Spike-Shaped Laser Damage Structures for Substrate Cleaving
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Solution Overview
Problem
Current methods for wafer dicing, such as diamond disk saws and laser ablation, face limitations in processing speed, kerf width, surface cracking, thermal damage, and debris contamination, particularly for thicker substrates and specialty wafers, which degrade device yield and performance.
Innovation Solution
A laser processing method using a focused pulsed laser beam with a 'spike'-shaped intensity distribution is applied to create deep and narrow damage areas within the substrate, allowing for efficient cleaving without multiple passes, thereby increasing production yield and reducing damage to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If diamond disk saw is used for dicing, then cutting capability is achieved, but processing speed is low and kerf width is wide
Solution Approach 1:
The patent replaces the mechanical diamond disk saw system with a laser-based processing system. The laser beam creates damage structures within the substrate through optical breakdown and multiphoton absorption, eliminating mechanical contact entirely. This substitution enables faster processing speeds while achieving narrower effective kerf widths through precise optical focusing, directly resolving the contradiction between speed and precision.
Solution Approach 2:
The patent changes the physical state and parameters of the laser beam to achieve deep, narrow damage structures. By using ultrafast laser pulses with specific wavelengths and focusing them to create spike-like damage zones, the process achieves both high speed and precision. The damage structures extend deeply into the substrate with minimal lateral spread, simultaneously improving processing speed and reducing kerf width.
2Speed
If laser ablation is used for dicing, then processing speed is improved, but kerf width becomes wide and thermal damage occurs
Solution Approach 1:
The patent employs periodic ultrafast laser pulsing to create damage structures. The pulsed nature of the laser allows for controlled energy deposition where each pulse creates a discrete damage zone. The short pulse duration prevents heat diffusion to surrounding areas, eliminating thermal damage while maintaining high processing speeds through rapid successive pulsing along the cut line.
Solution Approach 2:
The patent utilizes phase transition mechanisms through ultrafast laser pulses that induce optical breakdown and multiphoton absorption. The extreme peak powers during pulse peaks cause instantaneous material decomposition and plasma formation without significant thermal conduction. This non-thermal ablation mechanism achieves fast processing while avoiding the thermal damage and melted residuals characteristic of conventional laser ablation.
3Manufacturing precision
If multiple laser passes are used for thick substrates, then complete cleaving is achieved, but processing time increases and device performance deteriorates
Solution Approach 1:
The patent transitions from surface-level or shallow laser processing to deep three-dimensional damage structure formation. By focusing ultrafast laser pulses to create spike-like damage structures that extend deeply into the substrate thickness, the process achieves complete cleaving in a single pass. This dimensional approach to damage creation eliminates the need for multiple sequential passes, reducing processing time while maintaining complete cleaving effectiveness.
Solution Approach 2:
The patent creates preliminary damage structures within the substrate that prepare the material for subsequent mechanical cleaving. The ultrafast laser pulses pre-weaken the substrate along the intended cleavage line by creating internal damage zones, so that minimal additional force is needed to complete the separation. This preliminary action achieves complete cleaving in one pass without requiring multiple passes, thereby reducing processing time.
4Measurement precision
If high numerical aperture lens is used for stealth dicing, then focusing precision is improved, but depth of focus decreases and multiple cracks occur
Solution Approach 1:
The patent changes the laser pulse parameters and focusing conditions to create spike-like damage structures with extended depth. By using ultrafast pulses with specific duration and wavelength, combined with appropriate numerical aperture, the process achieves both precise focusing and sufficient depth of focus. The damage structures are confined to the focal region without creating lateral cracks, simultaneously achieving focusing precision and crack control.
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 rapid and precise separation of semiconductor devices from thick, hard substrates with minimal damage, improving processing speed and device quality by forming controlled cracks along the intended cleaving line without surface cracking or thermal damage.
Implementation Method 1
The surface of the work-piece is irradiated with a pulsed laser beam according to the predetermined cutting line under conditions sufficient to cause multi-photon absorption
Implementation Method 2
Another classical laser processing technology, namely laser ablation, is also limited by its low processing speed
Implementation Method 3
the beam is aligned to produce a focal spot (or condensed point: a high energy/photon density zone) inside the bulk of the work-piece
Data Source
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AI summary
This invention provides an effective and a method of laser processing for separating semiconductor devices formed on a single substrate (6) or separating high thickness, hard and solid substrates (6), which is rapid. During preparation of the device or substrate (6) for the cleaving/breaking/dicing procedure an area of damage (8, 11) is achieved by obtaining deep and narrow damage area along the intended line of cleaving. The laser processing method comprises a step of modifying a pulsed laser beam (1) by an focusing unit (1), such as that an "spike"-shaped beam convergence zone, more particularly an above workpiece material optical damage threshold fluence (power distribution) in the bulk of the workpiece (6) is produced. During the aforementioned step a modified area (having a "spike"-type shape) is created. The laser processing method further comprises a step of creating a number of such damage structures (8, 11) in a predetermined breaking line by relative translation of the workpiece (6) relative the laser beam (1) condensation point.