成果報告書詳細
管理番号20160000000725
タイトル*平成27年度中間年報 低炭素社会を実現する次世代パワーエレクトロニクスプロジェクト 窒化ガリウムパワーデバイスの実用化促進等に関する先導研究 窒化ガリウムパワーデバイス高出力化のための高放熱構造検証
公開日2016/8/23
報告書年度2015 - 2015
委託先名三菱電機株式会社
プロジェクト番号P10022
部署名IoT推進部
和文要約
英文要約Title: Pilot-study for development of high-power gallium nitride device/Study of efficient heat dissipator for gallium nitride devices with higher output power (FY2015-FY2016) FY2015 Annual Report

Thermal management of high-power gallium nitride (GaN) devices has been of crucial importance to exploit ever increasing output power of GaN devices. In this report, deposition of polycrystalline diamond on GaN by a microwave-plasma chemical vapor deposition (MP-CVD) method was examined with the aim of fabricating the GaN device in which dissipation of heat is enhanced by high thermal conductivity of diamond. Theoretical study was also carried out by simulating the temperature distribution in GaN devices to investigate the effectiveness of diamond heat dissipator.Polycrystalline diamond was deposited on Si substrate at various conditions to understand the deposition mechanism. Higher substrate temperature resulted in higher deposition rate and better crystal quality as evaluated by Raman spectroscopy. In-plane and out-of-plane thermal conductivity of the sample deposited at 940 °C reached 1540 W/mK and 1730 W/mK, respectively. These values are both well beyond the target value (1000 W/mK) aimed in this study.Deposition of an adhesion layer prior to diamond deposition was examined. Choice of the material is restricted by the following two requirements. The first one is that it has to suppress the exfoliation and cracking of GaN due to the strain generated by different thermal expansion coefficient of GaN and diamond. The second one is that the reaction of the material and GaN in high ambient temperature needs to be avoided. Among amorphous Si, micro-crystalline Si, SiN and diamond like carbon (DLC), amorphous Si and DLC are found to result in better adhesion and less reaction, and thus the most appropriate materials for the adhesion layer.Temperature distribution of GaN devices assembled on a conventional CuMo package with solder was estimated theoretically. Maximum temperature of GaN channel, where heat is generated is reduced by 36% by altering substrate material from SiC to diamond. Calculation also found that the channel temperature monotonically decreases as diamond thickness increases.
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