Picosecond Laser Substrate Processing for Crack-Free Dicing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current laser processing techniques for semiconductor and glass substrates are limited by high waste generation due to mechanical sawing and inefficiencies in laser dicing and welding, with excessive pulse energy causing microcracks and shock waves.
Innovation Solution
A novel pulsed laser processing method using picosecond-scale pulses with high repetition rates and overlapping pulses to achieve both nonlinear and linear absorption, reducing microcracking and waste by utilizing the residual heat for efficient energy transfer and thermal wave formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If mechanical sawing is used for dicing semiconductor wafers, then the cutting process is simple and reliable, but a considerable portion of semiconductor material is wasted as dust due to kerf width
Solution Approach 1:
The patent replaces mechanical sawing with laser processing to eliminate kerf width and material waste. The laser beam processes the wafer without physical contact, removing the need for mechanical blades that create wide cuts and dust. This substitution directly addresses the material loss problem while maintaining high productivity through rapid laser scanning.
Solution Approach 2:
The patent changes the processing parameter from mechanical force to optical energy concentration. By using focused laser beams with specific wavelengths and intensities, the process transforms material through ablation and melting rather than mechanical removal. This parameter change enables precise cutting with minimal material loss while preserving processing speed.
2Reliability
If pulse energy is increased to improve welding efficiency, then nonlinear absorption increases, but shock waves are induced into material causing micro level cracks
Solution Approach 1:
The patent employs periodic pulsed laser action with optimized pulse duration and repetition rate. By delivering energy in controlled pulses rather than continuous irradiation, the process allows thermal diffusion between pulses, preventing excessive heat accumulation and shock wave formation. This periodic action maintains welding efficiency while avoiding microcrack formation.
Solution Approach 2:
The patent optimizes laser parameter combinations including pulse duration, repetition rate, and peak power to achieve the desired balance. By adjusting these parameters, the process maximizes nonlinear absorption for efficient welding while keeping peak intensities below the threshold that generates harmful shock waves and microcracks in the material.
3Manufacturing precision
If femtosecond-scale laser pulses are used for micromachining transparent materials, then nonlinear absorption is achieved, but the processing speed is limited
Solution Approach 1:
The patent uses periodic pulsed laser action with repetition rates optimized for the specific material and geometry. By controlling the pulse frequency, the process maintains the precision benefits of short pulses while increasing the overall processing speed through higher repetition rates and reduced inter-pulse intervals, allowing faster material removal without sacrificing micromachining quality.
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 results in high-quality, crack-free microstructures with minimal waste, increased processing speed, and improved bending strength, enabling efficient dicing and welding of substrates with reduced peak power requirements.
Implementation Method 1
directing to the substrate from a laser source a plurality of sequential focused laser pulses... under conditions causing nonlinear absorption
Implementation Method 2
picosecond-scale laser pulses may induce at the substrate, in addition to nonlinear absorption, also considerable linear absorption effect
Implementation Method 3
the pulses being capable of locally melting the substrate... a structurally modified zone is formed to the substrate
Implementation Method 4
utilizing the residual heat for efficient energy transfer and thermal wave formation
Data Source
AI summary
The invention relates to a method and apparatus for processing substrates, such as glass and semiconductor wafers. The method comprises directing to the substrate from a laser source a plurality of sequential focused laser pulses having a predetermined duration, pulsing frequency and focal spot diameter, the pulses being capable of locally melting the substrate, and moving the laser source and the substrate with respect to each other at a predetermined moving velocity so that a structurally modified zone is formed to the substrate. According to the invention, the pulse duration is in the range of 20-100 ps, pulsing frequency at least 1 MHz and moving velocity adjusted such that the distance between successive pulses is less than ⅕ of the diameter of the focal spot. The invention can be utilized, for example, for efficient dicing, scribing and welding of materials which are normally transparent.