TW523444B - Polishing head with a floating knife-edge - Google Patents

Abstract

A polishing head with a floating knife-edge mechanism includes a base, a retaining ring secured to the base defining a pocket area beneath the base, and a lower assembly floating within the pocket area via a diaphragm seal. The lower assembly includes a disk-shaped support plate having a plurality of apertures distributed in a center region of the support plate, a clamp ring used to secure the diaphragm seal along a rim region of the support plate, and the floating knife-edge mechanism positioned between the rim region and the center region of the support plate.

Description

523444 V. Description of the invention (1) Field of invention The present invention relates to the field of chemical mechanical polishing (hereinafter referred to as CMP) in the semiconductor process, especially a novel polishing head design with a floating The barrier ring mechanism can obtain a better uniformity (uni formi ty) in the grinding process. Background Description During the fabrication of integrated circuits, it is unavoidable to deposit several layers of stacked structures of different materials on a wafer. As a result, the wafer surface is irregularly planar. Irregular wafer surfaces will cause some yellow light process problems, such as insufficient depth of focus (DOF) and image transfer deviation. Therefore, during the fabrication of integrated circuits, $ planarization technology, such as CMP technology, is often required to planarize the irregular surface of the wafer. Tradition: CMP technology is to press a wafer to be polished face down on a polished circle: Γ machine 1 Γ two on = polished wafer system by-weighed ^ ^ wafer is rotated with-fixed rotation axis: Hey machine Cheng Fang ^ should be rotated with another-rotation axis, then the metal layer is ground off. At present, the grinding head removed by "quote or -f and -f is popular in the industry is a type of polishing head called floating page 5 523444 invention description (2) moving (f 1 oat 1 ng) grinding head design. This design uses a flexible film (flexibl two merabrane) to fix a wafer support plate or back plate (support Piate) under a base. In the grinding stage, the gas can be pressurized on the wafer support plate to evenly distribute the downforce applied to the wafer backside. One of the problems often encountered in the traditional CMP process is that the Wafer transfer stage where the wafer is removed from the surface of the polishing pad. This difficulty is due to the adhesion between the polishing slurry on the polishing pad and the wafer, which makes it very difficult to remove the wafer from the polishing pad. The traditional solution is to use vacuum-chucking to suck up the wafer to overcome the adhesion between the polishing slurry and the wafer surface. In order to avoid the liquid or air from running in when the wafer is vacuum-sucked, a circular barrier ring structure is generally designed to extend downward on the periphery of the lower surface of the wafer support plate. The thickness of this barrier ring is generally about 1 cm, and it is fixed around the lower surface of the wafer support plate. When the polishing is completed, 'this barrier ring can engage the wafer' and form a good vacuum state 'to help the polishing head remove the wafer. Similar fixed barrier ring structure can refer to the ntanT grinding head designed for the Mirra CMP system of AppHed Materials. Although the conventional fixed-type barrier ring structure can help to form a good vacuum when moving the wafer, the fixed-type barrier ring structure creates a problem that cannot be ignored during the polishing process. This problem is commonly referred to as

523444 V. Description of the invention (3) The edge effect or fast band effect is mainly due to the fixed down ring structure providing a large downforce during grinding, which causes the wafer to be close to the fixed The polishing rate in the type of barrier ring region is faster than that of the wafer center. As a result, the polishing uniformity is reduced. SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a CMP apparatus capable of improving polishing uniformity. Another object of the present invention is to provide a novel polishing head design, which can simultaneously solve the problem of moving wafers' and obtain a good polishing uniformity. According to the purpose of the present invention, a preferred embodiment of the present invention discloses a polishing head for CMP, which includes: a base; a wafer edge retaining ring, Fixed on the pedestal, wherein the wafer edge lamination ring defines a pocket area (area) 'for accommodating a wafer; and a lower assembly) directly below the pedestal via a diaphragm ( A diaphragm seal is floating in the pocket area. The lower component includes: a circular plate having a plurality of openings distributed in a center region of the back plate; and a clamp ring for locking the diaphragm. In one edge area of the backplane (rim

523444

-A floating barrier ring mechanism is embedded between the center region and the edge region of the backplane. When performing a CMP polishing, the back plate can provide a nearly flat bottom and a uniform downforce (d0wnf0rce) to the wafer; and when the polishing is completed, the oceanic barrier ring mechanism can provide a consistent The protruding ring structure is lowered to improve the vacuum suction. according to? For the purpose of the present invention, the present invention discloses a lower part of a grinding head. There are three supporting plates with a plurality of openings distributed in the two Ϊ Ϊ I: area;-clamping ring 'is used to- The diaphragm is tightly locked in this area; and a floating barrier ring machine is lost between the middle ~ area and the edge area of the backplane. When grinding, the back plate can provide: a nearly flat bottom and uniform down pressure to a wafer. In the present invention: i: Φ The flat back plate bottom ΐ is capable of grinding, the grinding head can provide-', so the grinding uniformity can be improved. Clearly I understand =, the above and other purposes, features, and advantages of April can be explained in more detail. A preferred embodiment is described in detail with the accompanying drawings.

