Patent Application
20240293911
The present invention relates to a polishing pad and a wafer notch polishing method.
Japanese Patent Laid-Open No. 2019-46838, Japanese Patent Laid-Open No. 2019-118981, Japanese Patent Laid-Open No. 2020-49639 and Japanese Patent No. 5511266 disclose conventional polishing pads. The polishing pad disclosed in Japanese Patent Laid-Open No. 2019-46838, Japanese Patent Laid-Open No. 2019-118981 or Japanese Patent Laid-Open No. 2020-49639 is obtained by impregnating a nonwoven fabric with a paste and removing a solvent from the paste. The paste disclosed in Japanese Patent Laid-Open No. 2019-46838 is composed of urethane, a solvent such as dimethylformamide, polishing particles such as silica (SiO2), and alkali fine particles such as sodium carbonate. The paste disclosed in Japanese Patent Laid-Open No. 2019-118981 is composed of ether-based urethane and a solvent such as N,N-dimethylformamide. The paste disclosed in Japanese Patent Laid-Open No. 2020-49639 is composed of urethane, a solvent, and a water repellent. When the solvent is removed by drying or the like, the urethane solidifies in a state of bonding to the nonwoven fabric. The polishing pad disclosed in Japanese Patent No. 5511266 is manufactured using a paste in which a binder resin, polishing particles and a solvent are mixed together.
The polishing pad disclosed in Japanese Patent Laid-Open No. 2019-46838 is used to polish an outer circumferential edge part of a disc-shaped wafer made of silicon or the like, which is used to manufacture semiconductor elements. That is, the wafer is retained on a rotary table that is rotatable around a rotation center. At this time, a central axis of the wafer is positioned at the rotation center of the rotary table. The polishing pad is provided at an upper end of a spindle such that an outer circumferential end surface of the polishing pad abuts on the outer circumferential edge part of the wafer. Then, a predetermined load is applied to between the outer circumferential edge part of the wafer and the outer circumferential end surface of the polishing pad while a polishing liquid is supplied thereto, thereby causing the rotary table and the spindle to rotate. This makes it possible to polish the outer circumferential edge part of the wafer. Consequently, it becomes possible to reduce the number of defects in semiconductor apparatuses attributed to the outer circumferential edge part of the wafer.
However, some wafers may have a notch indicating an orientation of a crystal axis, aside from the central axis forming the center of an arc thereof. This is because, when a large-diameter wafer has an ordinary orientation flat indicating the orientation of the crystal axis, the area of a portion that has been removed from the wafer is large, thus resulting in a waste of the wafer.
For such a wafer having a notch, if a front surface or a rear surface thereof is polished with no measures taken for the notch, the wafer is chipped or cracked near the notch during the polishing process, thus resulting in a waste of the wafer.
Accordingly, one non-limiting object of the present teaching is to provide a polishing pad that enables reducing wastage of wafers having a notch as much as possible and a method for polishing the notch of such wafers. This object is achieved by the teaching according to claim 1. Further developments of the present teaching are described in the dependent claims.
A polishing pad of the present teaching is formed in an annular shape and is centered on a first rotation axis center,
In addition, a wafer notch polishing method of the present teaching includes:
In the polishing pad of the present teaching, the polishing surface is formed of the polishing body that includes the base material and the polishing particles. The base material is composed of the binder resin and the fibers and has the plurality of pores formed therein. In addition, the polishing particles are retained in the base material or in the pores. Therefore, when the notch of the wafer is polished with the polishing pad of the present teaching by the wafer notch polishing method of the present teaching, the polishing pad exhibits excellent followability to the notch when pressing the notch, therefore performing favorable polishing. Consequently, the wafer having the polished notch is unlikely to be or is not chipped or cracked near the notch during the process of polishing the front surface or the rear surface thereof.
Other aspects and advantages of the present invention should be clear from the working examples explained in the following description and shown in the attached drawings, from the illustrations in these drawings, and from the concept or gist of the present invention disclosed overall in the specification and these drawings.
In a polishing pad of the present teaching, a polishing surface is formed of a polishing body, and the polishing body includes a base material and polishing particles. The base material is composed of a binder resin and fibers and has a plurality of pores formed therein. The polishing particles are retained in the base material or in the pores.
As the binder resin, a thermoplastic polyurethane (TPU) resin, a polyethersulfone (PES) resin, a polyvinylidene fluoride (PVDF) resin, a polyvinyl fluoride resin, a vinyl fluoride/hexafluoropropylene copolymer, a vinylidene fluoride/hexafluoropropylene copolymer, a polyethylene resin, a polymethylmethacrylate resin or the like is adoptable. These binder resins may be used singly or may be used in a mixture of two or more kinds thereof.
