Composition for chemical mechanical polishing of tungsten, preparation method thereof and chemical mechanical polishing method

Abstract

The invention relates to the technical field of semiconductor manufacturing, in particular to a composition for chemical-mechanical polishing of tungsten, a preparation method of the composition and a chemical-mechanical polishing method.The composition for chemical-mechanical polishing of tungsten is prepared from grinding materials, acid, an oxidizing agent, a catalyst and a dispersing agent, the dispersing agent comprises fluorophosphonic acid diester. According to the composition, the problems of grinding material agglomeration and sedimentation are not prone to occurring, the polishing uniformity can be improved when a tungsten-containing material is polished, and scratches formed after polishing are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, in particular to a composition for chemical mechanical polishing of tungsten and a preparation method thereof and a chemical mechanical polishing method. Background Art

[0002] Chemical Mechanical Polishing / Planarization (CMP) is an important process in the field of semiconductor manufacturing, which is used to achieve global planarization of the surface of semiconductor films. With the rapid iteration of semiconductor technology and the continuous refinement of process technology, device processing has increasingly stringent requirements for the planarization of semiconductor film surfaces, which makes the key role of chemical mechanical polishing (CMP) technology in semiconductor manufacturing more and more significant.

[0003] Polishing composition (i.e., polishing liquid) is an important consumable in CMP process, which is mainly composed of three parts: abrasive, solvent, and chemical additives. The polishing liquid for metal tungsten CMP provided by the related art generally uses calcined fumed silica dispersed in water as an abrasive; compared with colloidal silica formed by a wet process, fumed silica as an abrasive has the advantages of low cost and larger specific surface area, but the stability of the colloid formed by fumed silica in water is far inferior to that of colloidal silica. The main reason is that when fumed silica is used as an abrasive, the electrostatic repulsion between particles is weak and the dispersibility is poor, so it is easy to agglomerate and settle; this is extremely unfavorable for the CMP process, and it is easy to cause problems such as poor polishing uniformity and increased scratches after polishing. Summary of the invention

[0004] The object of the present invention is to provide a composition for chemical mechanical polishing of tungsten, a preparation method thereof and a chemical mechanical polishing method. The composition for chemical mechanical polishing of tungsten of the present invention is not prone to problems of abrasive agglomeration and sedimentation, and can improve the uniformity of polishing and reduce scratches formed after polishing when polishing tungsten-containing materials; the preparation method of the present invention can ensure that the abrasive particles are effectively dispersed, and the polishing method of the present invention is simple and easy to operate, and can ensure good polishing quality.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a composition for chemical mechanical polishing of tungsten, wherein the raw materials of the composition include abrasive, acid, oxidant, catalyst, dispersant and solvent, wherein the abrasive includes fumed silica and the dispersant includes fluorophosphonic acid diester.

[0007] In an alternative embodiment, the dialkyl fluorophosphates include at least one of dimethyl fluorophosphate, diethyl fluorophosphate, and diisopropyl fluorophosphate.

[0008] In an alternative embodiment, the raw materials of the composition for chemical mechanical polishing of tungsten further include: a bactericide; and / or, the solvent includes at least one of an organic solvent and an inorganic solvent.

[0009] In an alternative embodiment, by mass percentage, the raw materials include: 0.50% - 30.00% of an abrasive, 0.10% - 2.00% of an acid, 0.50% - 5.00% of an oxidizing agent, 0.05% - 2.00% of a catalyst, 0.10% - 1.00% of a dispersant, 0.01% - 1.00% of a bactericide, 0.50% - 10.00% of an organic solvent, and the balance is an inorganic solvent.

[0010] In an alternative embodiment, the mass percentage of the dispersant is 0.30% - 0.70%.

[0011] In an alternative embodiment, the mass percentage of the dispersant is 0.50%.

[0012] In an alternative embodiment, the acid includes nitric acid; and / or,

[0013] the oxidizing agent includes hydrogen peroxide; and / or,

[0014] the catalyst includes at least one of cobalt salts and their hydrates; and / or,

[0015] the bactericide includes at least one of brominated derivatives of hydantoin; and / or,

[0016] the organic solvent includes at least one of tetrahydrofurfuryl alcohol, N,N-dimethylacetamide, diethylene glycol monomethyl ether, and γ-butyrolactone; and / or,

[0017] the inorganic solvent includes water.

[0018] In an alternative embodiment, the cobalt salts include at least one of cobalt sulfate, cobalt nitrate, and cobalt chloride.

[0019] In an alternative embodiment, the brominated derivatives of hydantoin include at least one of dibromohydantoin, dibromodimethylhydantoin, and bromochloroethylmethylhydantoin.

[0020] In a second aspect, the present invention provides a method for preparing a composition for chemical mechanical polishing of tungsten, which is used to prepare the aforementioned composition for chemical mechanical polishing of tungsten. The preparation method includes sequentially adding: an abrasive, an acid, a catalyst, a dispersant, and an oxidizing agent.

