A chemical mechanical polishing fluid

Abstract

This invention provides a chemical mechanical polishing slurry comprising abrasive particles, a complexing agent, an oxidizing agent, water, and at least one corrosion inhibitor. The polishing slurry provided by this invention exhibits high removal rates of titanium and silicon oxide insulating layers, a high selectivity ratio for cobalt removal from silicon oxide, and superior cobalt corrosion control and wafer surface morphology repair capabilities.

Description

Technical Field

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

[0002] The rapid development of integrated circuit technology has been accompanied by the continuous miniaturization of transistor geometry and interconnect metal dimensions. As the complexity of integrated circuits increases, using only one layer of metal interconnects is no longer sufficient. Modern integrated circuits have as many as 10 or more metal interconnect layers, separated by dielectric materials. Through-holes (vias) are then punched in the dielectric material for metal filling. A via itself is a vertically insulating channel; to enable circuit conduction, metal must be filled within the via, and electrical signals are transmitted between layers via interconnect wires. At the 180nm technology node, copper replaced aluminum as the interconnect wire because of its lower resistivity, better scalability, and higher current density. However, copper diffuses more easily into the dielectric material than aluminum, potentially causing short circuits. Therefore, tantalum and tantalum nitride are often used as diffusion barriers and adhesion promoters between copper and dielectric materials to improve the stability of integrated circuits. As semiconductor manufacturing processes advance to 32nm and below, not only does the number of metal interconnect layers increase significantly, but the distance between the wires and their dimensions also continue to shrink. The mean free path of copper is approximately 40 nm. Therefore, when the size of copper interconnects approaches 40 nm, the scattering of copper electrons at the sidewalls and grain boundaries increases, leading to a significant increase in copper resistivity and affecting circuit stability. As the width of copper interconnects continues to decrease, it becomes difficult to further thin the tantalum / tantalum nitride barrier diffusion layer beyond its existing thickness of a few nanometers. This results in the barrier diffusion layer accounting for an increasingly larger proportion of the copper interconnect cross-sectional area, even beginning to dominate the resistivity of the conductor itself and prolonging the RC response time. When the feature size of integrated circuits decreases to 14 nm, the tantalum / tantalum nitride barrier layer structure cannot achieve complete void-free filling of copper for copper interconnect structures, leading to defects such as voids and compression. Cobalt, as a new material in integrated circuit manufacturing processes, possesses advantages such as high hardness, high adhesion, low resistivity, low electron mean free path, and conformal deposition capabilities in high aspect ratio trenches, making it a preferred metal to replace copper as an interconnect material.

[0003] The connection structure between the metal wire and the semiconductor element on the silicon substrate is called a contact window, which is mainly connected by tungsten metal with titanium nitride as the barrier layer material. As the feature size of integrated circuits decreases to 7nm and below, traditional tungsten contact window structures face a series of problems: resistivity increases with decreasing thickness, conformal deposition cannot be achieved in narrow trench widths (20nm and below), and the diffusion barrier / substrate scaling constraint cannot be met. Cobalt, due to its advantages such as low resistivity, good substrate adhesion, high resistance to electromigration, good conformal deposition in high aspect ratio trenches, and good compatibility with thin substrates, has become the most promising contact window material to replace tungsten.

[0004] The introduction of cobalt alters the metallic environment involved in existing processes. Furthermore, cobalt's relatively reactive chemical properties mean that differences in electrochemical activity among different metals can lead to the formation of galvanic cells and electrochemical corrosion. Chemical mechanical polishing (CMP) is an essential global planarization technology for achieving high-density integration in integrated circuits. It combines the mechanical and chemical effects of the polishing slurry, achieving surface planarization through mechanical friction and chemical dissolution. However, CMP is a process prone to electrochemical corrosion; therefore, pitting and galvanic corrosion are common defects in cobalt CMP, leading to increased resistance and even device malfunction.

[0005] Figure 1-3 These are schematic diagrams of the semiconductor structure before polishing, after the first polishing step, and after the second polishing step, respectively. (See attached diagram.) Figure 1-3 The semiconductor structure includes:

[0006] The substrate 101 and the silicon oxide insulating layer 102 formed on the substrate include a plurality of grooves inside;

[0007] A titanium barrier layer 103 is applied to the surface of the silicon oxide insulating layer 102 and the inner wall of the groove.

