BACKGROUND [0001 ] Field of invention

[0002] The invention relates to chemical-mechanical polishing and more particularly to methods and products for replenishing a polishing slurry in a chemical-mechanical polishing apparatus. [0003] Description of Related Art

[0004] The chemical-mechanical polishing ("CMP") process is used in the manufacture of optical lenses and microelectronic devices to remove material from a workpiece such as a plastic or glass lens blank or a wafer and thereby create a very smooth, scratch-free surface. In a typical CMP process, a polishing slurry is introduced between the workpiece and a polishing pad that is pressed against the workpiece. One or both of the polishing pad and the workpiece are moved relative to the other so as to cause the polishing pad to wipe against the surface of the workpiece with the polishing slurry disposed therebetween. The polishing slurry typically comprises abrasive particles that are dispersed and suspended in a carrier fluid. The carrier fluid typically comprises one or more chemical compounds that influence the rate at which material can be physically abraded from the surface of the workpiece via the polishing pad and/or the abrasive particles. [0005] FIG. 1 schematically illustrates a polishing apparatus 1 0 such as is typically used in plastic lens product polishing applications. The apparatus 1 0 comprises a polishing machine 20 which supports a workpiece 30 such as a plastic lens blank. The polishing machine 20 presses a polishing pad 40 into contact with a surface 50 of the workpiece 30. A polishing slurry 60 is provided between the polishing pad 40 and the surface 50 of the workpiece 30. The polishing slurry 60 is supplied to the polishing machine 20 via a supply line 70 that is in fluid communication with a slurry tank 80. A pump 90 typically conveys the polishing slurry 60 from the slurry tank 80 to the polishing machine 20 through the supply line 70. [0006] In some applications, only one polishing machine 20 is fluidiy connected to the slurry tank 80. in other applications, a plurality of polishing machines 20 are connected to the same slurry tank 80 via supply lines 70. In FIG. 1 , both possibilities are illustrated by use of brackets, where reference character "n" represents a whole number equal to or greater than 1 . It will be appreciated that one pump 90 or a plurality of pumps could be utilized.

[0007] The capacity of the slurry tank 80 can vary from a few liters to hundreds of liters or more. The slurry tanks 80 in many commercial plastic lens polishing applications have a capacity of from about 35 to about 1 20 liters of polishing slurry 60. The slurry tank 80 is typically fitted with a mixing device 100, which helps prevent abrasive particles in the polishing slurry 60 from falling out of suspension and collecting as sludge in the slurry tank 80. The mixing device 1 00 can be a mechanical stirrer or pump or a combination of thereof.

[0008] The slurry tank 80 typically comprises a cover 1 1 0, which can be selectively opened or closed. The cover 1 10, when closed, keeps unwanted matter from entering the slurry tank 80 and reduces the evaporation rate of the polishing slurry 60. The cover 1 10, when opened, permits an operator to replenish the polishing slurry 60 in the slurry tank 80. [0009] A polishing slurry 60 typically comprises abrasive particles that are dispersed and suspended in a carrier fluid. The carrier fluid typically comprises one or more chemical compounds that influence the rate at which a material on the surface 50 of the workpiece 30 can be physically abraded from the surface 50 of the workpiece 30 via the polishing pad 40 and/or the abrasive particles in the polishing slurry 60. [0010] Polishing slurries are a consumable component of the CMP process that must be periodically replenished. Polishing slurries are typically preformulated and then packaged in rigid containers for shipment to end users. When it is time to replenish the polishing slurry in a polishing apparatus, the rigid container containing the preformulated polishing slurry is vigorously shaken while sealed in order to resuspend abrasive particles that have settled within the container during storage. Alternatively, the rigid container is opened and the abrasive particles are resuspended by means of a mechanical mixing or stirring device. Once an attempt has been made to resuspend the abrasive particles that have settled during storage, the cover 1 1 0 of the slurry tank 80 is opened and the polishing slurry 60 is poured from the rigid container into a slurry tank associated with the polishing apparatus. [001 1 ] It can be difficult to resuspend substantially all of the abrasive particles of a polishing slurry that have settled within a rigid container by means of shaking or stirring. Accordingly, residues comprising abrasive particles that were not successfully resuspended are often retained on the walls of the rigid container after the flowable portion of the polishing slurry has been poured into the slurry tank. The retention of abrasive particles in the rigid container can upset the intended weight ratio/balances of abrasive particles in the polishing slurry. Furthermore, the container bearing the residues is typically discarded, which creates waste and disposal concerns.

BRIEF SUMMARY

[0012] In view of the foregoing, the present invention is directed towards methods and products for replenishing a polishing slurry in a chemical-mechanical polishing apparatus that overcome the foregoing problems associated with conventional containers. In accordance with the invention, the preformulated polishing slurry is packaged within a container having flexible walls. In the preferred embodiment of the invention, the container having flexible walls comprises a pouch formed of a flexible film. When it is time to replenish the polishing slurry in a polishing apparatus, an operator manually squeezes the sealed container, which causes deformation of the container walls. The deformation of the container walls leads to the rapid and substantially complete resuspension of the abrasive particles into the polishing slurry. Once the abrasive particles have been sufficiently resuspended, the container having flexible walls is unsealed and the polishing slurry is poured into a slurry tank associated with the polishing apparatus. The present invention substantially reduces the amount of abrasive particle residue remaining within the container once the polishing slurry has been poured into the slurry tank. The present invention also substantially reduces the amount of waste. [001 3] The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic representation of a polishing apparatus used in a CMP process.

