Memory Array Staircase Sub-Treads for Higher Word Line Density
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Solution Overview
Problem
As memory systems scale to include more memory cells and word lines, the existing manufacturing process is inadequate to form lateral sub-treads on the treads of a staircase architecture for word line contacts, limiting the increase in the quantity of word line contacts per unit area.
Innovation Solution
The techniques described involve using multiple doped liner materials to form three or more lateral sub-treads on the treads of a staircase architecture for word line contacts, reducing the area consumed by the word line contacts and enabling a folded staircase design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the existing manufacturing process is used to form word line contacts, then the process is simple, but the quantity of word line contacts per unit area is limited
Solution Approach 1:
The patent divides each tread into multiple lateral sub-treads (first, second, third sub-treads), allowing multiple word line contacts to be formed on a single tread. This segmentation increases the quantity of word line contacts per unit area while maintaining a manageable manufacturing process through sequential formation steps
Solution Approach 2:
The patent extends the staircase architecture laterally by creating multiple sub-treads on each tread level, transitioning from a single contact per tread to multiple contacts per tread. This dimensional expansion in the lateral direction increases contact density without requiring additional vertical levels
2Productivity
If additional treads are added to increase word line contacts, then the quantity of contacts increases, but the total area consumed increases
Solution Approach 1:
Instead of adding vertical treads to increase contact quantity, the patent creates multiple lateral sub-treads on existing tread levels. This lateral dimensionality change allows multiple contacts to share the same vertical space, reducing the total area consumed while increasing contact density
3Productivity
If lateral sub-treads are formed to increase contact density, then the area consumed is reduced, but the manufacturing process becomes inadequate
Solution Approach 1:
The patent segments the sub-tread formation into distinct sequential steps (first sub-tread, second sub-tread, third sub-tread), making the complex manufacturing process manageable through systematic breakdown. Each sub-tread is formed in a separate step using standard semiconductor fabrication techniques
Solution Approach 2:
The patent performs preliminary actions by forming liner materials and sacrificial structures before creating the sub-treads. These preliminary structures guide the subsequent sub-tread formation process, making the manufacturing sequence more controllable and less complex
Data Source
AI summary
Methods, systems, and devices for staircase formation in a memory array are described. A first liner material may be deposited on a tread above a first contact surface and a portion of the first liner material may be doped. A second liner material may be deposited over the first liner and a portion of the second liner material may be doped. After doping the portions of the liner materials, the undoped portions of the liner materials may be removed so that the materials above a second contact surface can be at least partially removed via a first removal process. The doped portion of the first liner material may then be cut back so that a second removal process can expose the second contact surface and a third contact (while the first contact surface is protected from the removal process by the liner materials).