JPH10140399A - Pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively, conveniently and minutely form a thick pattern with high precision by using a conductive material provided with a stencil mask as an anode and applying a current between the anode and a cathode in an electrolyte soln. to electrolytically etch the surface. SOLUTION: A body 41 to be worked as an anode and gold, etc., as a cathode 43 are arranged in an electrolyte soln. 42. The body 41 is formed by arranging a stencil mask consisting of a patterned resist on a conductive material made of a metal such as Pb, Sn, Mo, Ni, Co, In, Cd, Fe, Ga, Zn, Cr, Ta, V, Mn, Ti, Al and Cu having 0.34V standard electrode potential. Besides, an aq. electrolyte soln. such as an electroplating bath and an electropolishing bath is appropriately used as the electrolyte soln. 42. A constant current is applied to both electrodes from a constant-current power source 44. The metal surface is electrolytically etched in this way to form a pattern having several nm to several mm size and several Å to several ten mm thickness.

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 fine pattern on a workpiece made of a conductive material, which method can be applied to manufacture of a micromachine or the like.

[0002]

2. Description of the Related Art In recent years, research and development on microfabrication for the purpose of manufacturing micromachines and the like have been vigorously pursued in conjunction with the progress of miniaturization technology of semiconductor integrated circuit elements. For a pattern having a pattern size of several μm or more and a thickness of several mm to several mm, “L
An "IGA process" has been developed. "LIGA" is the German word for Lithographie Galva
noformung It is a coined word that took the initials of Abformung. The "LIGA process" uses synchrotron radiation as a light source for transfer to form a mask (stencil mask) that is the basis of the pattern of the product.
Another feature is that an electrolytic plating method is used to form a pattern in the depth direction.

In general, the pattern size referred to here means the pattern pitch in the periodic pattern shown in FIGS. 1 and 2, but in the non-periodic pattern, the size of the diameter and the elliptical pattern are used for the circular pattern. For the major and minor diameters, for the square pattern, the dimensions of the sides, for the rectangular pattern, the dimensions of the long and short sides, and for the patterns of other shapes, these Means a dimension defined in a manner similar to.

As other forming methods, RIE, ion beam etching, wet etching, electrolytic plating and the like are known. Since the pattern forming method by the electrolytic plating method can be performed with inexpensive and simple equipment, it is very effective in terms of manufacturing cost. The pattern formation by the electrolytic plating method is easy to form a thick pattern and has excellent transfer characteristics.
Applications to the production of fine processing patterns such as diffraction gratings are being studied. A method for forming a pattern by electrolytic and electroless plating methods and a method for manufacturing an X-ray reflection type mask are disclosed in Japanese Patent Application No. Hei.
-11968 and Japanese Patent Application No. 7-171982. When a fine pattern is formed by electrolytic or electroless plating, it is generally performed under atmospheric pressure, so there is no need to use a vacuum system as in dry etching, and the cost is low compared to dry etching, In addition, the feature is that the line width control and the control of the cross-sectional shape and the like can be performed very easily.

[0005]

What is demanded of a microfabrication method for manufacturing a micromachine or the like is to form a fine, high-accuracy, and thick pattern at a low cost. The wet etching method and the RIE method cannot respond to this request. The reason is that the wet etching method and the RIE method require highly accurate process condition control that is almost impossible to realize industrially in order to accurately control the line width of a pattern having a large thickness. Because.

In addition, since the RIE method and the ion beam etching method are performed in a vacuum, a vacuum system such as an exhaust system and a vacuum tank is indispensable, and a large amount of equipment is required. It is not an advantageous method in terms of manufacturing cost. On the other hand, the electrolytic or electroless plating method can be generally performed at atmospheric pressure, and therefore is a low cost method as compared with the RIE method or the ion beam etching method. Is easy to control. However, there is a limit in applying this method to fabrication of a micromachine. This is because application to micromachines often requires the thickness of the pattern of the formed body to be several hundred μm or more (several mm or less), and it is necessary to create such a thick and highly accurate pattern by plating. Is impossible.

