Device and Method for Improved Cmp Process with Cmp Head

The semiconductor integrated circuit industry has experienced exponential growth. Technological advances in integrated circuit materials and design have produced generations of integrated circuits where each generation has smaller and more complex circuits than the previous generation. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing integrated circuits.

Chemical mechanical planarization (CMP) is a process that has enabled the use of thin film materials that enable features of relatively small size. CMP can planarize the surface of a semiconductor wafer after thin film deposition and patterning processes. CMP utilizes chemical and mechanical processes to planarize the semiconductor wafer. While highly beneficial, chemical mechanical planarization can also be susceptible to equipment failure resulting in damaged semiconductor wafers.

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Terms indicative of relative degree, such as “about,” “substantially,” and the like, should be interpreted as one having ordinary skill in the art would in view of current technological norms.

Embodiments of the present disclosure provide many benefits over traditional chemical mechanical planarization systems. Embodiments of the present disclosure utilize a CMP head that includes anti-electrostatic properties to prevent damage to the CMP head and to semiconductor wafers. In particular, embodiments of the present disclosure utilize a CMP head including at least a portion that is made of a blend of a Lewis acid polymer and a Lewis base polymer. The molar ratio of the Lewis acid polymer and Lewis base polymer results in a material that is highly resistant to the buildup of electrostatic charge during CMP processes. The lack of buildup of electrostatic charge during CMP processes results in a reduction in debris particles that are trapped or otherwise accumulate near a bottom portion of the CMP head and, in particular, at the edges of the semiconductor wafers. This helps prevent damage to integrated circuits that are formed at the edges of the wafers. Accordingly, embodiments of the present disclosure increase semiconductor wafer yields and reduce the need for technicians or experts to repair or replace damaged equipment. Instead, the anti-electrostatic CMP head prevents the accumulation of dangerous debris from the chemical mechanical planarization pad at the CMP head or edges of the wafer before the debris can damage the CMP head or the semiconductor wafer. The result is that time and resources are not wasted replacing equipment and scrapped semiconductor wafers.

is a simplified cross-sectional view of a CMP headthat is utilized in CMP processes, in accordance with some embodiments.is a side view of a CMP systemof which the CMP headofis part, in accordance with some embodiments.is a graph illustrating electrostatic properties of a CMP headof, in accordance with some embodiments. The description of the CMP headofwill also reference the illustrations of.

The CMP headofincludes a main CMP bodyand a retaining ring. The retaining ringis coupled or otherwise fixed to the main CMP body. The CMP headalso includes a membranewithin an interior of the CMP head. The CMP headholds a waferduring a CMP process. As will be set forth in more detail below, the components of the CMP headcooperate to help reduce or prevent damage to the waferand to the CMP head.

Prior to further description of the CMP headof, the description of the CMP systemwill be provided in relation to. The CMP systemincludes a platen, a CMP head, a slurry supply system, and a pad conditioner. The components of the CMP systemcooperate to provide an efficient CMP process that reduces the potential for damage to CMP equipment or semiconductor wafer. In particular, as will be set forth in more detail below, the CMP headhelps to prevent damage to CMP equipment and semiconductor wafers.

In one embodiment, the platenis a flat circular surface. The platenis configured to rotate during CMP processes. The platenmay rotate with a rotational velocity of between 20 RPM and 40 RPM, though other rotational velocities can be utilized without departing from the scope of the present disclosure. The platencan be coupled to a shaft that drives the rotation of the CMP platen. The platenmay have a diameter of about 50 cm to 75 cm, though platens of other sizes can be utilized without departing from the scope of the present disclosure.

The CMP systemincludes a CMP pad. The CMP padis positioned on top of the platen. The CMP padmay be circular and may have a diameter that is substantially identical to the diameter of the platen. The CMP padmay be coupled to the platenby fasteners, by suction (i.e., pressure differential), by electrostatic force, or in any suitable way. When the platenrotates, the CMP padalso rotates. The rotation of the CMP padis one of the factors that planarizes the semiconductor wafer, as will be described in more detail below.

