Methods for growing larger diamonds

Abstract

A method forms one or more diamonds. The method provides a growth chamber having a gas environment. A single crystal diamond substrate is placed in the growth chamber. Diamond material is deposited on the single crystal diamond substrate for epitaxial growth. The single crystal diamond substrate has a given crystal orientation. Growth is continued at a specified temperature, a specified pressure, and a gas content specified for the gas environment. The specified gas environment has a nitrogen concentration greater than about 0.5 ppm and less than about 5.0 ppm. The specified temperature is greater than about 650° C. and less than about 950° C. The specified pressure is greater than about 130 Torr and less than about 175 Torr.

Description

[0001] priority

[0002] This patent application claims priority to U.S. Provisional Patent Application No. 62 / 963,231, filed on January 20, 2020, entitled “METHOD OF GROWING LARGERDIAMONDS,” whose inventors are John Ciraldo and Jonathan Levine-Miles, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Exemplary embodiments of the present invention generally relate to growing crystals, and more particularly, exemplary embodiments relate to growing large diamonds using a chemical vapor deposition process. Background Art

[0004] Diamonds are used in a wide variety of applications. For example, they can be used to produce integrated circuits, or as lenses for laser systems. They can also be used simply as gemstones. However, manufacturing diamonds can create many technical challenges. Summary of the invention

[0005] According to one embodiment of the present invention, a method forms one or more diamonds. The method provides a growth chamber having a gas environment. A single crystal diamond substrate is placed in the growth chamber. Diamond material is deposited on the single crystal diamond substrate for epitaxial growth. The single crystal diamond substrate has a given crystal orientation. Growth is continued at a specified temperature, a specified pressure, and a gas content specified for the gas environment. The specified gas environment has a nitrogen concentration greater than about 0.5 ppm and less than about 5.0 ppm. The specified temperature is greater than about 650° C. and less than about 950° C. The specified pressure is greater than about 130 Torr and less than about 175 Torr.

[0006] Wherein, deposition includes using plasma assisted chemical vapor deposition technology. In some embodiments, the gas environment does not contain oxygen. However, in some embodiments, the gas environment may contain one or more of oxygen, argon, methane and hydrogen. In some embodiments, when the growth continues, the prescribed temperature and / or prescribed pressure changes.

[0007] Using the above method, diamonds can be formed having a maximum size greater than about 15 mm. In addition, multiple diamonds can be produced simultaneously. Epitaxial growth can be performed on a diamond surface. The diamond growth surface can have a (100) crystal orientation with a miscut / misorientation within a range of about ±5 degrees.

[0008] According to yet another embodiment, a method grows one or more diamonds. The method provides a seed crystal in a growth chamber. The seed crystal has a (100) crystal orientation with a miscut of about + or -5 degrees. A gas concentration in the growth chamber is set to about 1.5 ppm to about 5.0 ppm during a first time period. The temperature in the growth chamber is set to about 650° C. to 1100° C. The pressure in the growth chamber is set to about 135 torr to 175 torr.

[0009] The first time period may be between about 1 hour and 48 hours. The gas concentration in the growth chamber may be set to about 0.5 ppm to about 1.5 ppm in a second time period after the first time period. The second time period may be about 350 hours to about 750 hours. The diamond layer may be deposited to form a bulk diamond of about 3.5 carats to about 9 carats.

[0010] In some embodiments, a diamond layer is epitaxially grown on a seed crystal. The diamond layer may be heteroepitaxially or homoepitaxially grown. The seed crystal may be a diamond seed crystal. The bulk diamond may be continuously formed. For example, growth may not be stopped to remove undesirable polycrystalline material. In some embodiments, the layers may be deposited to form a bulk diamond of about 10 carats to about 20 carats.

[0011] In addition, a second diamond layer may be grown directly or indirectly on the first diamond layer. The second diamond layer preferably has a larger diameter, width and / or length than the first diamond layer. Thus, the diamond layer may grow outward.

