Research On Wet Chemical Etching System And Etching Behavior Of GaSb Semicondutor Substrate

GaSb is a composed of ?-? elements narrow band gap semiconductor materials,since its lattice constant matches with the ternary and four-element solid melt alloy materials whose spectral range is between 1.7 and 4.4 ?m,it has attracted much attention as a good substrate material.After a brief introduction of GaSb semiconductor properties and the development of GaSb-based devices,this paper analyzes and compares the advantages and disadvantages of the main etching technologies of GaSb materials(dry and wet)and their existing problems.On this basis,this paper takes wet etching as the research direction,researching a wet etching system of GaSb which includes etching solution formulation and process parameters,and the etching behavior in this etching system,as well as the influence factors of etching quality and etching rate in this system.Firstly,according to the macro morphology,micro morphology,surface roughness of the etched GaSb substrate and the etching rate,screening out the main components of etching solution,and then optimizing the formula of etching solution through the orthogonal experiment,so we get an inorganic-organic mixed acid etching solution,which contains 10 ml hydrochloric acid,10 ml hydrogen peroxide,5 ml phosphoric acid,8.0 g citric acid monohydrate and 50 ml deionized water.On this basis,optimizing the etching process parameters by orthogonal experiment,so we get the optimal etching process parameters with etching temperature of 40?,stirring frequency of 10 r/min and etching time of 10 min.As a result,we obtain a wet chemical etching system of inorganic-organic acid mixture for GaSb semiconductor substrate with moderate and controllable etching rate as well as fine etching quality.Secondly,exploring the etching behavior of GaSb semiconductor substrate in the above mentioned wet chemical etching system from three aspects:surface morphology texture and surface composition changes of the substrate before and after etching,and the dissolution reaction rate of the main elements in the etching process.According to the metallographic microscope,the texture distribution of etched GaSb substrate is uniform,the geometrical shape of texture changes from dendrite to irregular circle after etching reaction.According to the scanning electron microscope,there is no distinct insoluble particles on the surface of etched GaSb substrate which is flat and clean,and there is no significant difference from the polished surface before etching,this reflects that the insoluble substance containing Sb is fully complexed and dissolved in the process of reaction,.According to inspection and analysis of AFM,the surface roughness of GaSb substrate increases by 1.16nm compared with that before etching,and the surface fluctuation increases slightly after etching reaction.According to EDS analysis,the atomic percentage of Ga,Sb and O elements in the 1-2 ?m depth surface layer of etched GaSb substrate are respectively 48.9%,47.9%and 3.2%,and the atomic percentage of these three elements is close to that before etching,so it is less affected by etching reaction.According to inspection and analysis of XPS,the 10 nm depth surface layer of etched GaSb substrate is mainly composed of Ga2O3,Sb2O3 and Sb2O5,while before etching,it is mainly composed of Ga2O3,Sb elementary substance and Sb2O5,meanwhile,a small amount of GaSb and Ga elementary substance are found on the substrate surface before and after etching,which indicates that the etching rection mainly takes place in this deep surface layer,and the Sb elementary substance is completely oxidized to Sb2O3 during the reaction process.Through ICP-MS test and analysis,the reaction rates of Ga and Sb element are respectively 7.5363×10-5 mol/(L·min)and 1.6121×10-4 mol/(L·min)in the etching process,and the reaction rate of Sb element is significantly higher than that of Ga element.Finally,using single factor variable experiment,explores the specific influence law about the various components and process parameters on the quality of etched substrate and etching rate.Hydrogen peroxide and hydrochloric acid have a great influence on the etching rate,and the influence trend of these two components on the etching rate is also roughly similar,the etching rate increases with the rising of their volume fraction,reaches the extreme value first,then gradually drops and slows down,with a large overall rangeability.In addition,too high or too low of their volume fraction both have a significant adverse effect on the etching quality of substrate.Phosphoric acid and citric acid have a relatively slight effect on the etching rate,but they have a large effect on the etching quality of substrate.When the volume fraction of phosphoric acid in the etching solution is 3.75?6.10%,the surface of etched substrate is uniform and flat,as well as low surface roughness.When the mass concentration of citric acid in the etching solution is 51.28?120.48 g/L,the surface roughness of the substrate remains low after etching.The etching rate drops rapidly after the etching solution diluted with deionized water,when the dilution is more than three times,the etching rate drops slowly,meanwhile,there are some black insoluble substance adhered to the substrate surface.Etching temperature has a great influence on the etching rate,they are positively correlated,when the etching temperature exceeds 60?,the etching rate increases slowly,while the stirring frequency has a relatively little influence on the etching rate,this indicates that the reaction rate limiting mechanism dominates the etching process.When the GaSb substrate is etched in the etching solution for 10 min and 15 min,the thickness thinning is respectively 75 ?m and 100 ?m,the surface roughness(Rq)is respectively 2.35 nm and 3.71 nm.