Method of diamond thin film processing and three-dimensional integrated circuit
Patent Information
- Application Number
- CN202011241854.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-11-09
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2040-11-09
AI Technical Summary
现有技术中金刚石薄膜的加工效率较低，采用等离子体刻蚀方式难以有效提升。
By thermally modifying the target area of the diamond film, the stable diamond is transformed into the unstable carbon, and then combined with etching, the process is repeated alternately until the preset conditions are met to form a perforation.
It significantly improves the processing efficiency of diamond films, and the etching speed of unstable carbon is many times faster than that of diamond, thus reducing the processing time.
Smart Images
Figure CN114464525B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor processing technology, and in particular to a method for processing diamond thin films and three-dimensional integrated circuits. Background Technology
[0002] Diamond possesses excellent thermal conductivity. With the increasing maturity of diamond chemical vapor deposition (CVD) technology, diamond thin films are being used more and more widely as heat dissipation media, leading to the widespread application of diamond thin film perforation technology. Among related technologies, diamond thin film perforation utilizes plasma etching.
[0003] In the process of developing this application, the inventors discovered that the prior art has at least the following problems:
[0004] Diamond has strong chemical stability, and plasma etching is not very efficient for processing diamond films. Summary of the Invention
[0005] To address the low processing efficiency of diamond thin films in related technologies, this application provides a method for processing diamond thin films and a three-dimensional integrated circuit. The technical solution is as follows:
[0006] In a first aspect, a method for processing a diamond thin film is provided, the method comprising: performing a thermal modification treatment on a target area of a first surface of the diamond thin film to modify the diamond in the target area into unstable carbon; performing an etching treatment on the target area of the first surface of the diamond thin film to remove the unstable carbon; and repeatedly and alternately performing the thermal modification treatment and etching treatment on the target area until a preset termination condition is met.
[0007] The target area is a pre-defined area that needs to be perforated. Carbon exists in three forms: diamond, graphite, and amorphous carbon. Diamond is stable carbon, while graphite and amorphous carbon are unstable carbon.
[0008] The embodiment of this application describes a scheme in which a diamond film is deposited on a substrate. Then, a target area on the first surface of the diamond film is subjected to thermal modification. Thermal modification is essentially a heat treatment; by controlling the energy density, the morphology of carbon in the target area can be changed, transforming stable carbon into unstable carbon, that is, modifying diamond into graphite and amorphous carbon. The thermal modification process requires controlling the energy density within a certain range, which can be 1-100 J / cm². 2Specifically, a preset power density can be used to irradiate the target area for a preset duration. The product of the preset power density and the preset duration is the preset energy density, and its value is within the aforementioned range. After modifying the diamond into unstable carbon, the unstable carbon can be etched, thus forming a groove in the target area on the first surface of the diamond film. The thermal modification and etching processes are repeated alternately until the termination condition is met. In this way, the groove in the target area will become increasingly deeper. The termination condition can be determined according to requirements, such as reaching a certain number of repetitions, or the groove reaching a preset depth, etc.
[0009] Compared to the etching process, the thermal modification process takes a very short time, which can be basically ignored. In addition, because unstable carbon is much less chemically stable than diamond, the etching speed of unstable carbon is much faster than that of diamond. Generally, the etching speed of diamond is 10-20 μm / h, while the etching speed of unstable carbon is over 100 μm / h. Therefore, the processing efficiency of diamond films can be improved through the above methods.
[0010] In one possible implementation, the preset termination condition includes: repeatedly alternating between thermal modification and etching of the target area until the target number of repetitions is reached.
[0011] The scheme shown in this application embodiment allows the target value to be calculated based on the thickness of the diamond film and the energy density of laser or ion radiation during a single thermal modification process. First, the depth of diamond that can be modified in a single thermal modification process can be determined based on the energy density (the relationship between energy density and the depth of diamond modification can be determined experimentally beforehand). Then, the target value is obtained by dividing the thickness of the diamond film by this depth. To prevent substrate damage, during repeated alternating thermal modification and etching processes, a certain thickness of diamond can be retained at the bottom of the trench formed in the target area. The trench can then be subsequently opened up using other methods to obtain a through-hole. In this way, the target value can be calculated to be slightly less than the quotient of the diamond film thickness and the aforementioned depth.
