Bulk Acoustic Resonator Structure Without Oxide Sacrificial Layers
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Solution Overview
Problem
The existing preparation technology for film bulk acoustic resonators (FBARs) faces challenges in obtaining high-quality bulk acoustic resonators due to crystal mismatch between amorphous oxide layers and other layers, leading to reduced performance in BAW devices.
Innovation Solution
A bulk acoustic resonator is designed with a substrate having a first semiconductor layer, an insulating layer, and a second semiconductor layer, where a groove with a smooth contour is etched through the second semiconductor layer to form a protection part, allowing for the direct deposition of a seed layer, bottom electrode, piezoelectric layer, and top electrode, thereby avoiding the use of amorphous oxide layers as sacrificial layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an amorphous oxide layer is used as a sacrificial layer in the FBAR preparation process, then the cavity structure can be formed, but crystal mismatch occurs between the amorphous oxide layer and other layers, reducing the quality of the bulk acoustic resonator
Solution Approach 1:
The invention removes the amorphous oxide sacrificial layer from the process entirely. Instead, it uses a semiconductor layer (sacrificial layer 110) that matches the crystal structure of the piezoelectric layer 40, eliminating the crystal mismatch problem while still enabling cavity formation through selective release holes
Solution Approach 2:
The invention changes the material parameter of the sacrificial layer from amorphous oxide to semiconductor material with matching crystal structure. This parameter change ensures crystal compatibility with the piezoelectric layer while maintaining the sacrificial layer's functionality for cavity formation
2Manufacturing precision
If a smooth contour groove is etched to form a protection part, then the quality of deposited layers is improved, but the device complexity increases due to additional etching and protection steps
Solution Approach 1:
The protection part 120 is formed in advance before depositing the seed layer 20, bottom electrode 30, and piezoelectric layer 40. This preliminary action ensures that the groove has a smooth contour ready to receive these layers, improving their quality without requiring complex post-processing steps
Solution Approach 2:
The protection part 120 acts as an intermediary structure between the groove and the deposited layers. It maintains the smooth contour of the groove during subsequent processing steps and prevents over-release of the semiconductor layer, thereby protecting the quality of the final structure
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 enhances the quality of the seed layer, bottom electrode, piezoelectric layer, and top electrode, improving the overall performance of the bulk acoustic resonator by eliminating defects and maintaining the protection effect, thus preventing over-release and deformation of the semiconductor layer.
Implementation Method 1
The FBAR specifically utilizes the piezoelectric characteristics of the material to convert electric energy into acoustic energy
Implementation Method 2
an oxidation treatment is performed on the surface of the second semiconductor layer, so that a portion of the second semiconductor layer is converted into a first oxide layer
Data Source
AI summary
The present application provides a bulk acoustic resonator and a preparation method thereof, and a filter. The bulk acoustic resonator includes: a substrate, wherein the substrate includes a first semiconductor layer, an insulating layer and a second semiconductor layer, which are stacked in sequence; the surface of the second semiconductor layer is etched to form a groove, and the groove penetrates through the second semiconductor layer; and a protection part is formed in the groove, and a vertical section of the groove has a smooth contour.