JP4046175B2 - Fabrication method of fine structure element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an element for consumer equipment and a fine structure element used for communication.
[0002]
[Prior art]
The fine structure element is manufactured by applying a fine processing technique by lithography. The fine structure element includes fine beams as structural elements. That is, by applying a microfabrication technique by lithography, a fine beam such as a cantilever or a beam is produced in the fine structure element. The microstructure element uses the elastic and mechanical properties and functions of the fabricated beam. This fine structure element is generally called a micromachine or MEMS (Micro Electromechanical Systems), and is widely used as an element for consumer equipment such as a high-sensitivity sensor and an optical switch and for communication.
[0003]
The most important point in the fabrication of the microstructure element is the process of fabricating the beam having its elastic and mechanical functions. As an example thereof, FIG. 6 shows a process of manufacturing a cantilever, that is, a cantilever by lithography using silicon which is a semiconductor. In this manufacturing process, an SOI (Silicon on Insulator) substrate is used as shown in FIG. The SOI substrate is obtained by forming a silicon oxide thin film 102 and a single crystal silicon thin film 103 on a single crystal silicon substrate 101. The single crystal silicon substrate 101 is a substrate made of silicon crystal, and the silicon oxide thin film 102 is a silicon oxide film formed near the surface of the single crystal silicon substrate 101. The single crystal silicon thin film 103 is a single crystal silicon thin film that covers the silicon oxide thin film 102. Such SOI substrates are generally widely available on the market.
[0004]
The in-plane shape of the SOI substrate is processed into a mesa shape using a photolithography technique as shown in FIG. Next, as shown in FIG. 6C, only the silicon oxide thin film 102 is selectively etched using hydrofluoric acid. Thus, a silicon cantilever 103A having the same thickness as the single crystal silicon thin film 103 is manufactured.
[0005]
The silicon cantilever 103A formed in this way can be bent in the vertical direction. By detecting this bending, a highly sensitive position / acceleration sensor can be produced. An element characterized by externally controlling the bending of the silicon cantilever 103A by applying an electric field or the like from the outside is also widely applied to a probe of an atomic force microscope.
[0006]
[Problems to be solved by the invention]
By the way, the response speed of the fine structure element generated by the manufacturing process, for example, the response speed of the acceleration sensor using the cantilever is given by the reciprocal of the natural frequency of the cantilever. In general, the cantilever with a smaller element size has a higher natural frequency. Therefore, in order to enable high-speed response, the size of the cantilever must be reduced.
[0007]
However, the size of the cantilever cannot be reduced below the limit due to the processing accuracy of the current lithography technology. The typical length is about 1 micron in the case of photolithography, and about several tens of nanometers in the case of electron beam lithography.
[0008]
In the latter electron beam lithography technique, it is known that the crystallinity is greatly deteriorated by irradiation with high-energy and high-intensity electron beams in the exposure process and damage caused by subsequent etching. This deterioration in crystallinity significantly reduces the mechanical resonance characteristics of the beam, and thus adversely affects the detection sensitivity of an element such as a charge sensor using the mechanical resonance of the beam. Similar problems arise for any device including such extremely fine beams as structural elements, and limit the response speed and resonance characteristics of the device.
[0009]
An object of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing a microstructure element capable of manufacturing a beam which is smaller than the processing accuracy limit of the lithography technique and maintains high crystallinity.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention of claim 1 has a fine beam as a structural element and detects or drives its elastic displacement or mechanical movement as at least a part of the operating mechanism. in the method for manufacturing a microstructure element having, on the surface of the solid crystalline material used as the substrate, to form a monoatomic steps or monomolecular steps be subjected to a surface treatment, then, the solid crystalline material by crystal growth, the A first step of forming a bundle of monoatomic steps or monomolecular steps, a second step of selectively growing a beam material for constituting a beam along the bundle of steps, and the beam material A third step of forming a beam made of the beam material by selectively removing only the solid crystalline material underneath it by selective etching. A method for manufacturing a microstructure element according to.
[0011]
The invention according to claim 2, Oite the manufacturing method of a fine structure element according to claim 1 for the in the third step in a direction intersecting the beam material grown along the bundle of the step, the Perform mesa etching of a part of the beam material and the solid crystal material under the beam material to form a linear step, and then select only the solid crystal material under the grown beam material It is characterized by being removed by mechanical etching.
