A polishing head assembly and a polishing apparatus

Abstract

This application discloses a polishing head assembly and polishing equipment, relating to the field of chemical mechanical polishing (CMP) equipment processing technology. Specifically, it includes: a polishing head assembly comprising: a substrate; a retaining ring located below the substrate; and a gas film assembly located below the substrate and inside the retaining ring. The gas film assembly is radially divided into a central region, an intermediate region, and an edge region. The elastic modulus of the central region is a first modulus, the elastic modulus of the intermediate region is a second modulus, and the elastic modulus of the edge region is a third modulus. The second modulus is greater than the first modulus and less than the third modulus. This adapts to the differentiated working conditions of the substrate radially from the intrinsic properties of the gas film material, thereby effectively improving the flatness of the substrate after polishing.

Description

Technical Field

[0001] This application relates to the field of chemical mechanical polishing equipment technology, and more particularly to a polishing head assembly and polishing equipment. Background Technology

[0002] In the semiconductor manufacturing field, large-size, hard, and brittle substrates such as silicon carbide, sapphire, gallium nitride, and large silicon wafers are core materials for fabricating power devices, optoelectronic devices, and integrated circuits. With the rapid development of new energy vehicles, photovoltaic inverters, and rail transportation, the market demand for these substrates continues to grow, and substrates are rapidly iterating towards larger sizes (e.g., 8 inches and above) and ultra-thin designs. To meet the performance and reliability requirements of end devices, the global flatness, local smoothness, and edge contour integrity of the substrate surface must reach extremely high standards.

[0003] Chemical mechanical polishing (CMP) is a core process for achieving ultra-precision substrate planarization. The polishing equipment uses a polishing head to rotate the substrate and apply controllable pressure, removing surface material through the synergistic effect of mechanical grinding and chemical etching. The quality of this process directly determines the yield of subsequent epitaxial growth and chip fabrication. In this process, the polishing head assembly, as the core component that directly contacts and supports the back side of the substrate, is responsible for transmitting pressure and controlling the stress state on the substrate. Its material properties and mechanical response directly affect the uniformity of material removal.

[0004] However, in the polishing process of large-size hard and brittle substrates, existing polishing head assemblies generally adopt a homogeneous elastic gas film structure with a single material. Due to the natural radial linear velocity gradient, abrasive erosion intensity difference, strong acid medium corrosion degree difference, and substrate stress distribution difference during polishing of large-size substrates, the single material properties of the homogeneous gas film are difficult to match this complex non-uniform working condition, resulting in poor flatness of the substrate after polishing, which is difficult to meet the requirements of mass production. Summary of the Invention

[0005] In view of the above problems, this application provides a polishing head assembly and polishing equipment to improve the flatness of the substrate after polishing. The specific solution is as follows: In a first aspect, embodiments of this application provide a polishing head assembly, including: Matrix; A retaining ring is located on one side of the substrate; The air film assembly is located on the same side of the substrate as the retaining ring, and is located radially inside the retaining ring; The air-film assembly is divided into a central region, an intermediate region, and an edge region in a radial direction from the inside to the outside. The elastic modulus of the central region is the first modulus, the elastic modulus of the intermediate region is the second modulus, and the elastic modulus of the edge region is the third modulus. The second modulus is greater than the first modulus and less than the third modulus.

[0006] Optionally, the first modulus ranges from 1.2 MPa to 3.2 MPa; the second modulus ranges from 4.5 MPa to 7.5 MPa; and the third modulus ranges from 8.0 MPa to 12.5 MPa.

[0007] Optionally, the material of the central region is fluorosilicone rubber or fumed silica gel; the material of the intermediate region is polyurethane or corrosion-resistant fluororubber; and the material of the edge region is fluororubber or glass fiber reinforced fluorosilicone rubber.

[0008] Optionally, the central region is a circular area starting from the center of the air-supported membrane assembly, with a corresponding radial range of 40% to 60% of the radius of the air-supported membrane assembly; the middle region is an annular region surrounding the central region, with a corresponding radial range of 50% to 90% of the radius of the air-supported membrane assembly; and the edge region is an annular region surrounding the middle region, with a corresponding radial range of 80% to 100% of the radius of the air-supported membrane assembly.

[0009] Optionally, a first structure is provided at the junction between the central area and the intermediate area, and at the junction between the intermediate area and the edge area; The first structure includes at least one of a sealing structure and an anti-permeability structure.

[0010] Optionally, in the air-film assembly, the thickness of the central region, the intermediate region, and the edge region is the same, with a value ranging from 1mm to 10mm.

[0011] Optionally, the substrate is provided with a first air pressure chamber, a second air pressure chamber, and a third air pressure chamber arranged radially in sequence on the side facing the air film assembly; Wherein, the first air pressure chamber corresponds to the central area, the second air pressure chamber corresponds to the middle area, and the third air pressure chamber corresponds to the edge area; The air-film assembly seals the openings of the first air pressure chamber, the second air pressure chamber, and the third air pressure chamber, and forms the bottom surface of each chamber.

[0012] Optionally, the gas pressure in the first, second, and third pressure chambers ranges from 0 to 8 psi.

[0013] Optionally, the first, second, and third air pressure chambers are each provided with an anti-wrinkle limiting support structure.

[0014] Secondly, embodiments of this application provide a polishing apparatus, including the polishing head assembly described in the first aspect of this application.

