Al-SiC Electrostatic Chuck Structure for Thermal Uniformity
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Solution Overview
Problem
The mismatch in coefficient of thermal expansion (CTE) between aluminum-based and ceramic materials in electrostatic chucks used in plasma processing chambers leads to mechanical strain, limited thermal operating windows, and thermal nonuniformity, resulting in gaps that can create parasitic plasma and affect wafer temperature uniformity.
Innovation Solution
An electrostatic chuck system utilizing an aluminum silicon carbide (Al—SiC) base plate, which balances low CTE with high thermal conductivity, reducing bonding strain and improving thermal uniformity, and incorporating a ceramic plate bonded with a high thermal conductivity adhesive layer, along with a quartz or ceramic edge ring for reduced gap formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aluminum-based base plate is used, then thermal conductivity is high and manufacturing cost is low, but coefficient of thermal expansion mismatch with ceramic causes mechanical strain and thermal nonuniformity
Solution Approach 1:
The patent applies composite materials by using Al-SiC (aluminum-silicon carbide) as the base plate material instead of pure aluminum. This composite provides a balanced coefficient of thermal expansion that matches the ceramic plate better while maintaining high thermal conductivity, thereby reducing mechanical strain and thermal nonuniformity during thermal cycling.
2Ease of manufacture
If aluminum base plate is used, then manufacturing cost is low, but thermal nonuniformity affects wafer temperature uniformity
Solution Approach 1:
The Al-SiC composite base plate maintains the cost-effectiveness and manufacturability of aluminum while improving thermal uniformity across the wafer surface through its balanced thermal expansion properties that prevent bonding layer failure and hot spot formation.
3Device complexity
If ceramic plate is bonded to aluminum base plate, then electrostatic chuck structure is formed, but bonding layer undergoes significant mechanical strain at low temperatures
Solution Approach 1:
The patent changes the material parameter (coefficient of thermal expansion) of the base plate from pure aluminum to Al-SiC composite. This parameter change reduces the CTE mismatch with the ceramic plate, thereby significantly reducing mechanical strain on the bonding layer during thermal cycling between high and low temperatures.
4Temperature
If aluminum base plate with high CTE is used, then thermal conductivity is high, but gaps form between base plate and edge ring at some temperatures
Solution Approach 1:
The patent changes the CTE parameter of the base plate material to match the edge ring material (both Al-SiC and edge ring have similar CTE values). This parameter matching prevents gap formation between the base plate and edge ring during thermal cycling, eliminating parasitic plasma generation while maintaining high thermal conductivity.
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 Al—SiC base plate expands the thermal operating range, reduces mechanical strain, and enhances thermal uniformity across the wafer surface, allowing lower plasma processing temperatures with reduced etch byproduct deposition and plasma discharge.
Implementation Method 1
A bonding layer bonds the ceramic plate to the base plate
Implementation Method 2
The mismatch in coefficient of thermal expansion (CTE) between aluminum-based and ceramic materials
Implementation Method 3
high thermal conductivity, reducing bonding strain and improving thermal uniformity
Implementation Method 4
electrostatic chucks are used to support substrates being processed
Data Source
AI summary
An electrostatic chuck system for a plasma processing chamber is provided. A base plate comprising Al—SiC is provided. A ceramic plate is disposed over the base plate. A bonding layer bonds the ceramic plate to the base plate.