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US-12622186-B2 - Method of manufacturing diamond substrate

US12622186B2US 12622186 B2US12622186 B2US 12622186B2US-12622186-B2

Abstract

A method of manufacturing a diamond substrate includes: a step of placing a laser condensing unit 190 configured to condense laser light B so as to face an upper surface 10 a of a block 10 of single crystal diamond; and a step of forming a modified layer 20, which includes a processing mark 21 b of graphite and a crack 22 b extending along a surface ( 111 ) around the processing mark 21 b, along the surface ( 111 ) of the single crystal diamond at a predetermined depth from an upper surface of the block by radiating the laser light B on the upper surface 10 a of the block 10 from the laser condensing unit 190 under predetermined conditions and condensing the laser light B inside the block 10, and moving the laser condensing unit 190 and the block 10 in a relative manner two-dimensionally.

Inventors

  • Junichi Ikeno
  • Yohei Yamada
  • Hideki Suzuki
  • Rika Matsuo
  • Hitoshi Noguchi

Assignees

  • SHIN-ETSU POLYMER CO., LTD.
  • SHIN-ETSU CHEMICAL CO., LTD.
  • NATIONAL UNIVERSITY CORPORATION SAITAMA UNIVERSITY

Dates

Publication Date
20260505
Application Date
20220701
Priority Date
20210702

Claims (20)

  1. 1 . A method of manufacturing a diamond substrate comprising: a step of placing a laser condensing unit configured to condense laser light so as to face an upper surface of a block of single crystal diamond as a main surface of said upper surface; and a step of forming a modified layer, which includes a processing mark of graphite, along the surface (111) of the single crystal diamond, at a predetermined depth from the upper surface of the block, and a crack extending in a [1-10 ] direction from the processing mark to a surrounding area around the processing mark along the surface (111), by radiating the laser light on the upper surface of the block from the laser condensing unit and condensing the laser light inside the block, and moving the laser condensing unit and the block in a relative manner two-dimensionally, wherein the step of forming the modified layer includes a step of moving the laser condensing unit and the block in a relative manner in a predetermined scanning direction; and a step of moving the laser condensing unit and the block in a relative manner in a direction orthogonal to the scanning direction at a line pitch d, and wherein the line pitch dis set such that a relationship between the line pitch d and a length L extending from the processing mark along the surface (111) of the crack satisfies the length L> the line pitch d.
  2. 2 . The method of manufacturing a diamond substrate according to claim 1 , wherein the block has a substantially planar shape having an upper surface as the (111) surface of the single crystal diamond.
  3. 3 . The method of manufacturing a diamond substrate according to claim 2 , wherein the step of forming the modified layer includes moving the laser condensing unit and the block-in a in the relative manner direction orthogonal to the scanning direction at a predetermined interval.
  4. 4 . The method of manufacturing a diamond substrate according to claim 2 , wherein the step of forming the modified layer includes forming the modified layer at a predetermined depth over an entire surface of the upper surface.
  5. 5 . The method of manufacturing a diamond substrate according to claim 2 , further comprising a step of causing the block to spontaneously delaminate into a portion up to a depth from the upper surface to the modified layer, and a portion deeper than the modified layer.
  6. 6 . The method of manufacturing a diamond substrate according to claim 1 , further comprising: in the step of forming the modified layer the predetermined scanning direction is a [-1-12] direction or a [11-2] direction, and wherein the direction orthogonal to the scanning direction is a [−111] direction or a [1-10] direction.
  7. 7 . The method of manufacturing a diamond substrate according to claim 6 , wherein the laser light is pulsed laser light, and the graphite of the processing mark is formed by laser light reflected by a crack extending from another adjacent processing mark in at least one of the scanning direction and the direction orthogonal to the scanning direction.
  8. 8 . The method of manufacturing a diamond substrate according to claim 1 , wherein the step of forming the modified layer includes forming the modified layer at a predetermined depth over an entire surface of the upper surface.
  9. 9 . The method of manufacturing a diamond substrate according to claim 1 , further comprising a step of causing the block to spontaneously delaminate into a portion up to a depth from the upper surface to the modified layer, and a portion deeper than the modified layer.
  10. 10 . The method of manufacturing a diamond substrate according to claim 1 , wherein the laser light has a pulse width in a range of several ns to several hundred ns.
  11. 11 . The method of manufacturing a diamond substrate according to claim 1 , wherein in the step of forming the modified layer, the line pitch d is 50 μm to 100 μm.
  12. 12 . The method of manufacturing a diamond substrate according to claim 1 , wherein in the step of forming a modified layer, a processing mark directing toward a lower surface by a first scan line directing in a [-1-12] direction and a processing mark directing toward the upper surface by a second scan line directing in a [11-2] direction are formed by the laser light, and wherein a cleavage occurs in a [1-10] direction and the modified layer expands due to an expansion of the processing mark directing toward the upper surface.
  13. 13 . A method of manufacturing a diamond substrate comprising: a step of placing a laser condensing unit configured to condense laser light so as to face an upper surface of a block of single crystal diamond as a main surface of said upper surface; and a step of forming a modified layer, which includes a processing mark of graphite, along the surface (111) of the single crystal diamond, at a predetermined depth from the upper surface of the block, and a crack extending from the processing mark to a surrounding area around the processing mark and a crack extending in a [1-10] direction from the processing mark to a surrounding area around the processing mark along the surface (111), by radiating the laser light on the upper surface of the block from the laser condensing unit and condensing the laser light inside the block, and moving the laser condensing unit and the block in a relative manner two-dimensionally, wherein in the step of forming a modified layer, a processing mark directing toward a lower surface by a first scan line directing in a [-1-12] direction and a processing mark directing toward the upper surface by a second scan line directing in a [11-2] direction are formed by the laser light, and wherein a cleavage occurs in a [1-10] direction and the modified layer expands due to an expansion of the processing mark directing toward the upper surface.
  14. 14 . The method of manufacturing a diamond substrate according to claim 13 , wherein the block has a substantially planar shape having an upper surface as the (111) surface of the single crystal diamond.
  15. 15 . The method of manufacturing a diamond substrate according to claim 13 , wherein the step of forming the modified layer includes moving the laser condensing unit and the block in the relative manner in a direction orthogonal to the scanning direction at a predetermined interval.
  16. 16 . The method of manufacturing a diamond substrate according to claim 15 , wherein the step of forming the modified layer includes forming the modified layer at a predetermined depth over an entire surface of the upper surface.
  17. 17 . The method of manufacturing a diamond substrate according to claim 15 , further comprising a step of causing the block to spontaneously delaminate into a portion up to a depth from the upper surface to the modified layer, and a portion deeper than the modified layer.
  18. 18 . The method of manufacturing a diamond substrate according to claim 13 , wherein in the step of forming the modified layer, a scanning line of the laser light is scanned in a [-1-12] direction at a dot pitch, shifted by a line pitch in a [1-10] direction orthogonal to the [-1-12], and scanned in a [11-2] direction at a dot pitch.
  19. 19 . The method of manufacturing a diamond substrate according to claim 13 , wherein a growth height of the processing mark is 30 μm or less.
  20. 20 . The method of manufacturing a diamond substrate according to claim 13 , wherein the modified area is formed between a first portion and a second portion of the single crystal diamond.

