CN113122145A

CN113122145A - Chemical mechanical polishing solution

Info

Publication number: CN113122145A
Application number: CN201911407778.3A
Authority: CN
Inventors: 倪宇飞; 姚颖; 荆建芬; 黄悦锐; 马健; 杨俊雅; 蔡鑫元; 汪国豪; 陆弘毅
Original assignee: Anji Microelectronics Shanghai Co Ltd
Current assignee: Anji Microelectronics Shanghai Co Ltd
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2021-07-16
Also published as: WO2021135806A1; TW202126722A

Abstract

The invention provides a chemical mechanical polishing solution which comprises grinding particles, a metal corrosion inhibitor, a complexing agent, an oxidant and a polyoxyethylene polyoxypropylene block copolymer surfactant. The chemical mechanical polishing solution can effectively reduce and control the generation of excessive erosion of the edge of the boundary of a dielectric material and a copper wire, keeps the removal rate of higher tantalum and silicon dioxide, has a remarkable inhibiting effect on the removal rate of a low dielectric constant material, meets the requirements of polishing rate and selection ratio of various materials in the polishing process of a barrier layer, can well control the dishing depression after polishing, and meets the strict requirement on the polishing interface flatness in the advanced processing.

Description

Chemical mechanical polishing solution

Technical Field

The invention relates to a chemical mechanical polishing solution.

Background

In the integrated circuit manufacturing, the standard of the interconnection technology is increasing, and with the increase of the number of interconnection layers and the reduction of the process feature size, the requirement on the surface flatness of the silicon wafer is higher and higher, and without the capability of planarization, the creation of complex and dense structures on the semiconductor wafer is very limited, and the Chemical Mechanical Polishing (CMP) method is the most effective method for achieving the planarization of the whole silicon wafer.

The CMP process is the polishing of the surface of the integrated circuit using an abrasive-containing mixture and a polishing pad. In a typical chemical mechanical polishing process, a substrate is brought into direct contact with a rotating polishing pad, and a carrier is used to apply pressure to the backside of the substrate. During polishing, the pad and platen are rotated while maintaining a downward force on the back surface of the substrate, and an abrasive and chemically reactive solution (commonly referred to as a slurry or slurry) are applied to the pad, which reacts chemically with the film being polished to begin the polishing process.

With the development of integrated circuit technology to 45nm and below technology nodes and the sharp increase of interconnection wiring density, the RC coupling parasitic effect brought by resistance and capacitance in an interconnection system is rapidly increased, and the speed of a device is influenced. To reduce this effect, a low-capacitance low-k insulating material must be used to reduce the parasitic capacitance between adjacent metal lines, and the introduction of such a material poses a significant challenge to the process technology, especially chemical mechanical polishing (cmp) process, because the mechanical strength of the low-k material is weakened. In the CMP process, it is necessary to not only satisfy the requirements of polishing rate and selectivity of various materials in the barrier polishing process, but also control the surface flatness of the polished interface. As shown in fig. 1, the Edge-Over-Erosion (EOE) of the dielectric layer and the metal Edge is liable to occur during the CMP of the barrier layer, and the Dishing (Dishing) of the copper line is liable to occur after polishing. EOE is also known in some related literature and patents as "canine" (Fang) or edge crack etch (team), and this phenomenon occurs due to erosion of the dielectric material at the edges of the copper lines. EOE can have serious consequences when it is large, and it is desirable to minimize or eliminate this phenomenon during polishing. The butterfly-shaped recess is the recess in the copper wire, and the height difference between the dielectric layer and the lowest point in the Cu wire is used for representing the size. The reason why the dishing occurs is mainly that in the CMP process of the copper wiring, due to the fact that the physical and chemical properties of copper, a barrier layer and a dielectric layer are different, polishing rates of different materials are different, the copper removal rate is too high, the barrier layer material and the dielectric layer material are removed slowly, local over-polishing is easily caused, and severe dishing occurs.

Disclosure of Invention

The invention provides a chemical mechanical polishing solution, which aims to solve the requirements of polishing rate and selectivity of the chemical mechanical polishing solution to various materials, interface flatness and excessive edge erosion control after polishing in the process of polishing a barrier layer in a copper interconnection process in integrated circuit manufacturing.

Wherein the polyoxyethylene polyoxypropylene block copolymer surfactant has the following structure:

wherein x, y, z are integers greater than or equal to 0, x + z <400 and y < 100.

