Bonded Substrate with Strained Si1-xGex Film via Thermal Mismatch
Solution Overview
Problem
Conventional methods for producing bonded substrates with biaxial strain in Si1-xGex films are limited in introducing a large strain, as they rely on lattice mismatch and thermal expansion differences, which can result in insufficient strain levels.
Innovation Solution
A method involving a donor wafer and a handle wafer with different thermal expansion coefficients, where ions are implanted into the donor wafer, followed by surface activation, bonding, mechanical splitting, and epitaxial growth of Si1-xGex films, allowing for increased biaxial strain through thermal expansion mismatch during growth and cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional methods using lattice mismatch and thermal expansion differences are used to produce bonded substrates, then bonding is achieved, but the biaxial strain introduced in Si1-xGex films is insufficient
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter by selecting a handle wafer material (such as quartz or sapphire) with a significantly lower thermal expansion coefficient than the Si1-xGex film. This parameter change enables larger strain introduction during the cooling process after epitaxial growth, resolving the contradiction by achieving both bonding and high strain levels through controlled thermal parameter selection.
Solution Approach 2:
The patent directly utilizes the thermal expansion coefficient difference between the handle wafer and the Si1-xGex film to introduce biaxial strain. During cooling after high-temperature epitaxial growth, the handle wafer contracts more than the film, creating tensile strain in the film. This thermal expansion mechanism resolves the contradiction by providing a controllable method to achieve large strain levels while maintaining bonding integrity.
2Stress or pressure
If a handle wafer with lower thermal expansion coefficient is used, then larger biaxial strain is introduced, but the bonding strength may be affected
Solution Approach 1:
The patent performs preliminary surface activation treatment on the bonding surfaces of both the handle wafer and the Si1-xGex film before bonding. This preliminary action creates reactive groups on the surfaces that enhance bonding strength, ensuring that the strong bonding required to withstand thermal stress is achieved before the strain-introducing cooling process begins, thus resolving the contradiction between strain introduction and bonding strength.
Solution Approach 2:
The patent introduces an ion-implanted layer as an intermediary between the handle wafer and the Si1-xGex film. This intermediary layer, created by implanting ions such as hydrogen or noble gases into the handle wafer surface, serves as a buffer that accommodates thermal stress while maintaining strong bonding, thus enabling both large strain introduction and strong bonding strength simultaneously.
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 method enables the introduction of a larger biaxial strain in Si1-xGex films, enhancing their properties and facilitating their use in semiconductor devices and optical applications.
Implementation Method 1
implanting ions of any one or both of hydrogen and a noble gas into the donor wafer to form an ion-implanted layer
Implementation Method 2
performing a surface activation treatment on at least one of bonding surfaces of the donor wafer and the handle wafer
Implementation Method 3
thinning the donor wafer by splitting the donor wafer through application of a mechanical impact to the ion-implanted layer
Implementation Method 4
epitaxially growing a Si1-xGex (0<x<1) film or a Ge film on a surface of the thinned donor wafer
Implementation Method 5
since the lattice constant of the SiGe layer is larger than the lattice constant of the silicon layer, a biaxial strain is laterally introduced
Implementation Method 6
a biaxial strain is introduced in the Ge film due to the difference in expansion coefficient between Si and Ge
Data Source
AI summary
A method for producing a bonded substrate having a Si1-xGex (0<x≦̸1) film in which a larger than ever biaxial strain has been introduced. Specifically, the method involves at least the steps of: providing a donor wafer and a handle wafer having a thermal expansion coefficient lower than the donor wafer, implanting ions of any one or both of hydrogen and a noble gas into the donor wafer to form an ion-implanted layer, performing a plasma activation treatment on at least one of bonding surfaces of the donor wafer and the handle wafer, bonding the donor wafer to the handle wafer, splitting the donor wafer through application of a mechanical impact to the ion-implanted layer, performing a surface treatment on a split surface of the donor wafer, and epitaxially growing a Si1-xGex (0<x≦̸1) film on the split surface to thus form a strained Si1-xGex (0<x≦̸1) film on the bonded wafers.