Bonded Wafer Laser Crack Initiation for Chamfer Edge Removal
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Solution Overview
Problem
The existing methods for removing the chamfered edge from bonded wafers are time-consuming and can damage the wafers, especially when voids are present in the bonding layer, leading to potential damage during the edge removal process.
Innovation Solution
A method involving a modified layer forming step using a laser beam with multi-focused spots to create cracks that initiate the removal of the chamfered edge, allowing for efficient edge removal without damaging the bonded wafer, even when voids are present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the chamfered edge is removed by a cutting blade or grindstone during grinding, then the knife edge problem is solved, but the process becomes highly time-consuming and productivity decreases
Solution Approach 1:
The patent applies preliminary action by forming a modified layer and initiating cracks at the chamfered edge position before the actual grinding process begins. The laser creates a modified layer with specific orientation (15-50 degree depression angle) that prepositions crack formation sites, so that when grinding subsequently occurs, the chamfered edge is already primed for removal and the knife edge problem is prevented without requiring additional time-consuming steps during grinding.
2Object-affected harmful factors
If the chamfered edge is removed by cutting blade or grindstone, then edge sharpness is improved, but voids in the bonding layer can cause damage to the bonded wafer
Solution Approach 1:
The patent replaces the mechanical cutting blade or grindstone system with a laser-based modified layer formation system. The laser creates a modified layer and initiates cracks through thermal and stress effects rather than mechanical contact. This substitution eliminates the risk of mechanical damage to voids in the bonding layer while still achieving chamfered edge removal and preventing knife edge formation.
3Manufacturing precision
If multiple modified layers are formed with proper spacing, then crack propagation along bonding layer is enhanced, but the process complexity increases
Solution Approach 1:
The patent applies parameter changes by specifying precise intervals (10-380 μm) between multiple modified layers formed by the laser. By controlling the spacing parameter between modified layers, the patent ensures optimal crack propagation along the bonding layer interface. This parameter control achieves precise manufacturing precision for crack direction while the systematic approach keeps process complexity manageable through defined parameter ranges.
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 method efficiently removes the chamfered edge while preventing damage to the bonded wafer, enhancing productivity and ensuring the integrity of the wafer during the process.
Implementation Method 1
applying a laser beam having a wavelength transmittable through the first wafer to the first wafer from a reverse side thereof while positioning a focused spot of the laser beam within the first wafer to form a modified layer in the first wafer
Implementation Method 2
the focused spot of the laser beam includes multi-focused spots, and a line interconnecting the multi-focused spots forms a depression angle ranging from 15 to 50 degrees toward the outer circumferential portion of the first wafer
Data Source
AI summary
A method of processing a bonded wafer includes a modified layer forming step of applying a laser beam to a first wafer from a reverse side thereof while positioning a focused spot of the laser beam within the first wafer to form a modified layer in the first wafer and cracks developed from the modified layer and extending toward an outer circumferential portion of the first wafer along the bonding layer, and a grinding step of grinding the reverse side of the first wafer to thin down the first wafer. In the modified layer forming step, the focused spot of the laser beam includes multi-focused spots, and a line interconnecting the multi-focused spots forms a depression angle ranging from 15 to 50 degrees toward the outer circumferential portion of the first wafer with respect to a line parallel to a plane of the first wafer.