CN114369816A

CN114369816A - Chemical plating tank, chemical plating system and chemical plating method

Info

Publication number: CN114369816A
Application number: CN202011101458.8A
Authority: CN
Inventors: 邱咏达; 王秀枝; 江俊纬; 唐心陆; 洪志斌
Original assignee: Advanced Semiconductor Engineering Inc
Current assignee: Advanced Semiconductor Engineering Inc
Priority date: 2020-10-15
Filing date: 2020-10-15
Publication date: 2022-04-19

Abstract

An electroless plating bath, an electroless plating system including the same, and an electroless plating method using the same are provided. The chemical plating bath comprises a bath body and a rotatable bearing disc positioned in the bath body.

Description

Chemical plating tank, chemical plating system and chemical plating method

Technical Field

The application relates to an electroless plating bath, an electroless plating system and an electroless plating method.

Background

In order to provide more functions, a technology of incorporating two or more semiconductor substrates in a semiconductor substrate package is currently developed. In this technique, a semiconductor substrate may be stacked on another semiconductor substrate, and in order to communicate signals of the two semiconductor substrates with each other, a bonding structure must be prepared between the two semiconductor substrates so that the two semiconductor substrates are electrically connected to each other. It is desirable to prepare a good bonding structure that allows the semiconductor substrate package to function and at the same time achieves the goal of miniaturization of the semiconductor substrate package.

Disclosure of Invention

In some embodiments, the present application provides an electroless plating bath. The chemical plating bath comprises a bath body and a rotatable bearing disc positioned in the bath body.

In some embodiments, the present application provides an electroless plating system. The electroless plating system includes an electroless plating bath and one or more feedstock baths. The chemical plating bath comprises a bath body and a rotatable bearing disc positioned in the bath body.

In some embodiments, the present application provides an electroless plating method. The method comprises the steps of fixing an object to be plated on a rotatable bearing disc of an electroless plating bath; and injecting chemical plating solution into the chemical plating tank to plate a metal layer on the object to be plated.

Drawings

Aspects of some embodiments of the present application are readily understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that the various structures may not be drawn to scale and that the dimensions of the various structures may be arbitrarily increased or decreased for clarity of discussion.

FIG. 1 illustrates a cross-sectional view of an electroless plating bath according to some embodiments of the present application.

FIG. 2 illustrates a cross-sectional view of an electroless plating bath according to some embodiments of the present application.

FIG. 3 illustrates a schematic diagram of an electroless plating system according to some embodiments of the present application.

Fig. 4, 5, 6, and 7 illustrate various stages of an electroless plating process according to some embodiments of the present application.

FIG. 8 illustrates a bonding structure according to some embodiments of the present application.

FIG. 9 illustrates a bonding structure according to some embodiments of the present application.

Fig. 10 and 11 illustrate a joining structure according to some comparative embodiments of the present application.

The use of shared reference numbers throughout the figures and detailed description indicates the same or similar components. Embodiments of the present application will be readily understood by the following detailed description in conjunction with the accompanying drawings.

Detailed Description

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to be limiting. In the present application, in the following description, reference to the formation or disposition of a first feature over or on a second feature may include embodiments in which the first and second features are formed or disposed in direct contact, and may also include embodiments in which additional features may be formed or disposed between the first and second features such that the first and second features may not be in direct contact. In addition, the present application may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Embodiments of the present application are discussed in detail below. It should be appreciated, however, that the present application provides many applicable concepts that can be embodied in a wide variety of specific contexts. The particular embodiments discussed are merely illustrative and do not limit the scope of the application.

The present application provides a novel electroless plating bath, an electroless plating system comprising the same, and an electroless plating method using the same. The chemical plating bath comprises a bath body and a rotatable bearing disc positioned in the bath body. The plating object is placed on the rotatable bearing disc, the concentration of the plating solution can be homogenized by rotating the rotatable bearing disc, the thickness of the metal deposit is consistent, and the gas can be discharged by the centrifugal force. Therefore, the present invention can produce a bonded structure having a good structure between the two semiconductor substrates, and the resulting bonded structure has good reliability and electrical properties. Electroless plating, which is also known as electroless plating, allows the metal bonding structure to be completed at a relatively low temperature using electroless plating, compared to other prior art techniques.

