Multi-zone contour control for inconsistent underlayers

Abstract

During polishing, the substrate is monitored using an in-situ monitoring system to generate a sequence of signal values. For each of several regions, the sequence of signal values ​​from said region is converted into a sequence of effective thickness values. For each region, a function is fitted to the sequence of effective thickness values. The fitted function is used to determine the effective initial thickness profile of the layer at the start of polishing, and an adjusted target thickness profile is calculated based on the initial target profile, the initial thickness profile, and the effective initial thickness profile. Polishing parameters are modified based on the sequence of effective thickness values ​​and the adjusted target thickness profile.

Description

Technical Field

[0001] This disclosure relates to chemical mechanical polishing, and more specifically, to the monitoring of conductive layers during chemical mechanical polishing. Background Technology

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconductive, or insulating layers on a silicon wafer. Various manufacturing processes require planarization of the layers on the substrate. For example, one manufacturing step involves depositing a filler layer on a non-planar surface and then planarizing the filler layer. For some applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, metal layers can be deposited on a patterned insulating layer to fill trenches and holes in the insulating layer. After planarization, the remaining metal in the trenches and holes of the patterned layer forms vias, plugs, and traces to provide conductive paths between thin-film circuits on the substrate.

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

[0004] One challenge in CMP is determining whether the polishing process is complete—that is, whether the substrate layer has been planarized to the desired flatness or thickness, or when the required amount of material has been removed. Variations in paste composition, polishing pad conditions, the relative speed between the polishing pad and the substrate, the initial thickness of the substrate layer, and the load on the substrate can cause variations in the material removal rate. These variations lead to variations in the time required to reach the polishing endpoint. Therefore, defining the polishing endpoint solely as a function of polishing time can result in inhomogeneities within or between wafers.

[0005] In some systems, the substrate is monitored in situ during polishing, for example, using a polishing pad. One monitoring technique involves inducing eddy currents in the conductive layer and detecting changes in these eddy currents as the conductive layer is removed. Summary of the Invention

[0006] In one aspect, an initial thickness value of a conductive outer layer in a region on a substrate is received, and an initial target thickness value of the conductive outer layer in the region on the substrate is received. The initial thickness value is generated before polishing and represents the thickness of the outer layer in the region before polishing, and the initial target thickness profile is generated before polishing and represents the desired thickness of the outer layer in the region after polishing. The conductive outer layer on the substrate is polished, and the substrate is monitored during polishing using an in-situ monitoring system to generate a sequence of signal values, the signal values ​​depending on the thickness of the conductive outer layer and the thickness and / or conductivity of one or more underlying layers beneath the outer layer. The sequence of signal values ​​from the region is converted into a sequence of effective thickness values ​​for the region, wherein each effective thickness value includes contributions from the outer layer and the one or more underlying layers. A function is fitted to the sequence of effective thickness values, and the fitted function is used to determine an effective initial thickness value of the layer at the start of polishing, and an adjusted target thickness value is calculated based on the initial target value, the effective initial thickness value, and the initial thickness value. The polishing endpoint is detected or polishing parameters are modified based on the sequence of effective thickness values ​​and the adjusted target thickness value.

[0007] In another aspect, prior to polishing, an initial thickness profile of a conductive outer layer on a substrate is received, and an initial target thickness profile of the conductive outer layer on the substrate is also received. The initial thickness profile represents the thickness of the outer layer at multiple regions on the substrate before polishing, and the initial target thickness profile represents the desired thickness of the outer layer at the multiple regions after polishing. During polishing of the substrate, a sequence of signal values ​​is received from an in-situ monitoring system, the signal values ​​depending on the thickness of the conductive outer layer being polished and the thickness and / or conductivity of one or more underlying layers beneath the outer layer. For each of the multiple regions, the sequence of signal values ​​from the corresponding region is converted into a sequence of effective thickness values ​​for the corresponding region, wherein each effective thickness value includes contributions from the conductive outer layer and the one or more underlying layers, thereby providing multiple sequences of effective thickness values, wherein each of the multiple sequences corresponds to a corresponding region. For each of the multiple regions, a function is fitted to the sequence of effective thickness values, thereby providing multiple fitting functions, wherein each of the multiple fitting functions corresponds to a corresponding region. The plurality of fitting functions are used to determine the effective initial thickness profile of the layer at the start of polishing, and an adjusted target thickness profile is calculated based on the initial target thickness profile, the effective initial thickness profile, and the initial thickness profile. Polishing parameters are modified based on the plurality of effective thickness value sequences and the adjusted target thickness profile.

[0008] In another aspect, a method for determining the initial thickness profile of a layer on a substrate includes: polishing a conductive outer layer on a calibration substrate; monitoring the calibration substrate during polishing by repeatedly sweeping a sensor of an in-situ monitoring system across the calibration substrate to generate a first trajectory sequence, wherein each first trajectory in the first trajectory sequence corresponds to a sweep performed by the sensor, and each first trajectory includes a sequence of effective thickness values, the effective thickness values ​​depending on the thickness of the conductive outer layer and the thickness and / or conductivity of one or more underlying layers beneath the outer layer; detecting exposure of the one or more underlying layers beneath the outer layer; and after exposure of the one or more underlying layers, continuing to monitor the calibration substrate by sweeping the sensor of the in-situ monitoring system across the calibration substrate and generating a second trajectory including a sequence of underlying layer thickness values, the underlying layer thickness values ​​depending on the thickness of the one or more underlying layers. Thickness and / or conductivity; for each corresponding first trajectory from the first trajectory sequence, subtracting the second trajectory from the first trajectory to generate a modified first trajectory, thereby generating a modified trajectory sequence; for each corresponding region of the plurality of regions on the substrate and for each corresponding modified trajectory from the modified trajectory sequence, converting a portion of the signal value sequence of the corresponding region from the corresponding modified trajectory into a thickness value of the corresponding region, thereby providing a plurality of thickness value sequences, wherein each corresponding sequence of the plurality of sequences corresponds to a corresponding region; for each corresponding region of the plurality of regions, fitting a function to the thickness value sequence of the corresponding region, thereby providing a plurality of fitting functions, wherein each corresponding fitting function of the plurality of fitting functions corresponds to a corresponding region; and using the plurality of fitting functions to determine the initial thickness profile of the conductive layer at the start of polishing.

[0009] The methods, computer program products, and / or systems used to implement this aspect may include one or more of the following features.

[0010] Calculating the adjusted target thickness value may include calculating an adjustment based on the difference between the initial thickness value and the initial target value. Calculating the adjusted target thickness value may include subtracting the adjustment from the effective initial thickness value. Calculating the adjustment includes multiplying the difference between the initial thickness value and the initial target value by a constant. The constant may be between 1.0 and 1.2.

[0011] The function may be a linear function. Determining the effective starting thickness value may include extrapolating the function backward to the start time of the polishing. The in-situ monitoring system may be an eddy current monitoring system. The polishing endpoint may be detected by determining when the function equals the adjusted target thickness value. Fitting the function may include repeatedly fitting the function to a moving window of effective thickness values ​​from the sequence of effective thickness values.

