Substrate polishing apparatus and film thickness calculation method

Abstract

The present invention accurately measures the thickness of a film to be polished during substrate polishing. The substrate polishing apparatus includes: a polishing table provided with an eddy current sensor and configured to be rotatable; a polishing head facing the polishing table, configured to be rotatable, and capable of mounting a substrate on a surface facing the polishing table; and a control unit. The control unit is configured to use an output signal from the eddy current sensor to a reference substrate to generate mapping data indicating the arrangement of one or more metal structures locally present on the surface or inside of the reference substrate, and to generate mapping data indicating the arrangement of one or more metal structures locally present on the surface or inside of the reference substrate during polishing of a substrate to be polished having the same arrangement of metal structures as the reference substrate. A profile of an output signal of the eddy current sensor when the eddy current sensor passes through a certain track on a surface to be polished of the substrate to be polished is acquired, and a track through which the eddy current sensor corresponding to the profile passes on the surface to be polished of the substrate to be polished is determined based on the profile. Determining whether or not there is a metal structure on the determined track of the substrate to be polished on the basis of the mapping data, and correcting the profile of the output signal of the eddy current sensor to the substrate to be polished so that the signal value of the position at which the metal structure is determined to be present is reduced; and calculating the film thickness of the substrate to be polished on the basis of the corrected profile of the output signal of the eddy current sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to a substrate polishing apparatus and a film thickness calculation method. BACKGROUND

[0002] A CMP (Chemical Mechanical Polishing) apparatus is a kind of apparatus for manufacturing semiconductor components. A representative CMP apparatus is provided with a polishing table on which a polishing pad is mounted, and a polishing head on which a substrate is mounted. In the representative CMP apparatus, a polishing liquid is supplied to the polishing pad, and the substrate is polished in a state where the polishing pad is in contact with the substrate, in a manner that at least one of the polishing table and the polishing head is rotated.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-058955

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In substrate polishing, in order to measure the thickness of a film of a polishing target, an eddy current sensor can be used. The eddy current sensor is provided, for example, on a polishing table. The eddy current sensor moves along a certain track on the surface of a substrate along with rotation of the polishing table, and measures the thickness of the film at each point on the track (see, for example, Patent Document 1). However, when there is a local metal structure on the substrate in addition to the film (metal film) of the polishing target, accurate measurement of the thickness of the film of the polishing target, which is supposed to be measured, becomes difficult due to the influence thereof. SUMMARY OF THE INVENTION

[0008] According to one embodiment, there is provided a substrate polishing apparatus including: a polishing table provided with an eddy current sensor and configured to be rotatable; a polishing head opposed to the polishing table and configured to be rotatable, the polishing head being capable of mounting a substrate on a surface thereof opposed to the polishing table; and a control unit configured to: generate map data indicating a configuration of one or more metal structures locally present on a surface or inside of a reference substrate, using an output signal of the eddy current sensor with respect to the reference substrate; in polishing of a polishing target substrate having the same configuration of the metal structures as the reference substrate, acquire a profile of an output signal of the eddy current sensor when the eddy current sensor passes over a certain track on a polished surface of the polishing target substrate, determine a track on the polished surface of the polishing target substrate through which the eddy current sensor corresponding to the profile passes, based on the profile; determine whether or not there is a metal structure on the determined track of the polishing target substrate, based on the map data; correct the profile of the output signal of the eddy current sensor with respect to the polishing target substrate in such a manner that a signal value of a position determined to have the metal structure is reduced; and calculate a film thickness of the polishing target substrate, based on the profile of the output signal of the eddy current sensor after the correction. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a front view of a substrate polishing apparatus according to one embodiment.

[0010] Figure 2 is a cross-sectional schematic view showing a configuration of an exemplary substrate that is a target of polishing by a substrate polishing apparatus.

[0011] Figure 3 is a flowchart showing an outline of an operation of a substrate polishing apparatus according to one embodiment.

[0012] Figure 4 is a flowchart showing an algorithm of a method according to one embodiment of the present application.

[0013] Figure 5 is a flowchart showing an algorithm of a method according to one embodiment of the present application.

[0014] Figure 6 is a schematic view showing an exemplary track by an eddy current sensor on a substrate.

[0015] Figure 7 is an example of a sensor output map with respect to a reference substrate.

[0016] Figure 8 is a processing conceptual view of correcting a position of a maximum value (or a minimum value) in a sensor output map.

[0017] Figure 9 This is an example of mapped data.

[0018] Figure 10 This is an illustration of the correction process for the profile of the output signal of an eddy current sensor.

[0019] Figure 11 This is a flowchart illustrating the process of determining the trajectory of the eddy current sensor.

[0020] Figure 12 This is an example of sensor output mapping for a substrate being ground.

[0021] Figure 13 This is an example of the profile of the output signal of an eddy current sensor.

