Staircase Patterning via Linear Alignment Control
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Solution Overview
Problem
Current methods for forming three-dimensional memory devices face challenges in creating precise staircase contact regions, which are crucial for efficient memory array formation, due to limitations in patterning and etching processes.
Innovation Solution
A method involving an alternating stack of insulating and spacer material layers, where a linear mark is formed perpendicular to one direction and parallel to another, with staircase-forming processing steps that include trimming material layers and etch processes to create stepped surfaces, allowing for precise lateral offset and uniform width, facilitating the formation of terrace regions and memory stack structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional patterning and etching processes are used to form staircase contact regions, then the manufacturing process is simpler, but the manufacturing precision and uniformity of the staircase structures deteriorate
Solution Approach 1:
The patent divides the staircase formation process into multiple discrete steps, each forming one step of the staircase structure. This is achieved by iteratively applying trimming material layers and performing selective etching operations, where each iteration adds one horizontal level to the staircase contact region, enabling precise control over each individual step's dimensions and position
Solution Approach 2:
The patent employs preliminary alignment marks formed before the staircase formation process to guide subsequent patterning and etching operations. These marks establish reference features that ensure precise lateral positioning and uniform spacing of the staircase steps, enabling accurate formation without requiring complex real-time alignment systems
2Manufacturing precision
If complex multiple-step etching and trimming processes are used, then the manufacturing precision of staircase contact regions improves, but the productivity and manufacturing time deteriorate
Solution Approach 1:
The patent employs periodic repetition of the same trimming and etching sequence to form multiple staircase steps. Each iteration of the process cycle (forming trimming material layer → patterning → etching → removing trimming material) produces one uniform step, and by repeating this standardized cycle, the process achieves high precision through consistency while enabling parallel processing and optimization of each individual cycle
Solution Approach 2:
The patent controls the lateral offset distance and thickness parameters of each trimming material layer to precisely define the geometry of each staircase step. By carefully adjusting these parameters in each iterative cycle, uniform spacing and dimensional control are achieved across all steps, ensuring consistent staircase structure formation throughout the memory device
3Manufacturing precision
If linear alignment control features are used, then the manufacturing precision and lateral offset uniformity improve, but the device complexity increases
Solution Approach 1:
The patent designs the linear alignment marks to serve multiple functions: they provide lateral positioning references for staircase formation, define spacing between adjacent staircase structures, and enable verification of pattern alignment. This multi-functional alignment feature reduces the need for separate alignment elements and simplifies the overall device structure while maintaining high precision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the creation of three-dimensional memory devices with accurately formed staircase contact regions, enhancing memory array efficiency and reliability by ensuring uniformity and precision in the terrace and memory stack structures.
Implementation Method 1
each etch process transfers a pattern of the trimming material layer vertically through a set of layers within the alternating stack to form stepped surfaces
Implementation Method 2
each trimming process isotropically trims the trimming material layer
Data Source
AI summary
A linear mark extending perpendicular to a primary step direction of stepped terrace for a three-dimensional memory device can be employed as a reference feature for aligning a trimming material layer before initiating an etch-and-trim process sequence. The linear mark can be formed as a linear trench or a linear rail structure. The distance between a sidewall of each trimming material layer and the linear mark can be measured at multiple locations that are laterally spaced apart perpendicular to the primary step direction to provide statistically significant data points, which can be employed to provide an enhanced control of the staircase patterning process. Likewise, locations of patterned stepped surfaces can be measured at multiple locations to provide enhanced control of the locations of vertical steps in the stepped terrace.