JP2011176342A - Polishing method and wiring forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing method capable of preventing a preceding process in multi-step polishing from applying a load on a subsequent process. <P>SOLUTION: A polishing method includes: a first polishing step of polishing and removing most part of a first film formed on an object to be polished; a second polishing step of polishing and removing a residual part of the first film until a second film is exposed to a surface while a wiring part is left; a step of preliminarily setting the film thickness distribution of the first film in shifting from the first polishing step to the second polishing step; a step of measuring a first film thickness using an eddy current sensor during the first polishing step to obtain the film thickness distribution of the first film; and a step of adjusting polishing conditions in the first polishing step so that the obtained film thickness distribution of the first film agrees with the preliminarily set film thickness distribution of the first film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a polishing method, and more particularly to a polishing method for polishing and planarizing a polishing object such as a semiconductor wafer.
The present invention also relates to a wiring forming method, and more particularly to a wiring forming method for forming a wiring using a conductive film on a substrate such as a semiconductor wafer.

  In recent years, as semiconductor devices are highly integrated, circuit wiring is becoming finer and the distance between wirings is becoming narrower. In particular, in the case of photolithography having a line width of 0.5 μm or less, the depth of focus becomes shallow, so that the flatness of the imaging surface of the stepper is required. As one means for flattening the surface of such a semiconductor wafer, a polishing apparatus that performs chemical mechanical polishing (CMP) is known.

  This type of chemical mechanical polishing (CMP) apparatus includes a polishing table having a polishing pad on its upper surface and a top ring. Then, the semiconductor wafer is interposed between the polishing table and the top ring, and while supplying the polishing liquid (slurry) to the surface of the polishing pad, the semiconductor wafer is pressed against the polishing table by the top ring, and the surface of the semiconductor wafer Is polished flat and mirror-like.

JP 2002-113653 A Japanese Patent Laid-Open No. 10-58309 Japanese Patent Laid-Open No. 10-286758 JP 2003-133277 A JP 2001-237208 A

An object of this invention is to provide the grinding | polishing method which can prevent the front process in multistep grinding | polishing from applying a load to a back process.
Another object of the present invention is to provide a wiring forming method capable of forming a wiring without causing defects.

  According to the first aspect of the present invention, there is provided a polishing method capable of preventing a previous step in multi-step polishing, particularly two-step polishing, from placing a burden on a subsequent step. In this polishing method, a first polishing step for polishing and removing most of the first film formed on the object to be polished, a remaining portion of the first film is replaced with a second film leaving a wiring portion. And a second polishing step of polishing and removing until the surface is exposed. The film thickness distribution of the first film when shifting from the first polishing process to the second polishing process is set in advance. During the first polishing step, the thickness of the first film is measured by an eddy current sensor to obtain the film thickness distribution of the first film. The polishing conditions in the first polishing step are adjusted so that the obtained film thickness distribution of the first film matches the preset film thickness distribution of the first film.

  According to this method, it is possible to surely obtain the desired film thickness distribution while monitoring the actual film thickness distribution. That is, since the switching from the first polishing process to the second polishing process can always be performed with a desired film thickness distribution, it is possible to prevent the first polishing process from placing a burden on the second polishing process. Can do. In addition, dishing and erosion after the second polishing step can be suppressed, and the time of the second polishing step can be shortened. This leads to improved productivity and cost reduction.

  According to the second aspect of the present invention, there is provided a wiring forming method capable of forming a wiring without causing a defect. This wiring forming method has a first step of forming a flat conductive thin film on a substrate and a second step of removing the flat conductive thin film by chemical etching.

  In this way, after forming a flat conductive thin film on the substrate, the remaining conductive thin film is removed by chemical etching without mechanical action and requiring no electrical connection. Wiring can be formed without causing the above.

According to the polishing method of the present invention, it is possible to prevent a previous process in multi-step polishing from applying a load to a subsequent process.
According to the wiring forming method of the present invention, wiring can be formed without causing defects.

It is a top view which shows an example of a grinding | polishing apparatus. It is a longitudinal cross-sectional view which shows a part of grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a bottom view which shows an example of the retainer ring of the top ring shown in FIG. It is a bottom view which shows the other example of the retainer ring of the top ring shown in FIG. It is a bottom view which shows the other example of the retainer ring of the top ring shown in FIG. It is a bottom view which shows the other example of the retainer ring of the top ring shown in FIG. FIG. 2 is a plan view schematically showing a part of a polishing unit of the polishing apparatus shown in FIG. 1. It is a perspective view which shows the gas ejection mechanism used for the grinding | polishing unit shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a perspective view which shows the polishing pad of the polishing unit shown in FIG. It is an expansion longitudinal cross-sectional view of the polishing pad shown in FIG. FIG. 11 is an enlarged plan view showing a modification of the polishing pad shown in FIG. 10. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a perspective view which shows the modification of the polishing liquid supply nozzle used for the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a longitudinal cross-sectional view of the polishing liquid supply nozzle shown in FIG. It is a perspective view which shows the modification of the polishing liquid supply nozzle shown in FIG. It is a perspective view which shows the modification of the polishing liquid supply nozzle used for the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a perspective view which shows the modification of the polishing liquid supply nozzle shown in FIG. It is a perspective view which shows the modification of the polishing liquid supply nozzle used for the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a top view which shows the modification of the polishing liquid supply nozzle used for the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a schematic diagram which shows the modification of the polishing liquid supply nozzle used for the grinding | polishing unit of the grinding | polishing apparatus shown in FIG. It is a schematic diagram which shows the polishing liquid supply system in the conventional polishing apparatus. It is a schematic diagram which shows another polishing liquid supply system. FIG. 31A and FIG. 31B are schematic views showing a fluid pressure valve used in the polishing liquid supply system shown in FIG. It is a longitudinal cross-sectional view which shows the modification of the top ring shown in FIG. FIG. 33A to FIG. 33C are schematic views showing a planarization process of copper damascene wiring by CMP. FIG. 34A is a schematic diagram showing a state of over polishing, and FIG. 34B is a schematic diagram showing a state of insufficient polishing. It is a top view of the polish device used in order to carry out polish of a semiconductor wafer by rocking a polish supply nozzle. 36A is a graph showing a polishing rate in a semiconductor wafer in which the polishing liquid supply nozzle is swung in the polishing apparatus shown in FIG. 35, and FIG. 36B is a graph in the semiconductor wafer when the polishing liquid supply nozzle is not swung. It is a graph which shows a polishing rate.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 36B. In FIG. 1 to FIG. 36B, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a plan view showing an example of a polishing apparatus. As shown in FIG. 1, three wafer cassettes 10 can be mounted on this polishing apparatus. A travel mechanism 12 is provided along these wafer cassettes 10, and a first transfer robot 14 having two hands is disposed on the travel mechanism 12. The hand of the first transfer robot 14 can access the wafer cassette 10.