[0022] Figure 14 This is an example of a contour mapped from the sensor output. Detailed Implementation

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings described below, identical or equivalent constituent components are labeled with the same symbols, and repeated descriptions are omitted.

[0024] Figure 1 This is a front view of a substrate polishing apparatus 100 according to one embodiment. Figure 1 The substrate polishing apparatus 100 shown is a CMP (Chemical Mechanical Polishing) apparatus. However, the substrate polishing apparatus 100 is not limited to a CMP apparatus. The substrate polishing apparatus 100 can be any apparatus that polishes a substrate by rotating a polishing table equipped with an eddy current sensor.

[0025] The CMP apparatus 100 includes a grinding table 110, a grinding head 120, and a liquid supply mechanism 130. The CMP apparatus 100 further includes a control unit 140 for controlling the various components. The control unit 140 may include, for example, a storage device 141, a processor 142, and an input / output device 143.

[0026] A polishing pad 111 is detachably mounted on the upper surface of the polishing table 110. Here, the upper surface of the polishing table 110 refers to the surface of the polishing table 110 opposite to the polishing head 120. Therefore, the upper surface of the polishing table 110 is not limited to the surface located in the vertical direction. The polishing head 120 is positioned opposite the polishing table 110. A substrate 121 is detachably mounted on the surface of the polishing head 120 opposite to the polishing table 110. The liquid supply mechanism 130 is configured to supply polishing fluid, such as a slurry, to the polishing pad 111. Alternatively, the liquid supply mechanism 130 may also be configured to supply cleaning fluid or a chemical solution in addition to the polishing fluid.

[0027] The CMP apparatus 100 can lower the polishing head 120 via a vertical movement mechanism (not shown) to bring the substrate 121 into contact with the polishing pad 111. However, the vertical movement mechanism can also move the polishing table 110 vertically. The polishing table 110 and the polishing head 120 are rotated by a motor (not shown) or the like. The CMP apparatus 100 polishes the substrate 121 while it is in contact with the polishing pad 111 by rotating both the polishing table 110 and the polishing head 120.

[0028] The CMP apparatus 100 may further include air bladders 122 divided into multiple concentric circular sections. Air bladders 122 may be disposed on the polishing head 120. Air bladders 122 may also be disposed on the polishing table 110 as an addition or alternative. Air bladders 122 are components used to adjust the polishing pressure of the substrate 121 according to each region of the substrate 121. Air bladders 122 are configured to change volume due to the air pressure introduced into them. Fluids other than air, such as nitrogen or pure water, may also be introduced into the air bladders 122.

[0029] An eddy current sensor 150 is disposed inside the polishing table 110. The eddy current sensor 150 is positioned so that it passes through the center of the substrate 121 when the polishing table 110 rotates during polishing. The eddy current sensor 150 is configured to sense eddy currents in the conductive layer on the surface of the substrate 121. The eddy current sensor 150 is further configured to receive changes in impedance caused by the magnetic field generated by the eddy currents and output a signal corresponding to the thickness of the conductive layer on the surface of the substrate 121. By using the output signal from the eddy current sensor 150, the film thickness of the polishing target film on the surface of the substrate 121 can be determined.

[0030] Here, the factors affecting the output signal of the eddy current sensor 150 are not limited to the film of the polished object exposed on the outermost surface of the substrate 121 (the film formed over the entire outermost surface of the substrate 121). Figure 2 This is a cross-sectional schematic diagram showing the structure of an exemplary substrate 121, which is the object to be polished by the substrate polishing apparatus 100. (See diagram below.) Figure 2As shown, on the upper surface of the illustrated substrate 121, a dielectric film (e.g., a film made of silicon dioxide (SiO2) or the like) 202 is formed over its entire surface, and a metal film (e.g., a film made of copper (Cu) or the like) 204 is further formed on top of the dielectric film 202. The metal film 204 is the polishing target film located on the outermost surface of the substrate 121. Furthermore, the substrate 121 may have one or more penetrating electrodes 206 for conducting one side of it to the other side. Moreover, metal wiring 208 may be embedded in the dielectric film 202 on the substrate 121. When the eddy current sensor 150 passes over or near such penetrating electrodes 206 and metal wiring 208, eddy currents are also induced on these metal structures, thus affecting the output signal of the eddy current sensor 150. The signal value changes from the output signal of the eddy current sensor 150 when the penetrating electrodes 206 and metal wiring 208 are absent on the substrate 121. In other words, the penetrating electrode 206 and the metal wiring 208, which are local metal structures formed on the substrate 121, can cause noise in the output signal of the eddy current sensor 150. In addition, the metal structures are not limited to the penetrating electrode 206 or the metal wiring 208 embedded in the dielectric film 202 as described above; other examples may include wiring and vias exposed on the outermost surface of the substrate 121.

[0031] Figure 3 This is a flowchart illustrating the general operation of a substrate polishing apparatus 100 according to one embodiment.

