Dynamic Anode for Semiconductor Manufacturing

This disclosure relates to electroplating of semiconductor wafers.

Electroplating is a method used to apply a thin layer of metal onto the surface of another material, known as the substrate. In the case of semiconductors, the substrate is typically a silicon wafer. This process is integral to creating the intricate network of metal connections that form the circuits on microchips.

The role of electroplating in semiconductor manufacturing ties back to the need for highly conductive and reliable interconnections within the chip architecture. As devices become smaller and more complex, the demand for precision in creating these connections increases. Electroplating allows for the controlled deposition of metals like copper, which is favored for its electrical conductivity and compatibility with semiconductor processing.

Silicon wafers are a fundamental component of chip manufacturing. These wafers serve as the base upon which multiple layers of integrated circuits are built through various processes including lithography, etching, and doping. The electroplating of these wafers with metals is one of the final steps that create the pathways for electricity to flow throughout the chip. Electric current facilitates the transfer of metal ions from the anode to the cathode in a solution. This movement of ions across the solution to the wafer surface requires control of various factors such as voltage, current density, temperature, and the chemical composition of the electrolyte. These factors influence the rate of deposition, the purity of the metal layer, and the adhesion of the metal to the wafer.

An electrochemical deposition system includes several components to facilitate the plating process. The system includes a reactor wall that partially defines a chamber, allowing the flow of electrolyte through it. Within this chamber, there is a primary anode and a plating rotor designed to grip and suspend a substrate. This rotor also establishes a conductive path between the substrate and a power supply. When the chamber is filled with electrolyte and an electrical potential is applied to both the primary anode and the substrate via the power supply with the rotor and substrate immersed into the electrolyte, a complete circuit, and thus an electrochemical cell, is formed with the primary anode, substrate, and electrolyte. The reactor wall, in conjunction with the electrochemical cell, forms the reactor. Additionally, the system features a secondary anode positioned between the primary anode and the plating rotor. It is engineered to modify the plating rate angularly and radially along the substrate. As a result, the plating rate at various radii of the substrate and near its perimeter, adjacent to the secondary anode, varies as the substrate rotates within the reactor.

A method involves applying an electrical potential to both a primary anode and a substrate within an electrochemical deposition system. Concurrently, selected electrically active elements of a secondary anode, which is positioned adjacent to the substrate and located between the primary anode and the substrate, are activated. These selected electrically active elements generate localized electric fields, influencing the deposition process on specific areas of the substrate in close proximity to these elements.

An electrochemical deposition system comprises a tank and two types of anodes: primary and secondary. The primary anode is positioned within the tank in a manner that it remains spaced away from the substrate when the substrate is present. The secondary anode is placed adjacent to the substrate, situated between the primary anode and the substrate when the substrate is in the tank. The secondary anode has a set of electrically active elements. Additionally, the system includes one or more controllers that selectively activate specific electrically active elements of the secondary anode to influence the deposition process on the substrate.

These and other arrangements contemplated herein permit modification to non-radially symmetric features in a substrate, which can enable better uniformity in advanced packaging—a major area for growth. Moreover, for implementations in which a secondary anode spans the radius of the substrate either in physical dimension or effective dimension, it could be used to account for terminal effects (i.e., radial potential gradients across the substrate).

The embodiments presented here are only examples and should not be seen as the only possible configurations. It should be understood that other embodiments may vary significantly in form and detail. The diagrams included are not drawn to scale; certain features might be enlarged or reduced to highlight specific aspects of the components. Consequently, the specific structural and functional details provided in this document are intended for instructional purposes and should not be considered restrictive. These descriptions are meant to serve as a foundation for those experienced in the field to understand and implement the concepts discussed.

Electroplating is a process in semiconductor chip manufacturing, used to deposit thin metal layers onto silicon wafers. Typically, this process takes place in a reactor, often called an electroplating bath or tank, which contains the electrolyte solution and electrodes. The silicon wafer acts as the cathode, while the anode can be made from the metal intended for deposition. The reactor's design often allows for temperature control of the electrolyte, which can be helpful in achieving uniform metal deposition across the wafer.

