Method and apparatus for process endpoint prediction based on actual thickness measurements

A method for predicting an endpoint time of a semiconductor process at which a thickness of a target layer of a wafer occurs, the semiconductor process occurring in a chamber, the method comprising the steps of:

• receiving an actual thickness sample of the thickness of the layer and a figure of merit calculated for a first sample time;
• determining from the figure of merit whether the actual thickness sample is valid;
• updating a forecasted process rate using the actual thickness sample if the actual thickness sample is valid;
• and predicting the endpoint time from the forecasted process rate.

A method for predicting an endpoint time at which a thickness of a target layer of a wafer under process occurs, comprising the steps of:

• receiving an actual layer thickness sample of the layer calculated for a first sample time;
• determining if the actual layer thickness sample is valid using Holt's method;
• updating a forecasted process rate with the actual layer thickness sample using a Holt filter if the actual layer thickness sample is valid;
• predicting the endpoint time from the forecasted process rate;
• and
• controlling the process, using the endpoint time, to produce the layer at the desired thickness.

A method for predicting an endpoint time at which a desired thickness of a target layer of a wafer under process occurs, comprising the steps of:

• receiving an actual layer thickness calculated by a processor for a first sample time;
• calculating a raw process rate;
• comparing the raw process rate to a minimum process rate and a maximum process rate;
• determining the actual layer thickness is valid if the raw process rate is between the minimum and the maximum process rates;
• updating a forecasted process rate with the actual layer thickness if the actual layer thickness is valid;
• predicting the endpoint time from the forecasted process rate;
• and
• controlling the process, using the endpoint time, to produce the layer at the desired thickness.

A system for controlling a semiconductor process for a wafer within a process chamber and having at least one layer, the system comprising:

• a generator for generating and transmitting a source signal, having a first set of parameters, toward the wafer and for receiving a reflected signal, having a second set of parameters, from the wafer;
• a processor in communication with the generator for calculating for a first sample time an actual layer thickness and a figure of merit from a set of differences between the first and second sets of parameters;
• an endpoint detector in communication with the processor for using the figure of merit to determine if the actual layer thickness is within a predetermined range, for updating a forecasted process rate from the actual layer thickness if the actual layer thickness is within the predetermined range and for predicting an endpoint time from the forecasted process rate;
• and
• a controller in communication with the process chamber and the endpoint detector, the controller responsive to the endpoint time for generating control signals for controlling the semiconductor process.