JP4815758B2 - Polishing apparatus and polishing method - Google Patents

Description

The present invention is one of the planarization technique CMP; about the (Chemical Mechanical Polishing Chemical mechanical polishing) polishing apparatus and method for performing.

  In general, in a semiconductor device manufacturing process, it is widely known to use CMP, which is one of flattening techniques, for flattening a wafer substrate or the like. In CMP, a polishing surface of an object to be polished such as a wafer substrate and a polishing surface of a polishing pad are usually arranged to face each other, and a liquid polishing slurry having a function as an abrasive is supplied therebetween. The surface to be polished and the polishing surface are rubbed relatively. Thereby, the surface to be polished of the object to be polished is flattened by polishing.

  However, in recent years, with the progress of miniaturization and the like of semiconductor devices, there is an increasing demand for the degree of planarization by CMP. For this reason, for example, in CMP for flattening an oxide film or the like on a wafer substrate, it has been proposed to mix a surfactant as an additive into a polishing slurry (see, for example, Patent Documents 1 and 2). ). In CMP performed using a polishing slurry in which a surfactant is mixed, the surfactant can provide a protective effect on the surface to be polished, and concentrated polishing can be performed on convex portions on the surface to be polished. High planarization with few uneven steps after polishing can be realized, and the uniformity of polishing and the accuracy of the finished surface can be improved.

Japanese Patent Laid-Open No. 10-180616 JP 2001-15461 A

  However, in CMP performed using a polishing slurry mixed with a surfactant, high planarization can be obtained as compared with the previous generation performed using a polishing slurry not mixed with a surfactant. The polishing rate is lowered by the surfactant, and there is a possibility that the surface to be polished cannot be cut sufficiently. In addition, if the amount of cutting is insufficient, the in-plane distribution on the surface to be polished may be deteriorated. In such a case, even if a surfactant is mixed, the in-plane distribution is followed. As a result, the desired high flatness may not be obtained. The difficulty caused by such a lack of shaving leads to the fact that in the exposure process after CMP, for example, the focus cannot be adjusted due to uneven steps due to insufficient planarization.

  In this regard, it is conceivable to secure a sufficient amount of cutting by increasing the polishing time. However, when a polishing slurry in which a surfactant is mixed is used, if the polishing time is prolonged, the protective action of the surfactant on the surface to be polished increases near the end of polishing. The frictional force generated between the surface and the polished surface increases. Therefore, in the vicinity of the end of polishing, the agglomerated slurry or the like may cause a defect, and so-called dishing or scratching may occur. In addition, the lengthening of the polishing time becomes a factor that causes a reduction in the efficiency of semiconductor device manufacturing.

  Thus, since high planarization of the surface to be polished and securing of the polishing rate are in a trade-off relationship with each other, it is very difficult to achieve both in conventional CMP. In other words, conventional CMP has problems that it is difficult to realize high planarization required for the next-generation semiconductor manufacturing process, and that it is difficult to improve the yield of semiconductor device manufacturing and to improve efficiency.

  Therefore, the present invention provides a polishing apparatus, a polishing method, and a polishing slurry capable of ensuring a high polishing rate and obtaining a sufficient amount of cutting while enabling a highly flat surface to be polished after CMP. The purpose is to provide.

The present invention is a polishing apparatus devised to achieve the above object. That is, polishing on the surface to be polished is performed using a polishing slurry in which a surfactant is mixed but a magnetic material is not mixed, and a polishing slurry in which both a surfactant and a magnetic material are mixed This is performed in two stages, i.e., polishing performed with the use of .

The present invention is also a polishing method devised to achieve the above object. That is, polishing on the surface to be polished is performed using a polishing slurry in which a surfactant is mixed but a magnetic material is not mixed, and a polishing slurry in which both a surfactant and a magnetic material are mixed This is divided into two stages, that is, polishing performed using a metal .