Some electroplating systems for semiconductor wafers include components designed to promote precise and efficient metal deposition. The primary component, the plating bath, holds the electrolyte—a conductive solution rich in metal ions and supplemented with chemicals like brighteners and suppressors to optimize deposition rates and improve uniformity. The materials used for the tank can be selected for their resistance to corrosion and chemical instability, which helps prevent any contamination of the electrolyte.

In this setup, the anode dissolves into the electrolyte, replenishing it with metal ions, while the wafer, serving as the cathode, is where the metal ions deposit to form a solid layer. To maintain an even coating, the wafer is held in place by a wafer holder or carrier, which keeps it submerged and may also rotate.

The system's power supply provides the necessary electrical current for the electrochemical reaction, with settings for voltage and current that can be adjusted to meet specific requirements. To ensure a uniform concentration of metal ions around the wafer, mechanical agitators or pumps circulate the electrolyte in some arrangements in an attempt to maintain consistent plating quality.

Temperature control plays a role because plating characteristics can significantly be affected by thermal conditions. A dedicated system may regulate the bath temperature, and a control system equipped with software may continually adjust parameters like voltage, current, temperature, and agitation speed (if applicable) based on real-time sensor feedback.

Moreover, a filtration system may be used to keep the electrolyte free from particulates that could degrade the plating quality. Exhaust systems for fume handling and waste management protocols for disposing of used electrolytes and residues could also be used.

Before electroplating, wafers may be pre-coated with a thin seed layer of the metal, such as copper, using techniques like physical vapor deposition (PVD) or chemical vapor deposition (CVD). This seed layer helps ensure that the subsequent metal deposition is even and adheres well to the wafer. During the electroplating process, the wafer is cleaned to remove any contaminants, then immersed in the electroplating bath, and spun while a specific voltage is applied between the anode and the cathode. This process might include continuous agitation or disruption of the electrolyte as mentioned above to maintain an even distribution of metal ions.

Throughout the electroplating process, parameters such as metal layer thickness and uniformity may be monitored and adjusted. These adjustments are based on real-time measurements. The process typically concludes once the target metal layer thickness and uniformity are achieved, verified by techniques like optical reflectometry or electrical resistance measurement.

After electroplating, the wafers may undergo several post-processing steps including rinsing to remove any residual electrolyte, drying to prevent oxidation, and chemical mechanical planarization (CMP) in an attempt to promote flatness and uniformity of the metal layers.

Due to the spinning motion during the electroplating process, features located at the same radial distance from the center of the wafer often encounter similar levels of current density. This spinning method, however, introduces certain challenges that cannot be easily adjusted, such as radial asymmetry due to various right angles of die present on the wafer surface. Additional complications arise from the physical characteristics of the wafer itself, including irregularities at the wafer's edge, non-standard shapes of the die (e.g., square dye), and uneven open areas around the wafer perimeter. Anywhere on the wafer surface that an expanse of insulator material, such as a photoresist, sits adjacent to an area of conductive material, such as arrays of openings in the photoresist to expose underlying metal, current will crowd against the edges of the expanse of insulator. Shielding is the typical method by which to offset this crowding. Conventional shielding, however, is round in shape, resulting in combined areas of over-shielding and under-shielding. These and other factors can lead to non-uniform deposition of the plating material, particularly where linear areas of insulator/conductor interfaces are present, including die edges or non-round substrates. Furthermore, the process may lack sufficient dynamic adjustments for radial uniformity during electroplating, such as the ability to modify parameters for thin seed layers or adjust for advanced packaging techniques, which can further complicate the achievement of uniform electroplating results.

A second anode (monolithic or arrayed) in the chamber located much closer to the wafer and covering only a portion of the wafer area is thus proposed. This second anode may be divided into radial sections, each of which can be independently switched on and off. The wafer may be photographed or otherwise imaged coming into the plating tool to accurately define the non-radial pattern of the substrate. This model may be communicated to software that controls a power supply for the second anode. In this way, current can be modulated up and down, which causes a change in current density, according to the angular location of non-radial elements as they pass by the second anode. That is, wafer position may be tracked, and sections of the second anode turned on and off (or up and down) as needed corresponding to when more or less current to a particular area of the wafer is required. This allows for angular tuning and dynamic radial tuning. Thin seed, irregular open area, die edges, and non-round substrates can also be tuned. A resistor may be used to tune how much is plated by the main anode versus the second anode: 90% versus 10%, 70% versus 30%, etc.

