JP2008221344A - Conditioning method and conditioning liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove, by etching, the polishing product deposited on the surface of a machining electrode and/or a polishing pad while minimizing the effect, on polishing, of the components (residual components) of a conditioning liquid remaining on the surface of the machining electrode and/or the polishing pad after conditioning. <P>SOLUTION: The conditioning liquid used for conditioning the machining electrode and/or the polishing pad of a composite electrolytic polishing device at intervals of the polishing is formed by removing at least a corrosion inhibitor from an electrolyte including an organic acid and the corrosion inhibitor used during the polishing, and adding an oxidizer thereto. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a conditioning method for conditioning a processing electrode provided in a composite electropolishing apparatus that polishes a conductive material on the surface of an object to be polished by composite electropolishing, and a conditioning liquid used in the conditioning method. Composite electrolytic polishing equipment is used for polishing conductive films formed on the surface of electronic devices such as semiconductor devices and displays, and metal materials that require high-precision finishing such as vacuum equipment and high-pressure equipment. Is done.

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, a wiring recess is formed in an insulating film (interlayer insulating film) made of SiO ₂ , SiOF, SiOC, or a so-called low-k material on the substrate, and then the entire surface of the insulating film including the wiring recess is formed. Forming a barrier film made of titanium, tantalum, tungsten, ruthenium and / or alloys thereof, and forming a wiring metal film made of aluminum, copper, silver, gold, tungsten or alloys thereof on the surface of the barrier film In general, a wiring metal is embedded in the wiring recess, and then an extra wiring metal film and a barrier film formed other than the wiring recess are removed. In current high-speed devices, copper or a copper alloy is generally used as a wiring metal, and so-called low-k materials are used as an insulating film.

  In the damascene process, the formation of the wiring recess is often performed by dry etching or the like, and the barrier film is formed by a dry process such as PVD, CVD, or ALD. Examples of the method for forming the wiring metal film include a wet process such as electrolytic plating or electroless plating, and a dry process such as PVD, CVD, or ALD, but formation by electrolytic plating is widely performed. When forming a wiring metal film by electrolytic plating when the conductivity of the barrier film is low, a seed film for power feeding is formed in advance on the surface of the barrier film in succession to the formation of the barrier film. Is widely practiced. The excess wiring metal film and the barrier film are generally removed by a so-called flattening method such as chemical mechanical polishing (CMP) or electrolytic polishing (composite electrolytic polishing).

FIG. 1 shows an example of forming a copper wiring in a semiconductor device in the order of steps. As shown in FIG. 1A, an insulating film 302 made of, for example, SiO ₂ or a low-k material is deposited on a conductive layer 301a on a semiconductor substrate 301 on which a semiconductor element is formed. Inside, a via hole 303 and a trench 304 are formed by, for example, lithography / etching technique, a barrier film 305 made of Ta or TaN or the like is formed thereon, and a seed film 306 as a power supply film for electrolytic plating is formed thereon by sputtering or the like. To do.

  Then, as shown in FIG. 1B, the surface of the semiconductor substrate W is plated with copper so that the via hole 303 and the trench 304 of the semiconductor substrate W are filled with copper, and the wiring metal film is formed on the insulating film 302. A copper film 307 is deposited. Thereafter, the copper film 307, the seed film 306, and the barrier film 305 on the insulating film 302 are removed by chemical mechanical polishing (CMP) or the like to insulate the surface of the copper film 307 filled in the via hole 303 and the trench 304. The surface of the film 302 is substantially flush with the surface. As a result, as shown in FIG. 1C, a wiring 308 composed of the seed film 306 and the copper film 307 is formed inside the insulating film 302.

  In the semiconductor device wiring formation process, along with the introduction of the low-k material accompanying the reduction of the dielectric constant of the interlayer insulating film, the reduction of damage to the low-k material such as destruction or peeling of the low-k material during polishing becomes an issue. One solution is to lower the pressure of the polishing process. As a means for reducing the pressure, there is a composite electrolytic polishing in which a polishing action and an electrolytic action are combined. In composite electropolishing, when polishing is performed under conditions where the polishing pressure is constant, the polishing rate is characterized by an increase depending on the applied voltage, and a high polishing rate at a low polishing pressure is possible.

  For example, when a conductive film (conductive material) such as a copper film 307 formed on the surface of the substrate shown in FIG. 1 is polished by composite electrolytic polishing, it has a large number of through-holes and is disposed on the processing electrode. While the substrate is pressed against the polishing pad and the electrolytic solution is supplied, the substrate and the polishing pad are moved relative to each other while a voltage is applied between the substrate and the processing electrode. It has been confirmed that when such composite electrolytic polishing is performed, a phenomenon occurs in which a polishing product accumulates on the processing electrode side. If the polishing is continued while leaving this, the resistance between the substrate and the processing electrode is reduced. As a result, it may become difficult to control the polishing rate within the substrate surface. For this reason, it is necessary to remove the polishing product from the surface of the processing electrode by conditioning the processing electrode and / or the polishing pad performed at the polishing interval.

