Determining the orientation of the substrate at init.

Abstract

A method for processing a substrate includes polishing the front surface of the substrate on a first pad connected to a first platen. The method further includes transferring the substrate from the first pad to a second pad connected to a second platen using a carrier head. The method further includes moving the carrier head to a scanning position to position the edge of the substrate on an orientation sensor located at the rotation center of the second pad. The method further includes scanning the edge of the substrate using the orientation sensor to generate a signal. The method further includes analyzing the signal to locate a reference mark on the substrate and to determine the rotational orientation of the substrate relative to the carrier head.

Description

Technical Field

[0004] , , ,

[0001]

[0001] This disclosure relates to chemical mechanical polishing (CMP), and more particularly, to analyzing the endpoint of a CMP process.

Background Art

[0002]

[0002] Integrated circuits are typically formed on a substrate by continuously depositing conductive, semiconductive, and / or insulating layers on a semiconductor substrate. In various manufacturing processes, planarization of the layers on the substrate is required. For example, one manufacturing step includes depositing a fill layer on a non-planar surface and planarizing the fill layer. In certain applications, the fill layer is planarized until the top surface of the patterned layer is exposed. For example, a metal layer can be deposited on a patterned insulating layer to fill trenches and holes within the insulating layer. After planarization, the remaining portions of the metal within the trenches and holes of the pattern layer form vias, plugs, and lines to provide conductive paths between integrated circuits (ICs) on the substrate. As another example, a dielectric layer can be deposited on a patterned conductive layer and then planarized to enable subsequent photolithography steps.

[0003]

[0003] Chemical mechanical polishing (CMP) is a recognized method of planarization. In this planarization method, it is usually necessary to place the substrate on a carrier head. The exposed surface of the substrate, i.e., the surface with layer deposition, is usually arranged to abut against a rotating polishing pad. The carrier head applies a controllable load to the substrate to press the substrate against the polishing pad. Usually, a polishing slurry having abrasive particles is supplied to the surface of the polishing pad and spreads between the substrate and the polishing pad. The polishing pad and the carrier head rotate at a constant rotational speed respectively, and the abrasive slurry removes material from one or more layers.

[0004]

[0004] However, in conventional CMP processes, it is not possible to determine the rotational orientation of the substrate relative to the carrier head after the substrate has been transferred to the polishing pad. As a result, the rotational orientation of the substrate is unknown during the endpoint analysis of the conventional CMP process. In order to improve the endpoint analysis of the CMP process, it is necessary in the art to determine the rotational orientation of the substrate relative to the carrier head in situ. [Overview of the project]

[0005]

[0005] In one embodiment, a method for processing a substrate includes polishing the front surface of the substrate on a first pad connected to a first platen. The method further includes transferring the substrate from the first pad to a second pad connected to a second platen using a carrier head. The method further includes moving the carrier head to a scanning position to position the edge of the substrate on an orientation sensor located at the rotation center of the second pad. The method further includes scanning the edge of the substrate using the orientation sensor to generate a signal. The method further includes analyzing the signal to locate a reference mark on the substrate and to determine the rotational orientation of the substrate relative to the carrier head.

[0006]

[0006] In one embodiment, a method for polishing a substrate includes scanning the edges of the substrate using an orientation sensor located at the rotation center of the platen. The method further includes analyzing data acquired by the orientation sensor to determine the position of a reference mark on the substrate relative to a carrier head holding the substrate. The method further includes polishing the front surface of the substrate. The method further includes monitoring the front surface during polishing using an endpoint sensor embedded in the platen that scans the front surface. Monitoring includes identifying the portion of the front surface being scanned by the endpoint sensor using the determined position of the reference mark relative to the carrier head.

[0007]

[0007] In one embodiment, the polishing system includes a polishing station comprising a platen, a carrier head, an orientation sensor, a plurality of endpoint sensors, and a controller. The platen includes a polishing pad. The carrier head is configured to rotate the substrate. The orientation sensor is embedded in the platen at the center of rotation of the platen. The orientation sensor is configured to scan the edge of the substrate including a reference mark. The plurality of endpoint sensors are embedded in the platen around the orientation sensor. Each endpoint sensor is configured to monitor the surface of the substrate being polished on the pad. The controller communicates with the orientation sensor and the endpoint sensors. The controller is configured to analyze the data acquired by the orientation sensor to determine the position of the reference mark relative to the carrier head.

[0008]

[0008] To allow for a more detailed understanding of the above-described features of the Disclosure, a more detailed description of the Disclosure, which has been briefly summarized above, can be obtained by referring to embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings only illustrate exemplary embodiments of the Disclosure and should not be considered limiting in scope, and the Disclosure may permit other equally effective embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic top view of an exemplary chemical mechanical polishing (CMP) system. [Figure 2A] Figure 1 shows a schematic cross-sectional view of an exemplary polishing station of the CMP system according to an embodiment described herein. [Figure 2B] This is a top view of the front of a substrate polished on the polishing station shown in Figure 2A, according to an embodiment described herein. [Figure 3A] Figure 2A shows a schematic top view of a carrier head positioned at a scanning position on the polishing pad from the polishing station, according to an embodiment described herein. [Figure 3B]Figure 2A shows a top view of the front surface of a substrate scanned by the orientation sensor of the polishing station according to an embodiment described herein. [Figure 4] The following is an example signal obtained by the orientation sensor of the polishing station in Figure 2A, according to an embodiment described herein. [Figure 5] Figure 2A shows a top view of the front of the substrate, illustrating the scanning path of the endpoint sensor of the polishing station according to an embodiment described herein. [Figure 6] This graph shows an example trace acquired by an endpoint sensor during the CMP process. [Figure 7A] Figure 1 shows a partial cross-sectional view of a substrate being polished at the first polishing station of the CMP system according to an embodiment described herein. [Figure 7B] Figure 1 shows a partial cross-sectional view of a substrate after polishing at the first polishing station of the CMP system according to an embodiment described herein. [Figure 7C] Figure 1 shows a partial cross-sectional view of a substrate being polished at the second polishing station of the CMP system according to an embodiment described herein. [Figure 7D] Figure 1 shows a partial cross-sectional view of a substrate after polishing at the second polishing station of the CMP system according to an embodiment described herein. [Figure 8] This is a flowchart of a method for processing a substrate according to an embodiment described herein. [Figure 9] This is a flowchart of a method for processing a substrate according to an embodiment described herein. [Modes for carrying out the invention]

[0010]

[0023] For ease of understanding, the same reference numerals were used where possible to indicate identical elements common to the figures. It is assumed that elements and features of one embodiment may be usefully incorporated into other embodiments without further description.

[0011]

[0024] This specification discloses an apparatus and method for determining the rotational orientation of a substrate in situ. This rotational orientation is used to improve endpoint analysis of chemical mechanical polishing (CMP) processes.

[0012]

[0025] Figure 1 is a top view showing one embodiment of the CMP system 100. The CMP system 100 includes a factory interface module 102, a cleaner 104, a polishing module 106, and a controller 190. A substrate 115, such as a silicon wafer with one or more layers deposited on it, is processed within the CMP system 100 to polish the surface of the substrate 115.

[0013]

[0026] A wet robot 108 is provided to transfer the substrate 115 between the factory interface module 102 and the polishing module 106. The wet robot 108 may also be configured to transfer the substrate 115 between the polishing module 106 and the cleaner 104. The factory interface module 102 includes a dry robot 110 configured to transfer the substrate 115 between one or more cassettes 114, one or more transfer platforms 116, one or more measurement stations 117, and one or more pre-positioning stations 118 of the factory interface 102. The substrate 115 is loaded into the CMP system 100 via the cassettes 114. In one embodiment shown in Figure 1, four substrate storage cassettes 114 are shown. The dry robot 110 in the factory interface 102 has a range of motion sufficient to facilitate transfer between the four cassettes 114 and one or more transfer platforms 116. Optionally, the dry robot 110 may be mounted on rails or tracks 112 to position the robot 110 laterally within the factory interface module 102. The dry robot 110 is further configured to receive the substrate 115 from the cleaner 104 and return the cleaned and polished substrate to the substrate storage cassette 114.

