JP4620501B2 - Polishing pad - Google Patents

Description

The present invention provides chemical mechanical polishing (Chemical polishing) in the manufacturing process of semiconductor devices and the like.
The present invention relates to a polishing pad used for planarization of an object to be polished such as a silicon wafer by Mechanical Planarization (CMP).

  In the field of semiconductor manufacturing, with the high integration by miniaturization and multilayering of semiconductor elements, the planarization technology of semiconductor layers and metal layers has become an important elemental technology. When forming an integrated circuit on a wafer, if the layers are stacked without flattening the unevenness due to the electrode wiring or the like, the step becomes large and the flatness becomes extremely poor. Further, when the step becomes large, it becomes difficult to focus on both the concave portion and the convex portion in photolithography, and miniaturization cannot be realized. Therefore, it is necessary to perform a planarization process for removing irregularities on the wafer surface at an appropriate stage during the lamination. For the flattening process, an etching back method for removing uneven portions by etching, a film forming method for forming a flat film by plasma CVD (Chemical Vapor Deposition), a fluidizing method for flattening by heat treatment, a concave portion by selective CVD, etc. There is a selective growth method for embedding.

  The above method has problems that it is appropriate depending on the type of film such as an insulating film and a metal film, and that the region that can be flattened is extremely narrow. As a planarization technique that can overcome such problems, there is planarization by CMP.

  In the flattening process by CMP, while the polishing composition in which fine silica particles (abrasive grains) are suspended is supplied to the surface of the polishing pad, the pressed polishing pad and the silicon wafer as the object to be polished are relatively moved. By polishing the surface, the wafer surface over a wide range can be flattened with high accuracy.

  In the CMP processing step, a test wafer is processed periodically in order to perform an appropriate polishing process, and the processing result is confirmed, and then the product wafer is processed. However, the cost for using the test wafer is low. There is a problem that processing time is required. Therefore, in order to solve this problem, a method of measuring the progress of polishing in real time from the film thickness of the layer to be polished and feeding back the result is mainly employed. As a result, the detection accuracy of the processing end point is improved and polishing is performed efficiently.

  End point detection methods include torque measurement method, optical measurement method, capacitance measurement method, vibration analysis method, temperature measurement method, differential transformer method, ultrasonic thickness measurement method, electrical resistance measurement method, slurry analysis method, etc. Is in practical use.

  Among these methods, the optical measurement method is a method in which the film thickness of the layer to be polished is directly measured during the polishing process by spectral reflectance measurement. For example, the wafer being polished is irradiated with laser light, and the film thickness is measured by the reflectance.

  In this measuring method, it is necessary to secure an optical path of laser light from the measuring device to the wafer in the polishing pad in order to irradiate the wafer with laser light and receive reflected light during the polishing process. For example, it is conceivable to provide a through hole in a part of the polishing pad and fill the through hole with a transparent liquid such as water to secure the optical path of the laser beam. In this case, the slurry leaks from the through hole. Therefore, a configuration in which a window member having translucency is provided in the through hole is used (see Patent Document 1).

  However, various problems occur because the material and characteristics of the window member are different from those of other portions of the polishing pad.

  If the hardness of the window member is higher than the hardness of other parts, the hard window member will protrude from the other part with the usage time of the polishing pad, and scratches may occur or the wafer may be caught in the step. There are problems such as dropping out. Further, when the hardness of the window member is low, the window member itself is polished to deteriorate the translucency of the window member, and the irradiation light and the reflected light are diffused, or the window member is depressed, and the slurry and There is a problem that the polishing waste accumulates and scratches occur.

  With respect to these problems, the polishing pad described in Patent Document 2 forms a groove in the vicinity of the window member, and escapes the slurry or the like along the groove to prevent the slurry from reaching the surface of the window member. ing.

JP 2001-162520 A Japanese Patent Laid-Open No. 2002-1652

  The polishing pad described in Patent Document 2 cannot sufficiently release the slurry, and has not yet solved the problem caused by the window member.

  An object of the present invention is to provide a polishing pad capable of detecting a processing end point without deteriorating polishing characteristics.

The present invention provides a polishing pad in which recesses opened on the polishing surface side for polishing an object to be polished are provided so as to be distributed over the polishing surface.
The polishing pad is disc-shaped,
A peripheral portion of the through hole penetrating in the thickness direction of the polishing pad, have a non-working portion of the recess is not provided,
The through hole is a closed curve in which the cross-sectional shape in the polishing surface direction consists of only a curved portion, and the longitudinal direction is provided so as to be perpendicular to the radial direction of the polishing pad,
The non-processed portion is a polishing pad characterized in that a region in the rotation direction of the polishing pad is small and a region in the radial direction of the polishing pad is large .

