Large-platform low-dielectric-loss single crystal diamond sheet, preparation method and application thereof

Abstract

The invention discloses a preparation method and application of a large-platform low-dielectric-loss single-crystal diamond wafer, and belongs to the technical field of crystal growth, and the method specifically comprises the following steps: (1) carrying out chemical etching treatment on a single-crystal diamond seed wafer by using a Piranha solution, and then cleaning and drying the single-crystal diamond seed wafer; (2) putting the monocrystal diamond seed wafer treated in the step (1) into MPCVD equipment for plasma etching treatment and epitaxial layer growth regulation and control; and preparing to obtain the large-platform low-dielectric-loss single crystal diamond sheet. The process is simple, efficient and good in controllability, large-platform growth of the diamond can be achieved, the surface step bunching phenomenon is reduced, the prepared single crystal diamond sheet is smooth in surface, low in dielectric loss and high in crystal quality, and damage and edge breakage can be reduced during small-size machining.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal growth, and in particular relates to a large-platform low-dielectric-loss single-crystal diamond sheet, a preparation method and application thereof. Background Art

[0002] Diamond is a wide bandgap semiconductor material with excellent mechanical, thermal, acoustic, optical, electrical and other excellent properties. It has great application potential in many fields such as high-temperature and high-power power electronic devices, microwave power devices, deep ultraviolet light and high-energy particle detectors, biological and chemical sensors, etc. Single crystal diamond has high strength, high hardness, good optical properties, excellent electrical properties, good thermal conductivity, good wear resistance, low microwave loss, no grain boundaries, good airtightness, and excellent corrosion resistance and chemical stability. It is an ideal high-frequency, high-pressure and high-temperature dielectric material for devices. For example, the Chinese patent document with publication number CN118147747A discloses a large-size high-quality diamond crystal and its application. The diamond crystal is grown by splicing method, with a diameter of not less than 2 inches, and includes a first surface and a second surface opposite to the first surface. The first surface and / or the second surface have multiple atomic steps, the height of the atomic steps is 10 to 200nm, and the width is 2 to 60μm. The crystal surface can form a stable step flow, which has broad application prospects in semiconductor devices and quantum communications.

[0003] However, in the above invention, the single crystal diamond is grown in a step-like growth mode. The Chinese patent document with publication number CN108611680A discloses a method for growing high-speed and high-quality single crystal diamond. The invention grows high-quality single crystal diamond by setting a three-layer structure, especially an intermediate defect barrier layer, thereby solving the problem of the contradiction between high-speed growth and high-quality growth of single crystal diamond. In the invention, the single crystal diamond also grows in a step-like manner.

[0004] The step-like growth pattern of single-crystal diamond will inevitably lead to stress concentration and rough surface due to step bunching, which has an adverse effect on the preparation of high-quality device-level diamond materials. On the one hand, single-crystal diamond presents a step-like growth pattern, and the epitaxial layer presents step clustering, which leads to an increase in intrinsic roughness. The diffuse scattering on the rough surface leads to an increase in the absorption baseline, thereby increasing dielectric loss. On the other hand, stress concentration on these steps makes it easy to be damaged during the subsequent ultra-precision component processing. Therefore, in order to solve the above technical problems, it is necessary to regulate the growth pattern of single-crystal diamond and develop a method for preparing a large-platform low-dielectric-loss single-crystal diamond sheet. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a large-platform low-dielectric-loss single-crystal diamond sheet. The process is simple, efficient, and has good controllability. It can achieve large-platform growth of diamond and reduce surface step bunching. The obtained single-crystal diamond sheet has a smooth surface, low dielectric loss, and high crystal quality, and can reduce damage and edge collapse during small-size processing.

[0006] The specific technical solutions adopted are as follows:

[0007] A method for preparing a large-platform low-dielectric-loss single-crystal diamond sheet comprises the following steps:

[0008] (1) chemically etching a single crystal diamond seed wafer (commercial tool grade) using a Piranha solution, followed by cleaning and drying;

[0009] (2) placing the single crystal diamond seed wafer processed in step (1) into an MPCVD device for plasma etching and epitaxial layer growth regulation to prepare the large platform low dielectric loss single crystal diamond wafer;

[0010] The parameters of the plasma etching treatment stage are: hydrogen flow rate 350-450 sccm, reaction chamber pressure 8-12 KPa, etching temperature 750-800°C, etching time 20-40 min and microwave power 2000-3200 W;

[0011] The parameters of the epitaxial layer growth control stage are: methane flow rate is 8-16sccm, hydrogen flow rate is 200-420sccm, temperature is 800-1100°C, pressure is controlled at 8-18KPa, power is 2000-3800W, and growth time is 6-12h.

