Piezoelectric Layer Thinning via Ion Implantation and CMP
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Solution Overview
Problem
Existing methods for manufacturing electronic devices with piezoelectric layers, such as the Smart Cut™ method, result in surface defects due to the grinding step used for thinning the piezoelectric material.
Innovation Solution
A method involving ion implantation to amorphize the upper portion of the piezoelectric layer, followed by chemical-mechanical polishing, which allows for faster removal of the defective upper portion without damaging the underlying layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a grinding step is used to thin the piezoelectric layer, then the thickness is reduced, but surface defects are generated
Solution Approach 1:
The thinning process is divided into two distinct stages: a first polishing step that removes the ground surface and defects, and a second polishing step that achieves final precision thickness control. This segmentation allows each step to optimize for its specific function, resolving the contradiction between thickness reduction and surface quality.
Solution Approach 2:
A preliminary grinding step is performed before polishing to remove large amounts of material and create a uniform starting surface. This preliminary action enables the subsequent polishing steps to focus on achieving high precision and surface quality without being burdened by excessive thickness removal requirements.
2Reliability
If the piezoelectric layer is thinned to less than 10 μm, then the electrical characteristics are improved, but the removal rate by conventional polishing becomes too slow
Solution Approach 1:
The polishing process uses periodic action with distinct phases: a first polishing step with higher removal rate to quickly reduce thickness, followed by a second polishing step with lower removal rate for precision control. This periodic variation in polishing intensity optimizes both productivity and precision.
Solution Approach 2:
The polishing parameters are changed between two distinct steps: the first polishing step uses parameters optimized for high removal rate, while the second polishing step uses parameters optimized for high precision and surface quality. This parameter change allows the process to achieve both fast thinning and high precision.
3Manufacturing precision
If multiple polishing steps are used to improve surface quality, then the surface defects are reduced, but the manufacturing complexity increases
Solution Approach 1:
The two polishing steps are merged into a single continuous polishing process using the same polishing apparatus, rather than requiring separate equipment or processes. This merging reduces manufacturing complexity while still achieving the benefits of multiple polishing stages.
Solution Approach 2:
The same polishing apparatus performs both the first and second polishing steps with different parameters, making the equipment universal and multi-functional. This eliminates the need for separate polishing equipment for each step, reducing overall manufacturing 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 method effectively removes surface defects and achieves a smoother surface, enhancing the electrical characteristics and reducing the thickness of the piezoelectric layer while maintaining its integrity.
Implementation Method 1
a. the implantation of ions into the first layer so as to amorphize an upper portion of the first layer
Implementation Method 2
b. the removal of the upper portion by a chemical-mechanical polishing step
Data Source
AI summary
A method for thinning a first layer made of a piezoelectric material including: the implantation of ions into the first layer so as to amorphize an upper portion of the first layer, and the removal of the upper portion by a chemical-mechanical polishing step.