[0015] This application provides a polishing head assembly, in which the film gas assembly is radially divided into a central region, an intermediate region, and an edge region. The elastic modulus of the central region is a first modulus, the elastic modulus of the intermediate region is a second modulus, and the elastic modulus of the edge region is a third modulus. The second modulus is greater than the first modulus and less than the third modulus, which can provide differentiated mechanical support and pressure transmission capabilities to address the problems of radial linear velocity gradient and stress distribution differences that naturally exist during the polishing of large-size hard and brittle substrates. The low-modulus central region can achieve better flexible bonding and stress buffering, avoiding over-polishing caused by pressure concentration in the central area. The intermediate region with a medium modulus can balance structural support and elastic deformation capability, ensuring linear stability of pressure transmission to balance the overall material removal rate. The high-modulus edge region can strengthen the wafer edge support stiffness, constrain the edge material removal rate, and alleviate the problems of edge collapse and warping caused by insufficient edge support. Thus, from the intrinsic performance level of the film gas material, it adapts to the differentiated working conditions of the substrate radial direction, thereby effectively improving the flatness of the substrate after polishing. Attached Figure Description

[0016] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0017] Figure 1 This is a schematic cross-sectional view of the polishing head assembly provided in an embodiment of this application; Figure 2 A top view of the air-supported membrane assembly provided in an embodiment of this application; Figure 3 This is a schematic flowchart of the substrate polishing process provided in the embodiments of this application; Figure 4 The three-dimensional topographic cloud image of the substrate surface after processing by the polishing head of this application in Embodiment 1 is provided for the purpose of this application. Figure 5 The three-dimensional topography cloud image of the substrate surface after conventional polishing head processing is provided for Comparative Example 1 in this application embodiment; Figure 6 The three-dimensional topographic cloud image of the substrate surface after processing by the polishing head of this application in Embodiment 2 is provided as an example of this application. Detailed Implementation

[0018] The embodiments of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the claimed technical solutions and their equivalents. It should be noted that the implementation methods provided in the embodiments of this application can be combined with each other without contradiction.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] As described in the background section, during the polishing process of large-size hard and brittle substrates, there is a problem of poor substrate uniformity after polishing.

[0022] Existing semiconductor CMP polishing heads generally employ a homogeneous, single-material elastic film structure, which suffers from several inherent technical defects. Because the elastic modulus of the film is uniform across its entire surface, it cannot adapt to the stress requirements of different radial positions on large-size substrates. During polishing, the inflated film transmits pressure to the substrate. The single elastic modulus of the film easily leads to pressure concentration in the central region and insufficient support at the edges. Specifically, pressure concentration in the central region causes more material to be ground away from the substrate at that location, resulting in over-polishing of the center. Insufficient support stiffness at the edges fails to effectively constrain the material removal rate at the substrate edges, leading to defects such as edge collapse and edge warping. These defects ultimately increase the total thickness variation (TTV) (the difference between the thickest and thinnest parts of the substrate) and the local thickness variation (LTV) (thickness fluctuations within small local areas of the substrate), resulting in poor flatness after substrate polishing.

[0023] In addition to the aforementioned drawbacks, for substrates with high hardness, such as silicon carbide, which require high wear resistance, high-pressure, high-speed grinding and polishing are necessary. In this case, CMP polishing slurries contain high-hardness nano / micron-sized abrasive particles, and the gas film is subjected to long-term frictional erosion. The wear rate in the edge area is much higher than that in the center area. Homogeneous materials are prone to premature aging, damage, and air leakage, resulting in uneven overall service life and high replacement costs. At the same time, CMP generally uses a strong acid polishing slurry system. Conventional rubber and polymer gas films have limited resistance to acid and alkali corrosion and swelling. Under long-term operating conditions, the materials are prone to softening, deformation, and cracking, leading to a decrease in pressure transmission accuracy. Furthermore, larger silicon carbide substrates have a large area and high self-weight load. The limited stress buffering capacity of the homogeneous gas film makes it easy for local stress concentration to occur during polishing, inducing substrate microcracks, edge chipping, and surface scratches, resulting in a lower yield of the polished substrate.

[0024] In view of this, embodiments of this application provide a polishing head assembly, including: Matrix; A retaining ring is located on one side of the substrate; The air film assembly is located on the same side of the substrate as the retaining ring, and is located radially inside the retaining ring; The air-film assembly is divided into a central region, an intermediate region, and an edge region in a radial direction from the inside to the outside. The elastic modulus of the central region is the first modulus, the elastic modulus of the intermediate region is the second modulus, and the elastic modulus of the edge region is the third modulus. The second modulus is greater than the first modulus and less than the third modulus.

[0025] Figure 1 This is a schematic cross-sectional view of the polishing head assembly provided in an embodiment of this application, as shown below. Figure 1 As shown, the polishing head assembly described in this application has an overall axisymmetric circular structure, mainly including three core components: a substrate 11, a retaining ring 12, and an air film assembly 13. All components are arranged symmetrically about the geometric center of the air film assembly 13 to ensure that the substrate is subjected to uniform force during the polishing process.

[0026] The substrate 11 is the rigid support body of the polishing head assembly, and has a disc-shaped structure, located at the top of the entire polishing head assembly. The upper end of the substrate 11 is used to connect to the spindle of the polishing equipment, and can drive the entire polishing head assembly to rotate around its own axis under the drive of the spindle, and move up and down in the vertical direction to apply polishing pressure to the substrate.

[0027] The retaining ring 12 has a circular structure and is fixedly connected to the surface of the substrate facing the polishing pad, surrounding the outer side of the air film assembly 13. The inner diameter of the retaining ring is slightly larger than the outer diameter of the air film assembly, with a small gap of 0.1 mm to 0.5 mm between them to avoid frictional interference during operation. The main function of the retaining ring is to constrain the radial position of the substrate from the outside during polishing, preventing the substrate from being thrown out from under the polishing head under centrifugal force. The retaining ring is usually made of wear-resistant, corrosion-resistant, and self-lubricating engineering plastic. Optionally, the retaining ring can be made of polyetheretherketone (PEEK) or carbon fiber reinforced composite material, which is not limited in this application.

