Signal processing for finding substrate notches

Abstract

A notch finding apparatus, the apparatus comprising a sensor for generating a signal dependent on a proportion of a sensing area of the sensor covered by a substrate; and a controller configured to cause a motor to generate relative motion between a carrier head and the sensor such that the sensing area of the sensor scans along a circumference of the substrate and to detect an angular position of a notch in the edge of the substrate based on an initial signal from the sensor, including generating a second or higher order derivative signal from the initial signal.

Description

Technical Field

[0001] This disclosure relates to detecting the angular position of a substrate, such as the position of a substrate notch in a system like chemical mechanical polishing (CMP). Background Technology

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive layers, semiconductor layers, or insulating layers on a silicon wafer. The manufacturing process involves depositing a filler layer on a non-planar surface and planarizing this filler layer. For certain applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, a conductive filler layer may be deposited on a patterned insulating layer to fill trenches or holes in this insulating layer. After planarization, portions of the metal layer remaining between the raised patterns of the insulating layer form vias, plugs, and lines that provide conductive paths between thin-film circuits on the substrate. For other applications, such as oxide polishing, the filler layer is planarized until a predetermined thickness is left on the non-planar surface. Furthermore, planarization of the substrate surface is often required for optical flatbed printing.

[0003] Chemical mechanical polishing (CMP) is a recognized planarization method. This planarization method typically requires mounting the substrate on a carrier or polishing head. The exposed surface of the substrate is usually placed against a rotating polishing pad. The carrier head provides a controlled load on the substrate to push it against the polishing pad. An abrasive polishing slurry is typically applied to the surface of the polishing pad. Summary of the Invention

[0004] In one aspect, the notch-finding device includes a sensor that can generate a signal depending on the proportion of the sensing area of ​​the sensor covered by the substrate, and a controller configured to position a carrier head relative to the substrate by an actuator, the sensing area of ​​the sensor being located at the edge of the substrate, the controller causing a motor to generate relative motion between the carrier head and the sensor, such that the sensing area of ​​the sensor scans along the circumference of the substrate and detects the angular position of the notch at the edge of the substrate based on an initial signal from the sensor, including generating a second-order or higher-order derivative signal from this initial signal.

[0005] In another aspect, the notch-finding device includes a sensor that generates a signal depending on the proportion of the sensor's sensing area covered by the substrate, and a controller configured to position a carrier head relative to the substrate, the sensor's sensing area being located at the edge of the substrate, the controller causing a motor to generate relative motion between the carrier head and the sensor, such that the sensor's sensing area scans along the circumference of the substrate, and detects the angular position of the notch at the substrate edge based on an initial signal from the sensor, including generating a first-order or higher-order derivative signal from the initial signal and determining the angular position of the first-order or higher-order derivative signal having a maximum peak value or a minimum valley value.

[0006] The implementation may include one or more of the following potential advantages. The angular position of the carrier head relative to the substrate can even be determined for noise signals, such as those from a patterned substrate. The carrier head can be rotated to position the substrate notch at the desired angular position. More consistent polishing can be performed on wafer-by-wafer, thereby reducing inter-wafer uniformity (WTWNU). In-situ monitoring can be more reliable, thereby improving both intra-wafer uniformity (WIWU) and inter-wafer uniformity (WTWU).

[0007] Details of one or more implementation examples are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the specification, drawings, and claims. Attached Figure Description

[0008] Figure 1 This is a schematic top view of an example polishing device.

[0009] Figure 2 This is a schematic cross-sectional view of an example polishing device.

[0010] Figure 3 This is a schematic side view of an example pressure plate recess finder.

[0011] Figure 4A and 4B This is a schematic top view of a substrate with different notches.

[0012] Figure 5 This is a schematic bottom view of the substrate and retaining ring, showing the scan point path along the circumference of the substrate.

[0013] Figure 6 This is a schematic diagram showing how the intensity of reflected light changes with the direction of the carrier's head angle.

[0014] Figure 6A This is a schematic diagram showing how the intensity of reflected light changes with the direction of the carrier head angle for a patterned substrate.

[0015] Figure 6B This is a schematic diagram showing how the second derivative of the reflected light intensity varies with the position of the carrier head angle for a patterned substrate.

[0016] Figure 7 This is a schematic side view of another example of a notch finder between pressure plates, which includes two light sources.

[0017] Figure 8 This is a schematic side view of another example of a notch finder between pressure plates, which includes a camera.

[0018] Figure 9 This is a schematic side view of another example of a notch finder between pressure plates, which guides a beam of light through a water column.

