KR100636455B1 - Carrier head with controllable pressure and loading area for chemical mechanical polishing - Google Patents

Abstract

The carrier head for a chemical mechanical polishing apparatus includes a flexible thin film for applying a load to a substrate in a load region having a controllable size. One pressurizable chamber in the carrier head controls the size of the load region and the other chamber controls the pressure applied to the substrate in the load region.

Description

Carrier head with controllable pressure and load area for chemical mechanical polishing {CARRIER HEAD WITH CONTROLLABLE PRESSURE AND LOADING AREA FOR CHEMICAL MECHANICAL POLISHING}

1 is an enlarged perspective view of a chemical mechanical polishing apparatus.

2 is a cross-sectional view of a carrier head according to the present invention.

3 is an enlarged view of the substrate support assembly from the carrier head of FIG.

4A and 4B are cross-sectional views showing pressure and force distributions on a hydrodynamic flexible thin film.

5A and 5B are cross-sectional views illustrating a variable load region of the inner flexible thin film from the carrier head of FIG. 2 relative to the substrate.

6 is a graph illustrating the relationship between the diameter of the contact region and the pressure in the upper floating chamber.

7A and 7B are graphs showing the pressure and pressure derivative (dP / dT) of the lower floating chamber over time during substrate detection.

8 is a sectional view of a carrier head having an inner support plate.

9 is a cross-sectional view of a carrier head having a flexible thin film with ribs.

10 is a cross-sectional view of a carrier head having a flexible thin film in direct contact with a substrate in a variable load region.

11 is a sectional view of a carrier head having a valve for sensing the presence of a substrate.

※ Explanation of code about main part of drawing ※

100: carrier head 104: housing

104: base assembly 108: loading chamber

110: retaining ring 112: substrate support assembly

234: floating lower chamber 236: floating upper chamber

238: outer chamber

The present invention relates to chemical mechanical polishing of substrates, and more particularly to a carrier head for chemical mechanical polishing.

Integrated circuits are typically formed on substrates, particularly silicon wafers, by sequential deposition of conductive, semiconductive or insulating layers. After each layer is deposited, they are etched to form circuit features. As a series of layers are sequentially deposited and etched, the outer or top surface of the substrate, i.e. the exposed surface of the substrate, becomes increasingly uneven. Such non-uniform surfaces present problems at the photolithographic stage of the integrated circuit fabrication process. Therefore, it is necessary to periodically planarize the substrate surface.

Chemical mechanical polishing (CMP) is used as one of the planarization methods. Such planarization methods typically require that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is placed on a rotating polishing pad. The polishing pad can be a "standard" or fixed polishing pad. Standard polishing pads have a durable rough surface, while fixed polishing pads have abrasive particles retained in the container medium. The carrier head provides a controllable load, for example pressure, on the substrate to push the substrate against the polishing pad. Some carrier heads include a flexible membrane that provides a mounting surface for the substrate, and a retaining ring that holds the substrate below the mounting surface. The pressurization or exhaust of the chamber behind the flexible membrane controls the load on the substrate. If a standard pad is used, an abrasive slurry comprising at least one chemical reagent and abrasive particles is supplied to the surface of the abrasive pad.

The efficiency of the CMP process can be measured by its polishing rate, and the resulting finish (small dimension roughness member) and flatness (large dimension topological member) of the substrate surface. The polishing rate, finish and flatness are determined by the pad and slurry combination, the relative speed between the substrate and the pad, and the substrate compressive force against the pad.

A problem that arises repeatedly in CMP is the "edge effect", in which the so-called substrate edges tend to polish at a different speed than the substrate center. Edge effects typically result in non-uniform polishing at the periphery of the substrate, for example at the outermost 3-15 millimeters of a 200 millimeter (mm) wafer. A related problem is the so-called "central slow effect", in which the center of the substrate tends to be insufficiently polished.

It is an object of the present invention to solve the "edge effect" or "central slow effect" problem which occurs repeatedly in chemical mechanical polishing.

In one aspect, the invention relates to a carrier head for a chemical mechanical polishing apparatus. The carrier head includes a first pressurizable chamber at least partially coupled by a first flexible membrane, and a second pressable chamber disposed to apply downward force to the first chamber. The lower surface of the first flexible membrane provides a first surface for applying pressure to a substrate in a load region having a controllable size, wherein the first and second chambers are configured such that the first pressure of the first chamber is applied to the load region. And to control the pressure applied to the substrate in which the second pressure in the second chamber controls the size of the load region.

The practice of the present invention includes one or more of the following features. The vertically movable base may form at least a portion of the upper boundary of the second pressurizable chamber. The housing can be connected to the drive shaft and the third chamber can be disposed between the housing and the base. A retaining ring can be connected to the base to hold the substrate under the carrier head. The boundary between the first and second chambers may be formed by a rigid member or a flexible member, and the second chamber may generally form an annular volume or a cubic volume. The bottom surface of the first flexible thin film may provide a mounting surface for the substrate, or the second flexible thin film may extend below the first flexible thin film to provide a mounting surface for the substrate. The volume between the first and second flexible membranes forms a third pressurizable chamber. The first flexible thin film is movable in contact with the top surface of the second flexible thin film in the load region to apply pressure to the substrate. The bottom surface of the first flexible membrane may be textured to provide fluid flow therebetween when the first and second flexible membranes contact.

The first support structure is disposed inside the first chamber and the first flexible thin film can extend around the outer surface of the first support structure. The first spacer ring may be disposed outside the first chamber, the first flexible thin film being outwardly near the inner surface of the first spacer ring and near the upper surface of the first spacer ring. It can extend into a serpentine path between them. The second support structure can be disposed in a third chamber between the first and second flexible membranes and can be arranged to surround the first support structure. The second spacer ring can be disposed outside the third chamber on the first support ring, with the second flexible membrane supporting the second support near the inner surface of the second spacer ring and near the outside of the upper surface of the second spacer ring. It can extend in a sinuous path between the structure and the second spacer ring.

