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RF Match and Power Technology

Diagram of a Vacuum Variable Capacitor (VVC)
Example of Vacuum Variable Capacitor (VVC)

Electronic Variable Capacitor (EVCTM) Technology Revolutionizes Matching Network Capability

 

Current RF matching networks have been built on 1940s vacuum variable capacitor (VVC) technology, which was originally patented by Nikola Tesla in 1896. While slight enhancements have been made to the technology in that 120 years, its many moving parts have an analog limitation today of matching in 1-3+ seconds. The variation within that 1-3+ seconds also creates issues for process engineers, especially at leading-edge plasma processing.

Reno’s solid state Electronically Variable Capacitor (EVC) matching network is a digital array that switches capacitance in 10 µsec and offers auto-tune matching in less than 500 µsec. This run-to-run repeatable and accurate Instantaneous Match™ technology enables the precise, high aspect ratio, selectively anisotropic sharp-edge plasma processing required of today’s and tomorrow’s devices, including 3D structures.

Reno Solid State EVC™ Capacitor
Reno Solid State EVC™ Capacitor
Vacuum Variable Capacitor (VVC) and Reno Solid State EVC™ Capacitor

The significance of Reno’s revolutionary EVC technology to plasma processing can be compared with the impact of analog cassette tapes for playing music versus the digital revolution of smartphones. If you wanted to listen to song one and then song five on a cassette, you had to wait as the unwanted songs in between played. Similarly, if you light your plasma at one impedance using a VVC and then need to process at a different impedance, you wait for the motor to turn and tune to the matched position.  What is happening during that 1-3 seconds varies run-to-run. This variation in the VVC can be seen in the plasma instability and process variability.

The forward (Pf) and reflected (Pr) power plots are from a side-by-side comparison of a VVC-based matching network and an EVCTM-based matching network, running the same process recipe at the same conditions. Note significantly reduced tune time, enhanced plasma stability and elimination of plasma resonances.

 

Reno’s EVC digital array changes capacitance in 10 microseconds, enabling full auto-tuning to a matched position with low reflected power in less than 500 microseconds. Reno’s patented technology skips over millisecond improvement of the old technology to enable <14nm stable, accurate and repeatable plasma processing.

Existing VVC versus Reno VVC graphs

Delivered RF Power in Combined RF Matching Network/Generator

The efficiency and magnitude of forward power and reflected power have fueled the process challenges behind today’s RF generators and VVC matching networks in plasma processes. The time required to correct micro-arcing or plasma instability detection has created significant challenges at 14nm. Sending commands through multiple control systems over distances for generators to pull back power or asking matching networks to dither their stepper motors in search of low reflected power is just not fast enough in these analog-motor-driven systems.

 

Combining Reno’s two solid-state power generator and EVC matching network technologies into one mechanical package with one control system and microsecond step changes allows forward power and reflected power to evolve into efficient delivered power.