SUBSTRATE POLISHING HEAD FOR OPTICAL ENHANCEMENT ANALYSIS

Description

BACKGROUND

Field

Embodiments of the present disclosure generally relate to a chemical mechanical polishing of substrates, and more particularly to a carrier head with a flexible membrane for chemical mechanical polishing.

Description of the Related Art

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. The exposed surface of the substrate is placed against a rotating polishing pad. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. Some carrier heads include a flexible membrane that provides a mounting surface for the substrate, and a retaining ring to hold the substrate beneath the mounting surface. Pressurization or evacuation of a chamber behind the flexible membrane controls the load on the substrate. A polishing slurry, including at least one chemically-reactive agent, and abrasive particles, if a standard pad is used, is supplied to the surface of the polishing pad.

The effectiveness of a CMP process may be measured by looking through the substrate while the substrate is in an enclosed black box and using a halogen light source to detect anomalies on a surface of the substrate. A reoccurring problem in CMP method is a dark edge ring (DER) found on a surface of a substrate during inspection.

Therefore, there exists a need in the art for an improved methods and apparatus to remove the DER.

SUMMARY

In one embodiment, a polishing head, includes a housing, a perforated plate coupled to the housing, a flexible membrane disposed in the housing, and a retaining ring disposed around the membrane. The perforated plate includes a plurality of apertures disposed through the perforated plate. The plurality of apertures perforate at least 20% of a perforation surface of the perforated plate. The plurality of apertures comprise a first aperture and a second aperture. The flexible membrane and the perforated plate define a chamber. The flexible membrane includes a first surface facing the perforated plate and a second surface opposite the first surface.

In another embodiment, a polishing head, includes a housing, a perforated plate coupled to the housing, a flexible membrane disposed in the housing, and a retaining ring disposed around the membrane. The perforated plate includes a plurality of apertures disposed through the perforated plate. The flexible membrane and the perforated plate define a chamber. The flexible membrane includes a first surface facing the perforated plate and a second surface opposite the first surface. The second surface includes a surface roughness of at least 70 micro-inches (μin) and a co-efficient of dynamic friction between the membrane and a silicon based material of about 1.5 or less.

In another embodiment, a polishing system for semiconductor processing, includes a platen, a pad disposed on the platen, and a polishing head. The polishing head includes a housing, a perforated plate coupled to the housing, a flexible membrane, and a retaining ring disposed around the membrane. The perforated plate includes a plurality of apertures. The flexible membrane is disposed over the plurality of apertures of the perforated plate. The flexible membrane and the perforated plate define a chamber. The flexible membrane includes a first surface facing the perforated plate and a second surface opposite the first surface. The second surface includes a surface roughness of at least 70 μin.

In another embodiment, a polishing membrane for a polishing head, includes an annular flap configured to be coupled to the polishing head, and a surface configured to contact a substrate. The surface comprising a first zone having a roughness greater than 70 micro-inches.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of the disclosure and are therefore not to be considered limiting of its scope, as the disclosure may admit to other equally effective embodiments.

FIG. 1A is a schematic side view of an exemplary polishing station which may be used to practice the methods set forth herein, according to one or more embodiments.

FIG. 1B is a schematic plan view of a portion of a multi-station polishing system which may be used to practice the methods set forth herein, according to one or more embodiments.

FIG. 2 is a schematic side view of one embodiment of a polishing head, according to one or more embodiments.

FIG. 3 is a top view of the perforated plate of FIG. 2, according to one or more embodiments.

FIG. 4 is a top view of a perforated plate, according to one or more embodiments.

FIG. 5 is a top view of a perforated plate, according to one or more embodiments.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

The embodiments described herein provide a polishing head with a membrane and perforated plate that enables a reduction in the presence of a dark edge ring detected during optical analysis. The membrane includes modifications to the surface that contacts a substrate and the perforated plate includes modified aperture arraignments to account for modifications to the membrane surface.

It is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. It is envisioned that some embodiments of the present disclosure may be combined with other embodiments.

One or more embodiments of the present disclosure relate to chemical mechanical polishing (CMP) systems and processes used in the manufacturing of electronic devices. In particular, the apparatus and methods described herein enable enhanced optical and metrological inspection of a substrate by removing a dark edge ring disposed on a face of the substrate after a CMP operation.

FIG. 1A is a schematic side view of a polishing station 100a, according to one or more embodiments, which may be used to practice the methods set forth herein. FIG. 1B is a schematic plan view of a portion of a multi-station polishing system 101 comprising a plurality of polishing stations (100a, 100b, 100c), where each of the polishing stations 100a, 100b, 100c are substantially similar to the polishing station 100a described in FIG. 1A. In FIG. 1B at least some of the components with respect to the polishing station 100a described in FIG. 1A are not shown on the plurality of polishing stations 100a-c in order to reduce visual clutter.