[0012]
According to the present invention, in the first process, a single molecule or a bundle of monoatomic steps is formed by crystal growth. Then, the beam is produced by using the second process and the third process using selective growth and selective etching there. As a result, it is possible to produce a microstructure element having extremely fine and high-quality beams as compared with the conventional technique using lithography.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, an example in which an indium arsenic cantilever is formed as a beam of a fine structure element is taken as an example. In this embodiment, the (110) gallium arsenide substrate 1 slightly inclined by 5 degrees in the (111) A direction is used. The gallium arsenide substrate 1 introduced into the crystal growth apparatus is heated to 600 ° C. in a state where a sufficient amount of arsenic molecular beam sufficient to compensate arsenic detachment from the surface is supplied to the surface. As a result, the oxide film covering the surface of the gallium arsenide substrate 1 is thermally decomposed and evaporated. Thereby, a surface where gallium arsenide is exposed is formed. Furthermore, when the heating for 10 minutes or more is continued, the monomolecular steps on the surface of the gallium arsenide substrate 1 are evenly distributed by the thermal energy.
[0014]
Thus, as shown in FIG. 1, the monomolecular step 1A is formed on the gallium arsenide substrate 1 evenly distributed on the surface of the substrate.
[0015]
The monomolecular steps 1A evenly distributed on the surface of the gallium arsenide substrate 1 are gradually gathered by crystal growth of gallium arsenide using the first condition, and as shown in FIG. A bundle 1B is formed. This first condition will be described below.
[0016]
When a single molecular step bundle (or bundle of monoatomic steps) 1B is formed on the solid surface by crystal growth or surface treatment after crystal growth, and different materials are also grown on the surface, depending on the conditions, A phenomenon in which crystal growth proceeds selectively in a bundle and a thin-line semiconductor is formed has been reported in several material systems.
[0017]
For example, a gas source MBE using Arsine as a source of As on a gallium arsenide substrate 1 slightly tilted by 3 to 6 degrees in the (111) A direction from the (110) plane orientation. Using (molecular beam epitaxial growth), crystals are grown at a relatively slow growth rate (about 200 to 400 nanometers / hour) (first condition). Thereby, a bundle of molecular steps having a height of about 10 nanometers is formed. Japanese Journal of Applied Physics, Volume 34, Part 1, No. 8, 1995, Japanese Journal of Applied Physics, Vol. 34, Part 1, No. 8, 1995, 4411-4413. pp.4411-4413) by M. Takeuchi et al.
[0018]
In this way, a bundle 1B of monomolecular steps is formed on the gallium arsenide substrate 1 under the first condition. The above is the first process.
[0019]
When indium arsenide is crystal-grown using the second condition on the surface on which the monomolecular step bundle 1B is formed, indium arsenide grows selectively on the step bundle, as shown in FIG. A thin wire 2 of indium arsenide is formed. This second condition will be described below.
[0020]
On the bundle of single molecular steps (or bundle of single atom steps) formed by the first condition, the InAs adsorbed on a flat terrace portion without molecular steps, such as about 580 degrees, grew at a temperature at which it evaporates. Indium arsenide grows selectively along the bundle of steps (second condition). Japanese Journal of Applied Physics, Volume 38, Part 1, No. 8, 1999 (Japanese Journal of Applied Physics, Volume 38, Part 1, No. 8, 1999, 4673-4675) pp.4673-4675) by S.Torii et al.
[0021]
The reason why such a phenomenon occurs is that chemically active unpaired bonds are arranged at high density on the molecular step, so that chemical bonds are easily formed and crystal growth proceeds selectively. The fine line formed by this phenomenon is narrow and has a width of about nanometers. This fine wire has a much smaller size than a fine wire structure artificially produced by electron beam lithography. In addition, since the fine line formed by the natural phenomenon uses a high-purity and high-quality crystal growth technique, the above-described problem of crystallinity degradation due to electron beam lithography does not occur.
[0022]
Thus, the indium arsenic fine wire 2 is formed on the bundle 1B of monomolecular steps. The above is the second process.
