Long-time high-rate tungsten chemical mechanical polishing solution and application thereof

Abstract

The application discloses a long-time high-speed tungsten chemical mechanical polishing liquid and application thereof. The tungsten chemical mechanical polishing liquid comprises the following components in mass percentage: 0.1-5% of abrasive, 0.5-5% of oxidant, 0.001-0.05% of tungsten catalyst, 0.01-0.05% of stabilizer, 0.005-0.05% of surface quality improver, 0.001-0.003% of oxidase, and the balance is deionized water. The tungsten chemical mechanical polishing liquid has the characteristics of long-time high speed and good surface quality.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing technology, specifically to a long-term, high-rate tungsten chemical mechanical polishing slurry and its applications. Background Technology

[0002] In the manufacturing process of integrated circuits, thousands of structural units are often built on silicon wafer substrates. These structural units are further interconnected through multiple layers of metal to form functional circuits and components. With the continuous development of integrated circuits, the miniaturization of processing precision, and the increasing complexity of circuit functions, multilayered, high-performance three-dimensional structures have become the development trend of wiring. Under high current density, tungsten metal has good resistance to electron migration, does not form hillocks, has low stress, and can form good ohmic contacts with silicon. As a filler metal material for contact windows and vias in multilayer wiring, it has been widely accepted. For devices with a minimum feature size of 0.35μm and below, each layer of multilayer wiring must be globally planarized. Chemical mechanical polishing (CMP) is currently the best and only technology that can achieve global planarization. In multilayer wiring processes, residual tungsten outside the vias must be chemically mechanically polished to achieve global planarization before proceeding to the next layer of wiring; otherwise, it will lead to wire breakage.

[0003] CMP (Chemical Mechanical Polishing) is a process that uses an abrasive mixture and a polishing pad to polish the surface of integrated circuits. In a typical chemical mechanical polishing method, the substrate is brought into direct contact with a rotating polishing pad, and pressure is applied to the back of the substrate using a weight. During polishing, the pad and stage rotate while maintaining a downward force on the back of the substrate, spraying the abrasive and chemically active solution (often called polishing slurry or polishing paste) onto the pad. This polishing slurry reacts chemically with the film being polished to initiate the polishing process.

[0004] At FAB plants, tungsten chemical polishing slurries are generally not prepared and used immediately. They are usually mixed with polishing slurry and oxidant in a tank before use. A tank of polishing slurry needs to be used for about a week. This long period of time inevitably causes hydrogen peroxide to decompose. The decomposition of hydrogen peroxide leads to a decrease in hydrogen peroxide content, which further reduces the oxidation capacity and thus the polishing rate.

[0005] To increase production capacity, existing FAB manufacturers require tungsten chemical polishing slurries to maintain a stable high polishing rate for as long as possible, thereby increasing output. However, a high polishing rate inevitably leads to poor surface quality. Therefore, it is essential to obtain a tungsten chemical polishing slurry that offers both sustained high polishing rates and good surface quality. The main mechanism of tungsten chemical mechanical polishing is a planarization process achieved through both chemical and mechanical action. The chemical action oxidizes the tungsten to form a softer oxide layer, while the mechanical action removes the softer oxide layer, exposing new metal for re-oxidation. This process is repeated until the tungsten plug is planarized. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a tungsten chemical mechanical polishing slurry that offers high polishing speed over extended periods and excellent surface quality. By adding an oxidase and a surface quality improver, the tungsten chemical mechanical polishing slurry can maintain a high polishing speed over extended periods and achieve superior surface quality.

[0007] Another object of the present invention is to provide the application of this long-duration, high-rate tungsten chemical mechanical polishing slurry in tungsten chemical mechanical polishing.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A long-term, high-rate tungsten chemical mechanical polishing slurry comprises the following components in weight percentage: 0.1%-5% abrasive, 0.5%-5% oxidant, 0.001%-0.05% tungsten catalyst, 0.01%-0.1% stabilizer, 0.001%-0.05% surface quality improver, 0.001%-0.003% oxidase, and the balance being deionized water.

[0010] In one specific embodiment, the abrasive is colloidal silica, preferably silica prepared by commercial sol-gel method.