  Further, the polishing apparatus includes four polishing units 20, and these polishing units 20 are arranged along the longitudinal direction of the apparatus. Each polishing unit 20 includes a polishing table 22 having a polishing surface, a top ring 24 for holding the semiconductor wafer and polishing the semiconductor wafer while pressing the semiconductor wafer against the polishing table 22, and a polishing liquid on the polishing table 22. And a polishing liquid supply nozzle 26 for supplying a dressing liquid (for example, water), a dresser 28 for dressing the polishing table 22, and a mixed fluid of liquid (for example, pure water) and gas (for example, nitrogen). And an atomizer 30 that sprays the polishing surface from one or a plurality of nozzles.

  In the vicinity of the polishing unit 20, a first linear transporter 32 and a second linear transporter 34 for transporting the wafer along the longitudinal direction are installed, and the first linear transporter 32 is disposed on the wafer cassette 10 side. A reversing device 36 for reversing the wafer received from the first transfer robot 14 is arranged.

  In addition, the polishing apparatus includes a second transfer robot 38, a reversing device 40 that reverses the wafer received from the second transfer robot 38, four cleaning devices 42 that clean the polished semiconductor wafer, a reversing device 40, and And a transfer unit 44 for transferring the wafer between the cleaning machines. The second transfer robot 38, the reversing machine 40, and the cleaning machine 42 are arranged in series along the longitudinal direction.

  In such a polishing apparatus, the wafer in the wafer cassette 10 is introduced into each polishing unit 20 via the reversing machine 36, the first linear transporter 32, and the second linear transporter 34. In each polishing unit 20, the wafer is polished. The polished wafer is introduced into the cleaning machine 42 through the second transfer robot 38 and the reversing machine 40, and is cleaned there. The cleaned wafer is returned to the wafer cassette 10 by the first transfer robot 14.

  FIG. 2 is a longitudinal sectional view showing a part of the polishing unit 20. As shown in FIG. 2, the polishing table 22 of the polishing unit 20 is connected to a motor 50 disposed below the polishing table 22, and is rotatable about its axis as indicated by an arrow. A polishing pad (polishing cloth) 52 having a polishing surface is attached to the upper surface of the polishing table 22. The top ring 24 is connected to a top ring shaft 54, and a retainer ring 56 that holds the outer peripheral edge of the semiconductor wafer W is provided on the lower outer peripheral portion of the top ring 24.

  The top ring 24 is connected to a motor (not shown) and to a lifting cylinder (not shown). As a result, the top ring 24 can be moved up and down as indicated by an arrow and can rotate about its axis, and the semiconductor wafer W can be pressed against the polishing pad 52 with an arbitrary pressure. ing.

  In the polishing unit 20 having such a configuration, the semiconductor wafer W is held on the lower surface of the top ring 24, and the semiconductor wafer W is pressed against the polishing pad 52 on the upper surface of the rotating polishing table 22 by the lifting cylinder. Then, the polishing liquid Q is supplied onto the polishing pad 52 from the polishing liquid supply port 57 of the polishing liquid supply nozzle 26, and the polishing liquid Q exists between the polishing surface (lower surface) of the semiconductor wafer W and the polishing pad 52. Thus, the semiconductor wafer W is polished.

  Further, as shown in FIG. 2, an eddy current sensor 58 for measuring the film thickness of the semiconductor wafer W is embedded in the polishing table 22. The wiring 60 from the eddy current sensor 58 passes through the polishing table 22 and the support shaft 62 and is connected to the controller 66 via a rotary connector (or slip ring) 64 provided at the shaft end of the support shaft 62. . While the eddy current sensor 58 passes under the semiconductor wafer W, the film thickness of a conductive film such as a copper film formed on the surface of the semiconductor wafer W can be detected continuously on the passing locus. Yes.

  Here, with the demand for higher speed of semiconductor devices, it has been studied to use an insulating film between wirings in the device as a material having a lower dielectric constant (for example, a low-k material). Since such low dielectric constant materials are porous and mechanically brittle, the pressure applied to the semiconductor wafer during polishing (polishing pressure) in the planarization polishing process for copper damascene wiring using low-k materials Is required to be as small as possible (for example, 13.79 kPa (2 psi) or less).

  However, in general, the polishing rate in the polishing process depends on the polishing pressure and decreases as the polishing pressure decreases. Therefore, when polishing copper, a polishing liquid having a stronger chemical action may be used to compensate for such a decrease in the polishing rate. When a polishing liquid having such a strong chemical action is used, uniform and stable polishing characteristics cannot be obtained unless a more stable chemical reaction occurs between the polishing liquid and the copper film. For this reason, in a polishing process using a polishing liquid having a strong chemical action, it is desired to supply an unreacted polishing liquid more stably between the polishing pad and the semiconductor wafer.

  In this example, a groove is formed in the retainer ring 56 of the top ring 24 so that the polishing liquid is supplied more stably between the polishing pad 52 and the semiconductor wafer W. 3 is a bottom view showing an example of the retainer ring 56 of FIG. As shown in FIG. 3, a plurality of grooves 74 communicating the outer peripheral surface 70 and the inner peripheral surface 72 are formed at equal intervals in the circumferential direction on the bottom surface of the retainer ring 56. The example shown in FIG. 3 is a case where the rotation direction of the top ring 24 is clockwise, and the outer peripheral side opening 76 of each groove 74 is more clockwise than the inner peripheral surface side opening 78 (the rotation of the top ring 24). It is arranged at a position advanced in the direction). With such a groove 74, the polishing liquid can be supplied efficiently and stably between the semiconductor wafer W inside the retainer ring 56 and the polishing pad 52.

  Here, the opening ratio of the outer peripheral side openings 76 of these grooves 74 is determined by the strength of the chemical action of the polishing liquid, and is about 10% to about 50%. For example, when a certain polishing liquid is used, if the opening ratio is 0%, it is difficult to supply the polishing liquid between the polishing pad 52 and the semiconductor wafer W, and a sufficient polishing rate cannot be obtained. On the other hand, when the opening ratio of the outer peripheral side opening 76 is extremely high (for example, exceeding 50%), the polishing liquid once entering the inside of the retainer ring 56 through the groove 74 passes through another groove 74. As a result, the polishing liquid is hardly retained between the polishing pad 52 and the semiconductor wafer W. Therefore, when the opening ratio of the outer peripheral opening 76 is in the range of about 10% to about 50%, the polishing liquid can be effectively supplied between the polishing pad 52 and the semiconductor wafer W, and a stable polishing rate can be achieved. Can be obtained. Further, when the opening ratio of the outer peripheral side opening 76 is in the range of about 10% to about 50%, the inactive polishing liquid after reaction can be effectively discharged outside through the groove 74. In addition, the dimension of each groove | channel 74 and the pitch between the grooves 74 are set according to the aperture ratio of the outer peripheral side opening part 76 mentioned above.

  When the rotation direction of the top ring 24 is counterclockwise, as shown in FIG. 4, the direction of the groove 74 is preferably reversed from that in FIG. Alternatively, as shown in FIG. 5, the grooves 74 may be radially arranged at equal intervals so that the top ring 24 can be used regardless of which direction it rotates. In this case, as shown in FIG. 6, the inner peripheral side opening 78 of each groove 74 may be larger than the outer peripheral side opening 76.

