Lithographic mask structure and lithographic process

There is disclosed a lithographic mask structure which comprises a masking material support film and an annular support substrate for supporting the masking material support film at the periphery, the masking material support film containing a fluorescent substance. Also disclosed is a lithographic process for exposing a photosensitive material to irradiation with a radiation beam through a masking material support film provided with a masking material pattern-wise.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a lithographic process for exposing a 
photosensitive material to irradiation with a radiation beam through a 
masking material support film provided with a masking material 
pattern-wise, and also to a lithographic mask structure. 
2. Related Background Art 
X-ray lithography has many distinguished advantages over the conventional 
lithography using visible light or ultraviolet light owing to the 
properties proper to the X-rays such as rectilinear propagation, 
non-interference, low diffraction, etc., and thus has been regarded as an 
important and useful means for submicron lithography or quater-micron 
lithography. However, in spite of the many advantages over the 
conventional lithography using visible light or ultraviolet light, the 
X-ray lithography still has such a disadvantage as a low productivity that 
is, a high cost, owing to the power shortage of X-ray source, the low 
sensitivity of resist, the difficult alignment, the difficult choice of 
masking material, the difficult processing procedure, etc. and thus its 
practical application has been considerably delayed. 
A most successful practical resist among those so far disclosed in the 
literature, etc. on the lithography is polymethyl methacrylate (PMMA), 
which is also a successful resist for electron beams, which can 
particularly meet the requirement for less than 0.1 .mu.m, and thus no 
other competitive materials have been found yet. A still remaining 
important problem of X-ray lithography is a problem of sensitivity. It is 
said that the X-ray utilization efficiency of resist in the X-ray 
lithography is usually 0.3% at most, which is a cause for lowering the 
sensitivity. For example, in the case of PMMA using a Pd K.sub..alpha. 
beam as X-ray, it is said that the sensitivity is 1,000 to 2,000 
mJ/cm.sup.2, where the sensitivity is given by an X-ray irradiation dosage 
at the exposure. That is, the lower the irradiation dosage, the higher the 
sensitivity. A practical resist of high sensitivity is chloromethylated 
polystyrene (CMS), which has a sensitivity of about 100 mJ/cm.sup.2 under 
the same conditions as above. A condition for practical application of 
X-ray lithography is a necessary provision of X-ray resist having a 
sensitivity of not more than 10 mJ/cm.sup.2, and its development has been 
desired. 
Now, researches have been made for higher productivity in three directions, 
i.e. intensity of beam source, X-ray transmission of masking material 
support body and X-ray intransmission of masking material, and sensitivity 
of resist, but no rapid and remarkable development is expectable owing to 
many restricting factors. However, a higher sensitivity of resist can be 
an essential condition from a fact that a device would be damaged if the 
X-ray is too strong. It is needless to say that this condition is 
necessary and essential even if the properties of mask and beam source are 
improved in the future. 
Description will be made of X-ray lithographic mask below. In the 
lithography using visible light and ultraviolet light, a glass plate and a 
quartz plate are used as a masking material support body 
(light-transmissible body). However, the wavelength utilizable in the 
X-ray lithography is, for example, 1 to 200 .ANG.. The so far available 
glass plate or quartz plate has a large absorption in the X-ray wavelength 
region, and must be as thick as 1-2 mm to maintain flatness, with a 
failure to transmit the X-ray therethrough. Thus, the glass plate or 
quartz plate is not suitable as a material for X-ray lithographic masking 
material support body. 
Generally, the X-ray transmissivity depends on the density of a material, 
and thus inorganic or organic materials of low density have been studied 
as materials for an X-ray lithographic masking material support body, and 
include, for example, such inorganic materials as simple substances, e.g. 
beryllium (Be), titanium (Ti), silicon (Si), and boron (B), their 
compounds, etc. and organic materials such as polyimide, polyamide, 
polyester, poly-p-xylylene (trade name parylene) produced by Union 
Carbide, Co.,), etc. 
In an actual application of these materials as a material for X-ray 
lithographic masking material support body, it is necessary to make them 
into a thin film to make the X-ray transmission as high as possible. It is 
required that the film thickness is not more than a few .mu.m for the 
inorganic materials and not more than a few tens .mu.m for the organic 
materials. In the formation of a masking material support body (which will 
be hereinafter referred to as "a masking material support film") composed 
of, for example, an inorganic thin film or its composite film to this end, 
there has been proposed a process which comprises forming a film of 
silicon nitride, silicon oxide, boron nitride or silicon carbide on a 
silicon plate of good flatness by vapor deposition, etc., and then 
removing the silicon plate by etching. 
