Chapter 3 IBG and IAG junctions
3.6 Summary of IBG and IAG junctions
At first, in order to reduce thermal budget, NiGe formation temperature and time are tested by measuring the sheet resistance. The most appropriate recipe is formation at 350 oC for 5 minutes.
Next, the IBG junctions are discussed. On heavily-doped substrate, very poor junction characteristic is observed by high dose phosphorous ion implantation due to the fast diffusion of Ni by virtue of defects which are generated by ion implantation.
Fluorine ion implantation before NiGe formation could effectively suppress Ni diffusion and reduce the leakage current. Moreover, better junction characteristic was observed by ion implantation to a low dose due to the less defects resulting in less Ni diffusion. However, fluorine implantation before NiGe formation would enhance the Ni diffusion to degrade junction characteristic because the fluorine ion implantation induces extra defects.
On lightly-doped substrate, good junction characteristic is more easily to be
42
obtained than on heavily-doped substrate because the deeper junction depth on lightly-doped substrate so that the Ni diffusion would not destroy the junctions. In particular, after NiGe formation, the forward current obvious increases owing to the dopant segregation at the NiGe/Ge interface. Furthermore, either phosphorous or arsenic n+/p junction would have the dopant segregation effect. And the arsenic n+/p junctions have relatively low activation concentration inferred by the I-V characteristic.
Finally, because the IAG junctions have poor junction characteristic due to the segregated n+ layer is too thin to maintain good n-p junction and the Ni fast diffusion induces large leakage current, the IBG+IAG junctions were fabricated. The IBG+IAG junction could achieve shallow junction depth and raise the forward current at the same time.
43
Table 3-1 Correction factor of samples with different shape or size[80].
CF1(d/s) Circle Square Rectangle L/W=2
Rectangle L/W=3
Rectangle L/W=4
1.0 0.9988 0.9904
1.25 1.2467 1.2248
1.5 1.4788 1.4893 1.4893
1.75 1.7196 1.7238 1.7238
2.0 1.9475 1.9475 1.9475
2.5 2.3532 2.3541 2.3541
3.0 2.2662 2.4575 2.7000 2.7005 2.7005
4.0 2.9289 3.1127 3.2246 3.2248 3.2248
5.0 3.3625 3.5098 3.5749 3.5750 3.5750
7.5 3.9273 4.0095 4.0361 4.0362 4.0362
10.0 4.1716 4.2209 4.2357 4.2357 4.2357
15.0 4.3646 4.3882 4.3947 4.3947 4.3947
20.0 4.4364 4.4516 4.4553 4.4553 4.4553
32.0 4.4791 4.4878 4.4899 4.4899 4.4899
40.0 4.5076 4.5120 4.5129 4.5129 4.5129
Infinity 4.5324 4.5324 4.5324 4.5324 4.5324
44
Table 3-2 Metal/n-Ge contact resistance recorded by previous studies.
Contact Doping Activation Test Structure Contact Resistivity
(Ω-cm2)
Junction Depth
(nm)
Source
NiGe P+Sb IBG 500oC/RTA CTLM 5.5x10-7 200 [27]
NiGe As IBG 900oC/LSA CTLM 1.4x10-6 N.A. [25]
NiGe As IBG 800oC/LSA CTLM 5.0x10-5 30 [25]
NiGe P IBG 500oC/FA TLM 8.8x10-5 N.A. [68]
NiGex P IBG 500oC/FA TLM 3.5x10-6 N.A. [68]
Al P-epi None CTLM 4.6x10-5 N.A. [25]
Ti As I/I 600oC/RTA CTLM 1.0x10-3 N.A. [25]
Ti P I/I 650oC/N.A. CTLM 4.9x10-5 N.A. [66]
TaN P I/I 650oC/N.A. CTLM 2.7x10-5 300 [26]
NiGe P IBG +
As IAG
500oC/RTA CBKR 2x10-6 150 This
work
45
300 350 400
0 10 20 30 40 50 60 70 80
S h eet Resi st an ce (
squ are )
Temperature (
oC)
Fig.3-1 Sheet resistance as a function of annealing temperatures for 5 minutes of NiGe formation.
