JP2009094343A - Electrochemical polishing method and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical polishing method capable of increasing a polishing speed while preventing excessive polishing, such as dishing or erosion. <P>SOLUTION: When a voltage applied to a conductive film formed on the surface of a substrate is increased under a contact surface pressure of 0 between the surface of the substrate and a polishing pad, a voltage at a first change point C that a current density changes from increase to decrease is referred to as a minimum voltage. In addition, when the voltage is increased under a contact surface pressure having a finite value, a voltage at a second change point B that the current density changes from decrease after the increase to constant is referred to as a maximum voltage. In this case, the surface of the conductive film is polished while maintaining the voltage to be not lower than the minimum voltage and not higher than the maximum voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrolytic composite polishing method and a polishing method.

  As a wiring formation process of a semiconductor device, a so-called damascene process in which a wiring metal is buried in a wiring recess such as a trench or a via hole provided in an insulating film is being used. In this damascene process, as shown in FIG. 6A, a contact plug or a recess for forming a wiring (hereinafter referred to as “recess”) is formed in an insulating film (interlayer insulating film) 62 made of a so-called low-k material on a substrate. 63), and then a barrier metal film (hereinafter referred to as "barrier film") 64 made of titanium nitride or the like is formed on the entire surface of the interlayer insulating film 62 including the recess 63, and tungsten is formed on the surface of the barrier film 64. A metal conductive film (hereinafter referred to as “conductive film”) 66 is formed, and a metal conductive material is embedded in the recess 63. A recess 67 is formed on the surface of the conductive film 66 following the recess 63 of the interlayer insulating film 62. Thereafter, this is generally performed by removing the excess conductive film 66 and barrier film 64 formed outside the recess 63.

The removal of the conductive film 66 made of tungsten is performed by chemical mechanical polishing (CMP). As shown in FIG. 11, in the CMP, the slurry 52 is supplied to the conductive film on the surface of the substrate W, and the substrate W and the polishing pad 101 are moved relative to each other while pressing the surface of the substrate W against the polishing pad 101. Is polished (see, for example, Non-Patent Document 1). The slurry 52 contains abrasive grains and an oxidizing agent, and a tungsten oxide film is formed on the surface of the conductive film 66 shown in FIG. Since the tungsten oxide film formed on the upper stage H of the conductive film (outside the recess 67) is removed by contact with the polishing pad, the conductive film 66 on the upper stage H is polished. On the other hand, the tungsten oxide film formed in the lower part L of the conductive film (inside the recess 67) is not removed because it does not contact the polishing pad, and the lower conductive film 66 is not polished. Thereby, the level | step difference (recessed part 67) of the surface of the electrically conductive film 66 is eliminated.
Edited by Toshiro Tohi, “Detailed Semiconductor CMP Technology”, Industrial Research Council, December 2000, p277-p284

  The tungsten polishing method by CMP described above employs a mechanism in which an acidic slurry having a pH <4 is used to form a tungsten oxide film having a considerable thickness, and this tungsten oxide film is mechanically polished. There is a problem that the speed becomes low. In order to improve the polishing rate, a high polishing pressure is required in addition to the slurry containing a high concentration of abrasive grains. However, in this case, there is a problem that damage such as scratches or dishing (excessive polishing of the conductive film) easily occurs on the surface of the conductive film. Further, since the interlayer insulating film that should not be polished is also polished, there is a problem that erosion (excess polishing of the insulating film) is likely to occur.

  Therefore, an object of the present invention is to provide an electrolytic composite polishing method and a polishing method capable of quickly eliminating a step on the surface of a conductive film while preventing excessive polishing such as dishing and erosion. Although “electrolytic polishing” may be used as a derivative technique of “electrolytic polishing” in “electrolytic polishing”, the term “electrolytic composite polishing” is used in this specification.

  When the applied voltage is increased by bringing a pH 4-10 electrolytic solution into contact with the conductive film, the current density rapidly changes at a predetermined voltage. When the voltage applied to the conductive film is increased from 0, the current density increases in proportion to the voltage, but when the voltage is increased beyond the first change voltage at the first change point (for example, point A in FIG. 7). The current density turns from increasing to decreasing. When the voltage is further increased beyond the second change voltage at the second change point (for example, point B in FIG. 7), the degree of decrease in the current density is reduced, the current density is not reduced, and the value changes to a substantially constant value. When a voltage lower than the first change voltage is applied, a protective film that is soluble in the electrolyte is formed on the surface of the conductive film, but when a voltage higher than the second change voltage is applied, It is considered that a protective film that is insoluble in the electrolytic solution is formed on the surface of the conductive film.

  The inventor of the present application has found that the first and second change voltages described above change depending on the contact surface pressure between the substrate and the polishing pad. The higher the contact surface pressure, the higher the first and second change voltages and the higher the current density. When a voltage equal to or lower than the first change voltage (for example, the point C voltage in FIG. 7) when the contact surface pressure is 0 is applied, a protective film that is soluble in the electrolytic solution is formed on the entire surface of the conductive film. Further, when a voltage higher than the second change voltage (for example, the voltage at point B in FIG. 7) when the contact surface pressure is a finite value is applied, a protective film that is insoluble with respect to the electrolytic solution is formed on the entire surface of the conductive film. The These are the same regardless of the presence or absence of a step on the surface of the conductive film.

Accordingly, the present invention sets the voltage at which the current density changes from increasing to decreasing when the voltage is increased in a state where the contact surface pressure is 0 (for example, the voltage at point C in FIG. 7) as the minimum voltage, When the voltage is increased in a state where the pressure is finite, the voltage at which the current density changes so as not to decrease from the decrease after the increase (for example, the voltage at point B in FIG. 7) is set to the maximum voltage, and is equal to or higher than the minimum voltage. And the surface of the said electrically conductive film was grind | polished, maintaining the said voltage below the said maximum voltage.
According to this configuration, when there is a step on the surface of the conductive film, the upper step portion (for example, the upper step portion H in FIG. 8B) has a solubility in the contact surface pressure between the conductive film and the polishing pad. The protective film is formed, and the protective film is completely removed by polishing. In addition, an insoluble protective film is formed on the lower part where the contact surface pressure between the conductive film and the polishing pad is 0 (for example, the lower part L in FIG. 8B), and the protective film remains without being polished. . As a result, dissolution of the conductive film into the electrolytic solution is promoted at the upper stage, and dissolution of the conductive film is suppressed at the lower stage. Therefore, the step on the surface of the conductive film can be quickly eliminated.
In addition, since the polishing rate of the lower stage portion covered with the protective film is extremely slow, dishing is difficult to enter the conductive film. Further, since the polishing rate of the upper stage can be controlled by adjusting the applied voltage, the contact surface pressure between the polishing pad and the conductive film can be set low, and erosion can be suppressed.

