Composite Substrate for Elastic Wave Device Warpage Control
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Solution Overview
Problem
Elastic wave devices produced with composite substrates face issues of warpage and low strength, leading to degraded patterning accuracy and increased production costs due to the need for thickening and polishing of support substrates, which are costly and inefficient.
Innovation Solution
A composite substrate is formed by bonding a piezoelectric substrate with a support substrate of lower thermal expansion coefficient, where the support substrate is created by directly bonding two substrates of the same material at a strength allowing separation with a blade, reducing warpage and increasing strength, and the thickness is easily reduced post-production without polishing, thereby reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the support substrate is increased to suppress warpage and enhance strength, then the rigidity and strength are improved, but the device thickness becomes excessively large and polishing is required which increases production cost
Solution Approach 1:
The support substrate is segmented into a first substrate (bonded to piezoelectric substrate) and a second substrate (temporary support). This allows the support substrate to be thick during production for strength, then thinned by removing the second substrate after device fabrication, avoiding expensive polishing while reducing final device thickness.
Solution Approach 2:
The second substrate is bonded in advance to provide temporary support and strength during the device fabrication process. After electrodes and other components are formed, the second substrate is removed by blade separation, leaving a thinned support substrate without requiring polishing operations.
2Stability of the object's composition
If the thickness of the support substrate is increased to suppress warpage, then the warpage is reduced, but the device thickness becomes excessively large and polishing is required which increases production cost
Solution Approach 1:
The support substrate is divided into first and second substrates. The first substrate maintains the thick configuration during fabrication to suppress warpage, then is thinned by removing the second substrate after device completion, avoiding polishing costs while achieving final thin profile.
Solution Approach 2:
The second substrate is attached in advance to provide temporary structural stability and suppress warpage during the sensitive fabrication processes. After device formation, it is removed by blade insertion, leaving the first substrate at reduced thickness without requiring costly polishing.
3Stability of the object's composition
If a compensation layer is added to the back surface of the support substrate to suppress warpage, then the warpage is reduced, but the production cost increases
Solution Approach 1:
Instead of adding a compensation layer with matched thermal expansion coefficient, the invention changes the parameter of the support substrate itself by using a thick configurable structure (first substrate + second substrate). The second substrate is removed after fabrication, providing warpage suppression during production without adding permanent complex structures that increase cost.
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 approach effectively reduces warpage and enhances the strength of the composite substrate while minimizing production costs by allowing easy thickness reduction of the support substrate post-production, thus maintaining the commercial value of elastic wave devices.
Implementation Method 1
the support substrate is formed by directly bonding together a first substrate and a second substrate at a strength that allows separation with a blade
Implementation Method 2
a composite substrate formed by bonding a thin piezoelectric substrate onto a support substrate
Data Source
AI summary
A method for producing an elastic wave device includes steps of (a) preparing a first substrate and a second substrate, (b) irradiating a bonding surface of the first substrate and a bonding surface of the second substrate with one of plasma, neutral atom beams, and ion beams of an inert gas, (c) bonding the bonding surface of the first substrate and the bonding surface of the second substrate in a vacuum at room temperature so as to set a strength that allows the first and second substrates to be separated by insertion of a blade; (d) forming a composite substrate by bonding a piezoelectric substrate to another surface of the first substrate; (e) forming electrode on a surface of the piezoelectric substrate of the composite substrate; and then (f) removing the second substrate from the first substrate by separation with the blade.