KR100973828B1 - Glass nano fabrication method using deposition of metal thin film - Google Patents

Abstract

Glass nano processing method according to the present invention comprises the steps of: depositing by patterning a metal thin film on a glass substrate (patterning); Applying heat to the glass substrate on which the patterned metal thin film is deposited; Forming an electric field between the metal thin film and the glass substrate; Immersing the glass substrate on which the metal thin film is formed in an aqua regia or a piranha cleaning solution for a predetermined time to etch the glass substrate together with the metal thin film.

Glass, nano processing, iron thin film, molecular substitution, aqua regia

Description

Glass nano processing method using deposition of metal thin film {GLASS NANO FABRICATION METHOD USING DEPOSITION OF METAL THIN FILM}

The present invention relates to a glass nano-processing method, and more particularly to a glass nano-processing method that can be processed to a nano-scale three-dimensional structure by molecular substitution of the glass crystal structure.

In recent years, much attention has been paid to nanoscale fabrication as well as industrialization.

Nanoscale fabrication is largely divided into a top-down approach and a bottom-up approach. The top-down method is to create nanostructures by removing unwanted parts from thin films or lumps of material, and the bottom-up method is self-assembly in small dry blocks. Stacking up to make nanostructures.

Until now, the most popular method of making nanostructures is lithography, the most common of which uses electron beams.

The electron beam lithography is a patterning material that reacts with electrons using an electron beam, which is used in combination with lift-off, etching, and electro-deposition to create various nanoscale structures. use. However, electron beam lithography has a disadvantage of low productivity as a serial process, and has a fatal weakness when it is intended for mass production.

Therefore, a nano-imprint method that can compensate for the weakness of electron beam lithography has been in the spotlight. This nano-imprint method can produce a large number of nanostructures in a single time with a single stamp.

 Scanning probe microscopy (SPM) systems enable tip adjustment of molecular size with sub-nanoscale accuracy. Therefore, nanostructure fabrication has been attempted in various directions using the SPM system. However, the SPM system will also be serial work if working as a team, so the process itself is very slow and not suitable for mass production.

Self-assembly is based on the nanoparticles chemically or physically agglomerating together to form a structure, which is divided into physical self assembly and chemical self assembly.

Physical self-assembly is a phenomenon caused by entropy, which refers to the formation of a stable structure by naturally occurring interactions caused by particles colliding. The template-assist self-assembly forms a structure in a desired pattern. It is also possible. In chemical self-assembly, a molecular layer is formed by contact with molecular recognition, and a plurality of layers are formed based on this, thereby forming a complex structure.

The above-mentioned nano-processing methods have a disadvantage in that it takes a long time to produce a complex-scale nanoscale structure, and other relatively simple structures can be made faster but more complicated structures require more time. Most of this is.

Therefore, there is an urgent need for a new nanofabrication method capable of quickly and simply manufacturing a nanoscale structure having a complex shape so as to compensate for both of these disadvantages.

The present invention is to solve the above-mentioned problems, the glass nano-processing method according to the present invention is to make it easier and faster to process the shape of a more complex nano-scale structure by molecular replacement of the glass crystal atoms and metal atoms with each other. The purpose.

In order to achieve the above object, the glass nano-processing method according to the present invention comprises the steps of: depositing by patterning a metal thin film on the glass substrate (patterning); Applying heat to the glass substrate on which the patterned metal thin film is deposited; Forming an electric field between the metal thin film and the glass substrate; Immersing the glass substrate on which the metal thin film is formed in an aqua regia or a piranha cleaning solution for a predetermined time to etch the glass substrate together with the metal thin film.

The metal thin film may be formed by any one of sputtering or filament deposition, electron beam deposition, RF power deposition and flash deposition.

The metal thin film may be an iron thin film, and the glass substrate may include a borosilicate glass substrate.

The patterning and depositing the metal thin film may include forming a photoresist layer on the glass substrate and patterning the photoresist layer into a predetermined shape; Depositing a metal thin film on the glass substrate on which the photoresist layer is patterned; And patterning the metal thin film by performing a lift-off process on the glass substrate on which the metal thin film is deposited.

