AOD Beam Dithering for Scan Field Distortion Correction
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Solution Overview
Problem
Current laser processing technologies face challenges in achieving high-speed, precise control over feature dimensions and impedance in chip packaging due to limitations in beam positioning and power delivery, particularly at high velocities, leading to issues with thermal side effects and throughput.
Innovation Solution
The integration of an acousto-optic deflector (AOD) system with a galvanometer mirror and f-theta scan lens, controlled by a computer executing machine-readable instructions, to correct for scan field distortion and optimize laser beam positioning, allowing for high-speed and precise control of feature dimensions and impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional beam positioning systems (linear stages with galvo mirrors) are used, then the system structure is simple, but the beam position acceleration cannot meet high velocity processing requirements
Solution Approach 1:
The patent replaces traditional mechanical beam positioning systems (linear stages with galvo mirrors) with an acousto-optic deflector (AOD) system that uses acoustic waves to control beam position. This substitution eliminates mechanical moving parts, enabling beam position changes at microsecond timescales and achieving the required acceleration for high velocity processing while reducing mechanical complexity
Solution Approach 2:
The AOD system provides dynamic beam positioning capability where the beam position can be rapidly adjusted by changing acoustic wave frequencies and amplitudes. This dynamic control allows the system to adapt to high velocity processing requirements and complex trajectory changes without mechanical inertia limitations
2Productivity
If high peak power laser pulses are used to ablate material, then ablation efficiency is improved, but thermal side effects (melting, cracking, substrate damage) increase
Solution Approach 1:
The system uses periodic ultrafast laser pulses with precise timing and repetition rates to ablate material. The pulsed nature of the laser delivery, combined with AOD-controlled positioning, allows high peak power to be delivered in short bursts that remove material through ablation rather than melting, reducing thermal side effects while maintaining high productivity
Solution Approach 2:
The patent changes the temporal parameters of laser delivery by using ultrafast pulse widths and controlling pulse repetition rates. This parameter change allows the material to be processed in a regime where ablation dominates over thermal conduction, achieving high removal rates with minimal thermal damage to surrounding areas
3Adaptability or versatility
If optical systems with shaped intensity profiles are used to process features of arbitrary size and shape, then feature versatility is improved, but time delays increase when changing feature characteristics
Solution Approach 1:
The AOD system provides dynamic control of beam position and intensity profile without mechanical moving parts. By electronically adjusting acoustic wave parameters, the system can rapidly change feature size and shape characteristics in real-time during processing, eliminating the time delays associated with mechanical reconfiguration of optical systems
Solution Approach 2:
The system changes feature characteristics by dynamically adjusting AOD control parameters (acoustic frequency, amplitude, and phase) rather than physically reconfiguring optical components. This parameter-based control enables rapid adaptation to different feature requirements without mechanical intervention or time delays
4Ease of operation
If f-theta scan lens is used for beam focusing, then beam positioning is simplified, but scan field distortion occurs that prevents proportional displacement
Solution Approach 1:
The system uses feedback control where the actual beam position is monitored and compared to the desired position. AOD control parameters are then adjusted in real-time to compensate for scan field distortion from the f-theta lens, ensuring accurate beam placement while maintaining the simplicity of using a standard scan lens
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 efficient and precise laser processing at high velocities, minimizing thermal effects and maximizing throughput by ensuring consistent fluence distribution and accurate feature formation, even at high processing speeds.
Implementation Method 1
an acousto-optic deflector (AOD) system arranged in the beam path between the laser source and the galvanometer mirror system, the AOD system operative to deflect the beam path
Implementation Method 2
a galvanometer mirror system operative to rotate the beam path
Implementation Method 3
an f-theta scan lens arranged in the beam path such that the galvanometer mirror system is arranged along the beam path between the laser source and the f-theta scan lens. Generally, the f-theta scan lens is operative to focus the laser beam at a spot within a scan field
Implementation Method 4
Laser pulses with high peak power may be used to ablate the dielectric material while minimizing thermal side effects such as melting, cracking, and substrate damage
Data Source
AI summary
A system includes a laser source, a galvanometer mirror system, an f-theta scan lens and an acousto-optic deflector (AOD) system. The AOD system is operated to deflect a beam path along which a laser beam propagates in a manner that corrects for scan field distortion induced by one or both of the f-theta lens and galvanometer mirror system.