JP2022039574A - Apparatus and method for depositing cvd single crystal diamond - Google Patents

Abstract

To provide an apparatus and method for depositing a CVD single crystal diamond, capable of efficiently manufacturing high quality CVD single crystal diamond by observing the growth of CVD single crystal diamond in a real time.SOLUTION: An apparatus 1 for depositing a CVD single crystal diamond includes: a chamber 3; a light emission detector 7 placed on a sample support 4 in the chamber and for irradiating a substrate 5 for depositing the CVD single crystal diamond with incident light 9 to detect a reflection wave 6 reflected on the substrate 5; and a control part 8 for preparing a reflectance profile from the reflection wave 6 detected by the light emission detector 7. The control part 8 includes: a reflectance calculation part for calculating a reflectance by the intensity of the incident light 9 received from the light emission detector 7 and the intensity of the reflection wave 6; and a reflectance profile preparation part for preparing the reflectance profile showing the time change of the reflectance calculated by the reflectance calculation part.SELECTED DRAWING: Figure 1

Description

The present invention relates to a CVD single crystal diamond film forming apparatus for forming a CVD single crystal diamond, and a method for forming a CVD single crystal diamond.

Heteroepitaxial growth of diamond by CVD (Chemical Vapor Deposition) is one of the most important means for producing large single crystal diamond substrates. Since this method uses different types of single crystal substrates to grow single crystal diamonds, the size of the obtained diamond depends on the size of the single crystal substrate.

It is known that single crystal Ir is used as a seed substrate for forming a CVD single crystal diamond by heteroepitaxial growth, but it is difficult to obtain a bulk of single crystal Ir. For this reason, a heteroepitaxial iridium thin film grown on an MgO or YSZ / Si substrate is used. As a result, a diamond plate with a diameter of more than 90 mm has recently been realized.

The crystal quality of CVD single crystal diamond is not as good as that of diamond formed by the high pressure high temperature (HPHT) growth method. The generation of dislocations caused by the lattice mismatch between diamond and iridium is a problem to be solved in order to improve the crystal quality for practical use in semiconductor power devices. In order to solve this problem, it is necessary to observe the state of heteroepitaxial growth in real time.

As a method for observing the state in which the thin film is growing in real time, it is possible to apply an in-situ optical interferometry such as a laser reflection interferometry. For example, Patent Document 1 discloses an apparatus for in situ observing a film that grows when an AlAs thin film is formed on a GaAs substrate by MOCVD (metalorganic chemical vapor deposition). According to the document, it is possible to detect changes in the composition and growth rate of the substrate by irradiating the substrate with lasers of two different wavelengths and observing the rate of change in the interference pattern period.

Japanese Patent Application Laid-Open No. 8-193813

However, Patent Document 1 describes an example in which GaAs is formed on a GaAs substrate and AlAs is formed on the film, but the difference in the coefficient of thermal expansion between them is small and warpage occurs during the film formation. do not do. Since only the rate of change of the interference pattern is observed in this document, it is assumed that it will be applied in situations where various circumstances at the time of film formation must be taken into consideration, such as when forming films with significantly different coefficients of thermal expansion. It is necessary to interrupt the film formation and check the film formation status.

In the film formation of CVD single crystal diamond, it is desirable to use MgO, sapphire, etc. in order to form a high-quality Ir thin film, but the difference in thermal expansion coefficient between these and diamond is large. Therefore, it is considered difficult to apply the invention described in Patent Document 1 because warpage occurs during the formation of diamond. In addition, although it is necessary to set various conditions in order to form a high-quality diamond, the diamond film formation time is long, so if the film formation is interrupted for each condition, the film formation will be of high quality. It is extremely difficult to produce a CVD single crystal diamond.

Under such circumstances, further studies are needed so that the CVD single crystal diamond can be efficiently produced while getting closer to the quality of the diamond formed by the high pressure high temperature (HPHT) growth method.

Therefore, the subject of the present invention is a CVD single crystal diamond film forming apparatus capable of efficiently producing high-quality CVD single crystal diamond by observing the growth of the CVD single crystal diamond in real time, and a CVD single crystal diamond. Is provided.

