An edge-coupled light guide polishing pad-based photocatalytic polishing device and method

Abstract

This invention discloses a photocatalytic polishing device based on an edge-coupled light-guiding polishing pad, comprising a polishing disk and a polishing pad fixedly disposed on the surface of the polishing disk. At least one set of polishing heads movable vertically relative to the polishing pad is disposed above the polishing pad. A ring-shaped light source array is disposed along the circumference of the side edge of the polishing pad, the ring-shaped light source array consisting of multiple independently controllable light sources. Multiple grooves are disposed on the surface of the polishing pad, and both sides of the grooves are inclined. This invention also discloses a photocatalytic polishing method based on an edge-coupled light-guiding polishing pad. By using the polishing pad as a light waveguide medium, the light source is introduced laterally from the edge of the polishing pad and overflows upwards from the micro-grooves at the polishing interface, completely solving the problem of light obstruction by the wafer head and ensuring that the entire surface of the silicon carbide wafer is continuously subjected to uniform photocatalytic and photorheological excitation.

Description

Technical Field

[0001] This invention relates to a photocatalytic polishing device and method based on an edge-coupled light guide polishing pad, belonging to the field of ultra-precision processing of semiconductor materials and semiconductor equipment manufacturing technology. Background Technology

[0002] Silicon carbide (SiC), as a third-generation semiconductor material, possesses excellent properties such as a high bandgap and high thermal conductivity. However, its high Mohs hardness (close to 9.5) and extremely strong chemical stability make it a hard and brittle material that is extremely difficult to process. Chemical mechanical polishing (CMP) is the core technology for achieving sub-nanometer-level ultra-flat surface damage on SiC wafers.

[0003] In recent years, to overcome the bottleneck of high-efficiency ultra-precision polishing of SiC, the industry has developed polishing slurries and processing methods based on the dual coupling effect of photocatalysis and photorheology. This method generates highly reactive free radicals in situ in the working area through light irradiation, while simultaneously inducing a reversible phase transition in the polishing slurry to increase local viscosity, achieving dual photo-controlled dynamic regulation of chemical oxidation and mechanical shearing. However, to fully utilize the advantages of the aforementioned photoresponsive polishing slurries, the placement of the light source and the method of introducing the light field in the polishing device have become urgent engineering challenges. Existing light source placement methods mainly face the following three major difficulties: Top external light source: Light shines from above, but the area directly above the polishing interface is completely blocked by the opaque wafer carrier head. The light can only reach the outer edge of the polishing pad, resulting in a lack of in-situ illumination in the working area (the contact area between the wafer and the pad). The free radicals generated by photocatalysis have extremely short lifetimes (microseconds) and cannot effectively diffuse to the center of the wafer.

[0004] Bottom-windowed light source: A transparent quartz window is partially opened on the polishing pad and polishing disc, and the light source shines upwards. This method only illuminates the wafer when it passes through the window, resulting in an extremely low duty cycle. Furthermore, the hard quartz window disrupts the mechanical continuity of the polyurethane polishing pad, making it very easy to cause scratches on the wafer surface.

[0005] Pre-excitation light source in the pipeline: Illumination is performed in the supply pipeline before the polishing slurry is dripped. Although this avoids shading, it cannot utilize photorheological effects to provide in-situ high shear mechanical holding force at the wafer-polishing pad interface.

[0006] Therefore, how to design a novel light source introduction device that is unobstructed, fully covered, and does not compromise the mechanical consistency of the polishing pad, and achieve "in-situ emission from the interface", is a key challenge in the current field of light-assisted CMP equipment. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a photocatalytic polishing device and method based on an edge-coupled light guide polishing pad. By using the polishing pad as a light waveguide medium, the light source is introduced laterally from the edge of the polishing pad and overflows upward from the micro-grooves of the polishing interface, which completely solves the problem of light blocking by the wafer head and ensures that the entire surface of the silicon carbide wafer is continuously subjected to uniform photocatalysis and photorheological excitation.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A photocatalytic polishing device based on an edge-coupled light-guiding polishing pad includes a polishing disk and a polishing pad fixedly disposed on the surface of the polishing disk. At least one set of polishing heads that can move up and down relative to the polishing pad are disposed above the polishing pad. A ring light source array is disposed along the circumference of the side edge of the polishing pad. The ring light source array is composed of multiple independently controllable light sources. The surface of the polishing pad is provided with multiple grooves, and both sides of the grooves are inclined.

