Study On Wet Etching System And Behavior Of InAs Substrate And Its Application In Removing Substrate To Separate GaSb Film

As an advanced group Ⅲ-Ⅴ semiconductor bulk single crystal,InAs have become an important substrate material for manufacturing devices such as lasers,infrared detectors,and microwave devices.However,in the thinning and removal of InAs substrate,there are problems such as low etching rate and poor etching surface quality.Therefore,this paper proposed a new type of organic and inorganic mixed acid etchant,and analyzed the wet etching behavior charateristics,influencing factors,and applications in the separation of GaSb film by removing InAs substrate.Firstly,based on the etching rate,surface morphology and roughness,a dichotomy method was used to preliminarily determine the proportion of various components in the etchant.The orthogonal experiment was used to optimize the organic-inorganic mixed acid etchant for InAs substrate etching,which was HF:HNO₃:C₄H₆O₆:H₃PO₄:H₂O=10 m L:30 m L:5 g:5 m L:10 m L,and etching rate was 18μm/min,surface roughness was 1.36 nm.The results show that the surface of InAs substrate after etching in the above optimal etchant is still smooth,flat,and uniform.The atomic content ratio of In and As elements on the surface of InAs substrate after etching remain close to 1:1.InAs substrate mainly exist in the form of InAs compounds with some in the form of oxides In₂O₃,As₂O₃.Elemental As has no significant increase in surface oxide content.The thinning of InAs substrate can avoid the absorption of infrared light by InAs substrate.The inconsistent reaction rates of In and As elements results in an increase in the surface roughness of InAs by 0.505 nm.Secondly,the effects of the content of various components in the etchant and process parameters on the etching rate and surface quality of InAs substrate were studied.The results show HF and HNO₃ mainly affect the etching rate;H₃PO₄ and C₄H₆O₆ mainly affect InAs surface quality after etching;Deionized water as a diluent has a significant impact on the etching rate and surface quality of InAs substrate.HF:HNO₃:C₄H₆O₆:H₃PO₄:H₂O=10 m L:30 m L:5 g:5 m L:10 m L etchant is suitable for long-term use of InAs etching and obtaining high-quality surfaces.Etching rate of InAs substrate in the optimal etchant is a mixed mechanism of diffusion and reaction constraints.Thirdly,based on the different selectivity of InAs/GaSb in C₆H₈O₇/H₂O₂and C₄H₆O₆/H₂O₂ etchants with different volume ratios,it is concluded that C₆H₈O₇:H₂O₂=5:1 is the optimal etchant for InAs/GaSb selective etching.The ln V-T^-1 Arrhenius diagrams shows the etching rates of InAs and GaSb are limited by reaction and diffusion,respectively,resulting in high selectivity of InAs/GaSb in C₆H₈O₇:H₂O₂=5:1 etchant.SEM and AFM tests show that the surface of InAs and GaSb substrates is smooth after etching in this etchant,and Rq after etching is 2.8 nm and 1.29 nm.Finally,in order to research the effectiveness of removing InAs substrate with non selective etchant HF:HNO₃:C₄H₆O₆:H₃PO₄:H₂O=10 m L:30 m L:5g:5 m L:10 m L and selective etchant C₆H₈O₇:H₂O₂=5:1,GaSb film was grown on InAs substrate using magnetron sputtering technology.Results show that there are no obvious holes and pinholes on the surface of the epitaxial GaSb film and Rq=2.26 nm,GaSb film has good crystallinity.HF:HNO₃:C₄H₆O₆:H₃PO₄:H₂O=10 m L:30 m L:5 g:5 m L:10 m L etchant was used to thin the InAs substrate for epitaxial GaSb to about 20μm.Then,a selective etchant of C₆H₈O₇:H₂O₂=5:1 was used to remove the substrate to obtain high-quality GaSb film.Results show that Rq of the separated GaSb film is 1.25 nm,InAs substrate is completely removed.