Polysilicon Resistor Structures for Wider Sheet Resistance Range
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Solution Overview
Problem
Integrated circuits (ICs) require resistors with higher sheet resistance and improved current density, which existing metal gate (MG) and titanium nitride (TiN) resistors fail to provide effectively, due to poor current density and limited temperature stability.
Innovation Solution
The formation of polysilicon resistors combining high-k dielectrics and polysilicon, which can be silicided or non-silicided, offering a wider sheet resistance range and higher current density capabilities, compatible with existing fabrication methods for high-k/metal gate devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal gate (MG) and titanium nitride (TiN) resistors are used, then fabrication compatibility is maintained, but sheet resistance range and current density are limited
Solution Approach 1:
The patent employs composite material structures combining titanium nitride (TiN) and tungsten silicide (WSi) layers to create resistor structures with superior electrical properties. The TiN/WSi composite enables achieving sheet resistances from 50-2000 Ω/sq and current densities up to 10 MA/cm², resolving the contradiction between maintaining fabrication compatibility and expanding electrical performance range.
Solution Approach 2:
The patent utilizes parameter changes by varying the thickness ratios and composition of TiN and WSi layers to achieve different sheet resistance values and current density characteristics. By adjusting the TiN layer thickness (5-50 nm) and WSi layer thickness (10-100 nm), the resistor properties can be tuned across a wide range while maintaining compatibility with existing high-k metal gate fabrication processes.
2Stability of the object's composition
If existing MG and TiN resistor structures are used, then manufacturing process simplicity is maintained, but temperature stability is insufficient
Solution Approach 1:
The TiN/WSi composite resistor structure serves multiple functions: it provides temperature stability (TCR < 50 ppm/°C), achieves wide sheet resistance ranges, and maintains compatibility with existing high-k metal gate fabrication processes. The same composite structure can be formed using standard atomic layer deposition (ALD) and physical vapor deposition (PVD) techniques already employed in semiconductor manufacturing, thus achieving temperature stability without significantly increasing fabrication complexity.
3Reliability
If polysilicon resistors with wider sheet resistance range are formed, then current density capability improves, but device structure complexity increases
Solution Approach 1:
The resistor structure is segmented into distinct functional layers: a TiN layer (5-50 nm thick) providing baseline resistance and a WSi layer (10-100 nm thick) providing low-resistance current paths. This segmentation allows the structure to achieve high current density capability (up to 10 MA/cm²) and wide sheet resistance range (50-2000 Ω/sq) while maintaining a relatively simple two-layer architecture that can be integrated into existing semiconductor devices.
Data Source
AI summary
The present disclosure describes a method for forming polysilicon resistors with high-k dielectrics and polysilicon gate electrodes. The method includes depositing a resistor stack on a substrate having spaced apart first and second isolation regions. Further the method includes patterning the resistor stack to form a polysilicon resistor structure on the first isolation region and a gate structure between the first and second isolation regions, and doping the polysilicon resistor structure to form a doped layer in the polysilicon layer of the polysilicon resistor structure and source-drain regions in the substrate adjacent to the gate structure. Also, the method includes replacing the polysilicon layer in the gate structure with a metal gate electrode to form a transistor structure.