Further, the present invention provides a polishing pad provided so that concave portions opened on the polishing surface side for polishing an object to be polished are distributed over the polishing surface.
The polishing pad is disc-shaped ,
The peripheral portion of the through-hole penetrating in the thickness direction of the polishing pad, having a non-processed portion not provided with the recess,
The through hole has a cross-sectional shape in the polishing surface direction including a curved portion and a straight portion, the straight portion is a closed curve parallel to a tangent to the curved portion, and a longitudinal direction is perpendicular to the radial direction of the polishing pad. provided so as to,
The unprocessed portion, the polishing rotation direction of the area of the pad is small, a polishing pad, characterized in that provided as the radial region of the polishing pad is increased.

  Further, the present invention is characterized in that the through hole is provided such that a cross-sectional shape in the polishing surface direction is an elliptical shape, and a major axis direction is perpendicular to a radial direction of the polishing pad.

In the present invention, the length of the through hole in the longitudinal direction is 6 mm to 8 mm, and the length in the lateral direction is 3 mm to 5 mm.

  Further, the invention is characterized in that the shape of the unmachined portion in the polishing surface direction is a circular shape.

  In the present invention, the diameter of the non-processed portion is 15 mm to 60 mm.

  In the invention, it is preferable that the concave portion is one or a plurality of grooves for holding a slurry containing abrasive grains.

  In the invention, it is preferable that the recess is a plurality of holes for holding a slurry containing abrasive grains.

  According to the present invention, the polishing pad is provided so that the concave portions opened to the polishing surface side for polishing the object to be polished are distributed over the polishing surface.

  The polishing pad has a through-hole penetrating in the thickness direction, and has a non-processed portion which is a peripheral portion thereof and is not provided with the concave portion.

  Here, the through hole is provided for detecting the end point of the polishing process and serves as an optical path of the laser beam. By combining the through-hole and the non-machined part that is not provided with a recess, the slurry does not enter the through-hole without using a window member, and the processing end point can be detected, and polishing such as the polishing rate can be performed. The characteristics are not deteriorated.

Also, the closed curve cross-sectional shape of the through hole consists only of curved portions, for example an elliptical shape. The polishing pad has a disk shape, and is provided so that the longitudinal direction of the closed curve is perpendicular to the radial direction of the polishing pad.

Also, the cross-sectional shape of the through hole comprises a curved portion and a straight portion, said straight portion is parallel to the lines closed curve of the curved section. The polishing pad has a disk shape, and is provided so that the longitudinal direction of the closed curve is perpendicular to the radial direction of the polishing pad.

  By making the cross-sectional shape of the through hole as described above, there is no corner portion and no slurry leaks, and the contact with the object to be polished becomes smooth. In addition, by making the longitudinal direction perpendicular to the radial direction of the polishing pad, the rotation direction of the object to be polished and the short side direction are substantially parallel, so that it is possible to suppress the entry of slurry into the through-hole and the laser beam. The detection path can be sufficiently secured and the detection time can be extended, so that the detection accuracy can be improved. Furthermore, even if the slurry enters the through hole, the abrasive grains in the slurry are concentrated on the end in the long axis direction due to the surface tension of the water filling the through hole, so that the removal is easy.

Moreover, according to this invention, the longitudinal direction length of the said through-hole is 6 mm- 8 mm, and a transversal direction length is 3 mm-5 mm.

  When the length in the longitudinal direction and the length in the short direction are larger than the above ranges and the size of the through hole is increased, the polishing rate is lowered, and the processing detection accuracy is also lowered due to the entry of the slurry. On the other hand, if the size is smaller than the above range and the size of the through hole is reduced, the optical path of the laser beam cannot be secured, and the processing detection accuracy is lowered.

Moreover, according to this invention, the shape of the said grinding | polishing surface direction of the said non-processed part is circular.
Thereby, the area of a non-processed part can be made small and the fall of a polishing rate can be prevented. In addition, the polishing efficiency can be improved by increasing the region in the rotation direction of the polishing pad and decreasing the region in the radial direction.

Moreover, according to this invention, the diameter of the said non-processed part is 15 mm-60 mm.
When the diameter is larger than the above range, the polishing rate is lowered. When the diameter is smaller, the slurry easily enters the through hole and the processing detection accuracy is lowered.

  According to the present invention, the recess may be one or a plurality of grooves and a plurality of holes for holding slurry containing abrasive grains, or these may be distributed in a mixed manner.

