Patent Application
20230076493
An Application Data Sheet is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed Application Data Sheet is incorporated by reference herein in their entireties and for all purposes.
This invention relates to the formation of damascene interconnects for integrated circuits, and electroplating apparatuses which are used during integrated circuit fabrication.
Electroplating is a common technique used in integrated circuit (IC) fabrication to deposit one or more layers of conductive metal. In some fabrication processes it is used to deposit single or multiple levels of copper interconnects between various substrate features. An apparatus for electroplating typically includes an electroplating cell having a pool/bath of electrolyte and a clamshell designed to hold a semiconductor substrate during electroplating.
During operation of the electroplating apparatus, a semiconductor substrate is submerged into the electrolyte pool such that one surface of the substrate is exposed to electrolyte. One or more electrical contacts established with the substrate surface are employed to drive an electrical current through the electroplating cell and deposit metal onto the substrate surface from metal ions available in the electrolyte. Typically, the electrical contact elements are used to form an electrical connection between the substrate and a bus bar acting as a current source. However, in some configurations, a conductive seed layer on the substrate contacted by the electrical connections may become thinner towards the edge of the substrate, making it more difficult to establish an optimal electrical connection with the substrate.
Another issue arising in electroplating is the potentially corrosive properties of the electroplating solution. Therefore, in many electroplating apparatus a lipseal is used at the interface of the clamshell and substrate for the purpose of preventing leakage of electrolyte and its contact with elements of the electroplating apparatus other than the inside of the electroplating cell and the side of the substrate designated for electroplating.
Disclosed herein are lipseal assemblies for use in an electroplating clamshell for engaging and supplying electrical current to a semiconductor substrate during electroplating. In some embodiments, a lipseal assembly may include an elastomeric lipseal for engaging the semiconductor substrate and one or more contact elements for supplying electrical current to the semiconductor substrate during electroplating. In some embodiments, upon engagement, the elastomeric lipseal substantially excludes plating solution from a peripheral region of the semiconductor substrate.
In some embodiments, the one or more contact elements are structurally integrated with the elastomeric lipseal and include a first exposed portion which contacts the peripheral region of the substrate upon engagement of the lipseal with the substrate. In some embodiments, the one or more contact elements may further include a second exposed portion for making an electrical connection with an electrical current source. In certain such embodiments, the current source may be a bus bar of the electroplating clamshell. In some embodiments, the one or more contact elements may further include a third exposed portion connecting the first and second exposed portions. In certain such embodiments, the third exposed portion may be structurally integrated on a surface of the elastomeric lipseal.
In some embodiments, the one or more contact elements may include an unexposed portion connecting the first and second exposed portions, and the unexposed portion may be structurally integrated underneath a surface of the elastomeric lipseal. In certain such embodiments, the elastomeric lipseal is molded over the unexposed portion.
In some embodiments, the elastomeric lipseal may include a first inner diameter defining a substantially circular perimeter for excluding a plating solution from a peripheral region, and the first exposed portion of the one or more contact elements may define a second inner diameter that is larger than the first inner diameter. In certain such embodiments, the magnitude of the difference between the first inner diameter and the second inner diameter is about or less than 0.5 mm. In certain such embodiments, the magnitude of the difference between the first inner diameter and the second inner diameter is about or less than 0.3 mm.
In some embodiments, a lipseal assembly may include one or more flexible contact elements for supplying electrical current to the semiconductor substrate during electroplating. In certain such embodiments, at least a portion of the one or more flexible contact elements may be conformally positioned on an upper surface of the elastomeric lipseal and, upon engagement with the semiconductor substrate, the flexible contact elements may be configured to flex and form a conformal contact surface that interfaces with the semiconductor substrate. In certain such embodiments, the conformal contact surface interfaces with a bevel edge of the semiconductor substrate.
In some embodiments, the one or more flexible contact elements may have a portion which is not configured to contact the substrate when the substrate is engaged by the lipseal assembly. In certain such embodiments, the non-contacting portion comprises a non-conformable material. In some embodiments, the conformal contact surface forms a continuous interface with the semiconductor substrate, whereas in some embodiments, the conformal contact surface forms a non-continuous interface with the semiconductor substrate having gaps. In certain such later embodiments, the one or more flexible contact elements may include multiple wire tips or a wire mesh disposed on the surface of the elastomeric lipseal. In some embodiments, the one or more flexible contact elements conformally positioned on the upper surface of the elastomeric lipseal include conductive deposits formed using one or more techniques selected from chemical vapor deposition, physical vapor deposition, and electroplating. In some embodiments, the one or more flexible contact elements conformally positioned on the upper surface of the elastomeric lipseal may include an electrically conductive elastomeric material.
Also disclosed herein are elastomeric lipseals for use in an electroplating clamshell for supporting, aligning, and sealing a semiconductor substrate in the electroplating clamshell. In some embodiments, the lipseal includes a flexible elastomeric support edge and a flexible elastomeric upper portion located above the flexible elastomeric support edge. In some embodiments, the flexible elastomeric support edge has a sealing protrusion configured to support and seal the semiconductor substrate. In certain such embodiments, upon sealing the substrate, the sealing protrusion defines a perimeter for excluding plating solution. In some embodiments, the flexible elastomeric upper portion includes a top surface configured to be compressed, and an inner side surface located outward relative to the sealing protrusion. In certain such embodiments, the inner side surface may be configured to move inward and align the semiconductor substrate upon compression of the top surface, and in some embodiments, configured to move inward by about or at least 0.2 mm upon compression of the top surface. In some embodiments, when the top surface is not compressed, the inner side surface is located sufficiently outward to allow the semiconductor substrate to be lowered through the flexible elastomeric upper portion and placed onto the sealing protrusion without contacting the upper portion, but wherein upon placement of the semiconductor substrate on the sealing protrusion and compression of the top surface, the inner side surface contacts and pushes on the semiconductor substrate aligning the semiconductor substrate in the electroplating clamshell.
