Abstract:
Apparatus for a photo-induced process are provided, which implement a transparent film (instead of an optical window), to reduce light absorption loss that would result from use of an optical window. A photo-induced process apparatus eliminates problems of conventional systems which use optical windows, such as blurring an optical window and the surface of a light source, photo absorption loss due to the optical window and/or a purge cleaning gas, and dust generation by a moving part such as a flexible curtain. A photo-induced process apparatus efficiently utilizes light emitted from a light source.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an apparatus and method for solving blur problems on the surfaces of a light source and an optical window in a photo-induced process, and more particularly, to an apparatus and method for preventing a material produced by decomposition of a reaction gas at the time of deposition of a material by using a photo-induced process, that is, a photochemical vapor deposition (photo-CVD) or a material produced by photo-induced oxidation of a sample, etching, ashing, or the like from being attached to the surface of the light source or the optical window, in a reaction chamber of the photo-induced process apparatus. 
   2. Description of the Related Art 
   There is deposition of a material on a substrate, oxidation of a sample, etching, ashing, annealing, surface modification and cleaning, as a photo-induced process. A photo-CVD will be described below as a representative example. 
     FIGS. 1 and 2  show a conventional photo-CVD apparatus, respectively. 
   The  FIG. 1  technology is disclosed in U.S. Pat. No. 4,654,226. Based on the  FIG. 1  technology, a conventional technology preventing a blur phenomenon on an optical window will be described. Referring to  FIG. 1 , light beams B emitted from a plurality of light sources  100  provided in the atmosphere at the outside of a reaction chamber S pass through an optical window  110  and then are irradiated into the reaction chamber S. Here, if a reaction gas is made to flow into the reaction chamber S in the direction of an arrow mark (←), the reaction gas is decomposed by the irradiated light and thus a thin film is formed on the substrate  120  by using a chemical vapor reaction by a photo-induced process. Meanwhile, a flexible curtain  130  is installed between a substrate  120  and the optical window  110 . The flexible curtain  130  is continuously fed at a constant speed at the state where the flexible curtain  130  has been wound up around a lefthand roller in a roll form, and wound around a righthand roller. Here, since the flexible curtain  130  closely contacts the uppermost edge portion of the wall surface in a reaction room which is vertically placed, the reaction gas in the reaction chamber S is not made to reach the optical window  110 . However, a sealing between the uppermost edge portion of the vertical wall surface in the reaction room and the flexible curtain  130  is not perfect, the reaction gas leaks from a gap therebetween to cause the optical window  110  to be blurred. Thus, in the  FIG. 1  apparatus, a cleaning gas for an optical window purge is made to flow between the flexible curtain  130  and the optical window  110  in the direction of an arrow mark (→), to thereby prevent a blurring phenomenon of the optical window  110 . 
     FIG. 2  is a conceptual view for explaining a process for replacing an optical window blurred in another conventional photo-CVD apparatus, which is disclosed in U.S. Pat. No. 5,810,930. Further, a method for replacing a blurred optical window with a cleaned optical window without breaking a vacuum by using an optical window replacement apparatus, and a method for forming a thin film on a large-area substrate by using a photo-CVD apparatus equipped with an optical window replacement apparatus are also described in the U.S. Pat. No. 5,810,930. The operation of the optical window replacement apparatus will be described below referring to FIG.  2 . 
   When a photo-CVD process is completed at the state where the optical window  200  closely contacts the edge of an upper optical hole in the reaction chamber  210  by a mechanical compression force, an optical window which is blurred by attachment of a reaction product and a reaction gas is transferred to an optical window replacement chamber  220  by means of a mechanical driving apparatus. Then, a gate valve  230  is closed and a nitrogen gas or an inert gas (N) inserted through a first inlet  222 , to make the internal pressure become the state of the atmosphere. Then, a cover  240  is opened to replace the blurred optical window with a cleaned optical window  250  and then is closed. Then, the internal gas is discharged through an outlet  224  so that the optical window replacement chamber  220  becomes a high vacuum state, and then the gate valve  230  is re-opened to then transfer the cleaned optical window  250  to an optical window fixing chamber  260 . Thereafter, the optical window is made to closely contact a predetermined position, that is, the circumference of the upper optical hole of the reaction chamber  210 . When a process of forming a thin film on the substrate  270  with the photo-CVD apparatus is performed, a reaction gas is made to flow into the reaction chamber  210  through a reaction gas feed tube  216  and a nitrogen gas or an inert gas is made to flow into the fixing chamber  260  through an inlet  226 , as much as a desired amount of flow. Then, light is irradiated from a light source  280  at the state where the two chambers  210  and  260  have no pressure difference. The gas in the two chambers  210  and  260  is discharged through outlets  218  and  228 , respectively. By the above-described method, since the optical window is replaced at the state where the optical window fixing chamber  260  and the reaction chamber  210  are completely isolated from the optical window replacement chamber  220  by the gate valve  230 , the reaction chamber  210  is not exposed to the atmosphere semi-permanently. Thus, since the inside of the reaction chamber  210  is not polluted by oxygen, nitrogen, dust or the like in the air, a high-quality thin film can be formed. Also, since there is no friction between the thin film attached optical window surface and the other portions during detachment and movement of the optical window, dust may not be generated to thus maintain the reaction chamber to be in the clean state continuously. Also, since the light source can be inserted in a vacuum, and a pressure difference applied to both sides of the optical window is little during formation of the thin film, a thin optical window can be used to thus make a large-area thin film forming apparatus. 
