Patent Application
20240391054
This document claims priority to Japanese Patent Application No. 2023-077012 filed May 9, 2023, the entire contents of which are hereby incorporated by reference.
In a manufacture of semiconductor devices, various types of films are formed on a wafer, which is an example of a substrate. In a process of wiring and contact formation, after a film deposition process, the wafer is polished to remove unwanted portions of the film and surface irregularities. A Chemical mechanical polishing (CMP) is a typical technique for polishing wafers.
The CMP is performed by supplying a polishing liquid onto a polishing surface while sliding the wafer against the polishing surface. The film formed on the wafer is polished by a combination of mechanical action caused by abrasive grains contained in the polishing liquid or the polishing pad, and chemical action caused by chemical components of the polishing liquid.
In the CMP, a technology of polishing the entire surface of the wafer has been improved, but as miniaturization progresses, there is a demand to further reduce the variation in the film thickness of the wafer after polishing. In response to such demands, Japanese Patent Application Laid-Open No. 2021-112797 discloses a polishing head having a plurality of actuators (such as piezoelectric elements). The polishing head controls operations of each actuator to individually apply a pressing force to a plurality of regions of the wafer, thereby controlling the film thickness profile of the wafer.
However, in order to control the operation of each actuator, wiring must be connected to each of the actuators. In particular, in order to control the film thickness profile with higher accuracy, a large number of actuators must be arranged, and the number of wirings increases according to the number of actuators.
In a typical polishing apparatus, the polishing head must be continuously rotated in the same direction as the polishing table to keep a relative speed uniform over the entire surface of the wafer being polished. However, it is difficult to rotate the polishing head with numerous wires connected.
In order to solve such problems, a joint (e.g., rotary connector) could be connected to each wire, or each actuator could be controlled by means of wireless communication. However, such a method has the problem that the mechanism becomes more complicated, resulting in a larger overall size of the apparatus and increased cost.
Therefore, there is provided a polishing apparatus and a polishing method capable of accurately controlling a film thickness profile of a substrate by controlling each of pressing actuators without having a complicated mechanism.
Embodiments described below relate to a polishing apparatus and a polishing method.
In an embodiment, there is provided a polishing apparatus, comprising: a polishing structure having a polishing surface, the polishing structure comprising a scrolling polishing table configured to move in translation along a circular path, or a polishing belt configured to move linearly along a traveling direction; a polishing head configured to press a substrate against the polishing surface, the polishing head comprising a plurality of pressing actuators spread over an entire actuator holding surface of the polishing head and configured to independently press a specific portion of the substrate; and a head rotation mechanism configured to rotate the polishing head within a predetermined rotation angle range.
In an embodiment, the pressing actuators comprise a plurality of airbags configured to apply a pressing force to the substrate, and the airbags are connected to a plurality of fluid supply lines.
In an embodiment, the pressing actuators comprise a plurality of piezoelectric elements configured to apply a pressing force to the substrate, and the piezoelectric elements are connected to a plurality of control lines for controlling operations of the piezoelectric elements.
In an embodiment, in a case in which the polishing structure is the polishing table, the polishing apparatus comprises a liquid supply nozzle configured to supply a liquid onto the polishing surface through a flow hole formed in the polishing table.
In an embodiment, the pressing actuators comprise: a plurality of airbags configured to apply a pressing force to the substrate and connected to a plurality of fluid supply lines; and a plurality of piezoelectric elements configured to apply a pressing force to the substrate and being connected to a plurality of control lines.
In an embodiment, the polishing apparatus comprises a control box accommodating various devices configured to control operations of the pressing actuators, and the control box is configured to rotate together with the polishing head.
In an embodiment, the head rotation mechanism is configured to rotate reciprocatingly the polishing head within a predetermined rotation angle range.
In an embodiment, the head rotation mechanism comprises: a motor; a motor pulley connected to the motor; a gear formed on an outer circumferential surface of the polishing head; and a timing belt stretched between the motor pulley and the gear.
