CN116330130A

CN116330130A - Polishing head assembly with recess and cap

Info

Publication number: CN116330130A
Application number: CN202211665020.1A
Authority: CN
Inventors: 许致远; 林仁杰; 胡杰; 黄维章; 杨燿青
Original assignee: GlobalWafers Co Ltd
Current assignee: GlobalWafers Co Ltd
Priority date: 2021-12-23
Filing date: 2022-12-23
Publication date: 2023-06-27
Also published as: JP2023094608A

Abstract

A polishing head assembly having a recess and a cap for polishing a semiconductor wafer includes a polishing head. The recess is disposed along a bottom portion of the polishing head. The recess has a recessed surface. The cap is positioned within the recess. The cap includes an annular wall secured to the polishing head and a floor joined to the annular wall at a joint. The base plate extends across the annular wall and has an upper surface and a lower surface. The upper surface is spaced from the recessed surface to form a chamber therebetween. The resistance to deformation of the portion of the base plate proximate the joint is weakened to allow the portion of the base plate proximate the joint to deflect relative to the polishing head by pressure changes in the chamber.

Description

Polishing head assembly with recess and cap

Cross reference to related applications

The present application claims priority to U.S. provisional patent application No. 63/265,951, application No. 2021, 12/23, the entire disclosure of which is hereby incorporated by reference.

Technical Field

The present disclosure relates generally to polishing of semiconductor wafers and, more particularly, to a polishing head assembly having a recess and a cap.

Background

Semiconductor wafers are commonly used to produce Integrated Circuit (IC) chips on which circuitry is printed. Circuitry is first printed onto the surface of the wafer in a miniaturized form. The wafer is then separated into circuit chips. This miniaturized circuitry requires that the front and back surfaces of each wafer be very flat and parallel to ensure that the circuitry can be properly printed over the entire surface of the wafer. To achieve this, grinding and polishing processes are typically used to improve the flatness and parallelism of the front and back surfaces of the wafer after the wafer is cut from the ingot. A particularly good finish is required when polishing a wafer in preparation for printing miniaturized circuitry on the wafer by electron beam lithography or a photolithographic process (hereinafter "lithography"). The wafer surface on which the miniaturized circuitry is to be printed must be planar.

Polishing machines typically include a circular or ring-shaped polishing pad mounted on a turntable or platen to drive rotation about a vertical axis passing through the center of the pad and a mechanism for holding and pressing the wafer into the polishing pad. Wafers are typically mounted to the polishing head using, for example, liquid surface tension or vacuum/suction. A polishing slurry, typically comprising a chemical polishing agent and abrasive particles, is applied to the pad to increase the polishing interaction between the polishing pad and the surface of the wafer. This type of polishing operation is commonly referred to as Chemical Mechanical Polishing (CMP).

During operation, the pad rotates and the wafer is brought into contact with the pad and compresses the pad by the polishing head. During operation, the pad rotates and the wafer is brought into contact with the pad and compresses the pad by polishing. As the pad wears (e.g., after hundreds of wafers), the wafer flatness parameters degrade because the pad is no longer flat, but rather has a worn annular band that forms a recess along the polishing surface of the pad. This pad wear affects wafer flatness and may result in "dishing" or "convexity" or a combination thereof to result in a "w-shape".

When the flatness of the wafer becomes unacceptable, the worn polishing pad is replaced with a new polishing pad. Frequent pad replacement adds significant operating costs to the polishing apparatus, not only because of the large number of pads that need to be purchased, stored, and handled, but also because of the large downtime required to replace the polishing pad.

Accordingly, there is a need for a polishing apparatus that is capable of optimizing the flatness parameters by adjusting the wafer thickness shape for protrusions, depressions, and +/-w shapes during polishing.

This background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

Disclosure of Invention

In one aspect, a polishing head assembly for polishing a semiconductor wafer includes a polishing head and a cap. The polishing head has a recess along a bottom portion. The recess has a recessed surface. The cap is positioned within the recess. The cap includes an annular wall secured to the polishing head and a floor joined to the annular wall at a joint. The base plate extends across the annular wall and has an upper surface and a lower surface. The upper surface is spaced from the recessed surface to form a chamber therebetween. The resistance to deformation of the portion of the base plate proximate the joint is weakened to allow the portion of the base plate proximate the joint to deflect relative to the polishing head by pressure changes in the chamber.

In another aspect, a polishing head assembly for polishing a semiconductor wafer includes a polishing head and a cap. The polishing head has a top portion and a recess along a bottom portion. The recess has a recessed surface. A hole extends from the top portion through the recessed surface. The cap is positioned within the recess. The cap includes an annular wall having an aperture corresponding to the aperture. The holes and corresponding apertures receive fasteners to secure the annular wall to the recessed surface. The cap also includes a base plate joined to the annular wall at a joint. The base plate extends across the annular wall. The base plate has an upper surface and a lower surface. The upper surface is spaced from the recessed surface to form a chamber therebetween. The bottom plate is deflectable relative to the polishing head by pressure changes in the chamber. The resistance to deformation of the portion of the base plate proximate the joint is weakened to allow the portion of the base plate proximate the joint to deflect relative to the polishing head.

In another aspect, a polishing head assembly for polishing a semiconductor wafer includes a polishing head and a lid. The cap has an annular wall secured to the polishing head and a floor joined to the annular wall at a joint. The polishing head and the cap define a chamber between the polishing head and the bottom plate of the cap. The bottom plate is made of a metallic material capable of deflecting relative to the polishing head in response to pressure changes in the chamber. The thickness of at least one of the annular wall and the base plate is reduced in the vicinity of the joint to weaken the deformation resistance of the base plate in the vicinity of the joint.

Various improvements exist in the features associated with the above aspects. Further features may also be incorporated in the above mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For example, various features discussed below with respect to any of the illustrated embodiments may be incorporated into any of the above aspects, alone or in any combination.

