Drying and gas or vapor contact with solids – Process – Gas or vapor contact with treated material
Reexamination Certificate
2001-03-09
2002-08-13
Lazarus, Ira S. (Department: 3749)
Drying and gas or vapor contact with solids
Process
Gas or vapor contact with treated material
C034S074000, C034S408000, C034S409000, C034S410000, C034S412000, C034S443000, C034S467000, C134S011000, C134S030000, C134S031000, C134S095100, C134S902000
Reexamination Certificate
active
06430840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of and an apparatus for drying a wafer. More particularly, the present invention relates to a method of and an apparatus for drying a wafer using isopropyl liquid after the wafer is cleaned following a semiconductor manufacturing process.
2. Description of the Related Art
Semiconductor devices or semiconductor chips are manufactured by processing a wafer that is usually formed of silicon. The wafer is typically subjected to a series of semiconductor device manufacturing processes such as photolithography, chemical or physical vapor deposition and plasma etching.
After executing these processes, foreign material such as chemicals or dust remains on the surface of the wafer. In order to assure the quality of the semiconductor devices, the foreign material must be removed from the surface of the wafer. The cleaning process used to remove the foreign material involves both washing and drying the wafer.
In particular, the wafer may be washed using de-ionized water (hereinafter referred to as “DIW”). Because the DIW will eventually dissolve the silicon, the wafer must be completely dried after being washed with the DIW or else water spots will be formed.
In addition, a method of using isopropyl alcohol to enhance the drying of a wafer has been developed. For example, Japanese Patent Laid-Open Publication No. Hei 8-61846 discloses a method of directly spraying liquid isopropyl alcohol over a wafer, forming a mixture of the water and the isopropyl alcohol on the surface of the wafer, and volatilizing the mixture by means of a high temperature nitrogen gas. In addition, U.S. Pat. No. 6,029,371 issued to Kamikawa et al. discloses a method of drying a wafer by directly spraying a washed wafer with a drying gas comprising heated isopropyl alcohol and nitrogen.
Also, drying apparatuses using isopropyl alcohol are disclosed in U.S. Pat. No. 5,634,978 issued to Mohindra et al., U.S. Pat. No. 5,855,077 issued to Chang-Hyun Nam et al., U.S. Pat. No. 4,633,893 issued to McConnell et al., and U.S. Pat. No. 4,911,761 also issued to McConnell et al. These drying apparatuses execute a method in which the isopropyl alcohol is introduced as a mist over the cleaned wafer to eliminate the water on the wafer.
FIG. 1
shows one example of a conventional apparatus
100
that works on the Marangoni effect to dry the wafer using an isopropyl alcohol mist. The apparatus
100
includes a cleaning section (or a rinsing section)
110
containing a cleaning liquid (or rinsing liquid)
113
for cleaning (or rinsing) the wafer. The cleaning section
110
in turn includes an inner bath
112
having an upper open end, and an outer bath
116
covered with a lid
117
. The outer bath
116
and lid
117
enclose the inner bath
112
. A wafer
101
is immersed in the cleaning liquid
113
of the inner bath
112
for cleaning. Once the cleaning liquid
113
over-flows the inner bath
112
, the over-flown cleaning liquid
113
a
gathers in the outer bath
116
from where it is drained from the cleaning section
110
.
A cleaning liquid supply tube line
114
a
is connected to the inner bath
112
at the bottom thereof. First and second cleaning liquid drain tube lines
114
b
and
114
c
are connected to the inner bath
112
and the outer bath
116
, respectively, at the bottoms thereof. The cleaning liquid supply tube line
114
a
supplies the cleaning liquid
113
, such as DIW, to the inner bath
112
. The first cleaning liquid drain tube line
114
b
drains the cleaning liquid
113
a
which has over-flown the inner bath
112
into the outer bath
116
. The second cleaning liquid drain tube line
114
c
gradually drains the cleaning liquid
113
from within the inner bath
112
.
