JP4463084B2 - Dressing tools - Google Patents

Description

  The present invention relates to a dressing tool for conspicuous the surface of an abrasive cloth, and particularly to an abrasive cloth used for a chemical mechanical polishing (hereinafter abbreviated as “CMP”) method of a semiconductor device.

  In recent years, with the increase in the density of semiconductor devices, the focus margin of an exposure apparatus for transferring a pattern has been narrowed, and the conventional planarization methods such as the reflow method, SOG (Spin On Glass), and the like, and the etch back method have wide areas. Crossing flattening has become difficult. For this reason, a CMP method for polishing a semiconductor substrate by a mechanical action and a chemical action has come to be used.

  Hereinafter, a conventional polishing apparatus used in the CMP method has a table having a flat surface and capable of rotating motion. This table has a diameter of about 50 to 100 cm and is made of a highly rigid material. A polishing cloth having a thickness of about 1 to 3 mm is pasted on the surface of the table. The polishing apparatus includes a carrier having a size corresponding to the diameter of a semiconductor wafer having a surface parallel to the plane of the table above the table, and the carrier is driven by a spindle. Further, the polishing apparatus has a setting for recovering the polishing cloth surface in the vicinity of the table.

  After mounting a semiconductor wafer as an object to be polished on this carrier, the carrier is lowered onto a polishing cloth and a load of about 300 to 600 g / cm 2 is applied to the semiconductor wafer while supplying an abrasive, Polishing is performed by applying a rotational motion of about 20 to 50 rpm in the same direction to the carrier.

  In general, for example, a hard foamed polyurethane called IC1000 manufactured by Rodel in the United States is used as an abrasive cloth of the CMP method, and SC-1 manufactured by Cabot Corporation in the United States based on fumed silica is used as an abrasive. It is used.

  When a semiconductor wafer is polished using these materials as described above, the foam on the surface of the polishing cloth is clogged with silica, which is an abrasive, and the polishing rate decreases.

  Therefore, a process for recovering the surface of the polishing cloth by sharpening is performed simultaneously with the polishing of the semiconductor wafer or at regular intervals (for example, see Non-Patent Document 1).

  As a device for sharpening, generally a load is applied to a disk-shaped dressing tool in which diamond abrasive grains are fixed by nickel plating, a part for holding the dressing tool, and a part for holding the dressing tool, and And a driving arm for moving the dressing tool on the polishing cloth.

  The effect of the sharpening on the surface of the polishing cloth is to remove clogging with diamond abrasive grains and to return the surface roughness of the polishing cloth to the initial state before polishing.

  A conventional dressing tool will be described below. FIG. 4 shows a cross-sectional view of a conventional dressing tool. The diamond abrasive grains 13 are embedded in the nickel plating 14 and fixed so as not to drop off. The diamond abrasive grains 13 used in the CMP method generally have an average particle diameter of about 100 μm to 250 μm for CMP. The thickness of the nickel plating 14 is 60 to 60 times the average particle diameter of the diamond abrasive grains 13. It is set to about 70%.

  There are two methods of fixing the diamond abrasive grains 13: a settling solid difference method and a bagging fixing method. In any method, the diamond abrasive grains 13 are fixed over the entire surface of the material to be fixed. Therefore, there are diamond abrasive grains 13 in a state of floating from the base body 17.

  Since the diamond abrasive grains 13 in such a floating state can easily come into contact with the foam on the surface of the polishing cloth having waviness, aggregates of abrasive clogged in the foam are formed. It can be effectively removed.

  Therefore, the conventional dressing tool 10 described above has a problem that it is easily worn and has a short life because the binder is nickel plating 14. Further, there is a problem that the nickel plating 14 as a binding material is eluted into the working fluid and contaminates the wafer.

  Furthermore, if the arrangement of the diamond abrasive grains 13 is irregular, there is a problem that the distribution of the abrasive grains is not uniform and sufficient pad flatness cannot be obtained even when dressing with a constant pressure.

