JP5677004B2 - Polishing apparatus and method - Google Patents

Description

  The present invention relates to a polishing apparatus and method, and more particularly to a polishing apparatus and method for polishing and planarizing a polishing object (substrate) such as a semiconductor wafer.

  In recent years, with higher integration and higher density of semiconductor devices, circuit wiring has become increasingly finer and the number of layers of multilayer wiring has increased. When trying to realize multilayer wiring while miniaturizing the circuit, the step becomes larger while following the surface unevenness of the lower layer, so as the number of wiring layers increases, the film coverage to the step shape in thin film formation (Step coverage) deteriorates. Therefore, in order to carry out multilayer wiring, it is necessary to improve the step coverage and perform a flattening process in an appropriate process. Further, since the depth of focus becomes shallower as the optical lithography becomes finer, it is necessary to planarize the surface of the semiconductor device so that the uneven steps on the surface of the semiconductor device are kept below the depth of focus.

Accordingly, in the semiconductor device manufacturing process, a planarization technique for the surface of the semiconductor device is becoming increasingly important. Among the planarization techniques, the most important technique is chemical mechanical polishing (CMP). This chemical mechanical polishing uses a polishing apparatus to slide a substrate such as a semiconductor wafer onto the polishing surface while supplying a polishing solution containing abrasive grains such as silica (SiO ₂ ) onto the polishing surface such as a polishing pad. Polishing in contact.

  This type of polishing apparatus includes a polishing table having a polishing surface made of a polishing pad, and a substrate holding device called a top ring or a polishing head for holding a semiconductor wafer. When polishing a semiconductor wafer using such a polishing apparatus, the semiconductor wafer is pressed against the polishing surface with a predetermined pressure while the semiconductor wafer is held by the substrate holding apparatus. At this time, the semiconductor wafer is brought into sliding contact with the polishing surface by moving the polishing table and the substrate holding device relative to each other, so that the surface of the semiconductor wafer is polished to a flat and mirror surface.

  In such a polishing apparatus, when the relative pressing force between the semiconductor wafer being polished and the polishing surface of the polishing pad is not uniform over the entire surface of the semiconductor wafer, the pressing force applied to each part of the semiconductor wafer. Depending on the pressure, insufficient polishing or overpolishing occurs. In order to equalize the pressing force on the semiconductor wafer, a pressure chamber formed of an elastic film (membrane) is provided below the substrate holding device (top ring), and a pressure fluid such as compressed air is supplied to the pressure chamber. A polishing apparatus of the type that presses the semiconductor wafer against the polishing surface of the polishing pad by fluid pressure through an elastic film is also used.

JP 2007-324458 A JP 2006-128582 A JP 2004-349340 A JP 2007-196603 A

  As described above, in the polishing apparatus, polishing is performed by pressing a substrate such as a semiconductor wafer against the polishing pad. For substrate polishing, high controllability and stability are required over the entire substrate. In a polishing apparatus using a membrane, a plurality of pressure chambers divided in the radial direction are provided in the membrane, and each pressure along the radial direction of the substrate is controlled by controlling the pressure of the pressure fluid supplied to each pressure chamber. There is a type of polishing apparatus that can press a semiconductor wafer with different pressures for each region (each area). In this type of polishing apparatus, a polishing rate distribution is formed from the pressure difference between the pressure chambers.

  In a polishing device using a membrane (elastic film), tuning is performed by changing the pressure conditions on the membrane so that the polishing rate of the entire substrate is optimized (adjustment of polishing conditions to be performed with production stopped completely) To determine the polishing conditions. However, if the membrane that pressurizes the substrate is replaced, a polishing rate with poor reproducibility may be obtained, and tuning may be performed again or the membrane may be replaced.

  Therefore, in order to elucidate the reason why a polishing rate with poor reproducibility is obtained when the membrane is replaced, the present inventors measured the characteristics of the membrane itself and analyzed the measurement results, and replaced the membrane. The experiment of polishing the wafer was repeated. As a result, the following knowledge was obtained.

Membranes, which are rubber products, are molded with a mold, but there are differences in easiness of elongation due to individual differences such as dimensions, hardness, and elastic modulus. In a polishing method in which the substrate is pressed by extending the membrane, this difficulty in elongation is a pressure loss, and therefore polishing conditions such as pressure must be determined in consideration of the loss.
If there is an individual difference in easiness of elongation in the membrane itself, the polishing characteristics change when the consumable membrane is replaced, which is a factor that impairs the stability of the polishing performance. This instability is prominently seen on the outer periphery of the substrate, and it is necessary to deal with it by setting the polishing pressure in anticipation of instability in advance or selecting parts, but the former is fundamentally instability. The latter cannot be solved, and the latter causes a problem that the cost of consumables increases. A method of tuning the polishing recipe again according to the ease of elongation of the membrane is also conceivable, but this method significantly reduces productivity.

The polishing rate of the outer peripheral edge of the substrate is particularly affected by the ease of elongation of the membrane.
In the membrane used in the present invention, the side wall on the outermost periphery of the membrane is provided with a fold in consideration of easiness of elongation in the vertical direction. However, there is an individual difference in the easiness of elongation in the vertical direction. There are variations in direction. Since this side wall is a boundary between the atmospheric pressure and the polishing pressure, it must receive a lateral force, and it becomes impossible to give priority only to the ease of elongation in the vertical direction. This is because elongating in the horizontal direction hinders easiness in extending in the vertical direction.
In the case of a partition that divides the pressurizing area even on the same wall, there are pressure chambers on both sides of the partition, and the partition is stretched by the force of these two pressure chambers, so it is relatively unaffected by the ease of expansion. .
In controlling the polishing rate of the substrate, the most difficult area is the outer peripheral edge of the substrate. In this area called a so-called edge area, the variation in the extension amount of the membrane side wall is directly reflected as the variation in the polishing rate. The reason why it is difficult to control the polishing rate of the edge area is that it is difficult to control the rebound amount of the pad by retainer ring, and the change in temperature and slurry (abrasive) distribution due to the boundary surface between the polishing part and the non-polishing part is large. , Sometimes.

