Complementary Transistor Gate Dielectrics for Multi-Threshold Tuning
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Solution Overview
Problem
Existing technologies struggle to provide integrated circuits with a range of threshold voltages for transistors of complementary conductivities, necessitating improved materials and techniques to tune transistor threshold voltages for optimized device performance and reliability.
Innovation Solution
A multi-threshold scheme using dual dipole patterning in complementary transistor dielectrics, incorporating dipole dopants and work function metals to adjust the permittivity of gate dielectrics and shift threshold voltages, allowing for a broad span of threshold voltages with fine resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional transistor fabrication processes are used, then manufacturing simplicity is maintained, but the ability to provide transistors with multiple threshold voltages is insufficient
Solution Approach 1:
The patent applies local quality by selectively doping gate dielectric layers in specific transistor regions with dipole dopants (such as lanthanum, scandium, yttrium, or barium) to create different threshold voltages. Different portions of the gate dielectric receive different dopant concentrations or types, enabling n-type transistors and p-type transistors to have tailored threshold voltage characteristics without affecting other transistors. This localized modification allows multiple threshold voltage options within a single fabrication process.
Solution Approach 2:
The patent utilizes parameter changes by modifying the permittivity of gate dielectric layers through dipole dopant incorporation. By changing the chemical composition and electrical parameters of the gate dielectric (adding dipole moments), the threshold voltage of transistors is adjusted. The work function metals further modify the electrical parameters at the gate interface, enabling precise control over threshold voltage to achieve desired transistor characteristics for different circuit requirements.
2Reliability
If threshold voltage tuning techniques are implemented, then device performance is optimized, but processing complexity increases
Solution Approach 1:
The patent merges multiple functions into a unified processing approach. The dipole dopant incorporation simultaneously achieves threshold voltage tuning and gate dielectric formation in integrated steps. Work function metal deposition combines surface preparation, adhesion enhancement, and threshold voltage adjustment functions. This merging of operations reduces the overall processing complexity compared to separate, sequential steps for each function.
Solution Approach 2:
The gate dielectric layer serves multiple functions: it provides electrical insulation, enables threshold voltage tuning through dipole dopant incorporation, and forms the basis for work function metal integration. The dipole dopant addition serves both to modify permittivity for threshold voltage control and to enhance gate control over the channel. This multi-functionality reduces the need for separate dedicated structures or processes.
3Adaptability or versatility
If multiple threshold voltage transistors are provided, then design flexibility is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating dipole dopants into the gate dielectric layer during the dielectric formation process itself, before subsequent transistor fabrication steps. The work function metals are deposited and patterned in advance to establish threshold voltage characteristics early in the manufacturing process. This preliminary threshold voltage assignment simplifies later manufacturing steps and enables design flexibility without adding complexity to subsequent processing.
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 approach enables transistors with varied threshold voltages, enhancing device reliability by minimizing processing operations and reducing threshold voltage drift, while optimizing switching speed and leakage current characteristics.
Implementation Method 1
incorporating dipole dopants and work function metals to adjust the permittivity of gate dielectrics and shift threshold voltages
Implementation Method 2
incorporating dipole dopants and work function metals to adjust the permittivity of gate dielectrics and shift threshold voltages
Data Source
AI summary
An integrated circuit (IC) device includes n- and p-type transistors with and without threshold voltage shifts using a common dopant material in a gate dielectric. The IC device includes at least four threshold voltage for each of n- and p-type transistors. Besides volumeless doping of gate dielectrics, work function metals are used in both n- and p-type transistors. A single dipole dopant may be concurrently introduced into and through similar gate dielectrics in both n- and p-type transistors to achieve consistent threshold voltage shifts with minimal process variation.