SiGe Heteroepitaxial Bilayers With Sharper Si(110) Interfaces
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Solution Overview
Problem
Forming interfaces with good chemical abruptness in SiGe/Si multistacks on Si(110) substrates is challenging due to faster relaxation and more diffuse interfaces compared to Si(100) substrates, leading to carrier scattering and channel thickness variations in nanosheet field-effect transistors.
Innovation Solution
A method involving epitaxial growth of a monocrystalline silicon buffer layer on a Si(110) substrate, followed by alternating SiGe and Si pulses in the same reaction chamber without vacuum breaks, to form Si—SiGe bilayers, which reduces interface thickness and improves chemical abruptness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SiGe/Si multi-stacks are formed on Si(110) substrates, then the substrate utilization is improved, but the interface chemical abruptness deteriorates due to faster relaxation and more diffuse interfaces
Solution Approach 1:
A monocrystalline silicon buffer layer is epitaxially grown on the Si(110) substrate before forming the SiGe/Si multi-stack structure. This preliminary buffer layer preparation modifies the substrate surface to enable subsequent formation of sharp interfaces, resolving the contradiction between utilizing Si(110) substrates and achieving good interface chemical abruptness.
2Use of energy by stationary object
If alternating SiGe and Si pulses are deposited in the same reaction chamber without vacuum breaks, then the deposition continuity is improved, but the process complexity increases
Solution Approach 1:
The method employs periodic alternating pulses of SiGe and Si precursors within the same reaction chamber to deposit the multi-stack structure. This periodic deposition approach maintains continuous operation and sharp interfaces while managing process complexity through controlled cyclic precursor introduction.
3Ease of manufacture
If diffuse interfaces are formed in SiGe/Si multi-stacks on Si(110), then the deposition process is simplified, but carrier scattering increases and channel thickness variations occur
Solution Approach 1:
The monocrystalline silicon buffer layer is grown in advance on the Si(110) substrate to create a foundation that enables subsequent formation of sharp SiGe-Si interfaces. This preliminary preparation ensures uniform channel thickness and reduces carrier scattering, thereby improving device performance uniformity while maintaining a relatively simple deposition process.
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 enhances the epitaxial quality of Si—SiGe superlattices by reducing interface thickness and improving chemical abruptness, thereby improving the performance of nanosheet field-effect transistors.
Implementation Method 1
exposing the substrate to a first silicon precursor. Thus, a monocrystalline silicon buffer layer is epitaxially formed on the (110) silicon surface
Implementation Method 2
one or more bilayers are formed overlying the monocrystalline silicon buffer layer. A bilayer comprises a SiGe layer and a Si layer
Data Source
AI summary
Methods for forming structures that include forming a heteroepitaxial layer on a substrate are disclosed. The presently disclosed methods comprise epitaxially forming a buffer layer on the substrate. The substrate has a substrate composition. The buffer layer has a buffer layer composition. The buffer layer composition is substantially identical to the substrate composition. The presently disclosed methods further comprise epitaxially forming a heteroepitaxial layer on the buffer layer. The heteroepitaxial layer has a heteroepitaxial layer composition which is different from the substrate composition.