Ultrathin diamond carrier plate as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electronic packaging carrier plates, and discloses an ultrathin diamond carrier plate and a preparation method and application thereof.The preparation method comprises the steps that a heterogeneous substrate is selected, cleaned and subjected to seed crystal, and then a sacrificial layer is introduced; growing a compact and continuous ultrathin diamond film on the substrate pretreated in the step 1 through chemical vapor deposition; sequentially carrying out surface cleaning, activation and modification on the diamond film; constructing a metal layer structure required by conductive wiring and a heat dissipation substrate on the surface of the diamond carrier plate; the ultrathin diamond film deposited on the heterogeneous substrate is separated from the substrate, and a self-supporting diamond carrier plate is obtained; the heat-conducting property of the packaging substrate is remarkably improved, and an ultrathin structure with controllable thickness can be prepared; a reliable diamond film heterogeneous substrate growth and stripping process is provided, so that an independent support plate can be conveniently obtained from a growth substrate by the thin film; the metallization adhesive force of the surface of the carrier plate is enhanced, high-density circuit patterning on the surface of the substrate is supported, and the packaging reliability is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of functional materials, and relates to an electronic packaging carrier plate, in particular to an ultrathin diamond carrier plate and a preparation method and application thereof. BACKGROUND

[0002] At present, ceramic substrates (carrier plates) are widely used in the field of electronic packaging as chip packaging substrates, including alumina, aluminum nitride, silicon nitride and other materials. These traditional ceramic carrier plates have many shortcomings in terms of thermal conductivity, thickness control, electrical performance and the like: (1) Insufficient thermal conductivity: The thermal conductivity of Al2O3 ceramic is only about 15-35 W / (m·K), which is far from meeting the heat dissipation requirements of high heat flux devices. The thermal expansion coefficient and dielectric constant of Al2O3 are also relatively high, which can cause serious parasitic effects in high-frequency and high-power circuits. Although the dielectric performance of AlN ceramic is excellent and the thermal expansion coefficient is relatively matched with silicon, its maximum thermal conductivity can only reach about 260 W / (m·K), which has appeared a bottleneck in the face of the increasing packaging heat dissipation requirements. Si3N4 ceramic has high mechanical strength and good heat shock resistance, but its thermal conductivity (70-90 W / (m·K)) is relatively low, and the dielectric constant is also about 8-9, which is difficult to fully meet the extreme requirements of high thermal conductivity for high power density and miniaturized packaging.

[0003] (2) Limited thickness and flatness: Traditional ceramic substrates are usually made by sintering process, and the thickness is generally in the range of hundreds of microns to several millimeters. Due to the brittleness of the material and the process limitation, it is difficult to make the ceramic substrate very thin and maintain mechanical stability. When it is too thin, it is easy to crack or warp. Even if it is thinned by grinding, the thickness tolerance and uniformity are not easy to control accurately. In addition, the large thickness of the ceramic substrate increases the volume of the packaging, which is not conducive to the demand of highly integrated and miniaturized packaging.

[0004] (3) Limited electrical performance: Compared with new materials, the dielectric properties and insulation strength of traditional ceramics have reached the limit. For example, although SiC ceramic has high thermal conductivity, its dielectric constant is too high and its breakdown field strength is relatively low, which limits its application in high-frequency fields and is only suitable for packaging with lower integration. The dielectric constant of Al2O3 and Si3N4 is relatively high, which can increase the signal loss and parasitic capacitance in high-speed circuits. Overall, the existing ceramic carrier plate has performance trade-offs in pursuing high insulation, high frequency and low loss at the same time.

