A carrier head for chemical mechanical polishing and a chemical mechanical polishing apparatus

Abstract

The application discloses a carrier head and a chemical mechanical polishing device for chemical mechanical polishing, and relates to the technical field of semiconductor manufacturing. The carrier head comprises a base, a holding film, a floating seat, an adsorption disc and an adsorption film. The outer edge of the holding film is sealingly connected to the base, and the inner edge of the holding film is sealingly connected to the floating seat, so that the floating seat can vertically float relative to the base. The adsorption disc is fixedly connected below the floating seat. The top surface of the adsorption disc is provided with at least one concentric annular groove and at least one radial groove passing through the center of the adsorption disc. The concentric annular groove intersects with the radial groove to form a plurality of intersection points. The adsorption film is wrapped below and on the outer periphery of the adsorption disc. The bottom surface of the adsorption film is provided with a plurality of upwardly extending connecting ribs which are arranged in a radial manner. The positions of the connecting ribs on the adsorption disc correspond to the positions of the connecting ribs on the adsorption film, and the connecting ribs are provided with through holes at the intersection points. The connecting ribs pass through the through holes to fix the adsorption film to the adsorption disc.

Description

Technical Field

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

[0002] In semiconductor manufacturing, chemical mechanical polishing (CMP) is a key process for achieving wafer surface planarization in integrated circuit manufacturing. During CMP, a carrier head presses the wafer onto a rotating polishing pad, removing material through the synergistic effect of chemical etching and mechanical abrasion. The carrier head typically contains a flexible gas film. By filling the chamber between the gas film and the carrier head body with pressurized gas, the gas film expands and applies specific pressure to different areas on the back of the wafer, thereby adjusting the material removal rate in different radial regions of the wafer and controlling the uniformity of polishing. Furthermore, a retaining ring is usually provided on the outer periphery of the carrier head. During polishing, the bottom surface of the ring remains in contact with the polishing pad to prevent the wafer from sliding out from under the carrier head under centrifugal force.

[0003] However, the traditional bearing head structure described above has significant drawbacks for polishing third-generation semiconductor materials such as silicon carbide (SiC). SiC wafers have a front (Si face) and a back (C face). During polishing, the Si face is typically processed, while the C face comes into contact with the gas film within the bearing head. Due to the lower surface energy and coefficient of friction of the C face, and the fact that the gas film itself is a flexible component, the frictional force between the gas film and the wafer's C face is often less than the frictional force between the wafer's front face and the polishing pad. During polishing, especially when using high polishing pressure to increase the removal rate, the wafer easily overcomes the frictional force of the gas film, resulting in relative movement. This relative movement can cause scratches or reverse etching defects at the edge of the wafer's C face, a phenomenon known as "reverse etching on the back of the wafer," affecting wafer quality.

[0004] Meanwhile, SiC material has high hardness and strong chemical inertness, necessitating process pressures far exceeding those used in silicon polishing to achieve effective material removal. Under these high-pressure conditions, the wafer, under the combined action of the polishing pad and polishing fluid, will further exhibit a tendency to slip laterally, frequently impacting the inner side of the retaining ring of the bearing head. This causes damage to the inner side of the retaining ring, increasing consumable costs; furthermore, in severe cases, it can cause the wafer to slip out of the bearing head, resulting in fragmentation and scrap. Existing film-type bearing heads struggle to reliably hold the wafer while providing sufficient polishing pressure, necessitating a novel bearing head structure capable of stably adhering to the wafer and preventing relative movement even under high-pressure polishing.

[0005] Furthermore, silicon carbide differs significantly from traditional silicon materials in physical and chemical properties, which directly determines the special requirements for the bearing head design. Specifically: ① Hardness and brittleness: Silicon carbide has a Mohs hardness of up to 9.5, far exceeding the 6.5 of single-crystal silicon, and its fracture toughness is only about 1 / 3 of that of silicon. This means that if silicon carbide is subjected to non-uniform forces or local stress concentrations during polishing, it is extremely prone to edge chipping or wafer breakage. Therefore, the contact between the bearing head and the back of the wafer must be fully flexible and without hard protrusions to eliminate stress concentration points. ② Low surface energy of the C-plane: The surface energy of the C-plane (carbon termination surface) of silicon carbide is usually below 50 mJ / m², while the surface energy of the back of a silicon wafer is about 100-150 mJ / m². The significant reduction in surface energy results in extremely weak adhesion between the CVD-deposited silicon nitride and other dielectric films and the C-plane. The traditional gas film fixation method relying on friction is completely ineffective, and active vacuum adsorption is required for reliable fixation. ③ High Pressure Requirements: To achieve an effective material removal rate (MRR > 5 μm / h) for silicon carbide, the process pressure typically needs to reach 3-7 psi, which is 3-10 times higher than the traditional silicon polishing pressure (0.5-1.5 psi). Under this ultra-high pressure, the friction between the wafer and the polishing pad increases dramatically, and the driving force for lateral wafer slippage rises exponentially, placing extremely stringent requirements on the fixing ability of the bearing head. In summary, the special and demanding requirements of silicon carbide polishing can be summarized as three contradictory needs: "high pressure loading, continuous vacuum anti-slip, and flexible contact without damage." Traditional bearing head structures cannot simultaneously meet these three requirements, necessitating a completely new bearing head design. Summary of the Invention

[0006] In view of this, embodiments of this application provide a carrier head and a chemical mechanical polishing apparatus for chemical mechanical polishing, so as to at least partially solve the above-mentioned problems.