  FIG. 1 is a plan view of a polishing pad 1 according to an embodiment of the present invention. As shown in the overall view of the pad in FIG. 1 (a), the surface of the polishing layer that contacts the object to be polished of the polishing pad 1 is polished for the purpose of holding slurry and removing polishing debris. A groove 2 which is a recess opened on the polishing surface side is provided.

  The polishing pad 1 is used in a CMP apparatus and is placed on a rotating surface plate. At the time of polishing, the surface of the silicon wafer is polished by relative movement of the polishing pad 1 and the silicon wafer by being pressed against an object to be polished such as a silicon wafer held on the carrier portion of the CMP apparatus.

  The polishing pad 1 has a disc shape and has a two-layer structure consisting of a polishing layer for polishing in contact with an object to be polished and a cushion layer fixed to a surface plate, only from the polishing layer. Any one having a single layer structure may be used.

  For the polishing layer, a thermoplastic resin or a thermosetting resin is used. The resin is injected into a mold together with an additive such as a curing agent and cured at a predetermined temperature. As the resin, a foamable resin such as polyurethane is used. A nonwoven fabric etc. are used for a cushion layer.

  A through hole 3 penetrating in the pad thickness direction is provided in a region of the polishing pad 1 in contact with the silicon wafer in order to detect a processing end point. The light source of the processing end point detection laser light and the light receiving portion of the reflected light are installed at predetermined positions on the surface plate, and the position of the through hole 3 corresponds to this position so as to be the optical path of the laser light.

  In the present embodiment, the groove 2 is formed concentrically with the same center as the center of the polishing pad 1. The size of the groove 2 is appropriately selected depending on the type of the object to be polished, the purpose of polishing, etc. For example, the groove width is formed to be about 200 μm to 500 μm, the groove depth is about 300 μm to 1 mm, and between the centers of the grooves The groove pitch, which is the distance, is formed to be about 1 mm to 2 mm.

  The cross-sectional shape of the through-hole 3 in the polishing surface direction is a closed curve consisting only of a curved portion, for example, an elliptical shape. As shown in the enlarged view of the peripheral area A of the through-hole 3 surrounded by the broken line in FIG. 1B, the cross-sectional shape of the through-hole 3 is elliptical, and the longitudinal direction is perpendicular to the radial direction of the polishing pad 1. Thus, it is desirable to form the through hole 3 as described above.

  The cross-sectional shape of the through-hole 3 includes a curved portion and a straight portion, and the straight portion is a closed curve parallel to the tangent of the curved portion, for example, two semicircular portions that are curved portions as shown in FIG. 5 and the straight part 6 may be included, and the straight part 6 may be connected so as to be parallel to the tangent of the semicircular part 5 in the connecting part.

  By making the cross-sectional shape of the through hole 3 as described above, there is no corner portion and no slurry leaks, and the contact with the object to be polished becomes smooth. By making the longitudinal direction of the through-hole 3 perpendicular to the radial direction of the polishing pad, the rotation direction of the silicon wafer and the short-side direction are substantially parallel, and the entry of slurry into the through-hole 3 can be suppressed, Since a sufficient optical path of the laser beam can be secured and the detection time can be extended, the detection accuracy can be improved. Even if the slurry enters the through hole 3, the fine particles in the slurry are concentrated on the end in the major axis direction due to the surface tension of the water filling the through hole 3, so that the removal is easy.

As the size of the through-hole 3, the major axis a which is the length in the longitudinal direction is preferably 6 mm to 8 mm, and the minor axis b which is the length in the short direction is preferably 3 mm to 5 mm. More preferably, the major axis a is 6 mm to 7 mm, and the minor axis b is 3 mm to 4 mm. A desirable combination of diameters is a combination in which the major axis a is 6 mm and the minor axis b is 3 mm. When the major axis a and the minor axis b are increased and the size of the through hole 3 is increased, the polishing rate is lowered, and the processing detection accuracy is also lowered due to the entry of the slurry. If the major axis a and the minor axis b are reduced and the size of the through hole 3 is reduced, the optical path of the laser beam cannot be secured and the processing detection accuracy is lowered.

  In this invention, as shown in FIG.1 (b), the non-processed part 4 which does not give a groove process to the peripheral part of the through-hole 3 is provided. The non-processed portion 4 is a non-processed portion where a groove is not formed, although a groove should be originally formed.

