3D Semiconductor Etching Using Sub-Bandgap Laser Focal Spots
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Solution Overview
Problem
Conventional microfabrication techniques for semiconductor manufacturing are complex, time-consuming, and limited to creating two-dimensional structures, making it difficult to achieve three-dimensional features with smaller sizes.
Innovation Solution
Utilizing sub-bandgap-energy lasers to create holes in the semiconductor lattice through multi-photon absorption, combined with controlled electric fields and etching solutions, allows for selective etching of three-dimensional structures by positioning the focal spot within the semiconductor body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional microfabrication techniques are used, then manufacturing processes are well-established and reliable, but the process is complex, time-consuming, and limited to two-dimensional structures
Solution Approach 1:
The patent replaces conventional mechanical lithographic patterning and layer-by-layer deposition with a direct laser-based electrochemical etching system. The laser focuses energy to specific points in the semiconductor bulk, creating holes that migrate to the surface and enable localized etching, eliminating the need for complex photomask alignment and multiple deposition steps
Solution Approach 2:
The invention transitions from two-dimensional surface-based patterning to three-dimensional bulk processing by focusing laser energy at specific depths within the semiconductor. This allows direct creation of 3D structures with controlled geometry in the bulk material, rather than building up layers from the surface
2Manufacturing precision
If conventional lithographic techniques are used, then patterning is well-controlled, but feature sizes are limited and cannot achieve smaller dimensions
Solution Approach 1:
The patent changes the fundamental parameter of how holes are generated in the semiconductor - using laser-induced multi-photon absorption and electrochemical reactions instead of photolithographic chemical reactions. This allows precise control of hole generation location and density, enabling feature sizes below conventional lithographic limits
Solution Approach 2:
The invention introduces holes as an intermediary carrier between the laser energy and the etching process. The laser creates holes at specific locations, these holes migrate to the surface, and then enable localized electrochemical etching. This intermediary mechanism provides precise spatial control of the etching process
3Manufacturing precision
If layer-by-layer fabrication is used, then each layer can be precisely controlled, but the overall fabrication time is excessive
Solution Approach 1:
The patent enables continuous etching action by maintaining a constant supply of holes to the etching surface through ongoing laser illumination and hole migration. This eliminates the need to stop and restart for each layer deposition and removal cycle, allowing continuous material removal and significantly reducing total fabrication time
Solution Approach 2:
The laser pre-generates holes in the bulk semiconductor before etching occurs at the surface. This preliminary hole creation allows the etching process to proceed continuously without waiting for layer deposition and photolithographic preparation, as the hole supply is already established
4Shape
If conventional etching methods are used, then etching uniformity is maintained, but three-dimensional features cannot be created
Solution Approach 1:
The patent applies local quality by concentrating laser energy at specific points in the bulk semiconductor to create holes only where needed. This localized hole generation enables precise 3D feature creation with controlled geometry, while the surrounding unilluminated areas remain unaffected, maintaining overall process control and uniformity
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
Enables the precise etching of three-dimensional features with smaller dimensions than conventional methods, reducing complexity and time while maintaining control over the etching process.
Implementation Method 1
The sub-bandgap energy light emitted by the illumination source is focused to a sufficiently intense focal spot to cause multi-photon absorption (MPA) within the semiconductor. When this occurs, the photon energy of multiple photons is combined to exceed the bandgap energy of the semiconductor, exciting electrons from the valence band to the conduction band and thereby creating holes in the atomic lattice of the semiconductor at the focal spot of the illumination source.
Implementation Method 2
Holes at the exposed surface of the semiconductor cause oxidation of the semiconductor, which oxidation is subsequently etched by the etchant solution.
Data Source
AI summary
Various technologies are described herein pertaining to electrochemical etching of a semiconductor controlled by way of a laser that emits light with an energy below a bandgap energy of the semiconductor.