[0019] Figure 10This is a schematic side view of another example of a notch finder between pressure plates, which immerses one side of the substrate in a liquid bath.

[0020] The same numbers in the various figures represent the same elements. Detailed Implementation

[0021] In some polishing operations, the substrate is supported by a rotating carrier head and pressed against a rotating polishing pad. The rotation of the carrier head causes the substrate to rotate.

[0022] Aligning each substrate to a consistent angular orientation prior to chemical mechanical polishing is desirable because it allows for more reproducible polishing and in-situ monitoring of film thickness, especially for patterned wafers. Without being limited to any particular theory, a consistent angular orientation increases the likelihood that the sensor scans each substrate along a repeatable path, thus ensuring that the resulting signal varies over time across the same portion of the substrate on each wafer. This, in turn, improves the reliability of the pressure control algorithm, which enhances both intra-wafer uniformity (WIWU) and inter-wafer uniformity.

[0023] Hypothetically, the carrier head could simply rotate to a preset angular orientation before polishing begins, such as before lowering the substrate to contact the polishing pad. However, the angular position of the substrate relative to the carrier head may not remain fixed; the substrate may be subject to a "precession" effect, in which the substrate rotates relative to the carrier head. Therefore, relying solely on the carrier head orientation, such as that measured by a motor encoder, may not be sufficient.

[0024] Measuring the angular orientation of the substrate before a single polishing operation or two individual polishing operations (such as at a station between the two plates of a polishing system) is a technique for addressing this problem. For example, the light beam can be directed to the edge of the substrate, a detector can measure the intensity of reflected light, and the carrier head can rotate. As the notch passes the illuminated point, the amount of reflected light should change (e.g., decrease).

[0025] A further problem arises when the substrate becomes "stuck" in the carrier head during transfer between the two pressure plates: the center of the substrate may not be precisely aligned with the rotation axis of the carrier head. As a result, simply rotating the carrier head to scan the sensor along the circumference of the substrate may not work. For example, the sensor may move outside the radius of the substrate, causing signal loss. Furthermore, the signal from the sensor may be affected by variations in the radial position of the scanning substrate, which can override the effect of the notch on the signal, thus masking the placement of the notch.

[0026] The technique for handling this problem involves detecting and filtering sinusoidal changes in the signal from the sensor, and then detecting variations in this signal, such as a decrease in intensity indicating the appearance of a notch.

[0027] Figure 1This is a plan view of a chemical mechanical polishing apparatus 100 for processing one or more substrates. The polishing apparatus 100 includes a plurality of polishing stations 110. For example, the polishing apparatus may include three polishing stations 110a, 110b, and 110c. The polishing apparatus 100 also includes at least one carrier head 140, such as four carrier heads 140. The polishing apparatus 100 also includes a transfer station 104 for loading and unloading substrates from the carrier heads 140. The stations of the polishing apparatus 100, including the transfer station 104 and the polishing stations 110, may be positioned at substantially equal angular intervals around the center of the platform 106.

[0028] refer to Figure 2 Each polishing station 110 includes a polishing pad 130 supported on a rotatable pressure plate 120. The polishing pad 130 may have an outer polishing layer 132 and a softer backing layer 134 (see [link to relevant documentation]). Figure 2 The double-layer polishing pad 132 has a surface at the top that can provide a polishing surface 136.

[0029] Back Figure 1 For the polishing operation, a carrier head 140 is placed at each polishing station 110. Another additional carrier head 140 may be placed at a transfer station 122 to replace the polished substrate with an unpolished substrate while other substrates are being polished at polishing station 110.

[0030] The carrier head 140 is supported by a support structure such as a rotatable turntable or a bracket suspended on a track, which allows the carrier head to move along a path 106 that sequentially passes through each polishing station 110a-110c and transfer station 104.

[0031] refer to Figure 1 and Figure 2 Each polishing station 110 may include a port 160, such as at the end of arm 162, to dispense polishing fluid 164, such as an abrasive slurry, onto polishing pad 130. Each polishing station 110 of the polishing apparatus 100 may also include a pad adjusting device 170 to abrade the polishing pad 130 to maintain the polished surface 136 in a consistent abrasive state. For example, the adjusting device may include an adjusting head 172 having an adjusting disc located at the end of arm 174.

[0032] like Figure 2 As shown, each pressure plate 120 is rotatable about a shaft 122. For example, a motor 124 can rotate a drive shaft 126 to rotate the pressure plate 120.

