Chemical mechanical polishing solution for tungsten polishing

Abstract

The present application provides a chemical mechanical polishing solution for tungsten polishing, which comprises water, abrasive particles, a tungsten polishing accelerator, a stabilizer, a peroxide, a first corrosion inhibitor for tungsten, and a second corrosion inhibitor for tungsten. The synergistic effect of the two corrosion inhibitors in the chemical mechanical polishing solution of the present application can significantly reduce the static corrosion rate of tungsten, increase the polishing speed to static corrosion speed ratio of tungsten, improve the erosion defect in a graphic chip, and significantly improve the yield of products.

Description

Technical Field

[0001] This invention relates to the field of chemical reagents for semiconductor manufacturing, and more particularly to a chemical mechanical polishing slurry for tungsten polishing. Background Technology

[0002] With the continuous development of semiconductor technology and the increasing number of interconnect layers in large-scale integrated circuits, the planarization technology of conductive and insulating dielectric layers has become particularly critical. In the 1980s, chemical mechanical polishing (CMP) technology, pioneered by IBM, is considered to be the most effective method for global planarization.

[0003] Chemical mechanical polishing (CMP) combines chemical, mechanical, and combined actions. It typically consists of a polishing table with a polishing pad and a polishing head that holds the chip. The polishing head holds the chip in place, and the front side of the chip is pressed against the polishing pad. During CMP, the polishing head moves linearly across the polishing pad or rotates in the same direction as the polishing table. Simultaneously, a slurry containing an abrasive is dripped onto the polishing pad and spreads evenly due to centrifugal force. The chip surface achieves global planarization through the combined mechanical and chemical action.

[0004] The main mechanism of chemical mechanical polishing (CMP) of metal layers is believed to be that the oxidant first oxidizes the metal surface into a film, and the abrasive, represented by silica and alumina, mechanically removes the oxide film, resulting in a new metal surface that continues to be oxidized. These two actions work together.

[0005] Tungsten metal exhibits strong resistance to electron migration at high current densities and can form excellent ohmic contacts with silicon. Therefore, it can be used as a filler metal for contact windows and vias, as well as a diffusion barrier layer, in semiconductor devices. Consequently, polishing of tungsten metal is frequently involved in semiconductor manufacturing processes.

[0006] There are several methods for chemical mechanical polishing (CMP) of tungsten:

[0007] In 1991, FBKaufman et al. reported a method for using potassium ferricyanide for chemical mechanical polishing of tungsten ("Chemical Mechanical Polishing for Fabricating Patterned W Metal Features as Chip Interconnects", Journal of the Electro Chemical Society, Vol. 138, No. 11, November 1991).

[0008] US Patent 5340370 discloses a formulation for tungsten chemical mechanical polishing (CMP) containing 0.1 M potassium ferricyanide, 5% silicon dioxide, and acetate as a pH buffer. Potassium ferricyanide's widespread use is limited by its decomposition into highly toxic hydrogen cyanide under ultraviolet or sunlight exposure, and in acidic media.

[0009] US patents 5,527,423, 6,008,119, and 6,284,151 disclose methods for using an Fe(NO3)3, alumina system in tungsten mechanical polishing (CMP). This polishing system offers advantages in terms of static etching rate; however, the use of alumina as the abrasive leads to severe product defects. Furthermore, the high concentration of ferric nitrate makes the polishing solution highly acidic, severely corroding the equipment and generating rust, which contaminates the polishing pad. In addition, the high concentration of iron ions, being mobile metal ions, significantly reduces the reliability of semiconductor devices.

[0010] US Patents 5,225,034 and 5,354,490 disclose a method for polishing metals (copper) by using hydrogen peroxide and silver nitrate together as oxidants. However, in this polishing method, the amount of silver nitrate used is very large (greater than 2%), resulting in problems such as excessively high polishing solution costs, unstable abrasives that easily precipitate, and rapid decomposition of hydrogen peroxide.

