HV Transistor Stack Dipole Tuning for Threshold Voltage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Stacked high voltage transistor architectures face challenges in controlling transistor threshold voltage due to the constraints on work function metal thickness, which limits the ability to set and differentiate threshold voltages in integrated circuits, especially when operating at higher voltages.
Innovation Solution
Introduce a Vt shifting dipole material, such as a rare earth metal oxide, into the gate insulator stack of high voltage transistors to alter the threshold voltage, allowing for independent control of threshold voltages without relying solely on work function metal thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thicker gate dielectric is used in high voltage transistor architectures, then the transistor can operate at higher voltages, but the work function metal thickness is constrained more severely, limiting Vt control
Solution Approach 1:
A dipole layer is introduced as an intermediary element between the gate electrode and the channel region. This dipole layer modifies the electric field distribution and effectively shifts the threshold voltage without requiring changes to the work function metal thickness, thereby enabling Vt control in thick-gate-dielectric HV transistors
Solution Approach 2:
The invention changes the physical parameter of the gate insulator stack by introducing a dipole layer with specific dipole moment characteristics. This parameter change allows for threshold voltage shifting while maintaining the thick gate dielectric structure needed for high voltage operation
2Temperature
If work function metal thickness is reduced to accommodate thicker gate dielectric, then high voltage operation is enabled, but the ability to set and differentiate threshold voltages is lost
Solution Approach 1:
The dipole layer serves as a mediator that decouples the relationship between gate dielectric thickness and threshold voltage control. By placing dipoles at specific locations within the gate insulator stack, different threshold voltages can be achieved for HV and LV transistors while both use the same thick gate dielectric structure
Solution Approach 2:
Different concentrations or types of dipole materials are placed in different regions or layers of the gate insulator stack to create local variations in dipole moment. This allows different threshold voltages to be programmed in different transistor stacks (HV vs LV) while maintaining the same overall gate dielectric thickness
3Manufacturing precision
If multiple work function metals and/or metal layer thicknesses are used to achieve multiple threshold voltages, then Vt differentiation is possible, but fabrication process complexity increases
Solution Approach 1:
Instead of changing the work function metal composition or thickness, the invention changes the dipole layer parameters (material composition, thickness, or positioning) to achieve different threshold voltages. This simplifies the fabrication process by using a single work function metal layer while still enabling multiple Vt values through dipole layer variations
Solution Approach 2:
The gate insulator stack is transformed into a composite structure that includes the base gate dielectric material plus a dipole layer material. This composite structure provides an additional degree of freedom for threshold voltage control without affecting the work function metal layer
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
Enables effective differentiation of threshold voltages in high voltage and low voltage transistors by adjusting the dipole properties in the gate insulator stack, maintaining Vt control even with reduced work function metal thickness, thereby overcoming scaling limits.
Implementation Method 1
Introduce a Vt shifting dipole material, such as a rare earth metal oxide, into the gate insulator stack of high voltage transistors to alter the threshold voltage
Data Source
AI summary
Integrated circuitry comprising high voltage (HV) and low voltage (LV) ribbon or wire (RoW) transistor stack structures. In some examples, a gate electrode of the HV and LV transistor stack structures may include the same work function metal. A metal oxide may be deposited around one or more channels of the HV transistor stack, thereby altering the dipole properties of the gate insulator stack from those of the LV transistor stack structure.