WO2022115671A1

WO2022115671A1 - Brush for cleaning a substrate

Info

Publication number: WO2022115671A1
Application number: PCT/US2021/060931
Authority: WO
Inventors: Ara Philipossian; Yasa Sampurno; Jason Keleher; Katherine WORTMON-OTTO; Abigail LINHART
Original assignee: Araca, Inc.
Priority date: 2020-11-30
Filing date: 2021-11-29
Publication date: 2022-06-02
Also published as: TW202222443A

Abstract

A brush for cleaning a substrate, and a machine with a brush for cleaning a substrate, are described. Liquid is injected into an inlet end of the brush. The liquid flows through the brush and exits the brush, onto the substrate, along the longitudinal length of the brush. The brush uses physical and chemical means to create a flow rate of liquid exiting the brush that is approximately constant, or uniform, versus distance from the inlet end of the brush. The methods used to produce the approximately uniform liquid flow rate versus distance from the inlet end include varying the size, shape, and positioning of holes in a brush mandrel, varying the size, shape and positioning of pores or holes in a brush porous sleeve, and varying the irradiation characteristics and chemical response to irradiation of the porous sponge sleeve.

Description

BRUSH FOR CLEANING A SUBSTRATE

RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. provisional application no.

63/119,413, filed on November 30, 2020, and entitled "BRUSH FOR CLEANING A SUBSTRATE," the entirety of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present disclosure relates generally to post-CMP (Chemical Mechanical Planarization) substrate cleaning technology for a semiconductor manufacturing process. More particularly, the present disclosure relates to a Polyvinyl Acetal brush for cleaning a substrate such as a semiconductor wafer.

BACKGROUND

Polyvinyl Acetal (PVA) brushes are widely used in cleaning processes for semiconductor device manufacturing, and more specifically, to provide a post-CMP (Chemical Mechanical Planarization) process to clean the surface of substrates such as semiconductor wafers or the like. Here, direct contact is made between a rotating spongy PVA brush and a wafer surface in the presence of chemically-active agents. Particles on the wafer, for example, slurry residue, are chemically "loosened up" from the wafer surface via passivation layer formation, charge engineering, charge flipping, shear forces, and so on. The particles are then adsorbed on the brush asperities. The wafer and brush rotations as well as brush pressure in the presence of a cleaning fluid cause the particles to be dislodged from the wafer surface and carried away.

Substrate cleaning brushes may include nodules on their cylindrical surfaces which directly contact the substrate during cleaning. Forces such as a shear force formed by the interface between the brush and substrate may be affected by the manner in which the cleaning fluid is output from the brush nodules.

SUMMARY

In one embodiment, the present invention provides a brush for cleaning a substrate, comprising: a mandrel, comprising: a plurality of holes along a length of the mandrel, the holes extending from an inner surface of the mandrel defining a liquid cavity through an interior of the mandrel to an outer surface of the mandrel; and a brush sleeve. The brush sleeve comprises a bore extending through an interior of the brush sleeve and along a length from a first end of the brush sleeve to a second end of the brush sleeve for receiving the mandrel; a plurality of porous nodules having a non-linear arrangement about an outer surface of the brush sleeve; and a plurality of porous land areas between the nodules. The brush sleeve receives a source of liquid from the plurality of holes of the mandrel. The nodules and land areas dispense the liquid onto the substrate at a uniform flow rate from the first end of the brush sleeve to the second end of the brush sleeve.

In another embodiment, the present invention provides a machine for cleaning a substrate, the machine comprising: a brush, comprising: a mandrel, comprising: a plurality of holes along a length of the mandrel, the holes extending from an inner surface of the mandrel defining a liquid cavity through an interior of the mandrel to an outer surface of the mandrel; and a brush sleeve, comprising: a bore extending through an interior of the brush sleeve and along a length from a first end of the brush sleeve to a second end of the brush sleeve for receiving the mandrel; a plurality of porous nodules having a non-linear arrangement about an outer surface of the brush sleeve; and a plurality of porous land areas between the nodules, wherein: the brush sleeve receives a source of liquid from the plurality of holes of the mandrel, and the nodules and land areas dispense the liquid onto the substrate at a uniform flow rate from the first end of the brush sleeve to the second end of the brush sleeve.

In another embodiment, the present invention provides a method for cleaning a substrate, comprising: providing a mandrel, comprising: a plurality of holes along a length of the mandrel, the holes extending from an inner surface of the mandrel defining a liquid cavity through an interior of the mandrel to an outer surface of the mandrel; positioning a brush sleeve over the mandrel, the brush sleeve comprising: a bore extending through an interior of the brush sleeve and along a length from a first end of the brush sleeve to a second end of the brush sleeve for receiving the mandrel; a plurality of porous nodules having a non-linear arrangement about an outer surface of the brush sleeve; and a plurality of porous land areas between the nodules; receiving, by the brush sleeve from the plurality of holes of the mandrel, a source of liquid; and dispensing by the nodules and land areas, the liquid onto the substrate at a uniform flow rate from the first end of the brush sleeve to the second end of the brush sleeve.

Additional advantages and novel features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The advantages of the present teachings may be realized and attained by practice or use of various aspects of the methodologies, instrumentalities and combinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.

FIG. l is a view of a cleaning system that performs a post-CMP process to clean surfaces of semiconductor wafers.

FIG. 2A is an exploded view of a conventional PVA brush.

FIG. 2B is an assembled view of an operation of the conventional PVA brush of FIG. 2 A.

FIG. 2C is a front view of a cross-section of the PVA brush of FIGs. 2A and 2B.

FIG. 3 A is an exploded view of a PVA brush, in accordance with some embodiments.

