Double SOI Fabrication with Surface Smoothing for Second Bonding
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Solution Overview
Problem
The existing SMART CUT™ process for fabricating double semiconductor-on-insulator structures faces challenges in achieving a high-quality surface for bonding the second donor substrate, leading to defects and holes that affect the electrical performance and mechanical strength of the final structure.
Innovation Solution
A surface treatment process comprising rapid thermal annealing, thermal oxidation followed by deoxidation, long thermal annealing, and chemical-mechanical polishing is applied to the first transferred semiconductor layer to reduce roughness and defect density, thereby improving the bonding quality for the second layer transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two successive SMART CUT processes are used to fabricate double SOI structures, then the double semiconductor-on-insulator structure is obtained, but defects and holes are formed between the receiver substrate and the second donor substrate due to surface roughness and defect density
Solution Approach 1:
The patent applies preliminary surface treatment actions (chemical-mechanical polishing, thermal annealing, and oxidation-deoxidation sequences) to the first transferred semiconductor layer before the second bonding operation. These treatments are performed in advance to reduce surface roughness and defect density, ensuring that when the second donor substrate is bonded, the surface is sufficiently smooth and defect-free to prevent hole formation and ensure high bonding quality.
Solution Approach 2:
The patent changes physical and chemical parameters of the semiconductor layer surface through multiple treatments: mechanical polishing alters surface topology to reduce roughness, thermal annealing modifies temperature and crystalline structure to reduce defects, and oxidation-deoxidation sequences change chemical composition and surface properties. These parameter changes collectively transform the surface from a defective, rough state to a smooth, defect-free state suitable for high-quality bonding.
2Reliability
If surface treatments are applied to reduce roughness and defect density, then bonding quality improves, but the process complexity and number of steps increase
Solution Approach 1:
The patent merges multiple surface treatment operations (chemical-mechanical polishing, rapid thermal annealing, long thermal annealing, oxidation, and deoxidation) into a single integrated process flow between the first and second SMART CUT operations. Rather than treating these as separate, independent processes, they are combined into a unified surface preparation sequence that systematically addresses roughness and defects in a coordinated manner, improving bonding quality while managing overall process complexity through integration.
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 optimized surface treatment process significantly reduces the defect density and roughness of the first transferred semiconductor layer, minimizing the formation of holes and reducing the width of the peripheral ring, which enhances the bonding quality and mechanical strength of the double semiconductor-on-insulator structure.
Implementation Method 1
E1: rapid thermal annealing
Implementation Method 2
E2: a sequence including a thermal oxidation followed by a deoxidation
Implementation Method 3
E4: chemical-mechanical polishing
Data Source
AI summary
A method for fabricating a double semiconductor-on-insulator structure comprising the steps of: providing a first donor substrate and a handle substrate, forming a weakened zone in the donor substrate so as to delimit a first semiconductor layer to be transferred, bonding the first donor substrate to the handle substrate, a first electrically insulating layer being at the interface, and detaching at the weakened zone, treating the surface of the first transferred semiconductor layer comprising: a rapid thermal annealing, a thermal oxidation followed by a deoxidation, a smoothing heat treatment at a temperature of above 1000° C. in a non-oxidizing atmosphere, chemical-mechanical polishing, providing a second donor substrate of a second semiconductor layer to be transferred, transferring the second semiconductor layer, a second electrically insulating layer being at the interface.