Chemical vapor deposition with elevated temperature gas injection

Abstract

A chemical vapor deposition reactor and method. Reactive gases, such as gases including a Group III metal source and a Group V metal source, are introduced into a rotating-disc reactor and directed downwardly onto a wafer carrier and substrates which are maintained at an elevated substrate temperature, typically above about 400° C. and normally about 700-1100° C. to deposit a compound such as a III-V semiconductor. The gases are introduced into the reactor at an inlet temperature desirably above about 75° C. and most preferably about 100°-250° C. The walls of the reactor may be at a temperature close to the inlet temperature. Use of an elevated inlet temperature allows the use of a lower rate of rotation of the wafer carrier, a higher operating pressure, lower flow rate, or some combination of these.

1 . A chemical vapor deposition reactor comprising:
 (a) a chamber having one or more walls;   (b) a wafer carrier disposed within the chamber and arranged to hold one or more substrates so that surfaces of the substrates face upwardly within the chamber;   (c) a wafer carrier drive mechanism adapted to rotate the wafer carrier about a substantially vertical axis;   (d) a heater adapted to maintain the substrates at a substrate temperature of 400° C. or higher;   (e) one or more gas sources arranged to supply gases including a Group III metal source and a Group V compound;   (f) a flow inlet element communicating with the chamber above the carrier level, the flow inlet element being arranged to direct the gases downwardly toward the substrates; and   (g) a flow inlet temperature control mechanism arranged to maintain the flow inlet at an inlet temperature of above about 75° C.   
     
     
         2 . A reactor as claimed in  claim 1  further comprising a chamber temperature control mechanism arranged to maintain the walls of the chamber at a wall temperature between 75° C. and 250° C. 
     
     
         3 . A reactor as claimed in  claim 1  wherein the walls of the chamber have one or more inner surfaces substantially in the form of a surfaces of revolution about the axis. 
     
     
         4 . A reactor as claimed in  claim 3  wherein the wafer carrier is in the form of a disc having a generally horizontal upper surface and pockets in the upper surface for holding the substrates, the disc having an outer diameter, the inner surfaces of the reaction chamber defining a carrier region having diameter larger than the wafer carrier, the wafer carrier being disposed in the reaction region so that there is a gap between the disc and the inner surface of the chamber, the chamber having one or more exhaust ports communicating with the chamber below the wafer carrier. 
     
     
         5 . A reactor as claimed in  claim 4  wherein the inner surfaces of the reaction chamber define a flow region having a diameter smaller than the diameter of the carrier region, the flow region extending downwardly from the flow inlet element to the carrier region. 
     
     
         6 . A reactor as claimed in  claim 5  wherein the inner surfaces of the reaction chamber define an abrupt increase in diameter at the juncture of the flow region and the carrier region. 
     
     
         7 . A reactor as claimed in  claim 1  wherein the flow inlet element is arranged to direct the gases in a laminar plug flow having a cross-sectional area in a horizontal plane approximately equal to or larger than an area of the carrier and substrates in a horizontal plane.