[0032] In step 302, a polishing process is performed. Specifically, the substrate 121 is mounted on the polishing head 120, and slurry is supplied from the liquid supply mechanism 130. With the substrate 121 pressed against the polishing table 110 by the polishing head 120, both the polishing table 110 and the polishing head 120 rotate to polish the substrate 121. During polishing, a film representing the polishing target on the substrate 121 (e.g., based on the output signal of the eddy current sensor 150) is fabricated. Figure 2 The thickness of the metal film 204 in the substrate is mapped onto the substrate surface. The fabrication of the thickness mapping is described in detail below. The polishing process in step 302 continues until a predetermined end condition is met, such as until a pre-set polishing time has elapsed to polish the film to the desired degree. After the polishing process in step 302, the process proceeds to step 304.

[0033] In step 304, based on the film thickness mapping created above, it is determined whether to continue polishing the substrate 121. For example, it is determined whether the desired film thickness or film thickness profile has been achieved over the entire surface of the substrate 121 or at least a portion of the substrate 121. If the desired film thickness or film thickness profile has not been achieved, the process proceeds to step 306 in order to continue polishing the substrate 121. Alternatively, if the desired film thickness or film thickness profile has been achieved, the operation of the substrate polishing apparatus 100 ends.

[0034] In step 306, the polishing conditions of the polishing process are adjusted. For example, based on the film thickness mapping, an additional polishing duration is set. Furthermore, the control unit 140 can also increase or decrease the internal pressure of the airbag 122 based on the film thickness mapping, increasing the polishing pressure in areas with thicker film thickness (i.e., areas with lower polishing progress) and decreasing the polishing pressure in areas with thinner film thickness (i.e., areas with higher polishing progress). This control maintains a uniform polishing state of the substrate 121. The polishing process of step 302 is then performed again according to the adjusted polishing conditions.

[0035] Figure 4 and Figure 5 This is a flowchart of an algorithm for a film thickness calculation method according to one embodiment of the present invention, capable of removing or reducing noise in the output signal of the eddy current sensor 150 caused by local metallic structures on the substrate 121. As a preliminary step, the method includes a stage of generating mapping data representing the configuration of one or more metallic structures locally present on or inside the substrate surface. Figure 4 ); and using the pre-prepared mapping data to correct the output signal of the eddy current sensor 150, thereby accurately calculating the film thickness on the substrate in stages ( Figure 5 The processing of each flowchart can be performed by a processor (e.g., processor 142 of control unit 140).

[0036] First, refer to Figure 4 The flowchart illustrates the process of creating the mapping data. This preparatory stage uses a "reference substrate." The reference substrate is a substrate whose surface does not have a metal film formed. For example, in... Figure 2 In the illustrated substrate 121 (hereinafter referred to as the "polishing target substrate"), the substrate from which the metal film 204 is removed from its entire surface, exposing the dielectric film 202 on the outermost surface, is a reference substrate (hereinafter referred to as "reference substrate 121'" for convenience). For example, one or more of a plurality of polishing target substrates 121 of the same type (i.e., manufactured using the same manufacturing process) can be polished first as reference substrates 121'. Here, "same type substrate" means "a substrate on which the wiring pattern is at least the same in design".

[0037] In step 402, the output signal of the eddy current sensor 150 to the reference substrate 121' is acquired. Specifically, the output signal is acquired from the eddy current sensor 150 while rotating both the polishing head 120 and the polishing table 110, on which the reference substrate 121' is mounted, at a predetermined rotational speed. The eddy current sensor 150 moves along an arc-shaped track corresponding to the ratio of the rotational speed of the polishing table 110 to the rotational speed of the polishing head 120 to the reference substrate 121' (i.e., when viewed from the reference substrate 121'). For each revolution of the polishing table 110, the eddy current sensor 150 traverses the surface of the reference substrate 121' along an arc-shaped track with a predetermined curvature determined by the rotational speeds of the polishing table 110 and the polishing head 120. In the next rotation of the polishing table 110, it travels along an arc with the same curvature as the previous rotation, but through a track corresponding to a different arc. Therefore, signal values ​​at various points on these multiple arc-shaped tracks are continuously acquired from the eddy current sensor 150. Furthermore, since correct mapping data cannot be generated when the substrate is polished in step 402, step 402 is intended to be performed while water, rather than slurry, is supplied from the liquid supply mechanism 130 (i.e., water polishing process is performed). Thus, without polishing the reference substrate 121', signal values ​​from the eddy current sensor 150 corresponding to multiple tracks on the reference substrate 121' can be obtained.

