JP2000250200A - Lithography mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the transmitting efficiency of small quantity light of a lithography mask through a transmission window or to enhance the contact with a wafer. SOLUTION: The transmission window 2 formed on a light shielding film 1 is formed into a projection type structure filled with a transparent dielectric material. The transmission window 2 is formed by using a resist and processing a part of the light shielding film 1 with the selective oxidation, hydroxylation, nitriding or fluorination, electrical oxidation (anodic oxidation) carried out by using microprobe or heat oxidation by spot heating. The dielectric material to be the transmission window 2 is projected over the surface of the light shielding film 1. As a result, the distance between a sample surface and the transmission window is made close and near field light is efficiently supplied on the surface of an objective material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask / screen for fine processing for drawing a pattern finer than the wavelength of light, a fine processing apparatus such as a lithography apparatus and an etching apparatus using the same, and other near-fields. The present invention relates to a surface processing device utilizing the characteristics of light.

[0002]

2. Description of the Related Art A conventional lithography mask has a transmission window portion in which an opening 3 is formed by cutting by etching as shown in JP-A-10-78650 (FIG. 3). As described in JP-A-8-101492, a structure in which a transparent substance is filled in an opening 3 after cutting for the purpose of forming a phase shift film 5 (FIG. 4).
On the other hand, as described in JP-A-159969, the light-shielding film 1 is embedded in a recess formed by cutting the substrate 4 (FIG. 5). In these structures, the properties of the light as far-field light are used as they are to obtain the contrast between the light in the transmission part and the light in the light-shielding part.

[0003] Conventional lithography using the properties of near-field light is described in IEE, Elevens Annual International Workshop on Micro Electro Mechanical Systems, and MEMS 98 (1998).
Years), 488 to 493 (IEEE, 11t)
h Annual Int. Work. Micro
ElectroMechanic. Sys. , M
EMS98 (1998), PP488-493), the diffusion of chromium atoms in glass by applying an electric field,
A method for manufacturing a mask for forming a minute opening to be a hole is discussed.

[0004]

When the size of the opening 3 is large in a mask window such as a mask / screen, the amount of light passing through the opening 3 is substantially proportional to the area of the opening 3. Sufficient transmission efficiency can be obtained. However, it is known that when the diameter of the opening 3 is reduced to about one-fourth of the wavelength of light, the amount of light passing through the opening 3 is reduced more than the area ratio. When the transmission efficiency is reduced, not only is the light utilization efficiency reduced, but also light leaked from the surrounding light-shielding film 1 or the like easily becomes noise, which is not preferable. In addition, light transmitted through such a small mask window becomes light containing a large amount of near-field light localized near the opening, and therefore, is strongly attenuated by distance and has a high contact property with a medium that transmits light. If it is not good, the light use efficiency is further reduced.

In the conventional structure, the light shielding film 1
The portion that becomes the opening or the portion that becomes the opening 3 is directly cut by lithography to form a hole to form a hole, or the opening 3 is filled with another substance after cutting, so that the light transmitting portion / A non-transmissive part was formed. However, when a resist or the like is used, there is a problem that lithography of an extremely fine pattern and a step of filling a substance are increased. Furthermore, the transmission window thus manufactured is limited in light transmittance because of holes, or has good contact because it is a surface having the same height as the light-shielding film surface in polishing after filling. However, there is a problem in that a minute pattern is blurred due to the diffusion of light due to the absence of the filler material or the filling material protruding around the transmission window. In addition, in a method such as using a phase shift film, it is necessary to devise a design at a bending angle or an intersection of a pattern.

An object of the present invention is to improve the light transmission efficiency of the small-diameter transmission window, provide a mask / screen, etc., which are easy to manufacture, and provide a lithography apparatus / surface processing apparatus using the same. With the goal.

[0007]

In order to achieve the above object, the transmission window portion of the mask screen is a screen in which minute transmission windows are arranged, and each of the transmission windows is not a hole but a dielectric window. It has a convex structure filled with a substance. This can also be formed by oxidizing, hydroxylating, nitriding or fluorinating a part of the light shielding film material. As an oxidation method, there is an energization oxidation method using a probe such as a scanning probe microscope. At this time, a transition metal such as aluminum or titanium can be used as the light shielding film material.

