SOI Wafer Terrace Width Control via Peripheral Insulator Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The ion implantation delamination method for manufacturing SOI wafers results in poor flatness at the wafer's outer peripheral portion, leading to weak bonding and incomplete transfer of the SOI layer, which causes SOI islands to form and potentially delaminate, resulting in device failures and abnormalities in SOI film thickness distribution.
Innovation Solution
A method involving ion implantation of hydrogen or rare gas ions into a silicon single crystal bond wafer to form an ion-implanted layer, followed by bonding with a base wafer through an insulator film, and then delaminating at the ion-implanted layer, where the insulator film is etched from the outer peripheral end towards the center, while protecting the back surface insulator film to control terrace width and prevent SOI island formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the insulator film is etched from the outer periphery to improve SOI islands and control terrace width, then the terrace width can be controlled and SOI island formation can be prevented, but the insulator film on the back surface is also removed causing warp due to thermal expansion coefficient difference
Solution Approach 1:
The patent applies local quality by selectively etching the insulator film only at the outer peripheral portion of the wafer while preserving the insulator film at the central portion and back surface. This localized etching approach allows terrace width control and SOI island prevention at the periphery without causing wafer warp from complete insulator film removal, thus resolving the contradiction between manufacturing precision and shape maintenance.
Solution Approach 2:
The patent segments the insulator film removal process into two distinct zones: the outer peripheral portion where etching is performed to control terrace width and prevent SOI islands, and the central/portion where the insulator film is preserved to maintain wafer flatness. This spatial segmentation resolves the contradiction by applying different treatments to different regions of the same structure.
2Reliability
If the insulator film is completely removed to prevent SOI islands, then SOI island formation is prevented, but the bond wafer becomes flat while the SOI wafer warps convex due to thermal expansion difference
Solution Approach 1:
The patent prevents SOI islands by selectively removing the insulator film only at the outer peripheral portion where SOI islands typically form, while preserving the insulator film at the back surface and central regions. This localized approach maintains the reliability benefit of SOI island prevention while avoiding the harmful convex warp that would result from complete insulator film removal.
3Manufacturing precision
If ion implantation is performed to enable delamination, then the SOI layer can be transferred to the base wafer, but the bonding force becomes weak at the outer periphery due to polishing sag causing incomplete transfer
Solution Approach 1:
The patent performs preliminary etching of the insulator film at the outer peripheral portion before the delamination process. This preliminary action removes the insulator film in advance where bonding is weak due to polishing sag, ensuring that the SOI layer will transfer completely to the base wafer at these critical peripheral regions, thus resolving the contradiction between transfer completeness and bonding strength.
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
This method effectively controls the terrace width, prevents SOI island formation, and suppresses scratches and abnormalities in SOI film thickness distribution, ensuring high-quality SOI wafer production by avoiding shape mismatches and delamination issues.
Implementation Method 1
at least one type of gas ion selected from a hydrogen ion and a rare gas ion is ion-implanted into a silicon single crystal bond wafer from a surface thereof to form an ion implanted layer
Implementation Method 2
the bond wafer is delaminated at the ion implanted layer to fabricate an SOI wafer
Implementation Method 3
bringing a bonded wafer before delaminating the bond wafer at the ion implanted layer into contact with a liquid that enables dissolving the insulator film or exposing it to a gas that enables dissolving the insulator film while protecting the insulator film on a back surface
Data Source
Figure 1(a)~1(d)
Figure 2
Figure 3(a)~3(c)
AI summary
The present invention provides a method for manufacturing an SOI wafer including a step of forming an insulator film on an entire surface of a bond wafer before bonding, bringing a bonded wafer before delaminating the bond wafer at an ion implanted layer into contact with a liquid that enables dissolving the insulator film while protecting the insulator film on a back surface on the opposite side of a bonding surface of the bond wafer, or exposing the same to a gas that enables dissolving the insulator film, and thus etching the insulator film placed between the bond wafer and a base wafer from an outer peripheral end of the bonded wafer toward a center of the same. As a result, it is possible to provide the method for manufacturing an SOI wafer by which a width of a terrace can be controlled, generation of an SOI island can be prevented, and scratches and an abnormality in SOI film thickness distribution can be suppressed at the time of forming the insulator film on the bond wafer and performing bonding.