Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/26—Deposition of carbon only
  • C23C16/27—Diamond only
  • C23C16/278—Diamond only doping or introduction of a secondary phase in the diamond
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/26—Deposition of carbon only
  • C23C16/27—Diamond only
  • C23C16/274—Diamond only using microwave discharges
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
  • C30B25/02—Epitaxial-layer growth
  • C30B25/10—Heating of the reaction chamber or the substrate
  • C30B25/105—Heating of the reaction chamber or the substrate by irradiation or electric discharge
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
  • C30B25/02—Epitaxial-layer growth
  • C30B25/16—Controlling or regulating
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
  • C30B25/02—Epitaxial-layer growth
  • C30B25/16—Controlling or regulating
  • C30B25/165—Controlling or regulating the flow of the reactive gases
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/02—Elements
  • C30B29/04—Diamond

Definitions

• the present invention relates generally to single crystal diamond manufactured by chemical vapor deposition (CVD). More specifically, the invention is concerned with high quality, ultratough single crystal CVD diamond doped with boron. The invention also relates to methods of manufacturing the same.
• CVD chemical vapor deposition
• SC-CVD single-crystal CVD diamond
• This diamond material can be produced to exhibit a range of optical and mechanical properties, either by optimizing the CVD growth or by post-growth treatment.
• the hardness of the SC-CVD can be significantly enhanced by high-pressure/high-temperature (HPHT) annealing (Yan et al, Phys. Stat. SoL, 2004). This treatment also reduces the measured fracture toughness and provides a means by which to tune the hardness/toughness.
• HPHT high-pressure/high-temperature
• Diamond has been acknowledged as the hardest material known to man; the intrinsic hardness for natural single crystal diamond is around 100 GPa. As noted above, however, diamond is also known as a brittle material. It has been reported that fracture toughness (Kic) for type Ia diamond is between 7.0 and 8.4 MPa m 1/2 ; for type Ha diamond, Kic is 4.2 - 5.6 MPa m m (Novikov et al, J. Hard Mater., 1993; Patridge et al, Materials Science and Technology, 1994).
• SC-CVD single crystal CVD diamond
• MPCVD Microwave Plasma assisted Chemical Vapor Deposition
• a gas chemistry including H 2 /CH4/N 2 /O 2 has been used in the MPCVD process for diamond growth.
• the (100) growth was significantly enhanced by varying the growth conditions (including substrate temperature, pressure, N 2 and O 2 flow rate) and the color of the SC-CVD ranges from dark brown, to light brown, to near colorless, to colorless.
• Ultra high hardness (> 150 GPa) and toughness (> 30 MPa m 1/2 ) have been reported for such crystals (Yan et al, Physica. Status. Solidi., 2004).
• U.S. Patent No. 5,981,057 is directed to a CVD diamond layer containing boron dopant atoms in a concentration of at least 0.05 atomic percent.
• the diamond layer has an average tensile rupture strength of at least 600 MPa with the nucleation face in tension, and at least 300 MPa with the growth face in tension. Both tensile rupture strengths were measured by a three point bend test on a sample 11 mm in length, 2 mm in width, and with a thickness of
• U.S. Patent No. 7,201,886 is directed to a diamond tool comprising a shaped diamond having at least one layer of single crystal diamond heavily doped to create a visible color.
• the dopant can be boron.
• U.S. Patent No. 7,160,617 relates to a layer of single crystal boron doped diamond produced by CVD and having a total boron concentration which is uniform.
• U.S. PatentNo. 6,858,078 to Hemley et al which is incorporated herein by reference, is directed to an apparatus and method for diamond production.
• the disclosed apparatus and method can lead to the production of diamonds that are light brown to colorless.
• U.S. Patent Application No. 10/889,171 which is incorporated herein by reference, is directed to annealing single-crystal chemical vapor deposition diamonds. Important inventive features include raising the CVD diamond to a set temperature of at least 1500 0 C and a pressure of at least 4.0 GPa outside of the diamond stable phase.
• the present invention achieves its objective in part through the incorporation of boron into the diamond.
• the present invention relates to a single-crystal boron-doped diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 22 MPa m 1/2 .
• the method for growing single-crystal boron doped diamond of high toughness can include the following steps: i) placing a seed diamond in a heat sink holder made of a material that has a high melting point and high thermal conductivity to minimize temperature gradients across the growth surface of the diamond; ii) controlling the temperature of a growth surface of the diamond such that the temperature of the growing diamond crystals is in the range of about 900-1500 0 C; and iii) growing single-crystal diamond by microwave plasma chemical vapor deposition on the growth surface of a diamond in a deposition chamber 5 - 20% CH 4 ZH 2 , 5 - 20% O 2 ZCH 4 , 0 - 20 % N 2 ZCH 4 and a source of boron.
