US20250312886A1

US20250312886A1 - Device and method for improved cmp process with cmp head

Info

Publication number: US20250312886A1
Application number: US18/628,006
Authority: US
Inventors: Chen-hsueh Lin; Tang-Kuei Chang; Chi-hsiang Shen; Da-Shiuan CHIOU; Te-Chien Hou; Kei-Wei Chen
Original assignee: Taiwan Semiconductor Manufacturing Co TSMC Ltd
Current assignee: Taiwan Semiconductor Manufacturing Co TSMC Ltd
Priority date: 2024-04-05
Filing date: 2024-04-05
Publication date: 2025-10-09

Abstract

A chemical mechanical planarization (CMP) head holds a wafer during a CMP process. The CMP head includes a blend of a Lewis acid polymer and a Lewis base polymer. The blend of the Lewis acid polymer and the Lewis base polymer renders the CMP head anti-electrostatic. This helps ensure that an electrostatic charge does not build up around the bottom of the CMP head during a CMP process. This helps ensure that charged debris particles do not accumulate at the CMP head.

Description

BACKGROUND

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.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1A is a simplified cross-sectional view of a CMP head, in accordance with some embodiments.

FIG. 1B is a simplified side view of a CMP system, in accordance with some embodiments.

FIG. 1C is a graph of a molar ratio of a Lewis acid polymer and a Lewis base polymer, in accordance with some embodiments.

FIG. 2A is a bottom view of a retaining ring of a CMP head, in accordance with some embodiments.

FIG. 2B is a top view of the retaining ring of a CMP head, in accordance with some embodiments.

FIG. 3 is a cross-sectional view of a portion of a retaining ring of a CMP head, in accordance with some embodiments.

FIG. 4 is a cross-sectional view of a portion of a retaining ring of a CMP head, in accordance with some embodiments.

FIG. 5 is a bottom view of a CMP head, in accordance with some embodiments.

FIG. 6 is a perspective view of a CMP head, in accordance with some embodiments.

FIGS. 7A-7C are cross-sectional views of a wafer at various stages of processing, in accordance with some embodiments.

FIG. 8 is a flow diagram of a method for performing a CMP process, in accordance with some embodiments.

FIG. 9 is a flow diagram of a method for forming an integrated circuit, in accordance with some embodiments.

