Transparent Ceramic Reflector Plate for RTA Temperature Control
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Solution Overview
Problem
Existing reflector plates in semiconductor thermal processing chambers face issues with temperature measurement drift due to wafer byproduct deposition on pyrometer light pipes and reflective coatings, which are complex, costly, and prone to peeling, limiting their operating temperature and durability.
Innovation Solution
A reflector plate made from ceramic material, such as alumina, silicon carbide, or sapphire, with a reflective coating on its backside and apertures for pyrometer probes, allowing the coating to be shielded from byproducts and maintaining alignment with a baseplate for improved heat absorption and reduced deposition, using rare earth dopants to enhance heat retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a reflective coating is applied to the aluminum reflector plate, then temperature uniformity is improved, but the coating is prone to peeling and has a maximum operating temperature limit of 150°C
Solution Approach 1:
The patent uses a composite structure consisting of an aluminum reflector plate base with a reflective coating layer. This composite material approach allows the aluminum substrate to provide mechanical strength and thermal conductivity while the reflective coating provides the necessary optical properties for temperature uniformity, resolving the contradiction between operating temperature limit and durability
Solution Approach 2:
The patent modifies the operating parameters by limiting the maximum temperature to 150°C to prevent coating peeling. This parameter change resolves the contradiction by ensuring the coating remains within its safe operating range, maintaining reliability while still achieving functional temperature uniformity
2Measurement precision
If pyrometer light pipes protrude through the reflector plate, then temperature measurement capability is improved, but wafer byproduct material deposits on the light pipes causing measurement drift
Solution Approach 1:
The patent extracts the pyrometer light pipes from the main reflector plate structure by providing separate openings or apertures through which the light pipes pass. This separation allows the light pipes to be positioned for accurate temperature measurement while minimizing their exposure to wafer byproduct deposition, thus maintaining measurement stability
Solution Approach 2:
The patent introduces an intermediary structure (openings or apertures in the reflector plate) that mediates between the pyrometer light pipes and the processing chamber environment. This intermediary allows the light pipes to function accurately while reducing direct exposure to contaminating byproducts
3Measurement precision
If the reflective coating is exposed to the chamber environment, then temperature measurement capability is maintained, but byproduct deposition causes drift in temperature measurement
Solution Approach 1:
The patent extracts the reflective coating from direct exposure to the chamber environment by positioning it on the inner surface of the reflector plate, away from the wafer processing zone. This extraction maintains the coating's reflective function for temperature uniformity while preventing byproduct deposition that would cause measurement drift
Solution Approach 2:
The reflector plate structure itself acts as an intermediary, separating the reflective coating from the chamber environment. This intermediary protects the coating from direct exposure to byproducts while maintaining its optical functionality for temperature control and measurement
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 minimizes temperature measurement drift, extends the Mean Wafer Between Clean (MWBC), and increases the reflector plate's operating temperature, ensuring more accurate and durable temperature control during rapid thermal processing.
Implementation Method 1
a reflector plate aids in maintaining temperature uniformity as the reflector plate reflects heat radiation emitted from the wafer back toward the wafer
Implementation Method 2
thermal radiation is used to rapidly heat a substrate in a controlled environment to a maximum temperature of over nine hundred degrees above room temperature
Data Source
AI summary
The present invention generally relates to methods and apparatus for processing substrates. Embodiments of the invention include apparatuses for processing a substrate comprising a ceramic reflector plate, which may be optically transparent. The reflector plate may include a reflective coating and be part of a reflector plate assembly in which the reflector plate is assembled to a baseplate.