[0014]

[0027] Figure 1 shows an exemplary polishing module 106 that includes a plurality of polishing stations 124 in which a substrate 115 is polished while it is held in a carrier head 210 (e.g., a polishing head). Each polishing station 124 includes a conditioning assembly 132 and a polishing fluid supply module 135. Although polishing module 106 is shown to have three polishing stations 124, polishing module 106 may have more than three polishing stations 124. For example, polishing module 106 may have two pairs of polishing stations 124, with each pair of stations 124 processing the substrate 115 independently of the other pair. The polishing stations 124 are sized to interface with one or more carrier heads 210 to facilitate polishing of the substrate 115. The carrier heads 210 are coupled to carriages (not shown) mounted on overhead tracks 128, shown as dashed lines in Figure 1. The overhead track 128 allows for selective positioning of the carriage around the polishing module 106, thereby facilitating selective positioning of the carrier head 210 over the polishing station 124 and the load cup 122. In the embodiment shown in Figure 1, the overhead track 128 has a circular configuration that allows the carriage holding the carrier head 210 to rotate selectively and independently above and / or out of the load cup 122 and the polishing station 124. In addition, the overhead track 128 facilitates sweeping the rotating carrier head 210 against the polishing station 124 during polishing. The polishing station 124 will be described in more detail with reference to Figure 2.

[0015]

[0028] Each polishing station 124 includes a polishing pad 204 having a polishing surface (e.g., the polishing surface 204A in FIG. 2) capable of polishing the substrate 115. Each polishing station 124 includes a conditioning assembly 132 and a polishing fluid supply module 135. In one embodiment, the conditioning assembly 132 may include a pad conditioning assembly 140 that removes polishing debris and dresses the polishing surface of the polishing pad 204 by opening the pores of the polishing pad 204 using a pad conditioning disk 133. In another embodiment, the polishing fluid supply module 135 may include a fluid supply arm 134 for supplying slurry. In one embodiment, each polishing station 124 includes a pad conditioning assembly 132. In one embodiment, the fluid supply arm 134 is configured to supply a fluid stream (e.g., the slurry 222 in FIG. 2) to the polishing station 124. The polishing pad 204 is supported on a platen (e.g., the platen 202 in FIG. 2) that rotates the polishing pad 204 during processing. Each polishing station 124 includes a polishing pad 204 fixed to a rotatable platen 202. Various polishing pads 204 may be used at various polishing stations 124 to control the material removal of the substrate 115.

[0016]

[0029] At least one load cup 122, such as the two load cups 122 shown in FIG. 1, is near the lower right corner of the polishing module 106 between the polishing stations 124 closest to the wet robot 108. The load cup 122 can perform a plurality of functions, including cleaning the carrier head 210, receiving the substrate 115 from the wet robot 108, cleaning the substrate 115, and loading the substrate 115 into the carrier head (e.g., the carrier head 210 in FIG. 2).

[0017]

[0030] The substrate 115 typically has fiducial marks such as a notch, a flat end, or other types of features that can be used to identify the crystal orientation of the substrate 115 and to note the rotational orientation of the front surface of the substrate 115 with respect to the central axis. In certain embodiments, the factory interface module 102 may further include a pre-aligner 118 for positioning the substrate 115 in a known desired rotational orientation. By pre-aligning the substrate 115 in the desired rotational orientation, it becomes possible to transfer the substrate 115 to a load cup 122 having a known rotational orientation. Thus, the carrier head 210 can pick up the substrate 115 in a known rotational orientation with respect to the carrier head 210. For example, the pre-aligner 118 may include a fiducial mark detection system such as a light barrier sensor (not shown) to sense when the fiducial mark is at a particular angular position.

[0018]

[0031] In certain embodiments, the substrate 115 is placed within the measurement station 117 by the dry robot 110 before being placed on the transfer platform 116. For example, the dry robot 110 may transfer the substrate 115 from the pre-aligner 118 to the measurement station 117. The measurement station 117 is used to measure various aspects of the substrate 115. The measurement station 117 may use an optical sensor, an eddy current sensor, a resistance sensor, or other sensors to measure the substrate 115. For example, the measurement station 117 may measure the thickness of an upper layer on the patterned surface of the substrate 115. The controller 190 receives measurements that may be used to facilitate the processing of the substrate 115 within the CMP system 100. The dry robot 110 can transfer the substrate 115 to the transfer platform 116 after the substrate 115 has been measured within the measurement station 117.

[0019]

[0032] The wet robot 108 is configured to transfer the substrate 115 from the transfer platform 116 to one of the load cups 122. The rinsed carrier head 210 is moved above the load cup 122 along with the unpolished substrate 115. The unpolished substrate 115 is then chucked onto the carrier head 210, which then moves to a position above the pad 204 of the polishing station 124 to begin the CMP process.

[0020]

[0033] The controller 190 controls aspects of the CMP system 100 during the CMP process (e.g., polishing process, polishing treatment, polishing). In certain embodiments, the controller 190 is one or more programmable digital computers running digital control software. The controller 190 may include a CPU (e.g., processor) 191 located near the polishing apparatus, a programmable computer such as a personal computer. The controller may include memory 192 and support circuitry 193. The controller 190 can, for example, adjust the rotation of the polishing pads 204 and the carrier head 210 to perform a desired CMP process and facilitate monitoring of the endpoints of the CMP process. The CMP processing system 100 is powered by a power supply 180 (e.g., a power supply configured to power the components of the CMP processing system 100).

[0021]

[0034] The platen 202 and carrier head 210 each have rotation sensors, such as encoders, to determine their rotational position during the CMP process. As shown in Figure 1, a platen encoder 195, a first head encoder 196, and a second head encoder 197 are integrated into the controller 190. The platen encoder 195 is configured to determine the rotational direction (e.g., angle) of the platen 202 and pad 204. The first head encoder 196 is configured to determine the rotational direction of each carrier head 210. The second head encoder 197 is configured to determine the position of each carrier head 210 on the polishing pad 204 (e.g., along the sweep path 302 of the carrier head 210 in Figure 3A). Thus, the controller 190 can determine and track the rotational direction of the carrier heads 210 relative to the platen 202 during the CMP process. In some embodiments, each carrier head 210 has its own dedicated first head encoder 196 and second head encoder 197. In a further embodiment, the controller 190 may use an encoder and an internal timing element to calculate the rotational speed of the carrier head 210 and / or platen 202 and polishing pad 204.

[0022]

[0035] The substrate 115 may be polished at one or more of the polishing stations 124. For example, the carrier head 210 can remove the unpolished substrate 115 from the load cup 122. The carrier head 210 and the substrate 115 chucked therein are then moved to a first polishing station 124 (e.g., the polishing station 124 in the upper right corner of the polishing module 106 closest to the cleaner 104). A CMP polishing process is then performed on the first polishing station 124, such as removing a first layer formed on the substrate 115. Once the substrate 115 has finished polishing in the first polishing station 124, the carrier head 210 moves the substrate 115 to a second polishing station 124 (e.g., the polishing station 124 in the upper left corner of the polishing module 106) for additional CMP polishing. For example, the second polishing station 124 can polish the surface of the substrate 115 to form trench lines of a desired height. In some embodiments, the carrier head 210 and the substrate 115 may optionally be transferred from a second polishing station 124 to a third polishing station 124 (for example, the polishing station 124 in the lower left corner of the polishing module 106) to perform additional polishing on the substrate 115.

[0023]

[0036] After polishing, the carrier head 210 moves the polished substrate 115, chucked in the carrier head 210, above the load cup 122, where the polished substrate 115 is then placed inside the load cup 122. The wet robot 108 transports the polished substrate 115 from the load cup 122 to a cleaning chamber in the cleaner 104, where slurry residue and other contaminants accumulated on the surface of the substrate 115 during polishing are removed. In the embodiment shown in Figure 1, the cleaner 104 includes two pre-cleaning modules 144, two megasonic cleaner modules 146, two brush box modules 148, two spray jet modules 150, and two dryers 152. The dry robot 110 then removes the substrate 115 from the cleaner 104. In some embodiments, the dry robot 110 transports the substrate 115 to a measurement station 117 for further measurement. In certain embodiments, the post-polishing measurements can be used to adjust the polishing parameters for subsequent substrates. Finally, the dry robot 110 returns the circuit board 115 to one of the cassettes 114.

