CROSS-REFERENCES TO RELATED APPLICATION
This application claims the priority of Taiwanese patent application No. 102127168, filed on Jul. 29, 2013, which is incorporated herewith by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method for fabricating a pad conditioning tool for Chemical Mechanical Polishing (CMP) process, and more particularly to a method for fabricating a pad conditioning tool, which utilizes screen printing technique and a screen plate to transfer an image pattern so as to precisely control the thickness of thin film and the image pattern.
2. The Prior Arts
Rapid advance of semiconductor product demands minimizing width of circuit paths in the integrated circuit board. The more the circuits are integrated into a chip, the more planarization of surfaces in the semiconductor material is required, since formation of a circuit or thin film is obtained only after each deposition process. Since smoothing of the surface is required after formation of each, presently Chemical Mechanical Polishing (CMP) technique is generally applied in the production of a semiconductor, which in fact is a process of smoothing surfaces of silicone wafers or other base material with the combination of chemical and mechanical forces, so that it is named CMP.
Of late, a pad conditioning tool has been developed, which includes an integrally formed conditioning pad made from relatively hard sapphire material and the dressing particles which are exposed to an exterior more evenly and thus provides longer service life and efficient polishing rate. However, presently wet and dry etching processes are conducted in order to form the dressing particles. Prior to these processes, lithography process is conducted so as to distribute the dressing particles, to define a gap among the dressing particles and the size of the dressing particles. The etching process is conducted to confine the height, the size and the angle of the dressing particles. Since each dressing particle requires at least a height greater than 50 μm, selecting dry etching for forming a photoresist film on the sapphire substrate and taking into account of selectivity (Substrate/photoresist eliminating thickness ratio) smaller than 0.5 in each etching process, a photoresist film of over 100 μm should be coated on the sapphire substrate before going under the dry etching process. It is relatively difficult to evenly coat a photoresist film of over 100 μm on the sapphire substrate, and it is even more important for the lithographic exposure. In addition, since the sapphire material has a relatively high hardness, planarization thereof is not easy and the same, in turn, may affect the lithographic exposure.
The prior art method of transferring image pattern on the sapphire substrate includes applying photoresist film, exposure development and imprinting, after which etching process is conducted, thereby transferring an image pattern on the sapphire substrate. One feature of the above method resides in that several nano-scale tens or thousands meter of image pattern can be transferred. The disadvantages resides in that they are not suitable for generating relatively depth channels or trenches via etching process, like several nano-scale tens or thousands meter of channels, because firstly, relatively thinness of the thin-film cannot withstand the impact of ions during the etching process; secondly, the polymer materials are not suitable for high temperature sulfuric or phosphoric acid etching process. Even though, the service life of the lately developed pad conditioning tool is prolonged owing to provision of the dressing particles on two opposite side surfaces of the conditioning pad, the amount of used materials also increased, which is against the desire of the manufacturers, who want cost down object. The prior art lithographic exposure needs vacuum means to suction one side surface of the sapphire substrate in order to securely retain the former for applying a photoresist coating and overturning the sapphire substrate for another side surface for applying a photoresist coating may cause damage or scratches on the side surfaces. In case of forming through hole in the sapphire substrate for securing the same, vacuum means and applying a photoresist coating cannot be conducted. Moreover, since the sapphire substrate itself is transparent, the penetration of ultraviolet (UV) light through the sapphire substrate during the lithographic exposure may affect the photoresist coating on the other side surface, thereby causing low yield of double-sided photoresist coatings. These disadvantages resulting from the use of prior art pad conditioning tool need to be solved urgently by the manufacturers.
SUMMARY OF THE INVENTION
Therefore, a method for fabricating a pad conditioning tool, which does not suffer the disadvantages mentioned above, the tool serving a longer service life and providing high yield of the finished products is the primary objective of the present invention.