FIG. 3B is an assembled view of an operation of the PVA brush of FIG. 3 A.

FIGs. 3C-3E are cross-sectional views of the PVA brush of FIGs. 3A-3E.

FIG. 3F is a view of a PVA brush, in accordance with other embodiments.

FIG. 3G is a cross-sectional view of the PVA brush of FIG. 3F.

FIG. 4A is another view of a PVA brush including an enlarged view of a feature of the PVA brush, in accordance with some embodiments.

FIG. 4B is a closeup view of the PVA brush of FIG. 4A illustrating a removed nodule.

FIG. 4C is a cross-sectional view of the PVA brush of FIGs. 4A and 4B.

FIGs. 5A-5D are graphs of illustrative comparisons of liquid output flow rates, hydraulic mandrel hole diameters, mandrel hole densities, and brush pore porosities, respectively, of a conventional PVA brush of FIGs. 2A-2C and a PVA brush of FIGs. 3A-4C, in accordance with some embodiments.

FIG. 6A is a table illustrating comparative shear force measurements of a conventional PVA brush of FIGs. 2A-2C and a PVA brush of FIGs. 3A-4C, in accordance with some embodiments.

FIG. 6B is a bar graph illustrating comparative shear force measurements from the table of FIG. 6 A.

FIGs. 7A and 7B are illustrations of mean shear force contour plots comparing a conventional cleaning system and a cleaning system having the nodule-modified brush of FIGs. 3A-4C. FIGs. 8A-10F are graphs illustrating various Fast Fourier Transform (FFT) signals produced by a conventional cleaning system and a cleaning system having the nodule- modified brush of FIGs. 3A-4C.

FIG. 11 is a view of a cleaning system that performs a post-CMP process to clean surfaces of semiconductor wafers including a light source for irradiating a brush sleeve, in accordance with some embodiments.

FIG. 12 is a view of a cleaning system including a light source for irradiating a brush sleeve, in accordance with other embodiments.

FIGs. 13A-13C are graphs of illustrative comparisons of PVA matrix sensitivities to irradiation intensities, respectively, of a conventional PVA brush of FIGs. 2A-2C and a PVA brush of FIGs. 11-12, in accordance with some embodiments.

FIG. 14 is a graphical illustration of a pore structure of a PVA brush, in accordance with some embodiments.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent to those skilled in the art that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings.

Referring to FIG. 1, a cleaning system 10 includes a substrate cleaning brush 100 for cleaning and/or polishing a substrate, for example, a copper wafer 14. In some embodiments, the substrate cleaning brush 100 is a PVA brush. Although a PVA brush 100 is described, embodiments of the present inventive concept are not limited thereto and other types of substrate cleaning brushes may equally apply. The cleaning system 10 may include well- known machine components such as motors, electronics, actuators, and so on, but are not shown for brevity. During operation, direct contact is made between the PVA brush 100 and a surface of the wafer 14 in the presence of one or more chemically-active agents. Here, particles are first chemically removed from the wafer surface. The particles are then adsorbed on brush asperities. The wafer and/or brush may rotate during which the brush pressure in the presence of a cleaning fluid can dislodge and carry the particles away from the wafer surface. As shown in FIGs. 2A-2C, a conventional brush 200 has a mandrel 202. A plurality of holes 204 extend through and along a length of the mandrel 202. The core body 206 of the porous brush (constructed for positioning about the mandrel 202) has a plurality of nodules 208. The nodules 208 are equally spaced along the length of the core body 206. Rows of nodules 208 may extend about the circumference of the body 206 and may also be equally spaced. The nodules 208 may be porous so that fluid received from the holes 204 of the mandrel can form a plurality of fluid paths 212 from the inlet 203 of the mandrel 202 to the mandrel holes 204 and nodule pores through a central hole 211 in the mandrel 202 (one fluid path 212 is shown in the cross-section view of FIG. 2C, but a plurality of paths 212 are prevalent because of the porous configuration of the brush body 206). The nodules 208 are arranged on the brush 206 to provide a uniform pressure on the substrate during the cleaning process, and in doing so have a uniform configuration, for example, the same number of nodules arranged in rows along the length of the brush.

However, as shown in FIG. 2B, the flow rate of the cleaning fluid output from the nodule pores to the substrate 14 varies along the length of the brush 200. In particular, the flow is non-uniform from the end closest to the point of fluid injection into the mandrel to the terminal end 207. In particular, the right side portion of the brush sleeve 206 receives more fluid from the mandrel holes 204. The remaining fluid inside the mandrel 203, i.e., fluid not dispensed through nodules 208 at the right side, travels through the mandrel central hole to the closed terminal end 207 but its flow rate is reduced significantly due to the output of liquid through the holes near the input end 203. Therefore, the mandrel holes 204 near the closed end 207 of the mandrel 202 will have less amount of fluid to dispense as compared to the holes 204 on the right side. The non-uniform fluid output from the brush 200 can produce undesirable shear force variances during a cleaning operation, which in turn may result in an increase in wafer-level defects. Also, when the fluid does not dispense uniformly across the length of the brush, the brush’s cleaning capability with respect to removal of abrasive particles and residual chemical on top of the wafer surface is reduced. Moreover, when the fluid does not dispense uniformly across the brush, the fluid likewise is not output uniformly across the wafer.