Further, the polishing slurry is a polishing slurry used for polishing the surface to be polished of the object to be polished to flatten the surface to be polished, and is mixed with a ferromagnetic or paramagnetic magnetic substance. The

Polishing apparatus having the above structure, according to the polishing how the above procedure, magnetic ferromagnetic or paramagnetic the polishing slurry is mixed. Here, “ferromagnetism” refers to magnetism having magnetization (spontaneous magnetization) that exists without applying an external magnetic field. “Paramagnetism” refers to weak magnetism in which magnetization is induced in a direction parallel to a magnetic field when an external magnetic field is applied. In other words, the “magnetic body” referred to here is one that reacts to a magnetic field applied from the outside and is attracted in the direction in which the magnetic field is applied. Moreover, this magnetic substance functions as polishing abrasive grains when mixed in the polishing slurry.
Therefore, if a polishing slurry mixed with a magnetic material is used, it is possible to control whether or not the magnetic material does not contribute to polishing or not depending on the presence or absence of a magnetic field applied from the outside. In other words, by contributing only the surfactant without contributing to the polishing of the magnetic material, it is possible to reduce the uneven step after polishing and achieve high planarization, or to contribute the polishing of the magnetic material to the magnetic material. The high polishing rate can be ensured by the function of the abrasive grains.

Polishing apparatus of the present invention, according to the polishing how, by using the polishing slurry to which the magnetic material is mixed, because it can be controlled by the presence or absence of magnetic field applied whether or not to contribute to the polishing of the magnetic body from the outside Even if high planarization of the surface to be polished and securing of the polishing rate are in a trade-off relationship with each other, it is possible to achieve both by controlling the magnetic field. Therefore, the surface to be polished after CMP can be made highly flat, and a high polishing rate can be ensured and a sufficient amount of cutting can be obtained, so that a reduction in yield can be avoided and an efficient semiconductor device can be manufactured. It becomes possible, and it becomes easy to cope with the realization of the high flatness required for the next-generation semiconductor manufacturing process.

Hereinafter, the polishing apparatus according to the present invention based on the drawings, the polishing how, in concrete is described with the CMP apparatus and CMP how to perform CMP.

[Description of CMP apparatus]
First, the configuration of the CMP apparatus will be described. FIG. 1 is a schematic diagram showing a schematic configuration example of a CMP apparatus to which the present invention is applied. The CMP apparatus described here includes a polishing surface plate 2 having a polishing pad 1 attached on the upper surface, and a polishing head 3 that holds a wafer substrate as an object to be polished above the polishing surface plate 2. Each supply pipe 4 for supplying polishing slurry and pure water is disposed on the upper surface side of the polishing surface plate 2. When polishing the wafer substrate, the wafer substrate is mounted on the polishing head 3, the polishing head 3 and the polishing surface plate 2 are rotated, and the polishing head 3 is directed toward the polishing surface plate 2 in this state. By being lowered, the surface to be polished of the wafer substrate and the polishing pad 1 on the polishing surface plate 2 are slid and rubbed. That is, the surface to be polished of the wafer substrate is polished by relatively rubbing with the polishing slurry and pure water interposed while the surface to be polished of the wafer substrate and the polishing pad 1 are pressurized. It is supposed to be.

  Although such a configuration is substantially the same as that of a general CMP apparatus, the CMP apparatus described here has a characteristic configuration as described below. FIG. 2 is a schematic diagram showing a configuration example of a main part of a CMP apparatus to which the present invention is applied.

  As shown in the figure, in the CMP apparatus described here, a branch point 5 is provided in a supply pipe 4 for supplying a polishing slurry. By this branch point 5, the supply pipe 4 is connected to the upstream path 4 a located upstream of the polishing slurry from the branch point 5, and the downstream path located downstream from the branch point 5 of the polishing slurry. 4b, and one upstream path 4a branches into three downstream paths 4b. The number of branches is not necessarily three, but may be two or more (plural).

