Green chemical mechanical polishing composition and preparation method thereof

Abstract

The invention provides a green chemical mechanical polishing composition and a preparation method thereof, the polishing composition comprises, by mass, 0.1-5% of grinding particles, 0.01-3% of an oxidizing agent, 0.01-5% of a complexing agent and the balance water, and the complexing agent is maltol and / or ethyl maltol. In order to solve the technical problems that cobalt is large in hardness and difficult to remove, and especially the polishing rate is low in an alkaline environment, the maltol and / or ethyl maltol complexing agent is adopted to be matched with grinding particles and an oxidizing agent, the removal rate of the cobalt interconnection layer is remarkably increased, and better surface quality is obtained; and meanwhile, the used additive is green and environment-friendly, and conforms to the concept of green manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical mechanical polishing, and in particular relates to a green chemical mechanical polishing composition and a preparation method thereof, which are particularly suitable for chemical mechanical polishing of a cobalt interconnect structure. Background Art

[0002] There are many micro components such as transistors in the chip. Currently, copper is generally used to connect them together to achieve signal transmission, forming the so-called copper interconnect structure. However, when the chip feature size is reduced to the nanometer level, the resistivity of the copper wire increases significantly, leading to problems such as RC delay and thermal effect. At the same time, the probability of electron scattering increases, further increasing RC delay and the risk of electromigration. Therefore, the copper interconnect structure is gradually approaching its performance limit, and it is urgent to introduce new materials and technologies.

[0003] Metallic cobalt has advantages such as a smaller electron mean free path, excellent step coverage and anti-electromigration performance. It is considered to be one of the most promising interconnect materials to replace copper. Intel 7 technology uses cobalt interconnect structure, which effectively improves the problem of electromigration. However, the application of cobalt has caused a series of problems in chip production links such as chemical mechanical polishing (CMP). The CMP process combines the mechanical action of polishing liquid abrasive particles with the chemical action of other additives to achieve a high degree of flatness on the wafer surface, which helps to achieve multi-layer metal interconnection structure and improve chip performance and yield. Due to the more active chemical properties and higher hardness of cobalt, common polishing liquids are prone to severe corrosion or slow removal rate, which seriously affects the performance and production efficiency of devices. In addition, the additives used in commercial polishing liquids are often easy to pollute the environment, which is inconsistent with the concept of green manufacturing. Therefore, it is an urgent problem to select suitable additives to achieve a balance between low corrosion and high-speed removal under the premise of green environmental protection. Summary of the invention

[0004] In response to the technical problem, the present invention provides a green chemical mechanical polishing composition and a preparation method thereof. By adding maltol and ethyl maltol as complexing agents, the polishing rate of cobalt is effectively improved, and the surface quality after polishing is high.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A green chemical mechanical polishing composition comprises, by mass fraction, 0.1-5wt% of abrasive particles, 0.01-3wt% of an oxidant and 0.01-5wt% of a complexing agent, and the balance is water.

[0007] The complexing agent is maltol and / or ethyl maltol.

[0008] The abrasive particles are used to remove metal or metal reactants in contact with the abrasive particles by mechanical friction, thereby achieving the purpose of mechanical removal. The abrasive particles can be selected from silicon dioxide, cerium dioxide or aluminum oxide particles, wherein silicon dioxide sol is preferably used as the abrasive particles, and the particle size of the abrasive particles is preferably 20-200 nm.

[0009] The function of the oxidant is to oxidize the metal to the corresponding metal oxide or hydroxide. Preferably, the oxidant is selected from hydrogen peroxide.

[0010] Maltol and / or ethyl maltol corrode the dense metal oxides or hydroxides on the surface of the material, take away the metal ions, form a loose structure, assist in the mechanical removal of abrasive particles, and increase the polishing rate.

[0011] Preferably, the mixture comprises 1-3 wt % of abrasive particles, 0.6-1.5 wt % of oxidant and 0.5-1 wt % of complexing agent, calculated by mass fraction.

