Patent Application
20230373062
Chemical mechanical polishing processes are used to provide a planarization process during semiconductor manufacturing. Precise control of a polishing thickness and uniformity of the polish rate across a wafer are necessary to provide a polished film having a uniform thickness distribution.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The present disclosure is directed to a chemical mechanical polishing (CMP) apparatus using an integrated slurry mixer-dispenser and/or an in-process slurry mixture ratio change and methods of operating the same, the various aspects of which are described herebelow.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
Chemical mechanical polishing (CMP) is used in semiconductor manufacturing to enable an abrasive planarization process that provides a highly planar surface. High intra-wafer uniformity and high inter-wafer (i.e., wafer-to-wafer) uniformity of a CMP process is desired in providing polished structures having well-controlled and uniform thicknesses. According to an aspect of various embodiments of the present disclosure, a CMP system may use an integrated slurry mixer-dispenser to provide in-process slurry mixture ratio change. The in-process slurry mixture ratio change may be triggered upon sensing of a torque change in the drive motor for a platen. Further, the slurry mixture ratio may be continuously adjusted to provide a uniform removal rate by monitoring the torque in the drive motor for the platen. The various aspects of the present disclosure are described in detail herebelow.
Referring to
The CMP apparatus 100 includes a polishing pad 12 located on a top surface of a platen 10, a wafer carrier 40 configured to hold a substrate 41 such that a top surface of the substrate 41 is held against a surface of the polishing pad 12 of the platen 10. The CMP apparatus 100 also includes an integrated slurry mixer-dispenser 20 configured to generate slurry 22 by mixing at least two slurry components and to dispense slurry 22 over the top surface of the polishing pad 12, and a pad conditioning unit (30, 32) that is used to condition the top surface of the polishing pad 12.
The platen 10 may have a generally cylindrical shape, and may have a circular top surface that is large enough to accommodate the polishing pad 12. The polishing pad 12 may have a circular shape with a diameter that is at least twice the diameter of the substrate 41. For example, in embodiments in which the diameter of the substrate 41 is 300 mm, the diameter of the polishing pad 12 may be at least 600 mm. In embodiments in which the diameter of the substrate 41 is 450 mm, the diameter of the polishing pad 12 may be at least 900 mm. Generally, the ratio of the diameter of the polishing pad 12 to the diameter of the substrate 41 may be in a range from 2 to 6, such as from 2.5 to 4. The polishing pad 12 includes asperities and pores that define the pad texture. The asperities and pores may be arranged into unit cells that may be repeated across the polishing pad and to provide uniform pressure across the substrate 41 during polishing.
The platen 10 may be configured to rotate around a vertical axis VA passing through the geometrical center of the platen 10. For example, a platen motor assembly 8 may be provided underneath the platen 10 to provide a rotational motion to the platen 10 around the vertical axis (VA) passing through the geometrical center of the platen 10. The platen motor assembly 8 may comprise a drive motor 82 and an endpoint detection system 84 that monitors the removal rate (i.e., the polish rate) of the material of the substrate 41 during polishing steps. For example, the endpoint detection system 84 may measure the torque on the drive motor 82 as a basis for determining the removal rate (i.e., the polish rate) of the material of the substrate 41 during polishing steps. According to an aspect of various embodiments of the present disclosure, the endpoint detection system 84 may be configured to detect a change in a removal rate of materials from the substrate 41 and to generate an endpoint detection signal based on the change in the removal rate of the materials. The platen 10 may be configured to provide a rotational speed in a range from 10 revolutions per minute to 240 revolutions per minute.
The wafer carrier 40 may be configured to hold the substrate 41 on a bottom surface thereof, and to press the substrate 41 onto the top surface of the polishing pad 12. In one embodiment, the wafer carrier 40 may include a vacuum chuck configured to provide suction to the backside of the substrate 41. In one embodiment, differential suction pressures may be applied across different backside areas of the substrate 41. For example, the suction pressure applied to the center portion of the substrate 41 may be different from the suction pressure applied to the peripheral portion of the substrate 41 to provide uniform polishing rate across the entire area of the front side of the substrate 41 that contacts the polishing pad 12. In one embodiment, the wafer carrier 40 may include a retaining ring having an annular shape and configured to hold the substrate 41 therein so that the substrate 41 does not slide out from underneath the wafer carrier 40.
