BACKGROUND

Field

[0001] Embodiments of the present disclosure generally relate to semiconductor device manufacturing, and more particularly, to chemical mechanical polishing (CMP) systems used in semiconductor device manufacturing and substrate processing methods related thereto.

Description of the Related Art

[0002] Chemical mechanical polishing (CMP) is commonly used in the manufacturing of high-density integrated circuits to planarize or polish a layer of material deposited on a substrate. One common application of a CMP process in semiconductor device manufacturing is planarization of a bulk film, for example pre-metal dielectric (PMD) or interlayer dielectric (ILD) polishing, where underlying two or three-dimensional features create recesses and protrusions in the surface of the to be planarized material surface. Other common applications include shallow trench isolation (STI) and interlayer metal interconnect formation, where the CMP process is used to remove via, contact or trench fill material (overburden) from the exposed surface (field) of the layer of material having the STI or metal interconnect features disposed therein.

[0003] In a typical CMP process, a polishing pad is mounted to a rotatable polishing platen. A material surface of a substrate is urged against the polishing pad in the presence of a polishing fluid. Typically, the polishing fluid is an aqueous solution of one or more chemically active components and abrasive particles suspended in the aqueous solution, e.g., a CMP slurry. The material surface of the substrate is urged against the polishing pad using a substrate carrier. A typical substrate carrier includes a membrane, bladder, or a backing plate disposed against a backside surface of the substrate and an annular retaining ring circumscribing the substrate. The membrane, bladder, or backing plate is used to apply a downforce against the substrate while the substrate carrier rotates about a carrier axis. The retaining ring surrounds the substrate as the substrate is urged against the polishing pad and is used to prevent the substrate from slipping from the substrate carrier. Material is removed across the surface of the substrate in contact with the polishing pad through a combination of chemical and mechanical activity which is provided by the polishing fluid, the relative motion of the substrate and the polishing pad, and the downforce exerted on the substrate against the polishing pad.

[0004] Generally, CMP process performance is characterized with reference to a material removal rate from the surface of the substrate and the uniformity of the material removal rate (removal rate uniformity) across the surface of the substrate. In a dielectric bulk film planarization process, non-uniform material removal rate across the surface of the substrate can lead to poor planarity and/or undesirable thickness variation of the dielectric material remaining post CMP. In a metal interconnect CMP application, metal loss resulting from poor local planarization and/or non-uniform material removal rate can cause undesirable variation in the effective resistance of the metal features, thus affecting device performance and reliability. Thus, non-uniform material removal rate across the surface of a substrate can adversely affect device performance and/or cause device failure which results in suppressed yield of usable devices formed on the substrate.

[0005] Non-uniformities in the profile of a polishing pad may affect removal rates across the surface of substrates as the substrates pass over the non uniformities. If these non-uniformities are not accounted for, the polishing of each of the substrates may be non-uniform and adversely affect device performance. Current methods of accounting for polishing pad non-uniformities are destructive to the polishing pad or involve modeling of polishing pad wear. Current non-destructive methods and apparatus for measuring the polishing pad profile have poor resolution and accuracy.

[0006] Accordingly, what is need in the art are solutions to the problems described above. SUMMARY

[0007] Embodiments herein generally relate to chemical mechanical polishing (CMP) systems and methods for improving polishing pad conditioning operations.

[0008] In one embodiment, a pad conditioning assembly for a chemical mechanical polishing (CMP) apparatus is described. The pad conditioning assembly includes a conditioning disk, a first actuator coupled to the conditioning disk, a second actuator disposed radially outward of the conditioning disk, a conditioner arm coupling the first actuator and the second actuator, an arm displacement sensor coupled to the conditioner arm, and one or more conditioning disk displacement sensors coupled to the first actuator.