[0024]

[0037] Figure 2A shows a schematic cross-sectional view of the polishing station 124 of the CMP system 100 in Figure 1. As shown, the polishing station 124 further includes a plurality of endpoint detection sensors 224 and orientation sensors 250. A substrate 115 located within the carrier head 210 is shown engaged with the polishing surface 204A of a pad 204 connected to a platen 202.

[0025]

[0038] Figure 2B is a top view of the substrate 115 showing the front surface 230 of the substrate 115 as it engages with the polishing pad 204 during polishing. The front surface 230 includes a patterned portion 232 and an unpatterned portion 234. The patterned portion 232 (e.g., a patterned surface) is a portion of the substrate 115 on which multiple semiconductor devices are formed during one or more processes. As shown, the patterned portion 232 is divided into multiple full dies 233 arranged in a grid pattern. Each die 233 is a specific semiconductor device formed on the substrate 115. For example, a semiconductor device includes one or more layers formed by one or more processes such as physical vapor deposition (PVD) or atomic layer deposition (ALD).

[0026]

[0039] The unpatterned portion 234 is the portion of the front surface 230 surrounding the patterned portion 232. The semiconductor device is not formed on the unpatterned surface 234. The unpatterned portion 234 may be exposed to the same processing environment that forms the patterned portion 232. While the semiconductor device is being formed on the patterned portion 232, materials such as barrier metal may be deposited on the unpatterned surface 234. In some embodiments, the unpatterned portion 234 may be a partially patterned portion, which is incomplete and contains only a partial die. The surface area of ​​the unpatterned portion 234 may not be uniform around the patterned portion 232. As shown in Figure 2B, the surface area of ​​the unpatterned surface 234 varies around the patterned portion 232 depending on the shape of the patterned portion 232. Thus, the unpatterned surface 234 has portions with a larger surface area than other portions.

[0027]

[0040] The substrate 115 includes reference marks 236 at its edges, and consequently at the edges of the unpatterned portion 234. The reference marks 236 are fixed features formed on the substrate 115, depending on the doping type and crystal orientation of the substrate 115. While the reference marks 236 are shown as V-shaped notches formed at the edges of the substrate 115 in Figure 2B, the reference marks 236 may be other features. For example, the reference marks 236 may be one or more flat edges of the substrate 115.

[0028]

[0041] The substrate 115 has a first symmetry line 235 that passes through the center of a reference mark 236. The unpatterned surface 234 is generally symmetric with respect to this first symmetry line 235. Thus, there are first regions 237 on both sides of the symmetry line 235 adjacent to the reference mark 236, having substantially the same surface area. Furthermore, a second region 238, similar to the reference mark 236 and having a similar surface area to the first region 237, exists at the opposite end of the substrate 115. While the unpatterned surface 234 may be generally symmetric with respect to the first symmetry line 235, the circuits formed on the individual dies 233 of the patterned surface 232 may or may not be symmetric with respect to this first symmetry line 235.

[0029]

[0042] Returning to Figure 2A, the polishing pad 204 is fixed to the platen 202, for example, by using an adhesive such as a pressure-sensitive adhesive (PSA) layer (not shown) placed between the polishing pad 204 and the platen 202. The carrier head 210 facing the platen 202 and the polishing pad 204 mounted thereon includes a flexible diaphragm 212 configured to apply different pressures to the back surface of the substrate 115, which is positioned between the carrier head 210 and the polishing pad 204. The flexible diaphragm 212 is also configured to chuck the substrate 115 to the carrier head 210 in order to allow the carrier head 210 to move the substrate 115 around the polishing module 106. The carrier head 210 includes a carrier ring 218 surrounding the substrate 115, which holds the substrate 115 within the head 210 during polishing. While the carrier head 210 rotates around the carrier head axis 216, the flexible diaphragm 212 presses the front surface 230 (Figure 2B) of the substrate 115 against the polishing surface 204A of the polishing pad 204. During polishing, a downward force on the carrier ring 218 presses the carrier ring 218 against the polishing pad 204, improving the uniformity of the polishing process and preventing the substrate 115 from sliding off from under the carrier head 210. In certain embodiments, the carrier head 210 includes a shaft 211 having an axis collinear with the carrier head axis 216. In further embodiments, the platen 202 and the carrier head 210 each have a mechanism or motor (not shown) that drives their rotation.

[0030]

[0043] In some embodiments, both the platen 202 and the polishing pad 204 rotate around a common platen axis 205. In some embodiments, the polishing pad 204 rotates in the same direction as the carrier head 210. For example, both the polishing pad 204 and the carrier head 210 rotate counterclockwise. The polishing pad 204 and the carrier head 210 may rotate at the same speed or at different speeds during the polishing operation. As shown in Figure 2A, the polishing pad 204 has a larger surface area than the front surface area 230 of the substrate 115. However, in further embodiments, the polishing pad 204 has a smaller surface area than the front surface area 230 of the substrate 115.

[0031]

[0044] Figure 2A also shows one exemplary embodiment of the endpoint detection sensors 224. Each endpoint detection sensor 224 is positioned radially from the platen axis 205. The endpoint sensors 224 are positioned within a platen opening 226 formed in the platen 202, beneath an optically transparent feature 227 (e.g., a window) of the polishing pad 204. The endpoint detection sensors 224 direct light through the platen opening 226 and window 227 of the front surface 230 of the substrate 115 to detect characteristics of the front surface 230 as the endpoint sensor 224 passes beneath the substrate 115 during polishing. The controller 190 uses the data collected by the endpoint detection sensors 224 to determine when an endpoint of the CMP process has been reached. An endpoint may be, for example, when a desired thickness of the layer formed on the patterned surface 232 is reached. For example, an endpoint may be reached when the metal in a plurality of trench lines formed on the patterned portion 232 reaches a desired thickness.

[0032]

[0045] Although the endpoint detection sensor 224 is shown as an optical sensor, the endpoint sensor 224 may be any other suitable sensor capable of monitoring changes in the patterned portion 232 during the CMP process. For example, the endpoint sensor 224 may be an eddy current sensor or an inductive current sensor. The eddy current sensor and the inductive current sensor may be embedded in the platen 202 and / or pad 204, and the transparent features 227 and the opening 226 may be omitted. Although the polishing station 124 is shown to have three endpoint detection sensors 224 arranged around the orientation sensor 250, as demonstrated by the three transparent features 227 in Figure 1, the polishing station 124 may include fewer than three or more endpoint sensors 224.

[0033]

[0046] Each endpoint detection sensor 224 is positioned at a fixed distance from the rotation center of the platen 202 (e.g., the platen axis 205). The platen encoder 195 tracks the rotational position of the platen 202 and the pad 204. The controller 190 can determine the position of the endpoint sensors 224 as the platen 202 rotates, based on the fixed position of the endpoint sensors 224 and the rotational information obtained from the platen encoder 195.

[0034]

[0047] Figure 2A also shows the orientation sensor 250. As will be explained in relation to Figures 3A and 3B, the orientation sensor 250 is used to locate the reference mark 236 in place so that the controller 190 can determine the rotational orientation of the substrate 115 relative to the carrier head 210 and pads 204. The controller 190 can correlate the confirmed position of the reference mark 236 with the rotational orientation of the carrier head 210 because the substrate 115 rotates with the carrier head 210. The orientation sensor 250 is used to confirm the rotational orientation of the substrate 115 after it has been transferred from one polishing station 124 to another. In other words, it is not necessary to remove the substrate 115 from the polishing module 106, pass it through the cleaner 104, and place it in the pre-positioning unit 118 or measurement station 117 to confirm the rotational orientation of the substrate 115 before polishing it on the second or third polishing station 124.