A polishing head 42 may be provided over the wafer carrier 40. The polishing head 42 may comprise a rotation mechanism that provides rotation to the wafer carrier 40. In some embodiments, a gimbal mechanism may be provided between the rotation mechanism and the wafer carrier 40 so that the wafer carrier 40 tilts in a manner that provides maximum physical contact between the entire front surface of the substrate 41 and the polishing pad 12. The combination of the polishing head 42 and the wafer carrier 40 constitutes a wafer polishing unit (40, 42) that positions and rotates the substrate 41 in a manner that induces polishing of material portions on the front side of the substrate 41 through abrasion caused by sliding contact with the top surface of the polishing pad 12.
In one embodiment, the substrate 41 and the wafer carrier 40 may rotate around the vertical axis passing through the geometrical center of the wafer carrier 40. A polishing pivot pillar structure 44 may be affixed to a frame (not shown) of the CMP apparatus 100 such that the polishing pivot pillar structure 44 may rotate around a vertical axis passing through the geometrical center of the polishing pivot pillar structure 44. The vertical axis passing through the geometrical center of the polishing pivot pillar structure 44 is stationary relative to the frame of the CMP apparatus 100.
A polishing arm 46 mechanically connects the polishing head 42 to the polishing pivot pillar structure 44. Thus, upon rotation of the polishing pivot pillar structure 44 around the vertical axis passing through the geometrical center of the polishing pivot pillar structure 44, the polishing arm 46 may rotate around the vertical axis passing through the geometrical center of the polishing pivot pillar structure 44. The polishing head 42 may move around the vertical axis passing through the geometrical center of the polishing pivot pillar structure 44 over the polishing pad 12. Lateral movement of the wafer polishing unit (40, 42) over the polishing pad 12 may enhance uniformity of polish rate across the substrate 41 during the chemical mechanical polishing process.
The pad conditioning unit (30, 32) may be used to precondition the polishing pad 12 prior to, and/or during, the chemical mechanical polishing process that is used to polish material portions from the front surface of the substrate 41 that contacts the top surface of the polishing pad 12. In one embodiment, the pad conditioning unit (30, 32) may include a pad conditioning disk 30 and a conditioning head 32 that is configured to hold the pad conditioning disk 30. The pad conditioning disk 30 includes an abrasive bottom surface that con precondition the top surface of the polishing pad 12. Typically, the abrasive bottom surface of the pad conditioning disk 30 embeds abrasive particles such as diamond particles. The pad conditioning disk 30 is attached to the conditioning head 32 in a manner that enables rotation of the pad conditioning disk around a vertical axis passing through the geometrical center of the pad conditioning disk 30 without falling out from the conditioning head 32.
A conditioner pivot pillar structure 34 may be affixed to a frame (not shown) of the CMP apparatus 100 such that the conditioner pivot pillar structure 34 may rotate around a vertical axis passing through the geometrical center of the conditioner pivot pillar structure 34. The vertical axis passing through the geometrical center of the conditioner pivot pillar structure 34 may be stationary relative to the frame of the CMP apparatus 100.
A pad conditioner arm 36 mechanically connects the conditioning head 32 to the conditioner pivot pillar structure 34. A pad conditioner arm 36 mechanically connects the conditioning head 32 to the conditioner pivot pillar structure 34. Thus, upon rotation of the conditioner pivot pillar structure 34 around the vertical axis passing through the geometrical center of the conditioner pivot pillar structure 34, the pad conditioner arm 36 may rotate around the vertical axis passing through the geometrical center of the conditioner pivot pillar structure 34. The conditioning head 32 may move around the vertical axis passing through the geometrical center of the conditioner pivot pillar structure 34 over the polishing pad 12. Lateral movement of the pad conditioning unit (30, 32) over the polishing pad 12 may enhance uniformity of the surface condition of the polishing pad 12 after the pad preconditioning process.
