1. Field of the Invention
This invention relates to a vertical furnace for heat-treating a semiconductor, and more particularly to such a vertical furnace which is adapted to effectively and positively carry out the heat-treating of a semiconductor.
2. Description of the Prior Art
A conventional furnace for heat-treating a semiconductor which is known as a diffusion furnace in the art is typically the horizontal type constructed in such a manner as shown in FIG. 1. More particularly, the conventional heat-treating furnace is constructed to dispose a heater 20 on the inner wall of a furnace body 18 which is formed into a cylinder shape and laterally arranged. In the conventional furnace of such horizontal type, a material 52 to be heat-treated is put on a boat 14, which is driven by a driving means or motor 28 to be reciprocated in the directions indicated by arrows.
However, the conventional heat-treating furnace of the horizontal type described above has many disadvantages of, for example, being inferior in heat efficiency, requiring a large area for the installation, being nonuniform in temperature profile in the furnace, being troublesome in handling of a material to be subjected to heat-treating, and the like.
In order to effectively eliminate the above-described defects of the conventional horizontal type furnace, a vertical furnace for heat-treating a semiconductor has been proposed which is open at the upper end thereof. However, such a conventional vertical furnace of the top open type has a disadvantage that heat loss easily occurs because of the upper end being open. The vertical furnace has another problem that heat discharged from the furnace due to convection renders the operation of holding on a holder a material to be subjected to heat-treating in the upper portion of the furnace highly difficult. A further disadvantage of the furnace is that the falling of the holder due to, for example, misoperation often causes a silica tube to be damaged or broken. The furnace has still a further defect that it is highly difficult to remove from the furnace dust produced due to the above-described holding operation.
Also, the conventional vertical furnace is constructed in a manner such that a boat driving mechanism for carrying out the introduction and removal of a boat with respect to a furnace section is substantially arranged in an operation space, resulting in semiconductor heat-treated or to be subjected to heat-treating being polluted by dust produced due to the operation of the boat driving mechanism, and more particularly the rotation of a driving motor, the engagement of a driving shaft with a connecting member and the like.