TWI519384B - Grooved cmp polishing pad - Google Patents

Description

Grooved chemical mechanical polishing (CMP) polishing pad

The present invention relates generally to chemical mechanical polishing of substrates, and more particularly to a polishing pad having a grooved pattern for use in a chemical mechanical polishing system.

Compositions and methods for chemical mechanical polishing of the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries, CMP slurries, and CMP compositions) for the surface of chemical mechanical polishing (CMP) semiconductor substrates (e.g., integrated circuits) typically contain an abrasive, various additive compounds, and the like.

Chemical-mechanical polishing (CMP) involves simultaneous chemical and mechanical wear of a surface, such as a first layer of wear overlying, to expose a non-planar second layer surface on which the first layer is formed. One such method is described in U.S. Patent No. 4,789,648 (Beyer et al.). Briefly, Beyer et al. disclose the use of a polishing pad and a slurry to remove the first layer at a faster rate than the second layer until the surface of the overlying first layer of the material becomes the second layer of coverage. The upper surface coplanar CMP method. A more detailed explanation of the chemical mechanical polishing is found in U.S. Patent Nos. 4,671,851, 4,910,155 and 4,944,836.

In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and placed in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controlled pressure to the substrate, forcing the substrate against the polishing pad. The mat and the carrier and the substrate to which it is attached move relative to each other. The relative movement of the pad to the substrate is used to abrade the surface of the substrate to remove a portion of the material from the surface of the substrate, thereby polishing the substrate. Generally, the chemical activity of the polishing composition (for example, by an oxidizing agent, an acid, a base, or other additives present in the CMP composition) and/or the mechanical activity of the abrasive suspended in the polishing composition The substrate surface is further polished. Typical abrasive materials include ceria, yttria, alumina, zirconia, and tin oxide.

One problem in CMP is that the polishing slurry is distributed throughout the polishing pad. The CMP method requires interaction of the polishing pad, abrasive particles, and any reactants or chemicals in the polishing composition with the substrate to achieve the desired polishing results. The ineffective distribution of the slurry throughout the surface of the polishing pad may result in a reduction in polishing efficiency. Polishing pads typically include features such as apertures or textures (e.g., grooves, surface depressions, etc.) to help distribute the abrasive polishing slurry throughout the pad relatively evenly. The grooves are often a preferred textural feature because they can be designed to directly direct excess slurry to where it is needed. Grooved polishing pads are often characterized by the dimensions (e.g., width and depth) of the grooves and the spacing between the grooves (referred to as "pitch"). Examples of grooved mats include those disclosed in U.S. Patent No. 5,921,855 (Osterheld et al.), U.S. Patent No. 6,520,847 (Osterheld et al.), and U.S. Patent No. 6,736,847 (James et al.).

While conventional trench CMP pads have certain superior performance characteristics over, for example, porous pads, the related art still requires improved pad performance characteristics, such as improved pad life (e.g., due to reduced wear rate). The present invention addresses this need.

The present invention provides a polishing pad for use in a chemical mechanical polishing (CMP) process. In one embodiment, a pad includes a surface defining a plurality of grooves, the overlapping surfaces separating the grooves, the overlapping surfaces together defining a substantially planar polished surface, each groove having a depth of at least 10 mils And the width W _G , the overlapping surface separating any two adjacent grooves from each other having a width W _L , wherein the quotient of W _L /W _G is less than or equal to 3. In a preferred embodiment, the surface of the pad defines a series of concentric, substantially circular grooves. Preferably, each trench has the same W _G and each lap surface has the same W _L .

In another embodiment, the surface of the pad defines a helical groove having a depth of at least 10 mils and a width W _G having a helical lap surface depicting the helical groove profile. Width coefficient W _L of the spiral lap surface, and defining a substantially polishing surface plane. As in the above embodiment, the quotient of W _L /W _G is less than or equal to 3.

The polishing surface of the polishing pad of the present invention can be formed from any material suitable for use in a CMP pad. In a preferred embodiment, the polishing surface of the mat is formed from a thermoplastic polyurethane material. The mats may be constructed from a single layer or multiple layers of mat material (e.g., a substrate layer and a surface layer).

