KR101040676B1 - Smith-Purcell Free Electron Laser Device Fabrication Method using Employing Wet Etched Grating - Google Patents

Abstract

The present invention relates to a method for fabricating a Smith-Percell free electron laser device, which is a broadband, high power, small sized electromagnetic wave oscillation device using a metal lattice circuit fabricated by applying an anisotropic wet process of a silicon wafer and semiconductor processing technology. Applying an anisotropic wet process applied to silicon wafers for the fabrication of metal lattice circuits for the fabrication of Smith-Pursel free electron laser devices using circuits fabricated by wet process, the selective process is easy and relatively inexpensive. In addition, large metal grid circuits can be manufactured in large quantities in a short time. In addition, the grating circuit structure having a resonator type structure can increase the electric field strength on the upper surface of the grating circuit, which is important when interacting with the electron beam, thereby increasing the oscillation output and efficiency, which is necessary for the back wave oscillation. The minimum current can be reduced.

Smith-Pursel Free Electron Laser, Wet Process, Metal Lattice Circuit, Silicon Wafer

Description

Smith-Purcell Free Electron Laser Device Fabrication Method using Employing Wet Etched Grating}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a free electron laser device. In particular, Smith-Purcell (Smith-), which is a broadband, high-power, compact electromagnetic wave oscillation device employing a metal lattice circuit fabricated using anisotropic wet process and semiconductor processing technology of a silicon wafer. Purcell) relates to a method for manufacturing a free electron laser.

The oscillation element that generates electromagnetic waves is a Smith-Percell free electron laser device that generates electromagnetic waves from the millimeter wave band to the terahertz wave band or more. The one-dimensional periodic structure consisting of a metal lattice and an electron beam traveling through the circuit Interactions generate electromagnetic waves. As described above, in order to operate the Smith-Pursel free electron laser, a circuit having a metal lattice structure must be manufactured. Conventionally, processing methods such as deep reactive ion etching (DRIE) processing and deposition by plasma enhanced chemical vapor deposition (PECVD) are used. The circuit was produced through.

The DRIE processing method, which uses the collision and reaction of ions generated by plasma formation, can be used to process silicon wafers with directionality, to produce 3D structures, and to produce structures of several micrometers in size. In addition, expensive equipment is required to generate the plasma, which is expensive to process and fabricates a structure of several hundred micrometers in order to make the metal lattice circuit required in the electromagnetic region from the millimeter wave band to the terahertz wave (THz) band. It takes a lot of time due to the low etching (rate) process ratio, there is a problem that the sidewall removal process (Sidewall Scalping) occurs when manufacturing a tall structure. In addition, due to the size limitation of the chamber generating the plasma, it is difficult to produce the structure in large quantities in a short time.

PECVD, which is a deposition method using plasma, is suitable for manufacturing circuits of several micrometers in size, but is not suitable for manufacturing metal lattice circuits of various electromagnetic bands due to the limitation of the deposition height.

In order to manufacture a metal grid circuit that can be applied to a variety of electromagnetic wave bands as described above, there is a lack of a process technology that can be easily produced in a selective process, relatively inexpensive, mass production in a short time. In addition, the rectangular lattice circuit most commonly used in the related art has a form of a circuit having high efficiency and low output since the minimum oscillation current required for back wave oscillation is low.

Accordingly, an object of the present invention is to solve the above-described problems, and an object of the present invention is to fabricate a metal lattice circuit using an anisotropic wet process in the direction of the (100) direction of a silicon wafer and a semiconductor processing technique, thereby providing a selective process. The present invention provides a method for manufacturing a Smith-Pursel free electron laser device, which enables easy, relatively inexpensive, and large-scale fabrication of a large metal lattice circuit in a short time.

In addition, another object of the present invention is to have the above-described metal lattice circuit has a structure of the resonator type, the electric field strength on the upper surface of the lattice circuit is increased compared to the rectangular lattice circuit generally used when interacting with the electron beam It is possible to reduce the minimum oscillation current required for back wave oscillation, thereby improving the oscillation output and efficiency, and to provide a method for manufacturing a Smith-Percell free electron laser device.

