CMP POLISHING PAD WITH PHASE CHANGING MATERIALS

Description

FIELD

Embodiments of the present disclosure relate generally to Chemical Mechanical Polishing (CMP), and more particularly CMP polishing pads with phase changing materials (PCM).

BACKGROUND

The semiconductor industry has experienced rapid growth due to ongoing improvements in the integration density of a variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, improvement in integration density has resulted from iterative reduction of minimum feature size, which allows more components to be integrated into a given area.

While some integrated device manufacturers (IDMs) design and manufacture integrated circuits (IC) themselves, fabless semiconductor companies outsource semiconductor fabrication to semiconductor fabrication plants or foundries. Semiconductor fabrication consists of a series of processes in which a device structure is manufactured by applying a series of layers onto a substrate. This involves the deposition and removal of various dielectric, semiconductor, and metal layers. The areas of the layer that are to be deposited or removed are controlled through photolithography. Each deposition and removal process is generally followed by cleaning as well as inspection steps. Therefore, both IDMs and foundries rely on numerous semiconductor equipment and semiconductor fabrication materials, often provided by vendors. There is always a need for customizing or improving those semiconductor equipment and semiconductor fabrication materials, which results in more flexibility, reliability, and cost-effectiveness.

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. 1 is a block diagram illustrating an example CMP system in accordance with some embodiments.

FIG. 2 is a diagram illustrating an example of a temperature-heat relationship of a PCM in accordance with some embodiments.

FIG. 3 is a diagram illustrating the comparison between a temperature-heat relationship of a polishing pad without PCM and that of a polishing pad with PCM according to some embodiments.

FIG. 4 is a cross-sectional diagram illustrating an example of a polishing pad in accordance with some embodiment.

FIG. 5 is a cross-sectional diagram illustrating an example of a polishing pad in accordance with some embodiment.

FIG. 6 is a cross-sectional diagram illustrating an example of a polishing pad in accordance with some embodiment.

FIG. 7 is a flowchart diagram illustrating an example method for making a CMP polishing pad in accordance with some embodiments.

FIG. 8 is a diagram illustrating the method shown in FIG. 7 in accordance with some embodiments.

FIG. 9 is a flowchart diagram illustrating an example method for making a CMP polishing pad in accordance with some embodiments.

FIG. 10 is a diagram illustrating the method shown in FIG. 9 in accordance with some embodiments.

DETAILED DESCRIPTION OF THE INVENTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. 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.

In addition, source/drain region(s) may refer to a source or a drain, individually or collectively dependent upon the context. For example, a device may include a first source/drain region and a second source/drain region, among other components. The first source/drain region may be a source region, whereas the second source/drain region may be a drain region, or vice versa. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

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.

Some embodiments of the disclosure are described. Additional operations can be provided before, during, and/or after the stages described in these embodiments. Some of the stages that are described can be replaced or eliminated for different embodiments. Some of the features described below can be replaced or eliminated and additional features can be added for different embodiments. Although some embodiments are discussed with operations performed in a particular order, these operations may be performed in another logical order.

Overview

Chemical Mechanical Polishing (CMP) is a critical process used in semiconductor manufacturing to achieve the necessary planarity and smoothness of the wafer surfaces. This process is particularly vital in the fabrication of integrated circuits (ICs) and other microelectronic devices, where even minor surface irregularities can lead to significant performance issues or defects. CMP combines both chemical and mechanical forces to remove material from a wafer surface. CMP is commonly used in various applications, such as planarization for subsequent photolithography and etching steps, interlayer dielectric (ILD) planarization, trench planarization for shallow trench isolation (STI), metal polishing, and the like.

CMP typically involves the following components: abrasive slurry (or simply “slurry”), a CMP polishing pad (or simply a “polishing pad”), and a carrier head (e.g., a rotating wafer holder). Abrasive slurry is a mixture of abrasive particles suspended in a chemical solution and plays a dual role, namely providing the mechanical action through the abrasive particles and the chemical action through the solution, which reacts with the wafer material to facilitate its removal. The carrier head holds the wafer in place and applies pressure, ensuring uniform contact between the wafer and the polishing pad.

The wafer is placed on a rotating polishing pad, which provides the mechanical force necessary to achieve the desired planarity. The polishing pad can be made from various materials. However, there are some challenges related to the polishing pad. One of those is temperature regulation during the CMP process.