[0012] According to yet another embodiment, a method continuously grows one or more diamonds. The method provides a growth chamber having a gas environment. A single crystal substrate is placed in the growth chamber. Diamond material is deposited on the single crystal substrate for epitaxial growth. Growth continues at a specified temperature, a specified pressure, and a gas content specified for the gas environment. The specified gas environment may have a nitrogen concentration greater than 0% but less than about 0.0005%. The specified temperature may be greater than about 750°C and less than about 1150°C.

[0013] In some embodiments, the diamond layer may be grown for 350 to 750 hours to produce a bulk diamond of about 3.5 carats to about 20 carats. The maximum dimension of each successively grown diamond layer may be greater than the maximum dimension of the previous diamond layer on which the diamond layer was grown. In addition, in various embodiments, the diamond layer may be grown without stopping the growth process to remove polycrystalline material. In some embodiments, the prescribed pressure may be greater than about 100 Torr and less than about 200 Torr.

[0014] Various embodiments may be directed to a system (e.g., including a growth chamber) configured to grow diamond according to one or more of the various methods described herein. Additionally or alternatively, various embodiments may be directed to diamond grown using one or more of the various methods herein. For example, an exemplary embodiment may include diamonds of about 3.5 carats to about 20 carats that are continuously grown (e.g., without treatment to remove polycrystalline material). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Those skilled in the art will more fully appreciate the advantages of the various embodiments of the present invention from the following "Detailed Description of the Invention" discussed with reference to the accompanying drawings.

[0016] Figure 1A Bulk diamond grown using chemical vapor deposition according to an exemplary embodiment of the invention is schematically illustrated.

[0017] Figure 1B A larger bulk diamond grown using chemical vapor deposition according to an exemplary embodiment of the invention is schematically shown.

[0018] Figure 2 A method of growing bulk diamond according to an exemplary embodiment of the present invention is shown.

[0019] Figure 3 A top view of a platform on which a seed crystal is disposed for crystal growth according to an exemplary embodiment of the present invention is schematically shown.

[0020] Figure 4 A side view of diamond grown according to an exemplary embodiment of the present invention is shown.

[0021] Figure 5 is a side view of a diamond grown according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0022] In an exemplary embodiment, a method of increasing the growth rate is used to grow large diamonds. By providing favorable growth conditions within the growth chamber, the method advantageously reduces the growth of undesirable polycrystalline carbon that might otherwise grow. In particular, the inventors have discovered that one or more of the gas chemistry, temperature, pressure, and crystal orientation of the seed crystal within the chamber can be set to reduce the growth of polycrystalline material. Details of exemplary embodiments are discussed below.

[0023] Figure 1AA bulk diamond 10 grown using chemical vapor deposition according to an exemplary embodiment of the present invention is schematically shown. As known to those skilled in the art, the diamond 10 is epitaxially grown on a single crystal seed 12 (e.g., a single crystal diamond seed 12). Finally, a cut diamond 14 may be cut from the bulk diamond 10. However, as Figure 1A As shown, the size of the cut diamond 14 is limited by the size of the bulk diamond 10. Furthermore, as known to those skilled in the art, during epitaxial growth, polycrystalline material 16 begins to form on the periphery of the diamond 10 (and sometimes on the growth surface 18 of the diamond 10). As the polycrystalline material 16 begins to grow on the periphery of the growth surface 18, the diameter / width of each subsequent layer of the bulk diamond 10 becomes smaller and smaller because single crystal diamond 10 cannot grow on the polycrystalline material 16.

[0024] Figure 1B A larger bulk diamond 10 grown using chemical vapor deposition according to an exemplary embodiment of the present invention is schematically shown. Advantageously, the growth of polycrystalline material 16 (e.g., polycrystalline carbon) is hindered or avoided. Thus, the growth surface 18 is not obstructed by the polycrystalline material 16. In fact, the bulk diamond 10 is not only able to grow vertically, but also to grow diamond 10 outwards. This results in a relatively large bulk diamond 10, and ultimately a cut diamond 14.

