US20060289302A1

US20060289302A1 - Electroprocessing workpiece contact assemblies, and apparatus with contact assemblies for electroprocessing workpieces

Info

Publication number: US20060289302A1
Application number: US11/170,557
Authority: US
Inventors: Kyle Hanson
Original assignee: Semitool Inc
Current assignee: Semitool Inc
Priority date: 2005-06-28
Filing date: 2005-06-28
Publication date: 2006-12-28
Also published as: JP2008546913A; WO2007002656A2; TW200703546A; KR20080031753A; WO2007002656A3

Abstract

Contact assemblies and machines with contact assemblies for electroprocessing workpieces are disclosed herein. The contact assemblies include a support member and a contact member coupled to the support member. The support member includes an inner wall defining an opening configured to receive a workpiece. The contact member includes a mounting section connected to the support member and a plurality of contacts projecting from the mounting section. The individual contacts include a cantilevered segment projecting inwardly and downwardly to center a workpiece and a tip segment projecting inwardly and upwardly to provide electrical contact with the centered workpiece.

Description

TECHNICAL FIELD

The following disclosure is related to contact assemblies for providing an electrical potential to a microfeature workpiece for electroprocessing of the workpiece.

BACKGROUND

Electroprocessing (i.e., electroplating or electropolishing/etching) of microelectronic/microfeature workpieces, such as silicon wafers, typically involves immersing an electrically conductive surface on the device side of the workpiece in an electrolyte to establish a current path between an immersed electrode and a plurality of electrical contacts applied to the electrically conductive surface at the periphery of the workpiece. Consequently, selected species are deposited on the workpiece from the electrolyte (electroplating) or removed from the workpiece (electropolishing/etching) by applying a voltage differential between the workpiece electrical contacts and the immersed electrode such that a current path extends through the electrolyte between the immersed electrode and the electrically conductive surface.
Today, fabrication of semiconductor devices on workpieces such as silicon wafers involves depositing copper on the device side of the workpieces so as to form interconnecting copper lines and vias or removing copper from selected parts of the workpiece so as to isolate interconnecting copper lines and vias. Other microfeature devices are fabricated on workpieces by depositing copper, other metals, and other nonmetallic materials in a similar manner but without the formation of interconnecting lines or vias. In the course of fabrication, many such layers of lines, vias and other formations may be electroplated or subject to electropolishing/etching.
As workpiece diameters increase (typically today from 200 mm to 300 mm), device sizes diminish, and line and via dimensions become more extreme, the electrical contact system that provides electrical contact to the periphery of the device side of the workpiece must meet increasingly stringent specifications. In particular, plated film uniformity specifications are becoming increasingly narrow. Also, the surface area at the periphery of the wafer that is available for making electrical contact with the wafer is becoming increasingly smaller. These two, in particular, require employing more electrical contact points around the workpiece periphery and locating the contact points closer to the edge of the workpiece. Because workpieces, such as silicon wafers, are not identical in thickness or diameter—even though nominally the same—it is increasingly difficult to provide an electrical contact system that contacts the periphery of the workpiece within the narrow perimeter band that is not occupied by fabricated devices.
In order to make electrical contact in the small perimeter bands, it is common for the contact elements to be exposed to the electrolyte during an electroprocessing cycle. Where such “wet contact” elements are employed and as more numerous contact points are provided, there is an increasing tendency, in the case of electroplating, for many of the contact elements that make electrical contact at each contact point to become bonded to the electrically conductive surface on the workpiece during electroplating. This tendency makes removal of the workpiece from the contact system, following electroplating, problematic. This requires some means for dislodging the workpiece from the contact elements after completion of electroplating.
In the case of workpieces such as silicon wafers, the outer edge of the workpiece is rounded or beveled and the permissible band for making electrical contact is located immediately radially inward of the outer edge. As the specification for the size of the perimeter band on the workpiece is reduced, the contact elements that make electrical contact at each contact point risk missing the band by making contact (a) too far radially inward and thereby encroaching on the workpiece area reserved for devices, or (b) too far radially outward and thereby either missing the workpiece entirely or making contact on the edge. Because the workpiece mounting/holding system, within which the electrical contact system is located, must accommodate workpieces of varying sizes within a particular workpiece standard, making electrical contact at all points around the workpiece becomes problematic. This requires some means for centering each workpiece relative to the contact elements of the electrical contact system.
Conventional electroprocessing systems rotate the workpiece within the electrolyte. Consequently, electrical contact systems with “wet contact” elements cause flow disturbances and fluid turbulence as the workpiece and “wet contact” elements rotate in the electrolyte during electroprocessing. Fluid turbulence in the electrolyte adjacent to the electroprocessed workpiece surface can create bubbles and disrupt the hydrodynamic boundary layer, which adversely affects electroprocessing.

