A chemical mechanical polishing liquid for tungsten plugs with reduced dishing and its application

Abstract

This invention discloses a chemical mechanical polishing solution for tungsten plugs that reduces dishing and its application. The polishing solution comprises the following components by weight: 2%-20% abrasive, 0.5%-5% oxidizing agent, 0.01%-0.5% tungsten catalyst, 0.01%-0.05% corrosion inhibitor, and the remainder deionized water. The chemical mechanical polishing solution for tungsten plugs effectively removes tungsten and reduces dishing.

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 capable of reducing recess and application thereof. Background Art

[0002] With the continuous development of semiconductor technology and the increasing number of interconnect layers in large-scale integrated circuits, the planarization of conductive and insulating dielectric layers has become increasingly critical. Chemical mechanical polishing (CMP), pioneered by IBM in the 1980s, is currently considered the most effective method for global planarization.

[0003] Chemical mechanical polishing (CMP) involves chemical, mechanical, or a combination of these two processes. It typically consists of a polishing table with a polishing pad and a polishing head that supports the chip. The polishing head secures the chip and presses the front surface of the chip against the polishing pad. During CMP, the polishing head moves linearly across the polishing pad or rotates in the same direction as the polishing table. Simultaneously, a slurry containing an abrasive is dripped onto the polishing pad and spreads flat across it due to centrifugal action. This combination of mechanical and chemical forces results in global flattening of the chip surface.

[0004] The main mechanism of chemical mechanical polishing (CMP) of metal layers is believed to be: the oxidant first oxidizes the metal surface into a film, and the abrasive represented by silicon dioxide and aluminum oxide mechanically removes the oxide film, generating a new metal surface that continues to be oxidized. These two effects occur synergistically.

[0005] Tungsten metal, one of the targets of chemical mechanical polishing (CMP), is primarily used in chips as tungsten plugs. To form a tungsten plug, a hole with a high aspect ratio is created on the surface of the insulating layer through processes such as photolithography and etching. Metals such as Ti / TIN and W are then gradually deposited on top of the hole through processes such as CVD, forming a preliminary tungsten plug structure. Excess tungsten on the surface of the insulating layer is then removed using CMP. After a certain amount of tungsten is removed, both the tungsten and the insulating layer are simultaneously CMPed. During this process, the tungsten removal rate is typically much higher than that of the insulating layer. This large disparity in removal rates can lead to excessive tungsten removal, resulting in a depression at the plug and causing chip failure. Therefore, minimizing the occurrence of depressions during the planarization process is crucial. A suitable tungsten polishing slurry can regulate the tungsten removal rate, preventing it from exceeding the insulating layer removal rate and reducing the occurrence of depressions, thus playing a crucial role in device yield. For example, the prior art disclosed in patent CN101600773A uses imidazoles. However, these substances have a protective effect on static etching but have no effect on rate regulation. Therefore, adding azoles does not help with depression.

[0006] Therefore, it is very necessary to minimize the occurrence of dishing during the tungsten plug planarization process. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a tungsten plug chemical mechanical polishing solution that reduces concavity. By adding a corrosion inhibitor with a special structure, it can effectively reduce the generation of concavity during the tungsten plug planarization process, thereby improving the yield of WAFER.

[0008] Another object of the present invention is to provide an application of the dishing-reducing tungsten plug chemical mechanical polishing solution in tungsten chemical mechanical polishing.

[0009] In order to achieve the above object of the invention, the present invention adopts the following technical solutions:

[0010] A tungsten plug chemical mechanical polishing liquid for reducing dishing comprises the following components in percentage by mass: 2%-20% abrasive, 0.5%-5% oxidant, 0.01%-0.5% tungsten catalyst, 0.01%-0.05% corrosion inhibitor, and the remainder is deionized water.

[0011] In a preferred embodiment, the dishing-reducing tungsten plug chemical mechanical polishing solution comprises the following components by weight: 5%-15% abrasive, 1%-3% oxidant, 0.05%-0.2% tungsten catalyst, 0.01%-0.035% corrosion inhibitor, and the balance is deionized water.

[0012] In a specific embodiment, the corrosion inhibitor is selected from heterocyclic substances containing a nitro group and a non-conjugated structure.

[0013] In a preferred embodiment, the heterocyclic substance containing a nitro group and a non-conjugated structure is at least any one of 1,4-dinitrosopiperazine and 1-methyl-4-nitrosopiperazine.