[0011] In a preferred embodiment, the particle size of the colloidal silica is 10-150 nm; more preferably, the particle size of the colloidal silica is 50-80 nm.

[0012] In one 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.

[0013] In one specific embodiment, the content of the oxidant (e.g., hydrogen peroxide) is 2.5%.

[0014] In one specific implementation, the tungsten catalyst is ferric nitrate.

[0015] In one specific embodiment, the tungsten catalyst (e.g., ferric nitrate) content is 0.001%-0.05%, preferably 0.01%-0.03%.

[0016] In one specific embodiment, the stabilizer is an organic acid, such as one or more selected from malic acid, citric acid, tartaric acid, glycine, malonic acid, oxalic acid, etc., preferably malic acid.

[0017] In one specific embodiment, the stabilizer (e.g., malic acid) content is 0.01%-0.1%, preferably 0.03%-0.08%.

[0018] In one specific embodiment, the surface quality improver is selected from one or more of glutamic acid, serine, alanine, valine, tyrosine, histidine, lysine, and arginine, preferably arginine.

[0019] In one specific embodiment, the surface quality improver (e.g., arginine) content is 0.001%-0.05%, preferably 0.005%-0.02%.

[0020] In one specific embodiment, the oxidase is selected from either L-amino acid oxidase or D-amino acid oxidase; the oxidase content is 0.001%-0.003%.

[0021] In one specific implementation, the polishing solution has a pH value of 2.0-2.5.

[0022] In one specific implementation, the deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 megohms.

[0023] On the other hand, the aforementioned application of a long-term, high-rate tungsten chemical mechanical polishing slurry in tungsten chemical mechanical polishing.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention provides a tungsten chemical mechanical polishing slurry with long-term high-speed polishing and good surface quality. By adding specific surface quality improvers and oxidases, it achieves long-term high polishing speed and excellent surface quality, thereby enabling its application in the semiconductor field, especially in chemical mechanical polishing.

[0026] The polishing slurry of this invention incorporates amino acid-based substances as surface quality improvers, which form a protective layer on the tungsten surface through electrostatic interaction, reducing static corrosion and thus achieving good surface quality. Furthermore, by adding amino acids to the system, amino acid oxidase is added. Under the catalytic action of the oxidase, hydrogen peroxide is produced, compensating for the decrease in polishing efficiency caused by the decomposition of hydrogen peroxide and the resulting reduction in hydrogen peroxide content. This results in the development of a tungsten chemical mechanical polishing slurry that offers both long-lasting, high-speed polishing and excellent surface quality. Detailed Implementation

[0027] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0028] A tungsten chemical mechanical polishing slurry with long-term high-speed operation and good surface quality includes an abrasive, an oxidant, a catalyst, a stabilizer, a surface quality improver, an oxidase, and the remainder being deionized water.

[0029] In a preferred embodiment, a tungsten chemical mechanical polishing slurry with long-term high-rate and good surface quality comprises the following components in weight percentage: 0.1%-5% abrasive, 0.5%-5% oxidant, 0.001%-0.05% tungsten catalyst, 0.01%-0.1% stabilizer, 0.001%-0.05% surface quality improver, 0.001%-0.003% oxidase, and the balance being deionized water.

[0030] In a more preferred embodiment, a tungsten chemical mechanical polishing slurry with long-term high-rate and good surface quality comprises the following components in weight percentage: 0.1%-5% abrasive, 2.5% oxidant, 0.01%-0.03% tungsten catalyst, 0.03%-0.08% stabilizer, 0.005%-0.02% surface quality improver, 0.001%-0.003% oxidase, and the balance being deionized water.

[0031] The abrasive used is, for example, colloidal silica, preferably commercially prepared silica using the sol-gel method. Specifically, the particle size of the colloidal silica is 10-150 nm; preferably, the particle size is 50-80 nm. The effective particle size can be detected, for example, using dynamic light scattering (DLS) method. The mass percentage of colloidal silica in the polishing solution is 0.1%-5%, for example, including but not limited to 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, and 5%.