The CMP padcan be made of a porous material. In one example, the CMP padis made from a polymeric material having a pore size between 20 micrometers and 50 micrometers. The CMP padmay have a roughness of about 50 μm. Other materials, dimensions, and structures of a CMP padcan be utilized without departing from the scope of the present disclosure. The CMP padmay be substantially rigid.

The slurry supply systemsupplies a slurryonto the rotating CMP padduring the CMP process. The slurrycan include a solution of water and one or more corrosive compounds. The corrosive compounds are selected to chemically etch or remove one or more materials on the surface of the semiconductor wafer. Accordingly, the compounds in the slurryare selected based on the material or materials of the surface features of the semiconductor waferto be planarized. The slurry supply systemcan include a tankthat holds the slurryand a tubeor hose coupled between a nozzleand the tank. The nozzledelivers the slurryonto the rotating CMP padduring the CMP process.

In some embodiments, the abrasive in the slurrycan include silica or cerium oxide produced via colloidal process or calcined. The pH value of the slurrycan range between 2 and 9. In some embodiments, the slurry may include a tungsten inhibitor to prevent tungsten corrosion. The slurrycan provide a stable, fast removal rate greater than 500 Å per minute on wafer material such as tungsten, silicon, silicon oxide, silicon nitride, titanium nitride, or other materials.

The pad conditionerconditions the rotating CMP padduring the CMP process. During the CMP process, the top surface of the rotating CMP padexperiences wear from the planarization process. The top surface of the CMP padmay wear out unevenly such that depressions, valleys, and peaks may form in the CMP pad. The pad conditionerincludes a rotating pad conditioner headthat is pressed downward onto the rotating CMP pad. The rotating pad conditioner headincludes or is coated with a hard, durable material that can effectively sand down the surface of the CMP pad. In one example, the surface of the pad conditionerincludes a diamond material. The rotating head of the pad conditionersweeps across the surface of the rotating CMP padin a pattern selected to maintain a substantially even top surface of the CMP padduring the CMP process. Accordingly, the pad conditionerremoves or prevents the formation of depressions, ridges, valleys, or uneven features on the surface of the rotating CMP pad.

During the CMP process, the CMP headplaces the downward facing surface of the semiconductor waferinto contact with the rotating CMP pad. The CMP headmay also rotate the semiconductor waferduring the CMP process. Surface features of the downward facing surface of the semiconductor waferare planarized during the CMP process. The planarization is achieved by both mechanical and chemical processes. The mechanical aspect of the planarization is achieved by the physical effect of the CMP padrubbing down the bottom facing surface of the semiconductor wafer. The mechanical aspect of the planarization is akin to a very fine sanding process. The chemical aspect of the planarization is achieved by the chemical effect of the slurry on the materials of the surface features of the semiconductor wafer. The compounds in the solution of the slurry etch or otherwise react with and remove the materials of the surface features of the semiconductor wafer. The result of the CMP process is that the exposed bottom facing surface of the semiconductor waferbecomes substantially planar.

While the CMP process may be generally effective, several problems may arise that can damage the equipment of the CMP systemand the semiconductor wafer. For example, it is possible that some of the surface material of the pad conditionermay break off or otherwise become dislodged from the pad conditioner. This results in pad conditioner debris on the rotating CMP pad. The debris can include grains, particles, shards, or fragments of the material from the pad conditioner. The rotating CMP padmay carry the pad conditioner debris into contact with the retaining ringof the CMP head.

Another potential source of debrisis the crystallization of the slurry during the CMP process. When the slurry is provided onto the surface of the rotating CMP pad, the rotation of the CMP padcauses the slurry to flow toward the outer perimeter of the CMP padand off of the CMP pad. Nevertheless, it is possible that some portion of the slurry may not quickly flow off of the CMP pad. This portion of the slurry may crystallize.