Fig. 1 and 2 illustrate cross-sectional views of an electroless plating bath 1 according to some embodiments of the present application.

Referring to fig. 1, an electroless plating tank 1 includes a tank body 10 and a rotatable carrier plate 11 in the tank body. The top of the tank body 10 has an opening (not numbered in fig. 1), and the chemical plating tank 1 further includes a cover 15, wherein the cover 15 is disposed on the top of the tank body 10 and closes the opening.

The electroless plating tank 1 further comprises one or more inlets 17 fluidly connected to the tank body 10; and one or more outlets 18 fluidly connected to the tank 10. In some embodiments, the inlet 17 may be disposed on the side wall of the tank body 10, or on the cover body as shown in FIG. 1, and the electroless plating solution 20 may be injected into the electroless plating tank 1 through the inlet 17. The outlet 18 can be arranged on the side wall or the bottom of the tank body 10, and the waste plating solution after reaction can be discharged to the outside of the chemical plating tank 1 through the outlet 18.

The rotatable bearing disc 11 can rotate continuously or in pulses, and the stirring effect is generated by the rotation, so that the concentration of the plating solution is homogenized, and the metal deposition thickness is more uniform. In addition, the centrifugal force generated by the rotation can discharge impurities or gases (such as hydrogen generated by the chemical plating reaction) to avoid the impurities or gases remaining in the bonded structure and affecting the mechanical strength and electrical performance of the bonded structure. In some embodiments, the rotational speed of the rotatable carrier disc 11 is in the range of 0 to 300rpm, for example, 0rpm, 25rpm, 50rpm, 75rpm, 100rpm, 125rpm, 150rpm, 175rpm, 200rpm, 225rpm, 250rpm, 275rpm, or 300 rpm. In some embodiments, the chemical plating tank 1 comprises a rotating shaft 13, the rotatable carrying tray 11 is fixed in the tank body through the rotating shaft 13, and is continuously rotated or rotated in pulses through the rotating shaft 13. In some embodiments, the spindle 13 is disposed at the center of the rotatable carrier plate 11.

The rotatable carrier plate 11 may be a circular plate or other suitable shape. In some embodiments, the rotatable carrier plate 11 is a circular plate, which facilitates providing a steady centrifugal force when rotating. In some embodiments, the rotatable carrier tray 11 has a bottom 111 and sidewalls 112, and the sidewalls 112 are disposed at the edges of the bottom 111. In some embodiments, the sidewall 112 surrounds the edge of the bottom 111. In some embodiments, the rotatable carrier 11 has one or more holding members 16, such as two, three, four or more holding members 16, which can be used to fix the object 21 to be plated, and the holding members 16 can be arranged on the bottom 111 of the rotatable carrier 11. In some embodiments, the holding member 16 can move according to the size of the object to be plated to enhance the holding effect and adapt the rotatable carrier plate 11 to different sizes of objects to be plated.

The edge of the rotatable carrier disk 11 contains a sacrificial electrode 12. The sacrificial electrode 12 can be independently configured at the edge of the rotatable carrier plate 11; or on the inner surface of the side wall 112 of the rotatable carrier tray 11. In some embodiments, the sacrificial electrode 12 surrounds the edge of the rotatable carrier platter 11. The sacrificial electrode can enable impurities to be deposited or adsorbed on the sacrificial electrode, and the phenomenon that the impurities are deposited on the inner side wall of the tank body or are dissociated in the chemical plating solution to influence the deposition effect is avoided. In some embodiments, the sacrificial electrode 12 is a material that is not susceptible to corrosion by acids or bases, and impurities deposited or adsorbed thereon can be removed by cleaning. In some embodiments, the sacrificial electrode 12 comprises a noble metal (e.g., platinum) or stainless steel. In some embodiments, the sacrificial electrode 12 may be a mesh or a sheet. In some embodiments, the sacrificial electrode 12 is detachable, and when the deposit or the adsorbate reaches a certain thickness, the sacrificial electrode can be directly replaced by a new sacrificial electrode to continue the electroless plating reaction, and the used sacrificial electrode 12 is removed for cleaning, thereby improving the cleaning and electroless plating efficiency. In some embodiments, when the rotatable carrier plate rotates, the impurities move outwards due to centrifugal force, and can be intercepted by the sacrificial electrode disposed at the edge of the rotatable carrier plate 11 and deposited on the sacrificial electrode, thereby avoiding contamination of the whole electroless plating bath 1.