[0007] Based on an in-depth analysis of the specific requirements for silicon carbide polishing, this application proposes a bearing head structure consisting of a "fully flexible adsorption film + built-in channel connecting ribs". This structure, by designing the adsorption film as the sole contact element with the back of the wafer, utilizes its fully flexible nature to eliminate stress concentration and edge chipping risks that may occur when hard components contact the wafer. Through independent adsorption channels built into the connecting ribs, continuous and stable vacuum adsorption of the wafer is achieved throughout the polishing process, overcoming the defect of insufficient friction on the low surface energy C-surface. Simultaneously, through a pressure chamber independent of the adsorption channels, high polishing pressure can be applied independently without affecting adsorption stability, thus completely solving the technical challenge of simultaneously satisfying the three contradictory requirements of "high pressure, strong adsorption, and zero damage".

[0008] According to a first aspect of the embodiments of this application, a carrier head for polishing silicon carbide wafers is provided, comprising:

[0009] Matrix;

[0010] A membrane is maintained, its outer edge is sealed to the substrate, and its inner edge is sealed to a floating seat, so that the floating seat can float vertically relative to the substrate;

[0011] An adsorption plate is fixedly connected to the bottom of the floating seat. The top surface of the adsorption plate is provided with at least one concentric annular groove and at least one radial groove passing through the center of the adsorption plate. The concentric annular groove and the radial groove intersect to form multiple intersection points.

[0012] An adsorption membrane is provided on the lower part and outer periphery of the adsorption disk. The bottom surface of the adsorption membrane is provided with multiple upwardly extending connecting ribs, which are arranged radially.

[0013] Wherein, a through-hole is provided on the adsorption plate at the position corresponding to the connecting rib and at the intersection, and the connecting rib passes through the fixing hole to fix the adsorption film to the top surface of the adsorption plate.

[0014] The adsorption membrane and the bottom surface of the adsorption disk form a pressure chamber.

[0015] The adsorption plate is provided with a first vent hole that communicates with the pressure chamber, for providing positive or negative pressure to the pressure chamber;

[0016] The connecting rib has a through-type adsorption channel extending along its length. One end of the channel is connected to the bottom surface of the adsorption membrane, and the other end is connected to a second vent hole provided on the adsorption plate or substrate, which is used to provide adsorption negative pressure to the bottom surface of the adsorption membrane.

[0017] In some embodiments, the first vent is configured to provide positive pressure to the pressure chamber to apply polishing pressure to the silicon carbide wafer through the adsorption membrane during polishing.

[0018] In some embodiments, the first vent and the second vent are isolated from each other in the air path and are respectively connected to different air sources.

[0019] In some embodiments, the adsorption membrane covers the entire bottom surface and outer peripheral side surface of the adsorption disk from bottom to top, and a gap is left between the top surface of the adsorption membrane and the top surface of the adsorption disk to allow the adsorption membrane to expand or contract under the gas pressure in the pressure chamber.

[0020] In some embodiments, the top end of the connecting rib passes through the fixing hole and protrudes from the top surface of the adsorption disk; the top end of the connecting rib is fixed to the top surface of the adsorption disk by hot pressing or adhesive bonding.

[0021] In some embodiments, the connecting ribs and the adsorption membrane are integrally formed, and the number of ribs is 6, 8 or 12, and they are evenly spaced in the circumferential direction.

[0022] In some embodiments, the adsorption membrane is made of silicone rubber, fluororubber, or polyurethane elastomer; the retaining membrane is a silicone rubber membrane or a polyurethane membrane with a thickness of 0.2 mm to 1.0 mm.

[0023] In some embodiments, the bearing head further includes an annular flexible pressure diaphragm disposed above or around the adsorption disk for applying additional downward pressure to the edge region of the adsorption disk.

[0024] According to a second aspect of the embodiments of this application, a chemical mechanical polishing method is provided, which uses the bearing head described in any of the above claims, and includes the following steps:

[0025] S1, place the silicon carbide wafer below the adsorption film, so that the back side of the wafer contacts the bottom surface of the adsorption film;

[0026] S2, firstly, a first negative pressure is provided to the bottom surface of the adsorption membrane through the second vent and the adsorption channel to adsorb the wafer onto the bottom surface of the adsorption membrane; after the wafer is adsorbed, a second negative pressure is provided to the pressure chamber through the first vent to cause the adsorption membrane to contract upward and assist in tightening the wafer;

[0027] S3, stop providing the second negative pressure to the pressure chamber and switch to providing positive pressure to the pressure chamber, causing the adsorption film to expand downward and apply polishing pressure to the back side of the wafer; at the same time, maintain the first negative pressure in the adsorption channel unchanged, so as to keep the wafer radially fixed throughout the polishing process;

[0028] S4 drives the bearing head to rotate and press down to perform chemical mechanical polishing on the silicon carbide wafer.

