Composite Substrate Fabrication with Segmented Insulating Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for fabricating composite substrates with thin buried insulating layers, such as SOI substrates, face challenges in achieving improved electrical properties, particularly low Density of Interface Trap (DIT) values and breakdown voltage, due to the limitations of current heat treatment methods and plasma activation, which often result in increased defects and deteriorated electrical characteristics.
Innovation Solution
A method involving the formation of a first and second insulating layer on a support and source substrate, respectively, followed by plasma activation and molecular bonding to create a final insulating layer with controlled thickness and DIT values, ensuring the activated layer is only in the upper portion, thereby maintaining low DIT values and improved electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasma activation is applied to improve bonding energy at the interface, then bonding strength is improved, but electrical characteristics (DIT values) deteriorate significantly
Solution Approach 1:
The insulating layer is divided into two separate layers (first insulating layer and second insulating layer) with different thicknesses. The thinner second insulating layer is selectively plasma-activated while the thicker first insulating layer remains unactivated, thereby achieving both strong bonding and preserved electrical characteristics.
Solution Approach 2:
Plasma activation is applied locally only to the second insulating layer rather than uniformly to all insulating layers. This localized treatment ensures that bonding enhancement occurs at the critical interface while the electrical properties of the first insulating layer remain intact.
2Length of moving object
If the insulating layer thickness is reduced to achieve thin buried insulating layer, then the insulating layer forms integral part of electronic components, but the number of defects increases due to encapsulated contaminants
Solution Approach 1:
The insulating layer is segmented into two layers with different thicknesses and properties. The thinner second layer provides the necessary electrical characteristics while the thicker first layer serves as a robust bonding layer less susceptible to contamination during the bonding process.
Solution Approach 2:
The first insulating layer is formed in advance with sufficient thickness to act as a protective barrier during bonding, preventing contaminant encapsulation. This preliminary protective layer ensures that when the final thin insulating structure is achieved, defect density is minimized.
3Reliability
If heat treatment is applied to improve DIT values at interfaces, then electrical properties are improved, but the treatment loses effectiveness at deep-lying interfaces
Solution Approach 1:
The interfaces are segmented into two distinct types: interface I3 between the protective layer and active layer, and interfaces I1 and I2 at the deeper insulating layer boundaries. By making only the second insulating layer thin and plasma-activated, effective heat treatment can be applied to I3 while I1 and I2 maintain acceptable characteristics through the structural design itself.
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 achieves a composite substrate with a final insulating layer thickness of 50 nm or less, exhibiting DIT values of 1011 eV−1·cm−2 or less, and enhanced electron mobility, effectively improving the electrical performance and reducing defects at interfaces.
Implementation Method 1
plasma activation of at least one of the first and second insulating layers
Implementation Method 2
bonding the first and second substrates together by molecular bonding, such that the first and second insulating layers are in contact along a bonding interface and together form the final insulating layer
Data Source
AI summary
The invention specifically relates to methods of fabricating a composite substrate by providing a first insulating layer on a support substrate at a thickness of e1 and providing a second insulating layer on a source substrate at a thickness of e2, with each layer having an exposed face for bonding; providing plasma activation energy in an amount sufficient to activate a portion of the thickness of the face of the first insulating layer emp1 and a portion of the thickness of the face of the second insulating layer emp1; providing a final insulating layer by molecular bonding the activated face of the first insulating layer with the activated face of the second insulating layer; and removing a back portion of the source substrate while retaining an active layer comprising a remaining portion of the source substrate bonded to the support substrate with the final insulating layer interposed therein to form the composite substrate. The thicknesses e1, e2 of the first and second insulating layers are sufficient to provide the final insulating layer with a thickness of 50 nanometers or less, and the plasma activation energy and respective thicknesses e1, e2 of the first and second insulating layers are selected such that only respective thicknesses emp1 and emp2 of the faces of the first insulating layer and the second insulating layer are activated.