JP2008004615A - Method and apparatus for forming wiring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an insulation film on the surface of a substrate after surely cleaning the surface of a substrate wherein a wiring protective film is selectively formed on the exposed surface of wiring, while reducing a risk of current leak among wirings. <P>SOLUTION: A substrate is prepared wherein the surface of an embedded wiring formed inside an interlayer dielectric is selectively covered with a wiring protective film, the surface of the substrate is pre-cleaning by wet processing using a cleaning liquid, and then an insulation film is formed on the surface of the pre-cleaned substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wiring forming method and a wiring forming apparatus, and in particular, a buried wiring is formed by embedding a conductor (wiring material) such as copper or silver in a wiring recess provided on a surface of a substrate such as a semiconductor wafer, Furthermore, the present invention relates to a wiring forming method and a wiring forming apparatus used for selectively covering the surface of the embedded wiring with a wiring protective film to form a multilayer wiring structure.

  As a wiring formation process of a semiconductor device, a process (so-called damascene process) in which a metal (conductor) is embedded in a wiring groove and a contact hole is being used. This is because, after embedding a metal such as copper or silver in a wiring groove or contact hole previously formed in an interlayer insulating film, the excess metal is removed by chemical mechanical polishing (CMP) and planarized. Process technology.

  Conventionally, this type of wiring, for example, copper wiring using copper as a wiring material, prevents the thermal diffusion of the wiring material (copper) to the interlayer insulating film and improves electromigration resistance in order to improve reliability. Oxidation of the wiring material (copper) in an oxidizing atmosphere when a barrier film for improvement is formed on the bottom and side surfaces of the wiring, and then a semiconductor device having a multilayer wiring structure is formed by laminating an insulating film (oxide film) In order to prevent this, a method such as forming an antioxidant film is employed. Conventionally, a metal such as tantalum, titanium or tungsten or a nitride thereof is generally employed as this type of barrier film, and a nitride or carbide of silicon is generally employed as an antioxidant film.

  As an alternative to this, it has recently been studied to selectively cover the exposed surface of the embedded wiring with a wiring protective film made of a cobalt alloy, nickel alloy or the like to prevent thermal diffusion, electromigration and oxidation of the wiring. ing.

For example, as shown in FIG. 1, a fine recess (trench) 4 for wiring is formed inside an interlayer insulating film 2 made of SiO ₂ or Low-K material deposited on the surface of a substrate W such as a semiconductor wafer. A barrier layer 6 made of TaN or the like is formed on the surface, and a seed layer 7 is formed on the surface of the barrier layer 6 as necessary. Then, copper plating is performed to form a copper film on the surface of the substrate W, copper is embedded in the recesses 4, and then the surface of the substrate W is planarized by CMP (chemical mechanical polishing). Thus, a wiring 8 made of copper is formed inside the interlayer insulating film 2. Next, a wiring protective film (cover material) 9 made of a CoWP alloy, for example, obtained by electroless plating is selectively formed on the surface of the wiring (copper) 8 to protect the wiring 8.

In this way, after the exposed surface of the wiring 8 is covered with the wiring protection film 9 to protect the wiring 8, the insulating film 10 made of, for example, SiC, SiCN, or SiN is formed on the surface of the interlayer insulating film 2 and the wiring protection film 9. It is uniformly formed by CVD or the like, and then an upper interlayer insulating film made of SiO ₂ or Low-K material for forming wiring (upper layer wiring) inside is deposited on the surface of the insulating film 10.

A process of selectively forming a wiring protective film (cover material) 9 made of a CoWP alloy on the surface of the wiring 8 by general electroless plating will be described. First, a substrate W such as a semiconductor wafer subjected to a CMP process is immersed in, for example, dilute sulfuric acid or dilute hydrochloric acid at room temperature for about 1 minute to remove impurities such as CMP residues such as metal oxide film and copper on the surface of the interlayer insulating film 2. Remove. Then, after cleaning (rinsing) the surface of the substrate W with a cleaning solution such as pure water, the substrate W is immersed in, for example, a palladium solution (PdCl ₂ / HCl) at room temperature for about 1 minute. The exposed surface of the wiring 8 is activated by attaching Pd as a catalyst.