523444 V. Description of the invention (5) Detailed description of the invention Please refer to FIG. 1, which is a schematic cross-sectional view of a grinding head 100 according to the present invention. As shown in Figure 1, the grinding head 100 basically includes a housing 102, a base 104, a gimbal mechani sm 106, and a loading chamber 1 0 8-- Said round edge retaining ring 1 1 0 and lower assembly 112 (lower assembly). A wafer edge lamination ring lio defines a pocket area directly under the base 104 to accommodate a wafer 10. Some of the components described above are the basic elements that make up a polishing head, such as the housing 102, the base 104, and the wafer edge lamination ring 110, and are well known to those skilled in the art. A similar description of the grinding head can be found in U.S. Patent No. 6,244,942. The housing 102 is connected to a drive shaft, and during the grinding stage, a rotating shaft 90 drives the wafer 10 to rotate in a fixed direction. The rotating shaft 90 is substantially perpendicular to a polishing pad (not shown) during the grinding stage. A vertical hole 1 3 0 passes through the center of the housing 102. In addition, there are three pipes 132, 134, and 136 that pass through the housing 102 and are used to pneumatically control the down force of the polishing head 100 to the wafer 10. The O-ring (0-1 ^ 叩) 138 can form a gas-tight state between the pipes. The base 104 is basically a rigid ring-shaped or disc-shaped body and is located below the housing 102. At the bottom of the base 104, there are two elastic films 14 and 141.

Page 9 523444 V. Airbags 144 and 145 as defined in the description of the invention (6). The elastic films 14 and 141 are respectively fixed by clamp rings 142 and 143 which are locked to the base 104. The fixing points 148 and 149 are used to provide two ends of a hose ({16} ^ 1) 16 tube). By means of the pipeline 134, the pipeline 136, and the hose (not shown) ', the movements of the airbags 1 4 4 and 1 4 5 can be controlled, respectively. The pipeline 1 3 4 is externally connected with a first pump (not shown) to inject gas, such as air, into the air bag 144 'or to extract gas from the air bag 144. The pipeline 13 6 is connected to a second Kuriura (not shown) to inject gas, such as air, into the air bag 14 5 or to extract gas from the air bag 14 5.

The pressurizing system 108 is a space between the housing 102 and the base 104, and is used to apply a downward force or pressure to the base 104. The balance mechanism 106 can be regarded as a part of the base 104, which is used to keep the base 〇04 and the grinding level. The balance mechanism 106 includes a balance bar 150 and a flexure ring 152 locked on the base 104. · The balance bar 150 can make a small vertical slide within the axis profile (b u s h i n g) 1 5 4 to provide a vertical movement space of the base 104. In the middle of the balance bar 1 50 is a hollow tube 1560. The internal clamp ring 16 2 is used to clamp a diaphragm approximately 160 in a ring shape, and the outer ring 1 16 is used to clamp the membrane. The other end of the slice 1 6 0. This way: Come '^ 160 to isolate the space between the housing 102 and the base 104. ff-the third pump (not shown) and the connection through the pipeline 132 Can be filled into the pressurized tank 108 to control the application to the base 104

Page 10 523444 5. The pressure of invention description (7). The wafer edge lamination ring 11 0 is generally ring-shaped and is locked at a position below the periphery of the base 104. When the gas is filled into the pressurized chamber 108, the base 104 is pushed down because of the pressure of the gas, and at this time, the wafer edge pressing ring 1 is also pushed at the same time, thereby generating an applied force Pressure on the pad. An inner surface 1 2 6 of the wafer edge pressing ring 1 10 can engage the wafer 10 to prevent the wafer 10 from slipping out of the bottom of the grinding head 100 during grinding. The lower component 112 basically includes a support plate 114, an insert fiim 2i2, a diaphragm 210, a diaphragm fflembrane 22, and a clamp A clamp ring 23 0 and a floating barrier ring mechanism 240. A pressurizable chamber 109 is defined by the space separated by the crystal back cushion 2 1 2, the support back plate 11 4, the diaphragm 2 10, the base 1 104 and the balance mechanism 106. A fourth pump can be connected to the pressurized gas chamber 1 0 9 through a hollow pipe 1 56, and is controlled to be applied to the wafer by the gas pressure '10 9 injected into the pressurized gas chamber 1 0 Down pressure on 丨 〇. The support back plate 114 includes a plurality of apertures 172 evenly distributed in the center region of the greedy plate 1 1 4. The diaphragm 210 is generally a ring-shaped flexible material film, one end of which is clamped by the base i 04 and the wafer edge lamination ring Π 0, and the other end is locked by the clamping ring 230. Diaphragm

