Trench Spacer Structure for Lower Parasitic Capacitance in DRAM
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Solution Overview
Problem
As semiconductor devices become more highly integrated, parasitic capacitance and leakage currents increase, deteriorating their operating characteristics, necessitating a solution to minimize these effects.
Innovation Solution
A semiconductor device design incorporating a trench structure with a direct contact and bit line structures, along with a spacer structure that includes silicon oxide and air spacers, is employed to reduce parasitic capacitance and leakage currents. The spacer structure consists of multiple layers extending along the side surfaces and top surfaces of the bit line structures, with air spacers spaced apart to minimize dielectric constant and interface traps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor devices are highly integrated with miniaturized circuit patterns, then device density and integration level are improved, but parasitic capacitance and leakage currents increase
Solution Approach 1:
The patent divides the trench structure into multiple segments with different materials: a first spacer made of silicon oxide, a second spacer made of low-k material, and an air spacer. This segmentation allows each portion to contribute differently to reducing parasitic capacitance while maintaining structural integrity and electrical performance.
Solution Approach 2:
The patent employs a composite spacer structure combining multiple materials with different dielectric properties. The silicon oxide provides structural stability, the low-k material reduces parasitic capacitance, and the air spacer provides the lowest dielectric constant. This composite approach optimizes both electrical performance and mechanical strength.
2Object-generated harmful factors
If trench width is reduced to minimize parasitic capacitance, then parasitic capacitance is reduced, but manufacturing precision and alignment difficulty increase
Solution Approach 1:
The first spacer made of silicon oxide acts as an intermediary layer between the trench wall and the low-k material. This intermediary provides a stable foundation that facilitates precise formation of subsequent layers, reducing alignment difficulties while maintaining the narrow trench dimensions needed for low parasitic capacitance.
Solution Approach 2:
The patent applies different materials with specific properties to different locations within the trench structure. The silicon oxide is placed where structural stability is needed, the low-k material where capacitance reduction is critical, and the air spacer where maximum dielectric reduction is required. This local optimization balances manufacturing feasibility with electrical performance.
3Object-generated harmful factors
If air spacers are introduced to reduce parasitic capacitance, then parasitic capacitance is reduced, but device complexity and fabrication process difficulty increase
Solution Approach 1:
The complex spacer structure is segmented into three distinct functional layers: silicon oxide for structural support, low-k material for capacitance reduction, and air spacer for maximum dielectric reduction. This segmentation makes the complex structure manageable through standardized fabrication processes for each layer.
Solution Approach 2:
The patent changes the dielectric parameter (k-value) progressively from the silicon oxide layer through the low-k layer to the air spacer. This gradual parameter change allows for controlled reduction of parasitic capacitance while managing the complexity of the fabrication process through systematic material selection.
Data Source
AI summary
A semiconductor device includes a semiconductor substrate including a trench, a direct contact in the trench, the direct contact having a width smaller than a width of the trench, a bit line structure on the direct contact, the bit line structure having a width smaller than the width of the trench, a first spacer including a first portion and a second portion, the first portion extending along an entire side surface of the direct contact, and the second portion extending along the trench, a second spacer on the first spacer, the second spacer filling the trench, a third spacer on the second spacer, and an air spacer on the third spacer, the air spacer being spaced apart from the second spacer by the third spacer, wherein the first spacer includes silicon oxide.