Method of forming fine patterns

Sidewalls of patterned resist are reformed using a reforming agent selected from the group consisting of (a) a carbon trichloride radical, (b) a mixture of silicon ion and oxygen ion, (c) a mixture of carbon ion and carbon monoxide ion, (d) a chlorine radical, (e) aluminum trichloride liquid and (f) dibutyl magnesium liquid, and sidewall reformed portions are thus formed on the sidewalls of pattern resist. The not reformed portion of the patterned resist is removed away, and sidewall reformed portions are left on an object layer. The portion of object layer excluding the portion immediately below sidewall reformed portions is etched away, and fine patterns of object layer are formed as a result.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to methods of forming fine 
patterns, and more particularly, to a method of forming patterns arranged 
in parallel with each other at very fine intervals and having a very fine 
width. 
2. Description of the Background Art 
FIGS. 38-41 are cross sectional views and perspective views showing a 
semiconductor device in each step in the order of a conventional method of 
forming fine patterns. The fine patterns include interconnection patterns, 
bit lines, word lines etc. 
Referring to FIG. 38, a layer of object to be patterned (hereinafter 
referred to as object layer) 12 is formed on a support member 11 formed of 
a silicon dioxide film or the like. Object layer 12 is formed of 
polycrystalline silicon for example. Patterned resist 13 formed of novolak 
resin based positive photosensitive resin is formed on object layer 12. 
Referring to FIG. 38 and 39, using patterned resist 13 as mask, object 
layer 12 is etched to remove the portion other than immediately below 
patterned resist 13 with a removing agent (such as bromine radical) 15 for 
removing the object layer, and patterns 12A, 12B, 12C and 12D of the 
object are formed. 
Referring to FIGS. 40 and 41, patterned resist 13 is removed. 
By the above-described method, patterns arranged in parallel to each other 
at intervals D and having a width W are provided as illustrated in FIG. 
41. 
A problem associated with the above method will be now described. 
The width (W) of patterns 12A, 12B, 12C or 12D of the object provided 
according to the conventional method is determined by the pattern width of 
a light shielding film in the mask used (in the case of using positive 
photoresist) or the distance between light shielding films (in the case of 
using negative photoresist). Therefore fine patterns having a width and a 
size as small as or smaller than the minimum resolution achieved by 
lithography cannot be formed. In other words, the pattern width (W) and 
pattern distance (D) are each at least 0.25 .mu.m, and fine patterns 
having pattern width (W) and distance (D) smaller than this size cannot be 
formed. 
FIGS. 42A-42F are cross sectional views showing a semiconductor device in 
each step in the order of a method of forming fine patterns according to a 
prior art (Japanese Patent Laying-Open No. 2-5522) related to the present 
invention. 
Referring to FIG. 42A, resist 2 is formed on a support member 1. 
Referring to FIG. 42B, resist 2 is selectively irradiated with a 
ultraviolet beam, and a latent image 3 is formed. 
Referring to FIGS. 42B and 42C, developing resist 2 forms patterned resist 
13. 
Referring to FIG. 42D, a silylated layer 13a is formed on a surface of 
patterned resist 13 by irradiating support member 1 with a ultraviolet 
beam in vapor of hexamethyldisilazane (HMDS). Referring to FIGS. 42D and 
42E, silylated layer 13a formed on the top surface of patterned resist 13 
is removed by means of reactive ion etching. 
Referring to FIGS. 42E and 42F, the not silylated portion of resist 13 is 
etched away. Thus, fine patterns 16a are formed. 
According to the conventional technique, however, a reaction chamber for 
reacting the photosensitive resin and HMDS must be improved such that a 
far ultraviolet beam can be introduced into the reaction chamber, which 
complicates the device and pushes up the cost. 
SUMMARY OF THE INVENTION 
It is therefore an object of the invention to provide a method of forming 
patterns arranged in parallel with each other at fine intervals and having 
a fine width. 
Another object of the invention is to provide a method of forming fine 
patterns having a width and a distance smaller than a minimum resolution 
achieved by lithography. 
Yet another object of the invention is to provide a method of forming fine 
patters which can be implemented with a simple device. 
In a method of forming fine patterns according to a first aspect of the 
invention, an object layer is formed on a support member. Patterned resist 
having sidewalls opposite to each other is formed on the object layer. The 
one and the other sidewalls of the patterned resist are reformed using a 
reforming agent selected from the group consisting of (a) a carbon 
trichloride radical, (b) a mixture of silicon ion and oxygen ion, (c) a 
mixture of carbon ion and carbon monoxide ion, (d) a chlorine radical, (e) 
aluminum trichloride liquid and (f) dibutyl magnesium liquid, whereby a 
first reformed portion on the sidewall (hereinafter simply referred to as 
first sidewall reformed portion) is formed on the one sidewall of the 
patterned resist, and a second reformed portion on the sidewall 
(hereinafter referred to as second sidewall reformed portion) on the other 
sidewall. The not reformed portion of the patterned resist is removed, and 
thus the first sidewall reformed portion and the second sidewall reformed 
portion are left on the object layer. Using the first sidewall reformed 
portion and the second sidewall reformed portion as mask, the portion of 
the object layer excluding the portion immediately below the first and 
second sidewall reformed portions are etched away, and thus fine patterns 
of the object are formed. The first sidewall reformed portion and the 
second sidewall reformed portions are then removed. 