Also disclosed herein are methods of aligning and sealing a semiconductor substrate in an electroplating clamshell having an elastomeric lipseal. In some embodiments, the methods include opening the clamshell, providing a substrate to the clamshell, lowering the substrate through an upper portion of the lipseal and onto a sealing protrusion of the lipseal, compressing a top surface of the upper portion of the lipseal to align the substrate, and pressing on the substrate to form a seal between the sealing protrusion and the substrate. In some embodiments, compressing the top surface of the upper portion of the lipseal causes an inner side surface of the upper portion of the lipseal to push on the substrate aligning it in the clamshell. In some embodiments, compressing the top surface to align the substrate includes pressing on the top surface with a first surface of the cone of the clamshell, and pressing on the substrate to form a seal includes pressing on the substrate with a second surface of the cone of the clamshell.
In some embodiments, compressing the top surface to align the substrate includes pushing on the top surface with a first pressing component of the clamshell, and pressing on the substrate to form a seal includes pressing on the substrate with a second pressing component of the clamshell. In certain such embodiments, the second pressing component may be independently movable with respect to the first pressing component. In certain such embodiments, compressing the top surface includes adjusting the pressing force exerted by the first pressing component based upon the diameter of the semiconductor substrate.
Also disclosed herein are cup assemblies for holding, sealing, and providing electrical power to a semiconductor substrate during electroplating which include a cup bottom element including a main body portion and a moment arm, an elastomeric sealing element disposed on the moment arm, and an electrical contact element disposed on the elastomeric sealing element. The elastomeric sealing element, when pressed against by the semiconductor substrate, may seal against the substrate so as to define a peripheral region of the substrate from which plating solution is substantially excluded during electroplating, and the electrical contact element may contact the substrate in said peripheral region when the sealing element seals against the substrate so that the contact element may provide electrical power to the substrate during electroplating. In some embodiments, the main body portion does not substantially flex when the semiconductor substrate is pressed against the moment arm,
In some embodiments, the main body portion is rigidly affixed to another feature of the cup structure and the ratio of the average vertical thickness of the main body portion to the average vertical thickness of the moment arm is greater than about 5 so that the main body portion does not substantially flex when the semiconductor substrate is pressed against the moment arm. In some embodiments, the electrical contact element has a substantially flat but flexible contact portion disposed upon a substantially horizontal portion of the elastomeric sealing element. In some embodiments, the elastomeric sealing element is integrated with the cup bottom element during manufacturing.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented concepts. The presented concepts may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail so as to not unnecessarily obscure the described concepts. While some concepts will be described in conjunction with specific embodiments, it will be understood that these embodiments are not intended to be limiting.
An exemplary electroplating apparatus is presented in
In the depicted embodiment, the clamshell assembly (which includes the cup 101 and the cone 103) is supported by struts 104, which are connected to a top plate 105. This assembly (101, 103, 104, and 105) is driven by a motor 107 via a spindle 106 connected to the top plate 105. The motor 107 is attached to a mounting bracket (not shown). The spindle 106 transmits torque (from the motor 107) to the clamshell assembly causing rotation of a wafer (not shown in this figure) held therein during plating. An air cylinder (not shown) within the spindle 106 also provides a vertical force for engaging the cup 101 with the cone 103. When the clamshell is disengaged (not shown), a robot with an end effector arm can insert a wafer in between the cup 101 and the cone 103. After a wafer is inserted, the cone 103 is engaged with the cup 101, which immobilizes the wafer within apparatus 100 leaving a working surface on one side of the wafer (but not the other) exposed for contact with the electrolyte solution.
In certain embodiments, the clamshell assembly includes a spray skirt 109 that protects the cone 103 from splashing electrolyte. In the depicted embodiment, the spray skirt 109 includes a vertical circumferential sleeve and a circular cap portion. A spacing member 110 maintains separation between the spray skirt 109 and the cone 103.
For the purposes of this discussion, the assembly including components 101-110 is collectively referred to as a “wafer holder” (or “substrate holder”) 111. Note however, that the concept of a “wafer holder”/“substrate holder” extends generally to various combinations and sub-combinations of components that engage a wafer/substrate and allow its movement and positioning.
A tilting assembly (not shown) may be connected to the wafer holder to permit angled immersion (as opposed to flat horizontal immersion) of the wafer into a plating solution. A drive mechanism and arrangement of plates and pivot joints are used in some embodiments to move wafer the holder 111 along an arced path (not shown) and, as a result, tilt the proximal end of wafer holder 111 (i.e., the cup and cone assembly).
Further, the entire wafer holder 111 is lifted vertically either up or down to immerse the proximal end of wafer holder into a plating solution via an actuator (not shown). Thus, a two-component positioning mechanism provides both vertical movement along a trajectory perpendicular to an electrolyte surface and a tilting movement allowing deviation from a horizontal orientation (i.e., parallel to the electrolyte surface) for the wafer (angled-wafer immersion capability).
