Plasma Diced Wafers with Scallop-Vertical Sidewalls
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Solution Overview
Problem
Conventional mechanical sawing for dicing semiconductor wafers is time-consuming and can cause vibrations leading to cracks in dies, affecting yield and throughput.
Innovation Solution
Plasma dicing method using a passivation layer as a mask to singulate wafers into individual dies with scalloped and vertical sidewalls, avoiding mechanical sawing and its associated issues.
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 vibration-induced cracks
Solution Approach 1:
The patent replaces the mechanical sawing system with a plasma-based etching system. Instead of using a physical saw blade that mechanically cuts through the wafer, the invention uses plasma to chemically etch and remove material along the scribe lines, separating dies without mechanical contact. This substitution eliminates vibration-induced cracks and significantly improves both throughput and die reliability.
Solution Approach 2:
The patent changes the physical state and chemical properties of the cutting process by transitioning from mechanical force to plasma chemistry. By controlling plasma parameters such as gas composition, power, and pressure, the process achieves clean, precise cuts without mechanical stress. The plasma state allows for controlled material removal that prevents cracking while maintaining high speed.
2Ease of manufacture
If mechanical sawing is used to dice wafers, then the wafer can be separated into individual dies, but mechanical vibration causes cracks in the back-end dielectric
Solution Approach 1:
The patent replaces the mechanical sawing system with a plasma-based etching system. Instead of using a physical saw blade that mechanically cuts through the wafer, the invention uses plasma to chemically etch and remove material along the scribe lines, separating dies without mechanical contact. This substitution eliminates vibration-induced cracks and significantly improves both throughput and die reliability.
3Productivity
If plasma dicing is used instead of mechanical sawing, then throughput is improved and vibration issues are avoided, but a plasma dicing mask is required
Solution Approach 1:
The passivation layer, which is already present on the wafer for electrical protection and environmental shielding, is repurposed to serve as the plasma dicing mask. This multi-functional use of the existing layer eliminates the need for separate mask materials and simplifies the overall process, despite the added plasma etching step.
Solution Approach 2:
The existing passivation layer on the wafer automatically serves as the plasma dicing mask, eliminating the need for external mask materials. The process utilizes resources already present on the wafer surface, reducing additional material requirements and simplifying the process flow.
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
Improves processing throughput and reliability by eliminating vibration-induced cracking and notching, resulting in more reliable plasma diced dies.
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
Implementation Method 2
A first plasma etch is performed to etch a first portion of the processed wafer in the kerf regions from the top BEOL surface to an upper portion of the wafer. The first plasma etch produces scalloped sidewalls in the kerf regions.
Implementation Method 3
Laser is used to cut the passivation layer to form passivation openings to expose the top BEOL dielectric surface in kerf regions within the first and second saw streets
Data Source
AI summary
Reliable plasma dicing of wafers to singulate it into individual dies is disclosed. Laser processing is employed to form mask openings in a passivation stack of a processed wafer. The patterned passivation stack serves as a plasma dicing mask for plasma dicing the wafer. The sidewalls of the mask openings may be flat or vertical sidewalls. In other cases, the sidewalls of the mask openings are slanted or chamfered sidewalls. The plasma dices the wafer using first and second plasma etch steps. The first plasma etch step etches to form scalloped sidewalls on the first portion of the die and the second plasma step etches to form flat or vertical sidewalls on a second portion of the die. The second portion of the die is the lower portion of the substrate or wafer. This prevents backside notching to improve reliability.