Vacuum Tube Nonvolatile Memory with ONO Gate Dielectric
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Solution Overview
Problem
Vacuum tubes, despite their robustness in extreme environments and high frequency/power output, are limited by high energy consumption and replaced by solid-state devices due to ease of fabrication, low cost, and other factors, lacking efficient nonvolatile memory solutions.
Innovation Solution
A method for manufacturing a vacuum tube nonvolatile memory involving a substrate with sequential dielectric, source, gate, and drain layers, along with a gate dielectric and interlayer dielectric, forming a gate structure with controlled dimensions and annealing processes to achieve superior program and erase speed, retention time, and minimal gate leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum tubes are used for nonvolatile memory, then robustness in extreme environments and high frequency/power output are improved, but energy consumption increases
Solution Approach 1:
The vacuum tube structure is segmented into distinct functional layers including gate dielectric layer, charge trap layer, tunnel dielectric layer, and blocking dielectric layer. Each layer performs a specific function, allowing the device to achieve nonvolatile memory functionality while maintaining vacuum tube robustness and reducing energy consumption through optimized charge storage and retrieval mechanisms.
Solution Approach 2:
The patent employs composite dielectric structures combining multiple materials with different properties (e.g., oxide layers, nitride layers, oxynitride layers) to create the gate dielectric, tunnel dielectric, and blocking dielectric. This composite approach enables tailored electrical characteristics that balance robustness, charge retention, and energy efficiency.
2Power
If vacuum tubes are used for nonvolatile memory, then high frequency/power output is improved, but ease of fabrication deteriorates
Solution Approach 1:
The patent replaces traditional vacuum tube mechanical structures with a planar semiconductor fabrication approach. Multiple dielectric and conductive layers are deposited using standard semiconductor manufacturing techniques such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD), enabling vacuum tube functionality to be achieved with modern fabrication processes.
Solution Approach 2:
The invention transitions from the three-dimensional vacuum tube geometry to a two-dimensional planar structure with vertically stacked layers. This dimensional change allows the device to be fabricated using standard planar semiconductor processing techniques while maintaining the vacuum environment for high-frequency operation.
3Reliability
If gate structure is formed with precise dimensions, then gate controllability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs preliminary patterning steps where a mandrel structure is first formed, followed by conformal deposition of dielectric and conductive layers. The gate structure dimensions are controlled by the mandrel geometry and deposition thickness, which can be precisely controlled in advance, thereby achieving good gate controllability without requiring extremely tight final dimensional tolerances.
Solution Approach 2:
The invention controls gate structure dimensions by adjusting deposition parameters (thickness, uniformity) and etch parameters rather than relying solely on lithographic resolution. By changing process parameters such as deposition rate, temperature, and pressure, precise dimensional control is achieved with standard manufacturing capabilities.
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 provides a vacuum tube nonvolatile memory with enhanced program and erase speed, retention time, and gate controllability, overcoming the energy consumption limitations of vacuum tubes while maintaining robustness.
Implementation Method 1
The gate dielectric layer may be formed over the gate structure and may include oxide, oxynitride, silicon nitride, Al2O3, AlN or HfO
Implementation Method 2
The vacuum is intrinsically superior to the solid as carrier transport medium since it allows ballistic transport while the carriers suffer from optical and acoustic phonon scattering in semiconductors
Implementation Method 3
the method further comprises a step of annealing the source layer and the drain layer. annealing is performed in the environment of He, N2, Ar or H2. annealing is performed in the temperature range of 600 ̃1000° C.
Data Source
AI summary
The present invention relates to a method for preparing vacuum tube flash memory structure, to form a vacuum channel in the flash memory, and using oxide-nitride-oxide (ONO) composite materials as gate dielectric layer, wherein the nitride layer serves as a charge-trap layer to provide a blocking insulating between the gate electrode and the vacuum channel. The present structure exhibits superior program and erase speed as well as the retention time. It also provide with excellent gate controllability and negligible gate leakage current due to adoption ONO as the gate dielectric layer.