Patent Application
20070131542
This application relates to reaction vessels and methods of making and using such vessels in electrochemical processing of microelectronic workpieces.
Microelectronic devices, such as semiconductor devices and field emission displays, are generally fabricated on and/or in microelectronic workpieces using several different types of machines (“tools”). Many such processing machines have a single processing station that performs one or more procedures on the workpieces. Other processing machines have a plurality of processing stations that perform a series of different procedures on individual workpieces or batches of workpieces. In a typical fabrication process, one or more layers of conductive materials are formed on the workpieces during deposition stages. The workpieces are then typically subject to etching and/or polishing procedures (i.e., planarization) to remove a portion of the deposited conductive layers for forming electrically isolated contacts and/or conductive lines.
Plating tools that plate metals or other materials on the workpieces are becoming an increasingly useful type of processing machine. Electroplating and electroless plating techniques can be used to deposit nickel, copper, solder, permalloy, gold, silver, platinum and other metals onto workpieces for forming blanket layers or patterned layers. A typical metal plating process involves depositing a seed layer onto the surface of the workpiece using chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating processes, or other suitable methods. After forming the seed layer, a blanket layer or patterned layer of metal is plated onto the workpiece by applying an appropriate electrical potential between the seed layer and an electrode in the presence of an electroprocessing solution. The workpiece is then cleaned, etched and/or annealed in subsequent procedures before transferring the workpiece to another processing machine.
The plating machines used in fabricating microelectronic devices must meet many specific performance criteria. For example, many processes must be able to form small contacts in vias that are less than 0.5 μm wide, and are desirably less than 0.1 μm wide. The plated metal layers accordingly often need to fill vias or trenches that are on the order of 0.1 μm wide, and the layer of plated material should also be deposited to a desired, uniform thickness across the surface of the workpiece 5.
One concern of many processing stations is that it is expensive to fabricate certain types of electrodes that are mounted in the reaction vessels. For example, nickel-sulfur (Ni—S) electrodes are used to deposit nickel on microelectronic workpieces. Plating nickel is particularly difficult because anodization of the nickel electrodes produces an oxide layer that reduces or at least alters the performance of the nickel plating process. To overcome anodization, nickel can be plated using a chlorine bath or an Ni—S electrode because both chlorine and sulfur counteract the anodizing process to provide a more consistent electrode performance. Ni—S electrodes are preferred over chlorine baths because the plated layer has a tensile stress when chlorine is used, but is stress-free or compressive when an Ni—S electrode is used. The stress-free or compressive layers are typically preferred over tensile layers to enhance annealing processes, CMP processes, and other post-plating procedures that are performed on the wafer.
Ni—S electrodes, however, are expensive to manufacture in solid, shaped configurations. Bulk Ni—S material that comes in the form of pellets (e.g., spheres or button-shaped pieces) cannot be molded into the desired shape because the sulfur vaporizes before the nickel melts. The solid, shaped Ni—S electrodes are accordingly formed using electrochemical techniques in which the bulk Ni—S material is dissolved into a bath and then re-plated onto a mandrel in the desired shape of the solid electrode. Although the bulk Ni—S material only costs approximately $4-$6 per pound, a finished solid, shaped Ni—S electrode can cost approximately $400-$600 per pound because of the electroforming process.
Another concern of several types of existing processing stations is that it is difficult and expensive to service the electrodes. Referring to
The present invention is directed toward processing chambers and tools that use processing chambers in electrochemical processing of microelectronic workpieces. Several embodiments of processing chambers in accordance with the invention provide electrodes that use a bulk material which is much less expensive than solid, shaped electrodes. For example, these embodiments are particularly useful in applications that use nickel-sulfur electrodes because bulk nickel-sulfur materials are much less expensive than solid, shaped nickel-sulfur electrodes that are manufactured using electroforming techniques. Several embodiments of processing chambers are also expected to significantly enhance the ability to service the electrodes by providing electrode assemblies that are not obstructed by the head assembly or other components in a reaction chamber where the workpiece is held during a processing cycle. Many of the embodiments of the invention are expected to provide these benefits while also meeting demanding performance specifications because several embodiments of the processing chambers have a virtual electrode unit that enhances the flexibility of the system to compensate for different performance criteria.