[0029] According to a third aspect of the embodiments of this application, a chemical mechanical polishing apparatus is provided, which includes a polishing disc, a liquid supply device, a dressing device, and a bearing head as described in any of the above. The bearing head presses a silicon carbide wafer to be polished against a polishing pad above the polishing disc. The liquid supply device supplies polishing liquid between the polishing pad and the silicon carbide wafer. The dressing device is used to dress the surface of the polishing pad.

[0030] The beneficial effects of this application include:

[0031] a. Effectively avoids wafer backside damage: By setting radial connecting ribs with built-in adsorption channels on the bottom surface of the adsorption film, a continuous and stable adsorption negative pressure is provided to the wafer backside using an independent second ventilation path, ensuring that the wafer remains fixed in a state without relative movement to the carrier head throughout the polishing process. This completely eliminates the relative slippage between the wafer C-side and the carrier head caused by insufficient gas film friction, fundamentally solving the common wafer backside reverse etching defect in silicon carbide wafer polishing and improving wafer yield.

[0032] b. Significantly reduces the risk of retainer ring damage and slippage: During high-pressure polishing of silicon carbide wafers, the wafer is firmly fixed to the support head by the negative pressure generated by the adsorption channels. The wafer will not be displaced due to the lateral shear force of the polishing pad, thus avoiding repeated impacts of the wafer edge onto the inner side of the retainer ring. On the one hand, scratches and wear caused by impacts no longer occur on the inner side of the retainer ring, extending the service life of the retainer ring and reducing consumable costs; on the other hand, the risk of the wafer slipping out of the support head and resulting in fragmentation and scrapping is completely eliminated, improving process safety.

[0033] c. Independent control of adsorption fixation and polishing pressure application, adapting to high-pressure polishing processes: This application controls the "wafer fixation" function and the "polishing pressure application" function separately through two independent gas path channels. During the polishing stage, while maintaining a constant negative pressure within the adsorption channel, positive pressure can be independently applied to the pressure chamber to increase the polishing pressure. This dual-mode, independently controlled structural design allows the carrier head to stably adsorb the wafer under low pressure and maintain the wafer's precise position during high-pressure polishing. Simultaneously, the adsorption film can expand uniformly through the positive pressure in the pressure chamber, applying stable and controllable polishing pressure to the back of the wafer, significantly improving the polishing uniformity and surface accuracy of the silicon carbide wafer. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0035] Figure 1 This is a schematic diagram of a carrier head for polishing silicon carbide wafers according to an embodiment of this application;

[0036] Figure 2 yes Figure 1 A magnified view of a section at point A in the middle;

[0037] Figure 3 This is a schematic diagram of an adsorption plate provided in one embodiment of this application;

[0038] Figure 4 This is a schematic diagram of an adsorption membrane provided in an embodiment of this application;

[0039] Figure 5 yes Figure 4 A magnified view of a section at point B in the middle;

[0040] Figure 6 This is a schematic diagram of the bottom surface of the adsorption membrane provided in an embodiment of this application;

[0041] Figure 7 This is a schematic diagram of a floating seat provided in an embodiment of this application;

[0042] Figure 8 yes Figure 7 A magnified view of a section at point C;

[0043] Figure 9 This is a flowchart of a chemical mechanical polishing method provided in an embodiment of this application;

[0044] Figure 10 This is a schematic diagram of a chemical mechanical polishing apparatus provided in an embodiment of this application. Detailed Implementation

[0045] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0046] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0047] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0048] This application provides a carrier head for polishing silicon carbide wafers and a chemical mechanical polishing method using the carrier head. The carrier head, through a unique structure combining an adsorption film and an adsorption disk, achieves reliable adsorption and fixation of the silicon carbide wafer, and can independently control the adsorption force and polishing pressure under high-pressure polishing conditions. This effectively solves technical problems such as reverse etching of the wafer back, damage to the inner side of the holding ring, and wafer slippage during the silicon carbide wafer polishing process.

[0049] The following is a combination of... Figures 1 to 8 The carrier head 100 provided in the embodiments of this application will be described in detail.

[0050] Figure 1 This is a schematic diagram of a carrier head for polishing silicon carbide wafers according to an embodiment of this application. The carrier head 100 may include a substrate 10, a holding film 20, a floating seat 30, an adsorption disk 40, an adsorption film 50, a pivot seat 70, a holding ring 80, and a limiting ring 90.

[0051] The base 10 is generally disc-shaped and is used to fix other components of the support head 100. An upwardly extending shaft is provided at the center of the base 10. This shaft is used to cooperate with the pivot seat 70 described below to realize the rotational movement of the support head 100.

