Sony has announced two new SWIR image sensors for industrial imaging.
The sensors boast a pixel pitch of 5μm, smaller than traditional InGaAs pixel pitches that are currently restricted to around 10µm.
The sensor architecture also delivers high quantum efficiency even in the visible range, which enables imaging over wavelengths from 0.4μm to 1.7μm.
The new products employ Sony's SenSWIR technology, in which photodiodes are formed on an InGaAs layer and are connected via copper-to-copper bonding with the silicon readout circuit layer.
The two models are: IMX990, a 1/2-type sensor (8.2mm diagonal image size) with 1.34 megapixel resolution; and IMX991, a 1/4-type (4.1mm diagonal) with 0.34 megapixel resolution. Sample shipments are planned for June and July 2020.
Traditional SWIR image sensors, made using indium bumping to bond the InGaAs layer to the silicon layer, face manufacturing challenges to shrink the size of the pixels and increase pixel count. It is necessary to secure a certain bump pitch, which makes it difficult to achieve a smaller pixel size compared to current industrial CMOS sensors.
There are other issues with conventional SWIR sensors, including low sensitivity in the visible light spectrum. These factors have inhibited the penetration of SWIR imaging.
Sony's new sensors, based on the company's stacking technology using a copper-to-copper connection, means a 5μm pixel size can be achieved. This gives a high image quality and a more compact sensor size.
The technology is also used to make the top InP layer – which absorbs visible light – thinner, making it possible to transmit light to the InGaAs layer underneath. The means the sensor has high quantum efficiency even in the visible range.
The new products also support digital output, matching the performance of current CMOS image sensors for industrial equipment.
Going forward, Sony will propose these products for use in a wide range of industrial applications such as material selection, contaminant inspection, and semiconductor inspection, aiming to contribute to improved productivity.
Further reading:
Sense of purpose - Greg Blackman explores the work being done on InGaAs sensors, along with other types of novel sensor that could find their way into the machine vision market