[0005] Based on the above shortcomings, research on new heat dissipation substrate materials has been paid attention to. Among them, chemical vapor deposition (CVD) diamond is gradually becoming the focus of attention as a new generation of packaging carrier plate material due to its ultra-high thermal conductivity and excellent stability. Diamond is the material with the highest thermal conductivity (about 1000-2200 W / (m·K)) and extremely low thermal expansion coefficient (1.1×10 -6 / ℃). At the same time, diamond also has high resistivity and high dielectric strength, low dielectric constant and other electrical advantages. These characteristics make it show the potential of traditional materials in the field of semiconductor, high-frequency electronics and optical packaging. In recent years, the industry has tried to use diamond for high-power device heat dissipation substrate, mainly including: direct deposition of diamond thin film as substrate, and diamond and copper / aluminum and other high thermal conductivity metal composite to form a composite substrate. For example, some studies have made diamond / metal composite substrates by combining diamond particles with Ag, Cu and other metal substrates, which have shown excellent thermal management performance in the field of electronic packaging. Some companies have launched diamond copper clad plates using the AMB process, which use diamond sheets as substrates and double-sided copper foil to form a "sandwich" structure. The comprehensive thermal conductivity of this type of diamond substrate can reach 500-1800 W / (m·K), the thermal expansion coefficient can be adjusted in the range of 3×10 -6 ~6×10 -6 / ℃, and has high strength and good insulation performance, and the surface can be easily plated with nickel and gold to form a circuit. This progress has proved the application prospect of diamond substrate in the field of high-power lasers, 5G base stations, electric vehicles and other fields. However, the use of CVD diamond for packaging substrates still faces many challenges in the preparation process, and some patents and research have explored the deficiencies: (1) Film thickness uniformity and scale: CVD diamond thin film growth often has the problem of columnar grain growth. The grain size increases during the deposition process of thick film, resulting in uneven structure in the thickness direction, affecting the mechanical properties and isotropic heat dissipation. Patent CN119332342A proposes a "secondary nucleation" process during deposition to maintain consistent diamond grain size for long-term growth, avoiding the formation of obvious columnar crystals, thereby obtaining a millimeter-thick diamond film with uniform structure. It can be seen that without special process measures, it is still difficult to deposit a large-area, uniform and high-quality diamond film, and the preparation process stability and deposition rate need to be improved.

[0006] (2) Difficulty in nucleation on heterogeneous substrates: Diamond nucleation on non-diamond substrates needs to overcome a large interfacial energy barrier. Usually, the substrate surface must be roughened or pre-seeded with diamond crystals, otherwise direct deposition will be difficult to start uniform nucleation. For example, CN108505016A patent uses a highly polished molybdenum sheet as a substrate and uniformly spreads diamond micro-powder seeds on its surface to promote nucleation. Even so, the adhesion and survival rate of seeds on different material substrates are different, and diamond nucleation on some metal substrates (such as Ti, Cu, etc.) is particularly difficult - for example, titanium, which easily forms a loose and porous TiC transition layer during the initial deposition, hindering the formation of subsequent diamond nuclei. Therefore, how to achieve high-density and uniform distribution of crystal nuclei on heterogeneous substrates is one of the key difficulties in preparing high-quality diamond films.

[0007] (3) Thin film peeling process is complex: the preparation of independent diamond carrier plate usually needs to peel off the diamond film from the substrate after growth. However, due to the hard and brittle nature of the diamond film and the strong bonding force with the growth substrate, the peeling process is not easy to control. Existing methods include chemical etching and thermal stress. The chemical method such as dissolving the metal substrate with acid or etching off the silicon-based substrate with plasma has a long process and high cost; the thermal stress method uses the mismatch of thermal expansion between diamond and substrate to make the film automatically fall off when cooled. For example, in the above-mentioned molybdenum substrate method, the thick diamond film can sometimes be separated from the molybdenum sheet after cooling at the end of deposition, and if it is not completely detached, it needs to be manually assisted by mechanical knocking. This peeling method is uncertain, and if not careful, the film may crack or have edge defects, reducing the yield. For ultra-thin diamond films with a thickness of only a few tens of microns, peeling is even more difficult - it is necessary to ensure that the thin film is completely released and stress is detached from the substrate, and it cannot be broken due to uneven stress during the peeling process. The existing peeling process is too complex and has insufficient reliability.

[0008] (4) Poor adhesion of metallization: the bare diamond surface has high chemical inertness and poor wettability and bonding force with metal materials. Direct deposition or plating of conductors such as copper on the diamond surface often leads to easy peeling of the metal layer due to the lack of chemical bonding at the interface. In diamond / copper composites, the mismatched phonon-electron thermal conduction mechanism and the lack of good bonding at the interface not only reduce the thermal conduction efficiency, but also reflect the poor interfacial bonding strength. Some studies have introduced a transition adhesive layer (such as titanium, chromium and other metals that can form carbides) to improve the interface bonding by metallizing the diamond surface. However, in existing packaging substrates, the diamond metallization process for large areas and patterning is still immature. If the metal circuit is not firmly attached, it may peel off due to stress during subsequent packaging thermal cycles, seriously affecting device reliability.