  Therefore, Patent Document 1 proposes a dressing tool 10 that is replaced with an inorganic bond such as borosilicate glass instead of the nickel plating 14 that fixes the diamond abrasive grains 13, and discloses a method for preventing wafer contamination. .

Patent Document 2 proposes a dressing tool 10 in which diamond abrasive grains 13 are arranged two-dimensionally with regularity, and diamond abrasive grains 13 are arranged in a substantially uniform distribution. A method is disclosed in which the pressure is uniform.
Solid State Technology, Oct. 1994, p.66, left column 2nd line to right column 9th line JP 2001-239461 A JP 2002-127017 A

  However, even in Patent Document 1, the inorganic binder such as borosilicate glass is worn, and the diamond abrasive grains 13 may drop off, resulting in a short life. In addition, the worn inorganic binder may become an abrasive and damage the wafer.

  On the other hand, Patent Document 2 is effective in that the pressure to the nickel plating 14 holding the diamond abrasive grains 13 is uniform, but is not improved in terms of wear and elution of the nickel plating 14. It was enough.

  The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a dressing tool that can suppress the removal of diamond abrasive grains, suppress surface abrasion, and suppress contamination of metal components. It is to provide. Another object of the present invention is to provide a dressing tool in which the pressure applied to the diamond abrasive grains during dressing is made uniform to improve the dressing accuracy of the polishing cloth.

  In addition, when diamond abrasive grains are fixed to a ceramic substrate by metallized bonding or the like, the characteristics of the diamond abrasive grains are impaired by the high-temperature treatment at the time of bonding, so that it does not function as a dressing tool.

  Further, when diamond abrasive grains are bonded with an inorganic binder such as borosilicate glass, it is necessary to bond them at a high temperature. Therefore, in the manufacturing process, work efficiency is poor, and the diamond abrasive to the dressing tool body at the time of bonding is poor. There is a problem such as grain shift, and a method capable of working at a low temperature has been desired. However, simply holding the diamond abrasive grains on the dressing tool body with a resin or the like provides a sufficiently satisfactory dressing tool because the resin portion is easily eroded and the holding power of the diamond abrasive grains is insufficient. I couldn't.

Therefore, in view of the above problems, the present inventor is a dressing tool according to the present invention, in which diamond abrasive grains are held on the surface of a substrate via a binder, and the clogging is removed by sliding contact with the surface of the polishing pad. The diamond abrasive grains have a plurality of through holes into which the diamond abrasive grains are inserted, and the diamond abrasive grains are exposed from the through holes on the front surface side, and the back surface side is bonded to the surface of the substrate by the binder. The material of the said plate consists of zirconia, It is characterized by the above-mentioned .

  The through hole is characterized in that the opening portion on the front surface side is smaller than the back surface side.

  The binder is formed of an inorganic binder.

  The binder is formed of a resin material.

  The resin material is formed of an epoxy resin.

  The plate is made of zirconia.

  The substrate is made of alumina or zirconia.

  The diamond abrasive grains have an average particle size of 100 to 250 μm.

  According to the configuration of the present invention, the plate has a plurality of through-holes into which diamond abrasive grains are inserted, and the front side is exposed from the through-holes and the back side is on the substrate surface. Since it is what was joined via the joining material, a diamond abrasive grain can be firmly hold | maintained by the said plate, and omission can be prevented.

  Moreover, the said plate can arrange | position a diamond abrasive grain with sufficient precision only by forming the arrangement position of the through-hole into which a diamond abrasive grain is inserted previously. Therefore, uniform pressure can be applied during dressing, thereby enabling dressing with excellent flatness of the polishing pad.

  Furthermore, since the opening portion on the front surface side has a shape smaller than that on the back surface side, the through-hole can easily hold the diamond abrasive grains mechanically at the opening portion of the plate. However, even if the arrangement density is increased, it can be easily manufactured. Moreover, since it becomes possible to hold | maintain mechanically firmly in the opening part of a plate, falling-off | omission of a diamond abrasive grain can further be prevented.

  Further, by using the plate and using an inorganic binder for the binder, the elution of the metal component is eliminated, and the contamination of the metal component on the wafer can be prevented. The same effect can be obtained by forming the base material from alumina or zirconia, or forming the plate material from zirconia.

