Sapphire Electrostatic Chuck for High-Temperature Clamping
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Solution Overview
Problem
Conventional Johnsen-Rahbek electrostatic chucks cannot effectively clamp substrates at temperatures above 450C due to changes in dielectric layer resistivity, and they are not resistant to corrosive processing chemistries, limiting their application in semiconductor processing.
Innovation Solution
An electrostatic chuck with a sapphire top surface and an underlying ceramic layer joined by a high-temperature aluminum braze layer, capable of maintaining bulk resistivity within the range of 10E9 to 10E11 ohm-cm from 500C to 750C, providing Johnsen-Rahbek clamping and withstanding corrosive environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional dielectric layer is used in a Johnsen-Rahbek electrostatic chuck, then the chuck can provide clamping force at lower temperatures, but the bulk resistivity changes dramatically with temperature above 450C causing loss of clamping effectiveness
Solution Approach 1:
The patent applies parameter changes by selecting a dielectric material (sapphire) with specifically tailored electrical properties that maintain stable bulk resistivity across the high temperature range of 500-750C. This resolves the contradiction by changing the material parameter to achieve both high temperature operation and consistent clamping force.
Solution Approach 2:
The patent uses a composite structure combining sapphire dielectric layer with aluminum electrode and brazing layer. This composite material approach enables the chuck to withstand temperatures above 450C while maintaining appropriate resistivity for effective Johnsen-Rahbek clamping, resolving the temperature vs. reliability contradiction.
2Temperature
If conventional dielectric ceramics are used, then the chuck can operate at elevated temperatures, but the materials are not resistant to corrosive processing chemistries such as fluorine
Solution Approach 1:
The patent employs a composite material system where sapphire serves as the dielectric layer in contact with corrosive chemistries. Sapphire's inherent chemical inertness provides resistance to fluorine and other corrosive processing environments while maintaining high temperature capability, thus resolving the contradiction between temperature resistance and chemical corrosion resistance.
3Ease of manufacture
If the dielectric layer thickness is increased to facilitate manufacturing, then the clamp operating voltage can be reduced, but the resistivity changes more significantly with temperature
Solution Approach 1:
The patent changes the material parameter from conventional dielectric ceramics to sapphire, which has inherently stable resistivity characteristics across temperature. This allows the use of thicker dielectric layers for easier manufacturing and lower operating voltages without suffering from significant resistivity variations, thus resolving the contradiction between ease of manufacture and resistivity stability.
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 effective clamping at higher temperatures than previously possible, maintaining consistent resistivity and hermeticity, and allowing for the use in harsh semiconductor processing conditions, including fluorine chemistries, with improved thermal uniformity and the potential for reworkability.
Implementation Method 1
A top surface layer adapted for Johnsen-Rahbek clamping at temperatures above 450C. The top surface layer has a bulk resistivity in the range of 10E9 to 10E11 ohm-cm over a temperature range of 500C to 750C.
Implementation Method 2
The top surface is joined to a lower surface with a hermetic braze layer able to withstand processing temperatures above 450C and processing chemistries.
Data Source
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AI summary
An electrostatic chuck with a top surface adapted for Johnsen-Rahbek clamping in the temperature range of 500C to 750C. The top surface may be sapphire. The top surface can be attached to the lower portion of the electrostatic chuck using a braze layer able to withstand corrosive processing chemistries. A method of manufacturing an electrostatic chuck with a top surface adapted for Johnsen-Rahbek clamping in the temperature range of 500C to 750C is provided.