An ultrathin diamond carrier plate, a preparation method and application thereof

Abstract

The present application belongs to the technical field of electronic packaging carrier board, and discloses an ultrathin diamond carrier board and a preparation method and application thereof, the preparation method comprising: selecting a heterogeneous substrate, introducing a sacrifice layer after cleaning and seeding; growing a dense and continuous ultrathin diamond film on the substrate pretreated in step one through chemical vapor deposition; sequentially performing surface cleaning, activation and modification on the diamond film; constructing a metal layer structure required for conductive wiring and heat dissipation substrate on the surface of the diamond carrier board; separating the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supported diamond carrier board; significantly improving the heat conduction performance of the packaging substrate and being capable of preparing an ultrathin structure with controllable thickness; providing a reliable diamond film heterogeneous substrate growth and peeling process, so that the thin film can be easily obtained as an independent carrier board from the growth substrate; enhancing the metalization adhesion force of the surface of the carrier board, supporting high-density circuit patterning on the surface of the substrate, and improving the packaging reliability.

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:

[0003] (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.

[0004] (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 keep it mechanically stable. 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.

[0005] (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.

[0006] Based on the above shortcomings, research on new heat dissipation substrate materials has attracted attention. 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 Meanwhile, diamond also has high resistivity, high dielectric strength, low dielectric constant and other electrical advantages. These characteristics make it show potential in the fields of semiconductors, high-frequency electronics and optical packaging that traditional materials cannot achieve. In recent years, the industry has attempted to use diamond for high-power device heat dissipation substrates, mainly in the form of: direct deposition of diamond thin film as a substrate, and diamond combined with copper / aluminum and other high thermal conductivity metals to form a composite substrate. For example, some studies have combined diamond particles with Ag, Cu and other metal matrices to produce diamond / metal composite 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 overall thermal conductivity of this type of diamond substrate can reach 500-1800 W / (m·K), the thermal expansion coefficient can be adjusted within the range of 3×10 -6 ~6×10 -6 / ℃, and it 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 proven the application prospects of diamond substrates in high-power laser, 5G base station, electric vehicle 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 these challenges, but there are still shortcomings:

[0007] (1) Film thickness uniformity and scalability: CVD diamond thin film growth often has the problem of columnar grain growth. The grain size increases during the deposition process of thick films, leading to structural non-uniformity 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 large-area, uniform and high-quality diamond films, and the preparation process stability and deposition rate need to be improved.

[0008] (2) Difficulty in heterogeneous substrate nucleation: Diamond nucleation on non-diamond substrates requires overcoming a large interfacial energy barrier. Usually, the substrate surface must be roughened or pre-seeded with diamond crystals, otherwise uniform nucleation is difficult to initiate. 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 vary, 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 nuclei on heterogeneous substrates is one of the key difficulties in preparing high-quality diamond films.

[0009] (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, and if it is not completely detached, it needs to be manually assisted by mechanical knocking. This peeling method has uncertainty, and the film may be partially cracked or edge damaged with slight care, reducing the yield. For ultra-thin diamond film 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.

[0010] (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.

[0011] In summary, the ceramic carrier plate in the prior art gradually cannot meet the needs of high power density packaging in terms of performance, and the new carrier plate based on CVD diamond, although promising, has many defects and challenges in the preparation process, which need to be solved by innovative technical solutions. SUMMARY

[0012] 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.

[0013] In order to achieve the above object, the present application adopts the following technical solutions to achieve the above object:

[0014] A preparation method of an ultrathin diamond carrier plate, comprising the following steps:

[0015] Step one, selecting a heterogeneous substrate, cleaning, seeding and introducing a sacrificial layer;

[0016] Step two, growing a dense and continuous ultrathin diamond film on the substrate pretreated in step one by chemical vapor deposition;

[0017] Step three, sequentially performing surface cleaning, activation and modification on the diamond film;

[0018] Step four, constructing a metal layer structure required for conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate;

[0019] Step five, separating the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supporting diamond carrier plate.

[0020] The present application also has the following technical features:

[0021] Preferably, the substrate in step one includes a metal substrate and a non-metal substrate;

[0022] 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;

[0023] 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;

[0024] 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 rinse it with pure water, 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.