Drawings

FIG. 1 is a schematic view of a portion of a polishing apparatus;

FIG. 2 is a cross-sectional view of a polishing head assembly suitable for installation and use in the polishing apparatus shown in FIG. 1;

FIG. 3 is a cross-sectional view of the polishing head assembly shown in FIG. 1 with the bottom plate deflected only partially downward;

FIG. 4 is a cross-sectional view of an example polishing head assembly suitable for installation and use in the polishing apparatus shown in FIG. 1;

FIG. 5 is a cross-sectional view of another example polishing head assembly suitable for installation and use in the polishing apparatus shown in FIG. 1;

FIG. 6 is a cross-sectional view of yet another example polishing head assembly suitable for installing and using the polishing apparatus shown in FIG. 1;

FIG. 7 is a cross-sectional view of yet another example polishing head assembly suitable for installing and using the polishing apparatus shown in FIG. 1;

FIG. 8 is a cross-sectional view of yet another example polishing head assembly suitable for installing and using the polishing apparatus shown in FIG. 1; a kind of electronic device with high-pressure air-conditioning system

Like reference symbols in the various drawings indicate like elements.

Detailed Description

In general, and in embodiments of the present disclosure, suitable substrate "wafers" (which may also be referred to as "semiconductor wafers" or "silicon wafers") include single crystal silicon wafers, such as silicon wafers obtained, for example, by slicing wafers from a single crystal silicon ingot formed by the Czochralski method or the float zone method. Each wafer includes a central axis, a front surface, and a back surface parallel to the front surface. The front and rear surfaces are generally perpendicular to the central axis. The circumferential edges engage the front and rear surfaces. The wafer may be of any diameter suitable for use by those of skill in the art, including, for example, 200 millimeters (mm), 300mm, greater than 300mm, or even 450mm diameter wafers.

In one embodiment, a semiconductor wafer that has been previously rough polished such that it has rough front and back surfaces is first subjected to an intermediate polishing operation in which the front surface of the wafer is polished instead of the back surface to improve the flatness parameters or to smooth the front surface and remove handling scratches. To perform this operation, the wafer is placed against the polishing head assembly. In this embodiment, the wafer is held in place against the polishing head assembly by surface tension. The wafer is also placed on the turntable of the polisher with the front surface of the wafer contacting the polishing surface of the polishing pad.

A polishing head assembly mounted on the machine is capable of vertical movement along an axis extending through the wafer. As the turntable rotates, the polishing head assembly moves toward the wafer to push the wafer toward the turntable, thereby pressing the front surface of the wafer into polishing engagement with the polishing surface of the polishing pad.

Conventional polishing slurries containing abrasive particles and chemical etchants are applied to polishing pads. The polishing pad causes the slurry to act on the surface of the wafer to remove material from the front surface of the wafer, resulting in a surface that improves smoothness. As an example, the intermediate polishing operation preferably removes less than about 1 micron of material from the front side of the wafer.

The wafer is then subjected to a fertilisation polishing operation in which the front surface of the wafer is finish polished to remove the silicon gel (e.g. from DuPont Air Products Nanomaterials, LLC) of large size in an intermediate step

) Resulting in fine or "micro" scratches and high reflectivity of the wafer, without damaging the front surface. Intermediate polishing operations typically remove more wafers than finish polishing operations. The wafer may be polished in the same polisher used for intermediate polishing the wafer, as described above. However, a separate polisher may also be used for the finish polishing operation. The polishing slurry typically contains amino groups and a reduced concentration of colloidal silica is injected between the polishing pad and the wafer. The polishing pad processes the finish polishing slurry against the front surface of the wafer to remove any remaining scratches and blurs so that the front surface of the wafer is generally highly reflective and atraumatic.

Referring to FIG. 1, a portion of a polishing apparatus is schematically shown and indicated generally at 100. The polishing apparatus 100 may be used to polish a front surface of a semiconductor wafer W. It is contemplated that other types of polishing apparatus may be used.

The polishing apparatus 100 includes a wafer holding mechanism, such as a template including a backing film 110 and a retaining ring 120, a polishing head assembly 130, and a turntable 140 having a polishing pad 150. The backing film 110 is positioned between the polishing head assembly 130 and the retaining ring 120, and the retaining ring 120 receives the wafer W. The retaining ring 120 has at least one circular opening for receiving a wafer W to be polished therein.

In this embodiment, the wafer W is attached to and held against the polishing head assembly 130 by surface tension. To create surface tension, the wet saturated backing film 110 is attached to the polishing head assembly 130 by a pressure sensitive adhesive. The backing film 110 and the retaining ring 120 form a template or "wafer holding template". Backing film 110 is typically a soft polymeric mat or other suitable material.

The wafer W is then pressed into the wet saturated backing film 110 to remove or squeeze out most of the water or other suitable liquid. The squeeze-out water causes the wafer to be held to backing film 110 by surface tension and atmospheric pressure on the exposed surface of the wafer. This water extrusion mounts the wafer to the polishing head assembly 130.

Portions of the polishing head assembly 130 are flexible enough to deform in response to pressure changes applied to the polishing head assembly 130, and stiff enough not to deform when the wafer is pressed into the wet saturated template. The surface tension provides a constant holding force on the surface of the wafer. This constant holding force causes any deformation of the polishing head assembly 130 adjacent to the wafer to translate directly into proportional deformation of the wafer.

The function of holding the wafer W by surface tension is different from other known mechanisms that use a flexible membrane or vacuum to hold the wafer against the polishing head assembly. As is known in the art, when a wafer is pushed onto a flexible membrane, the flexible membrane deforms to create a space or vacuum cavity between the wafer and the flexible membrane. These vacuum pockets allow the film to pick up the wafer. Other films have vacuum holes that are connected to a vacuum to create a low pressure area to pick up the wafer.

The polishing apparatus 100 applies a force to the polishing head assembly 130 to vertically move the polishing head assembly 130 to raise and lower the polishing head assembly 130 relative to the wafer W and the turntable 140. The upward force raises the polishing head assembly 130 and the downward force lowers the polishing head assembly. As discussed above, downward vertical movement of the polishing head assembly 130 against the wafer W provides polishing pressure to the wafer to push the wafer into the polishing pad 150 of the turntable 140. As the polishing apparatus 100 increases the downward force, the polishing head assembly 130 moves vertically downward to increase the polishing pressure.