[0035]

[0048] By knowing the rotational orientation of the substrate 115 and the carrier head 210, as well as the position of each endpoint sensor 224 during polishing, the controller 190 can determine which portion of the front surface 230 of the substrate 115 is being scanned by a particular endpoint sensor 224. In other words, the controller 190 can correlate the position and orientation of the substrate 115 with the position of each endpoint sensor 224 during the polishing process.

[0036]

[0049] The orientation sensor 250 is positioned at the center of rotation of the platen 202 such that the axis of rotation of the sensor 250 is collinear with the platen axis 205. The endpoint sensor 224 is positioned around the orientation sensor 250 and orbits the platen axis 205 as the platen 202 rotates. To locate the reference mark 236, the carrier head 210 is moved to a scanning position as shown in Figure 2A (see also Figure 3A) so that the edge of the substrate 115 is positioned over the orientation sensor 250. This allows the orientation sensor 250 to scan the edge of the substrate 115 to locate the reference mark 236. In some embodiments, the orientation sensor 250 scans the edge of the substrate 115 as the carrier head 210 makes one or more full rotations around the carrier head axis 216 to locate the reference mark 236. In other embodiments, the reference mark 236 is located only after a partial rotation of the carrier head 210.

[0037]

[0050] In some embodiments, the orientation sensor 250 is an isotropic electromagnetic sensor, as shown in Figure 2A. In some embodiments, the orientation sensor 250 is an eddy current sensor, an optical sensor, or another sensor capable of detecting the reference mark 236. As shown, the orientation sensor 250 is partially embedded in both the platen 202 and the pad 204. In some embodiments, the orientation sensor 250 is embedded only in the platen 202 and covered by the pad 204.

[0038]

[0051] In some embodiments, the layer partially or completely covers the front surface 230, so that both the patterned portion 232 and the unpatterned portion 234 are completely or partially covered by the layer. This layer may be deposited to form another layer or feature on the die 233 of the patterned portion 232, which is polished in a CMP system. The orientation sensor 250 can scan the edge of the substrate 115 to locate the reference mark 236 even when the layer is deposited on both the patterned portion 232 and the unpatterned portion 234. For example, the orientation sensor 250 can obtain data indicating that a portion of the layer scanned by the orientation sensor 250 was on the underlying patterned portion 232 or unpatterned portion 234. In other words, the controller 190 can distinguish between the patterned portion 232 and the unpatterned portion 234 even if both are at least partially hidden by the same layer. In addition, the data acquired by the orientation sensor 250 can show variations in the scanned material (e.g., variations in the unpatterned area 234) even if the layer completely or partially covers the front surface 230.

[0039]

[0052] Figure 3A shows a schematic top view of the polishing station 124, indicating the carrier head 210 to scan position to locate reference mark 236. The conditioning assembly 132 and polishing fluid supply module 135 are omitted. The head 210 is movable relative to the pad 204 along the sweep path 302 to sweep the substrate 115 along the polishing surface 204A during the polishing process. The endpoint sensor 224 traverses the sweep path 302 as the platen 202 rotates. The endpoint sensor 224 passes below the substrate 115 when the carrier head 210 positions the substrate 115 at one or more positions along the sweep path 302 within the travel path of the endpoint sensor 224 as the platen 202 rotates.

[0040]

[0053] The carrier head 210 is shown in the scanning position, with the edge of the front surface 230 positioned at least partially above the orientation sensor 250. The carrier head 210 rotates relative to the orientation sensor 250 and the platen 202, while the orientation sensor 250 scans the edge of the substrate 115 to locate the reference mark 236. After the substrate 115 is transferred from one polishing station 124 to another within the polishing module 106, the carrier head 210 moves to the scanning position, allowing it to perform a scan 310 (see Figure 3B) of the front surface 230 to confirm the rotational orientation of the substrate 115.

[0041]

[0054] Figure 3B shows a scan 310 of the front surface 230 of the substrate 115 by the orientation sensor 250. The scan 310 shows the path the orientation sensor 250 takes under the front surface 230 to collect data as the carrier head 210 rotates the substrate 115 relative to the orientation sensor 250. The scan 310 is performed near the edge of the front surface 230. The scan 310 is brought close enough to the edge of the substrate 115 so that the scan 310 passes over a portion of the reference mark 236. In some embodiments, the orientation sensor 250 performs the scan 310 only under the unpatterned surface 234 when the carrier head 210 is in the scanning position. Alternatively, the orientation sensor 250 can complete the scan 310 along the edge of the substrate 115, passing over both the patterned surface 232 and the unpatterned surface 234.

[0042]

[0055] The orientation sensor 250 collects data about the front surface 230 along the scan 310. This data is sent to the controller 190 for analysis to determine the position of the reference mark 236. The first head encoder 196 simultaneously records the rotational position of the carrier head 210 while the orientation sensor 250 collects data along the scan 310. The controller 190 associates the data acquired from the orientation sensor 250 with the rotational position of the carrier head 210 from which the data was acquired. In other words, the controller 190 can match the data acquired from the orientation sensor 250 with the rotational position of the carrier head 210. This allows the controller 190 to analyze the data and determine the position of the reference mark 236 relative to the rotational orientation of the carrier head 210. Once the position of the reference mark 236 relative to the carrier head 210 is known, the rotational orientation of the substrate 115 can be determined.

[0043]

[0056] In some embodiments, the carrier head 210 rotates only once around the carrier head axis 216 for the orientation sensor 250 to collect sufficient data along the scan 310 to determine the position of the reference mark 236. In other embodiments, the carrier head 210 rotates more than one time to collect sufficient data along the scan 310 and determine the position of the reference mark 236.

[0044]

[0057] In some embodiments, both the platen 202 and the carrier head 210 rotate as the orientation sensor 250 scans the substrate 115. In other embodiments, the platen 202 remains stationary while the carrier head 210 rotates, allowing the orientation sensor 250 to scan the substrate 115. Once the rotational orientation of the substrate 115 is confirmed, the controller 190 can start rotating the platen 202 to initiate the CMP process.

[0045]

[0058] Figure 4 shows a graph 400 of an exemplary signal 401 of data collected by the orientation sensor 250 when scanning the front surface of a rotating substrate 115. This signal 401 indicates the signal intensity at various rotational positions of the carrier head 210. The scanned substrate 115 has a different front surface than the front surface 230 shown in Figures 2B and 3B. However, the scanned substrate 115 has a front surface with similar features to those described for the front surface 230. Therefore, the same reference numerals will be used to explain the analysis of signal 401. Furthermore, the signal generated by the orientation sensor 250 depends on the shape and / or material of the unpatterned portion 234 and the patterned portion 232. Therefore, signal 401 shown in Figure 4 is just one example of a signal obtained during scanning of an exemplary substrate 115 to illustrate how the controller 190 can locate the reference mark 236.

[0046]

[0059] The X-axis in Figure 4 indicates the rotational position of the carrier head 210. The Y-axis in Graph 400 indicates the signal intensity in arbitrary units (AU) at the rotational position of the carrier head 210. The signal intensity varies across the rotational direction of the head 210. This is because the signal reflects the characteristics of the material being scanned. In some embodiments, the orientation sensor 250 may register a stronger signal when scanning the material of the unpatterned portion 234 than the material on the patterned portion 232. For example, the orientation sensor 250 may register a stronger signal for barrier material on the unpatterned surface 234 than for material covering the patterned surface 232. A stronger signal may also be registered if the underlying barrier material on the unpatterned portion 234 is partially beneath layers formed on both the patterned portion 232 and the unpatterned portion 234. The signal intensity may correspond to the size of the area of ​​the unpatterned portion 234 scanned by the orientation sensor 250. In other words, variations in the unpatterned areas 234 result in variations in the signal. For example, a large spike 402 in the signal 401 corresponds to a portion of the unpatterned surface 234, which has a larger surface area than the surface area of ​​the unpatterned surface 234, and a smaller spike 403 corresponds to that. Even if the front surface 230 is completely or partially covered by a layer, differences in area variations in the unpatterned areas 234 can be detected. However, the overall signal intensity of a substrate 115 with a layer formed on the front surface 230 may be lower or higher than the signal intensity obtained when scanning a substrate 115 that does not have a layer that at least partially covers both the patterned areas 232 and 234. For example, if the layer covering both the patterned areas 232 and the unpatterned areas 234 is made of a conductive material such as metal, the signal will be higher.

