JP5585220B2 - CMP polishing liquid and polishing method using this CMP polishing liquid - Google Patents

Description

  The present invention relates to a CMP polishing liquid and a polishing method using the CMP polishing liquid.

  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 oxidizing agent and solid abrasive grains, and a metal oxide dissolving agent and a protective film forming agent (metal anticorrosive) are further added as necessary. Polishing is considered to have a basic mechanism of first oxidizing the surface of a metal layer with an oxidizing agent to form an oxide layer, and then scraping the oxide layer with solid abrasive grains.

  The oxide layer on the gold layer deposited on the groove (concave) does not touch the polishing cloth (polishing pad) so much that it does not have the effect of scraping with solid abrasive grains, but the metal deposited on the convex part that touches the polishing cloth. In the oxide layer on the surface of 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.

  And in this flip chip mounting method, a 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 substrate via the protruding electrode, Widely used.

  As a CMP polishing liquid, a polishing liquid to which a layer made of titanium nitride or tantalum nitride formed on a substrate is to be polished is known, and a protective film forming agent and an organic acid are added (for example, Patent Documents). 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 (for example, see Patent Document 3). Further, 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, for example, 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 a diketone, 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, for example, 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, no consideration has been given to polishing by CMP focusing on palladium among the noble metals. According to the knowledge of the present inventors, the polishing liquids of Patent Documents 2, 3, and 4 cannot easily oxidize palladium having high hardness. In addition, in the polishing liquids of Patent Documents 5, 6, and 7, platinum and ruthenium can be polished. However, it has been found that polishing does not proceed even when palladium is polished with the same polishing liquid.

  In the previous step of forming the protruding electrode, a base metal layer made of tantalum nitride or the like and a palladium layer are laminated on the surface of the substrate in this order so as to follow the unevenness of the substrate having unevenness on the surface. The And a palladium layer is grind | polished until the base metal layer located on the convex part of a board | substrate is exposed, and also a base metal layer and a palladium layer are grind | polished simultaneously until the convex part of a board | substrate is exposed. In this case, the polishing rate of both the palladium layer and the base metal layer must be sufficiently high.

  Furthermore, it is desired that the abrasive agglomeration and sedimentation does not occur more than before in the CMP polishing liquid.

  Accordingly, the present invention provides a CMP polishing liquid capable of improving the polishing rate of the palladium layer and suppressing the aggregation and settling of abrasive grains as compared with the case where a conventional polishing liquid is used while maintaining the polishing speed of the underlying metal layer. And a polishing method using the CMP polishing liquid.

  The present invention includes 1,2,4-triazole, phosphoric acids, an oxidizing agent, a first abrasive grain whose surface is anion-modified, and a second abrasive grain whose surface is not anion-modified. The average secondary particle diameter of the first abrasive grains and the second abrasive grains is 30 to 100 nm, and the degree of association between the first abrasive grains and the second abrasive grains is 1.7 to 2.3. The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 5.0 to 70.0 mass%, and the pH is 7 or less. A CMP polishing liquid is provided.

  The present invention also includes 1,2,4-triazole, phosphoric acids, oxidizing agents, an anion-modified surface, an average secondary particle size of 30 to 100 nm, and an association degree of 1.7 to 2. A first abrasive grain having a surface of which is not anion-modified and an average secondary particle diameter of 30 to 100 nm and an association degree of 1.7 to 2.3. The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 5.0 to 70.0 mass%, and the pH is 7 or less. A CMP polishing liquid is provided.

  In the CMP polishing liquid of the present invention, the polishing rate of the palladium layer can be improved and the agglomeration and settling of the abrasive grains can be suppressed while maintaining the polishing rate of the underlying metal layer as compared with the conventional polishing liquid.

  The first abrasive grains are preferably anion-modified with at least one selected from aluminate, sulfonic acid, carboxylic acid, nitric acid, phosphoric acid, carbonic acid and iodic acid. In this case, while maintaining the polishing rate of the base metal layer, the polishing rate of the palladium layer can be further improved as compared with the case where a conventional polishing liquid is used, and the aggregation and settling of abrasive grains can be further suppressed.

  The first abrasive grains preferably include at least one selected from alumina, silica, zirconia, titania and ceria. In this case, while maintaining the polishing rate of the base metal layer, the polishing rate of the palladium layer can be further improved as compared with the case where a conventional polishing liquid is used, and the aggregation and settling of abrasive grains can be further suppressed.

  The total content of the first abrasive grains and the second abrasive grains is preferably 0.1 to 10% by mass based on the total mass of the CMP polishing liquid. The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is preferably 20.0 to 60.0 mass%.

  The CMP polishing liquid of the present invention has a zeta potential of the first abrasive grains in a mixture containing 1,2,4-triazole, phosphoric acid, oxidizing agent, first abrasive grains, organic solvent, and water. -10 mV or less, and the zeta of the second abrasive grain in a mixture comprising 1,2,4-triazole, phosphoric acids, oxidizing agent, second abrasive grain, organic solvent, and water. It is preferable to apply a potential of -5 to 5 mV. In this case, while maintaining the polishing rate of the base metal layer, the polishing rate of the palladium layer can be further improved as compared with the case where a conventional polishing liquid is used, and the aggregation and settling of abrasive grains can be further suppressed.

  The oxidizing agent is preferably at least one selected from hydrogen peroxide, periodic acid, periodate, iodate, bromate, persulfate, and persulfate. In this case, while maintaining the polishing rate of the base metal layer, the polishing rate of the palladium layer can be further improved as compared with the case where a conventional polishing liquid is used, and the aggregation and settling of abrasive grains can be further suppressed.

  The CMP polishing liquid of the present invention preferably further contains an organic solvent.

  The CMP polishing liquid of the present invention is useful as a CMP polishing liquid for palladium polishing.

