Wafer rinsing apparatus

A wafer rinsing apparatus includes an ice making hopper for making ice particles by heat exchange between fine droplets of liquid to be frozen and low-temperature liquefied gas. The ice making hopper is connected to a separation device for separating the ice particles and vaporized gas generated from the low-temperature liquefied gas. The ice particles separated by the separation device are jetted onto a wafer by a jetting device, thereby rinsing the surface of the wafer.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to wafer rinsing apparatuses, and 
more particularly, wafer rinsing apparatuses with improved rinsing 
effects. 
2. Description of the Background Art 
Manufacturing processes of super large scale integrated circuit devices of 
the time demand a more efficient technique of rinsing wafer surface in 
order to improve a yield and quality of the devices. Contaminants such as 
resist residues, fine particles, organic films and native oxide films are 
among principal factors which determine a yield and performance of 
devices. For submicron devices, contaminated particles on the order of 0.1 
.mu.m should be removed. 
FIG. 5 is a schematic diagram showing a conventional wafer rinsing 
apparatus for rinsing a wafer by jetting ice particles on the wafer. 
The conventional wafer rinsing apparatus includes an ice making hopper 1 
for making ice particles by heat exchange between fine droplets of liquid 
to be frozen and low-temperature liquefied gas. Ice making hopper 1 is 
provided with a supply spray 2 for supplying fine droplets of liquid to be 
frozen to ice making hopper 1. The liquid to be frozen with particles 
removed by a filter 3 is fed to supply spray 2. Ice making hopper 1 is 
provided with a supply spray 4 of low-temperature liquefied gas 
(hereinafter simply referred to as liquefied gas). The liquefied gas is 
fed to supply spray 4 through a filter 5. Supply spray 4 and filter 5 are 
connected by a piping 20. Ice making hopper 1 is coupled to a spray means 
9. Jet nozzle 9 is arranged in a washing vessel 7. A wafer 6 is disposed 
in washing vessel 7. With reference to FIGS. 5 and 6, wafer 6 is held and 
rotated by a roller 8. Provided in washing vessel 7 is a pure water nozzle 
10 for spraying pure water onto the surface of wafer 6. 
Operation of the conventional wafer rinsing apparatus will be described. 
Particles included in liquefied gas such as liquid nitrogen are removed by 
filter 5. The liquefied gas with particles removed is fed to ice making 
hopper 1 by supply spray 4, thereby cooling ice making hopper 1 to about 
-100.degree. C.--150.degree. C. Then, particles included in liquid to be 
frozen such as pure water are removed by filter 3 and the pure water with 
the particles removed is supplied to the ice making hopper by supply spray 
2. The supply of the liquefied gas and that of the liquid to be frozen to 
ice making hopper 1 are carried out substantially at the same time. The 
fine droplets of the liquid to be frozen are made into ice particles 30 by 
heat exchange with the liquefied gas. The liquefied gas supply sprays 4 
are provided in plural in order to efficiently execute the heat exchange. 
The liquefied gas is sprayed into ice making hopper 1 and vaporized 
therein. Heat of the vaporization is used to make the fine droplets of 
liquid to be frozen into ice particles 30. The diameter of the obtained 
ice particles is several .mu.m-50 .mu.m. Ice making hopper 1 is made of 
SUS materials and filter 3 is made of SUS materials or ceramic materials. 
Ice particles 30 formed in ice making hopper 1 are drawn by jet nozzle 9 
disposed in washing vessel 7 and sprayed onto wafer 6. Jet nozzle 9 is 
formed by an ejector using dry air or nitrogen gas as a carrier gas. 
Wafer 6 is held by roller 8 provided in washing vessel 7. When the ice 
particles 30 are jetted, wafer 6 is moved up-and-down and rightward and 
leftward and rotated by roller 8, so that the ice particles 30 are jetted 
onto the entire surface of wafer 6. In addition, pure water is sprayed 
onto wafer 6 from pure water nozzle 10 in order to enhance a rinsing 
effect when the ice particles 30 are jetted. 
With the conventional wafer rinsing apparatus thus structured as shown in 
FIG. 5, dusts are formed at piping 20, ice making hopper 1, supply spray 4 
and filter 5 which contact with the liquefied gas, whereby particles such 
as Fe, Ni and Cr having a diameter smaller than that of the ice particles 
are formed. The particles, together with the ice particles 30, are jetted 
onto wafer 6 to contaminate and damage the same. 
