CMOS Sensor Types (FSI, BSI, Stacked BSI) Tutorial

Executive *******

*****'* ************ ******* ********* *** **** image *******, ******* *** ***** ***** power ***********, ****** *******, **-**** **********, and **** ********** **** *********** *** sensors. ****** **** *******, ************ ****-**** Illuminated (***) *** ******* *** *****, have ************* ******** ***** *********** *** noise *********, ********** ******* ***********. ******* BSI ******* ******* ********** ************ *** light *********** *** **** ** * higher ************* ****.

************ ******* ***** ***** ******** **** sensors (***, ******* ***), ********** *** high-end *** *********** ************ ********* ******** image ******* *** ***-***** ***********. ***** Stacked *** ******* ********* *** ******* edge ** ****** **********, ***** ****** manufacturing ********** *** **** ***** ***** use ** ******* ****** ********.

CMOS ***** ******

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CMOS ***** ****** ************

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CMOS ********** **** ***

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• Lower ***** ***********: CMOS sensors typically consume less power than CCD sensors, making them more suitable for battery-operated devices like smartphones and digital cameras.
• Faster *******: CMOS sensors can read out the pixel data more quickly than CCD sensors, allowing for faster frame rates in video and reducing the likelihood of motion blur in still images.
• On-chip **********: CMOS sensors can integrate more processing circuitry on the same chip, enabling features like noise reduction, color interpolation, and image stabilization to be performed directly on the sensor, resulting in faster processing times and improved image quality.
• ****-*************: *** *********** ******* *** **** sensors ** ******* ** **** **** for ***** ************* *******, ***** *** made ** ****** ** *********** **** sensors ** * ***** **** **** CCD *******.

*******, **** ******* ************* *** **** drawbacks ******** ** *** *******, ********* lower ***** *********** *** ****** ***** levels. ******** ** **** ********** **** significantly ******** ***** *******, ******* ** CMOS ******* ******** *** ******** ********** in *** ******* ********, ********** *** surveillance *******.

Different ***** ** **** ***** *******

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Front-side *********** (***) **** *******: In FSI sensors, the light first goes through the metal circuitry layer and then reaches the photodiodes. This design can lead to some light loss due to the metal wiring and other components obstructing the light path. FSI CMOS sensors were once the most common type of CMOS sensor but have largely been replaced by BSI sensors in recent years.

Back-side *********** (***) **** *******: BSI sensors address the light loss issue in FSI sensors by flipping the sensor's structure. The light hits the photodiodes first, where no metal wiring or other components block the light path, leading to improved light sensitivity and better low-light performance.

Time-of-flight (***) **** *******: ToF sensors are specialized CMOS sensors designed to measure distance by calculating the time it takes for light to travel from the sensor to an object and back. They emit light pulses and measure the time it takes for the pulses to reflect off an object and return to the sensor. ToF sensors are used in applications such as 3D imaging and robotics.

Infrared (**) **** *******: IR sensors are designed to detect infrared radiation, which is not visible to the human eye. These sensors are used in various applications, such as night vision, thermal imaging, remote sensing, and biometrics. These sensors are used for surveillance cameras to provide better low-light performance. Many surveillance cameras use active RGB and IR filters with their CMOS imager to capture images in full and low-light scenes.

Global ******* **** *******: In most CMOS sensors, the image is captured row by row, which can cause distortion when capturing fast-moving objects or scenes. This phenomenon is known as the rolling shutter effect. Global shutter CMOS sensors address this issue by capturing the entire image simultaneously, eliminating the rolling shutter effect, and making them suitable for high-speed photography, sports, and industrial imaging applications. However, these types of sensors are more expensive, limiting their use for surveillance.

Differences ******* *** *** *** **** *******

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• Structure *** *****-********* **********: As the incident light is first absorbed by the photodiode layer in the BSI CMOS sensors, they offer improved light sensitivity compared to FSI CMOS sensors.
• Quantum **********: BSI sensors generally have higher quantum efficiency than FSI sensors. Quantum efficiency refers to the ability of a sensor to convert incoming photons into electrical charges. The improved light-gathering capability of BSI sensors contributes to their higher quantum efficiency.
• Noise ***********: BSI sensors typically exhibit better noise than FSI sensors, as the improved light sensitivity allows for lower noise levels, especially in low-light conditions. This results in cleaner images with less noise.
• Cost *** **********: BSI sensors are generally more expensive and complex to manufacture than FSI sensors, as the process of flipping the sensor's structure and thinning the silicon substrate requires additional steps. However, the benefits of BSI technology, such as improved light sensitivity and low-light performance, often outweigh the additional costs.

Stacked *** **** ***** *******

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** ********** *** ********** ***** **** the ********** *****, ******* *** **** sensors *** ******* ******* **********:

• Faster ******* ******: Separating the photodiode layer and the processing layer allows for higher readout speeds, reducing the time it takes to process the image data and enabling faster frame rates for video recording and continuous still shooting.
• Improved ***** *******: The separation of the layers can also lead to better image quality, as the processing circuitry is less likely to interfere with the light-sensitive photodiodes, resulting in reduced noise levels and better overall performance.
• Additional ***************: The stacked design allows for more complex processing circuitry to be integrated directly into the sensor, enabling advanced features such as high dynamic range (HDR) imaging, slow-motion video recording, and advanced autofocus capabilities.

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Price **********

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Front-side *********** (***) **** *******: These sensors are generally less expensive than their BSI counterparts due to their simpler manufacturing process. However, FSI sensors have lower light sensitivity and performance than BSI sensors, making them less desirable for many modern applications.

Back-side *********** (***) **** *******: BSI sensors offer better light sensitivity and performance than FSI sensors but are generally more expensive due to the additional manufacturing steps required to flip the sensor's structure and thin the silicon substrate. Despite the increased cost, BSI sensors have become increasingly popular in smartphones, digital cameras, and other imaging devices due to their improved performance.

Stacked *** **** *******: Stacked BSI sensors are more expensive than non-stacked BSI or FSI sensors due to the increased complexity of stacking multiple layers of semiconductor material and integrating additional processing circuitry within the sensor. The increased cost is often justified by the improved performance, faster readout speeds, and advanced features that stacked BSI sensors offer.

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Determining **** **** ** *** ******

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Outlook *** ************ *******

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