  The present invention also includes a polishing step of polishing a substrate with a polishing cloth while supplying a CMP polishing liquid between the substrate and the polishing cloth, and the substrate is a substrate having a palladium layer and a base metal layer. The polishing liquid is 1,2,4-triazole, phosphoric acid, an oxidizing agent, a first abrasive grain whose surface is anion-modified, and a second abrasive grain whose surface is not anion-modified. The average secondary particle diameter of the first abrasive grains and the second abrasive grains is 30 to 100 nm, and the degree of association between the first abrasive grains and the second abrasive grains is 1.7 to 2.3. The ratio of the content of the first abrasive grain to the total content of the first abrasive grain and the second abrasive grain is 5.0 to 70.0% by mass, and the pH of the CMP polishing liquid is 7 The following polishing method is provided.

  The present invention also includes 1,2,4-triazole, phosphoric acids, oxidizing agents, an anion-modified surface, an average secondary particle size of 30 to 100 nm, and an association degree of 1.7 to 2. A first abrasive grain having a surface of which is not anion-modified and an average secondary particle diameter of 30 to 100 nm and an association degree of 1.7 to 2.3. A polishing liquid preparation step of blending to obtain a CMP polishing liquid, and a polishing step of polishing the substrate with the polishing cloth while supplying the CMP polishing liquid between the substrate and the polishing cloth. A substrate having a base metal layer, the ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 5.0 to 70.0 mass%, and CMP A polishing method in which the pH of the polishing liquid is 7 or less is provided.

  In the polishing method of the present invention, the polishing rate of the palladium layer can be improved as compared with the case where a conventional polishing liquid is used while maintaining the polishing rate of the underlying metal layer, and aggregation and sedimentation of abrasive grains can be suppressed.

  According to the CMP polishing liquid and polishing method of the present invention, while maintaining the polishing speed of the underlying metal layer, the polishing speed of the palladium layer is improved as compared with the case of using the conventional polishing liquid, and the aggregation and settling of abrasive grains is suppressed. can do. Further, in the polishing method of the present invention, after the CMP polishing liquid is prepared, it is possible to suppress the occurrence of agglomeration and settling of abrasive grains after being held at 30 ° C. for 6 months.

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 the specific example of 2nd Embodiment of the manufacturing method of the board | substrate which has a protruding electrode.

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

  The CMP polishing liquid of this embodiment (hereinafter sometimes simply referred to as “CMP polishing liquid”) contains at least 1,2,4-triazole, phosphoric acids, an oxidizing agent, and abrasive grains. The CMP polishing liquid of this embodiment can be mainly used as a CMP polishing liquid for palladium polishing.

(Abrasive grains)
The CMP polishing liquid contains abrasive grains whose surface is anion-modified (first abrasive grains) and abrasive grains whose surface is not anion-modified (second abrasive grains).

  Unlike normal abrasive grains, anion-modified abrasive grains need to be anion-treated. Since the reaction layer formed on the surface of the palladium layer is cationic, by making the surface of the abrasive grains anionic by anion treatment, the contact frequency between the abrasive grains and the surface of the palladium layer is increased, and polishing of the palladium layer is performed. There is a tendency to increase speed. On the other hand, since the reaction layer formed on the surface of the base metal layer such as tantalum nitride is anionic, the use of anion-modified abrasive grains decreases the contact frequency between the abrasive grains and the surface of the base metal layer. The polishing rate of the base metal layer tends to decrease. Therefore, in the CMP polishing liquid, a predetermined abrasive grain that has been anion-modified and a predetermined abrasive grain that has not been anion-modified are mixed and used, while maintaining the polishing rate of the underlying metal layer. The polishing rate of the palladium layer can be improved as compared with the case where the polishing liquid is used.

  The “anion treatment” means a treatment for imparting a structure that easily forms negative ions in the acidic or neutral region to the surface of the abrasive grains. In another aspect, in a CMP polishing liquid having a pH of 7 or less, it means a process of adding anion species to the abrasive grains so that the zeta potential of the abrasive grains changes in the negative direction.

  “Zeta potential” means the surface charge of the abrasive grain surface dispersed in the CMP polishing liquid. Specifically, the zeta potential can be measured using a zeta potential measuring device “Zetasizer 3000 HSA (trade name)” manufactured by Marvern Instruments.

  The zeta potential of the anion-modified abrasive grains is a mixture containing 1,2,4-triazole, phosphoric acids, an oxidizing agent, anion-modified abrasive grains, an organic solvent described later, and water. -10 mV or less is preferable, and -15 mV or less is more preferable. The lower limit value of the zeta potential of the anion-modified abrasive grains can be set to −50 mV or more. In the measurement of the zeta potential of the abrasive grains, the pH of the mixture is preferably 7 or less.

  The zeta potential of non-anion-modified abrasive grains includes 1,2,4-triazole, phosphoric acids, oxidizing agents, non-anion-modified abrasive grains, organic solvents described below, and water. In the mixture, −5 to 5 mV is preferable, and −3 to 3 mV is more preferable. In the measurement of the zeta potential of the abrasive grains, the pH of the mixture is preferably 7 or less.

  Specific examples of the anion-modified abrasive grains include alumina (fumed alumina, transition alumina, colloidal alumina), silica (fumed silica, colloidal silica), zirconia, titania, ceria, and the like. Among these, fumed alumina, transition alumina, fumed silica, colloidal silica, and colloidal alumina are preferable, and colloidal silica and colloidal alumina are more preferable in that generation of polishing scratches can be suppressed while maintaining a high polishing rate. Similar abrasive grains can be used for abrasive grains that are not anion-modified.

Anion modification will be further described with reference to an example in which silica is used as abrasive grains. Silica is SiO ₂ in general formula, but some silanol groups (Si—OH groups) are present at the terminal (surface). Since the hydrogen atom in the silanol group hardly dissociates in the acidic region, ordinary silica particles exhibit a zeta potential close to plus or zero in the acidic region. Here, by reacting the silanol group with an anionic species, silica particles having a group that is more likely to generate negative ions than the silanol group can be obtained on the surface.

Examples of such anionic species include aluminum compounds such as potassium aluminate [(AlO (OH) ₂ K], etc. More specifically, for example, the above-mentioned aluminate in a colloidal silica solution. By adding potassium and refluxing at 60 ° C. or higher, the silanol group can be made into “—Si—O—Al (OH) ₂ ” which is more easily ionized.

