A chemical mechanical polishing slurry for tungsten polishing

Abstract

The present invention aims to provide a chemical mechanical polishing (CMP) slurry for tungsten polishing, comprising: a chloroquine corrosion inhibitor, water, abrasive particles, a catalyst, a stabilizer, an oxidant, and a pH adjuster. The CMP slurry provided by the present invention can provide high tungsten polishing speeds and moderate silica polishing speeds. Most importantly, the composition exhibits low tungsten static corrosion, thereby improving the surface condition of the polished metal.

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] Today, the rapid development of semiconductor technology has made the miniaturization of devices a reality. A single integrated circuit substrate often carries hundreds of millions of functional components. These components form interconnect structures through conductive layers and multiple interconnects. Therefore, planarization technology for conductive and insulating dielectric layers has become crucial. Chemical mechanical polishing (CMP), pioneered by IBM in the 1980s, is considered the most effective method for global planarization. CMP involves chemical action, mechanical action, and a combination of both. Typically, the wafer is fixed to a polishing head, with its front side in contact with a polishing pad in the CMP equipment. Under pressure, the polishing head moves linearly on the polishing pad or rotates in the same direction as the polishing table. Simultaneously, a polishing composition ("slurry") is injected at a certain flow rate between the wafer and the polishing pad, and the slurry spreads evenly on the polishing pad due to centrifugal force. Thus, under the combined chemical and mechanical action, the wafer surface is polished and global planarization is achieved. CMP can be used to remove unwanted surface morphology and defects, such as rough surfaces, adsorbed impurities, lattice damage, scratches, etc.

[0003] In recent years, semiconductor manufacturing has increasingly used tungsten metal to fabricate through-hole connectors and contacts, while employing bonding layers such as TiN and Ti to connect them to SiO2. It is generally desirable to use CMP (Chemical Metallurgy Processing) to process the tungsten deposited layer to obtain a smooth, defect-free surface. However, unfortunately, the oxidants in the tungsten polishing slurry can corrode the metal, which is largely undesirable. It can lead to surface defects such as pitting and perforation. Severe metal corrosion can form deep tungsten pathways and ultimately affect the performance of semiconductor devices.

[0004] In recent years, the development of tungsten corrosion inhibitors has been a key focus in the development of polishing compositions. Early solutions, such as US Patent 6136711, used amino acids as tungsten polishing corrosion inhibitors. However, amino acid corrosion inhibitors have limited effectiveness in many systems, require large dosages, and often severely inhibit polishing speed, making them unsuitable for the diverse requirements of tungsten polishing. In recent years, small-molecule organic compounds and polymers containing multiple heteroatoms have often acted as tungsten corrosion inhibitors. For example, US Patent 10286518B2 found that thiol alkoxy compounds can inhibit tungsten corrosion and reduce erosion and butterfly defects during polishing. However, the inhibitory ability of thiol alkoxy compounds is limited and cannot effectively solve severe corrosion problems. Similarly, Chinese Patent CN 111094481A discloses the use of polyamino acids as tungsten corrosion inhibitors. This inhibitor can effectively suppress tungsten corrosion, but it affects the polishing speed. From these facts, it is clear that the development of highly effective tungsten corrosion inhibitors that do not significantly affect the polishing rate is urgent and necessary. Summary of the Invention

[0005] To overcome the aforementioned technical deficiencies, the present invention aims to provide a chemical mechanical polishing slurry for tungsten polishing. The slurry provided by the present invention can provide a high tungsten polishing rate and a moderate silicon oxide polishing rate. Most importantly, the composition exhibits low tungsten static corrosion, thereby improving the surface condition of the polished metal.

[0006] This invention discloses a chemical mechanical polishing fluid, comprising: chloroquine corrosion inhibitor, water, SiO2 abrasive particles, iron-containing catalyst, stabilizer, oxidant and pH adjuster.