   As described above, in the  FIG. 1  apparatus, the flexible curtain closely contacts the uppermost edge of the vertical wall surface in the reaction chamber and thus a space where a window purge cleaning gas flows between the flexible curtain and the optical window is isolated from the reaction chamber. However, since the sealing is not perfect, a blur phenomenon of the optical window cannot be effectively removed during deposition of a thin film. Also, when the flexible curtain is wound up in order to replace it with a new one during performing a thin film deposition or after completion of the thin film deposition, dust may be generated due to a friction with the uppermost edge of the reaction chamber wall surface closely contacting the flexible curtain. Also, in this apparatus, the optical window should be thick so that it can resist against the atmosphere. In addition, since an optical window purge cleaning gas is made to flow between the optical window and the flexible curtain, light absorption losses in the optical window and the purge cleaning gas cannot be ignored. Since this problem becomes further serious as the apparatus becomes larger, it is not nearly possible to fabricate a large-area apparatus with the structure that a light source is placed in the air and light is irradiated into the reaction chamber through the optical window. Also, a light source for emitting a vacuum ultraviolet light ray cannot be used with the structure that the light source is placed in the air. In order to solve the above-described problem, a structure that a light source is put in a space where an optical window purge cleaning gas flows, is disclosed in U.S. Pat. No. 4,654,226. By doing so, the optical window need not be used and it is possible to fabricate the large-area apparatus and use the vacuum ultra-violet light source. However, even in the structure of the light source placed in the vacuum, the surface of the light source cannot be prevented from being blurred by the material produced by the photo-chemical reaction due to the imperfect sealing between the reaction chamber and the flexible curtain as described above. 
   Meanwhile, according to the  FIG. 2  apparatus, a large-area thin film can be deposited. However, since a large-area optical window should be used as well in this case, the large-area thin optical window may be damaged during cleaning the large-area optical window physically, and it is also difficult to handle the large-area thin optical window. Thus, the optical window should be thick to a degree. Accordingly, the light absorption loss in the optical window cannot but increase. Also, a vacuum should be broken in an optical window replacement chamber every time when the optical window need to be replaced and the polluted optical window should be replaced with a cleaned optical window. Then, the optical window replacement chamber is discharged to be a high vacuum state. As a result, the working ratio of the apparatus becomes low. 
   SUMMARY OF THE INVENTION 
   To solve the above problems, it is an object of the present invention to provide a photo-induced process apparatus for removing a blurring problem of an optical window and the surface of a light source, a photo absorption loss problem in the optical window and by a purge cleaning gas, and a dust generation problem by a moving part such as a flexible curtain, and utilizing the light emitted from the light source efficiently. 
   It is another object of the present invention to provide a method for performing a photo-induced process using the above-described photo-induced process apparatus. 
