Laser Beam Processing Machine for Semiconductor Via Holes
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Solution Overview
Problem
Existing methods for forming via holes in semiconductor wafers to reach electrodes are inefficient due to the risk of electrode melting from heat accumulation during pulse laser beam processing, and high repetition frequencies reduce productivity.
Innovation Solution
A laser beam processing machine with an acousto-optic deflection system and controller that adjusts the optical axis of a pulse laser beam to ensure a minimum 150 μs time interval between pulses, allowing for efficient via hole formation without melting the electrodes, even at high repetition frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the repetition frequency of pulse laser beam is set to 6,600 Hz or less, then the time interval between pulses is 150 μs or more preventing electrode melting, but the number of pulses must be thinned reducing productivity
Solution Approach 1:
The patent applies dynamics by making the laser beam application position variable through optical axis deflection. The system dynamically adjusts which positions receive laser pulses based on deflection amounts, allowing high repetition frequency operation while distributing heat accumulation across multiple positions. This enables maintaining electrode integrity without thinning pulses, thus preserving productivity.
Solution Approach 2:
The patent introduces a new dimension of control by deflecting the optical axis of the laser beam in the processing-feed direction. Instead of only controlling pulse timing, the system adds spatial distribution as another dimension of control. By deflecting the beam to different positions sequentially, heat is distributed across multiple locations, preventing localized melting while allowing high repetition frequencies.
2Productivity
If the repetition frequency of pulse laser beam is set to 6,600 Hz or more, then productivity is improved, but heat accumulates in electrode causing melting
Solution Approach 1:
The system dynamically changes the application position of laser pulses by deflecting the optical axis. This dynamic positioning allows the system to operate at high repetition frequencies (6,600 Hz or more) while distributing thermal energy across multiple positions, preventing heat accumulation at any single electrode location and thus avoiding melting.
Solution Approach 2:
The patent segments the laser processing into multiple positional segments through optical axis deflection. Instead of concentrating all pulses on one position, the system divides the processing into sequential positions, with each position receiving a subset of pulses. This segmentation distributes heat load, enabling high repetition frequency operation without electrode damage.
3Manufacturing precision
If drilling is used to form via holes with diameters of 30 to 100 μm, then via holes can be formed, but productivity is insufficient and controlling accuracy is extremely difficult
Solution Approach 1:
The patent replaces the mechanical drilling system with a laser beam system. Instead of using physical drill bits that require precise mechanical positioning and suffer from wear and tool life limitations, the system uses focused laser beams that can be precisely controlled optically. This substitution enables both high precision (30-100 μm via holes) and high productivity through rapid laser processing.
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
The machine effectively forms via holes reaching electrodes without melting them, while maintaining high productivity by optimizing the time interval between laser pulses, thus improving the efficiency of the semiconductor wafer processing.
Implementation Method 1
an acousto-optic device for deflecting an optical axis of a pulse laser beam
Implementation Method 2
a method of efficiently forming a via hole reaching an electrode in a wafer having a plurality of devices on the front surface of a substrate and electrodes on each of the devices, by applying a pulse laser beam from the rear surface of the substrate
Data Source
AI summary
A laser beam processing machine includes a laser beam application device and a controller. The controller controls deflecting of the optical axis of a pulse laser beam from the laser beam application device in the processing-feed direction according to a plurality of processing position coordinates, and according to the frequency of the beam, to ensure that there is a predetermined time interval between pulses applied to the same processing position coordinates. One pulse is applied at a time to each of the plurality of processing position coordinates.