JP7131474B2 - Diamond layer manufacturing method - Google Patents

Description

The present invention relates to a diamond layer manufacturing method for forming a diamond layer on a substrate.

Conventionally, for example, Patent Document 1 proposes a diamond layer having nitrogen-vacancy centers (hereinafter also referred to as NV centers). When the NV center captures an electron and becomes a negatively charged NV ^- center, it is the only solid in the solid that allows manipulation and detection of a single spin by light at room temperature, resulting in a long coherence time. For this reason, diamond layers having NV centers are being studied for application to, for example, magnetic sensors.

The diamond layer having NV centers is manufactured, for example, as follows. That is, first, a substrate is prepared whose main surface has a predetermined off angle with respect to a predetermined plane (eg, (111) plane). In this case, since the substrate has an off-angle on the main surface, a kink, which is a step portion of atoms, is formed. Then, a diamond layer (that is, an atomic layer) is grown on this main surface along a predetermined surface by plasma-enhanced chemical vapor deposition (hereinafter simply referred to as plasma CVD) using microwaves.

At this time, in the plasma CVD method, a diamond layer is formed using a reactive gas containing nitrogen in addition to hydrogen and methane. As a result, nitrogen may be incorporated during the growth of the diamond layer, and the incorporation of nitrogen tends to form vacancies adjacent to the nitrogen. Thus, a diamond layer with NV centers is formed.

Japanese Patent Application Publication No. 2015-107907

By the way, for example, when a diamond layer having NV centers is used as a magnetic sensor, the higher the density of the NV centers, the higher the sensitivity of the magnetic sensor. Therefore, at present, it is desired to form NV centers at a high density.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method of manufacturing a diamond layer that allows NV centers to be formed at a high density.

In order to achieve the above object, claim 1 provides a method for producing a diamond layer (20) for growing a diamond layer (20) on a substrate (10), the method having a principal surface (10a) and a principal surface with respect to a predetermined plane. preparing a substrate having a predetermined off-angle and having an initial kink (11) formed on the main surface; and forming a diamond layer (20) having an NV center on the main surface. forming a new kink (12) on the main surface and performing a CVD method using a reaction gas containing nitrogen and methane to form a diamond layer having NV centers. and growing two-dimensionally along the plane direction of the predetermined plane.

According to this, since the diamond layer is two-dimensionally grown after the step of forming the new kink, nitrogen is easily taken in when the diamond layer is grown, and the density of the NV center can be increased.

It should be noted that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and specific components etc. described in the embodiments described later.

FIG. 4 is a cross-sectional view showing a manufacturing process for forming a diamond layer in the first embodiment; 1B is a cross-sectional view showing a manufacturing process for forming a diamond layer following FIG. 1A; FIG. FIG. 1B is a cross-sectional view showing a manufacturing process for forming a diamond layer following FIG. 1B; 1B is a perspective view of FIG. 1A; FIG. 1C is a perspective view of FIG. 1B; FIG. 1D is a perspective view of FIG. 1C; FIG. It is a schematic diagram which shows the structure of a chamber. It is a figure which shows the growth conditions of a diamond layer. It is a schematic diagram which shows NV center. FIG. 11 is a perspective view showing a step of forming a kink in the third embodiment;

An embodiment of the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, portions that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A method for manufacturing a diamond layer according to the first embodiment will be described with reference to FIGS. 1A to 1C and FIGS. 2A to 2C. It should be noted that the diamond layer 20 manufactured by the manufacturing method of the present embodiment is suitable for use in, for example, constructing a magnetic sensor element or the like. Also, FIG. 1A corresponds to a cross section taken along line IA-IA in FIG. 2A. FIG. 1B corresponds to a cross section taken along line IB--IB in FIG. 2B. FIG. 1C corresponds to a cross section along the IC--IC line in FIG. 2C.

First, as shown in FIGS. 1A and 2A, a diamond substrate 10 is prepared. In this embodiment, the diamond substrate 10 is prepared so that the main surface 10a has a predetermined off angle with respect to the (111) plane. In this embodiment, the (111) plane corresponds to the predetermined plane.

If the off-angle is too large, two-dimensional growth becomes difficult when growing the diamond layer 20, which will be described later, and the crystallinity deteriorates. Further, since the diamond substrate 10 has an off-angle, an initial kink 11, which is an atomic step portion, is formed on the main surface 10a.

Next, as shown in FIGS. 1B and 2B, a step of newly forming a plurality of new kinks 12 on the main surface 10a of the diamond substrate 10 is performed. That is, a step of increasing the kinks 11 and 12 on the main surface 10a of the diamond substrate 10 is performed. In this embodiment, the step of forming the new kink 12 is performed by three-dimensionally growing the diamond layer 20 by plasma CVD using microwaves.

Specifically, first, as shown in FIG. 3, a chamber 30 for plasma CVD is prepared. The chamber 30 of this embodiment includes a mounting table 31 on which the diamond substrate 10 is mounted. A heating device 32 for heating the diamond substrate 10 is accommodated in the mounting table 31 . Although not particularly shown in FIG. 3, the chamber 30 is provided with a waveguide through which microwaves are introduced, a pipe for introducing a reaction gas, which will be described later, and the like.