The polishing pad of the present invention provides polishing removal rate uniformity over extended use (e.g., polishing up to 650 semiconductor wafers) as compared to conventional grooved pads of similar construction but W _L /W _G equal to 7. Expected improvement.

In one embodiment, the polishing pad of the present invention includes a surface defining a plurality of grooves, preferably concentric and substantially circular grooves, separating the grooves by overlapping surfaces. Each trench has a depth of at least 10 mils and a width W _G , and the lap surface separating any two adjacent trenches from each other has a width W _L , wherein the quotient of W _L /W _G is less than or equal to three. Preferably, the plurality of trenches each have the same depth, and/or substantially the same W _G . Such landing surface is also preferably each have substantially the same W _L. Although the bottom of the trench can be rounded, resulting in a reduced width near the bottom of the trench, the width of each trench is preferably substantially uniform throughout the depth of the trench.

Figure 1 illustrates a top plan view of a polishing pad of the present invention. Pad 10 includes a surface layer 12 that defines concentric circular grooves 14 separated by lap surfaces 16, which form a frame for the pad surface. The lap surfaces 16 are substantially coplanar with one another, such as the peripheral surface 18 and the central surface 20. In general, the lap surface 16 defines a substantially coplanar polished surface.

Figure 2 shows a partial cross-sectional view of the surface 12 of Figure 1 along plane 2-2. The surface layer 12 is attached to the substrate layer 22. Groove 14 has a depth D _G, and a width W _G, and the landing surface 16 has a width W _L. The distance from the beginning of a trench to the beginning of the next trench is defined as the pitch P, which is equal to the sum of W _L and W _G . In the pad of the present invention, the W _L /W _G system is less than or equal to 3. The lap surface 16 is substantially coplanar, thereby forming a coplanar polishing surface for contacting the surface of the substrate to be polished, while the trench 14 provides a reservoir for polishing the polishing slurry and assisting the surface of the entire pad 10 The polishing slurry is directed and dispensed.

In another embodiment, the polishing pad of the present invention includes a surface defining a helical groove having a depth of at least 10 mils having a spiral lap surface depicting the contour of the spiral groove. The spiral lap surface defines a substantially planar polished surface. The trench has a width W _G and the lap surface has a width W _L , wherein the quotient of W _L /W _G is less than or equal to 3. Figure 3 provides a top plan view of this alternative embodiment. Pad 30 includes a substantially planar surface layer 32 in which a single helical groove 34 is formed which is contoured by a nested spiral lap surface 36. This spacing P equal to the sum of the widths of the grooves 34 and the overlapping surfaces 36 is also shown in FIG.

In each embodiment of the invention, each of the grooves in the surface of the polishing pad preferably has a depth of no more than 50 mils. In certain preferred embodiments, the depth of each groove is in the range of 10 to 50 mils, more preferably 15 to 40 mils.

If desired, the present invention in any given embodiment of the polishing pad of the embodiment, commercially W _L / W _G's may be less than or equal to 2, or less than or equal to 1.

In certain preferred embodiments, the W _L of each lap surface does not exceed 80 mils. In other preferred embodiments, the W _L of each lap surface is in the range of 30 to 60 mils. Each line trenches W _G preferably no more than 50 mil. In certain preferred embodiments, the W _G of each trench is in the range of 20 to 40 mils.

Table 1 illustrates certain specific examples of different trench sizes suitable for the polishing pad of the present invention.

The polishing pad of the present invention is particularly suitable for use with chemical-mechanical polishing equipment. Typically, the CMP apparatus includes a platen that moves during use and has a velocity due to orbital, linear, and/or circular motion, a polishing pad that is in contact with the platen and that is opposite the platen when moved Moving), and a carrier (which fixes a substrate that is polished by contact and movement relative to the surface of the polishing pad). Polishing of the substrate occurs by placing the substrate in contact with the polishing pad of the present invention and then moving the polishing pad relative to the substrate, thereby abrading at least a portion of the substrate to polish the substrate.

