Conductive Sample Holder for Electron Beam Exposure Charge-Up
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Solution Overview
Problem
Conventional electron beam exposure apparatuses face challenges in accurately exposing wafers of various shapes and sizes due to charge-up phenomena caused by electric charges accumulating on the electrostatic chuck, leading to reduced exposure accuracy and the need for large-scale modifications to accommodate different sample sizes.
Innovation Solution
A sample holder with a conductive circumferential portion exposed to the outside is used between the wafer and the electrostatic chuck, allowing electric charges to be released and preventing charge-up, enabling accurate electron beam exposure on wafers smaller than the chuck without modifying the apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrostatic chuck size is reduced to match smaller wafers, then charge-up phenomenon is prevented, but the apparatus cannot accommodate larger wafers
Solution Approach 1:
The electrostatic chuck system is segmented into a fixed main chuck and a removable sample holder. The sample holder can be exchanged to match different wafer sizes, while the main chuck remains constant. This segmentation allows the system to maintain optimal electrostatic field coverage for each wafer size without requiring modification of the entire apparatus.
Solution Approach 2:
The sample holder is designed with multi-functionality to serve different purposes: it provides electrostatic attraction for small wafers, acts as a support structure for various wafer sizes, and includes conductive portions that prevent charge-up. This universal design allows a single holder structure to accommodate multiple wafer sizes and configurations.
2Reliability
If different electrostatic chucks are used for different wafer sizes, then exposure accuracy is maintained, but apparatus modification is required
Solution Approach 1:
The system separates the electrostatic chuck into a permanent main chuck and removable sample holders. Only the sample holders need to be changed for different wafer sizes, not the entire electrostatic chuck assembly. This reduces apparatus modification complexity while maintaining exposure accuracy.
Solution Approach 2:
The sample holder acts as an intermediary between the main electrostatic chuck and the wafer. It transfers the electrostatic attraction force from the main chuck to the wafer, allowing the main chuck to remain fixed while adapting to different wafer sizes through holder exchange.
3Adaptability or versatility
If the dielectric is exposed to the outside around the wafer, then charge-up phenomenon occurs, but reducing chuck size limits wafer size accommodation
Solution Approach 1:
The sample holder is designed with different local properties: the central portion is made of dielectric material to provide electrostatic attraction, while the circumferential portion is made of conductive material to prevent charge-up. This local differentiation allows the holder to simultaneously enable small wafer exposure and prevent harmful charge-up effects.
Solution Approach 2:
The conductive circumferential portion converts the potentially harmful charge-up effect into a beneficial charge dissipation mechanism. By providing a conductive path at the edges, accumulated charges are safely discharged, preventing the charge-up phenomenon that would otherwise occur when dielectric is exposed around smaller wafers.
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 solution allows for precise electron beam lithography on wafers of various shapes without requiring extensive modifications to the electron beam exposure apparatus, maintaining exposure accuracy across different sample sizes.
Implementation Method 1
An electron beam exposure apparatus fixes a wafer to be exposed and corrects its flatness by electrostatically attracting and hold the wafer with an electrostatic chuck
Implementation Method 2
electric charges generated in the irradiation with the electron beam can be released to the outside by way of the conductive material, so that a charge-up phenomenon can be prevented
Data Source
AI summary
A sample holder to be disposed between an electrostatic chuck and a sample smaller than the upper surface of the electrostatic chuck is provided, the sample holder including: a base plate formed in the same size as the upper surface of the electrostatic chuck; a sample placement portion located on the upper surface of the base plate, and designed to place the sample thereon; and a circumferential portion being a portion of the upper surface of the base plate other than the sample placement portion, and having a conductive material exposed to the outside.