Isotopically Enriched Silicon Substrate With Oxygen δ-Doped Confinement
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Solution Overview
Problem
The presence of unwanted spin components due to 29Si nuclear spin in silicon substrates for quantum computers interferes with electron spin calculations, necessitating the use of 28Si-enriched layers and confinement methods like Fin structures or SOI, which face challenges in surface treatment and isotope diffusion during heat treatment.
Innovation Solution
A method involving the formation of Si and 28Si epitaxial layers using enriched silicon source gases, followed by oxygen δ-doped layers, to create a silicon substrate with high 28Si and 30Si content, enabling the formation of a single-electron transistor and suppressing nuclear spin effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 28Si epitaxial layer is formed using isotopically-enriched 28SiH4 gas, then the nuclear spin effect is suppressed, but the manufacturing cost increases
Solution Approach 1:
The patent changes the isotopic composition parameter of silicon from natural abundance to isotopically-enriched 28Si (99.99% or higher purity), which fundamentally alters the nuclear spin properties and suppresses the Zeeman effect that causes unwanted spin splitting
Solution Approach 2:
The patent performs preliminary isotopic enrichment of silicon before epitaxial growth, preparing the 28Si-enriched silicon material in advance so that the quantum device can be built with the required isotopic purity from the outset
2Ease of manufacture
If oxidation treatment is performed on 28Si, then the insulation layer is formed, but diffusion of silicon during heat treatment causes 29Si effect
Solution Approach 1:
The patent performs preliminary oxidation to form the insulation layer before any heat treatment that could cause diffusion, ensuring the isotopic purity is locked in before thermal processes occur
Solution Approach 2:
The patent uses an oxygen layer as an intermediary barrier that prevents silicon diffusion during subsequent heat treatment processes, protecting the isotopic composition from degradation
3Ease of operation
If Fin structure is used to confine electron, then single-electron transistor is formed, but surface treatment of silicon surface becomes difficult
Solution Approach 1:
The patent transitions from three-dimensional Fin structure confinement to a planar interface confinement approach, using a two-dimensional interface between 28Si epitaxial layer and oxidation layer to achieve electron confinement without the manufacturing complexity of vertical Fin structures
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 allows for the production of a silicon substrate suitable for quantum computers, capable of suppressing nuclear spin effects and facilitating stable electron confinement, thereby enhancing quantum computation performance.
Implementation Method 1
forming a Si epitaxial layer by epitaxial growth using a Si source gas as a silicon-based raw material gas, in which a total content of 28Si and 30Si in a whole silicon contained in the silicon-based raw material gas is 99.9% or more, on a silicon substrate
Implementation Method 2
forming an oxygen (O) δ-doped layer by oxidizing a surface of the Si epitaxial layer
Implementation Method 3
presence of unwanted spin components in the vicinity splits electron spin energy due to the Zeeman effect
Data Source
AI summary
A method for manufacturing a silicon substrate for a quantum computer, the method includes the steps of forming a Si epitaxial layer by epitaxial growth using a Si source gas as a silicon-based raw material gas, in which a total content of 28Si and 30Si in a whole silicon contained in the silicon-based raw material gas is 99.9% or more, on a silicon substrate, forming an oxygen (O) δ-doped layer by oxidizing a surface of the Si epitaxial layer, and forming a Si epitaxial layer by epitaxial growth using a Si source gas, in which a total content of 28Si and 30Si in a whole silicon contained in the silicon-based raw material gas is 99.9% or more, on the δ-doped layer.