Wafer Stage Alignment Using Optical Scans Before Ion Exposure
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Solution Overview
Problem
Semiconductor wafers often experience misalignments during ion exposure processes, leading to uniformity issues, process variations, and device defects due to uncorrected x-direction, y-direction, and rotational misalignments with the wafer holder.
Innovation Solution
A method and apparatus for detecting and correcting wafer misalignments using light emitter/detector pairs and rotational sensors to adjust the wafer stage, ensuring precise alignment before ion exposure, including x-direction, y-direction, and rotational corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wafer positioning is not corrected, then the ion exposure process can proceed without alignment adjustments, but within-wafer uniformity deteriorates and device defects increase
Solution Approach 1:
The patent performs alignment scans and detects misalignments in x-direction, y-direction, and rotation before the ion exposure process begins. The wafer stage is adjusted to correct these misalignments preliminarily, ensuring proper positioning before exposure occurs. This preliminary correction action prevents uniformity issues during the actual ion exposure process.
Solution Approach 2:
The patent employs light emitter/detector pairs to scan the wafer and detect misalignments. The detection system provides feedback about positional and rotational deviations, which are then used to adjust the wafer stage. This feedback loop continuously monitors and corrects alignment, maintaining within-wafer uniformity throughout the ion exposure process.
2Measurement precision
If multiple alignment scans are performed to detect misalignments, then positioning accuracy improves, but process time increases
Solution Approach 1:
The alignment detection process is segmented into three independent scan directions: x-direction scan, y-direction scan, and rotation scan. Each scan focuses on detecting misalignment in one specific dimension using dedicated light emitter/detector pairs. This segmentation allows for efficient, targeted measurement of misalignments without requiring a single complex comprehensive scan, improving detection accuracy while managing time effectively.
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
Improves within-wafer uniformity, reduces wafer-to-wafer process variations, and enhances device performance by ensuring uniform ion exposure across the wafer surface.
Implementation Method 1
x-direction light emitter/detector pair and a y-direction light emitter/detector pair
Implementation Method 2
rotational light emitter/detector pair configured to perform a rotational scan about a central axis of the ion beam
Implementation Method 3
ion beam generator configured to generate an ion beam
Data Source
AI summary
A method of correcting a misalignment of a wafer on a wafer holder and an apparatus for performing the same are disclosed. In an embodiment, a semiconductor alignment apparatus includes a wafer stage; a wafer holder over the wafer stage; a first position detector configured to detect an alignment of a wafer over the wafer holder in a first direction; a second position detector configured to detect an alignment of the wafer over the wafer holder in a second direction; and a rotational detector configured to detect a rotational alignment of the wafer over the wafer holder.