Low-defect tungsten plug chemical mechanical polishing solution and application thereof

Abstract

The invention discloses a low-defect chemical mechanical polishing solution for a tungsten plug and application thereof. The chemical mechanical polishing solution for the tungsten plug comprises the following components in percentage by mass: 2%-20% of a grinding agent, 0.5%-5% of an oxidizing agent, 0.01%-0.5% of a tungsten catalyst, 0.01%-0.05% of a special auxiliary agent and deionized water, wherein the special auxiliary agent is a high-molecular compound containing polyhydroxy and polycarboxyl, and the main chain of the special auxiliary agent is a repeating unit of an ether bond. The chemical mechanical polishing solution for the tungsten plug has the characteristics of high polishing speed, good surface quality, easiness in cleaning and the like.

Description

Technical Field

[0001] The invention relates to the technical field of chemical mechanical polishing, and in particular to a low-defect tungsten plug chemical mechanical polishing liquid and application thereof. Background Art

[0002] With the rapid development of semiconductor technology and Moore's Law, chemical mechanical polishing (CMP) plays an increasingly important role in chip manufacturing and processing. Currently, CMP is the only technology that can achieve global planarization.

[0003] The chemical mechanical polishing process combines chemical polishing and mechanical polishing to form a new type of polishing process. The main consumables are polishing liquid and polishing pad. The abrasive in the polishing liquid and the polishing pad both play a role in mechanical removal. In addition, the chemical additives in the polishing liquid play a role in chemical corrosion. Under the combined action of chemical corrosion and mechanical friction, the polishing workpiece is ground and polished to obtain a high-quality surface.

[0004] As the process becomes lower and lower, the line width becomes smaller and smaller, the requirements for defect control are becoming more and more stringent, especially the control of abrasive residue is very strict. Therefore, how to reduce the abrasive residue after polishing is an urgent problem to be solved. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a low-defect tungsten plug chemical mechanical polishing solution, which can ensure the low-defect characteristics of the tungsten chemical mechanical polishing solution by adding a special auxiliary agent.

[0006] Another object of the present invention is to provide application of the low-defect tungsten plug chemical mechanical polishing solution in tungsten chemical mechanical polishing.

[0007] In order to achieve the above invention object, the present invention adopts the following technical solution:

[0008] A low-defect tungsten plug chemical mechanical polishing liquid comprises the following components in percentage by mass: 2% to 20% of abrasive, 0.5% to 5% of oxidant, 0.01% to 0.5% of tungsten catalyst, 0.01% to 0.05% of special additive, and deionized water, wherein the special additive is a polymer compound containing polyhydroxyl and polycarboxyl groups, and the main chain is a repeating unit of ether bonds.

[0009] In a preferred embodiment, the number of repeating units of the ether bond repeating units in the main chain of the polymer compound is 6-10, and the number of hydroxyl groups and carboxyl groups is not less than 2.

[0010] In a more preferred embodiment, the polymer compound is sodium alginate.

[0011] In a specific embodiment, the abrasive is fumed silica, preferably commercial electronic grade fumed silica.

[0012] In a preferred embodiment, the specific surface area of ​​the fumed silica is 80 to 120 m 2 / g; further preferably, the particle size of the fumed silica in the aqueous solution is 100 to 180 nm.

[0013] In a specific embodiment, the oxidant is selected from one or more of hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium hypochlorite or potassium hypochlorite; preferably hydrogen peroxide.

[0014] In a specific embodiment, the tungsten catalyst is ferric nitrate.

[0015] In a specific embodiment, the pH value of the polishing liquid is 2.0-2.5.

[0016] In a specific embodiment, the deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 megohms.

[0017] On the other hand, the aforementioned low-defect tungsten plug chemical mechanical polishing solution is used in tungsten chemical mechanical polishing.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The tungsten plug chemical mechanical polishing liquid of the present invention reduces scratches, improves cleaning effect, and reduces particle residue by adding specific additives, thereby achieving more effective application in the semiconductor field, especially in chemical mechanical polishing.

[0020] The chemical mechanical polishing liquid for tungsten plugs of the present invention is added with a specific auxiliary agent. The polymer contains multiple hydroxyl groups and carboxyl groups, and the main chain is a repeating unit of ether bonds. The number of repeating units is preferably 6-10, and the number of hydroxyl groups and carboxyl groups in the structural unit is not less than 2. The following are the main reasons why it can reduce scratches, improve cleaning effects, and reduce particle residues: first, the polymer compound contains multiple hydroxyl groups, which can combine with the hydroxyl groups on the surface of tungsten metal to form a hydrophilic polymer film on the surface of tungsten metal, reduce particle scratches on tungsten plugs and reduce particle residues; second, the repeating unit of ether bonds can also form hydrogen bonds with the hydroxyl groups on the surface of tungsten metal to form a hydrophilic polymer film on the surface of tungsten metal, and the repeating unit containing ether bonds is hydrophilic and can be effectively spread on the surface of tungsten metal. Thirdly, the hydroxyl groups in the polymer compound can be combined with the hydroxyl groups on the surface of silica through hydrogen bonds or dehydration condensation, making the surface of silica negatively charged. Under pH conditions of 2-3, the surface of tungsten metal is also negatively charged, and the two groups repel each other, which can further reduce particle residue. In addition, the polymer compound is wrapped on the surface of silica, making it softer and reducing scratches on the tungsten plug. DETAILED DESCRIPTION