[0012] Converting the sequence of signal values ​​from the region into the sequence of effective thickness values ​​may include using a conversion algorithm to calculate a preliminary sequence of effective thickness values ​​from the effective thickness values, the conversion algorithm taking signal values ​​as input and producing thickness values ​​as output. The sensor of the in-situ monitoring system may perform multiple sweeps across the substrate to generate a sequence of trajectories, and each corresponding trajectory in the sequence of trajectories may be defined by thickness values ​​from the sequence of thickness values ​​for the corresponding sweep in the multiple sweeps. For each corresponding trajectory, edge reconstruction may be performed on the corresponding trajectory to generate a modified trajectory with modified thickness values, thereby generating a modified trajectory sequence. For each corresponding trajectory, an effective thickness value of the region may be calculated based on the modified thickness values ​​of the region from the corresponding trajectory, thereby generating the sequence of effective thickness values. Calculating the effective thickness value of the region based on the modified thickness values ​​may include averaging the modified thickness values ​​from the region.

[0013] The implementation can include one or more of the following advantages. When calculating the thickness of the layer being polished based on the monitored signal, this technique can compensate for the contribution of the conductive underlying layer (e.g., a doped substrate or metal layer) to the signal, even if the contribution of the underlying layer is inconsistent on a wafer-to-wafer basis. Therefore, the thickness of the layer being polished can be calculated with higher accuracy or reliability. The calculated thickness can be used to determine control parameters during the polishing process and / or to determine the endpoint of the polishing process. This can improve the reliability of control parameter determination and endpoint detection, avoid under-polishing of wafers, and reduce wafer-to-wafer non-uniformity (WTWNU) and intra-wafer non-uniformity (WIWNU).

[0014] Details of one or more implementations will be set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will become apparent from the description, the drawings, and the claims. Attached Figure Description

[0015] Figure 1 A schematic cross-sectional view of an example polishing station including an electromagnetic induction monitoring system is shown.

[0016] Figure 2A schematic top view of an example chemical mechanical polishing station is shown, illustrating the path of sensor scanning across the substrate.

[0017] Figures 3A-3C This is a schematic cross-sectional view of the substrate, showing the polishing process.

[0018] Figure 4 This is a schematic cross-sectional view showing an example magnetic field generated by an electromagnetic induction sensor.

[0019] Figure 5 An example signal graph from an eddy current sensor as a function of the conductive layer thickness is shown.

[0020] Figure 6 A flowchart is shown for a method of performing endpoint and profile control in chemical mechanical polishing.

[0021] Figure 7 It is a sequence diagram of thickness values.

[0022] Figure 8 It is a graph of two thickness value sequences from two different radial ranges on the product substrate.

[0023] Figures 9A-9C A flowchart illustrating another implementation of a method for performing endpoint and profile control in chemical mechanical polishing.

[0024] Figure 10 This is a graph showing two sequences of effective thickness values ​​from two different radial ranges during the polishing of the calibration substrate.

[0025] Figure 11 This is a graph showing two thickness value sequences from two different radial ranges derived from the polishing of the calibration substrate.

[0026] Figure 12 It is an effective thickness trajectory diagram of the polishing from the calibration substrate.

[0027] Figure 13 It is an effective thickness trajectory diagram from the over-polishing of the calibration substrate.

[0028] Figure 14 From Figure 12 and Figure 13 The thickness trajectory diagram derived from the trajectory.

[0029] Figure 15 It is an effective thickness trajectory diagram from the polishing of the product substrate. Detailed Implementation

[0030] One monitoring technique for polishing operations involves inducing eddy currents in a conductive layer on a substrate, for example, using an alternating current (AC) drive signal. During polishing, an eddy current sensor can measure the induced eddy currents in situ to generate a signal. Assuming the outermost layer undergoing polishing is a conductive layer, the signal from the sensor should depend on the thickness of the conductive layer. Based on this monitoring, control parameters for the polishing operation (such as the polishing rate) can be adjusted in situ. Furthermore, the polishing operation can be terminated based on an indication that the monitored thickness has reached the desired termination thickness.

[0031] In reality, the magnetic field generated by an eddy current sensor does not end within the outermost conductive layer but can extend into the underlying conductive layer or the substrate. Therefore, the signal generated by an eddy current sensor can depend on the conductivity of the semiconductor wafer and the presence of the underlying conductive layer. If the semiconductor wafer is undoped, as is commonly used in "blank" wafers for system calibration and in substrate wafers, then the wafer's resistance may be high enough that its presence has no detectable effect on the eddy current signal. However, for actual device manufacturing, wafers are typically doped, for various purposes, such as being highly doped. In this case, depending on the conductivity of the semiconductor wafer, the substrate may significantly contribute to the signal generated by the eddy current sensor. Therefore, thickness measurements based on the signal captured by the eddy current sensor may be inaccurate.

[0032] If the contribution of the substrate due to doping is known, then the calculation of the thickness of the layer being polished can take into account the contribution of the semiconductor substrate to the signal. However, during semiconductor device manufacturing, doping is often poorly controlled, whether across a given wafer or between wafers within a given production batch.

[0033] This disclosure relates to a technique for performing endpoint and profile control when the underlying layer (such as a doped semiconductor wafer) makes inconsistent contributions to signals from an eddy current sensor. An initial effective thickness profile can be calculated by calculating the polishing rate for each of a plurality of regions on a substrate based on signals from the sensor, and by extrapolating the effective thickness for each region backward to the start of the polishing operation. A deposition layer profile, representing the actual initial thickness of the deposited film, can then be subtracted from the effective initial thickness profile to provide an underlying layer profile, i.e., the underlying layer contribution in the form of the effective thickness. The underlying layer profile can then be added to a target thickness profile to produce an adjusted target thickness profile, which can be used for endpoint detection.

[0034] Figure 1 and Figure 2An example of a polishing station 20 in a chemical mechanical polishing system is shown. The polishing station 20 includes a rotatable disc-shaped worktable 24 on which a polishing pad 30 is located. The worktable 24 can be rotated about an axis 25. For example, a motor 22 can rotate a drive shaft 28 to rotate the worktable 24. The polishing pad 30 may be a double-layered polishing pad with an outer polishing layer 34 and a softer backing layer 32.

[0035] Polishing station 20 may include a supply port or a combined supply-flushing arm 39 to dispense polishing fluid 38 (such as abrasive slurry) onto polishing pad 30. Polishing station 20 may include a pad adjustment device with an adjustment disc to maintain the surface roughness of the polishing pad.

[0036] The support head 70 is used to hold the substrate 10 against the polishing pad 30. The support head 70 is suspended on a support structure 72 (e.g., a turntable or track) and connected to a support head rotation motor 76 via a drive shaft 74, allowing the support head to rotate about an axis 71. Optionally, the support head 70 can oscillate laterally, for example, on a slider on the turntable, by moving along the track, or by the rotational oscillation of the turntable itself.

[0037] The carrier head 70 may include a flexible membrane 80 having a substrate mounting surface for contacting the back side of the substrate 10. The membrane 80 may form a plurality of pressurizable chambers 82 to apply different pressures to different areas (e.g., different radial areas) on the substrate 10. The carrier head may also include a retaining ring 84 to hold the substrate beneath the membrane 80.

[0038] During operation, the stage rotates about its central axis 25, and the bearing head rotates about its central axis 71 and laterally translates across the top surface of the polishing pad 30. In the case of multiple bearing heads, each bearing head 70 can have independent control over its polishing parameters; for example, each bearing head can independently control the pressure applied to each corresponding substrate.

[0039] In some implementations, polishing station 20 includes a temperature sensor 64 to monitor the temperature of the polishing station or its components / components within the polishing station.

