Radiant energy – Supported for nonsignalling objects of irradiation – With source support
Reexamination Certificate
2000-10-20
2003-01-14
Berman, Jack (Department: 2881)
Radiant energy
Supported for nonsignalling objects of irradiation
With source support
C250S492100, C134S001000
Reexamination Certificate
active
06507031
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultraviolet light beam irradiating apparatus and method for irradiating the surface of a work such as a semiconductor silicon wafer or a substrate for producing a liquid crystal display, with an ultraviolet light beam to treat the surface, i.e., to oxidize and remove an organic material adhering to the surface, to directly oxidize the surface or to modify the surface.
2. Prior Art
A cleaning method using irradiation with an ultraviolet light beam is studied or used for/in part of the cleaning step in the production of a semiconductor integrated circuit or a liquid crystal display. The mainstream of the method is a method using a low-pressure mercury lamp as a light source. The low-pressure mercury lamp is a discharge lamp having spectra mainly in wavelengths of 186 nm and 254 nm.
When an oxygen-existing atmosphere such as air is irradiated with a low-pressure mercury lamp, oxygen molecules are dissociated to oxygen atoms O(
3
P).
O
2
+h&ngr;
(&lgr;=175−254
nm
)→
O
(
3
P
)+
O
(
3
P
)
The oxygen atom O(
3
P) generated above bonds to an ambient oxygen molecule which is not yet dissociated, to generate ozone (O
3
).
O
(
3
P
)+
O
2
→O
3
Ozone mainly absorbs light at and around a wavelength of 254 nm and has an absorption band in the wavelength of 220 to 300 nm. Therefore, O
3
exposed to a light having a wavelength of 254 nm from a low-pressure mercury lamp absorbs the light and dissociated into an exited-state oxygen atom O(
1
D) and an oxygen molecule (O
2
).
O
3
+h&ngr;
(&lgr;=220−300
nm
)→
O
(
1
D
)+
O
2
While a light at 186 nm has a photon energy of 6.7 eV, typical organic substances have a C—H bond energy of 3.5 eV and a C—O bond energy of 3.3 eV which are lower than the photon energy of a light at 186 nm. When an organic compound is irradiated with the above light, therefore, chemical bonds are broken, and further, the organic compound is dissipated and removed by the oxidation strength of ozone and active oxygen species generated by the above processes. When the above method is applied to a clean surface where no organic substances are present, a hydrophilic group such as an OH group or the like is introduced into the surface to render the surface of a work hydrophilic. This procedure is employed before the formation of a film for improving the adhesion of the film.
Meanwhile, for a more efficient method, a cleaning or modification method using an excimer lamp with xenon capable of radiating a light having a shorter wavelength sealed therein has been and is recently studied in place of a low-pressure mercury lamp.
In the excimer lamp, AC high voltage of several kV is applied to a quartz glass tube with xenon gas sealed therein to cause a barrier discharge, and xenon gas molecules are brought into a state of excited bonds, that is, an excimer (excimer state) and a light is emitted during a process from the above state back to their ground state, and the above method uses such a light. In a lamp with xenon gas sealed therein, a radiated light has a wavelength of 172 nm (half-width 14 nm).
The photon energy at 172 nm is 7.2 eV or higher than 6.7 eV of a low-pressure mercury lamp, and the chemical bonds are broken more effectively. Since a radiated light from a xenon excimer lamp contains almost no light at 220 to 300 nm, it neither can decompose ozone nor can generate active oxygen in an excited state. However, when oxygen molecules O
2
are irradiated with a light having a wavelength shorter than 175 nm, excited-state oxygen molecules O(
1
D) can be directly generated.
O
2
+h&ngr;
(−175
nm
)→
O
(
1
D
)+
O
(
3
P
)
As described above, the method using the xenon excimer lamp has many advantages over the method using a low-pressure mercury lamp in that the photon energy is high; excited-state oxygen atoms having high oxidation strength can be directly generated; a light radiated from the xenon excimer lamp has a quasi-single wavelength at 172 nm while light radiated from a low-pressure mercury lamp has spectrum at 186 nm, 254 nm, etc., and the efficiency of taking out (conversion to) vacuum ultraviolet light having a wave length of 200 nm or shorter on the basis of inputted energy (consumption power) is high.
Therefore, the actual cleaning efficiency is also high. The above cleaning or oxidation method using irradiation with ultraviolet light is called a UV/O
3
treatment, and the UV/O
3
treatment is generally carried out on a work placed in atmosphere. Generally, the efficiency of the UV/O
3
treatment increases with an increase in the intensity of UV light with which a work is irradiated, and it also increases with an increase in the concentration of ozone in a treatment atmosphere. In the method using a low-pressure mercury lamp in particular, irradiation at 186 nm is essential for generating ozone. However, light irradiated from a low-pressure mercury lamp has a far higher intensity at 254 nm than it has at 186 nm, and the concentration of ozone generated is not so high. For this reason, it is actual practice to externally introduce ozone generated with an ozone generator into the treatment atmosphere.
In integrated-circuit production process in which a throughput is considered essential, it is considered essential to decrease the length of a processing time, and studies are being made for a method that serves to shorten the UV/O
3
treatment time. The most general method is a method of rising the temperature of a substrate. “Theory and Practice of Ozone Utilization” (Realize K. K., issued in 1989, page 309, ISBN:4-947665-29-1) shows influences of the temperature of a work on the efficiency of the UV/O
3
treatment. According thereto, when the temperature of a work is 100° C., the rate of removal of organic substances is approximately 5 times higher than the rate at 30° C.
Further, “Preoxidation UV Treatment of Silicon Wafers” (J. Electrochem. Soc, Vol. 134, No.8, 1987, P. 2052, co-written by J. Ruzyllo, G. T. Duranko and A. M. Hoff) describes a method of increasing an oxidation rate by adding water vapor to a treatment atmosphere in the UV/O
3
treatment using a low-pressure mercury lamp. It is shown that, in the above method, the oxidation rate is increased by introducing oxygen gas into a bottle containing pure water warmed at 65° C. to generate water vapor and adding the water vapor to a treatment atmosphere.
While methods for increasing the oxidation rate are studied in various ways as described above, it is commercially desired to develop an ultraviolet light beam irradiating apparatus and method which can achieve the treatment for a shorter period of time.
It is an object of the present invention to provide an ultraviolet light beam irradiating apparatus and method for irradiating the surface of a work with an ultraviolet light beam to treat the surface, according to which the efficiency of the treatment is improved and the length of the treatment time period is shortened.
It is another object of the present invention to achieve the above object with a relatively simple apparatus constitution.
Gist of the Invention
SUMMARY OF THE INVENTION
The ultraviolet light beam irradiating apparatus for irradiating the surface of a work with an ultraviolet light beam to treat the work surface, provided by the present invention, comprises a bed for supporting the work in atmosphere, an ultraviolet light beam source for irradiating the surface of the work with a vacuum ultraviolet light beam having a wavelength of 175 nm or shorter, and inert gas inflow structure for allowing an inert gas, preferably one of nitrogen, helium and argon to flow into a space of the atmosphere on and above the surface of the work.
The above treatment of the work surface includes oxidation and removal of organic substances adhering to the surface, direct oxidation of the surface and modification of the surface.
In the above case, preferably, the above inert gas is mixed with water vapor and the mixture is allowed to
Jinbo Yosuke
Kobayashi Norio
Berman Jack
Hoya-Schott Corporation
Nixon & Vanderhye P.C.
LandOfFree
Apparatus and method of irradiating ultraviolet light does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method of irradiating ultraviolet light, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method of irradiating ultraviolet light will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3064484