Method for improving integrated circuit multi-layer wiring ruthenium CMP rate

Abstract

The invention relates to the related technical field of integrated circuit multi-layer wiring processes, and discloses a method for improving the integrated circuit multi-layer wiring ruthenium CMP rate, and the method comprises the steps: preparing a polishing solution containing nitrilotriacetic acid triammonium salt; and polishing the ruthenium barrier layer pattern sheet of the integrated circuit below 14nm by using the polishing solution. In the application of a large-scale integrated circuit, NTA (NH4) 3 can react with ruthenium oxide (but nonmetal ruthenium) on the ruthenium surface to generate a large number of complexes through the triple synergistic effect of NTA (NH4) 3, the oxidizing agent and the silica sol, the dissolving corrosion capacity on ruthenium and the ruthenium oxide is enhanced, meanwhile, the ruthenium and the ruthenium oxide are rapidly removed along with the mechanical effect, and therefore the ruthenium CMP removal efficiency is higher. According to the efficient removal synergistic effect method for Ru, the high removal rate and low surface defect of Ru can be taken into account, the CMP performance of the Ru barrier layer is remarkably improved, and therefore the performance of an integrated circuit is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field related to integrated circuit multilayer wiring process, and more specifically, particularly relates to a method for improving the ruthenium CMP rate of integrated circuit multilayer wiring. Background Art

[0002] With the development of integrated circuits, the current integration usually realizes interconnection structure through multi-layer wiring to reduce the line length and improve the operation speed. When realizing the dual Damascene process of multi-layer wiring, the photolithography process requires the consistency of the previous planarization process to maintain a length of 8 orders of magnitude; and chemical mechanical polishing (CMP) is currently the only technology to achieve the planarization of multi-layer wiring of integrated circuits. At present, in advanced technology node integrated circuits below 14nm, Ru is regarded as a promising integrated circuit barrier layer material due to its advantages such as low impedance, high melting point, superior barrier ability, good adhesion and wetting properties.

[0003] Despite this, Ru still faces many challenges in practical application. First, the inherent hardness of Ru is relatively high (Mohs hardness is 6.5), which makes SiO2 have limited effect on it in mechanical grinding. In addition, ruthenium has extremely high chemical stability and is difficult to react with most acids and bases. During the barrier layer CMP process, the removal rate of ruthenium is usually slow. This situation may cause ruthenium to remain on the surface of the dielectric layer, which may cause circuit short circuits and affect device performance, becoming a key challenge for Ru in integrated circuit applications.

[0004] Therefore, in view of this, the existing structure and defects are studied and improved, and a method for improving the ruthenium CMP rate of integrated circuit multi-layer wiring is provided, so as to achieve a more practical and valuable purpose. Summary of the invention

[0005] The present invention provides a method for improving the ruthenium CMP rate of integrated circuit multilayer wiring, which is used to overcome the above-mentioned defects in the prior art.

[0006] The purpose and efficacy of the method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits of the present invention are achieved by the following specific technical means:

[0007] A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits, comprising:

[0008] S1: Preparation of a polishing solution containing triammonium nitrilotriacetate (NTA(NH4)3):

[0009] Take silica sol, add deionized water to dilute, and obtain silica sol solution; mix oxidant, complexing agent NTA (NH4) 3, inhibitor, bactericide, and surfactant, dilute with deionized water, add silica sol solution, adjust to the required pH value with pH regulator, and stir evenly to obtain polishing liquid;

[0010] S2: using the polishing liquid to polish a ruthenium barrier layer pattern sheet of an integrated circuit multilayer wiring below 14 nm under the polishing conditions;

[0011] The polishing conditions are as follows: working pressure is 1-5Psi, polishing head speed is 88-108r / min, polishing disc speed is 100-110r / min, and polishing liquid flow rate is 200-300ml / min.

[0012] A further technical solution is that the preparation method of triammonium nitrilotriacetate (NTA(NH4)3) is as follows: nitrilotriacetic acid (NTA) and ammonia water are mixed according to the amount of substance (mass / molar mass) of 1:3, and after the reaction is completed, a complexing agent NTA(NH4)3 is obtained;

[0013] In a further technical solution, the polishing liquid also includes silica sol, oxidant, bactericide, inhibitor, surfactant, pH regulator and deionized water.

[0014] A further technical solution is that the components of the polishing liquid are, by mass percentage, 3-10% silica sol, 30.02-2% complexing agent NTA (NH4), 0.1-2% oxidant, 0.001-1% inhibitor, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance is deionized water. The pH value of the polishing liquid is 7.0-11.5.

[0015] According to a further technical solution, the particle size of the silica sol is 30nm-200nm.