  Specific examples of the anion species used in the anion treatment include aluminate, sulfonate, carboxylic acid, nitric acid, phosphoric acid, carbonic acid, and iodic acid. Among them, sulfonic acid, aluminate, nitric acid, carboxylic acid are exemplified. Of these, sulfonic acid, aluminate, and nitric acid are more preferable in that the polishing rate can be further increased.

  The total content of the anion-modified abrasive grains and the non-anion-modified abrasive grains is preferably 0.1 to 10% by mass based on the total mass of the CMP polishing liquid, and 0.2 to It is more preferable that it is 8.0 mass%. When the content is 0.1% by mass or more, a sufficient physical scraping action can be obtained, and the polishing rate by CMP tends to increase. Moreover, there exists a tendency which can further suppress that particle | grains aggregate and settle that content is 10 mass% or less. Furthermore, when the content is 10% by mass or less, an increase in polishing rate commensurate with the content tends to be obtained. Such a tendency is noticeable depending on the polishing rate of the palladium layer.

  The ratio of the content of the anion-modified abrasive grain to the total content of the anion-modified abrasive grain and the non-anion-modified abrasive grain is 5.0 to 70.0% by mass. Thus, it is possible to obtain a CMP polishing liquid capable of improving the polishing speed of the palladium layer as compared with the case of using a conventional polishing liquid while maintaining the polishing speed of the base metal layer and suppressing the aggregation and settling of abrasive grains. Can do. In this respect, the ratio of the content of the anion-modified abrasive grains is preferably 10.0 to 70.0% by mass, more preferably 20.0 to 70.0% by mass, More preferably, it is 20.0-60.0 mass%.

  The average primary particle size of the anion-modified abrasive grains and the non-anion-modified abrasive grains further suppresses the aggregation and sedimentation of the particles and suppresses the generation of scratches remaining on the polished surface after polishing. In view of this, it is preferably 60 nm or less, more preferably 55 nm or less, and still more preferably 50 nm or less. Further, the lower limit of the average primary particle diameter is not particularly limited, but is preferably 15 nm or more, and more preferably 20 nm or more in that a sufficient physical scraping action can be obtained.

Here, the “average primary particle diameter” of the abrasive grains refers to the average diameter of the particles that can be calculated from the BET specific surface area. From the measurement of the adsorption specific surface area (hereinafter referred to as the BET specific surface area) by the gas adsorption method, Calculated by (1).
D1 = 6 / (ρ × V) (1)
In the formula (1), D1 represents an average primary particle diameter (unit: m), ρ represents particle density (unit: kg / m ³ ), and V represents a BET specific surface area (unit: m ² / g).

More specifically, the abrasive grains are first dried with a vacuum freeze dryer, and the residue is finely crushed with a mortar (magnetic, 100 ml) to obtain a measurement sample, which is measured by BET specific surface area manufactured by Yuasa Ionics Co., Ltd. The BET specific surface area V is measured using an apparatus (trade name: Autosorb 6), and the average primary particle diameter D1 is calculated.
When the particles are colloidal silica, the density ρ of the particles is “ρ = 2200 (kg / m ³ )”. In this case, the following formula (2) is obtained, and the average primary particle diameter D1 can be obtained by substituting the BET specific surface area V (m ² / g) into the formula (2).
D1 = 2.727 × 10 ⁻⁶ / V (m) = 2727 / V (nm) (2)

  The average secondary particle diameter of the anion-modified abrasive grains and the non-anion-modified abrasive grains is 30 to 100 nm, and preferably 40 to 90 nm. If the average secondary particle diameter of the abrasive grains is 30 nm or more, the physical scraping action can be maintained, and the decrease in the polishing rate by CMP tends to be suppressed. Further, when the average secondary particle diameter of the abrasive grains is 100 nm or less, there is a tendency that aggregation and sedimentation of the particles can be suppressed.

  Here, the “average secondary particle diameter” of the abrasive grains can be measured using a dynamic light scattering type particle size distribution meter of the particle diameter of the abrasive grains in an aqueous dispersion in which the abrasive grains are dispersed in water. it can. The average secondary particle size of each of the anion-modified abrasive grains and the non-anion-modified abrasive grains is measured by preparing a dispersion containing only one of the abrasive grains for each of the abrasive grains. . The average secondary particle diameter is specifically obtained by the method shown below. First, a sample prepared by adjusting a dispersion liquid (medium: water) containing abrasive grains to an abrasive grain concentration of 12% by mass and adding 50 ml of 0.3% citric acid aqueous solution to 4 g of the sample and gently shaking Is a measurement sample. The value which measured this sample using the particle size measuring device (For example, Otsuka Electronics Co., Ltd. make, brand name: ELS-8000) is made into an average secondary particle diameter.

  The degree of association between the anion-modified abrasive grains and the non-anion-modified abrasive grains is 1.7 to 2.3 in terms of obtaining a good polishing rate. Here, “degree of association” means a value obtained by dividing the average secondary particle diameter by the primary particle diameter. When the degree of association of the abrasive grains is 1.7 or more, the weight per particle is suppressed from being reduced, the contact with the surface to be polished is promoted, and the decrease in the polishing rate tends to be suppressed. The lower limit is preferably 1.8 or more. In addition, when the degree of association of the abrasive grains is 2.3 or less, the number of particles is suppressed from being decreased, and the decrease in the polishing rate tends to be suppressed. The upper limit value is preferably 2.2 or less.

(1,2,4-triazole)
The CMP polishing liquid contains 1,2,4-triazole. 1,2,4-triazole is considered to form a complex with palladium together with phosphoric acids described later, and it is estimated that a good polishing rate can be obtained because the complex formed here is easily polished. The

  Further, it is considered that a nitrogen-containing compound can form a complex with palladium. However, according to the study by the present inventors, a compound other than 1,2,4-triazole can improve the polishing rate of the palladium layer. I know I can't. For example, with 1,2,3-triazole having a structure similar to that of 1,2,4-triazole and 3-amino-1,2,4-triazole, it is difficult to obtain a good polishing rate for the palladium layer.

