ABRASIVE CONDITIONER AND A METHOD OF FABRICATING THE SAME

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to Taiwan patent application no. 113134686 filed on Sep. 12, 2024.

BACKGROUND

1. Field of the Invention

The present invention relates to abrasive conditioners and fabrication methods thereof, in particular to abrasive conditioners for chemical-mechanical polishing pads that are used in semiconductor manufacturing processes.

2. Description of the Related Art

Chemical mechanical polishing (CMP) is an indispensable part in semiconductor manufacturing processes. Typically, a CMP pad is used in association with a slurry to remove materials from a substrate. After the CMP pad is used over a period of time, the grinding action of the CMP pad may diminish. Therefore the CMP pad has to be periodically conditioned with an abrasive conditioner to maintain a desirable grinding efficiency.

To condition the CMP pad, the abrasive conditioner typically has abrasive particles that are used to coarsen the working surface of the CMP pad. The abrasive particles have to be fixedly attached to the abrasive conditioner so that no separation of the abrasive particles occurs during the conditioning process, which may damage the CMP pad and/or the semiconductor device to be manufactured. It is also desirable that the abrasive particles can maintain a desirable cut rate during a service cycle of the conditioner to reduce the fabrication and maintenance costs. Various prior approaches have been proposed to fabricate abrasive conditioners. For example, Taiwan patent no.

TW 562719 discloses an abrasive conditioner for CMP pads that has each abrasive particle brazed to an individual metal rod and then attaches the metal rods to a metal plate.

Unfortunately, the conventional conditioners still fail to address some technical problems in an adequate manner. For example, Taiwan patent no. TW I306048 discloses a conditioner having abrasive particles attached to a substrate in such a way that the abrasive particles may wear down to be flush with the bonding layer extending between the abrasive particles, which would significantly reduce the effective working area of the abrasive particles and alter the grinding performance. If abrasive particles of relatively greater particle sizes were used to offer a desirable cut rate during an extended service cycle of the conditioner, the manufacture cost of the conditioner would be increased and leveling problems owing to a greater particle size variation range would adversely occur.

With respect to Taiwan patent no. TW 562719, the approach disclosed therein requires multiple processing steps, which include drilling holes in the metal plate, inserting the metal rods with the abrasive particles attached thereon in the holes, and then bonding the metal rods to the metal plate. These processing steps are complex in realization and contribute to increase the fabrication cost. Moreover, the height of the abrasive particles cannot be easily controlled with that approach.

Therefore, there is a need for an improved abrasive conditioner for CMP pads that is cost-effective to fabricate and maintain, and can provide a desirable cut rate, increase an effective working area and/or allow better height control for the arrangement of the abrasive particles.

SUMMARY

The present application describes an abrasive conditioner that can address at least the foregoing issues.

According to an embodiment, the abrasive conditioner includes a substrate having a plurality of protrusions on a side thereof, the protrusions being separated from one another by a plurality of depressions, and a plurality of abrasive particles respectively attached to the protrusions on a one-to-one correspondence basis via a bonding layer, wherein the bonding layer extends into the depressions.

Moreover, the present application describes a method of fabricating an abrasive conditioner. The method includes forming a plurality of protrusions and a plurality of depressions on a first side of a substrate, the protrusions being separated from one another by the depressions; forming a bonding layer on the first side of the substrate, the bonding layer covering entirely the protrusions and the depressions; positioning a plurality of abrasive particles on a one-to-one correspondence basis with respect to the protrusions; and respectively attaching the abrasive particles to the protrusions on a top thereof via the bonding layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating an embodiment of an abrasive conditioner;

FIG. 2 is a flowchart illustrating method steps for fabricating an abrasive conditioner;

FIGS. 3A to 3G are schematic views illustrating intermediate stages in a method of fabricating an abrasive conditioner; and

FIG. 4 is a schematic view illustrating a positioning plate used in a method of fabricating an abrasive conditioner.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a side view illustrating an embodiment of an abrasive conditioner 100. Examples of applications for the abrasive conditioner 100 may include, without limitation, chemical-mechanical polishing (CMP) processes in which the abrasive conditioner 100 can be used to condition a CMP pad. Referring to FIG. 1, the abrasive conditioner 100 includes a substrate 102, a plurality of abrasive particles 104 and a bonding layer 106. The bonding layer 106 is applied to cover a side of the substrate 102 to which the abrasive particles 104 can be fixedly attached with the bonding layer 106.

