Semiconductor Resistors with Different Resistances via Selective Diffusion
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Solution Overview
Problem
The process of fabricating semiconductor devices with resistors is complex and costly due to the need for different doping concentrations for resistors with varying resistances, which cannot be combined with other processes like forming source/drain or gate structures.
Innovation Solution
A method involving the formation of trench isolations and sacrificial layers on a semiconductor substrate, followed by implantation of doping ions and annealing to achieve resistors with different resistances, allowing for simultaneous fabrication of resistors and integration with source/drain or gate processes using silicide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If different doping concentrations are used to form resistors with different resistances, then the resistance values can be controlled precisely, but the fabrication process becomes complex and costly
Solution Approach 1:
The patent changes the physical state and concentration parameters of doping ions during the annealing process. By controlling annealing temperature and time, the doping concentration is dynamically adjusted - initially high for source/drain formation, then reduced through diffusion to achieve desired resistor values. This resolves the contradiction by achieving precise resistance control through parameter evolution rather than multiple discrete doping processes.
Solution Approach 2:
The patent performs preliminary doping ion implantation at high concentration to form both source/drain regions and resistor regions simultaneously. The subsequent annealing process then selectively reduces the doping concentration in resistor regions through controlled diffusion. This preliminary action eliminates the need for separate doping processes for different resistor values, simplifying the fabrication process while maintaining precision.
2Manufacturing precision
If separate doping processes are used for source/drain and resistors, then each structure can be optimized independently, but the overall fabrication time and cost increase
Solution Approach 1:
The patent merges the formation of source/drain regions and resistor regions into a single doping ion implantation process. Both structures receive the same initial high-concentration doping, followed by a unified annealing process that selectively modifies the doping concentration in resistor regions. This merging maintains independent optimization capability while dramatically improving fabrication efficiency by eliminating redundant process steps.
Solution Approach 2:
The doping ion implantation process is designed to serve multiple functions simultaneously: forming source/drain regions with high conductivity and forming resistor regions with controlled resistance. The subsequent annealing process universally treats both structures but achieves different outcomes through selective diffusion paths and concentration gradients, demonstrating multi-functionality that improves productivity without sacrificing optimization precision.
3Reliability
If high doping concentration is used for source/drain formation, then conductivity is sufficient, but the same concentration cannot be used for resistors as it would prevent achieving high resistance values
Solution Approach 1:
The patent applies dynamic control of doping concentration through the annealing process. Source/drain regions maintain high doping concentration for reliable conductivity, while resistor regions undergo controlled diffusion that dynamically reduces their doping concentration to achieve high resistance values. This temporal and spatial dynamic adjustment resolves the contradiction by allowing each structure to have the appropriate doping level at the appropriate time.
Solution Approach 2:
The patent creates local quality differences in doping concentration within the same semiconductor substrate. Source/drain regions retain high doping concentration for conductivity, while resistor regions develop localized low doping concentration through selective diffusion during annealing. This local differentiation enables both high conductivity and high resistance to coexist in the same device, resolving the contradiction between reliability and adaptability.
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 method simplifies the fabrication process by enabling the simultaneous creation of resistors with different resistances and reduces fabrication costs by integrating resistor formation with other semiconductor device processes.
Implementation Method 1
doping ions are implanted into the second portions
Implementation Method 2
the semiconductor substrate is annealed to homogenize the doping ions in the first resist region and the second resist region
Implementation Method 3
a portion of the doping ions are diffused out of the second resist region because the second sacrificial layer is removed
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, trench isolations, a sacrificial layer, a first resist protect oxide (RPO) layer, a second RPO layer and a silicide layer. The semiconductor substrate has first portions and second portions which are alternately disposed, and each of the second portions includes a first resist region with a first resistance, a second resist region with a second resistance and a silicide region. The second resistance is greater than the first resistance. The trench isolations are in the first portions. The sacrificial layer is on the first resist region. The first RPO layer is on the sacrificial layer. The first RPO layer together with the sacrificial layer have a first thickness. The second RPO layer is on the second resist region, in which the second RPO layer has a second thickness smaller than the first thickness. The silicide layer is on the silicide region.