Patent Application
20050191947
This invention relates to a retaining ring for use in chemical mechanical polishing.
An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive or insulative layers on a silicon substrate. One fabrication step involves depositing a filler layer over a non-planar surface, and planarizing the filler layer until the non-planar surface is exposed. For example, a conductive filler layer can be deposited on a patterned insulative layer to fill the trenches or holes in the insulative layer. The filler layer is then polished until the raised pattern of the insulative layer is exposed. After planarization, the portions of the conductive layer remaining between the raised pattern of the insulative layer form vias, plugs and lines that provide conductive paths between thin film circuits on the substrate. In addition, planarization is needed to planarize the substrate surface for photolithography.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head of a CMP apparatus. The exposed surface of the substrate is placed against a rotating polishing disk pad or belt pad. The polishing pad can be either a “standard” pad or a fixed-abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load on the substrate to push it against the polishing pad. The substrate is held below the carrier head with a retaining ring. A polishing liquid, such as a slurry including abrasive particles, is supplied to the surface of the polishing pad.
In one aspect, the invention is directed to a retaining ring that has not been use in device substrate polishing. The retaining ring has a generally annular body having a top surface, an inner diameter surface, an outer diameter surface and a bottom surface. The bottom surface has a target surface characteristic that substantially matches an equilibrium surface characteristic that would result from breaking-in the retaining ring with the device substrate polishing.
In one aspect, the invention is directed to a retaining ring for a chemical mechanical polisher having a generally annular body having a top surface, an inner diameter surface, an outer diameter surface and a bottom surface, wherein the bottom surface has a convex shape and wherein a difference in height across the bottom surface is between 0.001 mm and 0.05 mm.
In another aspect, the invention is directed to a retaining ring for a chemical mechanical polisher having a generally annular body having a top surface, an inner diameter surface, an outer diameter surface and a bottom surface, wherein the bottom surface includes a generally horizontal portion adjacent the inner diameter surface and a sloped portion adjacent the outer diameter surface.
In another aspect, the invention is directed to a retaining ring for a chemical mechanical polisher having a generally annular body having a top surface, an inner diameter surface, an outer diameter surface and a bottom surface, wherein the bottom surface includes a generally horizontal portion and rounded corners adjacent the inner diameter surface and the outer diameter surface.
In another aspect, the invention is directed to a retaining ring for a chemical mechanical polisher having a generally annular body having a top surface, an inner diameter surface, an outer diameter surface and a bottom surface, wherein the bottom surface includes a convex portion adjacent the inner diameter surface and a concave portion adjacent the outer diameter surface.
In another aspect, the invention is directed to a retaining ring for a chemical mechanical polisher having a substantially annular body having a top surface, an inner diameter surface adjacent to the top surface, an outer diameter surface adjacent to the top surface, and a bottom surface, where the bottom surface has a sloped first portion adjacent to the inner diameter surface and a sloped second portion adjacent to the outer diameter surface and the first portion is not planar with the second portion.
In another aspect, the invention is directed to a retaining ring for use in chemical mechanical polishing having a substantially annular body having a top surface, an inner diameter surface adjacent to the top surface, an outer diameter surface adjacent to the top surface, and a bottom surface, wherein the bottom surface has at least one frustoconical surface between the inner diameter to the outer diameter, and wherein a difference in height across the bottom surface is between 0.002 mm and 0.02 mm.
In another aspect, the invention is directed to a retaining ring having an annular body having a bottom surface with a shaped radial profile formed by lapping the bottom surface using a first machine dedicated for use in lapping the bottom surface of retaining rings.
In another aspect, the invention is directed to a retaining ring having an annular body having a bottom surface, an inner surface, an outer surface and a top surface configured for attachment to a carrier head, wherein the retaining ring includes a first portion and a second portion having different surface roughness.
