CN116635328A - Substrate for epitaxial growth of diamond crystal and method for producing diamond crystal - Google Patents
Substrate for epitaxial growth of diamond crystal and method for producing diamond crystal Download PDFInfo
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- CN116635328A CN116635328A CN202180086530.0A CN202180086530A CN116635328A CN 116635328 A CN116635328 A CN 116635328A CN 202180086530 A CN202180086530 A CN 202180086530A CN 116635328 A CN116635328 A CN 116635328A
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Abstract
The present invention provides a substrate for epitaxially growing diamond crystals, and a method comprising a step of epitaxially growing diamond crystals on the metal surface of the substrate. The substrate has at least a metal surface, the metal surface is a surface having a deviation angle phi exceeding 0 DEG, and the full width at half maximum of an X-ray diffraction peak from the (002) plane measured on the metal surface based on an X-ray rocking curve is 300 seconds or less.
Description
Technical Field
The present invention relates to a substrate for epitaxially growing diamond crystals and a method for producing diamond crystals.
Background
Diamond is expected to be a final semiconductor substrate (see, for example, patent document 1 and non-patent document 1). The reason for this is that diamond has many excellent characteristics, which are not superior as semiconductor materials, such as high thermal conductivity, high electron mobility or hole mobility, high dielectric breakdown field strength, low dielectric loss, and a wide band gap.
Patent document 1: japanese patent No. 4769428
Non-patent document 1: samoto et al Investigation of heterostructure between Diamond and iridium on sapphire, diamond & Related Materials (2008) 1039-1044
Disclosure of Invention
As a method for growing diamond, there is a method of epitaxially growing diamond crystals (i.e., heteroepitaxially growing) on a surface of a growth substrate made of a material different from diamond. As an example, as described in patent document 1 and non-patent document 1, a method of forming diamond crystals on the surface of an iridium (Ir) layer by a heteroepitaxial growth method is given. However, according to the studies of the present inventors, it is considered that it is difficult to epitaxially grow high-quality diamond crystals by the method described in patent document 1 and the method described in non-patent document 1.
In view of the above, an object of the present invention is to provide a new means for epitaxially growing high-quality diamond crystals.
The present inventors have conducted intensive studies to achieve the above object, and as a result, have newly found that: the following substrate for epitaxially growing diamond crystals (hereinafter also referred to as "substrate for crystal growth" or simply "substrate") can be used to obtain high-quality diamond crystals. The substrate for epitaxially growing diamond crystals has at least a metal surface, wherein the metal surface has a deviation angle phi exceeding 0 DEG, and the full width at half maximum of an X-ray diffraction peak from the (002) plane measured on the basis of an X-ray rocking curve in the metal surface is 300 seconds or less.
According to the crystal growth substrate of one embodiment of the present invention, diamond crystals are epitaxially grown on the metal surface, whereby high-quality diamond crystals can be obtained. In this regard, the inventors have assumed the following.
In the method described in patent document 1, an Ir layer is formed on the surface of a single crystal magnesium oxide (MgO) substrate, which is a positive substrate (just substrate) having a (100) surface, so that the surface becomes the (100) surface. Patent document 1 discloses a method of forming an ion-irradiated layer on the surface of the Ir layer and heteroepitaxially growing a diamond film on the surface of the ion-irradiated layer. The positive substrate is a substrate in which the surface of a base substrate (base substrate) is set to be a front surface (just plane) inclined at an angle of 0 ° from a desired crystal plane, and the (100) plane is set as the surface in patent document 1.
However, in the heteroepitaxial growth by the method described in patent document 1, it is considered that in the initial step of heteroepitaxially growing diamond crystals on the ion-irradiated layer, crystal defects occur when the diamond crystal nuclei fuse with each other, and crystallinity is lowered. When a positive substrate is used as the base substrate, diamond crystals are grown in a Volmer-Weber mode (island growth mode) in which three-dimensional growth is in an island shape. Therefore, it is supposed that the growth flow direction is not fixed in one direction, the diamond grains are fused to each other everywhere, and crystal defects are formed in a large number of fused portions (interfaces), and thus crystallinity is lowered.
In addition to this, the inventors confirmed that: if diamond crystals are formed on the positive substrate, crystal defects are formed due to the diamond crystals growing in a spiral shape.
In contrast, in the above-described substrate for crystal growth, the surface of the metal layer on which the diamond crystal is epitaxially grown has a deviation angle Φ exceeding 0 °. This can contribute to obtaining a high-quality diamond crystal by the above-mentioned substrate for crystal growth.
