[Interview] The World’s Smallest High-Definition Pixels: How Samsung Electronics Developed the ISOCELL HP3 Image Sensor

▲ Sungsoo Choi (left) from the Semiconductor R&D Center and Myoungoh Ki from the Advanced Sensor Development Team in Samsung Electronics’ System LSI business that developed the ISOCELL HP3.

The nail-sized camera lenses that are built into mobile devices have advanced extraordinarily since their inception. After becoming the first company in the industry to unveil CMOS image sensors (CIS) with 108 and 200 megapixels in 2019 and 2021 respectively, Samsung Electronics has recently surprised the market yet again with its ISOCELL HP3 image sensor, an image sensor packed with 200 million 0.56-micrometer (㎛)-pixels, the smallest pixels in the industry. Samsung is leading the image sensor market by creating proprietary technology and innovative memory semiconductor designs that can capture stunning images with high amounts of pixels. Through the announcement of the mass production of its ultra-high pixel image sensor, the ISOCELL HP3, the company has commercialized the development of 200MP mobile image sensors with ultra-small pixels. To learn more about how Samsung developed this industry leading ultra-high pixel image sensor, Samsung Newsroom spoke with Myoungoh Ki and Sungsoo Choi, developers from the System LSI business and the Semiconductor R&D Center respectively who played a leading role in the development of the new ISOCELL HP3. Smaller and Better: The First Company in the Industry To Commercialize 0.56㎛ Pixels An image sensor is a system semiconductor that converts light that enters the device through the camera lens into digital signals. From digital cameras and smartphones to laptops and cars, image sensors are built into all electronic products that come with a camera. The ISOCELL HP3 that Samsung has recently unveiled is an image sensor that packs 200 million 0.56㎛ pixels, the smallest pixels in the industry, in a 1/1.4” optical format.¹ Since 2019, Samsung has annually succeeded in reducing its pixel size to match the smallest size in the industry. Smaller pixels are needed in order to keep devices slim. “With a smaller unit pixel size, the physical size of the sensor and module can be reduced, allowing the size and width of the lens to be reduced as well,” explained Ki. “This can eliminate elements that interfere with the design of the device, such as a camera that protrudes, and can also reduce power consumption.”

While smaller pixels enable devices to be slimmer, maintaining image quality with smaller pixels is key. Developed using cutting-edge technology, the ISOCELL HP3, with a 12 percent smaller pixel size than the previous ISOCELL HP1 model, can reduce the camera module surface area in a mobile device by up to 20%. Despite its smaller pixel size, the sensor was developed using technology that maximizes full well capacity (FWC) and minimizes sensitivity loss. Additionally, new features were added to the sensor, including auto-focusing capabilities for all pixels and functions that enable high-speed video operation, along with enhanced color expression. Increased Light Absorption and Photo Diode Capacity Using Unique Technological Capabilities Smaller pixel size is ideal for creating smaller, slimmer devices but may result in less light entering the device or interference between adjacent pixels. Despite these challenges, Samsung was able to utilize the industry’s smallest pixels to create an innovative new sensor. “It’s all thanks to Samsung’s proprietary technological capabilities,” said Ki. “Samsung’s innovative technology is able to provide high performance even in much smaller devices.” Samsung succeeded in creating physical walls between pixels that are thinner and deeper by using its proprietary technology called Full Depth deep trench isolation (DTI), guaranteeing high performance even with 0.56㎛. DTI, the key technology of the ISOCELL, creates an insulated component between pixels, acting as an isolated wall to prevent light loss and improve optical performance. Developer Choi compared this technology to building a thin barrier between different rooms in a building. “In layman’s terms, it is the same as trying to create a thinner wall between your room and the room next door without affecting the soundproofing level,” explained Choi.