[0038] Figure 6 This is a schematic diagram showing an exemplary track of the eddy current sensor 150 on substrate 121 (reference substrate 121'). In this figure, the arc-shaped curved arrows indicate one track of the eddy current sensor 150 and the direction of travel of the eddy current sensor 150 on that track. Furthermore, the symbols "1" to "10" in the figure indicate the sequence numbers of the tracks traversed by the eddy current sensor 150. As the polishing table 110 and polishing head 120 rotate, the eddy current sensor 150 moves along the surface of substrate 121 in the order of tracks "1" to "10," while outputting signal values ​​at various points on the tracks.

[0039] in addition, Figure 6In this example, the angular interval θ between adjacent tracks is set to 36 degrees. When the grinding table 110 rotates 10 times, the eddy current sensor 150 follows the same track as before (track "10" followed by track "1"). In other words, the number of tracks traversed by the eddy current sensor 150 in this example is at most 10. However, in order to increase the number of measurement points based on the eddy current sensor 150, the number of tracks traversed by the eddy current sensor 150 is preferably sufficiently large. Therefore, the angular interval θ of the tracks can be set to, for example, 10 degrees or less, preferably 5 degrees or less, and more preferably 1 degree or less. The angular interval θ of the tracks can also be selected in such a way that the measurement points of the eddy current sensor 150 are sufficiently densely arranged on the substrate 121. The angular interval θ of the tracks can be arbitrarily set by combining the rotational speed of the grinding table 110 and the rotational speed of the grinding head 120.

[0040] Next, in step 404, a sensor output map for reference substrate 121' is created using the output signal of the eddy current sensor 150 obtained in step 402. The sensor output map is a distribution map of the magnitude of the output signal of the eddy current sensor 150 across the entire surface of substrate 121 (here, reference substrate 121'). As described, with respect to multiple tracks on reference substrate 121', signal values ​​of the eddy current sensor 150 for each measurement point on the tracks are obtained, and these signal values ​​are plotted on the XY plane, thereby enabling the creation of a sensor output map for reference substrate 121'. The XY coordinates of each measurement point on the track can be determined based on the track shape (curvature) determined by the rotational speed of the grinding table 110 and the grinding head 120, or based on signals from an encoder provided in the motor used to rotate the grinding table 110 and the grinding head 120.

[0041] Figure 7 This is an example 700 of a sensor output map for a reference substrate 121' prepared according to step 404. In this example, the signal value distribution of the eddy current sensor 150 at each measurement point is represented by density. The sensor output map 700 has a plurality of bright spots 702 dispersed in the plane of the reference substrate 121'. These bright spots 702 are areas where the signal values ​​of the eddy current sensor 150 are large, and correspond to local metallic structures provided on the reference substrate 121'. Figure 2 (e.g., the penetrating electrodes 206 and metal wiring 208). In addition, in the design of the final product (e.g., a semiconductor chip) manufactured from the substrate 121, the penetrating electrodes 206 are often arranged regularly (e.g., the penetrating electrodes 206 are arranged in a straight line and / or at equal intervals).

[0042] Next, in step 406, a maximum (or minimum) value is searched in the sensor output map created in step 404, and the location (i.e., XY coordinates) of the found maximum (or minimum) value is temporarily stored. The algorithm for searching the maximum (or minimum) value can be any appropriate known method, and its detailed description is omitted here.

[0043] Next, when correcting the position of the maximum (or minimum) value (if yes in step 408), proceed to step 410. In step 410, the position of each maximum (or minimum) value is corrected so that the multiple maximum (or minimum) values ​​found in step 406 are arranged in a straight line on the XY plane. Then, in step 412, the position of each maximum (or minimum) value is corrected so that the multiple maximum (or minimum) values ​​found in step 406 are arranged at equal intervals on the XY plane. Either step 410 or step 412 may be omitted. Alternatively, in step 412, correction may be performed by interpolating any missing maximum (or minimum) values.

[0044] Figure 8 This is a conceptual diagram illustrating the position correction process for the maximum (or minimum) values ​​in steps 410 and 412. As described, for example, when using a substrate 121 (reference substrate 121') with multiple penetrating electrodes 206 arranged linearly and at equal intervals, if the eddy current sensor 150 passes correctly directly above all the penetrating electrodes 206 as its trajectory, it is expected that the bright spots 702 on the sensor output map 700 created in step 404 will be correctly arranged linearly and at equal intervals. However, when the eddy current sensor 150 passes through a location slightly deviated from a certain penetrating electrode 206, the position of the bright spots 702 on the sensor output map 700 corresponding to that penetrating electrode 206 will deviate from the assumed linearly and at equal intervals position. Figure 8 In this diagram, point 702a represents the point where the position deviates. The other points 702b, 702c, ... are arranged in a straight line with equal intervals and without deviation. For the point 702a where the position deviates, the position 802a of the maximum value determined in step 406 is corrected in steps 410 and 412 to be a straight line with equal intervals, based on the positions 802b, 802c, ... of the maximum values ​​corresponding to the points 702b, 702c, ... where the position does not deviate. Therefore, regardless of the trajectory of the eddy current sensor 150, the position of the local metal structure (penetrating electrode 206 or metal wiring 208, etc.) provided on the reference substrate 121' can be accurately determined.

