KR102562321B1 - Method for Dry Etching of Copper Thin Films - Google Patents

Abstract

The present invention relates to a method for etching a copper thin film, and more particularly, by applying optimal etching process conditions including the concentration of a mixed etching gas including ethylenediamine, acetic acid and an inert gas to the copper thin film, It relates to a copper thin film etching method capable of providing a fast etching rate and a high anisotropy (or etching slope) etching profile (150 nm) without redeposition compared to the etching method of.

Description

Method for dry etching of copper thin films {Method for Dry Etching of Copper Thin Films}

The present invention relates to a method for etching a copper thin film, and more particularly, to a copper thin film using a mixed gas containing ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ), acetic acid (CH ₃ COOH) and an inert gas It relates to a copper thin film etching method applying optimal etching process conditions.

Copper is widely used as an electrode material in various devices, but in the field of semiconductor devices, it is used only in some devices and aluminum is used more widely. However, as the fine line width of the device is reduced to several nanometers (nm), the current density flowing through the aluminum wiring increases. This causes a problem in that the reliability of the device is lowered due to poor electromigration characteristics at a high current density in the case of conventional metal wires made of aluminum. Therefore, it is no longer possible to use aluminum metal electrodes and wires, and the need to use copper wires that can replace them has increased.

Copper has a lower resistivity than aluminum, so it is advantageous in terms of information processing speed of semiconductor devices (Al: 2.7 μΩcm, Cu: 1.7 μΩcm), and has a higher atomic weight and melting point than aluminum, so it has a high current In terms of density, it has the advantage of high resistance to electron transfer.

However, due to the nature of the copper material, it is difficult to make a compound, so typical dry etching cannot be implemented, and a special process called a damascene process is currently being developed and used. However, even in this damascene process, if the fine line width of a metal electrode or metal wiring is reduced to several nanometers (nm), the resistance of the electrode can increase. Therefore, the development of a copper dry etching process is a very important process technology for future device manufacturing. It is a situation that is attracting attention.

As a related art, Korea Patent Publication No. 2002-0056010 (July 10, 2002) discloses that a diffusion barrier is formed on a semiconductor substrate including a trench in a damascene process, and then copper wiring is formed through deposition of a copper film and a CMP process. In addition, in Korea Patent Registration No. 10-0495856 (2005.06.08.), after masking by patterning a hard mask on the copper layer, dry etching of the copper layer using an etching system containing chlorine atoms (Cl) Copper metal wires were fabricated through etching.

In general, there are wet etching and dry etching methods in the etching process of thin films for fine patterning, and as the size of patterns to be etched decreases to less than a few micrometers, it becomes difficult to apply wet etching. The need for dry etching is being highlighted.

The dry etching process is an etching method using a low-pressure plasma and can be divided into two types, an ion milling etching method and a reactive ion etching method, depending on the chemical reactivity of the plasma. ) The etching method uses argon (Ar) plasma, which is an inert gas, and the reactive ion etching method uses various chemical gases to perform etching.

Looking at prior art related to this, copper etching has been studied since the 1990s, but etching gas and etching technology for the dry etching process have not been developed until now. Initially, chlorine-based gases such as SiCl ₄ , CCl ₄ , Cl ₂ , and HCl were used, and etching gases such as HBr were also applied. At this time, since the etching rate of copper is very slow, hard masks such as metal or oxide films have been mainly used rather than general photoresist masks (Applied Phys. lett., 63, 2703 (1993)). When chlorine-based gases are used as etching gases, it is confirmed by SEM observation that the CuCl _x film grows on the copper thin film and the copper film becomes thicker rather than etching the copper thin film due to the formation of CuCl _x etching products. Fortunately, these CuCl _x compounds can be removed by HCl solution or H ₂ plasma treatment, but the result of the final copper etched pattern was not excellent and the etching of the micropattern was not achieved (J. Electrochem. Soc. , 148, G524 (2001), Thin Solid Films, 457 326 (2004)).

After that, hexafluoroacetylacetonate (hfac), a kind of organic chelator, is used and the substrate is heated to 90-160 ° C to form an organometallic compound containing hfac, which has a low melting point and boiling point and is highly volatile, so that the copper etching reaction is facilitated. It became. However, subsequent research results have not been reported, and it is presumed that the formation of micropatterns was not successful. After that, a research team at Georgia Institute of Technology attempted dry etching of copper thin films at low temperatures using hydrogen gas, and obtained excellent results, publishing many papers and registering patents. However, attempts were made on copper thin films using hydrogen and hydrogen/argon mixed gases and etching conditions suggested in these papers, but the results claimed by the Georgia Tech research team could not be reproduced.

In general, when etching a copper thin film, when ion milling using simple equipment and a physical etching mechanism is used, or when the size of the pattern is approximately 5 to 10 um or less, the etched as shown in (c) of FIG. Redeposition occurs around the pattern to form a fence shape. This is due to an etching mechanism in which a part of the thin film material is sputtered and removed purely by the collision energy of argon (Ar) cations without chemical reaction in the ion milling etching method.

Therefore, the current dry etching process for the copper thin film will be performed by deriving optimal etching processes by developing existing etching gases and new etching gases. Therefore, when copper thin films are etched for the manufacture of highly integrated devices, a reactive ion etching method applied with a chemical reaction should be applied instead of an ion milling method using a physical etching mechanism. In addition, recently, a high-density plasma reactive ion etching method has been applied, which has a high plasma density so that the etching rate is fast and the etching selectivity can be increased. In particular, since copper metal has very little or no reactivity, the etching rate is very slow, and therefore, the etching selectivity of the copper thin film for the etching mask is also very small. Therefore, when photoresist is used as a mask by general lithography, it is impossible to form an etched copper pattern according to etching conditions. At this time, etching should be performed using a thin film of metal (Ti, Ta, W, TiN, Cr, etc) or metal oxide (TiO ₂ , SiO ₂ , etc) as a mask instead of a photoresist, that is, a hard mask. .