[0012] In one possible implementation, the process of alternating thermal modification and etching is repeated until a preset termination condition is met, and further includes chemical mechanical polishing (CMP) of the second surface of the diamond film to form a through hole in the target area.
[0013] The solution described in this application involves repeatedly and alternately performing thermal modification and etching processes on the target area until the termination conditions are met. Then, a back-side grinding and polishing device can be used to remove the substrate. Next, CMP is performed on the second surface of the diamond film to remove a certain thickness, forming a through-hole in the target area. This method of forming through-holes by final grinding effectively protects the substrate and the underlying equipment, preventing equipment damage.
[0014] In one possible implementation, the thermal modification and etching processes on the target area are repeated alternately until a preset termination condition is met, and the process also includes CMP on the first surface of the diamond film.
[0015] The solution shown in this application embodiment can have a metal hard mask layer or not. In the case where no metal hard mask layer is used, after repeated thermal modification treatment, the opening of the groove formed in the target area will form an open-mouthed slope, which can be called a flared mouth. The flared mouth can be eliminated by CMP.
[0016] In one possible implementation, before thermally modifying the target area on the first surface of the diamond film, a metal hard mask layer is disposed on the area outside the target area on the first surface of the diamond film.
[0017] The embodiment of this application shows a scheme in which a metal hard mask layer is deposited on the first surface of a diamond film. A photoresist layer is coated on the metal hard mask layer. The portion of the photoresist layer corresponding to the target area is exposed. After exposure, the photoresist layer is treated with a developer. The photoresist corresponding to the exposed target area reacts chemically with the developer and is removed, exposing the underlying metal hard mask layer. The portion of the photoresist layer not corresponding to the target area is not exposed and therefore does not react with the developer. After these processing steps, the portion of the photoresist layer corresponding to the target area can be removed, that is, a processing pattern is formed on the photoresist layer. Then, the portion of the metal hard mask layer corresponding to the target area is etched. This process can be performed using dry anisotropic etching. Because the portion of the photoresist corresponding to the target area has been removed, the portion of the upper surface of the metal hard mask layer corresponding to the target area is not covered with photoresist, while other portions are covered with photoresist. The portions of the metal hard mask layer not covered by photoresist are etched away, exposing the underlying diamond film. The portions of the metal hard mask layer covered by photoresist are not etched away. Finally, the photoresist layer is removed using either a dry or wet stripping machine. This forms a processing pattern on the metal hard mask layer. After the above processing, the process of setting a metal hard mask layer on the first surface of the diamond film outside the target area is complete.
[0018] After repeatedly alternating between thermal modification and etching processes and meeting the termination conditions, the metal hard mask layer can be removed by wet etching using a metal etchant.
[0019] In one possible implementation, a target area on the first surface of the diamond film is thermally modified to convert the diamond in the target area into unstable carbon. This includes using a laser with a preset energy density to thermally modify the target area on the first surface of the diamond film, converting the diamond in the target area into unstable carbon, wherein the irradiation area of the laser is larger than the area of the target area. In some embodiments, the target area is circular, and the diameter of the laser is larger than the diameter of the target area.
[0020] In one possible implementation, a target area on the first surface of the diamond film is thermally modified to convert the diamond in the target area into unstable carbon. This includes: using ion radiation of a preset energy density to thermally modify the target area on the first surface of the diamond film to convert the diamond in the target area into unstable carbon, wherein the irradiation area of the ion radiation is larger than the area of the target area. In some embodiments, the target area is circular, and the diameter of the ion radiation is larger than the diameter of the target area.