In the present invention, when the voltage is increased in a state where the contact surface pressure is 0, the voltage at which the current density turns from increasing to decreasing (for example, the voltage at point C in FIG. 7) is set to the minimum voltage, and the contact When the voltage is increased in a state where the surface pressure is finite, the voltage at which the current density turns so as not to decrease from the decrease after the increase (for example, the voltage at point B in FIG. 7) is set as the maximum voltage, and the minimum It was set as the structure which grind | polishes the surface of the said electrically conductive film, maintaining the said voltage below the said maximum voltage more than a voltage.
According to this configuration, when there is a step on the surface of the conductive film, the current density of the upper part (for example, the upper part H of FIG. 8B) at which the contact surface pressure between the conductive film and the polishing pad has a finite value is obtained. The difference from the current density of the lower part where the contact surface pressure is 0 (for example, the lower part L of FIG. 8B) can be increased. This difference in current density corresponds to the difference in polishing rate between the upper and lower portions of the conductive film. Therefore, the step on the surface of the conductive film can be quickly eliminated.

The polishing rate of the conductive film is controlled by adjusting the pH of the electrolytic solution.
Since dissolution of the conductive film is promoted as the pH of the electrolytic solution increases, the polishing rate of the conductive film can be controlled by adjusting the pH of the electrolytic solution.

The electrolytic solution includes an additive that reacts with the conductive film to generate an electrically insulating material, and controls a polishing rate of the conductive film by adjusting a concentration of the additive.
As the concentration of the additive increases, a stronger protective film is formed and is difficult to remove by polishing. Therefore, the polishing rate of the conductive film can be controlled by adjusting the concentration of the additive.

The polishing rate of the conductive film is controlled by adjusting the number of rotations of the polishing pad.
As the number of revolutions of the polishing pad increases, the removal of the protective film proceeds and the dissolution of the conductive film is promoted, so that the polishing rate of the conductive film can be controlled by adjusting the number of revolutions of the polishing pad.

A polishing method comprising a polishing step of polishing the conductive film on the substrate surface by relatively moving the substrate and the polishing pad while pressing the substrate surface against the polishing pad with a predetermined contact surface pressure, In the state where the contact surface pressure is a finite value while moving relative to the polishing pad, when a voltage is applied while the electrolyte is in contact with the conductive film, and the voltage is increased, the current density increases. The threshold voltage is a voltage that changes so as not to decrease from the decrease of the threshold voltage, and the threshold voltage is maintained while the electrolytic solution is in contact with the conductive film in a state where the substrate and the polishing pad are not in contact before the polishing step. It has a protective film forming step of applying the above voltage to form a protective film on the surface of the conductive film.
According to this configuration, a protective film that is insoluble with respect to the electrolytic solution is formed by applying a voltage equal to or higher than the threshold voltage in the protective film forming step. In the next polishing step, the protective film formed on the upper part of the conductive film is removed by polishing, but the protective film formed on the lower part of the conductive film remains without being polished. Thereby, the level | step difference of the surface of an electrically conductive film can be eliminated rapidly.

The polishing process is a chemical mechanical polishing process or an electrolytic composite polishing process.
Since the protective film is formed before the polishing step, the step on the surface of the conductive film can be quickly eliminated regardless of which of chemical mechanical polishing and electrolytic composite polishing is employed.

  According to the present invention, when there is a step on the surface of the conductive film, a soluble protective film is formed on the upper portion where the contact surface pressure between the conductive film and the polishing pad has a finite value, and the protective film is polished. Is completely removed. In addition, an insoluble protective film is formed on the lower portion where the contact surface pressure between the conductive film and the polishing pad is 0, and the protective film remains without being polished. As a result, dissolution of the conductive film into the electrolytic solution is promoted at the upper stage, and dissolution of the conductive film is suppressed at the lower stage. Therefore, the step on the surface of the conductive film can be quickly eliminated.

(Substrate processing equipment)
FIG. 1 is a plan view showing an arrangement configuration of a substrate processing apparatus provided with an electrolytic composite polishing apparatus according to the present invention. The substrate processing apparatus 300 includes a load / unload stage that accommodates a substrate cassette 204 that stocks a large number of substrates W. A transport robot 202 having two hands is arranged on the traveling mechanism 200 so as to reach each substrate cassette 204 in the load / unload stage. The traveling mechanism 200 employs a traveling mechanism composed of a linear motor. By adopting a traveling mechanism composed of a linear motor, it is possible to stably and stably carry a substrate having a large diameter and an increased weight. An ITM (In-line Thickness Monitor) 224 that measures the film thickness on the substrate before or after polishing is disposed on the extended line of the traveling mechanism 200.

  Two drying units 212 are arranged on the opposite side of the substrate cassette 204 with the traveling mechanism 200 of the transfer robot 202 interposed therebetween. Each drying unit 212 is disposed at a position where the hand of the transfer robot 202 can reach. In addition, a substrate station 206 including four substrate platforms is disposed between the two drying units 212 at a position where the transfer robot 202 can reach.

  A transfer robot 208 is disposed at a position that can reach each drying unit 212 and the substrate station 206. A cleaning unit 214 is disposed at a position where the hand of the transfer robot 208 can reach so as to be adjacent to the drying unit 212. The rotary transporter 210 is arranged at a position where the hand of the transfer robot 208 can reach, and two electrolytic composite polishing apparatuses 250 according to the present embodiment are arranged at a position where the rotary transporter 210 and the substrate can be delivered.

  Each electrolytic composite polishing apparatus 250 includes a substrate head 1, a polishing table 100, a polishing pad 101 (see FIG. 2 and the like), an electrolytic solution supply nozzle (electrolytic solution supply unit) 102 that supplies an electrolytic solution to the polishing pad 101, and a polishing pad 101. A dresser 218 for performing dressing and a water tank 222 for cleaning the dresser 218.

(Electrolytic complex polishing equipment)
FIG. 2 is a schematic configuration diagram of the electrolytic composite polishing apparatus 250. As shown in FIG. 2, the substrate head 1 is connected to a head drive shaft 11 via a universal joint portion 10, and the head drive shaft 11 is connected to a head air cylinder 111 fixed to a swing arm 110. Has been. The head drive shaft 11 is moved up and down by the head air cylinder 111 to raise and lower the entire substrate head 1 and press the retainer ring 3 fixed to the lower end of the head body 2 against the polishing table 100. The head air cylinder 111 is connected to the compressed air source 120 via a regulator RE1, and the regulator RE1 can adjust the fluid pressure such as the air pressure of the pressurized air supplied to the head air cylinder 111. . Thereby, the pressing force with which the retainer ring 3 presses the polishing pad 101 can be adjusted.

  The head drive shaft 11 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 head motor 114 as a rotation drive unit is fixed to the swing arm 110, and the timing pulley 113 is connected to a timing pulley 116 provided in the head motor 114 via a timing belt 115. Accordingly, when the head motor 114 is driven to rotate, the rotary cylinder 112 and the head drive shaft 11 rotate together via the timing pulley 116, the timing belt 115, and the timing pulley 113, and the substrate head 1 rotates. The swing arm 110 is supported by a shaft 117 that is fixedly supported by a frame (not shown).

