Wafer Contact Evaluation via Electrostatic Chuck Voltage Difference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The evaluation of wafer charging is often marred by uneven charge distribution, leading to measurement errors and potential wafer damage due to unintended jumping during handling, and existing methods fail to provide a contactless and contamination-free assessment of charge uniformity and contact quality between the wafer and electrostatic chuck.
Innovation Solution
A method utilizing an electrostatic sensor, such as a Kelvin probe, sealed within a vacuumed chamber to measure charge distribution across the wafer's surface, and a system to evaluate the contact quality between the wafer and electrostatic chuck by introducing a voltage difference and monitoring capacitance changes, allowing for prediction of potential wafer jumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wafer is supported by the electrostatic chuck during evaluation, then the wafer can be held in position for measurement, but the charge distribution becomes uneven leading to measurement errors
Solution Approach 1:
The patent replaces the traditional mechanical contact support system with an electrostatic field-based support system. The electrostatic chuck uses electric fields to hold the wafer without mechanical contact, eliminating the distortion caused by physical contact while maintaining positional stability during measurement.
Solution Approach 2:
The patent introduces an intermediary evaluation method that measures the electrical parameters (capacitance, impedance) of the support elements indirectly. Instead of directly measuring wafer charge which is affected by uneven distribution, the system evaluates the support elements' electrical characteristics to infer wafer contact quality and charge uniformity.
2Productivity
If the wafer is moved away from the mechanical stage after evaluation, then the evaluation process is complete, but the wafer may jump and cause damage
Solution Approach 1:
The patent implements a feedback mechanism where the evaluation system monitors the electrical parameters of the support elements and wafer interaction. Based on this feedback, the system can predict potential jumping conditions and adjust the movement sequence or apply counteracting electrostatic forces to prevent wafer damage during transfer.
Solution Approach 2:
The patent performs preliminary evaluation of the wafer's electrical characteristics and support element conditions before the wafer is moved away from the mechanical stage. This preliminary assessment allows the system to identify high-risk scenarios and take preventive actions, such as adjusting electrostatic chuck voltage or modifying transfer timing, to prevent jumping and damage.
3Reliability
If multiple pins are used to ground the wafer, then the wafer can be discharged, but the grounding may fail due to insulating layers
Solution Approach 1:
The patent replaces the mechanical pin-contact grounding system with an electrostatic field-based discharge mechanism. Instead of relying on physical contact through pins that may be blocked by insulating layers, the system uses controlled electrostatic fields to discharge the wafer, ensuring reliable grounding without mechanical contact issues.
Solution Approach 2:
The electrostatic chuck serves multiple functions: it supports the wafer during evaluation, enables electrical parameter measurement, and provides controlled discharge capability. This multi-functionality eliminates the need for separate grounding pins and their associated complexity while improving grounding reliability.
4Object-affected harmful factors
If a contactless method is used to evaluate wafer charging, then contamination is prevented, but the ability to assess contact quality is lost
Solution Approach 1:
The patent uses the electrical parameters (capacitance, impedance) of the support elements as intermediary measurements. These parameters serve as proxies that provide information about wafer-contact quality without requiring direct physical contact between the measurement probe and the wafer, thus maintaining contamination-free evaluation while preserving diagnostic capability.
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 enables accurate, contactless, and contamination-free evaluation of wafer charging and contact quality, mitigating measurement errors and preventing wafer damage by predicting and preventing jumps during handling.
Implementation Method 1
A method utilizing an electrostatic sensor, such as a Kelvin probe, sealed within a vacuumed chamber to measure charge distribution across the wafer's surface
Implementation Method 2
a system to evaluate the contact quality between the wafer and electrostatic chuck by introducing a voltage difference and monitoring capacitance changes
Implementation Method 3
The wafer may be supported by an electrostatic chuck
Data Source
AI summary
A method, a non-transitory computer readable medium and a device. The method may include (a) introducing a voltage difference between an absolute value of a negative pole of the electrostatic chuck and an absolute value of a positive pole of the electrostatic chuck, the introducing occurs while the wafer is supported by the electrostatic chuck and is contacted by one or more conductive contact pins of the electrostatic chuck; (b) monitoring, by an electrostatic sensor that comprises a sensing element, a charge at a point of measurement located at a front side of the wafer, at different points of time that follow a start of the introducing of the voltage difference, to provide monitoring results; and (c) determining an electrical parameter of the contact between the wafer and the electrostatic chuck, based on the monitoring results.