Wafer electroplating method and wafer electroplating product

Abstract

The embodiment of the invention provides a wafer electroplating method and a wafer electroplating product thereof. The method comprises the following steps: preparing a seed layer on the surface of a wafer; photoetching the seed layer to obtain a to-be-electroplated region with a preset pattern; carrying out first electroplating operation on the to-be-electroplated area at a first preset current density to obtain a metal coating; and after the first electroplating operation is finished, carrying out second electroplating operation on the to-be-electroplated area at a second preset current density so as to enable the metal coating to reach a preset thickness, wherein the second preset current density is 65 to 75 times of the first preset current density. According to the method, the adhesion of the metal coating can be effectively enhanced, the metal coating is prevented from falling off, meanwhile, the maximum current capable of being used by the second electroplating operation is improved, and therefore the total duration of the electroplating process is effectively shortened.

Description

[Technical field]

[0001] The present application relates to the technical field of semiconductor device preparation, and in particular to a wafer electroplating method and a wafer electroplating product. [Background technology]

[0002] Electroplating is a technique that deposits a thin metal film on the surface of a substrate through an electrochemical process. Electroplating is widely used in the field of microelectronics. Electroplating can enhance the conductivity, corrosion resistance and wear resistance of the substrate. In addition, electroplating can also be used to form conductive paths, contact points and other functional structures in electronic devices.

[0003] With the continuous development of microelectronics technology, the size of electronic devices, especially large-scale integrated circuit chips, has been continuously reduced. For example, the width of electrode leads or the distance between electrode leads has been reduced to 0.3 mm. Accordingly, electronic devices have higher requirements on the coating quality of electroplating process, such as coating thickness and coating surface morphology.

[0004] The quality of the coating is easily affected by the various process parameters and production environment during the electroplating process, resulting in weak bonding between the coating and the substrate, which in turn leads to the coating falling off and failure. Such defects have a great impact on the reliability and service life of electronic devices. [Summary of the invention]

[0005] The wafer electroplating method and wafer electroplating product provided in the embodiments of the present application are intended to reduce the risk of coating shedding in related technologies.

[0006] In a first aspect, the embodiments of the present application provide the following technical solutions: a wafer electroplating method. The wafer electroplating method comprises the following steps: preparing a seed layer on the surface of a wafer; performing photolithography on the seed layer to obtain an area to be electroplated having a preset pattern; performing a first electroplating operation on the area to be electroplated at a first preset current density to obtain a metal coating; and after the first electroplating operation is completed, performing a second electroplating operation on the area to be electroplated at a second preset current density to make the metal coating reach a preset thickness; wherein the second preset current density is 65 to 75 times the first preset current density.

[0007] In a second aspect, the embodiments of the present application provide the following technical solution: a wafer electroplating product. The wafer electroplating product is prepared by the wafer electroplating method as described above.

[0008] The advantages of the wafer electroplating method provided by the embodiment of the present application are: by using the first electroplating operation and the second electroplating operation with different currents during the wafer electroplating process, on the one hand, the adhesion of the metal coating of the wafer electroplating product can be effectively enhanced, and the risk of the metal coating falling off can be reduced. On the other hand, the maximum current that can be used in the second electroplating operation can be increased, thereby achieving the effect of shortening the total electroplating time.

Brief Description of the Drawings

[0009] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0010] Figure 1 Schematic diagram of electroplating principle;

[0011] Figure 2 A method flow chart of a wafer electroplating method according to an embodiment of the present application;

[0012] Figure 3 A schematic diagram of a typical photolithography operation;

[0013] Figure 4 A flowchart of a wafer electroplating method according to another embodiment of the present application;

[0014] Figure 5 A flow chart of a method for cleaning a wafer assembly according to an embodiment of the present application;

[0015] Figure 6 A method flow chart of a wafer electroplating method according to another embodiment of the present application;

[0016] Figure 7 The adhesion test results of the metal plating layer of the wafer electroplating product prepared in Example 1;

[0017] Figure 8 The adhesion test results of the metal coating of the wafer electroplating product prepared in Example 2 are shown. [Specific implementation method]

[0018] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be an intermediate element at the same time, or it may refer to that the two elements are interactively connected through signals. When an element is considered to be "coupled" / "coupled to" another element, it may be directly coupled to the other element or there may be an intermediate element at the same time, or it may refer to that the two elements are interactively connected through signals.

[0020] The term "wafer" refers to a thin slice of semiconductor material used to manufacture microelectronic devices. Wafers are the basic material of semiconductor components and are processed through a series of processes to form various types of microelectronic devices.

