CN115160933B - Alkaline polishing solution for cobalt CMP of cobalt interconnection integrated circuit and preparation method thereof - Google Patents

Abstract

The invention is an alkaline polishing liquid for cobalt interconnection integrated circuit cobalt CMP and a preparation method thereof. The polishing fluid is composed of the following components, calculated in mass percentage: silica sol 1-8wt%, complexing agent 0.1-0.5wt%, inhibitor 0.002-0.03wt%, oxidant 0.20-1.00wt%, deionized water is the balance; the inhibitor is benzyl hydroxamic acid (BHA). The pH value of the invention is 8-9, it causes little corrosion to equipment, and the removal rate selectivity of cobalt and titanium nitride is significantly improved; the method is simple and suitable for industrial production.

Description

An alkaline polishing liquid for cobalt interconnect integrated circuit cobalt CMP and its preparation method

Technical field

The present invention relates to an alkaline polishing liquid used in the field of chip manufacturing and a preparation method thereof, in particular to an alkaline polishing liquid used for cobalt interconnect integrated circuit cobalt CMP and a preparation method thereof.

Background technique

Cu has the characteristics of low resistivity and strong resistance to electromigration, and is widely used as an interconnect material in integrated circuits with feature sizes of 65nm and below. However, when the technology node is reduced to 10nm and below, Cu as an interconnect material is increasingly unable to meet industrial requirements. Compared with Cu, Co has a smaller electron mean free path, making Co have a lower resistivity at feature sizes of 10nm and below; in addition, Co can work with thinner barrier layers, which is beneficial to further reducing features. size. These advantages make Co the main candidate interconnect material to replace Cu, and it is used by Intel for M0 and M1 layer interconnects.

The main requirements of the polishing fluid used for CMP rough polishing of cobalt interconnect structures are a high removal rate ratio of cobalt and titanium nitride and good post-polishing surface quality. Currently, the mainstream polishing fluid used for cobalt interconnect structure CMP mainly consists of silica sol, oxidant, complexing agent, nonionic surfactant, and inhibitor. Inhibitors are mainly azole inhibitors based on BTA. These inhibitors are toxic to the human body and can easily cause environmental pollution if not handled properly.

Contents of the invention

The object of the present invention is to provide an alkaline polishing liquid for cobalt interconnect integrated circuit cobalt CMP and a preparation method thereof in view of the shortcomings of the current technology. This polishing slurry uses (BHA) as an inhibitor, and can obtain very good polished surface quality with a very small amount (only one ten thousandth). The method of the invention is simple and suitable for industrial production.

In order to solve the above technical problems, the technical solution of the present invention is:

An alkaline polishing liquid for cobalt interconnection integrated circuit cobalt CMP. The polishing liquid consists of the following components, in terms of mass percentage:

The sum of the stated component proportions is 100%.

The pH value of the alkaline polishing solution is 8.0-9.0;

The complexing agent is glycine;

The inhibitor is benzohydroxamic acid (BHA);

The oxidizing agent is hydrogen peroxide (H ₂ O ₂ ).

The above-mentioned highly selective alkaline polishing liquid for rough polishing of cobalt interconnect structure CMP, the average particle size of the silica sol is 60-70nm, the dispersion is between ±5%, and a 100 micron pore size filter element is used for ultrafiltration .

The preparation method of the alkaline polishing liquid for cobalt interconnect integrated circuit cobalt CMP, the method includes the following steps:

Add silica sol, complexing agent, inhibitor and oxidant to deionized water according to the stated proportions, and stir under vacuum to obtain a polishing liquid.

Compared with the prior art, the beneficial effects of the present invention are:

When cobalt interconnects are CMP, the above-mentioned polishing fluid can effectively improve the removal rate selectivity; the polishing fluid is a weakly alkaline polishing fluid with a pH value of 8-9, which has little corrosion on the equipment; when used, a very small amount can Achieve very good polished wafer surface quality; after polishing, the removal rate selectivity ratio of cobalt and titanium nitride is significantly improved, reaching a maximum of 26.1; through electrochemical experiments, it is found that the addition of BHA greatly reduces the static corrosion rate of the cobalt film , the static corrosion rate without adding BHA is Minimum when adding BHA is/> The very low static corrosion rate greatly reduces the possibility of device defects; the polishing slurry is simple to prepare and meets the requirements of industrial scale production; it can improve the yield of the polished wafer surface, and the inhibitors are easy to remove, making it easier for subsequent processes. The cleaning process provides great convenience and effectively improves the surface quality of the wafer.

