Patent Application
20250196287
The present invention relates generally to systems and methods for polishing or lapping. The systems and methods can employ rotatable dops to polish lateral surfaces, such as diamond films disposed on a workpiece coupled with the dop.
Films, such as diamond films, can be used in various applications. For example, semiconductor devices (such as diamond diodes or transistors), semiconductor grafting applications (such as heterojunction devices), large area single crystalline diamond (SCD) wafers, optics, beamline detectors, quantum technologies, or other applications can include a diamond film. A dimension or roughness of the diamond film can be associated with properties thereof. For example, a (thermal or electrical) insulative property of diamond can vary with thickness, surface roughness, or a dimension of a semiconductor device, which can affect various interfacing portions corresponding to an adjustment of, for example, a turn-on voltage, leakage current, rectification, or switching speed. Further, a dimension of a large area SCD wafer can affect feasible production pathways such as the ability to produce a heterojunction via semiconductor grafting techniques.
A dop head can rotate about an axis perpendicular to a lateral surface of a polishing or grinding wheel, disk, or lap. The dop head can further rotate about one or more axes of the lateral surface. For example, the dop head can include a ball joint configured to rotate within a corresponding cavity of a housing. The dop head can couple with a workpiece to interface with the polishing or grinding wheel. A misalignment between the workpiece and the lateral surface can impose forces to self-level the dop head (e.g., via rotation of the ball joint about an axis of the lateral surface). The center of rotation of the ball joint can be disposed at, or proximal to, the lateral surface, such that frictional forces between the workpiece and the polishing or grinding wheel can generate little or no torque (e.g., responsive to lateral movement of the dop head along the surface of the grinding wheel). For example, the ball joint can include a hemispherical portion having a center of rotation at or proximal to the surface of the polishing or grinding wheel, disk, or lap.
In some aspects, the techniques described herein relate to a system. The system includes a rotatable member including a first surface configured to couple with a workpiece. The rotatable member is configured for receipt within a housing. The rotatable member is configured to rotate about an axis parallel to a lateral plane of the first surface. The rotatable member has a center of rotation for the axis parallel to the lateral plane which is less than one half of a radius of a substantially hemispherical portion of the rotatable member from the first surface.
In some aspects, the system further includes a linear actuator configured to apply a clamping force between the workpiece and a polishing wheel during the rotation of the rotatable member about the axis perpendicular to the lateral plane. The system can include a connection rod coupled with the linear actuator at a first end and the workpiece at a second end.
In some aspects, the coupling between the second end of the connection rod and the workpiece includes a non-rotatable coupling between the second end of the connection rod and a housing for the rotatable member and a gimbaled coupling between the rotatable member and the housing.
In some aspects, the housing includes a single integral portion radially surrounding a portion of the rotatable member.
In some aspects, the rotatable member includes the hemispherical portion having a first radial dimension. The rotatable member can include a second coupler portion having a second dimension less than the first radial dimension. The housing can include a first portion including a sidewall defining a central cavity, the first portion configured to receive the first hemispherical portion into a corresponding hemispherical sidewall portion. The housing can include a second portion configured to couple the second end of the connection rod with the first portion of the housing and having a lower surface that, when assembled with the first portion of the housing, defines a headspace above the second coupler portion of the rotatable member.
In some aspects, the substantially hemispherical portion is sub-hemispherical by an amount equal to a thickness of the workpiece and is configured to couple with a plurality of additional workpieces.
In some aspects, system includes a redresser including a second surface including a plurality of protrusions configured to resurface a polishing wheel, the second surface laterally extending a greater dimension than the first surface and configured for receipt with the housing.
In some aspects, system includes an environmental enclosure enclosing the rotatable member and the housing. The environmental enclosure is configured to maintain positive pressure (e.g., of filtered air within the environmental enclosure), relative to an environment external to the environmental enclosure.
In some aspects, the techniques described herein relate to a polishing apparatus. The polishing apparatus can include a rotatable member including a first surface configured to couple with a workpiece. The rotatable member can be configured for receipt within a housing. The rotatable member can be configured to rotate about an axis parallel to a lateral plane of the first surface. The rotatable member can have a center of rotation for the axis parallel to the lateral plane which is less than one half of a radius of a substantially hemispherical portion of the rotatable member from the first surface. The polishing apparatus can include the housing. The polishing apparatus can include a polishing arm configured to translate the rotatable member along the lateral plane. The polishing apparatus can include a motor configured to rotate the rotatable member about the axis perpendicular to the lateral plane.
In some aspects, the techniques described herein relate to a polishing apparatus, further including a pneumatic cylinder configured to apply a clamping force between the polishing arm and a connection rod coupled with the pneumatic cylinder at a first end via a thrust bearing and the housing at a second end.
In some aspects, the techniques described herein relate to a polishing apparatus, wherein the connection rod is coupled with the motor via a chain drive.
In some aspects, the techniques described herein relate to a polishing apparatus, wherein the rotatable member includes a retaining plate couplable with a second surface of the rotatable member, opposite from the first surface, the retaining plate configured to retain the rotatable member within a central cavity of the housing.
In some aspects, the techniques described herein relate to a polishing apparatus, wherein the housing includes a single integral portion radially surrounding a portion of the rotatable member.
