Polysilicon Resistor Structure for High-k Metal Gate Integration
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Solution Overview
Problem
Existing resistors in integrated circuits, such as those made of metal gate (MG) and titanium nitride (TiN), suffer from poor current density and limited sheet resistance, particularly when higher resistances are required, and are not compatible with high-dielectric constant dielectric materials used in field effect transistors.
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, compatible with high-k/metal gate fabrication processes, and integrated with transistor structures.
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 current density and sheet resistance range are limited
Solution Approach 1:
The patent employs composite material structures combining high-k dielectric materials (such as hafnium oxide, hafnium silicon oxide) with metal layers (titanium, titanium nitride, tungsten) to create resistor structures that achieve both high current density and wide sheet resistance range. The multi-layer composite structure allows optimization of electrical properties while maintaining fabrication compatibility.
Solution Approach 2:
The patent utilizes parameter changes by varying the thickness, composition, and doping levels of different layers in the resistor structure. By adjusting dielectric constant, layer thicknesses, and material ratios, the sheet resistance can be tuned across a wide range while maintaining high current density capability.
2Reliability
If high-k dielectric materials are used in transistors, then device performance is improved, but resistor compatibility and performance are degraded
Solution Approach 1:
The patent creates a universal resistor structure that is compatible with high-k/metal gate transistor fabrication processes. The same high-k dielectric layers used in transistors are also utilized in the resistor structures, allowing both device types to be fabricated using identical material stacks and process sequences, thereby achieving multi-functionality.
Solution Approach 2:
The patent merges the transistor and resistor fabrication processes by using the same high-k dielectric layers and metal gate formation steps for both device types. The resistor structures are formed by patterning and doping specific regions of the same material stack used for transistors, eliminating the need for separate fabrication processes.
3Reliability
If polysilicon resistors with high-k dielectrics are formed, then sheet resistance range and current density are improved, but fabrication process complexity increases
Solution Approach 1:
The patent performs preliminary actions by forming the high-k dielectric layers and metal gate structures first, before creating the resistor patterns. The resistor regions are defined by selective doping and silicidation of pre-formed material layers, avoiding the need for additional deposition steps and reducing overall process complexity.
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.