Roller brush with bristles for substrate cleaning

Abstract

A roller brush for cleaning a substrate following chemical mechanical planarization (CMP) of the substrate includes a generally cylindrical body having an outer surface; and a plurality of spaced-apart bristles projecting outwardly from and circumferentially around the outer surface of the cylindrical body and separated by a plurality of gaps. Each bristle of the plurality of spaced-apart bristles has a diameter, D, and a height, H, such that the ratio D / H is less than or equal to about 0.3.

Description

ROLLER BRUSH WITH BRISTLES FOR SUBSTRATE CLEANINGSummary

[0001] In some aspects of the present description, a roller brush for cleaning a substrate following chemical mechanical planarization (CMP) of the substrate, the roller brush including a generally cylindrical body having an outer surface, and a plurality of spaced-apart bristles projecting outwardly from and circumferentially around the outer surface of the cylindrical body and separated by a plurality of gaps. Each bristle of the plurality of spaced-apart bristles has a diameter, D, and a height, H, such that the ratio D / H is less than or equal to about 0.3.

[0002] In some aspects of the present description, a brush for cleaning a substrate following chemical mechanical planarization (CMP) of the substrate, the brush including a generally cylindrical body having an outer surface, and a plurality of spaced-apart bristles projecting outwardly from and circumferentially around the outer surface of the cylindrical body and separated by a plurality of gaps. The brush is configured to be rotated against the substrate during a cleaning of the substrate, and wherein each bristle of the plurality of spaced-apart bristles is configured to flex when in contact with the substrate such that a portion of a side of the bristle moves against the substrate.Brief Description of the Drawings

[0003] FIG. 1 illustrates a side view of a roller brush for cleaning a substrate typical to the prior art;

[0004] FIGS. 2A and 2B depict different views of a roller brush for cleaning a substrate following chemical mechanical planarization of the substrate, in accordance with an embodiment of the present description;

[0005] FIGS. 3A and 3B depict additional views of a roller brush for cleaning a substrate following chemical mechanical planarization of the substrate, in accordance with an embodiment of the present description;

[0006] FIGS. 4 A and 4B depict a roller brush for cleaning a substrate wherein the roller brush includes through-holes that allow a fluid to pass from an interior of the brush to an exterior of the brush, in accordance with an embodiment of the present description;

[0007] FIG. 5A illustrates how the bristles of a roller brush for clearing a substrate may include a porous material, in accordance with an embodiment of the present description; and

[0008] FIG. 5B is a perspective view of a system for cleaning a substrate, in accordance with an embodiment of the present description.Detailed Description

[0009] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0010] Roller PVA (poly vinyl acetal) brushes are typically used for cleaning of wafers post CMP (chemical mechanical planarization, also known as chemical mechanical polishing). PVA brushes typically contain nodules that are in the size range of 5-10 mm in diameter and approximately 5 mm in height. That is, the nodules are typically formed as squat “bumps” on the surface of the PVA brush with an aspect ratio (of diameter to height) that is often close to 1:1.

[0011] These nodules are soft, porous, compressible, and highly elastic, and can have good impact resistance, wicking properties, and wear resistance. They transfer the contact force to the wafer, help increase the CoF (coefficient of friction) without damaging the wafers and contribute to the cleaning of residues from the wafer surface. One of the issues with the use of these PVA brushes is the top surface of nodules (the surface facing away from the interior of the roller brush and meant to make direct contact with the substrate) contains a skin layer that needs an additional break-in step at the customer before use (the skin layer must be worn off during the break-in process). Also, when cleaning soft polymeric residues, the residue can clog the pores of the brush and degrade the cleaning performance significantly.

[0012] It has been found that closely-spaced, high-aspect ratio (for example, aspect ratios of diameter to height of 1: 10 or 1:20) features that can act like bristles when molded onto a film and adhered onto a core can be used to overcome the short comings of PVA brushes. The bristle design and material can be chosen to modulate the stiffness as well as the contact pressure of the bristles on the wafer. If the number of contact points are high enough, and the material is made soft enough, the bristle type brushes can do a good job of cleaning. As needed, porosity can be added on the bristle type brushes, and the surface of these bristles can be modified to make them more conducive to cleaning certain type of defects (zeta potential, hydrophilicity etc.).

[0013] One advantage to the use of a high-aspect ratio features (e.g., bristles) is that the features are flexed as they are pushed against the substrate such that the side of each bristle is in contact with the substrate, rather than the tip (top surface) of the bristle. This eliminates the lengthy break-in process required with the short, squat nodules of the typical brushes of the prior art, which are not able to flex and present only their top surface to the substrate.

