Fabrication Of The Au-layer With Nanometer Scale By Pulse Electroplating

This thesis focuses on the fabrication of obtaining nano-scale golden layer on thesubstrate of silicon by means of pulse electroplating. I try to analyze and find properfabrication parameters by studying the theoretical literatures, in order to obtain golden layerwith average dimension in the scale of nanometer. The main contents of this thesis are listedas following:Firstly, I started with researching theory of electrochemistry, analyzing the relationshipamong the parameters of electrode potential, over-potential and current density in the solution.During plating, the current density on the silicon substrate in the cathode has direct effect onthe dimension of grains in gold layer. From Nernst equation, we can set connection amongparameters aforementioned so as to accurately control the dimension of gold grains in the nextstep. Verified by following experiments, the result deduced by theory can be used to controldimension properly. The next step was to research Faraday law and then calculate thetheoretical thickness of gold layer. I will compare the real data of thickness from experimentsresults with the theoretical one, with the purpose of accurately controlling the thickness ofgold layer with given current density and plating time. In practice, experimental data wasclose to the theoretical data. Finally, by using theories of metal physics and Hoffman-Laurizentheory, I can obtain the change rule of the dimension of the gold grains. By comparing thesamples in the experiment with different parameters, that rule can be verified properly.In substantial procedures of electroplating, I shall choose proper gold solution thatpossesses steadiest chemical properties and observe the changing of ion concentration in thesolution and then carry out the following options sequentially:1. cut and clean the siliconwafers;2. forming a gold film with the thickness of near50nm by ion sputtering plating;3. make sure the compositions in the solution and adjust the PH value by ammonia;4.electroplating;5. clean the chips and observe their optical characteristics by opticalmicroscope;6. measure the thickness of gold layer by profiler;7. observe the micro-structurein the chip and measure the dimensions of gold grains by scanning electron microscope. Inexperiments, I need set different groups of parameters according to the theoretical analyzingand the results of series of experiments approached the theoretical values properly. From thepulse electroplating, I can obtain smooth gold layer with grain dimension of near150nm thatis larger than anticipation slightly.