[0028] The air film assembly 13 is fixedly connected to the side surface of the substrate 11 facing the polishing pad, and is located on the same side of the substrate 11 as the retaining ring 12, and is located radially inside the retaining ring 12. The air film assembly 13 is a circular thin sheet structure, and its diameter matches the diameter of the substrate to be processed, which can cover the entire back side of the substrate. The air film assembly 13 is the core functional component that directly contacts the back side of the substrate. When working, compressed air is introduced into the cavity between the air film assembly 13 and the substrate 11, and the air film will bulge downward, uniformly transmitting pressure to the substrate, while also buffering stress and protecting the hard and brittle substrate.

[0029] like Figure 2 As shown, Figure 2 This is a top view of the air-supported membrane assembly provided in this embodiment. The air-supported membrane assembly 13 is divided into three concentric continuous regions from the inside to the outside along its radial direction: a central region 131, a middle region 132, and an edge region 133. The central region 131 is located at the innermost side of the air-supported membrane assembly 13 and is a complete circular region; the middle region 132 surrounds the outer side of the central region 131 and is an annular region; the edge region 133 is located at the outermost side of the air-supported membrane assembly 13 and is an annular region surrounding the middle region 132. These three regions are closely connected to form a complete, gapless circular air-supported membrane assembly.

[0030] The elastic modulus 13 of the central region 131 is the first modulus, the elastic modulus of the middle region 132 is the second modulus, and the elastic modulus of the edge region 133 is the third modulus. Furthermore, the second modulus is greater than the first modulus and less than the third modulus, meaning the elastic modulus of the air-supported membrane assembly exhibits a gradient distribution that gradually increases from the center to the edge. The elastic modulus is a physical indicator that measures a material's resistance to elastic deformation. A smaller elastic modulus indicates a softer material that is more prone to elastic deformation; a larger elastic modulus indicates a harder material that resists deformation more effectively.

[0031] This radial gradient elastic modulus design can be specifically adapted to the naturally occurring radially differentiated working conditions during the polishing of large-size, hard, and brittle substrates. The low-modulus central region 131 is the softest, enabling better flexible adhesion to the back of the substrate. When pressure is applied by the polishing head, the central region 131 undergoes appropriate elastic deformation, naturally dispersing the concentrated stress in the central area and preventing excessive material removal rate due to excessive central pressure. This solves the common problem of over-polishing in the center of existing homogeneous gas films. The medium-modulus intermediate region 132 has a moderate hardness, providing sufficient structural support while retaining good elastic deformation capability. This ensures linear and stable pressure transmission from the substrate 11 to the substrate, keeping the material removal rate in the central region of the substrate uniform and playing a transitional role. The high-modulus edge region 133 is the hardest, providing the strongest edge support stiffness, effectively resisting downward deformation of the substrate edge region, and constraining the material removal rate in the edge region. This solves the problems of edge collapse and edge warping caused by insufficient edge support in existing homogeneous gas films.

[0032] Optionally, the air-supported membrane assembly can be prepared using an in-mold integrated composite molding process, in which three polymer materials with different elastic moduli are simultaneously injected into the same mold and cured under high temperature and pressure, forming a natural interlocking structure at the joint, resulting in high connection strength. Alternatively, it can be prepared using a high-strength sealing and bonding process, in which three components—the central area, the middle area, and the edge area—are prepared separately, and then bonded together with a high-strength, acid- and alkali-resistant sealant to form a complete air-supported membrane assembly. After preparation, the upper surface of the air-supported membrane assembly is sealed to the lower surface of the substrate by bonding or pressing, ensuring that no gas leakage occurs during inflation. It should be noted that the air-supported membrane assembly provided in this application can also be prepared using other processes, and this application does not limit the application to these methods.

[0033] It should also be noted that the polishing head assembly of this application has a wide range of applications. In addition to silicon carbide substrates, it can also be adapted to various commonly used semiconductor substrates such as silicon substrates, gallium nitride substrates, sapphire substrates, and gallium arsenide substrates. This application does not limit the substrate size and can be adapted to substrates of mainstream industry sizes such as 4 inches, 6 inches, 8 inches, and 12 inches. The polishing head assembly of this application can be used for processes such as thinning, double-sided rough grinding, fine grinding, and rework after polishing, and this application does not limit these applications.

[0034] Optionally, in one embodiment of this application, the value of the first modulus ranges from 1.2 MPa to 3.2 MPa. If the first modulus is lower than 1.2 MPa, the material in the central region is too soft and lacks elastic recovery ability. It is prone to permanent deformation under long-term pressure and will collapse excessively under polishing pressure, failing to stably transmit the pressure in the central region and instead easily causing local stress concentration. If the first modulus is higher than 3.2 MPa, the material in the central region is too hard and loses its core role of flexible bonding and stress buffering. It cannot effectively disperse the naturally occurring central pressure concentration during the polishing process and will still have the defect of over-polishing in the center, which is not essentially different from the technical problems of existing homogeneous gas films. The first modulus range provided in this embodiment enables the central region to have excellent flexible bonding performance while ensuring basic support capacity. It can effectively adapt to the small surface shape errors on the back of the substrate, uniformly disperse the concentrated stress in the central region, thereby adapting to the differentiated working conditions of the substrate radially and effectively improving the flatness of the substrate after polishing.

