Atomic Layer Deposition Passivation Techniques For HgCdTe Micro-mesa Arrays

The mercury cadmium telluride(HgCdTe)infrared detection technology is developing in the direction of miniaturization and complex structure based on the continuous promotion of the demand from the application domains of infrared detection.The passivation process of the high aspect ratio MESA chip is the key problem for the third generation and the fourth generation of HgCdTe infrared focal plane detectors.In recent years,atomic layer deposition(ALD)technology has been favored in the field of integrated circuits and semiconductor physics due to its unique self-limiting growth principle and is considered to be the most promising method to solve the passivation problem of HgCdTe MESA chips.This dissertation focuses on the low-temperature atomic layer deposition passivation technology for the HgCdTe MESA chip.The details are as follows:1.ZnS thin films have been successfully deposited using metal-organic compounds with ultra-low-temperature atomic layer deposition(ULT-ALD).The growth process of ZnS thin films was adjusted by changing the growth conditions,and the basic characteristics such as film thickness,morphology,and crystal structure were studied.2.Interface properties of ALD passivated metal-insulation-HgCdTe devices.It is found that the fixed charge of ALD passivation and traditional double layer passivation is-6.40×1011 cm-2 and 4.20×1012 cm-2,respectively.The fixed charge of the ALD passivation film is negative,which is more conducive to the passivation of p-type materials.At 77 K,the slow state densities of ALD passivation and traditional double-layer passivation are 2.61×1012,5.94×1011 respectively,and the hysteresis of ALD MIS CV is smaller.Further analysis by XPS shows that ALD ZnS can effectively reduce the surface states at the interface between HgCdTe and passivated layer.Further analysis by XPS shows that ALD ZnS can effectively reduce the surface states at the interface between HgCdTe and passivated film.3.The dark current and spectral characteristics of medium and long wave HgCdTe infrared detection chips are studied.The dark current characteristics and response spectra of HgCdTe chips with different passivation modes are compared and analyzed.Variable area analysis results show that the devices passivated by ALD ZnS can effectively suppress the surface leakage compared with the double-layer passivation process.Based on the surface analysis of the variable temperature test,ALD ZnS passivation shows a lower level of dark current in the high temperature field,which is suitable for the passivation of the next generation HgCdTe MESA chip.