In general, the thickness of a mask pattern (eg, a resist pattern) at the time of pattern formation is equal to or greater than the thickness of a pattern to be processed (generally, about 1.0 to 1.0). In order to form a pattern having a thickness of several hundred microns to several millimeters, the thickness of the mask pattern must be at least 1 mm.
You have to do more. In general, when forming a fine pattern having a pattern size of several μm or less, the thinner the resist thickness used at the time of drawing to form a mask is, the more preferable it is. In this case, the thickness of the mask is limited to several μm to several tens μm at most.
This is because the light absorption of ultraviolet light in the resist is high, and
This is because an amount of light sufficient to excite the photochemical reaction cannot be obtained below the resist layer of m or more. Therefore, it is impossible to form a pattern having a thickness of several hundreds of μm to several mm by the plating method using the single-layer resist method.

If a multilayer process used in an electronic device manufacturing process is used, a stencil mask having a thickness of several tens to 100 μm can be formed.
Although it is possible to form a pattern with a thickness of about 300 μm, the thickness is still insufficient, and the process becomes complicated. In addition, extremely precise process control is required to control the line width of the stencil mask with high precision. Therefore, the production cost increases.

For the above reasons, the thickness of the pattern cannot be made several hundred μm or more by the electrolytic or electroless plating method. The "LIGA process" was developed for this problem. This method has a high transmittance in the resist when forming a resist pattern, and also uses synchrotron radiation light, which has very little influence of diffraction, as an exposure light source.
It is easy to form a thick pattern. Since the wavelength range of the emitted light is several Å and the transmittance in the resist is extremely high, a resist pattern having a high aspect ratio can be formed. LIG
By the A process, from 400 μm of PMMA to 1
There is a report that a stencil mask pattern having a thickness of about mm was formed. Recently, the LIGA process has
It has been reported that a pattern having a thickness of about mm can be formed. However, a disadvantage of this technology is that generating synchrotron radiation requires enormous capital investment, and only a few facilities are currently available worldwide. Since the LIGA process cannot be easily applied to many people, it cannot be a preferable manufacturing technique of a micromachine having great potential for future development. It is inevitable that it will hinder the development of new technologies.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above circumstances, and provides a novel pattern capable of easily forming a pattern having a fine pattern size and a large pattern thickness using simple equipment. It is an object to provide a forming method.

[0011]

In order to solve the above problems, in the process of searching for a new pattern forming method, we happened to find that the surface of the conductive material in the electrolyte solution caused the current to flow using the conductive material as the anode. I noticed the phenomenon of electrolysis when she was flowing. Although this phenomenon has been known for a long time, there is no report that it was studied for its application to micromachines. Focusing on this phenomenon, as a result of earnest research that this may be applied to micromachines, a solid consisting of the conductive material with a stencil mask pattern arranged on the surface is used as an anode, and a counter electrode made of a conductive material is used as a cathode. When a constant current power supply is connected between both electrodes, the surface of the conductive material on the anode side is electrolyzed, and as a result, a pattern can be formed, and a pattern with a thickness of several hundred μm to several mm can be formed. I found something.

The present invention proposes a completely new micromachining method for easily forming a microstructure by forming a thick film pattern by electrolytic etching. That is, the present invention firstly provides a `` workpiece on which a stencil mask composed of at least a first conductive substance and formed of a patterned resist is arranged, and a cathode composed of a second conductive substance. Placing in an electrolyte solution, using the first conductive material as an anode, passing a current between the anode and the cathode, and etching the surface of the first conductive material by electrolysis ( Hereinafter, a pattern forming method (claim 1), which is characterized by an electrolytic etching method, is provided.

The present invention secondly provides a "pattern forming method according to claim 1, wherein the object to be processed is a substrate". Thirdly, the present invention provides "a pattern forming method according to claim 1, wherein the workpiece is a substrate on which a coating made of the first conductive substance is disposed."

