Thick aluminum preparation method, device and machine table

Abstract

The invention provides a thick aluminum preparation method and device and a machine table, and relates to the technical field of semiconductor manufacturing, and the method comprises the steps: firstly determining the technological parameters of a to-be-processed wafer according to the technological requirements, and determining a technological strategy according to the technological parameters; and finally, according to the process strategy, the metal layer of the wafer is circularly processed until the cycle number is reached, and each processing step comprises photoetching, etching and photoresist removing cleaning. According to the method, the metal layer of the wafer is processed for multiple rounds according to the generated process strategy, only the thickness and the etching mode of the photoresist need to be adjusted during each processing, other parameters do not need to be changed, the problem that the photoresist is not enough in the prior art is solved, meanwhile, the process complexity is reduced, and open debugging of technicians is facilitated. And meanwhile, through multi-round machining treatment, a small-angle opening can be formed without enhancing physical bombardment, the dry etching cavity environment is improved, the normal operation time of a machine table is prolonged, and the machining cost is reduced.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method, apparatus and machine for preparing thick aluminum. Background Technology

[0002] Currently, commonly used silicon carbide power devices typically use a 4µm thick aluminum-copper alloy for the top layer metal to meet the requirements of high current density, improved current distribution, and reduced resistance loss. For high-voltage, high-current power devices, the thickness of the top layer metal is usually ≥5µm, or even 6µm or more.

[0003] Thicker top metal layers require thicker photoresist (≥5µm, or even 6µm or more) for thick aluminum etching processes, which poses a significant challenge to the photolithography process. This can lead to issues such as excessively high viscosity causing the photoresist to be difficult to spread effectively, poor uniformity, and even production capacity problems. On the other hand, if a wet etching process is used to prepare the top metal pattern, it will inevitably face problems such as excessive lateral etching leading to photoresist floating.

[0004] Furthermore, to reduce the stress problem of the dielectric passivation layer in thicker top metal layers, the morphology of aluminum-copper dry etching is typically required to have a small angle (less than 65°). To ensure that the aluminum-copper morphology has a small angle, the dry etching process needs to increase the bias voltage or the proportion of large-molecule boron trichloride to enhance physical bombardment. The bombardment of the photoresist generates polymers, ultimately forming an inverted trapezoidal small-angle opening. However, this also results in a smaller selection ratio during aluminum etching, leading to a large amount of polymer in the etching chamber. The chamber environment is poor, requiring frequent maintenance and component replacement to keep the chamber environment clean, which significantly reduces the uptime of the machine. Summary of the Invention

[0005] The technical problem to be solved by this application is to provide a method, apparatus and machine for preparing thick aluminum, so as to overcome the problems that the top metal of silicon carbide power devices is thicker in the traditional technology, which requires thicker photoresist, resulting in failure to meet process requirements; and the problem that the use of stronger physical bombardment leads to a poor etching cavity environment and a significant reduction in the uptime of the machine.

[0006] In a first aspect, this application proposes a method for preparing thick aluminum, the method comprising: Determine the process parameters of the wafer to be processed according to the process requirements; Based on the process parameters, a process strategy is determined, wherein the process strategy includes the number of cycles, and the photoresist thickness and etching method used in each cycle; According to the process strategy, the metal layer of the wafer is processed in cycles until the number of cycles is reached; wherein each processing step includes photolithography, etching and resist removal cleaning.

[0007] In one embodiment, the etching method includes a first etching method and a second etching method; wherein the first etching method is determined based on etching time, and the second etching method is determined based on endpoint detection.

[0008] In one embodiment, the process parameters include aluminum linewidth, metal thickness, and etching thickness; the etching thickness includes a first etching thickness, which corresponds to the first etching method. The step of determining the process strategy based on the process parameters includes: Calculate the first ratio of the aluminum linewidth to the overlay accuracy; If the first ratio meets the preset conditions, the number of cycles is determined based on the metal thickness and the first etching thickness; Based on the number of cycles, select the etching method to be used in each cycle; Based on the etching thickness, the photoresist thickness used in each cycle is determined. In one embodiment, determining the number of cycles based on the metal thickness and the first etching thickness includes: Calculate a second ratio between the metal thickness and the first etching thickness. If the second ratio is an integer, use that integer as the number of iterations. Otherwise, round the second ratio up to the nearest integer and use that integer as the number of iterations.