SUMMARY

The present invention provides workpiece mounting/holding systems that include an electrical contact system designed to provide numerous electrical contacts on a workpiece within a narrow perimeter band. The electrical contact system accurately aligns and centers workpieces relative to the electrical contacts. The electrical contact system can provide electrical contact elements that exert an ejection force to break the mechanical bond that tends to form between the electrical contact elements and the workpieces after electroplating. The electrical contact system can provide additional means to exert an ejection force for breaking such mechanical bonds as an adjunct to the force exerted by the electrical contact elements. The electrical contact elements occupy only a small band around the perimeter of the workpieces, and project only a short distance into the electrolyte to reduce fluid turbulence.
The electrical contact system includes a plurality of electrical contact elements each of which has a cantilevered segment that projects from a contact mounting segment and ends with a contact tip segment. As a workpiece is inserted into the workpiece mounting/holding system for electroprocessing, the workpiece edge is forced to engage the cantilevered segment of each contact element and slide along the segment. The contact elements are oriented such that the force applied to move the workpiece along the cantilevered segments causes the segments to flex and be placed under strain and, consequently, the workpiece tends to center and align relative to the contact system as it is positioned in the contact system for electroprocessing.
The contact element tip segments, at the ends of the cantilevered segments, are oriented such that the workpiece engages the outer points of the tip segments as it is forced to its final position for electroprocessing within the contact system. As the workpiece reaches its final position, the outer points of the tip segments are drawn across the workpiece for a short distance and are flexed so as to be placed under strain. Consequently, when the workpiece is relieved from the insertion force following electroprocessing, the flexed tip segments return to their unstrained configuration, each pivoting about its junction with the contact element cantilevered segment, such that any mechanical bond formed between the tip outer points and the workpiece is broken. The relative configurations of the cantilevered segments and tip segments are such that, once the insertion force on the workpiece is removed and any mechanical bonds are broken, the cantilevered segments return to their unflexed condition and force the workpiece to slide back toward the location at which it entered the contact system. The contact element tip segments are short and are configured to project into the electrolyte by only a short distance to reduce fluid turbulence.
The electrical contact systems include a support member for the electrical contact elements that is configured in the form of a mounting ring with one or more electrical mounting members secured to the mounting ring. The mounting members are contact mounting segments that form a band of conductive material from which individual contact element cantilevered segments project. If more than one mounting member is provided, the mounting segments may be abutted to one another, end-to-end, when secured to the mounting ring so as to provide a continuous conductive ring. Alternatively, the mounting segments can be electrically isolated from adjacent mounting segments and yet also be secured to the mounting ring in an end-to-end fashion.
The mounting members can be fabricated from sheets of thin conductive material with multiple contact element cantilevered segments, and the tip segments associated with each cantilevered segment, being formed integrally with the mounting segments. Following formation of a mounting member into a contact mounting segment with integrally-formed contact element cantilevered and tip segments, the cantilevered and tip segments may be formed into their designed configurations. The tip segments may be formed to extend at an angle that is nearly 90 degrees from the cantilevered segments. The cantilevered segments may then be formed to extend at an obtuse angle from the mounting segment.
The workpiece mounting/holding system includes a workpiece backing member designed to move a workpiece into a processing position within the electrical contact system and hold the workpiece in that position during electroprocessing. When workpiece processing is completed, the backing member retracts to permit the workpiece to be removed from the mounting/holding system. The workpiece backing member may be provided with a vacuum system that can be activated at the completion of workpiece processing to hold the workpiece against the backing member as the backing member is retracted. This application of a vacuum system could assist in moving the workpiece so as to break any mechanical bonds formed between the electrical contact tip segments and the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side cross-sectional view of an electroprocessing system for applying an electrical potential to a workpiece in accordance with the invention.
FIG. 2A is an enlarged detail view from FIG. 1 illustrating a portion of a contact system contacting a workpiece.
FIG. 2B is a side cross-sectional view similar to FIG. 2A but with the workpiece absent.
FIGS. 3A-3C illustrate individual contacts of the contact assembly at various stages as the workpiece is loaded into the contact assembly.
FIGS. 4A-4C illustrate the tip segments of individual contacts of the contact assembly at various stages as the workpiece is loaded into the contact assembly.
FIGS. 5A and 5B illustrate a method for forming a contact member of the contact assembly.
FIG. 6 is an isometric view of the contact assembly mounted in a plating rotor.
FIG. 7A is a bottom isometric view of the contact assembly.
FIG. 7B is an enlarged isometric cross-sectional view of a portion of the contact assembly.
FIG. 8 is an isometric view of a reactor head of an electroplating reactor in which the contact assembly may be used.
FIG. 9 is a schematic side cross-sectional view of an electrochemical processing station in which the contact assembly may be used.
FIG. 10 is an isometric view of a processing apparatus in which the contact assembly may be used.