However, even in the case of etching the copper thin film by the reactive ion etching method, when an inappropriate etching gas or concentration of an inappropriate etching gas is used or an inappropriate etching process is applied, as shown in (c) of FIG. There is a problem that redeposition occurs on the side of the pattern etched together. In addition, when etching is performed with an etching gas or etching conditions that are not optimized, the occurrence of redeposition can be reduced, but as shown in FIG. )) or the side slope is etched very gently (FIG. 1(e)), causing a problem that is difficult to apply to the etching of the micropattern.

Therefore, the demand for a copper thin film etching technology capable of providing a fast etching rate and a high anisotropic etching profile through the development of an appropriate etching gas and control of its concentration is continuously increasing.

Korean Patent Publication No. 2002-0056010 (2002.07.10.) Korea Patent Registration No. 10-0495856 (2005.06.08.)

Applied Phys. Lett., 63, 2703 (1993) J. Electrochem. Soc., 148, G524 (2001), Thin Solid Films, 457 326 (2004)

The main object of the present invention is to form a pattern by etching using an orthodox dry etching method without patterning by the current damascene process for a copper thin film widely used as a semiconductor material such as electrodes and wiring. do. In order to achieve this, it is to develop a new suitable etching gas and use it to provide a copper thin film etching method that can provide a fast etching rate and a high anisotropic etching profile without re-deposition and without etching residue.

In order to solve the above problems, the present invention comprises the steps of (a) patterning a copper thin film with a hard mask and masking by etching; (b) converting a mixed gas containing ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ), acetic acid, and an inert gas into plasma; (c) etching the copper thin film using the hard mask masked in step (a) using the plasma generated in step (b);

In addition, the hard mask in step (a) may be any one selected from silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), TiO ₂ , Ti, TiN, Ta, W, or amorphous carbon. .

In addition, the volume ratio of ethylenediamine and acetic acid in step (b) may be in the range of 9:1 to 6:4.

In addition, the sum of the volumes of ethylenediamine and acetic acid in the mixed gas in step (b) may be in the range of 50 to 100 vol% with respect to the total mixed gas.

In addition, the process temperature in step (c) may be 10 ℃ to 20 ℃.

In addition, the plasma conversion in step (c) may be performed by injecting a mixed gas at a process pressure in the range of 0.1 to 1.3 Pa.

In addition, the plasma conversion in step (c) may be performed by applying 300 to 900 W of coil high frequency power (ICP rf power).

In addition, the plasmaization in step (c) may be performed by applying a dc-bias voltage of 200 to 400V.

In addition, the present invention provides a copper thin film produced by any one of the above methods and having an etching inclination of 70 degrees or more.

The copper thin film etching method according to the present invention applies the optimal etching process conditions together with the optimal etching gas and the optimal etching gas concentration, so that redeposition does not occur compared to the conventional copper thin film etching method, and etching residues are reduced. It can be applied to all devices and devices that use copper thin films by providing a fast etching rate and an etching profile with high anisotropy.

In addition, the copper thin film etching method according to the present invention can etch the copper thin film at a low temperature without requiring an additional configuration for heating the substrate, and etching of 150 nm line patterns is also possible.

