FDSOI Voltage Reference Using Undoped MOSFETs
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Solution Overview
Problem
In advanced technologies like SOI and FinFET, p-n diodes become unpredictable, leading to increased manufacturing costs for voltage reference structures, which are essential for providing a constant voltage irrespective of loading, manufacturing tolerances, power supply variations, and temperature changes.
Innovation Solution
Implementing a voltage reference device using fully depleted n-type and p-type MOSFETs with undoped bodies, connected in series and sharing identical gate stacks, to create diodes that can be switched between on and off states based on applied electrical potential, thereby canceling out manufacturing variations and providing a stable reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If p-n diodes are used for voltage reference in advanced technologies, then ease of manufacture is improved, but predictability and reliability deteriorate
Solution Approach 1:
The patent changes the operating parameters and physical structure by transitioning from traditional p-n diode junctions to MOSFET-based structures with undoped bodies. This parameter change enables the voltage reference to maintain predictability in advanced technologies while preserving manufacturing simplicity through standard CMOS processes.
Solution Approach 2:
The patent uses identical gate stacks for both n-type and p-type MOSFETs, creating symmetric copies of the same structure. This copying approach ensures that manufacturing variations affect both devices equally, allowing the differential configuration to cancel out process variations and maintain reliability.
2Reliability
If additional processing steps are added to make p-n diodes predictable, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The MOSFET-based voltage reference structure is self-compensating through its symmetric differential configuration. The identical gate stacks automatically cancel process variations without requiring additional processing steps or calibration, achieving reliability improvement without increased manufacturing complexity or cost.
3Manufacturing precision
If MOSFETs with identical gate stacks are used, then sensitivity to manufacturing variations is reduced, but device complexity increases
Solution Approach 1:
The patent employs asymmetric device types (n-type and p-type MOSFETs) in a symmetric configuration. While the device types differ, their identical gate stacks and complementary arrangement create overall symmetry that cancels manufacturing variations, achieving manufacturing precision without significant complexity increase.
Data Source
AI summary
An integrated circuit having a reference device and method of forming the same. A reference device is disclosed having: a fully depleted n-type MOSFET implemented as a long channel device having a substantially undoped body; and a fully depleted p-type MOSFET implemented with as a long channel device having a substantially undoped body; wherein the n-type MOSFET and p-type MOSFET are connected in series and employ identical gate stacks, wherein each has a gate electrically coupled to a respective drain to form two diodes, and wherein both diodes are in one of an on state and an off state according to a value of an electrical potential applied across the n-type MOSFET and p-type MOSFET.