JP5632267B2 - Polishing pad and method of manufacturing polishing pad - Google Patents

Description

  The present invention relates to a polishing pad and a method for manufacturing the polishing pad, and in particular, a polishing pad provided with a resin sheet in which a resin solution containing a soft resin is solidified by a wet coagulation method and foam is continuously formed therein, and the polishing pad It relates to the manufacturing method.

  Conventionally, various materials (objects to be polished) such as semiconductor devices have been polished using a polishing pad to ensure flatness. In the manufacture of semiconductor devices, a copper wiring layer and an insulating layer are usually formed sequentially to be multilayered, but polishing is performed on the surface (processed surface) after forming each layer. In recent years, as the degree of integration of semiconductor circuits has increased rapidly, miniaturization and multilayer wiring have been promoted for the purpose of higher density, and a technique for further flattening the processed surface has become important.

  Generally, in the manufacture of semiconductor devices, a chemical mechanical polishing (hereinafter abbreviated as CMP) method is used. In the CMP method, a slurry (polishing liquid) in which abrasive grains (polishing particles) are dispersed in an alkali solution or an acid solution is usually supplied. That is, the object to be polished (the processed surface thereof) is flattened by a mechanical polishing action by the abrasive grains in the slurry and a chemical polishing action by the alkali solution or acid solution.

  In the polishing process by the CMP method, a polishing pad provided with a resin sheet in which a hole is formed on a polishing surface for polishing an object to be polished is used. At the time of polishing, the processed surface is flattened by being supplied so that the abrasive grains are dispersed in the processed surface while being held in the openings formed in the polished surface. The resin sheet is usually formed by a dry molding method or a wet coagulation method. In the dry molding method, a resin sheet is formed by grinding the surface of a resin foam or by slicing the foam. As a technique for forming a foam, a technique for adding hollow fine particles in a resin solution (see, for example, Patent Document 1), a technique for generating gas during molding by adding water to a resin solution (for example, Patent Document 2) and the like are disclosed. On the other hand, in the wet coagulation method, after a resin solution in which a resin is dissolved in a water-miscible organic solvent is applied to a sheet-like base material, foaming is performed by replacing the organic solvent and the coagulation solution in an aqueous coagulation solution. A continuous resin sheet is formed. In the resin sheet obtained by the wet coagulation method, a dense skin layer is formed on the surface side, and a large number of foams are continuously formed in the resin inside the skin layer. This skin layer is removed by a grinding process such as buffing, and foamed holes formed inside are formed on the surface of the resin sheet. For the purpose of improving the surface flatness of an object to be polished, a polishing pad technique that limits the surface roughness of the surface of a resin sheet by a wet coagulation method has been disclosed (see Patent Document 3).

  When polishing a semiconductor device or the like with such a polishing pad, a dressing process is performed with a diamond abrasive disc while pure water is supplied to the polishing pad attached to the polishing apparatus. Thereafter, a work-in operation with a dummy work is performed to make the slurry familiar with the polishing pad, so-called break-in (start-up work). In order to increase the productivity of semiconductor devices and the like, it is important to shorten the time required for break-in.

Japanese Patent No. 3013105 JP 2005-68168 A JP 2004-291155 A

  However, in the resin sheet conventionally used for the polishing pad, especially the resin sheet by the wet coagulation method, in addition to the resin component and the pigment component, various surfactants are used as an auxiliary agent for stabilizing foam formation and film formability at the time of manufacture. Is added to the resin solution. For this reason, there exists a problem that surfactant remains in a resin sheet and the surfactant elutes at the time of a grinding | polishing process. When the surfactant is eluted, foaming is likely to occur, the slurry is aggregated, and the polishing performance such as the surface flatness and polishing rate of the object to be polished may be changed. In order to solve this, it is necessary to elute and remove the surfactant during the break-in operation, but it becomes a factor that hinders the reduction of the break-in time.

  An object of the present invention is to provide a polishing pad and a method for manufacturing the polishing pad that can shorten the start-up time during polishing.

In order to solve the above-mentioned problem, a first aspect of the present invention is a polishing pad comprising a resin sheet in which a resin solution containing a soft resin is solidified by a wet coagulation method and foam is continuously formed therein. In the resin solution, a poor solvent for the soft resin is mixed in a range of 0.2R to 4.5R in terms of a weight percentage with respect to a solid content of the soft resin, where R is a solidification value of the soft resin. The resin sheet is affixed to a rotatable surface plate, wets the entire surface with water, and is rotated by a brush dresser under a pressure of 400 Pa to 500 Pa while rotating the surface plate at a speed of 20 rpm to 30 rpm. perform brushing for at least 30 seconds, to wherein the foaming of the foaming test visually observed after standing for at least 1 minute is of no detection at said purpose vision observation .

