Piezoelectric Actuator Surface Damage Removal via CMP
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Solution Overview
Problem
Existing methods for forming microelectromechanical systems (MEMS) with piezoelectric materials often result in surface damage and non-uniformity, limiting the thickness and performance of piezoelectric actuators due to grinding and other processing techniques.
Innovation Solution
A method involving chemical mechanical polishing (CMP) to create a flat surface on piezoelectric material blocks, followed by bonding to a transfer substrate and subsequent polishing to remove surface damage, ensuring uniformity and preventing roll-off, with optional conductive layer formation and transfer substrate management to achieve uniform piezoelectric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If grinding is used to thin piezoelectric material, then material thickness can be reduced, but surface damage and cracks are introduced
Solution Approach 1:
The patent replaces the mechanical grinding process with a chemical mechanical polishing process. The polishing uses chemical reactions combined with mechanical removal to achieve thinning without the surface damage caused by pure mechanical grinding. This substitution allows thickness reduction while maintaining surface integrity and preventing cracks in the piezoelectric material.
Solution Approach 2:
The patent changes the processing parameters by using polishing instead of grinding, which fundamentally alters the material removal mechanism. The polishing process uses controlled chemical reactions and gentle mechanical action to remove material, changing the interaction parameters between the tool and piezoelectric material to avoid damage while achieving the desired thickness.
2Manufacturing precision
If polishing is used to remove surface damage, then surface quality improves, but processing time increases
Solution Approach 1:
The patent performs polishing as a preliminary action before final device assembly and testing. By removing surface damage early in the manufacturing process, subsequent processing steps can proceed without complications from surface defects, and the need for additional corrective processing is eliminated, ultimately reducing total manufacturing time despite the polishing step itself taking time.
3Productivity
If piezoelectric material is made thinner to improve device performance, then actuator performance improves, but surface damage becomes more significant
Solution Approach 1:
The patent replaces mechanical grinding with chemical mechanical polishing to thin the piezoelectric material. This substitution enables the creation of thinner piezoelectric layers (reducing the harmful impact of surface damage) because polishing removes material without causing the cracks and subsurface damage that would be catastrophic in thin structures. The chemical mechanical process gently removes material while maintaining integrity.
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 removes surface damage, ensures uniform piezoelectric properties, and allows for thicker, damage-free piezoelectric layers, enhancing the uniformity and performance of MEMS actuators by maintaining low total thickness variation and preventing roll-off issues.
Implementation Method 1
Piezoelectric materials can generate electricity or a voltage differential when subjected to mechanical stress. Alternatively, applying a voltage across a piezoelectric material can cause converse piezoelectricity, that is, the piezoelectric material mechanically deforms when a voltage is applied.
Implementation Method 2
The polishing can be chemical mechanical polishing
Data Source
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AI summary
Techniques are described for forming actuators having piezoelectric material. A block of piezoelectric material is bonded to a transfer substrate. The block is then polished. The polished surface is bonded to a MEMS body.