MEMS Vacuum Diode Conformal Anode for Uniform Electron Emission
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Solution Overview
Problem
Conventional field emission arrays, particularly Spindt type electron emission devices, face challenges in forming uniform emitter electrodes, leading to unstable electron emission characteristics due to difficulties in achieving the desired conical shape, resulting in varying field electron emission characteristics across the emission array.
Innovation Solution
A novel method for producing a cold cathode field emission vacuum diode using micro-electromechanical systems (MEMS) processing technology, involving the formation of columns with tips on a substrate, deposition of sacrificial oxide layers, and subsequent removal to create a conformal anode structure that conforms to the shape of the cathode tips, ensuring uniformity and stability in electron emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thin film deposition techniques are used to form Spindt tips, then the cathode structure can be created, but it is difficult to achieve uniform conical emitter electrodes across the substrate
Solution Approach 1:
The patent applies preliminary action by first depositing a conformal oxide layer over the entire substrate before forming the cathode patterns. This oxide layer serves as a sacrificial template that pre-establishes the uniform spacing and conical geometry for all emitter electrodes across the substrate, eliminating the difficulty of directly forming uniform cones through deposition alone.
Solution Approach 2:
The patent introduces a sacrificial oxide layer as an intermediary element between the substrate and the final cathode structure. This intermediary layer is deposited conformally, then patterned and removed in specific regions to reveal the conical emitter electrodes, thereby mediating the formation process to achieve uniformity without direct conical deposition.
2Reliability
If emitter electrodes are formed uniformly, then stable electron emission characteristic is achieved, but the device complexity increases due to additional processing steps
Solution Approach 1:
The patent changes the fabrication parameters from direct conical deposition to a multi-step process involving conformal oxide deposition, photolithography patterning, and selective removal. This parameter change in the fabrication approach enables uniform emitter formation across large substrates, achieving stable electron emission characteristics despite increased processing steps.
Solution Approach 2:
The patent segments the fabrication process into distinct stages: (1) conformal oxide deposition over the entire substrate, (2) photolithographic patterning to define emission regions, (3) selective oxide removal to expose conical emitters, and (4) final cathode formation. This segmentation allows each step to be optimized independently, achieving uniformity and reliability.
3Power
If the anode is positioned close to the cathode tips, then the electric field is enhanced and turn-on voltage is reduced, but the manufacturing precision required increases
Solution Approach 1:
The patent applies local quality by creating a conformal oxide layer that provides uniform thickness and spacing between the anode and cathode tips across the entire substrate. This local uniformity in the oxide layer thickness ensures consistent electric field enhancement and turn-on voltage characteristics across all emitter locations, compensating for the precision requirements.
Solution Approach 2:
The patent uses preliminary action by depositing the conformal oxide layer before final anode-cathode alignment. This pre-established oxide template defines the precise spacing geometry, allowing subsequent processing steps to achieve the required positioning accuracy by referencing the already-formed oxide structures rather than attempting direct precision positioning.
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 method achieves stable and uniform electron emission by enhancing the electric field at the cathode, reducing turn-on voltage, and increasing tunneling current, while minimizing variability across the array, thereby improving the overall performance of the field emission device.
Implementation Method 1
electrons emitted from the cathode (Spindt tip) are accelerated by the electric field between the cathode and the anode electrode
Implementation Method 2
The cathode has an approximately conical shape, to which a predetermined electric field is applied so as to emit electrons
Implementation Method 3
The method achieves stable and uniform electron emission by enhancing the electric field at the cathode
Implementation Method 4
depositing a conductive material in of the opening and on a surface of the dielectric to form an anode of the diode
Data Source
AI summary
Disclosed is an encapsulated micro-diode and a method for producing same. The method comprises forming a plurality columns in the substrate with a respective tip disposed at a first end of the column, the tip defining a cathode of the diode; disposing a sacrificial oxide layer on the substrate, plurality of columns and respective tips; forming respective trenches in the sacrificial oxide layer around the columns; forming an opening in the sacrificial oxide layer to expose a portion of the tips; depositing a conductive material in of the opening and on a surface of the substrate to form an anode of the diode; and removing the sacrificial oxide layer.