As the physical vapor deposition (PVD)processes used in semiconductor manufacturing become more complex, so too do requirements for accurate control of the power required to ignite, energize, and manipulate the plasma. Such control is essentialfor delivering high-quality thin-film morphologies. At the same time, managing arc events, including quick recovery from arc conditions,is a critical aspect ofsatisfying today’s yield and system uptime requirements. Because today’s thin-film PVD processes commonly deploy single- or dual-magnetron reactive sputtering techniques that require pulsed-DC power, the delivery, management, and monitoringof that power are all key considerations for semiconductor manufacturers.
PVD for Semiconductor Fabrication
They may have been at the heart of the back-end semiconductor fabrication process for many years but, thanks to proven reliability and relatively low cost, the PVD techniques used to create thin, high-purity metal oxide and metal nitride
filmsthrough sputtering still have a strong future. Research firm Mordor Intelligence, for example, estimates that the PVD equipment market was worth $19.35 billion in 2020 and predicts this growing at a rate of 8.9percenta year to reach $23.93 billion by 2026.
However, as transistor density increases and semiconductor processesscale down to deliver new architectures atever-smaller technologynodes, ensuring reliable PVD presents a growing number of challenges to semiconductor manufacturers. Among these are the need to better control the film morphology and ensureprecise deposition of thinner and thinner films inside high-aspect-ratio features. What’s more, a focus on maximum yield and productivity means such deposition must not only be accurate, but also must be done at very high speed in systems with maximum uptime. Fine control of the plasma used in the sputtering system combined with optimized arc management – including quick recovery from arc conditions while maintaining process and plasma –is needed to ensure the highest-quality coatings, maximize throughput, minimize the potential for damage to the target surface and extend the time between scheduled-maintenance shutdowns.
With today’s PVD processes commonly deploying single- or dual-magnetron reactive sputtering techniques that require pulsed-DC power, how the power is delivered, managed, and monitored is fundamental to meeting the needs outlined above. Choice of plasma power generator, therefore, is a critically important consideration for any PVD semiconductor fabrication process.
The intimate connection between the power supply and the plasma, and the influence the supply can have on plasma deposition has long been recognized. Pulsed DC has been used in reactive sputtering applications because the pulsed-DC waveform allows for inherent chargebuild-ups to clear during the off times. A controllable reverse voltage has improved on this for reactive sputtering with pulsed-DC power in which the periodic reversal of voltage clears charge build-up more effectively during a pulsing. This has grown in popularity thanks in part to its ability to reduce or prevent arcing created by charge build-ups.
In principle, pulsed DC is based on a shift in voltage or current from one power level to another ora shift in voltage from one polarity to the opposite, the latter being known as bipolar pulsed DC. Pulses can, in theory, be square or half sinusoidal. In practice, however, waveforms are impacted by factors such as nonlinearities of the plasma and, therefore, the shapes of the resulting power waveforms can bevery complex. Controlling these waveforms by managing the power supply output is one of the keys to fine tuning the sputtering process. Withthe most recentbipolarpulsed-DC power supply technologies, the level of waveform control available to manufacturers has increased considerably, allowing for control of both the dV/dt and dI/dt of the waveform.