In some aspects, the techniques described herein relate to a method of polishing diamond workpieces. The method can include coupling a workpiece with a first surface of a rotatable member. The method can include receiving the rotatable member within a housing non-rotatably coupled with a connection rod, the rotatable member configured to rotate about an axis parallel to a lateral plane of the first surface and having a center of rotation for the axis parallel to the lateral plane which is less than one half of a radius of a substantially hemispherical portion of the rotatable member from the first surface. The method can include applying a clamping force between the connection rod and a polishing wheel simultaneously to rotating the connection rod about the axis of the application of the clamping force.
In some aspects, the clamping force is transmitted via a thrust bearing along the axis.
In some aspects, multiple workpieces are coupled with the first surface.
In some aspects, the method includes removing the rotatable member from the housing; installing a redresser in the housing; and applying the clamping force to redress the polishing wheel.
In some aspects, coupling the workpiece with the first surface includes: forming an adhesive coating over a substrate; pressing the workpiece into the adhesive coating; forming a further adhesive over the workpiece; coupling the workpiece to the first surface using the further adhesive; and removing the substrate from the workpiece.
In some aspects, coupling the workpiece with the first surface includes: forming an adhesive coating over a substrate; laterally surrounding the substrate with a mold ring; pressing the workpiece into the adhesive coating; forming an epoxy layer over the workpiece; coupling the workpiece to the first surface using the epoxy layer; and removing the substrate from the workpiece.
In some aspects, coupling the workpiece with the first surface includes: affixing the workpiece to a vacuum chuck using a vacuum pump; coupling the workpiece to the first surface; and disengaging the vacuum pump to removing the workpiece from the vacuum chuck.
It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the subject matter disclosed herein.
The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several implementations in accordance with the disclosure and are not, therefore, to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.
Reference is made to the accompanying drawings throughout the following detailed description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.
A rotatable dop head can be configured to conform to a lateral surface, via rotation about an axis parallel to the surface. The dop head may further be configured for rotation about an axis perpendicular to the lateral surface, which may be referred to as a vertical axis. Various other axes perpendicular thereto may be referred to, generally, as lateral axes corresponding to various lateral planes. For example, a first lateral surface of a diamond film can be coupled to the dop head. The coupling can include, for example, bonding, adhering, soldering, friction-fitting, or otherwise coupling a workpiece including a diamond film to the dop head. In some embodiments, multiple instances of a workpiece are coupled with the dop head. The use of multiple workpieces can aid to increase an effective throughput, since the various workpieces can be simultaneously polished. Further, an increased lateral footprint of the multiple workpieces can aid the self-leveling of the dop head within a housing, since a moment of torque associated with the larger lateral surface can increase, owing to the greater effective leverage between the outer lateral surface of the multiple workpieces and the rotational center of the dop head.
The dop head can interface with a second lateral surface. The second lateral surface can include, for example, a flat or grooved alumina polishing wheel/disk having abrasive particles or oxidizing agents embedded thereon or configured to receive a slurry including abrasive particles or oxidizing agents. The rotatable dop head (or the wheel/disk) can be rotated, laterally passed over, or otherwise translated to grind or polish the surface of the diamond film or whole diamond. References to polishing can refer to various processes, including chemical mechanical polishing (CMP) or use of free abrasives in a slurry (as is sometimes referred to as lapping) without limiting effect.
The interaction between the first and second lateral surface can impart a force at an interface plane between the first surface and the second surface, corresponding to, for example, a precession or nutation thereof. The force can cause a rotation about the axis perpendicular to the lateral surfaces, which can lead to an uneven surface of the workpiece. For example, for lateral translations, a leading edge of the workpiece can receive additional grinding or polishing relative to a lagging edge, which can reduce a vertical dimension of the leading portion of the film or other workpiece (e.g., whole diamond). Likewise, an outer portion of the workpiece can receive additional grinding or polishing relative to an inner portion, where the dop head rotates along a vertical plane (e.g., where the leading edge is time-variable), which can result in a convex surface.
A rotatable member of the dop head having a center of rotation proximal to the interface plane can reduce a moment arm between the interface plane and the center of rotation of the dop head, relative to other approaches, such as an inclusion of a ball-joint including a spherical bearing (wherein the center of rotation is about one radius of the spherical bearing above the surface). The reduction in the moment arm can, in turn, reduce a torque applied to the dop head, such that a workpiece coupled to the dop head better conforms to the second surface, such that the grinding/polishing of a diamond film of the workpiece exhibits decreased convexity, relative to instances including larger moments. That is, a rotatable member can rotate to conform to a surface about an axis which is less (e.g., substantially less) than a radius of the hemispherical member from the interface surface. For example, a hemispherical member can include a moment of a rotation along a surface thereof, such that a moment arm between the interface plane and the member is defied by a z axis of a workpiece. A sub-hemispherical member can include a moment of a rotation forward of a face thereof (e.g., equal to a workpiece thickness), such that a moment arm can be zero. Intermediate values such as for a center of rotation which is less than one half of a radius of the substantially hemispherical portion, can also correspond to increased flatness, relative to other approaches.
