DYNAMIC ANODE FOR SEMICONDUCTOR MANUFACTURING

Abstract

An electrochemical deposition system includes a tank, a primary anode, and a secondary anode, all positioned within the tank. When a substrate is placed in the tank, the primary anode is situated at a distance from the substrate. The secondary anode is located closer to the substrate, positioned between the primary anode and the substrate. The secondary anode has one or more electrically active elements designed to affect the deposition process.

Claims

1. An electrochemical deposition system comprising: a reactor wall at least partially defining a chamber configured to permit flow of electrolyte therethrough; a primary anode; a plating rotor configured to grip and suspend a substrate in the chamber, and provide a conductive path between the primary anode and the substrate such that when electrolyte fills the chamber, application of electrical potential to the primary anode and substrate results in the primary anode, substrate, and electrolyte forming an electrochemical cell, and the reactor wall and electrochemical cell forming a reactor; and a secondary anode in the reactor between the primary anode and plating rotor and configured to alter a rate of plating angularly and radially along the substrate such that the rate in a vicinity of a perimeter of the substrate adjacent to the secondary anode changes as the substrate rotates within the reactor.

2. The electrochemical deposition system of claim 1, wherein the secondary anode includes a single electrically active element.

3. The electrochemical deposition system of claim 1, wherein the secondary anode includes a plurality of independently controllable electrically active elements.

4. The electrochemical deposition system of claim 1, where the secondary anode is further configured to generate an electric field responsive to application of electrical potential to the secondary anode and substrate.

5. The electrochemical deposition system of claim 1, wherein the primary anode and secondary anode are of a same material.

6. The electrochemical deposition system of claim 1, wherein a material of the secondary anode and a plating material are same.

7. The electrochemical deposition system of claim 1 further comprising one or more controllers programmed to, during operation of the electrochemical cell, switch a polarity of the primary anode and substrate.

8. The electrochemical deposition system of claim 7, wherein the one or more controllers are further programmed to match a polarity of the secondary anode to that of the primary anode or substrate.

9. A method comprising: while applying an electrical potential to a primary anode and substrate of an electrochemical deposition system, activating selected electrically active elements of a secondary anode adjacent to the substrate, and located between the primary anode and substrate such that the selected electrically active elements generate electric fields that affect deposition on areas of the substrate in a vicinity of the selected electrically active elements.

10. The method of claim 9 further comprising varying a voltage applied to the selected electrically active elements.

11. An electrochemical deposition system comprising: a tank; primary and secondary anodes disposed within the tank such that the primary anode is spaced away from a substrate when the substrate is present in the tank, and the secondary anode is adjacent to the substrate and between the primary anode and substrate when the substrate is present in the tank, the secondary anode including a set of electrically active elements; and a one or more controllers programmed to activate selected ones of the electrically active elements.

12. The electrochemical deposition system of claim 11, wherein the set includes a single electrically active element.

13. The electrochemical deposition system of claim 11, wherein the set includes a plurality of electrically active elements.

14. The electrochemical deposition system of claim 11, wherein the primary and secondary anodes are of a same material.

15. The electrochemical deposition system of claim 11, wherein a material of the secondary anode and a plating material are same.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a schematic diagram of an electroplating system.

[0010] FIG. 2 is a schematic diagram of a portion of an electroplating system including a multi-element secondary anode.

[0011] FIGS. 3 and 4 are top views of multi-element secondary anodes.

[0012] FIGS. 5A and 5B are top views of portions of a secondary anode and wafer.

DETAILED DESCRIPTION

[0013] 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.

[0014] 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.

[0015] Some electroplating systems for semiconductor wafers include components designed to promote precise and efficient metal deposition. The primary component, the plating bath, holds the electrolytea 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Referring to FIG. 1, an electroplating system 10 includes a container 12, a tank 14, primary and secondary anodes 16, 18, a sieve 20, a plating rotor 22, a wafer 24, electrolyte 26, a power source 28, and one or more controllers 30. The tank 14 is disposed within the container 12. The electrolyte 26 circulates through a chamber defined by walls of the tank 14. The primary and secondary anodes 16, 18, sieve 20, plating rotor 22, and wafer 24 are submerged in the electrolyte 26. A material of the primary and secondary anodes 16, 18 may be the same, and may be the same as the plating material. The secondary anode 18, in this example, is mounted to a wall of the tank 14 in close proximity to the wafer 24 such that the secondary anode 18 is between the sieve 20 and wafer 24. The sieve 20 is disposed between the primary and secondary anodes 16, 18 and has openings therein that disrupt flow of the electrolyte 26 as it circulates through the chamber. The plating rotor 22 grips the wafer 24 and rotates it during the plating process. The plating rotor 22 further provides a conductive path to the wafer 24. The power source 28 is connected with the primary anode 16 and plating rotor 22 and is also connected with the secondary anode 18 through resistors. In this arrangement, application of electrical potential to the primary anode 16 and wafer 24 by the power source 28 results in the primary anode 16, wafer 24, and electrolyte 26 forming an electrochemical cell, and a wall of the tank 14 and the electrochemical cell forming a reactor. The one or more controllers 30 exert control over the secondary anode 18, 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 anode 16 and wafer 24, and may match a polarity of the secondary anode 18 to that of the primary anode 16 or substrate 24. Use of the secondary anode 18 can thus alter a rate of plating radially along the wafer 24 and angularly as the wafer 24 spins relative to the secondary anode 18: Application of electrical potential to the secondary anode 18 and wafer 24 by the power source 28 results in the secondary anode 18 generating an electric field.

[0026] Referring to FIG. 2, a secondary anode 118 includes four elements 118A, 118B, 118C, 118D (an array). Switches 132A, 132B, 132C, 132D are associated with each of the elements 118A, 118B, 118C, 118D, respectively. A power source 128 is electrically connected with, and the one or more controllers 130 exert control over, each of the elements 118A, 118B, 118C, 118D. As a wafer rotates, none, all, or some the switches 132A, 132B, 132C, 132D may be selectively activated, resulting in application of electrical potential to selected ones of the elements 118A, 118B, 118C, 118D and the wafer 24, and generation of electric fields by the selected ones of the elements 118A, 118B, 118C, 118D. These electric fields would impact rates of electroplating localized to the proximity of the selected ones of the elements 118A, 118B, 118C, 118D to improve uniformity of deposition.

[0027] Referring to FIG. 3, a secondary anode 218 includes eight elements 218A, 218B, 218C, 218D, 218E, 218F, 218G, 218H and has a rectangular shape.

[0028] Referring to FIG. 4, a secondary anode 318 includes four elements 318A, 318B, 318C, 318D, and has a sector or pie shape.

[0029] Referring to FIGS. 5A and 5B, a wafer 424 defines a plurality of square sections 434. The wafer 424 is rotating clockwise from FIG. 5A to FIG. 5B. A secondary anode 418 includes a number of elements 418A, 418B, 418C, (three of which are shown). Depending on the position of the wafer 424 relative to the secondary anode 418, certain of the elements 418A, 418B, 418C, etc. are activated and others are not. In FIG. 5A, the elements 418B, 418C (and those elements extending toward a center of the wafer 424) are activated, and the element 418A is not. In FIG. 5B, all of the elements are activated. This affects the rate of plating around the perimeter of the wafer 424 as it rotates.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.