In another aspect, the present invention relates to a carrier head for chemical mechanical polishing having a base, a first flexible thin film portion, and a second flexible thin film portion. The first flexible thin film portion extends below the base and forms a first pressurizable chamber, the lower surface of the first flexible thin film portion providing a mounting surface for applying pressure to the substrate in a load region having a controllable size. . The second flexible thin film portion couples the first flexible thin film portion to the base to form a second pressurizable chamber, wherein the first pressure of the first pressurizable chamber controls the pressure applied to the substrate in the load region and the second chamber. The second pressure of controls the size of the load zone.

In another aspect, the present invention relates to a carrier head for chemical mechanical polishing having a base, a first flexible thin film portion, a second flexible thin film portion, and a third flexible thin film portion. The first flexible thin film portion extends below the base to form a first pressurizable chamber, and the bottom surface of the first flexible thin film portion provides a mounting surface for the substrate. The second flexible thin film portion extends below the base to form a second pressurizable chamber, wherein the bottom surface of the second flexible thin film contacts the top surface of the first flexible thin film in the load region having a controllable size. The third flexible thin film portion couples the second flexible thin film portion to the base and forms a third pressurizable chamber such that the first pressure in the second pressurizable chamber controls the pressure applied to the substrate in the load region, and the third chamber The second pressure within controls the size of the load zone.

In another aspect, the present invention relates to a chemical mechanical polishing carrier head having a first biasing member and a second biasing member. The first biasing member includes a first pressure chamber, the bottom surface of the first pressure chamber being limited by a flexible thin film that provides a first surface for applying a load to a substrate in a load region having a controllable size. . The second biasing member is connected to the first biasing member, and the second biasing member controls the pressure of the second biasing member to control the size of the load region and the first biasing member to the substrate in the load region. To control the vertical position of the first biasing member.

In another aspect, the invention has a flexible thin film that provides a mounting surface for a substrate, means for controlling the size of the load region where the load is applied to the substrate, and means for controlling the pressure applied to the substrate within the load region. It relates to a carrier head for chemical mechanical polishing.

In another aspect, the present invention relates to a method for chemical mechanical polishing of a substrate. In the method, the substrate is held in a polishing pad having a carrier head, a load is applied to the substrate in the load region having the first chamber of the carrier head, and the size of the load region is controlled by the second chamber of the carrier head, And a relative motion is formed between and the polishing pad.

In another aspect, the present invention relates to a method for detecting a substrate of a carrier head for a chemical mechanical polishing system. In the method, the chamber of the carrier head is connected to a pressure source. The pressure in the chamber is measured as a function of time and the pressure derivative in the chamber is calculated. Whether the substrate is adjacent to the substrate receiving surface of the carrier head is determined from the derivative.

The practice of the present invention includes the following features. If the derivative exceeds the threshold, it may indicate that the substrate is present, or if the derivative does not exceed the threshold, the substrate may not be present.

Advantages of the present invention may include the following. The pressure and load regions of the flexible thin film against the substrate can be varied to compensate for non-uniform polishing. Uneven polishing of the substrate is reduced, and flatness and finish of the resulting substrate are improved.

Other advantages and features of the present invention will become apparent from the following detailed description, including the drawings and the claims.

Referring to FIG. 1, one or more substrates 10 will be polished by a chemical mechanical polishing (CMP) apparatus 20. Descriptions of similar CMP devices are disclosed in US Pat. No. 5,738,574, which is incorporated herein by reference.

The CMP apparatus 20 includes a series of polishing stations 25 and a transfer station 27 for loading and unloading a substrate. Each polishing station 25 includes a rotatable platen 30 on which polishing pads 32 are positioned. If the substrate 10 is a 6 inch (150 millimeter) or 8 inch (200 millimeter) diameter disk, the platen 30 and polishing pad 32 may be about 20 inches in diameter. If the substrate 10 is a 12 inch (300 millimeter) diameter disk, the platen 30 and polishing pad 32 may be about 30 inches in diameter. During most polishing processes, the platen drive motor (not shown) rotates the platen 30 at 30 to 200 revolutions per minute, although lower or higher rotational speeds may be used. Each polishing station 25 may further include an associated pad adjusting device 40 to maintain the abrasive state of the polishing pad.

By a slurry / rinse arm 52 in which a slurry 50 containing a reactant (eg deionized water for oxide polishing) and a chemical reaction catalyst (eg potassium hydride for oxide polishing) are combined It may be supplied to the surface of the polishing pad 32. If polishing pad 32 is a standard pad, slurry 50 may also include abrasive particles (eg, silicon dioxide for oxide polishing). Typically, sufficient slurry is provided to cover and wet the entire polishing pad 32. The slurry / rinse arm 52 includes several spray nozzles (not shown) that provide a high pressure rinse of the polishing pad 32 at the end of each polishing and conditioning cycle.

The rotatable multi-head carousel 60 is supported by a central column 62 and rotated about the carousel axis 64 by a carousel motor assembly (not shown). The multi-head carousel 60 includes four carrier head systems 70 mounted on the carousel support plate 66 at uniform angular spacing near the carousel axis 64. Three of the carrier head systems place the substrate on a polishing station, and one of the carrier head systems receives the substrate at the transfer station and carries the substrate to the transfer station. The carousel motor can pivot the carrier head system and the substrate attached thereto near the carousel axis between the polishing station and the transfer station.