The aqua regia may be made of a volume ratio of HCl: HNO ₃ = 3 to 7: 1, and the piranha cleaning liquid may be made of a volume ratio of H ₂ SO ₄ : H ₂ O ₂ = 2 to 4: 1: 1.

As described above, the glass nanofabrication method of the present invention makes it possible to more easily and quickly process the shape of a nanoscale structure through etching after molecular substitution of a glass crystal atom and a metal atom.

In addition, the depth can be processed according to the thickness of the metal film pattern, the heat treatment temperature and the voltage intensity and the application time to form the electric field can be processed more effectively the shape of the more complex three-dimensional structure of the nano-scale.

First, the theoretical background of the glass nanofabrication method of the present invention will be described with reference to the accompanying drawings.

1A to 1D illustrate the theoretical background of the glass nanofabrication method of the present invention.

Referring to these drawings, the basic principle of the glass nanofabrication method of the present invention is that the etching process is performed by the weakening of the molecular structure caused by the substitution of molecules when two materials are exposed to heat and an electric field.

More specifically, as shown in FIG. 1A, an iron (Fe) thin film pattern is formed on the borosilicate glass substrate used as the glass substrate.

As shown in FIGS. 1B and 1C, when exposed to heat and an electric field, ferrous metal atoms (Fe) atoms forming a thin film pattern are molecularly substituted with boron (B) atoms in a crystal structure of a borosilicate glass substrate.

Therefore, as shown in FIG. 1D, the molecular substituted iron metal atoms (Fe) are larger in size than the boron (B) atoms, thereby weakening the molecular structure of the molecular substituted glass substrate. Therefore, when the molecular substituted glass substrate is etched in an etchant such as aqua regia or piranha cleaning solution, the weakened portion of the molecular structure is etched and processed.

In the glass nano-processing method as described above, not only iron (Fe) but also metal materials known as non blocking anode materials may be used in the same manner. Non blocking anode material refers to materials in which the material used as an anode is diffused into borosilicate glass during the anodic bonding process, and representative examples are silver (Ag), iron (Fe), and aluminum (Al). There is this.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments described below are merely to illustrate the invention, the invention is not limited thereto.

2 (a) to (e) is a view showing a glass nano processing method according to an embodiment of the present invention.

Glass nano-processing method according to the present embodiment comprises a photoresist layer patterning step, iron (Fe) thin film deposition step, iron thin film patterning step, heating step, electric field forming step, glass substrate etching step.

Referring to FIGS. 2A and 2B, a photoresist layer 20 is first formed on a glass substrate 10 and patterned.

Patterning of the photoresist layer 20 may be performed through a photolithography process using a chromium (Cr) mask. At this time, a mask pattern having a desired shape is transferred to the photoresist layer 20, and the photoresist layer 20 has a pattern having a predetermined shape.

Referring to FIG. 2C, an iron (Fe) thin film 30 is deposited on the glass substrate 10 on which the photoresist layer 20 is patterned.

Here, the atoms constituting the iron (Fe) thin film 30 and the atoms constituting the crystal structure of the glass substrate 10 may be molecularly substituted with each other.

Substitution of the crystal atoms in the crystal structure of the glass substrate 10 with the atoms of the iron thin film 30 is performed according to the Goldschmidt's rule. According to this Goldschmidt's rule, the difference in the size of the mutually substituted molecules should be within 15% and the difference in charge should be one or less. Therefore, the iron thin film 30 formed on the glass substrate 10 is made of atoms larger in size than the crystal atoms forming the glass crystal so as to weaken the molecular structure of the molecular substrate glass substrate 10 is substituted.

As such, when the iron thin film 30 is formed on the glass substrate 10, the thin film is formed in a thin film form, and the thin film should be formed at a relatively low temperature. Thus, the thin film generally includes thin film growth at low pressure and thus belongs to the category of vacuum deposition.

