A pre-wetting method before electroplating

Abstract

The present invention provides a pre-wetting method before electroplating, comprising the following steps: configuring a vacuum pressure value and a spray liquid pressure value according to the product type; obtaining the vacuum pressure value and the spray liquid pressure value, and controlling the vacuum pump to work according to the vacuum pressure value to reach the vacuum pressure value, and controlling the hydraulic regulating device according to the spray liquid pressure value to reach the spray liquid pressure value; driving the wafer carrier to rotate at a preset speed, and stopping vacuuming; opening the spray valve of the spray pipeline to spray pre-wet the wafer for a preset time; opening the air inlet valve until the preset air pressure value is reached in the pre-wetting chamber; and transferring the wafer to the electroplating chamber. The present invention can effectively solve the requirements of different aspect ratios and different line widths for pre-wetting pressure, improve the pre-wetting effect before electroplating, and is conducive to improving the combination between the subsequent electroplating layer and the seed layer, and preventing the photoresist from being damaged and causing the electroplating layer to interconnect and form a short circuit, thereby improving the yield after electroplating.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor integrated circuit packaging and relates to a pre-wetting method before electroplating. Background Art

[0002] In an era when Moore's Law is slowing down, advanced packaging has become one of the saviors of the future development of the semiconductor industry. Advanced packaging is essential to driving semiconductor innovation. The semiconductor industry is in a period of great transformation and has entered a disruptive development stage. Emerging megatrend-driven applications such as mobile applications, big data, artificial intelligence, 5G, high-performance computing, the Internet of Things, smart cars, Industry 4.0, and data centers will significantly affect the development of the semiconductor industry and bring huge opportunities to the entire supply chain. The electronic hardware that supports these emerging megatrends requires high computing power, high speed, more bandwidth, low latency, low power consumption, more functions, more memory, systems and integration, various sensors, and most importantly, low cost. These emerging trends will create business opportunities for various packaging platforms, and advanced packaging technology is an ideal choice to meet various performance requirements and complex heterogeneous integration needs. Therefore, advanced packaging occupies a large proportion of the semiconductor industry's assembly business.

[0003] Advanced packaging mainly includes 3D through silicon via (TSV), fan-out packaging, flip-chip packaging and fan-in WLP packaging. The bumping process refers to the process of growing bumps on the surface of the wafer, and then buckling the front side of the chip that was originally to be wired with gold wires on the substrate, connecting it to the substrate, and at the same time, the electrical signal is conducted through the bumps. This method is generally used for flip chips. Bumps mainly include pillar bumps (a solder joint process) and ball bumps (a solder joint process). First, the IC is led out to a specific area by electroplating a rewiring layer (RDL), and then solder material solder joints are electroplated in this area. Wafer-level packaging (WLCSP) refers to a large flip chip with no carrier in the middle. The solder balls are directly implanted on the silicon substrate. The WLCSP process mainly includes RDL, UBM (copper pillar plating) and ball implantation. As the core electroplating technology of Bumping and WLCPS processes, there is still a lot of room for improvement. Improving the quality of the coating is particularly important. In advanced packaging, pre-wetting and pre-plating micro-etching processes are required before electroplating. Before electroplating, the incoming photolithography wafers are first plasma cleaned to remove organic matter in the opening (mainly photolithography residual glue), and then the gas in the opening is discharged by spraying deionized water (a small amount of dilute sulfuric acid can be introduced into the surface of the seed layer for micro-etching to remove the oxide layer, and then deionized water is sprayed to clean the surface dilute sulfuric acid so that the inside of the opening is filled with deionized water. This micro-etching step can also be performed in the electroplating chamber). By rotating the wafer carrier, the excess liquid on the surface is removed under the action of centrifugal force to form a liquid film to protect the seed layer from oxidation. The wafer then enters the electroplating chamber for electroplating. Due to the high viscosity and tension of the plating solution, it is difficult to enter the opening. At this time, the deionized water remaining in the opening during the pre-wetting process can play a good role in guiding the flow, so that the electroplating solution can quickly and evenly enter the opening. After electroplating, the photoresist and seed layer are removed, and the electrical performance test is performed to complete the entire electroplating process.