  Further, in order to make the effect of the groove 74 of the retainer ring 56 more effective, the rotational speed of the top ring 24 is preferably 1/1 or less with respect to the rotational speed of the polishing table 22, but more preferably about 1 / 3 to about 1 / 1.5. In this case, the rotation direction of the polishing table 22 and the rotation direction of the top ring 24 may be the same direction, or may be opposite directions. By setting the rotational speeds of the polishing table 22 and the top ring 24 as described above and operating the polishing apparatus, it is possible to perform polishing with better uniformity.

  That is, when the rotational speed of the top ring 24 is high, the retainer ring 56 located on the outer peripheral portion of the top ring 24 inhibits the inflow of the polishing liquid between the polishing pad 52 and the semiconductor wafer W, thereby efficiently polishing. The liquid cannot be supplied. If the rotational speed of the top ring 24 is lowered, it becomes possible to efficiently supply the polishing liquid between the polishing pad 52 and the semiconductor wafer W through the groove 74 formed in the retainer ring 56 described above. It is possible to perform polishing with excellent uniformity.

  FIG. 7 is a plan view schematically showing a part of the polishing unit 20 of the polishing apparatus shown in FIG. As shown in FIG. 7, the atomizer 30 is disposed upstream of the top ring 24 in the rotational direction of the polishing table 22, and ejects a mixed fluid of cleaning liquid and gas toward the polishing pad 52. Function as. For example, a mixed fluid of nitrogen gas and pure water or chemical liquid is sprayed from the atomizer 30 toward the polishing pad 52. This mixed fluid is sprayed toward the polishing pad 52 in the state of 1) liquid fine particle formation, 2) solidification of fine particle solidified liquid, and 3) gasification of the liquid evaporation (these are referred to as atomization or atomization). Is done.

  By spraying the mixed fluid in the atomized state to the polishing pad 52 in this way, the polishing liquid and polishing debris that have fallen into the recess of the polishing pad 52 are scraped out by the gas in the mixed fluid, and further, pure water, chemical liquid, etc. It can be washed away with a cleaning solution. As a result, it is possible to effectively remove polishing liquid and polishing debris present on the polishing pad 52 that causes scratches.

  Usually, in CMP, polishing residues such as residual abrasive grains and polishing scraps (copper complex in copper polishing) exist on the polished surface after polishing. If these polishing residues are left untreated, the surface of the semiconductor wafer may be damaged in the subsequent polishing, or the chemical action of the polishing liquid may be suppressed and the polishing rate may be reduced. Therefore, it is desired that as much polishing residue as possible is not present on the polishing surface being polished. For this reason, in ordinary CMP, dressing of the polishing surface is performed by a dresser at intervals between polishings, and an atomizer that sprays a mixed fluid of a cleaning liquid and a gas onto the polishing surface by an atomizer to remove polishing residues from the polishing surface. Is done.

  As shown in FIG. 7, a discharge mechanism 80 that discharges the mixed fluid ejected from the atomizer 30 from the polishing pad 52 is disposed downstream of the atomizer 30 in the rotation direction of the polishing table 22. Further, a cover 82 that covers the atomizer 30 and the discharge mechanism 80 is provided above the atomizer 30 and the discharge mechanism 80. As a material of the cover 82, a material having water repellency such as a fluororesin is preferably used. The cover 82 may be opened with respect to the radial direction of the polishing table 22.

  The discharge mechanism 80 shown in FIG. 7 includes a contact member 84 that contacts the polishing pad 52 and a holding member (not shown) that holds the contact member. As the contact member 84, a member made of a material having a low friction coefficient is preferably used so that the amount of wear is reduced, and the contact member 84 is preferably made of a material having a high sealing property (liquid tightness). In this case, the discharge mechanism 80 includes a pressing mechanism (not shown) that presses the contact member 84 or the holding member, and makes the contact member 84 contact the polishing pad 52 while controlling the pressing force by the pressing mechanism. May be. As such a pressing mechanism, a cylinder mechanism or a ball screw mechanism using the pressure of a fluid such as gas or water can be used.

  By the way, in the conventional CMP, if atomizing is performed during polishing, the concentration of the polishing liquid is changed by introducing the cleaning liquid onto the polishing surface, thereby changing the polishing characteristics. No atomizing was done. According to this example, the cleaning liquid from the atomizer 30 can be immediately discharged to the outside of the polishing table 22 by the discharge mechanism 80 described above. Therefore, the polishing surface can always be kept clean, and the polishing characteristics of the polishing apparatus can be stabilized. Thus, according to the polishing apparatus of this example, atomization (in-situ atomization) by the atomizer 30 can be performed during polishing.

  Further, by combining dressing by the dresser 28 during polishing (in-situ dressing) and atomizing by the atomizer 30 (in-situ atomizing), the polishing pad 52 can be conditioned during polishing. . For this reason, the interval between grinding | polishing can be shortened and the throughput of an apparatus can be improved.

  In the example shown in FIG. 7, the contact member 84 extends in the radial direction of the polishing table 22, but the contact member 84 is inclined by a predetermined angle (0 ° to 90 °) with respect to the radial direction of the polishing table 22. It may extend in a different direction.

  Further, instead of the contact member 84 or in addition to the contact member 84, a gas ejection mechanism having a gas ejection port for ejecting gas toward the polishing pad 52 may be provided. FIG. 8 is a perspective view showing such a gas ejection mechanism 86. As shown in FIG. 8, the gas ejection mechanism 86 includes a plurality of gas ejection ports 88 that eject gas such as dry air and dry nitrogen toward the polishing pad 52, and the ejection amount, ejection pressure, and ejection of the ejected gas. A control unit (not shown) for controlling the direction is provided, and the cleaning liquid from the atomizer 30 can be discharged to the outside of the polishing table 22 by the ejection of gas from the gas ejection port 88. . In this case, it is preferable to eject the gas so as to have a fan shape like an air curtain. Moreover, it is good also as controlling the direction which ejects gas by making the shape of the gas ejection port 88 into a slit shape.

  Also with the discharge mechanism 80 having such a gas ejection mechanism 86, the cleaning liquid from the atomizer 30 can be immediately discharged to the outside of the polishing table 22. Therefore, the polishing surface can always be kept clean, and the polishing characteristics of the polishing apparatus can be stabilized.

  By the way, in LSI, high-speed performance, high integration, and low power consumption are achieved by miniaturization of wiring, and high performance is realized. As for the miniaturization of wiring as a whole, technological development has been carried out almost in accordance with the prediction of the International Semiconductor Technology Roadmap (ITRS). In addition, the transition to copper wiring with low resistance and low-k material with low dielectric constant advances along with the miniaturization of wiring, and demand for copper damascene flattening process (copper CMP process) increases as a flattening process. It is a prospect.

  Here, in the copper damascene planarization process, when integration with low-k materials or porous low-k materials is realized, in addition to further improvement of planarization characteristics due to miniaturization, the mechanical strength of these materials Therefore, it is necessary to take measures against material destruction at the time of polishing due to the low hardness.