[0009] In summary, the ceramic carrier plate in the prior art gradually cannot meet the needs of high power density packaging in terms of performance, while the new carrier plate based on CVD diamond has a promising prospect, but there are many defects and challenges in the preparation process, which need to be solved by innovative technical solutions. SUMMARY

[0010] In view of the deficiencies in the prior art, the purpose of the present application is to provide an ultra-thin diamond carrier plate and its preparation method and application, which significantly improves the thermal conductivity of the packaging substrate and can prepare an ultra-thin structure with controllable thickness; provides a reliable diamond film hetero-substrate growth and peeling process, so that the thin film can easily obtain an independent carrier plate from the growth substrate; enhances the metallization adhesion of the carrier plate surface, supports high-density circuit patterning on the substrate surface, and improves packaging reliability.

[0011] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A preparation method of an ultrathin diamond carrier plate, comprising the following steps: Step one, selecting a heterogeneous substrate, cleaning, seeding and introducing a sacrificial layer; Step two, growing a dense and continuous ultrathin diamond film on the substrate pretreated in step one by chemical vapor deposition; Step three, sequentially performing surface cleaning, activation and modification on the diamond film; Step four, constructing a metal layer structure required for conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate; Step five, separating the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supporting diamond carrier plate.

[0012] The application also has the following technical features: Preferably, the substrate in step one includes a metal substrate and a non-metal substrate; The metal substrate includes any one of Mo, W, Nb or high-purity alloy plates thereof with a thickness of 5-10 mm; the cleaning method of the metal substrate is to immerse the metal substrate in a mixed solution prepared by mixing 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 and heated to 80-100 ℃ for 10-15 min; the metal substrate is seeded by bias plasma, and a sacrificial layer is introduced by growing an oxidation thin layer on the surface of the metal substrate through thermal oxidation; The non-metal substrate includes any one of AlN ceramic, Al2O3 ceramic, Si3N4 ceramic or single crystal silicon with a thickness of 5-10 mm; The cleaning method of the non-metal substrate is to first immerse the non-metal substrate in acetone for 3-5 min under the condition of a vibration frequency of 80 kHz, then immerse it in anhydrous ethanol for 5-10 min, then wash it clean with pure water and then ultrasonically clean it in pure water for 8-10 min, and finally centrifugally dry it; the non-metal substrate is seeded by mechanical seeding, and a sacrificial layer is introduced by sputtering a metal thin layer on the surface.

[0013] Preferably, the growth method of the ultrathin diamond film in step two includes: S1, taking one side of the sacrificial layer of the substrate as a deposition surface, introducing a methane / hydrogen mixed gas into a vapor deposition device, setting the pressure to 1-3 kPa, the methane concentration to 5-20%, keeping the substrate temperature at 750-850 ℃, the hot wire temperature at 2000-2300 ℃, and the deposition time at 0.5-2 h; S2, adjusting the pressure to 3-10 kPa, the methane concentration to 1-5%, and adding 0.1-1% of O2 or CO2, keeping the substrate temperature at 850-950 ℃, the hot wire temperature at 2000-2300 ℃, and the deposition time at 0.5-2 h; S3, after the deposition is completed, gradually reduce the cavity temperature to room temperature at a cooling rate of 5-10℃ / min, and take out the substrate with the ultra-thin diamond film deposited.

[0014] Preferably, the cleaning method of the diamond surface in step three comprises: placing the self-supporting diamond film into a mixed solution prepared by mixing 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 and heating to 80-100℃ for 10-15 min.

[0015] Preferably, the activation method of the diamond surface in step three comprises: placing the self-supporting diamond film into a plasma cleaning machine, and treating with oxygen plasma under vacuum at a radio frequency power of 80-150 W and a pressure of 30-50 Pa for 5-10 min, or treating with argon plasma at 200-300 W for 2-5 min.

[0016] Preferably, the modification method of the diamond surface in step three comprises: oxidizing at 60-80℃ for 30-40 min by using concentrated HNO3 or HNO3+HF mixed acid, or treating with fluorine plasma for 5-15 min by using a reactive ion etcher to introduce functional groups.

[0017] Preferably, the construction method of the metal layer structure in step four comprises: sputtering a transition layer with a thickness of 100-150 nm, a diffusion barrier layer with a thickness of 100-200 nm and a functional layer with a thickness of 200-500 nm on the surface of the diamond film in sequence under the conditions of a vacuum degree of 0.2-0.5 Pa, a bias voltage of -60 to -100 V, a substrate temperature of 100-150℃ and a sputtering power of 3-5 kW by using a direct current magnetron sputtering; the sputtered metal of the transition layer comprises any one of Ti, Cr, W and Mo; the sputtered metal of the diffusion barrier layer comprises any one of Pt, Pd, Ni and Mo; the metal of the functional layer comprises any one of Au, Cu and Sn; the sputtered functional layer is patterned by defining a sputtering area by photolithography before sputtering.