[0021] In a third aspect, the present invention provides a method for chemical mechanical polishing, comprising: performing chemical mechanical polishing with the composition for chemical mechanical polishing of tungsten according to any one of the foregoing embodiments.

[0022] The composition for chemical mechanical polishing of tungsten according to the embodiments of the present invention has the following beneficial effects: The raw materials of the composition for chemical mechanical polishing of tungsten in this embodiment include abrasive, acid, oxidant, catalyst and dispersant. Among them, the abrasive includes fumed silica, and the dispersant includes diphosphonate fluoride. Using diphosphonate fluoride, which is a non-surfactant, as a dispersant to disperse fumed silica particles as the abrasive can significantly improve the dispersibility of fumed silica abrasive, thereby reducing the surface roughness of tungsten-containing materials after polishing, improving the uniformity after polishing, and reducing the scratch defects formed after polishing; among them, the reason why fumed silica has lower stability in water than colloidal silica formed by the wet process is mainly that the number of hydroxyl groups on its surface is small and the negative charge generated by the dissociation of hydroxyl groups is small. Therefore, the electrostatic repulsive force between fumed silica abrasive particles is small. The fluorine atom of diphosphonate fluoride is extremely easy to form a hydrogen bond with the hydroxyl group generated by the solvation of the fumed silica abrasive surface. The F-H hydrogen bond is strong, so that diphosphonate fluoride is firmly grafted onto the abrasive particles. At the same time, the double-bond oxygen atom of the phosphonic acid group faces outward and is the negative charge center of the molecule, which is equivalent to strengthening the negative charge of the abrasive particle surface, thereby increasing the electrostatic repulsive force and improving the dispersibility of fumed silica abrasive, and further improving the uniformity of polishing tungsten-containing materials using the composition for chemical mechanical polishing of tungsten provided by the embodiments of the present invention, and reducing the formation of scratches.

[0023] Moreover, the acid in the composition for chemical mechanical polishing of tungsten can be used to adjust the pH value of the composition and provide conditions for the chemical reaction of tungsten to ensure that a chemical reaction is reliably formed during the chemical mechanical polishing of tungsten-containing materials, thereby improving the efficiency of chemical mechanical polishing.

[0024] The oxidant can chemically react with tungsten under the action of the catalyst to oxidize tungsten into products such as tungsten oxide, forming a soft and loose film layer, so that under the grinding action of the abrasive, the formed loose film can be reliably ground off, that is, to ensure the efficiency and reliability of grinding and polishing. Specifically, the role of the catalyst is to catalyze the oxidant to undergo a Fenton reaction (Fenton reaction) to generate strongly oxidizing free radicals, and enable the free radicals to react with tungsten to form a soft and loose reactant film layer to ensure that the film layer can be efficiently and reliably removed by the abrasive.

[0025] The beneficial effects of the preparation method of the composition for chemical mechanical polishing of tungsten according to the embodiments of the present invention include: Adding the dispersant in a later order can improve the evenness of abrasive dispersion.

[0026] The method of chemical mechanical polishing according to the embodiments of the present invention has the following beneficial effects: The method of chemical mechanical polishing provided by the embodiments of the present invention uses the aforementioned composition for chemical mechanical polishing of tungsten as the working fluid (i.e., polishing fluid), which can effectively improve the polishing uniformity and reduce the scratches formed after polishing; moreover, this polishing method is simple and easy to operate. Detailed Embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0028] When fumed silica is used as the abrasive in the existing polishing fluid, the electrostatic repulsion between particles is weak, the dispersibility is poor, and problems such as agglomeration and sedimentation are likely to occur, affecting the polishing uniformity and effect. In the related art, a dispersant is added to the polishing fluid to improve the dispersibility of the abrasive.

[0029] The inventors have found through research that the dispersants used in the tungsten chemical mechanical polishing compositions provided by the related art usually include various different anionic and cationic surfactants, such as: lauryl sulfate, alkyl polyphosphate, dodecylbenzenesulfonate, diisopropylnaphthalenesulfonate, dioctyl sulfosuccinate, ethoxylated and sulfated lauryl alcohol, ethoxylated and sulfated alkylphenol, polyethyleneimine, ethoxylated fatty amine, and stearylbenzyl dimethyl ammonium chloride or stearylbenzyl dimethyl ammonium nitrate, polyethylene glycol, lecithin, polyvinylpyrrolidone, polyoxyethylene, isooctyl phenyl ether, polyoxyethylene nonyl phenyl ether, amine salts of alkyl aryl sulfonate esters, polyacrylate and related salts, polymethacrylate, etc.; the principle of these surfactants as dispersants is to reduce the interfacial energy of the abrasive particles or to generate steric hindrance by the adsorption of polymers on the abrasive grains to achieve reduction of agglomeration and improvement of the dispersion effect. However, the surfactants provided as dispersants in the related art have limited effect in reducing the interfacial energy, and the polymer adsorption is likely to generate a viscous bridge, which instead inhibits the further dispersion of the abrasive grains, especially it is difficult to disperse fumed silica as the abrasive.

