Chemical mechanical polishing solution and method of using same

Abstract

The present application provides a chemical mechanical polishing solution for barrier planarization and a method of using the same. The chemical mechanical polishing solution comprises abrasive particles, an azole compound, a complexing agent, an oxidizing agent, a water-soluble cellulose and water. The chemical mechanical polishing solution of the present application has certain repairing ability for dishing and erosion of dielectric layer after polishing of copper, and has no obvious influence on removal rate of tantalum, copper, silicon dioxide (TEOS) and low dielectric constant material, and meets the requirements of polishing rate, rate selection ratio and surface morphology after polishing of various materials in the barrier polishing process.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing, and more particularly to a chemical mechanical polishing slurry for barrier layer planarization and its application method. 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 Mechanical Polishing) is a process that uses a mixture of abrasives to polish the surface of integrated circuits. In a typical chemical mechanical polishing method, the substrate is placed in 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, applying abrasive and a chemically active solution (often called a polishing slurry or polishing paste) to the pad. This slurry reacts chemically with the film being polished to initiate the polishing process.

[0004] 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-k dielectric materials must be used to reduce the parasitic capacitance between adjacent metal lines. However, the introduction of low-k dielectric materials presents significant challenges to process technology, especially chemical mechanical polishing (CMP). CMP requires not only meeting the polishing rate and selectivity requirements of various materials during barrier layer polishing, but also possessing a strong ability to correct defects on the semiconductor device surface.

[0005] Therefore, in view of the problems existing in the prior art, it is an urgent problem to be solved in this industry to find a chemical mechanical polishing slurry that can be suitable for barrier layer polishing in copper interconnect process, achieve high removal rates of barrier layer and dielectric material under relatively mild conditions, and effectively control dishing and erosion. Summary of the Invention

[0006] To overcome the above-mentioned technical defects, the present invention provides a chemical mechanical polishing slurry for polishing the barrier layer. The chemical mechanical polishing slurry adds water-soluble cellulose and adjusts the cellulose content to regulate the repair ability of the barrier layer after polishing the dish-shaped depressions and dielectric layer erosion after the copper polishing process. It has no significant effect on the removal rate of tantalum, copper, silicon dioxide (TEOS) and Low-k materials, and meets the requirements of polishing rate and rate selection ratio of various materials during the polishing process.

[0007] This invention provides a chemical mechanical polishing fluid comprising abrasive particles, azole compounds, complexing agents, oxidizing agents, water-soluble cellulose, and water.

[0008] Preferably, the water-soluble cellulose is selected from hydroxyethyl cellulose, hydroxypropyl cellulose and / or hydroxypropyl methyl cellulose.

[0009] Preferably, the water-soluble cellulose has a viscosity-average molecular weight of 100,000-5,000,000.

[0010] Preferably, the water-soluble cellulose has a viscosity-average molecular weight of 200,000-3,000,000.

[0011] Preferably, the water-soluble cellulose has a mass percentage concentration of 0.0005%-0.2%.

[0012] Preferably, the water-soluble cellulose has a mass percentage concentration of 0.001%-0.1%.

[0013] Preferably, the abrasive particles are silicon dioxide; the mass percentage content of the abrasive particles is 2%-15%; and the particle size of the abrasive particles is 20-120 nm.

[0014] Preferably, the azole compound is selected from one or more of benzotriazole, methylbenzotriazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, carboxybenzotriazole, 5-methyl-tetrazole, 5-amino-tetrazole, 5-phenyltetrazole, mercaptophenyltetrazole, benzimidazole, naphthotriazole and / or 2-mercapto-benzothiazole.

[0015] Preferably, the mass percentage content of the azole compound is 0.001%-0.5%.

[0016] Preferably, the complexing agent is one or more of the following: oxalic acid, malonic acid, succinic acid, citric acid, tartaric acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, 2-hydroxyphosphonoacetic acid, polyaminopolyethermethylenephosphonic acid, diethylenetriaminepentamethylidenephosphonic acid, ethylenediamine, glycine, alanine, and / or ethylenediaminetetraacetic acid.

[0017] Preferably, the complexing agent has a mass percentage content of 0.01%-2%.

[0018] Preferably, the oxidant is hydrogen peroxide; the mass percentage content of the oxidant is 0.05%-1%.

[0019] Preferably, the pH value of the chemical mechanical polishing fluid is 8-12.

[0020] The present invention also discloses a method of using a chemical mechanical polishing slurry, wherein any of the above-described chemical mechanical polishing slurries is used for barrier layer planarization.

[0021] The chemical mechanical polishing slurry of the present invention not only meets the requirements for the removal rate and selectivity of various materials during the barrier layer polishing process, but also effectively corrects and controls dish-shaped depressions and dielectric layer erosion. Detailed Implementation

[0022] The advantages of the present invention are further illustrated below by way of embodiments, but the present invention is not limited to the scope of the embodiments described herein.

[0023] The chemical mechanical polishing slurry of the present invention can be prepared by the following method: mixing all components except the oxidant in proportion, adjusting the pH value to the required value with a pH adjuster (such as KOH or HNO3), adding the oxidant before use, and mixing evenly.

[0024] The reagents and raw materials used in this invention are all commercially available.

[0025] Table 1 shows the component contents of Comparative Examples 1-2 and Examples 1-13 of the present invention. When preparing the polishing solution according to the formulation in Table 1, first, mix all components except the oxidant thoroughly, then adjust the pH of the polishing solution to the required value using KOH or HNO3. Finally, before using the polishing solution, add the oxidant and mix thoroughly. Water is the balance.