[0052] A pivot seat 70 is disposed above the base 10, and a through hole is provided in the center of the pivot seat 70. The shaft portion of the base 10 is slidably inserted into the through hole of the pivot seat 70 and can move vertically therein. A connecting flange is provided on the top of the pivot seat 70 for fixed connection with an external drive shaft. When the external drive rotates, the pivot seat 70 rotates accordingly.

[0053] Figure 1 In this structure, the carrier head 100 also includes an annular diaphragm 61, which connects the pivot seat 70 and the substrate 10. Specifically, the inner edge of the annular diaphragm 61 is sealed to the pivot seat 70, and the outer edge of the annular diaphragm 61 is sealed to the substrate 10. The annular diaphragm 61 is made of a material with good elasticity and flexibility, such as silicone rubber, fluororubber, or polyurethane elastomer. The pivot seat 70 is integrally connected to the substrate 10 via the annular diaphragm 61, allowing the substrate 10 to rotate with the pivot seat 70. Simultaneously, due to the elastic properties of the annular diaphragm 61, the substrate 10 can also generate a certain floating displacement relative to the pivot seat 70 in the vertical direction. This floating structure is mainly used to change the position of the loaded wafer in the vertical direction to facilitate wafer loading and unloading.

[0054] Furthermore, a retaining membrane 20 is disposed between the substrate 10 and the floating seat 30. The outer edge of the retaining membrane 20 is sealed to the substrate 10, and the inner edge of the retaining membrane 20 is sealed to the floating seat 30. The retaining membrane 20 is also made of an elastic material, such as a silicone rubber membrane or a polyurethane membrane, with a thickness that can be set between 0.2 mm and 1.0 mm and an elongation at break greater than 300%. By filling the cavity between the retaining membrane 20 and the substrate 10 with pressurized gas, the floating seat 30 can be driven to move axially relative to the substrate 10. At the same time, due to the flexible connection characteristics of the retaining membrane 20, the floating seat 30 can tilt and float relative to the substrate 10 to a certain extent, further enhancing the adaptive compensation capability of the bearing head 100 for parallelism errors.

[0055] Figure 1 In the illustrated embodiment, the floating seat 30 is fixedly connected to the lower part of the retaining membrane 20 and moves as the retaining membrane 20 floats. The floating seat 30 is generally disk-shaped and is used to fix the adsorption plate 40.

[0056] Figure 7 This is a schematic diagram of a floating seat provided in one embodiment of this application. Figure 8 yes Figure 7 A magnified view of section C. The bottom surface of the floating seat 30 is provided with an edge groove 31. This edge groove 31 is located at the edge of the bottom surface of the floating seat 30 and has an annular or discontinuous groove structure. When the adsorption film 50 covers the lower and outer periphery of the adsorption disk 40, the top edge of the adsorption film 50 will adhere to the bottom surface of the floating seat 30. The presence of the edge groove 31 increases the contact area and friction between the adsorption film 50 and the bottom surface of the floating seat 30, thereby helping to fix the adsorption film 50 and preventing relative slippage or detachment of the adsorption film 50 during high-pressure polishing.

[0057] In this application, the adsorption disk 40 is fixedly connected to the lower part of the floating seat 30. The adsorption disk 40 is generally disc-shaped and made of a material with a certain degree of rigidity, such as ceramic, silicon carbide ceramic, stainless steel, or engineering plastic. The top surface of the adsorption disk 40 (i.e., the side facing the floating seat 30) is provided with at least one concentric annular groove 41 and at least one radial groove 42 passing through the center of the adsorption disk 40. Figure 3 In the illustrated embodiment, six concentric annular grooves 41 and eight radial grooves 42 are shown. However, those skilled in the art will understand that the number of concentric annular grooves 41 can be set to 3 to 8, and the number of radial grooves 42 can be set to 5 to 12, the specific number of which can be adjusted according to the actual polishing pressure partitioning requirements and wafer size. The concentric annular grooves 41 and radial grooves 42 intersect each other, forming multiple intersection points on the top surface of the adsorption disk 40. These intersection points are evenly distributed in the circumferential direction.

[0058] Figure 3 In the illustrated embodiment, the adsorption disk 40 is further provided with a through-hole 43. The position of the fixing hole 43 is precisely located at the intersection of the concentric annular groove 41 and the radial groove 42. The fixing hole 43 penetrates the top and bottom surfaces of the adsorption disk 40, and is used for supplying... Figure 2 The connecting rib 51 of the adsorption membrane 50 shown passes through it. Furthermore, a first vent 44 is provided in the central region of the adsorption disk 40. Figure 3The first vent 44 is located at the center of the adsorption disk 40, but it can also be slightly offset from the center of the adsorption disk 40 to connect to the pressure chamber. The first vent 44 penetrates the adsorption disk 40, with one end connected to the bottom surface of the adsorption disk 40, that is, connected to the pressure chamber described below, and the other end connected to an external air source through a pipeline; wherein, the external air source can be a positive pressure source or a negative pressure source.