During the CMP process, it is possible that the lateral edge of the wafercan collide with the retaining ring. It is possible that this repeated contact can result in a buildup of electrostatic charge at the retaining ring. If there is a buildup of electrostatic charge at the retaining ring, it is possible that charged debris particles from the debriscan be attracted to the retaining ringand can build up at the retaining ring. Some debris particles can accumulate at the interior edge of the retaining ring. This can result in trapped debris particles repeatedly contacting the wafer.

The contact of the pad conditioner debris with the semiconductor wafercan scratch, fracture, or otherwise damage the semiconductor wafer. If the semiconductor waferis damaged by the pad conditioner debris, then the semiconductor wafermay need to be scrapped. Additionally, the CMP padmay also be damaged when the pad conditioner debris comes between the surfaces of the CMP padand the semiconductor wafer. This can result in a CMP padthat needs to be scrapped or repaired. Furthermore, the accumulation of debris particles at the retaining ringcan result in damage to the retaining ring. The retaining ringmay need to be inspected, repaired, or replaced before CMP processes can begin again. Any of these occurrences leads to high costs in terms of time, resources, and money in order to fix the damage or scrap the semiconductor waferor the CMP pad. Furthermore, CMP processes may be interrupted for a period of time while repairs are made.

In order to reduce the buildup of debris particles at the retaining ring, the retaining ringin accordance with principles of the present disclosure is made of a material that is anti-electrostatic. As used herein, the term “anti-electrostatic” corresponds to a material that does not become electrostatically charged or only becomes weakly electrostatically charged. If the retaining ringcontacts the waferduring a CMP process, the retaining ringwill not become electrostatically charged, or will only become very weakly electrostatically charged. The result is that charged debris particles are not electrostatically attracted to the retaining ring. Because charged debris particles do not accumulate at the retaining ring, damage to the retaining ring, the wafer, and the padis prevented or reduced.

In some embodiments, the retaining ringis made of a blend of a Lewis acid polymer and a Lewis base polymer. A Lewis base polymer may, by itself, be prone to building up a positive electrostatic charge. If the retaining ringis made only of a Lewis base polymer, then the retaining ringmay tend to build a positive electrostatic charge during CMP processes. This can result in attracting negatively charged debris particles to the retaining ring, resulting in the various types of damage or other problems described above. A Lewis acid polymer may, by itself, be prone to building up a negative electrostatic charge. If the retaining ringis made only of a Lewis acid polymer, then the retaining ringmay tend to build a negative electrostatic charge during CMP processes.

The retaining ringofis made of a blend of a Lewis acid polymer and a Lewis base polymer. Because the retaining ringis made of a blend of a Lewis acid polymer and a Lewis base polymer, the retaining ringis largely anti-electrostatic. In other words, the tendency of the Lewis acid polymer to build up a negative electrostatic charge and the tendency of a Lewis base polymer to build up a positive electrostatic charge effectively work against each other to prevent electrostatic charge of either polarity from building up at the retaining ring. The lack of buildup of electrostatic charge at the retaining ringresults in prevention or a reduction in the buildup of charged debris particles at the retaining ring. This further results in prevention or a reduction in the various types of damage described above.

includes a graphillustrating anti-electrostatic properties of the blend of the Lewis acid polymer and the Lewis base polymer of the retaining ring, in accordance with some embodiments. The y-axis of the graphcorresponds to the zeta potential in millivolts of a retaining ring. The x-axis of the graphcorresponds to the molar ratio of the Lewis acid polymer to the Lewis base polymer of the retaining ring. The data potential corresponds to the propensity of the retaining ringto build an electrostatic charge.

If the molar ratio is close to zero (i.e., the retaining ringis nearly entirely a Lewis base polymer), then the zeta potential is highly positive. This corresponds to a relatively high propensity to build up a positive electrostatic charge. If the molar ratio is close to one (i.e., the retaining ringis nearly entirely a Lewis acid polymer), then the retaining ringhas a relatively high propensity to build up a negative electrostatic charge.

