JP2001066762A - Mask for proximity field optical exposure and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable irradiation a material to be exposed, such as a photoresist, with proximity field light at sufficient intensity and to solve the problem of fogging and durability by a small thickness of a light-shielding film with a mask for proximity field optical exposure which is formed with the light shielding film, in such a manner as to leave the apertures of prescribed patterns on the one surface side of a mask preform which is transparent with respect to exposure light. SOLUTION: A mask 20 for proximity field optical exposure is constituted by forming a light-shielding film 11, so as to leave the apertures 11a of the prescribed patterns on one surface side of the mask preform 10 which is transparent to the exposure light. A packing member 14, which is transparent to the exposure light is disposed in the apertures 11a so as to project at a prescribed height from the surface portion of the mask preform 10 formed with the light-shielding film 11 and is formed in a range, such that h-50 nm<=d<=h+50 nm is attained when the thickness of the light-shielding film 11 is defined as (d) and the projection height of the packing member 14 as (h).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a photomask used for near-field light exposure for transferring a fine pattern and a method for manufacturing the same.

[0002]

2. Description of the Related Art Recently, for example, lithographic LSI
In the manufacturing technology described above, the minimum dimension required for lithography is steadily miniaturized as the degree of integration increases. In order to meet such demands, the exposure wavelength has been shortened and lighting methods have been devised.However, when a line width of 0.1 μm or less is required, it is difficult to deal with such a method. Has become.

[0003] Exposure techniques such as exposure with shorter wavelength X-rays and electron beam exposure have been studied in the past, but these techniques have problems such as high cost of equipment used and low throughput. I have it.

[0004] In view of this point, in recent years, attention has been paid to the transfer of a fine pattern exceeding the diffraction limit of the wavelength and the near-field light exposure by using near-field light. This near-field light exposure uses a photomask (hereinafter simply referred to as a mask) having an opening finer than the wavelength of the exposure light, and an object to be exposed such as a photoresist is exposed to the near-field light leaking from the opening of the mask. This is a method of exposing. The near-field light described above has a smaller depth and range than the wavelength of the exposure light, so this near-field light exposure allows a pattern finer than the wavelength of the exposure light to be transferred to the object. Becomes In this case, since the depth of the near-field light seeping out from the mask is very shallow as described above, contact exposure is often used as the exposure method.

Conventionally, a mask used for this contact exposure has a light shielding film formed by adding an antireflection film to a metal film such as Cr on the surface of a mask base material made of glass or the like which is transparent to exposure light. Formed, a photoresist is applied thereon, and a resist pattern having an opening with a width smaller than the wavelength of the exposure light is formed by performing electron beam exposure or the like on this,
It has been manufactured by etching a light-shielding film using the resist pattern as a mask, and using the etched portion as a mask opening.

Alternatively, as shown in FIG. 6, a mask base material 1 made of glass or the like is prepared (FIG. 1 (1)), a photoresist is applied to the surface of the mask base material 1, and an electron beam exposure or the like is applied thereto. To form a resist pattern 2 having a line width narrower than the wavelength of the exposure light (FIG. 2B), and forming a light-shielding film 3 by sputtering Cr using the resist pattern 2 as a mask (FIG. 3C). A mask manufacturing method is also known in which the resist pattern 2 is removed and the removed portion is used as a mask opening 4 (FIG. 4D).

[0007]

In any of the conventional masks manufactured by the above-described methods, in any case, a light-shielding film is deposited in a form having openings of a predetermined pattern on a flat surface of a mask base material. It will be. When this mask is used for near-field light exposure, exposure light is incident on the mask base material from the side opposite to the above surface, and near-field light is exuded from the opening of the light-shielding film to be in close contact with the light-shielding film. It is used to expose a photoresist or the like arranged in close proximity by this near-field light.

However, a conventional mask having a structure in which a light-shielding film is deposited on a flat surface of a mask base material as described above basically has a light-shielding film because the propagation of near-field light from the mask base material is shallow. Cannot be formed sufficiently thick,
For this reason, various problems are caused. Less than,
This will be described in detail.