[0009] The aforementioned photocatalytic polishing device based on an edge-coupled light guide polishing pad is characterized in that: the polishing pad is made of modified polyurethane material with a light transmittance ≥10%, a thickness of 1.5mm-2.5mm, and a groove depth ≥0.254mm.

[0010] The aforementioned photocatalytic polishing device based on an edge-coupled light-guiding polishing pad is characterized in that: the grooves on the surface of the polishing pad are arranged in a grid pattern, the top width of the groove is 0.8 mm, the depth is 0.6 mm, the spacing between adjacent grooves is 8 mm, and the cross-section of the groove is a V-shaped structure.

[0011] The aforementioned photocatalytic polishing device based on an edge-coupled light guide polishing pad is characterized in that: eight independently controllable light sources are equally distributed on the side edge of the polishing pad, and the light sources inject ultraviolet / violet composite beams with wavelengths of 365~405nm.

[0012] The aforementioned photocatalytic polishing device based on an edge-coupled light guide polishing pad is characterized in that: the polishing disk is provided with a position sensor for detecting its position relative to the polishing head.

[0013] The aforementioned photocatalytic polishing device based on an edge-coupled light guide polishing pad is characterized in that: the side of the polishing pad (20) is polished and then used as the light-incident surface.

[0014] A polishing method using the aforementioned photocatalytic polishing device based on an edge-coupled light guide polishing pad includes the following steps: The polishing head presses the silicon carbide wafer onto the polishing pad, and the polishing liquid is continuously dripped onto the surface of the polishing pad; The polishing disc and polishing head rotate at their respective set speeds; The system dynamically controls the illumination of the light source corresponding to the polishing pad area covered by the silicon carbide wafer below the polishing head, while simultaneously controlling the other light sources to turn off, until the silicon carbide wafer polishing is completed.

[0015] The aforementioned photocatalytic polishing method based on edge-coupled light guide polishing pad is characterized in that: the surface area of ​​the polishing pad is divided into 8 corresponding sectors according to 8 independently controlled light sources; when a portion or all of the corresponding sector is covered by a silicon carbide wafer, the light source corresponding to that sector is controlled to be lit; when the silicon carbide wafer leaves the sector, the light source is immediately turned off.

[0016] The beneficial effects of this invention are: 1. Eliminate obstruction and achieve 100% in-situ full coverage illumination: The polishing pad is innovatively used as the optical waveguide medium. The light source is introduced laterally from the edge and overflows upward from the micro-groove of the polishing interface, which completely solves the problem of light obstruction by the wafer head and ensures that the entire surface of the silicon carbide wafer is continuously subjected to uniform photocatalysis and photorheological excitation. 2. Maintain mechanical consistency and avoid window scratches: There is no need to create a quartz transparent window on the polishing pad that would disrupt the mechanical uniformity. The original elastic modulus and mechanical continuity of the polishing pad are maintained by using the principle of total internal reflection light guiding, which fundamentally eliminates wafer scratch defects caused by "hard windows". 3. Adaptive local light field to optimize polishing slurry life and chip removal: Through sector tracking dynamic lighting mechanism, high viscosity and high chemical activity are only excited in the working area (directly below the wafer), while the non-working area remains in a light-proof state, avoiding excessive reaction and degradation of the polishing slurry throughout the entire wafer, perfectly meeting the kinetic requirements of photocatalytic-photorheological polishing slurry: "gelation and strong shear in the working area, and low viscosity and easy chip removal in the non-working area". Attached Figure Description