On the other hand, in non-patent document 1, although an attempt was made to epitaxially grow a diamond film on the surface of an Ir layer formed on a sapphire substrate having an off-angle, it was concluded that the epitaxial area was very small, and the measurement result of the XRD spectrum confirmed that diamond was not epitaxially grown (see left column of page 1043 of non-patent document 1). In this regard, the inventors of the present invention have assumed that the reason for this is that the low film quality of the Ir layer formed on the sapphire substrate in non-patent document 1 brings about the above-described results, and have further conducted intensive studies. Results recent findings: the substrate for crystal growth having a metal surface with a film quality having a deviation angle phi exceeding 0 DEG and a full width at half maximum of an X-ray diffraction peak from the (002) plane of 300 seconds or less as measured on the basis of an X-ray rocking curve is used as a surface on which diamond crystals are epitaxially grown, and a high-quality diamond crystal can be obtained.
In one embodiment, the offset angle Φ may be 3 ° or more and 18 ° or less.
In one embodiment, the metal may be a metal selected from group 8 elements, group 9 elements, and group 10 elements, and the metal surface may be a surface having the offset angle Φ in a <100> axis direction or a <110> axis direction with respect to a (100) plane.
In one embodiment, the substrate may have a metal layer on a base substrate, and the metal surface may be a surface of the metal layer.
In one embodiment, the base substrate may be a sapphire substrate, a Si substrate, or SrTiO 3 A substrate or YSZ substrate.
In one embodiment, the surface of the base substrate having the metal layer may be a surface having a deviation angle θ exceeding 0 °.
In one embodiment, the base substrate may be a sapphire substrate, and the surface of the sapphire substrate having the metal layer may be a surface having a deviation angle θ exceeding 0 ° in the M-axis or c-axis direction with respect to the a-plane, a surface having a deviation angle θ exceeding 0 ° in the [ -1101] axis or a-axis direction with respect to the R-plane, or a surface having a deviation angle θ exceeding 0 ° in the a-axis or c-axis direction with respect to the M-plane.
In one embodiment, the offset angle θ may be 3 ° or more and 20 ° or less.
In one embodiment, the above-described deviation angle θ, Φ= (0.89 to 0.9) ×θ+t (T: Φ value with respect to θ=0° or tolerance angle value when θ=0° is set) may be established.
In one embodiment, the substrate may have a plurality of steps connected in a stepwise manner to the metal surface.
One embodiment of the present invention relates to a method for producing a diamond crystal, comprising a step of epitaxially growing a diamond crystal on the metal surface of the substrate.
In one embodiment, the substrate may have a plurality of steps and steps on the metal surface, and the manufacturing method may include a step of epitaxially growing the diamond crystal in a surface direction of the steps with the steps being a starting point of epitaxial growth of a lattice arrangement.
According to one embodiment of the present invention, a substrate for epitaxially growing diamond crystals, that is, a substrate capable of epitaxially growing high-quality diamond crystals can be provided. Further, according to an aspect of the present invention, a method for producing a diamond crystal capable of producing a high-quality diamond crystal using the above substrate can be provided.
Drawings
Fig. 1 (a) is a perspective view showing one form of a crystal growth substrate (a metal block (bulk) substrate). (b) Is a perspective view showing one form of a substrate for crystal growth (a substrate having a base substrate and a metal layer).
Fig. 2 is a perspective view schematically showing steps formed by stepwise connection on the surface of the crystal growth substrate shown in fig. 1 (a).
Fig. 3 is a perspective view schematically showing steps formed by stepwise connection on the surface of the single crystal substrate for crystal growth shown in fig. 1 (b).
Fig. 4 is a side view of fig. 2.
Fig. 5 is a side view of fig. 3.
Fig. 6 is a perspective view schematically showing a state in which diamond crystals are grown stepwise from each step shown in fig. 2.
Fig. 7 is a perspective view schematically showing a state in which diamond crystals are grown stepwise from each step shown in fig. 3.
Fig. 8 is a graph showing the measurement results of the surface roughness Ra measured on the metal surfaces of the crystal growth substrates of the examples and the comparative examples.
FIG. 9 is a graph showing full width at half maximum (FWHM) measured on metal surfaces of crystal growth substrates of examples and comparative examples.
Fig. 10 is a graph showing full width at half maximum (FWHM) measured on the surface of a diamond crystal formed by epitaxial growth on the metal surfaces of the substrates for crystal growth of examples and comparative examples.
