JP2011114073A - Cmp polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CMP (Chemical Mechanical Polishing) polishing method, using a CMP polishing liquid for palladium polishing, which can improve a polishing rate of at least a palladium layer as compared with use of a conventional CMP polishing liquid. <P>SOLUTION: The CMP polishing method includes a polishing step in which a polishing pad is arranged opposite a palladium-layer side of a substrate having the palladium layer and while the CMP polishing liquid is supplied to between the palladium layer and polishing pad, the substrate is pressed against the polishing pad from the side opposite from the palladium layer to polish at least a part of the palladium layer with the polishing pad, and is characterized in that the CMP polishing liquid includes 1,2,4-triazole, phosphoric acids, an oxidant, and abrasive grins, and the polishing step includes a dressing step of dressing the polishing pad for ≥10% of a time T from the start to the end of polishing by the polishing pad in a period of the time T. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a CMP polishing method, and more particularly to a CMP polishing method for palladium polishing.

  In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (LSIs). The chemical mechanical polishing (CMP) method is one of them, and it is a technique frequently used in planarization of an interlayer insulating film layer, metal plug formation, and embedded wiring formation in an LSI manufacturing process, particularly in a multilayer wiring forming process. (For example, refer to Patent Document 1).

  The metal polishing liquid used in CMP generally has an oxidizer and solid abrasive grains, and a metal oxide solubilizer and a protective film forming agent (metal corrosion inhibitor) are further added as necessary. Polishing is considered to have a basic mechanism of first oxidizing the surface of the metal layer with an oxidizing agent and scraping the oxidized layer with solid abrasive grains.

  The oxide layer on the surface of the metal layer deposited on the groove (concave portion) does not touch the polishing pad so much and does not have the effect of scraping off with the solid abrasive grains, but the oxidation of the surface of the metal layer deposited on the convex portion that touches the polishing pad. In the layer, scraping proceeds. Therefore, as the CMP progresses, the metal layer on the convex portion is removed and the substrate surface is flattened (for example, see Non-Patent Document 1).

  On the other hand, with higher integration of semiconductor elements, there are demands for higher pin count, narrower pitch, and thinner mounting. Furthermore, wiring delay and noise prevention between the semiconductor element and the wiring board are also important issues. For this reason, a flip chip mounting method has been widely adopted as a connection method between a semiconductor element and a wiring board instead of a conventional mounting method mainly using wire bonding.

  In this flip chip mounting method, there is a wide solder bump connection method in which a protruding electrode is formed on an electrode terminal of a semiconductor element and bonded together to a connection terminal formed on the wiring board via the protruding electrode. in use.

Also, in the mounting method using wire bonding, there is a movement to adopt a copper wire instead of the gold wire used so far for the purpose of cost reduction. In this case, palladium or a palladium alloy is expected to be used for the bonding pad in order to improve reliability.

  As a CMP polishing liquid, a polishing liquid to which a protective film forming agent and an organic acid are added is known as a target for polishing a layer made of titanium nitride or tantalum nitride formed on a substrate (see Patent Document 2). ).

  Further, as an attempt to apply CMP to a layer made of copper, for example, a method using a polishing liquid to which 2-quinolinecarboxylic acid is added is known (see Patent Document 3). As an attempt to apply CMP to the nickel layer, for example, a method using a polishing liquid to which abrasive grains, an organic acid, and an oxidizing agent are added is known as a polishing liquid for an HDD magnetic head (see Patent Document 4).

  By the way, palladium is generally classified as “noble metal” together with platinum, ruthenium and the like. Attempts to apply CMP to such a noble metal layer include, for example, a polishing liquid to which a sulfur compound is added, a polishing liquid to which any of dikenton, a nitrogen-containing heterocyclic compound, or a zwitterionic compound is added, or a platinum group metal. A method using a polishing liquid to which an oxide is added is known (see Patent Documents 5, 6, and 7).

U.S. Pat. No. 4,944,836 Japanese Patent No. 3780767 Japanese Patent No. 3192968 JP 2006-297501 A International Publication No. 01/44396 Pamphlet US Pat. No. 6,527,622 Japanese Patent Laid-Open No. 11-121411

Journal of Electrochemical Society, Vol.138, No.11 (1991), 3460-3464

  However, until now, sufficient studies have not been made on polishing palladium by CMP. According to the knowledge of the present inventors, it has been found that the polishing liquids of Patent Documents 2, 3, and 4 are very difficult to polish palladium that is not easily oxidized and has high hardness. Further, in the polishing liquids of Patent Documents 5, 6, and 7, platinum and ruthenium can be polished. However, it has been found that the progress of polishing is very difficult even when palladium is polished with the same polishing liquid.

  Therefore, the present invention improves the polishing rate of the palladium layer as compared with the case of using a conventional polishing liquid, and can polish at a stable polishing rate even when polishing continuously for a long time or a plurality of sheets. An object of the present invention is to provide a CMP polishing method for a palladium layer.

In the present invention, a polishing pad is disposed opposite to a palladium layer side of a substrate having a palladium layer, and a CMP polishing liquid is supplied between the palladium layer and the polishing pad while the substrate is placed on the polishing pad from the side opposite to the palladium layer. And a polishing step of polishing at least a part of the palladium layer with a polishing pad for a time T. The CMP polishing liquid contains a) 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains. The above polishing process comprises a dressing process in which the polishing pad is sharpened for a time of 10% or more of T during the time T from the start of polishing by the polishing pad to the end of polishing. A CMP polishing method is provided.
Further, the CMP polishing liquid may be a CMP polishing liquid for palladium polishing which contains b) an organic solvent, 1,2,4-triazole, phosphoric acids, an oxidizing agent and abrasive grains.

