Method and apparatus for process endpoint prediction based on actual thickness measurements
First Claim
1. A method for predicting an endpoint time of a semiconductor process at which a thickness of a target layer of a wafer occurs, the method comprising the steps of:
- receiving an actual thickness sample of the layer calculated at a first sample time;
determining whether or not the thickness sample is valid;
updating a forecasted process rate using the thickness sample if the thickness sample is valid;
predicting the endpoint time from the forecasted process rate; and
controlling the process to generate the layer having the desired thickness.
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Abstract
In accordance with one aspect of the present invention, a method is provided for predicting the endpoint time of a semiconductor process for a layer of a wafer (14). The endpoint time is the time at which a predetermined thickness of the layer occurs. A layer thickness, calculated for a first sample time, is received. It is then determined whether or not the layer thickness lies within a predetermined range. If the layer thickness does lie within the predetermined range, it is used to update a forecasted process rate. The forecasted process rate is used to predict the endpoint time. The endpoint time is used to control the semiconductor process so that the layer of wafer (14) is formed having the predetermined thickness.
114 Citations
24 Claims
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1. A method for predicting an endpoint time of a semiconductor process at which a thickness of a target layer of a wafer occurs, the method comprising the steps of:
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receiving an actual thickness sample of the layer calculated at a first sample time; determining whether or not the thickness sample is valid; updating a forecasted process rate using the thickness sample if the thickness sample is valid; predicting the endpoint time from the forecasted process rate; and controlling the process to generate the layer having the desired thickness. - View Dependent Claims (2, 3, 4, 5)
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6. 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:
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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. - View Dependent Claims (7, 8, 9, 10, 11)
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12. 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:
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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. - View Dependent Claims (13, 14, 15, 16)
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17. 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:
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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. - View Dependent Claims (18, 19)
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20. A system for controlling a semiconductor process for a wafer within a process chamber and having at least one layer, the system comprising:
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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. - View Dependent Claims (21, 22, 23, 24)
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Specification