JP2012111654A - Single crystal diamond substrate and method for producing the same - Google Patents

Abstract

The present invention provides a mosaic single crystal having more excellent crystallinity by sharing information such as lattice constant and strain.
After synthesizing single-crystal diamond on a seed substrate by a vapor phase synthesis method, the seed substrate and the growth layer are separated in the vicinity of the growth interface, and arranged and arranged so that the separation surface becomes the upper surface. Diamond is epitaxially grown on two substrates to produce one bonded diamond substrate. Furthermore, by using the bonded diamond substrate obtained above as a seed substrate and repeating the same operation twice and three times, the single crystal substrate can be enlarged. Thereby, the unit A (derived from the surface of the seed crystal) having crystallographic characteristics of the seed crystal substrate, and the unit B (derived from the separation surface of the growth layer) having a mirror image relationship with the crystallographic characteristics of the seed crystal substrate A single-crystal diamond substrate with a mosaic arranged can be obtained.
[Selection] Figure 1

Description

  The present invention relates to the field of using single crystal diamond (cutting tools, anti-wear tools, precision tools, heat sinks, optical components, etc.).

  Conventionally, the single crystal diamond substrate has been a single crystal diamond of natural or high pressure synthesis method or a single crystal diamond formed on the substrate by a vapor phase synthesis method. Since it is extremely difficult to form a single crystal having a large size exceeding 10 mm in the natural or high pressure synthesis method, the size of the substrate is also limited in the single crystal of the gas phase synthesis method.

  Therefore, by arranging a plurality of single crystals and forming a single crystal film to be joined by a vapor phase synthesis method, the original substrate is removed, and a single mosaic single crystal substrate is formed. Is increased (Patent Documents 1 and 2). In this method, it is important that the crystal plane orientation (off angle: angle of deviation of the crystal plane with respect to the substrate plane) is not shifted as much as possible. If the crystal plane orientation is not neatly aligned, abnormally grown particles are generated at the crystal bonding interface, the crystal distortion cannot be controlled, and a single crystal with good crystallinity cannot be formed.

  As a method of aligning the plane orientation, the in-plane crystal orientation is also clean by using the (100) plane just plane or contacting the plane using a cleaved plane ((111) plane). (Patent Document 1). Thus, there has been an invention related to a substrate in which the plane orientation and the in-plane crystal orientation are aligned. However, in the angle, the deviation in units of ° can be suppressed. It was not possible to suppress the effects of. There is also a prior example using a substrate cut out from the same substrate. (Patent Documents 3 and 4) This is a very good example, but there is a possibility that crystallinity and impurities greatly fluctuate in the plate thickness direction.

Japanese Patent Laid-Open No. 06-227896 Japanese Patent Application Laid-Open No. 07-017994 JP 2005-272197 A JP 07-069795 A

Conventional mosaic single crystals have the same plane orientation of the substrate, but do not suppress distortion based on the crystallinity of the substrate. For example, when two or four substrates are joined side by side, the plane orientations of these substrates can be aligned by measuring or the like. However, strictly speaking, the substrates were grown from substrates having different lattice constants, strains, and the like due to different impurity concentrations in each substrate (FIG. 8).
It is an object of the present invention to obtain a mosaic single crystal having more excellent crystallinity by sharing such information as lattice constant and strain.

  As a result of intensive investigations to solve the above-mentioned problems, the present inventors have found a method of using a very thin crystal part of almost the same part of the substrate. The present invention has the following configuration.