[0040] refer to Figure 3AA polishing system can be used to polish substrate 10, which includes conductive material covering and / or embedded in a patterned dielectric layer. For example, substrate 10 may include a layer of conductive material 16 (e.g., a metal such as copper, aluminum, cobalt, or titanium) that covers and fills trenches in dielectric layer 14, such as silicon oxide or a high-k dielectric. Optionally, a barrier layer 18 (e.g., tantalum or tantalum nitride) may be lining the trenches and separating the conductive material 16 from dielectric layer 14. The conductive material 16 in the trenches can provide vias, pads, and / or interconnects in the finished integrated circuit. Although dielectric layer 14 is shown as being deposited directly on semiconductor wafer 12, one or more other layers may also be inserted between dielectric layer 14 and wafer 12.

[0041] Semiconductor wafer 12 can be a silicon wafer, such as single-crystal silicon; however, other semiconductor materials are also possible, such as gallium arsenide or gallium nitride. Furthermore, semiconductor wafer 12 can be doped, for example, with p-type or n-type doping. Doping can be uniform across the sides of the wafer, or the wafer can be selectively doped, for example, selectively doped according to the needs of manufacturing transistors in integrated circuits using the semiconductor wafer.

[0042] Initially, conductive material 16 covers the entire dielectric layer 14. As polishing proceeds, most of the conductive material 16 is removed, thereby exposing the barrier layer 18 (see...). Figure 3B Then, polishing continues to expose the patterned top surface of dielectric layer 14 (see...). Figure 3C Then, additional polishing can be used to control the depth of the trench containing the conductive material 16.

[0043] In some implementations, the polishing system includes additional polishing stations. For example, the polishing system may include two or three polishing stations. For instance, the polishing system may include a first polishing station with a first electromagnetic induction monitoring system and a second polishing station with a second electromagnetic induction current monitoring system.

[0044] For example, in operation, batch polishing of the conductive layer on the substrate can be performed at the first polishing station, and polishing can be stopped when the target thickness of the conductive layer is still present on the substrate. The substrate is then transferred to the second polishing station and polished until the bottom layer (e.g., the patterned dielectric layer) is reached.

[0045] Back Figure 1 The polishing system includes an in-situ eddy current monitoring system 100, which may be coupled to or considered to include a controller 90. The in-situ eddy current monitoring system 100 is configured to generate a signal that depends on the thickness of the conductive material 16 (e.g., metal) of the layer being polished.

[0046] During operation, the polishing system can use the in-situ eddy current monitoring system 100 to determine when the conductive layer reaches a target thickness (e.g., the target thickness of the metal layer covering the dielectric layer) and then stop polishing. Alternatively or additionally, the polishing system can use the in-situ eddy current monitoring system 100 to determine the thickness difference of the conductive material 16 across the substrate 10 and use this information during polishing to adjust the pressure in one or more chambers 82 in the bearing head 80 to reduce polishing non-uniformity. During polishing, measurements from the sensor 102 can be displayed on an output device to allow the polishing station operator to visually monitor the progress of the polishing operation; however, this is not required.

[0047] The sensor 102 of the in-situ monitoring system 100 can be mounted in a recess 26 in the worktable 20. The sensor 102 may include a magnetic core 104 at least partially positioned in the recess 26 and at least one coil 106 wound around a portion of the magnetic core 104. A drive and sensing circuitry 108 is electrically connected to the coil 106. The drive and sensing circuitry 108 generates a signal that can be sent to the controller 90. The circuitry 108 may include a capacitor connected in parallel with the coil 106. The coil 106 and the capacitor may together form an LC resonant groove. Although shown outside the worktable 24, some or all of the drive and sensing circuitry 108 may also be mounted inside the worktable 24. A rotary coupler 29 may be used to electrically connect components in the rotatable worktable 24 (e.g., the sensor 102 of the eddy current monitoring system 100) to components outside the worktable (e.g., the drive and sensing circuitry or the controller 90). Alternatively, the sensor 102 may communicate wirelessly with the controller 90.

[0048] refer to Figure 1 and Figure 4 The drive and sensing circuitry 108 applies an AC current to the coil 106, which generates a magnetic field 110 between the two poles 112a and 112b of the magnetic core 104. In operation, a portion of the magnetic field 110 extends into the substrate 10 as the substrate 10 intermittently covers the sensor 102.

[0049] If it is necessary to monitor the thickness of the conductive layer on the substrate, then when the magnetic field 110 reaches the conductive layer 16, the magnetic field 110 can generate eddy currents in the conductive layer. This modifies the effective impedance of the LC circuit.

[0050] However, magnetic field 110 may also penetrate "below" the layer being polished. Figure 4 The various conductive layers 18 (top in the view) penetrate into the semiconductor substrate 12. Therefore, the effective impedance of the LC circuit (and thus the signal from the driving and sensing circuit system 108) can also depend on the conductivity of the underlying conductive layer and the doping and resulting conductivity of the semiconductor substrate 12. For ease of illustration, Figure 4There is no patterning of the graphic layer in the middle.

[0051] The drive and sensing circuitry 108 may include a marginal oscillator coupled to the combined drive / sensing coil 106, and the output signal may be the current required to maintain the peak-to-peak amplitude of the sinusoidal oscillation at a constant value, as described in, for example, U.S. Patent No. 7,112,960. The drive and sensing circuitry 108 may also have other configurations. For example, separate drive and sensing coils may be wound around a magnetic core. The drive and sensing circuitry 108 may apply current at a fixed frequency, and the signal from the drive and sensing circuitry 108 may be the phase shift of the current in the sensing coil relative to the drive coil, or the amplitude of the sensed current, as described in, for example, U.S. Patent No. 6,975,107.

[0052] refer to Figure 2 As the stage 24 rotates, the sensor 102 sweeps along path 120, which passes beneath the substrate 10. By sampling signals from the circuitry 108 at specific frequencies, the circuitry 108 generates measurements at a series of sampling regions 94 spanning the substrate 10. For each sweep, the measurements from one or more sampling regions 94 can be selected or combined. Thus, after multiple sweeps, the selected or combined measurements provide a time-varying sequence.

[0053] Polishing station 20 may also include a position sensor 96, such as an optical interruptor, to sense when sensor 102 is under substrate 10 and when sensor 102 leaves substrate. For example, position sensor 96 may be mounted in a fixed position opposite to carrier head 70. Flag 98 may be attached to the periphery of stage 24. The attachment point and length of flag 98 are selected so that it can signal to position sensor 96 as sensor 102 sweeps under substrate 10.

[0054] Alternatively or additionally, polishing station 20 may include an encoder to determine the angular position of table 24.

[0055] Back Figure 1 The controller 90 (e.g., a general-purpose programmable digital computer) receives signals from the sensor 102 of the in-situ monitoring system 100. Since the sensor 102 sweeps beneath the substrate 10 with each rotation of the stage 24, information about the depth of the conductive layer (e.g., the body layer or conductive material in the trench) is accumulated in situ (once per stage rotation). The controller 90 can be programmed to sample signals from the in-situ monitoring system 100 when the substrate 10 substantially covers the sensor 102.

[0056] In addition, the controller 90 can be programmed to calculate the radial position of each measurement result and classify the measurement results by radial range, as discussed in U.S. Patent No. 6,399,501.