[0021] The term "metal plating" refers to a layer of metal with a specific thickness that is deposited on the surface of a substrate by an electrochemical reaction.

[0022] Metal plating can form a variety of functional structures such as connecting lines or contact points of microelectronic devices. Based on different practical application requirements, metal plating can use different metal materials. For example, copper (Cu) can provide good conductivity and relatively low cost. Gold (Au) can provide excellent stability and reliability.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0024] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0025] Figure 1 The figure is a schematic diagram of the electroplating principle, which shows how to form a metal copper coating through an electroplating device. Figure 1 As shown, the electroplating device 10 may be composed of a DC power supply 11 , an anode 12 , a cathode 13 , an electroplating solution 14 and a stirrer 15 .

[0026] The anode 12 and the cathode 13 are both immersed in the electroplating solution 14, and the DC power supply 11 is electrically connected to the anode 12 and the cathode 13 respectively to provide the electric energy required for electroplating.

[0027] During electroplating, the DC power supply 11 generates a current (the direction of the current is opposite to the direction of movement of the electrons ne-) flowing toward the anode 12. When the current passes through the anode 12, the metallic copper at the anode 12 loses electrons, is converted into copper ions (Cu2+) and is released into the electroplating solution 13.

[0028] Under the action of the electric field formed by the DC power supply, the copper ions (Cu2+) in the electroplating solution 14 move in the opposite direction of the current to the cathode 13. After reaching the cathode 13, the copper ions (Cu2+) can obtain electrons from the cathode 13, be reduced to metallic copper and deposited on the surface of the cathode 13.

[0029] As the electroplating time continues, the metal copper at the anode 12 gradually decreases and dissolves in the electroplating solution 13, and the metal copper deposited on the surface of the cathode 13 continues to increase until the metal coating reaches a desired thickness.

[0030] In addition, the agitator 15 is also activated during the electroplating process. The agitator 15 stirs the electroplating solution to ensure that copper ions are evenly distributed in the solution and to prevent particles from settling in the solution, thereby maintaining the activity of the electroplating solution 13 .

[0031] exist Figure 1 , the stirring method using the stirrer 15 is exemplarily shown. Alternatively, the stirring of the plating solution 14 can also be achieved by any other suitable type of equipment. For example, a magnetically driven rotor is set in the plating solution, and the rotor is driven to rotate by a stator that can provide a variable magnetic field to stir the plating solution.

[0032] In the process of implementing the present application, the applicant noticed that there is a contradiction between the electroplating time and the quality of the metal coating. On the one hand, the greater the electroplating current provided by the DC power supply 11, the faster the deposition speed of the metal element on the cathode 13, and the shorter the time required for the metal coating to reach the ideal thickness. On the other hand, the smaller the electroplating current provided by the DC power supply 11, the better the uniformity and adhesion of the metal coating of the metal element on the cathode surface.

[0033] In order to ensure sufficient adhesion between the metal coating and the substrate, and to ensure the performance and durability of the electroplated product, the electroplating current needs to be limited to a smaller upper limit value, which means that the total time required for electroplating cannot be shortened indefinitely. There is a contradiction between shortening the electroplating time and ensuring the quality of the metal coating.

[0034] In the process of realizing the present application, the applicant has found that: in the short period of time when electroplating is started, the deposited metal element can be very evenly distributed on the surface of the wafer as the substrate to be plated by using a small current. Since the evenly distributed metal element can provide a uniform conductive path, under the premise of ensuring the uniformity and adhesion of the metal coating, a larger current that exceeds the upper limit value can be used for rapid electroplating, thereby depositing a metal coating with an ideal thickness in a shorter time.

[0035] When the numerical ratio between the tiny current and the larger current used in the subsequent rapid electroplating is within a specific range, the time saved in the rapid electroplating operation that exceeds the upper limit value can be greater than the time consumed in the electroplating operation with a tiny current. This can partially resolve the contradiction between shortening the electroplating time and ensuring the quality of the metal coating, thereby achieving the effect of reducing the electroplating time and improving the electroplating efficiency.

[0036] According to the inventive concept provided by this application, it can be generally applied to the electroplating process of various different substrates to be plated. However, for the convenience of description and understanding, the wafer will be used as an example of the substrate to be plated to describe this application.

[0037] Figure 2 The method flow chart of the wafer electroplating method provided in the embodiment of the present application. Figure 2 As shown, the wafer electroplating method includes the following steps:

[0038] S100, preparing a seed layer on the surface of the wafer.

