Metrology Test Structure with Auxiliary Patterns for Diffraction
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Solution Overview
Problem
Current optical metrology methods face challenges in accurately measuring geometric and material properties of microelectronic devices with small critical dimensions and complex structures, particularly due to sensitivity to both relevant and irrelevant parameters, leading to difficulties in monitoring parameters of interest with high precision.
Innovation Solution
A test structure is designed with a main pattern and a large-pitch auxiliary pattern, configured to produce non-zero order diffraction responses that are sensitive to changes in parameters of interest, allowing for highly sensitive and ultra-low background noise measurements using dark-field optical measurement modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical reflectometry is applied to measure geometric and material properties of microelectronic devices, then broadband light reflection analysis provides information about structure geometry and material properties, but measurement sensitivity to parameters of interest is limited due to sensitivity to both relevant and irrelevant parameters
Solution Approach 1:
The test structure is segmented into distinct functional components: a main pattern that corresponds to the sample pattern for measuring parameters of interest, and auxiliary patterns with large pitch that generate non-zero order diffraction. This segmentation allows the measurement system to isolate and enhance sensitivity to specific parameters while filtering out irrelevant information through dark-field detection of only non-zero diffraction orders.
Solution Approach 2:
The invention changes the structural parameters of the test structure by introducing auxiliary patterns with large pitch (significantly larger than the main pattern pitch). This parameter change enables the generation of non-zero order diffraction that is highly sensitive to the dimensions of the main pattern features, thereby enhancing measurement sensitivity through controlled modification of the test structure geometry.
2Measurement precision
If standard test structures are used for metrology measurements, then measurement of geometric parameters is performed, but accuracy is limited due to small effect of parameters on measured spectra
Solution Approach 1:
The auxiliary patterns serve as an intermediary element that mediates between the illumination light and the main pattern features. By introducing these large-pitch auxiliary structures, the system creates non-zero order diffraction that acts as an enhanced intermediary signal, amplifying the effect of main pattern parameter variations on the measured spectra and thereby improving measurement accuracy.
3Measurement precision
If dark-field measurement mode is used with the designed test structure, then ultra-low background noise measurement is achieved, but requires specific test structure configuration with large-pitch auxiliary patterns
Solution Approach 1:
The test structure with large-pitch auxiliary patterns serves multiple functions: it generates non-zero order diffraction for dark-field measurement, provides sensitivity enhancement for main pattern parameter measurement, and maintains compatibility with standard optical metrology systems. This multi-functionality justifies the increased structural complexity by delivering superior measurement performance across multiple objectives.
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 enhances the sensitivity of optical measurements to parameters of interest while minimizing sensitivity to less relevant parameters, enabling accurate monitoring of deviations in geometric and material properties, particularly useful in modern semiconductor manufacturing processes.
Implementation Method 1
a high order diffraction from the test structure can be directed onto the light collection path
Data Source
AI summary
A test structure is presented for use in metrology measurements of a sample pattern. The test structure comprises a main pattern, and one or more auxiliary patterns. The main pattern is formed by a plurality of main features extending along a first longitudinal axis and being spaced from one another along a second lateral axis. The one or more auxiliary patterns are formed by a plurality of auxiliary features associated with at least some of the main features such that a dimension of the auxiliary feature is in a predetermined relation with a dimension of the respective main feature. This provides that a change in a dimension of the auxiliary feature from a nominal value affects a change in non-zero order diffraction response from the test structure in a predetermined optical measurement scheme, and this change is indicative of a deviation in one or more parameters of the main pattern from nominal value thereof.