Wafer grinding head, wafer grinding system and method of using the same

Abstract

Embodiments of the present invention relate to a wafer grinding head, a wafer grinding system, and a method of using the same. A wafer grinding head is provided. The wafer grinding head includes a carrier head, a plurality of piezoelectric actuators disposed on the carrier head, and a diaphragm disposed on the plurality of piezoelectric actuators. The plurality of piezoelectric actuators are configured to provide a mechanical force on the diaphragm and generate an electric charge when receiving a reaction force of the mechanical force through the diaphragm. Some embodiments of the present invention also disclose a wafer grinding system and a method for grinding a substrate using the wafer grinding system.

Description

Technical Field

[0001] Embodiments of the present invention relate to a wafer grinding head, a wafer grinding system, and a method of using the same. Background Art

[0002] The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have resulted in IC generations, each having smaller and more complex circuits than the previous generation. However, such advances have increased the complexity of processing and manufacturing ICs, and in order to implement such advances, it is necessary to develop IC processing and manufacturing systems and equipment.

[0003] CMP (Chemical Mechanical Polishing) is a process of smoothing a surface using a combination of chemical and mechanical forces. The process uses an abrasive and a corrosive chemical slurry (sometimes referred to as a colloid), and can be considered a mixture of chemical etching and free abrasive polishing. In the CMP process, the wafer is held against the polishing pad and rotated against the polishing pad. This removes material and tends to flatten any irregular surface configuration to make the wafer flat or planar. This may be necessary to prepare the wafer for forming additional circuit elements, and a polished wafer with a good polishing profile is crucial for the process, especially for advanced generation devices. Summary of the Invention

[0004] Embodiments of the present invention relate to a wafer grinding head, comprising: a carrier head; a plurality of piezoelectric actuators disposed on the carrier head; and a diaphragm disposed on the plurality of piezoelectric actuators, wherein the plurality of piezoelectric actuators are configured to provide a mechanical force on the diaphragm and generate an electric charge when receiving a reaction force of the mechanical force through the diaphragm.

[0005] Embodiments of the present invention relate to a wafer grinding system, comprising: a platen configured to allow a polishing pad to be disposed thereon; a grinding head configured to hold a substrate against the polishing pad, the grinding head including a plurality of piezoelectric actuators connected to one or more voltages and a diaphragm disposed between the plurality of piezoelectric actuators and the substrate; and a control unit electrically connected to the plurality of piezoelectric actuators and configured to receive signals of electric charges generated by the plurality of piezoelectric actuators.

[0006] Embodiments of the present invention relate to a method for polishing a substrate, which includes: receiving a substrate; using a polishing head to hold the substrate on a polishing pad, wherein the polishing head includes a carrier head, a first piezoelectric actuator disposed on the carrier head and configured to provide a first mechanical force on the substrate against the polishing head, and a diaphragm disposed between the substrate and the first piezoelectric actuator; applying a first voltage to the first piezoelectric actuator to generate the first mechanical force on the diaphragm and the substrate; receiving a first reaction force from the first mechanical force acting on the first piezoelectric actuator to generate a first signal corresponding to the first reaction force; comparing the first signal with a reference; and if the result of the comparison between the first signal and the reference exceeds a tolerance, then adjusting the first voltage applied to the first piezoelectric actuator according to the first signal to change the first mechanical force on the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Aspects of embodiments of the present invention are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with industry standard practice, various structures are not drawn to scale. In fact, for the sake of clarity of discussion, the dimensions of various structures may be arbitrarily increased or decreased.

[0008] Figure 1 is a schematic diagram of a CMP system according to some embodiments of the present invention.

[0009] Figure 2 is a schematic diagram of a polishing head for holding a substrate according to some embodiments of the present invention.

[0010] Figure 3 is a top perspective view of a plurality of plates according to some embodiments of the present invention.

[0011] Figure 4 is a top perspective view of a plurality of plates and a plurality of piezoelectric actuators according to some embodiments of the present invention.

[0012] Figure 5 is a top perspective view of a plurality of plates and a plurality of piezoelectric actuators according to some embodiments of the present invention.

[0013] Figure 6 is a top perspective view of a plurality of plates and a plurality of piezoelectric actuators according to some embodiments of the present invention.

[0014] Figure 7 is a schematic diagram of a polishing head for holding a substrate according to some embodiments of the present invention.

[0015] Figure 8 is a flowchart of a method according to some embodiments of the present invention.

[0016] Figure 9Schematic diagram of a grinding head for holding a substrate on a grinding pad according to some embodiments of the present invention.

[0017] Figure 10 Top perspective view showing the arrangement of a piezoelectric actuator and a plate according to some embodiments of the present invention.

[0018] Figures 11 to 12 Is of different operations of a method according to some embodiments of the present invention Figure 9 Enlarged view of the circled part in

[0019] Figure 13 Schematic diagram showing the electrical connection between a control unit and a plurality of piezoelectric actuators according to some embodiments of the present invention.

[0020] Figure 14 Schematic diagram showing a grinding head according to some embodiments of the present invention.