Note that the wafer holder 111 is used with a plating cell 115 having a plating chamber 117 which houses an anode chamber 157 and a plating solution. The chamber 157 holds an anode 119 (e.g., a copper anode) and may include membranes or other separators designed to maintain different electrolyte chemistries in the anode compartment and a cathode compartment. In the depicted embodiment, a diffuser 153 is employed for directing electrolyte upward toward the rotating wafer in a uniform front. In certain embodiments, the flow diffuser is a high resistance virtual anode (HRVA) plate, which is made of a solid piece of insulating material (e.g. plastic), having a large number (e.g. 4,000-15,000) of one dimensional small holes (0.01 to 0.050 inches in diameter) and connected to the cathode chamber above the plate. The total cross-section area of the holes is less than about 5 percent of the total projected area, and, therefore, introduces substantial flow resistance in the plating cell helping to improve the plating uniformity of the system. Additional description of a high resistance virtual anode plate and a corresponding apparatus for electrochemically treating semiconductor wafers is provided in U.S. patent application Ser. No. 12/291,356, filed on Nov. 7, 2008, which is hereby incorporated by reference herein in its entirety for all purposes. The plating cell may also include a separate membrane for controlling and creating separate electrolyte flow patterns. In another embodiment, a membrane is employed to define an anode chamber, which contains electrolyte that is substantially free of suppressors, accelerators, or other organic plating additives.
The plating cell 115 may also include plumbing or plumbing contacts for circulating electrolyte through the plating cell—and against the work piece being plated. For example, the plating cell 115 includes an electrolyte inlet tube 131 that extends vertically into the center of anode chamber 157 through a hole in the center of anode 119. In other embodiments, the cell includes an electrolyte inlet manifold that introduces fluid into the cathode chamber below the diffuser/HRVA plate at the peripheral wall of the chamber (not shown). In some cases, the inlet tube 131 includes outlet nozzles on both sides (the anode side and the cathode side) of the membrane 153. This arrangement delivers electrolyte to both the anode chamber and the cathode chamber. In other embodiments, the anode and cathode chamber are separated by a flow resistant membrane 153, and each chamber has a separate flow cycle of separated electrolyte. As shown in the embodiment of
In addition, plating cell 115 includes a rinse drain line 159 and a plating solution return line 161, each connected directly to the plating chamber 117. Also, a rinse nozzle 163 delivers deionized rinse water to clean the wafer and/or cup during normal operation. Plating solution normally fills much of the chamber 117. To mitigate splashing and generation of bubbles, the chamber 117 includes an inner weir 165 for plating solution return and an outer weir 167 for rinse water return. In the depicted embodiment, these weirs are circumferential vertical slots in the wall of the plating chamber 117.
As stated above, an electroplating clamshell typically includes a lipseal and one or more contact elements to provide sealing and electrical connection functions. A lipseal may be made from an elastomeric material. The lipseal forms a seal with the surface of the semiconductor substrate and excludes the electrolyte from a peripheral region of the substrate. No deposition occurs in this peripheral region and it is not used for forming IC devices, i.e., the peripheral region is not a part of the working surface. Sometimes, this region is also referred to as an edge exclusion area because the electrolyte is excluded from the area. The peripheral region is used for supporting and sealing the substrate during processing, as well as for making electrical connection with the contact elements. Since it is generally desirable to increase the working surface, the peripheral region needs to be as small as possible while maintaining the functions described above. In certain embodiments, the peripheral region is between about 0.5 millimeters and 3 millimeters from the edge of the substrate.
During installation, the lipseal and contact elements are assembled together with other components of the clamshell. One having ordinary skilled in the art would appreciated the difficultly of this operation, particularly, when the peripheral region is small. An overall opening provided by this clamshell is comparable to the size of the substrate (e.g., an opening for accommodating 200 mm wafers, 300 mm wafers, 450 mm wafers, etc.). Furthermore, substrates have their own size tolerances (e.g., +/−0.2 millimeters for a typical 300 mm wafer according to the SEMI specification). A particularly difficult task is alignment of the elastomeric lipseal and contact elements, since both are made from relatively flexible materials. These two components need to have very precise relative location. When a sealing edge of the lipseal and contact elements are positioned too far away from each other, insufficient or no electrical connection may be formed between the contacts and substrate during operation of the clamshell. At the same time, when the sealing edge is positioned too close to the contacts, the contacts may interfere with the seal and cause leakage into the peripheral region. For example, conventional contact rings are often made with multiple flexible “fingers” that are pressed in a spring-like action onto the substrate to establish an electrical connection as shown in the clamshell assembly of
Lipseal Assemblies Having Integrated Contact Elements
Provided herein are novel lipseal assemblies having contact elements integrated into elastomeric lipseals. Instead of installing and aligning two separate sealing and electrical components (e.g., a lipseal and a contact ring) in the field, the two components are aligned and integrated during fabrication of the assembly. This alignment is maintained during installation as well as during operation of the clamshell. As such, the alignment needs to be set and inspected only once, i.e., during fabrication of the assembly.
Lipseal assembly 302 also includes one or more contact elements 310 structurally integrated into lipseal 304. As stated above, contact element 310 is used for supplying an electrical current to the semiconductor substrate during electroplating. Contact element 310 includes an exposed portion 312 defining a second inner diameter that is larger than the first inner diameter of lipseal 304 in order to prevent interference with the sealing properties of lipseal assembly 302. Contact element 310 generally includes another exposed portion 313 for making an electrical connection with a source of electrical current such as a bus bar 316 of the electroplating clamshell. However, other connection schemes are also possible. For example, contact element 310 may be interconnected with distribution bus 314, which may be connected to bus bar 316.
As stated above, integration of one or more contact elements 310 into lipseal 304 is performed during fabrication of lipseal assembly 302 and is preserved during installation and operation of the assembly. This integration may be performed in a variety of ways. For example, an elastomeric material may be molded over contact element 310. Other elements, such as current distribution bus 314, may be also integrated into the assembly to improve rigidity, conductivity, and other functionalities of assembly 302.