On the other hand, the X-ray lithographic masking material (X-ray absorbing 
material, which will be hereinafter referred to as "a masking material") 
support on the above-mentioned masking material support film includes 
films of materials generally having a high density, for example, gold, 
platinum, tungsten, tantalum, copper, or nickel, preferably films having a 
thickness of 0.5 to 1 .mu.m. Such a masking material can be formed, for 
example, by forming a thin film of high density masking material 
throughout on a masking material support film, then applying a resist 
thereto, depicting a desired pattern on the resist by an electron beam, 
light, etc., and then forming the desired pattern by etching, or other 
means. 
In the conventional X-ray lithography as mentioned above, the masking 
material support film has a low X-ray transmissivity and thus must be made 
considerably thin to obtain a sufficient X-ray transmission. It has been a 
problem to make such a thin film. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a lithographic mask 
structure and a lithographic process with an effectively improved 
sensitivity of photosensitive material such as a resist, etc. and a better 
lithographic applicability, thereby solving the problems encountered in 
the prior art. 
Another object of the present invention is to provide a lithographic mask 
structure and a lithographic process capable of lithographic application 
under milder conditions of X-ray transmissivity, thickness, etc. of 
masking material support film. 
Another object of the present invention is to provide a lithographic mask 
structure which comprises a masking material support film and an annular 
support substrate for supporting the masking material support film at the 
periphery, the masking material support film containing a fluorescent 
substance. 
A further object of the present invention is to provide a lithographic mask 
structure which comprises a masking material support film and an annular 
support substrate for supporting the masking material support film at the 
periphery the masking material support film being composed of a 
fluorescent substance. 
Still a further object of the present invention is to provide a 
lithographic process which comprises exposing a photosensitive material to 
irradiation with a radiation beam through a masking material support film 
provided with a masking material patternwise, the masking material support 
film being composed of a fluorescent substance, a secondary radiation beam 
being generated from the fluorescent substance exposed to the radiation 
beam, and the photosensitive material being exposed to the secondary 
radiation beam and the radiation beam together. 
Still a further object of the present invention is to provide a 
lithographic process which comprises exposing a photosensitive material to 
irradiation with a radiation beam through a masking material support film 
provided with a masking material patternwise, the masking materail support 
film containing a fluorescent substance, a secondary radiation beam being 
generated from the fluorescent substance exposed to the radiation beam, 
and the photosensitive material being exposed to the secondary radiation 
beam and the radiation beam together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is particularly directed to the intensification of 
the effective sensitivity of a resist by the secondary radiation beam 
(fluorescent beam) generated from the masking material support film 
exposed to a radiation beam. For example, when an X-ray is used as a 
radiation beam, what plays a role of projecting a pattern onto the resist 
is this radiation beam as the principal beam. That is, the secondary 
radiation beam as an auxiliary beam plays a role of intensifying the 
sensitivity of a resist and must be below a given threshold value. The 
threshold value depends upon the baking of a resist, development 
conditions, etc. and cannot be specified. When, for example, the kind and 
the thickness of a resist, treating conditions such as baking conditions, 
etc., development conditions, factors of radiation beam source, such as 
kind, power, etc. are set, the threshold value can be determined by the 
emitted light wavelength range, emitted light efficiency, thickness and 
density of a fluorescent material. 
In the present invention, the secondary radiation beam in such a degree as 
not to exceed the threshold value is used to intensify the sensitivity on 
the basis of such resist characteristics that the resist is not sensitive 
to a radiation beam below the threshold value, but made sensitive to a 
radiation beam when it exceeds the threshold value. Thus, the power of the 
radiation beam as the principal beam for projecting a pattern is in such a 
degree as to only exceed the threshold value together with the secondary 
irradiation beam, and thus no large power is required. In other words, a 
clear pattern can be formed with a small power. 
In the present invention, a particularly effective radiation beam is an 
X-ray, and ultraviolet beams including a vacuum ultraviolet beam, electron 
beams, and ion beams have also a resist-sensitizing effect. 