In the manufacturing method of the Smith-Percell free electron laser device according to the present invention for achieving the above object, to produce a silicon lattice structure using a wet process using an etching mask using SiO ₂ or SiN. After deposition using a PECVD equipment, PR (Photoresist) is coated on SiO ₂ or SiN for patterning using ultraviolet light. After that, a lattice circuit structure of a desired electromagnetic wave frequency band is formed in PR through a patterning process and a developing process using ultraviolet rays. Then, a circuit structure is formed by using reactive ion etching (RIE) in the etching mask, and the remaining PR is removed using an Asher device. Next, the silicon wafer prepared for the wet process is first cleaned and the mixed mass of the solution is precisely adjusted to produce a desired circuit structure using KOH or HF used in the wet process, and the wet process is performed. By precisely controlling time and temperature, a metal lattice circuit for the Smith-Pursel free electron laser of the desired shape is produced. This process enables the fabrication of metal grid circuits from several micrometers to hundreds of micrometers in size.

In summary, a method of fabricating a Smith-Pursel free electron laser device, that is, an electromagnetic wave generating device, according to an aspect of the present invention, comprises using a lattice circuit of a lattice structure using an anisotropic wet process on a silicon wafer. Forming a step.

The grating circuit comprises gratings arranged in one dimension periodically.

The anisotropic wet process is a wet process in the crystal direction (100) direction of the silicon wafer.

The electromagnetic wave generating device manufactured according to the above method includes a silicon wafer in which a lattice structure is formed.

By using the anisotropic wet process, a metal lattice structure circuit may be formed by coating a lattice of an obliquely etched lattice structure with a metal material. The metal material is a gold-high conductive material.

By using the anisotropic wet process, the metal lattice structure circuit may be formed by coating the upper and left and right sidewalls of the lattice except the bottom surface of the silicon wafer between the lattice of the inclined lattice structure with a metal material.

The metal lattice structure circuit may be formed by coating the upper and lower surfaces and the left and right side walls of the lattice structures formed by completely etching to the opposite side of the silicon wafer by using the anisotropic wet process.

The anisotropic wet process of the lattice structure coated with the metal material may further include other silicon wafers or other dielectrics coated or not coated with the metal material by contacting and bonding to the side where the silicon wafer is etched.

In this case, electromagnetic waves may be generated on the metal lattice structure circuit by radiating an electron beam onto the metal lattice structure circuit using an electron gun of a cold cathode or a hot cathode.

The metal lattice structure circuit is a first metal lattice structure circuit, and further includes a second metal lattice structure circuit that is the same as the first metal lattice structure circuit, wherein each lattice of the first metal lattice structure circuit is the second metal. It may be arranged to face each lattice of the lattice structure circuit.

In this case, each grating of the first metal grating structure circuit may be disposed at a position aligned with each grating of the second metal grating structure circuit, and each grating of the first metal grating structure circuit is the second metal grating. Staggered with each grating of the structural circuit, each grating of one circuit may be disposed above the etch space between the gratings of the opposite circuit.

As described above, in the Smith-Pursel free electron laser device and the manufacturing method thereof according to the present invention, by producing a metal lattice structure circuit by an anisotropic wet process applied to a silicon wafer, the selective process is easy, and relatively expensive This inexpensive, tall metal grid structure can be manufactured in large quantities in a short time.

In addition, in the Smith-Percell free electron laser device and the manufacturing method thereof according to the present invention, due to the metal lattice structure circuit having the structure of the resonator type, it is possible to increase the electric field strength on the upper surface of the lattice important when interacting with the electron beam, This can increase the oscillation output and efficiency and reduce the minimum current required for oscillation.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view showing an etching section when an anisotropic wet process in the direction of (100) of a silicon wafer 11 is used according to an embodiment of the present invention.

When the anisotropic wet process is performed in the crystal direction 100 of the silicon wafer 11 shown in FIGS. 1 to 12 by etching, the angle between the (111) and (110) axes of the crystal structure is 54.74 degrees as shown in FIG. It is possible to obtain a crystal structure forming a. The Smith-Pursel free electron laser device according to the present invention can be manufactured by fabricating a circuit having a metal lattice structure showing a crystal structure using such an anisotropic wet process.

2 is a flowchart illustrating a method of manufacturing a Smith-Percell free electron laser device according to an embodiment of the present invention.

Hereinafter, with reference to FIG. 2, the anisotropic wet process to the (100) crystal direction of the silicon wafer 11, and the manufacturing process of the silicon 1-dimensional metal lattice structure circuit which applied the semiconductor processing technique are demonstrated. The metal lattice structure circuit is a structure in which the lattice is periodically arranged in one dimension, the surface of the lattice structure is coated with the conductive material 251, and the bottom is bonded to the silicon wafer coated with the conductive material.

