WET PROCESSING DEVICE WITH GAS-LIQUID MIXING

Description

TECHNICAL FIELD

The present disclosure relates to an apparatus for wet chemical processing.

BACKGROUND

Wet processes, also known as wet chemical processes, play a crucial role in various stages of semiconductor device fabrication. These processes involve actions like etching, plating, cleaning, and other treatments where a wafer or substrate is immersed in a chemical solution. During certain wet processing steps, such as electroless copper deposition, cleaning, or etching, gas is introduced at the bottom of the processing tank. The gas, discharged through multiple holes, forms bubbles that rise through the chemical solution and between the substrates—such as wafers, panels, or devices—positioned within the tank for processing.

These bubbles serve several functions. For instance, during plating, chemical reactions can produce byproducts, such as hydrogen bubbles, on the substrate surface. These byproducts hinder the chemical solution's access to certain areas, thereby negatively affecting film growth. Gas introduced at the bottom of the tank forms bubbles that help deliver oxygen or neutral gases to the substrate surface, dislodge reaction byproducts, or create pressure waves that drive flow into crevices or vias on the substrate. Additionally, the gas injection transfers momentum to the liquid flow, facilitating the transport of byproducts and precursors away from the substrate's boundary layer. This action introduces a level of randomness, akin to turbulence, within the chemical solution, enhancing the efficiency of wet processing. The rising bubbles create pressure waves and pulsations that disrupt the boundary layer on substrate surfaces and promote further mixing of the liquid near these surfaces.

Gas delivery in wet processing tanks therefore optimizes these chemical processes. Traditionally, spargers or sparger pipes are used to inject gas into the tank. However, such systems require additional space under the substrate basket for gas distribution pipes, which can pose challenges in tanks designed with laminar flow plates for directing chemical solutions. Positioning sparger pipes between the laminar flow plate and the substrates may obstruct the chemical solution's flow to the substrates, creating inefficiencies. The apparatus and methods presented in this disclosure aim to address these limitations. Nonetheless, the scope of the current disclosure is determined by its claims rather than its potential to resolve specific problems.

SUMMARY

Embodiments of an apparatus for wet chemical processing of substrates and related methods are disclosed.

In one embodiment, an apparatus for wet chemical processing of a plurality of substrates is disclosed. The apparatus comprises a processing tank configured to support the plurality of substrates. The apparatus may also include a flow plate disposed in the processing tank such that, when the plurality of substrates are supported in the processing tank, the flow plate is positioned below the plurality of substrates. The flow plate may include a plurality of orifices configured to discharge a liquid solution having a dispersion of gas bubbles therein towards the plurality of substrates.

In another embodiment, a method of wet chemical processing a plurality of substrates is disclosed. The method comprises positioning a plurality of substrates in a processing tank and directing a liquid solution having a dispersion of gas bubbles therein through a plurality of orifices of a flow plate positioned below the plurality of substrates. The method may also include conveying the liquid solution exiting the processing tank to a cavitation device, and replenishing the liquid solution with gas bubbles in the cavitation device. The method may further include recirculating the replenished liquid solution to the processing tank through the plurality of orifices of the flow plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, are used to explain the disclosed principles. In these drawings, where appropriate, reference numerals that illustrate the same or similar structures, components, materials, and/or elements in different figures are labeled similarly. It is understood that various combinations of the structures, components, and/or elements, other than those specifically shown, are contemplated and are within the scope of the present disclosure.

To ensure simplicity and clarity, the figures illustrate the general structure of the various described embodiments, omitting details of well-known components or features to prevent obscuring other key aspects. These omitted elements are familiar to those with ordinary skill in the art. Additionally, the features in the figures are not necessarily drawn to scale. Some dimensions may be exaggerated relative to others to enhance the understanding of the exemplary embodiments. It is understood by those skilled in the art that the figures should not be interpreted as accurately representing dimensions or proportional relationships unless explicitly stated otherwise. Furthermore, aspects described in relation to one embodiment or figure may also apply to and be used with other embodiments or figures, even if not explicitly mentioned.

FIG. 1 is a schematic illustration of an exemplary wet chemical processing apparatus of the current disclosure.

FIG. 2 is a schematic illustration of a portion of a flow plate of an exemplary apparatus, consistent with some embodiments of the current disclosure.

