Electrorheological tool, electrorheological tool setting device, and electrorheological tool setting method

Abstract

The present application relates to a kind of electrorheological cutters, electrorheological cutter setting device and electrorheological cutter setting method, electrorheological cutter includes the non-metal shaft being arranged along Z axis, electrode disc being arranged at the bottom of the non-metal shaft, electrode being arranged at the bottom of the electrode disc two ends along the non-metal shaft symmetry and there is interval, first magnet being arranged at the bottom of the electrode, and electrode barrier sheet being arranged between the gap of two electrode, the length of the electrode barrier sheet along Z axis is not more than the length of the electrode along Z axis.Electrorheological cutter setting device includes electrorheological cutter and polishing liquid storage tank, second magnet, magnetometer and stop sheet.Electrorheological cutter setting method is: by adjusting the interval of first magnet and second magnet, according to the magnetic field intensity between them, determine the polishing gap required between silicon wafer and electrode.Compared with prior art, the present application can effectively prevent the discharge phenomenon generated between electrode, and then improve electrorheological polishing stability.

Description

Technical Field

[0001] This invention relates to the field of electrorheological polishing, and in particular to an electrorheological tool, an electrorheological tool setting device, and an electrorheological tool setting method for stabilizing the polishing of silicon wafers. Background Technology

[0002] Silicon wafers have wide applications in the field of integrated circuits. The development of integrated circuits is inseparable from the development of semiconductor technology. As the core and foundation of semiconductor technology development, the processing quality of single-crystal silicon plays a decisive role in the performance of chips. Single-crystal silicon is a non-metallic ceramic material with small elastic and thermal deformation, belonging to hard and brittle materials. During precision machining, it is not prone to slippage and elastic deformation, and has high hardness and wear resistance, which makes it difficult to remove material during processing due to its low efficiency and high processing difficulty.

[0003] To address this, researchers both domestically and internationally have proposed techniques such as chemical mechanical polishing (CMP) and magnetorheological polishing (MRP) for monocrystalline silicon. Currently, CMP is the mainstream polishing method for silicon wafers. However, its application is limited to some extent due to the difficulty in adjusting and regenerating the polishing slurry. Furthermore, the short lifespan of the polishing slurry, the difficulty in adjusting and regenerating the solution concentration, environmental pollution, residual stress, and complex processing variables all contribute to the increasing difficulty of CMP meeting the needs of evolving scientific and technological advancements. MRP, on the other hand, remains costly due to the need to redesign the magnetic field generating device according to processing requirements. These methods, with their high processing costs and complex technologies, are difficult to apply in large-scale production. Therefore, there is an urgent need to explore a new polishing process for monocrystalline silicon.

[0004] Electrorheological polishing (EMR) is a non-contact polishing method that relies on the electrorheological effect under the influence of an electric field to process the surface of a workpiece. It is suitable for conductors and semiconductors. However, due to its low shear strength, it cannot effectively remove material from the workpiece surface. Based on this limitation of shear stress, researchers began to study the rheological properties of electrorheological fluids. Research reports indicate that some researchers have increased the maximum shear strength of electrorheological fluids by several orders of magnitude, naming it "giant electrorheological fluid." Giant electrorheological fluid is an insulating suspension containing high-dielectric-constant solid particles. It mainly consists of a dispersed phase, a dispersion medium, and additives. Compared to ordinary electrorheology, giant electrorheological polishing produces finer chain-like fibers with a more pronounced effect. Simultaneously, the shear strength of the polishing fluid can reach tens of times that of ordinary electrorheology, overcoming the low efficiency of ordinary electrorheology. Single-crystal silicon wafers not only require good shape accuracy but also surface roughness at the sub-nanometer level, free from surface and sub-surface damage layers and altered layers. Fortunately, the giant current-modulated polishing field is easy to establish, has low cost, strong polishing ability, and no subsurface damage or altered layer, thus showing its great application prospects in silicon wafer surface polishing.