[0045] Next, in step 414, the dimensions of the local metal structure on the reference substrate 121' are determined. For example, if the metal structure is a penetrating electrode 206, the diameter of the penetrating electrode 206 is determined. Furthermore, if the metal structure is a metal wiring 208, the wiring width and / or length can be determined. For example, the diameter of the penetrating electrode 206 can be predetermined based on the point size of the eddy current sensor 150 (i.e., the size of the area where the eddy current sensor 150 can detect the magnetic field), the distance between the eddy current sensor 150 and the reference substrate 121', and the actual dimensions (known design dimensions) of the penetrating electrode 206 on the reference substrate 121'. Alternatively, the diameter of the penetrating electrode 206 can also be determined based on the size of the bright spot 702 in the sensor output map 700 created in step 404. The size of the bright spot 702 in the sensor output map 700 can, for example, be determined as a region where the signal value is greater than a predetermined value, or it can be determined as a region where the signal value is greater than a predetermined ratio for each maximum value in the sensor output map 700.

[0046] Secondly, in step 416, based on the location of the maximum (or minimum) value on the sensor output mapping determined in step 406 (or the location of the maximum (or minimum) value corrected in steps 410 and 412), and the size of the metal structure determined in step 414, mapping data representing the configuration of local metal structures on the reference substrate 121' is generated. For example, it is possible to define... Figure 8 Multiple circles are formed centered on the positions of the maxima 802a', 802b, 802c, ... , represented by the symbol X. The diameter of the penetrating electrode 206 determined in step 414 is the radius of these multiple circles. Mapping data is generated, where the inside of the thus defined circles has a value of "1" and the outside has a value of "0". Thus, mapping data corresponding to the reference substrate 121' having multiple penetrating electrodes 206 can be obtained.

[0047] Figure 9 This is an example of how mapping data is made. The mapping data 900 consists of coordinate values ​​(XY coordinates) of each point on the XY plane of the substrate 121 surface and values ​​that identify whether each point on the substrate 121 is a metal structure (penetrating electrode 206 or metal wiring 208, etc.). Figure 9 In the illustrated mapping data 900, each point inside a plurality of black circles 902 has a value of "1", indicating that the corresponding area on the substrate 121 is the penetrating electrode 206. Furthermore, each point outside the black circles 902 has a value of "0". By using this mapping data 900, the location of local metallic structures (such as the penetrating electrode 206, metallic wiring 208, etc.) provided on the substrate 121 can be determined.

[0048] Secondly, refer to Figure 5The flowchart illustrates the process of correcting the output signal of the eddy current sensor 150 using mapping data and calculating the film thickness on the substrate. Furthermore, this process uses a "polished substrate" 121 (i.e., for example...). Figure 2 As shown, the substrate on which the metal film 204 of the object to be ground is formed is not the reference substrate 121'.

[0049] First, in step 502, the output signal of the eddy current sensor 150 to the substrate 121 to be polished is acquired. Specifically, the output signal is acquired from the eddy current sensor 150 while both the polishing head 120 and the polishing table 110, on which the substrate 121 to be polished are mounted, are rotated at a predetermined rotational speed. Step 502 is essentially the same as described above. Figure 4 Similarly, in step 402 of the flowchart, as the polishing table 110 and polishing head 120 rotate, the eddy current sensor 150 travels along an arc-shaped track on the surface of the substrate 121 to be polished. Correspondingly, signal values ​​at various points on the substrate 121 to be polished are continuously obtained from the eddy current sensor 150 along this track. Hereinafter, the series of signal values ​​obtained by the eddy current sensor 150 as it travels along a certain track will be referred to as the "profile" of the output signal of the eddy current sensor 150. Furthermore, in step 502 described... Figure 3 In step 302 of the flowchart, the polishing process can be performed during the polishing of the substrate 121.

[0050] Next, in step 504, based on the profile of the output signal of the eddy current sensor 150, the track on the grinding target substrate 121 through which the eddy current sensor 150 passes is determined. Details of this step 504 are provided in the following reference. Figure 11 Explanation follows.

[0051] Secondly, in step 506, the portion of the outline of the output signal of the eddy current sensor 150 obtained in step 502 that corresponds to the outer edge of the substrate 121 (e.g., a strip-shaped area a few millimeters inward from the end of the substrate 121) is masked. This is because it is assumed that the measurement accuracy of the eddy current sensor 150 is poor in the outer edge of the substrate 121, so it is preferable to exclude the signal value of the eddy current sensor 150 obtained from this portion from the subsequent calculations.

[0052] Secondly, in step 508, the profile of the output signal of the eddy current sensor 150 after processing in step 506 is standardized.

