CMP Substrate Notch Detection with Sinusoidal Offset Compensation
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Solution Overview
Problem
Existing chemical mechanical polishing (CMP) systems face challenges in consistently aligning substrates to a precise angular orientation due to precession effects and misalignment of the substrate's center with the carrier head's axis, leading to inconsistent polishing results and unreliable in-situ monitoring.
Innovation Solution
A polishing apparatus with a notch finding station that includes a sensor to detect the angular position of a substrate notch by generating a signal based on the proportion of the sensing region covered, compensating for sinusoidal variations, and adjusting the carrier head's position to align the substrate accurately before polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the substrate center is offset from the carrier head axis, then the substrate can be easily mounted and transferred, but the angular position detection becomes inaccurate and precession effects occur
Solution Approach 1:
The system uses a sensor to detect the angular position of the substrate notch and feeds this information back to the controller. The controller then adjusts the carrier head rotation to compensate for any offset, ensuring accurate angular alignment despite initial misalignment during mounting.
Solution Approach 2:
Before the actual polishing operation, the system performs a preliminary angular position detection and alignment procedure. The carrier head is rotated to specific angular positions based on sensor feedback, establishing accurate orientation before the polishing process begins.
2Productivity
If the carrier head rotates at high speed, then polishing productivity increases, but the precession effect and center offset cause inconsistent angular orientation
Solution Approach 1:
The angular position detection and alignment is performed before the high-speed polishing operation. By pre-establishing the correct angular orientation through sensor-based alignment, the system ensures consistent results throughout the high-speed polishing process without requiring continuous adjustment.
Solution Approach 2:
The system replaces complex mechanical alignment mechanisms with an optical/sensor-based detection system. Instead of using complex mechanical fixtures to ensure precise alignment, the system uses a sensor to detect the notch position and electronically controls the carrier head rotation to achieve the desired angular orientation.
3Device complexity
If no angular position detection is performed, then the device complexity is reduced, but wafer-to-wafer and within-wafer uniformity deteriorate
Solution Approach 1:
The patent replaces complex mechanical alignment systems with a simpler sensor-based detection system. A single sensor detects the angular position of the substrate notch, and the controller electronically calculates and applies the necessary corrections, achieving high reliability with reduced mechanical complexity.
Solution Approach 2:
The system changes the control parameter from mechanical alignment positions to angular orientation parameters. By detecting the angular position of the notch and using this parameter to control the carrier head rotation, the system achieves precise control with simpler hardware requirements.
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 enhances wafer-to-wafer uniformity and within-wafer uniformity by ensuring consistent angular orientation, improving the reliability of pressure control algorithms and in-situ monitoring during CMP processes.
Implementation Method 1
a sensor to generate a signal that depends on an proportion of a sensing region of the sensor that is covered by the substrate
Implementation Method 2
cause the motor to rotate the carrier head such that the sensing region of the sensor scans along a circumference of the substrate
Implementation Method 3
detect an angular position of a notch in an edge of the substrate based on a signal from the sensor, including compensating for a sinusoidal component of the signal resulting from an offset of the center of the substrate from the axis of rotation
Data Source
AI summary
A notch finding station includes a sensor to generate a signal that depends on an proportion of a sensing region of the sensor that is covered by the substrate, and a controller. The controller is configured to cause an actuator to position a carrier head relative to the sensor such that the sensing region of the sensor is at an edge of the substrate, cause the motor to generate rotational motion such that the sensing region of the sensor scans along a circumference of the substrate, and detect an angular position of a notch in the edge of the substrate based on a signal from the sensor, including compensating for a sinusoidal component of the signal resulting from an offset of the center of the substrate from the axis of rotation.