[0021] The solution shown in this application embodiment uses laser or ion radiation with a large irradiation area. This large irradiation area is used to scan the multilayer structure along a specific trajectory. Part of the laser or ion radiation is blocked by a metal hard mask layer. Therefore, the area on the first surface of the diamond film that is blocked by the metal hard mask layer will not undergo diamond modification, while the target area on the first surface of the diamond film is exposed to the laser or ion radiation. Under this radiation, the diamond in the target area will be modified into graphite and amorphous carbon. Using laser or ion radiation with a large irradiation area can increase the processing speed. Theoretically, if the irradiation area of the laser or ion radiation is the same as the area of the diamond film, the processing speed is the fastest. In this case, the laser or ion radiation does not need to perform scanning movement; the processing can be completed within a preset irradiation time.
[0022] By using laser or ion radiation with a large irradiation area, combined with a metal hard mask layer, the precision requirements of the equipment can be reduced, and costs can be controlled.
[0023] In one possible implementation, a target area on the first surface of the diamond film is thermally modified to convert the diamond in the target area into unstable carbon. This includes using multiple laser beams of preset energy density obtained by spectroscopy to thermally modify each target area on the first surface of the diamond film to convert the diamond in the target area into unstable carbon, wherein the irradiation surface of each laser beam is equal to the area of the corresponding target area.
[0024] Energy density is the energy per unit area.
[0025] The scheme shown in this application embodiment uses a laser device to split the laser emitted by the laser into multiple laser beams based on the processing pattern, and then directs these multiple laser beams onto different target areas on the first surface of the diamond film. The holes processed on the diamond film are used for metallization to form wires, so the cross-sectional shape of the holes (i.e., the shape of the target area) can generally be a circle or square of a preset size. Thus, by selecting the laser, the split laser beams can be made into a circle or square of a preset size. The thermal modification process requires controlling the energy density within a certain range, which can be 1-100 J / cm². 2 When performing radiation at a preset energy density, the power density of each laser beam obtained by beam splitting can be set to the preset power density by adjusting the laser power. The multiple laser beams after splitting are then used to irradiate each target area on the first surface of the diamond film for a preset duration. The product of the preset power density and the preset duration is the preset energy density, and its value is within the aforementioned range. Here, power density refers to the power per unit area.
[0026] By using laser beam splitting, the metal hard mask layer can be eliminated, reducing the number of processes. Furthermore, the scanning required for large-area laser irradiation is not necessary. Laser radiation only requires a preset duration, which can improve processing efficiency and energy utilization.
[0027] In one possible implementation, etching a target area on the first surface of the diamond film includes: etching the target area on the first surface of the diamond film using plasma.
[0028] In one possible implementation, the plasma composition includes one or more of oxygen (O2), carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), nitrogen (N2), sulfur hexafluoride (SF6), and argon (Ar).
[0029] Etching unstable carbon using plasmas of these materials can more effectively increase the etching rate.
[0030] In one possible implementation, the thermal modification and etching processes on the target area are repeated alternately until a preset termination condition is met, and then the holes formed in the target area are metallized.
[0031] The solution shown in this application embodiment can be metallized by electroplating to form a conductive metal, such as copper, in the hole. This results in a diamond film with conductive wires that penetrate both the upper and lower surfaces of the diamond film. Such a diamond film can be used as a bonding layer between dies, and the conductive wires can be used for electrical connections between dies. The diamond film also has good thermal conductivity, which can be used for temperature equalization and heat dissipation of the dies.
[0032] In a second aspect, a three-dimensional integrated circuit is provided, which includes multiple dies and a diamond film that has undergone the above-mentioned perforation and metallization processes, wherein the diamond film is disposed between different dies.