In the case where a transparent window is formed near the top of a projection of a light-shielding film deposited on a substrate having a conical projection, excitation conditions for surface plasmon are satisfied at the projection slope with respect to the wavelength of light used. By setting the thickness of the light-shielding film and the angle of the projection in this manner, higher efficiency can be achieved.

The improvement of the transmission efficiency aimed at by this structure is a concept independent of the sharpening of the drawing contour aimed at by the phase shift mask, and can be used separately.
Or a combination is also possible.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1: Mask transmission window on flat plate) FIG.
FIG. 3 is a diagram showing the most basic structure of a transmission window of a mask according to the present invention. In the conventional structure, as shown in FIG.
In the structure according to the present invention, the opening 3 which has been turned into an air hole by cutting is filled with a transparent dielectric material, and this is replaced with a transparent window 2. Light has a property that it tends to gather in a high refractive index part, that is, a part with a high dielectric constant.If the opening is an air hole, the light mode is reduced from the essential opening because the dielectric constant is low. While it is easy to escape, in the structure filled with transparent dielectric material,
Since the dielectric constant is kept high, light can be prevented from dispersing around the opening. Further, since the difference in the refractive index can be reduced, the reflection of light occurring before the opening can be suppressed. Thereby, the amount of light transmitted through the transparent window increases, and the transmission efficiency is improved. In particular, when a metal film is used as the light-shielding film, the ratio of the wavelength of light passing therethrough to the diameter of the opening is reduced, so that the shielding effect can be suppressed and the effect of improvement can be further obtained.

Such a structure can be manufactured by cutting the opening and refilling it with a dielectric substance. However, it is easier to chemically change a part of the light shielding film material to reduce the light transmittance. It can also be made by changing. When some transition metals such as titanium, chromium, tantalum, and tungsten, aluminum, and their alloys and compounds are used as the light-shielding film material, they are made transparent by oxidation, hydroxylation, nitridation, or fluoridation. Thus, a fine mask window can be formed without performing complicated procedures such as cutting and refilling. The conditions required for the light-shielding film material are as follows: (1) First, it must be a metal in order to have a light-shielding property that may be thin, (2) it must have a somewhat high melting point and have temperature resistance (500 ° C. or more). Further, (3) it is necessary that the metal itself is stable against moisture in the air, and the transition metal is mentioned as a material satisfying these properties.
Although aluminum is not a transition metal, the metal surface is stabilized by an oxide film formed on the surface in air,
Aluminum can also be used. Of these materials,
A material which is made transparent by oxidation, nitridation, fluoridation or the like and whose transparent compound is insoluble in water is a material which can be used for producing a stable structure. In particular, aluminum and titanium are suitable for anodic oxidation by energization and are one of the easy-to-use materials. In addition to oxidization, compounds that become more stable in the atmosphere by nitridation or fluoridation, such as chromium, are also available as options. Even if it becomes a hydroxide by reaction with water vapor after fluorination, it can be used as long as the hydroxide is insoluble in water. In addition, a material that is stabilized as a hydrate by bonding with water and also exhibits water insolubility can also be used. Titanium and chromium are one of the metals satisfying such properties.