The integrated slurry mixer-dispenser 20 may be configured to generate the slurry 22 by mixing at least two slurry components, and to dispense the slurry 22 over the top surface of the polishing pad 12. The at least two slurry components may include at least one solid slurry component and may include at least one liquid component. The at least one solid slurry component may include at least one abrasive material. The at least one liquid component may include an oxidant such as H2O2 and FeCl3.
The process controller 200 may be electrically connected to electrical components that control movement of various mechanical parts of the CMP apparatus 100. For example, the process controller 200 may be electrically connected to, and may be configured to control operation of, each of the platen motor assembly 8, the polishing pivot pillar structure 44, the wafer polishing unit (40, 42), the conditioner pivot pillar structure 34, the pad conditioning unit (30, 32), and the integrated slurry mixer-dispenser 20. For example, the process controller 200 may control the rotational speed of the platen 10, the polishing pivot pillar structure 44, the wafer carrier 40, the conditioner pivot pillar structure 34, and the pad conditioning disk 30, and may control the location of the slurry dispensation point and the rate of slurry dispensation.
Generally, the chemical mechanical polishing (CMP) apparatus 100 of the present disclosure may include a polishing pad 12 located on a top surface of a platen 10 configured to rotate around a vertical axis VA passing through the platen 10, a wafer carrier 40 configured to hold a substrate 41 and facing the polishing pad 12, and an integrated slurry mixer-dispenser 20 including at least two inlet ports 88 configured to receive a respective slurry component.
Referring to
According to an aspect of various embodiments of the present disclosure, the integrated slurry mixer-dispenser 20 comprises at least two in-line component-flow-control mass flow controllers 92. The at least two in-line component-flow-control mass flow controllers 92 may be configured to independently control a mass flow rate of a respective slurry component through a respective inlet port 88 within the at least two inlet ports 88. In the illustrated example, the at least two in-line component-flow-control mass flow controllers 92 may include a first in-line component-flow-control mass flow controller 92A, a second in-line component-flow-control mass flow controller 92B, a third in-line component-flow-control mass flow controller 92C, and a fourth in-line component-flow-control mass flow controller 92D. The size of each in-line component-flow-control mass flow controller 92 may be selected based on the necessary flow rate of the respective slurry component, and may be about 500 standard cubic centimeter per minute (sccm). In the illustrated example, the inlet ports 88 may comprise a first inlet port 88A, a second inlet port 88B, a third inlet port 88C, and a fourth inlet port 88D.
A component supply pipe 90 may be connected to each inlet port 88. Each component supply pipe 90 may comprise a first end that may be connected to a respective inlet port 88, and a second end that may be connected to a respective component supply tank in the facility support system. In the illustrated example, the component supply pipes 90 may include a first component supply pipe 90A that may be connected to the first inlet port 88A, a second component supply pipe 90B that may be connected to the second inlet port 88B, a third component supply pipe 90C that may be connected to the third inlet port 88C, and a fourth component supply pipe 90D that may be connected to the fourth inlet port 88D.
In an illustrative example, the integrated slurry mixer-dispenser 20 may include a mixer-dispenser frame 99 to which each of the at least two inlet ports 88 and the dispensation port 98 may be attached. At least two component feed pipes (91, 93) may be connected to a respective one of the at least two inlet ports 88, a mixing chamber 94 may be connected to each of the at least two component feed pipes (91, 93), and a dispensation pipe 104 connecting the mixing chamber 94 to the dispensation port 98. In one embodiment, a mixing coil 96 may be provided between the mixing chamber 94 and the dispensation pipe 104. In one embodiment, the mixing coil 96 may have a spiral shape, and may have a greater diameter than the component supply pipes 90 to enhance mixing of the various slurry components that pass through. In an illustrative example, the diameter of the mixing coil 96 may be in a range from 1.5 cm to 3.0 cm, and the diameter of the component supply pipes 90 may be in a range from 0.5 cm to 1.5 cm, although lesser and greater diameters may also be used.