In another aspect, the invention is directed to a retaining ring having an annular body having a bottom surface, an inner surface, an outer surface and a top surface configured for attachment to a carrier head, an inner edge between the inner surface and the bottom surface having a first radius of curvature, and an outer edge between the outer surface and the bottom surface having a second radius of curvature that is different from the first radius of curvature.
In another aspect, the invention is directed to a retaining ring having an annular body having a bottom surface, an inner surface, an outer surface and a top surface configured for attachment to a carrier head, wherein the bottom surface of the retaining ring includes polyamide-imide.
In yet another aspect, the invention is also directed to a lapping machine. The machine has a rotating platen, a plurality of restraining arms associated with the platen, each restraining arm operable to keep an object from moving along the path of the platen's rotation, while allowing the object to rotate about one or more points in the object. The machine also has an adaptor operable to couple a source of pneumatic pressure and a source of vacuum to at least one of the objects such that pneumatic pressure and vacuum can be applied to the object simultaneously.
In yet another aspect the invention is directed to an apparatus for forming a predetermined profile on a bottom surface of a retaining ring. The apparatus has a lapping table and a retaining ring holder. At least one of the lapping table and retaining ring holder is configured to apply a pressure differential across a width of the retaining ring.
In still another aspect, the invention is directed to a method of forming a retaining ring that includes removing material from a bottom surface of an annular retaining ring to provide a target surface characteristic. The removal is performed using a first machine dedicated for use in removing material from a bottom surface of retaining rings, and the target surface characteristic substantially matches an equilibrium surface characteristic that would result from breaking-in the retaining ring on a second machine used for polishing of device substrates.
In still another aspect, the invention is directed to a method of forming a surface profile on a bottom surface of a retaining ring. A bottom surface of an annular retaining ring is held in contact with a generally planar polishing surface. Non-rotational motion is created between the bottom surface and the polishing surface to wear the bottom surface until the bottom surface reaches an equilibrium geometry.
In still another aspect, the invention is direct to a method of forming a retaining ring. A retaining ring with an inner diameter surface, an outer diameter surface, a top surface and a bottom surface is formed. The bottom surface is lapped to provide a predetermined non-planar profile.
In still another aspect, the invention is directed to a method of forming a retaining ring. A retaining ring with an inner diameter surface, an outer diameter surface, a top surface and a bottom surface is formed. The bottom surface is machined to provide a predetermined non-planar profile.
In still another aspect, the invention is directed to a method of forming a retaining ring. A retaining ring with an inner diameter surface, an outer diameter surface, a top surface and a bottom surface is formed. The bottom surface is shaped to have two or more annular regions where at least one of the regions is not parallel to the top surface.
In still another aspect, the invention is directed to a method of forming a retaining ring. A retaining ring with an inner diameter surface, an outer diameter surface, a top surface and a bottom surface is formed. The bottom surface is shaped to provide at least one frustoconical surface from the inner diameter to the outer diameter, wherein a difference in height across the bottom surface is between 0.002 mm and 0.02 mm.
In still another aspect, the invention is direct to a method for shaping a retaining ring. A retaining ring having a bottom surface is provided. The bottom surface is lapped to form a shaped radial profile in the bottom surface, the lapping being performed using a first machine dedicated for use in lapping the bottom surface of retaining rings.
In still another aspect, the invention is directed to a method for shaping a retaining ring. A retaining ring having a bottom surface is provided. The bottom surface is lapped to form a shaped radial profile in the bottom surface, wherein during the lapping the ring is permitted to rotate freely about an axis of the ring.
In even another aspect, the inventions is directed to a method of using a retaining ring. A bottom surface of an annular retaining ring is lapped to provide a target surface characteristic, the lapping being performed using a first machine dedicated for use in lapping the bottom surface of retaining rings. The retaining ring is secured on a carrier head. A plurality of device substrates are polished with a second machine using the carrier head, wherein the target surface characteristic substantially matches an equilibrium surface characteristic that would result from breaking-in the retaining ring on the second machine.
