TWI529243B - Cleaning solution, cleaning method and damascene process using the same - Google Patents

Description

Cleaning solution, cleaning method using the cleaning liquid and setting process

The invention relates to a cleaning liquid, a cleaning method using the cleaning liquid and a damascene process.

The dual damascene process is a widely used technique in semiconductor manufacturing. To reduce the RC delay caused by parasitic capacitance, current dual damascene process studies use ultra low dielectric constant (ULK) materials as dielectric layers. In addition, as the components continue to be miniaturized, the titanium nitride hard mask layer is first formed on the dielectric layer, and the etching selectivity of the titanium nitride hard mask layer and the dielectric layer material is different. The desired pattern can be properly transferred to the dielectric layer.

However, since the pattern transfer is usually achieved by dry etching, during the etching process, the introduced reaction gas is simultaneously polymerized, and therefore, the organic polymer formed by the polymerization reaction is deposited on the surface of the element. . In addition, since the reactive gas used for etching the dielectric layer is mostly a fluorine-containing gas, these fluorine-containing gases tend to react with the titanium nitride hard mask layer to generate titanium fluoride (TiF _x ) on the surface of the element. The component profile is changed, the film layers are not normally turned on, or the leakage or short circuit is caused, thereby reducing the reliability of the component.

Especially in the deep submicron process, the effects of the above polymers and titanium fluoride residues are more pronounced. In addition, it has been found that the post-etch cleaning process has the effect of etching the exposed metal wires under the double damascene opening to affect the conduction capability of the device, or causing the dielectric layer to change the profile or cause the dielectric constant to rise. And other issues. Therefore, the post-etch cleaning process is an extremely important step for the dual damascene process.

The present invention provides a cleaning solution that can effectively remove residues containing a plurality of species.

The present invention provides a damascene process which can reduce the surface damage (copper loss) of the conductive layer, avoid the problem of dielectric constant increase or damage of the dielectric material or bridging between the dual damascene structures, and improve the reliability of the semiconductor element.

The present invention provides a method of cleaning which can effectively remove residues containing a plurality of species.

The invention provides a cleaning solution comprising 0.01-0.1 wt% hydrofluoric acid (HF); 1-5 wt% strong acid, the above strong acid is inorganic acid; 0.05-0.5 wt% ammonium fluoride; a carboxyl group-containing chelating agent; Triethanolamine (TEA); Ethylenediaminetetraacetic acid (EDTA); and water.

According to an embodiment of the invention, the strong acid comprises sulfuric acid (H ₂ SO ₄ ) or hydrochloric acid (HCl), preferably sulfuric acid (H ₂ SO ₄ ).

According to an embodiment of the invention, the carboxy-containing chelating agent comprises Oxalic acid.

According to an embodiment of the present invention, the cleaning liquid is composed only of the above components (a) to (g).

The invention further provides a damascene process, comprising providing a substrate having a conductive layer thereon and having a cap layer on the conductive layer, and then sequentially forming a dielectric layer and a metal hard mask layer on the cap layer, and then The metal hard mask layer, the dielectric layer and the cap layer are sequentially etched to form an opening to expose the conductive layer. Thereafter, the post-etch cleaning process is performed using a cleaning solution. The cleaning solution comprises: 0.01-0.1 wt% hydrofluoric acid; 1-5 wt% strong acid, the above strong acid is inorganic acid; 0.05-0.5 wt% ammonium fluoride; carboxyl group-containing chelating agent; triethanolamine; ethylenediamine four Acetic acid; and water. Thereafter, a conductive material is filled in the opening, and then the metal hard mask layer is removed.

According to an embodiment of the invention, the strong acid comprises sulfuric acid or hydrochloric acid, preferably sulfuric acid.

According to an embodiment of the invention, the carboxy-containing chelating agent comprises oxalic acid.

According to an embodiment of the present invention, the cleaning liquid is composed only of the above components (a) to (g).

According to an embodiment of the invention, the opening comprises a double damascene opening, a via opening or a contact opening.

According to an embodiment of the invention, the material of the metal hard mask layer comprises titanium, titanium nitride, tantalum, tantalum nitride, tungsten, tungsten nitride or a combination thereof.

According to an embodiment of the invention, the material of the cap layer comprises tantalum nitride, niobium oxynitride or tantalum carbide.

According to an embodiment of the invention, the dielectric layer comprises an ultra low dielectric constant material.

According to an embodiment of the invention, the damascene process further includes forming a buffer layer on the dielectric layer after forming the dielectric layer and forming the metal hard mask layer, and the material thereof comprises ruthenium oxide or bismuth oxynitride.

According to an embodiment of the invention, the method further comprises forming another cap layer on the metal hard mask layer, the material of which comprises tantalum carbide, tantalum nitride or hafnium oxynitride.