In the first aspect, a resin sheet obtained by coagulating a resin solution in which a poor solvent for a soft resin is mixed in a range of 0.2R to 4.5R in a weight percentage with respect to the solid content of the soft resin by a wet coagulation method is under pressure. Since foaming in the foaming test for brushing is not detected by visual observation, foaming due to break-in operation is suppressed, so that the start-up time during polishing can be shortened .

  According to a second aspect of the present invention, there is provided a polishing pad manufacturing method according to the first aspect, comprising: a resin solution obtained by mixing a soft resin, a good solvent for dissolving the soft resin, and a poor solvent for the soft resin. A preparatory step for preparing, and a sheet forming step for solidifying the resin solution into a sheet form in a coagulating liquid to form a resin sheet. In the preparatory step, the mixing ratio of the poor solvent is determined by coagulation of the soft resin. When the value is R, the weight percentage with respect to the solid content of the soft resin is in the range of 0.2R to 4.5R. In the second aspect, the mixing ratio of the poor solvent mixed in the resin solution in the preparation step is 0.2R to 4.5R in terms of weight percentage with respect to the solid content of the soft resin, where R is the solidification value of the soft resin. Therefore, the soft resin tends to aggregate before the resin solution is solidified in the sheet forming step, and the foam formation is stabilized without using a surfactant conventionally used as a stabilizer for foam formation. The polishing pad of this aspect can be easily produced. In this case, the soft resin may be a polyurethane resin, and the poor solvent may be water. At this time, the good solvent can be N, N-dimethylformamide or N, N-dimethylacetamide, and the poor solvent can be water.

According to the present invention, a resin sheet obtained by coagulation of a resin solution in which a poor solvent for a soft resin is mixed in a range of 0.2R to 4.5R by weight percentage with respect to the solid content of the soft resin by a wet coagulation method is applied under pressure. Since foaming in the foaming test for brushing is not detected by visual observation, foaming due to break-in operation is suppressed, so that it is possible to shorten the startup time during polishing.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is a photograph which shows the state of the foaming test of the polishing pad of Example 1, (A) shows the surface of the polishing pad before brushing, (B) shows the surface of the polishing pad after brushing, respectively. It is a photograph which shows the state of the foaming test of the polishing pad of the comparative example 7, (A) shows the surface of the polishing pad before brushing, (B) shows the surface of the polishing pad which produced foaming after brushing, respectively.

  Hereinafter, embodiments of a polishing pad to which the present invention is applied will be described with reference to the drawings.

<Configuration>
As shown in FIG. 1, the polishing pad 10 of the present embodiment has a urethane sheet 2 as a resin sheet made of polyurethane resin (soft resin) formed by a wet coagulation method.

  The urethane sheet 2 has a dense skin layer 2a formed at the time of film formation by a wet coagulation method on one surface side, and a nap layer 2b on the inner side of the skin layer 2a. The surface of the skin layer 2a forms a polishing surface P for polishing the object to be polished. The surface opposite to the skin layer 2a (hereinafter referred to as the back surface) is buffed so that the thickness of the urethane sheet 2 is uniform. That is, the thickness of the urethane sheet 2 is made uniform by performing the buffing process.

  In the nap layer 2b, the cells (foams) 3 that are vertically long and rounded in the thickness direction (longitudinal direction in FIG. 1) of the urethane sheet 2 are substantially uniformly dispersed. It is formed with. The length in the longitudinal direction of the cell 3 varies within the range of the thickness of the urethane sheet 2. The cell 3 is formed so that the hole diameter on the polishing surface P side is smaller than the hole diameter on the back surface side. That is, the cell 3 has a smaller diameter on the polishing surface P side than on the back surface side. The polyurethane resin between the cells 3 is formed in a microporous shape in which a large number of micropores (not shown) having a pore diameter smaller than that of the cells 3 are formed. The cells 3 and the fine holes (not shown) of the skin layer 2a and the nap layer 2b are communicated in a mesh shape with communication holes (not shown). That is, the urethane sheet 2 has a continuous foamed structure in which the cells 3 and the fine holes are continuously formed. For the urethane sheet 2, a soft polyurethane resin having a modulus of 30 MPa or less is used. Such a urethane sheet 2 is formed by mixing a predetermined amount of a poor solvent for a polyurethane resin in a resin solution containing the polyurethane resin. The urethane sheet 2 is mounted on a rotatable surface plate such as a polishing machine surface plate and wetted with water, and the surface plate is rotated at a speed of 20 to 30 rpm. The foaming in the foaming test in which a brush dresser is pressed against the urethane sheet 2 and brushing is performed for at least 30 seconds while applying a pressure of 400 to 500 Pa, and left to stand for at least 1 minute, is not detected. Here, “no detection” means that it is not recognized by visual observation.