  The present invention has been made on the basis of the above knowledge, and by inputting the characteristics of a membrane for pressing a substrate such as a semiconductor wafer against the polishing surface into the apparatus, the substrate is subjected to optimum polishing conditions according to the characteristics of the membrane. It is an object of the present invention to provide a polishing apparatus and method capable of polishing a metal.

A first aspect of the polishing apparatus of the present invention includes a polishing table having a polishing surface, a membrane that is an elastic film forming a pressure chamber to which a pressure fluid is supplied, and a top ring body that holds the membrane. And a top ring that presses the substrate against the polishing surface by fluid pressure by supplying a pressure fluid to the pressure chamber, and a control unit that controls each device in the apparatus. and changes the polishing conditions in accordance with the stretchability of the membrane by entering the stretchability.
According to the present invention, when the ease of elongation of the membrane measured in advance is input to the control unit, the control unit changes the polishing conditions according to the characteristics of the membrane. As a result, the substrate can be polished under optimal polishing conditions that match the characteristics of the membrane, so that when the membrane is replaced, individual differences can be corrected, even if there are individual differences in the membrane. An excellent polishing rate can be obtained.

In a preferred aspect of the present invention, the ease of elongation of the membrane is a parameter derived from rubber hardness.
According to the present invention, the ease of elongation of the membrane can be grasped by obtaining the rubber hardness of the membrane in advance. Therefore, polishing conditions such as polishing pressure applied to the membrane can be optimized according to the rubber hardness of the membrane. The rubber hardness is, for example, a hardness measured with a durometer.

In a preferred aspect of the present invention, the ease of stretching of the membrane is a parameter derived from the ease of stretching of rubber.
According to the present invention, the polishing pressure applied to the membrane can be set to an optimum value according to the easiness of the rubber constituting the membrane. For example, in the case of a membrane that is easy to stretch, the membrane is corrected by reducing the pressure of the fluid supplied to the pressure chamber, and in the case of a membrane that is difficult to stretch, the membrane is corrected by increasing the pressure of the fluid supplied to the pressure chamber. Even when is replaced, the polishing pressure applied to the substrate can always be set to an optimum value.

In a preferred aspect of the present invention, the ease of elongation of the membrane is an amount of elongation when the inside of the membrane is pressurized at a certain pressure.
According to the present invention, it is possible to grasp the ease of elongation of the membrane by measuring the amount of elongation when the inside of the membrane is pressurized at a certain pressure. And the pressure of the fluid applied to a membrane can be made into an optimal value according to the ease of extension of a membrane.

In a preferred aspect of the present invention, the elongation amount is derived from a result of weighting the elongation amount of the membrane surface for each range.
According to the present invention, when the elongation in the specific range (area) of the membrane has a larger influence on the polishing rate than the other ranges, the elongation amount of the specific range is weighted to obtain the elongation amount of the membrane. .

In a preferred aspect of the present invention, the amount of elongation is derived from the result of measuring the amount of elongation near the outermost periphery of the membrane surface.
According to the present invention, since the dispersion of the polishing rate often occurs in the vicinity of the outermost periphery of the substrate, the amount of elongation of the membrane is obtained from the result of intensive measurement in the vicinity of the outermost periphery of the membrane.

In the polishing method of the present invention, a substrate is held by a top ring having a pressure chamber formed of a membrane that is an elastic film, and a pressure fluid is supplied to the pressure chamber to press the substrate against the polishing surface by fluid pressure. A polishing method for polishing, wherein when the membrane is replaced, the ease of elongation of the membrane measured in advance is input to the apparatus, and the polishing conditions are changed.
According to the present invention, the polishing conditions can be changed in accordance with the ease of elongation, which is a characteristic of the membrane measured in advance. As a result, the substrate can be polished under optimal polishing conditions that match the characteristics of the membrane, so that when the membrane is replaced, individual differences can be corrected, even if there are individual differences in the membrane. An excellent polishing rate can be obtained.

The present invention has the following effects.
(1) Since the polishing conditions are changed according to the characteristics of the membrane measured in advance, the substrate can be polished under optimum polishing conditions according to the characteristics of the membrane. Therefore, when the membrane is replaced, even if there is an individual difference in the membrane, the individual difference can be corrected, and a polishing rate with excellent reproducibility can be obtained.
(2) Since the polishing conditions are changed in accordance with the amount of elongation of the membrane measured by the measuring instrument, even if the amount of elongation changes over time due to long-term use of the membrane, the amount of elongation can be changed every time or periodically. The substrate can be polished under the optimum polishing conditions in accordance with the measured elongation amount.
(3) Even if there is a variation in the amount of elongation in the circumferential direction of the membrane, when attaching the membrane to the top ring, it is attached to the substrate by tilting it so that the range with less elongation approaches the polishing surface. The pressure becomes uniform in the circumferential direction, and it is possible to ensure a uniform polishing profile in the circumferential direction.
(4) Even if there is a variation in the amount of elongation in the circumferential direction of the membrane, by changing the surface pressure distribution of the retainer ring in the circumferential direction, the polishing pressure applied to the substrate becomes uniform in the circumferential direction. It is possible to ensure a uniform polishing profile in the direction.

FIG. 1 is a schematic diagram showing the overall configuration of a polishing apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view of a top ring that constitutes a substrate holding device that holds a semiconductor wafer as an object to be polished and presses it against a polishing surface on a polishing table. FIG. 3A is a schematic diagram illustrating the behavior of the partition wall of the membrane when pressure fluid is supplied to the first pressure chamber and the second pressure chamber, and FIG. 3B illustrates pressure fluid in the third pressure chamber. It is a schematic diagram which shows the behavior of the side wall of a membrane when supplying is carried out. 4A, 4B, and 4C are schematic cross-sectional views showing the state of the membrane before and after supplying the pressure fluid to the pressure chamber. FIG. 5 is a schematic diagram showing an example of measuring the elongation of the membrane. FIG. 6 is a schematic view showing another example of measuring the amount of elongation of the membrane. 7A to 7C are graphs showing the relationship between the measurement result of the membrane elongation and the polishing rate, the graph showing the relationship between the polishing pressure and the polishing rate, and the measurement result of the membrane elongation and the corrected polishing pressure. It is a graph which shows the relationship. FIG. 8 is a schematic diagram for explaining the difference in the pressure control of the top ring between when the membrane easiness of stretching is not corrected and when it is corrected. FIG. 9 is a schematic diagram for explaining the difference in the operation procedure of the apparatus between when the membrane easiness of stretching is not corrected and when it is corrected. FIG. 10 is a schematic side view showing a method for measuring the amount of elongation of the membrane on the polishing apparatus. FIGS. 11A and 11B are schematic plan views showing a method for measuring the amount of elongation of the membrane on the polishing apparatus. 12A and 12B are schematic cross-sectional views showing a method for tilting the top ring. FIGS. 13A, 13B, and 13C are views showing an example in which the retainer ring pressure chamber is divided into three or six.