First, (a) the silicon wafer 210 is prepared and cleaned.

(b) SiO ₂ or SiN is deposited using PECVD as the insulating layer 221 to be used as an etching mask to fabricate a one-dimensional silicon lattice structure on the silicon wafer 210. Next, after cleaning the wafer on which the insulating layer 221 is deposited to proceed with a photo process, the PR (Photo-Resist) 222 is coated on the insulating layer 221 using a spin coater. do. After the PR 222 coating, a soft bake process is performed at an appropriate constant temperature to remove the solvent and improve the adhesion of the PR, and a constant lattice structure is patterned using a mask aligner. The photomask and the PR 222 may be aligned and exposed to an appropriate light source, and then patterned so that the PR 222 remains in a predetermined lattice structure through a developing process.

(c) When the PR 222 on the insulating layer 221 is patterned in a predetermined lattice shape, the insulating layer 221 of the portion where the PR 222 is not left is etched by a reactive ion etching (RIE) process, thereby forming 231. As described above, the insulating layer 221 may be patterned in a predetermined crystal lattice structure.

(d) After the insulating layer 221 is etched into a predetermined crystal lattice structure, the PR 232 remaining on the silicon wafer is removed through a process using an asher device. When the PR 232 remaining on the silicon wafer is removed, the silicon lattice structure is formed by performing an anisotropic wet process toward the (100) crystal direction of the silicon wafer as shown in FIG. 1 by using the patterned insulating layer 241 as an etching mask. . In this case, the silicon lattice structure may be etched to the lower surface of the silicon wafer by an etching solution such as KOH or HF to have an inclination of 54.74 degrees between the (111) crystal direction and the (110) crystal direction as shown in FIG. 1.

(e) Next, when the silicon lattice structure is formed as described above, the patterned insulating layer 241 used as an etching mask is removed through a RIE process, and then a conductive metal material 251 such as Au (gold) is removed. The top, bottom, and left and right sidewalls of the silicon lattice are coated to form a one-dimensional metal lattice structure circuit, and then another silicon wafer 250 coated with a conductive metal material such as Au is coated on its surface. They are joined together so as to be in contact with the upper surface (etched surface) of the above metal grid structure circuit.

3 is a cross-sectional view of a silicon one-dimensional metal lattice circuit in accordance with another embodiment of the present invention.

 3, in the step (d) of FIG. 2, in the anisotropic wet process of the silicon wafer in the (100) crystal direction, the wafer is etched only to a certain depth without etching to the lower surface of the silicon wafer, and then an appropriate plating method is applied. 1 shows a one-dimensional metal lattice structure circuit coated with a metal material on the top and left and right sidewalls of the silicon lattice except for the bottom surface between the silicon lattice.

4 is a cross-sectional view of a silicon one-dimensional metal lattice circuit according to another embodiment of the present invention.

FIG. 4 shows a structure in which another silicon wafer bonded to the top surface of the metal lattice structure circuit in step (e) of FIG. 2 is directly bonded to the top surface of the metal lattice structure circuit without coating of the metal material. Here, a dielectric layer such as a resin or an oxide film may be used instead of another silicon wafer which is brought into contact with and bonded to the upper surface of the metal lattice structure circuit.

5 is a view for explaining the generation of electromagnetic waves in the Smith-Percell free electron laser device according to an embodiment of the present invention.

5 illustrates a process of generating an electromagnetic wave using the electron beam 522 in order to use the metal lattice structure circuit 510 manufactured as the structure shown in FIGS. 2 to 4 as a Smith-Percell free electron laser device. For example, in the case where the electron beam 522 is radiated onto the metal lattice structure circuit 510 in the electron gun 521 of a cold cathode or a hot cathode, the electron beam 522 and the metal lattice structure circuit 510 according to the principle of Smith-Purcell. ) Can generate electromagnetic waves. The electron beam 522 emitted from the electron gun 521 may be absorbed by the opposite collector 523. In this case, the width, height, periodicity, etc. of the gratings of the metal lattice structure circuit 510 may be adjusted to generate an electromagnetic wave having a required frequency.

FIG. 6 is a view for explaining a two-dimensional PIC simulation structure of a Smith-Percell free electron laser device according to an embodiment of the present invention. A portion of 610 is enlarged and shown at 620.