In general, the depth of seepage of near-field light, that is, the distance from the surface of the mask base material in the above-described mask is only about several tens of nm. Therefore, in order to allow near-field light to reach an object to be exposed which is in close contact with or close to the light-shielding film, the thickness of the light-shielding film must be several tens nm or less.

When the thickness of the light-shielding film is as thin as about several tens of nanometers, defects such as pinholes are liable to occur therein, and the light-shielding film itself easily transmits light. There is a problem that the ratio of the light amounts (extinction ratio) becomes small and fog occurs when the object to be exposed has high sensitivity.

In particular, when exposing the mask in close contact with the object to be exposed, since the mechanical strength is low when the light-shielding film is thin, defects due to contact during operations such as alignment between the mask and the object to be exposed are reduced. And the durability of the mask becomes insufficient.

To cope with the above problem, it is conceivable to increase the thickness of the light-shielding film. However, if the thickness is increased to more than several tens of nm, near-field light will not reach the photoresist at all. Further, even when the light-shielding film is thinned to several tens of nm, there is attenuation of near-field light, and it is difficult to provide sufficient light intensity to the photoresist. , The light shielding film thickness is 50 nm
It can be said that the degree is the upper limit.

In view of the above circumstances, the present invention can irradiate an object to be exposed, such as a photoresist, with near-field light at a sufficient intensity, and on the other hand, can form a light-shielding film sufficiently thick to reduce fog and fog. An object of the present invention is to provide a near-field light exposure mask that can solve the problem of durability.

Another object of the present invention is to provide a method capable of manufacturing such a near-field light exposure mask.

[0015]

As described above, a near-field light exposure mask according to the present invention has a predetermined pattern of openings on one surface side of a mask base material that is transparent to exposure light. In the near-field light exposure mask in which a light-shielding film is formed, a filling member that is transparent to exposure light and protrudes from the mask base material surface portion where the light-shielding film is formed by a predetermined height is provided in the opening. It is characterized by being arranged.

In the above configuration, the thickness d of the light shielding film
Is h-50, where h is the projecting height of the filling member.
It is desirable that the range of nm ≦ d ≦ h + 50 nm be satisfied.

The above-mentioned filling member is preferably formed in a shape that becomes gradually thinner toward the tip end side.

The filling member may be formed by joining a member different from the base material to a flat mask base material surface, or may be formed integrally with the mask base material. Is also good.

On the other hand, one method of manufacturing a near-field light exposure mask according to the present invention is applied when the above-described filling member is formed by bonding a member different from the base material to a flat mask base material surface. After forming a light shielding film of a predetermined shape on a flat mask base material surface, a filling member is formed by embedding a member different from the mask base material in a portion where the light shielding film is not formed. It is characterized by doing.

Another method of manufacturing a near-field light exposure mask according to the present invention is applied when a filling member is formed integrally with a mask base material, and a flat mask base material surface is formed into a predetermined shape. A portion which is not etched is left as the filling member, and a light shielding film is formed on the etched portion.

In the above method of manufacturing a near-field light exposure mask, the thickness d of the light-shielding film is set to h−50 nm ≦ d ≦
In order to make the range of h + 50 nm, a method of polishing or etching back the surface of the mask on which the light-shielding film is provided and flattening it can be suitably used.

[0022]

In the near-field light exposure mask of the present invention, the filling member projecting from the surface of the mask base material on which the light-shielding film is formed by a predetermined height is disposed in the opening. Even if it is formed sufficiently thick, it is possible to irradiate the object to be exposed with near-field light oozing from the surface of the filling member without having an attenuation distance or with an extremely short attenuation distance. If the light-shielding film can be formed sufficiently thick in this way, the above-mentioned extinction ratio can be secured to a large extent, and fog and durability problems can be solved.