In a method of forming fine patterns according to a second aspect of the 
invention, an object layer is formed on a support member. Patterned resist 
having sidewalls opposite to each other is formed on the object layer. The 
one sidewall and the other sidewall of the patterned resist are reformed, 
whereby a first sidewall reformed portion is formed on the one sidewall of 
the patterned resist and a second sidewall reformed portion is formed on 
the other sidewall. Using the patterned resist including the first and 
second sidewall reformed portions as mask, the portion of the object layer 
excluding the portion immediately below the patterned resist is etched 
away, and patterns of the object are thus formed. The not reformed portion 
of the patterned resist is removed, and thus the first sidewall reformed 
portion and the second sidewall reformed portions are left on the patterns 
of the object. Using the first sidewall reformed portion and second 
sidewall reformed portion as mask, the portion of the object patterns 
excluding the portion immediately below the first and second sidewall 
reformed portions is etched away, and even finer patterns of the object 
are formed as a result. The first and second sidewall reformed portions 
are then removed away. 
In a method of forming fine patterns according to a third aspect of the 
invention, an object layer is formed on a support member. Patterned resist 
having sidewalls opposite to each other is formed on the object layer. 
Using the patterned resist as mask, the portion of the object layer 
excluding the portion immediately below the patterned resist is etched 
away, whereby patterns of the object are formed and at the same time the 
one and the other sidewalls of the patterned resist are reformed to form a 
first sidewall reformed portion on the one sidewall of the patterned 
resist and a second sidewall reformed portion on the other sidewall of 
patterned resist. The not reformed portion of the patterned resist is 
removed away, and the first sidewall reformed portion and the second 
sidewall reformed portion are left on the patterns of the object. Using 
the first and second sidewall reformed portions as mask, the portion of 
the patterns of the object excluding the portion immediately below the 
first and second sidewall reformed portions is etched away, and even finer 
patterns of the object are formed as a result. The first and second 
sidewall reformed portions are then removed away. 
In a method of forming fine patterns according to a fourth aspect of the 
invention, an object layer is formed on a support member. Patterned resist 
having sidewalls opposite to each other is formed on the object layer. 
Using the patterned resist as mask, the portion of the object layer 
excluding the portion immediately below the patterned resist is etched 
away, whereby patterns of the object are formed. The one and the other 
sidewalls of the patterned resist are reformed, and a first sidewall 
reformed portion is formed on the one sidewall of the patterned resist and 
a second sidewall reformed portion is formed on the other sidewall of the 
patterned resist. The not reformed portion of the patterned resist is 
removed, and the first and second sidewall reformed portions are thus left 
on the patterns of the object. Using the first and second sidewall 
reformed portions as mask, the portion of the patterns of the object 
excluding the portion immediately below the first and second sidewall 
reformed portions is etched away, and even finer patterns of the object 
are formed as a result. The first and second sidewall reformed portions 
are then removed away. 
By the method of forming fine patterns according to the first aspect of the 
invention, using the first and second sidewall reformed portions formed on 
the sidewalls of the patterned resist as mask, the portion of the object 
excluding the portion immediately below the first and second sidewall 
reformed portions is etched away. Fine patterns of the object layer are 
thus formed, and therefore patterns even finer than the minimum resolution 
achieved by the present lithography techniques can be provided. 
In addition, .the one and the other sidewalls of the patterned resist are 
reformed using as a reforming agent a carbon trichloride radical 
(CCl.sub.3.sup.*) which tends to dissociate with low energy, and therefore 
sidewall reformed portions containing a large amount of carbon can be 
formed on the sidewalls of the patterned resist. 
Furthermore, implanting into the sidewalls of patterned resist as a 
reforming agent two kinds of accelerated particles of (b) the mixture of 
silicon ion and oxygen ion, or (c) the mixture of carbon ion and carbon 
monoxide ion causes a chemical change forming a new bond at the sidewall 
surface of patterned resist, and a sidewall reformed portion having 
properties unremovable with a removing agent for etching away the object 
layer or a removing agent for removing the patterned resist can be formed. 
Use of a chlorine radical (Cl.sub.2.sup.*) as a reforming agent can form a 
sidewall reformed portion containing a large amount of carbon (C) with a 
carbon-carbon bond forming the patterned resist being cut. 
If the patterned resist is soaked in aluminum trichloride liquid or dibutyl 
magnesium liquid, aluminum or magnesium atoms permeate into the sidewalls 
of the patterned resist and form oxide. The oxide is not removed by the 
removing agent for etching away the object or the removing agent for 
removing the patterned resist. 
By the method of forming fine patterns according to the second aspect of 
the invention, using the first and second sidewall reformed portions as 
mask, the portion of patterns of the object excluding the portion 
immediately below the first and second sidewall reformed portions is 
etched away, and therefore even finer patterns of the object can be 
formed. 
By the method of forming fine patterns according to the third aspect of the 
invention, using the patterned resist as mask, the portion of the object 
layer excluding the portion immediately below the patterned resist is 
etched away, whereby patterns of the object are formed at which time the 
one and the other sidewalls of the patterned resist are reformed, and 
therefore a first sidewall reformed portion is formed on the one sidewall 
of the patterned resist and a second sidewall reformed portion on the 
other sidewall, and therefore the manufacturing process can be simplified. 
By the method of forming fine patterns according to the fourth aspect of 
the invention, using the patterned resist as mask, the portion of the 
object layer excluding the portion immediately below the patterned resist 
is etched away, and the patterns of the object are thus formed. 
Thereafter, using the first and the second sidewall reformed portions as 
mask, the portion of the patterns of the object excluding the portion 
immediately below the first and second sidewall reformed portions is 
etched away, and therefore even finer patterns of the object can be 
formed. 
The foregoing and other objects, features, aspects and advantages of the 
present invention will become more apparent from the following detailed 
description of the present invention when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the invention will be now described in conjunction with the 
accompanying drawings. 
EMBODIMENT 1 
FIGS. 1 to 6 are cross sectional views and perspective views showing a 
semiconductor device in each step in the order of a method of forming fine 
patterns according to Embodiment 1. 
Referring to FIG. 1, an object layer 120 such as of polycrystalline silicon 
is formed on a support member 110 of a silicon dioxide film or the like. 
