KR100869546B1 - Fabrication method of thin film pattern using atomic force microscope lithography - Google Patents

Abstract

The step for resist-related processing can be removed and the suitable resolution can be secured by forming a thin film pattern using the atomic force microscope lithography technique. The thin film pattern manufacturing method using the atomic force microscope lithography technique is provided. A step is for forming the first thin film on the substrate(10). A step is for forming the second thin film for the etching mask on the first thin film. A step is for forming the oxide pattern in a part of the second thin film by using the atomic force microscope(13). A step is for forming the etching mask for exposing a part of the first thin film by dry-etching the oxide pattern. A step is for dry etching the exposed part of the first thin film by using the etching mask.

Description

Fabrication Method Of Thin Film Pattern Using Atomic Force Microscope Lithography

The present invention is directed to a method of fabricating thin film patterns using atomic force microscopy lithography techniques.

In general, the lithography process of the semiconductor device manufacturing process is a core process technology of the semiconductor to form a circuit pattern by shining light on a substrate coated with a photosensitive film. In this lithography process, a laser is used as a light source, but as the fine line width is reduced, there is an optical limitation. Accordingly, new light sources such as extreme ultraviolet (EUV), electron beam, X-ray, and ion beam are being sought. Among them, extreme ultraviolet light and electron beam are spotlighted by the next-generation exposure technology.

Lithography processes currently in use or under development use KrF (248 nm) or ArF (193 nm) light sources and use transmissive masks with light shielding patterns, such as chromium, formed on a blank substrate. However, in the extreme ultraviolet (EUV) lithography technology, electromagnetic waves with wavelengths up to 13.4 nm are used as light sources. Since the light sources with short wavelengths have very high absorption, a transmissive mask cannot be used. Unlike, a reflective (or mirror) photomask is used.

The reflective mask used in the extreme ultraviolet exposure process may be referred to as a reflective multilayer thin film mirror that enables Bragg reflection. The multilayer thin film mirror uses a laminated structure of a molybdenum (Mo) layer and a silicon (Si) layer having a large difference in optical properties such as refractive index, and manufactures a multilayer thin film having better reflectivity than the molybdenum / silicon (Mo / Si) multilayer film. In order to produce a multilayer thin film using a variety of different materials. For example, US Pat. No. 6,229,652 suggests a Mo ₂ C / Be multilayer thin film structure, and US Pat. No. 6,228,512 presents a MoRu / Be multilayer thin film structure. An absorber pattern is formed on the wafer on the multilayer thin film to transfer the pattern onto the wafer using light reflected from the reflective mask.

Meanwhile, in forming an absorber pattern of an extreme ultraviolet mask, a lithography technique using atomic force microscopy (AFM) oxidation has been proposed to overcome the process limitations of the conventional electron beam lithography technique. Hereinafter, a lithography technique using atomic force microscopy (AFM) oxidation will be described in detail with reference to FIGS. 1 and 2.

As shown in FIG. 1, the probe 14 of the atomic force microscope 13 is brought close to the substrate on which the natural oxide film 12 is formed. Here, the substrate 10 may be made of silicon or metal.

When an electric field is applied between the probe 14 and the substrate 10 in the state in which a water column 16 formed by moisture in the air is formed, hydroxide ions OH ^_ formed by electrolysis are affected by the electric field. Is led to the substrate 10 through the natural oxide film 12. The hydroxide ions reaching the substrate 10 react with silicon or metal to form an oxide film 18 as shown in FIG. 2.

On the other hand, conventional lithography methods utilize resists developed for specific wavelengths or accelerated electrons. The use of the resist has a limitation on the thickness of the etchable thin film because the organic resist used as an etch mask during dry etching is etched faster than the thin film due to physical damage in the etching process. Therefore, as the thickness of the thin film to be etched becomes thicker, the resist becomes thicker, which causes a decrease in resolution. In addition, the production of complex patterns such as curves is inconvenient, and there is a problem that productivity is reduced due to the slow lithography speed.

