JP2016515303A - Substrate precession mechanism for CMP polishing head - Google Patents

Abstract

A substrate precession device for a carrier head is provided. The apparatus allows for rotational movement of the substrate relative to the carrier head, which is substrate precession during substrate polishing. Separating the carrier head and retaining ring assembly and moving them independently of each other can facilitate substrate precession during the CMP process. [Selection] Figure 2

Description

  Embodiments described herein generally relate to chemical mechanical polishing carrier heads. More specifically, the embodiments described herein relate to a substrate precession mechanism for a carrier polishing head.

  Typically, integrated circuits are formed by sequentially depositing a conductive layer, a semiconductive layer, an insulating layer, etc. on a silicon substrate. In certain manufacturing steps, a filling layer is deposited on the non-flat surface and then the filling layer is planarized until the non-flat surface is exposed. For example, a conductive fill layer can be deposited over the patterned insulating layer to fill trenches or holes in the insulating layer. The filling layer is then polished until the protruding pattern of the insulating layer is exposed. After planarization, the portions of the conductive layer remaining between the protruding patterns of the insulating layer form vias, plugs, and lines that become conductive paths between thin film circuits on the substrate. In addition, planarization is required to planarize the substrate surface for photolithography.

  Chemical mechanical polishing (CMP) is one accepted method of planarization. In this planarization method, it is usually necessary to place a substrate on a carrier head or polishing head of a CMP apparatus. The exposed surface of the substrate is disposed in contact with a rotating disk-shaped or belt-shaped polishing pad. The polishing pad may be a standard pad or a fixed abrasive polishing pad. A standard pad uses a durable roughened surface, whereas a fixed abrasive polishing pad uses abrasive particles held in a storage medium. The carrier head applies a controllable load to press the substrate against the polishing pad. The carrier head can have a retaining ring that keeps the substrate in place during polishing. A polishing liquid such as a slurry containing at least one chemically reactive agent and abrasive particles can be supplied to the surface of the polishing pad during polishing.

  Maintaining a uniform removal profile of the substrate is an important aspect of the CMP process. It may be desirable to maintain a relatively uniform profile in both the polar and radial directions across the surface of the substrate. Therefore, it may be important to adopt a method that reduces the local non-uniformity of the planarization profile.

  Embodiments described herein generally relate to a substrate precession mechanism for a CMP carrier head. A substrate precession apparatus for a CMP carrier head is provided. The apparatus allows for rotational movement of the substrate relative to the carrier head, which is substrate precession during substrate polishing. Separating the carrier head and retaining ring assembly can facilitate substrate precession during the CMP process by allowing the carrier head and retaining ring assembly to move independently of each other.

  In one embodiment, an apparatus for polishing a substrate is provided. The apparatus includes a head assembly and a retaining ring assembly. The retaining ring assembly includes an internal gear and a bearing disposed between the head assembly and the retaining ring assembly. The bearing is configured to separate the retaining ring assembly from the head assembly. A drive assembly configured to rotate the retaining ring assembly relative to the head assembly is also provided.

  In another embodiment, a retaining ring assembly for a polishing head is provided. The retaining ring assembly includes a retaining ring having an upper annular portion and a lower annular portion, and a carrier ring coupled to the upper annular portion. The retaining ring assembly further includes a bearing clamp coupled to the carrier ring and configured to receive the bearing, and an internal gear coupled to the bearing clamp.

  In another embodiment, a method for operating a polishing apparatus is provided. The method comprises providing a polishing head assembly and a retaining ring assembly. The retaining ring assembly is separated from the polishing head assembly. The method also includes rotating the polishing head at a first speed and rotating the retaining ring assembly at a second speed that is greater than the first speed.

  In order that the features of the present invention described above can be understood in detail, the present invention briefly described above will be described in detail below including the illustrated embodiments with reference to the accompanying drawings. Of course, the accompanying drawings are merely illustrative of exemplary embodiments of the invention, and the invention is intended to limit the scope of the invention as it encompasses other equivalent embodiments. It is not intended.

FIG. 5 is a partial cutaway view of a carrier head having a retaining ring assembly separated. It is a fragmentary perspective view of the carrier head of FIG. FIG. 6 is a schematic bottom view of a retaining ring assembly and a substrate.

