Flash Memory Programming via Impact Ionization
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Solution Overview
Problem
Current flash memory programming methods suffer from low efficiency, high power consumption, small read current, and damage to the tunnel oxide layer, which restricts further miniaturization and improves programming efficiency, reduces power consumption, and minimizes tunnel oxide damage.
Innovation Solution
A method involving a flash memory structure with a floating gate, where voltages are applied to form electric fields to generate electron-hole pairs, accelerate holes to create secondary electrons, and then inject tertiary electrons into the floating gate using a vertical electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot carrier injection (HCI) is used for programming flash memory, then programming can be performed, but programming efficiency is low (about 50%) and high voltage is needed which leads to high power consumption
Solution Approach 1:
The patent changes the programming mechanism from hot carrier injection to tunneling current-based programming. By applying a tunneling voltage (Vtun) to the control gate and a program voltage (Vprog) to the select gate, the patent creates a tunneling electric field that enables efficient electron injection into the floating gate. This parameter change in the programming mechanism achieves both high programming efficiency and low power consumption, resolving the technical contradiction between programming efficiency and power consumption.
2Productivity
If hot carrier injection is used for programming, then programming can be performed, but the Punch Through effect occurs when gate length is less than 110 nanometers, restricting further miniaturization
Solution Approach 1:
The patent changes the programming mechanism from hot carrier injection to tunneling current-based programming. The tunneling mechanism does not suffer from the Punch Through effect that plagues hot carrier injection in scaled devices. By using a tunneling electric field created between the control gate and substrate, the patent enables effective programming even when the gate length is reduced below 110 nanometers, thus resolving the contradiction between programming capability and device miniaturization.
3Productivity
If quantum tunneling is used for programming (as in NXP's 2T flash and Hsu's P-type channel flash), then programming can be performed, but read current is small and considerable damage is inflicted on the tunnel oxide layer
Solution Approach 1:
The patent applies local quality by creating a highly localized tunneling region between the control gate and the substrate directly beneath it. The tunneling electric field is concentrated in this specific region, allowing efficient electron injection into the floating gate without requiring high voltages across the entire tunnel oxide layer. This localized approach maintains tunnel oxide integrity while achieving effective programming, resolving the contradiction between programming capability and oxide layer reliability.
Solution Approach 2:
The patent uses partial action by applying the tunneling voltage (Vtun) only to the control gate during programming operations, rather than applying high voltages across the entire device structure. This targeted voltage application creates sufficient tunneling current for programming while minimizing stress on the tunnel oxide layer, thus resolving the contradiction between programming effectiveness and oxide layer preservation.
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 enhances programming efficiency, reduces power consumption, increases read current, and prevents the Punch Through effect, allowing for further miniaturization of flash memory devices.
Implementation Method 1
accelerating holes downward under the action of the electric field to collide with the substrate in the flash memory structure within a preset time, to generate secondary electrons
Implementation Method 2
enabling the secondary electrons to generate tertiary electrons under the action of a vertical electric field to inject the tertiary electrons into the floating gate
Data Source
AI summary
The present disclosure relates to a method for programming flash memory, which includes: providing a flash memory structure having a floating gate, and floating a source of the flash memory structure; separately applying voltages to a drain and a substrate, to form an electric field, and generating electron-hole pairs, to generate primary electrons, where the voltage applied to the substrate is less than the voltage applied to the drain; accelerating holes downward under the action of the electric field to collide with the substrate in the flash memory structure within a preset time, to generate secondary electrons; and separately applying voltages to a gate and the substrate, where the voltage applied to the substrate is less than the voltage applied to the gate, and enabling the secondary electrons to generate tertiary electrons to inject the tertiary electrons into the floating gate, to complete a programming operation.