(1) A single crystal diamond composed of a plurality of mosaic areas,
1. A single crystal diamond substrate, wherein units A having specific crystallographic features and units B having crystallographic features and mirror image features are arranged in a mosaic pattern.
More specifically,
A single crystal diamond consisting of a plurality of mosaic areas,
Units A having specific crystallographic features and units B having crystallographic features and mirror images are arranged in a mosaic pattern,
The unit A and the unit B are a structure in which a structure obtained by growing a crystal layer on a substrate is separated into two in a direction parallel to the growth surface, and the separation surfaces are arranged in the same direction. It is a single crystal diamond substrate characterized by having a relationship of two crystals.
(2) The single crystal diamond substrate according to (1), wherein the unit A and the unit B are periodically repeated.
(3) The single crystal diamond substrate as described in (1) or (2) above, wherein the unit A or unit B is a unit of 3 mm or more.
(4) The surface of the substrate is the (100) plane, and the inversion symmetry axis in the (100) plane of the unit A and the unit B whose crystallographic features are mirror images are parallel to <010> or <001>. The single crystal diamond substrate according to any one of the above (1) to (3), wherein
(5) Epitaxially growing diamond by vapor phase synthesis based on the seed crystal substrate, separating and separating the seed crystal substrate and the growth layer, so that the crystallographic features of the two separated substrates are mirror images The substrate area is increased by repeating the steps of arranging and arranging the separation surfaces on the top and arranging and arranging diamond to epitaxially grow on the arranged substrates to produce a single bonded substrate. (1) The manufacturing method of the single-crystal diamond substrate in any one of (4).
(6) Diamond is epitaxially grown on the seed crystal substrate by a vapor phase synthesis method, and the seed crystal substrate and the growth layer are separated by separation, and the crystallographic characteristics of the two separated substrates are mirror images. And a plurality of substrates by repeating the process of epitaxially growing and separating the diamond by vapor phase synthesis based on the seed crystal substrate and the growth layer, respectively.
Any one of the above (1) to (4), wherein the plurality of substrates are arranged with the separation surface as an upper surface, arranged, and one bonded diamond is epitaxially grown on the arranged substrates. The manufacturing method of the single-crystal diamond board | substrate of description.

  A single crystal substrate in which a plurality of single crystal substrates are connected in a mirror-inverted mosaic pattern can use a single crystal with a very close thickness among the base single crystals, so that it can be made a very uniform crystalline substrate. Has the advantage. Further, in the in-plane bonding portion, a crystalline material in the vicinity of the original substrate can be arranged nearby. Crystallization and loose bonding of impurities are possible. In addition to the laser cut, the side to be joined can use a joined surface by cleaving. This is very convenient for aligning the in-plane directions. As described above, the present invention has an effect that it is possible to produce highly uniform crystalline mosaic crystals.

It is the schematic showing an example of the manufacturing process of the single crystal diamond of this invention. It is the schematic explaining a part of characteristic of the manufacturing method of this invention. It is the schematic showing another example of the manufacturing process of the single crystal diamond of this invention. It is a figure showing an example of how to arrange seed boards. It is the schematic explaining a part of characteristic of the manufacturing method of this invention. It is a figure showing an example of the outline of the manufacturing method of the single crystal diamond of this invention. It is the schematic explaining the arrangement | positioning method of the board | substrate in an Example. It is the schematic explaining the manufacturing method of the conventional single crystal diamond.

  The single crystal diamond according to the present invention is a single crystal diamond composed of a plurality of mosaic-like areas, and a unit A having a specific crystallographic feature and a unit B having a crystallographic feature with the unit B Are arranged in a mosaic pattern. The unit A and the unit B are divided into two structures in which a crystal layer is grown on a substrate in a direction parallel to the growth surface, and the separation surfaces are arranged in the same direction. There is a relationship between two crystals.

As described above, the single crystal diamond of the present invention has units A and units B arranged in a mosaic. The units A and B may be randomly arranged, but are preferably arranged so as to repeat periodically. In particular, it is preferably arranged so as to form a checkered pattern as will be described later. Further, the unit A or the unit B is preferably a unit of 3 mm or more.
As described above, the crystallographic characteristics of the units A and B are mirror images, the crystal planes of the units A and B are (100) planes, and the inversion symmetry axis is parallel to <010> or <001>. Preferably there is.

  The single crystal diamond substrate of the present invention is obtained by epitaxially growing diamond by vapor phase synthesis based on the seed crystal substrate, separating the seed crystal substrate and the growth layer, and having the crystallographic characteristics of the two separated substrates. It can be manufactured by repeating the steps of arranging and arranging the separation surfaces with the upper surface so as to have a mirror image relationship, and epitaxially growing diamond on the arranged substrate to produce one bonded substrate.

Below, it demonstrates in detail based on drawing.
First, an original single crystal substrate (seed crystal substrate) is prepared, and single crystal diamond is synthesized on the substrate by a vapor phase synthesis method (FIG. 1). Thereafter, the seed crystal substrate and the growth layer are separated in the vicinity of the growth interface, the separated crystals are spread, and are arranged in a relationship of axis inversion. That is, as shown in FIG. 1, a diamond substrate is obtained by arranging and arranging each substrate so that the separation surfaces are on the upper surface, and epitaxially growing diamond on the two substrates by vapor phase synthesis. Make it. The joining boundary may be a laser cut surface, but is more preferably a cleaved surface. By doing so, the common outermost surface is of very close quality. Moreover, it is preferable that the inversion symmetry axis when arranging the seed crystal substrate and the growth layer so as to have a mirror image relationship is parallel to <010> or <001> in the (100) plane.