[0035] Optionally, in one embodiment of this application, the material of the central region is fluorosilicone rubber or fumed silica. Fluorosilicone rubber is a modified polymer material with fluorinated side groups introduced into the main chain of silicone rubber, possessing both the excellent resistance to strong acids and organic solvents of fluororubber and the high elasticity and low compression set of silicone rubber. Fumed silica is high-purity silica prepared using fumed silica as a reinforcing agent, possessing advantages such as low impurity content, good resilience, and low stress relaxation. The room-temperature static elastic modulus of both materials falls within the range of the aforementioned first modulus, allowing them to maintain stable mechanical properties under long-term immersion in strongly acidic polishing solutions without significant softening, swelling, or performance degradation. Furthermore, they do not release metal ions or organic pollutants, effectively preventing contamination of the semiconductor substrate. It should be noted that other materials can also be used in the central region, as long as their elastic modulus meets the range of the first modulus; this application does not impose any limitations on this.

[0036] Optionally, in one embodiment of this application, the value range of the second modulus is 4.5 MPa to 7.5 MPa. If the second modulus is lower than 4.5 MPa, the stiffness of the middle region is insufficient and cannot bear the stiffness difference between the central region and the edge region, resulting in a significant stiffness abrupt change at the junction of adjacent regions, causing annular thickness unevenness defects in the corresponding position of the substrate; if the second modulus is higher than 7.5 MPa, the hardness of the middle region is too high, and the elastic deformation capacity is insufficient, which cannot compensate for the initial surface shape fluctuation of the substrate itself, and it is also difficult to ensure the linear and stable transmission of pressure from the substrate to the substrate, resulting in large fluctuations in the material removal rate of the middle region; the second modulus range provided in this embodiment can take into account both structural support and elastic deformation capacity, achieve a smooth transition of stiffness, ensure the uniformity of pressure transmission throughout the entire region, and thus effectively improve the flatness of the substrate after polishing.

[0037] Optionally, in one embodiment of this application, the material of the intermediate region is polyurethane or corrosion-resistant fluororubber.

[0038] The polyurethane is a hydrolysis-modified thermosetting polyurethane, possessing excellent wear resistance, tear strength, and moderate elasticity. It maintains stable dimensional and mechanical properties under long-term friction conditions and is not prone to wear or cracking. The corrosion-resistant fluororubber is a medium-hardness fluororubber with optimized crosslinking density and acid / alkali resistance, exhibiting excellent resistance to strong acid corrosion and adapting to the harsh chemical environment of the CMP process. The room-temperature static elastic modulus of both materials falls within the range of the aforementioned second modulus, enabling a smooth transition and avoiding significant stiffness abrupt changes at the junction of adjacent areas. This ensures the linearity and uniformity of pressure transmission, effectively improving the flatness of the substrate after polishing. It should be noted that other materials can also be used in the intermediate region, as long as their elastic modulus meets the range of the second modulus; this application does not impose any limitations on this.

[0039] Optionally, in one embodiment of this application, the value range of the third modulus is 8.0 MPa to 12.5 MPa. If the third modulus is lower than 8.0 MPa, the edge region support stiffness is insufficient, and it cannot effectively resist the downward deformation of the substrate edge region. The problem of excessively fast edge material removal rate will still occur, making it difficult to fundamentally solve the defects of edge collapse and warping. If the third modulus is higher than 12.5 MPa, the edge region material is too hard and lacks elasticity, making it unable to achieve good flexible adhesion with the substrate edge. Instead, it is easy to cause excessive edge pressure and over-polishing of the edge. At the same time, the brittleness of the overly hard material increases significantly, and it is prone to cracking and breakage under long-term friction, erosion and acid and alkali corrosion, shortening the service life of the air film assembly. The third modulus range provided in this embodiment can ensure sufficient edge support stiffness while retaining the necessary elastic adhesion ability, effectively constraining the material removal rate of the edge region, alleviating the problem of edge collapse and warping caused by insufficient edge support, and thus effectively improving the flatness of the substrate after polishing.

[0040] Optionally, in one embodiment of this application, the material of the edge region is fluororubber or glass fiber reinforced fluorosilicone rubber.

[0041] Among them, fluororubber is a high-hardness binary or ternary fluororubber with excellent resistance to strong acid corrosion and wear resistance, providing sufficient support stiffness for the substrate edge and effectively constraining the material removal rate in the edge region. Glass fiber reinforced fluorosilicone rubber is a composite polymer material prepared by uniformly dispersing short-cut glass fibers in a fluorosilicone rubber matrix. Through the reinforcement of glass fibers, it retains the corrosion resistance and certain elasticity of fluorosilicone rubber, and its wear resistance and anti-aging properties are significantly improved compared to pure fluorosilicone rubber, which can extend the overall service life of the air-film module. The room temperature static elastic modulus of the above two materials both fall within the range of the aforementioned third modulus, which can ensure sufficient edge support stiffness while retaining the necessary flexible bonding ability, avoiding substrate damage caused by excessive edge hardness. It should be noted that other materials can also be used in the edge region, as long as their elastic modulus meets the range of the third modulus; this application does not impose any restrictions on this.

[0042] Optionally, in one embodiment of this application, the central region is a circular area originating from the center of the air-film assembly, with a corresponding radial range of 40% to 60% of the radius of the air-film assembly. If the radial range of the central region is less than 40% of the radius of the air-film assembly, the low-modulus flexible support area is too small and cannot effectively cover the core area where the pressure is concentrated in the center of the substrate, still easily leading to over-polishing in the center; if the radial range of the central region is greater than 60% of the radius of the air-film assembly, the low-modulus area is too large, resulting in insufficient overall support stiffness of the air-film and unstable pressure transmission in the middle area; the radial range of the central region provided in this embodiment can cover the pressure-concentrated area in the center of the substrate while ensuring the overall structural stability of the air-film. It should be noted that the radial range of the central region can also be adjusted according to the actual polishing process requirements, and this application does not limit it in this regard.

