CN113004800B - A chemical mechanical polishing liquid - Google Patents

Abstract

The present invention provides a chemical mechanical polishing liquid, comprising: abrasive particles, a catalyst, a stabilizer, a cross-linked macromolecular surface defect inhibitor, an oxidant, water and a pH regulator. The chemical mechanical polishing liquid of the present application can simultaneously polish tungsten, silicon oxide and silicon nitride, ensure a high polishing speed of tungsten while having a medium silicon oxide speed and a low silicon nitride speed, greatly reduce the surface defects of the silicon nitride surface after polishing, and achieve rapid flattening.

Description

A chemical mechanical polishing liquid

Technical Field

The invention relates to a chemical mechanical polishing liquid.

Background technique

Modern semiconductor technology is developing rapidly in the direction of miniaturization. Semiconductor integrated circuits contain silicon substrates and millions of components on them, forming interconnected structures through multi-layer interconnects. Layers and structures include a variety of materials, such as single crystal silicon, silicon dioxide, tungsten, silicon nitride and various other conductive, semi-conductive and dielectric materials. Thin layer structures of these materials can be manufactured by a variety of deposition techniques, such as physical vapor deposition (PVD), chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD), after which excess materials need to be removed. With the deposition and removal of multiple layers of materials, the top surface of the wafer becomes uneven. These unevenness may lead to various defects in the product, so the flattening technology of the conductive layer and the insulating dielectric layer becomes particularly important. In the 1980s, the chemical mechanical polishing (CMP) technology pioneered by IBM is considered to be the most effective method for global flattening.

Chemical mechanical polishing (CMP) is a combination of chemical action, mechanical action, and the combination of the two. Usually, the wafer is fixed on the grinding head and its front side is in contact with the polishing pad in the CMP equipment. Under a certain pressure, the grinding head moves linearly on the polishing pad or rotates in the same direction as the grinding table. At the same time, a polishing composition ("slurry") is injected between the wafer and the polishing pad at a certain flow rate, and the slurry is spread on the polishing pad due to centrifugal action. Thus, under the dual action of chemistry and mechanics, the surface of the wafer is polished and globally flattened. CMP can be used to remove unwanted surface morphology and surface defects, such as rough surface, adsorbed impurities, lattice damage, scratches, etc.

In the design and manufacture of semiconductor integrated circuits, tungsten is used to form interconnects and contact plugs. Chemical mechanical polishing is the preferred method for polishing tungsten. Since tungsten has a certain hardness, its polishing process is somewhat different from that of other metals. At the same time, in some practical applications of chemical mechanical polishing, there will be situations where tungsten, silicon oxide, and silicon nitride need to be polished simultaneously. Since the rate, depression, and surface defects of several different media need to be controlled, this poses a challenge to the design of the polishing composition. U.S. Patent No. 9567491 discloses a polishing composition that can polish tungsten, silicon oxide, and silicon nitride simultaneously, and describes a method for reducing tungsten depressions on patterned wafers, but does not propose measures to solve silicon nitride surface defects, and its tungsten removal rate is relatively slow relative to the silicon oxide removal rate. U.S. Patent No. 9771496 discloses a polishing composition containing a cyclic polysaccharide compound that can polish tungsten, silicon oxide, and silicon nitride simultaneously. This combination can greatly reduce the defects of silicon oxide, but it does not help to reduce the surface defects of silicon nitride. Chinese patent CN 104284960 discloses a highly selective polishing composition for silicon oxide/silicon nitride, which can control the defects of silicon nitride, but the combination cannot be used for tungsten polishing. Chinese patent CN105229110 discloses a polishing composition that can control the surface defects of silicon nitride, but the combination cannot be used for tungsten polishing. However, if the surface defects of silicon nitride after polishing are not well controlled, the dielectric layer deposited above it will be uneven, thereby affecting the wafer yield.

It can be seen that it is of great significance in this field to seek a polishing composition that can polish tungsten, silicon oxide, and silicon nitride simultaneously and can reduce surface defects of silicon nitride.

Summary of the invention

In order to solve the technical problems that the existing tungsten chemical mechanical polishing liquid cannot polish tungsten, silicon oxide and silicon nitride at the same time, and control the rates and surface defects of tungsten, silicon oxide and silicon nitride respectively, maintain a high tungsten polishing rate while having a medium silicon oxide rate and a low silicon nitride rate, and can reduce the surface defects of silicon nitride, the present invention provides a chemical mechanical polishing liquid, including: abrasive particles, a catalyst, a stabilizer, a cross-linked macromolecular surface defect inhibitor, an oxidant, water and a pH regulator.

Furthermore, the cross-linked macromolecular surface defect inhibitor is carbomer.

