Selective etching of p-GaN over Al0.25Ga0.75N in Cl2/Ar/O2 ICP plasma for fabrication of normally-off GaN HEMTs. (February 2021)

• Record Type: Journal Article
• Authors: Taube, Andrzej; Kamiński, Maciej; Ekielski, Marek; Kruszka, Renata; Jankowska-Śliwińska, Joanna; Michałowski, Paweł P.; Zdunek, Joanna; Szerling, Anna
• Is Part Of: Materials science in semiconductor processing. Volume 122(2021)
• Publication Date: 2021-02
• Subjects: dry etching -- Normally-off HEMT -- p-GaN -- ICP -- Selectivity; Semiconductors -- Periodicals; Integrated circuits -- Materials -- Periodicals; Semiconducteurs -- Périodiques; Circuits intégrés -- Matériaux -- Périodiques; Electronic journals; 621.38152
• DOI: 10.1016/j.mssp.2020.105450
• Languages: English
• ISSNs: 1369-8001

Abstract

Abstract: The article presents the results of development of selective etching of p-GaN over Al0.25 Ga0.75 N in Cl2 /Ar/O2 ICP plasma for fabrication of normally-off p-GaN gate GaN HEMTs using a laser reflectometry system for precise control of the etched material thickness. By optimizing etching process parameters such as oxygen flow, ICP power and chamber pressure, high etching selectivity of p-GaN over Al0.25 Ga0.75 N were obtained, with values up to 56:1. High etching selectivity and the control of etch rates of p-GaN and Al0.25 Ga0.75 N layers withing a wide range by changing the ICP process parameters enabled application of developed etching processes in the technology of fabrication of normally-off AlGaN/GaN HEMTs with a p-GaN gate. High threshold voltage of around 1.6 V and current densities up to 400 mA/mm were obtained. Electrical measurements have shown that the shortest 1 min Al0.25 Ga0.75 N overetch time after selective etching of the p-GaN layer results in best electrical parameters of fabricated devices. Graphical abstract: Image 1 Highlights: Results of development of selective etching of p-GaN over Al0.25 Ga0.75 N process using Cl2 /Ar/O2 ICP plasma were presented. High etching selectivity of p-GaN over Al0.25 Ga0.75 N enabled fabrication of normally-off AlGaN/GaN HEMTs. High VTH ~1.6 V, IDS up to 400 mA/mm, Ion /Ioff > 6x10 8 A/A, along with nearly ideal SS value of 63 mV/dec at RT were obtained.