The graphillustrates a range of molar ratios between about 0.2 and 0.8 between which the retaining ringis substantially anti-electrostatic. In other words when the molar ratio of the blend of the Lewis acid polymer and the Lewis base polymer is between 0.2 and 0.8, the retaining ring is sufficiently resistant to building an electrostatic charge of either polarity that charged debris particles do not accumulate substantially at the retaining ring. This range of molar ratios can result in a substantial reduction in damage to the wafer, the retaining ring, and the pad.

In some embodiments, the molar ratio of the blend of the Lewis base polymer and the Lewis acid polymer of the retaining ringis between 0.4 and 0.6. A molar ratio in this range can result in the retaining ringbeing highly anti-electrostatic such that there is substantially no electrostatic charge at the retaining ringduring a CMP process. Accordingly, charged debris particles are not attracted to and do not build up at the retaining ringwhen the retaining ringhas a molar ratio in this range. This results in prevention or substantial reduction in damage to the wafer, the retaining ring, and the pad. In some embodiments, the retaining ringhas a molar ratio substantially equal to 0.5. This results in very highly anti-electrostatic retaining ring, potentially improving on the benefits of the previously described range. As used herein, substantially equal to 0.5 can correspond to a molar ratio between 0.48 and 0.52. Other ratios can be utilized without departing from the scope of the present disclosure.

A Lewis acid can correspond to a chemical species that contains an empty orbital that is capable of accepting an electron pair from a Lewis base in order to form a Lewis adduct. A Lewis base is a chemical species that has a filled orbital containing an electron pair that is not involved in bonding, but that may form a dative bond with a Lewis acid to form a Lewis adduct. In some embodiments, a Lewis base may correspond to a nucleophile and a Lewis acid may correspond to an electrophile.

A Lewis base polymer is a Lewis base that is a polymer. A Lewis acid polymer is a Lewis acid that is a polymer. In some embodiments the Lewis acid polymer of the retaining ringincludes one or more of Teflon, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polystyrene (PS), polyvinylidene chloride (PVDC), or polyether ether ketone (PEEK). In some embodiments, the Lewis base polymer of the retaining ringincludes one or more of nylon, polyvinyl acetate (PVAc), polylactic acid (PLA), polymethyl methacrylate (PMMA), or polyphenylene sulfide (PPS). Other Lewis acid polymers and Lewis base polymers can be utilized without departing from the scope of the present disclosure.

The CMP headhas a width dimension (or diameter) D. The retaining ringhas a width dimension Dbetween the interior surfaceand the exterior surface. The retaining ringhas a height dimension D. The waferhas a diameter D. The dimension Dis based, in part, on the diameter of the wafersthat the CMP headis intended to hold. In some embodiments, the diameter Dof the waferis 300 mm. The dimension Dis between 305 mm and 450 mm. The dimension Dis between 1 mm and 50 mm. The dimension Dis between 5 mm and 100 mm. Other dimensions can be utilized without departing from the scope of the present disclosure. In particular, if the CMP headis intended to hold wafers of diameters other than 300 mm, then various dimensions of the CMP headmay be adjusted accordingly.

In some embodiments, the lateral edgeof the waferis separated from the interior surfaceof the retaining ringby a gap when the waferis held in the CMP head. The gap may have a value between 1 mm and 5 mm, though other dimensions may be utilized without departing from the scope of the present disclosure.

In some embodiments, the CMP headincludes an inflatable membranewithin an interior volume of the CMP head. The inflatable membranecan include a plastic bag that can be filled with nitrogen gas. When the membrane is inflated, air will be squeezed out, creating a vacuum force that holds the waferin place. Furthermore, the level of inflation of the membranecan be adjusted to provide a tunable downward force on the waferduring the CMP process. Other mechanisms can be utilized to hold the waferwithin the CMP headwithout departing from the scope of the present disclosure.

In some embodiments, the body portionof the CMP headis also made of a blend of a Lewis acid polymer and a Lewis base polymer as described in relation to the retaining ring. The body portionmay be entirely or partially composed of the blend of the Lewis acid polymer and the Lewis base polymer. The body portionmay have a molar ratio resulting in the body portionbeing substantially anti-electrostatic.