[0021] Figures 15 to 16 Top perspective view of a plurality of piezoelectric actuators according to some embodiments of the present invention. Detailed Description

[0022] The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. Specific examples of elements and arrangements will be described below to simplify the disclosure. Of course, these are only examples and are not intended to be limiting. For example, in the following description, "forming a first member above or on a second member" may include embodiments in which the first member and the second member are in direct contact, and may also include embodiments in which additional members may be formed between the first member and the second member such that the first member and the second member are not in direct contact. Additionally, the disclosure may repeat element symbols and / or letters in various examples. This repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0023] In addition, for ease of description, spatial relative terms such as "below", "beneath", "lower", "above", "upper", "on", "over" and the like may be used herein to describe the relationship of an element or member to another (other) element or member, as illustrated in the figures. The spatial relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be oriented in other ways (rotated 90 degrees or in other orientations) and the spatial relative descriptive words used herein may thus be interpreted accordingly.

[0024] As used herein, although terms such as "first", "second", and "third" describe various elements, components, regions, layers, and / or sections, such elements, components, regions, layers, and / or sections should not be limited by such terms. Such terms may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as "first", "second", and "third" as used herein do not imply a sequence or order.

[0025] Although numerical ranges and parameters setting forth the broad scope of this disclosure are approximations, the numerical values set forth in the specific examples should be reported as precisely as possible. However, any numerical value inherently contains certain inevitable errors resulting from the standard deviation found in the corresponding testing measurements. In addition, as used herein, the terms "substantially", "about", or "approximate" generally mean within the values or ranges that can be expected by one of ordinary skill in the art. Alternatively, the terms "substantially", "about", or "approximate" mean within the acceptable standard error of the mean considered by one of ordinary skill in the art. One of ordinary skill in the art should understand that the acceptable standard error may vary depending on the technology. Except in the operating / work examples, or unless otherwise expressly specified, all numerical ranges, amounts, values, and percentages disclosed herein (e.g., numerical ranges, amounts, values, and percentages of material quantities, durations, temperatures, operating conditions, ratio of amounts, and the like) should be understood to be modified in all instances by the terms "substantially", "about", or "approximate". Accordingly, unless indicated to the contrary, the numerical parameters set forth in this disclosure and the appended claims are approximations that may vary as desired. Finally, each numerical parameter should be construed in light of the number of significant figures reported and by applying ordinary rounding techniques. In this document, ranges may be expressed as from one endpoint to another endpoint or as between two endpoints. Unless otherwise specified, all ranges disclosed herein include the endpoints.

[0026] Generally, the design of the polishing head of current chemical mechanical polishing (CMP) systems allows for control of polishing uniformity. Current methods of polishing uniformity control utilize a diaphragm deformed by a pneumatic mechanism. Different air pressures are supplied to different cells of the diaphragm, and a number of air cells with different pressures in the diaphragm are provided to apply a downward force on the wafer for polishing control. However, the air cells are all adjacent, and interference occurs between adjacent air cells to affect the polishing uniformity control of the polishing head. For example, a first pressure is supplied to a first air cell of the diaphragm, and a second pressure is supplied to a second air cell of the diaphragm 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 softer and more flexible (the same material as the diaphragm), the second air cell also receives some pressure from the first air cell. Therefore, the second air cell has an altered air pressure that is actually greater than the original or target second pressure supplied to the second air cell, and the first air cell actually has an altered air pressure that is less than the original or target first pressure supplied to the first air cell. Therefore, the pressures supplied to different regions of the wafer are different from the target pressures, and the polishing uniformity of the polishing head cannot be effectively controlled.

[0027] The present disclosure provides a polishing head that includes a number of piezoelectric actuators for controlling the pressure applied to different regions of a wafer. The method of polishing profile control of the present disclosure utilizes a piezoelectric mechanism instead of a pneumatic mechanism to solve the air pressure interference problem described above. The present disclosure also provides a system including the polishing head and a method of polishing a substrate using the polishing head. Additionally, the elements, conditions, or parameters described in different embodiments may be combined or modified to form different combinations of embodiments, as long as the elements, parameters, or conditions used are not contradictory. For ease of illustration, element symbols having similar or identical functions and properties are repeated for different embodiments and figures.

[0028] Figure 1 is a schematic diagram of a CMP system 10 according to some embodiments of the present invention. As Figure 1 shown, the CMP system 10 includes a polishing head 100 and a platen 200. The polishing head 100 is configured to hold a substrate SB for CMP operations. The platen 200 is configured to allow a polishing pad 201 to be disposed thereon. When the CMP system 10 is in use, the polishing pad 201 is disposed on the platen 200, and the substrate SB is held by the polishing head 100 against the polishing pad 201. In some embodiments, the substrate SB is a wafer or a semiconductor substrate. In some embodiments, the polishing head 100 rotates along a centerline C100 (indicated using a dashed line) of the polishing head 100, and thus during the CMP operation, the substrate SB also rotates against the polishing pad 201. In some embodiments, the centerline C100 passes through the center of the substrate SB such that the center of the substrate SB is also the center of rotation of the substrate SB during the CMP operation. The following description is presented in conjunction with Figure 2 to illustrate the details of the polishing head 100.

[0029] In some embodiments, the CMP system 10 includes a slurry delivery unit 300 and a control unit 400. The slurry delivery unit 300 is disposed on the platen 200 and supplies and deposits a slurry 301 onto the polishing pad 201 during a CMP operation. The cooperation between the slurry 301 and the polishing pad 201 removes material on the substrate SB and tends to flatten any irregular surface configuration to make the substrate SB flat or planar. In some embodiments, the platen 200 rotates along a center line C200 (indicated by a dashed line), and thus also rotates the polishing pad 201 when the CMP system 10 is in use. The control unit 400 is electrically connected to the polishing head 100 and is configured to send and receive one or more signals to and from the polishing head 100 to adjust the polishing profile of the polishing head 100.

