Introduction
History of chemical vapor deposition (CVD) of diamond
Material properties
Diamond properties
Properties | Si | GaAs | SiC | Natural Diamond |
---|---|---|---|---|
Density (g/cm3) | 2.329 | 5.317 | 3.216 | 3.52 |
Melting point (°C) | 1412 | 1240 | 2540 | 3827 |
Hardness (GPa) | 8.5 | 7 | 24.8 | 100 |
Young’s modulus (GPa) | 130–180 | 85 | 700 | 1050–1200 |
Poisson’s ratio | 0.22–0.24 | 0.31–0.32 | 0.1–0.21 | |
Lattice constant (Å) | 5.43 | 5.65 | 4.36 | 3.57 |
Band Gap (eV) | 1.12 | 1.42 | 3.0 | 5.45 |
Carrier mobility Electron (cm2/V·s) | 1450 | 8500 | 400 | 1800–2000 |
Hole (cm2/V·s) | 500 | 400 | 50 | 1600–2100 |
Dielectric constant | 11.7 | 10.9 | 10 | 5.7 |
Breakdown voltage (× 106 V/cm) | 0.37–0.5 | 0.6 | 2–3 | 4–20 |
Intrinsic resistivity (Ω·cm) | 1 × 103 | 1 × 108 | 1 × 1016 | |
Thermal conductivity (W/cm·K) | 1.5 | 0.5 | 5 | 20 |
Thermal expansion coef. (× 10–6/°C) | 2.6 | 5.9 | 4.7 | 1.1 |
Different forms of diamond
Diamond Type | Nitrogen (ppm) | Boron (ppm) | Color |
---|---|---|---|
Ia | 2000 | – | Clear to yellow |
Ib | 100–1000 | – | Green, brown, yellow |
Ib | 1–100 | – | Yellow |
IIa | ~ 1 | – | Colorless clear |
IIb | ~ 1 | ~ 100 | Blue |
Density (g/cm−3) | Hardness (Gpa) | Young’s modulus (GPa) | sp3 (%) | H (at%) | Gap (eV) | Surface roughness | ||
---|---|---|---|---|---|---|---|---|
SCD | 3.52 | 100 | 1050–1200 | 100 | < 0.1 | 5.45 | ||
MCD (grain size ~ 0.5–10 μm) | 3.52 | 70–100 | 800–1200 | ~ 100 | < 1 | 5.45 | 400 nm – 1 μm | |
NCD (grain size 50–100 nm) | 30–75 | 800–1020 | > 50 | < 1 | 2–4.7 | 50–100 nm | ||
UNCD (grain size ~ 3–5 nm) | 3.50 | 88–98 | 916–980 | 95–98 | < 1 | 5.4–5.65 | 20–40 nm | |
DLC | ta-C (evaporated) | ~ 3.00 | 2–5 | 757 | 3–3.5 | 5–100 nm | ||
ta-C (MSIB) | 3.0 | 30–130 | 90 ± 5 | < 9 | 0.51.5 | 5–100 nm | ||
ta-C:H | 2.9 | 61 | 75 | 22–28 | ||||
a-C:H (hard) | 1.6–2.2 | 10–20 | 300 | 30–60 | 10–40 | 0.8–1.7 | 1–30 nm | |
a-C:H (soft) | 0.9–1.6 | < 5 | 300 | 50–80 | 40–65 | 1.6–4 | 1–30 nm | |
Graphite | 2.267 | 1–2 | 9.2–13 | 0 | -0.04 | |||
Glassy Carbon | 1.3–1.55 | 2–3 | 35 | ~ 0 | 0.01 |
Electrical conductivity of PCD
Surface electrical conduction
Electrical conductivity of bulk diamond
Piezoresistivity of PCD films
Material | Description | Gauge Factor (GF) |
---|---|---|
Metals | Composition | |
Nickle/Copper | 45% Ni, 55% Cu | 2.0–2.1 |
Copper | 100% | 2.6 |
Silver | 100% | 2.9 |
Platinum/Tungsten | 92% Pt, 8% W | 4.0 |
Platinum | 100% | 6.1 |
Nickel | 100% | –12.1 |
Material | Description | Gauge Factor (GF) |
---|---|---|
Semiconductors | Types | |
Single Crystal Silicon | p-type | 100–175 |
n-type | –133 | |
Poly-Silicon | p-type | 15–30 |
n-type | –30 | |
Germanium | p-type | 48.7–101.5 |
n-type | − 147 to − 157 | |
Poly-Germanium | p-type | 30 |
n-type | − 30 to − 40 | |
Silicon Carbide | n-type | − 55 to − 994 |
GF | ρ (Ω·cm) | Boron Concentration (cm−3) | Substrate | Deposition | Doping | References |
---|---|---|---|---|---|---|