In particular, if the thickness d of the light-shielding film is set in the range of h-50 nm ≦ d ≦ h + 50 nm, where h is the protrusion height of the filling member, the surface of the light-shielding film is aligned with the surface of the filling member. (When h = d) or 50n at the front side of the filling member surface, that is, on the side away from the mask base material.
m, or conversely, at a distance of up to 50 nm closer to the mask base material than the surface of the filling member.

When the surface of the light-shielding film and the surface of the filling member are aligned as described above, when the light-shielding film is brought into close contact with an object to be exposed such as a photoresist at the time of near-field light exposure using the mask, the proximity The surface of the filling member, which is the exuding surface of the field light, also comes into close contact with the object to be exposed. Therefore, the near-field light that has leaked from the surface of the filling member directly reaches the object to be exposed without having an attenuation distance, so that the object to be exposed can be irradiated with sufficient intensity by the near-field light.

Even when the light-shielding film is not brought into close contact with the object to be exposed at the time of the near-field light exposure, the near-field light oozing from the surface of the filling member has a small attenuation distance (the separation distance between the light-shielding film and the object to be exposed).
In this case, the object can be irradiated with near-field light with sufficient intensity.

On the other hand, since the thickness d of the light-shielding film is equal to the height h of the filling member, basically, the thickness d of the light-shielding film is increased by increasing the height h of the filling member. It can be as thick as needed. Therefore, the light-shielding film is made sufficiently thick to secure a large extinction ratio as described above, and fog and durability problems can be solved.

Also, when the surface of the light-shielding film is located in front of the surface of the filling member (when h <d), the step between both surfaces is set to 50 nm or less, which is the limit of near-field light arrival. . Therefore, when a light-shielding film is brought into close contact with an object to be exposed such as a photoresist at the time of near-field light exposure using the mask, the near-field light exuding from the surface of the filling member reaches the object with an attenuation distance of less than 50 nm. Therefore, also in this case, the object to be exposed can be irradiated with sufficient intensity by the near-field light.

If the thickness d of the light-shielding film is set so that the step between the surface of the light-shielding film and the surface of the filling member has a considerably small value even within a range of less than 50 nm, the light-shielding film is exposed during near-field light exposure. Even if it is slightly separated from the object to be exposed, the near-field light oozing from the surface of the filling member can reach the object to be exposed with an attenuation distance of less than 50 nm. Therefore, also in this case, the object to be exposed can be irradiated with sufficient intensity by the near-field light.

As described above, even when h <d, that is, when the thickness d of the light-shielding film is larger than the protrusion height h of the filling member, the light-shielding film is made larger by increasing the protrusion height h of the filler member. Can be made as thick as necessary. Therefore, also in this case, the fogging and durability problems described above can be solved by making the light-shielding film sufficiently thick.

Further, when the surface of the light-shielding film is located closer to the mask base material than the surface of the filling member (when d <h), an object to be exposed such as a photoresist is exposed during near-field light exposure using the mask. When the mask is brought into close contact, the surface of the filling member, which is a surface from which near-field light exudes, comes into close contact with the object to be exposed.
Therefore, the near-field light that has leaked from the surface of the filling member directly reaches the object to be exposed without having an attenuation distance, so that the object to be exposed can be irradiated with sufficient intensity by the near-field light.

Even when the mask is not brought into close contact with the object to be exposed at the time of near-field light exposure, the near-field light oozing from the surface of the filling member has a small attenuation distance (distance between the mask and the object).
In this case, the object can be irradiated with near-field light with sufficient intensity.

As described above, even when d <h, that is, when the thickness d of the light-shielding film is smaller than the protrusion height h of the filling member, the light-shielding film is made larger by increasing the protrusion height h of the filler member. Can be made as thick as necessary. Therefore, also in this case, the fogging and durability problems described above can be solved by making the light-shielding film sufficiently thick.

In the case of d <h, if the distance between the surface of the light-shielding film and the surface of the filling member is set too large, there is a concern that the resolution of the exposed image is reduced due to the spread of the near-field light. Therefore, in the present invention, h-50 is set so that the step between the light-shielding film surface and the filling member surface in this case does not exceed 50 nm.
nm ≦ d.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a procedure for fabricating a near-field light exposure mask according to the first embodiment of the present invention.