[0057] Since the sensor 102 sweeps under the substrate 10 each time the stage 24 rotates, information about the thickness of the conductive layer is accumulated in situ and on a continuous, real-time basis for each of the multiple different radial regions on the substrate.

[0058] Figure 5 The figure shows a graph 130 illustrating the relationship between the thickness of the conductive layer and the signal from the eddy current monitoring system 100 at a given resistivity. As shown, the given thickness D can be calculated from the signal S; K is a constant representing the signal value when the conductive layer thickness is zero.

[0059] The relationship curve 130 can be represented by a function in the controller 90, such as a polynomial function, like a second-order, third-order, or higher-order function. In the case of an undoped semiconductor wafer, the correlation between the signal S and the thickness D can be represented by the following equation: S = W1·D 2 + W2·D + W3 (Equation 1) Where W1, W2, and W3 are real coefficients. Therefore, the controller can store the values ​​of the function's coefficients, such as W1, W2, and W3, and the resistivity ρ0 to which the relationship curve 410 applies. Furthermore, the relationship can be represented by a linear function, a Bezier curve, or a non-polynomial function (e.g., an exponential or logarithmic function).

[0060] Furthermore, the relationship curves or thicknesses calculated for layers can take into account the processing temperature, i.e., the temperature of the polishing pad, polishing fluid, substrate, or some combination thereof. For example, the corrected thickness value D' can be calculated as follows: = D (ρ T / ρ0) ρ T = ρ X [1 + α ( T - T ini )] Where ρ X ρ0 is the resistivity of the conductive layer, and ρ0 is the resistivity used to generate the relationship curve 130. iniThe temperature used to generate the relationship curve 130 is T, which is the measured temperature of the process (e.g., from temperature sensor 64), and α is a constant that can be derived from experience or scientific textbooks.

[0061] Some variations in the signal strength from sensor 102 may be due to overlap between the measurement area of ​​sensor 102 and the substrate edge, rather than inherent variations in the thickness or conductivity of the layer being monitored. Therefore, this signal distortion can lead to errors in calculating the substrate thickness, particularly near the substrate edge. To address this issue, controller 90 can feed each thickness trajectory into a neural network configured to generate modified thickness trajectories that compensate for this signal distortion. This process is described in U.S. Patent Publication No. 2021-0379723. The resulting thickness measurements can be categorized according to radial range.

[0062] As mentioned above, the signal generated by the eddy current sensor also includes contributions from the underlying conductive layer and the doped semiconductor wafer. Because the eddy currents excited in the doped semiconductor wafer and the conductive layer are independent and separated by the insulating layer, the power losses in the doped silicon substrate and the insulating conductive film layer are additive and should generally follow the superposition principle of linear systems.

[0063] Unfortunately, in many cases, the doping of semiconductor wafers is not strictly controlled, and therefore can vary considerably across a single wafer and between wafers, and even within a given production batch. On the other hand, in some cases, the initial thickness of the conductive layer being polished is known with high precision and reliability. This may be the case, for example, when the deposition process used to form the conductivity is reliable, and the thickness of the conductive layer on a calibration substrate or a sample substrate from a production batch can be measured using other techniques, such as a four-point probe.

[0064] Figure 6 The flowchart illustrates process 200 for polishing a substrate and detecting the endpoint or adjusting polishing parameters during the polishing operation.

[0065] The controller 90 can receive and store the initial film thickness profile and the target thickness profile (202). This initial thickness profile can be a set of initial thickness values ​​representing the initial (i.e., pre-polishing) thickness of the conductive layer to be polished at each of a plurality of radial regions. The number of radial regions (and therefore the number of initial thickness values) can be equal to the number of independently controllable regions provided by the carrier head 140, for example... Figure 1The diagram shows three regions of the three concentric chambers 82a-82c. These values ​​can be obtained and entered by semiconductor foundry facility operators. For example, the thickness of the conductive layer on a calibration substrate or a sample substrate from a production batch can be measured (e.g., using a four-point probe technique) at each radial range. For N radial ranges, the initial thickness values ​​can be represented as ST1, ST2…ST N When using both the reference radial range and the dynamically controlled radial range, the target thickness value can be expressed as ST. R and ST D .

[0066] Similarly, the target thickness profile can be a set of target thickness values ​​representing the desired thickness to be achieved (i.e., after polishing) at each of the plurality of radial zones. Likewise, the number of target thickness values ​​can be equal to the number of initial thickness values ​​and equal to the number of independently controllable zones provided by the bearing head 140. For N radial ranges, the target thickness values ​​can be represented as TT1, TT2…TT N These values ​​can be selected by the semiconductor foundry facility operator based on the specifications of the integrated circuit being manufactured. When using a reference radial range and a dynamically controlled radial range, the target thickness value can be expressed as TT. R and TT D .

[0067] refer to Figure 2 and Figure 6 Each time sensor 102 sweeps under substrate 10, the eddy current monitoring system generates a series of measurement results in the form of raw signal values, corresponding to different sampling areas 94. Controller 90 categorizes these signal values ​​according to different radial ranges. These different radial ranges can be matched with the radial range of the initial thickness value, i.e., in a one-to-one relationship.

[0068] For each radial range, raw signal values ​​from one or more sampling areas 94 within the radial range can be selected or combined to provide a measurement result for the range, i.e., a signal value. Therefore, for each sweep, the eddy current monitoring system 100 generates one or more signal values ​​for each radial range. Thus, as polishing proceeds over time and the sensor 12 performs multiple sweeps, the eddy current monitoring system 100 generates a sequence of signal values ​​for each radial range (step 204).

[0069] refer to Figure 2 and Figure 5Each signal value (S) from the sequence is converted into an effective thickness value (D) (step 206), for example using a relationship curve 130, thereby generating a sequence of effective thickness values ​​for each radial range. The term "effective thickness value" is used because the value is calculated assuming the signal is entirely caused by the conductivity of the layer being polished. However, in reality, the signal includes contributions from the underlying layer and the doped substrate, whose conductivity may differ from that of the layer being polished, but is incorporated into the measurement as an additional thickness of the material being polished.

[0070] Figure 7 A diagram is shown (the diagram is shown for illustrative purposes only; no diagram needs to be generated or illustrated during operation), which illustrates a sequence 160 of effective thickness values ​​150 generated for a specific radial range, wherein the sensor 102 generates a signal value 200 each time it sweeps under the substrate 10.

[0071] For each radial range, a polynomial function (e.g., a first-order function, i.e., line 170) is fitted to a sequence 160 of effective thickness values ​​150 for that radial range (step 208). For example, robust regression can be used to perform the fitting. In particular, line 170 can be fitted to the effective thickness values ​​accumulated after polishing begins but before the first parameter change (e.g., the first change in bearing head pressure or other variables to improve polishing uniformity). Effective thickness values ​​from the initial one to three rotations of the stage can be excluded because the polishing rate may be unstable during this period. Furthermore, depending on when the bearing head pressure begins to change, effective thickness values ​​acquired after the pressure change should be excluded, such that the slope of line 170 thus represents the polishing rate for the associated radial range. Data from four to ten effective thickness values ​​may be sufficient to fit line 170; however, fitting of the line can also continue as polishing progresses.