  A cleaning solution such as pure water is generally used for conditioning the processing electrode and the polishing pad, but the polishing product deposited on the surface of the processing electrode whose surface is covered with the polishing pad is cleaned with a cleaning solution such as pure water. It is difficult to remove. For this reason, it is considered that the polishing product deposited on the surface of the processing electrode is removed by chemical etching. However, in order to perform chemical etching, it is necessary to replace the electrolytic solution on the surface of the processing electrode with an etching solution (chemical solution), and polishing components (residual components) of the etching solution remaining on the surface of the processing electrode after conditioning. Is concerned about the impact of In order to remove this concern, after the conditioning is completed, it is necessary to completely remove the etching solution on the processing electrode and the polishing pad and replace it with the electrolytic solution, and then start the next electrolytic processing. And rinse solution is required.

  The present invention has been made in view of the above circumstances, while reducing the influence on the polishing by the component (residual component) of the conditioning liquid remaining on the surface of the processing electrode and / or polishing pad after conditioning as much as possible. Alternatively, it is an object of the present invention to provide a conditioning method and a conditioning liquid used for the conditioning method that can remove the polishing product deposited on the surface of the polishing pad by etching.

  The invention according to claim 1 includes an organic acid and a corrosion inhibitor while applying a voltage between the conductive material on the surface of the object to be polished and the processing electrode disposed at a position facing the conductive material. The processing electrode and / or the polishing of the composite electropolishing apparatus for polishing the conductive material by rubbing a polishing pad disposed between the processing electrode and the conductive material against the surface of the conductive material in the presence of an electrolytic solution. In the conditioning method, the pad is conditioned at a polishing interval by using a conditioning liquid composed of a component obtained by removing at least the corrosion inhibitor from the electrolytic solution.

  By conditioning the machining electrode with a conditioning solution consisting of the main component of the electrolyte minus the corrosion inhibitor, etching is accelerated using the etching function of the electrolyte, thereby depositing on the surface of the machining electrode The polished polishing product can be removed by etching. In addition, the conditioning liquid itself has the same basic composition as the electrolyte component used during polishing, so the influence of the conditioning liquid component (residual component) remaining on the surface of the processing electrode after conditioning can be reduced as much as possible. Can be performed without time loss.

The invention according to claim 2 is the conditioning method according to claim 1, wherein the conditioning liquid further contains an oxidizing agent.
An oxidizing agent made of, for example, 0.1 to 5% of H ₂ O ₂ may be added to the conditioning liquid, thereby conditioning the processed electrode that promotes removal of the polishing product on the processed electrode surface. be able to.

According to a third aspect of the invention, the organic acid is acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, citric acid, aconitic acid, glyoxylic acid, glycol The conditioning method according to claim 1 or 2, comprising at least one of acid, lactic acid, gluconic acid, malic acid and tartaric acid.
As the organic acid, an acid coordinated with copper is desirable, and acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, citric acid, aconitic acid, glyoxylic acid, Examples include glycolic acid, lactic acid, gluconic acid, malic acid, and tartaric acid.

The invention according to claim 4 is the conditioning method according to claim 1 or 2, wherein the organic acid is composed of a strong acid having a sulfonic acid group.
The strong acid having a sulfonic acid group may be benzenesulfonic acid, methanesulfonic acid, taurine, cysteic acid, alkylbenzenesulfonic acid having 1 to 6 carbon atoms in total, or trifluoromethanesulfonic acid. 5. The conditioning method according to claim 4, wherein the conditioning method comprises one or more of fluorosulfonic acid and fluorosulfonic acid.

The invention according to claim 6 is a conditioning liquid used when conditioning a processing electrode and / or a polishing pad used for electrolytic processing, comprising one or more organic acids or salts thereof and a strong acid having a sulfonic acid group. It is a conditioning liquid characterized by comprising a component that contains one or more types and does not contain a corrosion inhibitor.
The invention according to claim 7 is the conditioning liquid according to claim 6, further comprising an oxidizing agent.

  According to the present invention, the processing electrode and / or the processing electrode for etching away the polishing product deposited on the surface of the polishing pad are conditioned using the etching function of the electrolytic solution used for the electrolytic processing, and after the conditioning The influence of the component (residual component) of the conditioning liquid remaining on the surface of the processing electrode and / or the polishing pad on the polishing can be reduced as much as possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following example, an example is shown in which the barrier film is exposed by removing the copper film (and the seed film) forming the wiring formed on the surface of the barrier film of the substrate as the object to be polished.

  2 is a plan view showing an example of a composite electrolytic polishing apparatus, and FIG. 3 is a longitudinal front view of FIG. For example, as shown in FIG. 1B, this composite electrolytic polishing apparatus fills the via hole 303 and the trench 304 with copper by performing copper plating on the surface, and as a wiring metal film on the insulating film 302. A substrate (polishing object) W on which the copper film 307 is deposited is prepared, and the surface of this substrate is polished to the position indicated by the line AA in FIG. The copper film 307 (and the seed film 306) as the conductive film (conductive material) is removed, and thereby the barrier film 305 is exposed. Then, by further removing the barrier film 305 on the insulating film 302, a wiring 308 composed of a seed film 306 and a copper film 307 is formed inside the insulating film 302 as shown in FIG.