The present invention has been made in view of the above, and by forming a thin film pattern using atomic force microscopy lithography technology, it is possible to eliminate the resist-related process steps, to secure a suitable resolution, and to have a simple and inexpensive process It is an object of the present invention to provide a method for manufacturing a thin film pattern using atomic force microscopy lithography technology.

The thin film pattern production method using the present invention atomic force microscope lithography technique as described above,

(a) forming a first thin film on the substrate;

(b) forming a second thin film for an etching mask on the first thin film;

(c) forming an oxide pattern on a portion of the second thin film using an atomic force microscope;

(d) dry etching the oxide pattern to form an etching mask exposing a portion of the first thin film; And

(e) dry etching the exposed first thin film portion using the etching mask;

It is configured to include, wherein the second thin film and the first thin film is characterized in that the etching selectivity during plasma etching is 1: 1.5 or more.

In particular, according to claim 1,

The second thin film is characterized in that it comprises a material capable of oxidation by atomic force microscopy.

In addition, the etching gas is characterized in that it comprises a carbon and a halogen group element.

In addition, the second thin film is characterized in that formed to a thickness of 2 to 10 nm.

In addition, the step (c),

A voltage of 4 to 25 V is applied between the probe of the atomic force microscope and the second thin film at a temperature of 15 to 40 ° C. and a humidity of 10 to 75%.

In addition, the step (c),

 An oxide is formed in the second thin film at a rate of 0.5 to 500 µm / s.

In addition, the step (e),

Etching the exposed first thin film portion at -80 to -45 V conditions.

According to the thin film pattern manufacturing method using the atomic force microscope lithography technology of the present invention as described above,

First, since process steps such as coating and developing of resists can be removed, a thin film pattern can be manufactured through a simple and inexpensive process.

Second, the resolution change of the pattern according to the resist thickness does not occur,

Third, by using atomic force microscope, it is possible to make minute manipulations of several units, and to make complex patterns such as curves.

Fourth, the present invention can etch a variety of metal and ceramic materials, semiconductor materials regardless of the thickness,

Fifth, it is possible to make a wider range of patterns and to utilize technology, since the pattern area that can be implemented is expanded.

Sixth, the thin film pattern with the same resolution can be obtained while simplifying the process complexity of the conventional electron beam lithography technology, and the cost reduction effect of the entire process can be achieved by reducing the environmental constraints and maintenance cost of the equipment. As it is excellent, considerable commercial and economic effects are expected.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. A singular expression includes a plural expression unless the context clearly indicates otherwise. In this application, the terms “comprise” or “have” are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

In general, cathodic oxidation lithography using an atomic force microscope induces a chemical reaction (oxidation) between the electrolyzed hydroxide ions and the thin film in the water column formed between the thin film and the probe to selectively form nanostructures. In the present invention, the etching mask is replaced with a material capable of being oxidized by an atomic force microscope instead of an organic material, thereby eliminating process steps such as coating, developing, and removing the resist.

Hereinafter, a method of manufacturing a thin film pattern according to the present invention will be described with reference to FIGS. 3 to 7.

Referring to FIG. 3, the first thin film 21 and the second thin film 22 are formed on the substrate 20.

First, the selection conditions of the respective thin film materials will be described. In the case of the second thin film 22, all the materials may be formed and deposited by atomic force microscopy (AFM) lithography, and in the case of the first thin film 21. It includes both depositable and coatable materials.

In addition, the material of the second thin film 22 and the first thin film 21 is selected so that the etching selectivity of the second thin film 22 and the first thin film 21 with respect to the used etching gas is 1: 1.5 or more. The reason will be described in more detail with reference to FIGS. 6 and 7 below.

Deposition of the first thin film 21 or the second thin film 22 is carried out at a DC power of 100 to 300 W, process pressure 0.3 to 5 mTorr in the argon dust using a sputtering equipment.

When the direct current power is less than 100 W, the ionization of the gas is unstable, so that the deposition rate is slow. When the direct current is more than 300 W, the substrate is damaged, the roughness becomes large, and the composition of the film becomes uneven. In addition, when the process pressure is less than 0.3 mTorr, the amount of gas is so small that the deposition is too slow, and above 5 mTorr, the process reduces surface uniformity.