[0032] The oxidant is, for example, one or more of hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium hypochlorite, or potassium hypochlorite, preferably hydrogen peroxide. The oxidant content in the polishing solution is 0.5% to 5% by mass, for example, including but not limited to 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%, preferably 2.5%. The oxidant is preferably added before use to avoid premature decomposition.

[0033] Ferric nitrate is preferably used as the tungsten catalyst, as both nitrate and iron ions are active. 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 content of ferric nitrate catalyst in the polishing solution is 0.001%-0.05%, for example, including but not limited to 0.001%, 0.0015%, 0.002%, 0.0025%, 0.003%, 0.0035%, 0.004%, 0.0045%, and 0.05%.

[0034] As a stabilizer, the stabilizer may be an organic acid, such as one or more of malic acid, citric acid, tartaric acid, glycine, malonic acid, and oxalic acid, preferably malic acid. The mass percentage content of the stabilizer in the polishing solution is 0.01%-0.1%, for example, including but not limited to 0.01%, 0.002%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.1%.

[0035] As the surface quality improver, for example, it may be glutamic acid, serine, alanine, valine, tyrosine, histidine, lysine, or arginine, preferably arginine. The mass percentage content of the surface quality improver in the polishing solution is 0.001%-0.05%, for example, including but not limited to 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, and 0.05%.

[0036] The oxidase is selected from L-amino acid oxidase and D-amino acid oxidase; the mass percentage content of the stabilizer in the polishing solution is 0.001%-0.003%, for example, including but not limited to 0.001%, 0.002%, and 0.003%.

[0037] Typically, the pH value of the long-term, high-rate tungsten chemical mechanical polishing slurry of the present invention is 2.0-2.5, which can be adjusted by acid or alkali, such as potassium hydroxide or nitric acid.

[0038] In this invention, "long-term high-rate" means that, compared to conventional tungsten chemical mechanical polishing slurry without added oxidase, the concentration of hydrogen peroxide decreases less within the same time period, thus maintaining a high polishing rate for a longer period of time. For example, after 3 days, the hydrogen peroxide content in the system decreases by less than 5%, and the polishing rate decreases by less than 3%, while the hydrogen peroxide content in tungsten chemical mechanical polishing slurry without added oxidase decreases by at least 40%, and the polishing rate decreases by 40%.

[0039] The oxidant can also be added before use, and those skilled in the art will understand that this should also be within the scope of protection of this invention.

[0040] The present invention will be further explained and illustrated below through more specific embodiments, but these do not constitute any limitation.

[0041] The main sources of the raw materials used in the following embodiments or comparative examples are as follows:

[0042] Colloidal silica, FUSO, Japan, particle size 10-180nm;

[0043] Arginine, glutamic acid, lysine and other amino acids were all purchased from Sinopharm Group Co., Ltd.

[0044] L-amino acid oxidase and D-amino acid oxidase were purchased from Shanghai Zhenke Biotechnology Co., Ltd.

[0045] All other unlisted chemical products were purchased from Sinopharm Group Co., Ltd.

[0046] The main detection methods are as follows:

[0047] Polishing rate MRR (angstroms per minute): After tungsten is chemically and mechanically polished, the thickness difference and mass difference of the tungsten target before and after polishing are measured using a thickness gauge and a balance to evaluate the polishing rate.

[0048] Roughness: The surface roughness after polishing was observed using an atomic force microscope from PARK in South Korea;

[0049] Hydrogen peroxide content: The hydrogen peroxide content was determined using an oxidation-reduction titrator.

[0050] The above testing methods all adopt industry standard processes, and will not be elaborated here.

[0051] The polishing solutions in the following examples and comparative examples were prepared according to the composition and content of each component in Table 1.

[0052] Table 1 Polishing slurry formulations for the examples and comparative examples.

[0053]

[0054]

[0055] Prepare the chemical mechanical polishing slurry according to the formula in the table, mix it evenly, adjust the pH value to 2.5 with nitric acid or KOH, add 2.5% hydrogen peroxide before use, and make up the mass percentage with water to 100% to obtain the tungsten chemical mechanical polishing slurry of each embodiment and comparative example of the present invention.

