Patent Number: 
Section: description

FIGS. 1(a) and 1(b) each show a substrate treatment device using dielectric barrier discharge lamps. FIG. 1(a) shows the device and the substrate in a cross sectional representation. FIG. 1(b) shows the state of the arrangement as shown in FIG. 1(a) viewed from underneath, i.e., the transmission window side. FIG. 1(b) is a representation illustrating the positional relationship between the discharge lamps and the substrate. Therefore, in FIG. 1(b) neither the transmission windows are shown nor the relationship of the substrate and the lamp unit to scale. The dielectric barrier discharge lamp 1, hereinafter also called a xe2x80x9cdischarge lampxe2x80x9d or a xe2x80x9clampxe2x80x9d, has an essentially rod shape. There are at least two lamps located in an essentially box-shaped lamp unit 2, one side of which is made as a transmission window 3 via which UV radiation, and especially vacuum UV radiation, is emitted onto a substrate P. The substrate P is transported in the direction of the arrow, as shown in the drawings. When transport is completed, the irradiation of the entire substrate surface is complete. Between the transmission window 3 and the substrate P there is a gap of a few millimeters. When oxygen which is present in this gap reacts to the vacuum UV light, active oxygen and ozone are produced. Due to the mutual interaction thereof with the vacuum UV light, treatment, such as elimination of organic impurities, or the like, can be carried out. Here the lamp unit 2 consists of, for example, stainless steel. One of its side walls is provided with a gas feed opening (not shown), while the other side wall is provided with a gas outlet opening (not shown). An inert gas such as nitrogen gas or the like is delivered from this gas feed opening. The inert gas together with the remaining oxygen gas is emitted from the gas outlet opening. When the substrate P is transported and irradiation treatment with the vacuum UV radiation takes place, as shown in FIG. 1(b), an area P1 is formed in part of the substrate P and is irradiated both with the discharge lamp 1a and also the discharge lamp 1b. With the arrangement of the at least two discharge lamps 1a and 1b, the area P1 is formed. FIG. 2(a) shows, like FIG. 1(b), the state of the lamp unit 2 viewed from underneath. FIG. 2(b) shows according to FIG. 2(a) the substrate and its transport state for information purposes. The bottom plate of the lamp unit 2 is provided with quartz glass 3 (3a, 3b) as the light transmission window according to the discharge lamps 1 (1a, 1b). The area outside the light transmission windows is made of stainless steel. According to the above described irradiation area P1, in which superposition takes place, light screening plates 4 (4a, 4b) are mounted on the respective light transmission window 3 (3a, 3b). These light screening plates 4 comprise, for example, aluminum and are arranged such that the sharp-cornered transmission windows are partially screened. By means of this arrangement, the area irradiated with the lamp 1a and the area irradiated with the lamp 1b are made such that directly underneath the light screening plates the area irradiated with the two lamps changes according to the respective transport of the substrate. On the borders between the areas irradiated with the two discharge lamps, there exists an area with superimposed irradiation, i.e., the area P1 in FIG. 1(b)), which is formed. Moreover, the amount of irradiation light can be made uniform in this area compared to other areas. The light screening plates 4 need not comprise a material different from that of unit 2. This means that the shape of the light transmission window can in itself also be identical to the shape illustrated in FIG. 2(a). By one such measure, even when the substrate is large, it is possible to advantageously prevent un-irradiated areas and the like from being formed. Furthermore, the disadvantage that some of the substrate is irradiated with excess UV radiation thereby damaging the substrate is eliminated. Furthermore, the non-uniformity of treatment is prevented by irradiation with the UV radiation in a roughly equivalent amount. The substrate treatment device can be determined not only by the arrangements of the discharge lamps, the light transmission windows, and the light shielding plates. Alternatives are possible taking into account the following exemplary conditions regarding the irradiation areas and the substrate. For example, in the case in which the radiant light from the lamps broadens, i.e., scatters, and is emitted onto the substrate, the area irradiated with the respective lamp must be measured and the cause and effect relationship regulated by the light screening means must be checked. The exemplary substrate treatment device is made as an extremely general application configuration such that the distance between the light transmission window and the substrate is a few millimeters, with a maximum of roughly 10 mm. The reason for this is that the vacuum UV light emitted by the dielectric barrier discharge lamps has a short radiation wavelength of less than or equal to 200 nm, as described above, and therefore for long residence in an oxygen atmosphere it is absorbed by oxygen. Since the distance between the window and the substrate is small, the light transmitted by the light transmission windows is emitted and broadens essentially in a straight line onto the corresponding substrate surface. It is also conventional for the same discharge lamps to be used and operated with the same rated output. In one such case, specifically in the case of a distance between the light transmission windows and the substrate is less than or equal to 10 mm, as a result of the arrangement and the area of the light transmission windows it is possible to essentially roughly determine the irradiation areas in the substrate and the above described area in which superposition takes place without checking the irradiation areas in the substrate. With respect to scattering of surface treatment, it is most advantageous to make the amount of irradiation per unit of area uniform on the entire surface of the substrate to be treated. This can be achieved in the above described case where the distance between the light transmission windows and the substrate is less than or equal to 10 mm by using discharge lamps, light transmission windows and light screening plates with the same arrangements, the same sizes and the same operating conditions and a symmetrical arrangement. This point is illustrated using, for example, FIGS. 3(a) and (b). FIGS. 3(a) and (b) show, like FIG. 2(b), a lamp unit viewed from underneath, with only the light transmission areas after screening by the screening plates being shown and the discharge lamps and the like not shown. FIG. 3(b) is an exemplary representation for an embodiment of the invention illustrating where the two transmission areas 3a and 3b shown in FIG. 3(a) have been temporarily pushed in the transport