As shown in FIG. 1A, the polishing station 100a includes a platen 102, a first actuator 104 coupled to the platen 102, a polishing pad 106 disposed on the platen 102 and secured thereto, a fluid delivery arm 108 disposed over the polishing pad 106, a polishing head 110 (shown in cross-section), and a pad conditioner assembly 112. Here, the polishing head 110 is suspended from a carriage arm 113 of a carriage assembly 114 (FIG. 1B) so that the polishing head 110 is disposed over the polishing pad 106 and faces there towards. The carriage assembly 114 is rotatable about a carriage axis C to move the polishing head 110, and thus a substrate 122 chucked therein, between a loading station 103 (FIG. 1B) and/or between polishing stations 100a-c of the multi-station polishing system 101. The loading station 103 includes a load cup 150 (shown in phantom) for loading a substrate 122 to the polishing head 110.

During substrate polishing, the first actuator 104 is used to rotate the platen 102 about a platen axis A and the polishing head 110 is disposed above the platen 102 and faces there towards. The polishing head 110 is used to urge a to-be-polished surface of a substrate 122 (shown in phantom), disposed therein, against the polishing surface of the polishing pad 106 while simultaneously rotating about a carrier axis B. Here, the polishing head 110 includes a housing 111, an annular retaining ring 115 coupled to the housing 111, a membrane 117 spanning the inner diameter of the retaining ring 115, and a substrate backing assembly 200 disposed between the housing 111 and the membrane 117. The retaining ring 115 surrounds the substrate 122 and prevents the substrate 122 from slipping from the polishing head 110 during polishing. The membrane 117 is used to apply a downward force to the substrate 122 and for loading (chucking) the substrate 122 into the polishing head 110 during substrate loading operations and/or between substrate polishing stations. For example, during polishing, a pressurized gas is provided to a carrier chamber 119 to exert a downward force on the membrane 117 and thus a downward force on the substrate 122 in contact therewith. Before and after polishing, a vacuum may be applied to the carrier chamber 119 so that the membrane 117 is deflected upwards to create a low pressure pocket between the membrane 117 and the substrate 122, thus vacuum-chucking the substrate 122 into the polishing head 110.

The substrate 122 is urged against the pad 106 in the presence of a polishing fluid provided by the fluid delivery arm 108. Typically, the rotating polishing head 110 oscillates between an inner radius and an outer radius of the platen 102 to, in part, reduce uneven wear of the surface of the polishing pad 106. Here, the polishing head 110 is rotated using a first actuator 124 and is oscillated using a second actuator 126.

Here, the pad conditioner assembly 112 comprises a fixed abrasive conditioning disk 120, e.g., a diamond impregnated disk, which may be urged against the polishing pad 106 to rejuvenate the surface thereof and/or to remove polishing byproducts or other debris therefrom. In other embodiments, the pad conditioner assembly 112 may comprise a brush (not shown).

Here, operation of the multi-station polishing system 101 and/or the individual polishing stations 100a-c thereof is facilitated by a system controller 136 (FIG. 1A). The system controller 136 includes a programmable central processing unit (CPU 140) which is operable with a memory 142 (e.g., non-volatile memory) and support circuits 144. The support circuits 144 are conventionally coupled to the CPU 140 and comprise cache, clock circuits, input/output subsystems, power supplies, and the like, and combinations thereof coupled to the various components of the polishing system 101, to facilitate control of a substrate polishing process. For example, in some embodiments the CPU 140 is one of any form of general purpose computer processor used in an industrial setting, such as a programmable logic controller (PLC), for controlling various polishing system component and sub-processors. The memory 142, coupled to the CPU 140, is non-transitory and is typically one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk drive, hard disk, or any other form of digital storage, local or remote.

Herein, the memory 142 is in the form of a computer-readable storage media containing instructions (e.g., non-volatile memory), that when executed by the CPU 140, facilitates the operation of the polishing system 101. The instructions in the memory 142 are in the form of a program product such as a program that implements the methods of the present disclosure (e.g., middleware application, equipment software application etc.). The program code may conform to any one of a number of different programming languages. In one example, the disclosure may be implemented as a program product stored on computer-readable storage media for use with a computer system. The program(s) of the program product define functions of the embodiments (including the methods described herein).

Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the methods described herein, are embodiments of the present disclosure.