[0016] In a further technical solution, the oxidant is a mixture of one or more of peroxides, transition metal salts, nitric acid and nitrates, and halogen oxygen salts.

[0017] In a further technical solution, the inhibitor is a mixture of one or more of BTA (benzotriazole), MBT (sodium mercaptobenzothiazole), TTA (methyltriazole), etc.

[0018] In a further technical solution, the fungicide is a mixture of one or more of methylisothiazolinone, kasone, potassium sorbate, benzoic acid, 5-chloro-2-methyl-4-isothiazoline-3-one, and 1-2-benzisothiazolin-3-one.

[0019] In a further technical solution, the surfactant is a mixture of one or more cationic surfactants, anionic surfactants, and nonionic surfactants.

[0020] In a further technical solution, the pH regulator is a mixture of one or more commonly used inorganic acids and bases such as KOH and boric acid.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses a polishing liquid containing a complexing agent NTA (NH4) 3 to polish ruthenium of an advanced technology node integrated circuit, which can greatly increase the ruthenium removal rate. The principle is as follows:

[0023] The mechanism of NTA(NH4)3 promoting Ru removal can be attributed to the "triple synergistic effect", namely: the interaction between the positive charge from NTA(NH4)3 ionization and SiO2 abrasive enhances the abrasive's adsorption capacity and cutting effect; the complexation effect from NTA(NH4)3 ionization on Ru and its oxide reduces the surface bond energy of Ru and the stability of the oxide, promoting the chemical dissolution of Ru; the ammoniation and complexation effect from NTA(NH4)3 ionization on Ru and its oxide increases the solubility and mobility of Ru oxide, accelerating the removal of Ru. Through the "triple synergistic effect" removal mechanism of the polishing liquid on the Ru surface, the removal rate of the barrier layer material is effectively improved, which is conducive to improving the rate selectivity of the wiring layer / barrier layer material, thereby improving the flatness of the integrated circuit and enhancing the electrical performance of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a schematic diagram of the molecular structure of the complexing agent NTA(NH4)3;

[0026] Figure 2 This is a comparison chart of the roughness after polishing of Example 1, Comparative Example 1, and Comparative Example 2;

[0027] Figure 3 This is a comparison diagram of the surface states after polishing of Example 1, Comparative Example 1, and Comparative Example 2;

[0028] Figure 4 Schematic diagram of the principle of increasing the removal rate for the complexing agent NTA(NH4)3. DETAILED DESCRIPTION

[0029] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0030] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] As attached Figure 1 To Attachment Figure 4 As shown:

[0033] The present invention provides a method for improving the ruthenium CMP rate of integrated circuit multi-layer wiring.

[0034] See attached Figure 1 To Attachment Figure 4 ,include:

[0035] Prepare a polishing liquid containing a complexing agent NTA (NH4) 3; then add the polishing liquid into a polishing machine to polish the graphic sheet to obtain a finished product;

[0036] The polishing conditions are as follows: working pressure is 1-5Psi, polishing head speed is 88-108r / min, polishing disc speed is 100-110r / min, and polishing liquid flow rate is 200-300ml / min.

[0037] In the above embodiment, the interaction between the positive charge from the ionization of NTA (NH4) 3 and the SiO2 abrasive enhances the adsorption capacity and cutting effect of the abrasive; the complexation effect of the ionization of NTA (NH4) 3 on Ru and its oxide reduces the surface bond energy of Ru and the stability of the oxide, and promotes the chemical dissolution of Ru; the ammoniation and complexation effect of the ionization of NTA (NH4) 3 on Ru and its oxide increases the solubility and mobility of Ru oxide, and accelerates the removal of Ru. Through the "triple synergistic effect" removal mechanism of the polishing liquid on the Ru surface, the removal rate of the barrier layer material is effectively improved, which is conducive to improving the rate selectivity of the wiring layer / barrier layer material, thereby improving the flatness of the integrated circuit and enhancing the electrical performance of the circuit.

[0038] In some embodiments of the present invention, the preparation method of triammonium nitrilotriacetate (NTA(NH4)3) is as follows: nitrilotriacetic acid (NTA) and ammonia water are mixed in a substance amount (mass / molar mass) of 1:3, and after the reaction is completed, a complexing agent NTA(NH4)3 is obtained; the specific operation is: ammonia water is continuously stirred in the same direction with a glass rod, and then NTA powder is slowly poured into the ammonia water, and at the same time, it is stirred evenly while mixing, and stirred for at least 3 minutes after pouring to ensure uniform stirring. After the reaction is completed, the complexing agent NTA(NH4)3 is obtained, and because the two undergo an acid-base neutralization reaction, the solubility of NTA is excellent, which reduces the complexity of the configuration process;

[0039] In some embodiments of the present invention, the components of the polishing liquid are, by mass percentage, 3-10% silica sol, 30.02-2% complexing agent NTA (NH4), 0.1-2% oxidant, 0.001-1% inhibitor, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance deionized water.

