Method of forming a photoresist pattern

A method of forming a photoresist pattern wherein a photoresist coating film of naphthoquinone diazide sulfonate of novolak is formed on a substrate layer, the photoresist coating film is exposed by selectively irradiating with near ultraviolet radiation of 350 to 450 nm through a photomask, and the exposed photoresist coating film is developed with an either a negative type or positive type developing solution. The resultant photoresist pattern is usable for manufacturing a highly integrated circuit such as LSI which requires fine processing techniques.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of forming a photoresist pattern. 
The photoresist pattern is specifically used for manufacturing 
semiconductor devices with a submicrometer resolution. 
2. Description of the Prior Art 
In the semiconductor technical field, there is a growing need for a higher 
integration of semiconductor devices. Accordingly, there is a severe 
technical demand for the production of fine photoresist patterns. One of 
the fine processing methods employs ionization radiation such as electron 
beams, X-rays, shortwavelength ultraviolet radiation, and the like, so as 
to form the photoresist pattern, and thereafter precisely transferring the 
photoresist pattern onto underlying layers, e.g., substrates by a 
dry-etching treatment in which ions or a plasma has been filled. 
As a transfer apparatus for forming a photoresist pattern for a fine 
process, an optical reduction type transfer apparatus (aligner) has been 
mainly used because of its properties of high resolution and high accuracy 
for alignment. As a light source for this type of transfer apparatus, a 
g-line emitted from a mercury vaper lamp and being in a region, of near 
ultraviolet region is most expected in view of its lower absorption in the 
optical system and higher light outputs. 
However, as a positive type photoresist for photolithography using the near 
ultraviolet radiation, a photoresist is used which is obtained by mixing a 
novolak resin and a naphthoquinone diazide of a photosensitive material 
due to its high resolution and dry etching resistance. Further, as a 
negative type photoresist, a photoresist obtained by mixing a polyvinyl 
phenol and a bisazide is used. This resist has high sensitivity at the 
i-line (365 nm). 
However, because light of a g-line (436 nm) is most expected as a light 
source for the optical reduction type transfer apparatus, the sensitivity 
of resins above the negative type photoresist is low. Further, the 
positive type photoresists pose difficulties in maintaining a good line 
width control over the topography because of the reflective notching 
caused by reflected light from the substrate. 
If negative and positive type photoresist patterns can be formed by 
selecting the proper developing solutions, it is possible to select a 
method by which a negative or positive type photoresist pattern can be 
easily obtained in accordance with the photoresist pattern. As a result, 
various merits are achieved in the manufacture of semiconductor devices. 
It is therefore an object of the present invention to provide a method of 
forming a negative or positive type photoresist pattern by using the 
proper negative or positive type developing solution and for forming a 
constant line width pattern even over the substrate topography. 
SUMMARY OF THE INVENTION 
The object of the invention may be accomplished by providing a method of 
forming a photoresist pattern according to the following steps. 
A coating film of naphthoquinone diazide sulfonate of novolak as a 
photoresist coating film is firstly formed on a substrate or other 
underlying layer. 
Then, this coating film is exposed by irradiating with near ultraviolet 
radiation of from 350 to 450 nm through a photomask of a desirable 
pattern, which is to be copied onto the coating film. 
In this case, if the light wavelength is below 350 nm, a negative pattern 
can be formed, but a positive pattern can not be formed. If the light 
wavelength is above 450 nm, the resist is not sensitized. Accordingly, a 
light source having the above wavelength region is used. 
Subsequently, when the negative pattern is formed, the irradiated coating 
film is developed with a negative type developing solution. To the 
contrary, when a positive pattern is formed, the irradiated coating film 
is developed with a positive type developing solution. 
Through such treating steps, it is possible to form the desired negative or 
positive type photoresist pattern on an underlying layer. 
According to the invention, it is preferable to use a developing solution 
of a nonpolar solvent such as a halogen-containing solvent and/or alkyl 
benzene solvent as the negative type developing solution. Otherwise, the 
negative type developing solution is preferably a solution which is made 
by mixing the nonpolar solvent with one or more solutions selected from 
the group consisting of cyclohexane, n-hexane and petroleum ether. 