[0009] In one embodiment, selecting the etching method for each processing step based on the number of cycles includes: During the loop, the second etching method is selected in the last loop, and the first etching method is selected in all other loops.

[0010] In one embodiment, the process parameters further include a selectivity ratio and a second etching thickness; wherein the second etching thickness corresponds to the second etching method; The step of determining the photoresist thickness for each processing step based on the etching thickness includes: Calculate the third ratio of the first etching thickness to the selection ratio, and determine the first photoresist thickness based on the third ratio and the process margin; Calculate the fourth ratio of the second etching thickness to the selection ratio, and determine the second photoresist thickness based on the fourth ratio and the process margin.

[0011] In one embodiment, the step of cyclically processing the metal layer of the wafer according to the process strategy until the number of cycles is reached includes: Before each processing operation, a new process formula is generated based on the photoresist thickness and etching method used. Based on the new process formula, and according to the photoresist thickness, photoresist is spin-coated onto the wafer surface, and exposed and developed using the same photomask to form a preset pattern; The etching method described above is used to remove the metal layer of an exposed area of ​​a predetermined thickness; wherein the predetermined thickness is related to the etching method. Clean the wafer to remove photoresist residue; Repeat the above steps until the number of repetitions reaches the stated number of cycles.

[0012] In one embodiment, the method further includes: During the processing, the wafer undergoes surface treatment, which includes any one or more of the following: surface activation, plasma cleaning, passivation, annealing, and surface roughening.

[0013] Secondly, this application also proposes a thick aluminum preparation apparatus, the apparatus comprising: The processing module is used to determine the process parameters of the wafer to be processed according to the process requirements; and to determine the process strategy according to the process parameters, wherein the process strategy includes the number of cycles, and the photoresist thickness and etching method used in each cycle; The processing module is used to perform cyclic processing on the metal layer of the wafer according to the process strategy until the number of cycles is reached; wherein each processing step includes photolithography, etching and resist removal cleaning.

[0014] Thirdly, this application also proposes a machine tool that uses the thick aluminum preparation method described in any one of the first aspects to process the metal layer of the wafer to be processed in order to obtain the desired metal structure.

[0015] The above-mentioned method, apparatus, and machine for preparing thick aluminum have at least the following advantages: This application first determines the process parameters of the wafer to be processed based on the process requirements. Based on these parameters, a process strategy is determined, including the number of cycles and the photoresist thickness and etching method used in each cycle. Finally, according to the process strategy, the metal layer of the wafer is processed in cycles until the required number of cycles is reached. Each processing step includes photolithography, etching, and photoresist removal and cleaning. This application performs multiple processing cycles on the metal layer of the wafer based on the generated process strategy. Each processing cycle only requires adjustment of the photoresist thickness and etching method, without changing other parameters. This solves the problem of insufficient photoresist coverage in traditional technologies, while also reducing process complexity and facilitating open debugging by technicians. Furthermore, the multi-cycle processing of this application can form small-angle openings without enhanced physical bombardment, improving the dry etching chamber environment, increasing machine uptime, and reducing processing costs. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a thick aluminum preparation method in one embodiment; Figure 2 This is a flowchart illustrating the steps for determining a process strategy in one embodiment; Figure 3 This is a schematic diagram of the first round of processing in one embodiment; Figure 4 This is a schematic diagram of the second round of processing in one embodiment; Figure 5 This is a structural block diagram of a thick aluminum preparation apparatus in one embodiment. Detailed Implementation

[0017] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] When using the terms “including,” “having,” and “comprising” as described herein, another component may be added unless explicitly qualifying terms such as “only,” “consisting of,” etc. are used. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0020] It should be understood that although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this application, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0021] In this application, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a direct connection or an indirect connection through an intermediate medium, or they can refer to the internal connection of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0022] Please see Figure 1 In one embodiment, a method for preparing thick aluminum is provided, specifically including the following steps: Step S102: Determine the process parameters of the wafer to be processed according to the process requirements.

