Patent Description:
A silicon wafer manufacturing process includes a single crystal growth process for producing a single-crystal ingot, a slicing process for slicing the single-crystal ingot to obtain a thin disk-shaped wafer, an edge grinding process for machining the outer circumferential portion of the wafer obtained through the slicing process in order to prevent cracking or distortion of the wafer, a lapping process for removing remaining damage to the wafer due to mechanical processing, a polishing process for mirror-polishing the wafer, and a cleaning process for removing an abrasive or foreign substances adhered to the polished wafer.

Among these processes, the wafer polishing process may be performed through various steps, including first polishing, second polishing, third polishing, and the like, and may be performed using a wafer polishing apparatus.

<FIG> is a perspective view of a general wafer polishing apparatus, <FIG> illustrates a side section of the surface of an example of the polishing pad of <FIG>, <FIG> is a plan view of another example of the polishing pad of <FIG>, and <FIG> is a view showing a method of forming grooves in the polishing pad through hot press processing and cutting processing.

As shown in <FIG>, a general wafer polishing apparatus may include a surface plate <NUM>, to which a polishing pad <NUM> is attached, a polishing head <NUM> configured to surround a wafer W and rotate on the surface plate <NUM>, and a slurry spray nozzle <NUM> configured to supply slurry S to the polishing pad <NUM>.

During a polishing process, the surface plate <NUM> may be rotated by a surface plate rotation shaft <NUM>, and the polishing head <NUM> may be rotated by a head rotation shaft <NUM> in the state of being in close contact with the polishing pad <NUM>. In this case, the slurry S supplied by the slurry spray nozzle <NUM> may polish the wafer W, which is in contact with the polishing pad <NUM>, while infiltrating into the wafer W located on the polishing head <NUM>.

Referring to <FIG>, in a final polishing (FP) process, a porous polishing pad <NUM> having therein a plurality of pores P is used to remove damage to the surface of the wafer. The polishing pad <NUM> having this configuration has the same structure as a backing film for supporting the wafer W. Surface tension is generated at the surface of the polishing pad <NUM> that is in contact with the wafer W. Surface tension tends to increase as the size of the wafer W increases.

In particular, because the wafer W of <NUM> or more greatly increases surface tension, even when the polishing process is completed, the polishing pad <NUM> is maintained in the state in which the wafer W is adsorbed thereon, thus making it difficult to separate the wafer W from the polishing pad <NUM>.

In order to solve this problem and realize smooth supply of slurry to the surface of the wafer, as shown in <FIG>, a polishing pad 13a having lattice-shaped grooves G formed in the surface thereof may be used. More specifically, the lattice-shaped grooves G may be formed in the surface of a polishing pad 13a-<NUM> or 13a-<NUM> through hot press processing in a high-temperature and high-pressure environment, as shown in <FIG>, or through cutting processing using a graver, as shown in <FIG>.

However, hot press processing has a problem in that the contact surface of the polishing pad 13a-<NUM> is thermally deformed when pressed by a press (not shown), whereby the surface in which the grooves G are formed is hardened. The polishing pad 13a-<NUM> manufactured using this method causes a phenomenon in which stress is concentrated on the edge of the wafer W that is adjacent to the grooves G during the wafer polishing process, thus leading to reduced flatness of the wafer.

In addition, in the case of the polishing pad <NUM>-<NUM> manufactured using cutting processing, because the surface finish of a cut surface is rough, impurities generated during cutting of the grooves G remain in the grooves G, thus leading to degradation in localized light scattering (LLS) quality.

A polishing pad, in which all features of the preamble of claim <NUM> are disclosed, is described in <CIT>.

It is an object of the present invention to provide a polishing pad for a wafer polishing apparatus and a manufacturing method, with which wafer polishing quality can be improved by preventing reduced flatness of a wafer or degradation in LLS quality while a wafer polishing process is performed.

This object is achieved by a polishing pad and a manufacturing method according to the enclosed independent claims. Advantageous features of the present invention are defined in the corresponding subclaims.

The present invention provides a polishing pad for a wafer polishing apparatus according to claim <NUM>.

The upper pad may further include film-coated surfaces coated on the front portion and the back portion, and the grid grooves may have the film-coated surfaces as inner walls.

The adhesive part may be an adhesive or an adhesive tape to which the back portion of the upper pad and a front portion of the lower pad are attached.

Cutting processing may be performed on the polishing pad having the grid grooves formed therein.

The upper pad may include a porous nap layer, and the lower pad may include a non-woven fabric layer.

