POSITIONING OF SEMICONDUCTOR SUBSTRATES IN A FURNACE
Methods of positioning semiconductor substrates in a furnace. One method determines a centered position of the substrates by conducting a heat treating to form an oxide layer on the substrate and measuring the substrate thickness at several points along its oxidized surface to determine a centered position. Also, a method of calibrating a device for heat treatment of the substrates, with the device including a positioner for providing the substrates on a retention support in the furnace. The positioner includes a memory unit that stores positioning parameters, and an actuator for positioning the substrate on the support according to the positioning parameters. The method includes positioning a test substrate on the support in a starting position according to starting parameters, determining a centered position for the test substrate, determining centering parameters corresponding to the centered position of the test substrate and storing the centering parameters in the memory unit.
1 . A method of determining a centered position of a semiconductor substrate placed in an annealing furnace in a starting position on a retention support, which comprises:
heat treating the substrate in its starting position for a sufficient time and at a sufficient temperature in the presence of a furnace gas to form a layer on the substrate;
measuring thickness of the substrate at several points, with the position of the measurement points on the substrate being known; and
determining, on the basis of the measured thicknesses and the starting position, a centered position for the substrate on the support.
2 . The method of claim 1 wherein the substrate is heat treated to form an oxide layer on the upper surface of the substrate.
3 . The method of claim 1 wherein the substrate is heat treated to form a nitride layer on the upper surface of the substrate.
4 . The method of claim 1 which further comprises measuring the thickness of the substrate at points concentrically arranged along the upper surface of the substrate.
5 . A method for calibrating a device for the heat treatment of semiconductor substrates, with the device comprising means for positioning semiconductor substrates on a retention support in a furnace, wherein the positioning means comprises a memory unit for storing positioning parameters, and an actuator for positioning a substrate on the support according to positioning parameters stored in the memory unit, wherein the method comprises:
positioning by the actuator a test substrate on the support in a starting position according to predetermined starting parameters;
determining a centered position for the test substrate according to the method of claim 1 ;
determining centering parameters corresponding to the centered position of the test substrate; and
storing the centering parameters in the memory unit of the positioning means.
6 . The method of claim 5 which further comprises repeating the method according to a given number of iterations, with the centering parameters determined at each iteration being taken as starting parameters for the next iteration.
7 . A device for the heat treatment of semiconductor substrates, comprising:
a furnace with a retention support for receiving such substrates;
a measurement unit for determining substrate thickness at several measurement points; and
positioning means comprising:
a memory unit for storing positioning parameters corresponding to the positions of the substrate on the support,
an actuator for positioning the substrate on the support according to positioning parameters stored in the memory unit; and
a processing unit for determining, as a function of a starting position and measurements by the measurement unit, a centered position and centering parameters based on the centered position;
such that the memory unit stores centering parameters so that the actuator is able to position semiconductor substrates on the support in the centered position.
8 . The device of claim 7 , wherein the processing means includes the memory unit and is operatively associated with the actuator for centering the substrates on the retention support.