[0014] According to some aspects of the present description, a roller brush for cleaning a substrate following chemical mechanical planarization (CMP) of the substrate (e.g., a wafer) includes a generally cylindrical body having an outer surface, and a plurality of spaced-apart bristles projecting outwardly from and disposed circumferentially around the outer surface of the cylindrical body andseparated by a plurality of gaps (i.e., spaces on the outer surface of the cylindrical body, generally between and surrounding each bristle, which do not have bristles). In some embodiments, each bristle of the plurality of spaced-apart bristles may have a diameter, D, and a height, H, such that the ratio of D / H is less than or equal to about 0.3, or about 0.2, or about 0.1, or about 0.07, or about 0.05.

[0015] In some embodiments, the cylindrical body may further include an interior having a longitudinal axis about which the cylindrical body may rotate (i.e., such that the bristles are rotated over, and flex against, the substrate when the roller brush is in operation). In some such embodiments, the outer surface of the cylindrical body may further include a plurality of through-holes disposed in one or more of the plurality of gaps. In some embodiments, each through-hole of the plurality of through-holes may extend from the outer surface of the cylindrical body into the interior (e.g., a hollow interior) of the cylindrical body. In some such embodiments, the interior of the cylindrical body may be configured to allow a flow of liquid (e.g., water, a liquid cleansing fluid, etc.) through the interior such that it exits the interior via the through-holes and circulates (flows) through the plurality of spaced-apart bristles. In some embodiments, this fluid may help to carry away material cleaned from the surface of the substrate and may help the bristles from being clogged by material.

[0016] In some embodiments, the roller brush may be configured to be rotated around its longitudinal axis and against the substrate during a cleaning of the substrate. In some embodiments, each bristle of the plurality of spaced-apart bristles may be configured to flex when in contact with the substrate such that a portion of a side of the bristle moves against the substrate. In some such embodiments, the portion of the side of the bristle in contact with the substrate may be larger (may have a substantially larger surface area) than a portion of a tip of the bristle in contact with the substrate. In some embodiments, the tip of the bristle may not make contact with the substrate, or may make only an edge contact with the substrate.

[0017] In some embodiments, the material of the bristles may be configured to optimize substrate cleaning efficiency. For example, in some embodiments, a flex modulus of a material of the plurality of bristles may be between about 1 MPa and about 1 GPa, as measured when the material has a moisture content of less than about 0.2% (i.e., when the material is substantially “dry”). In some embodiments, a hardness of the material of the plurality of bristles may be below about Shore A 90.

[0018] In some embodiments, a density of the plurality of bristles may be between about 2 and about 500 stems per square centimeter. In some embodiments, the average height, H, of each bristle may be between about 10 microns and about 10 millimeters. In some embodiments, an average diameter of each bristle of the plurality of bristles may be between about 10 microns and about 5 millimeters.

[0019] In some embodiments, each bristle of the plurality of bristles may have a porous structure. In some such embodiments, the porosity of each bristle of the plurality of bristles may be between about 0% and about 80%.

[0020] In some embodiments, each bristle of the plurality of bristles may include a material which is substantially hydrophilic. In some embodiments, the material may have water uptake ranging from about 0% up to about 100% of the weight of the material. In some embodiments, each bristle of the plurality of bristles may include a material which has a zeta potential which is negative. In some embodiments, each bristle of the plurality of bristles may include a material which has a zeta potential which is positive. In some embodiments, each bristle of the plurality of bristles may have a substantially cylindrical shape. In some embodiments, for example, each bristle of the plurality of bristles may exhibit a taper from a diameter of the bristle as seen at the base of the bristle decreasing as it approaches a tip of the bristle. In some such embodiments, the taper angle from the base of the bristle (widest point) toward the tip may be in a range of about 0 degrees to about 30 degrees.

[0021] In some embodiments, the material of the bristles of the plurality of bristles may include one or more of a polyamide, a rubber, a thermoplastic elastomer, and a polyurethane. For example, the material of the bristles, in some embodiments, may include, but is not limited to, one or more of following materials / material classes: PA66 (polyamide), PA6 (polyamide), rubbers, EPDM-based rubber modifiers, styrene-butadiene- styrene (SBS) block copolymer, styrene-ethylene-butylene- styrene (SEBS) based block co polymers, other thermoplastic elastomers, polyurethane. In some embodiments, varying levels of porosity may be added to the material during the forming of the material.

