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Infrared Semiconductor Laser Annealing Used for Formation of Shallow Junction

Published online by Cambridge University Press:  01 February 2011

Toshiyuki Sameshima
Affiliation:
[email protected], Tokyo A&T Univ., graduate school, 2-24-16, nakacho, Koganei, 184-8588, Japan, +81-42-388-7109
Yuta Mizutani
Affiliation:
[email protected], Tokyo A&T Univ., Koganei, 184-8588, Japan
Naoki Sano
Affiliation:
[email protected], Hightec Systems Corporation, Yokohama, 222-0033, Japan
Masao Naito
Affiliation:
[email protected], Nissin Ion Equipment Co., Ltd., Koka, N/A, Japan
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Abstract

We report continuous-wave (CW) infrared-semiconductor laser annealing of silicon implanted with boron atoms with assistance of diamond-like carbon (DLC) films as optical absorption layer in order to form shallow junctions. BF2 ions were implanted at 10 keV at doses of 1.5×1015 cm−2 thorough an 8-nm thick SiO2 layer. The effective boron dose implanted into silicon was 7.5c1015 cm−2 a half of the implantation dose. The initial boron distribution had a peak concentration of 6×1020 cm−3 at the silicon surface and a concentration of 1×1019 cm−3 at a depth of 27 nm. The samples were coated with 200-nm-thick DLC films. The samples were annealed by irradiation with a 940 nm continuous wave laser at 80 kW/cm2 with a beam diameter of 180 μm for 2.6 ms. Heat flow analysis estimated that the sample surface was heated to 1350°C for 1.5 ms by laser annealing. Laser annealing markedly reduced the sheet resistance to 531 Ω/sq. Boron atoms were almost completely activated with a carrier density close to the effective boron dose of 7.5×1014 cm−2. The in-depth profile of boron concentration hardly changed within 3 nm for laser annealing for 2.6 ms. The intermediate SiO2 layer effectively blocked carbon incorporation to a level below 1017 cm−3. These results show that the present laser annealing method is suitable to form shallow junction of a high dopant activation ratio. We will report low energy implantation of boron-cluster ions followed by the present infrared-semiconductor laser annealing in order to form a shallow junction with a depth less than 15 nm.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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References

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