Preparation Of Si-B Master Alloy For Polycrystalline Silicon Sputtering Target

As an important semiconductor material,silicon targets are widely used in the optical and information industries.Resistivity is an important indicator to measure the quality of silicon target.At present,the commonly used silicon target in the industry is p-type（B-doped）,and the resistivity is divided into low resistance（resistivity<0.02Ω·cm）and high resistance（resistivity>0.5Ω·cm）.When preparing low-resistance silicon targets,a large amount of B element needs to be doped into silicon.In order to reduce costs,elemental B or M-B（metal）alloys are usually used for the preparation of low-resistance silicon targets in the industry.However,when the elemental B is used for doping,the loss is high and the resistivity fluctuates greatly.However,when the B-containing alloy is used for doping,metal elements will be introduced,resulting in the formation of an intermediate phase between metal and silicon in the polysilicon,which affects the quality of the polysilicon target.Therefore,there is a need to develop a low-cost,pure Si-B master alloy to replace the elemental B and M-B alloys currently used in the industry.Aiming at the practical problems currently faced by the industry,the research on the preparation method of a new Si-B master alloy is carried out in this paper.Firstly,the Si-B master alloy was prepared by melting method and ball milling-forming method,and the phase,structure and morphology of the master alloy were analyzed respectively.It was found that the ball milling-forming method was the best method for preparing Si-B master alloy.craft.The main findings of this paper are as follows:（1）Si-B master alloy ingots with B additions（wt.%）of 0.8%and 2.5%were prepared by melting method.The master alloy ingots with B additions of 0.8%showed a small amount of B-containing precipitates,while the B additions A large amount of B-containing mesophase appeared in the 2.5%Si-B master alloy ingot.The two prepared Si-B master alloys were tested by ICP-OES,and the results showed that the absorption rate of B in the Si-B master alloy with B addition of 0.8%was 26.6%,while that of Si-B master alloy with B addition of 2.5%was26.6%.The absorption rate of B in the B master alloy ingot is 50.6%,and there is volatilization loss of B during the smelting process.Therefore,under the condition of high B doping,a part of B element is dissolved into the Si matrix,a part forms a B-containing mesophase,and a small amount of B is volatilized and lost during the smelting process.（2）The Si-B master alloy was prepared by ball milling-forming method,and the particle size of Si powder and B powder decreased obviously after ball milling.After ball milling,no new compound is formed between Si and B,and it still exists in the form of Si and B.At the same time,there are Si-B bonds and B-Si bonds between the Si element and the B element,which is presumably caused by the substitution of the Si atom by the B atom during the diffusion process.At the same time,there are Si-B bonds and B-Si bonds between the Si element and the B element,which is presumably caused by the substitution of the Si atom by the B atom during the diffusion process.（3）The effect of different ball milling time on the powder microstructure was studied.With the extension of the ball milling time,the particle size of the powder decreased and the specific surface area of the powder gradually increased.When the ball milling time is 9h,the powder particle size is maintained within 2μm,and the ball milling time is further extended to15h,and the powder particle size is maintained at about 1μm.At the same time,the XRD results showed that with the extension of the ball milling time,the intensity of the diffraction peaks gradually decreased,and the diffraction peaks of Si shifted,which was presumed to be due to"r_B<r_Si",As a result of the ball milling process,B atoms enter the Si matrix,resulting in the distortion of the Si lattice,resulting in changes in the intensity of the diffraction peak and the position of the diffraction peak.（4）The Si-B master alloy prepared by the ball milling-forming method was used for doping experiments to obtain a polycrystalline silicon ingot target with a target resistivity of0.010Ω·cm.The resistivity effect of the polycrystalline silicon ingot prepared by doping is better than that of other silicon ingots,the resistivity range is 0.0080-0.014Ω·cm,and the lateral resistance distribution is uniform.