The key to DTI is to create thinner and deeper silicone walls to increase the ISO and reduce crosstalk² since larger insulation components between pixels mean more light loss. By applying this technique to the 0.56㎛ pixels, Samsung increased light absorption and maximized photo diode (PD) capacity. Therefore, utilizing ultra-small pixels has become possible since more light per pixel can be stored and processed even with a smaller light receptor area. Auto-Focusing Feature for All 200 Megapixels Provides Increased Speed and Accuracy The Super Quad Phase Detection (QPD) technology, which was first used in the HP3, enables all 200 megapixels to focus by increasing the auto-focusing pixel intensity to 100%. The Super QPD offers a faster and more accurate auto-focusing feature by utilizing one lens over four pixels, enabling the measurement of all phase differences of the left, right, top and bottom sides of the photographed subject. Not only is auto-focusing accurate even when it is dark, but high definition is maintained even when zoomed in. To tackle the problem of poor image quality in low-light environments, Samsung utilized innovative pixel technology to ensure high quality images. “We utilized an upgraded version of Samsung’s proprietary Tetra²pixel technology which combines four or sixteen adjacent pixels to operate as one large pixel in low-light environments,” said Choi. The upgraded pixel technology enables high-resolution filming in 8K at 30 frames-per-second (fps) and in 4K at 120fps with no loss in the field of view. Moreover, it is possible to film 8K videos in ultra-high resolution with the same field of view as when taking photos.

Similar to low-light environments, it is also difficult to take photos when there is too much sunlight. In order to combat this problem, unique technology is needed to adjust the levels in photos to capture an image properly. “When there is too much or too little light, it is important to increase the dynamic range³ in order to take a natural photo that looks similar to what we see with our eyes,” said Ki. “By using the Smart-ISO Pro technology, which uses two conversion gains, and the Staggered High Dynamic Range (HDR)⁴ feature, which morphs three frames with different exposures (short exposure, medium exposure and long exposure) into one, it supports HDR photography that creates natural images even when shooting in imperfect lighting conditions, providing an optimal result.” Collaboration: The Key for Overcoming Technical Limitations and Enabling Fast Development During the development of the ISOCELL HP3, the developers faced various technical challenges. “As this was the first product that utilized the Super QPD technology, there was a lot of trial and error when utilizing a new structure that could not be found in existing Front Deep Trench Isolation (FDTI), and we also experienced issues that we had not anticipated in each development stage,” said Choi. Despite such a difficult development process, the new sensor was announced less than a year after the previous model was released. The two developers attributed this rapid product development and release to collaboration between different teams.

“Whenever we faced a technical issue, we responded by closely cooperating with different business divisions, our team and even overseas research centers,” said Ki. “We were able to create synergy by adding know-how to top tier products, such as memory chips from the Semiconductor R&D center, logic chips and more. This new product may be the biggest collaborative effort between different departments yet, including employees from the Semiconductor R&D Center, Pixel Development Team, foundry, researchers at the SSIR and all groups in the advanced development team, such as sensor design, pixel, solution, product technology, manufacturing and algorithm.” Pride in Leading Technical Prowess: Leading the Image Sensor Market While the image sensor market is expected to experience rapid growth due to increased demand for cameras and the diversification of related products, Samsung is setting trends for cameras in the next-generation mobile image sensor market by overcoming the limitations of pixel miniaturization. Samsung Newsroom asked the two developers how they felt about leading the technical development of the ISOCELL HP3, the first 200MP image sensor in the industry to use 0.56㎛ pixels. “I take great pride in the fact that we are creating trends in the image sensor market and I am confident that we will continue to lead in micropixel technology,” said Choi. “Since applications of image sensors are becoming more widespread in various industries, such as augmented reality (AR), virtual reality (VR) and the automobile industry, in addition to the smartphone industry, we will lead the development of future technologies and markets based on our unique technological capabilities,” said Ki, sharing his future ambitions.

Samsung has successfully created ultra-small devices that capture images in high definition through its innovative image sensor technology. Samsung will continue to lead the image sensor market through its unique innovations, such as the ISOCELL image sensor, that provide optimized and advanced experiences to its users.

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_{¹ The diameter of the area that is captured through the camera lens. ² A phenomenon where light interferes with the photodiodes of adjacent pixels. ³ The ratio between the brightest and darkest parts in a digital image. ⁴ technology that expands the scope of brightness by making the bright parts brighter and the dark parts darker, similar to how the actual human eye sees.}