The mechanism of dust formation is as follows. When liquid nitrogen 
contacts an inner wall surface of an ice making hopper made of the SUS 
materials, for example, the liquid nitrogen is vaporized on the inner wall 
surface of the ice making hopper to suddenly expand the hopper. Such 
sudden expansion peels off particles of such as Fe, Ni and Cr from the SUS 
materials to form dusts. 
SUMMARY OF THE INVENTION 
The present invention aims at providing a wafer rinsing apparatus improved 
to reduce dusts as described above. 
The present invention also aims at providing a wafer rinsing apparatus 
improved to prevent dusts of particles from being jetted onto the wafer. 
A wafer rinsing apparatus according to one aspect of the present invention 
includes an ice making hopper for making ice particles by heat exchange 
between fine droplets of liquid to be frozen and low-temperature liquefied 
gas. Connected to the above-described ice hopper is a separation means for 
separating the above-described ice particles and liquefied gas generated 
from the above-described low-temperature liquefied gas. The apparatus 
includes jetting means for jetting the above ice particles separated by 
the above separation means onto the wafer to rinse the surface of the 
wafer. 
According to a preferred embodiment of the present invention, the 
above-described separation means includes a cyclone. 
A wafer rinsing apparatus according to another aspect of the present 
invention includes an ice making hopper for making ice particles by heat 
treatment between fine droplets of liquid to be frozen and low-temperature 
liquefied gas. Attached to the above ice making hopper is a liquid to be 
frozen supplying means for supplying the above fine droplets of the above 
liquid to be frozen to the ice making hopper. Attached to the above ice 
making hopper is a filter means for removing particles included in the 
above low-temperature liquefied gas supplied to the ice making hopper. The 
above filter means is coupled to a supply piping for supplying the 
low-temperature liquefied gas to the above ice making hopper with the 
filter means provided therebetween. The apparatus includes a jetting means 
for jetting the above ice particles formed by the above ice making hopper 
onto the wafer. The apparatus further includes a cooling means for 
externally cooling the above filter means and the above supply piping down 
to the liquefidation temperature of the above low-temperature liquefied 
gas. 
In the wafer rinsing apparatus according to said one aspect of the present 
invention which includes the separation means for supplying ice particles 
and evaporated gas generated from low-temperature liquefied gas, particles 
formed from dusts are removed together with evaporated gas and separated 
from the ice particles. Therefore, no particle formed from the dust is 
mixed in the ice particles. 
In the wafer rinsing apparatus according to said another aspect of the 
present invention which includes a cooling means for externally cooling 
the ice making hopper, the filter means and the supply piping down to the 
liquefidation temperature of the low-temperature liquefied gas, contact 
between these components and the liquefied gas will not suddenly expand 
the liquefied gas. Dust formation is therefore suppressed. 
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 
One embodiment of the present invention will be described in the following 
with reference to the drawings. 
FIG. 1 is a schematic diagram showing a wafer rinsing apparatus according 
to one embodiment of the present invention. The wafer rinsing apparatus of 
the present embodiment includes an ice making hopper 1 for making ice 
particles by heat exchange between fine droplets of liquid to be frozen 
and a low-temperature liquefied gas. Ice making hopper 1 is provided with 
a supply spray 2 for supplying the liquid to be frozen to ice making 
hopper 1. Supply spray 2 is supplied with the liquid to be frozen through 
a filter 3. Ice making hopper 1 is provided with a supply spray 4 for 
supplying the low-temperature liquefied gas to ice making hopper 1. Supply 
spray 4 is supplied with the low-temperature liquefied gas through a 
filter 5. Ice making hopper 1 is provided with a separation means 11 for 
separating ice particles 30 and vaporized gas generated from the 
low-temperature liquefied gas. The structure of the separation means 11 
will be described later. Attached to separation means 11 is a filter 12 
which is a means for removing particles from the vaporized gas separated 
by the separation means. Attached to separation means 11, filter 12 and a 
jet nozzle 9 is a mixing means 13 for mixing the ice particles 30 
separated by separation means 11 with the vaporized gas with the particles 
removed by filter 12 and feeding the mixture to jet nozzle 9. 
Separation means 11 will be described in detail with reference to FIGS. 2 
and 3. FIG. 2 is a plan view of the separation means and FIG. 3 is a 
sectional view taken along line A-B of FIG. 2. The illustrated separation 
means is called a cyclone. 
In this apparatus, centrifugal force is applied by a rotating flow in a 
cylinder 11b to the mixture of the ice particles 30 and the vaporized gas 
fed through an inlet 11a. The centrifugal force separates the vaporized 
gas and the ice particles 30. The vaporized gas is exhausted through a 
vaporized gas outlet 11c, while the ice particles are discharged through 
an ice particle outlet 11d. 