The wavelength range of the secondary radiation beam is not particularly 
limited, but is practically 200 to 550 nm, when a wavelength range 
corresponding to the photosensitive range of the lithographic resist of 
the present invention is taken into account. A paticularly effective range 
is 300 to 450 nm, which is covered by most of the photolithographic 
resists as the photosensitive range and in which most of fluorescent 
materials emit the secondary radiation beams. 
The kind of the fluorescent materials is not particularly limited, and 
their typical examples are as follows: 
ZnS:Ag, ZnS:Cu. Al, Zn.sub.2 SiO.sub.4 :Mn, CaWO.sub.4, Ca.sub.2 MgSi.sub.2 
O.sub.7 :Ce, ZnO:Zn, ZnS:Cu, Y.sub.2 O.sub.2 S:Tb, YAlO.sub.3 :Ce.Ag, 
ZnS:Ag. Ga. Cl, ZnS:Zn+In.sub.2 O.sub.3, BaSi.sub.2 O.sub.5 :Pb, (Sr, 
Ca)B.sub.4 O.sub.7 :Eu.sup.2+, Ca.sub.2 B.sub.5 O.sub.9 Cl:Eu.sup.2+, 
Sr.sub.4 Si.sub.3 O.sub.8 Cl.sub.4 :Eu.sup.2+, BaMgAl.sub.14 O.sub.23 
:Eu.sup.2+, BaO.6Al.sub.2 O.sub.3 :Mn, BaSO.sub.4 :Pb, BaFCl:Eu.sup.2+, 
La.sub.2 O.sub.2 S:Tb, Gd.sub.2 O.sub.2 S:Tb, MgB.sub.4 O.sub.7 :Tb, 
Li.sub.2 B.sub.4 O.sub.7 :Cu, Ba.sub.2 Si.sub.2 O.sub.5 :Pb, NaI:Tl, 
CaF.sub.2 :Eu, MgF.sub.2 :Eu, KCl:Tl, CaS:Bi, .beta.CaSiO.sub.3 :Pb, 
BaSi.sub.2 O.sub.5 :Pb, Zn.sub.2 SiO.sub.4 :Ti, CaO.MgO.2SiO.sub.2 :Ti, 
Ca.sub.3 (PO.sub.4).sub.2 :Ce, Ca.sub.3 (PO.sub.4).sub.2 :Ce.Mn, Ca.sub.3 
(PO.sub.4).sub.2 :Tl, MgWO.sub.4, etc., and their mixtures. 
The colon in the chemical formulae of the foregoing fluorescent materials 
is a symbol showing that the element or ion at the right side of the colon 
in an additive. 
In the lithographic mask structure of the present invention, the masking 
material support film is composed of a fluorescent material or contains 
the fluorescent material. In the former case, the thickness of the masking 
material support film is preferable 2 .mu.m or more from the viewpoint of 
its strength and 10 .mu.m or less from the viewpoint of the radiation beam 
transmissibility. In the former case, various florescent materials can be 
used to form a masking material support film, and particularly it is 
preferable from the viewpoint of strength to use CaF.sub.2 :Eu and 
MgF.sub.2 :Eu. In the latter case, the masking material support film is in 
the form of a laminate film comprising, for example, a film of fluorescent 
material and a film of inorganic material such as silicon nitride, etc. or 
an organic material such as polyimide, etc. Particularly, a Laminate film 
with a film of organic material is effective from the viewpoint of the 
strength. laminate film is not limited to two layers, but may be in more 
than two layers. 
The material for a film of inorganic material in the laminate film can 
include ceramics of AlN, Al.sub.2 O.sub.3, BN, SiO.sub.2, SiC, aluminum 
oxynitride (7Al.sub.2 O.sub.3.3AlN), sialon (Si.sub.2 Al.sub.4 O.sub.4 
N.sub.4), etc. besides the above-mentioned, and the material for a film of 
organic material in the laminate film can include polyamide, 
poly-p-xylylene (trade name: parylene, produced by Union Carbide Co.,) 
(trademark), polyethylene terephthalate, polyacrylonitrile, 
polyethylenepentene copolymer, etc. 
It is desirable from the viewpoint of radiation beam transmissibility, etc. 
that the thickness of a film composed of the fluorescent material is 1 to 
5 .mu.m, and the entire thickness of a masking material support film is 
not more than a few tens .mu.m. 
Furthermore, in the latter case, the masking material support film may be 
such that fine particles of a fluorescent material are distributed in the 
masking material support film, besides the above-mentioned form. It is 
preferable that the fine particles have a size of not more than 1 .mu.m. 