[0023] Specifically, process requirements refer to a series of technical indicators, process constraints, and manufacturing precision specifications that must be met during semiconductor manufacturing to ensure product performance, yield, and reliability. These requirements typically cover aspects such as pattern size, etching depth, adhesion, material compatibility, and temperature limits. Before executing a process flow, it is necessary to determine the specific data of the process parameters to be executed, as well as the steps to be performed, based on the process requirements, and generate a process recipe. This allows the process to be executed sequentially on the current batch of wafers according to the aforementioned process recipe.

[0024] The process flow in this embodiment mainly includes photolithography, etching, and resist stripping and cleaning steps. The photolithography process parameters include photoresist parameters, spin coating parameters, soft baking parameters, exposure parameters, development parameters, and alignment parameters. Further, the photoresist parameters include photoresist type, photoresist thickness, and viscosity. The etching process parameters include etching type, gas type and ratio, etching power and frequency, temperature and pressure, time or endpoint control, and selectivity. The resist stripping and cleaning process parameters include resist stripping method, cleaning solution formulation, temperature and time, auxiliary treatments, and surface recovery.

[0025] Furthermore, in the embodiments of this application, the wafer to be processed is a silicon carbide power device, and its top metal is usually made of aluminum-copper alloy, and its metal layer is relatively thick, usually 4um; for high voltage and high current power devices, the thickness of the top metal is usually ≥5um, or even 6um or more.

[0026] Step S104: Determine the process strategy based on the process parameters, wherein the process strategy includes the number of cycles, the photoresist thickness and etching method used in each cycle.

[0027] Specifically, photolithography refers to the process of transferring tiny patterns from a photomask to photoresist using optical principles. This pattern transfer process is achieved by uniformly coating a layer of photoresist onto the wafer surface and then exposing and developing it. During the etching process of the metal layer, the photoresist can effectively protect the metal under the pattern from etching. The consumption of photoresist during etching is related to the selectivity ratio and the etching thickness. For example, if the selectivity ratio is 5:1 and the etching thickness of the metal is 1 μm, then the photoresist will be etched by 0.2 μm.

[0028] Etching refers to the process of removing the portion of material not protected by photoresist on the surface of a wafer using chemical or physical methods, thereby forming the desired patterns and structures on the wafer. Etching includes dry etching and wet etching. Dry etching includes By-Time etching and By EPD (End Point Detection) etching. By-Time etching controls the depth or extent of etching by setting the etching duration. By EPD etching determines when etching ends by detecting changes in certain characteristics during the etching process. EPD typically uses optical, gas, or electrical signals to monitor changes in the etching process in real time, ensuring that etching stops once the predetermined etching depth is reached.

[0029] Optionally, the etching method in the embodiments of this application includes a first etching method and a second etching method, wherein the first etching method is determined based on the etching time, i.e., the By Time etching process described above; and the second etching method is determined based on the endpoint detection, i.e., the By EPD etching process described above.

[0030] Photoresist removal cleaning refers to the process of removing residual photoresist from the wafer surface and cleaning impurities and residues on the wafer surface after etching is completed.

[0031] It should be noted that the process strategy here serves the same purpose as the process formulation mentioned above, both providing processing guidance during the execution of the process flow. The only difference is that the process formulation is used to complete one process flow, and all parameters within it are fixed; while the process strategy in this application embodiment is used to complete multiple process flows, and the photoresist thickness and etching method used in each cycle may be different, while all other parameters are constant values.

[0032] Step S106: Based on the process strategy, the metal layer of the wafer is processed in cycles until the required number of cycles is reached; wherein each processing step includes photolithography, etching and resist removal and cleaning.

[0033] The aforementioned thick aluminum preparation method involves multiple processing rounds of the wafer's metal layer. This solves the problems inherent in traditional technologies where insufficient photoresist thickness leads to unsustainable etching, while excessive thickness can result in issues such as high viscosity hindering effective photoresist spreading, poor uniformity, and even production capacity problems. In this application, only the photoresist thickness and etching method need to be adjusted each time, without changing other parameters, thus reducing process complexity and facilitating open debugging by technicians. Furthermore, the multi-round processing of this application allows for the formation of small-angle openings without enhanced physical bombardment, improving the dry etching chamber environment, increasing machine uptime, and reducing processing costs.

[0034] Please see Figure 2Optionally, the process parameters include the aluminum linewidth, metal thickness, and etching thickness; the etching thickness includes a first etching thickness, which corresponds to a first etching method. Based on the process parameters, a process strategy is determined, including: Step S202: Calculate the first ratio of the aluminum line width to the overlay accuracy.

