KR100295805B1 - Cobalt-based and copper-based multi-layer metal film etching solution and its manufacturing method and etching method using the same - Google Patents

Abstract

The present invention relates to a simultaneous etching solution of Co-based and Cu-based multi-layer metal films, a method of manufacturing the same, and an etching method using the same, wherein about 40 g of iron (III) chloride hexahydrate prepared by weighing is required at a required composition ratio. After mixing in 40 cc of pure water at 30 to 50 ° C., dissolving it uniformly using a stirrer to prepare an aqueous iron (III) chloride hexahydrate solution, and uniformly preparing the aqueous solution of iron (III) chloride hexahydrate and 2 cc of hydrofluoric acid using an agitator In order to prepare a final etching solution, the concentration of the aqueous solution of iron (III) chloride hexahydrate is 1 to 20 mol%, the concentration of hydrofluoric acid is 1 to 40 mol%, while the temperature during wet etching using the same By maintaining the temperature at about 30 to 50 ° C., Co and Cu-based multilayer metal films can be simultaneously etched while using a more economical wet etching method. It is a very useful invention.

Description

Cobalt-based and copper-based multilayer metal film etching solution, its manufacturing method and etching method using the same

The present invention relates to a simultaneous etching solution of the Co-based and Cu-based multi-layer metal film, a method for manufacturing the same, and an etching method using the same, and more particularly, iron chloride (III) capable of wet etching of Cu-based metals. Simultaneous etching solution for Co and Cu-based multilayer metal films, which is capable of wet etching of Co-based metals by adding hydrofluoric acid (HF) to an aqueous solution of hexahydrate, and a manufacturing method thereof and an etching method using the same will be.

In etching a Co-based and Cu-based multilayer metal film applied to a small magnetic device, a conventional wet etching method of each metal film is generally used, and a dry method is used if the etching is to be performed at the same time.

That is, among the etching solutions that can use the wet etching method for the Cu-based metal film, the etching solution that allows the wet etching method to be used for the Co-based metal film at the same time is not known. Since it was impossible to simultaneously etch the Cu-based and Cu-based multilayer metal films, the process was complicated by separately etching each metal film using a separate etching solution, and the cross section of the etched metal film was formed in a circular shape. There is a problem that it is difficult to form an accurate fine pattern because it has an isotropic structure.

In order to solve this problem, Co and Cu-based multilayer metal films are simultaneously etched by using a dry method such as ion milling, but this method requires a long time to etch and also has a problem that the equipment is expensive and economical. .

Therefore, the present invention was created to solve the above problems, and can simultaneously etch Co-based and Cu-based multilayer metal films by using a more economical wet etching method, and the anisotropic cross section is anisotropic during etching, thereby providing fine patterns. An object of the present invention is to provide a Co-Cu-based multilayer metal film simultaneous etching solution, a method for preparing the same, and an etching method using the same.

1 illustrates a cross-sectional structure of a CoNbZr / Cu / CoNbZr multilayer metal film prepared by sputtering.

Figure 2 shows the etching cross-section after etching the multi-layer metal film of Figure 1 using an etching solution according to the present invention,

3 is a graph showing the relationship between the etching depth and the etching time during the etching of the multilayer metal film of FIG. 1 by the etching solution according to the present invention;

4 is a graph illustrating an etching bias value according to an etching time when the multilayer metal film of FIG. 1 is etched by an etching solution according to the present invention.

FIG. 5 illustrates a pattern of a thin film inductor having a line width of 200 μm and a line spacing of 70 μm by etching the multilayer metal film of FIG. 1 using an etching solution according to the present invention.

Co- and Cu-based multi-layer metal film simultaneous etching solution according to the present invention for achieving the above object, a predetermined amount of water and hydrofluoric acid (HF) in iron (III) chloride hexahydrate (FeCl ₃ · 6H ₂ O) It is prepared by mixing, the concentration of the iron (III) chloride hydrate is characterized in that the concentration of 1 to 20 mol%, the concentration of the hydrofluoric acid is 1 to 40 mol%.

Co- and Cu-based multi-layer metal film simultaneous etching solution manufacturing method according to the present invention, iron (III) chloride hexahydrate (FeCl ₃ · 6H ₂ O) and a predetermined amount of water while maintaining a range of 30 to 50 ℃ mixed iron chloride (III) a first step of preparing an aqueous solution of hexahydrate; And a second step of mixing a predetermined amount of hydrofluoric acid (HF) with the aqueous solution of iron (III) chloride hexahydrate.