Another objective of the present invention is to provide a method for fabricating a pad conditioning tool includes the steps: preparing a sapphire substrate with a specific orientation plane, wherein the specific orientation plane is selected from a group consisting of a-plane, c-plane, r-plane, m-plane, n-plane and v-plane, utilizing screen printing technique and a screen plate in order to transfer an image pattern such that upon solidifying one side surface of the sapphire substrate is imprinted with the image pattern; and performing an etching process on the side surface of the sapphire substrate such that the side surface is formed with a plurality of micro dressing particles of specific structures.
In the method of the present invention, the materials for transferring the image pattern includes polymer or oligomer or monomer; a photoactive compound (PAC) or photo initiator; an additive, wherein the additive is one of durable wet etching or dry etching materials; and a solvent.
Preferably, the durable wet etching materials include nano-scale particles of SiO2 or TiO2.
Preferably, the sapphire substrate further has another side surface imprinted with another one of the image pattern.
Alternately, the sapphire substrate has opposite side surfaces, which are imprinted with the image patterns via the screen printing transfer technique.
In one step of the present invention, the image pattern imprinted on the side surface of the sapphire substrate via the screen printing transfer technique has a thickness greater than 50 μm, preferably has a thickness greater than 100 μm.
In one step of the present invention, the image pattern imprinted on the side surface of the sapphire substrate via the screen printing transfer technique is generally circular and has a diameter smaller than 50 μm.
In one step of the present invention, the image pattern imprinted on the side surface of the sapphire substrate via the screen printing transfer technique is generally circular and has a diameter smaller than 20 μm.
Preferably, the screen plate is selected from a group consisting of a natural screen fabric, to be more specific, the natural screen fabric is fabricated from natural silk; a composite fabric, to be more specific, the composite fabric is fabricated from nylon fiber, artificial filament of Polyester fiber, carbon fiber, UV fiber, colored fabric, high tensile fabric; and a metal fabric, the metal fabric is fabricated from metallic fibers via electroforming or acid etching process.
In one step of the present invention, the etching process is selected from a group consisting of a wet etching process and a dry etching process.
In one step of the present invention, each of the sapphire dressing particles is shaped like a symmetric truncated cone with a flat head, a symmetric cone, an asymmetric truncated cone with a flat head and an asymmetric cone.
One specific feature of the present invention resides in that transferring the image pattern on the side surface of the sapphire substrate is performed without the use of lithographic exposure so as to provide high efficient dressing particles. The screen printing technique includes single sided screen printing and double-sided screen printing to eliminate the bottle-neck problem encountered during use of the prior art pad conditioning tool.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings, in which:
FIG. 1 shows a block diagram illustrating the steps constituting a method of the present invention for fabricating a pad conditioning tool;
FIG. 2 shows a cross sectional view of a sapphire substrate with a specific orientation plane of the pad conditioning tool fabricated according to the method of the present invention;
FIGS. 3A˜3C illustrate the first embodiment of transferring an image pattern on a side surface of the sapphire substrate in the method of the present invention;
FIGS. 3D˜3G illustrate the first embodiment of performing etching process on the side surface of the sapphire substrate in the method of the present invention;
FIG. 4A illustrates a plurality of dressing particles on the sapphire substrate in the method of the present invention, wherein each dressing particle is shaped like a truncated symmetric cone with a flat head;
FIG. 4B illustrates a plurality of dressing particles on the sapphire substrate in the method of the present invention, wherein each dressing particle is shaped like a truncated asymmetric cone with a flat head;
FIG. 4C illustrates a plurality of dressing particles on the sapphire substrate in the method of the present invention, wherein each dressing particle is shaped like a symmetric cone;
FIG. 4D illustrates a plurality of dressing particles on the sapphire substrate in the method of the present invention, wherein each dressing particle is shaped like an asymmetric cone;
FIGS. 5A˜5C illustrate the second embodiment of transferring image patterns on two side surfaces of the sapphire substrate in the method of the present invention;
FIGS. 5D˜5G illustrate the second embodiment of performing etching process on two side surfaces of the sapphire substrate in the method of the present invention;
FIG. 6A illustrates a cross sectional view the sapphire substrate in the method of the present invention, wherein each dressing particle is shaped like a truncated asymmetric cone with a flat head;
FIG. 6B illustrates a cross sectional view of the sapphire substrate in the method of the present invention, wherein each dressing particle is shaped like a symmetric cone; and
FIG. 6C illustrates a cross sectional view of the sapphire substrate in the method of the present invention, wherein each dressing particle is shaped like an asymmetric cone.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIG. 1 shows a block diagram illustrating the steps constituting a method of the present invention for fabricating a pad conditioning tool. As illustrated, the method of the present invention for fabricating a pad conditioning tool includes; (a) preparing a sapphire substrate with a specific orientation plane, wherein the specific orientation plane is selected from a group consisting of a-plane, c-plane, r-plane, m-plane, n-plane and v-plane; (b) utilizing screen printing technique and a screen plate in order to transfer an image pattern such that upon solidifying one side surface of the sapphire substrate is imprinted with the image pattern; and (c) performing an etching process on the side surface of the sapphire substrate such that the side surface is formed with a plurality of micro dressing particles of specific structures.
