Chemical mechanical polishing solution

Abstract

This invention discloses a chemical mechanical polishing slurry for barrier layer planarization. The slurry comprises abrasive particles, an azole compound, an organic carboxylic acid, hydrogen peroxide, and water, and further includes a benzenesulfonic acid and / or benzenesulfonate surfactant. This slurry solves the problem of difficulty in controlling the removal rate of low dielectric constant (BD) and ultra-low dielectric constant (ULK) materials during polishing, meeting the requirements for the removal rate and selection ratio of various materials in barrier layer polishing processes, thus fulfilling the process requirements.

Description

Technical Field

[0001] This invention relates to a chemical mechanical polishing slurry, and more particularly to a chemical mechanical polishing slurry for barrier layer planarization. Background Technology

[0002] In integrated circuit manufacturing, the standards for interconnect technology are improving. As the number of interconnect layers increases and the feature size of the process shrinks, the requirements for the flatness of the silicon wafer surface are also increasing. Without the ability to planarize, it is very limited to create complex and dense structures on semiconductor wafers. Chemical mechanical polishing (CMP) is the most effective method to achieve planarization of the entire silicon wafer.

[0003] CMP (Chemical Motion Polishing) is a process that uses a mixture of abrasive particles to polish the surface of a wafer. In a typical CMP process, the wafer surface is brought into direct contact with a rotating polishing pad, and pressure is applied to the back of the wafer using a weight. During polishing, the polishing pad and stage rotate while maintaining a downward force on the back of the wafer, applying abrasive particles and a chemically active solution (often called a polishing slurry or polishing paste) to the polishing pad. This slurry reacts chemically with the wafer surface being polished to initiate the polishing process.

[0004] Copper CMP typically involves three steps. The first step uses high pressure to remove a large amount of copper. The second step reduces the polishing pressure to remove residual copper from the wafer surface and stop it on the barrier layer. The third step uses a copper barrier layer polishing slurry to polish the barrier layer. During the second step of removing residual copper, dish-shaped depressions may form on the wafer surface. To address this, a polishing slurry with a specific copper, barrier layer, and dielectric layer removal rate selectivity is usually used in the third step to repair the dish-shaped depressions.

[0005] With the advancement of integrated circuit technology to 45nm and below, and the rapid increase in interconnect density, the parasitic RC coupling effects caused by resistance and capacitance in interconnect systems are growing rapidly, affecting device speed. To mitigate this impact, low dielectric constant materials (k≤2.8) must be used to reduce the parasitic capacitance between adjacent metal lines. Currently, below the 28nm technology node, ultra-low dielectric constant materials (ULK, k≤2.5) are commonly used in the industry. Due to the high porosity and low hardness of ULK materials, mechanical damage problems such as material collapse and peeling are easily generated during polishing. Therefore, the introduction of ULK poses a significant challenge to process technology, especially chemical mechanical polishing (CMP). Due to process requirements, it is necessary to quickly remove the barrier layer (Ta / TaN), dielectric layer material TEOS, and low-k material (BD) and stop it on the ULK material surface. During the polishing process, in order to avoid unevenness caused by excessive differences in the removal rate of dielectric materials, it is necessary to adjust the removal rate of low-k material (BD) and ULK to ensure that the low-k material (BD) is effectively removed and stopped on the ULK surface. Moreover, during the polishing process, it is also necessary to strictly control the surface contaminant index and prevent metal corrosion, which places higher demands on the performance of the polishing fluid and the reliability of the process.

[0006] Low dielectric constant (k≤2.8) materials commonly used are tris / tetramethylsilanes. To further reduce RC time delay and increase the clock frequency of circuits, ultra-low dielectric constant materials based on diethoxymethylsilane and cyclohexene oxide (k≤2.5) have been developed. The difference between the two materials lies in the number of pores formed at the ends of the alkyl chains, the difference in hydrophilicity and hydrophobicity, and more importantly, the significant difference in mechanical strength. Commonly used surfactants, such as polyols and polyoxyethylene ethers, are difficult to control the polishing rate of the two materials, resulting in a much lower removal rate for low-k materials (BD) than for ULK materials, causing a large difference in removal rate. Summary of the Invention

[0007] To overcome the drawback of existing chemical mechanical polishing slurries where the removal rate ratio of low-k (BD) and ULK materials is difficult to control, this invention introduces benzenesulfonic acid and / or its salt surfactants. By adjusting the content of benzenesulfonic acid and / or its salt surfactants, the removal rates of low-k (BD) and ULK materials are adjusted, reducing the difference in removal rates between low-k (BD) and ULK materials, thus solving the requirements of actual production for the polishing rate selection ratio.