The substrate 102 may have any suitable shapes and dimensions. According to an example, the substrate 102 can have a circular shape, such as a 4-inch diameter circular substrate. The substrate 102 can be made of any materials containing metal alloys that have adequate mechanical strength and suitable chemical resistance, which may include, without limitation, stainless steel. The substrate 102 has two opposite sides 102A and 102B, and the abrasive particles 104 can be exemplarily attached to the side 102A of the substrate 102 via the bonding layer 106. More specifically, the side 102A of the substrate 102 has a plurality of protrusions 108 that are separated from one another by depressions 110, and the abrasive particles 104 can be affixed to the protrusions 108 outside the depressions 110 via the bonding layer 106. In particular, the abrasive particles 104 can be respectively attached to the protrusions 108 on a one-to-one correspondence basis so that each protrusion 108 is attached to only one single abrasive particle 104. The substrate 102 and the protrusions 108 can integrally form a single body of a same material. Various techniques can be applied to form the protrusions 108 from the substrate 102, which may include, without limitation, dry etching, wet etching, laser cutting, etc. The abrasive particles 104 attached with the bonding layer 106 are exposed on the top of the protrusions 108. The bonding layer 106 exposed on the side 102A of the substrate 102 can cover the protrusions 108 and extend into the depressions 110. According to an embodiment, the bonding layer 106 can entirely cover the protrusions 108 and the depressions 110 on the side 102A of the substrate 102.

The protrusions 108 can be distributed in any suitable patterns on the side 102A of the substrate 102, in accordance with a desirable layout of the abrasive particles 104. According to an embodiment, the protrusions 108 can be arranged in one annulus or multiple concentric annuluses. According to other embodiments, the protrusions 108 can be arranged in one or multiple arrays, one or multiple polygons, one or multiple rays around an axis, one or multiple helices, etc. Moreover, the protrusions 108 within one pattern may be arranged equidistant or at varying distances from one another.

Referring to FIG. 1, any two adjacent ones of the protrusions 108 are separated from each other by a depression 110, wherein each of the two adjacent protrusions 108 has a protrusion sidewall 114 projecting upward from a bottom surface 112 of the depression 110, and the bonding layer 106 covers the bottom surface 112 and the protrusion sidewalls 114 inside the depression 110. According to an embodiment, each protrusion sidewall 114 can project generally perpendicular to the bottom surface 112 of the depression 110. It will be appreciated, however, that the protrusion sidewall 114 can be tilted an angle relative to the bottom surface 112, e.g., the bottom surface 112 and the protrusion sidewall 114 can form an obtuse angle or an acute angle. The bonding layer 106 can continuously extend generally conformal to the profile of the bottom surface 112 and the protrusion sidewalls 114 inside each of the depressions 110. Moreover, the bonding layer 106 can be exposed between any two adjacent ones of the protrusions 108, and a height from the bottom surface 112 to a top of the two adjacent protrusions 108 differs from a height of the bottom portion of the bonding layer 106 that covers the bottom surface 112 inside the depression 110. The depressions 110 between the abrasive particles 104 may form relatively greater gaps that can assist in the removal of materials and/or polishing slurries. Moreover, the extension of the bonding layer 106 into the depressions 110 can provide a greater contact area to promote adhesion of the bonding layer 106.

The bonding layer 106 may include any suitable brazing materials, which may exemplarily include a mixture of a metal powder (e.g., made of nickel-chromium alloy) and an organic binder that is rolled and then processed to form a foil. Other suitable materials for the bonding layer 106 may include, without limitation, metal powders, polymer binders, metal plating layers, and like agents adapted to securely attach the abrasive particles 104 to the substrate 102. According to an embodiment, the bonding layer 106 can be about 35 μm to about 200 μm in thickness.