[0072] Calculate the effective thickness value at the start of the polishing operation (step 208). For example, based on the fitted polynomial function, the controller 90 extrapolates backward to determine the effective initial thickness value (PRE) of the substrate at the start of the polishing process. For N radial ranges, the effective initial thickness value can be represented as PRE. (F+S),1 PRE (F+S),2 ...PRE (F+S),N The subscript F+S indicates that the thickness value includes contributions from both the layer being polished and the underlying substrate. For the reference radial range, the effective starting thickness value can be expressed as PRE. (F+S),R For dynamically controlled radial range, the effective initial thickness value can be expressed as PRE. (F+S),D .

[0073] With the target thickness value, the initial thickness value, and the effective thickness value, the adjusted target thickness value can be calculated (step 210). Specifically, the adjusted target thickness value (AT) can be calculated as follows: AT = PRE (F+S) - (ST-TT) k Where k is a constant.

[0074] In some implementations, this calculation is performed only for a reference radial range from the group of radial ranges, for example, AT R = PRE (F+S),R - (ST R -TT R ) k. In some implementations, this calculation is performed for each radial range, for example, AT1 = PRE (F+S),1 - (ST1-TT1) k, AT2 = PRE (F+S),2 - (ST2-TT2) k, etc. If the calculation is performed for each radial range, then the same k value can be used for each range.

[0075] Without being limited to any particular theory, k can be one or both of the following: 1) compensation for the influence of the nonlinear relationship curve; and 2) crosstalk effect between the conductive layer being polished and the underlying layer, which causes the measurement results to not follow the superposition principle of linear systems. The constant k can be determined empirically and can be in the range of 1.0 to 1.2. For example, for a highly doped P++ silicon wafer, k can be about 1.04.

[0076] The controller 90 can use conventional algorithms to perform endpoint detection or contour control, i.e., calculate the adjustment of the bearing head pressure, but replace the target thickness value with the adjusted target thickness value in the endpoint or contour control algorithm (step 212).

[0077] For example, still refer to Figure 7 As polishing proceeds, controller 90 can push forward to determine the time when line 170 will equal (at 180) the adjusted target thickness value. This time provides the endpoint time (ET).

[0078] As another example, by replacing the target thickness value with an adjusted target thickness value in the contour control algorithm, the algorithm drives the polishing process to provide these adjusted target thickness values. For example, Figure 8A diagram (illustrated for process purposes only; no diagram is required during operation) illustrates two sequences of thickness values ​​generated for two different radial ranges. In this example, a first effective thickness value 152a is obtained, and a first line 172a is fitted to the first effective thickness value 152a for the first radial range. A second effective thickness value 152b is obtained, and a second line 172b is fitted to the second effective thickness value 152b for the second radial range. Assuming the first radial range is used as the reference radial range, the endpoint time ET... R It can be calculated that the first line 172a reaches the first adjusted target thickness value AT. R (At 182a) the time. Assuming the second radial range is used as the dynamic range, the endpoint time ET. D It can be calculated that the second line 172b reaches the first adjusted target thickness value AT. D (At 182b) the time. Controller 90 can calculate the target polishing rate 190 for the dynamic radial range starting at adjustment time T0, such that both the controlled radial range and the dynamic radial range reach their respective adjusted target thickness values ​​AT substantially simultaneously. R and AT D To achieve the target polishing rate of 190, the controller 90 can calculate adjustments to one or more polishing parameters, such as adjustments to the pressure in the region of the bearing head corresponding to the dynamic radial range. This calculation can be based on the Preston Equation. Therefore, even if the contribution of the underlying layers to the eddy current signal is inconsistent on a wafer-to-wafer basis, the resulting polishing profile should more closely match the target profile.

[0079] As an alternative to measuring the initial thickness value on the layer using a four-point probe, an in-situ monitoring system can be used to determine the effective initial thickness value for each radial region. Furthermore, the thickness of some regions can be represented using an offset relative to a reference region, rather than using absolute values. Processes using both techniques are described below, but each technique can be used independently.

[0080] Figures 9A-9C A method 300 for performing endpoint and profile control in chemical mechanical polishing is illustrated, the method comprising a process 302 for determining an initial thickness value for each radial region using an in-situ monitoring system. This process includes generating a thickness trajectory (304) during bulk polishing of a conductive layer on a calibration substrate, generating a thickness trajectory (306) once the conductive layer has been removed to expose the underlying layer, and processing the thickness trajectory to generate an initial thickness value for each radial range (308). Each of these steps will be described in more detail below.

[0081] Initially, reference Figure 9A A calibration substrate with the same layers and pattern as the product substrate is polished at polishing station 20. During the polishing of the outer conductive layer (step 310), the substrate is monitored using an in-situ eddy current monitoring system 160. (Reference) Figure 2 , Figure 9A and Figure 12 Each time sensor 120 sweeps under substrate 10, it generates a raw signal trajectory (step 312). Each signal value in the raw signal trajectory can be converted into a thickness value (step 314), for example, using the reference above. Figure 5 The calibration relationship discussed is used for conversion. This results in an effective thickness trajectory 300 for each sweep of sensor 102 under the calibration substrate.

[0082] like Figure 12 As shown, the effective thickness trajectory 250 includes a first portion 252, a second portion 254, and a third portion 256. The first portion corresponds to a position in the edge region of the substrate 10 when the sensor 102 crosses the leading edge of the substrate 10, the second portion corresponds to a position in the central region of the substrate 10, and the third portion corresponds to a position in the edge region when the sensor 102 crosses the trailing edge of the substrate 10. The signal may also include a portion 258 corresponding to the measurement result outside the substrate, i.e., a signal generated when the sensor head scans the region outside the edge of the substrate 10.

[0083] Although the first portion 252 and the third portion 256 are shown as smooth, and the second portion 254 is shown as flat, this is for simplicity only, and the real signal will include fluctuations caused by both noise and variations in layer thickness. Furthermore, although the effective thickness trajectory 250 is shown as continuous, it is actually provided by a sequence of individual effective thickness values.

[0084] Continue to refer to Figure 9A and Figure 12 As mentioned above, thickness measurements at the substrate edges may be inaccurate. Therefore, an edge reconstruction technique can be performed on each effective thickness trajectory 250 to generate a modified effective thickness trajectory 260 for each scan (step 316). In particular, each effective thickness trajectory 250 can be fed into a neural network configured to compensate for signal distortion at the substrate edges. This process is described in U.S. Patent Publication No. 2021-0379723. Each modified effective thickness trajectory 260 can be stored for subsequent processing.

[0085] refer to Figure 9A and Figure 10The thickness values ​​from each modified effective thickness trajectory 260 can be classified according to radial range, and the effective thickness value can be calculated for each radial range for each sensor sweep (step 320). For example, a sequence 164a of effective thickness values ​​154a is generated for a reference radial range, and a sequence 164b of effective thickness values ​​154b is generated for each dynamic radial range (for ease of illustration). Figure 10 (Only two sequences are illustrated). The effective thickness value can be generated by averaging the effective thickness values ​​from trajectory 260 over a specific radial range.

[0086] The controller 90 can detect when the conductive layer is polished away, exposing the underlying layer. In this state, the top surface of the underlying layer is exposed, but conductive material may remain in the trenches, forming wires, vias, etc. In one implementation, the controller 90 or operator can detect the slope change (at 184) of a line fitted to a sequence 164a of effective thickness values ​​154a in the reference area. For example, the controller 90 can repeatedly fit the line to the effective thickness value 154a from a moving window of three to ten effective thickness values ​​and calculate the polishing rate based on the slope of the line (step 322). If the slope change of the line exceeds a threshold, the controller 90 can use this as an indication that the underlying layer has been exposed (step 324). In some implementations, the slope change in the radial range alone is sufficient to indicate exposure. In some implementations, slope changes in both the radial and dynamic radial ranges need to be considered. Furthermore, other techniques, such as separate optical monitoring signals, can be used to determine the timing of underlying layer exposure.