[0008] Specifically, the present invention discloses a chemical mechanical polishing fluid, characterized in that it comprises: abrasive particles, azole compounds, organic acids, hydrogen peroxide, benzenesulfonic acid and / or benzenesulfonate surfactants, and water.

[0009] Furthermore, the benzenesulfonic acid surfactant is a C10-C16 alkylbenzenesulfonic acid or a polystyrenesulfonic acid;

[0010] Furthermore, the benzene sulfonate surfactant is a C10-C16 alkylbenzene sulfonate potassium salt or ammonium salt, or a polystyrene sulfonate potassium salt or ammonium salt;

[0011] Furthermore, the weight-average molecular weight of the polystyrene sulfonic acid, potassium salt or ammonium salt of polystyrene sulfonic acid is 45,000 to 1,000,000.

[0012] Further, the mass percentage concentration of the benzenesulfonic acid and / or benzenesulfonate surfactant is 0.001 to 0.05 wt%, preferably 0.001 to 0.02 wt%.

[0013] Furthermore, the abrasive particles are silicon dioxide; the mass percentage concentration of the abrasive particles is 3-15 wt%; and the particle size of the abrasive particles is 20-120 nm.

[0014] Further, the azole compound is benzotriazole, hydroxybenzotriazole, methylbenzotriazole, 5-aminotetrazole, or 1,2,4-triazole; the mass percentage concentration of the azole compound is 0.01–0.5 wt%.

[0015] Further, the organic acid is one or more of malic acid, citric acid, tartaric acid, malonic acid, and maleic acid; the mass percentage concentration of the organic acid is 0.05 to 0.2 wt%.

[0016] Furthermore, the hydrogen peroxide concentration is 0.1–1.0 wt%.

[0017] Furthermore, the pH value of this chemical mechanical polishing solution is 8–11.

[0018] The chemical mechanical polishing slurry of the present invention may also contain other additives in the art, such as pH adjusters and bactericides. The polishing slurry of the present invention can be concentrated and prepared; before use, it can be diluted with deionized water to the concentration range of the present invention and hydrogen peroxide can be added.

[0019] The chemical mechanical polishing slurry provided by this invention controls the removal rates of low-k and ULK materials by selecting benzenesulfonic acid and / or benzenesulfonate surfactants and adjusting the content of these surfactants, thereby reducing the difference in removal rates between the two materials. Furthermore, it has no significant impact on the removal rates of tantalum, copper, and silicon dioxide, thus meeting the requirements for substrate polishing rate selectivity during the polishing process. Detailed Implementation

[0020] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0021] Table 1 shows the composition and content of Examples 1-10 and Comparative Examples 1-2 of the present invention. According to the formula given in the table, all components except hydrogen peroxide are mixed evenly, and the pH value is adjusted to the required value with KOH or HNO3. Hydrogen peroxide is added before use, and the mixture is mixed evenly. Water is the balance. The polishing solution in this invention can also be prepared as a concentrated sample in advance, diluted with deionized water at a certain ratio, and hydrogen peroxide is added before use.

[0022] Table 1. Composition and content of Examples 1-10 and Comparative Examples 1-2 of the present invention

[0023]

[0024]

[0025] The polishing slurries used in the embodiments and comparative examples of the present invention were applied to polish copper (Cu), tantalum (Ta), silicon dioxide (TEOS), low dielectric (BD), and ultra-low dielectric constant (ULK) materials under the following conditions: Polishing machine: 12” Ebara machine; polishing pad: Fujibo pad; downforce: 134 hPa; rotation speed: polishing disc / polishing head = 93 / 87 rpm; polishing slurry flow rate: 300 ml / min; polishing time: 1 min. Specific results are shown in Table 2.

[0026] Table 2 shows the removal rates of copper (Cu), tantalum (Ta), silicon dioxide (TEOS), low dielectric (BD), and ultra-low dielectric (ULK) materials in the examples and comparative examples.

[0027]

[0028]

[0029] According to the data in Table 2, compared with Comparative Examples 1-2, the difference in removal rates (RR) between low-k materials (BD) and ULK materials is smaller in the data of Examples 1-10; benzenesulfonic acid surfactants, compared with polyols and polyoxyethylene ethers, can significantly reduce the difference in removal rates between the two materials, while having no significant effect on the removal rates of tantalum, copper, and TEOS; the difference in RR between low-k materials (BD) and ULK materials with benzenesulfonic acid surfactants whose molecular weight and concentration are outside the preferred range is greater than that within the preferred range.

[0030] Furthermore, in order to characterize the effect of the polishing slurry on the morphology of the wafer surface in this application, a patterned copper wafer was polished under the following conditions using the comparative examples and embodiments.

