Patent Application
20240383099
The present disclosure relates to chemical mechanical polishing of a semiconductor substrate. More specifically, the present disclosure relates to a multiple disk pad conditioning assembly for use in chemical mechanical polishing.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive, or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. This non-planar outer surface presents a problem for the integrated circuit manufacturer as a non-planar surface can prevent proper focusing of a photolithography apparatus in subsequent processes. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface.
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, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate and/or oscillate to provide additional motion between the substrate and polishing surface. Further, a polishing liquid, typically including an abrasive and at least one chemically reactive agent, may be spread on the polishing pad.
When the polisher is in operation, the pad is subject to compression, shear and friction producing heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects, sometimes referred to as “glazing,” reduce the pad's roughness and ability to apply and retain fresh slurry on the pad surface. It is, therefore, desirable to condition the pad by removing trapped slurry, and unmatting, re-expanding, or re-roughening the pad material. The pad can be conditioned after each substrate is polished, or after a number of substrates are polished, which is often referred to as ex-situ pad conditioning. The pad can also be conditioned at the same time substrates are polished, which is often referred to as in-situ pad conditioning.
Therefore, there is a need for a method and device that can reliably, quickly, and uniformly condition a polishing pad.
Embodiments described herein generally relate to systems and methods used for pad conditioning in a chemical mechanical polishing system. More particularly, embodiments herein provide for processes and methods to polish a conditioning pad using a multiple disk pad conditioner to allow for improved pad conditioning and uniform pad cutting pressure.
In an embodiment, a pad conditioning assembly is provided. The pad conditioning system includes a base, an arm coupled to the base, a first conditioning head coupled to the arm and coupleable to a first pad conditioning disk disposed at a first head distance from the first conditioning head, the first conditioning head including a first linear actuator configured to adjust the first head distance. The pad conditioning assembly further includes a second conditioning head coupled to the arm and coupleable to a second conditioning disk disposed at a second head distance from the second conditioning head, the second conditioning head including a second linear actuator configured to adjust the second head distance, a third conditioning head coupled to the arm and coupleable to a third conditioning disk disposed at a third head distance from the third conditioning head, the third conditioning head including a third linear actuator configured to adjust the third head distance.
Further, the pad conditioning assembly includes a drive system coupled to the base and configured to drive rotation of the first conditioning head, the second conditioning head, and the third conditioning head, and a controller. The controller is configured to rotate the arm into a starting position over a platen, receive sensor readings, determine whether the sensor readings are outside of a predetermined range, and upon determining that the sensor readings are outside of the predetermined range, adjust the first head distance, the second head distance, the third head distance, or a combination thereof.
In another embodiment, a method of conditioning a polishing pad is provided. The method includes receiving sensor readings from at least one pad thickness sensor disposed on an arm of a pad conditioning assembly, determining if the sensor readings are outside of a predetermined range, and, upon determining that the sensor readings are outside of the predetermined range, adjusting a first head distance of a first conditioning head, a second head distance of a second conditioning head, a third head distance of a third conditioning head, or a combination thereof, of the pad conditioning assembly based on the sensor readings.
In yet another embodiment, a chemical mechanical polishing (CMP) system is provided. The CMP system includes a polishing station including a carrier head configured to hold a substrate, a platen configured to hold a polishing pad, a pad conditioning assembly including a base, an arm coupled to the base, a first conditioning head coupled to the arm and coupleable to a first pad conditioning disk disposed at a first head distance from the first conditioning head, the first conditioning head including a first linear actuator configured to adjust the first head distance, a second conditioning head coupled to the arm and coupleable to a second conditioning disk disposed at a second head distance from the second conditioning head, the second conditioning head including a second linear actuator configured to adjust the second head distance, a third conditioning head coupled to the arm and coupleable to a third conditioning disk disposed at a third head distance from the third conditioning head, the third conditioning head including a third linear actuator configured to adjust the third head distance. The CMP system also includes a drive system coupled to the base and configured to drive rotation of the first conditioning head, the second conditioning head, and the third conditioning head, at least one pad thickness sensor.
Further, the CMP system includes a controller configured to rotate the arm into a starting position over a platen, receive sensor readings from the at least one pad thickness sensor, determine whether the sensor readings are outside of a predetermined range, and upon determining that the sensor readings are outside of the predetermined range, adjust the first head distance, the second head distance, the third head distance, or a combination thereof.