In the preferred embodiment of the present invention, the 
halogen-containing solvent is selected from of one or more solvents from 
the group consisting of monochlorobenzene, trichloroethylene, chloroform, 
dichloromethane and dichloroethane. 
Further, in a preferred embodiment of the present invention, the alkyl 
benzene solvent is selected from one or more solvents from the group 
consisting of xylene, toluene and benzene. 
Further, the positive type developing solution preferably contains one or 
more solvents selected from the group consisting of alcohol solvents, 
mixed solvents of acetate and alcohol, and mixed solvents of alkyl ketones 
and alcohol. 
In a preferred embodiment of the present invention, the alcohol solvent is 
consists of one or more solvents selected from the group consisting of 
isopropyl alcohol, n-butyl alcohol and methanol. 
Further, in the embodiment of the present invention, it is preferable to 
select isoamyl acetate from the group of the acetates and also to select 
methylisobutyl ketone from the group of alkyl ketones. 
As described above, according to the present invention, it is possible to 
form a photoresist coating film of a naphthoquinone diazide sulfonate of a 
novolak, expose the photoresist coating film by irradiating with near 
ultraviolet radiation, and to selectively use a negative or a positive 
type developing solution for the exposed photoresist coating film in 
accordance with the desirable pattern to be formed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A detailed description will now be made of the preferred embodiments 
according to the invention. 
It should be understood that the invention is not restricted to the 
specific embodiments of materials, numerical datum, etc., since similar 
effects can be achieved as those obtained by substituting other materials, 
numerical datum, etc. therefor. 
EXAMPLE I 
Referring to FIGS. 1A to 1C, naphthoquinone diazide sulfonate of novolak 
(referred as "NQN") was dissolved into methyl cellosolve acetate at the 
rate of 10 to 40 weight %, this solution was then filtered through a 
filter (not shown) having a throughhole diameter of 0.2 .mu.m and applied 
onto a silicon wafer 1 by way of a spin coating method, thereby forming 
the coating film 2 having a thickness of 0.7 .mu.m. This silicon wafer 1 
functions as a base or underlying layer. 
Then, this silicon wafer 1 having a photoresist coating film 2 of NQN was 
prebaked at a temperature of 70.degree. C. for about 30 minutes. 
Thereafter, the resist coating film 2 of NQN was treated by exposing with 
the g-line of a 250 W mercury lamp of a 1/5 optical reduction type aligner 
(not shown in detail). The exposure dose was 50 mJ/cm.sup.2. Accordingly, 
a photomask pattern 3 was transferred onto the NQN coating film 2. 
Thereafter, the wafer 1 having the exposed NQN coating film 2 was 
interbaked at a temperature range of 60.degree. to 130.degree. C., 
preferably 100.degree. C. for approximately 30 minutes. 
Such an interbaking treatment to the exposed NQN coating film 2 increases 
its sensitivity without lowering its resolution. 
According to this example, this NQN coating film 2 was developed for 35 
seconds by employing a mixture type developing solution containing a 
volume rate of 10:1 of monochlorobenzene and cyclohexane. The temperature 
of this developing solution was 23.degree. C. Subsequently, the coating 
film 2 was rinsed in cyclohexane for 10 seconds, so that concaves (not 
shown) were formed in the unexposed surface portions of the substrate or 
wafer 1, to which no ultraviolet radiation 10 had been projected because 
these portions were located under the photomask 3. Thus, a negative type 
photoresist pattern 5 was fabricated. 
Such a negative type photoresist pattern 5 has a clean, sharp and 
rectangular sectional plane and also can be resolved to a 0.6 .mu.m line 
and space pattern as observed with a scanning electron microscope. 
EXAMPLE II 
In this example, a substrate consisting of a silicon wafer and an alminum 
layer formed thereon instead of the silicon wafer 1 as described in FIG. 1 
was employed and the same film forming process as in the Example I was 
conducted. 