  As shown in FIGS. 2 and 3, the composite electrolytic polishing apparatus holds the substrate W detachably with the rotatable processing table (turn table) 10 and the surface (formation surface of the copper film 307) facing downward. The substrate holder (head) 12 that can move up and down and rotate, the electrolyte surrounding the processing table 10 and the substrate holder 12 and supplied to the upper surface of the processing table 10 during processing, and the processing table after processing There is provided a bottomed cylindrical processing chamber 14 for preventing the conditioning liquid and pure water supplied toward the upper surface of 10 from splashing to the outside. At the side of the processing chamber 14, a discharge port 14 a is provided for discharging a liquid such as an electrolytic solution accumulated inside to the outside. The substrate holder 12 is configured to be movable between a predetermined polishing position on the processing table 10 and a substrate delivery position on the side of the polishing position.

  On the upper surface of the processing table 10, a disk-shaped processing electrode 16 having a size covering almost the entire region of the processing table 10 is disposed, and the upper surface of the processing electrode 16 is covered with the polishing pad 18 over the entire region. The upper surface of the polishing pad 18 is a polishing surface. Inside the polishing pad 18, a large number of through holes 18 a penetrating vertically are provided. Thereby, the liquid such as the electrolyte supplied to the upper surface of the processing table 10 is held inside the polishing pad 18. During polishing, the processing electrode 16 and the conductive film such as the copper film 307 provided on the surface of the substrate W are electrically connected through the electrolytic solution held in the through hole 18 a of the polishing pad 18. In this example, the polishing pad 18 is composed of an IC-1000 manufactured by Nitta Haas, which has a large number of through holes 18a on the entire surface.

  If there are through holes over the entire surface, the entire polishing pad 18 may be formed with a grid-like or annular groove. Further, if the polishing pad 18 itself has liquid permeability, the polishing pad 18 may not necessarily have a through hole.

  An electrolytic solution supply nozzle 20 is disposed above the processing table 10 and supplies an electrolytic solution toward the upper surface of the processing table 10 during processing. The electrolytic solution supply nozzle 20 extends from an electrolytic solution storage tank 24 for temporarily storing the electrolytic solution 22, and an electrolytic solution supply line 26 provided therein with an electrolytic solution supply unit (not shown) such as a tube pump, a diaphragm pump, or a bellows pump. As shown in FIG. 2, it has many electrolyte solution supply ports 20a along the length direction, and is arrange | positioned so that the upper direction of the process table 10 may extend along a radial direction.

  As described in detail below, the electrolytic solution 22 includes, for example, an organic acid such as malonic acid, a strong acid having a sulfonic acid group such as methanesulfonic acid, and a corrosion inhibitor such as benzotriazole as a main component. Accordingly, an aqueous solution to which a water-soluble polymer compound, abrasive grains, a surfactant and the like are added is used.

  Further, a conditioning liquid supply nozzle 30 for supplying a conditioning liquid toward the upper surface of the processing table 10 after processing and a pure water supply nozzle 32 for supplying pure water for cleaning are disposed above the processing table 10. ing. The conditioning liquid supply nozzle 30 extends from a conditioning liquid storage tank 36 for temporarily storing the conditioning liquid 34, and a conditioning liquid supply line 38 provided with conditioning liquid supply means (not shown) such as a tube pump, a diaphragm pump or a bellows pump inside. As shown in FIG. 2, it has a large number of conditioning liquid supply ports 30a along the length direction, and is arranged so as to extend above the processing table 10 along the radial direction.

The conditioning liquid 34 is composed of a component obtained by removing the corrosion inhibitor component from the main component of the electrolytic solution 22, for example, an organic acid such as malonic acid, and a strong acid having a sulfonic acid group such as methanesulfonic acid. An aqueous solution to which an oxidizing agent such as ₂ O ₂ is added is used.

  A cylindrical power supply electrode 40 is disposed so as to be positioned outside the processing table 10 in the processing chamber 14 and have an upper surface substantially flush with the surface of the polishing pad 18. Thus, when the substrate holder 12 is lowered and the substrate W held by the substrate holder 12 is pressed toward the polishing pad 18 with a predetermined pressing force, the upper surface of the power supply electrode 40 is a copper film at the outer peripheral portion of the substrate W. It contacts the surface (lower surface) of the conductive film 307 or the like, thereby supplying power to the conductive film. When polishing, the processing electrode 16 is connected to the cathode of the power source 42, and the feeding electrode 40 is connected to the anode of the power source 42.

  Further, a dresser 44 that is located on the side of the substrate holder 12 and can be moved up and down and rotated, and mechanically dresses the polishing pad 18 in contact with the polishing pad 18, has a dressing position above the processing table 10 and the dressing. It is arranged so as to be freely movable between a retracted position on the side of the position. In this example, the dresser 44 is configured by attaching a plurality of circular brushes 46 in a ring shape on the lower surface of the peripheral edge.

  Next, composite electropolishing using this composite electropolishing apparatus will be described. First, the substrate holder 12 holding the substrate W with the surface facing downward is positioned at a predetermined position above the processing table 10. Next, while rotating the processing table 10, the electrolytic solution 22 is supplied from the electrolytic solution supply nozzle 20 toward the upper surface, and at the same time, the substrate holder 12 is lowered while rotating together with the substrate W, for example, 70 hPa (about 1 psi). ) The substrate W is pressed toward the surface of the polishing pad 18 with the following pressing force. When the power supply electrode 40 comes into contact with the conductive film such as the copper film 307 on the surface of the substrate W, the power supply electrode 40 is connected to the anode of the power source 42, and the processing electrode 16 is connected to the cathode of the power source 42. A predetermined voltage is applied between the conductive film such as the copper film 307 on the surface of the substrate W. As a result, an electrolytic reaction is caused on the surface of the conductive film such as the copper film 307 to be the anode to polish the conductive film. At this time, the processing electrode 16 and the surface of the conductive film such as the copper film 307 of the substrate W are filled with the electrolytic solution 22 and electrically connected through the through hole 18a provided in the polishing pad 18.

