Wafer polishing head, system thereof, and method using the same

A wafer polishing head is provided. The wafer polishing head includes a carrier head, a plurality of piezoelectric actuators disposed on the carrier head, and a membrane disposed over the plurality of piezoelectric actuators. The plurality of piezoelectric actuators is configured to provide mechanical forces on the membrane and generate an electrical charge when receiving counterforces of the mechanical forces through the membrane. A wafer polishing system and a method for polishing a substrate using the same are also provided.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, developments in IC processing and manufacturing systems and apparatuses are needed.

CMP (Chemical Mechanical Polishing) is a process of smoothing surfaces with a combination of chemical and mechanical forces. The process uses abrasives and corrosive chemical slurry (sometimes referred to as a colloid), and can be thought of as a hybrid of chemical etching and free abrasive polishing. In the CMP process, a wafer is pressed and rotated against a polishing pad. This removes material and tends to even out any irregular topography, making the wafer flat or planar. This may be necessary to prepare the wafer for the formation of additional circuit elements, and a polished wafer with a good polish profile is critical to the manufacturing process, especially for devices of advanced generations.

DETAILED DESCRIPTION

In general, the design of polishing heads of current chemical-mechanical polishing (CMP) systems allows control of the polish uniformity. The current method of polish uniformity control utilizes deformation of a membrane by a pneumatic mechanism. Different air pressures are supplied to different cells of the membrane, and several air cells with different pressures in the membrane are provided to exert downward force on a wafer for polish control. However, the air cells are all adjacent, and interference between neighboring air cells occurs, affecting the polish uniformity control of the polishing head. For instance, a first pressure is provided to a first air cell of the membrane, and a second pressure is provided to a second air cell of the membrane, which is directly adjacent to the first air cell. The first pressure is greater than the second pressure, and because the diaphragm separating the first air cell and the second air cell is soft and flexible, being the same material as the membrane, the second air cell also receives some pressure from the first air cell. As a result, the second air cell has an altered air pressure that is actually greater than the original or target second pressure provided into the second air cell, and the first air cell actually has an altered air pressure less than the original or target first pressure provided into the first air cell. Therefore, the pressures provided to different regions of the wafer are different from the target pressures, and the polish uniformity of the polishing head is not effectively controlled.

The present disclosure provides a polishing head including several piezoelectric actuators for controlling the pressures applied to different regions of the wafer. The method of polish profile control of the present disclosure utilizes a piezoelectric mechanism instead of a pneumatic mechanism to solve the air pressure interference issues illustrated above. The present disclosure also provides a system including the polishing head and a method for polishing a substrate using the polishing head. In addition, elements, conditions or parameters illustrated in different embodiments can be combined or modified to form different combinations of embodiments as long as the elements, parameters or conditions used are not conflicted. For ease of illustration, reference numerals with similar or same functions and properties are repeatedly used in different embodiments and figures.

FIG.1is a schematic diagram of a CMP system10according to some embodiments of the present disclosure. As shown inFIG.1, the CMP system10includes a polishing head100and a platen200. The polishing head100is configured to hold a substrate SB targeted to a CMP operation. The platen200is configured to allow a polishing pad201to be disposed thereon. When the CMP system10is in use, the polishing pad201is disposed on the platen200, and the substrate SB is held by the polishing head100against the polishing pad201. In some embodiments, the substrate SB is a wafer or a semiconductor substrate. In some embodiments, the polishing head100is rotated along a central line C100(indicated with a dashed line) of the polishing head100, and thus the substrate SB is also rotated against the polishing pad201during the CMP operation. In some embodiments, the central line C100passes through a center of the substrate SB so that the center of the substrate SB is also a center of rotation of the substrate SB in the CMP operation. Details of the polishing head100are illustrated in the following description along withFIG.2.

