Polishing pad and chemical mechanical polishing method

Abstract

The invention provides a polishing pad and a chemical mechanical polishing method, the polishing pad is in a disc shape and comprises a polishing surface and a plurality of grooves which are recessed inwards from the polishing surface of the polishing pad, and the plurality of grooves are arranged around the center of the disc-shaped polishing pad to divide a plurality of polishing areas. Each polishing area is provided with one or more through holes which are laterally through and used for fluid communication of the adjacent grooves, the distribution density of the grooves in the radial outward direction of the polishing pad has a decreasing tendency, and the number of the through holes has a decreasing tendency. According to the invention, the distribution uniformity of the polishing liquid on the polishing pad can be effectively improved, and the uniformity of a film-forming pattern in a chip is improved, so that the yield is improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, in particular to a polishing pad. Background Art

[0002] With the increase in the integration of semiconductor integrated circuits and the practical application of multi-layer wiring engineering, the graphics designed and produced on the wafer are gradually refined. At present, the chemical mechanical polishing process (CMP) is the most effective global flattening technology, and the application scenarios of the CMP process are increasing for various purposes. The chemical mechanical polishing process is to clamp the wafer by a rotating polishing head and press it on the rotating polishing pad with a certain pressure. The polishing agent composed of abrasive particles and chemical solution flows between the wafer and the polishing pad, and the wafer surface is flattened under the combined action of chemistry and mechanics. In the actual chemical mechanical polishing process, the problem of inconsistent film patterns in the wafer is more significant due to the influence of equipment structure, mode, and the entire process sequence. In addition, the oxide residue (Oxide Residue) on the processed surface after the CMP process, the poor interconnection structure composed of tungsten or copper, and the subsequent processes of CMP will also affect the consistency between the wafer film patterns, resulting in defects such as poor contact (Contact Not open) and excessive grinding at the edge of the wafer, which greatly affects the product yield.

[0003] At present, many methods such as membrane zone control of the polishing head and pad conditioning tuning are commonly used to improve the uniformity of the film pattern on the wafer. However, due to the influence of consumables such as the main body, positioning ring, and diaphragm of the polishing head, the above pressure adjustment will change as the polishing proceeds, which will lead to a low yield of devices located at the edge of the wafer. In addition, the above adjustment methods will complicate the operation and use of the chemical mechanical polishing process to varying degrees, increasing the difficulty of integrated circuit manufacturing.

[0004] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0005] In view of the shortcomings of the prior art mentioned above, the object of the present invention is to provide a polishing pad and a chemical mechanical polishing method, which are used to solve the problems of excessive difference in polishing rate of the wafer from the center to the periphery of the polishing pad during the execution of the existing chemical mechanical polishing process, inconsistency of the film pattern on the wafer, and inability to remove the by-products of the polishing liquid in time, thereby affecting the product yield.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention provides a polishing pad, which is disc-shaped as a whole, and includes a polishing surface and a plurality of grooves recessed inward from the polishing surface of the polishing pad, wherein the plurality of grooves are arranged around the center of the disc-shaped polishing pad to divide a plurality of polishing areas, each polishing area is provided with one or more through holes penetrating laterally for fluid communication between adjacent grooves, the distribution density of the grooves tends to decrease along the radial outward direction of the polishing pad, and the number of the through holes tends to decrease.

[0007] Optionally, N annular grooves are arranged concentrically from the center to the periphery of the polishing pad on the polishing surface to divide the first polishing area, the second polishing area to the N+1th polishing area in an annular nested arrangement; wherein N is an integer greater than or equal to 2.

[0008] Optionally, the number of through holes opened from the second polishing area to the (N+1)th polishing area around the center of the polishing pad has a tendency to decrease from N to 1, so as to be used for fluid connection between two adjacent annular grooves; wherein, the number of through holes used for fluid connection between the Mth annular groove and the (M+1)th annular groove is (N+1)-M through holes; wherein, M is a natural number greater than 1 and not greater than N.

[0009] Optionally, through holes extending in a radial direction or in a direction slightly angled to the radial direction are provided from the second polishing zone to the (N+1)th polishing zone around the center of the polishing pad, and the through holes provided in the (M+1)th polishing zone and the through holes provided in the Mth polishing zone have opening directions staggered from each other.

[0010] Optionally, the groove width of the annular groove from the center to the periphery of the polishing layer decreases successively, and the distance between two adjacent annular grooves remains unchanged.

