Patent Application
20240025013
Recent advances in material development has led to the use of new materials in various applications, such as semiconductor and optical applications. However, objects made of these advanced materials are difficult to polish. The polishing processes of these advanced material objects typically involve multiple steps to achieve the desired surface finish for their intended purposes. Diamond slurries have been effectively used at several stages of these polishing processes, especially at the first lapping stage.
One popular polishing method that can be used for objects made of advanced materials involves flooding the polishing pad or plate with slurry to polish the objects. One of the drawbacks of using this polishing method is that several scratches usually result in the polished objects, which are very difficult to remove in subsequent polishing steps. In addition, the polishing method is a costly method of polishing advanced materials because a significant amount of slurry is used for the polishing process.
Another popular polishing method that can be used for advanced materials involves applying a small amount of slurry on the polishing pad or plate to polish the objects made of the advanced material. Similar to the previous polishing method, one of the drawbacks of using this polishing method is that scratches and dings usually result in the polished objects. In addition, in most instances, the object surfaces are not adequately polished, which may require longer polishing time to improve the polished surface.
Apparatus and method for polishing objects uses a layer of diamond slurry on a polishing surface of a polishing structure that is formed by dispensing a set amount of diamond slurry onto the polishing surface. The thickness of the layer of diamond slurry is maintained by periodically dispensing another set amount of diamond slurry onto the polishing surface of the polishing structure.
A method for polishing objects in accordance with an embodiment of the invention includes dispensing a set amount of diamond slurry onto a polishing surface of a polishing structure so that a layer of diamond slurry is formed on the polishing surface, polishing an object on the polishing surface of the polishing structure with the layer of diamond slurry, and periodically dispensing another set amount of diamond slurry onto the polishing surface of the polishing structure so that the thickness of the layer of diamond slurry on the polishing surface is maintained. In some embodiments, the steps of this method are performed when program instructions contained in a non-transitory computer-readable storage medium are executed by one or more processors.
An apparatus for polishing surfaces of objects accordance with an embodiment of the invention includes a top-loading structure that is configured to secure an object to be polished, a polishing structure that provides a polishing surface on which the object secured on the top-loading structure is polished, and a slurry dispensing system that is configured to dispense a set amount of diamond slurry onto the polishing surface of the polishing structure to form a layer of diamond slurry on the polishing surface. The slurry dispensing system is further configured to periodically dispense another set amount of diamond slurry onto the polishing surface of the polishing structure to form and maintain a layer of diamond slurry on the polishing surface so that the thickness of the layer of diamond slurry on the polishing surface is maintained.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrated by way of example of the principles of the invention.
Throughout the description, similar reference numbers may be used to identify similar elements.
It will be readily understood that the components of the embodiments as generally described herein and illustrated in the appended figures could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussions of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.
Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the invention can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.
Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment of the present invention. Thus, the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
With reference to
As explained in detail below, the thin film polishing process performed by the thin film polishing machine 100 involves maintaining a very thin film or layer of slurry on the polishing surface by periodically spraying or brushing a predefined amount of slurry onto a polishing surface 102 of the thin film polishing machine 100. In some embodiments, the thin film polishing machine 100 may be a chemical mechanical polishing (CMP) machine. It is noted here that CMP polishing generally requires a significantly more slurry compared to thin film polishing.
