WAFER POLISHING APPARATUS FOR ADJUSTING HEIGHT OF WHEEL TIP

Abstract

In a wafer polishing apparatus, the height of the wheel tip can be adjusted. The wafer polishing apparatus includes a wheel tip constructed and arranged to be in direct contact with a wafer; a spindle shaft configured to receive power to enable rotation of the wheel tip; a wheel shank positioned at a lower part of the spindle shaft and supporting the wheel tip, the wheel tip not being directly fixed thereto; and a moving shaft having a first side on which the wheel tip is mounted and an opposite side to which the spindle shaft is connected, and relatively movable with respect to the spindle shaft.

Description

PRIORITY STATEMENT

This application claims the benefit of priority under 35 U.S.C. §119 from Korean Patent Application No. 10-2009-0113496, filed on Nov. 23, 2009, the contents of which are hereby incorporated herein by reference in their entirety.

BACKGROUND

1. Field

Example embodiments relate to a wafer polishing apparatus for adjusting a height of a wheel tip.

2. Description of Related Art

In the manufacturing of semiconductor devices, during one of the steps, the thickness of a semiconductor wafer is adjusted using a wafer thinning process. A conventional wafer thinning process is a wafer polishing process whereby an inactive surface of a wafer having no patterns is mechanically polished to reduce the thickness thereof.

As semiconductor packages continue to undergo further size reduction so that a compact and lightweight structure can be achieved, semiconductor devices installed in the semiconductor packages also require a compact and lightweight structure. This can be accomplished in part by a device-thinning process, a process which continues to be further developed.

SUMMARY

Example embodiments provide a wafer polishing apparatus capable of maximizing an exchange period of a wheel tip and minimizing the number of exchanges of wheel tips through height adjustment of the wheel tip.

Example embodiments also provide a wafer polishing apparatus capable of exchanging only a wheel tip and reusing a wheel shank by separating the wheel tip from the wheel shank.

It is to be understood that both the foregoing general description and the following detailed description are example and explanatory and are intended to provide further explanation of the inventive concept as claimed.

Example embodiments are directed to a wafer polishing apparatus including a spindle shaft rotated by a main motor; a wheel shank axially and rotatably coupled to the spindle shaft; a moving shaft engaged with the spindle shaft by a gear to be rotated; and a wheel tip coupled to the moving shaft and supported by the wheel shank, and constructed and arranged to polish a wafer.

In example embodiments, the gear may include a screw jack coupled to the moving shaft and having a female thread; and a lead screw coupled to the spindle shaft by a bearing and having a male thread.

In example embodiments, the wafer polishing apparatus may further include a step motor supported by the spindle shaft, and rotating the lead screw to straightly move the moving shaft with respect to the spindle shaft in a vertical direction.

In example embodiments, the wheel shank may include a spindle coupling part axially coupled to the spindle shaft; and a cover part having a slide groove and in which the wheel tip is supported or slid.

In example embodiments, the moving shaft may include a connecting part to which the screw jack is integrally coupled; and a slide part extending to a lower part of the connecting part and under which the wheel tip is mounted.

In example embodiments, the spindle shaft may include a plurality of connecting holes extending in an axial direction thereof, and the connecting part may be connected within the spindle shaft in a cross shape and slid along the connecting hole in a axial direction thereof.

Example embodiments are also directed to a wafer polishing apparatus including a rotatable spindle shaft; a wheel shank integrally fixed to the spindle shaft; a moving shaft variably fixed to the spindle shaft; and a wheel tip detachably mounted on the moving shaft.

In example embodiments, the wheel shank may include a slide hole configured to conceal the wheel tip other than an exposed portion of the wheel tip in direct contact with a wafer, and the moving shaft may include a slide part slid in the slide hole together with the wheel tip.

In example embodiment, the slide part may further include an attachment groove positioned at a first end and to which the wheel tip is detachably attached, and the attachment groove may have an open lower end opened so that the wheel tip can be inserted in an upward direction with respect to a longitudinal cross-section thereof.