According to such a CMP polishing method for palladium polishing, the palladium layer can be improved as compared with the case of using a conventional CMP polishing liquid, and can be polished at a desired polishing rate. a) CMP polishing liquid for polishing palladium containing 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains, or b) organic solvent, 1,2,4-triazole, phosphoric acid, oxidizing agent In addition, the use of a CMP polishing liquid for polishing a palladium containing abrasive grains facilitates the progress of palladium polishing, but as the polishing progresses, a palladium-containing compound adheres to the polishing pad, impairing the polishing of palladium. The Furthermore, this deposit cannot be removed by washing with acid, alkali or the like. As a result, there is a problem that the polishing rate of palladium is reduced and stable polishing cannot be performed.
On the other hand, according to the CMP polishing method for palladium polishing having the above-described configuration, when a palladium layer is polished continuously or / and continuously for a long time, a compound generated in the polishing is removed from above the polishing pad by the dressing of the polishing pad. By removing, polishing can be performed at a more stable polishing rate than when a conventional CMP polishing liquid is used.

  Such characteristics are remarkably superior even when CMP polishing liquids specifically disclosed in International Publication No. 2003/038883, International Publication No. 2000/039844, etc. are used. is there.

  The oxidizing agent is preferably at least one selected from hydrogen peroxide, periodic acid, periodate, iodate, bromate and persulfate, and the abrasive grains include alumina, silica, zirconia, titania and At least one selected from ceria is good.

  The concentration of the abrasive grains is preferably 0.1 to 10% by mass based on the total amount of the CMP polishing liquid for palladium polishing. By setting the concentration of the abrasive grains in the CMP polishing liquid for palladium polishing in this range, it is possible to keep the scraping action and at the same time suppress the aggregation and sedimentation of the particles.

  According to the CMP polishing method for palladium polishing of the present invention, the polishing rate of the palladium layer can be improved as compared with the case of using a conventional CMP polishing liquid, and polishing can be performed at a desired polishing rate. Also, according to the CMP polishing method for palladium polishing of the present invention, when the palladium layer is polished continuously for a long time or a plurality of continuously, polishing is performed at a more stable polishing rate than when the conventional CMP polishing method is used. be able to.

It is sectional drawing which shows 1st Embodiment of the manufacturing method of the board | substrate which has a protruding electrode. It is sectional drawing which shows 2nd Embodiment of the manufacturing method of the board | substrate which has a protruding electrode. It is sectional drawing which shows 3rd Embodiment of the manufacturing method of the board | substrate which has a protruding electrode. It is sectional drawing which shows the specific example of 3rd Embodiment. It is a perspective view which shows the use condition of the conventional pad dresser.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  In the CMP polishing method of the present invention, a polishing pad is disposed opposite to a palladium layer side of a substrate having a palladium layer, and a CMP polishing liquid is supplied between the palladium layer and the polishing pad, while the substrate is opposite to the palladium layer. And a polishing step in which at least a part of the palladium layer is polished for a time T with the polishing pad, and the CMP polishing liquid includes: a) 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive A CMP polishing liquid for palladium polishing containing grains. In the polishing step, the polishing pad is sharpened for a time of 10% or more of T during a time T from the start of polishing by the polishing pad to the end of polishing. Includes dressing process.

  A known pad dresser can be used for the sharpening. The pad dresser is preferably one that can scrape or roughen the surface of the polishing pad. In general, a dresser to which a grindstone is attached is often used, and the grindstone portion is an electrodeposition layer using diamond abrasive grains or a bond layer (metal bond, vitrified bond or resin bond) in which diamond abrasive grains are dispersed. Composed. Appropriate values can be adopted for the grain size, the degree of concentration, the width of the grindstone portion, etc. of the diamond abrasive grains according to the material of the polishing pad. In some cases, abrasive grains other than diamond may be used.

As a means for moving the pad dresser on the polishing pad, for example, a configuration similar to the conventional one as shown in FIG. 5 can be used. In the configuration of FIG. 5, the polishing platen 21 is fixed to the shaft 22 and can be rotated in the direction indicated by A by a driving device (not shown). A polishing pad 23 is attached on the polishing surface plate 21. The pad dresser 26 is coupled to the rotation fulcrum 25 by the swing arm 24, and is driven in the direction indicated by the arrow B by a driving device (not shown) for supplying power to the rotation fulcrum. It can be swung between the outer periphery. Thus, dressing of the polishing pad is performed.
It is preferable that the swinging speed of the swinging arm is set so that an appropriate value is selected between the inner peripheral portion and the outer peripheral portion of the polishing pad so that the finished state of the polishing pad surface is in an optimum state. Further, the pad dresser does not need to rotate, but it is preferable in terms of sharpening the polishing pad surface to provide a driving means so that the pad dresser can rotate.

  The dressing of the polishing pad is performed while the substrate is being polished. As a result, the substrate can be polished for a long time and / or a plurality of sheets continuously because removal of substances adhering to the polishing pad (for example, palladium complex) during polishing and polishing of the polishing pad can be performed simultaneously. It is possible to suppress a decrease in the polishing rate even when polishing the substrate.

  The dressing time of the polishing pad is preferably 10% or more of the polishing time T, and preferably 20% or more in that the palladium-containing compound on the polishing pad can be efficiently removed, where T is the polishing time. More preferably, it is particularly preferably 30% or more. The dressing of the polishing pad does not need to be performed once in succession, and may be performed twice or three or more times during polishing.