FIG. 2 shows a cross sectional view of the sapphire substrate with the specific orientation plane of the pad conditioning tool fabricated according to the method of the present invention. As shown, the sapphire substrate 1 is formed after through crystal nucleation and growth, crystallographic orientation, ingot coring, tail cutting, end plane grinding, cylindrical grinding, multi-wire saw cutting, single or double side lapping and polishing 11, 12 so as to define the specific orientation plane of the sapphire substrate 1. The specific orientation plane is selected from a group consisting of a-plane, c-plane, r-plane, m-plane, n-plane and v-plane. Preferably, the a-plane includes [11 20], [1 210], [2 110], [ 1120], [ 2110] and [ 12 10]; the c-plane includes [0001]; the r-plane includes [10 11], [ 101 1], [01 11], [0 111], [1 10 1] and [ 1101]; the m-plane includes [ 1010], [ 1100], [01 10], [10 10], [1 100] and [0 110]; the v-plane includes [44 83]; and the n-plane includes [22 43].
Referring to FIG. 3A, a screen plate 2 is prepared having a specific image pattern 32. The screen plate 2 is suctioned on the first side surface 11 of the sapphire substrate 1. Preferably, the screen plate 2 is selected from a group consisting of a natural screen fabric, to be more specific, the natural screen fabric is fabricated from natural silk; a composite fabric, to be more specific, the composite fabric is fabricated from nylon fiber, artificial filament of Polyester fiber, carbon fiber, UV fiber, colored fabric, high tensile fabric; and a metal fabric, the metal fabric is fabricated from metallic fibers via electroforming or acid etching process. In order to enhance and stability the screen printing and so as to effectively control the screen printing, metal silk fibers should be selected since the same provides after fabrication sufficient flexibility, excellent chemical resistance, high abrasive effect, fine resolution and do not generate static electricity. One disadvantage is that the cost of metallic silk fiber is relatively expensive and is not easy to recycle the same.
Referring to FIG. 3B, the materials 3 for transferring the image pattern include polymer or oligomer or monomer; a photoactive compound (PAC) or photo initiator; an additive; and a solvent. The above-mentioned additive is selected from one of the durable wet etching or dry etching materials including nano-scale micro dressing particles of SiO2 or TiO2. It is to note that the above-mentioned additive has never been used for transferring the image pattern onto the side surface of the sapphire substrate through the screen printing technique. Also note that the additive can withstand high temperature sulfuric or phosphoric acid etching process so as to enhance transfer of the image patterns on the sapphire substrate 1.
Two clampers 22 are used for clamping the periphery of the sapphire substrate 1. The transferring materials 3 are applied on the screen plate 2 via a scraper 21 in the same direction in order to transfer the image pattern 31 on the first side surface 11 of the sapphire substrate 1. Through the screen printing technique, the image pattern 31 imprinted on the first side surface 11 of the sapphire substrate 1 has a thickness greater than 100 μm, which is preferred to the height of the micro dressing particles (generally greater than 50 μm, 100 μm provides the maximum effect).
