| The amorphous semiconductor TeAsGeSi material has threshold switching characteristic,which can instantaneously transition from a high-impedance state to a conductive state when the applied voltage reaches a certain value,and returns to a high-impedance state after the pressure is removed.This material can be used as a selective switch in the form of a thin film.In the new phase change memory,it can greatly increase the storage speed,storage density and information security.The performance of the film depends on the quality of the target used.To prepare high-density,unif-orm-quality high-quality targets,the vacuum hot-pressing method was used to study the different performance of the alloy powder raw materials and the hot-press sintering process.The influence of the densification mechanism of the sintering process was analyzed.High-performance targets were coated with RF magnetron sputtering to characterize the film properties to verify the usefulness of the target.In order to study the difference in performance of different crystalline targets,alloy powders with different crystallinity were used as raw materials:alloy powders rapidly cooled after smelting were amorphous,and there were many holes on the surface of the pressed target,and the density was low;The powder obtained by cooling is a polycrystalline phase.The surface of the pressed target is smooth,and the structure is compact.Both the powder and the target have AszGeTe4,GeTe,As,and Si polycrystalline phases.The combined powder test results confirm that the sintering hot pressing temperature does not exceed 340?.In order to optimize the process conditions,the effect of different holding time on the performance of the target was studied.The crystal phase content of the target and the grain size of the main phase were calculated.Based on this,the densification mechanism was analyzed:heat preservation pressure 1h target material The density of the target is low,the processing time of 2h and 3h is higher,reaching 99%of the theoretical value.There is a small amount of As element loss in the 3h sintered target;the particles in the initial stage of sintering begin to be combined into a layered structure under the action of hot pressing.Grain refinement,medium-term average grain size grows,the layered structure is compact,and the density is further increased.At the later stage of sintering,the density of the target material decreases?and the As element is lost.Therefore,the optimum process is determined as the heat preservation pressure 2h.In order to verify the practicability of the target,the properties of the film were characterized:a film with a smooth surface,uniform thickness,and an elemental content was obtained with a high-density target;the film thickness was directly proportional to the coating time,and the deposition rate was directly proportional to the coating power.The heat treatment film can make its composition crystallize,the resistance of the material changes greatly,but the film loses heat and volatilizes.The current-voltage curve of the film shows that the material has a threshold switching characteristic.When the first applied voltage reaches 5.92v,the film is turned on,and the resistance transited from 6.8-7·1010?·mm to 2.1·10-8?·mm,the film maintains the threshold switching characteristics after many test cycles,and the threshold voltage remains basically unchanged,and the film application performance is good.In this paper,vacuum hot-pressing method is adopted,polycrystalline powder obtained by slow cooling after smelting is used as raw material,and the temperature is raised to 340?.under pressure of 40 MPa,and the pressure is maintained for 2 hours.The composition has a uniform distribution and a high theoretical density of 99.3%.Targets,which are subjected to coating experiments,have a thin film with a recyclable threshold switching characteristic,and the verification target can be used to prepare an amorphous semiconductor threshold switching layer film. |
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