In some embodiments, the CMP system10includes a slurry delivery unit300and a control unit400. The slurry delivery unit300is disposed over the platen200, and supplies and deposits slurry301on the polishing pad201when the CMP operation is performed. The cooperation between the slurry301and the polishing pad201removes material on the substrate SB and tends to even out any irregular topography, making the substrate SB flat or planar. In some embodiments, the platen200is rotated along a central line C200(indicated with a dashed line), and thus the polishing pad201is also rotated when the CMP system10is in use. The control unit400is electrically connected to the polishing head100and configured to send or receive one or more signals to or from the polishing head100in order to adjust a polish profile of the polishing head100.

In some embodiments, the CMP system10also includes a pad dresser500. The pad dresser500is disposed over the platen200and the polishing pad201, and faces the polishing pad201. During the CMP operation, the pad dresser500pushes on the polishing pad201with a downward force that brings the pad dresser500into contact with the polishing pad201. As the polishing pad201is rotated by the platen200during the CMP operation, the pad dresser500roughens a polish surface S201of the polishing pad201to provide mechanical mechanism of the polishing pad201on the substrate SB.

FIG.2is a schematic diagram of the polishing head100holding the substrate SB according to some embodiments of the present disclosure. The polishing head100includes a carrier head110, a plurality of piezoelectric actuators120, and a membrane130. The carrier head110is a main body of the polishing head100and is configured to house other elements and circuits of the polishing head100. The plurality of piezoelectric actuators120is disposed on the carrier head110, and the membrane130is disposed on the carrier head110and the plurality of piezoelectric actuators120. The plurality of piezoelectric actuators120are configured to provide mechanical forces on the substrate SB through the membrane130, and generate an electrical charge when receiving counterforces of the mechanical forces from the substrate SB through the membrane130. The mechanical forces from the piezoelectric actuators120are provided downward, pushing the substrate SB against the polishing pad201. The membrane130is disposed between the piezoelectric actuators120and the substrate SB. The membrane130is a monolithic structure and is made of soft and flexible material to prevent damage and contamination of the polishing head100from chemicals and abrasives of the slurry301. In some embodiments, the membrane130functions as a blocking film, preventing chemicals and abrasives of the slurry301from leaking into the polishing head100.

In some embodiments, the polishing head100further includes a retaining ring150, disposed on the carrier head110and surrounding the substrate SB and the membrane130. The retaining ring150is configured to hold the substrate SB during the CMP operation. In some embodiments, the retaining ring150also surrounds the plurality of piezoelectric actuators120. In some embodiments, the retaining ring150has a ring shape. In some embodiments, the retaining ring150is in contact with the polishing pad201during the performing of the CMP operation. As shown inFIG.2, the retaining ring150and a polish surface of the substrate SB can be aligned. In some embodiments, the retaining ring150is separated from the polishing pad201during the CMP operation as long as the substrate SB can be held by the retaining ring150.

In some embodiments, each of the plurality of piezoelectric actuators120has a cylindrical shape, and the piezoelectric actuators120are dispersed evenly or unevenly over the substrate SB, without completely overlapping the substrate SB. In some embodiments, as shown inFIG.2, the polishing head100further comprises a plurality of plates140, disposed between the membrane130and the plurality of piezoelectric actuators120, wherein the plurality of plates140are configured to equalize the mechanical forces from the piezoelectric actuators120to the substrate SB. The plurality of plates140can be made of same or different materials. The materials are selected from durable materials that can withstand mechanical loads and have high hardness and strength, and the materials of the plates are not limited herein. In some embodiments, the plurality of plates140collectively are substantially the same size and shape as the substrate SB and the membrane130. A number of plates of the plurality of plates140can be adjusted according to different embodiments. In the embodiments shown inFIG.2, the plurality of plates140includes plates141,142,143,144and145for the purpose of illustration. Size and shape of each of the plurality of plates140are not limited herein. In the following description, different sizes and shapes of the plurality of plates140according to different embodiments of the present disclosure are provided for the purpose of illustration.