Generally, the shape, the size, and the material of the various components of the integrated slurry mixer-dispenser 20 may be adjusted to enhance control of the material composition of the slurry 22, to minimize the amount of trapped slurry in the mixing coil 96 and the dispensation pipe 104, and to enhance mixing of the slurry components. Particularly, the interior components of the integrated slurry mixer-dispenser 20 may be changed to facilitate mixing of the various slurry components. For example, one or more stir bars 95 driven by a respective stir bar motor 97 may be added into the integrated slurry mixer-dispenser 20 to enhance the mixing of the slurry components.
At least two in-line component-flow-control mass flow controllers 92 may be connected to the at least two component feed pipes (91, 93). In this embodiment, each component feed pipe (91, 93) may comprise a first component feed pipe segment 91 extending between an inlet port 88 and a respective in-line component-flow-control mass flow controller 92, and a second component feed pipe segment 93 extending between the respective in-line component-flow-control mass flow controller 92 and the mixing chamber 94. Each of the at least two in-line component-flow-control mass flow controllers 92 may be configured to independently control a mass flow rate of a respective slurry component therethrough.
In an illustrative example, the first component supply pipe 90A may be connected to a first slurry component supply tank (not shown) including a first slurry component. The second component supply pipe 90B may be connected to a second slurry component supply tank (not shown) including a second slurry component. The third component supply pipe 90C may be connected to a third slurry component supply tank (not shown) including a third slurry component. The fourth component supply pipe 90D may be connected to a fourth slurry component supply tank (not shown) including a fourth slurry component. In this embodiment, the least two in-line component-flow-control mass flow controllers 92 may comprise a first in-line component-flow-control mass flow controller 92A located in the flow path of the first slurry component and configured to independently control the flow rate of the first slurry component, a second in-line component-flow-control mass flow controller 92B located in the flow path of the second slurry component and configured to independently control the flow rate of the second slurry component, a third in-line component-flow-control mass flow controller 92C located in the flow path of the third slurry component and configured to independently control the flow rate of the third slurry component, and a fourth in-line component-flow-control mass flow controller 92D located in the flow path of the fourth slurry component and configured to independently control the flow rate of the fourth slurry component.
Referring collectively to
An integrated slurry mixer-dispenser 20 may dispense the slurry 22 during the main polishing step and the terminal polishing step. The integrated slurry mixer-dispenser 20 may include at least two inlet ports 88 configured to receive a respective slurry component among the at least two slurry components, and may be configured to generate the slurry 22 by mixing the at least two slurry components. The integrated slurry mixer-dispenser 20 may include a dispensation port 98 that dispenses the slurry 22 over the polishing pad 12.
In one embodiment, the at least two slurry components may include a first slurry component and a second slurry component, and a mixture ratio of the slurry 22, which may include the ratio of a mass flow rate of the first slurry component to a mass flow rate of the second slurry component. The mixture ratio of the slurry 22 may be changed prior to performing the terminal polishing step and/or during the terminal polishing step. In one embodiment, the terminal polishing step may be performed after changing a mixture rate for the slurry 22. In one embodiment, the torque on a drive motor 82 of the platen 10 may be monitored during the terminal polishing step, and the torque on the drive motor 82 may be maintained within a target torque range by continually adjusting the ratio of the mass flow rate of the first slurry component to the mass flow rate of the second slurry component during the terminal polishing step, and/or any additional ratio(s) between a flow rate of any of the least two slurry components and a flow rate of another of the at least two slurry components.
In one embodiment, the endpoint detection system 84 configured to detect a change in a removal rate of materials from the substrate 41 and to generate an endpoint detection signal. The process controller 200 may be configured to receive the endpoint detection signal and to change at least one mass flow rate among mass flow rates of the at least two slurry components. In an illustrative example, the at least two slurry components comprise a first slurry component that flows through a first in-line component-flow-control mass flow controller 92A and a second slurry component that flows through a second in-line component-flow-control mass flow controller 92B, and the process controller 200 is configurated to change a ratio of a mass flow rate of the first slurry component to a mass flow rate of the second slurry component after receipt of the endpoint detection signal.