[0030] To improve the above problems, the present disclosure provides a composition for chemical mechanical polishing of tungsten. The raw materials of the composition include an abrasive, an acid, an oxidant, a catalyst, a dispersant, a bactericide, an organic solvent, and an inorganic solvent. Among them, the abrasive includes fumed silica, and the dispersant includes diphosphonate fluoride.

[0031] Using a phosphonic acid difluoride ester as a non-surfactant dispersant to disperse fumed silica particles as an abrasive can significantly improve the dispersibility of the fumed silica abrasive, thereby reducing the surface roughness of tungsten-containing materials after polishing, improving the uniformity after polishing, and reducing scratch defects formed after polishing. Among them, the reason why fumed silica has lower stability in water than colloidal silica formed by the wet process is mainly that the number of hydroxyl groups on its surface is small and the negative charges generated by the dissociation of hydroxyl groups are few. Therefore, the electrostatic repulsion force between fumed silica abrasive particles is small. The fluorine atoms of the phosphonic acid difluoride ester are extremely easy to form hydrogen bonds with the hydroxyl groups generated by the solvation on the surface of the fumed silica abrasive. The F-H hydrogen bond is strong, so the phosphonic acid difluoride ester is firmly grafted onto the abrasive particles. At the same time, the double-bond oxygen atoms of the phosphonic acid group face outward. The double-bond oxygen atoms of the phosphonic acid group are the negative charge centers of the molecule, which is equivalent to strengthening the negative charge on the surface of the abrasive particles, thereby increasing the electrostatic repulsion force and improving the dispersibility of the fumed silica abrasive, and further improving the uniformity of polishing tungsten-containing materials using the composition for chemical mechanical polishing of tungsten provided by the embodiments of the present invention, and reducing the formation of scratches.

[0032] Moreover, the acid in the composition for chemical mechanical polishing of tungsten can be used to adjust the pH value of the composition and provide conditions for the chemical reaction of tungsten to ensure that a chemical reaction is reliably formed during the chemical mechanical polishing of tungsten-containing materials, thereby improving the efficiency of chemical mechanical polishing.

[0033] The oxidant can chemically react with tungsten under the action of a catalyst to oxidize tungsten into products such as tungsten oxide, forming a soft and loose film layer, so that under the grinding action of the abrasive, the formed loose film can be reliably ground off, that is, to ensure the efficiency and reliability of grinding and polishing. Specifically, the role of the catalyst is to catalyze the oxidant to undergo a Fenton reaction to generate strongly oxidizing free radicals, and enable the free radicals to react with tungsten to form a soft and loose reactant film layer to ensure that the film layer can be efficiently and reliably removed by the abrasive.

[0034] The inventors have found through research that the polishing liquids provided by the related technologies are neutral or alkaline. The components in the neutral or alkaline polishing liquids are not conducive to the survival of microorganisms, that is, generally not many microorganisms will be generated, so there is no need to add a bactericide additionally. However, microorganisms usually like acidity. If the polishing liquid is acidic, it is easy to breed microorganisms, especially in high-temperature environments such as summer, the acidic polishing liquid is extremely prone to mildew. In order to reduce the breeding of microorganisms such as bacteria and fungi in the composition of the present disclosure to improve the problem that the composition is prone to mildew (especially effectively improving the problem of mildew of the composition under the working conditions of high temperature in summer), thereby improving the problems of reduction of the effective components in the composition and reduction of the polishing efficiency, a bactericide is added to the composition of the present disclosure.

[0035] Of course, in other embodiments, a bactericide may not be added, and other methods may be used to sterilize the composition.

[0036] In some embodiments, the solvent includes at least one of an organic solvent and an inorganic solvent, that is, the solvent may include an organic solvent and an inorganic solvent. In other embodiments, an organic solvent or an inorganic solvent may be selected alternatively.

[0037] The use of an organic solvent can ensure the effective dissolution of the dispersant to ensure the dispersibility in the composition system, thereby improving the uniformity of chemical mechanical polishing of tungsten-containing materials using the composition, reducing the generation of scratches, and improving the polishing efficiency.

[0038] The use of an inorganic solvent can ensure the effective dissolution and dispersion of other components in the composition except the dispersant and the abrasive to form a composition (i.e., polishing liquid) in which the raw materials are uniformly dispersed. At the same time, as a fluid carrier, the inorganic solvent can reliably carry the abrasive and other raw materials to flow on the surface of the tungsten-containing material to be polished when using the composition for chemical mechanical polishing of the tungsten-containing material, so as to ensure the reliability and efficiency of chemical mechanical polishing.