[0053] Secondly, in step 510, based on Figure 4The mapping data, created through the processing of the flowchart, extracts the coordinates of the portion overlapping with local metallic structures (e.g., penetrating electrodes 206 and metal wiring 208, etc.) of the grinding target substrate 121 from the track of the eddy current sensor 150 determined in step 504. For example, by... Figure 9 By superimposing the mapping data 900 of the illustrated example with the track of the eddy current sensor 150, the portion where the track of the eddy current sensor 150 overlaps with a local metallic structure of the substrate 121 being ground can be determined. More specifically, the values ​​at each point on the track of the eddy current sensor 150 that are "1" (i.e., ...) on the mapping data 900 can be compared. Figure 9 The point corresponding to the black circle 902 in the image is extracted as the part where the track of the eddy current sensor 150 overlaps with the local metal structure of the grinding object substrate 121.

[0054] Next, in step 512, the profile of the output signal of the eddy current sensor 150 is corrected using the result of step 510. Specifically, signal peaks are searched in the profile of the output signal of the eddy current sensor 150 after normalization in step 508, and it is determined whether the found peaks correspond to the position of the overlap between the track of the eddy current sensor 150 and the local metal structure of the grinding target substrate 121 as determined in step 510. If the peak of the profile corresponds to the position of the overlap, the profile of the output signal of the eddy current sensor 150 is corrected by attenuating the peak of the profile (in other words, reducing the signal value of the peak portion).

[0055] Figure 10 This is an example used to help understand the profile of the output signal of the eddy current sensor 150 before and after correction in the correction process of step 512. Figure 10 The horizontal axis of the graph represents the position of the eddy current sensor 150 on the track, and the vertical axis represents the standardized sensor output signal (i.e., the signal value of the eddy current sensor 150 after standardization in step 508). Figure 10In the example, the uncorrected contour 1002 has peaks Pa, Pb, Pc, Pd, Pe, Pf, Pg, Ph corresponding to the overlap between the track of the eddy current sensor 150 determined from the mapping data and the local metallic structure of the substrate 121 to be ground; and other peaks Pi, Pj, Pk, Pl, Pm, Pn. In the corrected contour 1004, the signal values ​​of the peaks Pa, Pb, Pc, Pd, Pe, Pf, Pg, Ph in the uncorrected contour 1002 and their vicinity are changed to predetermined values ​​smaller than the peak values ​​of each peak. More specifically, the signal values ​​near each peak Pa, Pb, Pc, Pd, Pe, Pf, Pg, Ph that correspond to the range of the overlap between the track of the eddy current sensor 150 and the local metallic structure of the substrate 121 to be ground (i.e., the range of values ​​"1" on the mapping data 900) are changed to predetermined values. The specified value could be, for example, the peak value of each wave peak multiplied by a specified attenuation rate (e.g., 30%). Alternatively, a larger attenuation rate could be set closer to the center of the wave peak. Furthermore, the wave peaks Pi, Pj, Pk, Pl, Pm, and Pn are not subject to correction and are retained as is in the corrected contour 1004.

[0056] Thus, by correcting the profile of the output signal of the eddy current sensor 150 based on the mapping data through steps 510 and 512, the noise generated in the output signal of the eddy current sensor 150 due to local metal structures contained in the substrate 121 to be polished can be removed or reduced.

[0057] Secondly, in step 514, in order to restore the original scale of the value after standardization in step 508, the reciprocal of the ratio of the multiplication of the signal value of the eddy current sensor 150 is multiplied by the corrected profile in step 512 during standardization.

[0058] Secondly, in step 516, for the profile processed in step 514, a moving average is calculated with respect to the direction along the track of the eddy current sensor 150 (i.e., Figure 10 (The moving average along the horizontal axis in the curve graph).

[0059] Next, in step 518, the signal value corresponding to the outer edge of the substrate 121 that was shielded in step 506 is combined with the contour processed in step 516.

[0060] Secondly, in step 520, for multiple adjacent tracks of the eddy current sensor 150, a moving average of the profile processed in step 518 is calculated. Furthermore, the moving average in step 516 is equivalent to a moving average in the radial direction of the substrate 121, and the moving average in step 520 is equivalent to a moving average in the circumferential direction of the substrate 121. Through these moving average processes, subtle noise present in the profile of the output signal of the eddy current sensor 150 can be removed.

[0061] Next, in step 522, based on the contours of the signal values ​​of multiple (overall) tracks of the eddy current sensor 150 obtained from the processing up to step 520, a film thickness map of the substrate 121 to be polished is created (refer to...). Figure 3 (Step 302). For example, for each of the multiple tracks of the eddy current sensor 150, the film thickness at each point on the track can be calculated based on the profile processed in step 520, and the film thickness at each point can be plotted on the XY plane, thereby creating a film thickness map representing the film thickness distribution on the substrate 121 to be polished. As described, because the noise caused by local metal structures on the substrate 121 to be polished is removed or reduced in the profile processed in step 520, a high-precision film thickness map can be obtained without being affected by the penetrating electrode 206, metal wiring 208, etc. on the substrate 121 to be polished.