[0030] In some embodiments, the CMP system 10 further includes a pad conditioner 500. The pad conditioner 500 is disposed on the platen 200 and the polishing pad 201 and faces the polishing pad 201. During a CMP operation, the pad conditioner 500 presses against the polishing pad 201 using a downward force that brings the pad conditioner 500 into contact with the polishing pad 201. When the polishing pad 201 is rotated by the platen 200 during a CMP operation, the pad conditioner 500 roughens the polishing surface S201 of the polishing pad 201 to provide a mechanical mechanism of the polishing pad 201 on the substrate SB.

[0031] Figure 2 is a schematic diagram of a polishing head 100 that holds a substrate SB according to some embodiments of the present invention. The polishing head 100 includes a carrier head 110, a plurality of piezoelectric actuators 120, and a diaphragm 130. The carrier head 110 is the main body of the polishing head 100 and is configured to house other components and circuits of the polishing head 100. The plurality of piezoelectric actuators 120 are disposed on the carrier head 110, and the diaphragm 130 is disposed on the carrier head 110 and the plurality of piezoelectric actuators 120. The plurality of piezoelectric actuators 120 are configured to provide a mechanical force on the substrate SB through the diaphragm 130 and generate an electric charge when receiving a reaction force of the mechanical force from the substrate SB through the diaphragm 130. The mechanical force from the piezoelectric actuators 120 is provided downward to push the substrate SB against the polishing pad 201. The diaphragm 130 is disposed between the piezoelectric actuators 120 and the substrate SB. The diaphragm 130 is a monolithic structure and is made of a soft and flexible material to prevent the polishing head 100 from being damaged and contaminated by the chemicals and abrasives of the slurry 301. In some embodiments, the diaphragm 130 acts as a barrier film to prevent the chemicals and abrasives of the slurry 301 from leaking into the polishing head 100.

[0032] In some embodiments, the polishing head 100 further includes a fixing ring 150 disposed on the carrier head 110 and surrounding the substrate SB and the diaphragm 130. The fixing ring 150 is configured to hold the substrate SB during the CMP operation. In some embodiments, the fixing ring 150 also surrounds a plurality of piezoelectric actuators 120. In some embodiments, the fixing ring 150 has an annular shape. In some embodiments, the fixing ring 150 contacts the polishing pad 201 during the execution of the CMP operation. As Figure 2 shown, the polishing surfaces of the fixing ring 150 and the substrate SB can be aligned. In some embodiments, the fixing ring 150 is separated from the polishing pad 201 during the CMP operation as long as the substrate SB can be held by the fixing ring 150.

[0033] In some embodiments, each of the plurality of piezoelectric actuators 120 has a cylindrical shape, and the piezoelectric actuators 120 are uniformly or non-uniformly distributed on the substrate SB without completely overlapping the substrate SB. In some embodiments, as Figure 2 shown, the polishing head 100 further includes a plurality of plates 140 disposed between the diaphragm 130 and the plurality of piezoelectric actuators 120, wherein the plurality of plates 140 are configured to balance the mechanical force from the piezoelectric actuators 120 to the substrate SB. The plurality of plates 140 can be made of the same or different materials. The material is selected from durable materials that can withstand mechanical loads and have high hardness and strength, and the material of the plates is not limited herein. In some embodiments, the entire plurality of plates 140 are generally the same size and shape as the substrate SB and the diaphragm 130. The number of plates of the plurality of plates 140 can be adjusted according to different embodiments. In Figure 2 the illustrated embodiment, for illustration purposes, the plurality of plates 140 include plates 141, 142, 143, 144, and 145. The size and shape of each of the plurality of plates 140 are not limited herein. In the following description, different sizes and shapes of the plurality of plates 140 according to different embodiments of the present invention are provided for illustration purposes.

[0034] Figure 3is a top perspective view of a plurality of plates 140 according to some embodiments of the present invention. When viewed from a top perspective, the plate 141 of the plurality of plates 140 has a circular shape, and each of the plates 142, 143, 144, and 145 has an annular shape. In some embodiments, the center C141 of the plate 141 is the rotation center of the plurality of plates 140. In some embodiments, the center line C100 of the polishing head 100 passes through the center C141 of the plate 141. In some embodiments, the center C141 coincides with the center of the diaphragm 130 and / or coincides with the center of the substrate SB. The plates 142, 143, 144, and 145 individually surround the plate 141 and are sequentially arranged outward from the plate 141. Since it is more difficult to control the polishing profile at the edge of the substrate SB than at the central region of the substrate SB, the width of the annular plate (the distance between the outer edges of adjacent plates measured along the axis passing through the center C141) decreases as the diameter of the plate (the distance between the outer edge of the plate and the center C141 measured along the axis passing through the center C141) increases. In other words, as Figure 3 shown, the widths W142, W143, W144, and W145 of the plates 142, 143, 144, and 145 gradually decrease as the distance from the center C141 (or the diameters D142, D143, D144, and D145 of the plates 142, 143, 144, and 145) increases. The width W142 of the plate 142 is greater than the width W143 of the plate 143, the width W143 is greater than the width W144 of the plate 144, and the width W144 is greater than the width W145 of the plate 145. The diameter D145 is greater than the diameter D144, the diameter D144 is greater than the diameter D143, and the diameter D143 is greater than the diameter D142.