[0005] However, research on the application of electrorheological (EMR) polishing on silicon wafer surfaces is limited. Furthermore, EMR polishing is typically performed at high voltages of several kilovolts, which can easily lead to insulation breakdown and discharge in humid air, further affecting the stability of EMR polishing. Therefore, stable EMR polishing is an urgent engineering problem that needs to be solved. Simultaneously, achieving tool setting operations in confined spaces is also a key issue driving the development of EMRs. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of existing electrorheological polishing, such as discharge phenomenon and unstable polishing, and to provide an electrorheological tool, an electrorheological tool setting device, and an electrorheological tool setting method for stable polishing of silicon wafers.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide an electrorheological cutting tool, comprising:

[0009] A non-metallic shaft, which is set along the Z-axis direction;

[0010] An electrode disk is located at the bottom of the non-metallic shaft;

[0011] Electrodes are symmetrically arranged at both ends of the bottom of the electrode disk along the non-metallic axis and are spaced apart;

[0012] A first magnet is disposed at the bottom of the electrode;

[0013] And an electrode barrier sheet disposed between the two electrode gaps;

[0014] The length of the electrode barrier along the Z-axis is no greater than the length of the electrode along the Z-axis.

[0015] More preferably, the length of the electrode barrier along the Z-axis is 1 / 2 of the length of the electrode along the Z-axis.

[0016] Furthermore, a first groove is provided at each of the top two ends of the electrode disk, the line connecting the first grooves is in the Y-axis direction, and a first bolt for fixing the electrode disk, the electrode and the magnet is provided in the first groove.

[0017] Furthermore, the first bolt is also provided with a first nut, the height of which is lower than the depth of the first groove.

[0018] Furthermore, the non-metallic shaft has a structure that is wider at the top and narrower at the bottom. The electrode disk is provided with a second groove that matches the bottom of the non-metallic shaft. The bottom of the non-metallic shaft is also provided with a second bolt for fixing the electrode disk and the non-metallic shaft. When the second bolt is tightened to secure the non-metallic shaft and the electrode disk, there is still a gap between the bottom of the non-metallic shaft and the electrode disk.

[0019] Furthermore, the electrode barrier includes a first feature portion and a second feature portion disposed at the bottom of the first feature portion, wherein the length of the first feature portion along the X-axis direction is greater than the length of the second feature portion along the X-axis direction.

[0020] Furthermore, the first feature portion is disposed on the upper surface of the two electrodes, the second feature portion is disposed in the gap between the two electrodes, and both ends of the second feature portion along the Y-axis direction extend beyond both ends of the electrodes along the Y-axis direction.

[0021] Furthermore, the electrode is an L-shaped electrode.

[0022] Furthermore, the first magnet is an L-shaped magnet.

[0023] The second technical solution of the present invention is to provide an electrorheological tool setting device, including an electrorheological tool as described in one of the above technical solutions, a polishing slurry storage tank, a second magnet, a magnetometer, and a stop plate. The polishing slurry storage tank is provided from top to bottom with a polishing cavity for placing a sample silicon wafer, a magnetometer measuring cavity for placing the magnetometer, and a magnet fixing cavity for placing the second magnet. The stop plate is located at the bottom of the second magnet and is used to fix the second magnet.

[0024] The third technical solution of the present invention is to provide an electrorheological tool setting method based on the electrorheological tool setting device described in the second technical solution above. The electrorheological tool setting method is as follows: the positive and negative terminals of the power supply are respectively connected to the first bolts at both ends of the electrode disk, the electrorheological tool is placed in the polishing chamber, the first magnet and the second magnet are aligned and the distance between them is adjusted, and the magnetic field strength between the first magnet and the second magnet is observed according to the magnetometer so that the magnetic field strength meets the required requirements, that is, the distance between the silicon wafer and the electrode is determined, and the power supply is turned on for polishing.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The electrode barrier of the present invention can effectively prevent discharge phenomena between electrodes and improve the stability during electrorheological polishing. In addition, the electrode barrier also stabilizes the structure of the two electrodes. The length of the electrode barrier in the Z-axis direction is less than the length of the electrode. This is to provide sufficient rheological space for the electrorheological fluid between the two electrodes, and also to provide space for exchange and renewal of the electrorheological fluid between the periphery and the two electrodes.

[0027] (2) The L-shaped electrode of the present invention adopts a symmetrical design and installation, which reduces the mechanical scratches caused by the L-shaped electrode to the silicon wafer.

[0028] (3) The present invention is applied to the electrorheological stability polishing of silicon wafers and has the advantages of no subsurface damage, simple structure and easy establishment of electric field. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the electrorheostat tool setting device.

[0030] Figure 2 This is a top view of the electrode disk.

[0031] Figure 3 This is a side view of the electrode barrier.

[0032] Figure 4 This is a schematic cross-sectional view of the assembly of the electrode barrier and the electrode.