  The supply pipe 4, that is, the upstream path 4 a and the downstream path 4 b are each configured by using a nonmagnetic material such as copper (Cu), stainless steel, aluminum (Al), brass, or the like as a piping material. Among these, the upstream path 4a is connected to a supply source of polishing slurry, and receives polishing slurry from the supply source. On the other hand, the downstream path 4b is provided with a valve 6 made of, for example, an electromagnetic valve in the vicinity of each discharge port, and the valve 6 can switch whether or not the polishing slurry is discharged from each discharge port. ing.

  A magnetic force generating means 7 for generating a magnetic force is disposed in the vicinity of the branch point 5 in the supply pipe 4. The magnetic force generating means 7 may be any means that can generate a magnetic force and generate a magnetic field in the vicinity of the branch point 5, and may be configured using a permanent magnet or an electromagnet.

  It is assumed that the magnetic force generating means 7 is disposed at least upstream from the branch point 5. “At least” means that if there is a magnetic force generating means 7 a arranged on the upstream side of the branch point 5, other magnetic force generating means 7 b, for example, a magnetic force generating means 7 b arranged on the downstream side of the branch point 5. Means that there may be. That is, a plurality of magnetic force generating means 7 a and 7 b may be arranged near the branch point 5 along the supply pipe 4. In this case, the magnetic force generating means 7a closest to the branch point 5 among the magnetic force generating means arranged upstream from the branch point 5 is capable of generating the largest magnetic force among the magnetic force generating means. Is desirable. From this, if the magnetic force generating means 7a and 7b are respectively arranged on the upstream side and the downstream side of the branch point 5, the upstream magnetic force generating means 7a can generate a large magnetic force, and It is conceivable to use an electromagnet whose size can be varied, and to use a permanent magnet that can be realized with a simple structure for the upstream magnetic force generating means 7b.

  In the case where an electromagnet is used as the magnetic force generating means 7a, a magnetic force adjusting means 8 for changing the magnitude of the magnetic force generated by the magnetic force generating means 7a is provided along with the magnetic force generating means 7a. And As the magnetic force adjusting means 8, for example, a volume circuit for adjusting the magnitude of the voltage applied to the magnetic force generating means 7a may be used.

  In addition, as shown in the figure, if the configuration is such that one upstream path 4a branches into three downstream paths 4b at the branch point 5 of the supply pipe 4, the magnetic force generating means 7 The supply pipe 4 is disposed so as to surround both sides of the supply pipe 4 or the periphery of the supply pipe 4. For example, when the number of branches is two, the magnetic force generation means 7 is provided only on one side. Good.

[Description of polishing slurry]
Next, the polishing slurry supplied through the supply pipe 4 configured as described above will be described in detail.

The polishing slurry supplied through the supply pipe 4 is a liquid that has a function as an abrasive when polishing the surface to be polished of the wafer substrate. Specific examples thereof include cerium oxide (ceria; CeO _2). ) Series are known. However, the polishing slurry is not necessarily limited to ceria, and may be silica, alumina, or iron nitrate.

  In addition, a surfactant as an additive is mixed in the polishing slurry in order to realize high planarization of the surface to be polished. As the surfactant, for example, polyacrylic acid ammonium salt or polycarboxylic acid ammonium salt is used. The surfactant may be mixed in the upstream path 4a of the supply pipe 4, or a one-component type polishing slurry preliminarily mixed with the surfactant is used as a supply source of the polishing slurry. You may make it carry out by inject | pouring.

  Such a polishing slurry is substantially the same as that used in a general CMP apparatus, but the polishing slurry described here has a characteristic configuration as described below. That is, the polishing slurry described here is mixed with a ferromagnetic or paramagnetic substance in addition to the surfactant. Here, “ferromagnetism” refers to magnetism having magnetization (spontaneous magnetization) that exists without applying an external magnetic field. “Paramagnetism” refers to weak magnetism in which magnetization is induced in a direction parallel to a magnetic field when an external magnetic field is applied. That is, the “magnetic body” referred to here is one that reacts to a magnetic field applied from the outside and is attracted in the direction in which the magnetic field is applied.

