KR102030548B1 - Method for Dry Etching of Copper Thin Films - Google Patents

Abstract

The present invention relates to an etching method of a copper thin film. More particularly, according to the present invention, in etching method of a copper thin film, optimal etching process conditions, including a type of etching gas, a concentration of etching gas, and process variables of etching, can be applied to a copper thin film, thereby providing fast etching speed and high isotropic (or etching slope) without re-evolving compared to conventional copper thin film etching methods.

Description

Dry etching method of copper thin film {Method for Dry Etching of Copper Thin Films}

The present invention relates to an etching method of a copper thin film, and more particularly, etching gases including alcohol (CH ₃ OH / Ar, C ₂ H ₅ OH / Ar) and acetic acid (CH ₃ COOH / Ar) with respect to the copper thin film. The present invention relates to an etching method of a copper thin film to which an optimal etching process condition is applied.

Copper is widely used as an electrode material in various devices, but in the semiconductor device sector, only a few devices are used and aluminum is more widely used. However, as the device's microwire width shrinks to several nanometers (nm), it increases the current density flowing through the aluminum wiring. This causes a problem that the reliability of the device is deteriorated due to poor electron transfer characteristics at high current density in the case of metal wiring made of conventional aluminum. Therefore, it is no longer possible to use aluminum metal electrodes and wiring, and there is a greater need for using copper wiring to replace them.

Since copper has a lower resistivity compared to aluminum, not only is it advantageous in terms of information processing speed of semiconductor devices (Al: 2.7 μΩcm, Cu: 1.7 μΩcm), but also has a high current due to its higher atomic weight and melting point than conventional aluminum. It has the advantage of high resistance to electron transfer even in density.

However, due to the nature of copper materials, it is difficult to make a compound, and thus, typical dry etching is not realized. Currently, a special process called a damascene process is developed and used. However, even in this damascene process, if the microwire width of the metal electrode or the metal wiring is reduced to several nanometers (nm), the resistance of the electrode due to the barrier can be increased. The situation is attracting attention as an important process technology.

As a related art, Korean Laid-Open Patent Publication No. 2002-0056010 (2002.07.10.) Forms a diffusion barrier on a semiconductor substrate including a trench in a damascene process, and then, copper wiring is formed through a deposition of a copper film and a CMP process. Also, Korean Patent Publication No. 10-0495856 (2005.06.08.) Patterned a hard mask on a copper layer and masked it, and then dried the copper layer using an etching system containing chlorine atom (Cl). Copper metal wiring was manufactured by etching.

In general, there are wet etching and dry etching methods for etching thin films for fine patterning. As the size of patterns to be etched is reduced to several micrometers or less or nanometers, it is difficult to apply wet etching. The necessity of dry etching using plasma which is faithful to is emerging.

The dry etching process is an etching method using a low pressure plasma. The dry etching process may be classified into an ion milling etching method and a reactive ion etching method by the chemical reaction of plasma. The etching method uses argon (Ar) plasma which is an inert gas, and the reactive ion etching method performs etching using various chemical gases.

Looking at the related art, copper etching has been studied since the 1990s, but notable etching gas and etching technology for the dry etching process have not been developed. Initially, chlorine-based gases such as SiCl ₄ , CCl ₄ , Cl ₂ , and HCl were used, and an etching gas such as HBr was also applied. At this time, since the etching rate of copper is very slow, hard masks such as metals or oxide films are used more than general photoresist masks (Applied Phys. Lett., 63, 2703 (1993)). In the case of using chlorine-based gases as an etching gas, the etching product of CuCl _x is generated and the CuCl _x film grows on the copper thin film rather than etching the copper thin film. Fortunately, these CuCl _x compounds could be removed by HCl solution or H ₂ plasma treatment, but the result of the etched pattern of copper was not good and the etching for the micropattern was not achieved (J. Electrochem. Soc. , 148, G524 (2001), Thin Solid Films, 457 326 (2004).

Subsequently, hexafluoroacetylacetonate (hfac), a kind of organic chelator material, is used, and the substrate is heated to 90-160 ° C to form an organic metal compound containing hfac, which has high melting point and low boiling point, thereby facilitating copper etching reaction. It became. However, subsequent studies have not been reported, and the side slope, that is, the etch slope of the etched copper thin film is only about 30 degrees. Subsequently, the Georgia Tech team attempted to dry etch the copper thin film at low temperature (~ 10 degrees) using hydrogen gas, obtaining excellent results, and publishing many papers and patents. However, attempts were made on copper thin films using the hydrogen and hydrogen / argon mixed gas and etching conditions presented in the papers, but the results of the Georgia Tech team did not reproduce the results.

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

Therefore, the current dry etching process for the copper thin film will be made by developing the existing etching gas and new etching gases to derive the optimal etching process. Therefore, in the case of etching the copper thin film for the production of highly integrated devices, the reactive ion etching method to which the chemical reaction is applied, rather than the ion milling method by the physical etching mechanism, should be applied. In recent years, high density plasma reactive ion etching has been applied to increase the etching speed and increase the etching selectivity due to the high plasma density. In particular, copper metal has very low or no reactivity, so the etching rate is very slow, and thus the etching selectivity of the copper thin film for the etching mask is very low. Therefore, when the photoresist is used as a mask by general lithography, it is impossible to form an etched copper pattern according to etching conditions. In this case, instead of photoresist, a thin film of metal (Ti, Ta, W, TiN, Cr, etc), metal oxide (TiO ₂ , SiO ₂ , etc) or Si ₃ N ₄ is used as a mask, that is, a hard mask is used. Should be etched.

