Master-slave partition cooperative pressurization polishing head and application thereof in wafer polishing

Abstract

The application discloses a polishing head with master-slave partition cooperative pressurization and application thereof in wafer polishing, and belongs to the technical field of polishing heads. The polishing head comprises a connecting module, a retaining ring flexible pressurization module and a master-slave partition cooperative pressurization module. The connecting module is connected with a main shaft of a host computer, and is internally provided with a plurality of gas channels, so that stable transmission of a plurality of gases can be realized. The retaining ring flexible pressurization module is driven by a ring-shaped air bag to deform, so as to pressurize the retaining ring and ensure that the retaining ring is closely attached to a polishing pad, thereby avoiding wafer slip during polishing. The master-slave partition cooperative pressurization module comprises a physically isolated master partition and a plurality of slave partitions. The master partition has a large pressurization capacity and can control the overall material removal rate of the wafer through large pressure. The slave partitions can finely control the surface topography of the wafer through small pressure, so that high material removal rate and high flatness polishing of the wafer are comprehensively realized. In addition, the module adopts a wedge-shaped guide mechanism, so that the tolerance of the polishing head to wafer thickness difference is improved, and the safety of the polishing process is enhanced.

Description

A master-slave partitioned collaborative pressure polishing head and its application in wafer polishing Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, specifically relating to a master-slave partitioned collaborative pressure polishing head and its application in wafer polishing. Background Technology

[0002] Chemical mechanical polishing (CMP) is a key technology for achieving local and global planarization of wafers and is widely used in the semiconductor manufacturing field. According to the Preston equation, polishing pressure and relative speed directly determine the material removal rate of the wafer, while the uniformity of polishing pressure distribution directly determines the flatness of the wafer.

[0003] With the rapid development of semiconductor technology, wafer size is gradually increasing, and the largest wafer size currently under research can reach 450mm, which makes the problem of polishing pressure distribution uniformity more prominent. At the same time, increasing polishing pressure may worsen its distribution uniformity, leading to uneven material removal rate distribution at different locations on the wafer, affecting wafer flatness and chip performance and reliability (Reference: Yeou-Yih Lin, Ship-Peng Lo, Finite element modeling for chemical mechanical polishing process under different back pressures, Journal of Materials Processing Technology, 2003, 140(1):646-652). In order to improve the uniformity of polishing pressure distribution, zone pressure technology has emerged (Reference: Dewen Zhao, Tongqing Wang, Yongyong He, Xinchun Lu, Effect of zone pressure on wafer bending and fluid lubrication behavior during multi-zone CMP process, Microelectronic Engineering, 2013, 108:33-38). However, existing zone pressure polishing heads have the following limitations:

[0004] 1) Coupling effects exist between different pressure zones, and these effects intensify with increasing pressure difference, making it difficult to control the uniformity of polishing pressure. With the rapid development of semiconductor technology, new applications, such as power devices, require novel semiconductor substrates, such as silicon carbide, gallium nitride, and diamond. However, unlike existing single-crystal silicon, these novel semiconductor substrates have high mechanical strength and strong chemical inertness, requiring high polishing pressure to achieve high material removal rates. This results in significant deformation in each zone of the gas film, easily leading to nonlinear pressurization and potentially exacerbating the coupling effect, making it difficult to control the uniformity of polishing pressure.

[0005] 2) The fixed distance between the gas film and the end face of the retaining ring makes the polishing head less tolerant of wafer thickness variations. When the wafer thickness varies significantly, the retaining ring needs to be re-machined to adjust the distance between the gas film and the end face of the retaining ring, which is a complex and costly process.

[0006] 3) Currently, there is a lack of unified standards in the design of the number and size of the various partitions in the partitioned pressure polishing head.

[0007] In summary, this invention specifically proposes a master-slave partitioned collaborative pressure polishing head and its application in wafer polishing, in order to overcome current limitations and achieve high material removal rate and high flatness polishing of wafers of different thicknesses. Summary of the Invention

[0008] To overcome the above-mentioned technical deficiencies, the present invention aims to provide a master-slave partitioned coordinated pressure polishing head and its application in wafer polishing. This polishing head can realize master-slave partitioned coordinated pressure, effectively control the uniformity of polishing pressure distribution, thereby comprehensively achieving high material removal rate and high flatness polishing of wafers, while improving the tolerance to wafer thickness differences and being suitable for polishing wafers with a wider thickness range.