[0017] Figure 1 This is a side view of a photocatalytic polishing device based on an edge-coupled light guide polishing pad according to the present invention; Figure 2 This is a top view of a photocatalytic polishing device based on an edge-coupled light guide polishing pad according to the present invention; Figure 3 for Figure 2 AA section view; Figure 4 This is a side view of the polishing pad of a photocatalytic polishing device based on an edge-coupled light guide polishing pad according to the present invention; Figure 5 This is a schematic diagram of the optical path inside the polishing pad of a photocatalytic polishing device based on an edge-coupled light-guiding polishing pad according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may include different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0020] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0021] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0022] like Figures 1-5As shown, a photocatalytic polishing device based on an edge-coupled light-guiding polishing pad includes a polishing disk 10 and a polishing pad 20 fixedly disposed on the surface of the polishing disk 10. At least one set of polishing heads 40 that can move up and down relative to the polishing pad 20 are disposed above the polishing pad 20. A ring light source array is disposed along the circumference of the side edge of the polishing pad 20. The ring light source array is composed of multiple independently controllable light sources 30. A plurality of grooves 21 are disposed on the surface of the polishing pad 20, and the two sides of the grooves 21 are inclined.

[0023] By controlling the light to enter from the side of the polishing pad 20, relying on the principle of total internal reflection, the light is transmitted forward by reflecting back and forth in a sawtooth pattern inside the polishing pad 20. For example... Figure 5 As shown, according to the principle of fiber optic waveguides, light is confined within this thin layer for lateral transmission. During transmission, some light encounters the inclined side of the trench 21. Since the incident angle no longer satisfies the condition of total internal reflection, this portion of light will overflow upwards from the trench 21. Figure 5 (As shown by the red arrow in the middle), while another portion of the light still satisfies the condition of total internal reflection and continues to propagate inside the polishing pad 20 ( Figure 5 (As indicated by the blue arrow in the middle). To better ensure that light can enter from the side of the polishing pad, the side of the polishing pad 20 is polished to serve as the light-incident surface.

[0024] The light overflowing from the groove 21 illuminates the polishing slurry on the surface of the polishing pad 20, thereby stimulating the slurry to generate a high concentration of free radicals. This rapidly oxidizes and softens the silicon carbide surface to be processed, while simultaneously inducing a local viscosity spike in the polishing slurry, forming a high-viscosity gel that "clamps" the abrasive grains, applying strong mechanical shearing force and improving the polishing effect. In this embodiment, the polishing pad is innovatively used as an optical waveguide medium. The light source is introduced laterally from the edge and overflows upward from the micro-grooves at the polishing interface, completely solving the problem of light blocking by the wafer head and ensuring that the entire surface of the silicon carbide wafer is continuously subjected to uniform photocatalysis and photorheological excitation.

[0025] Specifically, the polishing pad 20 is made of modified polyurethane material with a light transmittance ≥10% and a thickness of 1.5mm-2.5mm. The groove 21 has a depth ≥0.254mm. Specifically, a light transmittance >10% ensures that ultraviolet / violet light input from the edge can smoothly penetrate to the area of ​​the polishing pad surface in contact with the polishing slurry, effectively stimulating the photocatalyst (such as TiO2) in the polishing slurry to undergo a photocatalytic reaction, generating highly active free radicals. A thickness of 1.5mm-2.5mm balances light guiding and mechanical properties. Excessive thickness leads to increased light transmission attenuation and decreased light transmittance; excessive thinness affects the polishing pad's wear resistance, service life, and rigid support during processing. A depth ≥0.254mm, preferably 0.6mm, ensures sufficient flow and storage space for the polishing slurry, preventing dry friction caused by an excessively thin liquid film during polishing, and ensuring smooth discharge of polishing debris.

[0026] The grooves 21 on the surface of the polishing pad 20 are arranged in a grid pattern, ensuring a uniform distribution of the groove structure across the surface of the polishing pad 20. This facilitates more even light emission. The top width of each groove 21 is 0.8 mm, the depth is 0.6 mm, and the spacing between adjacent grooves is 8 mm. The groove 21 has a V-shaped cross-section, which facilitates light emission and allows byproducts such as grinding debris to be smoothly discharged with the polishing fluid. The 0.8 mm width and 8 mm spacing at the top of the grooves 21 optimize the contact area ratio of the polishing pad surface. A reasonable spacing and width ensure uniform polishing pressure distribution while maintaining a high density of light emission points. The V-shaped cross-section utilizes the refraction / reflection properties of the V-shaped sidewalls to guide light from the interior of the polishing pad to the surface more effectively. Simultaneously, the fully open inclined structure significantly reduces flow resistance, facilitating the smooth discharge of grinding debris and reaction byproducts with the polishing fluid and preventing groove blockage.