[0033] Each carrier head 140 is operable to support and abut against the polishing pad 130. Each carrier head 140 may include a retaining ring 142 to hold the substrate 10 below the flexible membrane 144. Each carrier head 140 may also include a plurality of independently controllable pressurized chambers defined by the membrane, such as three chambers 146a-146c, which can apply independently controllable pressure to the relevant area of ​​the flexible membrane 144, and thus also apply pressure to the substrate 10. Although for ease of illustration Figure 2 The diagram only shows three chambers, but in reality there can be one or two chambers, or four or more chambers, such as five chambers.

[0034] Each carrier head 140 is suspended from the support structure 150 and connected to a carrier head rotation motor 156 via a drive shaft 154, allowing the carrier head to rotate about axis 152. Alternatively, each carrier head 126 may be driven by a carriage on a track, a motor that radially vibrates the carrier head, or oscillate laterally by the rotational oscillation of the turntable itself.

[0035] During operation, the pressure plate rotates about its central axis 121, and each carrier head rotates about its central axis 127 and translates laterally across the top surface of the polishing pad.

[0036] The in-situ monitoring system may include a sensor 180 mounted in the pressure plate 120 to monitor the progress of the polishing operation and / or measure the thickness of the polished layer on the substrate 10. The sensor 180 may be an optical sensor, such as a spectrometer, eddy current sensor, capacitance sensor, tribology sensor, etc.

[0037] A controller 190, such as a programmable computer, is connected to each of the motors 126, 156 to independently control the rotational frequency of the pressure plate 120 and the carrier head 140. For example, each motor 156 may include an encoder 158 that measures the angular position or rotational frequency of the associated drive shaft 154. The associated drive shaft can individually reference the angular position identified by the encoder 158 to measure the number of rotations of the drive shaft.

[0038] The controller 190 is also connected to a pressure regulator to control the pressure in chambers 146a-146c. Specifically, the controller 190 can be configured to receive thickness measurements from an in-situ monitoring system and control the pressure in chambers 146a-146c to provide improved polishing uniformity.

[0039] Controller 190 may include a central processing unit (CPU) 192, memory 194, and support circuitry 196 such as input / output circuitry, power supply, frequency circuitry, cache, etc. The memory is connected to the CPU 192. The memory is a non-transitory computable readable medium and may be one or more readable memories such as random access memory (RAM), read-only memory (ROM), floppy disk, hard disk, or other forms of digital storage. Furthermore, although a single computer is shown, controller 190 may be a distributed system, such as one comprising multiple independently operating processors and memories.

[0040] refer to Figure 1 and Figure 3 The polishing apparatus 100 may also include one or more notch-finding stations 200. In some embodiments, a notch-finding station 200a is positioned at a point on path 106 between transfer station 104 and a first polishing station (such as polishing station 110a). One or more notch-finding stations 200b, 200c may be positioned on path 106 between two polishing stations 200 along the path 106 in which the carrier head 140 travels.

[0041] In some embodiments, the polishing system includes two interplate recess finding stations 200b and 200c. These two interplate recess finding stations 200b and 200c may be located on opposite sides of a polishing station (such as a second polishing station 110b) on path 106.

[0042] In some operating modes, the substrate orientation can be measured at the notch-finding station 200 located before polishing station 110 along path 106, and then the substrate moves forward along path 106 to polishing station 110 and is polished at polishing station 110. However, in some operating modes, the substrate orientation can be measured at the notch-finding station 200 located after polishing station 110 along path 106, and then the substrate moves backward along path 106 to polishing station 110 and is polished at polishing station 110. The substrate can then move forward along path 106 to the next polishing station, selectively stopping at the notch-finding station 200 before being polished by the next polishing station.

[0043] Figure 3 An embodiment of a notch-finding station 200 placed between two pressure plates 120 of two adjacent polishing stations 110 on a path is illustrated. The notch-finding station 200 includes an optical notch detector 210, which comprises a light source 212, a photodetector 214, and circuitry 216 for transmitting and receiving signals between the controller 190 and the light source 212 and the photodetector 214. The optical notch detector 210 can also be considered as including some functions, such as software, implemented in the controller 190.