Ultra-fine particles, that is, uniformly fine particles having sizes of a 
few tens to a few thousand .ANG., are particularly preferable, because 
they can be uniformly distributed in the masking material support film. 
The material for a masking material support film in which a fluorescent 
material is distributed is not particularly limited, but an organic 
material such as polyimide, etc. is preferable from the viewpoint of easy 
preparation. 
Examples of the present invention will be described below, referring to the 
accompanying drawings. 
EXAMPLE 1 
FIG. 1 is a schematic cross-sectional view of the main parts of a light 
exposure apparatus using a lithographic mask structure according to one 
embodiment of the present invention, where X-ray is used as a radiation 
beam. Numeral 1 is an annular support substrate, 2 is a fluorescent 
material layer formed by vapor deposition of .alpha.CaSiO.sub.3 Pb, etc., 
and 3 is a pattern-wise masking material formed from gold, etc., for 
example, 0.7 .mu.m thick. Numeral 4 is a film of polyimide, etc., 6 is a 
wafer of Si, etc., and 7 is a resist. Numeral 8 is a secondary radiation 
beam (fluorescent beam) generated from the fluorescent material layer 2. 
X-ray such as an RhL.sub.60 beam, etc. generally from an X-ray beam source 
(target) 10 is irradiated onto the resist 7 coated on the wafer 6 through 
an X-ray lithographic mask structure. The resist 7 is made from, for 
example, polymethylisopropenylketone (PMIPK), etc., onto which the X-ray 
transmitted through the masking material support film without absorption 
by the pattern-wise masking material 3 is irradiated to project the 
pattern of the masking material 3 thereon. In this case, the secondary 
radiation beam generated from the fluorescent material layer 2 has a peak 
of, for example, 300 nm and is irradiated onto the resist 7. 
EXAMPLE 2 
FIG. 2 is a schematic cross-sectional view of a lithographic mask structure 
according to another embodiment of the present invention, where a masking 
material support film is made from a fluorescent material. Numeral 1 is a 
silicon annular support substrate, 2 is a 6-mm thick, fluorescent material 
layer composed of CaF.sub.2 :Eu, and 3 is a 1-.mu.m thick, pattern-wise 
gold masking material 
On the other hand, a cyclized rubber-based resist OMR-83 (trademark of a 
product made by Tokyo Ohka K.K., Japan) is coated to a thickness of 1.5 
.mu.m on a silicon wafer (not shown in the drawing) in advance, and 
subjected to soft contact exposure with an RhL.alpha. beam through an 
X-ray aligner, and then to a specific development treatment. To obtain a 
specific pattern, it has been found that an irradiation dosage from a beam 
source of about one-fifth of the conventional power is enough when the 
present lithographic mask structure is used. 
The present lithographic mask structure can be prepared in the following 
manner. A fluorescent material CaF.sub.2 :Eu is vapor-deposited on a 
silicon wafer provided with oxide films (SiO.sub.2 layers) on both sides 
in an EB vapor deposition apparatus to form a fluorescent material layer. 
Then, a Ni film, 500 .ANG. thick, is formed on the fluorescent material 
layer, and then a PMMA-based resist OEBR-1000 (trademark of a product made 
by Tokyo Ohka K.K., Japan) is applied thereto, and prebaked, and a mask 
pattern is depicted on the resist by an EB depicting apparatus. A resist 
pattern is formed with a specific developing solution under development 
conditions. Then, gold plating is conducted with the nickel layer as an 
electrode to form a gold pattern. Then, a tar-based protective film is 
applied to the surface and the oxide film (SiO.sub.2) in the mask area at 
the back side is removed by a hydrofluoric acidnitric acid mixture. Then, 
electrolytic etching is conducted with an electrolytic solution containing 
about 3% of hydrofluoric acid to remove the Si wafer in the mask area. 
Then, the SiO.sub.2 layer in the mask area is removed with a hydrofluoric 
acid-nitric acid mixture. Then, the tar-based paint is removed with 
acetone, and then removal of the resist and the Ni layer by 30% nitric 
acid are carried out. A lithographic mask structure having a masking 
material support film of CaF.sub.2 :Eu monolayer as shown in this Example 
can be obtained. 