In order to improve the quality of CVD single crystal diamond, it is necessary to grasp the growth situation at the initial stage of film formation. Further, in order to efficiently produce the CVD single crystal diamond, it is necessary to grasp the growth status of the CVD single crystal diamond in real time without interrupting the film formation.

The incident light for observing the film formation of the CVD single crystal diamond in real time is reflected on both the surface of the Ir thin film and the surface of the growing diamond. Therefore, the reflected vibration based on the Fabry-Pérot interference theory can be applied to know the growth status of diamond. Therefore, the reflectance profile obtained by the reflected vibration can be obtained by using the device provided with the chamber provided with the light emission detector.

Here, it is necessary to investigate how the obtained reflectance profile contributes to the growth of diamond. Therefore, when the correlation between the reflectance behavior shown in the reflectance profile and the growth status of the CVD single crystal diamond was investigated, it was found that there is a correlation peculiar to the CVD single crystal diamond. This profile includes all various situations such as the situation where the thermal expansion coefficient of Ir and diamond is different from the substrate and warpage occurs, and it is a unique profile that fully reflects the film formation situation of CVD single crystal diamond. be. The present invention has been completed based on the finding that the film formation time in CVD can be accurately predicted based on the reflectance profile peculiar to CVD single crystal diamond.
The present invention obtained from these findings is as follows.

(1) A light emitting detector that is placed on a chamber and a sample table in the chamber and that irradiates an incident light on a substrate for forming a CVD single crystal diamond and detects a reflected wave reflected by the substrate, and emits light. It includes a control unit that creates a reflectance profile from the reflected wave detected by the detector, and the control unit calculates the reflectance based on the intensity of the incident light received from the emission detector and the intensity of the reflected wave. A CVD single crystal diamond film forming apparatus including a reflectance profile creating unit for creating a reflectance profile indicating a time change of the reflectance calculated by the reflectance calculating unit.

(2) The CVD single crystal diamond film forming apparatus according to claim 1, wherein the control unit includes a single crystal film forming determination unit for determining whether or not a CVD single crystal diamond is formed based on a reflectance profile.

上記（１）および（２）式中、ｎは屈折率であり、λは発光検出器から基板に照射される入射光の波長（ｎｍ）であり、Ｇ（λ）は、λにより算出される成長率であり、Ｔは反射率の周期（ｓ）であり、ｄは周期（ｓ）の間に成長するＣＶＤ単結晶ダイヤモンドの膜厚（ｎｍ）であり、Ｔ_ｄはＣＶＤ単結晶ダイヤモンドの膜厚であり、ｔはＴ_ｄの膜厚になるための成膜時間（ｓ）である。 (3) The CVD single crystal diamond formation according to claim 1 or 2, wherein the control unit includes a film formation time calculation unit that calculates the film formation time according to the following equations (1) and (2) based on the reflectance profile. Membrane device.

In the above equations (1) and (2), n is the refractive index, λ is the wavelength (nm) of the incident light emitted from the emission detector to the substrate, and G (λ) is calculated by λ. It is the growth rate, T is the period (s) of the reflectance, d is the film thickness (nm) of the CVD single crystal diamond that grows during the period (s), and T _d is the film of the CVD single crystal diamond. It is a thickness, and t is a film forming time (s) for achieving a film thickness of T _d .

(4) The CVD single crystal diamond film forming method using the CVD single crystal diamond film forming apparatus according to any one of claims 1 to 3, from the light emission detector by the reflectance calculation unit of the control unit. The reflectance is calculated from the intensity of the received incident light and the intensity of the reflected wave, and the reflectance profile creating unit of the control unit creates a reflectance profile showing the time change of the calculated reflectance. Single crystal diamond film formation method.

(5) The fourth aspect of claim 4, wherein the control unit includes a single crystal film formation determination unit, and the single crystal film formation determination unit determines whether or not CVD single crystal diamond is deposited based on the reflectance profile. CVD single crystal diamond deposition method.