As a result of this example, it can be seen that the resultant photoresist 
pattern can be resolved to a 0.7 .mu.m line and space pattern when 
observed by a scanning electron microscope. 
EXAMPLE III 
(Heat Resistance Experiments) 
The photoresist pattern fabricated according to the Example I was baked at 
a temperature of 150.degree. C. for 30 minutes. The edge portion of the 
baked photoresist pattern was not deformed when observed by a scanning 
electron microscope. 
For the sake of comparison, Az-1350J (i.e., the photoresist commercially 
available from Shipley corporation) was applied to the same substrate 
under the same conditions to form a conventional photoresist pattern. When 
a conventional photoresist pattern was baked at a temperature of 
150.degree. C., the edge portion thereof was deformed so that the 
sectional plane of the photoresist pattern was rounded. 
EXAMPLE IV 
First, the photoresist film was formed according to the same method as in 
the Example I, and then exposed at an exposure dose of 100 mJ/cm.sup.2. 
The exposed film was developed by using a developing solution consisting 
of a 10:1 volume ratio of xylene to cyclohexane at a temperature of 
23.degree. C. for 60 seconds. After the developed film was rinsed in 
cyclohexane, a negative type photoresist pattern can be obtained having a 
resolution of a 0.7 .mu.m line and space. 
EXAMPLE V 
A naphthoquinone diazide sulfonate of a novolak (NQN) was dissolved into 
methyl cellosolve acetate at the rate of 25 weight %, this solution was 
then filtered through a filter having a throughhole diameter of 0.2 .mu.m 
and applied onto the silicon wafer in a coating thickness of 0.8 .mu.m by 
using a spin coating method. 
Then, this silicon wafer having a photoresist coating of NQN was prebaked 
at a temperature of 60.degree. C. for about 30 minutes. After this 
prebaking, the resist coating of NQN was treated by contact-exposing with 
a 250 W mercury lamp. The dose amount was 100 mJ/cm.sup.2. The exposed 
film was developed by using trichloroethylene at a temperature of 
23.degree. C. for 30 seconds and rinsed with cyclohexane at a temperature 
of 23.degree. C. for 15 seconds. Then a negative type photoresist pattern 
was obtained. It was observed that the negative type photoresist pattern 
was resolved to a 1.0 .mu.m line and space pattern, and the thickness of 
the remaining coating film after development was 0.8 .mu.m. 
EXAMPLE VI 
A coating of a naphthoquinone diazide sulfonate of novolak (NQN) was formed 
and exposed as described in Example V. The coating was developed by using 
a solution containing 3 parts by weight of chloroform and 1 part by weight 
of cyclohexane at a temperature of 23.degree. C. for 15 seconds, and 
rinsed with cyclohexane for 15 seconds. 
Then, a negative type photoresist pattern was obtained. It can be seen that 
the negative type photoresist pattern was resolved to a 1.0 .mu.m line and 
space pattern. The thickness of the remaining coating film after the 
development was 0.78 .mu.m. 
EXAMPLE VII 
Referring back to FIGS. 1A to 1C, a silicon (Si) wafer 1 was prepared as a 
substrate. A naphthoquinone diazide sulfonate of a novolak (abbreviated as 
"NQN") as a photoresist material was used. This NQN was dissolved into 
methyl cellosolve acetate at a rate of 10 to 40 weight %. This solution 
was then filtered through a filter having a throughhole diameter of 0.2 
.mu.m and applied onto the silicon wafer 1, whereby the wafer 1 is coated 
by a film having a thickness of approximately 1 .mu.m. 
Then, this silicon wafer 1 having a photo resist coating film 2 of NQN was 
prebaked at a temperature of 70.degree. C. for about 30 minutes. After 
this baking, the resist film 2 of NQN was exposed through a photoresist 
mask 3 having a desired mask pattern by a 1/5 optical reduction type 
transfer apparatus (NA: 0.35) equipped with g-line of 350 W mercury lamp 
as a light source. The dose time within a one exposure process was 
determined as 450 msec. 