DETAILED DESCRIPTION

The following description discloses the details and features of several embodiments of contact assemblies, electrochemical processing reactors, and integrated tools for processing microfeature workpieces. The terms “microfeature workpiece” or “workpiece” refer to substrates on and/or in which microdevices are formed. Typical microdevices include microelectronic circuits or components, thin-film recording heads, data storage elements, microfluidic devices, and other products. Micromachines or micromechanical devices are included within this definition because they are manufactured in much the same manner as integrated circuits. The substrates can be semiconductive pieces (e.g., silicon wafers or gallium arsenide wafers), nonconductive pieces (e.g., various ceramic substrates), or conductive pieces (e.g., doped wafers). Also, the term electrochemical processing or deposition includes electroplating, electro-etching, anodization, and/or electroless plating. 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 include additional embodiments that are within the scope of the claims, but are not described in detail with respect to FIGS. 1-10.
The electrical contact system 100 depicted schematically in FIGS. 1, 2A and 2B, comprises a plurality of electrical contact elements 140 each of which has a cantilevered segment 142, a tip segment 144 and a mounting segment 130, and a support member 110 to which the contact elements 140 are attached. As will be described hereinafter, several contact elements 140 can be fabricated as a unitary structure in which the mounting segments 130 are not discrete, but constitute a continuous band of material with the several contact elements 140 projecting from that continuous band. The mounting surface 132 of the support member 110 may be electrically conductive such that the contact elements 140 become electrically conductive when the support member 110 is connected to a power source. As shown in FIG. 1, the electrical contact system 100 is suited for connection to a plating rotor 20 by means of connecting members 22 that connect the support member 110 to the rotor structure. The connecting members 22 may also provide electrical power through the plating rotor to the support member 110. The connecting members 22 may also provide for convenient attachment and removal of the contact system 100 from the plating rotor.
The support member 110 may be provided as a continuous ring or as a series of segments arranged in a ring, and FIGS. 1, 5 and 6A illustrate the support member as a continuous annular ring as would be suitable for use with a circular workpiece. The individual contact elements 140 are arranged around the support member 110 as seen in FIGS. 3 and 4A such that their cantilevered segments 142 project into the space 111 defined by and within the support member ring. With the contact system 100 oriented in a position to contact a workpiece at a processing position, and with the workpiece surface to be processed facing downward, the cantilevered segments 142 project inwardly and downwardly and the tip segments 144 project inwardly and upwardly, as seen in FIGS. 1, 2A and 2B.
The plating rotor 20, as seen in FIG. 1, includes a workpiece backing member 60 that extends and retracts relative to the support member 110 along the path “T” of FIG. 1. When the backing member 60 is retracted, it is removed from within the space 111 defined by the support member 110 so that a workpiece can be inserted into space 111 or removed from space 111. When the backing member 60 is extended with a workpiece in place within space 111, the backing member contacts the backside of the workpiece 101 and forces the workpiece to the processing position depicted in FIGS. 1 and 2A. As a consequence of the backing member 60 forcing the workpiece 101 to the processing position, the edge of the workpiece contacts the cantilevered segments 142 of the electrical contacts 140 and causes the cantilevered segments to bend from their condition shown in FIG. 2B toward the condition shown in FIG. 2A. Furthermore, as the workpiece is forced to the processing position shown in FIG. 2A, the tip segments 144 of the electrical contacts 140 contact the surface of the workpiece 101 to be processed so as to make electrical contact with that surface.
In the course of moving the workpiece 101 to the processing position shown in FIG. 2A, if the workpiece 101 is not axially centered within the space 111, the bending force exerted on the cantilevered segments 142 will be unequal from one side of the contact system 100 to the other, resulting in those cantilevered segments 142 under greater strain to urge the workpiece 101 to shift to an axially centered position. Furthermore, as the workpiece 101 is moved to the processing position shown in FIG. 2A and physical contact is made with the outer ends of the tip segments 144, workpiece contact with cantilevered segments 142 will cease, resulting in the sole electrical contact with the workpiece 101 being at the outer ends of the tip segments 144. This is described in more detail hereinafter with reference to FIGS. 3 and 4.
FIGS. 3A-3C illustrate the individual contacts 140 at various stages as the workpiece 101 is loaded into the contact assembly 100. With reference to the orientation shown in FIGS. 3A-3C, as the backing member 60 (FIG. 1) pushes the workpiece 101 upward in a direction P₁, the workpiece edge 102 of the workpiece 101 contacts and slides across the cantilevered segment 142 of the individual contacts 140. The force exerted by the edge 102 of the workpiece 101 on the cantilevered segment 142 causes it to bend and deflect in a direction S₁. If the workpiece 101 is off-center within the opening 111 such that the workpiece 101 bends the cantilevered segments 142 of the contacts 140 to a greater extent on one side of the contact assembly 100 than the other, the cantilevered segments 142 under greater strain will move the workpiece 101 in a direction Y so as to center and align the workpiece 101. Because of the design of the contact system 100, the tip segments 144 extend only a short distance onto the workpiece 101 and, therefore, it is important that the workpiece 101 be accurately centered within the opening 111 to insure that all tip segment contact is made around the workpiece 101 properly. Workpieces such as semiconductor wafers, and others, are manufactured within tolerance limits and are not uniformly exactly the same diameter. Therefore, the opening 111 must be sized to permit workpieces of small size variations to be inserted for processing. But the contact system 100 of this invention will properly position workpieces of various sizes within a given tolerance specification because of the configuration of the cantilevered segments 142. These cantilevered segments 142 extend into the opening 111 at an acute angle (relative to the loading path P₁) sufficient to cause the workpiece edge 102 to bear against the cantilevered segments 142 along a length of the segments that will cause the workpiece 101 to be axially aligned within the opening 111. An appropriate acute angle is 30 degrees to 60 degrees relative to the loading path P₁, not to exceed about 60 degrees at the first point of contact with the workpiece as shown in FIG. 3A or about 30 degrees at the point of final flexure as shown in FIG. 4C, and with a preferred unloaded acute angle being about 45 degrees.
The spring force built up in the cantilevered segments 142 will be greatest at the point where the workpiece 101 contacts the tips segments 144 as seen in FIG. 3C. This position is shown in enlarged detail in FIG. 4A. Just prior to the workpiece/contact condition shifting from sole contact with the cantilevered segments 142 to sole contact with the tip segments 144, the spring force built up within the cantilevered segments 142 will have caused the workpiece 101 to center. As the workpiece 101 is moved further in the direction P₁, the cantilevered segments 142 will continue to bend and deflect in the direction S₁such that the edge 102 of the workpiece 101 separates from the cantilevered segments 142 of the contacts 140.
As the workpiece 101 continues to advance from the position shown in FIG. 4A to the position shown in FIG. 4C, the transition segments (bends 143) of the contacts 140 widen so that the tip segments 144 pivot in the direction S₂such that an angle β between the tip and cantilevered segments 144 and 142 increases from an approximately 90 degrees to an obtuse angle. As the workpiece 101 moves to the position shown in FIG. 4C, the cantilevered segments 142 continue to flex about anchor points 138. Consequently, the tip segment edges 145 of the individual contacts 140 slide transversely across the surface of the workpiece 101 and advantageously remove oxides that may be on the surface of the workpiece 101 so as to insure a good electrical contact with the workpiece surface when the tip segment edges 145 reach their final position as shown in FIG. 4C.
