Method for controlling butterfly-shaped pits and corrosion pits of ruthenium barrier layer copper wiring

Abstract

The invention relates to the related technical field of integrated circuit multilayer wiring processes, and discloses a method for controlling butterfly pits and corrosion pits of ruthenium barrier layer copper wiring, which comprises the following steps: preparing a polishing solution containing active agents such as phosphate; taking silica sol, and adding deionized water for dilution to obtain a silica sol solution; a chelating agent, an oxidizing agent, phosphate, a sterilizing agent and a surface active agent are mixed, deionized water is added for dilution, then the silica sol solution is added, the PH value is adjusted to the needed PH value through a PH value adjusting agent, and the polishing solution is obtained after even stirring; polishing the ruthenium barrier layer pattern sheet of the integrated circuit below 14 nm by using the polishing solution; according to the method, the proper copper high-low rate difference and selection ratio are realized by utilizing the adsorption of phosphate on the copper wiring, so that relatively low butterfly pits and corrosion pits are achieved, and the flattening effect is achieved; compared with the traditional BTA and other file inhibitors, the phosphate ester is green and environment-friendly, and has no pollution to the environment.

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 controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring. Background Art

[0002] With the development of integrated circuits, following Moore's Law, the feature size continues to shrink. The number of transistors contained in integrated circuits has also increased significantly. Currently, integration usually uses multi-layer wiring to achieve interconnection structure to reduce line length and increase computing speed. When implementing 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, the resistivity, stability and step coverage of traditional barrier layer materials are difficult to meet the needs; metal ruthenium (Ru) has better performance in the above and is a new barrier layer material to replace Ta / TaN.

[0003] Ruthenium barrier CMP requires the simultaneous removal of barrier materials (ruthenium), dielectric materials (silicon dioxide), and wiring materials (copper) with completely different physical and chemical properties, and dishing and etch pits are important characterization parameters. The dishing on the surface is the distance from the center point of the wide-line copper recess to the dielectric on both sides; the etch pit is the distance from the center point of the thin-line dielectric recess to the dielectric on both sides. The goal of CMP is to achieve flatness. The presence of larger dishing and etch pits will inevitably lead to an uneven wafer surface, affecting the subsequent exposure lithography process.

[0004] Multilayer wiring copper CMP requires simultaneous CMP of copper, dielectric, barrier layer and other materials with completely different physical and chemical properties. Therefore, obtaining a controllable polishing rate ratio of different materials is the key to achieving lower butterfly pits and etch pits.

[0005] Wiring material copper is relatively softer than dielectric and barrier layer ruthenium, and its chemical properties are relatively active. Its CMP rate is usually faster than that of dielectric and barrier layer ruthenium. If it is not controlled, the copper wiring position will be removed more, forming pits, that is, butterfly pits. At the same time, the rate of thin lines and wide lines is different, that is, etch pits are formed. The common control method today is to use a polishing liquid containing corrosion inhibitors such as benzotriazole (BTA) to inhibit the copper rate and improve the rate selection ratio of copper to dielectric. Although BTA can effectively inhibit the corrosion of copper in butterfly pits and etch pit concave areas, BTA is a benzene ring compound with high toxicity and will pollute the environment. In addition, during the CMP process, BTA forms oxides, hydroxides, and Cu-BTA and other insoluble passivation films in butterfly pits and etch pit grooves. They have strong inertness and adhesion, and require strong mechanical action to remove, which brings great difficulties to the post-CMP cleaning and will cause residual defects on the metal surface.

[0006] Therefore, in view of this, the existing structure and defects are studied and improved, and a method for controlling butterfly pits and etch pits of ruthenium barrier layer copper wiring is provided, so as to achieve a more practical and valuable purpose. Summary of the invention

[0007] The present invention provides a method for controlling butterfly pits and etching pits of copper wiring in a ruthenium barrier layer, so as to overcome the above-mentioned defects in the prior art.