[0009] In another embodiment, an apparatus for substrate processing is described. The apparatus for substrate processing includes a polishing platen, a substrate carrier, and a pad conditioning assembly. The pad conditioning assembly includes a conditioning disk, a first actuator coupled to the conditioning disk, a second actuator disposed radially outward of the conditioning disk, a conditioner arm coupling the first actuator and the second actuator, an arm displacement sensor coupled to a bottom conditioner arm surface of the conditioner arm, and one or more conditioning disk displacement sensors disposed on a bottom actuator surface of the first actuator. The arm displacement sensor is configured to measure a first distance between the arm displacement sensor and a top surface of the polishing platen. The one or more conditioning disk displacement sensors are configured to measure a second distance between each of the conditioning disk displacement sensors and a portion of the conditioning disk.

[0010] In yet another embodiment, a method of substrate processing is described. The method of substrate processing includes urging a conditioning disk against a surface of a polishing pad and measuring a distance between a conditioning arm and a polishing platen disposed beneath the polishing pad. The conditioning arm is coupled to the conditioning disk via a first actuator. An orientation of the conditioning disk is determined using one or more conditioning disk displacement sensors. A thickness profile of the polishing pad is determined from the orientation of the conditioning disk. One or more conditioning parameters are changed after determining the thickness profile.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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 and are therefore not to be considered limiting of its scope, as the disclosure may admit to other equally effective embodiments.

[0012] Figure 1A is a schematic plan view of a polishing system, according to embodiments described herein.

[0013] Figure 1 B is a schematic cross-sectional view of the polishing system of Figure 1A, according to embodiments described herein.

[0014] Figure 2 is a schematic cross-sectional view of a portion of the polishing system of Figure 1A, according to embodiments described herein.

[0015] Figure 3 is a schematic cross-sectional view of a portion of the polishing system of Figure 1A with a conditioning disk in multiple locations, according to embodiments described herein.

[0016] Figures 4A-4C are schematic plan views of conditioning disks with different configurations of conditioning disk displacement sensors, according to embodiments described herein.

[0017] Figure 5 is a flow diagram of a method of forming a polishing pad thickness profile, according to embodiments described herein.

[0018] 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

[0019] The present disclosure is generally directed towards apparatus and methods used within CMP systems. The apparatus and methods described herein are more specifically directed towards the measurement of polishing pad profiles within a single polishing module. The apparatus includes an arm displacement sensor coupled to a conditioner arm of a pad conditioning assembly as well as one or more additional conditioning disk displacement sensors positioned to measure the displacement of a portion of the conditioning disk of the pad conditioning assembly. The arm displacement sensor is configured to measure the distance between the conditioner arm and the upper surface of the polishing platen. The one or more conditioning disk displacement sensors enable the measurement of the orientation of the conditioning disk as the conditioning disk is swept across a top surface of a polishing pad.

[0020] The combination of the arm displacement sensor and the conditioning disk displacement sensors enables a thickness profile of the polishing pad to be determined. The thickness profile may be continuously updated as the conditioning disk is swept across the surface of the polishing pad. The thickness profile enables the detection of grooves or divots within the top surface of the polishing pad. The use of a single arm displacement sensor may provide global estimates of the thickness profile of the polishing pad, but by adding conditioning disk displacement sensors, the accuracy and resolution of the polishing pad thickness measurements are improved.

[0021] Figure 1A is a schematic plan view of a polishing system, according to one embodiment, which is configured to practice the methods set forth herein. Figure 1 B is a schematic cross-sectional side view of the polishing system of Figure 1 A. Flere, the polishing system 100 includes a polishing platen 102, a substrate carrier 104, a fluid delivery arm 106, a pad conditioner assembly 108, and a system controller 110. The polishing platen 102 features cylindrical platen body 114 and a low-adhesion-material layer 116 disposed on a surface of the platen body 114 to provide a polishing pad-mounting surface 118. The platen body 114 is typically formed of a suitably rigid, light weight, and polishing fluid corrosion resistant material, such as aluminum, an aluminum alloy (e.g., 6061 Aluminum), or stainless steel. The low-adhesion-material layer 116 typically comprises a polymer material formed of one or more fluorine- containing polymer precursors or melt-processable fluoropolymers. The low- adhesion-material layer 116 desirably reduces the amount of force required to remove a polishing pad 112 from the polishing pad-mounting surface 118 once the polishing pad 112 has reached the end of its useful lifetime and further protects the metal of the platen body 114 from undesirable polishing fluid caused corrosion.