  For ease of understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to these figures. It is contemplated that elements and features of one embodiment may be advantageously incorporated into other embodiments without further listing.

  Embodiments described herein generally relate to a substrate precession mechanism for a CMP carrier head. A substrate precession device for a carrier head is provided. The apparatus enables substrate precession during substrate polishing, which is the rotational movement of the substrate relative to the carrier head. Separating the carrier head and the retaining ring assembly and moving them independently of each other can facilitate substrate precession during the CMP process.

  In general, varying pressures can be applied to various radial zones of the membrane member to create a backside pressure that can chuck the substrate to the CMP head. By varying the pressure throughout the zone, a predetermined removal profile is obtained in each radial zone. However, adjusting the pressure in the radial zone does not completely adjust the polar non-uniformity. The non-uniformity of the membrane member can cause a non-uniform removal profile within the substrate. Thus, by introducing “polar asymmetry” to the polishing process, the effect of local non-uniformity on the removal profile can be eliminated or reduced.

  The embodiments described herein are generally provided in connection with polishing a 300 mm substrate. However, the embodiments described herein can be adapted for polishing other sized substrates, such as 100 mm and 450 mm substrates. CMP heads that can be adapted to benefit from the embodiments described herein are described in Applied Materials, Inc. TITAN HEAD ™ or TITAN COUNTUR available from Santa Clara, CA. However, it is contemplated that carrier heads available from other manufacturers can be adapted to incorporate the embodiments described herein.

  FIG. 1 is a partial cutaway view of a conventional carrier head 100. The carrier head 100 includes a housing 106, a head assembly 102, and a retaining ring assembly 104. The housing 106 can be generally circular and can be connected to a drive shaft (not shown) and rotated with the drive shaft during polishing. There may be a passage (not shown) extending through the housing 106 for pneumatic control of the carrier head 100. The carrier head 100 also includes a retaining ring assembly 104 that includes a retaining ring 120, a carrier ring 140, a bearing clamp 110, and an internal gear 112. The bearing 130 can separate the head assembly 102 from the retaining ring assembly 104.

  FIG. 2 is a partial perspective view of the carrier head 100 of FIG. 1 having a head assembly 102 and a separate retaining ring assembly 104. The head assembly 120 can include a housing 106, which can be generally circular and can be connected to a drive shaft (not shown) and rotated with the drive shaft during polishing. it can. There may be a passage (not shown) extending through the housing 106 for pneumatic control of the carrier head 100. The carrier body 208 can be flexibly coupled to the housing 106, and the carrier body 208 can co-rotate with the housing 106. The carrier body 208 can also be coupled to a flexible membrane 250 that can be adapted to chuck the substrate 201 during the CMP process. The flexible membrane 250 can define a plurality of pressurizable chambers for chucking the substrate 201.

  As described above, the retaining ring assembly 104 can include a retaining ring 120, a carrier ring 140, a bearing clamp 110, and an internal gear 112. The carrier ring 140 can have a substantially ring-like structure. The carrier ring 140 can have an annular upper portion 244 and an annular lower portion 242. The annular upper portion 244 can be disposed adjacent to and below the bearing clamp 110. The annular lower portion 242 can be disposed adjacent to and above the retaining ring 120. The carrier ring 140 is disposed therein to receive a clamping device such as a screw or bolt (not shown) for coupling the bearing clamp 110, the carrier ring 140, and the retaining ring 120. Can have a recess or hole.

  The retaining ring 120 can be formed from two rings, a lower annular ring 224 and an upper annular ring 222. Lower annular ring 224 and upper annular ring 222 can be joined together. When the lower annular ring 224 and the upper annular ring 222 are joined, the two rings have substantially the same dimensions at the inner and outer diameters on their adjacent surfaces, so that the lower annular ring 224 and the upper annular ring 224 The annular ring 222 forms a flush surface where they are joined.

  In an embodiment constructed for a 300 mm substrate, the substrate 201 can have an outer diameter of about 11.1811 inches. In one embodiment, the inner diameter of the lower annular ring 224 can be between about 11.830 in and about 11.870 in, such as 11.852 in. In this embodiment, the gear ratio between the outer diameter of the substrate 201 and the inner diameter of the lower annular ring 224 can be about 0.99654. In another embodiment, the inner diameter of the lower annular ring 224 can be between about 11.890 in and about 11.950 in, such as about 11.912 in. In this embodiment, the gear ratio between the outer diameter of the substrate 201 and the inner diameter of the lower annular ring 224 can be about 0.99152.

