KR20030047905A - Grooved polishing pads and methods of use - Google Patents

Abstract

The grooves are CMP pads by placing the pads on a support surface where the working surface of the pads is spaced apart from the router bit and at least one protruding stop member adjacent the router bit and the outer end of the bit extends beyond the stop member. It is formed within. As the bit rotates, the relative axial movement between the bit and the pad causes the outer end of the bit to cut the initial recess in the pad. The relative transverse motion between the rotating bit and the pad then forms a groove extending transversely from the recess and having a depth substantially equal to the depth of the recess. Different transverse motions between the bit and the pad are used to create various groove patterns, depths that are precisely controlled by the stop member. Grooves may be formed in the polishing surface and / or on the opposite back side of the pad and a passage may be provided to connect the back grooves to the polishing surface or the front groove. Grooves in the polishing surface may be provided with an outlet through which the polishing slurry can flow while the polishing surface is in contact with the workpiece surface.

Description

GROOVED POLISHING PADS AND METHODS OF USE

Chemical mechanical polishing has been used for many years as a technique for polishing optical lenses and semiconductor wafers. Recently, chemical mechanical polishing has been developed as a means to planarize the intermetallic dielectric layer of silicon dioxide and to remove a portion of the conductive layer inside the integrated circuit device when they are fabricated on various substrates. For example, the silicon dioxide layer can formally cover the metal interconnect, so that the top surface of the silicon dioxide layer features a series of uneven steps corresponding to the bottom metal interconnect in height and width. Will be done.

Step height variations in the top surface of the intermetallic dielectric layer have some undesirable properties. Such uneven dielectric surfaces may interfere with the photo resolution of subsequent photolithographic processing steps, resulting in very difficult printing of high resolution lines. Another problem is the step that occurs when applying the second metal layer over the intermetal dielectric layer. If the step height is relatively large, the application of the metal may be insufficient and thus an open circuit may be formed over the second metal layer.

To solve these problems, various techniques have been developed to planarize the top surface of the intermetal dielectric layer. One such solution is to employ abrasive polishing, which eliminates steps that protrude along the top surface of the dielectric layer. According to this method, a silicon substrate wafer is mounted face down under the carrier and is pressed between the carrier and the table or platen covered with polishing pads which are continuously coated with abrasive in the form of slurry.

In addition, means are provided for placing the abrasive slurry on the top surface of the pad and forcing the substrate wafer against the polishing pad, resulting in planarization of the contacted surfaces of the wafer by movement relative to each other in the presence of the slurry of the platen and the substrate wafer. . Both the wafer and the table can be rotated with respect to each other to eliminate protruding steps. This abrasive polishing process continues until the top surface of the dielectric layer is substantially flat.

The polishing pad may be made of a uniform material, such as polyurethane or nonwoven fibers impregnated with a resin binder, or may be formed from a multilayer stack having non-uniform physical properties over the thickness of the pad. Polyurethane polishing pads are generally formed by placing a reactive composition into a mold, curing the composition to form a pad material, and then die cutting the pad material to the desired size and shape. The reactants forming the polyurethane or plastic binder may also be reacted in a cylindrical vessel. After molding, the cylindrically shaped pieces of pad material are cut into slices and used as polishing pads. Typical laminated pads may have multiple layers, such as sponges and elastic microporous polyurethane layers, laminated on a rigid but elastic support layer comprising porous polyester felt with a polyurethane binder. The polishing pad may generally have a thickness in the range of 50 to 80 mils, preferably about 55 mils, and a diameter in the range of 10 to 36 inches, preferably 22.5 inches.

The polishing pad may also have macrotextured workpiece surfaces produced by surface processing using various techniques, many of which exhibit undesirable surface characteristics that are expensive and vary greatly in depth. Surface features include waves, holes, creases, ridges, slits, depressions, protrusions, gaps, and grooves. Other factors influencing the surface texture of the macro pad of the polishing pad are the size, shape and distribution or spacing of surface features. The polishing pad may also have a microtextured surface caused by the bulk texture in the microrange of the pad resulting from factors inherent in the manufacturing process. Since polishing usually does not occur over the entire pad surface, the microtexture of the pad and the macrotexture formed by the surface treatment may be formed only in the portion of the pad where polishing occurs.

During the polishing process, the material removed from the wafer surface and the abrasive in the slurry, such as silica, are compressed and embedded in recesses, holes and other free spaces in the micro-range bulk texture of the polishing pad and the macro-range bulk texture near the pad surface. There is a tendency. One factor for achieving and maintaining high and stable polishing rates is to provide and maintain the pad surface in clean conditions. Another factor is to reduce or prevent the hydroplaning effect caused by the formation of a water film between the pad and the contact surface of the wafer. In addition, increasing the flexibility of the pad in a controlled manner has been determined to increase the uniformity of polishing, such as the uniformity of the polished wafer surface.