[0040] In some embodiments of the present invention, the pH value of the polishing liquid is 7.0-11.5. This is because an acidic environment easily generates toxic RuO4 gas, which poses a threat to the environment and human health, so an alkaline environment is preferably used for the Ru CMP polishing liquid.

[0041] In some embodiments of the present invention, the particle size of the silica sol is 30nm-200nm. The nano-scale silica sol abrasive mainly provides mechanical action during the CMP process. Abrasives with appropriate particle size play an important role in polishing rate, surface roughness, and surface defects.

[0042] In some embodiments of the present invention, the inhibitor is a mixture of one or more of BTA (benzotriazole), MBT (sodium mercaptobenzothiazole), TTA (methyltriazole), etc.

[0043] The surfactant is a mixture of one or more cationic surfactants, anionic surfactants, and nonionic surfactants in proportion. The surfactant can improve the dispersion of silica sol, prevent the polishing liquid from gelling, reduce the possibility of large agglomerated particles, reduce surface roughness, avoid defects such as scratches on the surface caused by large particles, and improve the surface quality after polishing.

[0044] In some embodiments of the present invention, the bactericide is a mixture of one or more of methylisothiazolinone, kason, potassium sorbate, benzoic acid, 5-chloro-2-methyl-4-isothiazolin-3-one, and 1-2-benzisothiazolin-3-one. The bactericide can sterilize the polishing liquid and effectively extend the service life of the polishing liquid.

[0045] In some embodiments of the present invention, the preparation method of the above-mentioned polishing liquid includes the following steps: taking silica sol, adding deionized water to dilute, and obtaining a silica sol solution; mixing a complexing agent NTA (NH4) 3, an oxidant, an inhibitor, a bactericide, and a surfactant, and diluting them with deionized water, and then adding the silica sol solution, stirring evenly to obtain a polishing liquid. The preparation method is simple in process, and a polishing liquid with good stability can be obtained, which is suitable for the needs of large-scale industrial production.

[0046] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0047] Example 1

[0048] A method for increasing the CMP rate of ruthenium for multi-layer wiring of integrated circuits, comprising the following steps:

[0049] Prepare 10 kg of polishing liquid: take 5% by mass of silica sol with a particle size of 60 nm, add deionized water to dilute to 5 kg, and obtain a silica sol solution; mix 0.04% by mass of complexing agent NTA (NH4) 3, 0.15% by mass of hydrogen peroxide, 0.04% by mass of inhibitor BTA, 0.5% by mass of fungicide and 0.06% by mass of surfactant, and dilute to 5 kg with deionized water, then add the above silica sol solution, stir evenly to obtain a polishing liquid, adjust the pH value of the polishing liquid to 9, and set aside;

[0050] The molecular formula of the above-mentioned complexing agent NTA(NH4)3 is shown in the attached Figure 1 ;

[0051] The above-mentioned fungicide is a mixture of methylisothiazolinone, kason, potassium sorbate and benzoic acid;

[0052] The surfactant is a mixture of sodium dodecyl sulfate, dodecylbenzenesulfonic acid, and fatty acid methyl ester ethoxylate;

[0053] Polishing: Add the polishing liquid into the Universal-300Plus polishing machine produced by Huahaiqingke, and polish under the conditions of working pressure Z1: 4.76Ps i, Z2: 2.01Ps i, Z3: 1.82Ps i, Z4: 1.92Ps i, Z5: 1.63Ps i; polishing head speed of 98r / min; polishing disc speed of 105r / min; polishing liquid flow rate of 250ml / min.

[0054] Comparative Example 1

[0055] Compared with Example 1, the polishing liquid in Comparative Example 1 does not contain complexing agent NTA(NH4)3.

[0056] Comparative Example 2

[0057] Compared with Example 1, the polishing liquid in Comparative Example 2 is a commercial polishing liquid.

[0058] Test Example 1

[0059] The 300 mm graphic sheet was polished by the methods of Example 1, Comparative Example 1 and Comparative Example 2, and the speed, surface roughness and surface state were compared after cleaning. The results are shown in Tables 1 and Figure 2-3 shown.

[0060]

[0061]

[0062] Table 1

[0063] From Table 1 and Figure 2-3 It can be seen that the removal rate of Ru is Rise to The increase was about 17 times. At the highest rate, the roughness of the Ru surface was only 0.205nm, and the surface state was also good. This shows that NTA(NH4)3 can take into account both high removal rate and low surface defects.

