Monoenergetic Ion Generation via Pulsed RF for Selective Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for generating ions in plasma tools, such as DC sources and tailored waveforms, result in high angular spread and low etch rates, making it difficult to achieve optimal etch profiles and selectivity between different material layers on a substrate.
Innovation Solution
The use of level-to-level voltage and frequency pulsing to generate monoenergetic ions, where the voltage levels or frequency levels are tuned to create a pulsed RF signal with a specific duty cycle, allowing for controlled etching of a top material layer without substantially etching a bottom layer, by maintaining a high voltage level for a short duration and a low voltage level for a longer duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DC sources or tailored waveforms are used to generate ions, then ions are produced for etching, but the ions exhibit high angular spread which decreases etch rate and directionality
Solution Approach 1:
The patent applies periodic pulsed RF signaling instead of continuous DC or tailored waveforms. The pulsed nature of the signal creates periodic ion generation and acceleration, which confines the ion angular spread while maintaining high etch rates through repeated pulses. This resolves the contradiction by using time-periodic action to achieve both directionality and productivity.
Solution Approach 2:
The patent dynamically adjusts RF signal parameters including pulse width, duty cycle, and power level to optimize ion beam characteristics. By making the ion generation process dynamic rather than static, the system can maintain narrow angular spread while achieving high etch rates through real-time parameter optimization.
2Productivity
If DC sources are used, then ions are generated, but the high reactance produces low current which reduces etch rate
Solution Approach 1:
The pulsed RF signal delivers power in periodic bursts rather than continuous low-level DC. This allows the system to overcome the high reactance limitation by providing high current during each pulse window, achieving both adequate current delivery and maintained etch rate through the periodic delivery mechanism.
Solution Approach 2:
The system prepares the plasma and ion generation conditions in advance during each pulse cycle, optimizing the ion production efficiency before the actual etching action occurs. This preliminary preparation allows maximum current utilization during the active etching phase.
3Manufacturing precision
If tailored waveforms are used, then ions are produced, but the high angular spread does not produce expected etch profile
Solution Approach 1:
The pulsed RF waveform creates distinct ion generation and acceleration phases separated by relaxation periods. This periodic structure produces narrow angular spread ion beams that maintain precise directional control throughout the etching process, achieving both accurate etch profiles and high etch rates through the rhythmic pulse structure.
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 increases the etch rate and selectivity of the top material layer while preventing significant etching of the bottom layer, resulting in a more precise and efficient etching process.
Implementation Method 1
The radio frequency signal creates ions of plasma within the plasma chamber
Implementation Method 2
The RF generator generates a pulsed RF signal that pulses between a high parameter level and a low parameter level... to generate plasma ions with the first energy band
Implementation Method 3
During a state in which the higher voltage level is sustained, there is a voltage spike experienced by a plasma sheath of plasma due to a small duty cycle of the higher voltage level and there is insufficient time to completely charge the plasma sheath to generate high energy ions
Implementation Method 4
The monoenergetic ions of plasma are generated using level-to-level voltage pulsing and/or level-to-level frequency pulsing where voltage levels or frequency levels or a duty cycle of the voltage levels, or a duty cycle of the frequency levels are tuned to generate the monoenergetic ions
Implementation Method 5
The first energy band is used to etch the first material layer at a rate that is self-limiting to the second material layer
Data Source
AI summary
Systems and methods for generating monoenergetic ions are described. A duty cycle of a high parameter level of a multistate parameter signal is maintained and a difference between the high parameter level and a low parameter level of the multistate parameter signal is maintained to generate monoenergetic ions. The monoenergetic ions are used to etch a top material layer of a substrate at a rate that is self-limiting without substantially etching a bottom material layer of the substrate.