The dressing pressure of the polishing pad is preferably 1 kPa or more, more preferably 2 kPa or more, and particularly preferably 3 kPa or more in that the palladium-containing compound on the polishing pad can be efficiently removed. Further, the upper limit of the sharpening pressure is preferably 150 kPa or less, more preferably 120 kPa or less, and particularly preferably 100 kPa or less from the viewpoint that excessive polishing of the polishing pad can be prevented. . By using the above polishing method, the poorly water-soluble palladium-containing compound is more efficiently removed from the polishing pad, and the polishing rate of the palladium layer is improved as compared with the conventional CMP polishing method. Polishing at a polishing rate is possible. According to the CMP polishing method for palladium polishing of the present invention, when the palladium layer is polished continuously for a long time or a plurality of sheets, polishing can be performed at a more stable polishing rate than when the conventional CMP polishing method is used. it can.

  In applying this polishing method, the surface to be polished of the substrate is pressed against the polishing pad of the polishing surface plate and a CMP polishing liquid is supplied between the surface to be polished and the polishing pad, The surface to be polished is preferably polished by moving the substrate relative to the polishing surface plate with a predetermined pressure applied to the opposite surface).

  As the polishing apparatus, for example, a general polishing apparatus having a motor capable of changing the number of rotations and having a surface plate to which a polishing pad can be attached and a holder for holding the substrate can be used. Although there is no restriction | limiting in particular as a polishing pad, A general nonwoven fabric, a foaming polyurethane, a porous fluororesin, etc. can be used. The polishing conditions are not particularly limited, but the rotation speed of the surface plate is preferably set to a low rotation of 200 rpm or less so that the substrate does not jump out.

  The pressure applied to the substrate pressed against the polishing pad (polishing pressure) is preferably 4 to 100 kPa, and more preferably 6 to 60 kPa from the viewpoint of uniformity within the substrate surface and pattern flatness. By using the CMP polishing liquid, the palladium layer can be polished at a high polishing rate at a low polishing pressure. The fact that polishing is possible with a low polishing pressure is important from the viewpoint of preventing peeling of the polishing layer, chipping, fragmentation, cracking, etc., and the flatness of the pattern.

  During polishing, a CMP polishing liquid is continuously supplied to the polishing pad by a pump or the like. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with a CMP polishing liquid. The substrate after polishing is preferably washed in running water, and then dried after removing water droplets adhering to the substrate using a spin dryer or the like.

  The palladium layer to be polished may be a layer containing palladium, and the palladium content in the palladium layer is usually 40 to 100% by mass, preferably 60 to 100% by mass with respect to the total mass of the palladium layer. is there.

  The substrate that exhibits the most effective CMP polishing liquid is a substrate having a palladium layer. Preferably, on a semiconductor wafer such as silicon, at least an insulating film layer, a nickel layer (referred to as a nickel-containing layer), palladium A layer is a substrate formed in this order. A base metal layer may be formed between the insulating film layer and the nickel layer.

  Examples of the material for forming the palladium layer include palladium, a palladium alloy, and other palladium compounds.

  Examples of the material for forming the nickel layer include nickel, a nickel alloy, and other nickel compounds.

  The base metal layer is a layer that prevents the conductive material from diffusing into the interlayer insulating film. Materials for forming the base metal layer include tantalum, tantalum alloy, tantalum nitride, other tantalum compounds, titanium, titanium alloy, titanium nitride, other titanium compounds, tungsten, tungsten nitride, tungsten alloy, or other tungsten compounds. Can be mentioned.

Examples of the insulating film layer include a SiO ₂ film, a SiN film, and a SiON film.

  Hereinafter, a polishing method using a CMP polishing liquid will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a first embodiment of a method for manufacturing a substrate having protruding electrodes, and the polishing method is applied to a part of the steps of the manufacturing method.

  The substrate shown in FIG. 1A includes a silicon wafer 1, an insulating film 2 having unevenness formed on the silicon wafer 1, and an under barrier metal layer 3 covering the uneven surface of the insulating film 2. . The under barrier metal layer 3 corresponds to a palladium layer. The under barrier metal layer 3 of such a substrate is polished using a CMP polishing liquid. Namely, a) CMP polishing liquid for palladium polishing comprising a) 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains between the under barrier metal layer 3 and the polishing pad, or b) an organic solvent. While supplying a CMP polishing liquid for palladium polishing containing 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains, the substrate is polished with a polishing pad to expose the convex portion of the insulating film 2 Let

  By such polishing, the under barrier metal layer 3 formed on the convex portion of the insulating film 2 is removed. FIG.1 (b) is sectional drawing which shows the board | substrate obtained by such grinding | polishing.

  Next, a resist pattern 4 is formed on the convex portion of the insulating film 2 from which the under barrier metal layer 3 has been removed so that the under barrier metal layer 3 formed on the concave portion of the insulating film 2 is exposed. FIG. 1C is a cross-sectional view showing the substrate on which the resist pattern 4 is formed.

  Next, the protruding electrode 5 is formed in the concave portion of the substrate on which the resist pattern 4 is formed by a method such as electroplating, and is protruded from the surface of the insulating film 2. FIG. 1D is a cross-sectional view showing the substrate on which the protruding electrodes 5 are formed. Finally, by removing the resist pattern 4, it is possible to obtain a substrate on which the protruding electrodes 5 are formed on the silicon wafer 1. FIG. 1E is a cross-sectional view showing the substrate having the protruding electrodes obtained as described above. The protruding electrode 5 is generally made of a material such as gold, silver, copper, nickel or solder.