[0039] The "seed layer" refers to a metal film layer with a thickness of nanometers formed on the surface of the wafer, which can promote the subsequent metal deposition during electroplating. It can be selected to use any suitable type of metal material according to the needs of the actual application, including but not limited to peptide, gold, copper, nickel or copper-nickel alloy, etc., as long as it can provide good chemical and physical stability.

[0040] Specifically, based on one or more actual needs such as cost, the seed layer on the surface of the wafer can be prepared by a variety of different technical means, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), printing or spraying.

[0041] Preferably, the required seed layer can be deposited on the surface of one or more wafers by magnetron sputtering. "Magnetron sputtering" is a type of physical vapor deposition technology. Its working principle is to apply a high voltage electric field to excite argon (or other inert gases) to form plasma in a vacuum environment. Subsequently, the ions in the plasma are used to bombard the target material to sputter out the material atoms in the target material. Finally, the sputtered material atoms are deposited on the surface of the wafer to form a seed layer.

[0042] The above-mentioned method of using magnetron sputtering to form a seed layer can effectively improve the density and stability of the seed layer, and can also prepare the seed layer of multiple wafers at the same time, which is beneficial to improving the overall efficiency of the entire electroplating method.

[0043] Alternatively, based on the consideration of reducing equipment costs, electron beam evaporation can also be used to deposit a seed layer on the surface of the wafer. "Electron beam evaporation" is another technology of physical vapor deposition. In a vacuum or near-vacuum environment, a high-energy electron beam is used to heat the target material to sublimate or evaporate it; further, the sublimated or evaporated material atoms are controlled to deposit on the surface of the wafer to form a seed layer.

[0044] S300, photolithography is performed on the seed layer to obtain an area to be electroplated showing a preset pattern.

[0045] Among them, "photolithography" is a micro-machining process that forms complex patterns on the surface of a specific substrate. It mainly includes three steps: photoresist coating, mask exposure and development. It can retain a specific shape of photoresist to form the required preset pattern on the surface of the seed layer to obtain the above-mentioned area to be electroplated.

[0046] Figure 3 The typical photolithography process is shown as an example. Figure 3 As shown, first, a photoresist 22 is uniformly coated on the surface of the seed layer 21 of the wafer 20. Then, a mask 24 is covered on the photoresist 22. Subsequently, an ultraviolet light source 23 is used to irradiate, and the complex pattern of the mask 24 is projected onto the uniformly coated photoresist 22. Afterwards, a developer is used to remove the photoresist 22 in the exposed area or the unexposed area ( Figure 3 2 ) whereby the desired complex pattern, ie, the area to be electroplated, is revealed on the surface of the seed layer 21.

[0047] In this application, for the sake of simplicity, the term "area to be electroplated" is used to refer to the area where a complex pattern is formed on the surface of the seed layer after the photolithography is completed, and the term "preset pattern" is used to refer to the complex pattern or graphic formed on the surface of the seed layer in step S300.

[0048] It is understandable that the specific pattern formed depends on the mask 24 used in the photolithography, which can be set and determined by technicians according to the requirements of the actual application scenario, and is not specifically limited here.

[0049] S510, performing a first electroplating operation on the area to be electroplated at a first preset current density to obtain a metal coating.

[0050] Among them, "electroplating operation" refers to the process of placing the substrate to be plated as the cathode and the cooperating anode target together in an environment surrounded by the electroplating liquid, and allowing the metal ions to receive electrons and be deposited on the surface of the substrate to be plated under the action of the electroplating current provided by the DC power supply.

[0051] Specifically, the anode target material and the electroplating solution can be determined according to the metal layer that is actually required to be electroplated. For example, when the substrate to be plated needs to be electroplated with copper metal, the anode target material can be selected to be a titanium basket and phosphor copper balls loaded therein, with the phosphor copper balls serving as a copper ion source; of course, in other embodiments of the present application, if the substrate to be plated needs to be electroplated with other types of metals, the anode target material can be adaptively adjusted.

[0052] Please continue reading Figure 3 After the electroplating operation, a metal coating will be formed on the surface of the to-be-plated area that is not covered by the photoresist, having the same shape as the preset pattern.

[0053] S520, after the first electroplating operation is completed, performing a second electroplating operation on the electroplating area at a second preset current density so that the metal coating reaches a preset thickness.

[0054] In this application, "first electroplating operation" and "second electroplating operation" are used to distinguish electroplating operations using different electroplating currents. The first electroplating operation refers to a process of preliminary slow electroplating using a smaller first preset current density, while the second electroplating operation refers to a process of rapid electroplating using a larger second preset current density, that is, the second preset current density is greater than the first preset current density.