  That is, the surface of the copper film 307 and the like of the substrate W serving as the anode is anodized, and at the same time, the corrosion inhibitor in the electrolytic solution 22 and the water solution added as necessary are added to the surface of the copper film 307 and the like. A protective film is formed by the conductive polymer compound. At this time, the copper film 307 or the like of the substrate W pressed toward the polishing pad 18 is moved relative to the polishing pad 18 and mechanically polished by the rotational motion of the substrate W and the rotational motion of the processing table 10. The protective film formed on the concave portions existing on the surface of the copper film 307 etc. of the substrate W is not removed, and the electropolishing proceeds only on the protective film formed on the convex portions existing on the surface of the copper film 307 etc. become. In this way, by selectively removing only the protective film on the convex portion of the protective film formed on the uneven surface on the surface of the copper film 307 etc. of the substrate W, the copper film 307 etc. Polishing while flattening.

  After the electrolytic polishing is completed, the supply of the electrolytic solution 22 to the polishing pad 18 is stopped, and the processing electrode 16 and the feeding electrode 40 are disconnected from the power source 42. Then, the surface of the substrate W is cleaned by rotating the substrate W while pressing it against the polishing surface of the polishing pad 18 at a low pressure and simultaneously supplying pure water to the polishing pad 18. Then, the substrate holder 12 is raised, and the cleaned substrate W is transported to the next process.

  After cleaning the substrate, conditioning of the processing electrode 16 and the polishing pad 18 using the conditioning liquid 34 and dressing of the polishing surface of the polishing pad 18 by the dresser 44 are performed. In this example, the dresser 44 is used in combination, but it is needless to say that only the processing electrode 16 and the polishing pad 18 using the conditioning liquid 34 may be conditioned.

  That is, the conditioning liquid 34 is supplied from the conditioning liquid supply nozzle 30 at a flow rate of, for example, 200 ml / min toward the polishing pad 18 while rotating the processing table 10 at a rotation speed of, for example, 30 rpm. Accordingly, the conditioning liquid 34 is caused to flow into the through hole 18 a of the polishing pad 18, and the surface of the processing electrode 16 and the surface including the inside of the through hole 18 a of the polishing pad 18 are brought into contact with the conditioning liquid 34. At the same time, the surface of the polishing pad 18 is dressed by rotating the dresser 44 at a predetermined rotational speed while pressing the lower surface (dressing surface) of the brush 46 of the dresser 44 against the polishing pad 18 with a predetermined pressure.

  Here, when an aqueous solution composed of a component obtained by removing the corrosion inhibitor component from the main component of the electrolytic solution 22 is used as the conditioning solution 34, the conditioning solution 34 has an etching function similar to that of the electrolytic solution 22. The etching is accelerated, and the polishing product deposited on the surface of the processing electrode 16 and further the polishing product deposited on the surface including the inside of the through hole 18a of the polishing pad 18 are etched away by the conditioning liquid. In addition, since the conditioning liquid itself has the same basic composition as the electrolytic solution component used during polishing, the conditioning liquid component (residual component) remaining on the surface including the inside of the through-hole 18a of the processing electrode 16 and the polishing pad 18 after conditioning. ) Can be reduced as much as possible, and the next electrolytic processing can be performed without time loss.

  When composite electrolytic polishing is performed as described above, it has been confirmed that a phenomenon occurs in which a polishing product is deposited on the processing electrode 16 side. The resistance between the conductive film and the processing electrode 16 may change, and it may be difficult to control the polishing rate in the plane of the substrate W. For this reason, the processing electrode 16 and the polishing pad 18 are conditioned during the polishing interval, and the polishing product is removed from the surface of the processing electrode 16.

  It should be noted that at least the polishing pad side surface of the dresser 44 is made of a conductive member, and the voltage at which the processing electrode 16 serves as an anode and the dresser 44 serves as a cathode is set to a voltage opposite to that during polishing. In this state, the same conditioning as described above may be performed, whereby the conditioning effect can be promoted. When applying a voltage during conditioning, a counter electrode is provided on the upper surface of the polishing surface instead of the dresser 44, a voltage is applied so that the processing electrode becomes an anode and the counter electrode becomes a cathode, and conditioning is performed only with a brush or a conditioning liquid. You may go.

  After the conditioning is completed, pure water, preferably ultrapure water is supplied from the pure water supply nozzle 32 toward the polishing pad 18 while rotating the processing table 10 at a rotational speed higher than that at the time of conditioning, for example, 50 to 100 rpm. Then, the surface including the processing electrode 16 and the inside of the through hole 18a of the polishing pad 18 is rinsed with pure water, preferably ultrapure water. This prepares for the next polishing.