[0018] Preferably, the method for separating the ultra-thin diamond film from the substrate in step five comprises any one of a laser scribing method and an interface embrittlement method.

[0019] The application also protects an ultra-thin diamond carrier prepared by the method as described above and the application thereof in the fields of semiconductor, high-frequency electronic and optical packaging.

[0020] Compared with the prior art, the application has the following technical effects: The present application can prepare controllable thickness ultra-thin structure, has extremely high thermal conductivity, provides reliable diamond film hetero-substrate growth and stripping process, enables thin film to be conveniently obtained from the growth substrate, enhances the metalization adhesion of the carrier plate surface, has extremely low roughness, supports high-precision nano-pattern manufacturing, realizes micro-nano patterning, improves packaging reliability; can be used for thermal expansion layer of electronic chips and thermal management platform of high-power devices, has high resistance to ensure the stability as an insulating material, and can be adjusted by surface engineering to be used for strain sensors, UV detectors and other devices. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Picture for Si substrate; Figure 2 Picture for growing diamond thin film on Si substrate by CVD; Figure 3 Picture after preparing metallization pattern on diamond thin film. DETAILED DESCRIPTION

[0022] The specific content of the present application is further explained in detail in combination with the following examples.

[0023] Example 1 The present example gives a preparation method of ultra-thin diamond carrier plate, including the following steps: Step one, select Si substrate with thickness of 5 mm, first immerse the Si substrate in acetone for 5 min under the condition of vibration frequency of 80 kHz, then immerse in anhydrous ethanol for 10 min, then wash with pure water, ultrasonic clean in pure water for 10 min, and finally centrifugal dry; the Si substrate is as shown in Figure 1 ; Mechanical seeding is adopted to obtain nucleation sites, the nucleation sites can reach 10 10 ~10 11 / cm 2 , so as to overcome the nucleation difficulty caused by high surface energy of external substrate surface, realize in-situ nucleation, smooth interface without large particles, improve the uniformity of thin film and substrate combination, and form continuous thin film in the initial deposition stage, so as to improve the uniformity and density of diamond thin film deposition; A thin layer of metal is introduced by surface sputtering as a sacrificial layer, and the metal layer is 300 nm thick as a sacrificial layer; the metal layer is Al; Step two, grow a dense and continuous ultra-thin diamond film on the substrate pretreated in step one by chemical vapor deposition; the specific method includes: S1, with the side of the substrate as the deposition surface, a methane / hydrogen mixed gas is introduced into the vapor deposition device, the pressure is set to 3 kPa, the methane concentration is 20%, the substrate temperature is kept at 850℃, the hot wire temperature is 2300℃, and the deposition time is 2 hours, at this stage, a high-density diamond crystal nucleus layer is formed to cover the substrate surface; S2, adjust the pressure to 10 kPa, the methane concentration to 5%, and add O2 1%, keep the substrate temperature at 950℃, the hot wire temperature at 2300℃, and the deposition time at 2 hours; deposit to a thickness of 80 microns; adding oxidants helps to etch non-diamond carbon phases and inhibit graphite deposition, ensuring film purity during long-term deposition; S3, after deposition, gradually reduce the cavity temperature to room temperature at a cooling rate of 10℃ / min, and take out the substrate with ultra-thin diamond film deposited; the product is as shown in Figure 2 ; Step three, the diamond thin film is sequentially subjected to surface cleaning, activation and modification; The cleaning method of the diamond surface includes: placing in a mixed solution prepared by mixing 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 and heating to 100℃ for 10 min; because the CVD diamond surface is usually terminated by hydrogen, it is hydrophobic and chemically inert, and the metal thin film is easy to form discontinuous island-shaped and not firmly attached on such surface, by treating with concentrated sulfuric acid, replacing the surface H atoms with O, the surface free energy and polarity can be increased, so that the metal atoms are more easily "wetted" and chemically bonded to the diamond surface; The activation method of the diamond surface is: placing the self-supporting diamond thin film into a plasma cleaning machine, and treating with oxygen plasma under vacuum at a radio frequency power of 150 W and a pressure of 50 Pa for 5 min, the oxygen plasma will oxidize a small amount of sp 2 impurity carbon (graphite or amorphous carbon) to CO / CO2 and volatilize, purifying the pure sp 3 surface; The modification method of the diamond surface is to oxidize with concentrated HNO3 at 80℃ for 30 min, which can form —NO2, —OH and —COOH, and improve the surface wettability; Step four, constructing the metal layer structure required for conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate; Under the conditions of vacuum degree 0.5 Pa, bias voltage -100 V, substrate temperature 150℃ and sputtering power 5 kW, a 150 nm thick Ti transition layer, a 200 nm thick Pt diffusion barrier layer and a 500 nm thick Au functional layer are sputtered on the surface of the diamond thin film in sequence by direct current magnetron sputtering; Before sputtering the functional layer, the sputtering area is patterned by photolithography; as shown in Figure 3 ; Step five, separating the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supporting diamond carrier plate; cutting through the film to the substrate along the boundary of the diamond film with an ultraviolet laser (such as 355 nm); then scanning and irradiating the substrate side with a laser of appropriate energy (such as infrared 1064 nm), and making the interface heat and debond by thermal expansion of the substrate to the laser.

