Manufacturing methods for quantum devices

Abstract

This invention provides a method for manufacturing quantum devices that can form optical waveguide sections with a desired shape. [Solution] A method for manufacturing a quantum device comprises the steps of: bonding a diamond substrate including a color center to a layer provided on a support substrate; etching the diamond substrate after the bonding step to form a first portion including the color center and a second portion having an inclined surface inclined with respect to the side wall of the first portion; forming a metal film on the inclined surface; and irradiating the side wall of the first portion with laser light reflected by the metal film to cut the first portion at a first position further away from the layer than the color center to form a first optical waveguide portion.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a quantum device.

Background Art

[0002] A diamond spin-based quantum computer that uses the electron spin of a color center, which is a composite defect of impurity atoms and vacancies in a diamond single crystal, as a quantum bit has been proposed (for example, Patent Document 1). Further, it is known to irradiate an object with a laser beam to cut the object (for example, Patent Documents 2-3). It is also known to form an optical device in a portion irradiated with a laser beam by irradiating a wide-bandgap semiconductor substrate with a laser beam (for example, Patent Document 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to form an optical waveguide portion made of diamond containing a color center, a diamond substrate containing a color center is thinned to a desired thickness. Here, it is conceivable to cut the diamond substrate to a desired thickness by irradiating the side wall of the diamond substrate with a laser beam. However, in this case, it may be difficult to form an optical waveguide portion having a desired shape.

[0005] One objective is to form an optical waveguide section with a desired shape. [Means for solving the problem]

[0006] In one embodiment, the method for manufacturing a quantum device is characterized by comprising the steps of: bonding a diamond substrate including a color center to a layer provided on a support substrate;, after the step of bonding the diamond substrate, etching the diamond substrate to form a first portion including the color center and a second portion having an inclined surface inclined with respect to the side wall of the first portion; forming a metal film on the inclined surface; and forming a first optical waveguide portion by reflecting laser light with the metal film and irradiating the side wall of the first portion, thereby cutting the first portion at a first position further away from the layer than the color center. [Effects of the Invention]

[0007] One aspect is that it is possible to form an optical waveguide section with a desired shape. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1(a) is a plan view of the quantum device according to Example 1, and Figure 1(b) is a cross-sectional view of AA in Figure 1(a). [Figure 2] Figures 2(a) to 2(c) are diagrams (part 1) showing the method for manufacturing a quantum device according to Example 1. [Figure 3] Figures 3(a) and 3(b) are diagrams (part 2) showing the method for manufacturing the quantum device according to Example 1. [Figure 4] Figures 4(a) and 4(b) are diagrams (part 3) showing the method for manufacturing the quantum device according to Example 1. [Figure 5] Figures 5(a) and 5(b) are diagrams (part 4) showing the method for manufacturing a quantum device according to Example 1. [Figure 6] Figures 6(a) and 6(b) are diagrams (part 5) showing the method for manufacturing the quantum device according to Example 1. [Figure 7] Figures 7(a) and 7(b) are diagrams (part 6) showing the method for manufacturing a quantum device according to Example 1. [Figure 8] Figures 8(a) and 8(b) are diagrams (part 7) illustrating the method for manufacturing a quantum device according to Example 1. [Figure 9] Figures 9(a) and 9(b) are diagrams (part 8) illustrating the method for manufacturing a quantum device according to Example 1. [Figure 10] Figures 10(a) and 10(b) are diagrams (number 9) showing a method for manufacturing a quantum device according to Example 1. [Figure 11] Figures 11(a) and 11(b) are diagrams (number 10) illustrating a method for manufacturing a quantum device according to Example 1. [Figure 12] Figures 12(a) and 12(b) are diagrams (part 11) illustrating the method for manufacturing a quantum device according to Example 1. [Figure 13] Figures 13(a) and 13(b) are diagrams (part 12) illustrating the method for manufacturing a quantum device according to Example 1. [Figure 14] Figures 14(a) and 14(b) are cross-sectional views of a diamond substrate when it is cut using a YAG laser beam. [Figure 15] Figures 15(a) and 15(b) are cross-sectional views of a diamond substrate when it is cut using a femtosecond laser beam. [Figure 16] Figure 16 shows an example of a processing apparatus used to cut a diamond substrate using femtosecond laser light. [Figure 17] Figure 17 shows an example of the processing apparatus in Example 1. [Figure 18] Figures 18(a) to 18(c) are cross-sectional views showing the irradiation of a metal film with laser light in Example 1. [Figure 19] Figures 19(a) to 19(d) are cross-sectional views showing a section of the first part of Modification 1 of Example 1. [Figure 20]Figs. 20(a) to 20(c) are cross-sectional views showing the first part and the second part in Modification 2 of Example 1. [Figure 21] Fig. 21(a) is a plan view of the quantum device according to Example 2, and Fig. 21(b) is a cross-sectional view taken along the line A-A of Fig. 21(a). [Figure 22] Figs. 22(a) and 22(b) are cross-sectional views (Part 1) showing the manufacturing method of the quantum device according to Example 2. [Figure 23] Figs. 23(a) and 23(b) are cross-sectional views (Part 2) showing the manufacturing method of the quantum device according to Example 2.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example

