Surface Heat Treatment of Silicon Wafer Using a Xenon Arc Lamp and Its Implant Activation Applications

Abstract

A surface heat-treatment method for semiconductor wafers using a xenon arc lamp is described. High absorption coefficients of silicon wafers in ultra violet (UV) region and short process time made selective surface heating possible. The surface melting of entire 150 mm diameter Si wafers was demonstrated in less than 2 s at a lamp power of 15 kW. By focusing UV light into a limited area on Si wafer surface, surface melting of a selectively exposed area was demonstrated at a much lower lamp power. The surface temperature ramp rate is estimated to be on the order of 1000 • C/s. Si wafers, with various implanted species (P + , As + , B + and BF 2 + ) and energies (1 keV-70 keV), were annealed for implant damage recovery and electrical activation using the Xe lamp under different scanning speeds. Sheet resistance and secondary ion mass spectroscopy (SIMS) depth profiling measurement results from the scanning rapid thermal annealing (RTA) successfully demonstrated the feasibility of the technique in semiconductor RTA processing applications. Electrical activation with desired levels of dopant diffusion can be achieved by optimizing process variables such as lamp power, distance between the lamp and Si wafer, area of light exposure and scanning speed. Rapid thermal annealing (RTA) is one of the hottest areas of interest in advanced Si device fabrication. Typical RTA systems employ either halogen lamps or a resistively heated furnace or susceptor as heat source. The lamp-based RTA systems have an excellent lot size flexibility as well as flexibility in controlling a process temperature profile while they have very poor energy efficiency and require complicated temperature measurement/control algorithms.1 Although the resistive heating-based RTA systems do not provide the same lot size flexibility, they provide equivalent process results at much higher energy efficiency. 2A very fast wafer heating and cooling, called "spike anneal" is proposed to electrically activate implant species while suppressing unwanted dopant diffusion during (ultra)shallow junction implant anneal.3,4 However, conventional tungsten halogen lamp-based RTA techniques heat the Si wafer and wafer temperature ramp up and ramp down rate are limited to ∼200• C/s and ∼90 • C/s, due to the balance amongst the heating/cooling characteristics of tungsten filaments, heat capacity of Si wafer and heat loss from the wafer, and so on. Increase in lamp power and/or number of lamps simply do not improve wafer temperature ramp up and ramp down characteristics. 5,6 Large size wafers make the fast wafer heating and cooling more difficult in conventional tungsten halogen lamp-based RTA techniques. The spike anneal using Ar arc lamp has been demonstrated. The reported wafer temperature ramp rate and cooling rate were 400• C/s and 180 • C/s, respectively. 5,7In advanced Si devices, all the active device regions are located at the top surface (up to 1 μm from the surface) of 600 ∼ 800 μm thick Si wafers. Selective surface heat-treatment is ideal from the viewpoint of f...

Room Temperature Photoluminescence Characterization of Silicon Wafers for In-Line Monitoring Applications

“…The PL study on ion implanted Si before and after activation annealing, under various temperature and time conditions, clearly showed the correlation between the envelope of PL spectra (i.e. P1/P2 ratio) and (residual) crystalline damage (8)(9)(10).…”