The lipseal assembly 302 illustrated in
Returning to
Lipseal Assemblies Having Flexible Contact Elements Which Form a Conformal Contact Surface
Electrical connection to the substrate may be significantly improved by increasing the contact surface between the contact elements and the substrate during the sealing of the substrate in the clamshell assembly and the subsequent electroplating. Conventional contact elements (e.g., “fingers” shown in
Described herein are lipseal assemblies having one or more flexible contact elements conformally positioned on an upper surface of an elastomeric lipseal. These contact elements are configured to flex upon engagement with semiconductor substrate and form a conformal contact surface that interfaces with the semiconductor substrate when the substrate is supported, engaged, and sealed by the lipseal assembly. The conformal contact surface is created when the substrate is pressed against the lipseal in a manner similar to the manner in which the seal is created between the substrate and the lipseal. Thus, pressing of the substrate against the contact element may cause the elastomeric material upon which the contact element is disposed to compress and exert a spring-like counter-force which may facilitate the conforming of the contact element to the shape of the substrate. However, despite the elastomeric material upon which the contact element is disposed being contiguous in some embodiments with the elastomeric material which forms the sealing interface, the sealing interface should generally be distinguished from the conformal contact surface formed between the contact element and the substrate even though the two surfaces may be formed adjacent to one another. It is also to be noted that when it is said herein that the conformal contact element “conforms” to the shape of the substrate, or more specifically “conforms” to the shape of the edge bevel region of the substrate, or that the forming of an electrical connection includes “conforming” of the contact element to the shape of the substrate, it should be understood that although this entails the shape of the contact element adjusting to match some portion of the shape of the substrate, it does not imply that the entirety of the contact element's shape adjusts to the shape of the substrate, or that the entire substrate's radial edge profile is matched by the shape of the contact element; instead, only that at least some portion of the contact element's shape is altered to approximately match some portion of the substrate's shape.
While the conformal nature of the flexible contact element 404 is important at the interface with the substrate, the remaining portion of flexible contact element 404 may also be conformal with respect to lipseal 402. For example, flexible contact element 404 may conformally extend along the surface of lipseal. In other embodiments, the remaining portion of the flexible contact element 404 may be made from other (e.g., non-conformal) materials and/or have a different (e.g., non-conformal) configuration. Therefore, in some embodiments, the one or more flexible contact elements may have a portion which is not configured to contact the substrate when the substrate is engaged by the lipseal assembly, and this non-contacting portion may comprise a conformable material, or it may comprise a non-conformable material.
Furthermore, it should be noted that although a conformal contact surface may form a continuous interface between the flexible contact element 404 and semiconductor substrate 406, it is not required to form a continuous interface. For example, in some embodiments, a conformal contact surface has gaps forming a non-continuous interface with the semiconductor substrate. Specifically, a non-continuous conformal contact surface may be formed from a flexible contact element 404 which comprises many multiple wire tips and/or a wire mesh disposed on the surface of the elastomeric lip seal. Even if non-continuous, the conformal contact surface follows the shape of the lipseal while the lipseal is being deformed during the closing of the clamshell.
Flexible contact element 404 may be attached to the upper surface of the elastomeric lipseal. For example, flexible contact element 404 may be pressed, glued, molded, or otherwise attached to the surface, as described above with reference to
Furthermore, although the portion of the flexible contact element 404 which interfaces with the substrate 406 (forming a conformal contact surface) is an exposed surface, other portions of the flexible contact element 404 may be unexposed, for example, being integrated underneath a surface of the elastomeric lipseal, in a manner somewhat similar to the integrated, albeit non-conformal, lipseal assembly illustrated in
In certain embodiments, a flexible contact element 404 includes a conductive layer of conductive deposits deposited on the upper surface of the elastomeric lipseal. The conductive layer of conductive deposits may be formed/deposited using chemical vapor deposition (CVD), and/or physical vapor deposition (PVD), and/or (electro)plating. In some embodiments, the flexible contact element 404 may be made of an electrically conductive elastomeric material.
Substrate Aligning Lipseals
As previously explained, the peripheral region of the substrate from which plating solution is excluded needs to be small, which requires careful and precise alignment of the semiconductor substrate prior to closing and sealing the clamshell. Misalignment may cause leaking on the one hand, and/or unnecessary covering/blocking of substrate working areas on the other. Tight substrate diameter tolerances may cause additional difficulties during alignment. Some alignment may be provide by the transfer mechanism (e.g., depending on the accuracy of a robot handoff mechanism), and by using alignment features such as snubbers positioned in the side walls of the clamshell cup. However, the transfer mechanism needs to be precisely installed and aligned during installation with respect to the cup (i.e., “taught” about relative position of other components) in order to provide precise and repetitive positioning of the substrates. This robot teaching and alignment process is rather difficult to perform, is labor intensive, and requires highly skilled personnel. Furthermore, the snubber features are difficult to install and tend to have big tolerance stack-ups because there are many parts positioned between the lipseal and snubbers.
