SOI Substrate Separation via Low-Temperature Thermal Stress
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Solution Overview
Problem
Conventional methods for manufacturing SOI substrates face challenges such as breakage, local cracks, and mechanical damage due to thermal property differences between substrates, particularly when using high-temperature processing, and mechanical separation methods introduce defects in the silicon thin film.
Innovation Solution
A method involving hydrogen ion implantation, surface activation treatment, and controlled heat treatment at 200°C to 350°C to peel off a silicon layer from a single-crystal silicon substrate bonded to a transparent insulating substrate, utilizing a heating plate to generate stress for separation while avoiding high-temperature processing and mechanical damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature heat treatment (400°C or higher) is used to separate the silicon thin film, then the silicon thin film can be thermally peeled off, but breakage and local cracks occur due to thermal property differences between substrates
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature (400°C or higher) processing to low-temperature (200°C to 350°C) processing. This parameter change enables silicon thin film separation while avoiding breakage and local cracks caused by thermal stress between substrates with different thermal expansion coefficients.
Solution Approach 2:
The patent replaces the conventional thermal stress mechanism with a combined mechanism involving hydrogen ion implantation layers and controlled low-temperature heating. The hydrogen ion-implanted layer acts as a pre-weakened separation plane, allowing thermal energy at lower temperatures to induce separation without causing substrate breakage.
2Object-affected harmful factors
If mechanical peeling method is used to separate the silicon thin film at room temperature, then thermal stress damage is avoided, but mechanical damage is introduced into the silicon thin film
Solution Approach 1:
The patent replaces direct mechanical peeling with a thermally-assisted separation process. By combining hydrogen ion implantation (creating a weakened layer) with controlled low-temperature heating (200°C to 350°C), the silicon thin film separates cleanly without mechanical contact damage, while avoiding the thermal stress problems of high-temperature conventional methods.
Solution Approach 2:
The hydrogen ion-implanted layer serves as an intermediary that facilitates separation. This implanted layer creates a plane of weakness that enables clean separation at low temperatures, acting as a mediator between the silicon substrate and the bonding substrate, allowing thermal energy to induce separation without direct mechanical force.
3Adaptability or versatility
If substrates made of different materials are bonded together, then manufacturing flexibility is improved, but breakage and local cracks occur due to difference in thermal properties
Solution Approach 1:
The patent changes the temperature parameter to a low range (200°C to 350°C) that is low enough to minimize thermal stress between dissimilar substrates but high enough to enable separation when combined with hydrogen ion implantation. This parameter change allows bonding of substrates with different thermal expansion coefficients without causing breakage.
Solution Approach 2:
The patent applies hydrogen ion implantation before bonding and before separation. This preliminary action creates a weakened layer in the silicon substrate that enables clean separation at low temperatures, preventing thermal stress damage when bonding substrates with different thermal properties.
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 approach results in an SOI substrate with superior film uniformity, crystal quality, and electrical characteristics, eliminating breakage and mechanical damage, and simplifying the manufacturing process by maintaining low-temperature processing.
Implementation Method 1
a first step of forming a hydrogen ion-implanted layer on the surface side of a first substrate which is a single-crystal silicon substrate
Implementation Method 2
the rear surface of the single-crystal Si substrate bonded to the insulating substrate is closely adhered on the heating plate kept at a temperature of 200°C or higher but no higher than 350°C to generate a temperature difference between the single-crystal Si substrate and the transparent insulating substrate, thereby producing a large stress between the both substrates and peeling off the silicon thin film
Data Source
AI summary
A heating plate (32) having a smooth surface is placed on a hot plate (31) which constitutes a heating section, and the smooth surface of the heating plate (32) is closely adhered on the rear surface of a single-crystal Si substrate (10) bonded to a transparent insulating substrate (20). The temperature of the heating plate (32) is kept at 200°C or higher but not higher than 350°C. When the rear surface of the single-crystal Si substrate (10) bonded to the insulating substrate (20) is closely adhered on the heating plate (32), the single-crystal Si substrate (10) is heated by thermal conduction, and a temperature difference is generated between the single-crystal Si substrate and the transparent insulating substrate (20). A large stress is generated between the both substrates due to rapid expansion of the single-crystal Si substrate (10), thus separation takes place at a hydrogen ion-implanted interface.