In an embodiment, the polishing apparatus comprises a control device configured to control an operation of each of the pressing actuators based on a film thickness profile of a surface to be polished of the substrate, and the control device is configured to identify a specific portion of the substrate based on a comparison result between a current film thickness profile and a target film thickness profile, and determine a target pressing actuator corresponding to the specific portion of the substrate.
In an embodiment, there is provided a polishing method, comprising: operating a polishing structure comprising a scrolling polishing table configured to move in translation along a circular path, or a polishing belt configured to move linearly along a traveling direction; operating a plurality of pressing actuators spread over an entire actuator holding surface of the polishing head and configured to independently press a specific portion of the substrate, to press the specific portion of the substrate against a polishing surface of the polishing structure; and rotating the polishing head within a predetermined rotation angle range.
In an embodiment, the polishing method comprising operating a plurality of airbags through a plurality of fluid supply lines connected to the airbags as the pressing actuators.
In an embodiment, the polishing method comprising operating a plurality of piezoelectric elements through a plurality of control lines connected to the piezoelectric elements as the pressing actuators.
In an embodiment, in a case in which the polishing structure is the polishing table, the polishing method comprising supplying a liquid from a liquid supply nozzle onto the polishing surface through a flow hole formed in the polishing table.
In an embodiment, the polishing method comprising: operating a plurality of airbags through a plurality of fluid supply lines connected to the airbags as the pressing actuators; and operating a plurality of piezoelectric elements through a plurality of control lines connected to the piezoelectric elements as the pressing actuators.
In an embodiment, the polishing method comprises rotating reciprocatingly the polishing head within a predetermined rotation angle range.
In an embodiment, the polishing method comprises identifying a specific portion of the substrate based on a comparison result between a current film thickness profile and a target film thickness profile, and determining a target pressing actuator corresponding to the specific portion.
The head rotation mechanism rotates the polishing head within a predetermined rotation angle range without continuously rotating the polishing head. Therefore, the film thickness profile of the substrate can be accurately controlled while preventing twisting of lines (i.e., control line, fluid supply line) connected to the pressing actuators. Furthermore, this configuration allows each of the pressing actuators to be controlled without having a complicated mechanism.
By pressing the substrate held by the polishing head against the polishing structure, the substrate can be polished without generating a relative motion on the polishing head side to make a relative velocity uniform across the entire surface to be polished.
Embodiments are described below with reference to the drawings. In the drawings described below, identical or equivalent components will be marked with the same symbol and duplicate explanations will be omitted. In the embodiments described below, the configuration of one embodiment not specifically described is the same as that of the other embodiments, and its duplicate description is omitted.
In this embodiment, the polishing structure 20 includes a polishing pad 22 having a polishing surface 22a, and a polishing table 21 supporting the polishing pad 22. The polishing table 21 has a flow hole 21a formed therein. The flow hole 21a extends toward the polishing pad 22 and is connected to an opening 22b formed in the polishing pad 22.
The liquid supply nozzle 31 is connected to a lower portion of the polishing table 21 and communicates with the flow hole 21a of the polishing table 21. The liquid supply nozzle 31 is connected to a liquid supply line 30 for supplying a liquid (e.g., polishing liquid or pure water). When the liquid is supplied from the liquid supply nozzle 31 through the liquid supply line 30, the liquid spurts (sprouts) from the polishing surface 22a through the flow hole 21a and the opening 22b.
As shown in
The wafer W to be polished is attached to the polishing head 10 by a robot hand RH at the load-and-unload position, and then moved to a polishing position by the polishing head 10. The polished wafer W is moved from the polishing position to the load-and-unload position by the polishing head 10, and is removed from the polishing head 10 at the load-and-unload position by the robot hand RH.