In addition, the present invention provides a method of manufacturing a polishing pad for a wafer polishing apparatus according to claim <NUM>.

In the lamination step, the nap layer and the non-woven fabric layer may be combined using an adhesive or an adhesive tape.

In the buffing step, the front portion of the upper pad in which the edges of the wedge grooves are included may be cut such that the grid grooves have a side section in which the bottom length is greater than the top length.

After the buffing step, a cutting step of cutting the polishing pad to an arbitrary size and shape may be further performed.

Before the film coating step, a mixing step of mixing raw materials of the nap layer may be performed.

According to a polishing pad for a wafer polishing apparatus and a manufacturing method therefor of the present invention, grid grooves, which are formed such that an entrance area contacting a wafer is smaller than a bottom area (i.e. the trapezoidal shape), may secure the smooth flow of slurry, may mitigate excessive surface tension with respect to a wafer, and may prevent reduced flatness of a wafer or degradation in LLS quality attributable to impurities during a wafer polishing process.

Hereinafter, embodiments will be elucidated via description thereof with reference to the accompanying drawings. In the following description of the embodiments, it will be understood that, when an element such as a layer (film), region, pattern, or structure is referred to as being "on" or "under" another element such as a substrate, layer (film), region, pad, or pattern, it can be "directly" on or under the other element, or can be "indirectly" formed such that an intervening element may also be present. In addition, it will also be understood that the criteria for "on" or "under" is on the basis of the drawing.

In the drawings, elements may be exaggerated in size, omitted, or schematically illustrated for convenience in description and clarity. Further, the sizes of elements do not indicate the actual sizes of the elements. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same parts. Hereinafter, embodiments will be described with reference to the accompanying drawings.

<FIG> is a side view of a portion of a polishing pad according to an embodiment of the present invention.

As shown in <FIG>, a polishing pad <NUM> for a wafer polishing apparatus according to an embodiment of the present invention may include an upper pad <NUM>, a lower pad <NUM>, and an adhesive part <NUM>.

The upper pad <NUM> is a part that forms an upper layer of the polishing pad <NUM> and is in contact with a wafer to polish the same. In more detail, the upper pad <NUM> does include a front portion, a back portion, and a plurality of grid grooves <NUM>. Here, the front portion and the back portion of the upper pad <NUM> may be coated with a film in which various raw materials are mixed.

The front portion may have a horizontal cut surface <NUM> from which a film-coated surface is removed. The cut surface <NUM> is formed through buffing processing, which will be described later.

The back portion is attached to the adhesive part <NUM> in the state of being coated with the film.

The grid grooves <NUM> may be arranged at regular intervals in the upper pad <NUM> in a form such that they penetrate the front portion and the back portion. For example, the grid grooves <NUM> may be arranged in the shape shown in <FIG>. Of course, in the polishing pad <NUM>, the intervals between the grid grooves <NUM> or the number of rows and columns constituting the grid grooves <NUM> may vary.

The grid grooves <NUM> have a side section in which the bottom length b is greater than the top length a. That is, the grid grooves <NUM> are formed such that the size of the entrance area contacting a wafer W is less than the size of the bottom surface area. The grid grooves <NUM> may be formed to have any of various sectional shapes in which the entrance area is smaller than the bottom surface area.

For example, as shown in <FIG>, according to the invention, unit members <NUM>, which form the grid grooves <NUM>, have a trapezoidal-shaped section in which the bottom length is less than the top length. The side surfaces of neighboring unit members <NUM> serve as sidewalls forming the grid grooves <NUM>. Therefore, the grid grooves <NUM> may be formed such that the sectional area thereof gradually increases from the front portion of the upper pad <NUM> to the back portion. That is, the grid grooves <NUM> have a trapezoidal-shaped side section in which the bottom length b is greater than the top length a. In addition, as described above, the grid grooves <NUM> may have film-coated surfaces as inner walls.

The trapezoidal-shaped grid grooves <NUM> may exhibit effects of securing the smooth flow of slurry on the surface of the upper pad <NUM> and minimizing surface tension with respect to the wafer. In addition, since the front portion of each grid groove <NUM>, i.e. the entrance contacting a wafer W, is narrower than the back portion (or the bottom surface), it is possible to minimize the discharge of impurities present in the back areas of the grid grooves <NUM> to the surface of the upper pad <NUM> and thus prevent the impurities from contaminating the wafer or adversely affecting the flatness of the wafer.

In addition, since the inner walls of the grid grooves <NUM> are coated with a film, the flow of the slurry may be further increased, and the generation of impurities may be reduced during the process of forming the grid grooves <NUM>.