[0031] The graphics chip is a commercially available 12-inch Sematech 754 graphics chip, and the film materials from top to bottom are Cu / Ta / TaN / TEOS / BD / ULK.

[0032] The polishing process consists of three steps: the first step is to remove most of the copper using commercially available copper polishing slurry; the second step is to remove the remaining copper using commercially available copper polishing slurry; and the third step is to remove the barrier layer (Ta / TaN), TEOS, and BD using the barrier layer polishing slurry of this invention, removing part of the ULK and stopping on the ULK layer.

[0033] Polishing conditions: The polishing machine was a 12” Ebara machine, the polishing pad was a Fujibo pad, the downforce was 134 hPa, the rotation speed was polishing disc / polishing head = 93 / 87 rpm, the polishing fluid flow rate was 300 ml / min, and the polishing time was 70 s.

[0034] The specific results are shown in Table 3.

[0035] Table 3 compares the corrective abilities of polishing slurries on patterned copper wafers after polishing in comparative and example cases.

[0036]

[0037]

[0038] The dish-shaped depressions mentioned in the table above refer to the dish-shaped depressions on the metal pad before the barrier layer is polished, and the dielectric layer erosion refers to the dielectric layer erosion on the dense line area (50% copper / 50% dielectric layer) with a line width of 0.18 micrometers and a density of 50%.

[0039] According to the data in Table 3, compared with Comparative Examples 1-2, the dish-shaped depressions and dielectric layer erosion after polishing with the polishing solution of Examples 1-10 are smaller, which can better correct the dish-shaped depressions and dielectric layer erosion generated on the wafer after copper polishing, so that the polished copper wafer can obtain a better wafer morphology.

[0040] It should be understood that all wt% mentioned in this invention refers to the percentage content by mass.

[0041] This invention discloses a chemical mechanical polishing slurry for barrier layer planarization. The slurry comprises abrasive particles, azole compounds, organic acids, hydrogen peroxide, and water, and further includes a benzenesulfonic acid and / or benzenesulfonate surfactant. This slurry solves the problem of difficulty in controlling the removal rate of low dielectric constant (BD) and ultra-low dielectric constant (ULK) materials during polishing; by reducing the difference in removal rates between the two materials, it meets the requirements for the removal rates and selection ratios of various materials in the barrier layer polishing process, thus fulfilling the process requirements.

[0042] 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 slurry, characterized in that, include: Abrasive particles, azole compounds, organic acids, hydrogen peroxide, benzenesulfonic acid and / or benzenesulfonate surfactants, and water.

2. The polishing slurry as described in claim 1, characterized in that, The benzenesulfonic acid surfactant is a C10-C16 alkylbenzenesulfonic acid or a polystyrenesulfonic acid.

3. The polishing slurry as described in claim 1, characterized in that, The benzene sulfonate surfactants are C10-C16 alkylbenzene sulfonate potassium salts or ammonium salts, or polystyrene sulfonate potassium salts or ammonium salts.

4. The polishing slurry as described in claim 3, characterized in that, The weight-average molecular weight of the polystyrene sulfonic acid and / or potassium or ammonium polystyrene sulfonic acid salts is 45,000 to 1,000,000.

5. The polishing slurry as described in claim 1, characterized in that, The mass percentage concentration of the benzenesulfonic acid and / or benzenesulfonate surfactant is 0.001 to 0.05 wt%.

6. The polishing slurry as described in claim 5, characterized in that, The benzenesulfonic acid and / or benzenesulfonate surfactants have a mass percentage concentration of 0.001 to 0.02 wt%.

7. The polishing slurry as described in claim 1, characterized in that, The grinding particles are silicon dioxide nanoparticles.

8. The polishing slurry as described in claim 1, characterized in that, The mass percentage concentration of the grinding particles is 3-15 wt%.

9. The polishing slurry as described in claim 1, characterized in that, The particle size of the grinding particles is 20-120 nm.

10. The polishing slurry as described in claim 1, characterized in that, The azole compounds are one or more of benzotriazole, hydroxybenzotriazole, methylbenzotriazole, 5-aminotetrazole, and 1,2,4-triazole.

11. The polishing slurry as described in claim 1, characterized in that, The mass percentage concentration of the azole compound is 0.01–0.5 wt%.

12. The polishing slurry as described in claim 1, characterized in that, The organic acid is one or more of malic acid, citric acid, tartaric acid, malonic acid, and maleic acid.

13. The polishing slurry as described in claim 1, characterized in that, The organic acid has a mass percentage concentration of 0.05–0.2 wt%.

14. The polishing slurry as described in claim 1, characterized in that, The hydrogen peroxide concentration is 0.1–1.0 wt%.

15. The polishing slurry as described in claim 1, characterized in that, The pH value of this chemical mechanical polishing slurry is 8–11.

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