FIG.3is a top view perspective of the plurality of plates140in accordance with some embodiments of the present disclosure. The plate141of the plurality of plates140has a circular shape, and each of the plates142,143,144and145has a ring shape from the top view perspective. In some embodiments, a center C141of the plate141is a center of rotation of the plurality of plates140. In some embodiments, the central line C100of the polishing head100passes through the center C141of the plate141. In some embodiments, the center C141is coincident with a center of the membrane130, and/or is coincident with a center of the substrate SB. The plates142,143,144and145individually surround the plate141and are sequentially disposed outward from the plate141. As control of the polish profile at the edge of the substrate SB is more difficult to attain than control of the polish profile at the central region of the substrate SB, a width of a ring-shaped plate (a distance between outer edges of adjacent plates measured along an axis passing through the center C141) decreases as a diameter of the plate (a distance between an outer edge of the plate to the center C141, measured along the axis passing through the center C141) increases. In other words, as shown inFIG.3, widths W142, W143, W144and W145of the plates142,143,144and145gradually decrease as distances from the center C141(or diameters D142, D143, D144, and D145of the plates142,143,144and145) increase. The width W142of the plate142is greater than the width W143of the plate143, the width W143is greater than the width W144of the plate144, and the width W144is greater than the width W145of the plate145. The diameter D145is greater than the diameter D144, the diameter D144is greater than the diameter D143, and the diameter D143is greater than the diameter D142.

Moreover, the plates141,142,143,144and145are separated from each other, and a distance between the adjacent plates is not limited herein. The distance can be adjusted depending on materials, thicknesses, and speed of rotation of the plates, as long as frictions generated during the CMP operation between the adjacent plates are not enough to influence a polish profile of the substrate SB, or gaps between the adjacent plates are not enough to influence the polish profile of the substrate SB.

FIG.4is a top view perspective of the plurality of piezoelectric actuators120on the plurality of plates140shown inFIG.3in accordance with some embodiments of the present disclosure. In the embodiments shown inFIG.4, each of the plates141,142,143,144and145is a monolithic structure, and in order to have a good control of a polish profile of the polishing head100, each of the plates141,142,143,144and145is connected to (or in contact with) one or more piezoelectric actuators120. In some embodiments, the plate141is connected to (or in contact with) one piezoelectric actuator120at the center C141. In some embodiments, the plurality of piezoelectric actuators120is grouped into a plurality of groups, wherein the piezoelectric actuators120in one group are all connected to (or in contact with) a single plate141,142,143,144or145. As shown inFIG.3, different groups of the plurality of piezoelectric actuators120are respectively connected (or in contact with) the different plates141,142,143,144and145. In some embodiments, the piezoelectric actuators120in the same group (or overlapping the same plate142,143,144or145) have substantially same distances to the center of rotation of the plurality of plates140, i.e., the center C141. As mentioned above, the center C141is coincident with a center of the membrane130, and/or is coincident with a center of the substrate SB. That is, in some embodiments, the piezoelectric actuators120in the same group (or overlapping the same plate142,143,144or145) have substantially same distances to the center of the membrane130or the center of the substrate SB.

For a purpose of good control of the polish profile of the polishing head100toward the edge portion, an arrangement of the piezoelectric actuators120from the center of the substrate SB toward the edge portion of the substrate SB is important. In some embodiments, a number of the piezoelectric actuators120in the same group increases toward the edge portion of the polishing head100. In the embodiments shown inFIG.4, the plate141is connected to only one piezoelectric actuator120, the plate142is connected to 8 piezoelectric actuators120, and each of the plates143,144and145is connected to 16 piezoelectric actuators120. In some embodiments as illustrated inFIG.3and above paragraphs, the widths W142, W143, W144and W145of the plates142,143,144and145gradually decrease as distances from the center C141(or diameters D142, D143, D144, and D145of the plates142,143,144and145) increase. Therefore, even each of the plates143,144and145are connected to a same number of piezoelectric actuators120, a good control of the polish uniformity of the substrate S toward the edge portion can be provided since the widths W143, W144and W145decrease toward the edge portion.