 However, even when etching a copper thin film by reactive ion etching, redeposition on the side of the etched pattern may be difficult when using an inappropriate etching gas concentration or an inappropriate etching process. There is a problem that occurs. In addition, when etching is performed with an etching gas or an etching condition that is not optimized, the occurrence of redeposition may be reduced, but as shown in (c) of FIG. Problems that are difficult to apply to etching occur.

Therefore, there is a continuing need for the development of an etching technology of a copper thin film that can provide an etching profile and a high anisotropy etching profile through proper etching gas and its concentration control.

Korean Laid-Open Patent Publication No. 2002-0056010 (2002.07.10.) Korea Patent Publication 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 a conventional dry etching method without a pattern 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, a new suitable etching gas has been developed and used to provide an etching method of a copper thin film which can provide an etching profile with high etching rate and high anisotropy without etching residue without redeposition.

In order to solve the above problems, the present invention comprises the steps of: masking by etching and patterning a copper thin film with a hard mask; (b) alcohols (R-OH; CH ₃ OH, C ₂ H ₅ OH ...), carboxylic acids (R-COOH; CH ₃ COOH ..), aldehydes (R-CHO; HCHO, CH ₃ CHO ..), ketones (R-CO-R ': CH ₃ COCH ₃ ..), esters (R-COO-R') containing at least one selected from the group comprising an inert gas Plasmaizing the mixed gas; And (c) etching the copper thin film masked in the step (a) using the plasma generated in the step (b).

Another example of the present invention comprises the steps of: (a) patterning and etching a copper thin film with a hard mask; (b) consisting of alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R') Plasmalizing one or more gases selected from the group and a mixed gas containing oxygen and / or ozone; And (c) etching using the hard mask masked in step (a) using the plasma generated in step (b).

In the etching method of the copper thin film of the present invention, the etching selectivity of the copper thin film with respect to the hard mask may be 0.5 to 12.

In addition, the present invention may be at least one selected from the group consisting of He, Ne, Ar and N ₂ as an inert gas, the hard mask is silicon dioxide (SiO ₂ ), Si ₃ N ₄ , TiO ₂ , TiN, Ti, Ta , W, Cr and carbon (C) can be selected.

In one example of the present invention, the mixed gas of step (b) is alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R '), 50-100 vol% of one or more gases selected from the group consisting of esters (R-COO-R '), the remainder may contain inert gases, and also oxygen and / or ozone without the use of inert gases It may be included in the mixed gas at a concentration of 5 to 15 vol%.

On the other hand, the present invention is the plasma of the step (b) is injected a mixed gas at a process pressure in the range of 0.13 ~ 1.3 Pa, the coil high frequency power (ICP rf power) of 300 W ~ 800 W, 200 ~ 400 V dc This can be done by applying a -bias voltage.

In addition, the present invention is the plasma of step (b) is a high-density plasma reactive ion etching method, self-enhanced reactive ion etching method, reactive ion etching method, atomic layer etching method including inductively coupled plasma reactive ion etching method (atomic layer) etching) and pulse-modulated high density plasma reactive ion etching.

The present invention also provides a copper thin film manufactured by any one of the above methods and having an etching slope of 70 ° or more.

In the etching method of the copper thin film according to the present invention, by applying the optimal etching process conditions and the optimum etching gas concentration and the optimum etching gas concentration, the etching residue without the redeposition compared with the etching method of the conventional copper thin film Fast etch rates and high anisotropic etch profiles can be applied to all devices and devices where copper thin films are used.

In addition, the present invention does not require an additional configuration for heating the substrate, and can etch the copper thin film at low temperature.