[0039] Optionally, calculated by mass percentage, the composition raw materials include: 0.50% - 30.00% of abrasive (for example: 0.50%, 1.00%, 5.00%, 10.00%, 15.00%, 20.00%, 25.00%, 30.00%, etc., not specifically limited here), 0.10% - 2.00% of acid (for example: 0.10%, 0.50%, 1.00%, 1.50%, 2.00%, etc., not specifically limited here), 0.50% - 5.00% of oxidant (for example: 0.50%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, 3.50%, 4.00%, 4.50%, etc., not specifically limited here), 0.05% - 2.00% of catalyst (for example: 0.05%, 0.10%, 0.20%, 0.50%, 1.00%, 1.50%, 2.00%, etc., not specifically limited here), 0.10% - 1.00% of dispersant (for example: 0.10%, 0.20%, 0.50%, 0.70%, 1.00%, etc., not specifically limited here), 0.01% - 1.00% of bactericide (for example: 0.01%, 0.05%, 0.10%, 0.20%, 0.50%, 0.70%, 1.00%, etc., not specifically limited here), 0.50% - 10.00% of organic solvent (for example: 0.50%, 1.00%, 2.00%, 5.00%, 7.00%, 10.00%, etc., not specifically limited here), and the balance is inorganic solvent.

[0040] The inventors' research found that the roughness after polishing is highly positively correlated with the abrasive content in the composition, that is, the higher the abrasive content, the greater the roughness after polishing, and the tungsten removal rate is also positively correlated with the abrasive content. Therefore, in order to ensure the tungsten removal rate and avoid excessive roughness after polishing, the mass percentage of abrasive grains is controlled to be 0.50% - 30.00%.

[0041] If the mass percentage of acid in the composition is less than 0.10%, it is difficult to reliably provide a chemical reaction environment for tungsten. If the mass percentage of acid is greater than 2.00%, a dense passivation layer will form on the surface of tungsten, making it difficult to reliably remove tungsten.

[0042] If the mass percentage of the oxidant is less than 0.50%, it is difficult to effectively form a soft and loose film layer with tungsten under the action of the catalyst, and thus it is difficult to ensure the reliability of chemical mechanical polishing. If the content of the oxidant is higher than 5.00%, it will accelerate the oxidation of tungsten. While forming some soft and loose film layers, a dense oxide layer will also be formed. The dense oxide layer has a high hardness, increasing the difficulty of mechanical removal, that is, the mechanical action cannot effectively remove the oxide layer, and the polishing process will become inefficient or even stagnant. Moreover, problems such as local over-polishing, ineffective polishing in some areas, reduced polishing uniformity, and increased surface roughness are likely to occur.

[0043] If the mass percentage of the catalyst is less than 0.50%, the catalytic efficiency is low, and it is difficult to improve the polishing efficiency. If the mass percentage of the catalyst is higher than 2.00%, there is a problem of cost waste.

[0044] If the mass percentage of the dispersant is less than 0.10%, it is difficult to reliably disperse the abrasive grains. If the mass percentage of the dispersant is higher than 1.00%, the large particles in the composition will instead increase, which is not conducive to the development of polishing and is likely to cause more scratches during polishing.

[0045] If the mass percentage of the bactericide is less than 0.01%, it is difficult to achieve effective sterilization. If the mass percentage of the bactericide is higher than 1.00%, there is a problem of cost waste.

[0046] If the mass percentage of the organic solvent is less than 0.50%, it is difficult to effectively assist the dispersant to ensure that the abrasive grains are evenly and reliably dispersed in the composition system. If the mass percentage of the organic solvent is higher than 10.00%, there is a problem of cost waste.

[0047] Optionally, the phosphonofluoridate diester includes at least one of dimethyl phosphonofluoridate, diethyl phosphonofluoridate, and diisopropyl phosphonofluoridate, that is, the dispersant may include one or more of dimethyl phosphonofluoridate, diethyl phosphonofluoridate, and diisopropyl phosphonofluoridate. Compared with the dispersants in the prior art, dimethyl phosphonofluoridate, diethyl phosphonofluoridate, and diisopropyl phosphonofluoridate, which are all phosphonofluoridate diester compounds, can all reduce the concentration of large particles, that is, they can all effectively disperse the abrasive grains in the composition and improve the polishing effect. Further, the inventors have found through research that among the above-mentioned phosphonofluoridate diester compounds, the order of the amplitude of reducing the concentration of large particles is dimethyl phosphonofluoridate > diethyl phosphonofluoridate > diisopropyl phosphonofluoridate; that is, dimethyl phosphonofluoridate has a better dispersion effect, and dimethyl phosphonofluoridate is preferably used as the dispersant in the present invention.

[0048] Optionally, the mass percentage of the dispersant is 0.30% - 0.70%. Optimizing the concentration of the dispersant is beneficial to ensuring the effective dispersion of the abrasive grains in the composition and more reliably improving the phenomenon that the concentration of large particles in the composition does not decrease but increases instead.