In some embodiments, the piezoelectric actuators120in a single group are evenly arranged on the plate142,143,144or145they are connected to.FIG.4shows an arrangement of the plurality of piezoelectric actuators120on the plurality of plates140from a top view perspective in accordance with some embodiments of the present disclosure. As shown inFIG.4, the piezoelectric actuators120disposed over the plate142are evenly distributed on the plate142, and are symmetrically arranged with respect to the center of rotation (i.e., the center C141in some embodiments). In some embodiments, the piezoelectric actuators120in a single group are arranged symmetric with respect to the center C141, but the disclosure is not limited thereto. In some embodiments, the piezoelectric actuators120in a single group are arranged along at least one circumferential line relative to the center C141or the central line C100. That is, at least two of the piezoelectric actuators120are located on the same circumferential line relative to the center C141. Therefore, the uniformity control of the polishing head100can be carried out along at least one circumferential line relative to the center C141. In some embodiments, for a purpose of good control of the polish uniformity, the piezoelectric actuators120in a single group are connected to a same voltage, and thus the piezoelectric actuators120in the same group can generate substantially same mechanical forces on the substrate SB against the polishing pad201. A similar arrangement can be applied to the piezoelectric actuators120on the plates143,144and145.

Sizes or shapes of the piezoelectric actuators120can be different. In some embodiments, as shown inFIG.4, the piezoelectric actuator120connected to the plate141is larger than the piezoelectric actuators120connected to other plates142,143,144and145. In some embodiments, a shape of the piezoelectric actuator120from the top view perspective can be other than a circle, and is not limited herein. In addition, a number of the piezoelectric actuators120on each of the plurality of plates140is not limited herein. In the embodiments shown inFIG.4, only one piezoelectric actuator120is connected to the plate141since one piezoelectric actuator120is enough to control the respective region of the substrate SB disposed underlying the plate141. In some embodiments, multiple piezoelectric actuators120are connected to the plate141.

FIG.5shows arrangements of the plurality of plates140and the piezoelectric actuators120in accordance with some embodiments of the present disclosure. The embodiment shown inFIG.5is similar to the embodiment shown inFIG.4. A difference between the embodiments ofFIGS.4and5is that each of the plates142,143,144and145are divided into several sectors in the embodiment shown inFIG.5(i.e., the plates142,143,144and145are not monolithic, but rather integrated structures). The sectors in a single plate142,143,144or145are adjacent to one another and are arranged to form the ring shape of the respective plate142,143,144or145. In some embodiments, each of the sectors is connected to (or in contact with) one of the piezoelectric actuators120. In some embodiments, the sectors are physically separated as shown inFIG.6.FIG.7is a schematic diagram of a polishing head101, wherein the polishing head101is similar to the polishing head100but includes the plurality of plates140as shown inFIG.6according to some embodiments of the present disclosure. As a gap between two adjacent sectors being too large, a control of polish profile can be more difficult and the polish uniformity of the substrate SB can decrease. Thus, in some embodiments, a distance D1between two adjacent sectors in the same group is greater than zero and less than 0.02 millimeters (mm). Similarly, the plates142,143,144and145can also be physically separated or in contact with each other depends on different applications as shown inFIGS.4to6. In some embodiments, a distance D2between two adjacent plates can be in a range of zero and 0.02 millimeters (mm).

As illustrated inFIGS.5and6, the plate farther away from the center C141is divided into more sectors for a purpose of better control of the polish uniformity of the substrate SB. In some embodiments, the plates142,143,144and145are divided along circumferential lines relative to the center C141. For a purpose of illustration, the plate142is evenly divided into 8 sectors1421, and the plate145is evenly divided into 16 sectors1451as shown inFIG.5. The piezoelectric actuators120in one plate have substantially the same distance to the center C141. In some embodiments, for a purpose of better control of the polish uniformity in different regions of the substrate SB with respective to each of the sectors, the piezoelectric actuators120are disposed at geographic centers of the respective sectors.

A benefit of aligning one sector to one piezoelectric actuator120is that every respective region of the substrate SB can be controlled individually. However, the present disclosure is not limited thereto. In some embodiments, each sector is connected to multiple piezoelectric actuators120. In such embodiments, the multiple piezoelectric actuators120connected to the same plate are evenly distributed on the plate. A number of piezoelectric actuators120connected one sector or one plate is not limited herein.