46
3 4 5
0 10 20 30 40 50 60 70 80
S h eet Resi st an ce (
squ are )
Time (min)
Fig.3-2 Sheet resistance as a function of annealing times at 350oC of NiGe formation.
47
30 35 40 45 50 55 60
100 200 300 400 500 600 700 800
NiGe (211) NiGe (020)
Intensity (c p s)
2 Theta (degree)
NiGe-Orthorhombic a = 5.381 Å b = 3.428 Å c = 5.811 Å
NiGe (111) NiGe (210) NiGe (112)
Fig.3-3 X-ray diffraction spectrum of the NiGe/Ge structure formed by 350C annealing shows polycrystal NiGe phases.
48
-1.0 -0.5 0.0 0.5 1.0
10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103
Current Dens ity (A/c m
2)
Voltage (V)
P,20keV,1x1015 P,50keV,5x1013
Fig.3-4 Current-voltage curve of conventional junctions of implantation by phosphorus at 20keV to a dose of 1x1015 cm-2 and 50keV to a dose of 5x1013 cm-2 and activation at 600oC for 60 seconds on heavily-doped substrate.
49
-1.0 -0.5 0.0 0.5 1.0
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Dosage (ions/cm2) 1x1015
5x1013 1x1013 5x1012
Cu rr en t Den sit y (A/cm 2 )
Voltage (V)
Fig.3-5 Current-voltage curve of conventional junctions of implantation by phosphorus at 50keV to a dose of 1x1015, 5x1013, 1x1013, 5x1012 cm-2 and activation at 600oC for 60 seconds in lightly-doped substrate.
50
-1.0 -0.5 0.0 0.5 1.0
10-5 10-4 10-3 10-2 10-1 100 101 102
Cu rr en t Den sit y (A/cm
2 )
Voltage (V)
Dosage (ions/cm2) 1x1015
5x1013 1x1013
Fig.3-6 Current-voltage of conventional junctions of implantation by arsenic at 30keV to a dose of 1x1015, 5x1013, 1x1013 cm-2 and activation at 600oC for 60 seconds in lightly-doped substrate.
51
-1 0 1
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Current Dens ity (A/c m
2)
Voltage (V)
300oC,5min 325oC,5min 350oC,5min 400oC,5min 450oC,5min
Fig.3-7 Current-voltage curves of IBG junctions forming with different formation temperature of implantation by phosphorus at 20keV to a dose of 1x1015 cm-2 and activation at 600oC for 60 seconds on heavily-doped substrate.
52
Fig.3-8 Diffusivity of elements in Ge [78].
53 325oC,5min
350oC,5min 400oC,5min 325oC,5min with F 350oC,5min with F 400oC,5min with F
-1 0 1
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Current Dens ity (A/c m2 )
Voltage (V)
Fig.3-9 Current-voltage curves of fluorine implantation before NiGe formation and IBG junctions with different formation temperature of implantation by phosphorus at 20keV to a dose of 1x1015 cm-2 and activation at 600oC for 60 seconds in heavily-doped substrate. The fluorine implantation is at 10keV to a dose of 1x1015 cm-2.
54
350oC,5min
350oC,5min with F 400oC,5min
400oC,5min with F 450oC,5min
450oC,5min with F
-1.0 -0.5 0.0 0.5 1.0
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Current Dens ity ( A/c m
2)
Voltage (V)
Fig.3-10 Current-voltage curves of fluorine implantation before NiGe formation and IBG junctions with different formation temperature implantation by phosphorus at 50keV to a dose of 5x1013 cm-2 and activation at 600oC for 60 seconds in heavily-doped substrate. The fluorine implantation is at 10keV to a dose of 1x1015 cm-2.