Accordingly, there are three problems in consistently achieving uniform and high quality polishing of the wafer surface by conventional pads. The first of these problems is the accumulation of abrasive particles and debris that accumulate between pads and wafers, causing uneven polishing and damage to both pads and wafers. Secondly, uneven polishing due to hydroplaning between the wafer and the pad during conventional processing results in a relatively high loss of yield resulting from the resulting wafer damage. Third, uneven polishing and wafer damage also result from excessively rigid pads produced by conventional manufacturing techniques. Therefore, a need exists for a method and apparatus for providing a polishing pad capable of consistently producing high quality wafers with uniformly polished surfaces.

Summary of the Invention

Therefore, the present invention provides a grooved polishing pad capable of consistently forming a uniformly polished surface on a high quality wafer. The apparatus for manufacturing a pad includes a platen having positioning posts for holding the polishing pad in the engaged position by a router for processing grooves in the working surface of the pad. In order to precisely adjust the depth of the groove when the groove is formed in the pad, the spacing mechanism provides a constant and accurate separation between the pad's working surface and the chuck that holds and rotates the router. A device of this type is disclosed in US patent application Ser. No. 09 / 605,869, filed June 29, 2000, entitled “Polishing Pad Grooving Method and Apparatus”. The entire contents of the application are incorporated herein by reference.

The pad is disposed on the support surface of the platen, the working surface of which is spaced apart from the router bit. The router chuck and the drive motor are supported opposite the pads by the frame. The spacing mechanism comprises at least one, preferably two or more stop members, which are mounted on a frame adjacent the opening through which the router bit passes. The outer end of the bit projects past the stop member, which is a pin screwed into the frame, preferably to be axially adjustable. A vacuum system is provided that first draws the pad against the outer end of the router bit and then applies a vacuum to the working surface of the pad to pull against the stop member.

When the router bit is rotated by the motor while vacuum is applied to the pad, the outer end of the bit cuts the initial recess (hole) in the pad to a predetermined depth below the pad's working surface. The depth of the recess is precisely limited by the stop member that comes into contact with the working surface of the pad when the rotating bit cuts the pad to form the initial recess. After the formation of the initial recess, the transverse mechanism creates a relative transverse motion between the rotating router bit and the pad while the vacuum maintains contact between the pad and the stop member.

This transverse movement causes the rotating bit to extend into the pad and cut a groove having a depth substantially equal to the depth of the initial recess. The lateral motion mechanism may include a top plate and a bottom plate suspended from the overhead beam and arranged to perform relative movement in the X-Y plane. For example, the top plate may be mounted on the overhead beam and may be driven in the X direction (direction along the X axis) by one or more power screws; The router frame suspended from the bottom plate is mounted on the top plate and driven in the Y direction by one or more power screws. As a variant, the platen may likewise be mounted to do this X-Y movement instead of the router frame, or both the platen and the router frame may be mounted to do this movement. The platen may also be rotated by the drive motor to provide additional means for causing lateral motion between the router bit and the pad.

It will be appreciated from the foregoing that the relative motion in the Z direction (direction along the Z axis) between the stop member and the pad may be provided by the vacuum as the vacuum pulls the pad toward the router bit and the stop member. If the polishing pad is flexible because of its large diameter and small thickness, it is not necessary to guide the movement of the pad. Moreover, significant pad motion along the Z axis may instead be avoided by moving the router bit along the Z axis and then using a vacuum to maintain bit depth in the lateral motion between the bit and the pad.

However, the movement of the pad along the Z axis may be guided by a plurality of, preferably two or more posts projecting outward from the platen along an axis parallel to the axis of rotation of the router bit. These guide posts may also hold the pad against rotation when the platen is rotated by the platen drive motor, which is particularly useful for grooved discs other than polishing pads, such as rigid disks of greater thickness and smaller diameter. Do. As already pointed out, the up and down transverse plates provide the transverse motion of the router bits relative to the pad along the X and Y axes. Therefore, the router bit may be moved relative to the pad according to the rectangular coordinates of X, Y and Z, or the cylindrical coordinates of R, θ and Z.