Fig. 11 is a graph showing full width at half maximum (FWHM) measured on the surface of a diamond crystal formed by epitaxial growth on the metal surfaces of the substrates for crystal growth of examples and comparative examples.
Fig. 12 is a graph showing growth rates of epitaxial growth of diamond crystals on metal surfaces of crystal growth substrates of examples and comparative examples.
Detailed Description
[ substrate for Crystal growth ]
One embodiment of the present invention relates to a substrate for epitaxial growth of diamond crystals, comprising at least a metal surface, wherein the metal surface has a surface having a deviation angle Φ exceeding 0 °, and the full width at half maximum of an X-ray diffraction peak from the (002) plane, measured on the basis of an X-ray rocking curve, in the metal surface is 300 seconds or less.
The crystal growth substrate will be described in more detail below. Hereinafter, description may be made with reference to the drawings. However, the present invention is not limited to the embodiments shown in the drawings.
The substrate has at least a metal surface. The diamond crystal can be epitaxially grown, i.e., heteroepitaxially grown, on such a metal surface.
In one embodiment, the substrate is a metal substrate (metal bulk substrate), and the surface of the metal substrate may be the metal surface. Fig. 1 (a) shows an example of a substrate of this type (perspective view). The surface 1a of the substrate 1 shown in fig. 1 (a) is the above-described metal surface. The surface 1a is a surface forming a main surface of the substrate 1.
In another embodiment, the substrate is a substrate having a metal layer on a base substrate, and the surface of the metal layer may be the metal surface. Fig. 1 b shows an example of a substrate of this type (perspective view). The substrate 2 shown in fig. 1 (b) has a metal layer 4 on the surface 3a of the base substrate 3. The metal layer 4 is directly laminated on the surface 3a of the base substrate 3. The surface 2a of the metal layer 4 is the metal surface. The surface 2a is a surface forming a main surface of the substrate 2. The substrate having the metal layer on the base substrate can suppress the amount of metal used compared with the metal bulk substrate, and therefore can suppress the manufacturing cost. This is preferable from the viewpoint of producing a large substrate at low cost as a substrate for crystal growth. In fig. 1 (b), the actual ratio of the thickness of the base substrate 3 to the thickness of the metal layer 4 is ignored for the sake of easy understanding of the drawing.
The metal may be 1 kind of metal selected from the group consisting of group 8 elements, group 9 elements and group 10 elements, or an alloy of 2 or more kinds thereof, and preferably 1 kind of metal selected from the above. Among these metals, iridium (Ir), platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), and the like are preferable from the viewpoint of reducing the substrate manufacturing cost.
In the case of a substrate having a metal layer on a base substrate, it is preferable that the base substrate is a sapphire substrate, a Si substrate, or SrTiO from the viewpoint of obtaining a low-cost and large-sized base substrate 3 Either a substrate or a YSZ (yttria stabilized zirconia) substrate. From the viewpoint of chemical stabilityFrom the viewpoint of ease in setting the deviation angle θ by polishing as described later, a sapphire substrate is preferable as the base substrate.
In any of the above modes, in the crystal growth substrate, the metal surface is a surface having a deviation angle Φ exceeding 0 °. The above-described faces are generally referred to as "off faces". The deviating surface is an inclined surface having a deviating angle (inclination angle) phi (but phi does not include 0 deg.) from the front surface having a desired crystal plane orientation.
The metal surface (offset surface) may have a plurality of steps and steps, more specifically, may have a plurality of steps connected in a stepwise manner.
Fig. 2 is a perspective view schematically showing steps formed in a stepwise manner on the surface 1a of the substrate 1 shown in fig. 1 (a), and fig. 4 is a side view of fig. 2.
Fig. 3 is a perspective view schematically showing steps formed in a stepwise manner on the surface 2a of the substrate 2 shown in fig. 1 (b). Fig. 5 is a side view of fig. 3.
As shown in the above figures, the surfaces 1a and 2a have an offset angle Φ by forming a plurality of steps 6 and 5.
Each step 6 is formed by connecting the elements of the above metal in a stepwise manner and flat at the atomic level. Since the step-like steps 6 spontaneously appear, it is suggested that the atoms of the metal elements are arranged nicely. The atomic scale of the step height H is a single step of one degree of atoms of the metal element forming the surface 1a or 2a, or a multi-step of two or more atoms. Further, the step width W and the step height H may be determined according to the deviation angle Φ.