Methods and systems in accordance with embodiments of the present inventive concept overcome the disadvantages of conventional PVA brushes and brush-mandrel systems by dispensing a liquid at a uniform fluid flow relative to a longitudinal axis of a PVA brush when output from the brush during a cleaning operation, e.g., a post-CMP cleaning process. Referring to FIGs. 3 A-3E, a PVA brush 300 comprises a mandrel 302 and a brush sleeve 306. The brush 300 may be part of a machine for cleaning substrates, but not limited thereto. In some embodiments, the mandrel 302 is a cylindrical shaped hollow mandrel comprising an inner surface that defines a liquid cavity (not shown), which may be a hole, bore, core, or the like, extending through a length of a direction of extension of the mandrel 302. The mandrel has an inlet 303 that provides an opening to the cavity for receiving a source of cleaning solution. The cleaning solution may include well-known cleaning fluids, for example, sodium dodecylbenzenesulfonate (SDBS), styrenesulfonic acid, and the like, and not limited thereto. The mandrel 302 has a terminal end 307 opposite the inlet 303 that provides a closed end of the liquid cavity so that a cleaning fluid can only output from a plurality of liquid flow holes 308 extending from the inner surface to the outer surface of the mandrel tangentially or perpendicular to the direction of extension along a longitudinal axis of the mandrel 302, which when inserted in the core of the brush sleeve 306 to form an operational PVA brush 300 may be referred to as a brush longitudinal axis extending from the inlet end to the terminal end.

The brush sleeve 306 includes a liquid cavity 311 (see FIG. 3D), including a core, bore, hole, or the like in which some or all of the mandrel 302 can be positioned so that the brush sleeve 306 can surround the mandrel. In particular, the liquid exits the mandrel 302 through the plurality of liquid flow holes 304, passes through the porous sponge sleeve 306, and is dispensed from the brush 300 onto the substrate at a liquid flow rate. In some embodiments, the brush sleeve 306 is porous and includes materials forming a network polymer sponge.

One or more than one physical characteristic of a polymeric network, for example, surface and/or depth modification of the polymeric network (described below), of the porous sponge sleeve 306 is varied along the brush longitudinal axis in order to produce the approximately uniform liquid flow rate versus the distance from the inlet end. Thus, in FIG. 3 A, the holes 304 of the mandrel 302 are spaced farther apart at the right side (liquid inlet end 303) of the brush, for example, at mandrel holes A and B separated by a distance LI where fluid injection occurs at the inlet 303 in order to reduce the amount of fluid being dispensed to the brush sleeve 306 at this region so that more fluid is delivered to the left side of the brush at the terminal end 307, for example, at mandrel holes C and D separated by a distance L2 less than LI. The separation of mandrel holes by decreasing distance between holes 304 from input end to terminal end permits a uniform flow of fluid along the corresponding length of the porous brush body 306 as shown in FIG. 3B. Also, greater amount of land area 309 may be present at the terminal end 307 than at the input end 303 due to the reduction in the number of nodules 308 at the terminal end 307 relative to the input end 303.

A feature of the PVA brush is the important of laterally uneven porosity arrangements with respect to PVA brush cleaning techniques. In some embodiments, porosity of the porous sponge sleeve 306, for example, the size, shape, and surface chemistry of pores in the porous sponge sleeve 306, increases from a minimum porosity value at the inlet end 203 to a maximum porosity value at the terminal end 307 to produce the approximately uniform liquid flow rate versus the distance from the inlet 303, shown by way of example in the graph illustrated in FIG. 5 A. In some embodiments, a pore size of the pores in the porous sponge sleeve 306 is in the range of about 5 nanometers to about 500 micrometers, and wherein the shapes can include any of oblong, circular, or other shapes. In some embodiments, a surface chemistry of the pores in the porous sponge sleeve 306 can be rendered hydrophilic or hydrophobic. In some embodiments, FIGs. 5A-5D may pertain to features exhibited by the bush 300 of FIGs. 3 A-3C and/or the brush 350 of FIGs. 3F and 3G.

During a post-CMP cleaning process, a cleaning liquid is injected into the liquid cavity 311 of the mandrel 302 through the inlet 303 (see FIG. 3C, which illustrates a cross-sectional view of the brush 300 at the inlet 303) and exits the mandrel flow holes 304. In some embodiments, the cleaning liquid includes one or more chemicals known for use in a post- CMP cleaning process. The liquid then passes through the pores in the sponge sleeve 306 and dispensed from the brush 300 at a uniform flow rate along the length of the brush 300 as shown in FIGs. 3B and 5 A. When referring to a uniform flow rate along the longitudinal axis of the brush 300, the liquid flow rate versus distance from the inlet 303 to the terminal end 307 is at or about a constant value. As used herein, a constant value may be calculated or measured. An actual constant value may be an approximation with respect to the measured or calculated constant value, for example, within about 10% of the actual constant value. For example, the liquid flow rate may be the same, or within 10% of the calculated or measured flow rate along the longitudinal axis of the brush 300. Here, a flow rate at or near the inlet 303 is the same as or within 10% of the flow rate anywhere along the length of the mandrel 302 including nodules and/or land areas, or recessed areas between the nodules, at or near the terminal end 307. As used herein, the flow rate refers to the flow rate through the pores of the brush (i.e. flow rate of the fluid through and exited the brush sleeve). At the steady state condition, the “overall flow rate” inside the mandrel cavity 311, through all the holes in the mandrel and through all the pores of the brush will be the same due to conservation of mass (i.e. in=out). Although a lateral uniform delivery of post-CMP cleaning chemicals to the brush/wafer described herein, this is achieved by the arrangement of the flow holes 308 along the longitudinal axis of the mandrel 302. In some embodiments, a method of delivery may include physical means. For example, as shown in FIGs. 5B-5D, a modification can be applied with respect to the hydraulic diameter of mandrel flow holes across the mandrel, density of the mandrel flow holes across the mandrel, and so on. In some embodiments, the holes or perforations in the brush mandrel 302 are constructed and arranged such that the fluid is allowed to travel across the entire length of the brush before it begins to travel radially through the brush and contact the wafer.