As shown in
The thin film polishing machine 100 also includes a top-loading structure 116, which is used to carry the object 113 for polishing. The top-loading structure 116 may be a polishing head or an object carrier, such as a wafer carrier, which can be rotated by a polishing head drive mechanism 118 via a polishing head shaft 120. The top-loading structure 116 will be referred to herein as the polishing head. The object 113 to be polished is attached to the polishing head 116 so that the object surface to be polished faces the polishing cover 108 on the platen 106. In an embodiment, the object 113 may be attached to the polishing head 116 using an adhesive, such as wax. In another embodiment, the object 113 may be attached to the polishing head 116 using vacuum. The polishing head drive mechanism 118 operates to rotate the polishing head shaft 120, which rotates the object 113 attached to the polishing head 116. The polishing head 116 may be rotated in the same direction as the platen 106 or in the opposite direction as the platen. The polishing head drive mechanism 118 also operates to move the polishing head 116 in downward and upward directions, as indicated by the arrow 122, so that the object 113 can be lowered to polish the object 113 on the polishing surface 102 of the polishing structure 104 and raised to remove the object 113 from the polishing surface. The polishing head drive mechanism 118 also provides downward force, i.e., force towards the platen 106, so that the object 113 is pushed onto the polishing surface 102 of the polishing structure 104 when the object is being polished. The polishing head drive mechanism 118 may further operate to move the polishing head 116 side-to-side in a lateral direction (i.e., in a direction parallel to the polishing surface 102 of the polishing structure 104), as indicated by the arrow 124, when the object 113 is being polished. The polishing head drive mechanism 118 may use one or more motors to rotate the polishing head shaft 120 at a fixed or varied rotational speed and move the polishing head 116 in a direction normal to the polishing surface 102 and in a direction parallel to the polishing surface 102. The polishing head drive mechanism 118 may be controlled by the controller 114. However, in other embodiments, the polishing head drive mechanism 118 may be controlled by another controller (which may be part of the polishing head drive mechanism 118) that is independent of the controller 114.
Similar to other polishing machines, the thin film polishing machine 100 uses slurry for polishing objects. In an embodiment, the slurry that is used by the thin film polishing machine 100 is agglomerate-free diamond slurry, which is slurry containing diamond particles that are not agglomerated or agglomeration free. However, unlike other polishing machines, the thin film polishing machine 100 operates to maintain a very thin film or layer 126 of slurry throughout the polishing process, which reduces the amount of slurry used for the polishing process and improves polishing results. The thin layer 126 of slurry is maintained by periodically spraying or brushing small amounts of slurry onto the polishing surface 102 of the polishing structure 104.
In order to produce and maintain the thin layer 126 of slurry, the thin film polishing machine 100 has a slurry dispensing system 128, which includes a supply 130 of slurry, a slurry delivery subsystem 132 and a spray nozzle 134 in the illustrated embodiment. In an embodiment, the supply 130 of slurry includes diamond slurry, which may be agglomerate-free diamond slurry, in a container. The slurry delivery subsystem 132 operates to deliver small amounts of the slurry to the spray nozzle 134 so that the slurry can be sprayed onto the polishing surface 102 of the polishing structure 104 to produce or maintain the thin layer 126 of slurry on the polishing surface 102. In an alternative embodiment, as illustrated in
The layer 126 of slurry that may be formed on the polishing surface 102 of the polishing structure 104 in accordance with an embodiment of the invention is shown in
To produce and maintain this thin slurry layer 126 on the polishing surface 102, a small amount of slurry should be periodically dispensed, e.g., sprayed or brushed, onto the polishing surface 102. The amount of slurry used for each application is dependent on the surface area of the polishing surface 102, in addition to the desired thickness of the slurry layer 126 on the polishing surface. In order to quantify the amount of slurry used in each dispensation or application, the ratio of milliliter (ml) per square inch, i.e., ml/inch, is introduced to normalize the slurry amount per area of the polishing surface. The amount of slurry used in each dispensation may be 0.1 ml/inch2 to 0.2 ml/inch2. In an embodiment, the amount of slurry used in each dispensation is 0.14 ml/inch2 to 0.18 ml/inch2. This amount of slurry is dispensed every 10 minutes to 20 minutes during the polishing of the object on the polishing surface 102. In an embodiment, the set amount of slurry is dispensed every 10 minutes to 15 minutes during the polishing of the object on the polishing surface 102.
Turning now to
The air compressor 404, which may or may not be located in the thin film polishing machine 100, provides compressed air for the slurry dispensing system 128 to pneumatically spray slurry onto the polishing surface 102. The compressed air from the air compressor 404 is supplied to the spray box 408 through the air pressure regulator 406, which controls the pressure of the compressed air. The air pressure regulator may have a built-in filter to remove or filter out any liquid or solid contaminants from entering an air line 410 to the spray box 408. In an embodiment, the air pressure regulator 406 may maintain air pressure in the air line 410 at ten (10) pounds per square inch (psi).