[0021] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0022] A low-defect tungsten plug chemical mechanical polishing liquid comprises the following components in percentage by mass: 2% to 20% abrasive, 0.5% to 5% oxidant, 0.01% to 0.5% tungsten catalyst, 0.01% to 0.05% special additive, and the rest is deionized water, wherein the special additive is a macromolecular compound, also known as a macromolecular polymer, and the macromolecular polymer contains multiple hydroxyl and carboxyl groups, and the main chain contains repeating units of ether bonds; preferably, the number of repeating units is 6-10, and the number of hydroxyl and carboxyl groups of the structural unit is not less than 2. That is, based on 100% of the polishing liquid, the abrasive accounts for 2 to 20%, the oxidant is 0.5 to 5%, the tungsten catalyst is 0.01 to 0.5%, the special additive is 0.01 to 0.05%, and the balance is water.

[0023] The abrasive agent is, for example, fumed silica, which may be commercial fumed silica, preferably having a specific surface area of ​​80 to 120 m 2 / g of fumed silica, the effective particle size of silica colloidal particles of the aqueous solution of the fumed silica dissolved in water is 100nm to 180nm, for example, 120nm, 150nm, 160nm, 170nm, etc. The effective particle size can be obtained by, for example, dynamic light scattering DLS method. The mass percentage of fumed silica in the polishing liquid is 2% to 20%, for example, including but not limited to 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%.

[0024] As the oxidant, for example, one or more of hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium hypochlorite or potassium hypochlorite, preferably hydrogen peroxide, i.e., hydrogen peroxide. The mass percentage content of the oxidant in the polishing liquid is 0.5% to 5%, for example, including but not limited to 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%. The oxidant is preferably added before use to avoid premature decomposition caused by premature addition.

[0025] As the tungsten catalyst, ferric nitrate is preferred, and both nitrate ions and iron ions thereof can work. In the presence of hydrogen peroxide oxidant, Fenton reaction occurs, which promotes the chemical mechanical polishing process and increases the polishing rate. The mass percentage content of the catalyst ferric nitrate in the polishing liquid is 0.01% to 0.5%, for example, including but not limited to 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.5%.

[0026] The special additive is a polymer compound, also known as a polymer, which contains multiple hydroxyl groups and carboxyl groups, and the main chain is a repeating unit of an ether bond, and the number of repeating units is 6-10, and the number of hydroxyl groups and carboxyl groups in the structural unit is not less than 2. This substance contains a polymer with multiple hydroxyl groups and multiple carboxyl groups, which can reduce scratches, improve dispersibility, and reduce particle residues. Together, they can obtain a tungsten plug chemical mechanical polishing liquid with low surface defects. The mass percentage content of the special additive in the polishing liquid is 0.01% to 0.05%, for example, including but not limited to 0.01%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, and 0.05%. In the present invention, the polymer is preferably sodium alginate.

[0027] Generally, the pH value of the low-defect tungsten plug chemical mechanical polishing solution of the present invention is 2.0-2.5, and can be adjusted by using an acid or an alkali, for example, potassium hydroxide or nitric acid.

[0028] The oxidant may also be added before use, and those skilled in the art will appreciate that this should also fall within the scope of protection of the present invention.

[0029] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0030] The main sources of raw materials used in the following examples or comparative examples are as follows:

[0031] Fumed silica, AERISOL from Evonik, Germany, micron grade, specific surface area 90g / m 2 ;

[0032] Sodium alginate (repeating unit number 8), Xi'an Kaixin Biotechnology Co., Ltd.

[0033] The main detection methods are as follows:

[0034] Scratches and particle residues: Detected using KLA's sp series defect detectors using the instrument's built-in standard procedures.

[0035] The polishing liquids of the following examples and comparative examples were prepared according to the ingredients and contents of the components in the following table.

[0036] A chemical mechanical polishing solution was prepared according to the formula in Table 1, mixed evenly, the pH value was adjusted to 2.5 with nitric acid or KOH, 0.5% to 5% hydrogen peroxide was added before use, and the mass percentage was supplemented with water to 100%, thereby obtaining a high-rate tungsten plug polishing solution according to each embodiment of the present invention and the comparative example.

