JP3723724B2 - Method for forming conductive pattern and method for manufacturing thin film capacitor element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a conductor pattern obtained by etching a metal film formed on a substrate to obtain a conductor pattern having a desired shape, and a method for manufacturing a thin film capacitor element having such a conductor pattern. The present invention relates to a taper processing method for forming a taper on an end face of a conductor pattern.
[0002]
[Prior art]
In recent years, with the development of integrated circuit technology, electronic circuits have been increasingly miniaturized, and small electronic circuit boards in which circuit elements such as capacitors and inductors are formed on a substrate as thin films have been developed. In such an electronic circuit board, a conductor pattern that constitutes an electrode portion of each circuit element is formed on the board, and this conductor pattern usually etches a metal film formed on the substrate into a desired shape. To be formed.
[0003]
Hereinafter, a method for forming such a conductor pattern will be described by taking a thin film capacitor element as an example. FIG. 4 is a plan view of a conventionally known thin film capacitor element, and FIG. 5 is a cross-sectional view taken along line AA of FIG. It is. As shown in these drawings, the conventional thin film capacitor element has a laminated structure of a lower electrode 11, a dielectric layer 12 and an upper electrode 13 formed in a thin film on a substrate 10, and the capacitance value of the capacitor is the same as that of the lower electrode 11. It is defined by the overlapping range of the upper electrode 13. An alumina substrate is generally used as the substrate 10, and the lower electrode 11 is formed by depositing a metal film such as Al or Cu on the substrate 10 by sputtering or plating, and etching it into a desired pattern shape. Formed by. The dielectric layer 12 is formed by depositing SiO ₂ or the like on the lower electrode 11 and the substrate 10 by sputtering or CVD, and etching it into a desired pattern shape. The patterned dielectric layer 12 is the lower electrode. 11 extends to the substrate 10 through the surface and side surfaces. The upper electrode 13 is formed by forming a metal film such as Al or Cu on the dielectric layer 12 and the substrate 10 by sputtering or plating, and etching the film into a desired pattern shape. Extends on the substrate 10 through the surface and side surfaces of the dielectric layer 12.
[0004]
In the thin film capacitor element thus configured, a good thin film capacitor element having a higher Q value can be obtained as the film thickness of the lower electrode 11 and the upper electrode 13 is increased. The film thickness of 13 is set in the range of several nm to 10 μm. Further, since the capacitance value per unit area is increased as the thickness of the dielectric layer 12 is reduced and the element shape of the thin film capacitor element can be reduced, the thickness of the dielectric layer 12 is generally 10 nm to The range is set to 1 μm or less.
[0005]
[Problems to be solved by the invention]
As described above, in this type of thin film capacitor element, the thickness of the lower electrode 11 is relatively large (for example, 2 μm) for the purpose of increasing the Q value, and for the purpose of reducing the element shape. Since the thickness of the dielectric layer 12 is relatively thin (eg, 0.3 μm), the film of the dielectric layer 12 in the vicinity of the corner (edge) of the lower electrode 11 as shown in part P of FIG. The thickness tends to become extremely thin. This is because a large step is generated at the corner of the lower electrode 11 by etching, and the coverage of the dielectric layer 12 is deteriorated at the step portion. This is particularly noticeable when the dielectric layer 12 is formed by sputtering. . As a result, there is a problem that the lower electrode 11 and the upper electrode 13 are short-circuited in the portion, and cannot function as a thin film capacitor element.
[0006]
The present invention has been made in view of the actual situation of the prior art, and an object thereof is a method of etching a metal film to taper an end face of a conductor pattern to a desired angle, and a short circuit between upper and lower electrodes. It is an object of the present invention to provide a thin film capacitor element that can prevent the above.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the method for forming a conductor pattern according to the present invention, a metal film forming step of forming a single layer metal film on a substrate, and a negative photoresist is used on the metal film. A resist pattern forming step for forming a resist pattern, and trigger formation for forming an undercut trigger portion at the interface of the metal film with the resist pattern by etching the metal film using isotropic etching An etching process that further etches the metal film using anisotropic etching to cause the trigger portion to greatly advance in the interface direction with respect to the depth direction; and isotropic etching of the metal film Etching up to the final depth using a main etching to advance the trigger portion by the same amount in the depth direction and in the interface direction to form a tapered portion A degree, by removing the resist pattern after performing these order, and forming a conductive pattern end face is tapered on the substrate.
[0008]
As described above, after the metal film is isotropically etched in advance to form an undercut trigger portion at the resist pattern interface, the trigger portion is greatly advanced in the interface direction by anisotropic etching. By adopting a series of processes in which the film is etched again to the final depth by isotropic etching to form a tapered portion, a conductor pattern having a tapered end face can be formed by etching, and the trigger portion. By changing the etching time during anisotropic etching, the taper can be controlled to a desired angle.