As described above, the light-shielding film material is oxidized,
When the material is made transparent by nitridation or fluoridation, at the same time, atoms such as oxygen, hydroxyl groups, nitrogen or fluorine are inserted into the original material, so that the volume expands and swells. As a result, as shown in FIG. However, it has a structure in which a certain curved surface protrudes from the surface of the light shielding film 1 in a convex shape. In the lithography on the wafer, only the transparent window, which is a light transmitting portion, can be selectively brought closer to the wafer surface in the lithography on the wafer, so that the light transmission efficiency can be increased. It is advantageous. In particular, light that has passed through a transparent window with a very small diameter contains many near-field light components that tend to rapidly attenuate with distance even in the air.
The effect of suppressing transmission loss is great. In addition, the structure in which the dielectric material protrudes in a convex shape tends to cause the concentration of the photoelectric field at the top of the protrusion, and has an effect of concentrating surrounding light. This phenomenon is significant when the radius of curvature at the top of the protrusion is shorter than the wavelength of light, and is effective with a minute mask window. In order to efficiently concentrate the electric field at one point, it is advantageous to make the radius of curvature at the top of the projection appropriately small, eliminate the convex portion around the projection, or increase the radius of curvature appropriately. Specifically, the shape may be close to a conical shape. The shape of the curved surface varies depending on the manufacturing method and manufacturing conditions, such as a spherical shape and a conical shape. However, in the transparent window formed by the energizing oxidation method described below (Example 2), depending on the oxidation conditions, a projection having a shape close to a conical shape is formed. Is obtained directly. Due to the effect of light condensing due to the concentration of the optical electric field, light around the transparent window is gathered at the center of the transparent window, and the effect of increasing the contrast between light and dark at the boundary between the light transmitting portion and the non-transmitting portion is also obtained. In addition, the formed transparent window,
It can be confirmed by a microscope image (measurement of transmitted light, measurement of surface unevenness) of a scanning probe microscope. Note that such a structure can be formed by refilling a dielectric material after cutting the opening.

Note that a structure in which a protective film or a material having a role of a protective film is further laminated on the above structure may be formed. By laminating the protective film, further chemical change can be prevented, and unnecessary transparency in the light shielding region can be prevented. In the case where the thickness of the protective film is as thin as several nm, which is sufficiently shorter than the wavelength of light, the above characteristics are not impaired.

Example 2 Production of a Transparent Window on a Flat Plate by Electrical Oxidation FIG. 7 shows a method of forming a single transparent window on a flat plate by electrical oxidation as an embodiment of the present invention. One point on the light-shielding film 1 deposited on the substrate 4 is an electrode 8
A power supply 9 is connected to the probe, and a portion serving as a transparent window is formed by anodic oxidation by applying a current to a contact point of the needle with the probe side being minus and the light-shielding film on the substrate side being plus.
As the probe, a conductive probe may be used as the probe of the scanning probe microscope, and this may be used as the electrode 8. Glass is used as the substrate 4, metallic titanium having a thickness of about 30 nm is used as the light-shielding film 1, and anodizing is performed in the air by 0.5 nm.
When a transparent window having a diameter of about a micron is formed, the setting force of the needle is about 150 nN, and the voltage of the power supply 9 is 15 to several tens of volts. These optimum values differ depending on the surface condition of the light-shielding film. The current limiter 7 is necessary to prevent abnormal heat generation in a minute area due to an overcurrent,
The limiting current value is about 100 nA. The energization time varies depending on conditions such as the thickness of the light-shielding film and the humidity in the atmosphere, but is several seconds to several hundred seconds.

If a conductive substrate is used as the substrate, a positive electrode can be used for the substrate instead of the light-shielding film. This can be realized by using a doped semiconductor wafer or the like as the substrate.

The transparent window can also be formed by oxidizing, hydroxylating, nitriding or fluorinating a part of the light-shielding film by a lithography technique using a resist or the like. When using a resist, apply the resist to the entire light-shielding film, make holes only by exposing only the transparent window forming part, and use this as a mask, and use oxygen, nitrogen or fluorine plasma in a vacuum chamber to form only the transparent window part. Can be formed by oxidizing / nitriding or fluorinating. There is also a method in which a cyclotron resonance plasma of oxygen / nitrogen or fluorine is used as an ion source to selectively implant ions of these radicals into a portion where a transparent window is formed.

