Plasma Chamber Wafer Biasing for Configurable Ion Energy Control
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Solution Overview
Problem
Existing high voltage pulse generators face challenges in achieving fast rise times and smooth output signals at high frequencies, often resulting in slow switching and inefficient energy transfer due to high stray inductance and capacitance, which can cause ringing and voltage overshoots.
Innovation Solution
A pulse generator system with a driver stage having low stray inductance, a transformer stage for voltage amplification, and a rectifier stage with galvanic isolation, capable of producing high voltage pulses with fast rise times and arbitrary waveforms, utilizing solid state switches like IGBTs and MOSFETs to manage energy transfer efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage pulse generators use conventional circuit designs with high stray inductance, then voltage amplification is achieved, but ringing and voltage overshoots occur due to inefficient energy transfer
Solution Approach 1:
The patent extracts and removes the harmful stray inductance from the circuit by using a transmission line structure where the characteristic impedance is matched to the load, eliminating the parasitic inductance that causes ringing and overshoot while maintaining voltage amplification capability
Solution Approach 2:
The patent changes the circuit parameters by using a transmission line with specific characteristic impedance (50-100 ohms) and controlled physical dimensions, transforming the circuit from a conventional high-inductance design to a low-inductance distributed parameter structure that prevents ringing
2Speed
If pulse generators use fast switching solid state switches, then rise time is reduced, but stray inductance causes ringing and voltage overshoots
Solution Approach 1:
The patent introduces a transmission line as an intermediary element between the solid state switch and the load, which acts as an impedance matcher and isolates the fast switching action from the load, allowing fast rise times without inducing ringing or overshoot
Solution Approach 2:
The patent uses periodic pulse generation with duty cycles between 0.1% and 99.9%, allowing the circuit to settle between pulses and preventing cumulative ringing effects while maintaining fast rise times through optimized switching frequencies
3Power
If conventional RF plasma reactors use standard electrode configurations, then plasma generation is achieved, but ion energy distribution lacks precision for controlled anisotropy
Solution Approach 1:
The patent applies dynamic voltage control to the substrate electrode, using pulsed bias voltages with variable amplitude and duration to dynamically adjust the ion energy distribution function, enabling precise control over ion bombardment energy and resulting film anisotropy
Solution Approach 2:
The system uses feedback control through the pulse generator to monitor and adjust the voltage applied to the substrate electrode, ensuring precise control of ion energy distribution based on desired etching anisotropy and film quality parameters
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves clean, high voltage output with minimal ringing and overshoot, enabling efficient energy delivery and precise control over pulse width and frequency, suitable for applications like RF plasma reactors.
Implementation Method 1
The transformer stage may be coupled with the driver stage such as, for example, through a balance stage and may include one or more transformers
Implementation Method 2
The rectifier stage may be coupled with the transformer stage and may have a stray inductance less than 1,000 nH
Implementation Method 3
The driver stage may include at least one of one or more solid state switches such as, for example, an insulated gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET)
Data Source
AI summary
Some embodiments include methods and systems for wafer biasing in a plasma chamber. A method, for example, may include: generating a first high voltage by a first pulsed voltage source using DC voltages and coupling the first high voltage to a wafer in the plasma chamber via at least one direct connection, the at least one direct connection enabling ion energy control in the plasma chamber; generating one or more of low and medium voltages by a second pulsed voltage source; coupling, capacitively, the one or more of low and medium voltages to the wafer; and pulsing the first high voltage and the one or more of low and medium voltages to achieve a configurable ion energy distribution in the wafer.