[0035] Step S204: If the first ratio meets the preset conditions, determine the number of cycles based on the metal thickness and the first etching thickness. Step S206: Select the etching method to be used in each cycle based on the number of cycles.

[0036] Step S208: Determine the photoresist thickness to be used in each cycle based on the etching thickness.

[0037] Specifically, in this embodiment, the wafer is a silicon carbide power device, and its top layer metal is typically an aluminum-copper alloy. This material has good conductivity and mechanical properties, making it suitable for high power density and high current density applications. The metal aluminum line width refers to the width of the top layer aluminum-copper alloy conductor; a wider line width results in a stronger current carrying capacity. Overlay accuracy refers to the alignment error of the new pattern relative to existing patterns during multiple photolithography processes. If the metal aluminum line width is much larger than the overlay accuracy, it means that the multiple photolithography patterns can stably fall on the structural area formed after the previous etching, without deviating from the edge or causing structural breakage. Even with slight offsets (overlay error), it will not cause the pattern to misalign or etch into the protected area, thus supporting the cyclic execution of the above process flow for thick metal layers.

[0038] Optionally, in this embodiment, the preset condition is determined as follows: if the first ratio is greater than or equal to 50, the preset condition is considered met. It should be understood that this value is based on empirical values ​​and can be adjusted according to process requirements in actual use. Using the above scheme, it is first determined whether the wafer to be processed meets the requirements of multiple photolithography and etching operations, ensuring the accuracy of pattern transfer after multiple processing rounds.

[0039] When the first etching method is By Time etching process, the first etching thickness is determined by the set etching rate and etching time. For safety reasons, the first etching thickness is set to be less than the maximum etching thickness of thick aluminum in conventional etching process.

[0040] The metal thickness is the thickness of the wafer's metal layer to be etched. By comparing the difference between the metal thickness and the first etching thickness, it can be determined how many process flows the wafer needs to undergo.

[0041] Optionally, the number of cycles is determined based on the metal thickness and the first etching thickness, including: Calculate the second ratio of the metal thickness to the first etching thickness. If the second ratio is an integer, use that integer as the loop count; otherwise, round the second ratio up to the nearest integer and use that integer as the loop count.

[0042] For example, if the metal thickness is 9 μm and the single etching thickness of a silicon carbide power device in conventional etching technology is 4 μm, then the second ratio is 9 / 4 = 2.25. This value is a decimal, so it is rounded up to the nearest integer, i.e., the second ratio is rounded to 3, and the number of cycles is 3. If the metal thickness is 8 μm and the etching thickness is 4 μm, then the second ratio is 2, and the number of cycles is 2. Using the above scheme, the single etching thickness is determined based on conventional technology to ensure that the process requirements are met. Furthermore, the number of cycles can be determined based on the single etching thickness and the metal thickness.

[0043] Optionally, the etching method for each processing step can be selected based on the number of cycles, including: During the cycle, the second etching method is selected in the last cycle, and the first etching method is selected in all other cycles.

[0044] Specifically, to simplify operation, in this embodiment, the last cycle is set to the second etching mode, while the previous cycles are all set to the first etching mode, and the etching parameters in the first etching mode are all the same, including etching thickness and etching time. In practical applications, the etching parameters used in the previous cycles can be further subdivided to achieve finer control of the etching process. For example, if the etching rate of the metal layer is 0.5 μm / min and the metal thickness is 9 μm, then the first etching thickness in the first and second cycles is 4 μm, the etching time is 8 minutes, and the etching thickness in the third cycle is 1 μm. Further, under the same conditions, the etching thickness in the first cycle can be set to 4 μm and the etching time to 8 minutes; the etching thickness in the second cycle can be set to 3 μm and the etching time to 6 minutes; and the etching thickness in the third cycle can be 2 μm.

[0045] Optionally, the process parameters also include a selection ratio and a second etching thickness; wherein the second etching thickness corresponds to the second etching method, and if the number of cycles is n, then the second etching thickness is the remaining thickness of the metal layer after (n-1) cycles of etching.