55
-1.0 -0.5 0.0 0.5 1.0
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Cu rr en t Den sit y (A/cm
2 )
Voltage (V)
Dosage (ions/cm2) 1x1015
5x1013 1x1013 5x1012
Fig.3-11 Current-voltage curve of IBG junctions of implantation by phosphorus at 50keV to a dose of 1x1015, 5x1013, 1x1013, 5x1012 cm-2 and activation at 600oC for 60 seconds in lightly-doped substrate.
56
-4 -3 -2 -1 0 1 2 3 4 5 6 7
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8
MG5
MG4
MG2 MG6
MG3 MG1
SG5a
SG3c
SG2c
Total Energy (eV)
Position (Angstrom)
NiGe(112)//Ge(001)_P
Ge
SG1a (Interface)
(a)
57
-4 -3 -2 -1 0 1 2 3 4 5 6 7
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8
MG5 MG4 MG6 MG3
MG2
MG1
SG5a
SG3a
SG2c
Total Energy (eV)
Position (Angstrom)
NiGe(112)//Ge(001)_AsGe (Interface)
SG1c
(b)
Fig.3-12 Total energy of the interfacial structure as a function of the dopant position.
One of the Ge atoms is replaced by (a) P atom and (b) As atom.
58
-1.0 -0.5 0.0 0.5 1.0
10-5 10-4 10-3 10-2 10-1 100 101 102
Cu rr en t Den sit y (A/cm
2 )
Voltage (V)
Dosage (ions/cm2) 1x1015
5x1013 1x1013
Fig.3-13 Current-voltage curves of IBG junctions forming with implantation by arsenic at 30keV to different dose and activation at 600oC for 60 seconds on lightly-doped substrate.
59
-1.0 -0.5 0.0 0.5 1.0
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Cu rr en t Den sit y (A/cm
2 )
Voltage (V)
600oC,10s 550oC,10s 500oC,10s
Fig.3-14 Current-voltage curves of IAG junctions with implantation by arsenic at 10keV to a dose of 1x1015 cm-2 with different annealing temperature.
60
(a)
(b)
Fig.3-15 Cross-sectional TEM micrography of the NiGe/Ge structure with IAG process after annealing at (a) 500C and (b) 550C for 10 sec.
61
-1.0 -0.5 0.0 0.5 1.0
10-5 10-4 10-3 10-2 10-1 100 101 102 103
Cu rr en t Den sit y (A/cm
2 )
Voltage (V)
MSB(500oC,10s)
Al
Fig.3-16 Current-voltage curve of IBG (phosphorus at 20keV to a dose of 1x1015 cm-2 and activation at 600oC for 10 seconds) + IAG(arsenic at 10keV to a dose of 1x1015 cm-2) junction with 500C for 10 seconds annealing.
62
10-6 10-5 10-4
0 20 40 60 80 100
Cu m u lat ive Per centage (%)
Specific Contact Resistivity (
-cm
2)
Al contact
IBG IBG+IAG with F
IBG+IAG w/o F
Fig.3-17 Cumulative distribution of contact resistivity extracted by the CBKR structure. The contact areas are 10x10, 5x5 and 3x3 um2.
63
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
1017 1018 1019 1020 1021
Depth (
m)
Co n centration ( 1/c m
3)
101 102 103 104 105 106
In te n sit y ( a.u.)
P Ge
Fig.3-18 Secondary ion mass spectrometer depth profiles of the conventional junction of implantation by phosphorus at 20keV to a dose of 1x1015 cm-2 and activation at 600oC for 10 seconds on lightly-doped substrate.
64
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
1017 1018 1019 1020 1021
Depth (
m)
Co n centration ( 1/c m
3)
101 102 103 104 105 106
In te n sit y ( a.u.)
P Ge
Ni
NiGe/Ge interface
Fig.3-19 Secondary ion mass spectrometer depth profiles of the NiGe-contacted junction formed by the IBG process of implantation by phosphorus at 20keV to a dose of 1x1015 cm-2 and activation at 600oC for 10 seconds on lightly-doped substrate.