Accordingly, disclosed herein are lipseals which are not only used for supporting and sealing the substrate in the clamshell but also for aligning the substrate in the clamshell prior to sealing. Various features of such lipseals will now be described with reference to
Lipseal 502 also includes a flexible elastomeric upper portion 505 located above the flexible elastomeric support edge 503. The flexible elastomeric upper portion 505 may include a top surface 507 configured to be compressed, and also an inner side surface 506. The inner side surface 506 may be located outward relative to the sealing protrusion 504 (meaning that the inner side surface 506 is located further from the center of a semiconductor substrate being held by the elastomeric lipseal than the sealing protrusion 504), and be configured to move inward (towards the center of a semiconductor substrate being held) when the top surface 507 is compressed by another component of the electroplating clamshell. In some embodiments, at least a portion of the inner side surface is configured to move inward by at least about 0.1 mm, or at least about 0.2 mm, or at least about 0.3 mm, or at least about 0.4 mm, or at least about 0.5 mm. This inward motion may cause the inner side surface 506 of the lipseal to contact the edge of a semiconductor substrate resting on the sealing protrusion 504, pushing the substrate towards the center of the lipseal and thus aligning it within the electroplating clamshell. In some embodiments, the flexible elastomeric upper portion 505 defines a second inner diameter (see
Elastomeric lipseal 502 may also have an integrated or otherwise attached contact element 508. In other embodiments, contact element 508 may be a separate component. In any event, whether or not it is a separate component, if contact element 508 is provided on inner side surface 506 of lipseal 502, then contact element 508 may also be involved in the aligning of the substrate. Thus, in these examples, if present, contact element 508 is considered to be a part of inner side surface 506.
Compression of the top surface 507 of the elastomeric upper portion 505 (in order to align and seal the semiconductor substrate within the electroplating clamshell) may be accomplished in a variety of ways. For instance, top surface 507 may be compressed by a portion of the cone or some other component of the clamshell.
In other embodiments, top surface 507 and substrate 509 are pressed by different components of the clamshell that may have independently controlled vertical positioning. This configuration may allow for independently controlling the deformation of upper portion 505 prior to pressing onto the substrate 509. For example, some substrates may have larger diameters than others. Alignment of such larger substrates may need and even require, in certain embodiments, less deformation than smaller substrates because there is a less initial gap between the larger substrates and inner side surface 506.
Methods of Aligning and Sealing a Substrate in a Clamshell
Also disclosed herein are methods of aligning and sealing a semiconductor substrate in an electroplating clamshell having an elastomeric lipseal. The flowchart of
After aligning the semiconductor substrate during operation 608, in some embodiments, the method proceeds by pressing on the semiconductor substrate in operation 610 to form a seal between the sealing protrusion and the semiconductor substrate. In certain embodiments, compressing the top surface continues during pressing on the semiconductor substrate. For example, in certain such embodiments, compressing the top surface and pressing on the semiconductor substrate may be performed by two different surfaces of the cone of the clamshell. Thus, a first surface of the cone may press on the top surface to compress it, and a second surface of the cone may press on the substrate to form a seal with the elastomeric lipseal. In other embodiments, compressing the top surface and pressing on the semiconductor substrate are performed independently by two different components of the clamshell. These two pressing components of the clamshell are typically independently movable with respect to one another, thus allowing compression of the top surface to be halted once the substrate is pressed upon and sealed against the lipseal by the other pressing component. Furthermore, the compression level of the top surface may be adjusted based upon the diameter of the semiconductor substrate by independently altering the pressing force exerted upon it by its associated pressing component.
These operations may be part of a larger electroplating process, which is also depicted in the flowchart of
Initially, the lipseal and contact area of the clamshell may be clean and dry. The clamshell is opened (block 602) and the substrate is loaded into the clamshell. In certain embodiments, the contact tips sit slightly above the plane of the sealing lip and the substrate is supported, in this case, by the array of contact tips around the substrate periphery. The clamshell is then closed and sealed by moving the cone downward. During this closure operation, the electrical contacts and seals are established according to various embodiments described above. Further, the bottom corners of the contacts may be force down against the elastic lipseal base, which results in additional force between the tips and the front side of the wafer. The sealing lip may be slightly compressed to ensure the seal around the entire perimeter. In some embodiments, when the substrate is initially positioned into the cup only the sealing lip is contact with the front surface. In this example, the electrical contact between the tips and the front surface is established during compression of the sealing lip.
Once the seal and the electrical contact is established, the clamshell carrying the substrate is immersed into the plating bath and is plated in the bath while being held in the clamshell (block 612). A typical composition of a copper plating solution used in this operation includes copper ions at a concentration range of about 0.5-80 g/L, more specifically at about 5-60 g/L, and even more specifically at about 18-55 g/L and sulfuric acid at a concentration of about 0.1-400 g/L. Low-acid copper plating solutions typically contain about 5-10 g/L of sulfuric acid. Medium and high-acid solutions contain about 50-90 g/L and 150-180 g/L sulfuric acid, respectively. The concentration of chloride ions may be about 1-100 mg/L. A number of copper plating organic additives such as Enthone Viaform, Viaform NexT, Viaform Extreme (available from Enthone Corporation in West Haven, Conn.), or other accelerators, suppressors, and levelers known to those of skill in the art can be used. Examples of plating operations are described in more detail in U.S. patent application Ser. No. 11/564,222 filed on Nov. 28, 2006, which is hereby incorporated by reference in its entirety herein for all purposes, but in particular for the purpose of the describing plating operations. Once the plating is completed and an appropriate amount of material has been deposited on the front surface of the substrate, the substrate is then removed from the plating bath. The substrate and clamshell are then spun to remove most of the residual electrolyte on the clamshell surfaces which has remained there due to surface tension and adhesive forces. The clamshell is then rinsed while continued to be spun to dilute and flush as much of the entrained electrolytic fluid as possible from clamshell and substrate surfaces. The substrate is then spun with rinsing liquid turned off for some time, usually at least about 2 seconds to remove some remaining rinsate. The process may proceed by opening the clamshell (block 614) and removing the processed substrate (block 616). Operational blocks 604 through 616 may be repeated multiple times for new wafer substrates, as indicated in
Oftentimes, a cup-and-cone electroplating clamshell design makes use of an elastomeric lipseal which is manufactured separately from the other components of the clamshell—i.e., the lipseal is often manufactured as a distinct component for later incorporation into the clamshell when assembled for operational use. Primarily, this stems from the fact that the other clamshell components are generally not composed of elastomeric material—rather being rigid pieces made from metals or hard plastics—and so typically a separate molding or fabrication process would be used for them. However, because the lipseal is made of a flexible elastomeric material, and because of its thin (and perhaps delicate) shape (e.g., see
Current approaches to cup assembly and sealing component manufacture may be improved upon by manufacturing the elastomeric sealing element in conjunction with the manufacture of the cup bottom element of the cup assembly of an electroplating clamshell design. In other words, it may be beneficial to fabricate the cup assembly, and in particular, the cup bottom element and elastomeric sealing element in an integrated fashion. One way of accomplishing this is to mold the elastomeric sealing element directly to (onto, over, etc.) the cup bottom element. This may be particularly effective if the elastomeric sealing element is physically smaller—for example, having a radial profile more local to the wafer edge region as opposed to extending too far radially outward into the cup assembly as in more conventional designs—the smaller sized sealing element being easier to form in place on the cup bottom element. However, it is also to be noted that in some embodiments a smaller sized elastomeric sealing element may allow integrated manufacture with the cup bottom via bonding, gluing, adhering with an adhesive, or otherwise affixing the sealing element to the cup bottom element in a precisely controlled manner so as to achieve the benefits described above, despite the elastomeric sealing element not being directly molded into the cup bottom element. In either case, integrated manufacture of an elastomeric sealing element having a reduced radial profile with the cup bottom element may enable the former to be more precisely manufactured and located within the cup bottom and thus reduce the size of a wafer substrate's edge exclusion region relative to other designs.