The mandrel 302 includes a plurality of liquid flow holes 304 extending from the mandrel inner surface communicating with the liquid cavity 311 to the mandrel outer surface. In some embodiments, the holes 304, or perforations or the like, in the brush mandrel 302 are constructed and arranged so that the fluid is allowed to travel across the entire length of the brush, i.e., through the brush core (where the mandrel is positioned) before the fluid travels radially through the body of the brush, i.e., the brush sleeve 306 through the nodules 308 and/or porous land areas 309 between the nodules 308 to the wafer 14. The land areas 309 and the nodules 308 comprise the same materials and therefore share more or less the same porous characteristics, such as the size, shape, and surface characteristics or chemistry of the pores of the polymeric network of the porous sponge sleeve. Physical characteristics of the plurality of liquid flow holes 304 vary along the brush longitudinal axis of the mandrel 302 in order to produce the approximately uniform liquid flow rate versus the distance from the inlet end 303. In particular, the number, dimensions, or other characteristics of the mandrel holes 304 may be different depending on the distance of the particular hole 304 from the inlet end 303.

As shown in FIG. 3 A, the spacing of the holes 304, perforations, or the like along the length of the mandrel 302 is non-uniform. More specifically, the number of holes 304 in a second region of the mandrel 302, e.g., the left half of the mandrel 302 or distalmost region from the injection point 303 upstream from the distal end, increases from the proximal end 303 to the terminal end 307. In other embodiments, the number of holes, perforations, or the like are arranged to increase along the length of the mandrel 302, and not necessarily the leftmost half of the mandrel 302. When coupled within the central hole of the brush sleeve 306, the transfer from the mandrel holes 304 to the porous sleeve nodules 308 and land areas 309 allow the cleaning liquid or related fluid to be output from the brush uniformly due at least in part to the non-uniform arrangement of mandrel holes 304 shown in FIG. 3A. In some embodiments, the diameter of each hole 304, perforation, or the like gradually increases along a length of the mandrel 302 from the inlet 303 at the proximal end to the distal end 307. In other embodiments, the diameter of the holes 304 at or near the distal end 307, for example, the left half of the mandrel 302 is greater than the diameter of the holes 304 at or near the proximal end, for example, the right half of the mandrel 302 having the inlet 303. Accordingly, a mandrel hole hydraulic diameter of a plurality of liquid flow holes increases along the length of the mandrel 302 from a minimum hole hydraulic diameter value at the inlet end 303 to a maximum hole hydraulic diameter value at the terminal end 307 to produce the approximately uniform liquid flow rate versus the distance from the inlet end. This variation of hydraulic diameter of mandrel flow holes is shown by way of example in FIG. 5B. In some embodiments, a hole density of the plurality of liquid flow holes 304 is increased from a minimum hole density value at the inlet end 303 to a maximum hole density value at the terminal end 307 to produce the approximately uniform liquid flow rate versus the distance from the inlet end 303, shown by way of example in FIG. 5C. For example, a number of holes per surface area of the mandrel increases along the axis from the inlet end 303 to the terminal end 307. In some embodiments, a hole hydraulic diameter of the plurality of liquid flow holes 304 increases from a minimum hole hydraulic diameter value at the inlet end 303 to a maximum hole hydraulic diameter value at the terminal end 307 to produce the approximately uniform liquid flow rate versus the distance from the inlet end 303. Other embodiments, include physical characteristics of the plurality of liquid flow holes that vary along the brush longitudinal axis in order to increase a liquid flow distance within the liquid cavity 311 before the liquid exits the mandrel 302.

In some embodiments, as shown in FIGs. 3F and 3G, the nodules 308 of a PVA brush 350 can have a plurality of holes 310, distinguished from pores in that the holes 310 are greater in width, diameter, and/or other dimension than the pores. The holes 310 may be formed by drilling or other technique to form fluid paths 312 A, 312 (generally, 312) extending from the nodules 308 through the body 306 to liquid cavity 311 receiving the mandrel 302. In some embodiments, the arrangement of holes 310 and corresponding fluid paths 312 may be uniform, i.e., the same number of holes 310 drilled in each nodule 308. In other embodiments, the arrangement of holes 310 may be non-uniform, for example, a greater number of holes 310 in each nodule 308 at the terminal end 307 than at the input end 303 to achieve a uniform output flow of fluid along the length of the brush 350. Drilling or otherwise formation of holes in the nodules in this manner can permit an increase of flow rate at the terminal end 307 to form the uninform output flow. The brush 350 may operate with a conventional mandrel 202, for example, shown in FIG. 2 A, or with a mandrel 302 described with respect to embodiments herein.

FIGs. 4A-4C illustrate views of the PVA brush 300 of FIGs. 3 AGE. FIG. 4B in particular illustrates an enlarged view of a feature of the PVA brush 300, in accordance with some embodiments.

The arrangement of nodules 408 extending from the core body 406 varies along the length of the core body 406. As shown in FIG. 4, the core body 406 is divided into four regions (A, B, C, D). In some embodiments, region A includes 50% of the surface area of the core body 206 and regions B, C, and D include the remaining 50% of the surface area. This may include gradually increasing the number of holes or gradually increase the diameter of the holes or perforations in the second half of the mandrel (i.e. the half that is the farthest away from the injection point upstream where regions B, C, and D are located). Alternatively, the diameter of holes or perforation can be such that they increase throughout the mandrel as the fluid travels downstream (i.e. not necessarily just in the “second half’).