[0047]

[0060] Signal 401 is generally repeated in some embodiments due to the symmetry of the unpatterned surface 234 around the first symmetry line 235, as shown in Figure 4. Thus, there is a pattern in signal 401 that the controller 190 can analyze to find the position of the reference mark 236 relative to the carrier head 210, and thus the rotational orientation of the substrate 115 in the carrier head 210. In some embodiments, the analysis of signal 401 includes determining candidate parts of the signal that correspond to parts of the substrate 115 that include the reference mark 236. Then, candidate reference mark signatures 407 corresponding to the reference mark 236 are analyzed. Once the reference mark signature 407 is found, the controller 190 can determine the rotational orientation of the substrate 115 relative to the carrier head 210.

[0048]

[0061] Signal 401 includes a first pair 405 and a second pair 406 of large spikes 402. Figure 4 shows each pair of spikes 405, 406 arranged in a dashed area for illustrative purposes. In this example, the large spikes 402 of signal 401 correspond to either the first region 237 or the second region 238 of the unpatterned surface 232. The first pair 405 and the second pair 406 of spikes have similar signal intensities due to the similarity of the surface areas of the first region 237 and the second region 238. In addition, a 180-degree rotation of the carrier head 210, indicated as D1, exists between the centers of the two pairs of spikes 405, 406. This is expected as it corresponds to the symmetry of the unpatterned surface 234.

[0049]

[0062] Each pair of spikes 402, 405, 406 is a candidate signal corresponding to a portion of the substrate 115 containing the reference mark 236. In other words, each spike pair 405, 406 could be a portion of the substrate having a first region 237 in which the reference mark 236 is located. The controller 190 knows that the reference mark 236 is at the rotational position of the carrier head 210 corresponding to one of the candidates. In this case, the reference mark 236 is in the trough between the first pair of spikes 402 405 and one of the second pairs of spikes 406. The controller 190 analyzes the signals of the candidates for the reference mark signature 407. In this example, the scanned substrate 115 had a notch for the reference mark 236. Signal 401 shows a slight dip between the second pair of large spikes 406 compared to the signal between the first pair of large spikes 405. This drop is caused by the notch being a break (e.g., a discontinuity) in the unpatterned surface 234, which causes the orientation sensor 250 to position a lower signal intensity at the rotational position of the carrier head 210. This signal drop is a reference mark signature 407. The reference mark signature 407 can be detected by comparing the candidate signal to a threshold, such as a threshold signal intensity. Thus, if the signal intensity meets or exceeds the threshold signal intensity, a reference mark 236 can be identified.

[0050]

[0063] The controller 190 can determine that the notch is between the first pair 405 of the large spikes 402, and that the center of the second pair 406 of the large spikes 402 is the opposite point on the substrate 115 to the notch. In some embodiments, the controller 190 can use the center of the reference mark signature 407 to determine the rotational position of the notch relative to the carrier head 210. Since the reference mark 236 is in a fixed position on the substrate 115, the controller can use the position of the reference mark 236 to determine the rotational orientation of the substrate 115. Furthermore, the controller 190 can determine that the illustrated point 410 in the signal corresponds to a point on the unpatterned surface of the substrate 115 that is 90 degrees from the reference mark 236 along the outer edge of the substrate 115.

[0051]

[0064] In some embodiments where the reference mark 236 is a flat surface (e.g., a flat edge) rather than a notch, the signal associated with the first region 237 is different from that of the second region 238 on the opposite side of the substrate. This is because the edge of the substrate on the opposite side of the flat surface is rounded, and the flat surface makes the surface area of ​​the first region 237 smaller than that of the second region 238. In certain embodiments, the controller 190 can distinguish the signal obtained from the first region 237 from the signal obtained from the second region 238 based on this difference in surface area.

[0052]

[0065] Alternatively, scanning a substrate 115 having a flat surface as a reference mark may result in a reference mark signature 407, which is a drop in signal intensity. As the carrier head 210 rotates the substrate 115 relative to the orientation sensor 250, the orientation sensor 250 may pass along or outside the edge of the flat surface. For example, the signal intensity may drop during the rotation period of the carrier head 210 as the orientation sensor 250 passes from under the front surface 230 and scans the empty space for a flat reference mark 236. As the orientation sensor 250 passes under the front surface 230, the signal intensity increases again. Thus, the drop in signal intensity is due to the orientation sensor 250 detecting a lack of material related to the front surface 230 of the substrate 115. The center of the reference mark 236 may correspond to the center of the signal intensity drop. In some embodiments, the controller 190 may use the signal intensity drop between two portions of the signal identified as a first region 237 candidate to determine the position of the center of the flat surface relative to the carrier head 210.

[0053]

[0066] Therefore, the controller 190 can analyze the signal 401 acquired from the orientation sensor 250 to determine a portion of the signal that is a candidate for a part of the unpatterned surface 234 containing the reference mark 236. A candidate portion of the signal may be a pair of spikes in the signal that are offset by 180 degrees from each other. In other words, the controller 190 can identify a pair of candidates on opposite sides of the substrate 115. Once a candidate pair is identified, the controller 190 can analyze each candidate for the reference mark signature 407, such as the decrease in signal intensity between the pair of spikes indicating the presence of the reference mark 236. The reference mark signature 407 may be determined by comparing the two candidates to determine which candidate has the lowest signal intensity between the peaks of the spikes.

[0054]

[0067] In some embodiments, the unpatterned surface 234 of the substrate 115 may have a shape that allows the signal to contain two or more pairs of candidates. In other words, other parts of the unpatterned surface 234 may have a similar surface area to the first region 237 and the second region 238. The controller 190 analyzes each pair of candidates to determine which candidates have the reference mark signature 407. By detecting the reference mark signature 407, the controller 190 can determine where the reference mark 236 is located relative to the carrier head 210.

[0055]

[0068] In some embodiments, the controller 190 may stop the analysis if a reference mark signature 407 is found before analyzing all candidates. For example, the controller 190 may identify multiple candidates. The controller 190 then analyzes each candidate until a reference mark signature 407 is found. If a reference mark signature 407 is found, unanalyzed candidates may not be analyzed by the controller 190. However, in some embodiments, each candidate is analyzed regardless of whether a reference mark signature 407 is found. For example, each candidate may be analyzed to confirm that the reference mark signature 407 is not a false positive.

[0056]

[0069] In some embodiments, the controller 190 locates the reference mark signature 407 by comparing the signal strengths of two or more candidates with a threshold. In other embodiments, the controller 190 can determine the position of the reference mark 236 when a threshold is met or exceeded, without the controller 190 making comparisons among multiple candidates. In other words, the controller 190 can locate the reference mark 236 after a partial rotation of the substrate 115, and thus can locate the carrier head 210 sufficiently to locate the reference mark 236.

[0057]

[0070] In some embodiments, the controller 190 locates the reference mark signature 407 without identifying candidates. For example, the controller 190 may compare the signal 401 to a threshold. The reference mark signature 407 is identified when the signal 401 meets or exceeds the threshold. For example, the reference mark signature 407 may be a decrease in signal intensity relative to a threshold of signal intensity. In some embodiments, the controller 190 may compare the reference mark signature 407 to other features in the signal to confirm that the location of the reference mark has been identified. For example, the controller 190 may compare the location of the reference mark signature to a signature associated with a first region 237.

[0058]

[0071] In some embodiments, the unpatterned portion 234 is not symmetric with respect to the line of symmetry. The controller 190 analyzes the signal up to a threshold, such as the signal intensity of a threshold, in order to determine the reference mark signature. For example, the controller 190 may analyze the signal for a drop above a signal intensity threshold. In some embodiments, the substrate 115 having an asymmetric unpatterned portion may include a region near the reference mark. This region generates a signal when scanned, which the controller 190 can identify as a candidate portion of the substrate containing the reference mark. This candidate is then analyzed for the reference mark signature 407.

