Abstract:
In a heating furnace for forming films on semiconductor substrates (1), holding means (2, 4) for holding semiconductor substrates (1) are provided with projections (3, 5) for holding at least part of bottom faces of the semiconductor substrates (1) horizontally with predetermined spacing between the projections.

Description:
This application is a continuation of application Ser. No. 884,924, filed July 10, 1986, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a semiconductor device manufacturing apparatus for manufacturing semiconductor devices on semiconductor substrates and more particularly, it relates to an improvement of a semiconductor device manufacturing apparatus including a vertical type of heating furnace for forming films on semiconductor substrates. 
     2. Description of the Prior Art 
     In the past, various semiconductor device manufacturing apparatus have been known for forming films, such as oxide films, nitride films, polysilicon films, on silicon substrates or the like for forming a semiconductor device. As such semiconductor device manufacturing apparatus, various oxidizing equipment and CVD (Chemical Vapor Deposition) equipment have been used. 
     Such semiconductor device manufacturing apparatus comprise a horizontal heating furnace, and others comprise a vertical heating furnace. The structure of a horizontal heating furnace is disclosed in, for example, an article by L.E. Katz et al. entitled &#34;High Pressure Oxidation of Silicon by the Pyrogenic or Pumped Water Technique&#34;, Solid State Technology, Dec. 1981, pp 87-93. In forming films, a plurality of semiconductor substrates are disposed approximately vertically in a horizontal heating furnace, whereas semiconductor substrates are juxtaposed horizontally with predetermined spacings in a vertical heating furnace. 
     FIG. 1 is a diagram showing a holder used for holding silicon wafers in a conventional vertical heating furnace. As a material of this holder, for example, quartz, silicon carbide, or polysilicon is used. In FIG. 1, each of three supports 8 of a holder 7 is formed with grooves 9 for inserting silicon wafers 1 in a longitudinal direction of each of the supports 8, with a predetermined spacing between grooves. The silicon wafers 1 are inserted into the grooves 9 one by one and then are placed within a vertical heating furnace of a semiconductor device manufacturing apparatus to be heated. Then, raw material gas for forming films on the silicon wafers 1 is introduced into this vertical heating furnace. 
     In a conventional semiconductor device manufacturing apparatus, a holder of silicon wafers is constructed as described above. If silicon wafers are inserted into grooves of the holder, a part of the silicon wafers inserted into the grooves becomes covered by a part of the support. This causes a problem in which the films formed do not grow uniformly, because raw material gas for forming films do not sufficiently reach this portion, and a difference in film thickness occurs on the surface of silicon wafers. 
     There also has been a problem in which this portion is contaminated by bringing a part of silicon wafers into contact with the edge of grooves by mistake in inserting silicon wafers into grooves. 
     SUMMARY OF THE INVENTION 
     A principal object of the present invention is to provide a semiconductor device manufacturing apparatus which drastically improves uniformity of thickness of films formed on the surface of semiconductor substrates, as well as can prevent the contamination of the surface caused in inserting the semiconductor substrates. 
     Briefly stated, the present invention is directed to a heating furnace for forming films on semiconductor substrates, in which holding means for holding semiconductor substrates are provided with projections for holding at least part of the bottom faces of semiconductor substrates horizontally, with predetermined spacing between the projections. 
     In accordance with the present invention, raw material gas flows uniformly over semiconductor substrates, resulting in films having uniform thickness. 
     These objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing a holder for conventional semiconductor substrates. 
     FIG. 2 is a diagram showing a holder for semiconductor substrates of an embodiment of the present invention. 
     FIG. 3 is a diagram showing a holder for semiconductor substrates of another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 is a diagram showing a holder for semiconductor substrates used in a semiconductor device manufacturing apparatus of an embodiment of the present invention. The holder comprises for example three supports, although they are not illustrated in FIG. 2. In FIG. 2, the respective supports 2 of this holder are provided with projections 3 horizontally relative to a longitudinal direction of each of the supports, with predetermined spacing between the projections 3, and semiconductor substrates, such as silicon wafers 1 are disposed approximately horizontally on these projections 3. Projections 3 may be provided so that silicon wafers 1 can be supported completely in the horizontal direction. However, in such a case, the silicon wafers 1 can cause rotational motion during formation of films and hence, to prevent this, projections 3 are provided so that silicon wafers 1 can be supported while slightly inclined. The spacings between projections 3 as disposed horizontally is such that raw material gas of films to be formed on the surface 11 of silicon wafers 1 flows smoothly. 
     Since in the present invention the semiconductor substrates are supported by the projections, as described above, instead of conventional grooves, raw material gas flows uniformly on the semiconductor substrates, permitting formation of films having uniform thickness. 
     FIG. 3 is a diagram showing another embodiment of the present invention. In FIG. 3, supports 4 of a holder are provided with projections 5 longer than projections 3 shown in FIG. 2. Projections 5 are provided with stepped portions 6, and silicon wafers 1 are engaged with these stepped portions 6. The location of projections 5 between supports 4 and the spacings between projections 5 are similar to the embodiment shown in FIG. 2. That is, projections 5 are arranged with such spacings that silicon wafers 1 can be held horizontally or with slightly inclined, and raw material gas can flow uniformly on the silicon wafers. 
     Since in the holder shown in FIG. 3 in comparison with the holder shown in FIG. 2, silicon wafers 1 are provided away from supports, the flow of raw material gas becomes more uniform. 
     As a material of the holders shown in FIG. 2 and FIG. 3, quartz, silicon carbide, polysilicon or the like is usually used, but it is not intended to be limited. 
     Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.