One embodiment of the invention is directed toward a processing chamber comprising a reaction vessel having an electro-reaction cell including a virtual electrode unit, an electrode assembly disposed relative to the electro-reaction cell to be in fluid communication with the virtual electrode unit, and an electrode in the electrode assembly. The virtual electrode unit has at least one opening defining at least one virtual electrode in the electro-reaction cell. The electrode assembly can include an electrode compartment and an interface element in the electrode compartment. The interface element can be a filter, a membrane, a basket, and/or another device configured to hold the electrode. The interface element, for example, can be a filter that surrounds a basket in which the electrode is positioned.
In a more particular embodiment, the electrode comprises a bulk electrode material, such as a plurality of pellets. The bulk electrode material can be contained in a basket, a filter, or a combination of a basket surrounded by a filter. In another embodiment, the electrode assembly comprises a remote electrode compartment that is outside of the electro-reaction cell so that a head assembly or the virtual electrode unit does not obstruct easy access to the electrode in the electrode compartment. In an alternate embodiment, the electrode assembly is positioned in the electro-reaction cell under the virtual electrode assembly, and the electrode is a bulk material electrode.
The following description discloses the details and features of several embodiments of electrochemical processing stations and integrated tools to process microelectronic workpieces. The term “microelectronic workpiece” is used throughout to include a workpiece formed from a substrate upon which and/or in which microelectronic circuits or components, data storage elements or layers, and/or micro-mechanical elements are fabricated. It will be appreciated that several of the details set forth below are provided to describe the following embodiments in a manner sufficient to enable a person skilled in the art to make and use the disclosed embodiments. Several of the details and advantages described below, however, may not be necessary to practice certain embodiments of the invention. Additionally, the invention can also include additional embodiments that are within the scope of the claims, but are not described in detail with respect to
The operation and features of electrochemical reaction vessels are best understood in light of the environment and equipment in which they can be used to electrochemically process workpieces (e.g., electroplate and/or electropolish). As such, embodiments of integrated tools with processing stations having the electrochemical processing station are initially described with reference to
A. Selected Embodiments of Integrated Tools with Electrochemical Processing Stations
The load/unload station 110 can have two container supports 112 that are each housed in a protective shroud 113. The container supports 112 are configured to position workpiece containers 114 relative to the apertures 106 in the cabinet 102. The workpiece containers 114 can each house a plurality of microelectronic workpieces 101 in a “mini” clean environment for carrying a plurality of workpieces through other environments that are not at clean room standards. Each of the workpiece containers 114 is accessible from the interior region 104 of the cabinet 102 through the apertures 106.
The processing machine 100 can also include a plurality of clean/etch capsules 122, other electrochemical processing stations 124, and a transfer device 130 in the interior region 104 of the cabinet 102. Additional embodiments of the processing machine 100 can include electroless plating stations, annealing stations, and/or metrology stations in addition to or in lieu of the clean/etch capsules 122 and other processing stations 124.
The transfer device 130 includes a linear track 132 extending in a lengthwise direction of the interior region 104 between the processing stations. The transfer device 130 can further include a robot unit 134 carried by the track 132. In the particular embodiment shown in
The processing chamber 200 includes an outer housing 210 (shown schematically in
The head assembly 150 holds the workpiece at a workpiece-processing site of the reaction vessel 220 so that at least a plating surface of the workpiece engages the electroprocessing solution. An electrical field is established in the solution by applying an electrical potential between the plating surface of the workpiece via the contact assembly 160 and one or more electrodes located at other parts of the processing chamber. For example, the contact assembly 160 can be biased with a negative potential with respect to the other electrode(s) to plate metals or other types of materials onto the workpiece. On the other hand, the contact assembly 160 can be biased with a positive potential with respect to the other electrode(s) to (a) de-plate or electropolish plated material from the workpiece or (b) deposit other materials onto the workpiece (e.g., electrophoretic resist). In general, therefore, materials can be deposited on or removed from the workpiece with the workpiece acting as a cathode or an anode depending upon the particular type of material used in the electrochemical process.
B. Selected Embodiments of Processing Chambers For Use in Electrochemical Processing Stations
The reaction vessel 412 includes an electro-reaction cell 420 and a virtual electrode unit 430 in the electro-reaction cell 420. The virtual electrode unit 430 can be a dielectric element that shapes an electrical field within the electro-reaction cell 420. The virtual electrode unit 430, for example, has an opening that defines a virtual electrode VE. The virtual electrode VE performs as if an electrode is positioned at the opening of the virtual electrode unit 430 even though the physical location of the actual electrode is not aligned with opening in the virtual electrode unit 430. As described in more detail below, the actual electrode is positioned elsewhere in contact with an electrolytic processing solution that flows through the electro-reaction cell 420. The electro-reaction cell 420 can be mounted on a flow distributor 440 that guides the flow of processing solution from the fluid passageway 416 to the electro-reaction cell 420.