[0025] Preferably, the growth method of the ultrathin diamond film in step two includes:

[0026] S1, in a vapor deposition device, with the one side of the substrate as the deposition surface, a methane / hydrogen mixed gas is introduced, the pressure is set to 1-3 kPa, the methane concentration is 5-20%, the substrate temperature is maintained at 750-850℃, the hot wire temperature is 2000-2300℃, and the deposition time is 0.5-2 h;

[0027] S2, the pressure is adjusted to 3-10 kPa, the methane concentration is 1-5%, and 0.1-1% of O2 or CO2 is added, the substrate temperature is maintained at 850-950℃, the hot wire temperature is 2000-2300℃, and the deposition time is 0.5-2 h;

[0028] S3, after the deposition is completed, the cavity temperature is gradually reduced to room temperature at a cooling rate of 5-10℃ / min, and the substrate with the ultra-thin diamond film deposited thereon is taken out.

[0029] Preferably, the cleaning method of the diamond surface in step three comprises: soaking 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.

[0030] Preferably, the activation method of the diamond surface in step three comprises: placing the self-supporting diamond film into a plasma cleaning machine, and using oxygen plasma to process under vacuum at a radio frequency power of 80-150 W and a pressure of 30-50 Pa for 5-10 min, or using argon plasma to bombard at 200-300 W for 2-5 min.

[0031] Preferably, the modification method of the diamond surface in step three comprises: oxidation with concentrated HNO3 or HNO3+HF mixed acid at 60-80℃ for 30-40 min, or fluorine plasma treatment with a reactive ion etcher for 5-15 min to introduce functional groups.

[0032] Preferably, the construction method of the metal layer structure in step four comprises:

[0033] Under the conditions of vacuum degree 0.2-0.5 Pa, bias voltage -60--100 V, substrate temperature 100-150℃, and sputtering power 3-5 kW, a transition layer of 100-150 nm thick, a diffusion barrier layer of 100-200 nm thick, and a functional layer of 200-500 nm thick are sequentially sputtered on the surface of the diamond film by direct current magnetron sputtering;

[0034] The sputtered metal of the transition layer comprises any one of Ti, Cr, W, and Mo;

[0035] The sputtered metal of the diffusion barrier layer comprises any one of Pt, Pd, Ni, and Mo;

[0036] The metal of the functional layer includes any one of Au, Cu and Sn;

[0037] The functional layer is sputtered to form a pattern by defining a sputtering area through photoetching patterning before sputtering.

[0038] Preferably, the method for separating the ultra-thin diamond film from the substrate in step five includes any one of a laser scribing method and an interface embrittlement method.

[0039] The application also protects an ultra-thin diamond carrier plate prepared by the method and its application in the fields of semiconductor, high-frequency electronics and optical packaging.

[0040] Compared with the prior art, the application has the following technical effects:

[0041] The application can prepare an ultra-thin structure with a controllable thickness, has extremely high thermal conductivity, provides a reliable diamond film hetero-substrate growth and peeling process, enables the thin film to be conveniently obtained as an independent carrier plate from a growth substrate, enhances the metallization adhesion of the surface of the carrier plate, has extremely low roughness, supports high-precision nanometer pattern manufacturing, realizes micro-nano patterning, improves packaging reliability, can be used for a thermal expansion layer of an electronic chip and a thermal management platform of a high-power device, has high resistance to ensure the stability of the ultra-thin structure as an insulating material, and can be used for strain sensors, UV detectors and other devices by adjusting the electric conductance through surface engineering. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Picture for Si substrate;

[0043] Figure 2 Picture for growing a diamond thin film on a Si substrate by CVD;

[0044] Figure 3 Picture after preparing a metallization pattern on the diamond thin film. DETAILED DESCRIPTION

[0045] The specific content of the application is further explained and described in detail in combination with the following examples.