[0010] Fig. 1(a) is a plan view of the quantum device 100 according to Example 1, and Fig. 1(b) is a cross-sectional view taken along the line A-A of Fig. 1(a). The directions parallel to the upper surface of the support substrate 10 and perpendicular to each other are defined as the X-axis direction and the Y-axis direction. The direction perpendicular to the X-axis direction and the Y-axis direction is defined as the Z-axis direction. As shown in Figs. 1(a) and 1(b), a sapphire layer 32 is provided on the support substrate 10, and the second optical waveguide portion 24 is formed by the sapphire layer 32. The second optical waveguide portion 24 extends in the Y-axis direction. The support substrate 10 is, for example, a silicon substrate with an oxide film, and has a silicon substrate 11 and a silicon oxide film 12 provided on the silicon substrate 11.

[0011] A first optical waveguide section 20 made of diamond is provided on the second optical waveguide section 24. The first optical waveguide section 20 has a color center 21 and a plurality of through holes 22 arranged in the Y-axis direction with the color center 21 in between. Because a plurality of through holes 22 are provided, the first optical waveguide section 20 is a photonic crystal optical waveguide section in which the refractive index repeatedly changes in the Y-axis direction. The color center 21 is, for example, an SnV center which is a composite defect of carbon-substituted tin (Sn) and a vacancy (V) adjacent to the tin (Sn). A material with a lower refractive index than diamond may be embedded in the through holes 22.

[0012] The first optical waveguide section 20 has a tapered shape in which the width in the X-axis direction of the tip portion 25 in the +Y and -Y directions gradually decreases. The width in the X-axis direction of the central portion 26 between the tip portions 25 is almost constant. The second optical waveguide section 24 has a large width in the X-axis direction of the portion 27 that does not overlap with the first optical waveguide section 20. The width in the X-axis direction of the portion 28 that overlaps with the tip portion 25 of the first optical waveguide section 20 gradually decreases toward the portion 29 that overlaps with the central portion 26, with the width in the X-axis direction of portion 29 being the smallest.

[0013] When an optical pulse is introduced into the second optical waveguide section 24, for example from the -Y direction, the optical pulse is transmitted through the second optical waveguide section 24 and the first optical waveguide section 20 and incident on the color center 21. Upon introduction of the optical pulse, the color center 21 emits a single-photon photon pulse. The photon pulse is transmitted through the first optical waveguide section 20 and the second optical waveguide section 24 in the +Y direction. The tip portion 25 of the first optical waveguide section 20 and the portion 28 of the second optical waveguide section 24 that overlaps with the tip portion 25 of the first optical waveguide section 20 have different shapes. That is, from the -Y direction to the +Y direction, the width of the tip portion 25 of the first optical waveguide section 20 gradually increases (decreases), while the width of the portion 28 of the second optical waveguide section 24 gradually decreases (increases). As a result, optical pulses and photon pulses are transmitted between the first optical waveguide section 20 and the second optical waveguide section 24.

[0014] [Manufacturing method] Figures 2(a) to 13(b) show the manufacturing method of the quantum device 100 according to Example 1. Figures 2(a) to 2(c) are cross-sectional views showing the manufacturing method of the quantum device 100 according to Example 1. In Figures 3(a) to 13(b), (a) in each figure is a plan view showing the manufacturing method of the quantum device 100 according to Example 1, and (b) in each figure is a cross-sectional view AA of (a) in each figure.

[0015] As shown in Figure 2(a), atoms such as tin (Sn) are ion-implanted into the surface 31 of a single-crystal diamond substrate 30, and then the diamond substrate 30 is annealed in a vacuum or inert gas atmosphere. This forms color centers 21 in the diamond substrate 30. The color centers 21 are SnV centers, which are composite defects consisting of, for example, carbon-substituted tin (Sn) and a vacancy (V) adjacent to the tin (Sn). For example, a focused ion beam method is used as the ion implantation method. The atoms to be ion-implanted may not be tin (Sn), but may be nitrogen (N), silicon (Si), germanium (Ge), lead (Pb), or boron (B). Multiple color centers 21 may be formed in the diamond substrate 30, and a color center 21 with good luminescence characteristics may be selected from among them. The thickness T1 of the diamond substrate 30 is, for example, 400 μm to 500 μm, and the length L1 is, for example, 4 mm to 5 mm. The depth D from the surface 31 of the diamond substrate 30 to the color center 21 can be controlled by the implantation energy in ion implantation, for example, between 30 nm and 100 nm.

