Results & Discussion
Chapter 5 Future Work
The higher Ge concentration of the SiGe, the higher current we might get. So more higher Ge concentration about 30 %, 40 %, 50 % can be try later to find the optimum of the Ge concentration for the device.
Increase the Ge concentration by oxidation may be a feasible way. The Ge segregation would happen when the SiGe film be oxidized. This could lead to higher Ge concentration in the SiGe film.
Metal electrode is also an important issue to be discussed. Another metal contact pad like TiN/W might be tried.
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Fig 1.1 Energy-band diagram of the Si/SiGe HBT
Table 1. Basic Properties of Si and Ge
Fig 1.2 The different kinds of strain shown in the diagram
Fig 1.3 Si1-xGex is epitaxially grown on the Si bulk to form the Si1-xGex/Si heterojunction.
Fig 1.4 The band offset of the valance band and conduction band was schematically illustrated
Fig 1.5 The Compressive in-plane strain in SiGe lifts degeneracy and splits the VB into heavy hole (hh) and light hole (lh) states with the hh defining the VB maxima.
Fig 1.6 The mechanism of the Strained-Si on relaxed SiGe layer.
Fig 1.7 Effective carrier mobility in the Si0.17Ge0.83 channel p MOSFET and in conventional Si n and p MOSFETs as a function of the vertical electric field at room temperature
Fig 1.8 Si cap critical thickness as a function of Ge % in the uniform SiGe layer.
Fig 1.9 NW nanosensor for pH detection. (A) Schematic illustrating the conversion of a NW FET into NW nanosensors for pH sensing. The NW is contacted with two electrodes, a source (S) and drain (D), for measuring conductance.
(B) Real-time detection of the conductance for an APTES-modified SiNW for pHs from 2 to 9; the pH values are indicated on the conductance plot.
Fig 1.10 Schematic diagram of (A) selective anodization of the silicon regions not masked by nanoparticles. (B) The volume expansion of the silicon led to a decreased height contrast between the particles and the substrate. (C) After a wet etching step, silicon columns capped with a nanoparticle were formed
Fig 1.11 The mechanisms of the laser ablation formation technique
Fig 1.12 (a) VLS mechanism : the flux droplet is a metal such as Au, Ag, Pd, Pt, Ni, or Cu are elements of the crystal phase dissolved in the metallic flux droplet.
(b) SLS mechanism : the flux droplet is In, and M and E are elements of the III-V semiconductor dissolved in the flux droplet.
Fig 1.13 Schematics of the process for silicon nanodevice fabrication involving an AFM lithography step. Inset: tranmission electron imcrography of a thinned Unibond SOI substrate showing the good crystalline structure of the Si upper layer.
Fig 1.14 (a) Band diagram for ohmic contace
(b) Band diagram for barrier contact; eVo is the built-in potential of the Schottky junction
Fig 1.15 A schematic of scanning tip gating, a negatively biased conductive tip is scanned across the nanowire
Fig 1.16 (a) I-V curves under different back gate voltages of –20, -10, 0, 10, and 20V.
(b) I-V curves under different tip gate voltages. Inset: schematic showing the circuit measurement setup. (c) Local energy band benging caused by positive SPM tip gate voltage, and (d) negative tip gate voltage, (e)At negative drain-source bias, energy diagram for zero bias SPM tip gating and (f) negatively biased tip gating.
Fig 2.1 The schematic of the sidewall spacer technology.
Fig 2.2 The schematic of the oxide grown by wet oxide is about 2000~3000Å.
(a) (b)
Fig 2.3 Define the AA region, we etch the oxide film to form each oxide step by the TEL 5000. The residue thickness of the oxide is around 300~500Å and this should be precisely controlled. (a) The top view, (b) The cross-section view
Fig 2.4 Before we deposited the SiGe film, we deposited amorphous Si film first.
This purpose is due to SiGe and SiO2 has a had adhesion. The thickness of the amorphous Si film is about 150Å.
(a) (b)
Fig 2.5 The SiGe film is deposited with the ultra-high-vaccum chemical vapor deposition. The SiGe film is about 800 Å. (a) The top view, (b) The cross-section view
(a)
Fig 2.6 After defining the SiGe pattern by the Mask #2, then etching the whole SiGe up by TCP poly etcher. (a) The schematic shows the top view.
(b)
Fig 2.6 (b) The schematics shows the side view, after etching the SiGe film.
(a)
(b) (c)
Fig 2.7 Remove one side of the parallel SiGe spacer. The schematics of the Mask #3.