In a typical chemical mechanical polishing process, the main polishing step removes a first material on a bottom surface of a substrate 41 at, or about, a preset removal rate using a first material concentration for the slurry 22 until an endpoint detection signal is generated by the endpoint detection system 84, for example, when an increase in torque on a drive motor 82 of the platen 10 above a threshold value is measured. The endpoint detection system 84 generates the endpoint detection signal upon measurement of the torque above the threshold value. In this embodiment, the material composition of the slurry 22 may be changed upon receipt of the endpoint detection signal by the process controller 200 to provide more effect removal of the first material selective to a second material on the bottom surface of the substrate 41 that functions as a stopping material. In this embodiment, the material composition of the slurry 22 may be changed so that the removal rate of the terminal polishing process increases.
In one embodiment, the process controller 200 may be configured with processor executable instruction to monitor the torque on the drive motor 82 of the platen 10 after the endpoint detection signal is generated, and to maintain the torque on the drive motor 82 within a target torque range by continually adjusting the at least one mass flow rate among the mass flow rates of the at least two slurry components.
According to another aspect of the present disclosure and referring collectively to
In one embodiment, the at least two slurry components may include a first slurry component and a second slurry component, and the process controller 200 may be configured to change a ratio of a mass flow rate of the first slurry component to a mass flow rate of the second slurry component after receipt of the endpoint detection signal. In one embodiment, the process controller 200 may be configured to monitor torque on a drive motor 82 of the platen 10 after the endpoint detection signal is generated, and to maintain the torque on the drive motor 82 within a target torque range by continually adjusting the ratio of the mass flow rate of the first slurry component to the mass flow rate of the second slurry component.
Referring to
Generally, the second exemplary CMP apparatus may include a polishing pad 12 located on a top surface of a platen 10 (such as the first platen 10A) configured to rotate around a vertical axis VA passing through the platen, a wafer carrier 40 (such as the first wafer carrier 40A) configured to hold a substrate 41 (such as a first substrate) and facing the platen 10 (such as the first platen 10A), and an integrated slurry mixer-dispenser 20 comprising at least two inlet ports 88 configured to receive a respective slurry component, configured to generate slurry 22 by mixing at least two slurry components provided through the at least two inlet ports 88, and comprising a dispensation port 98 configured to dispense the slurry 22 over the polishing pad 12 (such as the first polishing pad 12A).
The second exemplary CMP apparatus may include an additional polishing pad 12 located on a top surface of an additional platen 10 (such as a second platen 10B) configured to rotate around an additional vertical axis passing through the additional platen 10 (such as the second platen 10B), and an additional wafer carrier 40 configured to hold an additional substrate 41 and facing the additional polishing pad 12 (such as a second polishing pad located on the second platen 10B). The integrated slurry mixer-dispenser 20 comprises an additional dispensation port 98 (such as a second dispensation port 98B) configured to dispense the slurry 22 over the additional polishing pad 12 (such as the second polishing pad).
In one embodiment, each of the dispensation ports 98 may be connected to a respective injection-point mass flow controller 108 that controls the total amount of the slurry 22 that flows out of the respective dispensation port 98. In the illustrative example, the injection-point mass flow controllers 108 may comprise a first injection-point mass flow controller 108A connected to the first dispensation port 98A, a second injection-point mass flow controller 108B connected to the second dispensation port 98B, a third injection-point mass flow controller 108C connected to the third dispensation port 98C, and a fourth injection-point mass flow controller 108D connected to the fourth dispensation port 98D.
An additional endpoint detection system 84 may be provided on the additional platen (such as the second platen 10B). The additional platen may be configured to detect a change in a removal rate of materials from the additional substrate 41 (such as a second substrate) and to generate an additional endpoint detection signal. In embodiments in which two wafers 41 are simultaneously polished and the two endpoint detection systems 84 underlying two platens 10 generate endpoint detection signals at different times (i.e., with a finite time interval between the two endpoint detection signals), polishing on a wafer on which the earlier endpoint detection signal is generated may be minimized by reducing a downforce from an overlying wafer carrier 40.