[0022] Here, the pad-mounting surface 118 comprises a plurality of concentric zones 120a-c formed about a platen axis A. The plurality of concentric zones 120a-c include a circular (when viewed from top down) or annular first zone 120a, an annular second zone 120b circumscribing the first zone 120a, and an annular third zone 120c disposed radially outward from and circumscribing the second zone 120b. The pad-mounting surface 118 is split into sections, such a first pad-mounting surface 118a, a second pad-mounting surface 118b, and a third pad-mounting surface 118c correspond to each of the annular first zone 120a, the annular second zone 120b, and the annular third zone 120c respectively.

[0023] Here, the second pad-mounting surface 118b in the second zone 120b is recessed from a plane P a distance Zi. The plane P is defined by the pad-mounting surfaces 118a, c in the first and third zones 120a, c which in some embodiments, and as shown in Figure 1 B, are substantially co-planer with one another. In some embodiments, e.g., where the pad-mounting surfaces 118a,c in the first and third zones 120a,c are not co-planer with one another, the plane P may be defined by an object having a planer surface laid over and in contact with the first and third zones 120a,c to span the recessed second zone 120b. [0024] In Figure 1B, the second pad-mounting surface 118b in the second zone 120b is substantially planer and is parallel to a plane formed by the surfaces of the first and third zones 120a,c. Thus, the distance Zi is substantially constant across a width W of the recessed pad-mounting surface 118b in the second zone 120b. In other embodiments, the recessed surface in the second zone 120b is not parallel to the plane formed by the pad-mounting surfaces of the first and third zones 120a,c and/or is not substantially planer across the width W thereof.

[0025] Typically, the polishing pad 112 is formed of one or more layers of polymer materials and is secured to the pad-mounting surfaces 118a-c using a pressure sensitive adhesive. The polymer materials used to form the polishing pad 112 may be relatively compliant or may be rigid and formed with channels or grooves in the polishing surface thereof to allow the polishing pad 112 to conform to the recessed pad-mounting surface 118b in the second zone 120b and the pad-mounting surfaces 118a,c of the first and third zones 120a,c adjacent thereto. Thus, the polishing surface of the polishing pad 112 in each of the zones 120a-c has substantially the same shape and relative dimensions as described above for the pad-mounting surface 118 of the platen 102.

[0026] Here, the rotating substrate carrier 104 is used to exert a downforce against a substrate 113 to urge a material surface of the substrate 113 against the polishing pad 112 as the polishing pad 112 is rotated about the platen axis A. As shown, the substrate carrier 104 features a flexible membrane 124 and an annular retaining ring 126. During substrate polishing, the flexible membrane 124 exerts a downforce against a non-active (backside) surface of the substrate 113 disposed therebeneath. The retaining ring 126 surrounds the substrate 113 to prevent the substrate 113 from slipping from the substrate carrier 104 as the polishing pad 112 moves therebeneath. Typically, the substrate carrier 104 is configured to exert a downforce against the retaining ring 126 that is independent from the downforce exerted against the substrate 113. In some embodiments, the substrate carrier 104 oscillates in the radial direction of the polishing platen to, in part, reduce uneven wear of the polishing pad 112 disposed there beneath. [0027] Typically, the substrate 113 is urged against the polishing pad 112 in the presence of the one or more polishing fluids delivered by the fluid delivery arm 106. A typical polishing fluid comprises a slurry formed of an aqueous solution having abrasive particles suspended therein. Often, the polishing fluid contains one or more chemically active constituents which are used to modify the material surface of the substrate 113 thus enabling chemical mechanical polishing thereof.