The grooves cut in the polishing surface or the opposite back side of the pad by the relative lateral motion described above are left or right helical patterns, zigzag patterns each following a radius around the pad at different radii, concentric grooves, crosswise grooves, The spiral groove or zigzag can have inner and outer circular grooves in the region therebetween, inner and outer sector patterns having different spiral or zigzag patterns at different radii, or a combination of these and other patterns, so that the It will provide a polishing surface section having a uniform groove density or a different groove density. In addition, the patterned portion of the polishing surface of the pad may be limited to the area where the polishing of the wafer should occur.

The purpose of cutting the groove pattern on the back or back of the pad is to increase its flexibility. Another object is to provide a back groove that is connected to the front or polishing surface groove by a drilled or milled passage to form an outlet flow path for discharging the abrasive slurry from the polishing surface groove.

The depth of the front and / or rear grooves is also different for different patterns by axially adjusting the protruding depth of the stop member, which is preferably a symmetrical pin, or by adjusting the protruding length of the router bit relative to the axially fixed stop member. You can also change it. To provide pads with increased flexibility, grooves may be drilled to a depth of up to 80% of the pad thickness in the pads. Pad flexibility may also be adjusted by the total number of grooves provided, such as, for example, 8, 32, or 64 spiral patterns.

The grooves in the working surface or polishing surface of the CMP pad, whether alone or in combination with the back grooves, significantly reduce the hydroplaning effect during wafer polishing, and as a result very high polishing rates can be achieved. . A pattern with a large number of spiral grooves can effectively reduce the hydroplaning effect than a pattern with a small number of spiral grooves because more grooves pass through the wafer surface to be polished at the same time. The increased pad flexibility due to the selected groove pattern may also help to improve the polishing uniformity of the wafer surface. The groove density of the zigzag groove pattern may also be altered to adjust the polishing rate distribution inside other segments of the polishing pad surface, which may also improve the polishing uniformity within the wafer surface.

To further optimize the polishing process, the body of the pad may be made from a solid or porous organic material, such as polyurethane, which is strongly crosslinked to be very durable, or fibrous organic such as at least one of rayon and polyester fibers. It may be made from a material and it may also contain binders as well as solid or porous polyurethanes. The pad body may be manufactured as a single layer, or may be prepared by US Patent Application, filed June 23, 2000, entitled "Multilayered Polishing Pad, Method for Fabricating, and Uses Thereof". Multi-layers as disclosed in 09 / 599,514, the entire contents of which are hereby incorporated by reference.

The polishing pad provided by the present invention can be used to fabricate wafers of dielectric materials such as silicon dioxide, diamond-like carbon (DLC), spin-on-glass (SOG), polysilicon, and silicon nitride. Ideal for grinding The polishing pad may also be used to polish other wafers or disks such as copper, aluminum, tungsten and alloys of these and other metals.

The features, effects and advantages of the invention will be better understood from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings.

TECHNICAL FIELD The present invention relates to the field of manufacturing polishing pads, and more particularly, to providing a macrotextured surface on a polishing pad used for chemical-mechanical planarization (CMP) of semiconductor substrates. .

1 is a partial cross-sectional front view of the present invention, in which the main components are schematically illustrated,

FIG. 2 is a plan sectional view taken along line 2-2 of FIG. 1;

3 is a partially enlarged cross-sectional view of a portion of FIG. 1;

4 is an illustration of a polishing pad made in accordance with the present invention, wherein the groove pattern comprises eight left helix grooves starting near the center of the pad and ending near the outer edge of the pad's working surface;

5 is an illustration of a polishing pad made in accordance with the present invention wherein the groove pattern comprises 32 left helix grooves starting near the center of the pad and ending near the outer edge of the pad's working surface;

6 is an illustration of a polishing pad made in accordance with the present invention wherein the groove pattern comprises 64 right helix grooves starting near the center of the pad and ending near the outer edge of the pad's working surface;

7 shows a plurality of radially spaced zigzag grooves each having a groove pattern symmetrically formed along a substantially constant radius around the pad surface, wherein the groove densities of the innermost groove and the outermost groove are different from each other and with the intermediate groove. Another figure showing a polishing pad made according to the invention,

8 schematically shows a back groove connected to a portion where a groove of the polishing surface of the pad is not formed by a passage;

9 schematically illustrates a back groove connected by a passage to a front groove of the polishing surface of the pad;

10 is a view schematically showing the cross grooves on the rear surface of the polishing pad;

FIG. 11 shows schematically a different cross section of a groove in a polishing surface of a pad made of a single layer of uniform material, FIG.

12 schematically shows grooves of different depths in the polishing surface of a composite pad made from an upper pad of one material and a lower pad of another material, FIG.

