MOM Capacitor Noise Immunity via Substrate PN-Junction Diode
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Solution Overview
Problem
Noise from a p-type semiconductor substrate adversely affects the performance of metal-oxide-metal (MOM) capacitors in semiconductor devices, leading to issues like flicker noise, fixed pattern noise, and temporal noise in CMOS image sensors.
Innovation Solution
Incorporating a PN-junction diode with a p-type ion implanted region and an n-well surrounding the p-type ion implanted region below the capacitor, formed using specific ion implantation processes, to act as a barrier against noise propagation from the semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a p-type semiconductor substrate is used for MOM capacitor fabrication, then the capacitor structure can be formed with standard processes, but noise propagates from the substrate through the p-well and contact holes to the capacitor, degrading device performance
Solution Approach 1:
An n-well is introduced as an intermediary structure between the p-type substrate and the MOM capacitor. This n-well acts as a noise barrier that blocks noise propagation from the substrate to the capacitor while allowing the capacitor to maintain its standard fabrication process compatibility. The n-well serves as a mediating layer that isolates the capacitor from harmful substrate noise.
Solution Approach 2:
The patent applies preliminary anti-action by pre-establishing noise blocking measures before noise can affect the capacitor. The n-well and associated contact holes are formed in advance during the fabrication process to create a noise barrier that prevents substrate noise from reaching the capacitor, rather than attempting to filter or mitigate noise after it has propagated.
2Device complexity
If the capacitor is directly connected to the p-type substrate through contact holes, then the manufacturing process is simplified, but noise propagation occurs along the contact holes to the capacitor and other connected components
Solution Approach 1:
The n-well serves as an intermediary structure between the p-type substrate and the capacitor's first metal layer. Contact holes are formed through the n-well to connect to the p-type substrate, but the n-well itself acts as a noise barrier that blocks noise propagation while maintaining the electrical connection path. This intermediary structure prevents direct noise coupling from substrate to capacitor.
Solution Approach 2:
The patent applies local quality by creating a specific n-well region with different electrical properties than the surrounding p-type substrate. This localized n-well structure provides noise blocking functionality in the specific area where contact holes are formed, while the rest of the substrate maintains its original characteristics for other device operations.
3Device complexity
If noise from the substrate is allowed to propagate to the MOM capacitor, then the device structure remains simple, but performance is degraded due to flicker noise, fixed pattern noise, and temporal noise
Solution Approach 1:
The n-well acts as a mediating noise barrier that protects the MOM capacitor from substrate noise while maintaining overall device structural simplicity. This intermediary structure blocks noise propagation paths without requiring complex shielding or filtering circuits, thus improving reliability while adding minimal structural complexity.
Solution Approach 2:
The patent converts the potentially harmful direct connection between the p-type substrate and capacitor into a beneficial noise-blocking configuration. By introducing the n-well, the structure that initially seemed to simplify manufacturing actually creates a natural noise barrier, turning what could be a harmful direct path into a protected interface.
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 PN-junction diode effectively prevents noise from entering the MOM capacitor, enhancing the noise immunity of semiconductor devices and improving the performance of CMOS image sensors by reducing substrate-induced noise.
Implementation Method 1
a PN-junction diode in the semiconductor substrate and below the capacitor, the PN-junction diode comprising a p-type ion implanted region and an n-well located below the p-type ion implanted region and completely surrounding the p-type ion implanted region
Implementation Method 2
formed using specific ion implantation processes
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, an interlayer dielectric layer on the semiconductor substrate, a capacitor on the interlayer dielectric layer, and a PN-junction diode in the semiconductor substrate and below the capacitor. The PN-junction diode includes a p-type ion implanted region and an n-well located below the p-type ion implanted region and completely surrounding the p-type ion implanted region. The PN-junction diode in the semiconductor substrate may prevent noise from entering the capacitor to improve the noise immunity of the semiconductor device.