Compression gap control for post-CMP cleaning using pad-type chemical buffs

Abstract

Embodiments of the present disclosure include apparatus and method for cleaning a substrate. The method for cleaning a substrate includes rotating a substrate table with a first motor, supplying fluid to the surface of a substrate placed on the support surface of the substrate table of a cleaning module, rotating a cleaning pad at a cleaning speed, and using a controller to detect an initial torque value generated by a second motor, and lowering the cleaning pad using a lift actuator assembly until the controller detects a contact torque generated by the second motor. The contact torque is the torque when the pad processing surface of the cleaning pad contacts the surface of the substrate at the contact point. The method includes, by command from the controller, translating the cleaning pad toward the substrate by a cleaning distance. The cleaning pad is compressed by the translation of the cleaning pad by the cleaning distance. The pad processing surface of the cleaning pad is then translated across the entire substrate support surface.

Description

Technical Field

[0001]

[0001] The embodiments described herein generally relate to an apparatus used in the manufacture of electronic devices, and more particularly, to a cleaning module that can be used to clean the surface of a substrate in a semiconductor device manufacturing process.

Background Art

[0002]

[0002] Chemical mechanical polishing (CMP) is commonly used in the manufacture of high density integrated circuits to planarize or polish a layer of material deposited on a substrate. In a pre-cleaning module used in a CMP process, a rotating cleaning pad is pressed against a layer of material on the surface of the substrate. The material is removed across the entire layer of material through a combination of chemical and mechanical actions provided by the polishing fluid and the relative movement of the cleaning pad and the substrate. Conventional cleaning pads can damage the surface of the substrate. This is because the applied force is too large, and the particles of the polishing slurry are embedded in the cleaning pad, damaging the substrate surface.

[0003]

[0003] Therefore, there is a need for a system and method for polishing a surface that is susceptible to damage.

Summary of the Invention

[0004]

[0004] In some embodiments, a method for cleaning a substrate includes rotating a substrate table with a first motor, supplying fluid to the surface of a substrate placed on the support surface of the substrate table of a cleaning module, rotating a cleaning pad at a cleaning speed, and using a controller to detect an initial torque value generated by a second motor, and using a lift actuator assembly to lower the cleaning pad until the controller detects a contact torque generated by the second motor. The contact torque is the torque when the pad processing surface of the cleaning pad contacts the surface of the substrate at the contact point. The method includes, by command from the controller, moving the cleaning pad toward the substrate by a cleaning distance. The cleaning pad is compressed by the translation of the cleaning pad by the cleaning distance. The pad processing surface of the cleaning pad is then translated across the entire substrate support surface.

[0005]

[0005] In some embodiments, a pre-cleaning module for cleaning a substrate includes a rotatable substrate table. The rotatable substrate table includes a substrate support surface for supporting a substrate thereon. The pre-cleaning module also includes a pad carrier assembly. The pad carrier assembly includes a carrier column, a carrier arm coupled to the carrier column and extending radially outward from the axis of the carrier column, a lift mechanism coupled to the carrier arm, a lift actuator assembly coupled to the carrier arm and mechanically connected to the lift mechanism, and a pad carrier configured to be raised and lowered relative to the surface of the substrate table by the lift mechanism and the lift actuator assembly. The pad carrier includes a cleaning pad, a pad motor configured to rotate the cleaning pad around a central motor axis, and a shaft coupling the pad motor to the cleaning pad. The pre-cleaning module also includes a system controller configured to identify pad compression.

[0006]

[0006] In yet another embodiment, the pre-cleaning module includes a rotatable substrate table. The rotatable substrate table includes a substrate support surface for supporting a substrate thereon. The pre-cleaning module also includes a system controller configured to calculate the force applied to the pads based on pad compression, and a pad carrier assembly. The pad carrier assembly includes a carrier arm, a lift mechanism coupled to the carrier arm, and a lift actuator assembly coupled to the carrier arm and mechanically connected to the lift mechanism. The lift actuator assembly is configured to apply less than 30 N and is controlled by the system controller. The pre-cleaning module also includes a pad carrier configured to be moved by the lift mechanism and the lift actuator assembly. The pad carrier includes a pad motor, a shaft, and a pad coupled to the pad motor by the shaft, which is made of PVA material and can sense and communicate experienced torque values ​​in real time.

