Semiconductor device three-dimensional integration method based on graphical diamond bonding

Abstract

The invention relates to a semiconductor device three-dimensional integration method based on graphical diamond bonding. In order to improve the heat dissipation efficiency of a semiconductor device, a patterning and bonding technology is used, a surface activation sputtering method and a bonding surface secondary activation method are further used for improving an atomic diffusion bonding technology, the surface activation sputtering method is used, the high bonding degree of a bonding intermediate layer material to the diamond surface is improved, and by means of the technology, the heat dissipation efficiency of the semiconductor device is improved. The diamond-based semiconductor device can be prepared at low temperature and low pressure, and integration is realized in a low-temperature environment, so that the problem of interface thermal stress caused by overlarge difference of thermal expansion coefficients of diamond and semiconductor materials is solved, the interface thermal resistance of the middle layer is smaller, and the heat dissipation performance is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of heat dissipation of semiconductor devices, and particularly to a three-dimensional integration method of semiconductor devices based on patterned diamond bonding. Background Art

[0002] Semiconductor technology is the solid foundation of modern social information technology. With the development of technologies such as artificial intelligence, deep learning, new energy vehicles, and 5G / 6G communications, the demand for electronic devices continues to grow, and the requirements for their performance are also increasing. Therefore, semiconductor devices are gradually moving towards miniaturization and high power density. With the development of semiconductor devices towards high frequency, high power, and miniaturization, the heat accumulation is getting higher and higher, and the heat dissipation management of semiconductor devices has become a severe challenge. Traditional high-power semiconductor devices are limited by the limited thermal conductivity of the substrate material, and the heat in the active region continues to accumulate, thereby forming local hot spots, resulting in a significant reduction in their performance. Therefore, how to improve the heat dissipation performance of devices has become one of the key technical bottlenecks of high-power semiconductor devices. At the same time, in recent years, the price of synthetic polycrystalline diamond has been reduced through mass production. Diamond is a very effective thermal management material. It has the highest thermal conductivity among known materials, with a thermal conductivity of about 2200 W / m·K, which is about 5 times higher than that of copper with a thermal conductivity of about 398 W / m·K. Moreover, the specific heat capacity of diamond is about 4 times lower than that of copper, which are 6.115 and 24.47 (J / mol·K) respectively. This indicates that diamond can dissipate more heat from semiconductor devices to the heat dissipation system faster, so it is highly anticipated in the application as a heat dissipation substrate.

[0003] The existing diamond and semiconductor integration patent CN202410635190.8 uses the method of epitaxially growing diamond on a silicon wafer. After epitaxy, the non-diamond-growing surface of the silicon wafer is thinned, and then the diamond and the silicon wafer are polished respectively, and then semiconductor devices are fabricated based on the silicon substrate. The epitaxial growth diamond method used in this patent has a high temperature during growth, usually reaching above 700 °C. The thermal expansion coefficients of diamond and other semiconductor materials such as silicon are quite different. The integration of diamond and semiconductor achieved in a high-temperature environment will reduce the reliability of the integration; moreover, the epitaxial growth method will greatly increase the complexity of the process and extend the time cycle.

[0004] The prior art relates to the research results of the metallic bonding between diamond and semiconductor materials, such as the following paper: Room-temperature bonding of single-crystal diamond and Si using Au / Au atomic diffusion bonding in atmospheric air. Microelectronic Engineering Volume 195, 5 August 2018, Pages 68-73. After cleaning 5*5*0.3 mm diamond and 4-inch silicon wafers with H2SO4 / H2O2 solution, the diamond and silicon wafers were gold-plated, and then the diamond and silicon wafers were bonded to obtain diamond / silicon bonded samples. This method did not perform Ar ion beam activation treatment on the silicon wafers and diamond wafers after solution cleaning during magnetron sputtering coating, resulting in incomplete removal of the SiO2 oxide layer on the silicon wafers, which affected the subsequent bonding strength. At the same time, before bonding, since the bonding surfaces of the diamond and silicon wafers were not subjected to Ar ion beam re-activation treatment, the tiny contaminants on the surface of the bonded samples were not completely removed, and the metal layer was not activated, resulting in voids appearing in the center and around the bonded samples, which affected the bonding quality. Moreover, the diamond samples in this paper had a small area and were not bonded to semiconductor devices. Summary of the Invention