  In the polishing pad 10, a double-sided tape 7 is bonded to the back side of the urethane sheet 2 in order to attach the polishing pad 10 to a polishing machine (polishing apparatus). The double-sided tape 7 has a flexible film substrate made of polyethylene terephthalate (hereinafter abbreviated as PET). Each side of the substrate has an adhesive layer coated with an acrylic, urethane or epoxy adhesive. The double-sided tape 7 is bonded to the urethane sheet 2 with an adhesive layer on one side, and the adhesive layer on the other side is covered with a release paper 8. In this example, the base material 8 also has a function of supporting the entire polishing pad 10.

<Manufacturing>
The polishing pad 10 is manufactured through a bonding process in which the double-sided tape 7 and the urethane sheet 2 are bonded together after buffing the urethane sheet 2 formed by a wet coagulation method. In the wet coagulation method, a preparation process (preparation step) for preparing a resin solution containing a polyurethane resin, the resin solution is continuously applied to a film-forming substrate, and the resin solution is coagulated in an aqueous coagulation liquid to form a sheet of polyurethane resin. The urethane sheet 2 is produced through a sheet forming step (sheet forming step) to be formed into a shape and a washing / drying step of washing and drying the sheet-like polyurethane resin. Hereinafter, it demonstrates in order of a process.

  In the preparation step, a resin solution is prepared by mixing a predetermined amount of a polyurethane resin, a water-miscible organic solvent (good solvent) capable of dissolving the polyurethane resin, an additive, and a poor solvent for the polyurethane resin. As the organic solvent, N, N-dimethylformamide (hereinafter abbreviated as DMF), N, N-dimethylacetamide (DMAc), or the like can be used. In this example, DMF is used. As the polyurethane resin, a resin having a modulus of 30 MPa or less is selected from polyester, polyether, polycarbonate, and the like, and is dissolved in DMF so that the polyurethane resin becomes 30% by weight, for example. As the additive, a pigment such as carbon black for controlling the size and amount (number) of the cells 3 can be used. It is not necessary to add an auxiliary agent such as a hydrophilic activator that promotes cell formation or a hydrophobic activator that stabilizes the regeneration of polyurethane resin, which is conventionally used in wet coagulation methods. You may add the low foaming additive component which does not exert influence. The obtained solution is degassed under reduced pressure to prepare a resin solution.

  As a poor solvent to be mixed with the resin solution, water is a main component, and ethyl acetate, isopropyl alcohol, or the like can be added. In this example, water is used. The mixing amount of the poor solvent is adjusted so that the weight percentage with respect to the solid content of the polyurethane resin is in the range of 0.2R to 4.5R, where R is the coagulation value of the polyurethane resin to be used. The coagulation value R indicates the gel point of the resin, and can be determined as follows. That is, a polyurethane resin is dissolved in DMF as an organic solvent so as to be 1 wt% to prepare a polyurethane resin solution. 100 g of this polyurethane resin solution is stirred with a stirrer such as a stirrer while adjusting the temperature to 25 ° C. While stirring the polyurethane resin solution, a predetermined amount of a poor solvent (water) whose temperature is adjusted to 25 ° C. is dropped. The dripping amount (unit: ml) of the poor solvent required to reach a point where the polyurethane resin in the polyurethane resin solution gels and the cloudiness does not disappear is defined as a coagulation value R.

  In the sheet forming step, the resin solution prepared in the preparation step is continuously applied to the film forming substrate, and the resin solution is solidified in an aqueous coagulating liquid to form a sheet-like polyurethane resin. The resin solution is applied to the band-shaped film-forming substrate at a normal temperature by a coating apparatus so as to have a uniform thickness. In this example, a knife coater is used as the coating device. At this time, the application thickness (application amount) of the resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. In this example, in order to make the thickness of the urethane sheet obtained into the above-mentioned range, the coating thickness is adjusted to a range of 500 to 2000 μm. Although a flexible film, a nonwoven fabric, a woven fabric, or the like can be used as the film forming substrate, in this example, the film forming substrate is described as a PET film. The resin solution applied to the film forming substrate is guided into a coagulating liquid (water-based coagulating liquid) whose main component is water, which is a poor solvent for the polyurethane resin. As the coagulation liquid, an organic solvent such as DMF or DMAc can be mixed with water, but in this example, water is used.