[0016] As shown in Figure 2(b), after bonding the sapphire substrate to the support substrate 10, the sapphire substrate is polished to a desired thickness to form a sapphire layer 32. The thickness T2 of the sapphire layer 32 is, for example, 500 nm to 1000 nm. The support substrate 10 is, for example, a silicon substrate with an oxide film, and has a silicon substrate 11 and a silicon oxide film 12 provided on the silicon substrate 11. The support substrate 10 and the sapphire substrate are bonded using a direct bonding method, such as a room-temperature bonding method by surface activation. The sapphire substrate is polished using, for example, a chemical mechanical polishing (CMP) method.

[0017] As shown in Figure 2(c), the surface 31 of the diamond substrate 30 on which the color centers 21 are formed is bonded to the sapphire layer 32. The bonding of the diamond substrate 30 and the sapphire layer 32 is performed using a direct bonding method, such as a room-temperature bonding method using surface activation.

[0018] As shown in Figures 3(a) and 3(b), the diamond substrate 30 is cut by irradiating it with laser light 50 at a point approximately 10 μm away from the surface of the sapphire layer 32. This results in a diamond substrate 30 with a thickness of approximately 10 μm. For example, the diamond substrate 30 is cut by changing the position of the diamond substrate 30 relative to the focusing lens 51 in the X-axis and Y-axis directions, thereby scanning the focal position 52 of the laser light 50 in the X-axis and Y-axis directions. A nanosecond laser beam, such as a YAG laser beam, is used as the laser light 50. After cutting the diamond substrate 30 with the laser light 50, the cut surface may be planarized using, for example, a CMP method.

[0019] As shown in Figures 4(a) and 4(b), a mask layer 60 made of resist is formed on the diamond substrate 30. The mask layer 60 has a rectangular opening 61 and an opening 62 located away from the opening 61 in the X-axis direction. The side of the opening 62 on the side of the opening 61 is a nearly vertical surface, and the side opposite the opening 61 is an inclined surface, for example, at about 45°. The openings 61 and 62 extend in the Y-axis direction.

[0020] The diamond substrate 30 is etched using the mask layer 60 as a mask. For example, the diamond substrate 30 is etched by a reactive ion etching (RIE) method using oxygen gas (O2 gas) as the reaction gas. After that, the mask layer 60 is removed. As a result, as shown in Figures 5(a) and 5(b), a first portion 40 is formed which includes the color center 21 and has a side wall 41 which is substantially perpendicular to the upper surface of the sapphire layer 32, and a second portion 42 which has an inclined surface 43 which is inclined with respect to the side wall 41 of the first portion 40. The first portion 40 and the second portion 42 are formed by the diamond substrate 30 and are aligned in the X-axis direction and extending in the Y-axis direction. The width W of the first portion 40 is, for example, 200 nm to 500 nm. The shortest distance L2 in the X-axis direction between the first portion 40 and the second portion 42 is, for example, 2 μm to 3 μm. The inclination angle θ of the inclined surface 43 with respect to the upper surface of the sapphire layer 32 is, for example, 40° or more and 50° or less. The diagram shows a case where a third portion 44, made of a diamond substrate 30, is formed on the opposite side of the second portion 42, with the first portion 40 in between; however, the third portion 44 does not necessarily have to be formed.

[0021] As shown in Figures 6(a) and 6(b), a metal film 45 is formed on the inclined surface 43 of the second part 42 using, for example, a vacuum deposition method and a lift-off method. The metal film 45 is formed on a part of the inclined surface 43, extending in the Y-axis direction, similar to the second part 42. The metal film 45 is, for example, a gold (Au) film or an aluminum (Al) film. The thickness of the metal film 45 is, for example, 30 nm to 100 nm. Sputtering may be used instead of vacuum deposition. An adhesion layer such as a titanium film or a chromium film may be provided between the metal film 45 and the inclined surface 43.

[0022] As shown in Figures 7(a) and 7(b), the first part 40 is cut by reflecting the laser beam 46 off the metal film 45 and irradiating the side wall 41 of the first part 40. The laser beam 46 is, for example, a femtosecond laser beam. For example, the first part 40 is cut by changing the position of the support substrate 10 relative to a focusing lens (not shown) in the Z-axis and Y-axis directions and scanning the focal position of the laser beam 46 in the X-axis and Y-axis directions. The height H of the first part 40 after cutting is, for example, 300 nm to 500 nm.

[0023] As shown in Figures 8(a) and 8(b), the diamond substrate 30 other than the first portion 40 is removed. That is, the second portion 42 and the third portion 44 are removed. For example, the second portion 42 and the third portion 44 are removed by etching using a reactive ion etching method with oxygen gas as the reaction gas.

[0024] As shown in Figures 9(a) and 9(b), a mask layer 64 is formed on the sapphire layer 32 that covers the region of the first portion 40 in which the first optical waveguide portion 20 is to be formed, and has an opening 63 in the region other than the region in which the first optical waveguide portion 20 is to be formed. The mask layer 64 is formed, for example, from a resist.