[0007]

[0007] In order to understand in detail the features of the present disclosure described above, the present disclosure, which has been briefly summarized above, will be described in more detail with reference to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings show only exemplary embodiments and should not be considered to limit the scope of the present disclosure, and other equally valid embodiments may be permitted. [Brief explanation of the drawing]

[0008] [Figure 1]

[0008] This is a schematic plan view of an exemplary chemical mechanical polishing (CMP) treatment system using one or more pre-cleaning modules described herein. [Figure 2]

[0009] This is an isometric view of one side of an exemplary pre-cleaning module according to one or more embodiments. [Figure 3A]

[0010] This is a side cross-sectional view of an inclined embodiment of a pad carrier placement arm according to one or more embodiments. [Figure 3B]

[0011] This is a top cross-sectional view of an inclined embodiment of a pad carrier placement arm according to one or more embodiments. [Figure 3C]

[0012] This is a front cross-sectional view of an inclined embodiment of a pad carrier placement arm according to one or more embodiments. [Figure 3D]

[0013] This is a detailed diagram of an inclined embodiment of a pad carrier placement arm according to one or more embodiments. [Figure 4A]

[0014] This figure shows features formed on the processing surface of a cleaning pad according to one or more embodiments. [Figure 4B]

[0015] This figure shows features formed on the processing surface of a cleaning pad according to one or more embodiments. [Figure 5]

[0016] This is a flowchart for cleaning a pad processing surface according to one or more embodiments. [Figure 6]

[0017] This graph shows the Stribeck curve, which relates the friction of a hydraulic bearing to the Hershey number. Forms for carrying out the invention

[0009]

[0018] For ease of understanding, the same reference numerals have been used to indicate identical elements common to multiple figures, where possible. It is assumed that elements and features of one embodiment may be usefully incorporated into other embodiments without further description.

[0010]

[0019] Multiple embodiments described herein relate more broadly to apparatus used in the manufacture of electronic devices, and more particularly to chemical mechanical buffs, also known as pre-cleaning (PC) modules, which may be used to clean the surface of a substrate during a portion of a semiconductor device manufacturing process sequence.

[0011]

[0020] During the cleaning process performed within the PC module, the surface of a cleaning pad made of polyvinyl alcohol (PVA) material provides shear force across the entire surface of the substrate being cleaned. The cleaning pad is used to remove scratches and residues from the substrate surface due to the properties of the cleaning pad material, such as its mechanical strength and abrasion resistance. However, PVA material is typically thicker and comes in a larger form factor than other conventional CMP polishing pads, and in addition, it is hygroscopic, soft, and elastic. Therefore, PVA tends to retain fine particles, thereby resulting in the formation of scratches on the substrate surface under certain processing conditions.

[0012]

[0021] In several embodiments described herein, the PC module is adapted to apply a fluid-absorbing cleaning pad with a lower downforce and rotate the pad at a higher rotational speed, while measuring or determining the amount of downforce, as the cleaning pad moves parallel to the entire surface of the substrate, forming a hydrodynamic film between the cleaning pad and the substrate surface. In some embodiments, the downforce can be estimated by measuring the pad compression provided by an actuator coupled to a pad carrier coupled to the cleaning pad.

[0013]

[0022] Figure 1 is a schematic plan view of an exemplary chemical mechanical polishing (CMP) treatment system 100 using a pre-cleaning (PC) module 200 described herein, according to one or more embodiments. In Figure 1, certain parts of the housing and certain other internal and external components are omitted to more clearly show the PC module within the CMP treatment system 100. Here, the CMP treatment system 100 includes a first part 105 and a second part 106 coupled to and integrated with the first part 105. The first part 105 is a substrate polishing section comprising a plurality of stations (not shown).

[0014]

[0023] The second part 106 includes one or more post-CMP cleaning systems 110, which include a plurality of system loading stations 130, one or more substrate handlers (e.g., a first robot 124 and a second robot 150), a plurality of modules or stations 112, 140, 142, 170, and a PC module 200. In some embodiments, one or more cleaning systems 110 include a location-specific polishing (LSP) module 142, a measurement station 140, a vertical cleaning module 112, a drying unit 170, and / or a substrate handler 180. The PC module 200 is configured to process substrates 120 positioned substantially horizontally.

[0015]

[0024] The first robot 124 is positioned to transfer the substrate 120 to and from the system loading stations 130, for example, between a plurality of system loading stations 130 and a second robot 150, and / or between the CMP post-cleaning system 110 and the plurality of system loading stations 130. In some embodiments, the first robot 124 is positioned to transfer the substrate 120 between any of the system loading stations 130 and a processing system located nearby therein. For example, in some embodiments, the first robot 124 can be used to transfer the substrate 120 between one of the system loading stations 130 and a measurement station 140.

[0016]

[0025] The second robot 150 is used to transfer the substrate 120 between the first part 105 and the second part 106. For example, here, the second robot 150 is arranged to transfer the polished substrate 120 received from the first robot 124 to the first part 105 for polishing inside the first part 105. Then, the second robot 150 is used to transfer the polished substrate 120 from the first part 105, for example, from a transfer station (not shown) inside the first part 105, to one of the PC modules 200, and / or to transfer between various stations and the modules located in the second part 106. Alternatively, the second robot 150 can transfer the substrate 120 from a transfer station inside the first part 105 to one of the plurality of modules or stations 112, 140, 142, 170, 200. Here, each PC module 200 is arranged inside the second part 106 at a position close to the first part 105.