As shown in
When the elevation motor 5a is driven, the polishing head 10 (and the swing shaft 3, the swing arm 2) moves closer to (or away from) the polishing structure 20 through the protrusion 5c as the ball screw 5b rotates. The elevation mechanism 5 functions as a positioning mechanism to adjust a height of the polishing head 10 relative to the polishing structure 20. When polishing the wafer W, the elevation mechanism 5 positions the polishing head 10 at a predetermined height. In this state, the polishing head 10 presses the wafer W held on its lower surface against the polishing surface 22a.
The pressing actuators 11 are located behind the wafer W held by the polishing head 10. The carrier 13 has an actuator holding surface 8 that holds the plurality of pressing actuators 11. The pressing actuators 11 are spread over the entire actuator holding surface 8 and are configured to independently press a specific portion of the wafer W. In other words, the pressing actuators 11 are configured to press a plurality of regions of the wafer W onto the polishing surface 22a with different pressing forces.
In this embodiment, each of the pressing actuators 11 includes a piezoelectric element that applies a pressing force to the wafer W. Hereinafter, the pressing actuators 11 are referred to as the piezoelectric elements 11.
The polishing apparatus 1 includes a plurality of control lines 12 for controlling operations of the piezoelectric elements 11 and a control box 14 that accommodates devices necessary for controlling the operations of the piezoelectric elements 11 (see
The control lines 12 are accommodated in the carrier 13 and connected to the control box 14. The control box 14 accommodates various devices (e.g., inverter) for controlling a power (i.e., current, voltage) applied to each piezoelectric element 11. The control box 14 is mounted on the carrier 13 and is arranged above the piezoelectric elements 11.
The polishing apparatus 1 includes a plurality of aggregated wires 16 connected to the control box 14. The aggregated wires 16 are wiring for sending operation signals, such as power and control signals, to various devices in the control box 14, and extend to the outside through a through hole 2a formed in the swing arm 2. The operation signals sent to the various devices in the control box 14 through the aggregated wires 16 are adjusted by the various devices and sent to each piezoelectric element 11.
In this embodiment, the number of the aggregated lines 16 is smaller than that of the control lines 12, and the aggregated lines 16 have a larger diameter than the control lines 12. With this structure, the aggregated lines 16 can improve their durability against repeated bending caused by a pivoting operation of the swing arm 2.
In one embodiment, the polishing apparatus 1 does not necessarily have to include the aggregated line 16. In this case, the control lines 12, the number of which corresponds to the number of the pressing actuators 11, are connected to the control box 14 and extend to the outside through the through hole 2a of the swing arm 2.
In one embodiment, the control lines 12 are air lines and the piezoelectric elements 11 may be separate airbags. The aggregate line 16 is used for electrical control of the pressure control unit accommodated in the control box 14 and includes the air lines that supply the airbags.
As shown in
In the embodiment shown in
The support mechanism 25A includes a bearing 29 fixed to a lower surface of the polishing table 21, an eccentric shaft 28 rotatably supported by the bearing 29, and a motor 23 for rotating the eccentric shaft 28. The eccentric shaft 28 has two shaft portions 27 and 26 that are offset from each other by a predetermined eccentricity (i.e., an offset amount). The shaft portion 27 is rotatably supported by the bearing 29, and the shaft portion 26 is fixed to the motor 23.
As shown in
As shown in
With this configuration, the polishing head 10 is capable of rotating relatively to the swing arm 2. The control box 14 accommodated in the carrier 13 rotates together with the polishing head 10.
According to this embodiment, the head rotation mechanism 15 rotates the polishing head 10 including the pressing actuators 11 within a predetermined range of rotation angles without continuously rotating the polishing head 10. Therefore, the polishing head 10 can prevent twisting of the control line 12 caused by the continuous rotation of the polishing head 10, and can eliminate the need to add a rotary connector or the like to the aggregated line 16.
The predetermined rotation angle is determined to be an angle at which the control line 12 does not twist (or at which the control line 12 does not break due to twisting of the control line 12). For example, the rotation angle of the polishing head 10 is determined to be within a range of 0 degrees to 1080 degrees. Therefore, “continuous rotation” means rotation in one direction during polishing of the wafer W beyond the upper limit of the rotation angle thus determined.