Under the above conditions, the first thin film 21 is deposited, and the second thin film 22 is deposited thereon by 2 to 10 nm using a stuffer equipment.

If the thickness of the second thin film 22 is less than 2 nm, the uniformity may be lowered, such as not being partially deposited in the deposition process. If the thickness of the second thin film 22 is greater than 10 nm, the lithography process may be performed using an atomic force microscope. The second thin film 22 cannot be all oxidized, and the line width of the oxide increases in proportion to the depth due to the increase in the depth of the thin film to be oxidized.

Next, referring to FIG. 4, a voltage (tip cathode) of 4 to 25 V is applied between the probe 14 and the second thin film 22 using an atomic force microscope at 15 to 40 ° C. and a humidity of 10 to 75%. Thus, the oxide 24 of the second thin film is formed.

If the temperature is less than 15 ° C., the oxidation rate of the second thin film 22, which is a chemical reaction, is influenced, and thus, the oxide 24 is difficult to form and the pattern is uneven. When the temperature exceeds 40 ° C., the aspect ratio of the oxide pattern 24 may not be improved, and the equipment may be overwhelmed.

If the humidity is less than 10%, the water column 16 is not formed between the probe 14 and the second thin film 22, so that the second thin film 22 is not oxidized. If the humidity is greater than 75%, the water column 16 is too large. Is formed to increase the line width of the oxide 24 and lower the resolution. The applied voltage acts as an energy for decomposing water molecules in the water column 16 formed between the probe 14 and the second thin film 22 of the atomic force microscope. If 24 is not formed and exceeds 25V, damage of the probe 16 occurs and the line width of the oxide 24 becomes large.

On the other hand, the atomic force microscopy lithography technique is used, the speed at which the pattern can be formed is 0.01 to 2000 µm / s, and more preferably, the pattern can be stably formed at 0.5 to 500 µm / s. Below 0.5 μm / s, process time delays occur and resolution is lower, and above 500 μm / s, the pattern shape cannot be properly realized on a commercial atomic force microscope.

Therefore, if the deviation from the lithography conditions, it is not possible to form a pattern of the desired tens of nm size, it is not possible to form an oxide in the desired pattern.

Referring to FIG. 5, when the lithography process is finished through the above processes and conditions, an etching mask 22a exposing the first thin film by selectively removing the oxide 24 of the second thin film 22 through a dry etching process. ). Next, a first thin film pattern is formed by plasma etching the first thin film exposed using the etching mask 22a (28).

FIG. 7 is a cross-sectional view illustrating a method of etching a first thin film using an etching mask. Hereinafter, an etching method of a first thin film according to the present invention will be described in detail with reference to FIG. 7.

In general, physical and chemical dry etching involves ions, electrons, or photons impinging on the surface of the material to be etched by a physical method such as acceleration through an electric field, thereby first activating the surface materials, which are then activated in the reactor. Etching occurs by chemical reaction with existing species to produce volatile gases.

Therefore, as shown in FIG. 7, in the step of forming the thin film pattern by etching the exposed first thin film 28, the etching selectivity of the etching mask 22a and the first thin film 21 is increased during plasma etching. 1: A material of the thin films 21 and 22 is selected to be 1.5 or more, and the speed of ions colliding with the first thin film 21 and the etching mask 22a is controlled through the size of an applied electric field. As a result, the etching mask 22a may be prevented from being etched together with the first thin film 21.

In the above, the etching gas may be one or more gases including carbon and halogen elements. For example, CF ₄ or CCl ₄ may be mentioned.

Plasma etching is performed at 400 to 800 W, 45 to 80 V, and 5 to 30 mTorr process conditions, and the etching process conditions are conditions for selectively etching a specific material. A problem arises in that the second thin film 22 and its oxide 24, or the second thin film 22 and the first thin film 21 are etched together or the etching does not proceed.

In the present invention, the size of the electric field for preventing the second thin film 22 is etched is -80 V or more and -45 V or less. Here, when the magnitude of the voltage applied to the substrate is less than -80 V, the physical collision force of argon ions becomes too large during plasma etching, so that both the first thin film 21 and the etching mask 22a may be etched. If the size exceeds -45 V, the first thin film 21 may not be etched well.