Before turning to the figures, which illustrate certain exemplary embodiments in detail, it should be understood that the present disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting.
The dop head 102 includes a rotatable member 110 having a first surface 110A configured to couple with a workpiece 112. The workpiece 112 can include a diamond portion, such as a single crystalline diamond (SCD) or polycrystalline diamond (PCD) film formed over a surface thereof which may be referred to as an interface surface 112A. The interface surface 112A can interface with a second surface 122A of a grinding or polishing wheel 122 (sometimes referred to as a grinding or polishing disk). The rotatable member 110 can rotate about one or more axes. For example, the rotatable member 110 can rotate about the vertical axis 106, or a horizontal axis (e.g., into or out of the page or left/rightward, as depicted). For example, a center of rotation of the rotatable member 110 can be aligned, vertically, with the center of rotation of the connection rod 104; the force transmitted to a stationary dop head 102 can be centered about a point of application 120 centered along the workpiece. The center of rotation of the rotatable member 110 can be aligned, horizontally, with a center of a ball of a ball joint, such as a hemispherical ball joint or a super-hemispherical or sub-hemispherical ball joint (as depicted).
As the workpiece 112 advances along the polishing wheel 122, a frictional force 118 along the interface surface 112A can retard the progression of the dop head 102. According to a center of rotation of the rotatable member 110, a torque is generated which may be associated with a rotational displacement of the workpiece 112. That is, the torque can effectively tilt the workpiece 112 relative to the second surface 122A which may, in turn, cause non-planarity of a grinding or polishing of the interface surface 112A. Wherein the rotatable member 110 is a hemispherical ball joint, the center of rotation of such a ball joint can be disposed along a surface 110A thereof, such that a moment arm associated with the frictional force 118 can be negligible, or reduced relative to other approaches (e.g., extending from the interface surface 112A upward, the width of the workpiece 112). Particularly, the torque can be described as by the cross product of the frictional force 118 and a vector extending from the point of application 120 to the lateral center of rotation of the rotatable member 110 (e.g., (frictional force 118)*(moment arm (not depicted))*(sin θ)). Thus, as the length of the moment arm approaches zero, the corresponding torque applied to the rotatable member 110 approaches zero, and a rotation from the frictional force 118, in turn, approaches zero.
Such a moment arm can be less (e.g., orders of magnitude less) than an embodiment employing a spherical ball joint, wherein the moment art could extend for at least the radius of the spherical ball joint. Moreover, by adjusting the partial spherical section of the ball joint (e.g., employing a super hemispherical or sub-hemispherical rotatable member 110), the moment arm can be adjusted (e.g., reduced). For example, a sub-hemispherical rotatable member 110 which has an axial distance (e.g., from the tip of the dome to the center of the first surface 110A) which is less than the radius of the rotatable member 110 by an amount equal to the working piece can eliminate the torque (e.g., set the moment arm to zero).
A housing 108 can house the rotatable member 110, and include an opening therefor, the opening defined by an inner sidewall thereof, so that the rotatable member 110 can move within the housing 108. For example, the inner sidewall can be or include a substantially symmetrical portion to receive the rotatable member 110 according to various orientations thereof, to accommodate the movement of the rotatable member 110 to conform to the interface surface 112A between the workpiece 112 and the second surface 122A.
A vertical (z-height) variation of a polished surface can vary according to a particular material of a polishing wheel 122, a slurry, a vertical force applied to a dop assembly, and so forth. Some embodiments of the present disclosure can polish surfaces with z-height variation of less than two-hundred nanometers per millimeter (e.g., fifty nm or less, according to some implementations).
In some instances, as depicted, the differences in pressure can cause loss of contact, wherein the point of application 120 is disposed at an extreme (e.g., edge or corner) of the workpiece 112. Thus, a gravitational force 202 and a corresponding normal force 204 can be illustrated as point forces in the two-dimensional force-diagram 200. Thus, the rotational torque of the rotatable member 110 (which generates a leveling force) can be described as the normal force 204 times the vector, r2 206, extending from the point of application 120 to the center of rotation of the rotatable member 110 of the dop head 102. Such a leveling force can level the interface surface 112A with the second surface 122A to reduce pressure variation between portions of the workpiece 112. The reductions in pressure can, in turn, reduce variations in the z-height of the workpiece 112 (e.g., a film formed thereover).
Advantageously, such a geometry can avoid the depicted instance, wherein the point of application 120 is at an extreme of the workpiece 112, rather than being laterally centered on the workpiece 112 based on forces distributed throughout the workpiece 112. For example, in some embodiments in which the horizontal center of rotation of a ball joint is greater (e.g., greater than a radius of the ball joint, as in the case of a spherical ball joint), the combination of the greater moment arm, r2 206, with the smaller angle can cause the depicted position to be stable. Even in instances where the interface surface 112A of the workpiece 112 remains substantially colinear with the second surface 122A, such a leveling torque can aid in reducing z-height variation according to polishing/grinding processes according to a pressure applied to the various portions.
