RF Power Compensation in Plasma Etch Chambers
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Solution Overview
Problem
Variability in RF power delivery to plasma reactor chambers due to absorption by components with high magnetic permeability or resistivity, leading to inconsistent plasma processing across different chambers, especially when temperature or time-dependent materials are used.
Innovation Solution
A system and method that calculates an adjusted power set point by characterizing the no-plasma performance slope of a target chamber and a reference chamber, using voltage or current measurements to ensure power delivery matches that of a reference plasma, thereby compensating for power dissipation in components like RF coils and shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If typical calibration methods are used to measure power delivery at the input to the impedance matching network, then calibration is simple and quick, but accurate power delivery into the plasma cannot be ensured due to unmeasured variable power dissipation in components downstream
Solution Approach 1:
The system performs preliminary characterization of each plasma chamber's RF delivery system by measuring no-plasma voltage and current at multiple RF power levels to determine chamber-specific slopes before actual plasma processing. This preliminary action captures the unique absorption characteristics of each chamber's components, enabling accurate power delivery compensation without adding complexity to the main processing operation.
Solution Approach 2:
The system uses measured voltage and current values during plasma processing, combined with the pre-determined no-plasma slopes, to calculate actual power delivery to the plasma. This feedback mechanism continuously monitors and determines the real power delivered, allowing the system to compensate for variable power dissipation in downstream components and maintain accurate power control.
2Reliability
If RF current flows through components with high magnetic permeability or resistivity (such as nickel plating, mu-metal, or temperature-dependent materials), then shielding and magnetic properties are improved, but variable power absorption occurs leading to process variability between chambers
Solution Approach 1:
The system recognizes that each plasma chamber has unique local characteristics in its RF delivery path, including chamber-specific components with magnetic permeability or resistivity. By measuring the no-plasma slope for each individual chamber, the system captures the local absorption characteristics of that specific chamber's components, enabling tailored compensation for each location rather than using a generic calibration approach.
Solution Approach 2:
The system changes the operational parameters by measuring at multiple RF power levels to determine the slope of voltage or current versus power. This parameter-based approach characterizes how each chamber's components behave across different power conditions, allowing the system to account for non-linear power absorption in magnetic materials and temperature-dependent resistivity effects.
3Manufacturing precision
If temperature fluctuations or time-dependent material properties occur in RF current carrying components, then material performance may vary, but this causes RF power delivery variability and process shifts between wafers and chambers
Solution Approach 1:
The system performs preliminary characterization under actual operating conditions to capture the effective electrical properties of components including any temperature-dependent or time-dependent effects. By establishing the no-plasma slope before wafer processing, the system accounts for the actual state of components during operation, ensuring consistent compensation across multiple wafers and chambers.
Solution Approach 2:
Each plasma chamber performs its own self-characterization by measuring its unique no-plasma voltage and current response. This self-service approach allows each chamber to account for its own component variations, temperature effects, and aging characteristics without requiring external calibration of each individual component, maintaining manufacturing precision across the entire system.
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
Ensures accurate and consistent power delivery to the plasma in each chamber, reducing process variability and maintaining identical plasma conditions across multiple chambers.
Implementation Method 1
RF power absorption in components downstream of the calibration location... absorption properties changing over time, or due to temperature fluctuations
Implementation Method 2
impedance matching network... RF coil... plasma reactor chamber
Data Source
AI summary
A system and method of applying power to a target plasma chamber include, characterizing a no plasma performance slope of the target plasma chamber, applying a selected plasma recipe to a first wafer in the target chamber, the selected plasma recipe includes a selected power set point value and monitoring a recipe factor value on the RF electrode. A ratio of process efficiency is generated comparing the reference chamber and the target chamber, the generating using as inputs the no plasma performance slopes of the target chamber and the reference chamber and the monitored recipe factor value. An adjusted power set point value is calculated, the adjusted power set point configured to cause power delivered to a plasma formed in the target chamber to match power that would be delivered to a reference plasma formed in the reference chamber.