First, as shown in FIG. 1A, one surface of a mask base material 10 made of a flat quartz glass plate is
As an example, a 50 nm thick Cr film, and a 50 nm thick C film
A light shielding film 11 is formed by forming an r oxide film.

Next, after applying an electron beam resist on the light shielding film 11, it is baked. After that, a predetermined pattern is exposed on the resist by an electron beam, and PEB is exposed.
After performing (postexposure bake), the electron beam resist is developed with a dedicated developer to form a resist pattern 12 having a desired shape opening 13 having a width of 0.01 to 0.1 μm as shown in FIG. .

Next, using the resist pattern 12 as a mask, the light-shielding film 11 is removed by dry etching using CCl ₄ + O ₂ as an etching gas, as shown in FIG. Then, the resist pattern 12 is removed with a dedicated stripper, and is washed. Through the above processing, openings 11a having a predetermined pattern are formed in the light shielding film 11, as shown in FIG.

Next, SOG is applied on the light shielding film 11,
It is fired to deposit SiO ₂ 14 (FIG. 5 (5)).
Thereafter, by etching back using dry etching using CF ₄ until the SiO ₂ 14 on the surface of the light shielding film 11 disappears, the near-field light exposure mask 20 according to the first embodiment of the present invention is completed (FIG. 6)).

FIG. 2 shows an enlarged sectional shape of the near-field light exposure mask 20 according to the first embodiment. In the near-field light exposure mask 20, SiO ₂ 14 as a filling member is disposed in the opening 11a of the light shielding film 11, and SiO ₂ 14 from the surface of the mask base material 10 where the light shielding film 11 is formed. Is equal to the thickness d of the light-shielding film 11. That is, the surface of the SiO ₂ 14 and the surface of the light shielding film 11 are aligned.

When the light-shielding film 11 is brought into close contact with an object to be exposed such as a photoresist at the time of near-field light exposure using the mask 20 having such a structure, the surface of the SiO ₂ 14 serving as the near-field light seeping surface is exposed. It comes into close contact with things. Therefore, the near-field light that has permeated from the surface of the SiO ₂ 14 directly reaches the object to be exposed without having an attenuation distance, and the object to be exposed can be irradiated with sufficient intensity by the near-field light. .

Further, as described above, the light-shielding film 11
When the surface of the SiO ₂ 14 and the surface of the light-shielding film 11 are aligned with each other, the adhesion between the object to be exposed and the light-shielding film 11 is improved. Can be irradiated on the object to be exposed.

Even when the light-shielding film 11 is not brought into close contact with the object to be exposed at the time of near-field light exposure, if the distance between the light-shielding film 11 and the object to be exposed is set to 50 nm or less, it exudes from the surface of the SiO ₂ 14. Since the near-field light reaches the object to be exposed at an attenuation distance of 50 nm or less, the object to be exposed can be irradiated with the near-field light with sufficient intensity.

[0043] On the other hand, since the thickness d of the light blocking film 11 is aligned with the protrusion height h of the SiO ₂ 14, basically, the SiO ₂
By increasing the protrusion height h of the 14, the thickness d of the light-shielding film 11 can be increased as necessary. Therefore,
The fogging and durability problems described above can be solved by making the light-shielding film 11 sufficiently thick.

In the above embodiment, the SiO ₂ 14 is flattened by etch back. However, the flattening is not limited to this, and a conventionally known polishing method such as CMP may be applied. Can also. Further, in the above embodiment, SOG is used as the filler, but the SiOG is formed by vacuum deposition such as CVD or sputtering.
It is also possible to use ₂ .

In the above embodiment, the light-shielding film 11 is made of Cr. However, it is also possible to form the light-shielding film from a multilayer film made of another metal such as gold, or an alloy. Furthermore, as long as a sufficient extinction ratio can be ensured between the exposure light and the opening, a polymer, a metal-dispersed silica, or the like can be used as the light-shielding film material.