[0004] For products with large aspect ratios, the current pre-wetting process is prone to insufficient pre-wetting. For products with small line spacing, the current pre-wetting process is prone to damaging the photoresist, resulting in short circuits in subsequent plating. In addition, the current pre-wetting process also has problems with uneven water film or water film being blown dry, causing the seed layer to be oxidized, affecting subsequent electroplating.

[0005] Therefore, how to provide a new pre-wetting method before electroplating to fully pre-wet and prevent the photoresist from being damaged has become an important technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a pre-wetting method before electroplating to enhance the pre-wetting effect before electroplating, improve the bonding between the electroplating layer and the seed layer, and prevent the photoresist from being damaged and causing a short circuit between the electroplating layers.

[0007] To achieve the above-mentioned object and other related objects, the present invention provides a pre-wetting method before electroplating, comprising the following steps:

[0008] Configure vacuum pressure value and spray liquid pressure value according to product type;

[0009] Obtaining the vacuum pressure value and the spray liquid pressure value, and controlling the vacuum pump to work according to the vacuum pressure value so that the vacuum pressure value is reached in the pre-wetting chamber, and controlling the hydraulic regulating device according to the spray liquid pressure value so that the liquid pressure in the spray liquid pipeline reaches the spray liquid pressure value;

[0010] Driving the wafer stage to rotate at a preset speed and stopping vacuuming, wherein a wafer is placed on the wafer stage, and the wafer has a seed layer and a patterned photoresist layer on the seed layer;

[0011] Opening the liquid spray valve of the liquid spray pipeline to spray and pre-wet the wafer for a preset time;

[0012] Open the air inlet valve to introduce gas into the pre-wetting chamber until the pre-wetting chamber reaches a preset air pressure value;

[0013] The wafer is transferred into the electroplating chamber.

[0014] Optionally, in the step of introducing gas into the pre-wetting chamber until a preset air pressure value is reached in the pre-wetting chamber, before a first air pressure value is reached in the pre-wetting chamber, the liquid spray pipeline maintains a spraying state, and the first air pressure value is less than the preset air pressure value; after the first air pressure value is reached in the pre-wetting chamber, the liquid spray valve is closed to stop spraying.

[0015] Optionally, after closing the liquid spray valve to stop spraying, the wafer carrier maintains a rotating state to throw away excess spray liquid on the wafer surface until a protective liquid film of a preset thickness is formed on the wafer surface, and then the wafer carrier stops rotating.

[0016] Optionally, after the first air pressure value is reached in the pre-wetting chamber, the air inlet valve is closed to stop ventilation, and after the wafer carrier stops rotating, the air inlet valve is opened again until the preset air pressure value is reached in the pre-wetting chamber.

[0017] Optionally, the spray pre-wetting includes three stages, spraying deionized water in the first stage and the third stage, and spraying dilute sulfuric acid in the second stage to remove the oxide layer on the surface of the seed layer.

[0018] Optionally, the spraying time of the second stage is shorter than the spraying time of the first stage, and shorter than the spraying time of the third stage.

[0019] Optionally, the spraying time of the third stage is greater than the total spraying time of the first stage and the second stage.

[0020] Optionally, after the wafer is transferred into the electroplating chamber, the oxide layer on the surface of the seed layer is removed before electroplating.

[0021] Optionally, before or during spraying, the temperature of the spraying liquid is monitored, and if the temperature of the spraying liquid is higher than a preset temperature, subsequent steps are stopped.