In the CMP process, the polishing pad can experience heating due to a combination of mechanical and chemical interactions. One source of heating is mechanical friction. As the wafer is pressed against the polishing pad, the frictional forces generated by the abrasive particles in the slurry rubbing against both the wafer and the pad cause heat. The higher the contact pressure, the more friction and, consequently, more heat. The rotational movement of the polishing pad and the wafer also contributes to friction. Faster rotations increase frictional forces, leading to higher temperatures. Another source of heating is chemical reactions. The chemical reactions between the slurry and the wafer surface can be exothermic (i.e., releasing heat). For example, the oxidation and subsequent removal of materials like silicon dioxide or metal layers can generate heat.

This heating is an inherent aspect of the CMP process and can have significant implications for the effectiveness and quality of polishing. For instance, the heating can lead to the quick wear and degradation of the polishing pad. The heating can also impact slurry performance because the temperature rise can change the viscosity of the slurry, affecting its distribution and the efficiency of the polishing process. Higher temperatures can increase the rate of chemical reactions in the slurry, potentially leading to faster material removal but also increasing the risk of defects. Lastly, this heating can affect the wafer quality. Differential heating can cause thermal expansion in the wafer, leading to stress and potential defects such as warping or cracking. Excessive heat can exacerbate issues like dishing and erosion, particularly in softer materials or high pattern density features.

Moreover, temperature is one of the most crucial factors to control removal rates in the CMP process. However, the exact temperature at the interface between the polishing pad and the wafer during the CMP process is extremely hard to measure in real time. Controlling it in real time is even more challenging, if not impossible. Existing techniques, such as using thermoelectric pumps, specialized slurry compositions, or heating/cooling air to achieve temperature control, can only control the pad temperature outside the polishing zone.

In accordance with some aspects of the disclosure, a novel CMP polishing pad is provided. PCM is embedded in the CMP polishing pad. As will be explained further below, the embedded phase-change material allows for better temperature regulation.

Exemplary Polishing Pads with PCM

FIG. 1 is a block diagram illustrating an example CMP system 100 in accordance with some embodiments. In the example shown in FIG. 1, the CMP system (or “CMP apparatus”) 100 includes, among other components, a rotating wafer holder 114, a polishing pad 112, a rotating platform 126, and an abrasive slurry supply equipment 128. The rotating wafer holder 113 is operable to hold a wafer 110 to be subject a CMP process and rotate along an axis (which extends in a vertical direction, as shown in FIG. 1).

On the other hand, the polishing pad 112 is mounted to the rotating platform 126 by one or more adhesives (e.g., double-sided adhesive tapes, pressure-sensitive adhesives, epoxy adhesives, silicone adhesives, hot melt adhesives, contact adhesives, etc.). These adhesives ensure that the polishing pad 112 remains securely attached to the rotating platform 126 during the CMP process, allowing for consistent and reliable wafer planarization. The rotating platform 126 is operable to rotate along an axis (which extends in a vertical direction, as shown in FIG. 1). The rotational speed of the rotating platform 126 is different from that of the rotating wafer holder 113. In addition, although the axis of rotation of the rotating platform 126 and the axis of rotation of the rotating wafer holder 113 are not collinear, the axes are generally parallel.

The polishing pad 112 is applied to the wafer surface 122 at a specific pressure. As the CMP process combines both chemical and mechanical forces to remove material from the wafer surface 122, the necessary planarity and smoothness of the wafer surface 122 can be achieved.

The polishing pad 112 is a consumable item. Under normal wafer fabrication conditions, the polishing pad is replaced after a certain amount of usage time. The polishing pads 112 may be hard, incompressible pads or soft pads. For oxide polishing, hard and stiffer pads are generally used to achieve planarity. Softer pads are generally used in other polishing processes to achieve improved uniformity and smooth surfaces. The hard pads and the soft pads may also be combined in an arrangement of stacked pads for customized applications.

The abrasive slurry supply equipment 128 is disposed over the polishing pad 112. In one example, the abrasive slurry supply equipment 128 is a feed connected to a tank accommodating abrasive slurry to be used during the CMP process. When the CMP system 100 is in operation, the abrasive slurry supply equipment 128 is operable to dispense abrasive slurry 124 onto the polishing pad 112, and the abrasive slurry 124 is distributed on the polishing pad 112 due to the rotation of the rotating platform 126 (and therefore the rotation of the polishing pad 112).