[0033] The markings in the image are as follows:

[0034] 1 is a non-metallic shaft, 2 is a second bolt, 3 is a first nut, 4 is a first bolt, 5 is an electrode disk, 5-1 is a first groove, 5-2 is a second groove, 6 is an electrode, 7 is a first magnet, 8 is a silicon wafer, 9 is a magnetometer measuring chamber, 10 is a polishing fluid reservoir, 11 is a second magnet, 12 is a stop plate, 13 is an electrode blocking plate, 13-1 is a first feature part, 13-2 is a second feature part, and 14 is a power supply. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0036] In the following embodiments, unless otherwise specified, the functional components or structures are conventional components or structures used in the art to achieve the corresponding functions.

[0037] Example 1:

[0038] like Figure 1-4A current-routine cutting tool is provided, comprising a non-metallic shaft 1, an electrode disk 5, electrodes 6, a first magnet 7, and an electrode blocking plate 13. Both electrodes 6 and the first magnet 7 are L-shaped. The non-metallic shaft 1 has a structure that is wider at the top and narrower at the bottom. The electrode disk 5 has a second groove 5-2 that matches the bottom of the non-metallic shaft 1. The bottom of the non-metallic shaft 1 also has a second bolt 2 for fixing the electrode disk 5 and the non-metallic shaft 1. When the second bolt 2 is tightened, a gap remains between the bottom of the non-metallic shaft 1 and the electrode disk 5. Electrodes 6 are symmetrically arranged at both ends of the bottom of the electrode disk 5 along the non-metallic shaft 1, and the first magnet 7 is located at the bottom of the electrode 6. The electrode blocking plate 13 is located between the gaps of the two electrodes 6. A first groove 5-1 is formed at each end of the top of the electrode disk 5. A first bolt 4 for fixing the electrode disk 5, electrodes 6, and magnet 7 is located within the first groove 5-1. A first nut 3 is also provided on the first bolt 4, the height of which is less than the depth of the first groove 5-1. The electrode barrier 13 includes a first feature portion 13-1 and a second feature portion 13-2 disposed at the bottom of the first feature portion 13-1. The length of the first feature portion 13-1 along the X-axis is greater than the length of the second feature portion 13-2 along the X-axis. The first feature portion 13-1 is disposed at the top of the two electrodes 6, and the second feature portion 13-2 is disposed in the gap between the two electrodes 6. Both ends of the second feature portion 13-2 along the Y-axis extend beyond both ends of the electrodes 6 along the Y-axis. The length of the second feature portion 13-2 along the Z-axis is not greater than the length of the electrodes 6 along the Z-axis.

[0039] An electrorheological tool setting device includes an electrorheological tool, a polishing slurry reservoir 10, a second magnet 11, a magnetometer, and a stop plate 12. The polishing slurry reservoir 10 is provided from top to bottom with a polishing cavity for placing a sample silicon wafer 8, a magnetometer measuring cavity 9 for placing a magnetometer, and a magnet fixing cavity for placing the second magnet 11. The stop plate 12 is located at the bottom of the second magnet 11 and is used to fix the second magnet 11.

[0040] A current-ratio tool setting method, based on the aforementioned current-ratio tool setting device, is as follows: the positive and negative terminals of the power supply 14 are respectively connected to the first bolts 4 at both ends of the electrode disk 5; the current-ratio tool is placed in the polishing chamber; after aligning with the first magnet 7 and the second magnet 11, the distance between them is adjusted; and the magnetic field strength between the first magnet 7 and the second magnet 11 is observed using a magnetometer to ensure that the magnetic field strength meets the required requirements, that is, to determine the distance between the silicon wafer 8 and the electrode 6; and the power supply 14 is turned on for polishing.

[0041] In designing and manufacturing the electrorheological tool of this invention, to ensure the perpendicularity of the axis of the non-metallic shaft 1 to the L-shaped electrode 6, the entire tool assembly was mounted on the spindle of a lathe and machined. To ensure axial positioning, the end of the non-metallic shaft 1 was milled into a square head, and the square head end face was clearance-fitted with the electrode disk 5. To avoid affecting the installation of the electrode 6, a mounting hole for the second bolt 2 was machined in the center of the electrode disk 5, and the hole depth was greater than the height of the second bolt cap. For ease of manufacturing, all feature structures of the electrode disk 5 are hole-type structures, and the parts can be machined directly using a drilling machine.

