High rate tungsten plug chemical mechanical polishing solution and use thereof

Abstract

The application discloses a high-speed tungsten plug chemical mechanical polishing solution and application thereof. The tungsten plug chemical mechanical 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 rate accelerator, and the balance is deionized water. The tungsten plug chemical mechanical polishing solution has the characteristics of fast polishing rate, good surface quality and excellent stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical mechanical polishing technology, in particular to a high-speed tungsten plug chemical mechanical polishing solution and application thereof. BACKGROUND

[0002] With the continuous development of semiconductor technology and the continuous increase of large-scale integrated circuit interconnection layers, the planarization technology of conductive layer and insulating medium layer becomes particularly critical. In the 1980s, the chemical mechanical polishing (CMP) technology pioneered by IBM Corporation is considered to be the most effective method for global planarization.

[0003] Chemical mechanical polishing (CMP) is composed of chemical action, mechanical action and the combination of the two. It is usually composed of a polishing pad with a polishing pad and a polishing head for carrying the chip. The polishing head fixes the chip, and then presses the front surface of the chip on the polishing pad. When chemical mechanical polishing is performed, the polishing head moves linearly or rotates in the same direction as the polishing table. At the same time, the slurry containing the polishing agent is dropped on the polishing pad and spread on the polishing pad due to centrifugal force. The chip surface is globally planarized under the action of mechanical and chemical action.

[0004] The main mechanism of chemical mechanical polishing (CMP) of metal layer is believed to be that the oxidizing agent first oxidizes the metal surface into a film, and the polishing agent represented by silicon dioxide and aluminum oxide mechanically removes the oxide film to produce a new metal surface for continuous oxidation, and the two actions are performed cooperatively.

[0005] Metal tungsten, as one of the objects of chemical mechanical polishing (CMP), has strong resistance to electron migration at high current density and can form good ohmic contact with silicon, so it can be used as a filling metal and diffusion barrier layer for contact windows and via holes.

[0006] In order to improve production capacity, major FAB manufacturers require tungsten chemical polishing solution to improve polishing rate as much as possible to increase production. The main mechanism of tungsten chemical mechanical polishing is that chemical and mechanical actions are used to planarize 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 to expose new metal for oxidation and then removal, and the process is repeated to achieve the purpose of planarization of tungsten plug. The chemical action is the main one, and the mechanical action is the auxiliary one. The key step to improve the polishing rate is the chemical corrosion action. How to improve the chemical corrosion action is the key to the development of tungsten polishing solution, that is, how to effectively improve the chemical corrosion action through chemical additives to improve the polishing rate. SUMMARY

[0007] To solve the above problems, the application provides a high-speed tungsten plug chemical mechanical polishing solution, which can ensure high polishing speed of the tungsten chemical mechanical polishing solution by adding a speed promoter.

[0008] Another purpose of the application is to provide application of the high-speed tungsten plug chemical mechanical polishing solution in tungsten chemical mechanical polishing.

[0009] To achieve the above purposes, the application adopts the following technical scheme:

[0010] The high-speed tungsten plug chemical mechanical 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 speed promoter, and the rest is deionized water, wherein the speed promoter is an amino functional group compound with SP2 hybridization connected carbon atoms closely packed.

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

[0012] In a preferred embodiment, 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 ferric nitrate.

[0015] In a specific embodiment, the speed promoter is an amino functional group compound with SP2 hybridization connected carbon atoms closely packed, which is an amino porous carbon nanotube.

[0016] In a preferred embodiment, the length of the amino porous carbon nanotube is 8-15 nm.

[0017] In a specific embodiment, the pH value of the polishing solution is 2.0-2.5.

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

[0019] On the other hand, the application of the aforementioned high-speed tungsten plug chemical mechanical polishing solution in tungsten chemical mechanical polishing.

[0020] Compared with the prior art, the present application has the beneficial effects that:

[0021] The high-speed tungsten plug chemical mechanical polishing solution of the present application improves the removal rate of tungsten plug by adding specific rate accelerators, thereby realizing the application in the field of semiconductors, especially in chemical mechanical polishing.

[0022] The main reason why the amino porous carbon nanotube containing amino functional group compound with the SP2 hybrid connected carbon atom closely packed can be used as a rate accelerator is that: first, the porous structure can efficiently adsorb free oxygen, so that the reaction ① proceeds in the positive direction, thereby increasing the content of hydroxyl radicals in the reaction ②, and ultimately increasing the polishing rate; second, the carbon nanotube has a certain autocatalytic effect, which can accelerate the transfer of redox reaction electrons, so that the reaction occurs quickly and the polishing rate is improved; in addition, the amino functional group has a further catalytic effect to further accelerate the reaction; third, the porous carbon nanotube containing amino functional group has a complexing effect, which can complex the product in the reaction ③, thereby increasing the polishing rate.

[0023] Fe 3+ +H2O2=Fe 2+ +O2+2H + ①

[0024] Fe 2+ +H2O2+H - =Fe 3+ +H2O+OH·②

[0025] OH·+W=WO3③ DETAILED DESCRIPTION

[0026] 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.

[0027] A high-speed tungsten plug chemical mechanical polishing solution, comprising an abrasive, an oxidizing agent, a catalyst, a rate accelerator, and the rest is deionized water.

[0028] In one preferred embodiment, the high rate tungsten plug chemical mechanical 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 rate accelerator, and the rest is deionized water, wherein the rate accelerator is an amino-functional compound with close packing of SP2 hybridized carbon atoms, preferably an amino-porous carbon nanotube. That is, the polishing solution is 100%, of which the abrasive accounts for 2-20%, the oxidant accounts for 0.5-5%, the tungsten catalyst accounts for 0.01-0.5%, the rate accelerator accounts for 0.05-5%, and the rest is water.

