A polishing head device for a chemical mechanical polishing machine

Abstract

The present invention discloses a polishing head device for a chemical mechanical polishing machine, which comprises a fixing part and a polishing head. The fixing part includes a connecting shaft and a housing cover that are fixedly connected to each other. The housing cover is provided with a lower open cavity, and an annular airbag is arranged in the lower open cavity. The polishing head is detachably connected to the housing cover and is axially floatingly arranged in the lower open cavity. The polishing head includes a polishing head body and an elastic metal attachment plate. The periphery of the elastic metal attachment plate is hermetically and fixedly connected to the lower surface of the polishing head body. A pressure variable cavity is formed between the elastic metal attachment plate and the polishing head body. The polishing head body is provided with an air path channel communicating with the pressure variable cavity. The fixing part is provided with an air path joint, and the air path joint is connected to the air path channel through a connecting pipe. The elastic metal attachment plate changes between an upper concave state and a lower convex state with the change of the pressure in the pressure variable cavity. The annular airbag is used to apply a downward pressure to the polishing head body. The present invention simplifies the air path structure and can achieve rapid disassembly and replacement to adapt to the polishing process of wafers of different sizes.

Description

Technical Field

[0001] The present invention relates to a polishing head, and more particularly to a polishing head device for a chemical mechanical polishing machine. Background Art

[0002] During the polishing process of semiconductor wafers, chemical mechanical polishing (CMP) treatment needs to be performed on the front or back surface of the wafers. The CMP polishing head is used for the adsorption and fixation of the wafers, and controls the pressure on the wafers during the CMP processing. After the CMP treatment, the surface of the wafers can achieve a certain material removal amount, good surface finish, as well as good surface uniformity and flatness.

[0003] The existing CMP polishing heads adopt downward pressure and multi-zone pressure control on the back surface of the wafers. The multi-zone airbags on the back surface of the wafers can directly pressurize and control the wafers. For example, a segmented pressure-regulating airbag head mechanism and an airbag polishing device disclosed in a Chinese patent with the publication number CN112605786A. Such CMP polishing heads with multi-zone pressurization have many internal air paths and complex structures, resulting in a large number and complexity of the overall air path control components. Moreover, the multi-zone airbags have high material requirements, are easily contaminated and damaged, and have a high replacement cost. In addition, the traditional CMP polishing head is of an integral design. The loading and unloading of the wafers are carried out by manually lifting the wafer carrier or automatically loading and unloading the wafers. During the loading and unloading process, it is not easy for the system or the operator to understand the overall adsorption state of the wafers and the surface state of the airbags, which is likely to cause contamination or damage to the wafers. And for traditional CMP polishing, the polishing head is only applicable to wafers of one size. If the diameter of the wafers changes, the entire polishing head needs to be replaced. The process of replacing the polishing head is usually time-consuming and laborious. Summary of the Invention

[0004] Aiming at the defects of the above-mentioned prior art, the present invention provides a polishing head device for a chemical mechanical polishing machine, aiming to simplify the air path structure on the premise of realizing multi-zone pressure control, and at the same time facilitate the adaptation to chemical mechanical polishing of wafers of different sizes.

[0005] The technical solution of the present invention is as follows: A polishing head device for a chemical mechanical polishing machine, including a fixing part and a polishing head. The fixing part includes a connecting shaft and a housing cover that are fixedly connected to each other. The housing cover is provided with a lower opening cavity, and an annular airbag is arranged in the lower opening cavity. The polishing head is detachably connected to the housing cover, and the polishing head is axially floatingly arranged in the lower opening cavity. The polishing head includes a polishing head body and an elastic metal attachment plate. The periphery of the elastic metal attachment plate is hermetically and fixedly connected to the lower surface of the polishing head body. A pressure variable cavity is formed between the elastic metal attachment plate and the polishing head body. The polishing head body is provided with an air passage channel communicating with the pressure variable cavity. The fixing part is provided with an air passage joint, and the air passage joint is connected to the air passage channel through a connecting pipe. The elastic metal attachment plate changes between an upper concave state and a lower convex state with the change of pressure in the pressure variable cavity. The annular airbag is used to apply a downward pressure to the polishing head body.

