A tungsten chemical mechanical polishing liquid for reducing the EOE phenomenon and its application

Abstract

The present invention discloses a tungsten chemical mechanical polishing liquid for reducing the EOE phenomenon and its application. The tungsten polishing liquid comprises silica abrasive, iron salt catalyst, oxidant, stabilizer, block copolymer and water. The block copolymer in the present invention is copolymerized from two substances with specific structures. By using this block copolymer, the EOE phenomenon in tungsten polishing can be reduced and the polishing surface quality can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical polishing, and particularly relates to a tungsten chemical mechanical polishing liquid for reducing the EOE phenomenon and its application. Background Art

[0002] With the gradual reduction of the size of semiconductor devices and the continuous increase in the number of metal layers, the chemical mechanical polishing technology for metal layers and insulating dielectric layers has become particularly crucial.

[0003] As one of the objects of chemical mechanical polishing (CMP), tungsten metal has strong anti-electron migration ability under high current density, excellent hole filling ability, and can form a good ohmic contact with silicon. Therefore, it can be used as the filling metal and diffusion barrier layer for contact windows and via holes.

[0004] Edge-Over-Erosion (also known as Fang) is a common phenomenon in the tungsten CMP process. It refers to the phenomenon that during the polishing of a patterned wafer, the over-polishing at the pattern edge is much larger than other positions, resulting in a serious depression in this area. With the reduction of device size, in more advanced applications (such as 65nm and above), the performance requirements for CMP become more stringent. Nowadays, reducing or even eliminating EOE is a major concern in the CMP industry, but few studies on this phenomenon have been published.

[0005] Therefore, a new tungsten chemical mechanical polishing liquid is needed, which can reduce the EOE phenomenon, avoid obvious depressions at the pattern edge, thereby achieving flat polishing of the wafer and improving the surface quality. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies of the prior art and provide a new tungsten chemical mechanical polishing liquid, which can reduce the EOE phenomenon in the polishing of tungsten pattern wafers, achieve flat polishing of the wafer, and thus greatly improve the surface quality.

[0007] Another object of the present invention is to provide the application of this tungsten chemical mechanical polishing liquid in tungsten chemical mechanical polishing.

[0008] To achieve the above invention objects, the present invention adopts the following technical solutions:

[0009] A tungsten chemical mechanical polishing liquid for reducing the EOE phenomenon, comprising silica abrasive, iron salt catalyst, oxidant, stabilizer, block copolymer and water; wherein, the block copolymer Object is a diblock copolymer A-co-B.

[0010] In a preferred embodiment, based on mass percentage, the tungsten chemical mechanical polishing liquid comprises 1-10% of silica abrasive, 0.001-0.1% of iron salt catalyst, 1.5-2.5% of oxidant, 0.01-0.2% of stabilizer, 0.005-0.2% of block copolymer, and the balance is water.

[0011] In a more preferred embodiment, based on mass percentage, the tungsten chemical mechanical polishing liquid comprises 1-5% of silica abrasive, 0.01-0.1% of iron salt catalyst, 2.0% of oxidant, 0.05-0.2% of stabilizer, 0.01-0.2% of block copolymer, and the balance is water.

[0012] In a specific embodiment, the A polymer segment in the diblock copolymer A-co-B comprises a polycarboxyl or polyhydroxy structure. Preferably, the A polymer segment is any one of polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethylene glycol dicarboxylic acid, polyglycolic acid, polyglutamic acid, polylactic acid-glycolic acid, polyacrylic acid, polylactic acid, polycaprolactone, and dextran, etc.; the B polymer segment in the diblock copolymer A-co-B contains an amino structure, and the N atom therein is sp 3 hybridized. Preferably, the B polymer segment is any one of polyethyleneimine, polyacrylamide, polyhistidine, polylysine, and polyarginine, etc.

