Apparatus and method for evaluating contamination caused by organic substances deposited on substrate surface

Apparatus and a method for evaluating the contamination over the surface of a substrate for use in manufacturing semiconductor devices, liquid crystal devices and so on, said contamination being caused by contaminants, for instance airborne organic substances or the equivalent in the clean room atmosphere. For evaluation, there is measured with passage of time in the atmosphere having a substantially constant relative humidity the surface resistivity (R) of the substrate 104 by bringing electrodes 106 into close contact with an insulating film as formed on said substrate surface, or a contact angle (.alpha.) of a liquid-drop 207 dropped on the substrate 206. From this measurement, the degree of said contamination is judged by comparing the value of the surface resistivity or contact angle as measured immediately after rinsing the substrate, with the values of the same as measured after exposing the substrate to the objective atmosphere to be evaluated.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to apparatus and a method for evaluating 
contamination over a substrate surface which is caused by organic 
substances deposited on thereon, said substrate being used for 
manufacturing semiconductor devices, liquid crystal displays (LCD), and so 
forth. More particularly, the invention relates to apparatus and a method 
for evaluating contamination caused by the organic substances that are 
contained in the atmosphere of a clean room for manufacturing 
semiconductor devices, LCDs, and so forth, and are deposited on the 
surface of the semiconductor substrate, the glass substrate, or the like 
others. 
In the following description, the contamination of this kind is called 
`atmosphere originated organic contamination` for simplification. Also, in 
the following description, unless noted otherwise specially, an expression 
`a substrate` or `the substrate` represents the semiconductor substrate, 
the glass substrate, or the like others. 
2. Description of the Related Art 
In the clean room for manufacturing semiconductor devices, LCDs, and other 
sophisticated products, if organic substances contained in the clean room 
atmosphere adhere to the insulating film surface that is formed on the 
semiconductor substrate, the glass substrate, or the like others, they 
exert a bad influence on the electric characteristics of the semiconductor 
device and LCD, for instance causing increase of the leakage current and 
decrease of the breakdown voltage. It might be true that these organic 
substances deposited on the substrate surface can be readily removed by 
various rinsing techniques, for instance by the ultraviolet rays/ozone 
rinsing method. However, since several minutes have to be spent for 
rinsing one substrate, should it be needed to carry out such rinsing so 
often, the throughput of the production would be naturally reduced. 
Therefore, it is desirous to develop a simple method for quantitatively 
evaluating the atmosphere originated organic contamination. If such a 
evaluation method is developed and applied to the manufacturing process of 
semiconductor devices and LCDs, it will become possible to decompose and 
remove the organic substances deposited on the substrate surface by timely 
rinsing of the substrate before the atmosphere originated organic 
contamination reaches such a level that causes deterioration of their 
electric characteristics. Furthermore, it will become also possible to 
reduce the number of the steps of rinsing the substrate by carrying out it 
only when judged necessary in view of the contamination level as 
evaluated. 
It has been known that for evaluating the clean room atmosphere originated 
organic contamination over the semiconductor substrate and the glass 
substrate, the quantity of the organic substances deposited on the 
substrate surface is measured by using the method of X-ray photoelectron 
spectroscopy (referred to as XPS method hereinafter). In this XPS method, 
a substrate for use in sampling the contaminants (referred to as the 
sampling substrate hereinafter) is irradiated with the soft X-rays in the 
high vacuum circumstances, and the energy and the number of photoelectrons 
expelled out from said sampling substrate by this X-ray irradiation are 
measured by the spectrometer, thereby carrying out the 
qualitative/quantitative analysis of the elements existing on the sampling 
substrate surface. In the evaluation of the minute atmosphere originated 
organic contamination quantity over the substrate surface by the XPS 
method, the evaluation result is expressed as a ratio of the number of 
carbon atoms to the number of all the atoms existing within the objective 
region to be analyzed which extends to the depth of several tens 
angstroms(.ANG.) from the surface, or as a ratio of the number of carbon 
atoms to the atom number of the known elements existing in said objective 
region. 
Since the atmosphere originated organic contamination quantity can be 
measured with high precision by the XPS method, this method might be 
regarded as an effective means for evaluating the atmosphere that causes 
the atmosphere originated organic contamination over the semiconductor 
substrate and the glass substrate. However, this method indispensably 
requires a higher vacuum system and a spectrometer, so that it would 
highly cost as a whole. 
Briefly explaining the analysis by the XPS method, a sampling substrate 
with a clean surface is first prepared, and then, it is exposed to the 
objective atmosphere to be evaluated for a predetermined period of time. 
After this, the sampling substrate has to be transferred to an analyzing 
room for analysis by an analyzer. Accordingly, in the XPS method, sampling 
of the contaminants and analysis thereof have to be carried out at 
separate places. In other words, the analysis by the XPS method can not 
but be a so-called off-line analysis. Especially, if the XPS apparatus is 
located at a distance from the sampling point, there can be considered the 
possibility that the surface of the sampling substrate might be 
contaminated while it is transferred. Namely, the XPS method must be 
excellent for the R&D purpose. However, in the actual manufacturing 
process of semiconductor devices and LCDs, the atmosphere originated 
organic contamination has to be continuously monitored under the condition 
that the sampling by the sampling substrate and the analysis thereof can 
be carried out at an identical place. Therefore, it would be said that the 
XPS method is not so suitable for the purpose of a so-called in-line 
analysis. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a novel and 
improved apparatus and a method for simply and economically evaluating the 
atmosphere originated organic contamination over the surface of the 
semiconductor substrate, the glass substrate, and the like others. 
Further, another object of the invention is to provide a novel and improved 
apparatus and a method which are capable of judging the degree of the 
atmosphere originated organic contamination over the substrate surface at 
the actual site of manufacturing semiconductor substrates, glass 
substrates, and the like others, and are suitable for the in-line analysis 
of said organic contamination. 
Still further, another object of the invention is to reduce the number of 
the steps of rinsing the substrate unnecessarily, thereby increasing the 
throughput of the manufacturing process, and at the same time, to increase 
the yield of manufacturing by rinsing the substrate and/or removing the 
organic substances contained in the atmosphere in correspondence with 
necessity thereof. 
According to a first aspect of the invention, there is provided apparatus 
for evaluating the atmosphere originated organic contamination over the 
substrate surface. This evaluation apparatus comprises a substrate of 
which at least the surface is dielectric; a surface resistivity measuring 
device for measuring the electric resistance between at least two points 
on said substrate surface; an isolated space for accommodating said 
substrate; means for introducing a humidity regulated gas (for instance, 
inert gas and/or purified air) into said isolated space, said humidity 
regulated gas having a substantially constant relative humidity in said 
isolated space; means for introducing the objective gas to be evaluated 
into said isolated space; and means for evaluating the atmosphere 
originated organic contamination over the substrate surface in 
correspondence with the surface resistivity as measured by said surface 
resistivity measuring device. 
The surface resistivity measuring device as adopted by this evaluation 
apparatus may be constituted to have a plurality of conductive electrodes 
which are formed so as to closely get in contact with the insulating 
surface of said substrate. Also, the surface resistivity measuring device 
may be constituted to have a plurality of conductive electrodes which are 
movably formed so as to move back and forth against the insulating surface 
of said substrate. 
