JP5711525B2 - 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 more particularly, to a polishing pad including a resin sheet formed by a wet coagulation method and having a polishing surface on one side, and a method for manufacturing the polishing pad.

  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, 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 polishing processing of a semiconductor device by CMP method, a polishing pad that is usually formed by a dry molding method or a wet coagulation method and includes a resin sheet having an opening formed on a polishing surface for polishing an object to be polished is used. It has been. 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. In the dry molding method, the surface of the formed resin foam can be ground, or the pores of the polished surface can be formed by slicing the foam. As a technique for forming a foam by a dry molding method, a technique in which hollow fine particles are added to a resin solution at the time of molding (see, for example, Patent Document 1), gas is added at the time of molding by adding water to the resin solution. The technique (for example, refer patent document 2) etc. which generate | occur | produce is disclosed.

  However, the resin sheet obtained by the dry molding method is mainly a hard and independent foam type. For this reason, there exists a problem that the opening formed in the grinding | polishing surface becomes clogged with an abrasive grain, grinding | polishing waste, etc., and becomes easy to block | close. When the opening is closed, the abrasive grains and the like are likely to aggregate, and as a result, there is a risk of causing scratches (scratches) on the processed surface of the workpiece. In the polishing process of a semiconductor device, if a scratch is generated, there is a risk of cutting the wiring, which is a fatal defect. If the polishing process is interrupted and the surface is dressed, the holes are regenerated and the polishing process can be continued, but the polishing efficiency is reduced.

  On the other hand, as compared with a resin sheet formed by a dry molding method, a resin sheet formed by a wet coagulation method generally provides a continuous foam structure in which a large number of foams communicate with each other in a mesh shape. For this reason, although it becomes difficult to produce the obstruction | occlusion of the opening by aggregation of an abrasive grain etc., it is soft on the other hand, and even if it uses hard resin, it is difficult to raise hardness structurally. In addition, cells (giant pores) having a vertically conical shape and a maximum diameter of 100 μm or more are easily formed in the thickness direction of the resin sheet. In the resin sheet in which the conical cell is formed, the size of the opening in the polishing surface increases as the polishing surface wears with polishing. As a result, although the polishing rate increases, it becomes difficult to improve the flatness of the object to be polished.

  In order to avoid these problems, there has been a demand for a resin sheet in which pores are continuously formed without forming vertically long conical cells in a polishing pad used for polishing a semiconductor device. It is known that a resin sheet in which pores are formed can be easily obtained by increasing the coagulation value (gelation point) of the resin (for example, see Non-Patent Document 1). That is, when the gel point is increased, it becomes difficult to form a dense skin layer, and the mutual diffusion between the coagulating liquid and the solvent in the resin solution is facilitated. Holes are easily formed. From such a concept, a technique of a polishing pad using a resin sheet formed of a polar solvent-soluble polymer material having a gel point of 6 or more and having an average pore diameter of 30 μm or less is disclosed (Patent Document 3). reference).

Japanese Patent No. 3013105 JP 2005-68168 A Japanese Patent No. 4373152

Fukushima et al .: “Polyurethane sponge structure”, collection of polymer papers, Vol. 39, no. 9, pp. 543-548 (1982)

  However, in the technique of Patent Document 3, since the gel point of the polyurethane resin is increased, a polyester polyol-based polyurethane resin is generally used. Polyester-based polyurethane resins have poor hydrolysis resistance, particularly alkali hydrolysis resistance, and therefore, in the polishing process by the CMP method, the resin sheet may be deteriorated by being exposed to a polishing liquid. As a result, stable polishing cannot be continued, and the polishing rate and the flatness of the object to be polished are reduced. Further, when the pores are clogged due to accumulation of abrasive grains and polishing debris, scratches are generated on the object to be polished. If unevenness is formed on the polishing surface side of the resin sheet by embossing or the like, it is expected that the circulation property of abrasive grains and the discharge property of polishing waste are improved, and scratches are suppressed. However, if pore openings are formed on the surface of the recesses, the recesses are not easily subjected to compressive deformation during the polishing process, so that polishing debris or the like is easily stored in the openings, and scratch suppression is insufficient. Furthermore, according to the examination results of the present inventors, it was found that the ease of formation of pores and the coagulation value do not necessarily correlate, that is, the pores are formed even if the coagulation value is reduced. Yes. Therefore, if pores are formed and a resin sheet having resistance to alkali hydrolysis can be obtained which is less likely to cause storage of abrasive grains and polishing debris, refinement required for polishing processing of the above-described semiconductor devices, etc. It becomes possible to meet high precision.

  An object of the present invention is to provide a polishing pad capable of securing a polishing rate and suppressing scratches on an object to be polished, and a method for manufacturing the polishing pad, in view of the above-mentioned cases.

In order to solve the above-described problem, a first aspect of the present invention is a polishing pad including a resin sheet formed by a wet coagulation method and having a polishing surface on one surface side. The resin sheet has a flow start temperature of 150 ° C. It is formed of a polyurethane resin having a range of ˜220 ° C. and a coagulation value of less than 6, and a cell having a maximum diameter of 100 μm or more having a length in the thickness direction is not formed, and a large number of pores having an average pore diameter of 30 μm or less are formed. And formed on the one side of the surface by the surface on which the pores are formed, and between the projections forming the polishing surface and the pores on the surface. The hole is characterized in that it has a recessed portion whose diameter is reduced or closed from the pore of the protruding portion.

In the first aspect, by setting the flow start temperature of the polyurethane resin forming the resin sheet in the range of 150 ° C. to 220 ° C., it is easy to form the convex portions and the concave portions on one side, and the pores on the surface of the concave portions Since the opening can be more easily reduced or closed than the pores of the convex portion, and it becomes easy to suppress resin aggregation during sheet formation by the wet coagulation method , the thickness can be reduced even if the coagulation value of the polyurethane resin is less than 6. the average pore diameter maximum diameter 100μm or more cells having a length in the direction without formation Ri of easily formed following number of pores 30 [mu] m, solidification titer that was less than 6, hydrolysis resistance of the polyurethane resin Can be ensured and deterioration of the resin sheet can be suppressed .

