Unipolar Electrostatic Chuck for Fast Dechucking of Small Workpieces
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Solution Overview
Problem
Existing electrostatic chucks face challenges in reliably chucking and dechucking a large number of small workpieces, are costly, and have limited versatility due to complex configurations and material limitations, particularly in applications beyond semiconductor manufacturing.
Innovation Solution
An electrostatic chuck with a unipolar structure featuring a dielectric body with volume resistivity of 10^9 to 10^13 Ω·cm and a dechucking mechanism as a grounded conductor counter electrode, simplifying the design and enabling reliable chucking and dechucking of conductive and non-conductive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a Coulomb force-type electrostatic chuck uses a dielectric layer with high dielectric constant and high dielectric breakdown strength (e.g., polyimide), then the attraction force is improved, but the dechucking time increases and the structure becomes more complex
Solution Approach 1:
The patent changes the volume resistivity parameter of the dielectric layer from high (10^14 Ω·cm or higher for Coulomb type) to intermediate (10^9 to 10^13 Ω·cm), creating a Johnsen-Rahbeck force-type electrostatic chuck. This parameter change enables faster dechucking while maintaining sufficient attraction force, resolving the contradiction between attraction force and dechucking time.
2Loss of time
If a Johnsen-Rahbeck force-type electrostatic chuck uses a dielectric layer with volume resistivity of 10^9 to 10^13 Ω·cm, then the dechucking time is reduced, but the attraction force decreases compared to Coulomb force type
Solution Approach 1:
The patent employs bipolar charging with periodic reversal of voltage polarity between the internal electrode and counter electrode. This periodic action generates alternating Johnsen-Rahbeck forces that maintain strong attraction during the charging phase while enabling rapid dechucking during the discharge phase, resolving the contradiction between attraction force and dechucking time.
3Adaptability or versatility
If existing electrostatic chucks use complex configurations with bipolar charging methods, then the versatility is improved for different materials, but the device complexity and cost increase
Solution Approach 1:
The patent creates a universal electrostatic chuck design that can handle both conductive and non-conductive workpieces through the combination of Johnsen-Rahbeck force mechanism and bipolar charging. The intermediate volume resistivity dielectric layer (10^9 to 10^13 Ω·cm) serves multiple functions: enabling charge transfer for Johnsen-Rahbeck force while maintaining insulation, and working with both conductive and non-conductive attraction targets, thus achieving versatility without excessive complexity.
4Force
If the dielectric layer thickness is reduced to increase attraction force, then the attraction force is improved, but the risk of dielectric breakdown increases
Solution Approach 1:
The patent selects dielectric materials with intermediate volume resistivity (10^9 to 10^13 Ω·cm) that provide an optimal balance between enabling sufficient charge transfer for Johnsen-Rahbeck force generation and maintaining adequate electrical insulation to prevent breakdown, even when the dielectric layer thickness is reduced to increase attraction force.
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 electrostatic chuck achieves efficient, cost-effective, and versatile chucking and dechucking of small workpieces without increasing equipment size or complexity, with improved reliability and reduced potential drop, even for conductive materials.
Implementation Method 1
A Johnsen-Rahbeck force-type electrostatic chuck refers to an electrostatic chuck that includes a dielectric layer with a volume resistivity in a range of 10 9 to 10 13 Ω·cm
Implementation Method 2
a very small current flows from a back surface of an dielectric layer in contact with the internal electrode due to a low volume resistivity, and reaches a front surface of the dielectric layer
Implementation Method 3
a Coulomb force-type electrostatic chuck refers to an electrostatic chuck that includes a dielectric layer having a volume resistivity of 10 14 Ω·cm or more
Implementation Method 4
the configuration is regarded as a so-called capacitor consisting of the first and second electrodes arranged in parallel and a dielectric between the first and second electrodes
Implementation Method 5
a gradient force-type electrostatic chuck adopts a bipolar charging method, and has a configuration in which positive (+) and negative (-) electrodes have a comb-like pattern and are alternately arranged
Implementation Method 6
While the object to be attracted is dielectrically polarized in the electric field by the gradient force, the object to be attracted is attracted to the electrode having a strong electric field intensity by Coulomb's law
Data Source
Figure 1~2(b)
Figure 3(a)~3(b)
Figure 4
AI summary
An electrostatic chuck 101 having a unipolar structure includes: a dielectric body 2 including an electrode 23 and a dielectric layer 25 that covers the electrode 23 and has a volume resistivity of 109 to 1013 Ω·cm; and a dechucking mechanism including a dechucking member 1 that is a conductor, in which the dechucking member 1 is connected to ground and is a counter electrode of the electrode 23.