JP5160954B2 - Polishing method - Google Patents

Description

  The present invention relates to a polishing method for a substrate having a wiring formation structure including a metal film, a barrier film, and an insulating film, and more particularly to a polishing method for terminating polishing when an insulating film is removed by a predetermined thickness.

  In the wiring formation process of a semiconductor wafer, a chemical mechanical polishing (CMP) is performed after forming a metal film to be a wiring, and a polishing process is performed to remove an excess metal film that is not used for the wiring. In this polishing step, after the metal film is removed, the barrier film formed under the metal film is polished. Further, the hard mask film formed thereunder is polished, and the polishing is finished when the hard mask film reaches a predetermined thickness.

  Here, the hard mask film is an insulating film made of an insulating material and is formed so as to cover the interlayer insulating film. The interlayer insulating film has an insulating property like the hard mask film, and is formed of a low-k material that is a brittle material. The hard mask film is formed to protect the interlayer insulating film from physical processing by CMP.

FIG. 1 is a cross-sectional view showing an example of a multilayer structure for forming wiring. As shown in FIG. 1, a hard mask film 903 made of, for example, SiO ₂ is formed on an interlayer insulating film 902 made of SiO ₂ or a low-k material. A via hole 904 and a trench 905 are formed in the hard mask film 903 and the interlayer insulating film 902 by, for example, lithography / etching technology. Further, a barrier film 906 made of a metal such as Ta or TaN is formed on the surfaces of the hard mask film 903, the via hole 904, and the trench 905 by sputtering or the like. Further, the substrate is plated with copper to fill the via hole 904 and the trench 905 with copper, and a copper film 907 as a metal film is deposited on the barrier film 906.

  Thereafter, the copper film 907 and the barrier film 906 are removed by chemical mechanical polishing (CMP), and polishing is performed when the thickness of the hard mask film 903 reaches a predetermined thickness as shown by a dotted line in FIG. Is terminated. As a result, a wiring 910 made of copper filling the via hole 904 and the trench 905 is formed.

  The barrier film made of metal is polished to prevent a short circuit between the wirings, and is the same as the purpose of removing the metal film (copper film 907). On the other hand, the purpose of polishing the hard mask film is to remove the damaged part or the altered part because the hard mask film is damaged or altered by etching or the like when forming the via hole or trench.

  Furthermore, the wiring resistance of the metal wiring can be controlled by polishing the hard mask film. That is, when the barrier film is removed, the separation between the wirings is completed and no short circuit occurs, so that the wirings are formed at this stage. Here, by further continuing the polishing, the cross-sectional area of the wiring can be reduced and the wiring resistance can be changed.

  Management of wiring resistance is an important factor for device formation. That is, in the polishing process of the hard mask film, managing the polishing amount of the hard mask film is extremely important for ensuring the stability of the element. Therefore, in polishing the hard mask film, it is required to detect the polishing end point with high accuracy. For example, it is necessary to detect the polishing end point with an accuracy of the target thickness of the hard mask film ± 5 to 10 nm.

Since insulating films such as a hard mask film and an interlayer insulating film have optical transparency, optical means have been conventionally used as a method for measuring the thickness of these insulating films (see, for example, Patent Document 1). However, there are cases where the hard mask film and the interlayer insulating film are both made of light-transmitting SiO ₂ . In such a case, even if light is irradiated while the hard mask film is being polished, measurement of the film thickness becomes difficult due to the influence of the interlayer insulating film that is the underlying film. As a result, it was difficult to finish polishing when the hard mask film reached a desired thickness.

JP 2003-197587 A

  The present invention has been made in view of the above-described problems of the prior art, and provides a polishing method capable of terminating polishing when an insulating film such as a hard mask film is polished by a desired polishing amount. For the purpose.

In order to achieve the above-described object, one embodiment of the present invention includes an insulating film having a groove, a barrier film formed over the insulating film, and a metal film formed over the barrier film. A polishing method for polishing a substrate in which a part of the metal film is formed as a metal wiring in the groove, the first polishing step for removing the metal film, and the barrier film after the first polishing step. And a third polishing step for polishing the insulating film after the second polishing step, and the polishing state of the substrate is changed between the second polishing step and the third polishing step. The third polishing is performed when the output signal value of the eddy current sensor is monitored by an eddy current sensor and reaches a value obtained by subtracting a predetermined value from the output signal value of the eddy current sensor at the end of the second polishing step. The process is terminated.