[0055] It is worth noting that by setting the second current to 65 to 75 times the first current, the optimal balance between the electroplating effect and the total electroplating time can be achieved. While ensuring the good morphology and adhesion of the metal coating, the total time consumed by the electroplating operation can be shortened as much as possible.

[0056] The wafer electroplating method provided in the embodiment of the present application achieves a balance between electroplating quality and electroplating efficiency by appropriately setting the current ratio used in the first electroplating operation and the second electroplating operation, and effectively shortens the electroplating time while ensuring that the metal coating has sufficient adhesion.

[0057] In some embodiments, Figure 4 As shown, after the second electroplating operation is completed, the following steps may also be performed:

[0058] S700, cleaning the wafer assembly.

[0059] Among them, "wafer assembly" refers to the electroplated product including the wafer, seed layer and metal coating. The wafer assembly retains the metal coating on the surface of the wafer that matches the above preset pattern, which can be further used in the subsequent chip manufacturing process.

[0060] "Cleaning" refers to a series of processes to remove unwanted residues to make the surface of the wafer component sufficiently clean. It may include one or more treatments for different residues (such as plating solution remaining on the surface of the wafer component, photoresist layer attached to the surface of the wafer component, and other particles).

[0061] Specifically, Figure 5 As shown, the above-mentioned step of cleaning the wafer assembly may include:

[0062] S710. Use deionized water to quickly rinse the wafer assembly after the electroplating operation is completed.

[0063] Among them, "Quick Dump Rinse" (QDR) is a method of quickly rinsing samples. Through appropriate equipment design, the water in the rinsing process is quickly discharged, thereby avoiding the risk of re-deposition of particles.

[0064] S720, placing the wafer assembly after step S710 into acetone, using acetone as an organic solvent to dissolve and remove the photoresist layer on the surface of the wafer.

[0065] S730, use isopropyl alcohol (IPA) to clean the wafer components that have been soaked in acetone to remove residual acetone and other impurities.

[0066] S740. Use deionized water to clean the wafer assembly that has been cleaned with isopropyl alcohol to completely remove solvent residues so that the surface of the wafer assembly has sufficient surface cleanliness.

[0067] In some embodiments, in addition to controlling the magnitude of the electroplating current used in the first electroplating operation and the second electroplating operation, the electroplating duration of the two electroplating operations may also be controlled and optimized to further improve the electroplating quality and shorten the electroplating time.

[0068] The first electroplating time can be controlled within the range of 0.5 to 0.7 times the second electroplating time, so that the first electroplating operation can form a sufficiently uniformly distributed metal layer without excessively extending the total time required for electroplating, further optimizing the balance between electroplating efficiency and electroplating quality. In other words, this setting also prompts the second electroplating operation to be performed quickly after the first electroplating operation forms a dense and uniform thin film of more than 100 nanometers, avoiding the second electroplating operation from being performed for too long; of course, the electroplating current of this process cannot be too large.

[0069] Specifically, the first preset current density used in the first electroplating operation is 0.033 amperes per square decimeter (ASD) to 0.053 ASD, so as to slowly deposit a dense and uniform copper film in the area to be electroplated, and the duration of the first electroplating operation is controlled to be 10 minutes to 20 minutes. The second current used in the second electroplating operation is 0.95 ASD to 1.15 ASD (the ratio between the two is controlled to be about 70 times), so as to quickly further deposit a copper plating layer on the basis of the above-mentioned film, and when the second electroplating operation lasts for 20 minutes to 30 minutes, a copper plating layer with a thickness of about 20-30 um can be attached to the surface of the wafer while ensuring good electroplating quality.

[0070] After electroplating is completed, there will be stress between the wafer surface and the seed layer, and between the seed layer and the metal coating, which will drive the different layers to separate from each other. Such stress will reduce the adhesion of the metal coating, causing the metal coating of the wafer assembly to fail in adhesion, thereby affecting the reliability and service life of the semiconductor chip prepared based on the wafer assembly, and greatly reducing the yield of the chip.

[0071] In some embodiments, to help improve the adhesion of the metal coating, such as Figure 6 As shown, after step S700, the following steps may also be included:

[0072] S900, performing a rapid annealing operation on the wafer assembly under a protective atmosphere.

[0073] Among them, "Rapid Thermal Processing" (RTP) is a method of rapidly heating and cooling samples. It can be performed in a protective atmosphere such as nitrogen or in a vacuum environment by rapidly heating to the target annealing temperature, maintaining the set time, and rapidly cooling to room temperature.