The spray box 408 is used to mix the slurry pumped from the slurry supply 130 with the compressed air from the air pressure regulator 406 so that the slurry is atomized. The spray box 408 includes two inlets to receive the slurry and the compressed air and an outlet to output the atomized slurry to the spray nozzle 134. The spray nozzle 134 includes an opening to spray the atomized slurry onto the polishing surface 102. The spray nozzle 134 is positioned so that the atomized slurry is sprayed at an angle with respect to the normal of the polishing surface 102 so that the slurry is sprayed onto a large area of the polishing surface to produce a more uniform layer of slurry on the polishing surface with respect to the slurry layer thickness. In an embodiment, the spray nozzle 134 is positioned so that the atomized slurry is sprayed at an angle of thirty degrees (30%) to fifty degrees (50%), e.g., at an angle of forty-five degrees (45%), with respect to the normal of the polishing surface 102. In an embodiment, the spray nozzle 134 may be a tube.
In other embodiments, the slurry dispensing system 128 may use other mechanisms and/or methodologies to periodically spray a small amount of slurry onto the polishing surface 102. Although a manual spraying system may be used instead of the slurry dispensing system 128, the slurry amount for each spray during the polishing process would most likely be not consistent. That is, it will be very difficult, if not impossible, to spray the same desired amount of slurry for each application onto the polishing surface 102 using a manual spraying system.
In the embodiment in which the brush 136 is used instead of the spray nozzle 134, the air compressor 404, the air pressure regulator 406 and the spray box 408 are not needed. Thus, in this embodiment, the slurry delivery subsystem 132 only requires the pump 402 to pump slurry from the slurry supply 130 to the brush 136. In addition, the air line 410 is not required in this brushing type slurry dispensing system. The air can be shut off directly and the slurry drips on the platen 106 and dispersed using the brush 136. In an embodiment, the brush 136 may be positioned at an angle of thirty degrees (30%) to fifty degrees (50%), e.g., at an angle of forty-five degrees (45%), with respect to the normal of the polishing surface 102 and at a fixed position to contact the polishing surface 102 to brush the dispensed slurry on the polishing surface to produce or maintain the thin layer 126 of slurry on the polishing surface.
A thin film polishing process using the thin film polishing machine 100 in accordance with embodiments of the invention is now described with reference to a flow diagram of
Next, at step 504, the platen 106 with the polishing cover 108 is rotated by the controller 114 using the platen drive mechanism 110. Next, at step 506, the polishing head 116 with the object 113 is rotated by the controller 114 using the polishing head drive mechanism 118. In an embodiment, the platen 106 and the polishing head 116 are rotated in the same direction. In another embodiment, the platen 106 is rotated in one direction, e.g., the clockwise direction, and the polishing head 116 is rotated in the opposite direction, e.g., the counterclockwise direction. In some embodiments, steps 504 and 506 may be executed simultaneously or executed in different order.
Next, at step 508, a predefined amount of slurry is sprayed or brushed onto the polishing surface 102 of the polishing cover 108 on the platen 106 to form a thin slurry layer 126 on the polishing surface. The slurry that is sprayed or brushed may be diamond slurry, and the predefined amount of diamond slurry that is sprayed or brushed may be 0.1 ml/inch to 0.18 ml/inch2 with respect to the polishing surface area of the polishing cover 108. The thin slurry layer 126 that is formed on the polishing surface 102 may be 7 μm to 9 μm thick.
Next, at step 510, the object 113 is polished on the polishing surface 102 of the polishing cover 108 by the controller 114 by moving the polishing head 116 down onto the polishing surface 102 and applying downward force on the object using the polishing head drive mechanism 118. In an embodiment, the object 113 may also be moved laterally on the polishing surface 102 by the controller 114 using the polishing head drive mechanism 118.
Next, at step 512, as the object 113 is being polished on the polishing surface 102, another predefined amount of slurry is periodically sprayed or brushed onto the polishing surface 102 of the polishing cover 108 on the platen 106 to maintain the thin slurry layer 126 on the polishing surface. Again, the slurry that is periodically sprayed or brushed may be diamond slurry. The predefined amount of diamond slurry that is periodically sprayed or brushed onto the polishing surface 102 may be 0.1 ml/inch to 0.18 ml/inch2 with respect to the polishing surface area of the polishing cover 108, which may be the same amount of slurry that was initially sprayed or brushed onto the polishing surface 102 to form the thin slurry layer. The thin slurry layer 126 that is maintained may be 7 μm to 9 μm thick. In an embodiment, the predefined amount of slurry is periodically sprayed or brushed onto the polishing surface every 10 minutes to 15 minutes until the polishing of the object 113 on the polishing surface 102 has completed.