   To accomplish the above object of the present invention, there is provided a photo-induced process apparatus comprising: a reaction chamber housing having an opening on the central portion of an upper plate through which light is transmitted, and a support for supporting a sample or a substrate; a light source whose light emission plane faces the opening so that the light is irradiated into the reaction chamber through the opening; a transparent film installation and storage chamber housing located between the light emission plane of the light source and the reaction chamber opening, having an opening through which light is transmitted from the light source to the reaction chamber on the central portion of the upper plate and a lower plate, in which the lower plate is combined with the reaction chamber upper plate; a transparent film located horizontally in the transparent film installation and storage chamber housing, the transparent film transmitting the light from the light source; a first flange in which the light emission plane edge of the light source is welded along the circumference of the central opening; a second flange which is welded along the circumference of the installation and storage upper plate opening; an extension and contraction portion in which third flanges having the respective same size as those of the first and second flanges are welded on both ends thereof so that the first and second flanges are connected to the third flanges respectively in a manner of connecting the same sized flanges, to thereby make the light source, the transparent film installation and storage chamber housing, the reaction chamber housing in a single sealing space, and enable the light source to move up and down without breaking the vacuum; and a driving unit for moving the light source up and down. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above object and other advantages of the present invention will become more apparent by describing the preferred embodiments thereof in more detail with reference to the accompanying drawings in which: 
       FIG. 1  is a schematic view showing a conventional photo-chemical vapor deposition (photo-CVD) apparatus using a flexible curtain in order to prevent a blurring phenomenon on an optical window; 
       FIG. 2  is a schematic view for explaining a process of replacing a blurred optical window in another conventional photo-CVD apparatus; 
       FIG. 3  is a schematic view showing a photo-induced process apparatus according to the present invention; 
       FIG. 4  is a schematic view for explaining a process of performing a deposition process in the photo-induced process apparatus shown in  FIG. 3 ; and 
       FIG. 5  is a schematic sectional view for explaining another method process of connecting the light source and the flange in a photo-induced process apparatus according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Preferred embodiments of the present invention will be described with reference to the accompanying drawings. 
   Referring to  FIG. 3 , a photo-induced process apparatus according to the present invention does not use an existing optical window such as a quartz window having a high transitivity of an ultra-violet light ray region. The photo-induced process apparatus according to the present invention has a structure that the light emission plane of a light source  340  faces an opening for transmitting light in the upper portion of a reaction chamber  350 , in which a thermal-resistant transparent film  330  is horizontally installed in a space between the light emission plane of the light source  340  and the upper portion of the reaction chamber  350 , to thereby prevent a blur on the surface of the light source. A transparent film installation and storage chamber is connected to the upper portion of the reaction chamber  350 . The transparent film installation and storage chamber has an opening on the central portions of an upper plate  303  and a lower plate  304 , respectively. A feeding chamber  302  and a winding chamber  300  for separately storing two roles of transparent films  310  and  312  are provided in the left and right sides of the installation and storage chamber, respectively. A clean transparent film  330  of several tens micron (μm) thick wound around the transparent film role  310  in the lefthand feeding chamber  302  passes through lefthand and righthand rollers  324 ,  326 ,  322  and  320  in turn, and then wound around the transparent film role  312  in the righthand winding chamber  300 . Meanwhile, the central axis of an opening provided in the central portion of the upper plate  303  and the lower plate  304  in the installation and storage chamber housing coincides with that of the light emission plane of the light source  340  and the reaction chamber  350 . Also, the lower plate  304  in the transparent film installation and storage chamber housing is combined with the upper plate of the reaction chamber  350  in which an opening is formed, by a welding, an O-ring, a gasket or the like. In order to seal the upper plate opening in the transparent film installation and storage chamber and the light emission plane of the light source  340 , the light emission plane edge of the light source  340  is welded to the central opening circumference of a first flange  306 . Here, the surface of the light emission plane of the light source  340  and the lower plane of the first flange  306  are made to be placed on the same plane. In other words, the light emission plane of the light source  340  makes level with the lower plane of the first flange  306 , and then the first flange  306  is welded. The first flange  306  is made of stainless steel or any materials capable of welding with a material of the light emission plane. Also, in the case that the light source  340  may be damaged as the light source  340  is beyond endurance to the atmosphere, a part of or the whole remaining outer surface of the light source  340  except for the light emission plane of the light source  340  exposed to the installation and storage chamber opening is welded with a reinforced material so that the light source  340  can be endured to the atmosphere. 
   The reinforced material is stainless steel or a material which can be welded to the material of the surface of the light source. Then, a second flange  308  is welded along the circumference of the installation and storage chamber opening. The photo-induced process apparatus according to the present invention includes an extension and contraction portion  370  made of a formed bellows or a welded bellows having third flanges of the same sizes as those of the first and second flanges on either end thereof, in order to connect the third flanges with the first flange  306  and the second flange  308 , respectively. By using the extension and contraction portion  370 , the light source having the first flange is connected to the installation and storage chamber upper plate opening having the second flange. 