[0046] The photoresist thickness for each processing step is determined based on the etching thickness, including: Calculate the third ratio of the first etching thickness to the selectivity, and determine the first photoresist thickness based on the third ratio and the process margin; Calculate the fourth ratio of the second etching thickness to the selectivity, and determine the second photoresist thickness based on the fourth ratio and the process margin.

[0047] Specifically, the photoresist thickness is related to the etching thickness of the metal layer and the selectivity ratio. With a fixed selectivity ratio, the photoresist thickness and etching thickness are proportional. It should be understood that to ensure effective protection of the metal layer by the photoresist, in practical applications, the photoresist thickness should be greater than the theoretical value. Using this approach, a photoresist of the corresponding thickness is spin-coated onto the wafer surface before each processing stage, achieving the process requirements for thick aluminum etching without requiring a large amount of photoresist. Furthermore, the final photoresist thickness is determined based on the remaining metal thickness, which also reduces processing costs.

[0048] The aforementioned thick aluminum fabrication method first determines whether the wafer to be processed meets the requirements of multi-round processing based on the aluminum linewidth and overlay accuracy, ensuring the precision of pattern transfer. Secondly, it determines the single-etching thickness according to existing processes and sets the photoresist thickness and etching parameters of the previous rounds consistently, reducing process complexity and facilitating development and debugging by engineers. Thirdly, before each round of processing, a photoresist of the corresponding thickness is spin-coated onto the wafer surface, achieving the process requirements for thick aluminum etching without requiring a thicker photoresist layer. Simultaneously, multi-round processing allows for the formation of small-angle openings without enhanced physical bombardment, improving the dry etching chamber environment, increasing machine uptime, and reducing processing costs.

[0049] Optionally, depending on the process strategy, the metal layers of the wafer are cyclically processed until the required number of cycles is reached, including: Before each processing operation, a new process formula is generated based on the photoresist thickness and etching method used. Based on the new process formula, photoresist is spin-coated onto the wafer surface according to the photoresist thickness, and the same photomask is used for exposure and development to form a preset pattern; An etching method is used to remove the metal layer of the exposed area of ​​a preset thickness; the preset thickness is related to the etching method. Clean the wafer to remove photoresist residue.

[0050] Repeat the above steps until the number of repetitions reaches the required number of cycles.

[0051] Specifically, before each process step is executed, the process formula for that step must be called, and each step is executed sequentially according to the parameters in the process formula. In the embodiments of this application, only the photoresist thickness and etching method change in each round of processing, while the other parameters remain unchanged. Therefore, a new process formula is generated based on the photoresist thickness and etching method. It should be understood that, in order to simplify the scheme, the process parameters for the first few rounds are the same, and therefore, the process formulas used are also the same.

[0052] Furthermore, since the aluminum linewidth and overlay accuracy of the wafer in this application meet the preset requirements, the same photomask is used in each processing cycle.

[0053] The preset thickness is the etching thickness in each etching process. In the first few etching rounds in this application embodiment, the preset thickness refers to the first etching thickness, and in the last etching round, the preset thickness refers to the second etching thickness.

[0054] Optionally, the thick aluminum preparation method of this application further includes: During the processing, the wafer undergoes surface treatment, which includes any one or more of the following: surface activation, plasma cleaning, passivation, annealing, and surface roughening.

[0055] Specifically, surface activation treatment is performed before photolithography, especially after deposition on metal or oxide surfaces. Its purpose is to enhance the adhesion between the photoresist and the substrate surface (such as metal, SiO2, SiC, etc.) and prevent the photoresist from falling off during exposure and development.

[0056] Plasma cleaning is performed after the final metal pattern etching and before subsequent electrode or passivation processes. Its purpose is to remove metal residues and protect the edges of the pattern.

[0057] Passivation, annealing, and surface roughening are performed after the metal pattern has been finalized, before encapsulation or before the next metal bonding step. Their purpose is to improve metal adhesion or device performance. Please see Figure 3 and Figure 4 The following section uses a two-round processing method as an example to illustrate the thick aluminum preparation method of this application in detail with reference to the illustrations.