Figure 1 (a) is the structure of the sample before etching the hard mask and the copper thin film, and Figure 1 (b) shows that the hard mask is dry etched by C ₂ F ₆ /Ar gas and has a vertical etching slope of about 85 degrees or more. It is a picture of manufacturing SiO ₂ /Cu sample. Figure 1 (c) shows the case where a large amount of redeposition material is generated on the side of the copper thin film etched mainly by a physical sputtering etching mechanism as a result of etching the copper thin film using a patterned hard mask. d) shows the case where no redeposited material is formed on the etched side during etching, but etch residues remain on the pattern side, resulting in a rounded etching profile, and FIG. 1(f) is a diagram showing a copper micropattern in which the etching slope of the etched copper thin film is formed very gently even though no deposition material is formed. This is a view showing the vertical anisotropic etching profile found.
FIG. 2 shows the etching rate of the copper thin film and the SiO ₂ hard mask and the etching selectivity of the copper thin film to the SiO ₂ hard mask according to the change in the concentration of ethylenediamine in the mixed gas of ethylenediamine and argon.
Figure 3 shows the etching profiles of the copper thin film according to the change in the concentration of ethylenediamine in the mixed gas of ethylenediamine and argon.
Figure 4 fixes the volume ratio of ethylenediamine and acetic acid to 9: 1 in the mixed gas of ethylenediamine, acetic acid and argon, and changes the concentration ratio of ethylenediamine, acetic acid mixture and argon to concentrations of 25, 50, 75 and 100% The etching rate of the copper thin film and the SiO ₂ hard mask and the etching selectivity of the copper thin film to the SiO ₂ hard mask according to the concentration change are shown.
Figure 5 fixes the volume ratio of ethylenediamine and acetic acid to 9: 1 in the mixed gas of ethylenediamine, acetic acid and argon, and changes the concentration ratio of ethylenediamine, acetic acid mixture and argon to concentrations of 25, 50, 75 and 100% Etching profiles of copper thin films are shown.
6 is a mixture of ethylenediamine, acetic acid, and argon, in which the volume ratio of ethylenediamine and acetic acid is fixed at 4: 1, and the concentration ratio of the mixture of ethylenediamine and acetic acid and argon is changed to 25, 50, 75, and 100% concentration The etching rate of the copper thin film and the SiO ₂ hard mask and the etching selectivity of the copper thin film to the SiO ₂ hard mask according to the concentration change are shown.
Figure 7 fixes the volume ratio of ethylenediamine and acetic acid to 4: 1 in the mixed gas of ethylenediamine, acetic acid and argon, and changes the concentration ratio of ethylenediamine, acetic acid mixture and argon to 25, 50, 75 and 100% concentration Etching profiles of copper thin films are shown.
8 is a mixed gas of ethylenediamine, acetic acid and argon, by fixing the volume ratio of ethylenediamine and acetic acid to 7:3, and changing the concentration ratio of ethylenediamine, acetic acid mixture and argon to 25, 50, 75 and 100% concentration The etching rate of the copper thin film and the SiO ₂ hard mask and the etching selectivity of the copper thin film to the SiO ₂ hard mask according to the concentration change are shown.
Figure 9 fixes the volume ratio of ethylenediamine and acetic acid to 7: 3 in the mixed gas of ethylenediamine, acetic acid and argon, and changes the concentration ratio of ethylenediamine, acetic acid mixture and argon to concentrations of 25, 50, 75 and 100% Etching profiles of copper thin films are shown.
10 shows the change in the etching rate of the copper thin film and the SiO2 hard mask and the etching selectivity of the copper thin film with respect to the SiO2 hard mask according to the change in ICP rf power. The etching gas is a mixed gas of ethylenediamine, acetic acid, and argon. The volume ratio of ethylenediamine and acetic acid is fixed at 9:1, the concentration ratio of the mixture of ethylenediamine and acetic acid and argon is 85%, the dc-bias voltage is 300 V, and the process pressure is fixed at 0.67 Pa.
Figure 11 shows the change of the etching profile of the copper thin film according to the change of ICP rf power. The etching gas is a mixed gas of ethylenediamine, acetic acid, and argon. The volume ratio of ethylenediamine and acetic acid is fixed at 9:1, the concentration ratio of the mixture of ethylenediamine and acetic acid and argon is 85%, the dc-bias voltage is 300 V, and the process pressure is fixed at 0.67 Pa.
12 shows the change in the etching rate of the copper thin film and the SiO2 hard mask and the etching selectivity of the copper thin film with respect to the SiO2 hard mask according to the change of the dc-bias voltage. The etching gas is a mixed gas of ethylenediamine, acetic acid, and argon. The volume ratio of ethylenediamine and acetic acid is fixed at 9:1, the concentration ratio of the mixture of ethylenediamine and acetic acid and argon is 85%, ICP rf power is 500 W, and the process pressure is Fix at 0.67 Pa.
13 shows the change of the etching profile of the copper thin film according to the change of the dc-bias voltage. The etching gas is a mixed gas of ethylenediamine, acetic acid, and argon. The volume ratio of ethylenediamine and acetic acid is fixed at 9:1, the concentration ratio of the mixture of ethylenediamine and acetic acid and argon is 85%, ICP rf power is 500 W, and the process pressure is Fix at 0.67 Pa.
14 shows the change in the etching rate of the copper thin film and the SiO2 hard mask and the etching selectivity of the copper thin film with respect to the SiO2 hard mask according to the change in process pressure. The etching gas is a mixed gas of ethylenediamine, acetic acid, and argon. The volume ratio of ethylenediamine and acetic acid is fixed at 9:1, the concentration ratio of the mixture of ethylenediamine and acetic acid and argon is 85%, ICP rf power is 500 W, dc-bias The voltage is fixed at 300 V.
15 shows the change of the etching profile of the copper thin film according to the change of the process pressure. The etching gas is a mixed gas of ethylenediamine, acetic acid, and argon. The volume ratio of ethylenediamine and acetic acid is fixed at 9:1, the concentration ratio of the mixture of ethylenediamine and acetic acid and argon is 85%, ICP rf power is 500 W, dc-bias The voltage is fixed at 300 V.
16 shows (a) a mixed gas of ethylenediamine and argon, (b) a mixed gas containing ethylenediamine and acetic acid in a volume ratio of 9:1, and (c) a mixed gas containing ethylenediamine and acetic acid in a volume ratio of 4:1. These are the analysis results of optical emission spectroscopy for the generated plasma.
17 is an X-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy) analysis result of the surface of a copper thin film etched using acetic acid, ethylenediamine, a mixed gas of ethylenediamine and argon, or a mixed gas of acetic acid and argon.
18 is a 150 nm line pattern of a copper thin film etched using a mixed gas containing 85% (ethylenediamine + acetic acid) and 15% argon gas containing ethylenediamine and acetic acid in a volume ratio of 9: 1 Etching for a 150 nm line pattern Profile and transmission electron microscopy results.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclatures used herein are those well known and commonly used in the art.

Throughout the present specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

A method of etching a copper thin film according to the present invention includes the steps of (a) patterning a copper thin film with a hard mask and masking the copper thin film by etching; (b) converting a mixed gas containing ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ), acetic acid (CH 3 COOH), and an inert gas into plasma; (c) etching the copper thin film using the hard mask masked in step (a) using the plasma generated in step (b);

Hereinafter, the present invention will be described in detail step by step.

