Dummy Pillars as Bottom Contacts for Buried Diffusion Layers
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Solution Overview
Problem
Conventional techniques for forming contacts to buried diffusion layers in semiconductor memory devices require dummy pillar structures, which increase area overhead, processing complexity, and cost due to the need for additional rows of dummy pillars at array edges, especially when bottom contacts are nested within pillar structures.
Innovation Solution
The use of dummy pillars with specific doping regions and electrical connections to the substrate, which act as bottom contacts to reduce area overhead and processing complexity by eliminating the need for separate contacts to the buried diffusion layer, allowing for nested configurations without breaking the periodicity of the lithographic pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dummy pillar structures are used to ensure proper printing of active pillar structures near array edges, then lithographic pattern printing is improved, but area overhead significantly increases
Solution Approach 1:
The patent merges the functions of dummy pillars and bottom contacts by forming bottom contacts directly on dummy pillars during the same lithographic process. This integration eliminates the need for separate dummy pillar structures while maintaining proper printing of active pillar structures near array edges, thereby reducing area overhead while preserving lithographic precision.
Solution Approach 2:
The dummy pillars are given multiple functions: they serve both as structural elements to maintain lithographic pattern printing and as substrates for forming bottom contacts to buried diffusion layers. This multi-functionality eliminates the need for separate dedicated bottom contact structures, reducing overall area overhead.
2Reliability
If separate bottom contacts to buried diffusion are formed at array edges, then electrical connection is improved, but processing complexity significantly increases
Solution Approach 1:
The patent combines the formation of bottom contacts with the dummy pillar structure into a single integrated process step. Bottom contacts are formed on dummy pillars using the same lithographic and deposition processes, eliminating the need for separate processing steps for creating bottom contacts at array edges, thereby reducing processing complexity while maintaining electrical connection reliability.
3Area of stationary object
If nested bottom contacts are formed within pillar structures, then area efficiency is improved, but lithographic pattern printing deteriorates due to broken periodicity
Solution Approach 1:
The dummy pillars serve dual purposes: they maintain the periodic lithographic pattern for proper printing of active structures, and simultaneously provide substrates for nested bottom contacts to buried diffusion. This multi-functionality allows nested configuration that improves area efficiency while preserving lithographic pattern periodicity and printing quality.
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 the area overhead and processing complexity by using dummy pillars as bottom contacts, minimizing the need for additional rows and maintaining pattern periodicity, thereby enhancing the efficiency and cost-effectiveness of semiconductor memory device fabrication.
Implementation Method 1
The use of dummy pillars with specific doping regions and electrical connections to the substrate
Data Source
AI summary
Techniques for forming a contact to a buried diffusion layer in a semiconductor memory device are disclosed. The techniques may be realized as a semiconductor memory device. The semiconductor memory device may comprise a substrate comprising an upper layer, an array of dummy pillars formed on the upper layer of the substrate and arranged in rows and columns, and an array of active pillars formed on the upper layer of the substrate and arranged in rows and columns. Each of the dummy pillars may extend upward from the upper layer and have a bottom contact that is electrically connected with the upper layer of the substrate. Each of the active pillars may extend upward from the upper layer and have an active first region, an active second region, and an active third region. Each of the active pillars may also be electrically connected with the upper layer of the substrate.