Figure 1 schematically shows the side structure before and after the thin film etching, (a) is a thin film structure before etching, (b) is a conventional thin film structure etched by ion milling etching or reactive ion etching, (c ) Is a thin film structure etched by the conventional reactive ion etching method, (d) is the etch profile of the sample after the ideal etching.
FIG. 2 is a graph showing etching rate change and etching selectivity of a copper thin film and a SiO ₂ hard mask with respect to a change in the concentration of CH ₃ OH etching gas in an etching gas of CH ₃ OH / Ar. Etching conditions are ICP rf power of 500 W, dc-bias voltage of 300 V and gas pressure of 0.67 Pa.
3 is a SEM photograph of a copper thin film according to the concentration of CH ₃ OH in the CH ₃ OH / Ar mixed gas, (a) is a thin film etched in pure Ar, (b) is a thin film etched in 25% CH ₃ OH / Ar (c) is a thin film etched at 50% CH ₃ OH / Ar, (d) is a thin film etched at 75% CH ₃ OH / Ar, and (e) is a thin film etched at 100% CH ₃ OH. Etching conditions are ICP rf power of 500 W, dc-bias voltage of 300 V and gas pressure of 0.67 Pa.
Figure 4 is a graph showing the etching rate change and etching selectivity of the copper thin film and SiO ₂ hard mask for the change of the concentration of C ₂ H ₅ OH etching gas in the etching gas of C ₂ H ₅ OH / Ar. Etching conditions are ICP rf power of 500 W, dc-bias voltage of 300 V and gas pressure of 0.67 Pa.
FIG. 5 is a SEM photograph of a copper thin film according to C ₂ H ₅ OH concentration in a C ₂ H ₅ OH / Ar mixed gas, (a) is a thin film etched in pure Ar, and (b) is 25% C ₂ H ₅ A thin film etched from OH / Ar, (c) a thin film etched from 50% C ₂ H ₅ OH / Ar, (d) a thin film etched from 75% C ₂ H ₅ OH / Ar, (e) Is a thin film etched in 100% C ₂ H ₅ OH. Etching conditions are ICP rf power of 500 W, dc-bias voltage of 300 V, and gas pressure of 0.67 Pa.
6 is a result of etching by varying the ICP rf power in 100% C ₂ H ₅ OH etching gas (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 200 W of ICP rf power, (c) is 500 W ICP rf power, (d) is the etching profile of the copper thin film etched at 800 W ICP rf power. Standard etching conditions are 100% C2H5OH, 300 V dc-bias voltage, and 0.67 Pa process pressure.
7 is a result of etching by varying the dc-bias voltage in 100% C ₂ H ₅ OH etching gas (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 200 V The dc-bias voltage of (c) is the dc-bias voltage of 300 V, and (d) is the etching profiles of the copper thin film etched at the dc-bias voltage of 400 V. Standard etching conditions are 100% C ₂ H ₅ OH, 500 W ICP rf power, and 0.67 Pa process pressure.
8 is a result of etching by varying the process pressure in 100% C ₂ H ₅ OH etching gas (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 0.13 Pa, ( c) is 0.67 Pa and (d) is etch profile of copper thin film etched at process pressure of 1.3 Pa. Standard etching conditions are 100% C ₂ H ₅ OH, 500 W ICP rf power, and 300 V dc-bias voltage.
9 is a graph showing changes in etching rate and etching selectivity of a copper thin film and a SiO ₂ hard mask by etching by adding O ₂ gas to C ₂ H ₅ OH gas. Etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.
FIG. 10 is SEM images showing etching profiles of copper thin films according to the change of O ₂ gas in a mixed gas of O ₂ / C ₂ H ₅ OH, (a) 100% C ₂ H ₅ OH, (b) 6.7% O ₂ /93.3% C ₂ H ₅ OH, (c) 10% O ₂ /90% C ₂ H ₅ OH, (d) 20% O ₂ /80% C ₂ H ₅ OH, (e) 30% O ₂ / Copper thin films etched at 70% C ₂ H ₅ OH with etching conditions of 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.
FIG. 11 is a graph showing etching rate changes and etching selectivity of a copper thin film and a SiO ₂ hard mask with respect to a change in the concentration of CH ₃ COOH etching gas in an etching gas of CH ₃ COOH / Ar. Etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.
12 is a SEM photograph of a copper thin film according to the concentration of CH ₃ COOH in the mixed gas of CH ₃ COOH / Ar, (a) is a thin film etched in pure Ar, (b) is a thin film etched in 25% CH ₃ COOH / Ar (c) is a thin film etched in 50% CH ₃ COOH / Ar, (d) is a thin film etched in 75% CH ₃ COOH / Ar, and (e) is a thin film etched in 100% CH ₃ COOH / Ar. Etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.
FIG. 13 is an SEM image of a copper thin film according to the concentration of CH ₃ COOH in a mixed gas of CH ₃ COOH / Ar, which was etched under the same etching conditions as in FIG. 10, but was about 10% over-etched. (a) is a thin film etched in pure Ar, (b) is a thin film etched in 25% CH ₃ COOH / Ar, (c) is a thin film etched in 50% CH ₃ COOH / Ar, and (d) is Thin film etched in 75% CH ₃ COOH / Ar, (e) is thin film etched in 100% CH ₃ COOH. Etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.
14 is a result of etching by changing the ICP rf power in the etching gas of 50% CH ₃ COOH / Ar (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 300 W The ICP rf power of (c) is the ICP rf power of 500 W, (d) is the etching profiles of the copper thin film etched at 700 W ICP rf power. Standard etching conditions are 50% CH ₃ COOH / Ar, 300 V dc-bias voltage, and 0.67 Pa process pressure.
15 is a result of etching by varying the dc-bias voltage in the etching gas of 50% CH ₃ COOH / Ar (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 200 The dc-bias voltage of V, (c) is the dc-bias voltage of 300 V, and (d) are the etch profiles of the copper thin film etched at the dc-bias voltage of 400 V. Standard etching conditions are 50% CH ₃ COOH / Ar, 500 W ICP rf power, and 0.67 Pa process pressure.
16 is a result of etching by varying the process pressure in the etching gas of 50% CH ₃ COOH / Ar (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 0.13 Pa, (c) is 0.67 Pa, and (d) is etching profiles of copper thin film etched at a process pressure of 1.3 Pa. Standard etching conditions are 50% CH ₃ COOH / Ar, 500 W ICP rf power, and 300 V dc-bias voltage.
FIG. 17 is an XPS analysis result of a surface of a copper thin film etched under conditions of a copper thin film, 50% CH ₃ COOH / Ar, and 100% CH ₃ COOH before etching. (a) Cu 2p, (b) O 1s, (c) C 1s. Standard etching conditions are 500 W ICP rf power, 300 V dc-bias voltage, and 0.67 Pa process pressure.

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 nomenclature used herein is well known and commonly used in the art.