[0025] The first portion 40 is etched using the mask layer 64 as a mask. For example, the first portion 40 is etched by a reactive ion etching method using oxygen gas as the reaction gas. After that, the mask layer 64 is removed. As a result, a first optical waveguide portion 20 consisting of a diamond substrate 30 and including a color center 21 is formed, as shown in Figures 10(a) and 10(b).

[0026] As shown in Figures 11(a) and 11(b), a mask layer 66 having a plurality of apertures 65 arranged in the Y-axis direction on the first optical waveguide section 20, flanking the color center 21, is formed on the sapphire layer 32. The mask layer 66 is formed, for example, from resist. The planar shape of the apertures 65 is, for example, circular, but it may also be elliptical or rectangular.

[0027] The first optical waveguide section 20 is etched using the mask layer 66 as a mask. For example, the first optical waveguide section 20 is etched by a reactive ion etching method using oxygen gas as the reaction gas. After that, the mask layer 66 is removed. As a result, a plurality of through holes 22 are formed in the first optical waveguide section 20, aligned in the Y-axis direction, as shown in Figures 12(a) and 12(b). The plurality of through holes 22 are formed aligned in the Y-axis direction with the color center 21 in between when viewed from the +Z direction in a plan view.

[0028] As shown in Figures 13(a) and 13(b), a mask layer 68 is formed that covers the region where the second optical waveguide section 24 is to be formed and has an opening 67 adjacent to the region where the second optical waveguide section 24 is to be formed. The mask layer 68 is formed, for example, from a resist. Next, the sapphire layer 32 is etched using the mask layer 68 as a mask. For example, the sapphire layer 32 is etched by a reactive ion etching method using a chlorine-based gas (such as boron chloride (BCl3) gas) as the reaction gas. After that, the mask layer 68 is removed. As a result, as shown in Figures 1(a) and 1(b), a second optical waveguide section 24 consisting of the sapphire layer 32 and connected to the first optical waveguide section 20 is formed. Thus, the quantum device 100 according to Example 1 is formed.

[0029] Figures 14(a) and 14(b) are cross-sectional views of the diamond substrate 30 when it is cut using a YAG laser beam 70. As shown in Figures 14(a) and 14(b), when the diamond substrate 30 is cut by scanning the focal position 71 formed when the YAG laser beam 70 passes through the focusing lens 83, the cut surface 72 is tilted and a damage layer 73 is formed on the cut surface 72 due to the effects of heat. For this reason, when the diamond substrate 30 is cut using the YAG laser beam 70 to the height of the first optical waveguide section 20, the upper surface of the first optical waveguide section 20 becomes tilted and a damage layer 73 is formed.

[0030] Since a damaged layer 73 is formed, the diamond substrate 30 is cut by irradiating it with YAG laser light 70 at a distance of about 10 μm to 100 μm from the sapphire layer 32. After that, it is conceivable to polish the diamond substrate 30 by CMP or the like to the desired thickness. However, in this case, because the amount of polishing by the CMP method is large, the stress applied to the interface between the diamond substrate 30 and the sapphire layer 32 becomes large, and the diamond substrate 30 may peel off from the sapphire layer 32.

[0031] Figures 15(a) and 15(b) are cross-sectional views of the diamond substrate 30 when it is cut using a femtosecond laser beam 74. As shown in Figures 15(a) and 15(b), when the diamond substrate 30 is cut by scanning the focal position 75 of the femtosecond laser beam 74, the cut surface 76 becomes almost flat and no damage layer is formed on the cut surface 76. Therefore, the femtosecond laser beam 74 can be irradiated onto the diamond substrate 30 near the color center 21.

[0032] Figure 16 shows an example of a processing apparatus for cutting a diamond substrate 30 using femtosecond laser light 74. As shown in Figure 16, the laser 80 emits femtosecond laser light 74 based on instructions from the laser control device 81. The femtosecond laser light 74 is reflected by, for example, a mirror 82 and then incident on a focusing lens 83. The femtosecond laser light 74 is converted into focused light by the focusing lens 83 and focuses on the diamond substrate 30 (see also Figure 15(a)).

[0033] The support substrate 10 to which the diamond substrate 30 is bonded is placed on the stage 84. The stage 84 moves in the X-axis, Y-axis, and Z-axis directions according to instructions from the stage controller 85. Therefore, as the stage 84 moves and the diamond substrate 30 moves in the X-axis and Y-axis directions, the focal position 75 of the femtosecond laser beam 74 (see Figure 15(a)) is scanned in the X-axis and Y-axis directions, and the diamond substrate 30 is cut. However, when the stage 84 is moved in the X-axis direction to scan the femtosecond laser beam 74 in the X-axis direction, the support substrate 10 and the sapphire layer 32 may come into contact with the focusing lens 83. To avoid contact between the support substrate 10 and the sapphire layer 32 and the focusing lens 83, it is conceivable to use a focusing lens 83 with a long working distance. However, for the flattening of the cut surface 76 of the diamond substrate 30, it is preferable that the focal size of the femtosecond laser beam 74 be small, and for this purpose, it is preferable that the focusing lens 83 has high magnification. However, since it is currently difficult to realize a focusing lens with high magnification and a long working distance, it is difficult to form the first optical waveguide section 20 with the desired shape.