上記（１）および（２）式中、ｎは屈折率であり、λは発光検出器から基板に照射される入射光の波長（ｎｍ）であり、Ｇ（λ）は、λにより算出される成長率であり、Ｔは反射率の周期（ｓ）であり、ｄは周期（ｓ）の間に成長するＣＶＤ単結晶ダイヤモンドの膜厚（ｎｍ）であり、Ｔ_ｄはＣＶＤ単結晶ダイヤモンドの膜厚であり、ｔはＴ_ｄの膜厚になるための成膜時間（ｓ）である。 (6) The control unit includes a film formation time calculation unit, and the film formation time calculation unit calculates the film formation time according to the following equations (1) and (2) based on the reflectance profile, according to claim 4 or 5. The CVD single crystal diamond film forming method according to the above method.

In the above equations (1) and (2), n is the refractive index, λ is the wavelength (nm) of the incident light emitted from the emission detector to the substrate, and G (λ) is calculated by λ. It is the growth rate, T is the period (s) of the reflectance, d is the film thickness (nm) of the CVD single crystal diamond that grows during the period (s), and T _d is the film of the CVD single crystal diamond. It is a thickness, and t is a film forming time (s) for achieving a film thickness of T _d .

FIG. 1 is a schematic cross-sectional view of a CVD single crystal diamond film forming apparatus. FIG. 2 is a block diagram showing a hardware configuration of a light emission detector. FIG. 3 is a block diagram showing a functional configuration of the control unit. FIG. 4 is a flowchart of a film forming method using a CVD single crystal diamond film forming apparatus, and is a flowchart in the case where the control unit includes a reflectance calculation unit and a reflectance profile creating unit in FIG. FIG. 5 is a flowchart of a film forming method using a CVD single crystal diamond film forming apparatus, and is a case where the control unit includes a reflectance calculation unit, a reflectance profile creating unit, and a single crystal film forming determination unit in FIG. It is a flowchart. FIG. 6 is a diagram showing an example of the reflectance profile from the start of film formation to the lapse of 570 seconds, FIG. 6 (a) is a diagram showing the relationship between the film formation time and the temperature, and FIG. 6 (b). ) Is a diagram showing the relationship between the reflectance and the film formation time when incident light having a wavelength of 405 nm is used. FIG. 7 is a flowchart of a film forming method using a CVD single crystal diamond film forming apparatus, and FIG. 7A shows a reflectance calculation unit, a reflectance profile creating unit, and a film forming time in FIG. It is a flowchart when the calculation unit is provided, and FIG. 7B is the case where the control unit includes a reflectance calculation unit, a reflectance profile creation unit, a single crystal film formation determination unit, and a film formation time calculation unit in FIG. It is a flowchart of. FIG. 8 is a diagram showing the relationship between the growth rate of diamond and the film formation time, FIG. 8A is a diagram when incident light having a wavelength of 950 nm is used, and FIG. 8B is a diagram showing the wavelength. Is a diagram when incident light having a wavelength of 632 nm is used, and FIG. 8 (c) is a diagram when incident light having a wavelength of 405 nm is used. FIG. 9 is a diagram showing an example of a reflectance profile having a film forming time of up to 700 seconds. FIG. 10 is a diagram showing a growth state of CVD single crystal diamond. FIG. 11 is a diagram showing the relationship between the film thickness calculated from the reflectance profile and the measured value of the film thickness. FIG. 12 is a diagram showing the basic relationship between the change in the amplitude of the reflectance and the growth state of the diamond, and FIG. 12 (a) shows the reflectance profile under the ideal growth state, and FIG. 12 (a) shows the reflectance profile. b) shows the reflectance profile when the light absorption by the film is large, and FIG. 12 (c) shows the reflectance profile when the surface roughness of the diamond is increased.

Embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments.
FIG. 1 is a schematic cross-sectional view of the CVD single crystal diamond film forming apparatus 1. The CVD single crystal diamond film forming apparatus (hereinafter, may be simply referred to as “apparatus”) 1 places the substrate 5 on the sample table 4 in the chamber 3 provided with the view port 2 and is reflected by the substrate 5. It includes a light emitting detector 7 that detects a reflected wave 6 to determine the reflectance, and a control unit 8 that controls the film formation time of the CVD single crystal diamond. Each configuration will be described.

