KR20080058514A - Retaining ring with conductive portion - Google Patents

Abstract

A retaining ring for use with electrochemical mechanical processing is described. The retaining ring has a generally annular body formed with a conductive portion and a non- conductive portion. The non-conductive portion contacts the substrate during polishing. The conductive portion is electrically biased during polishing to reduce the edge effect that tends to occur with conventional electrochemical mechanical processing systems.

Description

Retaining ring with conductive portion {RETAINING RING WITH CONDUCTIVE PORTION}

The present invention relates to an apparatus and method for retaining a substrate during electrochemical mechanical processing.

Typically, an integrated circuit is formed on a substrate by successively depositing a conductive layer, semiconductor layer, or insulating layer on a silicon wafer. One manufacturing step involves depositing a filler layer on a non-flat surface and planarizing the filler layer until the non-flat surface is exposed. For example, a conductive fill layer, such as copper, is deposited on the patterned insulating layer to fill the trenches or holes in the insulating layer. The fill layer is then polished until the elevated pattern of insulating layer is exposed. After planarization, portions of the conductive layer remaining between the raised patterns of the insulating layer form vias, plugs, and lines, which lines provide conductive paths between the film circuits on the substrate. It is also necessary to planarize the substrate surface for photolithography.

Chemical mechanical polishing (CMP) is used as one planarization method. Typically, this planarization method requires mounting the substrate on a carrier or polishing head. The exposed surface of the substrate is positioned against a rotating polishing disk pad or belt pad. The polishing pad can be a "standard" pad or a fixed-abrasive pad. Standard pads have a durable roughened surface, while fixed-abrasive pads have wear particles held in a containment medium. The carrier head provides an adjustable load on the substrate to press the substrate against the polishing pad. A polishing liquid comprising at least one chemical reagent is supplied to the surface of the polishing pad. For example, if a standard pad is used, the polishing liquid may optionally include abrasive particles.

A variant of CMP that is particularly useful for copper polishing is electrochemical mechanical processing (ECMP). The ECMP process is similar to a conventional CMP process, but is designed to polish copper films with very small downward and shear forces, thus making them suitable for low-k / Cu techniques. In ECMP technology, conductive material is removed from the substrate surface by electrochemical dissolution concurrent with polishing of the substrate, with mechanical wear being small compared to conventional CMP processes. Electrochemical dissolution is effected by applying a bias between the cathode and the substrate surface, thereby removing conductive material from the substrate surface to the surrounding electrolyte.

Ideally, the ECMP process polishes the substrate layer to the desired flatness and thickness. Polishing beyond this point can result in overpolishing (excessive removal) of the conductive layer or film, which can result in increased circuit resistance. Insufficient polishing of the substrate, or insufficient polishing of the conductive layer (too little removal) can result in an electrical short. The initial thickness of the substrate layer, the polishing solution composition, the polishing pad state, the relative speed between the polishing pad and the substrate, and variations in the load on the substrate can result in variations in the material removal rate. Such deviation may occur across substrates or across a radius of a single substrate, such as when one area of a substrate is over-polished and poorly polished in another. The CMP apparatus may be selected to control the amount of polishing of the substrate.

In one aspect, the invention relates to a retaining ring for an electrochemical mechanical processing system.

The retaining ring includes a conductive portion having a bottom surface exposed to the environment and a substrate contact portion having an inner diameter surface, wherein the substrate contact surface is substantially free of damage caused by contact between the inner diameter surface and the substrate. And a lower surface of the conductive portion of the substrate contacting portion is in contact with the polishing surface.

In one embodiment, the retaining ring can be biased independently. The retaining ring can be biased by voltage separately from the substrate being polished, thereby allowing more control over overpolishing the edge of the substrate.

In another aspect, the present invention relates to a retaining ring having a conductive portion and a substrate contacting portion. The conductive portion has a top surface and a bottom surface. A substrate contact portion is formed on at least a portion of the inner diameter surface of the retaining ring, the substrate contact portion is formed of an insulating material and configured to contact the polishing surface during the polishing process.

In one aspect, the invention relates to a carrier head for electrochemical mechanical processing. The carrier head includes a base attached to the retaining ring. The retaining ring includes a conductive portion having an upper surface and a lower surface, and an insulating portion. The insulating portion has one or more openings extending through the insulating portion and exposing the lower surface of the conductive portion. The upper surface of the insulating portion is in contact with the lower surface of the conductive portion.

In another aspect, the present invention relates to a system for electrochemical mechanical processing. Such a system includes a polishing pad assembly and a carrier head. The carrier head is configured to contact the polishing pad assembly. The carrier head includes a base attached to the retaining ring. The retaining ring includes a conductive portion and an insulating portion having an upper surface and a lower surface. The insulating portion has one or more openings extending through the insulating portion and exposing the lower surface of the conductive portion, the upper surface of the insulating portion being in contact with the lower surface of the conductive portion. The first voltage source is electrically coupled to the conductive portion of the retaining ring.

In another aspect, a method of forming a retaining ring for electrochemical mechanical processing is disclosed. The method includes forming a conductive portion made of metal. The annular body is formed of a non-conductive material that is less rigid than metal, the annular body configured to contact a lower surface configured to contact the polishing surface, an inner diameter surface configured to contact the substrate during polishing, and a conductive portion Part. The conductive portion is secured to the annular body so that the inner diameter surface of the annular body is exposed.

In one aspect, the invention relates to a method of operating a system for electrochemical mechanical processing. The method includes electrically biasing the polishing pad assembly at a first voltage. The conductive retaining ring is electrically biased to a second voltage, wherein the first voltage is different from the second voltage. Relative motion is created between the substrate and the polishing pad assembly, where the substrate is held by the conductive retaining ring.

