BAW Resonator Lower Electrode Etching for Continuous Dielectric Coverage
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Solution Overview
Problem
The existing manufacturing process for bulk acoustic wave (BAW) resonator packages often results in a reverse slope on the lower electrode during dry etching, leading to short circuits and coverage failures between the upper and lower electrodes due to incomplete etching and inadequate dielectric layer coverage.
Innovation Solution
A method involving multiple etching processes with patterned hardmasks and different etching gases is used to shape the lower electrode, ensuring only a portion of its thickness is etched, preventing reverse slopes and allowing for continuous dielectric coverage, thereby preventing short circuits and coverage failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single dry etching process is used to pattern the lower electrode, then the manufacturing process is simple, but a reverse slope is generated on the lower electrode causing coverage failure and short circuits
Solution Approach 1:
The single etching process is divided into multiple sequential etching steps with different hardmask patterns. The first etching creates an initial pattern, the second etching refines the profile, and the third etching achieves the final precise shape. This segmentation allows each step to optimize for its specific purpose, preventing reverse slope formation while maintaining manufacturing feasibility.
Solution Approach 2:
Hardmask patterns are formed in advance before each etching step to pre-determine the etching profile. The preliminary hardmask patterns are designed to compensate for expected etching effects, ensuring that the final lower electrode profile meets the required specifications without reverse slope formation.
2Productivity
If the lower electrode is completely etched through, then the electrode is fully formed, but the dielectric layer cannot cover the electrode continuously causing short circuits
Solution Approach 1:
Instead of completely etching through the lower electrode in a single step, the process performs partial etching in multiple controlled steps. Each etching step removes only the necessary portion of the electrode material while leaving sufficient material to ensure continuous dielectric coverage. This partial action approach prevents both incomplete electrode formation and dielectric coverage failure.
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 prevents short circuits and coverage failures, enhancing the quality of the resonator package by ensuring the dielectric layer consistently covers the lower electrode, even at higher voltages, significantly reducing failure rates from 50% at 300V to 1% at 500V.
Implementation Method 1
Patterning of the ruthenium (Ru) metal may be often performed via a dry etching using a hardmask HM such as an oxide.
Implementation Method 2
A structure of an existing resonator package described above will be described on the basis of the capacitor.
Implementation Method 3
A BAW resonator generally includes a lower electrode, a piezoelectric layer, and an upper electrode
Data Source
AI summary
A resonator package and a method of manufacturing the same are provided. The method of manufacturing a resonator package involves etching a lower electrode with a hardmask, in which only a portion of a thickness of the lower electrode is etched to shape the lower electrode.