Heading into the 5G Era: Interview with Soitec

Article By : Lefeng Shao

5G roadmap will drive technology and applications for the next decade. In an interview with EE Times China, Luis Andia, senior manager RF business development at Soitec, discusses the company’s portfolio of engineered substrates for 5G applications and how Soitec plans to embrace the new business opportunities in the 5G era...

5G is designed to meet the ever-growing demand for bandwidth and download speed. Initial 5G deployment is occurring at frequencies below 6GHz worldwide. A second phase – already started in selected locations – is the deployment of new mmWave networks. Both networks will be required to meet the data consumption demand from 2025 onwards. According to the GSM Association (GSMA), 5G networks are likely to cover one-third of the world’s population and to account for as many as 1.2 billion connections by 2025. [caption id="attachment_10966" align="alignright" width="233"] Soitec‘s Luis Andia[/caption]
Soitec is convinced that the 5G roadmap will drive technology and applications for the next decade. In an interview with EE Times China, Luis Andia, senior manager RF business development at Soitec, discusses the company’s portfolio of engineered substrates for 5G applications and how Soitec plans to embrace the new business opportunities in the 5G era. EE Times China: Soitec has extended its RF enhanced Signal Integrity (RFeSI) substrate family with the introduction of RFeSI100 and claims it uses innovative materials on its constituent layers and on commercial RF-SOI substrates for the first time. What do these innovative materials specifically refer to? How has performance been improved by the addition of new materials? Luis Andia: Thanks to its core technology Smart Cut, Soitec can stack a large choice of materials and build a substrate that creates the highest value for the various RF applications. These materials include piezoelectric, compounds, silicon, silicon oxides, amongst others. RFeSI100 helps our customers to achieve the linearity and integration that is needed for very challenging smartphone applications, for example in antenna tuners. It also fits in other applications, such as instrumentation, WLAN, and high-end IoT. The introduction of a low permittivity material in our RFeSI family of products through RFeSI100 allows us to improve the linearity and reach an unprecedented level as low as -100dBm of second order harmonic content. For comparison, RFeSI90, the previous top end RFeSI substrate, offers a linearity level of -90 dBm of second order harmonic. RFeSI100 thus offers an improvement by 10dB in terms of linearity while maintaining the isolation and integration capability that is provided by a trap rich substrate. EE Times China: An optional feature RFeSI_T (“T” standing for temperature) is claimed to allow all substrates in the RFeSI family (RFeSI80, RFeSI90 and RFeSI100) to benefit from stable linearity at a temperature of 150 degrees Celsius. How does RFeSI achieve this? Luis Andia: We achieve this by using low permittivity materials in specific high resistivity wafers. By associating the right starting wafers with the right engineered layer of low permittivity silicon, we ensure that all products of our RFeSI family – RFeSI80, RFeSI90 and RFeSI100 – retain their respective linearity behavior at temperatures reaching 150 degrees Celsius. You can imagine that this helps our customers to introduce differentiated applications for fast growing new markets like automotive, cellular, and massive MIMO cellular infrastructure. RFeSI_T also brings significant added value to the smartphone market. We have all experienced that our smartphones sometimes are heating up, after prolonged use or under other circumstances, for example when they are too long exposed to metallic surfaces. The internal logic of the device then triggers a mechanism that limits the current consumption in order to help to cool down the smartphone. Limiting the current consumption obviously can hamper the RF performance, and some applications might stop working as expected – for example, the video streaming quality could be degraded. By keeping the linearity stable at temperatures of up to 150 degrees Celsius, RFeSI_T helps to minimize degradations of RF performance and of applications as video streaming even when the smartphone overheats. EE Times China: mmWave is another hot topic for the industry. When mobile terminals have to consider the coexistence of sub-6GHz and mmWave, what are the main challenges? What are the problems that RF-SOI can solve? Luis Andia: 5G uses a much larger frequency spectrum compared to 4G and operates in both, below 10GHz and in the mmWaves. That poses a considerable number of new challenges. Even without mmWave, packaging an increasing number of functionalities at such frequencies in a high-end smartphone with an unchanged form factor has become a major challenge. Smartphones have not become bigger and some models are even getting smaller. To integrate such new capabilities in a 5G smartphone, the use of RF modules is preferred over discrete RF devices. Trap rich RF-SOI performs particularly well in modules and thus helps to minimize different types of signal interference as crosstalk, digital noise, intermodulation and others that occur inevitably in the RF front end. Modules built on RF-SOI have therefore become a must, not only in high-end but also in mid- and even low-end 5G smartphones models. Moving on to mmWave, integrating such high frequencies in a smartphone was practically impossible a couple of years ago. The introduction of high-performance filtering – like those built on Piezoelectric-on-Insulator (POI) – combined