65
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
1017 1018 1019 1020 1021
Co n centration ( 1/c m
3)
Depth (
m)
101 102 103 104 105 106
In te n sit y ( a.u.)
Ge
Ni
P As
NiGe/Ge interface
Fig.3-20 Secondary ion mass spectrometer depth profiles of the NiGe-contacted junction formed by the IBG (implantation by phosphorus at 20keV to a dose of 1x1015 cm-2 and activation at 600oC for 10 seconds) + IAG (implantation by arsenic at 10keV to a dose of 1x1015 cm-2 and annealing at 500C and 10 seconds).
66
Chapter 4
Conclusions and Future Works
4.1 Conclusions
In the thesis, the thermal budget for NiGe formation is studied firstly. It is concluded that a 350 oC annealing for 5 minutes ensures that NiGe could completely form. The highest process temperature is limited to 500 C. Beyond that, agglomeration of the NiGe film occurs. In additon, the main NiGe crystal orientations are (2 1 0), (1 1 2), and (1 1 1) identified by XRD diffraction.
For the Al-contacted conventional junctions, good junction characteristic can be achieved on either heavily-doped or lightly-doped substrate. In particular, band-to-band tunneling can also be observed on the high doping concentration N+/P junction on heavily-doped substrate. Because the lower concentration of substrate would cause the wider depletion width, and the wider depletion width would cause the higher reverse bias current, therefore, the reverse bias current on lightly-doped substrate is higher than that on heavily-doped substrate. Besides, the reverse bias current of the arsenic implanted junction is higher than that of the phosphorus implanted junction because the activation ratio of arsenic is relatively lower than that of phosphorus so that the junction depth of the arsenic implanted junction is shallower.
Furthermore, the heavier arsenic atom would generate more defects than the lighter phosphorous atom. Therefore, the reverse bias current of the arsenic implanted junction is higher.
To evaluate the feasibility of the self-aligned metal germanide process, NiGe-contacted junctions are investigated. On heavily-doped substrate, very poor
67
junction characteristic is observed by high dose phosphorous ion implantation due to the fast diffusion of Ni by virtue of defects which are generated by ion implantation.
Fluorine ion implantation before NiGe formation could effectively suppress Ni diffusion and reduce the leakage current. Better junction characteristic is observed by ion implantation to a lower dose due to less defects resulting in less Ni diffusion.
However, fluorine implantation before NiGe formation would enhance the Ni diffusion to degrade junction characteristic because the fluorine ion implantation induces extra defects. On the other hand, good junction characteristic is more easily to be obtained on lightly-doped substrate than on heavily-doped substrate because the deeper junction depth on lightly-doped substrate so that the Ni diffusion would not destroy the junctions. In particular, after NiGe formation, the forward current increases obviously, in comparison with the Al-contacted junction, owing to the dopant segregation at the NiGe/Ge interface. The IBG junction with ion implantation to a lower dose has a higher degree of forward current improvement. Furthermore, either phosphorous or arsenic n+/p junction would have the dopant segregation effect, and the arsenic n+/p junctions have relatively low activation concentration inferred by the I-V characteristic.
The IAG junctions have poor junction characteristic due to the segregated n+ layer is too thin to maintain good n-p junction and the Ni fast diffusion induces large leakage current. The IBG+IAG junction could achieve shallow junction depth and raise the forward current at the same time. On the bases of first-principles calculations, NiGe formation would reduce the contact resistance on the P- doped and As-doped junctions (IBG process) while As would be a better choice for the implantation after NiGe process (IAG process). The measured NiGe/n-Ge contact resistance of the IBG process is about 2x10-5 -cm2 and the lowest contact resistance of the IBG+IAG process is 2x10-6 -cm2.
68
To sum up, the thesis proposed that the IBG junctions would be destroyed by Ni fast diffusion which depends on the amount of defects, and the dopant segregation effect could reduce the contact resistance. The IBG+IAG process can form a junction with shallower junction depth, lower leakage current, and lower contact resistance in comparison with previous studies.