Portions of the polishing head assembly 130 and polishing pad 150 and turntable 140 are rotated at a selected rotational speed by suitable drive mechanisms (not shown) known in the art. The rotational speeds of the polishing pad and the turntable may be the same or different. In some embodiments, the polishing apparatus 100 includes a controller (not shown) that allows an operator to select the rotational speed of both the polishing head assembly 130 and the turntable 140 and the downward force applied to the polishing head assembly.

Referring to fig. 2, a polishing head assembly 200 suitable for installation and use in the polishing apparatus 100 is shown. The polishing head assembly 200 includes a polishing head 210, a cap 240, and a belt 270. The polishing head 210 and/or the cap 240 are suitably made of a metallic material, such as aluminum or steel, or may be made of another suitable structural material. For example, the polishing head 210 and/or cap 240 may be formed from cast aluminum (e.g., available from Alcoa

Cast aluminum plate). Alternatively, the cap 240 may be made of a ceramic material (e.g., alumina), a plastic material, or a stainless steel material with a corrosion resistant coating (e.g., diamond-like carbon).

The polishing head 210 has a top 212 and a bottom 214 that are substantially parallel to each other. The polishing head 210 has a platen 220 and an annular member 230 extending downward from the platen 220. Recessed surface 216 is formed in bottom 214 of polishing head 210 by ring member 230 extending downward from platform 220. The annular member 230 has an outer surface 232 that is substantially perpendicular to the top 212 and bottom 214 of the polishing head 210. The outer surface 232 of the ring member 230 forms the circumference of both the polishing head 210 and the polishing head assembly 200. The ring member 230 has an inner surface 234 that is angled relative to the outer surface 232 such that the ring member 230 is thinnest at the bottom 214 of the polishing head 210. This taper of the ring member 230 provides a stiffer top section adjacent the platform 220. In other embodiments, the inner surface 234 may be substantially parallel to the outer surface 232.

Cap 240 has a base plate 242 and an upwardly extending annular wall 250 along the periphery of the base plate. Annular wall 250 has an outer surface 252 that mates with inner surface 234 of annular member 230. Thus, the outer surface 252 of the annular wall 250 is also angled to match the inner surface 234 of the annular member 230. The outer surface 252 of the annular wall 250 is attached to the inner surface 234 of the annular member 230 of the polishing head 210 by an adhesive (not shown). The adhesive may be an epoxy glue.

The bottom plate 242 extends across the bottom opening formed by the ring member 230. The bottom plate 242 has a top surface 244 and a bottom surface 246. The chamber 202 is formed between a top surface 244 of the bottom plate 242 and the recessed surface 216 of the polishing head 210. Annular member 230 and annular wall 250 define the radial boundary of chamber 202. The platform 220 and the overlapping annular member 230 and the annular wall 250 are thicker and adapted to be more rigid than the base plate 242.

The metal used in the polishing head assembly 200 may contaminate the wafer by the polishing chemistry or slurry being a source of metal ions. To prevent metal from the cap 240 from contaminating the slurry and wafer, a template including a backing film (such as the backing film 110 shown in fig. 1) and a retaining ring (such as the retaining ring 120 shown in fig. 1) may be used to create a barrier between the slurry and the cap 240. Backing film 110 is typically a thin soft polymer mat or other suitable material. Backing film 110 suitably comprises two or more layers of material (not shown). For example, backing film 110 may have an adhesive layer, a thin plastic film layer, a thin polyurethane foam or other nonwoven (e.g., felt) layer. The adhesive layer seals backing film 110 to bottom surface 246 of cap 240. The thin plastic film layer provides a protective barrier between the cap 240 and the slurry and/or wafer W. A layer comprising polyurethane foam or a non-woven material (e.g., felt) contacts the wafer and provides a surface similar to a polishing pad (e.g., polishing pad 150 shown in fig. 1). The retaining ring 120 extends downwardly from the backing film 110 and is typically a plastic material. The wafer is received by the retaining ring 120 and held against the backing film 110 by surface tension. Thus, the wafer does not directly contact cap 240.

To prevent metal from the polishing head assembly 200 from contaminating the slurry and wafer, the polishing head 210 and cap 240 are constrained by the belt 270 to form a barrier that prevents the slurry from contacting the metal and contaminating the wafer. The ring member 230 has side recesses 238 extending inwardly from the outer surface 232 at the bottom 214. The tab 248 extends outwardly from an annular wall 250 of the cap 240 opposite the base plate 242. The tab 248 and the side recess 238 each receive the strap 270 and may be sealed to the strap 270 by an adhesive, such as an epoxy glue. The band 270 may overlap the backing film 110 and/or the retaining ring 120 of the template to form a seal therebetween to prevent metal contamination from the polishing process of the polishing head 210. The strap 270 is made of plastic, such as polyetherimide (e.g., ULTEM available from Saint Foundation Ind. Co., ltd. (SABIC)) ^TM Resin 1000), polyetheretherketone, polyphenylene sulfide or polyparaphenyleneEthylene glycol diformate.

The polishing head assembly 200 is attached to a spindle (not shown) of the polishing apparatus 100. The spindle is a tube with a central passage (not shown). The central passage opens one end to the polishing head assembly 200 and connects the other end to a rotary connector (not shown). To regulate the pressure within the chamber 202, a pressurized source (not shown) is provided through the central passage and connected to the chamber passageway 222 (e.g., via a quick disconnect coupling plug). A chamber passageway 222 extends through the platform 220 to the chamber 202. A pressurized source (not shown) supplies pressurized medium or fluid back and forth to chamber 202 through a spindle (not shown). The pressurized source may provide a pneumatic supply for increasing or decreasing the pressure within the chamber 202 of the polishing head assembly 200.

