A polishing head and a polishing apparatus

Abstract

The embodiment of the present application discloses a polishing head and a polishing device, the polishing head comprising: a head body; a rubber pad connected to the lower surface of the head body, the rubber pad being arranged to be able to produce elastic deformation towards the lower based on the working pressure from the head body; a mold pad between the rubber pad and the silicon wafer to be polished, the shape of the upper surface of the mold pad is arranged so that when the polishing head polishes the silicon wafer, the upper surface of the mold pad can adapt to the elastic deformation of the rubber pad, so that the working pressure borne by the upper surface of the silicon wafer is uniform.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more particularly to a polishing head and polishing equipment. Background Technology

[0002] In the silicon wafer manufacturing process, final polishing (FP) is the last step in controlling the flatness and roughness parameters of the silicon wafer. Final polishing removes a certain amount of material from the silicon wafer surface to eliminate defects from previous processes and to achieve a mirror-like finish.

[0003] During photolithography (FP) operations, the most commonly used implementation method is chemical mechanical polishing (CMP). In CMP, a silicon wafer is pressed against a vibrating polishing table with a polishing pad using a polishing head, while a slurry of abrasive particles is supplied to the polishing pad. However, because the working pressure from the polishing head is often concentrated in the central area of ​​the polishing head, the distribution of working pressure transmitted to the surface of the silicon wafer to be polished is also uneven. Specifically, the force on the central area of ​​the silicon wafer is greater than that on other areas. This results in the amount of material removed from the central area of ​​the silicon wafer surface being greater than that removed from the edge areas during the polishing process, thus causing a deterioration in the flatness of the silicon wafer surface. Summary of the Invention

[0004] In view of this, embodiments of the present invention aim to provide a polishing head and polishing equipment that enable silicon wafers to be polished under uniform working pressure, thereby improving the quality of silicon wafer planarization.

[0005] The technical solution of this invention is implemented as follows:

[0006] In a first aspect, embodiments of the present invention provide a polishing head, the polishing head comprising: a head body; a rubber pad connected to a lower surface of the polishing head, the rubber pad being configured to undergo downward elastic deformation based on working pressure from the head body; and a mold pad located between the rubber pad and a silicon wafer to be polished, the upper surface of the mold pad being shaped such that when the polishing head polishes the silicon wafer, the upper surface of the mold pad can adapt to the elastic deformation of the rubber pad, so that the working pressure borne by the upper surface of the silicon wafer is uniform.

[0007] Secondly, embodiments of the present invention provide a polishing apparatus, the polishing apparatus including a polishing head according to the first aspect.

[0008] This invention provides a polishing head and a polishing device. The polishing head adds a mold pad between a rubber pad and a silicon wafer. The upper surface of the mold pad has a shape adapted to the elastic deformation of the rubber pad, which allows the working pressure to be uniformly transmitted to the entire upper surface of the silicon wafer located below the mold pad. This uniform working pressure presses the silicon wafer onto the polishing pad, achieving a uniform polishing removal amount on the silicon wafer surface, thereby improving the flatness of the silicon wafer surface. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of a conventional polishing equipment.

[0010] Figure 2 The image shows the morphology of the silicon wafer after polishing using conventional polishing equipment.

[0011] Figure 3 A schematic diagram of a polishing head provided in an embodiment of the present invention;

[0012] Figure 4 Top and front views of a mold pad provided for another embodiment of the present invention;

[0013] Figure 5 Top and front views of a mold pad provided for another embodiment of the present invention;

[0014] Figure 6 Top and front views of a mold pad provided for another embodiment of the present invention;

[0015] Figure 7 A schematic diagram of a polishing head provided in another embodiment of the present invention;

[0016] Figure 8 This is a schematic diagram of a polishing device provided in an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0019] After the DSP process, silicon wafers typically have minor surface damage. To remove this damage and create a mirror finish while continuously improving flatness, photolithography (FP) is usually performed. A typical FP process involves bringing a polishing head carrying the silicon wafer into contact with a polishing pad mounted on a lower platen. The silicon wafer surface undergoes a chemical reaction with colloidal slurry and chemicals supplied through a slurry tube, and is polished by a physical reaction caused by mechanical pressure.