[0027] Eight independently controllable light sources 30 are evenly distributed along the side edge of the polishing pad 20. The light sources 30 inject ultraviolet / violet composite beams with wavelengths of 365~405 nm. During actual polishing operations, the state of the polishing slurry is adjusted by dynamically controlling the lighting and extinguishing of these eight light sources in real time. Specifically, the surface area of ​​the polishing pad is divided into eight corresponding sectors according to the eight independently controllable light sources. When a portion or all of the corresponding sector is covered by the silicon carbide wafer, the light source corresponding to the covered sector is lit, and the light overflows upward in that area, thereby stimulating the polishing slurry to generate high-concentration free radicals, which rapidly oxidize and soften the SiC surface. At the same time, it induces a local viscosity spike in the polishing slurry, forming a high-viscosity gel that "clamps" the abrasive grains, applying strong mechanical shear removal force. When the sector leaves the silicon carbide wafer, the corresponding light source is immediately turned off. Because there is no light in that area, the polishing slurry instantly returns to a low-viscosity fluid, and the polishing debris and by-products generated during polishing are smoothly discharged from the polishing pad through the groove 21 with the low-viscosity fluid.

[0028] It should be noted that in this embodiment, the polishing head 40 is disposed at the edge of the polishing pad 20 (e.g., Figure 2 As shown in the figure, when the light source corresponding to the sector covered by the silicon carbide wafer below the polishing head 40 is lit, some light will be reflected into the adjacent unlit sector. However, the light reaching the unlit sector has weakened, and the area covered by silicon carbide is relatively small compared to the uncovered area. There is almost no light overflow in the unlit area far from the lit area. Therefore, the impact on the state of the polishing slurry is very small, and it will not have a substantial impact on the polishing effect.

[0029] In order to better control the lighting time of the light source corresponding to the sector covered by the silicon carbide wafer, a position sensor can be set on the polishing disk 10 to detect its position relative to the polishing head 40. Alternatively, the lighting time and duration of the corresponding light source 30 can be calculated by the rotation speed of the polishing head 40 and the polishing disk 10.

[0030] The present invention also provides a polishing method for a photocatalytic polishing device based on an edge-coupled light guide polishing pad, comprising the following steps: a polishing head 40 presses a silicon carbide wafer onto a polishing pad at a pressure of 250 g / cm², and a polishing liquid containing a TiO2 photocatalyst and a photosensitive rheology dispersant is continuously dripped onto the surface of the polishing pad 20. The polishing disc 10 and the polishing head 40 rotate at their respective set speeds; the light source 30 corresponding to the polishing pad 20 area covered by the silicon carbide wafer under the polishing head 40 is dynamically controlled to be lit, while the other light sources 30 are simultaneously controlled to be turned off, until the silicon carbide wafer polishing is completed.

[0031] The light source corresponding to the position directly below the silicon carbide wafer (working area) is illuminated. The side-injected light overflows upward through the trench, in-situ exciting the polishing slurry to generate a high concentration of free radicals, which rapidly oxidize and soften the SiC surface. At the same time, it induces a local viscosity surge in the polishing slurry, forming a high-viscosity gel that "clamps" the abrasive grains, applying strong mechanical shearing removal force. When the polishing pad 20 rotates away from under the wafer and enters the non-working area, the corresponding light source is turned off. Therefore, there is no light in this area, and the polishing slurry instantly returns to a low-viscosity fluid. The abrasive debris and by-products generated during polishing are smoothly discharged from the polishing pad with the low-viscosity fluid.