FIGS. 5A and 5B illustrate a method for forming the contact assembly 100 in accordance with the invention. For example, FIG. 5A is a top plan view of a sheet 228 of conductive material having a first portion 230 a and a second portion 230 b. The sheet 228 is stamped or cut using suitable techniques to form the first and second portions 230 a-b. The illustrated first and second portions 230 a-b are mirror images of each other, and each includes trapezoidal-shaped sections 240.
FIG. 5B is a top plan view of the first portion 230 a after separating the second portion 230 b. Next, the sections 240 are bent along a line A-A to form the tip segments 144 and the transition segments (bends 143) of the contacts 140, and the first portion 230 a is bent along a line B-B to form the cantilevered segments 142 of the contacts 140 that project at an obtuse angle from the mounting section 132. The first portion 230 a is then bent along lines C-C to contour the mounting segments 130 to generally conform to the configuration of the mounting surface 132 of the support member 110.
The sheet portions 230 a and 230 b, as thus formed, can be secured to the support member 110 by spot welds, screws, or other techniques. As shown in FIGS. 5A and 5B, mounting holes 239 are provided in portions 230 a and 230 b, and half holes 241 are provided in the ends of portions 230 a and 230 b, so that the thus-formed portions can be aligned end-to-end and welded or screwed to the support member 110. This end-to-end mounting of the sheet portions, thus formed, is illustrated in FIG. 7B.
The operation and features of the contact assemblies are best understood in light of the environment and equipment in which they can be used to electroprocess workpieces (e.g., electroplate and/or electropolish/electroetch). As such, the following description is divided into the following sections: (A) Reactor Heads Having Contact Assemblies; (B) Electrochemical Processing Stations Having Contact Assemblies; and (C) Integrated Tools and Electroprocessing Reactors.
A. Reactor Heads Having Contact Assemblies
FIG. 1 is a schematic side cross-sectional view of an electroprocessing system 10 for applying an electrical potential to a workpiece 101 in accordance with the invention. The electroprocessing system 10 includes a head assembly 20 for carrying the workpiece 101 and a reaction vessel 90 for containing a processing fluid. The head assembly 20 includes a driving member 30 for rotating the workpiece 101 in a direction R, a backing member 60 for positioning the workpiece 101 within the head assembly 20, and a contact assembly 100 for applying an electrical potential to the workpiece 101. During electroprocessing, the backing member 60 and the contact assembly 100 hold the workpiece 101 at a workpiece processing site in the reaction vessel 90 so that at least a processing surface of the workpiece 101 engages the processing fluid.
FIG. 2A is a side cross-sectional view of a portion of the contact assembly 100 in a loaded state with the workpiece 101 in the processing position, and FIG. 2B is a side cross-sectional view of the portion of the contact assembly 100 in an unloaded state without a workpiece. As shown in FIG. 8, the head assembly may be mounted for pivoting about a horizontal axis so as to enable the contact assembly to be turned from a “face-down” position shown in FIG. 1 to a “face-up” position shown in FIG. 8. In the FIG. 8 embodiment, when the contact assembly is in the illustrated “face-up” position and the backing member is retracted, a workpiece 101 with its surface to be processed can be loaded into the contact assembly with that surface “face-up”. After the workpiece is loaded and the backing member is extended to locate the workpiece in the stabilized condition in the head assembly shown in FIGS. 1 and 2A, the head assembly can be pivoted to the “face-down” position shown in FIG. 1 and lowered into reaction vessel 90 for processing. FIG. 6 is an isometric view of the contact assembly 100 turned over to the “face-up” position shown in FIG. 8.
As previously described and referring to FIGS. 2A, 2B and 7, the contact assembly 100 includes a support member 110 and a plurality of contacts 140. The individual contacts 140 have cantilevered segments 142 projecting generally inwardly in a first direction at an inclined angle relative to a loading path P (FIG. 7), and tip segments 144 projecting from the cantilevered segments 142 generally inwardly in a second direction relative to the loading path P. As shown in FIG. 7B, the “first direction” is downward and the “second direction” is upward. In accordance with the FIG. 8 embodiment, however, in which the workpiece is loaded into the head assembly when the head assembly is turned to the illustrated “face-up” position, the “first direction” is upward and the “second direction” is downward.
The contacts 140 are flexible and move between (a) a flexed first position (shown in FIG. 2A) when the workpiece 101 is fully loaded in the contact assembly 100, and (b) a second position (shown in FIG. 2B) when the workpiece 101 is not loaded in the contact assembly 100. The flexibility of the contacts 140 and the orientation of the cantilevered segment 142 of the individual contacts 140 enables precise centering of the workpiece 101. Specifically, the workpiece 101 will generally not be axially centered within the contact assembly 100. Because of the non-uniformity of workpiece diameters (even though the workpiece will be within specified tolerance limits) and because the opening 111 must be large enough to accommodate a reasonable range of workpiece diameters, the workpiece 101 will more often than not contact the cantilevered segments 142 of the contacts 140 “off center.” In addition to being flexible, the cantilevered segments 142 must be stiff enough to force the workpiece 101 into an axially centered position, as previously described. The cantilevered segments 142 of those contacts 140 under greater strain due to the off center workpiece 101 urge the workpiece 101 toward the contacts 140 on the opposite side of the contact assembly 100 as the workpiece 101 moves along the loading path P toward the tip segments 144. The contacts 140 thus center the workpiece 101. By centering and aligning workpieces in the contact assembly 100, the tip segments 144 of the contacts 140 are positioned to repeatably contact the workpieces within a small distance from the perimeter. This allows the tip segments 144 of the individual contacts 140 to occupy only a small perimeter region of the workpiece 101. Workpieces such as semiconductor wafers have an “exclusion zone” at the perimeter of the “device side” of the workpiece (the side of the workpiece on which processing is to occur, typically). The contacts 140 will provide reliable electrical contact with the workpiece processing surface within a narrow exclusion zone, thereby increasing the usable surface of the workpiece radially inward of the perimeter exclusion zone.
The transition segments (bends 143) of the individual contacts 140 also flex and the tip segments 144 consequently pivot as the workpiece 101 is loaded into the contact assembly 100 (FIG. 2A). This creates a strain on the transition and tip segments 143 and 144. During an electroplating process, electroplated metal tends to build up on the workpiece 101 around the tip edges 145, tending to attach the tip edges 145 to the workpiece 101. Because the tips segments 144 are much shorter, and consequently much stiffer, than the cantilevered segments 142, the strain created in the transition and tip segments 143 and 144 will cause the tip segments 144 to return to an unstrained condition when the backing member 60 is retracted, breaking the tip edges 145 loose from attachment to the workpiece 101. The strain created by flexure of the individual contacts 140 creates an ejection force to break the mechanical bond between the workpiece 101 and the contacts 140 as the workpiece 101 is unloaded after processing. The ejection force is produced as the contacts 140 spring back and return to their unflexed, original configuration. This feature facilitates separation of the workpiece 101 from the tip segments 144 of the individual contacts 140 without damaging the contacts 140.
