Semiconductor Device Multilevel Data Read Method
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Solution Overview
Problem
Existing semiconductor devices require multiple signal switches for reading multilevel data, leading to longer read times as the number of data levels increases, due to the need to adjust voltage levels accordingly.
Innovation Solution
A method for driving a semiconductor device where the potential of a bit line is precharged and then discharged through a transistor, allowing the potential to be read without switching the signal based on the number of data levels, utilizing a combination of silicon and oxide semiconductor transistors to enable one-time signal switching for reading multilevel data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a step-like read signal is supplied to read multilevel data, then data can be read by determining voltage level changes, but the number of signal switches increases with the number of data levels, leading to longer read times
Solution Approach 1:
The bit line potential is precharged to a predetermined level before the read operation begins. This preliminary action prepares the system state in advance, eliminating the need for multiple signal switches during the actual read process. The precharged state allows direct comparison with the stored data potential, enabling single-step reading regardless of the number of data levels.
Solution Approach 2:
Instead of changing the read signal voltage levels to match multiple data levels (conventional approach), the invention inverts the approach by keeping the read signal at a fixed level and comparing it against precharged bit line potentials that represent different data levels. This inversion of the comparison direction enables single-step reading.
2Adaptability or versatility
If the voltage level of the read signal is switched multiple times to read multilevel data, then all data levels can be read, but the reading process becomes slower
Solution Approach 1:
The precharged bit line structure enables a single read signal to universally access multiple data levels (4-level, 8-level, or higher) without requiring signal level switching. The same read signal waveform can read any number of multilevel data by simply changing the precharge voltage levels, providing universal multilevel reading capability with constant access speed.
Solution Approach 2:
The invention changes the parameter being adjusted from the read signal voltage level to the bit line precharge voltage level. By varying the precharge voltage parameter instead of the signal waveform, the system can access different data levels without slowing down the read process, maintaining constant access speed while preserving multilevel capability.
3Reliability
If multiple signal switches are used for reading multilevel data, then complete data reading is achieved, but the device complexity increases
Solution Approach 1:
The invention extracts the voltage level switching requirement from the read signal path and relocates it to the bit line precharge stage. This separation simplifies the read signal control to a single fixed level, eliminating the need for complex multi-level signal switching circuitry while maintaining complete data reading capability through the precharged bit line states.
Data Source
AI summary
To read multilevel data from a memory cell having a transistor using silicon and a transistor using an oxide semiconductor, without switching a signal for reading the multilevel data in accordance with the number of the levels of the multilevel data. The potential of the bit line is precharged, the electrical charge of the bit line is discharged via a transistor for writing data, and the potential of the bit line which is changed by the discharging is read as multilevel data. With such a structure, the potential corresponding to data held in a gate of the transistor can be read by only one-time switching of a signal for reading data.