  In order to solve these problems, it is conceivable to reduce the processing surface pressure (polishing pressure). In normal copper CMP, after a copper complex is formed, polishing proceeds by mechanically removing the copper complex. However, in the polishing liquid used in a normal CMP apparatus, since the strength of the formed copper complex is high, there is a problem that if the polishing pressure is lowered, the polishing rate is simultaneously lowered.

  Recently, polishing liquids have been developed that form copper complexes with low mechanical strength that can be mechanically removed even under low polishing pressure conditions. Since this type of polishing liquid has a strong chemical reactivity, the supply amount and distribution of the polishing liquid to the surface to be polished of the semiconductor wafer greatly affect the polishing rate and the in-plane uniformity of the polishing rate.

  In the conventional CMP apparatus, since the polishing liquid is supplied from one fixed polishing liquid supply port, the distribution of the supply amount of the polishing liquid to the surface to be polished of the semiconductor wafer is biased, and the in-plane uniformity of the polishing rate Gets worse. This is particularly noticeable when the relative speed between the polished surface and the semiconductor wafer is high. Moreover, the supply amount of useless polishing liquid increases, leading to an increase in polishing cost. Therefore, it is important how to uniformly and efficiently supply the polishing liquid to the surface to be polished of the semiconductor wafer.

  In this example, the polishing liquid supply port 57 (see FIG. 2) of the polishing liquid supply nozzle 26 is moved during polishing to supply the polishing liquid uniformly and efficiently to the surface to be polished of the semiconductor wafer. That is, as shown in FIG. 1, the polishing liquid supply nozzle 26 in this example is capable of turning about a shaft 27, and the polishing liquid supply nozzle 26 is turned by a turning mechanism (moving mechanism) during polishing. It is like that.

  The polishing liquid is supplied from the polishing liquid supply nozzle 26 onto the polishing pad 52, and the polishing liquid supplied onto the polishing pad 52 is transferred to the semiconductor wafer along with the relative movement between the top ring 24 and the polishing table 22. Is supplied to the surface to be polished. As described above, the polishing liquid supplied on the polishing pad 52 is top ring by rotating the polishing liquid supply nozzle 26 during polishing and moving the polishing liquid supply port 57 (see FIG. 2) at the tip thereof. With the relative movement between the polishing table 24 and the polishing table 22, the polishing liquid can be appropriately distributed on the polishing pad 52 so as to spread uniformly over the entire surface of the semiconductor wafer.

  Thus, according to the polishing liquid supply nozzle 26 in this example, the distribution of the supply amount of the polishing liquid to the surface to be polished of the semiconductor wafer can be made uniform. Therefore, the polishing rate can be improved and the in-plane uniformity of the polishing rate can be improved. Further, since efficient supply of the polishing liquid is realized, the amount of the polishing liquid used can be reduced, and the polishing cost can be reduced by eliminating the waste of the polishing liquid.

  In this example, the example in which the polishing liquid supply nozzle 26 is swung so as to draw an arc has been described, but the present invention is not limited to this. For example, the polishing liquid supply nozzle 26 may be moved linearly, or may be rotated, swinged, or reciprocated. Further, the moving speed of the polishing liquid supply nozzle 26 may be constant (for example, 50 mm / s) or may be changed during the movement. Further, a liquid amount control mechanism that changes the amount of the polishing liquid supplied from the polishing liquid supply port 57 during movement may be provided. The scanning range of the polishing liquid supply port 57 is preferably within a radius of the polishing table 22 and a range that covers the diameter of the semiconductor wafer.

  In the example shown in FIG. 1, the polishing liquid supply nozzle 26 extends in the radial direction of the polishing table 22. However, as shown in FIG. 9, the polishing liquid supply nozzle 26 is predetermined with respect to the radial direction of the polishing table 22. May extend in a direction inclined by an angle (0 ° to 45 °).

  Normally, in CMP, a semiconductor wafer is polished by the chemical mechanical action of a polishing liquid held on a polishing pad. However, the amount of polishing liquid held by a conventional polishing pad is small, and therefore most polishing liquids It was discharged from the polishing pad without being used. Since the polishing liquid is very expensive and greatly affects the polishing cost, it is necessary to improve the use efficiency of the polishing liquid in order to reduce the polishing cost.

  Further, in polishing where the polishing pressure is low (6.89 kPa (1 psi) or less) and the relative speed is high (2 m / s or more), the semiconductor wafer Sliding due to the hydroplaning phenomenon occurs with the polished surface. Such a phenomenon is caused by the fact that the polishing liquid is applied to the polishing surface when a concentric groove having a small cross-sectional area is formed on the polishing surface or when the polishing liquid is supplied onto the polishing surface from one central point of the polishing table. This is particularly noticeable when the supply is uneven. When such a hydroplaning phenomenon occurs, the polishing pressure does not act between the semiconductor wafer and the polishing surface, so that the polishing rate decreases. On the other hand, if the polishing liquid is positively discharged from the polishing surface, the holding power of the polishing liquid on the polishing surface becomes small, the polishing rate decreases, and the use efficiency of the polishing liquid decreases. For this reason, it is desired to hold an appropriate amount of polishing liquid on the polishing surface to form a uniform polishing liquid film on the polishing surface.

In order to satisfy such a demand, in this example, a groove having a cross-sectional area of 0.38 mm ² or more is formed on the surface of the polishing pad 52. FIG. 10 is a perspective view showing the polishing pad 52, and FIG. 11 is an enlarged sectional view of FIG. As shown in FIG. 10, a plurality of circular grooves 90 are concentrically formed on the surface of the polishing pad 52, and the pitch P ₁ (see FIG. 11) between the grooves 90 is 2 mm, for example. In the example shown in FIG. 11, the width W _{1 of the} groove 90 is 0.5 mm, the depth D ₁ is 0.76 mm, and the cross-sectional area of the groove 90 is 0.38 mm ² . Moreover, it is preferable that the depth of the groove 90 is larger than that of the conventional one, for example, 1 mm or more.

Further, as shown in FIG. 12, a concentric groove 90 and a linear thin groove 92 that connects the grooves 90 may be formed. Such a narrow groove 92 makes it difficult for the polishing liquid to receive centrifugal force. The narrow grooves 92 are preferably grooves inclined by a predetermined angle with respect to the circumferential direction. For example, the inclination angle α with respect to the circumferential direction is 30 °, and the pitch P ₂ between the narrow grooves 92 is 2 mm. The width of the narrow groove 92 is preferably about 30% of the width of the groove 90.

  In this example, an example in which the concentric grooves 90 are formed in the polishing pad 52 has been described, but the shape of the grooves 90 is not limited to this. For example, a spiral groove having the above-described cross-sectional area may be formed on the surface of the polishing pad 52. If a spiral groove having a constant angle (for example, 45 °) with respect to the normal direction is formed, the polishing liquid can be discharged by a constant centrifugal force.