  Next, after cleaning (rinsing) the surface of the substrate W with pure water or the like, for example, the substrate W is immersed in a CoWP plating solution having a liquid temperature of 80 ° C. for about 120 seconds to activate the surface of the activated wiring 8. Selective electroless plating is performed, and then the surface of the substrate W is cleaned (rinsed) with a cleaning liquid such as pure water. As a result, a wiring protective film 9 made of a CoWP alloy is selectively formed on the exposed surface of the wiring 8 to protect the wiring 8.

Here, it is known that the surface of the wiring whose surface is exposed is prevented from corrosion using a corrosion inhibitor such as BTA (benzotriazole) (see Patent Document 1). Prior to forming the insulating film on the surface of the substrate on which the embedded wiring is formed, the oxide film on the surface of the wiring protective film and the contaminants on the interlayer insulating film are removed (pre-cleaning) by dry processing such as plasma cleaning. Has been proposed (see Patent Document 2).
Japanese Patent No. 3705724 JP 2005-194598 A

  In dry cleaning using plasma or the like, plasma or the like in which erosive radicals are generated on the surface of the wiring is irradiated. For this reason, the wiring material such as copper scatters from the surface of the substrate with the irradiation of plasma or the like, and the wiring material scattered in the interlayer insulating film located between the wirings causes current leakage. Therefore, the process is adjusted so that wiring materials such as copper are not scattered.

  However, after forming a wiring protective film made of cobalt alloy, nickel alloy, etc. on the surface of the wiring, if the surface of the substrate is cleaned by a dry cleaning process adjusted so that wiring materials such as copper are not scattered, the wiring protective film A metal such as a cobalt alloy scatters from the surface of the substrate due to plasma having etching power against the surface, and the scattered metal adheres to the surface of the interlayer insulating film between the wirings, causing current leakage. This also applies to the case where the surface of the wiring protective film is prevented from corrosion by an anticorrosive agent such as BTA (benzotriazole), and the surface of the interlayer insulating film between the wirings is scattered by the BTA complex or Cu metal itself. If it adheres, current leakage will be caused.

  The present invention has been made in view of the above circumstances, and reliably cleans the surface of the substrate on which the wiring protective film is selectively formed on the exposed surface of the wiring while reducing the risk of current leakage between the wirings. Then, it aims at providing the wiring formation method and wiring formation apparatus which enabled it to form an insulating film on the surface of a board | substrate after an appropriate time.

  In the first aspect of the present invention, a substrate in which the surface of the embedded wiring formed inside the interlayer insulating film is selectively covered with a wiring protective film is prepared, and the surface of the substrate is pre-cleaned by a wet process using a cleaning liquid. A method of forming a wiring comprising forming an insulating film on the surface of a substrate after pre-cleaning.

  In this way, the surface of the substrate that selectively covers the surface of the embedded wiring formed in the interlayer insulating film with the wiring protective film is pre-cleaned by the wet treatment using the cleaning liquid, and this pre-cleaning is accompanied. While suppressing the metal such as cobalt alloy and BTA complex from the surface of the substrate and the scattered metal and BTA complex from adhering to the surface of the interlayer insulating film between the wirings, causing current leakage, The surface of the substrate can be reliably cleaned. As this cleaning liquid, for example, an acid having a weak etching power such as an organic acid is preferably used.

The invention according to claim 2 is the wiring forming method according to claim 1, wherein the wiring is made of copper or a copper alloy, and the wiring protective film is made of a cobalt alloy or a nickel alloy.
The invention according to claim 3 is characterized in that the insulating film is made of any material of SiC, SiCN, SiN, SiO ₂ , SiOCH, low dielectric constant siloxane, or low dielectric constant organic polymer. It is a wiring formation method of Claim 1 or 2.

A fourth aspect of the present invention is the wiring forming method according to any one of the first to third aspects, wherein the substrate is dried immediately after the pre-cleaning by the wet treatment.
As a method for drying the substrate, for example, at least one of a so-called spin dry method in which the substrate is rotated at a high speed and a method in which the substrate is heated and dried in a controlled gas atmosphere is employed.