[0017]

[0026] [[ID=​​​​In some embodiments, the operation of the CMP processing system 100 is directed by the system controller 160. The system controller 160 includes a programmable central processing unit (CPU) 161 operable with a memory 162 (e.g., non-volatile memory) and support circuitry 163. The support circuitry 163 is connected to the conventional CPU 161 and to various components of the CMP processing system 100 and includes a cache, a clock circuit, an input / output subsystem, a power supply, etc., and combinations thereof, to facilitate control of the various components. The CPU 161 is one of any form of general-purpose computer processor used in industrial settings, such as a programmable logic controller (PLC), for controlling various components and sub-processors of the processing system. The memory 162 is connected to the CPU 161 and is typically one or more readily available memories, such as random access memory (RAM), read-only memory (ROM), floppy disk drive, hard disk, or any other form of local or remote digital storage.

[0019]

[0028] Typically, the memory 162 takes the form of a non-transitory computer-readable storage medium (e.g., non-volatile memory) that includes instructions that, when executed by the CPU 161, facilitate the operation of the CMP processing system 100. The instructions in the memory 162 take the form of a program product, such as a program implementing the methods of the present disclosure. The program code may conform to any one of several different programming languages. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use in a computer system. The program(s) of the program product define the functionality of multiple embodiments, including the methods described herein.

[0020]

[0029] Exemplary, non-transient computer-readable storage media include, but are not limited to, (i) non-writable storage media on which information may be permanently stored (e.g., read-only memory devices in a computer, such as a CD-ROM disk readable by any type of solid non-volatile semiconductor memory device (e.g., a solid-state drive (SSD))), and (ii) writable storage media on which modifiable information is stored (e.g., a floppy disk in a diskette drive or hard disk drive, or any type of solid random-access semiconductor memory). When such computer-readable storage media carries computer-readable instructions that dictate the functions of the methods described herein, it constitutes an embodiment of the present disclosure. In other embodiments, the methods described herein or parts thereof are performed by one or more application-specific integrated circuits (ASICs) or other types of hardware implementations. In some other embodiments, the substrate processing and / or substrate handling methods described herein are performed by a combination of software routines, ASICs, and / or other types of hardware implementations. One or more system controllers 160 may be used with one or any combination of the various modular polishing systems described herein, and / or with their individual polishing modules.

[0021]

[0030] Figure 2 is an isometric view of an exemplary PC module 200 that may be used in the CMP processing system 100 described herein. In Figure 2, a portion of the lid 216 is omitted to more clearly show the internal components of the PC module 200.

[0022]

[0031] In some embodiments, the PC module 200 includes a chamber 210 having a container 214 and a lid 216, formed by a plurality of side panels that collectively define a processing area 212. The lid 216 may be removable for general maintenance. The processing area 212 of the PC module 200 further includes a rotatable substrate table 230, a pad adjustment station 280, and a pad carrier assembly 300 coupled to a rotatable carrier column 224. The pad carrier assembly 300 is movable at least between a first position on the substrate 120 and a second position on the pad adjustment station 280. The rotatable substrate table is connected to a table motor (not shown) that rotates the substrate table 230.

[0023]

[0032] Figure 3A is a side cross-sectional view of an exemplary pad carrier assembly 300 that may be used in the PC module 200 of Figure 2. The pad carrier assembly 300 includes a carrier arm 301 coupled to a carrier column 224, which extends radially outward from the column axis A1 and is positioned above the substrate table 230. The pad carrier assembly 300 is rotated between several positions by a column motor 315. The pad carrier assembly 300 also includes a lift actuator assembly 302 and a lift mechanism 305 driven by the lift actuator assembly 302. The lift actuator assembly 302 and the lift mechanism 305 may work together to raise and lower the pad carrier 307 to move it closer to or further away from the substrate table 230. The lift mechanism 305 allows the pad carrier 307 to have a travel distance between approximately 5 mm and approximately 15 mm, for example, 10 mm. The lift actuator assembly 302 and the lift mechanism 305 may enable the pad carrier 307 to generate a force between approximately 0.01 lbf (0.04 N) and 10 lbf (44.5 N) along the Z-axis, for example, approximately 6.7 lbf (30 N). The lift mechanism 305 may include at least a hard stop, a ball screw assembly, a lead screw assembly, and / or a displacement sensor. The lift mechanism 305 is connected to a linear rail assembly 317. The linear rail assembly 317 mechanically connects the lift mechanism 305 to the movable pad carrier 307. The movable pad carrier 307 is further coupled and connected to the cleaning pad 311 via a shaft 309. The linear rail assembly 317 maintains the motion of the pad carrier 307 perpendicular to the substrate 120 and may enable the pad carrier 307 to be connected to the linear rail assembly 317 at various angles to the vertical along a vertical axis A2 aligned with the Z-axis. The lift actuator 302 may include a motor or actuator, such as an electric, gas-pressure, and / or hydraulic motor or actuator, coupled to the lift mechanism 305 using a direct drive, belt and pulley, gas-pressure, and / or hydraulic configuration.