  FIG. 2 is a cross-sectional view showing a second embodiment of a method for manufacturing a substrate having protruding electrodes, and the above polishing method is also applied to a part of the steps of the manufacturing method. However, FIG. 2 shows only the substrate before applying the polishing method (FIG. 2 (a)) and the substrate having the finally obtained protruding electrode (FIG. 2 (b)). The steps of resist pattern formation, bump electrode formation, and resist pattern removal are performed in the same manner as in the first embodiment.

  The substrate shown in FIG. 2A includes a silicon wafer 1, an insulating film 2 having unevenness formed on the silicon wafer 1, a base metal film 6 covering the uneven surface of the insulating film 2, and a base metal film 6. An under barrier metal layer 3 formed thereon. The under barrier metal layer 3 corresponds to a palladium layer. The base metal film 6 is formed for the purpose of suppressing the diffusion of the components of the under barrier metal layer 3 into the silicon wafer 1 and improving the adhesion between the silicon wafer 1 and the under barrier metal layer 3.

  The under barrier metal layer 3 and the base metal film 6 of such a substrate are polished using a CMP polishing liquid. Namely, a) CMP polishing liquid for palladium polishing comprising a) 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains between the under barrier metal layer 3 and the polishing pad, or b) an organic solvent. While supplying a CMP polishing liquid for palladium polishing containing 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains, the substrate is polished with a polishing pad to expose the convex portion of the insulating film 2 Let By such polishing, the under barrier metal layer 3 and the base metal film 6 formed on the convex portion of the insulating film 2 are removed. Then, by performing resist pattern formation, bump electrode formation, and resist pattern removal on the substrate thus obtained in the same manner as in the first embodiment, the silicon wafer 1 shown in FIG. A substrate on which the protruding electrode 5 is formed can be obtained.

  FIG. 3 is a cross-sectional view showing a third embodiment of a method for manufacturing a substrate having protruding electrodes, and the above polishing method is also applied to a part of the steps of the manufacturing method. However, FIG. 3 shows only the substrate before application of the polishing method (FIG. 3A) and the substrate having the bump electrode finally obtained (FIG. 3B). The steps of resist pattern formation, bump electrode formation, and resist pattern removal are performed in the same manner as in the first embodiment.

  The substrate shown in FIG. 3A includes a silicon wafer 1, an insulating film 2 having unevenness formed on the silicon wafer 1, a base metal film 6 covering the uneven surface of the insulating film 2, and a base metal film 6. A first under-barrier metal layer 3b formed above and a second under-barrier metal layer 3a formed on the first under-barrier metal layer 3b are provided. The first under barrier metal layer 3b or the second under barrier metal layer 3a corresponds to a palladium layer.

  The first under barrier metal layer 3b, the second under barrier metal layer 3a, and the base metal film 6 of such a substrate are polished using a CMP polishing liquid. That is, between the second under-barrier metal layer 3a and the polishing pad, a) a palladium-polishing CMP polishing solution containing 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains, or b ) While supplying a CMP polishing liquid for palladium polishing containing an organic solvent, 1,2,4-triazole, phosphoric acid, oxidizer and abrasive grains, the substrate is polished with a polishing pad, and the protrusion of the insulating film 2 Expose the part. By such polishing, the first under barrier metal layer 3b, the second under barrier metal layer 3a, and the base metal film 6 formed on the convex portion of the insulating film 2 are removed. The substrate thus obtained is subjected to resist pattern formation, bump electrode formation, and resist pattern removal in the same manner as in the first embodiment, so that the silicon wafer 1 shown in FIG. A substrate on which the protruding electrode 5 is formed can be obtained.

  FIG. 4 shows an example in which the first under barrier metal layer in FIG. 3 is a nickel layer and the second under barrier metal layer is a palladium layer (a structure having two under barrier metals).

  The substrate shown in FIG. 4A is obtained by forming a base metal layer 15, a nickel layer 14 and a palladium layer 13 in this order on an uneven portion of an insulating film 12 provided on a silicon substrate 11. By using a CMP polishing liquid, the palladium layer 13, the nickel layer 14, and the base metal layer 15 can be polished to expose the protrusions of the insulating film 12 as shown in FIG. 4B.

  As another example of the polishing method using the CMP polishing liquid, there are a first polishing step in which the palladium layer 13 existing on the convex portion of the insulating film 12 is polished to expose the nickel layer 14, and the convexity of the insulating film layer 12. A second polishing step of polishing a part of the palladium layer 13 filling the concave portion of the insulating layer 12 by polishing the nickel layer 14 existing on the portion, the base metal layer 15, and the concave portion of the insulating film 12; Among these two polishing steps, a method using a CMP polishing liquid in at least the first polishing step is mentioned.

(1,2,4-triazole)
The CMP polishing liquid used in the polishing method according to the present invention contains 1,2,4-triazole as a complexing agent. A complexing agent is a substance that can coordinate with a metal to form a complex, but 1,2,4-triazole is also considered to form a complex with palladium together with phosphoric acids described below. It is presumed that a good polishing rate can be obtained because the complex formed in is easily polished. Further, it is considered that a nitrogen-containing compound can form a complex with palladium. However, according to studies by the present inventors, a compound other than 1,2,4-triazole can improve the polishing rate for the palladium layer. I can't. For example, even if 1,2,3-triazole having a similar structure or 3-amino-1,2,4-triazole is used instead of 1,2,4-triazole, a good polishing rate for the palladium layer is achieved. Hard to get.

