Patent Application
20120184194
The present disclosure relates to a Chemical Mechanical Polishing (CMP) polishing pad and a method for manufacturing the same, and more particularly, to a CMP polishing pad having holes formed by laser beams on the surface thereof in order to improve the stability of a CMP process and a method for manufacturing the same.
Semiconductors are devices obtained by high-density integration of electronic devices such as transistors or capacitors on a semiconductor substrate such as silicon, and are fabricated by using deposition, photolithography and etching technologies. Repetition of such deposition, photolithography and etching processes results in formation of a pattern having a specific shape. When the formation of patterns is repeated in a layered structure, a level difference gradually becomes severe at the top of the resultant structure. Such a severe level difference at the top of the structure makes the focus of a photomask pattern unclear in the subsequent photolithography process, thereby making it difficult to form a fine pattern.
One of the technologies including reducing the level difference on a substrate to increase resolution in photolithography is Chemical Mechanical Polishing (CMP). CMP includes polishing a substrate having a level difference mechanically and chemically to planarize the top of the substrate.
CMP polishing pads are consumable goods for use in polishing wafer surfaces and are essential for CMP processes. The slurry is present between the CMP polishing pad and the wafer surface during CMP to carry put chemical mechanical polishing of the wafer surface. Then, the used slurry is discharged to the exterior. To retain the slurry on the CMP polishing pad for a predetermined time, it is required for the CMP polishing pad to store the slurry thereon. Such slurry storability of the CMP polishing pad may be obtained by pores or holes formed on the polishing pad. In other words, the slurry is introduced into the pores or holes formed on the CMP polishing pad so that the semiconductor surface may be polished efficiently for a long time. In order to ensure that the CMP polishing pad inhibits leakage of the slurry and provides high polishing efficiency, it is required that the shapes of the pores or holes are controlled well and the physical properties, such as hardness, of the polishing pad are maintained in an optimized condition.
Conventional CMP polishing pads have been obtained by forming pores with an irregular size and arrangement inside polishing pads by a physical or chemical method.
One of the physical methods among the conventional methods for forming pores or holes on a CMP polishing pad is mixing a micro-sized material with a material for forming a polishing pad. In this case, it is required that a porous micro-sized material is placed in such a manner that it may be mixed well with a polishing pad material at the initial time of polishing pad fabrication. However, it is difficult to allow the micro-sized material to be mixed well with the polishing pad material by a physical method. Moreover, the micro-sized material is not uniform in size. In general, the average pore diameter of pores formed by a physical method is about 100 micrometers, but each pore has a diameter ranging from several tens micrometers to several hundreds micrometers. This results from a technical limitation in forming the pores. In addition, when fabricating a polishing pad, pores are randomly distributed at different positions due to the gravity. Thus, it is difficult to obtain a polishing pad having uniform quality. When the pores formed on the CMP polishing pad are not uniform in size or distribution, the polishing efficiency varies with position or time while a wafer is polished with a high precision.
One of the chemical methods for forming pores on a CMP polishing pad uses water or liquid capable of being converted into gas. When water or such liquid is introduced to polyurethane solution and then heated, pores are formed while the liquid is converted into gas. However, such a method for forming pores by using gas is still problematic in that maintenance of a uniform pore size is difficult. Therefore, there has been a need for developing a method for maintaining a uniform shape of the pores or holes formed on a CMP polishing pad and controlling the distribution of pores or holes as desired.
The present disclosure is directed to providing a CMP polishing pad having holes formed on the surface thereof, wherein the holes have a diameter controlled to a predetermined size.
The present disclosure is also directed to providing a method for manufacturing a CMP polishing pad having holes formed on the surface thereof, wherein the holes have a diameter controlled to a predetermined size.
In one general aspect, the present disclosure provides a CMP polishing pad having a plurality of holes formed on at least one surface thereof, wherein the holes are formed by dispersing a light-absorbing material in or on the surface of a CMP polishing pad and irradiating the light-absorbing material with laser beams.
According to an embodiment, the holes may have a diameter determined by the wavelength of the laser beams.
According to another embodiment, the diameter of the holes may be in proportion to the wavelength of the laser beams.
