Electric Field Gap Device for Low Overshoot Voltage ESD Protection
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Solution Overview
Problem
Existing ESD protection devices face a trade-off between constant capacitance and low overshoot voltage, which is inadequate for applications requiring both, and traditional methods struggle to effectively manage high overshoot voltages through field emission.
Innovation Solution
The development of an electric field gap device with sharp electrode tips formed by etching silicon substrates and oxidizing specific regions to create a controlled anode-cathode gap, utilizing a sacrificial layer to define the gap and prevent arcing, and employing shielding dielectric layers to enhance field emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a narrow gap between cathode and anode is used to enable field emission and low overshoot voltage, then overshoot voltage is reduced, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The patent applies preliminary action by forming a sacrificial layer (e.g., silicon dioxide) with a precisely controlled thickness that corresponds to the desired final gap size. This sacrificial layer is deposited beforehand with atomic layer precision using chemical vapor deposition (CVD), ensuring the gap dimension is predetermined with high accuracy before the actual gap formation process. The sacrificial layer serves as a template that defines the exact gap dimensions, eliminating the need for precise mechanical gap control.
Solution Approach 2:
The patent uses a sacrificial layer as an intermediary element to achieve the narrow gap. This intermediate material (such as silicon dioxide) is deposited between the cathode and anode structures, then selectively removed through etch access holes to create the final gap. The sacrificial layer mediates the gap formation process by providing a controlled, uniform thickness that translates directly to the desired gap size, enabling precise control of the 50 nm or smaller gaps required for field emission while simplifying the manufacturing process.
2Stability of the object's composition
If field emission is used to overcome non-linear capacitance and high overshoot voltage, then capacitance linearity improves, but device complexity increases due to the need for sharp electrode tips and narrow gaps
Solution Approach 1:
The patent applies self-service by using the substrate's own oxidation properties to create the sharp electrode tips required for field emission. Instead of adding separate fabrication steps to form sharp tips, the process utilizes thermal oxidation of the silicon substrate, which naturally forms tapered oxide structures with pointed tips at the channel openings. These self-formed sharp tips provide the necessary field enhancement for electron emission without requiring additional complex electrode fabrication processes.
Solution Approach 2:
The patent replaces mechanical fabrication methods with chemical processes to create the sharp electrode tips. Instead of using mechanical grinding, polishing, or lithographic patterning to form sharp tips, the invention uses thermal oxidation chemistry to grow silicon dioxide layers that self-organize into tapered structures with sharp apical regions. This chemical approach simplifies the device structure by eliminating the need for complex mechanical tip-forming equipment and processes.
3Manufacturing precision
If a sacrificial layer is used to define the anode-cathode gap, then gap precision improves, but manufacturing steps increase
Solution Approach 1:
The patent applies universality by making the sacrificial layer serve multiple functions simultaneously. The same sacrificial layer (such as silicon dioxide) is used for: (1) defining the precise gap dimension through its controlled thickness, (2) providing a planarization surface for subsequent electrode deposition, (3) serving as an etch stop layer during gap access hole formation, and (4) acting as a structural support during processing. By consolidating these multiple functions into a single layer, the patent avoids the need for separate layers for each function, thereby reducing overall device complexity despite the added precision step.
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 enables improved ESD protection by achieving a combination of constant capacitance and low overshoot voltage, effectively managing high discharge events while preventing arcing and enhancing heat conductivity.
Implementation Method 1
oxidising the substrate at the unshielded portion of the cathode channels, thereby to leave pointed non-oxidised substrate regions between the cathode channels
Implementation Method 2
Theoretical simulations show that a way to overcome a non-linear capacitance and a high overshoot voltage is by use of field emission. This approach makes use of a pair of spaced metal points which serve to initiate a field emission discharge.
Data Source
Figure 1~2c
Figure 3~5
Figure 6~7
AI summary
Substrate material is oxidised around side walls of a set of channels. A shielding structure means there is more oxide growth at the top than the bottom with the result that the non-oxidised substrate material area between the channels forms a tapered shape with a pointed tip at the top. These pointed substrate areas are then used to form cathodes.