Next, a step 514, after the object 113 has been polished for a set polishing duration, the polishing head 116 is raised from the polishing surface 102 and the object 113 is removed from the polishing head 116. In some embodiments, the object 113 may be manually removed from the polishing head 116. In other embodiments, the object 113 may be automatically removed from the polishing head 116 using a suitable object handling mechanism. Next, at step 516, the object 113 is then cleaned using an appropriate cleaning method, which may involve using rollers with cleaning solution to clean the polished surface of the object. In some embodiments, the object 113 may be transferred to a post-CMP cleaner to clean the polished object.
Next, at step 518, surface parameters of the object 113 are measured and recorded, which may be a manual or automated process. The surface parameters may include the thickness of the object at various locations on the object 113 to determine the results of the polishing. In some embodiments, the object 113 may be further polished when the surface parameters indicate that additional polishing is needed.
In some embodiments, at least some of the steps of the above process are automatically executed by the controller 114. In these embodiments, values for various polishing parameters, such as the set amount of slurry that is to be periodically sprayed or brushed and the time interval for each slurry spray or slurry brushing application, are input by a user and stored in a storage accessible by the controller 114. When initiated, various steps of the polishing process are automatically executed by the controller 114 using a stored polishing algorithm with the polishing parameter values. The polishing algorithm can be viewed as program instructions stored in a non-transitory computer-readable storage medium that can be executed by one or more processors to cause the thin film polishing machine 100 to perform the programmed steps.
The described thin film polishing process reduces the polishing duration with less slurry when compared to convention polishing processes. As an example, for polishing a sapphire object as a representative of hard material objects, the following table illustrates the advantages of the thin film polishing process in accordance with an embodiment of the invention in comparison with a conventional polishing process:
As shown in the above table, the conventional polishing process of sapphire took almost six (6) times with hundred (100) times more slurry as compared to the thin film polishing process using the same loading pressure. In addition, the convention polishing process created several scratches compared to the thin film polishing process. Furthermore, the surface roughness of the polished object was found to be slightly better for the thin film polishing process than the conventional polishing process, as indicated by the roughness average (Ra) values.
As another example, for polishing a zinc selenide (ZnSe) object as a representative of soft material objects, the following table illustrates the advantages of the thin film polishing process in accordance with an embodiment of the invention in comparison with a conventional polishing process:
As shown in the above table, the conventional polishing process of ZnSe took three (3) times more than that of the thin film polishing process with four (4) times more slurry as compared to the thin film polishing process using the same loading pressure. In addition, no scratches were created by the thin film polishing process.
A method of polishing objects in accordance with an embodiment of the invention is described with reference to
Although the operations of the method(s) herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operations may be performed, at least in part, concurrently with other operations. In another embodiment, instructions or sub-operations of distinct operations may be implemented in an intermittent and/or alternating manner.
It should also be noted that at least some of the operations for the methods may be implemented using software instructions stored on a computer useable storage medium for execution by a computer. As an example, an embodiment of a computer program product includes a computer useable storage medium to store a computer readable program that, when executed on a computer, causes the computer to perform operations, as described herein.
Furthermore, embodiments of at least portions of the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
The computer-useable or computer-readable medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device), or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disc, and an optical disc. Current examples of optical discs include a compact disc with read only memory (CD-ROM), a compact disc with read/write (CD-R/W), a digital video disc (DVD), and a Blu-ray disc.
In the above description, specific details of various embodiments are provided. However, some embodiments may be practiced with less than all of these specific details. In other instances, certain methods, procedures, components, structures, and/or functions are described in no more detail than to enable the various embodiments of the invention, for the sake of brevity and clarity.
Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. The scope of the invention is to be defined by the claims appended hereto and their equivalents.