In addition to or in place of the groove 90 described above, a plurality of holes having an opening area of 2.98 mm ² or more (holes having a diameter of 1.95 mm or more) may be formed in the polishing pad 52. Thus, by forming a plurality of holes having a large opening area on the surface of the polishing pad 52, the amount of polishing liquid retained on the polishing surface can be increased, and the use efficiency of the polishing liquid can be improved. The opening area of such a hole is preferably 3.14 mm ² (diameter 2 mm) or more, more preferably 19.63 mm ² (diameter 5 mm) or more. Moreover, the shape of the hole can be round or oval, and the arrangement of the holes can be concentric, staggered, latticed, or the like.

  Here, the CMP process mainly includes (1) a main polishing step of polishing the semiconductor wafer while pressing the semiconductor wafer against the polishing pad and supplying the slurry to the polishing pad; and (2) watering the slurry after polishing the semiconductor wafer. Instead, it consists of two steps, a water polishing step for polishing (cleaning) the semiconductor wafer. In the main polishing step (1), excess film material on the surface of the semiconductor wafer is removed by polishing, and in the water polishing step (2), slurry and polishing products adhering to the surface of the semiconductor wafer are washed and removed. Remove.

  As described above, with the miniaturization of the wiring structure, an insulating film with higher insulation is required, and porous low-k materials and the like are listed as candidates for highly insulating film materials. The material has a very low mechanical strength. Therefore, the polishing pressure in the conventional CMP apparatus was 13.79 to 34.47 kPa (2 to 5 psi), but in the future, it is required to be 13.79 kPa (2 psi) or less, and further 6.89 kPa (1 psi) or less. Is done.

  Thus, when a semiconductor wafer containing a low-k material is polished, it is necessary to perform polishing at a low polishing pressure (eg, 3.45 kPa (0.5 psi)). In this case, it is necessary to perform both the main polishing step and the water polishing step at a low polishing pressure. However, if the water polishing step is performed at a low polishing pressure, deposits such as slurry cannot be completely removed. May remain on the surface of the semiconductor wafer.

  Therefore, in this example, the water polishing process is performed as follows. After the main polishing step at a low polishing pressure, the semiconductor wafer is pressed against the polishing pad 52 at a pressure equal to or lower than that of the main polishing step, and the linear velocity is 1.5 m / s or more, preferably 2 m / s or more, more preferably The polishing table 22 is rotated so as to be 3 m / s or more. Pure water (DIW) is supplied onto the polishing pad 52 at a flow rate of 1 l / min to perform water polishing. Thereby, the surface of the wafer after low-pressure polishing can be properly cleaned. Alternatively, instead of pure water (DIW), chemical liquid polishing may be performed by supplying a chemical liquid such as a citric acid liquid that promotes the detachment of slurry attached to the surface of the wafer. Note that the same effect can be obtained by extending the time of the cleaning process from, for example, the usual 10 seconds to 20 seconds. However, in this case, the throughput is lowered, so that the above-described water polishing or chemical solution at high speed rotation is performed. It is preferable to perform polishing.

  In the example described above, the example in which the polishing liquid is supplied from the polishing liquid supply port 57 provided at the tip of the polishing liquid supply nozzle 26 has been described. However, the polishing liquid supply nozzle 26 is not limited thereto. For example, as shown in FIG. 13, a polishing liquid supply nozzle 26 a including a disk 100 in which a polishing liquid supply port 57 is formed and an arm 102 to which the disk 100 is attached can be used. In this case, the polishing liquid may be supplied while rotating only the disk 100 without rotating the arm 102, or the polishing liquid may be supplied while rotating the arm 102 and rotating the disk 100. Also good. Further, the arm 102 may be moved linearly. Furthermore, the moving speed of the polishing liquid supply port 57, that is, the moving speed of the arm 102 and / or the rotational speed of the disk 100 may be changed during the movement. Further, a liquid amount control mechanism that changes the amount of the polishing liquid supplied from the polishing liquid supply port 57 during movement may be provided.

  Further, as shown in FIG. 14, a polishing liquid supply nozzle 26b having a plurality of polishing liquid supply ports 57 can also be used. In this case, the polishing liquid supply nozzle 26b may be swung, moved linearly, rotated, swinged, or reciprocated. Further, the moving speed of the polishing liquid supply nozzle 26b may be changed during the movement. Further, a liquid amount control mechanism for individually controlling the amount of the polishing liquid supplied from each polishing liquid supply port 57 may be provided. Further, the hole diameter of each polishing liquid supply port 57 may be changed. For example, you may comprise so that the hole diameter of the polishing liquid supply port 57 may become small toward the inner side in the radial direction. In the example shown in FIG. 14, the polishing liquid supply nozzle 26 b extends in the radial direction of the polishing table 22. However, as shown in FIG. 15, the polishing liquid supply nozzle 26 is predetermined with respect to the radial direction of the polishing table 22. May extend in a direction inclined by an angle (0 ° to 45 °).

  Further, instead of moving the polishing liquid supply nozzle, the polishing liquid supply port may be moved within the polishing liquid supply nozzle. For example, as shown in FIG. 16, a polishing liquid supply nozzle 26c having a polishing liquid supply port 57a movable inside can be used. In the example shown in FIG. 16, the polishing liquid supply port 57 is linearly moved, but the present invention is not limited to this. For example, the polishing liquid supply port 57 may be swung, or may be rotated, swinged, or reciprocated. In this case, the polishing liquid may be supplied while moving only the polishing liquid supply port 57a without turning the polishing liquid supply nozzle 26c, or the polishing liquid supply nozzle 26c is turned and the polishing liquid supply port 57a is turned on. The polishing liquid may be supplied while being moved. Further, the moving speed of the polishing liquid supply port 57a may be changed during the movement. Further, a liquid amount control mechanism that changes the amount of the polishing liquid supplied from the polishing liquid supply port 57a during movement may be provided. Further, as shown in FIG. 17, a plurality of polishing liquid supply nozzles 26c shown in FIG. 16 may be provided.

  Further, as shown in FIG. 18, a polishing liquid supply nozzle 26d provided with a disk 100 having a plurality of polishing liquid supply ports 57 and an arm 102 to which the disk 100 is attached can be used. In this case, the polishing liquid may be supplied while rotating only the disk 100 without rotating the arm 102, or the polishing liquid may be supplied while rotating the arm 102 and rotating the disk 100. Also good. Further, the arm 102 may be moved linearly. Furthermore, the moving speed of the polishing liquid supply port 57, that is, the moving speed of the arm 102 and / or the rotational speed of the disk 100 may be changed during the movement. A liquid amount control mechanism for individually controlling the amount of polishing liquid supplied from each polishing liquid supply port 57 may be provided. Further, the hole diameter of each polishing liquid supply port 57 may be changed. For example, you may comprise so that the hole diameter of the polishing liquid supply port 57 may become small toward the inner side in the radial direction. In the example shown in FIG. 18, the polishing liquid supply ports 57 are arranged on the same circumference, but the polishing liquid supply ports 57 may be arranged concentrically on a plurality of circumferences, or simply. You may arrange | position on one straight line or several straight lines.