[0059]

[0072] The CMP system 100 can process one or more types of substrates 115 and complete one or more polishing steps. The shape of the unpatterned surface 234 is substantially constant across substrates of the same type. As a result, the orientation sensor 250 should generate similar signals for each substrate of the same type, regardless of whether the unpatterned surface 234 is symmetrical with respect to the line of symmetry. Thus, each type of substrate may have a reference signal stored in the controller 190, which includes a reference signature indicating the position of the reference mark 236. The type of substrate 115 can be input to the controller 190, allowing the controller 190 to determine the position of the reference mark 236 by comparing the actual signal from the orientation sensor 250 with the reference signal.

[0060]

[0073] In addition, the CMP process repeats the same desired polishing step for each type of substrate 115, so the material on the front surface 230 is consistent. For example, after polishing the first layer to a desired height at the first polishing station, a scan may be performed at the second polishing station 124 to locate the reference mark 236. Thus, the orientation sensor 250 should generate similar signals for each substrate of the same type at the same stage of the polishing process. The processing stage may also be input to the controller 190 in addition to the type of substrate, so that the controller 190 can determine the position of the reference mark 236 by comparing the actual signal from the orientation sensor 250 with the reference signal.

[0061]

[0074] In some embodiments, the reference signal is a candidate signal, and the reference mark signature is the portion of the candidate signal that satisfies or exceeds a threshold. In some embodiments, the actual signal is superimposed on the reference signal to determine the position of the reference mark. For example, the reference signal can be transformed several times, the reference signal can be roughly aligned with the actual signal, and the reference mark signature can be determined by aligning, for example, the reference signal 407 with the reference signature of the reference signal.

[0062]

[0075] During the CMP process, the controller 190 uses information collected from the platen encoder 195, the first head encoder 196, and the second head encoder 197 to determine and track the position of the carrier head 210 relative to the platen 202. In other words, the controller 190 knows where the carrier head 210 is on the rotating platen 202 at any given time, including knowing the rotational orientation of the carrier head 210 relative to the platen 202. Once the controller 190 has determined the rotational orientation of the substrate 115 relative to the carrier head 210, the controller 190 also knows the rotational orientation and position of the substrate 115 relative to the rotating platen 202 and the endpoint sensor 224 at any given time in the polishing process.

[0063]

[0076] The controller 190 uses the positional information of the substrate 115 and the platen 202 to determine which portion of the front surface 230 is scanned by each endpoint sensor 224 during endpoint analysis. In other words, since the position and rotational orientation of the substrate 115 relative to the head 210 and the platen 202 are known, the controller 190 can correlate the data collected by the endpoint sensors 224 to known positions on the front surface 230. The sweep position of the head 210 relative to the platen 202, and the rotation of both the carrier head 210 and the platen 202, can be adjusted so that each endpoint sensor 224 scans the same area (e.g., the same region) of the front surface 230 by traversing the same scan path multiple times during the CMP process. By acquiring data from the same area on the substrate, the endpoint sensors 224 acquire a constant signal in each scan that reflects the progress of the polishing process over time, thus repeatedly improving the signal-to-noise ratio of the data acquired by the endpoint sensors 224. By improving the signal-to-noise ratio, endpoint analysis is enhanced, allowing for more accurate determination of when the endpoint is reached, and resulting in the desired uniform polishing across the patterned surface 232.

[0064]

[0077] In conventional CMP processes, the orientation of the substrate 115 after transfer to the second polishing station 124 is unknown. As a result, the controller cannot correlate the collected data with known locations on the substrate surface and therefore does not know which parts of the substrate are being scanned during endpoint analysis. Consequently, endpoint analysis in conventional CMP processes is based on random portions of the substrate 115 scanned by the endpoint sensor. The CMP process disclosed herein, in which endpoint sensor data correlates with known locations on the substrate 115, improves endpoint analysis because the controller 190 and the operator can evaluate the CMP process over time across known areas of the substrate.

[0065]

[0078] Figure 5 shows a top view of the substrate 115 shown in Figure 2B, illustrating an exemplary first endpoint scanning path 501, an exemplary second endpoint scanning path 502, and an exemplary third endpoint scanning path 503 across the front surface 230. Each endpoint scanning path 501, 502, and 503 corresponds to the path of each endpoint sensor 224 of the polishing station 124 shown in Figure 3A (see window 227) as it passes under the front surface 230. As shown, each endpoint scanning path is arc-shaped due to the movement of the carrier head 210 and platen 202 during polishing. Each endpoint sensor 224 scans the outer surface multiple times along each endpoint scanning path 501, 502, and 503 during the CMP process to facilitate endpoint analysis. The data acquired by the endpoint sensors 224 along the scanning paths is used during endpoint analysis to determine when the polishing endpoints are reached. The orientation of the scanning paths relative to each other may vary depending on the relative positions of the endpoint sensors 224.

[0066]

[0079] In addition, the controller 190 may analyze data acquired at points where the scan paths of two or more endpoint sensors 224 intersect to evaluate the endpoints of the CMP process. For example, the controller 190 may analyze data acquired at point 511 where the first scan path 501 and the third scan path 503 intersect to analyze the endpoints of the CMP process. This data may be used to plot a trace of the CMP process. In addition, the controller 190 may analyze data acquired at point 512 where the second scan path 502 and the third scan path 503 intersect, and at point 513 where the first scan path 501 and the second scan path 502 intersect, to evaluate the endpoints of the CMP process. The data acquired at each of points 511, 512, and 513 may be used to plot another trace of the endpoint processing during endpoint analysis. In some embodiments, the controller 190 may also compare data acquired at points where the scan paths of two or more endpoint sensors 224 intersect to verify that the data acquired from each endpoint sensor 224 is consistent.

[0067]

[0080] The controller 190 can use the position and orientation of the substrate 115 to correlate the data acquired by the endpoint sensor 224 with each specific die 233 along the scanning path of the endpoint sensor 224. Thus, the endpoints of the CMP process can be evaluated based on one or more specific dies 233.

[0068]

[0081] In some embodiments, the positions of the carrier head 210 and platen 202 may be adjusted so that the endpoint sensor 224 passes under a desired die 233 once or more times during the CMP process to evaluate the progress of the CMP process on that particular die 233. In some embodiments, the carrier head 210 and platen 202 may be aligned so that the endpoint sensor 224 vibrates between different scanning paths along the front surface 230.

[0069]

[0082] In some embodiments, the carrier head 210 can be moved to a scanning position once or more times during the CMP process so that the orientation sensor 250 can scan the edge of the substrate 115 to determine the rotational orientation of the substrate 115 relative to the carrier head 210. If the rotational orientation of the substrate 115 changes, the controller 190 can use the updated orientation during endpoint analysis.

[0070]

[0083] Figure 6 shows a trace 600 generated from data acquired from the endpoint sensor 224 during the CMP process. This trace 600 can be used during endpoint analysis to determine when the polishing endpoint was reached. A separate trace 600 can be created for each endpoint sensor 224 to enable evaluation of the CMP process at various points on the substrate surface. For example, the progression of the trace 600 can be used to adjust the polishing speed by changing the pressure applied to the substrate 115 by the diaphragm 212.

[0071]

[0084] The signal from the endpoint sensor 224 can be sampled to generate one or more measurement values ​​610 for each scan of the endpoint sensor 224 across the substrate 115. Thus, across multiple scans, the endpoint monitoring system generates a sequence of measurement values ​​610. This sequence of measurement values ​​610 includes a trace 600. In some implementations, to generate the measurement values ​​610 of the trace 600, the measurement values ​​within a scan or from multiple scans may be averaged or filtered (e.g., a running average may be calculated). For example, each measurement value 610 may reflect measurement values ​​from two or more endpoint sensor paths that intersect and scan the same area of ​​the front 230. The accuracy of the trace 600 is increased because the endpoint sensors 224 scan the same area of ​​the substrate to acquire measurement values ​​610.