EXAMPLE 3 
In place of the X-ray, irradiation of far ultraviolet ray is carried out 
with the same mask structure as used in Example 2. In the lithography 
using a quartz plate having a pattern-wise chromium masking material on 
the surface, resist OMR-83 (trademark of a product made by Tokyo Ohka 
K.K., Japan) is not thoroughly cured, and the resist film peels off in the 
development, with a failure to form a resist pattern. With the 
lithographic mask structure of this Example, a satisfactory resist pattern 
can be formed. 
EXAMPLE 4 
FIG. 3 is a schematic cross-sectional view of a lithographic mask structure 
according to other embodiment of the present invention, where numeral 1 is 
an annular support substrate, 2 is a fluorescent material layer, 3 is a 
pattern-wise masking material, 4 is a film, and 5 is an adhesive. 
The mask of FIG. 3 is prepared in the following manner. At first, an 
equilaterally stretched polyimide film is pasted as a film 4 onto, for 
example, an annular support disk substrate 1 by an adhesive 5, and then 
BaFCl:Eu is vapor-deposited to a thickness of about 2 .mu.m as a 
fluorescent material layer 2 thereon in an electron beam vapor deposition 
apparatus. Then, a mask pattern is formed in the same steps as in Example 
2. 
In the light exposure, a cinnamate-based resist KPR (trademark of Kodak, 
USA) is coated as a resist to a thickness of about 2 .mu.m onto a silicon 
wafer provided with an oxide film, and then exposed to irradiation of 
X-ray (PdL.alpha. beam). It has been found that a good resist pattern can 
be formed with an irradiation dosage from a beam source of about 
one-fourth of the conventional power by using the present lithographic 
mask structure. 
EXAMPLE 5 
FIG. 4 is a schematic cross-sectional process view showing a process for 
preparing a lithographic mask structure according to further embodiment of 
the present invention, where the common or corresponding members to those 
of the preceding Examples are represented by identical reference numerals, 
and numeral 11 is a fluorescent material and 9 is a silicon plate. 
The lithographic mask structure of FIG. 4 can be prepared in the following 
manner. At first, ultrafine particles of fluorescent material 11 
(CaWO.sub.4) are distributed in a polyimide precursor P1Q (trademark of a 
product made by Hitachi Kasei Kogyo K.K., Japan), and the resulting 
dispersion is coated to a thickness of about 6 .mu.m onto a silicon plate 
9. Then, the coating is subjected to a specific curing (cross-linking) 
treatment to form a masking material support film as fluorescent material 
layer 2 containing the distributed fluorescent material 11. Then, a 
pattern-wise masking material of gold (Au) is formed on the mask material 
support film according to the same photolithographic process as in the 
preceding Examples. Then, the silicon plate 9 pasted on the annular 
support substrate 1 by the adhesive 5 is removed therefrom to prepare a 
lithographic mask structure. 
Then, a gelatin bichromate is applied to a thickness of about 2 .mu.m as a 
resist onto the silicon wafer and baked by soft contact with X-ray (RhLa 
beam). It has been found that a good pattern can be obtained with an 
irradiation dosage from a beam source of about one-fourth of the 
conventional power by using the present lithographic mask structure. 
EXAMPLE 6 
FIG. 5 shows a schematic cross-sectional view of the essential parts of a 
light exposure apparatus using a lithographic mask structure according to 
still further embodiment of the present invention, wherein numeral 2 is an 
annular support substrate, 22 is a fluorescent material layer formed by 
vapor deposition of, for example, BaSi.sub.2 O.sub.5 :Pb, etc., and 23 is 
a pattern-wise masking material of gold, etc., 0.7 .mu.m thick. Numeral 24 
is a film of polystylene terephthalate, etc., 25 is a wafer of Si, etc., 
26 is a resist, and 27 is a secondary irradiation beam (fluorescent beam) 
generated from the fluorescent material layer 22. 
X-ray such as a RhLa beam, etc. generated from an X-ray source (target) 28 
is irradiated onto the resist 26 coated on the silicon wafer 25 through 
the lithographic mask structure. The resist 26 is, for example, OMR-83 
(trademark of a produce made by Tokyo Ohka K.K., Japan), etc., onto which 
the X-ray transmitted through the mask material support film without 
absorption in the pattern-wise masking material 23 is irradiated to 
project the pattern of the masking material 23 onto the resist 26. In this 
case, the secondary irradiation beam 27 generated from the fluorescent 
material layer 22 has a peak of 350 nm and irradiated onto the resist 26. 
