CuA Optical Metrology Using CMOS Effective Medium Modeling
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Solution Overview
Problem
Existing optical metrology techniques struggle to accurately characterize CMOS under array (CuA) structures due to interference from underlying CMOS circuitry, leading to inaccurate measurements of memory array structures, especially as dimensions shrink and device complexity increases.
Innovation Solution
A multi-step modeling process is employed to decouple dispersion parameters of the CMOS effective medium from memory array structures, using accurate reference data to fix geometric parameters, followed by updating a measurement model to include these dispersion parameters, enabling accurate metrology measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical metrology is performed on CuA structures, then memory array structure measurements are obtained, but underlying CMOS circuitry interferes with measurement accuracy
Solution Approach 1:
The measurement model is segmented into distinct components: memory array structure parameters and CMOS effective medium parameters. This segmentation allows independent optimization and fitting of each component, reducing the interference effect of CMOS circuitry on memory array measurements by treating them as separate measurable entities within the composite structure.
Solution Approach 2:
An effective medium model is introduced as an intermediary representation of the underlying CMOS circuitry. This effective medium layer acts as a mediator that captures the collective optical response of complex CMOS structures without requiring detailed knowledge of individual CMOS components, thereby enabling accurate memory array measurements while accounting for CMOS interference.
2Measurement precision
If multi-step modeling process is used to decouple parameters, then measurement accuracy is improved, but model complexity increases
Solution Approach 1:
The multi-step modeling process performs preliminary actions by first fitting the memory array structure parameters independently, then subsequently fitting the CMOS effective medium parameters. This preliminary separation of fitting steps simplifies the overall optimization problem compared to simultaneous fitting of all parameters, reducing computational complexity while maintaining measurement accuracy.
Solution Approach 2:
The methodology skips intermediate detailed modeling steps by directly fitting effective medium parameters rather than modeling individual CMOS components. This rushing through the complex CMOS internal structure allows the model to bypass unnecessary computational steps while still capturing the essential optical response for measurement accuracy.
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 allows for isolated and accurate measurements of memory array structures by breaking undesirable correlations between CMOS and memory array parameters, enhancing measurement accuracy and robustness.
Implementation Method 1
The first measurement model incorporates a model of light-matter interaction with the CuA devices
Data Source
AI summary
A system may include a controller including one or more processors configured to execute program instructions causing the one or more processors to implement a measurement recipe by: receiving optical measurement data for training samples including complementary metal-oxide-semiconductor (CMOS) under array (CuA) devices, wherein the CuA devices include CMOS structures disposed beneath periodic memory array structures; developing a first measurement model for determining measurements of the CuA devices based on the optical measurement data, wherein the CMOS structures are modeled as a CMOS effective medium in the first measurement model; receiving reference data for the training samples; updating the first measurement model to a second measurement model that includes the values of dispersion parameters of the CMOS effective medium; receiving optical measurement data for test samples including CuA devices; and generating values of the one or more metrology measurements of the CuA devices based on the second measurement model.