As an example, in step (a), first, the hard mask/copper thin film is patterned with a photoresist mask to mask (a1) the hard mask/copper thin film, and C ₂ F ₆ /Ar gas is converted into plasma. Thereafter, silicon dioxide is etched from the masked hard mask/copper thin film using the generated C ₂ F ₆ /Ar plasma (a2). Thereafter, in order to remove the photoresist thin film, oxygen gas is converted into plasma, and the photoresist is removed from the thin film using the generated oxygen plasma (a3) to obtain a copper thin film masked with a hard mask. In this way, the copper thin film is etched using a hard mask in the thin film from which the photoresist is removed.

The hard mask used in step (a) is ceramic-based such as silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), and titanium dioxide (TiO ₂ ), metal-based such as Ti, TiN, Ta, and W, and amorphous hard masks. It may be one selected from carbon (amorphous carbon), but is not limited thereto. The hard mask is any material that exhibits a slow etching rate and high etching selectivity with respect to the etching gas of the present invention, and is preferably silicon dioxide (SiO ₂ ).

Patterning of the SiO ₂ hard mask is formed by patterning the SiO ₂ thin film by a lithography process using a general photoresist and then etching with a C ₂ F ₆ /Ar gas. The SiO ₂ thin film etched at a concentration of 25% to 30% C ₂ F ₆ has a vertical etching slope of about 85 degrees or more.

Figure 1 (a) is the structure of the sample before etching the hard mask, and Figure 1 (b) shows the hard mask is dry etched by C ₂ F ₆ /Ar gas and has a vertical etching slope of about 85 degrees or more SiO ₂ / It is a picture of manufacturing Cu sample.

In addition, as the organic chelator material in step (b), a mixed gas containing ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ) and acetic acid (CH 3 COOH) and an inert gas may be used. The gas is preferably at least one selected from the group consisting of He, Ne, Ar, and N ₂ .

If only pure inert gas (e.g. argon gas) is used as a conventional etching gas, problems such as a large amount of redeposition around the etched copper thin film occur because physical etching is performed by argon ions.

FIG. 1(c) shows a case in which a large amount of redeposition material is generated on the side of the copper thin film etched mainly by a physical sputtering etching mechanism as a result of etching the copper thin film using a patterned hard mask. FIG. (d) and FIG. 1(e) show that after etching, no redeposited material is formed on the etched side, but the etching gas and etching conditions are not appropriate, so the etching slope of the etched copper thin film is formed very gently, resulting in the formation of copper of the desired size. A fine pattern cannot be formed.

Therefore, the present invention, in order to improve the etching rate of the copper thin film, the etching selectivity of the copper thin film with respect to the hard mask, the etching slope and the etching rate, acetic acid (CH COOH) having a similar boiling point to ethylenediamine is added to (ethylenediamine + acetic acid + Etching of copper was performed using a mixture gas having an appropriate mixture concentration of inert gas).

In step (b), the mixing volume ratio of ethylenediamine and acetic acid is preferably in the range of 9:1 to 7:3. When the acetic acid exceeds 30% in terms of volume ratio with respect to ethylenediamine, the etching rate of the copper thin film may be improved, but a problem of re-deposition may occur, and ethylenediamine and acetic acid react in the mixed gas to form a white salt. It can be generated and deposited on the inner wall of the gas pipe to block the flow of flow.

In addition, when the mixed volume ratio of ethylenediamine and acetic acid in step (b) is in the range of 9: 1 to 7: 3, the sum of the volumes of ethylenediamine and acetic acid in the mixed gas is 50 vol% or more with respect to the total mixed gas Including is preferable in terms of improving the etching quality of the copper thin film.

That is, when a mixed gas containing ethylenediamine and an inert gas is used as an etching gas, if ethylenediamine is less than 50 vol%, a large amount of redeposition material is generated on the sidewall of the copper thin film, and if it exceeds 50 vol%, the copper thin film The redeposited material is gradually reduced on the sidewall of the , and an improved etching slope can be obtained. Therefore, since the etching profile of the obtained copper thin film is excellent, an anisotropic etching profile can be obtained.

Therefore, as shown in FIG. 1(f), the present invention uses the content ratio of ethylenediamine and acetic acid in the mixed gas in the range described above when etching the copper thin film, thereby reducing redeposition compared to the conventional copper thin film etching method. It is possible to manufacture a copper thin film having a highly anisotropic etching profile without any etching residue.

As an example, in the case of containing 100 vol% of an organic chelator material such as ethylenediamine in the mixed gas in step (b), the etching rate of the copper thin film is slow, but redeposition does not occur and etching of about 80 degrees or more slope is obtained.

Therefore, it is preferable to include 90 vol% or less of an organic chelator material such as ethylenediamine in the mixed gas in step (b) to increase process efficiency under an appropriate etching rate of the copper thin film.

That is, when the sum of the volumes of ethylenediamine and acetic acid in the mixed gas is used in the range of 50 to 90 vol% with respect to the total mixed gas, when etching the copper thin film, the copper thin film is redeposited on the sidewall of the copper thin film under an appropriate etching rate. This does not occur, and a high etching gradient can be obtained. If the amount of (ethylenediamine + acetic acid) in the mixed gas is less than 50 vol%, the amount of ethylenediamine added in the mixed gas is insufficient, resulting in a large amount of redeposited material on the sidewall of the copper thin film, and in the mixed gas (ethylenediamine + acetic acid ) In the case where the usage amount of 90 vol% is included, a problem in that the etching rate of the copper thin film is too slow may occur.