Referring to, an electroplating systemincludes a container, a tank, primary and secondary anodes,, a sieve, a plating rotor, a wafer, electrolyte, a power source, and one or more controllers. The tankis disposed within the container. The electrolytecirculates through a chamber defined by walls of the tank. The primary and secondary anodes,, sieve, plating rotor, and waferare submerged in the electrolyte. A material of the primary and secondary anodes,may be the same, and may be the same as the plating material. The secondary anode, in this example, is mounted to a wall of the tankin close proximity to the wafersuch that the secondary anodeis between the sieveand wafer. The sieveis disposed between the primary and secondary anodes,and has openings therein that disrupt flow of the electrolyteas it circulates through the chamber. The plating rotorgrips the waferand rotates it during the plating process. The plating rotorfurther provides a conductive path to the wafer. The power sourceis connected with the primary anodeand plating rotorand is also connected with the secondary anodethrough resistors. In this arrangement, application of electrical potential to the primary anodeand waferby the power sourceresults in the primary anode, wafer, and electrolyteforming an electrochemical cell, and a wall of the tankand the electrochemical cell forming a reactor. The one or more controllersexert control over the secondary anode, which includes in this example a single electrically active element, as well as monitors and adjusts parameters associated with operation of the reactor. It, for example, may switch a polarity of the primary anodeand wafer, and may match a polarity of the secondary anodeto that of the primary anodeor substrate. Use of the secondary anodecan thus alter a rate of plating radially along the waferand angularly as the waferspins relative to the secondary anode: Application of electrical potential to the secondary anodeand waferby the power sourceresults in the secondary anodegenerating an electric field.

Referring to, a secondary anodeincludes four elementsA,B,C,D (an array). SwitchesA,B,C,D are associated with each of the elementsA,B,C,D, respectively. A power sourceis electrically connected with, and the one or more controllersexert control over, each of the elementsA,B,C,D. As a wafer rotates, none, all, or some the switchesA,B,C,D may be selectively activated, resulting in application of electrical potential to selected ones of the elementsA,B,C,D and the wafer, and generation of electric fields by the selected ones of the elementsA,B,C,D. These electric fields would impact rates of electroplating localized to the proximity of the selected ones of the elementsA,B,C,D to improve uniformity of deposition.

Referring to, a secondary anodeincludes eight elementsA,B,C,D,E,F,G,H and has a rectangular shape.

Referring to, a secondary anodeincludes four elementsA,B,C,D, and has a sector or pie shape.

Referring to, a waferdefines a plurality of square sections. The waferis rotating clockwise fromto. A secondary anodeincludes a number of elementsA,B,C, (three of which are shown). Depending on the position of the waferrelative to the secondary anode, certain of the elementsA,B,C, etc. are activated and others are not. In, the elementsB,C (and those elements extending toward a center of the wafer) are activated, and the elementA is not. In, all of the elements are activated. This affects the rate of plating around the perimeter of the waferas it rotates.

Other embodiments are also contemplated. In one embodiment, an electrochemical deposition system includes a reactor wall that partially defines a chamber designed to facilitate the flow of electrolyte. Within this chamber, a primary anode and a plating rotor are configured to grip and suspend a semiconductor substrate, creating a conductive path between the primary anode and the substrate. When the chamber is filled with electrolyte, an applied electrical potential to the primary anode and the substrate establishes an electrochemical cell. Additionally, a secondary anode is strategically positioned between the primary anode and the substrate. This secondary anode is engineered to modulate the rate of plating angularly and radially along the substrate as it rotates, promoting uniform thickness and composition of the deposited layer.

In another embodiment, an electrochemical deposition system is enhanced by a secondary anode composed of a single or multiple independently controllable electrically active elements. This system includes a controller programmed to selectively activate these elements, creating localized electric fields that influence the deposition rate on targeted areas of the substrate. Among other things, this control is for developing complex and uniform plating patterns.