[0026] Table 1. Components and their contents in Comparative Examples 1-2 and Examples 1-17

[0027]

[0028]

[0029] Example 1

[0030] Under the following conditions, blank wafers of copper (Cu), tantalum (Ta), silicon dioxide (TEOS), and low dielectric (BD) were polished using the polishing slurries of Comparative Examples 1-2 and Examples 1-17, respectively, to compare the effects of different polishing slurries on the polishing rates of copper (Cu), tantalum (Ta), silicon dioxide (TEOS), and low dielectric (BD).

[0031] The specific polishing conditions were as follows: a 12” Reflexion LK polishing machine, a Fujibo pad, a downforce of 1.5 psi, a polishing disc / polishing head rotation speed of 93 / 87 rpm, a polishing fluid flow rate of 300 ml / min, and a polishing time of 1 min. The resistivity of copper and tantalum before and after polishing was measured using a metal thin film thickness gauge, and the thicknesses of copper and tantalum before and after polishing were calculated to obtain the removal rates of copper and tantalum. The thicknesses of TEOS and BD before and after polishing were measured using a non-metallic thin film thickness gauge to obtain the removal rates of TEOS and BD. The polishing results are shown in Table 2.

[0032] Table 2 shows the polishing rate test results for Comparative Example 1 and Examples 1-17.

[0033]

[0034]

[0035] As shown in Table 2, compared with Comparative Example 1, the addition of water-soluble cellulose with different molecular weights and contents to the polishing solutions 1-17 of the present invention does not affect the removal rate of the barrier layer Ta, silica (TEOS) and low dielectric material BD, thus ensuring a shorter polishing time and improving production capacity.

[0036] Example 2

[0037] Patterned copper wafers were polished using Comparative Examples 1-2 and Examples 1-4 under the following conditions.

[0038] The graphics chip is a commercially available 12-inch Sematech 754 graphics chip, and the film material from top to bottom is copper / tantalum / tantalum nitride / TEOS.

[0039] The polishing process consists of three steps: the first step is to remove most of the copper using commercially available copper polishing fluid; the second step is to remove the remaining copper using commercially available copper polishing fluid; and the third step is to remove the barrier layer (tantalum / tantalum nitride) and part of the TEOS using the barrier layer polishing fluid of this invention and stop it on the TEOS layer.

[0040] Polishing conditions: The polishing machine was a 12” Reflexion LK machine, the polishing pad was a Fujibo pad, the downforce was 1.5psi, the rotation speed was polishing disc / polishing head = 93 / 87rpm, the polishing fluid flow rate was 300ml / min, and the polishing time was 70s.

[0041] Table 3 compares the correction capabilities of patterned copper wafers after polishing in Comparative Examples 1-2 and Examples 1-4.

[0042]

[0043]

[0044] The dish-shaped recesses mentioned above refer to the dish-shaped recesses on the metal pad before the barrier layer is polished, and the dielectric layer erosion refers to the erosion of the dielectric layer on the densely packed region (50% copper / 50% dielectric layer) with a line width of 0.18 micrometers and a density of 50%.

[0045] Comparing Comparative Examples 1-2 with Example 1, it can be seen that when using azole compounds alone or cellulose alone, even though the polishing rate of the polishing solution is acceptable for each material, it does not have the ability to correct dish-shaped defects on the wafer surface. When azole compounds and cellulose are used simultaneously, compared with Comparative Examples 1-2, Examples 1-4, due to the addition of water-soluble cellulose, work synergistically with azole compounds to better correct dish-shaped depressions and dielectric layer erosion generated on the wafer during the previous process (after copper polishing), so that the polished copper wafers obtain a better wafer morphology.

[0046] Example 3

[0047] Patterned copper wafers were polished using Comparative Examples 1-2 and Examples 10-13 under the following conditions.

[0048] The graphics chip is a commercially available 12-inch Sematech 754 graphics chip, and the film material from top to bottom is copper / tantalum / tantalum nitride / TEOS / BD.

[0049] 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 (tantalum / tantalum nitride), silicon dioxide TEOS, and part of the BD using the barrier layer polishing slurry of the present invention, and finally stop on the BD layer.

[0050] Polishing conditions: The polishing machine was a 12” Reflexion LK machine, the polishing pad was a Fujibo pad, the downforce was 1.5psi, the rotation speed was polishing disc / polishing head = 93 / 87rpm, the polishing fluid flow rate was 300ml / min, and the polishing time was 70s.

[0051] Table 4 compares the correction capabilities of patterned copper wafers after polishing in Comparative Examples 1-2 and Examples 10-13.

[0052]

[0053]

[0054] As shown in Table 4, compared with the polishing slurries of Comparative Examples 1-2, Examples 10-13, due to the addition of water-soluble cellulose, synergistically with azole compounds, are better able to correct the dish-shaped depressions and dielectric layer erosion generated on the wafer during the previous process (after copper polishing), resulting in a better wafer morphology for the polished copper wafer. Therefore, the polishing slurry of the present invention is also suitable for polishing the barrier layer in low-dielectric material-copper interconnect processes.

[0055] It should be understood that all wt% mentioned in this invention refers to mass percentage content.

[0056] 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 solution for barrier planarization, comprising abrasive particles, an azole compound, a complexing agent, an oxidizing agent, a water-soluble cellulose, and water.

2. The chemical mechanical polishing solution of claim 1, wherein the viscosity average molecular weight of the water-soluble cellulose is 200,000 to 3,000,000.

3. The chemical mechanical polishing solution of claim 1, wherein the water-soluble cellulose has a mass percentage concentration of 0.001% to 0.1%.

4. The chemical mechanical polishing solution of claim 1, wherein the abrasive particles are silicon dioxide, and the particle size of the abrasive particles is 20 to 120 nm.

5. The chemical mechanical polishing solution of claim 1, wherein the oxidizing agent is hydrogen peroxide. ​ ​ ​ ​ ​ ​ ​ ​

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