Fig. 6 is a perspective view schematically showing a state in which stepped diamond crystals are grown from the respective steps shown in fig. 2 in a stepped flow.
Fig. 7 is a perspective view schematically showing a state in which stepped diamond crystals are grown from the respective steps shown in fig. 3 in a stepped flow.
In the production of diamond crystals having the surface 1a or 2a as a surface to be grown, the step 5 may serve as a starting point for epitaxial growth of the lattice arrangement of the diamond crystals. Therefore, as shown by the arrows (arrows starting from the step 5) in fig. 6 or 7, the direction in which diamond crystal growth proceeds in two dimensions can be aligned with the surface direction of the step 6. Crystal growth in which the directions in which diamond crystals are grown are aligned in one direction in this manner is called step flow growth. By fixing the growth flow direction of the diamond crystal on the surface 1a or 2a in one direction, the stepwise flow growth is promoted, and the degree of orientation matching of the diamond crystal can be improved, as a result, formation of crystal defects at the interface at the time of fusion of the diamond crystal flows with each other can be suppressed. This suppresses the decrease in crystallinity of the diamond crystal. Further, by fixing the growth flow direction in one direction, the spiral growth of the diamond crystal can be suppressed, and the formation of crystal defects can be suppressed. This can also suppress the decrease in crystallinity of the diamond crystal.
The deviation angle phi may be arbitrarily set in a range exceeding 0 deg.. As described in detail above, the above-described crystal growth substrate has a structure in which the metal surface on which the diamond crystal is epitaxially grown has a deviation angle Φ exceeding 0 °, which contributes to the production of high-quality diamond crystals by the above-described crystal growth substrate. The deviation angle Φ is preferably 3 ° or more and 29 ° or less, more preferably 3 ° or more and 18 ° or less, still more preferably 3 ° or more and 15 ° or less, and still more preferably 3 ° or more and 10 ° or less. Forming the metal surface in such a manner that the deviation angle phi has the above range can contribute to improving the film quality of the metal surface. Further, by setting the deviation angle Φ in the above range, the surface roughness of the metal can be reduced, and the surface roughness Ra can be suppressed to be lower than 3.5nm, for example. The surface roughness Ra may be, for example, 0.5nm or more, or may be lower than this value. The surface roughness Ra can be measured by a known surface roughness measuring instrument. Further, by setting the deviation angle Φ of the metal surface within the above range, the growth rate of diamond crystal epitaxially grown thereon can be further increased, and for example, a growth rate of 18 μm/h or more can be realized.
The metal surface of the crystal growth substrate serves as a surface to be grown for heteroepitaxial growth of diamond crystals. From the viewpoint of easiness in controlling the crystal growth direction of the diamond crystal and optimization of film quality (e.g., crystallinity) and surface roughness of the surface to be grown in the use of heteroepitaxial growth of the diamond crystal, it is preferable that the metal surface be a surface (inclined surface) having the above-mentioned deviation angle Φ in the <100> axis direction or the <110> axis direction with respect to the (100) surface.
On the surface 3a of the base substrate 3 shown in fig. 3, a deviation angle θ is formed (however, θ does not include 0 °). When the base substrate 3 is a sapphire substrate, the surface 3a having the metal layer 4 thereon is preferably a surface (inclined surface) having a deviation angle θ exceeding 0 ° in the M-axis or c-axis direction with respect to the a-plane, a surface (inclined surface) having a deviation angle θ exceeding 0 ° in the [ -1101] axis or a-axis direction with respect to the R-plane, or a surface (inclined surface) having a deviation angle θ exceeding 0 ° in the a-axis or c-axis direction with respect to the M-plane. From the viewpoint of controlling the growth direction of diamond crystals by optimizing the crystal plane orientation and the tilt axis direction in the epitaxial growth application of diamond crystals, it is preferable to define the base substrate 3 to be made of sapphire, and further to set the crystal plane orientation and the tilt axis direction of the surface 3a to any one of the above.
The deviation angle θ is preferably 3 ° or more and 29 ° or less, more preferably 3 ° or more and 20 ° or less, still more preferably 3 ° or more and 15 ° or less, and still more preferably 3 ° or more and 10 ° or less. The reason for this is that setting θ in the above range can further improve the crystallinity of the diamond crystal epitaxially grown on the surface 2 a.