Implementations of the invention may provide none, one or more of the following advantages. A radial profile of a bottom surface of a retaining ring may be shaped to improve polishing uniformity at a substrate edge. For example, a retaining ring with a thinner inner diameter may provide slower edge polishing, whereas a retaining ring with a thicker inner diameter can provide faster edge polishing. The radial profile of the retaining ring may be shaped for a particular process to reduce or eliminate any changes in the radial profile of the bottom surface as the ring wears during polishing. A retaining ring that does not change profile as it wears may provide improved substrate-to-substrate uniformity in the edge polishing rate. The retaining ring may be shaped to a desired radial profile to reduce or obviate any break-in process, thereby reducing machine downtime and cost of ownership. Because the break-in period may be reduced or eliminated, the retaining ring can be formed of a highly wear resistant material which would normally require lengthier break-in periods.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
A retaining ring 100 is a generally an annular ring that can be secured to a carrier head of a CMP apparatus. A suitable CMP apparatus is described in U.S. Pat. No. 5,738,574 and a suitable carrier head is described in U.S. Pat. No. 6,251,215, the entire disclosures of which are incorporated herein by reference. The retaining ring 100 fits into a loadcup for positioning, centering, and holding the substrate at a transfer station of the CMP apparatus. A suitable loadcup is described in U.S. patent application Ser. No. 09/414,907, filed Oct. 8, 1999, the entire disclosure of which is incorporated by reference.
As shown in
The upper portion 105 of the retaining ring 100 can include one or more passages, e.g., four drain holes spaced at equal angular intervals around the retaining ring, to provide pressure equalization, for injection of cleaning fluid, or expulsion of waste. These drain holes extend horizontally through the upper portion 105 from the inner surface 165 to the outer surface 150. Alternatively, the drain holes can be tilted, e.g., higher at the inner diameter surface than at the outer diameter surface, or the retaining ring can be manufactured without drain holes.
The upper portion 105 can be formed from a rigid or high tensile modulus material, such as a metal, ceramic or hard plastic. Suitable metals for forming the upper portion include stainless steel, molybdenum, titanium or aluminum. In addition, a composite material, such as a composite ceramic, can be used.
The second piece of the retaining ring 100, the lower portion 130, can be formed from a material that is chemically inert to the CMP process and may be softer than the material of the upper portion 105. The material of the lower portion 130 should be sufficiently compressible or elastic that contact of the substrate edge against the retaining ring 100 does not cause the substrate to chip or crack. However, the lower portion 130 should not be so flowable as to extrude into the substrate receiving recess 160 when the carrier head puts downward pressure on the retaining ring 100. The hardness of the lower portion 130 can be between 75 and 100 Shore D, e.g., between 80 and 95 Shore D. The lower portion 130 should also be durable and have high wear resistance, although it is acceptable for the lower portion 130 to wear away. For example, the lower portion 130 can be made of a plastic, such as polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyetheretherketone (PEEK), carbon filled PEEK, polyetherketoneketone (PEKK), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), polybenzimidazole (PBI), polyetherimide (PEI), or a composite material.
The lower portion may also have a flat top surface 135, a cylindrical inner surface 235, a cylindrical outer surface 230, respectively, and a bottom surface 155. Unlike the top portion 105, the lower portion's bottom surface 155 has a non-flat geometry or profile. In certain implementations, the shaped radial profile of bottom surface 155 can include curved, frustoconical, flat and/or stepped sections. A retaining ring with a shaped radial profile includes at least one non-planar portion on the bottom surface 155. Typically, it is advantageous for the radial profile of the bottom surface 155 of the retaining ring 100 to substantially match an equilibrium profile (discussed below) of the bottom surface 155 for the process in which the retaining ring 100 will be used. The equilibrium profile can be determined, for example, by experimentation (e.g., examining a worn retaining ring) or by software modeling.