[0059] In this application, the adsorption film 50 covers the lower part and outer periphery of the adsorption disk 40. The adsorption film 50 is a thin film structure with a certain degree of elasticity and flexibility, and can be made of materials such as silicone rubber, fluororubber, or polyurethane elastomer. The adsorption film 50 covers the entire bottom surface of the adsorption disk 40 and the outer peripheral side surface of the adsorption disk 40 from bottom to top, and the bottom surface of the adsorption disk 40 is the surface that contacts the back side of the wafer. The top edge of the adsorption film 50 is attached to the bottom surface of the floating seat 30 and is fixed by increasing friction through the aforementioned edge groove 31.

[0060] Furthermore, the bottom surface of the adsorption membrane 50 is provided with multiple upwardly extending connecting ribs 51. For example... Figure 6 As shown, multiple connecting ribs 51 are arranged radially, extending radially from the center area of ​​the bottom surface of the adsorption membrane 50 to the edge, and are evenly spaced in the circumferential direction. The number of connecting ribs 51 is preferably 6, 8, or 12, but is not limited to these. The connecting ribs 51 and the adsorption membrane 50 are preferably integrally formed, for example, by injection molding or compression molding, to ensure structural strength and dimensional accuracy.

[0061] Figure 5 yes Figure 4 In the enlarged view at point B, each connecting rib 51 has a through-type adsorption channel 511 extending along its length. One end of the adsorption channel 511 connects to the bottom surface of the adsorption membrane 50, and the other end extends to the top of the connecting rib 51. When the adsorption membrane 50 covers the adsorption disk 40, the connecting rib 51 passes through the fixing hole 43 at the corresponding position on the adsorption disk 40, so that the other end of the adsorption channel 511 connects to the second vent hole (not shown in the figure) provided on the adsorption disk 40 or the substrate 10. Through the second vent hole and the adsorption channel 511, an adsorption negative pressure can be provided to the bottom surface of the adsorption membrane 50, thereby firmly adsorbing the wafer onto the bottom surface of the adsorption membrane 50.

[0062] It is worth noting that when the adsorption membrane 50 covers the lower part and outer periphery of the adsorption disk 40, a closed space is formed between the top surface of the adsorption membrane 50 and the bottom surface of the adsorption disk 40. This space is the pressure chamber described in this application. The pressure chamber is formed by the adsorption membrane 50 and the bottom surface of the adsorption disk 40, and its shape is roughly a flat disc. The first vent 44 provided on the adsorption disk 40 communicates with the pressure chamber. Positive or negative pressure can be provided to the pressure chamber through the first vent 44. Due to the good elasticity of the adsorption membrane 50, when the pressure chamber is filled with positive pressure gas, the adsorption membrane 50 will expand downward (i.e., towards the wafer), applying uniform polishing pressure to the back side of the wafer placed below the adsorption membrane 50. When negative pressure is drawn into the pressure chamber, the adsorption membrane 50 will contract upward (i.e., towards the adsorption disk 40), assisting in tightening or releasing the wafer.

[0063] Therefore, the embodiments of this application implement two independent gas path control channels:

[0064] First air passage: It is connected to the pressure chamber between the adsorption membrane 50 and the bottom surface of the adsorption disk 40 through the first air hole 44. It is mainly used to provide positive pressure to the pressure chamber during the polishing stage to generate polishing pressure.

[0065] The second air passage is connected to the bottom surface of the adsorption membrane 50 through the second vent and the adsorption channel 511 inside the connecting rib 51. It is mainly used to provide a continuous adsorption negative pressure throughout the process to fix the wafer and prevent it from moving relative to the surface.

[0066] These two gas channels are isolated from each other and connected to different gas sources, allowing for independent control. This design enables the carrier head 100 to maintain reliable wafer adsorption while independently adjusting the polishing pressure without interference, making it particularly suitable for silicon carbide wafer processes requiring high pressure and long polishing times. Specifically, a negative pressure is maintained through the second gas channel to achieve reliable wafer adsorption; the positive pressure is adjusted through the first gas channel to independently regulate the polishing pressure.

[0067] Figure 1 In the illustrated embodiment, the carrier head 100 further includes a retaining ring 80. The retaining ring 80 is disposed on the outer periphery of the adsorption film 50 and located below the substrate 10. The retaining ring 80 is used to contact the polishing pad during polishing, confining the wafer within the area below the carrier head 100 and preventing the wafer from slipping out.

[0068] Furthermore, in some embodiments, the bearing head 100 may also include an annular flexible pressure diaphragm 60, such as Figure 2 As shown. The annular flexible pressure membrane 60 is disposed below the substrate 10 and above the adsorption disk 40, as... Figure 1As shown, by filling the annular flexible pressure membrane 60 with pressurized gas, the annular flexible pressure membrane 60 can expand downwards to apply additional downward pressure to the edge region of the adsorption disk 40 (i.e., the region corresponding to the wafer edge), thereby achieving fine adjustment of the polished morphology of the wafer edge. This plays an important role in improving the flatness of the wafer edge and preventing over-polishing of the edge.