[0008] The purpose and effect of the method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring of the present invention are achieved by the following specific technical means:

[0009] A method for controlling butterfly pits and etch pits of ruthenium barrier layer copper wiring, comprising:

[0010] S1: prepare a polishing liquid containing an active agent such as a phosphate ester:

[0011] Take silica sol, add deionized water to dilute, and obtain silica sol solution; mix chelating agent, oxidant, phosphate ester, bactericide, and surfactant, dilute with deionized water, add silica sol solution, adjust to the required pH value with pH regulator, and stir to obtain polishing liquid;

[0012] S2: using the polishing liquid to polish the ruthenium barrier layer pattern sheet of the integrated circuit multilayer wiring below 14 nm under the polishing conditions;

[0013] 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.

[0014] In a further technical solution, the phosphate ester includes a mixture of one or more of monoalkyl phosphate potassium salt (MAPK) or alcohol polyoxyethylene ether phosphate and isomeric alcohol polyoxyethylene ether phosphate, wherein the carbon chain is 7-18.

[0015] According to a further technical solution, the polishing liquid further comprises silica sol, a chelating agent, an oxidant, a bactericide, a surfactant, a pH regulator and deionized water, the polishing liquid does not contain BTA or other inhibitors, and the pH value of the polishing liquid is 6.0-11.5.

[0016] According to a further technical solution, the components of the polishing liquid are, by mass percentage, 0.5-10% silica sol, 0.02-2% chelating agent, 0.02-5% oxidant, 0.001-1% phosphate, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance deionized water.

[0017] According to a further technical solution, the particle size of the silica sol is 30nm-200nm.

[0018] In a further technical solution, the chelating agent is a mixture of one or more of glycine, glycine salt, citric acid, citrate, ethylenediaminetetraacetate, etc.

[0019] In a further technical solution, the oxidant is a mixture of one or more of peroxides, transition metal salts, nitric acid and nitrates, halogen oxygen salts, etc.

[0020] 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.

[0021] In a further technical solution, the surfactant is a mixture of one or more cationic surfactants, anionic surfactants, and nonionic surfactants.

[0022] 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.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses a polishing liquid containing phosphate to polish the ruthenium barrier layer copper wiring of advanced technology node integrated circuits, and controls butterfly pits and etch pits without using toxic and carcinogenic inhibitors such as BTA. The principle is as follows:

[0025] Phosphate surfactants such as MAPK are adsorbed on the Cu surface in a chemical and physical mixed adsorption manner. The surfactant MAPK has a polar hydrophilic group and a non-polar hydrophobic group. The polar hydrophilic group of MAPK will dissociate in the solution and exist in the form of MAPK-. - It will form Cu-MAPK passivation with Cu. The passivation adheres to the Cu surface. The exposed Cu decreases, which inhibits the oxidation of Cu to a certain extent, so the surface CuO content decreases. The isoelectric point (IEP) of CuO is greater than the pH value of the solution, and it is positively charged in the solution. Due to the effects of static electricity and hydrophobic groups, MAPK - The physical adsorption of MAPK will form a dense adsorption layer on the Cu surface. Therefore, with the addition of MAPK, the removal rate and static corrosion rate of Cu decrease. At the same time, since the convex parts are subjected to greater mechanical action, there will be a difference in removal rate at the concave and convex parts, that is, the copper rate is suppressed at the butterfly pit copper wiring and the etch pit wide line, and the butterfly pit and etch pit are improved, thereby achieving surface flattening.