As the fibers, polyethylene terephthalate (PET) fibers, polypropylene (PP) fibers, polyester fibers, aramid fibers, glass fibers, cellulose fibers, nylon fibers, vinylon fibers, polyethylene fibers, polyolefin fibers, rayon fibers, a low-density polyethylene resin, an ethylene-vinyl acetate resin, a synthetic rubber, a co-polymerized polyamide resin, a co-polymerized polyester resin or the like can be adopted. These fibers may be used singly or may be used in a mixture of two or more kinds thereof. In addition, the shape of the fibers such as the fiber length or thickness is also selectable.
As the polishing particles, silica, ceria, alumina, diamond, zirconia, titania, manganese oxide, barium carbonate, chromium oxide, boron carbide, iron oxide or the like is adoptable. These polishing particles may be used singly or may be used in a mixture of two or more kinds thereof.
According to the inventors' test results, it is preferable that the binder resin be a thermoplastic polyurethane resin and the fibers be polyethylene terephthalate fibers or polypropylene fibers. In this case, when the polishing pad presses a notch, the polishing pad exhibits excellent followability to the notch.
Particularly, according to the inventors' test results, it is preferable that the binder resin be in a range from 8.5 to 12.7 vol %, the polishing particles be in a range from 10.6 to 14.8 vol %, the fibers be in a range from 17.4 to 26.1 vol %, and the pores be in a range from 54.0 to 58.6 vol %. In addition, when the volume percent of the polishing particles is divided by the total of the volume percent of the binder resin and the volume percent of the fibers, the calculated value is preferably in a range from 0.30 to 0.48. In this case, the polishing pad exhibits excellent wear resistance and excellent polishing efficiency.
In addition, according to the inventors' test results, it is preferable that a density be in a range from 0.66 to 0.74 g/cm3, a durometer hardness be in a range from 30 to 38, and an elastic modulus be in a range from 93.4 to 257.5 N/mm2. In this case, the polishing pad exhibits excellent wear resistance and excellent polishing efficiency.
The fibers of the polishing pad may be fibers of a preformed fibrous web or may be discrete fibers. The fibrous web is formed of layers of fibers by arraying the fibers vertically, crossing the sequence of the fibers, or arraying the fibers randomly. A nonwoven fabric is made of fibrous webs in which fibers are bonded to each other.
The polishing pad of the present teaching is manufacturable by the following manufacturing method. This manufacturing method includes: a preparation step of preparing a binder resin, a paste containing a solvent that dissolves the binder resin and containing a numerous number of polishing particles, and a fibrous web;
A polishing body of the polishing pad to be obtained by the manufacturing method includes: a fibrous web as the fibers; and the binder resin and the polishing particles that are contained in the fibrous web. In this case, the preformed fibrous web is used as the fibers, and therefore the productivity of the polishing pad is high.
The paste contains the binder resin, a numerous number of the polishing particles, and the solvent. As the solvent, N-methyl-2-pyrolidon (NMP), dimethylformamide, dimethylsulfoxide, acetone, ethyl acetate, methyl ethyl ketone or the like is adoptable. These solvents may be used singly or may be used in a mixture of two or more kinds thereof. The solvents are selected according to the binder resin.
The paste may also contain alkali fine particles of sodium carbonate, piperazine, potassium hydroxide, sodium hydroxide, calcium oxide, potassium carbonate, magnesium oxide or the like. In addition, the paste may contain a water repellent such as a fluorine-based water repellent, a silicon-based water repellent, a hydrocarbon-based water repellent or a metal compound-based water repellent. Furthermore, the paste may contain a pigment such as an inorganic pigment, including titanium dioxide, calcium carbonate or carbon black, or an organic pigment, including an azo pigment or a polycyclic pigment. These may be used singly or may be used in a mixture of two or more kinds thereof.
When a polishing liquid is used, the polishing liquid may be pure water, may be oily, or may contain an acidic or alkaline chemical.
In another aspect of the present teaching, the polishing surface may have: a third surface that is continuous with a first surface and forms a tapered shape such that a distance between a first rotation axis center and the third surface becomes larger as the third surface approaches a second surface; and a fourth surface that is continuous with the second surface and forms a tapered shape such that a distance between the first rotation axis center and the fourth surface becomes larger as the fourth surface approaches the first surface. The third surface and the fourth surface preferably have an interior angle that is consistent with an opening angle of the notch. Specifically, because the opening angle of a notch is standardized to be 1100±20°, the interior angle between the third surface and the fourth surface is preferably set to 1100±20° if a wafer to be used has such a standard notch. In this case, the notch is polishable more suitably.
