WO2010052917A1 - Polishing head, polishing apparatus and substrate polishing body - Google Patents

Abstract

Disclosed is a polishing head which is capable of polishing a metal film of a substrate at a high speed and of preventing generation of scratches during polishing.  Also disclosed are a polishing apparatus and a substrate polishing body. A polishing head (10), to which a polishing tool (30) having a plurality of electrolyte solution-containing units (F1, F2) opened toward a polishing surface (31a) can be fitted, electrochemically and mechanically polishes a metal film (D1) formed on the surface layer of a device wafer (D) by being rotatively driven.  The polishing head comprises a tool holder (12) to which the polishing tool (30) is fitted with the polishing surface (31a) facing down in the vertical direction Z, an electrolyte solution supply passage (13) for supplying an electrolyte solution (E) to the electrolyte solution-containing units (F1, F2), and internal electric cables (15a, 15b) for feeding the electrical power for polishing from a power supply (2) to the electrolyte solution-containing units (F1, F2).

Description

Polishing head, polishing apparatus, and substrate polishing body

The present invention relates to a polishing head, a polishing apparatus, and a substrate polishing body suitable for electrochemically polishing a metal film on a substrate.

In semiconductor devices (semiconductor devices), wirings are stacked with high integration and miniaturization. As a method of layering the wiring, a process is adopted in which wiring is patterned on the surface of a semiconductor wafer, this is covered with an insulator such as silicon oxide, the next wiring is patterned, and this is repeated in order. .
In the process of patterning the wiring, the hole for the plug and the wiring groove are formed in an insulator such as silicon oxide (hereinafter referred to as an interlayer insulating film) by reactive ion etching or the like, and the hole for the plug and the wiring are formed thereon by copper plating. A conductor layer (metal film) is formed by simultaneously filling the groove with a copper wiring material. Thereafter, a so-called damascene method is employed in which excess metal on the surface of the conductor layer is removed by chemical mechanical polishing (CMP) and planarized to form wiring (for example, Patent Document 1). A platen rotary type polishing apparatus is used for CMP of the extra conductor layer.
In a platen rotary type polishing machine, a polishing pad of approximately the same size is attached to a rotating surface plate (platen) having a diameter more than twice the diameter of the semiconductor wafer, and the semiconductor wafer with the surface to be polished facing down is attracted to the head Then, the polishing pad is pressed against the surface to be polished, and the semiconductor wafer is polished while dripping the polishing liquid (slurry) onto the surface of the polishing pad.

However, since the platen rotary type polishing apparatus requires a platen diameter of more than twice the wafer diameter, there is a problem that the apparatus becomes large as the wafer diameter increases, and a problem that a large amount of polishing liquid (slurry) is consumed. Etc.

On the other hand, in recent years, introduction of a low dielectric constant material (so-called low-k material) for an interlayer insulating film has been studied for the purpose of reducing power consumption and operating speed of a semiconductor device. Since this low dielectric constant material has poor mechanical strength and chemical stability, the polishing by CMP or the like causes the conductor layer to be an interlayer insulating film due to the frictional force depending on the relative speed between the substrate and the polishing pad and the polishing pressure. May peel off. For this reason, a process capable of flattening while reducing the polishing pressure and maintaining a high polishing rate is desired.
Also, in the laminated wiring formation process of semiconductor devices, the thickness of the conductor layer of each wiring layer from the intermediate wiring layer (medium line) to the surface wiring layer (global line) tends to increase, and a higher polishing rate is desired. It is rare.
Furthermore, in the through via wiring formation process used in 3D LSI (three dimension large scale integration) in which semiconductor devices are stacked at wafer level or chip level and a plurality of semiconductor devices such as CPU and memory are mounted in one package, surplus Since the conductor layer reaches several tens of microns, there is a demand for further high-speed polishing.

Therefore, electrochemical mechanical polishing (eCMP) has been proposed as polishing capable of improving the planarization of the conductor layer as compared with CMP and capable of low pressure and high speed polishing. In eCMP, generally, a conductor layer and a plus electrode are connected, and the conductor layer and a minus electrode are connected via an electrolytic solution.

For example, in eCMP in Patent Document 2, a positive electrode is connected by bringing a conductive surface layer of a polishing pad into contact with a conductive layer.
However, since eCMP in Patent Document 2 is polished while the conductive surface layer and the conductor layer are in contact with each other, there is a possibility that the conductor layer is damaged.

JP 2008-91875 A Japanese Patent No. 4142554

An object of the present invention is to provide a polishing head, a polishing apparatus, and a substrate polishing body that are capable of polishing a metal film on a substrate and that are suitable for polishing without scratches.

The present invention solves the problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this. In addition, the configuration described with reference numerals may be improved as appropriate, or at least a part thereof may be replaced with another configuration.

In the first invention, the substrate polishing body (30, 230) provided with a plurality of electrolyte solution storage portions (F1, F2) opened in the polishing surface (31a) can be mounted, and by being driven to rotate, A polishing head that electrochemically and mechanically polishes a metal film (D1) provided on a surface layer of a substrate (D), the substrate polishing body being mounted with the polishing surface facing downward in the vertical direction Substrate polishing body mounting portion (12, 212A) to perform, electrolytic solution supply portion (13) for supplying the electrolytic solution (E) to the electrolytic solution storage portion, and polishing power from the power source (2) to the electrolytic solution storage portion And a power transmission unit (15a, 15b) for supplying to the polishing head.
According to a second aspect of the present invention, in the polishing head of the first aspect, the plurality of electrolyte solution storage portions (F1, F2) include anode electrodes (33, 233A), and the stored electrolyte solution (E) and the substrate (D) The electrolysis solution container (F1) for contacting the metal film (D1) and the cathode electrode (34, 234A) are brought into contact with each other. A polishing electrolyte container (F2) to be connected, and the power transmission unit (15a, 15b) connects the positive electrode (2a) of the power source (2) and the anode electrode of the energizing electrolyte container. The polishing head is characterized in that the negative electrode (2b) of the power source is connected to the negative electrode of the polishing electrolyte container.
According to a third aspect of the present invention, in the polishing head of the first or second aspect, the substrate polishing body (30, 230) is supplied from the electrolytic solution supply unit (13) and the electrolytic solution storage unit (F1, F2). The polishing head is characterized by comprising discharge portions (Ch1, Ch2, Ch201, Ch202) for discharging the electrolytic solution (E) accommodated in.

