The present disclosure relates to chemical mechanical polishing pad conditioners.
During the microelectronic device fabrication process, multiple integrated circuits are formed upon the surface of substrate. Examples of substrates include silicon wafers, gallium arsenide wafers, and the like. Each integrated circuit consists of microelectronic devices electrically interconnected with conductive traces known as interconnects. Interconnects are patterned from conductive layers formed on the surface of the substrate. The ability to form stacked layers of interconnects has allowed for more complex microelectronic circuits to be implemented in and on relatively small surface areas of the substrate. With the number of microelectronic circuits increasing and becoming more complex, the number of layers of a substrate are increasing. Accordingly, planarity of the substrate surface becomes an important aspect in semiconductor manufacturing.
Chemical mechanical polishing (CMP) is a method of planarizing the surface of a layer of a substrate. CMP combines chemical etching and mechanical abrasion to remove material from the surface of the substrate. During the CMP process, the substrate is attached to the head of a polishing tool and is inverted such that the integrated circuit-embodied surface opposably faces a polishing pad. A slurry containing abrasive particles and a chemical etchant is deposited onto the rotating polishing pad. The chemicals can soften or react with the exposed surface material on the substrate that is being planarized. The polishing pad is fixedly attached to a turntable or platen. The substrate is polished by placing the rotating substrate into contact with the polishing pad while the polishing pad is rotated on the platen. The surface of the integrated circuit-embedded surface of the substrate can be removed by the combined action of chemical softening of the exposed surface material and physical abrasion brought about by relative movement between the polishing pad, the slurry and the substrate.
As portions of the substrate are removed by the polishing pad, a combination of slurry and debris tends to clog and glaze the surface of the polishing pad, such that over time, the polishing pad becomes less effective at removing material from the substrate. The surface of the polishing pad is cleaned or conditioned by a CMP pad conditioning assembly, which has an abrasive surface that engages the polishing pad surface. Known CMP pad conditioning assemblies can have an abrasive surface that includes protrusions, mesas, or cutting edges and these may be coated with hard coatings like cubic boron nitride, diamond grit, or polycrystalline diamond. The abrasive surface of the pad conditioning assembly can itself become worn thereby rendering it less and less effective over time for reconditioning the CMP polishing pad. During conditioning of the CMP polishing pad, the pad conditioning assembly abrades the CMP pad and opens new pores and fresh pad surface for polishing.
The CMP process utilizes many consumables including the slurry and chemicals, the polishing pad, and the pad conditioning assembly. Replacing consumables can be time consuming and result in lost manufacturing yield and reduced wafer throughput. Some CMP processes require pad conditioning over the entire pad surface (no edge exclusion). Maintaining the co-planarity of a pad conditioning assembly with the polishing pad during this operation when the conditioning disk sweep recipe extends the pad conditioning assembly beyond the outer diameter of the polishing pad can be difficult and can result in damage or excess wear to the pad. For example, segmented conditioning disk designs can tilt once the conditioning disk extends beyond the outer diameter of the pad. This can result in non-uniform/excess pad wear at the perimeter of the pad and may even result in tearing of the pad.
In an effort to reduce consumable costs and reduce polishing tool downtime, semiconductor manufactures have begun utilizing the outer edges of the CMP polishing pad. Accordingly there is a continuing need for CMP pad conditioning assemblies that can condition CMP pads including the outer edges of the CMP pad.
The problem of pad conditioning assemblies causing excessive wear on a CMP pad during pad conditioning can be reduced or eliminated by a CMP pad conditioning assembly that includes a backing plate that has abrasive regions separated from one or more supporting structures by one or more channels. The CMP pad conditioning assembly includes a backing plate has a first face and a second face. The backing plate includes a mounting structure that can attach the backing plate of the conditioning assembly to a chemical mechanical planarization tool. The pad conditioning assembly further includes a plurality of abrasive regions on a first face of the backing plate, the abrasive regions can comprise one or more protrusions or cutting edges. A top of the protrusions or cutting edges reside in a first plane that has a first average height that can be measured from the first face of the backing plate. The CMP pad conditioning assembly also has one or more supporting structures that are on or fixed to the backing plate. The one or more supporting structures can be positioned between, and can be separated from, the abrasive regions by one or more channels. The one or more supporting structures can have a top surface, a bottom surface, and a thickness measured between the top and bottom surface. The top surface of the one or more supporting structures resides in a second plane that has a second average height that can be measured from the first face of the backing plate. The height of the tops of the protrusions or cutting edges of the first plane is greater than the height of the top surface of the second plane of the supporting structure(s).