In a first aspect, it is possible to make the additional PU resin and polyether or polycarbonate-based. At this time, the 100% modulus of the polyurethane resin may be in the range of 4 MPa to 20 MPa. In the resin sheet, the average pore diameter of the pores can be 1 μm or more. In the resin sheet, the formation ratio of pores per unit area in the cross section in the thickness direction may be in the range of 500 / mm ^{2 to} 50000 / mm ² . A through hole penetrating in the thickness direction may be further formed in the convex portion of the resin sheet.

The second aspect of the present invention is a method for manufacturing a polishing pad according to the first aspect, wherein a polyurethane resin having a flow start temperature in the range of 150 ° C. to 220 ° C. and a coagulation value of less than 6 is prepared. A preparation step, an application step of applying a resin solution in which the polyurethane resin prepared in the preparation step is uniformly dissolved in a polar solvent to a sheet-like base material in a uniform mixed state, and a base material in the application step A sheet forming step for forming a resin sheet by coagulating the resin solution applied to the aqueous coagulating liquid, and heat so that convex portions and concave portions are formed on one side of the resin sheet formed in the sheet forming step. An embossing step for performing embossing, and in the embossing step, pressurization is performed so that a position corresponding to the recess is heated. In this case, in the sheet forming step, water containing 30% by mass or more of a polar solvent may be used as the aqueous coagulating liquid. In the coating step, an organic solvent having a solubility in water smaller than that of the polar solvent in water may be mixed in the resin solution.

According to the present invention, a large number of pores with a limited size are formed in the resin sheet, and convex portions and concave portions are formed on one surface side, so that the circulating supply property of the polishing liquid is made uniform and the polishing waste can be discharged. In addition, the hydrolysis resistance of the polyurethane resin is ensured and the deterioration of the resin sheet is suppressed, so that the polishing rate can be secured, and the pores on the surface of the recesses are the pores of the protrusions. Since the polishing liquid is circulated and supplied without being stored in the recess and the polishing waste is discharged without being stored in the recess, the effect that the scratch on the object to be polished can be suppressed can be obtained.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is a top view which shows typically the positional relationship of the recessed part and convex part which were formed in the polishing pad of embodiment, (A) is the positional relationship in which the recessed part was formed in the grid | lattice form, (B) is a recessed part concentric. The positional relationships formed are shown respectively. It is process drawing which shows the outline of the manufacturing process of the polishing pad of embodiment. It is sectional drawing which shows typically the polishing pad of the other aspect to which this invention is applied. It is sectional drawing which shows the conventional polishing pad typically.

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

(Constitution)
The polishing pad 10 of this embodiment is provided with the urethane sheet 2 as a resin sheet made of a polyurethane resin, as shown in FIG. The urethane sheet 2 is formed into a sheet shape by a wet coagulation method, and has a polishing surface P for polishing an object to be polished on one surface side.

As the polyurethane resin forming the urethane sheet 2, a polycarbonate-based polyurethane resin having a flow start temperature in the range of 150 to 220 ° C., a coagulation value of less than 6, and a 100% modulus in the range of 4 to 20 MPa is used. The urethane sheet 2 is heat-embossed on one surface side, and has a convex portion 5 and a concave portion 6 formed between the convex portions 5. The surface of the convex portion 5 constitutes a polishing surface P for polishing the workpiece. In the polyurethane resin of the convex portion 5, a large number of pores 4 are formed in a substantially uniformly dispersed state. The pores 4 are formed in a substantially spherical shape, and have an average pore diameter of 1 μm or more and 30 μm or less. Further, the pores 4, formation ratio per unit area in the thickness direction of the sectional urethane sheet 2 has been adjusted to a range of 500 to 50,000 pieces / mm ^2. On the other hand, in the concave portion 6, the pores 4 formed at the same formation ratio as the pores 4 of the convex portion 5 are reduced in diameter or closed before the concave portion 6 is formed. For this reason, in the concave portion 6, micropores 4 s whose average pore diameter is smaller than the average pore diameter of the pores 4 are formed in the polyurethane resin, and the surface openings are reduced or closed. In the recess 6, the formation rate of the fine holes 4 s is smaller than the formation rate of the pores 4 in the projection 5 because the pores 4 are crushed.

  The pores 4 formed in the convex portion 5 and the micropores 4s formed in the concave portion 6 are smaller than the average pore diameter of the pores 4 and the micropores 4s by the solvent substitution during film formation by the wet coagulation method, and are several thousand times larger. A channel (not shown) having a hole diameter that cannot be visually recognized even when observed at a magnification of is communicated in a mesh shape. That is, the urethane sheet 2 has a microporous structure in which a large number of pores 4 and micropores 4s communicate with each other directly or through channels. In the urethane sheet 2, the skin layer formed at the time of film formation by the wet coagulation method is removed by grinding (buffing). For this reason, on the polishing surface P, that is, on the surface of the convex portion 5, the pores 4 are opened, and the aperture 4a is formed. The average pore diameter of the apertures 4 a per unit area on the polished surface P is in the range of 1 to 30 μm, which is the same as the average pore diameter of the pores 4. Since the pores 4 communicate with each other, the opening 4a communicates with the pores 4 through the channel. On the other hand, on the surface of the recess 6, the aperture formed by the grinding process is reduced in diameter or closed when the recess 6 is formed. For this reason, no aperture is (substantially) formed on the surface of the recess 6. That is, even if the opening is not completely closed, it does not have a size enough for the abrasive grains and polishing debris in the slurry to enter. In such a continuously formed urethane sheet 2 having a microporous structure, a cell having a vertically conical shape with a maximum diameter of 100 μm or more (hereinafter referred to as a giant pore) is formed by a conventional wet coagulation method. Deformation due to compression is less likely to occur compared to a sheet having holes.