In the crystal growth substrate, a full width at half maximum (FWHM) of an X-ray diffraction peak from the (002) plane measured on the basis of an X-ray rocking curve on the metal surface is 300 seconds or less. The present inventors have conducted intensive studies and as a result have newly found that: the surface to be grown on which diamond crystals are epitaxially grown has the above-described film quality, and can contribute to improvement of the crystal quality of diamond crystals formed on such surface to be grown. The FWHM may be, for example, 100 seconds or more or 150 seconds or more, but the smaller the value, the higher the film quality is, and thus the lower the value exemplified here is. Further, with respect to the unit of FWHM, "seconds" is generally expressed as "arcsec".
According to the substrate for crystal growth, a high-quality diamond crystal can be epitaxially grown by using the metal surface as a surface to be grown. Regarding the crystal quality of such diamond crystals, for example, in an X-ray rocking curve measurement, the full width at half maximum (FWHM: full Width at Half Maximum) of the diffraction peak from the diamond (004) face may be 220 seconds or less and/or the full width at half maximum (FWHM) of the diffraction peak from the diamond (311) face may be 600 seconds or less, for example.
An example of the method for producing a crystal growth substrate will be described below.
The substrate 1 (metal block substrate) shown in fig. 1 can be manufactured by, for example, the following method.
First, a metal substrate is prepared. The metal constituting the substrate may be 1 or an alloy of 2 or more kinds of metals selected from group 8 elements, group 9 elements and group 10 elements, and the details thereof are as described above.
Next, the offset angle Φ is formed on the surface of the metal substrate. As a method for forming the deviation angle Φ, there is mentioned polishing with suspended abrasive grains using slurry. Examples of the slurry include slurries containing diamond abrasive grains. As the grinder, a commercially available grinder can be used. The polishing is performed by holding the metal substrate on a polishing jig so that a deviation angle phi exceeding 0 deg. is formed from the crystal plane of the (100) plane, for example, using slurry and a polishing machine, and pressing the polishing machine against the surface of the metal substrate. The tilt axis direction of the offset angle phi may be set to tilt from the (100) plane toward the <100> axis direction or the <110> axis direction, for example, when the plane of the surface is oriented to the (100) plane. The offset angle Φ is as described above.
The substrate 2 shown in fig. 2 (substrate having the metal layer 4 on the base substrate 3) can be manufactured by, for example, the following method. The manufacturing steps repeated with the above-described manufacture of the substrate 1 are omitted or simplified.
On the substrateIn the production of the substrate 2, a base substrate 3 is prepared as a preceding step of producing the substrate 2 having a metal surface. The base substrate 3 can be manufactured by, for example, first preparing a base material of the base substrate 3 and shaping the outer shape thereof into a substrate shape. The base substrate 3 may be made of sapphire, si, srTiO, or the like 3 Or a base material of a block made of any one of YSZ materials.
When the base substrate 3 is made of sapphire, the surface 3a of the base substrate 3 may be defined as any one of an inclined surface forming an angle θ of deviation in the M-axis or c-axis direction along the a-plane, an inclined surface forming an angle θ of deviation in the [ -1101] axis or a-axis direction along the R-plane, or an inclined surface forming an angle θ of deviation in the a-axis or c-axis direction along the M-plane, from the viewpoint of an inclined surface capable of generating a stepwise flow growth. The deviation angle θ of the base substrate 3 is as described above. As a method for forming the deviation angle θ, suspended abrasive grain polishing using slurry is exemplified. For such polishing, the above description can be referred to.
Next, a metal layer 4 is formed on the surface 3 a. The metal constituting the metal layer may be 1 or an alloy of 2 or more kinds of metals selected from the group consisting of group 8 elements, group 9 elements and group 10 elements, and the details are as described above.
The metal layer 4 may be formed by a magnetron sputtering method using the above metal as a target. The magnetron sputtering method may be a high frequency (RF) magnetron sputtering method or a Direct Current (DC) magnetron sputtering method. The thickness of the metal layer to be formed may be, for example, 1.0 μm or more and 2.0 μm or less. In contrast, in the non-patent document 1 shown above, the thickness of the Ir layer formed on the sapphire substrate is 200nm (see table 2 of the document). The inventors of the present invention have conceived that such a metal layer having an extremely thin film has low film quality, and that forming the metal layer in a relatively thick film in the above-described range, for example, can contribute to improvement of the film quality of the metal layer to be formed. As shown in fig. 3 and 5, the surface 2a of the metal layer 4 formed on the surface 3a having the offset angle θ has the offset angle Φ and is stepped as shown by the steps 6 since the polishing treatment is not required thereafter. Further, regarding the deviation angle Φ formed on the metal surface 2a (i.e., the surface of the metal layer 4), the relationship of the primary regression equation of Φ= (0.89 to 0.9) ×θ+t may be established for the deviation angle θ possessed by the surface 3a of the base substrate 3. T is a tolerance angle value with respect to the value of phi of θ=0° or the value of phi when θ=0° is set. Thus, from the standpoint of ease of control of the value of phi relative to the value of theta, it is preferable that the primary regression equation of theta be used to correlate with phi. As described above, the offset angle Φ is preferably 3 ° or more and 18 ° or less. Regarding the tilt axis direction of the offset angle Φ, when the plane orientation of the surface 2a is the (100) plane, the tilt from the (100) plane toward the <100> axis direction or the <110> axis direction can be set.