The base plate 242 is a semi-rigid "flex board" that is made of the same material (e.g., metallic material) as the cap 240. The base plate 242 is adapted to deform or deflect accurately to change the pressure profile and polishing pressure profile, and yet is sufficiently rigid to mount and dismount the wafer on the backing film 110 by surface tension. The rigidity of the base plate 242 is such that it does not substantially deform during mounting of the wafer on the polishing head assembly 200. The base plate 242 may be substantially flat in an initial or undeflected state. As the polishing pressure increases and the pressure within the chamber 202 increases, the platen 242 temporarily deflects in a direction perpendicular to the polishing surface. The cap 240 is not permanently deflected or deformed by pressure. Based on the amount of pressurized medium or fluid supplied to chamber 202 and the polishing pressure, platen 242 has the following capabilities: into a pressure deflected or downward curved shape (shown in fig. 3), into a flat shape (shown in fig. 2) substantially parallel to the bottom surface of polishing head 210, and into an upward curved or convex shape (not shown). When the pressure in chamber 202 is adjusted and bottom plate 242 is deformed, the evenly distributed surface tension that mounts and holds the wafer on backing film 110 provides for direct deformation of the wafer. Increasing or decreasing the pressure within the chamber 202 may thereby cause the surfaces of the base plate 242 and wafer to bulge outwardly, remain flat, or retract.

The pressure change within the chamber 202 results in a change in a given or predetermined polishing pressure P. A pressurized source (not shown) may be connected to a controller (not shown) to monitor and adjust the pressure within the chamber 202. The controller may include a pressure regulator (not shown). The pressure may be manually adjusted based on the general wafer shape of the incoming lot, or may be electronically controlled from lot to lot, or even wafer to wafer. In some embodiments, a characteristic wafer profile is obtained from a batch of wafers, and the downward pressure applied to the wafers by the polishing head assembly 200 and the distribution of the pressure is varied by adjusting the pressure in the chamber 202. The polishing pressure can suitably vary from about 0.7P to about 1.3P. Thus, varying the polishing pressure P by varying the pressure within the chamber 202 provides an operator with the ability to control variables and adjust the wafer polishing shape. In some embodiments, the predetermined polishing pressure may be in the range from 1.0psi to 4.0 psi. In other embodiments, the predetermined polishing pressure may be less than 6.0psi.

Referring to fig. 3, the polishing head assembly 200 of fig. 2 is shown in which the portion 280 of the bottom plate 242 of the cap 240 deflects into a downward dome shape as a result of the increased pressure within the chamber 202. Changing the shape of the bottom plate 242 results in a resulting change in the force distribution of the polishing pressure across a wafer (e.g., wafer W shown in fig. 1) and thereby causes the wafer to bend in response. The change in force profile also results in a change in the rate at which material is removed from the wafer. In general, the removal rate increases as the normal equivalent stress applied between the wafer and the polishing pad 150 (shown in FIG. 1) increases. As the pressure within the chamber 202 increases or decreases, the portion 280 of the base plate 242 that deflects in response to pressure changes within the chamber 202 increases or decreases, respectively, these paradigm-equivalent stresses.

However, it is observed that the material removed from the wafer by the polishing head assembly 200 is significantly reduced near the edge of the wafer. This is because of the uneven stress distribution across the bottom plate 242 and in particular because of the lower normal equivalent stress applied between the edge of the wafer and the polishing pad 150. Even if the pressure within the chamber 202 of the polishing head assembly 200 increases, these normal equivalent stresses generally cannot increase.

The reason for the non-uniform stress distribution is that the bottom plate 242 of the polishing head assembly 200 does not deflect completely and uniformly in response to pressure increases and/or decreases within the chamber 202. This is due to the uneven deformation resistance across the base plate 242. As shown in fig. 3, the base plate 242 is joined to the annular wall 250 at a joint 290. The joint 290 acts as a hinge about which the base plate 242 may be temporarily deflected without permanent deformation relative to the polishing head 210. Due to the semi-rigidity of the base plate 242, the portion 280 of the base plate 242 has a suitable resistance to deformation to allow the portion 280 to deflect in response to pressure changes within the chamber 202. However, the resistance to deformation increases at the portion 282 of the base plate 242 proximate the joint 290. Thus, portion 282 does not deflect in response to pressure changes within chamber 202. Thus, increasing the pressure within the chamber 202 does not result in a corresponding increase in the normal equivalent stress applied between the edge of the wafer mounted to the portion 282 of the backing plate 242 and the polishing pad 150. The non-uniform normal equivalent stress distribution during polishing with the polishing head assembly 200 creates a non-uniform removal profile for the polished wafer. Further, portion 282 defines the periphery of base plate 242 and may extend from joint 290 to portion 280 a radial distance of up to about 30 mm. Thus, the non-uniform removal profile may cover a substantial portion of the wafer to result in unacceptable flatness of the wafer.

It is believed that the thickness of annular wall 250 proximate joint 290 and/or the thickness of base plate 242 proximate joint 290 may contribute to a relatively high resistance to deformation of portion 282 of base plate 242. The annular wall 250 adjacent the joint 290 is typically about 8mm thick. The thickness of annular wall 250 is measured as the distance between outer surface 252 and inner surface 253 of annular wall 250. The thickness of portion 282 of base 242 is typically from about 5mm to about 7mm. The thickness of the bottom plate 242 is measured as the distance between the top surface 244 and the bottom surface 246.