(a) Top view, (b) Side view, (c) The cross-section view
Fig 2.8 The figure show the Gate contact hole etching
Fig 2.9 After thermal coating Al for 5000 Å
Fig 2.10 Defined the Al contact pad in the Mask #05. And then sintering at T=430℃
for 30 min
Fig 2.11 The schematics of the two SiGe block film. There is no connection between the two block. This was used to make sure that the SiGe and Al film was etched completely in the isolation area.
Fig 2.12 The test structure of each block was used to calculate the contact resistance between Al/SiGe and Al/Poly-Si.
Fig 3.1 The Id-Vd of the Si0.93Ge0.07 nanowire with the length L=15μm.
Fig 3.2 The Id-Vd of the Si0.93Ge0.07 nanowire with the length L=50μm.
Fig 3.3 The Id-Vd of the Poly nanowire with the length L=5μm.
Fig 3.4 The Id-Vd of the Poly nanowire with the length L=15μm.
(a)
(b)
Fig 3.5 The Top view of the SEM of Si0.93Ge0.07 nanowire
(a)
(b)
Fig 3.6 The cross-section view of the SEM of Si0.93Ge0.07 nanowire
(a) The Si0.93Ge0.07 nanowire is 79.4 nm, 77.8 nm in the half width, and 149 nm, 142 nm in height.
(b) The Si0.93Ge0.07 nanowire is 78.3 nm, 72.1 nm in the half width and 149 nm, 148 nm in height.
(a)
(b)
Fig 3.7 The top view of the SEM of Poly-Si nanowire
(a)
(b)
Fig 3.8 The cross-section view of the SEM of Poly-Si nanowire
(b) The Poly-Si nanowire is 76.7 nm, 76.7 nm in the half width, and 189 nm, 174 nm in height.
(c) The Poly-Si nanowire is 71.6 nm, 76.7 nm in the half width, and 189 nm, 174 nm in height.
Fig 3.9 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=15μm.
Fig 3.10 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=30μm.
Fig 3.11 The Id-Vd of the Si0.8Ge0.2 nanowire with the length L=15μm.
Fig 3.12 The Id-Vd of the Si0.8Ge0.2 nanowire with the length L=30μm.
(a)
(b)
(c)
(d)
Fig 3.13(a)(b) The top view of the SEM of Si0.89Ge0.11 nanowire
The cross-section view of the SEM of Si0.89Ge0.11 nanowire
(c) The Si0.89Ge0.11 nanowire is 56.5 nm, 61.6 nm in width, and 86.9 nm, 97.2 nm in height.
(d) The Si0.89Ge0.11 nanowire is 44 nm in the half width, 49.1 nm in width and 85.9 nm in height.
Fig 3.14 The cross-section view of the SEM of Si0.8Ge0.2 nanowire. In this figure, it is evident that there is no nanowire in the side wall spacer
Poly-Si Si0.93Ge0.07 Si0.89Ge0.11 Si0.8Ge0.2
Etching
time 32 sec 16 sec 15 sec 17 sec
Height Width Height Width Height Width Height Width
189 82 149 81.7 84.1 44.3 150 -
Table 1. The diagram show all the lists of the nanowires we measured by SEM and the etching time of etching Poly-Si and SiGe on Mask #02
( The unit of the normalized current was A/V‧cm )
Table 2. The diagram show the lists of the normalized current we calculated. It is obvious that the Si0.89Ge0.11 has higher current
Fig 3.15 Show the normalized Id-Vd. It is obvious that the SiGe nanowire has higher current than Poly-Si one.
Fig 3.16 Show the normalized Id-Vd from 3 V to 5 V. It is obvious that the SiGe nanowire has higher current than Poly-Si one at the conducting region.
(a) Poly-Si
(b) Ge 7%
(c) Ge 11%
Table 3. Histograms of the (a) Poly-Si, (b) Si0.93Ge0.07, (c) Si0.89Ge0.11 show the nanowire diameters. The bar chart show a little Gaussian Distributions.
Fig 3.17 The Id-Vd of the Si0.93Ge0.07 nanowire with the length L=20μm after thermal annealing.
Fig 3.18 The Id-Vd of the Poly-Si nanowire with the length L=13μm after thermal annealing.
Fig 3.19 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=20μm after thermal annealing.
(a) Si0.89Ge0.11 (b) Poly-Si
Fig 3.20 Show the Source/Drain leakage current of the structure of (a) Si0.89Ge0.11, (b) Poly-Si.
Fig 3.21 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=4μm after S/D Ion Implantation.
Fig 3.22 The Id-Vd of the Poly-Si nanowire with the length L=5μm after S/D Ion Implantation.
Fig 3.23 The Id-Vd is normalized of the L=5μm which the Vg is fixed at –10V.
