Towards a deep submicron CMOS image sensor on a standard FDSOI process

Lab-on-chip is a very promising point-of-care technology, where the specimen is placed directly on a CMOS chip for imaging without the use of any labels or chemicals and with no intervening optical components. However, lab-on-chip technologies developed so far have been limited by the existing pixel size of CMOS image sensors. To be able to accurately resolve small biological samples, the sensor pixel size must be less than the size of the object under examination. For example, bacteria range from 500nm to 5μm and viruses from 30nm to 300nm and thus require image sensors with nanoscale dimensions. However, reducing the size of an image sensor is challenging. Light sensitivity greatly reduces at and below the optical diffraction limit due to increasingly poorer coupling. In addition, CMOS image sensors typically use a refractive microlens that will not scale due to diffraction limits below around 1.4 μm. Further, conventional colour filters are made of absorptive dyes or pigments that do not work at nanometer thicknesses.