KR20030029119A - Apparatus and method for chemical mechanical polishing of substrates - Google Patents

Abstract

The present invention discloses a chemical mechanical polishing system having a wafer carrier assembly. The wafer carrier assembly includes a wafer carrier support frame 52 and a wafer carrier head housing 56 rotatably mounted on the wafer carrier support frame 52, the wafer carrier base extending the wafer carrier base to the wafer carrier head. A bladder bellows 98 is operatively connected to the housing. Retaining ring 96 is also provided, which retaining ring bearing 142 allows for relative axial movement while suppressing relative radial movement between retaining ring 96 and wafer carrier head housing. And retaining ring bellows 144 to urge retaining ring 96 against the polishing member. The chamber formed by bladder bellows 98, the wafer carrier base, and the wafer carrier housing may be pressurized to load the wafer carrier base and wafer against the polishing member, regardless of any frictional load on the retaining ring.

Description

Apparatus and method for chemical mechanical polishing of a substrate {APPARATUS AND METHOD FOR CHEMICAL MECHANICAL POLISHING OF SUBSTRATES}

Semiconductor manufacturing is becoming more complex as the density of semiconductor devices increases. Such high density circuits typically require tightly spaced metal interconnect lines and multiple layers of insulating material such as oxides formed between and on the interconnect lines. Surface planarity of the semiconductor wafer or substrate is degraded as the layers are deposited. Usually, the surface of the layer has a topography consistent with the underlying layer, and as the number of layers increases, the nonplanarity of the surface becomes more pronounced.

To address these issues, a chemical mechanical polishing process is used. The chemical mechanical polishing process removes material from the surface of the wafer to provide a near plane. More specifically, chemical mechanical polishing processes are also used to fabricate interconnect lines. For example, when depositing copper leads or interconnect lines, a layer of entire metal is deposited on the surface of the wafer with grooves formed in the oxide layer. The metal layer is deposited by sputtering or vapor deposition, or by any other suitable conventional technique. Oxide layers, such as doped or undoped silicon dioxide, are usually formed by chemical vapor deposition (CVD). This metal layer covers the entire surface of the wafer and extends into the grooves. Thereafter, individual leads 16 are formed by removing the metal layer from the surface of the oxide. The CMP process is used to remove surface metal that leaves the leads in the grooves. These leads are insulated from each other by intervening oxide layers.

Generally, a chemical mechanical polishing (CMP) machine is used to execute the CMP process. Several types of CMP machines are used in the semiconductor industry. CMP machines typically use a rotating polishing platen with a polishing pad disposed thereon and a smaller diameter rotating wafer carrier that carries the wafer whose surface is planarized and polished. The surface of the rotating wafer is fixed or pressed against the rotating polishing pad. Slurry is supplied to the surface of the polishing while polishing the wafer.

One example of such a conventional system is disclosed in US Pat. No. 5,964,653. The carrier head disclosed in USP 5,964,653 includes a base and a flexible member connected to the base to form first, second, and third chambers. The pressure inside the chamber can be independently controlled such that the biasing forces of the corresponding portions of the flexible member against the wafer are independently controllable. The carrier head of USP 5,964,653 further comprises a flange attachable to the drive shaft and a gimbal to pivotally connect the flange to the base. The gimbal includes an inner race connected to the base, an outer race connected to the flange to form a gap therebetween, and a plurality of bearings located in the gap.

Since gimbals are used to align the wafer carrier with the polishing pad in known CMP systems, frictional loads on the wafer during polishing cannot be isolated from pressure distribution to the wafer. In particular, multiple degrees of freedom provided by the gimbal may convert the frictional load, which usually extends parallel to the surface of the wafer, into a normal force that extends perpendicularly to the surface of the wafer, unfavorably. In this case, the pressure of the wafer against the polishing pad is directly affected. The coupling of these frictional forces to the wafer affects the pressure distribution across the wafer, which in turn adversely affects the uniformity of material removal from the surface of the wafer. Therefore, there is a need for an improved CMP apparatus and method.

The present invention relates to a novel improved apparatus and method for chemical mechanical polishing of thin disks and, more particularly, to a substrate or wafer carrier for a chemical mechanical polishing machine.

This patent application is related to co-pending USP 09 / 628,471 and USP 09 / 628,962, the entire contents of which are incorporated by reference.

1 is a perspective view of a chemical mechanical polishing apparatus according to the present invention.

FIG. 2 is an enlarged perspective view of the wafer carrier assembly shown in FIG. 1.

3 is a cross-sectional view of the wafer carrier assembly shown in FIG. 2 showing a fluid connection system, taken along line 3-3.

4 is another cross-sectional view of the wafer carrier assembly shown in FIG. 2 showing an electrical connection system.

5 is a plan view of the wafer carrier head of the present invention.

6A, 6B and 6C are cross-sectional views of the wafer carrier head shown in FIG. 5 taken along lines A-A, B-B and C-C, respectively.

7 is a schematic representation of the pressure generated by the wafer carrier head of FIGS. 6A-6C against a wafer during a chemical mechanical polishing process in accordance with the present invention.

8 is a plan view of a flexible thin film according to an embodiment of the present invention.

9A and 9B are cross-sectional views of the flexible thin film of FIG. 8 taken along lines A-A and B-B, respectively.

10A and 10B are exploded perspective views of the wafer carrier head shown in FIGS. 6A-6C.

11 is a schematic block diagram of a control system according to an embodiment of the present invention.

