| 1. |
- Hållstedt, Julius, et al.
(författare)
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Application of selective epitaxy for formation of ultra shallow SiGe-based junctions
- 2004
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 114-115:SPEC. ISS, s. 180-183
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Tidskriftsartikel (refereegranskat)abstract
- Selective epitaxial growth (SEG) of B-, P- and As-doped Si1-xGex (0.12 < x < 0.26) layers on patterned substrates, aimed for source/drain ultra shallow junctions was investigated. The SiGe layers were deposited selectively on Si surface that is either unprocessed or previously in situ etched by HCl in the same run in a reduced pressure chemical vapor deposition reactor. In these investigations selectivity mode, pattern dependency (loading effect), defect generation and dopant incorporation in SiGe layers have been discussed. It was demonstrated that the growth rate increased in presence of B in SiGe while it decreased for P- and As-doped layers. The amount of Ge was constant for B-doped samples while it increased for As- and P-doped SiGe layers. The epitaxial quality was dependent on the Ge amount, growth rate and dopant concentration. The selectivity mode of the growth was dependent on B partial pressure, however, no effect was observed for P- or As-doping in SiGe layers. A resistivity value of similar to10(-3) Omega cm was obtained for B- and P-doped SiGe layers with optimized growth parameters.
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| 2. |
- Isheden, Christian, et al.
(författare)
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Formation of Ni mono-germanosilicide on heavily B-doped epitaxial SiGe for ultra-shallow source/drain contacts
- 2003
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Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. ; 745, s. 117-122
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Tidskriftsartikel (refereegranskat)abstract
- The formation of Ni germanosilicides during solid-state interaction between Ni and heavily B-doped strained epitaxial Si1-xGex films with x=0.18, 0.32 and 0.37 is studied. No NiSi2 is found in these samples even after annealing at 850 degreesC, which can be compared to the formation of NiSi2 at 750 T on Si(I 00). Resistance and diffraction studies for the Si0.82Ge0.18 sample indicate that NiSi0.82Ge0.18 forms and the NiSi0.82Ge0.18/Si0.82Ge0.18 structure is stable from 400 to 700 degreesC. For the NiSi1-uGeu formed in all Si1-xGex samples, where u can be different from x, a strong film texturing is observed. When the Ge fraction is increased from 18 at.% to 32-37 at.%, the morphological stability of the film is degraded and a substantial increase in sheet resistance occurs already at 600 degreesC. The contact resistivity for the NiSi0.8Ge0.2/Si0.8Ge0.2 interface formed at 550 T is determined as 1.2x10(-7) Omegacm(2), which satisfies the ITRS contact resistivity requirement for the 70 nm technology node.
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| 3. |
- Isheden, Christian, et al.
(författare)
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Formation of shallow junctions by HCl-based Si etch followed by selective epitaxy of B-doped Si1-xGex in RPCVD
- 2004
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 151:6, s. C365-C368
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Tidskriftsartikel (refereegranskat)abstract
- Formation of shallow source/drain junctions by using HCl-based Si etch followed by selective deposition of in situ heavily B-doped SiGe in a reduced pressure chemical vapor deposition reactor is presented. The etching parameters were optimized to obtain a smooth surface prior to deposition of the SiGe layers. In the epitaxy process, SiGe layers with a resistivity of 5 x 10(-4) Omega cm were obtained by tuning the partial pressure of the B and Ge precursors. A problem with selectivity in the epitaxy step was encountered when combing the etch and growth processes, but a practical solution is presented. Integration issues such as loading effect, pile-up, and defect generation have also been investigated.
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| 4. |
- Isheden, Christian, et al.
(författare)
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MOSFETs with recessed SiGe Source/Drain junctions formed by selective etching and growth
- 2004
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Ingår i: Electrochemical and solid-state letters. - : The Electrochemical Society. - 1099-0062 .- 1944-8775. ; 7:4, s. G53-G55
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Tidskriftsartikel (refereegranskat)abstract
- A source/drain extension process that uses HCl etching followed by selective growth of in situ B-doped SiGe is demonstrated. The two key process steps, etching and growth, are integrated by performing them consecutively in the same chemical vapor deposition reactor. The technique has the potential to solve end-of-the-roadmap requirements on junction depth, junction abruptness, and active doping concentration.
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| 5. |
- Isheden, Christian, et al.
