Phase-Controlled RF Etching for Vertical Recess Bottoms
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Solution Overview
Problem
In plasma etching processes for high aspect ratio semiconductors, there is a trade-off between improving etching rate, selection ratio, shape controllability, and reducing process time, with existing techniques either leading to etching failures or increasing process time due to rectangular or tapered bottom shapes of recesses.
Innovation Solution
A plasma processing apparatus with a specific RF power supply configuration, including a first RF power supply generating signals with varying power levels and a DC power supply, controls the RF signal phases to optimize etching, improving selection ratio, etching rate, and shape controllability while reducing process time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional RF power supply control is used in plasma etching, then the etching process can be completed, but the bottom shape of recesses becomes rectangular or tapered, leading to etching failures or increased process time
Solution Approach 1:
The patent applies periodic action by dividing the RF power supply into multiple distinct phases within each etching cycle. The first RF power supply operates during a first phase to deposit etchant, then stops during a second phase. The second RF power supply operates during a third phase for ion irradiation, then stops during a fourth phase. This periodic switching creates distinct temporal stages that enable precise control over the bottom shape formation, achieving vertical sidewalls while maintaining high etching rates
Solution Approach 2:
The patent implements dynamics by making the RF power supply configuration dynamically adjustable through phase shifting control. The controller dynamically adjusts the phase difference between the plasma generation RF signal and bias RF signal, and dynamically switches between different RF power supply modes (first and second RF power supplies) during the etching process. This dynamic control enables real-time optimization of the bottom shape formation, achieving vertical sidewalls without sacrificing etching rate
2Productivity
If the etching rate is increased to reduce process time, then productivity improves, but the bottom shape control deteriorates, causing rectangular or tapered recesses
Solution Approach 1:
The patent applies segmentation by dividing the etching process into distinct temporal phases with different RF power supply configurations. The first phase uses the first RF power supply for etchant deposition, the second phase stops both RF power supplies, the third phase uses the second RF power supply for ion irradiation, and the fourth phase stops both again. This segmentation allows each phase to be optimized independently, enabling high overall etching rate while achieving precise vertical bottom shape control during the ion irradiation phase
Solution Approach 2:
The patent implements dynamics by dynamically switching between different RF power supply modes and dynamically adjusting phase differences during the etching process. The controller dynamically transitions from the first RF power supply mode to the second RF power supply mode between phases, and dynamically adjusts the phase difference between plasma generation and bias RF signals. This dynamic control enables real-time optimization, achieving both high etching rate and precise vertical bottom shape formation
3Manufacturing precision
If phase control between plasma generation RF power and bias RF power is implemented, then selection ratio improves, but device complexity increases
Solution Approach 1:
The patent applies periodic action by implementing a structured four-phase cycle with regular switching between RF power supplies. Each phase has a defined duration and specific RF power supply configuration, creating a predictable periodic pattern. This periodic structure simplifies the control logic compared to continuous phase adjustment, as the system follows a repeating sequence that is easier to implement and maintain while still achieving high selection ratio through proper phase timing
Solution Approach 2:
The patent implements parameter changes by systematically varying RF power levels and phase differences across distinct phases. The first RF power supply operates at specific power levels during the first phase, then the second RF power supply operates at different power levels during the third phase. The phase difference between plasma generation and bias RF signals is adjusted to specific values during different phases. These controlled parameter changes improve selection ratio while the systematic nature of the changes keeps the control system manageable
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 apparatus achieves a higher selection ratio, more vertical bottom shape of recesses, and reduced process time by controlling RF signal phases and power levels, enhancing the overall efficiency of the etching process.
Implementation Method 1
a first RF power supply that is electrically connected to the upper electrode and generates a first RF signal, in which the first RF signal has a first power level during a first state within a repeating period and a zero power level during a second state, a third state, and a fourth state within the repeating period
Implementation Method 2
a second RF power supply that is electrically connected to the lower electrode and generates a second RF signal, in which the second RF signal has a zero power level during the first and second states, a second power level during the third state, and a third power level during the fourth state
Implementation Method 3
a DC power supply that is electrically connected to the upper electrode and generates a DC signal
Implementation Method 4
In order to prevent the occurrence of standing waves of multiple radio-frequency powers supplied into a processing container of a plasma processing apparatus, it has been proposed to perform a control for causing a predetermined phase difference between pulse waves of a plasma generation radio-frequency power and a bias radio-frequency power
Data Source
AI summary
A plasma processing apparatus includes: a chamber; a substrate support including a lower electrode; an upper electrode disposed above the substrate support; a first RF power supply that is electrically connected to the upper electrode and generates a first RF signal, in which the first RF signal has a first power level during a first state within a repeating period and a zero power level during second to fourth states within the repeating period; a second RF power supply that is electrically connected to the lower electrode and generates a second RF signal, in which the second RF signal has a zero power level during the first and second states, a second power level during the third state, and a third power level during the fourth state; and a DC power supply that is electrically connected to the upper electrode and generates a DC signal.