The lower portion 130 and the upper portion 105 are connected at their top 135 and bottom 110 surfaces, respectively, to form the retaining ring 100. When the upper portion 105 and lower portion 130 are aligned and mated, the outer diameter surface of the retaining ring 100 can have a unitary tapered surface 145 (e.g., wider at the top than at the bottom) between the two cylindrical surfaces 150 and 230. The two parts can-be joined using an adhesive, mechanical fasteners such as screws, or a press-fit configuration. The adhesive can be an epoxy, e.g., two-part slow-curing epoxy, such as Magnobond-6375™, available from Magnolia Plastics of Chamblee, Ga.
An enlarged view of one embodiment of the retaining ring is shown in
The bottommost portion of the bottom surface 155, e.g., the thickest portion, such as the planar region 215, can be closer to the inner diameter 165 than the outer diameter 150. Alternatively, as shown in
As shown in
Hypothetically, any number of regions can be machined on the bottom surface. However, because the difference D between the thinnest and thickest part of the lower part's profile typically vary less than by 0.02 mm, three regions are generally the maximum number of regions machined. Frustoconical regions can approximate the curved shape of the bottom surface of one of the retaining rings. Alternatively, the bottom surface of the ring can be formed with a curved surface or a curved portion.
Referring to
For the implementations shown in
Referring to
The bottommost portion of the bottom surface 155, such as the portion at a point 215, can be closer to the inner surface 235 than the outer surface 230, as shown in
The height difference D1 across the bottom surface, and thus (assuming that the top surface 135 is a planar surface) the thickness difference between the thickest and thinnest parts of the lower portion's profile, can be between 0.001 mm and 0.05 mm, e.g., between 0.002 mm and 0.01 mm. For example, the difference D1 can be generally around 0.0076 mm. (The Figures described herein are exaggerated and not to scale in order to show the radial profile more clearly; the curvature of the profile might not be apparent on visual inspection).
The lower edge 220 of the outer surface 230 can be above the lower edge 225 of the inner surface 235. The lowest point of the bottom surface 155 can be between 0.001 mm and 0.05 mm, e.g., between 0.002 mm and 0.01 mm, from the lower edge 225 of the inner surface 235. For example, D1-D2 can be generally around 0.0025 mm.
Referring to
Referring to
Referring to
Referring to
The height difference D3 across the bottom surface, and thus (assuming that the top surface of the lower portion is a planar surface) the thickness difference between the thickest and thinnest parts of the lower portion's profile, can be between 0.001 mm and 0.05 mm, e.g., between 0.01 mm and 0.03 mm. For example, the difference D3 can be between 0.0025 mm, 0.0076 mm or generally around 0.018 mm.
Although the discussion above has focused on the geometry of the bottom surface, the retaining ring can be formed with other surface characteristics that substantially match the equilibrium characteristics that would result from polishing. The bottom surface 155 can have a very smooth surface finish. For example, the bottom surface of the retaining ring may be formed with a target roughness average (RA) of bottom surface 155 can be less than 4 micro inch, less than 2 micro inch or 1 micro inch or less. In general, the retaining ring can have a surface roughness better than that achievable with conventional machining techniques. In addition, the retaining ring can be formed with regions of different roughness. For example, the bottom surface 155 of the retaining ring can have regions, e.g., concentric annular regions, of different surface roughness. In another implantation, the bottom surface 155 has a surface roughness less than that of the sides 230 and 235 (i.e., the bottom surface is smoother). These concepts could be applicable to any of the retaining rings described above, or even to retaining rings with an entirely flat bottom surface.