[0035] Furthermore, the plates 142, 143, 144, and 145 are separated from each other, and the distance between adjacent plates is not limited herein. The distance can be adjusted depending on the material, thickness, and rotation speed of the plates, as long as the friction generated during the CMP operation between adjacent plates is not sufficient to affect the polishing profile of the substrate SB, or the gap between adjacent plates is not sufficient to affect the polishing profile of the substrate SB.

[0036] Figure 4 is a top perspective view of a plurality of piezoelectric actuators 120 on the plurality of plates 140 shown in Figure 3 according to some embodiments of the present invention. In Figure 4In the illustrated embodiments, each of the plates 141, 142, 143, 144, and 145 is a single-piece structure, and in order to have good control of the grinding profile of the grinding head 100, each of the plates 141, 142, 143, 144, and 145 is connected to one or more piezoelectric actuators 120 (or in contact with one or more piezoelectric actuators 120). In some embodiments, plate 141 is connected to (or in contact with) piezoelectric actuator 120 at center C141. In some embodiments, the plurality of piezoelectric actuators 120 are divided into a plurality of groups, where the piezoelectric actuators 120 in a group are all connected to (or in contact with) a single plate 141, 142, 143, 144, or 145. As Figure 3 shown, different groups of the plurality of piezoelectric actuators 120 are respectively connected to (or in contact with) different plates 141, 142, 143, 144, and 145. In some embodiments, the piezoelectric actuators 120 in the same group (or overlapping the same plate 142, 143, 144, or 145) have a substantially the same distance to the center of rotation of the plurality of plates 140 (i.e., center C141). As mentioned above, center C141 coincides with the center of the diaphragm 130 and / or coincides with the center of the substrate SB. That is, in some embodiments, the piezoelectric actuators 120 in the same group (or overlapping the same plate 142, 143, 144, or 145) have a substantially the same distance to the center of the diaphragm 130 or the center of the substrate SB.

[0037] To well control the grinding profile of the grinding head 100 toward the edge portion, the arrangement of the piezoelectric actuators 120 from the center of the substrate SB toward the edge portion of the substrate SB is important. In some embodiments, the number of piezoelectric actuators 120 in the same group increases toward the edge portion of the grinding head 100. In Figure 4 the illustrated embodiments, plate 141 is connected to only 1 piezoelectric actuator 120, plate 142 is connected to 8 piezoelectric actuators 120, and each of plates 143, 144, and 145 is connected to 16 piezoelectric actuators 120. In some embodiments, as Figure 3 illustrated in the above paragraphs, W142, W143, W144, and W145 of plates 142, 143, 144, and 145 gradually decrease as the distance from the center C141 (or the diameters D142, D143, D144, and D145 of plates 142, 143, 144, and 145) increases. Therefore, even though each of plates 143, 144, and 145 is connected to the same number of piezoelectric actuators 120, good control of the grinding uniformity of the substrate SB toward the edge portion can be provided because W142, W143, W144, and W145 decrease toward the edge portion.

[0038] In some embodiments, the piezoelectric actuators 120 in a single group are uniformly arranged on the plates 142, 143, 144, or 145 connected thereto. Figure 4 A top perspective view showing the arrangement of the plurality of piezoelectric actuators 120 on the plurality of plates 140 according to some embodiments of the present invention. As Figure 4 shown, the piezoelectric actuators 120 disposed on the plate 142 are uniformly distributed on the plate 142 and are symmetrically arranged with respect to the rotation center (in some embodiments, the center C141). In some embodiments, the piezoelectric actuators 120 in a single group are symmetrically arranged with respect to the center C141, but the present disclosure is not limited thereto. In some embodiments, the piezoelectric actuators 120 in a single group are arranged along at least one circumferential line with respect to the center C141 or the center line C100. That is, at least two of the piezoelectric actuators 120 are located on the same circumferential line with respect to the center C141. Therefore, the uniformity control of the polishing head 100 can be implemented along at least one circumferential line with respect to the center C141. In some embodiments, in order to well control the polishing uniformity, the piezoelectric actuators 120 in a single group are connected to the same voltage. Therefore, the piezoelectric actuators 120 in the same group can generate substantially the same mechanical force against the polishing pad 201 on the substrate SB. A similar arrangement can be applied to the piezoelectric actuators 120 on the plates 143, 144, and 145.

[0039] The size or shape of the piezoelectric actuators 120 can be different. In some embodiments, as Figure 4 shown, the piezoelectric actuators 120 connected to the plate 141 are larger than the piezoelectric actuators 120 connected to the other plates 142, 143, 144, and 145. In some embodiments, from a top view perspective, the shape of the piezoelectric actuators 120 may not be circular, and it is not limited herein. Additionally, the number of piezoelectric actuators 120 on each of the plurality of plates 140 is not limited herein. In Figure 4 the embodiment shown, only one piezoelectric actuator 120 is connected to the plate 141 because one piezoelectric actuator 120 is sufficient to control the corresponding area of the substrate SB disposed under the plate 141. In some embodiments, a plurality of piezoelectric actuators 120 are connected to the plate 141.

