Focused Ion Beam Movable Sealing Valve Vacuum Segmentation
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Solution Overview
Problem
Charged particle beam lithography systems face increased takt time due to the need to move and reposition the vacuum envelope machine, causing vacuum level fluctuations and potential damage to semiconductor wafers during alignment and processing.
Innovation Solution
A focused ion beam system with a movable sealing valve and differential pumping device that maintains a high vacuum environment, using a metallic mesh fiducial alignment mark and current sensor to align and adjust the ion beam without exposing the target substrate, minimizing takt time and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the vacuum envelope machine is moved away from the target surface to replace the semiconductor wafer, then the semiconductor wafer can be replaced, but the gap between the tip of the beam emitter and the target surface cannot be kept at a high vacuum level, requiring time to move and regulate pressure
Solution Approach 1:
The vacuum system is segmented into two independent chambers: the first vacuum chamber housing the beam emitter and maintained at high vacuum continuously, and the second vacuum chamber for wafer handling. This segmentation allows wafer replacement in the second chamber without affecting the vacuum level in the first chamber, eliminating the need to move the vacuum envelope machine and maintaining continuous high vacuum at the beam emitter tip.
Solution Approach 2:
A transfer mechanism acts as an intermediary between the first and second vacuum chambers, allowing semiconductor wafers to be transferred from the wafer handling area to the beam emitter area without breaking the vacuum seal. This intermediary structure enables wafer replacement while maintaining continuous high vacuum in the beam emitter chamber.
2Measurement precision
If the charged particle beam lithography system is moved close to the semiconductor wafer to align the ion beam, then alignment can be performed, but the takt time required to complete processing increases due to repeated moving and repositioning
Solution Approach 1:
Alignment marks are pre-formed on the semiconductor wafer before it is placed in the processing position. The beam emitter is pre-positioned in a fixed location within the first vacuum chamber. This preliminary preparation eliminates the need for repeated movement and repositioning during alignment, allowing quick alignment by simply directing the beam at the pre-positioned marks.
Solution Approach 2:
The system employs dynamic positioning of the semiconductor wafer rather than moving the beam emitter. The wafer can be quickly positioned and repositioned in the second vacuum chamber while the beam emitter remains stationary in the first chamber, reducing mechanical movement time and maintaining continuous vacuum.
3Loss of time
If direct exposure of the semiconductor wafer to the charged particle beam is performed for alignment, then alignment information can be obtained quickly, but the semiconductor wafer will be damaged
Solution Approach 1:
Alignment marks are formed on the semiconductor wafer itself, serving as an intermediary target for alignment. The beam emitter directs the charged particle beam at these pre-formed marks on the wafer edge or surface, obtaining alignment information without requiring separate fiducial marks on external alignment pads. This allows direct wafer alignment while using minimal beam exposure that does not damage the wafer.
Solution Approach 2:
Only a small portion of the semiconductor wafer (the alignment marks area) is exposed to the charged particle beam during alignment, rather than the entire wafer surface. This partial exposure provides sufficient alignment information while minimizing the total beam dose and preventing damage to the functional areas of the wafer.
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 system significantly reduces processing time by maintaining a stable vacuum and preventing substrate damage during ion beam alignment and adjustments, enhancing the efficiency and accuracy of semiconductor wafer processing.
Implementation Method 1
a beam emitter which includes a focused ion beam optical system which controls an ion beam as produced by an ion source and emits the ion beam into an inner space
Implementation Method 2
The inner space is evacuated in a vacuum. A movable sealing valve is provided which selectively opens or closes the aperture
Data Source
AI summary
A focused ion beam system includes a beam emitter and an aperture. The beam emitter is equipped with a focused ion beam optical system which works to control an ion beam, as produced by an ion source, and emit the ion beam into an inner space. The aperture communicates with the inner space to permit the ion beam, as emitted from the beam emitter, to pass therethrough, thereby having a target substrate exposed to the ion beam. The inner space is evacuated in a vacuum. A movable sealing valve is provided which selectively opens or closes the aperture.