Memory Sector Trimmed Reference Currents Odd Even Word Line Read Errors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inconsistent cell current performance between memory cells corresponding to odd and even word lines in flash memory devices due to manufacturing process variations, leading to read errors and performance disparities.
Innovation Solution
Deriving different reference currents for unit cells corresponding to odd and even word lines by measuring cell currents when all unit cells on one word line are in a specific state, allowing for improved logic state determination and reduced read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single predetermined reference current is used for all memory cells, then the manufacturing process is simple, but read errors increase due to even-odd disparity between adjacent word lines
Solution Approach 1:
The patent divides the memory cells into two segments: even word line cells and odd word line cells. Different reference currents (first reference current for odd word lines, second reference current for even word lines) are determined separately for each segment based on their respective cell current distributions, thereby resolving the even-odd disparity issue while maintaining manufacturing simplicity
Solution Approach 2:
The patent applies local quality by providing different reference currents tailored to specific word line groups. The first reference current is optimized for odd word line cells while the second reference current is optimized for even word line cells, ensuring each group has the appropriate reference level for accurate read operations
2Reliability
If the specification limit of alignment shift is further restricted, then even-odd disparity is reduced, but manufacturing complexity and difficulty increase
Solution Approach 1:
Instead of controlling alignment shift during manufacturing, the patent changes the parameter approach by determining different reference currents based on measured cell current distributions. This shifts the solution from mechanical alignment control to electrical parameter adjustment, reducing manufacturing complexity while improving cell current consistency
3Reliability
If different reference currents are determined for odd and even word lines, then read errors are reduced, but the reference current determination process becomes more complex
Solution Approach 1:
The patent applies preliminary action by determining the first and second reference currents in advance through trimming operations. By pre-determining these reference currents based on cell current measurements before actual read operations, the system eliminates the need for complex real-time adjustments during reading, thereby improving reliability without significantly increasing operational complexity
Data Source
AI summary
A memory sector with trimmed reference currents, including eight unit cells corresponding to an even word line and eight unit cells corresponding to an odd word line, and each unit cell has erased state and programmed state, wherein the logic state of unit cell corresponding to the odd word line is determined by a first reference current based on cell currents of the 8 unit cells corresponding to the even word line in programmed state and cell currents of the eight unit cells corresponding to the odd word line in erased state, and the logic state of unit cell corresponding to the even word line is determined by a second reference current based on cell currents of the eight unit cells corresponding to the even word line in erased state and cell currents of the 8 unit cells corresponding to the odd word line in programmed state.