Each of the abrasive particles 104 arranged on top of the protrusions 108 protrude outside the bonding layer 106, and can have a portion buried in the bonding layer 106. According to an embodiment, the buried portion of the abrasive particle 104 inside the bonding layer 106 can have a thickness equal to or greater than about half of an average particle size or diameter of the abrasive particles 104, which can provide stable attachment of the abrasive particles 104. The abrasive particles 104 are made of high-hardness materials, which can include, without limitation, diamonds, cubic boron nitride, aluminum oxide, silicon carbide, etc.

Abrasive particles can typically have a particle size and a corresponding size variation range. Usually, the greater particle size, the greater size variation range. According to an embodiment, the particle size of the abrasive particles 104 may range from about 70 μm to about 400 μm, for example: all of the abrasive particles 104 arranged on the substrate 102 can have a particle size of about 70 μm, all of the abrasive particles 104 arranged on the substrate 102 can have a particle size of about 100 μm, all of the abrasive particles 104 arranged on the substrate 102 can have a particle size of about 170 μm, all of the abrasive particles 104 arranged on the substrate 102 can have a particle size of about 200 μm, or all of the abrasive particles 104 arranged on the substrate 102 can have a particle size of about 400 μm.

According to testing measures, when the selected abrasive particles have a particle size of about 100 μm, the height difference induced by the corresponding size variation range is about 6 μm; when the selected abrasive particles have a particle size of about 170 μm, the height difference induced by the corresponding size variation range is about 8 μm; and when the selected abrasive particles have a particle size of about 200 μm, the height difference induced by the corresponding size variation range is about 10 μm. Accordingly, using abrasive particles 104 of relatively smaller particle sizes can help to reduce the height difference among the abrasive particles 104 arranged on the substrate 102, and allows arranging a higher quantity of the abrasive particles 104.

Referring to FIG. 1, each protrusion 108 has a protrusion height H from the bottom surface 112 to a top of the protrusion 108, and has a bottom width W adjacent to the bottom surface 112. Moreover, any two adjacent ones of the protrusions 108 are separated by a protrusion spacing P, which can correspond to a distance within a depression 110 between the two protrusion sidewalls 114 of the two adjacent protrusions 108. The above parameters H, W and P can be set according to the size, quantity, and distribution pattern of the abrasive particles 104.

According to an embodiment, the protrusion height H can be equal to about 0.5 to about 1.5 times the particle size of the abrasive particles 104, and the bottom width W can be equal to about 2 to about 3 times the particle size of the abrasive particles 104. Assuming that the particle size of the abrasive particles 104 is between about 70 μm and about 400 μm, the protrusion height H can be between about 35 μm and about 600 μm, and the bottom width W can be between about 140 μm and about 1200 μm. For example, when the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 70 μm, the protrusion height H can be between about 35 μm and about 105 μm, and the bottom width W can be between about 140 μm and about 210 μm. When the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 100 μm, the protrusion height H can be between about 50 μm and about 150 μm, and the bottom width W can be between about 200 μm and about 300 μm. When the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 170 μm, the protrusion height H can be between about 85 μm and about 255 μm, and the bottom width W can be between about 340 μm and about 510 μm. When the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 200 μm, the protrusion height H can be between about 100 μm and about 300 μm, and the bottom width W can be between about 400 μm and about 600 μm. When the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 400 μm, the protrusion height H can be between about 200 μm and about 600 μm, and the bottom width W can be between about 800 μm and about 1200 μm.