(Substrate head)
3 is a sectional view showing the substrate head 1, and FIG. 4 is a bottom view of the substrate head 1 shown in FIG. As shown in FIG. 3, the substrate head 1 includes a cylindrical container-shaped head main body 2 having an accommodating space therein, and a retainer ring 3 fixed to the lower end of the head main body 2. The head body 2 is formed of a material having high strength and rigidity, such as metal and ceramics. The retainer ring 3 is made of a highly rigid resin such as PPS (polyphenylene sulfide) or an insulating material such as ceramics.

  The head body 2 is fitted to a cylindrical container-like housing part 2a, an annular pressure sheet support part 2b fitted inside the cylindrical part of the housing part 2a, and an outer peripheral edge part on the upper surface of the housing part 2a. And an annular seal portion 2c. The lower part of the retainer ring 3 fixed to the lower surface of the housing part 2a of the head body 2 protrudes inward. The retainer ring 3 may be formed integrally with the head body 2.

  The above-described head drive shaft 11 is disposed above the central portion of the housing portion 2 a of the head body 2, and the head body 2 and the head drive shaft 11 are connected by a universal joint portion 10. The universal joint portion 10 includes a spherical bearing mechanism that allows the head body 2 and the head drive shaft 11 to tilt relative to each other, and a rotation transmission mechanism that transmits the rotation of the head drive shaft 11 to the head body 2. 2, the pressing force and the rotational force of the head drive shaft 11 are transmitted to the head body 2 while allowing the tilting of the second drive shaft 11 to the head drive shaft 11.

  The spherical bearing mechanism is interposed between a spherical recess 11a formed at the center of the lower surface of the head drive shaft 11, a spherical recess 2d formed at the center of the upper surface of the housing portion 2a, and both recesses 11a, 2d. The bearing ball 12 is made of a high hardness material such as ceramics. The rotation transmission mechanism includes a drive pin (not shown) fixed to the head drive shaft 11 and a driven pin (not shown) fixed to the housing portion 2a. Even if the head body 2 is tilted, the driven pin and the driving pin are relatively movable in the vertical direction, so that they are engaged with each other by shifting their contact points, and the rotation transmission mechanism rotates the torque of the head driving shaft 11. Is reliably transmitted to the head body 2.

  In a space defined inside the head body 2 and the retainer ring 3 fixed to the head body 2 integrally, an elastic pad 4 that contacts a substrate W such as a semiconductor wafer held by the substrate head 1 and an annular shape The holder ring 5 and the substantially disc-shaped chucking plate 6 that supports the elastic pad 4 are accommodated. The elastic pad 4 is sandwiched between a holder ring 5 and a chucking plate 6 fixed to the lower end of the holder ring 5, and covers the lower surface of the chucking plate 6. Thereby, a space is formed between the elastic pad 4 and the chucking plate 6.

  A pressure sheet 7 made of an elastic film is stretched between the holder ring 5 and the head body 2. The pressure sheet 7 is formed of a rubber material having excellent strength and durability, such as ethylene propylene rubber (EPDM), polyurethane rubber, and silicon rubber. The pressure sheet 7 is fixed with one end sandwiched between the housing portion 2a of the head body 2 and the pressure sheet support portion 2b and the other end sandwiched between the upper end portion 5a of the holder ring 5 and the stopper portion 5b. ing. A pressure chamber 21 is formed inside the head main body 2 by the head main body 2, the chucking plate 6, the holder ring 5, and the pressure sheet 7. As shown in FIG. 2, a fluid path 31 made of a tube, a connector, or the like extends from the pressure chamber 21, and the pressure chamber 21 is supplied with a compressed air source via a regulator RE <b> 2 installed in the fluid path 31. 120.

  When the pressure sheet 7 shown in FIG. 3 is made of an elastic body such as rubber, and the pressure sheet 7 is sandwiched and fixed between the retainer ring 3 and the head body 2, the pressure sheet as an elastic body is used. Due to the elastic deformation of 7, a preferable plane cannot be obtained on the lower surface of the retainer ring 3. Therefore, in order to prevent this, in this example, the pressure sheet support portion 2b is provided as a separate member, and the pressure sheet 7 is sandwiched between the housing portion 2a of the head body 2 and the pressure sheet support portion 2b. It is fixed.

  Inside a space formed between the elastic pad 4 and the chucking plate 6, a center bag (center contact member) 8 as a contact member that contacts the elastic pad 4 and a ring tube (outer contact member) ) 9 is provided. In this example, as shown in FIGS. 3 and 4, the center bag 8 is disposed at the center of the lower surface of the chucking plate 6, and the ring tube 9 surrounds the periphery of the center bag 8. 8 is arranged outside. The elastic pad 4, the center bag 8 and the ring tube 9 are formed of a rubber material having excellent strength and durability, such as ethylene propylene rubber (EPDM), polyurethane rubber, silicon rubber, etc., like the pressure sheet 7. Yes.

  As shown in FIG. 3, the space formed between the chucking plate 6 and the elastic pad 4 is partitioned into a plurality of spaces by the center bag 8 and the ring tube 9, and the center bag 8 and the ring tube 9. A pressure chamber 22 is formed between them, and a pressure chamber 23 is formed outside the ring tube 9.

  The center bag 8 includes an elastic film 81 that contacts the upper surface of the elastic pad 4 and a center bag holder (holding part) 82 that detachably holds the elastic film 81. A screw hole 82a is formed in the center bag holder 82, and the center bag 8 is detachably attached to the center portion of the lower surface of the chucking plate 6 by screwing a screw 55 into the screw hole 82a. . A center pressure chamber 24 is formed in the center bag 8 by an elastic membrane 81 and a center bag holder 82.

  Similarly, the ring tube 9 includes an elastic film 91 that contacts the upper surface of the elastic pad 4 and a ring tube holder (holding portion) 92 that detachably holds the elastic film 91. A screw hole 92a is formed in the ring tube holder 92, and the ring tube 9 is detachably attached to the lower surface of the chucking plate 6 by screwing a screw 56 into the screw hole 92a. An intermediate pressure chamber 25 is formed in the ring tube 9 by an elastic membrane 91 and a ring tube holder 92.

  The pressure chambers 22, 23, the central pressure chamber 24, and the intermediate pressure chamber 25 are in fluid communication with fluid passages 33, 34, 35, 36 made of tubes and connectors, respectively. It is connected to a compressed air source 120 as a supply source via regulators RE3, RE4, RE5, and RE6 installed in the respective fluid passages 33 to 36. The fluid paths 31 and 33 to 36 are connected to the regulators RE2 to RE6 via a rotary joint (not shown) provided at the upper end of the head drive shaft 11.

  Pressurized fluid such as pressurized air is supplied to the pressure chamber 21 and the pressure chambers 22 to 25 above the chucking plate 6 through fluid passages 31 and 33 to 36 communicating with the pressure chambers. It has come to be. As shown in FIG. 2, the pressures of the pressurized fluid supplied to the pressure chambers can be adjusted by regulators RE <b> 2 to RE <b> 6 arranged on the fluid paths 31 and 33 to 36 of the pressure chambers 21 to 25. . Thereby, the pressure inside each pressure chamber 21-25 can be controlled independently, respectively, or it can be made atmospheric pressure or a vacuum.