[0025] Figure 2 shows the growth of an exemplary embodiment according to the present invention Figure 1B The method of forming a block of diamond 10 is shown. It should be noted that the process is a simplified form of a more complex process for growing diamond 10. As such, the actual process may have additional steps that are not discussed. Furthermore, some steps may be performed in a different order or in parallel with each other. Furthermore, in various embodiments, one or more steps may be optional. Therefore, the discussion of the process is illustrative and is not intended to limit the various embodiments of the present invention. Furthermore, although the process is primarily discussed with respect to producing a single diamond 10, Figure 2 The process may also be used to produce multiple diamonds 10 simultaneously (eg, within the same growth chamber) and / or sequentially.

[0026] The process begins at step 202, which provides a diamond seed 12 on which a block of diamond 10 is grown. The seed 12 can be obtained from natural or grown diamond. For example, the seed 12 can be a thin layer cut from the diamond 10 (e.g., laser cut). The seed 12 is preferably polished (e.g., mechanical polishing at 2800 RPM) to achieve a desired crystal orientation. Preferably, there is no polycrystalline region or polycrystalline material 16 on the seed 12. In some embodiments, the seed 12 is rectangular in shape (e.g., square). The seed 12 can have various sizes. Generally, the larger the growth size of the seed, the larger the grown diamond 10. Therefore, in some embodiments, the seed 12 can have a width and / or length of about 6 mm to about 15 mm (e.g., about 9 mm).

[0027] The inventors have discovered that the orientation of the seed crystal 12 affects the size of the grown diamond 10. As known to those skilled in the art, single crystals are anisotropic. By changing the crystal orientation, the properties of the growing crystal can be changed. In particular, the inventors have discovered that a (100) crystal orientation hinders the growth of polycrystalline material 16. In particular, it has been discovered that misorientation / miscut within a range of ±5 degrees on the (100) surface significantly reduces the occurrence of polycrystalline material 16 during growth, while advantageously enhancing the outgrowth of the diamond 10 (e.g., outgrowth at an angle of up to about 45 degrees).

[0028] Other crystal orientations for the growth of larger diamonds 10 include the (110) orientation, with or without a maximum misorientation of ±5 degrees. The inventors have found that the (110) orientation retards the growth of the polycrystalline material 16. However, the (110) orientation also retards the outward growth of the diamond 10 (relative to the (100) orientation). Therefore, the (110) orientation lacks some of the same growth advantages as the (100) orientation with a misorientation within the range of ±5 degrees (e.g., 2 degrees).

[0029] The process proceeds to step 204 where a seed crystal 12 is placed on a platform 20 in a diamond growth chamber. Figure 3 Schematically shown is a top view of a platform 20 with a seed crystal 12 disposed thereon. Diamond 10 is epitaxially grown on the seed crystal 12 using chemical vapor deposition. As the diamond 10 grows, the top surface of the diamond 10 may also be referred to as a growth surface 18. Thus, the growth surface 18 may have a miscut from the seed crystal 12 within a range of about ±5 degrees.

[0030] In some embodiments, Figure 3As shown, multiple seeds 12 can be placed in the reactor. For example, more than two seeds can be placed on the platform 20. In some embodiments, about 16 to about 32 seeds 12 can be placed on the platform 20 at the same time. Although the seeds 12 are shown on the platform 20 with a certain distance between them, in some embodiments, the seeds 12 can be positioned so that their edges are adjacent to each other. This "mosaic approach" uses multiple square diamond seeds 12 that are in contact with each other to form a "larger" seed 12. In this way, the diamond 10 film deposited on the seed 12 can be continuous on the seed 12. However, the mosaic technique suffers from several challenges, including poor repeatability and high crystalline defect density in the grown film (i.e., the grown layer) near the node of the individual seed 12. In order to help grow on the seed 12, the exemplary embodiment can advantageously maintain the nitrogen concentration in the chamber at about 1.5 ppm to about 5 ppm (e.g., 2 ppm) for about 1 hour to about 48 hours (e.g., 24 hours) to help the diamond 10 layer grow together.