On the other hand, the plasma formation in step (b) is performed by high-density plasma reactive ion etching including inductively coupled plasma reactive ion etching, magnetically enhanced reactive ion etching, reactive ion etching, atomic layer etching, and It may be performed by one method selected from the group consisting of pulse-modulated high-density plasma reactive ion etching.

In the step of etching using the plasma generated in step (b) (step (c)), the temperature of the substrate may be 10 °C to 25 °C. The present invention does not require a configuration for heating the substrate on which the copper thin film is loaded during etching, and etching can be performed at a low temperature by applying a cooling fluid of 10 to 25 ° C. to the substrate.

If the substrate needs to be heated to more than 150 degrees, first of all, it is not possible to use a vacuum seal such as an O-ring under the substrate, so a special substrate structure is manufactured, which increases the unit cost of the equipment. If heated, it causes diffusion of materials already deposited or patterned/etched on the substrate, causing unwanted materials (elements) to move up or down the thin film layer, changing or degrading the characteristics of the device.

In addition, plasmaification in step (c) may be performed by injecting a mixed gas at a process pressure in the range of 0.1 to 1.3 Pa, and preferably, a process pressure in the range of 0.1 to 0.4 Pa may be used. At this time, if the process pressure of plasmaization is lower than 0.1 Pa. The generated plasma is unstable, resulting in poor etching stability and reproducibility, and if it is higher than 1.3 Pa, the amount of ions and radicals in the plasma is relatively large, but their mean free path is small, resulting in frequent physical collisions. Accordingly, a slow etch rate and a low etch slope can ultimately be obtained.

In addition, plasmaization in step (c) may be performed by applying 300 to 900 W of coil high frequency power (ICP rf power), preferably 700 to 900 W of coil high frequency power (ICP rf power), can be used At this time, if the coil high frequency power is lower than 300 W, the polymer layer may be seriously deposited.

In addition, plasmaification in step (c) may be performed by applying a dc-bias voltage of 200 to 400V, and preferably may be used by applying a dc-bias voltage of 300 to 400V. At this time, when the DC-bias voltage is less than 200 V, the overall voltage applied to the sample to be etched is low, so that not only the amount of ions and radicals generated by plasma is transferred to the sample is reduced, but also due to the slow (weak) acceleration of ions. Due to this, a pattern with a slow etching rate and a low etching slope can be obtained and a polymer layer can be created, and a high DC-bias voltage exceeding 400 V can improve the etching rate and etching slope, but redeposition on the etching side Etch damage caused by ion bombardment or ion impact applied to the thin film may occur, resulting in deterioration of electrical characteristics of a device to be manufactured in the future.

Meanwhile, in the present invention, the etch selectivity means the etching rate of the copper thin film relative to the etching rate of the hard mask, and can be calculated as in Equation 1 below.

(Etching selectivity) = (Etching rate of copper thin film) / (Etching rate of hard mask) (Equation 1)

In addition, in the copper thin film produced by the copper thin film etching method according to the present invention, the etching selectivity of the copper thin film with respect to the hard mask is 0.25 to 0.6, and the etching slope of the copper thin film is 76 degrees or more, providing an excellent anisotropy profile. do.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, these examples are intended to explain the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited thereto.

Comparative Example 1: Ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ) / Ar

In the etching process, the SiO2 hard mask was etched in the first step. After that, a mixed gas of ethylenediamine and argon was selected, and the coil ICP power was 500 W, the dc-bias voltage applied to the substrate was 300 V, and the chamber pressure was 5 mTorr. was performed under the conditions of

FIG. 2 shows the etching rate of the copper thin film and the SiO ₂ hard mask and the etching selectivity of the copper thin film to the SiO ₂ hard mask according to the change in the concentration of ethylenediamine in the mixed gas of ethylenediamine and argon. As the concentration of ethylenediamine increases, the etching rate of copper and SiO ₂ thin films rapidly decreases. On the other hand, the etching selectivity of the Cu thin film to the SiO ₂ hard mask was maintained between 0.2 and 0.95. The fact that the etching rate of the copper thin film decreases as the concentration of ethylenediamine increases means that the etching mechanism of the copper thin film does not follow a typical reactive ion etching mechanism but mainly follows a physical sputtering mechanism by Ar ions.

3 shows etching profiles of a copper thin film according to a change in concentration of ethylenediamine in a mixed gas of ethylenediamine and argon. In the etching profile in pure argon of FIG. 3 (a), it is observed that copper redeposition occurs on the side etched by the etching mechanism by sputtering of argon ions. In the etching profile of the copper thin film etched at the concentration of 25% ethylenediamine in FIG. 3 (b), a slightly reduced redeposition material is observed on the side of the etching pattern than that observed in the etching profile by pure argon gas. At the concentration of 50% ethylenediamine in FIG. 3 (c), the redeposition of copper that occurred on the side of the etched copper thin film was significantly reduced, and at the concentration of 75% ethylenediamine in FIG. 3 (d), redeposition of copper did not occur. It is observed in the etching profile. Even in the case of 100% ethylenediamine in FIG. 3(e), the redeposition of the etching material on the side of the copper thin film did not occur. However, when the ethylenediamine concentration is 50% or more, it is confirmed that the etching rate of the copper thin film is remarkably slowed to about 10 nm/min or less.

Example 1: Ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ): acetic acid (CH ₃ COOH) (9:1) / Ar

Etching gas used when etching copper after SiO2 hard mask etching was a mixture of ethylenediamine and acetic acid in a volume ratio of 9:1 and a mixed gas containing argon, and other conditions were the same as those of Comparative Example 1.