[0020] Specifically, silicon wafers that have completed the DSP process are placed in a cleaning machine. After exiting the cleaning machine, they undergo FP (Production Process) operations. The complete FP process includes three polishing operations, as follows: First, the silicon wafer undergoes the first FP step, also known as stock polishing. This step removes surface defects caused by previous processes and creates a mirror finish. This step adjusts the abrasive particles and the flatness of the entire silicon wafer surface. After the stock polishing step, the second FP step is performed. This step adjusts the abrasive particles by using the minimum abrasive amount to adjust the roughness of the silicon wafer surface. After the second FP step, the third FP step is performed. This step adjusts the micro-roughness and fine particles of the silicon wafer surface and completes the finishing work. After completing the above three FP steps, the silicon wafer undergoes a simple surface cleaning in the equipment and is finally placed into the unloading cassette. Once the unloading cassette is full of silicon wafers, it enters the waiting process.

[0021] For the first FP step in the above workflow, i.e., the rough polishing step, during the operation, the conventional polishing equipment 10 used to perform this step is as follows: Figure 1As shown, the device 10 may include: a polishing table 11, a polishing pad 12 disposed on the upper surface of the polishing table 11 by means of adhesion or other methods, and a drive shaft 13 disposed below the polishing table 11. The polishing table 11 can be rotated by the drive shaft 13, so the polishing pad 12 can also rotate in response to the rotation of the polishing table 11. For example, when the drive shaft 13 rotates in a clockwise direction, the polishing table 11 and the polishing pad 12 rotate together in a clockwise direction. Furthermore, a polishing head 14 is disposed above the polishing table 11. The polishing head 14 may include at least: a head body 141 and a rotary drive 142 connected to the head body 141 by fasteners. Below the head body 141 is an assembly mold 143. A rubber pad 144 and a silicon wafer S to be polished are housed within a first receiving cavity CS1 formed by the assembly mold 143. The rubber pad 144 is connected to the head body 141, and compressed dry air (CDA) is supplied to the first receiving cavity CS1 of the assembly mold 143 through a vacuum / air pipe 145 to form a working pressure. This working pressure acts on the rubber pad 144 and is transmitted to the silicon wafer S to be polished via the rubber pad 144. It should be noted that the rotary drive 142 can rotate the head body 141, thereby causing the head body 141 and the silicon wafer S to be polished within the first receiving cavity CS1 of the assembly mold 143 to rotate in response to the rotation of the head body 141. For example, when the rotary drive 142 rotates counterclockwise, the head body 141 and the silicon wafer S to be polished also rotate counterclockwise. Understandably, the rotation directions of the drive shaft 13 and the rotary drive 142 may be the same or different. Furthermore, the device 10 may also include a nozzle 15 disposed in the space above the polishing pad 12 and near the center of the polishing pad 12, which can be connected to a storage tank for storing polishing fluid. Figure 1 (Not shown in the image), the flow rate of the polishing fluid is controlled by a valve.

[0022] During the polishing operation, the rotating polishing head 14 presses against the rotating polishing pad 12 with a certain working pressure. A polishing slurry, composed of submicron or nano-sized abrasive particles and a chemical solution, drips from the nozzle 15 onto the polishing pad 12, flowing between the surface of the silicon wafer S and the polishing pad 12. Then, under the transmission and centrifugal force of the polishing pad 12, the polishing slurry is evenly distributed on the polishing pad 12, thereby forming a thin film of polishing slurry between the silicon wafer S and the polishing pad 12. The chemical components in the polishing slurry react chemically with the surface material of the silicon wafer, converting insoluble substances into soluble substances or softening hard substances. These chemical reactants are then removed from the silicon wafer surface by the micromechanical friction of the abrasive particles and dissolved into the flowing slurry, thus achieving planarization through the alternating process of chemical film formation and mechanical film removal.

[0023] In addition, to promote the distribution of polishing slurry on the polishing pad, the device 10 may also include a vibrator 16 disposed on the polishing table 11, the vibrator 16 being configured to cause the polishing table to vibrate, thereby helping to adjust the distribution of the polishing slurry. Moreover, in order to be able to adjust the distribution of polishing slurry in a timely manner as needed, the device 10 also includes a transmission 17 for controlling the rotational speed of the drive shaft 13, thereby adjusting the rotational speed of the polishing table 11.

[0024] However, in the aforementioned polishing operation, because the working pressure is concentrated in the central area of ​​the rubber pad 144, the rubber pad 144 under stress has a concave arc shape. This means that the rubber pad 144 cannot evenly transmit the working pressure to the entire surface. The edges of the rubber pad 144 may even fail to act on the silicon wafer, meaning the working pressure cannot be transmitted to the edge areas of the silicon wafer. This results in the polishing removal amount at the edge areas of the silicon wafer surface being less than that in the central area. This uneven polishing removal ultimately leads to a deterioration in the flatness of the silicon wafer surface. For example, please refer to... Figure 2 The diagram shows the morphology of a silicon wafer after polishing using conventional polishing equipment. The curves represent the approximate amount of material removed during polishing of the corresponding portion of the wafer below the curve, while the values ​​below the curve represent the amount of material removed during polishing of that corresponding portion. If the incoming material itself has a large defect depth, requiring an increased removal amount in the final polishing process, the flatness will further deteriorate.

