Electrostatic Chuck With Segmented Protrusions For Thermal Stability
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Solution Overview
Problem
Existing electrostatic chucks face challenges in maintaining uniform thermal conductivity and constant temperature over time due to wear of protrusions and exposure to plasma during dry-cleaning processes, leading to variations in contact state and thermal conductivity, which affects processing consistency and introduces particles.
Innovation Solution
An electrostatic chuck design featuring a body with internal electrodes and protrusions, where minute projections on the protrusions' surfaces serve as mounting areas for the substrate, with controlled area and height to maintain consistent thermal conductivity and electrostatic attraction, and a composite sintered material of aluminum oxide and silicon carbide for enhanced durability and plasma resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the top surfaces of columnar protrusions are used as contact surfaces with the substrate, then the substrate can be supported and cooled, but the protrusions wear away over time due to repeated substrate loading, causing thermal conductivity to vary and making it difficult to maintain constant temperature
Solution Approach 1:
The contact surface is segmented into two distinct functional zones: columnar protrusions for mechanical support and cooling gas circulation, and a separate flat planar surface for thermal contact with the substrate. This segmentation prevents the thermal contact surface from wearing away, as it is not subjected to mechanical stress from substrate loading/unloading operations.
Solution Approach 2:
The thermal contact function is extracted from the columnar protrusions and relocated to a separate flat planar surface. The protrusions retain only their support and cooling functions, while the flat surface provides a stable, wear-resistant thermal interface with the substrate.
2Object-generated harmful factors
If the electrostatic attraction surface is directly exposed to plasma during waferless dry-cleaning, then foreign materials can be removed, but the surface state varies over time, causing contact state and thermal conductivity to vary
Solution Approach 1:
Different regions of the electrostatic chuck have different functional properties: the electrostatic attraction surface is designed for plasma exposure and cleaning, while the separate flat planar surface is designed for stable thermal contact. This local differentiation allows the thermal interface to remain protected from plasma damage while the attraction surface undergoes cleaning cycles.
3Temperature
If cooling gas is introduced through holes in the electrostatic chuck body, then the substrate can be cooled, but particles may be generated and the sealing of cooling gas may deteriorate due to protrusion wear
Solution Approach 1:
The cooling gas circulation function is extracted from the worn protrusion surfaces and repositioned to flow through channels formed between the flat planar surface and the substrate. This eliminates particle generation from protrusion wear while maintaining effective cooling through the sealed gap.
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 design allows for a wider temperature range maintenance and reduced thermal conductivity variation, ensuring consistent processing conditions and minimizing particle generation, even with repeated substrate loading and extended dry-cleaning processes.
Implementation Method 1
an internal electrode 6 for generating an electrostatic attraction force is arranged in parallel to the surface 2a
Implementation Method 2
the temperature of the flat substrate W is maintained at a constant value by a cooling gas flowing through the cooling gas introduction hole 5
Data Source
AI summary
An electrostatic chuck capable of widening a temperature range and reducing a variation in thermal conductivity between the electrostatic chuck and the flat substrate over time is provided. The chuck includes: a body that has an internal electrode for attracting a flat substrate by an electrostatic force provided therein, a plurality of protrusions formed on one surface of the body serving as an electrostatic attraction surface, and projections provided on the top surfaces of some or all of the plurality of protrusions. In the electrostatic chuck, a region of the top surface of each of the minute projections on which the flat substrate is loaded is referred to as a mounting surface, and the total area of the mounting surfaces of the minute projections is equal to or larger than 0.01% and equal to or smaller than 2% of the area of the electrostatic attraction surface.