In example embodiments, the slide part may further include a fastening hole passing through both sides thereof and at least the attachment groove, and a bolt may be fastened to the fastening hole to fix the wheel tip inserted into the attachment groove.

Example embodiments are also directed to a wafer polishing apparatus including: a wheel tip constructed and arranged to be in direct contact with a wafer; a spindle shaft configured to receive power to enable rotation of the wheel tip; a wheel shank positioned at a lower part of the spindle shaft and supporting the wheel tip, the wheel tip not being directly fixed thereto; and a moving shaft having a first side on which the wheel tip is mounted and a second side to which the spindle shaft is connected, and relatively movable with respect to the spindle shaft.

In example embodiments, the wheel shank may include a spindle coupling part coupled to the spindle shaft at an upper center thereof; and a cover part configured to expose a portion of the wheel tip at a lower edge thereof.

In example embodiments, the wheel tip may have a width W of 3 mm to 4 mm and a height H of 5 mm to 15 mm, and a height H1 of the wheel tip exposed from the cover part may be maintained within a range of 1 mm to 4 mm.

In example embodiments, the cover part may further include a slide hole through which the wheel tip can vertically pass, and as the slide part is slid downward from the slide hole, a height H2 of the wheel tip concealed by the cover part may be reduced, and the height H1 exposed from the cover part may be uniformly maintained within the range.

In example embodiments, the slide hole may correspond to a shape of the wheel tip, and may have a step between upper and lower parts thereof so that a hole gap at the upper part is larger then the thickness of the wheel tip, and a hole gap at the lower part is equal to or approximate to the thickness of the wheel tip with respect to a longitudinal cross-section thereof.

In example embodiments, a vertical surface of the step may be a surface configured to support the wheel tip, and a horizontal surface of the step may be a stopper surface to prevent the moving shaft from lowering any further.

In example embodiments, the moving shaft may include a connecting part movably connected to the spindle shaft; and a slide part to which the wheel tip is detachably attached.

In example embodiments, the wafer polishing apparatus may further include a variable means configured to fix the moving shaft to the spindle shaft during polishing or to vary a position of the moving shaft when the wheel tip is worn down.

In example embodiments, the variable means may be a screw gear assembly, and the screw gear assembly may include a screw jack formed at the moving shaft; a lead screw connected to the spindle shaft and passing through the screw jack; and a step motor configured to rotate the lead screw, wherein when the lead screw is rotated by the step motor, the screw jack moves longitudinally in a vertical direction depending on a rotational direction of the lead screw.

In example embodiments, the variable means may be a linear actuator, and the linear actuator may include a piston rod extending to be connected to the connecting part in a cross shape; and a linear step motor configured to move the piston rod in a longitudinal direction thereof, wherein when the linear step motor is driven, the piston rod moves longitudinally in a vertical direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments are described in further detail below with reference to the accompanying drawings. It should be understood that various aspects of the drawings may have been exaggerated for providing clarity.

FIGS. 1 and 2 are longitudinal cross-sectional views schematically depicting a grinder including a polishing apparatus and a chuck table in accordance with an example embodiment of the inventive concept.

FIG. 3 is a plan view illustrating the polishing apparatus in accordance with an example embodiment of the inventive concept.

FIG. 4 is a longitudinal cross-sectional view enlarging a portion “s” of FIG. 1 to illustrate attachment of a slide of a moving shaft to a wheel tip, and detachment of the slide from the moving shaft, in accordance with an example embodiment of the inventive concept.

FIGS. 5 and 6 are a perspective view and a longitudinal cross-sectional view illustrating the polishing apparatus in which a moving shaft is varied by a screw gear assembly in accordance with an example embodiment of the inventive concept.

FIG. 7 is a cross-sectional view taken along line II-II′ of FIG. 6.

FIG. 8 is a longitudinal cross-sectional view illustrating a worn-down state of the wheel tip in accordance with an example embodiment of the inventive concept.

