Dark Field Overlay Inspection for Semiconductor Alignment
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Solution Overview
Problem
Existing semiconductor fabrication processes face challenges in accurately measuring overlay mark errors due to wafer bending and deformation during film deposition and thermal treatment, making it difficult to inspect overlay marks on patterned layers using conventional tools.
Innovation Solution
A semiconductor fabrication system incorporating a network of tools including a film fabrication unit, lithography track unit, inspection unit, and control module, which utilizes both bright field (BF) and dark field (DF) inspection tools to perform pre- and post-film formation inspections, allowing for accurate overlay mark measurement and adjustment of film deposition conditions to maintain alignment and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If film layers are deposited over the patterned layer, then film formation is achieved, but overlay mark measurement becomes difficult
Solution Approach 1:
The patent performs overlay mark inspection using bright field mode before film deposition (pre-coating overlay inspection) and using dark field mode after film deposition (post-coating overlay inspection). This preliminary action of inspecting before film formation allows establishing a reference state, and the subsequent dark field inspection compensates for the difficulty of measuring overlay marks after film layers are deposited.
Solution Approach 2:
The patent changes the inspection parameter from bright field mode to dark field mode when film layers are present. Dark field mode provides enhanced contrast for overlay mark detection on top of deposited film layers, thereby maintaining measurement accuracy despite the presence of film layers that would otherwise obscure the marks.
2Productivity
If wafer bending and deformation occur during film deposition, then film formation process is completed, but overlay mark errors increase
Solution Approach 1:
The patent performs both pre-coating and post-coating overlay inspections to detect wafer bending and deformation caused by film deposition. By comparing the overlay mark positions before and after film formation, the system provides feedback on wafer deformation, enabling correction of alignment errors and maintaining manufacturing precision despite productivity demands.
Solution Approach 2:
The pre-coating overlay inspection establishes a baseline measurement before film deposition. This preliminary action allows subsequent comparison with post-coating measurements to quantify and correct for any wafer bending or deformation that occurs during the film formation process.
3Reliability
If thermal treatment is applied, then film processing is enhanced, but wafer deformation increases
Solution Approach 1:
The patent uses overlay mark inspection before and after thermal treatment to detect wafer deformation. This feedback mechanism allows the system to measure the extent of shape change caused by thermal processing, enabling subsequent alignment corrections to maintain film processing quality while accounting for thermal-induced deformation.
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 system enables precise overlay mark inspection and adjustment, improving image contrast and accuracy, thereby enhancing the alignment and overlay inspection processes, facilitating more reliable semiconductor fabrication.
Implementation Method 1
dark field (DF) inspection tool...improving image contrast and accuracy
Data Source
AI summary
The present disclosure provides a method for fabricating a semiconductor structure. The method comprises providing a substrate and a patterned layer formed on the substrate, one or more overlay marks being formed on the patterned layer; performing a pre-film-formation overlay inspection using a bright field (BF) inspection tool to receive a pre-film-formation data on the one or more overlay marks on the patterned layer; forming one or more layers on the patterned layer; performing a post-film-formation overlay inspection using a dark field (DF) inspection tool to receive a post-film-formation data on the one or more overlay marks underlying the one or more layers; and determining whether the pre-film-formation data matches the post-film-formation data.