Single-Sided Buried Strap Formation in DRAM Trench Capacitors
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Solution Overview
Problem
Traditional buried strap structures in semiconductor devices suffer from dopant out-diffusion and high conduction resistance due to complex manufacturing processes and high defect density, particularly in DRAM cells with trench capacitors.
Innovation Solution
A method for forming a single-sided buried strap using a self-aligned process, which involves forming a trench, depositing dielectric and conductive layers, and using gate structures to create an opening for electrical coupling, thereby reducing dopant out-diffusion and manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional buried strap structures are used with complex manufacturing processes, then the electrical connection between storage capacitor and access transistor is achieved, but dopant out-diffusion occurs resulting in serious sub-threshold leakage and high conduction resistance
Solution Approach 1:
The patent applies preliminary action by forming the buried strap structure before subsequent thermal processing steps. The strap is prepared in advance with proper doping, and then protected during later high-temperature processes that would otherwise cause dopant out-diffusion. This timing arrangement prevents the harmful effect before it occurs.
Solution Approach 2:
The patent introduces an intermediary material layer between the buried strap and the surrounding environment. This intermediary layer acts as a barrier that prevents dopant atoms from diffusing out of the strap during thermal processing, thereby eliminating the sub-threshold leakage problem while maintaining electrical connection stability.
2Ease of manufacture
If traditional etching/refilling processes are used for buried strap formation, then the strap structure is created, but high defect density is caused by these processes
Solution Approach 1:
The patent extracts and eliminates the problematic etching/refilling steps from the manufacturing process. Instead of using these complex processes to form the buried strap, the invention employs a simplified deposition-based approach that directly creates the strap structure without requiring subsequent etching and refilling operations, thereby dramatically reducing defect density.
Solution Approach 2:
The manufacturing process is designed to be self-aligning and self-forming, where the buried strap structure automatically positions itself correctly during the deposition process without requiring additional etching or refilling steps. This self-service approach eliminates the sources of defects associated with multi-step processes.
3Manufacturing precision
If conventional photolithography and multi-step processes are used, then precise pattern formation is achieved, but manufacturing complexity and process steps increase dramatically
Solution Approach 1:
The patent merges multiple separate process steps into a single integrated deposition process. The buried strap formation is combined with the surrounding dielectric layer formation in one continuous operation, eliminating the need for separate photolithography, etching, and refilling steps while maintaining precise pattern formation through self-alignment.
Solution Approach 2:
The deposition process serves multiple functions simultaneously: it forms the buried strap structure, creates the surrounding dielectric layers, and establishes the correct geometric relationships between all components. This multi-functional approach replaces the specialized single-function steps of conventional photolithography and etching.
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
The method effectively decreases dopant out-diffusion and conduction resistance while simplifying the manufacturing process by minimizing thermal impacts and eliminating the need for conventional photolithography, resulting in improved semiconductor device performance.
Implementation Method 1
forming a first dielectric layer on a sidewall of the higher portion of the trench
Implementation Method 2
using gate structures to create an opening for electrical coupling
Data Source
AI summary
A method for forming a semiconductor device with a single-sided buried strap is provided. The method includes the steps of providing a substrate with a trench, forming a semiconductor component in a lower portion of the trench to expose a higher portion of the trench, forming a first dielectric layer on a sidewall of the higher portion of the trench, forming a first conductive layer in the trench and adjacent to the first dielectric layer, forming a second dielectric layer on the first dielectric layer and the first conductive layer, forming a plurality of gate structures on the substrate, wherein one of the gate structures on the second dielectric layer is offset for a distance from the second dielectric layer, removing a portion of the second dielectric layer and a portion of the first dielectric layer to form an opening by using the gate structure as a mask, and forming a second conductive layer in the opening to electrically couple to the first conductive layer, whereby the semiconductor device with the single sided buried strap is formed.