6 | 1.2 × 1016 | Diamond/SiO2 | HFCVD | [203] | ||
5.4 | 4 | Undoped carbon | MPCVD | BCl3 | [102] | |
116 | 2.5 × 1018 | Si | DC plasma CVD | B2O3 powder | [206] | |
6–25 | 5–30 | SiO2 | HFCVD | boron powder | [67] | |
8 | 0.2 | Si | MPCVD | Boron compound solid wafer | [219] | |
10 | 2.2 | Si | MPCVD | Boron compound solid wafer | [219] | |
67 | 225 | Si | MPCVD | Boron compound solid wafer | [219] | |
100 | 300 | Si | MPCVD | Boron compound solid wafer | [219] | |
1000 | 300 | Undoped PCD | MPCVD | B2H6 | ||
7–9 | 0.1 | Si | MPCVD | B(CH3)3 in ethanol | [210] | |
70–75 | 100 | Si | MPCVD | B(CH3)3 in ethanol | [210] | |
0.1 | 1000 | Si | MPCVD | B(CH3)3 in ethanol | [210] | |
30–35 | 106 | Si | MPCVD | B(CH3)3 in ethanol | [210] | |
690 | Si | MPCVD | B(CH3)3 in ethanol | [211] | ||
283* | 0.27 | Undoped PCD | MPCVD | boron powder | [212] | |
4000** | 0.1 | |||||
6.7/8.9* | ~ 1020 | Undoped PCD | MPCVD | [213] | ||
25** | ~ 1020 | Undoped PCD | MPCVD | [213] | ||
33 | 3.15 | SiO2 | HFCVD | H3BO3 in methanol and acetone | [215] | |
50 | 2.65 | SiO2 | HFCVD | H3BO3 in methanol and acetone | [215] | |
40 | 28 | SiO2 | MPCVD | B(CH3)3 | [72] | |
8 ± 0.5 | 0.01 | SiO2 | MPCVD | B(CH3)3 | [217] |
Polycrystalline diamond (PCD) film technology
Chemical vapor deposition of PCD films
Seeding Method | Sonication/abrasion | Ben | DPR | Spray/paint | DPL with spin |
---|---|---|---|---|---|
Seeding Density (cm−2) | Up to 1010 | Up to 1011 | ~ 108 | Up to 1011 | 108–1011 |
Substrate Selectivity | Most dielectric & metal | Conductive Si or Metal | Most dielectric & metal | Most dielectric & metal | Hydrophilic surface (SiO2 & Si3N4) |
Substrate Surface Effects | Scratch surface, not good for thin film | No damage | No damage | No damage | No damage |
Uniformity & Controllability | Not uniform | Uniform & repeatable on whole wafer | Uniform & repeatable on whole wafer | Not uniform | Uniform & repeatable on whole wafer |
Methods | HFCVD | MPCVD | DC-arc Jet CVD | Combustion Synthesis | RFCVD |
---|---|---|---|---|---|
Growth Rate (μm/hr) | 0.1–10 | 0.1–10 | 30–150 | 4–40 | < 0.1 |
Subst. Temp. (°C) | 300–1000 | 300–1200 | 800–1000 | 600–1400 | 700–1200 |
Growth Area (cm2) | 5–900 | 5–100 | < 2 | < 3 | 100 |
Advantages | Simple, large area | Quality, stability | High rate, good quality | Simple, high rate | High quality |
Disadvantages | Contaminations, fragile filament | Rate | Contaminations, small area | Small area | Low rate, expensive |
Technique | Bulk Processing Temperature | Polishing mechanism | Shape limitations | Si A' limitations | Special requirements | Set-up | Equipment cost | Large area processing cost | Processing time(per cm!) | Reported roughness | Parametric freedom | Surface change(contamination) |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Mechanical hipping | Room | Abrasive wear | Only planar surfaces | No limit | None | Rigid and geometry sensitive | Low | Low | Few days | 210 nm | Small | Yes |