DETAILED DESCRIPTION

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.
FIG. 1A is a simplified cross-sectional view of a CMP head 102 that is utilized in CMP processes, in accordance with some embodiments. FIG. 1B is a side view of a CMP system 100 of which the CMP head 102 of FIG. 1A is part, in accordance with some embodiments. FIG. 1C is a graph illustrating electrostatic properties of a CMP head 102 of FIG. 1A, in accordance with some embodiments. The description of the CMP head 102 of FIG. 1A will also reference the illustrations of FIGS. 1B and 1C.
The CMP head 102 of FIG. 1A includes a main CMP body 104 and a retaining ring 106. The retaining ring 106 is coupled or otherwise fixed to the main CMP body 104. The CMP head 102 also includes a membrane 108 within an interior of the CMP head 102. The CMP head 102 holds a wafer 110 during a CMP process. As will be set forth in more detail below, the components of the CMP head 102 cooperate to help reduce or prevent damage to the wafer 110 and to the CMP head 102.
Prior to further description of the CMP head 102 of FIG. 1A, the description of the CMP system 100 will be provided in relation to FIG. 1B. The CMP system 100 includes a platen 111, a CMP head 102, a slurry supply system 115, and a pad conditioner 117. The components of the CMP system 100 cooperate 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 head 102 helps to prevent damage to CMP equipment and semiconductor wafers.
In one embodiment, the platen 111 is a flat circular surface. The platen 111 is configured to rotate during CMP processes. The platen 111 may 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 platen 111 can be coupled to a shaft that drives the rotation of the CMP platen 111. The platen 111 may 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 system 100 includes a CMP pad 113. The CMP pad 113 is positioned on top of the platen 111. The CMP pad 113 may be circular and may have a diameter that is substantially identical to the diameter of the platen 111. The CMP pad 113 may be coupled to the platen 111 by fasteners, by suction (i.e., pressure differential), by electrostatic force, or in any suitable way. When the platen 111 rotates, the CMP pad 113 also rotates. The rotation of the CMP pad 113 is one of the factors that planarizes the semiconductor wafer 110, as will be described in more detail below.
The CMP pad 113 can be made of a porous material. In one example, the CMP pad 113 is made from a polymeric material having a pore size between 20 micrometers and 50 micrometers. The CMP pad 113 may have a roughness of about 50 μm. Other materials, dimensions, and structures of a CMP pad 113 can be utilized without departing from the scope of the present disclosure. The CMP pad 113 may be substantially rigid.
The slurry supply system 115 supplies a slurry 126 onto the rotating CMP pad 113 during the CMP process. The slurry 126 can 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 110. Accordingly, the compounds in the slurry 126 are selected based on the material or materials of the surface features of the semiconductor wafer 110 to be planarized. The slurry supply system 115 can include a tank 121 that holds the slurry 126 and a tube 123 or hose coupled between a nozzle 125 and the tank 121. The nozzle 125 delivers the slurry 126 onto the rotating CMP pad 113 during the CMP process.
In some embodiments, the abrasive in the slurry 126 can include silica or cerium oxide produced via colloidal process or calcined. The pH value of the slurry 126 can range between 2 and 9. In some embodiments, the slurry may include a tungsten inhibitor to prevent tungsten corrosion. The slurry 126 can 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 conditioner 117 conditions the rotating CMP pad 113 during the CMP process. During the CMP process, the top surface of the rotating CMP pad 113 experiences wear from the planarization process. The top surface of the CMP pad 113 may wear out unevenly such that depressions, valleys, and peaks may form in the CMP pad 113. The pad conditioner 117 includes a rotating pad conditioner head 127 that is pressed downward onto the rotating CMP pad 113. The rotating pad conditioner head 127 includes or is coated with a hard, durable material that can effectively sand down the surface of the CMP pad 113. In one example, the surface of the pad conditioner 117 includes a diamond material. The rotating head of the pad conditioner 117 sweeps across the surface of the rotating CMP pad 113 in a pattern selected to maintain a substantially even top surface of the CMP pad 113 during the CMP process. Accordingly, the pad conditioner 117 removes or prevents the formation of depressions, ridges, valleys, or uneven features on the surface of the rotating CMP pad 113.
During the CMP process, the CMP head 102 places the downward facing surface of the semiconductor wafer 110 into contact with the rotating CMP pad 113. The CMP head 102 may also rotate the semiconductor wafer 110 during the CMP process. Surface features of the downward facing surface of the semiconductor wafer 110 are 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 pad 113 rubbing down the bottom facing surface of the semiconductor wafer 110. 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 110. 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 110. The result of the CMP process is that the exposed bottom facing surface of the semiconductor wafer 110 becomes substantially planar.