[0005] The object of the present invention is to improve the heat dissipation efficiency of semiconductor devices. The present invention uses the "graphitization + bonding" technology to replace ordinary bulk diamond with microchannel diamond. By using diamond graphitization technology, the surface of the diamond is etched to add microchannels on the diamond surface. By utilizing the high thermal conductivity of diamond and the high heat transfer performance of the microchannels, the heat dissipation efficiency of the diamond substrate is further improved. Then, using the atomic diffusion bonding technology, the graphitized diamond heat dissipation substrate is integrated with high-power semiconductor devices. By utilizing the high thermal conductivity and high heat transfer rate of the graphitized diamond substrate, the overall heat dissipation capacity of the device is improved, thereby further enhancing the electrical performance and reliability of the device. In the overall structure, by using the graphitized diamond substrate, the problem of uneven device temperature caused by hot spots during the heat dissipation of high-power semiconductor devices by ordinary bulk diamond substrates is solved, greatly improving the reliability and service life of the device. The atomic diffusion bonding technology is used for integration instead of technologies such as nano-silver paste sintering and eutectic soldering, which improves the thermal conductivity of the intermediate layer, reduces the interface thickness and interface thermal resistance between diamond and the device, and can achieve reliable integration under low-temperature and low-pressure environments, solving a series of problems caused by the difference in thermal expansion coefficients between diamond and semiconductor devices.

[0006] The three-dimensional integration method of semiconductor devices based on graphitized diamond bonding provided by the present invention includes the following steps:

[0007] (a) Pattern the diamond surface to increase the heat dissipation area of the diamond surface;

[0008] (b) Activate the diamond surface, including:

[0009] In a hydrothermal autoclave, use an H2SO4 / H2O2 solution to pickle the diamond at 180 °C to generate -OH groups on the surface; ultrasonically clean with acetone, ethanol, and ultrapure water in sequence, and dry with nitrogen;

[0010] (c) Use an Ar ion beam to bombard to activate the diamond surface and the bonding surface of the semiconductor device, and then coat the diamond surface and the bonding surface of the semiconductor device by magnetron sputtering. The coating includes: first sputter a high-adhesion metal layer, and the metals used in the high-adhesion metal layer include any one or a combination of two of Ti and Cr;

[0011] Then sputter a thermal conduction diffusion layer, and the metals used in the sputtered thermal conduction diffusion layer include any one or a combination of multiple of Ag, Cu, and Au;

[0012] (d) Use an Ar ion beam to treat the diamond surface and the bonding surface of the semiconductor device to remove metal surface impurities and activate the metal surface; bond the patterned diamond to the bonding surface of the semiconductor device by atomic diffusion bonding.

[0013] Preferably, in step (a), the patterning treatment includes: ultrasonically clean the diamond surface with acetone and ethanol solution, then wash with ultrapure water and dry; spin-coat photoresist on the diamond surface, control the rotation speed to form a photoresist layer, bake and cure, and then expose and develop; etch the diamond surface pattern by reactive ion etching (RIE);

[0014] The thickness of the photoresist layer is 200 - 800 nm, and the rotation speed range is 2000 - 6000 rpm.

[0015] Preferably, in step (c), the sputtering parameters of the high-adhesion metal layer are: target head power 80 W, vacuum degree 1×10 -6 Pa, deposition thickness 5 - 15 nm; the sputtering parameters of the thermal conduction diffusion layer are: target head power 100 W, vacuum degree 1×10 -6 Pa, deposition thickness 35 - 45 nm.

[0016] Preferably, the treatment of the diamond surface and the bonding surface of the semiconductor device using an Ar ion beam in step (d) includes: bombarding the surface of the metal layer with an Ar ion beam, with an Ar target head radio frequency power of 30 W and a duration of 100 s.

[0017] Preferably, the patterns obtained by the patterning process include one or both of microchannels and microcolumn structures.

[0018] Preferably, the bonding temperature for the atomic diffusion bonding is 200 °C, the pressure is 4 MPa, the vacuum degree is 1×10 -5 Pa, and the pressure holding time is 30 minutes.

[0019] Preferably, the semiconductor device is one of a power device, an optoelectronic device, or a sensor device.

[0020] In this patent, the diamond patterning technology is used to fabricate specific microstructures on the surface of a diamond substrate, such as microcolumns, trenches, or hole arrays, to enhance the heat dissipation effect. Among them, the microcolumn structure can reduce the thermal resistance by increasing the heat dissipation surface area, and the trench structure can optimize the heat dissipation path to guide heat conduction more efficiently. Compared with ordinary bulk diamond, these structures improve the heat dissipation performance and are more suitable for hot spot heat dissipation of high-power semiconductor devices. Compared with the high-power semiconductor devices relying on copper heat dissipation substrates, which are the mainstream in the current market, the heat dissipation performance is improved by 40%.

