Patent Description:
Semiconductor wafers are commonly used in the production of integrated circuit (IC) chips on which circuitry are printed. The circuitry is first printed in miniaturized form onto surfaces of the wafers. The wafers are then broken into circuit chips. This miniaturized circuitry requires that front and back surfaces of each wafer be extremely flat and parallel to ensure that the circuitry can be properly printed over the entire surface of the wafer.

<CIT> discloses a wafer polishing assembly that includes a head retainer assembly and a wafer carrier head movably coupled to the head retainer assembly using a plurality of retaining bolts.

To accomplish this, grinding and polishing processes are commonly used to improve flatness and parallelism of the front and back surfaces of the wafer after the wafer is cut from an ingot. A particularly good finish is required when polishing the wafer in preparation for printing the miniaturized circuits on the wafer by an electron beam-lithographic or photolithographic process (hereinafter "lithography"). The wafer surface on which the miniaturized circuits are to be printed must be flat.

Polishing machines typically include a circular or annular polishing pad mounted on a turntable or platen for driven rotation about a vertical axis passing through the center of the pad and a mechanism for holding the wafer and forcing it into the polishing pad. The wafer is typically mounted to the polishing head using for example, liquid surface tension or vacuum/suction. A polishing slurry, typically including chemical polishing agents and abrasive particles, is applied to the pad for greater polishing interaction between the polishing pad and the surface of the wafer. This type of polishing operation is typically referred to as chemical-mechanical polishing (CMP).

During operation, the pad is rotated and the wafer is brought into contact with and forced against the pad by the polishing head. The polishing head is typically assembled using epoxy glue. However, failure of the epoxy glue joints during the service life of the polishing head may cause undesirable effects, including loosening of parts, air leaks, wafer damage, and poor yield. Repair of these polishing heads is difficult because the head must be heated to release the remaining epoxy to allow complete disassembly of the head. After heat removal, few existing parts of the head assembly can be salvaged. Accordingly, there is a need for an improved polishing head assembly.

According to the present invention, a polishing head assembly is disclosed, as defined in claim <NUM>.

Generally, 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, for example, silicon wafers obtained by slicing the wafers from single crystal silicon ingots 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 back surfaces are generally perpendicular to the central axis. A circumferential edge joins the front and back surfaces. The wafers may be any diameter suitable for use by those of skill in the art including, for example, <NUM> millimeter (mm), <NUM>, greater than <NUM> or even <NUM> diameter wafers.

In one embodiment, a wafer that has previously been rough polished so that it has rough front and back surfaces is first subjected to an intermediate polishing operation in which the front surface of the wafer, but not the back surface, is polished to improve flatness parameters or to smooth the front surface and remove handling scratches. To carry out this operation, the wafer is placed against the polishing head assembly. In this embodiment, the wafer is retained in position against the polishing head assembly by surface tension. The wafer also is placed on a turntable of a polishing machine with the front surface of the wafer contacting the polishing surface of a polishing pad.

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

A conventional polishing slurry containing abrasive particles and a chemical etchant is applied to the polishing pad. The polishing pad works the slurry against the surface of the wafer to remove material from the front surface of the wafer, resulting in a surface of improved smoothness. As an example, the intermediate polishing operation preferably removes less than about <NUM> micron of material from the front side of the wafer.

The wafer is then subjected to a finish polishing operation in which the front surface of the wafer is finish polished to remove fine or "micro" scratches caused by large size colloidal silica, such as Syton® from DuPont Air Products Nanomaterials, LLC, in the intermediate step and to produce a highly reflective, damage-free front surface of the wafer. The intermediate polishing operation generally removes more of the wafer than the finishing polishing operation. The wafer may be finish polished in the same polishing machine used to intermediate polish the wafer as described above. However, a separate polishing machine may also be used for the finish polishing operation. A finish polishing slurry typically has an ammonia base and a reduced concentration of colloidal silica is injected between the polishing pad and the wafer. The polishing pad works the finish polishing slurry against the front surface of the wafer to remove any remaining scratches and haze so that the front surface of the wafer is generally highly-reflective and damage free.