[0069] Furthermore, the bearing head 100 also includes a limiting ring 90, which is disposed above the floating seat 30. The limiting ring 90 is positioned to match the position of the annular flexible pressure membrane 60, thereby reducing the vertical distance between the annular flexible pressure membrane 60 and the floating seat 30 and increasing the response speed of the annular flexible pressure membrane 60. That is, the annular flexible pressure membrane 60 only needs to be slightly inflated to abut against the limiting ring 90 and then transmit the pressure to the edge area of ​​the adsorption plate 40.

[0070] Figure 1 In this design, the inner surface of the limiting ring 90 is provided with a limiting wedge surface, and the lower end of the base 10 is provided with a base wedge surface. The limiting wedge surface and the base wedge surface are matched to rigidly limit the range of vertical movement of the base 10 relative to the pivot seat 70. It should be noted that the limiting wedge surface is a certain distance from the bottom surface of the limiting ring 90, and this distance is the distance of vertical movement of the base 10.

[0071] To further verify the technical effects of this application, this embodiment provides a set of comparative experimental data. The experiments used the same silicon carbide wafers (4H-SiC, 150mm in diameter, polished with the Si side facing down), and under the same polishing parameters (polishing pressure 5psi, polishing disk speed 60rpm, bearing head speed 55rpm, commercial SiC polishing slurry, polishing time 1h), polishing was performed using the bearing head of this application (experimental group) and a conventional typical bearing head structure (control group). The control group used a rigid adsorption disk combined with a soft pad, directly fixing the wafer through adsorption holes, and applying polishing pressure through an independent pressure chamber. This structure is used in the prior art to improve wafer fixation and pressure zone control. Each group polished 100 wafers, and the key indicators are as follows:

[0072]

[0073] The above experimental data fully demonstrate that, compared with typical bearing head structures in existing technologies, the "fully flexible adsorption film + built-in channel connecting rib" structure of this application has achieved significant and unexpected technical effects in the polishing process of silicon carbide wafers. Specifically: ① The defect rate on the back side of the wafer is completely eliminated. This is because the fully flexible adsorption film completely eliminates any point or line contact between the hard components and the back side of the wafer, avoiding scratches caused by stress concentration; ② The edge chipping rate is reduced from 2% to zero. This is because the adsorption film completely wraps around the back side of the wafer, achieving uniform pressure distribution, and the active vacuum adsorption provided by the connecting ribs prevents any lateral displacement of the wafer during polishing, thus eliminating collisions between the wafer edge and the retaining ring; ③ The retaining ring life is extended by 20 times, directly verifying that lateral slippage of the wafer is fundamentally suppressed. These data strongly support the inventiveness assertion of this application.

[0074] Furthermore, this application also provides a chemical mechanical polishing method, which uses the aforementioned bearing head 100 for chemical mechanical polishing, and its flowchart is shown below. Figure 9 As shown. This chemical mechanical polishing method includes the following steps:

[0075] Step 1 (S1): Place the silicon carbide wafer below the adsorption film 50, so that the back side of the wafer contacts the bottom surface of the adsorption film 50.

[0076] Specifically, the silicon carbide wafer to be polished is placed under the carrier head 100 by a robotic arm or manually, with the C-side (back side) of the wafer facing upwards and in contact with the bottom surface of the adsorption film 50 (i.e., the bottom surface of the connecting rib 51). At this point, the wafer is not yet fixed and requires subsequent adsorption steps.

[0077] Step 2 (S2): First, a first negative pressure is provided to the bottom surface of the adsorption membrane 50 through the second vent and adsorption channel 511 to adsorb the wafer onto the bottom surface of the adsorption membrane 50; after the wafer is adsorbed, a second negative pressure is provided to the pressure chamber through the first vent 44 to cause the adsorption membrane 50 to contract upward and help tighten the wafer.

[0078] Specifically, firstly, the negative pressure source corresponding to the second air path channel is activated, generating a first negative pressure within the adsorption channel 511. This negative pressure is transmitted to the opening on the bottom surface of the adsorption membrane 50, firmly adsorbing the back side of the wafer onto the adsorption membrane 50. After the wafer is reliably adsorbed, the negative pressure source corresponding to the first air path channel is activated again, providing a second negative pressure to the pressure chamber through the first vent 44, causing the adsorption membrane 50 to contract upwards as a whole. This action tightens the adsorption membrane 50, resulting in a tighter fit between the wafer and the bottom surface of the adsorption membrane 50, which helps in wafer positioning and air bubble release, ensuring that the wafer is adsorbed flat.

[0079] Step 3 (S3): Stop providing the second negative pressure to the pressure chamber and switch to providing positive pressure to the pressure chamber, causing the adsorption film 50 to expand downward and apply polishing pressure to the back side of the wafer; at the same time, maintain the first negative pressure in the adsorption channel 511 unchanged, so as to keep the wafer radially fixed throughout the polishing process.