The apparatus
100
for drying the wafer is also equipped with an isopropyl alcohol mist supply tube line
134
for supplying the isopropyl alcohol mist from an isopropyl alcohol supply unit (not shown). The isopropyl alcohol supply unit makes the isopropyl alcohol bubble by using nitrogen as a carrier gas to form the isopropyl alcohol mist. Then, the isopropyl alcohol mist and nitrogen are supplied to the upper portion of the outer bath
116
via the isopropyl alcohol mist supply tube line
134
. A diffuser
136
is furnished at the central portion of the lid
117
of the outer bath
116
for consistently diffusing the isopropyl alcohol mist and nitrogen throughout the inside of the outer bath
116
.
In addition, a nitrogen gas supply tube line
140
is connected to the lid
117
for supplying heated nitrogen gas into the outer bath
116
during the drying process to create a drying ambient.
The conventional apparatus
100
for drying a wafer operates as follows.
Once a wafer guide
103
loaded with wafers
101
is seated within the inner bath
112
, the cleaning liquid
113
, such as the DIW, is supplied to the inner bath
112
via the cleaning liquid supply tube line
114
a
to initiate the cleaning operation. The cleaning liquid is supplied into the inner bath
112
at such a rate that it overflows the inner bath
112
during the cleaning operation. The over-flown cleaning liquid
113
a
is gathered in the outer bath
116
and drained from the bottom of the outer bath
116
via the first cleaning liquid drain tube line
114
b.
Once the cleaning operation is complete, the process of drying the wafer
101
begins.
FIGS. 2A
,
2
B and
2
C are schematic diagrams illustrating the drying process.
Referring to
FIG. 2A
, after the cleaning process is complete, the nitrogen gas and the isopropyl alcohol mist entrained thereby are introduced via the isopropyl supply tube line
134
and diffuser
136
into the upper portion of the outer bath
116
. Thus, the ambient in outer bath
116
is converted into a drying ambient. At this time, approximately 50 cc of the isopropyl alcohol mist is supplied. Also, at this time, the heated nitrogen gas is supplied into the outer bath
116
via the nitrogen gas supply tube line
140
connected to the lid
117
.
Referring to
FIG. 2B
, the cleaning liquid
113
is drained via the drain tube line
114
c
while the nitrogen gas is supplied via the nitrogen gas supply tube line
140
. At this time, the cleaning liquid
113
is drained at a constant rate via the second drain tube line
114
c
. The height of the cleaning liquid
113
is decreased at a rate of about 3 mm/sec. During the draining operation, the water spots on the wafers
101
are eliminated by means of the Marangoni effect created by the isopropyl alcohol. Referring to
FIG. 2C
, once the cleaning liquid
113
is completely drained to a level below the wafers
101
, the last of the heated nitrogen gas is introduced into the outer bath
116
via the nitrogen supplying tube line
140
, thereby completing the drying process.
In addition to this conventional method, Japanese Patent Laid-Open Publication Nos. Hei 11-87305, Hei10-154689 and Hei10-22257 disclose methods of drying a wafer in which an isopropyl alcohol mist is used. In these methods, an isopropyl alcohol liquid layer is formed by the mist over a cleaning liquid, and the wafers are raised from the cleaning liquid into the isopropyl alcohol liquid layer, thereby drying the wafer.
According to all of these heretofore known methods, the mist of isopropyl alcohol is supplied to the outer bath using nitrogen as a carrier gas. Therefore, the amount of isopropyl alcohol injected into the outer bath is determined by measuring the reduction in the amount of isopropyl alcohol in the isopropyl alcohol supply unit. For this reason, the amount of isopropyl alcohol used for forming the isopropyl alcohol layer cannot be accurately determined. Furthermore, it is difficult to accurately control the amount of isopropyl alcohol being supplied.
Moreover, the isopropyl alcohol sprayed by the diffuser adheres to the side wall of the outer bath. In this case, the isopropyl alcohol is likely to fall as drops onto the wafer. These drops create wafer defects.
Additionally, a large amount of time is required to form from the mis
Lazarus Ira S.
O'Malley Kathryn S.
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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