Semiconductor Memory Read Control With Word-Line Kick Voltage
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Solution Overview
Problem
Existing NAND type flash memory devices face challenges in efficiently reading data due to variations in threshold voltage distributions and data allocation, leading to inaccuracies in data interpretation.
Innovation Solution
The semiconductor memory device employs a kick voltage applied to the word line before the read voltage, along with specific voltage levels for the transistors, to enhance data reading accuracy by controlling the state of memory cell transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a read voltage is applied directly to the word line, then the reading operation can be performed, but data reading accuracy deteriorates due to threshold voltage variations and data allocation issues
Solution Approach 1:
The patent applies a kick voltage to the word line before applying the read voltage. This preliminary action of applying kick voltage prepares the memory cell transistors by temporarily raising their threshold voltage, ensuring that only cells with threshold voltages below the kick voltage level are turned on during the subsequent read operation. This eliminates the need for complex voltage control schemes and directly addresses the accuracy issue caused by threshold voltage variations.
Solution Approach 2:
The patent changes the voltage parameter applied to the word line by introducing a kick voltage level that is higher than the read voltage level. This parameter change allows the system to temporarily modify the threshold voltage condition of memory cell transistors, ensuring accurate data reading even in the presence of threshold voltage variations and data allocation challenges.
2Reliability
If threshold voltage variations are present in memory cells, then data can be stored, but data interpretation becomes inaccurate
Solution Approach 1:
The kick voltage is applied as a preliminary action before reading. This temporary voltage pulse raises the threshold voltage of all memory cell transistors above the kick voltage level. When the read voltage is subsequently applied, only cells with original threshold voltages below the kick voltage level are turned on, ensuring accurate data interpretation regardless of the original threshold voltage variations in the memory cells.
3Measurement precision
If multiple voltage levels are used for transistor control, then data reading accuracy improves, but the control mechanism becomes more complex
Solution Approach 1:
The control mechanism is simplified by using a preliminary kick voltage action followed by a single read voltage application. Instead of requiring complex multi-level voltage control throughout the reading process, the system applies kick voltage first to establish the correct threshold voltage conditions, then applies the read voltage once to complete the data reading operation. This maintains high accuracy while significantly simplifying the control mechanism.
Data Source
AI summary
According to one embodiment, a semiconductor memory device includes first and second memory cells, a first word line, first and second sense amplifiers, first and second bit lines, a controller. The first and second sense amplifiers each include first and second transistors. The first bit line is connected between the first memory cell and the first transistor. The second bit line is connected between the second memory cell and the second transistor. In the read operation, the controller is configured to apply a kick voltage to the first word line before applying the read voltage to the first word line, and to apply a first voltage to a gate of the first transistor and a second voltage to a gate of the second transistor while applying the kick voltage to the first word line.