[0046] Example 1

[0047] This example gives a preparation method of an ultra-thin diamond carrier plate, including the following steps:

[0048] Step one, select a Si substrate with a thickness of 5 mm, first immerse the Si substrate in acetone for 5 min under the condition that the vibration frequency is 80 kHz, then immerse the Si substrate in anhydrous ethanol for 10 min, then wash the Si substrate clean with pure water and then ultrasonically clean the Si substrate in pure water for 10 min, and finally centrifugally dry the Si substrate; the Si substrate is as shown in Figure 1 ;

[0049] Nucleation sites can be obtained by mechanical seeding, and the number of nucleation sites can reach 10. 10 ~10 11 pcs / cm 2 This overcomes the nucleation difficulties caused by the high surface energy of the foreign substrate, achieves in-situ nucleation, has a smooth interface without large particles, improves the uniformity of the bonding between the film and the substrate, and can form a continuous film in the early stage of deposition, thereby improving the uniformity and density of diamond film formation.

[0050] A sacrificial layer is introduced by surface sputtering of a thin metal layer, with a thickness of 300 nm serving as the sacrificial layer; the metal layer is Al.

[0051] Step 2: A dense, continuous, ultrathin diamond film is grown on the substrate pretreated in Step 1 by chemical vapor deposition; the specific method includes:

[0052] 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 3 kPa, a methane concentration of 20%, a substrate temperature of 850℃, a hot wire temperature of 2300℃, and a deposition time of 2 h. During this stage, a high-density diamond nucleus layer is formed to cover the substrate surface.

[0053] S2. Adjust the pressure to 10 kPa, methane concentration to 5%, and add O2 to 1%. Maintain the substrate temperature at 950℃, hot wire temperature at 2300℃, and deposition time at 2 h. Deposit to a thickness of 80 micrometers. Adding an oxidant helps to etch the non-diamond carbon phase, inhibits graphite deposition, and ensures the purity of the film during long-term deposition.

[0054] S3. After deposition, the chamber temperature is gradually reduced to room temperature at a cooling rate of 10℃ / min, and the substrate with the deposited ultrathin diamond film is removed; the product is as follows. Figure 2 As shown;

[0055] Step 3: Perform surface cleaning, activation, and modification on the diamond film in sequence;

[0056] Cleaning methods for diamond surfaces include: 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 100°C, and soaking it for 10 minutes; since CVD diamond surfaces are usually hydrogen-terminated, making them hydrophobic and chemically inert, metal films on such surfaces tend to form discontinuous islands and are not firmly attached. By treating with concentrated sulfuric acid, the surface H atoms are replaced with O atoms, which increases the surface free energy and polarity, making it easier for metal atoms to "wet" and chemically bond to the diamond surface;

[0057] The activation method of the diamond surface is as follows: the self-supporting diamond film is put into a plasma cleaning machine, and oxygen plasma is used to treat 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) is oxidized into CO / CO2 and volatilized, and pure sp 3 Surface is purified.

[0058] The modification method of the diamond surface is to oxidize at 80℃ for 30 min with concentrated HNO3, which can form —NO2, —OH and —COOH, and improve the surface wettability.

[0059] Step four, constructing the metal layer structure required for the conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate.

[0060] 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 film in sequence.

[0061] Before sputtering the functional layer, the sputtering area is patterned by photolithography; as shown in Figure 3 ;

[0062] 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 ultraviolet laser (such as 355 nm); then scanning and irradiating the substrate side with laser of appropriate energy (such as infrared 1064 nm), and through the thermal expansion of the substrate to the laser, the interface is heated and detached.

[0063] The performance parameters of the diamond film prepared in Example 1 are shown in Table 1:

[0064] Table 1 Performance parameters of diamond film

[0065]

[0066] Example 2

[0067] This embodiment gives a preparation method of an ultrathin diamond carrier plate, which comprises the following steps:

[0068] Step one, select an AlN ceramic substrate with a thickness of 10 mm, and first immerse the AlN ceramic substrate in acetone under the condition of vibration frequency of 80 kHz for 3 min, then immerse it in anhydrous ethanol for 5 min, then rinse it with pure water and clean it with ultrasonic cleaning in pure water for 8 min, and finally centrifugal dry;

[0069] Mechanical seeding is used to obtain nucleation sites;

[0070] A sacrificial layer is introduced by surface sputtering of a thin metal layer, and a 500 nm thick metal layer is used as the sacrificial layer; the metal layer is Fe;

[0071] Step two: a dense and continuous ultrathin diamond film is grown on the substrate preprocessed in step one by chemical vapor deposition; the specific method includes:

[0072] S1: with one side of the sacrificial layer of the substrate as the deposition surface, a methane / hydrogen mixed gas is introduced into the vapor deposition equipment, the pressure is set to 1 kPa, the methane concentration is 5%, the substrate temperature is kept at 750℃, the hot wire temperature is 2000℃, and the deposition time is 0.5 h; in this stage, a high-density diamond crystal nucleus layer is formed to cover the substrate surface;

[0073] S2: adjust the pressure to 30 kPa, the methane concentration to 1%, and add CO2 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;

[0074] 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;

[0075] Step three: the diamond film is sequentially subjected to surface cleaning, activation and modification;

[0076] The cleaning method of the diamond surface includes: soaking in a mixed solution prepared by mixing concentrated sulfuric acid with a concentration of 98% and hydrogen peroxide with a concentration of 30% at a volume ratio of 3:1 and heating to 100℃ for 15 min; because the CVD diamond surface is usually terminated by hydrogen, it is hydrophobic and chemically inert, and the metal 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 can be more easily "wetted" and chemically bonded to the diamond surface;

[0077] The activation method of the diamond surface is: argon plasma is used to bombard for 5 min at 300 W; due to its physical sputtering effect, argon plasma can micro-etch the diamond surface to produce a nanoscale roughness, which is beneficial to mechanically "anchor" the subsequent plating layer;

[0078] The modification method of the diamond surface includes oxidation with HNO3+HF mixed acid at 60℃ for 30 min, which can form —NO2, —OH and —COOH, and improve the surface wettability;

[0079] Step four: a metal layer structure required for constructing conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate;

[0080] The DC magnetron sputtering is adopted to deposit a 100-nm-thick Cr transition layer, a 100-nm-thick Pd diffusion barrier layer and a 200-nm-thick Cu functional layer on the surface of the diamond film in sequence under the conditions of a vacuum degree of 0.2 Pa, a bias voltage of -60 V, a substrate temperature of 100℃ and a sputtering power of 3 kW;

[0081] The sputtering area is defined by photoetching patterning before sputtering the functional layer;

[0082] Step five, the ultrathin diamond film deposited on the heterogeneous substrate is separated 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, a micrometer-level graphitization layer is generated by scanning, the interface bonding force is reduced, then a 3M adhesive tape is stuck on the edge position of the surface of the diamond film, the adhesive tape is gently stretched along the edge cut on the substrate previously, and the diamond film is peeled off 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 caused by excessive stress or uneven force during the peeling process.

[0083] Example 3

[0084] The embodiment provides a preparation method of an ultrathin diamond carrier plate, including the following steps:

[0085] Step one, an Al2O3 ceramic substrate with a thickness of 10 mm is selected, the Al2O3 ceramic substrate is first immersed in acetone for 4 min under the condition of a vibration frequency of 80 kHz, then immersed in anhydrous ethanol for 8 min, then washed with pure water, and finally ultrasonically cleaned in pure water for 9 min and then centrifuged and dried;

[0086] Nucleation sites are obtained by mechanical seeding;

[0087] A sacrificial layer is introduced by surface sputtering of a metal thin layer, and a 400-nm-thick metal layer is used as the sacrificial layer; the metal layer is Cu;

[0088] Step two, a dense and continuous ultrathin diamond film is grown on the substrate pretreated in step one by chemical vapor deposition; the specific method includes:

[0089] S1, taking the side of the sacrificial layer of the substrate as a deposition surface, a methane / hydrogen mixed gas is introduced into a vapor deposition device, the pressure is set to 2 kPa, the methane concentration is 10%, the substrate temperature is kept at 800℃, the hot wire temperature is 2200℃, and the deposition time is 1 h, and in this stage, a high-density diamond nucleus layer is formed to cover the surface of the substrate;

[0090] S2, adjust the pressure to 8 kPa, the methane concentration is 4%, and add O2 0.5%, keep the substrate temperature 900℃, the hot wire temperature 2200℃, and the deposition time 1 h; deposit to 50 microns in thickness;

[0091] S3, after the deposition is completed, gradually reduce the cavity temperature to room temperature at a cooling rate of 8℃ / min, and take out the substrate on which the ultrathin diamond film is deposited;

[0092] Step three, sequentially perform surface cleaning, activation and modification on the diamond film;

[0093] 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;

