Research On Preparation And Characterization Of In Situ Nanodevices By Scanning Probe Technology

Scanning probe microscope(SPM)is a very popular characterization method in the field of nanotechnology.It can be used for high-precision imaging and in-situ surface measurement at nanometer or even atomic level,which greatly promotes the development of nanotechnology.In addition,scanning probe technology has nanometer level probe and precise control system,and it can also realize atomic manipulation,nano etching and other nano processing operations,which makes it have great development potential in the field of nano processing.At present,the key step in the field of micro electronic nano processing is photolithography.With the development of the industry,various new photolithography technologies are emerging.However,the development of photolithography equipment is a very complex and long process.The current photolithography technology still faces problems such as low resolution,high etching cost and complex process.Therefore,this paper proposes to use scanning probe technology to complete nano etching,so as to realize the preparation of small-size devices.The advantages of scanning probe technology,such as flexibility,low cost,high resolution,are introduced into the research of microelectronics technology,and a new method of small-size device preparation is proposed for the micro nano manufacturing industry.There is a strong polarization effect in GaN based heterostructures,which makes AlGaN/GaN heterostructures can obtain high-density two-dimensional electron gas(2DEG)even without doping.Therefore,GaN based devices have obvious advantages in light-emitting devices,microwave high-power devices and so on.In GaN based devices,high-frequency characteristics is a key research direction,and shortening gate length is an important condition to improve the frequency of GaN based devices.At present,GaN based devices under 100 nm still face many challenges,but the research on high-frequency characteristics of devices is very important,so the rapid preparation of short gate length and small size GaN based devices is one of the current research focuses.At present,there is no research on nano etching to control the properties of GaN based heterostructures.By means of in-situ nanoetching and scanning probe technology,the crystal structure at the interface of GaN based heterojunction materials is manipulated in-situ to realize the change of local two-dimensional electron gas concentration,and then the characteristics of GaN based materials and devices are manipulated and measured in-situ.On this basis,GaN based Schottky diodes can be prepared quickly and easily,and the minimum channel width can reach 50 nm.It provides a new method for the design of GaN based small-size devices and important experimental parameters for the study of high frequency characteristics of GaN based devices.In this paper,the nano etching methods and electrical properties of AlGaN/GaN materials and AlGaN/GaN HEMT devices are studied,and a new method to prepare small-size GaN based devices is proposed.The specific work includes the following parts:First,the equipment of nano etching is studied and determined.The advantages,disadvantages and feasibility of three kinds of nano etching instruments,step instrument,nano indentation instrument and atomic force microscope,are compared.Atomic force microscopy(AFM)has been selected as the instrument for nano etching and electrical characterization because of its advantages of nano scale high resolution,uniform etching,various modes and room temperature etching.Secondly,the application of AFM in AlGaN/GaN materials was studied by combining nano etching with in-situ characterization.Through experiments,the relationship between etching intensity and depth,and the relationship between etching times and depth were determined.The standard of etch intensity and etch times was determined.Nano etching of AlGaN/GaN materials by AFM has been successfully used to control the electrical transport properties of materials by mechanical etching.Thirdly,based on the previous experimental results,the application of AFM etching method in AlGaN/GaN HEMT devices is studied,including the nano etching and characterization analysis of two end devices and three end devices.The output and transfer characteristics of AlGaN/GaN devices are successfully controlled by AFM.Fourthly,a small-scale AlGaN/GaN Schottky diode with a minimum channel width of 50 nm was successfully fabricated by nanolithography with AFM.The AlGaN barrier layer was etched by AFM on AlGaN/GaN material.The 2DEG concentration of AlGaN/GaN heterojunction was changed by controlling the etching distance and depth,and a 50 nm wide conducting channel was reserved,thus a multi channel GaN based Schottky diode with a minimum width of 50 nm was obtained.The device has good rectifying characteristics.With the increase of the number of channels,the concentration of channel electron gas increases,and the on resistance of the device decreases,which is consistent with the theoretical expectation.This device preparation method has the advantages of small device size,diversified device structure,in-situ characterization and simple process,which provides a new idea for the preparation of nano size devices,which provides an important preparation method and experimental parameters for the follow-up study of small-size GaN based HEMT devices,and is of great significance for the study of high-frequency characteristics of GaN based devices.