[0028] The pad conditioner assembly 108 is used to condition the polishing pad 112 by urging a conditioning disk 128 against the surface of the polishing pad 112 before, after, or during polishing of the substrate 113. As shown in Figure 2, the pad conditioner assembly 108 includes the conditioning disk 128, a first actuator 130 for rotating the conditioning disk 128 about an axis C, a conditioner arm 132 coupling the first actuator 130 to a second actuator 134, a rotational position sensor 135, and a third actuator 136. The second actuator 134 is used to swing the conditioner arm 132 about an axis D to thus sweep the rotating conditioning disk 128 back and forth between an inner radius and an outer radius of the polishing pad 112. The position sensor 135 is coupled to the second actuator 134 and is used to determine the angular position of the conditioner arm 132, which in turn may be used to determine the radial location of the conditioning disk 128 on the polishing pad 112 as the conditioning disk 128 is swept thereover. The third actuator 136 is used to exert a downforce on the conditioning disk 128 as it is urged against the polishing pad 112. Here, the third actuator 136 is coupled to an end of the arm 132 at a location proximate to the second actuator 134 and distal from the conditioning disk 128.

[0029] Operation of the polishing system 100, including operation of the pad conditioning assembly 108, is facilitated by the system controller 110 (Figure 1 B). The system controller 110 includes a programmable central processing unit (CPU 140) which is operable with a memory 142 (e.g., non-volatile memory) and support circuits 144. 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 components 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. 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 the polishing system 100, to facilitate control of a substrate polishing process.

[0030] 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 100. 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. 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.). In some embodiments, the disclosure may be implemented as a program product stored on a non-transitory computer-readable storage medium for use with a computer system. Thus, the program(s) of the program product define functions of the embodiments (including the methods described herein).

[0031] Figure 2 is a schematic cross-sectional view of a portion of the polishing system 100 of Figure 1 A, according to embodiments described herein. The polishing system 100 is configured with an arm displacement sensor 238 and one or more conditioning disk displacement sensors 210a, 210b. The arm displacement sensor 238 and the conditioning disk displacement sensors 210a, 210b are configured to enable measurement of a thickness profile of the polishing pad 112. The thickness profile measures changes in the profile of the polishing pad 112 caused by recesses within the polishing pad-mounting surface 118 of the platen body 114 as well as non-uniformities in the polishing pad 112 caused by uneven wear or particle accumulation.

[0032] Typically, the conditioning disk 128 is coupled to the first actuator 130 using a gimbal 208 which allows the conditioning disk 128 to maintain a parallel relationship with the surface of the polishing pad 112 as the conditioning disk 128 is urged there against. Here, the conditioning disk 128 includes a conditioning disk holder 202 and a conditioning disk pad 204 disposed within the conditioning disk holder 202. The conditioning disk holder 202 is a polymer or plastic material, such as a fluorocarbon containing material. The plastic material may be polytetrafluoroethylene (PTFE) or polyether ether ketone (PEEK). The conditioning disk holder 202 has a thickness of less than about 10 mm, such as less than about 5 mm to enable conditioning disk displacement sensors 210a to measure the location of the conditioning disk pad 204 disposed therein. The conditioning disk pad 204 has a fixed abrasive conditioning surface, e.g., diamonds embedded in a metal alloy, and is used to abrade and rejuvenate the surface of the polishing pad 112, and to remove polish byproducts or other debris therefrom. Typically, the conditioning disk 128 has a diameter between about 80 mm and about 130 mm, such as between about 90 mm and about 120 mm, or for example, about 108 mm (4.25 inches). In some embodiments, the diameter of the conditioning disk 128 is less than the width W of the second zone 120b so that the conditioning disk 128 may maintain contact with the surface of the polishing pad 112 during conditioning thereof in the second zone 120b.