[0044] The light source 212 is positioned such that the carrier head 140 can be placed along path 106 (on which the substrate 100 can be scanned by the optical notch detector 210). Specifically, the light source 212 generates a light beam 220 that can be reflected by the substrate 10, and a light detector 214 is positioned to receive the light beam 222 reflected from the substrate 10. The light detector 214 can be positioned such that the light beam 220 and the reflected light beam 22 have the same angle of incidence, such as a position where the light detector 214 receives the reflected (rather than scattered) light. The angle of incidence on the substrate 10 can be perpendicular to the substrate surface, or a tilt angle of up to 80°, such as 30° or 45°. Although Figure 2 The diagram illustrates a beam 220 that propagates in a straight line to the substrate 10, and one or more mirrors may be placed in the optical path of the beam 220.

[0045] Light source 212 can produce substantially monotonic and / or parallel light. For example, light source 212 can be a laser in the visible wavelength range of 400-700 nm, as this makes aligning the sensor easier. However, infrared or ultraviolet light can be used. Alternatively, light source 212 can be operated to emit white light. For example, light source 212 can be a xenon lamp or a xenon-mercury lamp. Photodetector 164 can be a photometer, such as a detector that outputs a simple scalar signal representing the total light intensity. Alternatively, photodetector 164 can output multiple signals, each for a different wavelength range.

[0046] Alternatively, one or more optical fibers may be used to transmit light from the light source 212 to a location below the substrate, and / or to transmit light reflected from the substrate 10 to the detector 214. For example, a branched optical fiber may be used to transmit light from the light source 212 to the substrate 10 and back to the detector 214.

[0047] The notch-finding station 200 may include a mechanism for adjusting the vertical height of an optical component from which a light beam is directly transmitted to the substrate 10. For example, the optical component, including a mirror (if present), may be supported on an optical plate or frame 240. An actuator 242 may adjust the vertical position of the optical plate or frame 240. In some embodiments, the actuator 242 may also include an XY actuator system comprising two independent linear actuators to independently move the optical plate or frame 240 along two orthogonal axes. If an optical fiber is used, the actuator 242 may adjust the position of one end of the fiber.

[0048] In some embodiments, the shield 230 may be positioned between the carrier head 140 and the optical components (e.g., the light source 212 and the detector 214) of the optical notch detector 210 to prevent liquids that may be present on the substrate 10 or the retaining ring 142 from dripping onto and contaminating the optical elements. In this case, the beam 220 and the reflected beam 222 pass through the window 232 in the shield 230. The top surface of the shield 230 may be coplanar with the top surface of the pressure plate 120.

[0049] Purifying gas 234 can be guided from outlet 236 to flow over the bottom surface of window 232. This removes droplets from the bottom of window 232 and prevents condensation and fogging. The purifying gas can be nitrogen or filtered air.

[0050] Alternatively or additionally, the purifying gas may be directed to the irradiation point 224. The purifying gas may be a humid gas, such as that generated by passing deionized water and filtered air through an atomizer.

[0051] The output of circuit 216 can be a digital electronic signal transmitted to controller 190 for analysis. Similarly, light source 212 can be turned on or off in response to a control command in the digital electronic signal transmitted from controller 190 to optical notch detector 210. Alternatively, circuit 216 can communicate with controller 190 via wireless signal.

[0052] For certain procedures, it is useful to orient each substrate to a consistent angular position before polishing begins. If the polishing operation has some inherent angular variations due to the feature patterns on the substrate, a consistent starting angular position can improve the ability to compensate for these variations, for example, by applying different pressures to the chambers inside the carrier head. Furthermore, a consistent starting angular position increases the likelihood that the sensor 180 can trace a consistent series of paths between the wafer-by-wafer substrates, thereby making the processing of signals from the in-situ monitoring system more reliable.

[0053] The substrate 10 to be polished typically includes features that allow the substrate 10 to be angularly oriented at an angle, such as an angle to the notch. Reference points are typically defined by removing a portion of the substrate. For example, as... Figures 4A-4B As shown, the circular substrate 10 may have a notch 12 formed by removing a portion from the substrate edge 14. The substrate 10 may have a diameter D1 of 200 mm or 300 mm. Figure 4A As shown, the notch 12 can be triangular. This notch 12 can be relatively small, for example, its depth from the substrate edge 14 does not exceed 1 mm and its width along the circumference does not exceed 1 mm (for clarity, ...). Figure 4A The dimensions in the image are clearly exaggerated, but a typical notch is 3.5 mm deep and 1.7 mm wide. Or as... Figure 4B As shown, notch 1 It can be "flat".