As the plasma etching proceeds, the exposed first thin film portion is etched 28, and since the carbon layer 29 is formed on the etch mask 22a, the etch mask 22a and the first thin film 21 are formed. The etching selectivity of is gradually increased. Therefore, even if the thickness of the first thin film is thick, only the exposed first thin film is etched without damaging the etching mask 22a (28).

After the etching process, the desired thin film pattern 21a is finally produced.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are not intended to limit the scope of the present invention.

Example 1

Metal nanopattern fabrication process using atomic force microscopy (contact mode lithography)

40 nm)을 사용하여 접촉 모드에서 인가전압 12 V(Sample bias), 리소그래피 속도 0.5 ㎛/s로 크롬 기판 위에 산화물 패턴을 형성한다(XE-100, Park systems 社). 형성된 크롬 산화물은 높이 1.5 nm, 선폭 24.0 nm를 갖는다. CF4 가스 플라즈마를 이용한 건식 식각 공정을 700 W, 60 V, 20 mTorr로 1분 30초 진행하여 크롬 층의 손상 없이 크롬 산화물을 선택적으로 식각한다. 이어서 CF₄ 가스 플라즈마로 탄탈륨 층을 식각한다. 탄탈륨 식각 공정은 700 W, 65 V, 10 mTorr로 수행하였다. 공정을 마친 금속 패턴은 25-28 nm 선폭의 트렌치(trench) 형태를 갖는다. 15 nm tantalum and 3 nm chromium are deposited on a silicon substrate by using a sputtering device to prepare a substrate. Platinum coated silicon tip (Force constant 0.6 N / m, tip curvature) at 26.0 ° C and 43% humidity

40 nm) is used to form an oxide pattern on a chromium substrate at an applied voltage of 12 V (Sample bias) and a lithography rate of 0.5 μm / s (XE-100, Park Systems, Inc.). The formed chromium oxide has a height of 1.5 nm and a line width of 24.0 nm. Dry etching using CF4 gas plasma was performed at 700 W, 60 V, and 20 mTorr for 1 minute and 30 seconds to selectively etch chromium oxide without damaging the chromium layer. The tantalum layer is then etched with CF ₄ gas plasma. Tantalum etching process was performed at 700 W, 65 V, 10 mTorr. The finished metal pattern has a trench form with a 25-28 nm line width.

Example 2

Metal nanopattern fabrication process using atomic force microscopy (tapped mode lithography)

40 nm)을 사용하여 탭핑 모드에서 인가전압 12 V(Sample bias), 리소그래피 속도 10 ㎛/s로 크롬 기판 위에 산화물 패턴을 형성한다(Solver P-47, NT-MDT 社). 형성된 크롬 산화물은 높이 3.1 nm, 선폭 82.8 nm를 갖는다. 실시예 1에서와 동일한 조건으로 크롬 층의 손상 없이 크롬 산화물을 선택적으로 식각한다. 이어서 실시 예 1에서와 동일한 조건으로 탄탈륨 층을 식각한다. 공정을 마친 금속 패턴은 84-88 nm 선폭의 트렌치(trench) 형태를 갖는다.A substrate prepared in the same manner as in Example 1 was prepared, and a platinum coated silicon tip (Resonance frequence 325.00 kHz, Tip curvature at 23.0 ° C. and 31% experimental conditions)

40 nm) to form an oxide pattern on the chromium substrate at an applied voltage of 12 V (Sample bias) and a lithography rate of 10 μm / s (Solver P-47, NT-MDT). The formed chromium oxide has a height of 3.1 nm and a line width of 82.8 nm. The chromium oxide is selectively etched without damaging the chromium layer under the same conditions as in Example 1. The tantalum layer is then etched under the same conditions as in Example 1. The finished metal pattern has a trench shape with 84-88 nm line width.