  Hereinafter, an embodiment of a polishing apparatus according to the present invention will be described in detail with reference to FIGS. 1 to 13. 1 to 13, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a schematic diagram showing the overall configuration of a polishing apparatus according to the present invention. As shown in FIG. 1, the polishing apparatus includes a polishing table 100 and a top ring 1 that holds a substrate such as a semiconductor wafer that is an object to be polished and presses the substrate against a polishing surface on the polishing table.
The polishing table 100 is connected to a table rotation motor 103 disposed below the polishing table 100 and is rotatable around its axis. A polishing pad 101 is affixed to the upper surface of the polishing table 100, and the surface 101 a of the polishing pad 101 constitutes a polishing surface for polishing the semiconductor wafer W. A polishing liquid supply nozzle (not shown) is installed above the polishing table 100, and the polishing liquid (slurry) is supplied onto the polishing pad 101 on the polishing table 100 by this polishing liquid supply nozzle. ing.

  There are various types of polishing pads available on the market, such as SUBA800, IC-1000, IC-1000 / SUBA400 (double-layer cloth) manufactured by Rodel, Surfin xxx-5 manufactured by Fujimi Incorporated, Surfin 000 etc. SUBA800, Surfin xxx-5, and Surfin 000 are non-woven fabrics in which fibers are hardened with urethane resin, and IC-1000 is a hard foamed polyurethane (single layer). The polyurethane foam is porous (porous) and has a large number of fine dents or pores on its surface.

  The top ring 1 includes a top ring body 2 that presses the semiconductor wafer W against the polishing surface 101a, and a retainer ring 3 that holds the outer peripheral edge of the semiconductor wafer W so that the semiconductor wafer W does not jump out of the top ring. It basically consists of

The top ring 1 is connected to a top ring shaft 111, and the top ring shaft 111 moves up and down with respect to the swing arm 110 by a vertical movement mechanism 124. By moving the top ring shaft 111 up and down, the entire top ring 1 is moved up and down with respect to the swing arm 110 for positioning. A rotary joint 125 is attached to the upper end of the top ring shaft 111.
The vertical movement mechanism 124 that moves the top ring shaft 111 and the top ring 1 up and down includes a bridge 128 that rotatably supports the top ring shaft 111 via a bearing 126, a ball screw 132 attached to the bridge 128, and a column 130. And a top ring lifting motor 138 provided on the support base 129. The top ring lift motor 138 is composed of an AC servo motor. A support base 129 that supports the top ring lifting / lowering motor 138 is fixed to the swing arm 110 via a column 130.

  The ball screw 132 includes a screw shaft 132a connected to the top ring lifting / lowering motor 138, and a nut 132b into which the screw shaft 132a is screwed. The top ring shaft 111 moves up and down integrally with the bridge 128. Therefore, when the top ring raising / lowering motor 138 is driven, the bridge 128 moves up and down via the ball screw 132, and thereby the top ring shaft 111 and the top ring 1 move up and down.

  The top ring shaft 111 is connected to the rotary cylinder 112 via a key (not shown). The rotating cylinder 112 includes a timing pulley 113 on the outer periphery thereof. A top ring rotation motor 114 is fixed to the upper surface of the swing arm 110, and the timing pulley 113 is connected to a timing pulley 116 provided on the top ring rotation motor 114 via a timing belt 115. Therefore, when the top ring rotation motor 114 is driven to rotate, the rotary cylinder 112 and the top ring shaft 111 rotate together via the timing pulley 116, the timing belt 115, and the timing pulley 113, and the top ring 1 rotates. The swing arm 110 is supported by a top ring swing shaft 117 that is rotatably supported by a frame (not shown). A top ring swing motor 118 is connected to the top ring swing shaft 117. The polishing apparatus includes a control unit 50 that controls each device in the apparatus including the table rotation motor 103, the top ring rotation motor 114, the top ring swing motor 118, and the top ring lift motor 138.

  In the polishing apparatus configured as shown in FIG. 1, the top ring 1 can hold a substrate such as a semiconductor wafer W on its lower surface. The swing arm 110 is configured to be swingable about the top ring shaft 117, and the top ring 1 holding the semiconductor wafer W on the lower surface is polished from the receiving position of the semiconductor wafer W by the swing of the swing arm 110. It is moved above the table 100. Then, the top ring 1 is lowered to press the semiconductor wafer W against the surface (polishing surface) 101 a of the polishing pad 101. At this time, the top ring 1 and the polishing table 100 are rotated, and the polishing liquid is supplied onto the polishing pad 101 from the polishing liquid supply nozzle provided above the polishing table 100. Thus, the surface of the semiconductor wafer W is polished by bringing the semiconductor wafer W into sliding contact with the polishing surface 101a of the polishing pad 101.

Next, the top ring (polishing head) in the polishing apparatus of the present invention will be described. FIG. 2 is a schematic cross-sectional view of the top ring 1 that constitutes a substrate holding device that holds a semiconductor wafer as an object to be polished and presses it against a polishing surface on a polishing table. In FIG. 2, only main components constituting the top ring 1 are illustrated.
As shown in FIG. 2, the top ring 1 basically includes a top ring body 2 that presses the semiconductor wafer W against the polishing surface 101a and a retainer ring 3 that directly presses the polishing surface 101a. The top ring body 2 includes a top ring flange 21 at the top, a top ring spacer 22 at the middle, and a carrier 23 at the bottom. The top ring body 2 is formed of a resin such as an engineering plastic (for example, PEEK), a stainless material, or the like. An elastic film (membrane) 4 that is in contact with the back surface of the semiconductor wafer is attached to the lower surface of the top ring body 2. The elastic membrane (membrane) 4 is formed of a rubber material having excellent strength and durability, such as ethylene propylene rubber (EPDM), polyurethane rubber, silicon rubber and the like.