[0049] Optionally, the mass percentage of the dispersant is 0.50%; in this way, when the mass percentage of the abrasive grains is in the range of 0.50% - 30.00%, the uniform dispersion of the abrasive grains can be ensured, and the phenomenon that the concentration of large particles in the composition does not decrease but increases instead can be effectively avoided.

[0050] Optionally, the acid includes nitric acid. On the one hand, nitric acid can provide an acidic environment, and on the other hand, it can assist in oxidizing the tungsten film layer.

[0051] Optionally, the oxidant includes hydrogen peroxide. Hydrogen peroxide can reliably undergo the Fenton reaction under the action of a catalyst to generate free radicals with strong oxidizing properties, and its oxidation effect is strong and controllable.

[0052] Optionally, the catalyst includes at least one of cobalt salts and their hydrates. Using cobalt salts and / or hydrates of cobalt salts as the catalyst can ensure the reliable occurrence of the Fenton reaction to generate free radicals with strong oxidizing properties, so that the generated free radicals can effectively react with tungsten to form a soft reactant film layer, ensuring the effective removal of these film layers during the mechanical polishing process and ensuring a good polishing effect. Moreover, the catalytic effect of cobalt salts and / or hydrates of cobalt salts is stable, remarkable, and controllable.

[0053] Optionally, the cobalt salt includes at least one of cobalt sulfate, cobalt nitrate, and cobalt chloride.

[0054] Optionally, the bactericide includes at least one of brominated derivatives of hydantoin, where the brominated derivatives of hydantoin include bromohydantoin and its derivatives. The above-mentioned bactericides have prominent bactericidal effects, a wide range, and will not cause adverse effects on the polishing process.

[0055] Optionally, the brominated derivatives of hydantoin include at least one of dibromohydantoin, dibromodimethylhydantoin, and bromochloroethylmethylhydantoin.

[0056] Optionally, the organic solvent includes at least one of tetrahydrofurfuryl alcohol, N,N-dimethylacetamide, diethylene glycol monomethyl ether, and γ-butyrolactone. The fluorophosphonic acid diester has poor water solubility as a dispersant. Therefore, according to the principle of like dissolves like, selecting the above organic solvents can ensure the reliable dissolution of the dispersant, and the above organic solvents can be miscible with water in any proportion, which can ensure that the composition of the present disclosure can be dissolved more uniformly and fully.

[0057] Optionally, the inorganic solvent includes water, specifically deionized water.

[0058] The present disclosure also provides a chemical mechanical polishing method, which uses the composition for chemical mechanical polishing of tungsten in the above embodiments for chemical mechanical polishing.

[0059] In some specific examples, the method includes: controlling the down pressure to be 1.8 psi to 2.2 psi (for example: 1.8 psi, 2.0 psi, 2.2 psi, etc., which are not specifically limited here) during polishing, controlling the flow rate of the working fluid to be 200 mL / min - 300 mL / min (for example: 200 mL / min, 220 mL / min, 250 mL / min, 270 mL / min, 300 mL / min, etc., which are not specifically limited here), controlling the rotation speed of the polishing pad to be 90 rpm to 100 rpm (for example: 90 rpm, 93 rpm, 96 rpm, 100 rpm, etc., which are not specifically limited here), and controlling the rotation speed of the polishing head to be 80 rpm - 90 rpm (for example: 80 rpm, 83 rpm, 85 rpm, 87 rpm, 90 rpm, etc., which are not specifically limited here); wherein, the working fluid includes the composition for chemical mechanical polishing of tungsten described above.

[0060] The present disclosure also provides a preparation method for a composition for chemical mechanical polishing of tungsten. The preparation method is used to prepare the composition for chemical mechanical polishing of tungsten in the above embodiments, and it includes adding in sequence: abrasive, acid, catalyst, dispersant, oxidant.

[0061] In some embodiments, the composition for chemical mechanical polishing of tungsten further includes a bactericide, and the solvent includes an organic solvent and an inorganic solvent. The preparation method for the composition for chemical mechanical polishing of tungsten of the present disclosure includes adding in sequence: inorganic solvent, abrasive, acid, catalyst, organic solvent, dispersant, bactericide, oxidant. Adding the dispersant in a later order in this preparation method can improve the uniformity of the dispersion of the abrasive.

[0062] The chemical mechanical polishing method of the present disclosure uses the aforementioned composition for chemical mechanical polishing of tungsten as the working fluid (i.e., polishing fluid), which can effectively improve the polishing uniformity and reduce the scratches formed after polishing; moreover, this polishing method is simple and easy to operate.