[0026] This patent does not use toxic and carcinogenic BTA, achieving environmentally friendly innovation in key integrated circuit materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 It is a schematic diagram of the molecular structure of phosphate MAPK;

[0029] Figure 2 Schematic diagram of the generation of butterfly pits and etch pits in CMP of multi-layer ruthenium barrier copper wiring;

[0030] Figure 3 The copper and ruthenium rates in multi-layer wiring CMP vary with MAPK content;

[0031] Figure 4 Schematic diagram of comparison of butterfly pits before and after polishing in Example 1 of the present invention;

[0032] Figure 5 This is a comparative schematic diagram of the butterfly pit before and after polishing in Comparative Example 1 of the present invention;

[0033] Figure 6 Schematic diagram of the comparison of the butterfly pits before and after polishing in comparative example 2 of the present invention.

[0034] Figure 7Schematic diagram of the principle of phosphate ester controlling butterfly pits and etching pits. DETAILED DESCRIPTION

[0035] 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.

[0036] 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.

[0037] 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.

[0038] As attached Figure 1 To Attachment Figure 7 As shown:

[0039] The invention provides a method for controlling butterfly pits and etching pits of copper wiring in a ruthenium barrier layer.

[0040] See attached Figure 1 To Attachment Figure 7 ,include:

[0041] A polishing liquid containing phosphate is prepared; and the polishing liquid is added into a polishing machine to polish the graphic sheet to obtain a finished product;

[0042] 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.

[0043] In the above embodiment, the phosphate active agent such as MAPK is adsorbed on the Cu surface by chemical and physical mixed adsorption. The surfactant MAPK has a polar hydrophilic group and a non-polar hydrophobic group. The polar hydrophilic group of MAPK will dissociate in the solution to form MAPK.- In the form of MAPK - It will form Cu-MAPK passivation with Cu. The passivation adheres to the Cu surface. The exposed Cu decreases, which inhibits the oxidation of Cu to a certain extent, so the surface CuO content decreases. The isoelectric point (IEP) of CuO is greater than the pH value of the solution, and it is positively charged in the solution. Due to the effects of static electricity and hydrophobic groups, MAPK - It is physically adsorbed on the CuO surface, inhibiting the subsequent reaction of CuO to a certain extent. Under the synergy of chemical and physical effects, MAPK will form a dense adsorption layer on the Cu surface, so with the addition of MAPK, the removal rate and static corrosion rate of Cu become smaller. At the same time, due to the greater mechanical action on the convex part, the removal rate difference will occur in the concave and convex parts, that is, the copper rate is inhibited at the butterfly pit copper wiring and the etch pit wide line, and the butterfly pit and etch pit are improved, thereby achieving surface flattening.

[0044] In some embodiments of the present invention, the phosphate ester includes monoalkyl phosphate potassium salt (MAPK) or one or more mixtures of alcohol polyoxyethylene ether phosphate ester and isomeric alcohol polyoxyethylene ether phosphate ester, wherein the carbon chain is 7-18.

[0045] In some embodiments of the present invention, the components of the polishing liquid are respectively: 0.5-10% silica sol, 0.02-2% chelating agent, 0.02-5% oxidant, 0.001-1% phosphate, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance is deionized water. The polishing liquid does not contain inhibitors such as BTA and is green and environmentally friendly.

[0046] In some embodiments of the present invention, the pH value of the polishing liquid is 6.0-11.5.

[0047] 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.

[0048] In some embodiments of the present invention, the chelating agent is a mixture of one or more of glycine, glycine salt, citric acid, citrate, ethylenediaminetetraacetate, etc. The oxidizing agent is a mixture of one or more of peroxide, transition metal salts, nitric acid and nitrate, halogen oxyacid salt, etc. The chelating agent and oxidizing agent react chemically with copper, play a chemical role in the CMP process, and are the main factors in the copper removal rate.

[0049] 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.

[0050] 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.

[0051] In some embodiments of the present invention, the preparation method of the polishing liquid comprises the following steps: taking silica sol, adding deionized water to dilute, and obtaining a silica sol solution; mixing a chelating agent, an oxidant, a phosphate ester, a bactericide, and a surfactant, and diluting the mixture with deionized water, and then adding the silica sol solution, and stirring to obtain a polishing liquid. The preparation method has a simple process, and can produce a polishing liquid with good stability, which is suitable for the needs of large-scale industrial production.