Thermo- mechanical | 800–900 °C | Graphitization, dirTusion - | Only planar surfaces | Plate size | Need environ- mental control | Rigid and geometry sensitive | Low | Low | Tens of minutes | 5.5 run | Restricted | Yes |
CAMPF | > wc | Oxidation | Only planar surfaces | Plate size | None | Simple | Low | Low | A few hours | 49 nm | Restricted | Yes |
Laser | Room | Etching, evaporation | Non-planar surfaces possible | No limit | Need scanning of the samples | Simple | High | Medium | Few Seconds | 500 m | Large | Yes |
Ion beam | Room | Sputtering etching | Non-planar surfaces possible | Beam size | NeeJ high vacuum | Complex | High | High | Tens of hours | Mint | Restricted | Yes |
rn; | 700 = 0 | Sputtering | Non-planar surfaces possible | Plasma size | NeeJ high vacuum | Higid | High | Medium | Tens of minutes | 71 nm | Large | Yes |
Doping of PCD films
Patterning of PCD films for MEMS fabrication
Metal films for electrical contacts on diamond films
PCD films-based MEMS technologies
Dry etching of crystalline and polycrystalline diamond films
Residual stress in diamond films
Polishing and planarization of PCD films
Processes for miniaturization of PCD films-based MEMS structures
Diamond-based MEMS sensors, actuators and other devices
Diamond Film-based SAW MEMS devices
Diamond film-based Piezo-resistive MEMS sensors
PCD films-based MEMS gas sensors
PCD Films-based UV, X-ray and particle detectors
PCD field emission devices
Diamond films-based RF-MEMS
Resonator design | Quality factor Q | Measured frequency f0 | Actuation method | Mater |
---|---|---|---|---|
Cantilever [275] | 510 | ~ 230 kHz | Piezoelectric | SCD |
Doubly clamped beam [276] | 6225 | 3.022 MHz | Electrostatic | MCD |
Comb drive [278] | 36,460 | 27.352 kHz | Electrostatic | MCD |
Cantilever [277] | 15,260 | 384.9 kHz | Piezoelectric | MCD |
Cantilever [278] | 116,000 | 8–50 kHz | Piezoelectric | MCD |
Doubly clamped paddle [29] | 2400–3500 | 6–30 MHz | Piezoelectric | NCD |
Mesh membrane [29] | 3000 | 8–20 MHz | Piezoelectric | NCD |
Disk resonator[279] | 11,555 | 1.51 GHz | Electrostatic | NCD |
Doubly clamped beam [282] | ~ 3000 | 14–157 MHz | Magnetomotive | NCD |
Tuning fork [283] | 8000 | 37.0 MHz | Laser | NCD |
Square paddle (pillared) [283] | 1500 | 14.77 MHz | Laser | NCD |
Square paddle (freely suspended) [283] | 3000 | 13.85 MHz | Laser | NCD |
Ring resonator [283] | 5000 | 40.18 MHz | Laser | NCD |
Antenna structure [284] | 23,200 | 630.6 MHz | Magnetomotive | NCD |
Harp structure [281] | 600–2400 | 17–66 MHz | Magnetomotive | NCD |
Cantilever [4] | 11,460 | 11 kHz | Piezoelectric | UNCD |
Cantilever [285] | 5000–16,000 | 12–35 kHz | Piezoelectric | UNCD |
Cantilever [286] | 108 MHz | Piezoelectric | DLC (a-C) | |
Cantilever [280] | 3500 | KHz | Piezoelectric | DLC (ta-C) |
Diamond-based BioMEMS microfluidic channels
MEMS neural probes
PCD film encapsulation of Si-based MEMS devices
Ultrananocrystalline diamond (UNCD) film technology for environmental and human body implantable MEMS devices