A plasma generator and a coil (not shown) are provided in the chamber 3, and a plasma ball 10 is generated on the substrate 5 according to the film formation time calculated by the control unit 8. Further, a reaction gas introduction pipe 15 and an exhaust pipe 16 are connected to the chamber 3, and the reaction gas is introduced at the time of film formation and the gas after the reaction is exhausted. The chamber 3 is divided into upper and lower parts by a quartz window 14, and is configured so that the reaction gas is introduced in the vicinity of the substrate 5. A viewport 2 is provided on the ceiling 11 of the chamber 3. A heater (not shown) is provided on the sample table 4, and the substrate 5 is heated according to the film formation time.

The substrate 5 used when depositing diamond in the CVD single crystal diamond film forming apparatus 1 according to the present embodiment is a substrate that does not melt when forming diamond, such as MgO, sapphire, Si, and polycrystalline diamond. If so, there is no particular limitation. The diamond formed by the film forming apparatus of the present embodiment is preferably a heteroepitaxial CVD single crystal diamond.

The light emission detector 7 irradiates the substrate 5 with the incident light 9 through the viewport 2 provided in the chamber 3 and receives the reflected wave 6. FIG. 2 is a block diagram showing a hardware configuration of the light emission detector 7. The light emission detector 7 includes, for example, as shown in FIG. 2, a light source unit 7a and a detection unit 7b.

The light source unit 7a irradiates the substrate 5 with incident light 9 having a predetermined wavelength, and transmits intensity data of the incident light 9 set based on the output of a power source (not shown) to the control unit 8. The detection unit 7b detects the reflected wave 6 reflected on the substrate 5 and transmits the intensity data of the reflected wave 6 to the control unit 8. Further, the light emission detector 7 may be provided with a thermometer for measuring the surface temperature of the substrate 5, but may be arranged in any of the chambers 3. The thermometer transmits temperature data to the control unit 8 at any time.

The control unit 8 includes, for example, a CPU (Central Processing Unit), a memory, a non-volatile storage device, an input device such as a keyboard and a microphone, a monitor, a clock, an interface, and the like. Based on the information acquired from the interface, the CPU reads a program from the storage device in cooperation with the memory and executes a function described later. In addition, the CPU cooperates with the program to construct the following operations.

FIG. 3 is a block diagram showing a functional configuration of the control unit 8. The control unit 8 includes a reflectance calculation unit 8a and a reflectance profile creation unit 8b. Preferably, at least one of a single crystal film formation determination unit 8c and a film formation time calculation unit 8d is provided. When at least one of the single crystal film formation determination unit 8c and the film formation time calculation unit 8d is not provided, these functions can be manually supported.

The reflectance calculation unit 8a calculates the reflectance, which is the ratio of the intensity of the reflected wave 6 detected by the detection unit 7b to the intensity of the incident light 9 emitted from the light source unit 7a, and calculates the calculation result as the intensity of the reflected wave 6. Create a table to create a reflectance profile with the reception time of. The reflectance profile creating unit 8b creates a reflectance profile showing a time change of the reflectance from the reflectance data calculated by the reflectance calculation unit 8a.

As a specific example, the reflectance profile creating unit 8b reads the heating start time from the storage device, and calculates the film formation time at each reception time from the reception time of the reflected wave 6 associated with each reflectance. Then, for each reflectance and the data of the film forming time of each reflectance, a reflectance profile is created with the horizontal axis as the film forming time and the vertical axis as the reflectance. The single crystal film forming determination unit 8c determines whether or not CVD single crystal diamond is formed from the amplitude of the reflectance in the reflectance profile. The film forming time calculation unit 8d calculates the final film forming time by the formula (1) or the formula (2) described later based on the temperature profile. The film formation time calculation unit 8d may calculate the final film formation time when the single crystal film formation determination unit 8c determines that the CVD single crystal diamond is filmed.