Resist patterns 130 of width W arranged parallel to each other and having 
one sidewall 130a and the other sidewall 130b opposite to each other are 
formed on object layer 120. Herein width W corresponds to a minimum 
resolution achieved by the present lithography techniques. 
Referring to FIG. 2, as will be described later in detail, one sidewall 
130a and the other sidewall 130b of patterned resist 130 are reformed 
using a reforming agent selected from the group consisting of (a) a carbon 
trichloride radical, (b) a mixture of silicon ion and oxygen ion, (c) a 
mixture of carbon ion and carbon monoxide ion, (d) a chlorine radical, (e) 
aluminum trichloride liquid and (f) dibutyl magnesium liquid. By the 
reforming, a first sidewall reformed portion 132a is formed on one 
sidewall 130a of the patterned resist, and a second sidewall reformed 
portion 132b is formed on the other sidewall 130b of patterned resist. 
Referring to FIGS. 2 and 3, the portion of patterned resist 131 which has 
not been reformed is removed away, and thus first sidewall reformed 
portion 132a and second sidewall reformed portion 132b arranged in 
parallel to each other are left on object layer 120. 
Referring to FIG. 3, 4, and 5, using first sidewall reformed portion 132a 
and second sidewall reformed portion 132b as mask, the portion of object 
layer 120 excluding the position immediately below first and second 
sidewall reformed portions 132a and 132b is etched away with a removing 
agent 150 for removing the object. 
Referring to FIGS. 5 and 6, removal of first and second sidewall reformed 
portions 132a and 132b forms patterns 120A and 120B of the object having a 
fine width w and a fine distance d smaller than the minimum resolution 
achieved by the present lithography are formed. 
EMBODIMENT 2 
FIGS. 7 to 13 are cross sectional views and perspective views showing a 
semiconductor device in each step in the order of a method of forming fine 
patterns according to Embodiment 2. 
An object layer 120 is formed on a support member 110. Resist patterns 130 
arranged parallel to each other and having one sidewall and the other 
sidewall opposite to each other are formed on object layer 120. The one 
sidewall and the other sidewall of patterned resist 130 are reformed, and 
a first sidewall reformed portion 132a and a second sidewall reformed 
portion 132b are thus formed on the one and the other sidewalls of the 
patterned resist. 
Referring to FIGS. 8 and 9, using patterned resist 130 including first 
sidewall reformed portion 132a and second sidewall reformed portion 132b 
as mask, the portion of object layer 120 excluding the portion immediately 
below patterned resist 130 is etched away with a removing agent 150 for 
removing the object and patterns 125 of the object are thus formed. 
Referring to FIGS. 9 and 10, the not reformed portion 131 of patterned 
resist is removed away, and first sidewall reformed portion 132a and 
second sidewall reformed portion 132b arranged parallel to each other are 
left on the pattern 125 of the object. 
Referring to FIGS. 11 and 12, using first and second sidewall reformed 
portion 132a and 132b as mask, the portion of patterns 125 of the object 
excluding the portion immediately below first and second sidewall reformed 
portions 132a and 132b is etched away with removing agent 150 for removing 
the object. 
Referring to FIGS. 12 and 13, removal of first and second sidewall reformed 
portions 132a and 132b forms patterns 120A and 120B of the object having a 
fine width w and a fine distance d smaller than the minimum resolution 
achieved by the present lithography techniques. 
EMBODIMENT 3 
FIGS. 14 to 20 are cross sectional views showing a semiconductor device in 
each step in the order of a method of forming fine patterns according to 
Embodiment 3. 
Referring to FIG. 14, an object layer 120 is formed on a support member 
110. Patterned resist 130 arranged parallel to each other and having one 
sidewall 130a and the other sidewall 130b is formed on object layer 120. 
Referring to FIGS. 15 and 16, using patterns 130 as mask, the portion of 
object layer 120 excluding the portion immediately below patterned resist 
130 is etched away, patterns 125 of the object are thus formed, while 
reforming the one and the other sidewalls of each resist pattern, whereby 
a first sidewall reformed portion 132a is formed on one sidewall of resist 
pattern 130, and a second sidewall reformed portion 132b is formed on the 
other sidewall of resist pattern 130. 
In the figures, reference numeral 142 represents a reforming and removing 
agent capable of reforming the sidewalls of resist pattern 130 and etching 
away the object layer. 
Referring to FIGS. 16 and 17, the not reformed portion 131 of the resist 
pattern is removed away, and first sidewall reformed portion 132a and 
second sidewall reformed portion 132b arranged parallel to each other are 
left on patterns 125 of the object. 
Referring to FIGS. 18 and 19, using first and second sidewall reformed 
portions 132a and 132b as mask, the portion of patterns 120 of the object 
excluding the portion immediately below first and second sidewall reformed 
portions 132a and 132b is etched away. 
Referring to FIGS. 19 and 20, removal of first and second sidewall reformed 
portions 132a and 132b forms patterns 120A and 120B of the object having a 
fine width w and a fine distance d smaller than the minimum resolution 
achieved by the present lithography techniques. 
EMBODIMENT 4 
FIGS. 21 to 28 are cross sectional views showing a device in each step in 
the order of a method of forming fine patterns according to Embodiment 4. 
Referring to FIG. 21, an object layer 120 is formed on a support member 
110. Resist patterns 130 parallel to each other and having one sidewall 
130a and the other sidewall 130b opposite to each other are formed on 
object layer 120. 
Referring to FIGS. 22 and 23, using resist patterns 130 as mask, the 
portion of object layer 120 excluding the portion immediately below resist 
patterns 130 is etched away with a removing agent 150 for removing the 
object, and patterns 125 of the object are thus formed. 
Referring to FIG. 24, the one sidewall and the other sidewall of resist 
pattern 130 are reformed, first sidewall reformed portion 132a is thus 
formed on the one sidewall of resist pattern and second sidewall reformed 
portion 132b is formed on the other sidewall of resist pattern. 