[0013] In a preferred embodiment, the diblock copolymer A-co-B can be selected from polyethylene glycol-co-polyethyleneimine, polypropylene glycol-co-polyacrylamide, polyvinyl alcohol-co-polyethyleneimine, polyethylene glycol dicarboxylic acid-co-polyhistidine, polyglycolic acid-co-polyacrylamide, polyglutamic acid-co-polyhistidine, polylactic acid-glycolic acid-co-polylysine, polyethylene glycol-co-polylysine, polylactic acid-co-polyethyleneimine, dextran-co-polyethyleneimine, polycaprolactone-co-polyarginine, polyacrylic acid-co-polylysine, etc., but the copolymer A-co-B is not limited to the above combinations.

[0014] In a specific embodiment, the silica abrasive is silica sol or fumed silica. Preferably, the silica abrasive is silica sol.

[0015] In a specific embodiment, the iron salt catalyst is an iron salt that can ionize iron ions in an aqueous solution. The anion of the iron salt is not limited and can be an organic anion such as citrate, oxalate, gluconate, phthalate, etc., or an inorganic anion such as nitrate, sulfate, etc.; the iron salt is preferably ferric nitrate.

[0016] In a specific embodiment, the stabilizer is an organic acid. Preferably, the organic acid is selected from one or more of oxalic acid, malonic acid, succinic acid, citric acid, and tartaric acid, and more preferably malonic acid.

[0017] In a specific embodiment, the oxidant is hydrogen peroxide; preferably, the pH of the tungsten chemical mechanical polishing liquid is 2.0 - 2.5.

[0018] On the other hand of the present invention, there is the application of the aforementioned tungsten chemical mechanical polishing liquid in tungsten chemical mechanical polishing.

[0019] By adopting the above technical solutions, the present invention can obtain the following beneficial effects:

[0020] 1) A diblock copolymer A-co-B is added to the tungsten chemical mechanical polishing liquid of the present invention. The two ends of the diblock copolymer are adsorbed on the surfaces of silica and tungsten through hydrogen bonding and electrostatic interaction respectively, forming a protective film in the edge area of the pattern, avoiding the erosion of the edge by the polishing liquid, and thus reducing the occurrence of the EOE phenomenon.

[0021] 2) The diblock copolymer A-co-B added to the tungsten chemical mechanical polishing liquid of the present invention. The A chain in the diblock copolymer is often more hydrophilic and can be suspended in the solution, while the B chain is adsorbed on the surface of tungsten through electrostatic interaction, protecting the metallic tungsten from erosion, reducing defects such as dishing and erosion, and improving the surface quality of the wafer. Specific Embodiments

[0022] To better understand the technical solutions of the present invention, the following embodiments will further illustrate the methods provided by the present invention. However, the present invention is not limited to the listed embodiments, and should also include any other well-known changes within the scope of the claims of the present invention.

[0023] A tungsten chemical mechanical polishing liquid includes 1 - 10% by mass of silica abrasive, 0.001 - 0.1% of iron salt catalyst, 1.5 - 2.5% of oxidant, 0.01 - 0.2% of stabilizer, 0.005 - 0.2% of block copolymer, and the balance is water; wherein, the block copolymer is a diblock copolymer A-co-B. Preferably, the tungsten chemical mechanical polishing liquid includes 1 - 5% of silica abrasive, 0.01 - 0.1% of iron salt catalyst, 2.0% of oxidant, 0.05 - 0.2% of stabilizer, 0.01% - 0.2% of block copolymer, and the balance is water.

[0024] Specifically, the A polymer segment in the diblock copolymer A-co-B has a polycarboxyl or polyhydroxyl structure. Preferably, the A polymer segment is polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethylene glycol dicarboxylic acid, polyglycolic acid, polyglutamic acid, polylactic acid-glycolic acid, polyacrylic acid, polylactic acid, polycaprolactone, dextran, etc., but not limited thereto. The B polymer segment in the diblock copolymer A-co-B contains an amino structure, and the N atom therein is sp 3 hybridized. Preferably, the B polymer segment is polyethyleneimine, polyacrylamide, polyhistidine, polylysine, polyarginine, etc., but not limited thereto.

