Memory Array Staircase Layout for Higher Word Line Contact Density
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Solution Overview
Problem
The challenge in memory device manufacturing is the inadequate formation of lateral sub-treads in word line contacts, which limits the increase in the quantity of word line contacts per unit area, leading to inefficiencies in memory array design.
Innovation Solution
The formation of three or more lateral sub-treads in a staircase architecture for word line contacts is achieved by using multiple doped liner materials, where portions of the liner materials are selectively doped and then removed to expose additional contact surfaces, reducing the area consumed by word line contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional staircase formation is used for word line contacts, then the manufacturing process is simpler, but the quantity of word line contacts per unit area is limited
Solution Approach 1:
The patent divides the staircase structure into multiple discrete lateral sub-treads (first, second, third sub-treads) formed at different elevations. Each sub-tread is created through separate etching operations with protective masks, allowing independent formation and precise control of each contact level, thereby increasing the total number of contacts per unit area.
Solution Approach 2:
The patent implements a nested staircase architecture where lateral sub-treads are formed at progressively lower elevations, with each sub-tread nested within the structure of the previous level. This nested configuration allows multiple contact surfaces to be stacked vertically while maintaining compact horizontal footprint, increasing contact density.
2Quantity of substance
If more lateral sub-treads are formed to increase contact density, then the number of word line contacts per unit area increases, but the area consumed by contact structures increases
Solution Approach 1:
The patent transitions from a two-dimensional contact layout to a three-dimensional staircase structure with lateral sub-treads at multiple elevations. By utilizing the vertical dimension and creating offset contact surfaces at different heights, the design accommodates more contacts within the same horizontal footprint, effectively reducing area consumption per contact.
Solution Approach 2:
The staircase structure employs dynamic offset positioning where each lateral sub-tread is horizontally displaced relative to the previous level. This dynamic arrangement allows contact surfaces to be stacked vertically with minimal horizontal overlap, maximizing contact density while minimizing the total area occupied by the contact structure.
3Manufacturing precision
If selective doping and removal of liner materials is used to form sub-treads, then additional contact surfaces are exposed, but the manufacturing precision requirements increase
Solution Approach 1:
The patent uses liner materials as intermediary protective layers during the etching process. These liners are selectively deposited and removed to protect specific regions while exposing contact surfaces at desired elevations. The liner materials act as temporary masks that enable precise control over which contact surfaces are exposed at each manufacturing stage.
Solution Approach 2:
The patent employs selective doping of liner materials to alter their physical and chemical properties. By changing the doping concentration and composition of different liner layers, the process enables differential etching rates and selective removal, allowing precise control over contact surface exposure while managing the complexity of multi-layer liner processing.
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).