Referring to FIGS. 24 and 25, the not reformed portion 131 of the resist 
pattern is removed away, and first sidewall reformed portion 132a and 
second sidewall reformed portion 132b arranged parallel to each other are 
left on pattern 125 of the object. 
Referring to FIGS. 26 and 27, using first and second sidewall reformed 
portions 132a and 132b as mask, the portion of patterns 125 of the object 
excluding the portion immediately below first and second sidewall reformed 
portions 132a and 132b is etched away. 
Referring to FIGS. 27 and 28, removal of first and second sidewall reformed 
portions 132a and 132b forms patterns 120A and 120B of the object having a 
fine width w and a fine distance d smaller than the minimum resolution 
achieved by the present lithography techniques. 
EMBODIMENT 5 
FIGS. 29A to 29F are cross sectional views showing a semiconductor device 
in each step in the order of a method of forming fine patterns according 
to Embodiment 5, and used for illustrating in more detail how the 
sidewalls of the resist patterns according to Embodiment 1 are reformed. 
Referring to FIG. 29A, an object layer 120 such as of a polysilicon 
(SiO.sub.2) film is formed on a support member 110 for supporting the 
object formed of silicon dioxide (SiO.sub.2) film or the like. A resist 
pattern 130 formed of novolak resin based positive photosensitive resin 
for example is formed on object layer 120. 
Referring to FIG. 29B, a fixed amount of a reforming agent 140 of a carbon 
trichloride radical (CCl.sub.3.sup.*) is supplied on support member 110 
for a fixed time period. 
Referring to FIG. 29C, carbon trichloride radical 140 sticks to the surface 
of patterned resist 130 and the surface of object layer 120, and also 
enters into patterned resist 130. 
Referring to FIG. 29D, a removing agent 150 for removing the object such as 
a bromine radical (Br.sup.*) having directional dependance i.e. anisotropy 
is supplied onto support member 110. Since a carbon trichloride radical 
(CCl.sub.3.sup.*) which dissociates a carbon atom (C) with low energy 
dissociates with the energy imparted by removing agent 150 for removing 
the object, a thin carbon film is formed on the surface of patterned 
resist 130, and carbon atoms come into patterned resist 130 from the 
surface to form sidewall reformed portion 132. 
Referring to FIG. 29E, in the process of forming sidewall reformed portion 
132, part of object layer 120, in other words part of the polysilicon film 
forms a reaction product 730 such as silicon tetrachloride (SICl.sub.4) 
and silicon tetrabromide (SiBr.sub.4) to be removed, and part of patterned 
resist 130 forms a reaction product 731 such a carbon tetrachloride 
(CCl.sub.4) and carbon tetrabromide (CBr.sub.4) to be removed. Part of the 
carbon trichloride radical (CCl.sub.3.sup.*) returns to its ground state, 
and forms another reaction product, carbon tetrachloride 732. These 
reaction products dissipate externally. The upper end of patterned resist 
130 has partially removed by the function of removing agent 150 for 
removing the object. 
Finally as illustrated in FIG. 29F, formed on a sidewall of the patterned 
resist is a sidewall reformed portion 132 entered with a carbon thin film 
and/or carbon which cannot be completely removed with the removing agent 
for removing the patterned resist such as an oxygen radical (O.sup.*). 
Note that 131 represents the not reformed portion of the patterned resist. 
The above carbon trichloride radical (CCl.sub.3.sup.*) is produced by a 
commonly used plasma device as illustrated in FIG. 32. The plasma device 
includes a spare chamber CH71 and a reaction chamber CH72. In reaction 
chamber CH72, an electrode A(71) and an electrode B(72) are provided. 
Electrode B(72) also functions as a stand for an object. Gas G72 is 
supplied to electrode A(71) through a pressure regulator V72 and a flow 
rate regulator V72'. Gas G73 is supplied to electrode A(71) through a 
pressure regulator V76 and a flow rate regulator V76'. Reaction chamber 
CH72 is connected to a turbo molecular pump TMP7 through valve V73. Turbo 
molecular pump TMP7 is connected to a rotary pump RP72. Spare chamber CH71 
and reaction chamber CH72 are connected to each other through a gate valve 
V74. Spare chamber CH71 is connected to a rotary pump RP71 through valve 
V71. Spare chamber 71 is supplied with gas G71. Gas 71 is supplied into 
spare chamber CH71 through a pressure regulator V75 and a flow rate 
regulator V75'. 
Reaction chamber CH72 is connected to an electromagnetic wave generator RF 
through a coupling capacitor C. 
A carbon trichloride radical (CCl.sub.3.sup.*) can be produced by supplying 
a mixture gas of helium gas (G72) at a flow rate of 100 SCCM (Standard 
Cubic Centimeter Per Minute) via pressure and flow rate regulators V72 and 
V'72 and carbon tetrachloride gas (G73) at a flow rate in the range from 
60 to 80 SCCM via pressure and flow rate regulators V76 and V76', and then 
plasma-dissociating them under a pressure in the range from 1.0 to 1.5 
Torr. 
Sidewall reformed portion 132 formed with reforming agent 140 of carbon 
trichloride radical (CCl.sub.3.sup.*) comes to have such a property that 
ER.sub.01 (the rate at which the not reformed portion 131 of the patterned 
resist is removed) is in the range from 100 to 140 nm/min, and ER.sub.O2 
(the rate at which sidewall reformed portion 132 is removed by the 
removing agent for removing the object) is in the range from 25 to 35 
nm/min by the function of removing agent 150 for removing the object such 
as a bromine radical (Br.sup.*). 