Thus, by making the pressures inside the pressure chambers 21 to 25 independently variable by the regulators RE2 to RE6, the pressing force for pressing the substrate W against the polishing pad 101 via the elastic pad is changed to a portion of the substrate W. It can be adjusted for each (partition area).
Further, as shown in FIG. 3, a plurality of convex portions 42 are erected from the chucking plate 6 to the pressure chambers 22 and 23. The tip of the convex portion 42 is exposed to the surface of the elastic pad 4 through the opening 41. Further, a fluid passage 43 extends from the front end surface of the convex portion 42 and is connected to a vacuum source 121 shown in FIG. As a result, the substrate W can be vacuum-sucked at the tip surface of the convex portion 42 shown in FIG.

  As shown in FIG. 2, in the polishing table 100 of the electrolytic composite polishing apparatus 250, a sensor coil 228 of an ITM 226 made of, for example, an eddy current sensor for measuring the film thickness of a conductive film or the like on the substrate surface is embedded. The signal from the ITM 226 is input to the control unit 310, and the regulators RE3 to RE6 are controlled by the output from the control unit 310.

(Polishing table, polishing pad)
FIG. 5A is a longitudinal sectional view schematically showing a main part of the electrolytic composite polishing apparatus. A disc-shaped support member 254 is fixed to the upper surface of the polishing table 100. The support member 254 is made of a conductive material (metal, alloy, conductive plastic, or the like). The polishing pad 101 is attached to the upper surface of the support member 254, and the upper surface of the polishing pad 101 is a polishing surface. The polishing table 100 is connected to a rotation mechanism (not shown), so that the polishing table 100 can rotate integrally with the support member 254 and the polishing pad 101.

  The electrolyte supply nozzle 102 extends along the radial direction of the polishing pad 101. An electrolyte solution supply port 102 a is provided at the tip of the electrolyte solution supply nozzle 102. The supply port 102 a is located above the central portion of the polishing pad 101, and an electrolytic solution is supplied to the central portion of the polishing pad 101 from an electrolytic solution supply source (not shown) through the electrolytic solution supply nozzle 102. When the polishing pad 101 rotates, the electrolytic solution wets and spreads outward, and is filled between the substrate head 1 and the polishing pad 101 and into the plurality of through holes 101 a of the polishing pad 101.

  The support member 254 is connected to the negative electrode of the power source 252 and functions as a first electrode (cathode). Rollers, brushes, or the like are used as electrical contacts between the wiring extending from the power source 252 and the support member (cathode) 254. For example, as shown in FIG. 5A, the electrical contact 262 can be brought into contact with the side surface of the support member 254. The electrical contact 262 is preferably formed of a soft metal having a small specific resistance, such as gold, silver, copper, platinum, or palladium.

  A second electrode (power supply electrode) 264 connected to the positive electrode of the power supply 252 is disposed on the side of the polishing pad 101. The substrate head 1 is configured to bring the substrate W into contact with the polishing surface in a state where a part of the substrate W protrudes to the side of the polishing pad 101, so that the lower surface of the substrate W comes into contact with the second electrode 264. It has become. Thereby, power is supplied from the second electrode 264 to the conductive film of the substrate W. It is also possible to supply power from the second electrode 264 to the conductive film of the substrate W through the retainer ring. Then, the support member 254 as a cathode and the conductive film on the substrate W as an anode are electrically connected through an electrolytic solution filled in the through hole 101a of the polishing pad 101.

  FIG. 5B is a longitudinal sectional view schematically showing a main part of another electrolytic composite polishing apparatus. The support member 254 of the electrolytic composite polishing apparatus 250 basically includes a disk-shaped base 254b and a lid 254a that covers the upper surface of the base 254b. As described above, since the support member 254 functions as a cathode (first electrode), at least one of the lid 254a and the base 254b is made of a conductive material.

  A plurality of communication holes 255 are formed in the same position as the through hole 101 a of the polishing pad 101 in the lid 254 a of the support member 254. Furthermore, a plurality of communication grooves 256 that allow these communication holes 255 to communicate with each other are formed on the lower surface of the lid 254a. Note that a communication groove may be provided on the upper surface of the base 254b. At the center of the polishing pad 101, a first electrolyte receiving port 258A penetrating the polishing pad 101 vertically is formed. Further, the lid 254a has a second electrolyte receiving port 258B at the same position as the first electrolyte receiving port 258A. The second electrolyte receiving port 258B communicates with the plurality of communication grooves 256.

  With such a configuration, the electrolytic solution supplied from the supply port 102a of the electrolytic solution supply nozzle 102 passes through the first electrolytic solution receiving port 258A, the second electrolytic solution receiving port 258B, the communication groove 256, and the communication hole 255 in this order. It flows and reaches the through hole 101a. Then, an upward flow of the electrolyte toward the polishing surface is formed inside the through hole 101a, and the electrolyte is supplied to the polishing surface.

(First embodiment, electrolytic composite polishing method)
Next, the electrolytic composite polishing method according to the first embodiment will be described.
FIG. 6A is an explanatory diagram of the substrate before polishing. First, the film configuration of the substrate W to be polished in this embodiment will be described. On the surface of the substrate W made of silicon or the like, an interlayer insulating film 62 made of an insulating material such as a so-called Low-k material, SiO 2, SiOF, or SiOC is formed. On the surface of the interlayer insulating film 62, a contact plug and a recess 63 for forming a wiring are formed. A barrier film 64 made of titanium, tantalum, tungsten, ruthenium and / or an alloy thereof is formed to a thickness of about 10 nm on the surface of the interlayer insulating film 62 including the recess 63. The barrier film 64 is provided in order to prevent the metal material of the conductive film 66 described below from diffusing into the substrate W and to improve the adhesion between the conductive film 66 and the interlayer insulating film 62. On the surface of the barrier film 64, a conductive film 66 made of tungsten is formed to a thickness of about 500 to 600 nm. In the case where the conductive film 66 is formed by electrolytic plating, a seed film (not shown) serving as an electrode for electrolytic plating is formed on the surface of the barrier film 64. A recess 67 having a height of about 300 nm and a width of about 100 μm is formed on the surface of the conductive film 66 following the recess 63 of the interlayer insulating film 62.

Since only the conductive film 66 filled in the recess 63 of the interlayer insulating film 62 is used as a contact plug or a metal wiring, the conductive film 66 formed outside the recess 63 is unnecessary. Therefore, the excess conductive film 66 is removed by electrolytic composite polishing.
FIG. 6B is an explanatory diagram of electrolytic composite polishing. In electrolytic composite polishing, the electrolytic solution 50 is brought into contact with the conductive film on the surface of the substrate W to apply a voltage to the conductive film 66, and the substrate W and the polishing pad 101 are moved relative to each other while pressing the surface of the substrate W against the polishing pad 101 ( The surface of the conductive film 66 is polished.