Furthermore, according to this embodiment, it is not necessary to connect a joint (e.g., a rotary connector) to each control line 12, and it is not necessary to control each presser actuator 11 by wireless communication means. Therefore, there is no problem that the size of the polishing head 10 increases and the cost of the polishing apparatus 1 increases. Thus, according to this embodiment, the polishing head 10 can prevent twisting of the control line 12, and therefore it is possible to control each pressing actuator 11 without a complicated mechanism.
The polishing table 21, which moves in a translational motion along a circular path, can generate the same amount of relative movement over its entirety with respect to the surface to be polished of the wafer W. Therefore, under a condition of the same polishing pressure, the wafer W can be polished at a uniform polishing rate, in theory. With this configuration, the wafer W held by the polishing head 10 is pressed against the polishing surface 22a of the polishing pad 22 on the polishing table 21, which moves in the translational motion along a circular path, so that the wafer W can be polished without the polishing head 10 generating a relative motion for making the relative speed over the entire surface to be polished of the wafer W uniform.
When polishing the wafer W, the polishing head 10 holding the wafer W is lowered to press the wafer W against the polishing surface 22a of the polishing pad 22, and at the same time, the polishing liquid is supplied to the flow hole 21a of the polishing table 21 through the liquid supply nozzle 31. The polishing liquid supplied to the flow hole 21a is supplied onto the polishing surface 22a through the opening 22b of the polishing pad 22. In this manner, the polishing surface 22a of the polishing pad 22 polishes the surface to be polished of the wafer W in the presence of the polishing liquid.
The head rotation mechanism 15 rotates the polishing head 10 within a predetermined rotation angle range during polishing of the wafer W. A reason for rotating the polishing head 10 is as follows: The polishing surface 22a of the polishing pad 22 is not present in the opening 22b formed in the polishing pad 22.
When the polishing table 21 performs the translational motion while the rotation of the polishing head 10 is stopped, the opening 22b moves along a certain trajectory on the surface to be polished of the wafer W. Therefore, the surface to be polished of the wafer W on the trajectory of the opening 22b is not polished, and a uniformity of polishing of the wafer W on the trajectory of the opening 22b decreases.
Therefore, in order to improve the uniformity of polishing of the wafer W, the head rotation mechanism 15 rotates the polishing head 10 at a predetermined rotation speed. In one embodiment, the polishing head 10 may be rotated by the head rotation mechanism 15 and swung by the swivel motor 4.
In polishing using a continuously rotating polishing table, in order to generate a relative motion at a relatively uniform relative speed within a substrate surface, it is necessary to continuously rotate the polishing table and the polishing head at a predetermined rotation speed. On the other hand, in this embodiment, the necessary relative speed can be generated by the scroll motion of the polishing table 21. The polishing head 10 rotates for a purpose of preventing the transfer of the trajectory of the grooves and openings formed in the polishing pad 22 to the polishing operation.
Therefore, the rotation speed of the polishing head 10 may be relatively low. With this configuration, even if the control box 14 has a complex and delicate device, the control box 14 can be mounted on the polishing head 10 without being subjected to impacts caused by the high-speed rotation of the polishing head 10.
As shown in
The control device 50 is composed of at least one computer. The at least one computer may be one server or a plurality of servers. The control device 50 may be an edge server, a cloud server connected to a communication network such as the Internet or a local area network, or a fog computing device (gateway, fog server, router, etc.) installed in the network. The control device 50 may be servers connected by a communication network such as the Internet or a local area network. For example, the control device 50 may be a combination of an edge server and a cloud server.
The control device 50 is electrically connected to components of the polishing apparatus 1 (e.g., the swivel motor 4, the elevation motor 5a, the motor 15a, and the motor 23) and is configured to control the operations of these components.