Sputtering and thermal evaporation can be used as the vacuum evaporation method, and the thermal evaporation method includes filament evaporation, electron beam evaporation, RF power evaporation, and flash evaporation. It includes. Detailed description thereof will be omitted.

In this embodiment, a borosilicate glass substrate in which boron atoms are included in the glass crystal structure is illustrated. The borosilicate glass substrate may be a Pyrex glass wafer manufactured by Corning, USA.

Therefore, in the iron thin film 30 deposition step, the iron (Fe) metal is formed on the Pyrex glass substrate 10 on which the photoresist layer 20 is patterned by using an E-beam evaporator. do.

Referring to FIG. 2D, in the iron thin film patterning step, the iron thin film 30 is patterned by performing a lift off process on the glass substrate 10 on which the iron thin film 30 is deposited.

That is, when the glass substrate 10 on which the iron thin film 30 is deposited is immersed in a developer, a lift-off process is performed to remove the photoresist layer 20 from the glass substrate 10 and to deposit the iron thin film 30 thereon. Also removed together, only the iron thin film 30 deposited directly on the glass substrate 10 will remain to form a pattern.

Next, the glass substrate 10 on which the iron thin film 30 is deposited is heated, and an electric field is formed between the iron thin film 30 and the glass substrate 10.

At this time, a positive (+) pole is applied to the iron thin film 30, and a ground or negative (-) pole is applied to the glass substrate 10 to form an electric field, as shown in FIG. As described above, a voltage may be applied by contacting the stainless electrode 35 to the upper portion of the iron thin film 30 and contacting the silicon (Si) electrode 15 to the lower portion of the glass substrate 10. 3 also shows the glass substrate 10 heating system 12 together.

Thus, the boron (B) atoms forming the crystal structure of the glass substrate 10 and the iron (Fe) valence molecules of the iron thin film 30 pattern are subjected to electric field treatment on the glass substrate 10 on which the iron thin film 30 pattern is formed. Do it.

At this time, heat and electric field treatment should be performed at the same time, but different processing depths can be obtained according to the heat treatment temperature and voltage intensity applied to the glass substrate 10. Thus, the strength of the temperature and the voltage each serve as each major variable that determines the processing depth of the glass substrate 10.

Through such molecular substitution, the molecular structure of the surface of the glass substrate 10 corresponding to the shape of the iron thin film 30 pattern is weakened.

Referring to (e) of FIG. 2, in the glass substrate etching step, the glass substrate is etched together while removing the iron thin film 30 remaining on the glass substrate 10 after molecular substitution by heat and electric field treatment.

An aqua regia or piranha cleaning solution is used as an etchant to remove the iron thin film 30 pattern remaining on the glass substrate 10 and to etch and process the glass substrate 10. In particular, the aqua regia may be composed of HCl: HNO ₃ = 3 to 7: 1 volume ratio, Piranha washing liquid is H ₂ SO ₄ : H ₂ O ₂ = 2 to 4: 1 volume ratio. Preferably, the aqua regia may consist of a volume ratio of HCl: HNO ₃ : DI (H ₂ O) = 7: 1: 8 or a volume ratio of HCl: HNO ₃ = 3: 1, and the piranha cleaning solution is H ₂ SO ₄ : H ₂ O ₂ = 2: 1 volume ratio or H ₂ SO ₄ : H ₂ O ₂ = 4: 1 volume ratio.

As such, when aqua regia or piranha cleaning solution is used as an etchant for etching the glass, more precise etching is possible than when using HF as an etchant. That is, when HF is used as an etchant, there is a problem in which portions not desired to be etched are also etched, but there is no such problem when the aqua regia or piranha cleaning solution is used.

On the other hand, the etchant may be selectively applied according to the type of metal deposited on the glass substrate. That is, it is possible to apply a dedicated metal etchant corresponding to the metal thin film used.

Thus, by adjusting the thickness of the iron thin film 30 pattern, the heat treatment temperature and the strength of the voltage forming the electric field, it is possible to process the structure of the three-dimensional structure of different processing depths and more complex nano-scale.