  Further, as shown in FIG. 19, a polishing liquid supply nozzle 26e including a hollow roll 104 in which a plurality of polishing liquid supply ports 57 are formed may be used. The roll 104 is configured to be rotatable about a rotation axis parallel to the surface of the polishing table 22. The polishing liquid supply port 57 may be arranged linearly, spirally, or randomly. In this case, the polishing liquid may be supplied while rotating the roll 104, or the polishing liquid may be supplied while rotating and rotating the roll 104. Further, the moving speed of the polishing liquid supply port 57, that is, the rotational speed and / or the turning speed of the roll 104 may be changed during the movement. A liquid amount control mechanism for individually controlling the amount of polishing liquid supplied from each polishing liquid supply port 57 may be provided. Further, the hole diameter of each polishing liquid supply port 57 may be changed. For example, you may comprise so that the hole diameter of the polishing liquid supply port 57 may become small toward the inner side in the radial direction. Further, the roll 104 may be divided into a plurality of zones so that the polishing liquid supplied varies depending on the position of the roll 104 in the longitudinal direction. Furthermore, in the example shown in FIG. 19, the roll 104 of the polishing liquid supply nozzle 26 e extends in the radial direction of the polishing table 22, but the roll 104 has a predetermined angle (0 ° to 45 ° with respect to the radial direction of the polishing table 22. It may extend in a direction inclined by °).

  Further, as shown in FIG. 20, a polishing liquid supply nozzle 26f including a roll 104 in which a slit 106 as a polishing liquid supply port is formed may be used. In this case, the polishing liquid may be supplied while rotating the roll 104, or the polishing liquid may be supplied while rotating and rotating the roll 104. Further, the rotational speed and / or the turning speed of the roll 104 may be changed during the movement. Further, a liquid amount control mechanism for controlling the amount of polishing liquid supplied from the slit 106 may be provided. Further, the opening width of the slit 106 may be changed depending on the position. For example, the opening width of the slit 106 may be reduced as it goes inward in the radial direction. Further, the roll 104 may be divided into a plurality of zones so that the polishing liquid supplied varies depending on the position of the roll 104 in the longitudinal direction. Further, in the example shown in FIG. 20, the roll 104 of the polishing liquid supply nozzle 26 f extends in the radial direction of the polishing table 22, but the roll 104 has a predetermined angle (0 ° to 45 ° with respect to the radial direction of the polishing table 22. It may extend in a direction inclined by °).

  In the example shown in FIG. 20, the spiral slit 106 is formed in the roll 104, but a linear slit can also be used. FIG. 21 is a perspective view showing the polishing liquid supply nozzle 26g formed with a linear slit, and FIG. 22 is a longitudinal sectional view of FIG. As illustrated in FIG. 22, the polishing liquid supply nozzle 26 g includes a pressure holding unit 110 having a pressure chamber 108 therein, and a slit unit 114 that forms a slit 112 extending downward from the pressure holding unit 110. The pressure holding unit 110 controls the pressure of the polishing liquid Q supplied to the pressure chamber 108 and adjusts the flow rate of the polishing liquid Q discharged from the slit 112. Since the slit 112 is formed linearly, the polishing liquid Q is uniformly ejected from the slit 112 in the width direction. Further, as shown in FIG. 23, the pressure chamber 108 is divided into a plurality of chambers, and the polishing liquid is ejected so that the flow rate varies in the width direction by changing the flow rate of the polishing liquid Q supplied to each chamber. You can also. The polishing liquid supply nozzle 26g shown in FIGS. 21 and 22 may be arranged along the radial direction of the polishing table 22, or a predetermined angle (0 ° to 45 ° with respect to the radial direction of the polishing table 22). It may be arranged along a direction inclined by (°).

  Further, the polishing liquid supplied onto the polishing pad 52 can be dispersed using a polishing liquid supply nozzle 26h as shown in FIG. The polishing liquid supply nozzle 26h is provided with a disperse spreading plate (dispersion skirt) 116 for dispersing the polishing liquid Q ejected from the polishing liquid supply port 57. According to this polishing liquid supply nozzle 26h, the polishing liquid Q ejected from the polishing liquid supply port 57 is dispersed in multiple directions while flowing over the dispersion skirt 116, and is supplied to the polishing pad 52 in this dispersed state. . The dispersion skirt 116 may be provided with a groove or a resistance member that restricts the flow of the polishing liquid. Further, the surface of the dispersion skirt 116 may be roughened to provide resistance. As a material of the dispersion skirt 116, a material having chemical resistance such as a fluororesin is preferably used. Further, as shown in FIG. 25, a dispersion skirt 116 may be attached to the polishing liquid supply nozzle 26g shown in FIG.

  Further, the polishing liquid supplied onto the polishing pad 52 can be dispersed using a polishing liquid supply nozzle 26i as shown in FIG. The polishing liquid supply nozzle 26 i includes a disk-shaped nozzle body 118 and a dispersion plate 120 attached to the lower surface of the nozzle body 118. The polishing liquid is supplied onto the polishing pad 52 through a through hole (not shown) formed in the central portion of the nozzle body 118 and the dispersion plate 120. The lower surface of the dispersion plate 120 is made of a material having resistance. According to the polishing liquid supply nozzle 26 i, the polishing liquid supplied from the polishing liquid supply port 57 onto the polishing pad 52 is dispersed in multiple directions by the lower surface of the dispersion plate 120 until it comes out of the dispersion plate 120. The As the material of the dispersion plate 120, it is preferable to use a material having chemical resistance such as a fluororesin.

  In addition, as shown in FIG. 27, a dispersion plate 122 (contact member) that comes into contact with the polishing pad 52 is provided on the downstream side in the rotational direction of the polishing table 22 with respect to the polishing liquid supply nozzle 26 and supplied onto the polishing pad 52. It is also possible to disperse the polishing liquid. By this dispersion plate 122, the polishing liquid Q supplied from the polishing liquid supply nozzle 26 is diffused in the radial direction, and the distribution of the polishing liquid on the polishing pad 52 becomes uniform. The dispersion plate 122 is preferably formed of an elastic body having abrasion resistance such as a fluororesin. Further, the dispersion plate 122 may be arranged along the radial direction of the polishing table 22 or along a direction inclined by a predetermined angle (0 ° to 45 °) with respect to the radial direction of the polishing table 22. You may arrange. Further, the dispersion plate 122 may be kept stationary, but the dispersion plate 122 may be swung, linearly moved, rotated, swinged, or reciprocated. In this case, the moving speed of the dispersion plate 122 may be changed during the movement. In addition, as shown in FIG. 28, a plurality of slits 124 may be provided in the dispersion plate 122 and the polishing liquid Q may be dispersed through the slits 124. It is preferable that the slits 124 can be adjusted in size (width, height, pitch).