[0014] The present invention is also directed to a fourth aspect in which "the first conductive substance is made of a metal, and its standard electrode potential is 0.34.
V or less, and the pattern forming method according to any one of claims 1 to 3 (claim 4) is provided. Further, the present invention provides a fifth aspect in which “the metal is Pb, Sn, M
o, Ni, Co, In, Cd, Fe, Ga, Zn, C
5. The pattern forming method according to claim 4, wherein the metal is one or more metals selected from the group consisting of r, Ta, V, Mn, Ti, Al, and Cu. provide.

Further, the present invention provides a method according to any one of claims 1 to 5, wherein the current is kept constant during the etching, and the electrolyte solution is an aqueous electrolyte solution. The present invention also provides a pattern forming method according to the present invention (claim 6). In a seventh aspect of the present invention, the pattern forming method according to any one of claims 1 to 6, wherein a pattern formed on the workpiece has a size of several nm or more and several mm or less. 7) ”is provided.

The present invention eighthly provides that "the thickness of the pattern formed on the workpiece is not less than several angstroms and not more than several tens mm". The present invention also provides a pattern forming method according to the present invention (claim 8). Here, the aqueous electrolyte solution may be either an electrolytic plating bath or an electrolytic polishing bath.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the pattern forming method of the present invention will be briefly described below. First, a resist is applied as a stencil mask to a metal substrate or a substrate on which a metal film is arranged. Next, a negative image or a positive image of a required pattern is exposed on the resist surface. Next, perform development,
A resist pattern is formed. Next, these substrates are set in the electrolytic etching system shown in FIG. 3 and are etched under predetermined conditions to form a target pattern.

In order to form a pattern having a more complicated shape, a part of a pattern made of a conductive material finely processed by some other method is partially etched by the pattern forming method shown in the preceding paragraph, Alternatively, a more complicated pattern is formed by repeating the pattern forming method shown in the preceding paragraph a plurality of times. By using the pattern forming method according to the present invention, it is possible in principle to form a pattern having an unlimitedly large thickness even if the thickness of the stencil mask is small. That is, a layer made of a conductive material is placed on a substrate made of a conductive material or an insulating substrate, and the
As long as a resist pattern having a thickness of m is formed, a fine pattern having a desired pattern size and a pattern thickness of several tens of mm can be easily formed.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0020]

Embodiment 1 FIG. 1D is a cross-sectional view of a fine pattern formed according to Embodiment 1. A microfabrication method by the electrolytic etching method according to the first embodiment will be described with reference to FIG. First, a resist for electron beam (Tokyo Oka OEBR1000, FIG. 1B) is formed on a Cu substrate (FIG. 1A) 1 having an area of 100 mm × 100 mm and a thickness of 2 mm with a thickness of about 0.5 μm. Applied. Next, the resist surface was drawn by using an electron beam drawing apparatus, exposed, and developed and baked to form a resist pattern (FIG. 1B).
2). In the case of the present resist, the exposed portion of the resist was dissolved by development.

The resist pattern formed here functions as a stencil mask at the time of electrolytic etching, and the resist portion on the substrate remains without being electrolytically etched. As the cathode, a Cu substrate having an area of 20 mm × 20 mm and having Au deposited on both sides to a thickness of 0.1 μm by magnetron sputtering was used. A Cu substrate as a workpiece and a cathode were each placed in an aqueous electrolyte solution, each was connected to a constant current power supply, and a constant current was passed.
Note that a copper pyrophosphate bath was used for the aqueous electrolyte solution. The composition of the copper pyrophosphate bath was an aqueous solution of copper pyrophosphate 100 g / l, metallic copper 30 g / l, potassium pyrophosphate 300 g / l, and ammonia water 1 mol / l.

As the conditions for electrolytic etching, a current density of 1
0 mA / cm ² , pH 3-4, and bath temperature 50 ° C.
And At this time, the electrolytic etching rate was about 1.7 μm.
However, the electrolytic etching rate could be easily changed from 1 μm / min to 100 μm / min by changing the current density. In this embodiment, 500
Since a pattern having a depth of μm was required, the electrolytic etching was continuously performed for about 5 hours.