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.
Embodiments herein are generally directed to chemical mechanical polishing (CMP), and more specifically to a multiple disk pad conditioning assembly for use in chemical mechanical polishing.
Conventional design of a pad conditioning assembly for use in chemical mechanical polishing (CMP) deploys single pad conditioning head and disk with limited pad converge. The limited pad coverage leads to prolonged pad conditioning time which may produce scratch defects on the polishing pad to be conditioned. The present disclosure provides for a pad conditioning assembly with three in-line pad conditioning heads and disks for increased pad coverage, providing reduced pad conditioning time without sacrificing on performance metrics. Reduced conditioning time leads to better CMP scratch defect performance.
The present disclosure provides CMP processes that include an in-situ pad conditioning operation in which a conditioning assembly having multiple conditioning disks, e.g., a disk coated with abrasive diamond particles, is pressed against the rotating polishing pad to condition and texture the polishing pad surface concurrent with substrate polishing. The present disclosure also allows for ex-situ conditioning of the polishing pad using the multiple-disk assembly.
The multiple disk pad conditioning assembly 100 may include a base 110, an arm 112, a first conditioning head 120a, a second conditioning head 120b, and a third conditioning head 120c, as well as a first pad conditioning disk 130a mounted to the first conditioning head 120a, a second pad conditioning disk 130b mounted to the second conditioning head 120b, and a third pad conditioning disk 130c mounted to the third conditioning head 120c. Although the conditioning heads 120a, 120b, and 120c are shown having substantially equal spacing along the conditioning arm 112 of the multiple disk pad conditioning assembly 100, the spacing of the conditioning heads 120a, 120b, 120c may be set at any spacing useful for the particular conditioning process.
Each pad conditioning disk 130a, 130b, 130c may have a conditioning surface 132a, 132b, 132c with abrasive particles thereon. Each conditioning surface 132a, 132b, and 132c may be configured to rub against and abrade a surface 140S of a polishing pad 140. The first conditioning head 120a, the second conditioning head 120b, and the third conditioning head 120c may be configured to vertically move their respective pad conditioning disk 130a, 130b, 130c (as indicated by arrow 122) from an elevated retracted position to a lowered extended position such that each conditioning surface 132a, 132b, 132c may engage the polishing surface 140S of the polishing pad 140 on a platen 142. For example, each conditioning head 120a, 120b, 120c may include an actuator (not shown) that is configured to raise and lower each pad conditioning disk 130a, 130b, 130c along a respective head axis 124a, 124b, 124c. Such actuation of each pad conditioning disk 130a, 130b, 130c may increase or decrease the respective longitudinal or head distance 136a, 136b, and 136c and each actuator in each conditioning head 120a, 120b, and 120c may be controlled independently or in synchronization with each other. For example, the first conditioning head 120a may lower the first pad conditioning disk 130a, while the second conditioning head 120b and the third conditioning head 120c raise the second pad conditioning disk 130b and the third pad conditioning disk 130c such that the cutting pressure on the polishing surface 140S is evenly distributed.
The first conditioning head 120a, the second conditioning head 120b, and the third conditioning head 120c may further be configured to rotate their respective pad conditioning disk 130a, 130b, 130c about a respective head axis 124a, 124b, 124c. During conditioning, the conditioning disks 130a, 130b, and 130c coupled to the conditioning heads 120a, 120b, and 120c are rotated in a predefined direction. The predefined direction may be counter-clockwise or clockwise as viewed from a top side of the polishing station. The conditioning disks 130a, 130b, and 130c are driven by a single motor 116 imparting rotational force through a drive system 134 to the conditioning heads 120a, 120b, and 120c and the conditioning disks 130a, 130b, and 130c. The drive system may include one or more belts, chains, roller chains, sprockets, or other mechanisms to drive the rotation of the conditioning disks. The single motor 116 is coupled to a base shaft 116a which is coupled to an arm pulley 118. The drive system 134 is coupled to the arm pulley 118 and head pulleys 138a, 138b, 138c which are coupled to the respective conditioning heads 120. The single motor 116 rotates the base shaft 116a about the base axis 110A, rotating the arm pulley 118 and, through the drive system 134, rotating each of the head pulleys 138a, 138b, 138c. The rotation caused by the single motor 116 drives the conditioning disks 130a, 130b, and 130c during the conditioning process. Alternatively, individual motors (not shown) or gearing mechanisms (not shown) may be used to drive the conditioning disks 130a, 130b, and 130c independently.