In the wafer notch polishing method of the present teaching, in the second step, a distance between the front surface or rear surface of the wafer and the first rotation axis center is preferably caused to change. In this case, an edge part between the notch and the front surface or the rear surface is also polishable suitably, and the wafer having the polished notch is less likely to or is not chipped or cracked near the notch.
Working examples 1 to 10 according to the present teaching and comparative examples 1 and 2 are explained below.
First of all, as a preparation step, a binder resin, polishing particles, a solvent, and a fibrous web were prepared as described below. The fibrous web is formed in an annular shape and is centered on a first rotation axis center P, in the same manner as a polishing pad 1 to be manufactured, which is shown in
Thermoplastic polyurethane (TPU) resin
N-methyl-2-pyrrolidone (NMP)
Silica (SiO2) (Average particle diameter: 200 nm)
Polyethylene terephthalate (PET) fibers 100%, Basis weight: 1200 to 1700 g/m2
Polypropylene (PP) fibers 100%, Basis weight: 400 g/m2
As shown in table 1, the combination of the fibrous web and a paste was changed, and the binder resin, the polishing particles and the solvent were mixed in mass percent shown in table 1 to make pastes.
Then, in each example, the paste was brought into contact with the fibrous web while a load was applied to front and rear surfaces of the fibrous web to impregnate the fibrous web with the paste, thereby producing an impregnated body. The obtained impregnated body was dried, thereby removing the solvent from the impregnated body and causing the binder resin to solidify. Consequently, a polishing body is obtained.
An outer circumferential part and an inner circumferential part of the polishing body were removed using the first rotation axis center P as the center to obtain the polishing pad 1 of working examples 1 to 10 and comparative example 1. In each example, the polishing body includes the preformed fibrous web as the fibers, and therefore the productivity of the polishing pad 1 is high. The polishing pad 1 of comparative example 2 is the fibrous web itself as shown in table 1. In each example, the polishing pad 1 has an inner diameter ϕ1 of 152 mm, an outer diameter ϕ2 of 200 mm, and a thickness t of 4.5 mm as shown in
As shown in
As shown in
A 500×SEM image of the polishing pad 1 of working example 1 is shown in
Regarding the polishing pad 1 of working example 1 to 10 and comparative examples 1 and 2 obtained as described above, as shown in table 2, in each example, a volume percent Vg of the polishing particles, a volume percent Vb of the binder resin, a volume percent Vf of the fibrous web, and a volume percent Vp of the pores were calculated. A value was also calculated by dividing the volume percent Vg of the polishing particles by the total of the volume percent Vb of the binder resin and the volume percent Vf of the fibers. The calculated value in each example is also shown in table 2.
In addition, regarding the polishing pad 1 of working examples 1 to 10 and comparative examples 1 and 2, in each example, a density (g/cm3), a durometer hardness (D) and an elastic modulus (N/mm2) of the polishing surface 3 were also calculated. The calculated values are shown in table 3.
As shown in
As shown in
In addition, a polishing apparatus, which is shown in
In addition, as shown in
In addition, as polishing liquids, piperazine aqueous solutions containing different concentrations of silica (SiO2) as the polishing particles (Average particle diameter: 0.2 μm) were used.
Then, the notches 7 of 200 wafers 5 were polished in each example under the following conditions:
A partial enlarged plan view of a polished notch 7 is shown in
The wear amount of the polishing pad 1 per wafer, the polishing time and the presence or absence of an unpolished part, the particles, and the polishing liquid were evaluated. At this time, the presence or absence of an unpolished part was evaluated by checking the top (TOP-VN) of the notch 7, a front surface 5a part (A-VN) of the notch 7 and a rear surface 5b part (B-VN) of the notch 7.
The wear amount of the polishing pad 1 was evaluated by measuring the total wear amount after the notches 7 of the 200 wafers 5 were polished as follows: a rating of E (Excellent) was given if the total wear amount was less than 0.010 mm; a rating of G (Good) was given if the total wear amount was more than or equal to 0.010 mm and less than 0.020 mm; a rating of F (Fair) was given if the total wear amount was more than or equal to 0.020 mm and less than 0.050 mm; and a rating of P (Poor) was given if the total wear amount was more than or equal to 0.050 mm. If the outer diameter ϕ2 of the polishing pad 1 becomes less than or equal to 180 mm, the polishing pad 1 is discarded.