[0009] To achieve the above-mentioned technical objectives and effects, the present invention solves the above-mentioned problems through the following technical solutions:

[0010] A polishing head with master-slave partitioned coordinated pressurization, characterized in that it includes a connecting module, a retaining ring flexible pressurization module, and a master-slave partitioned coordinated pressurization module. One end of the connecting module is connected to the main spindle of the host machine via a clamp, and its interior has multiple air channels for stably transmitting multiple gas channels delivered by the main spindle to various functional areas inside the polishing head. The other end of the connecting module is connected to one end of the retaining ring flexible pressurization module via an annular airbag, and the other end of the retaining ring flexible pressurization module is connected to the master-slave partitioned coordinated pressurization module via an air film. Driven by the main spindle, the connecting module drives the retaining ring flexible pressurization module and the master-slave partitioned coordinated pressurization module to rotate and move. The retaining ring flexible pressurization module generates an adaptive shape through gas-driven annular airbag. The master-slave partitioned collaborative pressurization module maintains the ring's flexibility and ensures a tight fit with the polishing pad, preventing wafer slippage during polishing. It comprises a physically isolated master partition and multiple slave partitions. The master partition has a high pressurization capacity, allowing for control of the overall material removal rate of the wafer through high pressure. The slave partitions can finely control the surface morphology of the wafer through low pressure, thereby achieving high material removal rate and high flatness polishing. The master-slave partitioned collaborative pressurization module employs a wedge-shaped guide mechanism, which improves the polishing head's tolerance to wafer thickness differences, making it suitable for polishing wafers with a wider thickness range. Simultaneously, it ensures the safety of the polishing process. This safety design prevents excessive air pressure from causing air film rupture, avoiding safety accidents such as the master-slave partitioned collaborative pressurization module detaching and impacting the host unit.

[0011] Preferably, the connection module includes a connector and a connecting flange. The connector has multiple air passages for transmitting multiple gases. A hole is opened at the center of one end of the connector to form a clearance fit with the guide post of the retaining ring flexible pressurization module, ensuring smooth axial movement and radial stability of the polishing head during flexible pressurization. The connecting flange has multiple positioning structures to ensure alignment with the main spindle of the host machine. It also has a flange ball groove, which further ensures alignment with the main spindle of the host machine through uniform compression of the balls.

[0012] Preferably, the retaining ring flexible pressurization module includes an annular airbag pressure ring, an annular airbag, an end cap, a fixed cavity, a guide post, and a retaining ring. One end of the guide post is fixed in the fixed cavity by bolts, and the other end of the guide post forms a clearance fit with the connector of the connecting module. The annular airbag pressure ring is connected to the connector of the connecting module by bolts. One end of the annular airbag is located between the annular airbag pressure ring and the connector, and a seal is achieved by the compression of the annular airbag pressure ring and the connector. The end cap is connected to the fixed cavity by bolts, and the other end of the annular airbag is located between the end cap and the fixed cavity, and a seal is achieved by the compression of the end cap and the fixed cavity, thereby forming a chamber. Under gas drive, the annular airbag undergoes adaptive deformation, sequentially pushing the fixed cavity and the retaining ring to move, thereby flexibly pressurizing the retaining ring to ensure that it fits tightly against the polishing pad and avoids wafer slippage during polishing.

[0013] Preferably, the master-slave partitioned coordinated pressurization module includes a gas film, a moving plate, a moving coil assembly, and a fastening ring. The moving coil assembly includes an inner moving coil, a middle moving coil, and an outer moving coil. The gas film sealing ring of the gas film is located between the retaining ring and the fixed cavity. The sealing is achieved by the compression between the retaining ring and the fixed cavity, forming a master partition. Driven by the gas in the master partition, the moving plate is moved, and the force is transmitted to the wafer to pressurize the master partition, thereby controlling the overall material removal rate of the wafer. The gas film is divided into multiple independent partitions by an internal annular rib. The moving plate is connected to the moving coil assembly by bolts. The gas film is located between the moving plate and the moving coil assembly. The sealing of each slave partition is achieved by the compression of the internal annular rib of the gas film by the moving plate and the moving coil assembly. Driven by the gas in each slave partition, the slave partition is pressurized, thereby controlling the surface morphology of the wafer.

[0014] Preferably, the moving plate wedge-shaped surface of the moving plate cooperates with the upper end of the fixed cavity wedge-shaped surface of the fixed cavity to form a wedge-shaped guide mechanism, which is used to adjust the lower limit distance h1. The other end of the moving plate cooperates with the lower end of the fixed cavity wedge-shaped surface to adjust the upper limit distance h2. By coordinating the adjustment of h1 and h2, the tolerance of the polishing head to wafer thickness differences can be improved, making it suitable for polishing wafers with a wider thickness range. At the same time, the safety of the polishing process is ensured. This safety design can prevent the gas film from rupturing due to excessive air pressure and avoid safety accidents such as the master-slave partitioned coordinating pressurization module falling off the polishing head and causing impact to the host.