[0040] Figure 5 A view showing the arrangement of the plurality of plates 140 and the piezoelectric actuators 120 according to some embodiments of the present invention. Figure 5 The embodiment shown in Figure 4 is similar to the embodiment shown in Figure 4 The difference between Figure 5 and the embodiment of Figure 5In the illustrated embodiments, each of the plates 142, 143, 144, and 145 is divided into a plurality of sectors (i.e., the plates 142, 143, 144, and 145 are not single pieces but integrated structures). The sectors in a single plate 142, 143, 144, or 145 are adjacent to each other and are arranged to form an annular shape of the corresponding plate 142, 143, 144, or 145. In some embodiments, each of the sectors is connected to (or in contact with) one of the piezoelectric actuators 120. In some embodiments, the sectors are physically separated, as Figure 6 shown. Figure 7 is a schematic view of a polishing head 101 according to some embodiments of the present invention, wherein the polishing head 101 is similar to the polishing head 100 but includes Figure 6 a plurality of plates 140 shown. When the gap between two adjacent sectors is too large, it is more difficult to control the polishing profile and the polishing uniformity of the substrate SB is reduced. Therefore, in some embodiments, the distance D1 between two adjacent sectors in the same group is greater than 0 and less than 0.02 millimeters (mm). Similarly, the plates 142, 143, 144, and 145 may also be physically separated or in contact with each other, depending on Figures 4 to 6 the different applications shown. In some embodiments, the distance D2 between two adjacent plates may be in the range of 0 to 0.02 millimeters (mm).

[0041] As Figure 5 and 6 illustrated, to better control the polishing uniformity of the substrate SB, the plates farther from the center C141 are divided into more sectors. In some embodiments, the plates 142, 143, 144, and 145 are divided along a circumferential line relative to the center C141. For illustration, the plate 142 is evenly divided into 8 sectors 1421, and the plate 145 is evenly divided into 16 sectors 1451, as Figure 5 shown. The piezoelectric actuators 120 in the plates have substantially the same distance to the center C141. In some embodiments, to better control the polishing uniformity of different regions of the substrate SB with respect to each of the sectors, the piezoelectric actuators 120 are disposed at the geographical center of the corresponding sectors.

[0042] The benefit of aligning the sectors with the piezoelectric actuators 120 is that each corresponding region of the substrate SB can be individually controlled. However, the present disclosure is not limited thereto. In some embodiments, each sector is connected to a plurality of piezoelectric actuators 120. In such embodiments, the plurality of piezoelectric actuators 120 connected to the same plate are evenly distributed on the plate. The number of piezoelectric actuators 120 connected to the sectors or plates is not limited herein.

[0043] To further illustrate the advantages of the present disclosure, in the following description, a method M10 of polishing a substrate SB using a CMP system 10 is provided.

[0044] Figure 8 is a flowchart of method M10 according to some embodiments of the present invention. Method M10 includes several operations O101, O102, O103, O104, O105, and O106. In operation O101, substrate SB is received by CMP system 10 or provided to CMP system 10, and polishing pad 201 is placed on platen 200. In operation O102, substrate SB is held on polishing pad 201 by polishing head 100. To push substrate SB against polishing pad 201, one or more voltages are provided to a plurality of piezoelectric actuators 120. In some embodiments, different voltages are provided to different groups of piezoelectric actuators 120. In some embodiments, voltages are provided individually to respective piezoelectric actuators 120.

[0045] Figure 9 is a schematic diagram of polishing head 100 for holding substrate SB on polishing pad 201 according to some embodiments, and Figure 10 is to show Figure 9 a top perspective view showing the arrangement of a plurality of piezoelectric actuators 120 and a plurality of plates 140 of polishing head 100 shown in Figure 11 is an enlarged view of the circled portion in Figure 9 illustrating operation O103 of method M10. For illustration, polishing head 100 similar to that in Figure 2 is used in the following description to illustrate method M10, but it is not intended to limit this disclosure. In other embodiments, plates 140 shown in Figure 9 or Figure 5 may be used. Figure 6 The arrangement of piezoelectric actuators 120 and plates 140 in Figure 10 is similar to the arrangement in Figure 4 , but all piezoelectric actuators 120 have the same size and shape. Additionally, for illustration, in Figures 10 to 11 , only plates 141 and 142, the corresponding piezoelectric actuators 120, and the corresponding regions SB1 and SB2 of substrate SB are marked and described in the following description, but it is not intended to limit this disclosure.

[0046] Plates 141 and 142 overlap different regions SB1 and SB2 of substrate SB (as indicated by the dashed lines in Figure 9 ), thus, the mechanical forces applied to regions SB1 and SB2 of substrate SB are controlled by the corresponding piezoelectric actuators 120. As shown in Figures 10 to 11As shown, actuator 121 of piezoelectric actuator 120 is connected to plate 141, and a first voltage V1 is provided to actuator 121 to generate a mechanical force F1 on diaphragm 130 and region SB1 of substrate SB. Since plate 141 is made of a hard material, mechanical force F1 is uniformly applied to region SB1 of substrate SB through diaphragm 130. Similarly, a second voltage V2 is provided to one or more actuators 122 of piezoelectric actuator 120 adjacent to actuator 121 to generate a second mechanical force F2 on diaphragm 130 and region SB2 of substrate SB. In an embodiment where multiple actuators 122 are connected to plate 142, one or more second voltages are applied to all actuators 122 such that mechanical force F2 can be uniformly applied to region SB2 of substrate SB.

[0047] Figure 12 is an enlarged view of the circled portion in Figure 9 illustrating operation O104 of method M10. After substrate SB receives a mechanical force from piezoelectric actuator 120, a reaction force relative to the mechanical force is generated. As Figure 12 shown, a reaction force R1 originating from mechanical force F1 is generated, and reaction force R1 is received by actuator 121. Actuator 121 generates charge E1 due to the nature and characteristics of the piezoelectric actuator. Similarly, a reaction force R2 originating from mechanical force F2 is generated, and reaction force R2 is received by actuator 122. Then, actuator 122 generates charge E2. Charges E1 and E2 are based on reaction forces R1 and R2, and reflect the actual downward forces that push regions SB1 and SB2 of substrate SB against polishing pad 201 during the CMP operation.