  According to a fifth aspect of the present invention, there is provided a pre-cleaning unit for pre-cleaning the surface of the substrate in which the surface of the embedded wiring formed inside the interlayer insulating film is selectively covered with a wiring protective film by a wet process using a cleaning liquid. A wiring forming apparatus comprising an insulating film forming unit for forming an insulating film on a surface of a substrate after pre-cleaning.

The invention according to claim 6 is the wiring forming apparatus according to claim 5, further comprising a drying unit for drying the substrate immediately after the pre-cleaning by the pre-cleaning unit.
The invention according to claim 7 is characterized in that the drying unit comprises at least one of a spin dry unit that spin-drys the substrate by rotating the substrate at a high speed and a heat treatment drying unit that dries the substrate by heat treatment. It is a wiring formation apparatus of description.

The invention according to claim 8 is the wiring forming apparatus according to any one of claims 5 to 7, further comprising a flattening unit for flattening a surface of the insulating film.
The invention according to claim 9 further comprises an electroless plating unit that selectively forms a wiring protective film on the surface of the embedded wiring formed inside the interlayer insulating film. A wiring forming apparatus according to claim 1.
As a result, a series of processes for selectively forming the wiring protective film on the surface of the wiring by the electroless plating unit and then forming the insulating film on the surface of the substrate can be continuously performed.

A tenth aspect of the present invention is the wiring forming apparatus according to the ninth aspect, further comprising a plating pretreatment unit for performing a pretreatment for plating on the surface of the embedded wiring formed inside the interlayer insulating film.
The plating pretreatment unit includes a pre-cleaning unit for cleaning the surface of the substrate and a catalyst applying unit for applying a catalyst to the exposed surface of the wiring, and the catalyst applying unit is provided as necessary.

  According to the present invention, in the dry process in which radicals that are erosive to the alloy film such as plasma are generated on the surface of the substrate in which the surface of the embedded wiring formed inside the interlayer insulating film is selectively covered with the wiring protective film. In addition, by performing pre-cleaning with a wet process using a cleaning liquid, it is possible to perform cleaning reliably while reducing the risk of leakage current between the wirings. In addition, the selectivity of the wiring protective film can be improved, and the adhesion between the wiring protective film and the insulating film formed thereafter can be increased.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a plan layout view of the wiring forming apparatus according to the embodiment of the present invention. As shown in FIG. 2, the wiring forming apparatus includes a rectangular apparatus frame 20 and a load / unload unit 22 attached to the apparatus frame 20. A control unit 24 is provided on the outer wall of the apparatus frame 20. Is installed. Inside the apparatus frame 20, a pre-cleaning unit 26, a drying unit 28, an insulating film forming unit 30, and a planarizing unit 32 are arranged at the four corners, and are further sandwiched between these units. A first substrate transfer robot 34 and a second substrate transfer robot 36 for transferring substrates between the units are arranged.

  The pre-cleaning unit 26 is for cleaning (pre-cleaning) the surface of the substrate by a wet process using a cleaning liquid (chemical solution). In this example, the surface is faced down (face down) or faced up (face up). A substrate holder for holding and rotating a substrate and a number of spray nozzles are provided, and a cleaning solution (chemical solution) is sprayed from the number of spray nozzles toward the surface of the substrate held and rotated by the substrate holder. The surface is configured to be cleaned with a cleaning liquid. In this way, by cleaning the surface of the substrate with the cleaning liquid while flowing the cleaning liquid, it is possible to prevent the metal removed by the cleaning liquid from reattaching to the surface of the substrate.

  As this cleaning liquid, it is preferable to use an acid having a weak etching ability of, for example, about 0.1 to 10 nm / min as an etch rate for a cobalt alloy or a nickel alloy. Thereby, as described below, the etching amount of the wiring protective film 52 made of, for example, a cobalt alloy or a nickel alloy covering the surface of the wiring 50 can be minimized. Further, it is preferable to add an anionic surfactant in the cleaning solution so that the etched metal or the like does not re-adhere on the interlayer insulating film. By adding an organic acid to the cleaning liquid and forming a passive state of the complex on the surface of the wiring protective film 52, the growth of the oxide film on the surface of the wiring protective film 52 after cleaning can be suppressed. Furthermore, an anticorrosive agent such as BTA may be added to the cleaning liquid so that the cobalt alloy, nickel alloy, or the like does not dissolve in the cleaning liquid.