The polishing time and the presence or absence of an unpolished part were evaluated as follows: a rating of E (Excellent) was given if the polishing time was within 60 seconds and no unpolished part was present; a rating of G (Good) was given if the polishing time was within 120 seconds and no unpolished part was present; a rating of F (Fair) was given if the polishing time was within 180 seconds and no unpolished part was present; and a rating of P (Poor) was given if the polishing time was longer than or equal to 180 seconds and an unpolished part was present. It is noted that, if the notch 7 has a grinding mark (scratch) horizontally made during a preprocessing step before a polishing step and the grinding mark is found in microscopic observation, an unpolished part is determined to be present.
The particles were evaluated by observing the number of the particles in a 5 μm×5 μm surface with an electronic microscope: a rating of E (Excellent) was given if the number of the particles was 0; a rating of G (Good) was given if the number of the particles was less than or equal to 5; a rating of F (Fair) was given if the number of the particles was more than 5 and less than or equal to 10; and a rating of P (Poor) was given if the number of the particles was more than 10.
The polishing liquid was evaluated as follows: a rating of E (Excellent) was given if the concentration of the contained polishing particles was 0 ppm and polishing was possible; a rating of G (Good) was given if the concentration of the polishing particles was more than or equal to 1 ppm and less than 1000 ppm and polishing was possible; a rating of F (Fair) was given if the concentration of the polishing particles was more than or equal to 1000 ppm and less than 5000 ppm and polishing was possible; and a rating of P (Poor) was given if the concentration of the polishing particles was more than or equal to 5000 ppm and less than or equal to 10000 ppm and polishing was possible.
In the overall evaluation, a rating of G (Good) was given if a rating higher than or equal to a rating of F (Fair) was given to all of the wear amount, the polishing time and the presence or absence of an unpolished part, the particles, and the polishing liquid, and a rating of E (Excellent) was given if a rating higher than or equal to a rating of G (Good) was given to all of the above evaluation items. The results are shown in table 4.
Table 4 shows that, in the overall evaluation, a rating of E is given to the polishing pad 1 of working examples 1 and 6 to 10, and a rating of G is given to the polishing pad 1 of working examples 2 and 5. This is because, as shown in table 2, for the polishing pad 1 of working examples 1 to 10, the binder resin is in a range from 8.5 to 12.7 vol %, the polishing particles are in a range from 10.6 to 14.8 vol %, the fibers are in a range from 17.4 to 26.1 vol %, and the pores are in a range from 54.0 to 58.6 vol %. This is also because, for the polishing pad 1 of working examples 1 to 10, the value calculated by dividing the volume percent Vg of the polishing particles by the total of the volume percent Vb of the binder resin and the volume percent Vf of the fibers is in a range from 0.30 to 0.48. Furthermore, this is because, as shown in table 3, for the polishing pad 1 of working examples 1 to 10, the density is in a range from 0.66 to 0.74 g/cm3, the durometer hardness is in a range from 30 to 38, and the elastic modulus is in a range from 93.4 to 257.5 N/mm2.
In contrast, for the polishing pad 1 of comparative example 1, the wear amount is inferior and an unpolished part is present. For the polishing pad 1 of comparative working example 2, an inferior rating is given to the particles and the polishing liquid.
Therefore, according to the polishing pad 1 of working examples 1 to 10 and the wafer notch polishing method using thereof, it is found that it is possible to reduce wastage of the wafer 5 having the notch 7 as much as possible.
In addition, according to the polishing pad 1 of working examples 1 to 10 and the wafer notch polishing method using thereof, since the polishing body constituting the polishing surface 3 includes a numerous number of the polishing particles, a polishing liquid containing no or a small number of the polishing particles is usable. Thus, the number of the particles (polishing particles) remaining on the wafer 5 having the polished notch 7 is small, and therefore the wafer 5 is cleanable easily.
The description above explained the present teaching based on working examples 1 to 10, but the present teaching is not limited to the above-mentioned working examples and is applicable by modification where appropriate within a range that does not deviate from the gist thereof.
In working examples 1 to 10, the notch 7 of the wafer 5 made of Si was polished, but the polishing pad and the wafer notch polishing method of the present teaching are also applicable to, for example, polishing notches of wafers made of silicon carbide (SiC).
The present teaching is usable in manufacturing apparatuses of semiconductor apparatuses.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-032444 | Mar 2023 | JP | national |
| 2024-015232 | Feb 2024 | JP | national |