[0062] Secondly, refer to Figure 11 The flowchart details the process of determining the track of the eddy current sensor 150 in step 504 above.

[0063] In step 1102, a sensor output mapping for the substrate 121 to be polished is created. The sensor output mapping for the substrate 121 to be polished can be related to the sensor output mapping described in [the original text]. Figure 4 In step 404, the sensor output mapping for the reference substrate 121' is created using the same method, and the output signal of the polishing target substrate 121 is generated using the eddy current sensor 150. For example, the sensor output mapping for the polishing target substrate 121 can be created using the same method as... Figure 5 The process of the flowchart is to process the same type of polishing target substrate 121 as another one or more polishing target substrates 121, which are prepared in advance.

[0064] Figure 12 This is an example 1200 of the sensor output mapping of the substrate 121 to be ground. The value of the output signal of the eddy current sensor 150 can be profiled on any shape of line drawn on the sensor output mapping 1200 (e.g., line A-A' as shown in the figure). That is, the profile along any line on the mapping can be calculated based on the sensor output mapping 1200.

[0065] Secondly, in step 1104, the sensor output mapping of the polishing target substrate 121, created in step 1102, is extracted to obtain the sensor output mapping that corresponds to the sensor output mapping of the polishing target substrate 121. Figure 5The trajectory of the most similar contour to the contour of the output signal of the eddy current sensor 150 obtained in step 502 of the flowchart (e.g., the contour obtained during the grinding of the substrate 121). Furthermore, in step 1106, the trajectory extracted from the sensor output mapping is determined as the trajectory on the substrate 121 being ground by the eddy current sensor 150.

[0066] For example, the similarity of contours can be determined by summing the differences between the contour on a track mapped by the sensor output in step 1102 and the contour of the output signal of the eddy current sensor 150 obtained in step 502 at the corresponding measurement points. As an example, the two contours are most similar when the sum of the differences is minimized. Other methods can also determine similarity by comparing, for example, at least one of the crest shape, crest position, or crest size of the contour on a track mapped by the sensor output with at least one of the crest shape, crest position, or crest size of the contour of the output signal of the eddy current sensor 150. Alternatively, any method for determining the similarity of contours can be used.

[0067] For the processing of steps 1104 and 1106, refer to... Figure 12 to Figure 14 To be more specific. As an example, from Figure 12 The sensor output is mapped to cut out the contours on tracks A-A', B-B', and C-C'. The angular interval θ between each track can be, for example, less than 0.1 degrees, and the number of cut contours can be more than 4. Figure 12 The tracks A-A' are represented by straight lines, but the shape of each track can be an arc, just like the actual track. Figure 5 In step 502 of the flowchart, the following is obtained: Figure 13 The outline 1300 of the output signal of the eddy current sensor 150 shown.

[0068] The control unit 140 acquires the contours on each track of the sensor output mapping 1200. For example... Figure 12 There are 3 tracks shown. Therefore, in this example, as... Figure 14 As shown, three contours (contour A-A', contour B-B', and contour C-C') are obtained from the sensor output mapping 1200. Additionally, it is hoped that this will be understood as... Figure 14 The outline is not strictly reproduced. Figure 12 The sensor output maps a 1200-degree contour.

[0069] The control unit 140 uses any method for comparing similarity to determine the track with the contour 1300 that is most similar to the contour 1300 of the output signal of the eddy current sensor 150. For example, the control unit 140 can calculate the similarity based on the magnitude of the average quadratic error after normalizing the contour 1300 of the output signal of the eddy current sensor 150 with contours A-A', B-B', and C-C' obtained from the sensor output mapping 1200. In this example, contour C-C' is determined to be most similar to the contour 1300 of the output signal of the eddy current sensor 150. The control unit 140 can determine the track C-C' corresponding to contour C-C' as the track of the eddy current sensor 150 on the grinding target substrate 121.

[0070] The embodiments of the present invention have been illustrated above based on several examples. However, the embodiments described above are for ease of understanding of the present invention and are not intended to limit the present invention. The present invention can be modified and improved without departing from its spirit, and its equivalents are naturally included in the present invention. Furthermore, within the scope of solving at least a portion of the above-mentioned problems, or within the scope of achieving at least a portion of the effects, the constituent components described in the claims and specification can be arbitrarily combined or omitted.

[0071] Symbol Explanation

[0072] 100 substrate grinding apparatus

[0073] 110 grinding table

[0074] 111 Abrasive Pad

[0075] 120 grinding head

[0076] 121 substrate

[0077] 122 airbags

[0078] 130 Liquid Supply Unit

[0079] 140 Control Department

[0080] 141 storage devices

[0081] 142 processor

[0082] 143 Input / Output Devices

[0083] 150 Eddy Current Sensor

[0084] 202 dielectric film

[0085] 204 metal film

[0086] 206 Penetration Electrode

[0087] 208 metal wiring.