12 is a cross-sectional view of the wafer carrier head shown in FIG. 5 taken along the center according to another embodiment of the present invention.

13A and 13B are cross-sectional views of the flexible thin film of FIG. 8 taken along lines A-A and B-B, respectively, in accordance with another embodiment of the present invention.

It is therefore an object of the present invention to provide an improved chemical mechanical polishing apparatus and method.

More specifically, in one aspect of the present invention, a CMP apparatus and method comprising a wafer carrier capable of holding a wafer so that pressure distribution of the wafer to the polishing pad during polishing is independent of the frictional load applied on the wafer. Is provided.

In another aspect of the invention, a wafer pressure system for deflecting a wafer with respect to a polishing pad, and a wafer carrier having a retaining ring for wafer retention, wherein the pressure of the retaining ring against the polishing pad causes the wafer to deflect. A chemical mechanical polishing apparatus is provided that is controlled regardless of the wafer pressure system.

In another aspect of the invention, a wafer carrier comprises a flexible thin film having a plurality of chambers formed therein, each pressing against a wafer in a corresponding local region or region on the wafer, thereby providing a The amount is selectively controlled, thus controlling the degree of material removal rate in the corresponding local area on the wafer during the CMP process.

The above and other objects of the present invention provide a chemical mechanical polishing using a wafer carrier support frame, a wafer carrier head housing rotatably mounted on the wafer carrier support frame, and a wafer carrier assembly having a wafer carrier base. Achieved by the system, wherein the wafer carrier base transfers rotational torque from the wafer carrier head housing to the wafer carrier base regardless of the frictional load transferred from the wafer carrier base to the wafer carrier head housing during chemical mechanical polishing operation. A bellows for operatively connecting the base to the wafer carrier housing, if possible.

More specifically, the wafer carrier assembly includes a wafer carrier support frame, a wafer carrier head housing rotatably mounted on an e-wafer carrier support frame, and a wafer carrier base, the wafer carrier base from the wafer carrier head housing. And a bladder bellows for operatively connecting the wafer carrier base to the wafer carrier head housing such that rotational torque is transmitted to the wafer carrier base. The wafer carrier assembly includes a retaining ring operably connected to a retaining ring bearing that permits relative axial movement while constraining relative radial motion between the retaining ring and the wafer carrier head housing, and pressing the retaining ring against the polishing member. And a retaining ring bellows operatively connected to the retaining ring bearing. The chamber formed by the bladder bellows, wafer carrier base and wafer carrier head housing may be pressurized to load the wafer carrier base against the polishing member regardless of any frictional load on the retaining ring.

In another embodiment, the wafer carrier further comprises a flexible member connected to the base and having a plurality of chambers formed therein, the lower surface of the flexible member defining a plurality of inner portions each associated with the plurality of chambers. Provided on the wafer receiving surface to form a local region or area on the surface of the wafer, the pressure inside each of the chambers being independently controllable.

The accompanying drawings are incorporated in and form a part of this specification, and illustrate embodiments of the invention, which are a description of the invention and the description serve to explain the principles thereof.

An improved chemical mechanical polishing (CMP) system is provided. More specifically, the inventors considerably favor a chemical mechanical polishing apparatus and method comprising a wafer carrier capable of holding the wafer such that the pressure distribution of the wafer to the polishing pad is independent of the frictional load applied on the wafer during the polishing process. Developed. Further, in another embodiment, the chemical mechanical apparatus and method includes a wafer carrier having a wafer pressure system for biasing the wafer relative to the polishing pad, and a retaining ring for retaining the wafer, the method comprising: The pressure is controlled independent of the wafer pressure system which deflects the wafer. Further, in another embodiment of the present invention, the wafer carrier comprises a flexible thin film having a plurality of chambers formed therein, each of these chambers being pressed against the wafer independently and corresponding corresponding zones on the wafer surface. Or form a region. These chambers are pressurized independently to selectively control the amount of pressure applied to the chamber, thus controlling the extent of material removal rate in the corresponding local zone on the wafer surface during chemical mechanical processing.

Thus, quite advantageously, the present invention provides a wafer carrier that implements the desired design parameters for wafer retention and pressure application. One of the necessary functions for wafer holding is to support the frictional load on polishing. As can be seen in the prior art, according to the invention these loads are transferred to the spindle bearings without the use of gimbalstructures. In conventional systems, gimbals are typically used to align a wafer carrier with a pad. As mentioned above, with the gimbal device, the frictional load on the wafer is not isolated from the pressure distributed to the wafer during polishing, resulting in uniformity problems. In contrast, the present invention uses machine precision to isolate friction from pressure dispensed on the wafer, uses machine precision to align retaining rings and pads, and conforms behind the wafer by using a flexible thin film that aligns the wafer with the polishing pad surface. Is allowed. In addition to the independence of the pressure distribution from the frictional load on the wafer, the present invention also provides the independence of the retaining ring from the wafer pressure system, allowing independent control of the retaining ring pressure or position as desired from the nominal polishing pressure. This feature can improve the uniformity of the chemical mechanical polishing process by controlling the edge effects caused by the pads.

It will now be described in detail with respect to specific embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention has been described in connection with specific and preferred embodiments, those skilled in the art will understand that the invention is not intended to be limited to these embodiments. On the contrary, it is intended that the present invention cover alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Referring now to the drawings, the same components are designated by the same reference numerals throughout the several views, in which the chemical mechanical polishing apparatus 30 according to the invention comprises a plurality of polishing stations for supporting an abrasive polishing pad 34. 32), loading and cleaning combination station 36, and wafer carrier assembly 38.