The protrusion spacing P can correspond to a distance within a depression 110 between the two protrusion sidewalls 114 of two adjacent protrusions 108 that are located within a same pattern. Supposing that all of the abrasive particles 104 have a predetermined particle size, the quantity of the abrasive particles 104 arranged within the pattern can be increased when the protrusion spacing P is reduced, and the quantity of the abrasive particles 104 arranged within the pattern can be reduced when the protrusion spacing P is increased. According to an embodiment, the protrusion spacing P can be about 1.5 to about 20 times the particle size of the abrasive particles 104. Supposing that the particle size of the abrasive particles 104 is between about 70 μm and about 400 μm, the protrusion spacing P can be between about 105 μm and about 8000 μm. For example, when the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 70 μm, the protrusion spacing P can be between about 105 μm and about 1400 μm; when the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 100 μm, the protrusion spacing P can be between about 150 μm and about 2000 μm; when the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 170 μm, the protrusion spacing P can be between about 255 μm and about 3400 μm; when the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 200 μm, the protrusion spacing P can be between about 300 μm and about 4000 μm; and when the abrasive particles 104 arranged on the substrate 102 all have a particle size of about 400 μm, the protrusion spacing P can be between about 600 μm and about 8000 μm.

The elevated position of the abrasive particles 104 obtained with the structure of the protrusions 108 on the substrate 102 can provide multiple benefits, including: 1) the conditioning step would be less likely subjected to contamination by the bonding layer 106; 2) greater gaps are provided between the abrasive particles 104 so that the removal of materials and/or polishing slurries can be facilitated; and 3) problems related to clustering or drifting of the abrasive particles can be improved, and the abrasive particles can be securely attached to prevent undesirable separation.

In addition, the depressions 110 between the abrasive particles 104 can increase a distance from the bonding layer 106 to the abrasive particles 104, which can significantly increase the effective working area of the abrasive conditioner 100, wherein the effective working area can correspond to, e.g., a contact area between the abrasive conditioner 100 and a CMP pad to be conditioned. Since the abrasive particles 104 are attached to protrusions 108 that are directly formed from the substrate 102, the height of the abrasive particles 104 can be more easily controlled and the processing steps can be simplified.

According to an embodiment, the particle size for the abrasive particles 104 used in the abrasive conditioner 100 can be between about 100 μm and about 200 μm, such as a particle size of about 100 μm, a particle size of about 170 μm or a particle size of about 200 μm. By using abrasive particles of suitably selected particle sizes, the height difference among the abrasive particles 104 can be reduced, the cut rate decay can be slowed down, and the service cycle of the abrasive particles can be extended. Accordingly, the manufacture and maintenance cost can be reduced.

Chart 1 below provides experiment data obtained for various tested samples of abrasive conditioners, which include abrasive conditioners that incorporate abrasive particles having a particle size of about 100 μm (Example 3 and 4), and abrasive conditioners that incorporate abrasive particles of relatively smaller and greater particle sizes (Example 1 and 2). Example 3 and Example 4 differ in the arrangement and the quantity of the abrasive particles. The testing data include a pad wear rate (also referred to as “PWR decay” hereinafter) and a cut rate decay (also referred to as “CR decay” hereinafter). The testing data of the PWR decay and the CR decay are obtained through a polishing procedure applied on 150 wafers. More specifically, the testing of the PWR decay and the CR decay includes using a single CMP pad and a single abrasive conditioner in a polishing procedure applied on 150 wafers, wherein the abrasive conditioner is selected from one of Example 1 through 4 and is applied multiple times to condition the CMP pad during the polishing procedure. Then another one of Example 1 through 4 is selected to undergo the same polishing procedure applied on 150 wafers. The testing data of the PWR decay and the CR decay are thereby obtained for each of Example 1 through 4.

The data of Chart 1 show that in comparison to the particle sizes of 75 μm and 400 μm, using abrasive particles of the particle size 100 μm can substantially reduce the PWR decay and the CR decay of the abrasive conditioner. In particular, the PWR decay and the CR decay can be reduced to lower than 30%, i.e., the pad wear rate of the abrasive conditioner can be lower than about 30% after polishing the CMP pad.

In conjunction with FIG. 1, FIG. 2 is a flowchart of method steps for fabricating the abrasive conditioner 100, FIGS. 3A-3G are schematic views illustrating intermediate stages in the fabrication of the abrasive conditioner 100, and FIG. 4 is a schematic view illustrating an example of a positioning plate used in the fabrication of the abrasive conditioner 100.