  The retainer ring 3 is attached to the outer periphery of the top ring body 2. The retainer ring 3 is guided in its vertical movement by a ring-shaped retainer ring guide 25 fixed to the carrier 23 of the top ring body 2.

  The elastic membrane (membrane) 4 has a side wall 4s on the outermost periphery and a plurality of concentric partition walls 4k inside the side wall 4s, and the upper surface of the membrane 4 and the top ring are formed by the side walls 4s and the partition walls 4k. A circular first pressure chamber 5, an annular second pressure chamber 6, and an annular third pressure chamber 7 are formed between the lower surface of the main body 2. That is, the first pressure chamber 5 is formed at the center of the top ring body 2, and the second pressure chamber 6 and the third pressure chamber 7 are formed concentrically sequentially from the center toward the outer peripheral direction. In the top ring body 2, a flow path 11 communicating with the first pressure chamber 5, a flow path 12 communicating with the second pressure chamber 6, and a flow path 13 communicating with the third pressure chamber 7 are formed. A flow path 11 communicating with the first pressure chamber 5, a flow path 12 communicating with the second pressure chamber 6, and a flow path 13 communicating with the third pressure chamber 7 are connected via a rotary joint 125 (see FIG. 1). Each is connected to a pressure chamber pressurization line (not shown). Each pressure chamber pressurization line is connected to a pressure fluid source (not shown) via a pressure controller (not shown). In this example, there are three pressure chambers, but the number of pressure chambers varies depending on the type of film to be polished.

  A retainer ring pressure chamber 9 is also formed directly above the retainer ring 3 by an elastic membrane (membrane) 8. The elastic membrane (membrane) 8 is accommodated in a cylinder 24 fixed to the top ring flange 21. The retainer ring pressure chamber 9 is connected to a pressure chamber pressurization line (not shown) via a flow path 15 formed in the top ring body 2 and a rotary joint 125 (see FIG. 1). The pressure chamber pressurization line is connected to a pressure fluid source (not shown) via a pressure controller (not shown). Seal members are provided between the retainer ring guide 25 and the retainer ring 3, between the retainer ring 3 and the elastic membrane (membrane) 4, and between the cylinder 24 and the retainer ring guide 25, respectively. I try to prevent it.

  In the top ring 1 configured as shown in FIG. 2, as described above, the first pressure chamber 5 is formed in the central portion of the top ring body 2, and concentrically sequentially from the center toward the outer peripheral direction. The second pressure chamber 6 and the third pressure chamber 7 are formed, and the pressure of the fluid supplied to the first pressure chamber 5, the second pressure chamber 6, the third pressure chamber 7 and the retainer ring pressure chamber 9 is set in each pressure chamber. Each pressure can be adjusted independently by a pressure controller provided in the pressure line. Each pressure controller is connected to the control part 50 (refer FIG. 1), and those operations are controlled. The membrane 4 in the region of the first pressure chamber 5 presses the central portion of the semiconductor wafer W against the polishing pad 101, the membrane 4 in the region of the second pressure chamber 6 presses the intermediate portion of the semiconductor wafer W against the polishing pad 101, The membrane 4 in the region of the third pressure chamber 7 presses the outer peripheral portion of the semiconductor wafer W against the polishing pad 101. With such a structure, the pressing force for pressing the semiconductor wafer W against the polishing pad 101 can be adjusted for each region of the semiconductor wafer, and the pressing force for the retainer ring 3 to press the polishing pad 101 can be adjusted.

Next, a series of polishing processing steps by the polishing apparatus configured as shown in FIGS. 1 and 2 will be described.
The top ring 1 receives the semiconductor wafer W from the substrate transfer device and holds it by vacuum suction. The elastic membrane (membrane) 4 is provided with a plurality of holes (not shown) for vacuum-sucking the semiconductor wafer W, and these holes communicate with a vacuum source (not shown). The top ring 1 holding the semiconductor wafer W by vacuum suction is lowered to a preset setting position for polishing the top ring. At this polishing setting position, the retainer ring 3 is in contact with the surface (polishing surface) 101a of the polishing pad 101. However, before the polishing, the top ring 1 holds the semiconductor wafer W by suction. There is a slight gap (for example, about 1 mm) between the lower surface (surface to be polished) and the surface (polishing surface) 101a of the polishing pad 101. At this time, both the polishing table 100 and the top ring 1 are rotationally driven. In this state, a pressure fluid is supplied to the pressure chamber to expand the elastic film (membrane) 4 on the back surface side of the semiconductor wafer, so that the lower surface (surface to be polished) of the semiconductor wafer contacts the surface (polishing surface) of the polishing pad 101. The polishing of the semiconductor wafer is started by causing the polishing table 100 and the top ring 1 to move relative to each other. Then, by adjusting the pressure of the fluid supplied to each pressure chamber 5, 6, 7, 9, the pressing force for pressing the semiconductor wafer W against the polishing pad 101 is adjusted for each region of the semiconductor wafer, and the retainer ring 3 Adjusts the pressing force for pressing the polishing pad 101 and polishes the semiconductor wafer until the surface of the semiconductor wafer is in a predetermined state (for example, a predetermined film thickness).

Next, the behavior of the side wall 4s and the partition wall 4k of the membrane 4 when pressure fluid is supplied to the pressure chambers 5, 6, and 7 formed by the membrane 4 will be described. The partition wall 4k and the side wall 4s are provided with a "<"-shaped fold in consideration of elongability in the vertical direction.
FIG. 3A is a schematic diagram showing the behavior of the partition wall 4k of the membrane 4 when pressure fluid is supplied to the first pressure chamber 5 and the second pressure chamber 6. FIG. As shown in the upper diagram of FIG. 3A, when pressure fluid is supplied to the first pressure chamber 5 and the second pressure chamber 6, downward pressure is applied to the membrane 4, and the lower portion of FIG. As shown in the figure, the folding of the partition 4k extends up and down, and the lower surface of the membrane 4 expands downward. At this time, since the pressures of the first pressure chamber 5 and the second pressure chamber 6 act on both side surfaces of the partition wall 4k, a balance is obtained, and the folded shape of the "<" shape of the partition wall 4k does not collapse. The partition 4k extends by opening the corner. In FIG. 3A, the behavior of the partition wall 4k between the first pressure chamber 5 and the second pressure chamber 6 is shown, but the partition wall 4k between the second pressure chamber 6 and the third pressure chamber 7 may also be used. It is the same.