In order to further illustrate advantages of the present disclosure, in the following description, a method M10for polishing the substrate SB using the CMP system10is provided.

FIG.8is a flowchart of the method M10in accordance with some embodiments of the present disclosure. The method M10includes several operations O101, O102, O103, O104, O105, and O106. In the operation O101, the substrate SB is received by or provided to the CMP system10, and the polishing pad201is disposed on the platen200. In the operation O102, the substrate SB is held by the polishing head100on the polishing pad201. In order to push the substrate SB against the polishing pad201, one or more voltages are provided to the plurality of piezoelectric actuators120. In some embodiments, different voltages are provided to different groups of the piezoelectric actuators120. In some embodiments, voltages are provided individually to the respective piezoelectric actuators120.

FIG.9is a schematic diagram of the polishing head100holding the substrate SB on the polishing pad201in accordance with some embodiments, andFIG.10is a top view perspective showing arrangements of the plurality of piezoelectric actuators120and the plurality of plates140of the polishing head100shown inFIG.9.FIG.11is an enlarged view of the circled portion inFIG.9illustrating the operation O103of the method M10. The polishing head100inFIG.9being similar to the polishing head100inFIG.2is used in the following description to illustrate the method M10for a purpose of illustration but it is not intended to limit the present disclosure. In other embodiments, the plate140shown inFIG.5or6can be used. The arrangement of the piezoelectric actuators120and the plates140inFIG.10is similar to the arrangement inFIG.4, but all the piezoelectric actuators120have the same size and shape. In addition, for a purpose of illustration, inFIGS.10-11, only the plates141and142, respective piezoelectric actuators120and respective regions SB1and SB2of the substrate SB are labelled and described in the following illustration, but are not intended to limit the present disclosure.

The plates141and142overlap different regions SB1and SB2of the substrate SB as indicated by dashed lines inFIG.9, and thus, mechanical forces applied to the regions SB1and SB2of the substrate SB are controlled by the respective piezoelectric actuators120. As shown inFIGS.10-11, an actuator121of the piezoelectric actuators120is connected to the plate141, and a first voltage V1is provided to the actuator121to generate a mechanical force F1to the membrane130and the region SB1of the substrate SB. Since the plate141is made of a hard material, the mechanical force F1is evenly applied to the region SB1of the substrate SB through the membrane130. Similarly, a second voltage V2is provided to one or more actuators122of the piezoelectric actuators120adjacent to the actuator121to generate a second mechanical force F2on the membrane130and the region SB2of the substrate SB. In the embodiments having multiple actuators122connected to the plate142, one or more second voltages are applied to all the actuators122so that the mechanical force F2can be evenly applied to the region SB2of the substrate SB.

FIG.12is an enlarged view of the circled portion inFIG.10illustrating the operation O104of the method M10. After the substrate SB receives the mechanical forces from the piezoelectric actuators120, counterforces with respect to the mechanical forces are generated. As shown inFIG.12, a counterforce R1resulting from the mechanical force F1is generated, and the counterforce R1is received by the actuator121. The actuator121generates an electrical charge E1due to the properties and characteristics of a piezoelectric actuator. Similarly, a counterforce R2resulting from the mechanical force F2is generated, and the counterforce R2is received by the actuator122. The actuator122then generates electrical charges E2. The electrical charges E1and E2are based on the counterforces R1and R2, and reflect actual downward forces pushing the regions SB1and SB2of the substrate SB against the polishing pad201during the CMP operation.