[0094] The activation method of the diamond surface is to put the self-supporting diamond film into a plasma cleaning machine, and use oxygen plasma to process under the conditions of radio frequency power 80 W and pressure 30 Pa in vacuum for 8 min;

[0095] The modification method of the diamond surface includes oxidizing at 60℃ for 30 min with concentrated HNO3, which can form —NO2, —OH and —COOH, and improve the surface wettability; Step four, construct the metal layer structure required for the conductive wiring and heat dissipation substrate on the surface of the diamond carrier plate;

[0096] 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;

[0097] Before sputtering the functional layer, patternize by limiting the sputtering area through photolithography pattern;

[0098] Step five, separate the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supporting diamond carrier plate; cut through the film to the substrate along the boundary of the diamond film by using ultraviolet laser (such as 355 nm). Then, irradiate the substrate side with laser of appropriate energy (such as infrared 1064 nm), and make the interface bulge and debond by thermal expansion of the substrate through absorption of laser.

[0099] Example 4

[0100] Example 4 is basically the same as Example 3, and the only difference is that Si3N4 ceramic is used as the substrate.

[0101] Before sputtering the functional layer, patternize by limiting the sputtering area through photolithography pattern; as shown in Figure 3 ;

[0102] Example 5

[0103] The present embodiment provides a preparation method of an ultrathin diamond carrier plate, comprising the following steps:

[0104] Step one, 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 formation, high chemical purity and matched thermal expansion coefficient, to ensure the nucleation and thin film dense growth of high-quality diamond;

[0105] 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;

[0106] 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;

[0107] Step two, a dense and continuous ultrathin diamond film is grown on the substrate pretreated in step one by chemical vapor deposition; the specific method comprises:

[0108] S1, with one side of the sacrificial layer of the substrate as the deposition surface, a mixture of methane / hydrogen gas is introduced into the vapor deposition equipment, the pressure is set to 3 kPa, the methane concentration is 20%, the substrate temperature is maintained at 850℃, the hot wire temperature is 2000℃, and the deposition time is 2 h, at this stage, a high-density diamond nucleus layer is formed to cover the substrate surface;

[0109] S2, adjust the pressure to 10 kPa, the methane concentration to 5%, and add O2 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;

[0110] 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;

[0111] Step three, the diamond thin film is sequentially subjected to surface cleaning, activation and modification;

[0112] 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;

[0113] The activation method of the diamond surface is to place the self-supporting diamond thin film into a plasma cleaning machine, and treat it with oxygen plasma under vacuum at a radio frequency power of 100 W and a pressure of 40 Pa for 10 min;

[0114] The modification method of the diamond surface includes oxidizing with concentrated HNO3 at 70℃ for 35 min to form —NO2, —OH and —COOH, and improve the surface wettability.

[0115] Step four, constructing the metal layer structure required for the conductive wiring and heat dissipation substrate on the diamond carrier plate surface;

[0116] Under the conditions of vacuum degree 0.5 Pa, bias voltage -60 V, substrate temperature 100℃ and sputtering power 3 kW, a 150 nm thick W transition layer, a 200 nm thick Mo diffusion barrier layer and a 500 nm thick Au functional layer are sequentially sputtered on the surface of the diamond film by direct current magnetron sputtering; before sputtering the functional layer, the sputtering area is defined by photoetching pattern for patterning;

[0117] Step five, separating the ultrathin diamond film deposited on the heterogeneous substrate from the substrate to obtain a self-supported diamond carrier plate; using ultrafast laser focusing on the inside of the diamond film close to the interface, scanning generates a micron-level graphitized layer to reduce the interface bonding force, and then using 3M tape to stick at the edge position of the diamond film surface, along the edge cut on the substrate before, gently stretching the tape to peel off the diamond film from the substrate. This stretching process helps the diamond film to be smoothly separated from the substrate surface, can ensure the integrity of the diamond film, and avoids cracks in the diamond film during the peeling process due to excessive stress or uneven force.

[0118] Example 6

[0119] Example 6 is basically the same as Example 5, except that the thickness of the metal W selected as the substrate is 5 mm, and the activation method of the diamond surface in step three is to use argon plasma to bombard at 200 W for 5 min.

[0120] The modification method of the diamond surface is to use a reaction ion etcher to treat with fluorine plasma for 15 min to introduce functional groups.

