HCI-Programmed OTP ROM and PUF Circuits for Secure Low-Current Bits
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Solution Overview
Problem
Existing electronic circuits face issues such as visible void formation in one-time programmable (OTP) ROM leading to security vulnerabilities, high current requirements, and environmental sensitivity in PUF circuits, resulting in poor energy efficiency and increased error rates.
Innovation Solution
Utilizing hot carrier injection (HCI) to program memory bits in OTP ROM and PUF circuits, which involves reversing transistor polarity to induce electron kinetic energy for programming, allowing for smaller cell size, improved security, and reduced current requirements, and incorporating access transistors to isolate failed bitcells in parallel architectures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If void formation is used in OTP ROM to store data, then data storage is achieved, but resistance change becomes significant and voids become visible from top-down imaging, compromising security
Solution Approach 1:
The patent replaces the mechanical/physical void formation mechanism with an electrical field-based hot carrier injection mechanism. Instead of creating physical voids through high current stress, the invention uses controlled electrical fields to inject hot carriers into the oxide layer, achieving data storage through electrical charge trapping rather than physical material removal. This substitution eliminates the security vulnerability of visible voids while maintaining reliable data storage.
Solution Approach 2:
The patent changes the fundamental parameter of the programming mechanism from high current (10-30 mA) that creates voids to controlled voltage pulses that generate hot carriers. By changing the programming parameter from current-based to voltage-based, the invention achieves data storage without creating visible physical defects, thus resolving the security issue while preserving storage reliability.
2Reliability
If high programming currents (10 mA to 30 mA) are used to form voids in OTP ROM, then data storage is achieved, but current requirements and energy consumption increase significantly
Solution Approach 1:
The patent fundamentally changes the programming parameter from high current (10-30 mA) to controlled voltage pulses. The hot carrier injection mechanism uses voltage-driven carrier generation and injection, reducing current requirements by orders of magnitude while achieving the same data storage effect. This parameter change directly addresses the energy consumption issue.
Solution Approach 2:
The patent replaces the high-current-driven void formation mechanism with a voltage-driven hot carrier injection mechanism. This substitution eliminates the need for large programming currents, thereby dramatically reducing energy consumption while maintaining reliable data storage capability.
3Adaptability or versatility
If PUF circuit memory elements are used for cryptography, then security functions are enabled, but high sensitivity to environmental conditions increases error rate
Solution Approach 1:
The patent replaces the traditional CMOS logic-based PUF memory elements with hot carrier injection-based memory elements. This substitution changes the underlying physical mechanism from CMOS switching to hot carrier trapping, which provides better environmental stability and reduced sensitivity to temperature and voltage variations, thereby lowering the error rate while maintaining cryptographic functionality.
4Area of moving object
If electronic circuit size is reduced to meet scaling requirements, then device density increases, but current and voltage requirements become more stringent
Solution Approach 1:
The patent changes the programming mechanism parameter from current-based to voltage-based, enabling smaller device dimensions without proportionally increasing current requirements. The hot carrier injection mechanism is inherently more scalable to smaller dimensions because it relies on voltage-driven carrier generation rather than high current flow, thus resolving the scaling contradiction.
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
HCI provides secure, efficient memory storage with reduced cell size and energy consumption, while enhancing data security by making bit storage resistant to physical inspection and environmental conditions, and enabling bit-by-bit repair in parallel architectures.
Implementation Method 1
Utilizing hot carrier injection (HCI) to program memory bits in OTP ROM and PUF circuits, which involves reversing transistor polarity to induce electron kinetic energy for programming
Data Source
AI summary
Hot carrier injection (HCI) may be used to provide various improvements for one-time programmable (OTP) read-only memory (ROM) or physical unclonable function (PUF) circuits. HCI may be used to write a memory bit (e.g., logical 0 or 1), which may be used in OTP ROM. HCI may be used to provide improved programmable ROM (PROM) memory devices, such as to facilitate programming or to increase sensing window. HCI may also be used to write a memory bit in a PUF circuit. HCI may provide a cross-foundry portable PUF circuit that has an associated adjustable bit error rate (BER), which may be used to secure root key generation, or may be used to provide a unique identification (ID) for fuse replacement.