Backside Plasma Wafer Dicing to Prevent Die Notching
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Solution Overview
Problem
Conventional mechanical sawing techniques for dicing semiconductor wafers are time-consuming and can cause vibrations leading to cracks in dies, negatively impacting yields, while existing plasma dicing methods do not effectively address the need for reliable dicing from the back surface of wafers.
Innovation Solution
The method involves plasma dicing from the back surface of wafers using a patterned mask layer to singulate individual dies, which includes scalloped sidewalls and a backside mask layer for improved die strength and stability, avoiding notching and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical sawing is used to dice wafers, then the wafer can be separated into individual dies, but the process is time-consuming and causes vibrations leading to cracks
Solution Approach 1:
The patent replaces the mechanical sawing system with a plasma-based etching system. Instead of using a physical blade to cut the wafer, plasma is used to remove material and create dicing channels, eliminating mechanical contact and associated vibrations that cause cracks in the die structure.
Solution Approach 2:
The patent employs plasma (ionized gas) as the cutting medium to etch dicing channels through the wafer. The plasma process uses controlled gas flow and chemical reactions to remove material, providing a non-mechanical alternative to sawing that avoids vibration-induced cracking while maintaining high throughput.
2Productivity
If plasma dicing is used from the front surface, then throughput is improved and vibration is eliminated, but reliability issues occur due to notching
Solution Approach 1:
The patent inverts the conventional plasma dicing approach by etching from the back surface of the wafer instead of the front surface. This reversal allows the plasma process to create dicing channels without exposing the front surface to notching, thereby maintaining both high throughput and die strength.
Solution Approach 2:
The patent applies different treatment to different surfaces of the wafer. The front surface maintains its original structure with intact device layers, while the back surface is selectively etched to create dicing channels. This localized approach preserves the structural integrity of the die while enabling efficient separation.
3Reliability
If back surface plasma dicing is implemented, then die strength is enhanced and notching is prevented, but the process complexity increases
Solution Approach 1:
The patent performs preliminary preparation by applying a mask layer to the back surface of the wafer before plasma etching. This mask layer defines the dicing channel locations and protects areas that should not be etched, simplifying the overall process by pre-establishing the etch pattern rather than requiring complex real-time control.
Solution Approach 2:
The patent introduces a mask layer as an intermediary between the wafer structure and the plasma etching process. This mask layer serves as a template that guides the plasma removal, enabling precise dicing channel formation while protecting the front surface and device structures from direct plasma exposure.
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 improves the reliability and yield of plasma-diced dies by preventing backside notching and enhancing die strength, stability, and shear, thus overcoming the limitations of conventional dicing methods.
Implementation Method 1
plasma dicing entails mounting a wafer onto a wafer ring and inserting the wafer ring with the wafer into a plasma chamber for etching
Data Source
AI summary
Disclosed is a plasma diced die from the backside of the wafer using a back surface mask layer. The back surface mask layer remains on the backside of the die, serving as backside protection for the die. The plasma dicing may dice the wafer completely or partially. In the case of partial dicing, the partially diced wafer is expanded to singulate the wafer into individual dies by lateral force.