Another aspect of the invention relates to a method of forming a conductive retaining ring for electrochemical mechanical processing. The method includes providing a substantially annular conductive portion. The insulating portion is fastened to the lower surface of the conductive portion. The insulating portion has one or more openings extending through the insulating portion and exposing the lower surface of the conductive portion, the upper surface of the insulating portion being in contact with the lower surface of the conductive portion.

The practice of the invention will include one or more of the following features. The conductive portion or body may be annular. The conductive portion may be biased by an element in the polishing pad assembly. The conductive portion can be biased by a voltage source having electrical connections through the carrier head. The conductive portion may be formed of the same metal as the metal removed from the substrate by the ECMP process. The conductive portion can be operated in the retaining ring. The gap between the conductive portion and the bottom of the retaining ring can be maintained at a desired height, such as by a spring or spacer. The conductive portion may be formed of one or more metal types. The conductive portion may be a core of the second metal plated by the second metal. The conductive portion may surround a material having sufficiently non-rigid properties such that the inner diameter of the retaining ring is formed of a non-rigid material. The spacer may contact the bottom surface of the conductive portion. The spacer may be a conductive material, a non-conductive material, and / or a material that is substantially inert to the polishing process. The spacer may be formed of stainless steel. The spacing can be thin enough so that the conductive element associated with the polishing surface contacts the conductive portion of the retaining ring. The spring may apply sufficient downward force to the conductive portion such that the bottom surface of the spacer remains substantially planar with the bottom surface of the non-conductive portion. Instead of a spring, a pressure regulator may be in fluid communication with a recess above the conductive portion, to control the position of the conductive portion in the retaining ring. Instead of the spacer, a substrate contact portion may be located between the conductive portion and the polishing surface. By the substrate contact portion, a portion of the bottom of the conductive portion can be exposed to the surroundings. The size of the substrate contact portion can be determined such that contact between the conductive element of the polishing pad assembly and the conductive portion is prevented.

An anode, such as a conductive layer of the polishing pad assembly, may be supported by the polishing pad support. The anode can be electrically coupled to the second voltage source. The polishing pad assembly can include a counter-electrode. The counter-electrode is electrically coupled to the second voltage source. The system can include a control that can control the first voltage source. The system can include a current monitor configured to measure the current from the retaining ring. The conductive portion can be electrically coupled to the outer roller or in electrical contact with the spindle. The voltage source can be configured to apply a voltage of about 0V to about 1V to the conductive portion.

The retaining ring may comprise an upper annular portion having a lower surface in contact with the conductive portion. An actively-biased retaining ring may have a conductor extending through the upper annular portion and in electrical contact with the conductive portion. The upper annular portion may be less conductive than the conductive portion. The lower surface of the conductive portion may have a recess. The recess may be in fluid communication with the opening in the insulating portion. When the insulating portion is in contact with the polishing pad, even when pressure is applied to the retaining ring, the size of the insulating portion is determined so that contact between the conductive element and the conductive portion of the polishing pad assembly of the electrochemical mechanical processing system is prevented. Can be. The size can be determined such that the insulating portion has a sufficient thickness to prevent contact or the openings are narrow enough to prevent contact. Openings in the insulating portion may be holes or grooves. The conductive portion may be annular and may be formed of copper, gold, platinum, palladium, titanium, silver, rhodium, iridium, or one or more alloys of these materials.

One potential advantage of the present invention is that the electrically conductive retaining ring can be electrically biased. Electrical biasing of the retaining ring during ECMP polishing may improve polishing uniformity or polishing rate across the substrate (eg, “in-wafer uniformity”), particularly at the substrate edge. Due to improved polishing uniformity, improved process stability and improved yield may be obtained.

Forming a retaining ring having an inner diameter surface surrounded by a conductive ring and formed of a non-rigid material can reduce the likelihood of damaging the substrate when the substrate contacts the inner diameter surface of the retaining ring. The width of the actively-biased conductive ring can be selected so that the conductive portion of the ring is wide enough to contact the conductive portion of the polishing surface. The conductive ring may be formed from a plurality of conductive elements, and the plurality of conductive elements may be composed of a first metal that interacts with the ECMP process and a second metal that rarely interacts with or interacts with the process. . By forming the ring from two or more types of metals, it is possible to select the width of the ring so as to be in sufficient contact with the conductive portion and at the same time limit the interaction with the ammeter endpoint detector of the conductive ring.

The actively-biased retaining ring may be biased to a different voltage than the substrate. Thus, the speed of polishing the substrate edge can be adjusted. By adjusting the polishing rate of the substrate edge, the polishing uniformity over the substrate surface can be increased.

By using the same material as the material polished in the retaining ring, it is possible to increase the uniformity of the polishing rate across the substrate. In addition, the use of the same material ensures chemical compatibility with the substrate, thereby reducing the possibility of damage to the substrate. On the other hand, by using other materials that do not interact with the ECMP process, the useful life of the conductive portion of the retaining ring can be extended.

Forming one or more spacers between the conductive ring and the polishing surface can prevent the conductive ring from making direct contact with the polishing surface, thereby reducing frictional wear of the conductive ring and improving the life of the conductive ring. The spacing can be sized so that the conductive biasing element in the polishing pad assembly can contact the conductive ring. The spacer can control the gap between the bottom surface of the conductive ring and the bottom surface of the retaining ring. The spacer can be made of an inert material so that the spacer is not worn by the polishing process and the gap remains constant through the useful life of the retaining ring. In order to ensure that the spacer contacts the polishing surface, the conductive ring may also be pressed by a spring. Instead, the conductive ring can be operated to move closer or farther, for example, to the polishing surface, so as to have more control over the polishing process.

Hereinafter, one or more embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Other features, objects, and advantages of the invention will be understood from the description, the drawings, and the claims. Like elements are designated by like reference numerals in the accompanying drawings.