Each carrier head system 70 includes a polishing or carrier head 100. Each carrier head 100 independently rotates around its axis and independently laterally reciprocates in the spinning slot 72 formed in the carousel support plate 66. Carrier drive shaft 74 extends through slot 72 to connect carrier head rotation motor 76 (shown by quarter removal of carousel cover 68) to carrier head 100. There is one carrier drive shaft and motor for each head. Each motor and drive shaft can be held on a slider (not shown) that can be linearly driven along the slot by a radial drive motor to laterally reciprocate the carrier head.

During actual polishing, three carrier heads are placed on top of three polishing stations. Each carrier head 100 contacts the polishing pad 32 to lower the substrate. The carrier head holds the substrate in a proper position relative to the polishing pad and distributes the force against the backside of the substrate. The carrier head also transmits torque from the drive shaft to the substrate.

Referring to FIG. 2, the carrier head 100 includes a housing 102, a base assembly 104, a gimbal mechanism 106 (which can be an important part of the base assembly), a loading chamber 108, a retaining ring 110. ) And a substrate support assembly 112 that includes three pressurizable chambers, such as floating top chamber 236, floating bottom chamber 234, and outer chamber 238. A description of a similar carrier head was filed by Zuniga et al. On May 21, 1997, entitled “Carrier Head with Flexible Thin Films for Chemical Mechanical Polishing Systems,” and assigned to US assignee of the present application. / 861,260.

The housing 102 may be connected to the drive shaft 74 to rotate during polishing near the axis of rotation 107 which is substantially perpendicular to the surface of the polishing pad during polishing. The housing 102 may generally be circular in shape corresponding to the circular configuration of the substrate to be polished. Vertical bore 130 may be formed through the housing, and three additional passages 130 (only two passages 132, 134 are shown in FIG. 2) may be used to control the housing for pneumatic action of the carrier head. Can extend through. O-ring 138 may be used to form a tight fluid seal between the passage through the housing and the passage through the drive shaft.

Base assembly 104 is a vertically movable assembly disposed below housing 102. The base assembly 104 includes a rigid annular body 140, an outer clamp ring 164, a gimbal mechanism 106, and a lower clamp ring 144. The passage 146 may extend through the body of the gimbal mechanism, the annular body and the clamp ring, with two fixtures 148 extending the flexible tube between the housing 102 and the base assembly 104 to the substrate support assembly 112. May provide an attachment point for fluidly coupling passage 134 to one of the chambers, for example chamber 238. The second passageway (not shown) may extend through the annular body 140, and the two fixtures (also not shown) may provide a flexible tube between the housing 102 and the base assembly 104 to support the substrate support assembly 112. May provide an attachment point that couples an unshown passageway within the housing to a second chamber, eg, chamber 236.

The gimbal mechanism 106 allows the retaining ring to be pivoted about the housing 102 so that the retaining ring can be held substantially parallel to the surface of the polishing pad. Gimbal mechanism 106 includes gimbal rod 150 fixed in vertical bore 130 and curved ring 152 secured to annular body 140. The gimbal rod 150 can slide vertically along the bore 130 to provide vertical movement of the base assembly 104, but prevents any lateral movement of the base assembly 104 relative to the housing 102. Reduces the moment generated by the lateral force of the substrate against the retaining ring. Gimbal rod 150 may include a passage 154 extending the length of the gimbal rod to fluidly engage bore 134 to a third chamber, for example chamber 234, of substrate support assembly 112. have.

The loading chamber 108 is disposed between the housing 102 and the base assembly 104 such that a load, such as downward pressure or weight, is applied to the base assembly 104. In addition, the vertical portion of the base assembly 104 in relation to the polishing pad 32 is controlled by the loading chamber 108. The inner edge of the ring-shaped rolling partition 160 may be clamped to the housing 102 by an inner clamp ring 162. The outer edge of the rolling partition 160 may be clamped to the base assembly 104 by an outer clamp ring 164. Thus, the rolling partition 160 seals the space between the housing 102 and the base assembly 104 to form the loading chamber 108. A first pump (not shown) may be fluidly connected to the loading chamber 108 by passages 132 to control the pressure of the loading chamber and the vertical position of the base assembly 104.

Retaining ring 110 may be an annular ring secured to the outer edge of base assembly 104 by, for example, bolt 128. When fluid is pumped into the loading chamber 108 and the base assembly 104 is pushed downward, the retaining ring 110 is also pushed downward to apply a load to the polishing pad 32. The bottom surface 124 of the retaining ring 110 may be substantially flat or have multiple channels to facilitate the transfer of slurry from the exterior of the retaining ring to the substrate. The inner surface 126 of the retaining ring 110 confines the substrate to prevent the substrate from leaving below the carrier head.

2 and 3, the substrate support assembly 112 includes a flexible thin film 116, a flexible outer thin film 118, an inner support structure 120, an outer support structure 230, and an inner spacer ring 122. ), And an outer spacer ring 232. The support structures 120 and 230 and the spacer rings 122 and 232 can be "free-floating" without being fixed in the carrier head position and can be adequately maintained by the inner and outer flexible membranes.