[0033] The beneficial effects of the technical solutions provided in this application are:
[0034] In this embodiment, the duration of the thermal modification process is very short compared to the etching process, and can be basically ignored. In addition, because unstable carbon has much lower chemical stability than diamond, the etching speed of unstable carbon is much faster than the etching speed of diamond. Therefore, the processing efficiency of diamond films can be improved by the above method. Attached Figure Description
[0035] Figure 1 This is a flowchart of a method for processing diamond thin films provided in an embodiment of this application;
[0036] Figure 2 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0037] Figure 3 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0038] Figure 4 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0039] Figure 5 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0040] Figure 6 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0041] Figure 7This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0042] Figure 8 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0043] Figure 9 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0044] Figure 10 This is a flowchart of a method for processing diamond thin films provided in an embodiment of this application;
[0045] Figure 11 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0046] Figure 12 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0047] Figure 13 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0048] Figure 14 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0049] Figure 15 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0050] Figure 16 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0051] Figure 17 This is a schematic diagram of a diamond thin film processing method provided in an embodiment of this application;
[0052] Figure 18 This is a schematic diagram of the structure of a three-dimensional integrated circuit provided in an embodiment of this application. Detailed Implementation
[0053] This application provides a method for processing diamond thin films. The main body executing this method can be a processing line including equipment such as CVD equipment, photolithography equipment, etching equipment, laser equipment, chemical mechanical polishing (CMP) equipment, and electroplating equipment. The photolithography equipment can further include coating equipment, exposure equipment, and developing equipment. This processing line can be a fully automated line or a line combining automated and manual processes.
[0054] The following will describe the specific implementation methods. Figure 1The diamond thin film perforation process shown is explained in detail below:
[0055] Step 101: Set a metal hard mask layer on the first surface of the diamond film in the area outside the target area.
[0056] The target area is a pre-defined area that needs to be perforated.
[0057] In practice, technicians can design a processing pattern, marking the target areas that need to be perforated within the pattern. A single processing step typically produces a diamond film with a diameter of approximately 100-300 mm (e.g., 150 mm), which can include multiple target areas requiring perforation. Of course, theoretically, a diamond film with only one target area is also possible. The relevant equipment on the processing line (such as exposure equipment) can determine the location of the target areas based on the processing pattern and perform the corresponding processing.
[0058] After initiating the processing flow, the first step is to deposit diamond on a substrate to form a diamond film. This process can be performed using a CVD (CVD) machine. The thickness of the diamond film can be preset.
[0059] The second step involves depositing a metal hard mask layer on the first surface of the diamond film. This process can also be performed using CVD equipment. The first surface is the upper surface of the diamond film. The metal hard mask layer is made of a material with high thermal stability, which can maintain a good morphology under laser or ion radiation of a certain intensity. It also has a certain degree of chemical stability, so it will not react with the plasma used for etching the diamond film. The metal hard mask layer can be made of metal or metal oxide. Candidate materials include tantalum (Ta), tungsten (W), molybdenum (Mo), tantalum dioxide (TaO2), tantalum nitride (TaN), tungsten carbide (WC), etc. A single material or a mixture of multiple materials can be used.
[0060] The third step is to coat a photoresist layer onto the metal hard mask layer. This process can be performed using a photoresist coating device. The multilayer structure obtained after multiple deposition and coating processes can be as follows... Figure 2 As shown.
[0061] The fourth step is to remove the portion of the photoresist layer corresponding to the target area. Specifically, the portion of the photoresist layer corresponding to the target area is exposed. After exposure, the photoresist layer is treated with a developer. The photoresist corresponding to the exposed target area will react chemically with the developer and be removed, exposing the underlying metal hard mask layer. The portion of the photoresist layer not corresponding to the target area is not exposed and therefore will not react with the developer. After these processing steps, the portion of the photoresist layer corresponding to the target area can be removed; that is, a processing pattern is formed on the photoresist layer, such as... Figure 3 As shown. The exposure and development processes can be performed using separate exposure and development equipment.
[0062] The fifth step involves etching the portion of the metal hard mask layer corresponding to the target area. This process can be performed using an etching machine employing dry anisotropic etching. Because the portion of the photoresist corresponding to the target area has already been removed, the upper surface of the metal hard mask layer corresponding to the target area is not covered with photoresist, while the other portions are. The portion of the metal hard mask layer not covered with photoresist will be etched away, exposing the underlying diamond film; the portion of the metal hard mask layer covered with photoresist will not be etched away.
[0063] Step six: Remove the photoresist layer. This process can be performed using dry or wet photoresist stripping equipment. This creates the processing pattern on the metal hard mask layer, such as... Figure 4 As shown. After the above processing, the process of setting a metal hard mask layer on the first surface of the diamond film in the area outside the target area is completed.