[0012] Preferably, calculated by mass fraction, the mixture includes 3wt% abrasive particles, 0.6wt% oxidant and 0.5wt% complexing agent; or 3wt% abrasive particles, 0.6wt% oxidant and 1wt% complexing agent; or 1wt% abrasive particles, 0.6wt% oxidant and 1wt% complexing agent; or 3wt% abrasive particles, 1.5wt% oxidant and 1wt% complexing agent.

[0013] Preferably, the polishing composition further comprises a pH adjuster for adjusting the pH value of the polishing composition to 8-12.

[0014] Preferably, the pH adjuster is selected from potassium hydroxide or sodium hydroxide.

[0015] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned green chemical mechanical polishing composition, comprising: adding a complexing agent to deionized water according to a mass ratio to mix into a solution, adding abrasive particles and an oxidant to obtain the polishing composition.

[0016] Preferably, the process comprises: adding a complexing agent to deionized water according to a mass ratio to mix the solution, then adding a pH adjuster to adjust the pH value to 8-12, and then adding abrasive particles and an oxidant to obtain the polishing composition.

[0017] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art:

[0018] In order to solve the technical problem that cobalt is hard and difficult to remove, especially with a low polishing rate in an alkaline environment, the present invention proposes using a complexing agent of maltol and / or ethyl maltol in combination with abrasive particles and an oxidant to significantly improve the removal rate of the cobalt interconnect layer and obtain better surface quality. At the same time, the additives used are green and environmentally friendly, which is in line with the concept of green manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is an atomic force microscope image of the surface morphology of the cobalt wafer after being statically etched by the composition of Example 1 in the embodiment of the present invention;

[0020] Figure 2 This is an atomic force microscope image of the surface morphology of the cobalt wafer in the embodiment of the present invention after being statically etched by the composition of Comparative Example 1;

[0021] Figure 3 This is an atomic force microscope image of the surface morphology of the cobalt wafer in the embodiment of the present invention after being statically etched by the composition of Comparative Example 2;

[0022] Figure 4 This is an atomic force microscope image of the surface morphology of the cobalt wafer in the embodiment of the present invention after being statically etched by the composition of Comparative Example 3;

[0023] Figure 5 This is an atomic force microscope image of the surface morphology of the cobalt wafer in the embodiment of the present invention after being statically etched by the composition of Comparative Example 4;

[0024] Figure 6 An atomic force microscope image of the surface morphology of a cobalt wafer not treated with a polishing liquid in an embodiment of the present invention;

[0025] Figure 7 This is an atomic force microscope image of the surface morphology of the cobalt wafer after being polished by the polishing composition of Example 2 in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The green chemical mechanical polishing composition and its preparation method proposed by the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more clear according to the following description.

[0027] 1. Static corrosion

[0028] Weigh / measure the oxidizing agent hydrogen peroxide and the complexing agent respectively, mix them according to the component ratio shown in Table 1, and the balance is deionized water; use potassium hydroxide aqueous solution to adjust the solution pH to a specified value.

[0029] Table 1: Solution composition

[0030] Hydrogen peroxide / wt% Complexing agent pH Example 1 0.6 1wt% ethyl maltol 10 Comparative Example 1 0.6 none 10 Comparative Example 2 0.6 1wt% Glycine 10 Comparative Example 3 0.6 1wt% Malic acid 10 Comparative Example 4 0.6 1wt% citric acid 10

[0031] Static etching simulates the state of the wafer's depression during dynamic polishing. The wafers were placed in 100 ml of the above slurry and left to stand for 1 minute. After being taken out, they were immediately rinsed with deionized water and then dried with nitrogen. The surface roughness was measured using an atomic force microscope. The results are as follows: Figure 1-5 and as shown in Table 2. The results show that when other complexing agents are used, there is little difference between the wafer surface and the surface without complexing agent, that is, the corrosion degree is weak; when the complexing agent is ethyl maltol, the corrosion on the cobalt surface is the most severe, proving that its reaction with cobalt is more intense.

[0032] Table 2: Surface roughness of cobalt wafer after etching

[0033] Average roughness / nm Root mean square roughness / nm Example 1 2.764 3.482 Comparative Example 1 0.929 1.258 Comparative Example 2 1.241 1.695 Comparative Example 3 0.855 1.117 Comparative Example 4 0.740 0.960

[0034] 2. Chemical mechanical polishing

[0035] The abrasive silica sol, the oxidant hydrogen peroxide, and the complexing agent were weighed / measured respectively, and mixed according to the component ratio shown in Table 3, with the balance being deionized water; and the pH value of the solution was adjusted to a specified value using an aqueous potassium hydroxide solution.

