Research On The Behavior Of Transition Metal Fe And Cu In Silicon

The improvement of integrated circuit technology has greatly promoted the development of semiconductor industry.In the 21st century,with the development of Internet of Things and artificial intelligence,semiconductor industry has become the key to promoting the high-quality development of national economy.As a semiconductor material with many advantages,silicon has been widely used.At present,the characteristic linewidth of integrated circuits is gradually decreasing,and it has entered the era of nanometer scale.Transition metals have a more and more significant impact on the circuit.As transition metals,Fe and Cu are ubiquitous in silicon wafer processing.Their contamination and diffusion behavior in silicon wafers are of great research value.In this paper,the contamination behavior of Fe and the out-diffusion behavior of Cu in silicon wafer were studied.The silicon wafer was polished and etched under different conditions,and the effect of different surface states on the Fe contamination of silicon wafers was studied by surface photovoltaic method(SPV).The out-diffusion behavior of Cu in silicon wafers with different doping types and concentrations was studied by total reflection X-ray fluorescence spectrometer(TXRF)under different heat treatment conditions.The main conclusions are as follows:(1)The surface roughness of silicon wafers can affect the Fe contamination of the surface in solution.The rougher the surface of silicon wafer is,the larger the adsorption area of Fe ions will be.When the silicon wafer is immersed in the solution containing Fe ions,more Fe ions will be attached to the surface.(2)The hydrophobic surface has a small adsorption effect on Fe ions,while the hydrophilic surface has a strong adsorption effect on Fe ions.The hydrophobicity of surface of acid-etching silicon wafer enhance after the improved RCA cleaning ending with HF acid,and Fe ions are relatively difficult to adhere to the surface.They could be removed by rinsing with ultra-pure water;While the acid-etching silicon wafer is treated with SC-1 solution,the hydrophilicity of surface enhance and Fe ions adhere to the surface easily.And they are difficult to be removed by rinsing with ultra-pure water.(3)The damage formed on the surface of the silicon wafer has a strong adsorption effect on Fe ions.When the amount of removal of alkali-etching silicon wafer is less,the remaining grind damage layer on the surface after etch is deeper and the surface has a more stronger adsorption effect on Fe ions.The more Fe ions adsorbed on the surface cannot be removed by rinsing with ultrapure water and diffuse into the bulk of silicon wafer after annealing;When the surface of silicon wafer form soft damage by sandblasting or has scratches,the adsorption effect of the damaged area on Fe ions is strong and Fe contamination is serious.(4)For P-type silicon,Cu in lightly and heavily boron-doped silicon wafers can out-diffuse when wafers are annealed at low temperature(300?)for a long time(60min);Cu is more prone to out-diffusion in lightly boron-doped silicon wafers than in heavily boron-doped silicon wafers.As the annealing time increases at a higher temperature(650? or 850?),the amount of Cu diffused to the surface first increases;After a certain annealing time,the surface Cu will diffuse into the silicon wafers again and would be trapped in the bulk.For N-type silicon,when the heavily Sb-doped silicon wafers are annealed at low temperature(300?),there is no out-diffusion of Cu in the wafers,but stable out-diffusion occurs at 650?;And with the increase of annealing time,more Cu out-diffuse to the surface.however,at a higher temperature(850?),with the increase of annealing time Cu on the surface of the wafers reenter the bulk and are captured.In more heavily As-doped silicon wafers with<100>and<11 1>orientations,out-diffusion of Cu do not occurs as annealed at 300?,650? and 850?.