Design And Fabrication Of In-situ Nano Electrical Chip Based On Micro-and Nano-machining

With the development of integrated circuit technology,the improvement of device performance is mainly by reducing the feature size of integrated circuits.With the feature size of the device reduced to the nanoscale,there exist the following problems:(1)The power density increases with the elevation of the clock frequency and leakage current,which seriously affects the speed of the device.Compared with the traditional Moore's law era,in the More Moore era,the development of IC technology has been shifted from pursuing performance to the concern of power consumption and performance/power ratio.(2)The structure of device is becoming more and more complex,while there are still difficulties in the research on the relationship between device structure and material properties as well as the failure mechanism of devices.The solution to the difficulties,on one hand,is to develop new structures,mechanism and materials,aiming at high mobility channel materials.On the other hand,due to the quantum effects of nanoparticles,nanomaterials possess new physical properties under electric field loading.Therefore,to quantitatively describe the effect of various types of effects under electric field loading is the key to future devices.In order to obtain knowledge on the relationship between material properties and microstructure in in-situ,dynamic and electric field,the tool of in-situ transmission electron microscope(TEM)is essential.However,it is difficult to simultaneously solve the problems of small contact area,inability to in-situ construct multi-electrode devices and sample size limitation for in-situ electrical measurements.In this thesis,the design and fabrication of nano multi-electrode electrical chip based on micro-and nano-machining were proposed in view of the above-mentioned facts.An in-situ nano multi-electrode electrical platform was built by bonding with the holding structure.Compared with conventional design,the new platform has the following advantages:(1)The design of multi-electrode can achieve the in-situ construction of electronic devices,avoiding the damage caused by the sample preparation of ex-situ construction.(2)The size of electrodes reaches the nanoscale,which reduces the limitation of sample size.(3)Multiple contacts creates a large contact area,which is beneficial to the reduction of contact resistance.The design presented in this thesis is of significance for the in-situ study of the electrical properties of nanomaterials/devices with the evolution of the structure,as well as to realize the in-situ construction of the nanoscale devices.The main research contents and results are listed as follows:(1)First of all,in view of the current research of two prototypes of electrical measurement based on in-situ TEM,the structure of the electrical chip was proposed.Then the Micro-Electro-Mechanical System(MEMS)process of the chip was introduced and the main processes involved were discussed.Finally,the electrical chip array and their characterization results were shown.Besides,the reasons for the failed deposition of the metal line in the first tape-out were analyzed and the processing technology was improved.(2)In view of the fact that the existing technology cannot process multiple electrodes of the chip at nanosmeter scale,the nano-processing was performed on the basis of the MEMS process.Focused ion beam was used to etch the chip electrodes after the tape-out.Through the combination of wire cutting and rectangular cutting,a novel cutting method with high efficiency and accuracy has been found,which reduces the electrode gap to less than 100 nm.To verify the isolation of the electrodes after the focused ion beam cutting,C-V curves were respectively collected by the Keithley Instrument 4200-SCS with the probe of no-load,of single electrode and of two electrodes.It is found that the resistance of a single electrode is ~14 ohms,and two terminal electrodes keep isolated when the applied voltage is below 4.25 V.Besides,the electrodes are connected when the voltage is higher than 4.25 V.(3)Finally,on the basis of the existing optical holding structure which can carry the carbon film to package liquid cell,a holding structure was designed and fabricated,and in-situ nano multi-electrode electrical platform was successfully fitted into a standard STM-TEM holder.