  The content of 1,2,4-triazole is preferably 0.001 to 20% by mass based on the total mass of the CMP polishing liquid. When the content is 0.001% by mass or more, the polishing rate of the palladium layer by CMP tends to be further increased, and the lower limit is more preferably 0.01% by mass or more, and 0.05% by mass or more. Is more preferable. Further, when the content of 1,2,4-triazole is 20% by mass or less, saturation of the polishing rate of the palladium layer tends to be suppressed with respect to the content, and the upper limit is 15% by mass. % Or less is more preferable, 12 mass% or less is still more preferable, and 10 mass% or less is especially preferable.

(Phosphoric acids)
The CMP polishing liquid 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, and their condensates (including salts). Examples of phosphoric acids include phosphoric acid, hypophosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, pyrophosphorous acid, trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, polyphosphoric acid, tripolyphosphoric acid, and other condensations. Examples thereof include phosphoric acid and salts thereof. These phosphoric acids may be used alone or in combination of two or more.

  Examples of salts of phosphoric acids include salts of phosphoric acid anions and cations. Examples of phosphoric acid anions include phosphate ion, hypophosphate ion, phosphite ion, hypophosphite ion, pyrophosphate ion, pyrophosphite ion, trimetaphosphate ion, tetrametaphosphate ion, hexametaline Acid ions, polyphosphate ions, tripolyphosphate ions, and other condensed phosphate ions may be mentioned. Examples of cations include lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, titanium, zirconium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, silver, palladium, zinc , Ions of aluminum, gallium, tin, ammonium and the like.

  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.

  The phosphoric acid content is preferably 0.001 to 20% by mass based on the total mass of the CMP polishing liquid. When the content is 0.001% by mass or more, the polishing rate of the palladium layer by CMP tends to be further increased, and the lower limit is more preferably 0.01% by mass or more, and 0.02% by mass or more. Is more preferable. Further, when the content of phosphoric acid is 20% by mass or less, saturation of the polishing rate of the palladium layer with respect to the content tends to be suppressed, and the upper limit is more preferably 15% by mass or less. 10 mass% or less is still more preferable. Further, when the substrate having a nickel layer or the like in addition to the palladium layer and the base metal layer described later is polished, the above content is preferable.

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

  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 based on the total mass of the CMP polishing liquid. More preferably it is. When the content is 0.05% by mass or more, the metal is sufficiently oxidized, and the polishing rate of the palladium layer tends to be further increased. When the content is 20% by mass or less, the polished surface is hardly roughened. Tend. Hydrogen peroxide is usually available as hydrogen peroxide water. Therefore, when hydrogen peroxide is used as the oxidizing agent, the content is converted into the actual concentration. Further, when the substrate having a nickel layer or the like in addition to the palladium layer and the base metal layer described later is polished, the above content is preferable.

(Organic solvent)
The CMP polishing liquid preferably further contains an organic solvent. Since the organic solvent dissolves the poorly water-soluble palladium-containing compound produced during polishing and prevents the compound from adhering to the polishing cloth, it is estimated that the decrease in the polishing rate of the palladium layer can be suppressed. Among organic solvents, those that have a low reducing power and do not reduce palladium ions to palladium metal are preferred.

  As the organic solvent, those which can be arbitrarily mixed with water are preferable. Examples of the organic solvent include carbonate ester, lactone, glycol, glycol derivative, ether, alcohol, ketone, carboxylic acid ester and the like.

Examples of the carbonate ester include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.
Examples of lactones include butyrolactone and propyrolactone.
Examples of the glycol include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol.

  Examples of glycol derivatives include 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 monoethyl 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 Monopropyl 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 monobutyl ether, etc. Glycol monoether: 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 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 And the like.

Examples of the ether include tetrahydrofuran, dioxane, dimethoxyethane, polyethylene oxide, ethylene glycol monomethyl acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate and the like.
Examples of the alcohol include methanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol, and isopropanol.
Examples of the ketone include acetone and methyl ethyl ketone.
Examples of the carboxylic acid ester include ethyl acetate and ethyl lactate.

  Other examples of the organic solvent include phenols, dimethylformamide, n-methylpyrrolidone, sulfolane and the like. The said organic solvent can be used individually by 1 type or in mixture of 2 or more types.

  The content of the organic solvent is preferably 0.1 to 95% by mass based on the total mass of the CMP polishing liquid. There exists a tendency which can suppress that the grinding | polishing speed | rate of the palladium layer when the palladium layer is grind | polished continuously as this content is 0.1 mass% or more reduces gradually. In this respect, the lower limit is more preferably 0.2% by mass or more, and further preferably 0.5% by mass or more. Further, when the content of the organic solvent is 95% by mass or less, the solubility of the CMP polishing liquid component tends to be improved and the aggregation of abrasive grains tends to be further suppressed. In this respect, the upper limit value is more preferably 50% by mass or less, and further preferably 30% by mass or less.

(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 dishing characteristics.

  Specific examples of the metal anticorrosive include imines other than 1,2,4-triazole, azoles, mercaptans, etc. Among them, the suppression of the etching rate of the metal layer and the polishing rate of the metal layer can be mentioned. From the viewpoint of achieving both improvement, a nitrogen-containing cyclic compound is preferable. These can be used alone or in combination of two or more.

  Specifically, imines are dithizone, cuproin (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, 1-N, N-dimethylaminoethyl-5-tetrazole and the like.

  Specific examples of mercaptans include nonyl mercaptan and dodecyl mercaptan.

  When the metal anticorrosive agent is added, the content thereof is preferably in a range that does not impair the polishing rate improvement effect by 1,2,4-triazole and phosphoric acid, and achieves both an etching suppression function and a polishing rate. In this respect, the content is preferably 0.005 to 2.0% by mass based on the total mass of the CMP polishing liquid. The content of the metal anticorrosive is preferably 0.01% by mass or more, and more preferably 0.02% by mass or more, in that higher etching performance can be obtained. Moreover, 1.0 mass% or less is more preferable, and 0.5 mass% or less is still more preferable at the point which becomes easy to obtain suitable polishing rate for content of a metal anticorrosive.