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

The polishing apparatus <NUM> includes a wafer holding mechanism, e.g., a template comprising a backing film <NUM> and a retaining ring <NUM>, a polishing head assembly <NUM>, and a turntable <NUM> having a polishing pad <NUM>. The backing film <NUM> is located between a polishing head assembly <NUM> and the retaining ring <NUM>, which receives a wafer W. The retaining ring <NUM> has at least one circular opening to receive the wafer W to be polished therein.

The wafer W in this embodiment is attached to and retained against the polishing head assembly <NUM> by surface tension. To form the surface tension, the wet saturated backing film <NUM> is attached to the polishing head assembly <NUM> with a pressure sensitive adhesive. The backing film <NUM> and retaining ring <NUM> form a template or "wafer holding template. " The backing film <NUM> is generally a soft polymer pad or other suitable material.

The wafer W is then pressed into the wet saturated backing film <NUM> to remove or squeeze out the majority of the water or other suitable liquid. Squeezing out the water causes the wafer to be retained on the backing film <NUM> by surface tension and the atmospheric pressure on the exposed surface of the wafer. This squeezing out of the water mounts the wafer to the polishing head assembly <NUM>.

A portion of the polishing head assembly <NUM> is flexible enough to deform in response to a change in pressure applied to the polishing head assembly <NUM>, and stiff enough not to deform when the wafer is pressed into the wet saturated template. The surface tension provides a constant retaining force over the surface of the wafer. This constant retaining force causes any deformation of the polishing head assembly <NUM> adjacent to the wafer to be directly translated into proportional deformation of the wafer.

The retention of the wafer W by surface tension functions differently than other known mechanisms that use flexible membranes or vacuums to retain the wafer against the polishing head assemblies. Flexible membranes, as known in the art, deform to create space or vacuum pockets between the wafer and the flexible membrane when the wafer is pushed thereon. These vacuum pockets allow the membrane to pick up the wafer. Other membranes have vacuum holes, which are connected to a vacuum to create low pressure areas to pick up wafers.

The polishing apparatus <NUM> applies a force to the polishing head assembly <NUM> to move the polishing head assembly <NUM> vertically to raise and lower the polishing head assembly <NUM> with respect to the wafer W and the turntable <NUM>. An upward force raises the polishing head assembly <NUM>, and a downward force lowers the polishing head assembly. As discussed above, the downward vertical movement of the polishing head assembly <NUM> against the wafer W provides the polishing pressure to the wafer to urge the wafer into the polishing pad <NUM> of the turntable <NUM>. As the polishing apparatus <NUM> increases the downward force, the polishing head assembly <NUM> moves vertically lower to increase the polishing pressure.

A portion of the polishing head assembly <NUM> and polishing pad <NUM> and turntable <NUM> are rotated at selected rotation speeds by a suitable drive mechanism (not shown) as is 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 <NUM> includes a controller (not shown) that allows the operator to select rotation speeds for both the polishing head assembly <NUM> and the turntable <NUM>, and the downward force applied to the polishing head assembly.

With reference to <FIG>, an example polishing head assembly <NUM> for use in the polishing apparatus <NUM> is shown. The polishing head assembly <NUM> includes a polishing head <NUM>, a cap <NUM>, and a band <NUM>. The polishing head assembly <NUM> may also include a template comprising a backing film and retaining ring, for example, the backing film <NUM> and the retaining ring <NUM> (shown in <FIG>). The polishing head <NUM> has a top <NUM> and a bottom <NUM> that are substantially parallel with each other. The polishing head <NUM> has a platform <NUM> at the top <NUM> and holes <NUM> extending from the platform <NUM> through the bottom <NUM>.

The polishing head <NUM> has an annular member <NUM> extending downward from the platform <NUM> to the bottom <NUM>. The annular member <NUM> has an inner surface <NUM> and an outer surface <NUM>. The outer surface <NUM> forms the circumference of the polishing head <NUM>. The annular member <NUM> defines a recess along the bottom <NUM>, and the recess has a recessed surface <NUM> extending between the annular member <NUM>. The holes <NUM> extend from the platform <NUM> through the recessed surface <NUM> in this embodiment. As discussed in more detail below, a portion of the annular member <NUM> at the bottom <NUM> may have inlets <NUM>, <NUM> formed on the outer surface <NUM> and the inner surface <NUM>, respectively, that mate with the shape of band <NUM>.

