DC Bias Voltage Defect Control in RF Plasma Substrate Processing
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Solution Overview
Problem
Substrate processing systems using RF plasma face challenges in defect control due to particles suspended in the plasma that settle on substrates after RF excitation is turned off, leading to contamination and the need for prolonged chamber evacuation.
Innovation Solution
A substrate processing system applies a DC bias voltage to the electrodes before and after RF plasma extinction, altering the trajectories of charged particles and reducing defects by ensuring they bypass the substrate during evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chamber evacuation is prolonged to allow particles to settle, then particle contamination is reduced, but processing time increases
Solution Approach 1:
A DC bias voltage is applied to the substrate pedestal before the RF plasma is extinguished and maintained during substrate transfer. This preliminary action creates an electric field that repels charged particles away from the substrate surface, preventing particle deposition during the evacuation and transfer process, thereby reducing contamination without requiring prolonged evacuation time
Solution Approach 2:
The patent replaces the mechanical/time-based particle removal method (prolonged chamber evacuation relying on gravitational settling) with an electric field-based method (DC bias voltage application). This substitution actively controls particle trajectories using electrostatic forces, achieving particle repulsion and contamination prevention much faster than passive gravitational settling
2Object-affected harmful factors
If DC bias voltage is applied during substrate movement, then particle trajectories are controlled and defects are reduced, but system complexity increases
Solution Approach 1:
The DC bias voltage circuit is integrated with the existing RF plasma generation system, using the same electrode structure and power supply infrastructure. The bias voltage circuit shares components and control architecture with the RF system, allowing a single system to perform both RF plasma generation and DC bias particle control functions, thereby minimizing additional complexity
Solution Approach 2:
The DC bias voltage acts as an intermediary control mechanism between the RF plasma extinction event and the substrate transfer operation. By introducing this voltage mediator, the system can coordinate particle control with substrate movement timing, reducing defects without requiring complex mechanical synchronization mechanisms
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 DC bias voltage effectively reduces defect counts on substrates by managing the trajectories of particles during chamber evacuation, enhancing processing efficiency and minimizing contamination.
Implementation Method 1
electrostatic repulsion suspends the particles in the RF plasma at a plasma boundary or plasma sheath
Implementation Method 2
electrostatic repulsion suspends the particles in the RF plasma at a plasma boundary or plasma sheath
Data Source
AI summary
A substrate processing system includes a processing chamber and an upper electrode arranged in the processing chamber. A pedestal is configured to support a substrate during processing and includes a lower electrode. An RF generating system is configured to generate RF plasma between the upper electrode and the lower electrode by supplying an RF voltage. A bias generating circuit is configured to selectively supply a DC bias voltage to one of the upper electrode and the lower electrode. A start of the DC bias voltage is initiated one of a first predetermined period before the RF plasma is extinguished and a second predetermined period after the RF plasma is extinguished. A substrate movement system is configured to move the substrate relative to the pedestal while the DC bias voltage is generated.