[0063] Moreover, by controlling the down pressure, the flow rate of the working fluid, the rotation speed of the polishing pad, and the rotation speed of the polishing head, on the one hand, it can ensure high efficiency and high quality of polishing, and on the other hand, it can avoid forming polishing damage. Among them, too large a down pressure is likely to increase scratches, too small a down pressure is likely to lead to a decrease in polishing efficiency, too large a flow rate of the working fluid is likely to cause waste, too small a flow rate of the working fluid is difficult to ensure polishing efficiency, too fast rotation speeds of the polishing pad and the polishing head are likely to cause slippage (i.e., the polished wafer is likely to slip out of the polishing head), and too slow rotation speeds result in too low polishing efficiency.

[0064] The following further describes the present invention in detail with reference to embodiments.

[0065] Prepare the polishing fluids (i.e., the compositions for chemical mechanical polishing of tungsten) of each example and comparative example according to the formula in Table 1; among them, the average particle size of the abrasive grains is 150 nm of fumed silica. The raw material addition order of the polishing fluid is: inorganic solvent, abrasive, acid, catalyst, organic solvent, dispersant, bactericide, oxidant. Each raw material is a commercially available product, and the purity is above analytical pure; Comparative Examples 5-9 use surfactant-type dispersants as a control. Several dispersants are anionic surfactant (sodium dodecyl sulfate), cationic surfactant (polyethyleneimine), non-ionic surfactants (polyethylene glycol, polyvinylpyrrolidone, hydroxyethyl cellulose).

[0066] Table 1

[0067]

[0068]

[0069] Characterize the abrasive grain dispersibility of each example and comparative example:

[0070] Use the AccuSizer FX-Nano particle size analyzer of PSS Company in the United States to test the large particle concentration (particles with a particle size greater than 0.56 μm are regarded as large particles) of the composition after preparation and standing at normal temperature and pressure for 7 days. The large particles in the composition mainly come from agglomerated abrasive particles. Therefore, the large particle concentration can reflect the abrasive dispersibility of the polishing composition. The larger its value, the worse the dispersibility of the abrasive particles; the characterization results are shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] It should be noted that since the concentration of large particles is highly positively correlated with the abrasive content in the composition, that is, the higher the abrasive content, the greater the large particle concentration. Therefore, when comparing the effects of dispersants, it is compared under the same abrasive content.

[0075] From the comparison of the characterization results of Comparative Example 1 and Examples 1-4, Comparative Example 2 and Example 5, Comparative Example 3 and Example 6, and Comparative Example 4 and Examples 7-9, it can be seen that the addition of diphosphonate fluoride as a dispersant can significantly reduce the large particle concentration in the composition, indicating that the dispersibility of abrasive particles is improved; and at multiple abrasive contents, dimethyl diphosphonate can significantly reduce the large particle concentration.

[0076] Among them, from the comparison of the characterization results of Comparative Example 1 and Example 1, it can be seen that Example 1 with diphosphonate fluoride added as a dispersant can obviously reduce the large particle concentration more effectively than Comparative Example 1 without diphosphonate fluoride added.

[0077] From the comparison of the characterization results of Examples 1, 2, 3, and 4, it can be seen that as the mass fraction of dimethyl diphosphonate increases (the mass fraction of dimethyl diphosphonate gradually increases in Examples 1, 2, and 3), the large particle concentration in the composition first decreases and then increases. The mass fraction of dimethyl diphosphonate in Example 3 is 0.50%, and the large particle concentration is the smallest. That is, when the mass fraction of dimethyl diphosphonate gradually increases to 0.50%, the large particle concentration in the characterization results gradually decreases. When the mass fraction of dimethyl diphosphonate further increases from 0.50%, the large particle concentration in the characterization results gradually increases again. For example, when the mass fraction of dimethyl diphosphonate in Example 4 reaches 1.00%, the large particle concentration gradually increases again.

[0078] At the same time, by comparing the characterization results of Example 5 and Comparative Example 2, and comparing the characterization results of Example 6 and Comparative Example 3, it can be seen that when the mass fraction of dimethyl diphosphonate is 0.50%, the large particle concentration can be significantly reduced.

[0079] From the comparison of the characterization results of Examples 7, 8, 9 and Comparative Example 4, it can be seen that dimethyl diphosphonate (Example 7), diethyl diphosphonate (Example 8), and diisopropyl fluorophosphate (Example 9), all of which are diphosphonate fluoride compounds, have the effect of reducing the large particle concentration. The amplitude of reducing the large particle concentration is: dimethyl diphosphonate > diethyl diphosphonate > diisopropyl fluorophosphate. That is, dimethyl diphosphonate can more significantly reduce the large particles, and it is a more preferred dispersant.

[0080] From the comparison of the characterization results of Comparative Examples 5-9 and Examples 7-9, it can be seen that in terms of reducing the concentration of large particles, the phosphonofluoridate dispersants of Examples 7-9 are superior to the conventional surfactant-type dispersants such as sodium dodecyl sulfate in Comparative Example 5, polyethyleneimine in Comparative Example 6, polyethylene glycol in Comparative Example 7, polyvinylpyrrolidone in Comparative Example 8, and hydroxyethyl cellulose in Comparative Example 9.