An elastomeric sealing element manufactured in integrated fashion with the cup bottom may also employ substrate electrical contact elements which are different than those often used in other cup assembly designs. For instance, cup assemblies using a separately manufactured lipseal may employ contact fingers as contact elements which are made of hardened sheet metal (e.g., about 0.0005 to 0.005 inches thick) that flex and form a point or line electrical contact with the substrate upon closing of the clamshell. Such contacts may have an “L” shape at the contacting ends, and they may act as cantilevers. An example of such an embodiment is schematically illustrated in
The cup assemblies disclosed here which have integrated elastomeric sealing elements may employ electrical contact elements of a different sort having different features. Rather than use L-shaped contact fingers formed from hardened sheet metal and angled as cantilevers as illustrated in
An example of such a cup assembly having these and various other features is schematically illustrated in
Generally,
The broader view of the cup assembly presented in
The magnified views of cup assembly 700 presented in
In contrast, the main body portion 711 of cup bottom 701 is designed to be relatively thick (much thicker than the moment arm 713). As a result, the main body portion may be such that it does not substantially flex when the semiconductor substrate is pressed against the moment arm. Furthermore, not only is the main body portion of the cup bottom element rigid in itself, in some embodiments, the main body portion may also be designed such that it is rigidly affixed to another feature of the cup structure. For instance, in the embodiment shown in
Accordingly, the main body portion of the cup bottom element remains substantially rigid during operation and resists any flexing when force/pressure from cone 727 is transmitted to it through the substrate 731, the contact element 705, the sealing element 703, and ultimately through the moment arm 713. On the other hand, upon sufficient application of pressure to the substrate, the moment arm 713 is designed to be the component of the cup bottom 711 that flexes. The moment arm, however, may still be designed to be as short as possible so that it doesn't exhibit too much flex while still providing a radially sufficient horizontal surface to support the electrical contact element 705 and elastomeric sealing element 703. (Compare in
In addition, as mentioned, this pressure from the substrate 731 may also cause the portion of the elastomeric seal 703 underneath the contact element 705 to compress and produce a countervailing elastic force beneath the contact element which causes the contact element to flex and conform to the shape of the portion of the substrate contacting it. In particular, in some embodiments, when the elastomer underneath the contact element is compressed, the contact element may flex and adjust its shape so as to conform to the profile of the edge bevel region of the substrate. Once again, this feature may be promoted by the contact element being relatively thin and made from a flexible conductive material (as opposed to a hardened metal which exhibits spring-like behavior).
Details Regarding the Cup Bottom Element
As mentioned, the cup bottom element 701 resists significant flexing, aside from the small moment arm, when the wafer is pushed down. This may be because the cup bottom element 701 has a relatively thick main body portion 711 and a relatively short and thin moment arm 713 upon which the sealing element 703 is disposed upon.
The cup bottom element 701 may be generally ring-shaped and sized to accommodate semiconductor substrates of standard size, such as 200 mm, a 300 mm wafers or 450 mm wafers. The inner edge of the cup bottom element—or more specifically moment arm 713 in
As explained and shown in
Other detailed views of the cup bottom element are shown in
The design of the moment arm is generally such that it accommodates substantially all of the deflection of the cup bottom element during placement of a semiconductor substrate onto the cup. Thus, in certain embodiments, the moment arm has a thickness—the distance between the top and bottom of the moment arm in the direction of wafer insertion (i.e., its vertical height in
This vertical height/thickness may be quite thin relative to the thickness of the main body portion of the cup bottom element, as well-illustrated in
Moreover, in certain embodiments, the main body portion may have a maximum thickness (vertical height, top to bottom, perpendicular to the radially direction) of at least about 0.2 inches, or more particularly at least about 0.3 inches; in some embodiments, it may have a maximum vertical height of between about 0.2 and 1 inches. In terms of average vertical height/thickness, in certain embodiments, the main body portion may have an average vertical height of at least about 0.1 inches, or at least about 0.3 inches, or at least about 0.5 inches, or even more particularly at least about 1.0 inch. In some embodiments, the average vertical height of the main body portion may be between about 0.1 and 1.0 inches, or more particularly between about 0.2 and 0.5 inches.