4 shows that the volume ratio of ethylenediamine and acetic acid in a mixed gas containing ethylenediamine, acetic acid and argon is fixed at 9: 1, and the concentration ratio of the mixture (ethylenediamine + acetic acid) is changed to concentrations of 25, 50, 75 and 100% to show the etch rate and etch selectivity of the copper thin film and the SiO ₂ hard mask thin film. As the concentrations of ethylenediamine and acetic acid increased, the etch rates of copper and SiO ₂ films decreased rapidly, while the etch selectivity of Cu films to SiO ₂ hard masks remained between 0.2 and 0.85.

5 shows that the volume ratio of ethylenediamine and acetic acid in a mixed gas containing ethylenediamine, acetic acid and argon is fixed at 9: 1, and the concentration ratio of the mixture (ethylenediamine + acetic acid) is changed to concentrations of 25, 50, 75 and 100% to show the etching profiles of the copper thin film. In the concentration of pure Ar in FIG. 5 (a) and 25% (ethylenediamine + acetic acid) mixture in FIG. 5 (b), redeposition was observed on the side of the etched thin film, but at 50% ( ethylenediamine + acetic acid) mixture concentration and 75% (ethylenediamine + acetic acid) mixture concentration in Fig. 5(d), no redeposition was observed on the copper side. In addition, at the concentration of the 75% (ethylenediamine + acetic acid) mixture in FIG. 5(d) and the 100% (ethylenediamine + acetic acid) mixture in FIG. It shows a highly anisotropic etch profile.

In FIG. 3, in the mixed gas of 75% ethylenediamine and argon and in the etching condition of 100% ethylenediamine, the etching slope (about 70 to 80 degrees) of the copper thin film is gentle, while the etching gas containing a small amount of acetic acid in ethylenediamine In FIG. 5 using , it was observed that etching of the copper thin film having excellent anisotropy without redeposition (etching inclination of about 80 to 90 degrees) was achieved.

Example 2: Ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ): acetic acid (CH ₃ COOH) (4:1) / Ar

Etching gas used when etching copper after SiO2 hard mask etching is a mixture of ethylenediamine and acetic acid in a volume ratio of 4:1, and a mixed gas containing argon is used. Other conditions are the same as in Comparative Example 1.

Figure 6 fixes the volume ratio of ethylenediamine and acetic acid to 4: 1 in a mixed gas containing ethylenediamine, acetic acid and argon, and the concentration ratio of the mixture (ethylenediamine + acetic acid) is 25, 50, 70, 75 and 100% concentration It shows the etching rate and etching selectivity of the copper thin film and the SiO ₂ hard mask thin film by changing to . As the concentrations of ethylenediamine and acetic acid increased, the etch rates of copper and SiO ₂ films decreased rapidly, while the etch selectivity of Cu films to SiO ₂ hard masks remained between 0.2 and 0.85. By adding a small amount of acetic acid to the etching gas, the etching rate of the copper and SiO ₂ hard mask was slightly increased compared to the mixed gas of ethylenediamine and argon.

Figure 7 fixes the volume ratio of ethylenediamine and acetic acid to 4: 1 in a mixed gas containing ethylenediamine, acetic acid and argon, and the concentration ratio of the mixture (ethylenediamine + acetic acid) is 25, 50, 70, 75 and 100% concentration to show the etching profiles of the copper thin film. At the concentration of the 25% (ethylenediamine + acetic acid) mixture in FIG. 7(b), redeposition was observed on the side of the etched thin film, but at the concentration of the 50% (ethylenediamine + acetic acid) mixture in FIG. 7(c), At the concentration of 75% (ethylenediamine + acetic acid) mixture in FIG. 7(d) and the concentration of 100% (ethylenediamine + acetic acid) mixture in FIG. The etching slope of the copper thin film also shows a very high anisotropic etching profile of 80 to 90 degrees.

Example 3: Ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ): acetic acid (CH ₃ COOH) (7:3) / Ar

Etching gas used when etching copper after SiO2 hard mask etching is a mixture of ethylenediamine and acetic acid in a volume ratio of 7:3, and a mixed gas containing argon is used. Other conditions are the same as in Comparative Example 1.

8 is a mixed gas containing ethylenediamine, acetic acid and argon, by fixing the volume ratio of ethylenediamine and acetic acid to 7: 3, and changing the concentration ratio of the mixture (ethylenediamine + acetic acid) to 25, 50, 75 and 100% concentration to show the etch rate and etch selectivity of the copper thin film and the SiO ₂ hard mask thin film. As the concentrations of ethylenediamine and acetic acid increased, the etch rates of copper and SiO ₂ films decreased rapidly, while the etch selectivity of Cu films to SiO ₂ hard masks remained between 0.1 and 0.7. By adding a small amount of acetic acid to the etching gas, the etching rate of the copper and SiO ₂ hard mask was slightly increased compared to the mixed gas of ethylenediamine and argon.

9 is a mixed gas containing ethylenediamine, acetic acid and argon, by fixing the volume ratio of ethylenediamine and acetic acid to 7: 3, and changing the concentration ratio of the mixture (ethylenediamine + acetic acid) to 25, 50, 75 and 100% concentration to show the etching profiles of the copper thin film. At the concentration of 25% (ethylenediamine + acetic acid) mixture in FIG. 9 (a), redeposition was observed on the side of the etched thin film, but in FIG. In the concentration of 75% (ethylenediamine + acetic acid) mixture in FIG. 9(c) and 100% (ethylenediamine + acetic acid) mixture in FIG. The etching slope of the copper thin film also shows an excellent anisotropic etching profile of 70 to 80 degrees.