[0034] Figure 17 shows an example of the processing apparatus in Embodiment 1. As shown in Figure 17, in Embodiment 1, the laser beam 46 emitted by the laser 80a based on the instructions of the laser control device 81 is reflected by the mirror 82, passes through the focusing lens 83, and is then reflected by the metal film 45 and irradiated onto the side wall of the first portion 40. In this case, in order to scan the focal position of the laser beam 46 in the X-axis direction, the stage 84 should be moved in the Z-axis direction. Therefore, even without using a focusing lens 83 with a long work distance, contact between the focusing lens 83 and the support substrate 10 and the diamond substrate 30 is suppressed. Thus, a high-magnification focusing lens 83 can be used, and a first optical waveguide portion 20 with a desired shape can be formed.

[0035] According to Example 1, as shown in Figure 2(c), a diamond substrate 30 including a color center 21 is bonded to a sapphire layer 32 provided on a support substrate 10. As shown in Figures 4(a) to 5(b), the diamond substrate 30 is etched to form a first portion 40 including the color center 21 and a second portion 42 having an inclined surface 43 that is inclined with respect to the side wall 41 of the first portion 40. As shown in Figures 6(a) and 6(b), a metal film 45 is formed on the inclined surface 43. As shown in Figures 7(a) and 7(b), the first portion 40 is cut at a position further from the sapphire layer 32 than the color center 21 by reflecting laser light 46 off the metal film 45 and irradiating the side wall 41 of the first portion 40. As shown in Figures 9(a) to 10(b), the first portion 40 becomes the first optical waveguide portion 20. As shown in Figures 13(a), 13(b), and 1(a), 1(b), the sapphire layer 32 is etched to form the second optical waveguide section 24 connected to the first optical waveguide section 20. In this way, by reflecting the laser beam 46 with the metal film 45 and cutting the first section 40, the laser beam 46 can be focused using a high-magnification focusing lens, as explained in Figure 17. Therefore, the focal size of the laser beam 46 can be reduced to cut the first section 40, and the first optical waveguide section 20 with the desired shape can be formed.

[0036] Furthermore, in Example 1, as shown in Figures 3(a) and 3(b), the diamond substrate 30 is cut at a position further from the sapphire layer 32 than the position where the first portion 40 is cut in Figures 7(a) and 7(b), before forming the first portion 40 and the second portion 42. This reduces the amount of etching when etching the diamond substrate 30 to form the first portion 40 and the second portion 42 in Figures 4(a) to 5(b), allowing the first portion 40 to be formed in the desired shape. Thus, the first optical waveguide portion 20 can be formed in the desired shape.

[0037] Furthermore, in Example 1, as shown in Figures 7(a) and 7(b), a femtosecond laser beam is used for the laser beam 46 when cutting the first portion 40. This improves the flatness of the first portion 40, allowing the first optical waveguide portion 20 to be formed into a desired shape.

[0038] Furthermore, in Example 1, the first portion 40 is formed by etching the diamond substrate 30 on both sides of the color center 21, as shown in Figures 4(a) to 5(b). This reduces the amount of material cut when cutting the first portion 40 in Figures 7(a) and 7(b), allowing the first portion 40 to be formed into a desired shape. Thus, the first optical waveguide portion 20 can be formed into a desired shape.

[0039] Furthermore, in Example 1, as shown in Figures 3(a) and 3(b), the diamond substrate 30 is cut by irradiating the diamond substrate 30 with laser light 50. This makes it possible to suppress the delamination of the diamond substrate 30 from the sapphire layer 32 when thinning the diamond substrate 30.

[0040] Furthermore, in Example 1, as shown in Figure 5(b), the inclination angle θ of the inclined surface 43 with respect to the upper surface of the sapphire layer 32 is 40° or more and 50° or less. This makes it easier for the upper surface of the first portion 40 to be formed parallel to the upper surface of the sapphire layer 32 when the laser beam 46 is reflected by the metal film 45 and the first portion 40 is cut, as shown in Figures 7(a) and 7(b). Thus, the first optical waveguide portion 20 can be formed in the desired shape.

[0041] Here, we will describe the irradiation of the metal film 45 with laser light 46 when the tilt angle θ is 45°, less than 45°, and greater than 45°. Figures 18(a) to 18(c) are cross-sectional views showing the irradiation of the metal film 45 with laser light 46 in Example 1. Figure 18(a) is the case when the tilt angle θ is 45°, Figure 18(b) is the case when it is less than 45°, and Figure 18(c) is the case when it is greater than 45°.