In a preferred aspect of the present invention, the predetermined value is a change amount of an output signal value of the eddy current sensor corresponding to a predetermined polishing amount of the insulating film.

In a preferred aspect of the present invention, the first polishing step, the second polishing step, and the third polishing step hold the substrate with a substrate holder and press it against the polishing surface of the polishing pad on the polishing table, This is performed by rotating the substrate holder and the polishing table, and the end point of the second polishing step is the output signal value of the eddy current sensor, the temperature of the polishing surface, the torque current of the polishing table, the substrate It is detected by monitoring at least one of the torque currents of the holder.
In a preferred aspect of the present invention, during the second polishing step, the polishing state of the substrate is monitored by an optical sensor, and the change point between the output signal value of the eddy current sensor and the output signal value of the optical sensor is A polishing end point of the second polishing step is detected.

Another aspect of the present invention includes an insulating film having a groove, a barrier film formed on the insulating film, and a metal film formed on the barrier film, and a part of the metal film is a metal A polishing method for polishing a substrate formed in the groove as a wiring, the first polishing step for removing the metal film, and the second polishing step for removing the barrier film after the first polishing step; And a third polishing step for polishing the insulating film after the second polishing step, and during the second polishing step and the third polishing step, the polishing state of the substrate is monitored by an eddy current sensor, When the output signal value of the eddy current sensor reaches a value obtained by adding a predetermined value to the output signal value of the eddy current sensor at the end of polishing of the insulating film belonging to the next lower layer of the insulating film, 3 The polishing process is ended.
In a preferred aspect of the present invention, the first polishing step, the second polishing step, and the upper surface of the metal wiring and the upper surface of the insulating film are located in the same plane at the end of the third polishing step. The selection ratio of the slurry used as the polishing liquid in the third polishing step is adjusted.

  According to the present invention, it is possible to accurately determine the polishing amount of the insulating film using the output signal value of the eddy current sensor that changes in accordance with the height of the metal wiring adjacent to the insulating film. Accordingly, by terminating the polishing when the output signal value of the eddy current sensor reaches a predetermined threshold value, the insulating film can be accurately polished by a predetermined polishing amount (thickness).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a schematic diagram showing a cross-section during polishing of the wiring formation structure shown in FIG. 1, in which the barrier film on the hard mask film (insulating film) is removed, and the copper (metal wiring) in the hard mask film and the trench. Shows a state of being polished.

  In this embodiment, when polishing a hard mask film that is an insulating film, film thickness measurement and end point detection are performed using an eddy current sensor. As described above, when the hard mask film is polished, the metal wiring is also polished at the same time. Therefore, the output signal value of the eddy current sensor changes even when the hard mask film is polished. That is, there is a correlation between the thickness of the hard mask film and the height of the metal wiring (or the cross-sectional area of the wiring). In other words, there is a correlation between the amount of polishing of the hard mask film and the amount of change in the output signal value of the eddy current sensor. Here, the polishing amount of the hard mask film is expressed as a decrease in film thickness from the initial film thickness.

  On the basis of the above, the inventor has found that the output signal value of the eddy current sensor changes even when the hard mask film is polished, although the change is smaller than the output signal value obtained when the metal film is polished. Therefore, in the present invention, the thickness of the hard mask film, which is an insulating film, is indirectly measured using a change in the height (cross-sectional shape) of the metal wiring formed adjacent to the hard mask film.

  FIG. 3 is a graph showing changes in the output signal value of the eddy current sensor when the barrier film and hard mask film of the wiring formation structure shown in FIG. 1 are polished. FIG. 3 shows the output signal (M2) of the eddy current sensor when the second-layer wiring formation structure is being polished, and the eddy current when the third-layer wiring formation structure located on the upper layer is being polished. An output signal (M3) of the current sensor is shown. In this graph, the output signal value of the eddy current sensor from the polishing of the barrier film (barrier metal film) is shown.

  From the graph shown in FIG. 3, it can be seen that the change in the output signal value of the eddy current sensor becomes gentle after about 20 seconds from the start of polishing. This indicates that the barrier film has been removed. It can be seen that the output signal value of the eddy current sensor gradually decreases as the polishing progresses further. This indicates that the wiring is also polished along with the polishing of the hard mask film. Then, the polishing end point and the film thickness of the hard mask film are managed using the change in the output signal value at the time of polishing the hard mask film.