Fig 3.24 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=5μm after S/D Ion Implantation.
Fig 3.25 The Id-Vd of the Poly-Si nanowire with the length L=5μm after S/D Ion Implantation.
Fig 3.26 The Id-Vd is normalized of the L=4μm which the Vg is fixed at –10V. It is obvious that the current of SiGe nanowire is higher.
Fig 3.27 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=6μm after S/D Ion Implantation.
Fig 3.28 The Id-Vd of the Poly-Si nanowire with the length L=6μm after S/D Ion Implantation.
Fig 3.29 The Id-Vd is normalized which the Vg is fixed at –10V. It is obvious that the current of SiGe nanowire is higher.
( The unit of the normalized current was A/V‧cm )
Length Area S/D Implant Initial
L=5μm 13839 nm2 0.915 0.01147
L=5μm 13839 nm2 0.918 0.01312
Poly-Si
L=6μm 13839 nm2 0.962 -
L=4μm 3528 nm2 7.256 0.1178
L=5μm 3528 nm2 7.201 0.1168
Si0.89Ge0.11
L=6μm 3528 nm2 6.732 -
Table 4. The diagram list the current after S/D ion implantation then anneal at T=950
℃ for 30 min. Each term of the current was improved by the process due to reduce the contact resistance
Fig 3.30 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=2μm after S/D and Channel Ion Implantation.
Fig 3.31 The Id-Vd of the Poly-Si nanowire with the length L=2μm after S/D and Channel Ion Implantation.
Fig 3.32 The Id-Vd is normalized of the L=2μm which the Vg is fixed at –10V.
Fig 3.33 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=15μm after S/D and Channel Ion Implantation.
Fig 3.34 The Id-Vd of the Poly-Si nanowire with the length L=15μm after S/D and Channel Ion Implantation.
Fig 3.35 The Id-Vd is normalized of the L=15μm which the Vg is fixed at –10V.. It is obvious that the current of SiGe nanowire is higher.
Fig 3.36 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=30μm after S/D and Channel Ion Implantation.
Fig 3.37 The Id-Vd of the Poly-Si nanowire with the length L=30μm after S/D and Channel Ion Implantation.
Fig 3.38 The Id-Vd is normalized which the Vg is fixed at 10V and –10V. It is obvious that the current of SiGe nanowire is higher.
Fig 3.39 The Id-Vd of the Si0.89Ge0.11 nanowire with the length L=50μm after S/D and Channel Ion Implantation.
Fig 3.40 The Id-Vd of the Poly-Si nanowire with the length L=5μm after S/D and Channel Ion Implantation.
Fig 3.41 The Id-Vd is normalized which the Vg is fixed at 10V and –10V. It is obvious that the current of SiGe nanowire is higher.
Fig 3.42 The Id-Vd measured from –1V to 1V with different Vg change from –20V to 20V of the Si0.89Ge0.11 nanowire with the length L=10μm after S/D and Channel Ion Implantation.
Fig 3.43 The Id-Vd measured from –1V to 1V with different Vg change from –20V to 20V of the Poly nanowire with the length L=15μm after S/D and Channel Ion Implantation.
( The unit of the normalized current was A/V‧cm )
Table 5. The diagram list the current after S/D and Channel ion implantation then anneal at T=950℃ for 30 min. Each term of the current was improved by the process
( The unit of the normalized current was A/V‧cm ) Intrinsic Heat Treatment Source/Drain
Table 6. The table summary all the all we measured. The worlds in bold line are the average normalized current.
Intrinsic Heat Treatment Source/Drain Implantation
S/D, channel Implantation
Si0.89Ge0.11 0.1173 2.845 7.062 103.42
Poly-Si 0.0123 0.4 0.932 68.27
ratio 9.537 7.113 7.578 1.515
Table 7 The table compare the two average normalized current. The effect improvement of the SiGe is getting lower.
Fig 3.44 The Resistance-Length of the Si0.89Ge0.11 nanowire after S/D Ion Implantation. The test block is the which one contact pad. And from the extrapolation, we could get the contact resistance is 71.57Ω
Fig 3.45 The Resistance-Length of the Poly-Si nanowire after S/D Ion Implantation.
The test block is the which one contact pad. And from the extrapolation, we could get the contact resistance is 31.702Ω
Fig 3.46 (a) I-V on a 70 nm diameter. No doping (sweep –30V to 30V)
(b) I-V on a 150 nm diameter. SiH4:B2H6=1000:1 (sweep -20V to 20V) (c) I-V on a 150 nm diameter. SiH4:B2H6=2:1 (sweep 20V , 0V)