For example, the process controller 200 may be configured to change the at least one mass flow rate among the mass flow rates of the at least two slurry components only after receiving the endpoint detection signal and the additional endpoint detection signal. In this embodiment, the process controller 200 may be configured to reduce a downforce on the substrate 41 (such as the first substrate 41 underlying the first wafer carrier 40) until the additional endpoint detection signal (from the endpoint detection system 84 underlying the second platen 10B) is generated, or to reduce a downforce on the additional substrate 41 (such as the second substrate 41 underlying the second wafer carrier 40) until the endpoint detection signal (from the endpoint detection system 84 underlying the first platen 10A) is generated.
The process controller 200 in accordance with the various embodiments (including, but not limited to, embodiments described above with reference to
Alternatively, the process controller in accordance with the various embodiments (including, but not limited to, embodiments described above with reference to
Referring to
Referring to step 610 and
Referring to step 620 and
Referring to step 630 and
In one embodiment, the integrated slurry mixer-dispenser 20 may include a mixer-dispenser frame 99 to which each of the at least two inlet ports 88 and the dispensation port 98 is attached, at least two component feed pipes (91, 93) connected to a respective one of the at least two inlet ports 88, a mixing chamber 94 connected to each of the at least two component feed pipes (91, 93), and a dispensation pipe 104 connecting the mixing chamber 94 and the dispensation port 98.
Referring to step 640 and
Referring to all drawings and according to various embodiments of the present disclosure, a chemical mechanical polishing apparatus is provided, which comprise an in-process slurry composition change mechanism and a torque-based endpoint (EPD) signal system. Instantaneous change in the slurry composition during a polishing process enables an efficient CMP process that prevents low removal rate during a terminal polishing step (such as a touch-up polishing step).
In an embodiment, the chemical mechanical polishing (CMP) apparatus 100 may include: a polishing pad 12 located on a top surface of a platen 10 configured to rotate around a vertical axis VA passing through the platen 10; a wafer carrier 40 configured to hold a substrate 41 and facing the polishing pad 12; and an integrated slurry mixer-dispenser 20 that may include at least two inlet ports configured to receive a respective slurry component, configured to generate slurry by mixing at least two slurry components provided through the at least two inlet ports, and may include a dispensation port configured to dispense the slurry over the polishing pad.
In another embodiment, a chemical mechanical polishing (CMP) apparatus may be provided. The CMP apparatus 100 may include: a polishing pad 12 located on a top surface of a platen 10 configured to rotate around a vertical axis VA passing through the platen 10; a wafer carrier 40 configured to hold a substrate 41 and facing the polishing pad 12; an endpoint detection system 84 configured to detect a change in a removal rate of materials from the substrate 41 and to generate an endpoint detection signal; and a process controller 200 configured to receive the endpoint detection signal and to change a mixture rate for slurry comprising at least two slurry components and applied to the polishing pad 12.
The CMP apparatus of the present disclosure may be used for many types of CMP processes. For example, the CMP apparatus of the present disclosure may be used to minimize or eliminate metal corrosion and/or pits defect due to surfactant leakage during the polish process. Generally, effective removal of byproducts, debris, and excessive surfactant during an extended CMP process is very imperative since such residues lead to serious loading, dishing, and/or underpolish in localized pattern regions as well as reducing the overall removal rate. Traditional methods for residue removal include use of pad conditioners, which is time-consuming and reduces productivity of a CMP apparatus. The methods of the present disclosure uses real-time monitoring of torque on a drive motor 82 to detect a polish end point, and to use an integrated slurry mixer-dispenser 20 to adjust the composition of the slurry 22 and to correct the removal rate and to further control polish characteristics during a terminal polishing step.
It should be note that pre-mixing the slurry at the facility support systems fills the entire volume of a slurry transport line between the facility support systems and dispensation ports within the slurry having a same material composition throughout. The long slurry pipe between the facility support systems and the platens of conventional chemical mechanical polishing apparatuses may not be effectively emptied in time for any compositional change during a polishing process. Thus, in-process compositional change of slurries may not be provided in conventional chemical mechanical polishing apparatuses that employs a pre-mixed slurry that is generated at the facility support systems.