Referring to FIGS. 1 and 2A, the contact assembly 100 is a “wet contact” assembly, meaning that a section of the contacts 140 projects into the processing fluid during electroprocessing. Specifically, in the processing position with the workpiece 101 in contact with the electrolyte, the workpiece 101 is partially submerged face down in the processing fluid, and the tip segments 144 of the contacts 140 are immersed in the processing fluid below the workpiece 101. In order to minimize adverse effects to the plating process in the immediate vicinity of the immersed tip segments 144, transition segments 143 and portions of the cantilevered segments 142, the cantilevered segments 142 are formed so as to have a reduced planar profile. As shown in FIGS. 5A and 5B, this can be accomplished by forming the cantilevered segments 142 with trapezoidal profiles that are wider at their base (shown at line B-B) and narrower at their tips (shown at line A-A).
The contacts 140 may not be coated with a dielectric material such that the submerged section of the individual contacts 140 thieves material from the processing fluid near the perimeter of the workpiece 101. An advantage of this feature is that thieving reduces the thickness of the plated layer at the perimeter of the workpiece 101 so that the material plates more uniformly across the workpiece 101. This feature is particularly useful for applications in which it is desirable to reduce the thickness of a plated layer at the perimeter of the workpiece to compensate for edge effects.
Referring to FIGS. 2A and 2B, the contact assembly 100 further includes a dielectric splash guard 160 attached to the support member 110. The dielectric splash guard 160 projects from the support member 110 in a direction generally parallel to the contacts 140 and forms a skirt around the contacts 140 to protect the contacts 140. This protective feature enables a contact assembly to be stored, shipped, or placed on a flat surface with the tip segments 144 elevated off the flat surface. The dielectric splash guard 160 also assists in collecting in-situ rinse water after a rinse cycle.
The contact assembly 100 is particularly advantageous for electroprocessing large workpieces with small features. In addition to repeatedly centering the workpieces and enabling removal of the workpieces, the contacts also have a low-profile to mitigate turbulence and a high-density to enhance the uniformity of the current density. Several specific features of contacts in accordance with the invention are described in more detail with reference to FIGS. 6 and 7A-B.
FIG. 7A is a bottom isometric view and FIG. 7B is an enlarged isometric cross-sectional view of the contact assembly 100. Referring to both FIGS. 7A and 7B, the support member 110 has an opening 111 for receiving the workpiece 101 along the loading path P. The support member 110, more specifically, includes an inner wall 112, an outer wall 114 opposite the inner wall 112, a first wall 116, and a second wall 118 opposite the first wall 116. The illustrated outer wall 114 is tapered inwardly extending from the second wall 118 toward the first wall 116. The support member 110 further includes a rim 120 projecting radially inward from the inner wall 112 and defining a portion of the first wall 116. The rim 120 is sized such that the opening 111 (FIG. 7A) is large enough to receive the workpiece along the loading path P (FIG. 7A). The support member 110 is electrically conductive and composed of titanium with a layer of platinum plated onto the exterior surface. The illustrated support member 110 is a continuous ring, designed for a circular workpiece, but it can be a series of discrete curved segments arranged to accommodate a type of workpiece.
Referring only to FIG. 7B, the contacts 140 are parts of a contact member 130 having a mounting section 132 with a first edge 133 proximate to the rim 120 and a second edge 134 proximate to the junction between the inner and second walls 112 and 118. The illustrated mounting section 132 includes a plurality of generally planar segments 136 separated by corresponding bends 137 such that the mounting section 132 is generally annular or otherwise configured to accommodate the workpiece. The mounting section 132 is either a single conductive band that extends around the inner wall 112 of the support member 110 or several individual sections that are coupled together to form a ring-like conductor. In either case, the individual sections 136 of the mounting section 132 are in electrical communication with each other independent of the position of the contact assembly 100 or the workpiece. As previously described, the individual sections are abutted end-to-end and secured to the support member inner wall 112 by means of screws or rivets (not shown) inserted through mounting holes 239 and 241. The support member 110 provides an electrically conductive mounting for the contact assembly such as being fabricated of an electrically conductive material or having an inner wall 112 fabricated of an electrically conductive material, or by otherwise providing an appropriate power connection to the contact mounting section 132.
The contacts 140 are cantilevered fingers that project radially inward and generally downward from the mounting section 132. The contacts 140 and the mounting section 132 illustrated in FIGS. 7A and 7B are unitary components of the contact member 130. Specifically, the contacts 140 and mounting section 132 are integral portions of a common piece of sheet metal. The illustrated contact member 130 includes a bend 138 at the second edge 134 of the mounting section 132 so that the contacts 140 project into the opening 111 (FIG. 7A).
The cantilevered segment 142 of the individual contacts 140 projects inwardly from the mounting section 132 in a first direction at an inclined angle relative to the loading path P (FIG. 7A) and extends into a workpiece processing plane defined by a workpiece in a processing position. The tip segment 144 of the individual contacts 140 projects inwardly in a second direction at an inclined angle with respect to the loading path P, and extends back toward the workpiece processing plane. The orientation of the cantilevered segments 142 aligns and centers a workpiece within the opening 111 (FIG. 7A), and the angled orientation of the tip segments 144 ensures that the tip edges 145 contact the workpiece to electrically connect the contact assembly 100 to the workpiece. These aspects are described hereinabove in greater detail with reference to FIGS. 3A-4C.
In the illustrated contacts 140, the length of the cantilevered segments 142 is greater than the length of the tip segments 144 so that the tip edge 145 of the individual contacts 140 is positioned below the second wall 118 of the support member 110. An advantage of this feature is that the support member 110 will be positioned above the processing fluid while the contacts 140 are at least partially submerged within the processing fluid and contact the workpiece. As such, the support member 110 does not need a dielectric layer over the exterior surface to inhibit material from plating onto the member 110 and, furthermore, will not interfere with the flow of processing fluid along the processing plane.
The illustrated individual contacts 140 are tapered and have a first width W₁at the junction between the mounting section 132 and the cantilevered segment 142 and a second width W₂at the junction between the cantilevered segment 142 and the tip segment 144. As such, the distance between the tip segments 144 of adjacent contacts 140 is greater than the distance between the cantilevered segments 142 of adjacent contacts 140. Also, as described above, the contacts 140 are thin and flexible elements. For example, the illustrated contacts 140 and contact member 130 have a thickness of approximately 0.05 mm to approximately 1.25 mm. Although thin and flexible, the contacts 140 are stiff enough so that the strain imposed by loading a workpiece creates an ejection force for breaking the mechanical bond between workpieces and the contacts 140 when the backing member 60 is retracted. This feature facilitates separation of the workpieces from the contacts 140 without damaging the contacts 140.
The contacts 140 may be composed of a conductive material that is inert in the particular electroprocessing fluid. Suitable conductive materials include platinum/iridium alloys, platinum, stainless steel, tungsten, and/or molybdenum. For example, the contacts 140 can be composed of a platinum/iridium alloy having approximately 5-30% iridium, and more particularly about 20% iridium. The illustrated contacts 140 do not include a dielectric coating on the conductive material. As such, the contacts 140 thieve material from the processing fluid near the perimeter of the workpiece. This feature is particularly useful for applications in which it is desirable to reduce the thickness of a plated layer at the perimeter of the workpiece to compensate for edge effects.