  In some embodiments, the lower annular ring 224 and the upper annular ring 222 can be attached by bonding material (not shown) at their adjacent surfaces. The interface between the lower annular ring 224 and the upper annular ring 222 can prevent the slurry material from becoming trapped within the retaining ring 120. The bonding material can be an adhesive material such as a slow cure epoxy or a fast cure epoxy. High temperature epoxies can withstand the degradation of bonding materials due to high heat during the CMP process. In some embodiments, the epoxy comprises a polyamide and an aliphatic amine.

  Upper annular ring 222 has an inner surface 228 that can be adapted to couple to and support flexible membrane 250. Upper annular ring 222 may be formed from a material that may be more rigid than lower annular ring 224, such as a metal (eg, stainless steel, molybdenum, aluminum), a ceramic material, or other exemplary materials.

  The lower annular ring 224 can be disposed adjacent to and below the upper annular ring 222. The lower annular ring 224 can have a substrate holding surface 226 that can be adapted to hold the substrate 201 during the CMP process. The lower annular ring 224 may be formed from a material that is chemically inert during the CMP process, such as plastic, such as polyphenylene sulfide (PPS). The lower annular ring 224 can also be adapted to have durability and a low wear rate. The lower annular ring 224 may be sufficiently compressible so that the substrate 201 does not chip or crack even if the edge of the substrate 201 contacts the lower annular ring 224. However, the lower annular ring 224 should not be so elastic that the downward pressure on the retaining ring 120 will cause the lower annular ring 224 to protrude during the CMP process.

  The bearing clamp 110 can be substantially ring-like. The bearing clamp 110 may be disposed adjacent to and above the annular top 244 of the carrier ring 140. The bearing clamp 110 can be coupled to the carrier ring 140 by a fastener 213 such as a screw or a bolt. The bearing clamp 110 can be formed from a material such as a metal (eg, stainless steel, molybdenum, aluminum), a ceramic material, or other exemplary materials. The upper portion 216 of the bearing clamp 110 can provide support for the internal gear 112. The bearing clamp 110 can include a plurality of holes (not shown) that can be aligned with a plurality of holes (not shown) in the internal gear 112. The bearing receiving area 218 can be adapted to receive the bearing 130.

  The bearing 130 can be coupled between the bearing clamp 110 and the carrier body 208. The bearing 130 can include a first annular surface 232 that can be coupled to and disposed adjacent to a bearing receiving region 218 of the bearing clamp 110. A second annular surface 234 can be coupled to the carrier body 208 and disposed adjacent thereto. A plurality of balls 236 can be disposed between the first annular surface 232 and the second annular surface 234, and the balls can be adapted to separate the head assembly 102 from the retaining ring assembly 104. it can. The bearing 130 can provide the carrier head 100 with an additional degree of rotational freedom. This additional rotational freedom allows the retaining ring assembly 104 to rotate independently of the head assembly 102.

  The internal gear 112 can be substantially ring-like. The internal gear 112 can be formed from a material such as a metal (eg, stainless steel, molybdenum, aluminum), a ceramic material, or other exemplary materials. The internal gear 112 can be disposed adjacent to and coupled to the upper portion 216 of the bearing clamp 110. A plurality of holes (not shown) may be disposed through the internal gear 112 to receive fasteners (not shown) that can be adapted to secure the internal gear 112 to the bearing clamp 110. The hole can be adapted to A plurality of teeth 214 can constitute the internal surface of the internal gear 112.

  In some embodiments, the drive assembly 290 can be constructed to provide rotational movement to the retaining ring assembly 104 independent of the rotation of the head assembly 102. The drive assembly 290 includes a cover ring 258, a bracket 256, an actuator 260, a spindle 261, and a worm drive 262. The drive assembly 290 activates the transmission 292, thereby allowing the retaining ring assembly 104 to rotate relative to the head assembly 102.

