Samsung has returned this week the media luster to its ISOCELL sensors and has done so through a story, which actually ended up turned into two, about the reordering of its catalog. During the MWC of Shanghai, the version of the fair for the Asian market that is held at the end of June, Samsung announced changes in order to improve the understanding of its sensor catalog.
The Koreans took advantage of the fair held in China to rebuild their sensor line in four distinct categories: ISOCELL Bright, ISOCELL Fast, ISOCELL Slim and ISOCELL Dual, and the announcement of the latter was accompanied by the company’s first dual-lens sensor. And with this first advance of the Galaxy Note 8 we have asked ourselves, how do the photographic sensors of Samsung work and what do they contribute with different options?
Born in 2014
Although in fact its development took place months before and already with the launch of the Galaxy Note 3 tracks were left leading to its new range of sensors. Based on the BSI standard, Samsung decided to take a step forward and develop its own line of sensors for cameras, presenting ISOCELL and assembling the first exponent on board the Samsung Galaxy S5, which reached the market in the first half of 2014.
Samsung did not give many clues during his presentation but he made it abundantly clear that they would ride in the high ranges of his catalog, although with the passage of time they were running towards lower ranges. And now, with the new cataloging of its sensor line, we will see ISOCELL even in Samsung’s lower ranges. The ISOCELL Slim are destined to it.
ISOCELL is in the market since 2014, both for own consumption and to supply different manufacturers
As we mentioned, ISOCELL is nothing more than the evolution, understood by Samsung, of the BSI sensors. An evolution that achieves, among other improvements, up to 30% less disturbance in the image with backlit sensors. For practical purposes, and very briefly, ISOCELL aims to increase the sensitivity to light of CMOS sensors, something whose results we have seen at a good level from the Galaxy S6 and S6 Edge.
The truth is that, although complex, the operation of ISOCELL sensors is relatively easy to explain and all this is achieved by understanding the meaning of its name. Its technical name is 3D-Backside Illuminated Pixel with Front-Side Deep-Trench Isolation and Vertical Transfer Gate. Very complex, let’s stay with Isolated Cells or Isolated Cells. And with the play of words that also leads to ISO, the acronym that defines sensitivity to light.
How ISOCELL works
ISOCELL is based on a fairly clear concept: isolate each pixel from the others by means of a physical barrier in the sensor itself, so that the light captured by the lens and driven towards it does not produce the dreaded “bleeding” effect. This effect only distorts the color and illumination of the pixels based on the light received by the adjacent ones.
In ISOCELL, each pixel receives the light that it must receive and Samsung has achieved that the capacity of absorption of light grows up to 30%, although for this it had to solve the problem of the reduction of the surface of the photodiodes. If you create barriers to surround each pixel, or you increase the sensor or reduce the corresponding photodiode, that’s why Samsung had to redesign them. Another differentiating point in ISOCELL.
The key to ISOCELL is that in order to isolate the pixels, Samsung had to change the horizontal structure and move to a vertical
Samsung designed the new photodiodes to have a vertical structure, known as the Samsung VTG or Vertical Transfer Gate. This allowed the photographic sensor to be built using layers of light absorption, as opposed to the horizontal photodiodes of the rest of the BSI sensors. The result, isolated sensors and with a larger surface.
With this redesign, the crosstalk of the photodiodes was reduced from 19% of normal BSIs to 12.5% in their ISOCELL sensors. A noise reduction of 150 lux at only 105 lux was also achieved and allowed the photodiodes to capture light at a wider viewing angle. The latter is important since it enabled the use of lenses with more luminosity (letter f smaller) in mobile phones.
More light, thinner… and now Plus
In short, the vertical structure of the Samsung photodiodes has allowed them to capture more light in any situation, which has improved the performance of their camera modules in poorly lit environments, and has also improved the capture of information in each pixel. the image, which are now more faithful and allow a more precise processing. All with sensors that can be wider and have less height, allowing them to be thinner.
Since that launch in 2014, Samsung employs proprietary sensors in many of its terminals and also markets them for use in other brands and is, in its own right, the largest competitor of Sony’s IMX sensors in the mobile market, despite the fact that he also resorts to these in certain models of his catalog.
Over time, the ISOCELL sensors continued to evolve and in June 2018 the surname Plus came to the family. The Korean manufacturer announced that the line of camera equipment was taking a step forward, and did so by teaming up with Fujifilm. New insulation arrived to minimize light losses and ISOCELL Plus was born.
According to Samsung, the new ISOCELL Plus should be able to capture 15% more light in the same conditions as its predecessors, which would allow them to be built with 0.8 micrometer pixels while maintaining performance. Smaller pixels for smaller sensors, but that could also link the pixels together virtually thanks to the pixel binning that is starting to become fashionable.
A new material, an alliance with Fujifilm and new generations of Plus sensors
In a joint development with Fujifilm, Samsung introduces a new material for the isolation grids of its pixels, thus replacing the previously used metal. Less loss of light for more efficient photodiodes, and a greater fidelity in the capture of the image. New generations for the Koreans sensors that will give rise to new sensors for their phones and those of the competition.
We will see what course the ISOCELL take now, once Samsung has decided to strengthen the brand and place clear categories to identify each of them. As we know, Samsung is the leader in the semiconductor industry and mobile cameras are partly to blame for this. It will be interesting to see the evolution of ISOCELL in the coming months, and especially if there is a response from Sony to this new strategy of its competitor.