[0022] As described above, the pre-wetting method before electroplating of the present invention has the following advantages:

[0023] (1) The spray liquid control is a closed-loop control. The PID control valve opening is automatically adjusted by the PID control feedback device according to different electroplating pre-wetting procedures for different products, thereby controlling the spray liquid pressure. For products with deeper openings (such as pillar / solder products), a higher pressure (70±5PSI) is used, which will not damage the photoresist and can effectively discharge the gas in the deep holes. For products with smaller line spacing (such as RDL / WLCSP products), a lower pressure (10±2PSI) is used, which can effectively discharge the gas without damaging the small-width photoresist. During the micro-etching process, a small amount of dilute sulfuric acid (such as 1% concentration) is introduced to effectively remove the oxide layer on the surface of the seed layer to prevent the part of the seed layer covered by the oxide layer from being electroplated. A thermometer is added to the spray liquid outlet to monitor the spray liquid temperature in real time to prevent the spray liquid from evaporating faster due to excessive temperature, resulting in a decrease in vacuum and poor pre-wetting effect.

[0024] (2) The pre-wetting method before electroplating of the present invention uses different initial vacuum degrees for different types of products. For products with deeper openings (such as pillar / solder products), the vacuum pressure value is generally set to a lower value (such as 25±5 torr), which can reduce the loss of kinetic energy of the spray liquid by the gas, so that the spray liquid can enter the deep hole more easily, so that the deep hole is completely filled with water. The subsequent entry into the electroplating cavity can quickly mix the plating liquid with the water in the deep hole, and the plating liquid is drained to the deep hole, thereby forming an electroplating loop. For products with smaller line spacing (such as RDL / WLCSP products), the vacuum pressure value is generally set to a higher value (such as 125±10 torr), which can effectively discharge the gas in the wire groove, so that the spray liquid can enter the wire groove more fully, and can appropriately increase the resistance of the gas to the spray liquid, thereby reducing the kinetic energy of the spray liquid when washing the photoresist at the small line width, and protecting the photoresist from damage;

[0025] (3) The pre-wetting method before electroplating of the present invention continuously sprays liquid during the pre-breaking of vacuum after a period of pre-wetting, so as to protect the humidity of the wafer surface and prevent the wafer from being unevenly coated with water film or even having no water film in some areas due to the long time or too fast nitrogen inflation speed when the wafer is in the state of high vacuum to the state of normal pressure, thereby causing the surface of the seed layer to be oxidized before electroplating.

[0026] Therefore, the pre-wetting method before electroplating of the present invention can effectively solve the requirements of different aspect ratios and different line widths for pre-wetting pressure through pre-wetting chamber pressure control, improve the pre-wetting effect before electroplating, and is beneficial to improving the bonding between the subsequent electroplating layer and the seed layer, and prevent damage to the photoresist, resulting in short circuits caused by interconnection of the electroplating layers, thereby improving the yield after electroplating. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Shown is a flow chart for an electroplating process.

[0028] Figure 2 Shown are components of the apparatus used in the pre-wetting method before electroplating of the present invention.

[0029] Figure 3 Shown is a process flow chart of the pre-wetting method before electroplating of the present invention.

[0030] Figure 4 Shown is a schematic diagram of the RDL structure distribution within the chip.

[0031] Figure 5 Shown is a schematic diagram of the pillar / solder bump structure distribution within the chip.

[0032] Figure 6 Shown is a flow chart of the pressure control of the pre-wetting spray liquid before electroplating.

[0033] Figure 7 Shown is the flow chart of vacuum pressure control in the pre-wetting chamber before electroplating.