[0081] The polishing comparison was carried out using the polishing slurries of each example and comparative example: an Applied Materials Reflexion LK 12-inch polishing machine was used, the polishing pad was DuPont IC1000, and the diamond disk was Saesol C4. The specific polishing process parameters were: a down pressure of 2.0 psi, a working fluid flow rate of 250 mL / min, a polishing disk rotation speed of 93 rpm, a polishing head rotation speed of 87 rpm, and a polishing time of 1 min. The composition prepared and allowed to stand at normal temperature and pressure for 7 days was used as the polishing slurry for chemical mechanical polishing testing. A 12-inch tungsten wafer purchased from Silicon Valley Microelectronics, USA was used during polishing, and its tungsten layer thickness was

[0082] Testing of the polishing results:

[0083] The film thickness of the tungsten wafer before and after polishing was measured using a RT-30 four-probe film thickness gauge from Napson, Japan. The removal rate was calculated by dividing the difference in film thickness before and after polishing by the time. The RMS (root mean square) value of the surface roughness of a 5 μm × 5 μm area at the center point (Center), midpoint of the radius (Middle), and edge position (Edge) of the tungsten wafer surface after polishing was measured using an NX-20 atomic force microscope from Park, Korea. Five points (1 Center, 2 Middle, 2 Edge) were measured along the diameter of each wafer, and the average value was taken as the final roughness result. The number of scratches on the polished wafer was detected using a Surfscan SP2 wafer defect detection system from KLA, USA.

[0084] The test results are shown in Table 3.

[0085] Table 3

[0086]

[0087]

[0088] From the comparison of the test results between Comparative Example 1 and Examples 1-4, Comparative Example 2 and Example 5, Comparative Example 3 and Example 6, and Comparative Example 4 and Examples 7-9, it can be seen that the addition of the diphosphonate ester dispersant can significantly reduce the roughness after polishing, reduce the number of scratches, and has little effect on the tungsten removal rate; and in the case of multiple abrasive contents, the composition added with dimethyl diphosphonate can significantly reduce the roughness.

[0089] Among them, by comparing the polishing results of Example 1 and Comparative Example 1, it can be seen that adding a diphosphonate ester as a dispersant can reduce the roughness of polishing and reduce the scratches formed during polishing.

[0090] By comparing the polishing results of Examples 1, 2, 3, and 4, it can be seen that as the mass fraction of dimethyl diphosphonate increases (the mass fraction of dimethyl diphosphonate gradually increases in Examples 1, 2, and 3), the roughness after polishing first decreases and then increases. The mass fraction of dimethyl diphosphonate in Example 3 is 0.50%, and the roughness after polishing reaches the lowest point, that is, when the mass fraction of dimethyl diphosphonate gradually increases to 0.50%, the roughness of polishing gradually decreases; when the mass fraction of dimethyl diphosphonate increases from 0.50% to 1.00%, the roughness increases instead and the tungsten removal rate decreases significantly. At this time, there is a possibility that dimethyl diphosphonate is in excess, which not only causes a certain increase in roughness but also has a certain inhibition on the polishing of tungsten. For example, when the mass fraction of dimethyl diphosphonate in Example 4 reaches 1.00%, the roughness of polishing increases and the polishing is inhibited to a certain extent. Therefore, the preferred content of dimethyl diphosphonate is 0.50%.

[0091] By comparing the polishing results of Examples 7-9 and Comparative Example 4, it can be seen that dimethyl diphosphonate (Example 7), diethyl diphosphonate (Example 8), and diisopropyl fluorophosphate (Example 9), which are all diphosphonate ester compounds, all have the effect of reducing the roughness after polishing, and the reduction amplitude is dimethyl diphosphonate > diethyl diphosphonate > diisopropyl fluorophosphate, indicating that dimethyl diphosphonate is a more preferred dispersant.

[0092] By comparing the polishing results of Comparative Examples 5-9 and Examples 7-9, it can be seen that in terms of reducing the roughness after polishing, the diphosphonate ester dispersants in Examples 7-9 are superior to conventional dispersants such as sodium dodecyl sulfate in Comparative Example 5, polyethyleneimine in Comparative Example 6, polyethylene glycol in Comparative Example 7, polyvinylpyrrolidone in Comparative Example 8, and hydroxyethyl cellulose in Comparative Example 9.