FIG. 2 is a schematic side view of one embodiment of the polishing head 110 that may be used in the polishing system 101 of FIG. 1B.

As seen in FIG. 2, the substrate backing assembly 200 generally includes a gimbal rod 202 extending through the housing 111, a flexure ring 204 pivotally coupled to a distal end of the gimbal rod 202, and a perforated plate 206 coupled to the flexure ring 204. The carrier chamber 119 provides fluid and pressure communication between the gimbal rod 202 and the membrane 117 via a plurality of apertures 208 formed through the perforated plate 206. The perforated plate 206 is coupled to a vacuum channel 210 that creates a vacuum within a chamber 212. The membrane 117 is coupled perforated plate 206, which both partially define the chamber 212. The chamber 212 defines a chamber volume. The chamber volume is about 20 cubic centimeters to about 400 cubic centimeters. For example, the chamber 212 volume is about 20 cubic centimeters or greater.

As the vacuum channel 210 applies a vacuum to the chamber 212, the membrane 117 flexes into the chamber 212 through the plurality of apertures 208. As the membrane 117 flexes, the membrane 117 is able to hold the substrate 122 as the polishing head 110 translates over the pad 106. The retaining ring 115 is disposed around the membrane 117.

The membrane 117 includes a first surface 220, a second surface 222, a thickness between the first surface 220 and the second surface 222, and a durometer. The thickness is about 0.02 inches to about 0.06 inches, for example, about 0.03 inches. In some embodiments, the membrane 117 includes a hardness of about 40 A to about 65 A on the Shore A hardness scale (see ASTM D 2240) for example, about a 45 A to 60 A, for example, about a 60 A to 65 A, a minimum tensile strength of about 6 MegaPascal (Mpa) to about 8 Mpa/1100 PSI (see ASTM D 412-DIE C), a modulus at 50% Elongation of about 0.55 to about 0.76 Mpa/80 psi to about 110 psi (see ASTM D 412-DIE C), a modulus at 100% Elongation of about 0.90 MPA to about 1.20 MPA/131 PSI to about 174 PSI (see ASTM D 412-DIE C), and a minimum tear strength of about 25 Kilo-newton per meter to about 30 Kilo-newton per meter.

The membrane 117 is coupled to the perforated plate 206 by the first surface 220. The second surface 222 is disposed opposite the first surface 220. The second surface 222 includes a surface roughness of at least 70 micro-inches (μin). For example, the surface roughness of the second surface 222 is about 80 μin to about 140 μin. The second surface 222 is configured to be coupled to and restrain the substrate 122. The surface roughness of the second surface 222 is an average measurement across the second surface 222. In some embodiments the surface roughness of the second surface 222 is greater than 80 μin. In some embodiments the surface roughness of the second surface 222 is about 80 μin to about 140 μin.

In some embodiments, the membrane 117 is a silicon polishing membrane for the polishing head 110 and includes an annular flap 224 configured to be coupled to the polishing head 110. In some embodiments, the second surface 222 of the membrane 117 includes a first zone 226 and a second zone 228. In some embodiments, the first zone 226 covers an entirety of the second surface 222 and has a first surface roughness greater than 70 μin. In some embodiments, the first zone 226 is radially inward of the second zone 228 and does not cover the entire the second surface 222 and the second 228 zone has a second surface roughness with a difference of at least 5 micro-inches (μin) from the first surface roughness of the first zone 226.

The surface roughness of the second surface 222 may be calculated in terms of roughness average (Ra). In some embodiments, the surface roughness is the arithmetic average of the absolute values of the profile height deviations from the mean line, recorded within the evaluation length. In some embodiments, the surface roughness is calculated in terms of root mean square (RMS), measuring of peaks and valleys. For example, a surface roughness of about 71 μin Ra is about a 78 μin RMS. Similarly, a surface roughness of about 125 μin Ra is about a 137.5 μin RMS.

In some embodiments, the membrane 117 is manufactured so that a co-efficient of dynamic friction between the membrane 117 and a silicon-carbide surface is about 0.2 to about 1.1, for example, about 1.5 or less. The co-efficient of static friction between the membrane and a silicon based substrate is about 0.2 to about 1.1, for example, about 1.5 or less. In some embodiments, the membrane 117 is manufactured so that a co-efficient of dynamic friction between the membrane 117 and a silicon based material is about 0.2 to about 1.1, for example, about 1.5 or less. In some embodiments, the membrane 117 is manufactured so that a co-efficient of dynamic friction between the membrane 117 and a carbon face of the substrate 122 is about 0.2 to about 1.1, for example, about 1.5 or less.

