Semiconductor Memory Device Write Operation Control Circuit
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in performing write operations at high speeds due to the complexity and time-consuming nature of the program and verify operations.
Innovation Solution
A semiconductor memory device configuration that includes a memory string, word lines, a sense amplifier unit, and a control circuit, which executes a first pulse application, a precharge operation, and a second pulse application during a write operation to efficiently lower the threshold voltage of memory cell transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional program and verify operations are executed repeatedly to complete a write operation, then data is reliably written to the memory cell transistor, but the write operation time increases and writing speed decreases
Solution Approach 1:
The patent applies preliminary action by performing a precharge operation before the pulse application operation. The bit line is charged to a predetermined voltage level in advance, so that when the pulse application operation starts, the bit line already has the necessary voltage to immediately begin programming the memory cell transistor without requiring a lengthy charge-up phase during the write operation itself.
Solution Approach 2:
The write operation is segmented into distinct phases: precharge operation (charging the bit line) and pulse application operation (applying voltage pulses to program the cell). This segmentation allows each phase to be optimized independently, with the precharge phase preparing the bit line and the pulse application phase executing the actual programming, thereby reducing total write time while maintaining reliability.
2Measurement precision
If the bit line voltage is set based on data from latch circuit readout, then accurate data is written to the memory cell transistor, but the process complexity and time increase
Solution Approach 1:
The latch circuit stores the data to be written in advance during the precharge operation phase. The control circuit is pre-configured with the data values, eliminating the need for real-time readout and voltage setting during the pulse application operation. This preliminary preparation simplifies the voltage setting process while maintaining data accuracy.
Solution Approach 2:
The control circuit directly generates the appropriate bit line voltages based on pre-stored data without requiring external readout and processing operations. The system serves itself by using internally stored data to control the voltage application, reducing process complexity and time while ensuring accurate data writing.
Data Source
AI summary
A control circuit of a semiconductor memory device performs a write operation on a memory cell transistor of the semiconductor memory device by performing a first pulse application operation of lowering a threshold voltage of the memory cell transistor, a precharge operation, and then a second pulse application operation. In the precharge operation, in a state in which first and second select transistors connected to the memory cell transistor are turned on, a bit line connected to the memory cell transistor is charged by applying a ground voltage to a word line connected to a gate of the memory cell transistor and applying a voltage higher than the ground voltage to a source line. In the second pulse application operation, in a state in which the first select transistor is turned on and the second select transistor is turned off, a program voltage is applied to the word line.