Advanced High-Flow-Velocity Horizontal MOCVD Technology for Nitride Semiconductor Growth
Keitaro Ikejiri1 , Yudai Shimizu1, Mizuki Yamanaka1, Kenichi Eriguchi1, Kazutada Ikenaga1, Hiroki Tokunaga1
1 TAIYO NIPPON SANSO Corporation, 10 Okubo, Tsukuba, Ibaraki 300-2611 Japan
Abstract:
The expansion of nitride semiconductor applications, such as LEDs, lasers, and high-power electronics, requires MOCVD systems that can precisely control crystal growth while maintaining high throughput. In this context, the MOCVD process has conflicting requirements. For high-quality GaN or high-indium-content InGaN deposition, relatively high pressures are necessary. However, increasing pressure leads to enhanced parasitic growth, resulting in deteriorated crystal quality and uniformity. Conversely, lower pressures improve the thickness and composition uniformity of AlGaN and control the carbon concentration in GaN. The optimal MOCVD system for flexible control of nitride semiconductors must handle pressures from low to atmospheric while maintaining high-flow velocities through narrow channels. The challenge is to meet these requirements effectively in both R&D and mass production. Taiyo Nippon Sanso’s MOCVD system achieves this with a high-flow-velocity system using triple gas injectors in a horizontal reactor with a flow channel height under 10 mm, and a gas control system operating from low to atmospheric pressure. In addition, zone-divided resistive heating technology allows the system to accurately regulate temperatures even for large diameter wafers as well as wafers that deform into concave or convex shapes during high-temperature processes.
The system’s effectiveness was demonstrated with AlGaN growth. Using the SR4000 MOCVD system for a single 4-inch substrate, we controlled the Al composition in AlGaN by adjusting the TMA to total MO supply ratio (TMG + TMA) linearly. This method maintained a favorable Al composition distribution (in-plane max-min ≤ 1.5%) and thickness distribution (in-plane max-min/average < 5.0%) for 40% to 80% Al composition. The same approach applies to the UR26K MOCVD system, a large-scale production system for 6 x 8-inch substrates. Optimizing growth conditions achieved an Al composition distribution (in-plane and inter-plane max-min ≤ 0.2%) and thickness distribution (in-plane and inter-plane max-min ≤ 1.0 nm, average: 18.1 nm) in the AlGaN barrier layer of AlGaN/GaN HEMT on Si. We will also discuss the flow channel effectiveness using numerical simulations and InGaN crystal growth characteristics.
