The Study Of Effect Of Carbon Impurity On Oxygen-related Defects In Czochralski(Cz)Silicon

Over the past decade,nitrogen-doped silicon wafer has become a widely used material in integrated circuit because of its higher mechanical strength,better internal gettering performance and easier elimination of void defects.The introduction of carbon impurities is unavoidable,in the growth process of silicon and can only be controlled by appropriate processes.In this paper,the effects of higher concentrations of carbon impurity on the formation of N-O STDs,oxygen precipitates and oxygen thermal donor were studied.The main results were as follows:1.The effect of carbon impurities on the formation of N-O STDs at 650? heat treatment was studied.When the carbon concentration is low(3.4×1016cm-3),the formation of N-O STDs is almost unaffected.When the carbon concentration is high(5.1×1016 cm-3),the formation of N-O STDs is significantly inhibited.In the case of NCz wafers with high carbon concentration,some.of the interstitial oxygen atoms are trapped by carbon atoms to form C-O complex at 650?,so the interstitial oxygen atoms are significantly reduced,as a result,the formation of N-O STDs is inhibited.On the other hand,there may be interactions between carbon and nitrogen atoms,which in part inhibited the formation of N-O STDs.The effect of rapid thermal processing(RTP)at 1250?/60s on the formation of N-O STDs at 650? was studied.The formation of N-O STDs is almost free from the effect of rapid thermal procssing for ordinary nitrogen-doped silicon wafers(ie,the carbon impurity content is almost negligible).For nitrogen-doped silicon wafers with high carbon content,rapid thermal processing promotes the formation of N-O STDs.The preliminary analysis shows that rapid thermal processing eliminates the possible interaction between carbon and nitrogen atoms,and the released nitrogen atoms can participate in the formation of N-O STDs.Rapid thermal processing can also break up the smaller oxygen precipitates in silicon samples with higher carbon content,increasing the amount of interstitial oxygen and thereby promoting the formation of N-O STDs.2.The effect of carbon impurity on the behavior of oxygen precipitation(OP)in low-high two-step heat treatment was studied.Carbon impurity promotes the formation of oxygen precipitations,whether in the case of different nucleation time or different growth time of oxygen precipitates.On one hand,the C-O complex formed by the interaction between carbon and oxygen atoms can be used as the precursor of oxygen-precipitated heterogeneous nucleation,which reduces the potential barrier of nucleation of oxygen precipitate.On the other hand,the silicon lattice around the substitutional carbon atom is in a stretched state which is favorable for the release of compressive stress from nucleation of oxygen precipitates.The effect of carbon on the oxygen precipitation of nitrogen-doped silicones was more significant when 1250?/60s rapid thermal processing was used before low-high two-step heat treatment,which was due to the fact that carbon promoted the formation of vacancy-oxygen complexes(VO2)--the precursor of oxygen precipitated nucleation.3.The effect of carbon impurity on the formation of oxygen thermal donor was studied.Nitrogen impurity inhibit the formation of oxygen thermal donor.On the basis of the effect of nitrogen impurities,the carbon impurity can further inhibit the formation of oxygen thermal donor,and the higher the carbon concentration is,the more significant the inhibition effect is.The preliminary analysis suggests that the formation of C-O complex consumes a part of the interstitial oxygen atoms.In addition,a part of the substitutional carbon atoms undergoes "kick-out" mechanism,which consumes a portion of the intersial silicon atoms.The formation of thermal donor is dependent on the number of intersial oxygen atoms and intersial silicon atoms.