Er.sub.11 (the rate of removing the not reformed portion 131 of the 
patterned resist) given by the removing agent for removing the patterned 
resist such as an oxygen radical (O.sup.*) was in the range from 115 to 
135 nm/min, and Er.sub.12 (the rate of removing sidewall reformed portion 
132) was in the range from 15 to 25 nm/min. 
EMBODIMENT 6 
Another example of the process of reforming sidewalls of the patterned 
resist according to Embodiment 1 will be described in the following. 
In this embodiment, accelerated particles formed of two kinds of ions are 
used as a reforming agent for forming such a sidewall reformed portion. 
Referring to FIG. 30A, object layer 120 is formed on support member 110. 
Patterned resist 130 is formed on object layer 120. 
Referring to FIG. 30B, a reforming agent 141 of accelerated particles 
formed of two kinds of ions such as silicon ions (Si.sup.+) and oxygen 
ions (O.sup.+) or carbon ions (C.sup.+) and carbon monoxide ions 
(CO.sup.+) is supplied in a fixed amount for a fixed time period toward 
sidewalls of patterned resist 130. Reforming agent 141 either reacts with 
patterned resist 130 or enters into patterned resist 130, and a chemical 
change forming a new chemical bond such as Si-O and C-O occurs on the 
surface of patterned resist 130. 
As a result, referring to FIG. 30C, sidewall reformed portion 132 which has 
changed as far as a prescribed depth forms on the surface of patterned 
resist 130. In the FIG. 131 represents the not reformed portion of the 
patterned resist. 
Referring to FIG. 30D, a removing agent 150 for removing the object such as 
a bromine radical (Br.sup.*) having directional dependence i.e. anisotropy 
is supplied onto support member 110. 
Referring to FIG. 30F, object layer 120, the polycrystalline silicon film 
for example forms into a reaction product A(730) of silicon tetrabromide 
(SiBr.sub.4), part of patterned resist 130 forms into a reaction product 
B(731) of carbon tetrabromide (CBr.sub.4) for example, and part of the 
accelerated particles of reforming agent 141 which has come into patterned 
resist 130 forms into a reaction product C(732) of silicon tetrabromide 
(SiBr.sub.4) or carbon tetrabromide (CBr.sub.4). These reaction products 
dissipate externally. Supplying removing agent 150 for removing the object 
in a fixed amount for a fixed time period forms sidewall reformed portion 
130 containing chemical bonds of silicon (Si) and carbon (C) which cannot 
be completely removed with removing agent 150 for removing the object or 
the removing agent for removing the not reformed portion 131 of the 
patterned resist. 
The accelerated particles of reforming agent 141 can be produced with a 
commonly used ion implantation device. Accelerated particles can be 
directed obliquely toward patterned resist 130 by changing the angle at 
which the accelerated particles are irradiated. The depth to which the 
accelerated particles come into patterned resist 130 is determined by 
changing easily controllable ion energy. Therefore, the width (w) of 
sidewall reformed portion 132 can be readily controlled. For example for 
silicon ions (Si.sup.+) and oxygen ions (CO.sup.+) with an implantation 
energy of 50 keV in a dose of 10.sup.16 atoms/cm.sup.2, the depths of the 
highest portions of the concentration of the implanted ions are 115 nm and 
70 nm, and sidewall reformed portion 132 having a width corresponding to 
the depths is formed. ER.sub.01 by the removing agent for removing the 
object such as a bromine radical (Br.sup.*) is in the range from 50 to 70 
nm/min, and ERO.sub.2 is in the range from 15 to 25 nm/min. The removing 
agent for removing the patterned resist such as an oxygen radical 
(O.sup.*) was in the range from 115 to 135 nm/min and ER.sub.12 was in the 
range from 5 to 10 nm/min. 
EMBODIMENT 7 
FIGS. 31A to 31E are schematic representations for use in illustration of a 
process of reforming sidewalls of patterned resist in Embodiment 7. 
In this embodiment, a chlorine radical (Cl.sub.2.sup.*) capable of forming 
a sidewall reformed portion on the sidewall of patterned resist and of 
removing an object layer as well is used as a reforming agent. 
Referring to FIG. 31A, an object layer 120 is formed on a support member 
110. Patterned resist 130 is formed on object layer 120. 
Referring to FIG. 31B, a fixed amount of a chlorine radical 
(Cl.sub.2.sup.*), a reforming and removing agent 142 having directional 
dependence i.e. anisotropy is supplied onto support member 110 for a fixed 
time period. 
Referring to FIG. 31C, the chlorine radical (Cl.sub.2.sup.*) reacts with 
object layer 120 in other words polycrystalline silicon and forms into a 
reaction product A(730) of silicon tetrachloride (SiCl.sub.4). Part of 
patterned resist 130 forms into a reaction product B(731) such as carbon 
tetrachloride (CCl.sub.4). Part of the chlorine radical (Cl.sub.2.sup.*) 
returns to its ground state, and forms into another reaction product 
C(732), chlorine. These reaction products dissipate externally as 
illustrated in FIG. 31C. Although part of the surface of patterned resist 
130 dissipates in the form of reaction product B(731), since a chlorine 
radical (Cl.sub.2.sup.*) is more active than a carbon trichloride radical 
(CCl.sub.3.sup.*), the bond (-C-) of patterned resist 130 is cut off, and 
sidewall reformed portion 132 containing a large amount of carbon (C) 
forms on the side surface of patterned resist 130. Most of chlorine 
radicals (Cl.sub.2.sup.*) sticking onto the surface of object layer 120 
react with object layer 120, and dissipate externally in the form reaction 
product A(730) as illustrated in FIG. 31D, and thus function to remove 
object layer 120. As a result, supply of a fixed amount of chlorine 
radical (Cl.sub.2.sup.*) for a fixed time period removes object layer 120, 
and finally sidewall reformed portion 132 entered with a carbon thin film 
and/or carbon which cannot be completely removed with a removing agent 
(such as oxygen radical (O.sup.*)) for removing the not reformed portion 
of the patterned resist is formed on a sidewall of patterned resist 130 as 
illustrated in FIG. 31E. 