Suitable materials for forming at least a portion of the polishing pad of the present invention include, for example, polymers of various densities, hardnesses, thicknesses, compressibility, rebound resilience upon compression, and compression modulus. Non-limiting examples of such polymers include polyvinyl chloride, polyvinyl fluoride, nylon, fluorocarbon, polycarbonate, polyester, polyacrylate, polyether, polyethylene, polyamine, polyamine Acid esters, polystyrene, polypropylene, co-formed products thereof, and mixtures thereof. The surface of the polishing pad defining the plurality of grooves may comprise any such material. In a preferred embodiment, the surface defining the plurality of grooves or spiral grooves comprises a thermoplastic polyurethane. If desired, the mat of the present invention may be comprised of a single layer of material or may comprise two or more layers of material, such as a substrate layer and a surface layer.

Desirably, the CMP pad of the present invention may additionally include at least one light or other radiation-transmission window region for detecting and monitoring the polishing process in situ by analyzing light or other radiation reflected from the surface of the workpiece polished using the pad. A number of in-situ polishing endpoint detection systems and techniques are known in the art for in situ inspection and monitoring of polishing processes by analyzing light or other radiation reflected from the surface of the workpiece. Such methods are described, for example, in U.S. Patent No. 5,196,353 (Sandhu et al.), U.S. Patent No. 5,433,651 (Lustig et al.), U.S. Patent No. 5,949,927 (Tang), and U.S. Patent No. 5,964,643 (Birang et al. ). Ideally, the polishing endpoint can be determined based on the progress of the polishing workpiece to detect or monitor the polishing process, and it can be determined when the polishing process is terminated for a particular workpiece.

The following examples further illustrate the invention, but are not intended to limit its scope in any way.

Example 1

This example illustrates the superior removal rate stability and removal uniformity stability that can be achieved with the polishing pad of the present invention in copper CMP.

A polishing surface comprising a layer of a thermoplastic polyurethane pad comprising a width W _G are each a series of concentric circular grooves of 30 mil, 30 mil concentrically overlapping surfaces of separated (by the width W _L of the pitch is 60 mil ), and W _L /W _G is equal to 1. The same polishing pad was used on a copper-covered wafer using a commercially available polishing slurry (Cabot Microelectronics Corporation, Aurora, IL), and the polishing was repeated on a Mirra polisher under the following polishing conditions: a downward pressure of 1 psi (square inch). Psi), platen speed 93 revolutions per minute (rpm), carrier speed 87 rpm, and slurry feed rate 100 ml/min (mL/min). For comparison, concentric annular trenches separated by concentric annular lap surfaces were also used under the same conditions, but W _L was 70 mils and W _G was 10 mils (80 mils pitch), and W _L /W _G is a 7 similar polyurethane polishing pad polished copper covered wafer.

4 illustrates the change in copper removal rate for each pad relative to the number of wafers being polished, which shows the removal rates obtained at wafer 150 and wafer 650. Apparent from FIG. 4, with W _L / W _G is larger than the conventional pads 7 show Cu removal rate decreases, while having a W _L / W _G of the pad 1 of the present invention show unexpectedly Cu removal rate increases.

Figure 5 shows the percent removal stability observed for the same wafer (defined as WIWNU) or the non-uniformity of the wafer obtained with each pad (ie, the entire wafer except for the 5 mm edge) Relative standard deviation of Cu removal from point diameter scan). As can be seen in Figure 5, the pads of the present invention exhibit undesirably consistent removal uniformity stability as compared to conventional pads.

Example 2

This example illustrates the effect of the groove configuration on the wear rate of the pad.

Three polishing pads of the present invention comprising a thermoplastic polyurethane surface layer comprising a series of concentric circular grooves were used for the relative pad wear test. The test was performed on an IPEC polisher with a 7 ft-1b downforce, a 105 rpm platen speed, and a 100 rpm adjuster rotation speed. The regulator was purchased from 3M Company (Model A188). Deionized water was used and the test lasted for 40 minutes. The wear rate was calculated using data from the 10th minute to the 40th minute and normalized to mil/hour by multiplying by 2. The pads have the following dimensions: pad 60/20-W _G = 20 mil, W _L = 40 mil, pitch = 60 mil, W _L /W _G = 2; pad 60/30-W _G = 30 mil, W _L = 30 mil, pitch = 60 mil, W _L / W _G =1; and pad 40/20-W _G = 20 mil, W _L = 20 mil, pitch = 40 mil, W _L / W _G =1. For comparison, a similar polyurethane polishing pad was tested having concentric annular grooves separated by concentric annular lap surfaces with a W _L of 70 mils and a W _G of 10 mils (with a spacing of 80 mils). ), where W _L /W _G is 7 (pad 80/10).