The chemical mechanical polishing (CMP) apparatus 30 is provided to process one or more substrates and is particularly suitable for polishing the surface of the silicon wafer "W" to remove undesirable excess material. Several processing parameters must be accurately controlled and monitored to maximize wafer processing throughput, ie chemical mechanical polishing throughput. For example, slurry flow distribution to the platens, pressure distribution of the wafer against the platens, relative speeds of the wafer and polishing pad, and state of the polishing pad are important factors in determining the throughput of the chemical mechanical device.

The chemical mechanical polishing apparatus 30 includes a machine base 40 on which a table top 42 is mounted. This table top 42 supports a series of polishing stations 32 and loading and cleaning combination stations 36. The polishing station 32 and the loading / cleaning station 36 are linearly aligned. The loading / cleaning station 36 is capable of receiving individual wafers from a loading device (not shown), cleaning the wafers, loading the wafers into the wafer carrier assembly 38, wafers from the wafer carrier assembly 38. A plurality of functions, including the ability to receive them, to clean the wafers again, and finally to transfer the wafers to the loading / cleaning station 36.

Each polishing station 32 includes a rotatable platen 44 and an abrasive polishing pad 34 releasably fixed on the platen 44. The platen 44 is preferably dimensioned to have a diameter that is approximately 1.5 to 3 times larger than the diameter of the wafer being polished. This platen 44 may be a rotating aluminum or stainless steel plate driven by suitable means (not shown). Preferably the platen drive means and other components susceptible to generation of contaminating particles are located below the platen 44 and thus below the polishing pad 34. For most polishing processes, platen 44 rotates at approximately 50-500 revolutions per minute (rpm), although other speeds may be used.

The polishing pad 34 is preferably formed of a flexible and often porous material with a flexible polishing surface. The polishing pad is fixed to the platen by a pressure-sensitive adhesive layer. The polishing pad 34 may have a hard top layer and a softer bottom layer. This top layer may be polyurethane mixed with a filler. The bottom layer may consist of a compressed sensation fiber leached by urethane.

Each pad face may be stripped off by a pad conditioner 46 with a conditioner head 50 disposed on the arm portion 48, which arm portion 48 may be peeled off at any particular radius on the pad. Position and may be loaded against the pad while the relative motion is being generated. The pad conditioner 46 maintains the state of the polishing pad 34 to effectively transfer the slurry to the polishing interface of the pad and the wafer. The pad conditioner includes a wash station to remove slurry and wear material.

Slurry containing abrasive particles, such as silicon dioxide, in the transfer fluid, to the surface of the polishing pad 34 by means of a slurry supply port in the center of the platen 44 or a distributor tube on a pad (not shown), and If possible, chemical reaction catalysts such as potassium hydroxide are supplied. Alternatively, the slurry can be suspended through the wafer carrier to the surface of the pad. A sufficient amount of slurry is provided to maintain the maximum amount of removal of material from the surface of the wafer during polishing.

Above the machine base is a wafer carrier support frame 52. This wafer carrier support frame 52 is supported for linear movement along the table top 42 along the x axis along a suitable track. Wafer carrier support frame 52 supports wafer carrier 38 for movement within the xz-plane. The wafer carrier 38 receives and holds the wafers and presses the wafers against the polishing pad 34 on the platen 44 of each polishing station 32 for polishing the wafers. Wafer carrier support frame 52 and wafer carrier 38 preferably include a sealed cover plate and enclosure to minimize contamination of wafers by particles generated by their components.

During actual polishing, the wafer carrier 38 is located on or above the platen 44 of the polishing station 32. An actuator held inside the support frame 52 lowers the wafer carrier 38 and the wafer attached to the wafer carrier 38 with respect to the wafer carrier support frame 52 in contact with the polishing pad 34. . The wafer carrier 38 causes the wafer to be pressed against the polishing pad 34.

Referring to FIGS. 2, 3 and 4, wafer carrier 38 typically includes a wafer carrier head 56, a support having an actuator (not shown) for moving the wafer carrier 38 within the xz-plane. Frame 52, and drive assembly 58. The drive assembly 58 includes a mounting bracket 60 rigidly mounted on a support frame 52 (not shown in FIG. 3 or 4). This mounting bracket 60 has a through bore 62 having an axis extending approximately vertically above the table top 42. The drive assembly 58 also includes a cylindrical head shaft 64 connected to the mounting flange 60 rotatably concentrically by a suitable bearing assembly 66. This head shaft 64 rigidly supports the wafer carrier head body 68. The electric motor 70 rotates the wafer carrier head 56 about the wafer carrier frame 52. Preferably, a large diameter carrier motor 76 is used to provide clearance for the electrical conduits and through bores 62 containing fluid. The carrier motor 70 includes an electric motor stator 72 mounted on the mounting flange 60 and an electric motor rotor 72 mounted on the head shaft 64. Preferably, the motor 70 is a brushless DC motor to minimize the generation of contaminant particles. The components of the motor may be surrounded by a housing or protected by a cover to protect against inadvertent slurry splashes or other contaminants during operation of the chemical mechanical polishing apparatus / process.