Referring now to fig. 4, an example polishing head assembly 400 suitable for installation and use in the polishing apparatus 100 is shown. The polishing head assembly 400 includes the elements and components of the polishing head assembly 200 shown in fig. 2 and described above. In addition, the annular wall 250 of the cap 240 includes a first portion 254 joined to the base plate 242 to form the joint 290 and a second portion 256 extending from the first portion 254. The first portion 254 is defined by a recess 255 formed in the inner surface 253 of the annular wall 250 at the joint 290. The recess 255 may be U-shaped or may be substantially circular. The radius of the recess 255 is suitably above 1mm, for example from above 1mm to about 3mm, or about 2.5mm. The first portion 254 of the annular wall 250 has a thickness that is less than the thickness of the second portion 256. The thickness of the first portion 254 is dependent on the radius of the recess 255. The radius of the recess 255 is suitably such that the thickness of the first portion 254 does not decrease below 1.5mm. For example, the thickness of the first portion 254 may suitably be from about 2mm to about 5mm, or about 3mm. The recess 255 also forms a rounded corner 257 at the joint 290. Reducing the thickness of the first portion 254 and/or forming a rounded corner 257 via the recess 255 suitably weakens the resistance to deformation of the portion 282 of the base plate 242 proximate the joint 290 (shown in fig. 3).

The formation of the notches 255 and/or rounded corners 257 to attenuate the resistance to deformation of the portion 282 of the base plate 242 may be suitably performed using Computer Numerical Control (CNC) milling. In general, the notches 255 and/or the rounded corners 257 cannot be formed using conventional machining techniques, such as conventional grinding processes, for flattening the base plate 242 of the cap 240. However, it is contemplated that conventional processing techniques may be modified to form the recesses 255 and the rounded corners 257. In addition, for example, CNC milling may be used to provide the portion 282 of the base plate 242 having a thickness from about 5mm to about 6mm (e.g., 5.5 mm). The base plate 242 may suitably have a continuous thickness extending the entire diameter of the base plate 242 between the annular walls 250. Alternatively, the thickness of the base plate 242 may vary across the diameter of the base plate 242 between the annular walls 250.

Referring to fig. 5, another example polishing head assembly 500 suitable for installation and use in the polishing apparatus 100 is shown. Polishing head assembly 500 includes the elements and components of polishing head assembly 200 shown in fig. 2 and described above. In addition, the inner surface 253 of the annular wall 250 is angled inwardly toward the rounded corner 257 formed at the joint 290. The thickness of annular wall 250 at joint 290 is suitably reduced to a thickness of from about 3mm to about 5mm or about 3 mm. The inner surface 253 may be angled to match the outer surface 252 such that the thickness of the annular wall 250 is constant. Alternatively, the inner surface 253 may be angled such that the thickness of the annular wall 250 tapers inwardly along the annular wall 250 toward the joint 290 such that the annular wall 250 has a minimum thickness at the joint 290. Reducing the thickness of the annular wall 250 at the joint 290 and/or forming the rounded corners 257 suitably weakens the resistance to deformation of the portion 282 of the base plate 242 proximate the joint 290 (shown in fig. 3).

Forming the angled profile of the inner surface 253 to reduce the thickness of the annular wall 250 and forming the rounded corners 257 to weaken the resistance to deformation of the portion 282 of the base plate 242 may be suitably performed using Computer Numerical Control (CNC) milling. In general, the rounded corners 257 and the angled contours of the inner surface 253 cannot be formed using conventional machining techniques (e.g., conventional grinding processes) for flattening the base plate 242 of the cap 240. However, it is contemplated that conventional machining techniques may be modified to form the angled profile of the rounded corners 257 and the inner surface 253. In addition, for example, CNC milling may be used to provide the portion 282 of the base plate 242 having a thickness from about 5mm to about 6mm (e.g., 5.5 mm). The base plate 242 may suitably have a continuous thickness extending the entire diameter of the base plate 242 between the annular walls 250. Alternatively, the thickness of the base plate 242 may vary across the diameter of the base plate 242 between the annular walls 250.

Referring now to fig. 6, another example polishing head assembly 600 suitable for installation and use in the polishing apparatus 100 is shown. The polishing head assembly 600 includes a polishing head 610, a cap 640, and a strap 670. The polishing head 610 and/or cap 640 are suitably made of a metallic material, such as aluminum or steel, or may be made of another suitable structural material. For example, the polishing head 610 and/or cap 640 may be formed from cast aluminum (e.g., available from Alcoa

Cast aluminum plate). Alternatively, cap 640 may be made of a ceramic material (e.g., alumina), a plastic material, or a stainless steel material with a corrosion resistant coating (e.g., diamond-like carbon).

The polishing head 610 has a top 612 and a bottom 614 that are substantially parallel to each other. The polishing head 610 has a platform 620 and an annular member 630 extending downward from the platform 620. A recessed surface 616 is formed in the bottom 614 of the polishing head 610 by an annular member 630 extending downwardly from the platform 620. An aperture 618 extends from top 612 through platform 620 and through recessed surface 616.

The annular member 630 has an outer surface 632 that is substantially perpendicular to the top 612 and bottom 614 of the polishing head 610. The outer surface 632 of the annular member 630 forms the circumference of both the polishing head 610 and the polishing head assembly 600. The annular member 630 has an inner surface 634 that is substantially parallel to the outer surface 632.

Cap 640 has a bottom plate 642 and an upwardly extending annular wall 650 along the periphery of the bottom plate. The annular wall 650 has an outer surface 652 that mates with the inner surface 634 of the annular member 630 and is substantially parallel to the inner surface 634 of the annular member 630. The outer surface 652 of the annular wall 650 may be attached to the inner surface 634 of the annular member 630 of the polishing head 610 by an adhesive (not shown). The adhesive may be an epoxy glue. The annular wall 650 extends upwardly to a shoulder 692. Shoulder 692 has a top edge 694 that mates with recessed surface 616 of polishing head 610. An aperture 658 is formed in shoulder 692 at top edge 694 and corresponds to aperture 618. The holes 618 and corresponding apertures 658 receive fasteners (not shown), such as, for example, screws, to attach the cap 640 to the polishing head 610 by securing the top edge 694 of the shoulder 692 to the recessed surface 616. The fastener may suitably be formed of a plastics or metal material having a corrosion resistant coating. Additionally or alternatively, a cover (not shown) may cover at least a portion of the top 612 of the polishing head 610 to prevent polishing chemicals or slurries from contacting the fasteners and/or access holes 618 during the polishing process. Shoulder 692 may also include an o-ring (not shown) that forms a seal when top edge 694 is secured to recessed surface 616.

