The Mechanism Research Of Ultrasound Fine Atomization Chemical Mechanical Polishing

Although the traditional CMP technology meets the requirements of high surface quality in the IC processing, itself has many inherent defects which are difficult to overcome, they prevent the technology of CMP further popularized. To solve the common scientific and technical problems in the surface planarization processing of hard brittle materials, this paper puts forward the method of the ultrasound fine atomization CMP, its principle is as follows: In the polishing process, the polishing slurry which contains special chemical compositions is fine atomized by frequency controlled ultrasound, and become uniform micron grade liquid grain whose diameter between 5 to 25μm,and then,they will be imported into the polishing interface through a special way.The liquid grains have high specific surface area,they can absorb strongly on the surfaces of polishing pad and substrate, and engender strong activity, high efficiency chemical action with substrate material, and emerge a layer of chemical reaction film which has low shear strength in the surface of substrate, it can be friction removed by abrasive particle and polishing pad, this process repeat and repeat, so the nanometer level ultra precision surface will form.This article focuses on the theory problems which exist in the ultrasound fine atomization CMP. we studied quantitatively the generation, flow characteristics and attached characteristics of the atomized particle in atomization polishing. Research found that the atomization method used in this system can ensure the size of liquid particle 5.1 to 10.1 nm range and meet the need of the atomized polishing. Through the flow analysis of fog liquid in the atomizing polishing system,we got the theoreticals of the gas characteristic parameters of key position, they will paly guiding roles in the actual atomization polishing. Through the researchs of liquid particles adhesiveness, we found that the change of the temperature and pressure in the polishing space can significantly affect the adhesion properties of polishing slurry in practical operation. At the moment, we made the experiments of material removal rate of each element of chemical mechanical polishing,and we found that the grinding effects of abrasive particle is the main role of material removal in the polishing, the material removal rate caused by it accounts for the largest proportion of the total removal rate is 70.6%, and through the micro test to silicon wafer,we found that the surface roughness of silicon wafer reached to the nanometer level(<3.8 nm) after polishing process.Second, this paper carried through some quantitative analysis and calculate about the sliding friction and friction heat which exist on the polishing interface.We think that the friction include both the sticky friction between grain and workpiece and the distortion friction of workpiece in the atomization polishing,and we obtained their related expressions.In the calculation of friction heat,we first got the friction heat produced in the sliding friction between single particle and workpiece,then we spread to more particle and got the total friction heat, and obtained the expression of temperature rise in the atomization polishing. At the same time, through the depth test of nick, we can get some informations of the oxide film thickness. Using ANSYS, we analyse the distribution of the physical parameters in the polishing contact area, and found that the distribution of each parameter is not uniform, the stress and strain is bigger especially on edge of work, this makes the surface material removal have greatly not uniformity.Finally, this paper carried through some calculate about the wear of surface materials which exist on the polishing interface. We think that the surface wear of workpiece in the atomization polishing is due to abrasive wear, adhesive wear and corrosion wear of polishing slurry,and got the theoretical formula of wear. Also, this article made the nanometer indentation experiments of wafer surface,we found that the wafer surface form a layer of oxide film after corroded by homemade polishing, the hardness of oxide film is far less than the original material surface, it is beneficial to the subsequent machinery removed.The research results of this paper will provide theoretical support for the practical application of the ultrasonic fine atomization CMP method.