  Furthermore, since the binder is formed of a resin material such as an epoxy resin, it is possible to hold the diamond abrasive grains in an elastic state, and has an effect of preventing the diamond abrasive grains from degreasing. The presence of the plate allows the grease material to be used without being eroded by grinding scraps or grinding fluid. Since the resin material has high viscosity, the operation is easy, and the gap between the small-diameter hole formed in the plate and the diamond abrasive grains can be completely blocked. Furthermore, workability can be improved because there is no need to cure at a high temperature.

  Moreover, since the material of the said plate is formed from zirconia, the abrasion resistance with respect to a polishing cloth improves and it becomes possible to lengthen the lifetime of a dressing tool.

  And since the average particle diameter of the said diamond abrasive grain is 100-250 micrometers, it becomes possible to perform optimal sharpening.

  Hereinafter, the best mode for carrying out the present invention will be described.

  1-3 is a schematic sectional drawing which shows one Example of the dressing tool concerning this invention.

  The dressing tool 1 of the present invention shown in FIG. 1 is one in which diamond abrasive grains 3 are held on the surface of a base 7 via a binder 4 and are also brought into sliding contact with the surface of a polishing pad to remove clogging. It has a plurality of through holes 5 into which the abrasive grains 3 are inserted, the diamond abrasive grains 3 are exposed from the through holes 5 on the front surface side, and the back surface side is bonded to the surface of the base body 7 by the bonding material 4. It is characterized by having a plate 2. Hereinafter, each component will be described.

  The substrate 7 may be formed in a flat plate made of ceramic, and when ceramic is used, it is particularly preferable that the material is alumina or zirconia. In particular, the elution of the metal component can be prevented by forming the base material 7 from alumina or zirconia. Moreover, if the material of the base | substrate 7 is an alumina, the rigidity of the dressing tool 1 can be made high and manufacturing cost can be made cheap. On the other hand, if zirconia is used, the plate 2 and the substrate 7 can be made of the same material, the thermal expansion coefficient can be made the same, and there is an advantage that the change in accuracy is small even when the temperature is applied.

  In addition, as a mechanical characteristic of the base | substrate 7, it is preferable that Young's modulus is 190 GPa or more and Vickers hardness is 9 GPa or more. If the Young's modulus is lower than 190 GPa, the deformation due to mechanical load during processing or use becomes large, which is not preferable, and if the Vickers hardness is lower than 9 GPa, the diamond abrasive grains 3 are applied to the substrate 7. This is not preferable because biting occurs and the diamond abrasive grain height may change.

  Here, the following materials can be used as alumina.

(1) Alumina (Al ₂ O ₃ ) 99 to 99.9% by weight of silica (SiO ₂ ), magnesia (MgO), calcia (CaO) as a total of 0.1 to 1% by weight as a sintering aid After being added and formed into a desired shape, it is fired at a temperature of 1500 to 1800 ° C. in an air atmosphere or a vacuum atmosphere. (2) Yttria with respect to 93 to 99% by weight of alumina (Al ₂ O ₃ ) 1-7 wt% of zirconia (ZrO ₂ ) stabilized or partially stabilized with a stabilizer such as (Y ₂ O ₃ ), magnesia (MgO), calcia (CaO) or ceria (CeO ₂ ) , After being molded into a desired shape, and then fired at 1500 to 1700 ° C. in an air atmosphere, a hydrogen atmosphere or a nitrogen atmosphere (3) Alumina (Al ₂ O ₃ ) 60 to 80% by weight In addition, after adding titanium carbide (TiC) in an amount of 40 to 20% by weight to form a desired shape, it is possible to use one that is fired at a temperature of 1300 to 2000 ° C. in an air atmosphere or a reduced pressure atmosphere. .