Figure 6 provides a graphical representation of the pad wear rate in mil/hour for each pad tested. As shown in the data in Figure 6, for a given groove width (eg, 20 mil), as W _L /W _G drops from 2 to 1 (with pads 60/20 and 40/20, respectively), the pad The wear rate increases. In addition, for a given pitch (e.g., 60 mil), the wear rate increases as the groove width increases from 20 to 30 mils (pads 60/20 and 60/30, respectively).

Preferred embodiments of the invention have been described herein, including the best mode known to the inventors to carry out the invention. Variations of these preferred embodiments may become apparent upon reading the above description. The inventors intend for the skilled artisan to use such variations as appropriate, and the inventors intend to practice the invention other than as specifically described herein. Accordingly, the present invention includes modifications and equivalents of the subject matter recited in the appended claims. In addition, the present invention encompasses any combination of the above-described elements in all possible variations thereof, unless otherwise stated herein or otherwise clearly contradicted by the context.

10. . . Polishing pad

12. . . Surface layer

14. . . Concentric circular groove

16. . . Lap surface

18. . . Peripheral surface

20. . . Center surface

twenty two. . . Matrix layer

30. . . Polishing pad

32. . . Planar surface layer

34. . . Single spiral groove

36. . . Spiral lap surface

Figure 1 illustrates a top plan view of an embodiment of a polishing pad of the present invention comprising a plurality of circular concentric grooves;

Figure 2 provides a partial cross-sectional view of the pad of Figure 1;

Figure 3 illustrates an embodiment of a polishing pad of the present invention comprising a single spiral groove in a polishing surface;

Figure 4 is a graphical representation of the copper removal rate versus the number of wafers polished compared to conventional reference pads of the present invention;

Figure 5 is a graphical representation of the copper removal rate uniformity versus the number of wafers polished compared to conventional reference pads of the present invention;

Figure 6 shows a graphical representation of pad wear rates for a pad of the present invention as compared to conventional reference pads.

10. . . Polishing pad

12. . . Surface layer

14. . . Concentric circular groove

16. . . Lap surface

18. . . Peripheral surface

20. . . Center surface

Claims (7)

A polishing pad suitable for chemical-mechanical polishing of a substrate, the pad comprising a surface defining a plurality of grooves, the overlapping surfaces separating the grooves, the overlapping surfaces together defining a substantially coplanar polished surface, Each groove has a depth of at least 10 mils and a width W _G , wherein each groove has a W _G in the range of 20 to 40 mils, and any two adjacent grooves are separated by a lap surface, and the lap surface has a width W _L wherein the supplier W _L / W _G is less than or equal to the system 1, wherein the surface of each of the overlapping lines W _L in the range of 30 to 60mil, wherein each groove has substantially the same depth. A polishing pad according to claim 1, wherein the plurality of grooves comprise concentric, substantially circular grooves. A polishing pad according to claim 1, wherein the depth of each of the grooves is in the range of 10 to 50 mils. A polishing pad according to claim 1, wherein each of the grooves has substantially the same W _G . A polishing pad according to claim 1, wherein each of the overlapping surfaces has substantially the same W _L . A polishing pad suitable for chemical mechanical polishing of a substrate, the pad comprising a surface defining a spiral groove having a spiral splicing surface separating the spiral groove, the spiral lap surface defining a substantially coplanar polished surface The trench has a depth of at least 10 mils and a width W _G , wherein the W _G of each trench is in the range of 20 to 40 mils, and the lap surface has a width W _L , wherein the quotient of W _L /W _G is less than or Equal to 1, wherein the W _L of each lap surface is in the range of 30 to 60 mils, wherein each trench has substantially the same depth. A polishing pad according to claim 6, wherein the depth of the groove is in the range of 10 to 50 mils.