13 schematically shows different cross-sectional shapes for grooves in the polishing surface of a composite pad made from an upper pad of one material and a lower pad of another material, FIG.

14 illustrates a method of polishing a workpiece with a grooving pad made in accordance with the present invention.

The polishing pad groove forming method and apparatus of the present invention are shown in FIGS. The polishing apparatus has a platen 10 in which the polishing pad 12 is supported and held in a radial position fixed by a plurality of retaining posts 14. Each retaining post 14 is in the pad body such that the pad can be guided for axial movement away from the surface of the platen, as shown by arrow Z and the air gap 17 shown in FIG. 3. Or fit into a channel or recess 16 (FIG. 4) formed in the outer periphery of the pad and extending parallel to the center axis C of the pad. However, in order to allow movement of the axially adjustable router and / or flexible pads of sufficiently large diameter and small thickness to allow the grooves to be formed, the retaining posts 14 may be replaced with clamps without guiding functions. have.

The router bit 24, which is disposed opposite the working surface 22 of the pad 12, remains replaceable in the chuck 26 and is rotationally driven by the router motor 28. The router motor 28 is supported by a frame 30 surrounded by a casing 32, so that an annular space 34 is provided between the concentric wall of the frame and the casing, all of which are preferably cylindrical. The vacuum represented by arrow V is provided to annular space 34 by blower 36 attached to casing 32 by flexible hose 38. The platen 10 is supported to rotate in either direction by a drive shaft 18 driven by the platen motor 20. Thus, the router bit 24 may be rotated in either direction as indicated by arrow R1 and the platen 10 may also be rotated in either direction as indicated by arrow R2. 20 and 28 may be of a type capable of reverse rotation.

A plurality of stop pins 33 protruding parallel to the router bits at a distance less than the protruding distance of the router bits themselves are mounted on the bottom wall 31 of the frame 30 adjacent the passage for the router bits 24. . The difference between the protruding distance of the stop pin 33 and the protruding distance of the router bit defines the length of the end 37 of the bit, which corresponds to the depth of the desired groove cut by this end, With respect to the action will be described more fully below. The protruding length of the bit end 37 may be changed by rotating a pair of pinions 27 that engage a corresponding pair of racks 29 mounted on the router motor 28 shown in FIG. As another means for changing the protruding length of the bit end 37, the stop pin 33 is preferably screwed to the bottom wall 31 for axial adjustment. The stop pin 33 may have a hexagonal head portion 39 that allows rotational engagement by a corresponding tool.

The router is mounted to the overhead support member 40 by the transverse mechanism 42 to provide transverse movement of the router bit in the XY plane perpendicular to the axis of rotation of the router bit and the corresponding central axis C of the polishing pad. do. The lateral motion mechanism 42 may be any structure that provides accurate lateral motion of the router 24 in the XY plane, and the router support member 40 is attached to or part of an arm of the robot that is precisely controlled. As will be appreciated, it may not be necessary if the router support member 40 itself is movable in the XY plane.

For example, the exercise device shown in FIGS. 1 and 2 includes a lower plate 44 suspended from the upper plate 46 by two pairs of threaded eyelets 48, 50. Top plate 46 is suspended from two pairs of brackets 52, 53 by two other pairs of threaded eyelets 54, 56. A corresponding drive screw 58, which is rotationally driven by a reversely rotatable Y-axis motor 59, is screwed into each pair of eyelets 48, 50 to lower plate 44 along the Y-axis as shown by arrow Y. To provide reciprocating motion. Similarly, corresponding drive screws 60, which are rotated by the reversible X-axis electric motor 62, are respectively screwed into the pair of eyelets 54, 56 to move the X axis as shown by arrow X in FIG. Thus providing a reciprocating motion of the top plate 46.

An operation of the pad groove forming apparatus will be described with reference to FIGS. 1 to 3. The blower 36 is operated to generate a vacuum V in the annular passage 34. This vacuum generates an upward force in the direction of the arrow Z and / or holds the pad 12 against the axially adjustable stop pin 33 used to adjust the groove depth. The router bit 24 will extend past the end of the stop pin 33 by the length of the bit end 37 to cut the pad 12 as the bit is rotated by the router motor 28. The router is preferably operated after the vacuum is applied and adjusted vertically. Any upward movement of the pad in response to the vacuum V is guided by engagement between the retaining post 14 and the corresponding recess or channel 16, which may be in the body or outer periphery of the pad 12. The end 37 of the bit 24 protrudes past the tip of the stop pin 33 by a length of up to 80% of the pad thickness, such that the end of the bit may penetrate up to 80% of the pad thickness. Since the protruding length of the bit end 37 can be changed, the groove depth can be changed by rotating the pinion 27, rotating the stop pin 33, or combining these adjustments.