[0011] Optionally, a plurality of C-shaped grooves are arranged radially from the center of the polishing pad on the polishing surface to divide a corresponding number of C-shaped polishing areas, and the C-shaped polishing areas are provided with through holes circumferentially connecting adjacent C-shaped grooves.

[0012] Optionally, the C-shaped groove has a gradually increasing width change along the direction from the center to the periphery of the polishing pad.

[0013] Optionally, the polishing pad includes a hydrophilic polishing layer, and the grooves penetrate the hydrophilic polishing layer.

[0014] Optionally, each polishing area is provided with a through hole with a circular cross section, and the radius of the through hole is 0.1 mm-2 mm.

[0015] The present invention also provides a chemical mechanical polishing method, which is performed by using the polishing pad as described above.

[0016] As described above, the polishing pad of the present invention has the following beneficial effects: a plurality of grooves are arranged along the center to the periphery of the disc-shaped polishing pad, the plurality of grooves divide the polishing surface into a plurality of polishing areas, one or more through holes are opened laterally through the polishing areas, and the distribution density of the grooves is reduced along the center to the periphery of the polishing pad, the number of through holes has a tendency to decrease, the linear velocity difference of the grooves at different radial positions is reduced, and the polishing liquid can be redistributed during the polishing process, and the renewal rate of the polishing liquid from the center to the periphery of the polishing pad is adjusted to be close, which can effectively improve the uniformity of the distribution of the polishing liquid on the polishing pad, especially improve the polishing consistency by 10% to 30%, and can improve the uniformity of the film-forming pattern within the wafer, thereby improving the yield; in addition, by decreasing the groove width along the center to the periphery of the polishing pad, the flow difference of the polishing liquid at different radial positions during the polishing process is offset, and the polishing rate from the center to the periphery of the polishing pad is made consistent, which also saves the amount of polishing liquid used and reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a working schematic diagram of a chemical mechanical polishing device.

[0018] Figure 2 Shown is a top view of a typical structure of a chemical mechanical polishing pad.

[0019] Figure 3 Display as Figure 2 A cross-sectional view of a chemical mechanical polishing pad is shown.

[0020] Figure 4 Shown is a top view of a polishing pad according to the present invention.

[0021] Figure 5 A top view of another example of a polishing pad according to the present invention is shown.

[0022] Figure 6 Shown is a cross-sectional view of the polishing pad of the present invention.

[0023] Figure 7 A cross-sectional view showing another example of the polishing pad of the present invention.

[0024] Component number description

[0025] 2 Polishing head

[0026] 3 Polishing disc

[0027] 4 Polishing liquid supply system

[0028] 5 Workpiece

[0029] 6 Dresser

[0030] 41 Polishing liquid

[0031] 21 Polishing head body

[0032] 22 Locating ring

[0033] 2 Wafer

[0034] 12 Polishing head

[0035] 10 Polishing pad

[0036] 110 Circular polishing area

[0037] 120 Annular groove

[0038] 130 Slot or hole

[0039] 20 Polishing pad

[0040] 20a Polishing layer

[0041] 20b Bottom layer

[0042] 210 Annular polishing area

[0043] 220 Annular groove

[0044] 310 C-shaped polishing area

[0045] 320 C-groove

[0046] 230, 330 through hole DETAILED DESCRIPTION

[0047] In order to facilitate understanding of the present disclosure, the present invention will be described more fully below with reference to the relevant drawings. Embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0048] See also Figures 1 to 7. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0049] Figure 1 It shows a working schematic diagram of a chemical mechanical polishing device. Figure 1 As shown, the chemical mechanical polishing equipment includes a polishing head 2, a polishing disc 3, a polishing liquid supply system 4 and a dresser 6. The polishing head 2 includes a polishing head body 21, and a positioning ring 22 arranged on the lower surface of the polishing head body for clamping the workpiece 5; the polishing disc 3 is used to carry the polishing pad 10; the dresser 6 is configured to remove the glaze layer on the surface of the polishing pad to activate the polishing pad; the polishing liquid supply system 4 is installed above the polishing disc to deliver the polishing liquid to the polishing pad 41, and the abrasive particles provide mechanical grinding together with the polishing pad.