[0036] Table 3: Slurry composition

[0037]

[0038]

[0039] Process conditions:

[0040] The equipment used was a Kejing UNIPOL-1203 chemical mechanical grinder and polisher, the temperature was room temperature, the polishing table speed was 150 revolutions per minute, the polishing liquid flow rate was 200 milliliters per minute, the polishing head pressure was 1.5 pounds per square inch, and the polishing time was two minutes.

[0041] The chemical mechanical polishing liquids provided in Examples 2-5 and Comparative Examples 5-11 were used to perform chemical mechanical polishing on a two-inch cobalt wafer, and the polishing rate was calculated by weight loss method. The results are shown in Table 4.

[0042] Table 4 Cobalt wafer polishing rate

[0043]

[0044]

[0045] It can be seen from Table 4 that when the complexing agent is maltol or ethyl maltol, the polishing rate of cobalt is significantly improved, while the polishing rate is lower when there is no complexing agent or other complexing agents are used, which highlights the promoting effect of ethyl maltol or maltol in the chemical mechanical polishing process of cobalt.

[0046] The surface morphology was observed and the surface roughness was measured by atomic force microscopy, such as Figure 6-7 As shown in Figure 5 and Table 5. The results show that the surface quality of the cobalt wafer is significantly improved after polishing with the polishing solution containing ethyl maltol, which further proves the excellent effect of ethyl maltol in the polishing process.

[0047] Table 5 Surface roughness of cobalt wafer after polishing

[0048] Example Average roughness / nm Root mean square roughness / nm Blank control 2.395 3.564 Example 2 0.637 0.868

[0049] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A green chemical mechanical polishing composition, characterized in that: According to the mass fraction, it includes 0.1-5wt% of abrasive particles, 0.01-3wt% of oxidant and 0.01-5wt% of complexing agent, and the balance is water. The complexing agent is maltol and / or ethyl maltol.

2. The green chemical mechanical polishing composition according to claim 1, characterized in that: Calculated by mass percentage, it includes 3wt% of abrasive particles, 0.6wt% of oxidant and 0.5-1wt% of complexing agent.

3. The green chemical mechanical polishing composition according to claim 1 or 2, characterized in that: Calculated by mass fraction, it includes 3wt% of abrasive particles, 0.6wt% of oxidant and 0.5wt% of complexing agent; or 3wt% of abrasive particles, 0.6wt% of oxidant and 1wt% of complexing agent; or 1wt% of abrasive particles, 0.6wt% of oxidant and 1wt% of complexing agent; or 3wt% of abrasive particles, 1.5wt% of oxidant and 1wt% of complexing agent.

4. The green chemical mechanical polishing composition according to claim 1, characterized in that: The abrasive particles are selected from silicon dioxide or silicon dioxide sol.

5. The green chemical mechanical polishing composition according to claim 4, characterized in that: The particle size of the abrasive particles is 20-200 nm.

6. The green chemical mechanical polishing composition according to claim 1, characterized in that: The oxidizing agent is selected from hydrogen peroxide.

7. The green chemical mechanical polishing composition according to claim 1, characterized in that: The polishing composition further includes a pH adjuster for adjusting the pH value of the polishing composition to 8-12.

8. The green chemical mechanical polishing composition according to claim 7, characterized in that: The pH adjuster is selected from potassium hydroxide or sodium hydroxide.

9. A method for preparing the green chemical mechanical polishing composition according to any one of claims 1 to 8, characterized in that: include: According to the mass ratio, the complexing agent is added into deionized water to mix into a solution, and then abrasive particles and an oxidant are added to obtain the polishing composition.

10. The method for preparing the green chemical mechanical polishing composition according to claim 9, characterized in that: include: According to the mass ratio, the complexing agent is added to deionized water to mix into a solution, and then the abrasive particles and the oxidant are added, and then the pH adjuster is added to adjust the pH value to 8-12 to obtain the polishing composition.

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