[0072]

[0085] The sequence of measurement values ​​610 can be used, for example, to determine the endpoint or change of polishing parameters to reduce non-uniformity within the wafer. For example, a function 620 (measurement value versus time) can be fitted to the measurement values ​​610. Function 620 can be a polynomial function, for example, a linear function. The endpoint can be predicted based on the calculated time when the linear function 620 reaches a target value 630. In some embodiments, the endpoint is reached when the trace 600 passes a threshold. In some embodiments, the trace may reflect a measurement from an endpoint sensor on a particular die on the surface of the substrate. Thus, the endpoint of a particular die on the substrate can be evaluated during the CMP process.

[0073]

[0086] Figures 7A to 7D are cross-sectional views of a substrate 115 at various stages of a CMP process, illustrating an example of a copper CMP process using the CMP system 100 disclosed herein. Figure 7A shows a patterned portion 732 of the substrate 115 before undergoing CMP processing in a first processing station 124. The substrate 115 includes a dielectric layer 710 having a plurality of trenches 712. A barrier layer 720 is deposited on the dielectric layer 710, and a copper layer 730 is deposited on top of the barrier layer 720. The substrate 115 is transferred from a cassette 114 to a load cup 122. The substrate 115 is removed from the load cup 122 by a carrier head 210 and transferred to a first polishing station 124. The rotational orientation of the substrate 115 relative to the carrier head 210 can be determined by scanning the substrate 115 with a pre-aligner 118 before placing the substrate 115 in the load cup 122. Therefore, the first polishing station 124 does not have an orientation sensor 250. The substrate 115 is pressed against the polishing pad 204 to polish the upper part 732 of the copper layer 730 which is deposited on the upper part 722 of the barrier layer 720 which is deposited on the field 714 of the dielectric layer 710.

[0074]

[0087] Multiple endpoint sensors 224 on the first polishing station 124 monitor the progress of polishing the copper layer 730. Since the copper layer 730 is a continuous layer across the patterned surface 232, the endpoint sensors 224 may be eddy current sensors. The controller 190 evaluates the data acquired by the endpoint sensors 224 to determine when to reach the polishing endpoint of the upper 732 of the copper layer 730, causing the carrier head 210 to lift the substrate from the pad 204, and / or stopping the rotation of the carrier head 210 and / or platen 202. For example, the endpoint may be reached when the trace reaches a target value corresponding to when the upper 732 of the copper layer 730 has reached a desired thickness. This thickness may be selected to avoid completely removing the upper portion 732 that is polished with a high downward force on the first station 124 in order to avoid excessive dishing of the surface of the copper trench 734. Figure 7B shows the substrate 115 when the upper 732 of the copper layer 730 has reached a desired thickness.

[0075]

[0088] The substrate 115 can be polished in a two-station or three-station CMP process. In a two-station copper CMP process, the substrate 115 continues to be polished on the first station 124, but with a much lower downward force and a much lower copper removal rate to remove the remaining copper 732 on the upper 722 of the barrier layer 720. The controller 190 evaluates the data acquired by the endpoint sensor 224 to determine whether the polishing endpoint of the upper 732 has been reached in order to expose the isolated copper trenches 734 and upper 722 of the barrier layer 720. The carrier head 210 then moves the substrate to the second polishing station 124 for further processing. In a three-station copper CMP process, the substrate 115 is moved to the second polishing station 124 by the carrier head 210 to remove the remaining copper on the upper 722 of the barrier layer 720. This copper removal process is also monitored by an endpoint sensor 224 provided at the polishing station 124 to determine when the polishing endpoint has been reached. Next, the carrier head 210 moves the substrate to a third polishing station 124 for additional processing. Figure 7C shows the substrate 115 after the copper layer 730 has been removed from the top 722 of the barrier layer 720 in either a two-station or three-station copper CMP process.

[0076]

[0089] In the two-station copper CMP process, the front surface 230 is polished using a second polishing station 124 and carrier head 210 to achieve the desired height of the copper trench 734, shown as H1 in Figures 7C and 7D. The desired height H1 is based on the desired resistance of the copper in the trench 734. In other words, the height H1 is selected based on the desired resistance in the circuit formed by the copper trench wire 734. In the three-station copper CMP process, the front surface is polished using a third polishing station 124 and carrier head 210 to achieve the desired height H1 of the copper trench 734.

[0077]

[0090] After the carrier head 210 and substrate 115 are moved to the polishing station 124 for polishing to achieve a height H1 of the copper trench 734, the carrier head 210 is positioned to scan the substrate 115 using the orientation sensor 250. The data acquired during scanning is analyzed to find the position of the reference mark 236 relative to the carrier head 210, which indicates the rotational orientation of the substrate 115 relative to the carrier head 210.

[0078]

[0091] The substrate 115 is polished after the controller 190 determines the rotational orientation of the substrate 115 relative to the carrier head 210. Figures 7C and 7D show the progress of the CMP process on the substrate 115 in a second or third processing station 124 to achieve a desired height H1 of the copper trenches 734 after the upper portion 732 has been completely removed. The upper portion 722 of the barrier layer 720 deposited on the field 714 of the dielectric layer 710 is also removed as the front surface 230 is polished, as shown in the difference between Figures 7C and 7D. The field 714 of the dielectric layer 710 may be polished to achieve a desired height H1 of the copper trenches 734. The process endpoint is reached when each copper trench 734 has reached a desired height H1, as shown in Figure 7D. Each trench 734 is separated from the dielectric layer 710 by the trench portion 724 of the barrier layer 720.

[0079]

[0092] The endpoint sensor 224 of the polishing station 124 monitors the progress of polishing the barrier layer 720 and dielectric layer 710 of the substrate 115 to determine when the copper trench 734 reaches a desired height H1. In some embodiments, the endpoint sensor 224 is an inductive current sensor configured to monitor the endpoint of polishing the copper trench 734. For example, the endpoint of the polishing process performed at the second station 124 may be reached when the trace reaches a target value corresponding to the desired copper trench height H1. Once the endpoint is reached, the substrate 115 is then removed from the second station 124 and returned to the cassette 114 via the CMP system 100.

[0080]

[0093] Figure 8 shows a flow chart of an exemplary method 800 for processing a substrate. A controller 190 can control each step of method 800.

[0081]

[0094] In step 802, the substrate 115 is polished on a first pad 204 connected to a first platen 202 of a first polishing station 124. One or more endpoint sensors 224 may monitor the polishing endpoints of the front surface 230 of the substrate 115.

[0082]

[0095] In step 804, the substrate 115 is transferred by the carrier head 210 to the pad 204 of the second polishing station 124. Step 804 is performed after the first polishing station 124 has finished polishing the substrate 115.

[0083]

[0096] In step 806, the carrier head 210 moves to the scanning position and places the edge of the substrate 115 on the orientation sensor 250 located at the rotation center of the platen 202 connected to the pad 204.

[0084]

[0097] In step 808, the orientation sensor 250 scans the edge of the substrate 115 to generate a signal. The carrier head 210 rotates the substrate 115 relative to the platen 202 and the orientation sensor 250 while scanning the edge.

[0085]

[0098] In step 810, the signal is analyzed to locate the reference mark 236 on the substrate 115 and determine the rotational orientation of the substrate 115 relative to the carrier head 210.

[0086]

[0099] In some embodiments, step 810 includes determining one or more candidates for a portion of the signals on the substrate 115 that include a reference mark 236. The one or more candidates are then analyzed to obtain a reference mark signature. In some embodiments, the reference mark signature is a signal intensity drop. In some embodiments, the reference mark signature is identified when the signal intensity drop reaches or exceeds a threshold.

[0087]

[0100] In some embodiments, step 810 includes identifying at least one pair of candidates for a portion of the substrate containing a reference mark located 180 degrees apart. Each candidate is then analyzed for the reference mark signature.

