Abstract:
A thin film forming equipment and a method for forming thin films are provided which are capable of forming the thin film of high quality and of effectively preventing CVD material gas from leaking to surroundings at a low cost. The thin film equipment contains a substrate, a substrate holding device used to hold the substrate and a device used to provide an atmospheric gas to a surface of the substrate held by the substrate holding device, wherein an upper face of the substrate held by the substrate holding device and an upper face of the substrate holding device are almost on one plane.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a thin film forming equipment and a thin film forming method used for correcting defects in a substrate having a plane pattern structure such as a photomask, liquid crystal substrate or a like. 
     2. Description of the Related Art 
     Alaser CVD (Chemical vapor Deposition) method is disclosed in U.S. Pat. No. 4,801,352 in which a thin film is formed at a local place on a substrate by radiating a specified gas introduced at the local place on the substrate with a laser to decompose the substrate. 
     FIG. 4 is a cross-sectional view of conventional thin film forming equipment. As depicted in FIG. 4, a gas window  52  is mounted on a substrate  51 . The gas window  52  is so constructed that there is a small clearance (for example, of 0.5 mm) between an upper face of the substrate  51  and a lower face of the gas window  52 . The gas window  52  is provided with a gas retention chamber  53 , a gas introducing section  54 , a gas exhausting section  55  and a laser window  56 . The gas retention chamber  53  is a chamber for the retention of CVD materials such as gases of organic metal compounds or a like. The gas introducing section  54  is a section used for introducing the CVD materials into the gas retention chamber  53 . The gas exhausting section  55  is composed of ring-shaped trenches  55   a  formed in the circumference of the gas retention chamber  53  and of an exhausting section  55   c  connected through a hole  55   b , which is used for exhausting the gas discharged from the gas retention chamber  53 . The laser window  56  is used for radiating the CVD materials staying in the gas retention chamber  53  with the laser to decompose them. 
     The substrate  51  is held by the holder  57 . That is, the substrate  51  is held by hanging an end portion of the substrate  51  on a step section  57   a  of the holder  57 . A transmitting illuminating source  58  is used to check a quality of films formed by the CVD process. A lens  59  is used for collecting laser light. A flow of gases used as the CVD materials is shown by arrow marks in FIG.  4 . 
     However, following problems arise when the gas retention chamber  53  of the above equipment is positioned in the proximity of the end portion of the substrate  51  and the thin film is formed in the proximity of the end portion of the substrate  51 . Since there is a step area between the upper face of the substrate  51  and the upper face of the holder  57 , if the gas retention chamber  53  is positioned in the proximity of the end portion of the substrate  51 , the gas is suctioned from the exhausting section  55   c  through the ring-shaped trench  55   a  and the gas exhausted from the gas retention chamber  53  is to be ejected, air currents are influenced at the step area and the air flows into the gas retention chamber  53  as shown by the arrow “a” in some cases, causing degradation in the quality of the film formed by the CVD process. 
     Also, there are some cases in which gases used as the CVD materials are not completely ejected through the trench  55   a  from the exhausting section  55   c . In some cases, gases used as the CVD materials leak to surroundings. 
     SUMMARY OF THE INVENTION 
     In view of the above, it is an object of the present invention to provide a thin film forming equipment and a method for forming thin films which are capable of forming the thin film of high quality and of effectively preventing gases used as CVD materials or a like from leaking to surroundings at a low cost. 
     According to a first aspect of the present invention, there provided a thin film forming equipment including: 
     a substrate; 
     a substrate holding device used to hold the substrate; 
     a device used to provide atmospheric gas to a surface of the substrate held by the substrate holding device; and 
     whereby an upper face of the substrate held by the substrate holding device and an upper face of the substrate holding device are almost on one plane. 
     In the foregoing, a preferable mode is one wherein the substrate holding device has a cover body which is disposed in an area surrounding the substrate held by the substrate holding device and wherein an upper face of the cover body and the upper face of the substrate are almost on one plane. 
     Also, a preferable mode is one wherein the substrate holding device is provided with a trench along a circumference of the held substrate and the atmospheric gas is able to be ejected through the trench. 
     Also, a preferable mode is one wherein a sheet is provided at a boundary between the held substrate and the substrate holding device. 