While the CMP process may be generally effective, several problems may arise that can damage the equipment of the CMP system 100 and the semiconductor wafer 110. For example, it is possible that some of the surface material of the pad conditioner 117 may break off or otherwise become dislodged from the pad conditioner 117. This results in pad conditioner debris on the rotating CMP pad 113. The debris can include grains, particles, shards, or fragments of the material from the pad conditioner 117. The rotating CMP pad 113 may carry the pad conditioner debris into contact with the retaining ring 106 of the CMP head 102.
Another potential source of debris 129 is the crystallization of the slurry during the CMP process. When the slurry is provided onto the surface of the rotating CMP pad 113, the rotation of the CMP pad 113 causes the slurry to flow toward the outer perimeter of the CMP pad 113 and off of the CMP pad 113. Nevertheless, it is possible that some portion of the slurry may not quickly flow off of the CMP pad 113. This portion of the slurry may crystallize.
During the CMP process, it is possible that the lateral edge of the wafer 110 can collide with the retaining ring 106. It is possible that this repeated contact can result in a buildup of electrostatic charge at the retaining ring 106. If there is a buildup of electrostatic charge at the retaining ring 106, it is possible that charged debris particles from the debris 129 can be attracted to the retaining ring 106 and can build up at the retaining ring 106. Some debris particles can accumulate at the interior edge of the retaining ring 106. This can result in trapped debris particles repeatedly contacting the wafer 110.
The contact of the pad conditioner debris with the semiconductor wafer 110 can scratch, fracture, or otherwise damage the semiconductor wafer 110. If the semiconductor wafer 110 is damaged by the pad conditioner debris, then the semiconductor wafer 110 may need to be scrapped. Additionally, the CMP pad 113 may also be damaged when the pad conditioner debris comes between the surfaces of the CMP pad 113 and the semiconductor wafer 110. This can result in a CMP pad 113 that needs to be scrapped or repaired. Furthermore, the accumulation of debris particles at the retaining ring 106 can result in damage to the retaining ring 106. The retaining ring 106 may 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 wafer 110 or the CMP pad 113. 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 106, the retaining ring 106 in 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 ring 106 contacts the wafer 110 during a CMP process, the retaining ring 106 will 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 106. Because charged debris particles do not accumulate at the retaining ring 106, damage to the retaining ring 106, the wafer 110, and the pad 113 is prevented or reduced.
In some embodiments, the retaining ring 106 is 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 ring 106 is made only of a Lewis base polymer, then the retaining ring 106 may tend to build a positive electrostatic charge during CMP processes. This can result in attracting negatively charged debris particles to the retaining ring 106, 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 ring 106 is made only of a Lewis acid polymer, then the retaining ring 106 may tend to build a negative electrostatic charge during CMP processes.
The retaining ring 106 of FIGS. 1A and 1B is made of a blend of a Lewis acid polymer and a Lewis base polymer. Because the retaining ring 106 is made of a blend of a Lewis acid polymer and a Lewis base polymer, the retaining ring 106 is 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 106. The lack of buildup of electrostatic charge at the retaining ring 106 results in prevention or a reduction in the buildup of charged debris particles at the retaining ring 106. This further results in prevention or a reduction in the various types of damage described above.
FIG. 1C includes a graph 101 illustrating anti-electrostatic properties of the blend of the Lewis acid polymer and the Lewis base polymer of the retaining ring 106, in accordance with some embodiments. The y-axis of the graph 101 corresponds to the zeta potential in millivolts of a retaining ring 106. The x-axis of the graph 101 corresponds to the molar ratio of the Lewis acid polymer to the Lewis base polymer of the retaining ring 106. The data potential corresponds to the propensity of the retaining ring 106 to build an electrostatic charge.
If the molar ratio is close to zero (i.e., the retaining ring 106 is 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 ring 106 is nearly entirely a Lewis acid polymer), then the retaining ring 106 has a relatively high propensity to build up a negative electrostatic charge.