According to a fourth aspect of the present invention, the polishing head according to any one of the first to third aspects and the substrate polishing body (30, 230) are mounted with the polishing surface (31a) facing downward, A head driving unit that rotationally drives the polishing head, a table on which the metal film (D1) is provided on the surface layer and on which the substrate (D) having a diameter larger than the substrate polishing body is mounted, and a table that rotationally drives the table And a driving unit.

According to a fifth aspect of the present invention, there are provided a plurality of electrolytic solution storage portions (F1, F2) attached to any one of the first to third polishing heads and opened in the polishing surface (31a); A substrate polishing body comprising: a discharge portion (Ch1, Ch2, Ch201, Ch202) that discharges the electrolyte solution (E) supplied from the electrolyte solution supply portion (13) and stored in the electrolyte solution storage portion. It is.
According to a sixth invention, in the substrate polishing body of the fifth invention, the plurality of electrolyte solution storage portions (F1, F2) include anode electrodes (33, 233A), and the stored electrolyte solution (E) and the above An energizing electrolyte container (F1) for contacting the metal film (D1) of the substrate (D) and a cathode electrode (34, 234A), and the accommodated electrolyte and the metal film of the substrate A polishing substrate having a polishing electrolyte solution containing portion (F2) to be contacted.
According to a seventh invention, in the substrate polishing body of the sixth invention, the discharge portion (Ch1, Ch2, Ch201, Ch202) connects the plurality of energizing electrolyte storage portions (F1), and the substrate polishing body The through-electrolyte accommodating portion through-holes (Ch1, Ch201), which are through-holes that pass through the outside, are connected to the plurality of polishing electrolyte accommodating portions (F2), and the through-holes that go out of the substrate polishing body A polishing substrate, comprising: a polishing electrolyte solution storage part through hole (Ch2, Ch202).

According to the present invention, the following effects can be obtained.
(1) In the present invention, since the substrate polishing body is mounted and rotated with the polishing surface directed downward in the vertical direction, and the polishing power of the power supply is supplied to the electrolyte container, the metal film of the substrate It can grind in the state where the surface (surface to be polished) faces upward. In addition, since electrochemical polishing (eCMP) can be performed, polishing at a speed corresponding to the magnitude of the energized direct current can be performed, and high-speed polishing of the metal film can be performed.

(2) In the present invention, the electrolytic solution in the energizing electrolyte container and the metal film are brought into contact, the electrolytic solution in the polishing electrolyte container and the metal film in the substrate are brought into contact, and the positive electrode of the power source and the electrolyzing electrode Since the anode electrode of the liquid storage part is connected and the negative electrode of the power supply is connected to the anode electrode of the polishing electrolyte storage part, the positive electrode and the negative electrode of the power supply are connected to the metal film via the electrolyte. Can do. As a result, the metal film can be brought into contact only with the polishing surface layer of the substrate polishing body to perform electrochemical mechanical polishing. That is, since it is not necessary to mechanically contact the metal film with the electrode or the like in order to supply power to the metal film, the metal film can be prevented from being damaged.

(3) In the present invention, since the substrate polishing body includes a discharge unit that discharges the electrolytic solution stored in the electrolytic solution storage unit, the electrolytic solution is supplied and discharged by mounting the substrate polishing body on the polishing head. be able to. In addition, the gas generated in the electrolytic solution in the electrolytic solution storage part due to the electrochemical reaction accompanying the electrochemical mechanical polishing can be discharged together with the electrolytic solution.

(4) Since the present invention includes a table on which a substrate having a diameter larger than that of the substrate polishing body is provided, the substrate can be polished with a substrate polishing body having a diameter smaller than that of the substrate. Thereby, a grinding | polishing apparatus can be reduced in size.
Further, since the entire polishing surface of the substrate polishing body can be pressed against the substrate, the opening of each electrolyte solution storage portion of the substrate polishing body can be covered with the substrate. As a result, the electrolytic solution can be supplied and discharged in a state in which the electrolytic solution does not leak from the opening of each electrolytic solution storage part, so that the consumption of the polishing solution can be reduced.

(5) Since the present invention includes the energizing electrolyte accommodating portion through hole and the polishing electrolyte accommodating portion through hole, the electrolyte in the energizing electrolyte accommodating portion through hole and the polishing electrolyte accommodating portion penetrate The electrolyte solution in the hole can be electrochemically separated.

It is a perspective view of the polish device of a 1st embodiment. It is a longitudinal section of the polish device of a 1st embodiment. It is a reverse view of the grinding | polishing tool of 1st Embodiment. It is a perspective view when the polishing tool of 1st Embodiment is seen from diagonally lower side. It is a perspective view explaining the discharge mechanism of the polishing tool of a 1st embodiment. It is a longitudinal cross-sectional view which shows typically the grinding | polishing apparatus at the time of grinding | polishing of 1st Embodiment. It is a longitudinal cross-sectional view explaining the grinding | polishing process of the device wafer of 1st Embodiment. It is a figure which illustrates typically wiring formation of a device wafer of a 1st embodiment. It is a table | surface which shows the example of the time change of the voltage in the measuring method in process of 1st Embodiment, and an electric current. It is a perspective view when the polishing tool of 2nd Embodiment is seen from diagonally lower side.

An object of the present invention is to provide a polishing head, a polishing apparatus, and a substrate polishing body that can polish a metal film on a substrate at a high speed and that are suitable for polishing without scratches. A polishing head to be mounted in a state of being directed downward in the vertical direction, a wafer adsorbing unit to which a semiconductor device wafer substrate is mounted in a state of being directed upward in the vertical direction, and an inside of the head that supplies the electrolytic solution to the electrolytic solution storage unit This is realized by including an electrolytic solution supply path and an in-head electric cable for supplying power for polishing of the power source to the electrolytic solution storage unit.

