SiC Substrate Alignment Mark Asymmetry for Epitaxial Precision
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Solution Overview
Problem
The challenge in manufacturing silicon carbide semiconductor devices lies in achieving high alignment accuracy, particularly when the substrate surface is angled off relative to the {0001} plane, as conventional methods struggle with identifying alignment marks due to asymmetrical growth of epitaxial layers, leading to difficulties in precise alignment during semiconductor fabrication processes.
Innovation Solution
A method involving the formation of a first alignment mark with specific geometric configurations on a silicon carbide substrate, where a second alignment mark is created by epitaxial growth, allowing for image capture and edge recognition to improve alignment accuracy by capturing an image of one portion while excluding another, thereby enhancing the precision of substrate alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional alignment mark formation method is used on a silicon carbide substrate with an angled off surface, then the substrate can be processed, but alignment accuracy deteriorates due to asymmetrical epitaxial layer growth
Solution Approach 1:
The invention intentionally introduces asymmetry into the alignment mark structure by forming a protruding portion that extends in the off direction. This asymmetrical feature creates a distinct asymmetrical growth pattern in the epitaxial layer, which in turn produces an asymmetrical second alignment mark. This controlled asymmetry enables reliable edge recognition and improves alignment accuracy on angled substrates.
Solution Approach 2:
The alignment mark is divided into multiple regions: a first region forming the base structure, and a second region extending in the off direction that creates the protruding portion. This segmentation allows different parts of the alignment mark to serve different functions - the first region provides structural foundation while the second region enables reliable epitaxial growth patterns for accurate alignment.
2Manufacturing precision
If the main surface is angled off relative to the {0001} plane to enable certain device structures, then device performance can be improved, but alignment accuracy deteriorates due to difficulties in identifying alignment marks
Solution Approach 1:
The invention utilizes optical contrast differences (analogous to color changes) by creating a protruding portion that casts a shadow or creates light reflection differences when imaged. The asymmetrical protruding structure produces distinct optical characteristics in captured images, enabling reliable edge detection and alignment mark identification even on angled surfaces where conventional marks fail.
Solution Approach 2:
By forming a protruding portion that extends in the off direction, the invention creates an asymmetrical alignment mark structure that produces a distinctive asymmetrical pattern in the epitaxial layer. This asymmetrical second alignment mark provides clear visual or optical contrast that facilitates easy detection and precise measurement, solving the detection difficulty on angled substrates.
3Manufacturing precision
If a simple alignment mark structure is used, then manufacturing complexity is reduced, but alignment accuracy deteriorates due to inability to achieve precise edge recognition
Solution Approach 1:
The alignment mark is segmented into a first region and a second region extending in the off direction. This segmentation adds only minimal structural complexity - essentially one additional geometric feature - while enabling the formation of an asymmetrical second alignment mark through epitaxial growth. The segmented structure provides precise edge recognition capabilities without significantly increasing overall manufacturing complexity.
Solution Approach 2:
The protruding portion is formed in advance during the alignment mark fabrication process, before epitaxial growth occurs. This preliminary action of creating the asymmetrical geometric feature ensures that the subsequent epitaxial layer growth will naturally follow the asymmetrical pattern, enabling accurate alignment without requiring complex post-processing or additional manufacturing steps.
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 significantly improves alignment accuracy by allowing for precise identification of alignment marks, even on substrates with angled surfaces, leading to more accurate epitaxial growth and improved semiconductor device performance.
Implementation Method 1
A second alignment mark is formed on the first alignment mark by forming a silicon carbide epitaxial layer on the first alignment mark
Data Source
AI summary
A silicon carbide substrate having a main surface angled off in an off direction relative to a {0001} plane is prepared. A protruding first alignment mark is formed on the main surface of the silicon carbide substrate. A second alignment mark is formed on the first alignment mark by forming a silicon carbide epitaxial layer on the first alignment mark. The first alignment mark includes a first region and a second region, the second region being in contact with the first region and extending from the first region in the off direction. The second alignment mark includes a first portion formed on the first region and a second portion formed on the second region. An alignment step includes the step of capturing an image of the first portion while not including the second portion, and recognizing an edge of the first portion based on the image.