Method and apparatus for controlling the thickness of a gate oxide in a semiconductor manufacturing process

Abstract

A method and apparatus for controlling the growth of an oxide, such as a gate oxide, in a semiconductor device manufacturing process takes into consideration the ambient atmospheric pressure in order to reduce the variance in gate oxide thicknesses between wafer lots. The pressure in the oxide diffusion tube is maintained at a constant pressure near the ambient atmospheric pressure during the oxide diffusion process. Alternatively, the furnace time is changed from lot to lot as a function of changes in the ambient atmospheric pressure in order to maintain the gate oxide thickness at a constant value between wafer lots.

What is claimed is:  
     
         13 . An arrangement for controllably growing an oxide layer on an object in a semiconductor device manufacturing process, comprising: 
 an oxide diffusion tube; and    a gas supply arrangement that maintains a constant gas pressure within the oxide a diffusion tube during the growing of an oxide layer on an object, the constant gas pressure being approximately ambient atmospheric pressure.    
     
     
         14 . The arrangement of claim  13 , wherein the gas supply arrangement includes a low pressure source that creates a negative pressure within the oxide diffusion tube.  
     
     
         15 . The arrangement of claim  13 , wherein the gas supply arrangement includes a pressure pump that creates a positive pressure within the oxide diffusion tube.  
     
     
         16 . The arrangement of claim  13 , wherein the constant gas pressure is within a range between approximately ½ atmospheres below the ambient atmospheric pressure and approximately ½ atmospheres above the ambient atmospheric pressure.  
     
     
         17 . An arrangement for controllably growing an oxide layer on an object in a semiconductor device manufacturing process, comprising: 
 an oxide diffusion tube;    an ambient pressure monitor that determines the ambient atmospheric pressure;    a heater in thermal contact with the oxide diffusion tube to controllably heat the oxide diffusion tube;    a control arrangement coupled to the ambient pressure monitor and to the heater, the control arrangement controlling the heater to heat the oxide diffusion tube for an amount of time that is a function of the determined ambient atmospheric pressure.    
     
     
         18 . The arrangement of claim  17 , wherein the control arrangement includes means for dynamically controlling the heater in response to changes in the ambient atmospheric pressure during the growing of an oxide layer.  
     
     
         19 . The arrangement of claim  18 , wherein the means for dynamically controlling the heater includes means for changing the amount of time the heater will heat the oxide diffusion tube.  
     
     
         20 . The arrangement of claim  17 , wherein the control arrangement includes means for setting the amount of time the heater will heat the oxide diffusion tube, the amount of time remaining fixed throughout the growing of an oxide layer.  
     
     
         21 . A semiconductor device having a gate oxide layer formed by the process comprising the steps of: 
 positioning at least one wafer on which the gate oxide layer is to be grown within an oxide diffusion tube;    maintaining a constant pressure of gas within the oxide diffusion tube, the pressure being approximately ambient atmospheric pressure; and    growing the gate oxide layer on the wafer until a desired thickness of the gate oxide layer is achieved.