In some embodiments, the rotatable carrier plate 11 has an inclination angle with respect to the horizontal, so that the gas can be exhausted from the electroless plating reaction site by gravity, thereby avoiding the gas remaining in the bonding structure. In some embodiments, said tilt angle is greater than 0 ° and not greater than 60 °, for example, can be 3 °, 5 °, 10 °, 15 °, 20 °, 25 °, 30 °, 35 °, 40 °, 45 °, 50 °, 55 °, or 60 °. In some embodiments, the rotatable carrier plate 11 can be made to have an inclination angle by making the bottom of the electroless plating bath 1 have the inclination angle with respect to the horizontal direction. For example, in some embodiments as shown in fig. 2, the rotatable carrier plate 11 is disposed adjacent to the bottom of the electroless plating bath 1 and substantially parallel to the bottom of the electroless plating bath 1, the bottom of the electroless plating bath 1 and the rotatable carrier plate 11 having an inclination angle θ with respect to the horizontal direction.

In some embodiments, by rotating the rotatable bearing disk 11 and having the rotatable bearing disk 11 with an inclination angle with respect to the horizontal direction, the propagation effect of qi can be mediated by the action of heart force and gravity.

FIG. 3 illustrates a schematic diagram of an electroless plating system 3 according to some embodiments of the present application.

Referring to fig. 3, the electroless plating system 3 includes an electroless plating tank 1 and one or more raw material tanks (e.g., 31, 32, 33, and 34). The one or more raw material tanks are fluidly connected to the electroless plating tank 1, and the electroless plating solution stored in the raw material tank can be independently operated to be injected into the electroless plating tank 1. In some embodiments, the one or more material tanks may be selected from one or more of a copper (electrolyte) tank 31, a nickel (electrolyte) tank 32, a gold (electrolyte gold) tank 33, and a silver (electrolyte silver) tank 34, but not limited thereto. The copper plating bath 31, nickel plating bath 32, gold plating bath 33 and silver plating bath 34 may provide liquids for the reaction. Depositing copper, nickel, gold or silver on the object to be plated, and bonding two opposite metal structures on the object to be plated together through the deposited copper, nickel, gold or silver to form a bonding structure for providing electrical connection on the upper side and the lower side of the object to be plated.

In some embodiments, the electroless plating system 3 may further include a waste collection tank 35 and a cleaning bath 36. The

raw material tanks

31, 32, 33 and 34 and the cleaning liquid tank 36 are connected to the inlet 17 of the electroless plating tank 1 through pipes. In some embodiments, one or more valves 25 (or multiple valves) may be disposed between the raw material tank and the cleaning liquid tank and the inlet 17 of the chemical plating tank 1, and by switching the valves 25, a specific plating liquid may be introduced into the chemical plating tank for performing a chemical plating reaction, or a cleaning liquid (e.g., deionized water) may be introduced into the pipe or the chemical plating tank for cleaning. In some embodiments, two or more chemical plating solutions can be used sequentially for chemical plating reactions, and the cleaning solution is introduced into the chemical plating tank for cleaning before the chemical plating solutions are further purified, so as to avoid pollution caused by different chemical plating solutions. Furthermore, in some embodiments, one or more filtering devices (not shown in fig. 3) may be disposed between the raw material tank and the cleaning liquid tank and the inlet 17 of the electroless plating tank 1 to remove impurities in the electroless plating solution before the electroless plating solution is injected into the electroless plating tank 1. The waste liquid collecting tank 35 is connected to the outlet 18 of the electroless plating tank 1 through a pipe for collecting the spent plating liquid.