[0054] return Figure 3 During operation, the carrier head 140 is placed in the notch-finding station 200, and the substrate 10 is placed above and spaced apart from the optical element of the optical notch detector 210. Specifically, the carrier head 140 is positioned such that the beam 220 illuminates the illumination point 224 of the substrate 10, which contacts or overlaps with the edge 16 of the substrate. Rotation of the carrier head 140 causes the substrate 10 to rotate, thus sweeping the beam along the circumference of the substrate 10. Because the reflectivity of the film 144 differs from that of the substrate 10, the signal from the detector 214 should change when the notch 12 passes through the beam 220.

[0055] Hypothetically, a beam scanning along the circumference of the substrate would generate a uniform signal, except for variations caused by the notch position. However, in practice, the situation is more complex. First, during the loading operation at the transfer station, the center of the substrate may not be precisely aligned with the rotation axis of the carrier head. Second, during polishing, the substrate 10 may be laterally driven under the frictional force of the polishing pad and come into contact with the retaining ring 142. As a result, refer to Figure 5 The center point 16 of the substrate 10 may be offset from the rotation axis 152 of the carrier head. This causes the substrate edge 14 to be closer to the inner diameter surface 143 of the retaining ring 142 in one region (such as at point 18a), and further away from the inner diameter surface 143 of the retaining ring 142 in the opposite region (such as at point 18b). This gap can be greater than the depth of the notch 12, for example, 0.5-4 mm. Therefore, in order for the beam 220 to reliably capture the notch 12, the beam needs to be wide enough so that the notch 12 falls within the irradiation point 224, regardless of the angular position of the substrate 10 relative to the carrier head 140. Therefore, the irradiation point 224 may need to have a radial width of about 1-10 mm, for example, a diameter D2 of 5-10 mm for a circular irradiation point.

[0056] Ideally, the carrier head is positioned so that the irradiation point 224 does not overlap with the holding ring 142 of the carrier head. However, the carrier head may be positioned so that the irradiation point 224 overlaps with the holding ring 142. In this case, the holding ring will affect the signal from the irradiation point. However, since the holding ring rotates around the rotation axis 152, this effect should be consistent with the angular direction of the carrier head.

[0057] Now for reference Figure 5 and Figure 6 As the carrier head rotates, the illumination point 224 of the beam will scan along the edge of the substrate 10 (indicated by arrow A). As a result, the percentage of illumination points 224 reflected from the substrate 10 will change as the carrier head rotates.

[0058] Typically, it can be expected that the film has a lower reflectivity than the substrate 10. Therefore, at the angle α1 at which the substrate 10 is farthest from the holding ring 142, the reflected light should be at its minimum value I. MIN Conversely, at the point where the substrate 10 is closest to the retaining ring 142 and at an angle α2 that should be offset by 180° from α1, the reflected light should be at its maximum value I. MAX At other positions between α1 and α2, the reflected light should be at I. MIN and I MAX The variations between these values ​​cause the signal from the sensor to be in the form of a 250° sine wave, such as... Figure 6 As shown. In Figure 5 and 6 In this example, the substrate starts at angle α0, with the reflection intensity first decreasing and then increasing. However, this is not necessary; the phase of the sine wave 250 relative to the starting position α0 depends on the position of the point 18a closest to the holding ring along the circumference of the substrate 10.

[0059] When the carrier head is at the angular position α where the irradiation point 224 overlaps with the notch 12 X At that time, the intensity of the reflected light should decrease by 252. Since the notch 12 is relatively small compared to the illumination point 224, this decrease in intensity difference ΔI may be smaller than the amplitude (I) of the sine wave 250. MAX -I MIN ).

[0060] However, various techniques can still be used to detect this signal strength drop of 252, thereby detecting the angular position α of the notch 12. X For example, the derivative (such as the first derivative) of the reflected light intensity signal can be monitored, and the controller can detect where the first derivative exceeds a critical value. The location where the first derivative exceeds the critical value indicates the presence of notch 12.

[0061] As another example, a sine function can be fitted to the signal from the sensor, and this sine function can be subtracted from the signal. The resulting difference can then be analyzed to detect a drop of 252. As another example, the signal can be processed by a high-pass filter.

[0062] although Figure 6 The diagram illustrates a smooth sine wave 250, but in reality, the signal may be affected by noise. For example, refer to... Figure 6A Measuring the intensity signal of reflected light from a patterned substrate can generate a signal 250', which has signal variations caused by the measurement point passing through various metallized or non-metallized regions of the substrate (e.g., scribing and bare die). Although these variations are generated by a real source, they can still be considered as noise in order to detect the desired signal.

[0063] Other examples of distortion or noise include sensing through a portion of the holding ring (or the edge of the carrier head), the presence of water droplets in dry measurements or air bubbles in wet measurements, electrical / sensor noise, and mechanical and alignment noise.

