Pulsed-Voltage Plasma Biasing for Stable IEDF and Etch Profiles
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Solution Overview
Problem
Conventional plasma processing methods face challenges in maintaining a constant sheath voltage and achieving precise control over the ion energy distribution function (IEDF) at the substrate surface, leading to undesirable etch profiles and arcing issues due to cross-talk between RF sources during high aspect ratio etching in semiconductor manufacturing.
Innovation Solution
A plasma processing chamber design incorporating a pulsed-voltage waveform generator and filter assemblies to deliver a pulsed-voltage signal and an RF signal to the biasing electrode, with dielectric layers separating the electrodes, which helps maintain a nearly constant sheath voltage and control the IEDF, preventing power diversion and damage to RF sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional RF bias is used to achieve higher self-bias voltages, then ion acceleration towards substrate is improved, but ion energy distribution becomes uncontrolled leading to bowing of etched feature walls
Solution Approach 1:
The patent applies periodic pulsed voltage to the substrate electrode instead of continuous RF bias. By controlling the pulse width, frequency, and duty cycle, the system achieves precise control over the time-averaged self-bias voltage while maintaining a more uniform ion energy distribution. This periodic action allows separation of ion acceleration (during pulse) from ion arrival (after pulse), eliminating the dual-peak IEDF and associated bowing problems.
Solution Approach 2:
The system dynamically adjusts voltage parameters in real-time by switching between different pulse configurations. The controller can modify pulse width, amplitude, and frequency on-the-fly to optimize etch profiles for different feature sizes and aspect ratios, providing dynamic control over the etching process that static RF bias cannot achieve.
2Adaptability or versatility
If multiple RF sources are used to control plasma properties, then plasma density and ion energy control is improved, but cross-talk between sources causes power diversion and potential damage to RF sources
Solution Approach 1:
The patent segments the power delivery system into distinct functional components: a pulsed voltage source for substrate bias control and a separate RF source for plasma generation. This segmentation eliminates the harmful interactions and cross-talk that occur when multiple RF sources are combined, while retaining the ability to independently control plasma density and ion energy through the two separate channels.
Solution Approach 2:
The pulsed voltage source acts as an intermediary between the control system and the substrate, providing precise voltage control without the instability and cross-talk problems of RF sources. The RF source similarly acts as an intermediary for plasma generation, with its output filtered to remove harmful frequency components before reaching the substrate.
3Power
If RF frequency is reduced to achieve higher self-bias voltages, then etch anisotropy is improved, but difference in energy between IEDF peaks increases causing wall bowing
Solution Approach 1:
The patent fundamentally changes the voltage waveform parameter from sinusoidal RF to pulsed DC. This parameter change transforms the ion energy distribution from a dual-peak structure to a more uniform single-peak distribution, while still achieving high self-bias voltages. The pulse width and frequency can be adjusted to fine-tune the time-averaged voltage and ion flux, providing precise control over both etch anisotropy and profile uniformity.
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
This approach enables precise control over the IEDF and etch profile, reducing arcing and improving the reliability of high aspect ratio feature formation in semiconductor manufacturing by maintaining a stable sheath voltage and minimizing power losses.
Implementation Method 1
A first filter assembly is electrically coupled between the pulsed-voltage waveform generator and the biasing electrode, and a second filter assembly is electrically coupled between the radio frequency generator and the support base or the biasing electrode
Implementation Method 2
a first dielectric layer is disposed between the support base and the biasing electrode, and a second dielectric layer is disposed between the biasing electrode and the substrate supporting surface
Implementation Method 3
The power electrode can be capacitively coupled to the plasma of a processing system through a thick layer of dielectric material
Implementation Method 4
The non-linear, diode-like nature of the plasma sheath results in rectification of the applied RF field, such that a direct-current (DC) voltage drop, or 'self-bias', appears between the substrate and the plasma
Implementation Method 5
The plasma is created by using a radio frequency (RF) generator that is coupled to an RF electrode through an RF matching network
Data Source
AI summary
Embodiments of the disclosure provided herein include an apparatus and method for the plasma processing of a substrate in a processing chamber. More specifically, embodiments of this disclosure describe a biasing scheme that is configured to provide a radio frequency (RF) generated RF waveform from an RF generator to one or more electrodes within a processing chamber and a pulsed-voltage (PV) waveform delivered from one or more pulsed-voltage (PV) generators to the one or more electrodes within the processing chamber. The plasma process(es) disclosed herein can be used to control the shape of an ion energy distribution function (IEDF) and the interaction of the plasma with a surface of a substrate during plasma processing.