As shown in FIG. 1, the substrate 10 may be polished at the polishing station 20 of the ECMP apparatus. The ECMP apparatus may be provided with multiple polishing stations, but only one is shown for clarity. Similar conventional CMP polishing apparatus is described in US Pat. No. 5,738,574, which is incorporated herein by reference. The two basic differences between an ECMP device and a conventional CMP polishing device are firstly that in the ECMP polishing process an electrolyte is used on a platen, and secondly an electrical bias is applied to the substrate. In addition, to reduce the stress on the substrate and to prevent splashing of the electrolyte, the ECMP process will be run at a slow rotational speed.

The polishing station 20 includes a rotatable platen 24 on which the polishing pad assembly 30 is located. In order to maintain the condition of the polishing pad so that the polishing pad can effectively polish the substrate, each polishing station 20 can also include a pad conditioner device (not shown). The edge of the platen 24 has a barrier wall or weir 26 so that the polishing electrolyte 28 can be received on the polishing pad assembly 30 during polishing. Examples of electrolytes suitable for ECMP polishing are described in US Pat. No. 6,811,680, which is incorporated herein by reference. Electrolyte solutions used in electrochemical processes such as copper plating and / or copper anodic dissolution are Praxair, Danbury, Connecticut, under the trademark EP3.1, and Shipley Leonel, Philadelphia, Pennsylvania under the trademark Ultrafill 2000. It is supplied. Optionally, port 145 electrolyte 28 may include wear particles. The polishing electrolyte may be supplied through a port formed on the surface of the polishing pad or through a polishing liquid supply arm (not shown).

The polishing pad assembly 30 includes a non-conductive polishing layer 32 having a polishing surface 34, a non-conductive backing layer 36, which may be softer than the polishing layer 32, and a platen ( A counter-electrode layer 38 in contact with the surface of the substrate 24. Polishing layer 32 and backing layer 36 may be conventional two-layer polishing pads. The polishing layer 32 may consist of a molded or casted polyurethane, and / or a grooved surface, which may comprise, for example, a filler such as hollow microspheres. The backing layer 36 may consist of compressed felt fibers leached with urethane. The counter-electrode layer 38, the backing layer 36 and the polishing layer 32 may be assembled into one unit, for example the counter-electrode layer 38 may be adhesively attached to the backing layer 36. And thus the polishing pad assembly 30 may be secured to the platen 24.

As described above, the ECMP apparatus applies an electrical bias to the substrate 10. Various techniques can be used to apply such an electrical bias. As shown in FIG. 2A, in one embodiment, a bias is applied by an electrode extending through an opening in the non-conductive dielectric polishing layer to contact the substrate 10 during polishing. One or more openings 44 may be formed through both the pad layers 32, 36 and the counter-electrode layer 38. The electrodes may be rotatable conductive spheres (rollers) 40 fixed in the opening 44 and extending slightly above the polishing surface 34. Each conductive roller 40 may be constrained by the housing 46. In addition, a perforation 42 may be formed through the polishing layer 32 and the backing layer 36 to expose the counter-electrode layer 38. The voltage source 48 is connected to the conductive roller 40 and the counter-electrode layer 38, respectively, by electrical connections 48a and 48b (eg, conductive electrical connections embedded in a non-conductive platen), A voltage difference can be applied between the roller 40 and the counter-electrode layer 38. Such a system is disclosed in US Pat. No. 6,884,153, which is incorporated herein by reference.

As shown in FIG. 2B, in another embodiment, a bias is applied by electrodes embedded in the non-conductive dielectric polishing layer. The polishing pad assembly 30 'includes a non-conductive polishing layer 32 having a polishing surface 34, a non-conductive backing layer 36, which may be softer than the polishing layer 32, and play. And a counter-electrode layer 38 in contact with the surface of the tongue 24. Conductive element 49, such as a metal wire, is embedded in non-conductive dielectric polishing layer 32. At least a portion of the conductive element 49 protrudes upward from the polishing surface 34 to contact the substrate during polishing. A voltage difference is applied between the conductive element 49 and the counter-electrode layer 38 by the voltage source 48. Such polishing pads and related polishing systems are described in US Pat. No. 6,884,153.

As shown in FIG. 2C, in another embodiment, the polishing layer itself is conductive and applies a bias. For example, referring to FIG. 2C, the polishing pad assembly 30 ″ has a polishing surface 34 with a non-conductive polishing layer 32 ′, a non-conductive backing layer 36, and a platen 24. And a counter-electrode layer 38 in contact with the surface of the conductive polishing layer 32 'by dispersing conductive fillers, such as fibers or particles (including conductive coated dielectric fibers and particles), in the polishing pad. The conductive filler may be a carbon-based material, a conductive polymer, or a conductive metal such as gold, platinum, tin, or lead, etc. Conductive polishing layer 32 'and counter-electrode by voltage source 48 may be formed. A voltage difference is applied between the layers 38. Such polishing pads and related polishing systems are described in US Pat. No. 6,884,153.

Referring to FIG. 1, the carrier head 22 supplies the substrate 10 to the polishing station 20. The carrier head 22 is connected to the carrier head rotation motor 31 by a carrier drive shaft 25, whereby the carrier head can be independently rotated about its axis. In addition, the carrier head 22 can be independently oscillated laterally in a radial slot formed in a support plate of a rotatable, multi-head rotatable conveyor 37. Descriptions of suitable carrier heads 22 are described in US Pat. Nos. 6,422,927, 6,450,868 and 6,857,945, which are incorporated herein by reference.

During operation, the platen 24 is rotated about its central axis, the carrier head 22 is rotated about its central axis and translated laterally across the polishing surface 34 of the polishing pad. Thereby providing relative movement between the substrate 10 and the polishing pad 30. The carrier head 22 applies a controllable pressure on the substrate 10 during polishing. The carrier head 22 also holds the substrate 10 with a retaining ring 100 secured to the carrier head. Retaining ring 100 has conductive portion 60. Retaining ring 100 has a substantially circular body.