Then, the diamond substrate 10 is placed on the mounting table 31 in the chamber 30, and the diamond layer 20 is three-dimensionally grown along the plane direction of the (111) plane and the direction crossing the plane direction by the plasma CVD method. Specifically, when the diamond layer 20 is grown three-dimensionally, a reactive gas containing hydrogen, methane, etc. is introduced into the chamber 30, and control parameters for growing the diamond layer 20 are adjusted to grow the diamond layer 20 three-dimensionally. grow. In this embodiment, as shown in FIG. 4, when the diamond layer 20 is three-dimensionally grown, the ratio of methane in the reaction gas is 0.5 to 4%, the degree of vacuum in the chamber is 70 to 150 Torr, and diamond The surface temperature of the layer 20 is adjusted to about 700 to 900.degree. The surface temperature of the diamond layer 20 is adjusted by appropriately setting the temperature of the heating device 32 .

At this time, in the present embodiment, when the diamond layer 20 is grown three-dimensionally, the proportion of methane in the reaction gas is made higher than when the diamond layer 20 is grown two-dimensionally, and the degree of vacuum in the chamber 30 is increased. Raise. Further, when the diamond layer 20 is grown three-dimensionally, the temperature of the diamond substrate 10 is made lower than when the diamond layer 20 is grown two-dimensionally, which will be described later.

Therefore, when the diamond layer 20 is grown three-dimensionally, the number of atoms constituting the diamond layer 20 deposited on the main surface 10a increases, and the diamond layer 20 is grown more than when the diamond layer 20 is grown two-dimensionally, which will be described later. The energy possessed by the constituent atoms is lowered. Therefore, when the diamond layer 20 is grown three-dimensionally, the deposited atoms are less likely to migrate. In other words, when the diamond layer 20 is grown three-dimensionally, the control parameters are adjusted so that the deposited atoms are less likely to migrate. As a result, as shown in FIGS. 1B and 2B, the diamond layer 20 is three-dimensionally grown while a new kink 12 is formed in the diamond layer 20 . In other words, after this step is completed, a new kink 12 is formed in addition to the initial kink 11, and the total number of kinks 11 and 12 is increased.

Next, as shown in FIGS. 1C and 2C, a diamond layer 20 is two-dimensionally grown on the main surface 10a of the diamond substrate 10 along the plane direction of the (111) plane. In this embodiment, when the diamond layer 20 is grown two-dimensionally, the chamber 30 used for three-dimensional growth is used as it is. When the diamond layer 20 is grown two-dimensionally, a reaction gas containing nitrogen and the like is introduced into the chamber 30 in addition to hydrogen and methane, and the control parameters for growing the diamond layer 20 are adjusted. is grown two-dimensionally.

In this embodiment, as shown in FIG. 4, the ratio of methane in the reaction gas is 0.05-0.15%, the degree of vacuum in the chamber is 50-75 Torr, and the surface temperature of the diamond layer 20 is 900-1000.degree. Do it to the extent that it is. The surface temperature of the diamond layer 20 is adjusted by appropriately setting the temperature of the heating device 32 .

At this time, when the diamond layer 20 is grown two-dimensionally, the ratio of methane in the reaction gas is made lower than when growing the diamond layer 20 three-dimensionally, and the degree of vacuum in the chamber 30 is made lower. When the diamond layer 20 is grown two-dimensionally, the temperature of the diamond substrate 10 is made higher than when the diamond layer 20 is grown three-dimensionally.

Therefore, when the diamond layer 20 is grown two-dimensionally, fewer atoms are deposited on the main surface 10a and the atoms constituting the diamond layer 20 have higher energy than when grown three-dimensionally. Therefore, the deposited atoms move more easily, and the moved atoms stabilize at the positions of the kinks 11 and 12 . As a result, the diamond layer 20 grows two-dimensionally along the (111) plane.

In addition, when the diamond layer 20 is two-dimensionally grown, the diamond layer 20 is grown while incorporating nitrogen because the reaction gas contains nitrogen. Specifically, nitrogen is likely to be stabilized at the positions of the kinks 11 and 12 and easily incorporated at the positions of the kinks 11 and 12 in the same manner as the atoms forming the diamond layer 20 . In this case, in this embodiment, a step of forming a new kink 12 is performed before two-dimensional growth, and the number of kinks 11 and 12 is increased. Therefore, more nitrogen is taken into the diamond layer 20 .

Then, when nitrogen is incorporated, vacancies are formed at positions adjacent to the nitrogen, forming NV centers. In this case, in this embodiment, a diamond substrate 10 is used in which the main surface 10a has a predetermined off-angle with respect to the (111) plane. Therefore, when the diamond layer 20 is two-dimensionally grown, if nitrogen is taken in during the growth process, the next carbon or vacancies are positioned in the [111] direction with respect to the nitrogen. In addition, in the portion where nitrogen is arranged, vacancies are more stable in terms of energy than carbon is arranged. Therefore, as shown in FIG. 5, in the present embodiment, NV centers oriented in the [111] direction are likely to be formed. In other words, by growing the diamond layer 20 two-dimensionally as in this embodiment, the orientation of the NV centers can be aligned. In FIG. 5, N indicates nitrogen, C indicates carbon, and V indicates vacancies.