  As shown in FIG. 2A, on the polishing surface P, the concave portions 6 are formed in a lattice shape so as to be evenly positioned between the convex portions 5. In other words, the recess 6 is formed in a lattice groove shape on the polishing surface P. The widths of the convex portion 5 and the concave portion 6 can be adjusted within the range of the size of the urethane sheet 2. The surface of the convex portion 5 constitutes the polishing surface P, and it is preferable to set the width of the convex portion 5 to be larger than the width of the concave portion 6 in consideration of the efficiency of the polishing process.

  Here, the flow start temperature and coagulation value of the polyurethane resin will be described. The flow start temperature is a temperature at which the resin is softened. In this example, an orifice having an inner diameter of 1 mm and a length of 1 mm is used with a Koka-type flow tester (CFT-500D manufactured by Shimadzu Corporation), and a pressure of 10 kgf ( 98N), and the value measured at a heating rate of 3 ° C./min. The coagulation value is the same as the gel point, and in this example, the value measured as follows is shown. That is, a polyurethane resin solution dissolved in an organic solvent (N, N-dimethylformamide) was prepared so that the polyurethane resin was 1% by mass (wt%), and the temperature of 100 g of this polyurethane resin solution was adjusted to 25 ° C. While stirring with a stirrer, a poor solvent (water) at 25 ° C. is dropped. In this case, the amount of poor solvent (unit: ml) required to reach a point where the polyurethane resin gels and the cloudiness of the polyurethane resin solution does not disappear is shown.

  Further, the polishing pad 10 has a double-sided tape 7 attached to the surface of the urethane sheet 2 opposite to the polishing surface P for attaching the polishing pad 10 to a polishing machine. The double-sided tape 7 has a base material of a flexible film such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET), and an adhesive layer (not shown) such as an adhesive on both surfaces of the base material. ) Are formed. The double-sided tape 7 is bonded to the urethane sheet 2 with a pressure-sensitive adhesive layer on one side of the base material, and the pressure-sensitive adhesive layer on the other side (the side opposite to the urethane sheet 2) is covered with the release paper 8. The base material of the double-sided tape 7 also serves as the base material of the polishing pad 10.

(Manufacturing)
As shown in FIG. 3, the polishing pad 10 is prepared by preparing a urethane sheet by a wet coagulation method and performing hot embossing in an embossing process, and then bonding the obtained urethane sheet 2 and the double-sided tape 7 together. Manufactured. In the wet coagulation method, a preparation process for preparing a polyurethane resin and a polar solvent, a coating process in which a polyurethane resin is dissolved in a polar solvent, and a coating process for applying the resin solution in a sheet form to a film-forming substrate, the resin solution is coagulated in a coagulation liquid. A urethane sheet is produced through a sheet forming step for forming a sheet-like polyurethane resin, a washing / drying step for washing and drying the formed sheet-like polyurethane resin, and a buffing step for removing the skin layer by buffing. Hereinafter, it demonstrates in order of a process.

(Preparation process)
In the preparation step, a polyurethane resin, a water-miscible polar solvent and an additive capable of dissolving the polyurethane resin are prepared. As the polyurethane resin, a polycarbonate-based polyurethane resin having a flow start temperature in the range of 150 to 220 ° C., a coagulation value of less than 6, and a 100% modulus in the range of 4 to 20 MPa is used. As the polar solvent, for example, N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) or the like may be used. it can. In this example, DMF is used as the polar solvent. As the additive, a pigment such as carbon black, a hydrophilic activator that promotes foaming, a hydrophobic activator that stabilizes resin coagulation regeneration, and the like are used to control the size and amount (number) of the pores 4. be able to.

(Coating process)
In the application step, first, a resin solution is prepared using each material prepared in the preparation step. At this time, a polyurethane resin is dissolved in DMF so as to be, for example, 30 wt%, and a resin solution is prepared by defoaming under reduced pressure. The obtained resin solution is applied substantially uniformly in a sheet form to a belt-shaped film forming substrate by a coating device such as a knife coater at room temperature. 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. Although a cloth, a nonwoven fabric, etc. can also be used as a film-forming base material, in this example, a PET film is used.

(Sheet formation process)
In the sheet forming step, the resin solution applied to the film-forming substrate is continuously guided to a coagulating liquid (water-based coagulating liquid) whose main component is water which is a poor solvent for the polyurethane resin. In the coagulation liquid, the above-mentioned polar solvent is contained at a ratio in the range of 30 to 45 wt% in order to adjust the coagulation regeneration rate of the polyurethane resin. In this example, a coagulation liquid in which water and 35 wt% DMF are mixed is used. The resin solution coagulates in the coagulating liquid, and a sheet-like polyurethane resin having a continuous microporous structure is regenerated.

  Here, formation of the microporous structure accompanying regeneration of the polyurethane resin will be described. In the coagulation liquid, first, a film is formed at the interface between the resin solution and the coagulation liquid, and a skin layer is formed in the resin immediately adjacent to the film. Thereafter, regeneration of the polyurethane resin proceeds by a cooperative phenomenon of diffusion of DMF in the resin solution into the coagulation liquid and penetration of water in the coagulation liquid into the resin, that is, solvent substitution. Since DMF, which is a polar solvent used for dissolving the polyurethane resin, is contained in the coagulation liquid, the formation of the skin layer is delayed and the density becomes gentle as compared with the case where only water is used as the coagulation liquid. For this reason, since the substitution rate of DMF in the resin solution and water in the coagulation liquid is increased, the formation of giant pores is suppressed. Thereby, the pores 4 are formed inside the skin layer of the polyurethane resin. Since the substitution rate between DMF in the resin solution and water in the coagulation liquid is increased, the size of the pores 4 is in the range of an average pore diameter of 1 μm to 30 μm. Further, DMF removes the solvent from the resin solution and replaces it with water, whereby a channel is formed between the pores 4. Therefore, the obtained sheet-like polyurethane resin has a microporous structure in which a large number of pores 4 are formed substantially uniformly without forming huge pores.

