3D Memory Staircase Formation With Sequential Mask Trimming
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Solution Overview
Problem
The existing multi-cycle trim and etch processes for forming staircase structures in 3D memory devices suffer from low throughput and high costs, making it challenging to scale 3D memory devices as semiconductor technology advances.
Innovation Solution
A method is disclosed for forming staircase structures in 3D memory devices by creating an alternating layer stack over a substrate, using a mask stack to sequentially remove and trim layers, and repeating the process to form a staircase structure with a specific number of steps, which reduces fabrication complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If existing multi-cycle trim and etch processes are used to form staircase structures, then staircase structures can be formed to connect word lines, but the throughput is low and manufacturing cost is high
Solution Approach 1:
The patent applies preliminary action by forming the mask stack and performing multiple trimming operations before the final etching process. The mask stack is prepared in advance with specific thickness and pattern, and multiple trim cycles are performed to progressively shape the staircase structure. This preliminary preparation enables the subsequent etch process to be more efficient and reduces the need for repeated adjustments, thereby improving throughput while maintaining manufacturing precision.
Solution Approach 2:
The patent segments the staircase formation process into distinct stages: mask stack formation, multiple trimming cycles, and final etching. Each stage is optimized independently - the mask stack is formed with specific layer composition, trimming is performed in multiple passes with controlled removal amounts, and etching is executed in optimized cycles. This segmentation allows each process step to be refined separately, reducing overall manufacturing cost and improving throughput.
2Manufacturing precision
If existing multi-cycle trim and etch processes are used to form staircase structures, then staircase structures can be formed with required precision, but the fabrication complexity is high
Solution Approach 1:
The patent applies universality by using a single mask stack structure to perform multiple functions: it serves as the etch mask, the trim reference, and the structural template for the staircase formation. The same mask stack is used throughout all trimming and etching operations, eliminating the need for multiple different mask structures. This multi-functionality reduces fabrication complexity while maintaining the precision required for staircase structure formation.
Solution Approach 2:
The patent controls staircase structure precision by changing process parameters systematically - the amount of material removed in each trim cycle is controlled, the thickness of mask stack layers is precisely defined, and the etching depth in each cycle is regulated. By controlling these parameters rather than changing the fundamental process structure, the patent achieves high precision without proportionally increasing fabrication complexity.
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 method reduces the complexity and manufacturing cost of 3D memory devices while enabling efficient formation of staircase structures, improving the scalability of 3D memory devices.
Implementation Method 1
removing 2M of a portion of layer stacks of the alternating layer stack at each of the staircase regions using a first mask stack
Implementation Method 2
patterning the second mask stack to define the staircase regions over the alternating layer stack using a lithography process
Data Source
AI summary
A method for forming a staircase structure of 3D memory, including: forming an alternating layer stack on a substrate, forming a plurality of staircase regions where each staircase region has a staircase structure having a first number (M) of steps in a first direction; forming a first mask stack to expose a plurality of the staircase regions; removing (M) of the layer stacks in the exposed staircase regions; forming a second mask stack over the alternating layer stack to expose at least an edge of each of the staircase regions in a second direction; and repetitively, sequentially, removing a portion of (2M) of layer stacks and trimming the second mask stack.