When x + z is much greater than y, where the HLB value of the surfactant (the hydrophilic-lipophilic balance of the surfactant) is greater, a greater hydrophilicity is exhibited, such surfactants are typically used as wetting agents or O/W (i.e., hydrophilic-type) emulsifiers in applications in the art. At this time, if the concentration of the surfactant is too high, the polishing solution generates a large amount of foam during production, transportation and use, so that an optimal concentration window exists;

when x + z is far less than y, the HLB value of the surfactant is small, the surfactant has strong lipophilicity and obvious defoaming effect, and the surfactant can also be used as a W/O (oleophilic type) emulsifier; when the surfactant is added in a large amount in a system, the surfactant is difficult to disperse and dissolve due to poor hydrophilicity, and excessive addition can cause the phenomena of layering of part of the surfactant in the system, unstable polishing solution and the like.

Further, the molecular weight of the polyoxyethylene polyoxypropylene block copolymer surfactant is 1000-20000, preferably 1000-5000. The molecular weight of the surfactant may affect its inhibitory effect on excessive edge erosion to some extent. The mass percentage concentration of the polyoxyethylene polyoxypropylene block copolymer surfactant is 0.001-0.2 wt%, and preferably 0.005-0.1 wt%.

The grinding particles are silicon dioxide, and the mass percentage concentration of the grinding particles is 2-15 wt%, preferably 3-10 wt%. The particle size of the grinding particles is 20-150 nm, and preferably, the particle size of the grinding particles is 30-100 nm.

The metal corrosion inhibitor is an azole compound, preferably one or more of benzotriazole, methylbenzotriazole, 1,2, 4-triazole, 3-amino-1, 2, 4-triazole, carboxyl benzotriazole, 5-methyl tetrazole, 5-amino tetrazole, 5-phenyl tetrazole and mercapto phenyl tetrazole. The mass percentage concentration of the metal corrosion inhibitor is 0.005-0.5 wt%, preferably 0.01-0.2 wt%.

The complexing agent is organic acid and organic amine compound, preferably one or more of oxalic acid, malonic acid, succinic acid, citric acid, tartaric acid, glycine, alanine, hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, L-cysteine, ethylene diamine tetraacetic acid, ethylenediamine and/or triethanolamine. The mass percentage concentration of the complexing agent is 0.01-2 wt%, and preferably 0.05-1 wt%.

Wherein the oxidant is hydrogen peroxide, and the mass percent concentration of the oxidant is 0.05-1 wt%.

Wherein the pH value of the chemical mechanical polishing solution is 8-12, preferably 9-11.

The chemical mechanical polishing solution of the present invention may further contain other additives in the art, such as a pH adjuster and a bactericide.

The chemical mechanical polishing solution can be prepared by concentration, namely, grinding particles, a metal corrosion inhibitor, a complexing agent, water and a polyoxyethylene polyoxypropylene block copolymer surfactant are mixed to prepare a concentrated product; the concentrated preparation is diluted with deionized water and an oxidizing agent is added to the concentration range of the present invention before use.

It should be understood that wt% in the present invention refers to mass percent concentration.

Compared with the prior art, the invention has the advantages that:

the chemical mechanical polishing solution is suitable for a barrier layer polishing solution in a copper interconnection process, is used for a process of polishing a dielectric layer at least containing barrier metal tantalum, copper and silicon dioxide, or a process of polishing a dielectric layer at least containing barrier metal tantalum, copper, silicon dioxide and a low dielectric constant (low-k) material BD (BD refers to a black diamond material containing silicon, oxygen, carbon and hydrogen elements and similar to oxides), can effectively reduce and control the generation of excessive erosion of the edge of the dielectric material and the copper wire boundary, and has a remarkable inhibiting effect on the removal rate of a low-k dielectric material at the same time. The method prevents the low dielectric constant material BD with lower mechanical strength from causing mechanical damage, and meets the strict requirement on the flatness of the polishing interface in the advanced process.

Drawings

FIG. 1 is a surface topography profile of an Edge Over Erosion (EOE) phenomenon and a butterfly depression phenomenon after polishing, measured by a step profiler, after polishing with a chemical mechanical polishing solution of the prior art.