In the above embodiment, quartz glass is used as the mask base material. However, any other material such as a polymer, for example, a polymer may be used as the mask base material as long as it has a sufficient transmittance to exposure light. Applicable.

Next, a second embodiment of the present invention will be described. FIG. 2 schematically shows a procedure for manufacturing a near-field light exposure mask according to a second embodiment of the present invention. Here, first, HMDS (hexa) for enhancing adhesion is provided on one surface of the mask base material 10 made of a flat quartz glass plate.
After applying methyle disilazane treatment, an electron beam resist 30 is applied to the surface and baked (see FIG.
(1)). Next, gold is 10n thick to prevent charge up
about m.

After that, a pattern of a predetermined shape is exposed on the resist 30 by an electron beam, PEB is performed, and then gold is removed with an iodine-based etchant. Next, the electron beam resist 30 is developed with a special developing solution to form a resist pattern 30A as shown in FIG.

Next, as shown in FIG.
Using 0A as a mask, the mask base material 10 is etched with a buffered hydrofluoric acid by a predetermined amount (here, for example, 100 nm), and then the resist pattern 30A is removed using a resist stripper as shown in FIG. .

Next, as shown in FIG. 5 (5), Cr31 'is deposited by electron beam evaporation to a predetermined thickness (here, 300 nm as an example) which is equal to or greater than the etching depth. afterwards,
CMP until the unetched mask base material 10 is exposed
When Cr31 'is polished to form a light shielding film 31,
The near-field light exposure mask 40 according to the second embodiment of the present invention is completed (FIG. 6 (6)).

FIG. 4 shows an enlarged sectional shape of the near-field light exposure mask 40 according to the second embodiment. In the near-field light exposure mask 40, the opening 31a of the light shielding film 31 is partially filled with the mask base material 10, and the height of the mask base material 10 protruding from the surface portion where the light shielding film 31 is formed. H and the light shielding film
31 is equal to the thickness d. In other words, the mask base material
The surface of the protrusion 10 and the surface of the light shielding film 31 are aligned.

Therefore, also in this case, basically the same effects as in the first embodiment can be obtained. In addition, in the case of the present embodiment, since the portion of the mask base material 10 which is to be embedded with the light shielding film 31 is processed by isotropic wet etching, as shown in detail in FIG. Has a shape that becomes gradually narrower toward the distal end side, and a unique effect is thereby obtained.

That is, when the protruding portion of the mask base material 10 has the above-described shape, the attenuation of the exposure light can be further reduced. Further, as is clear from FIG. 3C, the width of the opening of the light shielding film 31 (that is, the width of the tip of the protruding portion of the mask base material 10) is formed smaller than the width of the resist pattern 30A. In order to realize a desired minute opening width, the resist pattern 30A may be formed to have a width larger than the opening width.
Can be easily formed.

In the second embodiment, isotropic wet etching is applied in order to etch a portion of the mask base material 10 which is to be a buried portion of the light shielding film 31.
In addition, even if dry etching such as reactive ion etching is applied, the protruding portion of the mask base material 10 can be formed in the above-described shape, and in this case, the above-described effect can be obtained.

In the second embodiment, vapor deposition is applied as a method for embedding Cr31 'in the above-described etched portion, but instead, a method such as plating, CVD, or coating may be applied.

The two embodiments in which the surface of the filling member filled in the opening of the light-shielding film and the surface of the light-shielding film are described above. However, as in the third embodiment shown in FIG. The surface of the light shielding film 11 is located ahead of the surface of the filling member (in this case, integrally formed by the mask base material 10) disposed in the opening 11a of the light shielding film 11 (h <d). ). In this case, the step between both surfaces is set to 50 nm or less, which is the limit of reaching near-field light. Thereby, as described in detail above, whether or not the close-field light exposure mask and the object to be exposed are in close contact with each other, the object to be exposed can be irradiated with sufficient intensity by the near-field light, The light-shielding film 11 can be formed sufficiently thick.

