By Jamie Liao, SEMI Taiwan

Market demand is driving development of 5G network standards, and commercial applications are expected to be introduced by 2020. As applications for next-generation communications are evolving, mobile devices need to promise better performance and higher resistance to heat, high power, voltage and radiation. For existing technologies, compound semiconductors like SiC and GaN are no doubt the best solutions because they perform better in terms of energy band gaps, saturation velocities, heat conductivity and breakdown field strength. In order to facilitate development of the industry, SEMI Taiwan worked with the National Chung-Shan Institute of Science and Technology (NCSIST) and the Taiwan Institute of Economic Research (TIER) to organize the Compound Semiconductor Seminar ─ Enabling Next Generation of Communications. ASE Group, Airoha Technology Corp., eLaser and WIN Semiconductors Corp. joined with SEMI Taiwan to explore the materials and technology trends of compound semiconductors.

Compound Semiconductor Technologies Continue to Advance

Speaking on upcoming 5G network with the theme “Highly Efficient 5G PA Design,” Dr. Jerry Lin, CTO of Airoha Technology Corp., said that while 5G networks perform better than existing standards in data speed and capacity, power consumption may not increase simultaneously. In order to achieve that, interior design of communications devices also need to evolve. As power amplifier (PA) is normally the most power-consuming component in traditional cellular networks, developers should start with PA if they want to address the challenge.

Dr. Lin added that in addition to optimizing circuit design, developers should also consider connectivity, modem chips, PA structure and PA devices. So which process will prevail in the area of 5G PA? Is it CMOS? Or GaAs/GaN? Dr. Lin presented a table and pointed out that GaAs/GaN has more advantage in “breakdown voltage,” “power handling,” “through wafer via” and “substrate loss,” while CMOS is doing better in self-testing, complex bias circuit design, signal processing, integration, configuration flexibility and low power voltage. Therefore, Dr. Lin believed that GaAa/GaN will continue to exist as performance is the main concern for the design of base stations used in 5G, 6G or even millimeter-wave networks. Meanwhile, CMOS will have a bigger chance with price-sensitive IoT equipments because it is energy efficient and cheap. As for hand-held devices, sub-6GHz equipments may still adopt hybrid structures like GaAs/GaN or CMOS+GaAs. CMOS is likely to dominate in the millimeter-wave market.

Dr. Kun Chuan Lin, General Manager of eLaser’s branch in the Hsinchu Science and Industrial Park, shared insight on the development of GaN epitaxial wafer process with a speech entitled “GaN on Si Epitaxy Technology Innovation.” He said that when electronics product design requires better heat resistance, breakdown voltage, electron saturation velocity and current density, semiconductor devices made with the GaN process can deliver high-power output in high-frequency environment. Therefore, the technology will have great potential in next-generation applications like automotive electronics, power management systems, industrial lighting, portable electronics devices, communications equipment, and consumer electronics products.

Dr. Lin said when GaN epi-wafer was adopted in LED devices, one 150mm wafer would contain tens of thousands, or even hundreds of thousands LED units so the yield loss caused by thousands of particles would be minor. But in the case of large-sized GaN power devices made of epi-wafers, each 150mm wafer has only 1,000 to thousands of chips and the number of particles pretty much decides the yield of power devices on epi-wafers. In comparison, the epitaxy technology of GaN-on-Si is more important because of its low particle counts, and innovative technologies will be needed in this area of epi-wafer manufacturing.

Next-generation Communications Frameworks Emerge: From Modules to Packaging and Testing

Dr. W.K. Wang, Technical Director of WIN Semiconductors Corp., discussed GaAs solutions for millimeter-wave front-end modules with a speech entitled “Advanced GaAs Solution for mmw FEM.” According to Dr. Wang, the GaAs pHEMT process has been long adopted in the area of wireless communications, such as peer-to-peer RF transmission and very small aperture terminal (VSAT.) Now, Win Semiconductors’ pHEMT and PIN diode technology platforms are already capable of providing solutions to performance and circuit requirements. He said GaAs technologies have been rapidly evolving in recent years so wafer package and multi-function devices can now be integrated into GaAs wafer fabrication. In addition, the technology to integrate pHEMT and PIN diode into PINHEMT will also enjoy great potential in the area of millimeter-wave front-end modules.

Dr. Wang also pointed out that 0.1um pHEMT can now be used to run E-band and D-band amplifiers, while Ka-Band Doherty amplifiers and low-noise amplifiers have been made possible through 0.15um pHEMT. As KA-band switches can be demonstrated in a GaAs PIN diode process, it proves that GaAs pHEMT/PIN is a suitable verification solution in millimeter-wave communications.

In a speech entitled “Next Wave RF & Photonics Packaging Solution,” Dr. Vincent Lin, Technical Director of ASE Group shared his insight on the challenge that Moore’s Law has slowed down. He said while volumes of data from existing mobile devices and cloud computing services are increasing, all chip technologies in the semiconductor industry have advanced in a slower manner. Therefore, cross-system integration will be the solution to bandwidth issues.

Dr. Lin said that mobile devices’ RF modules and silicon photonics in data centers are the key devices in cloud computing platforms now. Both of them need various materials, including compound semiconductors, silicon, passive devices, special crystals or multi-material high-speed connecting chips — with impedance matching and low insertion loss being the two key indicators to performance. Dr. Lin also demonstrated a new packaging platform of RF modules and silicon photonics modules that can serve as the best solution for the local industry.

In addition to these keynote speeches on latest trends and technologies in the market, the seminar also offered an opportunity for participants to interact and expand connections. Terry Tsao, president of SEMI Taiwan, said to promote development of Taiwan’s compound semiconductor industry, SEMI will continue to organize events where people in the industry can exchange opinions. SEMICON Taiwan 2017 will establish a Compound Semiconductor Pavilion for the first time, where international forums and get together to be held for industry insiders to share insight on future trends and technologies to help promote exchanges, collaboration and opportunities in the market.