The bottom plate 642 extends across the bottom opening formed by the annular member 630. The bottom plate 642 has a top 644 and a bottom 646. The chamber 602 is formed between a top surface 644 of the bottom plate 642 and the recessed surface 616 of the polishing head 610. Annular member 630 and annular wall 650 define a radial boundary of chamber 602. The platform 620 and the overlapping annular member 630 and the annular wall 650 are thicker and adapted to be more rigid than the bottom plate 642.

The metal used in the polishing head assembly 600 may contaminate the wafer by the polishing chemistry or slurry being a source of metal ions. To prevent metal from the cap 640 from contaminating the slurry and wafer, a template including a backing film (such as the backing film 110 shown in fig. 1) and a retaining ring (such as the retaining ring 120 shown in fig. 1) may be used to create a barrier between the slurry and the cap 640. Backing film 110 is typically a thin soft polymer mat or other suitable material. Backing film 110 suitably comprises two or more layers of material (not shown). For example, backing film 110 may have an adhesive layer, a thin plastic film layer, a thin polyurethane foam or other nonwoven (e.g., felt) layer. The adhesive layer seals backing film 110 to bottom surface 646 of cap 640. The thin plastic film layer provides a protective barrier between the cap 640 and the slurry and/or wafer W. A layer comprising polyurethane foam or a non-woven material (e.g., felt) contacts the wafer and provides a surface similar to a polishing pad (e.g., polishing pad 150 shown in fig. 1). The retaining ring 120 extends downwardly from the backing film 110 and is typically a plastic material. The wafer is received by the retaining ring 120 and held against the backing film 110 by surface tension. Thus, the wafer does not directly contact cap 640.

To prevent metal from the polishing head assembly 600 from contaminating the slurry and wafer, the polishing head 610 and cap 640 are constrained by the belt 670 to form a barrier that prevents the slurry from contacting the metal and contaminating the wafer. The annular member 630 has side recesses 638 extending inwardly from the outer surface 632 at the bottom 614 and inner recesses 639 extending inwardly from the inner surface 634. Tabs 648 extend outwardly from annular wall 650 of cap 640 opposite base plate 642. The tabs 648, side recesses 638, and interior recesses 639 each receive the strap 670 and may be sealed to the strap 670 by an adhesive, such as an epoxy glue. The strap 670 may overlap the backing film 110 and/or the retaining ring 120 of the template to form a seal therebetween to prevent metal contamination from the polishing process of the polishing head 610. The strap 670 is made of plastic, such as polyetherimide (e.g., ULTEM available from Saint Foundation Ind. Co., ltd. (SABIC)) ^TM Resin 1000), polyetheretherketone, polyphenylene sulfide or polyethylene terephthalate.

The strap 670 may be non-integral and composed of two or more segments. For example, the band 670 may be composed of three, four, five, or six segments. In these embodiments, the tape 670 may be sealed together at the segment joints (not shown) and sealed to the polishing head 610 and/or cap 640 using an adhesive such as an epoxy glue. To prevent the seal between the band 670 and the polishing head 610 and/or cap 640 from loosening due to an adhesive failure, the band 670 may include interlocking features to secure the band 670 to the polishing head assembly 600. For example, the band 670 may include a dovetail 672 that forms a joint with an upwardly extending member of the recess 639 and tab 648 formed on the inner surface 634 of the annular member 630. In addition to or in lieu of adhesive, a dovetail 672 may be used to secure the strap 670 to the polishing head 610 and/or cap 640.

Similar to the polishing head assembly 200 described in detail herein, the chamber 602 is pressurized with a pressurizing medium or fluid. The chamber 602 may be connected to a pressurized source (not shown) to provide pressurized medium or fluid to the chamber 602, as described herein with respect to the polishing head assembly 200. A pressurized source (not shown) is connected to the chamber passageway 622 (e.g., via a quick disconnect coupling plug). Chamber passageway 622 extends through platform 620 to chamber 602. Similar to the bottom plate 242 described in detail herein, the bottom plate 642 is a semi-rigid "flex plate" that is adapted to deform precisely to change the pressure profile and polish the pressure profile, and yet is rigid enough to mount and dismount the wafer on the backing film 110 by surface tension. The bottom plate 642 can be temporarily deflected relative to the polishing head 610 without permanent deformation. Adjusting the pressure in chamber 602 causes bottom plate 642 to deflect. In embodiments in which the shoulder 692 includes an o-ring (not shown), a seal formed at the junction of the top edge 694 and the recessed surface 616 may prevent leakage of pressurized medium or fluid from the chamber 602, thereby maintaining a given pressure in the chamber 602.

In addition to the shoulder 692, the annular wall 650 of the cap 640 includes a first portion 654 joined to a bottom plate 642 to form a joint 690, the bottom plate being temporarily deflectable about the joint 690 in response to pressure changes within the chamber 602. The first portion 654 is connected to a shoulder 692, with the second portion 656 extending between the first portion 654 and the shoulder 692. The thickness of the annular wall 650 is greatest at the shoulder 692, as shown in fig. 6. The first portion 654 is defined by a recess 655 formed in the annular wall 650 at the joint 690. The recess 655 may be U-shaped or may be substantially circular. Thus, the first portion 654 has a thickness that is less than the thickness of the second portion 656. For example, the thickness of the first portion 654 may be from about 3mm to about 5mm, or about 3mm. The recess 655 also forms a rounded corner 657 at the joint 690. Reducing the thickness of the first portion 654 and/or forming the rounded corners 657 via the recesses 655 suitably weakens the resistance to deformation of the portion of the bottom plate 642 proximate the joint 690, which would otherwise be substantially incapable of deflecting in response to pressure changes within the chamber 602. This floor portion may extend from the adapter 690 to the center of the floor 642 a radial distance of up to about 30 mm.