[001 5] FIG. 2 is front plan view of a preferred embodiment of a sealed flexible pouch containing a polishing slurry according to the invention.

[0016] FIGS. 3-5 are front plan views showing alternative embodiments of sealed flexible pouches containing polishing slurries according to the invention.

DETAILED DESCRIPTION

[001 7] FIG. 2 shows a preferred embodiment of a sealed flexible pouch 1 20 containing a polishing slurry 60 in accordance with the invention. The polishing slurry 60 comprises abrasive particles 1 30 and a carrier liquid 140. FIG. 2b schematically illustrated an enlarged portion of the pouch 1 20 bounded by a circular area. The size and spacing of the abrasive particles 1 30 illustrated in FIG. 2b is grossly exaggerated for the purpose of illustrating the invention. Conventionally, the abrasive particles 1 30 will have a very small diameter, which depending upon the particular application can range from a few nanometers to as large as several hundred microns. The composition of the abrasive particles 1 30 will depend upon the material to be removed from the workpiece 30. Abrasives used in CMP include, for example, alumina, silica, ceria, copper oxide, iron oxide, nickel oxide, manganese oxide, silicon carbide, silicon nitride, tin oxide, titania, titanium carbide, tungsten oxide, yttria, zirconia, and combinations thereof. [0018] The abrasive particles 1 30 are adapted to be suspended in the carrier liquid 14 such as, for example, water. However during shipment and storage of the pouch 1 20, at least a portion of the abrasive particles 1 30 will settle out and no longer be suspended in the carrier liquid 140. The settled abrasive particles 1 50 tend to collect in the corners, along the seams and/or within creases of the pouch 1 20. Settling is generally considered to be a time-dependent factor. Thus, the longer the polishing slurry 60 contained within the pouch 1 20 is at rest, the more settling of the abrasive particles that is likely to occur.

[001 9] As noted above, polishing slurries are conventionally packaged, shipped and stored in containers having substantially rigid walls (e.g., buckets, plastic jugs, jars etc.). It can be very difficult to resuspend and thus redisperse the settled abrasive particles in such containers via shaking and stirring. In many cases, a portion of the abrasive particles cannot be resuspended, and remains as a residue within the container. This residue is discarded together with the container.

[0020] In accordance with the present invention, the polishing slurry 60 is contained within a sealed flexible pouch 1 20 having walls that are adapted to be repeatedly deformed (e.g., by squeezing or kneading using one's hands). In order to facilitate deformation of the pouch 1 20, at least a portion of the pouch 1 20 is preferably formed of a flexible polymeric film. More preferably, most of the pouch 1 20 is formed of a flexible polymeric film. The composition of the polymer or polymers used to form the polymeric film is not per se critical. Examples include polymeric films comprising polyethylene (e.g., linear low density polyethylene - "LLDPE"), ethylene vinyl acetate ("EVA") polyesters and various other flexible film- forming polymers, copolymers and blends of polymers. The films can be formed of a single layer of one polymer, or can be formed as laminates of two or more layers of different film materials. It is preferable for at least a portion of the flexible polymeric film to be transparent, which allows for visual confirmation that substantially of the settled abrasive particles have been substantially resuspended via repeated deformation of the sealed flexible pouch.

[0021 ] In the embodiment of the invention illustrated in FIG. 2, the sealed flexible pouch 1 20 contains a polishing slurry 60 within a cavity 1 60 bounded substantially entirely by polymeric film. In the embodiment shown in FIG. 2, the pouch 1 20 has been formed by folding a polymeric film on itself and welding the folded polymeric film to itself along weld lines 1 70 so to define the cavity 1 60. The pouch 1 20 shown in FIG. 2 further comprises an opening 1 80 bounded entirely by weld lines, which can be used as a handle to lift the sealed flexible pouch 1 20. The sealed flexible pouch 1 20 also further comprises a notch 1 90, which facilitates tearing of the polymeric film at the weld line 1 70 to allow the polishing slurry 60 contained within the cavity 1 60 to be poured from the pouch 1 20. The notch 1 90 can be provided proximal to a narrowed portion 200 of the cavity, which facilitates pouring the polishing slurry 60 from the pouch 1 20.

[0022] FIGS. 3-5 show alternative embodiments of pouches 1 20 containing polishing slurries 60 according to the invention. The same reference numbers utilized in FIG. 2 are used to identify similar structures in FIGS. 3-5. The pouch 1 20 shown in FIG. 3 includes a rigid spout 21 0, which is welded into pouch 1 20. The spout 210 is covered by a cap 220, which is threadingly received on the spout 210. The cap 220 can be removed to unseal the pouch 1 20 and then replaced to reseal the pouch 1 20.