(First embodiment)
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a polishing apparatus 1 according to the first embodiment.
FIG. 2 is a longitudinal sectional view of the polishing apparatus 1 according to the first embodiment.
As shown in FIG. 1, the polishing apparatus 1 places a metal film D1 of a semiconductor device wafer D (wiring material substrate) on a table 21 with the metal film D1 facing upward in the vertical direction Z. An apparatus for electrochemical mechanical polishing (eCMP). That is, the polishing apparatus 1 has a structure capable of simultaneously performing electrochemical reaction and mechanical polishing of the metal film D1, as will be described below.
The polishing apparatus 1 includes a power source 2, an electrolyte supply device 3, a polishing head 10, a wafer carrier unit 20, a waste liquid tray 25, and a polishing tool 30 (substrate polishing body).

The power source 2 is a DC voltage supply device that supplies polishing power, which is power used for an electrochemical reaction in eCMP. The power source 2 includes a positive electrode 2a and a negative electrode 2b.
The electrolytic solution supply device 3 includes a tank (not shown) for storing the electrolytic solution E, a pump for sending the electrolytic solution E from the tank to the polishing head 10, a pipe 3a connected to the polishing head 10, and the like. .

(Configuration of polishing head 10)
As shown in FIG. 2, the polishing head 10 includes a base 11, a tool folder 12 (substrate polishing body mounting portion), an electrolyte supply path 13 (electrolyte supply portion), a rotary joint 14, and an in-head electric cable. 15 a and 15 b (power transmission unit), a head driving unit 16, and a hood 17.
The base 11 is a disk-shaped member that is the basis of the polishing head 10.
The tool folder 12 is a recess in which the lower surface of the base 11 is recessed according to the diameter of the polishing tool 30. The polishing tool 30 is mounted and held in the tool folder 12 by screwing or the like with the polishing surface 31a (see FIG. 4) directed downward in the vertical direction Z.

The electrolytic solution supply path 13 is a supply path for further sending the electrolytic solution E sent from the pipe 3 a to the base 11 to the polishing tool 30. The electrolytic solution supply path 13 is connected to the piping 3a of the electrolytic solution supply path 13 via the rotary joint 14, and is connected to the polishing head 10 to supply the electrolytic solution E to the rotating polishing head 10. Can do. The electrolyte supply path 13 includes a tubular portion that extends downward in the vertical direction from the rotary joint 14 and a portion that opens downward and that is recessed in the tool folder 12. The recessed portion in the tool folder 12 is provided with a plurality of ribs (not shown) provided radially from the center of the polishing head 10 in a radial row so that the mounted polishing tool 30 does not bend. It has become.

The in- head electric cables 15 a and 15 b are electric cables for transmitting the power of the power source 2 in the polishing head 10. The in- head electric cables 15a and 15b are connected to the external electric cables 2c and 2d connected to the positive pole 2a and the negative pole 2b of the power source 2 by means of electrical connection parts (not shown) such as slip rings. It is connected. Further, in the in- head electric cables 15a and 15b, the other terminal portions are connected to the in- head electric cables 15a and 15b. Thereby, the plus pole 2a and the in-head electric cable 15a are electrically connected, and the minus pole 2b and the in-head electric cable 15b are electrically connected.
Note that the in- head electric cables 15a and 15b are covered with an insulating material and do not short-circuit even if they are wired inside the electrolyte supply path 13.
The in- head electric cables 15a and 15b are connected to the polishing tool electric cables 36a and 36b (described later) via the connection terminals 15c and 15d (see FIG. 6) at the respective terminal portions on the polishing tool 30 side. The positive electrode 2a of the power supply 2 and the anode electrode 33 in the energizing electrolyte container F1 (see FIG. 6) are electrically connected, and the negative electrode 2b of the power supply 2 and the polishing electrolyte container F2 (see FIG. 6). The cathode electrode 34 is electrically connected. As a result, the in- head electric cables 15a and 15b transmit the power for polishing of the power source 2 to the electrolytic solution E in the respective electrolytic solution storage portions F1 and F2 (described later).

The head drive unit 16 is a device that rotationally drives the polishing head 10 equipped with the polishing tool 30 around the rotation axis Z1 in the vertical direction Z. The head driving unit 16 includes a motor M1 and a driving force transmission unit 16a such as a belt and a gear that transmits the driving force of the motor M1 to the base 11.
The head drive unit 16 may include a swinging device that moves the polishing head 10 in the XY plane direction, that is, the horizontal plane direction (the directions of arrows A and B shown in FIG. 1) by a cam mechanism or the like.
The hood 17 is for preventing waste liquid (electrolytic solution E after use of polishing) from being scattered around as the polishing head 10 rotates.

(Configuration of Wafer Carrier 20)
As shown in FIG. 2, the wafer carrier unit 20 includes a table 21, a wafer suction unit 22, a wafer support ring 23 (retainer ring), and a table driving unit 24.
The table 21 is a disk-shaped member on which the device wafer D is placed. The table 21 mounts the device wafer D in a state where the surface (surface to be polished) of the metal film D1 faces the upper side in the vertical direction Z.

The wafer suction unit 22 is a part for fixing the device wafer D to the table 21 by sucking the lower surface of the device wafer D. In order to suck the lower surface of the device wafer D, the wafer suction unit 22 includes a suction port 22a formed on the surface of the table 21, and a suction tube 22c that connects the suction port 22a and the suction device 22b. When the device wafer D is placed on the table 21 (on-load), the wafer suction unit 22 fixes the device wafer D by vacuum suction. Further, when the device wafer D is lowered from the table 21 after being polished by eCMP (off-loading), the wafer suction unit 22 releases the vacuum suction and releases the fixation. Note that, when the device wafer D is lowered from the table 21, the wafer suction unit 22 may be in a pressurized state as necessary.

The wafer support ring 23 is an annular member for preventing the device wafer D placed on the table 21 from moving in the radial direction. The wafer support ring 23 is made of, for example, a thermoplastic resin. The wafer support ring 23 has a thickness equal to or less than the thickness of the device wafer D, and is fixed to the upper surface of the table 21 with the edge of the device wafer D being fitted inside thereof. It contacts 30 polishing surface layers 31 (described later). Thus, the wafer support ring 23 can alleviate the polishing pressure of the polishing tool 30 from being concentrated on the edge of the surface of the device wafer D.
The table driving unit 24 is a device that rotationally drives the table 21 on which the device wafer D is placed about the rotation axis Z2 in the vertical direction Z. The table driving unit 24 includes a motor M2 and a driving force transmission unit 24a such as a belt or a gear that transmits the driving force of the motor M2 to the table 21.