[0087] With the underlying layers exposed, reference Figure 9B The calibration substrate can now be scanned during the "post-polishing" process. Specifically, after the underlying layer is exposed, the substrate is held on the polishing pad (step 330), and the stage 24 continues to rotate to scan the sensor 102 below the substrate 10, thereby generating a sequence of raw signal traces (step 332). To prevent material removal during this post-polishing process, the calibration substrate can be scanned with the polishing pad surface rinsed with deionized water (DIW) and / or with the chamber in the carrier head under low pressure (e.g., evacuated to atmospheric pressure or less than 0.1 psi). Polishing may be substantially absent during this post-polishing process; for example, the polishing rate may be less than 5%, such as less than 1% of the polishing rate during large-area polishing (in step 310).

[0088] refer to Figure 9B and Figure 13 Each signal value in the original signal trajectory can be converted into a bottom layer thickness value (step 334), for example, using the reference above. Figure 5The relationship curves discussed are used for conversion. For post-polishing processes, this will generate a bottom layer thickness trajectory 270 for each sweep of sensor 102 under the calibration substrate.

[0089] like Figure 13 As shown, the bottom layer thickness trajectory 270 also includes a first portion 272, a second portion 274, and a third portion 276. The first portion corresponds to a position in the edge region of the substrate 10 when the sensor crosses the leading edge of the calibration substrate, the second portion corresponds to a position in the central region of the substrate 10, and the third portion corresponds to a position in the edge region when the sensor 102 crosses the trailing edge of the substrate 10. The signal may also include a portion 278 corresponding to the measurement result outside the substrate, i.e., a signal generated when the sensor head scans the region outside the edge of the substrate 10.

[0090] Continue to refer to Figure 9B and Figure 13 As mentioned above, thickness measurements at the substrate edges may be inaccurate. Therefore, an edge reconstruction technique can also be performed on each bottom layer thickness trajectory 270 to generate a modified bottom layer thickness trajectory 280 for each scan (step 336). In particular, each bottom layer thickness trajectory 270 can be fed into a neural network configured to compensate for signal distortion at the substrate edges. This process is described in U.S. Patent Publication No. 2021-0379723. Each modified bottom layer thickness trajectory 280 can be stored for subsequent processing.

[0091] Using the adjusted effective thickness trajectory 260 (step 304) obtained from the large-area polishing of the conductive layer on the substrate and the adjusted bottom layer thickness trajectory 280 (step 306) obtained from the post-polishing scan of the substrate, the starting thickness value for each radial range can now be determined (step 308).

[0092] In particular, reference Figure 9B and Figure 14 A representative bottom thickness trajectory 282 (340) is generated from the adjusted bottom thickness trajectory 280. For example, one of the adjusted bottom thickness trajectories can be selected as the representative bottom thickness trajectory. Alternatively, the representative bottom thickness trajectory can be generated by averaging two or more adjusted bottom thickness trajectories. For example, the average bottom thickness trajectory DS(t) can be calculated as follows:

[0093] Where D i (t) represents an individual adjusted bottom layer thickness trajectory, while N is the number of bottom layer thickness trajectories.

[0094] Next, continue to refer to Figure 9B and Figure 14Subtracting the representative bottom layer trajectory 282 from each effective thickness trajectory 260 generates a thickness trajectory 290 for each scan of the substrate obtained in step 304 (step 342).

[0095] This trajectory can be called the "thickness trajectory" because by subtracting the underlying contribution from the effective thickness value, which includes both the substrate and the film thickness, only the contribution from the film thickness should remain.

[0096] refer to Figure 9B , Figure 11 and Figure 14 The thickness values ​​from each thickness trajectory 290 can be classified according to radial range, and the thickness value can be calculated for each radial range for each sensor sweep (step 344). For example, the thickness value for a specific radial range for a specific sweep. Therefore, a sequence 166a of thickness values ​​156a is generated for a reference radial range, and a sequence 166b of thickness values ​​156b is generated for each dynamic radial range (for ease of illustration, ...). Figure 11 (Only two sequences are illustrated). For example, the thickness values ​​for the radial range R1 to R2 can be generated by averaging the thickness values ​​from the corresponding portion 292 of the thickness trajectory 290.

[0097] For each radial range, a polynomial function (e.g., a first-order function, i.e., line 176) is fitted to a sequence 166a, 166b of thickness values ​​156a, 156b for that radial range (step 346). For example, robust regression can be used to perform the fitting. In particular, line 176 can be fitted to the thickness values ​​accumulated after polishing begins but before the underlying layer is exposed. Thickness values ​​from the initial one to three rotations of the stage can be excluded because the polishing rate may be unstable during this period. In some implementations, data from four to thirty thickness values ​​are sufficient to fit line 176.

[0098] The thickness value at the start of the polishing operation is calculated for each radial range (step 348). For example, based on the fitted polynomial function, the controller 90 backward extrapolates to determine the initial thickness value (PRE) of the substrate at the start of the polishing process on the calibrated substrate. For the reference radial range, the initial thickness value can be expressed as PRE. (F),R For dynamically controlled radial range, the effective initial thickness value can be expressed as PRE. (F),D The subscript F indicates that the thickness value should basically only represent the contribution of the conductive layer, that is, not the contribution of the underlying layer or substrate.

[0099] refer to Figure 9CFor some implementations, the initial thickness value of the dynamic radial range can be stored as an offset (349). For example, the offset ΔPRE can be stored for each dynamic radial range. D The calculation is as follows: ΔPRE (F),D = PRE (F),R - PRE (F),D .

[0100] The system should now be ready for polishing the product substrate. As mentioned above, refer to the target thickness values ​​TT for the radial range and dynamic radial range. R and TT D Typically provided by the operator, depending on the application and the integrated circuits manufactured on the product substrate. The target thickness value for the dynamic radial range can also be stored as an offset. For example, an offset ΔTT can be set for each dynamic radial range. D The calculation is as follows: ΔTT D = TT R - TT D .

[0101] Continue to refer to Figure 9C and Figure 15 The product substrate (350) is polished at polishing station 20, and the substrate is monitored using an in-situ eddy current monitoring system 160 during polishing of the exposed conductive layer. Sensor 102 generates a raw signal trajectory each time it sweeps under the substrate 10 (step 352). Each signal value in the raw signal trajectory can be converted into an effective thickness value (step 354), for example using the reference above. Figure 5 The relationship curves discussed are used for transformation. This generates an effective thickness trajectory 250' for each sweep of sensor 102 under the product substrate. Similar to the calibration substrate, thickness measurements at the edges of the product substrate may be inaccurate. Therefore, an edge reconstruction technique can be performed on each effective thickness trajectory 250' to generate a modified effective thickness trajectory 260' for each scan (step 356). In particular, each effective thickness trajectory 250' can be fed into a neural network configured to compensate for signal distortion at the substrate edges. This process is described in U.S. Patent Publication No. 2021-0379723.