A further embodiment of the electrochemical deposition system incorporates a feedback control system integrated with an array of sensors. These sensors continuously monitor parameters such as electrolyte flow rate, composition, temperature within the chamber, deposition thickness and placement, etc. The feedback control system dynamically adjusts the electrical potentials applied to one or more of the primary anode, secondary anode, and substrate in real-time, optimizing the deposition process. The secondary anode can be repositioned relative to the substrate during operation to fine-tune the angular and radial rate of plating.

Another embodiment involves a method for electrochemical deposition that, while applying an electrical potential to a primary anode and substrate, activates selected electrically active elements of a secondary anode positioned between the primary anode and substrate. These elements generate electric fields that control the deposition on specific substrate areas. The method may also include rotating the substrate at variable speeds and adjusting the electrical potentials based on deposition rate measurements.

An additional embodiment features an electrochemical deposition system with a tank housing primary and secondary anodes. The primary anode is spaced away from the substrate, while the secondary anode is adjacent to and positioned between the primary anode and the substrate. The secondary anode includes a set of electrically active elements managed by a programmable controller. This setup allows selective activation of the electrically active elements, creating specific plating patterns on the substrate. An integrated pump circulates the electrolyte to maintain conditions.

A further embodiment involves an electrochemical deposition system where a secondary anode is strategically placed close to a substrate and covers only specific areas. This secondary anode may be segmented into radial sections, each independently controllable via a control and power supply system. The substrate is imaged prior to entering the plating chamber, with this image data used to create a model of the substrate's non-radial pattern. This model is input into control software, which adjusts the power to each radial section of the secondary anode as the substrate rotates. This dynamic adjustment allows for fine-tuning of the current density to address variations such as die edges and non-round substrates, optimizing the deposition process for uniformity and quality.

In yet another embodiment, an electrochemical deposition system includes a secondary anode located proximate to the substrate, covering only portions of the substrate area, and divided into independently controllable radial sections. The system incorporates an imaging mechanism to capture detailed representations (e.g., pictures, etc.) of the substrate before it enters the plating tool, identifying its non-radial and other features. This information is processed by control software linked to the power supply of the secondary anode. The software tracks the substrate's position and modulates the current in the secondary anode sections, adjusting the current density according to the substrate's angular and radial position. One or more resistors may be incorporated to tune the proportion of plating done by the primary anode versus the secondary anode, providing flexible control over the deposition process.

Although this document describes example embodiments, it should be noted that these embodiments do not cover all the possible forms that might be claimed. Some secondary anodes may have shapes (e.g., circular, triangular, etc.) and numbers of elements (e.g., six, twenty-three, etc.) different than those shown. A power supply with multiple channels or two or more power supplies may be used, etc. The terminology used in this specification is for descriptive purposes only and not intended for limitation. It is acknowledged that modifications and variations can be made without straying from the essence and scope of the subject matter presented here.

The algorithms, methods, or processes described in this document can be implemented on various types of hardware and software systems. They can be executed on different computing devices including both dedicated electronic control units and programmable electronic control units. These computing systems can execute the described algorithms, methods, or processes from instructions and data stored in various forms. For instance, the information can be permanently stored on non-writable storage media like read-only memory (ROM) devices or alterably stored on writable storage media such as compact discs, random access memory (RAM) devices, and other magnetic or optical media.

Furthermore, the described algorithms, methods, or processes can be implemented as software executable objects. In some cases, they may be implemented directly in hardware using suitable components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or state machines. They can also be embodied in any combination of firmware, hardware, and software components, optimizing performance and flexibility according to specific application needs. This hybrid approach allows for tailored implementations that meet specific system requirements while providing the capability to adapt and evolve with technological advancements.

As previously mentioned, the features of various embodiments can be combined to create new embodiments of the invention that might not have been explicitly described or illustrated. Although certain embodiments may have been described as having advantages or being preferred over others or existing prior art in terms of specific characteristics, those skilled in the art will understand that compromises in one or more features may be necessary to optimize other overall system attributes. These attributes depend greatly on the specific application and implementation and may include factors such as strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, and ease of assembly, among others. Therefore, embodiments that may seem less desirable compared to others regarding one or more characteristics should not be considered outside the scope of this disclosure. In fact, such embodiments may be particularly advantageous for certain applications.