3D Memory Word Line Pad Layout to Prevent Contact Bridges
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Solution Overview
Problem
The integration density of two-dimensional semiconductor memory devices is limited by the area occupied by memory cells, and vertically stacked three-dimensional devices face issues with contact bridges between word lines due to increased horizontal width.
Innovation Solution
A 3D semiconductor memory device design where word lines share a common contact, increasing the size of word line pads and allowing for various contact patterns, reducing the risk of short-circuits and minimizing the area of the pad region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If word lines are spaced apart in the vertical direction to increase integration density, then the horizontal width of word lines must be increased, but this increases the risk of contact bridges between adjacent word lines
Solution Approach 1:
Adjacent word lines share a common contact pad, merging their individual contacts into a single shared contact structure. This reduces the total number of contacts and eliminates the contact bridges that would form between separately contacted word lines, thereby maintaining reliability while enabling higher integration density through vertical spacing.
Solution Approach 2:
The patent transitions from a horizontal arrangement of word lines to a vertical arrangement, utilizing the vertical dimension to increase integration density. By spacing word lines in the vertical direction rather than horizontally, the design achieves higher density without the contact bridge issues inherent in horizontal proximity.
2Quantity of substance
If the pad region area is reduced to increase integration density, then the manufacturing precision of contacts becomes more difficult to maintain
Solution Approach 1:
By merging adjacent word line contacts into shared contact pads, the patent reduces the total area required for pad structures. This area reduction is offset by the shared nature of the contacts, which simplifies the manufacturing process and maintains precision despite the reduced overall pad region area.
Solution Approach 2:
The shared contact pads serve multiple word lines simultaneously, making them universal contact structures. This multi-functionality allows a single contact pad to represent multiple word lines, reducing the total pad area while actually simplifying manufacturing requirements compared to individual dedicated contacts for each word line.
Data Source
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AI summary
A semiconductor memory device may include a substrate including a stack region and a pad region in a first horizontal direction, word lines extending in the first horizontal direction in the stack region, bit lines extending in a vertical direction in the stack region and spaced apart from one another in the first horizontal direction and a second horizontal direction, memory cells in the stack region and between the word lines and the bit lines, and a pad structure including word line pads spaced apart from each other in the vertical direction in the pad region. The word lines may include first and second word lines, which may be separated from each other in the second horizontal direction. The first and second horizontal directions may different. Each of the word line pads may be connected to the first and second words lines at a same vertical level.