[0011] US Patent 5958288 discloses a method for tungsten chemical mechanical polishing using ferric nitrate as a catalyst and hydrogen peroxide as an oxidant. It is important to note that while this patent mentions various transition metal elements, only iron has been experimentally proven to be significantly effective. Therefore, the practical application and scope of this invention are very limited. Although this method significantly reduces the amount of ferric nitrate used, the presence of iron ions leads to a Fenton reaction with hydrogen peroxide, causing the hydrogen peroxide to rapidly and violently decompose and become ineffective. Therefore, this polishing solution suffers from poor stability.

[0012] Based on US Patent 5958288, US Patent 5980775 and US Patent 6068787 add organic acids as stabilizers to improve the decomposition rate of hydrogen peroxide. However, after polishing, the grinding particles and by-products are difficult to clean on the chip surface, which poses a risk of causing defects.

[0013] US Patent 9566686 uses abrasive particles with a permanent positive charge (>15mV) and a quaternary ammonium salt corrosion inhibitor with a long alkyl chain. Although this system can effectively inhibit tungsten corrosion, the abrasive particle preparation is cumbersome and costly, the tungsten polishing rate is unstable, and the polishing speed of silicon oxide is relatively slow.

[0014] CN98809580.7 and CN200610077360.7 added a tungsten corrosion inhibitor to the hydrogen peroxide and iron system to inhibit tungsten corrosion.

[0015] The polishing slurries mentioned above share a common problem: while ensuring a high tungsten removal rate, they often fail to adequately protect the tungsten surface, leading to a high static corrosion rate. When the polishing slurry effectively protects the tungsten surface from corrosion by the etchant, the polishing speed of the tungsten material is affected by the corrosion inhibitor, resulting in a slower removal rate. Furthermore, these polishing slurries tend to penetrate deeper into the erosion defects of graphics chips. Summary of the Invention

[0016] To overcome the aforementioned technical deficiencies, the present invention aims to provide a chemical mechanical polishing slurry for tungsten polishing. This polishing slurry, through the synergistic effect of two corrosion inhibitors, can significantly reduce the static corrosion rate of tungsten, increase the ratio of polishing speed to static corrosion rate, improve erosion defects in graphics chips, and significantly improve product yield, demonstrating excellent market application prospects.

[0017] A chemical mechanical polishing slurry comprising: water, abrasive particles, tungsten polishing accelerator, stabilizer, peroxide, a first tungsten corrosion inhibitor, and a second tungsten corrosion inhibitor.

[0018] Furthermore, in the above-mentioned chemical mechanical polishing slurry, the first tungsten corrosion inhibitor is selected from amino acids; preferably, it is selected from one or more of glycine, arginine, histidine, lysine, glutamic acid, and proline; preferably, the mass percentage content of the first tungsten corrosion inhibitor ranges from 0.001% to 1.0%.

[0019] Further, in the aforementioned chemical mechanical polishing slurry, the second tungsten corrosion inhibitor is selected from an aminocyclic alcohol composed of two or three amino sugar molecules and one non-sugar moiety (called an aglycone) linked by an ether bond; preferably, the second tungsten corrosion inhibitor is selected from one or more of streptomycin sulfate, kanamycin, tobramycin, amikacin sulfate, neomycin sulfate, and gentamicin; preferably, the second tungsten corrosion inhibitor is neomycin sulfate. The mass percentage content of the second tungsten corrosion inhibitor ranges from 0.002% to 0.5%.

[0020] Furthermore, in the aforementioned chemical mechanical polishing slurry, the abrasive particles are selected from one or more of silica sol, fumed silica, alumina, cerium oxide, titanium oxide, and zirconium oxide. The mass percentage content of the abrasive particles ranges from 0.1% to 15%.

[0021] Furthermore, in the aforementioned chemical mechanical polishing slurry, the tungsten polishing accelerator is selected from one or more compounds that can provide iron ions; preferably, the tungsten polishing accelerator is ferric nitrate. The mass percentage content of the tungsten polishing accelerator ranges from 0.001% to 0.3%.

[0022] Furthermore, in the above-mentioned chemical mechanical polishing slurry, the stabilizer is selected from organic acids; preferably, the organic acid is selected from one or more of malonic acid, succinic acid, adipic acid, oxalic acid, citric acid, and phthalic acid; preferably, the stabilizer is malonic acid. The mass percentage content of the stabilizer ranges from 0.001% to 1%.

