EEPROM Word Line Formation With Self-Aligned Spacers
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Solution Overview
Problem
Existing EEPROM cell technologies face non-uniformity issues in word line widths due to shifting during patterning, which affects the performance and reliability of memory devices.
Innovation Solution
The formation of word lines between spacers in an EEPROM array using a self-aligning method, where spacers are placed between floating gates and electrode layers are filled to create word lines, ensuring consistent widths and avoiding shifting-related non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional patterning methods are used to form word lines, then the manufacturing process is simpler, but the word line width uniformity deteriorates due to shifting
Solution Approach 1:
The patent applies preliminary action by forming spacers on the sidewalls of floating gates before forming the word lines. These spacers serve as pre-positioned alignment references that guide the subsequent word line formation process, ensuring uniform width without requiring high-precision patterning alignment. The spacers are formed in advance to establish the exact position and width of the future word lines.
Solution Approach 2:
The patent introduces spacers as intermediary structures between the floating gates and the word lines. These spacers act as mediators that transfer the precise positioning information from the floating gates to the word lines, ensuring uniform word line width. The spacers serve as a bridging element that eliminates direct alignment requirements between floating gates and word lines.
2Reliability
If self-aligning method with spacers is used, then word line width uniformity is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The spacers are formed in advance on the sidewalls of floating gates as preliminary structures. This preliminary action establishes the exact width and position of word lines before the actual word line formation, ensuring uniformity and reliability. The pre-formed spacers eliminate the need for high-precision alignment during word line patterning, improving reliability while managing manufacturing complexity.
Solution Approach 2:
The spacers serve a dual function: they act as alignment references for word line formation and also serve as part of the final memory structure. The floating gates self-align with the spacers, and the electrode material automatically conforms to the spacer geometry, creating uniform word lines without requiring external alignment adjustments. This self-service mechanism improves reliability while reducing the need for complex alignment processes.
Data Source
AI summary
An array of programmable memory includes a first floating gate and a second floating gate disposed on a substrate along a first direction, two spacers disposed between and parallel to the first floating gate and the second floating gate, a first word line sandwiched by one of the spacers and the adjacent first floating gate, and a second word line sandwiched by the other one of the spacers and the adjacent second floating gate, and two first spacers disposed on the substrate, wherein one of the first spacer is disposed between the first word line and the first floating gate, and another spacer is disposed between the second word line and the second floating gate, wherein each spacer has substantially the same shape as each first spacer.