The waste liquid tray 25 is a container for accommodating the electrolytic solution E discharged from the polishing tool 30 during polishing.
The polishing apparatus 1 can polish the device wafer D with good in-plane uniformity even if the diameter of the polishing tool 30 attached to the polishing head 10 is slightly larger than the diameter of the device wafer D. In the present embodiment, the polishing apparatus 1 swings the polishing head 10 with respect to the device wafer D, so that it can be made smaller than the diameter of the device wafer D. In this case, the entire apparatus can be reduced in size.

(Configuration of polishing tool)
Next, the configuration of the polishing tool 30 will be described in detail.
FIG. 3 is a back view of the polishing tool 30 of the first embodiment (viewed from below the vertical direction Z shown in FIG. 2).
FIG. 4 is a perspective view of the polishing tool 30 according to the first embodiment as viewed obliquely from below.
FIG. 5 is a perspective view for explaining a discharge mechanism of the polishing liquid E of the polishing tool 30 of the first embodiment.

As shown in FIG. 4, the polishing tool 30 is laminated from the lower layer side to the upper layer side and is formed in a disc shape, and includes a polishing surface layer 31, an insulating layer 32, an anode electrode 33 and a cathode electrode 34, and an insulating layer 35. And polishing tool electrical cables 36a and 36b. Each layer is bonded with an adhesive, an adhesive sheet, or the like.
As shown in FIG. 3, the polishing tool 30 includes an energizing electrolyte container F1, a polishing electrolyte container F2, electrolyte supply pores 37 and 38, a waste liquid channel Ch1 (an energizing electrolyte). A housing portion through-hole) and a waste liquid channel Ch2 (polishing electrolyte housing portion through-hole).

As shown in FIG. 4, the polishing surface layer 31 is a member for removing a protective film G (described later) formed on the surface of the metal film D1 of the device wafer D during polishing. The polishing surface layer 31 is configured such that the lower polishing surface 31a contacts the surface of the metal film D1 of the device wafer D during polishing.
The polishing surface layer 31 is formed of a synthetic resin such as a urethane foam material having a high mechanical polishing ability. The polishing surface layer 31 does not have to be a single layer structure made of a single material, and may be a laminated structure with a cushioning material made of a synthetic resin support or foamed resin.
The insulating layer 32 is provided for forming the waste liquid channels ch1 and ch2.

The anode electrode 33 is an electrode formed of a conductive member in order to supply a positive voltage to the energizing electrolyte container F1.
As shown in FIG. 3, the anode electrode 33 has a shape in which fan-shaped portions 33a, 33b, and 33c are arranged at intervals of 120 ° and are connected by a central portion 33d. The anode electrode 33 is made of a low-resistance material such as metal (gold, copper, platinum, tungsten, titanium alloy, stainless steel, carbon, etc.) or a carbon material (amorphous carbon containing carbon as a main component, carbon fiber, graphite fiber, graphite) , Composite carbon materials with synthetic resins, etc.) can be used. In particular, in order to prevent dissolution of the anode electrode, a composite material in which tungsten or titanium is coated with artificial diamond doped with boron is preferable.

The cathode electrode 34 is an electrode formed of the same material as the cathode electrode 34 in order to supply a negative voltage to the polishing electrolyte container F2. The cathode electrode 34 has a shape in which fan-shaped portions 34a, 34b, and 34c are arranged at intervals of 120 °, and these are connected by an outer peripheral portion 34d.
As shown in FIG. 4, the anode electrode 33 and the cathode electrode 34 are stacked in the same layer so as to have a gap 33 e in the plane (XY plane) direction.

The insulating layer 35 is a member that insulates each electrode of the anode electrode 33 and the cathode electrode 34 from the base 11 of the polishing head 10. Further, the insulating layer 35 is provided with a step portion 35 a that enters the gap 33 e between the anode electrode 33 and the cathode electrode 34, and insulates between the anode electrode 33 and the cathode electrode 34.

The polishing tool electrical cable 36 a is connected to the inside of the anode electrode 33. The polishing tool electric cable 36a is inserted through the through hole of the insulating layer 35, guided to the upper side of the polishing tool 30, and connected to the in-head electric cable 15a via the connection terminal 15c (see FIG. 6).
The polishing tool electrical cable 36b is connected to the inside of the cathode electrode 34, is wired in the same manner as the polishing tool electrical cable 36a, and is connected to the in-head electrical cable 15b via the connection terminal 15d (see FIG. 6). .

The energizing electrolyte container F <b> 1 is configured by a plurality of through-holes communicating with the polishing surface layer 31 and the insulating layer 32 and the surface of the anode electrode 33 forming the bottom. The energizing electrolyte container F1 is formed in a range overlapping with the fan-shaped portions 33a, 33b, and 33c of the anode electrode 33 in the XY plane.
At the time of polishing, when the electrolytic solution accommodating portion F1 is filled with the electrolytic solution E and DC power is supplied, the electrolytic solution E and the metal film D1 of the device wafer D come into contact with each other, so that the conductive electrolyte accommodating portion F1 is brought into contact. The abutting portion of the metal film D1 and the anode electrode 33 form an electrochemical cell (an electrolysis cell C1 to be described later).

As with the energizing electrolyte container F1, the polishing electrolyte container F2 is configured by the through hole and the surface of the cathode electrode 34, and overlaps the fan-shaped portions 34a, 34b, and 34c of the cathode electrode 34 in the XY plane. Formed in the range.
At the time of polishing, when the electrolytic solution E is filled in the polishing electrolyte storage portion F2 and DC power is supplied, the electrolytic solution E and the metal film D1 of the device wafer D come into contact with each other, so that the polishing electrolytic solution storage portion F2 is contacted. An electrochemical cell (a polishing electrolytic cell C2 to be described later) is formed by the metal film D1 and the cathode electrode 34 at the abutting portion.

Thus, the two cells, the electrolysis cell for polishing and the electrolysis cell for polishing, are connected in series by the metal film D1, and the metal film D1 in contact with the polishing electrolyte container F2 is electrochemically polished. The That is, since the metal film D1 is not brought into contact with the electrode member, it is possible to prevent the metal film D1 from being damaged due to rubbing with the electrode member.

