Plasma Bias Circuit Tuning for Substrate Charging Control
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Solution Overview
Problem
Conventional DC pulse implementations in plasma processing face challenges due to substrate charging, which reduces the voltage differential between the plasma and the substrate surface, leading to inefficiencies in ion flux and energy distribution.
Innovation Solution
A plasma processing apparatus with a tunable electrical characteristic, utilizing a capacitive pre-coat layer and a tuning circuit with variable capacitance to adjust the RC time constant, allowing control over the DC pulse frequency and duty ratio without altering these parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If DC pulse frequency and duty ratio are manipulated to reduce substrate charging, then substrate charging is reduced, but ion energy distribution function changes undesirably
Solution Approach 1:
The patent changes the electrical parameters of the plasma processing chamber by introducing a capacitive pre-coat layer and tuning circuit, which modifies the RC time constant. This allows the system to maintain desired ion energy distribution while reducing substrate charging, as the electrical characteristic tuning decouples the relationship between pulse parameters and substrate charging effects
Solution Approach 2:
The capacitive pre-coat layer acts as an intermediary element between the DC pulse generator and the plasma. It introduces a controllable capacitance that mediates the charging effects on the substrate while preserving the ion energy distribution, effectively decoupling these two previously coupled effects
2Quantity of substance
If DC pulse frequency and duty ratio are increased to increase ion flux, then ion flux increases, but substrate charging increases
Solution Approach 1:
By tuning the RC time constant through the capacitive pre-coat layer and tuning circuit, the system can operate at higher DC pulse frequencies and duty ratios to increase ion flux while the modified electrical characteristics prevent excessive substrate charging, thus resolving the trade-off between ion flux and substrate charging
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 reduces substrate charging, enabling better control over ion energy distribution and flux, resulting in increased high-energy ion flux and reduced energy spread, thereby improving process efficiency.
Implementation Method 1
a capacitive pre-coat layer disposed between the DC coupling element and the plasma. The capacitive pre-coat layer increases the RC time constant of the DC current path according to the DC pulse frequency
Implementation Method 2
a source power coupling element configured to generate plasma in an interior of the plasma processing chamber by coupling source power to the plasma processing chamber
Data Source
AI summary
A plasma processing apparatus includes a plasma processing chamber, a source power coupling element configured to generate plasma in an interior of the plasma processing chamber by coupling source power to the plasma processing chamber, a DC pulse generator configured to generate a DC pulse train at a DC pulse frequency, a substrate holder disposed in the interior of the plasma processing chamber, a DC coupling element coupled to the DC pulse generator, a DC current path including the DC coupling element, the plasma, and a reference potential node in a series configuration, the DC coupling element being configured to bias the substrate holder relative to the reference potential node using the DC pulse train, and a capacitive pre-coat layer disposed between the DC coupling element and the plasma. The capacitive pre-coat layer increases the RC time constant of the DC current path according to the DC pulse frequency.