After the router bit 24 has sufficiently penetrated the pad, the bit is indicated by the arrows X, Y of FIG. 2, as determined by the contact between the tip of the stop pin 33 and the working surface 22 of the pad 12. Is moved radially relative to the pad in the XY plane as shown by. This XY movement may be achieved by simply moving the lower plate 44 and the upper plate 46 relative to each other by the operation of the motors 59 and 62, or such lateral movement may form a groove in which the router bit 24 spirals. May be combined with the rotation of the platen 10 about the central axis C while being moved radially.

The transverse movement of the lower plate 44 along the Y axis is caused by the rotation of the screws 58 which screw into the respective eyelets 48 and 50. The transverse movement of the upper plate 46 along the X axis is generated by the rotation of the screw 60 which is screwed into the eyelets 54 and 56. Rotation of the platen 10 is provided by rotation of the shaft 18 by the platen motor 20. Thus, the router bit 24 may be moved transversely relative to the polishing pad 12 in the X-Y plane of the rectangular coordinates X, Y or in the cylindrical coordinates R, θ. Further, the router bit may be moved up and down along the Z axis in both rectangular and cylindrical coordinates by rotation of the pinion 27 by the power of the pinion 27 by a conventional mechanism (not shown) or rotation of the attraction force.

The upward movement along the Z axis in both rectangular and cylindrical coordinates also causes the pad 12 to the tip of the stop pin 33 from the surface 22 of the platen 10 in response to the creation of a vacuum in the annular passage 34. Is provided by the When the vacuum application is stopped by stopping the blower 36, the pad is moved downward along the Z axis. Therefore, this movement of the pad 12 along the Z axis is caused by the pressure difference across the pad thickness generated by the vacuum (V). As a variant, the pressure difference causing this pad movement can be generated by blowing pressurized air down the pad through a series of air holes or nozzles (not shown).

Thus, the spiral groove formed by the present invention preferably starts at the center of the pad and ends near the outer edge of the pad (but not necessarily). The direction of the spiral pattern may be left as shown by the eight spiral grooves of FIG. 4 and 32 spiral grooves of FIG. 5, or may be right as shown by the 64 spiral grooves of FIG. 6. In Figs. 4 to 7, since the opposing edges of the actual grooves are so close that they cannot be represented as double lines, the grooves are represented by thick black solid lines for convenience of explanation. Carefully, since one continuous groove forms the pattern 70 of FIG. 4, the pattern 72 of FIG. 5, and the pattern 74 of FIG. 6, once the router bit is inserted, it is withdrawn until the pattern is completed and Should not be.

Spiral grooves on the pad surface will reduce the hydroplaning effect during polishing, and as a result very high polishing rates can be achieved. The greater the number of spiral grooves in the same surface area, the more effectively the hydroplaning effect can be reduced than the smaller number of spiral grooves, because at the same time more grooves are pressed against the pad surface during polishing of the pad surface. Because it passes across the surface. From this, it can be seen that the removal rate of the slurry abrasive used with the pad for polishing the wafer increases as the number of spiral grooves per unit area of the pad working surface increases. In addition, a large number of grooves can make the pad more flexible, which can help to improve the uniformity of wafer polishing.

FIG. 7 shows a zigzag groove pattern consisting of an outer groove 76, an inner groove 78 and three intermediate grooves 80, 81, 82. These grooves are individually formed by stopping the blower to remove the bit from the pad, repositioning the bit transversely relative to the pad, and then restarting the blower to insert the bit into the pad. However, the grooves 76, 78, 80, 81, 82 can be connected to each other, in which case the pattern is formed into one continuous groove so that the bit does not have to be drawn out from the pad in the middle. The groove pattern of FIG. 7 shows that the groove density may vary over different portions of the pad surface. This change in groove density can be used to adjust the polishing rate distribution depending on where the wafer is pressed against the polishing pad surface, which can also help to improve wafer polishing uniformity. In order to form the patterns shown in Figs. 4 to 7 and other complicated groove patterns, the positioning motors 20, 59, 62 are preferably controlled by a microprocessor (not shown).

Polishing uniformity is generally determined by varying parameters such as the polishing rate generated by varying the rotational speed of the wafer, the rotational speed of the polishing pad or the speed of the polishing belt, or the pressure from behind the wafer or from below the pad or belt. Or by changing other tool parameters. Other variables that affect polishing uniformity include the properties of consumables (eg, pads, bottom pads, and slurries).

