The Evolution Of Plasma Process Power

The year 1981 was notable for a variety of technology breakthroughs. It saw the inaugural mission of the Space Shuttle Columbia and the debut of the DeLorean car. The IBM PC, Commodore 64, and the ZX81 were among the personal computers to hit store shelves. It also marked the year, four decades ago, that Advanced Energy was founded and took its first steps towards a mission to enable customer innovation by delivering highly-engineered, application-critical, precision power solutions.

At that time, the Internet of Things (IoT), Industry 4.0, cloud computing, renewable energy, and other technologies that we increasingly take for granted were still in their infancy. Few could have predicted just how dramatic an impact the global electronics industry would have in the following 40 years, as it now touches almost every aspect of our daily lives. Fast forward to 2021, and it’s hard to imagine experiencing a global pandemic without access to the tools, platforms, systems, and infrastructure that modern electronics has made possible.

As electronics became ubiquitous, so too did the drive for continual improvement and productivity in a wide variety of industrial, medical, and consumer applications. And there remains intense pressure to increase the performance, enhance the functionality, reduce form factors, and raise efficiencies of electronics devices and manufacturing at both the component and system levels. Semiconductor manufacturers have responded to these requirements by designing ever more complicated devices, which, in turn, drive more complex processes for IC manufacturing and more sophisticated approaches to process management.

Drumbeat of process power innovation

Plasma process power for etching and deposition in semiconductor manufacturing has proceeded at the drumbeat of innovation that is Moore’s Law. RF power delivery systems have advanced in leaps and evolutions from the early days of transformer and tube-based RF power supplies with fixed matching networks. The Switch Mode Power Supply (SMPS) with auto-tuning matching networks was an early leap and enabled reliable, stable, and efficient power delivery for plasma processes in smaller form factors.

As a result, chamber modules could be more tightly packed, resulting in higher wafer output and lower overall cost per wafer. This was followed by the leap to hybrid digital/analog control to deliver high-precision continuous wave (CW) RF power. In recent years, the state of the art has evolved further to all-digital controls with frequency tuning, complex pulsing profiles and high-speed pulsing.

Another significant leap in this plasma process power evolution: RF power generator and match networks were integrated to provide fast tuning and direct power regulation. The compact form factor enables complex tool designs with minimized footprint in cost-sensitive semiconductor fab cleanrooms. In addition, mechanically-driven vacuum capacitors could be replaced with solid state switching in the matching network to provide speed, reliability and repeatability.

As process innovation drove more sophisticated etch patterning steps, the need to combine multiple frequencies arose. Multi-frequency RF power systems are now used to separate or decouple plasma density production from ion energy control – an important factor in high-aspect-ratio (HAR) etch applications. Today’s integrated RF power delivery systems increasingly provide additional process control knobs enabled by pulsing and measurement synchronization, tune-while-pulse, high-speed sub-microsecond fast tuning, and model-based matching algorithms to enable the speed and control of complex pulsing regimes.

Today, productivity and energy consumption are shifting the need to maximize throughput while keeping process power consumption as low as possible. Semiconductor OEMs and foundries are searching for ways to deliver power more efficiently. The goal has moved from simply increasing energy to delivering precise energy exactly where it is needed. This has led to a re-think in how power is managed in plasma-based applications and, with that re-think, the emergence of the asymmetric bias waveform generator.

Unlike conventional sinusoidal RF power sources, asymmetric bias waveform generators (eV source) produce near mono-energetic ion energy distributions (IEDs) by delivering power only where the plasma needs it. By providing more precise process control, eV source delivers optimized bias plasma performance needed for sensitive feature formation in HAR dielectric structures at high etch rates. Such technologies can help manufacturers to break a trend that has been pushing power requirements up to 100 kW per plasma chamber and as much as 1 MW per etcher by supporting advanced fabrication processes with as little as half or even a third of those power demands. In addition, because precise control produces less unused power, it reduces the potential for wafer damage due to heat.

The future of chip manufacturing

As the impact of the recent semiconductor shortage has all too clearly illustrated, the world is dependent on semiconductors. Whether it’s providing the cloud processing power demanded by our insatiable need for data, supporting new and emerging AI applications, optimizing manufacturing productivity, or getting more energy from renewables, there is no application untouched by advanced IC processing. The next 40 years will no doubt usher in more as yet unforeseen advances, led by the new generation of eV sources.

While it’s hard to envision what’s next in scaling below 1nm technology and with the accelerating shift to heterogenous integration (chiplets), it’s clear that the heart of critical etch and deposition process will continue to be plasma driven – and that process power will advance through leaps and evolutions to keep the drumbeat of innovation going.