[0048] Figure 13 is a schematic diagram showing the electrical connection between control unit 400 and Figure 10 multiple piezoelectric actuators 120 of polishing head 100 in Figure 13 In some embodiments, as Figure 8 shown, multiple piezoelectric actuators 120 are electrically connected to control unit 400. According to some embodiments and operations O105 and O106 of method M10, charges E1 and E2 are detected, and signals corresponding to charges E1 and E2 are generated and received by control unit 400. A determination operation as described in operation O105 is performed to compare the signals corresponding to charges E1 and E2 respectively. As

[0049] In some embodiments, actuators 122 connected to plate 142 are electrically connected together to generate charge E2. In some embodiments, actuators 122 connected to plate 142 are individually connected to voltage V2 and generate multiple charges E2 relative to each of the actuators 122. This configuration can be adjusted according to different embodiments to provide precise control of the polishing profiles of different regions of substrate SB. In some embodiments, piezoelectric actuators 120 in the same group are electrically connected to provide the same voltage, such that the piezoelectric actuators 120 in the same group can generate the same mechanical force. In some embodiments, piezoelectric actuators 120 in different groups are electrically isolated. In some embodiments, all piezoelectric actuators 120 are electrically isolated and can be individually controlled for greater flexibility in the control of mechanical force.

[0050] In some embodiments, the mechanical forces F1 and F2 generated by actuators 121 and 122 are different. However, the pressures in regions SB1 and SB2 of substrate SB can be substantially equal per unit area. In other words, the average pressure in region SB2 originating from mechanical force F2 should be substantially the same as the average pressure in region SB1 originating from mechanical force F1. The polishing head 100 including multiple plates 140 that are separately connected to different groups of piezoelectric actuators 120 but separated from each other can provide individual control of different regions of substrate SB without disturbing the uncontrolled pressures from adjacent air cells (as in conventional CMP apparatuses). Thus, different regions having different distances to the center of substrate SB can have uniform polishing uniformity. Additionally, the CMP system 10 can adjust the voltage provided to an individual plate 140 or individual piezoelectric actuator 120 in real time, and thus can provide a good polishing profile of substrate SB.

[0051] Thus, in some embodiments and according to operation O105, if the average pressures in regions SB1 and SB2 are different and the result of the comparison between the two corresponding signals exceeds a tolerance, then one or more of voltages V1 and V2 are adjusted by control unit 400 to adjust the corresponding mechanical forces F1 and F2. The tolerance can be experimental or theoretical data depending on different applications, and it is not limited herein. On the other hand, if it is determined based on the result of the comparison that the average pressures in regions SB1 and SB2 are substantially equal, then method M10 continues with operation O103 and voltages V1 and / or voltage V2 do not need to be adjusted.

[0052] The concepts and objectives of this disclosure are illustrated as using polishing head 100, but this disclosure is not limited herein. In the embodiments described above, the piezoelectric actuators 120 cannot individually fully cover the corresponding regions of substrate SB, and multiple plates 140 are used to uniformly apply the mechanical force from the piezoelectric actuators 120 to substrate SB. It should be noted that in some embodiments, Figure 6The plate 140 with separated sectors shown in [description] and the regions of the substrate SB corresponding to the gaps between adjacent sectors are negligible. Even if there are some regions of the substrate SB that cannot be directly covered by the sectors, the distances D1 and D2 between the adjacent sectors and the plate are controlled. Additionally, the member 130 is a monolithic and flexible structure, and the regions of the substrate SB corresponding to the gaps can still receive indirect mechanical forces. Therefore, good grinding uniformity of the substrate SB can be provided.

[0053] In some embodiments of the present invention, the piezoelectric actuators 120 are arranged together to form a circular shape that matches the shape of the substrate SB to completely cover the substrate SB. Therefore, the piezoelectric actuators 120 can also act as multiple plates 140.

[0054] Figure 14 A schematic diagram showing a polishing head 101 according to some embodiments of the present invention. The polishing head 101 is similar to the polishing head 100, but without multiple plates 140 and having a different configuration of piezoelectric actuators 120. As Figure 14 shown in [description], multiple piezoelectric actuators 120 are in contact with the diaphragm 130. To have a good polishing profile of the substrate SB, the number of actuators of the multiple piezoelectric actuators 120 and their configuration can be adjusted according to different embodiments. It should be noted that the piezoelectric actuators 120 can be in contact with or separated from adjacent piezoelectric actuators 120. The distance between two adjacent piezoelectric actuators 120 can also be in the range of 0 to 0.02 millimeters (mm).