direction of the substrate. If in this case the two transmission areas agree with one another without forming an area for superposition, the substrate in the lengthwise direction of the transmission windows is irradiated with uniform UV radiation. In this case, the uniform UV irradiation is enabled. Therefore the advantage is that the non-uniformity of treatment is eliminated. FIGS. 4(a) and (b) also illustrate an exemplary embodiment similar to that illustrated in FIGS. 3(a) and (b). In this exemplary embodiment, where the structure and the size of the light transmission areas 3a and 3b are identical to one another, a positional relationship can arise in which the two transmission areas come to rest one top of one another, such as in the case in which the light transmission areas 3a and 3b shown in FIG. 4(b) are temporarily pushed in the transport direction of the substrate. In this case, completely uniform irradiation cannot be achieved. Therefore, excess UV irradiation can be advantageously prevented. Thus, damage to the substrate can be prevented and, while at the same time the issues associated with non-uniformity of treatment can be reduced. An exemplary dielectric barrier discharge lamp is described below. FIG. 5(a) shows the entire arrangement of the dielectric barrier discharge lamp in a cross section. FIG. 5(b) is a sectional drawing according to line A-Axe2x80x2 shown in FIG. 5(a). The dielectric barrier discharge lamp 1 has an overall cylindrical shape and comprises, for example, synthetic quartz glass which acts as the dielectric during a dielectric barrier discharge and moreover transmits vacuum UV light. In the discharge lamp 1, an inside tube 11 and an outside tube 12 are located coaxially to one another, thus forming a double cylinder. By sealing the two ends, between the inside tube 11 and the outside tube 12 a discharge space 13 is formed in which through a dielectric barrier discharge, excimer molecules are formed. Moreover a discharge gas, for example xenon gas, is added, from which vacuum UV light is emitted from these excimer molecules. Numerical values by way of example are given below. In an exemplary discharge lamp 1, the total length is 800 mm, the outside diameter is 27 mm, the outside diameter of the inside tube 11 is 16 mm, the thickness of the inside tube 11 and the outside tube 12 is 1 mm and the discharge lamp 1 is operated with 400 W. The outer side of the outside tube 12 is provided with a network-like electrode 14. Within the inside tube 11 there is an inside electrode 15. The network-like electrode 14 is formed seamlessly and overall has a spring like property. Thus, good adhesive properties for the outside tube 12 can be obtained. The inside electrode 15 is tubular or can be essentially C-shaped with a partial gap in cross section and is located directly adjoining the inside tube 11. In the discharge space there can be a getter if necessary. Between the network-like electrode 14 and the inside tube 15, an alternating current source (not shown) is connected, from which excimer molecules are formed in the discharge space 13 and vacuum UV light is emitted. In the case in which the discharge gas is xenon gas, light with a wavelength of 172 nm is emitted. The dielectric barrier discharge lamp is not necessarily limited to the above described arrangement, but can also have an overall right parallel piped shape instead of an overall cylindrical shape. Furthermore, one of the electrodes can be present in the discharge space. Likewise, all discharge lamps using dielectric barrier discharge can be used with equal success. In the above described embodiment a specific example is described in which the lamp unit is attached and the substrate is transported. But the invention is not limited thereto, and as discussed above, the lamp unit can be transported and the substrate fixed. An arrangement in which the two are moved relative to one another would also produce acceptable results. Furthermore, the number of discharge lamps present in the lamp unit is not limited to two, but can comprise more than two discharge lamps. In this case, there is the case in which at least two discharge lamps are located next to one another in the transport direction of the substrate, and also the case in which at least two discharge lamps are located next to one another in the lengthwise direction of the lamps. Furthermore, the light screening means is not limited to that which comprises one lamp screening plate, but can also include an alternative embodiment in which, for example, a light screening film can be applied to the light transmission window. However, generally speaking there should be only one light transmission window arranged such that it forms the light screening area. In the above described embodiment, in the lamp unit there were two discharge lamps. But the invention can also be implemented through an arrangement in which in the lamp unit there is only one discharge lamp and there being more than one lamp units. Furthermore, an alternative exemplary can also be imagined in which the luminous outputs for several discharge lamps and the lamp arrangements can differ from one to another. In the above described embodiment, a case was described in which in the lamp unit the light transmission windows are formed by using a light transmission glass. But the light transmission glass is not always needed if the defect caused by the attenuation of the vacuum UV light by oxygen can be advantageously eliminated. In this case, the surface of the light radiation opening located in the lamp unit can be adjusted in relation to the irradiation areas. As was described above, the exemplary features of the substrate treatment device are that it has an arrangement in which an area is formed which is irradiated with several discharge lamps, and second, that there are light screening plates by which in this area the amount of irradiation is modified in relation to the transportation conditions of the substrate. Through the use of this first feature, it is possible to overcome the difficulties associated with the enlargement of the substrate encountered with conventional discharge lamps and moreover prevent an un-irradiated area from being formed. By means of the second feature, at least the disadvantage of damage of the substrate is advantageously eliminated from excess UV irradiation. Furthermore, by irradiation with UV radiation in a roughly identical amount, the non-uniformity of treatment can also be prevented. It is, therefore, apparent that there has been provided, in accordance with the present invention, a substrate treatment device. While this invention has been described in conjunction with a number of embodiments, it is evident that many alternatives, modifications, and variations would be or are apparent to those of ordinary skill in the applicable arts. Accordingly, the disclosure is intended to embrace all such alternatives, modifications, equivalents and variations that are within the spirit and scope of this invention.