METAL PLATING SYSTEM INCLUDING GAS BUBBLE REMOVAL UNIT
An electroplating apparatus includes an anode configured to electrically communicate with an electrical voltage and an electrolyte solution. A cathode module includes a cathode that is configured to electrically communicate with a ground potential and the electrolyte solution. The cathode module further includes a wafer in electrical communication with the cathode. The wafer is configured to receive metal ions from the anode in response to current flowing through the anode via electrodeposition. The electroplating apparatus further includes at least one agitating device interposed between the wafer and the anode. The agitating device is configured to apply a force to gas bubbles adhering to a surface of the wafer facing the agitating device.
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The present disclosure relates to a metal plating system, and more specifically, to a metal plating system including gas bubble removal unit.
Copper metallization is a key component for integrated circuits (ICs). As the industry demand for smaller sized ICs increases, plating-related defects in metal vias and interconnect lines are becoming more prominent. These plating defects ultimately affect the reliability of the ICs.
One such plating defect that has increased over the years is referred to as “hollow metal.” Hollow metal describes various point defects, such as voids, porosity etc., which occur in the metal vias and connection lines of the ICs. One cause of hollow metal may be attributed to conventional plating tools used to perform the metallization electroplating applied to IC wafer surfaces. More specifically, conventional plating tools dispose the wafer surface in a metallization solution in a downward-facing position towards an opposing anode of the plating tool. The plating process forms various metal vias and/or metal connections on the downward-facing surface. While the wafer is immersed, gas bubbles, such as air, may be trapped in the trenches and via holes trapping as a result of insufficiently fast and incomplete wetting of the trenches and vias with plating solution before plating starts. Hydrogen and/or air bubbles may also be formed in the solution during plating. They may be trapped in the trenches and vias. The bubbles also rise toward the surface and may encounter the wafer. The trapped bubbles may not be removed when using the currently used rotating disc configured plating tool. However, the trapped bubble may adhere to the bottom or side wall of the trenches and vias. These bubbles may block metal ions from reaching the conduction seed layer and forming the metal conductor by properly filling the trenches and vias. Accordingly, non-plated sections beneath the bubbles may occur, which ultimately causes hollow sections in the metal lines or vias, i.e., the hollow metal.
SUMMARYAccording to an embodiment, an electroplating apparatus includes an anode configured to electrically communicate with an electrical voltage and an electrolyte solution. A cathode module includes a cathode that is configured to electrically communicate with a ground potential and the electrolyte solution. The cathode module further includes a wafer in electrical communication with the cathode. The wafer is configured to receive metal ions from the anode in response to current flowing through the anode via electrodeposition. The electroplating apparatus further includes at least one agitating device interposed between the wafer and the anode. The agitating device is configured to apply a uniform agitation across a cathode module including a wafer surface and a shearing force to gas bubbles trapped in the trenches and vias created on a surface of the wafer facing the agitating device. In addition this agitating device will help to maintain an uniform diffusion layer over the large cathode i.e., wafer, surface which eventually enables plating having a uniform metal/alloy plating thickness. Uniform plating across the wafer surface results in uniform planarization by chemical mechanical polishing (CMP).
According to another embodiment, an agitating device to remove bubbles adhered to a surface of a wafer undergoing an electroplating process comprises a frame having an upper portion facing a wafer and a lower portion opposing the upper portion. The upper portion has a slot formed therethrough. The slot is configured to stream an electrolyte solution toward and past the surface of the wafer at an increased velocity.
Additional features are realized through the techniques of the various embodiments described herein. For a better understanding of the features, refer to the description and to the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. Various forgoing and other inventive features are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring now to
The power supply 102 includes a positive terminal 115 and a negative terminal 116. The power supply 102 may include a voltage source, a current source, or a voltage source and a current source. The power supply 102 is configured to output an electrical voltage, a current, or a voltage and a current. The power supply 102 may execute a voltage scan with a predetermined scan rate. The power supply 102 may also supply a constant voltage. In addition, the power supply 102 may generate a voltage output and then switched to a current output or vice versa. The voltage and current output may be a direct current (DC), a pulse or combination of different waveforms. The current may also have a value selected to achieve a desired current density.