The flexible inner thin film 116 has a central portion 200 to apply pressure to the substrate in the controllable area, a relatively thick annular portion 202 having an L-shaped cross section, and an annular extending from the corner of the L-shaped portion 202. Inner flap 204, annular outer flap 206 extending at the outer edge of the L-shaped portion 202 and near the inner support structure 120 to connect the L-shaped portion 202 and the central portion 200. Extending peripheral portion 208. The edge of the inner flap 204 is clamped between the curved ring 152 and the annular body 140, while the edge of the outer flap 206 is clamped between the outer clamp ring 164 and the lower clamp ring 144. do. The volume between the inner membrane 116 and the base assembly 104 sealed by the inner flap 204 provides a pressurizable floating lower chamber 234. The annular volume between the base assembly 104 and the base assembly 104 and the inner thin film 116 sealed by the inner flap 204 and the outer flap 206 forms a pressurizable floating upper chamber 236. A second pump (not shown) may be connected to an unshown passageway for sending fluid, for example gas, such as air, into and out of the floating upper chamber 236. A third pump (not shown) may be connected to an unshown passageway for sending fluid, for example gas, such as air, into and out of the floating lower chamber 234. The second pump controls the pressure of the upper chamber and the vertical position of the lower chamber, and the third pump controls the pressure of the lower chamber. As described in more detail below, the pressure in the floating upper chamber 236 controls the contact area of the inner membrane 116 relative to the top surface of the outer membrane 118. Thus, the second pump controls the substrate area, such as the load area, where pressure is applied, while the third pump controls the downward force on the substrate in the load area. The fourth pump controls the pressure of the outer chamber 238.

The outer membrane 118 is a central portion 210 extending below the outer support structure 230 to provide a mounting surface for engagement with the substrate, between the outer support structure 230 and the outer spacer ring 232 to be secured to the base assembly. A perimeter 212 extending in an serpentine path. For example, the edge of the outer thin film can be clamped between the lower clamp ring 144 and the retaining ring 110. The sealing volume between the inner membrane 116 and the outer membrane 118 forms a pressurizable outer chamber 238. Therefore, the outer chamber 238 can actually extend below the lower chamber 234. A fourth pump (not shown) may be connected to the passage 14 to direct fluid, for example gas, such as air, into and out of the outer chamber 238.

The inner support structure 120 may be a rigid annular washer body disposed inside the floating lower chamber 234 to maintain the inner membrane 116 in the desired shape. Optionally, the inner support structure can be a disc shaped body having a plurality of openings. The disc shaped support structure will provide a support surface to prevent damage due to substrate warpage.

The inner spacer ring 122 is a rigid annular body that may have a C-shaped cross section. The inner spacer ring may include a cylinder portion 190, an annular upper flange 192 and an annular lower flange 194. The inner spacer ring 122 may be disposed in the outer chamber 238 on the inner support structure 120. The annular lower flange 194 is supported by the inner support structure, while the annular upper flange 192 extends over the outer support structure 230 and the outer spacer ring 232.

The inner thin film 116 is an elastomer, an elastomeric coated fabric, or an elastic material such as Delaware, a thermal plastic elastomer (TPE) such as HYTREL ™ available from DuPont, Newark, or a compound of these materials. It may be formed of a flexible and elastic material. Preferably, the inner thin film 116 is somewhat less flexible than the outer thin film 118. As disclosed above, the controllable area of the central portion 200 of the inner membrane 116 may contact the top surface of the outer membrane 118 and apply a downward load on that surface. The load is transferred to the substrate in the load region through an external thin film. The lower surface of the central portion 200 of the inner membrane 116 may be textured, for example, with small grooves so that fluid can flow between them when the inner and outer membranes are in contact. The perimeter 208 of the inner membrane extends upward near the outer surface 180 of the inner support structure 120 and connects the lower flange 194 of the inner spacer ring 122 to connect to the lower edge of the L-shaped portion 202. ) And an upper surface 182 of the inner support structure. The L-shaped portion 202 of the inner thin film extends inside the cylinder portion 190 and over the annular top flange 192 of the inner spacer ring 122.

The outer support structure 230 holds the outer thin film 118 of the desired shape and the outer chamber 238 between the inner thin film 116 and the outer thin film 118 to seal the outer thin film against the substrate during vacuum chucking. Disposed within. In particular, the outer support structure 230 may have a rigid ring-shaped portion 170 having an annular protrusion 172 extending downward from the edge of the ring-shaped portion. Optionally, US application no. 08 / 861,260, filed August 8, 1997, by Steven M. Zuniga et al., Entitled “Carrier Head with Local Pressure Control for Chemical Mechanical Polishing Device” and assigned to the assignee of the present invention. As disclosed in the arc, the protrusion 172 can be placed in contact with the top surface of the outer membrane to selectively apply pressure to the selected substrate region. The protrusion 172 may be formed by firmly attaching a compressible layer of material to the lower surface of the ring-shaped portion 170.

The outer spacer ring 232 is an annular member disposed between the retaining ring 110 and the outer thin film 118. In particular, the outer spacer ring 232 may be disposed on the outer support structure 230. The outer spacer ring 232 includes a flange portion 186 extending outwardly toward the inner surface 126 of the retaining ring 110 to maintain the lateral position of the cylinder portion 184 and the outer spacer ring.

The outer thin film 118 is a circular sheet formed of a flexible and elastic material such as chloroprene or ethylene propylene rubber, or silicone. Note that the central portion 210 of the outer membrane forms the mounting surface for the substrate, while the perimeter 212 is the outer support structure 230 and the outer spacer to be clamped between the base assembly 104 and the retaining ring 110. It extends in a serpentine form between the rings 232. In particular, the perimeter 212 extends upward near the outer surface 174 of the outer support structure 230 and is inward between the flange portion of the outer spacer ring 232 and the upper surface 176 of the outer support structure 230. Direction and extends upward near the cylinder portion 184 of the outer spacer ring 232 to the edge portion 214 that is clamped between the lower clamp ring 144 and the retaining ring 110. To form a tight fluid seal. The “free-span” portion 216 of the outer membrane extends between the outer spacer ring 232 edge 214 and the outer diameter of the top surface. The outer thin film 118 may also include a thick film portion 218 extending upwardly between the inner spacer ring 122 and the outer spacer ring 232. The outer thin film may be pre-molded into a serpentine shape.