[0025] Specifically, the diblock copolymer A-co-B can be selected from polyethylene glycol-co-polyethyleneimine, polypropylene glycol-co-polyacrylamide, polyvinyl alcohol-co-polyethyleneimine, polyethylene glycol dicarboxylic acid-co-polyhistidine, polyglycolic acid-co-polyacrylamide, polyglutamic acid-co-polyhistidine, polylactic acid-glycolic acid-co-polylysine, polyethylene glycol-co-polylysine, polylactic acid-co-polyethyleneimine, dextran-co-polyethyleneimine, polycaprolactone-co-polyarginine, polyacrylic acid-co-polylysine, etc., but not limited thereto.

[0026] The pH of the tungsten chemical mechanical polishing liquid of the present invention is near the isoelectric point of the silica dielectric layer. Therefore, the silica is basically uncharged and the surface is rich in Si-OH structures, while the isoelectric point of metallic tungsten is about pH 1.5 and it has a strong negative charge at this pH.

[0027] Among them, the A polymer segment contains a carboxyl or hydroxyl structure, and the oxygen atom therein has a very strong electronegativity and can form a hydrogen bond with the Si-OH on the silica surface, thereby adsorbing on its surface; while the B polymer segment contains sp 3 hybridized N atoms, which are basically all protonated under acidic conditions and exist in the polishing composition in the form of positive charges, and can bind to the tungsten plug through strong electrostatic adsorption. Therefore, the diblock copolymer A-co-B tends to bind at the junction of the tungsten plug and the dielectric layer through hydrogen bond and electrostatic interactions, thereby forming a protective layer at the pattern edge and greatly reducing the generation of the EOE phenomenon.

[0028] The content of the block copolymer is 0.005-0.2%, for example, including but not limited to 0.005%, 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.15%, 0.2%, and preferably 0.01-0.2%.

[0029] The silica abrasive is silica sol or fumed silica, preferably silica sol. The amount of silica abrasive added is generally 1-10% of the total mass of the polishing liquid, for example, including but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. Preferably, the amount of silica abrasive added is 1-5% of the total mass of the polishing liquid.

[0030] The silica sol has a particle size of 40-200 nm. Preferably, the silica sol has a particle size of 60-120 nm. The silica sol may be any silica sol that meets the requirements, for example, it may be purchased from Nissan Chemical, Fuso, Dupont and Bayer, etc. Preferably, the silica sol is selected from Fuso's PL-2, PL-3, PL-5 or PL-7 (with particle sizes of 50, 70, 100 and 120 nm, respectively).

[0031] The amount of the iron salt catalyst added is generally 0.001%-0.1% of the total mass of the polishing liquid, for example including but not limited to 0.001%, 0.005%, 0.01%, 0.05%, 0.07%, 0.1%. Preferably, the amount of the iron salt catalyst added is 0.01%-0.1% of the total mass of the polishing liquid.

[0032] The oxidant is usually hydrogen peroxide, and the amount of the oxidant added is, for example, 1.5-2.5%, generally 2.0% based on the total mass of the polishing liquid, and is usually added separately before use to avoid premature decomposition. The pH of the tungsten chemical mechanical polishing liquid is adjusted to 2.0-2.5 by nitric acid or potassium hydroxide.

[0033] The stabilizer is an organic acid, for example, one or more selected from oxalic acid, malonic acid, succinic acid, citric acid, tartaric acid, etc., preferably malonic acid. The amount of the stabilizer added is generally 0.01-0.2% of the total mass of the polishing liquid, for example, including but not limited to 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.15%, 0.2%, preferably 0.05-0.2%.

[0034] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0035] Some of the diblock copolymers used in the examples, such as polyethylene glycol-co-polyethyleneimine, polylactic acid-co-glycolic acid-co-polylysine, and polyethylene glycol-co-polylysine, can be purchased from Hunan Huateng Pharmaceutical, Guangzhou Weihua Biotechnology, and Xi'an Qiyue Biotechnology, respectively.

[0036] To save costs, the above diblock copolymer can also be synthesized by itself as needed, and the synthesis route is shown below.