[0012] The method of the present invention is based on the surface treatment process of the single crystal diamond seed wafer and the regulation of the growth parameters, thereby realizing the preparation of a large platform low dielectric loss single crystal diamond sheet; the Piranha solution etching treatment and the hydrogen plasma etching treatment can not only effectively clean the sample surface, but also eliminate surface defects, which is beneficial to the regulation of the subsequent growth process, and the two-step etching treatment is indispensable.

[0013] Preferably, in step (1), the Piranha solution is a mixed solution of 98% H2SO4 solution and 30% H2O2 solution in a volume ratio of 7:3, and the single crystal diamond seed wafer is added to the Piranha solution and treated at 80-90°C for 10-12h.

[0014] Optionally, in step (1), after the chemical etching treatment, ultrasonic cleaning is performed using deionized water and alcohol in sequence, and then drying is performed using nitrogen.

[0015] Preferably, the parameters of the plasma etching treatment stage are: hydrogen flow rate 380-420 sccm, reaction chamber pressure 8-10 KPa, etching temperature 750-800° C., etching time 25-35 min and microwave power 2000-2500 W.

[0016] Preferably, the parameters of the epitaxial layer growth regulation stage are: methane flow rate is 12-16 sccm, hydrogen flow rate is 395-405 sccm, temperature is 950-1050°C, pressure is controlled at 15.7-16.3 KPa, power is 3600-3800 W, and growth time is 10-12 h.

[0017] The present invention also provides a large platform low dielectric loss single crystal diamond sheet prepared by the preparation method of the large platform low dielectric loss single crystal diamond sheet.

[0018] The large platform low dielectric loss single crystal diamond sheet has a flat surface, the surface step bunching phenomenon is reduced, and the dielectric loss reaches 10 in the range of 1.5 to 3.0 THz. -4 Magnitude, less than or equal to 1*10 -4 .

[0019] The present invention also provides the use of the large platform low dielectric loss single crystal diamond sheet in the preparation of optoelectronic devices.

[0020] After being polished, the large platform low dielectric loss single crystal diamond sheet can be used as a terahertz window sheet.

[0021] Preferably, the polishing conditions are: 800-1000 g load force, 10-20 m / s turntable speed and 5-10 cm / s feed speed for 60 min.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention adopts a two-step method, based on a large platform growth regulation strategy, starting from substrate processing and epitaxial layer growth control, to prepare a large platform low dielectric loss single crystal diamond sheet. The process is simple and efficient, has good controllability, high repetition rate, and is expected to achieve batch processing. The product single crystal diamond sheet has good quality stability.

[0024] (2) Compared with the traditional preparation method under the same conditions, the single crystal diamond sheet prepared by the present invention based on the large platform growth control strategy has low dielectric properties. The dielectric constant of commercially available tool-grade single crystal diamond seed sheets is about 5.9. After being processed by the method of the present invention, the dielectric constant of the large platform low dielectric loss single crystal diamond sheet grown is close to the natural 5.6.

[0025] (3) The single crystal diamond sheet prepared by the present invention based on the large platform growth control strategy has low dielectric loss and high crystal quality. The stress is reduced due to the reduction of step bunching, thereby reducing damage and edge collapse during small-scale processing.

[0026] (4) The large-platform low dielectric loss single-crystal diamond sheet prepared by the method of the present invention is very suitable for terahertz window materials (terahertz window sheets). The diamond window exhibits extremely high transmittance to terahertz waves, and the low dielectric constant and dielectric loss can effectively reduce the loss generated when the terahertz wave passes through the window. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The performance characterization results of the large platform low dielectric loss single crystal diamond sheet prepared in Example 1 and the single crystal diamond sheet prepared in Comparative Example 1, wherein (a) is the SEM image of Comparative Example 1, (b) is the SEM image of Example 1, and the black curve in (c) represents Comparative Example 1, and the red curve represents Example 1;

[0028] Figure 2 This is a diagram showing the influence of the large platform growth mode in Example 1 and the traditional step growth mode in Comparative Example 1 on the dielectric properties. DETAILED DESCRIPTION

[0029] The present invention is further illustrated below in conjunction with the examples and accompanying drawings. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0030] The single crystal diamond seed wafers used in the examples are all from Hebei Langfang Xiboer Diamond Technology Co., Ltd.