According to still another embodiment, the laser beams may have a median wavelength of 300-20,000 nm.
According to still another embodiment, the holes may have a diameter of 1-200 μm.
According to still another embodiment, the light-absorbing material may absorb light in a wavelength range of 300-15,000 nm.
According to still another embodiment, the light-absorbing material may be at least one material selected from the group comprising cyanine dyes, dithiolene dyes, diimmonium dyes, quinone dyes, rhodamine dyes, victoria dyes, methylene dyes, brilliant dyes, naphthalene dyes, repid-filter gelb, echtblau, pinaorthol dyes, pyrylium dyes, thionin dyes, nile blue dyes, cresyl dyes, oxazine dyes, resorufin dyes, resazurin dyes, pyronin dyes, acridine dyes and kiton dyes.
In a variant, there is provided a CMP polishing pad having a plurality of holes generated by forming a light-absorbing material layer on the surface of the polishing pad and irradiating the light-absorbing material layer with laser beams so that the laser beams penetrate through the light-absorbing material layer and the holes are formed to a predetermined depth of the polishing pad.
According to an embodiment, the light-absorbing material layer may be formed by spreading a light-absorbing material onto the surface of the polishing pad or by attaching a film having a light-absorbing material dispersed therein to the surface of the polishing pad.
In another general aspect, the present disclosure provides a method for manufacturing a CMP polishing pad, including: determining a diameter of holes to be formed on a CMP polishing pad; determining a particular type of laser to be used according to the diameter of holes; determining a particular type of light-absorbing material according to the type of laser; dispersing the light-absorbing material in the CMP polishing pad; and irradiating the CMP polishing pad having the light-absorbing material dispersed therein with the laser beams to form holes.
According to an embodiment, the diameter of holes may be in proportion to the wavelength of laser beams.
According to still another embodiment, the light-absorbing material may be at least one material selected from the group comprising cyanine dyes, dithiolene dyes, diimmonium dyes, quinone dyes, rhodamine dyes, victoria dyes, methylene dyes, brilliant dyes, naphthalene dyes, repid-filter gelb, echtblau, pinaorthol dyes, pyrylium dyes, thionin dyes, nile blue dyes, cresyl dyes, oxazine dyes, resorufin dyes, resazurin dyes, pyronin dyes, acridine dyes and kiton dyes.
According to still another embodiment, a plurality of holes is to be formed on the CMP polishing pad, and the distribution and depth of the holes may be controlled by varying the position of the polishing pad.
According to yet another embodiment, a plurality of holes is to be formed on the CMP polishing pad, and the distribution and depth of the holes may be controlled by varying the position of the laser.
The CMP polishing pad disclosed herein uses a light-absorbing material capable of absorbing light in a specific range of wavelengths on the surface thereof or therein, and thus allows formation of holes using laser beams. Therefore, it is possible to form holes having a desired diameter effectively on the CMP polishing pad by selecting the wavelength of laser beams and the light-absorbing material corresponding thereto according to the diameter of holes to be formed. In addition, since the holes are formed by laser beams, they may have a desired depth and distribution in the polishing pad. Further, it is possible to carry out a CMP process with high polishing efficiency and high process stability, depending on the type of a material to be polished or the composition of slurry.
The above and other objects, features and advantages of the present disclosure will become apparent from the following description of certain exemplary embodiments given in conjunction with the accompanying drawings, in which:
Hereinafter, the embodiments of the present disclosure will be described in detail with reference to accompanying drawings.
The CMP polishing pad disclosed herein has a plurality of holes formed on at least one surface thereof, wherein the holes are formed by dispersing a light-absorbing material in or on the surface of a CMP polishing pad and irradiating the light-absorbing material with laser beams. The holes are formed by laser beams, and have a diameter determined by the wavelength of the laser beams.
It is possible to maintain a uniform diameter of holes by forming the holes on the CMP polishing pad by using laser beams. The holes formed with a uniform diameter on the CMP polishing pad allow the CMP polishing pad to retain slurry for a predetermined time, thereby ensuring high CMP efficiency and process stability. Such formation of holes using laser beams is accomplished by irradiating the polishing pad with strong laser beams having a range of wavelengths capable of being absorbed by the CMP polishing pad so that the materials forming the polishing pad may be molten partially.