[0022] According to some aspects of the present description, a brush for cleaning a substrate following chemical mechanical planarization (CMP) of the substrate may include a generally cylindrical body having an outer surface, and a plurality of spaced-apart bristles projecting outwardly from and circumferentially around the outer surface of the cylindrical body and separated by a plurality of gaps. In some embodiments, the brush may be configured to be rotated against the substrate during a cleaning of the substrate. In some such embodiments, each bristle of the plurality of spaced-apart bristles may be configured to flex when in contact with the substrate such that a portion of a side of the bristle moves against the substrate. In some such embodiments, the portion of the side of the bristle (i.e., the amount of surface area) in contact with the substrate may be larger than a portion of a tip of the bristle in contact with the substrate. In some such embodiments, during a cleaning of the substrate, a tip of the bristle may make little to no contact, or only incidental contact, with the surface of the substrate.

[0023] In some embodiments, each bristle of the plurality of spaced-apart bristles may have a height, H, and a diameter, D, such that the ratio of H / D is greater than or equal to about 3, or greater than or equal to about 4, or greater than or equal to about 5, or greater than or equal to about 10, or greater than or equal to about 20.

[0024] In some embodiments, a flex modulus of a material of the plurality of bristles may be between about 1 MPa and about 1 GPa when measured when the material is “dry” (i.e., has a moisture content of less than about 0.2%). In some embodiments, the hardness of a material of the plurality ofbristles may be below about Shore A 90. In some embodiments, the density of the plurality of bristles may be between about 2 and about 500 stems per square centimeter.

[0025] Turning now to the figures, FIG. 1 illustrates a side (end) view of a roller brush for cleaning a substrate typical to the prior art. FIG. 1 depicts a typical roller brush 50 of the prior art, which is often formed of a poly vinyl acetal material (which is why they are often called PVA brushes). These PVA brushes 50 are typically used for cleaning of a substrate 30, such as a silicon wafer after chemical mechanical planarization, or CMP.

[0026] A PVA brush typically includes nodules 52 that are in the size range of 5-10 mm in diameter, d, and approximately 5 mm in height, h. Nodules 52 are typically formed as squat “bumps” on the surface of PVA brush 50. Nodules 52 often have an aspect ratio (diameter to height) that is often close to 1: 1.

[0027] One of the issues with the use of these PVA brushes 50 is the top surface 54 of nodules 52 (the surface facing away from the interior of PVA brush 50 and meant to make direct contact with substrate 30) contains a skin layer 55 that requires an additional break-in step at the customer before use. This break-in process includes rotating PVA brush 50 in a direction 45 such that skin layer 55 is substantially rubbed off due to friction against a top surface 32 of substrate 30. No useful work can be done by PVA brush 50 during the break-in process, and so finding a way to eliminate this extra step would be extremely advantageous.

[0028] FIGS. 2A and 2B depict different views of an embodiment of a roller brush incorporating high-aspect features for cleaning a substrate following chemical mechanical planarization of the substrate, according to the present description. FIGS. 2A and 2B should be considered together for the following discussion.

[0029] In some embodiments, roller brush 100 may incorporate a plurality of high-aspect ratio features, of bristles, 10, disposed circumferentially around the outer surface 22 of a cylindrical body 20. In some embodiments, bristles 10 may be separated by a plurality of gaps 15 (i.e., areas on outer surface 22 which do not have bristles 10).

[0030] In some embodiments, cylindrical body 20 may further include an interior with a longitudinal axis 40 about which cylindrical body 20 may rotate. In some embodiments, longitudinal axis 40 may be coincident with a central axis of cylindrical body 20, such that it is substantially equally distant from any points on outer surface 22 of cylindrical body 20. In some embodiments, the interior of cylindrical body 20 may be substantially hollow, or may be at least partially hollow (e.g., may include channels through with a fluid may be transported).

[0031] FIGS. 3A and 3B depict additional views of an embodiment of roller brush 100, according to the present description. Looking first at FIG. 3B, in some embodiments, bristles 10 may have a high-aspect ratio which allows the bristles to flex or bend when pushed against a substrate. For example, each bristle 10 of the plurality of spaced-apart bristles 10 may have a diameter, D, and a height, H, such that the ratio of D / H is less than or equal to about 0.3, or less than or equal to about0.2, or less than or equal to about 0.1, or less than or equal to about 0.07, or less than or equal to about0.05.

[0032] Turning now to FIG. 3A, the effect of such an aspect ratio is illustrated during the process of cleansing a substrate 30. When a roller brush 100 featuring a plurality of bristles 10 is rotated in direction 45 (for example), the bristles 10 may be flexed or bent as they pass over the outer surface 32 of substate 30. This allows a side surface 17 of bristle 10 to be the primary surface of contact with substrate outer surface 32, rather than a tip 13 of bristle 10 during the cleaning process. Because the tip 12 of bristle 10 may have little to no contact with substrate outer surface 32, there is no need to require a break-in period / process to wear down the tips 13 of bristles.