[0093] From the comparison of the test results of Examples 4-7 and Comparative Examples 1-4, it can be seen that in polishing compositions with different abrasive mass fractions, the degree of improvement of dimethyl fluorophosphonate on the roughness after polishing is also different. The larger the abrasive mass fraction in the composition, the worse the dispersion of the abrasive particles. That is, the abrasive addition amounts of Examples 4, 5, 6, and 7 gradually decrease, and the dispersion becomes gradually better. The roughness after polishing is larger when no dispersant is added (Comparative Examples 1-4). That is, the abrasive proportion in Comparative Example 1 is the largest at 30%, and the roughness after polishing in Comparative Example 1 is the largest. The more significant the improvement of dimethyl fluorophosphonate on the dispersion of a large number of abrasive grains. That is, the mass percentage of the abrasive in Example 4 is 30.00%. Example 4 significantly reduces the roughness after polishing by adding a dispersant. That is, when the abrasive mass fraction is 30%, dimethyl fluorophosphonate can reduce the roughness after polishing by about 75%. When the abrasive mass fraction drops to a lower value of 5% (corresponding to the comparison of Example 7 and Comparative Example 4), dimethyl fluorophosphonate can still reduce the roughness by about 18%.

[0094] Regarding the test results shown in Table 3, it should be noted that since the roughness after polishing is highly positively correlated with the abrasive content in the composition, that is, the higher the abrasive content, the larger the roughness after polishing. Therefore, when comparing the improvement effect of the dispersant on the roughness after polishing, it is compared under the same abrasive content. Similarly, the tungsten removal rate is also positively correlated with the abrasive content. The tungsten removal rates listed in the table are only for illustration, whether adding this dispersant under the same abrasive content will cause a change in the original tungsten removal rate, and there is no other meaning. On the contrary, it is meaningless to compare whether the addition of the dispersant will affect the tungsten removal rate between compositions with different abrasive contents.

[0095] In summary, the composition for chemical mechanical polishing of tungsten of the present invention is not prone to problems such as abrasive agglomeration and sedimentation, can improve the polishing uniformity when polishing tungsten-containing materials, and reduce the scratches formed after polishing. The preparation method of the present invention can ensure the effective dispersion of abrasive grains, and the polishing method of the present invention is simple, easy to operate, and can ensure good polishing quality.

[0096] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composition for chemical mechanical polishing of tungsten, characterized in that, The raw materials of the composition include an abrasive, an acid, an oxidizing agent, a catalyst, a dispersant, and a solvent. Among them, the abrasive includes fumed silica, and the dispersant includes a fluorophosphonic acid diester.

2. The composition for chemical mechanical polishing of tungsten according to claim 1, wherein The fluorophosphonic acid diester includes at least one of dimethyl fluorophosphonate, diethyl fluorophosphonate, and diisopropyl fluorophosphonate.

3. The composition for chemical mechanical polishing of tungsten according to claim 1, characterized in that, The raw materials of the composition for chemical mechanical polishing of tungsten further include: a bactericide; and / or The solvent includes at least one of an organic solvent and an inorganic solvent.

4. The composition for chemical mechanical polishing of tungsten according to claim 3, wherein The raw materials of the composition include the abrasive, the acid, the oxidizing agent, the catalyst, the dispersant, the bactericide, the organic solvent, and the inorganic solvent, and by mass percentage, it includes: 0.50% - 30.00% of the abrasive, 0.10% - 2.00% of the acid, 0.50% - 5.00% of the oxidizing agent, 0.05% - 2.00% of the catalyst, 0.10% - 1.00% of the dispersant, 0.01% - 1.00% of the bactericide, 0.50% - 10.00% of the organic solvent, and the balance is the inorganic solvent.

5. The composition for chemical mechanical polishing of tungsten according to claim 4, characterized in that, The mass percentage of the dispersant is 0.30% - 0.70%.

6. The composition for chemical mechanical polishing of tungsten according to any one of claims 1-5, characterized in that, The acid includes nitric acid; and / or The oxidizing agent includes hydrogen peroxide; and / or The catalyst includes at least one of cobalt salts and their hydrates, and the cobalt salts include at least one of cobalt sulfate, cobalt nitrate, and cobalt chloride.

7. The composition for chemical mechanical polishing of tungsten according to any one of claims 3-5, characterized in that, The bactericide includes a brominated derivative of hydantoin; and / or The organic solvent includes at least one of tetrahydrofurfuryl alcohol, N,N-dimethylacetamide, diethylene glycol monomethyl ether, and γ-butyrolactone; and / or The inorganic solvent includes water.

8. The composition for chemical mechanical polishing of tungsten according to claim 7, characterized in that, The brominated derivative of hydantoin includes at least one of dibromohydantoin, dibromodimethylhydantoin, and bromochloroethylmethylhydantoin.

9. A method for preparing a composition for chemical mechanical polishing of tungsten, characterized in that, The preparation method is used to prepare the composition for chemical mechanical polishing of tungsten according to any one of claims 1 - 8, which includes adding successively: an abrasive, an acid, a catalyst, a dispersant, and an oxidizing agent.

10. A method for chemical mechanical polishing, characterized in that, It includes: Performing chemical mechanical polishing with the composition for chemical mechanical polishing of tungsten according to any one of claims 1 - 8.

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