[0052] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0053] Example 1

[0054] A method for repairing D pits and etching pits by using a chelating agent in multi-layer copper wiring CMP, comprising the following steps:

[0055] Prepare 10 kg of polishing liquid: take 1% by mass of silica sol with a particle size of 80 nm, add deionized water to dilute to 5 kg, and obtain a silica sol solution; mix 2% by mass of glycine, 0.9% by mass of hydrogen peroxide, 0.9% by mass of phosphate MAPK, 0.5% by mass of fungicide and 0.6% by mass of surfactant, add deionized water to dilute to 5 kg, then add the above silica sol solution, stir evenly to obtain a polishing liquid, adjust the pH value of the polishing liquid to 7.5, and set aside;

[0056] The above phosphate is MAPK, and its molecular formula is shown in the attached Figure 1 ;

[0057] The above-mentioned fungicide is a mixture of methylisothiazolinone, kasone, potassium sorbate and benzoic acid;

[0058] The surfactant is a mixture of sodium dodecyl sulfate, dodecylbenzenesulfonic acid, and fatty acid methyl ester ethoxylate;

[0059] Polishing: Add the polishing liquid into the Universal-300Plus polishing machine produced by Huahaiqingke, and perform polishing under the conditions of working pressure Z1: 4.76Psi, Z2: 2.01Psi, Z3: 1.82Psi, Z4: 1.92Psi, Z5: 1.63Psi; polishing head speed is 98r / min; polishing disc speed is 105r / min; polishing liquid flow rate is 250ml / min.

[0060] Comparative Example 1

[0061] Compared with Example 1, the polishing liquid in Comparative Example 1 does not contain phosphate ester.

[0062] Comparative Example 2

[0063] In Comparative Example 2, compared with Example 1, the phosphate ester in the polishing liquid is replaced by BTA.

[0064] Test Example 1

[0065] Compared with Example 1, the concentration of phosphate in the polishing liquid was changed from 0% to 1.08% by mass, and a gradient test was conducted to compare the copper rate, static corrosion rate, and ruthenium barrier layer rate. The results are as follows: Figure 3 shown.

[0066] The removal rate of Cu was 1226nm / min without MAPK. The MAPK concentration had little effect on the removal rate of Cu / Ru when it was between 0 and 0.54mmol / L. When the concentration reached 0.54mmol / L, the removal rate of copper decreased rapidly with the increase of concentration. When the MAPK concentration was 0.9mmol / L, the removal rate of Cu was 511nm / min. The removal rate of Ru decreased slightly with the increase of inhibitor concentration, and the removal rate was 0.68nm / min when it reached 0.9mmol / L.

[0067] At the same time, as the MAPK concentration increases, the static corrosion rate of Cu slows down. When MAPK is not added, the static corrosion rate of Cu is 207nm / min, and when the MAPK concentration is 0.9mmol / L, the static corrosion rate of Cu is 9.4nm / min. The lower static corrosion rate can better control the depth of the dishing pits and the pits. When the MAPK concentration is 0.9mmol / L, the Cu removal rate is 511nm / min, the static corrosion rate is 9.4nm / min, and the Cu / Ru removal rate selection ratio is 752:1.

[0068] Test Example 2

[0069] The 300 mm pattern wafers were polished by the methods of Example 1, Comparative Example 1 and Comparative Example 2, respectively. After cleaning, the changes of D pits and etching pits of the wafers before and after the barrier layer polishing were measured using an atomic force microscope produced by Veeco Precision Instruments. The results are shown in Tables 1 and Figure 4-6 shown.