In the etching method using a simultaneous etching solution of Co-based and Cu-based multilayer metal films according to the present invention, a predetermined amount of water and hydrofluoric acid (HF) are mixed with iron (III) chloride hexahydrate (FeCl ₃ .6H ₂ O) to form iron chloride ( III) preparing a hexahydrate mixed solution; And a second step of simultaneously wet etching the Co-based and Cu-based multilayer metal films while maintaining the iron (III) hexahydrate mixed solution in a range of 25 to 30 ° C.

Most of the chemical reaction between the Co- and Cu-based multilayer metal film simultaneous etching solution according to the present invention, and the Co-based and Cu-based multilayer metal film is caused by the electrochemical principle, the metal participating in the chemical reaction is represented by the following reaction formula (1 It acts as an anode with the effect of increasing the flow of current, as in.

^{M → M + n + ne -} ······················ formula (1)

The reaction of the iron (III) chloride hexahydrate with pure water can be represented by the following reaction formula (2), and as can be seen from the above, the aqueous solution of the iron (III) chloride hexahydrate shows strong acidity.

nFeCl ₃ · 6H ₂ O + nH ₂ O + nCu → nFe (OH) ₃ + nHClReaction Scheme (2)

The reaction of Cu with an aqueous solution of iron (III) chloride hexahydrate according to Scheme (2) may be represented by two types of reactions as in Schemes (3) and (4) below.

_{nFeCl 3 · 6H 2 O + nH} 2 O + nCu → nFeOH 3 + nHCl + nCu 2+ + 2ne - ··· Scheme 3

_{nFeCl 3 · 6H 2 O + nH} 2 O + nCu → nFeCl 2 + nCuCl 2 + nH + + nOH - ··· Scheme 4

In fact, since the aqueous solution of iron (III) chloride hexahydrate shows strong acidity, it is thought that reactions such as the reaction equation (3) mainly occur in these reaction equations, and reactions such as the reaction equation (4) occur simultaneously in some of the solutions.

As can be seen from the above reaction scheme, the Cu film is reacted with Cl ⁻ ions in the aqueous solution of iron (III) chloride hexahydrate by reacting with HCl produced by the above reaction formula (3) as shown in the following reaction formula (5). After etching or forming CuCl ₂ as in Scheme (4), it is etched through dissolution again, and the rest of the solution is considered to act as a buffer solution.

^{nCu + nHCl → nCu 2+ + 2ne} - + nH + + nCl - ··········· Scheme 5

On the other hand, in general, when compared with the electrode potential value and the absolute value of the etching solution, the metal having a small electrode potential value is etched by the etching solution, the metal having a large electrode potential value is not etched by the etching solution, Pure Co metal is etched in the aqueous solution of iron (III) chloride because its electrode potential (E ₀ ) is -0.28V, which is smaller than the absolute value of _Cu electrode potential (E _Cu = 0.34 V). If it is not pure Co, such as Co alloy, the electrode potential value is rather higher than the electrode potential of the aqueous iron (III) chloride hexahydrate solution is hardly etched.

However, in the mixed etching solution according to the present invention, a small amount of hydrofluoric acid is added to the iron (III) chloride hexahydrate solution to prepare and mix, whereby the electrode potential of the aqueous solution of iron (III) chloride is higher than that of the Co-based alloy. Since it is high, it can be etched in the aqueous solution of iron (III) chloride hexahydrate, thereby enabling simultaneous etching of Co-based and Cu-based multilayer metal films.

In addition, when the etching time, the etching temperature and the solution component concentration are appropriately adjusted, an anisotropic structure can be obtained in the etching cross section.

In conclusion, the aqueous solution of iron (III) chloride can be used to etch Cu-based alloys, and because of the hydrofluoric acid added to the aqueous solution can etch Co-based alloys, the mixed etching solution according to the present invention. This allows both alloys to be etched simultaneously.

Hereinafter, an embodiment of a simultaneous etching solution of a Co-based and Cu-based multilayer metal film according to the present invention and an etching method using the same will be described in detail with reference to the accompanying drawings.

Example

First, 40 g of iron (III) chloride hexahydrate prepared by weighing at the required composition ratio is mixed with 40 cc of pure water, and then uniformly dissolved using a stirrer to prepare an aqueous solution of iron (III) chloride hexahydrate. At this time, since it is difficult to dissolve at room temperature and the temperature is too high, there is a problem due to toxicity due to evaporation, it is preferable to maintain the temperature of the pure water at 30 to 50 ℃,

Subsequently, the prepared aqueous solution of iron (III) chloride and 2 cc of hydrofluoric acid are uniformly mixed using a stirrer to prepare a final etching solution. The pH of the etching solution is measured using a pH meter.

Table 1 below shows the composition of each constituent material in the above process, and in general, the concentration of the aqueous solution of iron (III) chloride hexahydrate is 1-20 mol%, and the concentration of hydrofluoric acid is 1-40 mol%. do. At this time, it is also possible to further mix a predetermined amount of hydrochloric acid or nitric acid in the range of 0.5 mol% or less.

