Fiber Optic Temperature Probe With Protected Sensing Tip
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Solution Overview
Problem
Existing temperature sensors in semiconductor processing face challenges such as material degradation due to harsh environments, complexity in calibration, and variability in performance, leading to inaccurate measurements and fragile setups.
Innovation Solution
A fiber optic temperature sensor system with a sensing element separated from the optical fiber by a transparent boundary, using a controller to calculate temperature based on return beam characteristics, and a probe design that minimizes heat loss and protects the sensing material with a transparent window and encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phosphor sensing material is exposed to harsh environments with high temperatures and corrosive chemicals, then temperature sensing capability is achieved, but measurement reliability degrades over time due to phosphor attack and degradation
Solution Approach 1:
The probe is divided into distinct functional segments: a phosphor-protected sensing tip for measurement and a separate body for electronics and light source. This segmentation allows the phosphor to be isolated in a protected environment while maintaining sensing capability.
Solution Approach 2:
A transparent protective window (sapphire or diamond) is introduced as an intermediary between the phosphor sensing material and the harsh process environment. This window allows optical signals to pass through while protecting the phosphor from chemical attack and physical damage.
2Measurement precision
If contact between tip and measurement surface is maximized, then measurement accuracy improves, but heat loss from tip to probe body increases
Solution Approach 1:
The probe is segmented into a thermally isolated tip section and a body section. The tip contains the phosphor and makes contact with the measurement surface, while the body contains the light source and detector. This segmentation reduces thermal conduction path from tip to body, minimizing heat loss.
Solution Approach 2:
The light source and detector are extracted from the probe tip and placed in the probe body. This extraction allows the tip to be minimized in size and thermally isolated, improving contact measurement accuracy while reducing heat loss to the probe body.
3Measurement precision
If RTDs are used for temperature sensing on electrostatic chuck, then temperature measurement is achieved, but system complexity increases due to feedthrough requirements and wiring
Solution Approach 1:
The electrical RTD sensing system is replaced with an optical fiber-based phosphor thermometry system. Optical fibers can transmit temperature information without requiring electrical feedthroughs or complex wiring, significantly reducing system complexity while maintaining measurement capability.
Solution Approach 2:
Temperature information is copied from the measurement surface to the optical fiber tip via phosphor luminescence. The phosphor's luminescent properties encode temperature data that can be read remotely through the optical fiber, eliminating the need for direct electrical contact.
4Measurement precision
If multiple RTDs are used to improve temperature sensing coverage, then measurement capability improves, but number of wires and system complexity increase
Solution Approach 1:
A single optical fiber serves multiple functions: delivering light to the phosphor, collecting luminescent signals, and transmitting temperature information. This multi-functionality allows multiple sensing points to be achieved without proportionally increasing wiring complexity, as all signals can be multiplexed through the optical fiber 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
The system provides accurate temperature measurements with reduced heat loss and environmental exposure, improving durability and consistency across multiple sensors, allowing for easier calibration and scalable deployment.
Implementation Method 1
The light illuminates the phosphor which, in turn, luminesces visibly or in the near infrared
Implementation Method 2
an optical fiber which can deliver light to a sensing material
Implementation Method 3
thermographic phosphor sensors do not directly measure temperature but instead measure a physical property that exhibits strong temperature dependence, e.g., phosphorescence time decay
Data Source
AI summary
Embodiments of a temperature sensor system are disclosed. In one embodiment, the system includes a sensing element configured to be in thermal communication with a structural element of a semiconductor processing chamber, wherein the sensing element is configured to emit a return beam in response to a source beam emitted by a light source. The system further comprises an optical pathway spaced apart from the sensing element and where the optical pathway is configured to conduct the source beam to the sensing element and to conduct a portion of the return beam from the sensing element to a detector. A boundary is disposed between the optical pathway and the sensing element. The boundary is at least partially transparent to the source beam and to the return beam. The controller is configured to calculate a temperature of the sensing element based on at least one characteristic of the return beam.