Pulsed Voltage Waveform Generator for Plasma Sheath Collapse
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Solution Overview
Problem
The semiconductor industry faces challenges in producing high aspect ratio features due to difficulties in controlling ion energy in plasma-assisted etching processes, particularly in generating high voltage pulses with fast rise and fall times, which are essential for precise plasma processing in advanced semiconductor manufacturing.
Innovation Solution
A plasma processing system that employs a waveform generator with multiple switches to selectively incorporate voltage and current sources in the output current path, allowing for the generation of specific voltage waveforms with a sheath collapse stage and ion current stage, including current compensation, to control the plasma sheath and ion flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If standard electrical components are used to generate high voltage pulses with fast rise times and fall times, then the required steep slopes (>10 V/ns) can be achieved, but the device complexity and difficulty of compact integration increase significantly
Solution Approach 1:
The waveform generator is divided into multiple voltage stages (first voltage stage, second voltage stage, third voltage stage) with distinct functions. Each stage uses specific switch configurations to generate voltage pulses with different characteristics, allowing the system to achieve fast rise/fall times while managing complexity through functional segmentation
Solution Approach 2:
The patent employs dynamic switch control where switches are selectively opened and closed during different time periods to reconfigure the circuit topology. This dynamic reconfiguration allows the same hardware components to serve multiple functions and achieve variable pulse widths, voltages, and repetition rates without requiring separate dedicated circuits for each parameter
2Manufacturing precision
If high voltage DC pulses with steep slopes are generated to achieve fast rise and fall times, then plasma sheath control precision is improved, but the difficulty of producing such pulses with variable parameters increases
Solution Approach 1:
The patent implements variable pulse parameters by controlling the timing and state of switches during different time periods. The pulse width, voltage amplitude, and repetition rate can be independently adjusted by modifying switch control signals, allowing precise plasma sheath control while maintaining ease of parameter adjustment without requiring complex external circuitry
Solution Approach 2:
The waveform generator produces periodic voltage pulses with controllable repetition rates by cycling switches through specific on/off sequences. This periodic operation enables precise control of plasma sheath formation and collapse while simplifying the generation of variable parameter pulses through rhythmic switch actuation patterns
3Manufacturing precision
If sinusoidal RF waveforms are used for substrate biasing, then the plasma is formed and ions are accelerated, but the ability to control ion energy for smaller device feature sizes is insufficient
Solution Approach 1:
The patent inverts the traditional approach by using pulsed DC voltage instead of continuous sinusoidal RF waveforms for substrate biasing. This inversion allows for precise control of ion energy through the steep rise and fall times of the pulses, enabling better control over plasma sheath formation and ion acceleration for smaller device feature sizes
Solution Approach 2:
The waveform generator applies a sheath collapse stage before the ion current stage by generating a positive voltage pulse that collapses the plasma sheath. This preliminary action prepares the plasma for subsequent ion acceleration by removing the sheath barrier, enabling precise control of ion energy delivery to the substrate
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 the generation of desirable plasma-assisted processes by achieving precise control over the plasma sheath and ion energy distribution, improving the fabrication of high aspect ratio features in semiconductor devices.
Implementation Method 1
A plasma processing system that employs a waveform generator with multiple switches to selectively incorporate voltage and current sources in the output current path
Implementation Method 2
a plasma is formed over the substrate, and ions are accelerated from the plasma towards the substrate across a plasma sheath, i.e., region depleted of electrons, formed between the plasma and the surface of the substrate
Implementation Method 3
ions are accelerated from the plasma towards the substrate across a plasma sheath
Data Source
AI summary
Embodiments provided herein generally include apparatus, e.g., plasma processing systems, and methods for the plasma processing of a substrate in a processing chamber. Some embodiments are directed to a waveform generator. The waveform generator generally includes a first voltage stage having: a first voltage source; a first switch; and a second switch, where a first terminal of the first voltage source is coupled to a first terminal of the first switch, and where a second terminal of the first voltage source is coupled to a first terminal of the second switch. The waveform generator also includes a current stage coupled to a common node between second terminals of the first switch and the second switch, the current stage having a current source and a third switch coupled to the current source.