Regarding the height of the micro dressing particles, the image pattern imprinted on the side surface of the sapphire substrate via the screen printing transfer technique is generally circular and has a diameter smaller than 50 μm. In case, the diameter is smaller than 20 μm, the external surface area is relatively small and provides a more pressing force, and hence resulting in the best conditioning effect.
Referring to FIG. 3C, after removal of the screen plate 2 off the first side surface of the sapphire substrate, the solidifying process includes exposure of UV light, baking and adding chemical additive such that upon solidification, the image pattern 31 is imprinted on the first side surface 11.
FIGS. 3D˜3G illustrate the first embodiment of performing etching process on a side surface of the sapphire substrate in the method of the present invention.
As shown in FIG. 3D, etching process is conducted on the first side surface 11, which includes dry and wet etching methods. Preferably, the most preferred rate of less than 0.5 provides the best transferred image pattern.
Referring to FIG. 3E, after a period of wet etching process, the image pattern 31 is etched partially so as to form the micro structure 4.
Referring to FIG. 3F, after finishing of the etching process, the transferred image pattern 31 is partially wiped off and the first side surface 11 thereof is cleaned entirely.
FIG. 3G illustrates a cross sectional view of the sapphire substrate 1 fabricated according to the method of the present invention, wherein the micro structure 4 includes a plurality of micro dressing particles 41. Each micro dressing particle 41 is shaped like a truncated symmetric cone with a flat head.
Referring to FIGS. 4A˜4D, wherein, FIG. 4A illustrates a plurality of micro dressing particles 41 on the sapphire substrate 1 in the method of the present invention, wherein each micro dressing particle 41 is shaped like a truncated symmetric cone with a flat head; FIG. 4B illustrates a plurality of micro dressing particles 42 on the sapphire substrate 1 in the method of the present invention, wherein each micro dressing particle 42 is shaped like a truncated asymmetric cone with a flat head; FIG. 4C illustrates a plurality of micro dressing particles 43 on the sapphire substrate 1 in the method of the present invention, wherein each micro dressing particle 43 is shaped like a symmetric cone; and FIG. 4D illustrates a plurality of micro dressing particles 44 on the sapphire substrate 1 in the method of the present invention, wherein each micro dressing particle 44 is shaped like an asymmetric cone. It is to note that the sapphire substrate having the micro structure 4 of different configurations are achieved by the steps constituting the method of the present invention including the specific orientation plane, ratio of transferring materials and etching processes etc, a detailed description thereof is omitted herein for the sake of brevity.
FIGS. 5A˜3C illustrate the second embodiment of transferring image patterns on two side surfaces of the sapphire substrate in the method of the present invention.
Also referring again to FIG. 2, the cross sectional view of the sapphire substrate 1 has a specific orientation plane, wherein the specific orientation plane is selected from a group consisting of a-plane, c-plane, r-plane, m-plane, n-plane and v-plane. Preferably, the a-plane includes [11 20], [1 210], [2 110], [ 1120], [ 2110] and [ 12 10]; the c-plane includes [0001]; the r-plane includes [10 11], [ 10 11], [01 11], [0 111], [1 10 1] and [ 1101]; the m-plane includes [ 1010], [ 1100], [01 10], [10 10], [1 100] and [0 110]; the v-plane includes [44 83]; and the n-plane includes [22 43].
Referring to FIG. 5A, two screen plates 2 are prepared each having a specific image pattern 32. Preferably, each of the screen plates 2 is selected from a group consisting of a natural screen fabric, to be more specific, the natural screen fabric is fabricated from natural silk; a composite fabric, to be more specific, the composite fabric is fabricated from nylon fiber, artificial filament of Polyester fiber, carbon fiber, UV fiber, colored fabric, high tensile fabric; and a metal fabric, the metal fabric is fabricated from metallic fibers via electrocasting or acid etching process. In order to enhance stability and the screen printing so as to effectively control the screen printing, metal silk fibers should be selected since the same provides after fabrication sufficient flexibility, excellent chemical resistance, high abrasive effect, fine resolution and do not generate static electricity. One disadvantage is that the cost of metallic silk fiber is relatively expensive and is not easy to recycle the same.