Hereinafter, the experimental results of experiments using the thickness of the iron thin film 30 pattern, the heat treatment temperature, and the strength of the voltage forming the electric field as the respective variables will be described. Such experimental examples of the present invention are merely for illustrating the present invention and the present invention is not limited thereto.

Experimental Example 1

In this experiment, Pyrex 7740 glass wafer was used. First, a photolithography process using a Cr mask is performed using HMDS and AZ 5214E photoresist on a clean Pyrex wafer to form a pattern to be etched. And using an E-beam evaporator, Fe (iron) is deposited on the PR patterned wafer made earlier. In this experiment, the specimens were deposited with a thickness of 3000Å consistently. The specimen deposited up to Fe is immersed in acetone and subjected to a lift-off process. Heat and electric field treatment experiments were performed using these (Fe / Pyrex) specimens.

A system as shown in FIG. 3 was constructed, and a thermal / electric field was applied to the prepared specimen. A Schott laboratory stirrer SLR (with glass-ceramics heating zone) was used as a hot plate to heat the specimens, and MATSUSADA Precision Inc. The high voltage power source series of AU-50R1.2 was used. The field strength was always controlled by adjusting the voltage of the voltage source, while maintaining a constant distance between the electrodes (the retention distance in this experiment was about 500um, the thickness of the Pyrex wafer).

To apply the heat required for the experiment, set the desired temperature on the hot plate. In order to surely reach the set temperature, all experiments were performed after waiting about 30 minutes after setting the temperature.

To apply the desired voltage, adjust the knob of the high voltage source. By the way, setting a specific voltage is not done at once. For example, if you set 1.2kV, if you start the voltage from 0kV and raise the voltage quickly, the overvoltage of the high voltage source exceeds the maximum capacity from 0.4 ~ 0.5kV and the voltage source stops automatically. Therefore, if the voltage is slowly raised to the extent that no overcurrent flows and then waits for a certain time (1 ~ 2 minutes), the value of current decreases. Then increase the voltage once again and wait until the current decreases to set the desired 1.2kV.

The measurement of the thermal / electrical treatment time was recorded starting from the time when the same voltage was 0.8 kV or more, regardless of the final voltage or temperature setting. All experiments were conducted at room temperature and atmospheric pressure, with no special humidity control.

In this experiment, the solution used for iron removal and glass etching is aqua regia. As the aqua regia used, the composition ratio of HCl: HNO ₃ : DI (H ₂ O) = 7: 1: 8 was used as the volume ratio, and the temperature during etching was maintained at 80 ° C. The same glass etching results can be obtained by etching not only aqua regia but also piranha cleaning solution (H ₂ SO ₄ : H ₂ O ₂ = 2: 1, volume ratio). Data was obtained.

KLA Tencor Alpha-Step IQ profiler was used as the basis for measuring the step height of the finished specimen, and the etching form was directly confirmed by using a scanning electron microscope of JEOL. In the case of Alpha-Step measurement, since there is a basic slope due to the installation problem, appropriate leveling process was performed in each case to obtain an etching profile of the specimen itself.

When an electric field is applied to an iron patterned specimen in the manner described above, the patterned side of iron has a positive voltage and the other side is grounded. Then, if the specimen was immersed in the aqua regia of the above ratio for 1 hour, the glass etching with the removal of iron occurred.

In the case of thermally / electrically treated samples, when they come out at room temperature, the iron surface turns red and breaks like powder. This is because the oxidation process of iron occurred due to the high temperature / high voltage, and it appears that the stress difference between the outer surface and the lower surface of iron occurs when exposed to room temperature. In Figures 4a to 4c it can be seen that the specimen changes during the thermal / electrical treatment process.

Using the aqua regia, the finished specimens were etched by glass using an alpha-step profiler and observed using a microscope and SEM. Representative examples are shown in FIGS. 5A and 5B.

Experimental Example 2

The maximum depth at which the glass is etched depends on the temperature and voltage intensity applied during the heat / field treatment and the total heat / field treatment time. Therefore, the effect of each parameter change on the glass etching depth was examined through experiments.