[0023] The pouch 1 20 shown in FIG. 4 includes weld lines 1 70 that completely surround the cavity 1 60. The pouch 1 20 shown in FIG. 4 differs in this respect from the pouches 1 20 shown in FIGS. 2 and 3, which include a base portion 230 that is created by folding the flexible polymeric film and not by welding. The pouch 1 20 shown in FIG. 4 also does not include a spout or notch. Instead, the pouch 1 20 shown in FIG. 4 is provided with indicia 240, which indicates where the pouch 1 20 should be cut or sliced in order to allow for the polishing slurry 60 to be poured from the cavity 1 60. The pouch 1 20 shown in FIG. 4 also includes an opening 1 80 bounded by weld lines 1 70, which can serve as a handle. [0024] The pouch 1 20 shown in FIG. 5 includes a spout 21 0 and a cap 220. Furthermore, the pouch 1 20 shown in FIG. 5 includes a cavity 1 60 that is bounded entirely by weld lines 1 70, except for the portion containing the spout 210. It will be appreciated that there are literally unlimited configurations (size, handles, spouts, closures, markings for volume, shapes, stand-up, pillows, labels, color, etc.) of pouches that can be utilized in accordance with the invention. [0025] The cavity 160 of a sealed flexible pouch 1 20 preferably contains more than 1 liter but less than 10 liters of the polishing slurry 60. It is preferable for the cavity 1 60 not to be entirely filled to capacity with the polishing slurry 60. This allows the walls of the pouch 1 20 to be deformed by squeezing or kneading, which causes the polishing slurry 60 within the cavity to mix and become homogeneous. This also helps dislodge settled particles 1 50, which can more easily- become resuspended in the carrier liquid 140. For ease of handling, pouches 1 20 containing from about 1 .0 to about 3.0, or most preferably about 1 .9 liters, are preferred. [0026] The pouches 1 20 can be pre-manufactured and simply filled with preformulated polishing slurry 60 and sealed. Alternatively, the pouches 1 20 can be formed immediately prior to being filled with a polishing slurry 60. The pouches 120 can be filled using rotary or in-line filling machines, which are well know. Alternatively, the pouches 1 20 can be filled manually and sealed using a heated platen or RF welding equipment.

[0027] As noted, the sealed flexible pouches advantageously allow settled particles to be resuspended in the carrier liquid by squeezing, kneading or tilting the pouch back and forth. The manipulation or massaging of the pouch loosens the settled particles and thoroughly mixes the polishing slurry to form a substantially homogeneous mixture, which can then be easily poured into the slurry tank of a polishing apparatus. Little to no residue is left behind in the pouch, which is a significant improvement as compared to the use of conventional containers having rigid walls. After the polishing slurry has been poured from the pouch, the pouch can be discarded.

[0028] Pouches containing polishing slurries according to the invention are substantially more environmentally friendly than conventional polishing containers having rigid walls. They take up less warehouse/storage space. They produce less waste volume at the time of disposal. They reduce shipping costs due to weight reductions. They can be formed using <40% of the polymer necessary to form convention rigid containers.

[0029] in addition, they provide advantages to the end user.

The pouches are easy to handle during the filling operation.

Substantially all of the abrasive particles are resuspended, leaving virtually no residue in the pouch after the filling operation. This preserves the desired balance or ratio of abrasive particles to carrier liquid.

[0030] Thus, the present invention provides a method for replenishing a polishing slurry in a chemical-mechanical polishing apparatus having a slurry tank. The method comprises:

• providing a sealed flexible pouch containing a polishing slurry comprising abrasive particles and a carrier liquid, wherein the abrasive particles are adapted to be suspended in the carrier liquid but at least a portion of the abrasive particles are not suspended in the carrier liquid;

• repeatedly deforming the sealed flexible pouch for a time sufficient to suspend substantially all of the abrasive particles in the carrier fluid;

® unsealing the repeatedly deformed flexible pouch; and

• pouring at least a portion of the polishing slurry from the unsealed flexible pouch into the slurry tank of the chemical-mechanical polishing apparatus.

[0031 ] The repeatedly deforming step can be performed manually by repeatedly squeezing and releasing less than the entire sealed flexible pouch in one's hands so as to cause the polishing slurry contained in the cavity of the pouch to pulse back and forth between squeezes. The contents of the pouch can also be mixed by repeatedly tilting the sealed flexible container back and forth to thoroughly mix the polishing slurry contained therein. Automatic mixing equipment (shakers etc.) and sonic devices can also be utilized, if desired. [0032] In a preferred application, the polishing slurry dispensed between a polishing pad and a blank used to form a plastic optical lens. In such applications, a central slurry tank (also known in the art as a "process tank") is connected through distribution lines to a plurality of polishing apparatus. When the polishing slurry volume in the slurry tank drops to a predetermined level, the tank volume can be replenished in accordance with the method of the invention. [0033] Additional advantages and modifications will readily occur to those skilled in the art, Therefore, the invention in its broader aspects is not limited to the specific details and illustrative examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.