Self-Aligned Lateral Contact Elements in 3D Memory Devices
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently forming self-aligned lateral contact elements, particularly in creating stepped surfaces and replacing sacrificial material layers with conductive layers while maintaining precise control over etching processes.
Innovation Solution
The method involves forming an alternating stack of insulating and sacrificial material layers, patterning stepped surfaces, and using a common etching step to create memory and contact openings, followed by selective deposition of conductive materials to form plugs and via structures, ensuring accurate contact formation within retro-stepped dielectric regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple separate etching steps are used to form memory openings and contact openings, then each opening can be precisely controlled, but the processing time and manufacturing complexity increase
Solution Approach 1:
The patent combines the formation of memory openings and contact openings into a single common anisotropic etching step. The etch process simultaneously creates both types of openings through the alternating stack, eliminating the need for separate etching steps. This merging approach maintains precise control over opening formation while significantly reducing processing time and manufacturing complexity.
2Manufacturing precision
If conventional contact formation methods are used, then the process is simpler, but self-aligned lateral contact elements cannot be achieved with precise control
Solution Approach 1:
The patent employs preliminary actions to achieve self-aligned lateral contact elements. sacrificial material layers are pre-formed in specific patterns before the common etching step, and conductive plugs are pre-positioned in contact openings. These preliminary structures guide the subsequent etching process to automatically create properly aligned contact openings, eliminating the need for complex alignment procedures while achieving precise contact alignment.
3Manufacturing precision
If stepped surfaces are formed through multiple patterning steps, then precise stepped structures are achieved, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent segments the formation of stepped surfaces into distinct phases. First, sacrificial material layers are deposited in alternating patterns to create a segmented structure. Then, a single common anisotropic etching step selectively removes portions of these segmented layers to reveal precisely controlled stepped surfaces. This segmentation approach achieves high precision stepped structures while minimizing processing time by avoiding multiple patterning steps.
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 formation of self-aligned lateral contact elements with precise control, enhancing the integration of memory stack structures and reducing processing time and costs by employing a single anisotropic etching process for various openings.
Implementation Method 1
forming memory openings and contact openings through the alternating stack in a common first etching step
Implementation Method 2
forming conductive plugs by selectively depositing a conductive material from physically exposed cylindrical surfaces of the electrically conductive layers while suppressing deposition of the conductive material from dielectric surfaces
Data Source
AI summary
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers having stepped surfaces, memory stack structures extending through the alternating stack, a retro-stepped dielectric material portion overlying the stepped surfaces, and pillar-shaped contact-opening assemblies located within a respective pillar-shaped volume vertically extending through the retro-stepped dielectric material portion and a region of the alternating stack that underlies the retro-stepped dielectric material portion. Some of the pillar-shaped contact-opening assemblies can include a first conductive plug that laterally contacts a cylindrical sidewall of a respective one of the electrically conductive layers and a conductive via structure that contacts a top surface of the first conductive plug.