  In addition, by restricting the flow start temperature of the polyurethane resin used for the preparation of the resin solution to the above-mentioned range, the formation of the skin layer and partial aggregation of the polyurethane resin occurring inside the resin solution can be suppressed, and the substitution of DMF and water is performed. Is promoted. This is presumably because the polyurethane resin having a flow start temperature in this range has a relatively weak cohesive force among the polyurethane resins and the segmentation is easy to control. For this reason, the formation of giant pores is suppressed and the pores 4 are easily formed, so that a sheet-like polyurethane resin having a microporous structure is easily obtained.

(Washing / drying process)
As shown in FIG. 2, in the cleaning / drying process, the sheet-like polyurethane resin (hereinafter referred to as film forming resin) formed in the sheet forming process is washed in a cleaning solution such as water and remains in the film forming resin. After removing the DMF to be 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.

(Buffing process)
In the buffing process, a buffing process is performed on the surface side on which the skin layer of the film-forming resin dried in the cleaning / drying process is formed. In the film-forming resin, there is a variation in thickness during film formation by the wet coagulation method, so that the surface on the skin layer side is uneven by pressing a pressure welding jig with a flat surface on the surface opposite to the skin layer. Make it appear. This unevenness is removed by buffing. In this example, the film-forming resin produced continuously is subjected to buffing continuously or intermittently while being pressed against the pressing roller. In the urethane sheet formed by buffing the film-forming resin, the thickness is made uniform, and the opening 4a is formed on the surface.

(Embossing process)
In the embossing process, hot embossing is performed on the buffed surface side of the buffed urethane sheet to form the convex portions 5 and the concave portions 6. In this example, a lattice-shaped metal jig in which rectangular openings are formed in accordance with the formation positions of the convex portions 5 is used. By heating this jig and pressing it against the surface (buffed surface) of the film forming resin placed on the flat plate, the urethane sheet 2 having the convex portions 5 and the concave portions 6 is produced. At this time, the temperature of the jig is adjusted to a range of 120 to 140 ° C., and pressure treatment is performed for 1 to 5 minutes. In other words, the formation position of the concave portion 6 is heated and pressurized by the lattice-shaped jig, and the convex portion 5 is formed without being pressurized.

  The polishing pad 10 is manufactured by bonding the obtained urethane sheet 2 and the double-sided tape 7 together. At this time, the surface opposite to the polishing surface P of the urethane sheet 2 and the adhesive layer on the one surface side of the double-sided tape 7 are bonded together. The release paper 8 is left on the other side of the double-sided tape 7. Then, after cutting into a desired shape such as a circle or a square and a desired size, an inspection is performed to confirm that there are no scratches, dirt, foreign matter, or the like, and the polishing pad 10 is completed.

  When polishing an object to be polished, for example, a semiconductor device, the polishing pad 10 is mounted on a polishing surface plate of a polishing machine. When the polishing pad 10 is attached to the polishing surface plate, the release paper 8 is removed and the exposed adhesive layer is attached. For example, an object to be polished is held on a holding platen disposed opposite to the polishing platen via a holding pad. The object to be polished is pressed between the polishing surface plate and the holding surface plate, and the processing surface of the object to be polished is polished by rotating the polishing surface plate or holding surface plate while supplying the slurry. The slurry used here is colloidal silica having an average particle diameter of 50 nm as abrasive grains, and the abrasive grains are dispersed at a ratio of 5% by weight.

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

  Here, in order to make the explanation easy to understand, a conventional urethane sheet by a wet coagulation method will be described. In the polishing process by the CMP method, a polishing pad having a resin sheet in which holes are formed on the polishing surface by surface grinding or slicing of a resin foam formed by a dry molding method is usually used. . The processed surface is flattened by being supplied into the processed surface of the object to be polished while holding the abrasive grains in the opening formed in the polished surface. However, since the resin sheet formed by the dry molding method is mainly a hard and independent foam type, the opening on the polishing surface is likely to be clogged with abrasive grains or polishing debris. When the opening is closed, the abrasive grains and the like are likely to aggregate, and there is a possibility that the processed surface of the workpiece is scratched. If the polishing process is interrupted and the surface is dressed, the holes are regenerated and the polishing process can be continued, but the polishing efficiency is reduced. On the other hand, in the urethane sheet formed by the wet coagulation method, a continuous foamed structure in which a large number of foams communicated in a mesh shape is obtained. For this reason, although it becomes difficult to produce the obstruction | occlusion of the opening by aggregation of an abrasive grain etc., on the other hand, it is soft originally and it is difficult to raise hardness structurally. In addition, the wet coagulation method tends to form conical cells that are vertically long in the thickness direction, so if the polishing surface wears during polishing, the size of the holes on the polishing surface increases, and the flatness of the workpiece It becomes difficult to improve.