[0025] To improve the flatness of the polished silicon wafer surface, embodiments of the present invention propose an improved polishing head structure to transmit uniform working pressure to the silicon wafer surface, thereby improving the morphology parameters of the polished silicon wafer. Based on this, see [link to relevant documentation]. Figure 3 It illustrates a polishing head 20 provided in an embodiment of the present invention, which can replace... Figure 1 The polishing head 14 in the middle enables the uniform working pressure to be transmitted to the silicon wafer, so that the silicon wafer is polished under uniform working pressure, thereby improving the flatness of the polished silicon wafer.

[0026] like Figure 3 As shown, the polishing head 20 includes: a head body 141; a rubber pad 144 connected to the lower surface of the head body 141, the rubber pad 144 being configured to generate downward elastic deformation based on the working pressure from the head body 141; and a mold pad 21 located between the rubber pad 144 and the silicon wafer S to be polished, the upper surface of the mold pad 21 being shaped such that when the polishing head 20 polishes the silicon wafer S, the upper surface of the mold pad 21 can adapt to the elastic deformation of the rubber pad 144, so that the working pressure on the upper surface of the silicon wafer is uniform.

[0027] This invention provides a polishing head 20; and Figure 1 The polishing head 14 shown is different from the one shown. Figure 3 The polishing head 20 described herein adds a mold pad 21 between the rubber pad 144 and the silicon wafer S. The upper surface of the mold pad 21 has a shape that adapts to the elastic deformation of the rubber pad 144, so that the working pressure can be evenly transmitted to the entire upper surface of the silicon wafer S located below the mold pad 21. This presses the silicon wafer S onto the polishing pad 12 with uniform working pressure, achieving a uniform polishing removal amount on the silicon wafer surface, thereby improving the flatness of the silicon wafer surface.

[0028] As described above, during the polishing process, without the mold pad 21 set, for example... Figure 1 The polishing head 14 shown has a rubber pad 144 that applies to the silicon wafer S. However, because the rubber pad 144 may not perfectly fit the surface shape of the silicon wafer S after elastic deformation, for example, it is possible that only the central portion of the rubber pad 144 applies to the silicon wafer S, while gaps exist between the edge portions of the rubber pad 144 and the silicon wafer S. Figure 1 As shown. Therefore, preferably, see [reference needed]. Figure 3 and Figure 4 The upper surface of the mold pad 21 is concave arc shape, and the thickness of the mold pad 21 gradually increases from the center to the edge. Thus, the mold pad 21 can fill the gap between the elastically deformed rubber pad 144 and the silicon wafer S, so that the working pressure can be evenly transmitted to the entire surface of the silicon wafer.

[0029] Regarding the specific implementation of the mold pad 21, according to an embodiment of the present invention, the mold pad 21 can be integrally formed, such as... Figure 4 As shown. In another embodiment of the invention, the mold pad 21 can be formed separately and then joined together. For example, see... Figure 5 The mold pad 21 may include a first part 211 and a second part 212. The first part 211 is an annular shape with a flat bottom surface and its thickness gradually increases from the center outward in the radial direction. The second part 212 is a solid circular sheet. The first part 211 can be attached to one of the circular surfaces of the second part 212 through its bottom surface to form a whole.

[0030] To make the polishing head 20 provided in the embodiments of the present invention more cost-effective, preferably, see Figure 6The mold pad 21 may have a central through hole 213, so that when the rubber pad 144 undergoes elastic deformation, it can at least partially pass through the through hole 213 and act on the upper surface of the silicon wafer S. Thus, the maximum thickness of the mold pad 21 can be set to be small, as long as the mold pad 21 can fit in shape with the deformed rubber pad 144 to form a whole that can uniformly transmit the working pressure to the entire surface of the silicon wafer.

[0031] To prevent the silicon wafer S from shifting relative to the polishing head 20 during the polishing process, preferably, the silicon wafer is attached to the lower surface of the mold pad 21.

[0032] According to another preferred embodiment of the present invention, see Figure 3 The polishing head further includes an annular assembly mold 143 attached to the lower surface of the head body 141. The inner circumferential surface of the assembly mold 143 and the lower surface of the head body 141 together define a first receiving space CS1. When the polishing head polishes the silicon wafer, the rubber pad 144, the mold pad 21 and the silicon wafer S are received in the first receiving space CS1 to ensure that the head body and the silicon wafer are axially aligned.