[0037] 1. Synthesis of polycarboxyl and polyamino copolymer:

[0038] In the first step, due to the relatively low reactivity of carboxyl groups, polycarboxyl polymers need to be activated. Commonly used methods in the industry such as thionyl chloride method, triphosgene method, oxalyl chloride method, etc. are used for acyl chlorination (refer to "Xin Jianfeng, Ma Jihai, Zhang Shufen, Chen Shaorui, Li Haiyu. Review of Preparation Methods of Acyl Chlorides [J]. Hebei Chemical Industry, 2006(11): 16 - 18 + 20"). Taking the oxalyl chloride method as an example, add 1.65 g of polycarboxyl polymer to 100 mL of DCM (dichloromethane, solvent), then add 3 mL of oxalyl chloride at room temperature. After stirring evenly, add three drops of dry DMF (dimethylformamide, catalyst) to the mixture and stir overnight. After the reaction is completed, remove the excess oxalyl chloride in vacuo, add a small amount of water to quench the reaction, and then remove the solvent at 50 °C in vacuo to obtain the acyl chlorinated polycarboxyl polymer (refer to Z.Z. Wang, M.Y. Liu, Q. Huang, et al. Synthesis of Aspirin Prodrugs of β - Cyclodextrin on the Primary / Secondary Hydroxyl Sides [J]. J. Chem. Pharm. Res., 2012, 4(4): 2322 - 2324);

[0039] In the second step, the acyl chlorinated polycarboxyl polymer reacts with the polyamino polymer. The reaction activity of acyl chloride and amino group is very high, and this reaction can be carried out at low temperature. Prepare the polyamino polymer as a 30 wt% concentrated solution, add the acyl chlorinated polycarboxyl polymer obtained in the first step according to the same mass ratio, control the reaction temperature below 15 °C, and stir overnight to obtain the copolymer (refer to R.E. Kent, S.M. McElvain, Isobutyramide [J], Organic Syntheses Collect., 1955, 3: 490 - 493).

[0040] 2. Synthesis of polyhydroxyl and polyamino copolymer:

[0041] In the first step, use acetic anhydride (other acid anhydrides can also be selected, acetic anhydride is recommended as its hydrolysis rate at room temperature is slow and the reaction can be carried out in an aqueous medium) to acylate the hydroxyl groups. For example, add 30 g of polyhydroxyl polymer to 100 g of water, then add 3 g of acetic anhydride at room temperature, react at room temperature for 6 h, and after the reaction is completed, remove the solvent at 50 °C in vacuo to obtain the acylated hydroxyl polymer.

[0042] In the second step, carry out the synthesis of the copolymer in sequence according to the steps 1 and 2 in Method 1.

[0043] Table 1 shows the components and contents of the tungsten polishing liquids in Comparative Examples 1-3 and Examples 1-10 of the present invention. According to Table 1, the chemical mechanical polishing liquid was prepared by simple stirring and mixing. After mixing evenly, the pH value was adjusted to 2.0 - 2.5 with nitric acid or KOH. Hydrogen peroxide was added before use, and after mixing evenly, the balance was made up with water to obtain each example and comparative example of the present invention.

[0044] Table 1 Composition Table of the Polishing Liquids of Comparative Examples 1-3 and Examples 1-10

[0045]

[0046]

[0047] To verify the polishing effect of the polishing liquid of the present invention, the polishing liquids of Comparative Examples 1-3 and Examples 1-10 were polished.

[0048] The polishing conditions were as follows: the polishing machine was a Mirra polishing machine, the polishing pad was IC1010, the polishing pressure was 3.2 psi, the rotation speeds of the polishing head and the polishing plate were 93 / 87 rpm, and the flow rate of the polishing liquid was 100 mL / min.

[0049] The MIT 854 mask was used for pattern wafer research. After reaching the polishing end point, 40% over-polishing was carried out. The EOE was measured at 5 different positions from the center to the edge of the wafer using a Park NX-WAFER AFM, and three characteristic parameters, namely the erosion height, the EOE horizontal dimension, and the EOE vertical dimension, were recorded.

[0050] Three typical line widths of 0.18 - 0.18 - 50%, 0.5 - 0.5 - 50%, and 1.5 - 0.5 - 50% (W / S / D) were selected, and the average values of the above three characteristic parameters were recorded at the typical line widths, so as to compare the polishing effects of different polishing compositions in Table 1. The results are listed in Table 2.

