Printing a chemical mechanical polishing pad

Abstract

A method of fabricating a polishing layer of a polishing pad includes successively depositing a plurality of layers with a 3D printer, each layer of the plurality of polishing layers deposited by ejecting a pad material precursor from a nozzle and solidifying the pad material precursor to form a solidified pad material.

Claims

1. A method of fabricating a polishing pad, comprising: successively depositing and curing a first plurality of layers on a support to provide a lower portion of the polishing pad, wherein each layer of the first plurality of layers is deposited by ejecting droplets of a first liquid pad material precursor across a powderless first region, and curing solidifies the first liquid pad material precursor to form a first solidified pad material that spans the first region; successively depositing and curing a second plurality of layers on the first plurality of layers to provide an upper portion of the polishing pad comprising a polishing layer, wherein each layer of the second plurality of layers is deposited by ejecting droplets of a second liquid pad material precursor from a droplet ejection printer over a powderless second region that covers some portions of the first region, and curing solidifies the second liquid pad material precursor to form a second solidified pad material that is more rigid than the first solidified pad material and such that other portions of the first region over which the second liquid pad material is not dispensed provide a plurality of grooves in the polishing layer that extend to expose the first solidified pad material.

2. The method of claim 1, further comprising removing the first solidified pad material and the second solidified pad material from the support.

3. The method of claim 2, wherein the support comprises a rigid base.

4. The method of claim 2, wherein the second liquid pad material precursor has a different composition than the first liquid pad material precursor.

5. The method of claim 2, wherein the second liquid pad material precursor is cured by a different amount than the first liquid pad material precursor.

6. The method of claim 1, wherein curing the first liquid pad material precursor and curing the second liquid pad material precursor comprise ultraviolet (UV) curing.

7. The method of claim 6, wherein the second liquid pad material precursor comprises a monomer.

8. The method of claim 7, wherein the second liquid pad material precursor comprises a urethane monomer.

9. The method of claim 1, wherein a thickness of each layer of the second plurality of layers is less than 10% of a total thickness of the polishing layer.

10. The method of claim 9, wherein the thickness of each layer of the second plurality of layers is less than 5% of the total thickness of the polishing layer.

11. The method of claim 1, comprising curing the second liquid pad material precursor immediately upon deposition.

12. The method of claim 1, comprising curing an entire layer of the second liquid pad material precursor simultaneously after deposition of the entire layer of the second liquid pad material precursor.

13. The method of claim 1, wherein the grooves comprise 10%-75% of the total horizontal surface area of the polishing pad.

14. The method of claim 1, wherein plateaus between the grooves have lateral dimension of 0.1 to 2.5 mm.

15. The method of claim 1, wherein the grooves have a depth of 0.25 to 1.5 mm.

16. The method of claim 1, wherein the grooves have a widest lateral dimension of 0.1 to 2 mm.

17. The method of claim 1, wherein ejecting droplets of the first liquid pad material precursor comprises translating a nozzle across the support while the support remains stationary.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a schematic cross-sectional side view of an example polishing pad.

(2) FIG. 1B is a schematic cross-sectional side view of another example polishing pad.

(3) FIG. 1C is a schematic cross-sectional side view of yet another example polishing pad.

(4) FIG. 2 is a schematic side view, partially cross-sectional, of a chemical mechanical polishing station.

(5) FIG. 3 is a schematic cross-sectional side view illustrating a substrate in contact with the polishing pad of FIG. 1A.

(6) Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

(7) Referring to FIG. 1A-1C, a polishing pad 18 includes a polishing layer 22. As shown in FIG. 1A the polishing pad can be a single-layer pad that consists of the polishing layer 22, or as shown in FIG. 1C the polishing pad can be a multi-layer pad that includes the polishing layer 22 and at least one backing layer 20.

(8) The polishing layer 22 can be a material that is inert in the polishing process. The material of the polishing layer 22 can be a plastic, e.g., a polyurethane. In some implementations the polishing layer 22 is a relative durable and hard material. For example, the polishing layer 22 can have a hardness of about 40 to 80, e.g., 50 to 65, on the Shore D scale.