[0033] The arm displacement sensor 238 is connected to the conditioner arm 132, such that the arm displacement sensor 238 is positioned on a bottom surface 220 of the conditioner arm 132. The arm displacement sensor 238 is an inductive sensor, a capacitive sensor, or a laser sensor. In embodiments in which the arm displacement sensor 238 is an inductive sensor, the arm displacement sensor 238 is configured to measure eddy currents to determine a distance Z2 between an end of the arm displacement sensor 238 to the metallic surface of the platen body 114 disposed there beneath. The arm displacement sensor 238 and the position sensor 135 are used in combination to determine the recessed distance Z3 of the surface of the polishing pad 112 in the second zone 120b from the surfaces of the polishing pad 112 in the first and third zones 120a,c adjacent thereto. However, in some embodiments wherein the second zone 120b is narrower than the diameter of the conditioning disk 128, the distance Z2 measurements made by the arm displacement sensor 238 are only an estimate and may not account for the full shape or depth of the second zone 120b. The arm displacement sensor 238 may be either mechanically or remotely connected to the system controller 110. In embodiments in which the arm displacement sensor 238 is remotely connected to the system controller 110, the arm displacement sensor 238 includes a short range wireless (BLUETOOTH®), radio frequency, or wireless fidelity connection.

[0034] The conditioning disk displacement sensors 210a, 210b are coupled to the pad conditioner assembly 108, such as at the bottom surface 206 of the first actuator 130. The conditioning disk displacement sensors 210a, 210b as described herein are disposed directly above the conditioning disk 128. Proximity to the conditioning disk 128 improves measurement accuracy and precision when using the same type of conditioning disk displacement sensors 210a, 210b. Coupling the conditioning disk displacement sensors 210a, 210b to a portion of the pad conditioner assembly 108 that moves along with the first actuator 130 and the conditioning disk 128 provides a constant frame of reference to the conditioning disk 128 and eliminates the need to account for position of the first actuator 130 and the conditioning disk 128 across the surface of the polishing pad 112, thus reducing error. The conditioning disk displacement sensors 210a, 210b described herein are non-contact displacement sensors. Utilizing non-contact displacement sensors prevents problems, such as mechanical failure and wear, which occur as the conditioning disk 128 rotates.

[0035] As examples, the conditioning disk displacement sensors 210a, 210b may be inductive sensors, laser sensors, or capacitive sensors. In embodiments in which the conditioning disk displacement sensors 210a, 210b are inductive sensors, the conditioning disk displacement sensors 210a, 210b measure eddy currents to determine one or more distances Z4 or Z5 between an end of the conditioning disk displacement sensors 210a, 210b to the metallic surface of the conditioning disk pad 204 disposed there beneath. A first conditioning disk distance Z4 is measured by a first conditioning disk displacement sensor 210a. A second conditioning disk distance Z5 is measured by a second conditioning disk displacement sensor 210b. The first and second conditioning disk displacement sensors 210a, 210b are configured to measure a distance to different portions of the conditioning disk 128. The conditioning disk displacement sensors 210a, 210b are used in combination to determine orientation of the conditioning disk 128.

[0036] The orientation of the conditioning disk 128 as well as the arm displacement measured by the arm displacement sensor 238 enables a better polishing pad thickness profile to be created which accurately accounts for recesses or non-uniformities in thickness of the polishing pad 112. As the number of conditioning disk displacement sensors 210a, 210b is increased, the resolution and accuracy of the polishing pad thickness profile may be improved. The conditioning disk displacement sensors 210a, 210b may be either mechanically or remotely connected to the system controller 110. In embodiments in which the conditioning disk displacement sensors 210a, 210b are remotely connected to the system controller 110, the conditioning disk displacement sensors 210a, 210b include a short range wireless (BLUETOOTH®), radio frequency, or wireless fidelity connection.

[0037] Although the pad conditioner assembly 108 shown includes two conditioning disk displacement sensors 210a, 210b, in some embodiments there is only a single conditioning disk displacement sensor 210a or there are three or more conditioning disk displacement sensors 210a, 210b as shown in Figures 4A-4C. When utilizing a single conditioning disk displacement sensor 210a, only one degree of tilt of the conditioning disk 128 is able to be measured. When utilizing two conditioning disk displacement sensors 210a, 210b two degrees of tilt of the conditioning disk 128 are able to measured. When utilizing three or more conditioning disk displacement sensors 210a, 210b, all three degrees of tilt of the conditioning disk 128 are able to be measured. The use of additional conditioning disk displacement sensors 210a, 210b past three conditioning disk displacement sensors 210a, 210b assists in improving the resolution and precision of the conditioning disk tilt measurements and subsequently the polishing pad thickness profile.