Moreover, depending on the embodiment, the ratio of the average vertical height/thickness of the main body portion of the cup bottom element to the average vertical height/thickness of the moment arm may be greater than about 3, or more particularly said ratio may be greater than about 5, or even more particularly greater than about 20, depending on the embodiment.
Likewise, the radial width of the main body portion of the cup bottom element may be between about 0.5 and 3 inches or between about 0.75 and 1.5 inches. Generally, it is advantageously sized to allow rigid structural integration with the other elements of the cup.
It is also seen in
Thus, the moment arm 713 may be viewed as extending inward towards the substrate from the main body portion 711 of the cup bottom element 101 and therefore, in some embodiments, it may further be viewed as operating in cantilever fashion to physically support the edge of the substrate as it is received into the cup prior to an electroplating operation (as well as during the electroplating operation itself).
In addition to physically supporting the substrate, the moment arm supports the sealing element and appropriately locates it relative to the edge of the substrate so as to establish a leak tight seal, thereby forming the aforementioned electrolyte exclusion region near the substrate's edge.
Thus, the moment arm may be shaped to accommodate a ring-shaped sealing element which typically sits between the moment arm and the wafer during operation, such as ring-shaped sealing element 703 shown in the figures. In certain embodiments, the moment arm has a substantially straight or linear horizontal shape, without significant vertical features. In certain embodiments, the moment arm and the adjacent (radially outward) portion of the main body section of the cup bottom is shaped to form a mold for forming the elastomeric sealing element directly in the cup bottom—such as via molding through precursor polymerization (as described further below).
The material from which the cup bottom element is formed is typically a relatively rigid material. Furthermore, it may be made from a conductive or insulating material. In some embodiments, the cup bottom element is made from a metal such as titanium, or a titanium alloy, or stainless steel. In some embodiments, if it is made from a conductive material, the conductive material may be coated with an insulating material. In other embodiments, the cup bottom element is made from a non-conductive material such as a plastic such as PPS or PEEK. In other embodiments, the cup bottom is made from a ceramic material. In certain embodiments, the cup bottom element has a rigidity characterized by a Young's modulus of between about 300,000 and 55,000,000 psi, or more particularly between about 450,000 and 30,000,000 psi.
Details Regarding the Sealing Element (Lipseal)
Generally, the elastomeric sealing element is a ring-shaped element that fits snugly on top of the moment arm and, optionally, against the inner radial edge of the main body portion of the cup bottom. In certain embodiments, the sealing element has a radial width of about 0.5 inches or less, or about 0.2 inches or less, or between about 0.05 and 0.2 inches, or between about 0.06 and 0.10 inches. The overall radial width would generally be chosen sufficient to accommodate the wafer edge exclusion region associated with use of the apparatus. Likewise, the diameter of the elastomeric sealing element would generally be chosen appropriately for accommodating a standard wafer substrate such as a 200 mm, a 300 mm wafer or a 450 mm wafer.
The vertical thickness of the elastomeric sealing element may be between about 0.005 and 0.050 inches, or more particularly between about 0.010 and 0.025 inches. The thickness and shape of the sealing element may be chosen to facilitate substantially continuous contact between the sealing element and the substrate edge in order to form a substantially leak-tight seal between the sealing element and the substrate.
In certain embodiments, the sealing element has an L-shape (or a substantially L-like shape), where the small arm of the “L” extends upward at the inner radius of the sealing element. See, for example,
This small upward protrusion may engage with the wafer to provide a leak-tight seal. It can be seen in this example shown in
The Electrical Contact Element
The electrical contact element is made from a conductive material so that it can provide electrical current to the substrate during electroplating operations. Typically, the conductive material would be some sort of metal, alloy, etc. and it would be shaped and sized to sit on the upper surface of the moment arm, typically on top of the sealing element, but radially outward of the portion of the sealing element which forms the substantially leak-tight seal with the substrate. Such a configuration is illustrated in
In some embodiments, the electrical contact element may be flat and thin but may be formed into contact fingers which are oriented so that they point radially inward around the contact element's circumference. The contact fingers may aid in improving the quality, consistency, and/or uniformity of the electrical connection by being more vertically deformable/flexible when pressure is exerted on them by the substrate than if a solid strip of conductive material (even if thin and flat) was employed (thought in some embodiments, the latter would also be suitable for providing the requisite electrical connection).
