Many companies that buy silicon wafers do so to create CMOS sensors, a type of image sensor technology fundamental to digital cameras, smartphones, and many imaging devices. These sensors are able to convert real images and colors into digital information by containing millions of pixel sensors, each including a photodetector. And at the base of all of them, there is a single silicon wafer.
A CMOS sensor's starting substrate is a monocrystalline silicon wafer, often produced using the Czochralski (CZ) method. The diameter can vary depending on the fab’s capabilities, but it typically ranges from 100 mm to 300 mm.
The active pixel array will be the core of the image sensor, as this grid of pixels captures light. To manufacture it, a thin silicon dioxide (SiO₂) layer is first grown to insulate areas. Other dielectric and metal layers are then deposited on top to form transistors and metal interconnects.
Later, photolithography and doping define the pixel and transistor patterns. The silicon is doped through ion implantation to create n-type and p-type regions for transistors and photodiodes. Each pixel will include a photodiode that converts light into an electrical signal, which is formed in specially doped regions within the Si wafer.
CMOS sensors are unique because each pixel has its transistor(s) for readout. For that reason, this circuitry needs to be integrated directly on the same Si wafer.
After the electrical circuitry is complete, the color filter array is added. This part enables the sensor to capture color images by filtering light wavelengths. Typically, it is made with a Bayer pattern (red, green, and blue filters) applied over each pixel.
Then, microlenses are placed over each pixel to focus more light into the photodiodes. This boosts sensitivity and overall image quality.
Last but not least, the completed wafer is diced into individual CMOS sensor dies. Dies are packaged, wire-bonded, and integrated with lenses and electronics. Final testing ensures proper function, including noise levels, pixel response, and defect rates.
In imaging technology, complementary metal-oxide semiconductor (CMOS) sensors are essential. These sensors receive light entering the camera through the lens, and depending on how much of it strikes, each photodetector will build up an electrical charge. The digital camera converts the charge into a digital reading that establishes the color and light intensity measured at each photodetector.
If you’re considering manufacturing these types of sensors for imaging and cameras, contact Wafer World today for more information!