The electrode assembly 414 shown in the embodiment of
The interface element 460 can inhibit particulates and bubbles generated by the electrode 470 from passing into the processing solution flowing through the fluid passageway 416 and into the electro-reaction cell 420. The interface element 460, however, allows electrons to pass from the electrode 470 and through the electrolytic processing solution PS in the processing chamber 400. The interface element 460 can be a filter, an ion membrane, or another type of material that selectively inhibits particulates and/or bubbles from passing out of the electrode assembly 414. The interface element 460, for example, can be cylindrical, rectilinear, two-dimensional or any other suitable shape that protects the processing solution PS from particles and/or bubbles that may be generated by the electrode 470.
The electrode 470 can be a bulk electrode or a solid electrode. When the electrode 470 is a nickel-sulfur electrode, it is advantageous to use a bulk electrode material within the interface element 460. By using bulk Ni—S electrode material, the processing station 120 does not need to have solid, shaped electrodes formed by expensive electroforming processes. The bulk Ni—S electrode is expected to be approximately two orders of magnitude less than a solid, shaped Ni—S electrode. Moreover, because the bulk electrode material is contained within the interface element 460, the pellets of the bulk electrode material are contained in a defined space that entraps particulates and bubbles. Another benefit of this embodiment is that the bulk electrode material not only reduces the cost of Ni—S electrodes, but it can also be easily replenished because the electrode assemblies 414 are outside of the electro-reaction cell 420. Thus, the combination of a remote electrode assembly, a bulk-material electrode, and a virtual electrode unit is expected to provide a chamber that performs as if the actual electrode is in the electro-reaction cell for precise processing without having expensive solid, shaped electrodes or the inconvenience of working around the head assembly.
The processing station 120 can plate or deplate metals, electrophoretic resist, or other materials onto a workpiece 101 carried by the head assembly 150. In operation, a pump 480 pumps the processing solution through a particle filter 490 and into the electrode compartment 450. In this embodiment, the processing solution PS flows through a channel 452 adjacent to the interface element 460, and then through the fluid passageway 416 and the flow distributor 440 until it reaches the electro-reaction cell 420. The processing solution PS continues to flow through the electro-reaction cell 420 until it crests over a weir, at which point it flows into the tank 410. The primary flow of the processing solution PS accordingly does not flow through the interface unit 460, but rather around it. A portion of the processing solution PS flowing through the electrode compartment 450 may “backflow” through the interface element 460 and across the electrode 470 (arrow B). The portion of the processing solution PS that backflows through the interface element 460 can exit through an outflow (arrow 0) and return to the tank 410. The backflow portion of the processing solution PS that crosses over the electrode 470 replenishes ions from the electrode 470 to the bath of processing solution PS in the tank 410.
The electrons can flow from the electrode 470 to the workpiece 101, or in the opposite direction depending upon the particular electrical biasing between the workpiece 101 and the electrode 470. In the case of plating a metal onto the workpiece 101, the electrode 470 is an anode and the workpiece 101 is a cathode such that electrons flow from the electrode 470 to the workpiece 101. The electrons can accordingly flow through the interface element 460. It will be appreciated that the conductivity of the processing solution PS allows the electrons to move between the electrode 470 and the workpiece 101 according to the particular bias of the electrical field.
The processing chamber 500 can further include a plurality of fluid passageways 540 and flow distributor 550 coupled to the fluid passageways 540. Each electrode assembly 514a-f is coupled to a corresponding fluid passageway 540 so that fluid flows from each electrode assembly 514 and into the flow distributor 550. The electro-reaction cell 520 can be coupled to the flow distributor 550 by a transition section 560. The flow distributor 550 and the transition section 560 can be configured so that the processing solution PS flows from particular electrode assemblies 514a-f to one of the virtual electrode openings VE1-VE3.
The particular flow path from the electrode assemblies 514 to the virtual electrode openings are selected to provide a desired electrical potential for each one of the virtual electrodes VE1-VE3 and mass transfer at the workpiece (e.g., the weir 538). In one particular embodiment, a first flow F1 of processing solution through the first virtual electrode VE1 opening comes from the electrode assemblies 514b and 514e; a second flow F2 through the second virtual electrode opening VE2 comes from the electrode assemblies 514c and 514d; and a third flow F3 through the third virtual electrode VE3 opening comes from the electrode assemblies 514a and 514f. The particular selection of which electrode assembly 514 services the flow through a particular virtual electrode opening depends upon several factors. As explained in more detail below, the particular flows are typically configured so that they provide a desired distribution of electrical current at each of the virtual electrode openings.