[0088]

[0101] In some embodiments, step 810 includes analyzing the signal to identify a reference mark signature. In some embodiments, the reference mark signature is identified by comparing the signal to a threshold. In some embodiments, the reference mark signature is identified after a partial rotation of the carrier head 210 relative to the orientation sensor 250. In some embodiments, the reference mark signature is identified by comparing the signal to a reference signal of the same type of substrate.

[0089]

[0102] In step 812, the front surface 230 of the substrate 115 is polished in the second polishing station by simultaneously rotating the pad 204 and the carrier head 210. A diaphragm 212 in the carrier head 210 presses the substrate against the pad 204. One or more endpoint sensors 224 monitor the endpoints of the polishing process performed in the second polishing station. These endpoint sensors 224 acquire data used to determine the endpoints of the polishing process.

[0090]

[0103] In some embodiments of step 812, the rotational orientation of the substrate 115 relative to the carrier head 210 is used to determine which portion of the front surface 230 is being scanned along the scanning path of each endpoint sensor 224. The movement and rotation of the carrier head 210, as well as the rotation of the platen 202, may be adjusted so that each endpoint sensor 224 moves along the same scanning path multiple times during the polishing process to acquire data on the front surface along the scanning path.

[0091]

[0104] In some embodiments of step 812, a first die of a plurality of dies 233 formed on the pattern surface 232 is selected for endpoint analysis. The rotation and position of the carrier head 210, as well as the rotation of the platen 202, are adjusted to scan the first die. The first die may be scanned once or multiple times during the polishing process.

[0092]

[0105] In some embodiments of step 812, the carrier head 210 can be moved to a scanning position once or more times to allow the orientation sensor 250 to scan the edge of the substrate 115 and determine the rotational orientation of the substrate 115 relative to the carrier head 210. If the rotational orientation of the substrate 115 changes, the controller 190 can perform endpoint analysis using the updated orientation.

[0093]

[0106] Figure 9 shows a flowchart of an exemplary method 900 for processing the substrate 115. The controller 190 can control each step of method 900.

[0094]

[0107] In step 902, the orientation sensor 250, located at the rotation center of the platen 202, scans the edge of the substrate 115.

[0095]

[0108] In step 904, the data acquired by the orientation sensor is used to determine the position of a reference mark on the substrate relative to a carrier head 210 engaged with (e.g., held) the substrate 115. In some embodiments, step 904 includes identifying one or more candidates for a portion of the substrate 115 containing the reference mark 236, and then analyzing each candidate for the reference mark signature. In some embodiments, step 904 includes comparing the data to a threshold. The position of the reference mark is determined when the data meets or exceeds the threshold.

[0096]

[0109] In step 906, the front surface 230 of the substrate 115 is polished on a pad 204 connected to the platen 202.

[0097]

[0110] In step 908, an endpoint sensor 224 embedded in the platen 202 scans the front surface 230 during step 906. Data acquired from the endpoint sensor 224 is used to monitor the progress of polishing in order to determine when the polishing process has reached its endpoint. The position of the reference mark 236 relative to the carrier head 210 is used to identify which portion of the front surface 230 is being scanned by each endpoint sensor. In some embodiments, each endpoint sensor scans the same portion of the front surface 230 multiple times during the polishing process. For example, the position and rotation of the carrier head 210, as well as the rotation of the platen 202, may be adjusted so that each endpoint sensor 224 repeatedly moves along the same scanning path relative to the front surface 230 of the substrate 115, which has a known rotational orientation relative to the carrier head 210.

[0098]

[0111] The above description applies to embodiments of the present disclosure, but other embodiments and further embodiments of the present disclosure may be devised without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the following claims.

Claims

1. A method for processing a substrate, Polishing the front surface of the substrate on the first pad connected to the first platen, Using a carrier head, the substrate is transferred from the first pad to the second pad connected to the second platen, To position the edge of the substrate on the orientation sensor located at the rotation center of the second pad, the carrier head is moved to the scanning position, To generate a signal, the orientation sensor is used to scan the edge of the substrate, The signal is analyzed to locate the reference mark on the substrate and to determine the rotational direction of the substrate relative to the carrier head. Methods that include...

2. The method according to claim 1, wherein the reference mark is a notch or flat surface formed at the end of the substrate.

3. By analyzing the aforementioned signal, the position of the reference mark can be determined. To determine one or more candidates for a part of the substrate including the aforementioned reference mark, The method according to claim 1, comprising analyzing one or more candidates for a reference mark signature.

4. The method according to claim 3, wherein the reference mark signature is a decrease in the intensity of the signal.

5. The method according to claim 4, wherein the reference mark signature is identified by a decrease in signal intensity that reaches or exceeds a threshold.

6. Analyzing the signal to locate the reference mark means identifying at least one pair of candidates for a portion of the substrate including the reference mark, which is positioned at a 180-degree angle to the other. Analyze each candidate of the aforementioned pair with respect to the reference mark signature. The method according to claim 1, including the method described in claim 1.

7. The method according to claim 1, wherein analyzing the signal to locate the reference mark includes identifying the reference mark signature.

8. The method according to claim 7, wherein, with respect to the type of substrate, the reference mark signature is identified by comparing the signal with a threshold or a pre-stored reference signal signature of the reference mark.

9. The method according to claim 7, wherein the reference mark signature is identified after the partial rotation of the carrier head.

10. The front surface is polished by rotating the second pad and the carrier head, In order to determine the endpoint of polishing the front surface by the second pad, the front surface is monitored using multiple endpoint sensors. The method according to claim 1, further comprising:

11. Monitoring the aforementioned front surface is The method according to claim 10, comprising determining which portion of the front surface is being scanned by each endpoint sensor using the determined rotational orientation of the substrate relative to the carrier head.

12. The method according to claim 10, wherein monitoring the front surface includes moving each endpoint sensor multiple times along a scanning path along the front surface to acquire endpoint data of the front surface along the scanning path.

13. Monitoring the aforementioned front surface is Selecting a first die from among the multiple dies formed on the front surface, The rotation and position of the carrier head and the rotation of the second platen are adjusted to scan the first die. The method according to claim 10, including the method described in claim 10.

14. A method for polishing a circuit board, Using an orientation sensor located at the center of rotation of the platen, the edges of the substrate are scanned, The data acquired by the orientation sensor is analyzed to determine the position of the reference mark on the substrate relative to the carrier head holding the substrate, Polishing the front surface of the aforementioned substrate, Monitoring the front surface during polishing using an endpoint sensor embedded in the platen that scans the front surface, wherein the monitoring includes identifying the portion of the front surface being scanned by the endpoint sensor using a determined position of the reference mark relative to the carrier head. Methods that include...

15. The data acquired by the orientation sensor is analyzed to determine the position of the reference mark relative to the carrier head. Identifying one or more candidates for a portion of the substrate including the reference marks located at several distances, Analyzing each candidate for the standard mark signature and The method according to claim 14, including the method described in claim 14.

16. The data acquired by the orientation sensor is analyzed to determine the position of the reference mark relative to the carrier head. The method according to claim 14, comprising comparing the data with a threshold, wherein the position of the reference mark is determined when the threshold is met or exceeded.

17. The method according to claim 14, wherein the monitoring includes scanning a specific portion of the front surface multiple times using the endpoint sensor while the front surface is being polished.

18. A polishing system comprising a polishing station, The polishing station, A platen including a polishing pad, A carrier head configured to rotate the substrate, An orientation sensor embedded in the platen at the rotation center of the platen, configured to scan the edge of the substrate including a reference mark, A plurality of endpoint sensors embedded in the platen surrounding the orientation sensor, each endpoint sensor configured to monitor the surface of the substrate being polished on the pad, A controller that communicates with the orientation sensor and the endpoint sensor, and is configured to analyze the data acquired by the orientation sensor to determine the position of the reference mark relative to the carrier head. A polishing system equipped with the following features.

19. The polishing system according to claim 18, wherein the orientation sensor is an isotropic electromagnetic sensor.

20. The polishing system according to claim 18, further comprising at least one of a measuring tool or a pre-positioning station configured to determine the position of the reference mark before polishing the substrate.

Images