FIG. 9 is a longitudinal cross-sectional view showing exchange of the wheel tip in accordance with an example embodiment of the inventive concept.

FIGS. 10 and 11 are longitudinal cross-sectional views showing the polishing apparatus in which a moving shaft is varied by a linear actuator in accordance with an example embodiment of the inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various example embodiments will now be described more fully with reference to the accompanying drawings in which some example embodiments are shown. In the drawings, the thicknesses of layers and regions may be exaggerated for clarity.

Detailed illustrative embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. This inventive concept, however, may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein.

Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but on the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the inventive concept. Like numbers refer to like elements throughout the description of the figures.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.).

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof. Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or a relationship between a feature and another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the Figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, for example, the term “below” can encompass both an orientation which is above as well as below. The device may be otherwise oriented (rotated 90 degrees or viewed or referenced at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.

Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, may be expected. Thus, example embodiments should not be construed as limited to the particular shapes of regions illustrated herein but may include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle may have rounded or curved features and/or a gradient (e.g., of implant concentration) at its edges rather than an abrupt change from an implanted region to a non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation may take place. Thus, the regions illustrated in the figures are schematic in nature and their shapes do not necessarily illustrate the actual shape of a region of a device and do not limit the scope.

It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may be executed in the reverse order, depending upon the functionality/acts involved.

In order to more specifically describe example embodiments, various aspects will be described in detail with reference to the attached drawings. However, the inventive concept is not limited to example embodiments described.

FIGS. 1 and 2 are longitudinal cross-sectional views schematically illustrating a grinder including a polishing apparatus and a chuck table in accordance with an example embodiment of the inventive concept, and FIG. 3 is a plan view illustrating the polishing apparatus in accordance with an example embodiment of the inventive concept.

Referring to FIGS. 1 and 2, a grinder 10 for machining a wafer 2 to a desired thickness includes a chuck table 12 for fixing the wafer 2, and a polishing apparatus 100 for polishing the wafer 2.

The chuck table 12 has a seating surface on which the wafer 2 is seated. The wafer 2 is disposed such that a surface thereof including active circuitry faces the seating surface of the chuck table 12. The seating surface may have a vacuum suction port (not shown) for fixing the wafer 2 using a vacuum. The chuck table 12 may be driven to rotate the wafer 2. The rotational direction may be opposite to a rotational direction of the polishing apparatus 100.

The polishing apparatus 100 is disposed over the chuck table 12. The polishing apparatus 100 may be vertically, horizontally and reciprocally driven by a drive part 102. In addition, the polishing apparatus 100 may be rotated to polish the wafer 2.

The polishing apparatus 100 may include a wheel tip 110 in direct contact with the wafer 2, a main motor 120 for providing a rotational force to the wheel tip 110, a spindle shaft 130 connected to the main motor 120 and enabling rotation of the wheel tip 110, a wheel shank 140 for supporting the wheel tip 110 without the wheel tip 110 being directly fixed thereto, and for guiding the wheel tip 110 such that the wheel tip 110 moves downward, and being separable from the wheel tip 110 upon exchange of the wheel tip 110, and a moving shaft 160 having a lower part, to which the wheel tip 110 is fixed, and relatively moving with respect to the spindle shaft 130 such that the wheel tip 110 can be moved downward with respect to the wheel shank 140 when the wheel tip 110 is worn down, while being fixed to the spindle shaft 130 during the polishing operation.

An outer surface of the wheel tip 110, which performs the polishing operation, may be formed by mixing diamond particles, resin particles, etc., and sintering them. A plurality of wheel tips 110 having a predetermined height H and width W may be mounted at a lower part of the moving shaft 160 at predetermined intervals. The wheel tips 110 are disposed in a cylindrical shape when they are installed at the moving shaft 160. In example embodiments, the width W may be 3 to 4 mm and the height H may be 5 mm or more. More specifically, the height H may be 5 mm to 15 mm.