FIG. 2 is a surface topography profile of an Edge Over Erosion (EOE) phenomenon and a dishing phenomenon of a dielectric layer measured by a step profiler after polishing using a chemical mechanical polishing solution of a comparative example. The abscissa in the figure is the length of the path swept by the step profiler on the Sematech754 wafer surface, and the unit is micrometer; the ordinate is the surface relief measured by the probe in units of

Fig. 3 is a schematic diagram showing that the EOE phenomenon and the butterfly-shaped dishing phenomenon are significantly improved after the chemical mechanical polishing solution (example 1) added with the polyoxyethylene polyoxypropylene block copolymer surfactant is used for polishing.

Detailed Description

The advantages of the invention are explained in detail below with reference to the drawings and the embodiments.

Examples

The preparation method comprises the following steps: the chemical mechanical polishing solutions of comparative examples 1 to 3 and examples 1 to 17 were prepared according to the formulation in table 1, and each component was simply mixed, and the mass concentration was made up to 100% with water.

TABLE 1 formulations of comparative examples 1-3 and inventive examples 1-17

Effect example 1

Copper (Cu), tantalum (Ta), silicon dioxide (TEOS), and a low dielectric constant material BD were polished under the following conditions using the chemical mechanical polishing liquids of comparative examples 1 to 3 prepared according to the formulations in table 1 and the chemical mechanical polishing liquids of examples 1 to 17 of the present invention. Polishing conditions: the polishing machine is a 12' Reflexion LK machine, the polishing pad is Fujibo pad, the downward pressure is 1.5psi, the rotation speed is 93/87rpm, the flow rate of the polishing solution is 300ml/min, and the polishing time is 1 min. The removal rates of the polishing solutions of each comparative example and example were obtained for copper (Cu), tantalum (Ta), silicon dioxide (TEOS), and low dielectric constant material BD, and are shown in table 2.

TABLE 2 removal rates for copper (Cu), tantalum (Ta), silicon dioxide (TEOS), and low dielectric materials (BD) for comparative and inventive polishing solutions

The results are shown in table 2: the chemical mechanical polishing solution added with the polyoxyethylene polyoxypropylene block copolymer surfactant has little influence on the removal rate of copper, tantalum and TEOS, and simultaneously inhibits the light removal rate of the low dielectric constant material BD. In advanced processes, it is necessary to remove a portion of the low-k material (BD) and stop on the BD material, so the removal rate of BD cannot be too high in order to better control the polishing process. When the pH was too low (pH 7 as shown in comparative example 3), the removal rate of tantalum, TEOS was too low; when the pH is too high (example 17, pH 12), although the removal rate is satisfactory, the stability of the polishing solution is poor, which is not favorable for long-term storage.

Effect example 2

The chemical mechanical polishing liquids of comparative examples 1 to 3 and the chemical mechanical polishing liquids of examples 1 to 17 of the present invention prepared according to the formulations in table 1 were used to polish copper wafers with patterns under the following conditions. The patterned chip is a commercially available 12-inch Sematech754 patterned chip, the film layer material is copper/tantalum nitride/TEOS/BD from top to bottom, the polishing process is divided into three steps, the first step is to remove most of the copper by using a commercially available copper polishing solution, the second step is to remove the residual copper by using a commercially available copper polishing solution, and the third step is to remove the barrier layer (tantalum/tantalum nitride), silicon dioxide TEOS and part of the BD layer by using the barrier layer polishing solution of the invention and stop on the BD layer. Polishing conditions of the barrier layer polishing solution are as follows: the polishing machine is a 12' Reflexion LK machine, the polishing pad is Fujibo pad, the downward pressure is 1.5psi, the rotation speed is 93/87rpm, the flow rate of the polishing solution is 300ml/min, and the polishing time is 60 s. The measurement instrument is Bruker Dektak-XT. (the path length of the scan was 500 microns, measured along a straight line for the metal pads of the Sematech754 graphics chip). The butterfly depression and edge over-erosion depth results are shown in table 3, fig. 2, fig. 3.

TABLE 3 depth of dishing and Edge Over Erosion (EOE) after polishing with comparative polishing solution 1 and inventive polishing solution

The dishing recess refers to a recess on the metal pad before and after polishing the barrier layer, and the EOE refers to a sharp recess located at the edge of the metal pad and at the junction of the barrier layer and the copper line.