In addition, pre-mixing of the slurry at the facility support systems may cause storage of the slurry for a long time, and may cause self-acid effects and the surfactant accumulation effects within the slurry. In this embodiment, storage of the slurry in a facility support system tank for a long time may lower the pH value of the slurry, and the removal rate of the CMP process may be adversely affected due to the changes in the property of the slurry that follows a long term storage of the slurry in a pre-mixed state. In contrast, the CMP apparatus of the present disclosure mixes the slurry components “in process,” i.e., while the polishing operation proceeds within the CMP apparatus, and avoids such pH shift or surfactant accumulation in the slurry 22. Thus, the self-acid effects and surfactant accumulation effects may be eliminated in the CMP methods of the present disclosure.
According to an aspect of the present disclosure, the slurry surfactant ratio may be adjusted to directly prevent a long polish time due to low removal rate and/or to prevent underpolish at a later polishing step such as a terminal polishing step. In this embodiment, one of the slurry component may be a surfactant component, and the integrated slurry mixer-dispenser 20 of the present disclosure may be used to decrease the percentage of the surfactant component.
Generally, adjustment to the slurry composition during the polishing process of the present disclosure may be performed based on measurement of torque on the drive motor 82 for the platen 10, which may generate endpoint detection signals. Thus, real time adjustment to the slurry mix ratio may be made based on the endpoint detection signal. In an illustrative example, SRAM/logic region underpolish problems for dielectric CMP process (which may remove silicon oxide, silicon nitride, or polysilicon) may be alleviated or eliminated.
Use of the CMP apparatus of the present disclosure may lead to quality improvement to the slurry 22. For example, variations in the slurry pH due to a long idle time of the CMP apparatus may be eliminated and/or significantly reduced. Further, variations in the slurry composition may be made without changing any setting on the side of the facility support systems, thereby enabling rapid and effective testing of new CMP processes.
The CMP method of the present disclosure may be suitable for metal/backend CMP processes, and may prevent and/or reduce galvanic corrosion defects by dynamic in-process adjustment of slurry-protecting components within the slurry 22. For example, the percentage of a slurry-protecting component may be increased at a terminal polishing step to enhance protection of the polished metal surfaces from corrosion.
Since the slurry 22 of the present disclosure may be mixed within the integrated slurry mixer-dispenser 20 immediately before usage within the CMP apparatus, a mixed slurry 22 is not stored for a long time, but is consumed immediately after mixture and deterioration of properties of the slurry 22 is not a concern according to the CMP methods of the present disclosure. Further, the change in the material composition of the slurry 22 during the terminal polishing step may be adjusted based on the magnitude of the signal that generates the endpoint signals (such as the torque of the drive motor 82 as measured at the time of generation of the endpoint signal and/or as measured during the terminal polishing step).
While the present disclosure is described using an embodiment in which the integrated slurry mixer-dispenser comprises four inlet ports 88 and one dispensation port 98 or four dispensation ports 98, embodiments are expressly contemplated herein in which a different number of inlet ports 88 or a different number of dispensation ports 98 is used. Generally, the number of inlet ports 88 and the number of the dispensation ports 98 may be adjusted as needed. In an illustrative example, if three slurry components are mixed to generate the slurry 22, the number of the inlet ports 88 may be three. Each of the at least two in-line component-flow-control mass flow controllers 92 may comprise a closed-loop-control flow meter that may accurately control the flow rate of a respective slurry component.
The in-process mixing of the slurry 22 in the CMP apparatus of the present disclosure facilitates testing of the effects of the various slurry components without changing any setting on the facility support system side. For, example, the ratios among the components may be arbitrarily changed to test the effect of the respective ratio change on the removal rate on different materials (such as silicon oxide, silicon nitride, polysilicon, etc.)
