Phase Filter Design for Buried Defect Detection in Multilayer Stacks
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Solution Overview
Problem
Current semiconductor wafer inspection systems face challenges in detecting defects within multilayer structures, such as 3D NAND and DRAM, as these defects are often buried and difficult to identify without damaging the device, leading to reduced sensitivity and increased nuisance rates in optical inspections.
Innovation Solution
A phase filter is designed using electromagnetic simulations, such as Rigorous Couple Wave Analysis (RCWA), to enhance defect signals by compensating for the adverse effects of multilayer stacks, allowing for non-destructive detection of defects within these complex structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical inspection is performed on multilayer structures, then defect detection capability is required, but sensitivity is reduced and nuisance rates increase due to buried defects being difficult to detect
Solution Approach 1:
A phase filter is introduced as an intermediary component in the optical inspection system. The phase filter modifies the phase of scattered light waves to enhance the contrast between defect signals and the multilayer stack background, enabling improved detection sensitivity for buried defects without increasing nuisance rates
Solution Approach 2:
The patent changes the phase parameter of the optical waves scattered from the multilayer structure by using a phase filter. This parameter transformation converts the difficult-to-detect scattered light into enhanced defect signals that can be clearly distinguished from the complex multilayer background
2Measurement precision
If electromagnetic simulation is used to design phase filter, then defect signal enhancement is achieved, but computational complexity and design time increase
Solution Approach 1:
Electromagnetic simulations are performed in advance during the phase filter design stage to predict and optimize the phase filter's ability to enhance defect signals. By conducting these simulations beforehand, the phase filter is pre-optimized for specific multilayer stack configurations, avoiding iterative adjustments during actual inspection operations
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 phase filter significantly improves defect detection sensitivity, simplifies image analysis, and reduces nuisance rates by constructing and optimizing phase values at the collection pupil, enabling accurate identification and classification of buried defects.
Implementation Method 1
a design of a phase filter having a plurality of positions for changing a plurality of phases at a plurality of corresponding positions within the collection pupil of the optical inspection tool is determined so as to compensate for an adverse effect of the particular multilayer stack on obtaining a defect signal
Implementation Method 2
an electromagnetic simulation is performed of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system
Data Source
AI summary
Disclosed are methods and apparatus for facilitating defect detection in a multilayer stack. The method includes selection of a set of structure parameters for modeling a particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for an optical inspection system. Based on the set of structure and operating parameters, an electromagnetic simulation is performed of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system. Based on the simulated waves at the collection pupil, a design of a phase filter having a plurality of positions for changing a plurality of phases within a plurality of corresponding positions of the collection pupil of the optical inspection tool is determined so as to compensate for an adverse effect of the particular multilayer stack on obtaining a defect signal for the defect within such particular multilayer stack and/or to enhance such defect signal. The design of the phase filter is then provided for fabrication or configuration of a phase filter inserted within the optical inspection system for detection of defects in multilayer stacks with the same structure parameters as the particular multilayer stack. Methods and systems for inspecting a multilayer stack for defects are also disclosed.