The data in table 3 show that the cmp slurries of the examples of the present invention improve the EOE at the interface between the dielectric layer and the copper wire to a different degree, and the slurries of the present invention can adjust the dishing after polishing within a certain range by changing the concentration of the surfactant (see fig. 3, the dishing and the EOE phenomena in the examples of the present application are significantly suppressed), compared to the polishing slurry 1 of the comparative example (see fig. 2, in which the dishing and the EOE phenomena in the comparative example are significant) to which the polyoxyethylene polyoxypropylene block copolymer surfactant is not added; meanwhile, for the polishing solution using the grinding particles with different particle sizes, the addition of the polyoxyethylene polyoxypropylene block copolymer surfactant has a positive effect on the inhibition of excessive edge erosion. In conclusion, the chemical mechanical polishing solution can inhibit butterfly-shaped recession in a copper wire in the polishing process, and can effectively reduce and inhibit the phenomenon of excessive erosion of the edge of the boundary between a dielectric material and the copper wire.

By combining the table 2 in the effect example 1 and the table 3 in the effect example 2, it can be known that the chemical mechanical polishing solution of the present application can effectively reduce and control the generation of excessive erosion of the edge at the boundary between the dielectric material and the copper wire, and can well control the dishing recess; meanwhile, the polishing solution provided by the patent can meet the requirements of polishing rate and selectivity of various materials in the polishing process of the barrier layer, namely, the polishing solution can remarkably inhibit the removal rate of the low-k dielectric material while keeping the removal rate of the high tantalum and silicon dioxide, prevent the mechanical damage to the low-dielectric constant material with low mechanical strength and meet the strict requirement on the flatness of the polishing interface in the advanced process.

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

The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims

1. A chemical mechanical polishing solution comprises abrasive particles, a metal corrosion inhibitor, a complexing agent, an oxidant and a polyoxyethylene polyoxypropylene block copolymer surfactant, wherein the polyoxyethylene polyoxypropylene block copolymer surfactant has the following structure:

2. The chemical mechanical polishing solution according to claim 1, wherein the molecular weight of the polyoxyethylene polyoxypropylene block copolymer surfactant is 1000 to 20000.

3. The chemical mechanical polishing solution according to claim 2, wherein the polyoxyethylene polyoxypropylene block copolymer surfactant has a molecular weight of 1000 to 5000.

4. The chemical mechanical polishing solution according to claim 1, wherein the polyoxyethylene polyoxypropylene block copolymer surfactant is present in an amount of 0.001 to 0.2 wt%.

5. The chemical mechanical polishing solution according to claim 4, wherein the surfactant of the polyoxyethylene polyoxypropylene block copolymer is present in an amount of 0.005 to 0.1 wt%.

6. The chemical mechanical polishing solution of claim 1, wherein the abrasive particles are silica.

7. The chemical mechanical polishing solution according to claim 1, wherein the abrasive particles are present in a concentration of 2 to 15 wt%.

8. The chemical mechanical polishing solution according to claim 1, wherein the metal corrosion inhibitor is an azole compound.

9. The chemical mechanical polishing solution according to claim 8, wherein the azole compound is one or more of benzotriazole, methylbenzotriazole, 1,2, 4-triazole, 3-amino-1, 2, 4-triazole, carboxybenzotriazol, 5-methyl-tetrazole, 5-amino-tetrazole, 5-phenyltetrazole, and mercaptophenyltetrazole.

10. The chemical mechanical polishing solution according to claim 1, wherein the metal corrosion inhibitor is present in a concentration of 0.005 to 0.5 wt%.

11. The chemical mechanical polishing solution according to claim 1, wherein the complexing agent is an organic acid and/or an organic amine compound.

12. The chemical mechanical polishing solution according to claim 11, wherein the organic acid is oxalic acid, malonic acid, succinic acid, citric acid, tartaric acid, glycine, alanine, hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, L-cysteine, ethylene diamine tetraacetic acid, and the organic amine is ethylenediamine and/or triethanolamine.

13. The chemical mechanical polishing solution according to claim 1, wherein the complexing agent is present in a concentration of 0.01 to 2 wt%.

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

15. The chemical mechanical polishing solution according to claim 1, wherein the oxidizing agent is present in an amount of 0.05 to 1 wt%.

16. The chemical mechanical polishing solution according to claim 1, wherein the pH of the chemical mechanical polishing solution is 8 to 12.