To load the wafer against the surface of the polishing pad 34, the wafer carrier 38 and the wafer carrier head 56 are moved in the z direction until the wafer is pressed against the polishing pad 34. The wafer carrier 38 is lifted so that the wafer carrier head 56 and wafer are lifted away from the polishing pad while transferring the wafer between the polishing station 32 and the loading / cleaning station 36.

Preferably, the chemical mechanical polishing apparatus applies a force of approximately 2 to 10 pounds per square inch (psi) to the wafer, and the pressure may vary during polishing. The electric motor 70 rotates the wafer carrier head 56 at approximately 300 to 500 rpm and other speeds may be appropriately selected. As mentioned above, the platen 44 is rotated at about 300 to 500 rpm. The rotational speeds of the wafer carrier head and platen are preferably about the same, but are not completely consistent to average pad non-uniformity. Other speeds may be used depending on the application.

3 and 4 are different cross-sectional views illustrating the fluid system and the electrical system, respectively. 3 and 4, the tubular conduit 76 extends concentrically inside the head shaft 64. The tubular conduit 76 extends almost the length of the head shaft 64. This tubular conduit 76 includes a plurality of passageways 78, 80 for electrical and fluid lines. On top of this tubular conduit 76 both electrical rotary coupling or rotary electrical-pass-through 82 and fluid rotary coupling or rotary fluid passage 84 are actuated. Possibly mounted. Thus, the electrical and fluid circuits are driven from the non-rotating wafer carrier support frame 52 through the rotary couplings 82 and 84, respectively, and through the rotary head shaft 64. Operatively extended to 56). In particular, the plurality of fluid passages as well as the electrical circuit passages extend through the tubular conduits 76, allowing the electrical source and the plurality of pumps and / or valves to be operably connected to the wafer carrier head 56.

In the embodiment of FIG. 4 shown, an electrical passage 78 is provided for an electrical sensor that can be provided on the wafer carrier head 56 and for an electrical coupling of the electric motor. Each fluid chamber formed within the wafer carrier head 56, bladder, and retaining ring bellows, as described above, has six fluid passages (two of which are adapted to fluidly connect six independently controlled fluid sources). Also shown in FIG. 3 as 61, 63. This configuration allows the wafer carrier head 56 to act as a pressure change in a local area or region of the wafer surface relative to the polishing pad 34, as described in more detail below. This fluid passage is also used to pneumatically power the wafer carrier head 56 in such a way as to vacuum chuck the wafer to the bottom of the wafer carrier head 56.

3 and 4, the head shaft 64 includes a head shaft flange 86 extending radially from the bottom of the head shaft 64. Head shaft flange 86 is generally a disc-shaped body and includes passages 88 and 90, which correspond to electrical and fluid passages 78 and 80 in conduit 76.

In particular advantage, wafer carrier head 56 provides pressure distribution to the wafer without being affected by frictional loads within the machine. Specifically, referring to FIG. 5, a plan view of the wafer carrier 56, showing sections A-A, B-B, and C-C, respectively, corresponding to FIGS. 6A, 6B, and 6C. 6A, 6B and 6C and 10, wafer carrier head 56 is generally referred to as carrier head housing 68, carrier head base 92, flexible thin film 94 (also referred to as partitioned thin film). And a retaining ring 96, wherein the flexible membrane 94 has a backing plate on the carrier head base 92 to form a closed bladder 95 with a chamber formed therein. Is mounted on. The wafer carrier 38 of the present invention has a bladder 95 in the carrier head body 68 in such a way that the carrier head base 92 can accommodate misalignment between the wafer and the polishing pad 34. Use bladder bellows 98 to connect.

The wafer carrier body 68 is connected to the head shaft flange 86 by a wafer carrier top plate 100. The carrier head base 92 is operably connected to the carrier body by bladder bellows 98. Bladder bellows 98 is operably connected to and transfers torque to carrier base 92 and carrier head body 68 to rotate the head about an axis of rotation substantially perpendicular to the surface of polishing pad 34. . Bladder bellows 98 has a cavity that is pressurized, which is formed as a bias pressure, which balances the force of the flexible thin film on the wafer. This bias pressure may be changed to control the force applied on the thin film. Bladder bellows 98 is formed of any suitable material that allows transmission of torque, provides compliance in the z direction, and has a pressure capacity in the range of about 0 to 40 psia. Bladder bellows 98 is preferably formed of metal, but may also be formed of a flexible material, such as silicone or elastomer.

Both wafer carrier body 68 and wafer carrier top plate 100 include a plurality of through passages corresponding to electrical and fluid passages 78, 80 of conduit 76. In a preferred embodiment, six fluid system passages are formed in the wafer carrier top plate 100, two of which provide fluid to pressurize the bladder and retaining ring bellows, as described below. The fluid system passageway, with the remaining four being a fluid system passageway that pressurizes an optional region of the flexible membrane. The fluid passageway of the wafer carrier body 68 is fluidly connected to each fluid passageway in the wafer carrier base 92 by suitable pressure lines (not shown) that extend within the bladder bellows 98. An example of one fluid system passageway is shown in FIG. 6A, where the fluid passageway 101 extends through the wafer carrier top plate 100, and the fluid passageway 102 extends through the carrier head base 92, These fluid passages 101, 102 are connected by a flexible pressure line 105. 6C illustrates another fluid system, with passages 103 and 104 extending through wafer carrier top plate 100 and carrier head base 92 and connected by flexible pressure lines 107. Other similar fluid systems may be used, but are not particularly shown in cross section.