As described above, in this embodiment, a substrate having an off-angle is used, and the diamond layer 20 is two-dimensionally grown after the step of forming the new kink 12 is performed. Therefore, nitrogen is easily taken in when the diamond layer 20 is grown, and the density of NV centers can be increased.

(Second embodiment)
A second embodiment will be described. This embodiment differs from the first embodiment in that three-dimensional growth and two-dimensional growth are performed using different chambers 30 . Others are the same as those of the first embodiment, so description thereof is omitted here.

The basic manufacturing method of this embodiment is the same as that of the first embodiment. However, in this embodiment, two chambers 30 are prepared. When the diamond layer 20 is grown three-dimensionally, the diamond substrate 10 is placed in one of the chambers 30 . When the diamond layer 20 is grown two-dimensionally, the diamond substrate 10 is arranged in the other chamber 30 . The heating device 32 in each chamber 30 is set in advance to a predetermined temperature.

According to this, by setting the heating device 32 in each chamber 30 to a predetermined temperature in advance, it is not necessary to change the temperature of the heating device 32 when the diamond layer 20 is grown three-dimensionally and two-dimensionally. do not have. Therefore, the same effects as those of the first embodiment can be obtained while shortening the manufacturing time.

(Third Embodiment)
A third embodiment will be described. 3rd Embodiment changes the process of forming the new kink 12 with respect to 1st Embodiment. Others are the same as those of the first embodiment, so description thereof is omitted here.

Specifically, plasma etching is performed in the step of forming the new kink 12 . In this embodiment, as shown in FIG. 6, the new kink 12 is formed by plasma etching using oxygen plasma. That is, the new kink 12 is formed by roughening the main surface 10a.

Thus, even if the new kink 12 is formed by plasma etching, by growing the diamond layer 20 two-dimensionally after that, the same effects as in the first embodiment can be obtained. In addition, in this embodiment, by keeping the temperature of the heating device 32 of the chamber 30 for two-dimensional growth of the diamond layer 20 constant, it is not necessary to adjust the temperature of the heating device 32, so the manufacturing time is can be shortened.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the claims.

For example, in each of the above embodiments, the step of forming the new kink 12 and the step of two-dimensionally growing the diamond layer 20 may be alternately repeated. According to this, the thickness of the diamond layer 20 can be increased. Also, since the process of forming the new kink 12 is repeated, it is expected that the new kink 12 will be formed in the same way in each process. Therefore, it is expected that the density of the NV centers will be further increased, and that the variation of the NV centers in each atomic layer will be reduced.

Further, in each of the above-described embodiments, the diamond substrate 10 may have a predetermined off angle with respect to another plane instead of having an off angle with respect to the (111) plane.

Furthermore, in each of the above embodiments, other substrates may be used instead of the diamond substrate 10 as long as the diamond layer 20 is formed thereon.

Further, in the first and second embodiments, nitrogen may be contained in the reaction gas in the step of newly forming the new kink 12 . In this case, there is a possibility that NV centers will be formed even when the new kink 12 is newly formed, and the NV centers can be formed at a high density.

REFERENCE SIGNS LIST 10 diamond substrate 10a main surface 20 diamond layer

Claims (6)

A method of manufacturing a diamond layer, comprising growing a diamond layer (20) on a substrate (10), comprising:
preparing the substrate having a main surface (10a), the main surface having a predetermined off angle with respect to a predetermined surface, and an initial kink (11) formed on the main surface;
forming said diamond layer (20) having nitrogen-vacancy centers on said major surface;
In forming the diamond layer, a new kink (12) is newly formed on the main surface, and a chemical vapor deposition method is performed using a reaction gas containing nitrogen and methane to form the nitrogen-air layer. growing the diamond layer having hole centers two-dimensionally along the plane direction of the predetermined surface. In the formation of the new kink, chemical vapor deposition is performed using a reactive gas containing methane, so that the diamond layer is grown in the plane direction of the predetermined plane and in a direction crossing the plane direction of the predetermined plane. 2. The method for producing a diamond layer according to claim 1, wherein the new kink is formed by three-dimensional growth along the diamond layer. The three-dimensional growth for forming the new kink and the two-dimensional growth are each performed by arranging the substrate in a chamber (30), and the three-dimensional growth is the two-dimensional growth. 3. The method for producing a diamond layer according to claim 2, wherein the reaction gas has a high proportion of methane, a high degree of vacuum in the chamber, and a low temperature of the substrate, by allowing the reaction gas to flow. 4. The method of manufacturing a diamond layer according to claim 3, wherein said three-dimensional growth for forming said new kink and said two-dimensional growth are performed by arranging said substrates in different said chambers respectively. 2. The method for producing a diamond layer according to claim 1, wherein forming the new kink includes forming the new kink by performing plasma etching on the main surface. 6. The method for producing a diamond layer according to any one of claims 1 to 5, wherein the formation of the new kink and the two-dimensional growth are alternately repeated.

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