JPH0610159A - Formation of metallic film pattern - Google Patents

Abstract

PURPOSE:To obtain patterns of a high aspect ratio with a high accuracy by forming an insulating film of an anisotropic fine crystal having a surface bearing at which the crystal is hardly etched perpendicularly to the surface. CONSTITUTION:The insulating film (zinc oxide film) 7 is formed on a conductive substrate consisting of a quartz substrate 1 and a copper film 6. An etching resistant film (resist film) 8 is formed on its surface. The insulating film 7 is etched from the surface not coated with the mask 8 until the etching arrives at the surface of the substrate 6, by which the insulating film 7 is removed. A metallic film (copper film) 2 is packed in the removed parts by electroplating to form the desired metallic film pattern. The insulating film is constituted of the anisotropic fine crystal having the surface bearing at which the crystal is hardly etched perpendicularly to the surface. As a result, armatures of high ampere turns are obtd. in limited areas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal film pattern for producing a plane coil or the like used in a micromachine or the like.

[0002]

2. Description of the Related Art In recent years, research into miniaturization of mechanical elements has been actively conducted in the fields of medical care, biotechnology, industrial machinery and semiconductors. These are called micromachines, and are composed of drive elements called actuators, mechanical elements such as gears, sensing elements, and the like, and mechanical elements are mainly developed using silicon-based materials. In addition, a dream-like application example has been proposed in which these devices are combined with an IC, which is a brain, to perform advanced work in a micro world. These can be mass-produced by utilizing the semiconductor process, and there is a possibility that more intelligent parts and devices can be manufactured in a small number of steps by self-assembly.

However, for example, even one processing technique has many technical development problems. Consider an electromagnetic actuator as an example. The torque obtained by the actuator is almost proportional to the amount of magnetic flux generated in the armature coil, and the magnetic flux is determined by the ampere-turn of the armature coil, that is, (current amount x number of coil turns). It is necessary to increase the cross-sectional area of or to increase the number of strands. Since the size of the installation space of a micromachine is small, it is important to establish a processing technology that utilizes the limited space to the limit, in other words, does not create a wasted space.

In the axial gap type having an air gap in the output axis direction, each constituent element is formed in a plane using a semiconductor processing technique, and is laminated. As shown in FIGS. 2 (a) and 2 (b), the armature coil is a plane coil 21 formed in a clockwise spiral shape from the center to the outer periphery on a fan-shaped quartz substrate 1 having a central angle of 60 ° [Fig. Two
(a)] and a planar coil 22 [Fig. 2 (b)] formed in a counterclockwise spiral shape from the center to the outer periphery are laminated via an insulating film, and the center terminal 31 of the lower coil 21 is connected to the upper coil 22. By connecting to the central terminal 32 of the above, the magnetic flux in the same direction can be generated by the currents flowing through the coils 21 and 22. FIG. 3 shows the stacking method. A fan-shaped lower magnetic pole 4 is formed of iron or permalloy on a fan-shaped quartz substrate 1 [FIG. 3 (a)], and an interlayer insulating film 51 made of silicon oxide is formed on the fan-shaped lower magnetic pole 4.
Cover with [Fig. 3 (b)]. Then, a copper thin film is formed on the insulating film 51, and pattern etching is performed using a mask pattern formed in a spiral shape by a photo process to form the planar coil 21 [FIG. 3 (c)]. Then, it is covered again with the interlayer insulating film 52 to flatten the surface [FIG. 3 (d)].
Then, the planar coil 22 is formed by forming and patterning a copper thin film on the flattened surface, and at the same time, the planar coil 21 is connected through a connection hole (not shown) of the interlayer insulating film 52 [FIG. 3 (e)]. In this way, the planar coils 21 and 22 having different winding directions are repeatedly laminated to form multiple layers [FIG. 3 (f)].
]. The stator of the electromagnetic actuator is assembled from six such laminated bodies.

[0005]

In order to increase the ampere-turn of the coil of the electromagnetic actuator as described above,
When patterning each planar coil, etching with a high aspect ratio makes the spacing between coil strands much narrower than the width of the strands to increase the number of turns. It is necessary to prevent the area from decreasing.

As a conventional high-precision patterning method in which an etching end face is sharp for forming a plane coil, there is a method by a dry process. In the high-precision patterning method using a dry process, a coil is formed by ion beam etching using a metal mask such as tantalum having a large etching rate ratio with respect to the material to be processed, copper. At the same time, the accelerating voltage for extracting the ion beam is lowered, the etching rate ratio with copper is further increased, or the type of etching gas is changed. However, the coil forming by this method has a problem that the etching rate is slow and a large amount of processing takes time, and the process becomes complicated.

Another high-precision patterning method is a plating method. The formation by the plating method is a method in which an insulating plated frame having a pattern in which a desired shape is inverted is formed on a conductive substrate and copper is grown by plating in the opening of the frame to form a coil pattern. The most common method of forming a plating frame is using a photoresist. In this method, a visible light having a wavelength of about 400 nm is used, so that a vertical frame cross-sectional shape cannot be obtained due to light interference and diffraction. As a method of forming a plating frame having a vertical cross-sectional shape, the magazine IEEE Sensors and A
An example is the LIGA process announced by J. Morha et al. in ctuators (1991) p607. The LIGA process is a method of irradiating a short X-ray having a wavelength of 0.5 to 1Å to form a plating frame having a rectangular cross-section with a large aspect ratio. Also using this process, width (diameter) 500 μm, depth (axial length) 200 μm
This micromotor has been prototyped and its operation has been confirmed.