  The content of 1,2,4-triazole is preferably 0.001 to 20% by mass with respect to the total mass of the CMP polishing liquid. When this content is less than 0.001% by mass, the polishing rate of the palladium layer by CMP tends to be low, and the lower limit is more preferably 0.01% by mass, and 0.05% by mass It is particularly preferred that Further, if it exceeds 20% by mass, the polishing rate of the palladium layer tends to be saturated, and the upper limit is more preferably 15% by mass, further preferably 12% by mass, and 10% by mass. It is particularly preferred.

(Phosphoric acids)
The CMP polishing liquid used for the polishing method according to the present invention contains phosphoric acids. Phosphoric acids are thought to promote the polishing of the metal film by complexing and / or dissolving the metal oxidized by the oxidizing agent described later, and are presumed to have a function as a metal oxide dissolving agent for palladium. .

  As the compound having a function as a metal oxide solubilizer for palladium, various inorganic acids, organic acids, and the like can be considered, but according to the study by the present inventors, good polishing against palladium is possible with acids other than phosphoric acids. Getting speed is difficult.

  Phosphoric acids mean phosphoric acid, phosphorous acid and hypophosphorous acid, condensates thereof, and derivatives thereof (including salts) (for example, phosphoric acid, phosphoric acid derivatives, pyrophosphoric acid, pyrophosphoric acid derivatives) , Polyphosphoric acid, polyphosphoric acid derivatives, and salts thereof). Specific examples of phosphoric acids include phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, pyrophosphorous acid, polyphosphoric acid and the like. Examples of phosphoric acid salts are salts of phosphoric acid anions and cations. Examples of cations are lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium. There are ions such as barium, titanium, zirconium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, silver, palladium, zinc, aluminum, gallium, tin, and ammonium. These salts are either a first salt having one metal and two hydrogens in the molecule, a second salt having two metals and one hydrogen, or a third salt having three metals. Any of acid salts, alkaline salts and neutral salts may be used. These phosphoric acids may be used alone or in combination of two or more.

  The phosphoric acid content is preferably 0.001 to 20% by mass with respect to the total mass of the CMP polishing liquid. When the content is less than 0.001% by mass, the polishing rate of the palladium layer, the nickel layer, and the underlying gold layer by CMP tends to be small, and the lower limit is more preferably 0.01% by mass. Preferably, it is 0.02% by mass. Moreover, when it exceeds 20 mass%, the grinding | polishing rate of a palladium layer tends to be saturated, As an upper limit, it is more preferable that it is 15 mass%, and it is especially preferable that it is 10 mass%.

(Oxidant)
The oxidizing agent contained in the CMP polishing liquid used in the polishing method according to the present invention is a metal oxidizing agent used for the substrate for layer formation or the like. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), periodic acid, periodate, iodate, bromate, persulfate, etc. Among them, hydrogen peroxide is particularly preferable. These can be used individually by 1 type or in mixture of 2 or more types.

  In the case where the substrate is a silicon substrate including an integrated circuit element, contamination by alkali metal, alkaline earth metal, halide, or the like is not desirable, and thus an oxidizing agent that does not include a nonvolatile component is desirable. However, when the substrate to be applied is a glass substrate or the like that does not include a semiconductor element, an oxidant that includes a nonvolatile component may be used.

  The content of the oxidizing agent is preferably 0.05 to 20% by mass, more preferably 0.1 to 15% by mass, and 0.1 to 10% by mass with respect to the total mass of the CMP polishing liquid. It is particularly preferred that If this content is less than 0.05% by mass, metal oxidation is insufficient, and the polishing rate of the palladium layer, nickel layer, and underlying metal layer tends to be low, and if it exceeds 20% by mass, the polished surface is roughened. Tend to occur.

(Abrasive grains)
Specific examples of the abrasive grains include fumed alumina, transition alumina, fumed silica, colloidal silica, zirconia, titania, ceria, etc., among which fumed alumina, transition alumina, fumed silica, colloidal silica. Colloidal silica is more preferable because it can suppress the generation of polishing flaws while maintaining a high polishing rate.

  The content of the abrasive grains is preferably 0.1% by mass to 10% by mass and more preferably 0.2% by mass to 8.0% by mass with respect to the total mass of the CMP polishing liquid. If this content is 0.1% by mass or more, a physical scraping action can be obtained, and the polishing rate by CMP tends to increase. Moreover, if it is 10 mass% or less, it exists in the tendency which can suppress that a particle | grain coagulates and settles. Moreover, even if it contains an amount exceeding 10% by mass, there is a tendency that an increase in the polishing rate commensurate with the content is not observed. Such a tendency tends to be noticeable depending on the polishing rate of the palladium layer.

  The average primary particle diameter of the abrasive grains is preferably 300 nm or less, more preferably 200 nm or less, in terms of improving flatness and suppressing the generation of scratches remaining on the polished surface after polishing. It is particularly preferably 150 nm or less, and very preferably 100 nm or less. Further, the lower limit of the average primary particle diameter is not particularly limited, but is preferably 1 nm, more preferably 3 nm, and particularly preferably 5 nm in that sufficient physical scraping action can be obtained. Very preferably.

  The average secondary particle diameter of the abrasive grains is preferably 5 to 500 nm. In terms of improving flatness, the upper limit of the average secondary particle diameter is preferably 300 nm, more preferably 200 nm, and particularly preferably 100 nm. Further, the average secondary particle diameter is more preferably 5 nm, more preferably 10 nm in that the ability to remove the mechanical reaction layer (oxide layer) by the abrasive grains can be ensured and the polishing rate is increased. It is particularly preferred.

