Low CTE Semiconductor Pedestal with Segmented Heater Design
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Solution Overview
Problem
The limited selection of materials for semiconductor processing due to thermal expansion compatibility issues leads to difficulties in joining components, increased manufacturing costs, and potential contamination of wafers in semiconductor processing.
Innovation Solution
A support assembly with an application substrate having a low coefficient of thermal expansion, allowing for direct bonding of a heater layer and additional functional layers, and a second substrate that facilitates bonding to adjacent components while providing functions like gas distribution and cooling, using materials like aluminum-silicon alloys and insulating layers to manage thermal stress and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metallic materials (molybdenum, titanium, aluminum-silicon alloys) are used to form the pedestal to ensure CTE compatibility with ceramic substrates, then thermal expansion compatibility is improved, but manufacturing costs increase due to difficulty in manufacturing and machining
Solution Approach 1:
The pedestal is divided into two distinct parts: a lower pedestal body made of easy-to-manufacture material (aluminum, stainless steel, or other common metals) and an upper application substrate made of low-CTE material (ceramic or glass) that provides CTE compatibility with the heater layer. This segmentation allows each part to be optimized independently for its specific function.
Solution Approach 2:
The pedestal structure uses a composite construction combining a metallic pedestal body with a ceramic or glass application substrate. This composite approach leverages the advantages of both materials: the metallic body provides ease of manufacture and structural support, while the ceramic/glass substrate provides low CTE and chemical compatibility with the heater layer.
2Strength
If traditional metallic materials are used to form the pedestal, then structural support is provided, but contamination of wafers occurs if the exposed surface is not properly treated
Solution Approach 1:
The application substrate made of ceramic or glass acts as an intermediary between the metallic pedestal body and the processing environment. This intermediate layer provides a chemically inert surface that prevents contamination of wafers while the metallic body provides structural support. The application substrate essentially mediates between the structural requirements and the contamination prevention requirements.
3Reliability
If a limited number of materials are used to form the substrate to ensure CTE matching with the dielectric layer, then heater reliability is improved, but material selection is limited making joining to electrostatic chuck difficult
Solution Approach 1:
The heater structure is segmented into a substrate layer (which provides CTE matching with the dielectric layer for reliability) and a separate application substrate layer (which provides versatility for joining to different components like electrostatic chucks). This segmentation allows the substrate to be optimized for heater reliability while the application substrate can be selected for compatibility with various joining targets.
Solution Approach 2:
The application substrate serves multiple functions: it provides CTE compatibility with the heater layer, serves as a bonding interface for joining to electrostatic chucks or other components, and can be made from materials (ceramic or glass) that offer broad compatibility with different joining methods and components. This multi-functionality resolves the limitation of material selection.
4Reliability
If ceramic materials are used to form the substrate to achieve low CTE, then thermal expansion compatibility is improved, but manufacturing and machining difficulty increases
Solution Approach 1:
The structure is segmented so that the ceramic material is used only for the application substrate layer where CTE compatibility is critical, while the bulk pedestal body is made of easier-to-manufacture metallic materials. This reduces the overall amount of difficult-to-machine ceramic material while maintaining the CTE compatibility benefit where needed.
Solution Approach 2:
The pedestal uses a composite structure combining ceramic or glass application substrate with metallic pedestal body. This allows the system to achieve the CTE compatibility benefits of ceramic materials at the interface with the heater layer, while using more manufacturable metallic materials for the structural portion.
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 broader material selection, reduced manufacturing costs, improved reliability, and reduced contamination risks, allowing for more efficient and cost-effective semiconductor processing with enhanced thermal management and component bonding.
Implementation Method 1
a resistive heating layer on the dielectric layer
Implementation Method 2
The materials for the different functional layers and the substrate are carefully chosen to have compatible coefficient of thermal expansion (CTE) to reduce shear stress generated at the joining interfaces at elevated temperatures
Data Source
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AI summary
A support assembly for use in semiconductor processing includes an application substrate, a heater layer disposed directly onto the application substrate, an insulation layer disposed onto the heater layer, and a second substrate disposed onto the insulation layer. The heater layer is directly disposed onto the application substrate by a layered process such that the heater layer is in direct contact with the application substrate. The application substrate defines a material having a relatively low coefficient of thermal expansion that is matched to a coefficient of thermal expansion of the heater layer.