Region A includes a same or similar arrangement of nodules 408A as the conventional brush 200 of FIGs. 2A-2C. For example, the nodules 408 A are equally spaced along the length of the core body 206. Rows of the nodules 408A may also be equally spaced, for example, where the rows are parallel about the circumference of the body 206, for example, rows R1 and R2.

Region B includes fewer nodules 408B per predetermined area than the nodules 408A in region A, for example, few nodules per square inch. In another example, the nodules 408B in region A along row R1 has fewer nodules 408B than in row R2. In some embodiments, region B includes 10% fewer nodules 408B per square inch or related dimension than in region A. For example, as shown in FIG. 4B, nodule 408X is drilled out during formation of the brush 300. If these nodules were not removed from region 408B, then the nodule arrangement would be similar to the nodule arrangement in region A, or shown in the conventional configuration of FIG. 2.

Region C includes fewer nodules 408C per predetermined area than the nodules 408A or 408B. In some embodiments, region C includes 25% fewer nodules 408C per square inch or related dimension than in region A.

Region D includes fewer nodules 408D per predetermined area than the nodules 408A, 408B, or 408C. In some embodiments, region D includes 25% fewer nodules 408D per square inch or related dimension than in region D. For example, 40% of the nodules 408C are removed, e.g., drilled out, during formation of the brush 300. The gradual decrease in the number of nodules along a length of the brush 300 and the corresponding increase in landing area regions 409 permits a uniform flow of fluid from the brush 300. Referring again to FIGs. 3F and 3G, a gradual increase in the number holes in the nodules from input end to terminal end of the brush permits a uniform flow of fluid. Since the brush body 406 is porous, fluid outputs include a combination of nodules 408 and land areas 409 between the nodules 408. The nodule modification downstream of the cleaning solution inlet 403 is effective in equalizing the extent of out-flow across the lateral distance of the PVA brush 300. This may be combined with the corresponding increase in number of holes, etc. of the mandrel 406 downstream of the cleaning solution inlet 403. The relationship between the increasing number of mandrel holes aligned with the reduced number of nodules at the downstream end of the brush is illustrated in FIGs. 4A-4C.

Accordingly, the PVA brush 300 of FIGs. 3A-4C may provide a delivery technique that employs surface and depth modification of a polymeric network to enhance fluid delivery at the brush-wafer interface. The brush formed of PVA-related porous polymer material exhibits characteristics such as solubility to solvents, mechanical and thermal stability, non toxicity, and other separation capabilities. In some embodiments, the macro-porous structure of the brush body 406, e.g., size, shape, and surface chemistry, is different at the second half of the mandrel, i.e. the half that is the farthest away from the injection point such that more fluid is allowed to travel radially through the PVA brush 300 in segments that are further downstream of the injection point 403. In some embodiments, the micro-porous structure of the PVA brush 306, 300 in the second half of the mandrel, i.e. regions 408B, C, and D in FIG. 4A or regions shown in FIGs. 3B and 3C, such that more fluid is allowed to travel radially through the PVA brush 300 in segments that are further downstream of the injection point. In some embodiments, the brush 300 has a nano-porous structure (i.e. size and shape) throughout the depth of the PVA brush 300 along the second half of the mandrel 302 (i.e. the half that is the farthest away from the injection point) such that more fluid is allowed to travel radially through the PVA brush in segments, for example, segments B, C, D shown in FIG.

4A that are further downstream of the injection point 403. As described below, the average shear force and standard deviation of the average shear force can be reduced when the PVA brush 300 with this nodule arrangement is used, for example, when the nodules are removed by drilling or other removal technique as shown in FIG. 4B.

FIG. 6A is a table illustrating comparative shear force measurements of a conventional PVA brush of FIGs. 2A-2C and a PVA brush of FIGs. 3A-4C, in accordance with some embodiments. FIG. 6B is a bar graph illustrating comparative shear force measurements from the table of FIG. 6 A. In particular, the average shear force in the brush -fluid-wafer interface is shown as a function of brush and velocities, e.g., 100 to 300 RPM in each case, for a conventional brush 200 and embodiments of the PVA brush 300 shown in FIGs. 3 A-4C, respectively. The wafer and/or brush may rotate during which the brush pressure in the presence of a cleaning fluid can dislodge and carry the particles away from the wafer surface. For example, a wafer chuck of the like can provide a rotation rate for the wafer from 50-500 RPM, and a servo motor or the like can rotate the PVA brush 300 from 10-500 RPM. Shown is a significant reduction in the undesirable variance of shear forces when the brush 300 is constructed to have a combination of a non-uniform nodule and mandrel hole arrangement shown in FIGs. 3A-4C. The analysis of shear force data in the time and frequency domains can assist with elucidating the feature and construction of nodule placement density in the number and frequency of collision events at the wafer-brush interface at various applied loads. Collision events may refer to multi-body contacts or collisions among the wafer surface, brush nodules and particles (that need to be removed) in the presence of cleaning solution.

FIGs. 7A and 7B are illustrations of mean shear force contour plots comparing a conventional cleaning system and a cleaning system having the nodule-modified brush of FIGs. 3A-4C. It is well known that factors such as applied pressure, tool kinematics, physical and chemical properties of the brush and the cleaning fluid, wafer surface condition, cleaning time, and the magnitude of the shear forces at the brush-wafer interface are essential for effective particle removal. FIGs. 7A and 7B show shear force (in lb-force) trends in the form of contour plots for the conventional PVA brush 200 shown in FIG. 2 as compared to a brush 300 of FIGs. 3 A-4C. Shown is that the average shear force was reduced by 4% by the arrangement of porous nodules 408 in the brush 300.

