Auxiliary Layer CMP for BAW Resonator Electrode Planarity
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Solution Overview
Problem
Conventional methods for manufacturing patterned bottom electrodes in piezoelectric devices result in 'dishing' effects due to oxide CMP, leading to local variations in electrode and piezo layer thickness, which degrade the quality of BAW resonators by widening series resonance and reducing quality.
Innovation Solution
A method involving the use of an auxiliary layer with a lower removal rate than the planarization layer during chemical mechanical polishing, protecting the layer structure and ensuring a highly planar surface by selectively removing more material from the planarization layer than the auxiliary layer, thereby avoiding 'dishing' and maintaining electrode uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If planarization layer is removed to achieve planar surface, then surface flatness is improved, but material removal from underlying layers causes dishing
Solution Approach 1:
The auxiliary layer serves as a sacrificial intermediary that absorbs the mechanical stress and material removal effects during CMP. By having a lower removal rate than the planarization layer, it acts as a buffer that protects the layer structure from dishing while allowing the planarization layer to be effectively removed for surface flatness.
2Ease of manufacture
If conventional CMP process is applied, then planarization is achieved, but electrode uniformity and BAW resonator quality are degraded
Solution Approach 1:
The auxiliary layer is introduced as a protective intermediary that enables the CMP process to proceed effectively for planarization while preventing the harmful dishing effects that would otherwise degrade electrode uniformity and BAW resonator quality. This maintains ease of manufacture while improving reliability.
Solution Approach 2:
By depositing the auxiliary layer beforehand, the process prepares a protective barrier that prevents quality degradation during the subsequent CMP step, ensuring both ease of manufacture and high reliability of the final BAW resonator product.
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 achieves a highly planar surface for the bottom electrode, ensuring uniform deposition of the piezoelectric layer, enhancing electro-mechanical coupling and acoustic quality, and reducing spurious modes in BAW resonators.
Implementation Method 1
exposing the auxiliary layer by a chemical mechanical polishing process
Data Source
AI summary
A method for manufacturing a device on a substrate includes forming a layer structure on the substrate, forming an auxiliary layer on the layer structure, forming a planarization layer on the auxiliary layer and on the substrate, exposing the auxiliary layer by a chemical mechanical polishing process and removing at least partly the auxiliary layer to form a planar surface of the remaining auxiliary layer or of the layer structure and the planarization layer. The chemical mechanical polishing process has a first removal rate with respect to the planarization layer and a second removal rate with respect to the auxiliary layer and the first removal rate is greater than the second removal rate.