SiGe Heteroepitaxial Deposition via Oxygen Incorporation
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the lattice strain and dislocation issues in heteroepitaxial deposition of SiGe layers on silicon substrates, which affects carrier mobility and device performance, particularly due to the critical thickness limit beyond which SiGe layers relax and form misfit dislocations, leading to reduced device performance and potential failure.
Innovation Solution
A method involving a native oxide clean, controlled oxidation, and chemical vapor deposition of a thin, fully relaxed SiGe layer on a silicon substrate with a specific oxygen concentration, allowing for the deposition of a heteroepitaxial SiGe layer that is free of cross-hatches and strain, thereby minimizing dislocations and achieving maximum carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the thickness of SiGe layer is increased to achieve full relaxation, then the layer becomes fully relaxed, but misfit dislocations form at the film/substrate interface
Solution Approach 1:
The patent introduces oxygen into the SiGe layer during deposition as a preliminary action. This pre-introduced oxygen acts as nucleation sites that promote dislocation formation at controlled locations, allowing the layer to relax without forming harmful misfit dislocations at the film/substrate interface. The oxygen is incorporated during the deposition process itself, before the layer reaches critical thickness.
Solution Approach 2:
Oxygen serves as an intermediary element within the SiGe layer. It mediates the relaxation process by creating controlled defect structures that accommodate lattice mismatch. The oxygen atoms facilitate strain relaxation through a mechanism that prevents direct dislocation formation at the critical interface between SiGe and silicon substrate.
2Reliability
If the germanium content in SiGe layer is increased to enhance carrier mobility, then carrier mobility increases, but the critical thickness decreases leading to earlier relaxation
Solution Approach 1:
The patent changes the compositional parameter of the SiGe layer by introducing oxygen. This parameter change allows the layer to maintain higher germanium content for improved carrier mobility while preventing early relaxation. The oxygen incorporation fundamentally alters the relaxation behavior, enabling thicker layers with higher Ge content to remain strained beyond the conventional critical thickness.
Solution Approach 2:
Oxygen is introduced during the deposition process as a preliminary measure to prevent dislocation formation. This allows manufacturers to deposit thicker layers with higher germanium content without encountering the usual critical thickness limitations, thereby achieving both high carrier mobility and controlled layer thickness.
3Reliability
If the thickness of SiGe layer is reduced to minimize dislocations, then dislocation density decreases, but the layer cannot achieve full relaxation
Solution Approach 1:
Oxygen acts as an intermediary that enables full relaxation in thinner layers. By incorporating oxygen during deposition, the patent creates a mechanism for strain relaxation that does not require the layer to reach the conventional critical thickness. This allows thin layers to fully relax without forming harmful dislocations, as the oxygen facilitates alternative relaxation pathways.
Solution Approach 2:
The introduction of oxygen changes the physical and chemical parameters of the SiGe layer, fundamentally altering its relaxation behavior. This parameter change enables the layer to achieve full relaxation at reduced thicknesses, as the oxygen modifies the stress distribution and relaxation mechanisms within the film.
4Manufacturing precision
If oxidation is performed to prepare the substrate surface, then surface quality improves, but oxygen diffusion into SiGe layer may cause defects
Solution Approach 1:
The patent eliminates the separate oxidation step by incorporating oxygen introduction directly into the deposition process. This continuous approach ensures that oxygen is introduced at the precise moment and location needed - during layer formation - rather than as a separate pre-treatment step that could lead to uncontrolled oxygen diffusion and defects.
Solution Approach 2:
The deposition process itself serves the dual function of forming the SiGe layer and introducing the necessary oxygen. The system is self-sufficient, requiring no separate oxidation step. The oxygen is delivered through the deposition chamber atmosphere or precursors, allowing the deposition process to simultaneously achieve surface preparation and layer formation without the risks associated with separate oxidation steps.
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 enables the formation of a fully relaxed SiGe layer at a reduced thickness, enhancing carrier mobility, reducing deposition time and material costs, and minimizing defects, thus improving device performance and stability.
Implementation Method 1
depositing onto the oxidized surface of the Si substrate a heteroepitaxial layer of SiGe
Implementation Method 2
chemical vapor deposition of a thin, fully relaxed SiGe layer
Implementation Method 3
oxidizing a top surface of the Si substrate to form an oxidized surface
Data Source
AI summary
Some embodiments of the invention are related to manufacturing semiconductors. Methods and apparatuses are disclosed that provide thin and fully relaxed SiGe layers. In some embodiments, the presence of oxygen between a single crystal structure and a SiGe heteroepitaxial layer, and/or within the SiGe heteroepitaxial layer, allow the SiGe layer to be thin and fully relaxed. In some embodiments, a strained layer of Si can be deposited over the fully relaxed SiGe layer.