[0029] 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 aqueous solution of the fumed silica dissolved in water is 100-180 nm. The effective particle size can be detected by dynamic light scattering method (DLS method), for example. 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%.

[0030] 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 of the oxidant 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%, and 5%. The oxidant is preferably added before use to avoid premature decomposition.

[0031] As the tungsten catalyst, preferably ferric nitrate, both the nitrate ions and the iron ions can act. In the presence of hydrogen peroxide oxidant, Fenton reaction occurs, promoting the progress of chemical mechanical polishing and increasing the polishing rate. The mass percentage 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%, and 0.5%.

[0032] As the rate accelerator, it is selected from a compound containing amino functional group with close packing of carbon atoms connected by SP2 hybridization, such as amino porous carbon nanotube, which contains amino group and has excellent conjugated structure and at the same time is porous structure, all of which can improve the polishing rate and achieve high removal of tungsten plug. The mass percentage content of the rate accelerator in the polishing liquid is 0.05% to 0.5%, for example, including but not limited to 0.01%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%.

[0033] Generally, the pH value of the high-rate tungsten plug chemical mechanical polishing liquid is 2.0 to 2.5, which can be adjusted by acid or base, for example, potassium hydroxide or nitric acid is used to adjust the pH value.

[0034] 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.

[0035] The present application will be further explained and described below by more specific examples, but not constitute any limitation.

[0036] The main raw materials used in the following examples or comparative examples are as follows:

[0037] Fumed silica, Germany WACKER AERISOL, micron grade, specific surface area 90 g / m 2 ;

[0038] Amino porous carbon nanotube, Xianfeng Nanometer Co., Ltd.;

[0039] Porous carbon nanotube without amino group, Xianfeng Nanometer Co., Ltd.;

[0040] Hydroxyl porous carbon nanotube, Xianfeng Nanometer Co., Ltd.

[0041] The main detection methods are as follows:

[0042] Polishing rate MRR (Angstrom / min): after chemical mechanical polishing of tungsten, the thickness difference and mass difference of tungsten target before and after polishing are measured by thickness meter and balance to evaluate the polishing rate;

[0043] The above test methods all use standard process in the industry, which will not be repeated here.

[0044] 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.

[0045]

[0046]

[0047] The chemical mechanical polishing solution was prepared according to the formula in the table, mixed uniformly, the pH value was adjusted to 2.5 by nitric acid or KOH, 0.5% to 5% hydrogen peroxide was added before use, and water was added to make the mass percentage 100%, to obtain a high-speed tungsten plug polishing solution of each embodiment and the comparative example of the present application.

[0048] The chemical mechanical polishing solution of each embodiment 1 to 7 and comparative example 1 to 8 was used to polish the tungsten-containing wafer. The polishing conditions were: using Mirra polisher for polishing, using IC1010 polishing pad, polishing pressure was 4.2 psi, and polishing solution flow was 150 mL / min. The polishing rate of the above-mentioned polishing solution on tungsten was measured, and at the same time, the point corrosion detection of the polished tungsten target was carried out by using biological microscope.

[0049] From the above-mentioned embodiments 1, 3 to 5 and comparative examples 1 to 4, it can be found that the concentration of ferric nitrate and hydrogen peroxide has a certain effect on the improvement of tungsten polishing rate within a certain range.

[0050] From the above-mentioned embodiments 1 to 2 and comparative examples 5 to 6, it can be found that the concentration of rate promoter amino porous carbon nanotube has excellent effect on the improvement of rate within a certain range.

[0051] From the above-mentioned embodiments 5 and comparative examples 7 and 8, it can be found that the porous carbon nanotube without amino or hydroxyl porous carbon nanotube has certain difference in improving the polishing rate compared with the amino porous carbon nanotube.

[0052] In summary, compared with the prior art, the polishing solution of the present application has greatly improved the polishing rate after using fumed silica as abrasive and adding oxidant hydrogen peroxide and catalyst ferric nitrate, and has positive effect on tungsten chemical mechanical polishing after adding appropriate amount of rate promoter.

[0053] Although the content of the present application has been described in detail by the above preferred embodiments, 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 high rate tungsten plug chemical mechanical polishing solution, characterized by, A polishing solution comprising the following components by mass percentage: 2-20% abrasive, 0.5-5% oxidizing agent, 0.01-0.5% tungsten catalyst, 0.01-0.05% rate accelerator, and the balance deionized water, wherein the rate accelerator is a carbon atom tightly packed SP2 hybridization containing amino functional group compound; The SP2 hybridization carbon atom tightly packed containing amino functional group compound is an amino porous carbon nanotube; The abrasive is fumed silica; The oxidizing agent is selected from one or more of hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium hypochlorite or potassium hypochlorite; The tungsten catalyst is ferric nitrate.

2. The tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The abrasive is commercial electronic grade fumed silica.

3. The tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The specific surface area of the fumed silica is 80 to 120 m 2 / g.

4. The tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The particle size of the fumed silica in the aqueous solution is 100-180 nm.

5. The tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The oxidizing agent is hydrogen peroxide.

6. The tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The length of the amino porous carbon nanotube is 8-15 nm.

7. The tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The pH value of the polishing solution is 2.0-2.

5.

8. The tungsten plug chemical mechanical polishing liquid according to claim 1, wherein The deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 MΩ·cm.

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

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