The formation of the recesses 655 and/or fillets 657 to attenuate the resistance to deformation of the portion of the floor 642 proximate to the joint 690 may be suitably performed using Computer Numerical Control (CNC) milling. In general, the recesses 655 and/or the rounded corners 657 cannot be formed using conventional machining techniques, such as conventional grinding processes, for flattening the bottom plate 642 of the cap 640. However, it is contemplated that conventional processing techniques may be modified to form the recesses 655 and the rounded corners 657. In addition, for example, CNC milling may be used to provide a portion of the bottom plate 642 proximate the joint 690 having a thickness of from about 5mm to about 6mm (e.g., 5.5 mm). The bottom plate 642 may suitably have a continuous thickness extending the entire diameter of the bottom plate 642 between the annular walls 650. Alternatively, the thickness of the bottom surface 642 may vary across the diameter of the bottom plate 642 between the annular walls 650. For example, the bottom plate 642 may have a thickness that tapers inwardly from the center of the bottom plate 642 to the adapter 690, as described in further detail herein.

Referring to fig. 7, yet another example polishing head assembly 700 suitable for installation and use in the polishing apparatus 100 is shown. Polishing head assembly 700 includes the elements and components of polishing head assembly 600 shown in fig. 6 and described above. In this example, a portion 659 of the annular wall 650 extending between the shoulder 692 and the rounded corners 657 has an inner surface 653 that is angled relative to the outer surface 652. The thickness of the portion 659 of the annular wall 650 tapers inwardly from the shoulder 692 toward the adapter 690 such that the annular wall 650 has a minimum thickness at the adapter 690. The thickness of the annular wall 650 at the joint 690 is suitably reduced to a thickness of from about 3mm to about 5mm or about 3 mm. The reduction in thickness of the annular wall 650 from the shoulder 692 toward the adapter 690 and/or the formation of the rounded corners 657 suitably weakens the resistance to deformation of the portion of the bottom plate 642 proximate the adapter 690, which would otherwise be substantially incapable of deflecting in response to pressure changes within the chamber 602. This floor portion may extend from the adapter 690 toward the center of the floor 642 a radial distance of up to about 30 mm.

The formation of the angled profile of the inner surface 653 to reduce the thickness of the annular wall 650 and the formation of the rounded corners 657 to weaken the resistance to deformation of the portion of the bottom plate 642 proximate the joint 690 may be suitably performed using Computer Numerical Control (CNC) milling. In general, the rounded corners 657 and angled contours of the inner surface 653 cannot be formed using conventional machining techniques, such as conventional grinding processes, for flattening the bottom plate 642 of the cap 640. However, it is contemplated that conventional machining techniques may be modified to form rounded corners 657 and the angled profile of inner surface 653. Additionally, CNC milling may be used to provide a portion of the bottom plate 642 proximate the joint 690 having a thickness of from about 5mm to about 6mm (e.g., 5.5 mm). The bottom plate 642 may suitably have a continuous thickness extending the entire diameter of the bottom plate 642 between the annular walls 650. Alternatively, the thickness of the bottom plate 642 may vary across the diameter of the bottom plate 642 between the annular walls 650. For example, the bottom plate 642 may have a thickness that tapers inwardly from the center of the bottom plate 642 to the adapter 690 (shown in fig. 8).

Referring to fig. 8, another example polishing head assembly 800 suitable for installation and use in the polishing apparatus 100 is shown. Polishing head assembly 800 includes similar elements and components of polishing head assemblies 600 and/or 700 shown in fig. 6 and 7, respectively, and described above. In order to weaken the deformation resistance of the portion of the bottom plate 642 in the vicinity of the joint 690, the thickness of the bottom plate 642 tapers inwardly from the radial center C of the bottom plate 642 toward the joint 690. Thus, the thickness of the bottom plate 242 is greatest at the center C and decreases to a minimum thickness at the joint 690. The thickness of the bottom plate 642 may taper from about 5mm to 6mm or about 5.5mm from the thickness at center C to about 3mm to about 4mm or about 3mm at the joint 290. The thickness of the bottom plate 642 is tapered to reduce the thickness of the bottom plate 642 proximate the joint 690 to properly attenuate the resistance to deformation of the portion of the bottom plate 642 proximate the joint 690 that would otherwise be substantially incapable of deflecting in response to pressure changes within the chamber 602. This portion of the bottom plate 642 proximate the adapter 690 may extend from the adapter 690 up to a radial distance of about 30mm toward the radial center C of the bottom plate 642.

In the example polishing head assembly 800, the annular wall 650 of the polishing head assembly 800 may or may not include additional features to attenuate resistance to deformation of the portion of the bottom plate 642 proximate to the joint 690 described herein. For example, the portion 659 of the annular wall 650 extending between the shoulder 692 and the corner 696 may have an inner surface 653 that is substantially parallel to the outer surface 652 such that the thickness of the portion 659 is substantially constant. Alternatively, the thickness of the portion 659 may be reduced at the joint 690. For example, the inner surface 653 may be angled relative to the outer surface 652 such that the thickness of the portion 659 of the annular wall 650 tapers inwardly from the shoulder 692 toward the adapter 690 (as shown in fig. 7). In addition, the corners 696 at the joint 690 between the inner surface 653 of the annular wall 650 and the top surface 644 of the bottom plate 642 may be angled, or may be rounded (i.e., forming the rounded corners 657 shown in fig. 6 and 7). The thickness of the annular wall 650 at the joint 690 may suitably be about 8mm, or may be reduced to a thickness of from about 3mm to about 5mm or about 3 mm.

The formation of the tapered profile of the bottom plate 642 to attenuate the resistance to deformation of the portion of the bottom plate 642 proximate the joint 690 may be suitably performed using Computer Numerical Control (CNC) milling. In general, the tapered profile of the bottom plate 642 cannot be formed using conventional machining techniques for flattening the bottom plate 642 of the cap 640, such as conventional grinding processes. However, it is contemplated that conventional machining techniques may be modified to form the tapered profile of the bottom plate 642.