[0015] This invention also discloses a design method for the slave partition of a polishing head with master-slave partition coordinated pressure, used to determine the number and size of the slave partitions, including polishing test method, pressure detection method, and finite element calculation method. The corresponding design method can be selected according to the actual situation. In the design method, the uniformity involved is = (maximum value - minimum value) / (2 × average value) × 100%.

[0016] Specifically as follows:

[0017] 1) Polishing test method

[0018] S1. First, a polishing experiment was conducted on the coated wafer using a non-partitioned pressure polishing head to obtain the material removal rate distribution characteristics of the thin film on the wafer surface at different locations.

[0019] S2. Perform data analysis on the material removal rate at each of the above locations, and divide the annular region according to specific technical requirements. For example, if it is required that the uniformity be controlled within 5% (for ease of description, this invention uses 5% as an example, but is not limited to 5%), then calculate the uniformity according to the formula, and divide the area where the material removal rate uniformity falls within the range of 5% from the center to the edge of the coated wafer into an annular region.

[0020] S3. Based on the divided annular region, determine the number and size of the partitions.

[0021] 2) Pressure testing method

[0022] S1. First, pressure distribution characteristics on the wafer surface are collected using a pressure detection device (such as a thin-film pressure sensor).

[0023] S2. Perform data analysis on the above pressure distribution characteristics and divide the annular region according to specific technical requirements. For example, if it is required that the uniformity be controlled within 5% (for ease of description, this invention uses 5% as an example, but is not limited to 5%), then calculate the uniformity according to the formula, and divide the area where the pressure uniformity falls within the range of 5% from the center to the edge of the coated wafer into an annular region.

[0024] S3. Based on the divided annular region, determine the number and size of the partitions.

[0025] 3) Finite element method

[0026] S1. First, the finite element method is used to simulate the loading of the polishing head and obtain the pressure distribution characteristics on the wafer surface.

[0027] S2. Perform data analysis on the above pressure distribution characteristics and divide the annular region according to specific technical requirements. For example, if it is required that the uniformity be controlled within 5% (for ease of description, this invention uses 5% as an example, but is not limited to 5%), then calculate the uniformity according to the formula, and divide the area where the pressure uniformity falls within the range of 5% from the center to the edge of the coated wafer into an annular region.

[0028] S3. Based on the divided annular region, determine the number and size of the partitions.

[0029] This invention also discloses the application of a master-slave partitioned collaborative pressure polishing head in wafer polishing, mainly including the following steps:

[0030] S1. Prepare the polishing solution. Taking a single-crystal silicon wafer as an example (this can be extended to other semiconductor materials), the polishing solution mainly contains deionized water, abrasive particles, cationic additives, surfactants or polymer additives, with a pH value of 2-11. The abrasive particles are one or more of alumina, silicon oxide, and cerium oxide.

[0031] S2. Attach the back of the wafer to the gas film and apply negative pressure to the master-slave partition to adsorb and fix it.

[0032] S3. Move the polishing head to the polishing position and ventilate in sequence: First, ventilate the annular airbag area to ensure the retaining ring is tightly attached to the polishing pad. Then, ventilate the main partition. The pressure exerted by the retaining ring on the polishing pad is 2 to 3 times the pressure exerted by the main partition on the wafer to prevent wafer slippage during polishing. Finally, ventilate each slave partition according to the polishing technology requirements to synergistically control the overall material removal rate and surface morphology of the wafer.

[0033] S4. Set process parameters such as air pressure, rotation speed, polishing fluid flow rate, and polishing time, and start polishing.

[0034] S5. After polishing, negative pressure is applied to the master-slave partition to fix the wafer in place, and negative pressure is applied to the annular airbag area to lift the retaining ring. After the polishing head is moved to the designated position, a small positive pressure is introduced into the master-slave partition to release the adsorption and remove the wafer.

[0035] The present invention has the following beneficial effects:

[0036] 1. This invention adopts a master-slave partitioned collaborative pressurization method. The master partition can control the overall material removal rate of the wafer through high pressure, while multiple slave partitions can finely control the surface morphology of the wafer through low pressure. Through master-slave partitioned collaborative pressurization, high material removal rate and high flatness polishing of the wafer are achieved in a comprehensive manner.