  In addition, while supplying the cleaning liquid to the surface of the substrate, scrub cleaning may be performed by physically bringing a roll brush into contact with the surface. In this case, by appropriately adjusting the pH and composition of the cleaning liquid, it is possible to further reduce the reattachment of the removed metal or the like to the surface of the interlayer insulating film.

  As the pre-cleaning unit 26, a cleaning liquid is supplied from a nozzle to, for example, a central part of the rotating substrate surface so that the cleaning liquid spreads over the entire surface of the substrate by centrifugal force, or a porous liquid containing the cleaning liquid inside. A material that is brought into contact with the surface of the substrate while being rotated to clean the surface of the substrate may be used.

  In this example, the drying unit 28 is composed of a spin dry unit. First, a cleaning liquid made of pure water or the like is supplied to the surface of the substrate held by the substrate holder and rotated at a low speed so that the surface of the substrate is covered. Rinse cleaning is performed, and then the substrate is rotated at high speed to be spin-dried.

The insulating film forming unit 30 is for uniformly forming an insulating film 54 made of, for example, SiC, SiCN, or SiN on the entire surface of the substrate after the pre-cleaning as described below. (PE-CVD) unit. The insulating film 54 may be made of SiO ₂ or SiOCH material. The insulating film 54 may be a low-dielectric constant siloxane-based or low-dielectric-constant organic polymer-based material. In this case, as the insulating film forming unit 30, a unit adopting a coating type is used.
The flattening unit 32 is for flattening the surface of the insulating film 54 uniformly formed on the entire surface of the substrate as described below, and is composed of, for example, a CMP unit.

  Next, an example of wiring formation by this wiring forming apparatus will be described with reference to FIGS. First, as shown in FIG. 4A, a recess (trench) 42 is provided in the interlayer insulating film 40, a barrier layer 44 and a seed layer 46 are sequentially formed on the surface, and the surface of the seed layer 46 is made of copper. A metal film (copper film) 48 is formed, and excess metal material other than the recesses 42 is removed by CMP to flatten the surface to form a wiring 50 made of the copper film 48, and then the exposed surface of the wiring 50 is made of CoWP or the like. A substrate W on which a wiring protective film 52 made of cobalt alloy or nickel alloy is selectively formed is prepared.

  In this substrate W, impurities 60 may adhere to the surface of the interlayer insulating film 40, or an oxide film 62 may be formed on the surface of the wiring protective film 52. Prior to this, it is necessary to remove these impurities 60 and oxide film 62.

  Then, the substrate W is carried into the pre-cleaning unit 26 through the load / unload unit 22 by the first substrate transfer robot 34 (step 1). In the pre-cleaning unit 26, the surface of the substrate W is cleaned (pre-cleaning) by a wet process using a cleaning solution, and thereby, impurities 60 adhering to the surface of the interlayer insulating film 40 and the surface of the wiring protective film 52 are formed. The oxide film 62 is removed (cleaned) (step 2).

  As described above, the surface of the substrate W in which the surface of the embedded wiring 50 formed inside the interlayer insulating film 40 is selectively covered with the wiring protective film 52 is pre-cleaned by a wet process using a cleaning liquid. Along with cleaning, a metal such as a cobalt alloy, a BTA complex, or the like scatters from the surface of the substrate, and the scattered metal, the BTA complex, or the like adheres to the surface of the interlayer insulating film 40 between the wirings 50 and causes current leakage. While suppressing this, the surface of the substrate W can be reliably cleaned.

  Next, the substrate W after the pre-cleaning is transported to the drying unit 28 by the second substrate transport robot 36, and the surface of the substrate W is rinsed with pure water or the like by the drying unit 28. Spin and spin dry (step 3). Then, the substrate W after spin drying is transferred to the insulating film forming unit 30 by the second substrate transfer robot 36.