  Furthermore, by using the bonded diamond substrate obtained above as a seed substrate and repeating the same operation twice and three times, the single crystal substrate can be enlarged. Thereby, the unit A (derived from the surface of the seed crystal) having crystallographic characteristics of the seed crystal substrate, and the unit B (derived from the separation surface of the growth layer) having a mirror image relationship with the crystallographic characteristics of the seed crystal substrate A single-crystal diamond substrate with a mosaic arranged can be obtained. Since the crystal on the outermost surface is very close to the original crystal, impurities and crystallinity are very uniform (see FIG. 2). Since the crystals are aligned in the same plane, the same crystals are formed under the same conditions. The initial single crystal may be high pressure synthesized, but is more preferably IIa. Further, it is more preferably a CVD single crystal.

  The single crystal diamond substrate of the present invention is obtained by epitaxially growing diamond by a vapor phase synthesis method based on a seed crystal substrate, separating the seed crystal substrate and the growth layer, and crystallography of the two separated substrates. The separation surface is arranged on the upper surface so that the optical characteristics are mirror images, and the process of epitaxially growing diamond by the vapor phase synthesis method based on the seed crystal substrate and the growth layer, respectively, and separating and separating the plurality of layers is repeated. It is also possible to produce a substrate by arranging and arranging the plurality of substrates with the separation surface as an upper surface, and epitaxially growing one bonded diamond on the arranged substrate.

  In the above manufacturing method, as shown in FIG. 3, based on one single crystal diamond (seed crystal substrate), diamond is epitaxially grown by the CVD method, separated near the interface, and separated (see FIG. 3). First separation). At this time, the single crystal may be a high-pressure synthesized Ib type single crystal diamond, but the IIa type single crystal diamond is more consistent with undoped CVD diamond. Furthermore, it may be a single crystal diamond produced by a CVD method by some method. If the crystallinity of the single crystal diamond by the CVD method is good, the single crystal of epitaxial growth is a vapor phase synthesis method, which is better because the lattice matching is better.

  Next, based on the epitaxially grown substrate formed in the first separation and the original seed substrate, diamond is epitaxially grown by the CVD method, and the epitaxially grown substrate and the original substrate are separated and separated (second separation). . Repeating the same growth and separation multiple times will increase the number of substrates by a factor of 2. In these substrates, as shown in FIG. 5, the crystallinity (defects, transitions) is in the same arrangement relationship as the original seed substrate (2, 4, 6, 8 in FIG. 3), There are two types (1, 3, 5, and 7 in FIG. 3) that are just mirror images of the original substrate. Moreover, when this division method is repeated, almost the same number of the same substrates and inverted substrates are produced. Even if one of the substrates is lost or damaged in the middle, the other corresponding substrates also occur at the same rate, so the number is almost the same unless sorted.

  When the same number of substrates are uniformly arranged to form one diamond substrate, the unit A (derived from the surface of the seed crystal) having crystallographic characteristics of the seed crystal substrate and the crystallographic characteristics of the seed crystal substrate And a unit B having a mirror image relationship (derived from the separation surface of the growth layer) can be formed in a mosaic pattern, so that a single substrate having a surface having a surface with substantially the same crystallinity can be formed (FIG. 6). This crystal is almost a single crystal and can form a uniform substrate. The reason why the reversed substrate and the non-inverted substrate (non-inverted substrate) are distinguished from each other is to align the off-angle of the substrate (deviation from the crystallographic index plane of the substrate surface). When there is no off-angle, that is, when it is a just surface, it is not necessary to distinguish, but in the actual case, the substrate is strictly an off-angle. Since it is important to turn off the inversion substrate and the non-inversion substrate, when a single substrate is formed by arranging a plurality of substrates, it must not be arranged in a direction rotated by an axis perpendicular to the surface.

Further, the reason for using approximately the same number of inverted substrates and regular substrates (non-inverted substrates) is to use the substrates and the synthesis time effectively, so they may be arranged appropriately or with regularity. However, if the arrangement is symmetrical, the crystallinity as a whole is clean and less distorted. It is most preferable to arrange the inversion substrate and the non-inversion substrate in a checkered pattern (see FIG. 4).
Furthermore, a plurality of substrates may be prepared by repeating the synthesis and separation in advance, but when the two substrates are formed, they are arranged as a single substrate, as described above. You may start from and repeat in the same way. In this case, the inverted substrate and the non-inverted substrate naturally have a checkered pattern.
Any of the methods described in Patent Document 3 and Patent Document 4 may be used as the dividing method. However, the smaller the cutting allowance, the greater the effect. Therefore, a separation method using electrochemical etching is more preferable.