In some embodiments, the electroless plating system 3 may further include a pressure control device 26. In some embodiments, the pressure control device 26 can provide a low pressure environment in the electroless plating bath. In some embodiments, the pressure control device 26 is a vacuum pump. The low pressure environment promotes the flow of the electroless plating solution in the electroless plating bath to the object 21 from all directions, so that the thickness of the resulting plated metal layer is more uniform. In addition, the gas generated by the chemical plating reaction can be removed by the pressure control device (such as a vacuum pump) or even exhausted from the chemical plating bath, so that the gas can be further prevented from remaining in the bonding structure to influence the mechanical strength and the electrical performance of the bonding structure.

In some embodiments, the electroless plating system 3 can further include a control device 37, a drip tray 38, a flow meter 39a, a pressure gauge 39b, and other suitable devices. The control device 37 can independently control or set the temperature of each raw material tank and the chemical plating tank, the flow rate of the chemical plating solution, the rotation speed of the rotatable carrier plate, and the like. In some embodiments, the control device 37 is an electric cabinet. The flow meter 39a may be disposed at any suitable location (e.g., at the inlet 17, or on a separate conduit connected to each feedstock tank). The pressure gauge 39b may be disposed at any suitable location to monitor the pressure inside the electroless plating bath. The liquid containing tray 38 can be arranged below the chemical plating tank 1, the

raw material tanks

31, 32, 33 and 34 and the cleaning liquid tank 36, so as to avoid leakage liquid from polluting the work environment.

Fig. 4, 5, 6, and 7 illustrate various stages of an electroless plating process according to some embodiments of the present application. The following description will be made with reference to fig. 4, 5, 6, and 7, and fig. 1.

Fig. 4 and 5 illustrate the preparation of the plating object 21.

Referring to fig. 4, a first substrate 40 is provided. The first substrate 40 has a first patterned metal layer 41. The first patterned metal layer 41 includes an electrical connection structure (e.g., a metal pad, a metal pillar, or a metal bump)

Referring to fig. 5, a second substrate 50 is provided. The second substrate 50 has a second patterned metal layer 51, and the second patterned metal layer 51 has an electrical connection structure (e.g., a metal pad, a metal pillar, or a metal bump) corresponding to the first patterned metal layer 41. The second substrate 50 is disposed above the first substrate 40, the second patterned metal layer 51 faces the first patterned metal layer 41, and the electrical connection structure of the first patterned metal layer and the second patterned metal layer 41 corresponds to the electrical connection structure of the second patterned metal layer 51. One or more spacers 55 are disposed between the first substrate and the second substrate, so that the first patterned metal layer 41 does not contact the second patterned metal layer 51 (i.e., a distance is formed between the upper surface of the electrical connection structure of the first patterned metal layer 41 and the lower surface of the electrical connection structure of the second patterned metal layer 51), thereby completing the preparation of the object to be plated 21. By adjusting the height of the spacers 55, the distance between the two corresponding electrical connection structures of the second patterned metal layer 51 and the first patterned metal layer 41 can be adjusted.

Hereinafter, for convenience of description, the

symbols

41 and 51 may be used to refer to the first patterned metal layer and the second patterned metal layer, or to the electrical connection structure of the first patterned metal layer and the electrical connection structure of the second patterned metal layer.

Subsequently, referring to fig. 1, the object to be plated 21 is fixed on the rotatable carrying plate 11 of the chemical plating tank 1; and injecting a chemical plating solution 20 into the chemical plating tank 1, so that the chemical plating solution 20 performs a chemical plating reaction on the object 21 to be plated, and plating a metal layer on the object 21 to be plated by chemical plating (i.e., electroless plating) (refer to fig. 6, chemical plating metal layers 64 and 65).