[0034] Component number description

[0035] 1 Pre-wet the chamber

[0036] 2 Wafer

[0037] 3 Wafer stage

[0038] 4 Nozzles

[0039] 5 Liquid injection pipeline

[0040] 6 Air Inlet

[0041] 7 Vacuum port

[0042] 8 Rotation axes

[0043] 9 Pneumatic valve

[0044] 10 Vacuum pressure gauge

[0045] 11 Thermometer

[0046] 12. Pressure gauge

[0047] 13 Flow Meter

[0048] 14 Control valve

[0049] 15. PID control valve

[0050] 16 Deionized water

[0051] 17 Dilute sulfuric acid supply pipeline

[0052] 18 Dilute sulfuric acid

[0053] 19 Check valve

[0054] 20 Vacuum pipe

[0055] 21 Vacuum pump

[0056] 22 Gas-Liquid Separator

[0057] 23 Pneumatic valve

[0058] 24 Rewiring Layer

[0059] 24a, 24b Narrow pitch conductive lines

[0060] 25 Photoresist

[0061] 26 Bump

[0062] 27 Photoresist DETAILED DESCRIPTION

[0063] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0064] See also Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0065] In a pre-wetting method before advanced packaging electroplating (generally rack plating), the following steps are included: 1) manually adjusting a constant water spray pressure; 2) opening the nozzle pneumatic valve, the nozzle moves up and down in the vertical plane while the wafer does not move; 3) directly taking out the wafer after spraying, the water film thickness on different parts of the wafer surface is inconsistent (generally the top is thin or even has no water film, and the bottom water film is thicker or even dripping).

[0066] This method has the following disadvantages: 1) Non-vacuum pre-wetting, the presence of gas at the bottom of the product with a large aspect ratio makes it difficult for the pre-wetting liquid to enter the deep hole, resulting in insufficient pre-wetting (inadequate pre-wetting will result in the inability to form a plating circuit in the area after the wafer enters the plating solution because the viscosity of the plating solution is greater than that of deionized water, and the gas is sealed in the plating opening and cannot be discharged, so the area cannot be plated); 2) The constant pressure of the spray liquid is generally set to around 75PSI, for pillar / solder and large line spacing RDL / WLCSP products, but not for small line spacing products (because the lateral width of the photoresist of the small line spacing product is very narrow, it is very easy to be broken by the high-pressure spray liquid to form a coating short circuit); 3) The water film thickness on the wafer surface is inconsistent after pre-wetting, and a water-free film is easily formed on the top, resulting in oxidation of the seed layer, and dripping is easily formed at the bottom due to excessive water.

[0067] Another pre-wetting method before advanced packaging electroplating (generally cup plating) includes the following steps: 1) manually setting a constant vacuum pressure and spray liquid pressure; 2) when the vacuum pressure is reached, the wafer carrier starts to rotate, and when the rotation speed stabilizes, the spray liquid pneumatic valve is opened for spraying. The vacuum pressure is constant during this process; 3) after spraying, the excess deionized water on the surface is thrown out to form a layer of water film.

[0068] This method has the following disadvantages: 1) The spray liquid pressure is constant and is generally set to about 75PSI, which is suitable for pillar / solder and large line spacing RDL / WLCSP products, but not suitable for small line spacing products. If the pressure setting is reduced, the kinetic energy of the spray liquid will decrease, and it will be difficult for the spray liquid to enter the deep hole. It is not suitable for products with a large aspect ratio. During the process, the vacuum pressure of the chamber is constant and the vacuum degree is relatively high. After the pre-wetting is completed, it takes a long time for nitrogen to break the vacuum, which can easily dry the surface water film and cause the wafer surface to oxidize (in the process of transferring the wafer from the pre-wetting chamber to the electroplating chamber, the surface water film can effectively prevent the seed layer (such as the Cu seed layer) from contacting with the air and oxidizing); 2) The vacuum degree is constant. When the vacuum degree is too low, the air consumes too little kinetic energy of the spray liquid. When the spray liquid with a large kinetic energy impacts the photoresist on the small-pitch RDL / WLCSP product, the photoresist is damaged, causing the photoresist to break, thereby forming a short circuit after electroplating. The smaller the RDL / WLCSP line spacing, the greater the possibility of damage.

[0069] Therefore, the present invention improves the pre-wetting effect before electroplating through a new pre-wetting method before electroplating, improves the bonding between the electroplating layer and the seed layer, and prevents damage to the photoresist resulting in a short circuit caused by interconnection of the electroplating layers. The technical solution of the present invention is illustrated below through specific embodiments.