(Water-soluble polymer)
The CMP polishing liquid may 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 still more preferably 5000 or more. When the weight average molecular weight is 500 or more, a higher polishing rate tends to be obtained. The upper limit of the weight average molecular weight is not particularly limited, but is preferably 5 million or less from the viewpoint of solubility.

The weight average molecular weight can be measured by a gel permeation chromatography method (GPC) using a standard polystyrene calibration curve, and more specifically can be measured under the following conditions.
(Measurement condition)
Equipment used: Hitachi L-6000 <Product name>, manufactured by Hitachi, Ltd.
Column: Gel pack GL-R420 + Gel pack GL-R430 + Gel pack GL-R440 <Hitachi Chemical Co., Ltd., trade name, total of 3>
Eluent: Tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 1.75 ml / min.
Detector: L-3300RI (trade name, 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 polishing liquid does not decrease and the abrasive grains do not aggregate. A compound, a vinyl polymer, a glycol compound, etc. can be mentioned, These can be used individually by 1 type or in mixture of 2 or more types.

  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, for example, polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, Polyamic 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 Mention may be made of polycarboxylic acids such as salts, sodium polyamic acid and polyglyoxylic acid, polycarboxylic acid esters and salts thereof, and copolymers thereof.

  Furthermore, specific examples of the vinyl polymer used as the water-soluble polymer include polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein. Moreover, polyethylene glycol etc. can also be used as a glycol compound.

  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.

  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.

(water)
The CMP polishing liquid may contain water. Although there is no restriction | limiting in particular as water, Deionized water and ultrapure water are preferable. The content of water is not particularly limited, and may be the remainder of the content of other components.

(PH)
The pH of the CMP polishing liquid is 7 or less from the viewpoint of increasing the CMP polishing rate of the palladium layer. From the viewpoint that a predetermined polishing rate by CMP can be secured and a practical polishing liquid can be obtained, the pH is preferably 1 or more and 7 or less, more preferably less than 7. The pH is more preferably 1 to 5, and particularly preferably 1 to 4.

  The pH of the CMP polishing liquid can be measured with a pH meter (for example, F-51 (trade name) manufactured by Horiba, Ltd.). As a measured value of pH, two-point calibration is performed using a standard buffer (phthalate pH buffer solution pH: 4.01 (25 ° C.), neutral phosphate pH buffer solution pH 6.86 (25 ° C.)). After that, the electrode is put into a CMP polishing liquid, and a value after 2 minutes or more has been stabilized is adopted.

(Polishing method)
By using the CMP polishing liquid described above, the substrate having the palladium layer and the base metal layer can be polished. That is, a polishing process is provided for polishing a substrate with a polishing cloth while supplying a CMP polishing liquid containing at least 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains between the substrate and the polishing cloth. A method for polishing a substrate is provided. In the polishing step, for example, the surface of the substrate where the palladium layer and the base metal layer are exposed on the surface (surface to be polished) is polished.

  The polishing method of the present embodiment includes a polishing liquid preparation step of obtaining a CMP polishing liquid by blending at least 1,2,4-triazole, phosphoric acids, an oxidizing agent, and abrasive grains before the polishing process. It may be. In the polishing liquid preparation step, it is preferable to obtain a CMP polishing liquid by blending an organic solvent.

  In applying this polishing method, the surface to be polished of the substrate is pressed against the polishing cloth of the polishing surface plate and the CMP polishing liquid of this embodiment is supplied between the surface to be polished and the polishing cloth, 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 surface opposite to the surface to be polished.

  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 cloth can be attached and a holder for holding the substrate can be used. As the polishing cloth, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used.

  As polishing conditions, 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 cloth (polishing pressure) is preferably 4 to 100 kPa, and more preferably 6 to 50 kPa from the viewpoint of uniformity within the substrate surface and pattern flatness. By using the CMP polishing liquid of this embodiment, 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, it is preferable to continuously supply the CMP polishing liquid to the polishing cloth with a pump or the like. As this supply amount, it is preferable that the surface of the polishing pad is always covered with a polishing liquid (in a wet state). 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 substrate that exhibits the best effect of the CMP polishing liquid of this embodiment is a substrate having a palladium layer (referred to as a layer containing palladium) and a base metal layer. The CMP polishing liquid of this embodiment is applied to a substrate in which at least an insulating film layer, a base metal layer, a nickel layer (referred to as a layer containing nickel), and a palladium layer are formed in this order on a semiconductor wafer such as silicon. Is also suitable.

  Examples of the material forming the palladium layer include at least one selected from palladium, palladium alloys, and other palladium compounds.

  Examples of the material for forming the nickel layer include at least one selected from nickel, nickel alloys, and other nickel compounds.

  The base metal layer is a layer that prevents the conductive material from diffusing into the interlayer insulating film. As the material for forming the base metal layer, tantalum compounds such as tantalum nitride are mainly used, but as other materials, tantalum, tantalum alloys, etc., titanium, titanium alloys, titanium compounds such as titanium nitride, tungsten, tungsten nitride, tungsten Examples thereof include tungsten compounds such as alloys.

Examples of the insulating film layer include inorganic insulating films such as SiO ₂ film and SiN film, organosilicate glass, low-k films such as wholly aromatic ring-based Low-k films, and the like.

  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 formed on the silicon wafer 1 and having irregularities on the surface, and a base that covers the surface so as to follow the surface of the insulating film 2. The metal layer 3 and the under barrier metal layer 4 formed on the base metal layer 3 are provided. The under barrier metal layer 4 corresponds to a palladium layer. The formation of the base metal layer 3 is performed for the purpose of suppressing diffusion of components of the under barrier metal layer 4 to the silicon wafer 1 and improving adhesion between the silicon wafer 1 and the under barrier metal layer 4.

  First, the under barrier metal layer 4 of such a substrate is polished using a CMP polishing solution containing at least 1,2,4-triazole, phosphoric acids, an oxidizing agent, and abrasive grains. That is, while supplying the CMP polishing liquid between the under barrier metal layer 4 and the polishing cloth, the substrate is polished with the polishing cloth to remove the under barrier metal layer 4 formed on the convex portion of the insulating film 2. Thus, the underlying metal layer 3 located on the convex portion of the insulating film 2 and the under barrier metal layer 4 filling the outer peripheral portion of the concave portion of the insulating film 2 are exposed to the surface.

