Laser Wafer Separation With Real-Time Focus Tracking
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Solution Overview
Problem
Traditional methods for cutting semiconductor wafers from ingots result in variations in thickness and planarity, leading to inefficiencies and increased material waste, as well as challenges in achieving precise planarization and polishing, especially for large solid-state components.
Innovation Solution
A method involving a laser processing system that adjusts focus based on parameters like refractive index and processing depth, using a crack guidance region and a polymer-hybrid material for crack propagation, allowing for precise modifications within solid states with reduced reworking effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional sawing or wire cutting methods are used to cut wafers from ingots, then the cutting process can be performed, but variations in thickness and planarity occur due to wire wandering, leading to increased material waste and additional processing steps
Solution Approach 1:
The patent replaces traditional mechanical cutting methods (saws, wire cutting) with a laser-based modification system. The laser creates a damage layer at a controlled depth within the ingot, which then guides crack propagation to separate wafers. This substitution eliminates wire wandering and associated thickness variations while improving material efficiency through planar separation
Solution Approach 2:
The patent controls the laser processing parameters (energy density, pulse duration, wavelength) to create a damage layer at a precise depth within the ingot. By adjusting these parameters, the system achieves controlled crack propagation at the desired separation plane, ensuring uniform wafer thickness without the variations caused by mechanical cutting methods
2Manufacturing precision
If mechanical wedge compensation and autofocus are used to maintain laser focus, then some planarity tracking is achieved, but deviations in the μm range are difficult to achieve and planarization is impossible
Solution Approach 1:
The patent implements a feedback system using a distance sensor that continuously measures the actual distance from the laser head to the ingot surface. This measurement is fed back to the control system, which adjusts the laser head position in real-time to maintain precise focus. This closed-loop feedback enables dynamic compensation for surface deviations and achieves planarization
Solution Approach 2:
The patent transitions from static mechanical wedge compensation to a dynamic autofocus system. The laser head position is continuously adjusted based on real-time surface measurements, allowing the system to adapt to changing surface conditions during processing. This dynamic adjustment enables tracking of surface profiles and achievement of planar separation planes
3Measurement precision
If the distance from the laser head to the surface fluctuates, then the laser beam passes through different optical paths with different refractive indices, causing n-fold errors in the focus position
Solution Approach 1:
The patent uses a distance sensor to continuously measure the actual distance from the laser head to the ingot surface and feeds this information back to the control system. The control system calculates the required focus adjustment based on the measured distance and the known refractive index of the material, then adjusts the laser head position accordingly. This feedback mechanism compensates for optical path variations and maintains precise focus and modification depth
Solution Approach 2:
The patent replaces passive mechanical focus adjustment with an actively controlled system that uses optical feedback. The distance sensor and control system work together to dynamically adjust the laser head position, compensating for surface fluctuations and refractive index effects. This active control system achieves much higher precision than passive mechanical adjustment
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 enables precise creation of modifications within solid states, improving material efficiency and reducing reworking efforts by allowing for real-time focus tracking and correction, leading to higher yield and better quality of semiconductor wafers.
Implementation Method 1
A method involves a laser processing system (8) that adjusts its focus as a function of parameters such as refractive index and processing depth
Implementation Method 2
creating at least one modification (2) within a solid state (1), wherein the laser processing system (8) is adjusted for defined focusing of the laser beams
Implementation Method 3
arranging or creating a receiving layer (26) on the solid state (1), wherein the receiving layer (26) comprises, contains or consists of a polymer material
Implementation Method 4
A semiconductor wafer is formed from the ingot or boule by detachment because of the mechanical stresses caused by the great difference in thermal expansion coefficients
Implementation Method 5
the laser processing system (8) is adjusted continuously as a function of at least one parameter and preferably as a function of a plurality of parameters, in particular at least two parameters, for defined focusing of the laser beams
Data Source
AI summary
A method for separating a solid-state layer from a solid-state material includes: moving the solid-state material relative to a laser processing system; successively emitting a plurality of laser beams from the laser processing system to the solid-state material to create modifications within the solid-state material; adjusting the laser processing system for defined focusing of the plurality of laser beams and/or for continuous adjustment of energy of the plurality of laser beams as a function of at least one parameter; and detaching the solid-state layer from the solid-state material in a region of the modifications.