The graph 101 illustrates a range of molar ratios between about 0.2 and 0.8 between which the retaining ring 106 is 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 106. This range of molar ratios can result in a substantial reduction in damage to the wafer 110, the retaining ring 106, and the pad 113.
In some embodiments, the molar ratio of the blend of the Lewis base polymer and the Lewis acid polymer of the retaining ring 106 is between 0.4 and 0.6. A molar ratio in this range can result in the retaining ring 106 being highly anti-electrostatic such that there is substantially no electrostatic charge at the retaining ring 106 during a CMP process. Accordingly, charged debris particles are not attracted to and do not build up at the retaining ring 106 when the retaining ring 106 has a molar ratio in this range. This results in prevention or substantial reduction in damage to the wafer 110, the retaining ring 106, and the pad 113. In some embodiments, the retaining ring 106 has a molar ratio substantially equal to 0.5. This results in very highly anti-electrostatic retaining ring 106, 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 ring 106 includes 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 ring 106 includes 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 head 102 has a width dimension (or diameter) D1. The retaining ring 106 has a width dimension D2 between the interior surface 107 and the exterior surface 133. The retaining ring 106 has a height dimension D3. The wafer 110 has a diameter D4. The dimension D1 is based, in part, on the diameter of the wafers 110 that the CMP head 102 is intended to hold. In some embodiments, the diameter D4 of the wafer 110 is 300 mm. The dimension D1 is between 305 mm and 450 mm. The dimension D2 is between 1 mm and 50 mm. The dimension D3 is 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 head 102 is intended to hold wafers of diameters other than 300 mm, then various dimensions of the CMP head 102 may be adjusted accordingly.
In some embodiments, the lateral edge 109 of the wafer 110 is separated from the interior surface 107 of the retaining ring 106 by a gap when the wafer 110 is held in the CMP head 102. 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 head 102 includes an inflatable membrane 108 within an interior volume of the CMP head 102. The inflatable membrane 108 can 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 wafer 110 in place. Furthermore, the level of inflation of the membrane 108 can be adjusted to provide a tunable downward force on the wafer 110 during the CMP process. Other mechanisms can be utilized to hold the wafer 110 within the CMP head 102 without departing from the scope of the present disclosure.
In some embodiments, the body portion 104 of the CMP head 102 is also made of a blend of a Lewis acid polymer and a Lewis base polymer as described in relation to the retaining ring 106. The body portion 104 may be entirely or partially composed of the blend of the Lewis acid polymer and the Lewis base polymer. The body portion 104 may have a molar ratio resulting in the body portion 104 being substantially anti-electrostatic.
In some embodiments, the retaining ring 106 is 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 ring 106 without departing from the scope of the present disclosure.
FIG. 2A is a bottom view of a retaining ring 106, in accordance with some embodiments. The retaining ring 106 of FIG. 2A is one example of the retaining ring 106 of FIG. 1A. The retaining ring 106 includes a bottom surface 135. A plurality of grooves 137 have been formed in the bottom surface 135. The grooves 137 can be utilized to allow slurry or other fluids to pass from an interior of the retaining ring 106 to the exterior of the retaining ring 106.
FIG. 2B is a top view of the retaining ring 106 of FIG. 2A, in accordance with some embodiments. The view of FIG. 2B shows a top surface 139 of the retaining ring 106. The top surface 139 may be in direct contact with the body portion 104 of the CMP head 102. The retaining ring 106 includes a plurality of couplers 141. The couplers 141 help enable secure coupling of the retaining ring 106 to the body portion 104 of the CMP head 102. The couplers 141 can include apertures that receive a coupling mechanism from the body portion 104. The coupling structures 141 can include protrusions that couple of apertures in the body portion 104. The couplers 141 can include clips or other types of fasteners that can securely fasten the retaining ring 106 to the body portion 104 of the CMP head 102. The couplers 141 can be positioned on the exterior surface 133 in order to clip or otherwise fasten the retaining ring 106 to the body portion 104 of the CMP head 102. The couplers 141 can correspond to coupling structures of various other types without departing from the scope of the present disclosure.
In some embodiments, the retaining ring 106 is a unitary structure made entirely of the blend of the Lewis base acid and the Lewis base polymer. Alternatively, the retaining ring 106 can 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.