[0009]
The conductor pattern targeted by the present invention may be anything as long as it can be patterned into a desired shape by etching a metal film, and can be applied to, for example, electrode portions and microstrip lines of various circuit elements. It is particularly preferable to apply to the lower electrode of the thin film capacitor element. In this case, after the tapered lower electrode (conductor pattern) is formed on the substrate with the above-described configuration, the dielectric layer and the upper electrode are sequentially laminated on the lower electrode including the taper. Since the thickness of the body layer is made uniform, it is possible to reliably prevent a short circuit between the upper and lower electrodes due to poor coverage of the dielectric layer.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
1 is a plan view of a thin film capacitor element according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG. 3 is an explanatory view showing a manufacturing process of a lower electrode provided in the thin film capacitor element.
[0011]
As shown in FIGS. 1 and 2, the thin film capacitor element according to the present embodiment includes a lower electrode 2, a dielectric layer 3 and an upper electrode 4 sequentially stacked on a substrate 1. Consists of an alumina substrate (for example, purity 99.5%). The lower electrode 2 is made of a metal film such as Al or Cu patterned on the substrate 1, and the entire film thickness is set to about 2 μm in order to increase the Q value. As will be described later, the lower electrode 2 is formed by etching a metal film formed on the substrate 1 by sputtering, and the taper 2a is processed on the end face of the lower electrode 2 by this etching process. The dielectric layer 3 is formed by depositing SiO ₂ or the like on the lower electrode 2 and the substrate 1 by sputtering or CVD, and etching it into a desired pattern shape. The film thickness of the dielectric layer 3 is set to about 0.3 μm in order to reduce the size of the element. The patterned dielectric layer 3 covers the taper 2 a of the lower electrode 2 and extends onto the substrate 1. ing. The upper electrode 4 is formed by forming a metal film such as Cu or Ni on the dielectric layer 3 and the substrate 1 by sputtering or plating, and etching the film into a desired pattern shape, thereby achieving a high Q value. Therefore, the entire film thickness is set to 5 μm or more.
[0012]
In the thin film capacitor element configured as described above, the conductor pattern targeted by the present invention is the lowermost lower electrode 2, and the manufacturing process of the lower electrode 2 will be described below with reference to FIG.
[0013]
First, as a metal film forming step, an Al film 5 is formed on the substrate 1 to a thickness of about 2 μm by sputtering, and then as a resist pattern forming step, a negative type is formed on the Al film 5 as shown in FIG. A photoresist pattern (manufactured by Nippon Synthetic Rubber Co., Ltd .: JSR-CIR-709) is spin-coated at a thickness of 5 to 6 μm, and this is exposed / developed to form a resist pattern 6 having a desired shape on the Al film 5.
[0014]
Next, as shown in FIG. 3B, as the trigger formation step, the Al film 5 is initially etched (about 50 seconds) using an etching solution made of a mixed acid (phosphoric acid: nitric acid: acetic acid = 20: 3: 2). Then, an undercut trigger portion 5 a is formed in the Al film 5 so as to enter the interface direction from the end of the resist pattern 6. This initial etching is isotropic etching in which the etching amounts in the depth direction and the interface direction are equal, and a portion of the Al film 5 not covered with the resist pattern 6 is etched by a small amount by the initial etching.
[0015]
Next, as shown in FIG. 3C, as the interface etching step, the Al film 5 is anisotropically etched using an etchant made of hydrofluoric acid (hydrofluoric acid: nitric acid: water = 1: 5: 15) (about 1 to 5 minutes), the trigger portion 5a advances more in the interface direction than in the depth direction and becomes tapered. That is, the fluoric nitric acid used for this anisotropic etching has a property that the etching rate with respect to Al is slow but the adhesion of the negative photoresist is deteriorated. Although the etching amount is small, the trigger portion 5a has a larger etching amount in the interface direction than in the depth direction.
[0016]
Next, as shown in FIG. 3D, as the main etching step, the Al film 5 is again isotropically etched (about 150 by using an etching solution made of a mixed acid (phosphoric acid: nitric acid: acetic acid = 20: 3: 2). ~ 300 seconds), the portion of the Al film 5 not covered with the resist pattern 6 is completely etched, but the trigger portion 5a having a tapered shape advances by the same amount in the depth direction and in the interface direction, A tapered portion 5 b is formed on the end surface of the Al film 5 covered with the resist pattern 6.
[0017]
Thereafter, as shown in FIG. 3E, the resist pattern 6 is immersed in a stripping solution and wet stripped as a resist stripping process. As a result, the Al film 5 covered with the resist pattern 6 is exposed and the lower electrode 2 described above is removed. A taper 2 a corresponding to the taper portion 5 b of the Al film 5 is attached to the end face of the lower electrode 2.