[ method for producing diamond Crystal ]
One embodiment of the present invention relates to a method for producing a diamond crystal, comprising a step of epitaxially growing a diamond crystal on the metal surface of the crystal growth substrate.
The diamond crystal is heteroepitaxially grown on the metal surface by CVD (chemical vapor deposition: chemical Vapor Deposition) under a stepwise flow growth condition, for example. As CVD, known methods can be used, and examples thereof include microwave plasma CVD, dc plasma CVD, and hot filament CVD.
When the metal surface has a plurality of steps connected in a stepwise manner as described above, diamond crystals can be epitaxially grown in the surface direction of the steps by using the steps as starting points of epitaxial growth in lattice arrangement in the epitaxial growth. That is, the step 5 becomes a starting point in the epitaxial growth of the diamond crystal in the heteroepitaxial growth. As a result, the direction in which diamond crystal growth proceeds in two dimensions can be aligned with the surface direction of the step 6 as indicated by the arrow (each arrow starting from the step 5) in fig. 6 or 7. The thickness of the diamond crystal to be epitaxially grown can be set to be equal to or greater than the level of burying the step 5. The steps 5 are preferably formed perpendicular to the direction in which the diamond crystal grows (each arrow starting from the step 5 in fig. 6 or 7) and parallel to each other of the steps 5. This is because the progress of the stepwise growth is uniform, the lattice arrangement is also uniform, and the decrease in crystallinity of the diamond crystal can be suppressed.
The diamond crystal to be grown may be either single crystal or polycrystalline, and may contain impurities and/or dopants. In addition, if the surface of the diamond crystal (the surface on the opposite side to the surface 1a or 2 a) is considered to be general-purpose, it is preferable that either one of the crystal planes (100) or (110).
Examples
The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. Note that, where the above embodiments are repeated, description is omitted or simplified.
The following measurement conditions were used for the X-ray rocking curve measurement described below.
Tube ball: cu (Cu)
An external voltage: 45kV
An external current: 40mA
Scanning speed: 0.61 DEG/min
Divergence slit width: 1mm of
Scattering slit-light receiving slit: without any means for
Monochromator type: symmetrical four-crystal Ge220
Example 1
< production of substrate for Crystal growth >
As shown in fig. 1 (b), 3 and 5, a crystal growth substrate 2 composed of a base substrate 3 and a metal layer 4 was produced by the method described below.
A base substrate 3 having an inclined surface formed at an angle θ of 10 ° with respect to the a-plane in the c-axis direction as a surface 3a was made of sapphire. The offset angle θ is formed by grinding with suspended abrasive particles of the slurry.
An iridium layer having a film thickness of 1.0 μm or more and 2.0 μm or less is formed on the surface 3a by a magnetron sputtering method using iridium (Ir) as a target. The surface 2a of the iridium layer (metal layer) 4 thus formed has a plurality of steps connected in a stepwise manner, and has a deviation angle Φ shown in table 1 in the <110> axis direction with respect to the (100) plane.
The full width at half maximum (FWHM) of the X-ray diffraction peak from the (002) plane was obtained by measuring the X-ray rocking curve of the surface 2 a.
< epitaxial growth of diamond Crystal >
On the surface 2a of the substrate 2 fabricated as described above, diamond crystals were heteroepitaxially grown by direct-current plasma CVD under a stepwise flow growth condition. The thickness of the heteroepitaxially grown diamond crystal is set to be equal to or greater than the extent of the buried step 5. As a step flow growth condition by dc plasma CVD, the substrate temperature was 1000 ℃, the CVD furnace pressure was 100Torr, the hydrogen gas flow rate was 475 seem, and the methane gas flow rate was 25 seem.