The distribution and depth of the holes formed on the CMP polishing pad may be controlled by adjusting the position of the polishing pad or that of the laser.
When forming the holes on the CMP polishing pad by using laser beams, there is a certain limitation in laser beam absorbance of the CMP polishing pad depending on the wavelength range of laser beams and materials for forming the CMP polishing pad. In general, CMP polishing pads are made of polyurethane polymers, which have high absorbance to far IR rays and UV rays. When forming holes on a CMP polishing pad made of a polyurethane polymer, use of carbon dioxide laser beams having a wavelength of 10.64 μm makes it difficult to control the diameter of holes to 100 μm or less due to the wavelength of the carbon dioxide laser beams. If the holes formed on the CMP polishing pad have a diameter larger than 100 μm, the CMP process using the pad provides poor polishing efficiency. When UV laser beams having a smaller wavelength range than carbon dioxide laser beams are used instead of carbon dioxide laser beams, it is possible to control the diameter of the holes formed on the CMP polishing pad to an extent of several micrometers. However, in this case, it is still difficult to control the diameter to an extent of several tens micrometers. If the holes formed on the CMP polishing pad have a diameter as small as several micrometers, an excessively large number of holes are to be formed per unit area of the pad, resulting in an increase in processing time and degradation of production efficiency. In brief, when forming holes on a CMP polishing pad by using laser beams, the range of controllable hole diameters is in proportion to the wavelength range of laser beams. Therefore, laser units of near IR rays or visible rays may be used to form holes having a diameter of several tens micrometers on a CMP polishing pad. In this case, it is required for the materials forming the CMP polishing pad to absorb the light having the corresponding range of wavelengths.
To solve the above-mentioned problem, according to the present disclosure, a light-absorbing material is dispersed in a CMP polishing pad. When dispersing an adequate light-absorbing material is dispersed in a CMP polishing pad according to the wavelength range of laser beams used for forming holes, it is possible to freely control the diameter of holes within a range of several micrometers to several hundreds micrometers. In other words, a light-absorbing material selected according to the wavelength of laser beams is dispersed on the surface of or inside a CMP polishing pad so that the light absorbance to a range of near IR rays to visible rays may be increased. In this manner, it is possible to form holes on a polishing pad more efficiently.
Laser units generating light of a range of visible rays or near IR rays include GaAs lasers (0.83 μm), Nd-YAG lasers (1.06 μm) or HF lasers (2.8 μm). In addition to those lasers, various types of lasers capable of generating light of an adequate wavelength range may be used. The light-absorbing material may be selected according to the wavelength range of the light generated from a specific laser unit. Conventional dyes or organic or inorganic materials known to absorb the light of a specific wavelength range may be used. Particular examples of the light-absorbing material absorbing light of near IR wavelengths include cyanine dyes, dithiolene dyes, diimmonium dyes, quinone dyes, rhodamine dyes, victoria dyes, methylene dyes, brilliant dyes, naphthalene dyes, repid-filter gelb, echtblau, pinaorthol dyes, pyrylium dyes, thionin dyes, nile blue dyes, cresyl dyes, oxazine dyes, resorufin dyes, resazurin dyes, pyronin dyes, acridine dyes and kiton dyes. Particular examples of the cyanine dyes include phthalocyanine compounds, naphthalocyanine compounds, amino group-containing phthalocyanine compounds, fluorine-containing phthalocyanine compounds, etc. Particular examples of the dithiolene dyes include bis(dithiobenzyl) nickel complex compounds, bis(1,2-acenaphthylenedithilolite) nickel complex compounds, 4-tert-butyl-1,2-benzenedithiol nickel complex compounds, alkoxy group-containing bis(dithiobenzyl) nickel complex compounds, etc. Although some kinds of dyes are exemplified, various kinds of dyes other than the above-listed dyes may be used. Diimmonium dyes absorbing light within a wavelength range of 0.95-1.1 μm may also be used as a light-absorbing material according to the present disclosure. Light-absorbing materials absorbing light of a wavelength ranges corresponding to visible rays include rhodamine dyes absorbing green light with a wavelength range of 0.532 μm or the like.