When the wheel tip 110 has a width of 3 mm to 4 mm, the height H may be set to 3 mm to 5 mm. When the height H is larger than 5 mm, the wheel tip 110 is more susceptible to deformation or breakage. However, in an embodiment where the wheel tip 110 can be supported by the wheel shank 140 and the amount of exposed height H1 can be uniformly maintained, it is possible to prevent deformation or breakage of the wheel tip 110, even in a case where the height is 5 mm or more as described above.

While the wheel tip 110 may be integrally fixed to the moving shaft 160, the wheel tip 110 may be detachably attached thereto. That is, when the wheel tip 110 is detachably attached to the moving shaft 160, the wheel tip 110 can be independently separated from the moving shaft 160 when the wheel tip 110 is worn down, and thus, the wheel tip 110 can be replaced with a new one.

The wheel tip 110 may be a split-type that is divided into a plurality of bodies, or an integral type that is formed of a single body. In the case of the split-type, a plurality of wheel tips 110 may be discontinuously positioned in a circumferential direction at predetermined intervals. In addition, the wheel tips 110 may be disposed along at least two lines in a concentric manner.

The main motor 120 may be installed at one side of the driver 102 so that the polishing apparatus 100 can be driven on the chuck table 12 in a vertical, horizontal or reciprocal direction. The main motor 120 may be installed on the spindle shaft 130 to provide a rotational force to the spindle shaft 130.

The spindle shaft 130 is connected to the wheel shank 140 and the moving shaft 160, and may receive power from the main motor 120 to transmit the power to the wheel shank 140 and the moving shaft 160.

The wheel shank 140 reduces the exposed height H1 of the wheel tip 110 and uniformly maintains the exposed height H1 in order to prevent deformation of, or breakage of the wheel tip 110 during a polishing process. A spindle-coupling part 142 may be formed on an upper surface of the wheel shank 140 to be coupled to the spindle shaft 130. A cover 144 is formed at an edge of the wheel shank 140 to cover the wheel tip 110 other than the exposed part E thereof. The cover 144 may have a slide hole 152 through which the wheel tip 110 can pass. The slide hole 152 may have a shape that corresponds with that of the wheel tip 110.

The wheel tip 110 has a width W that is less than a width of a slide part 164 of the moving shaft 160, and therefore, the slide hole 152 of the cover 144, which can be configured to surround the slide part 164 when the wheel tip is worn (see FIG. 2), may further include a horizontal step 156 formed at its lower part. A gap is present between an inner vertical sidewall 154 of the slide hole 152 and the vertical surface of an upper portion of the wheel tip 110 within the slide hole 152, and little or no gap is present between the vertical surface of the step 156 and the lower portion of the wheel tip 110 so as to prevent movement of the wheel tip 110 relative to the slide hole 152. In addition, a horizontal surface of the step 156 may function as a stopper such that the slide part 164 cannot be lowered any further into the slide hole 152.

The moving shaft 160 may further include a connecting part 162 formed at its upper portion and slidably connected to the spindle shaft 130, and the slide part 164 formed at its lower part, on which the wheel tip 110 is mounted. The slide part 164 may correspond to the slide hole 152 to be vertically slid within, and surrounded by, the slide hole 152.

FIG. 4 is a longitudinal cross-sectional view enlarging a portion “s” of FIG. 1 to show attachment/detachment of a slide of a moving shaft to/from a wheel tip in accordance with an example embodiment of the inventive concept.

Referring to FIG. 4, an attachment groove 166 may be formed in an end of the slide part 164 to receive the wheel tip 110. The attachment groove 166 may be open at its lower part so that the wheel tip 110 can be inserted and fastened in an upward direction. A fastening hole 168 may be formed to pass through both sides of the slide part 164. The fastening hole 168 should pass through at least the attachment groove 166. When a bolt 172 is fastened to the fastening hole 168, the wheel tip 110 that is inserted into the attachment groove 166 is fixed.