Type of raw material Pure water (H ₂ O) Ferric chloride (III) hexahydrate (FeCl ₃ · 6H ₂ O) Foshan (HF) amount 40 cc 40 g 2 cc

FIG. 1 shows a cross-sectional structure of a CoNbZr / Cu / CoNbZr multilayer metal film prepared by sputtering, and before etching, the upper and lower CoNbZr films are not clearly distinguished by the Cu film of the intermediate layer.

The multilayer metal film of FIG. 1 is immersed for about 150 seconds in a container containing the etching solution of the composition to etch each metal film simultaneously. At this time, the etching temperature is carried out in the range of 20 ~ 60 ℃, more preferably maintain the range of 25 ~ 30 ℃. It is difficult to control the etching rate outside this temperature range, and the solution may volatilize at high temperatures, so the concentration may change.

2 shows a cross section of the multilayer metal film etched by the above method, and it can be seen that the etch cross section is formed of an anisotropic structure having a substantially vertical shape. In order to obtain an etching section of the anisotropic structure, the concentration of each component constituting the etching solution should be maintained well, and the etching prepared by changing only the concentration of hydrofluoric acid while maintaining the concentration of the aqueous solution of iron (III) chloride hexahydrate is constant. With the solution, excessive etching occurs or it is difficult to obtain etching of the anisotropic structure.

3 is a graph showing the relationship between the etching depth and the etching time when the CoNbZr / Cu / CoNbZr multilayer metal film is etched using the etching solution having the composition, wherein the slopes of the graphs are changed in three steps when viewed over the entire time period. First, the upper layer CoNbZr metal film is etched at a slow rate during the first etching time of 10 seconds, and the Cu metal film is etched at a fast etching rate of 90 nm / sec during the second second step of 10 to 120 seconds. It can be seen that the etching rate decreases again as the lower layer CoNbZr metal film is etched during the three steps, 120 to 150 seconds. From the graph, the etching rate in each layer can be known, and from this rate, the etching time according to the thickness of the etched metal film can be calculated. Scanning electron microscope (SEM) and step measuring instrument were used to investigate the etching process.

In general, during wet etching, etching in the vertical direction and etching in the horizontal direction occur at the same time. Therefore, in order to obtain a desired width, a width wider than the target width must be formed at the initial design to obtain a desired width after the final etching. Since the difference between the width and the target width is called an etch bias, it is very important to know the etch bias value in order to form a desired micropattern.

FIG. 4 is a graph showing an etching bias value according to an etching time when the etching solution of the composition is used. As the etching time increases, the graph shows an increase in linearity while satisfying the least square method. In the case of etching for 150 seconds, the etching bias is about 20 μm per side and 40 μm considering both sides.

FIG. 5 illustrates that a CoNbZr / Cu / CoNbZr multilayer metal film is etched using an etching solution having the composition to form a pattern of a thin film inductor having a line width of 200 μm and a line spacing of 70 μm.

Co- and Cu-based multi-layer metal film simultaneous etching solution according to the present invention as described above, while using a more economical wet etching method can simultaneously etch a Co-based and Cu-based multi-layer metal film, since the cross section is anisotropic during etching It is a very useful invention that is easy to form fine patterns.

Claims (5)

A Co-based and Cu-based multilayer metal film etching solution prepared by mixing a predetermined amount of water and hydrofluoric acid (HF) with iron (III) chloride hexahydrate (FeCl ₃ · 6H ₂ O). The Co-based and Cu-based multilayer metal film etching solution according to claim 1, wherein the concentration of iron (III) chloride is 1-20 mol%, and the concentration of hydrofluoric acid is 1-40 mol%. The Co-based and Cu-based multilayer metal film etching solution according to claim 2, further comprising a predetermined amount of nitric acid or hydrochloric acid. A first step of preparing an aqueous solution of 1-20 mol% of iron (III) chloride hexahydrate by mixing iron (III) chloride hexahydrate (FeCl ₃ · 6H ₂ O) and a predetermined amount of water while maintaining a range of 30-50 ° C .; And a second step of mixing 1-40 mol% of hydrofluoric acid (HF) with the aqueous solution of iron (III) chloride hexahydrate. A first step of preparing a mixed solution of iron chloride (III) hexahydrate by mixing a predetermined amount of water and hydrofluoric acid (HF) with iron (III) chloride hexahydrate (FeCl ₃ · 6H ₂ O); And a second step of simultaneously wet etching the Co-based and Cu-based multilayer metal films while maintaining the ferric chloride (III) hexahydrate mixed solution in a range of 25 to 30 ° C. 2.