[0024] The performance parameters of the diamond thin film prepared in Example 1 are shown in Table 1: Table 1 Performance parameters of diamond thin film Example 2 This example gives a method for preparing an ultrathin diamond carrier plate, comprising the following steps: Step one, select an AlN ceramic substrate with a thickness of 10 mm, and first immerse the AlN ceramic substrate in acetone for 3 min under the condition of a vibration frequency of 80 kHz, then immerse it in anhydrous ethanol for 5 min, then rinse it clean with pure water and then ultrasonically clean it in pure water for 8 min, and finally centrifugally spin dry; Obtain nucleation sites by mechanical seeding; Introduce a sacrificial layer by surface sputtering a thin layer of metal, and the 500 nm thick metal layer serves as the sacrificial layer; the metal layer is Fe; Step two, grow a dense and continuous ultrathin diamond film on the substrate pretreated in step one by chemical vapor deposition; the specific method comprises: S1, with the side of the sacrificial layer of the substrate as the deposition surface, introduce a mixture of methane / hydrogen gas into the vapor deposition equipment, set the pressure to 1 kPa, the methane concentration to 5%, maintain the substrate temperature at 750℃, the hot wire temperature at 2000℃, and the deposition time at 0.5 h, and in this stage, a high-density diamond nucleus layer is formed to cover the substrate surface; S2, adjust the pressure to 30 kPa, the methane concentration to 1%, and add CO2 0.1%, maintain the substrate temperature at 850℃, the hot wire temperature at 2000℃, and the deposition time at 0.5 h; deposit to a thickness of 30 microns; S3, after deposition, gradually reduce the cavity temperature to room temperature at a cooling rate of 5℃ / min, and take out the substrate with the ultrathin diamond film deposited thereon; Step three, sequentially perform surface cleaning, activation and modification on the diamond thin film; The cleaning method of the diamond surface comprises: being placed in a mixed solution prepared by mixing 98% sulfuric acid and 30% hydrogen peroxide with a volume ratio of 3:1 and heated to 100℃ for 15 min; since the CVD diamond surface is usually hydrogen-terminated, it is hydrophobic and chemically inert, and the metal thin film is easy to form discontinuous islands on such surface and is not firmly attached, by replacing the surface H atoms with O through concentrated sulfuric acid treatment, the surface free energy and polarity can be increased, so that the metal atoms are more easily "wetted" and chemically bonded to the diamond surface; The activation method of the diamond surface is: using argon plasma to bombard for 5 min at 300 W, argon plasma can micro-etch the diamond surface due to its physical sputtering effect, which can produce nanoscale roughness and is beneficial to mechanically "anchor" the subsequent coating layer; The modification method of the diamond surface comprises: using HNO3+HF mixed acid to oxidize at 60℃ for 30 min, which can form —NO2, —OH and —COOH to improve the surface wettability; Step four, constructing the metal layer structure required for the conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate; Under the conditions of vacuum degree 0.2 Pa, bias voltage -60 V, substrate temperature 100℃ and sputtering power 3 kW, a 100 nm thick Cr transition layer, a 100 nm thick Pd diffusion barrier layer and a 200 nm thick Cu functional layer are sequentially sputtered on the surface of the diamond film by using direct current magnetron sputtering; Before sputtering the functional layer, the sputtering area is patterned by photolithography; Step five, separating the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supported diamond carrier plate; an ultrashort laser is focused on the inside of the diamond film close to the interface, a micron-level graphitized layer is generated by scanning, the interface bonding force is reduced, then a 3M adhesive tape is stuck at the edge position of the surface of the diamond film, the adhesive tape is gently stretched along the edge cut on the substrate before, and the diamond film is peeled off from the substrate. This stretching process helps the diamond film to smoothly separate from the surface of the substrate, can ensure the integrity of the diamond film, and avoids cracks in the diamond film caused by excessive stress or uneven force during the peeling process.