[0070] This embodiment provides a pre-wetting method before electroplating. As an example, please refer to Figure 1 , showing the process steps of the pre-wetting method before electroplating (referred to as pre-wetting in the figure) in the electroplating process, wherein the photolithography material step and plasma cleaning step are performed before the pre-wetting step, and the electroplating step, photoresist stripping step, seed layer removal step, and electrical test step are continued after the pre-wetting step, and the electroplated products that pass the test are finally shipped. Among them, before the electroplating step, a micro-etching step is further included. The micro-etching step can be integrated into the pre-wetting step and performed in the pre-wetting chamber, or it can be performed in the electroplating chamber.

[0071] As an example, see Figure 2 , shown as a component of the device used in the pre-wetting method before electroplating, including a pre-wetting chamber 1, a wafer carrier 3 located in the pre-wetting chamber 1 and used to carry a wafer 2, a nozzle 4 located in the pre-wetting chamber 1, a spray pipeline 5 for conveying spray liquid to the nozzle 4, an air inlet 6 and a vacuum port 7 arranged on the wall of the pre-wetting chamber 1, wherein a rotating shaft 8 is provided under the wafer carrier 3; a spray valve, such as a pneumatic valve 9, is provided on the spray pipeline 5 for controlling the nozzle 4 to start / stop spraying, and an air intake valve (not shown) is provided on the air intake pipeline of the air inlet 6.

[0072] As an example, the device further includes a vacuum pressure gauge 10 connected to the pre-wetting chamber 1, and the liquid spraying pipeline 5 is also provided with a thermometer 11, a pressure gauge 12, a flow meter 13, a regulating valve 14, and a PID control valve 15. The liquid spraying pipeline 5 is connected to a spraying liquid supply device. In this embodiment, the spraying liquid is deionized water 16 as an example, and the liquid spraying pipeline 5 is also connected to a dilute sulfuric acid supply pipeline 17 for supplying dilute sulfuric acid 18, and a one-way valve 19 is provided on the dilute sulfuric acid supply pipeline 17.

[0073] As an example, the vacuum port 7 is connected to a vacuum pump 21 via a vacuum pipeline 20 , and a gas-liquid separator 22 and a pneumatic valve 23 are also provided on the vacuum pipeline 20 .

[0074] As an example, see Figure 3 , which is a process flow chart of the pre-wetting method before electroplating, comprises the following steps:

[0075] S1: Configure the vacuum pressure value and spray liquid pressure value according to the product type.

[0076] Specifically, on the production line, due to different process requirements for different products, the electroplating procedures used in the electroplating process are also inconsistent (generally each model of product has a corresponding electroplating procedure). Therefore, it is particularly important to set corresponding parameter requirements in the electroplating procedure to achieve automatic adjustment of the machine hardware.

[0077] For RDL / WLCSP products, the photoresist thickness is generally 5-20 microns, most of which are linear to define conductive lines, and some areas are other shapes. For example, see Figure 4 , which is a schematic diagram of the RDL structure distribution in the chip, includes a rewiring layer 24 and a photoresist 25 located around the rewiring layer 24, wherein the rewiring layer 24 includes narrow-pitch conductive lines 24a and 24b.

[0078] For pillar / solder products, the photoresist thickness is generally 65-110 microns, and the holes are independently formed with a high depth-to-width ratio, which is used for electroplating to obtain bumps. For example, see Figure 5 , which is a schematic diagram showing the distribution of the pillar / solder bump structure in the chip, including a bump 26 and a photoresist 27 located around the bump 26 .