(författare)
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pMOSFETs with recessed and selectively regrown Si1-xGex source/drain junctions
- 2005
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 8:1-3, s. 359-362
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Tidskriftsartikel (refereegranskat)abstract
- A new source/drain formation concept based on selective Si etching followed by selective regrowth of in situ B-doped Si(1-x)Ge(x)is presented. Both process steps are performed in the same reactor to preserve the gate oxide. Well-behaved transistors are demonstrated with a negligibly low gate-to-substrate leakage current.
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| 6. |
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| 7. |
- Isheden, Christian, et al.
(författare)
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Recessed and epitaxially regrown SiGe(B) source/drain junctions with Ni salicide contacts
- 2004
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Ingår i: Silicon Front-End Junction Formation-Physics And Technology. - : Springer Science and Business Media LLC. - 1558997601 ; , s. 49-54
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Konferensbidrag (refereegranskat)abstract
- Integration issues concerning recessed epitaxial SiGe(B) source/drain junctions formed by selective Si etching followed by selective epitaxial growth of in situ heavily B-doped Si1-xGex are presented. The concept is beneficial compared to conventional ion implanted junctions, since dopant activation above the solid solubility in Si can be obtained. When integrated in the PMOS process flow, the resulting Si1-xGex layer is very rough. Several possible causes for low quality epitaxy are discussed and improvements are proposed. It is suggested that the dopant type and/or concentration in the silicon substrate can have an effect on the process.
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| 8. |
- Isheden, Christian, et al.
(författare)
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Selective Si etching using HCl vapor
- 2004
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T114, s. 107-109
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Tidskriftsartikel (refereegranskat)abstract
- Selective Si etching using HCl in a reduced pressure chemical vapor deposition reactor in the temperature range 800-1000 degrees C is investigated. At 900 degrees C, the etch process is anisotropic, exhibiting the densely packed (100), (311) and (111) surfaces. This behavior indicates that the etch process is limited by surface reaction, since the etch rate in the directions with higher atomic concentration is lower. When the temperature is decreased to 800 degrees C, etch pits occur. A more isotropic etch is obtained at 1000 degrees C, however at this temperature the masking oxide is attacked and the etch surface is rough. Thus the temperature has to be confined to a narrow window to yield desirable properties under the present process conditions.
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| 9. |
- Isheden, Christian, 1976-
(författare)
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Source and drain engineering in SiGe-based pMOS transistors
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A new shallow junction formation process, based on selective silicon etching followed by selective growth of in situ B-doped SiGe, is presented. The approach is advantageous compared to conventional ion implantation followed by thermal activation, because perfectly abrupt, low resistivity junctions of arbitrary depth can be obtained. In B-doped SiGe layers, the active doping concentration can exceed the solid solubility in silicon because of strain compensation. In addition, the compressive strain induced in the Si channel can improve drivability through increased hole mobility. The process is integrated by performing the selective etching and the selective SiGe growth in the same reactor. The main advantage of this is that the delicate gate oxide is preserved. The silicon etching process (based on HCl) is shown to be highly selective over SiO2 and anisotropic, exhibiting the densely packed (100), (311) and (111) surfaces. It was found that the process temperature should be confined between 800 ºC, where etch pits occur, and 1000 ºC, where the masking oxide is attacked. B-doped SiGe layers with a resistivity of 5×10-4 Ωcm were obtained. Well-behaved pMOS transistors are presented, yet with low layer quality. Therefore integration issues related to the epitaxial growth, such as selectivity, loading effect, pile-up and defect generation, were investigated. Surface damage originating from reactive-ion etching of the sidewall spacer and nitride residues from LOCOS formation were found to degrade the quality of the SiGe layer. Various remedies are discussed. Nevertheless, high-quality selective epitaxial growth could not be achieved with a doping concentration in the 1021 cm-3 range. The maximum doping level resulting in a high-quality layer, with the loading effect taken into account, was 6×1020 cm-3. After this careful process optimization, a high-quality layer was obtained in the recessed areas. Finally, Ni mono-germanosilicide was investigated as a material for contact formation to the epitaxial SiGe layers in the recessed source and drain areas. The formation temperature is 550 ºC and it is stable up to 700 ºC. The observation of a recessed step and lateral growth of the silicide led to a detailed treatment of the contact resistivity of the NiSi0.8Ge0.2/Si0.8Ge0.2 interface using 2-D as well as 3-D modeling. Different values were obtained for square shaped and rounded contacts, 5.0x10-8 Ωcm2 and 1.4x10-7 Ωcm2, respectively.
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| 10. |
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