Scatterometry Target With Defect Features for Enhanced Sensitivity

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing scatterometry targets have limited sensitivity, which is inadequate for the increasing precision demands of shrinking feature sizes in lithographic processes, as they rely on uniform periodic features that degrade with introduced defects.

Innovation Solution

Incorporating intentionally introduced defects into a photonic crystal lattice of periodically spaced metrology features to enhance sensitivity to specific parameters of interest, leveraging the concept of photonic crystals to create 'allowed' states within the photonic bandgap, thereby increasing measurement accuracy and sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If uniform periodic features are used in scatterometry targets, then the target structure is simple and easy to manufacture, but the measurement sensitivity is limited

Engineering Contradiction:

Improvemeasurement sensitivityVSAvoidtarget structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by introducing defects at specific locations within the photonic crystal lattice. These localized defect features (such as missing holes, different sized holes, or shifted positions) create enhanced sensitivity to specific parameters of interest while the majority of the target maintains the simple periodic structure. This allows different regions of the target to serve different functions: the periodic regions provide overall structural stability and the defect regions provide enhanced measurement sensitivity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs asymmetry by intentionally introducing defect features that break the perfect periodicity of the photonic crystal lattice. These asymmetric defect features (such as holes of different sizes, missing features, or displaced elements) create unique optical responses that are highly sensitive to specific parameters. The asymmetric defects generate distinctive diffraction patterns that can be used to measure parameters with enhanced precision compared to uniform periodic structures.

Inventive Principle:

Principle #4Asymmetry

2Measurement precision

If larger feature sizes are used in scatterometry targets, then measurement sensitivity is improved, but the target cannot keep pace with shrinking feature sizes in lithographic processes

Engineering Contradiction:

Improvesensitivity to parameter of interestVSAvoidadaptability to shrinking feature sizes

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent utilizes parameter changes by varying the characteristics of defect features within the photonic crystal lattice. By changing parameters such as the size, shape, position, or type of defect features, the target can be optimized to measure different parameters of interest with high sensitivity. The defect features can be designed with specific dimensional parameters that enhance sensitivity to critical dimensions, overlay errors, or other lithographic parameters, allowing the target to adapt to different measurement needs and shrinking feature sizes.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If periodic features are used to maintain uniformity, then manufacturing is easier, but sensitivity to specific parameters of interest is degraded

Engineering Contradiction:

Improvesensitivity to parameter of interestVSAvoidtarget fabrication ease

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent applies segmentation by dividing the target into two functional segments: a large array of uniform periodic features that are easy to manufacture, and a smaller number of defect features with enhanced sensitivity properties. The periodic features can be fabricated using standard lithographic processes, while the defect features (though requiring additional processing steps) are localized and limited in number. This segmentation allows the majority of the target to maintain manufacturing simplicity while the defect regions provide the necessary measurement sensitivity.

Inventive Principle:

Principle #1Segmentation

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 introduction of defects in the target design significantly enhances sensitivity to parameters such as feature size, shape, and displacement, achieving improved accuracy and de-correlating undesirable process variations, surpassing the limitations of traditional targets.

Implementation Method 1

leveraging the concept of photonic crystals to create 'allowed' states within the photonic bandgap, thereby increasing measurement accuracy and sensitivity

Methodology Applied

Scientific EffectPhotonic bandgap: Photonic Crystal

Data Source

PatentUS7940386B1Scatterometry target employing non-periodic defect features to enhance or optimize target sensitivity to a parameter of interest

Publication Date: 2011.05.10 KLA CORP

AI summary

Embodiments of the invention include a target having a lattice of many periodically spaced and uniformly configured metrology features arranged in an array pattern over a target region. The lattice includes at least one defect region in the lattice, the defect region includes at least one intentionally introduced defect metrology feature. The defect feature configured to enable increased sensitivity of the target to a selected parameter of interest. The invention further encompassing associated methods of implementing the target and evaluating the parameter of interest.