  Further, as a method of forming a urethane sheet in which pores are continuously formed without forming conical giant pores by a wet coagulation method, the solidification value (gelation point) of a polyurethane resin to be used is increased. Are known. Increasing the gel point makes it difficult to form a dense skin layer, facilitating mutual diffusion between the coagulating liquid and the polar solvent inside the resin solution. Is easily formed. Compared to polyether-based and polycarbonate-based polyurethane resins, polyester-based polyurethane resins can increase the gel point, but they are poorly hydrolyzed, so they are exposed to polishing liquid during polishing by the CMP method. Urethane sheet tends to deteriorate. For this reason, it is difficult to continue the polishing process, and the polishing performance and the flatness of the object to be polished are reduced. Further, when the pores are clogged due to accumulation of abrasive grains and polishing debris, scratches are generated on the object to be polished. If unevenness is formed on the polishing surface side of the resin sheet by embossing or the like, it is expected that the circulation property of abrasive grains and the discharge property of polishing waste are improved, and scratches are suppressed. However, if pore openings are formed on the surface of the recesses, the recesses are not easily subjected to compressive deformation during the polishing process, so that polishing debris or the like is easily stored in the openings, and scratch suppression is insufficient. On the other hand, in order to improve hydrolysis resistance, a resin with a small gel point, such as a polyether-based or polycarbonate-based polyurethane resin, may be used. In this case, huge pores and pores are formed in the resin. Is done. As shown in FIG. 5, in the polishing pad 20 in which the convex portion 15 and the concave portion 16 are formed on the polishing surface P side using the urethane sheet 12 in which the giant pores 13 and the pores 4 are formed, the polishing surface P (convex) On the surface of the portion 15, an opening 13 a of the giant pore 13 is formed. By the embossing process, the pores 14 and the pores 4 remain formed in the convex portion 15, whereas the pores 14 are formed in the concave portion 16. The pores 14 are the ones in which the giant pores 13 are compressed without being closed, although they are compressed by the pressurization accompanying the formation of the recesses 16. For this reason, the openings 14a of the pores 14 are also formed on the surface of the recess 16. In the polishing pad 20, since the pressing force during the polishing process is not easily applied to the recess 16 and the pores 14 are not easily deformed, the slurry and polishing debris that has entered the pores 14 through the apertures 14a are not released and stay for a long time. May aggregate. If such agglomerates are accidentally released, the object to be polished will be scratched. The present embodiment is a polishing pad 10 that can solve these problems.

    In the polishing pad 10 of the present embodiment, the urethane sheet 2 is made of a polyurethane resin having a coagulation value of less than 6 in the flow start temperature range of 150 to 220 ° C. For this reason, in the sheet formation process at the time of production by the wet coagulation method, the formation of the skin layer and the aggregation of the polyurethane resin inside the resin solution are suppressed, and the replacement rate of DMF and water increases. On the other hand, when the coagulation value is less than 6, the affinity between the polyurethane resin and water is low, and the water penetration rate into the resin solution with respect to elution of DMF into the coagulation solution is slow. For this reason, the solidification of the resin solution is delayed and the density is easily increased. Therefore, in the urethane sheet 2 to be obtained, huge pores are not formed, and the pores are easily miniaturized, thereby having a continuous microporous structure in which the pores 4 communicate with each other through the channel. When the flow start temperature is too low, the sag of the urethane sheet 2 due to heat generation during the polishing process becomes large, so that the flatness of the object to be polished is impaired. On the other hand, if the flow start temperature is too high, the original resin becomes hard, and therefore scratches on the object to be polished are easily generated, which is not preferable.

  Moreover, in the polishing pad 10 of this embodiment, the opening 4a of the pore 4 is formed in the polishing surface P comprised by the surface of the convex part 5 of the urethane sheet 2. As shown in FIG. In addition, since the urethane sheet 2 is made of a polyurethane resin having a flow start temperature and a coagulation value in the above-described range, it is easy to form the convex portions 5 and the concave portions 6 by hot embossing, and the pores 4 in the concave portions 6 are reduced in diameter. Or it becomes easy to be blocked. For this reason, although the fine hole 4s is formed in the polyurethane resin of the recessed part 6, the opening is not formed in the surface. Accordingly, the abrasive grains are circulated and supplied in the convex portion 5 while entering and exiting the openings 4a, and the polishing liquid and polishing debris are not stored in the concave portion 6, but the polishing liquid is smoothly circulated and supplied by the concave portion 6 and the polishing debris is discharged. . As a result, accidental release of aggregates due to storage of the polishing liquid or the like is eliminated, so that it is possible to secure a polishing rate in the polishing process and improve flatness without causing scratches on the object to be polished.

Further, in this embodiment, the average pore diameter of the pores 4 formed in the convex portion 5 is adjusted to 1 μm or more and 30 μm or less, and the opening 4 a is formed on the polishing surface P. For this reason, when abrasion occurs on the polishing surface P side during the polishing process, the size of the opening 4a can be continued with almost no change due to the sequential opening of the internal pores 4. Can do. Thereby, since the highly accurate polishing process by the opening 4a becomes possible, the highly accurate flatness of the workpiece can be ensured. Further, in the present embodiment, formation ratio of pores 4 per unit area in a cross section in the thickness direction of the urethane sheet 2 is adjusted to a range of 500 to 50,000 pieces / mm ^2. If the formation rate of the pores 4 is less than 500 pieces / mm ² , the number of pores holding the abrasive grains is too small, so clogging due to accumulation of abrasive grains and polishing scraps is likely to occur, and scratches are generated on the object to be polished. It becomes. On the other hand, if the formation rate of the pores 4 exceeds 50000 / mm ² , the proportion of the voids of the urethane sheet 2 becomes too large, and it is difficult to ensure cushioning properties (elasticity) of the urethane sheet 2 and structurally It becomes unstable. By setting the formation ratio of the pores 4 within the above-described range, cushioning properties can be ensured while maintaining a stable structure. Considering the suppression of scratches, the formation rate of the pores 4 is more preferably in the range of 2500 to 50000 pieces / mm ² .

  Furthermore, in this embodiment, a polycarbonate-based polyurethane resin is used for forming the urethane sheet 2. By setting the flow start temperature of the polyurethane resin within the above-described range, a microporous structure can be formed even if the coagulation value is less than 6. By setting the coagulation value to less than 6, it is possible to ensure hydrolysis resistance of the polyurethane resin, that is, acid resistance and alkali resistance. Thereby, polishing performance such as a polishing rate can be secured for a long time even in polishing processing by CMP using acidic or alkaline slurry. Further, since the hydrolysis resistance is ensured, the deterioration of the urethane sheet 2 accompanying the polishing process is suppressed, so that the life of the polishing pad 10 can be improved.