As shown in the enlarged illustration of the polishing pad 112 at the right side of FIG. 1, the polishing pad 112 includes, among other components, a base portion 152, an interfacing portion 154, multiple grooves 160, a bottom surface 156, and a top surface 158. The base portion 152 is a cylindrical structure that provides support for the other components of the polishing pad 112. A pad body 151 is comprised of the base portion 152 and the interfacing potion 154. The base portion 152 provides a stable and rigid foundation for the polishing pad 112. The interfacing portion 154 is a top layer disposed on the base portion 152. The interfacing portion 154 is in contact with the wafer 110 during the CMP process.

The grooves 160 are channels that run through the interfacing portion 154 and allow for the flow of abrasive slurry 124 during the CMP process. The grooves 160 allow for evenly distributing the abrasive slurry 124 across the polishing pad 112 (and therefore the wafer surface 122). In one example, the grooves are arranged in the following manner: a first set of parallel grooves extend in a first horizontal direction, and as second set of parallel grooves extend in a second horizontal direction perpendicular to the first horizontal direction.

The bottom surface 156 is the surface of the polishing pad 112 that is in contact with the rotating platform 126. The top surface 158 is the surface of the polishing pad 112 that is in contact with the wafer 110.

Unlike conventional polishing pads, the polishing pad 112 according to some embodiments of the present application further includes phase-change material (PCM) embedded in the polishing pad 112. As will be explained further below, the embedded phase-change material allows for better temperature regulation. In the example shown in FIG. 1, the polishing pad 112 includes PCM microcapsules 170 embedded in the polishing pad 112.

In some examples, the diameter of the PCM microcapsules 170 is between 0.1 μm and 100 μm. In other examples, the diameter of the PCM microcapsules 170 is between 1 μm and 10 μm. In the example shown in FIG. 1, the PCM microcapsules 170 are substantially evenly distributed in the polishing pad 112. However, the PCM microcapsules 170 may also be unevenly distributed in the polishing pad 112 as needed. As one example, the PCM microcapsules 170 are characterized by a decreasing density or an increasing density moving from the top surface 158 toward the bottom surface 156. It should be understood that the diameter and density of the PCM microcapsules 170 in the polishing pad 112 may be adjusted accordingly as needed. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

It should be understood that PCM microcapsules 170 are exemplary rather than limiting, and other form of embedded PCM will be discussed below in greater details. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

A phase-change material (PCM) is a substance which releases/absorbs sufficient energy at phase transition to provide useful heat or cooling. Generally the transition will be from one of the first two fundamental states of matter (i.e., solid and liquid) to the other. The phase transition may also be between non-classical states of matter, such as the conformity of crystals, where the material goes from conforming to one crystalline structure to conforming to another, which may be a higher or lower energy state.

The energy released/absorbed by phase transition from solid to liquid, or vice versa, the heat of fusion is generally much higher than the sensible heat. Ice, for example, requires 333.55 J/g to melt, but then water will rise one degree further with the addition of just 4.18 J/g. Water/ice is therefore a very useful phase change material.

By melting and solidifying at the phase-change temperature (PCT), a PCM is capable of storing and releasing large amounts of energy compared to sensible heat storage. Heat is absorbed or released when the material changes from solid to liquid and vice versa or when the internal structure of the material changes. Accordingly, PCMs are sometimes referred to as latent heat storage (LHS) materials.

FIG. 2 is a diagram illustrating an example of a temperature-heat relationship of a PCM in accordance with some embodiments. As the temperature-heat curve 202 shows, a PCM is experiencing a heating process, which includes three stages 212, 214, and 216. At the first stage 212, the PCM is in the solid phase. At the third stage 216, the PCM is in the liquid phase. At the second stage 214 therebetween, the PCM is in a transition from the solid phase to the liquid phase.

As the PCM is heated from a first temperature T1, it absorbs sensible heat, causing its temperature to rise. The rate of temperature increase is determined by the specific heat capacity of the solid PCM. After absorbing the amount of heat equal to the difference between H1 and H0, the PCM reaches its phase-change temperature (PCT) 222, and it begins to transition from the solid phase to the liquid phase. During this phase change, the PCM absorbs a large amount of latent heat (in this example, the difference between H2 and H1) without a change in temperature. This latent heat is also known as the heat of fusion. As illustrated in FIG. 2, the temperature stays unchanged (i.e., a constant temperature) until the entire PCM has transitioned to the liquid phase, and the PCM keeps absorbing heat.