[0033] It should be noted that various design factors may be modified to fine tune the performance of the bristle roller brush 100 during the cleaning process. In some embodiments, for example, a flex modulus of a material of the plurality of bristles may be between about 1 MPa and about 1 GPa when the material is dry (e.g., has a moisture content of less than about 0.2%). In some embodiments, the hardness of the material of bristles 10 may be adjusted up or down as required, and, in some embodiments, the hardness of the material of bristles 10 may be below about Shore A 90. The density of the bristles 10 on and about the outer surface 22 of cylindrical body 20 may also be adjusted as necessary. In some embodiments, for example, the density of the plurality of bristles may be between about 2 and about 500 stems per square centimeter.

[0034] In some embodiments, the height, H, of bristles 10 may be between about 10 microns and about 10 millimeters. In some embodiments, a diameter, D, of each bristle 10 may be between about 10 microns and 5 millimeters. In some embodiments, embodiments, height H may represent an average height of the plurality of bristles 10, and diameter D may represent an average diameter of the plurality of bristles 10. That is, the plurality of bristles 10, may, in some embodiments, have a variable height and / or a variable diameter, as may be required of an application.

[0035] Other characteristics of the material used for bristles 10 may be adjusted to fine tune the cleaning process. In some embodiments, for example, each bristle 10 of the plurality of bristles 10 may include a material which is substantially hydrophilic. In some embodiments, each bristle 10 may include a material which has a zeta potential which is negative, or, in other embodiments, a zeta potential with is positive. Characteristics such as these can be adjusted to adjust the performance of bristle roller brush 100 (e.g., by changing or affecting the flow of a cleaning fluid used between roller brush 100 and substrate outer surface 32).

[0036] As shown in FIGS. 4 A and 4B, embodiments of roller brush 100 may feature a plurality of through-holes 24 which allow a fluid to pass from an interior 41 of roller brush 100 through the cylindrical body 20 to emerge via outer surface 22. These embodiments of roller brush 100 may be used to allow flow 26 of a fluid pumped into or fed through the interior 41 of cylindrical body 20 to pass through to outer surface 22 to flow past and through bristles 10. This fluid may allow bristles 10 to move more easily over substrate outer surface 32, to sweep particles removed from substrate outersurface 32 away from substrate 30, or to otherwise affect the performance of roller brush 100 as described elsewhere herein.

[0037] FIG. 5A illustrates how an embodiment of bristles 10a of a roller brush 100 may include a porous material. For example, the use of porous material in a bristles 10a may allow the bristles to store or retain a certain amount of fluid being passed between the outer surface 22 of cylindrical body 20 and outer surface 32 of substrate 30, which may create a more efficient fluid flow as required by the cleaning process. In some embodiments, a material of cylindrical body 20a may also include a porous material. In some embodiments, outer surface 22 of cylindrical body 20a and bristles 10a may be formed by a single process, such that outer surface 22 and bristles 10a form a single, integral piece. This also applies to non-porous elements described elsewhere herein. In some embodiments, a porosity of each bristle 10a of the plurality of bristles 10a may be between about 0% and about 80%. In some embodiments, a porosity of outer surface 22 of cylindrical body 20 may also be between about 0% and about 80%.

[0038] Finally, FIG. 5B is a perspective view of an embodiment of a system for cleaning a substrate, according to the present description. In some embodiments, system 300 may include a roller brush 100 (e.g., any of the embodiments of roller brush 100 described herein) with a plurality of bristles 10 which is rotated over the surface of a substrate 30 (e.g., a silicon wafer). In some embodiments, roller brush 100 may be attached to a controlling arm or other device 200 which moves roller brush 100 over substrate 30. In some embodiments, device 200 may also act as a conduit for a fluid 28 (e.g., a cleaning fluid) which may be directed through device 200 into an interior of roller brush 100 and out through through-holes 24 (see FIGS. 4A-4B) to interact with bristles 10 during the cleaning process.

[0039] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1.

[0040] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially equal” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially equal” will mean about equal where about is as described above. If the use of “substantially parallel” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantiallyparallel” will mean within 30 degrees of parallel. Directions or surfaces described as substantially parallel to one another may, in some embodiments, be within 20 degrees, or within 10 degrees of parallel, or may be parallel or nominally parallel. If the use of “substantially aligned” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially aligned” will mean aligned to within 20% of a width of the objects being aligned. Objects described as substantially aligned may, in some embodiments, be aligned to within 10% or to within 5% of a width of the objects being aligned.