  The initial substrate size is preferably 2 mm to 20 mm. A larger substrate is preferable, but a large substrate is difficult to obtain, so 3 mm to 10 mm is more preferable. Moreover, since it is preferable that the board | substrate which requires semiconductor processes, such as microfabrication, fits a wafer size, it is preferable that it is a multiple close | similar to 25.4 mm. That is, it is more preferable that the substrate has a size of 12 to 13 mm, 6 to 7 mm, 3 to 4 mm, and 5 ± 0.5 mm. It has been found that the efficiency is high in terms of effective use of the substrate.

  When joining a plurality of substrates side by side, the boundary may be cut by a laser, or may be cut by cleaving. Preferably, the substrate surface has an off angle of within 10 ° from the (100) plane, and is offset by 5 ° or more from the {110} direction to the {100} direction and is cut with a water column laser to obtain a good bonded state. This is preferable. Furthermore, it is preferable that the off direction is shifted by 5 ° or more from the cutting direction.

[Example 1]
A high-pressure synthetic single crystal diamond having a (100) plane, an off angle of 3 °, a size of 6 mm square, and a thickness of 300 μm was prepared, and the entire surface of the diamond having a depth of 0.5 to 1 μm was removed by RIE. . Next, carbon was implanted at an energy of 350 keV at a dose of 2 × 10 ¹⁶ cm ⁻² by ion implantation.

  Next, diamond was epitaxially synthesized by a vapor phase synthesis method. The synthesis conditions were set to prevent abnormal particles from growing. The methane concentration was as high as 5% or more (5%, 7%, 9%, and 12% were tested), and a very small amount of nitrogen was added. The amount of nitrogen tested 0.005%, 0.05%, 0.5%, 1%, 10%, 20% in terms of N / C ratio. The CVD epitaxial film grew about 300 μm.

  After the diamond film was grown, a portion 100 μm from the ends of the four sides was cut with a laser, and then the ion implantation layer was etched electrochemically. The ion-implanted layer was black after implantation and after CVD epitaxial growth, but when etched electrochemically, the black portion was removed and the substrate and the epitaxial film could be separated.

  Next, one side where the separated substrate and the epitaxial film were bonded was used as a common side, and the bonded surface was used as the upper surface for contact. (Arranged so that the hinges are opened when separating and arranging the substrates.) At this time, one side is in the <001> direction. Since the contact distance was set to be smaller than 30 μm, the two were joined by the film thickness growth of 50 μm or more. When growing 200 μm, only the surface was seen and the boundary was almost unknown. The resulting substrate is mirror image reversal from the right side of the original substrate (1), with the epitaxial plate (2) (separated substrate (2)) separated from the substrate (1) on the substrate (1). And are in a joined state.

  When the film was grown to 200 μm, ion implantation was performed under the same conditions as described above, and after further growth of 500 μm, the periphery was laser cut, and then the ion implanted layer was electrochemically etched and separated again. The separated substrate was spread so that the axis perpendicular to the hinge axis opened earlier was the hinge axis, and was further CVD-grown and joined as a single substrate. When the completed substrate is viewed from above, as shown in FIG. 7, there is a separation substrate (2) on the right side of the original substrate (1), and a substrate (1) below the original substrate (1). The epitaxial plate (3) (separated substrate (3)) grown again and separated again is joined with the mirror image inverted from the grown state, and next to the substrate (2) below (separated) On the right side of the substrate (3), the separation substrate (2) is grown as a substrate, and the epitaxial plate (4) (separation substrate (4)) separated again is mirror-inverted from the grown state. And is in a joined state.