[0064] Step 102: Using laser or ion radiation with a preset energy density, perform thermal modification treatment on the target area of the first surface of the diamond film to modify the diamond in the target area into unstable carbon.
[0065] Carbon exists in three forms: diamond, graphite, and amorphous carbon. Diamond is stable carbon, while graphite and amorphous carbon are unstable carbon. The irradiation area of lasers and ion radiation is larger than the area of the target region. Energy density is the energy per unit area.
[0066] In practice, thermal modification is essentially a heat treatment process. By controlling the energy density, the morphology of carbon in the target region can be changed, transforming stable carbon into unstable carbon, i.e., modifying diamond into graphite and amorphous carbon. Thermal modification requires controlling the energy density within a certain range; too high a density may damage the metal hard mask layer, while too low a density will fail to achieve the desired diamond modification. This range can be 1-100 J / cm³. 2 Specifically, laser or ion radiation with a preset power density can be used to irradiate the upper surface of the multilayer structure for a preset duration. The product of the preset power density and the preset duration is the preset energy density, and its value is within the aforementioned range. Here, power density refers to the power per unit area. Some laser or ion radiation will be blocked by the metal hard mask layer. Therefore, the area on the first surface of the diamond film that is blocked by the metal hard mask layer will not undergo diamond modification. However, the target area on the first surface of the diamond film is exposed to laser or ion radiation. Under laser or ion radiation, the diamond in the target area will be modified, becoming graphite and amorphous carbon, such as... Figure 5As shown. The laser or ion radiation used in this step can be a large-area laser or ion radiation, which scans the multi-layered structure above it along a specific trajectory. Using laser or ion radiation with the largest possible irradiation area can increase processing speed. Theoretically, if the irradiation area of the laser or ion radiation is the same as the area of the diamond film, the processing speed is the fastest. In this case, the laser or ion radiation does not need to perform scanning movement, and the processing can be completed after irradiation for a preset time. Of course, in practice, the irradiation area of the laser or ion radiation may not be that large. In this case, the laser or ion radiation can be controlled to perform a moving scan on the diamond film.
[0067] Step 103: Etch the target area on the first surface of the diamond film to remove unstable carbon.
[0068] In practice, plasma can be used to dry-etch the target area of the first surface of the diamond film. The thermally modified diamond film is exposed to plasma, the composition of which may include one or more of O2, CO, CO2, H2, N2, SF6, and Ar. The material of the metal hard mask layer is chemically stable to the plasma containing these substances and will not react with it. Thus, the area of the first surface of the diamond film covered by the metal hard mask layer is unaffected by the plasma, while the unstable carbon in the target area of the first surface of the diamond film is rapidly etched away, exposing the underlying diamond. This creates a groove in the target area of the first surface of the diamond film, such as... Figure 6 As shown. This step can be performed using etching equipment.
[0069] Step 104: Repeat the alternating thermal modification and etching processes on the target area until the preset termination conditions are met.
[0070] In practice, the thermal modification treatment in step 102 and the etching treatment in step 103 are repeated alternately, such as... Figure 7 , Figure 8 As shown, the grooves formed in the target area on the first surface of the diamond film become increasingly deeper.
[0071] The termination condition mentioned above during processing can be reaching a target number of repetitions. This target number can be calculated based on the thickness of the diamond film and the energy density of laser or ion radiation during a single thermal modification process. First, the depth of diamond that can be modified in a single thermal modification process can be determined based on the energy density of the single thermal modification process (the relationship between energy density and the depth of diamond modification can be determined experimentally beforehand). Then, the target number is obtained by dividing the thickness of the diamond film by this depth. To prevent substrate damage, during repeated alternating thermal modification and etching processes, a certain thickness of diamond can be retained at the bottom of the groove formed in the target area, such as... Figure 9 As shown, the groove can be further drilled using other methods to obtain a through hole. This allows the target value to be calculated slightly less than the quotient of the diamond film thickness and the aforementioned depth.