The bottom surface 155 of the lower portion 130 can also include unillustrated channels or grooves, e.g., twelve or eighteen channels, to permit a polishing fluid, such as slurry, which can include abrasives or be abrasive-free, to flow underneath the retaining ring 100 to the substrate in the substrate receiving recess 160. The channels can be straight or curved, can have a uniform width or be flared so as to be wider at the outer diameter of the retaining ring, and can have a uniform depth or be deeper at the inner surface 235 than at the outer surface 230. Each channel can have a width of about 0.030 to 1.0 inches, such as 0.125 inches, and may have a depth of 0.1 to 0.3 inches. The channels can be distributed at equal angular intervals around the retaining ring 100. The channels are typically oriented at an angle a, such as 45°, relative to a radial segment extending through the center of the retaining ring 100, but other angles of orientation, such as between 30° and 60°, are possible.
Having discussed various implementations of the retaining ring above, the use and method of manufacturing the retaining ring will be discussed below. In normal operation of the CMP apparatus, a robotic arm moves a 300 mm substrate from cassette storage to a transfer station. At the transfer station, the substrate is centered in the loadcup. The carrier head moves into place above the loadcup. Once the carrier head and loadcup are generally aligned with one another, the carrier head is lowered into position to collect the substrate. Specifically, the carrier head is lowered so that the bottom of the retaining ring's outer surface engages the inner surface of the loadcup.
Once the substrate has been loaded into the carrier head, the carrier head lifts away to disengage from the loadcup. The carrier head can move from the transfer station to each of the polishing stations on the CMP apparatus. During CMP polishing, the carrier head applies pressure to the substrate and holds the substrate against the polishing pad. During the polishing sequence, the substrate is located within the receiving recess 160 of the retaining ring 100, which prevents the substrate from escaping. Once polishing is completed, the carrier head returns to a position over the loadcup and lowers so that the retaining ring 100 is brought into and re-engages the loadcup. The substrate is released from the carrier head, and subsequently moved to the next step of the polishing sequence.
The bottom surface 155 of the retaining ring 100 contacts the polishing pad during the substrate polishing process. The profile of the retaining ring 100 affects the rate of substrate edge polishing. Typically, when the retaining ring is thinner at the inner diameter, the edge of the substrate is polished more slowly than when the retaining ring is flat across the bottom. Conversely, if the retaining ring is thicker at the inner diameter, the edge is polished faster.
A conventional “ideal” retaining ring is typically formed with the bottom surface having a generally flat radial profile. Thus, if a conventional “ideal” retaining ring were laid on a perfectly flat surface, all points of the conventional retaining ring's bottom surface ideally would touch the flat surface. While the bottom surface of an actual conventional retaining ring may have some degree of roughness or unevenness, the average radial profile of the ring can be determined by averaging multiple radial cross-sections of the ring, and this average radial profile will be generally flat. During polishing, the polishing pad wears away the bottom surface 155 of the retaining ring 100. Typically, wearing does not occur at an even rate radially across the bottom surface 155. This uneven wearing causes the bottom surface 155 to take on a non-flat geometry. For example, the portion of the bottom surface 155 that is closest to the inner diameter 165 of the retaining ring 100 can wear away faster than the portion of the bottom surface 155 of the retaining ring 100 that is closest to the outer diameter of the retaining ring 100. The wearing of the retaining ring 100 eventually comes to an equilibrium, such that the bottom surface of the retaining ring 100 retains the substantially same geometry as the ring wears until the process or polishing conditions change.
The equilibrium geometry of the retaining ring profile depends on the polishing process conditions, such as slurry composition, polishing pad composition, retaining ring down force, and platen and carrier head rotation rate. Other factors include the polishing pad stiffness, the retaining ring stiffness, the condition of the polishing pad surface, the polishing down force and the polishing velocity.
Polishing at the substrate edge will drift until the retaining ring 100 reaches equilibrium. To reduce substrate to substrate or across substrate polishing variation, the retaining ring can be “broken in” before being used in the polishing process. One way of breaking in a retaining ring is by simulating substrate polishing, using the same type of polishing apparatus as the rings will be use for polishing of device matters e.g., by pressing the retaining ring against a polishing pad so that the ring wears until it reaches the equilibrium geometry. However, a disadvantage of “break-in” is that it requires use of the polishing apparatus. As a result, the break-in process is down-time of the polishing apparatus during which no polishing can be performed, increasing cost of ownership.