  Specifically, the polishing is terminated when the output signal value of the eddy current sensor reaches a predetermined threshold value. As shown in FIG. 3, this threshold value is a value that is smaller by a value A1 than the output signal value when the barrier film is removed. This value A1 is a change amount of the output signal value of the eddy current sensor corresponding to a predetermined polishing amount of the hard mask film, and a correlation between the polishing amount of the hard mask film and the change amount of the output signal value of the eddy current sensor. Is a value obtained in advance.

  Here, the wiring density is different for each substrate. Therefore, the output signal value of the eddy current sensor can change according to the wiring density. Specifically, when the sensitivity of the eddy current sensor is the same, the change in the output signal value of the eddy current sensor will be relatively gradual on the board with a low wiring density, and the change in the output signal value on the board with a high wiring density Relatively steep.

  Therefore, if the wiring density of the substrate to be polished is known, the output signal value of the eddy current sensor or the eddy current sensor is obtained using the relationship between the wiring density acquired in advance and the output signal value of the eddy current sensor. Can be corrected or calibrated. This calibration makes it possible to determine the change in the output signal value of the eddy current sensor on an equivalent scale (ie, a standardized scale) without depending on the wiring density. The standardization of the scale means that standardized data can be collected, and the increase in data contributes to the stabilization of the polishing process.

  As the polishing process proceeds, a dent called erosion may occur on the surface to be polished as shown in FIG. In this case, the hard mask film remains outside the recess. However, the eddy current sensor only captures the wiring height (wiring cross-sectional area). Therefore, when it is desired to manage the wiring height, the output signal value of the eddy current sensor can be employed as it is without considering the effect of erosion.

  The occurrence of erosion may affect the subsequent wiring formation process. From this, slurry (polishing liquid) from polishing of the metal layer to polishing of the hard mask film so that the upper surface of the hard mask film and the upper surface of the wiring are located in the same plane at the end of polishing of the hard mask film It is preferable to adjust the selection ratio.

  Here, as described above, the output signal value of the eddy current sensor is affected by the wiring density. Therefore, the output signal value of the eddy current sensor can be corrected according to the wiring density, or the threshold value can be linked to the wiring density by multiplying the threshold value by a coefficient proportional to the wiring density. Furthermore, if the change in the output signal value is stable and the reproducibility is recognized to some extent, the polishing end point can be detected by calculating the differential value of the output signal value.

  In the graph of FIG. 3, the output signal value from the polishing of the barrier film is shown. However, in the actual polishing process, the polishing is performed from the polishing of a metal film such as copper or tungsten on the barrier film. Accordingly, the polishing process of the substrate includes a metal film polishing (first polishing process), a barrier film polishing process (second polishing process), and a hard mask film polishing process (third polishing process), and approximately three stages of polishing processes. Divided.

  Here, the end point of the second polishing process is that the change in the output signal value of the eddy current sensor becomes gentle. For example, the time point when the differential value of the output signal value of the eddy current sensor reaches a predetermined value can be set as the end point of the second polishing process. However, the switching point from the second polishing process to the third polishing process is not always clearly discriminated as shown in the graph of FIG. Therefore, the temperature of the polishing surface of the polishing pad, the torque current of the polishing table, or the torque current of the top ring can be measured, and the removal point of the barrier film can be detected using these measurement results and the output signal value of the eddy current sensor. preferable. For example, when the barrier film is removed and the hard mask film is exposed, the frictional force between the polishing pad and the substrate changes. Therefore, the temperature of the polishing surface of the polishing pad also changes. The configuration of a polishing apparatus including a polishing pad, a polishing table, a top ring, etc. will be described later.

  Further, by removing the barrier film which is a metal, light can be applied to the insulating layer which is the base film. Therefore, in addition to the eddy current sensor, the end point of the second polishing process may be detected using the output signal value of the optical sensor together.

Next, specific steps for determining the polishing end point threshold will be described.
At the initial stage of the polishing process, the correlation between the thickness of the hard mask film and the output signal value of the eddy current sensor is unknown. Therefore, first, the correlation between the amount of polishing of the hard mask film and the amount of change in the output signal value of the eddy current sensor is quantified as follows.