The above-described upper pad <NUM> forms one layer in which the grid grooves <NUM> are formed, and thus may be referred to as a nap layer of the polishing pad <NUM>. The nap layer <NUM> may include a porous suede material so as to have excellent performance in removing defects from a wafer and prevent the occurrence of defects.

The lower pad <NUM> is disposed below the upper pad <NUM> described above, and may be attached to the surface plate. The lower pad <NUM> may be referred to as a non-woven fabric layer of the polishing pad <NUM>. The lower pad <NUM> is coupled to the upper pad <NUM>, and supports the upper pad <NUM> so that the upper pad <NUM> functions stably.

The adhesive part <NUM> is located between the upper pad <NUM> and the lower pad <NUM>, and combines the upper pad <NUM> and the lower pad <NUM>. For example, the adhesive part <NUM> may be an adhesive or an adhesive tape to which the back portion of the upper pad <NUM> and the front portion of the lower pad <NUM> are attached.

The polishing pad <NUM> for a wafer polishing apparatus of the embodiment having the above-described configuration may solve a problem in which a wafer is not readily separated after a polishing process by securing the smooth flow of slurry and minimizing surface tension using the grid grooves <NUM>, which have a relatively narrow entrance and a relatively wide bottom (e.g. have a trapezoidal shape). In addition, it is possible to prevent reduced flatness of a wafer or degradation in LLS quality attributable to impurities during a wafer polishing process.

Hereinafter, a method of manufacturing the polishing pad <NUM> according to the present invention and the above-described structure of the polishing pad <NUM> will be described in more detail. Hereinafter, the upper pad <NUM> and the lower pad <NUM> of the polishing pad <NUM> will be referred to as a nap layer <NUM> and a non-woven fabric layer <NUM>.

<FIG> is a flowchart showing a method of manufacturing a polishing pad according to the present invention, <FIG> illustrates a film coating step performed on the nap layer of <FIG>, <FIG> illustrates a grooving step performed on the nap layer of <FIG>, <FIG> illustrates a post-grooving step performed on the nap layer of <FIG>, <FIG> illustrates a lamination step performed on the nap layer and the non-woven fabric layer of <FIG>, <FIG> illustrates a buffing step performed on the nap layer of <FIG> illustrates a polishing pad resulting from the buffing step of <FIG>.

As shown in <FIG>, in a method of manufacturing the polishing pad <NUM> according to an embodiment of the present invention, a step of mixing raw materials of the nap layer <NUM> is first performed (S100).

In the mixing step (S100), a nap layer <NUM> including a porous suede material may be manufactured by appropriately mixing the raw materials for forming the nap layer <NUM>.

Subsequently, a film coating step (S200) of coating a film on the nap layer <NUM> is performed. The film coating step (S200), as shown in <FIG>, may be a step of coating a polyethylene (PET) film on the surface of the nap layer <NUM>. A film may be coated on the front portion and the back portion of the nap layer <NUM> through the film coating step (S200).

Subsequently, a grooving step (S300) of forming wedge grooves <NUM> in the back portion of the nap layer <NUM> is performed. The grooving step (S300), as shown in <FIG>, is performed through hot pressing processing using a hot press. The wedge grooves <NUM> are not limited to a triangular shape, but may have any of various other shapes, such as a semicircular shape, in which the size of the back portion is greater than the size of the front portion. The shape of the wedge grooves <NUM> may be variously formed by changing the shape of the hot press.

According to the invention, the grid grooves <NUM> of the polishing pad <NUM> are formed by forming the wedge grooves <NUM> (refer to <FIG>) through the hot pressing processing performed on the back portion of the upper pad <NUM>.

As shown in <FIG>, a plurality of wedge grooves <NUM> are formed in the back portion of the nap layer <NUM> through the grooving step (S300). For example, the plurality of wedge grooves <NUM> may have an inverted-triangular-shaped section.

After the grooving step (S300), a lamination step (S400) of bonding the nap layer <NUM> and the non-woven fabric layer <NUM> is performed. The lamination step (S400), as shown in <FIG>, may be a step of combining the nap layer <NUM> and the non-woven fabric layer <NUM> using an adhesive or an adhesive tape. In this case, the back portion of the nap layer <NUM> is bonded to the front portion of the non-woven fabric layer <NUM> such that the wedge grooves <NUM> in the nap layer <NUM> are oriented downwards.