[0042] As shown in Figure 18(a), when the inclination angle θ is 45°, the mirror 82 and the focusing lens 83 are arranged side by side in the direction normal to the upper surface of the sapphire layer 32, and the laser beam 46 is incident on the metal film 45 from a direction perpendicular to the upper surface of the sapphire layer 32. This allows the laser beam 46 to be irradiated onto the side wall 41 of the first portion 40 from a direction perpendicular to the side wall 41. Thus, the upper surface of the first portion 40 is formed parallel to the upper surface of the sapphire layer 32.

[0043] As shown in Figures 18(b) and 18(c), when the inclination angle θ is less than or greater than 45°, the mirror 82 and the focusing lens 83 are arranged side by side in a direction appropriately inclined with respect to the normal direction of the upper surface of the sapphire layer 32. This allows the laser beam 46 to be irradiated onto the side wall 41 of the first portion 40 from a direction perpendicular to the side wall 41, so that the upper surface of the first portion 40 is formed parallel to the upper surface of the sapphire layer 32.

[0044] Furthermore, in Example 1, as shown in Figures 11(a) to 12(b), the first optical waveguide section 20 is etched to form a plurality of through holes 22 aligned in the Y-axis direction with the color center 21 in between. This results in a first optical waveguide section 20 which is a photonic crystal optical waveguide section in which the refractive index repeatedly changes in the Y-axis direction.

[0045] In Example 1, the support substrate 10 was shown as a silicon substrate with an oxide film, and the layer provided on the support substrate 10 was a sapphire layer 32. However, the invention is not limited to this case. The support substrate 10 may be a substrate other than a silicon substrate with an oxide film, as long as it enables the transmission of optical pulses and photon pulses through the second optical waveguide section 24. For example, it may be a silicon oxide substrate. Similarly, the layer provided on the support substrate 10 may be a layer other than the sapphire layer 32, as long as it enables the transmission of optical pulses and photon pulses. For example, it may be a silicon nitride layer, a silicon carbide layer, or a silicon oxide layer.

[0046] [Differentiation] Figures 19(a) to 19(d) are cross-sectional views showing the cutting of the first portions 40a to 40c in Modification 1 of Example 1. As shown in Figure 19(a), in Modification 1 of Example 1, multiple first portions 40a to 40c are arranged in the X-axis direction. The laser light 46 reflected by the metal film 45 is first irradiated onto the first portion 40a adjacent to the second portion 42. Therefore, as shown in Figure 19(b), the first portion 40a is first cut by the laser light 46.

[0047] After the first part 40a is cut, the laser beam 46 is irradiated onto the first part 40b. As a result, as shown in Figure 19(c), the first part 40b is cut by the laser beam 46. After the first part 40b is cut, the laser beam 46 is irradiated onto the first part 40c. As a result, as shown in Figure 19(d), the first part 40c is cut by the laser beam 46.

[0048] As shown in Modification 1 of Example 1, a plurality of first portions 40a to 40c may be formed sequentially from the inclined surface 43 of the second portion 42. Then, the plurality of first portions 40a to 40c may be sequentially cut by reflecting the laser light 46 off the metal film 45 and irradiating them sequentially. This makes it possible to easily form a high-density integrated first optical waveguide portion 20.

[0049] Figures 20(a) to 20(c) are cross-sectional views showing the first part 40a, 40b and the second part 42 in a modified example 2 of Embodiment 1. As shown in Figures 20(a) to 20(c), the second part 42 may have inclined surfaces 43 on both sides in the X-axis direction, each of which may be provided with a metal film 45. The metal films 45 provided on each inclined surface 43 may be connected to each other or separated from each other. Furthermore, the inclined surfaces 43 may be flat surfaces as shown in Figures 20(a) and 20(b), or curved surfaces as shown in Figure 20(c).

[0050] Multiple first parts 40a and 40b may be provided so as to sandwich the second part 42 in the X-axis direction. The first parts 40a and 40b may be cut by reflecting the laser beam 46 off the metal film 45 on each of the inclined surfaces 43 of the second part 42 and irradiating the first parts 40a and 40b with the laser beam 46.

[0051] As in the modified example 2 of Example 1, a plurality of first parts 40a and 40b that sandwich the second part 42 from the X-axis direction, and a second part 42 having inclined surfaces 43 on both sides in the X-axis direction may be formed. Then, the first parts 40a and 40b that sandwich the second part 42 may be cut by reflecting the laser light 46 off the metal films 45 provided on each of the inclined surfaces 43 on both sides of the second part 42 and irradiating them with the laser light. This makes it possible to reduce the number of second parts 42, that is, to reduce the formation area of ​​the second part 42, and thus the quantum device can be miniaturized.