[0041] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0042] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed:

1. A roller brush for cleaning a substrate following chemical mechanical planarization of the substrate, the roller brush comprising: a generally cylindrical body having an outer surface; and a plurality of spaced-apart bristles projecting outwardly from and disposed circumferentially around the outer surface of the cylindrical body and separated by a plurality of gaps; wherein each bristle of the plurality of spaced-apart bristles has a diameter, D, and a height, H, such that D / H is less than or equal to about 0.3.

2. The roller brush for cleaning a substrate of claim 1, wherein the cylindrical body further comprises an interior comprising a longitudinal axis about which the cylindrical body may rotate.

3. The roller brush for cleaning a substrate of claim 2, wherein the outer surface of the cylindrical body further comprises a plurality of through-holes disposed in one or more of the plurality of gaps, each through-hole of the plurality of through-holes extending from the outer surface of the cylindrical body into the interior of the cylindrical body; wherein the interior of the cylindrical body is configured to allow a flow of liquid through the interior such that it exits the interior via the through-holes and circulates through the plurality of spaced- apart bristles.

4. The roller brush for cleaning a substrate of claim 1, wherein the roller brush is configured to be rotated against the substrate during a cleaning of the substrate, and wherein each bristle of the plurality of spaced-apart bristles is configured to flex when in contact with the substrate such that a portion of a side of the bristle moves against the substrate.

5. The roller brush for cleaning a substrate of claim 4, wherein the portion of the side of the bristle in contact with the substrate is larger than a portion of a tip of the bristle in contact with the substrate.

6. The roller brush for cleaning a substrate of claim 1, wherein a flex modulus of a material of the plurality of bristles is between about 1 MPa and about 1 GPa when the material has a moisture content of less than about 0.2%.

7. The roller brush for cleaning a substrate of claim 1, wherein a hardness of a material of the plurality of bristles is below about Shore A 90.

8. The roller brush for cleaning a substrate of claim 1, wherein a density of the plurality of bristles is between about 2 and about 500 stems per square centimeter.

9. The roller brush for cleaning a substrate of claim 1, wherein the height, H, is between about 10 microns and about 10 millimeters.

10. The roller brush for cleaning a substrate of claim 1, wherein a diameter of each bristle of the plurality of bristles is between about 10 microns and 5 millimeters.

11. The roller brush for cleaning a substrate of claim 1, wherein each bristle of the plurality of bristles comprises a porous structure.

12. The roller brush for cleaning a substrate of claim 11, wherein a porosity of each bristle of the plurality of bristles is between about 0% and about 80%.

13. The roller brush for cleaning a substrate of claim 1, wherein each bristle of the plurality of bristles comprises a material which is substantially hydrophilic.

14. The roller brush for cleaning a substrate of claim 1, wherein each bristle of the plurality of bristles comprises a material which has a zeta potential which is negative.

15. The roller brush for cleaning a substrate of claim 1, wherein each bristle of the plurality of bristles comprises a material which has a zeta potential which is positive.

16. The roller brush for cleaning a substrate of claim 1, wherein a material of the bristles includes one or more of a polyamide, a rubber, a thermoplastic elastomer, and a polyurethane.

17. A brush for cleaning a substrate following chemical mechanical planarization of the substrate, the brush comprising: a generally cylindrical body having an outer surface; and a plurality of spaced-apart bristles projecting outwardly from and disposed circumferentially around the outer surface of the cylindrical body and separated by a plurality of gaps; wherein the brush is configured to be rotated against the substrate during a cleaning of the substrate, and wherein each bristle of the plurality of spaced-apart bristles is configured to flex when in contact with the substrate such that a portion of a side of the bristle moves against the substrate.

18. The brush for cleaning a substrate of claim 17, wherein the portion of the side of the bristle in contact with the substrate is larger than a portion of a tip of the bristle in contact with the substrate.

19. The brush for cleaning a substrate of claim 17, wherein, during a cleaning of the substrate, a tip of the bristle makes substantially no contact, or only incidental contact, with the substrate.

20. The brush for cleaning a substrate of claim 17, wherein each bristle of the plurality of spacedapart bristles has a height, H, and a diameter, D, such that H / D is greater than or equal to about 3.

21. The brush for cleaning a substrate of claim 17, wherein a flex modulus of a material of the plurality of bristles is between about 1 MPa and about 1 GPa when the material has a moisture content of less than about 0.2%.

22. The brush for cleaning a substrate of claim 17, wherein a hardness of a material of the plurality of bristles is below about Shore A 90.

23. The brush for cleaning a substrate of claim 17, wherein a density of the plurality of bristles is between about 2 and about 500 stems per square centimeter.

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