[0006] Further, when the elastic metal attachment plate is in an upper concave or lower convex state, the degree of upper concavity or lower convexity of the elastic metal attachment plate decreases from the center to the periphery.

[0007] Further, the polishing head includes an adsorption pad and a polishing template. The polishing template and the adsorption pad are fixedly arranged on the lower surface of the elastic metal attachment plate. The polishing template is annular and arranged around the adsorption pad. The adsorption pad is used to adsorb the wafer, and the polishing template is used to fix the wafer to prevent the wafer from running out and to control the height of the upper surface of the wafer protruding from the surface of the template.

[0008] Further, a limiting ring for pressing the inner ring of the annular airbag is arranged in the middle of the lower opening cavity, and the top of the polishing head body is radially limited by the limiting ring. During the polishing process, the limiting ring can limit the offset movement of the polishing head.

[0009] Further, the polishing head and the housing cover are floatingly connected through a pin-slot structure. The pin-slot structure includes a radial pin and an inverted J-shaped slot. The radial pin and the inverted J-shaped slot are respectively arranged on the cavity wall of the lower opening cavity and the side wall of the polishing head body.

[0010] Further, the air passage channel is provided with a quick connector, and the connecting pipe is a spiral hose.

[0011] Further, the connecting shaft extends into the housing cover and forms an annular cavity with the housing cover. The annular airbag is arranged in the annular cavity, and the air passage joint is arranged at the bottom end of the connecting shaft.

[0012] Further, a number of concentrically arranged annular pressure distribution grooves are provided on the bottom surface of the polishing head body in the area of the pressure variable cavity.

[0013] The advantages of the technical solution provided by the present invention are as follows:

[0014] An elastic metal attachment plate is used to replace the back pressure airbag, and only one air path is required to achieve different pressure controls at different positions with different radii during wafer polishing. Since the air path is simple, the polishing of wafers of different sizes can be adapted by replacing the movable polishing head, greatly improving the processing efficiency. Further, the polishing head and the outer shell cover are connected by a combination of radial pins and inverted J-shaped grooves, and with a simple structure, the disassembly and assembly of the polishing head are made more convenient and fast, and the axial movement of the polishing head can be restricted. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic structural diagram of a polishing head device for a chemical mechanical polishing machine according to an embodiment.

[0016] Figure 2 It is a schematic cross-sectional structural diagram of a polishing head device for a chemical mechanical polishing machine according to an embodiment.

[0017] Figure 3 It is a schematic structural diagram when the connecting shaft and the outer shell cover are inverted.

[0018] Figure 4 It is a schematic cross-sectional structural diagram of the polishing head.

[0019] Figure 5 It is Schematic Diagram A of the structure of the polishing head with the wafer surface facing down.

[0020] Figure 6 It is Schematic Diagram B of the structure of the polishing head with the wafer surface facing up.

[0021] Figure 7 It is a schematic structural diagram of the spiral hose. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will be further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading this description, various equivalent modifications of this description by those skilled in the art fall within the scope defined by the appended claims of this application.

[0023] Please refer to Figures 1 to 3As shown in the figure, the polishing head device for a chemical mechanical polishing machine in this embodiment includes a connecting shaft 1, a housing cover 2, and a polishing head 3. The connecting shaft 1 is provided with a fixed flange surface 101 for fixing with the housing cover 2 to form a fixed part for connecting with the chemical mechanical polishing machine. The bottom end of the connecting shaft 1 extends into the housing cover 2, and the housing cover 2 has a lower open cavity 201. An annular space 202 is formed between the extending connecting shaft 1 and the housing cover 2. A sealing ring 4 is arranged on the peripheral surface of the connecting shaft 1. The sealing ring 4 is used for sealing between the connecting shaft 1 and the housing cover 2 to seal the upper part of the aforementioned annular space 202. An annular airbag is arranged in the annular space 202 and is arranged around the bottom end of the connecting shaft 1.