Furthermore, the model of the carbomer is one or more of 934 (i.e., carbomer 934), 940 (i.e., carbomer 940) and 941 (i.e., carbomer 941), and the difference between carbomer 934, carbomer 940 and carbomer 941 is that the viscosities are different.

Furthermore, the concentration range of the carbomer of model 940 is 0.005% to 0.1%.

Furthermore, the concentration range of the carbomer of model 940 is 0.005% to 0.05%.

Furthermore, the abrasive particles are SiO ₂ .

Furthermore, the concentration of the abrasive particles ranges from 0.5% to 3%.

Furthermore, the concentration of the abrasive particles ranges from 1% to 3%.

Furthermore, the catalyst is selected from ferric nitrate nonahydrate.

Furthermore, the concentration of the ferric nitrate nonahydrate is in the range of 0.01% to 0.1%.

Furthermore, the concentration range of the ferric nitrate nonahydrate is 0.01% to 0.07%.

Furthermore, the stabilizer is a carboxylic acid that can complex with iron.

Furthermore, the carboxylic acid that can be complexed with iron is selected from one or more of phthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, citric acid, and maleic acid.

Furthermore, the carboxylic acid that can be complexed with iron is malonic acid.

Furthermore, the concentration range of the malonic acid is 0.05% to 0.3%.

Furthermore, the concentration range of the malonic acid is 0.1% to 0.27%.

Furthermore, the oxidant is H ₂ O ₂ .

Furthermore, the concentration range of the oxidant is 1-2%.

Furthermore, the pH adjuster is HNO ₃ .

Furthermore, the pH value is 2 to 4. When the pH is less than 2, the chemical mechanical polishing liquid is a dangerous substance, and when the pH is greater than 4, it will lead to defects such as unstable abrasive particles and Fe precipitation.

It should be understood that the % in the concentrations described in the present invention refers to mass concentration.

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

The chemical mechanical polishing liquid of the present application can simultaneously polish tungsten, silicon oxide and silicon nitride, and at the same time, ensure a high polishing speed of tungsten while having a medium silicon oxide speed and a low silicon nitride speed. At the same time, the chemical mechanical polishing liquid of the present application greatly reduces the surface defects of the silicon nitride surface after polishing by adding carbomer, suppresses the surface defects of silicon nitride, and achieves rapid planarization.

Detailed ways

The advantages of the present invention are described in detail below in conjunction with specific embodiments.

The chemical mechanical polishing composition for polishing tungsten of the present invention is described in detail below through specific examples to provide a better understanding of the present invention, but the following examples do not limit the scope of the present invention.

It should be understood that the % in the concentration described in the present invention refers to the mass percentage.

Example

Preparation method: Dissolve and mix all components according to the formula in Table 1 evenly, make up the mass percentage to 100% with water, and adjust the pH to the desired value with a pH regulator.

Table 1. Types of components and their corresponding concentrations in various examples and comparative examples

Effect example

The chemical mechanical polishing solutions of the embodiments and comparative examples in Table 1 were used to polish tungsten, silicon oxide, and silicon nitride wafers and measure the surface defects of silicon nitride wafers according to the following experimental conditions to obtain the results in Table 2.

Polishing method: The polishing machine is a 12-inch polishing machine (Reflexion LK) from Applied Materials, with a pressure of 3.0 psi, a polishing disc and polishing head speed of 93/87 rpm, a polishing pad of IC1010, a polishing liquid flow rate of 150 ml/min, and a polishing time of 1 minute.

Surface defect measurement method: Use KLA-Tencor's unpatterned wafer defect inspection system (SurfscanSP2) to measure the surface of silicon nitride and count defects with a diameter greater than 120 nm.

Table 2. Polishing rates of tungsten, silicon oxide, and silicon nitride in the examples and comparative examples, and the inhibitory effects on surface defects of silicon nitride

Examples 1-7 show that the chemical mechanical polishing liquid of the present invention can polish tungsten, silicon oxide and silicon nitride at the same time, and the polishing speed is: tungsten>silicon oxide>silicon nitride. At the same time, it can maintain a high tungsten polishing speed while having a medium silicon oxide speed and a low silicon nitride speed. At the same time, it has the ability to suppress surface defects of silicon nitride after polishing. Among them, the polishing speed of tungsten is positively correlated with the concentration of the oxidant, or the concentration of the abrasive particles, or the concentration of the catalyst, or the concentration of the oxidant. Specifically, in Table 2, the concentration of the oxidant in Examples 1-3 is 1.00%, and the corresponding tungsten polishing rates are 2356, 2318, and 2325, respectively; when the concentration of the oxidant is increased to 2.0% (such as Examples 4-7), the corresponding tungsten polishing rates are 3107, 3611, 3552, and 3409, respectively. Specifically, in Table 2, the concentration of the abrasive particles in Examples 1-3 is 1.0%, and the corresponding tungsten polishing rates are 2356, 2318, and 2325, respectively; when the concentration of the abrasive particles is increased to 2.0% (such as Example 4), the corresponding tungsten polishing rate is 3107; when the concentration of the abrasive particles is increased to 3.0% (such as Examples 5-7), the corresponding tungsten polishing rates are 3611, 3552, and 3409, respectively. Specifically, in Table 2, the concentration of the catalyst in Examples 1-3 is 0.01%, and the corresponding tungsten polishing rates are 2356, 2318, and 2325, respectively; when the concentration of the catalyst is increased to 0.05% (such as Example 4), the corresponding tungsten polishing rate is 3107; when the concentration of the catalyst is increased to 0.07% (such as Examples 5-7), the corresponding tungsten polishing rates are 3611, 3552, and 3409, respectively. Therefore, the polishing speed of tungsten can be adjusted by adjusting the amount of the oxidant, the abrasive particles, and the catalyst.