Description of the drawings

Figure 1 is an AFM image of the cobalt surface treated with 0.000g BHA inhibitor polishing liquid in Example 1.

Figure 2 is an AFM image of the cobalt surface treated with 0.048g BHA inhibitor polishing liquid in Example 2.

Figure 3 is an AFM image of the cobalt surface treated with 0.068g BHA inhibitor polishing liquid in Example 3.

Figure 4 is an AFM image of the cobalt surface treated with 0.274g BHA inhibitor polishing liquid in Example 4.

Detailed ways

In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the best embodiments.

Example 1:

Preparation of 1000g polishing fluid:

Take 50g of abrasive silica sol (from Jinwei Group Co., Ltd.), with a particle size of 60.0nm and a dispersion of ±5% (which is a polishing fluid mass concentration of 5%); add 2.25g of glycine and 16.7g of hydrogen peroxide respectively. (Among them, the mass concentration of hydrogen peroxide (H ₂ O ₂ ) is 30%, that is, 5g, which is a polishing fluid mass concentration of 0.5%); deionized water is the balance, and the pH of the polishing fluid is 8; The specific preparation method is as follows: silica sol, glycine and hydrogen peroxide are added to deionized water in sequence according to the component amount, and stirred evenly by vacuum negative pressure stirring. During the stirring process, the pH value is maintained at 8 by titrating potassium hydroxide. Finally, Make up the remaining amount with deionized water and continue stirring evenly.

Test monitoring: The pH of the polishing fluid is 8.0 and the particle size is 60.0nm.

Rate experiment: Use the prepared polishing fluid in the Alpsitec-E460 polishing machine, the working pressure is 1.5 psi, the polishing disk speed is 93 rpm, the polishing head speed is 87 rpm, and the polishing fluid flow is 300ml/min.

A cobalt sheet with a diameter of 3 inches and a thickness of 2 mm (purity is 99.99%), and a titanium nitride sheet with a diameter of 3 inches and a thickness of 2 mm (purity is 99.99%) are polished, and the average removal rate of cobalt and titanium nitride is measured: Cobalt for Titanium nitride is/> The removal rate selection ratio is relatively low, 15.1. The cobalt film was soaked in a solution with the same components but without silica sol. The surface roughness of the cobalt film was very large, as shown in Figure 1, reaching 10.4nm.

Example 2:

Preparation of 1000g polishing fluid:

Take 50g of abrasive silica sol, with a particle size of 60.0nm, a dispersion of ±5%, and a concentration of 5%; 2.25g of glycine; 16.7g of hydrogen peroxide (which contains the mass percentage of hydrogen peroxide (H ₂ O ₂ ) The concentration is 30%, that is, 5g, which is the polishing fluid mass concentration of 0.5%; inhibitor (BHA) 0.048006g; deionized water is the balance, and the polishing fluid pH is 8; the specific preparation method is as follows: silica sol, glycine, BHA and hydrogen peroxide are added to deionized water in sequence according to the component amounts, and stirred evenly by vacuum stirring. During the stirring process, the pH value is maintained at 8 by titrating potassium hydroxide, and finally the remaining balance is filled with deionized water. , continue to stir evenly.

Test monitoring: The pH of the polishing fluid is 8.0 and the particle size is 60.0nm.

Rate experiment: Use the prepared polishing fluid in the Alpsitec-E460 polishing machine, the working pressure is 1.5 psi, the polishing disk speed is 93 rpm, the polishing head speed is 87 rpm, and the polishing fluid flow is 300ml/min.