[0037] 2. The wedge-shaped guide mechanism provided by the present invention can improve the tolerance of the polishing head to wafer thickness differences, avoid frequent replacement of the polishing head due to wafer thickness changes, improve the versatility and production efficiency of the polishing head, and at the same time ensure the safety of the polishing process.

[0038] 3. The design method of the partition provided by the present invention is operable and provides a valid reference for the design of master-slave partition collaborative pressure polishing head. Attached Figure Description

[0039] Figure 1 is a schematic diagram of the overall structure of a master-slave partitioned collaborative pressurization polishing head according to the present invention.

[0040] Figure 2 is a schematic diagram of the connecting flange of the present invention.

[0041] Figure 3 is a schematic diagram of the master-slave partition collaborative pressurization principle of the present invention.

[0042] Figure 4 is a schematic diagram of the structure of the annular airbag of the present invention.

[0043] Figure 5 is a schematic diagram of the fixed cavity structure of the present invention.

[0044] Figure 6 is a schematic diagram of the retaining ring structure of the present invention.

[0045] Figure 7 is a schematic diagram of the structure of the moving plate of the present invention.

[0046] Figure 8 is a schematic diagram of the structure of the air film of the present invention.

[0047] Figure 9 is a schematic diagram of the moving coil assembly of the present invention.

[0048] Explanation of reference numerals in the attached drawings: 1. Retaining ring; 101. Liquid guide groove; 102. Countersunk hole; 2. Air film; 201. Air film sealing ring; 202. Air film groove; 203. Outer circle of air film; 204. Annular fascia; 205. Annular fascia; 3. Fixed cavity; 301. Wedge-shaped surface of fixed cavity; 302. Air passage of fixed cavity; 4. End cap; 5. Annular air bladder; 6. Annular air bladder pressure ring; 7. Connector; 8. Connecting flange; 8 01. Flange positioning hole; 802. Flange positioning groove; 803. Flange ball groove; 9. Guide post; 10. Moving plate; 1001. Moving plate partition sealing groove; 1002. Moving plate partition sealing groove; 1003. Moving plate wedge surface; 1004. Moving plate partition middle air passage; 1005. Moving plate partition inner air passage; 1006. Moving plate partition outer air passage; 11. Fastening ring; 12. Inner moving ring; 13. Middle moving ring; 14. Outer moving ring. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0050] As shown in Figures 1 to 9, the present invention provides a master-slave partitioned collaborative pressurization polishing head. As shown in Figure 1, it includes a connecting module, a retaining ring flexible pressurization module, and a master-slave partitioned collaborative pressurization module. One end of the connecting module is connected to the main spindle of the host machine (in this embodiment, the xCMP-150 polishing machine (manufactured by Yanghua Intelligent Manufacturing (Sichuan) Innovation Technology Co., Ltd.) is used as an example, but it is not limited to this) via a clamp. It has multiple air channels inside to stably transmit multiple gas channels delivered by the host spindle to various functional areas inside the polishing head. The other end of the connecting module is connected to one end of the retaining ring flexible pressurization module via an annular airbag 5. The other end of the retaining ring flexible pressurization module is connected to the master-slave partitioned collaborative pressurization module via an air film 2. Driven by the host spindle, the connecting module drives the retaining ring flexible pressurization module and the master-slave partitioned collaborative pressurization module to rotate and move. The retaining ring flexible pressurization module uses gas to drive the annular airbag 5 to generate adaptive deformation, flexibly pressurizing the retaining ring 1 to ensure its tight fit with the polishing pad and prevent wafer slippage during polishing. The master-slave partition collaborative pressurization module includes a physically isolated master partition and multiple slave partitions. The master partition has a large pressurization capacity and can control the overall material removal rate of the wafer through high pressure. The slave partitions can finely control the surface morphology of the wafer through low pressure, thereby comprehensively achieving high material removal rate and high flatness polishing of the wafer. The master-slave partition collaborative pressurization module adopts a wedge-shaped guide mechanism, which can improve the polishing head's tolerance to wafer thickness differences, making it suitable for polishing wafers with a wider thickness range. At the same time, it ensures the safety of the polishing process. This safety design can prevent the air film 2 from rupturing due to excessive air pressure, and avoid the master-slave partition collaborative pressurization module from falling off the polishing head and causing safety accidents such as impacting the host.