One feature of the contact assembly 100 illustrated in FIGS. 1-7 is that the flexible nature of the contacts 140 allows the tip segments 144 to project only slightly beyond the topographical surface of the workpiece 101 and improve the electrical connection between the contacts 140 and the workpiece 101. Moreover, the large number of individual contacts 140 enhances the uniformity of the electrical potential around the perimeter of the workpiece 101. Therefore, the contact assembly 100 is expected to further enhance the uniformity of the plated layer by providing a large number of contacts 140 that can adapt to different typographical features on the workpiece 101.
Referring back to FIGS. 2A, 2B, and 7B, the illustrated contact assembly 100 further includes a plurality of drain slots 122 extending through the support member 110. The drain slots 122 include a first end 124 at the first wall 116 and a second end 126 at the second wall 118. The drain slots 122 are positioned so that when the contact assembly 100 is spinning, the liquid present from a plating or rinsing step has an exit and will not drip onto the workpiece later when the contact assembly 100 is inverted.
A dielectric splash guard 160 is attached to the outer and second walls 114 and 118 of the support member 110. The splash guard 160 includes a first portion 162 and a second portion 164 projecting inwardly and downwardly from the first portion 162 in a direction generally parallel to the contacts 140. The second portion 164 projects downward a first distance D₁from the second wall 118 and the contacts 140 project downward a second distance D₂from the second wall 118 when a workpiece is not loaded in the contact assembly 100. The first distance D₁is greater than or equal to the second distance D₂so that the splash guard 160 forms a skirt around the contacts 140 to protect the contacts 140. The splash guard 160 also assists in collecting in-situ rinse water after a rinse cycle, and includes a plurality of slots 166 to sling rinse water during the rinse cycle.
Referring to FIGS. 6 and 8, the head assembly 20 further includes a slot 22 through which workpieces can ingress and egress, and the backing member 60 includes a plurality of tabs 62 for pressing a workpiece against the contact assembly 100. A workpiece is loaded into the contact assembly 100 face up such that the tabs 62 move the workpiece upwardly into the contact assembly 100 while the assembly 100 is oriented with the contacts 140 projecting generally upward. After loading, the workpiece 101 and contact assembly 100 are turned over so that the workpiece 101 faces down and the contacts 140 project downwardly from the support member 110 as illustrated in FIGS. 1-2B.
FIG. 8 illustrates a reactor head 350 of an electroprocessing reactor in which the contact assembly 100 can be used. The reactor head 350 includes a rotor assembly 330 and a stationary assembly 360. The rotor assembly 330 is configured to receive and carry an associated wafer or workpiece 101, position the workpiece 101 in a process-side down orientation within a reactor bowl, and rotate or spin the workpiece 101 while joining its electrically-conductive surface in the plating circuit of a reactor assembly. The reactor head 350 is typically mounted on a lift/rotate apparatus 370 that is configured to rotate the reactor head 350 from an upwardly-facing disposition, in which it receives the workpiece 101 to be plated, to a downwardly-facing disposition, in which the surface of the workpiece 101 to be plated is positioned downwardly in the reactor bowl for electroprocessing. A robotic arm 390 (sometimes referred to as an end effector) is typically employed for placing the workpiece 101 in position on the rotor assembly 330, and for removing the plated workpiece 101 from within the rotor assembly 330.
B. Electrochemical Processing Stations Having Contact Assemblies
FIG. 9 illustrates another environment in which the contact assembly 100 can be used. FIG. 9 is a schematic side cross-sectional view of an electrochemical processing station 420 having a head assembly 450 and a processing chamber 470. The head assembly 450 includes a spin motor 452, a rotor 454 coupled to the spin motor 452, and a contact assembly 100 carried by the rotor 454. The rotor 454 has a bellows 456 and a backing plate 460. The backing plate 460 moves transverse to a workpiece 101 (arrow T) between a first position in which the backing plate 460 contacts a backside of the workpiece 101 and a second position in which the backing plate 460 is spaced apart from the backside of the workpiece 101. The contact assembly 100 is removably coupled to the head assembly 450 by a plurality of shafts 459.
The processing chamber 470 defines a reactor that includes an outer housing 480 and a reaction vessel 490 in the housing 480. The reaction vessel 490 includes a plurality of electrodes 492 and a dielectric divider 494 for directing a flow of processing fluid between the electrodes 492 and the workpiece 101. The processing fluid, for example, flows over a weir (arrow F) and into the housing 480, from which the processing fluid is recycled. Alternatively, the reaction vessel 490 may include a single electrode. Suitable processing chambers are disclosed in U.S. patent application Ser. Nos. 10/729,349 and 10/860,384, which are incorporated by reference herein.
The head assembly 450 and the contact assembly 100 hold the workpiece 101 at a workpiece-processing site in the reaction vessel 490 so that at least a processing surface of the workpiece 101 engages the processing fluid. An electrical field is established in the fluid by generating an electrical potential between the surface of the workpiece 101 via the contact assembly 100 and the electrodes 492. For example, the contact assembly 100 can be biased with a negative potential with respect to the electrodes 492 to plate metals or other types of materials onto the workpiece 101. Alternatively, the contact assembly 100 can be biased with a positive potential with respect to the electrodes 492 to (a) de-plate the contacts 140 or electropolish plated material from the workpiece 101, or (b) deposit other materials onto the workpiece 101 (e.g., an 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.
C. Integrated Tools and Electroprocessing Reactors
FIG. 10 is an isometric view of a processing apparatus 500 having electrochemical processing stations 420. A portion of the processing apparatus 500 is shown in a cut-away view to illustrate selected internal components. The processing apparatus 500 includes a cabinet 502 having an interior region 504 defining an enclosure that is at least partially isolated from an exterior region 505. The illustrated cabinet 502 also includes a plurality of apertures 506 through which workpieces 101 can ingress and egress between the interior region 504 and a load/unload station 510.
The load/unload station 510 has two container supports 512 that are each housed within a protective shroud 513. The container supports 512 are configured to position workpiece containers 514 relative to the apertures 506 in the cabinet 502. The workpiece containers 514 each house a plurality of microfeature workpieces 101 in a “mini” clean environment for carrying the workpieces 101 through other environments that are not at clean room standards. Each of the workpiece containers 514 is accessible from the interior region 504 of the cabinet 502 through the apertures 506.
The processing apparatus 500 also includes a one or more workpiece cleaning stations and workpiece etching stations 522, as well as electrochemical processing stations, and a transfer device 530 in the interior region 504 of the cabinet 502. The transfer device 530 moves the microfeature workpieces 101 between the workpiece containers 514 and the processing stations 420 and 522. For example, the transfer device 530 includes a linear track 532 extending in a lengthwise direction of the interior region 504 between the processing stations 420. The illustrated apparatus 500 includes a first set of processing stations 420 arranged along a first row R₁-R₁and a second set of processing stations 420 arranged along a second row R₂-R₂. The linear track 532 extends between the first and second rows R₁-R₁and R₂-R₂of the processing stations 420. The transfer device 530 further includes a robot unit 534 carried by the track 532 that can access any of the processing stations 420 along the track 532. Suitable transfer devices are disclosed in U.S. Pat. Nos. 6,752,584; 6,749,391; 6,749,390; 6,318,951; and 6,322,119, all of which are incorporated by reference herein.
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. For example, the contact member can be manufactured using different methods than those described above with reference to FIGS. 5A and 5B, or the contacts 140 can be separate fingers attached directly to the support member 110 or the mounting section of a contact member 130. Moreover, the contact assemblies described above can be used in various types of reactors. Accordingly, the invention is not limited except as by the appended claims.

