Search of technological solutions aimed at reducing the number of image defects in a hybrid SWIR device

Objectives. The primary aim of this study is to minimize image defects in a hybrid photodetector with a sensitivity range of 0.95–1.65 μm, based on an InP/InGaAs photocathode. In order to achieve this, the surface quality of the photocathode must be improved prior to lift-off photolithography. In addition, the photolithographic process must be made highly reproducible.

Methods. In order to achieve this goal, a series of experiments on surface cleaning and improvement of the lift-off photolithography process were conducted. The following surface preparation methods were tested: chemical etching of the InGaAs surface; coating the photocathode surface with a protective photoresist layer before cutting the plate; using various photoresist removal methods (in dimethylformamide and plasma); and mechanical surface cleaning. In order to improve photolithography, experiments were conducted on drying times and photoresist methods, exposure and development modes were varied, and photoresist was replaced.

Results. Samples manufactured using the improved technology demonstrate a more than ninefold reduction in the average percentage of defects on the photocathode surface from 0.317% to 0.035%. Thanks to the improved quality of the photocathode surface, the image in the finished device is more uniform and the number of image defects significantly decreased. The process is highly reproducible.

Conclusions. Improvements in surface preparation technology, coupled with a reduction in the thickness of the photoresist used in lift-off photolithography lead to greater uniformity of images in hybrid devices and fewer defects. The proposed approach can be used for the mass production of high-sensitivity near-infrared hybrid photodetectors, making them competitive with those produced elsewhere.

1. Kriksunov L.Z. Spravochnik po osnovam infrakrasnoi tekhniki (Handbook of the Fundamentals of Infrared Technology). Moscow: Sovetskoe Radio; 1978, 400 p. (In Russ.).

2. Hansen M.P., Douglas S.M. Overview of SWIR detectors, cameras, and applications. In: Proceedings of SPIE 6939 Defense and Security Symposium (Thermosense XXX). 2008. P. 69390I-1–69390I-11. https://doi.org/10.1117/12.777776

3. Ainbund M.R., Egorenkov A.A., Pashuk A.V. Features of images of water, ice, snow, objects and a human formed by a hybrid television camera in the near-infrared range. Nauchno-tekhnicheskii vestnik informatsionnykh tekhnologii, mekhaniki i optiki = Scientific and technical journal of information technologies, mechanics and optics. 2021;21(5):619–625 (in Russ.). https://doi.org/10.17586/2226-1494-2021-21-5-619-625

4. Song H., Yeo S., Jin Y., Park I., Ju H., Nalcakan Y., Kim S. Short-Wave Infrared (SWIR) Imaging for Robust Material Classification: Overcoming Limitations of Visible Spectrum Data. Appl. Sci. 2024;14(23):11049. https://doi.org/10.3390/app142311049

5. Pavlovic M.S., Milanovic P.D., Stankovic M.S., Peric D.B., Popadic I.V., Peric M.V. Deep Learning Based SWIR Object Detection in Long-Range Surveillance Systems: An Automated Cross-Spectral Approach. Sensors. 2022;22(7):2562. https://doi.org/10.3390/s22072562

6. Wilson R.H., Nadeau K.P., Jaworski F.B., Tromberg B.J., Durkina A.J. Review of short-wave infrared spectroscopy and imaging methods for biological tissue characterization. J. Biomed. Opt. 2015;20(3):030901. http://doi.org/10.1117/1.JBO.20.3.030901

7. Egorenkov A.A., Zubkov V.I., Solomonov A.V., Mironov D.E, Pashuk A.V., Ainbund M.R. Hybrid matrix photodetector for infrared spectral range. Izvestiya SPbGETU “LETI” = Proceedings of Saint Petersburg Electrotechnical University. 2021;4:15–22 (in Russ.). https://www.elibrary.ru/wvtgwi

8. Enloe W., Sheldon R., Reed L., Amith A. Electron-bombarded CCD image intensifier with a GaAs photocathode. In: Proceedings of Symposium on Electronic Imaging: Science and Technology. 1992. P. 41–49. https://doi.org/10.1117/12.60337

9. Zhang Y., Chen J., Yang J., Fu M., Cao Y., Dong M., Yu J., Dong S., Yang X., Shao L., Hu Z., Cai H., Liu C., Huang F. Sensitive SWIR Organic Photodetectors with Spectral Response Reaching 1.5 μm. Adv. Mater. 2024;36(41):2406950. https://doi.org/10.1002/adma.202406950

10. Costello K.A., Davis G.A., Weiss R.E., Aebi V.W. Transferred electron photocathode with greater than 5% quantum efficiency beyond 1 micron, In: Proceedings SPIE 1449 (Electron Image Tubes and Image Intensifiers II). 1991. P. 40–50. https://doi.org/10.1117/12.44264

11. Musatov A.L., Izraelyants K.R., Korotkikh V.L., Filippov S.L., Russu E.V., Dyakonu I.I. Emission characteristics of semiconductor heterostructures with a Schottky barrier InGaAs-InP-Ag. Phizika i technika polyprovodnikov = Physics and Techniks of Semiconductors. 1990;24(9):1523–1530 (in Russ.).