[0038] In some embodiments, the pad conditioner assembly 108 is used to maintain the recessed relationship of the surface of the polishing pad 112 in the second zone 120b relative to the surfaces of the polishing pad 112 in the first and third zones 120a,c adjacent thereto. In those embodiments, the system controller 110 may be used to change a dwell time of the conditioning disk 128 and/or a downforce on the conditioning disk 128 in the second zone 120b. As used herein dwell time refers to an average duration of time a conditioning disk 128 spends at a radial location as the conditioning disk 128 is swept from an inner radius to an outer radius of the polishing pad 112 as the platen 102 rotates to move the polishing pad 112 there beneath. For example, the conditioning dwell time per cm ² of polishing pad surface area in the second zone 120b may be increased or decreased relative to the conditioning dwell time per cm ² of polishing pad surface area in one or both of the first and/or third zone 120a,c adjacent thereto.

[0039] Figure 3 is a schematic cross-sectional view of a portion of the polishing system 100 of Figure 1A with a conditioning disk 128 in multiple locations over a polishing pad 112. The conditioning disk 128 is shown at different heights and orientations. The conditioning disk 128 is configured to be rotated about the axis C while traveling across the surface of the polishing pad 112.

[0040] The conditioning disk 128 as described herein is shown at a first orientation Oi when the conditioning disk 128 is positioned over a portion of the polishing pad 112 without any defects or divots causing the conditioning disk 128 to tilt at an angle different from the resting position of the polishing pad 112. The first orientation Oi may be considered a home orientation or the resting position. [0041] The conditioning disk 128’ is shown as the conditioning disk 128’ is disposed at least partially over a divot or feature within the polishing pad 112. As shown herein, the divot or feature within the polishing pad 112 is caused by a divot or feature within the platen body 114, such as the second zone 120b of the pad-mounting surface 118b as described above. The conditioning disk 128’ is disposed at a second orientation O2 while over the divot within the polishing pad 112. The second orientation O2 is measured by measuring the first conditioning disk distance 2A and the second conditioning disk distance Z5. As shown herein, the first conditioning disk distance Z4 is less than the second conditioning disk distance Z5 and therefore the orientation of the conditioning disk 128’ is determined. Finer resolution of the features within the polishing pad 112 may be possible with smaller conditioning disks 128 and/or additional conditioning disk displacement sensors 210a, 210b.

[0042] The conditioning disk 128” is shown as the conditioning disk 128” is disposed at least partially over the same divot or feature within the polishing pad 112 as the conditioning disk 128’, but is disposed over a different portion of the divot or feature. As shown herein, the average height of both of the conditioning disks 128’, 128” as well as the respective first actuators 130 are the same. However, the orientations O2 and O3 of each of the conditioning disks 128’ and 128” are different. Without the conditioning disk displacement sensors 210a, 210b, the arm displacement sensor 238 would not be able to measure the orientation of the conditioning disks 128’ or 128”. Therefore, both of the conditioning disks 128’ and 128” would appear to be the same height. This is exaggerated when the conditioning disks 128 described herein pass over smaller features and divots. Therefore, the size and shape of the features or grooves are not accurately measured with only the use of the displacement sensor 238, but the additional use of the conditioning disk displacement sensors 210a, 210b enables the size and shape to be more accurately measured.

[0043] At yet another position on the polishing pad 112, a conditioning disk 128”’ is disposed partially over a non-uniformity within the polishing pad 112. The non-uniformity may be an area where the polishing pad 112 is narrower or thicker, such that the polishing pad 112 has been worn down a greater amount in one area. In this embodiment, the conditioning disk displacement sensors 210a, 210b measure the first conditioning disk distance 2A and the second conditioning disk distance Zs. The first conditioning disk distance Z4 being greater than the second conditioning disk distance Z5 indicates the fourth orientation O4 of the conditioning disk 128’”.