FIGS. 3A-3B are schematic illustrations of orifices on a flow plate, consistent with some embodiments of the current disclosure.

FIGS. 4A-4B are schematic illustrations of patterns of orifices on a flow plate, consistent with some embodiments of the current disclosure.

FIG. 5 is a schematic illustration of an orifice pattern, consistent with some embodiments of the current disclosure.

FIG. 6 is a flow chart illustrating an exemplary method of using the apparatus of FIG. 1.

DETAILED DESCRIPTION

Relative terms like “approximately,” “about,” “substantially,” etc. are used to accommodate practical or real-world variations in specified parameters. For instance, describing the dimension of a component (or a gap) as “about 10 mm” means that the dimension may not be exactly 10 mm due to practical factors such as manufacturing tolerances, tolerance stackups, or variations caused by environmental factors like temperature and pressure. In some cases, the context provided within the specification (e.g., figures or descriptions) may clarify the intended scope of the relative term. If it is not clear from the specification, all relative terms (such as “about,” “substantially,” “approximately,” etc.) indicate a possible variation of ±10% (unless noted otherwise or another degree of variation is specified). For example, a feature disclosed as being about “t” units wide (or length, thickness, depth, etc.) may vary in width from (t−0.1t) to (t+0.1t) units. As another example, a structure described as being substantially linear may deviate by ±10% from being linear. Further, a range described as varying from, or between, 5 to 10 (5-10), includes the endpoints (i.e., 5 and 10).

Unless otherwise defined, all terms of art, notations, and other scientific terms or terminology used herein have the same meaning as commonly understood by persons of ordinary skill in the art to which this disclosure belongs. Some components, structures, and/or processes described or referenced herein are well understood and commonly employed using conventional methodology by those skilled in the art. These components, structures, and processes will not be described in detail. All patents, applications, published applications and other publications referred to herein as being incorporated by reference are incorporated by reference in their entirety. If a definition or description set forth in this disclosure is contrary to, or otherwise inconsistent with, a definition and/or description in these references, the definition and/or description set forth in this disclosure controls over those in references incorporated by reference. None of the references described or referenced herein is admitted as prior art relative to the current disclosure.

As used herein, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a component can comprise A or B, then, unless specifically stated otherwise or infeasible, the component can comprise A, or B, or A and B. As a second example, if it is stated that a component can comprise A, B, or C, then, unless specifically stated otherwise or infeasible, the component can comprise A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent an exhaustive set of implementations. Instead, they are merely examples of apparatuses, systems, and methods consistent with aspects related to subject matter that may be recited in the appended claims. For example, although some embodiments are described in the context of a wet processing apparatus for electroless plating, the present disclosure is not so limited. Unless infeasible, embodiments described herein can be implemented in any type of wet processing apparatus (etching, cleaning, etc.).

As mentioned previously, the term “substrate” is used to generally refer to parts, such as, for example, wafers, panels, IC device(s), printed circuit boards (PCBs), semiconductor packages, etc. that may be subject to some type of wet chemical processing, for example, during fabrication. In the discussion below, some aspects of the current disclosure will be described with reference to a processing bath or tank used for electroless copper plating. However, as previously explained, this is only exemplary and embodiments of the current disclosure may be used with any wet chemical processing apparatus.

The following discussion outlines an exemplary apparatus and method for wet chemical processing, such as electroless copper plating of a substrate. However, this example is not limiting, as the principles described are broadly applicable to any type of wet chemical processing. Wet chemical processing serves various purposes, including material removal (wet etching), material deposition (plating, electroplating, etc.), substrate cleaning, and creating surface patterns through optical lithography techniques, all of which are useful in the fabrication of semiconductor and photonic devices.

Electroless copper plating is a chemical process that deposits an even layer of copper on the surface of a solid substrate, like glass, metal or plastic. The process may involve dipping one or more substrates in a water solution containing copper salts and a reducing agent such as formaldehyde. Unlike electroplating, electroless plating processes in general do not require passing an electric current through the bath and the substrate. The reduction of the metal cations in solution is achieved by purely chemical means, through an autocatalytic reaction.