  First, as Step 1, at least one substrate having hard mask films having different thicknesses is prepared. The prepared substrate may be a single substrate having hard mask films with different thicknesses by polishing a plurality of times, or may be a plurality of substrates having hard mask films with different thicknesses. . The prepared substrate may be a substrate having a known wiring density, and the hierarchy to which the hard mask film belongs may be the first hierarchy, the second hierarchy, or another hierarchy.

  In the following description, as an example, three substrates with a hard mask film polished by 10 nm, 30 nm, and 50 nm are prepared. These numerical values of 10 nm, 30 nm, and 50 nm indicate the polishing amount of the hard mask film (a reduction amount from the original film thickness).

As step 2, the height of the metal wiring adjacent to the hard mask film is measured by an eddy current sensor, and an output signal value for each polishing amount (10 nm, 30 nm, 50 nm) of the hard mask film is obtained.
Next, as step 3, the actual film thickness of each hard mask film is measured to determine the actual polishing amount. This measurement can be performed using a cross-sectional measurement using a scanning electron microscope (SEM) or an optical critical dimension (OCD) that optically measures the line width of a fine pattern. Unlike cross-sectional measurement by SEM, OCD is a non-destructive inspection, which reduces the number of scrapped substrates and contributes to productivity improvement. In the case of using OCD, only one substrate needs to be prepared.

  As Step 4, the hard mask film polishing amount (reduction from the original film thickness) and the amount of change in the output signal value of the eddy current sensor corresponding to the polishing amount are correlated, and the hard mask film polishing amount And quantifying the correlation between the change in the output signal value of the eddy current sensor. The polishing amount of the hard mask film may naturally not be 30 nm or 50 nm, but the output of the eddy current sensor can be obtained by quantifying the correlation between the polishing amount of the hard mask film and the amount of change in the output signal value. The polishing amount of the hard mask film can be obtained continuously from the signal value.

In step 5, the change amount of the output signal value of the eddy current sensor corresponding to the desired polishing amount of the hard mask film is obtained as a value A1.
In step 6, the reproducibility of the correlation between the polishing amount of the hard mask film and the change amount of the output signal value of the eddy current sensor is examined. If reproducibility is obtained, the product substrate which is the polishing target is polished. On the other hand, if reproducibility is not obtained, the process returns to step 2.

  The substrate is polished while the polishing state is monitored by an eddy current sensor, and the metal film is removed (first polishing step), the barrier film is removed (second polishing step), and the hard mask film is polished (third polishing step). Are performed sequentially. The threshold value serving as the polishing end point is obtained by subtracting the value A1 from the output signal value when removing the barrier film. Then, the polishing is finished when the output signal value of the eddy current sensor reaches this threshold value.

  As can be seen from FIG. 3, the output signal (M2) of the eddy current sensor when the second-level wiring formation structure is polished and the eddy current when the third-level wiring formation structure is polished. The sensor output signal (M3) shows almost the same graph shape. That is, it can be understood from this graph that the decreasing tendency of the output signal values of the second layer and the third layer are the same on the same substrate.

  Using this fact, a threshold value is determined by adding a predetermined value A2 to the output signal value of the eddy current sensor at the end of polishing of the lower layer, as shown in FIG. It is also possible to determine that the polishing is finished when the threshold is reached. Also in this case, the value A2 is obtained in advance using the sample substrate before the product substrate is polished. Since this polishing end point detection method uses the result of the lower layer, it is possible to prevent the hard mask film from being excessively shaved.

  The above embodiment is an explanation of the polishing of the hard mask film formed on the interlayer insulating film. On the other hand, there is a laminated structure in which a barrier layer is formed directly on an interlayer insulating film without using a hard mask film, and the metal film, the barrier film, and the interlayer insulating film are polished. The present invention is applicable even to a substrate having such a laminated structure.

  Next, a polishing apparatus for performing the above-described polishing will be described in detail with reference to the drawings. FIG. 5 is a plan view showing the overall configuration of the polishing apparatus, and FIG. 6 is a perspective view showing an outline of the polishing apparatus shown in FIG. As shown in FIG. 5, the polishing apparatus includes a substantially rectangular housing 1, and the interior of the housing 1 includes a load / unload section 2 and a polishing section 3 (3 a, 3 b) by partition walls 1 a, 1 b, 1 c It is partitioned into a cleaning unit 4.

