Reference Wafer Calibration for In-Situ Optical Temperature Metrology
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Solution Overview
Problem
Accurate wafer temperature measurement is difficult in semiconductor fabrication, particularly for non-contact sensors, due to tool-to-tool and chamber-to-chamber variations, and conventional calibration methods are cumbersome and inaccurate.
Innovation Solution
A reference wafer with distinct optical properties is used for in-situ calibration of temperature sensors, employing a first sensor to calibrate a second sensor based on optical emissivity and transmission, enabling precise temperature control during thermal etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods are used for temperature sensors, then calibration can be performed, but the calibration is cumbersome and inaccurate
Solution Approach 1:
The patent introduces an intermediary reference wafer with known optical properties (emissivity and transmission characteristics) that mediates between the temperature sensor and the actual measurement target. This reference wafer serves as a calibration standard that simplifies the calibration process while improving accuracy, directly resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent utilizes parameter changes in optical properties (emissivity and transmission) of the reference wafer at different temperatures to enable accurate sensor calibration. By measuring how these optical parameters change with temperature, the system achieves precise temperature measurement without complex calibration procedures
2Reliability
If tool-to-tool and chamber-to-chamber variations are present, then sensor readings vary, but achieving accurate temperature measurement becomes difficult
Solution Approach 1:
The patent applies local quality by creating distinct regions on the reference wafer with different optical properties (emissive region vs. transparent region). This local differentiation allows the system to calibrate and validate sensor readings across different tools and chambers, improving reliability while managing measurement complexity through localized reference standards
3Manufacturing precision
If accurate wafer temperature measurement is required for high etch selectivity processes, then process precision improves, but measurement difficulty increases
Solution Approach 1:
The reference wafer acts as an intermediary that bridges the gap between the optical sensor and the actual wafer temperature measurement challenge. By first calibrating the sensor against the reference wafer with known properties, the system enables accurate temperature measurement during etching processes, thereby achieving high etch selectivity without directly confronting the measurement difficulty
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 accurate and efficient temperature calibration of optical sensors in-situ, allowing for precise thermal control of substrates during etching, reducing defects and improving process consistency.
Implementation Method 1
an IR-emissive film on the first surface in a first region of the semiconductor substrate
Implementation Method 2
a second region of the first surface of the semiconductor surface is uncoated
Data Source
AI summary
Systems, methods, and devices for in-situ calibration of a second sensor use a first sensor, with the two sensors operating in different optical regimes and/or based on different optical effects. In some embodiments, the methods employ a reference wafer having two regions that have different optical properties to calibrate a temperature sensor. Prior to the in-situ calibration, the first sensor is calibrated over a range of temperatures. During the in-situ calibration, the first sensor reads a first spot in the first region of the reference wafer and a second sensor reads a second spot in the second region that is close to the first spot.