[0072] Alternatively, the termination condition can also be that the depth of the trench in the target area reaches a depth threshold. The depth of the trench in the target area can be monitored during the repeated alternating thermal modification and etching processes, and the thermal modification and etching processes can be stopped when the depth reaches the depth threshold.
[0073] Step 105: Perform CMP on the second surface of the diamond film to form through holes in the target area.
[0074] In practice, after repeatedly alternating between thermal modification and etching of the target area and meeting the termination conditions, the metal hard mask layer can be removed using a metal etchant via wet etching as described above. Then, the substrate beneath the diamond film can be removed, either by back-side grinding and polishing or by chemical removal. A certain thickness of diamond remains at the bottom of the trench in the target area. CMP can then be performed on the second surface (i.e., the lower surface) of the diamond film to remove a certain thickness, creating a through-hole in the target area.
[0075] In another possible approach, during step 104, the trench can be directly opened up to obtain a through hole by repeating alternating thermal modification and etching processes, thus eliminating the need for step 105.
[0076] Compared to the etching process, the thermal modification process takes a very short time, which can be basically ignored. In addition, because unstable carbon is much less chemically stable than diamond, the etching speed of unstable carbon is much faster than the etching speed of diamond. Therefore, the above methods can improve the processing efficiency of perforation on diamond films.
[0077] The following will describe the specific implementation methods. Figure 10The diamond thin film perforation process shown is explained in detail below:
[0078] Step 1001: Using multiple laser beams with preset energy densities obtained by spectral splitting, thermal modification treatment is performed on each target area of the first surface of the diamond film to modify the diamond in the target area into unstable carbon.
[0079] The target area is a pre-defined region that needs to be perforated. The area irradiated by each laser beam is equal to the area of the corresponding target region.
[0080] In practice, technicians can design a processing pattern, marking the target areas that need to be perforated within the pattern. A single processing step typically produces a diamond film with a diameter of approximately 100-300 mm (e.g., 150 mm), which can include multiple target areas requiring perforation. Of course, theoretically, a diamond film with only one target area is also possible. The relevant equipment on the processing line (such as exposure equipment) can determine the location of the target areas based on the processing pattern and perform the corresponding processing.
[0081] After initiating the processing flow, firstly, diamond is deposited on a substrate to form a diamond film. This processing step can be performed using a CVD (CVD) device. The thickness of the diamond film can be preset. Then, using a laser device, based on the processing pattern, the laser emitted by the laser is split into multiple laser beams, which are then directed onto different target areas on the first surface of the diamond film, such as... Figure 11 As shown.
[0082] In practical applications, the holes machined on diamond films are used to perform metallization processing to form wires. Therefore, the cross-sectional shape of the holes (i.e., the shape of the target area) can generally be a circle or square of a preset size. Thus, by selecting a laser, the laser beam obtained through beam splitting can be a circle or square of a preset size.
[0083] Furthermore, as introduced earlier, thermal modification is essentially a heat treatment that alters the morphology of carbon in the target region, transforming stable carbon into unstable carbon, i.e., modifying diamond into graphite and amorphous carbon. Thermal modification requires controlling the energy density within a specific range; too high a density may damage the metal hard mask layer, while too low a density will fail to achieve the desired diamond modification. This range can be 1-100 J / cm². 2When performing radiation at a preset energy density, the power density of each laser beam obtained by beam splitting can be set to the preset power density by adjusting the laser power. The multiple laser beams after beam splitting are used to irradiate each target area on the first surface of the diamond film for a preset duration. The product of the preset power density and the preset duration is the preset energy density, and its value is within the aforementioned range.
[0084] After laser irradiation of the target area on the first surface of the diamond film, the diamond in the target area will be modified into unstable carbon, such as... Figure 12 and Figure 13 As shown, Figure 12 This is a top view. Figure 13 This is a cross-sectional view. Because the laser only radiates into the target area, the diamond in areas outside the target area remains unchanged.
[0085] Step 1002: Etch the target area on the first surface of the diamond film to remove unstable carbon.