[0023] Furthermore, in the above-mentioned chemical mechanical polishing slurry, the peroxide is hydrogen peroxide. The mass percentage content of the oxidant ranges from 0.1% to 6%.

[0024] Furthermore, the aforementioned chemical mechanical polishing slurry also contains a pH adjuster;

[0025] Furthermore, the pH range of the aforementioned chemical mechanical polishing solution is 1-5.

[0026] The positive and progressive effects of this invention are as follows: the chemical mechanical polishing slurry for tungsten polishing provided by this invention can significantly reduce the static corrosion rate of tungsten and increase the ratio of tungsten polishing speed to static corrosion rate, thereby improving erosion defects in graphics chips. Attached Figure Description

[0027] Figure 1 This is a topographic image of the 0.18*0.18um 50% line region of the patterned wafer. Detailed Implementation

[0028] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0029] Table 1 shows the formulations of Examples 1-17 and Comparative Examples 1-6 of the chemical mechanical polishing fluid of the present invention. The chemical mechanical polishing fluid of the present invention can be prepared by mixing the components and their contents listed in Table 1 evenly in deionized water and adjusting the pH value to the required value with nitric acid or potassium hydroxide as a pH adjuster.

[0030] Table 1. Formulations of the chemical mechanical polishing slurry of the present invention in Examples 1-17 and Comparative Examples 1-6.

[0031]

[0032]

[0033]

[0034] The polishing slurry prepared according to the formula in Table 1 was used to polish tungsten wafers under the experimental conditions described below, and the static corrosion of the tungsten wafers by the polishing slurry was measured. The experimental results are shown in Table 2.

[0035] Specific polishing conditions: 12-inch polishing machine, pressure 3.5psi, polishing disc and polishing head speed 120 / 113rpm, polishing pad IC1000, polishing fluid flow rate 300ml / min, polishing time 1 minute.

[0036] Static corrosion test of tungsten: A square tungsten wafer (approximately 4cm × 4cm) was immersed in a preheated slurry at 45°C for 5 minutes, then removed, rinsed, and dried. Data were measured on the square tungsten wafer before and after immersion to obtain the sheet resistance of tungsten. The static corrosion rate of tungsten was then calculated, in units of angstroms per minute.

[0037] Table 2 shows the removal rate and static corrosion rate of tungsten and their rate ratios for Examples 1-17 and Comparative Examples 1-6.

[0038]

[0039]

[0040] Analysis of the data in Tables 1 and 2 shows that the test results of the removal rate and static corrosion rate of tungsten in Comparative Examples 1-6 indicate that the static corrosion rate of tungsten remains high even in the presence of a single corrosion inhibitor, resulting in a polishing rate to static corrosion rate ratio of less than 55, indicating that the polishing solution still significantly corrodes the tungsten.

[0041] The comparison results of Comparative Examples 1-4 and Examples 1-14 show that: the combination of the first tungsten corrosion inhibitor and the second tungsten corrosion inhibitor in the polishing solution significantly reduces the static corrosion rate of tungsten. Moreover, it can be seen that the corrosion inhibition effect of the polishing solution is significantly better than that of the polishing solution containing only a single tungsten corrosion inhibitor. That is, the two corrosion inhibitors in the polishing solution achieve a corrosion inhibition effect of 1+1>2 on tungsten, thereby significantly increasing the ratio of the polishing rate of tungsten to the static corrosion rate of tungsten. Thus, the embodiments of the present invention achieve, while ensuring the polishing rate of tungsten to a certain extent, a significant reduction in the corrosion of tungsten metal by the polishing solution and a reduction in defects on the surface of the polished wafer.

[0042] Under the experimental conditions described below, the W MIT754 patterned wafers were polished using the polishing solutions from Comparative Examples 5-6 and Examples 15-17, respectively. Then, a step profiler was used to polish the 0.18*0.18µm 50% line area of ​​the patterned wafer. Figure 1The surface morphology of the sample was measured, and the experimental results are shown in Table 3.

[0043] Specific polishing conditions: 12-inch polishing machine, pressure 3.5psi, polishing disc and polishing head speed 120 / 113rpm, polishing pad IC1000, polishing fluid flow rate 300ml / min.