Referring to FIGS. 2 and 3A, step 202 provides a substrate 102 having two opposite sides 102A and 102B of substantially planar surfaces. The substrate 102 can be of any suitable materials, e.g., stainless steel.

Referring to FIGS. 2 and 3B, step 204 forms the protrusions 108 and the depressions 110 on the side 102A of the substrate 102, wherein adjacent protrusions 108 are separated from each other by at least one depression 110. According to an embodiment, step 204 may include, without limitation, applying dry etching, wet etching or laser cutting on the substrate 102.

Referring to FIGS. 2 and 3C, step 206 forms the bonding layer 106 on the side 102A of the substrate 102 so that the bonding layer 106 entirely covers the protrusions 108 and the bottom surfaces 112 of the depressions 110. According to an embodiment, step 206 may include disposing a foil of a bonding material as the bonding layer 106 on the substrate 102, and then applying a pressing and rolling process so that the bonding layer 106 uniformly adheres to the top and the protrusion sidewalls 114 of the protrusions 108 as well as the bottom surfaces 112 of the depressions 110.

Referring to FIGS. 2, 3D and 3E, step 208 positions the abrasive particles 104 on the protrusions 108 of the substrate 102 on a one-to-one correspondence basis. According to an embodiment, step 208 may include using a positioning plate 300 as shown in FIG. 4, wherein the positioning plate 300 has a surface provided with a plurality of concavities 302. As shown in FIG. 3D, the abrasive particles 104 can be respectively placed and held in the concavities 302. The shape and size of each concavity 302 can be configured to match with the size of one abrasive particle 104, so that each concavity 302 accommodates only one single abrasive particle 104. Then the substrate 102 with the bonding layer 106 thereon is positioned so that the side 102A of the substrate 102 faces the abrasive particles 104 on the positioning plate 300 and the protrusions 108 on the side 102A are correspondingly aligned with the abrasive particles 104.

Referring to FIGS. 2 and 3F, step 210 then attaches the abrasive particles 108 to the protrusions 108 via the bonding layer 106. According to an embodiment, step 210 may include applying a pressing force on the positioning plate 300 and/or the substrate 102 so that the abrasive particles 108 partially penetrate into the bonding layer 106, and then applying a heating process for a predetermined time. The heating process may be exemplarily conducted in a high-temperature vacuum brazing furnace in which the bonding layer 106 is melted for brazing the abrasive particles 104 to the protrusions 108 of the substrate 102. Once it cools down and hardens, the bonding layer 106 can securely attach the abrasive particles 104 to the top of the protrusions 108. Then the positioning plate 300 is removed from the substrate 102 having the abrasive particles 104 attached thereon, which forms the abrasive conditioner.

FIGS. 3D and 3F illustrate an embodiment in which the positioning plate 300 provided with the concavities 302 is used to perform steps 208 and 210. FIG. 3G is a schematic view illustrating an alternative embodiment in which a positioning plate 320 provided with a plurality of holes 322 is used to perform steps 208 and 210. Referring to FIGS. 2 and 3G, step 208 can include placing the positioning plate 320 adjacent to the bonding layer 106 on the substrate 102 so that the holes 322 respectively correspond to the positions of the protrusions 108 of the substrate 102, and disposing the abrasive particles 104 in the holes 322 so that the abrasive particles 104 are positioned on a one-to-one correspondence basis with respect to the protrusions 108. The abrasive particles 104 placed in the holes 322 of the positioning plate 320 can contact with the bonding layer 106 on the substrate 102.

Step 210 can include applying a pressure through a board 330 positioned over the positioning plate 320 so that the abrasive particles 104 are pressed downward by the board 330 and partially penetrate the bonding layer 106, and then applying a heating process for a predetermined time. The abrasive particles 104 can be thereby securely attached to the top of the protrusions 108.

Realization of the structures and methods have been described only in the context of particular embodiments. These embodiments are meant to be illustrative and not limiting. An embodiment disclosing a numerical range having a higher limit and a lower limit may include smaller ranges between the higher limit and the lower limit. Many variations, modifications, additions, and improvements are thus possible. These and other variations, modifications, additions, and improvements may fall within the scope of the claims that follow.