[0043] Optionally, in one embodiment of this application, the intermediate region is an annular area surrounding the central region, with a corresponding radial range of 50% to 90% of the radius of the air-film assembly. If the radial range of the intermediate region is less than 50% of the radius of the air-film assembly, the transition area is too narrow, making it impossible to achieve a smooth stiffness transition between the central region and the edge region, and easily leading to obvious stiffness abrupt changes at the joint; if the radial range of the intermediate region is greater than 90% of the radius of the air-film assembly, it will compress the effective support range of the edge region, resulting in insufficient edge support stiffness and still easily causing edge collapse problems; the radial range of the intermediate region provided in this embodiment can form a sufficiently wide stiffness transition band, making the change in elastic modulus smoother and ensuring the uniformity of pressure transmission throughout the entire area. It should be noted that the radial range of the intermediate region can also be adjusted according to the actual polishing process requirements, and this application does not limit it in this regard.

[0044] Optionally, in one embodiment of this application, the edge region is an annular region surrounding the central region, with a corresponding radial range of 80% to 100% of the radius of the film membrane assembly. If the radial range of the edge region is less than 80% of the radius of the film membrane assembly, the high-modulus support area is too narrow, failing to provide sufficient support stiffness for the substrate edge and making it difficult to effectively constrain the edge material removal rate; if the radial range of the edge region is greater than 100% of the radius of the film membrane assembly, it will exceed the effective working range of the film membrane assembly, failing to contact the substrate edge and losing its edge support function; the radial range of the edge region provided in this embodiment can cover the area of ​​the substrate edge that is prone to collapse, effectively solving the problem of insufficient edge support. It should be noted that the radial range of the edge region can also be adjusted according to the actual polishing process requirements, and this application does not limit it in this regard.

[0045] Optionally, in one embodiment of this application, a first structure is provided at the junction between the central area and the intermediate area, and at the junction between the intermediate area and the edge area; wherein the first structure includes at least one of a sealing structure and an anti-permeability structure.

[0046] Since the air film assembly is made of three polymer materials with different elastic moduli, the interface between the different materials is the weak point of the air film assembly. During the polishing process, the air film assembly needs to withstand repeated inflation and deflation cycles, and is also immersed in a highly acidic polishing fluid containing hard abrasive particles for a long time. If no protective structure is set at the joint, gas leakage and polishing fluid penetration are likely to occur, which will affect the pressure transmission accuracy and the service life of the air film assembly.

[0047] Specifically, the sealing structure is mainly used to prevent gas leakage between adjacent areas and ensure the effectiveness of subsequent independent air pressure control. For example, the sealing structure can be an interlocking structure of annular bosses and grooves at the joint, with materials in adjacent areas interlocking to form a labyrinth seal, which can significantly improve the airtightness of the joint and avoid pressure interference between different air pressure chambers. The anti-permeability structure is mainly used to prevent acidic media and hard abrasive particles in the polishing fluid from penetrating to the joint interface, preventing corrosion, delamination, or detachment at the joint. For example, the anti-permeability structure can be a layer of high-strength acid-resistant sealant coated on the joint interface, or a polytetrafluoroethylene anti-permeability film embedded in the joint, which can effectively isolate the polishing fluid from contact with the joint interface.

[0048] In practical applications, a sealing structure or an anti-permeability structure can be set separately, or both can be set simultaneously to meet the requirements of airtightness and corrosion resistance. Setting the first structure can significantly improve the reliability and service life of the air-film assembly joint, ensuring the pressure transmission accuracy of the air-film assembly under long-term operating conditions. It should be noted that the first structure can also adopt other structural forms that can achieve sealing or anti-permeability functions; this application does not limit this.

[0049] Optionally, in one embodiment of this application, the thickness of the central region, the intermediate region, and the edge region in the air film assembly is the same, and the value ranges from 1 mm to 10 mm.

[0050] This embodiment employs a design with uniform thickness in three regions, which avoids the problem of uneven stiffness caused by thickness differences. The bending stiffness of a material is proportional to the cube of its thickness. If the thicknesses of different regions are different, even if the elastic moduli are matched, an additional stiffness gradient will appear, disrupting the preset pressure transmission law and causing uneven thickness defects at corresponding positions on the substrate. At the same time, the uniform thickness design simplifies the processing and molding of the air film assembly, ensures the overall flatness of the air film, and facilitates sealing and bonding with the substrate.

[0051] If the gas film thickness is less than 1 mm, the structural strength of the gas film is insufficient, making it prone to rupture and perforation under inflation pressure and repeated cyclic loading, and fatigue cracks are likely to occur with long-term use. Simultaneously, an excessively thin gas film exhibits poor pressure transmission linearity; even small pressure fluctuations can cause excessive deformation of the gas film, making it impossible to stably control the stress state of the substrate. If the gas film thickness is greater than 10 mm, the elastic deformation capability of the gas film decreases significantly, making it impossible to achieve good flexible adhesion to the back of the substrate, resulting in slow pressure transmission response and difficulty in quickly adapting to adjustments in process parameters. Furthermore, an excessively thick gas film increases component weight and material costs, and requires a larger gas volume during inflation, reducing the sensitivity of pressure regulation. The thickness range provided in this embodiment ensures sufficient elastic deformation capability while maintaining the structural strength and service life of the gas film, ensuring the stability and response speed of pressure transmission. It should be noted that the specific thickness of the gas film component can be adjusted according to the size of the substrate to be processed and the polishing process pressure; this application does not limit this.

