Study On Surface Corrosion Of Defects In Monocrystal Germanium Cutting Wafer

Monocrystal germanium is widely used in infrared field and solar energy aerospace applications.The requirement of flat surface for monocrystal germanium and the inner amount of dislocations get more and more attention.The technology of Czochralski crystal directly determines the dislocation density inside the germanium ingot.The cutting process of the germanium ingot determines the surface quality of germanium wafer,and the germanium wafer affects the production performance.Therefore,it is of great significance to study the damage layer,dislocation and other defects on the surface of germanium single crystal wafer to improve the production and processing of monocrystal germanium.At this stage,monocrystal germanium is mainly etched by HNO₃-HF system,which needs to polish first and then displays dislocations through preferential corrosion.There are many problems like complex steps,uncontrolled self-catalytic reaction,and terrible pollutions.In this paper,we focus on finding a new kind of excellent etchant to show the dislocation of monocrystal germanium,and to evaluate the surface quality of germanium by observing and calculating dislocation density.Using electron microscope to get the information of the damage layer caused by cross section of corrosion.Through the qualitative analysis,potassium permanganate was selected as the oxidant in the corrosive solution,and the influence of ultrasonic on the corrosion of the germanium chip was analyzed.The results showed that the surface of the germanium chip is damaged and couldn't accelerate the reaction.Through qualitative analysis,the conclusion that hydrofluoric acid must be added is obtained.In the follow-up experiment,according to the principle of acid corrosion,increasing the amount of hydrofluoric acid is good for germanium monocrystal forming flat surface and showing dislocations.After the temperature is lower,the surface of the germanium film is rough and dim under the circumstances of same ratio.When the temperature rises to a certain amount,the corrosion rate begins to improve,exhibiting flatter surface.But when the temperature is too high,that excellent flatness will decline.The ratio of etching solution also has a great influence on the corrosion of germanium,which is related to two processes involved in corrosion.Through the study of corrosion time,the result shows that the roughness of germanium film will not change obviously after 120 °C corrosion at 60 °C,and the morphology will also be stable.When the solution ratio of V?KMnO₄?:V?HF?:V?H₂SO₄?is 10:9:1 and the concentration of KMnO₄ is 0.4 mol/L,HF analysis is pure,the concentration of H₂SO₄ is 4 mol/L,at 60 °C for 120 minuter,dislocations and corrosion both show great levels.Finally,the germanium film was etched by the etching solution,through which the dislocations could be calculated.The damage layer of the germanium film could be observed by electron microscope,and the thickness of the damaged layer could also be measured.Taking the dislocation density and the thickness of the damage layer on the surface of the germanium chip into account,it is extraordinary to understand the surface quality of the germanium plate contributing to the improvement of its production and processing.