[0064] Its mechanism is as follows Figure 4 As shown in the figure: During the chemical mechanical polishing (CMP) process, the oxide on the ruthenium surface will be quickly worn away by mechanical action, exposing a fresh surface, which is continuously oxidized and complexed, thereby achieving the removal of ruthenium. After adding an oxidant such as H2O2, the concentration in the solution increases, which promotes the formation of ruthenium oxide. On this basis, after introducing NTA(NH4)3, the N atoms ionized by NTA(NH4)3 and the lone pair of electrons of the O atoms on the carboxyl group interact with the ruthenium oxide to form a large number of complexes. This effect significantly promotes the dissolution of the oxide on the ruthenium surface, thereby increasing the removal rate of ruthenium.

[0065] In addition, due to the amination-complexation effect of NTA(NH4)3 on Ru and its surface oxide, the ions can be hydrolyzed into, which can respectively ammoniate the ruthenium ions in, and into water-soluble complexes, and together desorb the ruthenium ions from the metal surface, thereby further improving the removal rate of ruthenium.

[0066] Finally, during the CMP process, the silica sol particles and the metal surface covered by oxide usually carry a negative charge. This same charge will induce electrostatic repulsion, thereby reducing the contact between the particles and the surface and reducing the polishing efficiency. Therefore, after the ions are introduced into the polishing liquid, these positive ions neutralize the negative charge, effectively reduce the electrostatic repulsion, increase mechanical friction, and thus improve the performance of Ru CMP.

[0067] From the experimental examples, it can be seen that NTA(NH4)3 has an excellent advantage in Ru CMP performance, making the removal rate of Ru reach This is the highest value in the existing experimental records of H2O2 system under the same experimental conditions, which is much larger than the commercial polishing liquid. The removal mechanism of NTA(NH4)3 with multiple factors can effectively improve the performance of Ru barrier layer CMP, providing a new perspective for the field of ruthenium CMP.

[0068] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A method for improving the CMP rate of ruthenium multilayer wiring of integrated circuits, comprising: S1: Preparation of a polishing solution containing triammonium nitrilotriacetate (NTA(NH4)3): Take silica sol, add deionized water to dilute, and obtain silica sol solution; mix oxidant, complexing agent NTA (NH4) 3, inhibitor, bactericide, and surfactant, dilute with deionized water, add silica sol solution, adjust to the required pH value with pH regulator, and stir evenly to obtain polishing liquid; S2: using the polishing liquid to polish a ruthenium barrier layer pattern sheet of an integrated circuit with a multi-layer wiring structure below 14 nm under the polishing conditions; The polishing conditions are as follows: working pressure is 1-5Psi, polishing head speed is 88-108r / min, polishing disc speed is 100-110r / min, and polishing liquid flow rate is 200-300ml / min.

2. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 1, characterized in that: The preparation method of triammonium nitrilotriacetate (NTA(NH4)3) is as follows: nitrilotriacetic acid (NTA) and ammonia water are mixed according to the amount of substance (mass / molar mass) of 1:3, and after the reaction is completed, the complexing agent NTA(NH4)3 is obtained.

3. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 1, characterized in that: The polishing liquid also includes silica sol, oxidant, bactericide, inhibitor, surfactant, pH value regulator and deionized water.

4. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 3, characterized in that: The components of the polishing liquid are: 3-10% silica sol, 30.02-2% complexing agent NTA (NH4), 0.1-2% oxidant, 0.001-1% inhibitor, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance deionized water. The pH value of the polishing liquid is 7.0-11.

5.

5. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 4, characterized in that: The particle size of the silica sol is 30nm-200nm.

6. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 4, characterized in that: The oxidant is a mixture of one or more of peroxides, transition metal salts, nitric acid and nitrates, and halogen oxyacid salts.

7. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 4, characterized in that: The inhibitor is a mixture of one or more of BTA (benzotriazole), MBT (sodium mercaptobenzothiazole), TTA (methyltriazole) and the like.

8. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 4, characterized in that: The bactericide is a mixture of one or more of methylisothiazolinone, kasone, potassium sorbate, benzoic acid, 5-chloro-2-methyl-4-isothiazolin-3-one and 1-2-benzisothiazolin-3-one.

9. A method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 4, characterized in that: The surfactant is a mixture of one or more cationic surfactants, anionic surfactants and nonionic surfactants.

10. The method for improving the CMP rate of ruthenium for multi-layer wiring of integrated circuits according to claim 4, characterized in that: The pH regulator is a mixture of one or more commonly used inorganic acids and bases such as KOH and boric acid.

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