The present invention also provides a method of cleaning suitable for use in a semiconductor process in which residual species to be removed include refractory metals, fluorine, oxygen, helium, carbon and copper, the method comprising performing a first cleaning process using a cleaning fluid. The above cleaning liquid comprises: 0.01-0.1 wt% hydrofluoric acid; 1-5 wt% strong acid, the above strong acid is inorganic acid; 0.05-0.5 wt% ammonium fluoride; carboxyl group-containing chelating agent; triethanolamine; ethylenediamine Tetraacetic acid; and water.

According to an embodiment of the invention, the strong acid comprises sulfuric acid or hydrochloric acid, preferably sulfuric acid.

According to an embodiment of the invention, the carboxy-containing chelating agent comprises oxalic acid.

According to an embodiment of the present invention, the cleaning liquid is composed only of the above components (a) to (g).

According to an embodiment of the invention, after the first cleaning process is performed with the cleaning liquid, a second cleaning process is performed with deionized water.

According to an embodiment of the present invention, the above cleaning liquid can effectively remove residues containing a plurality of species.

According to the embodiment of the invention, the damascene process can reduce surface damage (copper loss) of the conductive layer, avoid the problem of dielectric constant increase or damage of the dielectric material or bridging between the dual damascene structures, and improve the reliability of the semiconductor component.

According to an embodiment of the invention, the above cleaning method can effectively remove residues containing a plurality of species.

The above described features and advantages of the present invention will be more apparent from the following description.

Embodiments of the present invention provide a cleaning solution comprising hydrofluoric acid (HF), strong acid, ammonium fluoride (NH ₄ F), a carboxyl group-containing chelating agent, triethanolamine (TEA), ethylenediaminetetraacetic acid. (Ethylenediaminetetraacetic acid, EDTA) and water.

The content of hydrofluoric acid in the cleaning liquid is 0.01 to 0.1% by weight. The strong acid content is 1-5 wt%, and the strong acid is a mineral acid having a p K _a value of less than -1.74, such as sulfuric acid (H ₂ SO ₄ ) or hydrochloric acid (HCl). The content of ammonium fluoride is from 0.05 to 0.5% by weight. The chelating agent containing a carboxyl group is, for example, Oxalic acid. Water is the rest of the cleaning fluid. The water is, for example, deionized water. In one embodiment, the cleaning solution contains only hydrofluoric acid, strong acid, ammonium fluoride, a chelating agent containing a carboxyl group, triethanolamine, ethylenediaminetetraacetic acid, and water, and does not contain other components.

The above cleaning solution can be applied to the inlay process. The following is illustrated by a dual damascene process.

1A to 1E are schematic cross-sectional views showing a damascene process according to an embodiment of the invention.

Referring to FIG. 1A, a substrate 10 is provided having a conductive layer 20 thereon and a conductive layer 20 overlying the cap layer 30. The material of the conductive layer 20 is, for example, copper, copper aluminum alloy or copper aluminum alloy. The material of the cap layer 30 is, for example, tantalum nitride, niobium oxynitride or tantalum carbide. Next, a dielectric layer 40, a buffer layer 50, a metal hard mask layer 60, and a cap layer 65 are sequentially formed on the cap layer 30. The dielectric layer 40 includes an ultra low dielectric constant material (Ultra low-k, ULK). The ultra low dielectric constant material refers to a material having a dielectric constant of 2.5 to 2.7 or less. The ultra-low dielectric constant material is, for example, obsidian II (trade name of AMAT) and Dense ULK (trade name of NOVELLUS). The material of the buffer layer 50 is different from that of the dielectric layer 40, such as yttrium oxide or yttrium oxynitride. The metal hard mask layer 60 refers to a nitride including a metal or a metal in its material, such as titanium, titanium nitride, tantalum, tantalum nitride, tungsten, tungsten nitride or a combination thereof. The cap layer 65 may protect the metal hard mask layer 60, such as yttrium oxynitride, yttria, tantalum carbide or tantalum nitride, preferably yttrium oxynitride.

Thereafter, referring to FIG. 1B, a dual damascene opening 70 is formed in the cap layer 65, the metal hard mask layer 60, the buffer layer 50, the dielectric layer 40, and the cap layer 30 by a lithography and etching process. The conductive layer 20 is exposed at the bottom of the dual damascene opening 70. The dual damascene opening 70 is formed by a trench 72 that extends laterally above and a via opening 74 that extends longitudinally below. The method of forming the double damascene opening 70 may be performed by first forming the via opening 74 to form the trench 72, or by forming the via opening 72 in advance. The etching gas used in the etching process typically contains fluorine to remove metals such as refractory metals in the metal hard mask layer 60. During the etching process, a polymer is typically formed on the sidewalls of the dual damascene opening 70. In addition, during the etching process, the surface of the conductive layer 20 (such as a copper layer) exposed by the double damascene opening 70 is also derived from the formation of copper oxide (CuO _x ) or copper oxyfluoride (CuO _x F _y ). Copper loss and other issues. Thus, after forming the dual damascene opening 70, the residual species that need to be removed include refractory metals, fluorine, oxygen, helium, carbon, and copper.