Instead of the retaining ring with a polishing apparatus, the desired retaining ring profile can be shaped, e.g., created by machining the bottom surface of the ring, before the retaining ring is used in a polishing machine so that the bottom surface has the equilibrium that generally would result from a desired set of polishing conditions. Although a retaining ring can have a curved surface typically the machining process will create “flat” regions (i.e., regions with linear radial profiles, such as planar or frustoconical surfaces) which together approximate the geometry of a broken in retaining ring. The desired profile geometry is generally determined by using a retaining ring with the same process conditions that will be selected when the retaining ring is used to polish substrates until the retaining ring reaches its equilibrium geometry. This equilibrium geometry is repeatable given the same process conditions. Thus, this retaining ring profile can be a model for the machined retaining rings.
Referring to
Referring to
Alternatively, the machining can be performed using a modified lapping process to simulate the CMP environment. A variety of lapping machines can be used, such as machines that use rotational, dual rotational, vibratory, random vibratory, or orbiting motion. It can be noted that the lapping machine need not use the same type of relative motion as the polishing machine. In short, by lapping the bottom surface of the retaining ring under conditions that simulate the polishing environment, the bottom surface of the retaining ring will be worn into the equilibrium geometry. This equilibrium geometry is repeatable given the same process conditions. This lapping can be performed separately from the polishing apparatus and using less expensive machinery, thus reducing the costs of the break-in procedure.
A CMP machine typically includes many components that are not necessary for lapping table 300. For example, a CMP machine typically includes an endpoint detection system, a wafer load/unload station, one or more washing stations, motors to rotate and a carousel to move the carrier heads, and a robotic wafer transfer system. Typically, only one carrier head is used at a time per platen in a CMP machine, and the number of carrier heads can be one greater than the number of platens.
For example, a retaining ring 100 with a shaped radial profile in the bottom surface 155 can be formed using a lapping apparatus such as the lapping apparatus 300 in
Multiple retaining rings 320(1)-320(3) (e.g., retaining ring 100) can be lapped at once, and the lapping apparatus 300 can include multiple arms 330(1)-330(3) that hold the retaining rings 320(1)-320(3) during lapping. The arms 330(1)-330(3) can have one or more wheels 340 attached that allow retaining rings 320(1)-320(3) to rotate freely during lapping. Alternatively, the retaining rings 320(1)-320(3) could be forced to-rotate during lapping, but allowing the retaining rings 320(1)-320(3) to rotate freely simplifies the design and operation of the lapping apparatus 300. The amount time required to shape the retaining ring's profile (e.g., 20-60 minutes) typically depends on the desired profile and surface finish for the retaining ring, the material of the retaining ring, and the lapping process parameters.
The retaining rings 320(1)-320(3) can be secured to CMP carrier heads (e.g., carrier head 410, which can be, for example, a Contour or Profiler carrier head manufactured by Applied Materials) during the lapping process. The carrier heads can be coupled to a source of pneumatic pressure and vacuum (not shown) using an adaptor 490. The adaptor 490 can be designed so that pneumatic pressure and vacuum can be applied to the carrier head 410 simultaneously. Pneumatic pressure can be applied to the carrier heads (e.g., to shaft 440) to force the retaining rings 320(1)-320(3) against the platen 402 or lapping pad 420 during lapping. The pressure applied can be varied during lapping to control the speed of lapping and the shape of the radial profile of the bottom surfaces (e.g., bottom surface 155) of the retaining rings 320(1)-320(3). In one implementation, weights can be used on the carrier heads (e.g., instead of, or combined with, pneumatic pressure) to force the retaining rings 320(1)-320(3) against the platen 402 or lapping pad 420 during lapping.