In some embodiments, the membrane 117 is configured to allow the substrate 122 to translate during a polishing operation. For example, when the second surface 222 of the membrane 117 is less than 50 μin the substrate 122 is restrained from translating during a polishing operation. Without being bound by theory, the inventors believe that by incorporating the second surface 222 of the membrane 117 with an increased surface roughness, the dark edge ring can be reduced by the movement of the substrate 122 across the second surface 222.

FIG. 3 is a top view of the perforated plate 206 of FIG. 2, according to one or more embodiments. The perforated plate 206 includes a plurality of apertures, an inner wall surface 305, an outer wall surface 307, and a perforation surface 309. The plurality of apertures include a major aperture 301, a plurality of minor apertures 303. While the major aperture 301 and the plurality of minor apertures 303 are shown as 22 apertures, the major aperture 301 and the plurality of minor apertures 303 may be 12 or more apertures. The major aperture 301 is disposed coincident with a central axis B of the housing 111 (FIG. 2). The major aperture 301 includes a diameter D1 of about 1.2 inches to about 0.75 inches. For example, the diameter D1 of the major aperture 301 is at least 0.9 inches or larger.

The plurality of minor apertures 303 each include a diameter D2. In some embodiments, the diameter D2 of each of the plurality of minor apertures 303 is about 0.2 inches to about 1.5 inches, for example, about 0.25 inches to about 1 inch. The plurality of minor apertures 303 are radially disposed around the major aperture 301. The diameter D1 of the major aperture 301 is larger than the diameter D2 of each of the plurality of minor apertures 303. In some embodiments, the diameter D2 of each of the plurality of minor apertures 303 is less than 80% of the diameter D1 of the major aperture 301.

In some embodiments, the plurality of minor apertures 303 may be slots, slits, or other aperture shapes. In some embodiments, the perforated plate 206 includes a plate area of the perforation surface 309. The major aperture 301 and the plurality of minor apertures 303 form an aperture area of the perforation surface 309. The aperture area is a percentage of the surface area of the perforation surface 309 where the major aperture 301 and the plurality of minor apertures 303 form through holes through the perforation surface 309. In some embodiments, the aperture area is 33% or less of the plate area. In other words, the major aperture 301 and the plurality of minor apertures 303 form apertures through 33% or less of the total surface of the perforation surface 309.

In some embodiments, the plurality of minor apertures 303 include a plurality of first minor apertures 311 and a plurality of second minor apertures 313 disposed radially outward of the plurality of first minor apertures 311. The plurality of minor apertures 303 includes a ratio of the first minor apertures 311 to the second minor apertures 313 of 4:7 or less. For example, when there are 4 first minor apertures 311, there are 7 second minor apertures 313. In some embodiments, the ratio of the first minor apertures 311 to the second minor apertures 313 is a 1:1 ratio. The first minor apertures 311 have the diameter D2 and the second minor apertures 313 have a diameter D6. The diameter D6 of each of the second minor apertures 313 is about 0.5 inches to about 1 inch. In some embodiments, the diameter D2 of each of the first minor apertures 311 is at least 10% less than the diameter D6 of each of the second minor apertures 313.

In some embodiments, the plurality of apertures 301, 303 are less than 40 apertures. By having less than 40 apertures, the diameters of the plurality of apertures 301, 303 must be large enough for the aperture area to be 33% or less of the plate area.

The inner wall surface 305 defines the volume of the chamber 212 (FIG. 2). The inner wall surface 305 includes a diameter D3 of about 6 inches to about 6.3 inches. The outer wall surface 307 includes a diameter D4 of about 6.4 inches to about 6.7 inches. The perforated plate 206 includes an outer edge 319 that defines an outer diameter D5 of about 6.9 inches to about 7.5 inches. In some embodiments, the outer diameter D5 is about 10 inches or less. In some embodiments, the major aperture 301 and the plurality of minor apertures 303 are disposed through about 18% to about 27% of the area of the perforation surface 309 of the perforated plate 206. In some embodiments, the plurality of apertures perforating at least 20% of the perforated plate, for example, perforating about 20% to about 50% of the perforated plate.

The perforated plate 206 also includes a sensor aperture 321. The sensor aperture 321 is configured to allow optical sensing of the membrane 117 (FIG. 2) during a polishing operation. In some embodiments, the plurality of apertures 303 are disposed through about 40% to about 45% of the area of the perforation surface 309 of the perforated plate 406.

By having a larger diameter D1, the perforated plate 206 is able to retain a substrate using a high suction force in the center, thereby reducing potential damage to the substrate when a vacuum is applied to the chamber 212.

