Advanced activation and stability of ultra-shallow junctions using flash-assisted RTP
Advanced-logic device technology for the 65 nm node and beyond requires highly-activated, shallow, and abrupt dopant profiles (Int. Technol. Roadmap for Semicond., 2003). The combination of ion implantation and an advanced annealing technology is expected to provide solutions for these requirements. In contrast to spike annealing, a diffusion-less but highly activating, high-temperature, flash-assisted RTP annealing approach for the formation of ultra-shallow junctions will be demonstrated. The flash-assisted RTP technique is a promising method for achieving junction depth and sheet resistance values low enough to meet the performance specifications for the 65 nm node and beyond (Gelpey, et al., 2002, McCoy, et al., 2004). The optimal process for high activation during flash-assisted RTP involves a temperature ramp-up to an intermediate temperature between 700degC and 900degC and, once the intermediate temperature is reached, a very short, intense flash on the front side of the wafer induces a temperature jump up to 1325degC with a peak width of approximately 1.6 ms in a 100 ppm oxygen in nitrogen gaseous ambient. In this paper, we will present some of our recent p+MOS and n+MOS results on the fabrication of ultra-shallow junctions using flash-assisted RTP in crystalline and pre-amorphized silicon. It will be shown that such junctions are suitable for future technology generations. The measured "mechanical/electrical" sheet resistance values of the junctions are compared to Hall measurements on the same samples to gain an insight into the reliability of the destructive four-point probe (4PP) method for such extremely shallow junctions. Deactivation studies will be presented to examine the stability of the process to the required subsequent thermal processes
The Influence of the Amorphous Phase on Ion Distributions and Annealing Behavior of Group III and Group V Ions Implanted into Silicon
A study has been made of room‐temperature implantations of group III and group V ions into amorphous Si layers prepared by the previous implantation of Si ions into crystalline Si substrates. Neutron activation combined with anodic oxidation and HF stripping techniques was used to determine the proflies of the implanted ions for Ga71 and Sb121. Electrical evaluation of the implanted layers by Hall effect and sheet resistivity measurements in conjunction with layer removal techniques yielded profiles of the net electrically active species and the depth variation of mobility after annealing for 30 min in the temperature range 600°–900°C. The ion species studied were B11 (60–200 keV), Al27 (200 keV), Ga69&71 (140 and 280 keV), P31 (100–280 keV), As75 (280 keV), Sb121&123 (120 and 260 keV), and Bi209 (240 keV). The epitaxial regrowth of the amorphous phase at 600°C causes most of the implanted ions within this region to become electrically active and uncompensated for the ion species B, P, As, Sb, and Bi even for peak ion concentrations in excess of 1020 cm−3. For Al and Ga implants, the number of carriers was less than the number of implanted ions. The profiles obtained for these implantations into amorphous Si were compared with predictions based on the theory of Lindhard, Scharff, and Schiott.
Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose
Abstract Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1–1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.