Claims

1. A substrate grinding apparatus, characterized in that, have: A grinding table equipped with an eddy current sensor and configured to rotate; A grinding head, which is opposite to the grinding table and is configured to be rotatable, and a substrate can be mounted on the surface opposite to the grinding table; and Control Department The control unit is configured as follows: Using the output signal from the eddy current sensor to the reference substrate, mapping data representing the configuration of one or more metallic structures locally present on or within the surface of the reference substrate is generated. During the polishing of a target substrate having the same metallic structure as the reference substrate, the profile of the output signal of the eddy current sensor is obtained when the eddy current sensor passes through a certain track on the polished surface of the target substrate. Based on the profile, the trajectory of the eddy current sensor corresponding to the profile is determined on the surface of the substrate being polished. Based on the mapping data, it is determined whether there are any metal structures on the identified tracks of the substrate being ground. The profile of the output signal of the eddy current sensor to the substrate being polished is corrected in a manner that reduces the signal value at which the location of the metal structure is determined to exist. The film thickness of the substrate to be ground is calculated based on the profile of the corrected output signal of the eddy current sensor.

2. The substrate polishing apparatus as described in claim 1, characterized in that, The process of generating the mapping data includes the following process: correcting the position of each maximum or minimum value by arranging the multiple maximum or minimum values ​​of the output signal of the eddy current sensor in a linear manner across the entire surface of the reference substrate.

3. The substrate polishing apparatus as described in claim 1 or 2, characterized in that, The process of generating the mapping data includes the following steps: correcting or interpolating the positions of the maxima or minima by arranging the multiple maxima or minima of the output signal of the eddy current sensor in the entire surface of the reference substrate at equal intervals.

4. The substrate polishing apparatus as described in claim 1, characterized in that, The process of correcting the contour includes the following steps: reducing the peak corresponding to the position of the metal structure and the vicinity of the peak among the multiple peaks contained in the contour.

5. The substrate polishing apparatus as described in claim 4, characterized in that, The process of correcting the contour includes the following steps: among the multiple peaks contained in the contour, the peak corresponding to the position of the metal structure and the vicinity of that peak are reduced to be lower than the peaks not corresponding to the metal structure.

6. The substrate polishing apparatus as described in claim 4 or 5, characterized in that, The size of the nearby portion corresponds to that of the metal structure.

7. The substrate polishing apparatus as described in claim 1, characterized in that, The reference substrate is a substrate on which no metal film has been formed.

8. The substrate polishing apparatus as described in claim 1, characterized in that, The substrate to be ground is a substrate on which a metal film, which is the object to be ground, is formed on its surface.

9. The substrate polishing apparatus as described in claim 1, characterized in that, The metallic structure is a through electrode or metallic wiring formed on a substrate.

10. The substrate polishing apparatus as claimed in claim 1, characterized in that, The process of determining the trajectory based on the contour includes the following steps: Generate a sensor output map that represents the distribution of the magnitude of the output signal of the eddy current sensor across the entire surface of the substrate being ground; and The track with the contour most similar to the contour obtained in the grinding of the substrate is extracted from the sensor output mapping, and the extracted track is determined as the track of the eddy current sensor for the substrate being ground.

11. The substrate polishing apparatus as claimed in claim 1, characterized in that, It also features an airbag that can adjust the polishing pressure on the substrate being polished. The control unit is further configured to control the internal pressure of the airbag based on the film thickness calculated from the substrate to be ground.

12. A film thickness calculation method, which is a film thickness calculation method in a substrate polishing apparatus, the substrate polishing apparatus comprising: A grinding table, equipped with an eddy current sensor, and configured to rotate; and A grinding head, which is opposite to the grinding table and is configured to rotate, allows a substrate to be mounted on its surface opposite the grinding table. Its features are, Includes the following steps: Using the output signal of the eddy current sensor to the reference substrate, mapping data representing the configuration of one or more metallic structures that are locally present on or inside the surface of the reference substrate is generated; In the grinding of a grinding target substrate having a metal structure configured like the reference substrate, the profile of the output signal of the eddy current sensor is obtained when the eddy current sensor passes through a certain track on the ground surface of the grinding target substrate. Based on the profile, the track that the eddy current sensor corresponding to the profile passes through on the surface of the substrate being polished is determined. Based on the mapping data, it is determined whether there are any metal structures on the track identified on the substrate to be ground; The profile of the output signal of the eddy current sensor to the substrate being ground is corrected in such a way that the signal value at the location where the metal structure is determined to exist is reduced. and The film thickness of the substrate to be ground is calculated based on the profile of the corrected output signal of the eddy current sensor.

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