[0050] The chemical mechanical polishing process is completed by tightly attaching the workpiece to be processed, such as a wafer, in the polishing head to the rotating polishing surface or moving the wafer relative to the polishing surface in other ways under controlled temperature, pressure and chemical composition conditions. During the polishing process, the workpiece passes through the polishing head and acts on a rotatable polishing disk provided with a polishing pad according to a given pressure, while rotating relative to its own axis. The polishing liquid is usually an aqueous slurry, generally including abrasive particles, reactive chemical reagents such as transition metal chelate salts or oxidants, and additives such as solvents, buffers and passivators. The polishing liquid is transported to the contact interface between the workpiece and the polishing pad, and continuously reacts chemically with the surface of the workpiece. The surface material is removed through the mechanical action of the abrasive particles and the chemical action of the polishing liquid. The polishing pad is an important component of the CMP equipment. During the polishing process, the polishing pad has at least the following functions: 1) storing the polishing liquid; 2) removing the residual substances generated during the polishing process from the processing surface, such as oxide residues; 3) transmitting and carrying the mechanical load required in the processing removal process. Among the above-mentioned influencing factors, the surface structure and organization of the polishing pad will directly affect the performance of the polishing pad.

[0051] Figure 2 and Figure 3The top view and cross-sectional view of the typical structure of the chemical mechanical polishing pad are shown in FIG. Figure 2 As shown, the polishing pad 10 is in the shape of a disk, and includes a polishing surface and a plurality of annular grooves 120 nested around the center thereof to divide a plurality of annular polishing areas 110. The annular grooves 120 can store polishing liquid so that the polishing liquid can be continuously delivered to the surface of the surrounding polishing areas. Figure 2 As shown, through grooves or through holes are provided across a plurality of annular polishing areas for communicating the fluids between the annular grooves to adjust the amount of polishing liquid in different polishing areas.

[0052] However, the inventors of this case noticed that the above-mentioned polishing pad has the following deficiencies: when the chemical mechanical polishing pad rotates at high speed, the linear velocity difference between different radial positions leads to a greater centrifugal force at the position closer to the periphery of the polishing pad. Due to the difference in centrifugal force between different radial positions on the polishing pad, the slurry on the polishing pad has a tendency to increase flow from the center to the periphery of the polishing pad; therefore, the slurry is non-uniformly distributed along the radial direction of the polishing pad. Due to this non-uniform distribution of the slurry, the wafer is non-uniformly polished, thereby affecting the flatness of the wafer. In addition, since the polishing process is accompanied by the oxidation of the polishing liquid, oxidized molecules with weakened bond energy are generated on the processing surface of the wafer. The generated oxidized molecules are usually removed by mechanical action, and the removed materials are taken away by the polishing liquid. In the above process, the mechanical grinding and / or removal of the oxidized molecules is incomplete, and the retained oxide residues will cause surface defects or poor surface properties, and even affect the product yield.

[0053] In view of the above, the present invention proposes a polishing pad, which adjusts the groove size and distribution density of the polishing surface and adds flow holes to guide the distribution of the polishing liquid, so that the polishing liquid is more evenly distributed on the polishing pad, and the center to the periphery of the wafer have a closer polishing efficiency, which can improve the uniformity of the film-forming pattern within the wafer, thereby improving the yield, and can also save the amount of polishing liquid and reduce production costs.

[0054] Example

[0055] An embodiment of the present invention provides a polishing pad having two opposite surfaces, one of which is a polishing surface and the other is fixed to a polishing disk by an adhesive; the polishing pad is disc-shaped, and a plurality of grooves are arranged around the center of the disc-shaped polishing pad to divide a plurality of polishing areas, each polishing area is provided with one or more through holes penetrating laterally for fluid communication between adjacent grooves, and the arrangement density of the through holes tends to decrease successively along the radial outward direction of the polishing pad.

[0056] The polishing pad may have a composite structure, which includes a polishing layer 20a and a bottom layer 20b ( Figure 6In a preferred example, the material of the polishing layer 20a includes one of polyurethane, damping cloth, and non-woven fabric, and the polishing layer 20a is hydrophilic as a whole, or has a hydrophilic surface, which is conducive to the wetting of the polishing surface by the aqueous slurry as the polishing liquid.

[0057] In one implementation, the polishing layer includes a plurality of annular grooves arranged concentrically from the center to the edge to divide a plurality of annular polishing areas.

[0058] In some instances, the annular groove is configured as a circular groove, and the circular polishing area is divided accordingly, and the polishing layer includes N annular grooves arranged concentrically from the center to the edge, and multiple polishing areas arranged alternately with the circular grooves along the radial direction of the disc-shaped polishing pad; wherein N is an integer greater than or equal to 2. Figure 4 Shown is a top view of the polishing pad of the present invention. Figure 4 As shown, in a preferred example, the spacing between two adjacent annular grooves 220 from the center to the periphery of the polishing pad is equal, or tends to increase gradually. In this embodiment, the polishing surface is provided with a first polishing area in the shape of a disk, and a second polishing area to an (N+1)th polishing area in the shape of an annulus surrounding the first polishing area.