  When the polishing liquid supply means as shown in FIGS. 9 and 13 to 28 is used, the polishing pad 52 is similar to the pad with concentric grooves as shown in FIG. It is preferable to use one in which a plurality of regions divided in the radial direction are formed. By using such a polishing pad, the supplied polishing liquid is efficiently supplied to the polished surface of the semiconductor wafer while being held in each divided region without being mixed on the polishing pad.

  Incidentally, in the conventional CMP apparatus, when a plurality of polishing liquid supply ports are provided, a polishing liquid circulation system 502 having a large flow rate is provided outside the CMP apparatus 500 as shown in FIG. One polishing liquid supply line 504 is connected to the liquid circulation system 502. The polishing liquid supply line 504 branches into a plurality of lines 506 in the CMP apparatus 500 and is connected to each polishing liquid supply port. Therefore, depending on the shape of the polishing liquid supply nozzle, the difference in the amount of polishing liquid supplied from each polishing liquid supply port is likely to occur. For uniform polishing liquid supply, each polishing liquid supply port is adjusted and valves are installed. Was necessary.

  In this example, as shown in FIG. 30, a large-flow polishing liquid circulation system 210 including a polishing liquid tank 202, a pressure pump 204, a back pressure valve 206, and a pipe 208 is provided outside the polishing apparatus 200. ing. A plurality of polishing liquid supply lines 212 extend from each polishing liquid supply port 57, and these polishing liquid supply lines 212 are directly connected to the pipe 208 of the polishing liquid circulation system 210. With such a configuration, a uniform polishing liquid can be supplied to the semiconductor wafer, the polishing rate can be improved, and the in-plane uniformity of the polishing rate can be greatly improved.

  Here, as shown in FIG. 30, each polishing liquid supply line 212 is provided with a fluid pressure valve 214 as a flow rate adjusting valve for adjusting the flow rate of the polishing liquid supplied from the polishing liquid supply port 57. As shown in FIGS. 31 (a) and 31 (b), the fluid pressure valve 214 compresses the pipe 212a of the flexible polishing liquid supply line 212 by the pressure of the fluid to reduce the diameter of the pipe. Part 216. The tube compression unit 216 is disposed so as to surround the tube 212a. As shown in FIG. 31 (b), the flow rate of the polishing liquid Q flowing in the tube 212a is reduced by the tube 212a being throttled by the fluid pressure. Since the fluid pressure valve 214 restricts the tube 212a by the fluid pressure, wear of the tube 212a can be prevented.

  Here, the retainer ring of the top ring is (1) holding the outer peripheral edge of the object to be polished (semiconductor wafer), and (2) the polishing profile of the object to be polished by pressing the polishing surface (polishing pad). Control is in progress. When using a polishing liquid that forms a copper complex with low mechanical strength as described above in a state where the polishing surface pressure is low, pressing the excessive retainer ring against the polishing surface may cause polishing to the surface of the object to be polished. Limit the supply of liquid. Therefore, it is better that the pressing load on the polishing surface of the retainer ring is small. However, when the pressing load of the retainer ring is small, the polishing object is likely to jump out of the top ring. Therefore, there is a demand for a retainer ring that can prevent the polishing object from popping out even when the pressing load of the retainer ring is low.

  In order to meet such a demand, as shown in FIG. 32, the pressing member 300 that presses the polishing pad 52 to adjust the contact state between the semiconductor wafer W and the polishing pad 52, and the semiconductor wafer W is removed from the top ring 24. You may use the retainer ring 356 comprised from the ring-shaped guide member 302 which prevents popping out. The guide member 302 is disposed radially inward of the pressing member 300, that is, at a position close to the semiconductor wafer W. By using such a retainer ring 356, the polishing profile of the semiconductor wafer W can be controlled while preventing the semiconductor wafer W from jumping out of the top ring 24 even when the polishing pressure is low.

  Further, the position of the guide member 302 can be adjusted in the vertical direction by a screw or an air cylinder, and the height from the surface of the polishing pad 52 can be adjusted. The radial width of the guide member 302 is preferably 6 mm or less, and is preferably formed of a material having a hardness lower than that of the semiconductor wafer W.

  In the process of planarizing copper damascene wiring by CMP in a semiconductor device manufacturing process, the copper film is completely removed up to the barrier metal leaving the wiring part, but generally the process of removing the copper film up to the barrier metal As shown in FIGS. 33 (a) to 33 (c), (1) a large portion of the initial copper film 400 is removed at a high speed, the initial step is relaxed, and some copper film 400a remains. Step 1 (bulk copper polishing step, steps of FIGS. 33 (a) to 33 (b)) and the remaining copper film 400a are completely removed up to the top of the barrier metal 402, leaving the wiring portion 400b. The process (copper clear process, the process of FIG.33 (b) to FIG.33 (c)) is comprised.

  In the bulk copper polishing process, the initial step is reduced (flattened) as much as possible, and the copper film 400a is made as thin and uniform as possible to reduce the load on the copper clearing process. For example, it is preferable to polish so that the thickness of the residual copper film 400a after the bulk copper polishing step is about 100 to 150 nm, preferably 100 nm or less, and the thickness range is about 50 nm or less. In general, in the copper clearing process, as shown in FIG. 34A, polishing is performed at a low polishing pressure in order to suppress dishing 410 and erosion 412 after removing copper.

  Here, in the conventional CMP apparatus, the process switching timing is determined from the film thickness information at a specific position in the wafer surface. In this method, since the switching timing is determined regardless of the film thickness distribution during polishing, for example, even when the polishing profile changes, the film thickness at the position on the wafer to be measured becomes a predetermined value. As long as you do, the process will be switched.

  If there is a portion that is much thicker than the position to be measured at another position, as shown in FIG. 34 (b), a copper film residue 414 may be generated after the next copper clear process is completed. There is. On the other hand, when a portion having a very thin residual film exists at a position other than the position to be measured, dishing 410 or erosion 412 may occur at that position as shown in FIG. .

  In order to prevent such a problem, the following method can be employed. That is, the film thickness distribution of the copper film when shifting from the bulk copper polishing process to the copper clear process is set in advance and stored in the storage device. During the bulk copper polishing process, the film thickness distribution of the copper film of the semiconductor wafer is acquired by the eddy current sensor 58 (see FIG. 2). By simulation software, a preset film thickness distribution and a film thickness distribution acquired by the eddy current sensor 58 during polishing are instantaneously compared to simulate the polishing conditions necessary to obtain the set film thickness distribution. I do. Based on the polishing conditions obtained by the simulation, profile control by the top ring 24 is performed so as to obtain a set film thickness distribution. For example, control is performed to increase the polishing rate for a region where the polishing amount is insufficient in the current residual film distribution. By such profile control, as a result, the copper remaining film immediately before the copper clearing process is made uniform or has a predetermined film thickness distribution. Then, when the actual film thickness distribution matches the set film thickness distribution, the bulk copper polishing process is switched to the copper clear process.