  Furthermore, in the polyurethane resin that forms the urethane sheet 2, the balance between the soft segment and the hard segment, the degree of polymerization, and the degree of crosslinking are appropriately adjusted by setting the flow start temperature within the above-described range. Furthermore, in the urethane sheet 2, a polyurethane resin having a 100% modulus in the range of 4 to 20 MPa is used. Accordingly, the urethane sheet 2 is moderately softened by frictional heat generated during the polishing process, and an appropriate elastic force is exerted when pressing the object to be polished, thereby improving the flatness of the object to be polished. it can.

  Further, in the present embodiment, the skin layer formed at the time of film formation by the wet coagulation method is removed by buffing, and the opening 5 is formed on the polished surface P. The opening 5 has an average pore diameter per unit area adjusted to a range of 1 to 30 μm. For this reason, since the slurry is held at the time of polishing processing while being distributed substantially evenly between the object to be polished and the polishing pad 10, the flatness accuracy of the object to be polished can be improved.

  Furthermore, in this embodiment, the urethane sheet 2 has a continuous microporous structure. For this reason, stretchability will be suppressed because a huge pore is not formed. When huge pores are formed, the elasticity becomes large, making it easier to take in abrasive grains and polishing debris from the openings formed on the polishing surface, causing retention and aggregation and impairing the flatness of the object to be polished. is there. Therefore, in the urethane sheet 2, the stretchability is suppressed and the opening 5 is less likely to be blocked, so that the flatness of the object to be polished can be stably improved for a long period of time.

  In addition, in this embodiment, although the polycarbonate-type polyurethane resin was illustrated as resin which forms the urethane sheet 2, this invention is not limited to this. As the polyurethane resin of the urethane sheet 2, the flow start temperature may be in the above-described range, and a polyether-based or polyester-based polyurethane resin may be used instead of the polycarbonate-based one. In consideration of securing the hydrolysis resistance of the urethane sheet 2, it is preferable to set the solidification value of the polyurethane resin within the above-described range.

  Further, in this embodiment, the polar solvent used for dissolving the resin is mixed in the coagulation liquid at the time of forming the sheet by the wet coagulation method, that is, using the coagulation liquid in which water and DMF are mixed, Although the example which forms the urethane sheet 2 of a structure was shown, this invention is not restrict | limited to this. In order to obtain a microporous structure, it is only necessary to suppress the formation of a dense skin layer during coagulation regeneration and facilitate solvent substitution. Instead of mixing a polar solvent with the coagulation liquid, an adjustment solvent is added to the resin solution. This can also be realized. As the adjustment solvent, a solvent having a solubility in water smaller than that of DMF and capable of being uniformly mixed and dispersed in the resin solution without solidifying (gelling) the resin dissolved in DMF can be used. As such an adjustment solvent, a low polarity solvent such as ethyl acetate, isopropyl alcohol, hexane or the like can be used. In this case, solvent replacement at the initial stage of coagulation in the coagulation liquid is delayed, and it becomes difficult to form a dense skin layer, and as a result, a microporous urethane sheet can be obtained. Further, even if the solvent replacement is facilitated by increasing the solidification temperature, a microporous urethane sheet can be obtained in the same manner.

  Furthermore, in the present embodiment, an example of a lattice shape is shown as the arrangement of the convex portions 5 and the concave portions 6 on the polishing surface P, but the present invention is not limited to this. For example, instead of the lattice arrangement, as shown in FIG. Even in this case, it has been confirmed that the same effect as in the present embodiment can be obtained.

  Furthermore, although not specifically mentioned in the present embodiment, a through-hole penetrating in the thickness direction may be formed in the convex portion 5 of the urethane sheet 2. That is, as shown in FIG. 4, the through hole 9 can be formed in the convex portion 5. The through hole 9 can be formed, for example, by performing a punching process after the embossing process. The hole diameter of the through hole 9 may be about the same as the average hole diameter of the opening 4a, that is, in the range of 1 to 30 μm. In this way, since the polishing liquid and the polishing scraps easily flow into the through hole 9, clogging of the opening 4a can be suppressed, and the scratch suppressing effect on the object to be polished can be improved.

  Furthermore, in the present embodiment, an example in which the buff treatment is performed on the skin layer side of the film-forming resin obtained after coagulation regeneration is shown, but the present invention is not limited to this. In order to make the thickness of the urethane sheet 2 uniform, the surface opposite to the skin layer may be buffed, or both the skin layer side and the surface opposite to the skin layer may be buffed. Also good. In addition, a slice process or the like can be performed instead of the buff process. By making the thickness of the urethane sheet 2 uniform, the pressing force applied to the object to be polished at the time of polishing can be equalized, and the flatness of the object to be polished can be improved.

  Moreover, in this embodiment, although the double-sided tape 7 was bonded together to the surface side opposite to the grinding | polishing surface P of the urethane sheet 2, the example which the base material of the double-sided tape 7 serves as the base material of the polishing pad 10 was shown. Is not limited to this. For example, even if only the adhesive is provided in place of the double-sided tape 7, it can be attached to the polishing machine. Further, another base material may be bonded between the double-sided tape 7 and the urethane sheet 2. In consideration of handling when the polishing pad 10 is transported or mounted on a surface plate, it is preferable to have a base material.

  Further, although not particularly mentioned in the present embodiment, the urethane sheet 2 has at least a light transmitting portion that allows light transmission for optically detecting the polishing state of the object to be polished. It may be. It is preferable that the light transmission part is formed so as to penetrate through the entire thickness of the urethane sheet 2. In this way, for example, a light-emitting element such as a light-emitting diode provided on the polishing machine side or a light-receiving element such as a phototransistor detects the polishing state of the processing surface of the object to be polished through the light transmitting part during polishing can do. As a result, the end point of the polishing process can be properly detected, and the polishing efficiency can be improved.