Finally, it was possible to produce a single crystal substrate in which joint edges with partially uniform off angles could not be identified. When the crystallinity was examined by X-ray topography or the like, the target of defects such as dislocation was arranged in a mirror image relationship based on the original seed substrate. However, it was possible to fabricate a single crystal substrate that was firmly bonded and whose boundary was not visually recognized. In the case of a substrate with almost no dislocations, what is judged as the target was the density of the entire substrate. That is, the sides to be joined need to be cut very precisely in the <100> direction, but cannot be cut accurately in units of several tens of seconds. Therefore, even if the crystallinity in one crystal of the mosaic is in the range of several seconds in the X-ray rocking curve, there is a defect of several tens of seconds between the joined crystals. In X-ray topography, this shift is indicated by the density of X-rays. The shading has periodicity reflecting the crystalline periodicity. In addition, it was possible to determine whether or not the position of the diffraction spot was a crystallinity target having a mirror image relationship or periodicity. In other words, the area irradiated with X-rays is limited to one mosaic, the crystal is moved one area at a time, and when X-ray diffraction is taken, the position of the diffraction point is periodically mirror image-related by one area. The position was shifted so that
[Example 2]
As in Example 1, starting from the seed substrate, a substrate epitaxially grown by CVD was separated and manufactured. Unlike Example 1, a self-supported CVD epitaxially grown substrate was repeatedly produced using ion implantation, CVD episynthesis, laser cutting, and electrochemical etching without bonding the produced substrate and the original seed substrate.

At this time, the same ion implantation, CVD synthesis, laser cutting, and electrochemical etching were performed on the CVD epitaxially grown substrate produced simultaneously with the original seed crystal to produce a CVD epitaxially grown substrate. Eight substrates were produced by putting seed substrates. The substrate thickness was unified to 300 μm. The seed substrate is the substrate A, and the substrate that is first grown and separated from the substrate A is the separation substrate B (the mirror image is reversed from the growth state on the substrate A: the back surface is the front surface). The substrate thus obtained is designated as a separation substrate C (a mirror image inversion from the substrate A: the rear surface is the front surface), and a substrate grown and separated from the separation substrate B is a separation substrate D (a mirror image inversion from the separation substrate B). Further, separation substrates based on the substrate A and the separation substrates B, C, and D are sequentially referred to as separation substrates E, F, G, and H. The substrate that has been grown and separated undergoes mirror image reversal.
Crystallinity can be classified into two types, positive and inverted, and can be divided into a group of substrate A, separation substrate D, separation substrate F, separation substrate G and group of separation substrate B, separation substrate C, separation substrate E, separation substrate H. .

  The produced substrate was ion-implanted, and the separated surfaces were arranged as the upper surface. When the substrate was not rotated, but was translated and arranged in an open arrangement, the same off-angle as the original seed substrate could be maintained. Since the respective substrates were brought into contact with each other at an interval of 30 μm or less, they were easily joined when grown to about 50 μm.

  A further 1 mm thick film was grown on the bonded substrate, and the surface was polished to produce a very clean single crystal plate. When examined by X-ray topography, the same number of patterns as the seed substrate and mirror-inverted patterns were confirmed. The overall warpage was less when the inverted substrate and the non-inverted substrate were arranged so as to be symmetrical. That is, A, B, D, C in the first column as compared with the case where A, D, F, B are arranged in the first column and C, E, H, G are arranged in the second column in an appropriate order. By the way, the overall warpage was less when the second row was arranged in a checkered pattern with E, F, H, G.

Claims (6)

A single crystal diamond consisting of a plurality of mosaic areas,
1. A single crystal diamond substrate, wherein units A having specific crystallographic features and units B having crystallographic features and mirror image features are arranged in a mosaic pattern.   The single crystal diamond substrate according to claim 1, wherein the unit A and the unit B are periodically repeated.   The single crystal diamond substrate according to claim 1 or 2, wherein the unit A or the unit B is a unit of 3 mm or more.   The surface of the substrate is the (100) plane, and the inversion symmetry axis in the (100) plane of the unit A and the unit B whose crystallographic features are mirror images are parallel to <010> or <001>. The single crystal diamond substrate according to any one of claims 1 to 3.   Diamond is epitaxially grown by vapor phase synthesis based on the seed crystal substrate, the seed crystal substrate and the growth layer are separated and separated, and the separation surface is such that the crystallographic characteristics of the two separated substrates are mirror images. The substrate area is increased by repeating the steps of arranging, arranging, and epitaxially growing diamond on the arranged substrate to produce a single bonded substrate. 5. A method for producing a single crystal diamond substrate according to any one of 4 above. Diamond is epitaxially grown based on the seed crystal substrate by vapor phase synthesis, and the seed crystal substrate and the growth layer are separated and separated, so that the crystallographic characteristics of the two separated substrates are mirror images. Are arranged on the top surface, and a plurality of substrates are produced by repeating the process of epitaxially growing and separating the diamond by vapor phase synthesis based on the seed crystal substrate and the growth layer,
The single substrate according to any one of claims 1 to 4, wherein the plurality of substrates are arranged with a separation surface as an upper surface, arranged, and one bonded diamond is epitaxially grown on the arranged substrates. A method for producing a crystalline diamond substrate.

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