Stacked eFuse Over Lateral Bipolar Transistor for Smaller Footprint
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Solution Overview
Problem
Electrically programmable fuses (efuses) in triple well structures require a significantly larger surface area due to varying doping polarities and concentrations, leading to unpredictable resistance and reliability issues.
Innovation Solution
A structure incorporating a lateral bipolar transistor with an insulator layer isolating an efuse structure over a current path, allowing the transistor to heat and destroy a fuse link, reducing surface area requirements and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If efuse is implemented in triple well structure, then doping flexibility is improved, but surface area requirement increases significantly
Solution Approach 1:
The patent transitions from planar efuse structures to vertically stacked configurations where the efuse is positioned over the bipolar transistor in the vertical dimension. This allows the efuse to utilize the current path through the transistor without requiring additional lateral surface area, effectively moving the solution from a 2D layout constraint to a 3D spatial arrangement that reduces footprint while maintaining functionality.
Solution Approach 2:
The bipolar transistor serves dual functions: as an active switching device and as a heating element for efuse programming. The same transistor structure that provides logical functionality also generates the thermal energy needed to destroy the fuse link, eliminating the need for separate programming circuitry and reducing overall surface area requirements.
2Productivity
If efuse structure is placed over current path, then programming efficiency is improved, but risk of unintended circuit formation increases
Solution Approach 1:
The insulator layer acts as an intermediary barrier between the efuse structure and the bipolar transistor current path. It provides electrical isolation that prevents unintended circuit formation while still allowing thermal energy to pass through for fuse programming. The insulator mediates between the conflicting requirements of thermal coupling for efficient programming and electrical isolation for circuit integrity.
Solution Approach 2:
The patent segments the device into distinct functional layers: the bipolar transistor layer for switching and heating, the insulator layer for electrical isolation, and the efuse layer for programming. This segmentation allows each component to perform its function independently while maintaining proper boundaries, preventing unintended electrical connections while enabling efficient thermal interaction.
3Reliability
If insulator layer is added for isolation, then electrical isolation is improved, but device complexity increases
Solution Approach 1:
The insulator layer is formed using the same high-k gate dielectric material already present in the device stack, maintaining material homogeneity. This approach integrates the isolation function into the existing dielectric layers rather than introducing foreign materials, thereby reducing process complexity while achieving the required electrical isolation properties.
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 reduces surface area needs and improves efuse reliability by enabling controlled programming through thermal interaction with the bipolar transistor, preventing unintended circuit formation.
Implementation Method 1
The effectiveness and reliability of efuses and other device components depend partially on each component's ability to resist or prevent intended degradation from sources other than electrical current, e.g., gradual electromigration degradation
Implementation Method 2
an insulator layer over a portion of the semiconductor layer... wherein the insulator layer electrically isolates the efuse structure from the current path
Data Source
AI summary
Embodiments of the disclosure provide a circuit structure including an electrically programmable fuse (efuse) and lateral bipolar transistor. A structure of the disclosure includes a lateral bipolar transistor within a semiconductor layer and over a substrate. An insulator layer is over a portion of the semiconductor layer. An efuse structure is within a polycrystalline semiconductor layer and over the insulator layer. The efuse structure is over a current path through the lateral bipolar transistor.