Furthermore, said evaluation apparatus may be provided with means for 
generating ultraviolet rays by which said substrate accommodated in said 
isolated space can be irradiated, and also with means for introducing a 
cleaning gas into said isolated space, said cleaning gas containing at 
least oxygen. 
According to a second aspect of the invention, there is provided a method 
of evaluating the atmosphere originated organic contamination over the 
substrate surface. This evaluation method comprises the steps of 
introducing a humidity regulated gas (for instance, inert gas/purified 
gas) having a predetermined relative humidity, into an isolated space 
accommodating a substrate of which at least the surface is dielectric, and 
measuring the surface resistivity between at least two points on said 
substrate surface; introducing the objective gas to be evaluated into said 
isolated space, and exposing said substrate to said objective gas for a 
predetermined period of time; introducing a humidity regulated gas having 
the substantially same relative humidity as said predetermined relative 
humidity into said isolated space, and measuring the surface resistivity 
between at least two points on said substrate surface having been exposed 
to the objective gas; and evaluating the atmosphere originated organic 
contamination over the substrate surface in correspondence with the change 
in the surface resistivity as measured. 
Also, the method as described above may be constituted by adding the steps 
of introducing into said isolated space a cleaning gas containing at least 
oxygen after finishing evaluation of the atmosphere originated organic 
contamination, and irradiating said substrate surface with ultraviolet 
rays. Further, in the method, it may possible to perform the steps of 
purging the gas having existed in said isolated space during the preceding 
step before introducing the gas for the following step into said isolated 
space. 
The operation of the apparatus and method as constituted according to the 
first and second aspects of the invention will be described in the 
following. 
A substrate of which the surface is dielectric (for instance, formed of the 
insulating film, the ceramics, or the like) is set up in the isolated 
space. In this case, the organic substances have to be removed from the 
substrate surface in advance. Next, by the means for introducing the 
humidity regulated gas, the humidity regulated gas (for instance, inert 
gas and/or purified air), of which the relative humidity is kept at a 
predetermined value, is introduced to the isolated space, thereby the 
relative humidity in the isolated space being controlled to have said 
predetermined value. 
Then, a surface resistivity (Rsi) between at least two points on said 
substrate surface is measured by the surface resistivity measuring device. 
In this case, if the electrode portion of said measuring device is formed 
of a plurality of electrodes closely getting in contact with the 
insulating surface of the substrate, a measuring voltage is directly 
applied to those electrodes, thereby measuring the surface resistivity 
(Rsi) of the substrate surface immediately after removing the organic 
substances therefrom. In contrast to this, if the electrode portion of 
said measuring device is formed of a plurality of electrodes which can 
move back and forth against the dielectric surface of the substrate, a 
measuring voltage is applied to those electrodes after bringing them into 
close contact with said dielectric surface, thereby measuring the surface 
resistivity (Rsi) of the substrate surface immediately after removing the 
organic substances therefrom. 
After measurement of this surface resistivity (Rsi), the objective gas to 
be evaluated is introduced into said isolated space by the means for 
introducing the objective gas. For introduction of the objective gas, two 
ways are available: one is to compulsively supply the objective gas to the 
isolated space by such a gas supply means as an air pump, and the other is 
to naturally fill up the isolated space with the objective gas by opening 
an openable door in the atmosphere containing the objective gas, said door 
being arranged on the partition wall for separating the isolated space 
from said atmosphere. 
After exposing said substrate to said objective gas for a predetermined 
period of time, the isolated space is separated from the surrounding 
space, and the humidity regulated gas (for instance, inert gas and/or 
purified air) having the substantially same relative humidity as said 
predetermined relative humidity is again introduced into said isolated 
space by the means for introducing the humidity regulated gas, thereby 
controlling the relative humidity in the isolated space to make it 
substantially same as said predetermined value. Then, the surface 
resistivity (Rsf) is measured in the same manner as has been done 
previously. As the inventors of the present invention is discussing in 
connection with FIG. 2 in their paper entitled `Charge Leakage 
Characteristics of Glass Substrate for LCD` (The Institute of 
Electrostatics Japan, Vol. 18, No. 4, 1994, pp 364-370), the surface 
resistivity of the glass substrate contaminated with a certain quantity of 
organic substances largely depends on the relative humidity of the 
atmosphere to which the substrate is exposed during the measurement of its 
surface resistivity. Therefore, in case of putting the present invention 
into practice, it should be noted that the relative humidity of the 
humidity regulated gas which is used for measuring the surface resistivity 
(Rsf) of the substrate after exposure to the objective atmosphere, should 
be controlled to be substantially identical to that of the humidity 
regulated gas as used for measuring the surface resistivity (Rsi) of the 
substrate immediately after rinsing the substrate. 
In this way, the degree of the atmosphere originated organic contamination 
over the semiconductor substrate and the glass substrate can be obtained 
by the evaluation means as a ratio of the surface resistivity (Rsf) of the 
substrate as measured after exposure to the objective gas to the surface 
resistivity (Rsi) of the substrate as measured immediately after rinsing 
the substrate. Further, if the measurement of the surface resistivity 
(Rsf) is repeated, it can be known how the surface resistivity (Rsf) 
caused by the atmosphere originated organic contamination changes with 
passage of time. Accordingly, in this way, a period of time until the 
degree of atmosphere originated organic contamination exceeds a certain 
limit, in other words, the maximum allowable exposure time, can be known 
by measuring how much the surface resistivity as measured after exposure 
to the clean room atmosphere for a certain constant time is increased from 
that which has been measured immediately after rinsing the substrate. 
After finishing a series of measurements of the change with passage of time 
regarding the surface resistivity, the electrodes may be left as they are, 
if the electrode portion of the surface resistivity measuring device is 
formed of a plurality of electrodes closely getting in contact with the 
insulating surface of the substrate. In contrast to this, if the electrode 
portion of said measuring device is formed of a plurality of electrodes 
which can move back and forth against the dielectric surface of the 
substrate, the electrode portion is lifted up to separate it from the 
insulating surface of the substrate. After this, the cleaning gas 
containing at least oxygen is introduced into the isolated space by the 
means for introducing the cleaning gas, and at the same time, the 
ultraviolet ray generating means like the ultraviolet lamp irradiates the 
substrate surface in order to perform the ultraviolet/ozone cleaning for 
decomposing and removing the organic substances deposited on the substrate 
surface. The ozone gas generated in the isolated space during said 
irradiation is properly exhausted, and the evaluation apparatus comes to 
be on standby for performing the next measurement of the change with 
passage of time as for the surface resistivity. 
According to the third aspect of the present invention, there is provided 
apparatus for evaluating the atmosphere originated organic contamination 
over the surface substrate. This apparatus comprises a substrate; means 
for dropping a liquid-drop on the surface of the substrate (preferably, 
capable of dropping a liquid-drop on the desired point on the substrate 
surface); means for measuring the contact angle of said dropped 
liquid-drop (for instance, consisting of a light source for lighting the 
dropped liquid-drop and means for observing said dropped liquid-drop by 
optically magnifying the image of it); an isolated space for accommodating 
said substrate; means for introducing the objective gas to be evaluated 
into said isolated space; and means for evaluating the atmosphere 
originated organic contamination over the substrate surface in 
correspondence with the contact angle as measured. 