[0058] Figure 3 The diagram shown is a schematic of the first round of processing. Figure 3 From left to right, the diagrams show the wafer after the first round of photolithography, the wafer after the first round of etching, and the wafer after the first round of resist removal and cleaning. Figure 3 The first layer 1 is photoresist (PR); the second layer 2 is the main metal layer, made of aluminum (ALU); the third layer 3 is a barrier layer, made of titanium nitride (TiN); the fourth layer 4 is an adhesion layer, made of titanium (Ti); and the fifth layer 5 is the substrate. These second to fourth layers constitute the metal layers of the wafer to be processed in this embodiment.

[0059] Figure 4 The diagram shown is a schematic of the second round of processing. Figure 4 From left to right, the diagrams show the wafer after the second round of photolithography, the wafer after the second round of etching, and the wafer after the second round of resist removal and cleaning.

[0060] Before the first round of processing, a first process formula is generated according to the process requirements. The thickness of the photoresist in the first process formula is the first photoresist thickness, and the etching method is By Time etching process.

[0061] In the first round of processing, a photoresist of the first thickness is spin-coated onto the wafer surface. A photomask with a pre-designed pattern is placed between the light source and the wafer. The light source shines through the photomask onto the photoresist, and the light passes through the transparent area of ​​the photomask to illuminate the photoresist, causing a chemical reaction. After exposure, the photoresist is treated with a developer to form a pattern on its surface that matches the photomask pattern.

[0062] Furthermore, in a vacuum environment, a gas (such as chlorine or fluorine) is introduced into the reaction chamber, and plasma is generated by exciting the gas through a high-frequency electric field. The active ions and free radicals in the plasma will react chemically with the wafer surface material, converting it into gaseous products and removing them. After etching time, the metal layer of the first etching thickness is removed.

[0063] Finally, after etching is complete, the residual photoresist on the wafer surface is removed, and impurities and residues on the silicon wafer surface are cleaned.

[0064] Depend on Figure 3 It is evident that after the first etching, the thickness of the photoresist on the wafer is reduced, and the exposed area of ​​the metal layer loses some thickness, forming a small opening.

[0065] Furthermore, based on the first round of processing, a second round of processing is carried out on the wafer.

[0066] Before the second round of processing, a second process formula is generated according to the process requirements. The thickness of the photoresist in the second process formula is the second photoresist thickness, and the etching method is By EPD etching process.

[0067] In the second round of processing, a second-thickness photoresist is first spin-coated onto the wafer surface. The same photomask used in the first round of processing is then applied. After exposure and development, a pattern consistent with the photomask pattern is formed on the photoresist surface.

[0068] Furthermore, the metal layer of the second etching thickness is removed using the By EPD etching process.

[0069] Finally, after etching is complete, the residual photoresist on the wafer surface is removed, and impurities and residues on the silicon wafer surface are cleaned.

[0070] Depend on Figure 4 As can be seen, after two rounds of processing, the etching process of thick aluminum is completed, and the desired metal structure is obtained.

[0071] The aforementioned thick aluminum fabrication method first determines whether the wafer to be processed meets the requirements of multi-round processing based on the aluminum linewidth and overlay accuracy, ensuring the precision of pattern transfer. Secondly, it determines the single-etching thickness according to existing processes and sets the photoresist thickness and etching parameters of the previous rounds consistently, reducing process complexity and facilitating development and debugging by engineers. Thirdly, before each round of processing, a photoresist of the corresponding thickness is spin-coated onto the wafer surface, achieving the process requirements for thick aluminum etching without requiring a thicker photoresist layer. Simultaneously, multi-round processing allows for the formation of small-angle openings without enhanced physical bombardment, improving the dry etching chamber environment, increasing machine uptime, and reducing processing costs.

[0072] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0073] Based on the same inventive concept, this application also provides a thick aluminum preparation apparatus. This apparatus is applicable to the above-described thick aluminum preparation method. The solution provided by this apparatus is similar to the solution described in the above-described method. Therefore, the specific limitations of one or more apparatus embodiments provided below can be found in the limitations of the method above, and will not be repeated here.

[0074] Please see Figure 5 In one embodiment, the thick aluminum preparation apparatus includes a processing module and a machining module.

[0075] The processing module is used to determine the process parameters of the wafer to be processed according to the process requirements; and to determine the process strategy based on the process parameters, wherein the process strategy includes the number of cycles, as well as the photoresist thickness and etching method used in each cycle.