• the growth rate for such diamond is from 20 - 100 ⁇ mZh.
• the invention embraces single-crystal boron-doped diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 22 MPa TCL 12 .
• the hardness can be greater than about 60 GPa.
• FIG. 1 provides a Vickers Hardness vs. Fracture Toughness Plot for natural Ia, Ha, Ib,
• FIG. 2 depicts indentation patterns for various diamonds.
• FIG. 3 provides pictures of light brown, colorless, and faint blue boron doped
• FIG. 4 provides photoluminescence spectra for light brown, colorless and faint blue boron doped SC-CVD diamonds.
• FIG. 5 provides absorption coefficient of light brown, colorless and faint blue boron doped SC-CVD diamonds.
• FIG. 6 provides IR spectra of light brown, colorless, and faint blue boron doped
• FIG. 7 provides a photoluminescence spectrum of a boron/nitrogen doped single-crystal CVD diamond.
• FIG. 8 provides a modified Kanda diagram, wherein horizontal lines represent the relative concentration of nitrogen donors (ND) in each type of growth sector; inclined lines represent the concentration of boron acceptors, NA, in each type of growth sector as a function of the amount of boron dopant added to the synthesis capsule. See Reference (Burns et al, J.
• the present invention relates to further improvements in mechanical properties of single-crystal diamond fabricated by microwave plasma assisted chemical vapor deposition at high growth rates. Such further improvements can be observed after boron and/or nitrogen doping. Additional improvements can be observed when boron/nitrogen doping is performed in conjuction with low pressure/high temperature (LPHT) annealing, which is the subject of U.S. Patent Application No. 12/244,053 and U.S. Provisional Application No. 61/108,283, both of which are incorporated herein by reference. Boron/nitrogen incorporation can dramatically increase the toughness of single-crystal CVD diamond, leading to a material that can be termed ultratough.
• LPHT low pressure/high temperature
• LPHT annealing can enhance intrinsic hardness of this diamond by a factor of two without appreciable loss in fracture toughness.
• This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.
• Various boron containing single crystal diamonds were synthesized by high density MPCVD at 5 - 20% CU 4 ZU 2 , 5 - 20% O 2 ICU 4 , 0 - 20 % N 2 ZCU 4 , 100 - 400 Torr, and at temperatures ranging from 900 0 C to 1500 0 C. It must be noted that other gases can be subsituted for O 2 , such other gases containing oxygen within the molecule. Examples include carbon dioxide, carbon monoxide and water vapor.
• Boron can be added to the chemistry using any chemical compounds which include boron; other atoms within the molecule can include one or more of nitrogen, carbon, hydrogen and oxygen atoms in any phase.
• Substrates used to make the diamond of the invention were natural Ia or Ha, HPHT synthetic Ib, or SC-CVD with ( 100) surfaces.
• the top growth surface can be slightly off ( 100) plane, preferably between 0 and 20 degrees, and more preferably between 0-15 degrees. With an off axis angle lower than 1 degree, octahedral diamond with (111) faces begins to form, and (100) preferred growth can not continue.
• the growth layer can not be thicker than 100 microns. With an off axis angle higher than 20 degree, isolated (100) columns and steps will take place. Off angles between 1 and 20 degrees will generate a smooth step flow morphology free of hillocks, hence enlarging the single crystal diamond.
• a growth rate of 20 - 100 ⁇ m/h was recorded, which is a 10 - 100 times improvement compared with other B doped single crystal diamond growth (Arima et al, J. Crys. Growth, 2007).
• the color of the boron doped SC-CVD is tunable from dark brown, light brown, near colorless, colorless, faint blue to dark blue.
• Figure 3 shows three samples with colors of (a) light brown, (b) colorless, and (c) faint blue.
• the brown boron doped SC-CVD diamonds exhibited a broad band around 270 nm related to substitutional nitrogen and 550 nm due to the nitrogen vacancy center (Martineau et al, Gems & Gemology, 2004).
• the colorless boron doped SC-CVD diamonds have a much lower background and show extremely low (or no) trace of the 270 nm and 550 nm bands.
• extremely low (or no) nitrogen impurity was located, and a blue hue on the spectra was observed.
• Boron concentration can be determined by SIMS; uncompensated boron can also be determined by the integrated intensities of absorption coefficient of peaks at 1282, 2457, 2800 cm '1 (Prelas et al, Handbook of Industrial Diamonds and Diamond Films, Marcel Dekker, New York, USA, 1998; Gheeraert et al , Diamond and Relat. Mater., 1998).