FIG. 1 is a schematic illustration of an exemplary electroless plating (or another wet processing) apparatus 100 of the current disclosure. A plurality of substrates 50 may be disposed in an electroless plating solution 30 in a plating tank 40 of apparatus 100. In general, at least the portion of the substrates 50 that are to be plated may be submerged in solution 30. Typically, adjacent substrates of the plurality of substrates 50 may be spaced apart to allow the solution 30 to flow between the spaces and treat the exposed surfaces of the substrates 50. During operation, the plating solution in tank 40 may be removed from tank 40 through an outlet 32. In some embodiments, the removed plating solution may be treated (e.g., cleaned, filtered, etc.) and returned to tank 40 through a flow plate 10 as discussed below.

The composition of solution 30 in tank 40 varies depending on the application. For example, in some embodiments of electroless copper plating, solution 30 may consist of a water-based solution containing copper salts and a reducing agent such as formaldehyde. However, this specific composition is not mandatory, and any currently known or future plating solution may serve as solution 30. In cases where tank 40 is utilized for other processes, such as etching or cleaning, solution 30 may be a reagent appropriate for that specific application.

Regardless of the reagent type, solution 30 in embodiments of this disclosure is a suspension or dispersion containing bubbles (e.g., microbubbles or nanobubbles) of a gas dispersed within the reagent. For instance, when applied to electroless copper plating, as shown in FIG. 2, solution 30 may include a reagent 34 (e.g., a water solution with copper salts and a reducing agent) along with dispersed gas bubbles 36 (e.g., nitrogen, clean dry air or CDA, carbon dioxide, an inert gas, etc.). Similarly, when used for cleaning, solution 30 may consist of a reagent (e.g., water) with bubbles of gas (e.g., CDA) dispersed within it.).

Using a plating solution with dispersed gas bubbles offers several advantages over traditional solutions without them. The presence of the gas bubbles enhances the uniformity of the coating by promoting better agitation, which ensures even distribution of metal ions across the substrate, especially in complex or recessed areas. The bubbles also help activate the surface by removing impurities and oxides, improving adhesion and overall coating quality. They can reduce hydrogen embrittlement, a common issue in plating processes, by efficiently removing hydrogen gas from the substrate. Additionally, the gas bubbles enhance the penetration of the plating solution into narrow channels and intricate structures, ensuring complete and consistent coverage. This agitation effect minimizes defects like pits or voids, resulting in smoother finishes, and improves mass transport, accelerating deposition rates and increasing plating efficiency. Furthermore, the gas bubbles aid in dissipating heat, maintaining stable operating conditions and potentially reducing the need for additives, which lowers costs and environmental impact. Overall, the use of gas bubbles in plating solutions leads to higher-quality coatings, greater efficiency, and a more sustainable process.

Typically, the gas bubbles 36 are evenly dispersed throughout the liquid reagent 34. These gas bubbles 36 may be microbubbles or nanobubbles. Microbubbles typically range from about 1 mm to about 1 micron in diameter, and nanobubbles are below 1 micron or below 900 nanometers (or 0.9 microns) in diameter. Microbubbles are small but may be visible to the naked eye, while nanobubbles are usually invisible to the naked eye. These gas bubbles are significantly smaller than those found in traditional foams, resulting in a cloudy or milky appearance due to light scattering. In some cases, the suspension's (e.g., solution 30) stability may be enhanced by surfactants, proteins, or polymers, which prevent the bubbles from coalescing or bursting. With a high surface area-to-volume ratio, such a solution 30 exhibits distinct physical properties, including reduced density and enhanced buoyancy compared to the pure liquid.

For example, the presence of gas bubbles alters the physical properties of the solution. The density may slightly decrease due to the gas phase, while viscosity can increase depending on the concentration and size of the bubbles. Surface tension is typically reduced by surfactants, enhancing bubble stability and dispersion. Optically, the solution may appear turbid or milky as light scatters off the dispersed bubbles. The solution 30 may operate within a specific temperature range optimized for the plating processes. These characteristics collectively contribute to the efficiency of the plating process by improving surface wetting, promoting uniform chemical reactions, and aiding in the removal of byproducts.