[0031] Example 1

[0032] (1) adding a single crystal diamond seed wafer to a Piranha solution (a mixed solution of 98% H2SO4 solution and 30% H2O2 solution in a volume ratio of 7:3) and treating at 80°C for 12 hours, chemically etching the single crystal diamond seed wafer, and then ultrasonically cleaning it with deionized water and alcohol in sequence, and drying it with nitrogen after cleaning;

[0033] (2) placing the single crystal diamond seed wafer treated in step (1) into an MPCVD device for plasma etching treatment and epitaxial layer growth regulation; the parameters of the plasma etching treatment stage are: hydrogen flow rate of 400sccm, reaction chamber pressure of 8KPa, etching temperature of 800°C, etching time of 30min and microwave power of 2000W; the parameters of the epitaxial layer growth regulation stage are: methane flow rate of 12sccm, hydrogen flow rate of 400sccm, temperature of 1000°C, pressure controlled at 16KPa, power of 3800W; growth time of 12h; and the large platform low dielectric loss single crystal diamond wafer described above is prepared.

[0034] Example 2

[0035] (1) adding a single crystal diamond seed wafer to a Piranha solution (a mixed solution of 98% H2SO4 solution and 30% H2O2 solution in a volume ratio of 7:3) and treating at 80°C for 12 hours, chemically etching the single crystal diamond seed wafer, and then ultrasonically cleaning it with deionized water and alcohol in sequence, and drying it with nitrogen after cleaning;

[0036] (2) placing the single crystal diamond seed wafer treated in step (1) into an MPCVD device for plasma etching treatment and epitaxial layer growth regulation; the parameters of the plasma etching treatment stage are: hydrogen flow rate of 400sccm, reaction chamber pressure of 8KPa, etching temperature of 750°C, etching time of 30min and microwave power of 2000W; the parameters of the epitaxial layer growth regulation stage are: methane flow rate of 12sccm, hydrogen flow rate of 400sccm, temperature of 1000°C, pressure controlled at 16KPa, power of 3800W; growth time of 12h; and the large platform low dielectric loss single crystal diamond wafer described above is prepared.

[0037] Example 3

[0038] (1) adding a single crystal diamond seed wafer to a Piranha solution (a mixed solution of 98% H2SO4 solution and 30% H2O2 solution in a volume ratio of 7:3) and treating at 80°C for 12 hours, chemically etching the single crystal diamond seed wafer, and then ultrasonically cleaning it with deionized water and alcohol in sequence, and drying it with nitrogen after cleaning;

[0039] (2) placing the single crystal diamond seed wafer treated in step (1) into an MPCVD device for plasma etching treatment and epitaxial layer growth regulation; the parameters of the plasma etching treatment stage are: hydrogen flow rate of 400sccm, reaction chamber pressure of 8KPa, etching temperature of 800°C, etching time of 30min and microwave power of 2000W; the parameters of the epitaxial layer growth regulation stage are: methane flow rate of 16sccm, hydrogen flow rate of 400sccm, temperature of 1000°C, pressure controlled at 16KPa, power of 3800W; growth time of 10h; and the large platform low dielectric loss single crystal diamond wafer described above is prepared.

[0040] Example 4

[0041] (1) adding a single crystal diamond seed wafer to a Piranha solution (a mixed solution of 98% H2SO4 solution and 30% H2O2 solution in a volume ratio of 7:3) and treating at 80°C for 12 hours, chemically etching the single crystal diamond seed wafer, and then ultrasonically cleaning it with deionized water and alcohol in sequence, and drying it with nitrogen after cleaning;

[0042] (2) placing the single crystal diamond seed wafer treated in step (1) into an MPCVD device for plasma etching treatment and epitaxial layer growth regulation; the parameters of the plasma etching treatment stage are: hydrogen flow rate of 400sccm, reaction chamber pressure of 8KPa, etching temperature of 750°C, etching time of 30min and microwave power of 2000W; the parameters of the epitaxial layer growth regulation stage are: methane flow rate of 16sccm, hydrogen flow rate of 400sccm, temperature of 1000°C, pressure controlled at 16KPa, power of 3800W; growth time of 12h; and the large platform low dielectric loss single crystal diamond wafer described above is prepared.

[0043] Comparative Example 1

[0044] The method for preparing a single crystal diamond sheet in this comparative example is different from that in Example 1 only in that no plasma etching is performed, and epitaxial layer growth regulation is performed directly after chemical etching to prepare a single crystal diamond sheet.

