Wafer dryers for Semiconductor cleaning apparatuses

Details Wafer dryers for Semiconductor cleaning apparatuses Wafer dryers for Semiconductor cleaning apparatuses

2002-11-27

2004-06-15

Lazarus, Ira S. (Department: 3749)

Drying and gas or vapor contact with solids

Apparatus

Sheet, web, or strand

C034S323000, C034S487000, C034S614000, C134S902000

Reexamination Certificate

active

06748672

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a cleaning apparatus for semiconductor fabrication and, more particularly, to a wafer dryer for a cleaned wafer.
BACKGROUND OF THE INVENTION
With the trend toward a high integration density of semiconductor devices, particles remaining at a wafer surface have a great effect on device characteristics. Thus, wafer cleaning technologies for removing particles are recently getting significant in a semiconductor fabricating process.
In order to uniformly clean a wafer surface without damage, a wet cleaning technique is mainly used. As a wafer caliber increases while a chip size decreases, a bath system employing a wet station is widely used.
A wafer cleaning apparatus has baths containing different solutions so as to clean wafers through several cleaning steps. By passing the baths, the wafers are completely cleaned. The last cleaning step is to dry the completely cleaned wafers. They are dried by a wafer dryer.
A conventional wafer dryer is illustrated in FIG.
1
.
Referring to
FIG. 1
, a wafer dryer
100
includes an internal bath
10
, an external bath
20
, a wafer guide
30
, and a direction-adjusting valve
40
, drying means, a solution supply line
50
, and a solution drain line. The wafer dryer
100
serves to finally clean and dry wafers.
The drying means has an isopropyl alcohol (hereinafter referred to as “IPA”) nozzle
90
and a gas spray nozzle
80
for spraying N
2
gas. The solution drain line has a first drain line
60
and a second drain line
70
for faster draining solutions than the first drain line
60
.
A wafer cleaning solution is supplied to the internal bath
20
from the solution supply line
70
having a valve
522
for adjusting the amount of the supplied solution. The solution overflowing from the internal bath
10
is received into the external bath
20
. The solution overflowing from the external bath
20
is sent to the outside through an opened bottom of the external bath
20
. The wafer guide
30
is installed in the internal bath
10
to receive a plurality of wafers. Thus, they may be cleaned and dried at the same time. If the wafers are mounted upon the wafer guide
30
of the internal bath
10
containing the solution, particles remaining at the wafers float on the solution in the internal bath
10
. The floating particles are mixed with the solution overflowing to the external bath
20
to be sent to the outside.
After the particles are removed by the solution overflowing to the external bath
20
, IPA is sprayed into the internal bath
10
from the IPA nozzle
90
. The solution in the bath
10
, where an IPA liquid film is formed, is slowly drained through the first drain line
60
. A valve
62
for adjusting the amount of the drained solution is installed on the first drain line
60
. While the solution in the internal bath
10
is slowly drained, the particles attached to the wafer surface are removed by the surface tension of de-ionized (DI) water and the IPA. The DI water is exchanged into the IPA liquid film to be evaporated. A surface tension difference between the DI water and the IPA prevents re-attachment of the particles and serves to remove water from the wafer surface, which is called the “Marangoni Effect”.
If the solution in the internal bath
10
goes down to the lowest part of the wafer through the first drain line
60
, remaining solution is rapidly drained through the second drain line
80
. A valve
72
for adjusting the amount of the drained solution is installed on the second drain line
90
. A diameter of the second drain line
90
is greater than that of the first drain line
80
. Thus, a drain speed of the second drain line
70
is much higher than that of the first drain line
60
. After the solution in the internal bath
20
is completely drained, heated N
2
gas is sprayed from the gas spray nozzles
80
installed at an upper part of the internal bath
20
to dry the wafers. The gas spray nozzles
80
spray heated N
2
gas for drying wafers so as to suppress formation of an oxide layer on wafer surfaces. Moreover, the gas spray nozzles
80
continue to spray N
2
gas of normal temperature into the internal bath
10
during the entire process so that oxygen of a peripheral environment can be removed to suppress formation of an oxide layer on wafer surfaces.
Unfortunately, the above-described wafer dryer has a few problems as follows.
Firstly, both the first and second drain lines
60
and
70
drain a solution by means of the gravity. Thus, a solution-draining speed is varied according to the amount of the solution contained in the internal bath
10
. That is, the solution-draining speed becomes lower as the solution contained in the internal bath
10
is drained. As a result, time required for cleaning and drying wafers becomes longer and the reliability of the wafers is deteriorated.
Secondly, as the gas spray nozzles
80
directly spray N
2
gas of normal temperature downwardly toward a surface of the solution contained in the internal bath
10
, a wave is created at the solution surface when the solution is drained through the first drain line
60
, as shown in FIG.
2
. Thus, an IPA liquid film formed at a DI water surface is broken, and it is difficult that removing particles and drying wafers are achieved by way of the Marangoni Effect.
SUMMARY OF THE INVENTION
A feature of the present invention is to provide a wafer dryer which can maximally exert the Marangoni Effect by constantly keeping a solution drain speed.
Another feature of the present invention is to provide a wafer dryer which can stably maintain a surface of a drained solution without a wave.
According to the present invention, a wafer dryer for use in a semiconductor cleaning apparatus includes an internal bath for containing a solution, an external bath for containing a solution overflowing from the internal bath, a solution supply line for supplying a solution to the internal bath, a solution drain line for draining a solution from the internal bath when the wafer is dried, a pump for constantly maintaining a speed of the drained solution, and drying means for drying the wafer. A wafer to be cleaned and dried is submerged in the internal bath, and the pump is installed on the solution drain line.
The waver dryer further includes a direction adjusting valve which is installed to communicate with the internal bath and determines one of the solution supply line and the solution drain line to open to the internal bath. The solution supply line and the solution drain line are connected to the direction adjusting valve.
The solution drain line has a first drain line and a second drain line for more fast draining the solution contained in the internal bath than the first drain line. The pump is installed on the first drain line. A valve for adjusting the amount of the drained solution is installed on the first and second drain lines, respectively.
The drying means has an isopropyl alcohol (IPA) nozzle which is installed on the internal bath and sprays IPA into the internal bath, a first spray nozzle which is installed on the internal bath to a gas into the internal bath, and a second spray nozzle which is installed on all inner sidewalls of the external bath and has a plurality of holes for injecting a gas to the external bath.
The wafer dryer further includes a speed converting apparatus for adjusting a rotation speed of the pump to convert a speed of the drained solution. The solution is a de-ionized (DI) water.


REFERENCES:
patent: 5845660 (1998-12-01), Shindo et al.
patent: 5885360 (1999-03-01), Han et al.
patent: 6352083 (2002-03-01), Araki et al.
patent: 6430840 (2002-08-01), Jung
patent: 6510859 (2003-01-01), Kamikawa

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