NOVELTY - The apparatus comprises a crucible unit, a heating unit, a casting unit, a cooling unit, and a transfer unit. The crucible unit is configured to receive a raw silicon, and comprises a discharge port (115). The heating unit is provided to an outer wall and an external bottom surface of the crucible unit, and heats the crucible unit to melt the raw silicon in the crucible unit to form a molten silicon. The casting unit casts the molten silicon discharged through the discharge port of the crucible unit into a silicon substrate, and comprises a casting unit body (132).    USE - The apparatus is useful for manufacturing a silicon substrate that is useful for solar cells (claimed).    ADVANTAGE - The apparatus is capable of economically manufacturing the silicon substrate with high quality, increased productivity and improved energy conversion efficiency.    DETAILED DESCRIPTION - The apparatus comprises a crucible unit, a heating unit, a casting unit, a cooling unit, and a transfer unit. The crucible unit is configured to receive a raw silicon, and comprises a discharge port (115). The heating unit is provided to an outer wall and an external bottom surface of the crucible unit, and heats the crucible unit to melt the raw silicon in the crucible unit to form a molten silicon. The casting unit casts the molten silicon discharged through the discharge port of the crucible unit into a silicon substrate, and comprises a casting unit body (132) and an assistant heating mechanism. The cooling unit rapidly cools the cast silicon substrate. The transfer unit is disposed at one end of the cooling unit, and transfers the solidified silicon substrate. The casting unit comprising the casting unit body has a casting space, which is defined in the casting body, to be horizontally connected to the discharge port of the crucible unit. The assistant heating mechanism preheats the casting unit body to control a solidification temperature of the silicon substrate. The discharge port penetrates one sidewall of crucible unit to be disposed in a horizontal direction, and has a thickness of 100-400 mu m. The crucible unit further comprises a double crucible (114), a raw silicon gate, and a gas supply port. The double crucible comprises a graphite crucible (112) that defines a closed space, and a quartz crucible (113) inserted into the graphite crucible. The raw silicon gate penetrates a ceiling of the double crucible, and is configured for supplying the raw silicon into the double crucible. The gas supply port is separated from the raw silicon gate. An inert gas is supplied into the double crucible through the gas supply port, and compresses the molten silicon to induce discharge of the molten silicon. The heating unit comprises a first heating mechanism that is disposed along an outer wall of the double crucible, and a second heating mechanism that is disposed along an external bottom surface of the double crucible. The first and second heating mechanisms are separately controlled. Each of the first and second heating mechanisms is a heater and/or an induction coil. The casting space of the casting unit comprises a solidification region for primary solidification of the cast silicon substrate, and a stress relieving region for secondary solidification of the cast silicon substrate to relieve stress of the cast silicon substrate. The assistant heating mechanism comprises a first assistant heating mechanism that is positioned corresponding to the solidification region to primarily heat the cast silicon substrate, and a second assistant heating mechanism that is positioned corresponding to the stress relieving region to secondarily heat the cast silicon substrate. The transfer unit comprises a pair of rollers rotating in opposite directions. An INDEPENDENT CLAIM is included for a method for manufacturing a silicon substrate.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic sectional view of an apparatus for manufacturing a silicon substrate.    Graphite crucible (112)    Quartz crucible (113)    Double crucible (114)    Discharge port (115)    Casting unit body. (132)