Piezoelectric Substrate Bonding Structure to Suppress Oxide Interface Peeling
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Solution Overview
Problem
The existing bonding techniques for piezoelectric devices using lithium niobate or lithium tantalate substrates often result in low device characteristics due to crystallinity deterioration during ion injection and peeling issues at the silicon oxide interface, leading to reduced yield and device performance.
Innovation Solution
A bonded body is created with a supporting substrate having a silicon oxide bonding layer and a piezoelectric material substrate, where the supporting substrate surface features a flat part and concavities with structural defect parts above them, forming a silicon oxide matrix partitioned by these defects, which reduces peeling during polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If ion injection method is used to thin the piezoelectric substrate, then the substrate can be thinned, but the crystallinity is deteriorated resulting in low device characteristics
Solution Approach 1:
The substrate thinning process is segmented into two distinct methods: ion injection for initial thinning, followed by CMP polishing for final thickness control. This segmentation allows each method to be optimized independently, with CMP removing the damaged layer while achieving precise thickness control without further crystallinity damage.
Solution Approach 2:
CMP polishing acts as an intermediary process between ion injection and device fabrication. It removes the damaged crystalline layer created by ion injection and provides a fresh, undamaged surface for subsequent processing, thereby preserving device characteristics while achieving the desired thin substrate thickness.
2Manufacturing precision
If the piezoelectric material substrate is polished to reduce thickness, then processing denatured layer can be removed, but peeling occurs at the silicon oxide interface resulting in reduced yield
Solution Approach 1:
Concavities are formed on the silicon oxide bonding layer surface before the final thinning process. This preliminary action creates mechanical interlocking features that prevent peeling during subsequent CMP polishing, thereby maintaining high yield while achieving precise thickness control.
Solution Approach 2:
The solution transitions from a two-dimensional flat bonding interface to a three-dimensional structured interface with concavities. This dimensional change provides mechanical anchoring that prevents peeling during thinning, allowing precise thickness control without yield loss.
3Device complexity
If a flat bonding interface is used between silicon oxide and piezoelectric substrate, then the bonding structure is simple, but peeling occurs during polishing reducing yield
Solution Approach 1:
Concavities are formed on the bonding interface before assembly as a preliminary action. This simple preprocessing step creates mechanical interlocking features that significantly improve bonding reliability during polishing, achieving high yield without substantially increasing overall device complexity.
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 configuration effectively suppresses peeling at the interface, maintaining high device characteristics and yield by allowing the structural defect parts to absorb applied loads during processing.
Implementation Method 1
a piezoelectric element (111) and a supporting substrate (102) are bonded to each other
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(c)
Figure 3(a)~3(c)
AI summary
(Object) The object is, in bonding a piezoelectric material substrate of tantalum niobate or the like and a supporting substrate through a silicon oxide layer, to suppress the peeling along an interface between silicon oxide constituting the bonding layer and supporting substrate. (Solution) A bonded body includes a supporting substrate 3, a bonding layer 4 provided on a surface 3b of a supporting substrate 3 and composed of silicon oxide, and a piezoelectric material substrate of a material selected from the group consisting of lithium niobate, lithium tantalate and lithium niobate-lithium tantalate. A convexity 12 is provided on the surface 3b of the supporting substrate 3, and the bonding layer 4 includes a structural defect part 13 extending above the convexity 12.