Thereafter, referring to FIG. 1C, the etched chemical cleaning process 80 (or post-etch cleaning process) is performed using the cleaning solution described above to remove residues on the substrate 10 and remove the surface of the damaged conductive layer 20. The components of the cleaning solution include only hydrofluoric acid (HF), strong acid, ammonium fluoride (NH ₄ F), a carboxyl group-containing chelating agent, triethanolamine (TEA), Ethylenediaminetetraacetic acid (EDTA), and Water without other ingredients. The composition and content of the cleaning solution are as described above, and will not be described herein. The temperature of the chemical cleaning process 80 is, for example, 20 to 50 degrees Celsius. The time for performing the chemical cleaning process 80 is, for example, 60 seconds to 120 seconds.

Hydrofluoric acid, sulfuric acid and ammonium fluoride in the cleaning solution are used to provide fluoride ions and to adjust the pH value (pH). The carboxyl group-containing chelating agent (oxalic acid), triethanolamine (TEA) and Ethylenediaminetetraacetic acid (EDTA) in the cleaning solution can also be used as a chelating agent to dissolve the metal in the aqueous solution. And stabilizing the surface of the conductive layer to prevent the conductive layer from being oxidized again, and thus can be regarded as a surface oxidation inhibitor.

In more detail, the sulfuric acid in the cleaning liquid hardly reacts with the dielectric layer 40, so that the dielectric layer 40 is not damaged. However, sulfuric acid can react with an oxide (CuO _x ) or a copper oxyfluoride (CuO _x F _y ) on the surface of the conductive layer 20 to form a water-soluble copper ion (Cu ²⁺ ). The copper ions can be chelated with the chelating agent containing a carboxyl group in the cleaning liquid, and therefore, the problem of copper loss caused by the oxidation of the surface of the conductive layer 20 can be avoided. In addition, a mixture of sulfuric acid, hydrofluoric acid, and ammonium fluoride in the cleaning liquid produces SO ₃ F ⁻ . SO ₃ F ^- is a strong nucleophile that breaks the bond of Cu-R and achieves the purpose of removing residues.

Thereafter, referring to FIG. 1D, after the chemical cleaning process 80 is performed, the cleaning process 90 is performed. In one embodiment, the cleaning process 90 is performed immediately after the chemical cleaning process 80, and no other processes are included between the cleaning process 90 and the chemical cleaning process 80. The cleaning process 90 is carried out only with deionized water and does not contain other ingredients. The temperature of the cleaning process 90 can be room temperature, for example, 20 degrees Celsius to 30 degrees Celsius. The time for performing the cleaning process 90 is, for example, 30 seconds to 90 seconds. Thereafter, baking is performed. The baking temperature is, for example, 200 to 300 degrees Celsius, and the baking time is, for example, 30 minutes to 60 minutes.

Thereafter, referring to FIG. 1E, a conductive material (not shown) is formed on the double damascene opening 70 and the cap layer 65. The material of the conductive material includes copper. Thereafter, the conductive material on the cap layer 65 is removed by chemical mechanical polishing (CMP) or etch back, leaving the conductive material 100 in the dual damascene opening 70. Thereafter, the cap layer 65, the metal hard mask layer 60, and the buffer layer 50 are removed.

The above embodiment is illustrated by a dual damascene process. However, the present invention is not limited thereto, and the double damascene opening may be only a via opening or only a contact opening. Therefore, the above The cleaning solution can also be applied to a single damascene process.

In addition, the above cleaning liquid is not limited to application to the damascene process, and the above cleaning liquid of the present invention can be applied to any residual materials in the semiconductor process that need to be removed, including refractory metals, fluorine, oxygen, antimony, carbon and copper.

Experimental example

Forming an ultra-low dielectric constant dielectric layer, a hafnium oxynitride layer and a titanium nitride layer on the substrate on which the copper layer and the tantalum carbonitride layer have been formed, and then performing a lithography process and drying with a fluorine-containing gas The etching process forms a double damascene opening. Thereafter, the chemistry was carried out with a cleaning solution (0.06 wt% hydrofluoric acid, 3 wt% sulfuric acid, 0.1 wt% fluorinated ingot, 10 wt% oxalic acid, 10 wt% triethanolamine, 0.2 wt% ethylenediaminetetraacetic acid, and the balance water). The cleaning process is followed by a cleaning process with deionized water.

