Research On Making Micro Probes Used For Electro-optic Detection

Since 1970s the technology of Integrated circuits has progressed constantly.It is guided by Moore's Law,which says that the integration of ICs increase of 2 times every 18 months,and the cost reduces by half.The feature size of IC devices continues to shrink,currently the characteristic size has reached 45nm.With the development of the design and manufacturing technology of the programmable microprocessor chip,microelectronics chips are changed from a large-scale to very large scale integration.However the leakage of ICs,thermal effects,parasitic parameters and device model parameters,such as the issue of uncertainty is also exposed,and the design and manufacture technology of ICs are urgently needed to be improved.It is impossible that the reliability of the device with low finished product is increased by certain kind filtration procedure.And the device with high reliability is just fabricated by the high reliability design and technique.In order to ameliorate the design and fabrication technology in the investigation process,the inside characterization of ICs chip obtained in the investigation process need to be analyzed and diagnosed.At present,the applied check equipments are mostly listed as follows:Probe needle method,E-beam probing or scanning electron micro- scope method,Photoemissive sampling method,Photoconductivity switching sampling technology,Radiation microscope and Electro-optic Probing method.All the three kinds of measurements mentioned above have not yet satisfied the needs of the study and the developing of ICs because of their limitations.It is a important problem to ameliorate the Electro-optic sampling technique,and make it a kind of handy equipment applied in microelectronics chip inside characteriza- tion analysis at all times.The external EO probing technique overcame the limitations of the substrate materials,but brought new issues at the same time:first,in internal EO probing technique the substrate materials contact down to the signal transmission lines,the signal electric field can extend into the EO materials completely and distribute uniformity.For external EO probing technique,the separation between EO crystal and signal transmission lines product the air gap when the circuits to be tested.Here,the huge difference of the dielectric constant between EO material and ambience make the electric fields compressed in the air gap,only few part of the electric fields can extend into the EO crystal,so EO signal amplitude be reduced largely.For the same signal detection and amplification system,this means the voltage sensitivity is reduced.In the typical EO crystals,LiNbO₃ and LiTaO₃ have biggish EO coefficient, and their relative dielectric constant are 28 and 43 respectively,witch is larger than that of air further.Second,the tested EO signal is the un- distortion simulation of the voltage signal in the ICs,and the signal wave,the time and phase relaxations of the wave all accorded to the electric signal in ICs completely.But the amplitude of EO modulation signal lies on the lognitudinal component of the electric field issued from the electric signal transmission line;witch is influenced by the neighbor circuit layout. Third,the most fundamental work for the practical of external EO probing system is that the investigation and manufacture of probe tip material with thermally stability and large EO coefficient.All the EO probing systems reported by foreign investigators utilized inorganic EO crystal as the detector of modulation electric fields. For internal EO probing system,mentioned above,its application is limited by the substrate materials.So the calibration voltage measurement cannot be realized.This paper designed and fabricated a novel EO probe tip:An reflectivity(AR) coating(Al film) is evaporated onto the top surface of transparent substrate and an electric ITO film is evaporated onto its surface,the Al film has about 30%reflectance ratio on probing beam.An organic EO film is bonded onto the electric film.When probing the tested points,the electric film is grounded and the probe tip stands onto the transmission lines.As long as the vertical distance between the tested point on the lines and the reference electrode is not larger than that between the tested point and its neighboring conductor,the electric field issued from the electric signal transmission line and extended into the EO material,terminated in the grounded electric film completely.Here,the disturbance from circuit layout can be avoided so that the voltage calibration of EO signal can be carried out.In the EO probing method mentioned above,the configuration of probing tip,the fabrication of EO film and the transform from phase modulation to amplitude modulation of the probing beam are all original creation of this paper.This paper fabricated the organic\inorganic EO material utilizing sol- gel technique.The chromophores Disperse Red 1(DR1) is doped into the oxide matrix, the best concentration of solution,the heating treatment condition and poling approach have been obtained by experiments.The large EO coefficient ofγ₃₃ =10pm/V was obtained and the value was unvaried at room temperature.