Next, the film forming method of this embodiment will be described in detail with reference to FIG.
FIG. 4 is a flowchart of a film forming method using the CVD single crystal diamond film forming apparatus 1, and is a flowchart in the case where the control unit 8 includes a reflectance calculation unit 8a and a reflectance profile creating unit 8b in FIG. First, the substrate 5 is placed on the sample table 4 (S1). Then, the reaction gas is introduced into the chamber 3 from the reaction gas introduction pipe 15 (S2), the microwave generator 12 is activated, the microwave is irradiated to the substrate 5 via the waveguide 13 (S3), and the substrate 5 is used. Is heated (S4). When the temperature of the substrate 5 rises, plasma balls 10 are generated on the substrate 5 to form a diamond film. The heating temperature of the substrate 5 may be about 700 to 1000 ° C.

After the heating of the substrate 5 is started, the incident light 9 having a predetermined wavelength is irradiated from the light source portion 7a of the light emission detector 7, and the reflected wave 6 reflected on the surface of the substrate 5 is detected by the detection unit 7b. Observe diamonds in real time (S5). At the same time, the surface temperature of the substrate 5 may be measured.

The reflected wave 6 detected by the detection unit 7b is a reflected wave reflected on the surface of the Ir thin film when the diamond is not growing. When the diamond begins to grow, the reflected wave 6 is detected as an interference wave between the reflected wave reflected at the interface between the Ir thin film and the diamond and the reflected wave reflected at the surface of the diamond. Since the phase of the reflected wave reflected on the surface of the diamond gradually changes according to the thickness of the diamond, the intensity of the reflected wave 6 may be strengthened or weakened depending on the thickness of the diamond. Therefore, the amplitude of the reflectance, which is the ratio of the intensity of the incident light 9 to the intensity of the reflected wave 6, also varies depending on the film forming time. In this way, the reflectance calculation unit 8a calculates the ratio of the intensity of the reflected wave 6 detected by the detection unit 7b and the intensity of the incident light 9 emitted from the light source unit 7a at any time.

The reflectance profile creation unit 8b creates a reflectance profile based on the calculation result of the reflectance calculation unit 8a and the time received from the clock included in the control unit 8 (S6), and ends. After the reflectance profile is created, whether or not the CVD single crystal diamond is formed based on the reflectance profile displayed on the monitor, or the final film formation time is manually determined, and the film formation is performed after the final time has elapsed. Finish manually.

FIG. 5 is a flowchart of a film forming method using the CVD single crystal diamond film forming apparatus 1. In FIG. 3, the control unit 8 is a reflectance calculation unit 8a, a reflectance profile creating unit 8b, and a single crystal film forming determination unit. It is a flowchart when 8c is provided. In FIG. 5, it is determined whether or not the CVD single crystal diamond is formed after S6 in FIG. Since S1 to S6 in FIG. 5 are the same as S1 to S6 in FIG. 4, the description thereof will be omitted.

After the reflectance profile is started to be created by S6, the single crystal film forming determination unit 8c determines whether or not the CVD single crystal diamond is formed based on the reflectance profile (S7). When it is determined that the CVD single crystal diamond has begun to be deposited (S7, yes), the final film formation time is manually obtained, and the film formation is manually completed after the lapse of the final time. When it is determined that the CVD single crystal diamond has not been formed (S7, no), the film formation is terminated.

The judgment method is as follows, for example.
FIG. 6 is a diagram showing an example of the reflectance profile from the start of film formation to the lapse of 570 seconds, FIG. 6 (a) is a diagram showing the relationship between the film formation time and the temperature, and FIG. 6 (b). ) Is a diagram showing the relationship between the reflectance and the film formation time when the incident light 9 having a wavelength of 405 nm is used. According to FIG. 6A, it can be seen that the temperature of the substrate 5 reaches about 800 ° C. within 100 to 200 seconds in each case. It can also be seen that the temperature is constant from 200 to 570 seconds.

On the other hand, according to FIG. 6B, when the diamond does not grow and when the polycrystalline diamond is formed, the reflectance has no amplitude or is indistinguishable from noise. It can be seen that it shows only the amplitude. On the other hand, in the CVD single crystal diamond, the reflectance starts to decrease when the heating temperature is about 600 ° C., and the reflectance shows a minimum value when the heating temperature reaches about 800 ° C. After that, although the temperature is constant, the reflectance increases to about 300 seconds and shows a maximum value, then starts to decrease again and shows a minimum value, and vibration continues by repeating the minimum value and the maximum value. It can be seen that the period is about 200 seconds and the amplitude of the reflectance shows a large amplitude of about 0.1. For example, the average reflectance up to two cycles can be obtained, and when the amplitude when the average reflectance is 0 is 0.05 or more, it can be determined that the CVD single crystal diamond is formed. There is no limitation. For example, by setting such a threshold value, the single crystal film forming determination unit 8c can easily determine that the CVD single crystal diamond is formed.