For example, as the magnetic material, it is conceivable to use ferromagnetic iron (Fe), nickel (Ni), cobalt (Co), or a compound thereof, which is a ferromagnetic material. As the compound, MxMy (M = Fe, Co, at least one element selected from NI, N = boron (B), carbon (C), nitrogen (N), oxygen (O), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), chromium (Cr), gallium (Ga), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), hafnium (Hf), tantalum (Ta), tungsten (W), platinum (Pt), and gold (Au). . In addition, for example, it is conceivable to use a perovskite oxide (BiFeO ₃ and PLZT) having ferrimagnetism, which is a ferromagnetic material. This perovskite oxidation has both ferromagnetic and ferroelectric hysteresis characteristics. However, the magnetic material is not necessarily limited to these.

Figure 3 is an explanatory diagram showing a specific example of the components of the slurry for Migaku Ken. In the case of a ceria-based polishing slurry, it is conceivable that a surfactant and a magnetic substance are mixed at a component ratio as shown in the figure.

  In the polishing slurry mixed with the magnetic material as described above, the magnetic material functions as a dispersant for the slurry, and the surfactant is well dispersed. In addition, the magnetic substance functions as polishing abrasive grains by being mixed in the polishing slurry. Therefore, due to the mixing of the magnetic material, the polishing slurry increases the polishing rate by the magnetic material while maintaining the uneven step relief performance by the surfactant.

[Description of CMP Method]
Next, an example of a CMP processing operation performed by the CMP apparatus of this embodiment using a polishing slurry mixed with a magnetic material, that is, a CMP method to which the present invention is applied will be described.

  In performing CMP, the wafer substrate is mounted on the polishing head 3 of the CMP apparatus, the polishing head 3 and the polishing surface plate 2 are rotated, and the polishing head 3 is lowered toward the polishing surface plate 2 in this state. . Then, in a state where the surface to be polished of the wafer substrate and the polishing pad 1 are pressurized with each other, the surface to be polished and the polishing pad 1 are relatively rubbed with the polishing slurry and pure water interposed therebetween. Thus, the surface to be polished of the wafer substrate is polished. At this time, the polishing slurry is supplied from the supply source onto the polishing head 3 through the supply pipe 4.

  However, a magnetic substance is mixed in the supplied polishing slurry, and magnetic force generating means 7 is disposed in the vicinity of the branch point 5 in the supply pipe 4 through which the polishing slurry passes. For this reason, for example, if the polishing slurry is ceria-based by controlling the magnetic force generated by the magnetic force generating means 7 by utilizing the interaction (electric-magnetic effect) between magnetism and dielectricity. For example, the polishing slurry can be separated in the supply pipe 4 into (1) a slurry made of ceria + surfactant + magnetic material and (2) a slurry made of ceria + surfactant. That is, since the magnetic material is attracted to the vicinity of the outer periphery in the supply pipe 4 by the magnetic force generated by the magnetic force generation means 7, (1) slurry is collected near the outer periphery in the supply pipe 4, while the center in the supply pipe 4 is The slurry of (2) gathers in the vicinity. As a result, after passing through the branch point 5, the slurry of (1) flows to the side close to the magnetic force generating means 7 in the three downstream paths 4 b (see A and C in FIG. 2), and the magnetic force generating means 7. The slurry of (2) flows to the center far from the center (see B in FIG. 2), whereby the polishing slurry is separated into (1) and (2).

  Therefore, the supply of the polishing slurry onto the polishing head 3 is performed according to the following procedure. That is, when performing CMP, first, the magnetic force generating means 7 generates a magnetic force to separate the polishing slurry into the slurry (1) and (2), and the valve 6 in the downstream path 4b on the center side. Only the slurry of (2) is supplied onto the polishing head 3 from the downstream path 4b by setting only the valve 6 in the other downstream path 4b to the closed state. As a result, at the beginning of CMP, by polishing by flowing the slurry of (2), the protective action of the surfactant works, and the uneven step on the surface to be polished can be mitigated. That is, it is possible to realize high flatness with few uneven steps after polishing.

