Application of pulsed UV laser for dicing of arrays and linear of photodiodes based on MCT solid solution

Abstract

The modern systems of vision in infrared spectrum (IR) require elaboration of large-area nondefective imaging area with small pitch (less 40 μm) IR FPA. One of the directions is fabrication hybrid FPA, consisting of several of arrays of photodiodes based on MCT films (HgxCd1-xTe on GaAs substrates) and readout circuits on silicon. Substitution of photodiodes array of large-area imaging area on few arrays of smaller image size, allows having the imaging area of the required size without fault pixels. The main requirement is the permanent period of photodetectors on component imaging areas. without loss of pixels on lines of gaps of the butting between arrays. Using concentrated laser radiation, for scribing the surfaces MCT film on GaAs substrate, under concrete conditions, allows to realize offered above direction. The determination of the border of zone of the influence of the laser radiation on electric characteristic of p-n junction of the MCT films and technological ways of the reduction of area of influence of the laser radiation are presented in work. We had studied the change of parameters of photodiodes on base MCT films depending on distances before laser dicing grooves and condition of the laser radiation. As source of the laser radiation we used pulsed UV laser (LGI-21) at 0,34 μm wavelength with pulse duration 7 ns, frequency of repetition 50 - 100 Hz and power in pulse 2 KW. We founded condition of the laser dicing on distances 18 - 20 μm from photodiodes, when initial current-voltage characteristics of photodiodes are saved. We designed method of the laser dicing of linear photodiodes on MCT films, and we used it to create of multichips hybrid IR FPA. The result is non damage dicing of linear photodiodes on MCT films (λc =12 μm) on distances 18 - 20 μm from p-n junctions.