Depending on the film forming conditions, the time for preheating to 600 ° C. may be lengthened, or the heating time at 600 to 800 ° C. may be lengthened. Even in these cases, when the CVD single crystal diamond is formed, the magnitude of the amplitude in the initial stage of growth is about the same as in the case of the heating condition of FIG. 6A. Therefore, the single crystal film forming determination unit 8c can easily determine that the CVD single crystal diamond is formed.

FIG. 7 is a flowchart of a film forming method using the CVD single crystal diamond film forming apparatus 1, and FIG. 7A shows a reflectance calculation unit 8a and a reflectance profile creating unit 8b in FIG. It is a flowchart when the film formation time calculation unit 8d is provided, and in FIG. 7B, in FIG. 3, the control unit 8 has a reflectance calculation unit 8a, a reflectance profile creation unit 8b, a single crystal film formation determination unit 8c, and a single crystal film formation determination unit 8c. It is a flowchart when the film formation time calculation unit 8d is provided. Since S1 to S6 in FIG. 7 are the same as S1 to S6 in FIG. 4, the description thereof will be omitted. Also in the film formation method of this embodiment, the flowchart of FIG. 4 in which the reflectance calculation unit 8a and the reflectance profile creation unit 8b are used and the single crystal film formation determination unit 8c is not used, and the reflectance calculation unit 8a and the reflection The same steps as the flowchart of FIG. 5 using the rate profile creating unit 8b and the single crystal film forming determination unit 8c may be performed.

In FIG. 7A, after the reflectance profile is started to be created in S6, the film forming time calculation unit 8d calculates the final film forming time based on the reflectance profile (S8). Then, after the final film formation time has elapsed, the film formation is manually completed. When it can be predicted that the film formation of the CVD single crystal diamond will be performed with a high probability, S8 can be performed after S6 without performing the judgment by the single crystal film formation determination unit 8c. The final film formation time is calculated in S8, and after the final film formation time has elapsed, the introduction of the reaction gas, the irradiation of microwaves, and the observation of the substrate 5 are manually stopped, and the substrate 5 is cooled to complete the film formation process. do.

In FIG. 7 (b), when S7 of FIG. 5 is performed and it is determined in S7 that the CVD single crystal diamond is formed (S7, yes), the final film forming time is the same as in S8 of FIG. 7 (a). Is calculated, and the film formation is manually completed after the final film formation time has elapsed. When it is determined in S7 that the CVD single crystal diamond has not been formed (S7, no), the film formation is manually completed without calculating the final film formation time.
The method for calculating the final film formation time is as follows, for example.

The film forming time calculation unit 8d reads a program for calculating the film forming time from the storage device of the control unit 8, and based on the reflectance profile, the film forming time for the CVD single crystal diamond to have a desired film thickness. Is calculated. As the formula used for calculating the film formation time, for example, the following formula is preferably used.

In the above equations (1) and (2), n is the refractive index, λ is the wavelength (nm) of the incident light 9 emitted from the light emission detector 7 to the substrate 5, and G (λ) is due to λ. It is the calculated growth rate, T is the period (s) of the reflectance, d is the film thickness (nm) of the CVD single crystal diamond that grows during the period (s), and T _d is the CVD single crystal. It is a desired film thickness of diamond, and t is a film forming time (s) for achieving a film thickness of T _d .

n has been empirically derived to determine the refractive index of the CVD single crystal diamond, for example, G.I. Turri, S.M. Webster, Y. Chen, B. Wickham, A. Bennett, and M. et al. Bass, Opt. Matter. Express, 7, 855 (2017). It is calculated by the formula described in. Λ used in the equation (1) is the wavelength of the incident light 9 emitted from the light source unit 7a of the light emission detector 7 to the substrate 5, and receives the wavelength data from the light source unit 7a of FIG. The film thickness calculation unit 8d shown in FIG. 3 is composed of λ of the incident light 9, n calculated by the formula described in the above-mentioned document, and T obtained from the reflectance profile (1). By calculating the equation (2), t, which is the final film forming time until the desired film thickness is reached, is calculated.

