High-Voltage Level Shifter Using MOL Capacitor and Thin-Oxide Transistors
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Solution Overview
Problem
Conventional level shifters using thick-oxide transistors and capacitors are bulky and costly, and they damage thin-oxide transistors when exposed to high voltages, making them unsuitable for newer thin-oxide finFET technologies.
Innovation Solution
A level shifter design incorporating a middle-of-the-line (MOL) capacitor and thin-film transistors, where the input voltage is split between the MOL capacitor and the circuit, effectively thickening the oxide structure to tolerate high voltages without damaging thin-film transistors, and using advanced processing technologies to form high-density MOL capacitors compatible with finFET structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick-oxide transistors are used in level shifters to tolerate high voltages, then voltage tolerance is improved, but device area increases and manufacturing complexity increases
Solution Approach 1:
The level shifter circuit is segmented into multiple thin-oxide transistors arranged in series, where each transistor handles a portion of the total voltage. This segmentation allows the use of smaller thin-oxide devices instead of a single large thick-oxide device, achieving voltage tolerance through distributed voltage handling rather than requiring large oxide thickness
Solution Approach 2:
Intermediate voltage nodes are introduced between series-connected thin-oxide transistors, serving as mediators that distribute and manage the high voltage input. These intermediate nodes allow each transistor to operate within its safe voltage range while collectively handling the full input voltage, avoiding the need for thick-oxide structures
2Reliability
If thick-oxide transistors are used in level shifters to tolerate high voltages, then voltage tolerance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The level shifter uses homogeneous thin-oxide transistors throughout the circuit, matching the technology node of the core logic. This homogeneity eliminates the need for separate thick-oxide process modules, allowing standard thin-oxide fabrication processes to be used for both the level shifter and core circuits, thereby reducing manufacturing complexity and cost
Solution Approach 2:
The thin-oxide transistor design serves multiple functions: it acts as both the core logic element and the level shifter element. By making the level shifter compatible with standard thin-oxide processes, the same transistor technology and fabrication steps are used across the entire chip, eliminating the need for specialized thick-oxide processing equipment and procedures
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
The solution allows for safe voltage distribution to thin-film transistors, increasing the tolerated input voltage while avoiding the use of thick-oxide components, reducing area penalties and manufacturing costs, and ensuring compatibility with standard cell libraries and finFET technologies.
Implementation Method 1
a level shifter includes a middle-of-the-line (MOL) capacitor; and a circuit including at least one thin-film transistor coupled to the MOL capacitor, wherein an input voltage provided to the MOL capacitor is split between the MOL capacitor and the circuit
Data Source
AI summary
A level shifter according to some embodiments is disclosed. In some embodiments, a level shifter includes a middle-of-the-line (MOL) capacitor; and a circuit including at least one thin-film transistor coupled to the MOL capacitor, wherein an input voltage provided to the MOL capacitor is split between the MOL capacitor and the circuit. The MOL capacitor can be formed with a contact strip adjacent to a gate structure. A method of forming a level shifter using thin-oxide technologies includes forming a middle-of-the-line (MOL) capacitor; forming a circuit with one or more thin-film transistors; and coupling the MOL capacitor to the circuit such that an input voltage provided at the MOL capacitor is split between the MOL capacitor and the circuit.