As mentioned above, the electrical contact element is generally substantially radially symmetric and ring-shaped so that it may symmetrically contact the substrate being electroplated, and particularly symmetric over the portion of its surface that contacts the substrate. For this reason, it may also be referred to herein as a contact-ring. The radial shape of an example contact-ring is illustrated in the exploded view of the cup bottom element 101 shown
From these figures, one notes that the radially symmetry of the contact ring 705 may be broken outward of the actual substrate contact portion of the ring with likely less impact on its operation, since the radially outward portion isn't forming the electrical connection to the substrate. This is seen in the exploded view of the cup bottom element in
The electrical contact element/ring 705 has a diameter that accommodates the outer region of a seed layer on a standard semiconductor wafer substrate such as a 200 mm, a 300 mm wafer or a 450 mm wafer. It may be sized to lay flat on top of the sealing elastomer member 703. In certain embodiments, it may have a radial width of about 0.500 inches or less, or between about 0.040 and 0.500 inches, or more particularly between about 0.055 and 0.200 inches. The radial width of the contact ring is defined as the distance in the radial direction from the contact ring's outer radial edge to its inner radial edge, for example, defined by the radially inward extent of the contact fingers shown on the contact ring in
In certain embodiments, such as the example embodiment shown in
In certain embodiments, the contact ring is substantially flat and it may lie substantially flat on the elastomeric sealing element, which itself may lie flat upon the moment arm. This design should generally be distinguished from designs in which the contact ring has an L-shaped structure with the small leg of the L extending upward to contact the substrate, and also from designs employing cantilever-like contact-fingers such as those shown in
While the contact ring is shown to be completely flat in
The electrical contact element/ring may be made from a relatively flexible conductive material that can bend and/or deform to accommodate the shape of the substrate and the underlying elastomeric sealing element when the substrate is pressed against the moment arm during (or prior to) an electroplating operation. For instance, the electrical contact element/ring may be made from thin non-hardened sheet metal. Thus, the portion of the contact element which contacts the substrate may be a thin sheet of flexible and/or deformable metal about 0.01 inches thick or less, or more particularly about 0.005 inches thick or less, or even about 0.002 inches thick or less. The metal comprising the contact ring may comprise stainless steel. In some embodiments, the metal may comprises a precious metal alloy. Such alloys may include alloys of palladium, including palladium-silver alloys optionally containing gold and/or platinum. Palinery 7 made by DERINGER-NEY INC is an example.
Integrated Manufacturing of the Cup Assembly and the Elastomeric Sealing Element
Whereas oftentimes the elastomeric sealing element used to seal a substrate in an electroplating clamshell is a separate component which is user-installed into the clamshell prior to an electroplating operation, in various embodiments disclosed herein the cup assembly and its sealing element are integrated during the manufacturing process. In such cases, the elastomeric sealing element may be affixed to the cup bottom element during manufacturing by adhesion, molding, or another suitable process which inhibits the uncoupling of the elastomeric sealing element from the cup bottom element. As such, the elastomeric sealing element may be viewed as a permanent feature of the cup assembly rather than as a separate component.
In some embodiments, the elastomeric sealing element may be formed in situ inside the cup bottom element, for instance, by molding it directly into the cup bottom element. In this approach, a chemical precursor to the elastomeric material comprising the formed sealing element is placed in the location of the moment arm where the formed sealing element is to reside, and then the chemical precursor is processed so as to form the desired elastomeric material—such as by polymerization, curing, or other mechanism that converts the chemical precursor material into the formed elastomeric material having the desired final structural shape of the sealing element.
In other embodiments, the sealing element is pre-formed into its desired final shape and then integrated with the rigid (plastic or metal) cup bottom element during the manufacture of the cup assembly by affixing the sealing element to the appropriate location on the cup bottom element's moment arm via adhesive, glue, etc. or some other appropriate affixing mechanism.
Through integrated manufacture of the cup assembly with it's elastomeric sealing element, the sealing element can be formed more precisely into its desired shape, and positioned more precisely within the structure of the cup bottom element of the cup assembly than what is generally achieved with the manufacture of cup assembly and sealing elements as separate components. This allows, in conjunction with the rigid support of cup bottom element, the precise locating of the portion of the sealing element which contacts the substrate. Accordingly, because less margin for positioning error is required, sealing elements having reduced radial profiles may be employed, which in turn, allows the sealing element to be designed for contacting the substrate within the cup assembly significantly closer to the substrate's edge, reducing the edge exclusion region during electroplating operations. The combined thinner inner edge of seal element and cup bottom (specifically, its moment arm) will enhance the on-wafer plating performance, e.g., by minimizing/eliminating trapped air bubbles, for example.
System Controllers
In certain embodiments, a system controller is used to control process conditions during sealing the clamshell and/or during processing of the substrate. The system controller will typically include one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc. Instructions for implementing appropriate control operations are executed on the processor. These instructions may be stored on the memory devices associated with the controller or they may be provided over a network.
In certain embodiments, the system controller controls all of the activities of the processing system. The system controller executes system control software including sets of instructions for controlling the timing of the processing steps listed above and other parameters of a particular process. Other computer programs, scripts or routines stored on memory devices associated with the controller may be employed in some embodiments.
Typically, there is a user interface associated with the system controller. The user interface may include a display screen, graphical software to display process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc.
The computer program code for controlling the above operations can be written in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program.
Signals for monitoring the processes may be provided by analog and/or digital input connections of the system controller. The signals for controlling the processes are output on the analog and digital output connections of the processing system.
Lithographic Patterning
The apparatuses/processes described hereinabove may be used in conjunction with lithographic patterning tools or processes, for example, for the fabrication or manufacture of semiconductor devices, displays, LEDs, photovoltaic panels and the like. Typically, though not necessarily, such tools/processes will be used or conducted together in a common fabrication facility. Lithographic patterning of a film typically comprises some or all of the following steps, each step enabled with a number of possible tools: (1) application of photoresist on a workpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curing of photoresist using a hot plate or furnace or UV curing tool; (3) exposing the photoresist to visible or UV or x-ray light with a tool such as a wafer stepper; (4) developing the resist so as to selectively remove resist and thereby pattern it using a tool such as a wet bench; (5) transferring the resist pattern into an underlying film or workpiece by using a dry or plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF or microwave plasma resist stripper.
Other Embodiments
Although illustrative embodiments and applications of this invention are shown and described herein, many variations and modifications are possible which remain within the concept, scope, and spirit of the invention, and these variations would become clear to those of ordinary skill in the art after perusal of this application. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| 62085171 | Nov 2014 | US | |
| 61523800 | Aug 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15984211 | May 2018 | US |
| Child | 18050029 | US | |
| Parent | 14685526 | Apr 2015 | US |
| Child | 15984211 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13584343 | Aug 2012 | US |
| Child | 14685526 | US |