[0121] Example 7

[0122] Example 7 is basically the same as Example 5, except that the thickness of the metal Nb selected as the substrate is 5 mm, and the activation method of the diamond surface in step three is to use argon plasma to bombard at 300 W for 2 min.

[0123] The modification method of the diamond surface is to use a reaction ion etcher to treat with fluorine plasma for 5 min to introduce functional groups.

[0124] Example 8

[0125] Example 8 is substantially the same as Example 5, except that the high-purity alloy plates of Nb and Mo with a thickness of 5 mm are selected as the substrate, and the activation method of the diamond surface in Step 3 is to use argon plasma to bombard for 3 min at 220 W;

[0126] The modification method of the diamond surface is to use a reactive ion etcher to treat the diamond surface with fluorine plasma for 10 min to introduce functional groups.

[0127] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. 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, The method comprises the following steps: Step one, selecting a heterogeneous substrate, cleaning, seeding, and then introducing a sacrificial layer; the substrate includes a metal substrate and a non-metal substrate; The metal substrate adopts bias plasma seeding, and a thin layer of oxide is grown by thermal oxidation on the surface of the metal substrate to introduce the sacrificial layer; the non-metal substrate adopts mechanical seeding, and a thin layer of metal is introduced on the surface by sputtering to introduce the sacrificial layer; Step two, growing a dense and continuous ultrathin diamond film on the substrate pretreated in step one by chemical vapor deposition; The growth method of the ultrathin diamond film comprises: S1, taking one 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 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 O2 or CO2 0.1-1%, 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 deposition, gradually reduce the cavity temperature to room temperature at a cooling rate of 5-10℃ / min, and take out the substrate with the ultrathin diamond film deposited thereon; Step three, sequentially performing surface cleaning, activation, and modification on the diamond film; The modification method of the diamond surface comprises oxidizing at 60-80℃ for 30-40 min with concentrated HNO3 or HNO3+HF mixed acid, or treating with fluorine plasma of a reactive ion etcher for 5-15 min to introduce functional groups; 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-supported diamond carrier plate.

2. The method of claim 1, wherein the thickness of the diamond layer is less than 100 microns. 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 concentrated sulfuric acid with a concentration of 98% and hydrogen peroxide with a concentration of 30% at a volume ratio of 3:1 and heating to 80-100℃ for 10-15 min; 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, then immerse it in anhydrous ethanol for 5-10 min, then rinse it with pure water, then ultrasonically clean it in pure water for 8-10 min, and finally centrifugally dry it.

3. The method of claim 1, wherein the thickness of the diamond layer is less than 100 microns. The cleaning method of the diamond surface in step three comprises: immersing it in a mixed solution prepared by mixing concentrated sulfuric acid with a concentration of 98% and hydrogen peroxide with a concentration of 30% at a volume ratio of 3:1 and heating to 80-100℃ for 10-15 min.

4. The method of claim 1, wherein the thickness of the diamond layer is less than 100 microns. The activation method of the diamond surface in step three comprises: placing the self-supporting diamond film into a plasma cleaning machine, and treating the diamond film 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 the diamond film with argon plasma at 200-300 W for 2-5 min.

5. The method of claim 1, wherein the thickness of the diamond layer is less than 100 microns. The construction method of the metal layer structure in step four comprises: The transition layer, the diffusion barrier layer and the functional layer are sputtered 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--100 V, a substrate temperature of 100-150 ℃ and a sputtering power of 3-5 kW, wherein the transition layer has a thickness of 100-150 nm, the diffusion barrier layer has a thickness of 100-200 nm, and the functional layer has a thickness of 200-500 nm; The metal sputtered for the transition layer comprises any one of Ti, Cr, W and Mo; The metal sputtered for 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 sputtering area is defined by photolithography patterning before the functional layer is sputtered.

6. The method of claim 1, wherein the thickness of the diamond layer is less than 100 microns. The method for separating the ultrathin diamond film from the substrate in step five comprises any one of a laser scribing method and an interface embrittlement method.

7. An ultrathin diamond carrier prepared by the method according to any one of claims 1 to 6.

8. Use of the ultrathin diamond carrier according to claim 7 in the field of semiconductor, high-frequency electronic and optical packaging.

Images