The surface of the diamond crystal thus formed (the surface on the opposite side to the surface 2a of the substrate 2, i.e., the outermost surface of the diamond crystal) is a (100) plane.
Examples 2 to 8
< production of substrate for Crystal growth >
A crystal growth substrate 2 was produced by the method described in example 1, except that the tilt axis direction and/or the offset angle θ with respect to the a-plane were changed as shown in table 1.
In the manufactured substrate 2, the surface 2a of the iridium layer has a plurality of steps connected in a stepwise manner, and a surface having an offset angle Φ shown in table 1 in the <110> axis direction with respect to the (100) surface.
The full width at half maximum (FWHM) of the X-ray diffraction peak from the (002) plane was obtained by measuring the X-ray rocking curve of the surface 2a of each of the substrates 2 thus fabricated.
< epitaxial growth of diamond Crystal >
On the surface 2a of the substrate 2 fabricated as described above, diamond crystals were heteroepitaxially grown by the method described in example 1.
The surface of the diamond crystal thus formed (the surface on the opposite side to the surface 2a of the substrate 2, i.e., the outermost surface of the diamond crystal) is a (100) plane.
The above results are shown in table 1.
TABLE 1
Comparative example 1
A crystal growth substrate 2 was produced by the method described in example 1, except that a base substrate made of sapphire and having a positive substrate (θ=0°) on the a-plane was used as the base substrate 3. In the manufactured substrate 2, the surface 2a of the iridium layer is a front surface (Φ=0°).
The full width at half maximum (FWHM) of the X-ray diffraction peak from the (002) plane was obtained by measuring the X-ray rocking curve on the surface 2a, and the result was about 400 seconds.
On the surface 2a of the substrate 2 fabricated as described above, diamond crystals were heteroepitaxially grown by the method described in example 1.
Comparative example 2
In the film formation of the iridium layer, a crystal growth substrate 2 was produced by the method described in example 1, except that the film thickness of the iridium layer to be formed was 200nm as in the Ir layer described in non-patent document 1 described above.
In the substrate 2 thus produced, the surface 2a of the iridium layer was a surface having the same offset angle Φ as in example 1 in the <110> axis direction with respect to the (100) plane.
The full width at half maximum (FWHM) of the X-ray diffraction peak from the (002) plane was obtained from the X-ray rocking curve measurement of the surface 2a, and found to be 950 seconds.
Although heteroepitaxial growth of diamond crystals was attempted by the method described in example 1 on the surface 2a of the substrate 2 fabricated as described above, the epitaxial growth of diamond crystals was not possible as in the results described in non-patent document 1.
The FWHM values obtained for the substrate surfaces 2a of examples 1 to 8, comparative example 1 and comparative example 2 are collectively shown in fig. 9. In fig. 9, the "c-axis direction deviation" mark represents the measurement results of examples 1 to 4, the "m-axis direction deviation" mark represents the measurement results of examples 5 to 8, the "JUST" mark represents the measurement result of comparative example 1, and the "Ir film thickness 200nm" mark represents the measurement result of comparative example 2.
As an evaluation of crystallinity (crystal quality) of the diamond crystals formed in examples 1 to 8 and comparative example 1, X-ray rocking curve measurement was performed for each diamond crystal. In the X-ray rocking curve measurement, an X-ray diffraction peak of the diamond (004) face was obtained. In examples 1 to 4 and comparative example 1, the full width at half maximum (FWHM) of the X-ray diffraction peak on the diamond (311) surface was also obtained in the X-ray rocking curve measurement. The results obtained are shown in fig. 10 and 11.
Fig. 10 is a graph showing the full width at half maximum (FWHM) of the X-ray diffraction peaks from the diamond (004) surface obtained in examples 2 to 8 and comparative example 1, with respect to the value of the FWHM (in fig. 10, "Ir film (002) FWHM") obtained as described above for the substrate surface 2 a.
Examples 1 to 4 and comparative example 1 in fig. 11 show the full width at half maximum (FWHM) of the X-ray diffraction peak from the diamond (004) face and the full width at half maximum (FWHM) of the X-ray diffraction peak from the diamond (311) face.
From the results shown in fig. 10 and 11, it can be confirmed that: by using the substrate for crystal growth of the example, a diamond crystal having crystallinity of full width at half maximum (FWHM) in which an X-ray diffraction peak from the diamond (004) face shows an X-ray diffraction peak of 220 seconds or less can be epitaxially grown, and a diamond crystal having crystallinity of full width at half maximum (FWHM) in which an X-ray diffraction peak from the diamond (311) face shows an X-ray diffraction peak of 600 seconds or less can be epitaxially grown.