[0052] Optionally, in one embodiment of this application, the substrate is provided with a first pressure chamber, a second pressure chamber, and a third pressure chamber arranged radially in sequence on the side facing the air film assembly; Wherein, the first air pressure chamber corresponds to the central area, the second air pressure chamber corresponds to the middle area, and the third air pressure chamber corresponds to the edge area; The air-film assembly seals the openings of the first air pressure chamber, the second air pressure chamber, and the third air pressure chamber, and forms the bottom surface of each chamber.

[0053] The three air pressure chambers provided in this embodiment are independent sealed cavities, separated from each other by annular sealing partitions, and can be vented with compressed air at different pressures. This design complements the aforementioned air film assembly with radial gradient elastic modulus: the gradient elastic modulus provides basic differentiated mechanical support from the material itself, while the independent air pressure chambers provide dynamic pressure regulation capabilities from the process adjustment level. The combination of the two can achieve dual control over the radial force on the substrate.

[0054] If only a single, integrated air pressure chamber is used, a uniform pressure can only be applied to the entire air film, making it impossible to specifically adjust the pressure for differences in material removal rates in different radial regions. This makes it difficult to adapt to the differentiated needs of different substrate materials and sizes, as well as different process stages such as rough polishing and fine polishing. However, with a three-chamber independent design, the pressure in a specific area can be adjusted individually based on the real-time polishing effect: for example, if the removal rate in the central region is detected to be slow, the pressure in the first air pressure chamber can be appropriately increased; if a slight edge collapse trend is observed in the edge region, the pressure in the third air pressure chamber can be appropriately increased, further optimizing the uniformity of material removal across the entire area. The air film assembly directly serves as the bottom surface of each air pressure chamber, enabling the gas pressure within the chamber to be uniformly converted into surface pressure, which is then transmitted to the back side of the substrate through the corresponding air film, ensuring the continuity and uniformity of pressure transmission. It should be noted that the number and specific radial range of the air pressure chambers can also be adjusted according to actual process requirements, and this application does not limit this.

[0055] Optionally, in one embodiment of this application, the gas pressure of the first, second, and third pressure chambers ranges from 0 to 8 psi. Within this pressure range, the gas film assembly can be ensured to operate within its elastic deformation range, avoiding irreversible plastic deformation and rupture failure, while also balancing polishing efficiency and processing accuracy. It should be noted that the gas pressure of each pressure chamber can be adjusted independently according to the substrate material, size, and specific process stage; this application does not impose any limitations on this.

[0056] Optionally, in one embodiment of this application, the first air pressure chamber, the second air pressure chamber, and the third air pressure chamber are all provided with anti-wrinkle limiting support structures.

[0057] During repeated inflation and deflation cycles, air-film modules are prone to localized wrinkles, bulges, or excessive deformation due to uneven stress. Without anti-wrinkle limiting support structures, wrinkles generated by the air film can lead to interruption or uneven pressure transmission in the corresponding area, resulting in defects such as insufficient or excessive polishing on the substrate surface. At the same time, repeated folding of the air film can accelerate fatigue cracking of polymer materials and shorten the service life of the air-film module. In addition, excessive expansion of the air film can also disrupt the preset pressure transmission pattern, leading to loss of control over polishing precision.

[0058] The anti-wrinkle limiting support structure provides support and limitation for the air-film assembly: on the one hand, it constrains the deformation of the air film, preventing wrinkles during inflation and deflation; on the other hand, it limits the maximum downward deformation of the air film, avoiding excessive expansion. For example, the anti-wrinkle limiting support structure can employ radially distributed or concentrically ring-shaped limiting ribs along the circumference, which effectively provides support and limitation without hindering the normal elastic deformation of the air film. It should be noted that the specific form and arrangement of the anti-wrinkle limiting support structure can be adjusted according to the shape and size of the air pressure chamber, and this application does not limit this.

[0059] Furthermore, embodiments of this application also provide a substrate polishing method. Figure 3 This is a schematic flowchart of a substrate polishing method provided in an embodiment of this application. The method uses the aforementioned polishing head assembly to complete the substrate polishing process, and specifically includes the following steps: S301: Measurement of incoming film.

[0060] Select the substrate to be processed, pre-clean the substrate surface to remove surface-adhered impurities to avoid impurities interfering with the thickness measurement accuracy; perform surface flatness detection on the substrate.

[0061] S302: Select the polishing head.

[0062] The TTV value of the substrate is calculated based on the flatness data measured in step S301. The radial region of the substrate is divided into zones to determine the size range of the central zone, intermediate zone, and edge zone. The polishing head assembly of this application with the corresponding modulus zone specification is then selected.

[0063] S303: Chemical mechanical polishing.

[0064] The selected polishing head assembly is installed and fixed to the polishing equipment, and the substrate is polished using matching polishing consumables and process parameters.

[0065] Optionally, the polishing process is divided into two stages: rough polishing and fine polishing. After the rough polishing stage, an intermediate cleaning process can be added before continuing with the fine polishing process. In the rough polishing stage, the polishing pad can be a polyurethane polishing pad with a hardness of Shore D 70-100; the polishing fluid can be an alumina polishing fluid, with a pH value controlled at 3-5, a flow rate of 50-200 mL / min, and an ambient temperature maintained at 20-50℃; the processing speed is 0-120 rpm, the large disc speed is 0-120 rpm, the rough polishing time is 5-30 minutes, and both sides of the substrate are polished; the fine polishing stage can use a silicon oxide polishing fluid with a pH value of 5-7, performing fine polishing only on the silicon surface of the substrate, with a fine polishing time of 1-3 minutes, and using a damping material polishing pad. It should be noted that the above selection of polishing pads and polishing fluids, as well as the process parameters, are only examples and are not limited in this application.