을 요구하는데,

는 챔버(306)에서의 내부 압력(P₁)과 플렉시블한 박막을 둘러싸는 외부 압력(P₂) 사이의 차이며, A_c는 접촉 영역(308)의 표면적이다. 따라서, 접촉 영역(308)의 직경(D_c)은 다음에 의해 주어질 것이다:In operation, fluid is pumped in and out of the floating lower chamber 116 to control the downward pressure of the inner membrane 116 against the outer membrane 118 and therefore to the substrate, and the fluid is internal to the outer membrane 118. Pumped into and out of the floating upper chamber 236 to control the contact area of the membrane 116. The ability of the carrier head 100 to control the pressure and load region applied to the substrate is described with reference to the schematic diagrams of FIGS. 4A and 4B. With reference to FIG. 4A, the hydrodynamic and fairly schematic grinder 300 includes a “free floating” flexible thin film 302 forming a pressurizable chamber 306. Assuming no external pressure is applied to the flexible membrane 302, it will generally be spherical and have an internal pressure P ₁ . However, if the thin film is compressed between the rigid plate 304 and the substrate 10, the flexible thin film will deform into a circular shape that contacts the substrate with the circular contact area 308. Assuming that rigid plate 304 applies downward force P to flexible thin film 302, the equilibrium force is

Require

Is the difference between the internal pressure P ₁ in the chamber 306 and the external pressure P ₂ surrounding the flexible membrane, and A _c is the surface area of the contact region 308. Thus, the diameter D _c of the contact region 308 will be given by:

As a result, any circular contact profile and pressure can be achieved by a two-step process in which pressure P ₁ is selected and the applied force F is adjusted to determine the diameter of the load region. 4A and 4B illustrate the concept in a fairly schematic form, the invention can generally be practiced by applying a downward force to the free floating thin film chamber.

5A and 5B, the contact region of the inner membrane 116 to the outer membrane 118, and thus the load region in which pressure is applied to the substrate 10, is changed by varying the pressure in the floating upper chamber 236. Can be controlled. By pumping fluid out of the floating upper chamber 236, the L-shaped portion 202 of the inner membrane 116 is pulled upwards, thereby pulling the outer edge of the central portion 200 from the outer membrane 118. The diameter of the load zone is reduced. Conversely, by pumping fluid into the floating upper chamber 236, the L-shaped portion 202 of the inner membrane 116 is subjected to a downward force, resulting in contact with the outer membrane 118 so as to contact the center of the inner membrane ( 200) is pushed to increase the diameter of the load region. In addition, when the fluid is directed into the outer chamber 238, the L-shaped portion 202 of the inner membrane 116 is subjected to an upward force, as a result of which the diameter of the load region is reduced. Thus, in the carrier head 100, the diameter of the load zone will depend on the pressure in the upper chamber and the outer chamber.

An exemplary graph 400 of the diameter of the contact area according to the pressure in the upper chamber 236, the lower chamber 234 and the outer chamber 238 is shown in FIG. 6. Such graphs can be determined experimentally or calculated by finite element analysis. In the graph of FIG. 6, the x axis represents the pressure in the upper chamber 234 and the y axis represents the contact area. The set of graph lines 402-418 represents the relationship of upper chamber pressure to contact area at various pressures in lower chamber 236 and outer chamber 238, as summarized by the chart below.

 Graph line  Pressure P1 of the outer chamber 238  Pressure P2 of the lower chamber 234  P2-P1  402  1.0  1.5  0.5  404  1.0  2.0  1.0  406  3.0  3.5  0.5  408  3.0  4.0  1.0  410  3.0  4.5  1.5  412  5.0  5.5  0.5  414  5.0  6.0  1.0  416  5.0  6.5  1.5  418  5.0  7.0  2.0

The carrier head 100 may also be operated in a standard mode of operation in which the floating chambers 234 and 236 are evacuated or depressurized to rise from the substrate, and the outer chamber 238 applies a uniform pressure across the entire backside of the substrate. Pressurized.

As discussed previously, a recurring problem in CMP is uneven polishing of the substrate center. However, a controllable load region can be used to compensate for a polishing profile in which the center of the substrate is less polished by applying a sequence of polishing steps using different diameters of the load region. For example, the carrier head polishes an area of the substrate having a radius r ₁ for the first period T1, and a larger area having a radius r ₂ for the next second period T ₂ . For the next third period T ₃ , it can be used to polish a still larger area having a radius r ₃ . This allows different areas of the substrate to be polished depending on the overall time and pressure required to reduce the polishing unevenness.

As discussed above, another problem that arises repeatedly in CMP is non-uniform polishing near the edge of the substrate. However, the outer spacer ring 232 can be used to control the pressure distribution applied by the outer thin film 118 near the substrate edge. In particular, it was filed on October 9, 1998 by Steven Zuniga et al. Under the name " carrier head with flexible thin film for chemical mechanical polishing, " As disclosed in 09 / 169,500, the surface area of the upper surface of the outer spacer ring can be selected to adjust the relative pressure applied to the center of the outer thin film relative to the substrate periphery.

To remove the substrate from the polishing pad, the floating upper chamber 236 is pressed to lower the protrusion 172 of the outer support structure 230 with respect to the upper surface of the outer thin film 118. This allows the outer thin film to contact the substrate to form a seal. The floating lower chamber 234 is exhausted, for example connected to an external atmosphere, and the external chamber 238 is depressurized. This causes the outer membrane 118 to be pulled inward to vacuum chuck the substrate with the carrier head. Floating top chamber 236 is then depressurized to pull the inner and outer thin films upward and to lift the substrate from the polishing pad. Finally, the loading chamber 108 is evacuated to lift the base assembly 104 and substrate support assembly out of the polishing pad.

Operation of the carrier head 100 for loading a substrate into the carrier head at the transfer station 27, dechucking the substrate from the polishing pad at the polishing station 25, and unloading the substrate from the carrier head at the transfer station 27. Are summarized in the following table.