When using slurries with pads or belts, the size and type of abrasive particles (eg, different phases and structures of alumina, cerium oxide or silica particles) may be varied to obtain different polishing rates and planarization rates. Chemical additives may be added to the slurry to keep the abrasive particles suspended, to increase the polishing rate, to change the relative polishing rate of different materials, and to protect the polished workpiece from scratches and corrosion. By mixing chemicals and abrasives in the polishing slurry, polishing uniformity can be affected by speeding up polishing at the edge of the wafer and slowing down at the center or vice versa. Often, key parameters such as the choice between polishing rates of different materials play a top role in slurry design and may also fix polishing uniformity. In addition, it is nearly impossible to develop and implement a slightly different slurry composition that is most suitable for the different sets of abrasive tools currently used in the art.

For pads and lower pads, the hardness and porosity of the pads are the most common control properties for polishing uniformity. In addition, there are perforations, grooves or depressions that help to ensure a uniform distribution of slurry on the wafer surface when trying to obtain a uniform removal rate of polishing everywhere on the wafer during polishing. In the case of pad groove formation, all patterns currently used are uniform patterns of uniformly spaced straight, concentric or lattice patterns.

The present invention changes groove density across the pad to improve polishing uniformity. The effect on the polishing uniformity of changing the density of the groove pattern will be described below. Increasing the groove density in the polishing surface of the polishing pad in one area as compared to the other area makes it possible to distribute more slurry in areas of higher groove density than areas of lower groove density. Therefore, a higher polishing removal rate may be realized in a region having a higher groove density than a region having a lower groove density. This nonuniform groove density on the pad can compensate for the lack of polishing uniformity due to the lack of polishing tools and slurries, and can also compensate for prepolishing films having nonuniform thicknesses or previous nonuniform polishing rates. . For example, a wafer whose initial film thickness is thick at the edge and thin at the center has a pad similar to the pad of FIG. 7, with the highest groove density at the edge and center of the pad (eg, at the inner and outer edges of the wafer track during polishing). It may be polished to a uniform thickness across the wafer by using.

As a variant, a pad with a higher groove density at the center than the edge will have a faster removal rate at the center and thus a median profile will compensate for a thicker film. In addition, this concept of varying the groove density across the pad may be applied to different groove patterns and shapes than linear abrasive belts or pads. Another possible groove pattern is similar to that shown in FIGS. 4 to 6, but the spacing between adjacent spirals is finely spaced in one continuous spiral groove, or in some areas, that varies in different areas of the pad to achieve different groove densities. And concentric circles (or straight lines in the case of belt-type polishing pads) which are thickly spaced apart from other areas of the pads, but are not limited thereto.

Changing the groove pattern density may also affect the properties of the polishing pad. As shown in FIGS. 8 and 9, respectively, the grooves 84 may be added alone to the back of the pad or in combination with the grooves 86 on the front side. As shown in FIG. 10, the back only grooves 84, 85 may be made to increase the flexibility of the pad, for example when no front groove is desired. Grooves on the back of the pad may also provide one or more holes 88 (FIG. 8) through the pad as a means to alleviate wafer suction or to pass air, gas, or liquid or a combination thereof from the back of the pad to the front. By using it, it can communicate with the front surface of the pad. In addition, a hole or opening from the back to the front groove may be used as a probe receptacle capable of detecting the end or completion of the polishing process, or a minimum groove depth indicating excessive wear of the pad. Such openings or other openings may also be used without back grooves and may instead be aligned with the exit holes or passages of the platen supporting the pads. The grooves on the back of the pad may be in communication with the grooves on the polishing side through one or more openings 89 to mitigate wafer suction, as shown in FIG. 9 where the upper grooves are closed and terminated. This is an important consideration because wafer suction may interfere with the removal of the wafer from the polishing pad when the CMP step is complete. Timely removal of the wafer from the polishing pad can be performed by blowing air or liquid through the communication passage from the back surface.

In addition, as shown in FIGS. 11 and 13, the bottoms of the front and back grooves are instead of rectangular shape S1 to make it more difficult for abrasive debris to build up inside the grooves and / or to facilitate removal of debris from the grooves. It may be formed in a semi-circular shape (S2) or rounded corners (S3). In order to optimize the flexibility of the pad with the composite 90, the depth of the groove is bonded or otherwise fixed to the top surface of the lower pad 94 as shown by the respective grooves G1, G2, G3 of FIG. 12. It may be less than or greater than the thickness of the upper pad 92. In FIG. 13, lower pad 94 or an interlayer between upper pad 92 and lower pad 94 is constructed with a color different from that of upper pad 92 to allow for acceptable pad wear for polishing service of the pad. It is also contemplated to provide a means for determining the minimum degree of. As a variant, any type of bottom color indicator on or near the bottom of any groove may be provided for this purpose. To optimize polishing uniformity and minimize hydroplaning effects, the grooves may be continuous (open termination) or divided into one or more closed termination continuous segments.