  Here, foam formation will be described. In the resin solution used in the conventional wet coagulation method, a surfactant is added as an auxiliary for film formation, and a resin solution in which a polyurethane resin is dissolved in an organic solvent without mixing a poor solvent (water) is used. It is done. When this resin solution is guided into the coagulation liquid, a dense skin layer is first formed on the surface side of the resin solution over a thickness of about several μm. Thereafter, solvent substitution proceeds through the skin layer to form a foam structure. On the other hand, in this example, although the surfactant is not added to the resin solution, a foam structure similar to the conventional one is formed. Although this mechanism has not been fully elucidated, it is considered as follows. That is, when the poor solvent water is mixed in the resin solution, the polyurethane resin partially aggregates inside the resin solution before the resin solution is solidified. Along with this aggregation, it becomes difficult to form a dense skin layer in the coagulating liquid, and the infiltration of the coagulating liquid into the resin solution and the escape of the solvent into the coagulating liquid proceed without delay and are stably replaced. A sheet-like polyurethane resin having a continuous foam structure is formed by the progress of the substitution of DMF and coagulating liquid. When DMF is removed from the resin solution and DMF and the coagulating liquid are replaced, cells 3 and micropores (not shown) are formed in the polyurethane resin inside the skin layer 2a, and the cells 3 and micropores (not shown) are meshed. A communication hole (not shown) communicating in a shape is formed. At this time, since the PET film of the film formation substrate does not permeate water, desolvation occurs on the surface side (skin layer 2a side) of the resin solution, and cells 3 having a larger film formation substrate side than the surface side are formed. .

  In the washing / drying step, the sheet-like polyurethane resin (hereinafter referred to as film-forming resin) formed in the sheet forming step is washed and then dried. That is, after the film-forming resin is peeled from the film-forming substrate, the DMF remaining in the film-forming resin is removed by washing in a cleaning liquid such as water. After cleaning, the film forming resin is dried. In this example, a cylinder dryer having a cylinder having a heat source is used for drying the film-forming resin. The film-forming resin is dried by passing along the peripheral surface of the cylinder. The film-forming resin after drying is rolled up.

  When the buffing is performed, the surface opposite to the skin layer 2a of the film-forming resin dried in the cleaning / drying process, that is, the back surface is applied. In a film-forming resin formed by a wet coagulation method, thickness variation occurs when a resin solution is applied or a polyurethane resin is regenerated. By pressing a pressure welding jig having a flat surface on the surface of the film forming resin on the skin layer 2a side, irregularities appear on the back surface side of the film forming resin. This unevenness is removed by buffing. In this example, since the continuously formed film-forming resin has a belt shape, the buffing process is continuously performed while pressing the pressing roller. The urethane sheet 2 formed by buffing the film-forming resin has a uniform thickness.

  In the bonding step, the buffed surface (back surface) side of the urethane sheet 2 and the double-sided tape 7 are bonded together. At this time, the adhesive layer on one side of the double-sided tape 7 and the urethane sheet 2 are bonded together. The pressure-sensitive adhesive layer on the other side of the double-sided tape 7 is left with its surface covered with the release paper 8. Then, after cutting into a desired shape such as a circle and a desired size, an inspection is performed to confirm that there is no adhesion of scratches, dirt, foreign matter, etc., and the polishing pad 10 is completed.

  When polishing an object to be polished with the polishing pad 10, for example, a double-side polishing machine having two opposing surface plates is used. A polishing pad 10 is adhered to each of the two surface plates. When adhering the polishing pad 10 to the surface plate, the release paper 8 of the double-sided tape 7 is removed and the exposed adhesive layer is applied. A polishing liquid (slurry) containing abrasive particles is circulated and supplied between the object to be polished and the polishing pad 10, and at least one surface plate is rotated while pressure (polishing pressure) is applied to the object to be polished. Polish both sides.

<Action etc.>
Next, the operation and the like of the polishing pad 10 of this embodiment will be described.