The chlorine radical (Cl.sub.2.sup.*) can be produced with a commonly used 
plasma device as illustrated in FIG. 32. More specifically, a mixture gas 
of helium gas (G72) at a flow rate of 100SCCM through pressure and flow 
rate regulators V72 and V'72 and chlorine gas (G72) at a flow rate of 100 
SCCM through pressure and flow rate regulators V76 and V'76 is subjected 
to plasma-dissociation between electrode A(71) and electrode B(72) under a 
pressure of 250 mTorr. A generated reaction product is let out with helium 
gas (G72). If the temperature of a station (72) for an object is in the 
range from 50.degree. to 60.degree. C., a radio wave power is in the range 
from 220 to 260 W, and the distance between electrode A(73) and object 
(120) is 1.1 cm, object 120 is removed at such a rate at which ER.sub.20 
(the rate of removing the object with reforming and removing agent 142) is 
in the range from 450 to 500 nm/min, and sidewall reformed portion 132 
having a width in the range from 0.15 to 0.25 .mu.m forms. ER.sub.41 (the 
rate at which the not reformed portion 131 of the patterned resist is 
removed with reforming and removing agent 142) is in the range from 220 to 
260 nm/min, ER.sub.42 (the rate at which sidewall reformed portion 132 is 
removed with reforming and removing agent 142) is in the range from 60 to 
80 nm/min, and ER.sub.43 (the rate at which the support member for 
supporting the object is removed with reforming and removing agent 142) is 
in the range from 15 to 20 nm/min. 
Reforming and removing agent 142 or removing agent 150 for removing the 
object described above is formed with a commonly used plasma device as 
illustrated in FIG. 32. FIG. 33 is a representation showing the 
arrangement of an ashing device for generating a removing agent for 
removing the not reformed portion of the patterned resist. 
In FIG. 33, CH82 is a reaction chamber, and CH81 is a spare chamber for 
keeping an object for a while. RP81 and V81 are a rotary pump and a valve 
for exhausting spare chamber CH81. Gas 81 such as nitrogen is introduced 
into spare chamber CH81 through pressure and flow rate regulars V85 and 
V'85, and the chamber is exhausted by rotary pump RP81. After repeating 
introduction/exhaustion of the nitrogen gas, spare chamber CH81 is brought 
into a vacuum of 10.sup.-2 Torr, in which an object to be processed is 
kept. Reaction chamber CH82 installed with the object is brought into a 
vacuum of 10.sup.-4 Torr by a turbo molecular pump TMP8 and a rotary pump 
RP82, and the residual gas is let out. In the figure (MW) represents an 
electromagnetic wave generator. (80) is a microwave generated by 
electromagnetic wave generator (MW), and (81) is a waveguide. (82) is a 
teflon plate for matching waveguide 81 and reaction chamber CH82. An 
alumina (Al.sub.2 O.sub.3) window plate 83 partitions the space between 
waveguide 81 and reaction chamber CH82, and introduces microwave 80 from 
waveguide 81 into reaction chamber CH82. Reaction chamber CH82 is provided 
with a shower head 84. Reactive particles to function as a removing agent 
for removing the patterned resist is blown from shower head 84. Support 
member 110 is placed on a station 86 for an object. 
An oxygen radical (O.sup.*), an example of such a removing agent for 
removing the patterned resist is produced as follows as illustrated in 
FIG. 33. A microwave 80 at 2.45 GHz generated by electromagnetic wave 
generator (MW) is introduced into reaction chamber CH82 through waveguide 
81. Dissociating oxygen O.sub.2 gas (G83) under a pressure in the range 
from 1 to 2 Torr at a flow rate of 1000 SCCM through pressure and flow 
rate regulators V86 and V'86 provides an oxygen radical (O.sup.*). If the 
temperature of object station 86 is in the range from 100.degree. to 
200.degree. C., the microwave power is in the range from 400 to 1500 W, 
and the distance between the shower head from which oxygen radical 85 is 
discharged and the not reformed portion 131 of patterned resist is in the 
range from 5 to 6 cm, the not reformed portion 131 of patterned resist is 
removed away at a removing rate in the range from 1 to 2 .mu.m/min. 
EMBODIMENT 8 
In this embodiment, aluminum trichloride (AlCl.sub.3) liquid or dibutyl 
magnesium [Mg(Bu).sub.2 ] liquid is used as a reforming agent. For 
aluminum, aluminum trichloride (Alcl.sub.3) liquid is used. The aluminum 
trichloride liquid is produced by dissolving 1.8 mol/l aluminum 
trichloride into a solvent of nitrobenzene. For magnesium, dibutyl 
magnesium liquid or diethyl magnesium liquid is used. Dibuthyl magnesium 
liquid is produced by dissolving 0.7 mol/l dibutyl magnesium in a solvent 
of heptane. The diethyl magnesium liquid is produced by dissolving 0.7 
mol/l diethyl magnesium in a solvent of diethylether. The support member 
with the patterned resist formed thereon is soaked in the dibutyl 
magnesium liquid or diethyl magnesium liquid for one minute and then 
washed with toluene and then hexane. Then, drying is conducted by blowing 
nitrogen gas. The series of treatments are all conducted in nitrogen gas. 
Through these treatments, referring to FIG. 1, for example, metal atoms of 
aluminum or magnesium come into the surface of patterned resist 130 from 
its surface. These metals are oxidized with oxygen present in patterned 
resist 130 and form an inorganic substance. The inorganic substance and an 
organic substance of the patterned resist in the form of a matrix form 
sidewall reformed portions 132a and 132b. Sidewall reformed portions 132a 
and 132b are formed to have such a property that they are not removed with 
a removing agent for removing the object or a removing agent for removing 
the patterned resist. 