In some applications, the solution 30 in tank 40 (or directed to tank 40) may also be heated (or cooled) to a desired temperature. Heaters and coolers (not shown) may be used to heat or cool the solution 30. Although not shown in FIG. 1, in addition to plating tank 40, apparatus 100 may include other baths or tanks, such as for example, a pre-plating treatment bath, a collecting bath, and a rinsing bath, configured to perform different steps in the plating process. In some embodiments, the plurality of substrates 50 may move from one bath to another on, for example, rails.

Tank 40 may include an integrated flow plate 10 disposed in the solution 30. In some embodiments, as illustrated in FIG. 1, flow plate 10 may be positioned below the plurality of substrates 50 in tank 40. In some embodiments, flow plate 10 may be positioned on (e.g., coupled to, attached to, etc.) the underside of the tank 40 such that flow plate 10 forms the base of tank 40. As illustrated in FIG. 2, flow plate 10 may include orifices or orifices 20 configured to direct the solution 30 into the plating tank 40. Although not a requirement, in some embodiments, these perforations may be positioned on the top surface of the flow plate 10 that faces the plurality of substrates 50 in the tank. In some embodiments, the flow plate 10 may be configured to direct the solution 30 over an entire area of the substrates 50 in tank 40. In some embodiments, flow plate 10 may be configured to direct the solution 30 over the entire area of the base of the tank.

In general, the orifices 20 on the flow plate 10 may have any size and shape. Although not a requirement, in some embodiments, the orifices 20 may be circular and have a diameter between about 0.02 inches to 0.1 (or 0.005-0.2) inches. In some embodiments, the diameter of the orifices 20 may be adjusted, e.g., between 0.02-0.1 (or 0.005-0.2) inches. Circular orifices 20 are only exemplary, and in general, the orifices 20 may have any shape (e.g., square, rectangular, elliptical, etc.). Adjusting the size of the orifices 20 may allow flexibility in tailoring flow dynamics to specific process requirements. The size of the orifices 20 can be adjusted or varied by any method known in the art. For example, a flow plate 10 with pre-defined orifice sizes may be fabricated, and the size of the orifices 20 may be adjusted to suit a particular application by using inserts or fittings with variable-sized openings. For example, the inserts can be swapped out or adjusted to achieve the desired diameter. Another embodiment may employ flexible or deformable materials for the flow plate 10, such that the size of the orifices 20 can be modified by applying external pressure or tension. For instance, elastomeric plates can be designed with pre-formed orifices that expand or contract under mechanical or pneumatic adjustment. Additionally, multi-layer plates with aligned apertures can offer tunable orifice sizes by sliding the layers relative to each other, effectively changing the overlap area. Some embodiments may employ electronically actuated mechanisms, such as micro-valves or shape-memory materials, to dynamically adjust the orifice size during operation. Each approach offers distinct advantages, depending on the application, such as ease of customization, cost-effectiveness, or precision in controlling fluid dynamics.

The lower-density solution 30 (containing the gas bubbles 36) exiting the orifices 20 rises up through the space between the substrates 50 in the tank 40. The flow around the rising bubbles, and the flow in the space between the substrates 50, may be laminar. The rising bubbles may however push the liquid in different directions and create pressure waves and pulsations that may disrupt the boundary layer (on the substrate surfaces) and create additional mixing of the liquid in the space between the substrates 50. In an electroless process, these pressure waves may assist in dislodging bubbles of hydrogen that form on the surface of the substrates due to the electroless process. In some cases, the gas bubbles 36 may grow in size as they rise to the surface. In some cases, some of the bubbles 36 may separate from the reagent 34 and escape from the solution in the tank 40.

The spent solution 30 (e.g., the reagent 34 with any residual bubbles 36 dispersed therein) exiting the tank 40 through outlet 32 may be pumped (by a recirculating pump 60) to a cavitation device 70 that is configured to replenish the solution 30 with gas bubbles 36. The cavitation device 70 is designed to mix the spent liquid reagent 34 from the tank 40 with a gas 38 to produce the solution 30 containing a fine dispersion the gas 38 as gas bubbles 36 in the reagent 34. Cavitation device 70 may be any type of device (commercially available, specially created, etc.) configured to mix the gas 38 in the reagent 34 and produce solution 30.