As a particular advantage, the carrier head base 92 is connected to the wafer carrier head body 68 by bladder bellows 98. Bladder bellows 98 allows carrier base 92 to pivot about wafer carrier head body 68 such that wafer carrier base 92 remains substantially parallel to the surface of polishing pad 34. Can be. Specifically, bladder bellows 98 causes wafer carrier base 92 and a wafer mounted therein to rotate relative to polishing pad 34 and irregular polishing pad 34 in the wafer as a taper. Pivot to accommodate both misalignment of. Bladder bellows 98 also transmits downward pressure from the head shaft 64 to the carrier head base 92 regardless of the lateral load. Thus, bladder bellows 98 is isolated to form any lateral load from the wafer, such as a shear force generated by friction between the wafer and polishing pad 34. Thus, the pressure exerted by the flexible thin film 94 on the wafer against the polishing pad 34 is independent of any lateral load generated during the polishing process. In addition, the frictional load is isolated from the distribution of pressure on the wafer.

The inner surface 122 of the retaining ring 96, in relation to the bottom surface of the flexible thin film 94, forms a wafer receiving recess. As described in detail below, the retaining ring 96 prevents the wafer from leaving the wafer receiving recess and transfers lateral load from the wafer to the wafer carrier head body 68.

Flexible thin film 94 is connected to and extends below carrier base 92. The bottom surface of flexible thin film 94 provides a wafer receiving surface. The flexible thin film 94, when sealed to the base 92, has a first central chamber 106, a second annular chamber 108, a third annular chamber 110, and a fourth annular chamber 112. Form a closed bladder. While four chambers are shown and described, a plurality of different numbers of chambers may be used, and the invention is not limited to four chambers. The flexible thin film 94 is usually a circular sheet formed of a flexible and elastic material such as high strength silicone rubber. Preferably, the flexible thin film 94 is formed of a material having a Shore-A durometer hardness of 40 to 80. Flexible thin film materials should have good bonding properties with stainless steel or other backing plates and exhibit chemical resistance to acids and bases.

As a particular advantage, retaining ring 96 and retaining ring bellows 144 are provided. This aspect of the invention allows the lateral loads developed during polishing not to be transferred to the wafer, but to the wafer carrier body 68, or, preferably, to the shaft 64 by the retaining ring 96. do. This offers significant advantages over prior art wafer carriers.

The retaining ring 96 is mounted on an annular retaining ring mounting member 140 that is received in the annular groove of the retaining ring bearing 142. This retaining ring 96 may be retained by screw screws or by any other suitable means for constraining the retaining ring 96 in all directions. In an exemplary embodiment, the retaining ring bearing consists of a flexure member 142. Alternatively, the retaining ring bearing may be made of a hydrostatic bearing (not shown). Bending member 142 is interconnected with wafer carrier head body 68 by retaining ring bellows 144. Retaining ring bellows 144 is pressurized to bias retaining ring 96 relative to the polishing pad. Retaining ring bellows 144 may be formed of any suitable material that provides compliance in the z direction and has a pressure capacity in the range of about 0 to 40 psia. The retaining ring bellows can be made of plastic or metal, but plastic is preferred because the retaining ring bellows does not connect torque to the retaining ring, unlike bladder bellows.

As described above, the inner surface of the retaining ring 96 forms a wafer accommodating recess for accommodating the wafer 97 with respect to the bottom surface of the flexible thin film 94. Retaining ring 96 prevents the wafer from leaving the wafer receiving recess and transfers lateral load from the wafer to wafer carrier head body 68.

The flexure member 142 is further interconnected with the wafer carrier head body 68 by a thin annulus 146. In other embodiments, the flexure member 142 may be replaced with a bearing to allow relative movement. The thin annulus 146 allows vertical motion of the retaining ring 96 without affecting the load on the retaining ring 96. As an important advantage, this results in a lateral load on the retaining ring 96, regardless of the pressure of the retaining ring 96 against the polishing pad 34, and regardless of the pressure of the wafer against the polishing pad 34. Enable delivery. Since the pressure exerted by the retaining ring 96 on the polishing pad 34 can be controlled independently and precisely, the present invention enables control of edge effects such as edge high speed polishing. The load contribution by flexure member 142 may be measured by strain gauge 151 located on thin annulus 146 and may be minimized by the vertical movement of the wafer carrier by the actuator.

As described above, and as shown in more detail in FIGS. 8, 9A, and 9B, the flexible membrane 94 is connected to the back plate or carrier base 92, including a plurality of chambers 106, 108, 110, 112. To form a closed bladder. For example, the flexible membrane shown in FIG. 3 includes four concentric flanges 114, 116, 118 and 120 extending vertically, which, when connected to the carrier base 92, have a first central circular chamber 106, which is A second annular inner chamber 108 surrounding the first central circular chamber 106, a third annular intermediate chamber 110 surrounding the second annular inner chamber 108, and a third annular intermediate chamber 110. A surrounding fourth annular outer chamber 112 is formed. Pressurization of the chamber controls the downward pressure of the wafer against the polishing pad 34.

The flexible thin film may be composed of any suitable material, such as a flexible elastomer. Preferably, the flexible thin film is a silicone rubber material having Shore-A durometer hardness in the range of about 40-80. This flexible thin film should have good bonding properties with stainless steel and exhibit chemical resistance to acids and bases.