[0051] The connection module includes a connector 7 and a connecting flange 8. The connector 7 is made of polyetheretherketone (PEEK) material and has five gas channels (this embodiment uses five gas channels as an example, but is not limited to this), used to transmit five gas channels to various functional areas inside the polishing head. A 14mm diameter blind hole is formed at the center of one end of the connector 7 to form a clearance fit with the guide post 9, ensuring smooth axial movement and radial stability of the polishing head during flexible pressurization. Six through holes are formed at one end of the connector 7 for connection to the connecting flange 8 via bolts. Twelve threaded holes are formed at the other end of the connector 7 for... As shown in Figure 2, the connecting flange 8 is connected to the annular airbag pressure ring 6 by bolts. The connecting flange 8 is made of 316L stainless steel. A positioning hole 801 and a positioning groove 802 are opened on one end face of the connecting flange 8 to ensure the alignment of the polishing head with the main spindle of the host machine. The connecting flange 8 has a wedge-shaped interface to connect with the main spindle of the host machine through a clamp to ensure the tightness of the connection. A flange ball groove 803 is opened on the inner wall of the connecting flange 8. The ball is evenly squeezed to further ensure the alignment of the connection with the main spindle of the host machine, thereby avoiding centrifugal force offset caused by misalignment and ensuring polishing stability.

[0052] As shown in Figure 3, in principle, the retaining ring 1 is used to prevent lateral movement of the wafer. The annular airbag 5 is driven by gas to generate adaptive deformation, which sequentially pushes the fixing cavity 3 and the retaining ring 1 to move, thereby flexibly pressurizing the retaining ring P. r This ensures a tight fit with the polishing pad, preventing wafer slippage during polishing (slippage refers to the wafer leaving the polishing area). The main partition pressure P1 is applied to the entire wafer, allowing for control of the overall material removal rate through high pressure. The secondary partition pressures P2, P3, and P4 allow for fine control of the wafer's surface morphology through low pressure. By coordinating pressure application between the main and secondary partitions, the overall material removal rate and surface morphology of the wafer are simultaneously controlled, thereby achieving a comprehensive high material removal rate and high flatness polishing of the wafer.

[0053] The retaining ring flexible pressurization module includes an annular airbag pressure ring 6, an annular airbag 5, an end cap 4, a fixed cavity 3, a guide post 9, and a retaining ring 1. The annular airbag pressure ring 6 has 12 through holes and is connected to the connector 7 by bolts. The annular airbag 5 is made of rubber, as shown in Figure 4, and its structure is an inverted "U" shape. One end of the annular airbag 5 is located between the annular airbag pressure ring 6 and the connector 7, and the annular airbag 5 achieves a seal through the compression between the annular airbag pressure ring 6 and the connector 7. The other end of the annular airbag 5 is located between the end cap 4 and the fixed cavity 3. The end cap 4 has 12 through holes, and one end of the fixed cavity 3 has 12 threaded holes. The end cap 4 is connected to the fixed cavity 3 by bolts. The annular airbag 5 achieves a seal through the compression between the end cap 4 and the fixed cavity 3, thus forming a chamber. Under gas drive, the annular airbag 5 undergoes adaptive deformation, sequentially pushing the fixed cavity 3 and the retaining ring 1 to move, thereby flexibly pressurizing the retaining ring P. r This ensures that it fits tightly against the polishing pad, preventing wafer slippage during the polishing process.

[0054] As shown in Figure 5, one end of the fixed cavity 3 has 12 threaded holes and is connected to the end cap 4 by bolts. The fixed cavity 3 also has 4 threaded through holes. One end of the fixed cavity 3 has a threaded through hole connected to the connector 7 via an air pipe. The other end of the fixed cavity 3 has a threaded through hole connected to the master-slave partitioned collaborative pressurization module via an air pipe. This is used to stably transmit multiple gas streams to various functional areas of the master-slave partitioned collaborative pressurization module. One end of the fixed cavity 3 has 4 threaded holes at its center and is connected to one end of the guide post 9 by bolts. The other end of the guide post 9 is a cylinder with a diameter of 13.95mm-13.99mm and forms a clearance fit with the blind hole at the center of the connector 7. The other end of the fixed cavity 3 has 6 threaded holes and is connected to the retaining ring 1 by bolts.

[0055] As shown in Figure 6, the retaining ring 1 is made of polyetheretherketone material to ensure corrosion resistance and friction resistance. One end of the retaining ring 1 has 6 liquid guiding grooves 101 and 6 countersunk holes 102. The liquid guiding grooves 101 are used to transport polishing liquid to the polishing area, and the countersunk holes 102 are used to connect the retaining ring 1 to the fixing cavity 3 by bolts.