For example, cavitation device 70 may create a liquid solution with finely dispersed gas bubbles through a process called hydrodynamic cavitation. In this method, the liquid solution is rapidly passed through a chamber where it experiences drastic pressure fluctuations. These pressure changes create cavities or bubbles in the liquid. As the bubbles collapse, they generate intense local energy, which helps to break down the gas bubbles into extremely fine bubbles, often at the micro or nano scale. These small gas bubbles are evenly dispersed throughout the liquid solution.

Although not a requirement, in some embodiments, cavitation device 70 may consist of a mixing chamber where the liquid reagent 34 and the gas 38 are introduced through separate inlets. The liquid reagent 34 may flow into the chamber through a primary inlet 72 under pressure, while the gas 38 may enter through a secondary inlet 74. Although not shown in FIG. 1, cavitation device 70 may be equipped with flow regulators, valves, and other devices, to control the liquid and gas flow rate.

Within the mixing chamber of the cavitation device 70, the reagent 34 may be subjected to rapid changes in pressure, generated by components such as a high-speed rotor, ultrasonic transducers, or specially designed flow constrictions like venturi nozzles or orifice plates. These pressure variations induce cavitation, causing the gas to break into microbubbles or nanobubbles that disperse uniformly throughout the liquid reagent. As the cavitation bubbles collapse, they create intense local mixing and enhance the dissolution and dispersion of the gas into the liquid. The resulting solution 30 is a suspension or dispersion of gas bubbles 36 finely distributed in the liquid reagent 34. The solution 30 from the cavitation device 70 may be directed into the tank 40 through the flow plate 10. In some embodiments, agitation in the tank 40 resulting from the recirculating solution 30 may be controlled by modulating the flow of the gas 38 and the reagent 34 in the cavitation device 70 independently.

In some embodiments, as schematically illustrated in FIG. 3A, the orifices 20 on flow plate 10 may be arranged in a square (or a rectangular) grid. However, this is not a requirement, and as illustrated in FIG. 3B, the perforations may be arranged in any pattern. As illustrated in FIGS. 3A and 3B, in general, the orifices 20 may be arranged in linear arrays that extend in the same direction as the substrates 50 in tank 40 (or the length direction of tank 40). In some embodiments, the linear arrays may extend in the width direction of tank 40. With reference to FIG. 3A, the pitch (P_x and P_y) between the orifices 20 may be any value. In some embodiments, P_x and P_y may be approximately the same (e.g., P_x≈P_y). Although not a requirement, in some embodiments, P_x may be between about 0.1-0.5 (or 0.2-2.0) inch, and P_y may be between about 0.1-0.5 (or 0.1-1.0) inch. In some embodiments, the pitch between the orifices 20 may be selected based on the pitch of (or spacing between) the substrates 50 in tank 40. For example, the pitch between orifices 30 may be about (1/N) times the pitch of substrates 50 in tank 40 (or substrate pitch), where N≥1. In some embodiments, the substrate pitch may be between about 10-25 mm (about 0.39-0.98 inches).

In some embodiments, the horizontal pitch (P_x) or the vertical pitch (P_y) of the orifices 20 may be adjustable such that they may be varied (e.g., between about 0.1-0.5 (or 0.1-1.0) inch). The pitch may be varied by any known method. For example, in some embodiments, the pitch between the orifices 20 may be adjusted using mechanical actuators, such as motors or pneumatic/hydraulic systems. For example, actuators may be used to physically move the orifices 20 or the plate itself, allowing precise adjustments. In some embodiments, piezoelectric devices, which change the shape, size, or spacing between orifices 20 in response to an applied electric voltage. Shape memory alloys may be employed in some embodiments to electronically alter the shape, size, and spacing between orifices 20. In some embodiments, microfluidic valves may control the flow and spacing between orifices 20. Swappable inserts, deformable plates, sliding plates, etc. may also be used in some embodiments. The approach employed may depend on the application (e.g., levels of precision required, cost, etc.).

In general, the orifices 20 may be arranged in any pattern on flow plate 10. For example, in some embodiments, orifices 20 may be arranged such that exiting solution 30 is concentrated on the side of the substrates 50 where the desired processing occurs. For example, if tank 40 is used for a copper electroless deposition process to deposit copper on one side of the substrates 50, the orifices 20 may be arranged such that the solution 30 that exits the orifices 20 is concentrated on the side of the substrate 50 where copper deposition is desired. For example, the gas-filled solution 30 exiting the orifices 20 rise through the space between the substrates 50 with minimal obstruction by the substrates 50.