The cap <NUM> is positioned within the recess defined by the annular member <NUM>. The cap <NUM> includes a floor <NUM> surrounded by an annular wall <NUM> extending upward therefrom. The floor <NUM> has a top surface <NUM> and a bottom surface <NUM>. In this embodiment, the bottom surface <NUM> extends outward past the annular wall <NUM> to a tab <NUM>. As discussed in more detail below, the tab <NUM> may be shaped to mate with the band <NUM>. In other embodiments, the bottom surface <NUM> may not extend past the annular wall <NUM>, such that the annular wall <NUM> defines the outermost circumference of the cap <NUM>.

The annular wall <NUM> has an inside surface <NUM>, an outside surface <NUM>, a top portion <NUM> and a bottom portion <NUM>. The top portion <NUM> has a top edge <NUM> and apertures <NUM> formed at the top edge <NUM>. The apertures <NUM> extend into the top portion <NUM> and correspond to the holes <NUM>. The holes <NUM> and the corresponding apertures <NUM> receive fasteners <NUM> (e.g., screws) to removably secure the annular wall <NUM> to the recessed surface <NUM>, and thereby removably secure the cap <NUM> to the polishing head <NUM>. The top edge <NUM> of the annular wall <NUM> contacts the recessed surface <NUM> when the annular wall <NUM> is secured to the recessed surface <NUM>. The top portion <NUM> may also include an o-ring <NUM> at the top edge <NUM> which forms a seal when the annular wall <NUM> is secured to the recessed surface <NUM>.

As shown in <FIG>, the thickness of the annular wall <NUM> is greater at the top portion <NUM> than the bottom portion <NUM>. The thinner wall of the bottom portion <NUM> allows the bottom portion <NUM> to act as a hinge about which the floor <NUM> may temporarily deflect without permanently deforming relative to the polishing head <NUM>. For example, the floor <NUM> may temporarily deflect upward toward the polishing head <NUM> in response to downward vertical movement of the polishing head assembly <NUM> causing the cap <NUM> to contact a wafer (such as wafer W shown in <FIG>). The inside surface <NUM> of the annular wall <NUM> at the top portion <NUM> may be angled with respect to the outside surface <NUM>, such that the thickness of the top portion <NUM> is thickest at the top edge <NUM> and tapers downward toward the bottom portion <NUM>.

At least a portion of the outside surface <NUM> abuts the inner surface <NUM> of the annular member <NUM> when the cap <NUM> is secured to the polishing head <NUM>. Suitably, the outside surface <NUM> is substantially parallel to the inner surface <NUM>. In this embodiment, the height of the annular wall <NUM> is greater than the downward extension of the annular member <NUM> and the inner surface <NUM> of the annular member <NUM> circumscribes the top portion <NUM> of the annular wall <NUM>. In other embodiments, the annular member <NUM> may circumscribe more or less of the annular wall <NUM>.

The floor <NUM> is spaced from the recessed surface <NUM> when the cap <NUM> is secured to the polishing head <NUM>. As such, the annular wall <NUM>, the top surface <NUM> of the floor <NUM>, and the recessed surface <NUM> define a chamber <NUM> when the cap <NUM> is secured to the polishing head <NUM>. Because the top edge <NUM> contacts the recessed surface <NUM> when the annular wall <NUM> is secured to the recessed surface <NUM>, the height of the chamber <NUM> is determined by the height of the annular wall <NUM>. In some embodiments, the chamber <NUM> is pressurized with a pressurized media or fluid. The chamber <NUM> may be connected with a pressurized source (not shown) to provide a pressurized media or fluid to the chamber <NUM>. As discussed above, the floor <NUM> may be capable of temporarily deflecting relative to the polishing head <NUM> without permanently deforming. For example, adjusting pressure in the chamber <NUM> may cause deflection of the floor <NUM> to increase or decrease. In embodiments where the o-ring <NUM> is used, the seal formed between the top edge <NUM> and the recessed surface <NUM> by the o-ring <NUM> may prevent leakage of the pressurized media or fluid from chamber <NUM>, thereby maintaining a given pressure in the chamber <NUM>.

