Piezoelectric MIM Layout Using a Passivation Ledge to Prevent Delamination
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Solution Overview
Problem
Piezoelectric MIM devices experience premature breakdown due to high physical strain caused by high electrical fields, leading to delamination of the top electrode from the piezoelectric layer at a low bias voltage, which limits their operational range and reliability.
Innovation Solution
An improved manufacturing method involving an over-etch process and the formation of a passivation layer with a ledge in the piezoelectric structure, which acts as a clamp to prevent delamination by distributing the electrical stress evenly, thereby increasing the operational voltage before breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional piezoelectric MIM device structure is used, then the device can be manufactured with standard processes, but the device experiences premature breakdown due to high physical strain and delamination at low bias voltage
Solution Approach 1:
The piezoelectric layer is divided into two distinct regions: a top region with smaller footprint directly under the top electrode, and a bottom region with larger footprint. This segmentation allows the structure to better distribute electrical stress and prevent delamination at the electrode-piezoelectric interface, thereby increasing breakdown voltage while maintaining structural integrity.
Solution Approach 2:
Different regions of the piezoelectric structure are given different geometrical properties - the top region has reduced lateral dimensions compared to the bottom region. This local quality variation optimizes the electric field distribution, concentrating stress where needed while protecting critical interfaces, thus improving reliability without compromising overall strength.
2Ease of manufacture
If the top electrode is directly contacted to the piezoelectric layer without structural modification, then the manufacturing process is simpler, but delamination occurs at low bias voltage due to concentrated electrical stress
Solution Approach 1:
The piezoelectric layer is segmented into top and bottom regions with different lateral dimensions. The top region has smaller footprint matching the top electrode area, while the bottom region extends wider. This segmentation can be achieved through standard photolithography and etching processes, maintaining ease of manufacture while significantly improving reliability by preventing delamination through better stress distribution.
3Ease of manufacture
If the piezoelectric layer is uniformly thick and wide throughout, then the manufacturing process is straightforward, but high electrical fields cause concentrated physical strain leading to premature breakdown
Solution Approach 1:
The uniformly thick piezoelectric layer is modified by laterally etching the top region to create a stepped structure. This segmentation is achieved through a two-step etching process: first etching the top region to a smaller footprint, then etching the bottom region to a larger footprint. This maintains fabrication simplicity while dramatically improving resistance to electrical stress by distributing the physical strain across different regions.
Solution Approach 2:
The piezoelectric layer transitions from a two-dimensional uniform plane to a three-dimensional stepped structure with varying lateral dimensions at different heights. This dimensional change allows the structure to better manage electrical stress distribution, improving strength and resistance to breakdown while maintaining relatively simple manufacturing processes.
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
The solution effectively increases the structural integrity and reliability of the piezoelectric MIM device, allowing it to operate at higher voltages without premature breakdown, enhancing its performance and extending its operational range.
Implementation Method 1
Piezoelectric devices (e.g., piezoelectric actuators, piezoelectric sensors, etc.) are used in many modern day electronic devices
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an integrated chip including a dielectric structure sandwiched between a first electrode and a bottom electrode. A passivation layer overlies the second electrode and the dielectric structure. The passivation layer comprises a horizontal surface vertically below a top surface of the passivation layer. The horizontal surface is disposed above a top surface of the dielectric structure.