4.2 Future Works
In this thesis, dopant diffusion, dopant diffusion due to defects, Ni diffusion, and Ni diffusion due to defects and the mechanism of Ni diffusion are all necessary to be proved by SIMS analysis or other material analysis. Dopant diffusion model in Ge should be investigated thoroughly. Furthermore, the XRD analysis of NiGe after IBG and IAG process and the interaction between Ni and F to affect Ni diffusion also need to be done. Because F implantation may cause additional defects, CF4 plasma treatment could be studied to suppress Ni diffusion without implantation damage. In addition, although a low contact resistance has been achieved by IBG+IAG process, the contact resistance may be further reduced by improving the processes. At first, the implantation dosage of the IAG process can be raised to 3x1015 or 5x1015 to observe whether more dopants can segregate at the interface to form a higher concentration n+ layer to achieve lower contact resistance. Secondly, increasing the annealing time of the IAG process may also be another way to let more dopants segregate. Thirdly, whether forming other metal germanide or implanting other dopants could segregate more at the interface to reduce contact resistance need to be studied. Furthermore, improving the thermal stability of NiGe to enhance the segregation effect should also be studied. After all the processes are optimized, short channel Ge NMOSFET integrated the IBG+IAG S/D junctions should be fabricated in order to verify the
69
improvement on real MOSFETs.
However, previous research [38] shows that germanide overgrows over the SiO2
isolation by one-step high temperature annealing (330oC) and germanium voids left around the corner of isolation. This phenomenon could also be observed in the thesis as shown in Fig. 4-1. If the junctions are applied on Ge MOSFET, the voids would interrupt the connection between S/D and the inverted channel. Therefore, it is necessary to solve this problem. There is a method raised by [38] to avoid producing the voids - two-step NiGe formation process. As a result, NiGe two-step formation process applied on the IBG and IAG junctions should be studied.
70
Fig.4-1 Cross-sectional TEM micrography of the NiGe/Ge structure at the junction edge.
SiO
2Al
Ge
void
71
References
[1] D. P. Brunco, B. De Jaeger, G. Eneman, J. Mitard, G. Hellings, A. Satta, et al.,
"Germanium MOSFET Devices: Advances in Materials Understanding, Process Development, and Electrical Performance," J. Electrochem. Soc., vol.
155, pp. H552-H561, 2008.
[2] S. E. Thompson and S. Parthasarathy, "Moore's law: the future of Si microelectronics," Materials Today, vol. 9, pp. 20-25, 2006.
[3] K. Martens, B. De Jaeger, R. Bonzom, J. Van Steenbergen, M. Meuris, G.
Groeseneken, et al., "New interface state density extraction method applicable to peaked and high-density distributions for Ge MOSFET development," IEEE Electron Device Lett., vol. 27, pp. 405-408, 2006.
[4] C. Chi On, F. Ito, and K. C. Saraswat, "Nanoscale germanium MOS Dielectrics-part I: germanium oxynitrides," IEEE Trans. Electron Devices, vol.
53, pp. 1501-1508, 2006.
[5] C. Chi On, K. Hyoungsub, D. Chi, P. C. McIntyre, and K. C. Saraswat,
"Nanoscale germanium MOS Dielectrics-part II: high-k gate dielectrics,"
IEEE Trans. Electron Devices, vol. 53, pp. 1509-1516, 2006.
[6] Y. Oniki, H. Koumo, Y. Iwazaki, and T. Ueno, "Evaluation of GeO desorption behavior in the metal/GeO2/Ge structure and its improvement of the electrical characteristics," J. Appl. Phys., vol. 107, pp. 124113-1-124113-5, 2010.
[7] K. Kita, C. H. Lee, T. Nishimura, K. Nagashio, and A. Toriumi, "Study of Kinetic Behaviors of GeO in GeO2/Ge Stacks," ECS Tran., vol. 16, pp.