[0070]

[0071]

[0072] Table 1

[0073] From Table 1 and Figure 4-6 It can be seen that, since the phosphate ester is added in Example 1, the appearance of defects such as butterfly pits and etch pits is effectively suppressed, and the flattening effect is achieved. In Comparative Example 1, no phosphate ester is added, and the butterfly pits and etch pits are more serious. In Comparative Example 2, the BTA inhibitor is added, which can suppress the copper rate, improve the rate selectivity of copper and dielectric, and control the butterfly pits and etch pits to a certain extent; but it is toxic and carcinogenic. Therefore, the phosphate ester of the present invention can not only better control the butterfly pits and etch pits, but also improve the global consistency.

[0074] Its principle is as follows Figure 7 As shown in Figure 2, the surfactant MAPK has a polar hydrophilic group and a non-polar hydrophobic group. The polar hydrophilic group of MAPK will dissociate in the solution to form MAPK. - In the form of MAPK - It will form Cu-MAPK passivation with Cu. The passivation adheres to the Cu surface. The exposed Cu decreases, which inhibits the oxidation of Cu to a certain extent, so the surface CuO content decreases. The isoelectric point (IEP) of CuO is greater than the pH value of the solution, and it is positively charged in the solution. Due to the effects of static electricity and hydrophobic groups, MAPK - It is physically adsorbed on the CuO surface, inhibiting the subsequent reaction of CuO to a certain extent. Under the synergy of chemical and physical effects, MAPK will form a dense adsorption layer on the Cu surface, so with the addition of MAPK, the removal rate and static corrosion rate of Cu become smaller. At the same time, due to the greater mechanical action on the convex part, the removal rate difference will occur in the concave and convex parts, that is, the copper rate is inhibited at the butterfly pit copper wiring and the etch pit wide line, and the butterfly pit and etch pit are improved, thereby achieving surface flattening.

[0075] Therefore, the present invention provides a green and environmentally friendly method for controlling CMP butterfly pits and etch pits of ruthenium barrier layers of multi-layer wiring of integrated circuits at advanced technology nodes.

[0076] 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 controlling butterfly pits and etch pits in ruthenium barrier copper wiring, characterized in that: The following steps are involved: S1: prepare a polishing liquid containing an active agent such as a phosphate ester: Take silica sol, add deionized water to dilute, and obtain silica sol solution; mix chelating agent, oxidant, phosphate ester, bactericide, and surfactant, dilute with deionized water, add silica sol solution, adjust to the required pH value with pH regulator, and stir to obtain polishing liquid; S2: using the polishing liquid to polish the ruthenium barrier layer pattern sheet of the integrated circuit multilayer wiring 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. The method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring according to claim 1, characterized in that: The phosphate ester includes a mixture of monoalkyl phosphate potassium salt (MAPK) or alcohol polyoxyethylene ether phosphate ester and isomeric alcohol polyoxyethylene ether phosphate ester, wherein the carbon chain is 7-18.

3. The method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring according to claim 1, characterized in that: The polishing liquid also includes silica sol, chelating agent, oxidant, bactericide, surfactant, pH value regulator and deionized water. The polishing liquid does not contain BTA or other inhibitors, and the pH value of the polishing liquid is 6.0-11.

5.

4. The method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring according to claim 3, characterized in that: Calculated by mass percentage, the components of the polishing liquid are: 0.5-10% silica sol, 0.02-2% chelating agent, 0.02-5% oxidant, 0.001-1% phosphate, 0.03-2% bactericide, 0.0001-3% surfactant, and the balance deionized water.

5. The method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring according to claim 4, characterized in that: The particle size of the silica sol is 30nm-200nm.

6. The method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring according to claim 4, characterized in that: The chelating agent is a mixture of one or more of glycine, glycine salt, citric acid, citrate, ethylenediaminetetraacetate, etc.

7. The method for controlling butterfly pits and etch pits of ruthenium barrier layer copper wiring 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, halogen oxyacid salts, etc.

8. The method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring 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. The method for controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring 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 controlling butterfly pits and etching pits of ruthenium barrier layer copper wiring 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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