Once the PCM is completely melted, any additional heat increases the temperature of the liquid PCM. The rate of temperature rise is determined by the specific heat capacity of the liquid PCM. As shown in FIG. 2, the temperature rises from the PCT 222 to T2 after absorbing the amount of heat equal to the difference between H3 and H2.

It should be noted that although only the heating process of the PCM is illustrated in FIG. 2, one of ordinary skill in the art would appreciate a similar cooling process of the PCM. In a cooling process, when the PCM reaches its freezing point, it begins to transition from the liquid phase to the solid phase. During the transition, the PCM releases a large amount of latent heat without a change in temperature. Likewise, this latent heat is also known as the heat of fusion.

Referring back to FIG. 1, in the embodiment shown in FIG. 1, the polishing pad 112 includes PCM microcapsules 170 embedded in the polishing pad 112. The PCM microcapsules 170 comprises a PCM characterized by a melting temperature, and the melting temperature is within a predetermined range. In one example, the predetermined range is an operational temperature range of the CMP process. The operational temperature range of the CMP process is a temperature range at the interface between the polishing pad 112 and the wafer surface 122 during the CMP process. The operational temperature range of the CMP process can vary depending on several factors, including the specific materials being polished, the type of abrasive slurry 124 used, and the design of the CMP system 100.

In one example, the operational temperature range is between −5° C. and 200° C. Thus, the PCM is characterized by a melting temperature between −5° C. and 200° C. (e.g., −5° C., 20° C., 40° C., 60° C., 80° C., 100° C., 120° C., 140° C., 160° C., 180° C., 200° C. etc.). In another example, the operational temperature range is between 20° C. and 180° C. Thus, the PCM is characterized by a melting temperature between 20° C. and 180° C. (e.g., 40° C., 60° C., 80° C., 100° C., 120° C., 140° C., 160° C., etc.). In yet another example, the operational temperature range is between 40° C. and 160° C. Thus, the PCM is characterized by a melting temperature between 40° C. and 160° C. (e.g., 60° C., 80° C., 100° C., 120° C., 140° C., etc.). In still another example, the operational temperature range is between 60° C. and 140° C. Thus, the PCM is characterized by a melting temperature between 60° C. and 140° C. (e.g., 80° C., 90° C., 100° C., 110° C., 120° C., etc.).

FIG. 3 is a diagram illustrating the comparison between a temperature-heat relationship of a polishing pad without PCM and that of a polishing pad with PCM according to some embodiments. In the example shown in FIG. 3, the temperature-heat curve 302 corresponds to a polishing pad with PCM (e.g., the polishing pad 112 shown in FIG. 1), whereas the temperature-heat curve 304 corresponds to a polishing pad without PCM (i.e., a conventional polishing pad). It should be noted that only the second stage 214 (corresponding to the transition from the solid phase to the liquid phase) between the first stage (corresponding to the solid phase) and third stage (corresponding to the liquid phase) during a heating process is illustrated.

As shown in FIG. 3, because of the PCM microcapsules 170, the temperature of the polishing pad 112 remains constant (at the phase-change temperature 222, i.e., the melting point) during the CMP process, until the PCM microcapsules 170 all transition from the solid state to the liquid state. In contrast, the temperature of the polishing pad without PCM increases as it absorbs heat. Therefore, the polishing pad 112 with embedded PCM microcapsules 170 has a larger heat capacity and can regulate temperature better at the interface between the polishing pad 112 and the wafer surface 122. Importantly, the temperature regulation occurs at the polishing zone, while other techniques cannot achieve temperature regulation at the polishing zone.

As a result, the heating of the wafer 114 during the CMP process is better controlled, and the removal rate during the CMP process is controlled better. Thermal expansion in the wafer (which leads to stress and potential defects such as warping or cracking) caused by differential heating and dishing and erosion caused by excessive heat can be mitigated. In addition, quick wear and degradation of the polishing pad 112 is mitigated, and the negative impact on abrasive slurry performance is mitigated as well.

In some embodiments, the pad body (including the base portion 152 and the interfacing portion 154) comprises a polymer. In some examples, the polymer is a porous polymeric material. In one example, the polymer is polyurethane (“PU”). In another example, the polymer is polymethylmethacrylate (PMMA). In yet another example, the polymer is polytetrafluoroethylene (PTFE). In still another example, the polymer is a natural resin. In another example, the polymer is a synthetic resin. It should also be understood that these examples are exemplary, and other suitable materials may be employed as needed. It should also be understood that the base portion 152 and the interfacing portion 154 may comprise more than one of the polymers mentioned above. These materials are chosen for their ability to: (1) absorb and distribute slurry (the porous structure helps in holding and dispersing the abrasive slurry used in the CMP process); (2) provide a cushioning effect (the soft nature of the foam protects the wafer from excessive damage during the CMP process); and (3) maintain a consistent polishing rate (the pad's properties ensure a uniform removal of material from the wafer surface).