The electrolyte solution supply pore 37 is a through hole provided in communication with the anode electrode 33 and the insulating layer 35 in order to supply the electrolyte solution E to the electrolyte solution storage portion F1 for energization. The electrolyte supply pore 37 communicates with the electrolyte supply path 13 of the polishing tool 30 in a state where the polishing tool 30 is mounted on the polishing head 10 (see FIG. 2).
The electrolytic solution supply pore 38 is a through hole provided in communication with the cathode electrode 34 and the insulating layer 35 in order to supply the electrolytic solution E to the polishing electrolytic solution storage portion F2. The electrolyte supply pores 38 communicate with the electrolyte supply path 13 of the polishing tool 30 in a state where the polishing tool 30 is mounted on the polishing head 10 (see FIG. 2).

As shown in FIG. 4, the waste liquid channel Ch <b> 1 is a through hole for discharging the electrolytic solution E supplied and filled in the energizing electrolytic solution storage unit F <b> 1 to the outside of the polishing tool 30. The waste liquid channel Ch <b> 1 is formed by a slit that connects the through holes of the insulating layer 32 that form the energizing electrolyte housing part F <b> 1 in the radial direction and further passes outside.
As shown in FIG. 5, when the insulating layer 32 is laminated to form the polishing tool 30, this soot connects the energizing electrolyte container F <b> 1 in the radial direction R, opens to the outer peripheral portion, and comes out. Such a through-hole is configured to configure the waste liquid channel Ch1 (see FIG. 3).

As shown in FIG. 4, the waste liquid channel Ch <b> 2 is a through hole for discharging the electrolytic solution E supplied and filled in the polishing electrolytic solution storage part F <b> 2 to the outside of the polishing tool 30. The waste liquid channel Ch2 is formed by a slit that connects the through-holes of the insulating layer 32 that form the polishing electrolyte container F2 in the radial direction and further passes out.
As shown in FIG. 5, when the insulating layer 32 is laminated and the state of the polishing 30 is established, this slit connects the polishing electrolyte container F2 in the radial direction R, and further opens to the outer peripheral portion and comes out. Such a through hole is configured to configure a waste liquid channel Ch2 (see FIG. 3).

(Operation of polishing apparatus 1 during polishing, configuration of energizing cell C1 and polishing cell C2)
Next, the operation | movement at the time of grinding | polishing of the grinding | polishing apparatus 1, the cell C1 for electricity supply, and the cell C2 for grinding | polishing are demonstrated.
FIG. 6 is a vertical cross-sectional view (corresponding to the cross section taken along the line VI-VI in FIG. 3) schematically showing the polishing apparatus 1 during polishing according to the first embodiment.
(Supply of electrolyte E)
As shown in FIG. 6, when the electrolytic solution E is sent to the polishing head 10 by the electrolytic solution supply device 3, the electrolytic solution E is supplied to the polishing tool 30 through the electrolytic solution supply path 13 of the polishing head 10. Is done.
As shown in FIG. 5, the electrolyte E is further supplied to the energizing electrolyte container F <b> 1 through the electrolyte supply pores 37 of the polishing tool 30, and also passes through the electrolyte supply pores 38 of the polishing tool 30. Then, it is supplied to the polishing electrolyte container F2. Thereby, each electrolyte solution accommodating part F1, F2 will be in the state with which the electrolyte solution E was satisfy | filled. At the time of polishing, each electrolyte container F1, F2 is in a state in which the opening is covered with the device wafer D, so that excess electrolyte E does not leak. Thereby, the consumption of the electrolyte solution E can be reduced.

(Formation of energization cell C1 and polishing cell C2 and dissolution of metal film)
As shown in FIG. 6, the anode electrode 33 is connected to the positive electrode 2 a of the power source 2, while the cathode electrode 34 is connected to the negative electrode 2 b of the power source 2. Therefore, when a voltage is applied, the interface between the surface of the anode electrode 33 and the electrolytic solution E, the interface between the surface of the cathode electrode 34 and the electrolytic solution E, the surface of the metal film D1 and the energizing electrolytic solution container F1 are filled. Electrons are exchanged and current flows at the interface with the electrolyte solution E and at the interface between the surface of the metal film D1 and the electrolyte solution E filled in the polishing electrolyte container F2.
An energization cell C1 that is an electrochemical cell is formed by the metal film D1, the electrolyte E filled in the energization electrolyte container F1 and the anode electrode 33. On the other hand, a polishing cell C2, which is an electrochemical cell, is formed by the metal film D1, the electrolyte E filled in the polishing electrolyte container F2, and the cathode electrode 34. That is, the energization cell C1 and the polishing cell C2 are electrochemical cells connected in series via the metal film D1 as an electrical conductor.

For example, when an organic electrolyte that chelates with metal ions of the metal film D2 and a protective film forming agent are used in the electrolytic solution, oxygen gas O ₂ is generated from the surface of the anode electrode 33 in the energization cell C1.
In the polishing cell C2, hydrogen gas H ₂ is generated from the surface of the cathode electrode 34. When the metal film D1 is copper, for example, in the metal film D1 in contact with the electrolytic solution E, the dissolution reaction “Cu → Cu ^The metal film D1 is dissolved by “ ²⁺ + 2e ⁻ ”.

The electrolyte solution E can be an organic electrolyte solution such as citric acid, an aqueous electrolyte solution containing an inorganic acid such as phosphoric acid, or a salt such as copper sulfate as a main component. Agents and the like can be included. However, depending on the type of the main component and additive of the electrolytic solution E, cations in the electrolytic solution may be deposited on the metal film D1 exposed to the energization cell C1, so that the main component and additive of the electrolytic solution E It is necessary to select the type, concentration, etc.

(Discharge of electrolyte E)
As shown in FIG. 5, each electrolyte container F1, F2 has a form covered with a metal film D1, and therefore, by the supply pressure (discharge pressure) of the new electrolyte solution E of the electrolyte solution supply device 3, The electrolyte E in each electrolyte container F1, F2 is sent out to the waste liquid channels Ch1, Ch2 and discharged toward the outer peripheral side R1 in the radial direction R. Since the waste liquid channels Ch1 and Ch2 are provided in all the electrolytic solution storage portions F1 and F2, the electrolytic solution E supplied to all the electrolytic solution storage portions F1 and F2 can be discharged.
Since the waste liquid channel Ch1 and the waste liquid channel Ch2 are provided independently, the electrolyte solution E and the waste liquid channel in the waste liquid channel Ch1 are set to such an extent that the electrochemical reaction in each of the cells C1 and C2 is not disturbed. The electrolyte solution E in Ch2 can be insulated.

