Heater Assembly Copper Heat Spreaders Wafer Temperature Uniformity
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Solution Overview
Problem
Current heater designs for semiconductor wafers face challenges in achieving uniform temperature control due to thermal warpage and non-uniform heat distribution, primarily caused by the thermal insulating properties of dielectric materials and the poor heat conductivity of materials like stainless steel, leading to unwanted temperature gradients and process yield loss.
Innovation Solution
A compressed heating assembly with a heater cartridge featuring high conductivity copper heat spreaders that encase a composite heating element, including a multi-zone etched foil mica heater, to enhance heat transfer and maintain temperature uniformity across the wafer surface, using a stainless steel housing with copper heat conducting casing members that are selectively united to form heat conduits and maintain intimate contact with the heating element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dielectric materials are used to insulate the heating element, then electrical insulation is achieved, but thermal insulation causes non-uniform heat distribution and temperature gradients
Solution Approach 1:
A heat spreader layer with intermediate thermal conductivity is introduced between the heating element and the process chamber. This intermediary layer distributes heat uniformly while allowing sufficient thermal energy transfer, resolving the contradiction between needing electrical insulation and maintaining temperature uniformity.
Solution Approach 2:
The thermal conductivity parameter of the insulating material is optimized to a specific range that balances electrical insulation requirements with heat distribution needs. By changing the thermal conductivity parameter rather than using extreme insulation values, both electrical safety and thermal uniformity are achieved.
2Strength
If stainless steel housing is used for structural integrity, then mechanical strength is achieved, but poor heat conductivity causes thermal warping and temperature gradients
Solution Approach 1:
The housing structure uses a composite design combining stainless steel for mechanical strength with high thermal conductivity materials (such as aluminum or copper layers) for heat distribution. This composite approach simultaneously achieves structural integrity and thermal uniformity, eliminating thermal warping.
Solution Approach 2:
The housing is segmented into functional zones: structural components made of stainless steel for strength, and thermal management components made of high-conductivity materials for heat distribution. This segmentation allows each part to optimize its primary function while working together as a unified system.
3Productivity
If heating elements are placed closer to the wafer surface, then heating efficiency is improved, but temperature control precision deteriorates due to hot spots
Solution Approach 1:
The heating system employs local quality variation through a heat spreader with spatially varying thermal properties or a patterned heating element design. Different regions of the heating element provide different heat intensities, with higher power density at edges and lower at the center, preventing hot spots while maintaining overall heating efficiency.
Solution Approach 2:
A heat spreader layer acts as an intermediary between the heating element and wafer surface, decoupling the positioning of the heating element from its thermal effect on the wafer. This allows efficient heat transfer while the heat spreader's uniforming effect prevents localized hot spots, maintaining temperature control precision.
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 provides improved temperature control and uniformity by efficiently conducting heat across the wafer surface, reducing thermal warpage and enhancing process yield through precise heat distribution and independent zone control, while maintaining the integrity of the stainless steel housing in a clean room environment.
Implementation Method 1
high conductivity copper heat spreaders that encase a composite heating element, including a multi-zone etched foil mica heater, to enhance heat transfer
Implementation Method 2
a heater characterized by multiple, independently operable/controllable heating zones. Commonly, but not exclusively, heaters may be characterized by rods, wires, etched foils
Data Source
AI summary
An assembly suitable for controlling the temperature of a workpiece operatively engaged thereby is provided. The assembly generally comprises a housing characterized by first and second housing members sealingly united at their peripheries, and a heater cartridge enclosed within the housing and compressively retained interior of the sealingly united peripheries of the housing members. The heater cartridge comprises a heat conducting casing characterized by first and second heat conducting casing members and a composite heating element compressively retained between the heat conducting casing members. The first and second heat conducting casing members are selectively united interior of their peripheries so as to delimit heat conduits for the heater cartridge.