  The average primary particle diameter of the abrasive grains in the CMP polishing liquid can be measured using a transmission electron microscope (for example, S4700 manufactured by Hitachi, Ltd.).

  As a specific measuring method, for example, a composite solution containing the above two kinds of abrasive grains and other components are mixed to prepare a test solution, and an appropriate amount of this test solution is collected. The amount to be collected is determined in consideration of the abrasive content. For example, when the abrasive content is 1% by mass, about 0.2 cc is collected. The collected test solution is dried and observed.

The average secondary particle diameter of the abrasive grains refers to the average secondary particle diameter of the abrasive grains in the CMP polishing liquid. For example, a light diffraction / scattering particle size distribution meter (for example, COULTER N4SD manufactured by COULTER Electronics). Can be measured.
(Organic solvent)
The CMP polishing liquid can further contain an organic solvent.

As an organic solvent, what can be mixed with water arbitrarily is preferable.
For example, carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as butyrolactone and propyrolactone; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, and the like As glycol derivatives, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol Ethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monoethyl ether, tripropylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol monopropyl ether, diethylene glycol monopropyl ether, dipropylene glycol mono Propyl ether, triethylene glycol monopropyl ether, tripropylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, triethylene glycol monobutyl ether, tripropylene glycol Glycol monoethers such as butyl monobutyl ether; ethylene glycol dimethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, diethylene glycol diethyl ether, dipropylene Glycol diethyl ether, triethylene glycol diethyl ether, tripropylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol dipropyl ether, diethylene glycol dipropyl ether, dipropylene glycol dipropyl Glycols such as ether, triethylene glycol dipropyl ether, tripropylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dibutyl ether, diethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, triethylene glycol dibutyl ether, tripropylene glycol dibutyl ether Diether: ether such as tetrahydrofuran, dioxane, dimethoxyethane, polyethylene oxide, ethylene glycol monomethyl acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate; methanol, ethanol, propanol, n-butanol, n-pentanol, n- Hexano Alcohols such as isopropanol; acetone, ketones such as methyl ethyl ketone, ethyl acetate, carboxylic acid esters such as ethyl lactate; other phenols, dimethylformamide, n- methylpyrrolidone, and sulfolane. Among these, preferred organic solvents are glycols, glycol derivatives, alcohols, carbonic acid esters, and carboxylic acid esters, and more preferred organic solvents are glycols and carboxylic acid esters.

  The content of the organic solvent is preferably 0.1 to 95% by mass with respect to the total mass of the CMP polishing liquid. When the content is less than 0.1% by mass, the polishing rate for the palladium layer when the palladium layer is continuously polished tends to gradually decrease, and the lower limit is 0.2% by mass. Is more preferable, and it is especially preferable that it is 0.5 mass%. On the other hand, if it exceeds 95% by mass, the solubility of the CMP polishing liquid component tends to deteriorate or the agglomeration of the abrasive grains tends to be promoted, and the upper limit is more preferably 50% by mass. It is particularly preferable that the content is% by mass.

(Metal anticorrosive)
The CMP polishing liquid may further contain a metal anticorrosive. The metal anticorrosive is a compound that suppresses etching of the metal layer and improves the dishing property.

  Specific examples of the metal anticorrosive include imines, azoles other than 1,2,4-triazole, mercaptans, saccharides, and the like. Among them, the metal layer etching rate is suppressed and the metal layer is polished. A nitrogen-containing cyclic compound is preferable from the viewpoint of achieving both speeds. These can be used alone or in combination of two or more.

  Specifically, imines are dithizone, loin (2,2′-biquinoline), neocuproin (2,9-dimethyl-1,10-phenanthroline), bathocuproine (2,9-dimethyl-4,7-diphenyl-1). , 10-phenanthroline) and cuperazone (biscyclohexanone oxalyl hydrazone).

  Specifically, the azole is benzimidazol-2-thiol, triazinedithiol, triazinetrithiol, 2- [2- (benzothiazolyl)] thiopropionic acid, 2- [2- (benzothiazolyl)] thiobutyric acid, 2 -Mercaptobenzothiazole, 1,2,3-triazole, 2-amino-1H-1,2,4-triazole, 3-amino-1H-1,2,4-triazole, 3,5-diamino-1H-1 , 2,4-triazole, benzotriazole, 1-hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole, 4- Carboxyl-1H-benzotriazole methyl Ester, 4-carboxyl-1H-benzotriazole butyl ester, 4-carboxyl-1H-benzotriazole octyl ester, 5-hexylbenzotriazole, [1,2,3-benzotriazolyl-1-methyl] [1,2, , 4-Triazolyl-1-methyl] [2-ethylhexyl] amine, tolyltriazole, naphthotriazole, bis [(1-benzotriazolyl) methyl] phosphonic acid, tetrazole, 5-amino-tetrazole, 5-methyl-tetrazole 1-methyl-5-mercaptotetrazole and 1-N, N-dimethylaminoethyl-5-tetrazole.

  Specific examples of mercaptans include nonyl mercaptan and dodecyl mercaptan.

  Specific examples of the saccharide include glucose and cellulose. As the saccharide, a polysaccharide is preferably used.

  When the metal anticorrosive agent is contained, the content thereof is preferably in a range that does not impair the polishing rate improvement effect by 1,2,4-triazole and phosphoric acids, and achieves both an etching suppression function and a polishing rate. In this respect, the content is preferably 0.005 to 2.0 mass% with respect to the total mass of the CMP polishing liquid. In view of obtaining higher etching performance, it is more preferably 0.01% by mass or more, and further preferably 0.02% by mass or more. Moreover, it is more preferable to set it as 1.0 mass% or less at the point which becomes easy to obtain a suitable grinding | polishing rate, and it is especially preferable to set it as 0.5 mass% or less.