Also, it is preferable that the means for dropping liquid-drop and/or the 
substrate can be constituted to relatively move to each other, thereby 
enabling the liquid-drop to be dropped to a desired dropping point on the 
substrate surface. Further, in the above evaluation apparatus, there may 
be provided means for generating ultraviolet rays which is accommodated in 
the isolated space and is for irradiating the substrate surface and means 
for introducing a cleaning gas containing at least oxygen into said 
isolated space. 
According to the fourth aspect of the present invention, there is provided 
a method for evaluating the atmosphere originated organic contamination. 
This method comprising the steps of dropping a liquid-drop to at least one 
dropping point on the surface of the substrate accommodated in said 
isolated space, and measuring the contact angle of the dropped 
liquid-drop; introducing the objective gas to be evaluated into said 
isolated space, and exposing said substrate to said objective gas for a 
predetermined period of time; dropping another liquid-drop to at least 
another dropping point, which is different from said previous dropping 
point, on the substrate surface exposed to the objective gas, and then, 
measuring the contact angle thereof; and evaluating the atmosphere 
originated organic contamination over the substrate surface in 
correspondence with the change of the contact angle as measured. 
Also, the above evaluation method may additionally include the steps of 
introducing into said isolated space a cleaning gas containing at least 
oxygen after completing evaluation of the atmosphere originated organic 
contamination, and irradiating said substrate surface with ultraviolet 
rays. Further, the above evaluation method may include the step of purging 
the gas having existed in said isolated space during the preceding step, 
before introducing the gas for the following step into said isolated 
space. 
The operation of the apparatus and method as constituted according to the 
third and fourth aspects of the invention will be described in the 
following. 
As shown in FIG. 9, the apparatus and method as constituted based on the 
third and fourth aspects of the invention make use of the phenomenon that 
when an ultra-pure waterdrop is dropped on the substrate surface, the 
contact angle (.alpha.) of the waterdrop increases in response to the 
increase of the quantity of organic contaminants over the substrate 
surface. Namely, the silicon wafer surface covered by an oxide film and 
the glass substrate surface, which are free from contamination caused by 
the organic substances, are hydrophilic so that the contact angle thereof 
becomes smaller. Contrary to this, if they are contaminated with organic 
substances, they becomes hydrophobic so that the contact angle thereof 
becomes larger. Since this contact angle can be readily measured by 
optically magnifying the image of the waterdrop illuminated by the light 
source, the evaluation of contamination over the substrate surface can be 
simply carried out at a lower cost in comparison with the evaluation by 
the XPS method. 
In case of performing the evaluation, the substrate is set up inside the 
isolated space. In this case, the organic substances have to be removed 
from the substrate surface in advance. Next, a liquid-drop (for instance, 
ultra-pure waterdrop) is dropped on the substrate surface by the means of 
dropping the liquid-drop, which is for instance, a syringe arranged above 
the substrate. Then, the liquid-drop as dropped on the substrate surface 
is illuminated by the light source, and the contact angle of the 
liquid-drop on the substrate surface immediately after being rinsed is 
measured through the image of the liquid-drop magnified by a magnifying 
glass. 
After measuring the contact angle, the objective gas to be evaluated is 
introduced into said isolated space by the means for introducing the 
objective gas. In case of introducing the objective gas, two ways are 
available as previously described. Namely, one is to compulsively supply 
the objective gas to the isolated space by a gas supply means like an air 
pump, and the other is to naturally fill up the isolated space with the 
objective gas by opening an openable door in the atmosphere containing the 
objective gas, said door being arranged on the partition wall for 
separating the isolated space from the surrounding atmosphere. 
After exposing said substrate to said objective gas for a predetermined 
period of time, the isolated space is isolated from the circumferential 
atmosphere, and the substrate and/or the means for dropping the 
liquid-drop is relatively moved to each other in a horizontal plane, 
thereby dropping another liquid-drop on another dropping point of the 
substrate surface that is different from the point on which the preceding 
liquid-drops already exist. Next, the liquid-drop dropped on the substrate 
surface is illuminated by the light source, and the image of the 
liquid-drop in the light is observed by the magnifying glass, thereby 
measuring the contact angle of the liquid-drop after exposure to the 
objective gas for a predetermined period of time. 
In this way, the degree of the atmosphere originated organic contamination 
over the semiconductor substrate and the glass substrate can be obtained 
by the evaluation means as a change rate of the contact angle of the 
dropped liquid-drop as measured after exposure to the objective gas to the 
contact angle of the dropped liquid-drop as measured immediately after 
rinsing the substrate. Further, if the measurement of the contact angle is 
repeated, it can be known how the contact angle changes with passage of 
time by the atmosphere originated organic contamination. Further, a period 
of time until the degree of atmosphere originated organic contamination 
exceeds a certain limit, namely the maximum allowable exposure time, can 
be known by measuring how much the contact angle after exposure to the 
clean room atmosphere for a certain constant time is increased from the 
contact angle as measured immediately after rinsing the substrate. 
After finishing a series of measurements of the change with passage of time 
as to the contact angle, the cleaning gas containing at least oxygen is 
introduced into the isolated space by the means for introducing the 
cleaning gas, and at the same time, the ultraviolet ray generating means 
like the ultraviolet lamp irradiates the substrate surface in order to 
carry out the ultraviolet/ozone cleaning for decomposition and removal of 
the organic substances on the substrate. The ozone gas generated in the 
isolated space during the cleaning is properly exhausted, and the 
evaluation apparatus comes to stand ready for performing the next 
measurement of the change with passage regarding the contact angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In reference with the accompanying drawings, the invention will now be 
described in detail in the following, in connection with several exemplary 
embodiments of the apparatus and method for evaluating the atmosphere 
originated organic contamination over the substrate surface, which are 
constituted according to the present invention. 
First Embodiment 
First, the invention will be described in detail in connection with the 
first embodiment thereof. FIG. 1 is a schematic constitutional view 
showing apparatus for evaluating the atmosphere originated organic 
contamination over the substrate surface according to the first embodiment 
of the invention. As shown in the figure, the apparatus is provided with 
an isolated space 102 isolated from the outside. This isolated space 102 
may be constituted as a chamber that is isolated from the outside by means 
of partitions made of such a material as aluminum, for instance. In this 
isolated space 102, there is set up a glass substrate 104 (CORNING #7059, 
100.times.100 mm.sup.2 .times.1.1 mm.sup.t) having a clean surface 104a 
from which organic substances have been removed. The glass substrate 104 
has a plurality of metal electrodes 106 for use in measuring the surface 
resistivity, which are formed on both front and back surfaces of the glass 
substrate by evaporation. FIGS. 2(A) and 2(B) are schematic views showing 
the metal electrodes 106 formed on the glass substrate 104 by evaporation. 