[0102] Continue to refer to Figure 9C and return Figure 8The thickness values ​​from each modified effective thickness trajectory 260' can be categorized according to radial range, and the effective thickness value can be calculated for each radial range for each sensor sweep (step 360). For example, a sequence 162a of effective thickness values ​​152a is generated for a reference radial range, and a sequence 162b of effective thickness values ​​152b is generated for each dynamic radial range (for ease of illustration). Figure 8 (Only two sequences are illustrated). Each effective thickness value 152a, 152b can be generated by averaging the effective thickness values ​​from the corresponding portion of the corresponding effective thickness trajectory 260'. For example, the effective thickness values ​​for the radial range R1 to R2 can be generated by averaging the effective thickness values ​​from the corresponding portion 262 of the effective thickness trajectory 260'.

[0103] Once a sufficient number of effective thickness values ​​have been collected, a polynomial function (e.g., a first-order function, i.e., a line) is fitted to each sequence of effective thickness values ​​for the said radial range (step 362). For example, the first line 172a is fitted to a sequence 162a of thickness values ​​152a for the reference radial range. Furthermore, for each dynamic radial range, line 172b is fitted to a sequence 162b of effective thickness values ​​152b for the said dynamic radial range. Robust regression can be used to perform the fitting. Effective thickness values ​​from the first one to three rotations of the stage can be excluded, as the polishing rate may be unstable during this period. Also, depending on when the bearing head pressure begins to change, effective thickness values ​​acquired after any pressure change should be excluded, such that the slopes of lines 172a, 172b thus represent the polishing rate of the associated radial range before the pressure adjustment. Data from four to ten effective thickness values ​​may be sufficient to fit lines 172a, 172b.

[0104] Calculate the effective thickness value at the start of the polishing operation (step 364). For example, based on the fitted polynomial function, controller 90 extrapolates backward to determine the effective initial thickness value (PRE) of the substrate at the start of the polishing process. For a reference radial range, the effective initial thickness value can be expressed as PRE. (F+S),R For dynamically controlled radial range, the effective initial thickness value can be expressed as PRE. (F+S),D .

[0105] In some implementations, the effective starting thickness value of the dynamic radial range can be stored as an offset. For example, the offset ΔPRE can be stored for each dynamic radial range. D The calculation is as follows: ΔPRE (F+S),D = PRE (F+S),R - PRE (F+S),D .

[0106] With the target thickness value, the initial thickness value, and the effective thickness value, the adjusted target thickness value can be calculated for each radial range (step 366).

[0107] In particular, the adjusted target thickness value (AT) for the reference radial range. R It can be calculated as: AT R = PRE (F+S),R - (PRE (F),R -TT R ) k Where k is the constant discussed above.

[0108] In addition, the adjusted target thickness value (AT) for each dynamic radial range D It can be calculated as: AT D =AT R P+ ΔPRE (F+S),D - ΔPRE (F),D + ΔTT R .

[0109] The controller 90 can use conventional algorithms to perform endpoint detection or contour control, i.e., calculate the adjustment of the bearing head pressure, but replace the target thickness value with the adjusted target thickness value in the endpoint or contour control algorithm (step 370).

[0110] Continue to refer to Figure 8 A first effective thickness value 152a is obtained for a reference radial range, and a first line 172a is fitted to the first effective thickness value 152a. A second effective thickness value 152b is obtained for a dynamic radial range, and a second line 172b is fitted to the second effective thickness value 152b. End point time ET R The calculation is for the first line 172a to reach the first adjusted target thickness value AT. R The time (in 182a). The second radial range is used as the dynamic range, and the endpoint time ET. D The adjusted target thickness value AT for the second radial range is calculated for line 172b. D The time at (182b).

[0111] Controller 90 can calculate the target polishing rate 190 for the dynamic radial range starting at adjustment time T0, such that both the controlled radial range and the dynamic radial range reach their respective adjusted target thickness values ​​AT substantially simultaneously. R and AT DTo achieve the target polishing rate of 190, the controller 90 can calculate adjustments to one or more polishing parameters, such as adjustments to the pressure in the region of the bearing head corresponding to the dynamic radial range. This calculation can be based on the Preston Equation. Therefore, even if the contribution of the underlying layers to the eddy current signal is inconsistent on a wafer-to-wafer basis, the resulting polishing profile should more closely match the target profile.

[0112] The polishing apparatus and methods described above can be applied to various polishing systems. Either or both of the polishing pad or the carrier head can be moved to provide relative movement between the polishing surface and the substrate. For example, the stage can be circumferential rather than rotating. The polishing pad can be a circular (or some other shape) pad fixed to the stage. Some aspects of the endpoint detection system can be applied to linear polishing systems, such as when the polishing pad is a linearly moving continuous belt or roll-to-roll belt. The polishing layer can be a standard (e.g., filled or unfilled polyurethane) polishing material, a soft material, or a fixed abrasive. The term relative positioning is used to refer to relative positioning within the system or substrate; it should be understood that during the polishing operation, the polishing surface and the substrate can remain vertically oriented or in some other orientation.

[0113] The functional operation of the controller 90 can be implemented using one or more computer program products, that is, one or more computer programs tangibly embodied in a non-transitory computer-readable storage medium, for execution or control of its operation by a data processing device (e.g., a programmable processor, a computer, or a plurality of processors or computers).

[0114] Some embodiments of the invention have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. Therefore, other embodiments are also within the scope of the following claims.

Claims

1. A computer program product for controlling a polishing system, the computer program product residing on a non-transitory computer-readable medium and comprising instructions for causing one or more computers to perform the following operations: Prior to polishing, an initial thickness profile of the conductive outer layer on the substrate is received, the initial thickness profile representing the thickness of the outer layer at multiple regions on the substrate prior to polishing. Prior to polishing, an initial target thickness profile of the conductive outer layer on the substrate is received, the initial target thickness profile representing the required thickness of the outer layer at the plurality of regions after polishing; During the polishing of the substrate, a sequence of signal values ​​is received from an in-situ monitoring system, the signal values ​​depending on the thickness of the conductive outer layer being polished and the thickness and / or conductivity of one or more underlying layers beneath the outer layer; For each of the plurality of regions, the sequence of signal values ​​from the corresponding region is converted into a sequence of effective thickness values ​​for the corresponding region, wherein each effective thickness value includes contributions from the conductive outer layer and the one or more bottom layers, thereby providing a plurality of effective thickness value sequences, wherein each of the plurality of sequences corresponds to a corresponding region; For each of the plurality of regions, a function is fitted to the sequence of effective thickness values, thereby providing a plurality of fitting functions, wherein each of the plurality of fitting functions corresponds to a corresponding region; The plurality of fitting functions are used to determine the effective initial thickness profile of the layer at the start of polishing; The adjusted target thickness profile is calculated based on the initial target thickness profile, the effective starting thickness profile, and the starting thickness profile. and The polishing parameters are modified based on the multiple effective thickness value sequences and the adjusted target thickness profile.

2. The computer program product of claim 1, wherein the initial thickness profile is represented as the initial thickness of the first region and a corresponding initial thickness offset of each of the one or more second regions, wherein the initial target thickness profile is represented as the initial target thickness of the first region and a corresponding target thickness offset of each of the one or more second regions, and the effective initial thickness profile is represented as the effective initial thickness of the first region and a corresponding effective initial thickness offset of each of the one or more second regions.