After the electrolytic etching, the connection was disconnected from the constant current power supply, and the sample and the counter electrode were washed with pure water and dried (FIG. 1 (c)). Thereafter, the resist pattern used as a stencil mask on the sample substrate was removed (FIG. 1D). The resist pattern could be removed by, for example, washing with an organic solvent such as acetone, or oxygen ashing.

Through the above steps, a pattern having a thickness of 500 μm was formed on the substrate.

[0025]

[Embodiment 2] FIG. 2 (d) shows a fine pattern formed by the embodiment 2.
It is a cross section schematic diagram of a pattern. Referring to FIG.
A method for forming a pattern by electrolytic etching will be described. surface
On a 4 inch x 4 inch quartz substrate (Fig. 2 (a) -1)
Ni was deposited to a thickness of about 100 μm by electrolytic plating.
(FIG. 2 (a) -3). Electrolytic plating at this time is nickel sulfate
Solution as a plating bath, the bath temperature is about 50 ° C, and the current density is
About 0.03A / cm ^TwoAnd Quartz substrate from plating bath
After taking out, washing and drying, the resist for electron beam is put on the Ni layer.
(Tokyo Oka OEBR1000) to a film thickness of about 0.3μm
Coating by spin coating method, followed by pre-bake treatment
Was. Pattern writing on this resist using an electron beam writer
After that, post-baking and developing are performed, and
Then, stencil mask pattern was obtained (FIG. 2)
(b) -20). After drawing the resist, develop the electrolytic etch
The drawing was performed so that the part to be brushed was exposed.

A quartz substrate (namely, a workpiece) provided with a Ni layer on which a stencil mask is disposed and a cathode are each placed in an aqueous electrolyte solution, and each is connected to a constant current power supply.
A constant current was applied. As the cathode, a platinum substrate having an area of 15 mm × 15 mm was used. As the electrolyte aqueous solution, an aqueous solution of 450 g / l of nickel sulfamate, 30 g / l of boric acid, and 0.5 g / l of sodium lauryl sulfate was used. The electrolytic etching conditions were a current density of about 0.1 A / cm ² , pH
And the bath temperature was 50 ° C.

When patterning Ni having a thickness of 100 μm, the electrolytic etching time required about 50 minutes. The electrolytic etching rate largely depends on the current density, and is higher when the current density is higher and is lower when the current density is lower. That is, it is possible to set a current density that can be easily controlled by the thickness to be etched. In the case of the present embodiment, the voltage sharply increases when Ni is electrolytically etched to expose the quartz substrate. Therefore, the time when the voltage suddenly starts increasing is defined as the end point of the etching step.

Thus, a resist pattern having a thickness of about 0.3 μm is used as a stencil mask to form an about 10 μm thick Ni layer.
It was possible to process a pattern having a thickness of 0 μm (FIG. 2).
(c)). After the electrolytic etching, the sample surface was sufficiently washed with pure water and dried, and then the resist and the pattern used as the stencil mask were removed (FIG. 2D). For the removal of the resist pattern, for example, the resist pattern could be removed by washing with a commercially available stripping solution exclusively for resist, an organic solvent such as acetone, or an oxygen ashing method. Through the above steps, a Ni pattern having a thickness of about 100 μm could be formed. As described above, in Examples 1 and 2, each of Cu and Ni was used as a conductive material to be subjected to electrolytic etching. However, in general, when a metal is used as a conductive material, when selecting a metal, the standard electrode potential of the metal is used. It turns out that the values have to be taken into account. The standard electrode potential is a value indicating the tendency to ionize, and the smaller the value of the standard electrode potential is, the larger the absolute value is when the value of the standard electrode potential is negative.
The ionization tendency also increases. When a substance having a high ionization tendency is used as an anode in an aqueous solution, it is ionized and dissolved. In other words, a substance having a higher ionization tendency is more likely to perform electrolytic etching, and a substance having a lower ionization tendency is more difficult to perform electrolytic etching.

