MEMS Electrode Segmentation for Leakage Current Reduction
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Solution Overview
Problem
In liquid ejecting heads with a stacked structural body, the end portion of the second electrode layer is prone to breakage due to leakage current, leading to potential burnout, which compromises the reliability of the device.
Innovation Solution
A stacked structural body design where the first electrode layer and first dielectric layer extend farther than the second electrode layer, with a second dielectric layer covering the end of the second electrode layer and a third electrode layer electrically connected to the second electrode layer, dividing the voltage and reducing electric field strength on the dielectric layer, thereby inhibiting leakage current and breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second electrode layer is stacked on the dielectric layer in the conventional manner, then the device structure is simple, but the end portion of the second electrode layer is prone to breakage due to leakage current
Solution Approach 1:
The patent segments the electrode structure by introducing a third electrode layer that is electrically connected to the second electrode layer. This segmentation allows the voltage to be divided between the first dielectric layer and the second dielectric layer, reducing the electric field strength at the vulnerable end portion of the second electrode layer and preventing leakage current-induced breakage.
Solution Approach 2:
The third electrode layer acts as an intermediary element between the second electrode layer and the external circuit. By introducing this intermediate layer, the patent creates a voltage division mechanism that protects the end portion of the second electrode layer from high electric field stress and leakage current damage.
2Reliability
If the end portion of the second electrode layer is exposed without additional protection, then the manufacturing process is simple, but leakage current causes burnout and breakage
Solution Approach 1:
The patent applies preliminary protective action by stacking the second dielectric layer and third electrode layer over the end portion of the second electrode layer before final device assembly. This preliminary protection structure prevents leakage current from reaching the vulnerable end portion during subsequent manufacturing and operation steps.
Solution Approach 2:
The second dielectric layer and third electrode layer serve as a cushioning protection layer that absorbs and distributes the electrical stress before it can reach the end portion of the second electrode layer. This beforehand cushioning prevents burnout and breakage by reducing the electric field strength at the vulnerable location.
3Power
If voltage is concentrated on a single dielectric layer, then the electric field strength is high for effective actuation, but the dielectric layer is prone to breakdown from leakage current
Solution Approach 1:
The voltage application mechanism is segmented into two separate dielectric layers. The first dielectric layer between the first and second electrode layers maintains high electric field strength for effective actuation, while the second dielectric layer between the second and third electrode layers provides voltage division and protection, preventing concentration of voltage on a single layer.
Solution Approach 2:
Different regions of the device have different electrical characteristics. The drive region maintains high electric field strength for actuation, while the end portion region incorporates the third electrode layer to create a low electric field strength zone that prevents leakage current and protects against breakdown.
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 design effectively inhibits leakage current and breakage of the dielectric layer, enhancing the reliability of the liquid ejecting head by reducing electric field strength and distributing voltage across multiple dielectric layers.
Implementation Method 1
a piezoelectric layer that is a kind of a dielectric layer sandwiched between a first electrode layer and a second electrode layer is driven by applying voltage (electric signal) to the two electrode layers. This driving causes pressure changes to occur in the liquid in a pressure chamber and the pressure changers are utilized to eject the liquid from the nozzle.
Data Source
AI summary
A MEMS device includes a drive region having a stacked structural body in which a first electrode layer, a first dielectric layer, and a second electrode layer are stacked in that order. The stacked structural body extends from the drive region to a non-drive region that is outer than the drive region and, in an extending direction of the stacked structural body, the first electrode layer and the first dielectric layer extend farther outward than the second electrode layer. A second dielectric layer covering an end of the second electrode layer in the extending direction is stacked on the second electrode layer in the non-drive region and the first dielectric layer that is formed outer in the extending direction than the second electrode layer. A third electrode layer electrically connected to the second electrode layer is stacked on the second dielectric layer and on the second electrode layer in a region outside the second dielectric layer. In the extending direction, the end of the second electrode layer is formed more to a drive region side than a second dielectric layer-side end of the third electrode layer.