The current may be supplied according to a constant electrical potential condition, under constant electrical current condition or combination thereof (see
The container 104 may contain an electrolyte solution 117 capable of conducting an electrical current that induces a metallization plating process. The electrolyte solution 117 may comprise cupric ions and/or chlorine ions and sulfate ions that render the electrolyte solution 117 to be electrically conductive. According to at least one exemplary embodiment, the electrolyte solution 117 includes, but is not limited, to sulfuric acid (H2SO4), copper sulfate pentahydrate, 2N hydrochloric acid, sodium sulfate, etc. An electrolyte solution of sulfuric acid may range from 2-50 grams/liter (g/L), copper sulfate pentahydrate may range from 20-300 g/L and organic additives used as accelerator, levelers, suppressors and wetting agents. A solution of 2N hydrochloric acid may range from 0-5 milliliters/liters (ml/L), and a solution of sodium sulfate may range from 80-200 g/L. It can be appreciated that other solutions of acids, bases or salts may be used as the electrolyte solution 117. In addition, the electrolyte solution 117 may comprise either H2SO4 or chloride (Cl), and metal ions. The electrolyte metal ions comprises, for example, copper (Cu). In another embodiment, the solution comprises an acid copper plating solution including (1) a dissolved copper salt (e.g., as copper sulfate), (2) an acidic electrolyte (e.g., as sulfuric acid) in an amount sufficient to impart conductivity to the bath and (3) additives (e.g., surfactants, brighteners, levelers and suppressants). The bath may also contain a wetting agent to increase wettability of the wafer. Various wetting agents may be used including, but not limited to, anionic agents, cationic agents, amphoteric wetting agents that ionize when mixed with water, and non-ionic wetting agents.
In response to current flowing through the anode 108, metal ions from the anode 108 are transferred to the downward-facing surface of the wafer 113 via an electrodeposition process. As a result, copper vias and/or copper connection lines may be formed on the downward-facing surface of the wafer 113 and in the etched trenches and vias which are metalized with a very thin conducting seed layer, as discussed in greater detail below with respect to
The plating tool 106 is in electrical communication with the power supply 102 and is in fluid communication with the electrolyte solution 117. In at least one embodiment illustrated in
The cathode module 110 includes a cathode 111 coupled to a supporting plate 112. Various means may be used to connect the cathode 111 to the supporting plate 112 including, but not limited to, mechanical pins, fasteners, and a non-soluble conductive adhesive. Further, the cathode 111 may be connected to the supporting plate 112 using a universal joint 400. The universal joint 400 allows the cathode module 110 to move in a plurality of directions with respect to the axis (A). For example, the cathode module 110 may rotate about the axis, while still capable of tilting left, right or moving up and down.
The supporting plate 112 may be configured to rotate about an axis (A) extending perpendicular to cathode module 110. Hence, the cathode 111 may be rotated when the plate 112 rotates. The cathode module 110 further includes an interconnect (IC) wafer 113 connected in electrical communication to the cathode 111. A conductive alloy seed layer 114 may be formed on the IC wafer. Accordingly, the IC wafer 113 may rotate along with the supporting plate 112 and the cathode 111. In at least one embodiment, the supporting plate 112 may be selectively rotated. The cathode module 110, including the wafer 113, may be formed in various shapes including, but not limited to square, circular and other.
Referring now to
Referring again to
The plating tool 106 further includes at least one agitating device 120 configured to prevent air, hydrogen and/or other gas bubbles from becoming trapped inside the trenches and vias located beneath the cathode module 110 and adhering to the downward-facing surface of the wafer 113. The agitating device 120 may include a static agitating device that remains fixed or a dynamic agitating device that moves. When the wafer 113 is static, the dynamic agitating device will remove one or more bubbles from the wafer 113. When the wafer 113 is dynamic, a static agitation device will also maintain a constant well defined diffusion layer across the plating surface of the wafer 113.