The polishing head <NUM> and the cap <NUM> may be made of a structural material, such as steel, aluminum, ceramic or another suitable material. In some embodiments, the polishing head <NUM> and the cap <NUM> are made of cast aluminum (for example, MIC6® Aluminum Cast Plate available from Alcoa. ) In other embodiments, the cap <NUM> may be made of a ceramic, such as alumina, or plastic material. In embodiments that use a plastic material, a polyetherimide (for example, ULTEM ™ Resin <NUM> available from Saudi Basic Industries Corporation (SABIC)) may be used. A plastic cap <NUM> is substantially thicker than one made with either metal or ceramic. Caps made with a ceramic material have substantially thinner floors than those made with either metal or plastic.

Metal used in the polishing head assembly <NUM> has the potential to contaminate a wafer by being a source of metal ions through the polishing chemicals or slurry. To prevent metal from the polishing head <NUM> from contaminating the slurry and the wafer, the polishing head <NUM> is coated with epoxy, fluorocarbon, or another suitable, non-metallic material, to create a barrier to provide metal ion protection.

To prevent metal used in the polishing head assembly <NUM> from contaminating the slurry and wafer, and/or to prevent chemical exposure of the metal from the polishing chemicals or slurry, a portion of the polishing head <NUM> and/or the cap <NUM> is circumscribed by the band <NUM>. The band <NUM> forms a barrier between the slurry and the polishing head <NUM> and/or the cap <NUM>. The band <NUM> may be a non-metallic material. In some embodiments, the band <NUM> is made of plastic, such as polyetherimide (for example, ULTEM ™ Resin <NUM> available from Saudi Basic Industries Corporation (SABIC)), polyether ether ketone, polyphenylene sulfide, or polyethylene terephthalate.

In this embodiment, the band <NUM> circumscribes and may be sealed to a portion of the polishing head <NUM> at the bottom <NUM>, the portion of the outer surface <NUM> of the annular wall <NUM> not circumscribed by the polishing head <NUM>, and the tab <NUM>. The annular member <NUM> has a side inlet <NUM> that extends inward from the outer surface <NUM> at the bottom <NUM> of the polishing head <NUM>. A side recess <NUM> is formed between tab <NUM> and the bottom of annular member <NUM> and extends along the portion of the outside surface <NUM> of the annular wall <NUM> not circumscribed by the annular member <NUM>. The band <NUM> is sized and shaped to circumscribe the side inlet <NUM>, the side recess <NUM> and the tab <NUM> and form a seal therebetween.

In some embodiments, the band <NUM> is non-unitary and is made of two or more segments. For example, the band <NUM> may be made of three, four, five, or six segments. In these embodiments, the band <NUM> may be sealed together at the segment joints (e.g., segment joints <NUM> shown in <FIG>) and sealed to the polishing head <NUM> and/or the cap <NUM> using an adhesive, such as epoxy glue. To prevent the seal between the band <NUM> and the polishing head <NUM> and/or the cap <NUM> from coming loose due to adhesive failure, the band <NUM> may include an interlocking member <NUM> to secure the band <NUM> to the polishing head assembly <NUM>. For example, the band <NUM> may include a dovetail <NUM> which forms a joint with an inner inlet <NUM> formed on the inner surface <NUM> of the annular member <NUM> and with an inner recess <NUM> formed by an upward extending member of the tab <NUM>. The dovetail <NUM> may be used to secure the band <NUM> to the polishing head <NUM> and/or the cap <NUM> in addition to an adhesive or as an alternative.

In embodiments where the polishing head assembly <NUM> includes a template comprising a backing film and retaining ring, such as the backing film <NUM> and the retaining ring <NUM> shown in <FIG>, the band <NUM> may also overlap at least a portion of the template to prevent metal contamination of the slurry or wafer from the polishing head <NUM> and/or the cap <NUM>, and/or to prevent chemical exposure of the metal from the polishing chemicals or slurry.