Example 3 Production of a Transparent Window on a Flat Plate by Spot Heating FIG. 8 shows a method of forming a transparent window by spot heating using a laser beam. The laser beam 10 having sufficient intensity for spot heating is focused on the light-shielding film 1 through the lens 16 to locally heat the light-shielding film to 800 ° C. to 1000 ° C. or higher. If this is performed in an oxygen atmosphere or the atmosphere, the heated portion is thermally oxidized to form a transparent window having a small diameter. The size of the transparent window depends on the intensity, irradiation time, spot diameter,
Although it varies depending on the thickness of the light-shielding film, the thermal conductivity of the substrate 4 to be used, and the like, actually, the metal titanium (30 nm thick) on the glass substrate is used.
m) is used as a light-shielding film, and a laser beam having an intensity of about 20 mW is condensed and irradiated for a few seconds to form a transparent window having a diameter of about 2 μm. By optimizing these conditions, it is also possible to form a transparent window having a size smaller than the spot size of the collected light by utilizing heat diffusion to the surroundings. If the same operation as described above is performed in a nitrogen atmosphere, a transparent window can be formed by nitriding. When chromium metal is used as the light-shielding film, the transparent window formed by nitriding is excellent in terms of water resistance, and is suitable as a transparent window of a mask. The laser beam may be irradiated directly from the back side of the substrate, instead of being directly irradiated from the light shielding film side. In that case, the wavelength is shortened by the higher the refractive index of the substrate as compared with air, so that it is possible to further narrow the focused spot size. As a light source, an ordinary light bulb or the like may be used in addition to laser light as long as light intensity necessary for spot heating can be obtained.

FIG. 9 is a view showing an embodiment in which a lithography mask having this structure is manufactured by scanning a substrate. By fixing the optical axis of the laser beam 10 and modulating the intensity of the laser beam applied to the light-shielding film 1 while scanning the substrate 4, a mask having a transparent window 2 having an arbitrary pattern can be obtained. The transmittance can be arbitrarily changed by modulating the intensity of the laser beam, thereby changing the degree of oxidation / nitridation or fluorination.
It is possible to obtain a mask having an arbitrary pattern in which the intensity of transmitted light is arbitrarily modulated. Alternatively, the same mask can be obtained by fixing the substrate 4 side and scanning the laser beam 10 side. The same applies to Example 2.
In the energization oxidation method as described in the above section, it is also possible to modulate the scanning speed and the limiting current. In that case, the probe or the substrate is scanned.

Example 4 Fabrication of a Mask Having a Transparent Window on a Conical Protrusion FIG. 10 shows a mask having a fine transparent window according to the present invention, using a substrate having a conical projection 6. FIG. 7 is a diagram showing a method of forming a transparent window 2 as shown in FIG. 6 on the top of a protrusion. The materials and the conditions of oxidation / nitridation or fluorination are the same as in the second embodiment. When a transparent window is formed on the top of a projection, a conductive flat plate or a plate with a flat portion that can be regarded as a flat plate in a minute area is applied to the top of the projection as an electrode, and current is applied. In addition, a minute transparent window can be formed on the top of the protrusion. This method uses a (111) plane, (1)
The protrusions can be formed by lithography using the anisotropy of etching on the (00) plane or the like, and a thin metal plate can be placed on the protrusions to supply electricity.

In the structure shown in FIG. 6, a metal film is used as a light-shielding film material, and when a laser beam is incident on the projection from the back side of the substrate having the conical projection 6, the surface in the metal is used. When plasmon is used in combination, light propagates on the surface of the metal film, so that light can be collected from the light-shielding portion other than the transparent window to the top of the protrusion, so that the amount of light emitted from the top of the protrusion can be further improved. . The angle of the projection is set so that the laser beam incident from the back side of the substrate undergoes total reflection on the projection slope. The wavelength of surface plasmon that can be excited in a metal film is determined by the type of metal and the thickness of the metal film. The phase wavelength of this surface plasmon in the metal film and the phase wavelength of the totally reflected light on the projection slope are different. Under the same conditions, surface plasmons can be excited. The thickness of the light-shielding film, the thickness of the light-shielding film,
By adjusting the angle of the projection to form this structure, higher efficiency can be achieved.

This structure utilizes plasmon propagation,
Since the light around the transparent window can be collected at one point, it is advantageous in terms of the contrast between the transmissive part and the light-shielding part, and is particularly useful when it is desired to produce a mask that requires a pointwise contrast.

