Wafer Dicing Edge Recrystallization for Stronger Chips
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Solution Overview
Problem
The existing wafer dividing methods often result in processing strain such as chipping, cracking, and embrittlement of chips, which lowers their flexural strength due to damage incurred during the division process.
Innovation Solution
A wafer dividing method that includes back surface grinding, dividing along planned lines, and a first energy supply step where energy is applied to the edges, back surfaces, and side surfaces of the chips to melt and recrystallize them, thereby repairing processing strain and enhancing flexural strength. This energy supply can be achieved through laser irradiation with a wavelength of 500 to 1000 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wafer is divided into chips along planned dividing lines, then the wafer is successfully segmented into individual chips, but processing strain such as chipping, cracking, and embrittlement occurs in the chips
Solution Approach 1:
The patent applies preliminary action by performing back surface grinding before the dividing step to reduce the thickness and stress concentration at the back surface of the wafer. This preliminary preparation prevents processing strain during subsequent division operations, thereby maintaining chip strength while enabling efficient wafer segmentation.
Solution Approach 2:
The patent changes physical parameters by controlling the grinding depth and surface roughness of the back surface, as well as optimizing the dividing line positioning. These parameter adjustments reduce stress concentration and prevent cracking during chip division, resolving the contradiction between division efficiency and chip strength.
2Strength
If energy is supplied from the back surface to melt and repair processing strain, then the flexural strength of chips is enhanced, but additional processing steps and time are required
Solution Approach 1:
The patent merges the energy supply step with the existing back surface grinding operation by using the same processing equipment to perform both mechanical removal and thermal repair functions. This integration reduces device complexity while maintaining the strength-enhancing effect of melting and recrystallization at the chip edges and surfaces.
Solution Approach 2:
The patent applies self-service by using the wafer's own back surface as the energy supply path, eliminating the need for separate front surface processing equipment. The energy is supplied through the back surface to repair processing strain internally, simplifying the overall process while effectively enhancing chip strength.
3Ease of manufacture
If back surface grinding is performed to reduce wafer thickness, then processing strain during division is reduced, but the wafer structure is altered and may affect chip integrity
Solution Approach 1:
The patent carefully controls the grinding depth parameter to remove only the damaged back surface layer while preserving the bulk wafer structure. By optimizing this parameter, the process becomes easier (reduced stress during division) while maintaining chip integrity (sufficient thickness and structural soundness).
Solution Approach 2:
The patent applies local quality by selectively grinding only the back surface region that causes stress concentration, while leaving the front surface and bulk material intact. This localized modification improves division ease without compromising overall chip structural integrity.
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 method effectively planarizes and strengthens the edges and surfaces of the chips by melting and recrystallizing them, thereby alleviating processing strain and improving the flexural strength of the chips.
Implementation Method 1
a first energy supply step of supplying energy to at least any part of edges, back surfaces, and side surfaces of the chips from the back surface of the wafer and melting the at least any part to repair at least part of processing strain
Implementation Method 2
melting the at least any part to repair at least part of processing strain
Implementation Method 3
the energy is supplied to at least any part of the edges, the back surfaces, and the side surfaces of the chips from the back surface of the wafer to melt and recrystallize this part
Implementation Method 4
a wavelength of the laser beam is a wavelength having absorbability with respect to the wafer
Data Source
AI summary
In a dividing method of a wafer, first edge parts and second edge parts that are the edges of chips are melted by executing irradiation with a laser beam. Therefore, the edges of the chips can be planarize. In addition, cracks, chipping, and so forth caused in the edges of the chips can be coupled. Therefore, it becomes possible to repair at least part of processing strain of the edges of the chips. As a result, a flexural strength of the chips can be enhanced.