FIG.13is a schematic diagram showing electrical connections between the control unit400and the plurality of piezoelectric actuators120of the polishing head100inFIG.10. In some embodiments, as shown inFIG.13, the plurality of piezoelectric actuators120is electrically connected to the control unit400. In accordance with some embodiments and the operations O105and O106of the method M10, the electrical charges E1and E2are detected, and signals correspond to the electrical charges E1and E2are generated and received by the control unit400. A judgment operation as illustrated in the operation O105is performed to compare the signals respectively corresponding to the electrical charges E1and E2. As shown inFIG.8, the first signal can be one of the signals corresponding to the electrical charges E1and E2, and the reference can be another one of the signals or a default data, and it is not limited herein. The first signal and/or the reference can be one or more of the signals corresponding to different piezoelectric actuators120or different groups of the piezoelectric actuators120.

In some embodiments, the actuators122connected to the plate142are electrically connected together to generate one electrical charge E2. In some embodiments, the actuators122connected to the plate142are individually connected to the voltage V2and generate multiple electrical charges E2respective to each of the actuators122. Such configuration can be adjusted according to different embodiments in order to provide precise control of polish profiles of different regions of the substrate SB. In some embodiments, the piezoelectric actuators120in the same group are electrically connected to provide same voltages so that the piezoelectric actuators120in the same group can generate same mechanical forces. In some embodiments, the piezoelectric actuators120in different groups are electrically isolated. In some embodiments, all the piezoelectric actuators120are electrically isolated and can be controlled individually to have a higher flexibility of control of mechanical forces.

In some embodiments, the mechanical forces F1and F2generated by the actuators121and122are different. However, the pressure in the regions SB1and SB2of the substrate SB may be substantially equal per unit area. In other words, an average pressure in the region SB2resulting from the mechanical force F2should be substantially the same as an average pressure in the region SB1resulting from the mechanical force F1. The polishing head100including the plurality of plates140respectively connected to different groups of the plurality of piezoelectric actuators120but separated from each other can provide individual control to different regions of the substrate SB without interference of uncontrolled pressure from adjacent air cells as in the conventional CMP device. The different regions with different distances to the center of the substrate SB can therefore have uniform polish uniformity. In addition, the CMP system10can instantly adjust the voltage provided to an individual plate140or individual piezoelectric actuator120, and thus a good polish profile of the substrate SB can be provided.

Therefore, in some embodiments and in accordance with the operation O105, if the average pressures in the regions SB1are SB2different and the result of the comparison between the two corresponding signals exceeds the tolerance, one or more of the voltages V1and V2are adjusted by the control unit400in order to adjust the respective mechanical forces F1and F2. The tolerance can be an experimental or theoretical data depending on different applications, and it is not limited herein. On the other hand, if the average pressures in the regions SB1are SB2are determined to be substantially equal according to the result of the comparison, the method M10proceed to perform the operation O103, and no adjustment to the voltage V1and/or the voltage V2is required.

Concepts and purposes of the present disclosure are as illustrated using the polishing head100, but the present disclosure is not limited herein. In the embodiments illustrated above, the piezoelectric actuators120individually cannot entirely cover the respective regions of the substrate SB, and the plurality of plates140function to evenly apply the mechanical forces from the piezoelectric actuators120to the substrate SB. It should be noted that, in some embodiments, the plates140having separated sectors as shown inFIG.6is used, and regions of the substrate SB corresponding to the gaps between adjacent sectors may be negligible. Even there are some regions of the substrate SB may not directly covered by the sectors, the distances D1and D2between adjacent sectors and plates are controlled. In addition, the member130is a monolithic and flexible structure, and the regions of the substrate SB corresponding to the gaps can still receive indirect mechanical forces. Therefore, a good polish uniformity of the substrate SB can be provided.

In some embodiments of the present disclosure, the piezoelectric actuators120are collectively arranged to form a circular shape matching the shape of the substrate SB in order to entirely cover the substrate SB. Thus, the piezoelectric actuators120can also function as the plurality of plates140.

FIG.14shows a schematic diagram of a polishing head101in accordance with some embodiments of the present disclosure. The polishing head101is similar to the polishing head100but without the plurality of plates140and with different configurations of the piezoelectric actuators120. As shown inFIG.14, the plurality of piezoelectric actuators120is in contact with the membrane130. In order to have a good polish profile of the substrate SB, a number of actuators of the plurality of piezoelectric actuators120and their configurations can be adjusted according to different embodiments. It should be noted that, a piezoelectric actuator120can be in contact with or separated from an adjacent piezoelectric actuator120. A distance between two adjacent piezoelectric actuators120can be also in a range of zero and 0.02 millimeters (mm).