The first annular flange 114 may be secured in a first annular depression or groove on the bottom surface of the carrier base and is releasably received within the first annular recess. 124 and appropriately locked (locking). Similarly, the second, third and fourth insertion rings 126, 128 and 130 lock the second, third and fourth annular flanges, respectively, into the second, third and fourth annular recesses or grooves.

The pump or other suitable adjustable fluid pressure source (not shown) is a suitable fluid that extends through bladder bellows 98 through a rotating fluid coupling, conduit, head shaft flange 86, wafer carrier head body 68. And is operatively connected to the first chamber 106 by a suitable first fluid circuit extending through the line and through the wafer carrier head base 92. Similarly, second, third and fourth pumps or other adjustable fluid pressure sources are operably connected to the second, third and fourth chambers.

If the pump forces a gas, such as a fluid, preferably air, into one of the chambers, the pressure in that chamber will increase, and the front of the flexible thin film will be forced downward or outward relative to the wafer. This in turn forces the wafer against the polishing pad, since each of the chambers can be pressed independently, this allows selected local areas of the wafer to be polished at a faster rate than other areas.

More specifically, in a preferred embodiment, the flexible membrane 94 has a first annular inner portion 132, a second annular inner portion, respectively positioned below the first, second, third and fourth chambers. 134, a third annular intermediate portion 136 and a fourth annular inner portion 138. As such, the pressure in the chambers can control the downward pressure applied to the corresponding portion of the wafer relative to the polishing pad by each flexible thin film portion. Although four chambers have been described, two or more of any other number of chambers may be used, and the invention is not limited to this one illustrated embodiment.

In general, the outermost annular thin film portions 136 and 138 may be used to provide accurate pressure control of narrow edge regions near the edge of the wafer regardless of the pressure applied to the center and middle portions of the wafer. It is narrower in the radial direction compared to the portions 132, 134. In one embodiment, the first thin film portion 132, the second thin film portion 134, the third thin film portion 136 and the fourth thin film portion 138 have radial widths of approximately 30 mm, 30 mm, 25 mm and 15 mm. Have each.

The pressure in the chamber can be controlled independently, maximizing the uniformity of polishing of the wafer. The average pressure in any chamber can be controlled independently of the other chambers during polishing to compensate for non-uniform polishing.

The flexible thin film 94 is shaped to coincide with the backside of the wafer. For example, if the wafer is wrapped or bent, the flexible thin film will substantially fit the contour of the wrapped or bent wafer. In addition, flexible thin films will allow the wafer to conform to variations in thickness on the surface. Thus, particularly advantageously, the load on the wafer will remain almost uniform even if there is surface irregularity on the back side of the wafer.

In operation, the wafer is loaded onto the wafer in the wafer receiving recess while the backside of the wafer is in contact with the flexible thin film. This wafer may be held by vacuum-chuck force from the bottom of the flexible thin film 94. For example, inside one of the chambers of flexible thin film, preferably two chambers can be vacuumed to hold the wafer.

The surface of the wafer and the polishing pad are pressed against each other. The slurry is supplied to the interface between the wafer and the polishing pad. The wafer and polishing pad are typically both rotated, but this is not necessary. Either or both of the wafer and polishing pad may be moved linearly. As the polishing pad and wafer are pressed against each other, the material on the surface of the wafer is removed. An example of a chemical mechanical polishing process carried out with the apparatus of the present invention is disclosed in detail in co-pending USP 09 / 628,962, which is incorporated by reference in its entirety.

Quite advantageously, the present invention independently changes the pressure inside the chamber in the flexible membrane through separate fluid passage systems to urge the corresponding portions 132, 134, 136 against the wafer in corresponding local regions or regions on the wafer surface. To provide that. This allows the apparatus of the present invention to control and vary the amount of material removal in each of the local zones on the wafer surface. In particular, a plurality of zones are formed on the wafer surface, which correspond to chambers formed in the thin film that are associated with the wafer. Preferably, these zones are annular, but may be formed in any suitable shape. Referring to FIG. 7, one example of these zones is schematically illustrated and described in detail in co-pending USP 09 / 628,471. By varying the pressure in the chamber, the polishing rate on the wafer is controlled in local regions on the wafer corresponding to each of the adjacent chambers and portions.

Specifically, the pressure applied to the wafer is individually controlled by the pressure in each chamber as indicated by arrows P ₁ -P ₂ in FIG. 7. As a result, concentric zones or regions on the wafer surface can be polished at different speeds by controlling the pressure in the corresponding chamber 46. Although four zones are shown in the figure, two or more of any suitable number of zones may be formed. Further, although an annular shape is preferred for the outer zones, these zones may be of different shapes and are not limited to the annular shape. In a preferred embodiment, the membrane comprises four chambers forming four zones, which consist of one circular center zone and three annular concentric zones.

Preferably, the chemical mechanical polishing apparatus of the present invention will include one or more in-situ sensors that provide information regarding the progress of polishing of the wafer. The key parameter during polishing is the rate of material removal from the surface of the wafer. Thus, the sensor preferably has a spatial resolution approximately two to five times finer than the width of the area defined by the chamber in the flexible thin film. It will provide information on the removal rate with. This includes the effective spot size as well as the effective sample spacing of the sensor. Sample spacing is a function of the relative velocity between the sensor and the wafer and the sample rate used. The most appropriate type of sensor can vary depending on the type of material being removed. For example, when removing the oxygen layer, known interferometric sensors may be used. Alternatively, when removing the metal layer, a reflectance sensor may be desirable to measure the presence or absence of the metal layer on the surface of the wafer. In addition, the absence of metal may be used to signal the endpoint. One example of a sensor that may be used with the apparatus of the present invention is fully disclosed in co-pending USP 09 / 628,471, which is incorporated by reference in its entirety.

