Methods of analyzing water soluble contaminants generated...

Details Methods of analyzing water soluble contaminants generated... Methods of analyzing water soluble contaminants generated...

1999-06-11

2001-01-23

Williams, Hezron (Department: 2856)

Measuring and testing

Liquid analysis or analysis of the suspension of solids in a...

C405S128350, C210S170050

Reexamination Certificate

active

06176120

ABSTRACT:

FIELD OF THE INVENTION
The invention generally relates to the analysis of contaminants generated during microelectronic device processing.
BACKGROUND OF THE INVENTION
It is typically necessary to control the level of contaminants in a cleanroom such that microelectronic device processing may be effectively carried out. An example of a common contaminant is floating dust. Other conditions within the cleanroom, such as those relating to noise, vibration, temperature, and light intensity, may also be controlled such that optimum processing conditions may be obtained.
Regulating dust levels, temperature, and humidity in a cleanroom is especially important during integrated circuit (e.g., semiconductor) device fabrication design layout. Design layout typically encompasses a number of operations relating to, for example, pattern formation in water fabrication, inspection, assembly/packaging, final testing, and quality testing. In particular, wafer fabrication usually involves repetitive process steps such as diffusion, exposure, development, etching, and diffusion. Specifically, equipment and materials involved in these process steps should not be contaminated in order to potentially obtain maximum microelectronic device production yield, precision, and reliability.
In a typical processing operation, air entering the cleanroom is usually filtered in order to attempt to remove the contaminants, and the air is then typically circulated throughout the cleanroom. Although it may be possible to achieve a certain level of air cleanliness, it is often extremely difficult to achieve an extremely high cleanliness level by only employing the above filtering system. Although the level of cleanliness attained by using a conventional filtering system may be adequate for certain processes, a higher degree of cleanliness is often desirable.
The presence of water-soluble contaminants, such as those resulting from wet fabrication processing, often adversely affect production yield and integrated circuit device operation. For example, the presence of water-soluble ionic materials on wafer surfaces may haze or blur the surfaces and distort corresponding photoresists. Moreover, the ionic materials are capable of functioning as dopants which can negatively impact diffusion processes containing these materials.
In view of the above, it would be desirable to control the level of water-soluble contaminants which may be present in a cleanroom. Conventionally, cleanroom cleanliness is typically controlled by monitoring the total number of particles present in the cleanroom atmosphere irrespective of the water solubility of the particles. The solubility of the particles is often measured by techniques involving the use of a as denuder, chemiluminescence, or fluoroluminescence.
FIG. 1
illustrates a conventional denuder. As shown, the denuder comprises an inlet
11
which may be connected to an inlet tube (not shown) capable of taking reference air for analysis from various directions. An impactor
12
is also present and is equipped with an impact plate
13
. The denuder also includes a diffusion denuder
14
, an after filter
15
, and a sampling pump
16
. Collected air typically collides with the impact plate
13
of the impactor
12
to thereby separate from the particles, and subsequently form microparticles which are not separated by impactor
12
. More specifically, polar molecules such as SO
2
, NO
2
, or NH
3
are separated inside the diffusion denuder
14
composed of stainless steel. The polar molecules are then typically supplied to the sampling pump through filter
15
such that a sample for analysis may be obtained. Notwithstanding any potential advantage, the conventional denuder typically is not able to separately analyze water-soluble materials which may be present in the reference air.
A conventional chemiluminescent method typically involves chemically reacting materials to be analyzed and then analyzing any light which may be emitted by the materials as a result of the chemical reaction typically initiated by using a photo-amplified tube. According to the chemiluminescent method, a radiation impulse (e.g., ultraviolet rays) is applied, and the material typically yields a luminsecence which is subsequently analyzed. The chemiluminescent method, however, may be disadvantageous in that only one component is typically analyzed at a time. Thus, the technique is often inefficient.
In addition to the above, samples have been collected and analyzed by conventional spectroscopic analyzers. In particular, these techniques may be carried out by using a Jar method, an Impinger method, and the like.
The Jar method typically involves exposing a jar containing deionized water to the atmosphere such that water-soluble contaminants are able to dissolve therein. The water-soluble contaminants are then subsequently analyzed. Although the structure and application of the jar are relatively simple, the above may be undesirable in that collection times are typically long. As a result, collection efficiency may be inaccurate. Although a post collection treatment is often employed in conjunction with this apparatus, it still may be difficult to obtain an accurate measurement of the contaminants.
The Impinger method typically involves spraying an air sample toward water or another liquid which is used as a collection source. The above operation is usually carried out by using a double tube or an gas collector impinger. The contaminants contained within the air are collected by the water or other liquid and then are subsequently analyzed. Although the apparatus used in the Impinger method is relatively simple, the method is potentially disadvantageous in that an additional treatment step is often required prior to contaminant analysis.
There is a need in the art for systems (apparatus) and methods for analyzing water-soluble contaminants which address the problems often associated with conventional analysis techniques.
SUMMARY OF THE INVENTION
In attempting to address the problems noted above, in one aspect the invention provides methods of analyzing water-soluble contaminants. The methods comprise providing reference air streams having gaseous water present therein; condensing the reference air streams such that the gaseous water liquefies; pressurizing the liquefied water; and supplying the liquefied water to an analyzer.
In another aspect, the invention provides systems (apparatus) for analyzing water-soluble contaminants. The systems comprise air inlets that absorb reference air containing gaseous water therein; valves that control the flow of the reference air which are in fluid communication with the air inlets; condensers that condense the gaseous water in the reference air, the condensers being in fluid communication with the valves; pressurization pumps that pressurize the water condensed from the reference air, the pressurization pumps being in fluid communication with the condensers; and discharge pumps that discharge excess water contained in the reference air, the discharge pumps being in fluid communication with the condensers.
The present invention may be advantageous in that water-soluble contaminants may be analyzed with a higher level of reliability in comparison to conventional techniques.


REFERENCES:
patent: 3440865 (1969-04-01), Gamson
patent: 3584674 (1971-06-01), Nolan et al.
patent: 3726063 (1973-04-01), Magorien et al.
patent: 4012278 (1977-03-01), Mostofin et al.
patent: 4556538 (1985-12-01), Matsushita et al.
patent: 5441365 (1995-08-01), Duffney et al.
patent: 2 304 891 (1997-03-01), None

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