  Since a plurality of wirings are stacked via the interlayer insulating film, the surface of the substrate W needs to be flattened with the excess conductive film 66 removed. In the electrolytic composite polishing, a protective film 70 made of an electrically insulating material is formed on the surface of the conductive film 66 by applying a voltage to the conductive film 66. The protective film formed on the upper stage H of the conductive film 66 (outside the recess 67) is removed by contact with the polishing pad 101. As a result, the conductive film 66 of the upper stage portion H is dissolved in the electrolytic solution 50 and removed. On the other hand, the conductive film in the lower stage L (inside the recess 67) is shielded by the protective film 70 and does not dissolve in the electrolytic solution 50. Thus, the step of the conductive film is eliminated. As a result, as shown in FIG. 6C, the surface of the conductive film 66 and the exposed surface of the barrier film 64 are arranged on the same plane, and the substrate W is flattened.

  By the way, the tungsten polishing method by CMP employs a mechanism in which an acidic slurry having a pH <4 is used to form a tungsten oxide film having a considerable thickness, and this tungsten oxide film is mechanically polished. There is a problem that the speed becomes low. Therefore, in the electrolytic composite polishing method according to the present embodiment, an electrolytic solution having a pH of 4 to 10 is employed to form a protective film different from the conventional tungsten oxide film.

In the present embodiment, basically any electrolyte can be used as long as it has an appropriate conductivity (about 1 mS / cm). As the main electrolyte contained in the electrolytic solution, any material may be used as long as it provides appropriate conductivity and does not roughen the surface of the conductive film. Further, those that form a complex or chelate with tungsten and promote the dissolution of tungsten are preferable, and for example, an organic acid is preferably contained. As the organic acid, one or more kinds selected from the group of glycolic acid, pyrophosphoric acid, phosphoric acid, citric acid, malic acid, maleic acid, malonic acid, lactic acid, tartaric acid, succinic acid, and salts thereof Is preferably used. The pH range is preferably pH 4 to 10, which is likely to produce a complex or chelate in which tungsten is a soluble compound.
The electrolytic solution may contain a pH adjusting component. As the pH adjusting component, an alkali metal salt, an alkaline earth metal salt or the like is used, but an ammonium salt is preferable in order to prevent metal contamination.
The electrolyte solution may contain an additive that generates an electrically insulating substance. A primary amine polymer can be used as an additive for generating an electrically insulating substance. For example, an allylamine polymer (polymer having only a primary amino group in the side chain, molecular weight 1000 to 60000), allylamine hydrochloride polymer (molecular weight 1000 to 60000), allylamine hydrochloride / diallylamine hydrochloride copolymer (molecular weight 20000 to 20000) 100000), allylamine amide sulfate polymer (molecular weight 12000), allylaminoacetate / diallylamine acetate copolymer (molecular weight 100000), allylamine / dimethylallylamine copolymer (molecular weight 1000), partially methoxycarbonylated allylamine polymer (molecular weight) 15000), partially methylcarbonylated allylamine acetate polymer (molecular weight 15000) and the like. The primary amine polymer may be polyethyleneimine (molecular weight 1000 to 70000). Polyethyleneimine is a polymer having a branched structure containing primary, secondary, and tertiary amines in the molecule, and is effective because the primary amine is in the molecule.
The preferred concentration of the additive that produces the electrical insulating material is 0.01 to 5% by weight in the case of polyethyleneimine, more preferably 0.1 to 1% by weight, and the concentration is lower than 0.01% by weight. And the current suppression effect (electrical insulating property) is low. On the other hand, when the concentration is higher than 5% by weight, the enhancement of the current suppression effect with respect to the increase in the added amount tends to decrease. There is no. By adding this, the voltage range with high step resolution can be shifted to a lower level as will be described later.
The abrasive grains required a concentration of 10% or more in the case of CMP, but in this embodiment, a concentration of 1% or less is sufficiently effective. A surfactant may be added in order to improve the dispersibility of the abrasive grains. However, since the concentration of the abrasive grains is originally low, there is no major problem even if it is not added.
As an example of such an electrolytic solution, ammonium citrate (pH 8) is employed in the present embodiment.

The inventor of the present application experimented and evaluated the tungsten polishing rate by the method described below.
A processing experiment was performed using an electropolishing apparatus capable of processing only a portion corresponding to a diameter of 40 mm of the substrate. This device can control the electrode potential of the metal film formed on the substrate, and it is processed by polishing the exposed metal film with a polishing pad attached to a rotating polishing table while applying a voltage. Progresses.
Electrochemical measurement system HZ-3000 (made by Hokuto Denko Co., Ltd.) was used for measuring the electrode potential, and a silver / silver chloride electrode (Ag / AgCl) was used for the reference electrode. The polishing pad used was a foamed polyurethane pad (X-Y Groove grooved IC1000 single layer pad, manufactured by Nitta Haas Co., Ltd.) having a lattice-like groove on the surface.
An anodic polarization measurement (gradually increasing the electrode potential of the substrate) was performed using this apparatus, and the relationship between the applied voltage and the current flowing through the substrate was measured.
FIG. 7 is a graph showing the relationship between the potential of the conductive film and the current density. In FIG. 7, the current flowing per area to be polished on the substrate is defined as the current density, which is plotted on the vertical axis. As the current density is larger, the amount of the conductive film dissolved in the electrolytic solution is increased, and the polishing rate is increased. In FIG. 7, the horizontal axis represents the electrode potential. However, in an actual polishing apparatus, it is complicated to control with the electrode potential, so control is performed with the applied voltage between the substrate to be polished and the cathode. Therefore, in the following description, the expression of applied voltage is used for the electrode potential control of the substrate. The applied voltage indicates “the potential difference between the electrode potential of the substrate serving as the anode, the electrode potential of the support member (polishing table) serving as the cathode, and the potential difference between the anode and the cathode including the potential drop of the electrolytic solution”.

  When the applied voltage is increased by bringing a pH 4-10 electrolytic solution into contact with the conductive film, the current density rapidly changes at a predetermined voltage. When the voltage applied to the conductive film is increased from 0, the current density increases in proportion to the voltage. However, when the voltage is increased beyond the first change voltage at the first change point (for example, point A), the current density is increased. Turns from increasing to decreasing. Further, when the voltage is increased beyond the second change voltage at the second change point (for example, the B point), the degree of decrease in the current density is reduced, the current density is not reduced, and the value changes to a substantially constant value. When a voltage lower than the first change voltage is applied, a protective film that is soluble in the electrolyte is formed on the surface of the conductive film, but when a voltage higher than the second change voltage is applied, It is considered that a protective film that is insoluble in the electrolytic solution is formed on the surface of the conductive film.