[0056] Tungsten-containing wafers were polished using the chemical mechanical polishing slurries described in Examples 1-8 and Comparative Examples 1-6, respectively. The polishing conditions were as follows: a Mirra polishing machine was used with an IC1010 polishing pad; the polishing pressure was 4.2 psi; and the slurry flow rate was 150 mL / min. The polishing rate of the tungsten wafers was measured using the aforementioned slurries, and the roughness of the polished tungsten wafers was simultaneously inspected using an atomic force microscope. The results are shown in Table 2.

[0057] Table 2 Polishing Fluid Performance Test Data

[0058]

[0059] As can be seen from Example 3 and Comparative Examples 1 and 2 above, the content of catalyst and stabilizer has a significant impact on polishing rate and roughness.

[0060] As can be seen from the above Examples 3 and Comparative Examples 3 and 5, the content of surface quality improver has a significant impact on polishing rate and roughness.

[0061] As can be seen from the above Examples 3 and Comparative Examples 4 and 6, the content of oxidase has a significant impact on the decomposition rate of hydrogen peroxide and the stability of the rate after three days.

[0062] In summary, compared with the prior art, the polishing slurry of the present invention, when used in the tungsten chemical mechanical polishing process, exhibits the characteristics of long-term high polishing rate and high surface quality after using colloidal silica as an abrasive and adding appropriate amounts of oxidant hydrogen peroxide, catalyst ferric nitrate, stabilizer, surface quality improver, and oxidase.

[0063] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A long-term, high-rate tungsten chemical mechanical polishing slurry, characterized in that, It contains the following components by weight percentage: 0.1%-5% abrasive, 0.5-5% oxidant, 0.0015%-0.05% tungsten catalyst, 0.01%-0.1% stabilizer, 0.002%-0.05% surface quality improver, 0.001%-0.003% oxidase, and the balance being deionized water; The oxidant is hydrogen peroxide; The tungsten catalyst is ferric nitrate; The surface quality improver is selected from any one or more of glutamic acid, serine, alanine, valine, tyrosine, histidine, lysine, and arginine. The oxidase is selected from either L-amino acid oxidase or D-amino acid oxidase.

2. The tungsten chemical mechanical polishing slurry according to claim 1, characterized in that, The abrasive is colloidal silica.

3. The tungsten chemical mechanical polishing slurry according to claim 2, characterized in that, The abrasive is silica prepared by commercial sol-gel method.

4. The tungsten chemical mechanical polishing slurry according to claim 2, characterized in that, The colloidal silica has a particle size of 10-150 nm.

5. The tungsten chemical mechanical polishing slurry according to claim 4, characterized in that, The colloidal silica has a particle size of 50-80 nm.

6. The tungsten chemical mechanical polishing slurry according to claim 1, characterized in that, The content of the oxidant hydrogen peroxide is 2.5%.

7. The tungsten chemical mechanical polishing slurry according to claim 1, characterized in that, The ferric nitrate content is 0.01%-0.03% by mass.

8. The tungsten chemical mechanical polishing slurry according to claim 1, characterized in that, The stabilizer is an organic acid.

9. The tungsten chemical mechanical polishing slurry according to claim 8, characterized in that, The organic acid is selected from any one or more of malic acid, citric acid, tartaric acid, glycine, malonic acid, and oxalic acid.

10. The tungsten chemical mechanical polishing slurry according to claim 9, characterized in that, The organic acid is malic acid.

11. The tungsten chemical mechanical polishing slurry according to claim 10, characterized in that, The malic acid content is 0.03%-0.08% by mass.

12. The tungsten chemical mechanical polishing slurry according to claim 1, characterized in that, The surface quality improver is arginine.

13. The tungsten chemical mechanical polishing slurry according to claim 12, characterized in that, The arginine content is 0.005%-0.02% by mass.

14. The tungsten chemical mechanical polishing slurry according to claim 1, characterized in that, The deionized water is ultrapure water, and the resistivity of the ultrapure water is not less than 18 megohms.

15. The tungsten chemical mechanical polishing slurry according to claim 14, characterized in that, The polishing solution has a pH value of 2.0-2.

5.

16. The application of the long-term high-rate tungsten chemical mechanical polishing slurry according to any one of claims 1 to 15 in tungsten chemical mechanical polishing.

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