As shown in the figures, the metal electrodes 106 comprises a first 
electrode 106a which is formed, by evaporation, on the surface 104a of the 
glass substrate 104, having an almost circular shape placing its center at 
about the center of said surface 104a, a second electrode 106b which is 
prepared in the annular form coaxially surrounding the first electrode 
106a, and a grounding electrode 106c which is formed, by evaporation, on 
the back surface 104b of the glass substrate 104, having an almost 
circular shape. These electrodes 106 may be formed by directly depositing, 
by evaporation, a conductive material on the front and back surfaces 104a, 
104b of the glass substrate 104. Also, these electrodes 106 may be formed 
by first forming an insulating film over both front and back surface 104a, 
104b of the glass substrate 104, for instance by using the plasma CVD 
method, and then depositing the conductive material on the insulating film 
by using a sputtering apparatus. Furthermore, between the first and second 
electrodes 106a, 106b, there are connected in series a power source 108 
and an ammeter 110 as well, thereby a surface resistivity measuring device 
112 (a rectangular part surrounded by a dotted line in FIG. 1) being 
constituted. In FIG. 1, the surface resistivity measuring device is 
illustrated as if it had to be constituted including the substrate 104 and 
a part of the isolated space 102, but it should be noted that this has 
been done just for readers' easy understanding the constitution of the 
present embodiment. Accordingly, the surface resistivity measuring device 
112 is not limited to the described hereinabove, but may be of any type 
that can measure the electrical resistivity at least between two points on 
the surface of the sampling substrate 104. It should be also noted that 
the glass substrate is being used as the sampling substrate 104 in the 
present embodiment, but it is possible to use the other substrate as the 
sampling substrate in correspondence with an objective matter to be 
measured. For instance, a silicon wafer on which an insulating layer is 
formed, may be used as the sampling substrate if electrodes 106 are 
arranged on its surface so as to constitute the surface resistivity 
measuring device 112. 
Further, the isolated space 102 is constituted in such a manner that the 
pressurized and purified air having the humidity regulated by a humidifier 
114 can be introduced therein through a gas supply valve V1, that the 
oxygen gas can be introduced therein through a gas supply valve V2 from an 
oxygen cylinder 116, and further, that the objective atmosphere to be 
evaluated can be introduced through a gas supply valve V3. Still further, 
the isolated space 102 is connected with an exhaust valve V4 communicating 
with a humidity sensor 118, another exhaust valve V5 communicating with an 
exhaust pump 120, and still another exhaust valve V6 communicating with an 
air pump 122, respectively. The information on the relative humidity 
detected by the humidity sensor 118 is transmitted to a controller 124 
which in turn performs the feedback control of the humidifier 114 in 
correspondence with the value of the relative humidity as detected by said 
humidity sensor. In the upper potion of the isolated space 102, there is 
disposed an ultraviolet lamp 126 which emits ultraviolet rays to irradiate 
the surface 104a of the glass substrate 104. 
In order to measure the surface resistivity of the glass substrate 
immediately after rinsing it, valves V2, V5, V3, and V6 are closed while 
valves V1 and V4 are opened, and the pressurized humidity regulated gas 
which is controlled to have a predetermined relative humidity, is 
introduced into the isolated space 102. The pressurized humidity regulated 
gas can be produced by using a so-called flow distribution method i.e. by 
supplying the pressurized and purified air to the humidifier 114. The flow 
quantity distributed to the humidifier 114 is feedback controlled with the 
help of the humidity sensor 118 and the controller 124 which are disposed 
at the outlet side of the humidity regulated gas, so as to maintain the 
relative humidity in the isolated space 102 at a predetermined constant 
level. After the relative humidity in the isolated space 102 has reached a 
predetermined level, the voltage is applied to the electrode 106 for 
measuring the surface resistivity, thereby the initial surface resistivity 
(Rsi) of the clean glass substrate being measured by the surface 
resistivity measuring device 112. 
Since the surface resistivity of the substrate can be defined as the 
resistance per unit area, this is equivalent to the resistance per square 
meter of the material. Accordingly, the surface resistivity (Rs) can be 
calculated from the following expression (1). 
##EQU1## 
where RS : surface resistivity (.OMEGA.) 
c : circumferential length (mm) 
d : gap (mm) 
R : sheet resistivity as measured by the surface resistivity measuring 
device (.OMEGA.) 
When using the dimension of the electrodes as shown in FIG. 2(A), the 
expression (1) can be rewritten as the following expression (2). 
##EQU2## 
where D.sub.1 : outer diameter of electrode 106a (mm) 
D.sub.2 : inner diameter of electrode 106b (mm) 
Next, the objective atmosphere to be evaluated is sucked in the isolated 
space 102 by closing valves V1, V4, opening valves V3, V6, and operating 
the air pump 122. Then, the surface 104a of the glass substrate 104 is 
exposed to said objective atmosphere for a predetermined period of time. 
After completing the exposure of the substrate surface, valves V3, V6 are 
closed while valves V1, V4 are opened. Then, the controller 124 operates 
to return the relative humidity in the isolated space 102 to a 
predetermined relative humidity (substantially equal to the relative 
humidity at which the surface resistivity of the substrate was measured 
immediately after rinsing it). Then, the surface resistivity (Rs) of the 
substrate surface is measured by the surface resistivity measuring device 
112. Accordingly, if the measurement of the surface resistivity (Rsf) is 
repeated at regular intervals in the way as described above, it is 
possible to pursue or monitor the change with passage of time in respect 
of the quantity of organic contaminants on the clean substrate surface. 
As described hereinbefore, the isolated space 102 is provided with the 
ultraviolet (UV) lamp 126. After a series of measurements of the change 
with passage of time in respect of the surface resistivity are finished, 
valves V1, V4, V3, and V6 are closed while valves V2 and V5 are opened in 
order to supply the pressurized oxygen gas from the oxygen cylinder 116 to 
the isolated space 102. At the same time, the surface 104a of the 
substrate 104 is irradiated with UV rays from the UV lamp, thereby the 
organic contaminants deposited on the surface 104a being decomposed and 
removed by the so-called UV rays/ozone cleaning. After this UV rays/ozone 
cleaning, the valve V2 is closed while the valve V1 is opened keeping the 
valve V5 opened. Then, the exhaust pump 120 is driven to replace the gas 
in the isolated space 102 with the purified air, exhausting the ozone gas 
generated in the isolated space 102 during the UV rays/ozone cleaning. In 
this way, the evaluation apparatus comes to be on standby for measuring 
the change with passage of time in respect of the surface resistivity of 
the next clean glass substrate. 
FIG. 3 is a graph showing the relation between increasing rate of the 
surface resistivity (Rsf/Rsi) and the exposure time of the substrate to 
the objective atmosphere, the graph being prepared based on results of the 
surface resistivity measurement of the glass substrate according to the 
abovementioned measuring steps, using the clean room air and the purified 
air (the air resulting from removing the organic contaminants from the 
clean room air) as the objective atmosphere to be evaluated. During this 
measurement, the relative humidity of the isolated space was maintained at 
40%. As shown in this figure, in case of exposing the glass substrate to 
the clean room air, it is observed that its surface resistivity increases 
with passage of exposure time. Contrary to this, however, in case of 
exposing the same to the purified air, it is observed that its surface 
resistivity is hardly increased to the exposure time. 