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

Etching method of the copper thin film according to the present invention, (a) patterning and etching the copper thin film with a hard mask masking; (b) consisting of alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R') Plasmalizing the mixed gas containing at least one gas selected from the group and an inert gas; And (c) etching 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.

The present invention first masks the hard mask / copper thin film by patterning the hard mask / copper thin film with a photoresist mask, and plasmalizes the C ₂ F ₆ / Cl ₂ / Ar gas. Thereafter, silicon dioxide is etched from the masked hardmask / copper thin film using the generated C ₂ F ₆ / Cl ₂ / Ar plasma.

After etching the hard mask, in order to remove the photoresist thin film, the oxygen gas is plasmalized and the photoresist is removed from the thin film using the generated oxygen plasma. As described above, the copper thin film is etched using the hard mask in the thin film from which the photoresist is removed.

Select from the group consisting of alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R') The copper thin film is etched after the mixed gas including the at least one gas and the inert gas is plasmalized, and the inert gas may be at least one selected from the group consisting of He, Ne, Ar, and N ₂ . .

In a preferred embodiment of the present invention, the mixed gas is alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R '), esters One or more gases selected from the group consisting of (R-COO-R ') may contain 50 to 100 vol% and the rest may be composed of inert gas.

It is composed of alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R ') and esters (R-COO-R') If at least one gas selected from the group is 50 vol% or less, there is a problem in that redeposition occurs on the side of the etched thin film.

In addition, the group consisting of alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R') As the concentration of one or more gases selected from increases, the etch rate does not increase but decreases, not following a typical reactive ion etching mechanism. The gas is added to the pure argon gas to deposit a polymer containing CHx on the copper thin film, and an oxide film is formed on the surface by O or -OH groups, thereby reducing the overall etching rate of the thin film. In some materials, however, copper and -OH groups react to form etch products.

In addition, an example of the present invention is to etch a copper thin film using a hard mask on a thin film from which photoresist has been removed. Selected from the group consisting of alcohols (R-OH), carboxylic acids (R-COOH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R') The copper thin film may be etched by plasmalizing one or more gases and a mixed gas containing oxygen and / or ozone, and oxygen and / or ozone may be included in the mixed gas at a concentration of 5 to 20 vol%, 5-50 vol% is more preferable.

If oxygen and / or ozone is less than 5 vol%, the etch profile of the etched copper thin film does not redeposit but the etch slope of the copper thin film is lowered, and if oxygen and / or ozone is greater than 20 vol%, etch redeposit occurs. The etching slope is worse.

In a preferred embodiment of the present invention, the plasma of the mixed gas is a high density plasma reactive ion etching method, self-enhanced reactive ion etching method, reactive ion etching method, atomic layer etching method including inductively coupled plasma reactive ion etching method layer etching) and pulse-modulated high density plasma reactive ion etching.

The present invention does not require a configuration for heating a substrate loaded with a copper thin film during etching, the etching may be performed at a low temperature by applying a cooling fluid of 10 ~ 20 ℃ to the substrate. If the substrate needs to be heated above 150 degrees, it is impossible to use a vacuum seal such as O-ring under the substrate, so that special substrate structure is manufactured, which increases the cost of equipment. Heating causes the diffusion of materials that have already been deposited or patterned / etched onto the substrate, causing unwanted materials (elements) to move up or down the thin film layer to change or degrade the device's properties.

Plasmaization is preferred to inject a mixed gas at a process pressure in the range of 0.13 ~ 1.3 Pa, if lower than 0.13 Pa. As the generated plasma is unstable, there is a problem of inferior etching stability and reproducibility, and when it is higher than 1.3 Pa, the amount of ions, radicals, etc. in the plasma is relatively high, but the average free path thereof is small, so that physical collision occurs frequently. As a result, a problem arises in that a slow etching speed and a low etching slope are ultimately obtained.

The coil high frequency power (ICP rf power) is preferably 300 W ~ 800 W, if lower than 200 W there is a problem that serious redeposition occurs after etching.

The DC-bias voltage is preferably 200 to 400 V. When the DC-bias voltage is less than 200 V, the voltage applied to the sample to be etched is low, which not only reduces the amount of ions, radicals, etc. generated by plasma formation, but also is slow due to the slow (weak) acceleration of the ions. Patterns of etch rate and low etch slope can be obtained and redeposition can occur on the etch side, and high DC-bias voltages above 400 V can improve etch rate and etch slope, but the ion bombardment on the thin film Etch damage may occur, resulting in deterioration of electrical characteristics of the device to be manufactured.

On the other hand, by the copper thin film etching method of the present invention, the etching selectivity of the copper thin film to the hard mask is 0.5 to 12.

In addition, the hard mask may be selected from silicon dioxide (SiO ₂ ), Si ₃ N ₄ , TiO ₂ , TiN, Ti, Ta, W, Cr and carbon (C).

FIG. 2 is a diagram illustrating etching rates of copper thin films and silicon dioxide hard masks using CH ₃ OH / Ar etching gas, and etching selectivity of copper thin films for respective silicon dioxide hard masks. That is, the copper thin film is etched using a SiO ₂ hard mask and CH ₃ OH / Ar gas. The copper thin film was etched by changing the CH ₃ OH gas concentration from 25% to 50%, 75%, 100% from pure Ar in CH ₃ OH / Ar.