The reaction vessel 512 can also include a diffuser 610 projecting downward from the first partition 532. The diffuser 610 can have an inverted frusto-conical shape that tapers inwardly and downwardly within in a fluid passage of the flow distributor 550. The diffuser 610 can include a plurality of openings, such as circles or elongated slots, through which the processing solution can flow radially inwardly and then upwardly through the opening that defines the first virtual electrode VE1. In this particular embodiment, the openings 612 are angled upwardly to project the flow from within the flow distributor 550 radially inwardly and slightly upward. It will be appreciated that the diffuser 610 can have other embodiments in which the flow is directed radially inwardly without an upward or downward component. Additionally, the diffuser 610 may also be eliminated from certain embodiments.
The electrode assemblies 514b and 514e can be similar or even identical to each other, and thus only the components of the electrode assembly 514e will be described. The electrode assembly 514e can include a casing or compartment 620, an interface element 622 inside the casing 620, and a basket 624 inside the interface element 622. As explained above, the interface element 622 can be a filter, an ion membrane, or another type of material that allows electrons to flow to or from the electrode assembly 514e via the processing solution. One suitable material for the interface element 622 is a filter composed of polypropylene, Teflon®, polyethersulfone, or other materials that are chemically compatible with the particular processing solution. In the embodiment shown in
The electrode assembly 514e can further include a lead 630 coupled to the basket 624 and an electrode 640 in the basket 624. In the embodiment shown in
In the embodiment shown in
Referring to
The processing chamber 500 is expected to be cost efficient to manufacture and maintain, while also meeting stringent performance specifications that are often required for forming layers from metal or photoresist on semiconductor wafers or other types of microelectronic workpieces. One aspect of several embodiments of the processing chamber 500 is that bulk electrode materials can be used for the electrodes. This is particularly useful in the case of plating nickel because the cost of nickel-sulfur bulk electrode materials is significantly less than the cost of solid, shaped nickel-sulfur electrodes formed using electroforming processes. Additionally, by separating the electrode assemblies 514 from the electro-reaction cell 520, the head assembly or other components inside of the cell 520 do not need to be moved for electrode maintenance. This saves time and makes it easier to service the electrodes. As a result, more time is available for the processing chamber 50b to be used for plating workpieces. Moreover, several embodiments of the processing chamber 500 achieve these benefits while also meeting demanding performance specifications. This is possible because the virtual anode unit 530 shapes the electrical field proximate to the workpiece in a manner that allows the remote electrodes in the electrode assemblies 514 to perform as if they are located in the openings of the virtual electrode unit 530. Therefore, several embodiments of the processing chamber 500 provide for cost effective operation of a planarizing tool while maintaining the desired level of performance.
Another feature of several embodiments of the processing chamber 500 is that commercially available types of filters can be used for the interface element. This is expected to help reduce the cost of manufacturing the processing chamber. It will be appreciated, however, that custom filters or membranes can be used, or that no filters may be used.
Another aspect of selected embodiments of the processing chamber 500 is that the tank 510 houses the reaction vessel 512 in a manner that eliminates return plumbing. This frees up space within the lower cabinet for pumps, filters and other components so that more features can be added to a tool or more room can be available for easier maintenance of components in the cabinet. Additionally, in the case of electroless processing, a heating element can be placed directly in the tank 510 to provide enhanced accuracy because the proximity of the heating element to the reaction vessel 512 will produce a smaller temperature gradient between the fluid at the heating element and the fluid at the workpiece site. This is expected to reduce the number of variables that can affect electroless plating processes.
Still another aspect of several embodiments of the processing chamber 500 is that the virtual electrode defined by the virtual electrode unit 530 can be readily manipulated to control the plating process more precisely. This provides a significant amount of flexibility to adjust the plating process for providing extremely low 3-σ results. Several aspects of different configurations of virtual electrode units and processing chambers are described in PCT Publication Nos. WO00/61837 and WO00/61498; and in U.S. application Ser. Nos. 09/849,505; 09/866,391; 09/866,463; 09/875,365; Ser. No. 09/872,151; all of which are herein incorporated by reference in their entirety.
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
The applications claims the benefit of U.S. Application No. 60/316,597 filed on Aug. 31, 2001.
| Number | Date | Country | |
|---|---|---|---|
| 60316597 | Aug 2001 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10234442 | Sep 2002 | US |
| Child | 11505252 | Aug 2006 | US |