As shown in FIGS. 3A-3D, the retaining ring 100 includes a conductive body or portion. The conductive portion may comprise one or more bodies formed of a conductive material. The conductive material may be a metal such as, for example, a precious metal comprising copper, gold, platinum, palladium, rhodium or iridium. When several metals are exposed to the ECMP process, they can react in one of three ways. By dissolving the electrolyte, the metal dissolves into the electrolyte solution, oxygen evolution forms oxygen gas bubbles, and due to oxidation, a non-conductive coating can be formed on the metal. One or more conductive bodies can be coupled to each other so that current can be transferred from one body to a neighboring body or the conductive bodies can be electrically isolated from each other. The conductive portion may be in the form of a conductive ring 134. Conductive ring 134 may be solid and relatively thick, or may be a thin layer plated on a second material.

Conductive ring 134 surrounds, at least in part, a portion that is non-rigid relative to the conductive portion. That is, although the non-rigid portion 61 includes a material that is less rigid than the material forming the conductive ring 134, the non-rigid portion 61 still has rigid characteristics. Retaining ring 100 has an inner diameter surface 107 that contacts substrate 10 during polishing. At least the lower portion of the inner diameter surface 107 comprises a non-rigid portion 61. The non-rigid portion 61 is inert to the polishing process and can be sufficiently compressed so that the substrate is chipped when the edge of the substrate 10 contacts the inner diameter surface 107 of the retaining ring 100. Or it may be formed of a material that can prevent cracking. However, the retaining ring 100 should not be formed of a material that is elastic enough to extrude into the substrate receiving recess 140 when the carrier head applies downward pressure to the retaining ring 100. . In addition, although wear of the retaining ring 100 is allowed, the retaining ring 100 should be durable and have a low wear rate. The non-rigid portion 61 may have a Shore hardness of 75-100 D, for example 80-95 D. For example, the retaining ring 100 may comprise polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE) , Polybenzimidazole (PBI), polyetherimide (PEI), or composite materials.

The non-rigid portion 61 is coupled to the conductive ring 134 such that at least the inner diameter surface 107 of the retaining ring 100 includes the non-rigid portion 61. The non-rigid portion 61 may also be located along other surfaces of the conductive ring 134 including a surface, an upper surface, and a lower surface forming the outer diameter 142 of the retaining ring 100. Retaining ring 100 has a bottom surface 118 that contacts polishing surface 34 during polishing. The conductive ring 134 may be flush with the bottom surface 118 of the retaining ring 100 as shown in FIGS. 3A and 3D, or as shown in FIGS. 3B and 3C. It may be recessed from the bottom surface of 100). The bottom surface of the conductive ring 134 may be exposed in its entirety as shown in FIGS. 3A, 3B and 3D, or partially exposed as shown in FIG. 3C. At least partially exposed conductive ring 134 may at least interact with the electrolyte solution used in ECMP processing.

A retaining ring having conductive portions can be biased independently of the substrate, that is to say biased by an external voltage source, as described below and as referred to as an " actively-biased " retaining ring. do. Instead, a retaining ring with conductive portions may be biased in the same manner as the substrate is biased, that is to say biased by a component in a polishing pad such as, for example, the conductive element shown in FIGS. 2A-2C. Such retaining ring may be referred to as a "passively-biased" retaining ring.

Referring to FIG. 4, in some embodiments, ie in a passively-biased retaining ring embodiment, the retaining ring is partially surrounded by the non-rigid portion 61 of the retaining ring 100 and is provided with a voltage source. And a conductive portion 134 in electrical contact with 48. In one embodiment, the voltage source 48 is the same voltage source in electrical contact with the conductive element of the polishing pad assembly.

Referring to FIG. 5A, in one embodiment, the retaining ring 100 has an upper surface 121 that contacts the carrier head 22. The substrate receiving recess 140 of the retaining ring 100 is large enough to accommodate the substrate 10. In the case of a 300 mm substrate, the substrate receiving recess 140 is 300 mm or more in diameter. In the illustrated embodiment, the conductive portion 134 does not extend to the outer diameter 142.

Referring to FIG. 5B, in some embodiments, the retaining ring 100 is formed of an upper ring portion 153 and a lower ring portion 155. The upper ring portion 153 may be formed of a harder material than the lower ring portion 155. In one embodiment, the upper ring portion 153 is formed of a metal, such as stainless steel. A cavity 159 is formed in the lower ring portion 155. In some embodiments, the cavity 159 may extend into the upper ring portion 153. For example, by forcing the conductive ring 134 into the cavity, the conductive ring 134 is secured in the cavity 159. Conductive ring 134 may also be secured with an adhesive such as epoxy. The bottom of the conductive ring 134 is recessed recessed from the lower surface 118, so that the conductive ring 134 and the polishing surface 34 when the retaining ring 100 contacts the polishing surface 34. A gap 130 is formed therebetween. Typically, as the ring is used, the material of the non-rigid portion 61 of the lower ring portion 155 wears out. If the conductive ring 134 is formed of a material that dissolves during the ECMP process, the mono-conductive ring 134 will also wear. As the lower surface 118 of the retaining ring 100 wears, the gap 130 between the conductive ring 134 and the polishing pad may change. If the cavity 159 in which the conductive ring 134 is secured is deep enough, the conductive ring 134 may be pushed into the cavity 159, thereby maintaining the gap at the desired depth.

As shown in FIGS. 6A, 6B and 6C, in one embodiment, a spacer 171 is located between the conductive ring 134 and the polishing surface 34. The spacing 171 may control the gap 130 between the bottom surface 118 of the retaining ring 100 and the bottom surface of the conductive ring 134. Accordingly, the gap can be kept constant during the life of the retaining ring 100. In the passively-biased retaining ring, the spacing 171 is sized such that the conductive elements of the polishing pad assembly 30 can contact the conductive ring 134, as described below with reference to FIG. 9. It is decided. Spacer 171 is formed of a material that is inert to the ECMP process. Spacer 171 is formed of a non-conductive material or conductive material. In one embodiment, the spacer 171 is formed of stainless steel. The spacer 171 may be formed of each spacer unit fixed to the retaining ring 100 or the conductive ring 134. The spacers can be fitted and locked into the cavity. The spacers can also be formed integrally, such as a ring with openings, which allows electrical contact between the conductive ring 134 and the conductive portion of the polishing pad assembly 30.

