SOQ Substrate Manufacturing via Mechanical Delamination and Low-Temperature Annealing
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Solution Overview
Problem
The existing SOITEC method for manufacturing SOQ substrates faces challenges such as thermal strain and surface roughness due to thermal expansion coefficient differences between silicon and quartz substrates, requiring high-temperature processes that can lead to delamination or cracking, and result in uneven surface finishes.
Innovation Solution
A method involving ion implantation of hydrogen ions through an oxide film on a silicon substrate, followed by surface activation and bonding with a quartz substrate, mechanical delamination at room temperature, and hydrogen heat treatment at 1000°C or less to reduce surface roughness and achieve a mirror-finished surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal delamination is performed at 500°C or more using the SOITEC method, then delamination of the silicon thin film is achieved, but thermal strain causes delamination along the bonded surface or cracking
Solution Approach 1:
The patent changes the delamination mechanism from thermal to mechanical by using a laser beam to apply localized stress. This parameter change in the delamination method allows precise control of the delamination front position and eliminates thermal strain that causes cracking and delamination along bonded surfaces.
Solution Approach 2:
The patent replaces the thermal field (heat treatment at 500°C or more) with a mechanical field (laser-induced stress). The laser beam generates localized mechanical stress that propagates a delamination front through the silicon thin film without causing thermal strain, thus preventing cracking and bonded surface delamination.
2Strength
If high-temperature heat treatment (500°C or more) is applied to ensure satisfactory bonded state, then bonding strength is improved, but thermal strain causes delamination or cracking
Solution Approach 1:
The patent performs preliminary bonding at room temperature or low temperature before applying the laser beam for delamination. This preliminary bonding action ensures sufficient bonding strength without subjecting the substrates to high-temperature heat treatment that would cause thermal strain and cracking.
Solution Approach 2:
The patent substitutes thermal energy with mechanical energy from the laser beam for the delamination process. This allows the bonded structure to remain at low temperature throughout the delamination process, maintaining substrate integrity while achieving complete silicon thin film delamination.
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 lowers the manufacturing process temperature, reduces surface roughness, ensures uniform film thickness, and suppresses defects like transference defects and slip dislocations, resulting in a high-quality SOQ substrate with improved mechanical strength and surface smoothness.
Implementation Method 1
an ion implantation step of forming a hydrogen ion implanted layer on a main surface of a silicon substrate through an oxide film
Implementation Method 2
a surface treatment step of performing activation on at least one of a main surface of a quartz substrate and a main surface of the silicon substrate
Implementation Method 3
a step of performing hydrogen heat treatment on the silicon film at a temperature of 1000°C or less
Implementation Method 4
hydrogen heat treatment at 1000°C or less to reduce surface roughness and achieve a mirror-finished surface
Data Source
Figure 1(A)~1(G)
Figure 2(A)~2(B)
AI summary
To lower a process temperature for an SOQ substrate manufacturing process to reduce the degree of surface roughness of an SOQ film and provide a high-quality SOQ substrate. Hydrogen ions are implanted to a surface of a single crystal Si substrate 10 through an oxide film 11 to uniformly form an ion implanted layer 12 at a predetermined depth (average ion implantation depth L) from the surface of the single crystal Si substrate 10, and a bonding surface of the substrate undergoes a plasma treatment or an ozone treatment. An external shock is applied onto the single crystal Si substrate 10 and quartz substrate 20, which are bonded together, to mechanically delaminate a silicon film 13 from a single crystal silicon bulk 14. In this way, the SOQ film 13 is formed on the quartz substrate 20 through the oxide film 11. To further smooth the SOQ film surface, hydrogen heat treatment is performed at a temperature of 1000°C or less below a quartz glass transition point. When measuring surface roughness of an SOQ film after performing hydrogen heat treatment on a sample having surface roughness of about 5 nm in terms of RMS average value immediately after delamination, a satisfactory measurement result of 0.3 nm or less in terms of RMS average value was obtained.