Semiconductor Memory Voltage Generation Circuit
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Solution Overview
Problem
In multivalue NAND flash memory devices, the process of setting and adjusting write voltages for memory cells is complex and time-consuming due to the need for multiple threshold voltages and step voltages, requiring extensive data trimming and storage, which increases the number of items of data needed and prolongs the trimming process.
Innovation Solution
A semiconductor memory device with a memory cell array, a storage section for initial write voltage and correction values, and a voltage generating circuit that generates word line write voltages based on these values, allowing for optimized initial write voltage and step voltage adjustments, reducing the need for multiple data items and simplifying the data trimming process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple write voltages are generated for different pages and cells in multivalue memory, then the write operation can be performed accurately, but the number of items of data to be stored increases and the trimming process becomes longer
Solution Approach 1:
The write voltage generation is segmented into a base initial value stored in the storage section and correction values generated dynamically. This divides the complex task of managing multiple write voltages into a manageable structure where only one initial value needs to be stored and trimmed, while variations are handled through correction mechanisms during operation.
Solution Approach 2:
The write voltage is made dynamic by generating correction values based on the current write operation context (page, cell position, adjacent cells) rather than using fixed pre-stored values for each scenario. This allows the system to adapt the write voltage dynamically while avoiding the need to store and trim multiple static voltage profiles.
2Reliability
If multiple write voltages are generated for different pages and cells, then accurate writing can be achieved, but the device complexity increases due to more data storage requirements
Solution Approach 1:
The complex task of storing and managing multiple write voltage profiles is extracted and replaced by storing only a single initial value in the storage section. The complexity of handling different voltage requirements for different pages and cells is extracted and transformed into correction value calculations performed during the write operation rather than being stored in advance.
Solution Approach 2:
A single initial value stored in the storage section serves multiple functions across different pages and cells. Through the addition of correction values generated based on operation context, this single stored value effectively becomes the basis for multiple write voltage scenarios, eliminating the need for separate storage entries for each case.
3Productivity
If the initial value of write voltage is changed according to writing page and cell conditions, then write operation can be optimized, but the number of items of data to be trimmed increases
Solution Approach 1:
A single initial value is pre-stored in the storage section during manufacturing. This preliminary action eliminates the need to trim and store multiple different initial values for different pages and cells. The correction values are then calculated during operation based on the specific write conditions, optimizing write efficiency without requiring extensive preliminary trimming of multiple data items.
Data Source
AI summary
In a memory cell array, a plurality of memory cells connected to word lines and bit lines are arranged in a matrix. A storage section stores an initial value of a write voltage corresponding to a first write operation and a correction value for correcting the write voltage. A voltage generating circuit generates a word line write voltage in a first write operation or a second write operation on the basis of the initial value and correction value of the write voltage stored in the storage section.