In this embodiment, the substrate 5 was observed in real time with three types of incident light 9 of 405 nm, 632 nm, and 950 nm using an EpiCurve TT, which is an in situ measuring device manufactured by Raytec.

When these wavelengths are used, n is 2.459, 2.410, 2.392, respectively, according to the equations described in the above-mentioned documents. The growth rate is calculated using, for example, reflected vibration every 5 cycles. FIG. 8 is a diagram showing the relationship between the growth rate of diamond and the film formation time, FIG. 8A is a diagram when incident light 9 having a wavelength of 950 nm is used, and FIG. 8B is a diagram. It is a figure when the incident light 9 which has a wavelength of 632 nm is used, and FIG. 8 (c) is a figure when the incident light 9 which has a wavelength of 405 nm is used.

According to FIG. 6A, although the temperature is kept constant after 200 seconds, it can be seen in FIG. 8 that the growth rate increases at any wavelength. Therefore, in the film formation of diamond, the amount of increase in film thickness per unit time increases according to the film formation time, and it is understood that efficient film formation is possible with the passage of time. This is considered to be a phenomenon peculiar to CVD single crystal diamond.

As shown in FIG. 8, from the time dependence of the growth rate obtained from the equation (1), the final film formation time until the desired plate thickness is obtained can be estimated using the equation (2). After t has elapsed, the film forming process is completed as described above.

As described above, in the film forming apparatus according to the present embodiment in which the film forming method according to the present embodiment is carried out, it is not necessary to take out the substrate 5 from the chamber 3 and check the diamond film thickness during the film formation. Diamond can be efficiently formed without spending extra time. Further, in the present embodiment, it is possible to observe the growth status of the diamond in the early stage of growth, which is considered to be the most important for improving the quality of diamond, in real time. Therefore, the film forming conditions can be optimized in a short time, and as a result, the quality of diamond and the production efficiency can be improved at the same time.

In the CVD single crystal diamond film forming apparatus 1 according to the present embodiment, the growth status of diamond can be grasped from the reflectance profile. FIG. 9 is a diagram showing an example of a reflectance profile having a film forming time of up to 700 seconds. As shown in FIG. 9, it is necessary to observe and grasp the growth status at the time showing the characteristic waveform of the reflectance profile.

FIG. 10 is a diagram showing a growth state of CVD single crystal diamond. As shown in FIG. 10, diamond grains grow three-dimensionally up to the first local minimum of 405 nm, and a layer of diamond is formed at the first local minimum of 405 nm. After that, it grows two-dimensionally in the vertical direction of the substrate 5, and the film thickness of the layer becomes thicker.

FIG. 11 is a diagram showing the relationship between the film thickness calculated from the reflectance profile and the actual film thickness. The dotted line in FIG. 11 is the film thickness calculated from the reflectance profile, and it is assumed that the calculated value on the horizontal axis is the actual film thickness. The four points in FIG. 11 are the actual film thickness, and represent that the actual film thickness is 51 nm under the condition that the calculated value of λ is 41.18 nm. As is clear from FIG. 11, since R ² = 0.98, it can be seen that the calculated value and the measured value of the film thickness are quite close.

As described above, in the CVD single crystal diamond film forming apparatus 1 using the CVD single crystal diamond film forming method according to the present embodiment, the desired film is formed based on the reflectance profile by observing the growth in-situ. The time to thickness can be estimated accurately. Therefore, it is not necessary to interrupt the film forming process one by one and actually measure the growth state of the substrate 5, unlike the conventional case, and it is possible to realize efficient film formation of CVD single crystal diamond.