Referring to fig. 6, the electroless plating reaction may begin after the object 21 is partially or completely immersed in the electroless plating solution 20, at which time metal ions in the electroless plating solution begin to deposit on the top and sidewalls of the electrical connection structures 41 of the first patterned metal layer to form a patterned metal layer 64, and on the bottom and sidewalls of the electrical connection structures 51 of the second patterned metal layer to form a patterned metal layer 65. The plated metal layer 64 and the plated metal layer 65 are gradually thickened with time and finally connected together, and form a bonding structure 100 together with the electrical connection structure of the first patterned metal layer and the

electrical connection structures

41 and 51 of the second patterned metal layer, and the first substrate 40 can be electrically connected to the second substrate 50 through the bonding structure 100. The metallization layer 64 and the metallization layer 65 are substantially made of the same material. In some embodiments, an interface exists where metallization layer 64 and metallization layer 65 join. In some embodiments, no or only a non-distinct interface exists where metallization layer 64 and metallization layer 65 join. In some embodiments, the bonding structure is comprised of metal, and thus may be referred to as a metal bonding structure; in some embodiments, the bonding structure is an interconnect structure between two or more semiconductor substrates, and thus may also be referred to as a semiconductor bonding structure.

In some embodiments, the first substrate 40 may be a wafer or a chip. In some embodiments, the second substrate 50 may be a wafer or a chip. For example, the object to be plated 21 shown in fig. 5 and 6 includes a first substrate 40 and a second substrate 50, and both the first substrate 40 and the second substrate 50 are wafers.

Fig. 7 illustrates a plated item 21' according to some embodiments of the present application with respect to fig. 6. The plating object 21 'shown in fig. 7 has a structure similar to that of fig. 6, however, in the plating object 21' shown in fig. 7, the first substrate 40 is a wafer, and the

second substrates

50a and 50b are chips.

Singulation may be performed after completion of the bonding structure 100 as shown in fig. 6 or 7.

Fig. 8 illustrates a joining structure 200 according to some embodiments of the present application. The bonding structure 200 includes corresponding upper and lower

electrical connection structures

41 and 51; first metallization layers 64 and 65 respectively plated on the

electrical connection structures

41 and 51; and second metallization layers 66 and 66' plated on the first metallization layers 64 and 65, respectively. The second metallization layers 66 and 66 'are joined together (i.e., the upper surface of the second metallization layer 66 meets or is coplanar with the lower surface of the second metallization layer 66'). The second metal plating layer and the first metal plating layer are made of different materials. In some embodiments, the bonding structure 200 may be prepared by sequentially using different plating solutions, for example, a first plating solution may be first injected into an electroless plating bath to plate the first plated

metal layers

64 and 65 on the electrical connection structure 41 of the first patterned metal layer and the electrical connection structure 51 of the second patterned metal layer, respectively; then, a second plating solution is injected into the electroless plating bath to plate second plated metal layers 66 and 66 'on the first plated

metal layers

64 and 65, respectively, the second plated metal layers 66 and 66' gradually thicken with time, and finally are connected together, and form a joint structure 200 together with the first plated

metal layers

64 and 65, the electrical connection structure 41 of the first patterned metal layer, and the electrical connection structure 51 of the second patterned metal layer, so that the first substrate 40 can be electrically connected to the second substrate 50 through the joint structure 200.

The bonding structure having two or more layers of dissimilar metallization is prepared using a dissimilar plating solution, which allows the bonding structure to have multiple advantages (superior performance, relatively low cost, etc.). For example, gold has excellent oxidation resistance and excellent electrical performance, but is expensive and slow in deposition rate, and thus, in some embodiments, a first electroless plating solution (e.g., copper) containing a cheap and fast-deposition-rate metal is used to perform a first electroless plating, a

first metal layer

64 and 65 is deposited on the

electrical connection structures

41 and 51, and after the

first metal layer

64 and 65 reach a certain deposition thickness, a second electroless plating solution containing gold is switched to perform a second electroless plating, and a second metal layer 66 and 66' is deposited on the

first metal layer

64 and 65, thereby completing the bonding structure. Therefore, time and cost can be saved, and the obtained bonding structure has excellent electrical property and oxidation resistance.