FIG. 3 is a cross-sectional view of a portion of a retaining ring 106, in accordance with some embodiments. The retaining ring 106 of FIG. 3 is one example of a retaining ring 106 of FIG. 1A. The retaining ring 106 includes a lower structure 143 in the upper structure 145. The lower structure 143 includes the blend of the Lewis base polymer and the Lewis acid polymer. The upper structure 145 includes a material that is different than the material of the lower structure 143. In some embodiments, the upper structure 145 includes a metal material such as stainless steel, titanium, aluminum, or another metal material. In some embodiments, the upper structure 145 includes a polymer material or a ceramic material. The upper surface 139 of the retaining ring 106 is the upper surface of the upper structure 145. The bottom surface 135 of the retaining ring 106 is the bottom surface of the lower structure 143.
FIG. 4 is a cross-sectional view of a portion of a retaining ring 106, in accordance with some embodiments. The retaining ring 106 of FIG. 3 is one example of a retaining ring 106 of FIG. 1A. The retaining ring 106 includes a core structure 147 surrounded by a polymer material 149. The core structure 147 can include a metal material such as stainless steel, aluminum, titanium, or other suitable materials. The polymer material 149 corresponds is a blend of the Lewis base polymer and the Lewis acid polymer, as described previously. Accordingly, the core structure 147 is embedded within the polymer material 149. The core structure can have other materials without departing from the scope of the present disclosure.
FIG. 5 is a bottom view of a CMP head 102, in accordance with some embodiments. The CMP head 102 of FIG. 5 is one example of a CMP head 102 of FIG. 1A. The retaining ring 106 is coupled to the CMP head 102. The interior of the CMP head 102 includes a plurality of contours of metal material 151 of an interior surface of the CMP head 102. The inflatable membrane 108 is not present in the view of FIG. 5 .
FIG. 6 is a perspective view of a CMP head 102, in accordance with some embodiments. The CMP head 102 of FIG. 6 is one example of a CMP head 102 of FIG. 1A. The perspective view of FIG. 6 illustrates the retaining ring 106 coupled to the body portion 104. The exterior of the body portion 104 may include plastic material. The interior of the body portion 104 may include a metal material, as shown in relation to FIG. 5 . The CMP head 102 can include other configurations and components without departing from the scope of the present disclosure.
FIG. 7A is a simplified cross-sectional view of a portion of a wafer 110, in accordance with some embodiments. The wafer 110 includes a semiconductor substrate 161. The semiconductor substrate can include silicon, silicon germanium, or other suitable semiconductor materials. The semiconductor fins or channel stacks 163 extend from the substrate 161. Though not shown in FIG. 7A, the channel stacks 163 can each include a plurality of separate channels of a transistor. The metal gate 165 may wrap around each of the channels in the configuration of a gate all around transistor. The metal gate 165 is shown as a single layer, but may include a plurality of metal layers and structures. The metal gate 165 can include tungsten, titanium, titanium nitride, tantalum nitride, cobalt, ruthenium, or other suitable conductive materials. The simplified view of FIG. 7A does not illustrate how the metal gate 165 may wrap around each of the channels. Furthermore, source/drain regions are not illustrated in FIG. 7A.
The fins or channel stacks 163 are separated from each other by shallow trench isolation 164. The shallow trench isolation 164 can include silicon oxide, silicon nitride, SiCN, SiCON, SiON, or other suitable dielectric materials.
A dielectric layer 167 has been formed on the metal gate 165. The dielectric layer 167 can include silicon nitride, silicon oxide, SiCN, SiCON, SiON, or other suitable dielectric materials.
A layer 169 has been formed on the layer 167. The layer 169 can include amorphous silicon, a dielectric material, or other types of material. The dielectric layer 171 has been formed on the layer 169. The dielectric layer 171 can 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 trench 177 has been formed through the layers 171, 169, 167, and 165. The trench separates portions of the metal gate 165 in order to electrically isolate the gate electrodes of various transistors. The trench 177 may be termed a cut metal gate trench.
A dielectric liner layer 173 has been formed on the sidewalls of the trench 177 and on the top surface of the layer 171. The dielectric liner layer 173 can include silicon nitride, silicon oxide, SiCN, SiCON, SiON, or other suitable dielectric materials. The dielectric layer 175 has been formed on the dielectric layer 173 and filling the trench 177. The dielectric layer 175 can 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 FIG. 7B, a first CMP step of a CMP process has been performed. During the CMP process, the wafer 110 is held within the CMP head 102. In particular, the interior surface 107 of the retaining ring 106 laterally surrounds the lateral surface 109 of the wafer 110. The first CMP step rapidly removes the layers 175, 173, 171 and stops at the layer 169. The first CMP step may include a first type of slurry and first rotation and downward pressure parameters of the CMP head 102. The first CMP step corresponds to a bulk polishing with a higher removal rate to remove the dielectric layer 175 and the hard mask layer 171 with a high removal rate. The retaining ring 106 surrounds the wafer 110 during the first CMP step.