If the ratios of the flow rates of the slurry components are fixed during a polish process, removal rate may decrease over time. In some embodiments of the present disclosure, changing a ratio of flow rates among the slurry components may correct the decrease in the removal rate and prevent an excess increase in the polish time. In an illustrative example in which a CMP process polishes silicon nitride and polysilicon using a slurry 22 containing a mixture of a first slurry component 1000NC and a second slurry component 6300AD, a decrease in the ratio of the flow rate of the first slurry component to the flow rate of the second slurry component induces a decrease in the removal rate for silicon nitride and a decrease in the removal rate for polysilicon. The torque on the drive motor 82 of the platen 10 depends on the ratio of the removal rate of silicon nitride to the removal rate of polysilicon. The endpoint of a main polishing process may be detected by monitoring the torque on the drive motor 82, and the flow rate of the first slurry component, the flow rate of the second slurry component, and the ratio of the flow rate of the first slurry component to the flow rate of the second slurry component may be adjusted based on the desired change in the overall removal rate and the desired selectivity of the polishing process.
According to various embodiments of the present disclosure, the endpoint detection process of the present disclosure may be used during the polishing process to monitor the polishing process. Changes in the torque of the drive motor 82 due to platen friction changes may be detected to enable stopping of each polishing step on different film layers during the polishing process. Generally, a change in the detected friction force correlated with formation of a new type of interface between the substrate 41 and the polishing pad 12, which occurs when the polishing process polishes one type of film in the substrate 41 completely and another type of film in the substrate 41 contacts the polishing pad 12.
Generally, the material composition of the slurry 22 may be adjusted in-process, i.e., during the polishing process within a polishing step or between polishing steps, to provide different polishing process conditions. Such polishing process conditions may be arbitrarily adjusted within a polishing step or between polishing steps to achieve clear wafer polishing while minimizing underpolish and while minimizing overpolish.
According to an aspect of the present disclosure, an additive slurry component may also be added to the integrated slurry mixer-dispenser 20 to enhance the mixing and the removal rate.
The integrated slurry mixer-dispenser 20 may replace traditional facility loops to reduce the production cost, and to enhance quality of the slurry and to minimize the variations in the slurry quality.
The CMP process of the present disclosure may be used for front-end-of-line (FEOL) CMP processes as well as back-end-of-line (BEOL) CMP processes. In embodiments in which the CMP process of the present disclosure is used for BEOL CMP processes, surfactant concentration in the slurry 22 may be changed mid-process to prevent metal exposal corrosion, which may occur in-process once electrochemical measurement device is mounted to the CMP apparatus.
The CMP apparatus of the present disclosure provide various benefits compared to prior art CMP apparatuses. For example, the integrated slurry mixer-dispenser 20 of the present disclosure may prevent slurry pH changes due to a long idle effect because the slurry 22 is mixed during the CMP process.
In one embodiment, the integrated slurry mixer-dispenser 20 may be made primarily of at least one anti-acid anti-corrosion material, such as polytetrafluoroethylene (PTFE). In one embodiment, the integrated slurry mixer-dispenser 20 may be positioned underneath, at, or, above, the polishing surface(s). In one embodiment, a plurality of platens 10 may be provided, and the integrated slurry mixer-dispenser 20 may be positioned at the center of the plurality platens 10 underneath the polishing surface to minimize the volume taken by the integrated slurry mixer-dispenser 20.
Generally, the various embodiments of the present disclosure may be used to provide an enhanced CMP process using an in-process change of slurry composition.
Various illustrative logical blocks, modules, circuits, and algorithm operations described in connection with the various embodiments may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and operations have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the claims.
The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Alternatively, some operations or methods may be performed by circuitry that is specific to a given function.
In one or more embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a non-transitory computer-readable medium or a non-transitory processor-readable medium. The operations of a method or algorithm disclosed herein may be embodied in a processor-executable software module that may reside on a non-transitory computer-readable or processor-readable storage medium. Non-transitory computer-readable or processor-readable storage media may be any storage media that may be accessed by a computer or a processor. By way of example but not limitation, such non-transitory computer-readable or processor-readable media may include RAM, ROM, EEPROM, FLASH memory, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of non-transitory computer-readable and processor-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a non-transitory processor-readable medium and/or computer-readable medium, which may be incorporated into a computer program product.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