[0059] In another implementation, the polishing layer 20a includes a plurality of C-shaped grooves extending radially from the center to the edge to divide into a plurality of C-shaped polishing areas. Figure 5 A top view of another example of a polishing pad according to the present invention is shown. Figure 5 As shown, in some examples, a plurality of C-shaped grooves 320 are alternately arranged along the circumferential direction and extend from the center to the periphery of the polishing layer, and the C-shaped polishing area 310 has a gradually decreasing distribution density along the direction from the center to the periphery of the polishing pad, so that the distribution density of the C-shaped grooves along the radial outward direction of the polishing pad has a decreasing trend.

[0060] One or more through holes are provided laterally through the polishing area to allow fluid communication between adjacent annular grooves. In some examples, the number of through holes provided in the annular polishing area along the radial outward direction of the polishing pad has a decreasing trend. As the polishing pad is driven by the polishing disk to rotate, the linear velocity gradually increases from the center to the outer edge of the polishing pad. Positions with different linear velocities will cause inconsistent polishing efficiencies within the wafer and affect the fluidity of the polishing liquid. Figure 2 The through grooves or through holes shown have an improved utilization rate of the polishing liquid from the center to the edge of the polishing pad based on the above scheme, and adjust the distribution uniformity of the polishing liquid from the center to the edge of the polishing pad.

[0061] In a specific example, the number of through holes used for fluid connection between the first annular groove and the second annular groove is N, and the number of through holes used for fluid connection between the Mth annular groove and the (M+1)th annular groove is (N+1)-M through holes; wherein M is a natural number greater than 1 and not greater than N; wherein the through holes used for fluid connection between the Mth annular groove and the (M+1)th annular groove laterally penetrate the Mth annular polishing area; that is, the outermost annular polishing area may only have one through hole, and the remaining annular polishing areas may have multiple through holes arranged circumferentially. Figure 4 As shown, preferably, between the first polishing area and the outermost annular polishing area, the through holes 230 opened on the annular polishing area 210 are arranged at equal angles in the circumferential direction, which is conducive to maintaining the uniformity of the polishing liquid around the groove. It should be noted that the number and distribution of through holes opened on the polishing surface shown in the figure are used as an example to illustrate the present invention, but the scope of the present invention is not intended to be limited thereto. For example, the number of through holes opened in the annular polishing area from the center to the periphery of the polishing pad can be reduced layer by layer or in a step-by-step manner, and the amplitude of the reduction can be constant or linear.

[0062] Further, each annular polishing area is provided with a through hole extending in a radial direction or in a direction slightly angled to the radial direction, so as to allow the grooves connected by the through hole to flow along a quasi-straight line or a quasi-streamline shape. In this case, by positioning the through holes opened to the same annular groove with a circumferential angle, the through holes opened to the same annular groove in two adjacent annular polishing areas have opening directions staggered from each other, which promotes the circumferential flow of the polishing liquid along the groove, and can further improve the distribution uniformity of the polishing liquid, which is conducive to increasing the renewal rate of the polishing liquid, thereby ensuring the removal efficiency of the surface material and improving the consistency of the film formation pattern in the wafer. In this embodiment, the cross section of each through hole can be set to a circular through hole, for example, the radius of the circular through hole is 0.1mm-2mm.

[0063] The polishing layer can have grooves of the same or different widths. Figure 6 A schematic cross-sectional view of the polishing pad of the present invention is shown. Figure 6 As shown in FIG. 1 , the groove width of the annular groove 220 from the center to the periphery of the polishing layer decreases successively, and the distance between two adjacent annular grooves remains unchanged. During the polishing process, the slurry is continuously supplied to the polishing pad through one or more nozzles, and the polishing pad rotates with the polishing platform to distribute the polishing liquid to the surface of the polishing layer. Figure 3 In the case where the groove width remains unchanged, based on the above technical solution, the groove width of the annular groove from the center to the periphery of the polishing layer decreases successively, so that the amount of polishing liquid contained has a tendency to gradually decrease, offsetting the flow increase of the polishing liquid at the periphery of the wafer, and improving over-grinding at this position.