In addition, by using information about initial coating thickness and polishing time on the wafer, endpoint information may be used to calculate an estimate of removal rate, which may be used to predict polishing characteristics of subsequent wafers. Thus, the information provides a means for controlling chemical mechanical polishing parameters, such as pressure velocity when polishing subsequent wafers, etc., which is referred to as " run-to-run " control. In addition, a simultaneous endpoint signal indicated by the reflectance sensor may be used to reduce the removal rate in each local area on the wafer for real time control.

Various methods may be used to provide process control for compartmentalized membrane and feedback techniques. For example, for oxygen removal or polishing, thickness information may be used to measure the removal rate, whereby the pressure is controlled to affect the removal rate independently in either of the zones. The primary description of the removal rate is the application of the Preston's equation, which describes the calculation of the material removal rate (MRR) by the equation MRR = kpPV, where kp is influenced by all processing parameters. Is constant, P is the applied pressure, and V is the relative velocity. Thus, the pressure may be changed to linearly affect the removal rate. Further description of these process conditions can be found in co-pending USP 09 / 628,962.

During metal polishing, the available information represents a local endpoint for a particular zone or area. Using this information, further overpolishing of the wafer surface may be reduced within the zone by reducing the pressure applied to the corresponding compartments. This information may also be used on subsequent wafers to adjust the pressure distribution such that the local endpoint for each pressure zone is reached close to the same time.

11 schematically shows an example of control. 11 shows a block diagram of an example of a control system that may be used in the present invention. This control system generally consists of a process controller 200, a pressure distribution controller 202, a sensor 205 and a wafer database 204. Process controller 200 receives data generating process parameters or recipes, and sends commands to chemical mechanical polishing machine 206 to control the chemical mechanical polishing process. Also connected to the process controller 200 and the chemical mechanical polishing machine 206 is a pressure distribution controller 200 that controls the pressure inside the chamber of the flexible membrane.

Pressure distribution controller 202 receives data via two routes. First, the pressure distribution controller 202 receives from the sensor 205 representative data of the reflectance measurements in each zone directly on the wafer. Pressure distribution controller 202 includes hardware and software that receives reflectance measurements, determines the appropriate pressure adjustments needed (if necessary to adjust) within each zone, and, within the zone in question And selectively transmits a signal to chemical mechanical polishing to appropriately adjust the pressure.

In another embodiment, pre-determined pressure profile values and / or thresholds for each zone are stored in the wafer database 204. These values are then sent to process controller 200 or pressure distribution controller 202. The pressure distribution controller compares these values with the actual, real-time reflectance values from the sensor 205 and sends a signal to the chemical mechanical polishing machine 206 to appropriately adjust the pressure in the respective zones. Additional data, such as the pre-polishing thickness of the wafer 208 and / or the post-polishing thickness of the wafer 210, may be sent to the wafer database to determine appropriate pressure regulation. Might help.

In other embodiments of the invention, model based detection may be used to monitor and control chemical mechanical processes. Specifically, model-based control is provided for real-time adjustment of chemical mechanical polishing process parameters to better tailor the chemical mechanical polishing process to the most effective and efficient process. The above-described detection system is mainly provided for the selective adjustment of the pressure in the zone, providing for almost uniform polishing of local areas of the wafer. This minimizes the occurrence of overpolishing in some areas and under-polishing in other areas. The model-based detection system, in addition to providing near uniform polishing of the wafer, also provides real-time control of several other chemical mechanical polishing systems, thereby improving the overall chemical mechanical polishing process.

Thus, information from the wafer prior to polishing can be quite useful for process control. This is called "feed-forward" control. Information about pre-polished wafers is also useful. This is called "run-to-run" control. In-situ measurements of the wafer surface state during polishing provide "real time" control.

12 is a cross-sectional view of the wafer carrier head shown in FIG. 5 taken along the center in accordance with another embodiment of the present invention. As described above, the thin film consists of four concentric chambers 251, 252, 253, 254. Walls forming these chambers are in turn connected to rigid supports 259, 260, 262 and 262, respectively. These rings are mounted to the bottom of the flexible member 263. The flexible member 263 is mounted to the underside of the bias plate 264. The bias plate 264 includes a plurality of concentric chambers 255, 256, 257, 258, which control the pressures acting on the rigid rings 259, 260, 261, 262, respectively. Thus, once the assembly is positioned for polishing by moving the bias plate 264 to the correct vertical position, the pressure in the chambers 251, 252, 253, 254 is adjusted so that a wafer (not shown) is pressed against the polishing pad (not shown). At the same time, the pressure in the chambers 255, 256, 257, 258 may be changed to control the pressure exerted by the sidewalls of the chamber on the wafer. The pressure in the chambers 255, 256, 257, 258 will be adjusted to maintain the smoothest transition between adjacent thin film sections.