FIG. 4 is a top view of a perforated plate 406, according to one or more embodiments. The perforated plate 406 may be the perforated plate 206 (FIG. 2).

The perforated plate 406 includes a plurality of apertures 403 disposed in an annular pattern. The plurality of apertures 403 include a first set of apertures 421, and second set of apertures 423, and a third set of apertures 425. While shown as 37 apertures, the number of apertures of the plurality of apertures 403 may be 12 or more apertures. Each aperture of the plurality of apertures 403 includes a diameter D7 of about 0.4 inches to about 0.6 inches.

The first set of apertures 421 is disposed at a radius R1. Radius R1 is between about 0.85 inches and about 1.05 inches. The second set of apertures 423 is disposed at a radius R2. Radius R2 is between about 1.7 inches and about 1.9 inches.

The third set of apertures 425 is disposed at a radius R4. Radius R4 is between about 2.6 inches and about 2.8 inches. The perforated plate 406 also includes a sensor aperture 427. The sensor aperture 427 is configured to allow optical sensing of the membrane 117 (FIG. 2). In some embodiments, the plurality of apertures 403 are disposed through about 40% to about 45% of the area of the perforation surface 309 of the perforated plate 406.

In some embodiments, the perforated plate 406 also includes a sensor aperture 427. The sensor aperture 427 is configured to allow optical sensing of the membrane 117 (FIG. 2) during a polishing operation.

In some embodiments, by having a consistent diameter D7 and over 40% perforated area of the total area of the perforation surface 309, the perforated plate 406 is able to retain a substrate using a consistent suction force over the perforation surface 309, thereby reducing potential damage to the substrate when a vacuum is applied to the chamber 212.

In some embodiments, the plurality of apertures 403 are less than 40 apertures. By having less than 40 apertures, the diameters of the plurality of apertures 403 must be large enough so that over 40% of the total area is the perforated area of the perforation surface 309.

FIG. 5 is a top view of a perforated plate 506, according to one or more embodiments. The perforated plate 506 may be the perforated plate 206 (FIG. 2).

The perforated plate 506 includes a plurality of apertures 503 disposed in an annular pattern. The plurality of apertures 503 includes a first aperture 521, a first array of apertures 523, and a second aperture 525. While shown as 12 apertures, the number of apertures of the plurality of apertures 403 may be at least 12 or more apertures. The first aperture 521 is disposed in the center of the perforated plate 506. Each aperture of the first array of apertures 523 includes a diameter D8. In some embodiments, the diameter D8 is about 0.9 inches to about 1.1 inches. In some embodiments, the first aperture 521 has a larger diameter than the diameter D8 of each aperture of the first array of apertures 523. For example, the diameter of the first aperture 521 is at least 10% larger than the diameter of each aperture of the first array of apertures 523. In some embodiments, the diameter D8 of each of the each aperture of the first array of apertures 523 is about 0.8 inches to about 1.2 inches. For example, the diameter D8 is at least 0.9 inches or larger.

The perforated plate 506 also includes a sensor aperture 511. The sensor aperture 511 is configured to allow optical sensing of the membrane 117 (FIG. 2). The sensor aperture 511 is disposed opposite from the second aperture 525. For example, the first aperture 521 and the first array of apertures 523 are disposed between the sensor aperture 511 and the second aperture 525. The sensor aperture 509 has a diameter of 60% or less than the diameter D8 of the plurality of apertures 503. For example, the sensor aperture 511 has a diameter about 0.4 inches to about 0.6 inches. In some embodiments, the plurality of apertures 503 are disposed through about 35% to about 40% of the area of the perforation surface 309 of the perforated plate 506.

In some embodiments, by having a diameter D8 being at least 0.9 inches or larger and the plurality of apertures 503 being over 35% forming a perforated area of the total area of the perforation surface 309, the perforated plate 506 is able to retain a substrate using a consistent suction force over the perforation surface 309 what a membrane has a surface roughness of 70 micro-inches (μin), or more. The characteristics described above reduce the potential damage to the substrate when a vacuum is applied to the chamber 212.

In some embodiments, the plurality of apertures 503 are less than 40 apertures. By having less than 40 apertures, the diameters of the plurality of apertures 503 must be large enough so that over 35% of the total area is the perforated area of the perforation surface 309.

By changing the surface properties of the membrane 117, such as increasing the surface roughness, an increase in the vacuum strength to chuck the substrate 122 is needed. To accommodate the increase, the apertures in the perforated plate 206, 406, 506 are arranged to account for the change in surface properties. Such a change in the surface properties allows the polishing head to retain the substrate 122 during translation and prevents the formation of a dark edge ring during a substrate polishing operation.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.