     Furthermore, a preferable mode is one wherein the thin film forming equipment provides the atmospheric gas to a surface of the substrate held by the substrate holding device and forms the thin film on the substrate by decomposing the atmospheric gas and wherein the thin film forming equipment further includes gas introducing means for introducing the atmospheric gas, a gas retention chamber for retention of the introduced gas using the gas introducing means, gas discharging means for discharging gas ejected from the gas retention means and laser radiating means for decomposing gas staying at the gas retention chamber by laser irradiation. 
     According to a second aspect of the present invention, there is provided a method for forming a thin film on a substrate by decomposing gas introduced to a surface of a substrate held by a substrate holding device including a step of preventing the gas introduced to the surface of the substrate from being influenced by outside air. 
     According to a third aspect of the present invention, there is provided a method for forming a thin film on a substrate by introducing gas to a surface of a substrate held by a substrate holding device, by radiating the introduced gas with laser, by decomposing the introduced gas and then by suctioning and discharging decompositional by-products, including a step of preventing the gas introduced to the surface of the substrate from being influenced by outside air. 
     In the foregoing, it is preferable that the upper face of the substrate and the upper face of the substrate holding device are almost on one plane to prevent gas introduced on the substrate surface from being influenced by outside gas. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a cross-sectional view of thin film forming equipment according to a first embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of thin film forming equipment according to a second embodiment of the present invention; 
     FIG. 3 is a perspective view of the thin film forming equipment according to the second embodiment; and 
     FIG. 4 is a cross-sectional view of conventional thin film forming equipment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Best modes of carrying out the present invention will be described in further detail using various embodiments with reference to the accompanying drawings. 
     First Embodiment 
     FIG. 1 is a cross-sectional view of thin film forming equipment according to a first embodiment of the present invention. As shown in FIG. 1, the gas window  2  is so displaced that there is a small clearance (0.5 mm) between an upper face of the substrate  1  and a lower face of the gas window  2 . 
     The gas window  2  is comprised of a gas retention chamber  3 , a gas exhausting section  5  (including an exhausting section  5   c  communicating with trench  5   a  and trench  5   b  through a hole  5   b ) and a laser window  6 . The gas retention chamber  3  is a chamber for the retention of CVD (Chemical Vapor Deposition) materials such as gases of organic metal compounds or a like. The gas introducing section  4  is used for introducing the CVD materials into the gas retention chamber  3 . The gas exhausting section  5  is used for exhausting gases discharged from the gas retention chamber  3 . The laser window  6  is used for radiating the CVD materials staying in the gas retention chamber  3  with the laser to decompose them. 
     The substrate  1  is held by the holder  7 . That is, the substrate  1  is held by hanging an end portion of the substrate  1  on a step portion  7   a  of a holder  7 . A transmitting illuminating source  8  is used to check a quality of a film formed by the CVD process. A lens  9  is for collecting laser light. Configurations of the equipment shown in FIG. 1 differ greatly from those of the equipment in FIG. 4 in that the former(Present Embodiment) has a cover while the latter (Prior Art) does not. As shown in FIG. 1, according to the first embodiment, the equipment is provided with the cover  10  in a manner that it covers an upper face of the holder  7  surrounding the substrate  1 . This allows an upper face of the substrate and an upper face of the cover  10  on the holder  7  to be on one plane. 
     An end portion  10   a  of the cover  10  disposed opposite to the substrate  1  is formed in a tapered form. This can prevent the cover  10  from contacting with one end of the substrate  1  at a time of opening and closing of the cover  10 . According to the present embodiment, even if the thin film is formed by the same CVD method as in the prior art shown in FIG. 4, the flow-in of air does not occur, unlike in the case of the prior art in FIG. 4 in which the flow-in of air is shown by an arrow “a”. That is, during a formation of the thin film, since outside air (i.e., oxygen) does not flow into the gas retention chamber  3 , gases used as the CVD materials introduced into the gas retention chamber  3  are not influenced by the outside air. Therefore, the thin film of a high quality can be formed by the CVD process. Also, gases used as the CVD materials do not leak to the surroundings. Since these effects can be obtained simply by providing the cover  10 , the first embodiment of the present invention can be carried out very simply and at a low cost. The material for the CVD, i.e., Cr (CO) 6  is introduced by a carrier gas (Ar gas with a flow-rate of 200 sccm (standard cubic centimeter per minute)) into the gas retention chamber  3  in a manner that a pressure of Cr(CO) 6  is at 0.3 Torr. A discharging flow-rate at the gas exhausting section is set to 600 sccm. The Cr thin film is then formed in proximity to the end portion of the substrate by laser radiation and the CVD process. 