Claims

1. A workpiece holder for holding a workpiece and providing electrical contact to the workpiece in an electroprocessing system to apply an electrical potential to a workpiece when the workpiece is positioned in a processing position, the workpiece holder comprising:

(a) a workpiece backing member axially extendable relative to a support member for moving a workpiece from a loading position to a processing position along a loading path; and

(b) a contact assembly including,

the support member defining an opening for receiving a workpiece; and

a plurality of contacts arranged around the perimeter of the support member opening and connected to the support member, each individual contact consisting of a cantilevered segment projecting into the support member opening at an acute angle relative to the loading path so as to be contacted by a perimeter edge of the workpiece as the workpiece is moved to the processing position, and a tip segment integral with and projecting from the cantilevered segment so as to contact and support the workpiece when the workpiece is moved to the processing position, the cantilevered segments being so constructed and arranged to guide and center the workpiece as the workpiece is moved by the workpiece backing member to the processing position, and the tip segments being so constructed and arranged to provide tip edges that electrically contact the workpiece at the processing position.

2. The workpiece holder of claim 1 wherein the cantilevered segments are integral with a contact mounting section and the contact mounting section is fastened to the support member.

3. The workpiece holder of claim 1 wherein the contact assembly further comprises several mounting sections aligned end-to-end and fastened to the support member, and each of the mounting sections have several integral contacts.

4. The workpiece holder of claim 1 wherein the cantilevered segments project at an acute angle of between about 30 degrees to 60 degrees relative to the loading path.

5. The workpiece holder of claim 1 wherein the cantilevered segments have a trapezoidal planar profile that tapers from a wider base to a narrower outer end, and the tip segments extend from the cantilevered segment outer ends.

6. The workpiece holder of claim 1 wherein each tip segment extends approximately perpendicular to the integral cantilevered segment.

7. The workpiece holder of claim 1 wherein the cantilevered segments do not contact the workpiece when the workpiece is in the processing position.

8. The workpiece holder of claim 1 wherein the support member has an electrically conductive inner wall defining the opening, and wherein the cantilevered segments are integral with a contact mounting section and the contact mounting section is fastened to the support member inner wall.