In some embodiments, the retaining ringis manufactured utilizing an extruder. A linear polymer of the Lewis base and a Lewis acid powder are blended and fed into the extruder. The blend is then melted. The melted polymer solution is then extruded to fill a mold of the retaining ring. Other processes can be utilized to form the retaining ringwithout departing from the scope of the present disclosure.

is a bottom view of a retaining ring, in accordance with some embodiments. The retaining ringofis one example of the retaining ringof. The retaining ringincludes a bottom surface. A plurality of grooveshave been formed in the bottom surface. The groovescan be utilized to allow slurry or other fluids to pass from an interior of the retaining ringto the exterior of the retaining ring.

is a top view of the retaining ringof, in accordance with some embodiments. The view ofshows a top surfaceof the retaining ring. The top surfacemay be in direct contact with the body portionof the CMP head. The retaining ringincludes a plurality of couplers. The couplershelp enable secure coupling of the retaining ringto the body portionof the CMP head. The couplerscan include apertures that receive a coupling mechanism from the body portion. The coupling structurescan include protrusions that couple of apertures in the body portion. The couplerscan include clips or other types of fasteners that can securely fasten the retaining ringto the body portionof the CMP head. The couplerscan be positioned on the exterior surfacein order to clip or otherwise fasten the retaining ringto the body portionof the CMP head. The couplerscan correspond to coupling structures of various other types without departing from the scope of the present disclosure.

In some embodiments, the retaining ringis a unitary structure made entirely of the blend of the Lewis base acid and the Lewis base polymer. Alternatively, the retaining ringcan include multiple structures coupled together. The multiple structures can both include the blend of the Lewis acid polymer and the Lewis base polymer. Alternatively, one or more of the structures can include a material other than the blend of the Lewis base polymer and the Lewis acid polymer.

is a cross-sectional view of a portion of a retaining ring, in accordance with some embodiments. The retaining ringofis one example of a retaining ringof. The retaining ringincludes a lower structurein the upper structure. The lower structureincludes the blend of the Lewis base polymer and the Lewis acid polymer. The upper structureincludes a material that is different than the material of the lower structure. In some embodiments, the upper structureincludes a metal material such as stainless steel, titanium, aluminum, or another metal material. In some embodiments, the upper structureincludes a polymer material or a ceramic material. The upper surfaceof the retaining ringis the upper surface of the upper structure. The bottom surfaceof the retaining ringis the bottom surface of the lower structure.

is a cross-sectional view of a portion of a retaining ring, in accordance with some embodiments. The retaining ringofis one example of a retaining ringof. The retaining ringincludes a core structuresurrounded by a polymer material. The core structurecan include a metal material such as stainless steel, aluminum, titanium, or other suitable materials. The polymer materialcorresponds is a blend of the Lewis base polymer and the Lewis acid polymer, as described previously. Accordingly, the core structureis embedded within the polymer material. The core structure can have other materials without departing from the scope of the present disclosure.

is a bottom view of a CMP head, in accordance with some embodiments. The CMP headofis one example of a CMP headof. The retaining ringis coupled to the CMP head. The interior of the CMP headincludes a plurality of contours of metal materialof an interior surface of the CMP head. The inflatable membraneis not present in the view of.

is a perspective view of a CMP head, in accordance with some embodiments. The CMP headofis one example of a CMP headof. The perspective view ofillustrates the retaining ringcoupled to the body portion. The exterior of the body portionmay include plastic material. The interior of the body portionmay include a metal material, as shown in relation to. The CMP headcan include other configurations and components without departing from the scope of the present disclosure.

is a simplified cross-sectional view of a portion of a wafer, in accordance with some embodiments. The waferincludes a semiconductor substrate. The semiconductor substrate can include silicon, silicon germanium, or other suitable semiconductor materials. The semiconductor fins or channel stacksextend from the substrate. Though not shown in, the channel stackscan each include a plurality of separate channels of a transistor. The metal gatemay wrap around each of the channels in the configuration of a gate all around transistor. The metal gateis shown as a single layer, but may include a plurality of metal layers and structures. The metal gatecan include tungsten, titanium, titanium nitride, tantalum nitride, cobalt, ruthenium, or other suitable conductive materials. The simplified view ofdoes not illustrate how the metal gatemay wrap around each of the channels. Furthermore, source/drain regions are not illustrated in.