FIG. 4 is a graph showing the relation between increasing rate of the 
surface resistivity (Rsf/Rsi) and quantity of organic contaminants 
(carbon/silicon) deposited on the substrate surface, the graph being 
prepared based on the measurement of the quantity of organic contaminants 
deposited on the surface 104a of the substrate 104 by the XPS method. In 
this case, the relative humidity of the isolated space is maintained 40% 
during the measurement of the surface resistivity. As shown in this 
figure, the surface resistivity increases corresponding to the increase in 
the quantity of organic contaminants. Accordingly, if this relation is 
made use of, it becomes possible to convert the measured value of the 
increasing rate of the surface resistivity into the quantity of the 
organic contaminants deposited on the glass substrate surface. For 
instance, if the glass substrate is exposed one by one to different 
various objective atmospheres for a predetermined period of time, and then 
the increasing rate of the surface resistivity is measured, it can be 
known from the results of respective measurements how much they contribute 
to contamination of the substrate surface as the sources thereof. Also, if 
the identical glass substrate is kept in a specific atmosphere and its 
surface resistivity is repeatedly measured at regular intervals, it can be 
monitored whether the atmosphere originated organic contamination against 
the glass substrate surface is below the allowable level or not. 
Second Embodiment 
The second embodiment of the invention will now be described in detail in 
the following. FIG. 5 is a schematic constitutional view showing the 
apparatus for evaluating the atmosphere originated organic contamination 
over the substrate surface. Regarding the constituents of the second 
embodiment shown in FIG. 5, which perform the substantially same functions 
as those of the first embodiment shown in FIG. 1, like reference numerals 
are assigned thereto, and no explanation thereabout will be made for 
avoiding redundant repetition thereof. 
The second embodiment is different from the first embodiment shown in FIG. 
1 in the following point. Namely, the different point is that one of 
partitions separating the isolated space 102 from the space surrounding 
thereof is provided with an openable door 102a, so that the atmosphere of 
said space can naturally flow in the isolated space 102 to fill it up 
therewith when the door 102a is opened. In connection with provision of 
this door 102a, valves V3, V6 and the exhaust pump 122 are eliminated, and 
the UV lamp 126a is disposed on the side portion of the isolated space so 
that the UV lamp does not disturb the opening and shutting movement of the 
door 102a. In the first embodiment, since the objective atmosphere to be 
evaluated can be compulsively supplied to the isolated space 102, the 
objective atmosphere to be evaluated may be located remote from the site 
where the isolated space 102 stands. For instance, the air in the storage 
room or chamber of materials to be kept clean, for instance silicon wafers 
and LCD glass substrates, can be introduced into the isolated space if 
there is provided the piping connecting therebetween. Contrary to this, 
according to the second embodiment, the objective atmosphere to be 
evaluated has to be the atmosphere surrounding the isolated space. For 
instance, this corresponds to the case where the objective atmosphere is 
the clean room atmosphere surrounding the isolated space. 
Next, it is explained how the atmosphere originated organic contamination 
is evaluated according to the second embodiment. 
First, there is provided an isolated space 102 separated from the 
atmosphere surrounding thereof, and a glass substrate 104 having the 
surface 104a which is made free from the organic substances by rinsing the 
substrate, is disposed in the isolated space 102. Then, valves V1, V4 are 
opened keeping valves V2, V5 closed, and the pressurized humidity 
regulated gas, of which the relative humidity is controlled to be a 
predetermined value by a humidifier 114, is introduced into the isolated 
space 102 through said humidifier. After the relative humidity in the 
isolated space 102 has reached said predetermined value, the voltage is 
applied to the electrode 106 for measuring the surface resistivity, and 
the initial surface resistivity (Rsi) of the clean glass substrate is 
measured by a surface resistivity measuring device 112. 
Next, valves V1, V4 are closed while the door 102a is opened to fill up the 
isolated space 102 with the objective atmosphere to be evaluated, thereby 
exposing the surface 104a of the glass substrate 104 to the objective 
atmosphere for a predetermined period of time. Immediately after 
completion of this exposure process, the door 102a is closed. Then, valves 
V1, V4 are opened for recovering said predetermined relative humidity of 
the isolated space 102 (substantially equal to the relative humidity at 
which the surface resistivity of the substrate was measured immediately 
after rinsing it). After recovery of said relative humidity, the surface 
resistivity (Rsf) is measured. In this manner, in the same way as has been 
done in connection with the first embodiment, the change with passage of 
time in respect of the quantity of organic contaminants deposited on the 
clean substrate surface 104a can be pursued or monitored by repeating the 
measurement of the surface resistivity (Rsf) at regular intervals. The 
isolated space 102 is also provided with the UV lamp 126a as in the case 
of the first embodiment. After completing a series of measurements of the 
change with passage of time in respect of the surface resistivity, valves 
V1, V4 and the door 102a are closed while valves V2, V5 are opened, and 
then, the pressurized oxygen gas is supplied to the isolated space 102 
from an oxygen cylinder 116. At the same time, the surface 104a of the 
substrate 104 is irradiated with UV rays, thereby the organic contaminants 
deposited on the surface 104a being decomposed and removed by means of the 
so-called UV rays/ozone cleaning. At this time, in the same manner as in 
the case of the first embodiment, the ozone gas generated in the isolated 
space 102 is exhausted by an exhaust pump 120. In this way, the evaluation 
apparatus comes to be in the standby position for measurement of the 
change with passage of time in respect of the surface resistivity of the 
next clean glass substrate. 
Third Embodiment 
The third embodiment of the present invention will now be described in 
detail in the following. FIG. 6 is a schematic constitutional view showing 
the apparatus for evaluating the atmosphere originated organic 
contamination. As to the constituents of the third embodiment shown in 
FIG. 6, which perform the substantially same functions as those of the 
first and second embodiments, like reference numerals are assigned to 
them, and no explanation thereabout will be made for avoiding redundant 
repetition thereof. 
The third embodiment is different from the first and second embodiments in 
the following point. Namely, instead of forming the first and second 
electrodes 106a and 106b on the surface 104a of a glass substrate 104, the 
first and second electrodes 106a', 106b' are disposed on the surface 128a 
of a base plate 128 arranged opposing to the surface 104a of the glass 
substrate 104. As shown in FIG. 7(A), the first electrode 106a' having an 
almost circular shape is formed almost at the center of the opposing 
surface 128a of the base plate 128 while the second electrode 106b' is 
prepared in the annular form coaxially surrounding the first electrode 
106a'. Accordingly, if the opposing surface 128a of the base plate 128 is 
viewed from the glass substrate side, there will be seen such an electrode 
arrangement that is equivalent to what is shown in FIG. 2(A). The first 
and second electrodes are connected with the surface resistivity measuring 
device (not shown). In the same manner as in the first and second 
embodiments, an electrode 106c' of an almost circular shape is formed on 
the back surface 104b of the glass substrate 104 (see FIG. 2(B)). 
A rod 128b is firmly fitted on the upper surface of the base plate 128 and 
is connected with a not shown driving mechanism, thereby enabling the base 
plate 128 to move back and forth with respect to the surface 104a of the 
glass substrate 104. In the first and second embodiment as explained in 
the above, the glass substrate 104 may be just placed in the isolated 
space 102 and it is not always necessary for the glass substrate to be at 
a specific fixed place within the isolated space. In the third embodiment, 
however, as will be described later, it is needed to bring the opposing 
surface 128a of the base plate 128 into contact with the surface 104a of 
the glass substrate 104 when measuring the surface resistivity, so that 
the glass substrate 104 has to be mounted on a stage 130 so as to receive 
a pushing force applied by the base plate. 
Next, there will be explained about how to evaluate the atmosphere 
originated organic contamination over the substrate surface according to 
the third embodiment. 