With reference to <FIG>, another example polishing head assembly <NUM> for use in the polishing apparatus <NUM> is shown. The polishing head assembly <NUM> includes a polishing head <NUM>, a cap <NUM>, and a band <NUM>. The polishing head assembly <NUM> may also include a template comprising a backing film and retaining ring, for example, the backing film <NUM> and the retaining ring <NUM> (shown in <FIG>). The polishing head <NUM> has a top <NUM> and a bottom <NUM> that are substantially parallel with each other. The polishing head <NUM> has a platform <NUM> at the top <NUM> and holes <NUM> extending from the platform <NUM> through the bottom <NUM>.

The polishing head <NUM> has an annular member <NUM> extending downward from the platform <NUM> to the bottom <NUM>. The annular member <NUM> has an inner surface <NUM> and an outer surface <NUM>. The outer surface <NUM> forms the circumference of the polishing head <NUM>. The annular member <NUM> defines a recess along the bottom <NUM>, and the recess has a recessed surface <NUM> extending between the annular member <NUM>. The holes <NUM> extend from the platform <NUM> through the recessed surface <NUM> in this embodiment. The annular member <NUM> has a bottom edge <NUM> at the bottom <NUM> which is overlapped by, and may be sealed to, the band <NUM>.

The cap <NUM> is positioned within the recess defined by the annular member <NUM>. The cap <NUM> includes a floor <NUM> surrounded by an annular wall <NUM> extending upward therefrom. The floor <NUM> has a top surface <NUM> and a bottom surface <NUM>. In this embodiment, the bottom surface <NUM> extends outward past the annular wall <NUM> to a tab <NUM>. In other embodiments, the bottom surface <NUM> may not extend past the annular wall <NUM>, such that the annular wall <NUM> defines the outermost circumference of the cap <NUM>.

The floor <NUM> is spaced from the recessed surface <NUM> when the cap <NUM> is secured to the polishing head <NUM>. As such, the annular wall <NUM>, the top surface <NUM> of the floor <NUM>, and the recessed surface <NUM> define a chamber <NUM> when the cap <NUM> is secured to the polishing head <NUM>. Because the top edge <NUM> contacts the recessed surface <NUM> when the annular wall <NUM> is secured to the recessed surface <NUM>, the height of the chamber <NUM> is determined by the height of the annular wall <NUM>. In some embodiments, the chamber <NUM> is pressurized with a pressurized media or fluid. The chamber <NUM> may be connected with a pressurized source (not shown) to provide a pressurized media or fluid to the chamber <NUM>. As discussed above, the floor <NUM> may be capable of temporarily deflecting relative to the polishing head <NUM> without permanently deforming. For example, adjusting pressure in the chamber <NUM> may cause deflection of the floor <NUM> to increase or decrease. In embodiments where the o-ring <NUM> is used, the seal formed between the top edge <NUM> and the recessed surface <NUM> may prevent leakage of the pressurized media or fluid from the chamber <NUM>, thereby maintaining a given pressure in the chamber <NUM>.

To prevent metal used in the polishing head assembly <NUM> from contaminating the slurry and wafer, and/or to prevent chemical exposure of the metal from the polishing chemicals or slurry, a portion of the polishing head <NUM> and/or the cap <NUM> is circumscribed by the band <NUM> forming a barrier between the slurry and the polishing head <NUM> and/or the cap <NUM>. The band <NUM> may be a non-metallic material. In some embodiments, the band <NUM> is made of plastic, such as polyetherimide (for example, ULTEM ™ Resin <NUM> available from Saudi Basic Industries Corporation (SABIC)), polyether ether ketone, polyphenylene sulfide, or polyethylene terephthalate.

In this embodiment, the band <NUM> circumscribes and may be sealed to the portion of the outer surface <NUM> of the annular wall <NUM> not circumscribed by the polishing head <NUM>, and to the tab <NUM>. The band <NUM> may also be sealed to the annular member <NUM> at the bottom edge <NUM>. The band <NUM> may be sealed to the polishing head <NUM> and/or the cap <NUM> using an adhesive, such as epoxy glue. To prevent the seal between the band <NUM> and the polishing head <NUM> and/or the cap <NUM> from coming loose due to adhesive failure, the band <NUM> may be a unitary one-piece band. The unitary one-piece band <NUM> may also be held in place by interference fit between the band <NUM> and the tab <NUM>, and between the band <NUM> and the bottom edge <NUM>, when the cap <NUM> is secured to the polishing head <NUM>.

