Extremely proximity gettering for semiconductor devices

We investigated the gettering efficiency of iron and nickel in Czochralski (CZ) silicon wafers depending on crystalline nature such as interstitial-silicon-dominant or vacancy-dominant crystal growth. After a typical heat treatment for dynamic random access memories (DRAMs), the density of silicon oxide precipitates in the vacancy-dominant crystal regions was approximately two orders higher than interstitial-silicon-dominant crystal regions. After a DRAM heat treatment, irons were preferably gathered at vacancy-dominant crystal region while nickels were selectively at only an interstitial-silicon-dominant crystal region. Silicon wafers designed with extreme gettering ability via rapid thermal annealing (RTA) at 1150 °C for 10 s using NH3 and Ar gas mixture produced the “M” shape of oxygen precipitates in which the peak density of the precipitates was in the range of ∼3 × 1010 cm−3 while the bulk density was in the range of ∼2 × 109 cm−3. The RTA silicon wafer completely eliminated irons and nickels from the wafer surface that are gathered at oxygen precipitates in silicon bulk during a DRAM heat treatment.