Laser Beam Processing Machine Dual-Energy Via Hole Formation
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Solution Overview
Problem
The existing methods for forming via holes in semiconductor wafers using pulse laser beams face challenges in removing metal contaminants from the inner walls of the holes, which can diffuse into the substrate and reduce device quality, and the drilling process is not productive due to the need for precise control and potential damage to electrodes.
Innovation Solution
A laser beam processing machine is designed with two pulse laser beams of different energy densities (20 to 60 J/cm2 and 3 to 20 J/cm2) and spot diameters (0.75 to 0.9 D and 0.2 to 0.3 D) to form via holes and efficiently remove metal contaminants from the inner walls using trepanning processing, ensuring the substrate is not damaged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pulse laser beam is applied to form via holes in the substrate, then via holes can be efficiently formed reaching the bonding pads, but metal atoms from the bonding pads are scattered and adhere to the inner peripheral walls of the via holes as metal contaminants
Solution Approach 1:
The laser beam application process is segmented into two distinct stages with different energy densities: a first stage (20-60 J/cm²) for forming the via hole through the substrate, and a second stage (3-20 J/cm²) for cleaning metal contaminants from the inner walls. This segmentation allows each stage to be optimized for its specific function, resolving the contradiction between efficient via hole formation and contaminant removal.
Solution Approach 2:
The invention converts the harmful effect of laser-induced metal atom scattering into a beneficial cleaning process. By applying a second laser beam with lower energy density along the inner walls of the formed via hole, the previously scattered metal atoms are removed through controlled ablation or vaporization, transforming the contamination problem into an effective cleaning mechanism.
2Manufacturing precision
If a drill is used to form via holes in the semiconductor wafer, then precise control can be achieved to avoid damaging electrodes, but productivity is reduced due to the need for extreme accuracy and the small diameter of via holes (100 to 300 μm)
Solution Approach 1:
The invention replaces the mechanical drilling system with a laser beam-based system. The laser beam can be precisely positioned and controlled to form via holes with diameters of 50 μm or less, achieving the required manufacturing precision while dramatically improving productivity. The laser beam's ability to be rapidly repositioned and its non-contact nature eliminate the speed-accuracy trade-off inherent in mechanical drilling.
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 bonding pads while efficiently removing metal contaminants from the inner walls, preventing diffusion into the substrate and improving device quality without compromising the substrate's integrity.
Implementation Method 1
a first laser beam application means for applying a first pulse laser beam having an energy density per one pulse of 20 to 60 J/cm2
Implementation Method 2
a second laser beam application means for applying a second pulse laser beam having an energy density per one pulse of 3 to 20 J/cm2
Data Source
AI summary
A laser beam processing machine comprising a chuck table for holding a workpiece, a laser beam application means for applying a laser beam to the workpiece held on the chuck table, a processing feed means for moving the chuck table and the laser beam application means relative to each other in a processing-feed direction and an indexing-feed means for moving the chuck table and the laser beam application means in an indexing-feed direction perpendicular to the processing-feed direction, wherein the laser beam application means comprises a first laser beam application means for applying a first pulse laser beam having an energy density per one pulse of 20 to 60 J/cm2 and a second laser beam application means for applying a second pulse laser beam having an energy density per one pulse of 3 to 20 J/cm2.