  Cover ring 258 may be disposed adjacent to and over a portion of carrier body 208. Cover ring 258 can be coupled to carrier body 208 such that cover ring 258 and the elements coupled thereto move in the same rotational manner as head assembly 102. The bracket 256 can be disposed on and coupled to the upper surface 259 of the cover ring 258. The bracket 256 can be adapted to support the actuator 260 in a fixed position. An actuator 260 such as an air motor can be coupled to the pressure source 274 via a transport line 272. The pressure source 274 can be adapted to provide pressurized gas or fluid to the actuator 260 via the transport line 272. A spindle 261 extends from the actuator 260 and a worm drive 262 can be coupled to the spindle 261. The actuator 260 generally imparts rotational movement to the spindle 261 and rotates the worm drive 262.

  Transmission 292 can be actuated by worm drive 262. The transmission 292 includes a worm gear 264, a spur gear 268, a drive shaft 266, and a shaft encoder 270. The worm gear 264 can be disposed around the first end 265 of the drive shaft 266. The worm gear 264 can be coupled to the worm drive 262 and can be adapted to transmit the rotational movement of the worm drive 262 to the drive shaft 266. Spur gear 268 can be disposed about drive shaft 266 in region 269 below worm gear 264 and substantially parallel to teeth 214 of internal gear 112. The spur gear 268 can transmit the rotational movement of the drive shaft 266 to the internal gear 112. Thus, the retaining ring assembly 104 can be rotated independently of the rotation of the head assembly 102.

  The shaft encoder 270 can be disposed on the drive shaft 266 under the spur gear 268. A shaft encoder 270, such as an electromechanical device, can convert the rotational motion of the drive shaft 266 into an analog code or a digital code. Shaft encoder 270 can be coupled to a controller (not shown), which can be coupled to actuator 260. The controller can be adapted to control the rotational speed at which the retaining ring 104 rotates relative to the head assembly 102.

  A housing assembly 280 can be disposed within a portion of the carrier body 208 and can be adapted to receive the drive shaft 266. The housing assembly 280 can have a bottom 286 and a plurality of side walls 282. A second end 267 of the drive shaft 266 can be disposed within the housing assembly 280. A plurality of bearings 284 may also be disposed within the housing assembly 280. A plurality of bearings 284 may be disposed between the side wall 282 of the housing assembly 280 and the drive shaft 266. A plurality of bearings 284 may couple the drive shaft 266 to the housing assembly 280 and allow the drive shaft 266 to rotate relative to the housing assembly 280.

  In some embodiments, the retaining ring assembly 104 can be driven at a speed greater than the rotational speed at which the head assembly 102 can be rotated. For example, during a 60 second CMP polishing process, the head assembly 102 can be rotated at a speed to achieve about 60 rpm to about 120 rpm. In this example, the rotational speed of the retaining ring assembly 104 may be greater than the rotational speed of the polishing head, which can facilitate substrate precession. It is contemplated that the retaining ring assembly 104 can rotate in the same direction or in the opposite direction relative to the direction of rotation of the head assembly 102. In addition, the substrate precession may be affected by the rotation direction of the polishing pad that presses the substrate 201 to polish.

  FIG. 3 is a schematic bottom view of the retaining ring assembly 104 and the substrate 201. The inner diameter of the retaining ring assembly 104 may be larger than the outer diameter of the substrate 201. A rotation direction 306 of the retaining ring assembly 104 facilitates rotation 308 of the substrate 201 in a direction relative to a head assembly (not shown), such as the head assembly 102 (see FIG. 2). The rotation 308 of the substrate 201 relative to the head assembly can be defined as substrate precession as discussed above.

  As described above, substrate precession is the degree of rotation or slip that the substrate 201 experiences against the membrane 250 on the head assembly 102. By promoting substrate precession, it is believed that any possible local non-uniformity of the substrate removal profile can be “averaged” over a given polishing time. It is believed that the polar asymmetry created by the substrate precession causes an averaging effect on the local non-uniformity of the membrane 250 or polishing pad. This local non-uniformity can result in a non-planar removal profile and therefore it can be advantageous to reduce the effects of this local non-uniformity.