[0007] Furthermore, the structure of the chloroquine-based corrosion inhibitor is shown in Formula 1:

[0008]

[0009] Furthermore, the corrosion inhibitor is selected from chloroquine phosphate, and its structure is shown in Formula 2:

[0010]

[0011] Furthermore, the mass percentage content of the chloroquine phosphate corrosion inhibitor ranges from 0.005% to 0.05%.

[0012] Furthermore, the mass percentage content of the grinding particles ranges from 0.5% to 3%.

[0013] Furthermore, the mass percentage content of the grinding particles ranges from 1% to 3%.

[0014] Furthermore, the iron-containing catalyst is ferric nitrate nonahydrate.

[0015] Furthermore, the mass percentage content of the iron-containing catalyst ranges from 0.01% to 0.1%.

[0016] Furthermore, the mass percentage content of the iron-containing catalyst ranges from 0.01% to 0.03%.

[0017] Furthermore, the stabilizer is an organic stabilizer.

[0018] Furthermore, the organic stabilizer is a carboxylic acid that can complex with iron.

[0019] Furthermore, the carboxylic acid that can complex with iron is one or more of phthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, citric acid, and maleic acid.

[0020] Furthermore, the stabilizer is malonic acid.

[0021] Furthermore, the stabilizer has a mass percentage content ranging from 0.01% to 0.09%.

[0022] Furthermore, the stabilizer has a mass percentage content ranging from 0.01% to 0.06%.

[0023] Furthermore, the oxidant is H2O2.

[0024] Furthermore, the oxidant has a mass percentage content of 2-4%.

[0025] Furthermore, the pH adjuster is HNO3.

[0026] Furthermore, the pH value of the chemical mechanical polishing solution is 2-4.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] This invention provides a chemical mechanical polishing composition that can significantly reduce the static corrosion rate of tungsten while maintaining a good polishing rate. The corrosion inhibition mechanism in this technology can be explained as follows: the corrosion inhibitor has three nitrogen atoms, located on the quinoline ring and the aliphatic chain, respectively. At pH 2–4, it produces multiple R4N+ (R is a carbon atom or hydrogen) structures, which form a rivet group and adsorb onto the negatively charged tungsten metal surface, thereby protecting the metal surface. Simultaneously, because this corrosion inhibitor is a small molecule compound, it has little effect on the polishing rate of tungsten at certain concentrations. Detailed Implementation

[0029] The advantages of the present invention will be further illustrated below with reference to specific embodiments.

[0030] Following the formulations given in Table 1, all components were dissolved and mixed thoroughly. Water was added to bring the mass percentage to 100%, and the pH was adjusted to the desired value using a pH adjuster. Polishing solutions for Examples 1-9 and Comparative Examples 1-4 were obtained. All reagents used in this invention are commercially available.

[0031] Table 1 Formulations of Examples 1-14 and Comparative Examples 1-8

[0032]

[0033]

[0034]

[0035] The polishing slurry prepared according to the formula in Table 1 was subjected to polishing rate test and tungsten static corrosion test under the following experimental conditions. The experimental results are shown in Table 2.

[0036] Specific polishing conditions: pressure 2.0psi, polishing disc and polishing head speed 93 / 87rpm, polishing pad IC1010, polishing fluid flow rate 150ml / min, polishing machine 12” Reflexion LK, polishing time 1min.

[0037] Static corrosion test of tungsten: Immerse a tungsten wafer of about 3cm×3cm into a preheated polishing slurry at 45℃ for 2 minutes, remove and rinse, and then test the static corrosion data using the four-point probe method.