As the zirconia, 3～9Mol% of yttria _(Y 2 _{O 3)} in partially stabilized zirconia (ZrO ₂₎ and, 16～26Mol% magnesia (MgO) in partially stabilized zirconia _(ZrO 2), or after forming 8～12Mol% of calcia (CaO) in partially stabilized zirconia (ZrO ₂₎ and 8～16Mol% of ceria zirconia partially stabilized with (CeO ₂₎ a (ZrO ₂₎ into a desired shape, What was baked at the temperature of 1400-1700 degreeC in air | atmosphere atmosphere or a vacuum atmosphere can be used.

  The binder 4 is preferably a material having sufficient bonding strength and toughness, and is preferably an inorganic binder mainly composed of SiO2, such as boron silicate glass or quartz glass. Alternatively, the binder 4 may be a resin material. The resin material is preferably a polyimide resin, a urethane resin, a fluorine resin, or an epoxy resin. Among them, the epoxy resin is particularly optimal in terms of bonding strength, chemical resistance, hardness, and aging.

  If the binder 4 is an inorganic binder, the firing temperature for curing needs to be 600 ° C. or less that does not impair the characteristics of the diamond abrasive grains 3, and the firing temperature is preferably lower. Moreover, even if it is a resin material, if the hardening temperature is a temperature which does not impair the characteristic of the diamond abrasive grain 3, there will be no problem. If it is the above-mentioned resin material, the curing temperature has no problem.

  Metal contamination can be suppressed by using an inorganic material or a resin material as the binder 4.

The plate 2 is preferably made of ceramics, and particularly preferably made of zirconia (ZrO ₂ ) as a material. Moreover, as a mechanical characteristic of the plate 2, a thing with a high toughness value is preferable, and if K1c is 5 or more, it is preferable. Furthermore, it is more preferable if the Young's modulus is 190 GPa or more and the Vickers hardness is 9 GPa or more.

  Since the material of the plate 2 is formed of zirconia, it is possible to obtain an effect of preventing the bonding material 4 from being eroded, and it is possible to improve wear resistance and prevent breakage from the edge portion. Moreover, since zirconia has a high strength and toughness value, it is easy to process a thin wall, and even if the diamond abrasive grains 3 have a small diameter, a plate 2 suitable for that can be provided. Further, it is preferable to combine the base body 7 with zirconia so that the base 7 and the plate 2 have the same thermal expansion coefficient, and the change in accuracy of the dressing tool due to heat can be reduced.

  A through hole 5 is formed at a predetermined position in the plate 2, and diamond abrasive grains 3 are inserted into the through hole 5.

  Here, the thickness of the plate 2 is determined by the grain size of the diamond abrasive grains 3, and is such a thickness that the diamond abrasive grains 3 to be used are exposed to 20 to 40% from the through-holes 5 on the surface side of the plate 2. That's fine.

  The size d1 of the through-hole 5 is determined by the particle diameter of the diamond abrasive grains 3, and can be held without penetrating the diamond abrasive grains 3, and set to a size that can ensure the set protrusion height of the diamond abrasive grains 3. Good.

  Moreover, the arrangement | sequence of the through-hole 5 is free, for example, may be arrange | positioned by the same positional relationship like the grid of a grid, and the shape arrange | positioned radially may be sufficient.

  It is preferable that the cross-sectional structure of the through-hole 5 and the opening portion d1 on the front surface side are smaller than the back surface side, as shown in FIG. 1, a taper shape with a small diameter on the front surface side, or as shown in FIG. It is preferable that the shape has a step diameter.

  Even if the structure of FIG. 3 is used, it is possible to hold the diamond abrasive grains 3 through the binding material 4. However, by using the structure of FIG. 1 or FIG. The effect of preventing the diamond abrasive grains 3 from falling off is obtained. Therefore, it is preferable that the opening d1 on the front surface side has a smaller shape than the back surface side.

  The diamond abrasive grain 3 may be either synthetic diamond or natural diamond, and is preferably a blocky type in which crystals are grown.

  The average particle diameter of the diamond abrasive grains 3 is preferably 100 to 250 μm, and if it is smaller than 100 μm, the thickness of the plate 2 is thin, and the production becomes difficult. Further, the diameter of the through hole 5 becomes small, and high precision machining becomes difficult, and the diamond abrasive grains 3 cannot be held by the plate 2. On the contrary, if it is larger than 250 μm, it is necessary to increase the distance between the diamond abrasive grains 3, and it becomes difficult to apply a uniform pressure to the polishing pad. Therefore, the average particle diameter of the diamond abrasive grains 3 is preferably 100 to 250 μm, and more preferably 120 to 200 μm.

