SOI Substrate Fabrication via Visible Light Embrittlement
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Solution Overview
Problem
Conventional methods for manufacturing SOI substrates, such as the SOITEC and SiGen methods, face issues with thermal expansion coefficient differences between silicon and handle substrates like quartz and sapphire, leading to cracking or separation of bonded wafers during high-temperature treatments.
Innovation Solution
A method involving ion implantation of silicon wafers, surface activation treatments, and controlled heat treatments followed by visible light irradiation to embrittle the ion-implanted layer, allowing for the transfer of a silicon thin film to a transparent insulating substrate without thermal delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature heat treatment (near 500°C) is applied to generate microcavities for delamination, then the silicon thin film can be transferred to the handle substrate, but the bonded wafer may crack due to large difference in thermal expansion coefficient between silicon and handle substrates
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature (near 500°C) treatment to a lower temperature range (150-350°C), which is sufficient to activate the ion-implanted layer for delamination while avoiding thermal stress-induced cracking. This parameter optimization resolves the contradiction between achieving effective delamination and maintaining bonded wafer integrity.
2Strength
If heat treatment at 200°C or higher is applied to increase bonding strength, then the bonding strength of bonded interface increases, but separation may occur due to warpage of bonded wafer with different substrate types
Solution Approach 1:
The patent applies ion implantation as a preliminary action before bonding and heat treatment. This pre-treatment creates a controlled weak interface at the ion-implanted layer that enables uniform delamination at lower temperatures, preventing warpage-induced separation while maintaining adequate bonding strength during the process.
3Manufacturing precision
If visible light irradiation is applied to embrittle the ion-implanted layer, then the silicon thin film can be transferred without thermal delamination, but the process requires precise control to avoid excessive embrittlement
Solution Approach 1:
The patent replaces thermal energy with optical energy (visible light irradiation) to embrittle the ion-implanted layer. This substitution allows for precise spatial and temporal control of the embrittlement process, achieving uniform film transfer while avoiding the thermal stress problems associated with conventional high-temperature methods.
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
Effectively prevents breakage and cracking of bonded wafers by controlling the thermal expansion mismatch, enabling efficient formation of SOI substrates with improved bonding strength and uniformity.
Implementation Method 1
irradiating visible light with a wavelength within the range 400 to 700 nm at a side of the transparent insulating substrate of the laminate toward the ion-implanted layer of the silicon wafer or the silicon wafer with an oxide film to embrittle an interface of the ion-implanted layer
Implementation Method 2
subjecting the bonded wafer to a heat treatment at 150°C or higher but not higher than 350°C so as to obtain a laminate
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Provided is an SOI substrate manufacturing method which, in this order, includes; a step of forming an ion implanted layer (2) by implanting ions into a silicon wafer (5) or a silicon wafer (5) provided with an oxide film (7); a step of performing surface activation treatment to the surface of a transparent insulating substrate and the surface of the ion-implanted silicon wafer and/or the surface of the ion-implanted silicon wafer provided with the oxide film; a step of bonding the silicon wafer (5) or the silicon wafer (5) provided with the oxide film (7) with the transparent insulating substrate (3); a step of obtaining a bonded body (6) by performing heat treatment to the bonded substrate at 150° C or higher but not higher than 350° C; and a step of forming an SOI layer (4) by making brittle the interface of the ion-implanted layer (2) by radiating visible light from the side of the transparent insulating substrate (3) of the bonded body (6) toward the ion-implanted layer (2) of the silicon wafer (5) or that of the silicon wafer (5) provided with the oxide film (7), and by transferring a silicon thin film onto the transparent insulating substrate (3).