In some versions of the CMP pad conditioner assembly, the first average height of the first plane is greater than the second average height of the second plane by between 25 microns and 200 microns. In other versions of the CMP pad conditioned assembly, the first average height of the first plane is greater than the second average height of the second plane by between 50 microns and 100 microns.
In some versions of the pad conditioning assembly the abrasive regions are equally spaced or essentially equally spaced about the backing plate and separated by channels from the one or more supporting structures positioned between the abrasive regions.
In some versions of the pad conditioning assembly, a coating of polycrystalline diamond and/or diamond grit can be deposited on all or a portion of the abrasive regions.
In some versions of the pad conditioning assembly, the abrasive regions can be segments fixed to the backing plate while in some other versions the abrasive regions can be formed integrally with the backing plate. A combination of fixed and integral abrasive regions can also be used.
In other versions of the CMP pad conditioning assembly, the assembly includes a backing plate that has a first face and a second face, the backing plate includes a mounting structure and the mounting structure can be used to secure the conditioning assembly to a chemical mechanical planarization tool. The conditioning assembly includes one or more abrasive regions on the first face of the backing plate that can have an abrasive coating and/or one or more protrusions. The abrasive coating or tops of the protrusions when present, can reside in a first plane that has a first average height measured from the first face of the backing plate. The one or more supporting structures on the first face of the backing plate can be positioned between the abrasive regions and may be separated from the abrasive regions. The one or more supporting structures have a top surface, the top surface of the one or more supporting structures reside in a second plane that has a second average height measured from the first face of the backing plate, the first average height of the first plane is greater than the second average height of the second plane. The one or more supporting structures can include one or more channels in a surface and/or can form channels with one or more abrasive regions.
The pad conditioning assembly in some versions can have one or more channels comprising the supporting structures, the channels formed between the one or more abrasive regions and the one or more supporting structures. The channels can have parallel or non-parallel side walls.
The pad conditioning assembly can include versions in which the support structure is a single piece. The support structure can be a polymeric material.
As illustrated with reference to
In some versions of the pad conditioning assembly, the abrasive regions are equally spaced or essentially equally spaced about the backing plate and the one or more supporting structures are positioned between the abrasive regions.
In some versions of the pad conditioning assembly, a coating of polycrystalline diamond and/or diamond grit can be deposited on a portion of the abrasive regions and the support structures are free of a coating of polycrystalline diamond and/or diamond grit.
The plurality of abrasive segments can be spaced about the pad and collectively form a co-planar abrasive surface that has an average height above the top surface of the supporting structure(s) fixed to the backing plate.
In some versions of the CMP pad conditioning assembly, a plurality of non-abrasive supporting structures can be spaced between the abrasive regions with channels separating the supporting structures and the abrasive regions. In other versions, the supporting structure can be a single unitary piece fixed to the backing plate. The supporting structures can have a thickness and include a top surface that is parallel, but not co-planar, with the average height of the top of the abrasive regions.
Because the supporting structure(s) are lower in height than the average height of the tops of the abrasive regions, the supporting structures have reduced load or in some versions are not load bearing during the pad conditioning process. CMP pad debris from the reconditioning of the pad as well as slurry and liquid can flow between the polishing pad and the top surface of the support structure so that pad debris, slurry and liquid can be removed from the CMP pad. The one or more channels between the abrasive regions and the supporting structures also aid in the removal of pad debris, slurry, and liquid.
