Fraunhofer IMS develops UV-transparent coating for image sensors

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“We’ve developed a new process step,” said Werner Brockherde, head of department at Fraunhofer IMS, “that allows us to produce a protective coating with the same properties but which is permeable to blue and UV light.” The trick is to increase the proportion of nitrogen in the coating. “This reduces the absorption of shortwave light,” explains Brockherde.

The new coating material will absorb less light of an energy higher than blue light, which means the sensor becomes more sensitive at the blue and UV range. “This makes CMOS image sensors suitable for use in wavelength ranges down to 200 nanometers,” explained Brockherde. “With standard passivation the limit was about 450 nanometers.”

To change the structure of the silicon nitride for the coating, the Fraunhofer research scientists had to fine-tune the deposition parameters such as pressure and temperature.

The process development should revolutionize UV spectroscopic methods to improve their accuracy and enable CMOS image sensors to take up a new role in professional microscopy, e.g. in fluorescence microscopes, providing scientists with images of even greater detail.

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