In some embodiments, the PCM comprises paraffin wax. Paraffin wax is a petroleum product that is a mixture of hydrocarbons. It is a solid at room temperature and has a low melting point. The melting point of paraffin wax typically ranges from 48° C. to 66° C., and the exact melting point can vary depending on the specific composition of the paraffin wax, enabling it to be adapted for the temperature regulation purposes described above. Factors that can determine the melting point includes: molecular weight, branching (branched-chain paraffin wax generally has a lower melting point than straight-chain paraffin wax), and additives (the presence of additives can affect the melting point). In one example, the PCM comprises paraffin wax that comprises hydrocarbons with chain lengths ranging from 10 to 60 carbon atoms. In one example, the melting point of the paraffin wax is between −5° C. and 200° C., tunable based on the factors described above.

In some embodiments, the PCM comprises fatty acids. Fatty acids are organic compounds that are the building blocks of fats and oils. They are long chains of carbon atoms with a carboxylic acid group at one end. Likewise, the melting point of fatty acids vary depending on their structure and chain length. Generally, saturated fatty acids with longer carbon chains have higher melting points than unsaturated fatty acids or those with shorter chains. As an example, stearic acid (18 carbons) has a melting point of about 69.6° C. As another example, palmitic acid (16 carbons) has a melting point of about 63.1° C. As yet another example, lauric acid (12 carbons) has a melting point of about 44.2° C. In one example, oleic acid (18 carbons and 1 double bond) has a melting point of about 13.4° C. In another example, linoleic acid (18 carbons and 2 double bonds) has a melting point of about −5° C. In one example, the PCM comprises fatty acids that comprise hydrocarbons with chain lengths ranging from 10 to 30 carbon atoms. In one example, the melting point of the fatty acids is between −5° C. and 200° C., tunable based on the factors described above.

In some embodiments, the PCM comprises polyethylene glycol (PEG). PEG is a synthetic polymer widely used in various industries due to its unique properties. It is a flexible, water-soluble polymer that exhibits excellent biocompatibility and non-toxicity. Likewise, the melting points of PEG typically ranges from 50° C. to 65° C. The melting point varies depending on the molecular weight and specific type of PEG. Higher molecular weight PEGs may have higher melting points. In one example, the PCM comprises PEG characterized by a molecular weight between 600 g/mol and 6000 g/mol. In one example, the melting point of the fatty acids is between −5° C. and 200° C., tunable based on the factors described above.

It should be noted that, in some implementations, a combination of two or more materials described above can be employed as needed. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

It should be understood that although PCM microcapsules 170 are used as one of many implementation examples, there are other implementations within the scope of disclosure in accordance with the spirit articulated herein. For instance, FIGS. 4-6 shows examples of such implementations.

FIG. 4 is a cross-sectional diagram illustrating an example of a polishing pad in accordance with some embodiment. In the example shown in FIG. 4, the polishing pad 112 includes, among other components, a base portion 152, an interfacing portion 154, multiple grooves 160, a bottom surface 156, and a top surface 158. Likewise, the base portion 152 is a cylindrical structure that provides support for the other components of the polishing pad 112. The base portion 152 provides a stable and rigid foundation for the polishing pad 112. The interfacing portion 154 is a top layer disposed on the base portion 152. The interfacing portion 154 is in contact with the wafer 110 during the CMP process.

The grooves 160 are channels that run through the interfacing portion 154 and allow for the flow of abrasive slurry 124 during the CMP process. The grooves 160 allow for evenly distributing the abrasive slurry 124 across the polishing pad 112 (and therefore the wafer surface 122). The bottom surface 156 is the surface of the polishing pad 112 that is in contact with the rotating platform 126. The top surface 158 is the surface of the polishing pad 112 that is in contact with the wafer 110.

Unlike the PCM microcapsules 170 shown in FIG. 1, the polishing pad 112 shown in FIG. 4 includes a PCM layer 402 embedded in the base portion 152. As explained above, the embedded phase-change material of the PCM layer 402 allows for better temperature regulation.

