Tungsten plug chemical mechanical polishing solution with reduced scratching

Abstract

The application discloses a tungsten plug chemical mechanical polishing solution capable of reducing scratches and application thereof. The polishing solution comprises the following components in mass percentage: 2-20% of abrasive, 0.5-5% of oxidant, 0.01-0.5% of tungsten catalyst, 0.01-0.05% of a substance containing polyhydroxy and carboxyl, and the rest is deionized water. The polishing composition has the characteristics of fast polishing rate, good surface quality, excellent stability and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical mechanical polishing technology, and particularly relates to a tungsten plug chemical mechanical polishing solution capable of reducing scratches and application thereof. BACKGROUND

[0002] Chemical mechanical polishing (CMP) is a process of polishing a workpiece by chemical action, mechanical action and the mutual cooperation of the two, so as to achieve planarization. When chemical mechanical polishing is performed, the polishing head moves in the same direction as the polishing table on the polishing pad, but there is a certain speed difference between the two. At the same time, the polishing liquid is dropped onto the polishing pad, and due to the rotation of the polishing pad, the polishing liquid is evenly spread on the polishing pad. Through the chemical action of the polishing liquid and the mechanical action of the polishing pad and the abrasive in the polishing liquid on the polishing workpiece, the polishing workpiece is planarized.

[0003] At present, the main mechanism of chemical mechanical polishing (CMP) of a metal layer is believed to be that an oxidizing agent first oxidizes the metal surface to form an oxide film with low hardness, and then the oxide film is removed by an abrasive, and a new metal surface is continuously oxidized by the oxidizing agent, and the two actions are alternately performed.

[0004] The reason why tungsten is selected as the plug material is mainly due to its own properties. As one of the objects of chemical mechanical polishing (CMP), tungsten has strong resistance to electron migration at high current density and can form a good ohmic contact with silicon, so it can be used as a plug to connect the upper and lower metal layers to serve as a conductor.

[0005] The competition among existing FAB manufacturers is very fierce. In order to improve productivity, major FAB manufacturers have put forward higher requirements for tungsten chemical polishing liquid - to improve the polishing rate and thus increase the yield. However, the main mechanism of tungsten chemical mechanical polishing is the combined action of chemical and mechanical action to planarize the tungsten plug. The chemical action is to oxidize tungsten to form an oxide layer with lower hardness, and the mechanical action is to remove the softer oxide layer by mechanical action, and then expose the new metal to be oxidized again, and then removed, and so on, so as to achieve the purpose of planarization of the tungsten plug. In order to pursue higher polishing efficiency, FAB manufacturers currently use fumed silica as an abrasive, but fumed silica itself has high hardness and many corners, which leads to more scratches.

[0006] Therefore, it is necessary to improve the existing polishing abrasive or polishing liquid to achieve a better balance and consideration in terms of polishing efficiency and polishing quality. SUMMARY

[0007] In order to solve the scratch of the tungsten plug, the application provides a tungsten plug chemical mechanical polishing solution for reducing scratches, by adding a substance containing polyhydroxy and carboxyl, the tungsten chemical mechanical polishing solution can have high polishing rate and reduce the occurrence of scratches, thereby improving the yield of WAFER.

[0008] Another purpose of the application is to provide the application of the tungsten plug chemical mechanical polishing solution for reducing scratches in tungsten chemical mechanical polishing.

[0009] In order to achieve the above purposes, the application adopts the following technical solutions:

[0010] The tungsten plug chemical mechanical polishing solution for reducing scratches comprises the following components in mass percentage: 2%-20% of abrasive, 0.5%-5% of oxidant, 0.01%-0.5% of tungsten catalyst, 0.01%-0.05% of the substance containing polyhydroxy and carboxyl, and the rest is deionized water.

[0011] In a preferred embodiment, the tungsten plug chemical mechanical polishing solution for reducing scratches comprises the following components in mass percentage: 5%-15% of abrasive, 2%-4% of oxidant, 0.1%-0.4% of tungsten catalyst, 0.02%-0.04% of the substance containing polyhydroxy and carboxyl, and the rest is deionized water.

[0012] In a specific embodiment, the abrasive is fumed silica, preferably commercial electronic-grade fumed silica; more preferably, the specific surface area of the fumed silica is 80-120 m 2 / g; further preferably, the particle size of the fumed silica in aqueous solution is 100-180 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 a ferric salt, preferably ferric nitrate.

[0015] In a specific embodiment, the substance containing polyhydroxy and carboxyl is selected from one or more of D-ribose hexanoic acid and L-rhamnose acid, preferably L-rhamnose acid.