According to another embodiment, the light-absorbing material may be dispersed on the surface of the CMP polishing pad. When the light-absorbing material is dispersed in the polishing pad, it is miscible with the polyurethane polymer forming the polishing pad or it is dispersed uniformly in the polyurethane polymer in the form of particles. On the contrary, when the light-absorbing material is dispersed on the surface of the polishing pad, the particle-like light-absorbing material is distributed and dispersed predominantly on the surface of the polishing pad, or is applied to the surface of the polishing pad. When the particle-like light-absorbing material is distributed predominantly on the surface of the polishing pad, it is assumed that a higher proportion of the particle-like light-absorbing material is distributed on the bottom surface of the polishing pad due to the gravity during the fabrication of the polishing pad. This may be applied advantageously to formation of holes having a relatively small depth on the polishing pad. The other embodiment in which the light-absorbing material is applied to the surface of the polishing pad may be applied advantageously to dispersion of a light-absorbing material having low miscibility with the materials forming the polishing pad on the polishing pad.
According to still another embodiment, the light-absorbing material may be formed as a separate layer on the surface of the CMP polishing pad. Methods for forming a light-absorbing material as a separate layer on the CMP polishing pad include methods for spreading a light-absorbing material onto the polishing pad, and methods for coating a film containing a light-absorbing material on the polishing pad. The former may include spreading a light-absorbing material onto the surface of the polishing pad through a spin coating process, etc., spreading a solid-phase light-absorbing material onto the surface of the polishing pad through a vapor phase deposition process, or adding a particle-like light-absorbing material to a solution containing a polymer resin and a solvent and spreading the solution onto the surface of the polishing pad. The latter may include dispersing a light-absorbing material in a film and coating the film on the surface of the polishing pad, or spreading a light-absorbing material onto the surface of a film and coating the film on the surface of the polishing pad. Herein, the film may be formed of a polymer resin and may be coated on the polishing pad by using an adhesive or hot press. When the light-absorbing material is formed as a separate layer on the surface of the polishing pad, laser beams irradiated to the polishing pad are absorbed first by the light-absorbing material formed on the polishing pad and then penetrate through the pad, so that holes are formed to a predetermined depth. Thus, such a light-absorbing material formed as a separate layer on the surface of the CMP polishing pad increases light absorbance while not changing the intrinsic physical properties of the CMP polishing pad.
The diameter of the holes formed on the CMP polishing pad may be controlled within a wide range according to the particular type of CMP process and that of the material to be polished. The diameter of the holes formed on the CMP polishing pad may be 1-200 μm. When the hole diameter is smaller than 1 μm, an excessively large number of holes are formed per unit area of a polishing pad, resulting in degradation of production efficiency of polishing pads. When the hole diameter is larger than 200 μm, it is difficult to retain slurry in the polishing pad. The laser beams used for forming the holes may have a wavelength ranging from 300 nm to 20,000 nm. In addition, the light-absorbing material dispersed in the polishing pad may absorb the light within a wavelength range of 300 nm to 15,000 nm. The wavelength range of laser beams is determined considering the diameter of the holes formed on the CMP polishing pad. The absorption wavelength range of the light-absorbing material is determined in such a manner that it compensate for a deficiency in the light absorption wavelength range of a polyurethane polymer.
When forming holes in a CMP polishing pad by using laser beams, the holes may be distributed in various manners. The holes may be arranged in a regular, random, chaos or fractal pattern, or a combination thereof. The arrangement of holes may be selected considering the material to be polished, particular type of slurry or wafer size, etc. For example, the distribution of the holes formed on the CMP polishing pad may be realized in such a manner that a higher proportion of holes is present at the center and the number of holes gradually decreases toward the peripheral portion, or a smaller proportion of holes is present at the center and the number of holes gradually increases toward the peripheral portion. The former case provides the CMP polishing pad with lower hardness at the center thereof and allows slurry feed to be concentrated at the center. The latter case results in a contrary effect. The distribution of holes may be controlled diversely according to the pattern shape of a material subjected to CMP or the structure of a CMP system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2009-0069960 | Jul 2009 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR2010/002728 | 4/30/2010 | WO | 00 | 4/2/2012 |