                          Loading behavior  step  Initial state  Subassembly Retract  Thin film extensions  Pushing substrate into thin film  Wafer gripping  Out  exhaust  exhaust  pressure  exhaust  vacuum  bottom  exhaust  exhaust  exhaust  exhaust  exhaust  Top  exhaust  vacuum  vacuum  vacuum  vacuum  ring  vacuum  vacuum  vacuum  vacuum  vacuum

The time delay can be taken after the expansion, pushing and gripping steps, respectively.

                          Dechucking Behavior  step  Initial state  Seal strength                                       Board Gripping  Lifting the substrate from the pad  Lifting ring from pad  Out  exhaust  exhaust  vacuum  vacuum  vacuum  bottom  exhaust  exhaust  exhaust  exhaust  exhaust  Top  exhaust  pressure  pressure  vacuum  vacuum  ring  pressure  pressure  pressure  pressure  vacuum

The time delay can be taken after the sealing, gripping and lifting steps, respectively.

                          Unloading behavior  step  Initial state  Subassembly Extension  Board side  Substrate Ejection  Membrane shrinkage  Out  vacuum  vacuum  exhaust  exhaust  exhaust  bottom  exhaust  exhaust  exhaust  pressure  exhaust  Top  vacuum  pressure  exhaust  exhaust  Aeration  ring  vacuum  vacuum  pressure  vacuum  vacuum

Time delays can be taken after the falling and discharging phases respectively.

To determine whether the substrate has been successfully attached to the carrier head after a loading or dechucking operation, the CMP apparatus may perform a substrate detection procedure. This procedure begins with the outer chamber 238, the upper floating chamber 236 and the loading chamber 108 under vacuum, and the lower floating chamber 234 is evacuated. Lower floating chamber 234 is connected to the pressure source at a fixed pressure. Referring to FIG. 7A, the pressure in the lower floating chamber is measured over time. Referring to FIG. 7B, the first derivative dP / dt of the pressure of the lower floating chamber is calculated as the chamber is pressurized. If no substrate is present, the lower chamber will wheel outward and have a room to expand. In contrast, if the substrate is present and chucked in the carrier head, the volume of the lower chamber will be limited and consequently the pressure in the lower chamber will rise faster. Thus, the substrate can be detected by determining whether the derivative dP / dt exceeds the threshold C ₁ . This threshold C ₁ can be determined experimentally. If the derivative dP / dt exceeds the threshold C ₁ , the substrate is present. On the other hand, if the derivative dP / dt does not exceed the threshold C ₁ , the substrate does not exist. Lower floating chamber 234 may be returned to vacuum after the substrate detection procedure is complete.

Referring to FIG. 8, in another embodiment, the carrier head 100a includes a disc shaped inner support plate 120a that provides a barrier between the floating upper chamber 236a and the floating lower chamber 234a. The inner thin film 116a defines a central portion 200a, an edge portion 240 fixed to the base assembly 104a, and an annular inner region or flap 242 fixed to the outer edge 244 of the inner support plate 120a. It is a circular sheet having. The central portion 200a of the inner thin film extends below the inner support plate 120a to form the floating lower chamber 234a, while being sealed by the edge 240 of the support plate and the inner thin film 116a. The volume between the base assemblies forms the floating upper chamber 236a. The disc shaped inner support plate 120a increases the contact area between the floating upper chamber 236a and the floating lower chamber 234a.

The outer support structure 230a includes a ring-shaped portion 170a, an annular flange portion 178a that projects upwardly from the inner edge of the ring-shaped portion 170a, and a protrusion extending downward from the outer edge of the ring-shaped portion 170a. A top surface of the outer thin film 188a, including 172a. The flange portion 178a of the outer support structure 230a may be fixed to the inner support plate 120a or the inner thin film 116a. Optionally, outer support structure 230a may be free floating in outer chamber 238.

The carrier head 100a functions in a similar form to the carrier head 100. In particular, the pressure of the floating upper chamber 236a controls the contact area of the inner thin film to the upper surface of the outer thin film, and the pressure of the floating lower chamber 234a controls the pressure applied to the substrate in the load region. To remove the substrate from the polishing pad, the floating top chamber 236a is pressed to exert a protrusion 172a on the outer support structure 230a against the top surface of the outer thin film 118a. This compresses the outer thin film against the substrate such that a tight fluid seal is formed therebetween. The floating lower chamber is then evacuated and the outer chamber 238a is depressurized to pull the outer membrane against the inner membrane. Finally, the floating upper chamber is depressurized to pull the substrate out of the polishing pad.

Referring to FIG. 9, in another embodiment, the carrier head 100b includes an outer membrane 118b having an annular lip 250. When the outer chamber 238c was evacuated, it was filed on August 31, 1998 by Zuniga et al. Under the name " carrier head for chemical mechanical polishing " and assigned to the assignee of the present invention and referenced herein. As disclosed in 09 / 149,806, the lip 250 can be pulled against the substrate 10 to form a seal and improve vacuum chucking of the substrate when the outer chamber 238c is evacuated.

Referring to FIG. 10, in another embodiment, the carrier head 100c includes a single flexible membrane 118c and a disc shaped support structure 122c. The central portion 260 of the flexible membrane 118c extends below the support structure 122c to provide a mounting surface for the substrate to engage. The perimeter 262 of the flexible membrane extends upwardly in the vicinity of the cylindrical edge 264 of the support structure. Periphery 262 is an inner flap 266 clamped between clamp ring 268 and upper surface 270 of support structure 122c, and a spacer ring clamped between retaining ring 110c and annular body 140c. Outer flap 272 circumferentially surrounding 120c. Thus, the volume between the support structure 122c and the flexible membrane 118 forms a pressurized floating lower chamber 234c, which is sealed by the base assembly 104 and the inner and outer flaps 266 and 272. The volume between the support structures 122c forms a pressable floating upper chamber 236c.