[0056] The master-slave partitioned coordinated pressurization module includes a gas film 2, a moving plate 10, a moving coil assembly, and a fastening ring 11. The moving coil assembly includes an inner moving coil 12, a middle moving coil 13, and an outer moving coil 14. The gas film sealing ring 201 of the gas film 2 is located between the retaining ring 1 and the fixed cavity 3. The sealing is achieved by the compression of the retaining ring 1 and the fixed cavity 3, forming a master partition. Under the gas drive of the master partition, the moving plate 10 is pushed to move, and the force is transmitted to the wafer to achieve pressurization of the master partition, thereby controlling the overall material removal rate of the wafer. The gas film 2 is divided into multiple independent partitions by an internal annular rib. The moving plate 10 is connected to the moving coil assembly by bolts. The gas film 2 is located between the moving plate 10 and the moving coil assembly. The sealing of each slave partition is achieved by the compression of the internal annular rib of the gas film 2 by the moving plate 10 and the moving coil assembly. Under the gas drive of each slave partition, the slave partition is pressurized, thereby controlling the surface morphology of the wafer.

[0057] In this embodiment, the master-slave partition coordinated pressurization can synchronously control the overall material removal rate and surface morphology of the wafer. Given that there is a coupling effect between the slave partitions of the gas film 2, and that this coupling effect is enhanced as the pressure difference increases, the polishing head with master-slave partition coordinated pressurization can, on the one hand, control the overall material removal rate of the wafer through high pressure, and on the other hand, finely control the surface morphology of the wafer through low pressure.

[0058] As shown in Figure 7, the moving plate 10 is made of 316L stainless steel. One end of the moving plate 10 has three regions, each with 10 through holes. These regions are connected to the moving coil by bolts. Moving plate partition sealing grooves 1001 and 1002 are provided between adjacent regions to accommodate the annular fascia 204 and 205 of the air film 2, respectively. The moving plate 10 has air passages 1004, 1005, and 1006 in the moving plate partition, which are connected to the threaded through holes of the fixed cavity 3 via air pipes to deliver gas to each slave partition of the partitioned collaborative pressurization module.

[0059] The moving plate 10's wedge-shaped surface 1003 engages with the upper end of the fixed cavity wedge-shaped surface 301 of the fixed cavity 3 to form a wedge-shaped guide mechanism, which is used to adjust the lower limit distance h1. The other end of the moving plate 10 engages with the lower end of the fixed cavity wedge-shaped surface 301 to adjust the upper limit distance h2. By coordinating the adjustment of h1 and h2, the polishing head's tolerance to wafer thickness differences can be improved, making it suitable for polishing wafers with a wider thickness range, while ensuring the safety of the polishing process.

[0060] As shown in Figure 8, the air film 2 is made of silicone material with elasticity and adsorption. The air film 2 is provided with an air film sealing ring 201, which is located between the retaining ring 1 and the fixed cavity 3. The sealing is achieved by the compression of the retaining ring 1 and the fixed cavity 3, forming the main partition. By adjusting the air pressure, the moving plate 10 is moved, and the force is transmitted to the wafer, thereby controlling the overall material removal rate of the wafer. The air film 2 is divided into 3 independent regions by an internal annular fascia (this embodiment takes 3 independent regions as an example, but is not limited to this). There are annular fascia 204 and annular fascia 205. The annular fascia 204 and fascia 205 are respectively located in the moving plate partition sealing groove 1001 and moving plate partition sealing groove 1002 of the moving plate 10. The moving plate 10 is connected to the moving ring by bolts. The sealing of each slave partition is achieved by the compression of the annular fascia 204 and annular fascia 205 of the air film 2 by the moving plate 10 and the moving ring, forming slave partitions. By adjusting the pressure of each slave partition, the surface morphology of the wafer is controlled.

[0061] As shown in Figure 9, the moving coil assembly consists of an inner moving coil 12, a middle moving coil 13, and an outer moving coil 14. Each moving coil has an oblique angle at adjacent locations to accommodate the annular fascia 204 and 205 of the air film 2, and to provide sufficient space for the deformation of the annular fascia, preventing distortion due to insufficient space during the expansion and deformation of the air film 2, which would then affect the polishing effect. The inner moving coil 12, middle moving coil 13, and outer moving coil 14 each have 10 vent holes and threaded holes. The vent holes are used to transmit air transported through the air passages of the moving plate 10. The gas film in the moving coil assembly is eventually transmitted to each slave partition. Under the drive of the gas, the gas film in the slave partition deforms and transmits the force to the wafer, thereby pressurizing the slave partition and controlling the surface morphology of the wafer. The threaded holes in the moving coil assembly correspond to the through holes in the moving plate 10 and are connected by bolts. Through the connection of the moving coil assembly, the gas film 2 and the moving plate 10, the master and slave partitions are finally pressurized in a coordinated manner, and the overall material removal rate and surface morphology of the wafer are controlled synchronously, thereby achieving high material removal rate and high flatness polishing of the wafer.