The described embodiments reduce the resistance to deformation of the bottom plate of the cap of the polishing head assembly, which would otherwise be substantially incapable of deforming in response to pressure changes within the chamber of the polishing head assembly. Embodiments achieve a more uniform removal profile across the polished wafer. By weakening the portion of the bottom plate that would otherwise be substantially incapable of deforming in response to pressure changes within the chamber, the distribution of normal, etc. forces applied between the wafer and the polishing pad is more uniform during polishing. In particular, the normal equivalent stress applied between the edge of the wafer and the polishing pad can be better controlled to fine tune the removal profile near the edge of the wafer.

As used herein, the terms "about," "substantially," "essentially," and "approximately" when used in connection with a range of dimensions, concentrations, temperatures, or other physical or chemical properties or characteristics are meant to cover variations that may be present in the upper and/or lower limits of the range of properties or characteristics, including variations resulting from, for example, rounding, measurement methods, or other statistical variations.

When introducing elements of the present disclosure or the embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., "top," "bottom," "side," "lower," "upper," etc.) is for convenience of description and does not require any particular orientation of the described items.

As various changes could be made in the above constructions and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A polishing head assembly for polishing a semiconductor wafer, the polishing head assembly comprising:

a polishing head having a recess along a bottom portion, the recess having a recessed surface; a kind of electronic device with high-pressure air-conditioning system

A cap positioned within the recess, the cap comprising:

an annular wall fixed to the polishing head; a kind of electronic device with high-pressure air-conditioning system

A base plate joined to the annular wall at a joint, the base plate extending across the annular wall, the base plate having an upper surface and a lower surface, the upper surface being spaced from the recessed surface to form a chamber therebetween, wherein resistance to deformation of a portion of the base plate proximate the joint is weakened to allow the portion of the base plate proximate the joint to deflect relative to the polishing head by pressure changes in the chamber.

2. The polishing head assembly of claim 1, wherein the annular wall comprises a first portion having a first thickness and a second portion having a second thickness, the first portion being joined to the bottom plate, the second portion extending from the first portion, the first thickness being less than the second thickness to weaken the deformation resistance of the portion of the bottom plate proximate the joint.

3. The polishing head assembly of claim 2, wherein the first thickness is from about 3mm to about 5mm.

4. The polishing head assembly of claim 3, wherein the first thickness is about 3mm.

5. The polishing head assembly of claim 2, wherein the bottom plate has a continuous thickness from about 5mm to about 6 mm.

6. The polishing head assembly of claim 2, wherein:

the polishing head has a top portion and a bore extending from the top portion through the recessed surface;

the annular wall further includes a shoulder extending from the second portion, the shoulder having an aperture corresponding to the bore; and is also provided with

The aperture and the corresponding aperture receive a fastener to secure the shoulder of the annular wall to the recessed surface of the polishing head.

7. The polishing head assembly of claim 1, wherein a thickness of the annular wall tapers inwardly toward the joint such that the thickness of the annular wall is minimal proximate the joint to weaken the deformation resistance of the portion of the bottom plate proximate the joint.

8. The polishing head assembly of claim 7, wherein the thickness of the annular wall proximate the joint is from about 3mm to about 5mm.

9. The polishing head assembly of claim 7, wherein the thickness of the annular wall proximate the joint is about 3mm.

10. The polishing head assembly of claim 7, wherein the bottom plate has a continuous thickness from about 5mm to about 6mm.

11. The polishing head assembly of claim 1, wherein a thickness of the bottom plate tapers inwardly toward the joint such that the thickness of the bottom plate is at a minimum at the portion proximate the joint to weaken the deformation resistance of the portion of the bottom plate proximate the joint.

12. The polishing head assembly of claim 11, wherein the thickness of the bottom plate is greatest at a center of the bottom plate.

13. The polishing head assembly of claim 12, wherein the thickness of the bottom plate at the portion proximate the joint is about 3mm and the thickness of the bottom plate at the center is from about 5mm to about 6mm.

14. The polishing head assembly of claim 1, wherein the cap is made of a metallic material.

15. The polishing head assembly of claim 1, wherein the annular wall is secured to the polishing head by an adhesive.

16. A polishing head assembly for polishing a semiconductor wafer, the polishing head assembly comprising:

a polishing head having a top portion and a recess along a bottom portion, the recess having a recessed surface and a hole extending from the top portion through the recessed surface;

a cap positioned within the recess, the cap comprising:

an annular wall having an aperture corresponding to the aperture, wherein the aperture and corresponding aperture receive a fastener to secure the annular wall to the recessed surface; a kind of electronic device with high-pressure air-conditioning system

A base plate joined to the annular wall at a joint, the base plate extending across the annular wall, the base plate having an upper surface and a lower surface, the upper surface being spaced from the recessed surface to form a chamber therebetween, the base plate being deflectable relative to the polishing head by pressure changes in the chamber;

wherein resistance to deformation of a portion of the base plate proximate the joint is weakened to allow the portion of the base plate proximate the joint to deflect relative to the polishing head.

17. The polishing head assembly of claim 16, wherein a thickness of the bottom plate tapers inwardly toward the joint such that the thickness of the bottom plate is at a minimum at the portion proximate the joint to weaken the deformation resistance of the portion of the bottom plate proximate the joint.

18. The polishing head assembly of claim 17, wherein the thickness of the bottom plate at the portion proximate the joint is about 3mm and the thickness of the bottom plate at a center of the bottom plate is from about 5mm to about 6mm.

19. The polishing head assembly of claim 16, wherein the cap is made of a metallic material.

20. A polishing head assembly for polishing a semiconductor wafer, the polishing head assembly comprising:

a polishing head; a kind of electronic device with high-pressure air-conditioning system

A cap having an annular wall fixed to the polishing head and a bottom plate joined to the annular wall at a joint;

wherein the polishing head and the cap define a chamber between the polishing head and the floor of the cap;

wherein the bottom plate is made of a metallic material capable of deflecting relative to the polishing head in response to pressure changes in the chamber; and is also provided with

Wherein the thickness of at least one of the annular wall and the base plate is reduced in the vicinity of the joint to weaken the deformation resistance of the base plate in the vicinity of the joint.