[0044] The combination of the conditioning disk displacement sensors 210a, 210b and the arm displacement sensor 238 enables accurate measurement of the non-uniformity within the polishing pad 112 caused by the second zone 120b of the pad-mounting surface 118b. The combination of the conditioning disk displacement sensors 210a, 210b and the arm displacement sensor 238 further enables a controller to determine if the non-uniformity is caused by the polishing pad 112 having an uneven thickness or the shape of the platen body 114 beneath the polishing pad 112.

[0045] Figures 4A-4C are schematic plan views of conditioning disks 128 with different configurations of conditioning disk displacement sensors 210a- 21 Od. The different configurations of the conditioning disk displacement sensors 210a-210d include different orientations and numbers of the conditioning disk displacement sensors 210a-210d. The radial angle a around the rotation axis C of the conditioning disk 128 may be changed.

[0046] The conditioning disk displacement sensors 21 Oa-21 Od may also be positioned either radially inward or radially outward from the first actuator 130, such that the conditioning disk displacement sensors 21 Oa-21 Od may not be disposed on the bottom surface of the first actuator 130, but are still configured to be oriented to measure a displacement of a portion of the conditioning disk 128. In some embodiments (not shown), the conditioning disk displacement sensors 21 Oa-21 Od are disposed on a side surface of the first actuator 130 and oriented to measure the displacement of the conditioning disk 128.

[0047] As shown in the first configuration 400a of Figure 4A, only two conditioning disk displacement sensors 210a, 210b are utilized. The conditioning disk displacement sensors 210a, 210b are disposed on the bottom surface of the first actuator 130. The conditioning disk displacement sensors 210a, 21 Ob are aligned along a plane E. The plane E is aligned with and passes through the axis C. In the first configuration 400a, the conditioning disk displacement sensors 210a, 210b are disposed at a radial angle a of about 180 degrees with respect to one another. In other embodiments, two conditioning disk displacement sensors 210a, 210b may be used, but the radial angle a is changed to an angle other than 180 degrees, such that the sensors 210a and 210b are positioned on different planes,- to enable measurement of another degree of freedom of the conditioning disk 128.

[0048] As shown in the second configuration 400b of Figure 4B, three conditioning disk displacement sensors 210a, 210b, 210c are utilized. The three conditioning disk displacement sensors are centered around the axis C and disposed at a radial angle a of to one another, such that each of the conditioning disk displacement sensors 210a, 210b, 210c are disposed on separate planes which intersect at the axis C, but are not the same. The first conditioning disk displacement sensor 210a is disposed on a first plane F, the second conditioning disk displacement sensor 210b is disposed on a second plane G, and the third conditioning disk displacement sensor 210c is disposed on a third plane H. Each of the first plane F, the second plane G, and the third plane H, have a radial angle a disposed there between. The radial angle a is about 10 degrees to about 170 degrees, such as about 10 degrees to about 150 degrees, such as about 10 degrees to about 120 degrees, such as about 45 degrees to about 120 degrees, such as about 90 degrees to about 120 degrees.

[0049] As shown in the third configuration 400c of Figure 4C, four conditioning disk displacement sensors 210a, 210b, 210c, 21 Od are utilized. The four conditioning disk displacement sensors 210a, 210b, 210c, 21 Od are centered around the axis C and disposed at a radial angle a with respect to one another, such that the conditioning disk displacement sensors 210a, 210b, 210c, 21 Od are disposed on separate planes, which intersect at the axis C, but are not the same. The first conditioning disk displacement sensor 210a is disposed on a first plane I, the second conditioning disk displacement sensor 210b is disposed on a second plane J, the third conditioning disk displacement sensor 210c is disposed on a third plane K, and the fourth conditioning disk displacement sensor 21 Od is disposed on a fourth plane L. Each of the first plane I, the second plane J, the third plane K, and the fourth plane L, have a radial angle a disposed there between. The radial angle a is about 10 degrees to about 110 degrees, such as about 10 degrees to about 100 degrees, such as about 45 degrees to about 100 degrees, such as about 60 degrees to about 90 degrees. In one embodiment, plane I and plane K are the same plane as shown. In one embodiment, which may be combined with other embodiments, plane J and plane L are the same plane as shown. In other embodiments, all four planes are separate planes.