First, there is mounted on the stage 130 of the isolated space 102 the 
glass substrate 104 having the clean surface 104a that is made free from 
the organic substances by rinsing it. Then, valves V1, V4 are opened 
keeping valves V2 and V5 closed, and the pressurized humidity regulated 
gas of which the relative humidity is controlled to have a predetermined 
value by a humidifier 114 is supplied to the isolated space 102 through 
said humidifier. After the relative humidity in the isolated space has 
reached said predetermined value, the base plate 128 resting above the 
surface 104a of the glass substrate 104 (FIG. 7(C)) is moved downward to 
bring the first and second electrodes 106a', 106b' formed on its surface 
128a into close contact with the opposing surface 104a of the glass 
substrate 104 (FIG. 7(B)). Then, the voltage is applied across the first 
and second electrodes 106a', 106b', thereby measuring the initial surface 
resistivity (Rsi) of the clean glass substrate by means of a not shown 
surface resistivity measuring device. 
Next, the base plate 128 is moved upward to expose the surface 104a of the 
substrate 104 to the atmosphere of the isolated space 102, and at the same 
time, valves V1, V4 are closed while valves V3 and V6 are opened, and 
then, the objective atmosphere to be evaluated is sucked into the isolated 
space 102 by operating an air pump 122, thereby exposing the surface 104a 
of the glass substrate 104 to the objective atmosphere for a predetermined 
period of time. After completion of this exposure process, valves V3, V6 
are closed while valves V1, V4 are opened. The relative humidity of the 
isolated space 102 is made to again return to the predetermined relative 
humidity (substantially equal to the relative humidity at which the 
surface resistivity of the substrate was measured immediately after 
rinsing it) with the help of the controller 124. Then, the base plate 128 
is again moved downward to bring the first and second electrodes 106a' and 
106b' into close contact with the surface 106 of the glass substrate 104. 
Then, the surface resistivity (Rsf) is measured by means of said not shown 
surface resistivity measuring device. In such a manner as described above, 
the change with passage of time in respect of the quantity of organic 
contaminants on the clean substrate surface can be pursued or monitored by 
repeating the measurement of the surface resistivity (Rsf) at regular 
intervals. 
The isolated space 102 is provided with a UV lamp 126a installed on the 
side partition wall in the same manner as in the case of the second 
embodiment. After a series of measurements of the change with passage of 
time in respect of the surface resistivity is finished, valves V1, V4, V3, 
V6 are closed while valves V2, V5 are opened to supply the pressurized 
oxygen gas to the isolated space 102 from an oxygen cylinder 116. At the 
same time, the surface 104a of the substrate 104 is irradiated with UV 
rays from said UV lamp, thereby the organic contaminants deposited on the 
surface 104a being decomposed and removed through the so-called UV 
rays/ozone cleaning. After this UV rays/ozone cleaning, the valve V2 is 
closed while the valve V1 is opened keeping the valve V5 opened. Then, the 
inside of the isolated space 102 is made to replace with the purified air, 
exhausting the ozone gas generated in the isolated space 102 during said 
UV rays/ozone cleaning by operating an exhaust pump 120. In this way, the 
evaluation apparatus gets in the standby position for measurement of the 
change with passage of time in respect of surface resistivity of the next 
dean glass substrate. 
Fourth Embodiment 
Next, the fourth embodiment as shown in FIG. 8 will be described in the 
following. In this fourth embodiment, its constituents which perform the 
substantially same functions as those of the first through third 
embodiments, are given like reference numerals, and no explanation 
thereabout will be made for avoiding redundant repetition thereof. This 
fourth embodiment is achieved by applying the constitution of the third 
embodiment to the isolated space 102 having the openable door 102a as 
described in the second embodiment. Accordingly, in the same manner as in 
the case of the second embodiment, if the door 102a is opened, the 
atmosphere surrounding the isolated space 102 can naturally flow into the 
isolated space to fill up its inside therewith. Therefore, to be different 
from the third embodiment, there disappear the valves V3, V6 and the 
exhaust pump 122 of the third embodiment. A UV lamps 126a is disposed on 
the side portion of the isolated space not so as to disturb the opening 
and shutting movement of the door 102a. 
Next, there will be explained about how to evaluate the atmosphere 
originated organic contamination over the substrate surface according to 
the fourth embodiment. 
First, there is mounted on the stage 130 located in the isolated space 102 
the glass substrate 104 having the clean surface 104a which is made free 
from the organic substances by rinsing. Then, valves V1, V4 are opened 
keeping valves V2, V5 closed, and the pressurized humidity regulated gas 
which is controlled so as to have a predetermined relative humidity by a 
humidifier 114, is supplied to the isolated space 102 through said 
humidifier. After the humidity inside the isolated space has reached said 
predetermined relative humidity, a base plate 128 is moved downward to 
bring the first and second electrodes 106a' and 106b' into close contact 
with the surface 104a of the glass substrate 104. Then, the voltage is 
applied across the first and second electrodes 106a' and 106b', thereby 
measuring the initial surface resistivity (Rsi) of the clean glass 
substrate by means of a not shown surface resistivity measuring device. 
Next, the base plate 128 is lifted upward to expose the surface 104a of the 
substrate 104 to the atmosphere in the isolated space 102 and at the same 
time, valves V1 and V4 are closed while the door 102a is opened to fill up 
the isolated space 102 with the objective atmosphere to be evaluated, 
thereby exposing the surface 104a of the glass substrate 104 to the 
objective atmosphere for a predetermined period of time. After completion 
of this exposure process, the door 102a is closed while valves V1 and V4 
are opened. The relative humidity of the isolated space 102 is made to 
again return to the predetermined relative humidity (substantially equal 
to the relative humidity at which the surface resistivity of the substrate 
was measured immediately after rinsing it). Then, the base plate 128 is 
again moved downward to bring the first and second electrodes 106a' and 
106b' into close contact with the surface 104a of the glass substrate 104. 
Then, the voltage is applied across the electrodes, and the surface 
resistivity (Rsf) of the substrate 104 having been exposed to the 
objective atmosphere is measured by means of a not shown surface 
resistivity measuring device. 
In the same manner as described in the preceding embodiments, the change 
with passage of time in respect of the quantity of organic contaminants on 
the clean substrate surface can be pursued or monitored by repeating the 
measurement of the surface resistivity (Rsf) at regular intervals. The 
isolated space 102 is provided with the UV lamp 126a like the preceding 
embodiments. After a series of measurements of the change with passage of 
time in the surface resistivity are finished and the base plate 128 is 
lifted up, valves V1, V4 and the door 102a are closed while valves V2 and 
V5 are opened so as to supply the pressurized oxygen to the isolated space 
102 from an oxygen cylinder 116. At the same time, the surface 104a of the 
substrate 104 is irradiated with UV rays, thereby the organic contaminants 
deposited on the surface 104a being decomposed and removed by means of the 
so-called UV rays/ozone cleaning. At this time, in the same way as in the 
case of the preceding embodiments, the ozone gas generated in the isolated 
space is exhausted by an exhaust pump 120. In this way, the evaluation 
apparatus comes to stand ready to measuring the change with passage of 
time in respect of the surface resistivity of the next clean glass 
substrate. 