In that apparatus, a 6- .mu.m thick polyethylene terephthalate film is used 
as a film 24, a 5- .mu.m thick BaSi.sub.2 O.sub.5 :Pb film is used as a 
fluorescent material layer 22, and 0.7-.mu.m thick gold film is used as a 
masking material 23, where the fluorescent material layer 22 is provided 
by dispersing BaSi.sub.2 O.sub.5 in polyvinyl alcohol (PVA) and removing 
the water therefrom in a drying over at about 95.degree. C. The resist 26 
is provided by applying a cyclized rubber-based resist OMR-83 (trademark 
of a product made by Tokyo Ohka K.K., Japan) to a thickness of 1.5 .mu.m 
to the wafer 25, in advance, subjecting the resist to soft contact light 
exposure with a RhL.alpha. beam through an X-ray aligner under reduced 
pressure of 5.times.10.sup.-3 Torr, followed by a specific development 
treatment. It has been found that an irradiation dosage from a beam source 
of about one-third of the conventional power is enough with the present 
lithographic mask structure. 
EXAMPLE 7 
A 6 .mu.m-thick polyethylene terephthalate film is used as a film 24 and a 
3 .mu.m-thick ZnS:Ag film is used as a fluorescent material layer 22, 
where ZnS:Ag is vapor-deposited onto the polyethylene terephthalate film 
24 in an EB vapor deposition apparatus to form the ZnS:Ag film. The resist 
26 is a 1- .mu.m thick film of polymethylisopropenylketone (PMIPK). It has 
been found by the same light exposure as in Example 6 that the resist 26 
has an effective sensitivity 3 times as high as the conventional one. 
EXAMPLE 8 
The film 24 is a 6- .mu.m thick poly-p-xylylene (trade name : YLENE, 
produced by Union Carbide Co.,) film, and the fluorescent material layer 
22 is a 5- .mu.m thick YAlO.sub.3 :Ce film, where YAIO.sub.3 :Ce is 
vapor-deposited onto the film 24 in an EB vapor deposition apparatus to 
form the YA10.sub.3 :Ce film. The resist 26 is a 1.2- .mu.m thick film of 
OMR-83 (trademark of a product made by Tokyo Ohka K.K., Japan). It has 
been found by the same light exposure as in Example 7 of that the resist 
26 has an effective sensitivity 4 times as high as the conventional one. 
EXAMPLE 9 
The film 24 is a 6- .mu.m thick LUMIRRORR (trademark of a product made by 
Toray, Japan) film, the fluorescent material layer 22 is a 2-.mu.m thick 
ZnS:Ag film, the masking material 23 is a 0.8-mm thick gold film, and the 
resist 26 is a 1- .mu.m thick film of OMR-83 (trademark of a product made 
by Tokyo Ohka K.K., JAPAN). It has been found by the same light exposure 
as in Example 7 that the resist 26 has an effective sensitivity 5 times as 
high as the conventional one. 
EXAMPLE 10 
FIG. 6 is a schematic cross-sectional view of a lithographic mask structure 
according to still further embodiment of the present invention, where the 
same patternwise irradiation as in Example 9 is carried out with the 
lithographic mask structure as shown in FIG. 6. Numeral 24a is a 6-.mu.m 
thick polyimide film, 22 is a fluorescent material layer of CaF; Eu 
vapor-deposited to a thickness of 1 .mu.m, thereon by sputtering vapor 
deposition, and 24 is a 0.2- .mu.m thick polyimide film. It has been found 
that the resist 26 has an effective sensitivity 4 times as high as the 
conventional one. 
The present lithographic mask structure covers the following three types. 
(1) A masking material only whose peripheral part is supported by an 
annular support substrate, 
(2) A masking material provided in a film state on the entire surface of 
the masking material support film, and 
(3) A masking material provided pattern-wise. 
As described in detail above, the present invention can improve the 
effective sensitivity of a photosensitive material by irradiation of a 
secondary irradiation beam generated from a fluorescent material to the 
photosensitive material since the masking material support film for a 
lithographic mask structure to be exposed to a radiation beam is composed 
from the fluorescent material or contains the fluorescent material, and 
thus can attain a good lithography. Furthermore, strict conditions such as 
X-ray transmissivity, thickness, etc., of the masking material support 
film can be lessened in the present lithographic mask structure. 
Furthermore, the present lithographic mask structure can attain a good 
lithography without providing any additional light source, that is, by 
using the conventional lithographic apparatus as such.