Referring generally to
The rotatable member 110 can include a coupler portion 304 to interface with a housing 108, connection rod 104, or other aspect of the dop assembly. The coupler portion 304 can limit a rotation of the hemispherical portion 302, by interfacing with an inner sidewall of the housing 108 at a limit of rotation, to retain the hemispherical portion 302 within the housing 108. In some embodiments, the coupler portion 304 is omitted. For example, the normal force 204 to the gravitational force 202 can retain the hemispherical portion 302 within the housing 108. In some embodiments, the coupler portion 304 includes a retention mechanism. For example, a retention mechanism can couple to the housing 108 or to the connection rod 104. The retention mechanism can include a ball and joint socket, gimbal system, turret bearing, magnetic coupling, or so forth. For example, the depicted coupler portion 304 can include an inner sidewall defining an opening to receive a pin (not depicted). The pin can allow rotation about an axial dimension of the pin, and an opening in the housing 108 for the pin can be larger than the pin to allow further rotation (e.g., perpendicular to the axial dimension of the pin). As is depicted, the coupler portion 304 can be coupled to the hemispherical portion 302 via a neck 306 having a diameter of less than either of the hemispherical portion 302 or the coupler portion 304. The neck 306 can be configured for receipt in the housing 108 to retain the rotatable member 110 (e.g., the housing 108 can include sidewalls defining a cavity having a central necked portion to retain the rotatable portion therein).
A first sidewall portion 404 defining an upper portion of a central cavity of the housing 108 can be configured to receive or otherwise couple with a connection rod 104. For example, the first sidewall portion 404 can include or interface with an opening 402 for threads, a pin-opening, welds, screws, or other fasteners to couple the housing 108 to the connection rod 104. A second sidewall portion 406 (between the first sidewall portion 404 and a third sidewall portion 408) defining a central portion of a central cavity can receive a coupler portion 304 of the rotatable member 110. The central portion of the cavity defined by the second sidewall portion 406 can be radially larger than the coupler portion 304 so as to allow rotation of the rotatable member 110, about axes disposed on a lateral surface (e.g., of the interface surface 112A). The central cavity defined by the second sidewall portion 406 can be substantially symmetrical such that a rotation of the rotatable member 110 is substantially equal in various rotational axes, wherein a rotation of the rotatable member 110 in one or more lateral axes are limited by an interference between the coupler portion 304 and the housing 108.
The third sidewall portion 408 defines a lower portion of the central cavity configured to receive the hemispherical portion 302 of the rotatable member 110. For example, the hemispherical portion 302 can couple with the housing via a gimbaled coupling where the hemispherical portion 302 can rotate within the lower portion of the central cavity defined by the third sidewall portion 408, and rotate at least somewhat along a perpendicular axis (to self-level). In various embodiments, protectants or lubricants (e.g., grease, oil, or so forth) can be received along the various sidewalls of the housing 108. The sidewall portion 408 of the housing 108 (and/or the hemispherical portion 302, in some embodiments), can be coated to protect the joint and reduce friction. For example, the coating can include thin film diamond-like carbon. Such films can include thin films deposited according to physical vapor deposition (PVD), or other techniques. Protectants or lubricants can reduce a frictional force 118 opposing movement of the rotatable member 110 within the housing 108, reduce an ingestion of an abrasive slurry compound into the housing 108, or so forth. Further, sealants such as gaskets, O-rings, liquid sealants, or so forth can be included within a housing 108 to prevent, for example, ingress of slurries or egress of the various lubricants, coatings, or other protectants contemplated by the present disclosure.
One or more openings 410, adhesives, protrusions, etc. can be configured to adhere one or more portions of the housing 108 to each other. For example, a threaded or smooth opening 410 configured to receive captive or other fasteners can be provided. In some embodiments, a retention mechanism receiver can be provided to receive a retention mechanism configured to couple the rotatable member 110 within the housing 108. For example, as indicated above, such a retention mechanism can include a pin, ball and joint socket, gimbal system, turret bearing, magnetic coupling, or so forth. The housing 108 (e.g., the first sidewall portion 404 thereof) can further include one or more portions to contribute a weight to control a gravitational force 202. For example, the portions can be removable from or integral to (e.g., cast, welded, or so forth) other housing portions.
The second housing portion 500 includes a first sidewall portion 504 having an opening 502 formed therein, a second sidewall portion 506 and a third sidewall portion 508 such sidewall portions may be symmetrical or substantially symmetrical with corresponding sidewall portions of the first housing portion 400. The second housing portion 500 includes various openings 510 or other portions configured to couple with a further housing portion, with or without a further fastener. The second housing portion 500 can further include a retention mechanism receiver configured to receive one or more retention mechanisms associated with a housing 108, to retain the rotatable member 110 therein. References to the sidewall portions or openings of the assembled housing 108 may refer to the sidewall portions of the first housing portion 400, but, when assembled, or for housings including a single integral portion radially surrounding the rotatable member 110, such references will generally also apply to the corresponding portions of the second housing portion 500, or to the single integral portion.
As described above with regard to the dop head 102 of
A first sidewall portion 404 defining the central housing cavity is configured to receive a coupler portion 304 (a coupler plate) of the dop head 102. The first sidewall portion 404 is laterally and vertically spaced from the rotatable member 110 (from a coupler portion 304 thereof), so to allow the rotatable member 110 to self-level within the housing 108. In some embodiments, the first sidewall portion 404 is configured to limit a leveling rotation of the dop head 102. For example, a substantially horizontal wall can be configured to interfere the coupler portion 304 to limit leveling rotation in excess of polishing leveling.
