Wafer Cutting via Peripheral Dicing Street Detection
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Solution Overview
Problem
The existing wafer cutting technologies face challenges in accurately determining the layout of dicing streets on a wafer covered with opaque materials like molding compound, leading to reduced precision and throughput during the cutting process.
Innovation Solution
A wafer cutting apparatus equipped with a camera and processing unit that analyzes visual data from a moving camera path along the wafer's peripheral area to detect and calculate the locations and directions of dicing streets, using a triggerable camera and controlled lighting for efficient data acquisition and high-speed image capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wafer is covered with opaque material (molding compound) to protect and encapsulate the dice, then the structural integrity and protection of the wafer is improved, but the ability to visually detect and measure the dicing streets is lost
Solution Approach 1:
The patent removes the molding compound from the peripheral area of the wafer before the cutting process to expose the dicing streets. This preliminary action allows the imaging system to detect and measure the dicing street positions accurately, while the central area remains covered for protection. The removal is performed in advance so that subsequent cutting operations can proceed with precise positioning.
2Loss of information
If the camera continuously captures images during wafer movement to ensure complete coverage, then the detection completeness is improved, but the data processing time and system complexity increase
Solution Approach 1:
The system pre-calculates the expected coordinates where dicing streets should be located based on the wafer layout and pitch information. This preliminary calculation allows the imaging system to selectively capture images only at these predetermined locations rather than continuously during movement, reducing data processing requirements while ensuring all dicing streets are detected.
Solution Approach 2:
The imaging system moves rapidly through the wafer periphery and selectively captures images only at calculated dicing street locations, skipping intermediate positions. This approach reduces the total number of images that need to be processed while still achieving complete detection of all dicing streets, thereby reducing system complexity and processing time.
3Productivity
If the camera captures images at high speed to maintain productivity, then the throughput is improved, but the image quality and measurement precision may deteriorate
Solution Approach 1:
The system implements periodic image capture at predetermined intervals corresponding to the expected dicing street locations. Rather than continuous capture, the imaging system triggers image acquisition periodically at calculated coordinates, allowing high-speed movement between captures while ensuring accurate positioning at each measurement point. This maintains both throughput and precision.
Solution Approach 2:
The patent replaces mechanical positioning and continuous imaging with a calculation-based approach. The system calculates expected dicing street coordinates using known pitch values and wafer geometry, then positions the camera and triggers imaging at these computed locations. This substitution of mechanical continuous scanning with calculated positional sampling maintains precision while enabling high-speed operation.
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
Enables fast and accurate detection of dicing street locations and directions, enhancing the precision and throughput of the cutting process even when the central area of the wafer is covered with opaque material.
Implementation Method 1
a camera (240) arranged to view a peripheral area of the wafer (61)
Implementation Method 2
a lighting device (260) aimed at a position where a centre of a field of view of the camera (240) intersects the wafer surface (2)
Data Source
AI summary
A wafer cutting apparatus comprises a wafer positioning device for holding a wafer that is substantially covered with an opaque material such as molding compound and that has an exposed peripheral area, and for displacing the wafer relative to a wafer inspection system comprising a camera having a field of view. To perform visual data acquisition of said dicing street portions, the wafer is displaced such that a center of the camera's field of view follows a path along the exposed peripheral area of the wafer. A processing unit analyzes the visual data acquired for detecting or calculating locations and directions of the dicing streets. A wafer cutting tool cuts the wafer along straight lines between the dicing street portions which have been detected or calculated by the processing unit.