[0064] Therefore, in any case, distinguishing between the dropout 252' caused by the notch and noise can be particularly difficult for "wet" substrates (i.e., substrates that have been polished and therefore have water droplets) and patterned substrates. In some embodiments, appropriate signal processing can compensate for these distortions or noise.

[0065] For example, to address these issues, the signal can be processed by one or more filters. Specifically, the signal can be processed by a low-pass filter to eliminate high-frequency noise, such as noise caused by high-density substrate pattern features or scattering media such as water droplets.

[0066] This filtered or unfiltered signal can then be normalized back to the original signal filtered by a low-pass filter.

[0067] The second derivative of the resulting (after selective filtering and normalization) reflected light intensity signal can be monitored. In some implementations, the second derivative of the signal is compared to a critical value. Figure 6B A graph illustrating the second derivative signal 250” generated from the second derivative of the intensity signal (e.g., signal 250') is shown, which is a function of the angular position of the carrier head of the patterned substrate. The controller can detect at which angular positions the second derivative signal 250” exceeds a threshold value 254; this position indicates the presence of the notch 12. Alternatively, the controller can detect the angular position of the maximum peak or minimum valley of the second derivative signal 250” during a full rotation of the CMP head. This indicates the location of the notch. Alternatively, a similar technique can be used to monitor the first, third, or higher derivatives of the resulting reflected light signal.

[0068] In some implementations, the substrate can be scanned in each of multiple complete rotations. The notch can be detected in each rotation, and the angular positions of the notch, such as αX1, αX2, ..., αX, from multiple scans 1, 2, ..., N can be compared. N When all detected angular positions are within a critical value (e.g., 2°), the angular position can be reported as the notch angular position. When the detected angular positions are not within the critical value, for example, the angular position with the highest signal-to-noise ratio can be reported as the notch angular position.

[0069] The encoder output of drive shaft 156 represents a signal indicating the angular position of an arbitrary (but fixed) point on the drive shaft. Once the angular position α of the carrier head detecting the notch is known... X Where this point is located, the angular offset Δα of the notch 12 relative to the carrier head can be calculated. This fixed point may be at α0, in which case Δα = αX But more usually Δα=α F -α X .

[0070] Knowing the angular offset Δα, the carrier head can be rotated before the polishing process (e.g., before lowering the substrate 10 to contact the polishing pad) to bring the substrate 10 to the desired starting substrate angular direction α. D For example, the carrier head can be rotated to the initial carrier head angle α. S Here α S = α D -Δα.

[0071] Figure 7 An embodiment of the optical notch detector 210 is illustrated, which includes two light sources 212a and 212b that generate light beams of different wavelengths, and a beam combiner 246 that combines the light beams into a single incident beam 220. For example, the first light source 212a can generate infrared light, while the second light source 212b can generate blue light.

[0072] For patterned substrates, excessive noise may exist at certain wavelengths due to the pattern. However, noise from the pattern can be reduced by selecting an appropriate wavelength. For a given pattern, there should be a consistent wavelength with optimal performance. Controller 190 causes optical notch detector 210 to sequentially scan substrate 10 using each light source 212a, 212b, and then determines which light source provides a signal with lower noise. In some embodiments, light sources can be combined or selected individually for better performance. Controller 190 can then use one or more light sources to monitor other substrates with the same pattern. That is, controller 190 maintains a database that stores identification information for different patterns, where each pattern has an associated light source or wavelength.

[0073] Figure 8 An embodiment of the optical notch detector 210 is illustrated, which includes a camera 260 having a viewing area 262 of a substrate 10. In this embodiment, the camera 260 can capture an image or a sequence of images of the substrate 10 when the substrate is at the notch-finding station 20. In the illustrated embodiment, the viewing area 262 spans the entire substrate 10. However, if the viewing area is smaller than the substrate 10, a combination of multiple images can be used to construct a complete image of the substrate; this may involve rotation and scanning of the carrier head.

[0074] The controller 190 can use image processing technology to process an image or image sequence to determine the location of the notch and thus determine the angular orientation of the substrate 10.

[0075] In some implementations, the controller 190 may then use image processing techniques to determine the angular orientation of the substrate's patterns (e.g., scribing and chips). This can provide a preliminary estimate of the substrate's angular orientation, which can then be refined by detecting the location of notches.