[0042] The tool setting principle of this invention is as follows: since the distance between parallel magnets remains constant, the magnetic field strength also remains constant. Therefore, this invention designs a magnetometer measuring cavity 9 with a magnetometer placed between the first magnet 7 and the second magnet 11. The magnetometer is used to measure the magnetic field strength between the first magnet 7 and the second magnet 11. By observing the size of the magnetometer, the distance between the current electrode 6 and the silicon wafer 8 is determined. This invention requires the distance between the silicon wafer 8 and the electrode 6 to be 0.3mm. Therefore, at the required distance, there must be a constant magnetic field strength, thereby realizing the tool setting operation of electrorheological tools.

[0043] Example 2:

[0044] Based on Embodiment 1, this embodiment specifies that the length of the L-shaped electrode 6 along the Y-axis is 10mm, and the gap between the two electrodes 6 is 1mm (i.e., the length of the second feature portion 13-2 of the electrode barrier 13 along the X-axis). The two ends of the second feature portion 13-2 of the electrode barrier 13 along the Y-axis also exceed the two ends of the electrode 6 along the Y-axis by 1.5mm. The length of the second feature portion 13-2 along the Z-axis is 5mm. The first feature portion 13-1 of the electrode barrier 13 is disc-shaped and has a diameter of 8mm (i.e., the diameter of the mounting hole).

[0045] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A current-modulated cutting tool, characterized in that, include: Non-metallic shaft (1), which is set along the Z-axis direction; An electrode disk (5) is located at the bottom of the non-metallic shaft (1). Electrodes (6) are symmetrically arranged at both ends of the bottom of the electrode disk (5) along the non-metallic axis (1) and spaced apart. A first magnet (7) is provided at the bottom of the electrode (6); And an electrode barrier (13) disposed between the two electrodes (6). The length of the electrode barrier (13) along the Z-axis is not greater than the length of the electrode (6) along the Z-axis. The non-metallic shaft (1) has a structure that is wider at the top and narrower at the bottom. The electrode disk (5) is provided with a second groove (5-2) that matches the bottom of the non-metallic shaft (1). The bottom of the non-metallic shaft (1) is also provided with a second bolt (2) for fixing the electrode disk (5) and the non-metallic shaft (1). When the second bolt (2) tightens the non-metallic shaft (1) and the electrode disk (5), there is still a gap between the bottom of the non-metallic shaft (1) and the electrode disk (5). The electrode barrier (13) includes a first feature portion (13-1) and a second feature portion (13-2) disposed at the bottom of the first feature portion (13-1). The length of the first feature portion (13-1) along the X-axis is greater than the length of the second feature portion (13-2) along the X-axis. The first feature portion (13-1) is disposed on the upper surface of the two electrodes (6), and the second feature portion (13-2) is disposed in the gap between the two electrodes (6). Both ends of the second feature portion (13-2) along the Y-axis extend beyond both ends of the electrodes (6) along the Y-axis.

2. The electrorheological cutting tool according to claim 1, characterized in that, The electrode disk (5) has a first groove (5-1) at each of its top ends. The line connecting the first grooves (5-1) is in the Y-axis direction. The first groove (5-1) is provided with a first bolt (4) for fixing the electrode disk (5), the electrode (6) and the magnet (7).

3. The electrorheological cutting tool according to claim 2, characterized in that, The first bolt (4) is also provided with a first nut (3), the height of which is lower than the depth of the first groove (5-1).

4. The electrorheological cutting tool according to claim 1, characterized in that, The electrode (6) is an L-shaped electrode.

5. A current-modulated cutting tool according to claim 1, characterized in that, The first magnet (7) is an L-shaped magnet.

6. A current-varying tool setting device, characterized in that, The device includes an electrorheological cutting tool as described in any one of claims 1-5, a polishing slurry reservoir (10), a second magnet (11), a magnetometer, and a stop plate (12). The polishing slurry reservoir (10) is provided from top to bottom with a polishing cavity for placing a sample silicon wafer (8), a magnetometer measuring cavity (9) for placing the magnetometer, and a magnet fixing cavity for placing the second magnet (11). The stop plate (12) is located at the bottom of the second magnet (11) and is used to fix the second magnet (11).

7. A current-variable tool setting method, characterized in that, Based on the current-varisted tool setting device as described in claim 6, the current-varisted tool setting method is as follows: connect the positive and negative terminals of the power supply (14) to the first bolts (4) at both ends of the electrode disk (5), place the current-varisted tool in the polishing cavity, align the first magnet (7) and the second magnet (11) and adjust the distance between them, and observe the magnetic field strength between the first magnet (7) and the second magnet (11) according to the magnetometer so that the magnetic field strength meets the required requirements, that is, determine the distance between the silicon wafer (8) and the electrode (6), and turn on the power supply (14) to polish.

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