Fig. 8 shows the surface roughness Ra obtained by measurement under the following measurement conditions for the surfaces 2a of the crystal growth substrates of examples 1 to 8 and comparative example 1. In fig. 8, the "c-axis direction" indicates the measurement results of examples 1 to 4, the "m-axis direction" indicates the measurement results of examples 5 to 8, and the "JUST" indicates the measurement result of comparative example 1.
Measurement device: hitachi-t-end atomic force microscope L-trace
Measurement area: 5 μm by 5 μm
Scanning frequency: 0.6Hz
From the results shown in fig. 8, it can be confirmed that: in the substrates for crystal growth of examples 1 to 8, the surface 2a serving as the surface to be grown in epitaxial growth of diamond crystals was a surface having a surface roughness Ra of less than 3.5nm and high smoothness.
The growth rates of the diamond crystals in examples 2 to 4 and comparative example 1 are shown in fig. 12. As shown in FIG. 12, the growth rate of comparative example 1 (off angle 0 DEG) was 14 μm/h, whereas in the examples, diamond crystals could be epitaxially grown at a growth rate of 18 μm/h or more.
Symbol description:
1. 2 substrate for crystal growth
1a, 2a metallic surface
3 base substrate
3a surface of base substrate
4 Metal layer
5 steps
6 steps
Height of H step
W step width
Angle of deviation of phi and theta
Claims (12)
1. A substrate for epitaxially growing diamond crystals, wherein,
the substrate has at least a surface made of metal,
the metal surface is a surface having a deviation angle phi exceeding 0 DEG, and
the full width at half maximum of an X-ray diffraction peak from the (002) plane measured on the basis of an X-ray rocking curve in the metal surface is 300 seconds or less.
2. The substrate of claim 1, wherein the offset angle Φ is 3 ° or more and 18 ° or less.
3. The substrate according to claim 1 or 2, wherein,
the metal is selected from group 8 element, group 9 element and group 10 element, and
the metal surface is a surface having the offset angle phi with respect to the (100) plane in the <100> axis direction or the <110> axis direction.
4. The substrate according to any one of claim 1 to 3, wherein,
the substrate has a metal layer on a base substrate
The metal surface is a surface of the metal layer.
5. The substrate of claim 4, wherein the base substrate is a sapphire substrate, a Si substrate, a SrTiO 3 A substrate or YSZ substrate.
6. The substrate of claim 4 or 5, wherein the surface of the metal layer having the base substrate is a face having a deviation angle θ exceeding 0 °.
7. The substrate according to any one of claims 4 to 6, wherein,
the base substrate is a sapphire substrate,
the surface of the sapphire substrate with the metal layer is as follows:
a plane having a deviation angle theta exceeding 0 deg. in the m-axis or c-axis direction with respect to the a-plane,
a plane having a deviation angle θ of more than 0 ° in the [ -1101] axis or a-axis direction with respect to the R plane, or
A plane having a deviation angle θ exceeding 0 ° in the a-axis or c-axis direction with respect to the M plane.
8. The substrate according to claim 6 or 7, wherein the offset angle θ is 3 ° or more and 20 ° or less.
9. The substrate according to any one of claims 6 to 8, wherein, for the offset angle θ, Φ= (0.89 to 0.9) x θ+t holds,
t is a value of phi with respect to θ=0° or a tolerance angle value when θ=0° is set.
10. The substrate according to any one of claims 1 to 9, wherein the metal surface has a plurality of steps connected in a stepwise manner.
11. A method of producing a diamond crystal, comprising the step of epitaxially growing a diamond crystal on the metal surface of the substrate according to any one of claims 1 to 10.
12. The method for producing a diamond crystal according to claim 11, wherein,
the substrate has a plurality of steps on the metal surface; and is also provided with
The method includes a step of epitaxially growing the diamond crystal in a surface direction of the step with the step as a starting point of epitaxial growth of a lattice arrangement.
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| JP2020-213490 | 2020-12-23 | ||
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| JP2021-147187 | 2021-09-09 | ||
| JP2021147187 | 2021-09-09 | ||
| PCT/JP2021/047757 WO2022138788A1 (en) | 2020-12-23 | 2021-12-23 | Substrate for epitaxially growing diamond crystal and method for manufacturing diamond crystal |
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