Electrostatic Chuck Porous Ceramic Focus Ring Cooling
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Solution Overview
Problem
In semiconductor manufacturing, the yield of semiconductor wafers decreases due to non-uniform etching rates at the wafer edge portion, leading to increased temperature and heat accumulation at the focus ring, which affects chip yield and plasma processing efficiency.
Innovation Solution
An electrostatic chuck design with a ceramic dielectric substrate for wafer clamping and a less dense ceramic layer for focus ring clamping, allowing for increased gas supply and cooling efficiency, while maintaining low particle generation and plasma resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dense ceramic sintered body is used for the focus ring clamping surface, then particle generation is suppressed and plasma resistance is ensured, but heat accumulation increases and cooling efficiency decreases
Solution Approach 1:
The patent applies a porous ceramic layer as the clamping surface for the focus ring instead of a fully dense ceramic sintered body. The porous structure allows cooling gas to penetrate through the ceramic layer and directly contact the focus ring, significantly improving heat dissipation while maintaining adequate plasma resistance for reliable operation.
Solution Approach 2:
The patent implements different ceramic densities in different regions: the wafer clamping surface uses a dense ceramic sintered body for low particle generation, while the focus ring clamping surface uses a porous ceramic layer for efficient cooling. This local differentiation resolves the contradiction between plasma resistance and heat management.
2Temperature
If cooling gas flow rate is increased to improve thermal uniformity, then heat accumulation is reduced, but particle generation increases due to contact and sliding
Solution Approach 1:
The porous ceramic layer acts as a filter that allows cooling gas to pass through while trapping particles generated by gas contact and sliding. This enables effective cooling with higher gas flow rates without the harmful particle generation that would occur with conventional dense ceramic surfaces.
3Object-generated harmful factors
If dense ceramic is used throughout the electrostatic chuck, then particle generation is minimized, but cooling efficiency and thermal uniformity deteriorate
Solution Approach 1:
The patent differentiates the ceramic structure by region: dense ceramic for the wafer clamping area (minimizing particles) and porous ceramic for the focus ring clamping area (maximizing cooling). This local quality differentiation resolves the contradiction between particle generation and cooling efficiency.
Solution Approach 2:
The electrostatic chuck employs a composite structure combining dense ceramic and porous ceramic in different regions. This composite material approach allows the system to simultaneously achieve low particle generation in the wafer area and high cooling efficiency in the focus ring area.
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 enhances thermal uniformity and reduces particle generation, improving chip yield by efficiently cooling the focus ring and maintaining plasma resistance, thus addressing the issues of heat accumulation and non-uniform etching.
Implementation Method 1
The electrostatic chuck applies electrical power for electrostatic clamping to an embedded electrode and clamps a substrate such as a silicon wafer, etc., by an electrostatic force.
Implementation Method 2
a gas inlet path for introducing a cooling gas; a second electrostatic chuck part configured to clamp a focus ring on the second part, including a ceramic layer that includes at least one through-hole for introducing a cooling gas
Data Source
AI summary
An electrostatic chuck includes: an electrically-conductive base plate including a first part, a second part at an outer circumference of the first part, and a gas inlet path for introducing a cooling gas; a first electrostatic chuck part configured to clamp a wafer on the first part, including a ceramic dielectric substrate that includes an embedded first clamping electrode and at least one through-hole communicating with the gas inlet path; and a second electrostatic chuck part configured to clamp a focus ring on the second part, including a ceramic layer that includes at least one through-hole for introducing a cooling gas and that includes at least a first layer contacting the focus ring when the second electrostatic chuck part clamps the focus ring, in which the first layer is less dense than the ceramic dielectric substrate. Thereby, the electrostatic chuck can increase the device yield.