The wheel tip 110 may be readily broken or deformed when excessive stress is applied thereto, because the wheel tip 110 is formed by mixing and sintering resin powder, resulting in a relatively fragile component. Therefore, a shock absorbing material 174 may be further installed in the attachment groove 166 between the bolt 172 and the wheel tip 110. When or after the wheel tip 110 is inserted into the attachment groove 166 and then the bolt 172 is fastened thereto, the shock absorbing material 174 is positioned between the bolt 172 and the wheel tip 110. As a result, the stress applied to the wheel tip 110 is attenuated by the bolt 172. Here, an inner space may be expanded such that the shock absorbing material 174 can be installed in the attachment groove 166.

FIGS. 5 and 6 are a perspective view and a longitudinal cross-sectional view illustrating the polishing apparatus in which the vertical position of a moving shaft 160 relative to the wheel shank 140 is varied by a screw gear assembly in accordance with an example embodiment of the inventive concept, and FIG. 7 is a cross-sectional view taken along line II-II′ of FIG. 6.

Referring to FIGS. 5, 6 and 7, the connecting part 162 may have a cross (+) shape in cross-section in the spindle shaft 130 so as to increase its durability and to improve the balance thereof. The number of connecting holes 132 corresponding to the number of connecting parts 162 may be formed in the spindle shaft 130 so that the connecting parts 162 can be slidably connected to the spindle shaft 130. For this purpose, a predetermined space for mounting the connecting part 162 may be formed in an inner upper part of the spindle shaft 130.

Referring to FIG. 6, the moving shaft 160 may further include a variable means for variably coupling the moving shaft 160 to the spindle shaft 130. That is, the variable means can be configured to fix the connecting part 162 of the moving shaft 160 to the spindle shaft 130 at one side, and move with respect to the spindle shaft 130 at the other side. The variable means may comprise, in one embodiment, a screw gear assembly 180.

The screw gear assembly 180 may include a screw jack 182 installed at the moving shaft 160, and a lead screw 184 installed at the spindle shaft 130. The screw jack 182 may include a female thread, and the lead screw 184 may include a male thread. The lead screw 184 is installed to pass through the screw jack 182. When the lead screw 184 is rotated, the screw jack 182 moves in a vertical direction relative to the lead screw.

A step motor 186 may be fixedly installed at one side in the spindle shaft 130 to rotate the lead screw 184. Since the step motor 186 has a rotator (not shown) rotated to a certain angle per input pulse provided from the exterior, the step motor 186 is appropriately used for automatic control. That is, since the rotator is rotated in proportion to the number of pulse signals output from a controller (not shown), the step motor 186 can be readily controlled by a microprocessor.

An upper end of the lead screw 184 is connected to the step motor 186, and a lower end of the lead screw 184 is connected to the spindle shaft 130. The upper end of the lead screw 184 connected to the step motor 186 is connected to the output rotator (not shown) of the step motor 186. The lead screw 184 may be connected to the spindle shaft 130 through a bearing 188 so that the spindle shaft 130 is not rotated with the lead screw 184.

FIG. 8 is a longitudinal cross-sectional view illustrating a worn-down state of the wheel tip in accordance with an example embodiment of the inventive concept, and FIG. 9 is a longitudinal cross-sectional view showing exchange of the wheel tip in accordance with an example embodiment of the inventive concept.

Referring to FIGS. 8 and 9, when the lead screw 186 is rotated by the step motor 186, only the moving shaft 160 connected to the screw jack 182 moves longitudinally in a vertical direction, depending on a rotational direction of the lead screw 184, and the spindle shaft 130 is not moved by the bearing 188.

While a conventional step motor enables rotational movement, since a linear step motor enables straight movement, a linear actuator including the linear step motor may be used as a means for moving the moving shaft.

FIGS. 10 and 11 are longitudinal cross-sectional views showing the polishing apparatus in which a moving shaft is varied by a linear actuator in accordance with an example embodiment of the inventive concept. Referring to FIGS. 10 and 11, the variable means in accordance with another example embodiment of the inventive concept may include a linear actuator 190 for moving an object in a straight, longitudinal direction.