Referring to FIG. 7A, in one embodiment, the retaining ring includes a mechanism for maintaining contact between the polishing surface and the spacer 171. Such mechanism may be the spring 162, or other suitable mechanism device for applying downward force to the conductive ring 134.

Referring to FIG. 7B, in one embodiment, conductive ring 134 may be controllably positioned. A pressure regulator (not shown) may be coupled to the opening 166 formed in the upper surface 121 of the retaining ring 100. The pressure regulator may be located within the carrier head or within a structure coupled to the carrier head. The pressure regulator can actuate the conductive ring 134 as follows. The pressure in the cavity 159 may be high, thereby pressing the conductive ring towards the polishing surface 34. In some cases, conductive ring 134 may contact conductive surface 34. For example, by forming a vacuum, the pressure in the cavity can be reduced, thereby pulling the conductive ring 134 out of the polishing surface. The conductive ring 134 is secured to the retaining ring 100 so that the conductive ring can be moved up and down within the cavity 159. In this embodiment of the retaining ring a spacer may optionally be used.

The conductive portion may comprise one or more conductive materials. The conductive ring 134 is a single band of first material that interacts with the ECMP process, such as a metal that dissolves into the electrolyte solution or forms gas bubbles, and a metal that does not dissolve or cause oxygen evolution into the electrolyte solution. It may include one or more bands of a second material that interact less with the ECMP process. The second metal is in electrical contact with the conductive element of the polishing pad assembly 30 and transfers voltage to the first metal. For example, as shown in FIG. 8, two annular bands 180 of a first metal, such as stainless steel, can surround an annular band 182 of a second metal, such as copper, gold, or platinum. The first metal may comprise a smaller percentage, for example about 25%, of the total width of the ring than the second metal. Additional bands of the first metal may also be formed in the conductive ring 134.

Features formed at the bottom of the retaining ring may also be formed at the bottom surface of the conductive ring 134. In one embodiment, grooves 190 may be formed in the lower surface 118 of the lower ring portion 155, and grooves 190 may also be formed in the conductive ring 134. The groove 190 allows the polishing electrolyte 28 to be transferred from the outside of the retaining ring 100 to the recess 140 of the retaining ring.

As shown in FIG. 9, the conductive ring 134 of the passively-biased retaining ring is positioned inside the retaining ring 100, so that the conductive portion of the polishing pad assembly 30 is connected to the conductive ring ( 134). The height of the spacer 171 (as shown in FIG. 6) must be low enough so that the conductive element of the polishing pad assembly 30 can contact the conductive ring 134. In the embodiment shown, conductive sphere 40 extends above polishing layer 32. The sphere 171 is equal to or thinner than the thickness of the exposed portion of the sphere 40. The width 138 of the conductive ring 134 is wide enough to make the electrical contact with the conductive sphere 40 more reliable. Typically, at least two spheres 40 are in contact with the conductive ring 134 at any time during polishing.

Referring to FIG. 10, the conductive ring of the passively-biased retaining ring may also be used with a polishing pad assembly that does not have protruding electrodes for biasing the conductive ring. When the polishing pad assembly 30 includes a conductive polishing layer 32 or a non-conductive polishing layer with conductive elements embedded therein, a conductive spacer 171 is positioned between the conductive ring 134 and the polishing surface 34. A conductive polishing layer 32 can then bias the conductive ring. Conductive spacer 171 may be formed of stainless steel or other suitable low conductivity metal.

Referring to FIG. 11, a conductive ring 134 that can be controllably positioned is positioned against the polishing surface. To move the conductive ring 134 relative to the polishing surface, a pressure regulator (not shown) raises the pressure in the cavity 159 in which the conductive ring 134 is fixed. To move the conductive ring 134 away from the polishing surface, a pressure regulator reduces the pressure in the cavity 159 to form a vacuum.

As shown in FIGS. 12 and 13, the actively-biased retaining ring includes a conductive portion 156. The conductive portion 156 may be fastened to the upper ring portion 153 by screws, bolts or other suitable fasteners, or may be bonded to the upper ring portion 153 by adhesives or epoxy or the like. The upper ring portion 153 may include one or more openings or passages 151 extending from the inner diameter surface 107 to the outer surface 142 such that fluid may pass through the upper ring portion 153.

Conductive portion 156 has a bottom surface in partial contact with insulating portion 160. Insulating portion 160 may be forcibly fitted to conductive portion 156, or may be bonded to conductive portion 156 by an adhesive, epoxy, or the like. The bottom surface 118 of the insulating portion 160 contacts the polishing pad during the polishing process. The insulating portion 160 prevents the conductive portion 156 from making electrical contact with any conductive portion of the polishing pad assembly 30, such as an electrode. Insulating portion 160 is a non-conductive material, such as plastic, for example polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyetheretherketone (PEEK), polybutylene terephthalate (PBT), poly Tetrafluoroethylene (PTFE), polybenzimidazole (PBI), polyetherimide (PEI), or composite materials. The material may be inert to the polishing process. The insulating portion 160 may comprise a material that is less rigid than the material forming the conductive portion 156, but the insulating portion 160 is still relatively rigid. The insulating portion 160 may have a thickness thicker than the substrate 10 to be polished. Thickness thicker than the substrate 10 reduces the likelihood of contact between the conductive portion 156 and the substrate 10. If the insulating portion 160 is not thicker than the substrate 10, a ring of insulating material may be formed on the inner edge of the retaining ring 100 to insulate the wafer from the conductive portion 156.

