System and method for suppression of wafer temperature drift in cold-wall CVD systems
AssigneeNXP B.V.
InventorWiebe De Boer
Life of this patent
Estimating the term…
Abstract
An apparatus and corresponding method are disclosed that uses one or more optical fibers in a susceptor that monitor radiation emitted by the backside of the susceptor. The optical fibers are filtered and converted into an electrical signal. A control system is used to maintain a constant wafer temperature by keeping the electrical signal constant during the deposition cycle. This overcomes problems caused by varying wafer temperature during non-selective epitaxial and poly-silicon growth on patterned wafers at low temperatures and reduced pressure.
Claims20
A wafer manufacturing apparatus comprising:
- a susceptor including a support for a wafer, the wafer including a topside and a bottom side;
- at least one optical fiber connected to the susceptor so that radiation from the bottom side of the wafer can be monitored;
- an optical signal measurer coupled to the at least one optical fiber, the optical signal measurer generating an electrical signal responsive to the radiation measured from the bottom side of the wafer;
- and
- a control system that is configured to maintain a deposition temperature of the wafer by
- calibrating the optical signal measurer by
- measuring a temperature of the susceptor at a first gas pressure;
- determining a signal level of the electrical signal when the measured temperature of the susceptor is at the deposition temperature, and by
- keeping, during a subsequent deposition cycle at a second gas pressure that is less than the first gas pressure, the electrical signal constant at the determined signal level.
A method for manufacturing a wafer using an epitaxy process that involves heating the wafer to a deposition temperature, the method comprising the steps of:
- during a high-pressure calibration mode:
- heating a susceptor and a wafer at a high-gas pressure;
- receiving an optical radiation signal from a backside of the wafer;
- filtering out a spectrum of the radiation signal for which the wafer is opaque;
- converting the filtered radiation signal into an electrical signal;
- measuring the temperature of a susceptor holding the wafer, and
- storing a value of the electrical signal when the measured temperature of the susceptor corresponds to the deposition temperature;
- and during a subsequent deposition process carried out at a lower-gas pressure than the high-gas pressure:
- controlling a wafer temperature by keeping, the electrical signal constant at the stored value.
Dependencies are inferred from the claim text.