Description

CROSS REFERENCE TO RELATED APPLICATION This application is based upon and claims the benefit of priority under 35 U.S.C. § 119 from Japanese Patent Application No. 2021-110836 filed on Jul. 2, 2021, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a method of manufacturing a diamond substrate, and more particularly to a method of manufacturing a diamond substrate by processing single crystal diamond using laser light. BACKGROUND Conventionally, silicon carbide (SiC) and gallium nitride (GaN) have been provided as semiconductor materials suitable for power devices instead of silicon (Si). However, diamond semiconductors have attracted attention as a next-generation material because they have a higher dielectric breakdown field, a higher power control index, and the highest thermal conductivity as compared with the above semiconductor materials, and research and development have been advancing toward practical application. Further, since a nitrogen-vacancy (NV) center in diamond is capable of highly sensitive magnetic detection at room temperature, this is expected to be applied to magnetic sensors, and research and development in this field have also been conducted (see WO 2015/107907 A1). Single crystal diamond which is expected to be applied to these semiconductors is synthesized by a high pressure and high temperature (HPHT) method and homoepitaxial growth, and these synthesis methods make it difficult to increase the area of a bulk substrate of single crystal diamond for use in semiconductor processes. Accordingly, a chemical vapor deposition (CVD) method has been applied in which single crystal diamond is heteroepitaxially grown by using a single crystal magnesium oxide (MgO) as a base crystal, because this CVD method is advantageous in increasing the area. In the heteroepitaxial growth by means of the CVD method, a bulk crystal of single crystal diamond, which is grown in the same orientation as the crystal orientation of the base MgO crystal, is obtained. That is, a bulk crystal of diamond with a crystal orientation [100] is obtained when the crystal orientation of the base MgO crystal is [100], and a bulk crystal of diamond with a crystal orientation [111] is obtained when the crystal orientation of the base MgO crystal is [111]. In the application of single crystal diamond to a magnetic sensor, it is necessary to form a high-density NV center and align the orientation axes of the NV center. Since a technique for orienting a high-density NV center in the [111] direction has been established by the CVD method, there has been an increasing need for a (111) bulk crystal using single crystal diamond having a main surface as a (111) surface (see WO 2015/046294 A1 and JP 2021-080153 A). SUMMARY Meanwhile, a bulk crystal of single crystal diamond obtained by heteroepitaxial growth is sliced and processed into a plate-like substrate, but diamond is hard and not easy to be processed. As a method for processing into a substrate, a smart cut technique is used in which a defective layer is introduced by ion implantation and is removed by etching to thereby perform delamination, but there has been a problem that a device in a high vacuum environment is required for ion implantation, and the processing time is long. Although it is possible to perform delamination with a thickness of several μm, there have been no cases of delamination with a thickness of several hundred μm. Other methods for processing into a substrate include polishing a bulk crystal of single crystal diamond, which is separated from abase crystal, to a desired thickness, or applying chemical mechanical polishing (CMP). Further, single crystal diamond obtained by means of the conventional HPHT method is processed to slice an ingot, or a block made by further cutting an ingot to a fixed length, into a substrate, but there has been a problem that a loss occurs as a cutting margin. Since it is especially difficult to polish a bulk crystal of single crystal diamond with the [111] orientation, the development of a manufacturing method for obtaining a (111) substrate has been required. As described above, there has been a need for a manufacturing method in which a hulk crystal, an ingot, or a block of (111) single crystal diamond, which is expected to be applied to a high-precision magnetic sensor, is sliced into a substrate with a reduction in processing loss due to a cutting margin by means of a relatively simple method. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a diamond substrate by which a (111) substrate is manufactured with little processing loss from a bulk crystal of single crystal diamond with an [111] orientation, which is heteroepitaxially grown by a CVD method, and from an ingot or a block of single crystal diamond obtained by an HTHP method. In order to solve the ab