The linear actuator 190 may include a piston rod 192 that extends to be connected to the connecting part 162 of the moving shaft 160 in a cross shape, and a linear step motor 194 for moving the piston rod 192. The piston rod 192 may be slid straightly along one side of the spindle shaft 130 to prevent the piston rod 192 from moving horizontally when the moving shaft 160 is driven.

The linear actuator 190 may be an electrically-powered type for receiving electric power, a hydraulic type for receiving hydraulic power, or a pneumatic type for receiving pneumatic pressure. Among them, when the electrical linear step motor 194 is used as the linear actuator 190, since the piston rod 192 can be straightly moved by a rotational force of the linear step motor 194 and driven step by step according to a control signal output from a controller (not shown), it is possible to precisely control a moving distance of the moving shaft 160.

Hereinafter, methods of using a wafer polishing apparatus in accordance with example embodiments of the inventive concept will be described.

Referring to FIG. 1, in a final step of a wafer manufacturing process for forming a predetermined pattern on a wafer 2, a rear surface polishing process for lapping the wafer 2 to a desired thickness is performed. The rear surface polishing process is performed to improve heat radiation of a semiconductor device bonded during a semiconductor package process, flatten the surface of the semiconductor device, and reduce the thickness thereof.

First, a wafer 2 is seated on a seating surface of a chuck table 12. An inactive surface of the wafer 2 is oriented in an upward direction. A polishing apparatus 100 is moved downward toward the chuck table 2 by a drive part 102 so that the wheel tip 110 can contact the inactive surface of the wafer 2. When a main motor 120 is driven, the spindle shaft 130 is rotated to polish the rear surface of the wafer 2 using the wheel tip 110. Next, in a state in which the wheel tip 110 is in contact with the inactive surface of the wafer 2, the polishing apparatus 100 is moved horizontally by the driver 102.

Referring to FIG. 2, after repeated rear surface polishing process operations, the wheel tip 110 is worn down. Therefore, an exposed height H1 of the wheel tip 110 is reduced. When the exposed height H1 becomes reduced in this manner, the wheel tip 110 is lowered to maintain the exposed height H1 within a range of 1 mm to 4 mm.

Hereinafter, adjustment of the height of the wheel tip will be described in detail.

Referring to FIG. 6, as the step motor 186 rotates, the lead screw 184 is rotated. Since the spindle shaft 130 is connected to the lead screw 184 by a bearing 188, the relative heights of the step motor 186 and the spindle shaft 130 are maintained in a fixed state. However, the moving shaft 160 engaged with the lead screw 184 through a screw jack 182 moves in a downward direction. That is, since the lead screw 184 is a male screw and the screw jack 182 is a female screw, rotation of the lead screw 184 is converted into longitudinal movement of the screw jack 182. A connecting part 162 coupled to the screw jack 182 moves to lower the moving shaft 160 to a desired distance.

Referring to FIG. 8, an operator can determine whether the exposed height H1 of the wheel tip 110 is reduced. It can be more precisely determined using a distance sensor or a proximity sensor. When reduction in the exposed height H1 of the wheel tip 110 is determined using the naked eye or the sensor, the step motor 186 can be driven to uniformly maintain the exposed height H1 within a predetermined or desired range. In addition, referring to FIGS. 10 and 11, when a linear step motor 196 is driven to straightly move a piston rod 192, the exposed height H1 can also be uniformly maintained.

While the exposed height H1 of the wheel tip 110 can be uniformly maintained through the height adjustment, the concealed height H2 is gradually reduced. When the length of the wheel tip 110 cannot be adjusted any further, one side of the connecting part 162 of the moving shaft 160 contacts one side of the spindle coupling part 142 of the wheel shank 140, or one side of the slide part of the moving shaft 160 contacts a horizontal surface 156 of the step of the cover part 144 of the wheel shank 140. In particular, when a contact sensor is installed at the contact part, it is possible for an operator to readily determine an exchange time of the wheel tip 110.