10 is a mixture of ethylenediamine, acetic acid and argon, in which the volume ratio of ethylenediamine and acetic acid is fixed at 9: 1, and the concentration ratio of the (ethylenediamine + acetic acid) mixture is fixed at a concentration of 85% to form a copper thin film and SiO ₂ It shows the etch rate and etch selectivity of the hard mask thin films, and the etching conditions are 300 W-900 W ICP rf power, 300 V dc-bias voltage, and 0.67 Pa process pressure.

11 shows the same etching conditions as FIG. 10, FIG. 11(a) shows ICP rf power of 300 W, FIG. 11(b) shows ICP rf power of 500 W, FIG. 11(c) shows 700 W ICP rf power, and FIG. 11(d) are the etching profiles of the copper film etched at 900 W ICP rf power. Standard etching conditions are 300 V dc-bias voltage and 0.67 Pa process pressure.

As a result, the etching rate of Cu and SiO2 increased linearly as the ICP rf power increased. The etching selectivity of the copper thin film for the SiO2 hard mask was about 0.3-0.5.

In terms of the etching profile, redeposition did not occur on the etched side under all conditions, and it was observed that the etching profile was slightly improved and the etching anisotropy increased as the rf power gradually increased. At the etching conditions of 700 W and 900 W, no redeposition material was observed on the side of the hard mask and copper thin film after etching, and a very steep etching slope of about 75 degrees was observed. In general, when the ICP rf power is increased, the plasma density in the reactor is increased, and more radicals and more positive ions are generated, so that the etching rates of the thin films are increased and the anisotropy of the etching profile is also helpful.

12 is a mixture of ethylenediamine, acetic acid and argon, in which the volume ratio of ethylenediamine and acetic acid is fixed at 9: 1, and the concentration ratio of the (ethylenediamine + acetic acid) mixture is fixed at a concentration of 85% to obtain a copper thin film and SiO ₂ The etching rate and etch selectivity of the hardmask thin films are shown, and the etching conditions are 500 W ICP rf power, 200-400 V dc-bias voltage, and 0.67 Pa process pressure.

FIG. 13 shows etching profiles of copper thin films etched at 200 V dc-bias voltage in FIG. 13 (a), 300 V in FIG. 13 (b), and 400 V in FIG. 13 (c) under the same etching conditions as those in FIG. . Standard etching conditions are 500 W ICP rf power, 200–400 V dc-bias voltage and 0.67 Pa process pressure.

As a result, as the dc-bias voltage increased, the etching rate of the copper thin film and the SiO2 hard mask increased linearly, and consequently, the etching selectivity of the copper thin film to the SiO2 hard mask also increased from about 0.2 to 0.5.

No redeposited material was observed on the side of the etched copper thin film under all conditions, and the etching slope (etch anisotropy) improved as the dc-bias voltage increased. Under the etching condition of 400 V, the etching slope improved to about 75 degrees or more. It became.

When the dc-bias voltage increases, positive ions in the plasma are attracted to the substrate with higher energy and collide strongly, so that the thin film is removed or the etching products remaining on the surface are removed, resulting in an overall increase in the etching rate of the thin film and a clean etching profile. is obtained However, an excessive dc-bias voltage may cause a sputtering effect of the thin film due to excessive energy of positive ions, and may remain as a redeposited material after etching.

14 is a mixture of ethylenediamine, acetic acid and argon, in which the volume ratio of ethylenediamine and acetic acid is fixed at 9: 1, and the concentration ratio of the (ethylenediamine + acetic acid) mixture is fixed at a concentration of 85% to form a copper thin film and SiO ₂ It shows the etch rate and etch selectivity of hardmask thin films, and the etching conditions are 500 W ICP rf power, 300 V dc-bias voltage, and 0.13-01.3 Pa process pressure.

FIG. 15 shows etching profiles of copper thin films etched under the same etching conditions as those of FIG. 14 at process pressures of 0.13 Pa in FIG. 15 (a), 0.67 Pa in FIG. 15 (b), and 1.3 Pa in FIG. 15 (c). Standard etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.13-1.3 Pa process pressure.

As a result, as the process pressure increased, the etching rates of the copper and SiO2 thin films gradually decreased, and the etching selectivity of the copper thin film to the SiO2 hard mask showed a slight change within the range of about 0.38 to 0.41.

In terms of the etching profile of the copper thin film, it was observed that the etching slope was improved as the process pressure was lowered. That is, the etching slope of the copper thin film etched at 0.67 Pa was about 70 degrees, but the etching slope when etched at 0.13 Pa was slightly improved to about 76 degrees, and no redeposited material was observed after etching. On the other hand, in the case of etching at 1.3 Pa, the etching slope slightly decreased to about 65 degrees.

These results show that at a low pressure of 0.13 Pa, the mean free path is greatly increased, so that radicals or ions generated in the plasma reach the thin film surface effectively without collision, so that more radicals and ions are transferred to the thin film surface through chemical reactions and sputtering. By participating in the reaction, the effect of increasing the etching rate and improving the etching profile is obtained.