(Embodiment 5: Fine Drawing / Processing by Near-Field Photolithography) FIGS. 11 to 14 show another embodiment of the present invention. FIG. 3 is a diagram showing a structure of a wafer to be processed.

FIGS. 11 and 12 are a bird's-eye view and a cross-sectional view, respectively, of a screen in which a large number of transparent windows shown in FIG. 1 are arranged to provide a screen for near-field photolithography. FIGS. 11 and 12 show a case where a large number of transparent windows 2 having a small diameter such that the size of any one of the vertical, horizontal, and diameter is equal to or less than a quarter of the wavelength in the air of the light used for exposure. When arranged in a plane at short intervals like
The screen generates near-field light containing a large amount of evanescent light components. The intensity distribution 12 of the near-field light generated in this manner rapidly attenuates with distance as the distance from the transparent window 2 increases, particularly, in the lateral direction, so that it is not necessary to use a means such as a phase shift method. A fine pattern can be drawn.

FIG. 13 is a cross-sectional view of a case where a mask and a wafer are brought into contact when a screen for generating near-field light is used as a mask for lithography.

Exposure light 13 incident from the mask side passes through the substrate 4 and the transparent window 2 and passes through the wafer 1 to be transferred.
The resist photo-sensitive film 14 applied on 5 is exposed. According to the present embodiment, due to the abrupt lateral attenuation characteristic of the near-field light, it is possible to draw a fine pattern without using a means such as a phase shift method.
The projecting transparent window 2 improves the contact with the resist photosensitive film 14 on the wafer 15 and has an effect that generated near-field light is efficiently transmitted to the resist photosensitive film 14.

FIG. 14 is a cross-sectional view when the mask and the wafer are brought into contact when the lithography mask of FIG. 13 is used in combination with a conventional phase shift method.

Exposure light 13 incident from the mask side passes through the substrate 4 and the transparent window 2 and reaches the resist photosensitive film 14, at which time an optical path passing through the phase shift film 5
An optical path that does not pass through the phase shift film 5 can be made.
Thereby, similarly to the conventional phase shift method, it is possible to further sharpen an image between adjacent patterns. According to this structure, an optical path that does not pass through the phase shift film and an optical path that does not pass can be clearly separated, so that there is an advantage that it is easy to design a mask at a pattern edge or a corner.

[0029]

As described above, according to the present invention, it is possible to form a structure in which the openings of the mask are filled with a transparent dielectric. Since light does not have to escape from the transmission window, the light transmission efficiency can be improved. In the manufacture of the mask, a complicated step of cutting extremely small holes and refilling the substance can be omitted.

Further, the transparent window manufactured according to the present invention has a structure that protrudes from the surface of the light-shielding film in a convex shape, so that in light application such as optical recording, the light-collecting efficiency can be increased and the contact with the recording medium can be improved. The light transmission efficiency can be improved. When applied to a mask or the like, this leads to an improvement in the reliability in lithography of a fine structure.

According to this structure, in lithography using near-field light, the light transmission efficiency of the mask window and the contrast with the light-shielding film can be improved, so that the processing pattern can be increased in density and the processing throughput can be improved. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a transmission window of a mask according to the present invention.

FIG. 2 is a sectional structural view of a transmission window of a conventional mask.

FIG. 3 is a cross-sectional structural view of a conventional semiconductor mask obtained by only cutting a light shielding film.

FIG. 4 is a cross-sectional structural view of a conventional semiconductor mask filled with a transparent material after cutting a light shielding film.

FIG. 5 is a sectional structural view of a conventional semiconductor mask in which a light shielding film is embedded after cutting a substrate.

FIG. 6 is a sectional structural view of a mask to which the present invention is applied when a substrate having a conical projection is used as the substrate.

FIG. 7 is a view showing a manufacturing method when a transparent window of a mask on a flat plate according to the present invention is manufactured by an anodic oxidation method.

FIG. 8 is a view showing a manufacturing method when a transparent window of a mask on a flat plate according to the present invention is manufactured by spot heating using a laser beam.