After the lamination step (S400), a buffing step (S500) of buffing the front portion of the nap layer <NUM> is performed. The buffing step (S500) is a process of removing the surface of the nap layer <NUM>. In the buffing step (S500), as shown in <FIG>, the front portion of the nap layer <NUM> may be buffed so that the edge of each wedge groove <NUM>, i.e. the apex of the triangle, is cut. Therefore, after the buffing step (S500), the nap layer <NUM> has a thickness h1-<NUM> that is less than the thickness h1-<NUM> in the lamination step (S400), and has a cut surface <NUM> at the front portion thereof.

Here, the cut surface <NUM> may be referred to as a buffed surface. According to the invention, the nap layer <NUM>, which has the cut surface <NUM> at the front portion thereof, may solve the problems with the front portion formed through the conventional hot press processing, in which a portion adjacent to the grooves G is thermally deformed. Therefore, the polishing pad <NUM> according to the invention, which has the cut surface <NUM> at the front portion thereof, does not have a thermally deformed surface, thereby preventing direct contact between a wafer and a thermally deformed layer when contacting the wafer during the polishing process, reducing over-polishing of the side surface of the wafer, and consequently improving polishing quality.

When the buffing step (S500) is completed, as shown in <FIG>, the nap layer <NUM> is formed such that the unit members <NUM> forming the grid grooves <NUM> have a trapezoidal-shaped section in which the bottom length is less than the top length. Therefore, the grid grooves <NUM> may be formed such that the sectional area thereof gradually increases from the front portion of the nap layer <NUM> to the back portion. That is, the grid grooves <NUM> have a trapezoidal shape in which the bottom length b is greater than the top length a, so that the entrance area that comes into contact with a wafer is smaller than the bottom area. In addition, the grid grooves <NUM>, as described above, may have film-coated surfaces as inner walls.

The grid grooves <NUM> having the above-described shape may exhibit effects of securing the smooth flow of slurry on the surface of the upper pad <NUM> and minimizing surface tension with respect to the wafer. In addition, since the entrance of the front portion of each grid groove <NUM> is narrower than the back portion, it is possible to minimize the discharge of impurities present in the back area of each grid groove <NUM> to the surface of the upper pad <NUM>, thus preventing the impurities from contaminating the wafer or adversely affecting the flatness of the wafer.

After the buffing step (S500), a cutting step (S600) of cutting the polishing pad <NUM> to an arbitrary size and shape may be performed. In the cutting step (S600), the polishing pad <NUM> may be cut on a sheet-by-sheet basis so as to have an arbitrary size and shape. For example, in the cutting step (S600), the edge of the polishing pad <NUM> may be cut so that the polishing pad <NUM> has a circular-shaped, elliptical-shaped, or rectangular-shaped section. Subsequently, a quality inspection step (S700) of inspecting the quality of the manufactured polishing pad <NUM> may be performed.

As described above, according to the polishing pad <NUM> for a wafer polishing apparatus and the manufacturing method therefor of the present invention, the trapezoidal-shaped grid grooves <NUM> may secure the smooth flow of slurry, may mitigate excessive surface tension with respect to a wafer, and may prevent reduced flatness of a wafer or degradation in LLS quality attributable to impurities during a wafer polishing process.

The features, structures, effects, and the like described in association with the embodiments above are incorporated into at least one embodiment of the present invention, but are not limited only to the one embodiment. Furthermore, the features, structures, effects, and the like exemplified in association with respective embodiments can be implemented in other embodiments by combination or modification by those skilled in the art, within the scope of the appended claims.

Claim 1:
A polishing pad for a wafer polishing apparatus, comprising:
an upper pad (<NUM>) comprising a front portion having a cut surface (<NUM>) and configured to come into contact with a wafer (W), a back portion located below the front portion, and a plurality of grid grooves (<NUM>) penetrating the front portion and the back portion;
a lower pad (<NUM>) disposed below the upper pad (<NUM>), the lower pad (<NUM>) being configured to be attachable to a surface plate; and
an adhesive part (<NUM>) located between the upper pad (<NUM>) and the lower pad (<NUM>), the adhesive part (<NUM>) being configured to combine the upper pad (<NUM>) and
the lower pad (<NUM>),
characterized in that
the grid grooves (<NUM>) are formed such that an entrance area that comes into contact with the wafer (W) is smaller than a bottom area;
the grid grooves (<NUM>) have a trapezoidal-shaped side section in which a bottom length is greater than a top length; and
the grid grooves (<NUM>) are formed by buffing the front portion of the upper pad (<NUM>) in which edges of wedge grooves formed through hot pressing processing performed on the back portion of the upper pad (<NUM>) are included.