[0079] In this embodiment, when the product type includes RDL products or WLCSP products, the configured vacuum pressure value is relatively high, such as 120-130torr, and the configured spray liquid pressure value is relatively low, such as 8-12PSI (pressure unit, pounds-force / square inch). A higher vacuum pressure value represents a lower vacuum degree and more gas. Since the line groove is relatively shallow, a lower spray liquid pressure value can discharge the gas in the line groove without damaging the small-width photoresist. More gas in the cavity can appropriately increase the resistance of the gas to the spray liquid, reduce the kinetic energy of the spray liquid when flushing the photoresist at the small line width, and further protect the photoresist from damage. When the product type includes pillar products When using pillar products or solder products, the configured vacuum pressure value is relatively low, such as 20-30torr, and the configured spray liquid pressure value is relatively high, such as 70-75PSI. A lower vacuum pressure value means a higher vacuum degree and less gas. Since the openings of pillar products or solder products are deeper, a higher spray liquid pressure will not damage the photoresist and can effectively discharge the gas in the deep holes. Less gas in the cavity can reduce the loss of gas to the kinetic energy of the spray liquid, so that the spray liquid can enter the deep hole more easily, so that the deep hole is completely filled with water. The subsequent entry into the electroplating cavity can quickly mix the plating solution with the water in the deep hole, and the plating solution is drained to the deep hole, thereby forming an electroplating circuit.

[0080] As an example, the required vacuum pressure value and the required spray liquid pressure value are set through the electroplating procedure (specifically, it can be a pre-wetting procedure before electroplating in the electroplating procedure).

[0081] S2: Obtain the vacuum pressure value and the spray liquid pressure value, and control the vacuum pump to work according to the vacuum pressure value so that the vacuum pressure value is reached in the pre-wetting chamber, and control the hydraulic regulating device according to the spray liquid pressure value so that the liquid pressure in the spray pipeline reaches the spray liquid pressure value.

[0082] As an example, select the electroplating program that the product needs to call, automatically read the vacuum pressure value and spray liquid pressure value set by the electroplating program through the machine software, control the vacuum pump to evacuate the pre-wetting chamber so that the vacuum degree is within the set range, and control the PID (proportional integral differential controller) control feedback device to automatically adjust the pressure in the spray liquid pipeline so that the pressure is within the pre-set range of the pre-wetting program before electroplating. Among them, vacuuming can extract the air in the specific hole structure inside the wafer, and can reduce the loss of gas to the kinetic energy of the spray liquid, so that the deionized water can completely enter the specific structure in the subsequent spraying process, thereby achieving the effect of complete pre-wetting.

[0083] As an example, see Figure 6 , which is a flow chart of the pressure control of the pre-wetting spray liquid before electroplating, including the following steps:

[0084] (1) The electroplating process sets the required pressure;

[0085] (2) The software writes the required pressure to the PID;

[0086] (3) PID control valve controls the opening;

[0087] (4) The pressure gauge reads the pressure. If the pressure meets the requirements, proceed to step (5). If it is not within the set pressure range, return to step (2);

[0088] (5) Open the pneumatic valve;

[0089] (6) The rotatable nozzle starts working.

[0090] As an example, see Figure 7 , which is a flow chart of vacuum pressure control of the pre-wetting chamber before electroplating, including the following steps:

[0091] (1) The electroplating process requires vacuum pressure;

[0092] (2) The software writes the required pressure to the control module;

[0093] (3) Vacuum pumping;

[0094] (4) The pressure gauge reads the pressure. If the pressure meets the requirement, proceed to step (5). If the pressure does not meet the requirement, return to step (3);

[0095] (5) Start the pre-wetting process.

[0096] S3: driving the wafer stage to rotate at a preset speed and stopping vacuuming, wherein a wafer is placed on the wafer stage, and the wafer has a seed layer and a patterned photoresist layer on the seed layer;

[0097] Specifically, when the vacuum pressure value and the spray liquid pressure value meet the requirements, the wafer carrier is rotated at a specific speed (eg, 600 rpm) and the vacuum pneumatic valve is closed.

[0098] S4: opening the liquid spray valve of the liquid spray pipeline to spray and pre-wet the wafer for a preset time.

[0099] Specifically, when the wafer stage speed is stabilized, the liquid spray valve is opened, and at the same time, a rotatable nozzle connected to the liquid spray pipeline begins to rotate in a fan-shaped range at a preset speed (for example, back and forth every 3 seconds) to spray and pre-wet the wafer.

