Semiconductor Spacer Thickness Optimization for Parasitic Capacitance
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Solution Overview
Problem
The complexity of semiconductor device fabrication increases with highly integrated structures, requiring innovative techniques to manage spacer thicknesses differently for cell bit lines and peripheral gates to improve performance and reduce parasitic capacitance and short channel effects.
Innovation Solution
A semiconductor device design where the cell bit line and peripheral gate structures are formed at the same level but with different spacer thicknesses, using silicon nitride or silicon oxynitride layers for offset spacers and silicon oxide for peripheral gate spacers, with specific thickness ratios and layer configurations to optimize parasitic capacitance and short channel effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the same spacer thickness is used for both cell bit line and peripheral gate structures, then the fabrication process is simpler, but parasitic capacitance of bit line increases and short channel effects in peripheral gate are not sufficiently suppressed
Solution Approach 1:
The patent applies local quality by configuring different spacer thicknesses for different functional regions: the bit line offset spacer has a first thickness optimized for minimizing parasitic capacitance, while the peripheral gate offset spacer has a second thickness (greater than the first) optimized for suppressing short channel effects. This region-specific optimization resolves the contradiction by allowing each structure to have the spacer thickness best suited to its electrical performance requirements.
2Reliability
If thicker spacers are used for peripheral gate to suppress short channel effects, then short channel effects are reduced, but bit line parasitic capacitance increases
Solution Approach 1:
The patent segments the spacer structure into distinct components with different thicknesses: the bit line offset spacer (first thickness) and the peripheral gate offset spacer (second thickness, greater than first). This segmentation allows each spacer to be independently optimized for its specific function, enabling thick spacers for peripheral gate short channel effect suppression while maintaining thin spacers for bit line parasitic capacitance minimization.
3Object-generated harmful factors
If thinner spacers are used for bit line to reduce parasitic capacitance, then parasitic capacitance is minimized, but peripheral gate short channel effects are not sufficiently suppressed
Solution Approach 1:
The patent implements local quality by assigning different spacer thickness characteristics to different functional areas: thin bit line offset spacers (first thickness) for parasitic capacitance minimization and thick peripheral gate offset spacers (second thickness) for short channel effect suppression. This localized optimization resolves the contradiction by allowing each region to have the spacer thickness best suited to its electrical performance requirements.
4Reliability
If different spacer thicknesses are used for cell bit line and peripheral gate, then electrical performance is optimized, but fabrication process complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the bit line offset spacer and peripheral gate offset spacer in a predetermined sequence during the fabrication process. The spacers are formed as part of the self-aligned multiple patterning process, where the first and second offset spacers are created using controlled deposition and etching steps that establish their different thicknesses early in the manufacturing sequence, thereby managing fabrication complexity through structured process design.
Data Source
AI summary
A semiconductor device includes a substrate including a cell area and a peripheral area, the cell area having an active region defined by an isolation region, a cell gate structure below an upper surface of the substrate in the cell area, the cell gate crossing the active region, a bit line structure above an upper surface of the substrate in the cell area, the bit line structure including bit line offset spacers on at least two side surfaces thereof, and a peripheral gate structure above an upper surface of the substrate in the peripheral area, the peripheral gate structure including peripheral gate offset spacers and peripheral gate spacers on at least two side surfaces thereof.