523444 V. Description of the invention (8) 210 The composition of 210 can be rubber or artificial rubber (61 & hitting 0 ^^^ (: _ ^ 〇 & 1 ^ (1fibric)), such as NYLNONT domain NOMEXTM, or glass Fiber, etc. The crystal back cushion 2 1 2 is a disc-shaped film, which can be composed of a polymer material, which also has openings corresponding to the back plate 114. The elastic film 2 2 0 can be relatively hard The crystal back cushion pad 2 1 2 is made of a slightly soft polymer material. The elastic film 2 2 0 is more sensitive to pressure and can buffer the down pressure applied to the wafer 'and can compensate for the tinyness of the back plate 114 or the back of the wafer. Uneven surface. In the preferred embodiment of the present invention, the elastic film 2 2 0 extends upward around the back plate 11 4 to the periphery of the upper end of the back plate 11 4 and is locked by the clamping ring 2 3 0. Floating barrier ring The mechanism 2 40 is a ring shape embedded between the central region and the edge region of the support back plate 114. The floating barrier ring mechanism 24o includes a discontinuous upper structure 2 41 and a continuous lower ring Structure 2 4 2. In the grinding stage, the continuous lower ring structure 2 4 2 is facing the back plate The part is retracted, so that the back plate 11 14 can provide a nearly flat bottom 12 and a uniform down force to the wafer 10. Please refer to FIG. 1 and FIG. 2 at the same time. FIG. Top view of the back plate 11 4. The position of the floating barrier ring mechanism 2 40 of the present invention can be clearly seen from FIG. 2. For the convenience of explanation, other components of the lower component Π 2, such as the crystal back cushion 2 2 and 2. The diaphragm 2 and the clamping ring 23 0 are not shown in Fig. 2. In Fig. 2, the backplane 11 4 of the branch building includes a central area 3 1 0 and an edge area 3 1 2. As described above, the back The central area 3 1 0 of the plate 11 4 includes a plurality of openings 1 7 2. The screw holes 3 3 0 are scattered

$ 12 pages 523444 V. Description of the invention (9) The edge area 312 of the back plate / 14 is used to lock the diaphragm 210 and the elastic film 2 2 0. The floating barrier ring mechanism 2 40 includes a discontinuous upper structure 2 4 1 and a continuous lower annular structure 242. The superstructure 241 has a strip-shaped distribution and is arranged between the central region 31 and the edge region 312 of the back plate Π4. Each superstructure 2 4 1 is accommodated in a groove 3 1 4, and between two adjacent grooves 3 1 4 is a connection part 3 丨 6, so that the central area 3 4 of the back plate η 4 And the edge regions 3 1 2 are interconnected.

+ Then, please refer to FIG. 3A and FIG. 3β, wherein FIG. 3A is an enlarged cross-sectional schematic view of the present invention along the tangent line AA of FIG. FIG. 3B is an enlarged cross-sectional view of the present invention along the tangent line AA of FIG. 2, showing a part of the lower component 1 12 and the grinding head 100 in a vacuum suction state.

As shown in FIG. 3A, in a grinding stage, the edge area 3 1 0 of the back plate 1 1 4 is supported by an inflatable air bag 1 4 4. At this time, the floating blocking ring mechanism 2 4 0 remains in a floating state. That is, the airbag 1 4 5 does not apply any pressure to the floating barrier ring mechanism 240. In other embodiments of the present invention, the airbag ι45 maintains a smaller pressure than the pressure of the airbag 144. As shown in Figure 3b, when the wafer is removed from the surface of the polishing pad after grinding, the air in the pressurized chamber 109 is evacuated to suck the wafer 1 through the elastic membrane 2 2 0 vacuum. . At the same time, the discontinuous superstructure 241 of the oceanic barrier ring mechanism 240 is pushed down by the inflatable airbag 1 45, and the continuous lower structure 242 of the floating barrier ring mechanism 240 is extended downward from the bottom of the original flat back plate Protruding about 1 to 2 cm

