Pretreatment system for analyzing impurities contained in flat sample

A pretreatment system for analyzing impurities contained in a flat sample contains a cylindrical lower case having a stepped portion on which the flat sample is seated. The stepped portion is formed in an circumferential inner surface of the cylindrical lower case. A cylindrical upper case is detachably attached to an upper surface of the lower case, and has a supply passage through which a predetermined amount of pretreatment solution can be supplied to the flat sample. A cover closes off the upper surface of the upper case.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a pretreatment system for analyzing 
impurities contained in a flat sample, and more particularly, to a 
pretreatment system for analyzing impurities contained in a flat sample 
where a pretreatment solution is applied on, for example, the surface of a 
wafer for semiconductor manufacturing, or a glass for a liquid crystal 
display, to dissolve impurities and thereby to easily analyze and estimate 
metal contamination and ion contamination. 
2. Description of the Related Art 
Generally, in semiconductor manufacturing processes, detecting wafer 
contamination is crucial to increase productivity and to control 
contamination levels. Although particle contamination can be identified by 
a high intensity light or an electronic microscope, metal contamination or 
ion contamination formed on the surface of a wafer can by identified by a 
pretreatment process. 
In the conventional pretreatment process, as shown in FIG. 1, a 
pretreatment solution such as distilled water, HF, H.sub.2 O.sub.2, or 
HNO.sub.3, etc. is first dropped onto the surface of a sample 10, such as 
a flat wafer or a glass for a liquid crystal display, and then the surface 
is scanned in the direction of an arrow as shown in FIG. 1. Then, the 
pretreatment solution having impurities absorbed and dissolved therein is 
collected, and the contamination level is analyzed by an atomic absorption 
spectrometer or a high performance ion chromatography. 
The pretreatment process of the prior art can analyze contamination levels 
to some extent in certain situations, such as when the sample is a wafer 
made from pure silicon and the wafer has not passed through an integrated 
circuit forming process. However, when a integrated circuit, etc. is 
formed on the wafer, or a layer such as polycrystalline silicon, Si.sub.3 
N.sub.4, etc. is deposited onto the surface of the wafer, it is very 
difficult not only to scan the surface of the sample, but also to 
determine the proper amount of the pretreatment solution to be supplied to 
the sample. This is because the amount of pretreatment solution varies 
with changes in surface conditions, such as hydrophilic properties. 
Accordingly, the amount of the collected pretreatment solution is changed 
each time, thereby making it difficult to implement quantitative analysis. 
Furthermore, when the pretreatment solution is held for a long time to 
sufficiently dissolve the impurities in the pretreatment solution, the 
pretreatment solution is apt to become contaminated due to surrounding 
environmental conditions. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention has made in an effort to solve one or 
more of the problems occurring in the prior art, and it is an object of 
the present invention to provide a pretreatment system for analyzing 
impurities contained in a flat sample, in which a constant amount of 
pretreatment solution is supplied to the surface of a flat sample, which 
is placed in an enclosed space, so that a scanning process is not 
necessary and the amount of collected pretreatment solution is made 
constant, whereby quantitative analysis can be easily performed. 
It is another object of the present invention to provide a pretreatment 
system for analyzing impurities contained in a flat sample, which can 
prevent foreign substances from flowing into the sample and the 
pretreatment solution, so that the sample does not become contaminated. 
According to one aspect of the present invention, there is provided a 
pretreatment system for analyzing impurities contained in a flat sample, 
comprising: a cylindrical lower case having a central opening defining a 
lower circumferential inner surface; a stepped portion, formed in the 
lower circumferential inner surface of the cylindrical lower case, on 
which the flat sample is seated; a cylindrical upper case, having a 
central opening defining an upper circumferential inner surface, the 
cylindrical upper case being detachably attached to an upper surface of 
the lower case and having a supply passage through which a predetermined 
amount of pretreatment solution can be supplied to the flat sample; and a 
cover detachably attached to an upper surface of the cylindrical upper 
case for closing off the cylindrical upper case. 
According to another aspect of the present invention, the lower and upper 
cases are made from polytetrafluoroethylene resin. 
According to another aspect of the present invention, the supply passage is 
formed on the upper and inner circumferential surfaces of the upper case. 
According to still another aspect of the present invention, the supply 
passage is formed to have a diverging width toward the sample so that the 
pretreatment solution can easily flow toward the sample. 
According to yet still another aspect of the present invention, the lower 
surface of the cover is formed to define an inclined surface which is 
downwardly projected in a center portion thereof. 
By the features of the present invention, since it is possible to supply a 
constant amount of pretreatment solution to the surface of a flat sample, 
a scanning process is not necessary and the amount of collected 
pretreatment solution is made constant, whereby quantitative analysis can 
be easily performed. Also, foreign substances are prevented from flowing 
into the sample and the pretreatment solution, so that the sample does not 
become contaminated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Hereinafter, a pretreatment system for analyzing impurities contained in a 
flat sample in accordance with an embodiment of the present invention will 
be described in greater detail with reference to FIGS. 2 through 4. 