[0050] Figure 5 is a flow diagram of a method 500 of forming a polishing pad thickness profile, according to embodiments described herein. The polishing pad thickness profile is a map of the polishing pad thickness and orientation. The polishing pad thickness profile may be continuously or periodically updated using the sensors and methods described herein. Knowing the thickness profile of the polishing pad enables for dwell time of the conditioning disk 128 as well as the substrate carrier 104 to be adjusted accordingly.

[0051] During the method 500 a conditioning disk, such as the conditioning disk 128, is urged against a top surface of a polishing pad, such as the polishing pad 114 during an operation 502. The conditioning disk may be swept across the top surface of the polishing pad as the conditioning disk and polishing pad rotate. The pressure at which the conditioning disk is pressed onto the polishing pad as well as the dwell time may be predetermined or adjustable values.

[0052] After beginning to urge the conditioning disk against the polishing pad, a distance between the conditioning arm, such as the conditioning arm 132, and a polishing platen, such as the platen body 114, is measured during another operation 504. The polishing platen is disposed beneath the polishing pad. The distance is measured using one or more arm displacement sensors, such as the arm displacement sensor 238. The arm displacement sensor is configured to measure the distance to a polishing pad-mounting surface, such as the polishing pad-mounting surface 118.

[0053] During another operation 506, an orientation of the conditioning disk is determined using one or more conditioning disk displacement sensors, such as the conditioning disk displacement sensors 210a-d. The orientation of the conditioning disk may be determined by measuring the tilt in a single direction or in multiple directions, such that a 3-dimensional image of the conditioning disk tilt may be obtained. Obtaining the orientation of the conditioning disk during the operation 506 is performed simultaneously with the measurement of the distance between the conditioning arm and the polishing platen during the operation 504. Obtaining the two measurements simultaneously enables the two measurements to be correlated and a more accurate thickness measurement of the polishing pad may be obtained at any given time.

[0054] The measurement operations 504, 506 may be looped to measure the thickness of the polishing pad at different locations. After measuring the thickness of the polishing pad using the combined conditioning disk orientation and arm displacement measurements, a thickness profile of the polishing pad is determined during another operation 508. During the operation 508, a data table is propagated with thickness measurements of the polishing pad. In some embodiments, the thickness measurements taken during the operations 504, 506 overwrites previous thickness measurements or thickness estimates, such that a thickness profile of a polishing pad is continuously updated during the operation 508. The thickness profile of the polishing pad may be a three dimensional profile measurement, such that a three dimensional map of the polishing pad is created.

[0055] Once the thickness profile of the polishing pad is determined, one or more conditioning parameters may be changed based upon the determined thickness profile of the polishing pad during another operation 510. The one or more conditioning parameters may be the dwell time of the conditioning disk on the polishing pad, the pressure exerted by the conditioning disk on the polishing pad, the rate of process fluid injection onto the polishing pad, the substrate carrier dwell time and pressure, or another process parameter. In some embodiments, if a portion of the polishing pad is determined to be below a certain thickness or if the profile of the polishing pad is outside of an acceptable uniformity level, the polishing operations may be ceased and the polishing pad may be removed before replacing the polishing pad with a new polishing pad.

[0056] Apparatus and methods described herein enable more accurate thickness measurement of a polishing pad during chemical mechanical polishing operations. The thickness of the polishing pad may be measured using a combination of an arm displacement sensor coupled to a conditioning disk arm as well as one or more conditioning disk displacement sensors. The thickness measurements may be mapped to determine a thickness profile of the polishing pad, and process conditions, such as conditioning disk dwell time may be altered.

[0057] 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.