[0074] Specifically, the target annealing temperature of the rapid annealing operation can be set at 350° C. to 380° C., and the annealing time is controlled at 10 minutes to 15 minutes. The rapid annealing furnace is used to complete the rapid heating and cooling processes.

[0075] The embodiments of the present application can eliminate stress and optimize interlayer bonding as much as possible through rapid annealing operations on wafer components, thereby improving the adhesion of metal coatings and ensuring the reliability and yield of semiconductor chips.

[0076] After the cleaning operation in step S700 is completed, it cannot always ensure that the wafer assembly has the required quality and surface cleanliness due to the influence of various factors such as the characteristics of the wafer itself and the production environment.

[0077] In some embodiments, in order to improve the stability and reliability of the finished product quality, please continue to refer to Figure 6 Before executing step S900, the following steps may also be included:

[0078] S800 , performing a surface residue inspection operation on the wafer assembly to determine the inspection result of the wafer assembly.

[0079] Among them, the "inspection operation" is the process of judging and screening whether the surface of the wafer component meets specific quality standards based on the results of microscope observation. For example, checking the quality of the metal coating and detecting whether there are residual particles on the surface.

[0080] Specifically, five inspection positions, namely the top, bottom, left, right and center of the wafer assembly, are selected, and the surface morphology of the metal coating at these inspection positions and whether there are any residual particles that have not been removed on the surface are observed through a crystal phase microscope.

[0081] After step 800 is executed, corresponding operation steps may be executed according to specific inspection results. Specifically, when the inspection result indicates that there is residue on the surface of the wafer assembly, step S700 is executed, and when the inspection result indicates that there is no residue on the surface of the wafer assembly, step S900 is executed.

[0082] The inspection operation before the rapid annealing operation in the embodiment of the present application can screen and troubleshoot the wafer components to ensure that the final product can meet the set quality standards and have good reliability. Moreover, the screening results provided by the inspection operation feedback can also reflect the specific conditions of the cleaning operation and the electroplating operation, providing guidance for the optimization and adjustment of their process parameters.

[0083] Before the electroplating operation, it is usually necessary to perform appropriate surface cleaning on the patterned wafer obtained after photolithography to provide a clean surface to ensure that the metal coating has sufficient adhesion. Patterned wafer refers to the intermediate product after photolithography, which includes the wafer and the seed layer that reveals the area to be electroplated.

[0084] The typical method is to use an acid solution to dissolve and remove surface impurities of the patterned wafer (also referred to as "pickling"). However, each link in the production line process required for pickling is highly corrosive, which is highly harmful to operators. Moreover, the pickling recovery operation is relatively cumbersome.

[0085] In order to minimize the series of defects caused by pickling, in some embodiments, please continue to refer to Figure 6 , the electroplating method also includes the following steps:

[0086] S400 , performing an oxygen plasma cleaning operation on the patterned wafer.

[0087] Among them, "oxygen plasma cleaning operation" is a series of processing processes that use oxygen plasma generated by ionizing oxygen under a high-frequency electric field to react with organic matter and convert it into carbon dioxide and water, thereby removing surface residues on the patterned wafer.

[0088] Specifically, the patterned wafer may be placed in a cleaning device first, and then, after being cleaned for a preset time at a preset cleaning power, it is taken out of the cleaning device and a series of subsequent steps are performed.

[0089] The embodiment of the present application uses oxygen plasma cleaning operation to replace acid cleaning to achieve surface cleaning of patterned wafers. Compared with the acid cleaning method that uses an acid solution to dissolve and remove surface residues, the oxygen plasma cleaning operation is more environmentally friendly and has less impact on the environment. It also does not require the installation of a complex wastewater and waste gas recovery system and recovery operation. Moreover, each link of the entire cleaning process is not too corrosive, avoiding harm to operators and significantly reducing the danger.

[0090] In order to ensure the surface cleanliness and adhesion of the seed layer, in a preferred embodiment, an ultrasonic cleaning operation may be performed on the wafer before the seed layer is prepared on the surface of the wafer.

[0091] Among them, "ultrasonic cleaning operation" is a process of removing particles, grease and other pollutants on the surface of an object by using the impact force generated by the cavitation effect when ultrasonic waves propagate in liquid. Specifically, the ultrasonic cleaning operation can include the following series of operation steps:

[0092] First, the wafer is placed in an ultrasonic cleaning tank and cleaned under the action of ultrasound. In the ultrasonic cleaning tank, anhydrous ethanol or isopropyl alcohol can be used as a cleaning solvent.

[0093] Then, after a preset cleaning time, the wafer is taken out and rinsed with deionized water. The preset cleaning time can be controlled at 10 minutes to provide a sufficient cleaning effect.