  Next, the underlying metal layer 3 and the under barrier metal layer 4 exposed on the surface are polished using the CMP polishing liquid of the present embodiment. That is, while supplying a CMP polishing liquid containing at least 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains between the exposed substrate surface and the polishing cloth, the substrate is polished with the polishing cloth, The base metal layer 3 and the under barrier metal layer 4 are removed, and the convex portion of the insulating film 2 is exposed. FIG.1 (b) is sectional drawing which shows the board | substrate obtained by such grinding | polishing.

  Next, a resist pattern 5 is formed on the convex portion of the insulating film 2 from which the under barrier metal layer 4 has been removed by a known method so that the under barrier metal layer 4 formed on the concave portion of the insulating film 2 is exposed. Form. FIG. 1C is a cross-sectional view showing the substrate on which the resist pattern 5 is formed.

  Next, the protruding electrode 6 is formed in the concave portion of the substrate on which the resist pattern 5 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 6 are formed.

  Finally, by removing the resist pattern 5, it is possible to obtain a substrate on which the protruding electrodes 6 are formed on the silicon wafer 1. FIG. 1E is a cross-sectional view showing a substrate having the protruding electrodes 6 obtained as described above. The protruding electrode 6 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, in FIG. 2, only the substrate before applying the polishing method (FIG. 2 (a)) and the substrate having the bump electrode finally obtained (FIG. 2 (b)) are shown. Each process of resist pattern formation, bump electrode formation, and resist pattern removal is performed in the same manner as in the first embodiment described above with reference to FIG.

  The substrate shown in FIG. 2A is formed on the silicon wafer 1, the insulating film 2 formed on the silicon wafer 1 and having irregularities on the surface, and the surface of the insulating film 2 so as to follow the surface. A base metal layer 3, a first under barrier metal layer 4a formed on the base metal layer 3, and a second under barrier metal layer 4b formed on the first under barrier metal layer 4a. ing. The first under barrier metal layer 4a or the second under barrier metal layer 4b corresponds to a palladium layer.

  The base metal layer 3, the first under barrier metal layer 4a, and the second under barrier metal layer 4b of such a substrate are polished using the CMP polishing liquid of the present embodiment. That is, while supplying a CMP polishing liquid containing at least 1,2,4-triazole, phosphoric acid, oxidizing agent and abrasive grains between the second under barrier metal layer 4b and the polishing cloth, the substrate is covered with the polishing cloth. Polishing is performed to expose the convex portions of the insulating film 2. By such polishing, the base metal layer 3, the first under barrier metal layer 4a, and the second under barrier metal layer 4b 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 6 is formed can be obtained.

  FIG. 3 shows an example in which the first under barrier metal layer 4a in FIG. 2 is a nickel layer and the second under barrier metal layer 4b is a palladium layer (structure having two under barrier metals).

  The substrate shown in FIG. 3A is obtained by forming a base metal layer 13, a nickel layer 14, and a palladium layer 15 in this order on the concavo-convex portion of the insulating film 12 provided on the silicon substrate 11. By using the CMP polishing liquid of this embodiment, the base metal layer 13, the nickel layer 14, and the palladium layer 15 can be polished to expose the protrusions of the insulating film 12 as shown in FIG.

  As another example of the polishing method using the CMP polishing liquid, a first polishing step in which the palladium layer 15 existing on the convex portion of the insulating film 12 is polished to expose the nickel layer 14, and the convex portion of the insulating film 12 is used. Polishing the underlying metal layer 13, the nickel layer 14, and the palladium layer 15 embedded in the outer periphery of the concave portion of the insulating film 12 to expose the convex portion of the insulating film 12; And a method using a CMP polishing liquid in at least one of the two polishing steps.

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

  The CMP polishing liquids used in Examples 1 and 2 and Comparative Examples 1 to 20 are based on the total mass of the CMP polishing liquid, and 5% by mass of abrasive grains shown in Tables 1 to 3 and 30% hydrogen peroxide as an oxidizing agent. 10% by weight of water, 5% by weight of phosphoric acid as a metal oxide solubilizer, 5% by weight of propylene glycol as an organic solvent, 0.5% by weight of 1,2,4-triazole as a complexing agent, and pure water in the balance It was prepared to contain.

In addition, the following were prepared as an abrasive grain.
Abrasive grain A: Colloidal silica abrasive grain B having an average primary particle diameter of 35 nm and an average secondary particle diameter of 67 nm B: Colloidal silica abrasive grain having an average primary particle diameter of 55 nm and an average secondary particle diameter of 114 nm C: Average primary particle diameter of 19 nm, average secondary Colloidal silica abrasive grain D having a primary particle diameter of 29 nm: Colloidal silica abrasive grain F having an average primary particle diameter of 35 nm and colloidal silica abrasive grain having an average secondary particle diameter of 55 nm E: Average primary particle diameter of 12 nm and an average secondary particle diameter of 23 nm Colloidal silica abrasive grains G having a primary particle diameter of 15 nm and an average secondary particle diameter of 39 nm: Colloidal silica abrasive grains having an average primary particle diameter of 24 nm and an average secondary particle diameter of 64 nm: An average primary particle diameter of 31 nm and an average secondary particle diameter of 87 nm Colloidal silica

  Also, some of the abrasive grains A to H are used to produce anion grains modified with sulfonic acid, anion grains modified with aluminate, and cation modified grains with amino groups. did.

The average primary particle diameter and average secondary particle diameter of the abrasive grains whose surface was modified were measured as follows.
(Average primary particle size)
The abrasive grains are dried with a vacuum freeze dryer, and the residue is finely crushed with a mortar (magnetic, 100 ml) to obtain a measurement sample. This is a BET specific surface area measuring device (trade name: Autosorb 6) manufactured by Yuasa Ionics Co., Ltd. ) Was used to measure the BET specific surface area and the average primary particle size was calculated.