[0024]

[0033] As shown in Figure 3A, the vertically movable pad carrier 307 is positioned on the distal end 313 of the carrier arm 301. The pad carrier 307 supports the cleaning pad 311 above the substrate 120. The pad carrier 307, the lift mechanism 305, and the lift actuator assembly 302 are all mechanically connected to generate the movement of the pad carrier 307 along the linear rail 317 relative to the surface 120a of the substrate. The pad carrier 307 is coupled to the pad 311 by a shaft 309. In some embodiments, the pad carrier 307 is sized to support a cleaning pad 311 having a diameter between approximately 20 mm and 150 mm, for example between approximately 70 mm and 130 mm, for example, approximately 120 mm. In some embodiments, the pad carrier positioning arm 301 supports a larger cleaning pad 311 compared to a conventional pre-cleaning module. The cleaning pad 311 may contain polyvinyl alcohol (PVA) according to some embodiments, but other materials are also considered. In some embodiments, the carrier arm 301, lift actuator assembly 302, lift mechanism 305, pad carrier 307, and shaft 309 are made from materials including metals, including stainless steel, but other materials are also considered to achieve desired weight, vibration characteristics, and corrosion resistance. The height H defines the distance between the pad processing surface 311a and the substrate support surface 230a. The height H can be adjusted by the lift actuator 302 and the lift mechanism 305 and calculated and controlled by the system controller 160. As will be further described below, it has been found that during processing, the contact force (i.e., downforce) and the overall pre-cleaning process results can be controlled more precisely and consistently by controlling the travel distance (e.g., cleaning distance), i.e., the distance over which the cleaning pad 311 engages with or compresses the substrate surface 120a after the cleaning pad 311 contacts the substrate surface 120a during the downward movement of the pad carrier 307.

[0025]

[0034] Variations in the mechanical properties of the cleaning pads over time, or from the properties of individual cleaning pads, as well as inherent friction within the system (e.g., friction between the lift mechanism 305 and the linear rail 317), have been found to significantly affect the ability of the pre-cleaning module to consistently control the contact force generated between the pad processing surface 311a and the substrate surface 120a, particularly when low contact forces (e.g., <10 Newtons (N)) are required during the pre-cleaning process. However, the accuracy of the height H dimension has been found to be controllable with a position repeatability of ±4 μm in increments as small as approximately 10 μm to approximately 40 μm by using closed-loop sensing techniques (e.g., position control using encoders) with, for example, a ball screw actuator, a linear rail slide, and a system controller. In some embodiments, a high level of precision and accuracy allows the application of pressure by the cleaning pad 311 to the substrate 120 to be identified more accurately than by pressure sensors alone.

[0026]

[0035] Figure 3B shows a top view of a portion of a pad carrier assembly 300 according to several embodiments. As shown, the pad carrier 307 includes a pad motor 308 and a frame 306 for supporting and mounting the pad carrier 307 to a linear rail 317. The frame 306 may include any structural material that can be used to mount to the linear rail 317 and hold the pad motor 308. The pad motor 308 rotates the cleaning pad 311 around a central motor axis A3. In one embodiment, the pad motor 308 can rotate the pad 311 at cleaning speeds between approximately 150 RPM and approximately 4500 RPM, for example, approximately 250 RPM to approximately 1500 RPM, and in yet another embodiment, approximately 750 RPM to approximately 2500 RPM. The pad motor 308 can sense and communicate the torque value experienced in real time. The pad carrier 307 also includes a frame 306 with metal brackets having side supports that resist bending during cleaning operations, and a lower plate configured to support and / or fix the pad motor 308. In some embodiments, the pad motor 308 of the pad carrier 307 may be mounted on a linear rail 317 at different orientation angles θ (see, for example, Figures 3C and 3D). Without being bound by theory, the different angles allow the cleaning pad 311 and the pad processing surface 311a to achieve a controlled amount of contact area on the substrate surface 120a. The pad motor 308 can rotate the cleaning pad 311 at a rate between approximately 500 RPM and approximately 3000 RPM, for example, at 1500 RPM.

[0027]