[0094] Finally, the wafer rinsed with deionized water is dried. The wafer rinsed with deionized water can be dried by low temperature drying or nitrogen drying to keep it dry for subsequent processing.

[0095] The wafer electroplating method of the present application is described in detail below in combination with one or more specific examples to fully illustrate and verify the inventive concept of the present application.

[0096] Embodiment 1:

[0097] The wafer is used as the substrate to be plated, the plating area is 0.35dm2, and the plating metal is copper. The following processing steps are performed on the substrate to be plated:

[0098] Step 1: Use anhydrous ethanol as the cleaning solvent, place the wafer in an ultrasonic cleaning tank for ultrasonic cleaning for 10 minutes, then take it out. Rinse the wafer with deionized water and dry it.

[0099] Step 2: Electromagnetic sputtering is used to deposit a seed layer on the surface of the wafer. The metal material of the seed layer is titanium Ti and gold Au.

[0100] Step 3: Through photolithography, a to-be-plated area with a preset pattern is formed on the seed layer to obtain a patterned wafer.

[0101] Step 4: Add the prepared plating solution into the plating tank and set the plating temperature to room temperature.

[0102] Step 5: Use a DC pulse power supply as the electroplating power supply, and use a titanium basket with phosphor bronze balls inside as the anode target. The DC pulse power supply is electrically connected to the titanium basket and the hanger of the plated material to provide a specific electroplating current.

[0103] Step 6: Use a plasma cleaning machine to perform oxygen plasma cleaning on the patterned wafer obtained after step 3 to remove the residual glue and surface particles that are not completely developed by photolithography. The cleaning power is 200w and the cleaning time is 3 minutes.

[0104] Step 7: After the patterned wafer cleaned by oxygen plasma in step 6 is fixed on the hanger, the anode target and the hanger with the substrate to be plated are placed in the electroplating tank as the cathode, and immersed in the electroplating solution for electroplating. During electroplating, the DC pulse power supply is controlled to provide a current of 0.525A, the current density is 1.5ASD, and the electroplating is continued for 60 minutes until a 25um thick electroplated copper layer is deposited.

[0105] Step 8: After the electroplating in step 7 is completed, take out the wafer assembly from the electroplating tank and use high-pressure water washing to remove the residual electroplating solution on the surface.

[0106] Step 9: After step 8 is completed, acetone is first used to dissolve the photoresist on the wafer surface. Then, isopropyl alcohol is used to clean and remove the residual chemicals and particles on the wafer surface. Finally, deionized water is used for final cleaning to obtain the final wafer electroplating product.

[0107] Step 10: Place the cleaned electroplated wafer under a crystal phase microscope and use the five-point method to inspect the surface to observe the morphology of the electroplated layer and determine whether there are any unwashed particles remaining on the surface. The sampling points of the five-point method are the top, bottom, left, right and center of the surface of the electroplated wafer.

[0108] Step 11: Use a tensile shear force device to perform a push-pull force test on the wafer electroplated product that has passed the surface inspection in step 10 to determine the adhesion of the metal coating on the wafer electroplated product.

[0109] Among them, the tension and shear force equipment is a kind of testing equipment based on the force-deformation law of materials. Its specific use process is: first, clamp the sample to be tested on the clamping device. Then, the equipment applies different tension or shear force to the sample to be tested through the probe, and determines the deformation of the sample to be tested through sensor detection. Finally, according to the applied force and the sensor detection results, the force-deformation curve and mechanical parameters of the material are calculated.

[0110] This embodiment uses Dage4000 push-pull force test equipment. During the test, after the wafer electroplating product is clamped and fixed, the probe of the test equipment is controlled to probe down to a position close to the surface of the seed layer (3-5um from the surface), and then it is scratched along the set path across the area of ​​the wafer electroplating product with a metal coating. The force applied by the probe is gradually increased until the metal coating is scratched off and fails. The sensor of the push-pull force test equipment collects and determines the magnitude of the force applied by the probe.

[0111] Figure 7 The figure shows how the force applied by the probe changes with time as determined by the sensor. Figure 7 As shown, when the probe uses a force of 15.57g, the metal coating on the surface of the wafer electroplating product can be scratched off.

[0112] Embodiment 2:

[0113] The wafer is used as the substrate to be plated, the plating area is 0.35dm2, and the plating metal is copper. The following processing steps are performed on the substrate to be plated:

[0114] Step 1: Use anhydrous ethanol as the cleaning solvent, place the wafer in an ultrasonic cleaning tank for ultrasonic cleaning for 10 minutes, then take it out. Rinse the wafer with deionized water and dry it.