As shown in FIG. 6, oxygen gas O ₂ and hydrogen gas H ₂ are generated in the electrolytic solution E of the energization cell C1 by the above-described electrochemical reaction. On the other hand, the electrolyte E of the polishing cell C2, to hydrogen gas H ₂ is generated, and if copper ions by the dissolution reaction of the copper is increased, sometimes deposited (plated) on the cathode electrode 34 surface.
For this reason, when the electrolytic solution E is not discharged, the electrochemical reaction in each of the cells C1 and C2 is stagnant. On the other hand, the polishing apparatus 1 of the present embodiment supplies and discharges the electrolyte solution E in the electrolyte solution storage portions F1 and F2, thereby generating oxygen gas generated in the electrolyte solution storage portions F1 and F2. O ₂ and hydrogen gas H ₂ can also be discharged together with the electrolyte E. As a result, the polishing apparatus 1 always keeps the electrolyte solution E in the electrolyte solution storage portions F1 and F2 in a fresh state and does not stagnate the electrochemical reaction.

(Mechanical polishing)
In order to polish the metal film D1 of the device wafer D with good flatness, a protective film forming agent is added to the electrolytic solution E. When the electrolytic solution E to which the protective film forming agent is added is used, the protective film G is formed on the surface of the metal film D1 exposed to the polishing cell C1, and the protective film G is removed and the surface of the metal film D1 is subjected to the electrolytic solution. If not exposed to E, the electrochemical reaction will stagnate.
As shown in FIG. 2, the polishing apparatus 1 has the polishing head 10 in a state where the polishing surface 31 a of the polishing surface layer (see FIG. 4) of the polishing tool 30 is in contact with the metal film D <b> 1 of the device wafer D horizontally. And the table 21 are rotationally driven to move the polishing tool 30 and the device wafer D relative to each other. By this relative movement, the polishing apparatus 1 can remove the protective film G formed on the metal film D1 with the polishing surface 31a.

For this reason, the polishing apparatus 1 only needs to perform this relative movement under a polishing pressure that is sufficient to remove the protective film G. Therefore, the polishing pressure can be significantly reduced as compared with CMP.
Further, the polishing apparatus 1 can reduce the diameter of the polishing tool 30 as compared to the rotary type polishing apparatus. For this reason, since the amount of the electrolyte E in an unactuated state is small and the working efficiency of the electrolyte E on the substrate can be increased, the consumption of the electrolyte E can be reduced.
Furthermore, since the polishing apparatus 1 polishes the metal film D1 by eCMP, it can polish at a speed corresponding to the magnitude of the energized direct current, and can polish the metal film D1 at a high speed.

(Mechanism of wiring formation by eCMP)
Next, the mechanism of wiring formation by eCMP according to this embodiment will be described.
FIG. 7 is a longitudinal sectional view for explaining a polishing process of the device wafer D of the first embodiment.
FIG. 7A shows a state before polishing, FIGS. 7B to 7E show a state during polishing, and FIG. 7F shows a state after polishing. In the following description, the surface to be polished (upper surface in the figure) will be referred to as the upper surface, and the opposite surface will be described as the lower surface (lower surface in the figure).
First, the configuration of the device wafer D will be described.
As shown in FIG. 7A, before polishing, the device wafer D is laminated with a metal film D1, a barrier metal D2, and an interlayer insulating film D3 from the upper layer side (the transistor portion is omitted in the figure). To show.)

The metal film D1 is a layer for configuring the wiring of the device wafer D, and is formed, for example, by laminating copper using a technique such as plating. The metal film D1 is polished within the device wafer D by polishing so that the portion laminated in the wiring groove D3a provided by recessing the upper surface of the interlayer insulating film D3 remains (see FIG. 7F). Wiring. In the metal film D1, a depression (concave part D1a) may be formed in a portion of the interlayer insulating film D3 stacked in the range of the wiring groove D3a. However, even if the recess D1a is formed in the metal film D1, the polishing tool 30 of the present embodiment can uniformly polish the metal film D1 as described later.

The barrier metal D2 is provided to prevent the metal atoms of the metal film D1 from migrating to the interlayer insulating film D3. As the barrier metal D2, a material having a high melting point and conductivity, for example, a metal such as tantalum, tantalum nitride, or nickel nitride, and a metal nitride can be used.
The interlayer insulating film D3 is an insulating layer (film) for insulating between the wiring layers of the device wafer D.

Next, the polishing process for the device wafer D will be described.
In the state shown in FIG. 7A, when the metal film D1 of the device wafer D and the electrolyte E of the polishing electrolyte container F2 come into contact with each other, a polishing cell C2 (see FIG. 6) is formed, and the metal film D1 is dissolved and removed from the surface of the upper surface, and at the same time, as shown in FIG. An electrochemical protective film G (copper complex layer) is formed on the surface, which becomes a passive film, and dissolution of the metal film D1 stops.
Since the polishing surface layer 31 of the polishing tool 30 is moved relative to the device wafer D by the polishing apparatus 1 (see FIG. 1), the protective film G is mechanically removed. At this time, the protective film G formed in the concave portion D1a does not contact the polishing tool 30 (or the mechanical frictional force due to the contact is less than that of the convex portion), so that the convex portions D1c and D1d of the metal film D1 are not formed. Only the formed protective film G is removed.

Then, as shown in FIG. 7C, if the metal of the convex portions D1c and D1d of the metal film D1 is exposed, only the exposed portions are dissolved and removed by the polishing cell C2 and formed again. The protective film G is mechanically removed.
The steps as described above are repeated instantaneously, and the polishing tool 30 can electrochemically and mechanically polish the metal film D1 to make the removal rate of the convex portions D1c and D1d faster than the concave portion D1a. And the grinding | polishing tool 30 can make the surface of the metal film D1 into a plane as shown in FIG.7 (d).