Sidewall reformed portions 132a and 132b treated with dibutyl magnesium 
liquid exhibit the following property. For example, ER.sub.01 (the rate at 
which the not reformed portion 131 of patterned resist is removed 
secondarily by the removing agent for removing the object) with removing 
agent 150 for removing the object is in the range from 50 to 70 nm/min, 
and ER.sub.02 (the rate at which sidewall reformed portions 132a and 132b 
are removed with removing agent 150 for removing the object) is in the 
range from 5 to 15 nm/min. 
In addition, ER.sub.11 (the rate at which the not reformed portion 131 of 
patterned resist is removed with the removing agent for removing patterned 
resist) with the removing agent for removing the patterned resist is in 
the range from 115 to 135 nm/min, and ER.sub.12 (the rate at which 
sidewall reformed portions 132a and 132b are removed with the removing 
agent for removing the patterned resist) is in the range from 5 to 15 
nm/min. 
In this embodiment, the patterned resist is soaked in aluminum trichloride 
liquid or dibutyl magnesium liquid, and the liquid is made to permeate 
into the surface of the patterned resist and thus sidewall reformed 
portions 132a and 132b are formed. The width (w) of sidewall reformed 
portions 132a and 132b can be controlled based on time for soaking. 
As a removing agent for removing a sidewall reformed portion, a 
hydrofluoric acid aqueous solution or a buffer hydrofluoric acid aqueous 
solution is used. The hydrofluoric acid aqueous solution used has a volume 
ratio of water and hydrofluoric acid (HF content: 50%) of 10-50:1. The 
buffer hydrofluoric acid aqueous solution used has a volume ratio of 
ammonium fluoride (NH.sub.4 F content: 40%) and hydrofluoric acid of 
5-10:1. Removal of a sidewall reformed portion with the removing agent for 
removing the sidewall reformed portion also has a mechanism of removing by 
the function of a so-called lift off effect, and the removing rate 
ER.sub.22 (the rate at which sidewall reformed portions 132a and 132b are 
removed with the removing agent for removing the sidewall reformed 
portions) is 5 to 6 seconds. For the removing time, ER.sub.20 (the rate at 
which object 120 is removed with the removing agent for removing sidewall 
reformed portion) and ER.sub.23 (the rate at which support member 110 is 
removed with the removing agent for removing sidewall reformed portion) 
are very small. 
EMBODIMENT 9 
In this embodiment, a carbon trichloride radical and a mixture of silicon 
ion and oxygen ion are selected as a reforming agent for forming a 
sidewall reformed portion. Using the carbon trichloride radical, one and 
the other sidewalls of patterned resist are reformed. Then, using the 
mixture of silicon ion and oxygen ion, one and the other sidewalls of 
patterned resist are once again reformed. By such a method, the advantages 
of both (by the first reforming treatment and the second reforming 
treatment) are exhibited, and high performance sidewall reformed portions 
are formed. 
EMBODIMENT 10 
In this embodiment, a carbon trichloride radical and a mixture of carbon 
ion and carbon monoxide ion are selected as reforming agents for forming 
sidewall reformed portions. One and the other sidewalls of patterned 
resist are reformed with the carbon trichloride radical. Then, using the 
mixture of carbon ion and carbon monoxide ion, the one and the other 
sidewalls of patterned resist are once again reformed. By such a method, 
both advantages are synergistically exhibited, and sidewall reformed 
portions with excellent performance are provided. 
EMBODIMENT 11 
In this embodiment, a chlorine radical and a mixture of silicon ion and 
oxygen ion are selected as reforming agents for forming sidewall reformed 
portions. With the chlorine radical, one and other sidewalls of patterned 
resist are reformed. Then, with the mixture of silicon ion and oxygen ion, 
the one and the other sidewalls of patterned resist are once again 
reformed. By such a method, both advantages are synergistically exhibited, 
and sidewall reformed portions obtained will give excellent performance. 
EMBODIMENT 12 
In this embodiment, a chlorine radical and a mixture of carbon ion and 
carbon monoxide ion are selected as reforming agents for forming sidewall 
reformed portions. With the chlorine radical, one and the other sidewalls 
of patterned resist are reformed. Then, with the mixture of carbon ion and 
carbon monoxide ion, the one and the other sidewalls of patterned resist 
are once again reformed. By such a method, both advantages are 
synergistically exhibited, and sidewall reformed portions obtained will 
give excellent performance. 
EMBODIMENT 13 
In this embodiment, aluminum trichloride liquid and a mixture of silicon 
ion and oxygen ion are selected as reforming agents for forming sidewall 
reformed portions. Using the aluminum trichloride liquid, one and the 
other sidewalls of patterned resist are reformed. Then, with the mixture 
of silicon ion and oxygen ion, the one and the other sidewalls of 
patterned resist are once again reformed. By such a method, both 
advantages are synergistically exhibited and the sidewall reformed 
portions obtained will have excellent performance. 
EMBODIMENT 14 
In this embodiment, aluminum trichloride liquid and (c) a mixture of carbon 
ion and carbon monoxide ion are selected as reforming agents for forming 
sidewall reformed portions. One and the other sidewalls of patterned 
resist are reformed using the aluminum trichloride liquid. Then, with the 
mixture of carbon ion and carbon monoxide ion, the one and the other 
sidewalls of patterned resist are once again reformed. By such a method, 
both advantages are synergistically exhibited, and sidewall reformed 
portions obtained will give excellent performance. 
EMBODIMENT 15 
In this embodiment, (f) dibutyl magnesium liquid, and (b) a mixture of 
silicon ion and oxygen ion are selected as reforming agents for forming 
sidewall reformed portions. Using the dibutyl magnesium liquid, one and 
the other sidewalls of patterned resist are reformed. Then, with the 
mixture of silicon ion and oxygen ion, the one and the other sidewalls of 
patterned resist are once again reformed. By such a method, both 
advantages are synergistically exhibited, and sidewall reformed portions 
formed will give excellent performance. 