FIG.15is a top view perspective of the plurality of piezoelectric actuators120shown inFIG.14according to some embodiments of the present disclosure. In the embodiments, the plurality of piezoelectric actuators120includes an actuator121having a circular shape and disposed at a center (or a center of rotation) of the plurality of piezoelectric actuators120corresponding to a central region (e.g., region SB1) of the substrate SB. The plurality of piezoelectric actuators120also includes an actuator122having a ring shape and surrounding the actuator121. The actuator122overlaps a region SB2surrounding the region SB1of the substrate SB. The plurality of piezoelectric actuators120further includes an actuator123surrounding the actuator122, an actuator124surrounding the actuator123, and an actuator125surrounding the actuator124. Configuration and arrangement of the plurality of piezoelectric actuators120from the top view perspective are similar to the configuration and arrangement of the plurality of plates140as shown inFIG.3, and repeated description is omitted herein. The piezoelectric actuators120include hard materials and are able to evenly provide mechanical forces to the respective regions of the substrate SB without the plurality of plates140disposed therebetween.

In some embodiments, one or more of the plurality of piezoelectric actuators120include several sectors.FIG.16is a top view perspective of the plurality of piezoelectric actuators120as shown inFIG.14according to some embodiments of the present disclosure. The sectors in a single actuator122,123,124or125are adjacent to one another and are arranged to form the ring shape of the respective actuator122,123,124or125. Each sector of the actuator122,123,124or125can be individually connected to different voltage sources, and thus different sectors corresponding to different regions of the substrate SB can be individually adjusted to allow precise control of the polish profile of the substrate SB. Configuration and arrangement of the sectors of the plurality of piezoelectric actuators120are similar to the plurality of plates140as shown inFIG.5, and repeated description is omitted herein. In addition, it is noted that only the structure of the polishing head101is illustrated herein for a purpose of illustration, and the polishing head101can also applied in the system10and the method M10.

Some embodiments of the present disclosure provide a wafer polishing head. The wafer polishing head includes a carrier head, a plurality of piezoelectric actuators disposed on the carrier head, and a membrane disposed over the plurality of piezoelectric actuators. The plurality of piezoelectric actuators is configured to provide mechanical forces on the membrane and generate an electrical charge when receiving counterforces of the mechanical forces through the membrane.

Some embodiments of the present disclosure provide a wafer polishing system. The system includes a platen, a polishing head, and a control unit. The platen is configured to allow a polishing pad to be disposed thereon. The polishing head is configured to hold a substrate against the polishing pad, and includes a plurality of piezoelectric actuators and a membrane. The plurality of piezoelectric actuators is connected to one or more voltages. The membrane is disposed between the plurality of piezoelectric actuators and the substrate. The control unit is electrically connected to the plurality of piezoelectric actuators, and configured to receive a signal of an electrical charge generated by the plurality of piezoelectric actuators.

Some embodiments of the present disclosure provide a method for polishing a substrate. The method includes several operations. A substrate is received, and is held by a polishing head on a polishing pad. The polishing head includes a carrier head, a first piezoelectric actuator and a membrane. The first piezoelectric actuator is disposed on the carrier head and configured to provide a first mechanical force on the substrate against the polishing pad, and the membrane is disposed between the substrate and the first piezoelectric actuator. A first voltage is provided to the first piezoelectric actuator to generate the first mechanical force to the membrane and the substrate. A first counterforce resulting from the first mechanical force is received by the first piezoelectric actuator, and a first signal corresponding to the first counterforce is generated by the first piezoelectric actuator. The first signal is compared with a reference, and the first voltage to the first piezoelectric actuator is adjusted according to the first signal in order to change the first mechanical force on the substrate if a result of the comparison between the first signal and the reference exceeds a tolerance.