In the state of FIG. 7D, since the upper surface of the metal film D1 is flat, the portion up to the upper surface of the barrier metal D2 (the portion in the range H1 shown in FIG. 7D) is electrochemical at the same polishing rate. It is mechanically removed and the state shown in FIG.

7 (e), the device wafer D is in a state where the metal film D1 and the barrier metal D2 are exposed on the upper surface. In the case of multilayer wiring, the interlayer insulating film D3 is exposed (the state shown in FIG. 7F), and an interlayer insulating film is further deposited thereon. Therefore, it is necessary to simultaneously remove the metal film D1 and the surface layer on the upper surface of the barrier metal D2 made of a material different from that of the metal film D1 (the portion in the range H2 shown in FIG. 7E) to the surface of the interlayer insulating film D3. These removals are performed by conventional chemical mechanical polishing (CMP) as the second step using the above-described multi-platen multi-head type polishing apparatus. Further, when it is necessary to correct the dishing (a state in which the metal film D1 is excessively polished and removed), the interlayer insulating film D3 is chemically and mechanically polished as a third step.

As described above, the electrochemical mechanical polishing is performed by polishing the metal film D1 of the device wafer D from the state shown in FIG. 7A to the state shown in FIG. The mechanical removal of the protective film and the dissolution removal of the metal (electrochemical removal) can be performed in a well-balanced manner, and the surface can be flattened while maintaining the in-plane uniformity with a high polishing rate.

(Example of eCMP end point detection method)
FIG. 8 is a diagram schematically illustrating the wiring formation of the device wafer D of the first embodiment.
FIG. 8A shows a state before polishing, in which wiring grooves or via holes are formed in the device wafer D (Si substrate), and after the barrier metal is formed, the metal film D1 is deposited to a thickness H. It is a figure which shows the state made.
FIG. 8B shows a state after polishing by eCMP and shows a state in which the metal film D1 is processed into a desired state.

In the state of FIG. 8B, all the metal film D1 deposited on the convex portion of the barrier metal D2 is removed, and the surface of the metal film D1 of the wiring portion D1e and the surface of the convex portion of the barrier metal D2 are on the same horizontal plane. It is in a state.
When processing into the state of FIG.8 (b), the method of measuring the thickness of the metal film D1 during a process and stopping a process at an end point (processing end point) is common.
If the end point is too early (insufficient polishing), as shown in FIG. 8C, the metal film D1 remains on the surface of the convex portion of the barrier metal D2, and an electrical short circuit occurs between the wirings. On the other hand, if the end point is too late (excessive polishing), as shown in FIG. 8D, the thickness of the metal film D1 of the wiring portion D1e is reduced (desching), and the wiring resistance is increased. End up.

A torque measurement method or an electric resistance measurement method is used as the measuring method during processing.
In the torque measurement method, a torque value generated on the rotation axis of the wafer carrier unit 20 or the polishing head 10 is monitored, and a change in the torque value due to a change in film quality of the metal film D1 and the barrier metal D2 is detected. The electrical resistance measurement method is a method of measuring the thickness of the metal film D1 being processed by utilizing the fact that the metal sheet resistance is inversely proportional to the film thickness.
The measuring method during processing of this embodiment is to monitor the output voltage of the power source 2 (DC power supply device) and use the point where the output voltage reaches a certain value as a detection point (hereinafter referred to as DP). Therefore, it is not necessary to use a measuring device, and can be easily implemented.

FIG. 9 is a diagram illustrating an example of temporal changes in voltage and current when eCMP is performed under the power supply conditions set to the current value I and the voltage V2 in the measuring method during processing according to the first embodiment.
The in-process measurement method of the first embodiment is a polishing method in which the voltage value in the range 9b is a detection point and a certain time (T) from the detection point is a polishing end point.
The power supply 2 outputs a power supply voltage necessary for the electrolytic solution resistance and the electrochemical dissolution reaction voltage of the metal as shown in the range 9a with respect to the set current value I, but as shown in the range 9b, the metal When the film thickness decreases, the sheet resistance of the metal film D1 increases and the power supply output voltage gradually increases. Then, as shown in the range 9c, when all the metal film D1 is removed, most of the power source current is utilized for the oxygen gas generation reaction on the surface of the barrier metal D2, and the voltage rises. The limit voltage V2 is reached. At this time T2, the output current of the power source 2 decreases to a current value I2 corresponding to the limit voltage V2.

When the limit voltage V2 of the power source 2 is set to a value V1 that is higher than the voltage value in the range 9a and lower than the limit voltage V2, the output current of the power source 2 decreases in the range 9b. At this time T1, the metal film D1 remains on the surface of the convex portion of the barrier metal D2. Using the time point T1 as a detection point, the remaining metal film D1 can be polished up to a predetermined time T with the reduced current I1, and the remaining metal film D1 can be removed.

According to this method, even when the thickness H (see FIG. 8A) of the metal film D1 is different between lots and between lots, the metal film D1 can be automatically processed into the state shown in FIG. 8B.
In this method, the set values of the current I and the voltage V1 differ depending on the process conditions such as the diameter and polishing speed of the device wafer D and the type (particularly composition) of the electrolyte E. However, once set, it can be applied to a device wafer D having a different thickness H of the metal film D1.

(Second Embodiment)
Next, a second embodiment of a polishing apparatus to which the present invention is applied will be described.
The polishing apparatus of the second embodiment is a modification of the configuration of the polishing tool 30 of the first embodiment.
Note that, in the following description and drawings, the same reference numerals or the same reference numerals are given to the portions that perform the same functions as those in the first embodiment described above, and overlapping descriptions will be omitted as appropriate.

FIG. 10 is a perspective view (a view corresponding to FIG. 4 of the first embodiment) when the polishing tool 230 of the second embodiment is viewed obliquely from below.
The polishing tool 230 is different from the polishing tool 30 of the first embodiment in that the waste liquid channels Ch201 and Ch202 are formed by recessing the polishing surface 231a of the polishing surface layer 231.

By providing the waste liquid channels Ch201 and Ch202 on the polishing surface 231a, the polishing tool 230 can easily form the waste liquid channels Ch201 and Ch202, and can be manufactured at low cost.
In addition, the polishing surface layer 231 can be manufactured at a lower cost if the polishing surface layer 231 and the insulating layer 232 are integrally formed of the same insulating material.

