Wafer Alignment Marks for Thin-Substrate Singulation
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Solution Overview
Problem
Traditional singulation methods for semiconductor substrates, particularly those less than 50 microns thick, result in die chipping and cracking, leading to reduced yield and reliability issues due to the inability of cameras to align through vacuum chucks and tape, and the need for improved alignment and singulation techniques.
Innovation Solution
The method involves creating alignment marks on one side of the wafer using a camera and forming grooves or marks on the opposite side through lasering, sawing, or scribing, allowing for precise alignment and singulation without relying on traditional alignment hardware, and reducing the metal layer thickness to enhance die strength and minimize cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional singulation methods are used on substrates less than 50 microns thick, then singulation can be performed, but die chipping and cracking occur leading to reduced yield
Solution Approach 1:
The method performs preliminary alignment mark creation on the first side of the substrate before singulation. Alignment marks are formed in die streets using a camera system, enabling precise alignment to be established in advance. This preliminary alignment action allows subsequent singulation to proceed with high precision, reducing mechanical stress and preventing die chipping and cracking during the cutting process.
Solution Approach 2:
The invention replaces traditional mechanical alignment hardware with an optical camera-based alignment system. Instead of using complex mechanical alignment tools that require physical contact and precise mechanical positioning, the system uses optical imaging to detect alignment marks and calculate singulation paths. This substitution reduces mechanical stress on thin substrates while maintaining or improving alignment precision.
2Measurement precision
If traditional alignment hardware is used, then alignment can be performed, but cameras cannot align through vacuum chucks and tape
Solution Approach 1:
Instead of attempting to align through the vacuum chuck and tape from the conventional side, the invention inverts the approach by creating and detecting alignment marks on the first side of the substrate that is accessible to the camera. The alignment marks are formed in die streets on the surface, allowing the camera to directly image and measure alignment features without penetrating the vacuum chuck or tape barrier. This inversion simplifies the alignment system while maintaining precision.
Solution Approach 2:
The system creates optical copies (images) of alignment marks on the substrate surface using a camera. These alignment marks serve as visual references that can be detected and measured optically. By copying the alignment information into visible mark patterns on the substrate, the system enables non-contact, optical measurement that works through vacuum chucks and tape, eliminating the need for complex mechanical alignment hardware.
3Strength
If metal layer thickness is reduced to enhance die strength, then die cracking is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The invention uses optical measurement and camera-based alignment to achieve precise positioning and thickness control of metal layers without relying on complex mechanical measurement systems. The camera system can detect alignment marks and measure features with high precision, enabling accurate control of metal layer thickness even at reduced levels. This optical substitution provides non-contact measurement that is more precise and less intrusive than mechanical gauges.
Solution Approach 2:
The system performs preliminary alignment and measurement actions before metal layer deposition or thinning. By establishing precise alignment marks and measuring substrate features in advance, the system can guide subsequent metal layer processing with high accuracy. This preliminary measurement action enables precise thickness control without requiring complex real-time monitoring during the metal layer formation process.
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 reduces the risk of die breakage during singulation, enhances yield, and improves device reliability by providing accurate alignment and minimizing damage to the semiconductor substrates.
Implementation Method 1
aligning the wafer using a camera focused on the first side of the wafer
Implementation Method 2
creating a plurality of alignment marks on a second side of the wafer through lasering
Data Source
AI summary
Implementations of a method of making a plurality of alignment marks on a wafer may include: providing a wafer including an alignment feature on a first side of the wafer. The method may include aligning the wafer using a camera focused on the first side of the wafer. The wafer may be aligned using the alignment feature on the first side of the die. The wafer may also include creating a plurality of alignment marks on a second side of the wafer through lasering, sawing, or scribing.