  In the present embodiment, the urethane sheet 2 is formed by mixing a polyurethane resin, a good solvent DMF and a poor solvent water. For this reason, continuous foam formation can be stabilized without adding a surfactant conventionally used as a stabilizer for foam formation. This is because the formation of the conventional dense skin layer is suppressed in the coagulating liquid in the sheet forming step, so that the replacement of DMF in the resin solution with water in the coagulating liquid proceeds without delay, It is considered that a continuous foam structure was formed. Further, by not adding a surfactant to the resin solution, the surfactant is not eluted during the polishing process, so that no foaming is detected in the foaming test, and foaming during the polishing process can be suppressed. Thereby, the start-up time by the running-in operation can be shortened, and the efficiency of the polishing process can be improved.

  In this embodiment, the amount of water mixed in the resin solution is in the range of 0.2R to 4.5R in terms of weight percentage with respect to the solid content of the polyurethane resin when the solidification value of the polyurethane resin used is R. It has been adjusted to be. If the water mixing amount is less than 0.2R, the foamed structure is insufficient and stable film formation becomes difficult, and the resulting urethane sheet has a surface state (a state where minute irregularities are seen). On the other hand, when the amount of water mixed exceeds 4.5R, the poor solvent is mixed with the resin solution, so that the aggregation of the polyurethane resin in the resin solution increases and the uniformity of the resulting urethane sheet is impaired. Become. Therefore, by mixing water in the above-described range, foam formation can be stabilized and the urethane sheet 2 can be made uniform.

  In this embodiment, water is mixed into the resin solution, and an example in which the surfactant conventionally used for stabilizing foam formation is not added is shown, but the present invention is not limited to this, A surfactant may be added as long as it has a low foaming property that does not affect the foaming test. The amount of the surfactant added is preferably at least one-tenth or less, considering that the surfactant mixed in the conventional resin solution is about 1 to 5 wt%. By reducing the addition amount of the surfactant, the foaming property can be suppressed as in the present embodiment, and the decrease in the polishing rate and the flatness of the object to be polished can be suppressed during the polishing process. Moreover, since the urethane sheet produced by the conventional wet coagulation method has a continuous foam structure, it takes time until the surfactant mixed in the resin solution does not elute. For this reason, even when foaming is not recognized by the break-in before grinding | polishing process, foaming may arise with the surfactant eluted by performing grinding | polishing process for a long time, pressurizing. From such a point of view, in the present embodiment, as the above-described foaming test, conditions are set such that the range of the rotational speed and the applied pressure is determined, the brushing time is at least 30 seconds, and the standing time is at least 1 minute.

  Moreover, although the example which uses a polyurethane resin as a soft resin and uses water as a poor solvent was shown in this embodiment, this invention is not limited to these. The soft resin may be soft, and for example, a resin such as polyethylene may be used. Moreover, as a poor solvent, water should just be made into a main component, and the poor solvent with respect to the soft resin to be used, for example, ethyl acetate, isopropyl alcohol, etc. can be mixed and used.

  Furthermore, in this embodiment, although the example of the foaming structure in which many vertically long cells 3 were formed on the urethane sheet 2 in the thickness direction of the urethane sheet 2 was shown, the present invention is not limited to this. . For example, by changing the composition of the resin solution or the coagulating liquid, it is possible to obtain a urethane sheet having no foamed cell 3, that is, a microporous foam structure as a whole.

  Furthermore, in this embodiment, the back surface side of the urethane sheet 2 is buffed and an example having the skin layer 2a is shown, but the present invention is not limited to this. The skin layer 2a may be removed by buffing so that the pores of the cells 3 are formed on the polished surface P. In this way, the polishing rate can be improved by the slurry entering and leaving the cell 3 through the openings. In consideration of making the thickness of the urethane sheet 2 uniform, it is preferable that the skin layer side or the back surface side is buffed. Of course, slice processing may be performed instead of buff processing.

  Next, examples of the polishing pad 10 manufactured according to the present embodiment will be described. A comparative polishing pad manufactured for comparison is also shown.

Example 1
In Example 1, a polyester polyurethane resin was used. This polyurethane resin had a 100% modulus of 6 MPa and a water tolerance (coagulation value R) of 11.0. Water tolerance was measured by the following procedure. That is, a polyurethane resin is dissolved in DMF to prepare a polyurethane resin solution having a resin solid content of 1 wt%. 100 g of this polyurethane resin solution is precisely weighed in an Erlenmeyer flask (300 ml), and the Erlenmeyer flask is placed on a 10-point type original. While stirring the polyurethane resin solution in the Erlenmeyer flask with a stirrer, water is dropped into the Erlenmeyer flask in an environment of 20 ° C. The printed original is visually read from above the Erlenmeyer flask, and the amount of water dripped until the polyurethane resin solution becomes cloudy and cannot be read is read as water tolerance.