   As a result, the flanges  306  to which the light source  340  is attached, the extension and contraction portion  370 , the transparent film installation and storage chamber housing, and the reaction chamber housing are combined in turn to form a single sealing space. During the photo-induced process, the temperature of the surface of the light source can rise up to approximately 400° C. as being the case. Accordingly, if a polymer group material is used as a transparent film, the transparent film is melted and torn or deformed and damaged. In the case that the transparent film is torn due to the high temperature of the light source surface, the reaction gas flows into the installation and storage chamber so that a thin film is deposited on the light source surface. Accordingly, an original purpose of using the transparent film is meaningless. Also, when the transparent film is deformed, the vacuum ultra-violet light ray generated from the light source is not irradiated into the reaction chamber uniformly. Accordingly, a uniformity of the thin film to be deposited through the reaction in the reaction chamber is lowered and thus it is impossible to obtain a deposition which can be regenerated. In order that the high temperature of the light source surface does not influence upon the transparent film, a cylinder  390  of a metal or ceramic material for preventing the direct contact of the light source and the transparent film is vertically inserted into the central opening circumferential portion of the first flange. The inserted cylinder  390  mates with the central opening circumferential portion of the first flange through a welding work, or may be detachably inserted by using a connection groove formed on the central opening circumferential portion of the first flange. However, a connection ring to be fitted into the connection groove is needed on the upper end of the cylinder. A number of small holes are formed on the inserted cylinder within the limit that the structure is not deformed so that gas can be smoothly passed. A groove is formed on the lower end circumferential portion of the cylinder to insert an O-ring therein to in order to maintain a sealing without damaging the transparent film, when the cylinder contacts the transparent film. 
   As shown in  FIG. 4 , in order to form a thin film, the light source  340  is made to lag downwards vertically, in which the lower end portion of the cylinder  390  connected to the central opening circumference of the first flange  306  by means of a welding work or a detachable mariner while pushing down the transparent film  330  is fitted with the transparent film  330  and slightly closely contacts the O-ring  358 . Here, the extension and contraction portion  370  using the formed bellows or welded bellows is contracted to thus accomplish the objective without destruction of the vacuum in the reaction chamber. In this state, the reaction gas is filled in the reaction chamber  350  through the first inlet  318 . Then, the reaction gas is discharged through a first outlet  319  so that the pressure in the reaction chamber becomes a predetermined pressure, and the light from the light source  340  is irradiated to thereby form a thin film. Here, a nitrogen gas or an inert gas is made to flow through a third inlet  384  and to discharge through a third outlet  386  so that the pressure of the transparent film installation and storage chamber  302  and the winding chamber  300 , that is, the pressure of the installation and storage chamber is slightly higher than or equal to the reaction chamber  350 . By doing so, the reaction gas in the reaction chamber  350  is prevented from being leaked into the installation and storage chamber via the O-ring  358  at maximum, and the damage of the transparent film is prevented due to the pressure difference in the two upper and lower space isolated by the transparent film. In the apparatus for forming a large-area thin film, the transparent film lags downwards or swells upwards due to the pressure difference between the upper and lower portions of the transparent film. Support nets  362  and  364  which are weaved roughly with a minute line of the transparent thermal-resistant material or metal material are installed in one or both sides of the upper and lower of the transparent film, to thereby prevent the transparent film from lagging downwards or swelling upwards. In this case, the support nets  362  and  364  should use sufficiently thin and roughly weaved nets so that an absorption loss of light emitted from the light source is minimized, and be also designed to have as many intensities as downward lagging or upward swelling of the transparent film due to the pressure difference between the upper and lower portions of the transparent film can be physically supported. Here, the support nets  362  and  364  are installed in both or one of the reaction chamber  350  and the transparent film installation and storage chamber so that it can be detached according to the purpose of the photo-induced process apparatus. It is preferable that the support nets are installed above the transparent film, that is, in the installation and storage chamber rather than in the reaction chamber during performing a photo-CVD, since dust can be suppressed. In this case, the pressure of the installation and storage chamber need to be set slightly lower than the pressure of the reaction chamber. Also, at the time of the photo-induced process which does not blur the surface of the light source, the transparent film should not be necessarily used. A heater  356  for adjusting the temperature of a substrate  352  is internally installed in the substrate heating support  354  supporting the substrate  352 . The position of the substrate  352  is adjusted by the up and down movement of the substrate heating support  354  in the reaction chamber so that a deposition process can be performed at an optimal condition. A driving device (not shown) for the up and down movement of the substrate heating support  354  is installed in the outside of the reaction chamber  350 . An extension and contraction portion  360  formed of a bellows for the up and down movement of the substrate heating support is provided so that the vacuum in the reaction chamber  350  is not destructed at the time of the up and down movement of the substrate heating support  354 . Thus, the extension and contraction portion  360  can extend or contract. 