FIG. 9 is a view showing a manufacturing method according to the present invention when a mask having an arbitrary pattern is manufactured by spot heating while scanning a substrate.

FIG. 10 is a diagram showing a method of forming a mask window according to the present invention by anodic oxidation when a transparent window is formed on the top of a projection using a substrate having a conical projection.

FIG. 11 is a bird's-eye view of the structure of the mask when the present structure is used as a screen mask for generating near-field light.

FIG. 12 is a cross-sectional structural view of a mask when the present structure is used as a screen mask for generating near-field light.

FIG. 13 is a sectional structural view of a mask and a sample when the present structure is used as a lithography screen to which near-field light is applied.

FIG. 14 is a cross-sectional structural view of a mask and a sample when the present structure is used as a lithography screen in combination with a phase shift film.

[Explanation of symbols]

 1. 1. Light shielding film Transparent window 3. Opening 4. Substrate 5. Phase shift film 6. 6. conical projection 7. Current limiter Electrode 9. Power supply 10. Laser light 11. Lens 12. 12. Near-field light intensity distribution Exposure light 14. 14. resist photosensitive film Wafer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sumio Hosaka 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo F-term in Central Research Laboratory, Hitachi, Ltd. 2H095 BA03 BB27 BC05 BC24

Claims (16)

[Claims] An optical system for limiting a light transmitting area, comprising a light-shielding film portion having a finite thickness and being optically opaque or translucent, and a transmission window portion having a higher transmittance than the light-shielding film portion. Means, or an optical means for generating near-field light, the transmission window portion is filled with a dielectric substance, and only the transmission window portion is selectively formed into a more convex shape than the light-shielding film surface. A lithography mask that is protruding. 2. An optical device for limiting an area through which light is transmitted, comprising a light-shielding film portion having a finite thickness and being optically opaque or translucent, and a transmission window having a higher transmittance than the light-shielding film portion. Window means is filled with an oxide, a hydroxide, a nitride, a fluoride or a hydrate of a light-shielding film material. A lithography mask characterized by the above-mentioned. 3. The structure according to claim 1, wherein the light-shielding film material is deposited on a substrate having a conical projection, and a transparent window is formed near the top of the projection. Lithography mask. 4. The structure according to claim 3, wherein the thickness of the light-shielding film and the tip angle of the projection are set such that surface plasmons are excited in the light-shielding film on the projection slope with respect to the wavelength of light to be used. A lithography mask characterized by the above-mentioned. 5. A lithography mask in which a protective film or a material having a role of a protective film is further laminated on the structure according to claim 1. 6. A lithography mask according to claim 1, wherein said light-shielding film is made of aluminum or a transition metal, or an alloy or compound of a combination thereof. 7. The mask according to claim 1, wherein
A method for forming a mask window, wherein a transparent window portion is formed by selectively oxidizing, hydroxylating, nitriding, or fluorinating a part of a light-shielding film using a lithography technique. 8. The mask according to claim 1, wherein
A method for forming a mask window, characterized in that a transparent window portion is formed by energizing a part of a light-shielding film. 9. The mask according to claim 3, wherein
A method for forming a mask window, characterized in that a transparent window portion is formed by applying a conductive flat plate or an electrode having a flat portion which can be regarded as a flat plate in a minute area to the top of a projection, and conducting an electric current. 10. A mask window forming method according to claim 1, wherein the transparent window portion is formed by thermally oxidizing a part of the light shielding film by spot heating or nitriding by heat. . 11. An apparatus for producing a transparent window of a mask on the top of a projection by the forming method according to claim 9. 12. An apparatus for producing a transparent window of a mask by the forming method according to claim 10. 13. A mask manufacturing apparatus for manufacturing the mask according to claim 1. 14. A mask pattern exposure apparatus using the mask according to claim 1. 15. A method utilizing a steep attenuation characteristic of evanescent light generated by using the structure according to claim 1.
Surface processing equipment. 16. A steep attenuation characteristic of evanescent light generated by using the structure according to any one of claims 1 to 6,
Micro processing equipment.