[0076] Figure 9 An optical notch detector is illustrated, which guides a beam 220 through a column of water. In this embodiment, the branched optical fiber has two branch ends individually connected to the light source and the detector, and a trunk 270 located within a tube 272. Liquid 274 (e.g., deionized water) can be pumped from a liquid source 276 and flows through the tube 272. During measurement, a substrate 10 can be placed above the trunk end of the optical fiber. The height of the substrate 10 relative to the top of the tube 272 and the flow rate of the liquid 274 are selected such that when the liquid 274 overflows the tube 272, the liquid 274 fills the space between the end 270 of the optical fiber and the substrate 10.

[0077] Figure 10 An optical notch detector 210 is illustrated, wherein at least the surface of a substrate is placed in a reservoir 280. A notch-finding station 200 includes a housing or container 292 containing liquid 294. A portion of the substrate 10 and a carrier head (such as the bottom surface of a retaining ring 142) can be immersed in the liquid 284 (such as deionized water) in the reservoir 280. The thickness of the substrate 10 is... Figure 10 The extent of the damage is exaggerated; in reality, the back side of the substrate may be below the surface 284a of the liquid 284 in the reservoir 280. The backbone end 270 of the optical fiber may extend through the housing 292 into the reservoir 280 to be positioned near the edge of the substrate 10.

[0078] Whether Figure 9 still Figure 10 In this case, during operation, light is emitted from the light source, passes through the liquid 274 or 284 to reach the surface of the substrate 10, is reflected by the surface of the substrate 10, enters the trunk end 270 of the optical fiber, and returns to the detector.

[0079] Although the above description focuses on notch-finding stations with optical notch detectors that use reflected light intensity or imaging, notch detectors can also use other types of sensors.

[0080] For example, a notch detector can be used using confocal microscopy or laser displacement measurement. For instance, a confocal microscope or laser displacement sensor can be used to measure the height distribution in an area scanned along the circumference of the substrate. The height difference between the bottom surface of the substrate and the bottom surface of the film or other backing surfaces supporting the substrate can be detected. This indicates the location of the notch feature.

[0081] As another example, a notch detector can use capacitive sensing technology. In this example, the notch detector is a capacitive sensor, and the capacitance signal generated by scanning the sensor along the circumference of the substrate can be analyzed to detect the notch.

[0082] The above-described polishing apparatus and method can be applied to various polishing systems. The pressure plate can move around a track rather than rotate. The polishing pad can be a circular (or other shaped) pad pressed tightly against the pressure plate. The polishing layer can be a standard polishing material (such as polyurethane with or without filler), a soft material, or a fixed abrasive.

[0083] The controller and other computing device portions of the system described herein may be implemented in the form of digital electronic circuitry or computer software, firmware, or hardware. For example, the controller may include a processor for executing a computer program stored in a computer program product, such as a non-transitory machine-readable storage medium. This computer program (also referred to as a program, software, software application, or program code) may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a standalone program or as a module, element, subroutine, or other unit suitable for use in a computing environment.

[0084] In the context of a controller, “configuration” means that the controller has the necessary hardware, firmware, or software or combination thereof to perform the required functions when operating (rather than simply being programmable to perform the required functions).

[0085] Various embodiments have been described. However, it should be understood that various modifications can be made without departing from the spirit and scope of this specification. Therefore, other embodiments are also within the scope of the following claims.

Claims

1. A notch finding device, the device comprising: A sensor for generating a signal that depends on the proportion of the sensor's sensing area covered by a substrate; and Controller, the controller is configured to This causes the actuator to position the carrier head relative to the substrate, and the substrate has the sensing area of ​​the sensor at the edge of the substrate; This causes the motor to generate relative motion between the carrier head and the sensor, so that the sensing area of ​​the sensor scans along the circumference of the substrate; and Detecting the angular position of the notch in the edge of the substrate based on an initial signal from the sensor includes generating a second-order or higher-order derivative signal from the initial signal.

2. The apparatus of claim 1, wherein the controller is configured to apply a low-pass filter to the initial signal to generate a filtered signal, and to generate the second-order or higher-order derivative signal from the filtered signal.

3. The apparatus of claim 2, wherein the controller is configured to normalize the filtered signal to generate a filtered and normalized signal, and to generate the second-order or higher-order derivative signal from the filtered and normalized signal.

4. The apparatus of claim 1, wherein the controller is configured to generate a second derivative signal from the initial signal.

5. The apparatus of claim 1, wherein the controller is configured to compare the second-order or higher-order derivative signal with a critical value and determine an angular position at which the second-order or higher-order derivative signal is outside the critical value.

