Laser Beam Reshaping for Uniform Semiconductor Wafer Drilling
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Solution Overview
Problem
The existing laser beam machining systems face challenges in efficiently forming uniform depth holes in semiconductor wafers without damaging the electrodes, due to Gaussian energy distribution and the need for multiple irradiations, which results in poor productivity and risk of melting the bonding pads.
Innovation Solution
A laser beam machining system that includes a pulsed laser beam oscillator, a condenser, and laser beam reshaping means, such as an aspherical lens or a mask, to reshape the energy distribution into a top hat shape, combined with acousto-optical deflection means for precise beam scanning, allowing for efficient formation of uniform depth holes without damaging the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Gaussian distributed laser beam is used for machining, then the laser beam can be easily generated, but the machining depth becomes non-uniform and the bonding pad melts
Solution Approach 1:
The patent changes the energy distribution parameter of the laser beam from Gaussian to top-hat distribution using a beam reshaping device. This transformation ensures uniform energy density across the beam cross-section, resulting in uniform machining depth and preventing overheating of the bonding pad while maintaining ease of laser beam generation
Solution Approach 2:
The patent introduces a beam reshaping device as an intermediary component between the laser beam source and the workpiece. This device transforms the Gaussian distributed laser beam into a top-hat distributed beam, thereby achieving uniform machining depth without directly modifying the laser source itself
2Manufacturing precision
If the same work position is irradiated multiple times to form a through-hole, then the hole depth increases, but the bonding pad may be damaged due to excessive energy accumulation
Solution Approach 1:
The patent changes the energy distribution parameter from Gaussian to top-hat distribution, which spreads the energy more uniformly across the beam cross-section. This reduces peak energy density at any single point, allowing multiple irradiations to achieve the required hole depth without exceeding the damage threshold of the bonding pad
Solution Approach 2:
The patent employs periodic pulsed laser irradiation with controlled timing and duration. By using short pulses with adequate intervals, the system accumulates the necessary energy for through-hole formation while allowing heat dissipation between pulses, preventing thermal damage to the bonding pad
3Manufacturing precision
If a drill is used to form through-holes with small diameters of 100 to 300 μm, then the holes can be formed, but the productivity is poor
Solution Approach 1:
The patent replaces the mechanical drilling system with a laser beam machining system. This substitution eliminates mechanical contact, reduces tool wear and preparation time, and enables faster material removal through direct energy deposition, thereby significantly improving productivity while maintaining precise control of small hole diameters (100-300 μm)
Solution Approach 2:
The patent uses high-frequency pulsed laser irradiation to rapidly form through-holes. The periodic pulse delivery allows for efficient material ablation and vaporization, achieving through-hole formation in a fraction of the time required by mechanical drilling, thus dramatically improving productivity
4Productivity
If acousto-optical deflection means is used for beam scanning, then the laser beam can be rapidly scanned to improve productivity, but the system complexity increases
Solution Approach 1:
The patent introduces acousto-optical deflection means as an intermediary device to control laser beam direction. This component uses acoustic waves to modulate the optical path, enabling rapid and precise beam scanning without mechanical moving parts, thereby improving productivity while adding only moderate system complexity
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 solution enables the efficient formation of uniform depth holes reaching the electrodes without opening any holes in the electrodes, improving productivity and ensuring precise machining by reshaping the energy distribution and using acousto-optical deflection for precise scanning.
Implementation Method 1
laser beam reshaping means which is disposed between the pulsed laser beam oscillator and the laser beam scanning means and by which the energy distribution of the pulsed laser beam oscillated from the pulsed laser beam oscillator is reshaped into a top hat shape
Implementation Method 2
laser beam scanning means disposed between the pulsed laser beam oscillator and the condenser and operative to deflect the pulsed laser beam to be inputted to the condenser
Implementation Method 3
a condenser for condensing the pulsed laser beam oscillated from the pulsed laser beam oscillator
Implementation Method 4
the work is irradiated with one pulse of a laser beam when the portion, corresponding to the X and Y coordinate data on the minute hole to be formed in the work, of the work has been brought to a position directly under a condenser of the laser beam irradiation means
Data Source
AI summary
A laser beam machining system including a chuck table for holding a work, and a laser beam irradiation unit for irradiating the work held on the chuck table with a laser beam, wherein the laser beam irradiation unit includes: a pulsed laser beam oscillator for oscillating a pulsed laser beam; a condenser for condensing the pulsed laser beam oscillated from the pulsed laser beam oscillator; a laser beam scanning unit disposed between the pulsed laser beam oscillator and the condenser and operative to deflect the pulsed laser beam to be inputted to the condenser; and a laser beam reshaping unit which ids disposed between the pulsed laser beam oscillator and the laser beam scanning unit and by which the energy distribution of the pulsed laser beam oscillated from the pulsed laser beam oscillator is reshaped into a top hat shape.