[0032] In this embodiment, the surface area of ​​the polishing pad 20 is divided into eight corresponding sectors according to eight independently controlled light sources 30. When a portion or all of a corresponding sector is covered by a silicon carbide wafer, the light source 30 corresponding to that sector is turned on. When the silicon carbide wafer leaves the sector, the light source is immediately turned off. The lighting and extinguishing of the light sources 30 can be determined by detecting the position of the polishing head 40 relative to the polishing pad 20 using a position sensor, or by calculating the relative position of the polishing head 40 and the polishing disc 10 based on their rotation speed, thereby controlling the lighting and extinguishing of the corresponding light sources 30. Both of these techniques are existing conventional techniques and will not be elaborated further here.

[0033] In summary, this invention provides a photocatalytic polishing device and method based on an edge-coupled light-guiding polishing pad. By using the polishing pad as a light waveguide medium, the light source is introduced laterally from the edge of the polishing pad and overflows upward from the micro-grooves of the polishing interface, which completely solves the problem of light blocking by the wafer head and ensures that the entire surface of the silicon carbide wafer is continuously subjected to uniform photocatalysis and photorheological excitation.

[0034] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A photocatalytic polishing device based on an edge-coupled light-guiding polishing pad, comprising a polishing disk (10) and a polishing pad (20) fixedly disposed on the surface of the polishing disk (10), wherein at least one set of polishing heads (40) movable vertically relative to the polishing pad (20) is disposed above the polishing pad (20), characterized in that: The polishing pad (20) has a ring light source array along its circumference at the side edge. The ring light source array consists of multiple independently controllable light sources (30). The surface of the polishing pad (20) has multiple grooves (21), and both sides of the grooves (21) are inclined.

2. The photocatalytic polishing device based on an edge-coupled light guide polishing pad according to claim 1, characterized in that: The polishing pad (20) is made of modified polyurethane material with a light transmittance of ≥10% and a thickness of 1.5mm-2.5mm. The groove (21) has a depth of ≥0.254mm.

3. The photocatalytic polishing device based on an edge-coupled light guide polishing pad according to claim 2, characterized in that: The grooves (21) on the surface of the polishing pad (20) are arranged in a grid pattern. The top width of the groove (21) is 0.8 mm, the depth is 0.6 mm, the spacing between adjacent grooves is 8 mm, and the cross-section of the groove (21) is a V-shaped structure.

4. A photocatalytic polishing device based on an edge-coupled light guide polishing pad according to any one of claims 1-3, characterized in that: The polishing pad (20) has eight independently controllable light sources (30) evenly distributed on its side edge, and the light sources (30) inject ultraviolet / violet composite beams with wavelengths of 365~405 nm.

5. The photocatalytic polishing device based on an edge-coupled light guide polishing pad according to claim 1, characterized in that: The polishing disc (10) is provided with a position sensor for detecting its position relative to the polishing head (40).

6. The photocatalytic polishing device based on an edge-coupled light guide polishing pad according to claim 1, characterized in that: The side of the polishing pad (20) is polished to serve as the light-receiving surface.

7. A polishing method using the photocatalytic polishing apparatus based on an edge-coupled light-guiding polishing pad as described in any one of claims 1-6, characterized in that: Includes the following steps: The polishing head (40) presses the silicon carbide wafer onto the polishing pad, and the polishing liquid is continuously dripped onto the surface of the polishing pad (20); The polishing disc (10) and the polishing head (40) rotate at their respective set speeds; The light source (30) corresponding to the area of ​​the polishing pad (20) covered by the silicon carbide wafer under the dynamic control polishing head (40) is lit, and the other light sources (30) are turned off at the same time until the silicon carbide wafer polishing is completed.

8. The photocatalytic polishing method based on an edge-coupled light guide polishing pad according to claim 7, characterized in that: The surface area of ​​the polishing pad (20) is divided into 8 corresponding sectors according to 8 independently controlled light sources (30). When a part or all of the corresponding sector is covered by a silicon carbide wafer, the light source (30) corresponding to that sector is controlled to be lit. When the silicon carbide wafer leaves the sector, the light source is immediately turned off.

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