In order to verify the operation characteristics of the Smith-Pursel free electron laser device by the metal lattice structure circuit 600 fabricated as shown in FIGS. 2 to 4, the simulation was performed by using two-dimensional PIC (Particle-In-Cell) codes. . Here, it is assumed that the lattice length of the same structure in the Z direction is formed to a size of 1m.

Similar to FIG. 5, the electron beam 622 is generated by the electron gun 621 positioned on the left side of the circuit, and is incident on the collector 611 located on the right end after traveling on the circuit. Here, the electron beam energy for the simulation is 50 KeV, the electron beam current intensity is 600 A / m, the thickness of the electron beam is 20 micrometers, the distance between the electron beam 622 and the metal grid structure circuit 600 is 20 micrometers. The lattice period of the metal lattice structure circuit is 200 micrometers, and the distance of the top surface of one metal lattice 623 is 125 micrometers in width, and the total number of metal lattice is simulated using the lattice circuit as an example. The electron beam 622 traveling over the metal lattice structure circuit 600 generates electromagnetic waves in the Y direction through interaction with the circuit. Such a circuit 600 can be used as a Smith-Percell free electron laser device that oscillates surface mode 0.41 THz and propagation mode 0.82 THz.

FIG. 7 shows the X-axis change at 2.9 ns to see how the electron beam traveling over the circuit 600 of the Smith-Percell free electron laser device is spatially modulated after interaction with the circuit in the same simulation as FIG. 6. This is the result of measuring the energy (PX). As shown in FIG. 7, it can be seen that the electromagnetic beam of the Smith-Purse free electron laser is oscillated by the electron beam 622 interacting with the metal lattice structure circuit 600.

FIG. 8 shows the magnetic field Z component (tesla) and the frequency component of the magnetic field Z component (tesla / GHz) of electromagnetic waves radiated over the metal lattice circuit 600 of the Smith-Purse free electron laser device in the simulation as shown in FIG. 6. Giving. The electromagnetic waves generated by the interaction between the circuit 600 and the electron beam 622 are radiated above the circuit 600, and the frequency components of the generated electromagnetic waves consist of 0.41 THz, the surface mode of the grating circuit, and 0.82 THz, the propagation mode. It can be confirmed.

FIG. 9 is a diagram for describing a two-dimensional PIC simulation structure of a conventional Smith-Percell free electron laser device having a rectangular lattice circuit.

For the circuit structure having the same frequency component as that of the circuit 600 of FIG. 6, the rectangular lattice circuit has a thickness of 72 micrometers, a lattice period of 193 micrometers, and the total number of metal lattices is 35, and the energy of the electron beam, Current intensity, thickness, and distance between circuits were used under the same conditions as in FIG. 6 simulation.

FIG. 10 is a result of measuring the intensity of electromagnetic waves radiated onto the metal lattice circuit in the structure of FIG. 9 with time variation in 6 mm of the Y axis. Here, the output result is a two-dimensional PIC simulation showing the output intensity per 1m of electromagnetic waves generated when the grating length of the circuit is assumed to be 1 m in the Z direction.

As shown in FIG. 10, in the circuit 600 of the Smith-Percell free electron laser device manufactured by the wet process according to an embodiment of the present invention, the oscillation of the circuit is generated after about 0.5 ns after generating the electron beam. 1.5 ns after the start, it stably emits electromagnetic waves and shows that the operation of the Smith-Pursel free electron laser is stabilized. However, when the conventional rectangular circuit is applied, the rear wave oscillation does not occur, thereby generating very little output. In this case, when the wet-processed lattice circuit is used, the electric field strength on the upper side of the lattice circuit increases due to the resonator-type lattice circuit structure, thereby lowering the minimum oscillation current required for back wave oscillation, and increasing the oscillation output and efficiency. It can be seen that.

11 is an embodiment of a structure in which two metal lattice circuits are arranged up and down according to the present invention. As shown in FIG. 11, two metal lattice circuits manufactured according to embodiments of the present invention are disposed so that the lattices face each other up and down, so that the lattice of one circuit is aligned and arranged on the lattice of the opposite circuit, and between the circuits. The electromagnetic beam may be emitted by emitting an electron beam.

12 is an embodiment of a structure in which two metal lattice circuits are alternately arranged up and down according to the present invention. As shown in FIG. 12, two metal lattice circuits manufactured according to embodiments of the present invention are disposed so that the lattices face each other up and down, so that the lattice of one circuit is placed on the etching space between the lattices of the opposite circuit. In addition, electromagnetic waves may be generated by radiating an electron beam between circuits.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a view showing an etched cross section when an anisotropic wet process in the direction of (100) of a silicon wafer is used according to an embodiment of the present invention.

