W-Mesa Street Structure for Laser Dice Separation
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Solution Overview
Problem
Laser-based separation of semiconductor dice can cause thermal shock and damage due to debris generation, which affects the integrity and functionality of the dice.
Innovation Solution
A W-mesa shaped street is created by forming two slots on either side of the wafer, with a protective coating applied over the wafer, allowing the laser to separate the dice in the center of the mesa, protecting the dice from debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser is used to separate the dice by cutting the wafer in the street area, then the dice can be separated efficiently, but thermal shock and high temperatures may cause portions of the wafer to damage the dice via thrown particles or reformed material
Solution Approach 1:
The street area is divided into two separate slots instead of one continuous cut, creating a W-mesa structure. This segmentation allows the laser to cut on either side of the dice rather than directly adjacent to them, reducing debris generation and protecting the dice from damage while maintaining separation efficiency
Solution Approach 2:
A protective coating is applied to the wafer surface as an intermediary layer between the laser cutting process and the dice. This coating protects the dice from debris and thermal shock during laser separation, allowing efficient cutting while preventing damage to the semiconductor devices
2Reliability
If a protective coating is applied over the wafer before laser separation, then the dice are protected from debris, but the process complexity increases due to additional coating and removal steps
Solution Approach 1:
A disposable protective coating is applied to the wafer before laser separation and then removed after the process. This temporary protective layer is inexpensive and single-use, providing reliable protection during the critical separation step while adding minimal complexity to the overall manufacturing 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
The W-mesa design effectively shields the dice from debris, reducing damage and ensuring the integrity and functionality of the semiconductor devices during the separation process.
Implementation Method 1
a laser is used to separate the dice by cutting the wafer 100 in the street area 102. However, thermal shock and high temperatures created by the laser may cause portions of the wafer to damage the dice 101 via 'thrown' particles or reformed material
Implementation Method 2
thermal shock and high temperatures created by the laser may cause portions of the wafer to damage the dice 101
Implementation Method 3
A 'W' shaped cross section is created by forming two slots, on either side of the streets of a wafer of devices
Data Source
AI summary
A method for fabricating an epitaxial structure includes providing a wafer comprising one or more epitaxial layers. The wafer is divided into dice where the area between the dice are called streets. Each street has a slot formed on either side of the street. The slots penetrate through the epitaxial layer but not the substrate leaving a portion of the epitaxial layer intact between the slots creating a “W” shaped cross section. A protective layer is then formed on the wafer. A laser may be used to singulate the wafer in to individual dice. The laser divides each street between the slots. The barrier walls of the epitaxial layers protect the individual dice from debris created by laser separation.