EMBODIMENT 16 
In this embodiment, (f) a dibutyl magnesium liquid and (c) a mixture of 
carbon ion and carbon monoxide ion are selected as reforming agents for 
forming sidewall reformed portions. Using the dibutyl magnesium liquid, 
one and the other sidewalls of patterned resist are reformed. Then, with 
the mixture of carbon ion and carbon monoxide ion, the one and the other 
sidewalls of patterned resist are once again reformed. By such a method, 
both advantages are synergistically exhibited, and sidewall reformed 
portions formed will give excellent performance. 
EMBODIMENT 17 
This embodiment relates to a method of further working fine patterns 
obtained according to the above-described methods. 
Referring to FIG. 34A, an object layer 120 is formed on a support member 
110. Patterned resist 130 is formed on object layer 120. 
Referring to FIG. 34B, A sidewall of patterned resist 130 is reformed and a 
sidewall reformed portion 132 is formed. Using patterned resist 130 
including sidewall reformed portion 132 as mask, the portion of object 
layer 120 excluding the portion immediately below patterned resist 130 is 
etched away, and a pattern 125 of the object is thus formed. 
Referring to FIGS. 34C and 34D, the not reformed portion 131 of patterned 
resist 130 is removed away, and sidewall reformed portion 132 is left on 
pattern 125 of the object. 
Referring to FIG. 34E, using sidewall reformed portion 132 as mask, the 
portion of pattern 125 of the object excluding the portion immediately 
below sidewall reformed portion 132 is etched away. 
Referring to FIG. 34F, by removal of the sidewall reformed portion, a pair 
of fine patterns 120A and 120B parallel to each other, and a pair of fine 
patterns 120C and 120D linking ends of the pair of fine patterns 120A and 
120B are formed. 
FIG. 35A corresponds to FIG. 34F. 
Referring to FIG. 35B, in order to expose pair of fine patterns 120C and 
120D, resist 130 is applied on pattern 120 of the object. 
Referring to FIGS. 35B and 35C, using resist 130 as mask, pair of fine 
patterns 120C and 120D are etched away. Then, removal of resist 130 
provides a pair of fine patterns 120A and 120B arranged parallel to each 
other as illustrated in FIG. 35D. 
EMBODIMENT 18 
FIG. 36A and 36D are perspective views showing a method of forming fine 
patterns according to Embodiment 18. FIG. 36A corresponds to FIG. 34F. 
Referring to FIGS. 36A and 36B, resist 130 is formed on fine pattern 120 so 
as to expose only one fine pattern 120D of pair of fine patterns 120C and 
120D arranged parallel to each other. 
Referring to FIG. 36C, using resist 130 as mask, the one fine pattern 120D 
is etched away. 
Referring to FIGS. 36C and 36D, removal of patterned resist 130 forms a 
pair of fine patterns 120A and 120B arranged parallel to each other and a 
fine pattern 120C linking their ends. 
EMBODIMENT 19 
FIGS. 37A to 37D are perspective views showing a method of forming fine 
patterns according to Embodiment 19. 
FIG. 37A corresponds to FIG. 34F. 
Referring to FIG. 37B, resist 130 is formed on a support member 110 so as 
to expose fine pattern 120B, part of fine pattern 120C, and part of fine 
pattern 120D. Referring to FIGS. 37B and 37C, using patterned resist 130 
as mask, fine pattern 120B, part of fine pattern 120C and part of fine 
pattern 120D are etched away. Resist 130 is then removed away. 
Referring to FIG. 37D, a fine pattern formed of fine pattern 120A, part of 
fine pattern 120C and part of fine pattern 120D is formed. 
By the method of forming fine patterns according to the first aspect of the 
invention, using first and second sidewall reformed portions formed on 
sidewalls of patterned resist as mask, the portion of the object layer 
excluding the portion immediately below the first and second sidewall 
reformed portions are etched away, and fine patterns of the object layer 
are thus formed. As a result, patterns even finer than the minimum 
resolution achieved by the present lithography techniques are provided. 
By the method of forming fine patterns according to the second aspect of 
the invention, using first and second sidewall reformed portions as mask, 
the portion of patterns of the object excluding the portion immediately 
below the first and second sidewall reformed portions is etched away, and 
therefore even finer patterns of the object can be formed. As a result, 
patterns finer than the minimum resolution achieved by the present 
lithography techniques can be advantageously provided. 
By the method of forming fine patterns according to the third aspect of the 
invention, using patterned resist as mask, the portion of the object layer 
excluding the portion immediately below the patterned resist is etched 
away, patterns of the object are thus formed, while reforming one and the 
other sidewalls of the patterned resist, thus a first sidewall reformed 
portion is formed on the one sidewall of patterned resist and a second 
sidewall reformed portion on the other sidewall of patterned resist, and 
therefore the manufacturing process is simplified. 
By the method of forming fine patterns according to the fourth aspect of 
the invention, using patterned resist as mask, the portion of the object 
layer excluding the portion immediately below the patterned resist is 
etched away, and thus patterns of the object are formed. Then, using the 
first and second sidewall reformed portions as mask, the portion of the 
patterns of the object excluding the portion immediately below the first 
and second sidewall reformed portions is etched away, and therefore even 
finer patterns of the object can be formed. As a result, patterns even 
finer than the minimum resolution achieved by the present lithography 
techniques can advantageously be provided. 
Although the present invention has been described and illustrated in 
detail, it is clearly understood that the same is by way of illustration 
and example only and is not to be taken by way of limitation, the spirit 
and scope of the present invention being limited only by the terms of the 
appended claims.