(9) As shown in FIG. 1A, the polishing layer 22 can be a layer of homogeneous composition, or as shown in FIG. 1B the polishing layer 22 can include abrasive particles 28 held in a matrix 29 of plastic material, e.g., polyurethane. The abrasive particles 28 are harder than the material of the matrix 29. The abrasive particles 28 can be from 0.05 wt % to 75 wt % of the polishing layer. For example, the abrasive particles 28 can be less than 1 wt % of the polishing layer 22, e.g., less than 0.1 wt %. Alternatively, the abrasive particles 28 can be greater than 10 wt % of the polishing layer 22, e.g., greater than 50 wt %. The material of the abrasive particles can be a metal oxide, such as ceria, alumina, silica or a combination thereof.

(10) In some implementations, the polishing layer includes pores, e.g., small voids. The pores can be 50-100 microns wide.

(11) The polishing layer 22 can have a thickness D1 of 80 mils or less, e.g., 50 mils or less, e.g., 25 mils or less. Because the conditioning process tends to wear away the cover layer, the thickness of the polishing layer 22 can be selected to provide the polishing pad 18 with a useful lifetime, e.g., 3000 polishing and conditioning cycles.

(12) On a microscopic scale, the polishing surface 24 of the polishing layer 22 can have rough surface texture, e.g., 2-4 microns rms. For example, the polishing layer 22 can be subject to a grinding or conditioning process to generate the rough surface texture. In addition, 3D printing can provide small uniform features, e.g., down to 200 microns.

(13) Although the polishing surface 24 can be rough on a microscopic scale, the polishing layer 22 can have good thickness uniformity on the macroscopic scale of the polishing pad itself (this uniformity refer to the global variation in height of the polishing surface 24 relative to the bottom surface of the polishing layer, and does not count any macroscopic grooves or perforations deliberately formed in the polishing layer). For example, the thickness non-uniformity can be less than 1 mil.

(14) Optionally, at least a portion of the polishing surface 24 can include a plurality of grooves 26 formed therein for carrying slurry. The grooves 26 may be of nearly any pattern, such as concentric circles, straight lines, a cross-hatched, spirals, and the like. Assuming grooves are present, then the polishing surface 24, i.e., the plateaus between the grooves 26, can be 25-90% of the total horizontal surface area of the polishing pad 18. Thus, the grooves 26 can occupy 10%-75% of the total horizontal surface area of the polishing pad 18. The plateaus between the grooves 26 can have a lateral width of about 0.1 to 2.5 mm.

(15) In some implementations, e.g., if there is a backing layer 20, the grooves 26 can extend entirely through the polishing layer 22. In some implementations, the grooves 26 can extend through about 20-80%, e.g., 40%, of the thickness of the polishing layer 22. The depth of the grooves 26 can be 0.25 to 1 mm. For example, in a polishing pad 18 having a polishing layer 22 that is 50 mils thick, the grooves 26 can have a depth D2 of about 20 mils.

(16) The backing layer 20 can be softer and more compressible than the polishing layer 22. The backing layer 20 can have a hardness of 80 or less on the Shore A scale, e.g., a hardness of about 60 Shore A. The backing layer 20 can be thicker or thinner or the same thickness as the polishing layer 22.

(17) For example, the backing layer can be an open-cell or a closed-cell foam, such as polyurethane or polysilicone with voids, so that under pressure the cells collapse and the backing layer compresses. A suitable material for the backing layer is PORON 4701-30 from Rogers Corporation, in Rogers, Conn., or SUBA-IV from Rohm & Haas. The hardness of the backing layer can be adjusted by selection of the layer material and porosity. Alternatively, the backing layer 20 can be formed from the same precursor and have the same porosity as the polishing layer, but have a different degree of curing so as to have a different hardness.

(18) Turning now to FIG. 2, one or more substrates 14 can be polished at a polishing station 10 of a CMP apparatus. A description of a suitable polishing apparatus can be found in U.S. Pat. No. 5,738,574, the entire disclosure of which is incorporated herein by reference.

(19) The polishing station 10 can include a rotatable platen 16 on which is placed the polishing pad 18. During a polishing step, a polishing liquid 30, e.g., abrasive slurry, can be supplied to the surface of polishing pad 18 by a slurry supply port or combined slurry/rinse arm 32. The polishing liquid 30 can contain abrasive particles, a pH adjuster, or chemically active components.