[0031] At step 206, the gas chemistry in the CVD growth chamber is set to produce favorable growth conditions. In particular, the concentration of nitrogen is adjusted / set so that it is about 0.5 ppm to about 5.0 ppm of the total gas concentration in the chamber. The inventors have found that this range of nitrogen enables diamond 10 to grow outward, taking into account the other factors discussed herein.

[0032] Figure 4 A side view of a diamond 10 grown in accordance with an exemplary embodiment of the present invention is shown. As shown, the diamond 10 grows outwardly from the seed 12 (e.g., at an angle of about 45 degrees). In various embodiments, the layer of diamond 10 may grow outwardly at an angle of about 1 degree to about 45 degrees. In some embodiments, the growth is isotropic (e.g., 45 degrees). Therefore, the growth surface 18 and subsequent layers of diamond 10 eventually grow larger (e.g., larger width and length, diameter, etc.) than the initial seed 12.

[0033] When the concentration of nitrogen is above about 5.0 ppm, the diamond 10 begins to grow vertically rather than outward. That is, the diamond 10 does not outward grow to the same extent as at lower nitrogen concentrations. At the other end of the range, nitrogen concentrations less than 0.5 ppm were found to have a negligible effect on outward growth.

[0034] Another consideration is that higher nitrogen concentrations tend to provide the gemstone with an undesirable (depending on the application) color (i.e., not colorless). Although the color range of diamond 10 is acceptable, the above nitrogen concentrations may produce diamonds with a diamond color of D, E, or F on the GIA (Gemological Institute of America) scale. Therefore, some embodiments may use nitrogen concentrations of about 0.5 ppm to 1.5 ppm.

[0035] In some embodiments, the concentration of nitrogen can vary throughout the growth cycle. For example, for the first time period (e.g., the first 24 hours), the concentration of nitrogen can be as much as 2ppm. The nitrogen concentration can then be reduced to about 1ppm in the second time period (e.g., 350 to 720 hours). By starting with a higher initial concentration in the first time period, the outward growth of the crystal is assisted at the beginning of the process. When using a mosaic method, this is particularly helpful because the seeds 12 (e.g., 16 to 36 seeds) can be gathered together faster, reducing the possibility that the seeds 12 are not expected to move from their initial position (e.g., otherwise it may occur during a slower growth period). By growing the seeds 12 in a higher nitrogen environment (e.g., about 2ppm to about 5ppm), the diamond 12 grows into a single plate across all the seeds 12. This helps to reduce or prevent defects that may propagate from the seeds 12. In some embodiments, a higher nitrogen concentration may exist for several hours before the concentration drops to less than about 2ppm. Therefore, in some embodiments, the first time period may be less than 24 hours, less than 12 hours, less than 6 hours, or about 3 hours.

[0036] Back to Figure 2 In the process of growing the diamond 10, the temperature in the growth chamber is set at step 208. Exemplary embodiments set and / or maintain the temperature in the growth chamber at about 650°C to about 950°C. The inventors have found that temperatures below 650°C result in larger growth of the diamond 10, but the quality of the diamond 10 is lower. On the other hand, temperatures greater than about 950°C produce high-quality diamonds, but it is difficult to grow large diamonds 10. In particular, higher temperatures provide excellent growth conditions for the polycrystalline material 16. However, as previously described, the polycrystalline material 16 prevents the diamond 10 from growing outward. Some embodiments may heat the chamber at about 1100°C to about 1200°C to produce high-quality diamonds, but smaller in size.