Pad conditioning assemblies can include abrasive regions or abrasive segments that are affixed to an underlying backing plate or formed integrally with the backing plate. The term abrasive region includes abrasive segments and combinations of abrasive regions and abrasive segments. The abrasive regions can have one or more protrusions or a cutting edges, and in some versions the protrusions or cutting edges can be of two or more different average heights. The abrasive regions or abrasive segments in some versions of the CMP pad conditioning assembly can be bonded or fixed to the backing plate using an adhesive such as an epoxy or mechanical devices such as bolts. The backing plate can be attached to the CMP polishing tool. Examples of pad conditioner assemblies including separate backing plate and conditioning segments are disclosed in PCT Pub. No.: WO/2012/122186 (International Application No.: PCT/US2012/027916). In some versions the pad conditioning assemblies can have integral abrasive regions with features like protrusions or a cutting edges formed or machined into the backing plate as illustrated in
A plurality of protrusions on the abrasive regions can include but are not limited to those that have a geometrical cross section or those that are irregularly shaped as disclosed in Patent Cooperation Treaty Publication. No.: WO/2012/122186. For example, the protrusion may approximate a pyramid, an elongated cylinder, various needle shapes with a blunted or tapered point, or other suitable shape for conditioning a CMP pad. Protrusions can also refer to cutting edges which are elongated or blade like structures as disclosed in Patent Cooperation Treaty Publication. No. WO/2015/143278 A1. The abrasive region or segment can include a plurality of elongated protrusions that protrude in a forward direction that is normal to the pad contacting face of the abrasive region. Each elongated protrusion includes a base that defines a width and a length, the length being greater than the width and defining an elongate axis of the elongated protrusion. Each elongated protrusion further defines at least one ridge line that is elongated and in substantial alignment with the length. Accordingly, each ridge line is elongate in the direction of the elongate axis. In various embodiments, a ratio of the base length to the base width is in the range of 2 to 20 inclusive. A non-limiting example of the dimensions of the base width and the base length is 150 μιηm and 500 μιηm respectively. Combinations of protrusions and cutting edges can also be used in the abrasive regions or abrasive segments of the pad conditioning assemblies. The protrusions or cutting edges have a height above the top surface 374 of the abrasive region. In some versions this height can range from about 50 microns to about 200 micron. The density of protrusions or cutting edges in the abrasive regions can vary. In some versions the density of protrusions or cutting edges is about 2 to about 6 per square millimeter of abrasive region. In some pad conditioning assemblies, the abrasive regions or abrasive segments are absent protrusions and instead can have diamond grit or other hard ceramic bonded or brazed to the abrasive region.
A coating of polycrystalline diamond or other hard ceramic like polycrystalline cubic boron nitride can cover at least the distal extremities of the protrusions or cutting edges. Diamond grit or other hard ceramic grit like cubic boron nitride grit can also coat a portion of the protrusions or cutting edges. A combination of diamond grit or other hard ceramic and a coating of polycrystalline diamond or coating other hard ceramic like polycrystalline cubic boron nitride can be used to coat a portion of all of the protrusions or cutting edges. The hard coating may be atop the abrasive region or protrusions.
The pad conditioner assembly includes a supporting structure or one or more supporting structures that stabilizes the pad conditioning assembly during use along the outside edge of a CMP pad polishing pad. The supporting structure can be made of a material that is chemically compatible with the chemical mechanical planarization process chemicals and slurry. The material can be a plastic or polymer and can include polymer composites. One example of a polymer that can be used for the support structure is chlorinated polyvinyl chloride that has a chlorine content above 57% by weight to as high as 70% by weight. In some versions of the CMP pad conditioning assembly the support structure is made of a chlorinated polyvinyl chloride with a chlorine content of 62% by weight to 69% by weight.
The supporting structure has a top surface and a bottom surface. The bottom surface is fixed to the pad conditioner backing plate. The top surface of the supporting structure is closest to the CMP pad during use of the pad conditioner. The bottom surface of the supporting structure can be fixed to the pad conditioner backing plate by mechanical bolts or by using an adhesive. The support structure can be free of a hard coating on its top surface.
The height of the top surface of the supporting structure measured from the top surface of the backing plate (the surface to which the bottom surface of the supporting structure is fixed) is less than the height of the the tops of the protrusions or cutting edges measured to the backing plate surface. The difference in height between the tops of the protrusions or cutting edges and the top of the support structure can be measured by placing a flat substrate across the protrusions or cutting edges and determining an average distance to the top surface of the support structure.
The difference in height between the the tops of the protrusions or cutting edges and the top surface of the support structure is large enough that material removed from the CMP pad by the protrusions or cutting edges during pad conditioning is also removed from underneath the pad conditioning assembly while also providing tilt stability to the conditioning assembly when it is used on the outside edge of the CMP pad.
The top surface of the support structure is slightly recessed relative to the tops of the protrusion or cutting features. In the pad conditioning assembly, the first average height of the protrusions or cutting edges is greater than the second average height of the top surface of the support structure. In some versions of the pad conditioning assemblies, the top surface height or top average surface height of the support structure as measured from the top average surface of the backing plate is 25 microns to 200 microns below the average height of the tops of the protrusions or cutting edges. In other versions of the pad conditioning assemblies, the top surface height or top average surface height of the support structure as measured from the top average surface of the backing plate can be 50 microns to 100 microns below the tops of the average height of the protrusions or cutting edges. The supporting structures can include a top surface that is not co-planar with the top of the abrasive region(s).
