SOI Wafer Terrace Control via Selective Insulator Etching
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Solution Overview
Problem
In the manufacturing of SOI wafers using the ion implantation separation method, the existing technologies face challenges in controlling the terrace width, preventing the occurrence of SOI islands, and inhibiting warping due to the limitations of accelerating voltage and thermal expansion coefficient differences between insulator films and silicon, leading to defects and low bonding strength.
Innovation Solution
A method involving ion implantation into a bond wafer to form a layer, bonding with a base wafer through an insulator film, and selectively etching the insulator film from the outer circumference towards the center while protecting the back surface film, to control the terrace width and prevent SOI islands, using a solution like hydrogen fluoride to dissolve the insulator film without heat treatment, and optionally performing low-temperature heat treatment to enhance bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the insulator film is etched from the outer circumference to improve the terrace and prevent SOI islands, then a part of the insulator film on the back surface of the base wafer is removed, causing large warp in the SOI wafer after separation
Solution Approach 1:
The patent applies local quality by selectively etching only specific regions of the insulator film while preserving others. The etching is performed only on the insulator film at the bonding interface between the bond wafer and base wafer, while the insulator film on the back surface of the base wafer is protected and retained. This localized differentiation resolves the contradiction by improving terrace quality through selective etching while preventing warp by preserving the back surface insulator film.
Solution Approach 2:
The patent segments the insulator film into functionally distinct regions: the insulator film at the bonding interface is etched to create the terrace and prevent SOI islands, while the insulator film on the back surface is protected and retained to maintain wafer flatness. This segmentation allows each region to serve its specific function without interfering with the other, resolving the contradiction between terrace quality and wafer warp.
2Manufacturing precision
If the insulator film is etched to control the terrace width, then the bonding strength between bonded wafers is reduced, making the SOI layer hard to be transferred
Solution Approach 1:
The patent applies preliminary action by performing the etching of the insulator film at the bonding interface before the separation process. This timing allows precise control of the terrace width to be established in advance, while the bonding strength is maintained at the optimal level for subsequent separation. The etching creates the desired terrace geometry without compromising the bonding interface integrity during the bonding phase.
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 the formation of SOI islands, and reduces warping, ensuring high-quality SOI wafers with improved bonding strength and reduced defects.
Implementation Method 1
implanting at least one gas ion selected from a hydrogen ion and a rare gas ion into a bond wafer (10) composed of silicon single crystal from a surface of the bond wafer to form a layer (11) of the implanted ion
Implementation Method 2
the bonded wafer (14) before separating the bond wafer (10) along the layer of the implanted ion is brought into contact with a liquid (15) capable of dissolving the insulator film (13) or exposed to a gas capable of dissolving the insulator film (13), such that a second part (13a) of the insulator film is etched
Data Source
Figure 1(a)~1(d)
Figure 2(a)~2(c)
AI summary
The present invention provides a method for manufacturing an SOI wafer, in which an insulator film is formed at least on all surfaces of a base wafer, and while protecting a first part of the insulator film on a back surface on the opposite side from a bonded surface of the base wafer, a bonded wafer before separating a bond wafer along a layer of the implanted ion is brought into contact with a liquid capable of dissolving the insulator film or exposed to a gas capable of dissolving the insulator film, such that a second part of the insulator film interposed between the bond wafer and the base wafer is etched from an outer circumferential edge of the bonded wafer and toward the center of the bonded wafer. The method can control the terrace width, prevent the occurrence of an SOI island, and inhibit warping of the SOI wafer in a bonding process with a base wafer having an insulator film formed thereon.