Back to FIG. 1, for example, an ejector is used as mixing means 13. 
Operation will be described in the following. 
The mixture of the ice particles 30 and the vaporized gas before entering 
separation means 11, includes particles, that is, dusts. As is already 
described, the dusts are formed as a result of contact between the SUS 
materials used for ice making hopper 1, supply spray 4, filter 5 and 
piping 20 for liquefied gas, and low-temperature liquefied gas. When these 
mixtures including dusts enter separation means 11, most of the dusts are 
discharged through vaporized gas outlet 11a together with the vaporized 
gas as shown in FIG. 3. 
Back to FIG. 1, the dusts included in the vaporized gas are removed by 
filter 12. The vaporized gas with the dusts removed is mixed with the ice 
particles 30 fed through ice particle outlet 11d in mixing means 13. The 
ice particles 30 and the vaporized gas mixed in mixing means 13 are fed to 
jet nozzle 9 and jetted onto a wafer 6. 
According to the present embodiment, the mixture of the ice particles 30 
and the vaporized gas fed to jet nozzle 9 barely includes dust, whereby 
the effect of rinsing wafer 6 is enhanced. 
Efficiency of roving dusts included in the ice particles 30 and the 
vaporized gas formed in ice making hopper 1 is determined by a separation 
efficiency of separation means 11 and an efficiency of filter 12 of 
capturing dusts. 
FIG. 4 is a schematic diagram showing a wafer rinsing apparatus according 
to another embodiment of the present invention. 
The apparatus of the present embodiment includes an ice making hopper 1 for 
making ice particles 30 by heat exchange between fine droplets of liquid 
to be frozen and a low-temperature liquefied gas. Ice making hopper 1 is 
provided with a supply spray 2 for supplying the liquid to be frozen to 
ice making hopper 1. Supply spray 2 is supplied with the liquid to be 
frozen, that is, pure water which has passed through a filter 3. Ice 
making hopper 1 is provided with a supply spray 4 for supplying the 
low-temperature liquefied gas to ice making hopper. Supply spray 4 is 
supplied with the low temperature liquefied gas which has passed through a 
filter 5. Supply spray 4 and filter 5 are connected by a supply piping 20. 
The apparatus includes a cooling chamber 14 provided to surround ice 
making hopper 1, supply spray 4, filter 5 and supply piping 20. Cooling 
chamber 14 is filled with low-temperature liquefied gas 50, so that ice 
making hopper 1, supply spray 4, the filter and supply piping 20 are 
cooled down to the liquefidation temperature of the low-temperature 
liquefied gas. The low-temperature liquefied gas enters cooling chamber 14 
through a supply inlet 21, while the vaporized gas is exhausted through an 
outlet 22. Since ice making hopper 1, supply spray 4, filter 5 and supply 
piping 20 are cooled down to the liquefidation temperature of the 
low-temperature liquefied gas in the apparatus according to the present 
embodiment, contact of the low-temperature liquefied gas with these 
components will not cause the liquefied gas to abruptly expand 
(vaporized). As a result, formation of dusts is reduced. The mixture of 
the ice particles 30 and the vaporized gas fed to jet nozzle 9 therefore 
includes less dust. As a result, the effect of rinsing wafer 6 is 
enhanced. 
Although in the above described embodiment, a description was made of a 
case in which liquid nitrogen gas is employed, the present invention is 
not limited thereto but may suitably employ liquid oxygen, liquid 
nitrogen, liquid helium, etc. 
As is described in the foregoing, since the wafer rinsing apparatus 
according to the first aspect of the present invention includes a 
separation means for separating ice particles and vaporized gas generated 
from a low-temperature liquid gas, particles formed from dusts are removed 
together with the vaporized gas and separated from the ice particles. 
Therefore, the ice particles have no particles mixed. As a result, the ice 
particles fed to a jet nozzle include no dust, which enhances a wafer 
rinsing effect. 
With an ice making hopper, a filter means and a cooling means for 
externally cooling a supply piping down to a liquefidation temperature of 
a low-temperature liquefied gas, contact of the liquefied gas with these 
components will not abruptly expand the liquefied gas in this wafer 
rinsing apparatus according to the second aspect of the present invention. 
Formation of dusts is suppressed accordingly. As a result, a mixture of 
ice particles fed to a jet nozzle and a vaporized gas includes less dust, 
which increases a wafer rinsing effect. 
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.