[0066] S304: Cleaning inspection.

[0067] After polishing, the substrate is cleaned, and then the flatness of the cleaned substrate is tested. The TTV value of the substrate is then calculated again.

[0068] Optionally, the cleaning process can use SC1 cleaning solution. SC1 solution is prepared by mixing ammonia, hydrogen peroxide and ultrapure water in a volume ratio of 1:2:5 to 1:5:100. The cleaning is usually carried out at room temperature, with a single cleaning time of 40 to 120 seconds and a supply flow rate of 300 to 1500 mL / min.

[0069] Optionally, the flatness test described above can be a full-area multi-point measurement with 100 to 20,000 measurement points. The TTV value of the substrate is calculated based on the measurement data. Other thickness measurement methods can also be used in the field, and this application does not limit them.

[0070] The inventors discovered that by using the polishing head assembly of this application to polish the substrate, the TTV value of the polished substrate can be stably controlled within 1.0 μm. Furthermore, through actual process verification, the polishing head of this application, through differentiated material selection in different zones, uses a highly wear-resistant and acid-resistant material in the edge zone to resist the abrasive erosion of polishing fluid and the chemical corrosion of strong acid media; the center zone uses a flexible material to reduce fatigue loss caused by reciprocating deformation, improving the defect of premature failure at the edge of traditional homogeneous gas films. The overall continuous service life of the gas film is increased by more than 30% compared with traditional homogeneous gas films. With the independent pressure chamber structure in different zones, pressure can be applied in different zones according to the substrate surface morphology. Even when the gas film is used to the end of its life, the overall pressure response state remains basically consistent with that in the early stage of use, realizing stable TTV control throughout the entire life cycle of substrate polishing.

[0071] To more clearly demonstrate the differences in stability and polishing precision between the proposed heterogeneous film polishing head assembly and the traditional homogeneous film polishing head assembly after long-term continuous operation, the applicant set up a set of parallel control verification experiments. To ensure the comparability of the test results, this verification experiment strictly followed the single variable principle. The embodiments of this application and the traditional comparative examples were carried out under the same test conditions, and the unified test settings were as follows: the same batch of 8-inch silicon carbide substrates were used as test materials; the same chemical mechanical polishing equipment was used, with the same process parameters; and the same optical profilometer was used to complete the surface scanning and TTV value detection.

[0072] Specifically, the polishing head air film provided in this application is arranged radially with the center as the reference: the central area 1 has a radial range of 0-60mm and is made of high-resilience fluorosilicone rubber; the middle area 2 has a radial range of 60-90mm and is made of hydrolysis-resistant modified high-elastic polyurethane; the edge area 3 has a radial range of 90-100mm and is made of high-modulus acid-resistant fluororubber; traditional polishing heads use an integral homogeneous air film without differentiated material design for different areas.

[0073] In this verification test, Example 1 uses the partitioned heterogeneous gas film polishing head of this application to perform CMP processing test under the condition of cumulative use of 60h. The specific steps include: firstly, selecting the substrate to be tested and detecting the surface flatness; assembling the polishing head of this application with a cumulative use time of 60h to the processing equipment to complete the step-by-step CMP polishing of the substrate; after polishing, cleaning the substrate and detecting the surface thickness.

[0074] Meanwhile, the applicant added Comparative Example 1, which uses an existing conventional homogeneous air film polishing head for a cumulative 60 hours of use and is subjected to CMP control testing. The only difference between Comparative Example 1 and Example 2 is the type of polishing head; all other process parameters are the same as in Example 1.

[0075] In addition, the applicant added Example 2, which uses the partitioned heterogeneous air film polishing head of this application to conduct a CMP control test under the condition of cumulative use for 100 hours. The only difference from Example 1 is the cumulative use time of the polishing head, and all other process parameters are the same as those in Example 1.

[0076] After processing, an optical profilometer was used to collect three-dimensional thickness contour maps of the surface profiles of the test samples in Example 1, Comparative Example 1, and Example 2, respectively. The corresponding figures are as follows: Figure 4 , Figure 5 , Figure 6 All cloud map legends are in μm, and the colors from purple to red represent substrate thickness from thin to thick.

[0077] like Figure 4 As shown, Figure 4The three-dimensional morphology cloud image of the substrate surface after processing by the polishing head of this application in Example 1 provides an embodiment of this application. It can be seen that the substrate thickness transitions smoothly and evenly along the radial direction, the color gradient is continuous and regular, the overall surface shape is close to an ideal plane, the thickness fluctuation range is significantly narrowed, and there are no obvious local protrusions or depressions. The measured TTV of the finished substrate is 0.645μm. Figure 5 As shown, Figure 5 The three-dimensional morphology cloud image of the substrate surface after processing with a conventional polishing head, provided as an embodiment of this application, shows that the thickness distribution of the finished substrate is disordered, with obvious abrupt thickness changes in local areas, and the overall surface exhibits a distorted shape with higher outer edges and lower inner edges. The measured TTV of the finished substrate is 3.494 μm. Figure 6 As shown, Figure 6 The three-dimensional topography cloud image of the substrate surface after processing by the polishing head of this application in Example 2 is provided as an embodiment of this application. After 100 hours of cumulative use of the polishing head of this application, the substrate surface of Example 2 still maintains a uniform and smooth transition state. The measured TTV of the finished substrate is 0.552μm, and the value is still stably controlled below 1μm.