12. Aebi V., Costello K., Davis G., LaRue R., Weiss R. Near IR Photocathode Development. In: Proceedings of 1997 Meeting of the IRIS Specialty Group on Active System. 1997. Tucson. US.

13. Wang X., Shi M., Su L., Yang L., Deng X., Zhang Y., Tan H. NEA GaAs photocathode for electron source: From growth, cleaning, activation to performance. Mater. Today Phys. 2025;52:101680. https://doi.org/10.1016/j.mtphys.2025.101680

14. Sun Y., Liu Z., Pianetta P. Surface dipole formation and lowering of the work function by Cs adsorption on InP(100) surface. Vac. Sci. Technol. A. 2007;25(5):1351–1356. https://doi.org/10.1116/1.2753845

15. Dolgikh A.V., Leonov I.A. High resolution scanning ellipsometry as test method of NEA-photocathode surface cleanliness in image intensifier tubes manufacture. Prikladnaya Fizika = Applied Physics. 2007;4:121–123 (in Russ.). https://www.elibrary.ru/iadlst

16. Tereshchenko O.E., Shaibler G.É., Yaroshevich A.S., et al. Low-temperature method of cleaning p-GaN(0001) surfaces for photoemitters with effective negative electron affinity. Phys. Solid State. 2004;46(10):1949–1953. https://doi.org/10.1134/1.1809437 [Original Russian Text: Tereshchenko O.E., Shaibler G.É., Yaroshevich A.S., Shevelev S.V., Terekhov A.S., Lundin V.V., Zavarin E.E., Besyulkin A.I. Low-temperature method of cleaning p-GaN(0001) surfaces for photoemitters with effective negative electron affinity. Fizika Tverdogo Tela. 2004;46(10):1881–1885 (in Russ.). https://www.elibrary.ru/rczyer ]

17. Machucaa F., Liu Z., Sun Y., Pianetta P., Spicer W.E., Pease R.F.W. Simple method for cleaning gallium nitride (0001). Am. Vac. Soc. A. 2002;20(5):1784–1786. https://doi.org/10.1116/1.1503782

18. Pastuszka S., Terekhov A.S., Wolf A. ‘Stable to unstable’ transition in the (Cs, O) activation layer on GaAs (100) surfaces with negative electron affinity in extremely high vacuum. Appl. Surf. Sci. 1996;99(4):361–365. https://doi.org/10.1016/0169-4332(96)00106-7

19. Jin M., Zhang Y., Chen X., Hao G., Chang B., Shi F. Effect of surface cleaning on spectral response for InGaAs photocathodes. Appl. Opt. 2015:54(36):10630–10635. https://doi.org/10.1364/AO.54.010630

20. Choi I-C., Kim H-T., Yerriboina N.P., Lee J.H., Teugels L., Kim T-G., Park J-G. Post-CMP Cleaning of InGaAs Surface for the Removal of Nanoparticle Contaminants for Sub-10nm Device Applications. ECS J. Solid State Sci. Technol. 2019;8(5): 3028–3034. https://doi.org/10.1149/2.0051905jss

21. Na J., Lim S. Elemental behaviors of InGaAs surface after treatment in aqueous solutions. Microelectron. Eng. 2019;212: 27–36. https://doi.org/10.1016/j.mee.2019.04.002

22. Brussaard G.J.H., Letourneur K.G.Y., Schaepkens M., van de Sanden M.C.M., Schram D.C. Stripping of photoresist using a remote thermal Ar/O2 and Ar/N2/O2 plasma. J. Vac. Sci. Technol. B. 2003;21(1):61–66. https://doi.org/10.1116/1.1532021

23. Kim J.H., Choi N., Kim Y.-H., Kim T.-S. Thickness dependence of the lithographic performance in 193nm photoresists. In: Proceedings of SPIE 6153, Advances in Resist Technology and Processing XXIII. 2006. V. 615337. https://doi.org/10.1117/12.655777