  The load / unload unit 2 includes two or more (three in FIG. 5) front load units 20 on which wafer cassettes for stocking a plurality of substrates are placed. These front load portions 20 are arranged adjacent to each other in the width direction (direction perpendicular to the longitudinal direction) of the polishing apparatus. The front load unit 20 can be equipped with an open cassette, a SMIF (Standard Manufacturing Interface) pod, or a FOUP (Front Opening Unified Pod). Here, SMIF and FOUP are sealed containers that can maintain an environment independent of the external space by accommodating a wafer cassette inside and covering with a partition wall.

  In addition, a traveling mechanism 21 is laid along the front load unit 20 in the load / unload unit 2, and the first transport that can move along the arrangement direction of the front load unit 20 on the traveling mechanism 21. A robot 22 is installed. The first transfer robot 22 can access the wafer cassette mounted on the front load unit 20 by moving on the traveling mechanism 21. The first transfer robot 22 has two hands on the upper and lower sides. For example, the upper hand is used to return the polished substrate to the wafer cassette, and the lower hand is used to transfer the substrate before polishing. It can be used for both upper and lower hands.

  Since the load / unload unit 2 is an area where the cleanest state needs to be maintained, the inside of the load / unload unit 2 is always at a higher pressure than any of the outside of the apparatus, the polishing unit 3 and the cleaning unit 4. Maintained. In addition, a filter fan unit (not shown) having a clean air filter such as a HEPA filter or a ULPA filter is provided above the traveling mechanism 21 of the first transfer robot 22. Clean air from which steam and gas have been removed is constantly blowing downward.

  The polishing unit 3 is a region where the substrate is polished, and includes a first polishing unit 3a having a first polishing unit 30A and a second polishing unit 30B therein, a third polishing unit 30C, and a fourth polishing unit 30D. And a second polishing section 3b having the inside. The first polishing unit 30A, the second polishing unit 30B, the third polishing unit 30C, and the fourth polishing unit 30D are arranged along the longitudinal direction of the apparatus as shown in FIG.

  The first polishing unit 30A includes a polishing table 300A that holds a polishing pad, a top ring 301A that holds the substrate and presses the substrate against the polishing surface of the polishing pad on the polishing table 300A, and polishing of the polishing pad. A polishing liquid supply nozzle 302A for supplying a polishing liquid (for example, slurry) or a dressing liquid (for example, pure water) to the surface, a dresser 303A for dressing the polishing pad, a liquid (for example, pure water), and a gas And an atomizer 304A for spraying the fluid mixture (for example, nitrogen) from the nozzle onto the polishing surface.

  Similarly, the second polishing unit 30B includes a polishing table 300B, a top ring 301B, a polishing liquid supply nozzle 302B, a dresser 303B, and an atomizer 304B. The third polishing unit 30C includes a polishing table 300C, , A top ring 301C, a polishing liquid supply nozzle 302C, a dresser 303C, and an atomizer 304C. The fourth polishing unit 30D includes a polishing table 300D, a top ring 301D, a polishing liquid supply nozzle 302D, and a dresser. 303D and an atomizer 304D.

  The first polishing section 3a includes four transport positions along the longitudinal direction (first transport position TP1, second transport position TP2, third transport position TP3, and fourth transport position TP4 in order from the load / unload section side). 1), the first linear transporter 5 for conveying the substrate is disposed. A reversing device 31 for reversing the substrate received from the first transport robot 22 is disposed above the first transport position TP1 of the first linear transporter 5, and a lifter 32 that can be moved up and down is disposed below the reversing device 31. Is arranged. Also, a pusher 33 that can be moved up and down below the second transfer position TP2, a pusher 34 that can be moved up and down below the third transfer position TP3, and a pusher 34 that can move up and down below the fourth transfer position TP4. Possible lifters 35 are respectively arranged.

  The second polishing unit 3b is adjacent to the first linear transporter 5 and has three transport positions along the longitudinal direction (the fifth transport position TP5 and the sixth transport position in order from the load / unload unit side). The second linear transporter 6 that transports the substrate between the TP6 and the seventh transport position TP7 is disposed. A lifter 36 that can be moved up and down below the fifth transport position TP5 of the second linear transporter 6, a pusher 37 below the sixth transport position TP6, and a pusher 38 below the seventh transport position TP7. Are arranged respectively.

  As shown in FIG. 6, the first linear transporter 5 includes four stages capable of linear reciprocation, that is, a first stage, a second stage, a third stage, and a fourth stage. These stages have a two-stage configuration on the top and bottom. That is, the first stage, the second stage, and the third stage are arranged in the lower stage, and the fourth stage is arranged in the upper stage.