[0025] Example 3 The present embodiment provides a method for preparing an ultrathin diamond carrier plate, comprising the following steps: Step one, select an Al2O3 ceramic substrate with a thickness of 10 mm, first immerse the Al2O3 ceramic substrate in acetone for 4 min under the condition of vibration frequency of 80 kHz, then immerse it in anhydrous ethanol for 8 min, then rinse it with pure water and ultrasonically clean it in pure water for 9 min, and finally centrifugal dry; Mechanical seeding is used to obtain nucleation sites; The sacrificial layer is introduced by surface sputtering of a thin layer of metal, and the 400 nm thick metal layer serves as the sacrificial layer; the metal layer is Cu; Step two, growing a dense and continuous ultra-thin diamond film on the substrate pretreated in step one by chemical vapor deposition; the specific method comprises: S1, taking the side of the sacrificial layer of the substrate as the deposition surface, introducing methane / hydrogen mixed gas into the vapor deposition equipment, setting the pressure to 2 kPa, the methane concentration to 10%, maintaining the substrate temperature at 800℃, the hot wire temperature at 2200℃, and the deposition time at 1 h; in this stage, a high-density diamond crystal nucleus layer is formed to cover the substrate surface; S2, adjusting the pressure to 8 kPa, the methane concentration to 4%, and adding O2 0.5%, maintaining the substrate temperature at 900℃, the hot wire temperature at 2200℃, and the deposition time at 1 h; depositing to a thickness of 50 microns; S3, after the deposition is completed, gradually reducing the cavity temperature to room temperature at a cooling rate of 8℃ / min, and taking out the substrate with the ultra-thin diamond film deposited thereon; Step three, sequentially performing surface cleaning, activation, and modification on the diamond film; The cleaning method of the diamond surface is to immerse the diamond surface in a mixed solution prepared by mixing 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 and heated to 90℃ for 12 min; The activation method of the diamond surface is to place the self-supporting diamond film into a plasma cleaning machine, and use oxygen plasma to process under vacuum at a radio frequency power of 80 W and a pressure of 30 Pa for 8 min; The modification method of the diamond surface comprises oxidizing at 60℃ for 30 min with concentrated HNO3, which can form —NO2, —OH and —COOH, and improve the surface wettability; Step four, constructing a metal layer structure required for conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate; Under the conditions of vacuum degree 0.3 Pa, bias voltage -80 V, substrate temperature 120℃, and sputtering power 4 kW, a 120 nm thick Mo transition layer, a 150 nm thick Ni diffusion barrier layer, and a 300 nm thick Sn functional layer are sequentially deposited on the surface of the diamond film by direct current magnetron sputtering; Before sputtering the functional layer, the sputtering area is defined by photolithography patterning; Step five, separating the ultra-thin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supporting diamond carrier plate; a UV laser (such as 355 nm) is used to cut through the film to the substrate along the boundary of the diamond film. Then, a laser with appropriate energy (such as infrared 1064 nm) is used to scan and irradiate the substrate side, and the interface is heated and raised to debond by the thermal expansion of the substrate due to the absorption of the laser.

[0026] Example 4 Example 4 is substantially the same as Example 3, except that Si3N4 ceramic is used as the substrate.