[0100] Before or during spraying, the temperature of the spray liquid is monitored by a thermometer. If the temperature of the spray liquid is higher than the preset temperature, the subsequent steps are stopped. This is because when the spray liquid is higher than a certain temperature, it will accelerate vaporization, affecting the vacuum degree of the pre-wetting chamber, thereby affecting the process. In this embodiment, when the deionized water temperature is monitored to be higher than 30 degrees Celsius, the machine will generate an alarm and will not perform subsequent actions.

[0101] As an example, the spray pre-wetting includes three stages. In the first stage, deionized water is sprayed to drive out the remaining gas in the electroplating opening and fill it with deionized water. In the second stage, dilute sulfuric acid is sprayed to remove the oxide layer on the surface of the seed layer. In the third stage, deionized water is continuously sprayed to rinse the dilute sulfuric acid on the wafer surface and in the opening and fill it with deionized water. In other words, the micro-etching step is integrated into the pre-wetting step.

[0102] As an example, the concentration of the dilute sulfuric acid is less than 2wt%. In this embodiment, dilute sulfuric acid with a concentration of about 1wt% that has been diluted in advance and cooled to room temperature is used (if the concentration is too high, more heat will be dissipated when diluted on the wafer surface). The spraying time of the second stage is less than the spraying time of the first stage, and less than the spraying time of the third stage. The spraying time of the third stage is greater than the total spraying time of the first stage and the second stage. For example, during the spraying process, 3 to 5 seconds of dilute sulfuric acid can be mixed in to micro-etch the seed layer to remove the oxide layer. If the total spraying time is 60s, dilute sulfuric acid can be mixed in the process of 10 to 15s, and only deionized water is sprayed for the rest of the time.

[0103] Of course, in other embodiments, the spray pre-wetting may also spray deionized water from beginning to end. After the wafer is subsequently transferred to the electroplating chamber, the oxide layer on the surface of the seed layer is first removed, and then electroplating is performed. In other words, the micro-etching step is performed in the electroplating chamber. Micro-etching in the electroplating chamber can be performed in the following manner: when the electroplating chamber is not powered on, the wafer is kept rotating at a certain speed for a period of time (for example, 30-60 seconds), and the oxide layer is removed by using the acidity in the plating solution. Of course, if the plating solution is a non-acidic plating solution, the micro-etching step must be performed in the pre-wetting chamber.

[0104] As an example, after closing the liquid spray valve to stop spraying, the wafer carrier maintains a rotating state to throw away excess spray liquid on the wafer surface until a protective liquid film of a preset thickness is formed on the wafer surface, and then the wafer carrier stops rotating.

[0105] S5: Open the air inlet valve to introduce gas into the pre-wetting chamber until the pre-wetting chamber reaches a preset air pressure value.

[0106] As an example, the nitrogen pneumatic valve is opened to smoothly break the vacuum in the pre-wetting chamber, and the preset air pressure value is normal pressure.

[0107] It should be pointed out that, since it takes a long time for the pre-wetting chamber to change from a high vacuum state to a normal pressure state, or because the nitrogen gas filling speed is too fast, it is easy to cause uneven water film on the wafer surface or even no water film in some areas, which causes the wafer surface to be oxidized before electroplating. Therefore, in this embodiment, before the first air pressure value is reached in the pre-wetting chamber, the liquid spray pipeline maintains a spraying state (in this case, the liquid spray valve in the above step S4 does not need to be closed) to protect the humidity of the wafer surface and prevent the moisture on the wafer surface from being blown dry; after the first air pressure value is reached in the pre-wetting chamber, the liquid spray valve is closed to stop spraying and the air inlet valve is closed to stop ventilation, and after the liquid spray valve is closed to stop spraying, the wafer carrier maintains a rotating state to throw out the excess spray liquid on the wafer surface until a protective liquid film of a preset thickness is formed on the wafer surface, and then the wafer carrier stops rotating.