The materials 3 for transferring the image patterns on the first and second side surfaces 11, 12 includes polymer or oligomer or monomer; a photoactive compound (PAC) or photo initiator; an additive; and a solvent. The above-mentioned additive is selected from one of the durable wet etching (H2SO4+H3PO4) or dry etching materials (BCl3+Cl2+Ar) including nano-scale micro dressing particles of SiO2 or TiO2. It is to note that the above-mentioned additive has never been used for transferring the image patterns onto the side surfaces of the sapphire substrate through the screen printing technique. Also note that the additive can withstand high temperature sulfuric or phosphoric acid etching process so as to enhance transfer of the image pattern on the sapphire substrate 1.
After defining the image patterns 31 on two screen plates 2, they are suctioned on the first and second side surfaces 11, 12 of the sapphire substrate 1.
Referring to FIG. 5B, two clampers 22 are used for clamping the periphery of the sapphire substrate 1. The transferring materials 3 are applied on the screen plates 2 via two scrapers in the same direction in order to transfer the image patterns 31 on the first and second side surfaces 11, 12 of the sapphire substrate 1 respectively. Through the screen printing technique, the image patterns 31 imprinted on the first and second side surfaces 11, 12 of the sapphire substrate 1 each has a thickness greater than 100 μm, which is preferred to the height of the micro dressing particles (generally greater than 50 μm, 100 μm provides the maximum effect).
The materials 3 for transferring the image patterns on the first and second side surfaces 11, 12 are the same as the previous ones, the only difference resides in that the density of transferring materials differ owing to different ground gravity relative to the first and second (upper and lower) side surfaces 11, 12. The density should be adjusted according to the actual requirement.
Referring to FIG. 5C, after removal of the screen plates 2 off the first and second side surfaces of the sapphire substrate, the solidifying process includes exposure of UV light, baking and adding chemical additive such that upon solidification, the image patterns 31 are imprinted on the first and second side surfaces 11, 12 respectively.
FIGS. 5D˜5G illustrate the second embodiment of performing etching process on two side surfaces of the sapphire substrate in the method of the present invention.
Referring to FIG. 5D, etching processes are conducted on the first and second side surfaces 11, 12 which include dry and wet etching methods. Preferably, the wet etching method is preferred to herein.
Referring to FIG. 5E, after a period of wet etching process, the image patterns 31 are etched partially so as to form the micro structure 4.
Referring to FIG. 5F, after finishing of the etching process, the transferred image patterns 31 are partially wiped off and the first and second side surfaces 11, 12 thereof are cleaned entirely.
FIG. 5G illustrates a cross sectional view of the sapphire substrate 1 fabricated according to the method of the present invention, wherein the micro structure 4 includes a plurality of micro dressing particles 41. Each micro dressing particle 41 is shaped like a truncated symmetric cone with a flat head.
Referring to FIGS. 6A˜6C, wherein FIG. 6A illustrates a cross sectional view of the sapphire substrate 1 in the method of the present invention, wherein each micro dressing particle 42 is shaped like a truncated asymmetric cone with a flat head; FIG. 6B illustrates a cross sectional view of the sapphire substrate in the method of the present invention, wherein each micro dressing particle 43 is shaped like a symmetric cone; and FIG. 6C illustrates a cross sectional view of the sapphire substrate in the method of the present invention, wherein each micro dressing particle 44 is shaped like an asymmetric cone. It is to note that the sapphire substrate having the micro structure 4 of different configurations are achieved by the steps constituting the method of the present invention including the specific orientation plane, ratio of transferring materials and etching processes etc, a detailed description thereof is omitted herein for the sake of brevity.
It is to note that owing to the formation of micro dressing particles on two side surfaces of the sapphire substrate 1, in case the micro dressing particles on one side surface get blunt after a long period of use, the micro dressing particles on the other side surface thereof can be applied, thereby prolonging the service life of the pad conditioning tool fabricated according to the method of the present invention.
Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
Patent Application
20150027063