In some embodiments, as depicted in FIG. 4A, the orifices 20 on flow plate 10 can be arranged as nested quadrangles or rectangles to form different zones A-D that can be independently tuned. This means that the flow rate of the solution 30 entering tank 40 through zones A, B, C, and D can be varied independently. This arrangement of orifices 20 in nested quadrangles is merely an example, and the orifices can be grouped in any pattern. For instance, in another embodiment shown in FIG. 4B, a rectangular array of orifices 20 can be grouped into different zones A-D, and the flow rate of the solution entering through these zones can be independently controlled.

With reference to FIG. 5, in some embodiments, the size or spacing of the orifices 20 can be adjusted to ensure that the flow rate of the solution 30 exiting the orifices in the region (marked P) under the substrates 50, or a basket carrying the substrates, differs from the regions outside (marked Q, R, S, T). For example, the orifices 20 in region P may be larger or smaller than those in the other regions (e.g., Q, R, S, T). Additionally, or alternatively, the orifices 20 in region P can be spaced closer together or further apart compared to those in regions Q, R, S, T. In some embodiments, the size or spacing of the orifices in regions Q, R, S, T may be identical and different from that in region P, or they may all vary. By using differently sized or spaced orifices 20 in regions P, Q, R, S, and T, the flow rate of the solution 30 entering the tank 40 through these regions can be independently controlled. It is also contemplated that, in some embodiments, orifices may only be present in region P.

Flow plate 10 may optionally include temperature control (e.g., one or more heaters) so that the solution 30 may be heated to predetermined temperatures before directed into tank 40. The size of flow plate 10 may depend on the application (e.g., the size of tank 40, size of substrates 50, number of substrates 50, etc.). In one exemplary embodiment, twelve (12) substrates spaced apart by between about 10 mm-25 mm (about 0.39-0.98 inches), with each substrate having a size of about 510 mm×515 mm (about 20.07×20.27 inches) may be positioned in a tank having a length of about 27 inches, a width of about 15 inches, and a height of about 24 inches. In such an embodiment, flow plate 20 may have a size substantially equal to (or slightly smaller than) the size of the tank 40. In other words, flow plate 10 may have a length slightly less than 27 inches and a width slightly less than 15 inches so the flow plate 10 may be snugly received in tank 40.

In some embodiments, flow plate 10 may form the base of tank 40. Flow plate 10 may have any thickness. In some embodiments, the thickness of flow plate 10 may be between about 0.5-4.0 inches. It should be noted that a rectangular flow plate is merely exemplary. In general, flow plate 10 may have any shape. In some embodiments, the shape of flow plate 10 may depend on the shape of the tank of the wet processing apparatus. Flow plate 10 may be constructed of any suitable material such as, for example, Teflon, Perfluoroalkoxy alkanes (PFA), polypropylene, high density polyethylene (HDPE), or another suitable metal such as stainless steel, titanium etc.

FIG. 6 is a flow chart of an exemplary process 200 of using a disclosed wet processing apparatus 100. One or more substrates 50 may be disposed in a tank 40 of the wet processing apparatus containing a solution 30 comprising gas bubbles 36 dispersed in a liquid reagent 34. (Step 210). As explained previously, the type of solution 30 depends on the application. In some embodiments, the one or more substrates 50 may be at least partially submerged in the solution 30 in the tank. In some embodiments, a plurality of substrates 50 may be spaced apart from each other at a pitch (constant or variable pitch) and disposed in the tank 40. The substrates 50 may be spaced apart such that adjacent substrates 50 are spaced apart from each other.