  The inventor of the present application has found that the first change voltage and the second change voltage described above change depending on the contact surface pressure between the substrate W and the polishing pad. In FIG. 7, the thick solid line is the case where the contact surface pressure is 0.5 psi (the contact surface pressure is a finite value, which corresponds to polishing at the upper step of the step on the conductive film surface), and the thick broken line is the contact surface pressure of 0 psi ( This is a case where the contact surface pressure is 0 and corresponds to the lower step of the step on the conductive film surface. When the contact surface pressure is a finite value, the first change point is point A, when the contact surface pressure is a finite value, the second change point is B point, and when the contact surface pressure is 0, the first change point is The second change point when the C point and the contact surface pressure are 0 is defined as the D point. The higher the contact surface pressure, the higher the first and second change voltages and the higher the current density. The first change voltage (point C voltage) and the second change voltage (point D voltage) when the contact surface pressure is 0 are the first change voltage (point A voltage) when the contact surface pressure is a finite value, and Each is about 0.5 V lower than the second change voltage (point B voltage).

Here, the range where the applied voltage is 0 to C point voltage is α region, the range of C point voltage to B point voltage is β region, and the range above B point voltage is γ region. The range from the point C voltage to the point A voltage is the δ region.
FIG. 8 is an explanatory diagram of a protective film formation state when the voltage of each region is applied to the conductive film, FIG. 8A shows the case of the α region, and FIG. 8B shows the β region. FIG. 8C shows the case of the γ region.

When a voltage in the α region is applied, a protective film 71 that is soluble in the electrolytic solution 50 is formed as shown in FIG. In the case where there is a step on the surface of the conductive film, the protective film 71 is completely removed by polishing at the upper stage H where the contact surface pressure between the polishing pad 101 and the conductive film 66 has a finite value.
When a voltage in the γ region is applied, a protective film 72 that is insoluble in the electrolytic solution 50 is formed as shown in FIG. In the case where there is a step on the surface of the conductive film, the protective film 72 remains without being polished in the lower step portion L where the contact surface pressure between the polishing pad 101 and the conductive film 66 is zero.

On the other hand, when a voltage in the β region is applied, as shown in FIG. That is, a soluble protective film is formed on the upper portion H where the contact surface pressure between the polishing pad 101 and the conductive film 66 has a finite value, and the protective film is removed by polishing. In addition, an insoluble protective film 72 is formed on the lower step L where the contact surface pressure between the polishing pad 101 and the conductive film 66 becomes zero, and the protective film 72 remains without being polished.
In this embodiment, electrolytic composite polishing is performed while maintaining the applied voltage in the β region. Thereby, dissolution of the conductive film 66 in the electrolytic solution is promoted in the upper stage portion H and suppressed in the lower stage portion L. Therefore, the step on the surface of the conductive film 66 can be quickly eliminated.

  Further, when a voltage in the β region is applied, the polishing rate of the lower step portion L covered with the protective film 72 becomes extremely slow, so that the conductive film 66 is less likely to be dished. Further, since the polishing rate of the upper stage portion H can be controlled by adjusting the applied voltage, the contact surface pressure between the polishing pad 101 and the conductive film 66 can be set low, and erosion can be suppressed. For example, the contact surface pressure, which was about 4 psi in the conventional CMP, can be set to about 2 psi in this embodiment.

As described above, the larger the current density, the higher the polishing rate.
As shown in FIG. 7, in the α region where the applied voltage is 0 to the point C voltage, the voltage increases both when the contact surface pressure is a finite value (0.5 psi) and when the contact surface pressure is 0 (0 psi). Along with this, the current density increases. On the other hand, in the δ region between the point C voltage and the point A voltage, the current density when the contact surface pressure is set to a finite value continues to increase, but the current density when the contact surface pressure is set to 0 starts to decrease. . Therefore, the current density difference ΔIδ between when the contact surface pressure in the δ region is finite and when the contact surface pressure is 0 is always larger than the current density difference ΔIα in the α region. The difference in current density between when the contact surface pressure is a finite value and when the contact surface pressure is 0 actually corresponds to the difference in polishing rate between the upper and lower steps of the step on the conductive film surface. Therefore, by polishing while maintaining the applied voltage in the δ region, the difference in polishing speed between the upper and lower steps of the step on the conductive film surface increases, so the step on the conductive film surface can be quickly eliminated. Can do.

In FIG. 7, the thick line indicates a case where an additive that generates an electrical insulating substance is not included in the electrolytic solution, and the thin line indicates a case where 1% by weight of polyethyleneimine (PEI) is added as an additive that generates an electrical insulating substance. To express. The solid line indicates the case where the contact surface pressure between the polishing pad and the substrate is 0.5 psi, and the broken line indicates the case where the contact surface pressure is 0 psi.
It can be seen that the current density is increased when the additive that generates the electrically insulating substance is not included (or the concentration is low). The reason for this is considered to be that a stronger protective film is formed as the concentration of the additive that generates the electrically insulating substance is higher, and is difficult to remove by polishing. Therefore, when it is desired to increase the polishing rate, an electrolytic solution having a low concentration of an additive that generates an electrically insulating substance may be used. Conversely, when it is desired to reduce the polishing rate in order to polish a thin conductive film or accurately stop polishing, an electrolytic solution having a high concentration of an additive that generates an electrically insulating substance may be used. Note that FIG. 7 shows that the first and second change voltages increase when the additive that generates the electrical insulating substance is not included (or the concentration is low). Therefore, it is desirable to adjust the applied voltage according to the concentration of the additive that generates the electrically insulating substance.

FIG. 9 is a graph showing the relationship between applied voltage and current density when the pH of the electrolytic solution is changed. In the experiment of FIG. 9, an electrolyte solution having pH 4, pH 6, pH 8, and pH 9 (without an additive that generates an electrical insulating material) is employed.
It can be seen that the current density increases as the pH of the electrolyte increases. The reason is considered to be that dissolution of the conductive film is promoted as the pH of the electrolytic solution increases. Therefore, when it is desired to increase the polishing rate, an electrolytic solution having a high pH may be used. Conversely, when it is desired to reduce the polishing rate, an electrolytic solution having a low pH may be used. Note that FIG. 9 indicates that the first and second change voltages increase as the pH of the electrolyte increases. Therefore, it is desirable to adjust the applied voltage according to the pH of the electrolytic solution.

FIG. 10 is a graph showing the relationship between applied voltage and current density when the number of revolutions of the polishing pad is changed. In the experiment of FIG. 10, an electrolytic solution that does not contain an additive that generates an electrically insulating substance is used. In FIG. 10, a thick line is a case where the rotation speed is 250 rpm, and a thin line is a case where the rotation speed is 50 rpm. The solid line indicates the case where the contact surface pressure between the polishing pad and the substrate is 0.5 psi, and the broken line indicates the case where the contact surface pressure is 0 psi.
It can be seen that the current density increases as the number of revolutions of the polishing pad increases. The reason is considered to be that the removal of the protective film proceeds and the dissolution of the conductive film is promoted as the number of rotations of the polishing pad increases. Accordingly, when it is desired to increase the polishing rate, the number of rotations of the polishing pad may be increased. Conversely, if it is desired to reduce the polishing rate, the number of revolutions of the polishing pad may be reduced. The number of rotations of the polishing pad can be changed during polishing. It can be seen from FIG. 10 that the first and second change voltages increase as the number of revolutions of the polishing pad increases. Therefore, it is desirable to adjust the applied voltage according to the number of rotations of the polishing pad.