[0052] Furthermore, the inclined surface 43 of the second part 42 may be a flat surface as shown in Figures 20(a) and 20(b), or it may be a curved surface as shown in Figure 20(c). When the inclined surface 43 is a flat surface, it becomes easier to direct the laser beam 46 to desired positions on the first parts 40a and 40b when the laser beam 46 is reflected by the metal film 45. [Examples]

[0053] Figure 21(a) is a plan view of the quantum device 200 according to Example 2, and Figure 21(b) is a cross-sectional view AA of Figure 21(a). As shown in Figures 21(a) and 21(b), in the quantum device 200, the second optical waveguide section 24 is removed below the central portion 26 of the first optical waveguide section 20. That is, the second optical waveguide section 24 is separated below the central portion 26 of the first optical waveguide section 20. In addition, the second portion 42 and the third portion 44, which are made of the diamond substrate 30, remain on the sapphire layer 32. The other configurations are the same as in Example 1, so their description is omitted.

[0054] [Manufacturing method] Figures 22(a) to 23(b) are cross-sectional views showing the manufacturing method of the quantum device 200 according to Example 2. Figures 22(a) and 23(a) are plan views showing the manufacturing method of the quantum device 200 according to Example 2, and Figures 22(b) and 23(b) are cross-sectional views AA of Figures 22(a) and 23(a). First, the same steps as in Figures 2(a) to 7(b) of Example 1 are carried out. Then, while leaving the second portion 42 and the third portion 44 made of the diamond substrate 30 intact, the same steps as in Figures 9(a) to 13(b) of Example 1 are carried out. As a result, the first optical waveguide portion 20 and the second optical waveguide portion 24 are formed as shown in Figures 22(a) and 22(b).

[0055] As shown in Figures 23(a) and 23(b), a mask layer 90 is formed on the support substrate 10, having an opening 91 that exposes the side surface of the second optical waveguide portion 24 where it overlaps with the central portion 26 of the first optical waveguide portion 20. The mask layer 90 is formed, for example, from a resist. Next, using the mask layer 90 as a mask, the second optical waveguide portion 24 where it overlaps with the central portion 26 of the first optical waveguide portion 20 is removed by etching. For example, by using a reactive ion etching method with a chlorine-based gas as the reaction gas and a low bias voltage, the second optical waveguide portion 24 where it overlaps with the central portion 26 of the first optical waveguide portion 20 is etched. After that, the mask layer 90 is removed. As a result, as shown in Figures 21(a) and 21(b), the second optical waveguide portion 24 is separated below the central portion 26 of the first optical waveguide portion 20. Thus, the quantum device 200 according to Example 2 is formed.

[0056] According to Example 2, as shown in Figures 23(a) and 23(b), a mask layer 90 is formed that covers the first optical waveguide section 20 and has an opening 91 that exposes the portion of the second optical waveguide section 24 that overlaps with the first optical waveguide section 20. Then, as shown in Figures 21(a) and 21(b), the portion of the second optical waveguide section 24 that overlaps with the first optical waveguide section 20 is removed using the mask layer 90. As a result, the second optical waveguide section 24 is divided at the lower side by the central portion 26 of the first optical waveguide section 20, so that the optical pulses transmitted through the second optical waveguide section 24 can be efficiently incident onto the color center 21.

[0057] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims.

[0058] Furthermore, the following additional information is disclosed regarding the above explanation. (Note 1) A method for manufacturing a quantum device, comprising: a step of bonding a diamond substrate including a color center to a layer provided on a support substrate; a step of etching the diamond substrate after the step of bonding the diamond substrate to form a first portion including the color center and a second portion having an inclined surface inclined with respect to the side wall of the first portion; a step of forming a metal film on the inclined surface; and a step of reflecting laser light with the metal film and irradiating the side wall of the first portion to cut the first portion at a first position further away from the layer than the color center to form a first optical waveguide portion. (Note 2) The method for manufacturing a quantum device according to Note 1, further comprising the step of etching the layer to form a second optical waveguide connected to the first optical waveguide. (Note 3) The method for manufacturing a quantum device according to Note 2, further comprising the steps of: forming a mask layer that covers the first optical waveguide portion and has an opening that exposes a portion of the second optical waveguide portion that overlaps with the first optical waveguide portion; and removing the overlapping portion of the second optical waveguide portion using the mask layer. (Note 4) The method for manufacturing a quantum device according to Note 1 or 2, further comprising the step of cutting the diamond substrate at a second position further away from the layer than the first position, before the step of forming the first and second portions. (Note 5) The method for manufacturing a quantum device according to Note 1 or 2, characterized in that the laser light is femtosecond laser light. (Note 6) The method for manufacturing a quantum device according to Note 1 or 2, characterized in that the step of forming the first portion is to form the first portion by etching the diamond substrate on both sides of the color center. (Note 7) The method for manufacturing a quantum device according to Note 4, characterized in that the step of cutting the diamond substrate is to cut the diamond substrate by irradiating the diamond substrate with laser light at the second position. (Note 8) The method for manufacturing a quantum device according to Note 1 or 2, further comprising the step of etching the first optical waveguide portion to form a plurality of through holes aligned in one direction with respect to the color center. (Note 9) The method for manufacturing a quantum device according to Note 1 or 2, characterized in that the inclination angle of the inclined surface with respect to the upper surface of the layer is 40° or more and 50° or less. (Note 10) The method for manufacturing a quantum device according to Note 1 or 2, characterized in that the step of forming the first part is to form a plurality of first parts arranged sequentially from the inclined surface of the second part, and the step of cutting the first part is to sequentially cut the plurality of first parts by reflecting the laser light with the metal film and irradiating the side walls of the plurality of first parts sequentially. (Note 11) The method for manufacturing a quantum device according to Note 1 or 2, characterized in that the step of forming the first part and the second part is to form a plurality of first parts that sandwich the second part from one direction and the second part having the inclined surfaces on both sides in the one direction, and the step of cutting the first part is to cut the plurality of first parts by reflecting the laser light off the metal films provided on the inclined surfaces on both sides of the second part and irradiating the plurality of first parts that sandwich the second part. (Note 12) The method for manufacturing a quantum device according to Note 1 or 2, characterized in that the inclined surface is a flat surface or a curved surface. (Note 13) The method for manufacturing a quantum device according to Note 1 or 2, characterized in that the support substrate is a silicon substrate with an oxide film or a silicon oxide substrate, and the layer is a sapphire layer, a silicon nitride layer, a silicon carbide layer, or a silicon oxide layer. [Explanation of symbols]