The results show that the chemical cleaning process is carried out with the above cleaning solution, and then the cleaning process is carried out with deionized water, which can effectively remove the residue in the process, and does not cause damage to the surface of the dielectric layer or the copper layer after cleaning. Or the problem that the dielectric layer K value rises and the formed double damascene structure does not bridge, so that the reliability of the semiconductor element can be improved.

Comparative Examples 1 to 6

A double damascene opening was formed in the manner of the above experimental example. Thereafter, post-etch cleaning was performed with a cleaning liquid containing various compositions, followed by washing with deionized water, and the results are shown in Table 1.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

10. . . Base

20. . . Conductive layer

30. . . Roof layer

40. . . Dielectric layer

50. . . The buffer layer

60. . . Metal hard mask

65. . . Roof layer

70. . . Double metal inlay opening

72. . . ditch

74. . . Via window opening

80. . . Chemical cleaning process

90. . . Cleaning process

100. . . Conductive material

1A to 1E are schematic cross-sectional views showing a damascene process according to an embodiment of the invention.

10. . . Base

20. . . Conductive layer

30. . . Roof layer

40. . . Dielectric layer

50. . . The buffer layer

60. . . Metal hard mask

65. . . Roof layer

70. . . Double metal inlay opening

80. . . Chemical cleaning process

Claims (19)

A cleaning solution comprising: (a) 0.01-0.1 wt% hydrofluoric acid (HF); (b) 1-5 wt% strong acid, the strong acid is a mineral acid; (c) 0.05-0.5 wt% ammonium fluoride (d) a chelating agent containing a carboxyl group; (e) triethanolamine (TEA); (f) Ethylenediaminetetraacetic acid (EDTA); and (g) water. The cleaning solution of claim 1, wherein the strong acid comprises sulfuric acid (H ₂ SO ₄ ) or hydrochloric acid (HCl). The cleaning solution according to claim 1, wherein the carboxyl group-containing chelating agent comprises Oxalic acid. The cleaning liquid described in the first aspect of the patent application is composed only of the above components (a) to (g). An inlay process includes: providing a substrate having a conductive layer thereon and having a cap layer on the conductive layer; sequentially forming a dielectric layer and a metal hard mask layer on the cap layer; sequentially etching The metal hard mask layer, the dielectric layer and the cap layer form an opening to expose the conductive layer; and an etching process is performed using a cleaning liquid, the cleaning liquid comprises: (a) 0.01-0.1 Wt% hydrofluoric acid; (b) 1-5 wt% strong acid, the strong acid is a mineral acid; (c) 0.05-0.5 wt% ammonium fluoride; (d) a carboxyl group-containing chelating agent; (e) triethanolamine (f) ethylenediaminetetraacetic acid; and (g) water; filling a conductive material in the opening; and removing the metal hard mask layer. The inlay process of claim 5, wherein the strong acid comprises sulfuric acid or hydrochloric acid. The inlay process of claim 5, wherein the carboxyl group-containing chelating agent comprises oxalic acid. The inlay process of claim 5, wherein the cleaning liquid consists only of the components (a) to (g) above. The inlay process of claim 5, wherein the opening comprises a double damascene opening, a via opening or a contact opening. The inlay process of claim 5, wherein the material of the metal hard mask layer comprises titanium, titanium nitride, tantalum, tantalum nitride, tungsten, tungsten nitride, or a combination thereof. The inlay process of claim 5, wherein the material of the cap layer comprises tantalum nitride, tantalum carbonitride or tantalum carbide. The damascene process of claim 5, wherein the dielectric layer comprises an ultra low dielectric constant material. The damascene process of claim 5, further comprising forming a buffer layer on the dielectric layer after forming the dielectric layer and forming the metal hard mask layer, the buffer layer material comprising ruthenium oxide Or bismuth oxynitride. The inlay process of claim 13, further comprising forming another cap layer on the metal hard mask layer, the material of the other cap layer comprising tantalum carbide, tantalum nitride or niobium oxynitride. . A cleaning method suitable for a semiconductor process of a residual species to be removed, including refractory metal, fluorine, oxygen, helium, carbon and copper, the method comprising: performing a first cleaning process using a cleaning liquid, the cleaning liquid comprising: (a) 0.01-0.1 wt% hydrofluoric acid; (b) 1-5 wt% strong acid, the strong acid is a mineral acid; (c) 0.05-0.5 wt% ammonium fluoride; (d) a carboxyl group-containing chelating agent (e) triethanolamine; (f) ethylenediaminetetraacetic acid; and (g) water. A method of cleaning as described in claim 15 wherein the strong acid comprises sulfuric acid or hydrochloric acid. The method of cleaning according to claim 15, wherein the carboxyl group-containing chelating agent comprises oxalic acid. The method of cleaning according to claim 15, wherein the cleaning liquid consists only of the above components (a) to (g). The method of cleaning according to claim 15, wherein after the first cleaning process is performed with the cleaning liquid, a second cleaning process is performed with deionized water.