[0036] Figure 3C is a front cross-sectional view of an exemplary pad carrier assembly 300 showing a pad motor 308 of a pad carrier 307 mounted on a lift mechanism 305 at an angle θ. The pad carrier 307 may be mounted on a linear rail 317 at an angle theta (θ). Thereafter, the motion of the pad carrier 307 may be perpendicular to axis A2, but the pad processing surface 311a of the cleaning pad 311 will not be coplanar with the substrate surface 120a. For example, the central motor shaft A3 may be positioned at an angle θ with respect to the vertical axis A2 and therefore not aligned with the direction of motion of the linear rail 317. The pad carrier assembly 300 may also include a fluid nozzle 314 positioned near the pad carrier 307. The fluid nozzle 314 is configured to spray a fluid 321 onto the substrate 120. The pad carrier assembly 300 may include one or more fluid nozzles 314 depending on the operating requirements of the pre-cleaning process. In some embodiments, there may be multiple nozzles 314. In this case, some nozzles 314 are coupled to the carrier arm 301, and some nozzles 314 are not coupled. According to some embodiments, the pad carrier 307 is maintained at an angle θ. The angle θ is defined as the angle between the vertical axis A2 and the motor axis A3. According to some embodiments, the pad processing surface 311a may be aligned with the XY plane. In several other embodiments, the pad processing surface 311a is inclined at an angle θ from the XY plane. In some embodiments, the angle θ is greater than zero and up to about 45 degrees from the XY plane, for example, between about 1 degree and about 10 degrees, for example, about 5 degrees. When the cleaning pad 311 is inclined with respect to the surface of the substrate 120a, it is believed that the cleaning pad 311 can absorb the fluid 321 more effectively than when the pad processing surface 311a is positioned parallel to the substrate surface 120a.

[0028]

[0037] During processing, the fluid 321 supplied by the nozzle 314 may include polishing fluid, cleaning liquid, and / or cleaning solution. For example, the fluid 321 may include one or more of deionized water, acids, bases, aqueous-based slurry compositions, chelating agents, or other useful cleaning fluids. The (one or more) nozzles 314 may be configured to supply liquid, mist, or other forms of fluid 321 to the substrate 120 and the substrate table 230.

[0029]

[0038] Conventional pad carrier assemblies typically rely on pressure sensors to determine the pressure applied by the cleaning pad, but pressure sensors have been shown to be inaccurate when used with elastic materials such as the cleaning pad material. For example, a pressure sensor may have an accuracy of only + / - 0.4 psi. Several embodiments described herein can measure pressure by using a change in height H to determine the amount of compression of the cleaning pad 311, and then use the height data to more accurately control the amount of pressure applied to the surface of the substrate. A change in travel distance can be measured with considerably more accuracy than a change in pressure and can be derived from a lift actuator assembly 302 coupled to the lift mechanism 305 and / or at least a sensor in the lift mechanism 305. The sensor in the lift actuator assembly 302 and / or the lift mechanism 305 may be a displacement sensor to provide feedback, but its position is controlled by a controller 160. In some embodiments, the controller 160 has at least two control loops for determining the position of the pad in motion. Multiple embodiments described herein can measure changes in height H with precision and accuracy ranging from + / -10 microns to approximately + / -40 microns, and can determine an applied pressure as low as 0.04 psi using a compression criterion with an accuracy of + / -0.01 psi. For example, a pressure as low as 0.04 psi can be achieved for a pad diameter of approximately 150 mm. When the pad 311 is compressed by the lift actuator assembly 302 and the lift mechanism 305, the exact pressure value can be determined using a compression criterion (e.g., a lookup of a data table of calculated compression-pressure relationships) instead of the pressure sensor alone. Modifications from conventional designs have resulted in the remarkable advantage of being able to accurately reproduce and apply a pressure as low as 0.04 psi. This can be on the order of the desired applied cleaning pad pressure used or controlled during the pre-cleaning chamber cleaning process. Improvements are described further below.

[0030]

[0039] Figure 3D shows a detailed diagram of the interaction between at least the pad 311, the fluid 321 (e.g., the solution dispensed from the nozzle 314), and the surface 120a of the substrate 120. The interaction can be characterized by a Hershey number, as described below with respect to Figures 5 and 6. For example, a Hershey number greater than 1 is used to create a hydraulic film between the cleaning pad and the surface of the substrate when the fluid 321 is provided. This hydraulic film helps to clean the surface of the substrate 120a.

[0031]

[0040] Figures 4A and 4B show several embodiments of the cleaning pad 311. In these embodiments, the pad processing surface 311a has different pad patterns 400a, 400b according to several embodiments. As shown in Figure 4A, the pad processing surface 311a may have a base surface 403 on which abrasive features 401 are arranged radially around the pad center 407. In some embodiments, as shown in Figure 4A, the features 401 are rounded raised bosses or radial mesa. The features 401 may be raised, for example, between about 1 mm and about 10 mm from the base surface 403. In another embodiment, the features 401 may be recessed between about 1 mm and about 10 mm from the base surface 403. Furthermore, the features 401 may include diameters between about 1 mm and about 150 mm, for example, between 5 mm and 20 mm. Although shown as round, the features 401 may also be square, triangular, or other shapes. Furthermore, feature 401 can also be positioned in other patterns, such as spiral, helical, random, and / or linear arrangements.

[0032]

[0041] As shown in Figure 4B, according to some embodiments, the padding surface 311a may have multiple abrasive features, including spokes (e.g., pencil-shaped) 405 arranged as a radial spoke pattern around the center 407 of the pad 311. In one embodiment, the spokes 405 may be raised from about 1 mm to about 10 mm relative to the base surface 403. In another embodiment, the spokes 405 may be recessed from 1 mm to about 10 mm relative to the base surface 403. As shown, the pad 311 has a pattern including four spokes 405, but in several other embodiments, the pad 311 may have a good few or many spokes 405, e.g., one to about at least 12 spokes 405. The spokes 405 may or may not have equal radial lengths. For example, the spokes 405 may be centered between the pad center 407 and the radially separated edges of the pad 311, and may further be about 10 mm to 60 mm, e.g., 40 mm.

