Wafer Dicing via Region-Based Best-Fit Alignment
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Solution Overview
Problem
Current methods for dicing wafers of light emitting devices, such as LEDs, face challenges in yield improvement due to misalignment and sidewall offsets caused by sequential breaking and conventional alignment algorithms, which can lead to incorrect cutting and reduced efficiency in separating individual or grouped devices.
Innovation Solution
A method involving non-sequential breaking patterns and region-based best-fit line alignment using fiducials to determine dicing streets, with the use of shallow pilot grooves for kerf position detection and deep singulation grooves for separation, reduces sidewall offsets and improves yield by aligning dicing streets more accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sequential breaking is used to separate the wafer, then the process is simple and easy to control, but sidewall offsets and misalignment occur reducing yield
Solution Approach 1:
The wafer is divided into multiple regions, and dicing streets are determined in a non-sequential pattern by region rather than processing the entire wafer sequentially. This segmentation allows parallel determination of dicing street positions across different regions, maintaining process simplicity while improving alignment precision through localized best-fit line calculations.
Solution Approach 2:
Fiducials are positioned on the wafer beforehand, and best-fit lines are pre-calculated for each region based on these fiducials. This preliminary action enables accurate dicing street positioning without requiring sequential measurement and adjustment during the breaking process, thereby improving alignment precision while maintaining ease of manufacture.
2Ease of manufacture
If conventional alignment algorithms are used, then the process is straightforward, but misalignment and sidewall offsets reduce efficiency
Solution Approach 1:
Instead of applying a single conventional alignment algorithm uniformly across the entire wafer, the invention applies local best-fit line alignment algorithms to each individual region. This local quality approach allows each region to be aligned independently with its own optimal reference frame, improving separation efficiency while keeping the overall process straightforward through automated regional processing.
Solution Approach 2:
The invention transitions from conventional one-dimensional sequential alignment to a two-dimensional regional grid system where dicing streets are determined across multiple regions simultaneously. This dimensional change enables parallel processing of alignment calculations, improving productivity while maintaining process straightforwardness through systematic regional decomposition.
3Reliability
If deep singulation grooves are used for separation, then the separation is effective, but sidewall offsets increase reducing yield
Solution Approach 1:
Shallow pilot grooves are created beforehand at the intended dicing street locations to guide the subsequent deep singulation groove formation. This preliminary action ensures that the deep grooves follow the correct paths determined by best-fit line alignment, maintaining sidewall alignment precision while achieving effective separation through the deep grooves.
Solution Approach 2:
Shallow pilot grooves serve as intermediaries between the alignment calculation and the final deep singulation groove formation. These pilot grooves transfer the positional information from the best-fit line determination to the deep cutting process, ensuring that effective separation is achieved without introducing sidewall offsets.
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 enhances the precision and efficiency of wafer separation by minimizing sidewall offsets and misalignment, thereby improving the yield of individual or grouped light emitting devices.
Implementation Method 1
a laser is often used in the process of dicing a semiconductor wafer such that individual devices (or dies) manufactured from the semiconductor wafer are separated from each other. The dies on the wafer are separated by streets and the laser may be used to cut the wafer along the streets.
Data Source
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Figure 5A~5C
Figure 6A~6C
AI summary
Embodiments of the invention are directed to a method of separating a wafer of light emitting devices. The light emitting devices are disposed in rows. The method includes dividing the wafer into a plurality of regions. Each region comprises a plurality of rows of light emitting devices and a first region is wider than a second region. For each region, the method includes determining a position of first and second dicing streets. The dicing streets are located between the rows of light emitting devices. The method includes determining, using the position of the first and second dicing streets, positions of a plurality of dicing streets disposed between the first and second dicing streets. The method includes cutting the wafer along streets.