CH ₃ was the etching rate of OH gas copper thin film and the hard mask as concentration increases of decreases at the same time gradually, and therefore the etching rate of a Cu thin film is faster than the etching rate of a SiO ₂ hard mask, SiO ₂ copper on hardmask Etch selectivity for the thin film was obtained a value of 5 or more.

As a result, as the CH ₃ OH gas increases, the etching rate does not increase but decreases, which does not follow the typical reactive ion etching mechanism. This is because CH ₃ OH gas is added to the pure argon gas, and a polymer containing CHx is deposited on the copper thin film. An oxide film is formed on the surface by -OH group, and thus the overall etching rate of the thin film is reduced.

3 is a SEM photograph showing an etching profile of SiO ₂ / Cu thin film etched by changing the CH ₃ OH gas concentration using a CH ₃ OH / Ar etching gas, (a) is a thin film etched in pure Ar, ( b) is a thin film etched at 25% CH ₃ OH / Ar, (c) is a thin film etched at 50% CH ₃ OH / Ar, (d) is a thin film etched at 75% CH ₃ OH / Ar, (e) is a thin film etched in 100% CH ₃ OH. Etching conditions are ICP rf power of 500 W, dc-bias voltage of 300 V and gas pressure of 0.67 Pa.

Copper that was etched in pure argon was observed to have a significant redeposition on the pattern side, which is the result of the physical sputtering of the argon ions on the copper thin film. As the CH ₃ OH concentration increased from 25% to 100%, redeposition on the side of the etched Cu thin film was gradually reduced and not observed, but the etch gradient was observed to gradually decrease.

4 is a view showing the etching rate of the copper thin film and the silicon dioxide hard mask using the C ₂ H ₅ OH / Ar etching gas and the etching selectivity of the copper thin film for the silicon dioxide hard mask. That is, the copper thin film is etched using a SiO ₂ hard mask and C ₂ H ₅ OH / Ar gas. The copper thin film was etched by changing the C ₂ H ₅ OH gas concentration from 25% to 50%, 75%, 100% from pure Ar at C ₂ H ₅ OH / Ar.

C ₂ H ₅ OH is the concentration of the gas increases the etching rate of the copper thin film and the hard mask reduces at the same time progressively according as was because the etching rate of a Cu thin film is faster than the etching rate of a SiO ₂ hard mask, SiO ₂ for the hard mask The etching selectivity with respect to the copper thin film obtained the value within the range of 3-12.

As a result, the etching rate did not increase with increasing C ₂ H ₅ OH gas, similar to the case of CH ₃ OH, and did not follow the typical reactive ion etching mechanism. This is because C ₂ H ₅ OH gas is added to the pure argon gas to deposit a polymer containing CHx on the copper thin film, the oxide film is formed on the surface by the -OH group, the overall etching rate of the thin film is determined to be reduced. The etching rate of the copper thin film in the C ₂ H ₅ OH gas was slower than that of the copper thin film in the CH ₃ OH gas, due to the generation of polymers containing more CHx from the C ₂ H ₅ OH gas. do.

5 is a SEM photograph showing an etching profile of SiO ₂ / Cu thin film etched by changing the C2H5OH gas concentration in C ₂ H ₅ OH / Ar gas, (a) is a thin film etched in pure Ar, (b) is Thin film etched at 25% C ₂ H ₅ OH / Ar, (c) thin film etched at 50% C ₂ H ₅ OH / Ar, (d) etched at 75% C ₂ H ₅ OH / Ar (E) is a thin film etched in 100% C ₂ H ₅ OH. Etching conditions are ICP rf power of 500 W, dc-bias voltage of 300 V, and gas pressure of 0.67 Pa.

Copper that was etched in pure argon was observed to have significant redeposition on the side of the pattern, which is the result of the physical sputtering of the argon ions on the copper thin film. Redeposition was observed on the side of the etched copper thin film at a concentration of 25% C ₂ H ₅ OH / Ar. As the concentration of C ₂ H ₅ OH increased, the redeposition on the side of the copper thin film gradually decreased. No redeposition was observed in% C ₂ H ₅ OH. On the other hand, the slope of the etched thin film side, that is, the etching slope gradually decreased as the concentration of C ₂ H ₅ OH increased.

FIG. 6 shows the etching characteristics by changing the ICP rf power among the etch parameters ICP rf power, dc-bias voltage, and process pressure at 100% C ₂ H ₅ OH. The etch rate, etch selectivity and etch profile of copper thin film and silicon dioxide hard mask were investigated by changing ICP rf power to 200W, 500W, 800W.

As the ICP rf power increased, the etching rate of Cu increased almost linearly, but the SiO ₂ etching rate increased slightly. The etching selectivity of the copper thin film with respect to the SiO ₂ hard mask was changed between about 0.5 to 12.

In terms of etch profile, redeposition increased after etching under rf power of 200 W. At 800 W etching conditions, some redeposition materials were observed on the side of the hard mask and the copper thin film after etching, but the etching slope was greatly improved. In general, increasing the ICP rf power increases the plasma density in the reactor, which results in more radicals and more cations, which increases the etch rates of the thin films and helps in the anisotropy of the etch profile.