In some embodiments, a second sidewall portion 406 is provided between the first sidewall portion 404 and the third sidewall portion 408, as a kink in the central housing cavity. This kink can be configured to retain the rotatable member 110 within the cavity. For example, when elevating the dop assembly 700 from a polishing pad, the coupler portion 304 of the rotatable member 110 can interface with the second sidewall portion 406 to limit a relative vertical movement of the rotatable member 110 and the housing 108. In order to insert or remove the rotatable member 110 from the housing 108, the coupler portion 304 of the rotatable member 110 may not be integral thereto, as is depicted in
As is further depicted, a flat bottom surface of the rotatable member 110 is depicted with fiducial markings 804 or other alignment aids, as may aid in the coupling of workpieces thereto. As is depicted, the fiducial markings 804 can provide an indication of a single, centrally located position of the dop head 102, or can indicate multiple surfaces to couple various workpieces 112 therewith. For example, the depicted crosshair pattern may be provided for various mounting locations along the surface, in some embodiments. The fiducial markings 804 may be implemented as a visual reference, or mechanical aid (e.g., groves to couple with corresponding grooves of a workpiece or standoff). The housing 108 may be configured to receive various rotatable member-types, including various embodiments disclosed in the present disclosure. Further, the housing 108 can receive further end-effectors, such as the redresser of
Providing the redresser 900 with a mating surface 902 compatible with a same retaining plate as the rotatable member 110 or as otherwise adapted to interface with other components of a dop assembly can reduce a duplication of further components. For example, the depicted redresser 900 can be substituted for the rotatable member 110 of
The process to redress or resurface the polishing wheel 122 can involve the same motions and forces described in the operation of the CMP system (e.g., rotation about the dop assembly axis, sweeping of the dop assembly, and rotation of the polishing wheel). Polishing pressure, and rates of rotation and sweeping may differ from the CMP process, in some embodiments. For example, oxidizing slurry may be omitted from the resurfacing process. The slurry may be substituted for deionized water or other solvents to flush polishing debris from the polishing wheel 122. In some embodiments, the wheel 122 may be flushed with an aqueous slurry of free abrasive particles such as diamond, boron carbide, silicon carbide, or otherwise, in order to modify the process and tailor the final roughness or finish of the resurfaced wheel 122.
The second housing portion 500 further includes second opening 608 perpendicular to the openings 510. The second opening 608 is configured to receive a pin 702 to couple the rotatable member 110 with a connection rod 104, as may be received by the second housing portion 500 via a third opening 1002 in line with the housing cavity.
Referring generally to
An embodiment of a polishing apparatus 31 is illustrated. Polishing apparatus 31 can be employed to finely polish epitaxially grown, synthetic diamond workpieces 33 such as one including an outer diamond film layer on a base wafer substrate layer. In one example, the combined layers of diamond 33 and the underlying substrate both have a generally rectangular peripheral shape of about 3-100 mm in a height and/or width dimension, such as about 3×3 mm, about 5×5 mm, or about 10×10 mm. The combined layers of diamond 33 also can be about 1 mm thick, with the outer film layer being less than 50 microns thick, such as less than 10 microns thick, (e.g., less than 4 microns thick, for a workpiece that is part of an electronic component such as a transistor or diode). The diamonds can be made using a chemical vapor deposition reactor in accordance with U.S. Pat. No. 10,541,118 entitled “Methods and Apparatus for Microwave Plasma Assisted Chemical Vapor Deposition Reactors”; and/or commonly owned U.S. Pat. No. 5,474,808 entitled “Method of Seeding Diamond” which issued to Aslam on Dec. 12, 1995. These patents are hereby by reference in their entirely and for all purposes. Other diamond growth techniques may be employed, such as hot filament or liquid alcohol plasma processes.
Polishing apparatus includes a polishing wheel or lap 41, a chemical slurry dosing assembly 43 including a drip tube 44, a positioning arm 45, a holder or dop 47, a sweeping platform 49 and a sweeping transmission 51. In some embodiments, lap 41 has a rigid and chemically inert, alumina ceramic polishing layer with multiple spaced apart, concentric and circular grooves 63 therein. Radial grooves may also be provided in the lap 41. Each groove has a width of less than 0.5 mm to carry and distribute the chemical slurry 64. Furthermore, lap 41 rotates on top of a central pedestal 65, within a tub 67, on top of a table 69. The pedestal extends through a hole in the table and an electric motor 71 is coupled to and operably rotates pedestal 65 and lap 41 when energized. An outlet tube 73 is coupled to tub 67 to remove the used chemical slurry 64.
For an example implementation, the lap preferably rotates at a speed of 50 to 500 rpm and more preferably 100-150 rpm. Once every 2-10 minutes during polishing, the lap is rinsed with between 20-100 mL of HPLC water in order to keep abrasive residue and oxidized byproducts from accumulating. The excess slurry and water are rinsed off of the lap and into the tub, which drains into a waste container for disposal. The polishing apparatus is housed in a surrounding and sealed environmental enclosure which is continuously flushed with a filtered air supply (e.g., 0.5 μm final filtration) or a laminar flow high-efficiency particulate air filtered cabinet enclosure, such as a Purair® Flow-36 model. The air flow is sufficient to provide positive pressure to reduce, eliminate and prevent the introduction of undesired particles into the process. The chemical slurry and the polishing process are conducted at room temperature, and preferably without a heater.