Referring to FIG. 9, when it is determined that the wheel tip 110 needs to be exchanged, the moving shaft 160 is made to move in an upward direction. At this time, the step motor 186 is driven in a direction opposite to the rotational direction to adjust the length of the wheel tip 110. The moving shaft 160 is spaced apart from the wheel shank 140, and the wheel tip 110 is exchanged with a new one using a space therebetween.

When the bolt 172 is separated from the slide part 164, the wheel tip 110 is removed from the attachment groove 166. A new wheel tip having a height of 5 mm to 15 mm, for example, is installed in the attachment groove 166. The new wheel tip 110 is then fastened to the slide part 164 using the bolt 172.

The step motor 186 is driven such that the wheel tip 110 is exposed from the cover part 144 to a range of 1 mm to 4 mm upon polishing. Following proper adjustment of the length of the wheel tip 110, the polishing is performed again.

In general, an initial polishing load may be increased after exchange of the wheel tip 110. In order to adjust the initial polishing load, a dressing process is performed. However, when the number of exchanges of the wheel tips 110 is increased and the number of dressing processes is also increased, a time for quality stabilization is consumed in proportion thereto. Since the exchange cycle of the wheel tip 110 of the embodiment is lengthened and the number of exchanges is reduced, the time for quality stabilization can be improved.

In addition, even in a case where the wheel tip 110 is worn down, there is no need to dispose of the wheel shank 140 together with the wheel tip 110. In a state in which the wheel shank 140 is fastened, only the moving shaft 160 is moved upward, and then, the wheel tip 110 can be exchanged.

Names and functions of elements having no reference numeral or elements having only reference numerals will be readily apparent from other drawings and descriptions thereof in this specification.

As can be seen from the foregoing, a wafer polishing apparatus in accordance with the technical sprit of the inventive concept can accomplish the following effects.

First, as the exchange period of the wheel tip is lengthened and the number of exchanges of wheel tips is reduced, it is possible to reduce the number of dressing processes for adjusting an initial polishing load upon exchange of the wheel tip, and thus, the time consumed for quality stabilization can be absolutely reduced.

Second, since only the wheel tip is exchanged, with a wheel shank remaining, it is possible to reuse the wheel shank to reduce overall fabrication costs.

The foregoing is illustrative of example embodiments and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in example embodiments without materially departing from the novel teachings and advantages. Accordingly, all such modifications are intended to be included within the scope of this inventive concept as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims.

Claims

1. A wafer polishing apparatus comprising:

a spindle shaft rotated by a main motor;

a wheel shank axially and rotatably coupled to the spindle shaft;

a moving shaft engaged with the spindle shaft by a gear to be rotated; and

a wheel tip coupled to the moving shaft and supported by the wheel shank, constructed and arranged to polish a wafer.

2. The wafer polishing apparatus according to claim 1, wherein the gear comprises:

a screw jack coupled to the moving shaft and having a female thread; and

a lead screw coupled to the spindle shaft by a bearing and having a male thread.

3. The wafer polishing apparatus according to claim 2, further comprising a step motor supported by the spindle shaft, and rotating the lead screw to straightly move the moving shaft with respect to the spindle shaft in a vertical direction.

4. The wafer polishing apparatus according to claim 2, wherein the wheel shank comprises:

a spindle coupling part axially coupled to the spindle shaft; and

a cover part having a slide groove in which the wheel tip is supported or slid.

5. The wafer polishing apparatus according to claim 2, wherein the moving shaft comprises:

a connecting part to which the screw jack is integrally coupled; and

a slide part extending to a lower part of the connecting part and under which the wheel tip is mounted.

6. The wafer polishing apparatus according to claim 5, wherein:

the spindle shaft comprises a plurality of connecting holes extending in an axial direction thereof, and

the connecting part is connected within the spindle shaft in a cross shape, and slid along the connecting hole in an axial direction thereof.