FIG. 7 shows the etching rate, etching selectivity, and etching rate of the copper thin film and silicon dioxide hard mask by changing the dc-bias voltage, which is an etch variable under the etching gas condition of 100% C ₂ H ₅ OH, from 200 V to 300 V and 400 V. Etch profiles were investigated. Figure 7 (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is a dc-bias voltage of 200 V, (c) is a dc-bias voltage of 300 V, (d) Etch profiles of copper thin films etched at 400 V dc-bias voltage. Standard etching conditions are 100% C ₂ H ₅ OH, 500 W ICP rf power, and 0.67 Pa process pressure.

dc-bias voltage is 200 V increased to 400 V as thus was an etching rate of the copper film is gradually increased in the SiO _2, so the etching rate of the hard mask is not a significant change, SiO ₂ is also etch selectivity of the copper thin film for the hard mask Was changed in the range of about 6 to 12.

According to the results of etching profile, the copper thin film etched under the condition of 200 V dc-bias voltage showed no redeposition material on the etching side, and the redeposition material did not show the etching side under the condition of 400 V dc-bias voltage. Etch inclination increased slightly. In general, it is judged that the change of dc-bias voltage does not affect the etching profile of copper thin film under the current etching gas condition of 100% C ₂ H ₅ OH.

As the dc-bias voltage increases, the cations in the plasma are attracted to the substrate with greater energy and collide strongly, removing the thin film or removing the etch products remaining on the surface, which increases the overall etch rate of the thin film. Obtained. However, in 100% C ₂ H ₅ OH etching gas, the amount of cations generated in the plasma is limited, which does not affect the etching profile.

8, the etching rate, etching selectivity, and etching profiles of copper thin films and silicon dioxide hard masks were examined by changing the process pressures, which are etch parameters, under etching gas conditions of 100% C ₂ H ₅ OH. The copper thin film was etched by changing the process pressure at 0.13 Pa, 0.67 Pa, 1.3 Pa. 8 (a) shows the etching rate and etching selectivity of the copper thin film and the silicon dioxide mask, (b) is 0.13 Pa, (c) is 0.67 Pa, and (d) is etched copper at a process pressure of 1.3 Pa. Etch profiles of. Standard etching conditions are 100% C ₂ H ₅ OH, 500 W ICP rf power, and 300 V dc-bias voltage.

The etching rate of the copper thin film was slightly decreased at 1.3 Pa and the etching rate of SiO ₂ was slightly decreased. The etch selectivity of the copper thin film on the SiO ₂ hard mask was varied between about 3 and 12 and was the highest at the process pressure of 0.67 Pa. As the process pressure of etching decreased to 0.13 Pa, the etching slope increased significantly, and even at 1.3 Pa, the etching slope increased slightly.

 These results indicate that at low pressures of 0.13 Pa, the mean free path is greatly increased so that radicals or ions generated in the plasma effectively reach the thin film surface without colliding, and thus more radicals and ions are chemically reacted with the thin film surface and sputtering. Participation in the reaction results in an improvement in the etching profile.

9 is a graph showing changes in etching rate and etching selectivity of a copper thin film and a SiO ₂ hard mask by etching by adding O ₂ gas to C ₂ H ₅ OH gas. Etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.

Oxygen is added to the etching gas to oxidize the copper thin film to copper oxide to increase the reactivity with ethanol gas. When the oxygen gas was added in small amounts, the copper thin film was slightly decreased, and the etching rate of the SiO ₂ hard mask was almost unchanged. Etch selectivity was almost unchanged, but was slightly decreased when 40% oxygen was added.

FIG. 10 is SEM images showing etching profiles of copper thin films according to the change of O ₂ gas in a mixed gas of O ₂ / C ₂ H ₅ OH, (a) 100% C ₂ H ₅ OH, (b) 6.7% O ₂ /93.3% C ₂ H ₅ OH, (c) 10% O ₂ /90% C ₂ H ₅ OH, (d) 20% O ₂ /80% C ₂ H ₅ OH, (e) 30% O ₂ / Copper thin films etched at 70% C ₂ H ₅ OH with etching conditions of 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.

The etching profile of the copper thin film etched in 100% C ₂ H ₅ OH was about 66 degrees without the redeposition. However, when 6.7-10% O ₂ gas was added, etch redeposition did not occur and the etch inclination also improved by about 70 degrees. However, when 20% or more of O ₂ gas was added, etching redeposition occurred or the etching slope became worse.

FIG. 11 is a diagram illustrating etching rates of copper thin films and silicon dioxide hard masks using CH ₃ COOH / Ar etching gas, and etching selectivity of copper thin films for respective silicon dioxide hard masks. That is, the copper thin film is etched using a CH ₃ COOH / Ar gas using a SiO ₂ hard mask. The copper thin film was etched by changing the CH ₃ COOH gas concentration from 25% to 50%, 75%, 100% from pure Ar in CH ₃ COOH / Ar.

Since the etching rate of the copper thin film and the hard mask reduces at the same time as gradually as the concentration of CH ₃ COOH gas increases were the etching rate of the Cu film is faster than the etching rate of a SiO ₂ hard mask, SiO ₂ thin copper film on the hard mask The etching selectivity for was obtained in the range of 2-3.

As a result, similarly to the case of CH ₃ OH and C ₂ H ₅ OH CH ₃ COOH gas gas increases, therefore the etching rate is decreased rather than increased by not follow the typical reactive ion etching mechanism. This is because CH ₃ COOH gas is added to pure argon gas, and a polymer containing CHx is deposited on the copper thin film. An oxide film is formed on the surface by O and -OH groups, and thus the overall etching rate of the thin film is reduced. The etching rate of the copper thin film in the CH ₃ COOH gas was slower than that of the copper thin film in the CH ₃ OH and C ₂ H ₅ OH gases.

