Wafer Surface Potential Monitoring for Temperature Mapping
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Solution Overview
Problem
Temperature variation across wafers during semiconductor processing introduces non-uniformities in processing parameters, reducing yield and requiring effective monitoring methods that are rapid, provide high spatial resolution, and do not require expensive equipment.
Innovation Solution
A method correlating peak wafer temperature with changes in wafer surface charge or surface potential, using a thermocouple wafer with embedded thermocouples and a control wafer, to determine spatial temperature distribution without needing pre-processing measurements, employing a quadratic relationship and non-contact metrology tools like the PDM FAaST2000 or QUANTOX systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional temperature monitoring methods are used, then temperature data can be obtained, but the equipment is expensive and the process is time-consuming
Solution Approach 1:
The patent replaces traditional mechanical/physical temperature sensing systems (thermocouples, infrared cameras) with an electrical measurement system. By measuring wafer surface potential through electrical contacts and using a calibrated relationship between surface potential and temperature, the system achieves temperature monitoring without expensive specialized equipment.
Solution Approach 2:
The patent creates an electrical proxy for temperature measurement. Instead of directly measuring temperature, it measures wafer surface potential which correlates with temperature through a calibrated relationship. This indirect measurement approach uses standard electrical measurement equipment rather than specialized temperature sensing equipment.
2Measurement precision
If comprehensive temperature mapping is performed, then high spatial resolution is achieved, but the measurement time increases
Solution Approach 1:
The patent divides the wafer surface into multiple measurement locations (e.g., center, edge, and intermediate points). By measuring surface potential at these discrete locations rather than continuously across the entire surface, the system achieves spatial temperature distribution data with high resolution while keeping measurement time practical.
3Measurement precision
If pre-processing measurements are required, then accurate baseline data is obtained, but the process becomes more complex and time-consuming
Solution Approach 1:
The patent performs preliminary calibration by processing a reference wafer with known temperature characteristics through the same processing step. The surface potential measurements from this calibration wafer establish the relationship between surface potential change and temperature, which is then used for subsequent measurements without requiring pre-processing measurements of production wafers.
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
Enables rapid, high-resolution monitoring of wafer temperature variations during processing, allowing for improved process control and robust development without additional equipment or contamination risks, applicable to various processing steps.
Implementation Method 1
A first wafer to be characterized for its peak temperature spatial distribution during the processing step is processed through the processing step. Following the processing step the wafer surface charge or surface potential is measured at a plurality of locations on the first wafer.
Implementation Method 2
The measuring step can comprise a corona discharge for biasing a surface of the first wafer.
Data Source
AI summary
A method of measuring temperature across wafers during semiconductor processing includes the step of providing a correlation between a peak wafer temperature during a processing step and a change in wafer surface charge or surface potential following the processing step. A first wafer to be characterized for its peak temperature spatial distribution during the processing step is processed through the processing step. The wafer surface charge or surface potential at a plurality of locations on the first wafer are measured following the processing step. A peak temperature spatial distribution for the first wafer is then determined based on the correlation and the wafer surface charge or surface potential measured in the measuring step.