  FIG. 3B is a schematic diagram showing the behavior of the side wall 4 s of the membrane 4 when the pressure fluid is supplied to the third pressure chamber 7. As shown in the upper diagram of FIG. 3B, when a pressure fluid is supplied to the third pressure chamber 7, a downward pressure is applied to the membrane 4, and as shown in the lower diagram of FIG. The lower surface of the membrane 4 swells downward. Since the side wall 4s is a boundary between the atmospheric pressure and the polishing pressure (the pressure of the third pressure chamber 7), there is a large pressure difference between the inside and outside of the side wall 4s, as shown in the upper and lower views of FIG. A lateral pressure is applied to the side wall 4s, and the side wall 4s swells radially outward (lateral direction). As described above, when the side wall 4s extends in the horizontal direction, the shape of the "<"-shaped folding is also lost, and the ease of extension in the vertical direction is hindered. In order to prevent the side wall 4s from bulging in the lateral direction, the rigidity (wall thickness) of the side wall 4s may be increased. However, the ease of the side wall 4s in the vertical direction is also hindered.

4A, 4B, and 4C are schematic cross-sectional views showing the state of the membrane 4 before and after supplying the pressure fluid to the pressure chamber. 4A, 4 </ b> B, and 4 </ b> C, half of the top ring 1 is illustrated, and the retainer ring 3 on the outer peripheral side of the membrane 4 is not illustrated.
FIG. 4A is a diagram illustrating a state of the membrane 4 when no pressure fluid is supplied to any pressure chamber. As shown in FIG. 4A, when the pressure fluid is not supplied to the pressure chamber, the lower surface of the membrane 4 is in a state close to the carrier 23.
FIG. 4B is a diagram illustrating a state of the membrane 4 when a pressure fluid is supplied to the third pressure chamber 7. As shown in FIG. 4 (b), when the pressure fluid is supplied to the third pressure chamber 7 with the lower surface of the membrane 4 in a free state to pressurize the outermost peripheral area of the membrane 4, It can be seen that the area Ae does not extend uniformly.
FIG. 4C is a diagram showing the state of the membrane 4 when pressure fluid is supplied to the first pressure chamber 5, the second pressure chamber 6, and the third pressure chamber 7. As shown in FIG. 4C, when the semiconductor wafer W is held on the lower surface of the membrane 4 and pressure fluid is supplied to the first pressure chamber 5, the second pressure chamber 6, and the third pressure chamber 7, the membrane 4 swells. Then, the lower surface of the semiconductor wafer W is pressed against the polishing pad 101. In this case, the elongation of the outermost area Ae of the membrane 4 is slightly smaller than the elongation of other areas. The degree of expansion of the outermost area Ae of the membrane 4 affects the pressure distribution of the wafer. In FIG. 4C, a gap is illustrated between the outermost peripheral area Ae of the membrane 4 and the wafer. Arise.

The ease of stretching of the membrane can be grasped by the amount of swelling when a certain pressure is applied to the inside of the membrane. In addition, since the easiness of elongation can be grasped from the hardness, the wall thickness, and the dimensions of each part, it may be indexed as the easiness of elongation from these individual measurements. For example, in the case of rubber hardness, since the tendency is determined by the material lot, it is also possible to manage by the lot.
Hereinafter, a method of directly measuring the swelling of the membrane will be described. However, if it is an element related to easiness of elongation, it can be replaced by the following method.
There are individual differences in the easiness of membrane extension. Therefore, before the manufactured membrane is shipped, or before the user attaches it to the apparatus, the swelling under a certain pressure condition is measured. At this time, the surface of the membrane should be pressurized without any obstructions, a jig for setting the membrane to apply pressure, a control device for always applying equal pressure, and for accurate measurement. Various devices such as sensors (contact type or non-contact type) and rotating jigs for measuring at equal intervals are prepared.

FIG. 5 is a schematic diagram showing an example of measuring the elongation of the membrane. In the example shown in FIG. 5, a contact-type distance measuring sensor 52 is used as means for measuring the amount of elongation of the membrane.
Measure the amount of change when inflated by applying pressure to the inside of the membrane, starting from the uninflated state or the position of the mounting jig. In FIG. 5, the membrane 4 is attached to a mounting jig 51 having the same structure as the top ring, and the membrane 4 is expanded by supplying a pressure fluid to the pressure chamber 7 on the outermost periphery. ) Is measured by the contact-type distance measuring sensor 52. One measurement point may be used, but in order to eliminate the influence of measurement variations and singularities, an average value may be obtained by scanning a plurality of evenly or all around. Since variations in the polishing rate often occur at the outer peripheral edge of the substrate, it is better to measure the elongation intensively at the outer peripheral edge of the membrane, but this is determined by where the fluctuation that you want to manage exists. Become. However, depending on the structure of the membrane, there may be a case where it is possible to more reliably grasp the tendency of elongation by measuring the part other than the part where the variation occurs.

Here, taking into account that the ease of stretching of the membrane varies when the inside of the membrane is pressurized at a certain pressure, the amount of stretching of the membrane is measured for each predetermined range in the radial direction of the membrane. If the elongation in a specific range (area) of the membrane has a greater influence on the polishing rate than the other ranges, predetermined weighting is performed according to the measurement result of the amount of elongation of the membrane.
For example, the membrane elongation measured in the outermost area (area) of the membrane is X ₁ , the membrane elongation measured in the radial direction slightly inward (area) is X ₂ , and the inner range (area) the elongation amount of the membrane measured in) and X _3. The weighting coefficients for the respective measurement results X ₁ , X ₂ , X ₃ are a, b, c. Here, the weighting coefficient a for the measurement result at the outermost peripheral portion is set to the largest numerical value. The average elongation amount of the weighted membrane is obtained by (aX ₁ + bX ₂ + cX ₃ ) / (a + b + c).
The measured surface of the part to be measured is most easily correlated with the polishing rate, but the elongation of the sidewall itself or the lateral elongation of the sidewall may be measured.