However, the rotational speeds, rinse flow rates, or other aspects of the lap will vary according to material selections, pressure, dop head dimensions, a size, quantity, or geometry of workpieces mounted to the dop head 102, and other aspects of the present disclosure. For example, in another example implementation, the lap may rotate at a speed of 20-600 rpm and more preferably 100-150 rpm. The lap may be rinsed with between 20-300 mL of HPLC water or deionized (DI) water in order to keep abrasive residue and oxidized byproducts from accumulating.
Slurry dosing system 43 is a CMP process using the aqueous slurry 64 which contains a strong oxidizing agent such as potassium permanganate, at least one acid such as phosphoric acid, and abrasive particles. The abrasive particles are each less than 3 μm in size and are softer than the diamond, for example boron carbide, silicon carbide, silicon dioxide (quartz), or other material, which are kept in suspension through continuous stirring, agitation, or oscillation (swirling of the vessel). Deionized or HPLC water is used as a solvent in this solution. The employment of separate slurry bottles/reservoirs may be used to prevent auto reaction of the oxidizing agent with the other components. For example, one bottle can contain an oxidizer and HPLC water (or deionized water). The other bottle can contain an acid, such as phosphoric acid, which is added to accelerate reaction of the oxidizer. The free abrasive particles may be added to either bottle depending on chemical compatibilities of the selected slurry constituents (or provided via a further reservoir). Both bottles are attached to the pump and their respective tubes may join together at least somewhat before dripping on the wheel or may remain separate depending on reaction chemistry of the selected slurry constituents.
The slurry is continuously agitated using a magnetic stirrer 81. A slurry reservoir 83 is shielded from light exposure during operation by an outer cover or coating. A peristaltic pump 85 delivers slurry to the lap during operation, through feeding tubes 44. The slurry delivery rate may correspond to a size or quantity of workpieces 112 (e.g., a surface area in contact with the wheel 122. For example, a 250 mm diameter wheel can utilize a drip rate of between 10-1000 mL per hour.
Dop 47 includes a foot 101 having an arcuately curved and tapered upper surface 103, and a substantially flat bottom surface 105 to which diamond workpiece 33 is temporarily mounted. An adhesive secures the diamond to the foot for polishing and thereafter, the adhesive is softened so the diamond can be removed. A partially spherical ball 107 is trapped within a partially undercut cavity or socket internal to foot 101, and an internally threaded nut 111 is mounted to an upper end of the ball. A rotatable joint is created by ball 107 rotating within socket of foot 101, such that the ball and nut may rotate in any direction relative to the foot.
Moreover, foot 101, ball 107 and nut 111 are all preferably made of stainless steel to resist corrosion or pitting by the chemical slurry during polishing. Grease or another oil-based lubricant can be packed into the socket and the joint is sealed (e.g., with PTFE tape 113 or a flexible elastomeric boot) to deter entry of the chemical slurry and/or removal of the grease. The tape also allows multidirectional swiveling of foot 101 relative to ball 107 but deters rotation of the foot about an axial centerline 114 of shaft 121. Sealing is beneficial since the slurry particles may otherwise deteriorate the fine ball and socket movement desired especially given the downward polishing forces employed (e.g., less than 5 kg/cm2 of diamond workpiece polishing surface area, and more preferably about 2.8 kg/cm2 of surface area).
Dop 47 further includes a vertically elongated shaft 121 having external threads 123 at its upper and lower ends. A pin 125 radially projects outwardly adjacent the lower end of shaft 121, in a direction perpendicular to the vertically elongated axis of the shaft. The lower threads of shaft 121 mate within nut 111 such that foot 101 is moveable relative to the fixed ball 107 and attached shaft.
A hollow and cylindrical sleeve 131 is also vertically elongated and concentrically surrounds a majority of shaft 121. Sleeve 131 includes an openly accessible notch or slot 133 adjacent a bottom thereof. Additionally, a collar 135 and flange 137 are affixed at an opposite top of sleeve 131. An upstanding engagement structure 139, such as a cylindrical finger, projects from a top surface of flange 137 offset from a centerline of the shaft. Pin 125 of shaft 121 is received within notch 133 of sleeve 131 such that the shaft must rotate with the sleeve.
A dop-driving motor actuator 141 is mounted to an upstanding bracket and post assembly 143, which is adjustably secured to arm 45 via a horizontally elongated rail 145. A driven sprocket 147 is rotated by actuator 141 to move a closed loop chain 149. A passive sprocket 151 is engaged with and rotated in response to movement of chain 149.