6. The apparatus of claim 1, wherein the controller is configured to determine an angular position at which the second- or higher-order derivative signal has a peak or a trough.

7. The apparatus of claim 1, wherein the controller is configured to cause the motor to generate relative motion between the carrier head and the sensor, such that the sensing area of ​​the sensor scans once along the circumference to acquire the initial signal.

8. The apparatus of claim 1, wherein the controller is configured to cause the motor to generate relative motion between the carrier head and the sensor, such that the sensing area of ​​the sensor scans multiple times along the circumference to obtain the initial signal.

9. The apparatus of claim 1, wherein the controller is configured to detect the angular position of the notch from each individual scan in the plurality of scans to generate a plurality of possible angular positions, each of the plurality of possible angular positions corresponding to an individual scan.

10. The apparatus of claim 9, wherein the controller is configured to compare each of the plurality of possible angular positions with each other.

11. The apparatus of claim 10, wherein the controller is configured to determine whether the plurality of possible angular positions are within a critical difference.

12. The apparatus of claim 11, wherein the controller is configured to set a determined angular position of the notch based on at least one of the possible angular positions, in response to determining the plurality of possible angular positions in the critical value difference.

13. The apparatus of claim 12, wherein the controller is configured to, in response to determining that the plurality of possible angular positions are not in the critical difference, determine which possible angular position from the plurality of possible angular positions corresponds to the second- or higher-order derivative signal having the highest signal-to-noise ratio peak in the plurality of scans.

14. The apparatus of claim 9, wherein the controller is configured to determine, from the plurality of possible angular positions, which possible angular position corresponds to the peak of the second- or higher-order derivative signal having the highest signal-to-noise ratio in the plurality of scans.

15. The apparatus of claim 1, wherein the sensor comprises an optical sensor including a light source for generating a light beam that illuminates the surface of the substrate, and a detector for detecting reflected light and generating a signal representing the intensity of the reflected light.

16. A polishing apparatus, wherein the apparatus comprises: Multiple stations, including a first station that is a polishing station or a transfer station and a second station that is a polishing station; A carrier head for supporting a substrate, the carrier head being movable by an actuator along a path from the first station to the second station; A motor for rotating the carrier head about an axis; and The notch finding device according to claim 1.

17. The apparatus of claim 16, the apparatus comprising a notch-finding station placed in the path between the first station and the second station, wherein the sensor is located in the notch-finding station.

18. A computer program product comprising a non-transitory storage medium, the non-transitory storage medium being encoded with instructions to cause one or more computers: This causes the actuator to position the carrier head relative to the substrate, and the substrate has the sensing area of ​​the sensor at the edge of the substrate; This causes the motor to generate relative motion between the carrier head and the sensor, so that the sensing area of ​​the sensor scans along the circumference of the substrate; and Detecting the angular position of the notch in the edge of the substrate based on an initial signal from the sensor includes generating a first-order or higher-order derivative signal from the initial signal.

19. A notch finding device, the device comprising: A sensor for generating a signal that depends on the proportion of the sensor's sensing area covered by a substrate; and Controller, the controller is configured to This causes the actuator to position the carrier head relative to the substrate, and the substrate has the sensing area of ​​the sensor at the edge of the substrate; This causes the motor to generate relative motion between the carrier head and the sensor, so that the sensing area of ​​the sensor scans along the circumference of the substrate; and Detecting the angular position of the notch in the edge of the substrate based on an initial signal from the sensor includes generating a first-order or higher-order derivative signal from the initial signal and determining at which angular position the first-order or higher-order derivative signal has a maximum peak or minimum valley.

20. A polishing apparatus, the apparatus comprising: Multiple stations, including a first station that is a polishing station or a transfer station and a second station that is a polishing station; A carrier head for supporting a substrate, the carrier head being movable by an actuator along a path from the first station to the second station; A motor, the motor being used to rotate the carrier head about an axis; A sensor for generating a signal that depends on the proportion of the sensor's sensing area covered by a substrate; and Controller, the controller is configured to This causes the actuator to position the carrier head relative to the substrate, and the substrate has the sensing area of ​​the sensor at the edge of the substrate; This causes the motor to generate relative motion between the carrier head and the sensor, so that the sensing area of ​​the sensor scans multiple times along the circumference to obtain an initial signal; Multiple possible angular positions are generated from each individual scan in the multiple scans to detect the angular position of the notch on the substrate, where each possible angular position corresponds to one individual scan; and Select an angle position from the plurality of angle positions.

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