  Next, the manufacturing method about the dressing tool of this invention is demonstrated.

  The plate 2 is formed of ceramics, preferably zirconia raw material powder, using a CIP, mechanical press or doctor blade to obtain a formed shape. Next, the obtained shaped body is processed into a desired size by cutting, and then fired in an air atmosphere to obtain a sintered body. Further, after firing, grinding is performed with a diamond grindstone on a surface grinder to obtain a predetermined size. At this time, the thickness dimension of the plate 2 is preferably about 200 to 250 μm because it can withstand the processing load of post-processing and is easy to handle.

  Moreover, the through-hole 5 formed in the plate 2 may be formed in a cutting process after obtaining a generated shape, or may be formed in a grinding process after obtaining a sintered body.

  Here, it is preferable that the raw material used for CIP and a mechanical press is a granulated powder containing an organic binder, and the raw material used for a doctor blade needs to be a slurry form.

  The diamond abrasive grains 3 are held and arranged in the through holes 5 formed in the plate 2, and the surface side diameter of the through holes 5 is ground by a diamond grinding wheel using a machining center. Form with.

  The size d1 of the through hole 5 is set such that the protrusion height of the diamond abrasive grain 3 from the surface side through hole 5 is 20 to 40% of the particle diameter. The cross-sectional shape of the through hole 5 is desirably the shape shown in FIG.

  Thereafter, the thickness of the plate 2 is processed to a final thickness of 60 to 80% of the grain size of the diamond abrasive grains 3. At this time, the parallelism of the thickness of the plate 2 is desirably 10 μm or less.

The thickness processing of the plate 2 is preferably lapping processing to suppress warping due to processing distortion.

Next, the diamond abrasive grains 3 are inserted and arranged from the back side of the through holes 2 of the plate 2, and the diamond abrasive grains 3 are formed near the outer side of the plate 2 where the through holes 5 on the front side of the plate 2 are not processed. It is supported on a smooth base plate through a spacer having the same dimensions as the protruding height.

  The material of the base plate needs to be poor in wettability with the binding material 4, and is preferably a carbon base plate.

  The substrate 7 is made of ceramic, preferably alumina or zirconia powder, by CIP or mechanical press, cut into a predetermined shape, and fired to obtain a sintered body. The obtained sintered body is ground by a diamond grindstone with a surface grinder to obtain a finished substrate 7 having a predetermined thickness. At this time, the parallelism of the thickness of the substrate 7 is desirably 10 μm or less.

  Moreover, it is preferable that the ceramic raw material used for CIP and a mechanical press is the granulated powder containing an organic binder.

  The paste of the binding material 4 is applied to one side of the base 7 and the back side of the plate 2, and the base 7 is set so as to be in close contact with the plate 2 on the back side of the plate 2 on which the diamond abrasive grains 3 are arranged.

More preferably, the bonding material 4 is filled in the gaps between the through holes 5 and the diamond abrasive grains 3 when the bonding material 4 is applied to the back side of the plate 2. This is because the diamond abrasive grains 3 can be held more firmly.

  Thereafter, heat treatment is performed again to vitrify the binder 4 and bond the substrate 7 and the plate 2 together. The heat treatment temperature is preferably 600 ° C. so as not to impair the characteristics of the diamond abrasive grains 3.

  Thereafter, the outer edge of the plate 2 is processed along the outer edge of the substrate 7, the bonding material 4 protruding from the surface of the plate 2 is removed with a grindstone, and the diamond abrasive grains 3 are exposed to obtain the dressing tool 1.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
After a powder of 99% alumina is formed by CIP, it is cut into a desired shape, fired in a temperature range of 1600 to 1700 ° C., and then ground to provide a base 7 having an outer diameter of 20 mm and a thickness of 6.25 mm. Formed. In particular, the thickness of the substrate 7 at that time was finished to a thickness accuracy of ± 0.01 or less by grinding.

