3D NAND Staircase Contact Patterning With Etch Stop Islands
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Solution Overview
Problem
Current 3D NAND fabrication methods face challenges with increased processing complexity, time, and conductive layer degradation due to serial patterning and etching, especially as the number of layers increases.
Innovation Solution
The use of multiple etch stop layers in the substrate processing method to prevent conductive layer degradation, allowing for simultaneous etching of contacts, reducing processing steps and time, and enhancing device yield and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If serial patterning is used for contact patterning in staircase substrate processing, then the number of patterning steps increases with the number of layers, but the processing time increases and conductive material erosion occurs in underlying layers
Solution Approach 1:
The patent divides the contact patterning process into two independent stages: first forming contact holes through the etch stop layer to reach the conductive layer, then separately forming contact pads on the conductive layer. This segmentation allows simultaneous processing of multiple layers without sequential delays, reducing total patterning time while maintaining precision for each stage independently.
Solution Approach 2:
The etch stop layer is deposited and patterned in advance before the conductive layer is formed. This preliminary action creates a pre-defined template that guides subsequent contact hole formation, enabling parallel processing of multiple contact holes across different layers without requiring sequential patterning steps, thus reducing overall processing time.
2Manufacturing precision
If serial patterning is used for contact patterning in staircase substrate processing, then the number of patterning steps increases with the number of layers, but conductive material erosion occurs in underlying layers
Solution Approach 1:
The etch stop layer serves as an intermediary barrier between the patterning process and the conductive layer. It absorbs the etching action and protects the conductive layer from direct exposure to etchants, preventing material erosion while still allowing precise contact hole formation through the etch stop layer to reach the conductive layer underneath.
Solution Approach 2:
The patent separates the contact hole formation process from the contact pad formation process, with the etch stop layer defining the contact holes in a first stage and the conductive layer receiving contact pads in a second stage. This segmentation prevents repeated etching of the conductive layer, maintaining its integrity while achieving precise contact alignment.
3Quantity of substance
If the number of layers in staircase substrate increases, then storage capacity increases, but processing complexity and time increase
Solution Approach 1:
The etch stop layer serves multiple functions simultaneously: it acts as a barrier layer to prevent conductive material erosion, as a patterning template for contact hole formation, and as a protective layer during subsequent processing steps. This multi-functionality reduces the number of separate processing steps required, thereby reducing processing complexity even as the number of layers increases.
Solution Approach 2:
The etch stop layer is formed and patterned in advance before the conductive layers are fully assembled, creating a universal template that guides contact hole formation across all layers simultaneously. This preliminary action eliminates the need for sequential patterning of each layer, reducing processing complexity and time while maintaining the ability to handle increased layer counts for higher storage capacity.
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 reduces manufacturing costs and time while maintaining the integrity of conductive layers, improving device yield and throughput even as the number of layers in 3D NAND structures increases.
Implementation Method 1
forming a conformal etch stop layer over a staircase layer stack substrate
Implementation Method 2
exposing the amorphous layer to a hydrogen plasma
Implementation Method 3
selectively depositing, using an area selective deposition process, etch stop regions within the first openings
Data Source
AI summary
A method of forming contacts includes forming a conformal etch stop layer over a staircase layer stack substrate, the staircase layer stack substrate including a plurality of steps on a substrate, each step including a pair of a first layer and a second layer and having a sidewall extending from one step to another step. The method further includes patterning the etch stop layer to remove portions of the etch stop layer covering the sidewalls of the steps and form islands of the etch stop layer. The method further includes replacing the second layer with a conductive material and simultaneously forming contact features through the islands of the etch stop layer to the conductive material, the contact features to different steps of the plurality of steps having different lengths.