[0108] Specifically, the first air pressure value is less than the preset air pressure value, for example, about 400 torr. After the wafer stage stops rotating, the air inlet valve is opened again to fill nitrogen until the pre-wetting chamber reaches normal pressure, then the chamber is opened to take out the wafer to complete pre-wetting.

[0109] As an example, during the inflation process, the gas flow rate is controlled to fill slowly at a rate of 30 torr / second to prevent the water film from being damaged.

[0110] S6: transferring the wafer into the electroplating chamber.

[0111] At this point, the pre-wetting process before electroplating is completed and the subsequent electroplating process can be carried out.

[0112] In summary, the pre-wetting method before electroplating of the present invention can effectively solve the requirements of different aspect ratios and different line widths for pre-wetting pressure through pre-wetting chamber pressure control, improve the pre-wetting effect before electroplating, and is beneficial to improving the bonding between the subsequent electroplating layer and the seed layer, and prevent damage to the photoresist, resulting in short circuits caused by interconnection of the electroplating layers, thereby improving the yield after electroplating.

[0113] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A pre-wetting method before electroplating, characterized in that: The following steps are involved: Configure vacuum pressure value and spray liquid pressure value according to product type; Obtaining the vacuum pressure value and the spray liquid pressure value, and controlling the vacuum pump to work according to the vacuum pressure value so that the vacuum pressure value is reached in the pre-wetting chamber, and controlling the hydraulic regulating device according to the spray liquid pressure value so that the liquid pressure in the spray liquid pipeline reaches the spray liquid pressure value; Driving the wafer stage to rotate at a preset speed and stopping vacuuming, wherein a wafer is placed on the wafer stage, and the wafer has a seed layer and a patterned photoresist layer on the seed layer; Opening the liquid spray valve of the liquid spray pipeline to spray and pre-wet the wafer for a preset time; Open the air inlet valve to introduce gas into the pre-wetting chamber until the pre-wetting chamber reaches a preset air pressure value; transferring the wafer into an electroplating chamber; Among them, in the step of introducing gas into the pre-wetting chamber until a preset air pressure value is reached in the pre-wetting chamber, before a first air pressure value is reached in the pre-wetting chamber, the liquid spray pipeline maintains a spraying state, and the first air pressure value is less than the preset air pressure value; after the first air pressure value is reached in the pre-wetting chamber, the liquid spray valve is closed to stop spraying.

2. The pre-wetting method before electroplating according to claim 1, characterized in that: After closing the liquid spray valve to stop spraying, the wafer carrier maintains a rotating state to throw away excess spray liquid on the wafer surface until a protective liquid film of a preset thickness is formed on the wafer surface, and then the wafer carrier stops rotating.

3. The pre-wetting method before electroplating according to claim 2, characterized in that: After the first air pressure value is reached in the pre-wetting chamber, the air inlet valve is closed to stop ventilation, and after the wafer carrier stops rotating, the air inlet valve is opened again until the preset air pressure value is reached in the pre-wetting chamber.

4. The pre-wetting method before electroplating according to claim 1, characterized in that: The spray pre-wetting includes three stages. Deionized water is sprayed in the first stage and the third stage, and dilute sulfuric acid is sprayed in the second stage to remove the oxide layer on the surface of the seed layer.

5. The pre-wetting method before electroplating according to claim 4, characterized in that: The spraying time of the second stage is shorter than the spraying time of the first stage, and shorter than the spraying time of the third stage.

6. The pre-wetting method before electroplating according to claim 4, characterized in that: The spraying time of the third stage is greater than the total spraying time of the first stage and the second stage.

7. The pre-wetting method before electroplating according to claim 1, characterized in that: After the wafer is transferred into the electroplating chamber, the oxide layer on the surface of the seed layer is removed first, and then electroplating is performed.

8. The pre-wetting method before electroplating according to claim 1, characterized in that: Before or during spraying, the temperature of the spray liquid is monitored. If the temperature of the spray liquid is higher than a preset temperature, subsequent steps are stopped.

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