The PCM layer 402 is characterized by a thickness t. In some examples, the thickness t is between 0.1 μm and 100 μm. In other examples, the thickness t is between 1 μm and 10 μm. The PCM layer 402 is also characterized by a depth d, measured from the interface between the interfacing portion 154 and the base portion 152. In some examples, the depth d is between 1% and 10% of the thickness h of the base portion 152. In some examples, the depth d is between 10% and 20% of the thickness h of the base portion 152. In some examples, the depth d is between 20% and 30% of the thickness h of the base portion 152. In some examples, the depth d is between 30% and 50% of the thickness h of the base portion 152. The combination of t, d, and h can be fine-tuned to fit different circumstances. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

In some examples (like the one shown in FIG. 4), the horizontal cross-section of the PCM layer 402 has the same size as that of the base portion 152. In other examples, the horizontal cross-section of the PCM layer 402 is smaller than that of the base portion 152. In some examples, the horizontal cross-section of the PCM layer 402 is circular. In some examples, the horizontal cross-section of the PCM layer 402 and the horizontal cross-section of the base portion 152 are concentric circles. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 5 is a cross-sectional diagram illustrating an example of a polishing pad in accordance with some embodiment. In the example shown in FIG. 5, the polishing pad 112 includes, among other components, a base portion 152, an interfacing portion 154, multiple grooves 160, a bottom surface 156, and a top surface 158. Likewise, the base portion 152 is a cylindrical structure that provides support for the other components of the polishing pad 112. The base portion 152 provides a stable and rigid foundation for the polishing pad 112. The interfacing portion 154 is a top layer disposed on the base portion 152. The interfacing portion 154 is in contact with the wafer 110 during the CMP process.

The grooves 160 are channels that run through the interfacing portion 154 and allow for the flow of abrasive slurry 124 during the CMP process. The grooves 160 allow for evenly distributing the abrasive slurry 124 across the polishing pad 112 (and therefore the wafer surface 122). The bottom surface 156 is the surface of the polishing pad 112 that is in contact with the rotating platform 126. The top surface 158 is the surface of the polishing pad 112 that is in contact with the wafer 110.

Unlike the PCM microcapsules 170 shown in FIG. 1, the polishing pad 112 shown in FIG. 5 includes multiple PCM tracks 502a, 502b, 502c, 502d, 502e, and 502f (collectively, 502) embedded in the interfacing portion 154. As explained above, the embedded phase-change material of the multiple PCM tracks 502 allows for better temperature regulation. Placing the PCM in the interfacing portion enhances the temperature regulation function since the PCM of the PCM tracks 502 becomes closer to the top surface 158, which is the interface between the polishing pad 112 and the wafer 110 during the CMP process. However, closer to the top surface 158 also means that the PCM of the PCM tracks 502 is more likely to be exposed after the top of the top surface 158 is worn out. This tradeoff offers more design flexibility under different circumstances. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Each of the PCM track 502 is characterized by a thickness t. In some examples, the thickness t is between 0.1 μm and 100 μm. In other examples, the thickness t is between 1 μm and 10 μm. Each of the PCM track 502 is also characterized by a width w. In some examples, the width w is between 0.1 μm and 100 μm. In some examples, the width w is between 1 μm and 10 μm. Similarly, the depth, namely the distance between the upper surface of the PCM track 502 and the top surface 158, may vary as needed. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

In the example shown in FIG. 5, the PCM tracks 502 are disposed in each of the protrusions (i.e., the portion of the interfacing portion 154 between two neighboring grooves 160). It should be understood that other patterns can be employed as needed in other implementations. For example, the PCM tracks 502 can be disposed in a portion (80%, 50%, 25%, etc.) of the protrusions. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 6 is a cross-sectional diagram illustrating an example of a polishing pad in accordance with some embodiment. In the example shown in FIG. 6, the polishing pad 112 includes, among other components, a base portion 152, an interfacing portion 154, multiple grooves 160, a bottom surface 156, and a top surface 158. Likewise, the base portion 152 is a cylindrical structure that provides support for the other components of the polishing pad 112. The base portion 152 provides a stable and rigid foundation for the polishing pad 112. The interfacing portion 154 is a top layer disposed on the base portion 152. The interfacing portion 154 is in contact with the wafer 110 during the CMP process.