Furthermore, the control device 50 is electrically connected to the aggregated line 16 (and the control line 12), and is configured to control the operation of each of the pressing actuators 11. For example, the control device 50 is configured to control the operation of each pressing actuator 11 based on a film thickness profile of the surface to be polished of the wafer W.
For example, the film thickness measurement device is a stand-alone film thickness measurement device that is arranged outside the polishing apparatus 1 and measures the film thickness of the wafer W in a stationary state. In one embodiment, the film thickness measurement device may be a film thickness sensor 40 that is arranged inside the polishing apparatus 1.
As shown in
In this state, the head rotation mechanism 15 (and/or the swing arm 2) is operated, whereby the film thickness sensor 40 detects a signal corresponding to the film thickness of the wafer W. The control device 50 measures the film thickness of the wafer W based on the signal detected by the film thickness sensor 40, and creates the film thickness profile.
In the embodiment shown in
Thereafter, the control device 50 compares the current film thickness profile created based on the film thickness measured by the film thickness measurement device (or the film thickness sensor 40) with a target film thickness profile (see step S102), and identifies the specific portion of the wafer W to be polished more aggressively (or more aggressively) (see step S103). The target film thickness profile is stored in advance in the storage unit 50a. The target film thickness profile may be created based on past experimental data or theoretical data.
Based on the identified specific portion of the wafer W, the control device 50 determines the pressing actuator 11 (i.e., the target pressing actuator 11) corresponding to the specific portion and a pressing force of the target pressing actuator 11.
For example, the control device 50 calculates a distribution of a target polishing amount of the wafer W based on a comparison result between the current film thickness profile and the target film thickness profile, and determines the pressing force of the pressing actuators 11 including the target pressing actuator 11 in order to achieve the target polishing amount within a predetermined polishing time. Thereafter, the control device 50 operates the pressing actuators 11 including the target pressing actuator 11 to apply the determined pressing force to the wafer W, thereby eliminating the variation in film thickness.
The pressing actuators 11 spread over the entire actuator holding surface 8 are distributed along the radial direction and the circumferential direction of the polishing head 10, and independently press specific portions of the wafer W. Therefore, the control device 50 can operate the pressing actuators 11 to accurately control the film thickness profile of the wafer W.
The pressing actuators 11 may be arranged in a grid pattern or in a concentric pattern as long as they are arranged over the entire actuator holding surface 8 of the polishing head 10. In one embodiment, the pressing actuators 11 may be arranged randomly.
After starting polishing the wafer W (see step S104), during polishing the wafer W, the control device 50 measures the film thickness of the wafer W using the film thickness sensor 40 arranged on the fixed table 41 (see step S105). More specifically, the control device 50 operates the swing arm 2 to move the polishing head 10 to above the film thickness sensor 40. The film thickness sensor 40 detects a signal corresponding to the film thickness of the wafer W held by the polishing head 10, and the control device 50 measures the film thickness of the wafer W based on the signal detected by the film thickness sensor 40.
The control device 50 determines whether or not a polishing end point of the wafer W has been reached based on the measured film thickness of the wafer W (see step S106). For example, the control device 50 determines the polishing end point when a difference in film thickness between the thickest and thinnest portions of the wafer W falls within a predetermined range.
When the control device 50 determines the polishing end point (see “YES” in step S106), the control device 50 finishes the polishing of the wafer W (see step S107). On the other hand, when the control device 50 does not determine the polishing end point (see “NO” in step S106), the control device 50 continues polishing the wafer W.
In a typical polishing apparatus, the polishing head 10 needs to be rotated at high speed to polish the wafer W. In this case, due to frictional force, the wafer W slips in the circumferential direction relative to the polishing head 10. As a result, the control device 50 must measure a slip of the wafer W in real time and constantly change the target pressing actuator 11 for polishing a specific portion of the wafer W in accordance with the slip of the wafer W.