As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, Various deformation | transformation and a change are possible like the deformation | transformation form mentioned later, and these are also these. Within the technical scope. In addition, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments. In addition, although embodiment mentioned above and the deformation | transformation form mentioned later can also be used in combination as appropriate, detailed description is abbreviate | omitted.

(Deformation)

(1) In each embodiment, although the polishing apparatus showed the example which performs eCMP of the metal film of a device wafer, it is not limited to this. For example, the polishing apparatus may electroplate the device wafer by applying polar (positive and negative) voltages opposite to those in the embodiment. Thus, the polishing apparatus can be used for generation of a metal film (embedding of a wiring material).
In this case, an electrolytic solution having a basic electrolytic solution containing the same metal ion as that of the metal film as a main component may be used. For example, when the metal film is copper, an electrolytic solution containing additives such as carriers, brighteners, and levelers used in a copper wiring process of a semiconductor device can be used.
In addition, the polishing apparatus can alternately perform the embedding of the wiring material and the eCMP by alternately switching the polarity of the power source to form the wiring of the semiconductor device.

(2) In each embodiment, the example in which the diameter of the polishing tool is smaller than the diameter of the device wafer has been described, but the present invention is not limited to this. The diameter of the polishing tool may be equal to or larger than the diameter of the device wafer. In this case, the surface of the metal film (non-polishing surface) and the polishing surface of the polishing tool can be brought into uniform contact without variation without having to swing the polishing head, so that in-plane uniformity is good. Polishing is possible. In addition, since a configuration for swinging the polishing head is not required, the configuration of the polishing apparatus can be simplified.

(3) In each embodiment, although the electrolytic solution in the energizing electrolyte container and the electrolytic solution in the polishing electrolyte container have been described as being electrically insulated, the present invention is not limited to this. For example, a groove (connecting portion) for connecting the energizing electrolyte accommodating portion and the polishing electrolyte accommodating portion to the polishing surface of the polishing tool is provided, and the electrolytic solution and the energizing electrolyte accommodating portion of the polishing electrolyte accommodating portion are provided. The electrolytic solution may be electrically connected to some extent. In this case, the polishing power is bypassed by the electrolytic solution in the connection path, so that the electrolytic polishing efficiency is reduced to some extent. On the other hand, by bypassing the polishing power, it is possible to reduce the electrolytic current that breaks the protective film formed in the concave portion of the metal film (the concave portion D1a shown in FIG. 7), thereby improving the flatness of the metal film. can do.
In the case of providing a connecting portion for bypassing the polishing power, it is easier to design and manufacture by providing the connecting portion separately than using the connecting portion and the waste liquid channel.

1,200A, 200B Polishing device 2 Power supply 3 Electrolyte supply device 10, 210A, 210B Polishing head 12, 212A Tool folder 13 Electrolyte supply path 15a, 15b Electric cable in the head 16 Head drive unit 20 Wafer carrier unit 21 Table 22 Wafer Adsorption part 23 Wafer support ring 24 Table drive part 30,230A, 230B Polishing tool 31,231A, 231B Polishing surface layer 33,233A Anode electrode 34,234 A Cathode electrode 37,38 Electrolyte supply pore C1 Current supply cell C2 Polishing cell Ch1, Ch2, Ch201B, Ch202B Waste liquid channel E Electrolyte F1 Electrolyte container for energization F2 Electrolyte container for polishing F2

Claims (7)

1. Polishing that can attach a substrate polishing body provided with a plurality of electrolytic solution containing portions opened on the polishing surface and electrochemically polish the metal film provided on the surface layer of the substrate by being driven to rotate. Head,
   A substrate polishing body mounting portion for mounting the substrate polishing body in a state where the polishing surface is directed downward in the vertical direction;
   An electrolytic solution supply unit for supplying an electrolytic solution to the electrolytic solution storage unit;
   A power transmission unit for supplying power for polishing power to the electrolyte container;
   A polishing head comprising:
2. The polishing head according to claim 1, wherein
   The plurality of electrolyte solution storage portions are:
   An electrolysis solution container for energization that has an anode electrode and makes the contained electrolyte solution contact the metal film of the substrate;
   A polishing electrolyte container having a cathode electrode and contacting the accommodated electrolyte and the metal film of the substrate;
   The power transmission unit is
   Connecting the positive electrode of the power source and the anode electrode of the energizing electrolyte container,
   Connecting the negative pole of the power source and the negative pole of the polishing electrolyte container,
   A polishing head characterized by
3. In the polishing head according to claim 1 or 2,
   The substrate polishing body includes a discharge unit that discharges the electrolyte solution supplied from the electrolyte solution supply unit and stored in the electrolyte solution storage unit,
   A polishing head characterized by
4. The polishing head according to any one of claims 1 to 3,
   A head drive unit that mounts the substrate polishing body with the polishing surface facing downward, and rotationally drives the polishing head;
   A table on which a metal film is provided on a surface layer and the substrate having a diameter larger than that of the substrate polishing body is placed;
   A table drive unit for rotationally driving the table;
   A polishing apparatus comprising:
5. It is mounted on the polishing head according to any one of claims 1 to 3,
   A plurality of electrolytic solution containing parts opened in the polishing surface;
   A discharge unit for discharging the electrolyte solution supplied from the electrolyte solution supply unit of the polishing head and stored in the electrolyte solution storage unit;
   A substrate polishing body characterized by the above.
6. In the substrate polishing body according to claim 5,
   The plurality of electrolyte solution storage portions are:
   An electrolysis solution container for energization that has an anode electrode and makes the contained electrolyte solution contact the metal film of the substrate;
   A polishing electrolyte container containing a cathode electrode and bringing the accommodated electrolyte into contact with the metal film of the substrate;
   A substrate polishing body characterized by the above.
7. The substrate polishing body according to claim 6,
   The discharge part is
   Connecting the plurality of energizing electrolyte accommodating parts, and energizing electrolyte accommodating part through-holes which are through-holes extending out of the substrate polishing body;
   Connecting a plurality of the polishing electrolyte accommodating portions, and comprising a polishing electrolyte accommodating portion through-hole that is a through-hole extending out of the substrate polishing body,
   A substrate polishing body characterized by the above.

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