[0078] In this verification test, the substrate TTV after processing by the conventional process (Comparative Example 1) was 3.494 μm; the substrate TTV after processing by the process of this application (Example 1) was 0.645 μm, which is 81.5% lower than the conventional process TTV; the substrate TTV after processing by the process of this application (Example 2) for a cumulative period of 100 hours was 0.552 μm, which is 84.2% lower than the conventional process TTV.

[0079] It is evident that traditional homogeneous film polishing heads, during long-term use, suffer irreversible material loss due to the continuous abrasive erosion and acidic polishing fluid corrosion of the edge areas. This results in a severe imbalance in edge pressure response, eliminating the conventional over-polishing phenomenon. Instead, insufficient edge grinding removal capacity leads to low substrate edge polishing, ultimately resulting in a surface defect with a higher outer diameter and a lower inner diameter, causing the substrate TTV to significantly exceed the standard. The polishing head of this application, through a zoned differentiated material selection design, features high-modulus rubber at the edges with excellent wear resistance and chemical corrosion resistance, while the flexible rubber in the center can buffer fatigue wear caused by repeated deformation. Within a 60-hour usage cycle, the finished product TTV can be stably controlled to 0.645μm. Even after continuous use for 100 hours, the mechanical properties of the film in each zone do not show significant deterioration, and the substrate TTV after processing remains as low as 0.552μm. This solves the problems of localized premature aging and inconsistent pressure response throughout the entire cycle in traditional homogeneous film polishing heads, improving the long-term processing accuracy and service life of the polishing head.

[0080] In addition, this application also provides a polishing device, including the polishing head assembly provided in any of the foregoing embodiments.

[0081] In summary, the polishing head assembly and polishing equipment provided in this application adopt a heterogeneous composite gas film structure with radial gradient elastic modulus. Through differentiated material design with low modulus at the center, medium modulus in the middle, and high modulus at the edges, it adapts to the radially differentiated working conditions in the polishing process of large-size hard and brittle substrates from the intrinsic material level. This effectively solves the core problems of traditional homogeneous gas films, such as over-polishing at the center, edge collapse, and local premature aging, thereby effectively improving the flatness of the substrate after polishing. At the same time, the polishing head assembly provided in this application does not add any additional production steps and is suitable for the mass production processing needs of semiconductor substrates of various sizes and materials, with significant technical advantages and industrial application value.

[0082] The various embodiments in this specification are described in a progressive, parallel, or combined manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

[0083] It should be noted that, in the description of this application, the accompanying drawings and embodiments are illustrative rather than restrictive. The same reference numerals throughout the embodiments identify the same structures. It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in an article or device comprising the aforementioned element.

[0084] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polishing head assembly, comprising: include: Matrix; A retaining ring is located on one side of the substrate; The air film assembly is located on the same side of the substrate as the retaining ring, and is located radially inside the retaining ring; The air-film assembly is divided into a central region, an intermediate region, and an edge region in a radial direction from the inside to the outside. The elastic modulus of the central region is the first modulus, the elastic modulus of the intermediate region is the second modulus, and the elastic modulus of the edge region is the third modulus. The second modulus is greater than the first modulus and less than the third modulus.

2. The polishing head assembly according to claim 1, characterized in that, The value range of the first modulus is 1.2 MPa to 3.2 MPa; The second modulus ranges from 4.5 MPa to 7.5 MPa. The value range of the third modulus is 8.0 MPa to 12.5 MPa.

3. The polishing head assembly according to claim 2, characterized in that, The material of the central region is fluorosilicone rubber or fumed silica gel. The material of the intermediate region is polyurethane or corrosion-resistant fluororubber; The material of the edge region is fluororubber or glass fiber reinforced fluorosilicone rubber.

4. The polishing head assembly according to claim 1, characterized in that, The central region is a circular area originating from the center of the air-supported membrane module, and the corresponding radial range is 40% to 60% of the radius of the air-supported membrane module. The intermediate region is an annular area surrounding the central region, and the corresponding radial range is 50% to 90% of the radius of the air-film assembly; The edge region is a ring-shaped area surrounding the middle region, and the corresponding radial range is 80% to 100% of the radius of the air film assembly.

5. The polishing head assembly according to claim 1, characterized in that, A first structure is provided at the junction between the central area and the intermediate area, and at the junction between the intermediate area and the edge area; The first structure includes at least one of a sealing structure and an anti-permeability structure.

6. The polishing head assembly according to claim 1, characterized in that, In the air-film assembly, the thickness of the central region, the intermediate region, and the edge region is the same, and the value ranges from 1mm to 10mm.

7. The polishing head assembly according to claim 1, characterized in that, The substrate has a first air pressure chamber, a second air pressure chamber, and a third air pressure chamber arranged radially in sequence on the side facing the air film assembly. Wherein, the first air pressure chamber corresponds to the central area, the second air pressure chamber corresponds to the middle area, and the third air pressure chamber corresponds to the edge area; The air-film assembly seals the openings of the first air pressure chamber, the second air pressure chamber, and the third air pressure chamber, and forms the bottom surface of each chamber.

8. The polishing head assembly according to claim 7, characterized in that, The gas pressure in the first, second, and third pressure chambers ranges from 0 to 8 psi.

9. The polishing head assembly according to claim 7, characterized in that, The first, second, and third air pressure chambers are all equipped with anti-wrinkle limiting support structures.

10. A polishing device, characterized in that, Includes the polishing head assembly as described in any one of claims 1-9.

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