[0044] Table 3. Comparison of erosion defects in Examples 15-17 and Comparative Examples 5-6

[0045]

[0046] The comparative results of Comparative Examples 5-6 and Examples 15-17 show that: Comparative Examples 5 and 6 used only a single corrosion inhibitor, which, when polishing WMIT 754 patterned wafers, resulted in larger erosion defects in the fine-line areas of the wafers, achieving [the desired effect]. As shown in Examples 15-17, when a combination of two corrosion inhibitors is used, the erosion defects in the fine line area are significantly improved after polishing of the W MIT 754 patterned wafer, and the size of the erosion defects is reduced by at least half. Thus, in the embodiments of the present invention, the two corrosion inhibitors work together to achieve a corrosion inhibition effect of 1+1>2 on tungsten.

[0047] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing liquid for polishing tungsten, characterized by comprising: a colloidal silica abrasive; and a surfactant. Comprising: water, abrasive particles, a tungsten polishing accelerator, a stabilizer, a peroxide, a first tungsten corrosion inhibitor, and a second tungsten corrosion inhibitor; the first tungsten corrosion inhibitor is one or more amino acids; the second tungsten corrosion inhibitor is selected from the group consisting of a compound in which two or three amino sugar molecules and an amino cyclitol are connected by an ether bond; the tungsten polishing accelerator is one or more compounds that provide iron ions; the stabilizer is selected from organic acids; the pH of the chemical mechanical polishing liquid is 1-5; the mass percentage content of the first tungsten corrosion inhibitor is 0.001%-1.0%; the mass percentage content of the abrasive particles is 0.1%-15%; the mass percentage content of the tungsten polishing accelerator is 0.001%-0.3%; the mass percentage content of the stabilizer is 0.001-1%; the mass percentage content of the peroxide is 0.1%-6%; the mass percentage content of the second tungsten corrosion inhibitor is 0.002%-0.5%.

2. The chemical mechanical polishing liquid according to claim 1, wherein The second tungsten corrosion inhibitor is selected from one or more of kanamycin, tobramycin, and gentamicin.

3. A chemical mechanical polishing liquid for tungsten polishing, characterized by comprising: a colloidal silica abrasive; and a surfactant. Comprising: water, abrasive particles, a tungsten polishing accelerator, a stabilizer, a peroxide, a first tungsten corrosion inhibitor, and a second tungsten corrosion inhibitor; the first tungsten corrosion inhibitor is one or more amino acids; the second tungsten corrosion inhibitor is selected from one or more of streptomycin sulfate, amikacin sulfate, and neomycin sulfate; the tungsten polishing accelerator is one or more compounds that provide iron ions; the stabilizer is selected from organic acids; the pH of the chemical mechanical polishing liquid is 1-5; the mass percentage content of the first tungsten corrosion inhibitor is 0.001%-1.0%; the mass percentage content of the abrasive particles is 0.1%-15%; the mass percentage content of the tungsten polishing accelerator is 0.001%-0.3%; the mass percentage content of the stabilizer is 0.001-1%; the mass percentage content of the peroxide is 0.1%-6%; the mass percentage content of the second tungsten corrosion inhibitor is 0.002%-0.5%.

4. The chemical mechanical polishing liquid according to claim 3, wherein The second tungsten corrosion inhibitor is neomycin sulfate.

5. The chemical mechanical polishing liquid according to claim 1 or 3, wherein The abrasive particles are selected from one or more of silica sol, fumed silica, alumina, ceria, titania, and zirconia.

6. The chemical mechanical polishing liquid according to claim 1 or 3, wherein The tungsten polishing accelerator is selected from one or more of ferric nitrate, ferric sulfate, and ferric chloride.

7. The chemical mechanical polishing liquid according to claim 1 or 3, wherein The organic acid is selected from one or more of malonic acid, succinic acid, adipic acid, oxalic acid, citric acid, and phthalic acid.

8. The chemical mechanical polishing liquid according to claim 1 or 3, wherein The organic acid is malonic acid.

9. The chemical mechanical polishing liquid according to claim 1 or 3, wherein The peroxide is hydrogen peroxide.

10. The chemical mechanical polishing liquid according to claim 1 or 3, wherein The amino acid is selected from one or more of glycine, arginine, histidine, lysine, glutamic acid, and proline.

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