FIGs. 8A-10F are graphs illustrating various Fast Fourier Transform (FFT) signals produced by a conventional cleaning system and a cleaning system having the nodule- modified brush of FIGs. 3A-4C. In particular, FIGs. 8A-8C are graphs illustrating FFT amplitudes of a conventional brush, for example, a conventional brush 200 shown in FIGs. 2A-2C operating at 100 RPMs while the wafer 14 is rotating at 100, 200, and 300 RPMs, respectively. FIGs. 8D-8F are graphs illustrating amplitudes of a PVA brush in accordance with embodiments of the present inventive concept, for example, shown in FIGs. 3A-4C. Accordingly, the data shown in FIGs. 6A-7B may be used for producing the graphs in FIGs. 8A-8F. Shown in the comparison between FIGs. 8A-8C and 8D-8F are significant differences in shear force FFT spectra were observed between the two brushes, and in particular, an improved smoothing effect shown in FIGs. 8D-8F. It is clear that the nodule biased brushes results in a “smoothing effect” which can be related to the nature of the interfacial dynamics (kinetics of defect removal) that are present in the cleaning process. Smoothing of the FFT is correlated to the reduction of shear forces with the nodule biasing but can also indicate significant changes in the delivery and transport of the cleaning chemistry and debris (nanoparticles/organic residue) at the brush/wafer interface. This smoothing effect is indicative of a milder p-CMP cleaning process as evident by the changes in the FFT spectra and supported by the reduction in shear force. Furthermore, it should be noted that the use of FFT spectra to correlate to interfacial dynamics can be a significant method for the design of consumable for advanced node p-CMP cleaning processes.

FIGs. 9A-9F and 10A-10F illustrate similar differences but with the brush rotating at 200 RPM and 300 RPM, respectively.

FIG. 11 is a view of a cleaning system 1100 that performs a post-CMP process to clean surfaces of semiconductor wafers including a light source 1102 A for irradiating a brush body 1106, in accordance with some embodiments. The brush body 1106 may have a mandrel similar to or the same as that described in other embodiments herein. The brush body 1106 and mandrel can therefore be collectively referred to as a PVA brush, for example, similar to or the same as the PVA brush 300 of FIG. 4 but not limited thereto.

The light source 1102A is constructed and arranged to generate a source of light radiation, preferably in the ultraviolet (UV), visible, and/or infrared (IR) spectrum but not limited thereto, that is directed to the brush body 1106 and that changes the characteristics of the PVA matrix of the porous sleeve of the brush body 1106, or more specifically, the porous sleeve of the body 1106. In preferable embodiments, the light source 1102 includes a plurality of light-emitting diodes 1104 positioned along a length of the light source 1102 A that irradiate the brush body 1106 along a length of the brush body 1106. The majority of or all of the circumferential surface of the brush body 1106 can be irradiated because the brush body 1106 can be rotated to expose the surface of the brush body 1106 to the light source 1102A positioned above or otherwise proximal to the length of the brush body 1106. In some embodiments, the light source 1102 A extends along a horizontal axis parallel to the horizontal axis of the brush body 1106. The light source 1102A may be stationary and the brush body 1106 is rotated by a motor or the like so that the pores emitting cleaning fluid are uniformly and repeatedly exposed to the light emitted from the LEDs 1104. Although the light source 1102 A is shown and described as being external to the brush body 1106, in other embodiments, the light source 1102 A is positioned inside the brush body 1106, for example, co-located with or part of the mandrel in the core of the brush body 1106 so that the LEDs 1104 are positioned at or near the mandrel holes for irradiating the polymeric matrix of the brush body 1106 from the interior of the brush body 1106.

The application of a source of light radiation to a polyvinyl alcohol (PVA) matrix of the porous sponge sleeve 1106 can modulate the relationship of liquid flow rate and the distance of liquid flow from the inlet end to produce a uniform liquid flow rate versus the distance from the inlet end. In particular, the irradiation of the PVA matrix modulates interfacial fluid dynamics of the matrix. For example, the dynamics of complex cleaning fluids are important to understand with respect to their impact on the wafer surface. By irradiating the PVA matrix of the porous sleeve of the brush body 1106, the manner in which cleaning flow is output from the PVA brush can be modified to provide a uniform liquid flow rate along the length of the brush.

In some embodiments, the photo-excitable functionalities in the PVA polymer matrix can be non-uniform laterally (i.e., more concentrated downstream of the injection point) such that the cleaning solution can flow more liberally in areas of the PVA brush where more pores are expanded through illumination. In some embodiments, the photo-excitable functionalities in the PVA polymer matrix are uniform laterally, but the light source 1102B of the irradiation system 1200 is non-uniform in the lateral direction of the brush as shown in FIG. 12. Increasing irradiation downstream of the injection point, the cleaning solution can flow more liberally in areas of the PVA brush with higher illumination intensity. The brush shown in FIG. 12 can be the same as any brush shown in FIGs. 1-11, such as a conventional brush or a brush according to embodiments herein such as brush 300, etc.

FIGs. 13 A illustrates a comparison of sensitivities of a PVA matrix of a conventional brush 200 of FIG. 2 and a PVA brush 300, 1100 to irradiation intensities produced by the light source 1102A shown in FIG. 11, in accordance with some embodiments. In FIG. 11, the LEDs 1104 of light source 1102A are separated from each other in a uniform manner, i.e., an equal distance from each other. A first graph 1301 illustrates a baseline or zero sensitivity of the PVA matrix to irradiation produced by the light source 1102 and applied to the conventional PVA brush 200. A second graph 1302, on the other hand, shows that the sensitivity varies from a minimum sensitivity value at the inlet end 1103 to a maximum sensitivity value at the terminal end 1107 to produce the approximately uniform liquid flow rate versus the distance from the inlet end 1103.