  Polishing with the slurry (2) is performed until a desired flatness is obtained. Specifically, for example, it can be determined from the torque change of the polishing surface plate 2 whether or not the protective action of the surfactant has ended. Therefore, the end of polishing may be determined based on the detection result of the torque change.

  After the polishing with the slurry of (2) is finished, the valve 6 in the downstream path 4b on the central side is then closed, and the valve 6 in the other downstream path 4b is switched to the open state. Only the slurry (1) is supplied onto the polishing head 3 from the downstream path 4b. At this time, when there are two downstream paths 4b as shown in FIG. 2, the slurry of (1) may be supplied from only one or both. The same applies when there are two or more downstream paths 4b.

  When the slurry of (1) is supplied, the polishing rate is improved by the magnetic substance contained in the slurry while maintaining the protective effect of the surfactant on the surface to be polished. This is because the magnetic body functions as abrasive grains and the magnetic body is larger than ceria, silica, or the like, and promotes polishing more. Therefore, after the polishing with the slurry of (2) is finished, the function of the magnetic material as polishing abrasive grains works by flowing the slurry of (1), and a high polishing rate for the surface to be polished can be secured. It becomes like this. That is, it is possible to ensure a sufficient amount of cutting without requiring a long polishing time.

  FIG. 4 is an explanatory diagram showing a specific example of the state of the surface to be polished before and after CMP. Here, a case where CMP is performed on an interlayer insulating film as shown in FIG. 4A, specifically, a case where CMP is performed on a gate electrode 11 having a height of 150 nm embedded with an oxide film (NSG film) 12 will be described. . The global level difference before CMP is about 150 nm. For such an interlayer insulating film, the conventional CMP could not secure a sufficient polishing rate, and as shown in FIG. 4B, the remaining film thickness of 330 nm had to be further cut by about 30 nm. As described above, if the two-step polishing with the slurry of (1) and (2) is performed, the concentration of convex portions on the surface to be polished by the surfactant is promoted, the step relief effect is accelerated, and the effect of the magnetic substance Since the polishing rate is also improved (to reduce the effect of protecting the surface to be polished by the surfactant), as shown in FIG. 4 (c), the desired flatness (global level difference of about 20 nm) is obtained and sufficient grinding is performed. The amount can be secured.

Above, according to the CMP apparatus and CMP how described in the present embodiment, since the magnetic material in the polishing slurry is mixed, or did not contribute to the polishing the magnetic material, or so as to contribute This can be controlled by the presence or absence of an external magnetic field. In other words, by contributing only the surfactant without contributing to the polishing of the magnetic material, it is possible to reduce the uneven step after polishing and achieve high planarization, or to contribute the polishing of the magnetic material to the magnetic material. The high polishing rate can be ensured by the function of the abrasive grains.

  In particular, as described in the present embodiment, if the polishing of the surface to be polished is performed in two stages of polishing with the slurry of (2) and polishing with the slurry of (1), the surface to be polished Even if there is a trade-off relationship between high planarization and securing of the polishing rate, it is possible to achieve both. In other words, the two-step polishing makes it possible to achieve a high leveling of the surface to be polished after CMP, while ensuring a high polishing rate and obtaining a sufficient amount of cutting. Therefore, the exposure process after CMP is not focused due to uneven steps due to insufficient planarization, and the agglomerated slurry or the like near the end of polishing causes a defect, resulting in dishing or scratching. As a result, it is possible to realize an efficient semiconductor device manufacturing while avoiding a decrease in yield, and it is also easy to meet the high planarization required for the next-generation semiconductor manufacturing process.

  In the present embodiment, when the polishing is performed in two stages, the case where the polishing with the slurry of (2) is first performed and the polishing with the slurry of (1) is then performed is taken as an example. Of course, is not limited to this, and may be vice versa.

