Test Structure Auxiliary Pattern Asymmetry Metrology
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Solution Overview
Problem
Accurate characterization of geometrical and material properties in microelectronic devices becomes increasingly challenging as critical dimensions shrink and devices become more complex, with conventional metrology methods struggling to detect subtle asymmetries and misalignments in patterned structures.
Innovation Solution
A test structure with an auxiliary pattern is designed to induce asymmetry, enhancing the sensitivity of optical measurements by creating a link between pattern parameters and symmetry breaking, allowing for the detection of misalignments and deviations in patterned layers through optical response analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metrology methods are used for measuring pattern parameters, then the measurement process is simple, but the measurement precision is insufficient for detecting subtle asymmetries and misalignments
Solution Approach 1:
The patent applies asymmetry by introducing an auxiliary pattern that breaks the symmetry of the test structure. This auxiliary pattern is specifically designed to create asymmetric optical responses when certain pattern parameters (such as overlay accuracy or critical dimensions) deviate from target values. The asymmetric design enables the measurement system to detect subtle misalignments and asymmetries that would be invisible in a perfectly symmetric structure, thereby resolving the contradiction between measurement precision and device complexity.
2Productivity
If the critical dimensions are reduced to increase device density, then the productivity increases, but the difficulty of detecting and measuring pattern parameters increases
Solution Approach 1:
The patent uses an auxiliary pattern as an intermediary element that mediates between the small-scale pattern features and the optical measurement system. This auxiliary pattern acts as a magnifier or amplifier, converting subtle variations in small critical dimensions into larger, more detectable optical signal changes. By introducing this intermediary structure, the system can accurately measure nanoscale features without requiring direct high-resolution imaging, thus resolving the contradiction between increased device density and measurement difficulty.
3Ease of operation
If optical reflectometry is applied to repeating arrays of identical elements, then the measurement process is straightforward, but the sensitivity to asymmetry and misalignment is reduced
Solution Approach 1:
The patent deliberately introduces asymmetry through the auxiliary pattern while maintaining the overall repeating array structure. The auxiliary pattern is positioned and designed such that it creates asymmetric optical responses only when specific parameters (such as overlay accuracy or critical dimensions) are out of specification. This approach preserves the ease of measuring repeating arrays while simultaneously enhancing the sensitivity to asymmetry and misalignment, as the asymmetric auxiliary pattern acts as a built-in indicator for these deviations.
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 approach significantly improves the accuracy of metrology measurements by differentiating between symmetric and asymmetric conditions, enabling precise control of patterning processes and identifying errors in complex microelectronic devices.
Implementation Method 1
broadband light is shone on a sample and collected after being reflected from it
Implementation Method 2
analyzing the reflectance of different wavelengths and in addition polarization components of the incident light
Data Source
AI summary
A test structure for use in metrology measurements of a sample pattern formed by periodicity of unit cells, each formed of pattern features arranged in a spaced-apart relationship along a pattern axis, the test structure having a test pattern, which is formed by a main pattern which includes main pattern features of one or more of the unit cells and has a symmetry plane, and a predetermined auxiliary pattern including at least two spaced apart auxiliary features located within at least some of those features of the main pattern, parameters of which are to be controlled during metrology measurements.