[0080] Specifically, once the wafer is reliably adsorbed, the negative pressure source of the first gas path channel is shut off, ceasing the supply of negative pressure to the pressure chamber. Then, the positive pressure source of the first gas path channel is opened, and positive pressure gas, such as compressed air or nitrogen, is introduced into the pressure chamber through the first vent 44. As the pressure in the pressure chamber increases, the adsorption film 50 expands downwards, applying a uniform and adjustable polishing pressure to the back of the wafer. Simultaneously, the second gas path channel maintains a constant first negative pressure within the adsorption channel 511, ensuring continuous wafer adsorption. This "dual-mode" operation ensures that the wafer remains radially positioned throughout the high-pressure polishing process, preventing slippage due to friction from the polishing pad.

[0081] Step 4 (S4): Drive the bearing head 100 to rotate and press down to perform chemical mechanical polishing on the silicon carbide wafer.

[0082] Specifically, the pivot seat 70 is rotated by an external drive shaft, and the rotation is transmitted through the annular film 61, the substrate 10, the holding film 20, the floating seat 30, and the adsorption disk 40, ultimately causing the adsorption film 50 and the adsorbed silicon carbide wafer to rotate together. Simultaneously, the bearing head 100 presses down, causing the front side (Si side) of the wafer to contact the rotating polishing pad at a set pressure. Polishing slurry is supplied between the wafer and the polishing pad. Under the combined action of chemical etching and mechanical polishing, the material on the front side of the wafer is gradually removed, achieving planarization.

[0083] Throughout the polishing process, the positive pressure supplied to the pressure chamber by the first air passage can be adjusted in real time according to process requirements, thereby dynamically adjusting the polishing pressure. Simultaneously, the negative pressure within the adsorption channel 511 is kept stable to ensure that the wafer does not undergo radial slippage. After polishing is complete, the positive pressure in the pressure chamber and the negative pressure in the adsorption channel are released sequentially, allowing the polished wafer to be easily removed.

[0084] In addition, this application also provides a chemical mechanical polishing apparatus 1000, the schematic diagram of which is shown below. Figure 10 As shown.

[0085] A chemical mechanical polishing (CMP) apparatus 1000 may include a polishing disc 300, a polishing pad 200, a dressing device 400, a liquid supply device 500, and... Figure 1 The carrier head 100 is shown.

[0086] The polishing pad 200 is disposed on the upper surface of the polishing disk 300 and rotates together with it along the axis Ax; the horizontally movable bearing head 100 is disposed above the polishing pad 200, and the substrate to be polished is loaded on its lower surface; the trimming device 400 includes a trimming arm and a trimming head, which is disposed on one side of the polishing disk 300, and the trimming arm drives the rotating trimming head to swing to trim the surface of the polishing pad 200; the liquid supply device 500 is disposed on the upper side of the polishing pad 200 to distribute the polishing liquid on the surface of the polishing pad 200.

[0087] During the polishing operation, the bearing head 100 presses the surface of the substrate to be polished against the surface of the polishing pad 200. The bearing head 100 rotates and reciprocates radially along the polishing disc 300, gradually removing impurities from the substrate surface in contact with the polishing pad 200. Simultaneously, the polishing disc 300 rotates, and the liquid supply device 500 sprays polishing liquid onto the surface of the polishing pad 200. Under the chemical action of the polishing liquid, the relative movement between the bearing head 100 and the polishing disc 300 causes the substrate to rub against the polishing pad 200 for polishing.

[0088] During chemical mechanical polishing, the dressing device 400 is used to dress and activate the surface morphology of the polishing pad 200. Using the dressing device 400, impurity particles remaining on the surface of the polishing pad, such as abrasive particles in the polishing slurry and waste material detached from the substrate surface, can be removed. It can also smooth out the surface deformation of the polishing pad 200 caused by abrasion, ensuring the consistency of the surface morphology of the polishing pad 200 during polishing, thereby maintaining a stable polishing removal rate.

[0089] Figure 10 In the illustrated embodiment, the top surface of the adsorption disk 40 of the support head 100 is provided with a concentric annular groove 41 and a radial groove 42, which intersect to form an intersection point, and a fixing hole 43 is provided at the intersection point. The adsorption membrane 50 covers the lower part and outer periphery of the adsorption disk 40, and its bottom surface is provided with radially arranged connecting ribs 51. The connecting ribs 51 pass through the fixing hole 43 to fix the adsorption membrane 50 to the adsorption disk 40. A pressure chamber is formed between the adsorption membrane 50 and the bottom surface of the adsorption disk 40. Positive or negative pressure is provided to the pressure chamber through the first vent hole 44. At the same time, a through adsorption channel 511 extending along the length direction is provided inside the connecting rib 51, and an independent adsorption negative pressure is provided to the bottom surface of the adsorption membrane 50 through the second vent hole. This mechanical fixing method of "radial connecting ribs passing through fixing holes" combined with the dual air path control structure of "pressure chamber and adsorption channel being independent of each other" realizes the decoupled control of wafer adsorption fixation and polishing pressure application.