  As shown in Table 1 below, in Example 1, polyurethane resin was dissolved in DMF so as to be 30 wt%, and 2.5 parts of poor solvent water and 32. A resin solution was prepared by mixing 14 parts of an additive solution containing 5 parts and 25 wt% carbon black. In this resin solution, the rate of water addition to the polyurethane resin is 8.3%. Since the water tolerance is 11.0, the water addition rate is 0.75 times the water tolerance and satisfies the range of 0.2R to 4.5R.

  The urethane sheet 2 was produced using the obtained resin solution, and the polishing pad 10 of Example 1 was produced. As shown in Table 2 below, in the sheet forming step, the resin solution showed a temperature of 21.6 ° C. and a viscosity of 70.8 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be peeled off without any trouble. In the obtained urethane sheet 2, the surface state (surface state of the skin layer 2a) was good and formed substantially flat, and the foam formation state by microscopic observation of the cross section was also good. Moreover, in the urethane sheet 2, the shrinkage rate was 7.1%. This shrinkage rate is obtained from the application width of the resin solution and the width of the urethane sheet 2.

(Example 2 to Example 3)
In Example 2 to Example 3, as shown in Table 1, the procedure was the same as Example 1 except that the mixing ratio of water and DMF to 100 parts of the resin solution was changed. That is, in Example 2, 5 parts of water and 30 parts of DMF were mixed, and in Example 3, 10 parts of water and 25 parts of DMF were mixed. As a result, the water addition rate is 16.7% in Example 2, 1.52 times the water tolerance, 33.3% in Example 3, and 3.03 times the water tolerance. In any case, the water addition rate satisfies the range of 0.2R to 4.5R.

  The urethane sheet 2 was produced using the obtained resin solution, and the polishing pad 10 of Example 2 and Example 3 was manufactured, respectively. As shown in Table 2, in Example 2, the resin solution in the sheet forming step showed a temperature of 21.7 ° C. and a viscosity of 78.5 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be peeled off without any trouble. In the obtained urethane sheet 2, the surface state was good and formed substantially flat, and the foam formation state by microscopic observation of the cross section was also good. In this urethane sheet 2, the shrinkage rate was 7.0%. In Example 3, the resin solution in the sheet forming step showed a temperature of 24.2 ° C. and a viscosity of 109.3 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be peeled off without any trouble. In the obtained urethane sheet 2, although the surface state was slightly curled, it was formed to be substantially flat, and the foam formation state by microscopic observation of the cross section was also good. In this urethane sheet 2, the shrinkage rate was 9.1%.

(Comparative Examples 1 to 2)
As shown in Table 1, Comparative Example 1 was the same as Example 1 except that 35 parts of DMF was mixed without mixing water in the resin solution. Comparative Example 2 was the same as Example 1 except that 20 parts of water and 15 parts of DMF were mixed with 100 parts of the resin solution. Thus, in Comparative Example 2, the water addition rate is 66.7%, which is 6.06 times the water tolerance. Therefore, Comparative Example 2 is a polishing pad in which the water addition rate does not satisfy the range of 0.2R to 4.5R.

  Using the obtained resin solution, a urethane sheet was produced, and polishing pads were produced. As shown in Table 2, in Comparative Example 1, the resin solution in the sheet forming process showed a temperature of 23.0 ° C. and a viscosity of 64.3 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be peeled off without any trouble. In the obtained urethane sheet, although the surface state was good and formed substantially flat, some unevenness was observed in the foamed state. In this urethane sheet, the shrinkage rate was 6.8%. On the other hand, in Comparative Example 2, since aggregation occurred in the resin solution, film formation by the wet coagulation method could not be performed. This is presumably because the proportion of water mixed in the resin solution was too large.

Example 4
In Example 4, a polyether-based polyurethane resin was used. The polyurethane resin had a 100% modulus of 8.5 MPa and a water tolerance (coagulation value R) of 4.6. As shown in Table 3 below, in Example 4, polyurethane resin was dissolved in DMF so as to be 30 wt%, and 5 parts of poor solvent water, 30 parts of DMF and pigment were added to 100 parts of this solution. A resin solution was prepared by mixing 14 parts of a solution in which additives such as the above were dispersed. In this resin solution, the addition ratio of water to the polyurethane resin is 16.7%. Since the water tolerance is 4.6, the water addition rate is 3.63 times the water tolerance and satisfies the range of 0.2R to 4.5R.