[0033]

[0042] The advantages of the pad carrier assembly 300 include greater accuracy and precision in force and pressure readings through the use of position control, allowing for better and more reproducible control of the amount of pressure applied to the substrate when low downforce is required during the cleaning process. It has been found that pressure sensors alone do not provide sufficient accuracy and cannot generate consistent cleaning pad contact pressure when using elastic cleaning pads with low downforce.

[0034] Torque position

[0043] The controller 160 is configured to analyze at least three motor torques at different times during a typical cleaning process. These torques may include an initial torque value, a contact torque value, and a cleaning torque value. The initial motor torque causes the pad motor 308 to allow the cleaning pad 311 to rotate freely above the substrate, since the cleaning pad 311 is not yet in contact with the surface of the substrate 120. The contact torque is generated when the pad 311 comes into contact with the surface of the substrate 120, but the pad 311 is not significantly compressed. The cleaning torque value is the motor torque generated by the pad motor 308 after the pad 311 has been driven a certain distance into the substrate 120.

[0035]

[0044] For example, as the pad 311 rotates and is lowered to contact the substrate 120, the controller 160 monitors the load on the pad motor 308 in relation to torque. The contact torque value is established when the controller 160 reads the change from the initial torque to an increase in torque as the pad 311 makes contact with the substrate 120. The contact torque indicates that the pad 311 has made contact with the substrate, but the pad is not yet significantly compressed. The pad 311 is then driven into the substrate 120 by the cleaning distance, and the cleaning torque is analyzed for process monitoring.

[0036] Pressure-distance

[0045] Instead of the conventional closed-loop direct pressure measurement type of control, it has been found that controlling the position of the cleaning pad 311 relative to the surface of the substrate 120 allows for more accurate and precise application of pressure by the cleaning pad 311 to the surface 120a of the substrate 120. After the cleaning pad 311 contacts the surface of the substrate, a desired amount of downforce and / or pressure applied by the cleaning pad 311 can be determined empirically or derived from modeling as a function of the distance traveled by the pad carrier 307 and the cleaning pad 311. The controller 160 then begins to measure the pad deformation with respect to the distance the cleaning pad 311 has been driven into the substrate 120, i.e., the cleaning distance. Then, using a known value of pad compression, in some embodiments, the controller 160 can determine the amount of pressure and / or force applied by the pad 311 to the substrate 120 based on the amount of pad compression, using pad material data. These techniques allow very low pressures to be applied precisely and accurately by the cleaning pad 311. For example, pad 311 can apply a pressure of less than 1 psi, e.g., 0.04 psi, onto a pad with a diameter of 134 mm.

[0037] Hydrodynamic effects

[0046] The combination of the material of the pad 311 and the ability to precisely control the position of the pad carrier 307 relative to the surface of the substrate 120, combined with the use of higher rotational speeds provided by the motor in the PC module 200, has been found to enable the generation of a hydraulic effect as the pad processing surface 311a moves parallel to the entire surface of the substrate.

[0038]

[0047] Figure 6 shows the relationship between the Streibeck curve and the Hershey number for the formation of a hydraulic film. The Hershey number is the dynamic viscosity (Pa·s = N·s / m) in relation to velocity (m / s). 2The coefficient of friction μ is a dimensionless number obtained by multiplying by the Hershey number and dividing by the load per unit length of the bearing (N / m), and is related to the coefficient of friction μ when the height of the hydraulic film is at least 50 times greater than the dimensions of the molecules in the fluid 321. Very thin films have higher viscosity, and when the fluid film is about 5 nm in size, the film begins to exhibit solid properties and can be helpful in cleaning processes. The Striveck curves shown in the graph of Figure 6 are the frictional properties of a liquid under conditions that typically straddle the boundary between the mixed regime and the hydraulic regime. The three regimes from left to right are the direct contact regime, the mixed lubrication regime, and the hydraulic regime. Each regime is defined by the Hershey number, which can be determined using various techniques (see also ASTM D2266, e.g.). This measurement concept is described in Hersey, Mayo, The Laws of Lubrication of Horizontal Journal Bearings, Journal of Washington Academy of Sciences, 4, 1914.

[0039]

[0048] As shown in Figure 6, the horizontal axis (h) is the Hershey number. The Hershey number is related to the height of the film between the elastic solid and the rigid body. The force applied to the pad 311 is important for accurately and precisely determining the Hershey number. For example, the rigid solid may be the substrate 120, the elastic solid may be the PVA pad, and the film height may be the film formed in the interaction between the fluid 321, the pad 311, and the substrate 120. Without being constrained by theory, the spring constant of the pad material and the deformation of the pad can be used to generate the load applied to the pad 311 with more precision than a pressure sensor alone. Knowing the precise pressure applied by the pad 311 allows for the determination of an accurate Hershey number, ensuring that the operating conditions can be maintained at the appropriate position along the Stribeck curve. Using the formulated Hershey number, process parameters can be identified that ensure the Hershey number remains, for example, between 1 and 10.

