Sequential RF Pulse Control for Plasma Sheath Stabilization
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Solution Overview
Problem
Current semiconductor fabrication processes face challenges in controlling plasma density and ion energy during plasma-based etching, particularly in maintaining high plasma density while minimizing ion energy to prevent damage to substrates, especially when using high bias voltages that can sputter protective coatings like photoresist materials.
Innovation Solution
The method involves generating multiple sequential pulses of RF power with varying profiles, where the first pulse has higher power for a shorter duration followed by a lower power pulse for a longer duration, and these pulses are separated by a third duration, allowing for precise control of plasma density and ion energy through the use of dual DC power supplies to manage the RF signal generation system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high bias voltage is applied to increase plasma density, then plasma density is improved, but ion energy increases causing damage to substrates and protective coatings
Solution Approach 1:
The patent applies periodic pulsed RF power delivery instead of continuous power, creating alternating high-power and low-power phases. During the high-power phase, plasma density is enhanced; during the low-power phase, ion energy is reduced. This temporal modulation allows the system to achieve high plasma density while minimizing ion-induced damage to substrates and protective coatings like photoresist.
Solution Approach 2:
The system dynamically adjusts RF power levels in real-time through pulsed delivery, transitioning between different power states. The RF generator modulates power output based on process requirements, creating a dynamic control mechanism that optimizes plasma density while controlling ion energy. This dynamic adjustment enables precise control over plasma characteristics without static compromises.
2Quantity of substance
If continuous RF power is supplied to maintain plasma density, then plasma density is improved, but ion energy remains elevated causing substrate damage
Solution Approach 1:
The patent implements periodic pulsed RF power supply with alternating high-power and low-power phases. During high-power phases, plasma density is maintained or enhanced; during low-power phases, ion energy is reduced. This periodic modulation breaks the continuous high ion energy state, allowing plasma density benefits while minimizing substrate damage from excessive ion energy.
Solution Approach 2:
The system prepares for potential substrate damage by preemptively reducing RF power during specific phases of the pulse cycle. Before ion-induced damage can occur during high-power phases, the system transitions to low-power phases that allow plasma sheath relaxation and ion energy reduction, preventing damage before it happens.
3Productivity
If high RF power is applied to achieve high etch rates, then productivity is improved, but selectivity and material damage control worsen
Solution Approach 1:
The patent uses periodic pulsed RF power delivery to achieve high etch rates during high-power phases while maintaining selectivity through low-power phases. The alternating power states allow aggressive etching when needed while providing recovery periods that preserve protective coatings and maintain process selectivity, resolving the trade-off between productivity and precision.
Solution Approach 2:
The system dynamically modulates RF power levels to optimize the balance between etch rate and selectivity. By transitioning between high and low power states, the system can achieve high productivity during active etching phases while maintaining manufacturing precision during low-power phases, enabling both high etch rates and good selectivity control.
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 increased plasma density at the substrate level without elevating ion energy, thereby reducing material damage and enhancing etching precision, particularly useful in applications requiring high etch rates and selectivity while preserving protective coatings.
Implementation Method 1
The plasma is often generated by applying radiofrequency (RF) power to a process gas in a controlled environment
Implementation Method 2
applying radiofrequency (RF) power to a process gas in a controlled environment, such that the process gas becomes energized and transforms into the desired plasma
Data Source
AI summary
Multiple, sequential pulses of radiofrequency power are supplied to an electrode of a plasma processing chamber to control a plasma within the plasma processing chamber. Each of the pulses of radiofrequency power includes a first duration over which a first radiofrequency power profile exists, immediately followed by a second duration over which a second radiofrequency power profile exists. The first radiofrequency power profile has greater radiofrequency power than the second radiofrequency power profile. The first duration is less than the second duration. And, the sequential pulses of radiofrequency power are separated from each other by a third duration. A radiofrequency signal generation system is provided to generate and control the multiple, sequential pulses of radiofrequency power.