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A DC POWER SUPPLY FOR HIGH POWER RF PULSING APPLICATIONS

IP.com Disclosure Number: IPCOM000241899D
Publication Date: 2015-Jun-05

Publishing Venue

The IP.com Prior Art Database

Abstract

Modern semiconductor processing applications frequently require a pulsed RF waveform to be applied to a plasma processing chamber for etching or deposition. A typical implementation of a pulsed RF generator consistors of a DC power supply feeding an RF amplifier. When the amplifier turns on, a large current is suddenly demanded from the power supply, causing pulse droop. When the amplifier turns off, the cessation of current draw can cause a large voltage overshoot on the power supply output. To prevent pulse droop or overshoot, a very large capacitor bank is usually connected between the power supply and RF amplifier. A negative side effect of the capacitor bank is heavy damage to the amplifier if a short circuit occurs – the energy of the capacitors is instantaneously discharged into the faulty circuit. Lower energy storage also allows faster response of the DC supply for applications such as envelope tracking. The proposed invention uses an auxilliary converter to steer the charge from an offline storage element (see capacitor Ca in the figure below). This allows the main DC-DC converter energy storage to be relatively small, yet allows the system to deal with the sudden changes in supply current caused by pulsing.

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A DC Power Supply for High Power RF Pulsing Applications

Overview

Modern semiconductor processing applications frequently require a pulsed RF waveform to be applied to a plasma processing chamber for etching or deposition. A typical implementation of a pulsed RF generator consistors of a DC power supply feeding an RF amplifier. When the amplifier turns on, a large current is suddenly demanded from the power supply, causing pulse droop. When the amplifier turns off, the cessation of current draw can cause a large voltage overshoot on the power supply output. To prevent pulse droop or overshoot, a very large capacitor bank is usually connected between the power supply and RF amplifier. A negative side effect of the capacitor bank is heavy damage to the amplifier if a short circuit occurs - the energy of the capacitors is instantaneously discharged into the faulty circuit. Lower energy storage also allows faster response of the DC supply for applications such as envelope tracking.

The proposed invention uses an auxilliary converter to steer the charge from an offline storage element (see capacitor Ca in the figure below). This allows the main DC-DC converter energy storage to be relatively small, yet allows the system to deal with the sudden changes in supply current caused by pulsing.

L

   Isolated DC-DC Converter

C

1

Pulsing RF Load

Ca

Figure 1: Pulsed RF Power System of the present invention

 Bidirectional DC-DC converter



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Benefits

• Enable highly repeatable RF pulse envelopes for critical thin film plasma processes that require precise plasma EEDF (Electron Energy Distribution Function) control

• Stabilize DC supply reactions to fast load changes induced by pulsing of the RF amplifier

• Provide a fixed DC supply voltage for low voltage, high current pulsed RF amplifiers such as VHF and UHF VDMOS, LDMOS

• Reduce DC supply rail voltage undershoot and overshoot during pulsing ON and OFF (or high amplitude/low amplitude)


• Reduce DC supply rail voltage recovery time
• Reduce DC supply volume, weight and cost

Embodiments

• Isolated DC-DC converter can be single flyback, forward, push-pull, full bridge, half-bridge and/or variations; two or more isolated dc-dc converters in parallel at input side, in parallel or series at output side. Secondary rectifier can be full bridge, center tapped, current doubler and/or their variations.

• Bidirectional DC-DC converter can be single Buck/Boost and/or its variations; two or more Buck/Boost converter in parallel or series at input side, in parallel at output side.


• Power switches can be MOSFET, IGBT, transistor and/or and other kind.

• Anti-parallel diode of power switches can be body diodes and/or external parallel diodes.
• Energy storage capacitor can be any type of capacitor, ultra-capacitor and/or battery

2


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Prior art 1:

US 6577515 B2 Patent Date: Jun. 10 2003. US 2003/0031036 A1 Pub. Date: Feb.13,2003 Advanced Micro Devices, Inc. Sunnyvale, CA.

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