One pump may be connected to the floating upper chamber 236c by a passage 154 in the gimbal rod 150, and the other pump may include a passage 280 in the housing 102, a passage 280 in the base assembly 104c. And a passage 282 through the support structure 122c to the floating lower chamber 234c. Fixtures 284 and 286 provide attachment points for flexible tube fabrication that fluidly couple the passageway through the support assembly and the base assembly to connect passageway 134 to floating lower chamber 234c.

The bottom surface 274 of the support structure may have a protrusion 276 extending downward from the outer edge of the structure. In addition, a plurality of grooves 278 may be formed in the lower surface 274 of the support structure 122c so that fluid may be discharged between the support structure and the flexible membrane.

By controlling the pressure in the upper and floating lower chambers, the contact pressure and load region of the thin film 118c flexible to the substrate can be controlled. To remove the substrate from the polishing pad, the floating upper chamber 236c is pressed to lower the protrusion 276 to form a seal between the substrate and the flexible thin film, and the floating lower chamber 234c vacuums the substrate into the carrier head. Vacuumed to chuck.

Referring to FIG. 11, in another embodiment, the carrier head 110d, similar to the configuration for the carrier head 100c, supports the support structure 122d to fluidly couple the upper chamber 236d to the lower chamber 234d. It may include an internal valve 300. The valve 300 includes a disc shaped valve body 302 and an annular valve flange 304. The valve body 302 may be secured to the opening 306 in the support structure 122d, and the valve flange 304 may be securely secured to the upper surface 312 of the support structure 122d. The annular seal 308 is secured to the shallow depression 310 in the upper surface 312 surrounding the opening 306. Multiple vertical channels 314 may be formed through the disk-shaped valve body 302 on the seal 308 to fluidly couple the lower chamber 234d and the upper chamber 236d. The valve flange 304 functions as a bend spring that biases the valve body 302 downward so that the vertical channel 314 is adjacent the annular seal 308 to close the valve. However, if the valve body 302 is forced upward, the seal will no longer contact the valve body and fluid will leak through the channel 314. As such, valve 300 will be open and lower chamber 234d and upper chamber 236d will be in fluid communication through channel 314.

The valve 300 can be used to detect whether the substrate is chucked to the flexible thin film 118d. In particular, the first measurement of pressure in the upper chamber 234d may be performed with a pressure gauge (not shown) after the upper chamber is pressurized but before the lower chamber is evacuated. The upper chamber 234d must be separated from the pump that pressurizes or evacuates the chamber. Next, after the lower chamber is evacuated, a second measurement of the pressure in the upper chamber is performed by a pressure gauge. The first and second pressure measurements can be compared to determine if the substrate was successfully vacuum chucked to the carrier head.

If the substrate was successfully vacuum chucked, the flexible thin film 118d would be kept in close proximity to the substrate by the low pressure pocket between the substrate and the flexible thin film. Eventually, the valve 300 will remain biased in the closed position and the pressure in the upper chamber may remain constant or increase. On the other hand, if the substrate is not present or is not vacuum chucked to the carrier head, the flexible thin film 118d will be deflected upward when the lower chamber 234d is evacuated. Thus, the flexible membrane will apply an upward force to the valve body 302 and open the valve 300, so that the lower chamber 234d and the upper chamber 236d will be fluidly coupled. This allows fluid to exit through the lower chamber 234d and out of the upper chamber 236d. As a result, the final pressure of the upper chamber will be lower than if the substrate was properly attached unless the substrate was present or not vacuum chucked to the flexible thin film. This difference can be detected to determine if the substrate has been chucked to the carrier head. A similar apparatus and method for detecting substrate presence in a carrier head has been filed by Boris Govzman et al. On May 23, 1997 under the name "carrier head with substrate detection mechanism for chemical mechanical polishing systems". US Patent Application No. 08 / 862,350, assigned to the assignee and referenced herein.

Various configurations for the carrier head to carry out the invention will be possible. For example, the floating upper chamber can be annular or cubic in volume. The upper and lower chambers may be separated by a flexible thin film or by a relatively rigid support or support structure. The substrate may be in direct contact with the flexible thin film in the variable load region, or the inner thin film may contact the inner surface of the outer thin film in the variable contact region. The support structure may be ring-shaped or disc-shaped with openings.

Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that modifications may be made without departing from the spirit and scope of the invention. Also, the scope of the invention is defined by the appended claims.

According to the present invention a uniform chemical mechanical polishing of the substrate is provided.

Claims (32)