The fins or channel stacksare separated from each other by shallow trench isolation. The shallow trench isolationcan include silicon oxide, silicon nitride, SiCN, SiCON, SiON, or other suitable dielectric materials.

A dielectric layerhas been formed on the metal gate. The dielectric layercan include silicon nitride, silicon oxide, SiCN, SiCON, SiON, or other suitable dielectric materials.

A layerhas been formed on the layer. The layercan include amorphous silicon, a dielectric material, or other types of material. The dielectric layerhas been formed on the layer. The dielectric layercan correspond to a hard mask layer. The hard mask layer can include silicon nitride, silicon oxide, SiCN, SiCON, SiON, or other suitable dielectric materials. A trenchhas been formed through the layers,,, and. The trench separates portions of the metal gatein order to electrically isolate the gate electrodes of various transistors. The trenchmay be termed a cut metal gate trench.

A dielectric liner layerhas been formed on the sidewalls of the trenchand on the top surface of the layer. The dielectric liner layercan include silicon nitride, silicon oxide, SiCN, SiCON, SiON, or other suitable dielectric materials. The dielectric layerhas been formed on the dielectric layerand filling the trench. The dielectric layercan include silicon nitride, silicon oxide, SiCN, SiCON, SiON, or other suitable dielectric materials. The various layers can be formed by thin film deposition processes or other deposition processes.

In, a first CMP step of a CMP process has been performed. During the CMP process, the waferis held within the CMP head. In particular, the interior surfaceof the retaining ringlaterally surrounds the lateral surfaceof the wafer. The first CMP step rapidly removes the layers,,and stops at the layer. The first CMP step may include a first type of slurry and first rotation and downward pressure parameters of the CMP head. The first CMP step corresponds to a bulk polishing with a higher removal rate to remove the dielectric layerand the hard mask layerwith a high removal rate. The retaining ringsurrounds the waferduring the first CMP step.

In, a second CMP step of the CMP process has been performed. A second slurry different than the first slurry may be used during the second CMP step in order to remove the layersand. Furthermore, the second CMP step removes a portion of the gate metaland the fins or channel stackssuch that the metal gateof each transistor is electrically isolated from the others. The second CMP step etches at a rate that is slower than the etching rate of the first CMP step. Furthermore, the second CMP step may utilize other rotation and downward pressure parameters of the CMP head. The second CMP step corresponds to a bulk polishing to achieve a smooth surface. The retaining ringsurrounds the waferduring the second CMP step.

Because the anti-electrostatic retaining ringis mounted on the CMP headduring the first and second CMP step of the CMP process, an electrostatic charge does not build up at the retaining ring. This results in a reduction or complete prevention of gathering of charged debris particles at the retaining ring. This further results in reduced damage to the wafer.

is a flow diagram of a method, in accordance with some embodiments. The methodcan utilize components, processes, and systems described in relation to. At, the methodincludes rotating a CMP pad. One example of a CMP pad is the CMP padof. At, the methodincludes supplying a slurry onto the pad. One example of a slurry is the slurryof. At, the methodincludes holding a wafer with a CMP head including a retaining ring that is a blend of a Lewis acid polymer and Lewis base polymer surrounding a lateral edge of the wafer. One example of a wafer is the waferof. One example of a CMP head is the CMP headof. One example of a retaining ring is the retaining ringof. One example of a lateral edge is the lateral edgeof. At, the methodincludes placing the wafer in contact with the CMP pad.