Multi-Stage Substrate Etching for Terahertz Oscillators
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Solution Overview
Problem
Existing multi-stage substrate etching methods result in irregular etching, leading to deviations in depth, radius of curvature, T-shape wall faces, and overhang structures, which are unsuitable for precise terahertz oscillator fabrication.
Innovation Solution
A method involving sequential mask pattern formation and etching on multiple substrates, followed by bonding and re-etching to create uniform step structures, using sacrificial layers and precise alignment key patterns to maintain etching quality and prevent irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-stage etching is performed sequentially on a single substrate, then deep step structures can be formed, but irregular etching occurs causing depth deviation, radius of curvature, T-shape wall faces, and overhang structures
Solution Approach 1:
The etching process is divided into two independent stages performed on separate substrates. First substrate etching and second substrate etching are conducted independently, then the substrates are bonded together. This segmentation prevents irregular etching patterns (T-shape walls, overhangs) that occur in sequential single-substrate etching, while maintaining the ability to create deep step structures.
Solution Approach 2:
The first substrate is etched to a predetermined depth before bonding with the second substrate. This preliminary etching action establishes a precise depth reference that prevents depth deviation in the final structure. The pre-etched first substrate serves as a stable foundation that guides subsequent etching of the second substrate, ensuring uniform etching depths.
2Shape
If deep etching is performed to create step structures, then 3D microstructures can be formed, but overhang structures and irregular wall faces occur
Solution Approach 1:
The formation of deep step structures is achieved by segmenting the etching process across two separate substrates. Each substrate is etched independently to controlled depths, then bonded together. This approach creates clean vertical wall faces without the T-shape irregularities and overhangs that result from attempting to etch deep structures in a single continuous process.
3Adaptability or versatility
If sequential mask deposition and etching are repeated multiple times, then various step structures can be fabricated, but process time and complexity increase
Solution Approach 1:
Multiple step structures are fabricated by dividing the work into two parallel etching stages on separate substrates rather than performing multiple sequential etching cycles on a single substrate. This segmentation reduces the total number of mask deposition and etching cycles required, thereby reducing fabrication time while still achieving versatile step structure configurations through the bonding of pre-patterned substrates.
Data Source
AI summary
A method of multi-stage substrate etching is provided. The method comprises the steps of: forming a first mask pattern on one surface of a first substrate; forming a hole by etching the first substrate using the first mask pattern as an etching mask; forming a second mask pattern on one surface of a second substrate; forming a hole by etching the second substrate to a predetermined depth using the second mask pattern as an etching mask; bonding the first and second substrates together such that an etched surface of the first substrate faces an etched surface of the second substrate; forming a third mask pattern on the second substrate; and forming a hole passing through the second substrate by etching the second substrate using the third mask pattern as an etching mask, whereby it is prevented the occurrence of a radius of curvature in the bottom surface and the overhang structure occurring on a step surface, so that etching quality is improved, a precise bonding between the substrates is obtained using the alignment key positioned on each substrate, and a multi-layer process is carried out.