[0024] As a preferred embodiment, in this embodiment, a circle of protrusions 203 is provided on the cavity wall of the lower open cavity 201 of the housing cover 2. The protrusions 203 are flush with the bottom surface of the connecting shaft 1. The outer circle of the annular airbag film 204 is sealed and fixed on the lower surface of the protrusions 203 through a fixing ring 205, and the inner circle of the annular airbag film 204 is sealed and fixed on the bottom surface of the connecting shaft 1 through a limiting ring 102. The limiting function of the limiting ring 102 in addition to fixing the airbag film 204 will be described later. The airbag film 204 closes the annular space 202 between the connecting shaft 1 and the housing cover 2 to form an annular airbag. A pressurized air path 103 is opened on the connecting shaft 1. The pressurized air path 103 is communicated with the annular airbag, and the annular airbag is inflated through the pressurized air path 103 to form the downward pressure of the polishing head 3.

[0025] Another air path 104 is also provided in the middle of the connecting shaft 1. This air path 104 is used to supply compressed air to the polishing head 3. The air path 104 forms an air path joint 105 at the bottom of the connecting shaft 1. Please combine Figure 7 As shown, the air path joint 105 is connected to the head end of a spiral hose 5, and a quick-connect plug 501 is arranged at the tail end of the spiral hose 5 for connecting with the polishing head 3.

[0026] Please further combine Figure 2 、 Figure 4 、 Figure 5 and Figure 6As shown, the polishing head 3 is axially floating and arranged in the lower opening cavity 201. In some embodiments, radial pins are arranged on the cavity wall of the lower opening cavity 201, and axial grooves are arranged on the side wall of the polishing head 3. The axial movement of the polishing head is restricted by the cooperation of the pins and the grooves. In order to facilitate the disassembly and assembly of the polishing head 3, the pins can be set to be retractable. In this embodiment, as a preferred method, the pin-slot structure adopted includes a radial pin 206 and an inverted J-shaped slot 301, wherein the radial pin 206 is fixedly arranged on the cavity wall of the lower opening cavity 201. The inverted J-shaped slot 301 is arranged on the side wall of the polishing head 3 and includes three parts, namely an axial through slot 301a, a transverse slot 301b and an axial limiting slot 301c. The radial pin 206 is introduced from the axial channel 301a, passes through the transverse slot 301b and reaches the axial limiting slot 301c, and then the axial movement of the polishing head 3 can be restricted. Generally, three groups of pin-slot structures are arranged between the polishing head 3 and the outer shell cover 2.

[0027] The polishing head 3 specifically includes a polishing head body 302, an elastic metal attachment plate 303, an adsorption pad 304 and a polishing template 305, and the inverted J-shaped slot 301 is arranged on the side wall of the polishing head body 302. A concave cavity 302a is arranged at the top of the polishing head body 302 and is in radial clearance fit with the limiting ring 102 at the bottom end of the connecting shaft 1, so as to restrict the radial offset of the polishing head 3 during axial floating. A quick connector 306 is arranged on the polishing head body 302 for docking with the quick connector 501 at the tail end of the spiral hose 5. The quick connector 306 on the polishing head body 302 is communicated with an air passage 302b of the polishing head body 302, and the air passage 302b extends to the lower surface of the polishing head body 302.

[0028] On the lower surface of the polishing head body 302, the periphery of the elastic metal attachment plate 303 is fixedly connected to the polishing head body 302, and the periphery of the elastic metal attachment plate 303 and the polishing head body 302 are sealed by a sealing ring 308 provided on the lower surface of the polishing head body 302. Thus, a pressure variable chamber 307 is formed between the elastic metal attachment plate 303 and the lower surface of the polishing head body 302. The air passage 302b of the polishing head body 302 communicates with the pressure variable chamber 307. When the pressure in the pressure variable chamber 307 changes due to the change of the gas pressure introduced, the elastic metal attachment plate 303 generates an upward concave or downward convex deformation. Considering the anti-corrosion requirements, the material of the elastic metal attachment plate 303 can be aluminum alloy, stainless steel or titanium alloy. In this embodiment, when the pressure in the pressure variable chamber 307 = 0.18 Mpa, the surface of the elastic metal attachment plate 303 is flat; when the pressure in the pressure variable chamber 307 > 0.18 Mpa, the surface of the elastic metal attachment plate 303 is in a convex state; when the pressure in the pressure variable chamber 307 < 0.18 Mpa, the surface of the elastic metal attachment plate 303 is in a concave state. Whether the elastic metal attachment plate 303 is upward concave or downward convex deformed, the degree of upward concave or downward convex of the elastic metal attachment plate 303 decreases from the center to the periphery, that is, the surface is in a certain arc shape.