  Next, the electrolyte solution 22 used for the composite electropolishing by the composite electropolishing apparatus and the conditioning solution 34 used for the conditioning of the processing electrode 16 and the polishing pad 18 will be described.

  The electrolytic solution 22 has (1) one or more organic acids or salts thereof, (2) one or more strong acids having a sulfonic acid group, and (3) a corrosion inhibitor (nitrogen-containing heterocyclic compound) as a main component. And (4) a water-soluble polymer compound, (5) a pH adjuster, (6) abrasive grains, and (7) a surfactant are added as necessary. Furthermore, the electrolytic solution 22 may contain (8) a conductive material to be polished, such as copper, in its components.

The conditioning liquid 34 is a component obtained by removing the corrosion inhibitor component from the main component of the electrolytic solution 22, that is, (1) one or more organic acids or salts thereof included in the electrolytic solution 22, and (2) a sulfonic acid group. Has one or more strong acids. For example, an oxidizing agent composed of 0.1 to 5% of H ₂ O ₂ may be added to the conditioning liquid 34, thereby performing conditioning that promotes removal of the polishing product on the surface of the processing electrode. it can.

  In this example, copper is polished, but as the conductive material to be polished, in addition to copper, for example, copper alloy, silver or its alloy, gold or its alloy, aluminum or its alloy Tungsten, alloys thereof, nitrides, carbides, nitrogen carbides, titanium, alloys thereof, nitrides, carbides, nitrogen carbides, tantalum, alloys thereof, nitrides, carbides, nitrogen carbides, ruthenium, alloys thereof, and combinations thereof. Can be mentioned.

  The organic acid contained in common in the electrolytic solution 22 and the conditioning solution 34 needs to form a soluble complex with a metal such as copper to be polished. That is, it is coordinated and dissolved in an aqueous solution, and at least an organic acid needs to be dissolved in water. It is preferable that the organic acid has one or more carboxyl groups (—COOH) in the molecule and one or more hydroxy groups (—OH) together with the carboxyl groups. These organic acids also have a pH buffering action that stabilizes the pH of the liquid.

  Examples of the carboxylic acid having one carboxyl group include formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, sorbic acid, glyoxylic acid, pyruvic acid, levulinic acid, benzoic acid, m -Toluic acid, acetylsalicylic acid, etc. are mentioned. Examples of the carboxylic acid having two or more carboxyl groups include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, α- Examples thereof include ketoglutaric acid, aconitic acid, phthalic acid, and pyromellitic acid. Examples of the carboxylic acid having at least one hydroxy group together with a carboxyl group include citric acid, glycolic acid, lactic acid, gluconic acid, malic acid, tartaric acid, oxalic acetic acid, salicylic acid, m-hydroxybenzoic acid, gentisic acid, protocatechuic acid, Examples thereof include gallic acid, glucuronic acid, sialic acid, and ascorbic acid.

  Examples of these carboxylic acid salts include potassium salts, ammonium salts, alkylamine salts, and hydroxylamine salts. One of these may be added to the liquid or a mixture of two or more may be added.

  Among the organic acid groups listed above, those that can be particularly preferably used are malonic acid, succinic acid, citric acid, glycolic acid, lactic acid, gluconic acid, malic acid, or tartaric acid. It has been confirmed that when a polishing experiment is performed using an electrolytic solution to which these organic acids are added, a smooth processed surface can be obtained at a relatively high processing speed.

  The concentration of the organic acid needs to be equal to or lower than the saturation solubility at the processing temperature. This is because when the saturation solubility is exceeded, the organic acid is precipitated in the liquid and stable processing cannot be performed. For example, the solubility of maleic acid is 78% by weight (25 ° C.). On the other hand, if the concentration of the organic acid is lower than 0.1%, the supply amount of the organic acid coordinated with the dissolved metal to the surface of the processed portion is insufficient, the processing does not proceed quickly, and the processing surface becomes rough. Problems arise. On the other hand, if the concentration is low, the pH buffering action is not sufficient. For the above reasons, the concentration of the organic acid is preferably 0.1 to 80% by weight, and more preferably 1 to 50% by weight.

  The strong acid having a sulfonic acid group, which is commonly contained in the electrolytic solution 22 and the conditioning solution 34, is for accelerating the etching action of the solution and increasing the conductivity of the solution so that a current for processing can easily flow. . Here, the strong acid means a pKa having a logarithm of the reciprocal of the first dissociation constant indicating the strength of the acid is 3 or less.

  In general, when a strong acid is used, the potential at which copper dissolution begins is low. That is, copper can be processed with a low applied voltage. However, when sulfuric acid, nitric acid or perchloric acid is used, the roughening of the processed surface is severe due to copper etching, etc., and phosphoric acid has a high viscosity in the concentration range where surface gloss can be obtained, so the voltage required for processing copper There are problems such as relatively high. On the other hand, for example, when methanesulfonic acid is used, it has been confirmed that the voltage required for copper processing is low, the processing surface is relatively smooth, and good processing characteristics can be obtained.