Page 13 523444 5. Description of the invention (ίο) Thickness. In short, the main technical feature of the present invention is that a floating barrier ring mechanism 2 40 is used for the lower component π 2 of the polishing head. The floating barrier ring mechanism 2 40 is embedded between the central region 3 1 0 and the edge region 3 1 2 of a back plate 11 4 and includes a discontinuous superstructure 2 41 and a continuous lower annular structure 242. The floating barrier ring mechanism 24 of the present invention is controlled by a unique airbag 145. By using the present invention, the bottom of the plate can be flattened during grinding, so as to improve the uniformity of grinding. The #Fujia embodiment of the month, all applications and modifications according to the present invention 'shall fall within the scope of the patent of the present invention. The above description is only an equivalent change and scope of the patent scope of the present invention. 523444 Brief description of the drawings Brief description of the diagrams Figure 1 is a schematic cross-sectional view of the grinding head of the present invention; Figure 2 is a top view of the back plate in the lower assembly of the present invention; The enlarged cross-sectional view shown shows a part of the lower components and the grinding head in a grinding state; and FIG. 3B is an enlarged cross-sectional view shown along the tangent line AA ′ of the present invention, showing a part in a vacuum suction state Lower components and grinding head.

Explanation of the symbols in the figure 10 Wafer 90 Rotating shaft 100 Grinding head 102 Housing 104 Base 106 Balancing mechanism 108 Pressurizing chamber 109 Pressurizing ·. Chamber 110 Wafer edge crimping ring 112 Lower assembly 114 Supporting back plate 124 Bottom 126 Inner surface 132 pipe 134 pipe 136 pipe 138 0-ring 142 clamp ring 143 clamp ring 144 outer air bag 145 inner air bag 148 fixing point 149 fixing point 150 balance bar 152 bending ring 154 bushing

Page 15 523444 Brief description of the drawings 156 Duct 160 Diaphragm 162 Internal clamp ring 164 External clamp ring 172 Opening 210 Diaphragm 212 Crystal back buffer 塾 220 Elastic membrane 230 Clamping ring 240 Floating barrier ring mechanism 241 Superstructure 242 Substructure 310 Central area 312 Edge area 314 Groove 316 Connection

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Claims (1)

523444 VI. Application for patent scope 1. A polishing head for chemical mechanical polishing (CMP), the polishing head package contains: a base; A wafer edge retaining ring is fixed on the base, wherein the wafer edge retaining ring defines a pocket area directly below the base to receive a wafer ( (wafer); and a lower assembly (floating) in the pocket area via a diaphragm seal. The lower assembly includes: a circular plate with a plurality of openings (Aperture ·) is distributed in a center region of the backplane; a clamp ring is used to lock the diaphragm to a rim region of the backplane; and a floating A barrier ring mechanism is embedded between the center region and the edge region of the backplane; wherein when a CMP polishing is performed, the backplane can provide a near-flat bottom and a uniform downforce to the crystal Circle; Γ When the grinding is completed, the floating barrier ring mechanism can provide a pressure ring structure protruding downward to improve vacuum suction. 2 · The grinding head as described in item 1 of the patent application scope, wherein the action of the floating blocking ring mechanism is controlled by a separate inner ring bladder and Lipu Page 17 ^ 23444 i · ^ Special = The grinding head of item 丨 of the application scope, wherein when the grinding is completed, the pressing structure protrudes downward by about 1 to 2 cm (mi 1 1 meter). 4. The polishing head according to item 1 of the patent application scope, wherein the lower component further comprises an elastic film and a crystal back cushion (insert f 1 m) located between the wafer and the back plate. 5. The polishing head according to item 4 of the scope of patent application, wherein the elastic film is fixed to the edge region of the back plate. 6. The polishing head according to item 1 of the patent application scope, wherein when a CMP grinding is performed, the surrounding pressure of the back plate can be adjusted by an outer ring airbag. 7. —A lower assembly of a grinding head, the lower assembly comprising: a supporting back plate having a plurality of openings distributed in a central area of the back plate; a clamping ring for locking a diaphragm to the An edge region of the backplane; and a floating barrier ring mechanism embedded between the center region and the edge region of the backplane; wherein when a CMP grinding is performed, the backplane can provide a near-flat bottom and a uniform Down pressure to a wafer. Page 18 523444 6. Scope of patent application 8. The lower component of the scope of patent application item 7, wherein the floating barrier ring mechanism includes a discontinuous upper structure and a continuous lower annular structure. 9. The lower component of the scope of patent application item 8, wherein when the grinding is completed, the continuous lower annular structure can engage the wafer to improve vacuum suction. 10. If item 7 of the patent application scope further includes f Μ a base; and w a wafer edge retaining ring, fixed on the base; wherein the wafer edge lamination A pocket area is defined just below the base to receive the wafer, and the lower assembly is floating in the pocket area through a diaphragm seal. Inside. 1 1. The lower component of item 7 of the patent application scope, wherein the action of the floating blocking ring mechanism is controlled by a separate inner ring bladder and pump. Γ Page 19