Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Reexamination Certificate
1999-06-28
2002-03-26
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
C438S301000
Reexamination Certificate
active
06362082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
A method of improving short channel effects is described. More particularly, the present invention involves the use of implants in the channel region of an MOS transistor to inhibit the lines of force from extending from the source to the drain of an MOS transistor.
2. Description of Related Art
FIG. 1
is a side cross-sectional view of an NMOS transistor
10
known in the art. A conventional transistor
10
generally includes a semiconductor generally comprising a silicon layer
16
having a source
20
and a drain
18
separated by a channel region
22
. A thin oxide layer
14
separates a gate
12
, generally comprising polysilicon, from the channel region
22
. In the device
10
illustrated in
FIG. 1
, the source
20
and drain
18
are n+ regions having been doped by arsenic or phosphorous. The channel region
22
is generally boron doped. (Note that for both the source
20
and drain
18
regions and the channel region
22
other materials may also be used.) Fabrication of a transistor such as the device
10
illustrated in
FIG. 1
is well-known in the art and will not be discussed in detail herein.
The speed or velocity (v) of the current through the channel region
22
is a function of the mobility (&mgr;) of the channel region, as expressed by the formula v=&mgr;E wherein E represents the electric field across the channel region
22
. Because E is generally a constant value, the higher the carrier mobility (&mgr;) of a device the faster the device can function. As the demand for faster devices continually grows in the industry, the desire for a device having an increased mobility also increases. Thus, a method for fabricating a device having an increased carrier mobility would be desirable.
Another issue that arises when dealing with transistors of the present art involves current leakage from the source to the drain. One of the limiting factors in the scaling of transistors to smaller dimensions is the inability of the gate to fully control the channel region. As the source and drain junctions approach one another, the lines of force resulting from the potential applied to the drain terminate on the source junction, causing Drain-induced Barrier Lowering (DIBL). This DIBL results in leakage current between the source and drain, and at short enough channel lengths, results in failure of the device. Thus, a method of reducing current leakage would allow for the fabrication of transistors fabricated on a smaller scale.
SUMMARY OF THE INVENTION
A method of reducing short channel effects in a transistor is described. First, a substance is implanted in a substrate. The substrate is then annealed such that the implanted substance forms at least one void in the substrate. Then, a transistor having a source, a drain, and a channel region is formed on the substrate, wherein the at least one void is in the channel region of the transistor.
REFERENCES:
Lifetime control in silicon devices by voids induce by He ion implantantion. V. Raineri et al., J. Appl Phys 79 (12) Jun. 15 1996 pp9012-9016.*
Cavity Formation and impurity Gettering in He-Implanted, Follstaedt et al. Journal of Eelectronic Materials, vol. 25, No. 1. 1996. pp 151-157.*
Rare gas bubbles in muscovite mica implanted with xenon and kryton. j.Mater. Res, vol. 9, No. 12, Dec. 1994. pp.3095-3107.
Microstructure of Al203 and MgA1204 preimplanted with H, He, C and irradiated with Ar+oins*. Elsevier Science B.V. Journal of Nuclear Materials 209 (1994) pp. 191-203.
Density Reproduction: A Mechanism for Amorphization at High Doses. E.D. Specht, D.A. Walko, and S. J. Zinkle. Mat. Res. Soc. Symp. Proc. vol. 316. 1994 Materials Research Society. pp. 241-246.
Gas bubbles in glass melts under micogravity, Part 2, Helium diffusion. V. Jeschke and G.H. Frischat. Physics and Chemistry of Glasses vol. 28, No. 5, Oct. 1997. pp 177-182.
Modification Effects in Ion-implanted SiO2 Spin-on-Glass. N. Moriya, Y. Shacham-Diamond, R. Kalish. J. Electrochem. Soc. vol. 140, No. 5, May 1993. The Electrochemical Society, Inc. pp1442-1450.
Helium bubbles in silicon: Structure and optical properties. R. Siegele, G.C. Weatherly, H.K. Haugen, D. J. Lockwood,and L.M. American Institute of Physics. Appl. Phys. Lett. (11), 1Mar.13 1995. pp 1319-3449.
Helium-Induced Porous Layer Formation in Sllicon. A. Van Veen, C.C. Griffioien, and J.H. Evans. Material Research Society. Mat. Res. Soc. Symp. Proc. vol. 107. Mar. 1988. pp 449-454.
Lifetime control in silocon devices by voids induce by He ion implantation. V. Raineri, G. Fallica, and S. Libertino. J. Appl. Phys. 79 (12). Jun. 15 1996. 1996 American institute of Physics. pp 9012-9016.
Interaction of Cavitiesand Dislocations in Semiconductors. D.M. Follstaedt, S.M. Myers, S R. Lee, J.L. Reno, R.L. Dawson, and J. Han. Mat. Res. Soc. Symp. PRoc. vol. 438. 1997 Materials Research Society. pp 229-234.
Microstructural Properties of Helium Implanted Void Layers in Silicon as Related to Front-Side Gettering. J.W. Medernach, T.A. Hill, S.M. Myers, and T.J. Headly. J. Electrochem. Soc., Sol. 143, No. 2. Feb. 1996, pp 725-735.
Cavity Formation and Inputirt Gettering in He-Implanted Si. D.M. Follstaedt, S.M. Myers, G.A. Petersen, and J.W. Medernach. Journal of Electronic Materials, vol. 25, No. 1. 1996. pp151-156.
Cavity and Nucleation and Evolution in He-Implanted Si and GaAs. D.M. Follstaedt, S.M. Myers, G.A. Petersen, and J.C. Barbour. Mat. Res. Soc. Symp., Proc. vol. 396. 1996 Materials Research Society. pp 801-806.
Radiation damage adn implanted He atom interaction during void formation. V. Raineri and . Saggio. Appl. Phys. Lett. 71 (12), Sep. 1997. pp1673-1675.
Doyle Brian S.
Roberds Brian
Blakely , Sokoloff, Taylor & Zafman LLP
Intel Corporation
Le Dung A
Nelms David
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