9. The workpiece holder of claim 8 wherein the individual contacts have a first width at a junction between the mounting section and the cantilevered segments and a second width at a junction between the cantilevered and tip segments, and wherein the first width is greater than the second width such that adjacent tip segments are separated from one another.

10. The workpiece holder of claim 1 for use in an electroplating operation wherein the cantilevered segments flex during loading of the workpiece onto the tip segments such that retraction of the workpiece backing member causes the tip edges of the tip segments to break loose from an electroplated workpiece surface created in the electroplating operation.

11. The workpiece holder of claim 1 further comprising a skirt ring attached to the support member and extending therefrom so as to extend beyond the contacts when the workpiece is removed from the contacts.

12. The workpiece holder of claim 11 wherein the support member and skirt ring are provided with fluid drain apertures for draining electroprocessing fluid away from the workpiece during processing.

13. A contact assembly for use in an electrochemical processing system to apply an electrical potential to a microfeature workpiece, the contact assembly comprising:

a support member having an inner wall defining an opening configured to receive the workpiece along a loading path; and

a plurality of contacts coupled to the support member, the individual contacts including a cantilevered segment and a tip segment integral with and projecting from the cantilevered segment, the cantilevered segment projecting inwardly in a first direction along the loading path, the tip segment projecting inwardly in a second direction along the loading path, the first direction being opposite the second direction, wherein the individual contacts are in electrical communication with each other independent of the position of the workpiece.

14. The contact assembly of claim 13 for use in an electroplating operation wherein the cantilevered segments flex during loading of the workpiece onto the tip segments such that retraction of a workpiece backing member causes tip edges of the tip segments to break loose from an electroplated workpiece surface created in the electroplating operation.

15. The contact assembly of claim 13, further comprising an outer dielectric member projecting in the first direction from the support member.

16. The contact assembly of claim 13, further comprising a contact member having a mounting section attached to the inner wall of the support member and the plurality of contacts projecting from the mounting section, wherein the mounting section and the contacts are integral components of the contact member.

17. The contact assembly of claim 13, further comprising a contact member having a mounting section attached to the inner wall of the support member and the plurality of contacts projecting from the mounting section, wherein the individual contacts have a first width at a junction between the mounting section and the cantilevered segments and a second width at a junction between the cantilevered and tip segments, and wherein the first width is greater than the second width such that the distance between the cantilevered segments of adjacent contacts is less than the distance between the tip segments of adjacent contacts.

18. A reactor for electroprocessing of workpieces, the reactor comprising:

a vessel for holding an electroprocessing fluid;

a plurality of electrodes disposed relative to the vessel and dielectrically separated from one another to provide an electrical potential in the vessel;

a head assembly movable relative to the vessel between a load/unload position and a processing position, and including a workpiece backing member axially extendable relative to a support member for moving a workpiece from a loading position to a processing position along a loading path; and

a contact assembly carried by the head assembly, the contact assembly comprising

the support member defining an opening for receiving the workpiece; and

19. The reactor of claim 18 wherein the cantilevered segments are integral with a contact mounting section and the contact mounting section is fastened to the support member.

20. The reactor of claim 18 wherein contact assembly further comprises several mounting sections aligned end-to-end and fastened to the support member, and each of the mounting sections have several integral cantilevered segments.

21. The reactor of claim 18 wherein the cantilevered segments project at an acute angle of between about 30 degrees to 60 degrees relative to the loading path.

22. The reactor of claim 18 wherein the cantilevered segments have a trapezoidal planar profile that tapers from a wider base to a narrower outer end, and the tip segments extend from the cantilevered segment outer ends.

23. The reactor of claim 18 wherein each tip segment extends approximately perpendicular to the integral cantilevered segment.

24. The reactor of claim 18 wherein the cantilevered segments do not contact the workpiece when the workpiece is in the processing position.

25. The reactor of claim 18 wherein the support member has an electrically conductive inner wall defining the opening, and wherein the cantilevered segments are integral with a contact mounting section and the contact mounting section is fastened to the support member inner wall.

26. The reactor of claim 18 for use in an electroplating operation wherein the cantilevered segments flex during loading of the workpiece onto the tip segments such that retraction of the workpiece backing member causes tip edges of the tip segments to break loose from an electroplated workpiece surface created in the electroplating operation.

27. The reactor of claim 18 further comprising a lift/rotate assembly configured to rotate the head assembly from an upwardly facing disposition for receiving the workpiece to a downwardly facing disposition for placing the workpiece in the vessel for electroprocessing.

28. An electroprocessing apparatus comprising:

(a) a cabinet having an interior region within which workpieces may be processed;

(b) a plurality of workpiece processing stations located within the interior region, at least one of such stations comprising a reactor for electroprocessing of workpieces, the reactor comprising:

a vessel for holding an electroprocessing fluid;

the support member defining an opening for receiving the workpiece; and

a plurality of contacts arranged around the perimeter of the support member opening and connected to the support member, each individual contact consisting of a cantilevered segment projecting into the support member opening at an acute angle relative to the loading path so as to be contacted by a perimeter edge of the workpiece as the workpiece is moved to the processing position, and a tip segment integral with and projecting from the cantilevered segment so as to contact and support the workpiece when the workpiece is moved to the processing position, the cantilevered segments being so constructed and arranged to guide and center the workpiece as the workpiece is moved by the workpiece backing member to the processing position, and the tip segments being so constructed and arranged to provide tip edges that electrically contact the workpiece at the processing position;

(c) a load/unload station for delivering workpieces to the interior region and for receiving workpieces from the interior region; and

(d) a workpiece transfer for delivering workpieces to and from processing stations in the interior region.

29. The electroprocessing apparatus of claim 28 wherein the processing stations include at least one workpiece cleaning station.

30. The electroprocessing apparatus of claim 28 wherein the processing stations include at least one workpiece etching station.