The polishing head <NUM> has an annular member <NUM> extending downward from the platform <NUM> to the bottom <NUM>. The annular member <NUM> has an inner surface <NUM> and outer surface <NUM>. The outer surface <NUM> forms the circumference of the polishing head <NUM>. The annular member <NUM> defines a recess along the bottom <NUM>, and the recess has a recessed surface <NUM> extending between the annular member <NUM>. The holes <NUM> extend from the platform <NUM> through the recessed surface <NUM> in this embodiment. The annular member <NUM> has a bottom edge <NUM> at the bottom <NUM> which is overlapped by, and may be sealed to, the band <NUM>.

The annular wall <NUM> has an inside surface <NUM>, an outside surface <NUM>, a top portion <NUM> and a bottom portion <NUM>. The top portion <NUM> has a top edge <NUM> and apertures <NUM> formed at the top edge <NUM>. The apertures <NUM> extend into the top portion <NUM> at top edge <NUM> and correspond to the holes <NUM>. The holes <NUM> and the corresponding apertures receive fasteners <NUM> (e.g., screws) to removably secure the annular wall <NUM> to the recessed surface <NUM>, and thereby removably secure the cap <NUM> to the polishing head <NUM>. The top edge <NUM> of the annular wall <NUM> contacts the recessed surface <NUM> when the annular wall <NUM> is secured to the recessed surface <NUM>. The top portion <NUM> may also include an o-ring <NUM> at the top edge <NUM> which forms a seal when the annular wall <NUM> is secured to the recessed surface <NUM>.

In this embodiment, the band <NUM> circumscribes and may be sealed to the portion of the outer surface <NUM> of the annular wall <NUM> not circumscribed by the polishing head <NUM>, and to the tab <NUM>. The band <NUM> may also be sealed to the annular member <NUM> at the bottom edge <NUM>. The band <NUM> may be secured to the polishing head <NUM> and/or the cap <NUM> using an adhesive, such as epoxy glue. To prevent the seal between the band <NUM> and the polishing head assembly <NUM> from coming loose due to adhesive failure, the band <NUM> may be a unitary one-piece band. The unitary one-piece band <NUM> may also be held in place by interference fit between the band <NUM> and the tab <NUM>, and between the band <NUM> and the bottom edge <NUM>, when the cap <NUM> is secured to the polishing head <NUM>. In this embodiment, tab <NUM> has an o-ring <NUM> which forms a seal between the tab <NUM> and the band <NUM>. The o-ring <NUM> may add an additional seal to prevent chemical exposure inside the joint between the band <NUM> and the polishing head assembly <NUM>. The o-ring <NUM> may also compensate for possible undesirable clearance due to tolerance stack.

Features of the above-described embodiments have several advantages. For example, by attaching the polishing head assembly using fasteners in place of epoxy, problems associated with epoxy joint failure, which is a main cause of failure during the service life of the polishing head assembly, can be reduced or eliminated. When the polishing head assembly does need repair, the fasteners allow for disassembly of the polishing head assembly without the use of heat or other destructive action to reduce maintenance time which may help salvage parts. Reassembly of the polishing head assembly may take place without applying a new material coat to the polishing head assembly, if coating is used. An indexing pin may be used to ensure the parts are put together in the original orientation which may avoid the need for repeated lapping of parts. The indexing pin may therefore prevent flatness issues associated with reassembly of conventional polishing head assemblies using fasteners (e.g., screws). Additionally, by securing a top edge of the annular wall of the cap to the recessed surface of the polishing head, leakage of pressurized media or fluid from the chamber of the polishing head assembly can be prevented. This seal may further be improved by using an o-ring at this connection. Also, the non-metallic band prevents contact between the polishing chemicals or slurry and the polishing head assembly, maintaining the service life of the polishing head and cap.