[0029] In a preferred embodiment, a plurality of concentrically arranged annular pressure distribution grooves 302c are formed on the lower surface of the polishing head body 302 for optimizing the pressure distribution.

[0030] The polishing template 305 and the adsorption pad 304 are fixedly arranged on the lower surface of the elastic metal attachment plate 303, wherein the polishing template 305 is annular and arranged around the adsorption pad 304. The adsorption pad 304 is used to adsorb the wafer 6, and the polishing template 305 is used to fix the wafer 6 to prevent the wafer 6 from running out, and to control the height of the upper surface of the wafer 6 protruding from the surface of the template 305. Considering that the removal amount during chemical mechanical polishing is generally in the range of several hundred nanometers to several micrometers, the thickness design of the polishing template 305 and the adsorption pad 304 is: the thickness of the adsorption pad 304 + the thickness of the wafer 6 - the thickness of the polishing template 305 - the thickness of the back glue of the polishing template 305 = 30 - 50 um (the protruding state after the free-state wafer 6 is placed in the polishing template 305), and the compression amount of the adsorption pad 304 is about 50 micrometers. During polishing, the whole polishing head is pressed down onto the polishing platen. Since the adsorption pad 304 will also be compressed under force at the same time, the adsorbed wafer 6 will shrink inward, and finally the surface of the protruding wafer 6 is flush with the surface of the polishing template 305. The surface of the wafer 6 and the surface of the polishing template 305 are on the same horizontal plane, so as to ensure the consistency of the polishing of the surface of the wafer 6.

[0031] The method of using the polishing head device of the chemical mechanical polishing machine of this embodiment is as follows:

[0032] Step 1. Placement of the wafer 6: Place the polishing head flat on the operating table with the polishing template 305 facing up. Sprinkle a certain amount of water on the adsorption pad 304, and then place the wafer 6 on the adsorption pad 304 at the center of the polishing template 305. Gently rotate and squeeze the wafer 6 to remove the excess water in the adsorption pad 304.

[0033] Step 2. Installation of the polishing head: Flip the polishing head with the wafer 6 adsorbed in Step 1 so that the side with the quick-connect joint faces up. Quickly connect the quick plug of the spiral hose to the quick-connect joint of the polishing head; align the center of the polishing head with the center of the connecting shaft 1, and then align the axial through-hole of the inverted J-shaped groove on the side of the polishing head with the center of the radial pin of the outer housing 2; Hold the polishing head up with both hands until it can no longer move up. At this time, the radial pin is at one end of the transverse groove of the inverted J-shaped groove; Rotate the polishing head clockwise (looking down from the top of the polishing head) so that the radial pin is in the axial limiting groove of the inverted J-shaped groove; Release both hands. At this time, the polishing head drops and can freely hang above the three radial pins. At this time, the radial pin is at the top position of the axial limiting groove.

[0034] Step 3. Chemical mechanical polishing: The chemical mechanical polishing machine moves the entire polishing head device towards the polishing platen. When the wafer 6 contacts the platen surface, continue to move until the radial pin is at the center of the axial limiting groove of the inverted J-shaped groove and stop. At this time, the pressurized gas path of the connecting shaft 1 introduces gas at a set pressure, and the annular airbag bulges downward, pressing on the top annular area of the polishing head body 302 to apply a downward pressure to the polishing head; At the same time, the gas path at the center of the connecting shaft 1 inputs gas at a set pressure and is input into the pressure variable chamber 307 through the spiral hose; The pressure in the pressure variable chamber 307 can change the shape of the elastic metal attachment plate 303, which also changes the pressure of the elastic metal attachment plate 303 on different areas of the wafer 6. Appropriate process parameters can enable the wafer 6 to achieve good planarization polishing and achieve good surface flatness and surface uniformity.

