Showerhead Electrode Backing Member Thermal Expansion Alignment
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Solution Overview
Problem
Plasma processing apparatuses face challenges in controlling particulate contamination during semiconductor fabrication, particularly due to the misalignment of gas passages in components with different thermal expansion coefficients, leading to defects and reduced yield.
Innovation Solution
A showerhead electrode assembly with a metallic backing member and silicon inner electrode, where gas passages are misaligned at ambient temperature but become concentric at elevated processing temperatures, and the use of an elastomeric bonding material with varying thickness to accommodate thermal stresses, along with a radially larger aluminum through holes to minimize exposure to plasma and reduce particle generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If gas passages in the backing member are made larger to reduce plasma exposure, then particle generation is reduced, but misalignment with electrode passages worsens at ambient temperature
Solution Approach 1:
The patent utilizes differential thermal expansion between the silicon inner electrode and aluminum backing member to achieve passage concentricity at operating temperature. The aluminum backing member has a higher coefficient of thermal expansion than silicon, causing it to expand more when heated, which compensates for the initial misalignment and brings the passages into concentric alignment during plasma processing operations.
2Object-generated harmful factors
If passages in the backing member are made radially larger, then exposure to plasma environment is minimized, but thermal stress in bonding material increases
Solution Approach 1:
The patent employs an elastomeric bonding material with non-uniform thickness distribution to locally accommodate thermal stresses. The bonding material is thicker in regions experiencing higher thermal stress, providing enhanced stress distribution and accommodation in those specific areas while maintaining the overall structural integrity and minimizing plasma exposure through the radially larger passages.
3Manufacturing precision
If misalignment at ambient temperature is increased, then concentricity at elevated temperature is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates pre-calculated misalignment of gas passages during the manufacturing process. The passages in the aluminum backing member are intentionally positioned with a specific offset from concentricity at ambient temperature, based on thermal expansion calculations. This preliminary positioning ensures that when the assembly is heated to operating temperature, the differential thermal expansion automatically brings the passages into concentric alignment, eliminating the need for complex real-time adjustment mechanisms.
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
This configuration reduces the generation of aluminum fluoride particles and minimizes defects, enhancing the yield and reliability of semiconductor processing by maintaining concentricity and reducing shear stresses in the bonding material.
Implementation Method 1
The first member includes a plasma-exposed surface and a first coefficient of thermal expansion. The second member attached to the first member includes a plurality of second through openings corresponding to the openings in the first member, the second member and having a second coefficient of thermal expansion greater than the first coefficient of thermal expansion. The first and second openings are misaligned at ambient temperature and the openings in the first member and the openings in the second member are substantially concentric when heated to an elevated processing temperature.
Data Source
AI summary
Components of a plasma processing apparatus includes a backing member with gas passages attached to an upper electrode with gas passages. To compensate for the differences in coefficient of thermal expansion between the metallic backing member and upper electrode, the gas passages are positioned and sized such that they are misaligned at ambient temperature and substantially concentric at an elevated processing temperature. Non-uniform shear stresses can be generated in the elastomeric bonding material, due to the thermal expansion. Shear stresses can either be accommodated by applying an elastomeric bonding material of varying thickness or using a backing member comprising of multiple pieces.