  The shape of the non-processed portion 4 in the pad plane direction is the maximum of the distance between the longitudinal and lateral ends of the through-hole 3 and the outer periphery of the non-processed portion 4 (hereinafter referred to as “non-processed length”). The ratio between the value and the maximum value is not 1, that is, a shape that is not similar to the cross-sectional shape of the through-hole 3 in the plane direction, and is provided in a circular shape centered on the elliptical center of the through-hole 3, for example. By forming the non-processed portion 4 into a circular shape, the area of the non-processed portion is reduced, and a reduction in the polishing rate is prevented. By making the shape non-similar to that of the through hole 3, the polishing area is improved by reducing the area in the rotation direction of the polishing pad and increasing the area in the radial direction.

  As the size of the non-processed portion 4, the diameter d is preferably 15 mm to 60 mm. More desirably, it is 25 mm to 40 mm, and 25 mm is most desirable. When the diameter d increases, the polishing rate decreases. When the diameter d decreases, the slurry easily enters the through hole 3 and the processing detection accuracy decreases.

  The maximum unprocessed length (unprocessed length in the pad radial direction) X is desirably 5 mm to 28.5 mm, and the minimum unprocessed length (unprocessed length in the pad rotating direction) Y is 3. 5 mm to 28 mm is desirable. More desirably, the maximum value X is 10.5 mm to 18.5 mm, and the minimum value Y is 9 mm to 17 mm. Most preferably, the long diameter a of the through-hole 3 is 6 mm, the short diameter b is 3 mm, and the diameter d of the unprocessed portion 4 is 25 mm, so that the maximum value X is 11 mm and the minimum value Y is 9.5 mm. It is.

  The polishing pad 1 having the non-processed part 4 as described above can be manufactured, for example, as follows.

  A polishing pad to be grooved is sucked and fixed on the surface of the surface plate of the curved groove processing machine, and the groove 2 is formed by pressing the cutting blade against the pad surface while rotating the surface plate.

  In a portion corresponding to the non-processed portion 4 of the polishing pad, a recess is formed on the surface of the surface plate, and a suction port is also provided at the bottom of the recess. When the pad is sucked and fixed to the surface plate, the portion corresponding to the non-processed portion 4 is fixed in a recessed state, so that the tip of the cutting blade does not contact and the non-processed portion where the groove 2 is not formed.

  The size (diameter d) of the unprocessed portion can be obtained as desired by changing the size, shape, etc. of the recess.

  The through hole 3 may be formed either before or after grooving, and as a forming method, an existing method such as a method of forming at the time of molding or a method of cutting and forming after molding can be used. .

  In the above description, the polishing pad provided with the grooves 2 formed on concentric circles has been described. However, the shape of the grooves 2 is not limited to this, and may be provided in a spiral shape or a lattice shape as shown in FIG. The groove processing when the groove 2 is provided in a spiral shape is almost the same as the concentric processing, the portion corresponding to the non-processed portion 4 is recessed, the polishing pad is rotated, and the cutting blade is set to the radius of the polishing pad. Move in the direction. Further, in the case where it is provided in a lattice shape, as in the case of the concentric circle shape, the portion corresponding to the non-machined portion 4 is recessed, the surface plate or the cutting blade is moved in the linear direction, and then the direction orthogonal to the previous direction Move to.

  Furthermore, although the polishing pad provided with the groove has been described above, the polishing pad is not limited to the groove and may be a polishing pad provided with a plurality of holes. This hole has a diameter of about 0.5 mm to 2 mm, which is smaller than the diameter of the through hole 3, and the distance between the centers of the holes is formed to be about 2 mm to 10 mm. For the hole processing, an existing processing method such as a method using a mold or a method using a drill or a laser can be used. Further, the grooves and holes may be mixed and distributed.

  Below, the examination example which examined the magnitude | size (major axis, minor axis) of the through-hole 3 and the magnitude | size (diameter) of the non-processed part 4 is demonstrated.

-Size of the through hole First, the influence on the polishing rate and the processing end point detection accuracy when the size of the through hole was changed was examined.

  The used polishing pad is made of a polyurethane foam resin and has a diameter of 743 mm. The formed grooves had a groove width of 200 μm, a groove depth of 375 μm, and a groove pitch of 1.5 mm.

The size of the through hole, the long diameter 6 mm, the minor diameter 3mm ones (Study Example 1), the major axis 7 mm, minor axis 4mm ones (Study Example 2), major axis 8 mm, the minor diameter 5mm ones (Study Example 3) Using. The size of the non-processed portion 4 is the same in each study example with a diameter of d25 mm.
The examination results are shown in Table 1.

Symbols in the tables, ◎ has high practicality (polishing rate, without affecting the detection accuracy), ○ is low practicality (polishing rate, there little affect the detection accuracy) and indicates that.