[0037] Preferably, exemplary embodiments set and / or maintain the temperature in the growth chamber at about 750° C. to about 850° C. The inventors have determined that this range provides excellent quality diamond 10 while allowing isotropic outgrowth.

[0038] The process proceeds to step 210, which sets the pressure in the growth chamber. Exemplary embodiments maintain the pressure in the chamber in a range of approximately 100 torr to 200 torr to optimize growth conditions. The inventors have determined that pressures at the higher end of this range cause the diamond 10 to grow faster. However, in a manner similar to temperature, the growth of the polycrystalline material 16 is proportional to the increasing pressure. Thus, when the pressure (or temperature) increases beyond a certain range, the diameter / width of the diamond 10 decreases as it grows (see, for example, FIG. 21A ). Figure 1A). Thus, in some embodiments, it may be advantageous to maintain the pressure in the chamber in a range of about 135 Torr to about 175 Torr (e.g., if the temperature is at the higher end of the ranges described herein).

[0039] The process then proceeds to step 212, which uses chemical vapor deposition to grow a large diamond 10. The diamond 10 may be grown using the aforementioned crystal orientation, gas chemistry, temperature range, and / or pressure range.

[0040] It should be appreciated that exemplary embodiments enable continuous growth of large diamonds (i.e., without stopping growth to remove polycrystalline material 16). Thus, exemplary embodiments can continuously grow diamonds 10 larger than 3.5 carats. Some embodiments can continuously grow diamonds 10 of about 5 to 6 carats (e.g., in about 700 to 750 hours). Exemplary embodiments can grow large diamonds 10 up to 9 carats or more. For example, some embodiments can grow diamonds of about 10 carats to about 20 carats. The continuous growth of large diamonds 10 enables scalability of diamond 10 growth without the need to start and stop the growth process to remove polycrystalline material 16. Thus, exemplary embodiments can grow large diamonds faster and with fewer steps than prior art processes.

[0041] Additionally, the conditions within the chamber may be varied during the growth of the diamond 10. For example, some embodiments may advantageously grow the diamond 10 at the lower end of the temperature and pressure ranges described herein for a certain first period of time. After a certain amount of growth, the temperature and / or pressure may be increased to the higher end of the ranges described herein. Although the diamond will no longer grow outward at the higher end of these ranges, this growth variation may be used to advantage. Figures 1A to 1B As shown, the cut diamond 14 generally tapers gradually toward the top. Thus, exemplary embodiments can increase the growth rate and reduce the diameter / width of the bulk diamond 10 while still maintaining a given size of cut diamond 14. For example, the tapered end can be predetermined for a particular cut diamond 14 size. After the bulk diamond 10 grows to or beyond the tapered end, the settings in the chamber can be adjusted so that the diameter of the diamond 10 can begin to grow faster without growing outward. In fact, the diamond can begin to grow inward, as long as it does not grow inward enough to provide insufficient bulk material for the desired cut diamond 14.

[0042] The process then proceeds to step 214, where the diamond 10 is cut for its specific application. Exemplary embodiments provide high quality diamonds that can be used in jewelry. However, some embodiments may also produce diamonds suitable for optical applications or to be used as seeds 12. In some other embodiments, if multiple seeds 12 are bonded together during growth, the diamond 10 may be cut so that the seeds 12 (e.g., in a mosaic pattern) can be separated.

[0043] Thus, using these techniques, some embodiments produce larger diamonds for use as gemstones, substrates, industrial equipment, and the like. For example, some embodiments can produce larger and larger substrates from sequentially produced batches. For example, a 9 mm single crystal square seed crystal 12 labeled can be used to produce a larger single crystal square substrate (e.g., 13 mm), which itself can then be used to produce an even larger single crystal substrate (e.g., 19 mm). For a given application, this process can be repeated to produce substrates of appropriate size. Note that some embodiments do not use square substrates, but rather use non-square rectangular substrates, circular substrates, or substrates having other shapes (e.g., irregular shapes).