[0027] The sputtering functional layer is patterned by photoetching to define a sputtering area before sputtering; Figure 3 as shown. Example 5 The present embodiment provides a preparation method of an ultrathin diamond carrier plate, comprising the following steps: In order to avoid graphite inclusions in the growth process, a metal Mo with a thickness of 10 mm is selected as the substrate, which has high carbide forming property, high chemical purity and matched thermal expansion coefficient, so as to ensure the nucleation and thin film dense growth of high-quality diamond; The cleaning method is to immerse the substrate in a mixed solution prepared by mixing 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 and heated to 80℃ for 10 min; The metal substrate is subjected to bias plasma seeding, and a sacrificial layer is introduced by growing an oxide thin layer on the surface of the metal substrate through thermal oxidation; Step two, grow a dense and continuous ultrathin diamond film on the substrate pretreated in step one by chemical vapor deposition; the specific method comprises: S1, with one side of the sacrificial layer of the substrate as the deposition surface, introduce methane / hydrogen mixed gas into the gas deposition equipment, set the pressure to 3 kPa, the methane concentration to 20%, keep the substrate temperature at 850℃, the hot wire temperature at 2000℃, and the deposition time at 2 h, at this stage, a high-density diamond crystal nucleus layer is formed to cover the surface of the substrate; S2, adjust the pressure to 10 kPa, the methane concentration to 5%, and add O2 0.1%, keep the substrate temperature at 850℃, the hot wire temperature at 2000℃, and the deposition time at 0.5 h; deposit to a thickness of 30 microns; S3, after deposition, gradually reduce the cavity temperature to room temperature at a cooling rate of 10℃ / min, and take out the substrate with ultrathin diamond film deposited thereon; Step three, sequentially clean, activate and modify the diamond thin film; The cleaning method of the diamond surface is to immerse the substrate in a mixed solution prepared by mixing 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 and heated to 100℃ for 10 min; The activation method of the diamond surface is to place the self-supporting diamond thin film into a plasma cleaning machine, and use oxygen plasma to treat under vacuum at a radio frequency power of 100 W and a pressure of 40 Pa for 10 min; The modification method of the diamond surface comprises oxidizing at 70℃ for 35 min with concentrated HNO3, which can form —NO2, —OH and —COOH, and improve the surface wettability; Step four, constructing the metal layer structure required for the conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate; The W transition layer of 150 nm, the Mo diffusion barrier layer of 200 nm and the Au functional layer of 500 nm were sequentially deposited on the surface of the diamond film by direct current magnetron sputtering under the conditions of vacuum degree 0.5 Pa, bias voltage -60 V, substrate temperature 100℃ and sputtering power 3 kW; the sputtering area was defined by photoetching pattern before sputtering the functional layer to perform patterning; Step five, separating the ultrathin diamond film deposited on the hetero-substrate from the substrate to obtain a self-supporting diamond carrier plate; an ultrashort laser is focused on the inside of the diamond film close to the interface to scan and generate a micron-level graphitization layer, thereby reducing the interface bonding force; then, a 3M adhesive tape is stuck to the edge position on the surface of the diamond film, and the tape is gently stretched along the edge cut on the substrate previously to peel the diamond film from the substrate. The stretching process helps the diamond film to be smoothly separated from the surface of the substrate, ensures the integrity of the diamond film, and avoids cracks in the diamond film caused by excessive stress or uneven force during the peeling process.

[0028] Example 6 Example 6 is basically the same as Example 5, except that a metal W with a thickness of 5 mm is selected as the substrate, and the activation method of the diamond surface in step three is to use argon plasma to bombard for 5 min at 200 W. The modification method of the diamond surface is to use a reactive ion etcher to treat with fluorine plasma for 15 min to introduce functional groups.

[0029] Example 7 Example 7 is basically the same as Example 5, except that a metal Nb with a thickness of 5 mm is selected as the substrate, and the activation method of the diamond surface in step three is to use argon plasma to bombard for 2 min at 300 W. The modification method of the diamond surface is to use a reactive ion etcher to treat with fluorine plasma for 5 min to introduce functional groups.

[0030] Example 8 Example 8 is basically the same as Example 5, except that a high-purity alloy plate of metals Nb and Mo with a thickness of 5 mm is selected as the substrate, and the activation method of the diamond surface in step three is to use argon plasma to bombard for 3 min at 220 W. The modification method of the diamond surface is to use a reactive ion etcher to treat with fluorine plasma for 10 min to introduce functional groups.

[0031] The above merely describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an ultrathin diamond carrier plate, characterized in that, Includes the following steps: Step 1: Select a heterogeneous substrate, clean it, seed it, and then introduce a sacrificial layer; Step 2: A dense and continuous ultrathin diamond film is grown on the substrate pretreated in Step 1 by chemical vapor deposition. Step 3: Perform surface cleaning, activation, and modification on the diamond film in sequence; Step 4: Construct the metal layer structure required for conductive wiring and heat dissipation substrate on the surface of the diamond substrate; Step 5: Separate the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supporting diamond carrier.