Further, the first conditioning head 120a, the second conditioning head 120b, and the third conditioning head 120c may each include a linear actuator 128 (e.g., first linear actuator 128a, second linear actuator 128b, and third linear actuator 128c) configured to cause longitudinal motion (e.g., along arrow 122 of first conditioning disk 130a, second conditioning disk 130b, and third conditioning disk 130c, respectively, along the head axes 124a, 124b, and 124c. Each linear actuator 128 may be a pneumatic actuator, for example a pneumatic motor or pneumatic cylinder, a hydraulic actuator, a piezoelectric actuator, a mechanical actuator, an electro-mechanical actuator, or a combination thereof. Each of the first linear actuator 128a, second linear actuator 128b, and third linear actuator 128c may be controlled individually or in combination with each other, such as first linear actuator 128a and second linear actuator 128b or second linear actuator 128b and third linear actuator 128c. For example, the linear actuator 128a, second linear actuator 128b, and third linear actuator 128c may adjust the longitudinal or head distance 136a, 136b, and 136c of each conditioning disk 130a, 130b, and 130c such that the head distances 136a, 136b, and 136c may be identical or may differ to cause different cutting pressures on the polishing surface 140S for customized conditioning of the polishing pad 140. The pressure applied to each of the conditioning disks 120a, 120b, and 120c is adjusted such that one or more of the conditioning disks 120a, 120b, and 120c is placed in contact with the polishing pad 140.
The arm 112 may be configured to rotate about a base longitudinal axis 110A such that the first conditioning head 120a, the second conditioning head 120b, and the third conditioning head 120c may sweep across the polishing pad surface 140S with a reciprocal motion. The base 110 can include an actuator 114 that is configured to rotate a portion of the arm 112 about the base axis 110A. The actuator 114 may be any suitable actuator that provides rotational motion, for example a direct current motor, a synchronous or asynchronous motor, an alternating current motor, a stepper motor, a servomotor, or a combination thereof. The base 110 is thus configured to cause the arm 112 and the conditioning heads 120a, 120b, and 120c to sweep across a surface of the polishing pad 140.
The rotating motion of the pad conditioning disks 130a, 130b, 130c and the reciprocating motion of the first conditioning head 120a, the second conditioning head 120b, and the third conditioning head 120c may cause each conditioning surface 132a, 132b, 132c to condition the polishing surface 140S of the polishing pad 140 by abrading the polishing surface 140S to remove contaminants and to retexture the surface.
At least one pad thickness sensor 150 may be disposed on the arm 112 and configured to determine the thickness of the polishing pad 140. For example, the pad thickness sensor 150 may determine a distance between the arm 112 and the polishing pad 140 then calculate the pad thickness using system parameters such as the distance from the arm 112 to the platen 142 and the tilt of the arm 112 relative to the base 110. The at least one pad thickness sensor 150 may be placed near a conditioning head, such as the first conditioning head 120a, or near multiple conditioning heads, such as near each of the conditioning heads 120a, 120b, and 120c.
The above-described pad conditioning assembly 100 is controlled by a processor based system controller, such as a controller 160, which may be coupled to a user interface 168. For example, the controller 160 is configured to control each of the linear actuators 128, the movement of the arm 112, and the rotation of the pad conditioning disks 130a, 130b, and 130c. Further the controller may be configured to receive input from the at least one pad thickness sensor 150. The controller 160 includes a programmable central processing unit (CPU) 162 that is operable with a memory 164, support circuits 166, the user interface 168 configured to display information and receive user input, a mass storage device, an input control unit, and a display unit (not shown), such as power supplies, clocks, cache, input/output (I/O) circuits, and the like, coupled to the various components of the pad conditioning assembly 100 to facilitate control of the substrate processing. Further the controller may be configured to receive input such as from the at least one pad thickness sensor 150 or the user interface 168. The controller 160 also includes hardware for monitoring substrate processing through sensors in the pad conditioning assembly 100.