  By such a method, it is possible to surely obtain the desired film thickness distribution while monitoring the actual polished shape (film thickness distribution). In other words, since switching from the bulk copper polishing process to the copper clear process can always be performed with a desired film thickness distribution, it is not affected by process fluctuations in the bulk copper polishing process (polishing rate fluctuation or polishing profile fluctuation), The copper clearing process can always be started under certain conditions. Therefore, the load on the copper clear process, which is the next process, can be minimized. This not only contributes to suppressing the dishing 410 and erosion 412 after the copper clearing process, but also contributes to shortening the time of the copper clearing process (suppressing excessive polishing time), thereby improving productivity and reducing costs. Is also connected.

  When polishing the conductive film on the semiconductor wafer in the wiring formation step, defects existing when the polishing is completed (for example, residual 414 on the surface of the semiconductor wafer of the conductive film, scratches and pits 416 (FIG. 34A) And FIG. 34 (b))) not only affects the next wiring formation process but also affects the deterioration of the electrical characteristics of the finally formed electric circuit. Therefore, it is desired to eliminate these defects at the end of polishing.

  In CMP, the remaining conductive film is polished (over-polished) more than the initial film to eliminate the remaining conductive film 414. In general, when over-polishing is performed for a long time, FIG. ), Dishing 410 and erosion 412 occur in the wiring portion. Further, since polishing is performed by a mechanical action, generation of scratches and pits 416 is inevitable.

  Generally, the remaining conductive film 414 is difficult to polish and remove, and thus requires excessive overpolishing. In this case, dishing 410, erosion 412, and scratches and pits 416 are likely to occur. In order to avoid this, the above-described bulk copper polishing step is performed by CMP, the subsequent copper clearing step by CMP is stopped when the remaining copper film is 50 nm or less, and the subsequent copper clearing step is performed by chemical etching. A method of removing the film can be used. As described above, if the copper clear process is performed by chemical etching without mechanical action, the copper film can be polished without causing defects.

  Etchant in chemical etching includes acids such as sulfuric acid, nitric acid, halogen acids (especially hydrofluoric acid and hydrochloric acid), alkalis such as aqueous ammonia, and oxidizing agents such as hydrogen peroxide and acids such as hydrogen fluoride and sulfuric acid. Can be used. Further, the thickness of the conductive thin film is measured in the bulk copper polishing step, and when the measured thickness becomes a predetermined thickness, preferably 100 nm or less, the bulk copper polishing step is switched to the copper clear step. Is preferred. In this case, the film thickness is measured by an optical sensor that measures the film thickness by irradiating the conductive film with light, and an eddy current sensor that detects the eddy current generated in the conductive film and measures the film thickness (see FIG. 2). At least one of a torque detection sensor that detects the rotational torque of the polishing table 22 and measures the film thickness of the conductive film, and an ultrasonic sensor that measures the film thickness by applying ultrasonic waves to the conductive film may be used. it can.

  The above-described chemical etching is not limited to the bulk copper polishing step in which a thin copper film is formed using a CMP apparatus, and can be combined with other processes. That is, after various processes for forming a flat conductive thin film on a substrate, the conductive thin film can be removed by chemical etching.

  For example, after forming a thin film by electropolishing, the thin film may be removed by chemical etching. Since the electropolishing can be performed without using a mechanical action, the generation of scratches and pits 416 is reduced, but the conductive film remains (for example, on an insulating material) that is not electrically connected. If a minute conductive film formed on the substrate is left), the remaining conductive film cannot be removed. However, after forming a flat conductive thin film by electropolishing, if the conductive thin film is removed by chemical etching that does not require electrical connection, the conductive film can be removed without causing defects. Can do. In this case, the electrolytic polishing method is not limited to a specific one. For example, either electropolishing using an ion exchanger or electropolishing without using an ion exchanger may be used. In electropolishing, it is preferable to use ultrapure water, pure water, or a liquid or electrolytic solution of 500 μS / cm or less. For example, the above-described electrolytic polishing may be performed using an electrolytic processing apparatus described in Japanese Patent Application Laid-Open No. 2003-145354.

  Moreover, after forming a thin film by flat plating, the thin film can also be removed by chemical etching. Furthermore, in the above-described example, the case where the copper film (Cu) is formed and removed has been described. However, the present invention is not limited to this. For example, after forming a conductive thin film containing at least one of Ta, TaN, WN, TiN, and Ru, the thin film may be removed by chemical etching.

  In the polishing apparatus shown in FIG. 35, the polishing liquid supply nozzle 26 was swung during the actual polishing to polish the semiconductor wafer. FIG. 36A is a graph showing the results at this time. As can be seen from comparison with the graph in FIG. 36B in which the polishing liquid supply nozzle 26 is not swung, the in-plane uniformity of the semiconductor wafer is improved by swinging the polishing liquid supply nozzle 26 during polishing. Improved.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 20 Polishing unit 22 Polishing table 24 Top ring 26 Polishing liquid supply nozzle 28 Dresser 30 Atomizer (fluid ejection mechanism)
52 Polishing pad (polishing cloth)
56, 356 Retainer ring 57 Polishing liquid supply port 58 Eddy current sensor 70 Outer peripheral surface 72 Inner peripheral surface 74 Groove 80 Discharge mechanism 82 Cover 84 Contact member 86 Gas ejection mechanism 88 Gas ejection port 100 Disc 116 Dispersion skirt 120, 122 Dispersion plate 124 Slit 210 Polishing liquid circulation system 212 Polishing liquid supply line 300 Pressing member 302 Guide member 400 Copper film 402 Barrier metal

Claims (10)

A first polishing step of polishing and removing most of the first film formed on the polishing object;
A second polishing step of removing the remaining portion of the first film by polishing until the second film is exposed on the surface leaving a wiring portion;
Presetting the film thickness distribution of the first film when shifting from the first polishing step to the second polishing step;
Measuring a thickness of the first film with an eddy current sensor during the first polishing step to obtain a film thickness distribution of the first film;
Adjusting the polishing conditions in the first polishing step so that the obtained film thickness distribution of the first film matches the preset film thickness distribution of the first film;
A polishing method characterized by comprising:   When the acquired film thickness distribution of the first film coincides with the preset film thickness distribution of the first film, the process shifts from the first polishing process to the second polishing process. The polishing method according to claim 1. A first step of forming a flat conductive thin film on a substrate;
A second step of removing the flat conductive thin film by chemical etching;
A wiring formation method comprising:   The wiring forming method according to claim 3, wherein the first step is performed by chemical mechanical polishing.   The wiring forming method according to claim 3, wherein the first step is performed by electropolishing.   The wiring forming method according to claim 5, wherein the electrolytic polishing is electrolytic polishing using an ion exchanger.   The etchant for the chemical etching is at least one of sulfuric acid, nitric acid, halogen acid, hydrogen peroxide, ammonia water, and a mixture thereof. Wiring formation method.   The first step is characterized in that, in the first step, the thickness of the conductive thin film is measured, and the first step is terminated when the measured thickness reaches a predetermined thickness. The wiring formation method according to any one of 3 to 7.   The wiring formation method according to claim 8, wherein the predetermined thickness is 100 nm or less.   The wiring forming method according to claim 3, wherein the conductive thin film includes at least one of Cu, Ta, TaN, WN, TiN, and Ru.

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