A cobalt sheet with a diameter of 3 inches and a thickness of 2 mm (purity is 99.99%), and a titanium nitride sheet with a diameter of 3 inches and a thickness of 2 mm (purity is 99.99%) are polished, and the average removal rate of cobalt and titanium nitride is measured: Cobalt for Titanium nitride is/> The removal rate selection ratio is relatively low, 18.3. The cobalt film was soaked in a solution with the same components but without silica sol. As shown in Figure 2, the surface roughness of the cobalt film was 8.64nm.

Example 3:

Other steps are the same as Example 2, except that the inhibitor (BHA) is 0.06857g;

After polishing, the average removal rate of cobalt and titanium nitride was measured: Cobalt is Titanium nitride is/> The removal rate selection ratio is relatively high, 22.8. As shown in Figure 3, the surface roughness of cobalt is 6.03nm.

Example 4:

Other steps are the same as in Example 1, except that the inhibitor (BHA) is 0.27428g;

After polishing, the average removal rate of cobalt and titanium nitride was measured: Cobalt is Titanium nitride is/> The removal rate selection ratio is relatively low, 18.7. As shown in Figure 4, the surface roughness of cobalt is 7.96nm.

It can be seen from the above examples that the optimization is used to obtain the ratio. In Experimental Example 1, when BHA is not added, the removal rate selectivity is low and the surface quality is poor. When BHA is added, the removal rate selectivity increases and the surface quality is effectively improved. Experimental example 3 has the highest selectivity and the best surface quality when adding 0.06857g. The addition of BHA effectively protects the wafer and is very beneficial to improving the yield of the wafer.

How the above alkaline slurry used during CMP of cobalt interconnect structures works:

Silica sol (nanoscale silica) is an abrasive with moderate hardness (Mohs hardness 6 to 7), good dispersibility, and small particle size. The state of the wafer surface after polishing can be greatly improved. Silica sol is milky white and translucent. It is a colloidal substance formed by the diffusion of silica colloid in pure water. Silica sol is non-toxic and tasteless, has little environmental pollution, and is an ideal abrasive.

Glycine is a white crystal or crystalline powder with a sweet taste and a melting point of 232 to 236°C. It is soluble in water and insoluble in ethanol and ether. It is an effective complexing agent. It can undergo complex reactions with copper, iron, cobalt and other metal ions in acidic, neutral and alkaline solutions to form soluble complexes to achieve the purpose of removing metal surface oxides. The inhibitor benzohydroxamic acid (BHA) is a white crystalline solid, which is often used as an effective collector for refractory minerals such as smithsonite and wolframite. It has the function of simultaneously inhibiting the corrosion of cobalt and titanium nitride and protecting the low-K dielectric layer. As for the oxidant hydrogen peroxide (H ₂ O ₂ ), it is environmentally friendly, pollution-free and cheap. Its decomposition products in the solution are only water and oxygen, without other pollutants. It does not introduce metal ions and is easy to clean after CMP. It is suitable for in industrial production.

The above is a detailed description of the alkaline polishing slurry for rough polishing of cobalt interconnect CMP and its preparation method with reference to specific embodiments. This is illustrative rather than restrictive, and several implementations can be listed according to the limited scope. Therefore, changes and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.

Matters not covered in the present invention are known technologies.

Claims (1)

1. The alkaline polishing solution for cobalt CMP of the cobalt interconnection integrated circuit is characterized by comprising the following components in percentage by mass:

the sum of the component proportions is 100%;

the complexing agent is glycine;

the inhibitor is Benzoic Hydroxamic Acid (BHA);

the oxidant is hydrogen peroxide (H) ₂ O ₂ )；

The average particle diameter of the silica sol is 60-70nm, the dispersity is +/-5%, and a filter element with a 100-micrometer pore diameter is used for ultrafiltration;

the pH value of the alkaline polishing solution is 8.0-9.0;

the preparation method of the alkaline polishing solution for cobalt CMP of the cobalt interconnection integrated circuit comprises the following steps:

sequentially adding silica sol, complexing agent, inhibitor, oxidant and deionized water according to the proportion, and stirring to obtain polishing solution.