  Since the lower stage and the upper stage are installed at different heights, the lower stage and the upper stage can freely move without interfering with each other. The first stage transports the substrate between the first transport position TP1 and the second transport position TP2 (which is the substrate transfer position), and the second stage is connected to the second transport position TP2 (at the substrate transfer position). The substrate is transported between the third transport position TP3 and the third stage transports the substrate between the third transport position TP3 and the fourth transport position TP4. The fourth stage transports the substrate between the first transport position TP1 and the fourth transport position TP4.

  The second linear transporter 6 has substantially the same configuration as the first linear transporter 5. That is, the fifth stage and the sixth stage are arranged in the upper stage, and the seventh stage is arranged in the lower stage. The fifth stage transports the substrate between the fifth transport position TP5 and the sixth transport position TP6 (which is the substrate transfer position), and the sixth stage connects with the sixth transport position TP6 (at the substrate transfer position). The substrate is transported between the seventh transport position TP7 and the seventh stage transports the substrate between the fifth transport position TP5 and the seventh transport position TP7.

  As can be seen from the use of slurry at the time of polishing, the polishing portion 3 is the most dirty (dirty) region. Therefore, exhaust is performed from the periphery of each polishing table so that particles in the polishing unit 3 are not scattered to the outside, and the pressure inside the polishing unit 3 is adjusted to the outside of the apparatus, the surrounding cleaning unit 4, and the load / unload. By making it lower than the load part 2, scattering of particles is prevented. Usually, an exhaust duct (not shown) is provided below the polishing table, and a filter (not shown) is provided above, respectively, and purified air is ejected through these exhaust duct and filter. Down flow is formed.

  The cleaning unit 4 is an area for cleaning the substrate after polishing, and includes a second transfer robot 40, a reversing device 41 for inverting the substrate received from the second transfer robot 40, and four cleanings for cleaning the substrate after polishing. And a transfer unit 46 that transfers the substrate between the reversing machine 41 and the cleaning machines 42 to 45. The second transfer robot 40, the reversing machine 41, and the cleaning machines 42 to 45 are arranged in series along the longitudinal direction of the polishing apparatus. In addition, a filter fan unit (not shown) having a clean air filter is provided above the washing machines 42 to 45, and clean air from which particles have been removed by this filter fan unit is always directed downward. Is blowing. Further, the inside of the cleaning unit 4 is constantly maintained at a pressure higher than that of the polishing unit 3 in order to prevent inflow of particles from the polishing unit 3.

  The transport unit 46 has a plurality of arms for holding the substrate, and the arms can move the plurality of substrates simultaneously in the horizontal direction between the reversing machine 41 and the cleaning machines 42 to 45. Yes. As the cleaning machine 42 and the cleaning machine 43, for example, a roll-type cleaning machine that rotates a roll-like sponge arranged above and below and presses against the front and back surfaces of the substrate to clean the front and back surfaces of the substrate is used. it can. Further, as the cleaning machine 44, for example, a pencil type cleaning machine that presses and cleans the substrate while rotating a hemispherical sponge can be used.

  As the cleaning machine 45, for example, the back surface of the substrate can be rinsed, and the substrate surface can be cleaned using a pencil type cleaning machine that presses and cleans the hemispherical sponge while rotating. The cleaning machine 45 includes a stage for rotating the chucked substrate at a high speed, and has a function (spin dry function) for drying the cleaned substrate by rotating the substrate at a high speed. In addition, in each of the cleaning machines 42 to 45, in addition to the roll type cleaning machine and the pencil type cleaning machine described above, a megasonic type cleaning machine that performs cleaning by applying ultrasonic waves to the cleaning liquid may be additionally provided. .

  The shutter 10 is installed between the reversing machine 31 and the first transport robot 22, and when the substrate is transported, the shutter 10 is opened and the substrate is transferred between the first transport robot 22 and the reversing machine 31. . Also, between the reversing machine 41 and the second transfer robot 40, between the reversing machine 41 and the primary cleaning machine 42, between the first polishing unit 3a and the second transfer robot 40, and the second polishing unit 3b. Shutters 11, 12, 13, and 14 are also provided with the second transfer robot 40, respectively, and when the substrate is transferred, the shutters 11, 12, 13, and 14 are opened to transfer the substrate.

