Wafer Laser Machining Control Using Plasma Luminance Feedback
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Solution Overview
Problem
Existing laser machining devices struggle to check the machined state of grooves in real time, particularly when dealing with wafers containing Low-k films, as surface observations are limited and require post-machining inspection.
Innovation Solution
A laser machining device equipped with an observation image acquiring unit, luminance detector, and machined state assessing unit that assesses the machined state in real time by detecting plasma luminance and using correspondence information to determine groove depth and temperature, with noise suppression from scattered light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surface observation using a microscope is performed to check the machined state, then observation capability is provided, but the information obtained is limited to surface level and real-time assessment of groove depth is not possible
Solution Approach 1:
The patent replaces the mechanical/optical microscope observation system with a plasma luminance detection system. By detecting the luminance of plasma generated during laser machining, the system obtains information about the internal machined groove depth in real-time, overcoming the limitation of surface-only observation.
Solution Approach 2:
The patent introduces plasma luminance as an intermediary indicator to infer the machined groove depth. The plasma generated during laser machining emits light whose luminance correlates with the groove depth, allowing indirect measurement of the internal structure without direct visual observation.
2Manufacturing precision
If laser machining is performed to form machined grooves along streets, then Low-k film removal is achieved, but real-time monitoring of the machined state is not possible requiring post-machining inspection
Solution Approach 1:
The patent implements real-time feedback control by continuously monitoring plasma luminance during laser machining and using this information to assess the machined state. This allows immediate detection of machining quality and enables real-time adjustment of machining parameters, eliminating the need for time-consuming post-machining inspection.
Solution Approach 2:
The machining process itself generates plasma that serves as a natural indicator of the machined state. By detecting the plasma luminance, the system uses the machining process's own byproduct for self-monitoring, eliminating the need for separate inspection processes.
3Ease of manufacture
If blade cutting is used to divide the wafer, then simple cutting is achieved, but simultaneous cutting of Low-k film and substrate is difficult
Solution Approach 1:
The patent replaces mechanical blade cutting with laser machining. The laser can simultaneously ablate both the Low-k film and the substrate through thermal effects, achieving precise simultaneous cutting that mechanical blades cannot accomplish due to material hardness differences.
Solution Approach 2:
The patent changes the cutting mechanism from mechanical to thermal by using laser energy. By controlling laser parameters such as power, pulse duration, and scanning speed, the system can selectively and simultaneously remove both Low-k film and substrate materials with different physical properties.
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 precise, real-time assessment of machined groove states, allowing for improved machining quality and consistency by adjusting laser conditions based on detected luminance and energy correlations.
Implementation Method 1
a laser machining device forming a machined groove along a street on a wafer by relatively moving a laser optical system in a machining feed direction along the street and emitting laser light from the laser optical system to the street
Implementation Method 2
a luminance detector configured to detect a luminance of a plasma generated at the machining spot by emission of the laser light based on the observation image
Data Source
AI summary
The laser machining device includes an observation image acquiring unit configured to repeatedly acquire an observation image of a machining spot of laser light emitted from a laser optical system to a street on a wafer while a machined groove is being formed, a luminance detector configured to detect a luminance of a plasma generated at the machining spot by emission of the laser light based on the observation image every time the observation image acquiring unit acquires the observation image, a correspondence information obtaining unit configured to obtain correspondence information indicating a correspondence relationship among the luminance, energy of the laser light and a machined state of the machined groove, and a machined state assessing unit configured to assess the machined state with reference to the correspondence information based on the luminance and known energy of the laser light every time the luminance detector detects the luminance.