  Next, after forming the zirconia powder by CIP, cutting into a desired shape, firing at 1400-1500 ° C., and then grinding to produce a plate 2 of 25-30 mm square, the plate φ20 In this range, a plurality of through holes 5 having a small diameter φ0.15 to 0.16 mm and a large diameter φ0.18 to 0.2 mm are opened and processed in a lattice shape with a pitch of 1 mm, and a thickness of 0.13 mm Zirconia plate was made. At that time, the thickness processing of the zirconia plate was performed by lapping in order to suppress warping due to processing distortion.

  Next, in a state where the diamond abrasive grains 3 having an average particle diameter of φ160 μm are inserted from the large diameter side of the tapered through hole 5 of the plate 2, the large diameter side is turned up and the through hole 5 is not processed. A .03 mm spacer is inserted and set on a carbon base plate, and a base 7 coated with silica sol as a bonding material 4 is placed on one side of the base 7 and the back side of the plate 2 and heat treated at 200 ° C. for bonding. Agent 4 was vitrified.

  By the way, the reason why it is set on the carbon plate is to prevent the dressing tool 1 and the base plate from being fixed by the protruding adhesive.

  After the heat treatment, the excess portion of the plate 2 was cut with a diamond grindstone along the outer diameter of the substrate 7, and the bonding agent 4 that protruded from the outer diameter and the surface of the plate 2 was removed with a PVA grindstone. The protruding height of the diamond abrasive grain 3 at this time was 20 to 40 μm.

  Twelve dressing tools 1 thus manufactured were manufactured and adjusted as necessary so that the dimensional variation was 40 μm or less from the back surface of the dressing tool 1 to the tip of the diamond abrasive grain 3 projected.

  Next, when the dressing tool 1 thus manufactured was attached and rounded on an alumina φ100 mm disk, a polishing cloth having an excellent surface with a flatness of 10 μm was obtained.

  Further, when this polishing cloth was used for processing by the wafer CMP method, contamination from the wafer with metal components could not be confirmed.

(Example 2)
When the binder 4 in Example 1 described above was made of the material shown in Table 1, the contamination of the metal component from the wafer was evaluated.

  As a result of Table 1, it was confirmed that the materials shown in the table can be used without any problem as the binding material 4 of the dressing tool of the present invention.

In Table 1, No. 6 Ni electrodeposition is a Ni electrodeposition dressing tool conventionally used.

It is a schematic sectional drawing which shows one Example of the dressing tool which concerns on this invention. It is a schematic sectional drawing which shows one Example of the dressing tool which concerns on this invention. It is a schematic sectional drawing which shows one Example of the dressing tool which concerns on this invention. It is a schematic sectional drawing which shows the conventional dressing tool.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10 ... Dressing tool 2 ... Plate 3, 13 ... Diamond abrasive grain 4 ... Binding material 7, 17 ... Base | substrate 14 ... Nickel plating d1 ... Opening part

Claims (7)

In the dressing tool that removes clogging by holding the diamond abrasive grains on the surface of the substrate via the binding material and slidingly contacting the surface of the polishing pad,
The diamond abrasive grains have a plurality of through holes into which the diamond abrasive grains are inserted, the diamond abrasive grains are exposed from the through holes on the front surface side, and the back surface side is bonded to the substrate surface with the binder. With a plate ,
A dressing tool, wherein the plate is made of zirconia .   The dressing tool according to claim 1, wherein the through hole has a shape in which the opening portion on the front surface side is smaller than the back surface side.   The dressing tool according to claim 1, wherein the binding material is formed of an inorganic binding material.   The dressing tool according to claim 1, wherein the binding material is formed of a resin material.   The dressing tool according to claim 4, wherein the resin material is formed of an epoxy resin.   The dressing tool according to any one of claims 1 to 5, wherein the substrate is made of alumina or zirconia.   The dressing tool according to any one of claims 1 to 6, wherein an average particle diameter of the diamond abrasive grains is 100 to 250 µm.

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