Pre-positioned Dummy Word Line for Fast Erase in Memory
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Solution Overview
Problem
Non-volatile memory apparatuses with semi-circle drain-side select gates (SC-SGD) face inefficiencies due to slow erase speed of edge word lines, leading to shallow erase of memory cells, which affects data retention and programming efficiency.
Innovation Solution
A memory apparatus and method that include a dummy word line and a control mechanism to determine when a dummy positioning operation is needed, adjusting the threshold voltage of memory cells connected to the dummy word line to facilitate faster erase and programming operations, thereby improving the erase speed of edge word lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If etching technology is used to create semi-circle drain-side select gates, then die size is reduced, but erase speed of edge word lines becomes slow
Solution Approach 1:
The dummy word line is pre-programmed to a specific threshold voltage state before actual data programming operations. This preliminary positioning of the dummy word line threshold voltage enables faster erase operations on edge word lines by having the dummy structure already in the optimal state to facilitate charge removal, thus resolving the slow erase speed issue without compromising the compact semi-circle SGD structure
2Area of stationary object
If etching technology is used to create semi-circle drain-side select gates, then die size is reduced, but programming efficiency is affected
Solution Approach 1:
By pre-positioning the dummy word line to an optimal threshold voltage state before data programming, the system prepares the electrical environment in advance. This preliminary action reduces the time and voltage required for subsequent programming operations on edge word lines, thereby improving programming efficiency while maintaining the space-saving semi-circle SGD architecture
3Speed
If dummy word line is used to improve erase speed, then erase speed increases, but device complexity increases
Solution Approach 1:
The dummy word line serves multiple functions: it acts as a shielding structure during erase operations to enhance electric field distribution, provides a reference for threshold voltage control, and facilitates charge removal from edge word lines. By making this single structure multi-functional, the patent achieves faster erase speeds without proportionally increasing device complexity
Data Source
AI summary
A memory apparatus and method of operation are provided. The apparatus includes memory cells connected to word lines including a dummy word line and other data word lines. The memory cells are disposed in memory holes and configured to retain a threshold voltage. A control means is coupled to the word lines and the memory holes and is configured to determine whether one of the word lines being programmed in a program operation is a particular one of the word lines adjacent the dummy word line needing a dummy positioning operation. The control means is also configured to program the memory cells connected to the dummy word line to adjust the threshold voltage to a predetermined position threshold voltage in the dummy positioning operation in response to determining the one of the plurality of word lines being programmed in the program operation is the particular one of the word lines.