[0115] Step 2: Electromagnetic sputtering is used to deposit a seed layer on the surface of the wafer. The metal material of the seed layer is titanium Ti and gold Au.

[0116] Step 3: Through photolithography, a to-be-plated area with a preset pattern is formed on the seed layer to obtain a patterned wafer.

[0117] Step 4: Add the prepared plating solution into the plating tank and set the plating temperature to room temperature.

[0118] Step 5: Use a DC pulse power supply as the electroplating power supply, and use a titanium basket with phosphor bronze balls inside as the anode target. The DC pulse power supply is electrically connected to the titanium basket and the hanger of the plated material to provide a specific electroplating current.

[0119] Step 6: Use a plasma cleaning machine to perform oxygen plasma cleaning on the patterned wafer obtained after step 3 to remove the residual glue and surface particles that are not completely developed by photolithography. The cleaning power is 200w and the cleaning time is 3 minutes.

[0120] Step 7: After the patterned wafer cleaned by oxygen plasma in step 6 is fixed on the hanger, the anode target and the hanger with the substrate to be plated are placed in the electroplating tank as the cathode, and immersed in the electroplating solution for the first electroplating operation. In the first electroplating operation, the DC pulse power supply is controlled to provide a small current of 15mA for electroplating, the current density is 0.043ASD, and the electroplating time is 15 minutes to form a relatively dense and uniform metal coating.

[0121] Step 8: After the first electroplating operation in step 7 is completed, the DC pulse power supply is controlled to provide a large current of 1.05A for electroplating, the current density is 3ASD, and the electroplating time is 25 minutes, until a plated metal copper layer with a thickness of 25um is deposited.

[0122] Step 9: After the electroplating in step 8 is completed, take out the wafer assembly from the electroplating tank and use high-pressure water washing to remove the residual electroplating solution on the surface.

[0123] Step 10: After step 9 is completed, first use acetone to dissolve the photoresist on the surface of the wafer component. Then, use isopropyl alcohol to clean and remove the remaining chemicals and particles on the surface of the wafer component. Finally, use deionized water for final cleaning.

[0124] Step 11: Place the cleaned wafer assembly under a crystal phase microscope and use the five-point method to perform surface inspection to observe the morphology of the electroplating layer and determine whether there are any uncleaned particles remaining on the wafer surface. The sampling points of the five-point method are the top, bottom, left, right and center of the surface of the wafer assembly.

[0125] Step 12: Place the wafer assembly that has passed the surface inspection in step 11 into a rapid annealing furnace for rapid annealing to obtain the final wafer electroplating product. The annealing temperature of the rapid annealing treatment is 370°C, and the annealing is performed for 10-15 minutes in a nitrogen protective atmosphere.

[0126] Step 13: Use a tensile shear force device to perform a push-pull force test on the wafer electroplated product after rapid annealing to determine the adhesion of the metal coating on the wafer electroplated product.

[0127] Among them, the tension and shear force equipment is a kind of testing equipment based on the force-deformation law of materials. Its specific use process is: first, clamp the sample to be tested on the clamping device. Then, the equipment applies different tension or shear force to the sample to be tested through the probe, and determines the deformation of the sample to be tested through sensor detection. Finally, according to the applied force and the sensor detection results, the force-deformation curve and mechanical parameters of the material are calculated.

[0128] This embodiment uses Dage4000 push-pull force test equipment. During the test, after the wafer electroplating product is clamped and fixed, the probe of the test equipment is controlled to probe down to a position close to the surface of the seed layer (3-5um from the surface), and then it is scratched along the set path across the area of ​​the wafer electroplating product with a metal coating. The force applied by the probe is gradually increased until the metal coating is scratched off and fails. The sensor of the push-pull force test equipment collects and determines the magnitude of the force applied by the probe.

[0129] Figure 8 The figure shows how the force applied by the probe changes with time as determined by the sensor. Figure 8 As shown, the peak of the force curve shows that when the probe uses a force of 48.84g, the metal coating on the surface of the wafer electroplating product can be scratched off.

[0130] Comparative Analysis of Embodiments:

[0131] 1) By Figure 7 and Figure 8 Comparison between the force curves shown shows that the wafer electroplating product obtained by the wafer electroplating method of Example 2 consumes a greater force to make the metal plating layer fall off and fail than the wafer electroplating product obtained by the conventional wafer electroplating method of Example 1. In other words, the bonding force between the metal plating layer and the substrate of the wafer electroplating product obtained by Example 2 is significantly improved compared with the wafer electroplating product obtained by Example 1.