A stream of the solution 30 (with gas bubbles 36 dispersed in a liquid reagent 34) may be directed into the tank through a plurality of orifices 20 on a flow plate 10 positioned below the substrates 50 in the tank 40. (Step 220). In some embodiments, the solution 30 may be directed from the flow plate 10 towards the substrates 50. For example, the orifices 20 may be positioned on a surface of the flow plate 10 that faces the substrates 50 (e.g., the top surface of the flow plate 10) such that the solution 30 exiting the flow plate 10 is directed towards the substrates 50. In some embodiments, the flow rate of the solution 30 exiting the orifices 20 in all regions of the flow plate 10 may be a constant over time. In some embodiments, the flow rate of the solution 30 exiting the flow plate 10 through different zones of the flow plate 10 may be independently varied. In some embodiments, the solution 30 may be directed into the tank 40 through the flow plate (i.e., step 220) in a pulsating manner. As used herein, a pulsating or oscillating flow (as opposed to a constant flow) refers to a flow of the solution 30 into the tank 40 with periodic variations in the flow rate of the solution 30. The flow rate may oscillate in a rhythmic or a random manner.

After passing through the spaces between the substrates 50, the spent solution from the tank 40 may be directed to a cavitation device 70 (Step 230). In some embodiments, a recirculating pump 60 may be used to transfer the spent solution 30 from the tank 40 to the cavitation device 70. The cavitation device 70 rejuvenates the spent solution 30 by adding gas bubbles 36, preparing it for continued processing in tank 40 (Step 240). During this step, the cavitation device 70 mixes the spent solution 30 from the tank 40 with a gas 38, producing a solution containing a fine dispersion of gas bubbles 36 in the reagent 34. The rejuvenated solution 30 is then recirculated back into tank 40 through the orifices 20 in the flow plate 10 (Step 250).

Discharging the solution 30, containing finely dispersed gas bubbles 36, into the tank 40 through the flow plate 10 located below the substrates 50 disrupts the boundary layer on the substrates'surfaces and enhances their processing. This method, known as process 200, can be applied to any wet chemical process such as electroless plating, etching, or cleaning. The specific type of solution 30, including the reagent 34 and gas bubbles 36, will depend on the application of process 200, whether it is electroless plating, etching, or cleaning.

Wet chemical processes, such as electroless copper plating, are limited by mass transfer (or kinetic transport). At low deposition rates, copper at the interface between the plating solution and the substrate surface can be replenished through diffusion. However, as deposition rates surpass diffusion rates, the deposition rate may decrease and even drop to zero. This issue is particularly problematic when plating narrow features with a high aspect ratio, as the geometry of the structure hinders plating solution replenishment. The disclosed flow plate directs a solution 30 with a fine dispersion of microscopic or nanoscopic gas bubbles, creating a uniform random or turbulent flow throughout the tank 40. This enables the replenishment of the plating solution 30 on all areas of the substrate surface, thereby improving the plating process.

In some embodiments, an apparatus crafted for wet chemical processing of multiple substrates is disclosed. The apparatus comprises a processing tank, designed to accommodate and support the substrates. Within this tank, a strategically positioned flow plate is located beneath the substrates when they are in place. This flow plate is equipped with a multitude of orifices that are precisely engineered to discharge a liquid solution infused with a fine dispersion of gas bubbles. The purpose of these gas bubbles is to enhance the interaction between the liquid solution and the substrate surfaces, thereby improving the efficiency and effectiveness of the wet chemical processes, such as plating, etching, or cleaning. The design ensures a uniform distribution of the solution across all substrate areas, optimizing the overall processing performance.

A method for wet chemical processing of a plurality of substrates is also disclosed. The method involves several steps. First, the substrates are positioned within a processing tank specifically designed to accommodate them. Then, a liquid solution infused with finely dispersed gas bubbles is directed through a series of orifices in a flow plate located beneath the substrates. After passing through the substrates, the liquid solution exits the tank and is conveyed to a cavitation device. In this device, the solution is replenished with gas bubbles, rejuvenating it for further processing. Finally, the replenished solution is recirculated back into the processing tank through the flow plate's orifices, ensuring continuous and effective wet chemical processing of the substrates.

Although the current disclosure is described with reference to a wet processing apparatus for electroless plating, this is only exemplary. Persons of ordinary skill in the art would recognize that the disclosed apparatus can be used for any wet processing application. Furthermore, although some features were disclosed with reference to specific embodiments, a person skilled in the art would recognize that this is only exemplary, and the features are applicable to all disclosed embodiments. Other embodiments of the apparatus, its features and components, and related methods will be apparent to those skilled in the art from consideration of the disclosure herein.