[0062] This invention also discloses a design method for the slave partitions of a polishing head with master-slave partitioned coordinated pressurization, used to determine the number and size of the slave partitions. The method includes polishing test methods, pressure testing methods, and finite element calculation methods, and the appropriate design method can be selected according to the actual situation. The uniformity involved in the design method is calculated as (maximum value - minimum value) / (2 × average value) × 100%.

[0063] Specifically as follows:

[0064] 1) Polishing test method

[0065] S1. First, a polishing experiment was conducted on the coated wafer using a non-partitioned pressure polishing head to obtain the material removal rate distribution characteristics of the thin film on the wafer surface at different locations.

[0066] S2. Perform data analysis on the material removal rate at each of the above locations, and divide the annular region according to the specific technical requirements. For example, if it is required that the uniformity be controlled within 5% (this embodiment takes 5% as an example, but it is not limited to this), then calculate the uniformity according to the formula, and divide the area where the material removal rate uniformity falls within the range of 5% from the center to the edge of the coated wafer into an annular region.

[0067] S3. Based on the divided annular region, determine the number and size of the partitions.

[0068] 2) Pressure testing method

[0069] S1. First, pressure distribution characteristics on the wafer surface are collected using a pressure detection device (such as a thin-film pressure sensor).

[0070] S2. Perform data analysis on the above pressure distribution characteristics and divide the annular region according to specific technical requirements. For example, if it is required that the uniformity be controlled within 5% (this embodiment takes 5% as an example, but it is not limited to this), then calculate the uniformity according to the formula. From the center to the edge of the coated wafer, the area where the pressure uniformity falls within the range of 5% is divided into an annular region.

[0071] S3. Based on the divided annular region, determine the number and size of the partitions.

[0072] 3) Finite element method

[0073] S1. First, the finite element method is used to simulate the loading of the polishing head and obtain the pressure distribution characteristics on the wafer surface.

[0074] S2. Perform data analysis on the above pressure distribution characteristics and divide the annular region according to specific technical requirements. For example, if it is required that the uniformity be controlled within 5% (this embodiment takes 5% as an example, but it is not limited to this), then calculate the uniformity according to the formula. From the center to the edge of the coated wafer, the area where the pressure uniformity falls within the range of 5% is divided into an annular region.

[0075] S3. Based on the divided annular region, determine the number and size of the partitions.

[0076] This invention also discloses the application of a master-slave partitioned collaborative pressure polishing head in wafer polishing, mainly including the following steps:

[0077] S1. Prepare the polishing solution. Taking a single-crystal silicon wafer as an example (this can be extended to other semiconductor materials), the polishing solution mainly contains deionized water, abrasive particles, cationic additives, surfactants or polymer additives, with a pH value of 2-11. The abrasive particles are one or more of alumina, silicon oxide, and cerium oxide.

[0078] S2. Attach the back of the wafer to the gas film and apply negative pressure to the master-slave partition to adsorb and fix it.

[0079] S3. Move the polishing head to the polishing position and ventilate in sequence: First, ventilate the annular airbag area to ensure the retaining ring is tightly attached to the polishing pad. Then, ventilate the main partition. The pressure exerted by the retaining ring on the polishing pad is 2 to 3 times the pressure exerted by the main partition on the wafer to prevent wafer slippage during polishing. Finally, ventilate each slave partition according to the polishing technology requirements to synergistically control the overall material removal rate and surface morphology of the wafer.

[0080] S4. Set process parameters such as air pressure, rotation speed, polishing fluid flow rate, and polishing time, and start polishing.

[0081] S5. After polishing, negative pressure is applied to the master-slave partition to fix the wafer in place, and negative pressure is applied to the annular airbag area to lift the retaining ring. After the polishing head is moved to the designated position, a small positive pressure is introduced into the master-slave partition to release the adsorption and remove the wafer.

