Tungsten plug chemical mechanical polishing solution capable of reducing Key and application of tungsten plug chemical mechanical polishing solution

Abstract

The invention discloses a tungsten plug chemical mechanical polishing solution capable of reducing Key and application of the tungsten plug chemical mechanical polishing solution. The tungsten plug chemical mechanical polishing solution 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 protective additive and deionized water, wherein the protective auxiliary agent is a compound containing a conjugated structure and containing amino and carboxyl. The chemical mechanical polishing solution for the tungsten plug has the characteristics of high polishing speed, few Key defects, good surface quality and the like.

Description

Technical Field

[0001] The invention relates to the technical field of chemical mechanical polishing, and in particular to a tungsten plug chemical mechanical polishing liquid for reducing key holes and an 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. 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 more and more advanced and the line width becomes smaller and smaller, the requirements for defect control are becoming more and more stringent, especially the key hole defect, which directly leads to device failure and greatly reduces the chip yield. The key hole defect is caused by two reasons. One part comes from the chemical deposition process. If the metal deposition is not dense in this process, it will cause the occurrence of key hole. On the other hand, it comes from the chemical mechanical polishing process. In this process, the corrosive polishing liquid contacts the metal to form galvanic corrosion, which also causes the occurrence of key hol defects. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a tungsten plug chemical mechanical polishing solution for reducing key holes, and by adding a protective auxiliary agent, it can ensure that the generation of key hole defects is reduced during the chemical mechanical polishing process.

[0006] Another object of the present invention is to provide an application of a chemical mechanical polishing solution for reducing a tungsten plug of a key hole in chemical mechanical polishing of tungsten.

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

[0008] A chemical mechanical polishing liquid for reducing key holes of tungsten plugs 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 protective aid, and deionized water, wherein the protective aid is a compound containing a conjugated structure and containing amino and carboxyl groups.

[0009] In a specific embodiment, the compound containing a conjugated structure and containing an amino group and a carboxyl group is azobenzene-4-benzoic acid.

[0010] In a specific embodiment, the abrasive is fumed silica, preferably commercial electronic grade fumed silica.

[0011] 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.

[0012] 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.

[0013] In a specific embodiment, the tungsten catalyst is ferric nitrate.

[0014] In a specific embodiment, the pH value of the polishing liquid is 2.0-2.5.

[0015] In a specific embodiment, the deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 MΩ.CM.

[0016] On the other hand, the aforementioned tungsten plug chemical mechanical polishing solution for reducing key holes is used in tungsten chemical mechanical polishing.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The tungsten plug chemical mechanical polishing liquid of the present invention reduces the key hole defects caused by the corrosion of the polishing liquid by adding a specific auxiliary agent, thereby achieving more effective application in the semiconductor field, especially in chemical mechanical polishing.

[0019] The tungsten plug chemical mechanical polishing liquid of the present invention reduces the occurrence of KEY hole defects by adding specific additives. The protective additive is a compound containing a conjugated structure and containing an amino group and a carboxyl group. The reason why the KEY hole defects can be reduced is mainly due to the following reasons: first, the pH of the tungsten polishing liquid is usually around 2-3. Under this pH value, the tungsten surface is negatively charged and can be adsorbed on the surface by electrostatic action with the protonated amino group in the polymer compound to form a protective film, thereby reducing the occurrence of galvanic corrosion and thus reducing the occurrence of key holes; second, the carboxyl group carries a negative charge under acidic conditions, which is opposite to the charge carried by the protonated amino group, and can reduce the electrostatic action with the tungsten surface to a certain extent, thereby avoiding the problem of too low polishing rate or cleaning residue; third, the compound contains a benzene ring conjugation and a double bond structure, which can quickly transfer the charge and avoid charge concentration, resulting in the occurrence of galvanic corrosion. The above three effects can greatly reduce the occurrence of KEY hole defects, thereby improving the yield of the chip. DETAILED DESCRIPTION

[0020] 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.

[0021] A chemical mechanical polishing liquid for reducing key holes of tungsten plugs, comprising 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 protective aid, and deionized water, wherein the protective aid is a compound containing a conjugated structure and containing amino and carboxyl groups, preferably azobenzene-4-benzoic acid. For example, 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 protective aid is 0.01 to 0.05%, and the balance is deionized water. It is well known to those skilled in the art that other commonly used additives, such as fungicides, can be added to the polishing liquid according to process requirements, and after adding a small amount of fungicide, the balance is water.

[0022] 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%.

[0023] 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.

[0024] 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%.

[0025] The protective agent is a compound containing a conjugated structure and an amino group and a carboxyl group, preferably azobenzene-4-benzoic acid. The mass percentage content of the protective agent 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%, 0.05%.

[0026] Generally, the pH value of the chemical mechanical polishing solution for reducing the key hole 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.

[0027] 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.

[0028] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0029] The main sources of raw materials used in the following examples or comparative examples are as follows:

[0030] Fumed silica, AERISOL from Evonik, Germany, micron grade, specific surface area 90g / m 2 ;

[0031] Azobenzene-4-benzoic acid, Sinopharm Group Co., Ltd.

[0032] The main detection methods are as follows:

[0033] Polishing rate MRR (angstroms / minute): After chemical mechanical polishing of tungsten, the thickness difference and mass difference of the tungsten target before and after polishing are measured with a thickness gauge and a balance to evaluate the polishing rate;

[0034] KEY Hole defect: The cross section of the tungsten plug wafer is observed by scanning electron microscopy, and the number of KEY HOLE defects in the cross section of the tungsten plug crystal is determined by scanning electron microscopy.

[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, 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 of each embodiment of the present invention and the comparative example.

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

[0038]

[0039] The chemical mechanical polishing liquids of Examples 1 to 5 and Comparative Examples 1 to 5 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 1.

[0040] Table 2 Table 1 Performance test results of polishing liquid of embodiment and comparative example

[0041] Polishing liquid MRR(A / min) KEY HOLE quantity Example 1 3285 9 Example 2 3613 5 Example 3 3464 6 Example 4 3278 9 Example 5 3289 11 Comparative Example 1 2973 15 Comparative Example 2 2893 19 Comparative Example 3 3008 21 Comparative Example 4 3512 44 Comparative Example 5 2658 17

[0042] 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, the polishing rate is greatly improved, and after adding a suitable amount of azobenzene-4-benzoic acid substance, the occurrence of KEY HOLE defects can be significantly reduced.

[0043] 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 chemical mechanical polishing solution for reducing the size of a tungsten plug of a key hole, 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 protective auxiliary agent, and deionized water, wherein the protective auxiliary agent is a compound containing a conjugated structure and containing amino and carboxyl groups.

2. The chemical mechanical polishing liquid for tungsten plug according to claim 1, characterized in that: The compound containing a conjugated structure, an amino group and a carboxyl group is azobenzene-4-benzoic acid.

3. 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.

4. The chemical mechanical polishing liquid for tungsten plug according to claim 3, 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.

5. 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.

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

7. 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.

8. 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 MΩ.CM.

9. Use of the tungsten plug chemical mechanical polishing solution for reducing key holes according to any one of claims 1 to 8 in tungsten chemical mechanical polishing.

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