[0051] Table 2 Polishing Effects of Comparative Examples 1-3 and Examples 1-10

[0052]

[0053]

[0054]

[0055]

[0056] As shown in Table 2, no relevant polymer was added in Comparative Example 1, and a single polymer was added in Comparative Example 2 and Comparative Example 3. It can be seen that the erosion heights of Comparative Example 1 and Comparative Example 3 are relatively similar at each line width, while the erosion value of Comparative Example 2 has decreased. This is because the added polyethylene glycol can bind to the silica surface through hydrogen bonds, providing a certain protective effect on the silica. However, compared with the examples, the EOE horizontal or vertical dimensions of the three comparative examples are much larger, indicating that a very serious EOE phenomenon occurs at the pattern edges in the comparative examples, and the joint between the two materials is over-polished.

[0057] Through the protective effect of the block copolymer, the EOE phenomenon of the pattern wafers in Examples 1-10 was well suppressed. The EOE horizontal dimension and vertical dimension decreased significantly, and at the same time, the erosion height also decreased significantly, improving the planarization efficiency and achieving a better planarization effect.

[0058] In summary, when the tungsten polishing liquid of the present invention is applied to the chemical mechanical polishing of pattern wafers, it can effectively reduce the EOE phenomenon and also has a certain inhibitory effect on erosion, making the polished wafer have better surface quality.

[0059] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. Those skilled in the art can understand that some modifications or adjustments can be made to the present invention under the teaching of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A tungsten chemical mechanical polishing liquid for reducing the EOE phenomenon, characterized in that, In terms of mass percentage, the tungsten chemical mechanical polishing liquid comprises 1-10% of silica abrasive, 0.001-0.1% of ferric salt catalyst, 1.5-2.5% of oxidant, 0.01-0.2% of stabilizer, 0.005-0.2% of block copolymer, and the balance is water; wherein, the block copolymer is diblock copolymer A-co-B; The B polymer segment in the diblock copolymer A-co-B contains an amino structure, and the N atom therein is sp3 hybridized; The A polymer segment in the diblock copolymer A-co-B is any one of polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethylene glycol dicarboxylic acid, polyglycolic acid, polyglutamic acid, polylactic acid-glycolic acid, polyacrylic acid, polylactic acid, polycaprolactone or dextran; the stabilizer is organic acid; The pH of the tungsten chemical mechanical polishing liquid is 2.0-2.

5.

2. The tungsten chemical mechanical polishing liquid according to claim 1, wherein In terms of mass percentage, the tungsten chemical mechanical polishing liquid comprises 1-5% of silica abrasive, 0.01-0.1% of ferric salt catalyst, 2.0% of oxidant, 0.05-0.2% of stabilizer, 0.01-0.2% of block copolymer, and the balance is water.

3. The tungsten chemical mechanical polishing liquid according to claim 1, wherein The B polymer segment in the diblock copolymer A-co-B is any one of polyethyleneimine, polyacrylamide, polyhistidine, polylysine or polyarginine.

4. The tungsten chemical mechanical polishing liquid according to any one of claims 1 to 3, characterized in that, The silica abrasive is silica sol or fumed silica.

5. The tungsten chemical mechanical polishing liquid according to any one of claims 1 to 3, characterized in that, The ferric salt catalyst is a ferric salt that can ionize ferric ions in aqueous solution.

6. The tungsten chemical mechanical polishing liquid according to claim 5, wherein, The ferric salt catalyst is ferric nitrate.

7. The tungsten chemical mechanical polishing liquid according to any one of claims 1 to 3, characterized in that The oxidant is hydrogen peroxide.

8. The tungsten chemical mechanical polishing liquid according to claim 1, wherein, The stabilizer is one or more of oxalic acid, malonic acid, succinic acid, citric acid, tartaric acid.

9. The tungsten chemical mechanical polishing liquid according to claim 8, wherein, The stabilizer is malonic acid.

10. Application of the tungsten chemical mechanical polishing liquid according to any one of claims 1 to 9 in tungsten chemical mechanical polishing.

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