  The urethane sheet 2 was produced using the obtained resin solution, and the polishing pad 10 of Example 4 was produced. As shown in Table 4 below, in the sheet forming step, the resin solution showed a temperature of 24.3 ° C. and a viscosity of 109.6 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be easily peeled (compared to the case of Example 1). In the obtained urethane sheet 2, the foamed state was good although a slight amount was observed in the surface state. In this urethane sheet 2, the shrinkage rate was 16.9%.

(Comparative Example 3 to Comparative Example 4)
As shown in Table 3, Comparative Example 3 was the same as Example 4 except that the resin solution was not mixed with water but 35 parts of DMF was mixed. Comparative Example 4 was the same as Example 4 except that 10 parts of water and 25 parts of DMF were mixed with 100 parts of the resin solution. Thus, in Comparative Example 4, the water addition rate is 33.3%, which is 7.24 times the water tolerance. Therefore, Comparative Example 4 is a polishing pad whose water addition rate does not satisfy the range of 0.2R to 4.5R.

  Using the obtained resin solution, a urethane sheet was produced, and polishing pads were produced. As shown in Table 4, in Comparative Example 3, the resin solution in the sheet forming step showed a temperature of 23.3 ° C. and a viscosity of 76.5 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be easily peeled off. In the obtained urethane sheet, some surface roughness was observed, and some unevenness was also observed in the foamed state. In this urethane sheet, the shrinkage rate was 22.2%. On the other hand, in Comparative Example 4, since aggregation occurred in the resin solution, film formation by the wet coagulation method was not possible. This is presumably because the proportion of water mixed in the resin solution was too large.

(Example 5)
In Example 5, a polycarbonate-based polyurethane resin was used. This polyurethane resin had a 100% modulus of 8.5 MPa and a water tolerance (coagulation value R) of 3.8. As shown in Table 5 below, in Example 5, polyurethane resin was dissolved in DMF so as to be 30 wt%, and 5 parts of poor solvent water, 30 parts of DMF and pigment were added to 100 parts of this solution. A resin solution was prepared by mixing 14 parts of a solution in which additives such as the above were dispersed. In this resin solution, the addition ratio of water to the polyurethane resin is 16.7%. Since the water tolerance is 3.8, the water addition rate is 4.39 times the water tolerance and satisfies the range of 0.2R to 4.5R.

  The urethane sheet 2 was produced using the obtained resin solution, and the polishing pad 10 of Example 5 was produced. As shown in Table 6 below, in the sheet forming step, the resin solution showed a temperature of 23.4 ° C. and a viscosity of 272.1 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be easily peeled off. In the obtained urethane sheet 2, although the surface state was slightly roughened, the foam formation state was good. In this urethane sheet 2, the shrinkage rate was 10.0%.

(Comparative Example 5 to Comparative Example 7)
As shown in Table 5, Comparative Example 5 was the same as Example 5 except that the resin solution was not mixed with water but 35 parts of DMF was mixed. Comparative Example 6 was the same as Example 5 except that 10 parts of water and 25 parts of DMF were mixed with 100 parts of the resin solution. Thus, in Comparative Example 6, the water addition rate is 33.3%, which is 8.76 times the water tolerance. Therefore, Comparative Example 6 is a polishing pad in which the water addition rate does not satisfy the range of 0.2R to 4.5R. In Comparative Example 7, Comparative Example 5 except that an anionic surfactant (manufactured by DIC Corporation, Crisbon Assister SD-11) was added to the same resin solution as that used in Comparative Example 5 as a foaming modifier. And so on. The addition amount of the foaming modifier was 3 wt% with respect to the resin solid content. That is, Comparative Example 7 is a conventional polishing pad.