  It is also contemplated that the substrate precession can be defined by the relationship between the outer diameter of the substrate 201 and the inner diameter of the retaining ring assembly 104. The relationship between the outer diameter of the substrate 201 and the inner diameter of the retaining ring assembly 104 can be described in terms of gear ratio. The smaller the gear ratio between the inner diameter of the retaining ring assembly 104 and the outer diameter of the substrate 201, the greater the substrate precession.

  It is further contemplated that driving the retaining ring assembly 104 at a speed greater than the speed of the head assembly 102 can further facilitate substrate precession. In one embodiment, the rotational speed of about 60 rpm of the head assembly 102 and the inner diameter of about 11.852 in of the retaining ring assembly 104 can be combined to achieve a substrate precession of about 90 °. In another embodiment, the rotational speed of about 90 rpm of the head assembly 102 and the inner diameter of about 11.852 inches of the retaining ring assembly 104 can be combined to achieve a substrate precession of about 135 °. In another embodiment, the rotational speed of about 120 rpm of the head assembly 102 and the inner diameter of about 11.852 inches of the retaining ring assembly 104 can be combined to achieve a substrate precession of about 100 °. The gear ratio of the above embodiment can be approximately 0.99654. In the embodiments described above, the retaining ring assembly 104 can co-rotate or reversely rotate at a rotational speed greater than the rotational speed of the head assembly 102.

  In one embodiment, the rotational speed of about 60 rpm of the head assembly 102 and the inner diameter of about 11.912 inches of the retaining ring assembly 104 can be combined to achieve a substrate precession of about 180 °. In another embodiment, the rotational speed of about 90 rpm of the head assembly 102 and the inner diameter of about 11.912 inches of the retaining ring assembly 104 can be combined to achieve a substrate precession of about 270 degrees. In another embodiment, the rotational speed of about 120 rpm of the head assembly 102 and the inner diameter of about 11.912 inches of the retaining ring assembly 104 can be combined to achieve a substrate precession of about 360 °. The gear ratio of the above embodiment can be about 0.99152. In the embodiments described above, the retaining ring assembly 104 can co-rotate or reversely rotate at a rotational speed greater than the rotational speed of the head assembly 102.

  While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope of the invention is As defined by the appended claims.

Claims (15)

An apparatus for polishing a substrate,
A head assembly;
A retaining ring assembly,
An internal gear, and a retaining ring assembly comprising a bearing disposed between the head assembly and the retaining ring assembly and configured to separate the retaining ring assembly from the head assembly;
A drive assembly configured to rotate the retaining ring assembly relative to the head assembly. The head assembly further comprises:
A housing;
The carrier body,
The apparatus of claim 1, comprising a flexible membrane.   The apparatus of claim 1, wherein the head assembly further comprises a cover plate coupled to the drive assembly. A first gear;
A second gear,
A shaft encoder;
The apparatus of claim 1, further comprising a transmission comprising a drive shaft.   The apparatus of claim 4, wherein the first gear is rotatably coupled to the drive assembly.   The apparatus of claim 4, wherein the second gear is rotatably coupled to the internal gear.   The apparatus of claim 4, wherein the first gear and the second gear are coupled to the drive shaft. The drive assembly comprises:
An actuator,
A spindle coupled to the actuator;
The apparatus of claim 1, comprising a worm drive coupled to the spindle.   The apparatus of claim 8, wherein the actuator is a pneumatic motor.   The apparatus of claim 1, wherein the internal gear comprises a plurality of teeth.   The apparatus of claim 1, wherein an inner diameter of the retaining ring assembly is between about 11.830 inches and about 11.870 inches.   The apparatus of claim 1, wherein an inner diameter of the retaining ring assembly is between about 11.890 inches and about 11.950 inches. A retaining ring assembly for a polishing head comprising:
A retaining ring having an upper annular portion and a lower annular portion;
A carrier ring coupled to the upper annular portion;
A bearing clamp coupled to the carrier ring and configured to receive a bearing;
A retaining ring assembly comprising an internal gear coupled to the bearing clamp.   The apparatus of claim 13, wherein the bearing separates the retaining ring assembly from a polishing head assembly. A method of operating a polishing apparatus,
Providing a polishing head assembly and a retaining ring assembly separated from the polishing head assembly;
Rotating the polishing head at a first speed; and rotating the retaining ring assembly at a second speed greater than the first speed.

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