3. The computer program product of claim 1, wherein the plurality of regions includes a reference region and a dynamic control region, and wherein the instructions for modifying the polishing parameters include instructions for performing the following operations: The expected endpoint time of the reference region is calculated based on the fitting function of the reference region, at which time the effective thickness of the reference region will reach the adjusted target thickness of the reference region; and The pressure in the bearing head of the dynamic control zone is adjusted to adjust the polishing rate of the dynamic control zone, so that the expected effective thickness of the dynamic control zone will reach the adjusted target thickness of the dynamic control zone at the expected end time in the reference zone.

4. The computer program product of claim 3, wherein the function is a linear function.

5. The computer program product of claim 4, wherein the instructions for calculating the expected endpoint time of the reference region include instructions for pushing the function forward to the time when the effective thickness of the reference region reaches the adjusted target thickness of the reference region.

6. The computer program product of claim 4, wherein the initial thickness profile is represented as the initial thickness of the reference region and the corresponding initial thickness offset of each of the one or more dynamic control regions, wherein the initial target thickness profile is represented as the initial target thickness of the reference region and the corresponding target thickness offset of each of the one or more dynamic control regions, and the effective initial thickness profile is represented as the effective initial thickness of the reference region and the corresponding effective initial thickness offset of each of the one or more dynamic control regions.

7. The computer program product of claim 1, wherein the thickness value sequence defines a trajectory sequence, wherein each corresponding trajectory in the trajectory sequence corresponds to a corresponding sweep in multiple sweeps of the in-situ monitoring system's sensor across the substrate.

8. The computer program product of claim 7, comprising instructions for performing edge reconstruction on each respective trajectory to generate a modified trajectory having a modified thickness value, thereby generating a sequence of modified trajectories.

9. The computer program product of claim 8, comprising instructions for calculating, for each corresponding trajectory, an effective thickness value of the region based on the modified thickness value from the region, thereby generating the plurality of effective thickness value sequences.

10. The computer program product of claim 9, wherein the instructions for calculating the effective thickness value of the region based on the modified thickness value include instructions for averaging the modified thickness values ​​from the region.

11. The computer program product of claim 1, wherein the instructions for calculating the adjusted target thickness profile include instructions for calculating a plurality of adjustments based on the difference between the initial thickness profile and the initial target profile, the plurality of adjustments including adjustments for each of the plurality of regions.

12. The computer program product of claim 11, wherein the instructions for calculating the adjusted target thickness profile include instructions for subtracting the adjustment for the corresponding region from the effective starting thickness value of the corresponding region for each of the plurality of regions.

13. The computer program product of claim 12, wherein the instructions for calculating the plurality of adjustments include instructions for multiplying the difference between the starting thickness profile and the initial target profile by a constant.

14. The computer program product of claim 13, wherein the constant is between 1.0 and 1.

2.

15. A chemical mechanical polishing method, the method comprising: Prior to polishing, an initial thickness profile of the conductive outer layer on the substrate is received, the initial thickness profile representing the thickness of the outer layer at multiple regions on the substrate prior to polishing. Prior to polishing, an initial target thickness profile of the conductive outer layer on the substrate is received, the initial target thickness profile representing the required thickness of the outer layer at the plurality of regions after polishing; Polish the conductive outer layer on the substrate; During the polishing of the substrate, a sequence of signal values ​​is received from an in-situ monitoring system, the signal values ​​depending on the thickness of the conductive outer layer being polished and the thickness and / or conductivity of one or more underlying layers beneath the outer layer; For each of the plurality of regions, the sequence of signal values ​​from the corresponding region is converted into a sequence of effective thickness values ​​for the corresponding region, wherein each effective thickness value includes contributions from the conductive outer layer and the one or more bottom layers, thereby providing a plurality of effective thickness value sequences, wherein each of the plurality of sequences corresponds to a corresponding region; For each of the plurality of regions, a function is fitted to the sequence of effective thickness values, thereby providing a plurality of fitting functions, wherein each of the plurality of fitting functions corresponds to a corresponding region; The plurality of fitting functions are used to determine the effective initial thickness profile of the layer at the start of polishing; The adjusted target thickness profile is calculated based on the initial target thickness profile, the effective starting thickness profile, and the starting thickness profile. and The polishing parameters are modified based on the multiple effective thickness value sequences and the adjusted target thickness profile.

16. The method of claim 1, wherein the initial thickness profile is represented as the initial thickness of a first region and a corresponding initial thickness offset for each of one or more second regions, wherein the initial target thickness profile is represented as the initial target thickness of the first region and a corresponding target thickness offset for each of the one or more second regions, and the effective initial thickness profile is represented as the effective initial thickness of the first region and a corresponding effective initial thickness offset for each of the one or more second regions.

17. A polishing system, the polishing system comprising: The worktable is used to support the polishing pad; A support head is used to hold the substrate in contact with the polishing pad; A motor is used to generate relative motion between the support head and the worktable; An eddy current monitoring system is used to monitor the substrate during polishing and generate a sequence of signal values ​​that depend on the thickness of the conductive outer layer being polished and the thickness and / or conductivity of one or more underlying layers beneath the outer layer. and The controller is configured as follows: Prior to polishing, the initial thickness profile of the conductive outer layer on the storage substrate, the initial thickness profile representing the thickness of the outer layer at multiple regions on the substrate prior to polishing; Prior to polishing, an initial target thickness profile of the conductive outer layer on the substrate is stored, the initial target thickness profile representing the required thickness of the outer layer at the plurality of regions after polishing; Receive the signal value sequence from the in-situ monitoring system; For each of the plurality of regions, the sequence of signal values ​​from the corresponding region is converted into a sequence of effective thickness values ​​for the corresponding region, wherein each effective thickness value includes contributions from the conductive outer layer and the one or more bottom layers, thereby providing a plurality of effective thickness value sequences, wherein each of the plurality of sequences corresponds to a corresponding region; For each of the plurality of regions, a function is fitted to the sequence of effective thickness values, thereby providing a plurality of fitting functions, wherein each of the plurality of fitting functions corresponds to a corresponding region; The plurality of fitting functions are used to determine the effective initial thickness profile of the layer at the start of polishing; The adjusted target thickness profile is calculated based on the initial target thickness profile, the effective starting thickness profile, and the starting thickness profile. and The polishing parameters are modified based on the multiple effective thickness value sequences and the adjusted target thickness profile.

18. The system of claim 17, wherein the plurality of regions includes a reference region and a dynamic control region, and wherein the controller is configured to: The expected endpoint time of the reference region is calculated based on the fitting function of the reference region, at which time the effective thickness of the reference region will reach the adjusted target thickness of the reference region; and The pressure in the bearing head of the dynamic control zone is adjusted to adjust the polishing rate of the dynamic control zone, so that the expected effective thickness of the dynamic control zone will reach the adjusted target thickness of the dynamic control zone at the expected end time in the reference zone.

19. The system of claim 17, wherein the function is a linear function.

20. The system of claim 18, wherein the controller is configured to calculate the expected endpoint time of the reference region by pushing the function forward to the time when the effective thickness of the reference region reaches the adjusted target thickness of the reference region.

21. The system of claim 17, wherein in the controller, the initial thickness profile is represented as an initial thickness of a first region and a corresponding initial thickness offset for each of one or more second regions, wherein the initial target thickness profile is represented as an initial target thickness of the first region and a corresponding target thickness offset for each of the one or more second regions, and the effective initial thickness profile is represented as an effective initial thickness of the first region and a corresponding effective initial thickness offset for each of the one or more second regions.

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