The grooves 160 are channels that run through the interfacing portion 154 and allow for the flow of abrasive slurry 124 during the CMP process. The grooves 160 allow for evenly distributing the abrasive slurry 124 across the polishing pad 112 (and therefore the wafer surface 122). The bottom surface 156 is the surface of the polishing pad 112 that is in contact with the rotating platform 126. The top surface 158 is the surface of the polishing pad 112 that is in contact with the wafer 110.

Unlike the PCM microcapsules 170 shown in FIG. 1, the polishing pad 112 shown in FIG. 5 includes multiple a PCM structure 602. The PCM structure includes a base plate 604 and multiple PCM protrusions 606 protruding upwardly from the upper surface of the base plate 604. The base plate 604 is disposed in the base portion 152. The PCM protrusions 606 extend from the base plate 604 into the interfacing portion 154. In the example shown in FIG. 6, the PCM protrusion 606 are horizontally aligned with the protrusions of the interfacing portion 154. In some implementations, the interfacing portion 154 is conformally disposed on the PCM structure 602. Since the base plate 604 is disposed in the base portion 152 and the PCM protrusions 606 extend into the interfacing portion 154, the PCM structure 602 has both the benefits of the PCM layer 402 shown in FIG. 4 and the PCM tracks 502 shown in FIG. 5. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Exemplary Method for making the CMP Polishing Pads

FIG. 7 is a flowchart diagram illustrating an example method 700 for making a CMP polishing pad in accordance with some embodiments. In the example shown in FIG. 7, the method 700 includes operations 702, 704, 706, and 708. Additional operations may be performed. Also, it should be understood that the sequence of the various operations discussed above with reference to FIG. 7 is provided for illustrative purposes, and as such, other embodiments may utilize different sequences. These various sequences of operations are to be included within the scope of embodiments. FIG. 8 is a diagram illustrating the method 700 shown in FIG. 7 in accordance with some embodiments.

At operation 702, polymers or polymer precursors and phase-change materials (PCMs) are added to solvents. As shown in FIG. 8, a polymer and a PCM are added to the solvent in a container 802. In some embodiments, the polymer is selected from the group consisting of: polyurethane, polymethylmethacrylate (PMMA), polytetrafluoroethylene (PTFE), a natural resin, and a synthetic resin. In some embodiments, the PCM is selected from the group consisting of paraffin wax, fatty acids, and polyethylene glycol (PEG). The solvent is capable of dissolving or suspending the polymer and the PCM.

At operation 704, the solvent is cured to obtain a CMP polishing pad chunk (sometimes also referred to as a CMP polishing pad “cake”). Curing is a process that transforms a liquid mixture into a solid state. Curing can involve evaporation, chemical reactions, or other physical changes. In one implementation, operation 504 comprises stirring the solvent. As a result, the PCM is distributed essentially evenly, in the form of PCM microcapsules (like the PCM microcapsules 170 shown in FIG. 1). In some embodiments, operation 504 comprises applying the solvent to a mold or a substrate. For example, the mold can be of the desired shape and size of the final product or intermediate structures. In some embodiments, operation 504 comprises evaporating the solvent. Techniques such as ambient curing, heat curing, and vacuum curing may be employed depending on the materials chosen as the PCM. In some circumstances, chemical reactions may occur. In some embodiments, once the solvent has evaporated or the chemical reaction is complete, the solidified product is allowed to cool to room temperature. As shown in FIG. 8, a CMP polishing pad chunk 812 is obtained.

At operation 706, the CMP polishing pad chunk is skived into multiple slices 822. The thickness of each slice corresponds to the height of the pad body 151 shown in FIG. 1.

At operation 708, the multiple slices are milled to create a plurality of grooves on each slice. A milling process is a manufacturing process that involves removing material from a workpiece using a rotating cutter. In some embodiments, a slot milling process is employed. A cutter is fed into the slice 822, creating multiple grooves like the grooves 160 shown in FIG. 1. As a result, a CMP polishing pad like the CMP polishing pad 112 shown in FIG. 1 is obtained.

FIG. 9 is a flowchart diagram illustrating an example method 900 for making a CMP polishing pad in accordance with some embodiments. In the example shown in FIG. 9, the method 900 includes operations 902, 904, 906, 908, 910, and 912. Additional operations may be performed. Also, it should be understood that the sequence of the various operations discussed above with reference to FIG. 9 is provided for illustrative purposes, and as such, other embodiments may utilize different sequences. These various sequences of operations are to be included within the scope of embodiments. FIG. 10 is a diagram illustrating the method 900 shown in FIG. 9 in accordance with some embodiments.