Brief Introduction to UNCD film technology
UNCD film growth via microwave plasma chemical vapor deposition (MPCVD) using conventional diamond nanoparticle-based seeding of substrate surfaces
UNCD film growth using MPCVD bias enhanced nucleation-bias enhanced growth (BEN-BEG) process
UNCD film growth using hot filament chemical vapor deposition (HFCVD) Process
UNCD film growth via HFCVD using conventional diamond nanoparticle-based Seeding of Substrate Surfaces
Diamond Flim Structure | H2 flow (sccm) | CH4 flow (sccm) | Ar flow (sccm) | Grain size |
---|---|---|---|---|
MCD | 200 | 2 | 0 | 3–5 µm |
MCD | 50 | 2 | 50 | ~ 1 µm |
NCD | 30 | 2 | 70 | 100 s nm |
NCD | 20 | 2 | 80 | 20–50 nm |
NCD | 15 | 2 | 85 | 10–20 nm |
UNCD | 10 | 2 | 90 | 3–5 nm |
UNCD film growth via HFCVD bias enhanced nucleation-bias enhanced growth (BEN-BEG) Process
Integrated CMOS (Driver)/RF-MEMS switches with fast charging/discharging ultrananocrystalline diamond film dielectric
-
I–V measurements indicate that grain boundaries control to large extent the new paradigm charging/discharging behavior exhibited by UNCD films.
-
Measurements of the voltage needed to release the switch membrane indicate that this value decreases after charging, which suggests that charging appears to be in the bulk instead of the surface of UNCD [326].
-
Measurements of switch release voltage for RF-UNCD-MEMS switches showed that this Voltage decreases monotonically from 13 V to 0 when the charging time is increased from 10 to 500 μs. This rate of voltage’ decrease correlates with a time constant of 95 μsec, which are far superior, under comparable fields of 106 V/cm, to the time constant (10 s) of RF-MEMS switches with SiO2 or SiNx dielectric layers [326].
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Other measurements showed 5–6 orders of magnitude quicker recovery times for RF-UNCD/MEMS switches than for RF-MEMS switches with SiO2 or SiNx dielectric layers. Switches kept in the “on” position for 100 s recovered back to their original condition. In less than 50 µsec. This implies that if switches are cycled off once out of every 100 s, they will be fully recovered from any effects of charging and are ready to be reused anew; thus, the RF-UNCD/MEMS switches have to be turned off only for 0.00005% of the timeline to operate without charging failure.
Integrated multifunctional piezoelectric oxides/ultrananocrystalline diamond (UNCD™) films for a new generation of biomedical MEMS sensors and energy generation devices
Property | Si | SiC | Diamond |
---|---|---|---|
Lattice constant (Å) | 5.43 | 4.35 | 3.57 |
Cohesive energy (eV) | 4.64 | 6.34 | 7.36 |
Young’s modulus (GPa) | 130 | 450 | 1200 |
Shear modulus (GPa) | 80 | 149 | 577 |
Hardness (kg/mm2) | 1000 | 3500 | 10,000 |
Fracture strength (GP) | 1.0 | 5.2 | 5.3 |
Flexural strength (MPa) | 127.6 | 670 | 2944 |
Friction coefficient | 0.4–0.6 | 0.2–0.5 | 0.01–0.04 |