[0055] Figure 15 is according to some embodiments of the present invention Figure 14 A top perspective view of the multiple piezoelectric actuators 120 shown in [description]. In an embodiment, the multiple piezoelectric actuators 120 include an actuator 121 having a circular shape and disposed at the center (or rotation center) of the multiple piezoelectric actuators 120 corresponding to the central region (such as region SB1) of the substrate SB. The multiple piezoelectric actuators 120 also include an actuator 122 having an annular shape and surrounding the actuator 121. The actuator 122 overlaps with a region SB2 surrounding the region SB1 of the substrate SB. The multiple piezoelectric actuators 120 further include an actuator 123 surrounding the actuator 122, an actuator 124 surrounding the actuator 123, and an actuator 125 surrounding the actuator 124. From a top view perspective, the configuration and arrangement of the multiple piezoelectric actuators 120 are similar to Figure 3 the configuration and arrangement of the multiple plates 140 shown in [description], and the repeated description is omitted herein. The piezoelectric actuators 120 include a hard material and are capable of uniformly providing mechanical forces to the corresponding regions of the substrate SB without multiple plates 140 being disposed between the piezoelectric actuators 120 and the substrate SB.

[0056] In some embodiments, one or more of the multiple piezoelectric actuators 120 include a plurality of sectors. Figure 16According to some embodiments of the present invention Figure 14 A top perspective view of the plurality of piezoelectric actuators 120 shown in Figure 14 . The sectors in a single actuator 122, 123, 124, or 125 are adjacent to each other and are arranged to form an annular shape of the corresponding actuator 122, 123, 124, or 125. Each sector of the actuators 122, 123, 124, or 125 can be individually connected to a different voltage source. Thus, different sectors corresponding to different regions of the substrate SB can be individually adjusted to allow precise control of the grinding profile of the substrate SB. The configuration and arrangement of the sectors of the plurality of piezoelectric actuators 120 are similar to Figure 5 the plurality of plates 140 shown in Figure 5 , and a repeated description thereof is omitted herein. Additionally, it should be noted that only the structure of the grinding head 101 is illustrated herein for the purpose of illustration, and the grinding head 101 can also be applied to the system 10 and the method M10.

[0057] Some embodiments of the present invention provide a wafer grinding head. The wafer grinding head includes: a carrier head; a plurality of piezoelectric actuators disposed on the carrier head; and a diaphragm disposed on the plurality of piezoelectric actuators. The plurality of piezoelectric actuators are configured to provide a mechanical force on the diaphragm and generate an electric charge when receiving a reaction force of the mechanical force through the diaphragm.

[0058] Some embodiments of the present invention provide a wafer grinding system. The system includes a platen, a grinding head, and a control unit. The platen is configured to allow a grinding pad to be disposed thereon. The grinding head is configured to hold a substrate against the grinding pad and includes a plurality of piezoelectric actuators and a diaphragm. The plurality of piezoelectric actuators are connected to one or more voltages. The diaphragm is disposed between the plurality of piezoelectric actuators and the substrate. The control unit is electrically connected to the plurality of piezoelectric actuators and is configured to receive a signal of the electric charge generated by the plurality of piezoelectric actuators.

[0059] Some embodiments of the present invention provide a method for polishing a substrate. The method includes a number of operations. A substrate is received and held on a polishing pad by a polishing head. The polishing head includes a carrier head, a first piezoelectric actuator, and a diaphragm. The first piezoelectric actuator is disposed on the carrier head and configured to provide a first mechanical force on the substrate against the polishing head, and the diaphragm is disposed between the substrate and the first piezoelectric actuator. A first voltage is applied to the first piezoelectric actuator to generate the first mechanical force on the diaphragm and the substrate. A first reaction force resulting from the first mechanical force is received by the first piezoelectric actuator, and a first signal corresponding to the first reaction force is generated by the first piezoelectric actuator. The first signal is compared with a reference, and if the result of the comparison between the first signal and the reference exceeds a tolerance, the first voltage applied to the first piezoelectric actuator is adjusted according to the first signal to change the first mechanical force on the substrate.

[0060] The structures of several embodiments have been outlined above so that those skilled in the art can better understand aspects of the present disclosure. Those skilled in the art should understand that they can readily use the present disclosure as a basis for designing or modifying other processes and structures for implementing the same purposes and / or achieving the same advantages as the embodiments introduced herein. Those skilled in the art should also recognize that such equivalent structures should not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations can be made to this disclosure without departing from the spirit and scope of the present disclosure.