2 is a flowchart illustrating a method of manufacturing a Smith-Percell free electron laser device according to an embodiment of the present invention.

3 is a cross-sectional view of a silicon one-dimensional metal lattice circuit according to another embodiment of the present invention.

4 is a cross-sectional view of a silicon one-dimensional metal lattice circuit according to another embodiment of the present invention.

5 is a view for explaining the generation of electromagnetic waves in the Smith-Percell free electron laser device according to an embodiment of the present invention.

FIG. 6 is a view for explaining a two-dimensional PIC simulation structure of a Smith-Percell free electron laser device according to an embodiment of the present invention.

7 is a result of measuring the spatially modulated state of the electron beam traveling over the circuit of the Smith-Percell free electron laser device according to an embodiment of the present invention after interaction with the circuit at 2.9 ns according to the X-axis change. .

FIG. 8 shows the frequency components of the magnetic field Z component and the magnetic field Z component of electromagnetic waves radiated over the metal lattice circuit of the Smith-Percell free electron laser device according to the embodiment of the present invention.

FIG. 9 is a view for explaining a two-dimensional PIC simulation structure of a conventional Smith-Purse free electron laser device having a rectangular lattice circuit.

FIG. 10 is a result of measuring the intensity of electromagnetic waves radiated onto the metal lattice circuit in the structure of FIG.

11 is an embodiment of a structure in which two metal lattice circuits are arranged up and down according to the present invention.

12 is an embodiment of a structure in which two metal lattice circuits are alternately arranged up and down according to the present invention.

Claims (13)

A lattice circuit is formed on the silicon wafer using an anisotropic wet process, Using the anisotropic wet process to form a metal lattice structure circuit by coating a metal material on the lattice of the inclined etched lattice structure, And a method for generating electromagnetic waves over the metal lattice structure circuit by radiating an electron beam onto the metal lattice structure circuit using an electron gun of a cold cathode or a hot cathode. A lattice circuit is formed on the silicon wafer using an anisotropic wet process, A metal lattice structure circuit is formed by coating the upper and left and right sidewalls of the lattice except the bottom surface of the silicon wafer between the lattices of the inclined lattice structure using the anisotropic wet process with a metal material, And a method for generating electromagnetic waves over the metal lattice structure circuit by radiating an electron beam onto the metal lattice structure circuit using an electron gun of a cold cathode or a hot cathode. A lattice circuit is formed on the silicon wafer using an anisotropic wet process, The metal lattice structure circuit is formed by coating the upper and lower sides and the left and right walls of the lattice structure formed by etching to the opposite side of the silicon wafer using the anisotropic wet process with a metal material, And a method for generating electromagnetic waves over the metal lattice structure circuit by radiating an electron beam onto the metal lattice structure circuit using an electron gun of a cold cathode or a hot cathode. The method of claim 3, The anisotropic wet process of the lattice structure coated with the metal material for the electromagnetic wave generation, characterized in that the other side of the silicon wafer is not etched with the metal material, or the other dielectric is bonded to the side where the silicon wafer is etched. Device fabrication method. The method according to any one of claims 1 to 3, The grating circuit comprises a grating arranged periodically in one dimension characterized in that the device for generating electromagnetic waves. The method according to any one of claims 1 to 3, And said anisotropic wet process is a wet process in the crystal direction (100) direction of said silicon wafer. The method according to any one of claims 1 to 3, The electromagnetic wave generating device is a method for producing electromagnetic waves, characterized in that the Smith-Percell free electron laser device. The method according to any one of claims 1 to 3, The metal material is a method for producing an electromagnetic wave, characterized in that the gold. The method according to any one of claims 1 to 3, By using the metal lattice structure circuit as the first metal lattice structure circuit, a second metal lattice structure circuit similar to the first metal lattice structure circuit is further manufactured, And a lattice of the first metal lattice structure circuit facing each lattice of the second metal lattice structure circuit. 10. The method of claim 9, And each grating of the first metal grating structure circuit is disposed at a position aligned with each grating of the second metal grating structure circuit. 10. The method of claim 9, Wherein each lattice of the first metal lattice structure circuit is staggered with each lattice of the second metal lattice structure circuit, and each lattice of one circuit is disposed on an etching space between the lattice of opposite circuits. How to make. delete delete

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