[0082] In summary, this invention provides a targeted design for a master-slave partitioned collaborative pressure polishing head, which can comprehensively achieve high material removal rate and high flatness polishing of wafers. The provided flexible pressure module with retaining ring can prevent wafer slippage during polishing, and the provided wedge-shaped guide mechanism can improve the polishing head's tolerance to wafer thickness differences, avoiding frequent polishing head replacements due to different wafer thicknesses, improving the versatility and production efficiency of the polishing head, while ensuring the safety of the polishing process. In addition, the proposed slave partitioning design method can provide a useful reference.

[0083] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A polishing head with master-slave partitioned collaborative pressurization, characterized in that: The assembly includes a connection module, a retaining ring flexible pressurization module, and a master-slave partitioned collaborative pressurization module. One end of the connection module is connected to the main spindle of the host machine via a clamp. It has multiple air channels inside to stably transmit multiple gas channels delivered by the host spindle to various functional areas inside the polishing head. The other end of the connection module is connected to one end of the retaining ring flexible pressurization module via an annular airbag (5). The other end of the retaining ring flexible pressurization module is connected to the master-slave partitioned collaborative pressurization module via an air film (2). Driven by the host spindle, the connection module drives the retaining ring flexible pressurization module and the master-slave partitioned collaborative pressurization module to rotate and move. The retaining ring flexible pressurization module generates adaptive deformation through gas-driven annular airbag (5) to flexibly pressurize the retaining ring (1) to ensure that it fits tightly against the polishing pad and avoids wafer slippage during polishing. The master-slave partitioned collaborative pressurization module achieves high material removal rate and high flatness polishing of the wafer by coordinating and controlling the pressure of the master and slave partitions. The master-slave partitioned collaborative pressurization module includes a gas film (2), a moving plate (10), a moving coil assembly, and a fastening ring (11). The moving coil assembly includes an inner moving coil (12), a middle moving coil (13), and an outer moving coil (14). The gas film sealing ring (201) of the gas film (2) is located between the retaining ring (1) and the fixed cavity (3). The sealing is achieved by the compression between the retaining ring (1) and the fixed cavity (3), forming the master partition. Under the gas drive of the master partition, the moving plate (10) is pushed to move, and the force is transmitted to the wafer. The main partition is pressurized to control the overall material removal rate of the wafer. The gas film (2) is divided into multiple independent partitions by an internal annular fascia. The moving plate (10) is connected to the moving coil by bolts. The gas film (2) is located between the moving plate (10) and the moving coil. The moving plate (10) and the moving coil squeeze the annular fascia inside the gas film (2) to seal each slave partition. Under the gas drive of each slave partition, the slave partition is pressurized to control the surface morphology of the wafer.

2. The polishing head with master-slave partitioned collaborative pressurization according to claim 1, characterized in that: The moving plate (1003) of the moving plate (10) cooperates with the upper end of the fixed cavity wedge surface (301) of the fixed cavity (3) to form a wedge guide mechanism, which is used to adjust the lower limit distance h1. The other end of the moving plate (10) cooperates with the lower end of the fixed cavity wedge surface (301) to adjust the upper limit distance h2. By coordinating the adjustment of h1 and h2, the tolerance of the polishing head to the wafer thickness difference can be improved, and it can be used for wafer polishing with a larger thickness range, while ensuring the safety of the polishing process.

3. An application of a master-slave partitioned coordinated pressurization polishing head according to any one of claims 1-2 in wafer polishing, mainly comprising the following steps: S1, preparing a polishing slurry, wherein the polishing slurry mainly contains deionized water, abrasive particles, cationic additives, and surfactants, with a pH value of 2-11, wherein, The abrasive particles are one of aluminum oxide, silicon oxide, and cerium oxide; S2, attach the back of the wafer to the gas film, and apply negative pressure to the master and slave partitions to adsorb and fix it; S3, move the polishing head to the polishing position and introduce air in sequence: first, introduce air to the annular airbag area to make the retaining ring fit tightly against the polishing pad, then introduce air to the master partition, wherein the pressure of the retaining ring acting on the polishing pad is 2 to 3 times the pressure of the master partition acting on the wafer, to avoid wafer slippage during polishing, and finally, according to the polishing technology requirements, introduce air to each slave partition to coordinate and control the overall material removal rate and surface morphology of the wafer; S4, set the process parameters of air pressure, rotation speed, polishing fluid flow rate, and polishing time, and start polishing; S5, after polishing, apply negative pressure to the master and slave partitions to adsorb and fix the wafer, apply negative pressure to the annular airbag area to lift the retaining ring, and after the polishing head moves to the designated position, introduce a small positive pressure to the master and slave partitions to release the adsorption and remove the wafer.

Images