Further, contrary to the example of FIG. 5, the surface of the light shielding film 11 is positioned closer to the mask base material than the surface of the filling member disposed in the opening 11a of the light shielding film 11 (d <h). It does not matter. Also in that case, the step on both surfaces is set to 50 nm or less, which is the limit of reaching near-field light. Thereby, as described in detail above, whether or not the close-field light exposure mask and the object to be exposed are in close contact with each other, the object to be exposed can be irradiated with sufficient intensity by the near-field light, The light-shielding film 11 can be formed sufficiently thick.

When d <h, the step between the surface of the light-shielding film and the surface of the filling member does not exceed 50 nm in order to prevent the resolution of the exposure image from deteriorating due to the spread of near-field light. h−50 nm ≦ d.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a procedure for manufacturing a near-field light exposure mask according to a first embodiment of the present invention.

FIG. 2 is a schematic side sectional view showing a main part of the near-field light exposure mask according to the first embodiment.

FIG. 3 is a schematic view for explaining a procedure for manufacturing a near-field light exposure mask according to a second embodiment of the present invention.

FIG. 4 is a schematic side sectional view showing a main part of a near-field light exposure mask according to the second embodiment.

FIG. 5 is a schematic side sectional view showing a main part of a near-field light exposure mask according to a third embodiment of the present invention;

FIG. 6 is a schematic view illustrating a procedure for manufacturing a conventional near-field light exposure mask.

[Explanation of symbols]

10 Mask base material 11 Light-shielding film 11a Opening of light-shielding film 12 Resist pattern 13 Opening of resist pattern 14 SiO ₂ 20 Near-field light exposure mask 30 Electron beam resist 30A Resist pattern 31 Light-shielding film 31 'Cr 40 For near-field light exposure mask

Claims (9)

[Claims] 1. A near-field light exposure mask in which a light-shielding film is formed on one surface side of a mask base material that is transparent to exposure light so as to leave an opening of a predetermined pattern. A near-field light exposure, wherein a filling member projecting from the surface of the mask base material on which the light-shielding film is formed and projecting a predetermined height and transparent to exposure light is disposed in the formed opening. For mask. 2. The thickness d of the light-shielding film is h-50 nm ≦ d ≦ h + 50, where h is the height of the protrusion of the filling member.
2. The near-field light exposure mask according to claim 1, wherein the thickness is in the range of nm. 3. The near-field light exposure mask according to claim 1, wherein the filling member disposed in the opening has a shape that becomes gradually thinner toward a tip end side thereof. 4. The near field according to claim 1, wherein the filling member is formed by bonding a member different from the base material to a flat mask base material surface. Light exposure mask. 5. The method according to claim 1, wherein the filling member is formed integrally with a mask base material.
The mask for near-field light exposure according to any one of the preceding claims. 6. The method for producing a near-field light exposure mask according to claim 4, wherein the light-shielding film is not formed after a light-shielding film having a predetermined shape is formed on a flat mask base material surface. A method for manufacturing a near-field light exposure mask, wherein the filling member is formed by embedding a member different from a mask base material in a portion. 7. The method for producing a near-field light exposure mask according to claim 5, wherein a flat mask base material surface is etched into a predetermined shape at a predetermined depth, and a portion left without being etched is removed. A method for producing a near-field light exposure mask, wherein a light-shielding film is formed on the etched portion as a filling member. 8. The thickness d of the light shielding film is set to h−50 nm ≦ d
8. The method of manufacturing a near-field light exposure mask according to claim 6, wherein a surface of the mask on which the light shielding film is disposed is planarized by polishing so as to satisfy a range of ≤h + 50 nm. 9. The thickness d of the light shielding film is set to h−50 nm ≦ d
8. The method for manufacturing a near-field light exposure mask according to claim 6, wherein the mask surface on which the light-shielding film is disposed is planarized by etch-back so as to satisfy the range of ≤h + 50 nm.