FIG. 13B illustrates a comparison of irradiation intensities of a PVA matrix of a conventional brush 200 of FIG. 2 and a PVA brush 300, 1100, in accordance with some embodiments. However, the light source 1102B is used which includes a non-uniform arrangement of LEDs 1104, i.e., a greater number of LEDs per inch at the terminal end 1107 than at the inlet end 1103. An irradiation intensity of the irradiation of the PVA matrix of the porous sponge 1106 varies from a minimum irradiation intensity value, e.g., 200nm, at the inlet end 1103 to a maximum irradiation intensity value, e.g., 800nm, at the terminal end 1107 to produce the approximately uniform liquid flow rate versus the distance from the inlet end. A wavelength of the irradiation of the PVA matrix of the porous sponge 1106 varies along the longitudinal axis of the PVA brush 1100 to produce the approximately uniform liquid flow rate versus the distance from the inlet end.

FIG. 13C further illustrates another possible method in which a plurality of the light emitters/sources that each of 1104 may be emitting at different wavelengths (i.e. UV, visible or IR range). In FIG. 13C, an arrangement of light emitters is shown that can locally affect three different regions. Other embodiments may affect more than three different regions. Accordingly, a fully tunable PVA brush is provided for a more effective cleaning effect.

FIG. 14 is a graphical illustration of a pore structure of a PVA brush, in accordance with some embodiments. The covalently linked photoactive functionality derived from the class of molecules can undergo a switchable isomerization upon irradiation with light in ultraviolet, visible, or infrared ranges switchable isomerization is defined as the conformational realignment of the molecular structure, such as expansion or contractions, within a polymer network of the PVA matrix, to impart changes in the polymer network that enhance or impede fluid flow through the brush pore matrix. The molecules can be of particular classes such azobenzene and stilbene derivatives.

The photo-excitable functionalities in the PVA polymer matrix can provide enhanced adsorption and complexation abilities to add in transport of defect generating debris at the brush wafer interface. In some embodiments, macromolecules such as spiropyrans, cyclodextrin, Schiff base ligands, and cyclic polyamines are integrated, either covalently or non-covalently, into the PVA matrix to enhance contaminant removal, i.e., metal ions and/or organometallic complex residues). The addition of redox-active molecules as secondary crosslinking agents can control the microporous nature while adding surface activity to modulate the adhesion of slurry nanoparticles to the wafer surface (i.e., increase in chemical activity). For example, secondary crosslinking agents can control the porous nature of the PVA matrix while adding surface activity to modulate the adhesion of slurry nanoparticles to a substrate surface (i.e., increase in chemical activity), and wherein the realignment, or photoisomerization will alter the available surface area of the polymer matrix to further enhance the interfacial interactions such as hydrogen bonding, metal ligand complexes, and pi-stacking.

In some embodiments, the PVA matrix comprises a covalently linked bond having a photo-excitable functionality. The abovementioned interfacial fluid dynamics may occur due to the integration of covalently linked photo-excitable functionalities in the PVA polymer matrix expanding and contracting when exposed by the external light source irradiation. In some embodiments, the covalently linked bond is expanded when the irradiation has a wavelength in the range of the ultraviolet, visible, and infrared light spectrums. In some embodiments, the PVA matrix comprising a covalently linked bond having a photo-excitable functionality provides a covalently linked bond that is contracted when the irradiation has a wavelength in the range of the ultraviolet, visible, and infrared light spectrums. In some embodiments, a wavelength of the irradiation of the PVA matrix of the porous sponge varies along the brush longitudinal axis to produce the approximately uniform liquid flow rate versus the distance from the inlet end.

A covalently linked bond of the PVA matrix is derived from a molecule that undergoes switchable isomerization upon the irradiation with light in ultraviolet, visible, or infrared ranges, wherein switchable isomerization is defined as the conformational realignment of the molecular structure, such as expansion or contractions, within a polymer network of the PVA matrix, to impart changes in the polymer network that enhance or impede fluid flow through the brush pore matrix.

The photo-excitable functionality of the covalently linked bond provides enhanced absorption, adsorption and complexation abilities to transport defect generating debris at an interface between the brush and the substrate, and wherein the realignment, or photoisomerization will alter the available surface area of the polymer matrix to further enhance the interfacial interactions such as hydrogen bonding, metal ligand complexes, and pi-stacking.

While the foregoing has described what is considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.

Claims

What is claimed is:

1. A brush for cleaning a substrate, comprising: a mandrel, comprising: a plurality of holes along a length of the mandrel, the holes extending from an inner surface of the mandrel defining a liquid cavity through an interior of the mandrel to an outer surface of the mandrel; and a brush sleeve, comprising: a bore extending through an interior of the brush sleeve and along a length from a first end of the brush sleeve to a second end of the brush sleeve for receiving the mandrel; a plurality of porous nodules having a non-linear arrangement about an outer surface of the brush sleeve; and a plurality of porous land areas between the nodules, wherein: the brush sleeve receives a source of liquid from the plurality of holes of the mandrel, and the nodules and land areas dispense the liquid onto the substrate at a uniform flow rate from the first end of the brush sleeve to the second end of the brush sleeve.

2. The brush of claim 1, wherein the brush sleeve is formed of a Polyvinyl Alcohol (PVA) matrix.

3. The brush of claim 1, wherein the length of the mandrel extends from an inlet end at the first end of the brush sleeve to a closed terminal end at the second end of the brush sleeve.

