Wafer Surface Shape Detection Using Matrix Light Spot Scanning
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Solution Overview
Problem
Conventional differential interference optical systems for semiconductor wafer surface shape measurement face challenges in reducing restoration errors while maintaining resolution, as they can only observe phase plane shifts relative to shear direction, leading to increased errors with higher integration of random noise and reduced resolution with increased sampling pitch.
Innovation Solution
A surface shape detection device and method that includes a light spot scanning unit, interference light detection mechanism, and surface shape restoration processing unit, where the design distance is set larger than the quantization distance interval, allowing for reduced restoration errors while maintaining resolution by integrating interference light information at predetermined intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sampling pitch is increased to reduce the number of integration times and restoration error, then the restoration error is reduced, but the measurement resolution deteriorates
Solution Approach 1:
The patent transitions from one-dimensional sequential scanning to two-dimensional matrix array scanning. By using a matrix array of multiple light spots arranged in rows and columns, the system captures surface information across multiple spatial dimensions simultaneously. This dimensional expansion allows the sampling pitch to be increased while maintaining effective measurement resolution through the distributed spatial sampling of the matrix array.
Solution Approach 2:
The patent divides the scanning function into multiple independent light spots arranged in a matrix array. Instead of using a single scanning beam that requires fine sampling, the system segments the measurement task across multiple spatially distributed light spots. This segmentation allows each spot to operate at a larger effective pitch while the collective array maintains high measurement resolution through spatial distribution.
2Productivity
If the sampling pitch is increased to reduce integration times, then the productivity is improved, but the measurement precision deteriorates
Solution Approach 1:
The patent implements periodic scanning action where the matrix array of light spots systematically scans across the surface in a structured pattern. The scanning proceeds row by row or column by column, creating a periodic measurement sequence. This periodic action allows the system to use larger effective sampling pitches while maintaining measurement precision through the systematic, repeating scan pattern that covers the entire surface area efficiently.
Solution Approach 2:
By expanding from one-dimensional scanning to two-dimensional matrix array scanning, the system adds a spatial dimension to the measurement process. This dimensional change enables simultaneous multi-point measurement across the surface, effectively reducing the total integration time required while maintaining measurement precision through the distributed spatial sampling capability of the matrix array.
3Productivity
If multiple light spots are used to scan the surface, then the productivity is improved, but the device complexity increases
Solution Approach 1:
The patent creates multiple copies of the light source and optical path by using a matrix array of light spots. Instead of using a single complex scanning system, the invention replicates the basic light-spot measurement unit across multiple positions in a matrix configuration. This copying approach increases productivity by enabling parallel measurement at multiple points while keeping each individual light spot unit relatively simple in structure.
Solution Approach 2:
The matrix array of light spots serves multiple functions simultaneously: it provides parallel scanning capability, enables area-wide surface measurement, and maintains the differential interference measurement function at each spot. This multi-functionality increases productivity by combining what would otherwise require separate systems into a single integrated matrix array structure.
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 solution effectively reduces restoration errors of wafer surface shape detection while maintaining measurement resolution, improving accuracy and reliability in surface shape analysis.
Implementation Method 1
an interference light detection mechanism that detects interference light of light obtained by scanning a surface of an inspection target with a plurality of the light spots separated by a predetermined design distance
Data Source
AI summary
A surface shape detection device using differential interference optics achieves restoration error reduction of a surface shape while maintaining resolution. The surface shape detection device includes: a light spot scanning unit such as a wafer rotation direction drive unit that scans a wafer surface with a light spot; an interference light detection mechanism such as a differential interference optical system that detects interference light of light obtained by scanning a surface of an inspection target with a plurality of the light spots separated by a predetermined design distance; and a surface shape restoration processing unit such as a wafer surface shape restoration unit that samples, at a predetermined quantization time interval, and calculates information of the interference light, and performs restoration processing on a surface shape of the wafer, in which the predetermined design distance is larger than a quantization distance interval corresponding to the predetermined quantization time interval.