[0064] In some examples, the width of the second annular groove to the Nth annular groove shows a trend of gradually decreasing. For example, the width of the second annular groove is 2mm to 3mm, and the width of the third annular groove is 0.2mm to 0.5mm less than that of the second annular groove. Similarly, the width of the (M+1)th annular groove is 0.2mm to 0.5mm less than that of the Mth annular groove. Further, the groove can be configured to have a steep sidewall, for example, Figure 6 The annular groove 220 shown has steep sidewalls; or Figure 7 As shown, the annular groove 420 has an inclined sidewall so that the annular groove has an increasing width from the bottom toward the opening.

[0065] The present invention also provides a chemical mechanical polishing method. In this embodiment, the polishing pad described in the previous embodiment is preferably used to perform the chemical mechanical polishing method, which includes the following steps:

[0066] S1: Install the polishing pad on the polishing plate;

[0067] S2: placing the wafer to be processed in the positioning ring of the polishing head so that the processing surface of the wafer contacts the polishing surface of the polishing pad.

[0068] S3; providing a polishing liquid to the polishing surface of the polishing pad;

[0069] S4: applying pressure with a polishing head to move the wafer relative to the polishing pad, thereby flattening the processed surface of the wafer.

[0070] In step S1, the wafer to be processed includes one of a dielectric layer and a metal layer located above a substrate.

[0071] In step S2, a polishing head is used to apply pressure to the wafer to be processed so that its processing surface abuts against the polishing surface of the polishing pad.

[0072] In step S4, the processed surface of the wafer is planarized using a polishing pad, and the planarization includes rough grinding and fine polishing. In some examples, the processed surface of the wafer is planarized while being intermittently purged with a gas to promote the removal rate of materials such as oxide residues from the processed surface.

[0073] In some examples, the chemical mechanical polishing method can be applied to planarization of an interlayer dielectric layer in a front-end-of-line (FEOL) process and fabrication of a metal interconnect structure, such as a copper interconnect structure or a tungsten contact plug, in a back-end-of-line (BEOL) process.

[0074] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A polishing pad, characterized in that: The polishing pad is disc-shaped as a whole, and includes a polishing surface and a plurality of grooves recessed inward from the polishing surface of the polishing pad. The plurality of grooves are arranged around the center of the disc-shaped polishing pad to divide a plurality of polishing areas. Each polishing area is provided with one or more through holes penetrating laterally for fluid communication between adjacent grooves. The distribution density of the grooves tends to decrease along the radial outward direction of the polishing pad, and the number of the through holes tends to decrease.

2. The polishing pad according to claim 1, characterized in that: N annular grooves are arranged concentrically from the center to the periphery of the polishing pad on the polishing surface to divide the first polishing area, the second polishing area to the N+1th polishing area arranged in an annular nested manner; wherein N is an integer greater than or equal to 2.

3. The polishing pad according to claim 2, characterized in that: The number of through holes opened from the second polishing area to the (N+1)th polishing area around the center of the polishing pad has a tendency to decrease from N to 1, so as to be used for fluid connection between two adjacent annular grooves; wherein, the number of through holes used for fluid connection between the Mth annular groove and the (M+1)th annular groove is (N+1)-M through holes; wherein, M is a natural number greater than 1 and not greater than N.

4. The polishing pad according to claim 2, characterized in that: Through holes extending in a radial direction or in a direction slightly angled to the radial direction are provided from the second polishing zone to the (N+1)th polishing zone around the center of the polishing pad, and the through holes provided in the (M+1)th polishing zone and the through holes provided in the Mth polishing zone have opening directions staggered from each other.

5. The polishing pad according to claim 2, characterized in that: The groove width of the annular groove from the center to the periphery of the polishing layer decreases successively, and the distance between two adjacent annular grooves remains unchanged.

6. The polishing pad according to claim 1, characterized in that: A plurality of C-shaped grooves are arranged radially from the center of the polishing pad on the polishing surface to divide a corresponding number of C-shaped polishing areas, and the C-shaped polishing areas are provided with through holes circumferentially connecting adjacent C-shaped grooves.

7. The polishing pad according to claim 6, characterized in that: The C-shaped groove has a gradually increasing width variation from the center to the periphery of the polishing pad.

8. The polishing pad according to claim 1, characterized in that: The polishing pad includes a hydrophilic polishing layer, and the grooves penetrate through the hydrophilic polishing layer.

9. The polishing pad according to claim 1, characterized in that: Each polishing area is provided with a through hole with a circular cross section, and the radius of the through hole is 0.1 mm-2 mm.

10. A chemical mechanical polishing method, characterized in that: The chemical mechanical polishing method is performed using the polishing pad according to any one of claims 1 to 9.

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