(Second embodiment, electrolytic composite polishing method)
Next, an electrolytic composite polishing method according to the second embodiment will be described.
In the first embodiment, the polishing process was performed while maintaining the voltage applied to the conductive film within a predetermined range. On the other hand, the second embodiment is different in that a protective film forming step of forming a protective film by applying a predetermined voltage to the conductive film is performed before the polishing step. Note that detailed description of portions having the same configuration as in the first embodiment is omitted.

  First, a protective film forming step of forming a protective film on the surface of the conductive film is performed by bringing the electrolytic solution into contact with the conductive film on the surface of the substrate and applying a voltage to the conductive film. Here, a voltage equal to or higher than the second change voltage at the second change point (for example, point D in FIG. 7) when the contact surface pressure is 0 is applied. Thereby, as shown in FIG. 8C, it is considered that a protective film 72 insoluble in the electrolytic solution 50 is formed. The protective film 72 is irreversibly formed on the entire surface of the conductive film 66, and does not change even when the applied voltage is lowered to the second change voltage or lower.

  After this protective film forming step, a normal electrolytic composite polishing step is performed. Then, the protective film 72 formed on the upper stage portion H of the conductive film 66 is removed by polishing, but the protective film 72 formed on the lower stage portion L of the conductive film 66 remains without being polished. Thereby, dissolution of the conductive film 66 in the electrolytic solution is promoted in the upper stage portion H and suppressed in the lower stage portion L. Therefore, the step on the surface of the conductive film 66 can be quickly eliminated.

(Modification)
You may perform a chemical mechanical polishing (CMP) process after the protective film formation process mentioned above.
FIG. 11 is a schematic view of a CMP apparatus. In the CMP, the surface of the conductive film is polished by supplying the slurry 52 to the conductive film on the surface of the substrate W and moving the substrate W and the polishing pad 101 relative to each other while pressing the surface of the substrate W against the polishing pad 101. is there. Even when the CMP process is performed after the protective film forming process, the protective film 72 formed on the upper stage H of the conductive film 66 is removed by polishing as shown in FIG. The protective film 72 formed in the portion L remains without being polished. Thereby, dissolution of the conductive film 66 in the electrolytic solution is promoted in the upper stage portion H and suppressed in the lower stage portion L. Therefore, the step on the surface of the conductive film 66 can be quickly eliminated.

  The technical scope of the present invention is not limited to the above-described embodiment and its modifications, and includes various modifications made to the above-described embodiment and the like without departing from the spirit of the present invention. . That is, the specific materials and configurations described in the embodiments and the like are merely examples, and can be changed as appropriate.

(Polishing pad)
In addition, the following can be employed as the polishing pad.
As for the type of the polishing pad, an independent foamed polyurethane pad or a continuous foamed suede pad can be used. Moreover, when using the electrolyte solution which does not contain an abrasive grain, you may use the fixed abrasive pad which rebounded the abrasive grain with the binder. The abrasive grains include cerium oxide (Ce0 ₂ ), alumina (A1 ₂ 0 ₃ ), silicon carbide (SiC), silicon oxide (Si0 ₂ ), zirconia (Zr0 ₂ ), iron oxide (FeO, Fe ₂ O ₃ , Fe ₃ 0 ₄ ), manganese oxide (Mn0 ₂ , Mn ₂ 0 ₃ ), magnesium oxide (MgO), calcium oxide (CaO), barium oxide (BaO), zinc oxide (ZnO), barium carbonate (BaC0 ₃ ), calcium carbonate (CaC0 ₃ ), diamond (C), or a composite material thereof can be used. As binders, phenol resin, aminoplast resin, urethane resin, epoxy resin, acrylic resin, acrylated isocyanurate resin, urea-formaldehyde resin, isocyanurate resin, acrylated urethane resin, acrylated epoxy resin, etc. shall be adopted. Is possible. In addition, a conductive pad having a conductive surface on at least a part of the polishing surface may be used for the purpose of securing power supply to the surface of the conductive film to be polished.

  Here, regarding the groove shape of the polishing pad, one or more of (1) concentric circular grooves, (2) eccentric grooves, (3) polygonal grooves (including lattice grooves), (4) spiral grooves, (5) radiation Grooves, (6) parallel grooves, (7) arc-shaped grooves, and combinations thereof may be formed. These groove shapes affect the retention and discharge of the electrolyte. For example, concentric circular grooves and eccentric grooves have an effect that the electrolytic solution is held on the polishing pad because the flow path is closed. On the other hand, the polygonal grooves and the radiation grooves have an effect of accelerating the inflow of the electrolyte into the object to be polished and the discharge of the electrolyte out of the polishing pad. In order to increase the efficiency of inflow, outflow, and holding of the electrolyte into the surface of the substrate to be processed, the groove width, groove pitch, and groove depth are appropriately adjusted in the polishing pad surface to obtain grooves in the polishing pad. The density distribution may be adjusted. For example, the groove width / depth should be 0.4 mm or more, and the groove pitch should be at least twice the groove width. Considering the flow of the electrolyte, the groove width / depth is preferably 0.6 mm or more. Also, for the purpose of activating the flow of the electrolyte between the grooves, auxiliary grooves (for example, a plurality of fine grooves formed between concentric circular grooves, a thin groove formed between thick lattice grooves, etc.) ) May be provided. As for the cross-sectional shape of the groove, a V groove may be employed in addition to the square groove and the round groove. When promoting the discharge of the electrolytic solution from the groove, a forward groove inclined downstream in the rotation direction may be formed in consideration of the rotation direction of the polishing table on which the polishing pad is mounted. Conversely, when suppressing discharge of the electrolytic solution from the groove, a reverse groove inclined toward the upstream side in the rotation direction may be formed. Further, one or more through holes may be formed on the surface of the polishing pad for the purpose of holding the electrolytic solution.

  Further, the shape of the contact surface between the polishing pad and the wafer affects the mechanical removal of the protective film produced by the electrolytic reaction. In order to increase the mechanical action on the contact surface, a sharp contact surface shape is preferable, and examples thereof include a cone shape, a polygonal pyramid shape, a pyramid shape, and a prism shape. Here, depending on the object to be polished, if the contact surface shape is too sharp, it may cause scratches and the like. As a measure for avoiding this, a shape with a flat top surface such as a truncated cone or a truncated pyramid may be mentioned. In addition, examples of the shape that further reduces the mechanical action on the contact surface include a cylinder, an elliptic cylinder, and a hemisphere. The arrangement of these shapes may be a regular shape such as a lattice, a staggered pattern, or a triangular arrangement, or a random shape in order to eliminate the regularity. A plurality of these shapes may exist in the polishing surface of the polishing pad, and the density distribution may be adjusted.