(Water-soluble polymer)
The CMP polishing liquid can contain a water-soluble polymer in that the flatness after polishing can be improved. In view of the above, the weight average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 1500 or more, and particularly preferably 5000 or more. The upper limit of the weight average molecular weight is not particularly specified, but 5 million is preferable from the viewpoint of solubility. When the weight average molecular weight is less than 500, a high polishing rate tends not to be exhibited.

The weight average molecular weight can be measured using a standard polystyrene calibration curve by gel permeation chromatography (GPC), and more specifically can be measured under the following conditions.
Equipment used: Hitachi L-6000 (manufactured by Hitachi, Ltd.)
Column: Gel pack GL-R420 + gel pack GL-R430 + gel pack GL-R440 [manufactured by Hitachi Chemical Co., Ltd., 3 in total]
Eluent: Tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 1.75 ml / min.
Detector: L-3300RI [manufactured by Hitachi, Ltd.]

  The water-soluble polymer having a weight average molecular weight of 500 or more is not particularly limited as long as the solubility of the components of the CMP polishing liquid does not decrease and the abrasive grains do not aggregate. Specifically, polysaccharides, polycarboxylic acids A compound, a vinyl polymer, a glycol polymer, etc. can be mentioned, These can be used individually or in mixture of 2 or more types. The water-soluble polymer may be a homopolymer composed of a single monomer or a copolymer (copolymer) composed of two or more monomers.

  Specific examples of the polysaccharide used as the water-soluble polymer include alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan and pullulan. Specific examples of the polycarboxylic acid compound used as the water-soluble polymer include polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, and polyamide. Acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, polyamic acid, polyamic acid ammonium salt And polycarboxylic acids such as polyamic acid sodium salt and polyglyoxylic acid, polycarboxylic acid esters and polycarboxylic acid salts.

  Furthermore, specific examples of the vinyl polymer used as the water-soluble polymer include polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein. Polyethylene glycol or the like can also be used.

  When the above water-soluble polymer compound is used, if the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, contamination with alkali metal, alkaline earth metal, halide, etc. is not desirable. Is desirable. This is not the case when the substrate is a glass substrate or the like.

  Among the above water-soluble polymer compounds, pullulan, polymalic acid, polymethacrylic acid, polyacrylic acid, polyacrylamide, polyvinyl alcohol and polyvinyl pyrrolidone, esters thereof and ammonium salts thereof are capable of being highly flattened. preferable.

  In the case of containing a water-soluble polymer, the content of the water-soluble polymer is preferably 5% by mass or less, more preferably 2% by mass or less, based on the total mass of the CMP polishing liquid. If this content is 5% by mass or less, aggregation of abrasive grains can be suppressed.

(CMP polishing liquid)
The CMP polishing liquid can be obtained by mixing the above compounds. It is preferable to adjust the ratio of the compound constituting the CMP polishing liquid so as to obtain a suitable content of each compound described above. The ratio of the compound constituting the CMP polishing liquid for palladium polishing is in the above range, and during polishing with CMP using this polishing liquid, the polishing pad is dressed for 20% or more of the polishing time, The polishing rate of the palladium layer can be improved, and polishing can be performed at a stable polishing rate even when a plurality of sheets are continuously polished.

(PH)
The pH of the CMP polishing liquid is preferably 1 to 12 from the viewpoint of increasing the CMP polishing rate of the palladium layer. If pH is 1-6, there exists a tendency which can ensure the grinding | polishing speed by predetermined | prescribed CMP, and it can become a practical CMP polishing liquid. The pH is more preferably 1 to 5, and particularly preferably 1 to 4.

  Hereinafter, the present invention will be described by way of examples. In addition, this invention is not restrict | limited to these Examples.

(CMP polishing conditions)
The CMP polishing used in Examples 1 to 3 and Comparative Examples 1 to 7 was performed on an unpolished substrate using the following apparatus and conditions.
Polishing device: Mirra (Applied Materials)
CMP polishing liquid flow rate: 200 mL / minute Polishing substrate: Silicon substrate polishing pad formed by sputtering a palladium layer having a thickness of 0.3 μm: Foam polyurethane resin having closed cells (manufactured by Rohm and Haas Japan, Model number IC1000)
Polishing pressure: 29.4 kPa (4 psi)
Relative speed between substrate and polishing platen: 68 m / min Polishing time: 1-3 minutes Polishing pad dress condition: shown in Table 1 (during polishing: In-situ, before polishing: Ex-situ)
Polishing pad dressing time: Cleaning shown in Table 1: After CMP treatment, cleaning with ultrasonic water was performed, followed by drying with a spin dryer.

(CMP polishing liquid preparation method)
The CMP polishing liquid used in Examples 1 to 3 and Comparative Examples 1 to 7 is 10% by mass of colloidal silica (average secondary particle diameter 43 nm) as abrasive grains and 30% as an oxidizing agent with respect to the total mass of the CMP polishing liquid. It was prepared by containing 10% by mass of hydrogen peroxide, 0-5% by mass of the metal oxide solubilizer shown in Table 1, 0-0.5% by mass of the complexing agent shown in Table 1, and pure water in the balance. .

(Liquid property evaluation)
Measurement temperature: 25 ± 5 ° C
pH: Measured with model number F-51 manufactured by HORIBA.

