Thin film forming apparatus

Claim 1

A thin film forming apparatus of a pressure-reduced reaction type for forming a thin film on a substrate under a pressure reduced condition, comprising: a reaction chamber; substrate support means for supporting the substrate in said reaction chamber, said support means including a heating susceptor having an outer circumferential margin which is spaced by a gap from an inner wall surface of said reaction chamber; a material gas nozzle which is located directly above said substrate and ejects a material gas flow into said chamber toward said substrate perpendicular to an upwardly facing major surface of said substrate; and means for preventing said material gas flow from engaging walls of said chamber as it travels from said material gas nozzle to said substrate, including a control gas nozzle which is disposed above said substrate and encircles said material gas nozzle, said control gas nozzle ejecting into said chamber a control gas flow which encircles said material gas flow and which forcibly re-orients laterally expanding portions of said material gas flow in a direction toward said substrate; wherein said chamber has a gas outlet on an opposite side of said susceptor from said material gas nozzle, said outlet having a diameter larger than the width of said susceptor, wherein said material gas flow at the exit of said material gas nozzle has a speed faster than that of said control gas flow adjacent thereto, and wherein the total gas flow passing through said gap has a speed faster than a speed of the total gas flow above said substrate.