[0008] Cobalt 104 metal is filled in the groove.

[0009] Currently, the chemical mechanical polishing (CMP) process for cobalt mainly consists of two steps: Step 1: Removal of the cobalt coating. A cobalt polishing slurry is used to remove a large amount of cobalt at a high material removal rate, and polishing is stopped at the titanium barrier layer by endpoint detection. Because this step has a very high cobalt removal rate while the titanium removal rate is almost zero, a dish-shaped depression easily forms at the cobalt location at the polishing endpoint. Step 2: Removal of the titanium barrier layer, part of the silicon oxide insulating layer, and cobalt using a cobalt barrier layer polishing slurry. This repairs the dish-shaped depressions formed after the first polishing step, achieving planarization and reducing surface defects after polishing. Summary of the Invention

[0010] To overcome the aforementioned technical deficiencies, the present invention aims to provide a chemical mechanical polishing slurry. The polishing slurry provided by the present invention exhibits high removal rates of titanium and silicon oxide, as well as a high selectivity ratio for cobalt removal from silicon oxide, and demonstrates superior cobalt corrosion control and wafer surface morphology repair capabilities.

[0011] This invention discloses a chemical mechanical polishing fluid comprising abrasive particles, a complexing agent, an oxidizing agent, water, and at least one corrosion inhibitor.

[0012] Optionally, the corrosion inhibitor is selected from one or more of C11-C18 potassium carbofuranate and C10-C20 potassium alkylbenzene sulfonate.

[0013] Optionally, the mass percentage concentration of the corrosion inhibitor is 0.01 to 0.1 wt%.

[0014] Optionally, the complexing agent is selected from one or more of histidine, glycine, alanine, valine, tryptophan, serine, threonine, aspartic acid, asparagine, glutamic acid, and glutamine.

[0015] Optionally, the concentration of the complexing agent is 0.05 to 0.2 wt%.

[0016] Optionally, the abrasive particles are silicon dioxide; the mass percentage concentration of the abrasive particles is 1-10 wt%; and the particle size of the abrasive particles is 20-100 nm.

[0017] Optionally, the oxidant is hydrogen peroxide; the mass percentage concentration of the oxidant is 0.1 to 1 wt%.

[0018] Optionally, the pH of the chemical mechanical polishing solution is 8 to 11.

[0019] The polishing solution of this invention also contains conventional additives commonly used in the art, such as pH adjusters and bactericides. The polishing solution of this invention can be concentrated and prepared; before use, it can be diluted with deionized water and an oxidant can be added to the concentration range specified in this invention.

[0020] Compared with existing technologies, the above technical solution has the following advantages:

[0021] 1. The chemical mechanical polishing slurry provided by the present invention can meet the requirement of high selectivity of silicon oxide to cobalt removal rate in cobalt polishing process, and has good repair ability for dish-shaped depressions generated after the first polishing step.

[0022] 2. The chemical mechanical polishing slurry provided by the present invention has a low cobalt static corrosion rate, which can reduce the occurrence of cobalt corrosion during chemical mechanical polishing. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the semiconductor structure before polishing;

[0024] Figure 2 This is a schematic diagram of the semiconductor structure after the first polishing step.

[0025] Figure 3 This is a schematic diagram of the semiconductor structure after the second polishing step.

[0026] Figure label:

[0027] 101-Substrate;

[0028] 102-Silicon oxide insulating layer;

[0029] 103-Titanium barrier layer;

[0030] 104-Metallic Cobalt. Detailed Implementation

[0031] 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.

[0032] Table 1 shows the comparative polishing solutions 1-3 and the polishing solutions 1-17 of the present invention. According to the formulas given in the table, mix all components except the oxidant thoroughly. Adjust the pH to the desired value using a pH adjuster (such as potassium hydroxide or nitric acid). Add the oxidant and mix thoroughly before use. The polishing solutions of the present invention can also be prepared as concentrated samples in advance, diluted with deionized water at a certain ratio, and then the oxidant is added before use.

[0033] Table 1 compares polishing slurries 1-3 with polishing slurries 1-17 of the present invention.