Example 3

Metal nanopattern fabrication process using atomic force microscopy (tapped mode, CNT tip)

 A substrate prepared in the same manner as in Example 1 was prepared and applied voltage in tapping mode using a carbon nanotube tip (Resonance frequence 388.07 kHz, length 700 nm, diameter 15-20 nm) at 26.5 ° C. and 43% experimental conditions. An oxide pattern is formed on the chromium substrate at a sample bias (V) and a lithography rate of 4 μm / s (Solver P-47, NT-MDT). The formed chromium oxide has a height of 1.9 nm and a line width of 23.0 nm. The chromium oxide is selectively etched without damaging the chromium layer under the same conditions as in Example 1. The tantalum layer is then etched under the same conditions as in Example 1. The finished metal pattern has a trench shape with a 24-27 nm line width.

In the above embodiment, the first thin film is described as being limited to tantalum and the second thin film is chromium, but the second thin film and the first thin film according to the present invention have an etching selectivity of at least 1.5 when plasma etching, and the second thin film is Any material capable of forming an oxide by atomic force microscopy is possible.

As described above, the present invention is a technique of forming an oxide pattern on a second thin film by using atomic force microscopy lithography and fabricating a trench-type thin film pattern by selective dry etching using a high etching ratio. Nanolithography may be directly performed on the deposited thin film substrate to be used as a fabrication technique for a mask or an integrated circuit requiring a precise pattern. Such thin film patterns can be applied not only to optical lithography masks, but also to fabricating reflective masks that will be utilized in extreme ultraviolet lithography. In addition, the atomic force microscope can be used to fabricate thin film patterns with a few tens of nm line width, which can be used to form thin film patterns in integrated circuit fabrication, thereby significantly reducing the process cost.

While the invention has been shown and described with respect to certain preferred embodiments, the invention is not limited to these embodiments, and those of ordinary skill in the art claim the invention as claimed in the appended claims. It includes all the various forms of embodiments that can be implemented without departing from the spirit.

1 and 2 are cross-sectional views of processes for describing a lithography technique using a general atomic force microscope oxidation method.

3 to 7 are cross-sectional views of processes for explaining a method of manufacturing a thin film pattern using an atomic force microscope lithography technique according to an embodiment of the present invention.

<Description of Signs of Major Parts of Drawings>

10 substrate 12 natural oxide film

13: atomic force microscope 14: atomic force microscope probe

16: water column 18: oxide

20: substrate 21: first thin film

21a: first thin film pattern 22: second thin film

22a: second thin film pattern 24: oxide pattern

26: etched oxide pattern 28: etched first thin film

29: carbon layer formed on the second thin film.

Claims (7)

(a) forming a first thin film on the substrate; (b) forming a second thin film for an etching mask on the first thin film; (c) forming an oxide pattern on a portion of the second thin film using an atomic force microscope; (d) dry etching the oxide pattern to form an etching mask exposing a portion of the first thin film; And (e) dry etching the exposed first thin film portion using the etching mask; And the second thin film and the first thin film have an etching selectivity of 1: 1.5 or more during plasma etching. The method according to claim 1, The second thin film is a thin film pattern manufacturing method using an atomic force microscopy lithography technique, characterized in that comprises a material capable of oxidizing by atomic force microscope. The method according to claim 1, The etching gas is a thin film pattern manufacturing method using atomic force microscopy lithography technology, characterized in that containing the carbon and halogen element. The method according to claim 1, The second thin film is a thin film pattern manufacturing method using atomic force microscopy lithography technology, characterized in that to form a thickness of 2 to 10 nm. The method according to claim 1, In step (c), A method of fabricating a thin film pattern using atomic force microscopy lithography, wherein a voltage of 4 to 25 V is applied between a probe of an atomic force microscope and the second thin film at a temperature of 15 to 40 ° C. and a humidity of 10 to 75%. The method according to claim 1, In step (c),  A method of fabricating a thin film pattern using atomic force microscopy lithography, characterized in that an oxide is formed in the second thin film at a rate of 0.5 to 500 μm / s. The method according to claim 1, In step (e), A method of fabricating a thin film pattern using atomic force microscopy lithography which etches the exposed first thin film portion at -80 to -45 V.

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