[0037] Table 1 Polishing liquid formula table of examples and comparative examples

[0038]

[0039]

[0040] The chemical mechanical polishing liquids of Examples 1 to 5 and Comparative Examples 1 to 11 were used to polish the wafers containing tungsten. The polishing conditions were: polishing with a Mirra polisher, using an IC1010 polishing pad, a polishing pressure of 4.2 psi, and a polishing liquid flow rate of 150 mL / min. The polishing rate of the above polishing liquid on tungsten was measured, and the scratches and particle residues were detected by an sp defect detector at the same time. The test results are shown in Table 2.

[0041] Table 2 Table 1 Performance test results of polishing liquid of embodiment and comparative example

[0042] Polishing liquid MRR(A / min) Number of scratches >200nm residual particles Example 1 3285 15 33 Example 2 3613 5 20 Example 3 3464 6 18 Example 4 3278 9 23 Example 5 3289 11 32 Comparative Example 1 2968 8 25 Comparative Example 2 2973 15 29 Comparative Example 3 2893 19 37 Comparative Example 4 3008 21 47 Comparative Example 5 3512 44 189 Comparative Example 6 2658 17 39 Comparative Example 7 2987 78 198 Comparative Example 8 2811 83 207 Comparative Example 9 2600 99 45 Comparative Example 10 3000 33 40 Comparative Example 11 3098 29 38

[0043] It can be found from the comparative examples 1 to 4 of the above embodiment 3 that the concentrations of ferric nitrate and hydrogen peroxide have a certain effect on improving the tungsten polishing rate within a certain range.

[0044] It can be found from the above Example 3 and Comparative Examples 5-6 that the concentration of sodium alginate (n=8) has a significant effect on the rate, scratches and particle residue within a certain range.

[0045] It can be found from the above Example 3 and Comparative Examples 7 to 8 that the number of sodium alginate repeating units has a significant effect on scratches and particle residues.

[0046] From the above Example 3 and Comparative Example 9, it can be found that under acidic conditions, sodium alginate has a significant effect on scratches, speed and particle residue.

[0047] From the above Example 3 and Comparative Examples 10-11, it can be found that sodium alginate containing multiple hydroxyl and carboxyl groups and a main chain of ether bond repeating units has a significant effect on scratches, speed and particle residue.

[0048] In summary, compared with the prior art, the polishing liquid of the present invention is used in the process of tungsten chemical mechanical polishing. After using fumed silica as an abrasive and adding the oxidant hydrogen peroxide and the catalyst ferric nitrate, its polishing rate is greatly improved, and after adding a suitable amount of sodium alginate, scratches and particle residues can be significantly reduced.

[0049] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A low-defect tungsten plug chemical mechanical polishing solution, characterized in that: The invention comprises the following components in percentage by weight: 2% to 20% of abrasive, 0.5% to 5% of oxidant, 0.01% to 0.5% of tungsten catalyst, 0.01% to 0.05% of special auxiliary agent, and deionized water, wherein the special auxiliary agent is a polymer compound containing polyhydroxyl and polycarboxyl groups, and the main chain is a repeating unit of ether bond.

2. The chemical mechanical polishing liquid for tungsten plug according to claim 1, characterized in that: The number of repeating units of the ether bond repeating units in the main chain of the polymer compound is 6-10, and the number of hydroxyl groups and carboxyl groups is not less than 2.

3. The chemical mechanical polishing liquid for tungsten plug according to claim 1 or 2, characterized in that: The polymer compound is sodium alginate.

4. The chemical mechanical polishing liquid for tungsten plug according to claim 1, characterized in that: The abrasive is fumed silica, preferably commercial electronic grade fumed silica.

5. The chemical mechanical polishing liquid for tungsten plug according to claim 4, characterized in that: The specific surface area of ​​the fumed silica is 80 to 120 m 2 / g; preferably, the particle size of the fumed silica in the aqueous solution is 100-180 nm.

6. The chemical mechanical polishing liquid for tungsten plug according to claim 1, characterized in that: The oxidant is selected from one or more of hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium hypochlorite or potassium hypochlorite; preferably hydrogen peroxide.

7. The chemical mechanical polishing liquid for tungsten plug according to claim 1, characterized in that: The tungsten catalyst is ferric nitrate.

8. The chemical mechanical polishing liquid for tungsten plug according to claim 1, characterized in that: The pH value of the tungsten plug chemical mechanical polishing solution is 2.0-2.

5.

9. The chemical mechanical polishing liquid for tungsten plug according to claim 1, characterized in that: The deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 megohms.

10. Use of the low-defect tungsten plug chemical mechanical polishing solution according to any one of claims 1 to 9 in tungsten chemical mechanical polishing.

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