   Meanwhile, when a thin film is completely formed, a supply of a nitrogen gas or inert gas and a reaction gas is stopped, and then these gases are discharged through the first and third outlets  319  and  386 . For the purpose of cleaning the reaction chamber, a nitrogen gas or inert gas is supplied to the reaction chamber through the second inlet  314 , and then a process of discharging the supplied gas through the second outlet  316 , that is, a purging is repeated three or four times. Then, the reaction chamber is discharged through the first outlet  319  to a high vacuum degree. When a purging is performed or a high vacuum discharging is performed in the reaction chamber so that the pressure difference between both sides of the transparent film does not occur in the above-described processes, an inert gas is made to flow into and a high vacuum discharging is made to the transparent film installation and storage chamber. Then, if the light source  340  is raised up vertically to an original position, the transparent film is supported by the rollers  324 ,  326 ,  322  and  320 , and becomes again the state as shown in FIG.  3 . Then, a portion which is blurred by attachment of the film is replaced with a new clean transparent film by winding up the righthand role  312 . In this way, formation of the thin film and replacement of the transparent film are performed alternately. Thus, the reaction chamber  350  can be maintained at a high purity constantly without being exposed to the atmosphere, until a clean film in the feeding chamber  302  is consumed out, to thereby form a high-quality thin film. Here, for the needed photo-induced process, the substrate  352  should be installed on the substrate heating support  354  in the reaction chamber  350 , and then a load-lock chamber (not shown) and a substrate transfer mechanism (not shown) should be provided in order to avoid the vacuum in the reaction chamber  350  from being destructed when the substrate  354  is taken out from the reaction chamber  350  after the process has been completed. Also, a gate valve (not shown) is installed between the reaction chamber  350  and the load-lock chamber. The gate valve should be always closed in the case other than a substrate transferring process for installation and collection of the substrate  352 , to thereby isolate the reaction chamber  350  and the load-lock chamber (not shown). In the case that the transparent film is consumed out in the feeding chamber, the completely consumed film role  312  is taken out by opening the second opening  382  in the winding chamber  300 . After opening the first opening  380  in the feeding chamber  302 , a clean transparent film role is mounted to load the transparent film as shown in FIG.  3 . Then, the openings  380  and  382  are closed, to then discharge the feeding chamber  302 , the winding chamber  300  and the reaction chamber  350  to a high vacuum degree simultaneously. In this case, a purging need to be performed three or four times by using a purge cleaning gas. In the present invention, no optical window is used. Thus, the light emitted from the light source can be used very effectively. 
   Also, when a thin film is formed as shown in  FIG. 4 , while the light source  340  assumes the function of part of the upper plate in the photo-CVD apparatus, that is, the function o fresisting against the atmosphere, the inside of the reaction chamber of the vacuum state faces the light emission plane in which the transparent film  330  is interposed between the former and the latter. Accordingly, the light source emitting the light of the vacuum ultra-violet light ray region can be used. In this case, a transparent film  330  having a high light transitivity of the vacuum ultra-violet light ray region should be used. Also, it is preferable that part of or the whole outer surface of the light source except for the light emission plane is wrapped with a stiff material such as stainless steel so that the light source can be endured to the atmosphere. A water cooler tube  342  is provided along the circumference of the light source  340  in order to prevent the light source from being overheated. An air cooler electric fan may be used other than the water cooler tube  342 . In the case that a large-area light source such as an excimer lamp is used as the light source  340 , it is possible to make a photo-CVD apparatus capable of making a large-area substrate. Also, other than the excimer lamp, a light source which emits light of vacuum ultra-violet light ray region or ultra-violet light ray region such as a heavy hydrogen discharging tube, a Xenon (Xe) lamp, a low-pressure mercury lamp or the like is used, the short-wavelength light of the region can be easily used. As described above, a method of welding a flange  306  of the material such as stainless steel to the edge of the light emission plane of the light source  340  can be used as a method of connecting the light source  340  to an extension and contraction portion  370  while securing a sealing of the reaction chamber  350 . However, in order to mitigate inconveniences of welding a light source to a flange during replacement of the light source or manufacturing of the light source, a light source  340  and a flange  500  are connected to a hinge  520  and an O-ring  510  is used, to thereby maintain a sealing in the reaction chamber as shown in FIG.  5 . 
   As described above, the present invention can realize a photo-induced process apparatus which can efficiently utilize light emitted from a light source, in particular, vacuum ultra-violet light, and remarkably enhance a working efficiency in comparison with an existing apparatus. Also, the photo-induced process apparatus according to the present invention is very simple and practical, to thereby easily perform a photo-induced process with respect to a large-area substrate. 
   The present invention is not limited to the above-described embodiments. It is apparent to one who has an ordinary skill in the art that there may be many modifications and variations within the same technical spirit of the invention.