During the course of the study, we investigated the electrolytic etching characteristics of various materials as anodes. As a result, they have found that the possibility of electrolytic etching depends heavily on its ionization tendency. That is, although Au, Pt, and Ag cannot perform electrolytic etching, Cu, Sn, M
With o, Cr, etc., electrolytic etching was possible. As a result of investigating this phenomenon, the standard electrode potential was 0.34.
It has been found that electrolytic etching is possible for substances having a voltage of V or less, but electrolytic etching is not possible for substances having a standard electrode potential of 0.7 V or more. The metal material preferably used for pattern formation is such that the standard electrode potential is 0.1.
Pb, Sn, Mo, Ni, Co, In, C of 34 V or less
d, Fe, Ga, Zn, Cr, Ta, V, Mn, Ti,
One or more metals selected from the group consisting of Al and Cu.

[0030]

As described above, according to the pattern forming method by the electrolytic etching method of the present invention, a constant current is applied to the sample surface in an aqueous electrolyte solution only by forming a resist pattern having an appropriate thickness in advance. A pattern can be formed by an extremely simple method. The main equipment may be a constant temperature water bath, a constant current power supply, a device for recording etching conditions, and the like.

Since it is not necessary to use a vacuum system unlike the reactive ion etching method (RIE) or the ion beam etching method, it is possible to form an equivalent or larger fine pattern with a very inexpensive apparatus configuration, and to form a very thick pattern. Can be formed. The aqueous electrolyte solution does not differ in composition from a general electrolytic plating solution, and the composition of the solution can be roughly controlled by the use time and the like, so that the management is easy. A stencil mask (for example, a resist pattern) having a thickness of about 1 μm
A pattern having the above thickness can be formed. Further, in order to miniaturize the pattern size, since the pattern formation is performed faithfully to the mask pattern, it is only necessary to make the mask pattern fine. Furthermore, the number of steps in the pattern formation process is smaller than that in the case where the reactive ion etching method or the like is used, and the microfabrication method is extremely excellent in productivity.

Further, as the most important effect, when the method of forming a fine pattern by electrolytic etching according to the present invention is used, a part of a pattern made of a conductive material finely processed by any method is further reduced by the method of the present invention. By partially etching in, or by repeating the method of forming this fine pattern a plurality of times,
Further, a pattern having a more complicated shape can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a forming process of a pattern forming method according to a first embodiment.

FIG. 2 is a schematic cross-sectional view illustrating a forming process of a pattern forming method according to a second embodiment.

FIG. 3 is a schematic cross-sectional view of an electrolytic etching system in the pattern forming method according to the first or second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2, 20 ... Mask (For example, resist pattern) 3 ... Layer to be etched (also used as an electrode layer) 4 ... Pattern thickness 5 ... Pattern size 41 ... Sample (processing) 42) Electrolyte solution 43 ... Cathode 44 ... Constant current power supply 45 ... Thermostat 46 ... Thermometer

Claims (8)

[Claims] 1. A workpiece comprising at least a first conductive substance, on which a stencil mask made of a patterned resist is arranged, and a cathode made of a second conductive substance are placed in an electrolyte solution. Placed, using the first conductive material as an anode, passing a current between the anode and the cathode, and etching the surface of the first conductive material by electrolysis (hereinafter referred to as electrolytic etching). Method for forming a pattern. 2. The pattern forming method according to claim 1, wherein the workpiece is a substrate. 3. The pattern forming method according to claim 1, wherein the workpiece is a substrate on which a coating made of the first conductive material is disposed. 4. The method according to claim 1, wherein the first conductive material comprises a metal,
4. The pattern forming method according to claim 1, wherein the standard electrode potential is 0.34 V or less. 5. The method according to claim 1, wherein the metal is Pb, Sn, Mo, Ni, C
o, In, Cd, Fe, Ga, Zn, Cr, Ta, V,
5. A metal selected from the group consisting of Mn, Ti, Al, and Cu, or two or more metals.
4. The pattern forming method according to 1. 6. The pattern forming method according to claim 1, wherein said current is kept constant during etching, and said electrolyte solution is an electrolyte solution. 7. The pattern forming method according to claim 1, wherein the size of the pattern formed on the workpiece is several nm or more and several mm or less. 8. The pattern forming method according to claim 1, wherein the thickness of the pattern formed on the workpiece is not less than several angstroms and not more than several tens of mm. .