FIG. 9 illustrates a bonding structure according to some embodiments of the present application. By using the chemical plating tank, the chemical plating system and the chemical plating method, a bonding structure with uniform thickness of a plurality of plated metal layers can be provided between two substrates, and the obtained bonding structure has less impurities and residual gas. As shown in fig. 9, the second substrate 50 is disposed above the first substrate 40, the first substrate 40 has adjacent

electrical connection structures

411 and 412, and the second substrate 50 has adjacent

electrical connection structures

511 and 512. The distance between two adjacent electrical connection structures (411 and 412, 511 and 512) is D1. The electrical connection structure 411 corresponds to the electrical connection structure 511, and the electrical connection structure 412 corresponds to the electrical connection structure 512. The distance between two opposite electrical connection structures (411 and 511, 412 and 512) is H. Metallization layers 641 and 651 are deposited to a thickness T1 on the first set of

electrical connection structures

411 and 511, respectively. Metallization layers 642 and 652, having a thickness T2, are deposited over the second set of

electrical connection structures

412 and 512, respectively. Because the rotatable bearing disc is arranged in the chemical plating tank, the object to be plated is placed on the rotatable bearing disc, the concentration of the chemical plating solution can be homogenized by rotating the rotatable bearing disc, and the gas generated by the chemical plating reaction can be exhausted, the chemical plating metal layers with relatively consistent thickness (T1 is substantially the same as T2, or has only small difference) can be prepared at different positions, and no gas residue or only trace gas residue exists between the two connected chemical plating metal layers (641 and 651, 642 and 652) in the bonding structure.

Fig. 10 and 11 illustrate a joining structure according to some comparative embodiments of the present application. In the comparative examples of fig. 10 and 11, the electroless plating solution is continuously injected using a micro flow channel device (not shown), and the electroless plating solution enters a reaction tank (not shown) through the object to be plated from an inlet 91 and then flows toward an outlet 92. However, the flow field direction of the technology is single, which causes the thickness of the plated chemical plating metal layer to be uneven according to different positions.

As shown in fig. 10, the thickness T1 of the deposited layer of the metallization layers (641 and 651) near the inlet 91 is greater than the thickness T2 of the deposited layer of the metallization layers (642 and 652) near the outlet 92, and the difference between T1 and T2 is large, so that when the first set of

electrical connection structures

411 and 511 are bonded through the metallization layers 641 and 651, the second set of

electrical connection structures

412 and 512 are not bonded, which affects the electrical performance of the resulting semiconductor device structure. To complete the bonding of the second set of

electrical connection structures

412 and 512, the plating time must be increased.

As shown in 11, after the plating time is lengthened, the deposition thickness of the metallization layers (641 and 651) near the inlet 91 is increased to T3, and the deposition thickness of the metallization layers (642 and 652) near the outlet 92 is increased to T4, however, if the distance D1 between two adjacent electrical connection structures (411 and 412, 511 and 512) is too small, the two adjacent electrical connection structures (411 and 412, 511 and 512) may be joined together due to the deposition thickness of the metallization layers being too thick, resulting in a short circuit risk and poor reliability.

Compared to the comparative examples of fig. 10 and 11, using the electroless plating bath, the electroless plating system and the electroless plating method according to the present application, a bonding structure having a uniform thickness of a plurality of plated metal layers between two substrates can be provided, and even when the distance D1 between two adjacent electrical connection structures (411 and 412, 511 and 512) is reduced (e.g., to 16 μm or less), the two adjacent electrical connection structures are not bonded together. Therefore, the chemical plating tank, the chemical plating system and the chemical plating method of the present application contribute to achieving the goal of miniaturization. In addition, the micro flow channel device used in the comparative examples of fig. 10 and 11 is suitable only for metal butting between small-sized substrates, which is disadvantageous for mass production; the chemical plating tank, the chemical plating system and the chemical plating method are suitable for metal butt joint between large-size substrates, and are beneficial to mass production.

Unless otherwise specified, spatial descriptions such as "above," "below," "upper," "left," "right," "lower," "top," "bottom," "vertical," "horizontal," "side," "above," "below," "upper," "above," "below," and the like are indicated with respect to the orientation shown in the figures. It is to be understood that the spatial descriptions used herein are for purposes of illustration only and that actual implementations of the structures described herein may be spatially arranged in any orientation or manner provided that the embodiments of the present application are not biased by such arrangements.