(20) The substrate 14 is held against the polishing pad 18 by a carrier head 34. The carrier head 34 is suspended from a support structure, such as a carousel, and is connected by a carrier drive shaft 36 to a carrier head rotation motor so that the carrier head can rotate about an axis 38. The relative motion of the polishing pad 18 and the substrate 14 in the presence of the polishing liquid 30 results in polishing of the substrate 14.

(21) Referring to FIG. 3, at least the polishing layer 22 of the polishing pad 18 is manufactured using a 3D printing process. In the manufacturing process, thin layers of material are progressively deposited and fused. For example, droplets 52 of pad precursor material can be ejected from a nozzle 54 of a droplet ejecting printer 55 to form a layer 50. The droplet ejecting printer is similar to an inkjet printer, but uses the pad precursor material rather than ink. The nozzle 54 translates (shown by arrow A) across a support 51.

(22) For a first layer 50a deposited, the nozzle 54 can eject onto the support 51. For subsequently deposited layers 50b, the nozzle 54 can eject onto the already solidified material 56. After each layer 50 is solidified, a new layer is then deposited over the previously deposited layer until the full 3-dimensional polishing layer 22 is fabricated. Each layer is applied by the nozzle 54 in a pattern stored in a 3D drawing computer program that runs on a computer 60. Each layer 50 is less than 50% of the total thickness of the polishing layer 22, e.g., less than 10%, e.g., less than 5%, e.g., less than 1%.

(23) The support 51 can be a rigid base, or be a flexible film, e.g., a layer of polytetrafluoroethylene (PTFE). If the support 51 is a film, then the support 51 can form a portion of the polishing pad 18. For example, the support 51 can be the backing layer 20 or a layer between the backing layer 20 and the polishing layer 22. Alternatively, the polishing layer 22 can be removed from the support 51.

(24) Solidification can be accomplished by polymerization. For example, the layer 50 of pad precursor material can be a monomer, and the monomer can be polymerized in-situ by ultraviolet (UV) curing. The pad precursor material can be cured effectively immediately upon deposition, or an entire layer 50 of pad precursor material can be deposited and then the entire layer 50 be cured simultaneously.

(25) However, there are alternative technologies to accomplish 3D printing. For example, the droplets 52 can be a polymer melt that solidifies upon cooling. Alternatively, the printer creates the polishing layer 22 by spreading a layer of powder and ejecting droplets of a binder material onto the layer of powder. In this case, the powder could include additives, e.g., the abrasive particles 28.

(26) The 3D printing approach eliminates the need for making expensive and time consuming molds. The 3D printing approach also eliminates several conventional pad manufacturing steps such as molding, casting and machining. Additionally, tight tolerances can be achieved due to the layer-by-layer printing approach. Also, one printing system (with printer 55 and computer 60) can be used to manufacture a variety of different polishing pads, simply by changing the pattern stored in the 3D drawing computer program.

(27) In some implementations, the backing layer 20 can also be fabricated by a 3D printing process. For example, the backing layer 20 and polishing layer 22 could be fabricated in an uninterrupted operation by the printer 55. The backing layer 20 can be provided with a different hardness than the polishing layer 22 by using a different amount of curing, e.g., a different intensity of UV radiation.

(28) In other implementations, the backing layer 20 is fabricated by a conventional process and then secured to the polishing layer 22. For example, the polishing layer 22 can be secured to the backing layer 20 by a thin adhesive layer, e.g., as a pressure-sensitive adhesive.

(29) A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, either the polishing pad, or the carrier head, or both can move to provide relative motion between the polishing surface and the substrate. The polishing pad can be a circular or some other shape. An adhesive layer can be applied to the bottom surface of the polishing pad to secure the pad to the platen, and the adhesive layer can be covered by a removable liner before the polishing pad is placed on the platen. In addition, although terms of vertical positioning are used, it should be understood that the polishing surface and substrate could be held upside down, in a vertical orientation, or in some other orientation.

(30) Accordingly, other implementations are within the scope of the following claims.