with RF-SOI and the related progress in foundry technologies, circuit design, packaging and many others have made this possible. Trap rich RF-SOI enables the high level of integration required to put together a full mmWave front end. Low noise amplifiers, switches, power amplifiers, couplers, control logic and other support functions can all be integrated in a single front-end IC that can be packaged in a very compact form factor. Furthermore, for an even higher level of integration, Soitec offers a power efficient solution, Fully-Depleted SOI (FD-SOI), that helps foundries to build platforms that enable their customers to integrate not only the mmWave RF front end but also the mmWave transceiver. Both offerings, trap rich RF-SOI and FD-SOI, are complementary and provide Soitec’s customers and their customers the needed flexibility when building a 5G sub-6GHz + mmWave smartphone, a small cell, pico cell, fixed wireless access node or any other connected device. EE Times China: Different communication devices such as smartphones and cars require differentiated technologies for their RF front ends. How does Soitec adapt the cost and deal with the performance trade-offs to increase the adoption? Luis Andia: RF-SOI brings unique RF characteristics to the RF front-end modules, such as RF signal linearity and integrity, low insertion loss, high integration and the associated small footprint at low cost. There is currently no other technology that can provide a similar value. By using differentiated engineered materials associated with the right starting wafers, Soitec provides three families of RF-SOI products: High-Resistive SOI (HR-SOI) for the lowest cost and good enough performance for mass markets as IoT, legacy 3G and 4G cellular discrete RF blocks; iFEM-SOI for applications like WLAN and 5G NR IoT, which require a high integration of RF and logic/digital support functions with value optimized substrates; and finally RFeSI for the most demanding RF applications such as smartphones, automotive and some massive MIMO infrastructure front ends. Each of these products offers unique features, providing RF designers the needed flexibility when designing their particular applications. Soitec is continuously innovating to bring the advantages associated with trap rich RF-SOI to the RF front-end market with the right value, at the right cost and at the right time. To further complete our offering of engineered substrates, FD-SOI is a multifunctional platform that is capable of integrating multiple functions such as digital, analog, radio frequency, and high voltage into a single power efficient system-on-chip. Soitec’s GaN-on-silicon and GaN-on-SiC epitaxial wafers are particularly suited for the power amplifier market for sub-6GHz base stations and mobile phones. Based on POI optimized substrates, new SAW filters can provide built-in temperature compensation and can be implemented on a single chip integrating multiple filters. This is particularly advantageous for the combined use of many frequency bands without interference and to achieve high-speed data transmissions in 5G RF front ends. EE Times China: The development of 5G is promoting RF integration and modularization. Soitec has prepared a variety of solutions, including the use of RF-SOI for switching devices and antenna tuners, POI for the production of high-performance surface acoustic wave (SAW) filters, and GaN for power amplifiers. What is the secret sauce of Soitec’s success? Luis Andia: The RF integration and modularization is at the core of RF-SOI’s success. Soitec is working hard to bring the advantage of trap-rich RF-SOI to all new vertical markets and 5G enabled applications. The engineered substrates market is no longer a niche market and has attracted a lot of attention from the whole RF ecosystem, from telecom operators, ODMs/OEMs down to RF service providers. Soitec has built successful partnerships with all the different players in this ecosystem. This enables us to have an excellent understanding of the trends in RF systems architectures, structured by function and technology. It also helps us to make sure that our engineered substrates are compatible with advanced packaging and testing techniques, from MHz to mmWave frequencies. EE Times China: 5G is one of the important industries driving economic growth in China, and the demand for RF-SOI substrates is surging rapidly. What information can Soitec share in terms of capacity planning, especially in the Chinese market, over the next few years? Luis AndiaChina has largely demonstrated its capacity to innovate in 5G, and Soitec is always attentive to its needs in terms of technology and production capacity. Driven by the success of 5G, and not only for the cellular RF front end but also for emergent applications like connected cars, edge computing, massive MIMO, and many others, Soitec is currently engaged in capacity expansions at its own sites in France and Singapore and at its Simgui partner site in Shanghai. In the near term, Soitec’s SOI capacity in 300mm will reach 2M substrates per year while that of 200mm will reach 1.5M substrates per year. Further capacity expansions are under consideration and will be planned and implemented to match market demand. Besides this SOI capacity expansion, Soitec will be able to produce close to half a million POI substrates per year very rapidly. Our GaN and SiC capacity will also ramp up very rapidly in order to reliably match our customers’ timelines. Soitec is well-positioned and prepared to scale up its production capabilities and respond to our customers’ needs in a timely, efficient, cost-conscious and tailored manner.

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