[0014] In a specific embodiment, the abrasive is colloidal silica, preferably ultra-high purity colloidal silica.

[0015] In a preferred embodiment, the colloidal silica is fumed silica with a specific surface area of ​​80-120 m 2 / g; further preferably, the particle size of the fumed silica in the aqueous solution is 100-180 nm.

[0016] 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.

[0017] In a specific embodiment, the tungsten catalyst is an iron salt, preferably iron nitrate.

[0018] In a specific embodiment, the deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 megohms.

[0019] In a specific embodiment, the pH value of the tungsten plug chemical mechanical polishing solution is 2.0-2.5.

[0020] Another aspect of the present invention is the use of the aforementioned dishing-reducing tungsten plug chemical mechanical polishing solution in tungsten chemical mechanical polishing.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] The tungsten plug dishing-reducing chemical mechanical polishing solution of the present invention reduces dishing caused by the tungsten plug during polishing by adding the corrosion inhibitor of the specific structure, thereby effectively improving the yield of the WAFER, thereby realizing application in the semiconductor field, especially in chemical mechanical polishing.

[0023] The corrosion inhibitor of the present invention is a heterocyclic substance containing a nitro group and a non-conjugated structure. The main reason why it can be used as a corrosion inhibitor is that the heterocyclic nitrogen substance containing a nitro group and a non-conjugated structure can reduce the removal rate of the tungsten plug mainly due to two factors: first, the nitro group has a reducing property and reacts with hydroxyl radicals, thereby reducing the oxidation of the tungsten plug to a softer oxide layer, ultimately reducing the polishing rate; second, the non-conjugated structure gives the heterocyclic nitrogen substance a strong protonation ability, resulting in a positive surface charge, which effectively adsorbs on the tungsten surface to form a protective layer, thereby inhibiting the chemical reaction of tungsten. The combination of these two factors effectively reduces the occurrence of dishing and has a positive effect on the planarization effect. DETAILED DESCRIPTION

[0024] 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.

[0025] A chemical mechanical polishing liquid for tungsten plugs with reduced dishing comprises an abrasive, an oxidant, a catalyst, a corrosion inhibitor, and the remainder is deionized water.

[0026] In a preferred embodiment, the dishing-reducing tungsten plug chemical mechanical polishing solution comprises the following components by weight: 2%-20% abrasive, 0.5%-5% oxidizing agent, 0.01%-0.5% tungsten catalyst, 0.01%-0.05% corrosion inhibitor, and the remainder being deionized water. The corrosion inhibitor is at least one of a nitro-containing, non-conjugated heterocyclic substance, such as 1,4-dinitrosopiperazine or 1-methyl-4-nitrosopiperazine. Specifically, based on 100% of the polishing solution, the abrasive comprises 2-20%, the oxidizing agent 0.5-5%, the tungsten catalyst 0.01-0.5%, the corrosion inhibitor 0.05-5%, and the balance water.

[0027] Wherein, as the abrasive, for example, is fumed silica, which can be commercial fumed silica, preferably with a specific surface area of ​​80-120 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-180nm. The effective particle size can be obtained by, for example, detecting by dynamic light scattering (DLS) method. The mass percentage of fumed silica in the polishing liquid is 2%-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%, preferably 5%-15%.

[0028] The oxidizing agent can be, 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 oxidizing agent is present in the polishing liquid in an amount of 0.5% to 5% by weight, including, but not limited to, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%, preferably 1% to 3%. The oxidizing agent is preferably added before use to avoid premature decomposition due to premature addition, as is well known to those skilled in the art.

[0029] The tungsten catalyst can be an iron salt, i.e., a salt compound containing iron ions, such as, but not limited to, iron nitrates, hydrochlorides, sulfates, and hydrochlorides. Preferably, it is ferric nitrate, in which both nitrate ions and iron ions can function. In the presence of hydrogen peroxide oxidant, a Fenton reaction occurs, promoting the chemical mechanical polishing process and increasing the polishing rate. The mass percentage of the catalyst ferric nitrate in the polishing liquid is 0.01%-0.5%, such as, but not limited to, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, and 0.5%, preferably 0.05%-0.2%.

[0030] The corrosion inhibitor is selected from a heterocyclic substance having a nitro group and a non-conjugated structure, such as at least one of 1,4-dinitrosopiperazine and 1-methyl-4-nitrosopiperazine. The mass percentage of the pitting corrosion inhibitor in the polishing liquid is 0.01%-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%, preferably 0.01%-0.035%.