[0061] Symbol Explanation

[0062] 10: Chemical Mechanical Polishing (CMP) System

[0063] 100: Polishing Head

[0064] 101: Polishing Head

[0065] 110: Carrier Head

[0066] 120: Piezoelectric Actuator

[0067] 121: Actuator

[0068] 122: Actuator

[0069] 123: Actuator

[0070] 124: Actuator

[0071] 125: Actuator

[0072] 130: Diaphragm

[0073] 140: Plate

[0074] 141: Plate

[0075] 142: Plate

[0076] 143: Plate

[0077] 144: Plate

[0078] 145: Plate

[0079] 150: Fixed Ring

[0080] 200: Pressing Plate

[0081] 201: Grinding Pad

[0082] 300: Slurry Delivery Unit

[0083] 301: Slurry

[0084] 400: Control Unit

[0085] 500: Pad Trimmer

[0086] 1421: Sector

[0087] 1451: Sector

[0088] C100: Center Line

[0089] C141: Center

[0090] C200: Center Line

[0091] D1: Distance

[0092] D2: Distance

[0093] D142: Diameter

[0094] D143: Diameter

[0095] D144: Diameter

[0096] D145: Diameter

[0097] E1: Charge

[0098] E2: Charge

[0099] F1: Mechanical Force

[0100] F2: Second Mechanical Force

[0101] M10: Method

[0102] O101: Operation

[0103] O102: Operation

[0104] O103: Operation

[0105] O104: Operation

[0106] O105: Operation

[0107] O106: Operation

[0108] R1: Reaction force

[0109] R2: Reaction force

[0110] S201: Grinding surface

[0111] SB: Substrate

[0112] SB1: Region

[0113] SB2: Region

[0114] V1: First voltage

[0115] V2: Second voltage

[0116] W142: Width

[0117] W143: Width

[0118] W144: Width

[0119] W145: Width

Claims

1. A wafer grinding head, comprising: A carrier head; A plurality of piezoelectric actuators disposed on the carrier head; A diaphragm disposed on the plurality of piezoelectric actuators, wherein the plurality of piezoelectric actuators are configured to provide a mechanical force on the diaphragm and generate an electric charge when receiving a reaction force of the mechanical force through the diaphragm; And A plurality of plates disposed between the diaphragm and the plurality of piezoelectric actuators, wherein the plurality of plates include a first plate having a circular shape and at least a second plate having an annular shape surrounding the first plate.

2. The wafer grinding head according to claim 1, wherein the distance between two adjacent plates in the plurality of plates is in the range of 0 to 0.02 millimeters.

3. The wafer grinding head according to claim 1, wherein the width of the plurality of plates gradually decreases as the distance from the rotation center of the plurality of plates increases.

4. The wafer grinding head according to claim 1, wherein the second plate includes a plurality of sectors adjacent to each other and arranged to form the annular shape.

5. The wafer grinding head according to claim 4, wherein each of the sectors is connected to one of the plurality of piezoelectric actuators.

6. The wafer grinding head according to claim 1, wherein the second plate is a monolithic structure and is connected to some of the plurality of piezoelectric actuators.

7. The wafer grinding head according to claim 1, wherein the first plate is connected to one of the plurality of piezoelectric actuators.

8. The wafer grinding head according to claim 1, wherein the plurality of piezoelectric actuators are in contact with the diaphragm.

9. The wafer grinding head according to claim 8, wherein the plurality of piezoelectric actuators include a first actuator having a circular shape and at least a second actuator having an annular shape surrounding the first actuator.

10. The wafer grinding head according to claim 9, wherein the second actuator includes a plurality of sectors adjacent to each other and arranged to form the annular shape.

11. A wafer grinding system, comprising: A platen configured to allow a polishing pad to be disposed thereon; A grinding head configured to hold a substrate against the polishing pad, the grinding head including: A plurality of piezoelectric actuators connected to one or more voltages; A diaphragm disposed between the plurality of piezoelectric actuators and the substrate; and A plurality of plates disposed between the diaphragm and the plurality of piezoelectric actuators, wherein the plurality of plates include a first plate having a circular shape and at least a second plate having an annular shape surrounding the first plate; and A control unit electrically connected to the plurality of piezoelectric actuators and configured to receive a signal of an electric charge generated by the plurality of piezoelectric actuators, wherein the plurality of piezoelectric actuators are divided into a plurality of groups, and the piezoelectric actuators in one group are all connected to a single voltage and have a substantially same distance to the center of the diaphragm.

12. The wafer grinding system according to claim 11, wherein the one or more voltages are adjusted by the control unit according to the signal of the electric charge generated by the plurality of piezoelectric actuators.

13. The wafer grinding system according to claim 11, wherein the piezoelectric actuators are all electrically isolated from each other.

14. The wafer grinding system according to claim 11, wherein one or more of the piezoelectric actuators in one of the plurality of groups define an annular shape, and different groups of the plurality of groups define a plurality of concentric ring shapes.

15. The wafer grinding system according to claim 11, further comprising: a slurry delivery unit configured to apply a slurry to the polishing pad.

16. A method for grinding a substrate, comprising: receiving a substrate; holding the substrate on a polishing pad using a grinding head, wherein the grinding head includes: a carrier head; a first piezoelectric actuator disposed on the carrier head and configured to provide a first mechanical force on the substrate against the polishing pad; a second piezoelectric actuator adjacent to the first piezoelectric actuator, wherein the first piezoelectric actuator and the second piezoelectric actuator overlap different regions of the substrate; a diaphragm disposed between the substrate and the first piezoelectric actuator and between the substrate and the second piezoelectric actuator; and a plurality of plates disposed between the diaphragm and the first piezoelectric actuator and the second piezoelectric actuator, wherein the plurality of plates includes a first plate having a circular shape and at least a second plate having an annular shape surrounding the first plate; applying a first voltage to the first piezoelectric actuator to generate the first mechanical force on the diaphragm and the substrate; receiving a first reaction force from the first mechanical force on the first piezoelectric actuator to generate a first signal corresponding to the first reaction force; comparing the first signal with a reference; and adjusting the first voltage applied to the first piezoelectric actuator according to the first signal.

17. The method according to claim 16, wherein the first voltage is adjusted by a control unit electrically connected to the first piezoelectric actuator.

18. The method according to claim 16, wherein if the result of the comparison between the first signal and the reference exceeds a tolerance, the first mechanical force on the substrate is changed by the adjustment of the first voltage.

19. The method according to claim 18, wherein a second voltage is applied to the second piezoelectric actuator to generate a second mechanical force on the substrate, and the second mechanical force is different from the first mechanical force.

20. The method according to claim 18, further comprising: applying a second voltage to the second piezoelectric actuator to generate a second mechanical force on the substrate in a second region; and receiving a second reaction force from the second mechanical force on the second piezoelectric actuator to generate a second signal corresponding to the second reaction force, wherein the second signal is compared with the first signal as the reference.

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