As used herein, the terms "approximately," "substantially," "essentially," and "about" are used to describe and explain minor variations. When used in conjunction with an event or circumstance, the terms can refer to an instance in which the event or circumstance occurs precisely as well as an instance in which the event or circumstance occurs in close proximity. For example, when used in conjunction with numerical values, the terms can refer to a range of variation that is less than or equal to ± 10% of the stated numerical value, e.g., less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%. For example, a first value can be considered "substantially" the same as or equal to a second value if the first value varies from less than or equal to ± 10% of the second value, such as less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%. For example, "substantially" perpendicular may refer to a range of angular variation of less than or equal to ± 10 ° from 90 °, e.g., less than or equal to ± 5 °, less than or equal to ± 4 °, less than or equal to ± 3 °, less than or equal to ± 2 °, less than or equal to ± 1 °, less than or equal to ± 0.5 °, less than or equal to ± 0.1 °, or less than or equal to ± 0.05 °.

Two surfaces can be considered coplanar or substantially coplanar if the displacement between the two surfaces is no greater than 5 μm, no greater than 2 μm, no greater than 1 μm, or no greater than 0.5 μm. A surface can be considered substantially flat if the displacement between the highest and lowest points of the surface is no greater than 5 μm, no greater than 2 μm, no greater than 1 μm, or no greater than 0.5 μm.

As used herein, the singular terms "a" and "the" may include plural referents unless the context clearly dictates otherwise.

As used herein, the terms "conductive", "electrically conductive", and "conductivity" refer to the ability to carry electrical current. Conductive materials generally indicate those materials that exhibit little or zero opposition to current flow. One measure of conductivity is siemens per meter (S/m). Typically, the electrically conductive material is one having an electrical conductivity greater than approximately 104S/m (e.g., at least 105S/m or at least 106S/m). The conductivity of a material can sometimes change with temperature. Unless otherwise specified, the electrical conductivity of a material is measured at room temperature.

Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

While the present application has been described and illustrated with reference to particular embodiments thereof, such description and illustration are not to be considered limiting. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the application, as defined by the appended claims. The illustrations may not be drawn to scale. Due to manufacturing processes and tolerances, there may be a difference between the artistic rendition in this application and the actual device. There may be other embodiments of the application that are not specifically illustrated. The specification and drawings are to be regarded in an illustrative rather than a restrictive sense. Modifications may be made to adapt a particular situation, material, composition of matter, method, or process to the objective, spirit and scope of the present application. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to particular operations performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form equivalent methods without departing from the teachings of the present application. Accordingly, unless specifically indicated herein, the order and grouping of the operations is not a limitation of the present application.

Claims

1. An electroless plating bath comprising:

a trough body; and

a rotatable bearing disc positioned in the trough body.

2. The electroless plating bath according to claim 1 wherein the rotatable carrier plate has an oblique angle with respect to the horizontal.

3. The electroless plating bath of claim 1 wherein an edge of the rotatable carrier plate comprises a sacrificial electrode.

4. The electroless plating bath according to claim 1 wherein the rotatable carrier plate has a retaining feature.

5. The electroless plating bath of claim 1 wherein the sacrificial electrode surrounds the edge of the rotatable carrier plate.

6. An electroless plating system, comprising:

the electroless plating bath according to any of claims 1 to 5; and

one or more raw material tanks.

7. The electroless plating system of claim 6 wherein the one or more feedstock tanks are fluidly connected to the electroless plating tank and are independently operable to inject the electroless plating solution stored in the feedstock tanks into the electroless plating tank.

8. The electroless plating system of claim 6 further comprising a filtration device to remove impurities from the electroless plating solution prior to injection into the electroless plating tank.

9. The electroless plating system of claim 6 further comprising a pressure control device, the pressure control device being a vacuum pump.

10. The electroless plating system of claim 6 wherein the one or more feedstock reservoirs are selected from one or more of a copper plating reservoir, a nickel plating reservoir, a gold plating reservoir, and a silver plating reservoir.