[0031] Typically, the pH value of the dishing-reducing tungsten plug chemical mechanical polishing solution is 2.0-2.5, which can be adjusted with acid or base, such as potassium hydroxide or nitric acid, or with acids or bases commonly used in the art.

[0032] 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.

[0033] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0034] The main sources of raw materials used in the following examples or comparative examples are as follows:

[0035] Fumed silica, Evonik AERISOL, Germany, micron-sized, surface area 90 g / m 2 ;

[0036] 1,4-Dinitrosopiperazine, 1-Methyl-4-nitrosopiperazine, analytical grade, Sinopharm Group

[0037] The main detection methods are as follows:

[0038] Tungsten plug recess depth The depth of the depression is detected by a step profiler.

[0039] The above test methods all adopt industry standard processes and will not be described in detail here.

[0040] 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.

[0041]

[0042]

[0043] A chemical mechanical polishing solution was prepared according to the formula in the table, mixed evenly, and the pH value was adjusted to 2.0-2.5 with nitric acid or KOH. Before use, 0.5%-5% hydrogen peroxide was added, and the mass percentage was supplemented with water to 100%. The tungsten plug polishing solution for reducing dishing according to the embodiments of the present invention and the comparative example was obtained.

[0044] Tungsten wafers were polished using the chemical mechanical polishing solutions of the above examples and comparative examples. Polishing conditions were: a Mirra polisher, an IC1010 polishing pad, a polishing pressure of 2.5 psi, and a polishing solution flow rate of 150 mL / min. The polishing rates of the tungsten targets were measured using the above polishing solutions, and pitting corrosion tests were performed on the polished tungsten targets using a biological microscope. The test results are listed in the table above.

[0045] It can be found from the above Examples 1, 3-5 and Comparative Examples 1-4 that the concentrations of ferric nitrate and hydrogen peroxide must be within a certain range to have a certain effect on improving the tungsten polishing rate.

[0046] It can be found from the above Examples 2 and 6 and Comparative Examples 5-6 that the concentration of the corrosion inhibitor has an excellent effect in reducing the degree of dishing within a certain range.

[0047] From the above Example 6 and Comparative Example 7, it can be found that the connection of nitro groups to the conjugated structure will affect its reducibility and ultimately affect the polishing effect.

[0048] In summary, compared with the prior art, the polishing liquid of the present invention is used in the chemical mechanical polishing process of tungsten. After using fumed silica as an abrasive and adding the oxidant hydrogen peroxide and the catalyst ferric nitrate, its polishing rate is greatly improved. After adding an appropriate amount of corrosion inhibitor, the pitting situation is greatly improved, which has a positive effect on the chemical mechanical polishing of tungsten.

[0049] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. Those skilled in the art will appreciate that, based on the teachings of this specification, modifications or adjustments may be made to the present invention. Such 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 tungsten plugs to reduce dishing, 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 corrosion inhibitor, and the balance is deionized water; The corrosion inhibitor is a heterocyclic substance containing a nitro group and a non-conjugated structure, and is selected from at least one of 1,4-dinitrosopiperazine and 1-methyl-4-nitrosopiperazine; The oxidant is selected from one or more of hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium hypochlorite or potassium hypochlorite; The tungsten catalyst is an iron salt.

2. The chemical mechanical polishing solution for tungsten plugs according to claim 1, characterized in that: The invention comprises the following components in percentage by mass: 5%-15% of abrasive, 1%-3% of oxidant, 0.05%-0.2% of tungsten catalyst, 0.01%-0.035% of corrosion inhibitor, and the balance is deionized water.

3. The chemical mechanical polishing liquid for tungsten plug according to claim 1 or 2, characterized in that: The abrasive is colloidal silicon dioxide.

4. The chemical mechanical polishing liquid for tungsten plugs according to claim 3, characterized in that: The colloidal silica is fumed silica with a specific surface area of ​​80-120 m 2 / g.

5. The chemical mechanical polishing liquid for tungsten plugs according to claim 4, characterized in that: 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 or 2, characterized in that: The oxidant is hydrogen peroxide.

7. The chemical mechanical polishing liquid for tungsten plug according to claim 1 or 2, characterized in that: The tungsten catalyst is ferric nitrate.

8. The chemical mechanical polishing liquid for tungsten plugs according to claim 1 or 2, characterized in that: The deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 MΩ / cm.

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

5.

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

Images