Wafer Surface Inspection Using External Retroreflector Segmentation
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Solution Overview
Problem
Existing methods for determining the distance and inclination of a wafer's surface during inspection are limited by the need for large optical components and space, which interferes with the measurement process and restricts accurate positioning.
Innovation Solution
A method using two radiation sources and detectors positioned outside the inspection range, emitting collimated beams at a flat angle to the surface, allowing simultaneous determination of height and inclination without interfering with the inspection optics, by analyzing the shift of reflected beams on a spatially resolving detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical components with large opening angle are used for inspection, then measurement precision is improved, but device complexity and space requirements increase
Solution Approach 1:
The inspection system is divided into two independent parts: the inspection assembly (with its optical components) and the position determination assembly (with radiation source and detector). This segmentation allows each part to be optimized independently - the inspection assembly can use large aperture components for high precision while the position determination assembly uses a separate, simpler configuration that does not interfere with the inspection range.
Solution Approach 2:
A retroreflector is introduced as an intermediary element to enhance the position determination capability. The retroreflector receives radiation from the source and directs it back toward the detector, amplifying the signal and improving measurement precision without requiring the radiation source or detector to be positioned closer to the sample surface, thus avoiding interference with the inspection optics.
2Measurement precision
If additional optical components are inserted into the inspection path for position determination, then measurement precision is improved, but reliability deteriorates due to interference with measurement
Solution Approach 1:
The system separates position determination functions from the inspection path. The radiation source and detector are positioned outside the inspection range, with the retroreflector serving as an intermediary to reflect radiation back through the inspection assembly. This segmentation ensures that the position determination components do not interfere with the inspection measurement while still providing accurate position information.
Solution Approach 2:
The retroreflector acts as an intermediary that enables position determination without requiring direct placement of radiation sources or detectors in the inspection path. By reflecting radiation back through the inspection assembly, it provides a clean signal path that does not interfere with the inspection optics or measurement process.
3Measurement precision
If radiation source and detector are positioned close to the sample for position determination, then measurement precision is improved, but device complexity increases due to space constraints
Solution Approach 1:
The retroreflector serves as an intermediary that allows the radiation source and detector to be positioned at a distance from the sample while maintaining measurement precision. The retroreflector reflects radiation back through the inspection assembly, effectively extending the measurement range without requiring the source and detector to occupy space close to the sample surface, thus reducing the overall footprint of the inspection assembly.
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
Enables precise and non-invasive measurement of surface position, reducing interference and increasing resolution, allowing for accurate control of surface height and inclination without additional optical components in the inspection path.
Implementation Method 1
detecting radiation from the radiation source reflected by the inspected surface with a spatially resolving detector
Data Source
AI summary
The invention relates to an arrangement for analyzing an at least partially reflective surface of a wafer or other objects, containing a holder for holding the object; an inspection arrangement arranged at a distance in the region in front of the surface to be analyzed; and a measurement arrangement for determining the distance and/or inclination of the surface for the inspection arrangement; characterized be a radiation source, the radiation of which is directed towards the surface to be analyzed at an angle; and a spatially resolving detector for receiving the radiation from the radiation source that is reflected from the surface to be analyzed, wherein the radiation source and the detector are arranged outside the region necessary for the inspection between the inspection arrangement and the surface to be analyzed.