[0044] The exemplary embodiments preferably use a plasma-assisted CVD process with the required process conditions described above to produce single crystal diamond. Figure 5 A side view of a diamond 10 grown using these processes is shown. The diamond 10 has a relatively rectangular base that is consistent with the seed 12 and expands outward in a tapered manner. For example, the tapered end can be about 45 degrees, where it grows one unit upward and one unit outward.

[0045] While various embodiments are applicable to homoepitaxial applications (e.g., growing a diamond layer on a diamond seed), other embodiments are applicable to heteroepitaxial applications (e.g., growing a diamond layer on a non-diamond seed). Such applications may reduce the formation of polycrystalline material near the edge of the substrate. It should also be understood that while the above discussion relates to growing large diamonds, in some embodiments, non-diamond materials may also be grown in a similar manner under the conditions described herein.

[0046] Although the above discussion discloses various exemplary embodiments of the present invention, it should be apparent that those skilled in the art can make various modifications that will achieve some of the advantages of the present invention without departing from the true scope of the invention.

Claims

1. A method of forming one or more diamonds, the method comprising: include: providing a growth chamber having a gas environment; placing a single crystal diamond substrate in the growth chamber; depositing diamond material on the single crystal diamond substrate for epitaxial growth, the single crystal diamond substrate having a given crystal orientation; outgrowing single crystal diamond on the single crystal diamond substrate at a specified temperature, a specified pressure, and a specified gas content for the gas environment, The nitrogen concentration of the prescribed gas atmosphere during the first growth period is 2 ppm to 5 ppm. The specified temperature is greater than 650°C and less than 950°C, The specified pressure is greater than 130 Torr and less than 175 Torr; and In a second growth period after the first growth period, a predetermined gas atmosphere is changed so that the nitrogen concentration is 0.5 ppm to 1.5 ppm.

2. The method of claim 1, wherein depositing comprises using a plasma assisted chemical vapor deposition technique. The method of claim 1 , wherein the gas environment is free of oxygen.

4. The method of claim 1, wherein the gas environment comprises one or more of argon, methane, and hydrogen.

5. The method of claim 1, wherein diamonds formed by depositing the diamond material have a maximum dimension greater than 15 mm.

6. The method of claim 1 further comprising producing a plurality of diamonds simultaneously.

7. The method of claim 1, wherein the prescribed temperature increases within a range of greater than 650°C and less than 950°C as growth continues.

8. The method of claim 1, wherein the regulation increases within a range of greater than 130 Torr and less than 175 Torr as growth continues.

9. The method of claim 1, wherein the growth surface of the diamond has a (100) orientation with a mis-cut / mis-orientation within a range of ±5 degrees.

10. A method of growing one or more diamonds, the method include: providing a single crystal diamond seed crystal in a growth chamber, the seed crystal having a (100) crystal orientation with an off-cut of + or -5 degrees; setting the gas concentration in the growth chamber to 2.0 ppm to 5.0 ppm during a first time period; Setting the temperature in the growth chamber to 650° C. to 1100° C.; setting the pressure in the growth chamber to 135 torr to 175 torr; growing a first single crystal diamond layer on a substrate; changing the gas concentration in the growth chamber to 0.5 ppm to 1.5 ppm during a second time period after the first time period; A second single crystal diamond layer is grown directly or indirectly on the first single crystal diamond layer, the second single crystal diamond layer having a greater width and / or length than the first single crystal diamond layer.

11. The method of claim 10, wherein the first period of time is from 1 to 48 hours.

12. The method of claim 10, wherein the second period of time is from 350 hours to 750 hours.

13. The method of claim 10, further comprising depositing the layers to form a bulk diamond of 3.5 carats to 9 carats.

14. The method of claim 13, wherein the mass of diamond is formed continuously.

15. The method of claim 10, further comprising depositing the layers to form a bulk diamond of 10 carats to 20 carats.

16. The method of claim 10, further comprising outgrowing a diamond layer.

Images