  In the insulating film forming unit 30, as shown in FIG. 4B, an insulating film 54 made of, for example, SiC, SiCN, or SiN is uniformly formed on the entire surface of the substrate W (step 4), whereby the interlayer insulation is formed. The surfaces of the film 40 and the wiring protective film 52 are covered with an insulating film 54 for protection. Then, the substrate on which the insulating film 54 is formed is transferred to the flattening unit 32 by the second substrate transfer robot 36, and the surface of the insulating film 54 is flattened by the flattening unit 32 as shown in FIG. (Step 5).

Next, the substrate W with the surface of the insulating film 54 planarized is carried out to the load / unload unit 22 by the first substrate transfer robot 34 (step 6), thereby completing a series of processes. This on the surface of the insulating film 54, as shown in FIG. 5, the upper layer of the interlayer insulating film 56 made of SiO ₂ or Low-K material such as an internal wiring (upper wiring) is formed is formed, thereby, The wiring is multilayered.

  In this example, the insulating film 54 made of SiN or the like is formed on the surface of the substrate W, and the rising interlayer insulating film 56 is formed on the surface of the insulating film 54. The rising interlayer insulating film 56 may be directly formed on the surface of the substrate W by the forming unit 30, and the surface of the interlayer insulating film 56 may be planarized by the planarizing unit 32.

  A substrate in which a wiring protective film is formed on the surface of the wiring is prepared, an insulating film is directly formed on the surface of the substrate, and the leakage current between the wirings is measured. The result of measuring the leakage current between wirings after preparing a substrate with a wiring protective film on the surface of the wiring, and then dry-cleaning the surface of this substrate using plasma, and then forming an insulating film on the surface of the substrate Is shown by curve 2 in FIG. Prepare a substrate on which the wiring protective film is formed on the surface of the wiring. After the surface of this substrate is wet-cleaned using a cleaning liquid in the same manner as described above, an insulating film is formed on the surface of the substrate, The result of measuring the leakage current is shown in FIG. 6 by curve 3 (present invention).

  Comparing curve 1 and curve 2, it can be seen that the leak current of curve 2 is larger than that of curve 1 at about 40% of measurement points. This is because, during dry cleaning, the wiring protection film (alloy film) on the wiring is etched and scattered, and the leakage current partially deteriorates due to the particles or clusters adhering to the interlayer insulating film between the wirings. It is thought that. On the other hand, when curve 1 and curve 3 (the present invention) are compared, it can be seen that the leakage current of curve 3 (the present invention) is smaller than that of curve 1 at all measurement points. This is presumably because the metal current or film remaining on the interlayer insulating film between the wirings was removed by appropriate wet cleaning to shift the leakage current in a direction to be improved.

  FIG. 7 is a plan layout view of a wiring forming apparatus according to another embodiment of the present invention. In this example, a pre-cleaning unit 70, a catalyst application unit 72, an electroless plating unit 74, and a second drying unit 76 are further provided as plating pretreatment units in the apparatus frame 20 in the wiring forming apparatus shown in FIG. Is.

The second drying unit 76 includes a heat treatment drying unit that heats and dries the substrate in a controlled gas atmosphere. The controlled gas atmosphere is a gas atmosphere having a reducing power on the metal oxide containing either H ₂ or NH ₃ or an inert gas atmosphere containing either N ₂ or Ar.

According to this example, in FIG. 4A, a substrate before forming the wiring protective film 52 on the surface of the wiring 50, that is, a substrate after the CMP process is prepared. Then, the substrate is transported to a pre-cleaning unit 70 as a plating pretreatment unit, and immersed in, for example, room temperature dilute sulfuric acid or dilute hydrochloric acid for about 1 minute to clean the surface of the substrate. (Rinse) with the cleaning solution. Then, the substrate is transported to a catalyst application unit 72 as a plating pretreatment unit, where the substrate is immersed in, for example, a room temperature palladium solution (PdCl ₂ / HCl) for about 1 minute, and Pd as a catalyst is formed on the surface of the wiring. After activating the exposed surface of the wiring, the surface of the substrate is washed (rinsed) with pure water or the like.