With reference to <FIG> and <FIG>, a perspective view and a partial cross section, respectively, of the polishing head assembly <NUM> of <FIG> are shown. As discussed above, the polishing head assembly <NUM> includes polishing head <NUM>, cap <NUM>, and band <NUM>. The cap <NUM> has the floor <NUM>, which has the bottom surface <NUM> extending outward to the tab <NUM>. As shown in <FIG> and <FIG>, the polishing head assembly <NUM> also includes a template <NUM>. The template <NUM> includes a backing film <NUM> and a retaining ring <NUM>. The retaining ring <NUM> extends downward along the perimeter of the backing film <NUM> to form a circular opening that receives a wafer W (shown in <FIG>). In some embodiments, a height of the retaining ring <NUM> is less than a height of the wafer W, which facilitates reducing or eliminating the contact of retaining ring <NUM> with a polishing pad, such as the polishing pad <NUM> (shown in <FIG>), during operation. The wafer W of this embodiment is retained against backing film <NUM> by surface tension.

To prevent metal used in the cap <NUM> from contaminating the slurry and the wafer W, the backing film <NUM> of the template <NUM> is sealed to the bottom surface <NUM> of the cap <NUM> using a pressure sensitive adhesive. The backing film <NUM> is generally a thin soft polymer pad or other suitable material. The backing film <NUM> suitably includes two or more layers of material (not shown). For example, backing film <NUM> may have an adhesive layer, a thin plastic film layer, and a thin polyurethane foam, or other non-woven material (e.g., felt), layer. The adhesive layer seals the backing film <NUM> to the bottom surface <NUM> of the cap <NUM>. The thin plastic film layer provides a protective barrier between the cap <NUM> and the slurry and/or the wafer W. The layer comprising polyurethane foam or non-woven material (e.g., felt) contacts the wafer W and provides a surface similar to that of a polishing pad (such as the polishing pad <NUM> shown in <FIG>). The retaining ring <NUM> extends downward from the backing film <NUM> and is generally a plastic material. The wafer W is received by the retaining ring <NUM> and is retained against the backing film <NUM> by surface tension. As such, the wafer W does not directly contact the cap <NUM>.

In this embodiment, the template <NUM> has a circumference greater than the circumference of the cap <NUM> and extends outward from the tab <NUM>. The cap <NUM> is circumscribed by the band <NUM>, which overlaps an outer portion of the template <NUM> at overlap surface <NUM>. The backing film <NUM> of the template <NUM> is sealed to the bottom surface <NUM>, and to the band <NUM> at overlap surface <NUM>, using a pressure sensitive adhesive. Together, the band <NUM> and the template <NUM> form a protective seal between the slurry and the wafer W and the polishing head <NUM> and the cap <NUM> to prevent the slurry and the wafer W from directly contacting the polishing head <NUM> and the cap <NUM>.

The embodiments described herein provide the ability to disassemble a polishing head assembly without the use of heat or other destructive action and enable an efficient and economical repair of the polishing head assembly. The embodiments described herein also provide the ability to attach a polishing head assembly using fasteners, while maintaining the desired flatness and other specifications of a polished wafer.

Claim 1:
A polishing head assembly (<NUM>) for polishing of semiconductor wafers, the polishing head assembly comprising:
a polishing head (<NUM>) having a top portion and a downwardly extending annular member (<NUM>) defining a recess along a bottom portion, the recess having a recessed surface (<NUM>), and holes (<NUM>) extending from the top portion through the recessed surface;
a cap (<NUM>) positioned within the recess, the cap having an annular wall (<NUM>) and a floor (<NUM>) extending across the annular wall, the floor having a bottom surface (<NUM>) and a top surface (<NUM>) and being spaced from the recessed surface to form a chamber (<NUM>) between the recessed surface and the top surface, wherein the annular wall has apertures (<NUM>) corresponding to the holes (<NUM>), and wherein the cap is made of a metallic material; and
a band (<NUM>) circumscribing a first portion (<NUM>) of the annular wall, wherein the band is made of a non-metallic material;
wherein the annular member circumscribes a second portion (<NUM>) of the annular wall; and
wherein the holes and the corresponding apertures receive fasteners (<NUM>) to removably secure the annular wall of the cap to the recessed surface of the polishing head such that the height of the chamber (<NUM>) is determined by the height of the annular wall when the annular wall and the recessed surface are secured.