In addition to the force applied to the carrier head, pneumatic pressure can be applied to one or more chambers 470 between the shaft 440 and the retaining ring 320(1), which lifts the shaft 440 away from the ring (though the shaft 440 and ring remain coupled) and allows the self-gimbaling effect of the carrier head to operate. The amount of pressure applied in the chamber 470 (e.g., 0.5 psi) can be balanced with the amount of force applied to the shaft 440 (e.g., 60-100 lbs.) so that the shaft 440 and the retaining ring 320(1) remain properly aligned.
The retaining rings 320(1)-320(3) can be lapped while holding substrates or without substrates. If the carrier head includes a membrane 450 with a substrate receiving surface, vacuum can be applied to a chamber 460 behind the membrane 450 to draw the membrane 450 away from the lapping pad 420 and prevent the membrane 450 from contacting the lapping pad 420 or the platen during lapping. This can help prevent membrane breakage when the retaining rings 320(1)-320(3) do not hold substrates.
The process parameters used during lapping (e.g., retaining ring down force, platen rotation rate, lapping pad composition, and slurry composition) can be matched to the process parameters of a CMP process in which the retaining rings 320(1)-320(3) will be used after the retaining rings 320(1)-320(3) are lapped. Substrates such as a dummy substrate 480 (e.g., a quartz or silicon wafer) can be placed inside the retaining rings 320(1)-320(3) during lapping to protect the carrier head membrane 450 and to simulate more closely the process parameters of the CMP process. For example, the membrane 450 can push the dummy substrate 480 against the lapping pad 420 to simulate the CMP process. In one implementation, one of the retaining rings 320(1)-320(3) is replaced with a conditioner (e.g., a diamond disc) capable of abrading the polishing pad 420 to restore a rough surface texture to the pad.
Referring to
Referring to
The edge of the lapping table 302 can support a cylindrical retaining wall 610. The retaining wall 610 prevents the lapping fluid from flowing over the side of the lapping table 302, and captures the retaining ring 100 in the event that a retaining ring escapes from beneath one of the covers 600. Alternatively, the lapping fluid may flow off the edge of lapping table to be captured and recirculated or to be discarded.
Referring to
The cover 600 can provide three functions. First, the cover 600 protects the outer surfaces of the retaining ring 100 (i.e., the surfaces other than the bottom surface 155) from wear or damage during the lapping process. Second, the cover 600 applies a load to the retaining ring which can be about the same as the load which will be applied during the polishing process. Third, the sloped portion 332 of the cover 600 applies a differential load across the retaining ring width, so that the retaining ring 100 resulting from the machining process will have a taper on its bottom surface, e.g., sloped downwardly from its outside inward as shown in
Referring to
Referring to
A weight 310 can be placed or secured on top of the disk-shaped body 702 so that the downward load on the retaining ring during the break-in process generally matches the load applied during the substrate polishing operation. Alternatively, a dampening spring can be positioned to press the holder 700 and retaining ring onto the pad 204. The dampening spring may help prevent the holder 700 from “jumping” off the pad 204 during vibrational movement.
One or more resilient bumpers 312 can be secured to the sides of the retaining ring holder 700. For example, the bumper 312 can be an O-ring that surrounds the retaining ring holder 700.
The table 202 is supported by a drive mechanism 222 that drives the table in random vibrational movement. The retaining ring holder 700 is free floating on the table 202, and thus will move in a random vibratory path across the table. The bumper 312 causes the retaining ring holder 700 to bounce off the retaining wall 212, thereby contributing to the random motion of the holder and preventing damage to the holder or retaining ring from the retaining wall.
In another implementation, illustrated in
Referring to
Referring to
Referring to
The platen can be configured to rotate, orbit, vibrate, oscillate, or undergo random motion relative to the carrier head. In addition, the carrier head can undergo a fixed rotation, or it can be free to rotate under the applied lateral force from the lapping pad.