  FIG. 7 is a schematic diagram showing the configuration of the first polishing unit 30A. As shown in FIG. 7, a polishing pad 310A is fixed on the polishing table 300A. The polishing table 300A is connected to a motor (not shown) disposed below the polishing table 300A and is rotatable about an axis. The top ring 301A is connected to a motor and a lifting cylinder (not shown) via a top ring shaft 311A. Thereby, the top ring 301A can be moved up and down and can rotate around the top ring shaft 311A. The substrate W is held on the lower surface of the top ring 301A by vacuum suction or the like. The upper surface of the polishing pad 310A constitutes a polishing surface with which the substrate W is slidably contacted.

  The substrate W held on the lower surface of the top ring 301A is pressed by the polishing pad 310A on the rotating polishing table 300A while being rotated by the top ring 301A. At this time, the polishing liquid is supplied from the polishing liquid supply nozzle 302A to the polishing surface (upper surface) of the polishing pad 310A, and the substrate W is polished in a state where the polishing liquid exists between the substrate W and the polishing pad 310A. The polishing table 300A and the top ring 301A constitute a mechanism for moving the substrate W and the polishing surface relative to each other.

  An eddy current sensor 312A is embedded in the polishing table 300A, and a signal indicating the film thickness of the substrate W is output to the determination unit 313A. The determination unit 313A receives the output signal of the eddy current sensor and detects the polishing end point according to the method described above. When the polishing end point is detected, the determination unit 313A transmits a signal indicating the polishing end point to the control unit 314A, and the control unit 314A receives this signal and ends the polishing operation. Since the second polishing unit 300B, the third polishing unit 300C, and the fourth polishing unit 300D have the same configuration as the first polishing unit 300A, description thereof is omitted.

  According to the polishing apparatus having such a configuration, it is possible to perform series processing for continuously polishing one substrate with four polishing units and parallel processing for simultaneously polishing two substrates.

  In the case of processing a series of substrates, the substrate is a wafer cassette of the front load unit 20, a first transfer robot 22, a reversing device 31, a lifter 32, a first stage of the first linear transporter 5, a pusher 33, and a top ring 301A. → Polishing table 300A → Pusher 33 → Second stage of first linear transporter 5 → Pusher 34 → Top ring 301B → Polishing table 300B → Pusher 34 → Third stage of first linear transporter 5 → Lifter 35 → Second transport Robot 40 → Lifter 36 → Fifth stage of second linear transporter 6 → Pusher 37 → Top ring 301C → Polishing table 300C → Pusher 37 → Sixth stage of second linear transporter 6 → Pusher 38 → Top ring 301D → Polishing Table 300D → Pusher 38 The seventh stage of the second linear transporter 6 → the lifter 36 → the second transfer robot 40 → the reversing machine 41 → the transfer unit 46 → the cleaning machine 42 → the transfer unit 46 → the cleaning machine 43 → the transfer unit 46 → the cleaning machine 44 → the transfer unit. 46 → Washing machine 45 → First transfer robot 22 → Transfer is carried out along the path of wafer cassette of the front load unit 20.

  When the substrate is processed in parallel, one substrate is the wafer cassette of the front load unit 20 → the first transfer robot 22 → the reversing device 31 → the lifter 32 → the first stage of the first linear transporter 5 → the pusher 33 → the top. Ring 301A → Polishing table 300A → Pusher 33 → Second stage of first linear transporter 5 → Pusher 34 → Top ring 301B → Polishing table 300B → Pusher 34 → Third stage of first linear transporter 5 → Lifter 35 → First 2 transfer robot 40-> reversing machine 41-> transfer unit 46-> cleaning machine 42-> transfer unit 46-> cleaning machine 43-> transfer unit 46-> cleaning machine 44-> transfer unit 46-> cleaning machine 45-> first transfer robot 22-> front load unit It is conveyed by a route called 20 wafer cassettes.

  The other substrate is the wafer cassette of the front load unit 20 → the first transfer robot 22 → the reversing device 31 → the lifter 32 → the fourth stage of the first linear transporter 5 → the lifter 35 → the second transfer robot 40 → the lifter 36. → 5th stage of the second linear transporter 6 → Pusher 37 → Top ring 301C → Polishing table 300C → Pusher 37 → Sixth stage of the second linear transporter 6 → Pusher 38 → Top ring 301D → Polishing table 300D → Pusher 38 → 7th stage of second linear transporter 6 → lifter 36 → second transfer robot 40 → reversing machine 41 → transfer unit 46 → cleaning unit 42 → transfer unit 46 → cleaning unit 43 → transfer unit 46 → cleaning unit 44 → transfer Unit 46 → washing machine 45 → first transfer robot 22 → front load unit It is conveyed in a path that 0 of the wafer cassette.