  Hereinafter, 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, diphenylmethane-4,4′-diisocyanate (MDI) polyether-based polyurethane resin (flow start temperature 185 ° C., coagulation number 4.6) having a 100% modulus of 8 MPa is used for producing the urethane sheet 2. It was. This polyurethane resin was dissolved in DMF so that the solid content concentration was 30 wt% to prepare a resin solution. When the resin solution was applied to the film-forming substrate, the clearance of the coating apparatus was set to 1.6 mm, and a coagulation liquid in which water and 15 wt% DMF were mixed was used. After the buff treatment on the skin layer side, heat embossing was performed at 145 ° C. for 3 minutes in a lattice shape in which the width of the convex portion 5 was 3 mm and the width of the concave portion 6 was 1 mm. As a result of observing the cross section of the obtained urethane sheet 2, it was confirmed that cells of 100 μm or more were not formed, the average pore diameter of the pores 4 was 8 μm, and the formation ratio was about 10,000 / mm ² . In the recess 6, the pore 4 was almost completely closed. The urethane sheet 2 and a double-sided tape 8 having a PET base material were bonded together to produce a polishing pad 10 of Example 1 (see also FIG. 1).

(Example 2)
In Example 2, the same polyurethane resin as in Example 1 was used. In the preparation of the resin solution, a mixed solvent in which a part of DMF was replaced with ethyl acetate having a solubility in water smaller than the solubility of DMF in water was used. The amount of ethyl acetate was adjusted to a mass ratio of 2/3 with respect to the polyurethane resin. A polishing pad 10 of Example 2 was produced in the same manner as in Example 1 except that a resin solution was prepared by dissolving a polyurethane resin in a mixed solvent of ethyl acetate and DMF so that the solid content concentration was 30 wt%. In the obtained urethane sheet 2, it was confirmed that cells having a size of 100 μm or more were not formed, the average pore diameter of the pores 4 was 5 μm, and the formation rate was about 20000 pieces / mm ² . In the recess 6, the pore 4 was almost completely closed.

(Comparative Example 1)
In Comparative Example 1, the same polyurethane resin as in Example 1 was dissolved in DMF to prepare a resin solution, and the polishing of Comparative Example 1 was performed in the same manner as in Example 1 except that the resin solution was coagulated in a water-only coagulating liquid. A pad was manufactured. That is, Comparative Example 1 is a conventional polishing pad 20 (see also FIG. 5). In the obtained urethane sheet, cells of 100 μm or more were formed, and it was confirmed that the average pore diameter of the pores 4 was 12 μm and the formation rate was about 1000 / mm ² . Moreover, in the recessed part 16, the pore 4 was not obstruct | occluded and the pore 14 was recognized.

(Example 3)
In Example 3, a diphenylmethane-4,4′-diisocyanate (MDI) polycarbonate-based polyurethane resin having a 100% modulus of 8 MPa (flow start temperature: 200 ° C., coagulation value: 3.8) was used in the same manner as in Example 1. A urethane sheet was prepared. After the buff treatment was performed on the skin layer side of the urethane sheet, heat embossing was performed at 160 ° C. for 3 minutes in a lattice shape in which the width of the convex portion 5 was 3 mm and the width of the concave portion 6 was 1 mm. In the obtained urethane sheet 2, it was confirmed that cells having a size of 100 μm or more were not formed, the average pore diameter of the pores 4 was 4 μm, and the formation rate was about 15000 pieces / mm ² . In the recess 6, the pore 4 was almost completely closed. After the urethane sheet 2 and the double-sided tape 8 were bonded together, through holes 9 having a diameter of 2 mm were formed at a pitch of 10 mm by punching to manufacture the polishing pad 10 of Example 3 (see also FIG. 4).

Example 4
In Example 4, the polishing pad 10 of Example 4 was produced in the same manner as in Example 2 except that the same polyurethane resin as in Example 3 was used. In the obtained urethane sheet 2, it was confirmed that cells having a size of 100 μm or more were not formed, the average pore diameter of the pores 4 was 3 μm, and the formation rate was about 15000 pieces / mm ² . In the recess 6, the pore 4 was almost completely closed.

(Comparative Example 2)
In Comparative Example 2, a polishing pad of Comparative Example 2 was produced in the same manner as Comparative Example 1 except that the same polyurethane resin as in Example 3 was used. That is, Comparative Example 2 is a conventional polishing pad 20 (see also FIG. 5). In the obtained urethane sheet, cells of 100 μm or more were formed, and it was confirmed that the average pore diameter of the pores 4 was 9 μm and the formation rate was 1000 / mm ² . Moreover, in the recessed part 16, the pore 4 was not obstruct | occluded and the pore 14 was recognized.

(Comparative Example 3)
In Comparative Example 3, an example was used except that diphenylmethane-4,4′-diisocyanate (MDI) polyether polyurethane resin (flow start temperature 280 ° C., coagulation number 7.2) having a 100% modulus of 18 MPa was used. In the same manner as in Example 1, a urethane sheet was produced. After the buff treatment was performed on the skin layer side of the urethane sheet, heat embossing was performed at 160 ° C. for 3 minutes in a lattice shape in which the width of the convex portion 15 was 3 mm and the width of the concave portion 16 was 1 mm. In the obtained urethane sheet, cells of 100 μm or more were formed, and it was confirmed that the average pore diameter of the pores 4 was 9 μm and the formation rate was 1000 / mm ² . Moreover, in the recessed part 16, the pore 4 was not obstruct | occluded and the pore 14 was recognized.