[0035] Step 4. Disassembly of the polishing head: After the chemical mechanical polishing is completed, the chemical mechanical polishing machine lifts the entire polishing head device away from the polishing platen. Without the support of the polishing platen, the polishing head drops and freely hangs above the three radial pins again. The pressurized gas path of the connecting shaft 1 is connected to a vacuum to evacuate the gas above the annular airbag, causing the annular airbag to move away from the polishing head; The gas path at the center of the connecting shaft 1 returns to atmospheric pressure; Hold the polishing head up with both hands until it cannot move, and then rotate the polishing head counterclockwise (looking down from the top of the polishing head) so that the radial pin is in the axial through-hole of the inverted J-shaped groove; Hold the polishing head and let it fall naturally. The radial pin exits the inverted J-shaped groove, and the polishing head completely retracts outside the outer housing 2 until the quick-connect plug of the spiral hose is seen; Disconnect the connection between the spiral hose and the polishing head. At this time, the polishing head is completely disassembled. After flipping, the wafer 6 can be seen. It can be rinsed with a water gun and taken out for cleaning and inspection; After the wafer 6 is taken out, the surfaces of the adsorption pad 304 and the template 305 can be rinsed.

[0036] Through experimental verification, the polishing head device for a chemical mechanical polishing machine of the present invention can achieve rapid disassembly and installation of the polishing head, and indexes such as surface flatness and surface consistency after polishing meet the application requirements.

Claims

1. A polishing head device for a chemical mechanical polishing machine, characterized in that, It includes a fixed part and a polishing head. The fixed part includes a connecting shaft and a housing cover that are fixedly connected to each other. The housing cover is provided with a lower opening cavity. A ring-shaped airbag is arranged in the lower opening cavity. The polishing head is detachably connected to the housing cover. The polishing head is axially floatingly arranged in the lower opening cavity. The polishing head includes a polishing head body and an elastic metal attachment plate. The periphery of the elastic metal attachment plate is hermetically and fixedly connected to the lower surface of the polishing head body. A pressure variable cavity is formed between the elastic metal attachment plate and the polishing head body. The polishing head body is provided with an air passage communicating with the pressure variable cavity. The fixed part is provided with an air passage joint. The air passage joint is connected to the air passage through a connecting pipe. The elastic metal attachment plate changes between an upward concave state and a downward convex state as the pressure in the pressure variable cavity changes. The ring-shaped airbag is used to apply a downward pressure to the polishing head body. The polishing head and the housing cover are floatingly connected through a pin groove structure. The pin groove structure includes a radial pin and an inverted J-shaped groove. The radial pin and the inverted J-shaped groove are respectively arranged on the cavity wall of the lower opening cavity and the side wall of the polishing head body. The connecting shaft extends into the housing cover and forms an annular cavity with the housing cover. The ring-shaped airbag is arranged in the annular cavity. The air passage joint is arranged at the bottom end of the connecting shaft.

2. The polishing head device for a chemical mechanical polishing machine according to claim 1, wherein, When the elastic metal attachment plate is upward concave or downward convex, the degree of upward concavity or downward convexity of the elastic metal attachment plate decreases from the center to the periphery.

3. The polishing head device for a chemical mechanical polishing machine according to claim 1, characterized in that, The polishing head includes an adsorption pad and a polishing template. The polishing template and the adsorption pad are fixedly arranged on the lower surface of the elastic metal attachment plate. The polishing template is annular and arranged around the adsorption pad.

4. The polishing head device for a chemical mechanical polishing machine according to claim 1, characterized in that, A limiting ring for pressing the inner ring of the ring-shaped airbag is arranged in the middle of the lower opening cavity. The top of the polishing head body is radially limited by the limiting ring.

5. The polishing head device for a chemical mechanical polishing machine according to claim 1, wherein, The air passage is provided with a quick connector. The connecting pipe is a spiral hose.

6. The polishing head device for a chemical mechanical polishing machine according to claim 1, characterized in that, A number of concentrically arranged annular pressure distribution grooves are provided on the bottom surface of the polishing head body in the area of the pressure variable cavity.

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