Laser Focus Correction Using Reference Grooves on Wafers
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Solution Overview
Problem
Existing laser machining methods for semiconductor wafers face challenges in accurately correcting the focus positions of split and line lasers, leading to uneven blade wear and difficulties in detecting laser grooves, especially due to displacement issues and debris patterns.
Innovation Solution
A laser light correction method involving trimming and hollowing machining on a positioning workpiece with a material that facilitates detection, using a microscope to detect grooves, and adjusting the focus positions of split and line lasers based on these detections, with the option of using polyimide film or alignment paper and single pulse lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the outer circumferential excess region of the wafer is machined to correct laser positions, then the focus position correction is achieved, but some laser grooves may be formed into inappropriate shapes causing uneven blade wear
Solution Approach 1:
The patent divides the wafer into two distinct regions: a device region where precise groove shaping is critical for blade wear prevention, and an outer circumferential excess region where focus position correction is performed. By segmenting the machining area, the system can apply different machining strategies to each region, correcting laser focus positions using grooves formed in the excess region while preserving groove quality in the device region.
2Difficulty of detecting and measuring
If patterns or debris are present on the wafer, then it becomes difficult to detect laser groove positions, but the focus position correction cannot be performed
Solution Approach 1:
The patent introduces an intermediary reference groove that is distinct from the functional grooves needed for device separation. This reference groove serves as a dedicated detection target that is easier to identify using microscopy, even in the presence of patterns or debris. The reference groove acts as a mediator between the laser machining system and the detection system, enabling accurate focus position correction without being obscured by wafer patterns or processing debris.
3Device complexity
If only one condenser lens is used to switch between split laser and line laser, then device complexity is reduced, but focus position displacement occurs on the wafer
Solution Approach 1:
The patent performs focus position correction as a preliminary action before actual device machining. By forming reference grooves and detecting their positions in advance, the system identifies and corrects focus position displacements caused by condenser lens switching. This preliminary correction ensures that subsequent machining operations maintain accurate focus positions regardless of the condenser lens configuration used.
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 enables accurate correction of laser positions, preventing focus displacement and ensuring precise machining quality by facilitating the detection of laser grooves and adjusting the focus positions effectively.
Implementation Method 1
a step of performing trimming machining on a positioning workpiece in which at least a laser irradiation surface includes a material that facilitates detection of a laser-irradiation mark, the trimming machining in which a split laser is focused on the laser irradiation surface via a laser optical system... and performing hollowing machining in which a line laser is focused on the laser irradiation surface via the laser optical system
Data Source
AI summary
The laser light correction method includes: a step of performing trimming machining on a positioning workpiece in which a laser irradiation surface includes a material that facilitates detection of a laser-irradiation mark, the trimming machining in which a split laser is focused on the laser irradiation surface via a laser optical system while moving the laser optical system in the machining feed direction relative to the positioning workpiece to form a first groove having two rows parallel to each other in a machining feed direction, and performing hollowing machining in which a line laser is focused on the laser irradiation surface via the laser optical system to form a second groove; a step of detecting the first groove and the second groove by a microscope; and a step of correcting focus positions of the split laser and the line laser based on detection results of the first and second grooves.