Referring to
In yet another implementation, the carrier 360 and the retaining ring 100 can be formed of materials with similar coefficients of thermal expansion, but the carrier 360 and retaining ring 100 can be heated to different temperatures. For example, the retaining ring holder could be brought to a temperature above that of the retaining ring. Consequently, the retaining ring holder will expand, causing the holder to bend outwardly as shown in
In addition to breaking in of the retaining ring as described above, the lapping apparatus can be used to lap the top surface of the retaining ring and/or the bottom surface of the carrier head. For this operation, the polishing pad is replaced by a metal lapping plate. The metal lapping-plate can itself be lapped to defined flatness and can be electroplated to resist the corrosive effects of the slurry. Alternatively, the top of the table could be electroplated and used for lapping of the top surface of the retaining ring and/or the bottom surface of the carrier head. The lapping process can use the same motion as the break-in process, e.g., random vibration or elliptical motion.
After the retaining rings have been lapped by lapping apparatus to form a shaped profile on the bottom surfaces of the rings, the retaining rings can be removed from the lapping apparatus and secured to a CMP machine to be used in polishing wafers (e.g., silicon integrated-circuit wafers). Retaining rings can be lapped at a manufacturing facility and then shipped to a semiconductor fab to be used. Retaining rings can be lapped using a machine that is dedicated to lapping retaining rings. The lapping machine can be used primarily to lap retaining rings, and silicon substrates typically will not be polished using the lapping machine, though silicon substrates can be used as dummy substrates.
In review, a retaining ring can be formed by removing material from a bottom surface of an annular retaining ring to provide a target surface characteristic. The removal can be performed using a first machine dedicated for use in removing material from a bottom surface of retaining rings, and the target surface characteristic can substantially match an equilibrium surface characteristic that would result from breaking-in the retaining ring on a second machine used for polishing of device substrates. Thus, a retaining ring that has not been use in device substrate polishing can have a generally annular body having a top surface, an inner diameter surface, an outer diameter surface and a bottom surface, and the bottom surface can have a target surface characteristic that substantially matches an equilibrium surface characteristic that would result from breaking-in the retaining ring with the device substrate polishing.
A number of embodiments of the invention have been described, but other implementations are possible, and it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
For example, various sections of the inner or-outer surfaces 150, 230, 165 and 235 can have straight, sloped, or mixed straight and sloped geometry. Various other features, such as ledges or flanges, can be present on the upper surface 115 to permit the retaining ring to mate to the carrier head. The holes for screws or screw sheaths can be formed on the flange portion.
As another example, the retaining ring 100 can be constructed from a single piece of plastic, using, for example, PPS, instead of being formed from a separate upper portion 105 and lower portions 130.
Although various positional descriptors, such as “top” and “bottom” are used, these terms are to be understood as relative to the polishing surface, as the retaining ring can be used in polishing systems in which the substrate is face up, face down, or in which the polishing surface is vertical.
The present invention has been described in terms of a number of embodiments. The invention, however, is not limited to the embodiments depicted and described. Rather, the scope of the invention is defined by the appended claims.
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, elements and components described with one system or retaining ring can be used in conjunction with another system or retaining ring. Accordingly, other embodiments are within the scope of the following claims.
This application claims the benefit of priority under 35 U.S.C. 119(e)(1), of U.S. provisional application 60/520,555, filed Nov. 13, 2003, U.S. provisional application 60/580,759, filed Jun. 17, 2004, U.S. provisional application 60/556,569, filed Mar. 26, 2004, U.S. provisional application 60/603,068, filed Aug. 19, 2004 and U.S. provisional application 60/580,758, filed Jun. 17, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60520555 | Nov 2003 | US | |
| 60580759 | Jun 2004 | US | |
| 60556569 | Mar 2004 | US | |
| 60603068 | Aug 2004 | US | |
| 60580758 | Jun 2004 | US |