Referring to at least one embodiment illustrated in
The plating system 106 may further include a pump configured to force the electrolyte solution through the slot 122. Accordingly, the stream generated by the pump may have an increased velocity that weakens the adhering force of the bubbles against the down-facing surface of the wafer 113. However, it is appreciated that the pump may be located outside of the container 104, and may include a tube system (not shown) that conveys solution to the slot 122. Although the pump may assist in flowing the stream of solution through the slot 122, it is appreciated that the pump is not required. For example, the rotation of the cathode module 110 may generate a shearing force that induces a partial vacuum between the wafer 113 and the agitating device 120 such that solution and gas bubbles are drawn from the vias and trenches.
The electroplating apparatus 100 may further include a filter unit 123 that is disposed between the anode 108 and the cathode module 110, and that extends between opposing inner walls of the container 104. The filter unit 123 may include a sac filter or a membrane, and is configured to separate a solution inside the container into a plating solution including additives and a virgin made solution (VMS) excluding the additives. The anode 108 may be disposed in the VMS, while the cathode module 110 is disposed in the plating solution 117. The additives may include brightener, suppressor, leveler, surfactant, wetting agent.
Referring to
In another embodiment, a plating tool 106″ may include a plurality of agitating devices 120A-120C, as illustrated in
Referring to
Turning now to
Referring to
In at least one embodiment, the slot 508 is shaped such that a slot opening increases as the slot 508 extends toward the middle of the upper section 504. The slot 508, for example, may be formed to have a diamond-shape such that the slot-opening gradually increases as the slot 508 extends toward the center. Bubbles which adhere to the downward-facing surface of the wafer 113 congregate most at the center of the wafer. Forming a slot 508 having a slot opening that increases at the center of the upper section 504 permits the agitating device 500′ to be positioned such that maximum velocity of the stream flowing through the slot 508 is focused at the center of the downward-facing wafer 113 where the highest concentration of bubbles typically exist. It is appreciated that the slot 508 may have a shape other than the described above. The slot 508 is shaped in such a fashion so that a substantially uniform shear force is generated between the solution and the wafer when the wafer is rotated throughout the entire 360° circle. For example, the slot may 508 be shaped in such a way that the plating solution velocity is highest near the center of the wafer. The slot 508 may also be formed such that a force may be delivered therethrough to dislodge any bubbles on the downward facing surface.
Referring now to
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Referring now to
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Referring to
The wafer 113 may be electroplated according to an electrical current profile. An example of a current profile is illustrated in
Turning now to
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
The flow diagrams depicted herein are just one example. There may be many variations to this diagram or the operations described therein without departing from the scope of the claims. For instance, the operations may be performed in a differing order or steps may be added, deleted or modified. All of these variations are considered a part of the scope of the claimed features.
While various embodiments have been described, it will be understood that those skilled in the art, both now and in the future, may make modifications to the embodiments which fall within the scope of the following claims. These claims should be construed to maintain the proper protection for the invention.
Claims
1. An electroplating apparatus, comprising:
- an anode coupled to an electrical voltage and an electrolyte solution;
- a cathode module including a cathode coupled to a ground potential and the electrolyte solution, the cathode module further including a wafer in electrical communication with the cathode, the wafer configured to receive metal ions from the anode via electrodeposition in response to current flowing through the anode; and
- at least one agitating device interposed between the wafer and the anode, the agitating device configured to apply a force to gas bubbles adhering to at least one of a surface, trenches, and vias of the wafer facing the at least one agitating device.
2. The electroplating apparatus of claim 1, wherein the cathode module is fixed at a stationary position and the agitating device is configured to move with respect to the cathode module.
3. The electroplating apparatus of claim 2, wherein the at least one agitating device includes a uniformly solid frame disposed a distance beneath a center region of the wafer.
4. The electroplating apparatus of claim 3, wherein the at least one agitating device includes a first agitating device configured to reciprocate at a predetermined frequency in a lateral direction with respect to the surface of the wafer without traversing beyond the center region.
5. The electroplating apparatus of claim 4, wherein the at least one agitating device includes second and third agitating devices, the second agitating device disposed adjacent a first side of the first agitating device and configured to reciprocate at a predetermined frequency in a lateral direction with respect to the surface of the wafer, and the third agitating device disposed adjacent a second side of the first agitating device opposite the first side and configured to reciprocate at a predetermined frequency in a lateral direction with respect to the surface of the wafer.