As a carrier head 70 for a chemical mechanical polishing device, First pressurizable chamber 234 at least partially constrained by first flexible membrane 116—the lower surface of the first flexible membrane 116 may apply pressure to a substrate in a load region having a controllable size. Providing a first surface for application; And A second pressurizable chamber 236 positioned to apply downward force to the first chamber, The first chamber and the second chamber are configured to control the pressure at which the first pressure in the first chamber is applied to the substrate in the load region and the second pressure in the second chamber to control the size of the load region. Carrier head for chemical mechanical polishing apparatus, characterized in that. The method of claim 1, And a vertically movable base (104) forming at least a portion of the upper boundary of the second pressurizable chamber (236). The method of claim 2, And a housing (102) connectable to the drive shaft (74) and a third chamber (108) disposed between the housing (102) and the base (104). The method of claim 3, wherein And a retaining ring (110) connected to said base (104) to hold said substrate under said carrier head (70). The method of claim 1, A carrier head for a chemical mechanical polishing apparatus, characterized in that a rigid member (202) forms a boundary between the first chamber and the second chamber. The method of claim 1, A carrier head for a chemical mechanical polishing device, characterized in that a flexible member (204, 206) forms a boundary between the first chamber and the second chamber. The method of claim 1, And said second chamber generally defines an annular volume. The method of claim 1, And said second chamber generally defines a cubic volume. The method of claim 1, A bottom surface of the first flexible membrane 116 provides a mounting surface for the substrate. The method of claim 1, And a second flexible membrane (118) extending below the first flexible membrane (116) to provide a mounting surface for the substrate. The method of claim 10, A volume between the first flexible membrane (116) and the second flexible membrane (118) forms a third pressurizable chamber (238). The method of claim 11, And a first support structure 120 disposed in the first chamber, wherein the first flexible membrane 116 extends near an outer surface of the first support structure 120. Carrier head for polishing device. The method of claim 12, A second support structure 230 disposed in the third chamber 238 between the first flexible thin film 116 and the second flexible thin film 118 and disposed to surround the first support structure 120. Carrier head for chemical mechanical polishing apparatus further comprising. The method of claim 13, And the second support structure (230) is generally annular in shape. The method of claim 14, And a first spacer ring 122 disposed in the third chamber 238 between the first flexible thin film 116 and the second flexible thin film 118, wherein the first flexible thin film 116 is provided. Is sinuous between the first structure 120 and the first spacer ring 122 near the inner surface of the first spacer ring 122 and outward near the upper surface of the first spacer ring 122. A carrier head for a chemical mechanical polishing apparatus, characterized by extending in a path. The method of claim 15, And a second spacer ring 232 disposed outside the third chamber 238 on the second support structure 230, wherein the second flexible thin film 118 is the second spacer ring 232. Characterized in that it extends outwardly near the inner surface and outward near the upper surface of the second spacer ring 232, between the second support structure 230 and the second spacer ring 232. Carrier head for chemical mechanical polishing apparatus. The method of claim 16, A portion of the first spacer ring 122 extends over a portion of the second spacer ring 232 such that pressurization of the second chamber applies a downward force to the second support structure 230. Carrier head for chemical mechanical polishing device. The method of claim 17, The second support structure (230) includes a carrier head for a chemical mechanical polishing apparatus, characterized in that it comprises an annular projection extending downward to contact the upper surface of the second flexible membrane (118). The method of claim 10, The first flexible membrane 116 can move in contact with the upper surface of the second flexible membrane 118 in the load region to apply pressure to the substrate. . The method of claim 19, The lower surface of the first flexible membrane 116 is textured to provide a fluid flow therebetween when the first and second flexible membranes 118 contact. head. The method of claim 1, And further comprising a first support structure (120) disposed in the first chamber, wherein the first flexible membrane (116) extends near the outer surface of the first support structure (120). Carrier head for mechanical polishing device. The method of claim 21, Carrier head for chemical mechanical polishing apparatus, characterized in that the first support structure (120) is generally annular shape. The method of claim 21, The first support structure (120) comprises a generally disc shaped body having a plurality of openings. The method of claim 21, And a first spacer ring 122 positioned outside the first chamber, wherein the first flexible thin film 116 is near the inner surface of the first spacer ring 122 and the first spacer ring ( 122. A carrier head for a chemical mechanical polishing apparatus, characterized in that it extends outwardly near the upper surface of the first surface, in a winding path between the first structure (120) and the first spacer ring (122). A carrier head for chemical mechanical polishing, Base 104; A first flexible thin film portion 116 extending below the base 104 and forming a first pressurizable chamber 234-a lower surface of the first flexible thin film portion 116 has a controllable size Providing a mounting surface for applying pressure to a substrate in the region; And A second flexible thin film portion 204, 206 that couples the first flexible thin film portion 116 and the base 104 and forms a second pressurizable chamber 236, the first pressable The first pressure in the chamber 234 controls the pressure applied to the substrate in the load region, and the second pressure in the second chamber controls the size of the load region. . A carrier head for chemical mechanical polishing, Base 104; A first flexible thin film portion 118 extending below the base to form a first pressurizable chamber 238, wherein a lower surface of the first flexible thin film portion provides a mounting surface for the substrate; A second flexible thin film portion 116 extending below the base 104 and forming a second pressurizable chamber 234-the lower surface of the second flexible thin film portion 116 has a load having a controllable size In contact with the top surface of the first flexible thin film in the region; A third flexible thin film portion 202, 204 that couples the base 104 and the second flexible thin film portion 116 and forms a third pressurizable chamber 236, wherein the second pressurizable The first pressure of the chamber 234 controls the pressure applied to the substrate in the load region, and the second pressure of the third pressurizable chamber 236 controls the size of the load region. Carrier head for mechanical polishing. A carrier head for chemical mechanical polishing, A first biasing member comprising a first pressure chamber 234, wherein a lower surface of the first pressure chamber provides a first surface for applying a load to a substrate in a load region having a controllable size. Limited by one thin film 116; And A second biasing member 202, 204, and 206 connected to the first biasing member, wherein the second biasing member controls a vertical position of the first biasing member, thereby providing a second biasing member. Is controlling the size of the load region and the first biasing member controls the pressure applied to the substrate in the load region. A carrier head for chemical mechanical polishing, A flexible thin film 118 that provides a mounting surface for the substrate; Means (202, 204, 236) for controlling the size of a load region to which a load is applied to the substrate; And Means (116, 234) for controlling the pressure applied to the substrate in the load region. A method for chemical mechanical polishing of a substrate, Holding the substrate against the polishing pad with a carrier head; Applying a load to a substrate in a load region into a first chamber (234) in the carrier head; Controlling the size of the load region with a second chamber (236) in the carrier head; Forming a relative motion between the substrate and the polishing pad. delete delete delete

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