[0018]
In the case of manufacturing the above-described thin film capacitor element, the lower electrode 2 is formed on the substrate 1 through the steps shown in FIG. 3, and then SiO ₂ is formed on the lower electrode 2 by sputtering (0. The dielectric layer 3 is patterned so as to cover the taper 2a of the lower electrode 2 by etching this SiO ₂ layer using a positive photoresist. Thereafter, an Al film is formed on the dielectric layer 3 to a thickness of 5 μm or more by sputtering, and this Al film is isotropically etched using a negative type photoresist to thereby form the Al film on the dielectric layer 3. The upper electrode 4 may be formed in a pattern, thereby obtaining a thin film capacitor element as shown in FIGS.
[0019]
According to the thin film capacitor element according to the present embodiment configured as described above, the end surface of the lower electrode 2 is processed into a trapezoidal shape by attaching a taper 2a, so that it was sputtered so as to cover the taper 2a. The film thickness of the dielectric layer 3 is made uniform, and a short circuit between the upper and lower electrodes 2 and 4 due to the poor coverage of the dielectric layer 3 can be reliably prevented. Further, in the interface etching step shown in FIG. 3C, the etching amount in the interface direction with respect to the depth direction of the trigger portion 5a is changed by adjusting the etching time when the trigger portion 5a is anisotropically etched. The angle of the tapered portion 5b formed in the subsequent main etching process can be freely controlled. Specifically, when the length in the interface direction of the taper portion 5b is X and the length in the depth direction is Y, X can be increased to about 2 to 20 times with respect to Y by adjusting the anisotropic etching time. Since it becomes long, the taper 2a of a desired angle can be attached to the end surface of the lower electrode 2. Therefore, when the film thicknesses of the lower electrode 2 and the dielectric layer 3 are changed corresponding to the Q value, the element shape, etc. required for the thin film capacitor element, the taper 2a of the lower electrode 2 is changed according to these film thicknesses. What is necessary is just to set to an appropriate angle, and the film thickness of the dielectric material layer 3 can be made uniform by it.
[0020]
In the embodiment, the case where Al is used as the metal film for forming the lower electrode 2 has been described. However, the lower electrode 2 may be formed using a highly conductive metal material other than Al, for example, a Cu film. Is possible. In this case, the process of forming the lower electrode 2 is basically the same as that shown in FIGS. 3A to 3E, and in the interface etching process shown in FIG. The film may be anisotropically etched. In the trigger forming step shown in FIG. 3B and the main etching step shown in FIG. 3D, for example, ammonium persulfate: chloride instead of the mixed acid in the case of the Al film 5 is used. It is necessary to perform isotropic etching of the Cu film using an etching solution comprising sodium: water = 87.6 g: 62.4 g: 2 liters.
[0021]
【The invention's effect】
The present invention is implemented in the form as described above, and has the following effects.
[0022]
After the metal film formed on the substrate is isotropically etched in advance to form an undercut trigger part at the interface of the resist pattern, this trigger part is greatly advanced in the interface direction by anisotropic etching, and then If a series of steps of etching the metal film again to the final depth by isotropic etching to form a tapered portion is adopted, a conductor pattern having a tapered end face can be formed by etching, The taper can be controlled to a desired angle by changing the etching time when anisotropically etching the trigger portion.
[0023]
Further, after applying the above-described method of forming a conductor pattern to the lower electrode of the thin film capacitor element to form a tapered lower electrode (conductor pattern) on the substrate, a dielectric layer and a dielectric layer are formed on the lower electrode including the taper. When the upper electrodes are sequentially stacked, the film thickness of the dielectric layer is made uniform by the taper of the lower electrode, so that a short circuit between the upper and lower electrodes due to poor coverage of the dielectric layer can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is a plan view of a thin film capacitor element according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is an explanatory view showing a manufacturing process of a lower electrode provided in the thin film capacitor element.
FIG. 4 is a plan view of a conventional thin film capacitor element.
5 is a cross-sectional view taken along line AA in FIG.
[Explanation of symbols]
1 Substrate 2 Lower electrode 2a Taper 3 Dielectric layer 4 Upper electrode 5 Al film (metal film)
5a Trigger part 5b Taper part 6 Resist pattern

Claims (2)

A metal film forming process for forming a single layer metal film on a substrate, a resist pattern forming process for forming a resist pattern on the metal film using a negative photoresist, and the metal film isotropic. Etching using etching to form an undercut trigger portion at the interface of the metal film with the resist pattern, and further etching the metal film using anisotropic etching it allows a surface etching step of advancing greatly toward the interface with the trigger portion in the depth direction, by etching to a final depth using isotropic etching the metal film, the depth of the trigger portion The resist pattern is peeled after the main etching step of forming the taper portion by proceeding in the same amount in the direction of the direction and the direction of the interface in these order. The method of forming a conductive pattern, and forming a conductive pattern end face is tapered on the substrate.   The conductor pattern formed by the method according to claim 1 is a lower electrode, and a dielectric layer is formed on the lower electrode including a taper of its end face, and then an upper electrode is formed on the dielectric layer. A method for manufacturing a thin film capacitor element.

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