Insulating portion 160 has one or more openings 173 that allow the electrolyte solution to contact conductive portion 156 during polishing. The opening 173 may be a round, oval, square or other shaped perforation. The insulating portion 160 may have one opening 173 or a plurality of openings 173. The openings may include axial grooves, circular grooves, or the like. The opening 173 is small enough to prevent a portion of the polishing pad assembly 30 from making direct contact with the conductive portion 156. About 5% to about 95% of the bottom surface of the conductive portion 156 may be exposed to the electrolyte solution.

Conductive portion 156 may have recess 172 at the bottom surface. The recess is in fluid communication with the opening 171 in the insulating portion 160. The recess 172 allows fluid to flow to remove bubbles from the opening 173 during polishing. Some or all of the recesses may be in fluid communication with two or more openings 173 to facilitate bubble removal. Instead, insulating portion 160 may have recesses that allow openings 173 to be in fluid communication with each other.

Referring to FIG. 14, conductive portion 156 is electrically connected to a power source, for example voltage supply 50. By external rollers or spindles, electrical contacts can be formed between the voltage source and the conductive portion 156. In one embodiment, an electrical connection to the ring is created by an external conductive member 23 (see FIG. 16 and the description below) that contacts the outside of the conductive portion 156 of the ring, such as a roller or brush. In another embodiment, current is delivered to the rotating head by roll-ring, slip-ring, or mercury feedthrough. Instead, the conductive portion 181 includes a wire attached to the retaining ring 100 to provide an electrical connection between the roll-ring and the conductive portion 156. In one embodiment, conductive portion 181 contacts conductive portion 156 and provides an electrical connection between voltage source 50 and conductive portion 156. The conducting portion 181 may extend through the upper ring portion 153 of the retaining ring 100 and through the rotating shaft of the carrier head, or along the outer wall of the upper portion 153. The conductive portion 181 may be formed of a conductive material and may include the same material as the conductive portion 156 is formed.

Referring to FIG. 15, the conductive portion 156 of the retaining ring 100 is electrically coupled to the first terminal of the first voltage source 50. The conductive portion of the polishing pad assembly 30 is electrically coupled to the second terminal of the voltage source 50. The first terminal of the second voltage source 50 is electrically coupled to the conductive portion of the first voltage source 50 and the polishing pad assembly 30. The second terminal of the second voltage source 48 is electrically coupled to the counter-electrode 38 of the polishing pad assembly 30. As a result, the voltage source 50 may bias the retaining ring 100 against the anode, i.e., the conductive portion of the polishing pad assembly 30 in contact with the substrate 10 and / or the substrate 10. As shown in FIG. Other configurations for biasing the retaining ring, the substrate and the counter electrode are also suitable, for example a first voltage between the counter electrode and the conductive portion of the retaining ring and between the counter electrode and the conductive portion of the polishing pad assembly. There is a second voltage or a first voltage between the conductive portion of the retaining ring and the conductive portion of the polishing pad assembly and the second voltage between the retaining ring and the counter-electrode. Voltage source 50 may bias retaining ring 100 to a desired potential, for example, from about −5V to about 5V, about 0V to about 1V. Since the insulating portion 160 prevents the conductive portion 156 from contacting the conductive element of the polishing pad assembly 30, the retaining ring 100 is independently biased by the voltage source 50. Thus, the polishing pad assembly 30 may be biased V1 with the same or different potential as the retaining ring 100 (V2).

The sensor or ammeter 51 is in electrical communication with the retaining ring 100 to measure the current from the retaining ring 100 as described below. Voltage source 50, power source 48, and ammeter 51 may be in communication with computer 52. The computer 52 may control the voltages applied to the retaining ring 100 and the substrate 10. In addition, the computer 52 may be configured to monitor current in the system, as described below.

In the case where the conductive portion 156 is biased, an anodic reaction occurs on the conductive portion 156, which causes the cathode current I3. As the voltage in the ring increases, the current from the ring also increases. The sensor may be in electrical contact with the conductive portion 156 to measure the current I2 from the retaining ring 100. The cathode current I3 can be compensated for by measuring the current I2 flowing through the retaining ring 100. Subtracting the current I2 from the ring from the cathode current I3 results in the dissolution current I1 from the substrate. The dissolution current I1 can be monitored to provide a profile of material removal from the substrate and to measure the material removal rate. There may be several cathodes in the system. The configuration of the measurement current described above can be used to control the removal profile for the substrate. Other configurations may be used to monitor or control other parameters.

When no voltage is applied to the retaining ring 100, the function of the retaining ring 100 is similar to the standard retaining ring. When a voltage of 0V or higher is applied, biasing of the retaining ring 100 may slow down the metal removal rate from the edge of the substrate 10 during polishing. As the voltage applied to the retaining ring 100 increases, the removal rate decreases. When a negative voltage is applied to the retaining ring 100, the removal rate is increased at the edge of the substrate 10.

In one embodiment, a standard retaining ring 100 without conductive portions is used to polish the substrate. An insulated conductive member in a manner similar to the conductive retaining ring 100 described above may be located on the polishing surface. The conductive member can be positioned adjacent to the substrate to be polished. In one embodiment, the conductive member surrounds the non-conductive retaining ring. In this embodiment, the conductive member need not be rotated with the non-conductive retaining ring. When the carrier head is moved from one platen to the next platen, the conductive member may remain on the first platen without moving to the next platen along the carrier head.

By using one or a combination of the above-described features, the substrate can be polished using an ECMP process. The carrier head transfers the substrate to the polishing station, and the substrate surface to be polished at the polishing station comes into contact with the polishing surface of the polishing pad assembly. Appropriate electrolyte solution is supplied to the polishing surface.

If an actively-biased retaining ring is used, a first voltage is applied between the counter-electrode and the substrate. A second voltage is applied between the substrate and the conductive portion of the retaining ring. The substrate and the conductive portion can be biased independently of the counter-electrodes and can be biased against each other. The carrier head can control the magnitude of the pressure applied to the retaining ring. Despite the pressure applied by the carrier head, the conductive portion of the polishing pad device does not contact the conductive portion of the retaining ring. Instead, only the electrolyte solution is in contact with the conductive portion.