12 is a SEM photograph showing an etching profile of SiO ₂ / Cu thin film etched by varying the concentration of CH ₃ COOH gas in the CH ₃ COOH / Ar gas, (a) is a thin film etched in pure Ar, (b) is A thin film etched at 25% CH ₃ COOH / Ar, (c) a thin film etched at 50% CH ₃ COOH / Ar, (d) a thin film etched at 75% CH ₃ COOH / Ar, (e) Is a thin film etched in 100% CH ₃ COOH. Etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.

Copper that was etched in pure argon was observed to have significant redeposition on the pattern side, which is the result of the physical sputtering of the argon ions on the copper thin film. Redeposition was observed on the side of the etched copper thin film at a concentration of 25% CH ₃ COOH / Ar. As the concentration of CH ₃ COOH increased, redeposition on the side of the copper thin film gradually decreased and 75% CH ₃ COOH Little redeposition was observed at / Ar and 100% CH ₃ COOH.

In general, redeposition after etching was considerably reduced in gas of CH ₃ COOH / Ar than in gas of alcohol. On the other hand, the slope of the etched thin film side, that is, the etch slope gradually decreased as the CH ₃ COOH concentration was increased.

FIG. 13 is an SEM image of a copper thin film according to the concentration of CH ₃ COOH in a mixed gas of CH ₃ COOH / Ar, which was etched under the same etching conditions as in FIG. 10, but was about 10% over-etched. (a) is a thin film etched in pure Ar, (b) is a thin film etched in 25% CH ₃ COOH / Ar, (c) is a thin film etched in 50% CH ₃ COOH / Ar, and (d) is Thin film etched in 75% CH ₃ COOH / Ar, (e) is thin film etched in 100% CH ₃ COOH. Etching conditions are 500 W ICP rf power, 300 V dc-bias voltage and 0.67 Pa process pressure.

Even when pure argon gas was used, all of the redeposited materials were removed after etching, and the etching redeposited materials were removed from both the SiO ₂ hardmask and the copper side even under the etching conditions with increased CH ₃ COOH concentration. An etching profile with an etching slope of about 85 degrees or more was obtained under etching conditions of 100% CH ₃ COOH.

14 is a result of etching by changing the ICP rf power in the etching gas of 50% CH ₃ COOH / Ar (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 300 W The ICP rf power of (c) is the ICP rf power of 500 W, (d) is the etching profiles of the copper thin film etched at 700 W ICP rf power. Standard etching conditions are 50% CH ₃ COOH / Ar, 300 V dc-bias voltage, and 0.67 Pa process pressure.

The etching rate of Cu increased linearly with increasing ICP rf power, but the SiO ₂ etching rate slightly increased. The etching selectivity of the copper thin film on the SiO ₂ hard mask was about 2.5.

In terms of etch profile, redeposition was decreased after etching under rf power of 300 W, and the etch slope was about 45 degrees without significant change. However, in the etching condition of 700 W, no redeposition material was observed from the side of the hard mask and the copper thin film after etching, and the steep etch slope of about 75 degrees was observed. In general, increasing the ICP rf power increases the plasma density in the reactor, which results in more radicals and more cations, which increases the etch rates of the thin films and helps in the anisotropy of the etch profile.

15 is a result of etching by varying the dc-bias voltage in the etching gas of 50% CH ₃ COOH / Ar (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) 200 The dc-bias voltage of V, (c) is the dc-bias voltage of 300 V, and (d) are the etch profiles of the copper thin film etched at the dc-bias voltage of 400 V. Standard etching conditions are 50% CH ₃ COOH / Ar, 500 W ICP rf power, and 0.67 Pa process pressure.

As the dc-bias voltage increased, the etching rate of the copper thin film was increased, but the etching rate of the SiO ₂ hard mask was slightly increased. As a result, the etching selectivity of the copper thin film with respect to the SiO ₂ hard mask also increased from about 1.8 to 3.

The copper thin film etched under the condition of 200 V dc-bias voltage showed some redeposition material on the etch side and the etching slope was about 30 degrees, and redeposition was also observed under the condition of 300 V dc-bias voltage. The etch slope improved to about 45. At 400 V, most of the redeposit material disappeared after etching, and the etching slope improved to about 75 degrees.

As the dc-bias voltage increases, the cations in the plasma are attracted to the substrate with greater energy and collide strongly, eliminating the thin film or removing the etch products remaining on the surface, which increases the overall etch rate of the thin film. Obtained.

16 is a result of etching by changing the process pressure in the etching gas of 50% CH ₃ COOH / Ar (a) shows the etching rate and etching selectivity of the copper thin film and silicon dioxide mask (b) is 0.13 Pa, (c) is 0.67 Pa, and (d) is etching profiles of copper thin film etched at a process pressure of 1.3 Pa. Standard etching conditions are 50% CH ₃ COOH / Ar, 500 W ICP rf power, and 300 V dc-bias voltage.

As the process pressure increased, the etch rate of the copper and SiO ₂ thin films gradually decreased, and as a result, the etching selectivity of the copper thin film with respect to the SiO ₂ hardmask varied within the range of about 2.4 to 2.9.