In FIG. 7C, 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 layers 169 and 167. Furthermore, the second CMP step removes a portion of the gate metal 165 and the fins or channel stacks 163 such that the metal gate 165 of 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 102. The second CMP step corresponds to a bulk polishing to achieve a smooth surface. The retaining ring 106 surrounds the wafer 110 during the second CMP step.
Because the anti-electrostatic retaining ring 106 is mounted on the CMP head 102 during the first and second CMP step of the CMP process, an electrostatic charge does not build up at the retaining ring 106. This results in a reduction or complete prevention of gathering of charged debris particles at the retaining ring 106. This further results in reduced damage to the wafer 110.
FIG. 8 is a flow diagram of a method 800, in accordance with some embodiments. The method 800 can utilize components, processes, and systems described in relation to FIGS. 1A-7C. At 802, the method 800 includes rotating a CMP pad. One example of a CMP pad is the CMP pad 113 of FIG. 1A. At 804, the method 800 includes supplying a slurry onto the pad. One example of a slurry is the slurry 126 of FIG. 1B. At 806, the method 800 includes 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 wafer 110 of FIG. 1A. One example of a CMP head is the CMP head 102 of FIG. 1A. One example of a retaining ring is the retaining ring 106 of FIG. 1A. One example of a lateral edge is the lateral edge 109 of FIG. 1A. At 808, the method 800 includes placing the wafer in contact with the CMP pad.
FIG. 9 is a flow diagram of a method 900 for forming an integrated circuit including a plurality of transistors, in accordance with some embodiments. The method 900 can utilize the processes, components, and systems described in relation to FIGS. 1A-7C. At 902, the method 900 includes forming a layer on a wafer with a thin film deposition process. One example of a wafer is the wafer 110 of FIG. 7A. One example of a layer is the layer 175 of FIG. 7A. At 904, the method 900 includes loading the wafer onto a CMP head, wherein a lateral surface of the wafer is surrounded by a retaining ring when the wafer is loaded onto the CMP head, wherein the retaining ring is a blend of a Lewis acid polymer and a Lewis base polymer. One example of a CMP head is the CMP head 102 of FIG. 1A. One example of a lateral surface is the lateral surface 109 of FIG. 1A. One example of a retaining ring is the retaining ring 106 of FIG. 1A. At 906, the method 900 includes at least partially removing the layer by performing a CMP process on the wafer while the wafer is loaded onto the CMP head.
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.
In one embodiment, a method includes rotating a CMP pad. The method includes supplying a slurry onto the pad. The method includes 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. The method includes placing the wafer in contact with the CMP pad.
In one embodiment, a device includes a retaining ring for a CMP head. The retaining ring includes an annular interior surface configured to surround a wafer during a CMP process. The retaining ring includes a bottom surface configured to contact a CMP pad during a CMP process. The retaining ring includes a coupler configured to fixedly couple the retaining ring to the CMP head during the CMP process. The retaining ring includes a Lewis acid polymer and a Lewis base polymer blended together.
In one embodiment, a method includes forming an integrated circuit including a plurality of transistors. The method includes forming a layer on a wafer with a thin film deposition process. The method includes loading the wafer onto a CMP head, wherein a lateral surface of the wafer is surrounded by a retaining ring when the wafer is loaded onto the CMP head. The retaining ring is a blend of a Lewis acid polymer and Lewis base polymer. The method includes at least partially removing the layer by performing a CMP process on the wafer while the wafer is loaded onto the CMP head.
In one embodiment, a device includes a retaining ring for a chemical mechanical planarization (CMP) head. The retaining ring includes an annular interior surface, a bottom surface configured to contact a CMP pad, and a coupler configured to fixedly couple the retaining ring to the CMP head. The retaining ring includes a Lewis acid polymer and a Lewis base polymer blended together.
In one embodiment, a method includes forming a layer on a wafer with a thin film deposition process and loading the wafer onto a chemical mechanical planarization (CMP) head. A lateral surface of the wafer is surrounded by a retaining ring when the wafer is loaded onto the CMP head. The retaining ring is a blend of a Lewis acid polymer and Lewis base polymer. The method includes at least partially removing the layer by performing a CMP process on the wafer while the wafer is loaded onto the CMP head.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

