Lithographically defined carbon growth templates for ELOG of GaN

• Published in: Journal of crystal growth Vol. 310; no. 12; pp. 3113 - 3116
• Main Authors: Burckel, D.B., Fan, Hongyou, Thaler, G., Koleske, D.D.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2008; Elsevier
• Subjects: A3. Metalorganic chemical vapor deposition; A3. Pendeoepitaxy; Applied sciences; B2. Semiconducting materials; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electronics; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; General studies of phase transitions; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microelectronic fabrication (materials and surfaces technology); Nucleation; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Theory and models of film growth; 68.55 Ln; A3. Pendeoepitaxy; B2. Semiconducting materials; 81.15 Gh; A3. Metalorganic chemical vapor deposition; Crystal growth; Epitaxial layers; Nucleation; Lithography; Template reaction; Etching; Selectivity; Aspect ratio; Adhesion; Carbon; MOCVD; Gallium nitride; Microelectronic fabrication; Growth mechanism; Resists; Heteroepitaxy; Thermal annealing; III-V semiconductors
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2008.03.023

We report the initial use of lithographically defined carbon growth templates for use as an epitaxial lateral overgrowth (ELOG) mask for metalorganic chemical vapor deposition (MOCVD) heteroepitaxial GaN on sapphire. Interferometric lithography is used to define high aspect ratio structures in SU-8, which are then pyrolyzed in a reducing atmosphere up to 1200 °C. The resist structures convert to amorphous carbon, shrinking 80% in the vertical direction and 53% in the horizontal direction, but maintain their pattern geometry and adhesion to the substrate. These templates are capable of surviving GaN nucleation layer growth temperatures (∼530 °C), GaN crystal growth and high-temperature annealing up to 1050 °C. This new approach to ELOG offers several advantages, requiring fewer processing steps, and favorable selectivity tendencies as well as the capability to create growth masks which are difficult or impossible to fabricate using a top–down etching approach.