[0059] 10...Support substrate, 11...Silicon substrate, 12...Silicon oxide film, 20...First optical waveguide section, 21...Color center, 22...Through hole, 24...Second optical waveguide section, 25...Tip section, 26...Central section, 27...Section, 28...Section, 29...Section, 30...Diamond substrate, 31...Surface, 32...Sapphire layer, 40...First section, 41...Side wall, 42...Second section, 43...Inclined surface, 44...Third section, 45...Metal film, 46...Laser beam, 50...Laser beam, 51...Focusing lens, 52...Focal position, 60 ...mask layer, 61...aperture, 62...aperture, 63...aperture, 64...mask layer, 65...aperture, 66...mask layer, 67...aperture, 68...mask layer, 70...YAG laser beam, 71...focal position, 72...cross-section, 73...damage layer, 74...femtosecond laser beam, 75...focal position, 76...cross-section, 80, 80a...laser, 81...laser control device, 82...mirror, 83...focusing lens, 84...stage, 85...stage controller, 90...mask layer, 91...aperture, 100, 200...quantum device

Claims

1. A process of bonding a diamond substrate including a color center to a layer provided on a support substrate, The process of joining the diamond substrate, followed by etching the diamond substrate to form a first portion including the color center and a second portion having an inclined surface inclined with respect to the side wall of the first portion, The process of forming a metal film on the inclined surface, A method for manufacturing a quantum device, comprising the step of forming a first optical waveguide portion by reflecting laser light with the metal film and irradiating the side wall of the first portion, thereby cutting the first portion at a first position further away from the layer than the color center.

2. The method for manufacturing a quantum device according to claim 1, further comprising the step of etching the layer to form a second optical waveguide portion connected to the first optical waveguide portion.

3. A step of forming a mask layer having an opening that covers the first optical waveguide portion and exposes the portion of the second optical waveguide portion that overlaps with the first optical waveguide portion, The method for manufacturing a quantum device according to claim 2, further comprising the step of removing the overlapping portion of the second optical waveguide using the mask layer.

4. The method for manufacturing a quantum device according to claim 1 or 2, further comprising the step of cutting the diamond substrate at a second position further away from the layer than the first position, prior to the step of forming the first and second portions.

5. The method for manufacturing a quantum device according to claim 1 or 2, characterized in that the laser light is femtosecond laser light.

6. The method for manufacturing a quantum device according to claim 4, characterized in that the step of cutting the diamond substrate is to cut the diamond substrate by irradiating it with laser light at the second position.

7. The method for manufacturing a quantum device according to claim 1 or 2, characterized in that the inclination angle of the inclined surface with respect to the upper surface of the layer is 40° or more and 50° or less.

8. The step of forming the first and second parts involves forming a plurality of first parts that sandwich the second part from one direction, and the second part having the inclined surfaces on both sides in that one direction. The method for manufacturing a quantum device according to claim 1 or 2, characterized in that the step of cutting the first portion is to cut the plurality of first portions by reflecting the laser light off the metal films provided on the inclined surfaces on both sides of the second portion and irradiating the plurality of first portions that sandwich the second portion.

9. The method for manufacturing a quantum device according to claim 1 or 2, characterized in that the inclined surface is a flat surface or a curved surface.

10. The support substrate is a silicon substrate with an oxide film or a silicon oxide substrate. The method for manufacturing a quantum device according to claim 1 or 2, characterized in that the aforementioned layer is a sapphire layer, a silicon nitride layer, a silicon carbide layer, or a silicon oxide layer.

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