If a passively-biased retaining ring is used, power is supplied to a voltage source electrically coupled to the counter-electrode layer. The voltage source can be in direct contact with the substrate and in electrical contact with a conductive element that can be in direct or indirect contact with the conductive ring of the retaining ring, for example, an electrode, electrical wire or conductive pad, as described above. do. When the conductive element is in electrical contact with the substrate and the conductive ring, the substrate and the conductive ring are biased.

When using one retaining ring, relative motion is created between the polishing pad assembly and the substrate. Such movement can be caused by one or more actions, which include the carrier head moving the substrate, the carrier head rotation and the platen rotation. As the substrate is processed, copper is removed from the substrate into the electrolyte solution.

Electrically biasing the conductive portion of the retaining ring may improve copper uniformity between the center of the substrate 10 and the edge of the substrate 10. Without wishing to be bound by any theory, the inclusion of the conductive portion in the retaining ring will ensure that a substantially uniform voltage is applied across the edge region of the substrate, thereby improving the uniformity of the electrolyte solution across the edge of the substrate. will be. In particular, in the absence of a conductive ring, ECMP can cause excessive polishing at the edges. This edge effect is presumed to be caused by the non-uniformity of the voltage produced by the substrate edge. However, the addition of a conductive ring enables effective control of the potential of the electrolyte at the edge of the substrate and can extend the edge of the conductive region, thus eliminating the cause of voltage non-uniformity from the edge of the substrate. In other words, the edge of the region where the non-uniform voltage is applied is no longer the edge of the substrate, but beyond the edge of the substrate. Locally, at the edge of the substrate, the potential can be more uniform.

When using an actively-biased ring, insulating portion 160 may prevent conductive portion 156 from contacting polishing pad assembly 30. By preventing direct contact of the conductive portion 156 and the polishing pad assembly 30, it is possible to independently bias the retaining ring 100 and the substrate 10. Since the retaining ring 100 can be biased independently, the rate of material removal at the edge of the substrate can be adjusted.

The spacer prevents at least a portion of the conductive portion from contacting the polishing pad assembly 30. If the conductive portion is formed of copper, contact between the copper and the polishing pad assembly 30 may cause a chemical reaction to wear the conductive portion. Preventing chemical reactions can reduce the loss of copper material in the conductive ring during polishing. Generally, the non-conductive and conductive portions of retaining ring 100 are formed of different materials that wear at different rates. By including the spacing 171 in the retaining ring 100, the bottom surface 118 of the retaining ring 100 and the area where the conductive ring is located, in particular, the bottom of the retaining ring 100 wears out during polishing. In this case it is possible to maintain flatness over the area where the conductive ring is located.

By using two metals for the conductive portion, it is possible to form a narrow band of first metals that interact more strongly with the electrolyte solution during processing. If a current-based endpoint detection system is used with an ECMP device as described in US Publication No. US 2004-0182721 A1, referred to herein, and if the conductive ring is formed of copper, copper may interfere with the endpoint detection system. Can be. In particular, dissolution of copper from the conductive portion can produce noise that offsets the current signal generated for dissolution of copper from the substrate. Limiting the amount of current generated by the metal ring, ie reducing the area of the conductive portion, may reduce this disturbance. In one embodiment, the portion of the ring comprising the high conductivity metal is as small as possible but still large enough to remove the edge effect from the edge of the substrate. In a passively-biased ring, forming a conductive portion of low and high conductivity metal can form a sufficiently wide conductive ring, thereby ensuring contact between the conductive portion and the conductive element of the polishing pad assembly 30. Can be. The second material transfers the applied voltage to the first metal. In a passively-biased or actively-biased ring, the desired effect of eliminating edge effects from the substrate edge can be achieved by allowing the low conductivity metal to transfer voltage to the high conductivity metal. At the same time, reducing the area of high conductivity metal of the conductive ring reduces interference with endpoint detection. In addition, the second metal is less expensive than the first metal, which makes the ring manufacture cheaper.

By forming a conductive portion of the same material as the material being removed from the substrate, for example copper, it is possible to increase the uniformity of the effect of the ECMP polishing process over the edge of the substrate and to shift the edge influence to the retaining ring. Typically, copper may be compatible with the chemicals of the substrate. Other metals, such as nickel, may diffuse into the substrate, rendering the device formed from the substrate unusable. By using other materials such as gold, platinum, palladium or silver, the lifetime of the conductive portion can be increased. If copper is in contact with the polishing surface, the copper will behave in the same way as copper is removed from the substrate. Non-cuprous metals will not be acted in the same way as copper, ie oxygen release will occur instead of electrolyte dissolution, and non-copper metals are not quickly removed from the conductive portion. In metals such as gold, oxygen release can occur.

Forming the lower ring portion 155 with a material that is inert to the polishing process and does not easily cause chipping or balance of the substrate provides a suitable edge for contacting the substrate 20 and reduces the likelihood of damage to the substrate 20. . By fixing the conductive portion in the retaining ring of such inert material, it is possible to take both the advantages of the inert material and the advantages of the conductive material, as described above.

By forming the conductive portion so that the conductive portion acts in the retaining ring, the conductive portion can be moved and the gap can be cleaned. The debris collected in the retaining ring can be cleaned. If the ECMP system has multiple platens for polishing the substrate, the rate of polishing the substrate edge can be controlled by moving the conductive substrate back and forth relative to the polishing surface. By forming the conductive portion to be operable, the process can be better controlled.