187-194, 2008.
[8] N. Lu, W. Bai, A. Ramirez, C. Mouli, A. Ritenour, M. L. Lee, et al., "Ge diffusion in Ge metal oxide semiconductor with chemical vapor deposition HfO2 dielectric," Appl. Phys. Lett., vol. 87, pp. 051922-1-051922-3, 2005.
[9] E. Simoen and J. Vanhellemont, "On the diffusion and activation of ion-implanted n-type dopants in germanium," J. Appl. Phys., vol. 106, pp.
103516-1-103516-4, 2009.
[10] C. O. Chui, K. Gopalakrishnan, P. B. Griffin, J. D. Plummer, and K. C.
Saraswat, "Activation and diffusion studies of ion-implanted p and n dopants in germanium," Appl. Phys. Lett., vol. 83, pp. 3275-3277, 2003.
[11] C. O. Chui, L. Kulig, J. Moran, W. Tsai, and K. C. Saraswat, "Germanium n-type shallow junction activation dependences," Appl. Phys. Lett., vol. 87, pp.
091909-1-091909-3, 2005.
[12] P. Tsouroutas, D. Tsoukalas, I. Zergioti, N. Cherkashin, and A. Claverie,
"Diffusion and activation of phosphorus in germanium," Mater. Sci. Semicond.
72
Process., vol. 11, pp. 372-377, 2008.
[13] T. Liu and M. K. Orlowski, "Arsenic diffusion in boron-doped germanium,"
Electronics Lett., vol. 49, pp. 154-156, 2013.
[14] T. Nishimura, K. Kita, and A. Toriumi, "Evidence for strong Fermi-level pinning due to metal-induced gap states at metal/germanium interface," Appl.
Phys. Lett., vol. 91, pp. 123123-1-123123-3, 2007.
[15] M. Kobayashi, A. Kinoshita, K. Saraswat, H. S. P. Wong, and Y. Nishi, "Fermi level depinning in metal/Ge Schottky junction for metal source/drain Ge metal-oxide-semiconductor field-effect-transistor application," J. Appl. Phys., vol. 105, pp. 023702-6-1-023702-6, 2009.
[16] A. Dimoulas, P. Tsipas, A. Sotiropoulos, and E. K. Evangelou, "Fermi-level pinning and charge neutrality level in germanium," Appl. Phys. Lett., vol. 89, pp. 252110-1-252110-3, 2006.
[17] F. A. Trumbore, Solid Solubilities of Impurity Elements in Germanium and Silicon, 1960.
[18] A. Satta, E. Simoen, T. Clarysse, T. Janssens, A. Benedetti, B. De Jaeger, et al.,
"Diffusion, activation, and recrystallization of boron implanted in preamorphized and crystalline germanium," Appl. Phys. Lett., vol. 87, pp.
172109-1-172109-3, 2005.
[19] R. Duffy and M. Shayesteh, "Germanium Doping, Contacts, and Thin-Body Structures," ECS Tran., vol. 45, pp. 189-201, 2012.
[20] G. Nicholas, B. De Jaeger, D. P. Brunco, P. Zimmerman, G. Eneman, K.
Martens, et al., "High-Performance Deep Submicron Ge pMOSFETs With Halo Implants," IEEE Trans. Electron Devices, vol. 54, pp. 2503-2511, 2007.
[21] R. Li, H. B. Yao, S. J. Lee, D. Z. Chi, M. B. Yu, G. Q. Lo, et al.,
"Metal-germanide Schottky Source/Drain transistor on Germanium substrate for future CMOS technology," Thin Solid Films, vol. 504, pp. 28-31, 2006.
[22] A. Delabie, F. Bellenger, M. Houssa, T. Conard, S. Van Elshocht, M. Caymax, et al., "Effective electrical passivation of Ge(100) for high-k gate dielectric layers using germanium oxide," Appl. Phys. Lett., vol. 91, pp.
082904-1-082904-3, 2007.