When the thickness of the iron is 300nm, the temperature was 530 ℃ experiments for 30 minutes while changing the intensity of the voltage to 1kV, 1.3kV, 1.5kV. The depth of the finally obtained glass etching can be seen in FIG. 6. At the voltage above 1.5kV, there was a difficulty in severely discharging in the air, but in the lower voltage section, as shown in FIG. 6, the depth of final etching increases linearly as the voltage increases. can see.

Experimental Example 3

In order to see the difference in depth etched according to the temperature change, iron thickness 300nm and 1kV, the treatment time was fixed to 30 minutes and the experiment was carried out while changing the temperature 500 ℃, 530 ℃, 550 ℃, the results are shown in Figure 7 It was. At 500 ℃ and below, no noticeable results were observed. Above 550 ℃, the test was not performed because it exceeds the limit of the hot plate device used and the annealing point of glass. As with the voltage change experiments, the final etch depth increases linearly with increasing temperature within a given interval.

Experimental Example 4

Finally, the change in etching depth for the longer heat / electric treatment time was examined. The experiment was performed while increasing the treatment time under the conditions of 300 nm, 1.3 kV, and 530 ° C iron thickness. As shown in FIG. 8, it can be seen that as the processing time increases, the final glass etching depth also increases linearly.

As a result, a suitable combination of temperature, voltage intensity, and thermal / field treatment time can be adjusted to achieve the desired glass etch depth.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1A to 1D illustrate the theoretical background of the glass nanofabrication method of the present invention.

2 (a) to (e) is a view showing a glass nano processing method according to an embodiment of the present invention.

3 is a schematic diagram of a heat / field treatment system for implementing a glass nanofabrication method according to an embodiment of the present invention.

4A to 4C are photographs showing changes in Fe / Pyrex samples according to heat and electric field treatments in the glass nanofabrication method according to an embodiment of the present invention, and FIG. 4A is a Fe / Pyrex sample, and FIG. 4B is Only the heat was briefly applied and FIG. 4C shows the sample after the heat / field treatment.

5a is an alpha-step measurement graph of measuring a cross section of a sample after performing the glass nanofabrication method according to an embodiment of the present invention, and FIG. 5b is a cross-sectional SEM photograph of the sample.

6 is a graph showing the relationship between the processing depth according to the magnitude of the applied voltage in the glass nano processing method according to an embodiment of the present invention.

7 is a graph showing the relationship between the processing depth according to the heat treatment temperature in the glass nano processing method according to an embodiment of the present invention.

8 is a graph showing the relationship between the processing depth according to the heat / electric field treatment time in the glass nano processing method according to an embodiment of the present invention.

Claims (7)

Patterning and depositing a metal thin film on the glass substrate; Applying heat to the glass substrate on which the patterned metal thin film is deposited; Forming an electric field between the metal thin film and the glass substrate; Etching the glass substrate together with the metal thin film by immersing the glass substrate on which the metal thin film is formed in aqua regia or piranha cleaning solution for a predetermined time. Glass nano processing method comprising a. The method of claim 1, The metal thin film is formed by the thermal evaporation method of any one of sputtering or filament deposition, electron beam deposition, RF power deposition and flash deposition. The method of claim 1, The metal thin film is an iron thin film glass nano processing method. The method of claim 1, Patterning and depositing the metal thin film, Forming a photoresist layer on the glass substrate and patterning the photoresist layer into a predetermined shape; Depositing a metal thin film on the glass substrate on which the photoresist layer is patterned; And And performing a lift-off process on the glass substrate on which the metal thin film is deposited to pattern the metal thin film. The method of claim 1, The glass substrate is a glass nano processing method comprising a borosilicate glass substrate. The method of claim 1, The aqua regia is glass nano processing method consisting of HCl: HNO ₃ = 3 to 7: 1 by volume ratio. The method of claim 1, The piranha cleaning solution is glass nano processing method consisting of a volume ratio of H ₂ SO ₄ : H ₂ O ₂ = 2 to 4: 1.

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