  The strong acid having a sulfonic acid group that can be preferably used includes methanesulfonic acid, benzenesulfonic acid, taurine, cysteic acid, alkylbenzenesulfonic acid having 1 to 6 carbon atoms in total, trifluoromethanesulfonic acid, or Examples thereof include fluorosulfonic acid, and one or more of these can be used. The concentration of the strong acid having a sulfonic acid group is preferably 0.1 to 20% by weight, and more preferably 5 to 20% by weight. If the concentration of the strong acid having a sulfonic acid group is too low, the electrical conductivity of the liquid will be low and current will not flow easily. For this reason, it is preferable that the density | concentration of the strong acid which has a sulfonic acid group is 5 weight% or more. On the other hand, if the concentration of the strong acid having a sulfonic acid group exceeds 20% by weight, the saturated solubility of the organic acid and other components in the liquid may be reduced, thereby causing precipitation.

  The corrosion inhibitor contained in the electrolytic solution 22 is preferably a nitrogen-containing heterocyclic compound, and forms a compound with a metal such as copper to be processed, and forms a protective film on the metal surface. What is known as a compound which suppresses corrosion may be sufficient. Such a corrosion inhibitor has an effect of promoting flattening in order to suppress excessive processing and prevent dishing and the like.

  Examples of corrosion inhibitors that can be preferably used include benzotriazole and its derivatives, which are conventionally known corrosion inhibitors for copper. In addition to the above-described effects of promoting flattening, indole, 2-ethylimidazole, benzimidazole, 2-mercaptobenzimidazole, 3-amino-1,2,4-triazole, 3-amino- 5-methyl-4H-1,2,4-triazole, 5-amino-1H-tetrazole, 2-mercaptobenzothiazole, 2-mercaptobenzothiazole sodium, 2-methylbenzothiazole, (2-benzothiazolylthio) acetic acid, 3- (2-benzothiazolylthio) propionic acid, 2-mercapto-2-thiazoline, 2-mercaptobenzoxazole, 2,5-dimercapto-1,3,4-thiadiazole, 5-methyl-1,3,4 -Thiadiazole-2-thiol, 5-amino-1,3,4-thiadiazole-2 Thiol, pyridine, phenazine, acridine, 1-hydroxypyridine-2-thione, 2-aminopyridine, 2-aminopyrimidine, trithiocyanuric acid, 2-dibutylamino-4,6-dimercapto-s-triazine, 2-anilino-4 , 6-dimercapto-s-triazine, 6-aminopurine, 6-thioguanine, and combinations thereof.

  When the concentration of the corrosion inhibitor is low, the formation of a protective film becomes insufficient, so that excessive etching occurs in a metal such as copper and a flat processed surface cannot be obtained. On the other hand, even if it is below the saturation solubility, if the concentration of the corrosion inhibitor is too high, the protective surface is excessively formed on the metal surface such as copper, the processing speed is reduced, and the processing surface cannot be uniformly processed. It also causes rough and pits. From the above, the concentration of the corrosion inhibitor is preferably 0.001 to 5% by weight, and more preferably 0.02 to 2% by weight.

  The water-soluble polymer compound contained in the electrolytic solution 22 is effective in forming a protective film together with a corrosion inhibitor, suppressing excessive etching, and flattening the surface of a metal such as copper. In addition, in an electrolytic solution containing a water-soluble polymer compound, the viscosity of the electrolytic solution near the surface of a metal surface (processed surface) such as copper is increased, so that a viscous film is formed on minute concave and convex portions present on the metal surface. Is formed, and fine irregularities are also polished to obtain a glossy surface.

  Among the water-soluble polymer compounds that can be preferably used, polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, polyethylene glycol, polyisopropylacrylamide, polydimethylacrylamide, One or more types selected from methacrylamide, polymethoxyethylene, polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl pyrrolidone, and the like can be given.

  As these water-soluble polymer compounds, those having a mass average molecular weight of 1,000 to 500,000 can be used. If the weight average molecular weight exceeds 500,000, it will not dissolve in the electrolyte solution and cause aggregation with corrosion inhibitors and abrasive grains. If the weight average molecular weight is less than 1,000, sufficient protection is provided for metal surfaces such as copper. A film cannot be formed and the planarization performance deteriorates. The mass average molecular weight of the water-soluble polymer compound is preferably 1,000 to 100,000, and more preferably 2,000 to 25,000.

  The concentration of the water-soluble polymer compound is preferably 0.005 to 5% by weight and 0.01 to 2% by weight in order not to reduce the processing rate of electropolishing and to suppress excessive processing action. More preferably it is.

  In order to adjust the pH of the electrolytic solution 22, a pH adjusting agent may be added to the electrolytic solution 22. As a preferable pH adjuster, alkali is mainly used, and one or more kinds selected from ammonia, alkylamine, hydroxyamine, polyamine, alkali metal compound (for example, potassium hydroxide), and alkaline earth metal compound can be selected. The alkali concentration is generally 0.1 to 20% by weight, and may be appropriately determined depending on the use of the workpiece, the material, the concentration of the organic acid or organic acid salt and strong acid contained, and the pH to be adjusted.

  The pH of the preferable electrolytic solution 22 is 2-10. When the pH of the electrolytic solution 22 is low, corrosion resistance must be taken into consideration in the material selection of the composite electrolytic polishing apparatus, and the processing speed is increased while the roughness of the processed surface is increased, and the metal such as copper is increased. Excessive etching advances and it becomes difficult to obtain a flat processed surface. When the pH of the electrolytic solution 22 is high, formation of a protective film between the corrosion inhibitor and / or the water-soluble polymer compound and copper may be insufficient, and the planarization action may be insufficient. Therefore, the pH of the electrolytic solution 22 is particularly preferably 3 to 6 when flattening is required on a glossy surface having a high processing speed and no surface roughness as in a copper wiring process of a semiconductor substrate.