The above description relates to a method for optimizing the performance of a CMP polishing pad. When such an optimum pad is combined with a selected slurry of suitable abrasive particle size, pH, and the like, a more advanced CMP polishing process of metal and dielectric films can be realized. To further optimize the polishing process, the body of the pad is strongly crosslinked so that it can be made from a solid or porous organic material, such as a durable polyurethane, or from a fibrous organic material, such as at least one of rayon and polyester fibers. The material may also contain binders as well as solid or porous polyurethanes.

FIG. 14 illustrates polishing the wafer 95 with a slurry S and a polishing pad 96 having two spiral grooves 97 and 98 attached to the platen 100. In FIG. 14, a holder 102 is disposed over the polishing pad 96 to support the wafer 95 and to press the wafer against the polishing surface 99 of the polishing pad 96. During polishing, the holder 102 may be rotated by the drive shaft 104 and the platen 100 may be rotated by the drive shaft 106. Holder 102 and platen 100 may rotate clockwise or counterclockwise as indicated by arrows R1 and R2, holder 102 being in the same or opposite direction as platen 100. You can also rotate. Preferably, the holder 102 and the platen 100 are both rotated counterclockwise, for example along the groove shown in FIG. 14, in the same direction as the direction of the spiral groove from its inner end to its outer end. As also shown in FIG. 14, the grooves 97, 98 have outlets (open ends) 114, 116, the pads 96 have holes 118, 120 at the inner groove ends, and the platen ( 100 has fluid passageways 122 and 124 to provide a flow path for discharging the slurry from the groove.

While the holder and platen are rotated, the holder 102 may swing back and forth across the polishing pad as indicated by arrow O1. A slurry of abrasive particles is provided on abrasive surface 99 as spray S, which is supplied by hose 110 and discharged by nozzle 108. The nozzle 108 is mounted on the rocking member 112 so that the spray S may also rock back and forth across the polishing pad as indicated by arrow O2.

Typically, CMP involves the development of separate polishing slurries with different abrasives such as W, SiO ₂ , Al or Cu and separate polishing pads for each type of wafer or other workpiece, respectively. One of the main drawbacks to this approach is that CMP depends on the chemical reaction between the slurry and the workpiece and the mechanical interaction between the pad, slurry and the workpiece. This improves the slurry flow entering and exiting the polishing surface of the pad, and undesirable mechanical effects such as hydroplaning, in which the pad and workpiece to be polished slide through each other with little friction, resulting in no effective polishing rate. To prevent the grooved polishing pad of the present invention was developed.

The present invention also combines special slurry and grooved polishing pads to improve the polishing rate of various materials and to improve polishing uniformity. By selecting a particular slurry / pad combination, the polishing process can be effectively enhanced by avoiding areas of hydroplaning to improve mechanical friction as well as improving slurry flow in and out of the material to be polished. One example is using pads based on grooved polyurethane and slurry based on silica for oxide wafer polishing. Another example is a grooved pad made from binder and / or polyurethane impregnated fibers and used with a slurry based on alumina for polishing Cu and W metals. It has been found that pad conditioning and groove formation are possible by using polyurethane coated fibers to relieve tears of composite pads made from natural or synthetic soft fibers. Thus, by combining the grooved pad of the present invention with the optimum polishing chemistry for a particular workpiece, the advantages of substantial polishing rate and polishing uniformity are obtained.

Those skilled in the art will appreciate that various modifications and alterations to the elements and steps of the present invention are possible without affecting their function upon encountering the present disclosure. For example, as described above as an example, the pressure difference is applied to maintain the pad with respect to the stop member, the nature and shape of the pad support structure and the router support structure, and the stop member for adjusting the depth of the groove. The structure for providing relative lateral motion between the device and router bits and the pad may vary widely depending on current and future techniques for providing the functionality of these systems and components. For example, the platen may have an array of air passages and outlets for providing a cushion of pressurized air under the pad to provide all or part of the pressure differential for holding the pad against the stop member. In addition to the rotation of the platen and pads, the platen and pads move in the XY plane by mounting the platen drive motor on a lateral motion mechanism similar to the mechanism 42 for mounting the router motor as described above. May be Combinations of front and / or back groove patterns, depths and / or shapes other than those described above, and other types of fluid passages within the pads and / or their support platens may also be desired. Accordingly, while the preferred embodiments have been shown and described in detail above by way of example, further modifications and examples are possible without departing from the scope of the invention as set forth in the claims below.