[0090] During the polishing process, the adsorption channel 511 continuously provides negative pressure to firmly fix the wafer, preventing radial slippage due to high polishing pressure. This fundamentally avoids back-side etching defects and damage to the inner side of the holding ring during silicon carbide wafer polishing. Simultaneously, the pressure chamber independently adjusts the positive pressure, causing the adsorption film 50 to expand uniformly, applying stable and controllable polishing pressure to the back side of the wafer. Through the above structural innovations, this application enables chemical mechanical polishing equipment to stably process hard and brittle materials such as silicon carbide, significantly improving polishing yield and process safety.

[0091] Those skilled in the art will recognize that the units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the embodiments of this application.

[0092] The above embodiments are only used to illustrate the embodiments of this application, and are not intended to limit the embodiments of this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of this application. Therefore, all equivalent technical solutions also fall within the scope of the embodiments of this application, and the patent protection scope of the embodiments of this application should be defined by the claims.

Claims

1. A support head for polishing silicon carbide wafers, characterized in that, include: Matrix; A membrane is maintained, its outer edge is sealed to the substrate, and its inner edge is sealed to a floating seat, so that the floating seat can float vertically relative to the substrate; An adsorption plate is fixedly connected to the bottom of the floating seat. The top surface of the adsorption plate is provided with at least one concentric annular groove and at least one radial groove passing through the center of the adsorption plate. The concentric annular groove and the radial groove intersect to form multiple intersection points. An adsorption membrane is provided on the lower part and outer periphery of the adsorption disk. The bottom surface of the adsorption membrane is provided with multiple upwardly extending connecting ribs, which are arranged radially. Wherein, a through-hole is provided on the adsorption plate at the position corresponding to the connecting rib and at the intersection, and the connecting rib passes through the fixing hole to fix the adsorption film to the top surface of the adsorption plate. The adsorption membrane and the bottom surface of the adsorption disk form a pressure chamber. The adsorption plate is provided with a first vent hole that communicates with the pressure chamber, for providing positive or negative pressure to the pressure chamber; The connecting rib has a through-type adsorption channel extending along its length. One end of the channel is connected to the bottom surface of the adsorption membrane, and the other end is connected to a second vent hole provided on the adsorption plate or substrate, which is used to provide adsorption negative pressure to the bottom surface of the adsorption membrane.

2. The bearing head according to claim 1, characterized in that, The first vent is configured to provide positive pressure to the pressure chamber to apply polishing pressure to the silicon carbide wafer through the adsorption membrane during polishing.

3. The bearing head according to claim 1, characterized in that, The first vent and the second vent are isolated from each other in the air path and are connected to different air sources respectively.

4. The bearing head according to claim 1, characterized in that, The adsorption membrane covers the entire bottom surface and outer peripheral side of the adsorption disk from bottom to top, and there is a gap between the top surface of the adsorption membrane and the top surface of the adsorption disk to allow the adsorption membrane to expand or contract under the gas pressure in the pressure chamber.

5. The bearing head according to claim 1, characterized in that, The top end of the connecting rib passes through the fixing hole and protrudes from the top surface of the adsorption plate; the top end of the connecting rib is fixed to the top surface of the adsorption plate by hot pressing or adhesive bonding.

6. The bearing head according to claim 1, characterized in that, The connecting ribs and the adsorption membrane are integrally formed, and there are 6, 8 or 12 of them, which are evenly distributed in the circumferential direction.

7. The bearing head according to claim 1, characterized in that, The adsorption membrane is made of silicone rubber, fluororubber or polyurethane elastomer; the retaining membrane is a silicone rubber membrane or a polyurethane membrane with a thickness of 0.2 mm to 1.0 mm.

8. The bearing head according to claim 1, characterized in that, It also includes an annular flexible pressure membrane, disposed above or around the adsorption disk, for applying additional downward pressure to the edge region of the adsorption disk.

9. A chemical mechanical polishing method, characterized in that, Using the bearing head according to any one of claims 1 to 8 includes the following steps: S1, place the silicon carbide wafer below the adsorption film, so that the back side of the wafer contacts the bottom surface of the adsorption film; S2, firstly, a first negative pressure is provided to the bottom surface of the adsorption membrane through the second vent and the adsorption channel to adsorb the wafer onto the bottom surface of the adsorption membrane; after the wafer is adsorbed, a second negative pressure is provided to the pressure chamber through the first vent to cause the adsorption membrane to contract upward and assist in tightening the wafer; S3, stop providing the second negative pressure to the pressure chamber and switch to providing positive pressure to the pressure chamber, causing the adsorption film to expand downward and apply polishing pressure to the back side of the wafer; at the same time, maintain the first negative pressure in the adsorption channel unchanged, so as to keep the wafer radially fixed throughout the polishing process; S4 drives the bearing head to rotate and press down to perform chemical mechanical polishing on the silicon carbide wafer.

10. A chemical mechanical polishing apparatus, characterized in that, The device includes a polishing pad, a liquid supply device, a trimming device, and a bearing head as described in any one of claims 1 to 8. The bearing head presses the silicon carbide wafer to be polished against a polishing pad above the polishing pad. The liquid supply device supplies polishing liquid between the polishing pad and the silicon carbide wafer. The trimming device is used to trim the surface of the polishing pad.

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