[0021] In this patent, the surface activation sputtering method and the secondary activation method of the bonding surface are used to improve the atomic diffusion bonding technology. Using the surface activation sputtering method is beneficial to improving the high bonding degree of the bonding intermediate layer material to the diamond surface. Using this technology, diamond-based semiconductor devices can be fabricated at low temperature and low pressure. And because the integration is achieved in a low-temperature environment, compared with the epitaxial growth of diamond using the MPCVD method, the problem of interfacial thermal stress caused by the too large difference in the thermal expansion coefficients of diamond and semiconductor materials is solved. At the same time, because the intermediate layer uses a metal material with high thermal conductivity and the thickness is nanoscale, compared with the nano-silver sintering method, eutectic welding method, etc. in the market, the interfacial thermal resistance of the intermediate layer is smaller and the heat dissipation performance is higher.

[0022] For the diamond wafers used in this patent, diamond wafers that have been directly purchased and processed, such as cutting, polishing, can be directly integrated with finished semiconductor devices. Compared with the epitaxial growth using the MPCVD method, the process time cycle can be effectively reduced, the process complexity can be reduced, and the problem that the device layer needs to be carried out after the epitaxial growth using the MPCVD method can be avoided, thereby improving the product yield. Description of the Drawings

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. These drawings are not necessarily drawn to scale. In the drawings:

[0024] Figure 1This is a schematic structural diagram of the product obtained by the present invention. The meanings of the numbers in the figure are as follows: 1. Semiconductor device layer; 2. Intermediate device layer; 3. Diamond intermediate layer; 4. Patterned diamond substrate. Detailed implementation manners

[0025] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] As Figure 1 shown, the structure of this patent is generally divided into three parts: a patterned diamond sheet, a surface-activated sputtered metal nano-intermediate layer, and a semiconductor device. Among them, the intermediate layer is divided into a diamond surface intermediate layer and a semiconductor device surface intermediate layer. The main key technologies of this patent are diamond surface patterning, diamond surface activation treatment (hydrothermal autoclave high-temperature treatment), surface-activated sputtering, and low-temperature and low-pressure secondary activation atomic diffusion bonding, which play a key role in enhancing heat dissipation and increasing integration reliability in the whole, and determine the performance improvement and service life increase of the device.

[0027] Material requirements: diamond surface roughness < 1 nm, semiconductor device bonding layer roughness < 1 nm

[0028] 1. Diamond surface patterning

[0029] First, use solutions such as acetone and ethanol to ultrasonically clean the diamond surface to remove organic impurities. Subsequently, after cleaning the diamond surface with ultrapure water, bake it at 150 - 200 °C to remove excess surface moisture, so as to enhance the adhesion of the photoresist and prevent bubbles from generating during photoresist coating. Subsequently, use a high-speed spin coater to drop the photoresist onto the diamond surface at a rotation speed of 2000 - 6000 rpm, and the thickness of the photoresist is controlled by the rotation speed. After spin coating is completed, bake the diamond at 80 - 150 °C for 2 - 5 minutes to cure the photoresist film. Subsequently, expose the designed microchannels, microcolumns and other patterns onto the diamond surface, and use a developer to remove the unexposed areas. Finally, use reactive ion etching (RIE) to etch the diamond surface patterns to complete the diamond surface patterning.

[0030] 2. Diamond surface activation treatment (hydrothermal autoclave high-temperature treatment)

[0031] One of the key technologies of this patent is to use the surface-activated sputtering coating method to deposit a metal film on the surface of diamond and semiconductor devices. However, due to the high chemical inertness of the diamond surface, it is difficult to achieve surface adhesion of the metal layer without special treatment of the diamond surface. This patent adopts processes such as ultrasonic cleaning with acetone, rinsing with ethanol, and high-temperature pickling in a hydrothermal autoclave with H2SO4 / H2O2 solution at 180 °C. While removing organic substances and impurities on the surface of the diamond wafer, -OH high-energy groups are attached to the diamond surface, enhancing the surface activity of the diamond and improving the adhesion of the metal film.