The conditioning heads 120a, 120b, and 120c include mechanisms to attach the conditioning disks 130a, 130b, and 130c to the conditioning heads 120a, 120b, and 120c (such as mechanical attachment systems, e.g., bolts or screws, or magnetic attachment systems) and mechanisms to rotate the conditioning disks 130a, 130b, and 130c around the respective head axis 124a, 124b, and 124c (such as drive belts through the arm or rotors inside the conditioner head). In embodiments of the present disclosure the conditioning heads 120a, 120b, and 120c and the conditioning disks 130a, 130b, and 130c are driven by the single motor 116 to cause each conditioning head 120a, 120b, and 120c rotate at the same revolutions-per-minute (RPM). In one example, each conditioning head 120a, 120b, and 120c is rotated at substantially the same RPM, or similar RPM (+/−20%), as the RPM of the platen 142. In alternate embodiments, the conditioning disks 130a, 130b, and 130c may be rotated at different RPMs through use of differing motors, different gearing, or other rotational control mechanisms.
The carrier head 210 is suspended from a support structure 214, e.g., a carousel or a track, and is connected by a drive shaft 216 to a carrier head rotation motor 218 so that the carrier head can rotate about an axis 218A. Optionally, the carrier head 210 can oscillate laterally, e.g., on sliders on the support structure 214, or by rotational oscillation of the support structure 214 itself. In operation, the platen 142 is rotated about its central axis 144, and the carrier head 210 is rotated about its central axis 218A and translated laterally across the top surface of the polishing pad 140. Where there are multiple carrier heads 210, each carrier head 210 can have independent control of its polishing parameters, for example each carrier head 210 can independently control the pressure applied to each respective substrate 212.
The carrier head 210 can include a flexible membrane 220 having a substrate mounting surface to contact the back side of the substrate 212, and a plurality of pressurizable chambers 222 to apply different pressures to different zones, e.g., different radial zones, on the substrate 212. The carrier head 210 can also include a retaining ring to hold the substrate 212.
The polishing station 200 can include a supply port or a combined supply-rinse arm 230 to dispense a polishing liquid 232, such as slurry, onto the polishing pad 140
The polishing station 200 also includes an embodiment of the multiple disk pad conditioning assembly 100 of the present disclosure. In one embodiment, the multiple disk pad conditioning assembly 100 of the present disclosure comprises a plurality of conditioning heads linearly arranged. In the example illustrated in
A cleaning station 300, which contains a cleaning liquid for rinsing or cleaning the conditioning disks 130a, 130b, and 130c, may be used in conjunction with the multiple disk pad conditioning assembly 100. As shown in
As shown in
As shown in
Due to the variation in linear speed of a rotating polishing pad 140 with the radius of the rotating pad, the rotational speed of each of the conditioning disks 130a, 130b, and 130c may be adjusted relative to their radial position on the polishing pad as the arm 112 is swept across the polishing pad. In one example, when the arm 112 is aligned with the radius of the platen 142 (e.g., solid lined multiple disk pad conditioning assembly 100) the conditioning head 120c is rotated at angular speed that is greater than the angular speed of the conditioning head 120b, which has an angular speed that is greater than the angular speed of the conditioning head 120a. In another example, when the arm 112 is aligned in a tangential relationship to a radius of the platen 142 (e.g., dashed multiple disk pad conditioning assembly 100), the conditioning head 120c can be rotated at an angular speed that is similar to the angular speeds of the conditioning head 120b and the conditioning head 120a, since the linear speeds of the pad experienced by each of conditioning heads will be similar. In embodiments of the present disclosure the conditioning heads 120a, 120b, and 120c and polishing pad 140 (i.e., platen) are both driven at a varying RPM during a pad conditioning process. In one processing configuration, the conditioning heads 120a, 120b, and 120c and polishing pad 140 are driven at substantially the same RPM, or similar RPM (+/−20%), at each instant in time during the pad conditioning process.