[0040]

[0049] Figure 5 is a flowchart showing a polishing process 500 according to an embodiment of the present disclosure. The process 500 may be performed in a PC module, such as a PC module 200. This PC module is controlled by a system controller, such as a system controller 160. The process 500 is started in step 502 when the controller 160 flows a fluid 321 through (one or more) nozzles 314 onto the pad processing surface 311a of a pad 311 and the substrate surface 120a of a substrate 120 placed on a rotatable substrate table 230. The fluid 321 may be configured to clean or polish the substrate 120 (for example, a substrate with a copper layer on top). Once the system controller 160 begins to flow the fluid 321 onto the substrate surface 120a, the pad 311 is rotated by a pad motor 308 mounted on a pad carrier 307. The system controller 160 communicates to the pad motor 308 the speed at which the pad 311 is to be rotated and controls the rotation accordingly. The system controller 160 reads an initial torque value from the pad motor 308 before lowering the pad 311 to the substrate surface 120a.

[0041]

[0050] Once the initial torque value is established, in step 504, the controller 160 causes the lift actuator assembly 302 and the lift mechanism 305 to lower the pad 311 via the pad carrier 307. While the pad 311 is rotating, the controller waits to detect the contact torque value generated by the pad motor 308 when the pad processing surface 311a contacts the substrate surface 120a. The contact torque value will occur at the contact point, which is defined by the gap formed between the pad processing surface 311a and the substrate support surface 230a of the rotatable substrate table 230.

[0042]

[0051] Next, in step 506, the controller 160 drives the pad carrier 307 and the cleaning pad 311 toward the substrate 120 by a cleaning distance that compresses the pad 311. The cleaning distance is generally defined as the pad compression or pad deformation when the pad 311 is driven toward the substrate surface 120a. The actual pressure exerted by the pad 311 toward the substrate 120 has been found to be more accurately determined by using a lookup in a data table utilized by the system controller 160 or by using empirically derived equations than by the pressure sensor alone. Precise control of the cleaning distance allows for precise control of the amount of pressure applied to the substrate 120a in low-pressure applications due to the elastic properties of the cleaning pad 311. The interaction between the fluid 321, the rotation of the pad processing surface 311a, and the substrate surface 120a generates a cleaning torque that can be measured on the pad motor 308. The cleaning torque will vary as a function of height H. Once the cleaning pad 311 has moved the cleaning distance, the PC module 200 performs the cleaning process 508. In the cleaning process 508, the cleaning pad 311, positioned at θ relative to the surface of the substrate 120, moves in parallel across the entire surface of the substrate in precise motion using the column motor 315. This is done while a fluid 321 is supplied to the surface of the substrate 120a and the pad processing surface 311a of the cleaning pad 311. The cleaning torque is monitored during the process to ensure a consistent process. If a deviation in torque is observed by the controller 160, a signal is issued indicating that an error has occurred. Once the substrate 120 is cleaned and the pad is lifted in the process 510, the process is completed.

[0043]

[0052] According to several embodiments of the flow diagram in Figure 5, the method for cleaning the substrate 120 includes placing the substrate 120 in the pre-cleaning module 200, rotating the substrate table 230, and supplying fluid 321 toward the substrate support surface 230a of the substrate table 230. The method further includes rotating the rotating pad 311 at a predetermined cleaning speed and detecting the initial torque value generated by the pad motor 308 with the controller 160. The pad 311 is then lowered by the lift actuator assembly 302 until the controller 160 detects the contact torque generated by the pad motor 308 at the contact point formed in the torque increase (but before the cleaning pad 311 is compressed). The cleaning pad 311 is then moved toward the substrate support surface 230a by a cleaning distance, compressing the pad by the cleaning distance. The pad 311 is then translated across the entire substrate support surface 230a.

[0044]

[0053] Multiple embodiments disclosed herein enable precise pressure control and the generation of a hydraulic effect. This effect may include a hydraulic film formed in the interaction between the pad 311 and the substrate 120. The hydraulic film is believed to minimize the number of scratches generated on the substrate surface 120a. This effect is particularly useful for cleaning and polishing substrates containing metals and / or substrates with delicate surfaces, such as substrates with copper (Cu) surfaces. In addition to generating a hydraulic film, the advantages described herein include holding the pad 311 at an angle θ and / or using pad feature 401, which further enables the pad 311 to absorb fluid 321 itself. This angle and feature ensure that the pad 311 is always filled with fluid, maintaining the hydraulic effect. These features alone and / or in combination have shown remarkable benefits of an improved cleaning process with less damage to the substrate surface 120a. The improvements described herein may also be applied to substrates with sensitive coatings, such as substrates with copper coatings. Another example of the advantages is an improvement in the process of removing metal, metal oxides, and polishing slurry from the substrate surface 120a during the cleaning process after the polishing process and / or the process of using abrasives mixed in the slurry.