13A and 13B are cross-sectional views of the flexible member in FIG. 8, taken along lines A-A and B-B, in accordance with another embodiment of the present invention. Membrane 270 is divided into annular compartments by a ring of flexible tubing 272, also referred to as chamber dividing tube. The ends of the tubes are sealed together to form a continuous ring. In some locations along the circumference of the chamber dividing tube 272 there is a smaller inner-chamber restrictor or tube 274, which is inside and outside the chamber dividing tube 272. It serves as a flow restriction for fluid flow into the furnace. This allows communication of adjacent pressure compartments. Since the pressure in each compartment is maintained through the active control system, the small limiter or tube 274 causes the pressure inside the chamber dividing tube 272 to be the average of two adjacent chambers. This ensures the most appropriate pressure in the transition from one chamber to another. It is important that the inner-chamber limiter 274 provides a higher flow resistance than the passage from the pressure regulator into the pressure chamber. It is also important that the flow resistance presented by the inner-chamber limiter 274 is the same for each restriction.

To date, improved apparatus and methods for chemical mechanical polishing of semiconductor wafers have been disclosed. The specific embodiments of the invention described above have been presented for the purposes of illustration and description. These examples are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously, many modifications and variations are possible in light of the above detailed description. For example, the apparatus of the present invention may be used in the field of back polishing. These embodiments have been chosen and described in order to best explain the principles and practical application of the invention, thereby facilitating various embodiments that vary from the invention, to those skilled in the art, to suit the particular use contemplated. Can be done.

Claims (15)

As a wafer carrier assembly for use in a chemical mechanical polishing system: A wafer carrier support frame; A wafer carrier head housing rotatably mounted on the wafer carrier support frame; A wafer carrier base; A retaining ring, comprising: a retaining ring operatively associated with a retaining ring bearing that constrains relative radial motion between the retaining ring and the wafer carrier housing while permitting relative axial motion; A retaining ring bellows for operatively connecting said retaining ring bearing to press said retaining ring against a polishing member; And A bladder bellows operatively connecting said wafer carrier base to said wafer carrier head housing such that rotational torque is transmitted from said wafer carrier head housing to said wafer carrier base; The chamber formed by the bladder bellows, the wafer carrier base and the wafer carrier head housing may be pressurized to load the wafer carrier base against the polishing member, regardless of any frictional load on the retaining ring. Assembly. The wafer carrier assembly of claim 1, wherein the retaining ring bearing is a flexure member. The wafer carrier assembly of claim 1, wherein the retaining ring bearing is a hydraulic bearing. The wafer carrier assembly of claim 1, wherein the retaining ring bellows is pressurized to a pressure in the range of approximately 0-40 psia. 10. The system of claim 1, further comprising partitioned flexible members connected to the wafer carrier base and forming a plurality of chambers, And a lower surface of the flexible member provides a wafer receiving surface having a plurality of internal portions each associated with the plurality of chambers individually such that the pressure within each of the chambers is independently controllable. 2. The system of claim 1, further comprising: a mounting flange connected to the wafer carrier support frame and having a substantially vertical through bore; A cylindrical head shaft rotatably connected to said mounting flange and disposed concentrically in said through bore; And And an electric motor having a stator mounted on the mounting flange and a rotor mounted on the cylindrical head shaft. 6. The wafer carrier of claim 5, wherein the flexible member comprises first, second, third and fourth flanges, each of the flanges forming a first, second, third and fourth chamber. A wafer carrier assembly each secured to the bottom surface of the base. The method of claim 1, wherein the first chamber is circular and has a radial width of approximately 30 mm, the second chamber is annular and has a radial width of approximately 30 mm, the third chamber is annular and has a radial width of approximately 25 mm, and the The fourth chamber is annular and has a radial width of approximately 15 mm. The wafer carrier assembly of claim 1, wherein the bladder bellows is pressurized to a pressure in the range of approximately 0-40 psia. As a wafer carrier assembly for use in a chemical mechanical polishing system: A wafer carrier support frame; A wafer carrier head housing rotatably mounted on the wafer carrier support frame; A wafer carrier base; A retaining ring, comprising: a retaining ring operatively associated with a retaining ring bearing that constrains relative radial motion between the retaining ring and the wafer carrier housing while permitting relative axial motion; A retaining ring bellows for operatively connecting said retaining ring bearing to press said retaining ring against a polishing member; A bladder bellows for operatively connecting said wafer carrier base to said wafer carrier head housing such that rotational torque is transmitted from said wafer carrier head housing to said wafer carrier base; And A partitioned flexible member connected to the wafer carrier base and forming a plurality of chambers, the lower surface of the flexible member being individually controllable from the plurality of chambers such that the pressure within each chamber is independently controllable. A flexible member each providing a plurality of associated internal portions to the wafer receiving surface, The chamber formed by the bladder bellows, the wafer carrier base and the wafer carrier head housing may be pressurized to load the wafer carrier base against the polishing member, regardless of any frictional load on the retaining ring. Assembly. 12. The apparatus of claim 10, further comprising: a mounting flange connected to the wafer carrier support frame and having a substantially vertical through bore; A cylindrical head shaft rotatably connected to said mounting flange and disposed concentrically in said through bore; And And an electric motor having a stator mounted on the mounting flange and a rotor mounted on the cylindrical head shaft. 12. The method of claim 11, further comprising a tubular conduit extending concentrically within the head shaft, The tubular conduit includes a plurality of passages for connecting fluid lines to independently pressurize the bellows and the plurality of chambers. The wafer carrier assembly of claim 10, wherein the retaining ring bearing is a flexure member. The wafer carrier assembly of claim 10, wherein the retaining ring bearing is a hydraulic bearing. 11. The wafer carrier assembly of claim 10, wherein the retaining ring bellows and the bladder bellows are each independently pressurized to a pressure in the range of approximately 0-40 psia.