Fifth Embodiment 
Next, there will be explained referring to FIG. 10 the method and apparatus 
for evaluating the atmosphere originated organic contamination over the 
substrate surface according to the fifth embodiment of the present 
invention. The apparatus is provided with an isolated space 202 as in the 
preceding embodiments. This isolated space 202 can be constituted as a 
chamber which is isolated from the atmosphere surrounding it by means of 
partitions made of such a material as aluminum, for instance. In this 
isolated space 202, there is provided a stage 204 for receiving on it a 
glass substrate 206 having a clean glass surface 206a from which organic 
substances have been removed. Above the glass substrate 206, there is 
provided a syringe 208 for dropping an ultra-pure waterdrop 207 shown in 
FIG. 9 on the glass surface 206a. The stage 204 is associated with a 
transfer mechanism (not shown) capable of making the stage 204 rotate 
and/or parallelly transfer in a horizontal plane, so that there can be 
varied the dropping point of the waterdrop 207 dropped from the syringe 
208 to the glass substrate 206. 
Further, a pair of opposing partitions of the isolated space 202 are 
provided with observation window 210a, 210b by one each. On the outside of 
one observation window 210a, there is provided a light source 212 for 
illuminating the waterdrop 207 dropped on the glass substrate 206 while on 
the outside of the other observation window 210b, there is provided means 
for enlarging an image 214, for instance a microscope or a magnifying 
glass for observing and measuring the image of the waterdrop by enlarging 
it. Accordingly, a contact angle a of the waterdrop on the substrate 
surface can be measured by illuminating the waterdrop 207 dropped on the 
substrate 206 and observing it with the help of the magnifying glass 214. 
It is made possible to introduce into the isolated space 202 a cleaning gas 
containing at least oxygen supplied from a cylinder 214 through a gas 
supply valve V11 and also the objective atmosphere to be evaluated can be 
introduced into the isolated space through a gas supply valve V12. The 
isolated space 202 is further connected with an exhaust valve V13 
communicating with an exhaust pump 216 for exhausting the cleaning gas, 
and still further connected with an exhaust valve V14 communicating with 
an air pump 218 for exhausting the objective atmosphere. Also, there is 
provided on the upper portion of the isolated space 202 a UV 220 for 
irradiating the surface 206a of the glass substrate 206 with UV rays at 
the time of rinsing the substrate. 
Next, there will be explained about how to evaluate the atmosphere 
originated organic contamination over the substrate surface by means of 
the evaluation apparatus as described above. 
First, as to the clean substrate immediately after rinsing it, the 
measurement of the contact angle is carried out by using the magnifying 
glass 214. After this, valves V11, V13 are closed while valves V12, V14 
are opened, thereby introducing the objective atmosphere into the isolated 
space 202 by operating the air pump 218. Then, after exposing the surface 
206a of the substrate 206 to the objective atmosphere for a predetermined 
period of time and measuring the contact angle of the waterdrop at that 
time, the stage 204 is driven to transfer the substrate 206 mounted 
thereon in a horizontal plane. As described above, the present embodiment 
is constituted in such a manner that the stage 204 is driven, but it may 
be constituted in such a manner that the syringe 208 can be transfer in a 
horizontal plane keeping the substrate 206 (stage 204) standing still. In 
short, when there is finished the measurement of the contact angle about 
one waterdrop dropped at one dropping point on the substrate surface, the 
stage 204 or the syringe 208 is turned or horizontally transferred to 
receive another waterdrop at another dropping point on the substrate 
surface that has never received any waterdrop so far, and then, the next 
measurement of the contact angle is carried out about another waterdrop. 
In this manner, if the measurement of the contact angle is repeated at 
regular intervals, there can be pursued or monitored the change with 
passage of time in respect of the quantity of organic contaminants on the 
substrate surface. 
After a series of measurements of the change with passage of time in 
respect of the contact angle are finished, valves V12, V14 are closed 
while valves V11, V13 are opened in order to introduce the cleaning gas 
containing at least oxygen supplied from the cylinder 214 into the 
isolated space 202. Further, the surface 206a of the substrate 206 is 
irradiated with UV rays from the UV lamp 220, thereby the organic 
contaminants deposited on the surface 206a being decomposed and removed by 
means of the so-called UV rays/ozone cleaning. After this UV rays/ozone 
cleaning, the valve 11 is closed while the valve 12 is opened keeping the 
valve V13 opened for expelling the ozone gas generated in the isolated 
space 202 at the time of cleaning thereof in order to replace it with the 
objective atmosphere. In this way, the evaluation apparatus comes to be 
stand ready to measure the change with passage of time with regard to the 
contact angle of the waterdrop dropped on the next clean glass substrate. 
FIG. 11 is a graph showing the relation between the time of exposing the 
substrate to the objective atmosphere and the contact angle, which has 
been obtained through the measurements of the contact angle. In these 
measurements, the glass substrates (CORNING #7059, 100.times.100 mm.sup.2 
.times.1.1 mm.sup.t) were used as sampling substrates while the clean room 
air and the purified air (resulting from removing the organic contaminants 
from the clean room air) were used as the objective atmosphere to be 
evaluated. As will been seen from the graph, in case of exposing the glass 
substrate to the clean room air, the contact angle increases with passage 
of exposure time. On the other hand, in case of exposing the same to the 
purified air, the contact angle is hardly increased. FIG. 12 is a graph 
showing relation between the contact angle and the organic contaminant 
quantity (carbon/silicon) deposited on said CORNING glass substrate, which 
has been measured by the XPS method. As shown in this graph, the contact 
angle increases corresponding to the increase in the quantity of organic 
contaminants deposited on the glass substrate (carbon /silicon), so that 
if the relation of FIG. 12 is made use of, it becomes possible to convert 
the measured value of the contact angle increasing rate into the quantity 
of the organic contaminants deposited on the glass substrate surface. For 
instance, if the glass substrate is exposed one by one to different 
objective atmospheres for a predetermined period of time and then the 
increasing rate of the contact angle is measured, it can be known from the 
results of respective measurements how much they contribute to 
contamination of the substrate surface as the sources thereof. Also, if 
the identical glass substrate is kept in a specific atmosphere and its 
contact angle is repeatedly measured at regular intervals, it can be 
continuously monitored whether the atmosphere originated organic 
contamination against the glass substrate surface is kept below the 
allowable level or not. 
Sixth Embodiment 
The sixth embodiment of the invention will now be described in detail in 
the following. FIG. 13 is a schematic constitutional view of the apparatus 
for evaluating the atmosphere originated organic contamination over 
substrate surface contamination. With regard to the constituents of the 
sixth embodiment shown in FIG. 13, which perform the substantially same 
functions as those of the fifth embodiment shown in FIG. 10, like 
reference numerals are assigned thereto, and no explanation thereabout 
will be made for avoiding redundant repetition thereof. 
The sixth embodiment is different from the fifth embodiment shown in FIG. 
10 in the following point. Namely, the sixth embodiment is constituted in 
such a manner that the partition for separating the isolated space 202 
from the atmosphere surrounding it is provided with an openable door 202a, 
so that the atmosphere can naturally flow into the isolated space 202 to 
fill it up therewith when the door 202a is opened. In connection with 
provision of this door 202a, valves V12, V14 and the exhaust pump 218 are 
removed while a bypass valve V15 is added for introducing the atmosphere 
into the isolated space 202. In the fifth embodiment, the objective 
atmosphere to be evaluated is compulsively supplied to the isolated space 
202, so that the objective atmosphere may exist remote from the site at 
which the isolated space 202 is located. For instance, the air in the 
storage room or chamber of materials like silicon wafers and LCD glass 
substrates, can be introduced into the isolated space, if providing the 
piping connecting therebetween. Contrary to this, according to the sixth 
embodiment, the objective atmosphere to be evaluated has to be the 
atmosphere surrounding the isolated space. For instance, this is the case 
that the objective atmosphere is the atmosphere of the clean room. 