[0076] The processing module is used to perform cyclic processing on the metal layer of the wafer according to the process strategy until the required number of cycles is reached; each processing step includes photolithography, etching, and resist removal and cleaning.

[0077] Optionally, the etching method includes a first etching method and a second etching method, wherein the first etching method is determined based on etching time; and the second etching method is determined based on endpoint detection. Process parameters include aluminum linewidth, metal thickness, and etching thickness; the etching thickness includes a first etching thickness, which corresponds to the first etching method. The processing module determines a process strategy based on the process parameters, including: calculating a first ratio between the aluminum linewidth and the overlay accuracy; determining the number of cycles based on the metal thickness and the first etching thickness, provided the first ratio meets preset conditions; selecting the etching method for each cycle based on the number of cycles; and determining the photoresist thickness for each cycle based on the etching thickness. The preset conditions are determined as follows: if the first ratio is greater than or equal to 50, the preset conditions are considered met.

[0078] Optionally, the processing module determines the number of cycles based on the metal thickness and the first etching thickness, including: calculating a second ratio of the metal thickness to the first etching thickness; if the second ratio is an integer, then using the integer as the number of cycles; otherwise, rounding the second ratio up to the nearest integer and using that integer as the number of cycles.

[0079] Optionally, the processing module selects the etching method for each processing step based on the number of cycles, including: selecting the second etching method in the last cycle and selecting the first etching method in all other cycles.

[0080] Optionally, the process parameters also include a selectivity ratio and a second etching thickness; wherein the second etching thickness corresponds to a second etching method. The processing module determines the photoresist thickness for each processing step based on the etching thickness, including: calculating a third ratio of the first etching thickness to the selectivity ratio, and determining the first photoresist thickness based on the third ratio and process margin; calculating a fourth ratio of the second etching thickness to the selectivity ratio, and determining the second photoresist thickness based on the fourth ratio and process margin.

[0081] Optionally, the processing module performs cyclic processing on the metal layer of the wafer according to the process strategy until the required number of cycles is reached. This includes: before each processing action, generating a new process formula based on the photoresist thickness and etching method used; based on the new process formula and the photoresist thickness, spin-coating photoresist onto the wafer surface, and exposing and developing it using the same photomask to form a preset pattern; using an etching method to remove the metal layer of the exposed area of ​​the preset thickness; wherein the preset thickness is related to the etching method; cleaning the wafer to remove photoresist residue; and repeating the above steps until the required number of cycles is reached.

[0082] Optionally, the processing module is also used to perform surface treatment on the wafer during the processing, including any one or more of surface activation, plasma cleaning, passivation, annealing, and surface roughening.

[0083] The aforementioned thick aluminum fabrication apparatus first determines whether the wafer to be processed meets the requirements of multi-round processing based on the aluminum linewidth and overlay accuracy, ensuring the precision of pattern transfer. Secondly, it determines the single-etching thickness according to existing processes and sets the photoresist thickness and etching parameters of the first few rounds consistently, reducing process complexity and facilitating development and debugging by technicians. Thirdly, before each round of processing, a photoresist of the corresponding thickness is spin-coated onto the wafer surface, achieving the process requirements for thick aluminum etching without requiring a thicker photoresist layer. Simultaneously, multi-round processing allows for the formation of small-angle openings without enhanced physical bombardment, improving the dry etching chamber environment, increasing machine uptime, and reducing processing costs.

[0084] Each module in the aforementioned thick aluminum preparation apparatus can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the operations corresponding to each module.

[0085] Based on the same inventive concept, this application also provides a machine tool that uses the thick aluminum preparation method disclosed in the above embodiments to process the metal layer of the wafer to be processed in order to obtain the desired metal structure. The wafer to be processed is a silicon carbide power device, and its top metal layer is typically made of an aluminum-copper alloy with a relatively thick layer, usually 4 μm; for high-voltage, high-current power devices, the thickness of the top metal layer is typically ≥5 μm, or even 6 μm or more.