From the above examination, the major axis a of the through hole 3 is desirably 6 mm to 8 mm, and the minor axis b is desirably 3 mm to 5 mm. More preferably, the major axis a is 6 mm to 7 mm, and the minor axis b is 3 mm to 4 mm. The most desirable combination of diameters was found to be a combination of a major axis a of 6 mm and a minor axis b of 3 mm.

-Size of unmachined part Next, the influence on the polishing rate and the processing end point detection accuracy when the size of the unmachined part was changed was examined.

  The used polishing pad is made of a polyurethane foam resin and has a diameter of 743 mm. The formed grooves had a groove width of 210 μm, a groove depth of 350 μm, and a groove pitch of 1.5 mm.

The size of the unprocessed portion, a straight diameter 15 mm (Study Example 4), having a diameter of 25 mm (Study Example 5), having a diameter of 40 mm (Study Example 6), having a diameter of 60 mm (Study Example 7), the diameter The size of the through hole 3 is 70 mm (examination example 8 ), the major axis a is 6 mm, and the minor axis b is 3 mm, which is the same in each examination example.
The examination results are shown in Table 2.

Regarding the symbols in the table, ◎ is highly practical (the polishing rate and detection accuracy are not affected), ○ is less practical (the polishing rate and detection accuracy are slightly affected), and △ is difficult to use (polishing rate and detection) The accuracy is reduced ) .

  From the above examination, the diameter d of the non-processed portion 4 is desirably 15 mm to 60 mm. More desirably, it is 25 mm to 40 mm, and it was found that 25 mm is most desirable.

The following examples were produced according to the examination results.
A diameter of 743 mm and made of a polyurethane foam resin was provided with a through hole having a major axis of 6 mm and a minor axis of 3 mm and an unprocessed portion having a diameter of 25 mm. Regarding the groove, a groove width of 230 μm, a groove depth of 375 μm, a groove pitch of 1.5 mm, and a groove width of 450 μm, a groove depth of 755 μm, and a groove pitch of 1.78 mm were prepared.

  When a polishing test was performed using these examples, the polishing rate and the processing end point detection accuracy were not decreased.

1 is a plan view of a polishing pad 1 according to an embodiment of the present invention. It is a figure which shows the other example of the cross-sectional shape of the through-hole 3. FIG. It is an enlarged view of the through-hole periphery of other embodiment.

Explanation of symbols

1 Polishing pad 2 Groove 3 Through hole 4 Unprocessed part

Claims (8)

In the polishing pad provided so that the recesses opened on the polishing surface side for polishing the object to be polished are distributed over the polishing surface,
The polishing pad is disc-shaped,
A peripheral portion of the through hole penetrating in the thickness direction of the polishing pad, have a non-working portion of the recess is not provided,
The through hole is a closed curve in which the cross-sectional shape in the polishing surface direction consists of only a curved portion, and the longitudinal direction is provided so as to be perpendicular to the radial direction of the polishing pad,
The polishing pad, wherein the non-processed portion is provided such that a region in the rotation direction of the polishing pad is small and a region in the radial direction of the polishing pad is large . In the polishing pad provided so that the recesses opened on the polishing surface side for polishing the object to be polished are distributed over the polishing surface,
The polishing pad is disc-shaped ,
The peripheral portion of the through-hole penetrating in the thickness direction of the polishing pad, having a non-processed portion not provided with the recess,
The through hole has a cross-sectional shape in the polishing surface direction including a curved portion and a straight portion, the straight portion is a closed curve parallel to a tangent to the curved portion, and a longitudinal direction is perpendicular to the radial direction of the polishing pad. provided so as to,
The unprocessed portion, the small region of the rotating direction of the polishing pad, radial Migaku Ken pad you characterized in that region is provided so as to be larger in the polishing pad. The through hole, the a cross-sectional shape of the polishing surface direction elliptical polishing pad of claim 1, wherein the major axis direction is provided such that the radial and vertical polishing pad. Longitudinal length is 6 mm~8mm, polishing pad according to any one of claims 1 to 3, wherein the lateral direction length is 3mm~5mm of the through hole. The polishing pad according to any one of claims 1 to 4 , wherein a shape of the unprocessed portion in the polishing surface direction is a circular shape. The polishing pad according to claim 5 , wherein a diameter of the unprocessed portion is 15 mm to 60 mm. The recess, the polishing pad according to any one of claims 1-6, characterized in that the one or more grooves for holding slurry containing abrasive grains. The recess, the polishing pad according to any one of claims 1-6, characterized in that the plurality of holes for holding the slurry containing abrasive grains.

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