[0032] First, place the diamond in an acetone solution and ultrasonically clean it for 15 minutes. This step can effectively remove the organic residue on the diamond during the processing. Subsequently, use an ethanol solution to ultrasonically clean the diamond wafer after ultrasonic cleaning with acetone for 5 minutes to dissolve the residual acetone solution on the diamond surface. Then, wash the diamond surface with ultrapure water to remove the residual ethanol on the diamond surface. Subsequently, use an SPM solution (H2SO4 / H2O2 solution 3:1) to activate and clean the diamond surface, further removing the impurities on the diamond surface and attaching -OH high-energy groups to the diamond surface, enhancing the diamond surface activity and increasing the coating adhesion. However, due to the extremely high chemical inertness of the diamond surface, conventional semiconductor cleaning and activation processes do not work well on diamond. Therefore, high-temperature cleaning in a hydrothermal autoclave is required for the surface activation cleaning of diamond. The SPM solution completely covers the diamond wafer and does not exceed 2 / 3 of the total volume of the hydrothermal autoclave. Then, raise the temperature to 180 °C and place it in a heating box for 2 hours to allow it to react fully. After the temperature drops to 25 °C, take out the diamond wafer. Then, rinse the residual acid solution on the diamond surface with ultrapure water and blow-dry the diamond surface with nitrogen for later use.

[0033] 3. Coating of Diamond / Semiconductor Devices by Surface Activation Sputtering Method

[0034] After completing the diamond surface patterning and surface activation manufacturing processes, place the diamond wafer in a magnetron sputtering coating device and deposit a film on the non-patterned surface of the diamond by gradient sputtering method. The entire coating process mainly includes the following steps. First, before coating, ultrasonically clean the diamond surface again with alcohol and acetone solution to ensure that there are no organic pollutants on the diamond surface. Subsequently, place the diamond in a magnetron sputtering machine and perform a vacuum pumping process to make the chamber vacuum degree reach 1×10 - 6 Pa; Subsequently, perform Ar ion beam bombardment treatment on the diamond surface. By bombarding the diamond surface with high-energy Ar ion beams, the diamond surface is activated, further improving the diamond surface activity and removing tiny impurities on the diamond surface. The radio frequency power of the Ar ion beam target head: 30 W, duration: 100 s; Subsequently, perform high-adhesion layer sputtering coating (metals such as Ti, Cr can be used). At a target head power of 80 W and a vacuum degree of 1×10-6 Deposit a 5 - 15 nm high - adhesion metal layer under the condition of -6 Pa; subsequently, perform sputtering coating of a high - thermal - conductivity and high - diffusivity layer (metals such as Ag, Cu, Au can be used), and deposit a 35 - 45 nm high - thermal - conductivity and high - diffusivity layer under the condition of a target head power of 100 W and a vacuum degree of 1×10

[0035] Coat a small amount of Ti and Cr layers, which can improve the adhesion between diamond and the nano - metal layer; bombarding the diamond and the bonding surface of the semiconductor device with an Ar ion beam can improve the surface activity of the diamond and the bonding surface of the semiconductor device, enabling the adhesion between the diamond and the semiconductor device and the nano - metal layers such as Ti and Cr to be improved again; and due to the relatively high thermal conductivity of Cu, Ag, and Au, coating with Cu, Ag, and Au layers can effectively reduce the interfacial thermal resistance of the intermediate layer and improve the overall heat dissipation ability of the device. At the same time, due to the small - size effect and surface effect, better diffusion can occur between the nano - metal intermediate layers formed by surface - activated sputtering coating, which helps to improve the bonding reliability.

[0036] 4. Low - temperature and low - pressure secondary activation atomic diffusion bonding

[0037] After completing the surface coating of the diamond and the semiconductor device, place the diamond and the semiconductor device into the bonding machine, and then evacuate the cavity of the bonding machine. When the vacuum degree reaches 1×10 -5Under Pa environment, bombard the gold-plated layers on the surfaces of diamond and semiconductor with Ar ion beam to achieve secondary activation of the surfaces of diamond and semiconductor devices. The specific process is as follows: RF power of Ar target head: 30 W, duration: 100 s. By bombarding with Ar ion beam, the oxide layers on the surfaces of some metals (such as Cu, Ag) can be removed, and the metal activity of the gold-plated layers on the surfaces of diamond and semiconductor devices can be enhanced again, and the diffusion efficiency of the gold-plated layers can be improved. Then, fix the diamond and semiconductor devices with a laser alignment fixture and perform alignment operations to make their gold-plated surfaces face each other. Since all processes are carried out in a vacuum environment, it can ensure that there are no gas impurities on the surfaces of diamond and devices. Subsequently, heat the bonding machine platen to make the platen temperature reach 200 °C. The diffusion reaction of metal atoms will intensify with the increase of temperature. By raising the temperature, the self-diffusion and inter-diffusion reactions of the metal in the gold-plated layer are accelerated. When the bonding machine platen reaches the specified temperature, start to apply pressure to the diamond and semiconductor devices, the pressure is 4 MPa, and the pressure rise time is 180 s. After reaching the specified pressure, maintain the pressure. Compensate for the height difference generated by the surface patterning of diamond through pressurization to ensure complete fitting of the diamond and semiconductor devices. After maintaining the heating and pressurization state in the vacuum environment for 30 minutes, start to cool down while maintaining the pressure and vacuum environment. After the temperature drops to 25 °C, release the pressure and break the vacuum to complete the low-temperature and low-pressure secondary activation atomic diffusion bonding of diamond and semiconductor devices, and take out the sample.