In this embodiment, the polishing apparatus 1 is configured to polish the wafer W by pressing the wafer W against the polishing surface 22a of the polishing pad 22 on the polishing table 21 that moves in the translational motion along a circular path. With this configuration, the polishing head 10 does not need to rotate at high speed, so that it is possible to prevent the wafer W from slipping in the circumferential direction relative to the polishing head 10 due to frictional force between the polishing pad 22 and the wafer W.
For example, after starting polishing of the wafer W, the control device 50 operates the swing arm 2 to position the peripheral portion of the wafer W outside the polishing table 21, and in this state, operates the head rotation mechanism 15 to rotate the polishing head 10. By such an operation, the peripheral portion of the wafer W protruding from the polishing table 21 rotates, and the film thickness sensor 40 detects the notch position Nt of the wafer W. The control device 50 can identify the notch position Nt of the wafer W based on a detection signal of the film thickness sensor 40.
The notch position Nt is a reference position of an angle in the circumferential direction of the wafer W. The storage unit 50a stores a relationship between a rotation angle of the polishing head 10 at the start of polishing the wafer W and the notch position Nt. Therefore, the control device 50 determines the slip of the wafer W based on the relationship between the rotation angle of the polishing head 10 and the notch position Nt.
If the wafer W is slipped, the control device 50 calculates a correction amount corresponding to the slip of the wafer W, and based on the calculated correction amount, changes an initial target pressing actuator 11 specified at the start of polishing the wafer W. By such a change, even if the wafer W is slipped due to polishing of the wafer W, the control device 50 can accurately control the film thickness profile of the wafer W.
The polishing belt 60 includes two belt rollers 62A, 62B, and a belt 61 stretched between the belt rollers 62A, 62B. The belt rollers 62A, 62B are configured to rotate in the same direction. The belt 61 rotates by driving the belt rollers 62A, 62B.
The belt 61 has a polishing surface 61a formed on its surface. Therefore, by lowering the polishing head 10 that holds the wafer W and pressing the wafer W against the polishing surface 61a of the rotating belt 61, the wafer W is polished. When polishing the wafer W, the belt 61 located below the wafer W moves linearly along its traveling direction.
The polishing apparatus 1 includes a liquid supply nozzle 70 arranged upstream of the polishing head 10 in the traveling direction of the belt 61. Similar to the liquid supply nozzle 31, the liquid supply nozzle 70 is configured to supply a liquid (e.g., polishing liquid or pure water).
The polishing belt 60, which moves linearly, can produce the same relative movement amount with respect to the surface to be polished of the wafer W. Therefore, by pressing the wafer W held by the polishing head 10 against the polishing surface 61a, it is possible to polish the wafer W without causing relative movement on the polishing head 10 side to equalize the relative speed across the entire surface to be polished of the wafer W.
In another embodiment, the polishing belt may be moved linearly using a so-called roll-to-roll mechanism in which the polishing belt is wound around an unwinding roller and then wound up by a take-up roller.
In the embodiment, the airbags 111 may be arranged in a grid pattern or in a concentric pattern as long as they are arranged over the entire actuator holding surface 8 of the polishing head 10. In one embodiment, the airbags 111 may be arranged randomly.
The polishing apparatus 1 includes a plurality of fluid supply lines 112 connected to a plurality of airbags 111. The number of the fluid supply lines 112 corresponds to the number of the airbags 111. The control box 14 accommodates various devices (e.g., electropneumatic regulators, valves, etc.) for controlling a compressed gas supplied to each airbag 111. The fluid supply lines 112 and the control lines 12 (see
In this embodiment, the head rotation mechanism 15 rotates the polishing head 10 within a predetermined range of rotation angles without continuously rotating the polishing head 10. There is no need to connect a joint (e.g., rotary joint) to each fluid supply line 112. Therefore, problems such as an increase in the size of the polishing head 10 or an increase in the cost of the polishing apparatus 1 do not arise.
In one embodiment, the embodiment shown in
The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-077012 | May 2023 | JP | national |