FIG. 12 is a diagram showing the basic relationship between the change in the amplitude of the reflectance and the growth state of the diamond, and FIG. 12A shows the reflectance profile in the ideal growth state, and FIG. 12 (a) shows the reflectance profile. b) shows the reflectance profile when the light absorption by the film is large, and FIG. 12 (c) shows the reflectance profile when the surface roughness of the diamond is increased. In FIG. 12A, when the film thickness increases with the passage of time, the phase of each reflected wave 6 gradually shifts, so that the amplitude of the reflectance becomes constant. In FIG. 12B, as the film thickness increases, the crystal quality of diamond and the state of the interface differ, so that the maximum value decreases and the minimum value increases. In FIG. 12 (c), since the quality of the interface deteriorates due to the increase in the surface roughness of the diamond, the intensity of both the reflected wave 6 at the surface and the reflected wave 6 at the interface becomes low, and the reflectance gradually decreases. Decreases to.

As described above, when an abnormality occurs in the vibration of the reflectance in the reflectance profile, it can be seen that cracks or the like occur at the time of film formation. Therefore, in view of this result, a guideline for further improving the quality of diamond can be obtained.

1 CVD single crystal diamond film forming apparatus, 2 view port, 3 chamber, 4 sample table, 5 substrate, 6 reflected wave, 7 light emission detector, 7a light source unit, 7b detector unit, 8 control unit, 8a reflectance calculation unit, 8b Reflectivity profile creation unit, 8c single crystal film formation judgment unit, 8d film formation time calculation unit, 9 incident light, 10 plasma balls, 11 ceiling, 12 microwave generator, 13 waveguide, 14 quartz window, 15 reaction gas Introductory pipe, 16 exhaust pipe

Claims (6)

A light emitting detector that irradiates incident light on a chamber and a substrate for forming a CVD single crystal diamond on a sample table in the chamber and detects reflected waves reflected by the substrate, and the light emission. It is equipped with a control unit that creates a reflectance profile from the reflected wave detected by the detector.
The control unit includes a reflectance calculation unit that calculates the reflectance based on the intensity of the incident light received from the light emission detector and the intensity of the reflected wave, and a time change of the reflectance calculated by the reflectance calculation unit. A CVD single crystal diamond film forming apparatus comprising a reflectance profile creating unit for creating the reflectance profile. The CVD single crystal diamond film forming apparatus according to claim 1, wherein the control unit includes a single crystal film forming determination unit for determining whether or not the CVD single crystal diamond is formed based on the reflectance profile. The CVD single crystal diamond film formation according to claim 1 or 2, wherein the control unit includes a film formation time calculation unit that calculates the film formation time according to the following equations (1) and (2) based on the reflectance profile. Device.

In the above equations (1) and (2), n is the refractive index, λ is the wavelength (nm) of the incident light emitted from the emission detector to the substrate, and G (λ) is the λ. Is the growth rate calculated by, T is the period (s) of the reflectance, d is the film thickness (nm) of the CVD single crystal diamond that grows during the period (s), and T _d. Is the film thickness of the CVD single crystal diamond, and t is the film forming time (s) for achieving the film thickness of T _d . A CVD single crystal diamond film forming method using the CVD single crystal diamond film forming apparatus according to any one of claims 1 to 3.
The reflectance is calculated by the reflectance calculation unit of the control unit based on the intensity of the incident light received from the light emission detector and the intensity of the reflected wave, and the reflectance profile creation unit of the control unit calculates the reflectance. A CVD single crystal diamond film forming method comprising creating the reflectance profile showing the calculated time change of the reflectance. The fourth aspect of claim 4, wherein the control unit includes a single crystal film formation determination unit, and the single crystal film formation determination unit determines whether or not the CVD single crystal diamond is formed based on the reflectance profile. CVD single crystal diamond film formation method. The control unit includes a film formation time calculation unit, and the film formation time calculation unit calculates the film formation time according to the following equations (1) and (2) based on the reflectance profile, according to claim 4 or 5. The CVD single crystal diamond film forming method according to the above method.

In the above equations (1) and (2), n is the refractive index, λ is the wavelength (nm) of the incident light emitted from the emission detector to the substrate, and G (λ) is the λ. Is the growth rate calculated by, T is the period (s) of the reflectance, d is the film thickness (nm) of the CVD single crystal diamond that grows during the period (s), and T _d. Is the film thickness of the CVD single crystal diamond, and t is the film forming time (s) for achieving the film thickness of T _d .

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