(Comparative Example 4)
In Comparative Example 4, a polishing pad of Comparative Example 4 was produced in the same manner as Comparative Example 2 except that the same polyurethane resin as in Comparative Example 3 was used. That is, Comparative Example 4 is a conventional polishing pad 20 (see also FIG. 5). In the obtained urethane sheet, cells of 100 μm or more were formed, and it was confirmed that the average pore diameter of the pores 4 was 8 μm and the formation rate was 1000 / mm ² . Moreover, in the recessed part 16, the pore 4 was not obstruct | occluded and the pore 14 was recognized.

(Evaluation)
About the polishing pad of each Example and the comparative example, it grind | polished on the following grinding | polishing conditions, and measured the polishing rate, polishing flatness, and the presence or absence of the scratch. As an object to be polished, a substrate in which an insulating film of tetraethoxysilane having a thickness of 1 μm was formed on a silicon wafer having a diameter of 12 inches by chemical vapor deposition (CVD) (thickness uniformity of the insulating film: 14.5 CV%). 2%) was used. The polishing rate represents the amount of polishing per minute in terms of thickness, and was determined from the thickness measurement results at 17 locations for the insulating film of the substrate before and after polishing. In the thickness measurement, the measurement was performed in the DBS mode of an optical film thickness measuring instrument (manufactured by KLA Tencor, ASET-F5x). Further, the polishing flatness (CV%) was obtained from the thickness variation (standard deviation / average value) of the insulating film measured at 17 locations. In the scratch evaluation, 25 substrates were repeatedly polished three times in succession, and the 5th substrate from the 21st to the 25th substrate after polishing was processed with a high-pattern-less wafer surface inspection apparatus (Surfscan SP1DLS, manufactured by KLA Tencor). Measurement was performed in the sensitivity measurement mode, and the presence or absence of scratches on the substrate surface was evaluated. The measurement results of the polishing rate, polishing flatness, and the presence or absence of scratches are shown in Table 1 below.
(Polishing conditions)
Used polishing machine: F-REX300 manufactured by Ebara Corporation
Polishing speed (rotation speed): surface plate rotation speed 70 rpm, polishing head rotation speed 71 rpm
Processing pressure: 220 g / cm ²
Slurry: Colloidal silica slurry (Cabot, trade name SS25 diluted to 2 times volume with pure water)
Slurry supply amount: 200ml / min

  As shown in Table 1, the polishing rates of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 having the conventional urethane sheet 12 were 211 nm / min, 209 nm / min, and 201 nm / min, respectively. 202 nm / min. The polishing flatness is improved after polishing as compared to CV% before polishing = 14.2%, but 11.2%, 10.8%, 7.8%, and 8.1, respectively. %Met. On the other hand, in the polishing pad 10 of Example 1, Example 2, Example 3 and Example 4, the polishing rates were 223 nm / min, 238 nm / min, 208 nm / min, and 213 nm / min, respectively, and the polishing flatness The properties were also improved to 4.5%, 3.7%, 5.9% and 5.2%, respectively. From this, it became clear that the polishing pad 10 of each example can improve the flatness accuracy. In addition, as a result of repeating the polishing process with the polishing pads of the examples and comparative examples, the occurrence of scratches was observed in the polishing pad 20 of each comparative example, whereas in the polishing pad 10 of each example, In any case, no scratch was observed. Therefore, it was confirmed that the polishing pad 10 can obtain stable polishing performance over a long period of time while maintaining the uniformity of flatness.

  Since the present invention provides a polishing pad capable of securing a polishing rate and suppressing scratches on an object to be polished and a method for manufacturing the polishing pad, the present invention contributes to the manufacture and sales of the polishing pad. Has availability.

P Polished surface 2 Urethane sheet (resin sheet)
4 pore 4a opening 4s micropore 5 convex portion 6 concave portion 10 polishing pad

Claims (9)

In a polishing pad comprising a resin sheet formed by a wet coagulation method and having a polishing surface on one side, the resin sheet is made of a polyurethane resin having a flow start temperature in the range of 150 ° C. to 220 ° C. and a coagulation value of less than 6. A cell having a maximum length of 100 μm or more having a length in the thickness direction is not formed, and a large number of pores having an average pore diameter of 30 μm or less are formed. A convex portion that constitutes the polishing surface by the surface on which the aperture is formed, and a concave portion that is formed between the convex portions and in which the pores on the surface are reduced in diameter or closed from the pores of the convex portion. A polishing pad comprising: The polishing pad according to claim 1 , wherein the polyurethane resin is polyether-based or polycarbonate-based. The polishing pad according to claim 2 , wherein the polyurethane resin has a 100% modulus in a range of 4 MPa to 20 MPa. The polishing pad according to claim 1 , wherein the resin sheet has an average pore diameter of 1 μm or more. 5. The polishing pad according to claim 4 , wherein the resin sheet has a formation ratio of the pores per unit area in a section in a thickness direction of 500 / mm ^{2 to} 50000 / mm ² .   The polishing pad according to claim 1, wherein the resin sheet further includes a through-hole penetrating in the thickness direction in the convex portion. A method for producing a polishing pad according to any one of claims 1 to 6 ,
A preparation step of preparing a polyurethane resin having a flow start temperature in the range of 150 ° C. to 220 ° C. and a coagulation value of less than 6 ;
An application step of applying a resin solution in which the polyurethane resin prepared in the preparation step is uniformly dissolved in a polar solvent to a sheet-like substrate in a uniform mixed state;
A sheet forming step in which the resin solution applied to the substrate in the application step is solidified in an aqueous coagulating liquid to form a resin sheet; and
An embossing step of performing hot embossing so that a convex portion and a concave portion are formed on one side of the resin sheet formed in the sheet forming step;
Including
In the embossing step, pressurization is performed so that a position corresponding to the concave portion is heated. The manufacturing method according to claim 7 , wherein, in the sheet forming step, water containing 30% by mass or more of the polar solvent is used as the aqueous coagulating liquid. In the coating step, the resin solution, a manufacturing method of claim 7, solubility in water is characterized by mixing small organic solvents than water solubility of the polar solvent.

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