Temperature Probe With Shielded Light Pipe for Plasma Chamber
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Solution Overview
Problem
Temperature measurement in hostile environments, such as plasma ashing chambers in the semiconductor industry, requires sensors that can withstand extreme temperatures and plasma conditions, yet existing sensors often fail to provide accurate and reliable readings due to direct plasma exposure and thermal conductivity issues.
Innovation Solution
A temperature probe design featuring a hollow, opaque, insulating standoff with a side-hole, a cap coated with phosphor or a thermocouple, and a shielded light pipe that allows for optical communication through a feed-through in the chamber wall, providing insulation and minimizing plasma interference, while maintaining good thermal contact with the object being measured.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is directly exposed to plasma in an ashing chamber, then temperature measurement can be performed, but the sensor reliability deteriorates due to plasma damage and thermal conductivity issues
Solution Approach 1:
The temperature probe is segmented into distinct functional zones: the standoff provides structural support and electrical isolation, the cap houses the temperature sensor and provides thermal contact with the wafer, and the shield protects the light pipe from plasma. This segmentation allows each component to be optimized for its specific function while protecting the sensor from hostile plasma environments.
Solution Approach 2:
The cap acts as an intermediary between the wafer and the temperature sensor, providing thermal contact with the wafer while isolating the sensor from direct plasma exposure. The shield serves as an intermediary protective barrier that allows optical signals to pass through while blocking plasma particles and energy from reaching the light pipe.
2Object-affected harmful factors
If the standoff is made opaque to block plasma, then plasma interference is reduced, but light transmission for temperature measurement is blocked
Solution Approach 1:
The shield is designed with spatially varying optical properties: it is opaque in the radial direction to block plasma particles and energy, but transparent or translucent in the axial direction to allow light transmission to and from the light pipe. This local quality differentiation allows the shield to simultaneously protect against plasma interference and enable optical temperature measurement.
Solution Approach 2:
The shield is constructed from composite materials or layered structures that combine plasma-blocking properties with optical transmission properties. This allows the shield to selectively block harmful plasma factors while permitting light transmission for the temperature measurement function.
3Illumination intensity
If the light pipe sensing end is polished at a 45-degree angle, then light reflection and transmission are optimized, but manufacturing precision requirements increase
Solution Approach 1:
The light pipe sensing end is polished at a specific angle (45 degrees) to optimize light reflection and transmission geometry. This parameter optimization ensures that light from the source is efficiently directed onto the phosphor coating and that the emitted light is efficiently collected and transmitted back through the light pipe, maximizing the optical signal strength for temperature measurement.
4Measurement precision
If the cap is coated with phosphor for optical temperature measurement, then non-contact temperature sensing is enabled, but the coating must withstand extreme temperatures and plasma conditions
Solution Approach 1:
The phosphor coating is applied to the cap in advance, before the cap is installed in the plasma environment. The cap itself serves as a protective substrate that shields the phosphor coating from direct plasma bombardment and extreme thermal stress, allowing the coating to function at elevated temperatures without degrading rapidly.
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 solution enables accurate and reliable temperature measurements in hostile environments by isolating the sensor from plasma interference and ensuring consistent thermal contact, improving measurement consistency and accuracy over time.
Implementation Method 1
a phosphor temperature probe, the probe comprising: a hollow, opaque, insulating standoff mounted on a floor of the chamber, the standoff having a side-hole; a cap fixed to the top of the standoff, the bottom surface of the cap being coated with a phosphor
Implementation Method 2
a light pipe disposed perpendicularly to the standoff; and a shield disposed around and coaxial with the light pipe
Implementation Method 3
the sensing end of the light pipe being polished at a 45-degree angle to the axis of the light pipe
Implementation Method 4
a hollow, opaque, insulating standoff mounted on a floor of the chamber
Implementation Method 5
a shield disposed around and coaxial with the light pipe, wherein the shield is opaque with an opening that allows transmission of light between the sensing end of the light pipe and the phosphor
Data Source
AI summary
A temperature probe for use in a chamber. The temperature probe includes a hollow standoff mounted on a floor of the chamber, and equipped with a side-hole. The temperature probe further includes a cap fixed to the top of the standoff. The bottom surface of the cap includes a coating. The temperature probe also includes a light pipe disposed perpendicularly to the standoff and a shield disposed around the light pipe. A top surface of the cap is co-planar with a bottom surface of an object whose temperature is being measured. A sensing end of the light pipe is inserted into the side-hole of the standoff. An opening in the shield allows transmission of light between the sensing end of the light pipe and the coating. The light pipe and the shield pass through a feed-through in a sidewall of the chamber.