After this exposure, the resist film 2 formed on the substrate 1 was 
interbaked at a temperature in the order of 100.degree. C. for 
approximately 30 minutes, and then developed. 
This development was firstly conducted at a temperature of 23.degree. C. 
for 50 seconds by use of a mixed solution having a 10:1.5 volume ratio of 
monochlorobenzene and cyclohexane as the first developing solution. As a 
result, a negative type photoresist pattern 5 was obtained (see FIG. 1C). 
It was recognized that the negative type pattern 5 could be resolved to a 
0.6 .mu.m line and space pattern by observing with a scanning type 
electron microscope. 
EXAMPLE VIII 
Referring now to FIGS. 2A to 2C, a description will be made of a second 
development with the same photoresist coating film 2 as in FIGS. 1A to 1C. 
A mixed solution of a 1:1 volume ratio of isoamyl acetate acid and 
isopropyl alcohol were used as a second developing solution. The coating 
film 2 was developed with this second solution at a temperature of 
23.degree. C. for 30 seconds. As a result, a positive type photoresist 
pattern 6 was formed. It can be seen that the positive type pattern 6 was 
resolved to a 0.7 .mu.m line and space pattern by observed with a scanning 
electron microscope. 
As is apparent from the foregoing, in accordance with the present 
invention, that identical photoresist material can be employed to form 
either negative or positive photoresist patterns by merely choosing the 
type of developing solutions used. 
EXAMPLE IX 
In this example, as to the exposed resist coating film obtained by a series 
of photoresist films previously described in Example VII, the following 
development was conducted under the below mentioned developing solutions 
and developing conditions. 
(1) A mixed developing solution containing a 1:1.5 volume ratio of 
isopropyl acetyl acetate and isopropyl alcohol was employed at a 
temperature of 23.degree. C. and a developing time of 20 seconds. 
(2) A mixed developing solution containing a 1:2 volume ratio of 
methylisobutyl ketone and isopropyl alcohol was used at a temperature of 
23.degree. C. and a developing time of 25 seconds. 
(3) A mixed developing solution containing a 1:1.5 volume ratio of isoamyl 
acetate and n-butyl alcohol was utilized at a temperature of 23.degree. C. 
and a developing time of 30 seconds. 
In all three cases, positive type photoresist patterns could be obtained 
according to the invention. 
EXAMPLE X 
In this example, the resultant photoresist coating film as described in 
Example VII was contact-exposed with a mercury (Hg) lamp of 250 W. The 
exposure time was selected to be 10 seconds. After the heating treatment 
of the exposed photoresist at a temperature of 100.degree. C. for 30 
minutes, the photoresist was developed at a temperature of 23.degree. C. 
for 50 seconds using a mixed developing solution containing 1:0.15 volume 
ratio of monochlorobenzene and isopropyl alcohol, thereby a negative type 
photoresist pattern being obtained. It can be seen that the negative type 
photoresist pattern was resolved to a 0.5 .mu.m line and space pattern by 
observation with a scanning electron microscope. 
EXAMPLE XI 
A exposed photoresist coating film was developed at a temperature of 
23.degree. C. for 30 seconds by using a mixed developing solution 
containing a 1:1 volume ratio of isoamyl acetate and isopropyl alcohol. As 
a result, a positive type pattern photoresist was obtained. This positive 
type photoresist could be resolved to a 0.5 .mu.m line and space. 
As is understood from the above mentioned Examples, in case of forming the 
negative and positive type photoresist patterns, there is an advantage 
that the photoresist patterns of high resolution are obtained since a NQN 
film does not swell with the developing solution. 
Another advantage is that, in case of forming the photoresist patterns on 
the reflective and/or steped surface of the underlying layer, the mask 
patterns are precisely transferred onto the photoresist coating film, 
thereby forming correct, clean and sharp photoresist patterns, since the 
light absorption coefficient of the NQN film to the exposure radiation of 
the wavelength range of 350 to 450 nm is large and therefore the 
sensitivity of the NQN film is high and the patterning precision is not 
influenced by the light reflected from the surface of the underlying 
layer. 