[0034]

[0035]

[0036] Using comparative polishing slurries 1-3 and polishing slurries 1-17 of the present invention, cobalt (Co), silicon oxide (Oxide), and titanium (Ti) were polished under the following conditions: Polishing machine: 12-inch Ebara machine; polishing pad: Fujibopad; downforce: 1.0 psi; rotation speed: polishing disc / polishing head = 93 / 87 rpm; polishing slurry flow rate: 300 ml / min; polishing time: 1 min.

[0037] The comparative polishing solutions 1-3 and the polishing solutions 1-17 of this invention were placed in a constant temperature water bath at 50°C. Co wafers were then immersed in the different polishing solutions. After 5 minutes, they were removed and rinsed with deionized water, and the subsequent values ​​were measured. Static etching rate = (thickness before immersion - thickness after immersion) / 5. The results are shown in Table 2.

[0038] Table 2 compares the removal rates of cobalt (Co), silicon oxide, and the barrier layer titanium (Ti) and the static corrosion rate of cobalt (Co) using polishing slurries 1-3 and polishing slurries 1-17 of the present invention.

[0039]

[0040]

[0041] The results are shown in Table 2. Compared with Comparative Examples 1-3, Examples 1-17 showed a significant reduction in the static corrosion rate of cobalt after adding the cobalt corrosion inhibitor of the present invention, thus preventing corrosion of cobalt during chemical mechanical polishing. The removal rate of cobalt can be effectively controlled by adding different types of corrosion inhibitors or changing their concentration. Furthermore, the selectivity of silicon dioxide for cobalt removal rate can be effectively controlled by changing the particle size, the mass percentage concentration of the abrasive particles, or the concentration of the cobalt corrosion inhibitor.

[0042] Furthermore, in order to characterize the repair effect of the polishing slurry in the present invention on the dish-shaped depression formed in the first polishing step, the patterned cobalt wafer was polished using comparative polishing slurries 1-3 and polishing slurries 1-6 of the present invention under the following conditions.

[0043] The graphics wafer is a commercially available 12-inch Sematech 754 graphics chip, and the film materials from top to bottom are cobalt / titanium / Oxide.

[0044] The polishing process consists of two steps. The first step uses a commercially available cobalt polishing slurry to remove most of the cobalt. The second step uses the cobalt barrier layer polishing slurry of this invention to remove the barrier layer titanium and part of the silicon oxide, leaving it on the silicon oxide layer. Polishing conditions: The polishing machine was a 12-inch Ebara machine, the polishing pad was a Fujibo pad, the downforce was 1.0 psi, the rotation speed was polishing disc / polishing head = 93 / 87 rpm, the polishing slurry flow rate was 300 ml / min, and the polishing time was 1 min. The experimental results are shown in Table 3: Table 3 compares the repair capabilities of polishing slurries 1-3 and polishing slurries 1-6 of this invention on patterned cobalt wafers after polishing to remove dish-shaped depressions.

[0045]

[0046] According to the data in Table 3, compared with Comparative Examples 1-3, Examples 1-6 can better correct the dish-shaped depressions generated on the wafer after the first polishing step, so that the polished cobalt wafer has better morphology and flatness.

[0047] It should be understood that all wt% mentioned in this invention refers to mass percentage concentration.

[0048] 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, It contains abrasive particles, complexing agent, oxidant, water, and at least one corrosion inhibitor.

2. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The corrosion inhibitor is selected from one or more of C11-C18 potassium carbofuranate and C10-C20 potassium alkylbenzenesulfonate.

3. The chemical mechanical polishing slurry as described in claim 2, characterized in that, The corrosion inhibitor has a mass percentage concentration of 0.01–0.1 wt%.

4. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The complexing agent is selected from one or more of histidine, glycine, alanine, valine, tryptophan, serine, threonine, aspartic acid, asparagine, glutamic acid, and glutamine.

5. The chemical mechanical polishing slurry as described in claim 4, characterized in that, The complexing agent has a mass percentage concentration of 0.05–0.2 wt%.

6. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The abrasive particles are silica nanoparticles; the mass percentage concentration of the abrasive particles is 1-10 wt%; and the particle size of the abrasive particles is 20-100 nm.

7. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The oxidant is hydrogen peroxide, and the mass percentage concentration of the oxidant is 0.1 to 1 wt%.

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

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