Absolute Overlay Reference for Multi-Layer Wafer Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor fabrication methods face challenges in maintaining accurate pattern alignment due to the destruction or coverage of alignment marks during film deposition and etching processes, leading to overlay errors that accumulate with each layer, resulting in poor device performance.
Innovation Solution
A method involving a reference pattern independent of the wafer's working surface, which is used to align subsequent patterns by capturing images and performing image analysis to calculate overlay values, allowing for precise alignment without relying on conventional alignment marks. This reference pattern can be positioned below or within the wafer and is unaffected by lithographic processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment marks are used on the wafer surface, then alignment can be performed for pattern placement, but the alignment marks are covered or removed during film deposition and etching processes, causing overlay errors to accumulate
Solution Approach 1:
The reference pattern is moved from the two-dimensional wafer surface to a third dimension by positioning it on a reference plate below the wafer or embedding it within the wafer structure. This dimensional transition allows the reference pattern to remain accessible and unaffected by surface-level processing steps such as film deposition and etching, thereby preventing overlay error accumulation while maintaining alignment accuracy.
Solution Approach 2:
A reference plate is introduced as an intermediary component between the wafer and the alignment system. The reference pattern on the reference plate serves as a stable mediator for alignment measurements, allowing the wafer to be aligned without relying on surface marks that are vulnerable to processing damage. This intermediary structure isolates the reference function from the processing environment.
2Manufacturing precision
If alignment marks are repeatedly created and corrected through multiple lithographic steps, then subsequent patterns can be aligned, but the process becomes complex and time-consuming
Solution Approach 1:
The reference pattern is prepared in advance on a separate reference plate or embedded in the wafer before the lithographic patterning process begins. This preliminary preparation of the alignment reference eliminates the need to repeatedly create and locate alignment marks during each lithographic step, simplifying the alignment process while maintaining manufacturing precision.
Solution Approach 2:
The reference pattern serves as a self-contained alignment reference that automatically provides the necessary alignment information for each lithographic step. Instead of requiring external intervention to create new alignment marks at each stage, the system continuously references the same stable pattern, reducing process complexity while maintaining alignment accuracy.
3Productivity
If conventional alignment methods are used where each layer references the previous layer, then patterns can be sequentially formed, but overlay errors accumulate with additional layers
Solution Approach 1:
The reference pattern is positioned in a different dimensional context (below the wafer or embedded within it) rather than on the surface, allowing it to serve as a stable reference for all layers without being affected by surface processing. This enables consistent reference to the same absolute position across multiple layers, preventing overlay error accumulation while maintaining multi-layer fabrication productivity.
Solution Approach 2:
The reference pattern on the reference plate serves as a universal reference for all lithographic steps and all layers in the fabrication process. Instead of requiring separate alignment marks for each layer or step, this single reference pattern provides consistent alignment information throughout the entire multi-layer fabrication sequence, maintaining both productivity and precision.
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 prevents overlay errors by providing a consistent, wafer-independent reference for pattern alignment, ensuring accurate and precise registration of layers and reducing the need for repeated alignment mark creation and correction, thereby improving manufacturing yields.
Implementation Method 1
capturing the image of the reference pattern via quantum tunneling imaging or infrared (IR) transmission imaging
Implementation Method 2
capturing the image of the reference pattern via quantum tunneling imaging or infrared (IR) transmission imaging
Data Source
AI summary
A method of processing a wafer is provided. The method includes providing a reference pattern for patterning a wafer. The reference pattern is independent of a working surface of the wafer. A placement of a first pattern on the working surface of the wafer is determined by identifying the reference pattern to align the first pattern. The first pattern is formed on the working surface of the wafer based on the placement.