A further advantage is that the edge portions of the photoresist patterns 
are not deformed when baked at a temperature of the order of 200.degree. 
C. since the NQN film has better heat resistance at a temperature in the 
order of 200.degree. C. 
A still further advantage is that the underlying layer having formed 
thereon the photoresist patterns can be subjected to a plasma etching 
treatment, since the NQN material has excellent resistance to dryetching. 
The following Experimental Example will illustrate why the photoresist 
coating film is irradiated with ultraviolet radiation at a wavelength of 
350-450 nm, especially as opposed to lower values. 
EXPERIMENTAL EXAMPLE 
A naphthoquinone diazide sulfonate of a novolak (NQN) was dissolved into 
methyl cellosolve acetate in the amount of 25 weight percent. This 
solution was then applied onto a silicon wafer by using a spin coating 
method. This silicon wafer having a photoresist coating of NQN was baked 
in an oven at a temperature of 60.degree. C. for 30 minutes. The thickness 
of the photoresist coating of the NQN was 1 .mu.m. Then, the resist 
coating of NQN was exposed with light through a filter from a 250 W 
mercury lamp or a 500 W Xe-Hg lamp. The exposed film was dipped into a 
solution of isoamyl acetate so as to observe whether or not the 
photoresist was dissolved in the solution. The results of the experiments 
are shown in the following Table 1. 
TABLE 1 
______________________________________ 
Condition of the Exposure 
Dose Amount 
Dissolvability 
______________________________________ 
(1) No exposure dissolves 
(2) Cutting of wavelengths .lambda. 
2 J/cm.sup.2 
dissolves 
below 350 nm 
(filter used: UV-34, 
HOYA Co., Ltd.) 
(3) Cutting of wavelengths .lambda. 
300 mJ/cm.sup.2 
dissolves 
below 300 nm 2Jm/cm.sup.2 
does not dissolve 
(filter used: UV-30, 
HOYA Co., Ltd.) 
(4) Contact exposure by using 
500 mJ/cm.sup.2 
dissolves 
a condenser lens which 
4J/cm.sup.2 
does not dissolve 
transmits the light of 
wavelengths .lambda. &gt; 350 nm at 
a transmittance of more than 
90% and that of wavelength 
range 300-350 nm at a trans- 
mittance of a few percent 
(5) Xe-Hg lamp (500 W) 
50 mJ/cm.sup.2 
does not dissolve 
220 nm &lt; .lambda. &lt; 280 nm 
(filter used: CM-250, 
Canon Co., Ltd.) 
______________________________________ 
It is known that NQN is dissolved in a solution of isoamyl acetate if a 
crosslinking reaction does not arise. 
NQN is dissolved in a solution of isoamyl acetate when NQN is exposed to 
light, its wavelengths below 250 nm being cut off, at the exposure amount 
of 2 J/cm.sup.2. Therefore, in that case, no crosslinking reaction arises. 
In the case of exposure to light in which the wavelengths below 300 nm are 
cut off, 
(a) when NQN is exposed with the light at the exposure amount of 300 
mJ/cm.sup.2, it is dissolved in the solution of isoamyl acetate, and 
therefore the crosslinking reaction does not arise; and 
(b) when NQN is exposed to light at an exposure amount of 2 J/cm.sup.2, it 
is not dissolved in a solution of isoamyl acetate and, accordingly, the 
crosslinking reaction arises. 
Furthermore, in a case where the photoresist of NQN is exposed to light 
having a wavelength range of 220-280 nm, it does not dissolve in the 
solution of isoamyl acetate when the exposure amount of the light if 50 
mJ/cm.sup.2. Therefore, crosslinking of NQN occurs. 
As is understood from the above description, crosslinking of NQN 
efficiently occurs when the photoresist is exposed to light having a 
wavelength range of 220-280 nm. Crosslinking also occurs when the 
photoresist is exposed to light having a wavelength at or about 300 nm 
with the increased amount of exposure. However, it can be seen that no 
crosslinking of NQN occurs when the photoresist is exposed by light having 
a wavelength more than 350 nm. 