(Average secondary particle size)
The average secondary particle diameter was measured as follows using a dispersion liquid in which abrasive grains were dispersed in water as a sample. Specifically, first, a sample in which a dispersion liquid (medium: water) containing the abrasive grains was adjusted to an abrasive grain concentration of 12% by mass was prepared, and 4% of the sample was mixed with 50% of 0.3% by mass citric acid. In addition, lightly shaken samples were used as measurement samples. This measurement sample was measured using a particle size measuring device (trade name: ELS-8000, manufactured by Otsuka Electronics Co., Ltd.), and the value of the obtained average particle size was defined as the average secondary particle size.

(PH)
The measurement temperature of the CMP polishing liquid was 25 ± 5 ° C., and the pH was measured using a product name: F-51 manufactured by Horiba, Ltd.

(Zeta potential)
The zeta potential of the abrasive grains was measured using a zeta potential measuring device “Zetasizer 3000 HSA (trade name)” manufactured by Marvern Instruments. When the CMP polishing liquid contains two types of abrasive grains, one abrasive grain is 5% by mass, 30% hydrogen peroxide water is 10% by mass, phosphoric acid is 5% by mass, and propylene glycol is 5% by mass. A mixture containing 0.5% by mass of 1,2,4-triazole and pure water in the balance was prepared for each of the two types of abrasive grains, and the zeta potential of the abrasive grains in the mixture was measured.

The substrate to be polished was polished under the following polishing conditions using the CMP polishing liquid prepared above.
(CMP polishing conditions)
Polishing device: Mirra (Applied Materials)
CMP polishing liquid flow rate: 200 mL / min Polishing substrate: silicon substrate on which a palladium layer having a thickness of 0.3 μm is formed by sputtering, and silicon substrate on which a tantalum nitride layer having a thickness of 0.2 μm is formed by sputtering : Expanded polyurethane resin with closed cells (Rohm and Haas Japan Co., Ltd., trade name: IC1000)
Polishing pressure: 29.4 kPa (4 psi)
Relative speed between substrate and polishing platen: 68 m / min Polishing time: 1 minute Cleaning: After CMP treatment, cleaning with ultrasonic water was performed, followed by drying with a spin dryer.

(Abrasive product evaluation items)
Polishing rate: The film thickness difference of the film to be polished before and after polishing was converted from the electrical resistance value, and the polishing rate of the palladium layer and the tantalum nitride layer polished and washed under the above conditions was obtained from the following formula. However, for Comparative Examples 18 and 19, only the polishing rate of the palladium layer was calculated. The target value of the palladium polishing rate is 70 nm / min or more, and the target value of the tantalum nitride polishing rate is 120 nm / min or more.
(PdRR) = (Difference in palladium layer thickness before and after polishing) / (Polishing time (minutes))
(TaNRR) = (Difference in film thickness of tantalum nitride layer before and after polishing) / (Polishing time (minutes))

(Presence or absence of coagulation sedimentation)
As an accelerated test for examining the presence or absence of coagulation sedimentation when stored at room temperature (30 ° C) for 6 months, the polishing liquid placed in a container (with a transparent outer wall) was allowed to stand for 2 weeks in a thermostatic bath set at 60 ° C. The aggregation and sedimentation after the check was confirmed visually. The case where the coagulation sedimentation of an abrasive grain was not confirmed was evaluated as preferable.

Tables 1 to 3 show the palladium polishing rate, the tantalum nitride polishing rate, the presence or absence of coagulation sedimentation in Examples 1 and 2 and Comparative Examples 1 to 20, respectively. In Tables 1 to 3, the superscript symbols for the abrasive grains indicate the following.
0: Abrasive grains not surface-modified-1: Abrasive grains anion-modified with sulfonic acid-2: Abrasive grains anion-modified with aluminate +: Abrasive grains cation-modified with amino groups

  Hereinafter, the results shown in Tables 1 to 3 will be described in detail. In Examples 1 and 2, the same oxidizing agent, metal oxide solubilizer, and complexing agent as in Comparative Examples 1 to 20 are added. 10% by mass of 30% hydrogen peroxide as an oxidizing agent, 5% by mass of phosphoric acid as a metal oxide solubilizer, and 0.5% by mass of 1,2,4-triazole as a complexing agent are added.

The CMP polishing liquid of Example 1 has abrasive grains A ⁰ having an average secondary particle diameter of 67 nm, the degree of association of 1.9, and a pH of 1.5, with a zeta potential of 2.0 mV. the surface of the anion-modified average secondary particle diameter 71 nm, degree of association 2.1, using the abrasive ^{a -1} zeta potential of -30.7mV at pH 1.5, the content of the abrasive grains ^{a -1} Is added in an amount of 1.25% by mass based on the total mass of the CMP polishing liquid so that 25% of the total amount of abrasive grains is 25%.

  In Example 1, the palladium polishing rate exceeds 73 nm / min and the target value of 70 nm / min, the tantalum nitride polishing rate exceeds 165 nm / min and the target value of 120 nm / min, and the abrasive grains do not coagulate and settle. It was confirmed.

The CMP polishing liquid of Example 2 was used as abrasive grains A ⁰ having an average secondary particle diameter of 67 nm, the degree of association of 1.9, and a pH of 1.5. the surface of the anion-modified average secondary particle diameter 71 nm, degree of association 2.1, using the abrasive ^{a -1} zeta potential of -30.7mV at pH 1.5, the content of the abrasive grains ^{a -1} Is added in an amount of 2.5% by mass on the basis of the total mass of the CMP polishing liquid so as to be 50% of the total amount of abrasive grains.

  In Example 2, the palladium polishing rate exceeds 76 nm / min and the target value of 70 nm / min, the tantalum nitride polishing rate exceeds 125 nm / min and the target value of 120 nm / min, and the abrasive grains do not coagulate and settle. It was confirmed.

  In Comparative Examples 1 to 20, abrasive grains A to H having different average secondary particle diameter, degree of association, and zeta potential at pH 1.5 are used. As shown in Tables 1 to 3, in Comparative Examples 1 to 20, any one or more of the palladium polishing rate, the tantalum nitride polishing rate, and the presence or absence of coagulation sedimentation could not satisfy the target value.