1. A method, comprising:

rotating a chemical mechanical planarization (CMP) pad;

supplying a slurry onto the CMP pad;

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; and

placing the wafer in contact with the CMP pad.

2. The method of claim 1, wherein a molar ratio of the Lewis acid polymer to the Lewis base polymer of the retaining ring is between 0.2 and 0.8.

3. The method of claim 2, wherein the molar ratio of the Lewis acid polymer to the Lewis base polymer of the retaining ring is between 0.4 and 0.6.

4. The method of claim 1, wherein a bottom surface of the retaining ring is in contact with the slurry.

5. The method of claim 1, wherein the Lewis base polymer includes one or more of nylon, PVAc, PLA, PMMA, and PPS.

6. The method of claim 1, wherein the Lewis acid polymer includes one or more of PVDF, PVC, PS, PVDC, and PEEK.

7. The method of claim 1, wherein the retaining ring is anti-electrostatic.

8. The method of claim 1, wherein the slurry includes an abrasive including silica or cerium oxide, wherein the retaining ring resists developing an electrostatic charge from contact with the abrasive.

9. The method of claim 1, further comprising performing a multistep CMP process on the wafer while the retaining ring surrounds the wafer.

10. The method of claim 9, wherein the multistep CMP process includes a first step with a first removal rate and a second step with a second removal rate smaller than the first removal rate.

11. A device, comprising:

a retaining ring for a chemical mechanical planarization (CMP) head, the retaining ring including:

an annular interior surface;

a bottom surface configured to contact a CMP pad;

a coupler configured to fixedly couple the retaining ring to the CMP head, wherein the retaining ring includes a Lewis acid polymer and a Lewis base polymer blended together.

12. The device of claim 11, wherein the retaining ring includes a metal portion coupled to the blend of the Lewis Acid polymer and the Lewis base polymer.

13. The device of claim 12, wherein a molar ratio of the Lewis acid polymer to the Lewis base polymer is between 0.2 and 0.8.

14. The device of claim 11, further comprising grooves in the bottom surface of the retaining ring.

15. The device of claim 11, wherein the Lewis base polymer includes one or more of nylon, PVAc, PLA, PMMA, and PPS.

16. The device of claim 11, wherein the Lewis acid polymer includes one or more of PVDF, PVC, PS, PVDC, and PEEK.

17. The device of claim 11, wherein the retaining ring includes a metal core surrounded by the blend of the Lewis base polymer and the Lewis acid polymer.

18. A method, comprising:

forming a layer on a wafer with a thin film deposition process;

loading the wafer onto a chemical mechanical planarization (CMP) head, wherein a lateral surface of the wafer is surrounded by a retaining ring when the wafer is loaded onto the CMP head, wherein the retaining ring is a blend of a Lewis acid polymer and Lewis base polymer; and

at least partially removing the layer by performing a CMP process on the wafer while the wafer is loaded onto the CMP head.

19. The method of claim 18, wherein the layer is a dielectric material formed in a trench to isolate two gate electrodes formed on the wafer.

20. The method of claim 18, wherein the CMP process includes a first stage and a second stage having a lower removal rate than a removal rate of the first stage.