Meanwhile, in the case of usual contact exposure with an ultra-high 
pressure mercury lamp, a condenser lens is used, which lens cuts off the 
shorter wavelengths and therefore the photoresist of NQN is exposed mainly 
with light having wavelengths of 436 nm (g-line), 405 nm (h-line) and 365 
nm (i-line). In that case, crosslinking of NQN does not occur if NQN is 
exposed to the light at the usual amount of exposure (100-200 
mJ/cm.sup.2). 
As described above, patterning of NQN can be attained by using light having 
a wavelength range of 350-450 nm without causing a crosslinking reaction 
among the molecules of NQN, which is understood from the fact that a 
positive type photoresist pattern is formed by using the same exposure 
treatment. 
According to the present invention, patterning is attained without the aid 
of crosslinking. Therefore, photoresist patterns of high resolution are 
attained and the photoresist forming the patterns is easily separated or 
excluded by a solvent, for example, acetate, methyl isobutyl ketone, 
acetone or the like. 
The following Comparative Examples illustrate the advantages of Applicant's 
methods over that of the prior art. 
COMISON EXAMPLE I 
The conventional photoresist of AZ-1305J (commercially available from 
Shipley corporation) was coated over a silicon wafer with a coating 
thickness of 1.0 .mu.m so as to form a photoresist film. Subsequently, the 
photoresist film was prebaked at a temperature of 80.degree. C. for 20 
minutes, and thereafter exposed under an exposure dose of 80 mJ/cm.sup.2 
by the same reduction type projection apparatus as in Example I. When the 
exposed film was developed for 60 seconds by use of monochlorobenzene at a 
temperature of 23.degree. C. as a developing solution, both the exposed 
portion and unexposed portion of the resist film were not dissolved, so 
that no photoresist pattern could be formed. This is because quinone 
diazide of AZ-1350J as a photosensitive agent might be converted into 
indene carboxylic acid, whereas naphthoquinone and a photosensitive agent 
were not dissolved by the nonpolar solvent such as monochlorobenzene, so 
that no photoresist pattern could be formed. 
COMISON EXAMPLE II 
A photoresist coating film of AZ-1350J was formed on an aluminum substrate 
under the same conditions as in the comparison example I, and then 
exposed. When the exposed photoresist film was developed with an alkaline 
developing solution, the photoresist pattern having a line width more than 
or equal to 1 .mu.m could be fabricated, but the pattern having a line 
width less than 1 .mu.m, i.e., submicrometer could not be formed. 
COMISON EXAMPLE III 
AZ-1350 J (photoresist commercially available from Shipley corporation) was 
applied onto a silicon wafer in a coating thickness of 1 .mu.m to form a 
photoresist coating film was exposed as described in Example VII. 
The exposed resist was developed by using a solution containing the AZ 
developing solution diluted with water at a ratio of 1:1 at a temperature 
of 23.degree. C. for 20 seconds. A positive type photoresist pattern was 
obtained. Observing this resist pattern, it could be recognized that a 1.0 
.mu.m line and space pattern was obtained. 
Then, a sample obtained by the same exposure conditions was developed with 
monochlorobenzene at a temperature of 23.degree. C. for 2 minutes. 
However, no resist pattern was formed. 
Furthermore, another sample resist film obtained by the same exposure 
conditions was developed with a developing solution in which 1 part by 
weight of isoamyl acetate is mixed with 1 part weight of isopropyl alcohol 
at a temperature of 23.degree. C., but no pattern was formed. And 
furthermore, this resist coating film was developed only with an isoamyl 
acetate solution. As a result, the resist was dissolved over the wafer 
surface, and no pattern was formed. 