[0086] The aforementioned machine can process wafers with large linewidths and thick aluminum. During processing, firstly, based on the aluminum linewidth and overlay accuracy, it is determined whether the wafer meets the requirements for multi-round processing, ensuring the accuracy of pattern transfer. Secondly, the single etching thickness is determined according to existing processes, and the photoresist thickness and etching parameters for the first few rounds are set consistently, reducing process complexity and facilitating development and debugging by technicians. Thirdly, before each round of processing, a photoresist of the corresponding thickness is spin-coated onto the wafer surface. This eliminates the need for thick photoresist to meet the process requirements of thick aluminum etching. Furthermore, multi-round processing allows for the formation of small-angle openings without enhanced physical bombardment, improving the dry etching cavity environment, increasing machine uptime, and reducing processing costs.

[0087] Please note that the above embodiments are for illustrative purposes only and do not imply any limitation on this application.

[0088] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0089] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing thick aluminum, characterized in that, include: Determine the process parameters of the wafer to be processed according to the process requirements; Based on the process parameters, a process strategy is determined, wherein the process strategy includes the number of cycles, and the photoresist thickness and etching method used in each cycle; According to the process strategy, the metal layer of the wafer is processed in cycles until the number of cycles is reached; wherein each processing step includes photolithography, etching and resist removal cleaning.

2. The method according to claim 1, characterized in that, The etching method includes a first etching method and a second etching method; wherein, the first etching method is determined based on etching time, and the second etching method is determined based on endpoint detection.

3. The method according to claim 2, characterized in that, The process parameters include aluminum linewidth, metal thickness, and etching thickness; the etching thickness includes a first etching thickness, which corresponds to the first etching method. The step of determining the process strategy based on the process parameters includes: Calculate the first ratio of the aluminum linewidth to the overlay accuracy; If the first ratio meets the preset conditions, the number of cycles is determined based on the metal thickness and the first etching thickness; Based on the number of cycles, select the etching method to be used in each cycle; Based on the etching thickness, the photoresist thickness used in each cycle is determined.

4. The method according to claim 3, characterized in that, Determining the number of cycles based on the metal thickness and the first etching thickness includes: Calculate a second ratio between the metal thickness and the first etching thickness. If the second ratio is an integer, use that integer as the number of iterations. Otherwise, round the second ratio up to the nearest integer and use that integer as the number of iterations.

5. The method for preparing thick aluminum according to claim 3, characterized in that, The step of selecting the etching method for each processing step based on the number of cycles includes: During the loop, the second etching method is selected in the last loop, and the first etching method is selected in all other loops.

6. The method for preparing thick aluminum according to claim 4, characterized in that, The process parameters also include a selectivity ratio and a second etching thickness; wherein the second etching thickness corresponds to the second etching method; The step of determining the photoresist thickness for each processing step based on the etching thickness includes: Calculate the third ratio of the first etching thickness to the selection ratio, and determine the first photoresist thickness based on the third ratio and the process margin; Calculate the fourth ratio of the second etching thickness to the selection ratio, and determine the second photoresist thickness based on the fourth ratio and the process margin.

7. The method for preparing thick aluminum according to claim 1, characterized in that, The step of cyclically processing the metal layer of the wafer according to the process strategy until the specified number of cycles is reached includes: Before each processing operation, a new process formula is generated based on the photoresist thickness and etching method used. Based on the new process formula, and according to the photoresist thickness, photoresist is spin-coated onto the wafer surface, and exposed and developed using the same photomask to form a preset pattern; The etching method described above is used to remove the metal layer of an exposed area of ​​a predetermined thickness; wherein the predetermined thickness is related to the etching method. Clean the wafer to remove photoresist residue; Repeat the above steps until the number of repetitions reaches the stated number of cycles.

8. The method for preparing thick aluminum according to claim 1, characterized in that, The method further includes: During the processing, the wafer undergoes surface treatment, which includes any one or more of the following: surface activation, plasma cleaning, passivation, annealing, and surface roughening.

9. A thick aluminum preparation apparatus, characterized in that, The device includes: The processing module is used to determine the process parameters of the wafer to be processed according to the process requirements; and to determine the process strategy according to the process parameters, wherein the process strategy includes the number of cycles, and the photoresist thickness and etching method used in each cycle; The processing module is used to perform cyclic processing on the metal layer of the wafer according to the process strategy until the number of cycles is reached; wherein each processing step includes photolithography, etching and resist removal cleaning.

10. A machine tool, characterized in that, The machine tool uses the thick aluminum preparation method according to any one of claims 1-8 to process the metal layer of the wafer to be processed in order to obtain the desired metal structure.

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