[23] R. Zhang, T. Iwasaki, N. Taoka, M. Takenaka, and S. Takagi, "High mobility Ge pMOSFETs with 1nm thin EOT using Al2O3/GeOx/Ge gate stacks fabricated by plasma post oxidation," in VLSI Symp. Tech. Dig., pp. 56-57, 2011.
[24] S. Takagi, R. Zhang, S. H. Kim, N. Taoka, M. Yokoyama, J. K. Suh, et al.,
"MOS interface and channel engineering for high-mobility Ge/III-V CMOS,"
in IEDM Tech. Dig., 2012, pp. 23.1.1-23.1.4.
73
[25] K. Martens, A. Firrincieli, R. Rooyackers, B. Vincent, R. Loo, S. Locorotondo, et al., "Record low contact resistivity to n-type Ge for CMOS and memory applications," in IEDM Tech. Dig., 2010, pp. 18.4.1-18.4.4.
[26] Z. Wu, C. Wang, W. Huang, C. Li, H. Lai, and S. Chen, "Ohmic Contact Formation of Sputtered TaN on n-Type Ge with Lower Specific Contact Resistivity," ECS J. Solid State Sci. Technol., vol. 1, pp. P30-P33, 2012.
[27] G. Thareja, S. L. Cheng, T. Kamins, K. Saraswat, and Y. Nishi, "Electrical Characteristics of Germanium n+/p Junctions Obtained Using Rapid Thermal Annealing of Coimplanted P and Sb," IEEE Electron Device Lett., vol. 32, pp.
608-610, 2011.
[28] T. Shibata, K. Hieda, M. Sato, M. Konaka, R. L. M. Dang, and H. Iizuka, "An optimally designed process for submicron MOSFETs," in IEDM Tech. Dig., 1981, pp. 647-650.
[29] D. B. Scott, Y. C. See, C. K. Lau, and R. D. Davies, "Considerations for scaled CMOS source/drains," in IEDM Tech. Dig., 1981, pp. 538-541.
[30] N. Yokoyama, T. Ohnishi, K. Odani, H. Onodera, and M. Abe, "Ti/W silicide gate technology for self-aligned GaAs MESFET VLSIs," in IEDM Tech. Dig., 1981, pp. 80-83.
[31] S. Gaudet, C. Detavernier, A. J. Kellock, P. Desjardins, and C. Lavoie, "Thin film reaction of transition metals with germanium," J. Vac. Sci. Technol. A, vol.
24, pp. 474-485, 2006.
[32] J. Y. Spann, R. A. Anderson, T. J. Thornton, G. Harris, S. G. Thomas, and C.
Tracy, "Characterization of nickel Germanide thin films for use as contacts to p-channel Germanium MOSFETs," IEEE Electron Device Lett., vol. 26, pp.
151-153, 2005.
[33] Q. Zhang, N. Wu, T. Osipowicz, L. K. Bera, and C. Zhu, "Formation and Thermal Stability of Nickel Germanide on Germanium Substrate," Jpn. J.
Appl. Phys., vol. 44, pp. L1389-L1391, 2005.
[34] D. R. Gajula, D. W. McNeill, B. E. Coss, H. Dong, S. Jandhyala, J. Kim, et al.,
"Low temperature fabrication and characterization of nickel germanide Schottky source/drain contacts for implant-less germanium p-channel metal-oxide-semiconductor field-effect transistors," Appl. Phys. Lett., vol. 100, pp. 192101-1-192101-3, 2012.
[35] S. Hong-Sik, O. Se-Kyung, K. Min-Ho, J. Jae-Hyung, O. Jungwoo, P. Majhi, et al., "Improvement of thermal stability of Ni-germanide with co-sputtering of nickel and palladium for high performance Ge CMOSFET," in ISDRS Dig., 2011, pp. 1-2.
[36] S. Gaudet, C. Detavernier, C. Lavoie, and P. Desjardins, "Reaction of thin Ni
74
films with Ge: Phase formation and texture," J. Appl. Phys., vol. 100, pp.