  According to the CMP polishing liquid of the present invention and the polishing method using this CMP polishing liquid, while improving the polishing rate of the palladium layer as compared with the case of using the conventional polishing liquid while maintaining the polishing rate of the underlying metal layer, Not only can aggregation and settling of abrasive grains be suppressed, but also the tantalum nitride can be polished at a desired polishing rate.

  DESCRIPTION OF SYMBOLS 1 ... Silicon wafer, 2 ... Insulating film, 3 ... Base metal layer, 4 ... Under barrier metal layer, 4a ... 1st under barrier metal layer, 4b ... 2nd under barrier metal layer, 5 ... Resist pattern, 6 ... Projection electrode, 11 ... silicon substrate, 12 ... insulating film, 13 ... base metal layer, 14 ... nickel layer, 15 ... palladium layer.

Claims (18)

1,2,4-triazole, phosphoric acid, an oxidizing agent, a first abrasive grain whose surface is anion-modified, and a second abrasive grain whose surface is not anion-modified,
The average secondary particle diameter of the first abrasive grains and the second abrasive grains is 30 to 100 nm,
The association degree of the first abrasive grains and the second abrasive grains is 1.7 to 2.3,
The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 5.0 to 70.0 mass%,
A CMP polishing liquid for palladium polishing , having a pH of 7 or less. 1,2,4-triazole, phosphoric acid, oxidizing agent, first anodically modified surface, an average secondary particle size of 30 to 100 nm and an association degree of 1.7 to 2.3 And a second abrasive grain having an average secondary particle diameter of 30 to 100 nm and an association degree of 1.7 to 2.3, the surface of which is not anion-modified,
The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 5.0 to 70.0 mass%,
A CMP polishing liquid for palladium polishing , having a pH of 7 or less.   The CMP polishing liquid according to claim 1 or 2, wherein the first abrasive grains are anion-modified with at least one selected from aluminate, sulfonic acid, carboxylic acid, nitric acid, phosphoric acid, carbonic acid, and iodic acid.   The CMP polishing liquid according to any one of claims 1 to 3, wherein the first abrasive grains include at least one selected from alumina, silica, zirconia, titania and ceria.   5. The total content of the first abrasive grains and the second abrasive grains is 0.1 to 10% by mass based on the total mass of the CMP polishing liquid, according to claim 1. CMP polishing liquid.   Any of Claims 1-5 whose ratio of content of the said 1st abrasive grain with respect to the sum total of content of said 1st abrasive grain and said 2nd abrasive grain is 20.0-60.0 mass%. The CMP polishing liquid according to claim 1.   In a mixture containing the 1,2,4-triazole, the phosphoric acid, the oxidizer, the first abrasive grain, an organic solvent, and water, the zeta potential of the first abrasive grain is -10 mV or less. In the mixture containing the 1,2,4-triazole, the phosphoric acid, the oxidizing agent, the second abrasive grain, an organic solvent, and water, the second abrasive grain The CMP polishing liquid according to any one of claims 1 to 6, which gives a zeta potential of -5 to 5 mV.   The oxidant is at least one selected from hydrogen peroxide, periodic acid, periodate, iodate, bromate, persulfate, and persulfate, according to any one of claims 1 to 7. The CMP polishing liquid as described.   The CMP polishing liquid according to any one of claims 1 to 8, further comprising an organic solvent. A polishing step of polishing the substrate with the polishing cloth while supplying a CMP polishing liquid between the substrate and the polishing cloth;
The substrate is a substrate having a palladium layer and a base metal layer,
The CMP polishing liquid is 1,2,4-triazole, phosphoric acid, an oxidizing agent, a first abrasive grain whose surface is anion-modified, and a second abrasive whose surface is not anion-modified. Containing grains,
The average secondary particle diameter of the first abrasive grains and the second abrasive grains is 30 to 100 nm,
The association degree of the first abrasive grains and the second abrasive grains is 1.7 to 2.3,
The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 5.0 to 70.0 mass%,
A polishing method, wherein the CMP polishing solution has a pH of 7 or less. 1,2,4-triazole, phosphoric acid, oxidizing agent, first anodically modified surface, an average secondary particle size of 30 to 100 nm and an association degree of 1.7 to 2.3 And a second abrasive grain having an average secondary particle size of 30 to 100 nm and an association degree of 1.7 to 2.3, the surface of which is not anion-modified, and a CMP polishing liquid. A polishing liquid preparation step to obtain;
A polishing step of polishing the substrate with the polishing cloth while supplying the CMP polishing liquid between the substrate and the polishing cloth,
The substrate is a substrate having a palladium layer and a base metal layer,
The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 5.0 to 70.0 mass%,
A polishing method, wherein the CMP polishing solution has a pH of 7 or less. The polishing method according to claim 10 or 11 , wherein the first abrasive grains are anion-modified with at least one selected from aluminate, sulfonic acid, carboxylic acid, nitric acid, phosphoric acid, carbonic acid, and iodic acid. The polishing method according to any one of claims 10 to 12 , wherein the first abrasive grains include at least one selected from alumina, silica, zirconia, titania and ceria. Wherein the first abrasive grains and the total content of the second abrasive is 0.1 to 10 mass% based on the total mass of the CMP polishing liquid according to any one of claims 10-13 Polishing method. The ratio of the content of the first abrasive grains to the total content of the first abrasive grains and the second abrasive grains is 20.0 to 60.0 mass%, any one of claims 10 to 14 . The polishing method according to claim 1. In the mixture in which the CMP polishing liquid contains the 1,2,4-triazole, the phosphoric acid, the oxidizing agent, the first abrasive grains, an organic solvent, and water, the first abrasive grains A mixture containing 1,2,4-triazole, phosphoric acids, the oxidizing agent, the second abrasive, an organic solvent, and water. The polishing method according to any one of claims 10 to 15 , which gives a zeta potential of -5 to 5 mV of the second abrasive grain. The oxidant is at least one selected from hydrogen peroxide, periodic acid, periodate, iodate, bromate, persulfate, and persulfate according to any one of claims 10 to 16. The polishing method described. The polishing method according to any one of claims 10 to 17 , wherein the CMP polishing liquid further contains an organic solvent.

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