In the drawings, the pretreatment system of the present invention includes 
a lower case 20, an upper case 30 and a cover 40. Each of the lower case 
20 and the upper case 30 is formed with a central opening defining an 
inner circumferential surface. A stepped portion 21 is formed in the 
circumferential inner surface of the lower case 20, and a flat sample 10, 
such as a wafer or a glass for a liquid crystal display, is seated on the 
stepped portion 21. A first plurality of through holes 22 are formed in 
the body of the lower case 20 to axially extend therealong, the first 
plurality of through holes 22 being spaced apart from each other. 
The upper case 30 is coupled to the upper surface of the lower case 20 to 
fixedly maintain the sample 10 seated on the stepped portion 21. A 
reversed stepped portion 31 is formed in the circumferential inner surface 
of the upper case 30, which contacts the upper surface of the sample 10. A 
second plurality of through holes 32 are formed in the body of the upper 
case 30 to axially extend therealong, the second plurality of through 
holes 32 being spaced apart from each other and in alignment with the 
first plurality of through holes 22. 
On the upper surface and the circumferential inner surface of the upper 
case 30, there is defined a supplying passage 33 through which a 
pretreatment solution can be supplied from the outside. Specifically, as 
shown in FIG. 2, the supplying passage 33 has a first portion formed on 
the upper surface of the upper case and a second portion formed on the 
circumferential inner surface of the upper case. Preferably, the second 
portion of the supplying passage 33 is formed to have a diverging width 
toward the sample 10 so that the pretreatment solution can flow easily 
toward the sample 10 and be dispersed onto the sample 10. It is preferable 
that the pretreatment solution supplied through the supplying passage 33 
be selected from a group consisting of HF of 1 weight %, HF of 5 weight %, 
H.sub.2 O.sub.2 of 5 weight %, and HNO.sub.3 of 5 weight %. 
The lower case 20 and the upper case 30 are coupled to each other by a 
plurality of bolts 35 passing through the through holes 22 and 32 and a 
plurality of nuts 36 locked to ends of the plurality of bolts 35. To the 
circumferential outer surface of the upper case 30, there are secured a 
pair of handles 34 in an opposed manner to ensure that the pretreatment 
system of the present invention can be easily moved. 
The cover 40 is disposed on the upper surface of the upper case 30 to close 
the upper portion of the upper case 30. The lower surface of the cover 40 
is formed to define an inclined surface 41 which is downwardly projected 
in the center portion thereof. Adjacent the edge of the cover 40, there 
are formed a third plurality of through holes 42 through which the 
plurality of bolts 35 can be inserted, respectively. On the center portion 
of the upper surface of the cover 40 a grip 43 is provided. 
It is preferable that the lower case 20, the upper cases 30 and the cover 
40 are made from polytetrafluoroethylene resin to ensure durability and 
exhibit anti-chemical properties. 
The operation of the pretreatment system for analyzing impurities contained 
in a flat sample, constructed as mentioned above, will be fully described 
hereinafter. 
After the lower case 20, upper case 30, cover 40, bolts 35 and nuts 36 are 
cleaned by using a cleaning solution, these components are rinsed by 
overflowing a distilled water for more than 3 hours. Then, the lower case 
20 and upper case 30 are dried in a purified nitrogen gas. The flat sample 
10, such as a wafer for semiconductor manufacturing or a glass for a 
liquid crystal display, is seated on the stepped portion 21 of the lower 
case 20, and the upper case 30 is coupled to the upper surface of the 
lower case 20. By this, the reversed stepped portion 31 of the upper case 
30 is contacted with the upper surface of the flat sample 10 seated on the 
stepped portion 21 of the lower case 20 to fixedly hold the flat sample 
10. By passing the plurality of bolts 35 through the through holes 22 and 
32 and locking the plurality of nuts 36 onto the ends of the plurality of 
bolts 35, the lower case 20 and the upper case 30 are securely coupled to 
each other. Then, a predetermined amount of the pretreatment solution is 
supplied onto the upper surface of the sample 10 through the supplying 
passage 33 formed on the upper case 30, and then the cover 40 is 
positioned onto the upper surface of the upper case 30 to maintain the 
sample 10 in an enclosed space. As mentioned above, it is preferable that 
the pretreatment solution supplied through the supplying passage 33 be 
selected from a group consisting of HF of 1 weight %, HF of 5 weight %, 
H.sub.2 O.sub.2 of 5 weight %, and HNO.sub.3 of 5 weight %. 
After the predetermined amount of the pretreatment solution is supplied 
onto the upper surface of the sample 10, into which the impurities are 
dissolved, the contamination level can be analyzed by using an atomic 
absorption spectrometer or a high performance ion chromatography. At this 
time, since the cover 40 is provided on the upper case 30, the sample 10 
can be held in an enclosed state, by which the contamination of the sample 
10 due to foreign substances, and volatilization of the pretreatment 
solution, can be effectively prevented. 
As a result, the pretreatment system of the present invention, constructed 
as described above, provides certain advantages. Since it is possible to 
supply a constant amount of pretreatment solution to the surface of a flat 
sample, a scanning process is not necessary and the amount of collected 
pretreatment solution is made constant, whereby quantitative analysis can 
be easily performed. Also, foreign substances are prevented from flowing 
into the sample and the pretreatment solution, so that the sample does not 
become contaminated. 
In the drawings and specification, there have been disclosed typical 
preferred embodiments of the invention and, although specific terms are 
employed, they are used in a generic and descriptive sense only and not 
for purposes of limitation, the scope of the invention being set forth in 
the following claims.