  The electrolytic solution 22 preferably contains abrasive grains. The abrasive grains have an action of mechanically removing metals such as copper, but in the present invention, an action of mechanically removing the metal protective film formed of the corrosion inhibitor and the water-soluble polymer compound appropriately. There is also. By the action of the abrasive grains, an extra protective film is removed, and the processing speed in the composite electropolishing is sufficiently increased.

  As an abrasive grain which can be preferably used as the electrolytic solution 22, one or more kinds selected from alumina, colloidal silica, fumed silica, zirconium oxide, cerium oxide, titanium oxide, and manganese oxide can be exemplified. Among these, alumina, colloidal silica, or fumed silica is preferably used.

  In the case of functioning effectively as electrochemical mechanical polishing, the concentration of abrasive grains in the electrolytic solution 22 is preferably 10% by weight or less, and in order to exert the effect of abrasive grains, the concentration of abrasive grains is 0. It is necessary to be 0.01% by weight or more. On the other hand, the effect of removing the protective film is effective by using fixed abrasive grains such as a polishing pad even if there are no abrasive grains dispersed in the electrolytic solution 22 and contacting the polishing pad with a metal surface such as copper. Therefore, in such a case, there is no need to have abrasive grains in the electrolytic solution, and of course, combined use with fixed abrasive grains is also possible. When using abrasive grains, if the concentration of the abrasive grains exceeds 10% by weight, the aggregation of the abrasive grains increases, and the viscosity of the electrolytic solution may become extremely high. Electropolishing by depositing abrasive grains on the work surface may occur. It may cause inhibition and scratching. For this reason, the optimal abrasive grain concentration is 0.05 to 2% by weight.

  The electrolytic solution 22 may contain a surfactant. The surfactant is not particularly limited as long as it improves the dispersibility of the abrasive grains, and any of cationic, anionic, amphoteric and nonionic can be used. For example, as the anionic surfactant, alkyl ether carboxylate, alkyl sulfate, alkyl sulfonate, amide sulfonate, alkyl allyl sulfonate, naphthalene sulfonate, or a formalin condensate thereof is used. As the cationic surfactant, for example, an aliphatic amine salt or an aliphatic ammonium salt is used. These are appropriately selected and used depending on the concentration of the abrasive grains and the pH of the electrolytic solution 22. The surfactant is preferably an anionic surfactant, particularly preferably an alkyl sulfonate or a naphthalene sulfonic acid formalin condensate.

  The conductivity of the electrolytic solution 22 is desirably 5 to 200 mS / cm. When the conductivity of the electrolytic solution 22 is low, the applied voltage or current must be increased in order to increase the processing speed. In this case, the current efficiency decreases due to oxygen generation, the generation of pits on the processing surface, There is an adverse effect on the planarization effect due to the destruction of the protective film. Therefore, it is desired to perform electropolishing at a lower voltage, and for this purpose, the conductivity of the electrolytic solution is preferably 5 to 200 mS / cm.

  In order to suppress polishing rate improvement and surface roughness of the polished surface in electrolytic polishing, it is desirable that the electrolytic solution 22 contains a conductive material to be polished, such as copper, in its components. The concentration of the conductive substance such as copper in the electrolytic solution is 0.001% by weight or more, more preferably 0.005% by weight or more, and still more preferably 0.01% by weight or more. This promotes diffusion of a conductive substance from the surface of the object to be polished, such as copper, or a polishing product containing the same into the electrolytic solution during polishing. The concentration of the conductive substance, for example, copper in the electrolytic solution 22 is 10% or less, preferably 1% or less. This is because when the concentration of the conductive material is 1% or more, the conductive material component in the electrolytic solution is likely to consume other electrolytic solution components in the electrolytic solution. In the case where the conductive material is a compound, a plurality of conductive material components may be included in the electrolytic solution in accordance with the component ratio.

  Examples of the composition of the electrolytic solution 22 include (1) 2 to 80% by weight of organic acid, (2) strong acid having 2 to 20% by weight of sulfonic acid group, and (3) 0.01 to 1% by weight of corrosion inhibition. An agent, (4) 0.01 to 1% by weight of a water-soluble polymer compound, (5) 0.01 to 2% by weight of abrasive grains, and (6) about 0.01 to 1% by weight of a surfactant. It contains and what adjusted pH to 2-10 is mentioned. The electrolyte solvent is deionized water, preferably ultrapure water.

Examples of the composition of the conditioning liquid 34 include (1) 2 to 80 wt% organic acid, (2) 2 to 20 wt% strong acid having a sulfonic acid group, and (3) 0.1 to 5 wt% oxidation. those with agent (e.g. _H 2 _{O 2)} can be mentioned.

