Epitaxial Silicon Wafer Modified Layer for Carbon Diffusion Control
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Solution Overview
Problem
Conventional methods of irradiating silicon wafers with cluster ions containing carbon and hydrogen to enhance gettering capability result in carbon diffusion into thin epitaxial layers, leading to point defects and deteriorating electrical properties, while reducing the carbon dose insufficiently reduces gettering capability.
Innovation Solution
Irradiate silicon wafers with a low dose of C2Hy and SiHx cluster ions to form a modified layer, inhibiting carbon diffusion and maintaining gettering capability by forming EOR defects and sharp carbon concentration peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high dose of carbon-containing cluster ions is used to enhance gettering capability, then heavy metal trapping ability is improved, but carbon diffuses into the epitaxial layer causing point defects and deteriorating electrical properties
Solution Approach 1:
The patent segments the ion beam into two distinct components: carbon-containing cluster ions (for gettering) and silicon-containing cluster ions (for defect suppression). This segmentation allows each component to perform its specific function independently, resolving the contradiction between achieving high gettering capability and preventing carbon-induced point defects.
Solution Approach 2:
The patent uses a composite ion beam consisting of multiple types of cluster ions (carbon-based and silicon-based) with different functions. The carbon-containing ions provide gettering capability while silicon-containing ions suppress point defect formation, creating a synergistic effect that resolves the technical contradiction.
2Object-generated harmful factors
If the carbon dose is reduced to prevent point defects, then carbon diffusion is inhibited, but sufficient gettering capability cannot be obtained
Solution Approach 1:
The patent separates the functions of gettering and defect prevention into two different ion components. Carbon-containing ions are responsible solely for gettering, while silicon-containing ions are responsible for suppressing point defects, allowing each to operate at optimal doses without interfering with the other's function.
Solution Approach 2:
Silicon-containing cluster ions act as an intermediary that mitigates the harmful effects of carbon implantation. The silicon ions suppress point defect formation and reduce carbon diffusion, enabling the use of carbon ions for gettering without suffering from the usual detrimental effects.
3Reliability
If cluster ion irradiation is performed to form a modified layer, then gettering sites are created, but carbon concentration increases in the epitaxial layer during growth
Solution Approach 1:
The patent segments the ion beam composition to include both carbon-containing cluster ions (which create gettering sites) and silicon-containing cluster ions (which suppress carbon diffusion). This segmentation allows the modified layer to form with adequate gettering capability while the silicon component actively prevents excessive carbon concentration in the subsequent epitaxial layer.
Solution Approach 2:
Silicon-containing cluster ions serve as an intermediary that reduces carbon diffusion during epitaxial growth. The silicon atoms in the modified layer act as a barrier or sink that prevents carbon from migrating into the epitaxial layer, thereby controlling the carbon concentration while maintaining gettering functionality.
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
The method produces epitaxial silicon wafers with sufficient gettering capability and minimal carbon diffusion, preventing point defects and enhancing device performance.
Implementation Method 1
a step of irradiating a surface of a silicon wafer with a cluster ion beam including SiHx ions and C2Hy ions to form a modified layer that is located in a surface layer portion of the silicon wafer and that contains a solid solution of constituent elements of the cluster ion beam
Implementation Method 2
carbon present at a high concentration in the modified layer diffuses into the silicon epitaxial layer during the epitaxial growth and during the device formation process
Data Source
AI summary
A method of producing an epitaxial silicon wafer includes irradiating a surface of a silicon wafer with a beam of cluster ions containing SiHx ions (at least one of the integers 1 to 3 is selected as x of the SiHx ions) and C2Hy ions (at least one of the integers 2 to 5 is selected as y of the C2Hy ions) to form a modified layer that is located in a surface layer portion of the silicon wafer and that contains as a solid solution of the constituent elements of the cluster ion beam, and further includes forming a silicon epitaxial layer on the modified layer of the silicon wafer. The dose of the SiHx ions is 1.5×1014 ions/cm2 or more.