[0038] Table 2 Polishing rates and static corrosion test results of Examples 1-10 and Comparative Examples 1-8

[0039]

[0040]

[0041] As can be seen from Tables 1 and 2, the chemical mechanical polishing slurries of Examples 1-10 can not only achieve high-speed polishing of tungsten, but also exhibit moderate polishing speeds for silicon oxide. Importantly, in the presence of the corrosion inhibitor chloroquine phosphate, the polishing composition can exhibit a very low static corrosion rate on the metal. Moreover, the experimental results of Examples 1-10 show that, especially when using the preferred chloroquine phosphate as the corrosion inhibitor, the corrosion inhibition effect of the polishing slurry on tungsten gradually increases with the increase of the amount of corrosion inhibitor. Preferably, in the presence of 0.05% or more of chloroquine phosphate, static corrosion can be reduced to 3 A / min or less, or even to 0. However, it should also be noted that when the amount of chloroquine phosphate exceeds a certain limit, although it can further reduce the static corrosion rate of tungsten, it will have a significant suppressive effect on the tungsten polishing speed (Examples 4-6), but will not affect the polishing speed of silicon oxide.

[0042] A comparison of Comparative Example 1 and Examples 1-4 revealed that, with the same composition and content of grinding particles, catalyst, stabilizer, oxidant, and pH, the addition of chloroquine phosphate corrosion inhibitor effectively suppressed the static corrosion of tungsten (compared to a static corrosion rate of 133 A / min in Comparative Example 1, the static corrosion rate of tungsten decreased significantly after the addition of chloroquine phosphate corrosion inhibitor). Furthermore, by adjusting the dosage of the chloroquine phosphate corrosion inhibitor, the static corrosion rate of tungsten can even be reduced to almost zero.

[0043] By comparing Comparative Examples 3-4 with Examples 2 and 4, it was found that fragment compounds of chloroquine phosphate, such as quinoline, could not inhibit corrosion.

[0044] Comparison of Examples 5-6 and Examples 2 and 4 revealed that compounds with a terminal tertiary amine structure similar to chloroquine phosphate aliphatic chain, such as triethylamine, could not inhibit corrosion.

[0045] By comparing Comparative Examples 7-8 with Examples 2 and 4, it was found that compounds with a fatty chain diamine structure similar to chloroquine phosphate, such as 1,6-hexanediamine, not only failed to inhibit corrosion, but also aggravated the corrosion of tungsten.

[0046] A comparison of Comparative Examples 1-4 and Example 2 revealed that the corrosion inhibition effect of chloroquine phosphate is produced by the synergistic effect of its multiple functional groups. Compounds that do not contain or only contain some or similar functional groups cannot achieve the corrosion inhibition effect on tungsten materials.

[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. It comprises: chloroquine corrosion inhibitor, water, SiO2 abrasive particles, iron ion containing catalyst, organic stabilizer, oxidizing agent and pH regulator; the mass percentage content of the chloroquine corrosion inhibitor ranges from 0.005% to 0.07%; the mass percentage content of the abrasive particles ranges from 0.5% to 3%; the mass percentage content of the iron ion containing catalyst ranges from 0.01% to 0.1%; the organic stabilizer is a carboxylic acid capable of complexing with iron; the mass percentage content of the organic stabilizer ranges from 0.01% to 0.09%; the oxidizing agent is H2O2; the mass percentage content of the oxidizing agent is 2-4%; the pH value of the chemical mechanical polishing liquid is 2-4; the chloroquine corrosion inhibitor is chloroquine phosphate, the structure of which is shown in the following formula: 。 2. The chemical mechanical polishing liquid according to claim 1, wherein, the mass percentage content of the abrasive particles ranges from 1% to 3%.

3. The chemical mechanical polishing liquid according to claim 1, wherein, the iron ion containing catalyst is ferric nitrate nonahydrate.

4. The chemical mechanical polishing liquid according to claim 1, wherein, the mass percentage content of the iron ion containing catalyst ranges from 0.01% to 0.03%.

5. The chemical mechanical polishing liquid according to claim 1, wherein, the carboxylic acid capable of complexing with iron is one or more of phthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, citric acid and maleic acid.

6. The chemical mechanical polishing liquid according to claim 1, wherein, the organic stabilizer is malonic acid.

7. The chemical mechanical polishing liquid according to claim 1, wherein, the mass percentage content of the organic stabilizer ranges from 0.01% to 0.06%.

8. The chemical mechanical polishing liquid according to claim 1, wherein, the pH regulator is HNO3.

Images