By independently biasing the conductive portion of the ring through the carrier head as opposed to biasing the conductive portion with the conductive element of the polishing pad assembly 30, a smaller conductive portion can be formed. Less contact with the electrolyte requires less conductive material. There is no need for a multi-band shaped conductive portion as shown in FIG.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications are possible within the spirit and scope of the invention. For example, a retaining ring can be used with a polishing device other than a polishing pad, for example a polishing belt. In order to mount the conductive ring without a cavity formed between the retaining ring and the conductive ring, a recess in which the conductive ring is fixed may be formed. The conductive ring can be replaced with two or more individual conductive bodies. Elements described as being used with a passively-biased retaining ring may be used with an actively-biased retaining ring or vice versa. Accordingly, other embodiments will be included in the claims.

All citations described herein are incorporated by reference in their entirety.

1 is a side view showing a partial cross-sectional view of an ECMP polishing station.

2A is a cross-sectional view of an ECMP polishing station with a conductive roller.

2B is a side view of an ECMP polishing station having conductive elements on the polishing surface of the polishing pad.

2C is a cross-sectional view of an ECMP polishing station having a conductive polishing surface.

3A-3D are partial cross-sectional views of another embodiment of a retaining ring having conductive portions.

4 is a side cross-sectional view partially showing an ECMP polishing station having a retaining ring with conductive portions;

5A is a perspective view of a retaining ring with conductive portions.

5B is a cross-sectional view of one embodiment of a retaining ring for use with an ECMP system.

6A is a cross-sectional view of one embodiment of a retaining ring for use with an ECMP system.

6B and 6C are perspective views of a retaining ring with conductive portions and one or more spacers.

7A is a cross-sectional view of a retaining ring with a spring-loaded conductive ring.

7B is a cross-sectional view of a retaining ring having a conductive ring that can be controllably positioned.

8 is a bottom view of a portion of the retaining ring with grooves.

9 is a cross-sectional perspective view of a retaining ring having conductive portions in contact with electrodes of an ECMP system.

10 is a cross-sectional view of a retaining ring having a spacer in contact with the conductive polishing layer of the polishing apparatus.

11 is a cross-sectional view of a retaining ring having a conductive portion that can be in contact with and in controllable positioning of a conductive polishing layer of a polishing apparatus.

12 is a cross-sectional view showing a retaining ring having an insulating portion and a conductive portion.

FIG. 13 is a bottom view showing the insulating and conductive portions of the retaining ring along with the cross section of the retaining ring; FIG.

14 is a perspective view of one embodiment of a retaining ring for use with an ECMP system.

15 and 16 are side views of ECMP polishing stations having retaining rings that can be biased independently.

Claims (15)

As carrier head for electrochemical mechanical processing: Conducting unit; Base; And A retaining ring attached to the base, The retaining ring comprises a conductive portion having an upper surface and a lower surface, and an insulating portion, The upper surface of the insulating portion is in contact with the lower surface of the conductive portion, The conductive portion is in electrical communication with the conductive portion of the retaining ring. Carrier head for electrochemical mechanical processing. The method of claim 1, The insulating portion follows the outer diameter of the retaining ring Carrier head for electrochemical mechanical processing. As a system for electrochemical mechanical processing: A polishing pad support; A carrier head configured to contact the polishing pad support; And A first voltage source, The carrier head comprises a base and a retaining ring attached to the base, The retaining ring comprises a conductive portion and an insulating portion having an upper surface and a lower surface, The conductive portion is connected to a power source via a conductive portion, an upper surface of the insulating portion is in contact with a lower surface of the conductive portion, and the first voltage source is electrically coupled to the conductive portion of the retaining ring. System for electrochemical mechanical processing. The method of claim 3, wherein And a polishing pad assembly supported by the polishing pad support, wherein the polishing pad assembly includes a corresponding electrode. System for electrochemical mechanical processing. The method of claim 4, wherein The corresponding electrode is electrically coupled to a second voltage source. System for electrochemical mechanical processing. The method of claim 3, wherein The conductive portion comprises one or more recesses System for electrochemical mechanical processing. The method of claim 3, wherein The insulating portion comprises one or more grooves System for electrochemical mechanical processing. The method of claim 3, wherein The conductive portion is in electrical contact with the spindle. System for electrochemical mechanical processing. As a method of operation of the system for electrochemical mechanical processing: Electrically biasing the polishing pad assembly to a first voltage; Electrically biasing a conductive retaining ring to a second voltage different from the first voltage; And Generating relative movement between the substrate held by the conductive retaining ring and the polishing pad assembly. Method of operation of the system for electrochemical mechanical processing. A method of forming a conductive retaining ring for electrochemical mechanical processing: Providing a substantially annular conductive portion configured to be connected to a power source via a connection; And Fastening an insulating portion to a lower surface of the conductive portion, The upper surface of the insulating portion is in contact with the lower surface of the conductive portion Method for forming a conductive retaining ring. As a retaining ring for electrochemical mechanical processing: A conductive portion having a bottom surface exposed to the periphery; And A substrate contact portion forming an inner diameter surface, The substrate contact portion is formed of an insulating material that is less rigid than the conductive portion, the substrate contact portion has a bottom surface for contacting the polishing pad, and the bottom surface of the conductive portion is relative to the bottom surface of the conductive portion. Relatively recessed Retaining ring for electrochemical mechanical processing. The method of claim 11, An upper surface of the substrate contacting portion is in contact with a lower surface of the conductive portion, the substrate contacting portion allowing at least a portion of the lower surface of the conductive portion to be exposed to the periphery Retaining ring for electrochemical mechanical processing. As the retaining ring: A conductive portion having a bottom surface exposed to the periphery; And A substrate contact portion forming an inner diameter surface, The substrate contact portion is formed of an insulating material that is less rigid than the conductive portion, the conductive portion forms an annular conductive ring, the annular conductive ring being a first portion formed of a first metal and a second different from the first metal. Comprising a second portion formed of a metal Retaining ring. The method of claim 13, The first metal and the second metal form concentric annular rings, the first metal being located between the inner diameter surface of the annular body and the second metal. Retaining ring. The method of claim 13, The first metal comprises copper and the second metal comprises stainless steel Retaining ring.

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