  FIG. 6 is a schematic view showing another example of measuring the amount of elongation of the membrane. In the example shown in FIG. 6, a non-contact distance measuring sensor 53 is used as a means for measuring the amount of elongation of the membrane. The non-contact distance measuring sensor 53 includes, for example, a laser distance measuring sensor, and can measure the amount of elongation (ΔL) of the membrane in a non-contact manner. The bulge may be captured optically by devising such that the membrane 4 does not transmit or does not transmit the laser. In this case, instead of spot measurement, there is a method of measuring the bulge curve with a certain width, and if this method is used, the bulge ease can be measured and managed more precisely. A contact-type distance measuring sensor can do the same, but a method for shortening the measurement time such as automatic feed control of the probe is desired. As the non-contact distance measuring sensor, an ultrasonic sensor can be used in addition to the laser distance measuring sensor.

As shown in FIG. 5 and FIG. 6, the unit of the ease of elongation measured is mm. In order to use this information for correcting the polishing rate, a conversion formula is required.
7A to 7C are graphs showing the relationship between the measurement result of the membrane elongation and the polishing rate, the graph showing the relationship between the polishing pressure and the polishing rate, and the measurement result of the membrane elongation and the corrected polishing pressure. It is a graph which shows the relationship.
Here, a simplified description will be given, but it is assumed that, for example, when the swelling of the membrane is measured at a pressure of 100 hPa, the measurement results of 4.5 mm, 5.5 mm, and 5.0 mm are obtained. The 4.5 mm product, which is the smallest solid, the intermediate 5 mm product, the largest 5.5 mm product, and the individual filling the space between them are each subjected to a polishing test at a surface pressure of 200 hPa, and the polishing rate is measured. As shown in FIG. 7A, the average polishing rate of the edge area of 4.5 mm products (for example, the outermost circumference of 2 to 3 mm) is 450 nm / min, 5 mm products are 500 nm / min, 5.5 mm products are 550 nm / min. Suppose that there is a proportional relationship between them. Furthermore, it is assumed that the pressure change necessary to make the polishing rate of this edge area ± 50 nm / min is 200 ± 20 hPa. In this case, basically, the higher the pressure, the higher the polishing rate. That is, as shown in FIG. 7B, when the pressure is 180 hPa, the polishing rate can be 450 nm / min, when 200 hPa, 500 nm / min, and when 220 hPa, 550 nm / min.

If there is a proportional relationship between these results, a difference of ± 0.5 mm in elongation amount at a surface pressure of 200 hPa can be expressed as a relationship of ± 20 hPa in terms of pressure. Under such conditions, when a polishing condition with a pressurized pressure of 200 hPa is adopted using a membrane (5 mm product) with an elongation measurement result of 5 mm, as shown in FIG. If a 5 mm membrane (4.5 mm product) is attached, correct the edge pressure to 220 hPa, and if a 5.5 mm membrane (5.5 mm product) is attached, correct the edge pressure to 180 hPa. Thus, using a membrane (5 mm product) with an elongation measurement result of 5 mm, it is possible to obtain a polishing result equal to that when the applied pressure is 200 hPa. In other words, the relational expression of the corrected polishing pressure (to keep the polishing amount constant) corresponding to the elongation in this case is
(1) Polishing pressure after correction (hPa) = − 40 (hPa / mm) × Elongation measurement result value (mm) +400 (hPa)
(See FIG. 7C).
Further, as shown in FIG. 7A, the result of the polishing test, the relational expression between the elongation at the polishing pressure of 200 hPa and the polishing rate is:
(2) Polishing rate (nm / min) = 100 (nm / (min × mm)) × elongation measurement result value (mm)
Furthermore, as shown in FIG. 7B, the relational expression between the polishing pressure and the polishing rate when using a membrane with an elongation measurement result of 5 mm is
(3) Polishing rate (nm / min) = 2.5 (nm / (min × hPa)) × (polishing pressure (hPa)
Thus, equation (1) is derived from the relationship between (2) and (3).
These formulas can be applied only to the range approximated by the above formula.

When the membrane whose elongation has been measured is attached to the apparatus, the polishing pressure obtained by the above formula is reflected in the polishing recipe. The polishing recipe includes polishing time, substrate polishing pressure, retainer ring pressure, polishing table and top ring rotation speed, slurry flow rate, dressing pressure, dressing rotation speed, etc. These values are determined. However, if there are many recipes and there are multiple polishing conditions (polishing steps) for polishing a single substrate, the input man-hours are very large, resulting in increased work costs (labor costs) and equipment downtime. Become.
Therefore, by inputting the measurement results of easiness of elongation in mm or numerical values (parameters representing easiness of elongation, derived from hardness (frequency) and elongation amount (mm), etc.) to the device. Introducing software that automatically corrects the polishing recipe. In this case, the above formula is for the case where the center pressure is 200 hPa, but the degree of influence of the ease of elongation is higher as the polishing pressure is lower, and the influence is relatively lower as the polishing pressure is higher.

For example, it is assumed that the degree of influence of the easiness of elongation of the membrane under the specific polishing conditions is 0.7 when the surface pressure is 300 hPa, 1.3 when the surface pressure is 200 hPa, and 1.3 when the surface pressure is 100 hPa. If there is a proportional relationship to this degree of influence, these relational expressions are as follows:
Polishing pressure = recipe setting pressure +
(Recipe set pressure / 5) (1.6-Recipe set pressure × 0.003) (5-Elongation measurement result value)
It is expressed by
That is, in the above example, as a correction factor, the value of the recipe setting pressure per 1 mm elongation (recipe setting pressure / 5) and the degree of influence (1.6−recipe setting pressure × 0. 003) and how much the measured elongation of the membrane is shorter than the standard 5 mm (5-elongation measurement result value). Here, the degree of influence is obtained by subtracting the degree of influence corresponding to the recipe setting pressure (recipe setting pressure × 0.003) from the degree of influence between the surface pressures of 100 hPa and 300 hPa.
In this example, it was assumed that the polishing pressure matched to the membrane was obtained. However, it can be corrected more directly by increasing / decreasing the position (top ring height) of other elements that can compensate for easiness of elongation. Is possible. Of course, if considered simply, it may be sufficient to compensate for the amount that does not stretch as it is, but since there is also the presence or absence of the object to be polished (the degree of freedom of swelling), some conversion formula is still necessary.