The method 500 begins in block 502, and an arm of a multiple disk pad conditioning assembly (e.g., arm 112 of the multiple disk pad conditioning assembly 100) is rotated into a starting position over a platen (e.g., platen 142) using a controller such as controller 160 in block 504. The platen 142 may have a polishing pad disposed on its surface, such as polishing pad 140. The starting position of the arm 112 may be relative to the platen 142 or the polishing pad 140. Once the arm 112 is in the starting position, the controller 160 may receive initial sensor readings from at least one pad thickness sensor (e.g., pad thickness sensor 150) disposed on the arm 112 in block 506. The initial sensor readings may correspond to the pad thickness of the polishing pad prior to undergoing a pad conditioning process and may be derived from a distance between the arm 112 and the polishing pad 140, a distance between the arm 112 and the platen 142, a tilt of the arm 112 relative to a base (e.g., base 110) of the pad conditioning assembly 100, or a combination thereof. The initial sensor readings for each pad thickness sensor 150 may be stored in the memory 164 of the controller 160. The controller 160 determines whether the initial sensor readings are within a first predetermined range of pad thickness in block 508. If the initial sensor readings are outside of the first predetermined range, the controller 160, in block 510, may then adjust one or more of the one or more pad conditioning disks 130 to a position along a longitudinal axis 124. The position of the one or more pad conditioning disks 130 may be predetermined or calculated to be a distance from polishing pad surface polishing pad 140S based on the thickness of polishing pad 140.
After the one or more pad conditioning disks 130 are adjusted, the controller 160 may then rotate platen 142, one or more pad conditioning disks 130, or both to condition the polishing pad polishing pad 140 in block 512 during the pad conditioning process. While the polishing pad polishing pad 140 is undergoing the pad conditioning process, the controller 160 may receive in-process sensor readings from one or more pad thickness sensors 150 corresponding to the pad thickness of polishing pad polishing pad 140 in block 514.
The controller 160, in block 516, then determines if any of the head distances 136 of the one or more pad conditioning disks 130 need to be adjusted by determining if the in-process sensor readings fall outside of a second predetermined range. The second predetermined range may be any desired value such as a percentage change from the initial sensor readings, a set pad thickness, or a percentage of an in-process sensor reading from another one or more pad thickness sensors 150. For example, the controller 160 may determine that a head distances 136 needs to be decreased if the pad thickness has decreased by more than 5% of the initial sensor readings. In another example, the controller 160 may determine that the head distances 136 needs to be decreased when the pad thickness reaches a thickness of 10 mils. In another example where there are two one or more pad thickness sensors 150, the controller 160 may determine that a first head distances 136 need to be decreased when the second one or more pad conditioning disks 130 reaches its desired thickness as determined by the second one or more pad thickness sensors 150. The first predetermined range and the second predetermined range may be set as desired and may be different or equal to each other.
If the controller 160 determines that the in-process sensor readings are within the second predetermined range, the method 500 returns to block 514. However, if the controller 160 determines that the in-process sensor readings fall outside of the second predetermined range, the controller 160 will adjust one or more of the one or more pad conditioning disks 130 based on the in-process sensor readings in block 518. For example, if the in-process sensor readings from a second one or more pad thickness sensors 150 exceeds the second predetermined range (e.g., the pad thickness is too high) and the in-process sensor readings from a third one or more pad thickness sensors 150 falls below the second predetermined range, the controller 160 may decrease the second head distance (e.g., head distance 136b) of the second pad conditioning disks 130b and increase the third head distance (e.g., head distance 136c) of the third pad conditioning disks 130c.
After adjustment in block 518, the method 500 returns to block 514. Upon returning to block 514, the controller 160 may receive subsequent sensor readings (e.g., subsequent in-process sensor readings) from the at least one pad thickness sensor 150 and perform subsequent adjustments of the head distances 136. The method 500 continues until completion of the polishing pad conditioning process at block 520.
The present disclosure provides a multiple disk pad conditioning assembly that can reduce time for pad conditioning. The multiple disk pad conditioning assembly provides additional pad coverage and more efficient conditioning to occur as multiple conditioning surfaces may concurrently contact and abrade the polishing pad surface during a pad conditioning process. Thus, conditioning process times may be reduced, and the useful life of the conditioning elements may be extended in comparison to conventional pad conditioning assemblies utilizing a single conditioning surface.
When introducing elements of the present disclosure or exemplary aspects or embodiment(s) thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements.
The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B and object B touches object C, the objects A and C may still be considered coupled to one another—even if objects A and C do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly in physical contact with the second object.