Next, there will be explained about how to evaluate the atmosphere 
originated organic contamination over substrate surface according to the 
sixth embodiment. 
First, a substrate 206 is mounted on a stage 204 arranged in the isolated 
space 202 isolated from the atmosphere surrounding it, the surface 206a of 
said substrate being made free from organic substances by cleaning. A 
syringe 208 is provided above the glass substrate 206 in order to drop an 
ultra-pure waterdrop 207 on the surface 206a of the glass substrate 206. 
The stage 204 is associated with a transfer mechanism (not shown) capable 
of making the stage 204 rotate and/or parallelly transfer in a horizontal 
plane, in order to vary the dropping point of the waterdrop 207 to be 
dropped out of the syringe. First, a waterdrop 207 is dropped on the 
surface 206a of the glass substrate 206 immediately after rinsing and 
then, the contact angle (.alpha.) is measured by a magnifying glass 214, 
illuminating the waterdrop with the light from a lighting source 212. 
After the measurement of the contact angle, the door 202a is opened, 
thereby the isolated space 202 being naturally filled up with the 
objective atmosphere. The change with passage of time in regard to the 
quantity of the organic contaminants deposited on the glass substrate can 
be pursued or monitored by repeating the measurement of the contact angle 
(.alpha.) at regular intervals. The isolated space 202 is provided with 
the UV lamp 220, so that after completing a series of measurements of the 
change with passage of time in regard to the contact angle, the door 202a 
is closed while valves V11, V13 are opened to introduce the cleaning gas 
containing at least oxygen supplied from the cylinder 214 into the 
isolated space 202. At the same time, the surface 206a of the substrate 
206 is irradiated with UV rays, thereby the organic contaminants deposited 
on the surface being decomposed and removed by means of the so-called UV 
rays/ozone cleaning. After this UV rays/ozone cleaning, the valve 11 is 
closed while the bypass valve 15 is opened keeping the valve V13 opened 
for expelling the ozone gas generated in the isolated space 202 at the 
time of cleaning thereof by operating the exhausting pump 216, replacing 
the ozone gas with the objective atmosphere. In this way, the evaluation 
apparatus enters in the state standing ready for the measurement of the 
change with passage of time in respect of the contact angle of the 
waterdrop dropped on the next clean glass substrate. 
According to the present invention as explained in the above in connection 
with several embodiments thereof, the degree of the atmosphere originated 
organic contamination over a substrate made of silicon, glass, and so 
forth, can be evaluated by measuring the change with passage of time in 
respect of the surface resistivity of the insulating surface of the 
substrate, or by measuring the change with passage of time in regard to 
the contact angle of the waterdrop dropped on the surface of the 
substrate. Namely, according to the present invention, by evaluating the 
increasing quantity of the surface resistivity or the contact angle as to 
the substrate surface after being exposed to the clean room atmosphere in 
view of the initial value thereof as measured using the clean substrate 
surface immediately after rinsing it, it becomes possible to judge the 
allowable exposure period of time beyond which the atmosphere originated 
organic contamination exceeds a certain limit, in other words, the 
so-called maximum allowable exposure time indicative of the time limit 
that the substrate is able to stand against the exposure to the clean room 
atmosphere without inviting any irreparable damage. 
Especially, in the manufacturing process of semiconductor devices and LCD 
products, the clean substrate surface immediately after having been 
treated in one film formation process by sputtering or plasma CVD, can not 
but be exposed to the clean room atmosphere while it is transferred to the 
other film formation process. Accordingly, if there can be known by the 
present invention the maximum allowable exposure time for which the clean 
substrate is allowed to be exposed to the clean room atmosphere, the 
following countermeasures may be taken: 1) trying to transfer the clean 
substrate to the next film formation process within the maximum allowable 
exposure time, 2) in case the substrate happens to be exposed to the clean 
room atmosphere exceeding the maximum allowable exposure time, trying to 
rinse it again, and 3) in case the progress of the production is impeded 
with too short maximum allowable exposure time as determined for the time, 
trying to extend the maximum allowable exposure time by filtering the 
organic contaminants in the clean room atmosphere with an active carbon 
filter or the like to lower the concentration of airborne contaminants or 
organic substances. 
Needless to say, the present invention is not limited to the preferable 
embodiments as described above, and it is understood that variations and 
modifications may be made by anyone skilled in the art within the scope of 
technological concept as recited in the attached claims for patent, but as 
a matter of course, those should belong to the technological scope 
according to the present invention. 
For instance, in the above preferable embodiments, the invention is 
described in connection with the case where the glass substrate is used 
for the purpose of sampling the atmosphere originated organic 
contaminants. Needless to say, however, it is possible to use various 
types of substrates other than the glass substrate as a sampling 
substrate, for instance a silicon wafer or the others that are actually 
used in the production process. In case of evaluating the atmosphere 
originated organic contamination based on the change in the surface 
resistivity, the surface of the sampling substrate has to be dielectric, 
but it is not always necessary for the substrate surface to be dielectric 
in case of using the contact angle for evaluation of the contamination, 
thus the invention being applicable to the sampling substrate having a 
conductive surface. 
Furthermore, the isolated space may be the space that is just isolated from 
the atmosphere surrounding it, so that it is of course possible to 
constitute the isolated space apart from the production line set up in the 
clean room in such a manner that the objective clean room atmosphere can 
be introduced into the isolated space through the piping connecting it 
with the clean room, or to dispose the isolated space having an openable 
door directly in the clean room to introduce the objective clean room 
atmosphere thereinto through the openable door. 
Although the ultraviolet lamp is installed inside the isolated space in the 
above embodiments, it is possible to dispose it outside the isolated space 
and to irradiate the substrate with ultraviolet rays by means of a 
suitable optical system. 
Furthermore, as to the surface resistivity measuring device and the contact 
angle measuring device, only an example is described in the above. 
Accordingly, it is understood that variations and modifications may be 
made by anyone skilled in the art without departing from the gist of the 
present invention. 
As has been discussed above, according to the present invention, the 
atmosphere originated organic contamination on the semiconductor 
substrate, the glass substrate, and so forth, can be readily evaluated by 
using commercial and economical measurement instrument like the surface 
resistivity measuring device and the contact angle measuring device. 
Further, according to the present invention, the contamination by organic 
substances can be evaluated at the same place as the sampling substrate 
exposed to the objective atmosphere is collected, so that the degree of 
the atmosphere originated organic contamination is judged just at the 
production site of the semiconductor substrate or the glass substrate, 
thus it being possible to constitute an evaluation system suitable for the 
in-line analysis. 
Still further, according to the present invention, by properly carrying out 
the evaluation of the atmosphere originated organic contamination over the 
substrate surface, it becomes possible not only to enhance the throughput 
in the production process by reducing the number of unnecessary process of 
rinsing the substrate, but also to increase the production yield by 
rinsing the substrate upon need and/or by removing organic substances from 
the atmosphere by filtration.