[0023]
Thereafter, mesa etching is performed on the surface of the gallium arsenide substrate 1 at room temperature using a solution in which sulfuric acid, water, and hydrogen peroxide water are mixed in a ratio of 5: 25: 1 using photolithography, as shown in FIG. As described above, a linear step 1C is formed in a direction intersecting with the thin wire 2 of indium arsenide. Thereafter, only gallium arsenide is selectively etched for several tens of seconds at room temperature using a solution in which ammonia, water, and hydrogen peroxide are mixed at 1: 30: 120. Thereby, the indium arsenic cantilever 2A is formed as shown in FIG. The above is the third process.
[0024]
As described above, according to this embodiment, when the in-plane shape of the fine structure is cut out, the lithography technique is performed by cutting out the thin line grown along the bundle of steps by selective etching without using the lithography technique. It is possible to produce a beam that is smaller than the processing accuracy limit of the above and maintains high crystallinity.
[0025]
As a result, an indium arsenic cantilever 2A, which is an extremely fine and high-quality semiconductor cantilever having a length of 30 nanometers, a width of 10 nanometers, and a thickness of 6 nanometers, which cannot be produced by electron beam lithography, could be produced. .
[0026]
The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention.
[0027]
For example, in this embodiment, a linear step is formed by mesa etching after forming a thin line. However, even when the substrate is cut by cleavage and selective etching is performed from the cross section, the essential part of the present invention is Obviously, it does not deviate.
[0028]
Further, in this embodiment, a cantilever structure called a so-called cantilever beam has been described. However, in the range not departing from the essential part of the present invention, other cantilever structures such as a cantilever structure in which both sides are fixed to a substrate are used. Needless to say, the present invention can be applied to any microstructure that can be elastically displaced or mechanically moved.
[0029]
Furthermore, in this embodiment, indium arsenide is used as the material of the cantilever and gallium arsenide is used as the substrate material. However, as a material constituting these, not only a semiconductor but also a single crystal thin film such as a metal, an insulator, a superconducting material, etc. It goes without saying that all kinds of solid materials to which the growth method can be applied can be used.
[0030]
【The invention's effect】
As described above, according to the present invention, a bundle of single molecules or monoatomic steps is formed by crystal growth, and a beam is produced by using selective growth and selective etching thereon, thereby producing a conventional beam. Compared with a technique using lithography, an element having extremely fine and high-quality beams can be manufactured. Thereby, it is possible to manufacture a micromachine and a MEMS element in which response speed and detection sensitivity are remarkably improved.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a method for manufacturing a microstructure element according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a method for manufacturing a microstructure element according to an embodiment of the present invention.
FIG. 3 is a schematic view showing a method for manufacturing a microstructure element according to an embodiment of the present invention.
FIG. 4 is a schematic view showing a method for manufacturing a microstructure element according to an embodiment of the present invention.
FIG. 5 is a schematic view showing a method for manufacturing a microstructure element according to an embodiment of the present invention.
FIG. 6 is a schematic view showing a conventional process for producing a cantilever using silicon which is a semiconductor.
[Explanation of symbols]
1 Gallium Arsenide Substrate 1A Monomolecular Step 1B Monomolecular Step Bundle 1C Linear Step 2 Indium Arsenic Fine Wire 2A Indium Arsenic Cantilever

Claims (2)

In a method for manufacturing a fine structure element having a fine beam as a structural element and detecting or driving its elastic displacement or mechanical movement as at least a part of an operation mechanism,
On the surface of the solid crystalline material used as the substrate, to form a monoatomic steps or monomolecular steps be subjected to a surface treatment, then, by crystal growth of the solid crystalline material, flux of the monoatomic steps or monomolecular step A first step of forming
A second step of selectively growing a beam material for constituting the beam along the bundle of steps;
And a third step of forming a beam made of the beam material by selectively removing only the solid crystal material below the beam material after the growth of the beam material, and forming a beam made of the beam material. . In the third step, mesa etching of a part of the beam material and the solid crystalline material under the beam material is performed in a direction intersecting with the beam material grown along the bundle of steps , 2. The method for producing a microstructure element according to claim 1, wherein a linear step is formed, and thereafter, only the solid crystal material under the grown beam material is removed by selective etching.

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