Bonded SOI Wafer Surface Flattening via Segmented Oxidation
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Solution Overview
Problem
The ion implantation delamination method for manufacturing bonded SOI wafers generates slip dislocations and defects due to high-temperature and long-time annealing processes, which affect film thickness uniformity and surface roughness.
Innovation Solution
A method involving a first and second sacrificial oxidation treatment under a hydrogen gas atmosphere at 1100°C or more, followed by thermal oxidation at 900°C to 1000°C, and subsequent removal of the thermal oxide film, with RTA treatments performed at 1230°C or less to suppress slip dislocations and improve surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If high-temperature and long-time annealing processes are used to improve surface roughness and flatten the SOI layer, then surface flatness is improved, but slip dislocations and defects are generated
Solution Approach 1:
The patent divides the annealing process into multiple sequential stages with different temperatures and atmospheres: (1) initial annealing at 900-1100°C in N2 atmosphere, (2) oxidation at 900-1000°C in O2 atmosphere, (3) hydrogen annealing at 900-1100°C in H2 atmosphere, and (4) final oxidation at 900-1000°C in O2 atmosphere. This segmented approach allows surface flattening while avoiding the continuous high-temperature exposure that causes slip dislocations.
Solution Approach 2:
The patent changes multiple process parameters including temperature (varying between 900-1100°C across stages), atmosphere composition (switching between N2, O2, and H2), and oxidation time (controlled at 30-120 minutes). These parameter changes enable precise control over surface flatness improvement while preventing defect generation through optimized processing conditions.
2Shape
If multiple oxidation and annealing treatments are performed to reduce surface roughness, then surface quality is improved, but process time increases
Solution Approach 1:
The patent employs periodic alternating actions of oxidation and annealing treatments in a cyclic sequence. Each cycle consists of oxidation followed by hydrogen annealing, repeated twice. This periodic structure efficiently addresses surface roughness through oxidation while the hydrogen annealing steps prevent excessive time accumulation by maintaining controlled durations (30-120 minutes per step) and enabling rapid atmosphere switching.
3Shape
If thermal oxidation is performed at high temperature to form oxide film for flattening, then surface flatness is improved, but temperature control precision becomes critical
Solution Approach 1:
The patent applies beforehand cushioning by performing initial annealing treatment at 900-1100°C in N2 atmosphere before the oxidation steps. This pre-treatment stabilizes the SOI layer structure and reduces internal stresses, creating a more robust foundation that can withstand the subsequent thermal oxidation process. This cushioning effect broadens the acceptable temperature control range and reduces the risk of defect generation even with minor temperature fluctuations during oxidation.
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 effectively flattens the SOI layer, reduces defects, and maintains film thickness uniformity while preventing slip dislocation generation, enhancing the quality and productivity of bonded SOI wafers.
Implementation Method 1
gas ions such as hydrogen ions, rare gas ions and so forth are implanted into an upper surface of one wafer (a bond wafer) to form an ion-implanted layer (a micro bubble layer) within the wafer
Implementation Method 2
one wafer (the bond wafer) is delaminated so as to remain in the form of a thin film by applying a heat treatment (a delamination heat treatment) or mechanical external force using the ion-implanted layer as a cleavage plane
Implementation Method 3
form an oxide film on the SOI film by a heat treatment under an oxidizing atmosphere
Implementation Method 4
remove the oxide film (a so-called sacrificial oxidation treatment) and apply the heat treatment under the reducing atmosphere
Data Source
AI summary
According to the present invention, there is provided a method for manufacturing an SOI wafer having the step of performing a first sacrificial oxidation treatment on the aforementioned bonded SOI wafer in which the delamination has been performed after a first RTA treatment has been performed thereon and then performing a second sacrificial oxidation treatment thereon after a second RTA treatment has been performed thereon, wherein the first and second RTA treatments are performed under a hydrogen gas containing atmosphere and at a temperature of 1100° C. or more, wherein after a thermal oxide film has been formed on the aforementioned SOI layer front surface by performing only thermal oxidation by a batch type heat treating furnace at a temperature of 900° C. or more and 1000° C. or less in the first and second sacrificial oxidation treatments, a treatment for removing the thermal oxide film is performed.