[0045] Sample analysis

[0046] The response of diamond materials at high THz frequencies is determined by many factors, including surface roughness, defects / voids, sp 2 Phase content (and quality grade) and dissociation surface and other factors. For example, a rough surface will raise the absorption baseline through the surface diffusion effect; pore defects with a size comparable to the wavelength will significantly increase the transmission loss of terahertz waves; sp 2The existence of phases will participate in different vibration modes, acting as additional absorption sources, resulting in an increase in dielectric loss values, which greatly reduces transmission efficiency. The present invention realizes the "large platform growth mode" of single crystal diamond through a two-step method, thereby regulating dielectric properties and stress.

[0047] The SEM image of the large platform low dielectric loss single crystal diamond sheet prepared in Example 1 is as follows: Figure 1 As shown in (b), it can be seen that the method of the present invention can achieve large platform growth of diamond, reduce the surface step bunching phenomenon, and the surface of the single crystal diamond sheet obtained is flat. The SEM image of the single crystal diamond sheet obtained in Comparative Example 1 is as follows: Figure 1 As shown in (a) in the figure, it can be seen that it presents an obvious step-like growth pattern.

[0048] Compared with the conventional step-type growth mode of Comparative Example 1, the root mean square roughness of the large platform low dielectric loss single crystal diamond sheet prepared by the method of the present invention is reduced from 5nm (step-type growth mode) to 0.4-1.0nm within an area of ​​5μm*5μm, and the height difference of the growth steps is reduced from 30nm to 3-4nm, and the crystal quality is better ( Figure 1 (c) in the figure.

[0049] Further comparison of the effects of the large platform growth mode of the present invention and the step-type growth mode of the traditional method on dielectric properties shows that Figure 2 As shown, it can be seen that the single crystal diamond sheet prepared by the large platform growth control strategy of the present invention has low dielectric properties, and the dielectric constant is close to the natural 5.6.

[0050] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a large platform low dielectric loss single crystal diamond sheet, characterized in that: The following steps are involved: (1) chemically etching the single crystal diamond seed wafer using a Piranha solution, then cleaning and drying; (2) placing the single crystal diamond seed wafer processed in step (1) into an MPCVD device for plasma etching and epitaxial layer growth regulation to prepare the large platform low dielectric loss single crystal diamond wafer; The parameters of the plasma etching treatment stage are: hydrogen flow rate 350-450 sccm, reaction chamber pressure 8-12 KPa, etching temperature 750-800°C, etching time 20-40 min and microwave power 2000-3200 W; The parameters of the epitaxial layer growth control stage are: methane flow rate is 8-16sccm, hydrogen flow rate is 200-420sccm, temperature is 800-1100°C, pressure is controlled at 8-18KPa, power is 2000-3800W, and growth time is 6-12h.

2. The method for preparing a large platform low dielectric loss single crystal diamond sheet according to claim 1, characterized in that: In step (1), a single crystal diamond seed wafer is added to a Piranha solution and treated at 80 to 90° C. for 10 to 12 hours.

3. The method for preparing a large platform low dielectric loss single crystal diamond sheet according to claim 1, characterized in that: In step (1), after chemical etching, ultrasonic cleaning is performed using deionized water and alcohol in sequence, and then drying is performed using nitrogen.

4. The method for preparing a large platform low dielectric loss single crystal diamond sheet according to claim 1, characterized in that: The parameters of the plasma etching treatment stage are: hydrogen flow rate 380-420 sccm, reaction chamber pressure 8-10 KPa, etching temperature 750-800°C, etching time 25-35 min and microwave power 2000-2500W.

5. The method for preparing a large platform low dielectric loss single crystal diamond sheet according to claim 1, characterized in that: The parameters of the epitaxial layer growth control stage are: methane flow rate is 12-16 sccm, hydrogen flow rate is 395-405 sccm, temperature is 950-1050°C, pressure is controlled at 15.7-16.3 KPa, power is 3600-3800 W, and growth time is 10-12 h.

6. A large-platform low-dielectric-loss single-crystalline diamond sheet prepared according to the method for preparing a large-platform low-dielectric-loss single-crystalline diamond sheet according to any one of claims 1 to 5.

7. Use of the large platform low dielectric loss single crystal diamond sheet according to claim 6 in the preparation of optoelectronic devices.

8. The use of the large platform low dielectric loss single crystal diamond sheet according to claim 7 in the preparation of optoelectronic devices, characterized in that: The large platform low dielectric loss single crystal diamond sheet is polished and used as a terahertz window sheet.

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