At operation 902, polymers are added to solvents. As shown in FIG. 10, a polymer is added to the solvent in a container 1002. In some embodiments, the polymer is selected from the group consisting of: polyurethane, polymethylmethacrylate (PMMA), polytetrafluoroethylene (PTFE), a natural resin, and a synthetic resin. The solvent is capable of dissolving or suspending the polymer or polymer precursors and the PCM.

At operation 904, the mixture is cured to obtain a CMP polishing pad chunk. Curing is a process that transforms a liquid mixture into a solid state. Curing can involve evaporation, chemical reactions, or other physical changes. In one implementation, operation 904 comprises stirring the solvent. In some embodiments, operation 904 comprises applying the solvent to a mold or a substrate. For example, the mold can be of the desired shape and size of the final product or intermediate structures. In some embodiments, operation 904 comprises evaporating the solvent. Techniques such as ambient curing, heat curing, and vacuum curing may be employed depending on the materials chosen as the PCM. In some circumstances, chemical reactions may occur. In some embodiments, once the solvent has evaporated or the chemical reaction is complete, the solidified product is allowed to cool to room temperature. As shown in FIG. 10, a CMP polishing pad chunk 1012 is obtained.

At operation 906, the CMP polishing pad chunk is skived into multiple slices 1022. The thickness of each slice corresponds to the height of the base portion 152 shown in FIG. 1.

At operation 908, a PCM layer 1024 is deposited on a top surface of the first slice, one of the multiple slices 1022. In some embodiments, the PCM layer is made of a PCM selected from the group consisting of paraffin wax, fatty acids, and polyethylene glycol (PEG).

At operation 910, the PCM layer 1024 is encapsulated by a cover plate 1026 to form a pad body, which includes the first slice 1022 and the cover plate 1026. As shown in FIG. 10, the PCM layer 1024 is encapsulated or embedded in the pad body. In some implementations, the cover plate 1026 is attached to the first slice 1022 using adhesive. In one example, the adhesive is applied to the periphery of the first slice 1022 and the top surface of the PCM layer 1024. In other implementations, the cover plate 1026 is bonded to the first slice 1022 using bonding pads. In one example, the bonding pads are located at the periphery of the first slice 1022 and the top surface of the PCM layer 1024. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

At operation 912, the pad body is milled to create a plurality of grooves on each slice. A milling process is a manufacturing process that involves removing material from a workpiece using a rotating cutter. In some embodiments, a slot milling process is employed. A cutter is fed into the pad body, creating multiple grooves like the grooves 160 shown in FIG. 1. As a result, a CMP polishing pad like the CMP polishing pad 112 shown in FIG. 4 is obtained.

In addition, the CMP polishing pads 112 shown in FIGS. 5 and 6 can be fabricated by creating a mold of a specific shape (having grooves) and applying polymer solvent, followed by applying PCM in the grooves, followed by applying more polymer solvent. After curing, the structure is flipped over. Since the CMP polishing pads 112 typically have a diameter of about 30 inches, these processes can be implemented with enough precision.

SUMMARY

In accordance with some aspects of the disclosure, a chemical mechanical polishing (CMP) polishing pad used by a CMP system is provided. The CMP polishing pad comprises: a pad body comprising a base portion and an interfacing portion disposed on the base portion; and a phase-change material (PCM) embedded in the pad body, wherein the PCM is characterized by a melting temperature within an operational temperature range of a CMP process conducted by the CMP system.

In accordance with some aspects of the disclosure, a method for making a chemical mechanical polishing (CMP) polishing pad used by a CMP system is provided. The method comprises: adding polymers or polymer precursors and a phase-change material (PCM) to solvents; curing the solvent to obtain a CMP polishing pad chunk; skiving the CMP polishing pad chunk into a plurality of slices; and milling the plurality of slices to create a plurality of grooves on each slice.

In accordance with some aspects of the disclosure, a method for making a chemical mechanical polishing (CMP) polishing pad used by a CMP system is provided. The method comprises: adding polymers or polymer precursors to solvents to obtain a mixture; curing the mixture to obtain a CMP polishing pad chunk; skiving the CMP polishing pad chunk into a plurality of slices comprising a first slice; depositing a phase-change material (PCM) layer on a top surface of the first slice; encapsulating the PCM layer by a cover plate to form a pad body comprising the first slice and the cover plate; and milling the pad body to create a plurality of grooves on the pad body.

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.