  Further, according to the CMP apparatus and the CMP method described in the present embodiment, the supply pipe 4 is provided with the branch point 5, and the magnetic force generating means 7 is disposed in the vicinity of the branch point 5. That is, the polishing slurry mixed with the magnetic material is separated into the slurry (1) and (2) using the magnetic force generated near the branch point 5. Therefore, it is possible to achieve both high planarization of the surface to be polished and securing of the polishing rate by supplying only one type of polishing slurry from the supply source. In addition, the separation of the one type of polishing slurry into the slurry (1) and (2) can be easily performed without requiring a complicated configuration. These are very useful for simplifying the apparatus and process for performing CMP and reducing costs.

  In particular, when generating the magnetic force in the vicinity of the branch point 5, as described in the present embodiment, if the magnetic force is generated at least upstream from the branch point 5, (1) and (2) The slurry can be reliably separated. Then, each can be made to flow in a separate downstream path 4b. For this reason as well, when a plurality of magnetic force generating means 7a and 7b are arranged along the supply pipe 4, it is desirable that the one upstream from the branch point 5 can generate a large magnetic force. .

  Further, as described in the present embodiment, if the magnitude of the magnetic force generated by the magnetic force generating means 7a can be adjusted by the magnetic force adjusting means 8, the size of the supply pipe 4 and the polishing slurry in the supply pipe 4 can be adjusted. Depending on the flow rate (flow velocity), the mixing amount of the magnetic material in the polishing slurry, the type of the magnetic material, etc., an appropriate magnetic force is applied to the magnetic force generating means 7a in separating the slurry of (1) and (2). Can be generated. Therefore, even when the polishing slurry is adjusted and flowed according to the polishing conditions, versatility with respect to the polishing conditions and the like can be sufficiently ensured such that the change in the conditions can be flexibly dealt with. .

It is a schematic diagram which shows the schematic structural example of the grinding | polishing apparatus which concerns on this invention. It is a schematic diagram which shows the principal part structural example of the grinding | polishing apparatus which concerns on this invention. It is an explanatory diagram showing a specific example of a component of the Migaku Ken slurry. It is explanatory drawing which shows a specific example of the state of the to-be-polished surface before and behind grinding | polishing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Polishing pad, 2 ... Polishing surface plate, 3 ... Polishing head, 4 ... Supply pipe, 4a ... Upstream path, 4b ... Downstream path, 5 ... Branch point, 6 ... Valve, 7, 7a, 7b ... Magnetic force generation Means, 8 ... Magnetic force adjusting means

Claims (8)

A polishing apparatus that performs polishing using a polishing slurry on a surface to be polished in an object to be polished to flatten the surface to be polished,
Polishing of the surface to be polished using a polishing slurry in which a surfactant is mixed but not a magnetic material, and polishing in which both the surfactant and the magnetic material are mixed Polishing equipment that is divided into two stages: polishing using slurry.   2. The supply pipe for supplying the polishing slurry is provided with a branch point where the path of the supply pipe is divided into a plurality of parts, and magnetic force generating means for generating a magnetic force is provided in the vicinity of the branch point. The polishing apparatus as described.   The polishing apparatus according to claim 2, wherein the magnetic force generating means is disposed at least upstream of the supply pipe from the branch point.   The polishing apparatus according to claim 2, further comprising a magnetic force adjusting unit that varies a magnitude of the magnetic force generated by the magnetic force generating unit. A polishing method for performing polishing using a polishing slurry on a surface to be polished in an object to be polished to flatten the surface to be polished,
Polishing of the surface to be polished using a polishing slurry in which a surfactant is mixed but not a magnetic material, and polishing in which both the surfactant and the magnetic material are mixed A polishing method that is performed in two stages: polishing using a slurry.   Polishing in which the surface active agent is mixed but the magnetic material is not mixed, using a magnetic force generated in the vicinity of a branching point of the polishing slurry supply pipe. 6. The polishing method according to claim 5, wherein the slurry is separated into a slurry for polishing and a polishing slurry in which both the surfactant and the magnetic substance are mixed.   The polishing method according to claim 6, wherein the magnetic force is generated at least upstream of the supply pipe from the branch point. The polishing method according to claim 6, wherein the magnitude of the magnetic force can be adjusted.

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