IR-Aligned Stealth Laser Wafer Edge Trimming for Bonded Wafers
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Solution Overview
Problem
The existing wafer edge trimming processes face challenges in precision and accuracy, leading to potential damage and peeling issues during the bonding of semiconductor wafers, as conventional methods rely on scanning cameras for alignment, which can be imprecise and cause defects.
Innovation Solution
The implementation of an infrared (IR) alignment process integrated with a stealth laser apparatus and a blade trimming method, where the IR alignment improves precision to within 3 micrometers, allowing for the formation of a stealth damage region within the second wafer, enabling precise removal of outer edges without direct contact and subsequent grinding to minimize defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scanning cameras are used for alignment in conventional wafer edge trimming, then the alignment process is simple, but the alignment precision is poor leading to defects
Solution Approach 1:
The patent replaces the mechanical/optical scanning camera alignment system with an infrared laser-based alignment system. The infrared laser apparatus emits laser beams that are detected by sensors to determine wafer position and orientation, achieving sub-micrometer alignment precision (within 3 micrometers) compared to the millimeter-level precision of conventional scanning cameras. This substitution of alignment methodology directly resolves the contradiction by prioritizing measurement precision over device simplicity.
Solution Approach 2:
The patent introduces infrared laser beams as an intermediary medium for alignment. The laser beams serve as a precise reference that interacts with the wafer and bonding interface, enabling accurate measurement of wafer position and orientation. The infrared wavelength provides superior penetration and detection capabilities compared to visible light cameras, achieving the required 3 micrometer precision while maintaining a manageable system complexity through standardized laser components.
2Productivity
If blade trimming is used to remove outer edges, then material removal is efficient, but the abrasive surface damages the wafer
Solution Approach 1:
The patent replaces the direct mechanical contact of the blade with the wafer surface with a non-contact infrared laser processing method. The infrared laser creates a damage-free cut by heating and separating the material without abrasive contact. This substitution eliminates the harmful abrasive damage caused by conventional blade trimming while maintaining high productivity through the efficiency of laser material processing.
Solution Approach 2:
The patent utilizes phase transitions of material under infrared laser irradiation to achieve damage-free trimming. The infrared laser energy causes localized heating and phase change (melting/vaporization) of the wafer material at the cutting line, enabling clean separation without mechanical abrasion. This phase transition mechanism allows efficient material removal without the damaging contact forces inherent in blade-based methods.
3Reliability
If conventional alignment methods are used, then the process is simple, but peeling and damage occur during bonding
Solution Approach 1:
The patent replaces conventional optical camera alignment with an infrared laser-based alignment and processing system. The infrared laser apparatus provides precise alignment (within 3 micrometers) and simultaneously performs damage-free trimming through non-contact laser processing. This integrated system improves bonding reliability by eliminating misalignment-induced peeling and abrasive damage, justifying the increased system complexity through superior performance.
Solution Approach 2:
The patent merges the alignment function and the trimming function into a single integrated infrared laser apparatus. The same infrared laser system that provides precise alignment also performs the actual trimming operation, eliminating the need for separate alignment and trimming systems. This merging improves bonding reliability by ensuring that alignment and processing are coordinated, while the complexity increase is offset by consolidating functions rather than adding separate systems.
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 accuracy and reliability of wafer edge trimming, reducing peeling risks and resulting in smooth, defect-free edges, thereby improving the reliability of integrated circuits formed from bonded wafers.
Implementation Method 1
an infrared camera is integrated into the stealth laser apparatus and/or the blade; the infrared camera is configured to locate alignment marks on the first wafer
Implementation Method 2
a damage region is formed within the second wafer at a desired depth using a stealth laser apparatus
Implementation Method 3
a grinding apparatus is configured to remove an initial top portion of the second wafer; subsequent grinding to minimize defects
Data Source
AI summary
In some embodiments, the present disclosure relates to a method that includes aligning a stealth laser apparatus over a wafer using an infrared camera coupled to the stealth laser apparatus. The stealth laser apparatus is used to form a stealth damage region within the wafer that is continuously connected around the wafer and separates an inner region from an outer region of the wafer. The stealth damage region is also arranged at a first distance from an edge of the wafer and extends from a first depth to a second depth beneath a top surface of the wafer. Further, the method includes forming a groove in the wafer to separate the outer region from the inner region of the wafer. The outer region of the wafer is removed using a blade, and a top portion of the inner region of the wafer is removed using a grinding apparatus.