Moreover, finger 139 of flange 137 engages within a hole 153 of passive sprocket 151 to cause sleeve 131 and, in turn, shaft 121 and its coupled ball 107 to rotate in response to activation of actuator 141. Accordingly, foot 101 and its attached diamond workpiece 33 also rotate in response to activation of actuator 141. A wing nut 155 and Bellville spring 157 or washer secure the passive sprocket on top of flange 137. Bolted connections between bracket and post assembly 143 and rail 145 allow for assembly of the chain and also for taking up slack during use. It is alternately envisioned that a pulley and belt assembly, enmeshed gears, pneumatic or hydraulic fluid pistons, or other mechanical transmissions may be employed between actuator 141 and sleeve 131.
A vertically elongated adapter block 165 is secured between a pair of shoulders 167 upstanding from a horizontally elongated and bifurcated intermediate section 169 of arm 45. Adapter block 165 includes a central bore within which sleeve 131 and shaft 121 are disposed. A T-shaped end section 171 of arm 45 extends in a transverse direction perpendicular to an elongation direction of intermediate section 169. Bores are located in end section 171 within which are mounted threaded screw legs 173 secured by mounting collars. Legs 173 downwardly project from micrometers 177 which allow for gross or large scale leveling of dop 47 during initial machinery setup.
A sweeping motor actuator 1121 and associated output shaft 1123 operably rotate an output disk 1125. A pivot 1127 at a proximal end of a sweep rod 1129 is radially offset from a central rotational axis 1131 of output shaft 1123 and disk 1125 to create eccentric movement of the rod. A pivot 1133 at a distal end of rod 1129 is coupled to circular platform 49; pivot 1133 is also radially offset from a central rotational axis 1135 of the platform. The pivots are rod end bearings, such as Heim joints, so disk 1125 can operate at a constant unidirectional rpm to affect the sweeping motion. Disk 1125, rod 1129 and platform 49 are all part of the sweeping transmission 51 which causes the platform to rotate or oscillate back and forth within a five- to fifteen-degree range.
Feet 175 of micrometers 177 are received within slots or receptacles in an upper surface of platform 49. Furthermore, feet 175 are magnetically coupled to magnetic areas 179 of the platform. This allow for easy disassembly of arm 45 from platform 49 so that the polished condition of the diamond workpiece can be ascertained at a different location and the diamond workpiece can be quickly removed in a tool-free manner when polishing is completed. Alternately, feet 175 may be bolted or otherwise mechanically attached to platform 49, however, some of the present advantages may not be realized. Bearings and additional supporting bracketry may be provided for all moving components in the present apparatus.
A laterally enlarged wheel 181 is threadably enmeshed with a jack screw 183 which allows platform 49 to be manually raised and lowered to provide gross adjustment during initial machinery setup. The arm assembly makes three-point contact when placed on the polishing unit; the diamond resting on the grooved ceramic lap and the two micrometers resting on the platform. The load on the diamond as it rests on the lap is about 325 g. Thus, for a 3.5×3.5 mm workpiece this results in a pressure of about 2.65 kg/cm2 (260 kPa) on the diamond. If necessary, weights can be added or removed to the arm in order to adjust the downward pressure on the diamond. Therefore, gravity acting on the arm and attached components preferably supplies the only downward force on the dop which pushes the diamond workpiece 33 against the polishing lap 41.
The ball and socket joint for dop 47 beneficially provides a fine and delicate self-leveling feature permitting the diamond workpiece to swivel but not rotate relative to the shaft. This feature is advantageous in at least two ways: first, the traditional time-consuming step of “balancing” the diamond is eliminated; and second, the diamond remains in intimate contact with the lap's surface during the sweeping and lap-rotational movements. Actuator 141 causes the diamond to rotate with shaft 121 about axis 114 at a rate of 3 to 20 rpm, and more preferably 6 to 10 rpm, during polishing. Rotating the dop and diamond is beneficial in that no one area of the diamond workpiece acts solely as the leading edge, which can result in unevenness in the removal of material from the diamond's surface.
Moreover, the use of the present self-leveling dop permits the chemical polishing of diamond surfaces without first needing to grind the diamond in a gross manner so that it is parallel to the lapping surface before CMP is started. It is also noteworthy that the self-leveling feature allows polishing of the diamond surface with very little diamond removal, thereby improving quality and processing cycle time and enabling the polishing of thin epitaxially grown layers such as those used for electronics applications.
The back-and-forth diamond sweeping motion across the lap advantageously prevents the diamond from remaining at a single polishing location long enough to produce uneven wear on the lap's surface. Also, the process is monitored by visually inspecting the diamond's surface using differential interference contrast microscopy. Once the polishing is judged complete, the adhesive is softened by heating the dop and the diamond can be removed. For example, at least the rotatable member 110 of the dop head 102 may be removed and heated or soaked in a solvent in order to release the diamond workpiece.
An alternate embodiment of the present polishing apparatus 301 is illustrated in
A post 311 is affixed to a tabletop 313. A generally inverted U-shaped arm 315, with a horizontally elongated intermediate section 317, has a proximal section 319 rotatably coupled about post 311 with a bearing or other coupling therebetween. A sweeping motorized actuator A and associated transmission rotate arm 317 back and forth relative to post 311. Furthermore, a driving motorized actuator B and associated transmission, attached to a distal section 321 of arm 317, operably rotate the shaft and foot of dop 305 without the need for a chain and sprockets. This embodiment is more compact and requires less components than the preferred embodiment.
