Device and method for ensuring planarity of a semiconductor wafer during epitaxial growth

1. Device to ensure planarity of a semiconductor wafer during growth at an increased temperature in a growth chamber arranged in a reactor housing where the device includes:

a growth chamber having a port to allow the deposition of at least one wafer on a rotating susceptor in the growth chamber and the withdrawal of the wafer from the growth chamber, where the growth chamber further has an inlet channel for a supply of process gases and an outlet channel for a discharge of not consumed process gases in order to create a process gas flow between said channels,

separate heaters are arranged adjacent to the growth chamber to heat the rotating wafer by means of individually controlled heating zones both above and under the wafer,

an instrument arranged to measure the bending of the wafer,

an automatic control circuit is arranged to use data from any one of:

a) temperature sensors

b) measured data of the power to the heaters, and

c) the instrument measuring bending of the wafer,

to change the temperature in said individually controlled heating_zones so that bending of the wafer is minimized;

wherein the device comprises three heaters positioned below the growth chamber and three heaters positioned above the growth chamber, the heaters being arranged in groups.

2. The device according to claim 1 , whereby the growth chamber is heated at the inflow of the process gases into the growth chamber with a first and a fourth heater in a first group of heaters; a second and a fifth heater in a heater group of heaters heat the growth chamber in its central part; while a third and a sixth heater in a third group of heaters heat the growth chamber at the process gases outflow from the growth chamber.

3. The device according to claim 1 , where the wafer bending is measured by an instrument which calculates the bending by means of laser light sent towards the wafer and reflected from at least two points on the wafer surface.

4. The device according to claim 3 , wherein the instrument is arranged to calculate an angle between a laser beam incident to the wafer and the laser beam reflected from the wafer at at least two points on the wafer and to calculate therefrom if bending of the wafer is present.

5. Method to ensure planarity of a semiconductor wafer during growth at an increased temperature in a device according to claim 1 , comprising the steps of:

measuring bending of the wafer by an instrument sending laser beams towards the wafer,

adjusting, by an automatic control circuit, the supply of energy to one or some of the heaters to counteract initiated measured bending.

6. The method according to claim 5 , further comprising the step of:

individual heaters are controlled individually with respect to energy supply to them.

7. The method according to claim 6 , further including the step of:

the temperature of the upper or lower part of the growth chamber is controlled by controlling the upper and lower heaters independently of one another.

8. The method according to claim 7 , further including the step of:

when indication at a bending measurement that the edges of the wafer are higher than the central parts thereof, the automatic control circuit ensures that the temperature is raised at the upper side of the wafer in the outer parts thereof by means of increased energy supply to anyone of heaters located above the wafer at the outer parts thereof.

9. The method according to claim 8 , further including the step of:

when indication at a bending measurement that the edges of the wafer are lower than the central parts thereof, the automatic control circuit ensures that the temperature is raised at the lower side of the wafer in the outer parts thereof by means of increased energy supply to anyone of heaters located under the wafer at the outer parts thereof.