year for validation of expected advantages in growth rate enhancement and suppression of the gas temperature. Firstly, we conducted measurements of optical-emission-spectra (OES) of the discharge region, and found that the intensities for such short pulse widths are much higher than that of the continuous wave (CW) mode. We found that, by utilizing the short pulse-modulated discharge, the power efficiency of the growth could be improved into more than two times higher than that of the CW mode.

2. Wafer machining
2-1. Laser machining
Diamond wafer machining such as slicing and planarization of diamond wafer by laser machining was conducted.
Firstly, "slicing from surface" process was studied using a UV laser. As a result, the depth of about 2 mm was achieved. Secondly, "Slicing by internal modification and successive etching" was tried using a femtosecond laser.
Planarization was tried by surface ablation. Laser spot was scanned and the diamond was ablated with constant depth in large area. As a result, surface roughness of the ablated area was ~1.7 um after 10 um-depth ablation.

2-2. Planarization of wafer
In order to reduce the defects in the CVD grown layer, it is necessary to smooth the growth surface of the substrate without any damages. We developed a sacrificial layer etching and chemical mechanical polishing as surface smoothing method. RF etching apparatus was used. We demonstrated the step cancellation of 1 um on a diamond substrate by this planarization process.

3. Theoretical study on diamond power device
This research work evaluated the static and dynamic characteristics of diamond Schottky barrier diode. The device under test (DUT) is supplied from AIST. The forward conduction and reverse blocking current and voltage characteristics are evaluated at first. The DUT is evaluated to have voltage ratings of 150V from leakage current in reverse blocking characteristics. Then, reverse bias voltage dependency of capacitance and effective series resistance are evaluated. The high impurity concentration in the drift region of the device is observed from large terminal differential capacitance and low effective series resistance. Finally, the reverse recovery characteristics of the diode was evaluated with fabricating test circuit. The diode turns off fast and blocks reverse voltage. There was no reverse current found in turn off operation of diode. Thus, DUT actually shows unipolar characteristics of power device.
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