(Example 1)
An electrolyte solution comprising malonic acid, methanesulfonic acid, and benzotriazole (corrosion inhibitor) as main components, polyacrylic acid (molecular weight: 5000), methanol and a surfactant added to the abrasive, and malonic acid In addition, a conditioning liquid containing methanesulfonic acid and hydrogen peroxide (H ₂ O ₂ ) was prepared. Then, using the composite electrolytic polishing apparatus shown in FIGS. 2 and 3, the conditioning liquid is supplied to the upper surface of the processing table 10 at a flow rate of 200 ml / min while rotating the processing table 10 at a rotation speed of 30 rpm. The electrode 16 and polishing pad 18 were conditioned for 2 minutes.

Then, while rotating the processing table 10 at a rotation speed of 60 rpm, ultrapure water was supplied to the upper surface of the processing table 10 at a flow rate of 200 ml / min, and the rinsing process of the processing electrode 16 and the polishing pad 18 was performed for 2 minutes. . Thereafter, while rotating the processing table 10 at a rotational speed of 100 rpm, an electrolytic solution was supplied to the upper surface of the processing table 10 at a flow rate of 100 ml / min, and the copper film formed on the surface of the semiconductor wafer was polished for 1 minute.
As a result, no surface roughness was observed on the copper film surface (polished surface) of the semiconductor wafer, and both the glossy surface and the level difference elimination property were good.

(Comparative Example 1)
A mixed solution of sulfuric acid and hydrogen peroxide solution was used as a conditioning solution, and the other conditions were the same as in Example 1. The processing electrode 16 and the polishing pad 18 were conditioned and rinsed, and formed on the surface of the semiconductor wafer. The copper film was polished.
As a result, surface roughness was observed on the copper film surface (polished surface) of the semiconductor wafer, and the step resolution was poor.

  Therefore, after conditioning the processing electrode 16 and the polishing pad 18, the pH of the surface of the polishing pad 18 (or in the through hole 18a) is supplied while supplying ultrapure water to the upper surface of the processing table 10 at a flow rate of 200 ml / min. The relationship between the rinse time and the rotation speed of the processing table 10 was examined. The results are shown in Table 1.

According to Table 1, in Example 1, the rinsing process for supplying ultrapure water to the upper surface of the processing table 10 at a flow rate of 200 ml / min is performed for 2 minutes while rotating the processing table 10 at a rotation speed of 60 rpm. The rinsing process can be completed so as not to affect the next electropolishing. In Comparative Example 1, if the rinsing process is performed under the same conditions as in Example 1, the electropolishing may be affected. It can be seen that it takes 10 minutes, five times that of Example 1, to complete the rinsing process, and therefore five times as much ultrapure water is required. In Comparative Example 1, the rinsing process can be completed in 5 minutes by increasing the rotational speed of the processing table to 120 rpm. Thus, when the rotational speed of the processing table is increased, the conditioning liquid ( Scattering of the chemical solution becomes a problem.
In addition, this invention is applicable not only to the electrolyte solution quoted in the said Example but another electrolyte solution. That is, a conditioning liquid composed of the same main component as the electrolytic solution used in the electrolytic processing is applied to the conditioning without a component (for example, a corrosion inhibitor) that suppresses the removal of electrolytic processing by-products. .

It is a figure which shows an example of the conventional manufacturing method of a copper wiring board in order of a process. It is a top view which shows an example of an electropolishing apparatus. FIG. 3 is a longitudinal front view of FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Processing table 12 Substrate holder 16 Processing electrode 18 Polishing pad 18a Through-hole 20 Electrolyte supply nozzle 22 Electrolyte 24 Electrolyte storage tank 26 Electrolyte supply line 30 Conditioning liquid supply nozzle 32 Pure water supply nozzle 34 Conditioning liquid 36 Conditioning liquid storage Tank 38 Conditioning liquid supply line 40 Power supply electrode 42 Power supply 44 Dresser 306 Seed film 307 Copper film 308 Wiring

Claims (7)

  In the presence of an electrolytic solution containing an organic acid and a corrosion inhibitor while applying a voltage between the conductive material on the surface of the object to be polished and the processing electrode disposed at a position facing the conductive material, the processing electrode The processing electrode and / or the polishing pad of a composite electrolytic polishing apparatus that polishes the conductive material by rubbing a polishing pad disposed between the conductive material and the conductive material at the polishing interval, A conditioning method comprising performing conditioning using a conditioning solution comprising a component obtained by removing at least the corrosion inhibitor from an electrolytic solution.   The conditioning method according to claim 1, wherein the conditioning liquid further includes an oxidizing agent.   The organic acid is acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, citric acid, aconitic acid, glyoxylic acid, glycolic acid, lactic acid, gluconic acid, malic acid The conditioning method according to claim 1, wherein the conditioning method comprises one or more of tartaric acid and tartaric acid.   The conditioning method according to claim 1 or 2, wherein the organic acid comprises a strong acid having a sulfonic acid group.   The strong acid having a sulfonic acid group is any one of benzenesulfonic acid, methanesulfonic acid, taurine, cysteic acid, alkylbenzenesulfonic acid having 1 to 6 carbon atoms in total, trifluoromethanesulfonic acid, and fluorosulfonic acid. The conditioning method according to claim 4, comprising the above. A conditioning liquid used for conditioning a processing electrode and / or a polishing pad used for electrolytic processing,
A conditioning liquid comprising a component containing at least one organic acid or a salt thereof and at least one strong acid having a sulfonic acid group and no corrosion inhibitor.   The conditioning liquid according to claim 6, further comprising an oxidizing agent.

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