     In the conventional equipment ( 10  as shown in FIG. 4) not having the cover, a transparent film having no light-interceptive characteristic is formed at a position being by 10 mm inside from the end portion of the substrate  51 . The resulting film shows that oxygen (air) has entered into the gas retention chamber  53 . That is, due to the flow-in of oxygen into the gas retention chamber  53 , the film formed by the CVD process is not metal chromium, but chromium oxide, resulting in the formation of the transparent film described above. The analysis of a concentration of Cr by collecting the gas flowing around the gas window  52  has revealed that the concentration of Cr exceeds 1 ppm (when converted to gas concentration). This shows that the gas Cr (CO) 6  has leaked to the surroundings. 
     In contrast, in the equipment provided with the cover  10  according to the first embodiment as shown in FIG. 1, a desired light-interceptive Cr film is formed even at the end portion of the substrate  1 . This shows that no oxygen (air) has flowed into the gas retention chamber  3  and the film formed by the CVD process is metal chromium. The analysis of the concentration of Cr by collecting the gas flowing around the gas window  52  has revealed that the concentration of Cr is not more than 0.05 ppm (within the limit of measurement). This shows that the gas Cr(CO) 6  has not leaked to the surroundings. 
     As described above, unlike in the case of the prior art shown in FIG. 4, according to the present embodiment, by providing the cover  10 , the step section  7   a  can be removed. However, if the depth of a step section  7   a  of the holder  7  is equal to a thickness of the substrate  1 , the step can also be removed without the cover  10 . There is, however, a problem in that it is difficult to take the substrate  1  from the holder  7  easily. 
     Second Embodiment 
     FIG. 2 is a cross-sectional view of thin film forming equipment according to a second embodiment of the present invention. FIG. 3 is a perspective view of the thin film forming equipment according to the second embodiment. 
     In the thin film forming equipment according to the second embodiment, a holder  7  is provided with trenches  11  along the circumference (on 4 sides) of the substrate  1  and these trenches  11  are communicating with discharging ports  12 . The cover  10  is of a type of rotational movement opening and closing with hinges  13 . Configurations of the thin film forming equipment of the second embodiment are the same as those of the first embodiment except those described above and the same reference numbers in the second embodiment designate corresponding parts in the first embodiment. Detailed description of the same configuration is omitted accordingly. 
     In the thin film forming equipment according to the second embodiment, by providing the holder  7  with the trenches  11  and the discharging port  12 , the leak of the CVD materials to the surroundings can be more completely prevented. Moreover, even if the clearance between the substrate  1  and the cover  10  becomes larger somewhat, the leak of the CVD materials can be avoided and the degradation in quality of the film to be formed is small. For example, in the first embodiment, the clearance between the substrate  1  and the cover  10  is set to be 0.1 mm. However, in the second embodiment, even if the clearance is set to 0.3 mm, the leak of the CVD materials and the degradation of the film quality can be successfully prevented. This means that high accuracy in attaching the cover  10  is not required so much, making easy the mounting of the cover  10 . Furthermore, since the clearance between the substrate  1  and the cover  10  can be somewhat larger, the damage to the substrate at a time of opening and closing can be minimized. 
     Also, according to the second embodiment, a sheet  14  (for example, a Teflon sheet with thickness of 30 μm) is provided along an aperture of the cover  10  (as shown by dashed lines in FIG.  3 ). When the cover  10  is closed at the substrate  1  disposed on the holder  7 , since an end of the sheet  14  is positioned fitly along an end portion of the substrate  1 , even if the clearance between the substrate land the cover  10  is somewhat wide, neither the leak of the CVD material gas nor degradation of the film to be formed occurs. Therefore, the clearance of 0.5 mm between the substrate  1  and the cover  10  is possible to achieve the above purposes. 
     As described above, according to the present invention, the thin film of high quality can be formed and the leak of the CVD material gas to the surroundings can be prevented at a low cost. 
     It is apparent thus that the present invention is not limited to the above embodiments but may be changed and modified without departing from the scope and spirit of the invention. 
     Finally, the present application claims the priority of Japanese Patent Application No. Hei11-080506 filed on Mar. 24, 1999, which is herein incorporated by reference.