4. The brush of claim 1, wherein the liquid flow rate versus distance from the inlet end to the closed terminal end is a constant value, and wherein the liquid flow rate is uniform through the liquid cavity of the mandrel due to varying physical characteristics of the plurality of holes along the length of the mandrel.

5. The brush of claim 4, wherein the nodules include holes in communication with the liquid flow holes of the mandrel, the nodule holes constructed and arranged to produce the uniform liquid flow rate versus the distance from the inlet end.

6. The brush of claim 4, wherein a hole hydraulic diameter of the plurality of liquid flow holes increases from a minimum hole hydraulic diameter value at the inlet end to a maximum hole hydraulic diameter value at the terminal end to produce the approximately uniform liquid flow rate versus the distance from the inlet end.

7. The brush of claim 4, wherein the physical characteristics of the plurality of liquid flow holes are varied along the brush longitudinal axis in order to increase a liquid flow distance within the liquid cavity before the liquid exits the mandrel.

8. The brush of claim 4, wherein one or more physical characteristics of a polymeric network of the sponge sleeve is varied along the brush longitudinal axis in order to produce the uniform liquid flow rate versus the distance from the inlet end.

9. The brush of claim 4, wherein a porosity of the sponge sleeve increases from a minimum porosity value at the inlet end to a maximum porosity value at the terminal end to produce the uniform liquid flow rate versus the distance from the inlet end.

10. The brush of claim 1, wherein the liquid flow rate versus the distance from the inlet end is modulated by irradiation of a polyvinyl alcohol (PVA) matrix of the sponge sleeve to produce the approximately uniform liquid flow rate versus the distance from the inlet end, wherein the irradiation of the PVA matrix modulates interfacial fluid dynamics of the matrix.

11. The brush of claim 10, wherein the PVA matrix of the sponge sleeve comprises a covalently linked bond having a photo-excitable functionality, wherein the covalently linked bond is expanded when the irradiation has a wavelength in the range of ultraviolet to visible to infrared.

12. The brush of claim 10, wherein the PVA matrix of the sponge sleeve comprises a covalently linked bond having a photo-excitable functionality, wherein the covalently linked bond is contracted when the irradiation has a wavelength in the range of ultraviolet to visible to infrared.

13. The brush of claim 10, wherein a sensitivity of the PVA matrix to the irradiation varies from a minimum sensitivity value at the inlet end to a maximum sensitivity value at the terminal end to produce the approximately uniform liquid flow rate versus the distance from the inlet end.

14. The brush of claim 10, wherein an irradiation intensity of the irradiation of the PVA matrix of the sponge varies from a minimum irradiation intensity value at the inlet end to a maximum irradiation intensity value at the terminal end to produce the approximately uniform liquid flow rate versus the distance from the inlet end.

15. A machine for cleaning a substrate, the machine comprising: a brush, comprising: a mandrel, comprising: a plurality of holes along a length of the mandrel, the holes extending from an inner surface of the mandrel defining a liquid cavity through an interior of the mandrel to an outer surface of the mandrel; and a brush sleeve, comprising: a bore extending through an interior of the brush sleeve and along a length from a first end of the brush sleeve to a second end of the brush sleeve for receiving the mandrel; a plurality of porous nodules having a non-linear arrangement about an outer surface of the brush sleeve; and a plurality of porous land areas between the nodules, wherein: the brush sleeve receives a source of liquid from the plurality of holes of the mandrel, and the nodules and land areas dispense the liquid onto the substrate at a uniform flow rate from the first end of the brush sleeve to the second end of the brush sleeve.

16. The machine of claim 15, wherein the liquid flow rate versus distance from the inlet end to the closed terminal end is a constant value, and wherein the liquid flow rate is uniform through the liquid cavity of the mandrel due to varying physical characteristics of the plurality of holes along the length of the mandrel and/or holes extending through the nodules to the mandrel.

17. The machine of claim 15, wherein the liquid flow rate versus the distance from the inlet end is modulated by irradiation of a polyvinyl alcohol (PVA) matrix of the sponge sleeve to produce the approximately uniform liquid flow rate versus the distance from the inlet end, wherein the irradiation of the PVA matrix modulates interfacial fluid dynamics of the matrix.

18. A method for cleaning a substrate, comprising: providing a mandrel, comprising: a plurality of holes along a length of the mandrel, the holes extending from an inner surface of the mandrel defining a liquid cavity through an interior of the mandrel to an outer surface of the mandrel; positioning a brush sleeve over the mandrel, the brush sleeve comprising: a bore extending through an interior of the brush sleeve and along a length from a first end of the brush sleeve to a second end of the brush sleeve for receiving the mandrel; a plurality of porous nodules having a non-linear arrangement about an outer surface of the brush sleeve; and a plurality of porous land areas between the nodules; receiving, by the brush sleeve from the plurality of holes of the mandrel, a source of liquid; and dispensing by the nodules and land areas, the liquid onto the substrate at a uniform flow rate from the first end of the brush sleeve to the second end of the brush sleeve.

19. The method of claim 18, wherein the liquid flow rate versus distance from the inlet end to the closed terminal end is a constant value, and wherein the liquid flow rate is uniform through the liquid cavity of the mandrel due to varying physical characteristics of the plurality of holes along the length of the mandrel and/or holes extending through the nodules to the mandrel.

20. The method of claim 18, wherein the liquid flow rate versus the distance from the inlet end is modulated by irradiation of a polyvinyl alcohol (PVA) matrix of the sponge sleeve to produce the approximately uniform liquid flow rate versus the distance from the inlet end, wherein the irradiation of the PVA matrix modulates interfacial fluid dynamics of the matrix.