By comparing Comparative Examples 1-2 and Examples 1-7, it is found that on the basis of the same abrasive particles, catalysts, stabilizers, oxidants and pH, adding carbomer (e.g., carbomer 934, carbomer 940, carbomer 941) significantly improves the surface defects of silicon nitride after polishing. Specifically, it can be found through Examples 1-3 and Comparative Example 4 that on the basis of the same abrasive particles, catalysts, stabilizers, oxidants and pH, adding carbomer (carbomer 934, carbomer 940, carbomer 941) significantly improves the surface defects of silicon nitride after polishing, and the surface defects of silicon nitride are reduced from about 900 to about 300. Similarly, the same conclusion can be drawn through Example 4 and Comparative Example 2. The same conclusion can be drawn through Examples 5-7 and Comparative Examples 1 and Comparative Example 3. In addition, it can be drawn through Examples 5-7 that on the basis of the same abrasive particles, catalysts, stabilizers, oxidants and pH, as the amount of carbomer continues to increase, the number of defects decreases accordingly, and is only one-ninth of the number when carbomer is not added at most. At the same time, the amount of carbomer does not have much effect on the polishing speed. Specifically, when the concentration of carbomer 940 is 0.015% (Example 5), the corresponding silicon nitride surface defects are 162; when the concentration of carbomer 940 is 0.050% (Example 5), the corresponding silicon nitride surface defects are 147; when the concentration of carbomer 940 is 0.100% (Example 5), the corresponding silicon nitride surface defects are 101 (about one ninth of the silicon nitride surface defects 976 in Comparative Example 1).

By comparing Comparative Example 3 with Example 5, it is found that the chemical mechanical polishing solution obtained by adding the monomer acrylic acid of carbomer has no ability to correct the defects of silicon nitride after polishing. Specifically, on the basis of the same abrasive particles, catalyst, stabilizer, oxidant and pH, and the concentration of carbomer 940 in Example 5 is consistent with the concentration of acrylic acid in Comparative Example 3, the chemical mechanical polishing solution of Example 5 has the ability to inhibit the surface defects of silicon nitride, which is reduced from 976 in Comparative Example 1 to 162 relative to Comparative Example 1; while the composition in Comparative Example 3 has no ability to inhibit the surface defects of silicon nitride, because the surface defects of Comparative Example 3 are similar to those of Comparative Example 1.

The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims (6)

1. A chemical mechanical polishing liquid, comprising abrasive particles, a catalyst, a stabilizer, a cross-linked macromolecular surface defect inhibitor, an oxidant, water and a pH adjuster, wherein the cross-linked macromolecular surface defect inhibitor is Carbomer Model 940, and the concentration range of the Carbomer Model 940 is 0.005% to 0.1%; The abrasive particles are SiO ₂ , and the concentration of the abrasive particles is in the range of 0.5% to 3%; The catalyst is selected from ferric nitrate nonahydrate, and the concentration range of the ferric nitrate nonahydrate is 0.01% to 0.1%; The stabilizer is malonic acid, and the concentration range of the malonic acid is 0.05% to 0.3%; The oxidant is H ₂ O ₂ , and the concentration range of the oxidant is 1-2%; The pH value is 2-4. 2. The chemical mechanical polishing liquid as claimed in claim 1, wherein the concentration range of the carbomer with model number 940 is 0.005% to 0.05%. 3 . The chemical mechanical polishing solution as claimed in claim 1 , wherein the concentration of the abrasive particles is in the range of 1% to 3%. 4 . The chemical mechanical polishing solution according to claim 1 , wherein the concentration of the ferric nitrate nonahydrate is in the range of 0.01% to 0.07%. 5 . The chemical mechanical polishing solution according to claim 1 , wherein the concentration of the malonic acid is in the range of 0.1% to 0.27%. The chemical mechanical polishing solution according to claim 1 , wherein the pH adjuster is HNO ₃ .