[0086] In practice, plasma can be used to etch the target area of the first surface of the diamond film. The thermally modified diamond film is exposed to plasma, the composition of which can include one or more of O2, CO, CO2, H2, N2, SF6, and Ar. The unstable carbon in the target area of the first surface of the diamond film is rapidly etched away, exposing the underlying diamond. The required etching time is relatively short, and because diamond has strong chemical stability, it can be considered that the diamond will not be etched at all within a short time. This creates a groove in the target area of the first surface of the diamond film, such as... Figure 14 As shown. This step can be performed using etching equipment.
[0087] Step 1003: Repeat the alternating thermal modification and etching processes on the target area until the preset termination conditions are met.
[0088] In practice, the thermal modification treatment in step 1001 and the etching treatment in step 1002 are repeated alternately, such as... Figure 15 , Figure 16 As shown, the grooves formed in the target area on the first surface of the diamond film become increasingly deeper.
[0089] The termination condition mentioned above during processing can be reaching the target number of repetitions. This target number can be calculated based on the thickness of the diamond film and the laser energy density in a single thermal modification process. First, the depth of diamond that can be modified in a single thermal modification process can be determined based on the laser energy density of the single thermal modification process (the relationship between energy density and diamond modification depth can be determined experimentally beforehand). Then, the target number is obtained by dividing the thickness of the diamond film by this depth. To prevent substrate damage, during repeated alternating thermal modification and etching processes, a certain thickness of diamond can be retained at the bottom of the groove formed in the target area, such as... Figure 17 As shown, the groove can be further drilled using other methods to obtain a through hole. This allows the target value to be calculated slightly less than the quotient of the diamond film thickness and the aforementioned depth.
[0090] Alternatively, the termination condition can also be that the depth of the trench in the target area reaches a depth threshold. The depth of the trench in the target area can be monitored during the repeated alternating thermal modification and etching processes, and the thermal modification and etching processes can be stopped when the depth reaches the depth threshold.
[0091] Step 1004: Perform CMP on the first surface of the diamond film.
[0092] During implementation, after repeated alternating thermal modification and etching processes reach the termination condition, an open, beveled surface, referred to as a flared opening, may form at the edge of the target area on the first surface of the diamond film. At this point, CMP treatment can be performed on the first surface to grind away a certain thickness of diamond, thus removing the flared opening. The thickness of the grinding process can be determined by the depth of the flared opening.
[0093] It should be noted that in this processing flow, a metal hard mask layer can also be set on the first surface of the diamond film before step 1001. The specific processing method can be the same as the previous process. If a metal hard mask layer is set, the CMP processing in step 1004 can be omitted. If a metal hard mask layer is not set, then the CMP processing in step 1004 is performed.
[0094] Step 1005: Perform CMP on the second surface of the diamond film to form through holes in the target area.
[0095] In practice, the substrate beneath the diamond film can be removed first. This can be done by back-side grinding and polishing equipment or by chemical removal. A certain thickness of diamond remains at the bottom of the trench in the target area. CMP can be performed on the second surface (i.e., the lower surface) of the diamond film to grind away a certain thickness, thus forming a through-hole in the target area.
[0096] In another possible approach, during step 1003, the trench can be directly opened to obtain a through hole by repeating alternating thermal modification and etching processes, thus eliminating the need for step 1005.
[0097] Compared to the etching process, the thermal modification process takes a very short time, which can be basically ignored. In addition, because unstable carbon is much less chemically stable than diamond, the etching speed of unstable carbon is much faster than the etching speed of diamond. Therefore, the above methods can improve the processing efficiency of perforation on diamond films.
[0098] After any of the above processing steps, the perforation of the diamond film is completed. Subsequently, the holes formed in the target area of the diamond film can be metallized.
[0099] In practice, the holes can be metallized by electroplating to form a conductive metal, such as copper, within them. This results in a diamond film with conductive wires running through both the top and bottom surfaces of the film. Such a diamond film can be used as a bonding layer between dies, and the conductive wires can be used for electrical connections between dies. The diamond film also has good thermal conductivity, which can be used for uniform temperature dissipation of the dies.