[0016] In a specific embodiment, the pH value of the polishing solution is 2.0-2.5.

[0017] In a specific embodiment, the deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 MΩ / cm.

[0018] Another aspect of the present application, the foregoing reducing scratch tungsten plug chemical mechanical polishing solution in tungsten chemical mechanical polishing.

[0019] Compared with the prior art, the present application has the advantages of:

[0020] The reducing scratch tungsten plug chemical mechanical polishing solution of the present application can maintain the stability of the abrasive and reduce the generation of scratches without inhibiting the polishing rate, thereby improving the yield of WAFERA and achieving the application in the field of semiconductors, especially in chemical mechanical polishing. DETAILED DESCRIPTION

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

[0022] A reducing scratch tungsten plug chemical mechanical polishing solution, comprising an abrasive, an oxidizing agent, a tungsten catalyst, a substance containing polyhydroxy and carboxyl, and the rest being deionized water.

[0023] Specifically, a reducing scratch tungsten plug chemical mechanical polishing solution, comprising the following components in mass percentage: 2%-20% of an abrasive, 0.5%-5% of an oxidizing agent, 0.01%-0.5% of a tungsten catalyst, and 0.01%-0.05% of a substance containing polyhydroxy and carboxyl, and the rest being deionized water, i.e. taking the polishing solution as 100%, wherein the abrasive accounts for 2-20%, the oxidizing agent accounts for 0.5-5%, the tungsten catalyst accounts for 0.01-0.5%, the substance containing polyhydroxy and carboxyl accounts for 0.01%-0.05%, and the rest is water.

[0024] Among them, as the abrasive, for example, fumed silica, the fumed silica can be a commercial fumed silica, preferably a fumed silica with a specific surface area of 80-120 m 2 / g, and the effective particle size of the silica colloidal particles of the fumed silica aqueous solution dissolved in water is 100-180 nm. The effective particle size can be detected by dynamic light scattering method DLS method. The mass percentage of fumed silica in the polishing solution 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%, and 20%.

[0025] As the oxidizing agent, for example, one or more of hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium hypochlorite or potassium hypochlorite, preferably hydrogen peroxide, i.e. hydrogen dioxide. The mass percentage content of the oxidizing agent in the polishing solution is 0.5%-5%, for example, including but not limited to 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%. The oxidizing agent is preferably added before use to avoid possible premature decomposition caused by premature addition.

[0026] As the tungsten catalyst, for example, a salt containing iron, preferably ferric nitrate, both the nitrate ion and the iron ion of which can act. In the presence of hydrogen peroxide oxidizing agent, Fenton reaction occurs, promoting the progress of chemical mechanical polishing and increasing the polishing rate. The mass percentage content of the catalyst ferric nitrate in the polishing solution is 0.01%-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%.

[0027] As the substance containing polyhydroxy and carboxyl, for example, D-ribose hexanoic acid and / or L-rhamnose acid, preferably L-rhamnose acid. The mass percentage content of the substance containing polyhydroxy and carboxyl in the polishing solution 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%, 0.05%.

[0028] Generally, the pH value of the tungsten plug chemical mechanical polishing solution for reducing pitting corrosion is 2.0-2.5, which can be adjusted by acid or base, for example, potassium hydroxide or nitric acid can be used to adjust the pH value, and acids or bases commonly used in the art can also be used to adjust the pH value.

[0029] Among them, the oxidizing agent can also be added before use, and those skilled in the art can understand that this should also be within the protection scope of the present application.

[0030] The present application can maintain the stability of the abrasive fumed silica under acidic conditions and reduce scratches by adding a substance containing multiple hydroxyl groups and carboxyl groups to the polishing liquid. The principle of maintaining the stability of the abrasive fumed silica under acidic conditions is that the hydroxyl groups in the substance can form strong binding force with the hydroxyl groups on the surface of the fumed silica through chemical bonding, and the carboxyl groups can ionize hydrogen ions to make the surface of the fumed silica negatively charged, thereby maintaining the stability of the fumed silica. On the other hand, the principle of reducing scratches is that the substance containing hydroxyl groups and carboxyl groups is chemically bonded to the fumed silica to form a relatively soft layer of substance on the surface of the fumed silica, which is similar to a relatively soft protective layer, so that the scratches on the tungsten plug can be reduced without inhibiting the polishing rate. In addition, the substance containing multiple hydroxyl groups has sufficient active sites to combine with the hydroxyl groups on the surface of tungsten, thereby improving the polishing rate. Therefore, the present application has three innovations: one is to maintain the stability of the abrasive, the second is to reduce scratches, and the third is to improve the polishing rate.