It is sectional drawing which shows an example of wiring formation structure. It is a schematic diagram which shows the cross section in the grinding | polishing of the wiring formation structure shown in FIG. 3 is a graph showing a change in an output signal value of an eddy current sensor when polishing a barrier film and a hard mask film of the wiring formation structure shown in FIG. It is sectional drawing which shows the erosion which generate | occur | produces at the time of grinding | polishing. It is a top view which shows the whole structure of a grinding | polishing apparatus. It is a perspective view which shows the outline | summary of the grinding | polishing apparatus shown in FIG. It is a schematic diagram which shows the structure of a 1st grinding | polishing unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Load / unload part 3 Polishing part 4 Cleaning part 5,6 Linear transporter 10-14 Shutter 20 Front load part 21 Traveling mechanism 22 1st conveyance robot 30A, 30B, 30C, 30D Polishing unit 31,41 Inversion machine 32 Lifters 33, 34, 37, 38 Pushers 35, 36 Lifters 40 Second transfer robots 42-45 Cleaning machine 46 Transfer units 300A, 300B, 300C, 300D Polishing tables 301A, 301B, 301C, 301D Top rings 302A, 302B, 302C , 302D Polishing liquid supply nozzles 303A, 303B, 303C, 303D Dressers 304A, 304B, 304C, 304D Atomizer 310A Polishing pad 311A Top ring shaft 312A Eddy current sensor 313A Determination unit 314 Control unit

Claims (6)

An insulating film having a groove; a barrier film formed on the insulating film; and a metal film formed on the barrier film, wherein a part of the metal film is formed in the groove as a metal wiring. A polishing method for polishing a substrate,
A first polishing step for removing the metal film;
A second polishing step for removing the barrier film after the first polishing step;
A third polishing step for polishing the insulating film after the second polishing step;
During the second polishing step and the third polishing step, the polishing state of the substrate is monitored with an eddy current sensor,
The third polishing step is ended when the output signal value of the eddy current sensor reaches a value obtained by subtracting a predetermined value from the output signal value of the eddy current sensor at the end of the second polishing step. Polishing method. The polishing method according to claim 1 , wherein the predetermined value is a change amount of an output signal value of the eddy current sensor corresponding to a predetermined polishing amount of the insulating film. The first polishing step, the second polishing step, and the third polishing step are:
Hold the substrate with the substrate holder and press against the polishing surface of the polishing pad on the polishing table,
Performed by rotating the substrate holder and the polishing table;
The end point of the second polishing step is monitored by monitoring at least one of the output signal value of the eddy current sensor, the temperature of the polishing surface, the torque current of the polishing table, and the torque current of the substrate holder. The polishing method according to claim 1 , wherein the polishing method is detected. During the second polishing step, the polishing state of the substrate is monitored with an optical sensor,
The polishing method according to claim 1, characterized in that the transition points of the output signal value of the optical sensor and the output signal value of the eddy current sensor, for detecting the polishing end point of the second polishing step. An insulating film having a groove; a barrier film formed on the insulating film; and a metal film formed on the barrier film, wherein a part of the metal film is formed in the groove as a metal wiring. A polishing method for polishing a substrate,
A first polishing step for removing the metal film;
A second polishing step for removing the barrier film after the first polishing step;
A third polishing step for polishing the insulating film after the second polishing step;
During the second polishing step and the third polishing step, the polishing state of the substrate is monitored with an eddy current sensor,
When the output signal value of the eddy current sensor reaches a value obtained by adding a predetermined value to the output signal value of the eddy current sensor at the end of polishing of the insulating film belonging to the next lower layer of the insulating film. Migaku Ken how to, characterized in that to end the third polishing step. A polishing liquid is used in the first polishing step, the second polishing step, and the third polishing step so that the upper surface of the metal wiring and the upper surface of the insulating film are located in the same plane at the end of the third polishing step. The polishing method according to any one of claims 1 to 5, wherein a selection ratio of a slurry to be used is adjusted.

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