FIG. 16 shows the results of optical emission spectroscopy (OES) measurement of active components in plasma generated from ethylenediamine and argon, mixed gases of ethylenediamine, acetic acid and argon. Figure 16 (a) is a mixed gas of ethylenediamine and argon, and Figure 16 (b) is an OES result measured while changing the concentration ratio of a mixture of ethylenediamine and acetic acid and argon by fixing the volume ratio of ethylenediamine and acetic acid to 9:1 16(c) is an OES result obtained by fixing the volume ratio of ethylenediamine and acetic acid to 4:1 and changing the concentration ratio between ethylenediamine and acetic acid mixture and argon.

In the case of the mixed gas of ethylenediamine and argon in FIG. 16 (a), as the concentration of ethylenediamine increases, the concentrations of [CN] and [H] gradually increase, and in particular, the strength of [CN] increases significantly, resulting in a copper thin film The probability of reaction with can be predicted. In the case of FIG. 16 (b), the intensity of [CN] and [H] increased as the concentration of the mixed gas of ethylenediamine and acetic acid increased, but in the case of the mixed gas of ethylenediamine and argon in FIG. 16 (a) Intensity of each active species was more or less decreased. In addition, the maximum intensity of [CN] was confirmed at a concentration of 75% (volume ratio of ethylenediamine and acetic acid is 9:1). In the case of FIG. 16 (c), the volume ratio of ethylenediamine and acetic acid was 4:1, and the intensity of [CN] and [H] was greatly reduced, which means a decrease in the reaction between active species and the copper thin film, and the etching rate It may appear as a decrease in or deterioration of an etch profile.

17 is a result of XPS analysis on the surface of a copper thin film etched using a mixture of acetic acid, ethylenediamine and argon, ethylenediamine and acetic acid mixture and argon gas. These are the results of a narrow scan of (a) Cu 2p, (b) C 1s, and (c) N 1s. Looking at the Cu 2p narrow scans in FIG. 17(a), in the case of ethylenediamine gas, the compound of CuCN is found on the surface of the etched copper thin film. This means that ethylenediamine and copper thin film caused a surface reaction, and acetic acid gas and argon gas were added to ethylenediamine, so that the concentration of the mixed gas of ethylenediamine and acetic acid composed of ethylenediamine and acetic acid in a mixing ratio of 9:1 was 25%, As the concentration increased to 50%, 75%, and 100%, the peak intensity of CuCN gradually increased, and these results also indicate that ethylenediamine and the copper thin film caused a surface reaction. In the C 1 s narrow scan of FIG. 17 (b), as the concentration of ethylenediamine gas increases and the concentration of the mixed gas of ethylenediamine and acetic acid increases, the polymer thin film containing CC/CH generated on the surface decreases, and CuCN It is believed that the reaction product increases. In the case of the N 1 s narrow scan of FIG. 17 (c), a very strong peak of CuCN is observed when etching with ethylenediamine gas, and -[CHCNH ₂ CH ₂ ]-, a material containing N at a position of about 399.7 eV, is It is expected to be formed on the surface of the etched copper thin film. As the concentration of the mixed gas of ethylenediamine and acetic acid increases, the peak of CuCN tends to increase, and the presence of -[CHCNH ₂ CH ₂ ]-, an unidentified peak at about 399.7 eV, is also expected. In conclusion, it is judged that ethylenediamine gas helps to form etching anisotropy as a thin film containing CC/CH/CN is instantly deposited on the copper surface by conducting a surface reaction with the copper thin film under the current etching conditions. It can be seen that these results are in good agreement with the etch rate and etch profile results for each gas presented above.

18(a) is etched at a concentration of 85% (ethylenediamine + acetic acid) mixture by fixing the volume ratio of ethylenediamine and acetic acid to 9: 1 in a mixed gas containing ethylenediamine, acetic acid and argon, and the SiO2 hard mask is formed. It is an etch profile of the removed copper film. As a line pattern of 150 nm, the etching slope of the side surface is about 76 degrees. Figure 18 (b) shows the etching profile of the TEM magnified at high magnification of the SEM picture observed in (a). It shows an anisotropic etching profile with no redeposition on the side of the etched copper thin film.

In the above, specific parts of the content of the present invention have been described in detail, and for those skilled in the art, these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. will be blind Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (9)

(a) patterning the copper thin film with a hard mask and masking it by etching;
(b) converting a mixed gas containing ethylenediamine ((NH ₂ ) ₂ C ₂ H ₄ ), acetic acid (CH ₃ COOH), and an inert gas into plasma;
(c) etching the copper thin film using the hard mask masked in step (a) using the plasma generated in step (b);
The volume ratio of ethylenediamine and acetic acid in the mixed gas is in the range of 9: 1 to 6: 4, and the sum of the volumes of ethylenediamine and acetic acid is in the range of 50 to 100 vol% with respect to the total mixed gas. Copper thin film, characterized in that etching method.
According to claim 1,
The hard mask in step (a) is silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), TiO ₂ , Ti, TiN, Ta, W, or amorphous carbon, characterized in that any one selected from Etching method of copper thin film.
delete delete According to claim 1,
The etching method of the copper thin film, characterized in that the process temperature in step (c) is 10 ℃ to 25 ℃.
According to claim 1,
Plasmaization in step (c) is performed by injecting a mixed gas at a process pressure in the range of 0.1 to 1.3 Pa.
According to claim 1,
Plasmaization in step (c) is performed by applying coil high frequency power (ICP rf power) of 300 to 900 W.
According to claim 1,
Plasmaization in step (c) is performed by applying a dc-bias voltage of 200 to 400V.
A copper thin film produced by the method according to any one of claims 1, 2, 5 to 8 and having an etching inclination of 76˚ or more.