Composite Electrostatic Rods for Ion Beam Stability
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Solution Overview
Problem
Conventional electrostatic lenses in ion implantation systems experience vibrations in graphite rods, leading to fluctuations in the electric field and ion beam non-uniformity, resulting in micro-striping on wafers, which reduces throughput and worsens with larger substrates.
Innovation Solution
The introduction of composite electrostatic rods with a metallic core and a graphite or low-contamination outer portion, increasing the natural frequency of the rods to reduce vibrations and stabilize the ion beam, thereby enhancing beam uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional graphite rods are used in electrostatic lenses, then low contamination is achieved, but vibrations occur leading to micro-striping and reduced throughput
Solution Approach 1:
The patent applies composite materials by combining a metallic core (providing structural strength and high natural frequency to reduce vibrations) with a graphite or low-contamination outer coating (providing low contamination properties). This composite structure resolves the contradiction by simultaneously achieving low contamination and reduced vibrations for improved throughput.
Solution Approach 2:
The patent applies local quality by assigning different material properties to different parts of the rod: the metallic core provides mechanical strength and vibration resistance, while the outer coating provides low contamination. Each part performs its specific function locally, resolving the contradiction between contamination control and vibration reduction.
2Object-generated harmful factors
If graphite rods are used in electrostatic lenses, then low contamination is achieved, but rod vibrations cause electric field fluctuations and ion beam non-uniformity
Solution Approach 1:
The composite rod structure combines a metallic core with high natural frequency (reducing vibrations) with an outer coating of low-contamination material. This resolves the contradiction by simultaneously maintaining beam uniformity through vibration reduction and minimizing contamination.
Solution Approach 2:
Different regions of the rod have different material properties: the core provides vibration stability for beam uniformity, while the outer surface provides low contamination. This local differentiation resolves the contradiction between reliability and contamination control.
3Productivity
If scan speed is increased to improve throughput, then productivity increases, but micro-striping worsens due to rod vibrations
Solution Approach 1:
The composite rod structure enables higher scan speeds by eliminating vibrations through the high natural frequency metallic core, while maintaining beam uniformity. This resolves the contradiction between productivity and manufacturing precision.
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 increased natural frequency of the composite electrostatic rods results in more rapid electric field fluctuations, averaging out ion beam non-uniformities and reducing micro-striping, allowing for higher scan speeds and improved substrate throughput.
Implementation Method 1
Conventional electrostatic lenses in ion implantation systems experience vibrations in graphite rods, leading to fluctuations in the electric field
Implementation Method 2
By applying different combinations of voltage potentials to the multiple electrodes, the D1 deceleration lens can manipulate ion energies and cause the ion beam to hit a target wafer at a desired energy
Implementation Method 3
The introduction of composite electrostatic rods with a metallic core and a graphite or low-contamination outer portion, increasing the natural frequency of the rods
Data Source
AI summary
A composite electrostatic rod may include a body comprising a length L and cross sectional area A. The body may include an outer portion comprising a first material, and a core comprising a second material different than the first material and surrounded by the outer portion, wherein a natural frequency of the composite electrostatic rod is greater than that of a graphite rod having the length L and cross sectional area A.