[0045]

[0054] While the above description applies to embodiments of the present disclosure, other embodiments and further embodiments of the present disclosure may be devised without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the following claims.

Claims

1. A method for cleaning a circuit board, The first motor is used to rotate the circuit board table. To supply fluid to the surface of a substrate placed on the support surface of the substrate table of the cleaning module, Rotate the cleaning pad at the cleaning speed. By using the controller, the initial torque value generated by the second motor is detected. Lowering the cleaning pad by using the lift actuator assembly until the controller detects a contact torque generated by the second motor when the pad processing surface of the cleaning pad contacts the surface of the substrate, wherein the pad processing surface contacts the surface of the substrate at the contact point, The command from the controller moves the cleaning pad toward the substrate by a cleaning distance, and the cleaning pad is compressed by the parallel movement of the cleaning pad by the cleaning distance, and A method comprising moving the pad processing surface of the cleaning pad in parallel over the entire support surface of the substrate.

2. The method according to claim 1, wherein the pressure experienced by the cleaning pad on the surface of the substrate is at least less than 0.5 psi.

3. The method according to claim 1, wherein a hydraulic film is formed on the pad processing surface of the cleaning pad.

4. The method according to claim 1, further comprising calculating the force applied to the cleaning pad based on the pad compression.

5. The method according to claim 1, wherein the cleaning pad comprises a polyvinyl alcohol (PVA) material.

6. The method according to claim 1, wherein the washing speed is between approximately 750 RPM and approximately 2500 RPM.

7. A pre-cleaning module for cleaning a circuit board, A rotatable substrate table having a substrate support surface for supporting a substrate on top, The pad carrier assembly comprises, Career column, A carrier arm is coupled to the carrier column and extends radially outward from the axis of the carrier column. A lift mechanism coupled to the carrier arm, A lift actuator assembly coupled to the carrier arm and mechanically connected to the lift mechanism, and The pad carrier is configured to be raised and lowered relative to the surface of the substrate table by the lift mechanism and the lift actuator assembly, and the pad carrier is Cleaning pads, A pad motor configured to rotate the cleaning pad around a central motor shaft, and The pad motor is provided with a shaft that connects to the cleaning pad, The aforementioned pre-cleaning module further, A pre-cleaning module equipped with a system controller configured to identify pad compression.

8. The pre-wash module according to claim 7, wherein the pad carrier is configured such that the central motor shaft is at a certain angle with respect to the vertical axis of the pad carrier.

9. The pre-wash module according to claim 8, wherein the angle is between approximately 0.01 degrees and approximately 6 degrees.

10. The pre-cleaning module according to claim 7, wherein the cleaning pad comprises a polyvinyl alcohol (PVA) material.

11. The pre-cleaning module according to claim 7, wherein the pad treatment surface of the cleaning pad includes a plurality of abrasive features.

12. The pre-cleaning module according to claim 11, wherein the polishing features include a plurality of mesa arranged as a radial pattern extending from the surface of the pad.

13. The pre-cleaning module according to claim 11, wherein the polishing feature includes a plurality of spokes arranged as a radial pattern extending from the surface of the pad.

14. The pre-wash module according to claim 7, wherein the system controller is configured to read pad compression with an accuracy of approximately + / - 10 micrometers (μm) to approximately + / - 40 μm, and can determine the applied pressure from a compression reference having an accuracy of + / - 0.04 psi.

15. A pre-cleaning module, A rotatable substrate table having a substrate support surface for supporting a substrate on top, A system controller configured to calculate the force applied to the pad based on the pad's compression, The pad carrier assembly comprises, Carrier arm, A lift mechanism coupled to the carrier arm, A lift actuator assembly coupled to the carrier arm and mechanically connected to the lift mechanism, configured to apply less than 30 N, and controlled by the system controller, and The pad carrier is configured to be moved by the lift mechanism and the lift actuator assembly, and the pad carrier is A pad motor that can detect and communicate torque values ​​experienced in real time. shaft, and A pre-cleaning module comprising a pad, which is coupled to the pad motor by the shaft, and which includes a pad made of PVA material.

16. The pre-cleaning module according to claim 15, wherein the cleaning pad further includes a pad pattern.

17. The pre-wash module according to claim 16, wherein the pad pattern is a radial spoke pattern.

18. The pre-washing module according to claim 15, wherein the pad processing surface is at a certain angle.

19. The pre-washing module according to claim 18, wherein the pad processing surface is inclined between approximately 1 degree and approximately 5 degrees.

20. The pre-cleaning module according to claim 15, wherein the pad motor can rotate the pad between approximately 750 RPM and approximately 2500 RPM.

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