2. The method for preparing the ultrathin diamond carrier plate as described in claim 1, characterized in that, The substrate mentioned in step one includes a metallic substrate and a non-metallic substrate; The metal substrate comprises any one of Mo, W, Nb or their high-purity alloy plates with a thickness of 5-10 mm; the cleaning method of the metal substrate is to immerse it in a mixed solution of 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1, and heat it to 80-100°C for 10-15 min; the metal substrate is seeded by bias plasma, and a sacrificial layer is introduced by thermally oxidizing an oxide thin layer on the surface of the metal substrate; The non-metallic substrate includes any one of AlN ceramic, Al2O3 ceramic, Si3N4 ceramic or single crystal silicon with a thickness of 5-10 mm; The non-metallic substrate cleaning method is as follows: under the condition of vibration frequency of 80 kHz, the non-metallic substrate is first immersed in acetone for 3-5 min, then immersed in anhydrous ethanol for 5-10 min, then rinsed with pure water, and then ultrasonically cleaned in pure water for 8-10 min, and finally centrifuged and dried; the non-metallic substrate is mechanically seeded and a sacrificial layer is introduced by sputtering a thin metal layer on the surface.

3. The method for preparing the ultrathin diamond carrier plate as described in claim 1 or 2, characterized in that, The method for growing the ultrathin diamond film described in step two includes: S1. Using one side of the sacrificial layer of the substrate as the deposition surface, a methane / hydrogen mixture is introduced into the vapor deposition equipment, with a pressure of 1~3 kPa, a methane concentration of 5~20%, a substrate temperature of 750~850℃, a hot wire temperature of 2000~2300℃, and a deposition time of 0.5~2 h. S2. Adjust the pressure to 3~10 kPa, methane concentration to 1~5%, and add O2 or CO2 0.1~1%, maintain substrate temperature at 850~950℃, hot wire temperature at 2000~2300℃, and deposition time at 0.5~2 h; S3. After deposition, the chamber temperature is gradually reduced to room temperature at a cooling rate of 5~10℃ / min, and the substrate with the deposited ultrathin diamond film is removed.

4. The method for preparing the ultrathin diamond carrier plate as described in claim 1, characterized in that, The cleaning method for the diamond surface described in step three includes immersing the diamond in a mixed solution of 98% sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1, heating it to 80-100°C, and soaking it for 10-15 minutes.

5. The method for preparing the ultrathin diamond carrier plate as described in claim 1, characterized in that, The activation method for the diamond surface described in step three includes: placing the self-supporting diamond film into a plasma cleaner and treating it with oxygen plasma at a radio frequency power of 80~150 W and a pressure of 30~50 Pa under vacuum for 5~10 min, or bombarding it with argon plasma at 200~300 W for 2~5 min.

6. The method for preparing the ultrathin diamond carrier plate as described in claim 1, characterized in that, The diamond surface modification method described in step three includes oxidation with concentrated HNO3 or a HNO3+HF mixed acid at 60~80℃ for 30~40 min, or treatment with reactive ion etching fluorine plasma for 5~15 min to introduce functional groups.

7. The method for preparing the ultrathin diamond carrier plate as described in claim 1, characterized in that, The method for constructing the metal layer structure described in step four includes: DC magnetron sputtering was used to sequentially deposit a 100-150 nm thick transition layer, a 100-200 nm thick diffusion barrier layer, and a 200-500 nm thick functional layer on the surface of a diamond film under the conditions of vacuum degree 0.2~0.5 Pa, bias voltage -60 ~ -100V, substrate temperature 100~150℃, and sputtering power 3~5 kW. The metal sputtered in the transition layer includes any one of Ti, Cr, W, and Mo; The metal sputtered by the diffusion barrier layer includes any one of Pt, Pd, Ni, and Mo; The metal of the functional layer includes any one of Au, Cu, and Sn; Before sputtering the functional layer, the sputtering area is patterned by defining the sputtering area using photolithography.

8. The method for preparing the ultrathin diamond carrier plate as described in claim 1, characterized in that, The method for separating the ultrathin diamond film from the substrate as described in step five includes either laser scribing or interface embrittlement.

9. An ultrathin diamond substrate prepared by the method described in any one of claims 1 to 8.

10. An application of the ultrathin diamond substrate as described in claim 9 in the fields of semiconductors, high-frequency electronics and optical packaging.

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