The support structure can be positioned between abrasive segments or abrasive regions. Both the support structure and/or the abrasive segments or abrasive regions can be fixed, integrally cut or formed in the backing plate, or any combination of these. For example,
The form of the one or more supporting structure(s) and the form of the one or more abrasive segment(s) or abrasive region(s) is not limited to any particular geometry or shape. The shapes can be chosen to provide uniform conditioning of the underlying CMP pad and provide channels between the supporting structure(s) and abrasive segments or regions that allow flow of CMP pad debris, slurry, and liquid from between the CMP pad and the pad conditioning assembly. For example,
The support structure can have a thickness. In some versions the support structure thickness is in a range of 1900 microns to 6500 microns or the support thickness can be from about 1900 microns to about 6500 microns. In some other versions the support structure thickness is in a range of 1900 microns to 2500 microns or the support thickness can be from about 1900 microns to about 2500 microns. In addition to channels between abrasive segments or abrasive regions and supporting structures, the top surface of the supporting structure can have channels in its surface to further facilitate debris, slurry, and liquid flow from between the CMP pad and the pad conditioning assembly during use. These support structure surface channels can be formed in the supporting structure and can for example be straight or curved.
Regardless of the shape of the channels at any point along their length, the one or more channels can have a largest or maximum depth at any point as measured from the top surface of the one or more supporting structures to the top surface of the backing plate. In some versions f the pad conditioning assembly, that maximum depth of the channel at any point along its length can be 6500 microns or less. In some versions the one or more channels can have a largest or maximum depth as measured from the top surface of the one or more supporting structures to the bottom of the channel that is between 2500 microns to 500 microns or about 2500 microns to about 500 microns.
Similarly, the one or more channels such as 350 that can be characterized by a channel width along the length of the channel. The channels can have parallel or non-parallel walls. In some versions of the pad conditioning assembly, the channel width can have a largest dimension that is between 100 microns and 2500 microns or about 100 microns and about 2500 microns. In some other versions of the pad conditioning assembly the channel width can have a largest dimension that is between 1500 microns and 2500 microns or about 1500 microns and about 2500 microns.
In some versions of the pad conditioning assembly, a plurality of non-abrasive supporting structures can be spaced between the abrasive segments. In other versions, for example as shown in
In some versions of the pad conditioning assembly, the channels for pad debris, slurry, and liquid flow can be formed between the abrasive regions and the support structures, can be formed in the support structure itself, or any combination of these. The channels can have a greatest depth from the top surface of the support structure, for example 344, down to the top surface of the backing plate 384. In some other versions, the depth of the channel can be less than 2500 microns, for example as shown by the channels 742 in
The channels can have non-parallel side walls that diverge in width from an inside diameter of the backing plate towards the outer diameter of the backing plate. In some versions of the channels have essentially parallel side walls. A combination of parallel and non-parallel channel side wall can also be used.
A mounting structure secures the backing plate to a chemical mechanical planarization tool. The mounting structure may include through holes or partial through holes in the backing plate that can be used to secure the pad conditioning assembly to the polishing tool with bolts and the like.
The conditioner head of a CMP tool includes a CMP pad conditioning assembly that during the CMP process is brought into contact with the polishing pad. The CMP pad conditioning assembly is generally positioned at a bottom of the conditioner head and can rotate around an axis. The tops of the protrusions or cutting edges on the abrasive segment face down toward the CMP polishing pad and contact the surface of the CMP polishing pad during the conditioning process. During the pad conditioning and polishing process, both the polishing pad and the CMP pad conditioning assembly rotate so that these protrusions or cutting edges move relative to the surface of the polishing pad, thereby abrading and retexturizing the surface of the polishing pad. Versions of the CMP pad conditioning assembly can be swept to the outer diameter and in some versions beyond the outer diameter of the polishing pad without causing non-uniform/excess pad wear at the perimeter of the CMP pad.
After the CMP pad conditioning assembly illustrated in
While various pad conditioning assemblies are described, it is to be understood that this disclosure is not limited to the particular molecules, compositions, designs, methodologies or protocols described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present disclosure which will be limited only by the appended claims.
It must also be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to an “supporting structure” is a reference to one or more supporting structures and equivalents thereof known to those skilled in the art, and so forth. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention. All publications mentioned herein are incorporated by reference in their entirety. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. All numeric values herein can be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In some embodiments the term “about” refers to ±10% of the stated value, in other embodiments the term “about” refers to ±2% of the stated value. While compositions and methods are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions and methods can also “consist essentially of” or “consist of” the various components and steps, such terminology should be interpreted as defining essentially closed or closed member groups. It is also to be appreciated that features, layers and/or elements depicted herein are illustrated with particular dimensions and/or orientations relative to one another for purposes of simplicity and ease of understanding, and that the actual dimensions and/or orientations may differ substantially from that illustrated herein.