As described above, although the LIGA process is promising, it requires large-scale and complicated equipment because it utilizes synchrotron radiation. Further, the pattern mask also needs to be thin enough to transmit X-rays, and extremely precise technology is required. The object of the present invention is to solve these problems,
It is an object of the present invention to provide a method for forming a metal film pattern having a high aspect ratio, which can describe a thin film pattern having a raised cross section by etching a thin film by a simple method.

[0009]

In order to achieve the above object, the metal film pattern forming method of the present invention comprises forming an insulating film on a conductive substrate, and forming an etching resistant mask on the surface of the insulating film. The desired metal film is formed by etching the surface of the insulation film that is not covered with the mask, removing the insulation film until it reaches the substrate surface, and filling the removed portion of the insulation film with the metal film by electroplating. It is a method of forming a pattern, and the insulating film is made of anisotropic microcrystals having a plane orientation that is difficult to etch almost perpendicularly to the surface. Then, it is effective that the anisotropic crystallites are made of zinc oxide. Further, the conductive substrate has a surface layer made of the same metal as the metal to be plated on the insulating substrate, and after the metal film is filled and formed, the metal surface layer on the substrate below is removed together with the remaining portion of the insulating film. Is effective.

[0010]

In general, since the bond energies are different between plane orientations having different crystal symmetries, the crystal properties are different and anisotropy occurs. Such anisotropy can be inherited even in microcrystals, which are aggregates of crystal grains. The etching rate, which depends on the dissociation rate of atoms, also differs depending on the crystal plane orientation,
If the plating frame is made of an insulating microcrystalline layer and its side wall, which is perpendicular to the surface, is configured with a plane orientation that is difficult to etch, it becomes possible to process the microcrystalline layer with a high aspect ratio by etching. It can be used to form a metal layer pattern with raised sidewalls.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 (a) to 1 (f) in which the same parts as those in FIGS. 1 (a) to 1 (f) show only one coil layer of the stator of the electromagnetic actuator.
This is the part corresponding to steps (c) and (d). First, a copper film 6 serving as a plating electrode is vapor-deposited on a quartz substrate 1 [FIG.
(a)] Next, a microcrystalline zinc oxide film 7 having a thickness of 5 μm was formed on the substrate at 200 ° C. to 400 ° C. in a high vacuum by a sputtering method [FIG. 1 (b)]. Subsequently, the coil pattern was transferred to the resist film 8 by using a normal photo process [Fig.
(c)]. Further, the zinc oxide film 7 was patterned by dry etching using a mixed gas of CF ₄ and O ₂ as a reaction gas [FIG. 1 (d)]. Then, after removing the resist film 8, a copper film 6 having a thickness of 5 μm was formed by plating the copper film 6 as an electrode, and the zinc oxide film 7 was removed by using nitric acid [FIG. 1 (e)]. Next, after the exposed copper film 6 was also removed by etching, the silicon oxide film 5 was formed by the CVD method and flattened [FIG. 1 (f)]. After that, if a silicon oxide film is further laminated on the flat surface of the silicon oxide film 5 to form an interlayer insulating film and the process returns to the step of FIG. 1A, the laminated structure of the coil pattern 2 can be formed.

The taper angle θ of the coil pattern 2 obtained in this example was 80 °. However, when an isotropic amorphous silicon oxide film was used instead of the anisotropic zinc oxide microcrystalline film 7, θ was only 65 °. Although the plating frame is formed of zinc oxide by the sputtering method in the above-mentioned examples, the vapor deposition method, the ion beam sputtering, the molecular beam epitaxial method, etc. can be applied to the formation technology of the anisotropic insulating film, and the material is oxidized. It goes without saying that other anisotropic insulators can be used in addition to zinc.

[0013]

According to the present invention, a plating frame for performing fine processing of a metal film pattern by a plating method is formed by anisotropically etching an anisotropic microcrystalline insulating layer. A pattern with a high aspect ratio close to ° was obtained with high accuracy. Therefore, a multi-stage laminated planar coil of an electromagnetic actuator as a micromachine can be manufactured by this method to obtain an armature with a high ampere-turn in a limited area.

[Brief description of drawings]

FIG. 1 (a) shows a plane coil manufacturing process of one embodiment of the present invention.
To (f) in cross section

FIG. 2 shows an example of a pattern of a plane coil manufactured according to the present invention, and (a) and (b) are plan views of each layer plane coil.

FIG. 3 is a cross-sectional view showing a conventional planar coil manufacturing process in the order of (a) to (f).

[Explanation of symbols]

 1 Quartz substrate 2 Copper film 5 Silicon oxide film 6 Copper film 7 Zinc oxide film 8 Resist film

Claims (3)

[Claims] 1. An insulating film is formed on a conductive substrate, an etching resistant mask is formed on the surface of the insulating film, and etching is performed from the surface of the insulating film not covered with the mask until insulation reaches the substrate surface. This is a method of forming a desired metal film pattern by removing the film and filling the removed portion of the insulation film with a metal film by electroplating. A method of forming a metal film pattern, which comprises an anisotropic fine crystal. 2. The anisotropic crystallite of zinc oxide.
A method for forming a metal film pattern as described. 3. The conductive substrate has a surface layer made of the same metal as the metal to be plated on the insulating substrate, and after the metal film is filled and formed, the remaining portion of the insulating film and the metal surface layer of the underlying substrate are provided. The method for forming a metal film pattern according to claim 1 or 2, wherein the metal is removed.