(Abrasive product evaluation items)
Polishing rate: The polishing rate of the palladium layer polished and washed under the above conditions was determined from the following formula ((PdRR) = (thickness difference of the palladium layer before and after polishing) / (polishing time (minutes))). The film thickness difference before and after polishing was calculated from the electric resistance value.

  Table 1 shows the palladium polishing rate for polishing for 1 minute, 2 minutes and 3 minutes in Examples 1 to 3 and Comparative Examples 1 to 7 and the rate of decrease in the palladium polishing rate for 3-minute polishing relative to 1-minute polishing.

  Hereinafter, the results shown in Table 1 will be described in detail. In Example 1, the polishing pad was dressed for 33% of the initial time during polishing of the substrate. As the CMP polishing liquid, a metal oxide solubilizer containing 5% by mass of phosphoric acid and a complexing agent of 0.5% by mass of 1,2,4-triazole was used. In Example 1, the palladium polishing rates for 1 minute and 3 minutes are 65 nm / min and 58 nm / min, respectively, which are higher than those of Comparative Examples 1 to 7, and the rate of decrease in palladium polishing rate of polishing for 3 minutes relative to polishing for 1 minute. However, the value was 11%, which was lower than that of Comparative Example 1.

  In Example 2, the polishing pad was dressed for 66% of the initial polishing time while the substrate was being polished. As the CMP polishing liquid, a metal oxide solubilizer containing 5% by mass of phosphoric acid and a complexing agent of 0.5% by mass of 1,2,4-triazole was used. In Example 2, the palladium polishing rates for 1 minute and 3 minutes were 68 nm / min and 66 nm / min, respectively, which were higher than those of Comparative Examples 1 to 7, and the rate of decrease in palladium polishing rate of polishing for 3 minutes relative to polishing for 1 minute. However, the value was 3%, which was lower than that of Comparative Example 1.

  In Example 3, the polishing pad was always dressed during the polishing of the substrate. As the CMP polishing liquid, a metal oxide solubilizer containing 5% by mass of phosphoric acid and a complexing agent of 0.5% by mass of 1,2,4-triazole was used. In Example 3, the palladium polishing rates for 1 minute, 2 minutes, and 3 minutes were 70 nm / minute, 71 nm / minute, and 70 nm / minute, respectively, higher values than Comparative Examples 1 to 7, and 3 for 1 minute polishing. The rate of decrease in the palladium polishing rate for minute polishing was 0%, which was lower than that of Comparative Example 1.

  In Comparative Examples 5 and 7, the CMP polishing liquid contains phosphoric acid as a metal oxide dissolving agent, but the polishing rate is very low. However, it can be seen that the polishing rate is greatly improved by containing 1,2,4-triazole as a complexing agent in addition to phosphoric acid as in Comparative Example 2. However, the polishing rate reduction rate was very large. In Examples 6 to 10, in addition to the phosphoric acid and 1,2,4-triazole used in Comparative Example 2, by containing an organic solvent, the palladium polishing rate decreases while maintaining a high palladium polishing rate. The rate could be greatly reduced.

  In Comparative Examples 4 and 6, the CMP polishing liquid contains phosphoric acid as a metal oxide dissolving agent, but the polishing rate is very low. However, it can be seen that the polishing rate is improved by containing 1,2,4-triazole as a complexing agent in addition to phosphoric acid as in Comparative Example 1. In Examples 1 to 3, instead of the Ex-situ dress used in Comparative Example 1, a polishing method using an In-situ dress is used to maintain a high palladium polishing rate while maintaining a palladium polishing. The rate of speed reduction could be greatly reduced.

  DESCRIPTION OF SYMBOLS 1 ... Silicon wafer, 2, 12 ... Insulating film, 3 ... Under barrier metal layer, 3a ... 2nd under barrier metal layer, 3b ... 1st under barrier metal layer, 4 ... Resist pattern, 5 ... Projection electrode, 6 , 15 ... Underlying metal film, 11 ... Silicon substrate, 13 ... Palladium layer, 14 ... Nickel layer. DESCRIPTION OF SYMBOLS 21 ... Polishing surface plate, 22 ... Axis, 23 ... Polishing pad, 24 ... Swing arm, 25 ... Rotating fulcrum, 26 ... Pad dresser, A ... Rotation direction of polishing surface plate, B ... Vibration direction of pad dresser

Claims (6)

A polishing pad is disposed opposite to the palladium layer side of a substrate having a palladium layer, and a CMP polishing liquid is supplied between the palladium layer and the polishing pad, and the substrate is removed from the side opposite to the palladium layer. And a polishing step of polishing at least a part of the palladium layer with the polishing pad.
The CMP polishing liquid is a CMP polishing liquid containing 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains,
The polishing process includes a dressing process in which the polishing pad is sharpened for a time of 10% or more of T during a time T from the start of polishing by the polishing pad to the end of polishing. .   The CMP polishing method according to claim 1, wherein the oxidizing agent is at least one selected from hydrogen peroxide, periodic acid, periodate, iodate, bromate, and persulfate.   The CMP polishing method according to claim 1, wherein the abrasive grains are abrasive grains made of at least one selected from alumina, silica, zirconia, titania, and ceria.   The CMP polishing method according to any one of claims 1 to 3, wherein the content of the abrasive grains is 0.1 to 10% by mass based on the total mass of the CMP polishing liquid.   The CMP polishing method according to any one of claims 1 to 4, wherein the CMP polishing liquid further contains an organic solvent.   The CMP polishing method according to claim 5, wherein the organic solvent is at least one selected from glycol, glycol derivative, alcohol, carbonate ester, and carboxylate ester.

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