u00b0 to about 90 u00b0 the injector tube and baffles may be made of the same or different materials generally any materials that will be inert to the process and that will be able to withstand the process conditions of temperature and pressure will be adequate the material must withstand a maximum temperature of about 950 u00b0 c and pressures ranging from about 300 to about 600 millitorrs preferred materials are stainless steel and quartz although other materials with similar properties may be used returning to fig1 and 2 note that the temperature variation or 34 skew 34 across the reaction chamber 13 and boat 15 are different in the prior art design fig1 the skew is roughly 50 u00b0 c while the skew using the novel injector tube of the present invention is only roughly 10 u00b0 c this change is critical in that wafers located at the top of the boat receive approximately the same temperature conditions as those of the middle and bottom of the boat the temperatures reflected in fig1 show that the temperature at the top third of the boat must be roughly 50 u00b0 c higher than the remainder of the boat in order to improve across load uniformity of film thickness if a.