In addition to the above, as a means for correcting the ease of elongation of the membrane, a means for correcting the polishing pressure acting on the substrate by changing the air pressure (pressure in the pressure chamber) during polishing, changing the surface pressure of the retainer ring, etc. There are also means for correcting by changing the polishing action, such as the flow rate of the slurry, the temperature of the polishing table, the number of rotations of the polishing table and the top ring, and naturally these may be combined.
Furthermore, individual differences of membranes change with long-term use, so the degree of influence may be changed according to the number of processed sheets and the total polishing time.

Next, the difference in the top ring pressure control and the difference in the operation procedure of the apparatus between the case without correction and the case with correction will be described with reference to FIG. 8 and FIG.
In FIG. 8, the diagram on the left side is a diagram illustrating a control method of the pressure controller in the case where there is no correction of the ease of elongation of the membrane. As shown in the figure, when a polishing recipe is input, the device controller (control unit) calculates a command value according to the recipe, outputs the calculated command value to the DA converter, controls the pressure controller, and performs top ring The pressure in each pressure chamber is controlled.
In FIG. 8, the diagram on the right side is a diagram showing a control method of the pressure controller in the case where there is a correction for the ease of elongation of the membrane. As shown in the figure, when a polishing recipe is input, the device controller (control unit) calculates a command value that takes into consideration the ease of elongation of the input membrane, and outputs the calculated command value to the DA converter. The pressure controller is controlled to control the pressure in each pressure chamber of the top ring 1. Therefore, it is possible to polish at an optimum polishing pressure in consideration of the ease of elongation of the membrane.

In FIG. 9, the diagram on the left side is a diagram showing an operation procedure that can occur when the ease of stretching of the membrane is not corrected. As shown in the figure, when the used membrane is exhausted, it is replaced with a new membrane. Then, the polishing profile changes, and defective products appear in the process of inspecting the flatness of the film thickness on the wafer surface, etc., and production is temporarily stopped. Therefore, the polishing profile is checked and the correction amount is tuned. Then change the recipe and restart production.
In FIG. 9, the diagram on the right side is a diagram showing an operation procedure when there is a correction for the ease of elongation of the membrane. As shown in the figure, the amount of elongation and material properties are measured during membrane manufacture. Then, the ease of elongation is indexed from the measurement result. When the membrane is attached to the apparatus, an index of easiness of elongation inherent to the membrane is input to the apparatus. Based on the numerical value, the apparatus corrects the recipe and polishes. Therefore, even if the membrane is changed, the polishing profile does not change.

  In the above embodiment, the easiness of stretching of the membrane is measured before the device is mounted, but there is also a method of measuring the membrane while it is attached to the device. In this case, the measurement equipment and measurement points are the same as above, but it must be noted that the membrane surface is wet with water or slurry, so remove this water especially in the case of non-contact type measuring instruments. Must. Therefore, moisture may be removed by blowing the membrane surface with compressed air or the like. The measurement sensor is installed in a range where the top ring swings, such as a substrate transfer device (pusher) or the side of the polishing table.

FIG. 10 is a schematic side view showing a method for measuring the amount of elongation of the membrane on the polishing apparatus.
As shown in FIG. 10, the distance measuring sensor 55 that measures the amount of elongation of the membrane is installed on the side of the polishing table 100 adjacent to the polishing table 100. The distance measuring sensor 55 is a contact type or non-contact type sensor. In addition, a cleaning nozzle 56 is installed in a range where the top ring 1 swings and below the top ring 1. The cleaning nozzle 56 can inject pure water, compressed air, and N ₂ . Pure water, compressed air, and N ₂ sprayed from the cleaning nozzle 56 can be properly used as necessary. For example, when it is desired to measure the amount of elongation of the membrane 4 after polishing, pure water is sprayed from the cleaning nozzle 56 to clean the membrane 4 to remove the slurry from the membrane 4, and after cleaning, compressed air or N ₂ is supplied to the membrane 4 Then, the moisture is removed from the membrane 4, and then the extension amount of the membrane 4 is measured by the distance measuring sensor 55. FIG. 10 shows a polishing liquid supply nozzle 102 for supplying a polishing liquid (slurry) onto the polishing pad 101.

  FIGS. 11A and 11B are schematic plan views showing a method for measuring the amount of elongation of the membrane on the polishing apparatus. The top ring 1 is swingable between a polishing position (shown in FIG. 11A) and a measurement position (shown in FIG. 11B) by a swing arm 110. When the top ring 1 swings to the measurement position, as shown in FIG. 10, the distance measurement sensor 55 measures the membrane elongation. Note that the membrane is cleaned by the cleaning nozzle 56 before the measurement as described above.

The timing for measuring the amount of elongation of the membrane by the method shown in FIG. 10 and FIG. 11 is measured periodically immediately after the membrane is attached and thereafter at a certain period, and after the measurement, the result is corrected.
Since individual differences in membranes change with long-term use, it is also possible to change the degree of influence according to the number of processed sheets and total polishing time in the same way. It is also possible to make corrections.
In addition, it is desirable to keep the distance between the membrane and the substrate constant in order to ensure the stability of polishing. This is possible if the retainer ring has a mechanism capable of operating independently from the top ring main body and a mechanism capable of making the distance between the top ring main body and the polishing surface constant. Therefore, as a desirable form, the required elongation amount and easiness of elongation of the membrane are made constant in such a configuration, or the recipe is corrected from the easiness of elongation grasped as in the present invention.

  Furthermore, by grasping not only the individual differences in the easiness of the membrane, but also the tendency in one individual, the polishing variation in the circumferential direction appearing in the polishing profile can be corrected. The bulge variation that occurs during the manufacturing process of the membrane often has a maximum value and a minimum value of 180 degrees in the circumferential direction. This is because a thick portion and a thin portion are generated because there is play when the molds are combined. That is, the thick part is difficult to stretch and the thin part is easy to stretch. In such a case, it is possible to ensure a uniform polishing profile in the circumferential direction by inclining the top ring by the difference in elongation.

