Ultra Shallow Junction Formation by RTA at High Temperature for Short Heating Cycle Time
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ABSTRACT In accordance with decrease of device size, ultra shallow junctions are required for realizing superior device performance. Enhanced diffusion caused by implantation is a crucial factor to realize ultra shallow junctions. Not only implant but also RTA conditions are key factors to suppress enhanced diffusion. In this paper, process conditions to minimize enhanced diffusion are discussed. Implant ion species, energy, dose and beam current parameters are investigated for implantation and temperature, time and ramping rate parameters are investigated for RTA. Important result is that optimization of not only implant but also RTA conditions should be carried out in order to fabricate ultra shallow junctions. INTRODUCTION According to the technology road map, an ultra shallow junction is required in the extension region on either side of transistor gate. Devices with a gate length of 0. 2 5 ;P m are in
the production phase and devices with 0.13-0.18 rn m are under development. Thus, 0.1 u m devices will be fabricated soon. In this generation, the junction depth of extension region is estimated to be approximately 30nm. In order to fabricate such an ultra shallow junction, many factors should be considered. Junction depth and sheet resistance[ 1-3] are very simple factors. Junction leakage current[4] is also important, because of abrupt carrier profiles. Since gate oxide thickness becomes thinner than 3 nm, control of both dopant penetration through gate oxides[561 and gate depletion is critical. Gate oxide degradation caused by damage during doping is also an important factor. From the point of accurate control of not only extension and deep source/drain profiles, but also channel and well dopant profiles, dose control is an essential factor, because junction depth strongly depends on dopant dose and also re-distribution of other dopant is affected by point defects generated during implant process, followed by annealing. Contamination control is very important in this device generation. Many methods have been proposed to fabricate ultra shallow junctions. Requirements for ultra shallow junction formation methods are as follows; uniformity, reproducibility, throughput, controllability, clean technology, etc. Since device fabrication has been carried out using 200 mm wafers at present, 300 mm wafers will be soon used in order to reduce chip cost. In 300mm
Mat. Res. Soc. Symp. Proc. Vol. 532 0 1998 Materials Research Society
wafer production, most of the processes will be changed from batch type to single type tools. Therefore, uniformity, reproducibility and controllability are essential factors for single wafer processes. Dose control is very critical to determine junction depth accurately. Energy control and implant ion selection are also important to suppress dopant tail, physical and electrical damage. Clean circumstances during implantation is also an important factor, because screen films can not be used in low energy implantation due to significant dose loss within the screen film itself. Method Ultra
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