Embodiments of the present apparatus and method of chemical-mechanical polishing of single-crystal or polycrystalline diamonds create a surface roughness of less than 2 nm and more preferably 0.1-0.3 nm. This process has applications in electronics and particle detectors, among other fields.
Referring
A polishing arm 2102 is mounted fixed to a post 2104 which protrudes from the case of the polishing apparatus 2100. The case is also referred to as a polishing system or polishing table, without limiting effect. The post 2104 is attached to a motor or actuator, as may be disposed within or under the system or table, which induces alternating partial axial rotations of the post 2104. The rotation of the post 2104 causes a sweeping motion of the polishing arm 2102, and hence, of a workpiece 112 (or workpieces 112) across the surface of the polishing wheel 122. That is, a diamond 33 or other workpiece 112 coupled with the dop assembly 700 mounted to the arm 2102 is moved across the polishing wheel 122 so as to abrade the surface of the workpiece 112 to polish such as surface.
In the depicted embodiments, a motor housing 2106 is provided as a cylindrical assembly to house the motor or actuator to drive the axial rotation of the polishing head, via a chain 2112 of a chain drive to the sprocket 2108 seen above the dop head 102. A downward force may be applied to the dop head 102, resulting in a normal force exerted upon the workpiece 112 by the polishing wheel 122.
The downward force can be imparted via a series of weights 2110 coupled with the dop head assembly 700 (e.g., via the polishing arm 2102) to increase the axial load on the workpiece 112, allowing the user to adjust polishing pressure according to a selected weight. An illustrative example of a weighted polishing arm 2102 is provided in
As indicated above, the end effector of the dop assembly 700 can be replaced. The replacement can include swapping a rotatable member 110 having separate workpieces coupled therewith. The replacement can include coupling other end effectors with the polishing apparatus 2100, such as the redresser 900 of
The environmental enclosure 2202 can include an air filter, such as the laminar flow high-efficiency particulate air filtered cabinet enclosure, as descried above with regard to
Referring generally to
However, the operations provided herein can be used to couple any number of workpieces 112 with a rotatable member 110, according to an available lateral surface 110A of the rotatable member 110, and force available to form a contact pressure between the workpieces 112 and a polishing wheel 122.
Referring now to
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Referring generally to
The vacuum chuck 3102 can fluidly couple with a vacuum pump 3104 to affix the workpieces on a first surface 3102A. For example, the workpieces 112 can be placed over fluidic passages 3202 in the first surface 3102A. In some embodiments, a number and spacing of the fluidic passages 3202 can be configured to receive a fixed number of workpieces 112 (e.g., twenty-four 7×7 mm workpieces). In some embodiments, the fluidic passages 3202 can be arranged in a multi-footprint configuration to receive various numbers or sizes of workpieces 112 (e.g., a lesser number of larger workpieces may be affixed by blocking multiple of the fluidic passages 3202).
As for other techniques described herein, the vacuum chuck 3102 can include or interface with standoffs 3106 to maintain a distance between the first surface 110A and the lower surface of the workpieces 112. For example, the standoffs 3106 can maintain a thickness of the second adhesive 2402 for workpieces 112 of a same thickness, or vary the thickness of the second adhesive 2402 to account for variance in workpiece 112 thickness. The vacuum pump 3104 may be disengaged from the vacuum chuck 3102 to decouple any affixed workpieces 112.
While various embodiments of the present invention have been disclosed, it should also be appreciated that other variations may be employed. For example, additional or alternate actuators, motion transmission or slurry components may be used, however, many of the performance advantages may not be achieved. It is alternately envisioned that alternate shapes and sizes may be utilized, although some of the preferred advantages may not be realized. Furthermore, additional or fewer processing steps can be used, although some benefits may not be obtained. It should also be appreciated that any of the preceding embodiments and features thereof can be mixed and matched with any of the others in any combination depending upon the final product and processing characteristics desired. Variations are not to be regarded as a departure from the present disclosure, and all such modifications are intended to be included within the scope and spirit of the present invention.
As used herein, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, the term “a member” is intended to mean a single member or a combination of members, “a material” is intended to mean one or more materials, or a combination thereof.
As used herein, references to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. References to at least one of a conjunctive list of terms may be construed as an inclusive OR to indicate any of a single, more than one, and all of the described terms. For example, a reference to “at least one of ‘A’ and ‘B’” can include only ‘A’, only ‘B’, as well as both ‘A’ and ‘B’. Such references used in conjunction with “comprising” or other open terminology can include additional items.
As used herein, the terms “about” and “approximately” generally mean plus or minus 10% of the stated value. For example, about 0.5 would include 0.45 and 0.55, about 10 would include 9 to 11, about 1000 would include 900 to 1100.
It should be noted that the term “exemplary” as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such term is not intended to connote that such embodiments are necessarily extraordinary or superlative examples).
The terms “coupled,” “connected,” and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.
It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.
While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular inventions. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings and tables in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Thus, particular implementations of the invention have been described. Other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.
This application claims priority to and the benefit of U.S. Provisional Application No. 63/610,242, filed Dec. 14, 2023, which is incorporated herein by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63610242 | Dec 2023 | US |