[0038] Utilize the high self-diffusion properties of metals such as Ag-Ag, Cu-Cu, Au-Au, and the inter-diffusion of metals such as Ti-Au, Ti-Ag, Ti-Cu to achieve the integration of diamond and semiconductor devices. After the diamond and semiconductor devices after film coating enter the bonding machine, evacuate again to activate the gold-plated layer on the surface with Ar ion beam. While removing the oxide layer on the metal surface, the surface activity of the metal layer is increased again, which can significantly improve the quality of the bonding surface of diamond and semiconductor devices, thereby increasing the reliability of the devices. At the same time, the high thermal conductivity of metals such as Cu, Ag, Au and the ultra-thin thickness (100 nm) of the intermediate layer can effectively reduce the interface thermal resistance of the intermediate layer, making the heat transfer efficiency between the device and the diamond further improved.

[0039] As described above, it is only a part of the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A three-dimensional integration method for semiconductor devices based on graphitized diamond bonding, characterized in that It includes the following steps: (a) Pattern the diamond surface to increase the heat dissipation area of the diamond surface; (b) Activate the diamond surface, including: In a hydrothermal autoclave, use an H2SO4 / H2O2 solution to pickle the diamond at 180 °C to generate -OH groups on the surface; ultrasonically clean with acetone, ethanol, and ultrapure water in sequence, and dry with nitrogen; (c) Bombard with an Ar ion beam to activate the diamond surface and the bonding surface of the semiconductor device, and then coat the diamond surface and the bonding surface of the semiconductor device by magnetron sputtering. The coating includes: first sputter a highly adhesive metal layer, and the metals used in the highly adhesive metal layer include any one or a combination of two of Ti and Cr; Then sputter a thermal conduction diffusion layer, and the metals used in the sputtered thermal conduction diffusion layer include any one or more combinations of Ag, Cu, and Au; (d) Use an Ar ion beam to process the diamond surface and the bonding surface of the semiconductor device to remove metal surface impurities and activate the metal surface; bond the patterned diamond to the bonding surface of the semiconductor device by atomic diffusion bonding.

2. The three-dimensional integration method of semiconductor devices based on patterned diamond bonding according to claim 1, wherein In step (a), the patterning process includes: ultrasonically clean the diamond surface with an acetone and ethanol solution, then wash with ultrapure water and dry; spin-coat a photoresist on the diamond surface, control the rotation speed to form a photoresist layer, bake and cure it, and then expose and develop; etch the diamond surface pattern by reactive ion etching (RIE); The thickness of the photoresist layer is 200 - 800 nm, and the range of the rotation speed is 2000 - 6000 rpm.

3. The three-dimensional integration method of semiconductor devices based on patterned diamond bonding according to claim 1, wherein In step (c), the sputtering parameters of the high-adhesion metal layer are: target head power 80 W, vacuum degree 1×10 -6 Pa, deposition thickness 5 - 15 nm; the sputtering parameters of the heat conduction and diffusion layer are: target head power 100 W, vacuum degree 1×10 -6 Pa, deposition thickness 35 - 45 nm.

4. The three-dimensional integration method of a semiconductor device based on patterned diamond bonding according to claim 1, wherein In step (d), the use of an Ar ion beam to process the diamond surface and the bonding surface of the semiconductor device includes: bombarding the surface of the metal layer with an Ar ion beam, with an Ar target head radio frequency power of 30 W and a duration of 100 s.

5. The three-dimensional integration method of a semiconductor device based on patterned diamond bonding according to claim 1, characterized in that The pattern obtained by the patterning process includes one or two of a microchannel and a microcolumn structure.

6. The three-dimensional integration method of a semiconductor device based on patterned diamond bonding according to claim 1, wherein, The bonding temperature of the atomic diffusion bonding is 200 °C, the pressure is 4 MPa, the vacuum degree is 1×10 -5 Pa, and the pressure holding time is 30 minutes.

7. The three-dimensional integration method of a semiconductor device based on patterned diamond bonding according to claim 1, wherein The semiconductor device is one of a power device, an optoelectronic device, or a sensor device.

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