7. A wafer polishing apparatus comprising:

a rotatable spindle shaft;

a wheel shank integrally fixed to the spindle shaft;

a moving shaft variably fixed to the spindle shaft; and

a wheel tip detachably mounted on the moving shaft.

8. The wafer polishing apparatus according to claim 7, wherein:

the wheel shank comprises a slide hole configured to conceal the wheel tip other than an exposed portion of the wheel tip in direct contact with a wafer, and

the moving shaft comprises a slide part slid in the slide hole together with the wheel tip.

9. The wafer polishing apparatus according to claim 8, wherein the slide part further comprises an attachment groove positioned at a first end and to which the wheel tip is detachably attached, and

the attachment groove has an open lower end so that the wheel tip can be inserted in an upward direction with respect to a longitudinal cross-section thereof.

10. The wafer polishing apparatus according to claim 9, wherein:

the slide part further comprises a fastening hole passing through both sides thereof and at least the attachment groove; and

a bolt is fastened to the fastening hole to fix the wheel tip inserted into the attachment groove.

11. A wafer polishing apparatus comprising:

a wheel tip constructed and arranged to be in direct contact with a wafer;

a spindle shaft configured to receive power to enable rotation of the wheel tip;

a wheel shank positioned at a lower part of the spindle shaft and supporting the wheel tip, the wheel tip not being directly fixed thereto; and

a moving shaft having a first side on which the wheel tip is mounted and a second side to which the spindle shaft is connected, and relatively movable with respect to the spindle shaft.

12. The wafer polishing apparatus according to claim 11, wherein the wheel shank comprises:

a spindle coupling part coupled to the spindle shaft at an upper center thereof; and

a cover part configured to expose a portion of the wheel tip at a lower edge thereof.

13. The wafer polishing apparatus according to claim 12, wherein the wheel tip has a width W of 3 mm to 4 mm and a height H of 5 mm to 15 mm, and a height H1 of the wheel tip exposed from the cover part is maintained within a range of 1 mm to 4 mm.

14. The wafer polishing apparatus according to claim 12, wherein:

the cover part further comprises a slide hole through which the wheel tip can vertically pass, and

as the slide part is slid downward from the slide hole, a height H2 of the wheel tip concealed by the cover part is reduced, and the height H1 exposed from the cover part is uniformly maintained within the range.

15. The wafer polishing apparatus according to claim 14, wherein the slide hole corresponds to a shape of the wheel tip, and has a step between upper and lower parts thereof so that a hole gap at the upper part is larger then the thickness of the wheel tip, and a hole gap at the lower part is equal to or approximate to the thickness of the wheel tip with respect to a longitudinal cross-section thereof.

16. The wafer polishing apparatus according to claim 15, wherein:

a vertical surface of the step is a surface configured to support the wheel tip, and

a horizontal surface of the step comprises a stopper surface to prevent the moving shaft from lowering any further.

17. The wafer polishing apparatus according to claim 11, wherein the moving shaft comprises:

a connecting part movably connected to the spindle shaft; and

a slide part to which the wheel tip is detachably attached.

18. The wafer polishing apparatus according to claim 17, further comprising a variable means configured to fix the moving shaft to the spindle shaft during polishing or to vary a position of the moving shaft when the wheel tip is worn down.

19. The wafer polishing apparatus according to claim 18, wherein the variable means is a screw gear assembly, and

the screw gear assembly comprises: a screw jack formed at the moving shaft; a lead screw connected to the spindle shaft and passing through the screw jack; and a step motor configured to rotate the lead screw, wherein when the lead screw is rotated by the step motor, the screw jack moves longitudinally in a vertical direction depending on a rotational direction of the lead screw.

20. The wafer polishing apparatus according to claim 18, wherein the variable means is a linear actuator, and

the linear actuator comprises: a piston rod extending to be connected to the connecting part in a cross shape; and a linear step motor configured to move the piston rod in a longitudinal direction thereof, wherein when the linear step motor is driven, the piston rod moves longitudinally in a vertical direction.