6. The electroplating apparatus of claim 5, further comprising at least one ultrasonic transducer coupled to the wafer, the ultrasonic transducer configured to generate pulses at a predetermined frequency such that the wafer vibrates.
7. The electroplating apparatus of claim 6, further comprising a current buffle unit interposed between the agitating device and the anode, the buffle unit configured to improve current distribution between the anode and the cathode such that a resistance drop in a seed layer between an edge and a center of the wafer is compensated.
8. The electroplating apparatus of claim 1, wherein the agitating device is fixated within the electrolyte solution, and wherein the cathode module is configured to rotate about an axis extending perpendicular to the cathode.
9. The electroplating apparatus of claim 8, wherein at least one agitating device includes a frame having an upper portion disposed a distance beneath a center region of the wafer, the upper portion having a slot formed therethrough to stream solution at a predetermined velocity toward the center region of the wafer.
10. The electroplating apparatus of claim 9, wherein a velocity of streaming electrolyte increases from an edge of the wafer to the center region of the wafer such that a maximum velocity of the streaming electrolyte exists at the center region.
11. The electroplating apparatus of claim 10, wherein the slot is diamond-shaped such that a velocity of the solution streamed at a center of the opening is greater than a velocity of the solution streamed at ends of the opening.
12. The electroplating apparatus of claim 11, further comprising at least one ultrasonic transducer coupled to the wafer, the ultrasonic transducer configured to generate pulses at a predetermined frequency and intensity such that the wafer vibrates.
13. The electroplating apparatus of claim 12, further comprising a current buffle unit interposed between the agitating device and the anode, the current buffle unit configured to provide a current distribution at the cathode.
14. The electroplating apparatus of claim 13, further comprising:
- a power supply configured to generate the electrical current, the power supply configured to provide the voltage and the ground potential; and
- a container configured to contain the electrolyte solution, the cathode module, and the anode immersed in the electrolyte solution.
15. The electroplating apparatus of claim 14, further comprising a universal joint that couples the axis to the cathode module, the cathode module configured to rotate via axis and tilt with respect to the axis via the universal joint.
16. An agitating device to remove bubbles adhered to a surface of a wafer undergoing an electroplating process, the agitating device comprising:
- a frame having an upper portion facing a wafer and a lower portion opposing the upper portion; and
- at least one of the lower portion and the upper portion having a slot formed therethrough and configured to stream an electrolyte solution toward the wafer at an increased velocity.
17. The electroplating apparatus of claim 16, wherein a maximum opening of the slot is located at a center region of the at least one lower portion and upper portion.
18. A method of electroplating a wafer via electrolyte solution, comprising:
- rotating the wafer at a predetermined speed;
- tilting the wafer at a predetermined angle with respect to the electrolyte solution;
- vibrating the wafer at a predetermined frequency;
- applying a voltage to the wafer;
- immersing the wafer in the electrolyte solution at the predetermined angle, the predetermined frequency and the voltage to inhibit formation of at least one of air and hydrogen bubbles to a surface of the wafer; and
- electroplating the surface of the wafer via the electrolyte solution.
19. The method of claim 18, further comprising leveling the wafer with respect to the electrolyte solution and inhibiting the vibration in response to immersing a predetermined amount of the wafer in the electrolyte solution.
20. The method of claim 19, wherein the speed ranges between 80 RPM and 100 RPM, and the predetermined angle ranges between 0.5 degrees and 5 degrees.
Type: Application
Filed: Mar 13, 2013
Publication Date: Sep 18, 2014
Applicant: INTERNATIONAL BUSINESS MACHINES CORPORATION (Armonk, NY)
Inventors: Shafaat Ahmed (Newburgh, NY), Michael P. Chudzik (Danbury, CT), Lubomyr T. Romankiw (Briancliff Manor, NY)
Application Number: 13/800,201
International Classification: C25D 5/20 (20060101); C25D 7/12 (20060101);