[0132] Therefore, the wafer electroplating method provided in the embodiment of the present application can effectively improve the adhesion of the metal coating. The metal coating has a strong bonding force with the wafer surface and will not fall off easily, thereby effectively increasing the reliability and stability of the wafer electroplating product.

[0133] 2) The target thickness of the metal coating of Example 1 and Example 2 is 25 um. The total electroplating time consumed by Example 1 to obtain the metal coating of the target thickness is 60 minutes (the duration of step 7 of Example 1), while the total electroplating time consumed by Example 2 to obtain the metal coating of the target thickness is: 15 minutes + 25 minutes = 40 minutes (the sum of the durations of steps 7 and 8 of Example 2).

[0134] By comparing the total electroplating time of the two embodiments, it can be seen that although the second embodiment adds step 7 of electroplating with a small current, which consumes 15 minutes, based on the relatively uniform and dense metal layer provided by step 7, a significantly larger current can be used for electroplating in step 8 compared with step 7 of the first embodiment, which greatly saves the time required for depositing a metal coating of a specific thickness.

[0135] Therefore, relative to Example 1, the time saved in step 8 of Example 2 is greater than the time consumed in step 7, thereby obtaining a shorter electroplating time. In other words, the wafer electroplating method of Example 2 can improve the electroplating efficiency while ensuring the quality of the electroplating layer, thereby shortening the total time required for electroplating. Even if the embodiment of the present application is described as an example in which the second preset current density is about 70 times the first preset current density, it should be understood that the second preset current density can also be appropriately floated on this basis, for example, as described above, the second preset current density is 65 to 75 times the first preset current density, and for another example, the second preset current density is 68 to 72 times the first preset current density.

[0136] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Under the concept of the present application, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present application as described above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A wafer electroplating method, characterized in that: include: preparing a seed layer on a surface of the wafer; Performing photolithography on the seed layer to obtain an area to be electroplated showing a preset pattern; Performing a first electroplating operation on the area to be electroplated at a first preset current density to obtain a metal coating; as well as After the first electroplating operation is completed, performing a second electroplating operation on the area to be electroplated at a second preset current density so that the metal coating reaches a preset thickness; Wherein, the second preset current density is 65 to 75 times of the first preset current density.

2. The wafer electroplating method according to claim 1, characterized in that: The first electroplating time is 0.5 to 0.7 times the second electroplating time; The first electroplating duration is the duration of the first electroplating operation, and the second electroplating duration is the duration of the second electroplating operation.

3. The wafer electroplating method according to claim 2, characterized in that: The metal plating layer is a copper plating layer; Among them, the first preset current density is 0.033ASD~0.053ASD, the second preset current density is 0.95ASD~1.15ASD, the first electroplating time is 10 minutes~20 minutes, the second electroplating time is 20 minutes~30 minutes, and the preset thickness is 20um~30um.

4. The wafer electroplating method according to claim 1, characterized in that: After performing a second electroplating operation on the area to be electroplated at a second preset current density, the method further includes: Under a protective atmosphere, a rapid annealing operation is performed on a wafer assembly, wherein the wafer assembly includes the wafer, the seed layer and the metal coating layer.

5. The wafer electroplating method according to claim 4, characterized in that: The rapid annealing operation includes: annealing at 350° C. to 380° C. for 10 to 15 minutes.

6. The wafer electroplating method according to claim 4, characterized in that: Before performing a rapid annealing operation on the wafer assembly under a protective atmosphere, the method further comprises: Clean the wafer components.

7. The wafer electroplating method according to claim 6, characterized in that: After the wafer assembly is cleaned, the method further comprises: Performing an inspection operation on the wafer assembly for surface residues; If the inspection result indicates that there is residue on the surface of the wafer assembly, the step of cleaning the wafer assembly is repeated.

8. The wafer electroplating method according to claim 1, characterized in that: Before performing a first electroplating operation on the to-be-plated area at a first preset current density, the method further comprises: performing an oxygen plasma cleaning operation on the patterned wafer; Wherein, the patterned wafer comprises: the wafer and a seed layer with the area to be electroplated exposed; The oxygen plasma cleaning operation includes: placing the patterned wafer in a cleaning device, and continuously cleaning the wafer for a preset time period at a preset cleaning power.

9. The wafer electroplating method according to claim 1, characterized in that: The step of preparing a seed layer on the surface of the wafer specifically includes: A metal film is deposited on the surface of one or more of the wafers by magnetron sputtering to form the seed layer.

10. A wafer electroplating product, characterized in that: The wafer electroplating product is prepared by the wafer electroplating method according to any one of claims 1 to 9.

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