GaN, từ sáng tạo đến sản xuất hàng loạt

Today, GaN is set to be an indispensable technology for power and RF applications in the coming years. Established Si and SiC companies are eager to enter this emerging market, but moving from innovation to mass production raises significant challenges. Last June, Ezgi Dogmus from Yole Group, along with David Haynes and Michelle Bourke from Lam Research, presented a webcast addressing these concerns. They were joined by Yann Lamy from CEA-Leti and Taha Ayari from Yole Group to further discuss the topic. Here are their key insights.

With its remarkable intrinsic characteristics, including high carrier density, high electron mobility and wide bandgap energies, GaN is a material that enables high-frequency, high-power applications. As a result, the GaN power and RF markets are surging ahead, exceeding $4 billion in 2029, with impressive CAGR23-29 projections of 41% and 10%, respectively. Those figures are extracted from two new Yole Group’s analyses: RF GaN 2024 report and Power GaN 2024 report.

Since 2019, Power GaN devices have been firmly embraced by the consumer sector. It is expected to remain the main driver of growth in this market, with significant contributions from data center and automotive applications. Infineon Technologies, STMicroelectronics, ROHM and Nexperia will not remain the only high-volume GaN transistor manufacturers for long. The power GaN ecosystem is evolving rapidly with coming entrants such as Mitsubishi Electric and Vishay, and notable acquisitions like Infineon-GaN Systems, STMicroelectronics-Exagan and Renesas-Transphorm.

RF GaN is a more established market than power GaN. After starting with military radar applications in the 1990s, RF GaN devices expanded their presence in 4G-5G telecom infrastructures in the 2010s, dethroning Si LDMOS. GaN-on-Si and GaN-on-SiC will play key roles in the 6G era, potentially alongside RF-SOI, SiGe and InP-based devices. Other mass market opportunities include satellite communications and handset power amplifiers. GaN-on-Si is a potential candidate to replace GaAS in the Sub-7 GHz or in the FR3 handset frequency ranges. However, challenges such as cost, low voltage capability, and linearity issues need to be solved.

Performance degradation of GaN transistors during manufacturing processes is a major concern. For commercial applications, a negative bias is necessary to turn the device from the on-state (D mode) to the off-state (E mode). Various structural approaches, such as recessed gate MISHEMT and p-GaN under gate HEMT, have been considered. However, the 2D electron gas (2DEG) layer is highly sensitive to damage during manufacturing. GaN active layers are subject to substrate state modification, lattice disorder introduction, and species trapping, all of which can reduce 2DEG density and impact overall transistor performance. To mitigate this, careful attention must be paid to the etching, passivation, and cleaning steps.

Each structure of power or RF HEMTs presents its own set of challenges, and steady-state etch processes inherently result in plasma-induced damage. Experiments combining steady-state etch, atomic layer etch (ALE), and/or pulsed plasma processing have demonstrated major benefits, including reduced damage (Rsheet post-etch reduced by half) and ultra-low surface roughness (post-etch roughness < 1 nm).

Lam Research and CEA Leti have also worked on developing low-damage, conformal films that can be used as a passivation layer in GaN device manufacturing, with the constraint of low hydrogen content. The partners have successfully demonstrated reduced damage during the passivation stage through the implementation of pulsed plasma treatments.

The cleaning stage also presents its own challenges in surface preparation of GaN/AlGaN, contamination control and bevel management, all of which were also raised during the discussion.

Source: www.yolegroup.com