[0033] According to another preferred embodiment of the present invention, see Figure 7 The polishing head 20 further includes an assembly mold 143 attached to the lower surface of the head body 141. The inner circumferential surface of the assembly mold 143 and the lower surface of the head body 141 together define a first receiving space CS1. The rubber pad 144 is received in the first receiving space CS1. The mold pad 21 is attached to the lower surface of the assembly mold 143 and has a circumferential flange 214 extending downward from the edge of the lower surface of the mold pad 21. The inner circumferential surface of the circumferential flange 214 and the lower surface of the mold pad 21 together define a second receiving space CS2. When the polishing head 20 polishes the silicon wafer S, the silicon wafer S is received in the second receiving space CS2 to ensure that the head body 141 and the silicon wafer S are axially aligned.

[0034] To adapt to different applications, preferably, the diameter and thickness of the mold pad 21 are set according to the magnitude of the working pressure.

[0035] Specifically, the dimensions of the mold pad 21, such as its diameter and thickness, can be set differently for different working pressure ranges to better transmit the working pressure evenly to the silicon wafer. As an example of the present invention, when the working pressure of the polishing head is between 3 kPa and 18 kPa, the working pressure can be divided into four ranges: 3 kPa to 7 kPa, 7 kPa to 11 kPa, 11 kPa to 15 kPa, and 15 kPa to 18 kPa. Different specifications of mold pads can be set for these four ranges. For example, when the working pressure is in the range of 3 kPa to 7 kPa, the overall thickness of the mold pad 21 can be set to approximately 5 mm, and the width can be set in the range of 50 mm to 100 mm.

[0036] Since the mold pad 21 is used to balance the uneven pressure transmitted from the rubber pad 144, it is preferably made of epoxy resin.

[0037] See Figure 8 The present invention also proposes a polishing device 30, which is compatible with... Figure 1 Compared to the polishing equipment 10 shown, the polishing equipment 30 includes a polishing head 20 according to the above description.

[0038] It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict.

[0039] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A polishing head, characterized in that, The polishing head includes: Head body; A rubber pad is attached to the lower surface of the head body, the rubber pad being configured to undergo downward elastic deformation based on the working pressure from the head body; A mold pad is located between the rubber pad and the silicon wafer to be polished. The upper surface of the mold pad is shaped such that when the polishing head polishes the silicon wafer, the upper surface of the mold pad can adapt to the elastic deformation of the rubber pad, so that the working pressure on the upper surface of the silicon wafer is uniform. The upper surface of the mold pad is a concave arc shape, wherein the thickness of the mold pad gradually increases from the center to the edge.

2. The polishing head according to claim 1, characterized in that, The mold pad has a centrally located through hole, allowing the rubber pad to at least partially pass through the through hole and act on the upper surface of the silicon wafer when the rubber pad undergoes the elastic deformation.

3. The polishing head according to claim 1, characterized in that, The silicon wafer is attached to the lower surface of the mold pad.

4. The polishing head according to any one of claims 1 to 3, characterized in that, The polishing head also includes an annular assembly mold attached to the lower surface of the head body. The inner circumferential surface of the assembly mold and the lower surface of the head body together define a first receiving space. When the polishing head polishes the silicon wafer, the rubber pad, the mold pad, and the silicon wafer are received in the first receiving space to ensure that the head body and the silicon wafer are axially aligned.

5. The polishing head according to any one of claims 1 to 3, characterized in that, The polishing head further includes an annular assembly mold attached to the lower surface of the head body. The inner circumferential surface of the assembly mold and the lower surface of the head body together define a first receiving space, in which the rubber pad is received. The mold pad is attached to the lower surface of the assembly mold, and the mold pad has a circumferential flange extending downward from the edge of the lower surface of the mold pad. The inner circumferential surface of the circumferential flange and the lower surface of the mold pad together define a second receiving space. When the polishing head polishes the silicon wafer, the silicon wafer is housed in the second receiving space to ensure that the head body and the silicon wafer are axially aligned.

6. The polishing head according to claim 1 or 2, characterized in that, The diameter and thickness of the mold pad are set according to the working pressure applied by the polishing head.

7. The polishing head according to any one of claims 1 to 3, characterized in that, The mold pad is made of epoxy resin.

8. A polishing device, characterized in that, The polishing equipment includes the polishing head as described in any one of claims 1 to 7.

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