  Next, the substrate is transported to the electroless plating unit 74, where the substrate is immersed in a CoWP plating solution having a liquid temperature of 80 ° C. for about 120 seconds, for example. Electrolytic plating is performed, and then the surface of the substrate W is cleaned (rinsed) with a cleaning liquid such as pure water. As a result, as shown in FIG. 4A, a wiring protective film 52 made of a CoWP alloy is selectively formed on the exposed surface of the wiring 50 to protect the wiring 50.

  The subsequent processing is almost the same as in the above example. In this example, the substrate spin-dried by the drying unit (spin dry unit) 28 is transported to the second drying unit (heat treatment drying unit) 76. The substrate is completely dried by the second drying unit 76.

According to this example, the electroless plating unit 74 selectively forms a wiring protective film on the surface of the wiring, and thereafter, a series of processes for forming the insulating film 54 on the surface of the insulating film forming unit 30 substrate is continued. Can be done.
In addition, when the wiring protective film can be formed without applying a catalyst, or when the plating pretreatment (precleaning and catalyst application) can be performed with one processing solution, the catalyst application unit 72 is omitted. Can do.

It is sectional drawing which shows the state which formed the wiring protective film on the surface of the embedded wiring. It is a plane layout view showing a wiring formation device of an embodiment of the invention. It is a flowchart of the example of wiring formation by the wiring formation apparatus shown in FIG. It is a figure which shows the wiring formation example by the wiring formation apparatus shown in FIG. 2 in order of a process. It is sectional drawing which shows the state which formed the upper-layer interlayer insulation film on the surface of the insulation film. It is a graph which shows the result of having measured the leakage current between wiring. It is a plane | planar arrangement | positioning figure which shows the wiring formation apparatus of other embodiment of this invention.

Explanation of symbols

20 Equipment frame 22 Load / unload unit 24 Control unit 26 Pre-cleaning unit 28 Drying unit (spin dry unit)
30 Insulating film forming unit 32 Flattening unit 40 Interlayer insulating film 42 Recess 50 Wiring 52 Wiring protective film 54 Insulating film 56 Interlayer insulating film 70 Pre-cleaning unit (plating pretreatment unit)
72 Catalyst application unit (Plating pretreatment unit)
74 Electroless Plating Unit 76 Drying Unit (Heat Treatment Drying Unit)

Claims (10)

Prepare a substrate that selectively covers the surface of the embedded wiring formed inside the interlayer insulating film with a wiring protective film,
Pre-clean the surface of the substrate with a wet process using a cleaning solution,
A wiring formation method, comprising: forming an insulating film on a surface of a substrate after pre-cleaning.   The wiring formation method according to claim 1, wherein the wiring is made of copper or a copper alloy, and the wiring protective film is made of a cobalt alloy or a nickel alloy. The wiring formation according to claim 1, wherein the insulating film is made of any material of SiC, SiCN, SiN, SiO ₂ , SiOCH, low dielectric constant siloxane, or low dielectric constant organic polymer. Method.   The wiring forming method according to claim 1, wherein the substrate is dried immediately after the pre-cleaning by the wet treatment. A pre-cleaning unit that pre-cleans the surface of the substrate that selectively covers the surface of the embedded wiring formed in the interlayer insulating film with a wiring protective film by a wet treatment using a cleaning liquid;
A wiring forming apparatus comprising an insulating film forming unit for forming an insulating film on a surface of a substrate after pre-cleaning.   6. The wiring forming apparatus according to claim 5, further comprising a drying unit that dries the substrate immediately after pre-cleaning by the pre-cleaning unit.   The wiring forming apparatus according to claim 6, wherein the drying unit includes at least one of a spin dry unit that spin-drys the substrate by rotating the substrate at a high speed and a heat treatment drying unit that dries the substrate by heat treatment.   The wiring forming apparatus according to claim 5, further comprising a planarizing unit that planarizes a surface of the insulating film.   9. The wiring forming apparatus according to claim 5, further comprising an electroless plating unit that selectively forms a wiring protective film on a surface of the embedded wiring formed inside the interlayer insulating film. 10. The wiring forming apparatus according to claim 9, further comprising a plating pretreatment unit for performing a plating pretreatment on the surface of the embedded wiring formed inside the interlayer insulating film.

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