As apparent from the above Examples and comparison Example, when the 
coating film of naphthoquinone diazide sulfonate of novolak (NQN) was 
exposed with near ultraviolet radiation, either negative type or positive 
type photoresist can be determined merely by selecting the developing 
solution for the exposed photoresist. The reason is considered as follows: 
Quinon diazide group of NQN is decomposed by a near ultraviolet radiation, 
and converted into carboxylic acid. Then the polarity appears in the 
exposed region of NQN. The polar region is not dissolved in 
monochlorobenzene which is a nonpolar solvent. As a result, a negative 
type photoresist pattern is formed by the insoluble polar region. 
To the contrary, when using a polar solvent as the developing solution, the 
only exposed and larger polar region of NQN is dissolved in the polar 
solvent, and a positive type photoresist pattern is formed by an insoluble 
region of NQN. 
As described in the comparison Examples, in AZ-1350J which is a mixture of 
novolak and naphthoquinone diazide, a change of naphthoquinone diazide 
into carboxylic acid is the same as that of NQN. However, it may be 
considered that a change of polarity throughout this photoresist is small. 
Actually, it is impossible to form a photoresist pattern by using the 
difference of this polarity. 
COMISON EXAMPLE IV 
Using the same photoresist coating film on the silicon substrate as 
obtained in the Example I, the development was performed with various 
types of developing solutions. The results of the development are shown in 
Table 2. 
TABLE 2 
______________________________________ 
developing composition 
solution (volume ratio) 
property result 
______________________________________ 
1st methyl buthyl 
10:5 positive 
no 
ketone, and type photoresist 
cyclohexane pattern is 
formed 
2nd isoamyl acetate, 
10:2 positive 
no 
and cyclohexane type photoresist 
pattern is 
formed 
3rd dioxan, and 10:4 positive 
no 
cyclohexane type photoresist 
pattern is 
formed 
4th isopropyl alcohol positive 
no 
type photoresist 
pattern is 
formed 
______________________________________ 
In the first to third development examples, the dissolution of the exposed 
portion of the photoresist coating film was done relatively faster than 
that of the unexposed portions thereof. The photoresist coating film 
represents the positive type property. The thickness of the remaining film 
was thinner than 0.1 .mu.m. In the fourth development example, the 
unexposed portion of the photoresist coating film was not completely 
dissolved, whereas the thickness of the exposed portion thereof was 
approximately 0.1 .mu.m. 
The developing solutions used in the first to fourth development examples 
represent a positive type property. However, no photoresist pattern could 
be formed. 
While the present invention has been described using a specific embodiment, 
it should be understood that further modifications and changes can be made 
without departing from the scope of the present invention. 
For example, as the developing solutions, there can be used solutions other 
than the above-described kinds of solutions. As the positive type 
developing solutions, polar solvents such as methanol, isopropyl alcohol 
and/or the other alcohols, isoamyl acetate and/or the other acetates, 
methyl-butyl ketone and/or the other alkyl ketones, or other desired 
developing solutions may be used. These developing solutions may be used 
by mixing one or more solvents selected from the group consisting of these 
alcohols, acetates and alkyl ketones. 
As the negative type developing solutions, nonpolar solvents such as 
monochlorobenzene, xylene, toluene, benzene, dichlorobenzene, 
trichlorobenzene and trichloroethylene or other preferable nonpolar 
solvents may be used. Mixed solutions of one or more nonpolar solvents 
selected from the above-mentioned group and one or more solvents selected 
from the group consisting of cyclohexane, n-hexane, petroleum ether and 
the other desired solvents may be used as the developing solutions. 
Furthermore, the coating film need not be directly coated on the substrate, 
but on other underlying layers. 
Finally, it is also possible to employ as the exposure light, electron 
beams, x-rays or the like having wavelengths other than 350 to 450 nm. 
As previously described in detail, according to the method of forming the 
photoresist pattern of the invention, either positive type or negative 
type photoresist patterns can be formed by selecting the developing 
solution because of the naphthoquinone diazide sulfonate of a novolak is 
used, and exposed to near ultraviolet radiation in the wavelength range of 
350 to 450 nm. 
Accordingly, the photoresist pattern of the present invention is preferably 
used for manufacture of highly integrated circuits such as LSI which 
requires fine processing, e.g., submicrometer processing.