【公開日：2025.06.10】【最終更新日：2025.05.23】
課題データ / Project Data
課題番号 / Project Issue Number
24TT0039
利用課題名 / Title
GaNおよびSiCデバイスと作製プロセスの研究開発
利用した実施機関 / Support Institute
豊田工業大学 / Toyota Tech.
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者）/Internal Use (by ARIM members)
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）加工・デバイスプロセス/Nanofabrication（副 / Sub）計測・分析/Advanced Characterization
【重要技術領域 / Important Technology Area】（主 / Main）高度なデバイス機能の発現を可能とするマテリアル/Materials allowing high-level device functions to be performed（副 / Sub）量子・電子制御により革新的な機能を発現するマテリアル/Materials using quantum and electronic control to perform innovative functions
キーワード / Keywords
化合物半導体/ Compound semiconductor,光学顕微鏡/ Optical microscope,エレクトロデバイス/ Electronic device,蒸着・成膜/ Vapor deposition/film formation,光リソグラフィ/ Photolithgraphy
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
Villamin MariaEmma
所属名 / Affiliation
豊田工業大学大学院工学研究科
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
朽木 克博さん、 豊田中央研究所
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
岩田直高
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）,共同研究/Joint Research
利用した主な設備 / Equipment Used in This Project
TT-016：エリプソメーター
TT-017：表面形状測定器（段差計）
TT-003：原子層堆積装置
TT-015：デジタルマイクロスコープ群
TT-006：マスクアライナ装置
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
The aim of this project is to fabricate GaN and SiC device structure. In this report, we showed how we utilized the ARIM equipment, especially using the ALD machine, in the Toyota Technological Institute Cleanroom in order to fabricate these devices: (1) pGaN/AlGaN/GaN based power devices, (2) Mg-doped GaN cloverleaf van der pauw (CVNP) structure for laser annealing, and (3) SiC MOS devices for quantum sensing. Devices (1) & (2) are part of the Kakenhi projects in our laboratory (岩田直高特任教授研究室). In pGaN HEMT fabrication, two ALD deposited films are needed to fabricate the devices: silicon dioxide (SiO2) and silicon nitride (SiN) films. The deposited SiO2 film was used as SiO2-photomask with mesa patterns during the isolation mesa etching process. Whereas, the deposited SiN film was used as a passivation layer for the devices. We have successfully fabricated GaN power devices with good isolation and passivation layer using ALD deposited SiO2 and SiN film, respectively. Device (2) is used to investigate ArF laser for pGaN activation on Mg-doped GaN wafer. Similar to the HEMT fabrication, the cloverleaf mesa pattern was formed using dry etcher with SiO2-photomask pattern. On the other hand, the fabrication of SiC devices are part of an on-going project between our laboratory and the Toyota Central Research Laboratory under the National Institute for Quantum Science and Technology (QST) Strategic Innovation Promotion Program SIP3 program “Promoting Application of Advanced Quantum Technologies to Social Challenges”. DC characteristic results of device 1 are shown in the IWN 2024 conference [1], whereas, the resistivity of the ArF activated pGaN layer with CVNP structure (not shown here) were published in Journal of Optical Engineering [2].
実験 / Experimental
Wafer structure of the HEMT device include a super lattice buffer layer, a GaN layer, an AlGaN layer, and a p-type GaN layer on a silicon substrate. Briefly, the p-GaN HEMT device fabrication process are as follows: (a) etching of pGaN mesa, (b) etching of GaN mesa for device isolation, (c) deposition of Ti/Al/Ti/Au and annealing to make ohmic contact for the source and drain contact, (d) deposition of Ni/Au for the pGaN gate contact, and (e) deposition of SiN film for passivation. From the above process, the ALD depositions of SiO2 film were mainly used in the p-GaN etching (a) and device mesa etching (b) using a dry etcher. The SiO2-photomask with mesa patterns was used because SiO2 can withstand the Cl2 gases during etching. Specifically, to make SiO2-photomask, all samples and a dummy silicon substrate (as reference SiO2 thickness) were first deposited with a SiO2 film. Afterwards, the mesa patterns were transferred to the SiO2 film by using standard photolithography and the excess SiO2 film were wet chemically (BHF solution) etched. Lastly, photoresist were stripped using photoresist remover. On the other hand, for the CVNP structure, the wafer structure used include 200um-thick Mg-doped GaN layer (unactivated pGaN) and an undoped GaN layer on a Sapphire substrate. Similar to the HEMT process mentioned above, standard photolithography and metal deposition were used to make CVNP structure. The fabrication steps are as follows: (i) thick SiO2 film deposition using ALD, (ii) cloverleaf mesa pattern formation via etching, (iii) In/Au contact formation, and (iv) metal contact annealing at 450°C using RTA. The resistivity at different laser irradiation power used to activate the pGaN CVNP structure were then investigated. In SiC device fabrication, wafers were first cleaned using piranha cleaning and acetone, methanol & water, and then the oxide layer were deposited using ALD with BEMAS as precursor and substrate temperature of 250C. Using standard photolithography and lift off, the metal contact and circular pattern were done. Al metal was deposited on top and bottom of the wafer using sputtering machine. C-V measurement were done (not shown in this report).
結果と考察 / Results and Discussion
A representative of samples deposited with SiO2 using ALD is shown in Fig. 1. The thickness of the deposited SiO2 film is about 150nm using an ellipsometer. This thickness value is very close to the target deposition SiO2 thickness. These results shows that ALD thickness control on deposited film is very good, which is important for the etching process during the device fabrication. The etch rate of SiO2: GaN is 1:5, thus SiO2 is etched much slower than GaN under the BCl3 etching conditions. Thus, the deposited SiO2 film is enough to etch 100nm GaN to make the mesa. The etched mesa height is ~100um measured using an alpha step profiler. This height is close to target, which is enough to cut the channel layer to isolate each devices on the wafer. Furthermore, the fabricated CVNP structure after laser irradiation is shown in Fig. 2. It can be seen that the cloverleaf pattern mesa is clearly defined and the irradiation mark is at the center, which indicates that local pGaN activation using this structure is possible. The SiC wafer after deposited 50-nm-thick SiO2 is shown in Fig. 3. Using an ellipsometer, we have verified that the deposited oxide was around 49.37 nm with index of refraction 1.46 which are close the target 50nm thickness and Nf = 1.45.
図・表・数式 / Figures, Tables and Equations
Fig.1 ALD deposited device 1: pGaN-GAD samples
Fig. 2 Device 2: laser irradiated CVNP
Fig. 3 Device 3: SiO2- ALD deposited SiC substrate
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
Reference[1] N. Iwata & M.E. Villamin, International Workshop on Nitride Semiconductors (IWN) 2024, Poster 68, Hawai USA, Nov. 4, 2024. [2] M.E Villamin, R. Roca, I. Kamiya, & N. Iwata, Opt. Eng. 63(9), 096101 (2024), doi: 10.1117/1.OE.63.9.096101.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
-
Maria Emma Villamin, Electrical and structural properties of ArF excimer laser activation of Mg-doped GaN small area mesa device, Optical Engineering, 63, (2024).
DOI: 10.1117/1.OE.63.9.096101
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
- N. Iwata & M.E. Villamin, International Workshop on Nitride Semiconductors (IWN) 2024, Poster 68, Hawai USA, Nov. 4, 2024.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件