Method of adjusting process variables in a processing flow

1. A method of adjusting process variables in a processing flow that comprises a sequence of processing steps, the method comprising:

testing processed samples to determine sample parameters of the tested samples;

analyzing said sample parameters in relation to the process variables applied in the processing steps to determine the impact of the process variables on the sample parameters;

modifying the process variables in an attempt to change the sample parameters towards predetermined target values; and

repeating the sequence of processing steps with the modified process variables;

wherein the analyzing step includes, for given samples:

automated matching between patterns of process variables applied for said samples and patterns of corresponding sample data sets of parameters determined from said samples;

quantifying the degree of match in terms of score values associated with patterns of process variables; and

determining the significance of said score values in terms of significance values calculated based on the deviation of the parameters in the sample data sets from said predetermined target values.

2. The method of claim 1 , wherein the processing flow is a semiconductor technology development flow and the processing steps involve application of different patterns of processing variables to different samples in a lot of semiconductor wafers.

3. The method of claim 2 , wherein the patterns of processing variables comprise process splits in which different values of a single process variable, or of a combination of process variables, are applied to different samples in a lot.

4. The method of claim 3 , wherein the patterns of processing variables comprise virtual cross-splits derived from said process splits by combining the application of process variables from different process splits to each sample of a lot.

5. The method of claim 1 , wherein the degree of match between patterns of process variables and sample data sets of parameters determined from said samples is quantified by:

determining data subsets within said sample data sets of parameters;

calculating first subordinate score values which reflect the degree of homogeneity within said data subsets;

calculating second subordinate score values which reflect the degree of deviation between different said data subsets; and

combining said first and second subordinate score values into single super-ordinate score values applying principles of fuzzy logic.

6. The method according to claim 5 , wherein said significance values are determined by:

determining sample parameter group-ranges within the sample data sets of parameters;

calculating ratios of said sample parameter group-ranges to predetermined specification ranges; and

normalizing the calculated ratios to obtain normalized significance score values.

7. The method according to claim 6 , wherein maximum super-ordinate score values are determined from said super-ordinate score values and said normalized significance score values applying principles of fuzzy logic.

8. The method according to claim 7 , wherein matched patterns of process variables and patterns of sample data parameters are ranked according to said overall score value.

9. The method according to claim 1 , wherein said significance values are determined by:

determining sample parameter group-ranges within the sample data sets of parameters;

calculating ratios of said sample parameter group-ranges to predetermined specification ranges; and

normalizing the calculated ratios to obtain normalized significance score values.

10. The method according to claim 9 , wherein maximum super-ordinate score values are determined from said super-ordinate score values and said normalized significance score values applying principles of fuzzy logic.

11. The method according to claim 10 , wherein matched patterns of process variables and patterns of sample data parameters are ranked according to said overall score value.