• uncompensated boron concentration is calculated from the following equation:
• Single-crystal diamond was synthesized by high density microwave plasma chemical vapor deposition (MPCVD) at 5 - 20% CH 4 ZH 2 , 0 - 0.2% N 2 ZCH 4 , at 150 - 220 torr and at temperatures ranging from 1100 0 C to 1300 0 C, as measured by a two-color infrared pyrometer.
• MPCVD high density microwave plasma chemical vapor deposition
• h-BN Hexagonal boron nitride
• the decomposition of h-BN in the plasma system supplies a sufficient amount of boron for the doping process.
• a growth rate of 20 - 100 umZh was recorded.
• CVD layers were separated from the substrates by a Q-switched Nd: YAG laser, followed by fine polishing to remove any residual carbon.
• Undoped SC-CVD crystals free of visible defects in the size range of 0.2 mm to 6 mm were selected for LPHT annealing.
• the 6 kW 2.45 GHz MPCVD reactor was used for annealing, which was carried out with a measured diamond surface temperature 1600 - 2200 0 C at gas pressures between 150 and 300 torr.
• Quantifying mechanical properties such as fracture toughness for materials such as diamond is challenging. Historically, Vickers micro-hardness testing techniques have been used to evaluate both the hardness and fracture toughness of diamond (Novikov et al., Diam.
• Hardness-fracture toughness data are plotted in Fig. 1 for natural type-la, type-IIa, synthetic type-Ib, SC-CVD, LPHT treated SC-CVD, and boron/nitrogen doped SC-CVD.
• the hardness Hy is determined by the applied load P and the indentation size 2a, according to
• the type Ia and Ha diamonds measured here have Kic values of 8 ( ⁇ 4) MPa m 1/2 , and that of type I-b synthetic diamond is 10 ( ⁇ 2) MPa m m .
• SC-CVD diamond grown with H 2 ZCHVN 2 chemistry has a Vickers-based fracture toughness measure of 15 ( ⁇ 5) MPa m 1/2 , 50% higher than type I-b synthetic diamond.
• the calculated fracture toughness of the boron doped SC-CVD diamond is higher than 22 MPa m 1/2 . This material has highly enhanced fracture toughness on this scale compared with values obtained on undoped SC-CVD diamond, without compromising the hardness [78 ( ⁇ 12) GPa].
• the measurements further reveal that the LPHT annealed SC-CVD exhibits ultrahard characteristics (measured hardness of at least ⁇ 125 GPa) without an appreciable reduction in toughness (K JC — 12 - 16 MPa m ). This contrasts with the results obtained previously for SC-CVD subjected to high pressure/high temperature (HPHT) annealing (Yan et al, Phys. Stat. Sol., 2004). Recently, annealing studies of these diamonds under low pressure/high temperature (LPHT) conditions (> 1600 0 C, ⁇ 300 torr; i.e., outside the diamond stable field) revealed major changes in optical properties, including decreases in visible absorption (Meng et al, Proc. Nat.
• FIG. 7 A representative photoluminescence spectra and images of the diamond material studied are shown in Fig. 7. High quality diamond crystals exhibit the prominent second-order Raman feature. The bands assigned to NV 0 centers around 575 nm and NV " centers around 637 nm demonstrate the incorporation of nitrogen in the diamond structure. Changes in infrared spectra after LPHT annealing were similar to those found after HPHT processing (Meng et al. , Proc. Nat. Acad. Sci. U.S.A., 2008). Without being bound by theory, measurements to date lead the inventors to propose that the interaction among nitrogen, boron and adjacent carbon atoms give rise to the enhanced toughness.
• the enhanced optical and mechanical properties of the diamond materials described here may find useful applications as optical windows in harsh environments, mechanical testing, abrasive machining, laser optics, and transparent shielding and MEMS devices.
• the low cost, large area LPHT annealing process may be an alternative to HPHT annealing and could have important industrial applications.
• ultratough boron doped diamonds examples include, but are not limited to, the following: non-ferrous materials machining, micromachining and nanomachining (graphite, high silicon alloy machining in automotive industry); rock/oil drilling where extremely high toughness diamonds are needed; high pressure anvils with tunable conductivity and higher toughness to carry on high pressure limits; and high temperature and severe environment electro sensors.
• the high toughness of the boron doped diamonds also makes them a potential candidate for titanium machining for aerospace industry.

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• 2009
  • 2009-05-05 TW TW098114858A patent/TWI457475B/zh not_active IP Right Cessation
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