 In terms of the etching profile of the copper thin film, it was observed that the etching slope improved as the process pressure decreased. That is, the etching slope of the copper thin film etched at 0.67 Pa was 45 degrees, but the etching slope at 0.13 Pa was slightly improved to about 75 degrees, and the redeposition material was removed after etching to ensure a clean etching profile. On the other hand, in the case of etching at 1.3 Pa, the etching slope was not significantly different from the process pressure of 0.67 Pa.

These results indicate that at low pressures of 0.13 Pa, the mean free path is greatly increased so that radicals or ions generated in the plasma effectively reach the thin film surface without colliding, and thus more radicals and ions are chemically reacted with the thin film surface and sputtering. Participation in the reaction results in an increase in the etching rate and an improvement in the etching profile.

FIG. 17 shows the etching of a copper thin film under etching conditions of 50% CH ₃ COOH / Ar and 100% CH ₃ COOH under etching conditions of 500 W of ICP rf power, 300 V of dc-bias voltage and 0.67 Pa of process pressure. XPS analysis was performed on the surfaces of the etched thin film and the copper thin film before etching.

Looking at the narrow scan results for the Cu 2p peak in FIG. 17 (a), the surface of the copper thin film before etching is partially oxidized with Cu ₂ O, and after etching with CH ₃ COOH, a larger amount of Cu _{2 is formed on} the surface of the copper thin film. O and CuO were observed and the compound was expected to be Cu (OH) ₂ or Cu (CH ₃ COO) ₂ under etching conditions of 100% CH ₃ COOH.

Figure 17 (b) in a, O 1s peak of narrow scan of a road in the copper foil surface prior to etching was observed that the copper oxide of Cu ₂ O and CuO 50% CH ₃ In the conditions of the COOH / Ar Cu ₂ O in the etched copper surface The oxides of and CuO were observed, and the amount was slightly increased and the Cu (OH) ₂ compound was found under the etching condition of 100% CH ₃ COOH, which is consistent with the analysis of Cu 2p.

Finally, FIG. 17 (c) is a graph showing narrow scans of the C 1s peak. When the copper thin film is etched with CH ₃ COOH / Ar gas, it is observed that carbides containing CH or CC are formed on the surface of the copper thin film. Particularly in the etching gas condition of 100% CH ₃ COOH, a significant amount of carbide (CHx-) is found on the surface of the copper thin film.

This causes a decrease in the etching rate of the copper thin film, but a kind of protective film is formed on the side of the thin film to be etched to increase the vertical anisotropic etching, thereby increasing the etching slope. As a result of the narrow scan of Cu 2p and O 1s, the etching product of Cu (OH) ₂ or Cu (CH ₃ COO) ₂ , which has relatively low melting point and boiling point, is generated and removed under the etching condition of 100% CH ₃ COOH. It is considered that redeposition did not occur.

Claims (10)

(a) patterning and etching a copper thin film with a hard mask;
(b) one or more gases and inerts selected from the group consisting of alcohols (R-OH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R') Plasmalizing the mixed gas containing the gas; And
(c) etching using the hard mask masked in step (a) using the plasma generated in step (b),
The step (c) is the etching method of the copper thin film, characterized in that for applying a cooling fluid of 10 ~ 20 ℃ to the substrate on which the copper thin film is loaded. (a) patterning and etching a copper thin film with a hard mask;
(b) at least one gas and oxygen selected from the group consisting of alcohols (R-OH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R') And / or plasmalizing the mixed gas containing ozone; And
(c) etching using the hard mask masked in step (a) using the plasma generated in step (b),
The step (c) is the etching method of the copper thin film, characterized in that for applying a cooling fluid of 10 ~ 20 ℃ to the substrate on which the copper thin film is loaded. The etching method of claim 1, wherein the etching selectivity of the copper thin film with respect to the hard mask is 0.5 to 12. 4. The method of claim 1, wherein the inert gas is at least one selected from the group consisting of He, Ne, Ar, and N ₂ . The copper of claim 1, wherein the hard mask is selected from silicon dioxide (SiO ₂ ), Si ₃ N ₄ , TiO ₂ , TiN, Ti, Ta, W, Cr, and carbon (C). Etching method of thin film. According to claim 1, wherein the mixed gas of step (b) is alcohols (R-OH), aldehydes (R-CHO), ketones (R-CO-R '), esters (R-COO-R' Etching method of a copper thin film, characterized in that it comprises 50 ~ 100 vol% of one or more gases selected from the group consisting of. The method of claim 2, wherein the oxygen and / or ozone is included in the mixed gas at a concentration of 5 to 20 vol%. According to claim 1 or 2, wherein the plasma of step (b) is injected a mixed gas at a process pressure in the range of 0.13 ~ 1.3 Pa, Coil high frequency power (ICP rf power) of 200 W to 800 W, 200 Etching method of a copper thin film, characterized in that performed by applying a dc-bias voltage of ~ 400 V. According to claim 1 or 2, wherein the plasma of step (b) is a high-density plasma reactive ion etching method, self-enhanced reactive ion etching method, reactive ion etching method, atomic layer including inductively coupled plasma reactive ion etching method An etching method of a copper thin film, characterized in that carried out by one method selected from the group consisting of etching (atomic layer etching) and pulse-modulated high density plasma reactive ion etching. A copper thin film produced by the method according to any one of claims 1, 2, 4, 6 and 7, and having an etching slope of 70 ° or more.

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