Claims (22)

In a workpiece polishing pad, A body having a substantially flat polishing surface and at least one elongated groove disposed in the grooved portion of the polishing surface, wherein, when the pad rotates, the grooved portion over the entire workpiece surface in contact with the polishing surface. Lost Workpiece Polishing Pads. The method of claim 1, Used with an abrasive slurry provided on the polishing surface, the spiral groove communicating with at least one fluid outlet such that the slurry is external to the groove through the outlet while the polishing surface is in contact with the surface of the workpiece. Can spill into Workpiece Polishing Pads. The method of claim 1, The groove has a bottom surface extending between opposing side walls Workpiece Polishing Pads. The method of claim 1, A plurality of radially extending grooves or one continuous radially extending groove providing a plurality of groove channels disposed to pass over the workpiece surface during contact with the rotating abrasive surface, The number of channels is a function of distance from the center portion of the pad Workpiece Polishing Pads. The method of claim 1, The polishing surface of the pad has at least one spiral groove Workpiece Polishing Pads. The method of claim 5, The polishing surface of the pad has at least eight spiral grooves Workpiece Polishing Pads. The method of claim 5, The polishing surface of the pad has at least 32 spiral grooves Workpiece Polishing Pads. The method of claim 5, The polishing surface of the pad has at least 64 spiral grooves Workpiece Polishing Pads. The method of claim 1, The polishing surface of the pad has at least one zigzag groove extending on either side of a substantially constant radius to provide a zigzag groove pattern in the annular segment of the polishing surface. Workpiece Polishing Pads. The method of claim 9, The polishing surface of the pad has a plurality of surfaces each extending to either side of a substantially constant radius to provide a different groove pattern to each of the plurality of annular segments of the polishing surface to change the groove density between the annular segments. Having the zigzag groove Workpiece Polishing Pads. The method of claim 1, Further comprising means in the groove for determining the degree of wear of the polishing surface caused by the service of the pad. Workpiece Polishing Pads. The method of claim 1, Further comprising at least one groove in the back of the pad to increase pad flexibility Workpiece Polishing Pads. The method of claim 1, Further comprising a fluid passage connecting at least one groove on the back of the pad and the at least one groove on the polishing side to provide fluid communication between the polishing surface and the ambient pressure. Workpiece Polishing Pads. The method of claim 13, The groove on the back side of the pad communicates with the groove on the polishing side to discharge the slurry out of the polishing side groove. Workpiece Polishing Pads. The method of claim 1, Further comprising at least one fluid passageway connecting the back side of the pad to the polishing side to provide fluid communication between the polishing surface and ambient pressure Workpiece Polishing Pads. The method of claim 1, And at least one groove on the back surface of the pad, the back groove communicating with the polishing side via a fluid passage through which gas, liquid or a combination thereof is passed. Workpiece Polishing Pads. The method of claim 3, wherein The bottom surface of the groove has a semi-circular shape or rounded corner shape so that abrasive debris can be easily removed from the groove. Workpiece Polishing Pads. The method of claim 1, The body of the pad includes an upper pad and a lower pad, and the depth of the groove is less than or equal to the thickness of the upper pad, and the depth is selected to optimize the flexibility of the pad. Workpiece Polishing Pads. The method of claim 1, The groove may be open terminated to be continuous, or have multiple closed terminations to provide a plurality of continuous groove segments. Workpiece Polishing Pads. The method of claim 1, The body of the pad includes a solid organic material, a porous organic material, or a fibrous organic material containing a binder and at least one of rayon and polyester fibers. Workpiece Polishing Pads. In the method of polishing the surface of the workpiece, (1) selecting a polishing pad comprising a substantially flat polishing surface and a body having at least one elongated groove disposed in the groove forming portion of the polishing surface, wherein the groove forming portion contacts the polishing surface when the pad is rotated. Selecting the polishing pad, which spans the surface of the entire workpiece, (2) placing the pad on a rotatable platen in the polishing tool; (3) mounting said workpiece in a holder of said polishing tool; ④ supplying the polishing slurry to the surface of the pad, ⑤ moving the workpiece, the pad, or both the workpiece and the pad while the polishing surface is in contact with the workpiece surface. Method of polishing the workpiece surface. The method of claim 21, The pad or both the pad and the platen have at least one fluid passageway for discharging the slurry out of the groove. Method of polishing the workpiece surface.