(Thickness detection sensor)
In the embodiment of FIG. 2, an example of using an eddy current sensor as a method of detecting the residual film thickness of the conductive film has been shown. However, in addition to this, an optical monitor, fluorescent X-ray film thickness measurement, voltage / current change, etc. May be used.
The optical monitor uses the fact that the reflected light intensity changes due to light interference, such as a method of irradiating measurement light through a pad hole from a light source embedded in the table, or a state where the substrate is overhanged outside the polishing table. The measurement method etc. can be used.
Fluorescent X-ray film thickness measurement utilizes the fact that the intensity of fluorescent X-rays generated when primary X-rays are irradiated onto a measurement object changes with respect to the film thickness and is embedded in a table during polishing. Measurement is performed by irradiating the conductive film with primary X-rays from the X-ray source.
The change in voltage / current utilizes the fact that the electrical resistance changes according to the film thickness of the conductive film to be measured. In this method, the film thickness is calculated from the electrical resistance by measuring the change in current at a constant voltage or by measuring the change in voltage at a constant current. According to this method, since the film pressure can be detected by monitoring the voltage and current during polishing, it can be used easily.

For example, in the polishing of a conductive film including a conductive film on a barrier film or a barrier film on an insulating film, a method for detecting a state where the polishing of the conductive film is completed (polishing end point) is other than the above-described film thickness detection method. In addition, a method for observing changes in the polishing pad surface temperature and the substrate surface temperature, a method for observing changes in the friction force between the substrate and the polishing pad, a method for observing changes in the surface image, and components in the slurry and electrolyte Examples thereof include a method of looking at changes in oxide concentration and ion concentration derived from a conductive film.
In the method of observing changes in the polishing pad surface temperature and the substrate surface temperature, the temperature of the substrate surface is measured through measurement of the pad surface temperature with a radiation thermometer or through a hole provided in the polishing pad with a radiation thermometer embedded in the table. A method of measuring can be used.
In the method of observing the change in the frictional force between the polishing pad and the substrate, the method used is to measure the change in the drive current of the table or substrate holder on which the polishing pad is mounted, or the change over time in the vibration amplitude at a specific frequency for the substrate holder. it can.
In the method of observing the change in the substrate surface image, the change in the color of the substrate surface and the change in the two-dimensional image of the substrate surface by the CCD are measured by a chromaticity sensor embedded in the table through a hole provided in the polishing pad. A method is available.
In the method of observing changes in the slurry and the components in the electrolyte (by-product oxide concentration, conductive film ion concentration), the change in the conductive film-derived ion concentration in the polishing liquid discharged from the polishing table is measured. A method to do is available.

It is a top view which shows the arrangement configuration of a substrate processing apparatus. It is a schematic block diagram of an electrolytic composite polishing apparatus. It is sectional drawing of a substrate head. It is a bottom view of a substrate head. It is a longitudinal cross-sectional view which shows the principal part of an electrolytic composite polishing apparatus schematically. It is explanatory drawing of electrolytic composite grinding | polishing. It is a graph which shows the relationship between the electric potential of an electrically conductive film, and current density. It is explanatory drawing of the protective film formation state when the voltage of each area | region is applied. It is a graph which shows the relationship between the applied voltage at the time of changing pH of electrolyte solution, and a current density. It is a graph which shows the relationship between the applied voltage at the time of changing the rotation speed of a polishing pad, and a current density. It is a longitudinal cross-sectional view which shows the principal part of a chemical mechanical polishing apparatus roughly.

Explanation of symbols

A, C: First change point B, D: Second change point H: Upper step portion L ... Lower step portion W ... Substrate 1 ... Substrate head 50 ... Electrolyte solution 52 ... Slurry 63 ... Recess 64 ... Barrier film 66 ... Conductive film 67 ... Recess 70, 71, 72 ... Protective film 100 ... Polishing table 101 ... Polishing pad 102 ... Electrolyte supply nozzle 252 ... Power supply 254 ... Support member

Claims (9)

While contacting the electrolytic solution with the conductive film formed on the substrate surface and applying a voltage to the conductive film, the substrate and the polishing pad are relatively moved while pressing the substrate surface against the polishing pad with a predetermined contact surface pressure. An electrolytic composite polishing method for polishing the surface of the conductive film by moving the conductive film,
The electrolyte has a pH of 4 to 10,
When the voltage is increased with the contact surface pressure being 0, the voltage at which the current density turns from increasing to decreasing is set as the minimum voltage,
In the state where the contact surface pressure is a finite value, when the voltage is increased, the voltage that turns so that the current density does not decrease from the decrease after the increase is set as the maximum voltage,
An electrolytic composite polishing method comprising polishing the surface of the conductive film while maintaining the voltage at the minimum voltage or more and the maximum voltage or less. While contacting the electrolytic solution with the conductive film formed on the substrate surface and applying a voltage to the conductive film, the substrate and the polishing pad are relatively moved while pressing the substrate surface against the polishing pad with a predetermined contact surface pressure. An electrolytic composite polishing method for polishing the surface of the conductive film by moving the conductive film,
The electrolyte has a pH of 4 to 10,
When the voltage is increased with the contact surface pressure being 0, the voltage at which the current density turns from increasing to decreasing is set as the minimum voltage,
In the state where the contact surface pressure is a finite value, when the voltage is increased, the voltage at which the current density turns from increasing to decreasing is set as the maximum voltage,
An electrolytic composite polishing method comprising polishing the surface of the conductive film while maintaining the voltage at the minimum voltage or more and the maximum voltage or less.   The electrolytic composite polishing method according to claim 1, wherein a polishing rate of the conductive film is controlled by adjusting a pH of the electrolytic solution. The electrolytic solution includes an additive that reacts with the conductive film to generate an electrically insulating material,
The electrolytic composite polishing method according to claim 1, wherein a polishing rate of the conductive film is controlled by adjusting a concentration of the additive.   The electrolytic composite polishing method according to claim 1, wherein the polishing rate of the conductive film is controlled by adjusting the number of rotations of the polishing pad.   The electrolytic composite polishing method according to claim 1, wherein the conductive film is a tungsten film. A polishing method comprising a polishing step of polishing the conductive film formed on the substrate surface by relatively moving the substrate and the polishing pad while pressing the substrate surface against the polishing pad with a predetermined contact surface pressure,
In the state where the contact surface pressure is a finite value while relatively moving the substrate and the polishing pad, a voltage is applied while the electrolyte is in contact with the conductive film, and the voltage is increased. The threshold voltage is the voltage that turns so as not to decrease from the decrease after the increase.
Before the polishing step, in a state where the substrate and the polishing pad are not in contact with each other, the surface of the conductive film is protected by applying a voltage higher than the threshold voltage while bringing the electrolytic solution into contact with the conductive film. A polishing method comprising a protective film forming step of forming a film.   The polishing method according to claim 7, wherein the polishing step is a chemical mechanical polishing step or an electrolytic composite polishing step.   9. The polishing method according to claim 7, wherein the conductive film is a tungsten film.

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