[0100] This application also provides a three-dimensional integrated circuit (3D IC), which includes multiple dies and a diamond film after the above-mentioned perforation and metallization treatment, wherein the perforated and metallized diamond film is disposed between different dies.
[0101] A typical die can consist of a silicon substrate layer and a dielectric layer. A diamond film can be placed between the dielectric layers of two adjacent dies, or between the silicon substrate layer of one die and the dielectric layer of another die, or between the silicon substrate layers of two adjacent dies. Figure 18 An example of a three-dimensional integrated circuit structure is given. The perforation processing method for the diamond thin film can employ any of the methods mentioned in the above embodiments. Metallization treatment within the holes of the diamond thin film yields conductive wires, which can be used for data transmission between dies on both sides. The dies generate heat during processing, and the heat generation on the die surface is uneven. The diamond thin film, with its excellent thermal conductivity, can effectively homogenize the temperature and dissipate heat.
[0102] The above description is merely one embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for processing diamond thin films, characterized in that, The method includes: Diamond is deposited on a substrate to form a diamond film; A target area on the first surface of a diamond film is thermally modified to convert the diamond in the target area into unstable carbon. The target area on the first surface of the diamond film is etched to remove the unstable carbon. The thermal modification and etching processes on the target area are repeated alternately until a preset termination condition is met. When the termination condition is met, a certain thickness of diamond exists at the bottom of the groove in the target area of the diamond film. The substrate is removed, and the second surface of the diamond film is chemically mechanically polished (CMP) to remove a certain thickness of diamond, thereby forming a through-hole in the target area.
2. The method according to claim 1, characterized in that, The preset termination conditions include: The thermal modification and etching processes on the target area are repeated alternately until the target number of repetitions is reached.
3. The method according to claim 1 or 2, characterized in that, The process of repeatedly and alternately performing the thermal modification and etching processes on the target area until a preset termination condition is met further includes: CMP is performed on the first surface of the diamond film.
4. The method according to claim 1 or 2, characterized in that, Before performing thermal modification treatment on the target area of the first surface of the diamond film, the method further includes: A metal hard mask layer is disposed on the first surface of the diamond film in the area outside the target area.
5. The method according to claim 4, characterized in that, The thermal modification treatment of the target region on the first surface of the diamond film, modifying the diamond in the target region into unstable carbon, includes: A laser with a preset energy density is used to thermally modify a target area on the first surface of a diamond film, thereby modifying the diamond in the target area into unstable carbon. The irradiation area of the laser is larger than the area of the target area.
6. The method according to claim 4, characterized in that, The thermal modification treatment of the target region on the first surface of the diamond film, modifying the diamond in the target region into unstable carbon, includes: Using ion radiation of a preset energy density, a target area on the first surface of a diamond film is thermally modified to convert the diamond in the target area into unstable carbon, wherein the irradiation surface of the ion radiation is larger than the area of the target area.
7. The method according to claim 1 or 2, characterized in that, The thermal modification treatment of the target region on the first surface of the diamond film, modifying the diamond in the target region into unstable carbon, includes: Multiple laser beams with preset energy densities obtained by spectral splitting are used to thermally modify each target area on the first surface of the diamond film, thereby modifying the diamond in the target area into unstable carbon. The irradiation surface of each laser beam is equal to the area of the corresponding target area.
8. The method according to claim 1 or 2, characterized in that, The etching process on the target area of the first surface of the diamond film includes: The target area of the first surface of the diamond film is etched using plasma.
9. The method according to claim 8, characterized in that, The plasma composition includes one or more of O2, CO, CO2, H2, N2, SF6, and Ar.
10. The method according to claim 1 or 2, characterized in that, The process of repeatedly and alternately performing the thermal modification and etching processes on the target area until a preset termination condition is met further includes: The holes formed in the target area are then metallized.
11. A three-dimensional integrated circuit, characterized in that, The three-dimensional integrated circuit includes multiple dies and a diamond film processed by the method described in any one of claims 1-10, wherein the processed diamond film is disposed between different dies.