  12A and 12B are schematic cross-sectional views showing a method for tilting the top ring. As shown in FIG. 12A, spacer grooves 22g and 23g are provided in the top ring spacer 22 and the carrier 23 of the top ring 1, and when the membrane 4 is attached to the top ring 1, it is grasped where it is difficult to stretch. The spacer 60 is mounted at a position corresponding to a location (phase) where the maximum value of the elongation difficulty is. Thus, by arranging the spacer 60 at a position (phase) where the membrane is difficult to stretch, a gap is generated between the top ring spacer 22 and the carrier 23 as shown in FIG. In addition, when the membrane is attached to the apparatus, it can be attached so as to be inclined with respect to the polishing table. As other specific means for inclining, there is a method in which an inclined spacer is inserted between the top ring shaft 111 and the top ring 1 or an attachment portion of the ball spline nut portion of the top ring shaft 111 is inclined. Since the amount of tilting is basically small, for example, a shim may be inserted between the carrier 23 and the top ring spacer 22. If it is designed on the assumption that it is tilted in advance, a counterbore may be prepared so that the shim fits stably. In addition, if it is a clearance of this level, the O-rings at the connecting portion of the pipe between the top ring spacer 22 and the carrier 23 will not lose their functions.

Further, as a method of correcting the variation, there is a method of changing the surface pressure distribution of the retainer ring instead of tilting the membrane. This is because, for example, the retainer ring pressure chamber that generates the retainer ring surface pressure is divided into three in the circumferential direction, and the pressure of each of the divided pressure chambers is independently controlled to change the surface pressure distribution of the retainer ring. I can do it.
FIGS. 13A, 13B, and 13C are views showing an example in which the retainer ring pressure chamber is divided into three or six. In FIG. 13A, three retainer ring pressure chambers 9a, 9b, and 9c are formed by providing three retainer ring airbags. In FIG. 13B, six retainer ring pressure chambers 9a, 9b, 9c, 9d, 9e, 9f are formed by providing six retainer ring airbags. Of course, the retainer ring 3 is also divided into three or six parts corresponding to the pressure chambers.
FIG.13 (c) is an example of sectional drawing which shows the top ring 1 provided with the divided retainer ring pressure chamber and the retainer ring. As shown in FIG. 13C, the retainer ring airbag constituting each retainer ring pressure chamber is formed of an elastic membrane (membrane) 8 as in FIG.
The retainer ring pressure chambers 9a to 9c (FIG. 13 (a)) and 9a to 9f (FIG. 13 (b)) are respectively connected to individual flow paths 15a to 15c (FIG. 13 (a)) and 15a to 15f (FIG. 13). 13 (b)) is connected to a pressure line (not shown).

  As shown in FIGS. 13A to 13C, when the retainer ring pressure chamber is divided into three or six parts, it is easy to swell to which phase when the membrane is attached, as in the method of tilting with the shim. Check if there is a maximum or minimum value, for example, control the pressure of the retainer ring pressure chamber so that the surface pressure of the retainer ring is small in the range where the bulge is small, that is, the polishing rate decreases, and conversely The pressure in the retainer ring pressure chamber is controlled so that the surface pressure of the retainer ring is increased within a range where the swelling is large, that is, the polishing rate is increased. This is a case where the polishing rate of the edge portion of the substrate increases when the retainer ring surface pressure is small. However, since there is a reverse tendency if the polishing process is different, the above-mentioned magnitude relationship is not limited to this example.

  Although the embodiment of the present invention has been described so far, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention may be implemented in various different forms within the scope of the technical idea.

1 Top ring 2 Top ring body 3 Retainer ring 4 Elastic membrane (membrane)
4k partition wall 4s side wall 5 first pressure chamber 6 second pressure chamber 7 third pressure chamber 8 elastic membrane (membrane)
9 Retainer ring pressure chamber 11, 12, 13, 1415 Flow path 21 Top ring flange 22 Top ring spacer 22g, 23g Spacer groove 23 Carrier 24 Cylinder 25 Retainer ring guide 50 Controller 51 Mounting jig 52 Contact type distance measuring sensor 53 Non Contact type distance measuring sensor 55 Distance measuring sensor 56 Cleaning nozzle 60 Spacer 100 Polishing table 101 Polishing pad 101a Polishing surface 102 Polishing liquid supply nozzle 103 Table rotation motor 110 Swing arm 111 Top ring shaft 112 Rotating cylinder 113 Timing pulley 114 Top ring rotation Motor 115 Timing belt 116 Timing pulley 117 Top ring swing shaft 118 Top ring swing motor 124 Vertical movement mechanism 125 Rotary joint 126 Bearing 1 28 Bridge 129 Support stand 130 Post 132 Ball screw 132a Screw shaft 132b Nut 138 Top ring lift motor

Claims (7)

A polishing table having a polishing surface;
It has a membrane, which is an elastic membrane that forms a pressure chamber to which pressure fluid is supplied, and a top ring body that holds the membrane. By supplying the pressure fluid to the pressure chamber, the substrate is pressed against the polishing surface by the fluid pressure. And a top ring to
A control unit for controlling each device in the apparatus,
The said control part changes polishing conditions according to the ease of elongation of a membrane by inputting the ease of elongation of the membrane measured beforehand, The polishing apparatus characterized by the above-mentioned.   The polishing apparatus according to claim 1, wherein the ease of elongation of the membrane is a parameter derived from rubber hardness.   The polishing apparatus according to claim 1, wherein the ease of extension of the membrane is a parameter derived from the ease of extension of rubber.   The polishing apparatus according to claim 1, wherein the ease of elongation of the membrane is an amount of elongation when the inside of the membrane is pressurized at a certain pressure.   The polishing apparatus according to claim 4, wherein the elongation amount is derived from a result of weighting the elongation amount of the membrane surface for each range.   The polishing apparatus according to claim 4, wherein the elongation amount is derived from a result of measuring an elongation amount in the vicinity of the outermost periphery of the membrane surface. A polishing method in which a substrate is held by a top ring having a pressure chamber formed by a membrane that is an elastic membrane, and a pressure fluid is supplied to the pressure chamber so that the substrate is pressed against the polishing surface by fluid pressure and polished. ,
A polishing method, wherein when the membrane is replaced, the ease of elongation of the membrane measured in advance is input to the apparatus, and the polishing conditions are changed.

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