034306-1-034306-10, 2006.
[37] F. Nemouchi, D. Mangelinck, C. Bergman, G. Clugnet, P. Gas, and J. L. Labar,
"Simultaneous growth of Ni5Ge3 and NiGe by reaction of Ni film with Ge,"
Appl. Phys. Lett., vol. 89, pp. 131920-3, 2006.
[38] D. P. Brunco, K. Opsomer, B. De Jaeger, G. Winderickx, K. Verheyden, and M.
Meuris, "Observation and Suppression of Nickel Germanide Overgrowth on Germanium Substrates with Patterned SiO2 Structures," Electrochem.
Solid-State Lett., vol. 11, pp. H39-H41, 2008.
[39] F. Nemouchi, V. Carron, J. L. Lábár, L. Vandroux, Y. Morand, T. Morel, et al.,
"Formation of NiGe through germanium oxide on Ge(001) substrate,"
Microelectronic Eng., vol. 107, pp. 178-183, 2013.
[40] S.-L. Hsu, C.-H. Chien, M.-J. Yang, R.-H. Huang, C.-C. Leu, S.-W. Shen, et al., "Study of thermal stability of nickel monogermanide on single- and polycrystalline germanium substrates," Appl. Phys. Lett., vol. 86, pp.
251906-1-251906-3, 2005.
[41] O. Nakatsuka, A. Suzuki, A. Sakai, M. Ogawa, and S. Zaima, "Impact of Pt Incorporation on Thermal Stability of NiGe Layers on Ge(001) Substrates," in IWJ Tech. Dig., 2007, pp. 87-88.
[42] S. Zhu, M. B. Yu, G. Q. Lo, and D. L. Kwong, "Enhanced thermal stability of nickel germanide on thin epitaxial germanium by adding an ultrathin titanium layer," Appl. Phys. Lett., vol. 91, pp. 051905-1-051905-3, 2007.
[43] M.-H. Kao, "A Study on the Contact Resistance Reduction in Metal/n-type Germanium Contacts," Master thesis, Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, 2012.
[44] A. V. Thathachary, K. N. Bhat, N. Bhat, and M. S. Hegde, "Fermi level depinning at the germanium Schottky interface through sulfur passivation,"
Appl. Phys. Lett., vol. 96, pp. 152108-1-152108-3, 2010.
[45] A. Dimoulas, P. Tsipas, A. Sotiropoulos, and E. K. Evangelou, "Fermi-level pinning and charge neutrality level in germanium," Appl. Phys. Lett., vol. 89, p.
252110-1-252110-3, 2006.
[46] J. Y. J. Lin, A. M. Roy, A. Nainani, Y. Sun, and K. C. Saraswat, "Increase in current density for metal contacts to n-germanium by inserting TiO2 interfacial layer to reduce Schottky barrier height," Appl. Phys. Lett., vol. 98, pp.
092113-1-092113-3, 2011.
[47] K. Ikeda, Y. Yamashita, N. Sugiyama, N. Taoka, and S.-i. Takagi, "Modulation of NiGe/Ge Schottky barrier height by sulfur segregation during Ni germanidation," Appl. Phys. Lett., vol. 88, pp. 152115-1-152115-3, 2006.
75
[48] J.-R. Wu, Y.-H. Wu, C.-Y. Hou, M.-L. Wu, C.-C. Lin, and L.-L. Chen, "Impact of fluorine treatment on Fermi level depinning for metal/germanium Schottky junctions," Appl. Phys. Lett., vol. 99, pp. 253504-1-253504-3, 2011.
[48] J.-R. Wu, Y.-H. Wu, C.-Y. Hou, M.-L. Wu, C.-C. Lin, and L.-L. Chen, "Impact of fluorine treatment on Fermi level depinning for metal/germanium Schottky junctions," Appl. Phys. Lett., vol. 99, pp. 253504-1-253504-3, 2011.