  Using the obtained resin solution, a urethane sheet was produced, and polishing pads were produced. As shown in Table 6, in Comparative Example 5, the resin solution in the sheet forming step showed a temperature of 23.6 ° C. and a viscosity of 103.8 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be easily peeled off. In the obtained urethane sheet, some surface roughness was observed, and some unevenness was also observed in the foamed state. In this urethane sheet, the shrinkage rate was 26.1%. On the other hand, in Comparative Example 7, the resin solution in the sheet forming step showed a temperature of 23.2 ° C. and a viscosity of 108.2 dPa · s. In the coagulation liquid, no lifting from the film forming substrate was observed, and the surface state of the resin solution was good. After the film-forming resin was formed, the film-forming substrate could be easily peeled off. In the obtained urethane sheet, the surface state was good and formed substantially flat, and the foam formation state by microscopic observation of the cross section was also good. In this urethane sheet, the shrinkage rate was 11.6%. Further, in Comparative Example 6, since aggregation occurred in the resin solution, film formation by the wet coagulation method could not be performed. This is presumably because the proportion of water mixed in the resin solution was too large.

(Evaluation of foaming property)
About the polishing pad of each Example and the comparative example, foaming property was evaluated as follows. That is, each polishing pad was cut into a circle having a diameter of 740 mm and adhered to a surface plate of a polishing machine (F-REX300, manufactured by Ebara Manufacturing Co., Ltd.). Wet the whole. A large brush dresser (manufactured by Ebara Manufacturing Co., Ltd., part number C-4111-216-0001 “Full-scale hard brush body”) is mounted on a polishing machine, and while rotating at 14 rpm, it is pressed against a polishing pad at a pressure of 465 Pa while polishing. The entire area of the pad was brushed for 30 seconds. The brush dresser was separated from the polishing pad, and after standing for 1 minute, the foaming condition was observed visually. The foaming property was evaluated in two stages: ◯: no foaming was observed, and x: foaming was large and hindered the polishing process. The evaluation results of foaming properties are shown in Table 2, Table 4, and Table 6, respectively.

  As shown in FIGS. 3A and 3B, the polishing pad of Comparative Example 7 showed foaming after brushing (see arrow F). This is thought to be because, during the production of the polishing pad of Comparative Example 7, a surfactant was added as a foaming modifier to the resin solution, so that the surfactant was eluted during foaming and foaming occurred. In the polishing pad in which such foaming occurs, it is expected that the abrasive grains contained in the polishing liquid are aggregated during the polishing process, resulting in generation of scratches on the object to be polished and a decrease in the polishing rate. On the other hand, in the polishing pad 10 of Example 1, as shown in FIGS. 2A and 2B, even when the polishing pad 10 adhered to the surface plate was wetted with water and brushed, foaming was observed. There wasn't. Moreover, as shown in Table 2, Table 4, and Table 6, foaming was not recognized in the polishing pad 10 of Examples 1-5. Therefore, in the polishing pad 10, since foaming is suppressed, the startup time can be shortened during the polishing process, and the polishing process can be stably performed without causing the flatness of the object to be polished and the decrease in the polishing rate. Can be expected to continue.

  Since the present invention provides a polishing pad that can shorten the start-up time during polishing, it contributes to the manufacture and sale of the polishing pad, and thus has industrial applicability.

P Polished surface 2 Urethane sheet (resin sheet)
2a Skin layer 2b Nap layer 3 Cell (foam)
10 Polishing pad

Claims (4)

In a polishing pad provided with a resin sheet in which a resin solution containing a soft resin is solidified by a wet coagulation method and foam is continuously formed inside, a poor solvent for the soft resin is contained in the resin solution . When the solidification value is R, the weight percentage with respect to the solid content of the soft resin is mixed in the range of 0.2R to 4.5R , and the resin sheet is pasted on a rotatable platen. A foaming test in which the entire surface is wetted with water, brushed with a brush dresser under a pressure of 400 Pa to 500 Pa while rotating the platen at a speed of 20 to 30 rpm, and visually observed after standing for at least 1 minute. A polishing pad characterized in that the foaming in is not detected by visual observation . It is a manufacturing method of the polishing pad according to claim 1 ,
Preparing a resin solution in which a soft resin, a good solvent for dissolving the soft resin, and a poor solvent for the soft resin are mixed; and
A sheet forming step of solidifying the resin solution into a sheet in a coagulating liquid to form a resin sheet;
Including
In the preparation step, the mixing ratio of the poor solvent is in a range of 0.2R to 4.5R in terms of a weight percentage with respect to a solid content of the soft resin, where R is a solidification value of the soft resin. Manufacturing method. The manufacturing method according to claim 2 , wherein the soft resin is a polyurethane resin, and the poor solvent contains water as a main component. 4. The production method according to claim 3 , wherein the good solvent is N, N-dimethylformamide or N, N-dimethylacetamide, and the poor solvent is water.