[0031] The present application will be further explained by more specific examples below, but not constitute any limitation.

[0032] The main raw materials used in the following examples or comparative examples are as follows:

[0033] Fumed silica, Germany WACKER AERISOL, micron grade, specific surface area 90 g / m 2 ;

[0034] Ferric nitrate, hydrogen peroxide, D-ribose hexanoic acid, L-rhamnose acid, hydroxybenzoic acid, analytical pure, China National Pharmaceutical Group Corporation.

[0035] The main detection methods are as follows:

[0036] Polishing rate MRR (Angstrom / min): After the tungsten is chemically mechanically polished, the thickness difference and mass difference of the tungsten target before and after polishing are measured by a thickness meter and a balance to evaluate the polishing rate;

[0037] Scratches: The tungsten target is detected by a microscope, and the number of scratches is recorded.

[0038] The above test methods all adopt standard process in the industry, which will not be described here.

[0039] The polishing liquid of the following examples and comparative examples is prepared according to the composition and content of each component in the following table:

[0040] The chemical mechanical polishing liquid is prepared according to the formula in the table, mixed uniformly, the pH value is adjusted to 2.0-2.5 by nitric acid or KOH, hydrogen peroxide is added before use, and the mass percentage is made up to 100% with water, to obtain the tungsten plug chemical mechanical polishing liquid for reducing scratches of each example and comparative example of the present application.

[0041]

[0042]

[0043] The chemical mechanical polishing solution of the above examples and comparative examples were used to polish the wafer containing tungsten respectively. The polishing conditions were as follows: using Mirra polisher to polish, using IC1010 polishing pad, polishing pressure was 4.2 psi, and the flow rate of polishing solution was 150 mL / min. The polishing rate of tungsten was measured, and the scratch of the polished tungsten target was detected by using biological microscope at the same time, and the detection results were listed in the above table.

[0044] From the data in the table, compared with the prior art, the polishing solution of the present application has greatly improved the polishing rate in the tungsten chemical mechanical polishing process after using fumed silica as abrasive and adding oxidant hydrogen peroxide and catalyst ferric nitrate, and has greatly improved the scratch after adding appropriate amount of substance containing polyhydroxy and carboxyl, and has positive effect on the chemical mechanical polishing of tungsten.

[0045] Although the content of the present application has been described in detail by the above preferred examples, it should be recognized that the above description should not be considered as a limitation of the present application. Those skilled in the art can understand that some modifications or adjustments can be made to the present application under the teaching of the present specification. These modifications or adjustments should also be within the scope defined by the claims of the present application.

Claims

1. A chemical mechanical polishing slurry for reducing scratches in tungsten plugs, characterized in that, The polishing solution comprises the following components in the following mass percentages: 2%-20% of abrasive, 0.5%-5% of oxidant, 0.01%-0.5% of tungsten catalyst, 0.01%-0.05% of a substance containing polyhydroxy and carboxyl, and the rest is deionized water. The substance containing polyhydroxy and carboxyl is selected from one or both of D-ribose hexanoic acid and L-rhamnose acid; and the pH value of the polishing solution is 2.0-2.

5. The abrasive is fumed silica, the oxidant is hydrogen peroxide, and the tungsten catalyst is ferric nitrate.

2. The scratch-reducing tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The polishing solution comprises the following components in the following mass percentages: 5%-15% of abrasive, 2%-4% of oxidant, 0.1%-0.4% of tungsten catalyst, 0.02%-0.04% of a substance containing polyhydroxy and carboxyl, and the rest is deionized water.

3. The scratch-reducing tungsten plug chemical mechanical polishing liquid of claim 1, wherein The abrasive is commercial electronic-grade fumed silica.

4. The scratch-reducing tungsten plug CMP fluid of claim 3, wherein, The specific surface area of the fumed silica is 80-120 m 2 / g.

5. The scratch-reducing tungsten plug CMP solution of claim 4, wherein, The particle size of the fumed silica in aqueous solution is 100-180 nm.

6. The scratch-reducing tungsten plug chemical mechanical polishing liquid according to claim 1 or 2, wherein The substance containing polyhydroxy and carboxyl is L-rhamnose acid.

7. The scratch-reducing tungsten plug chemical mechanical polishing liquid according to claim 1 or 2, wherein The deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 MΩ / cm.

8. Use of the tungsten plug chemical mechanical polishing solution according to any one of claims 1-7 in tungsten chemical mechanical polishing.

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