Method for detecting variance in semiconductor processes
View Patent ↗A method of detecting variance by regression model has the following steps. Step 1 is preparing the FDC data and WAT data for analysis. Step 2 is figuring out what latent variable effect of WAT data by Factor Analysis Step 3 is utilizing Principal Component Analysis to reduce the number of FDC variables to a few independent principal components. Step 4 is demonstrating how the tools and FDC data affect WAT data by Analysis of covariance model, and constructing interrelationship among FDC, WAT and tools. The interrelationship can point out which parameter effect WAT significantly. By the method, when WAT abnormal situation happened, it is easier for engineers to trace where the problem is.
1. A method for detecting variation in semiconductor processes, comprising the following steps:
collecting, respectively:
a plurality of tool process data from a plurality of process tools,
a plurality of first raw data associated with a wafer acceptance test (WAT) system, and
a plurality of second raw data associated with a fault detection and classification (FDC) system;
pre-processing said first raw data and said second raw data by an operation management unit;
via a feature extract device, generating a plurality of correlation data by processing the first raw data using a first statistic analysis method, the first statistic analysis method being factor analysis (FA),
wherein the steps of the FA for processing the plurality of first raw data comprise:
selecting the plurality of first raw data,
locating common potential factors causing a variation in the plurality of first raw data based on the plurality of first raw data,
rotating the common potential factors of the plurality of first raw data in order to calculate the plurality of correlation data, wherein the common potential factors of the plurality of first raw data define a lowest bound of the variation in the plurality of first raw data so as to determine a number of common potential factor selection;
via a latent variable extract device, identifying a plurality of global index data by processing the second raw data using a second statistic analysis method;
via a variance detect device, building a plurality of interrelationship indices by processing the tool process data, global index data, and the correlation data using a third statistic analysis method; and
identifying an essential reason causing such a semiconductor process variation based on the plurality of interrelationship indices by the operation management unit.
2. The method for detecting variation in semiconductor processes according to claim 1 , wherein the tool process data represents the wafer process data employed by deposition tools, etch tools or lithograph tools.
3. The method for detecting variation in semiconductor processes according to claim 1 , wherein the plurality of first raw data represents the electrical test data of a plurality of wafers tested by the WAT system.
4. The method for detecting variation in semiconductor processes according to claim 1 , wherein the plurality of second raw data is provided by the FDC system, and the plurality of second raw data indicates the variation detection values detected and measured on each wafer by the FDC system in each real-time process state.
5. The method for detecting variation in semiconductor processes according to claim 1 , wherein meaningless detection values are filtered out from the plurality of first raw data and the plurality of second raw data in the pre-processing step.
6. The method for detecting variation in semiconductor processes according to claim 1 , wherein a correlation matrix is used to estimate a similarity among the plurality of first raw data.
7. The method for detecting variation in semiconductor processes according to claim 1 , wherein determining the number of factors of the plurality of first raw data is based on experience of engineers to determine the number of factors.
8. The method for detecting variation in semiconductor processes according to claim 1 , wherein the second statistic analysis method is a Principal Component Analysis (PCA).
9. The method for detecting variation in semiconductor processes according to claim 8 , wherein the steps of PCA for processing the second raw data comprise: classifying the plurality of second raw data, performing a linear conversion of the plurality of second raw data, which linear conversion converts the plurality of second raw data existing in an original coordinate system into a plurality of second raw data existing in a new coordinate system, in which the new coordinate system has a plurality of new axles respectively referred as a first new axle, a second new axle, . . . , and a Nth new axle; locating a projecting amount of the second raw data projected onto the plurality of new axles, acquiring a plurality of first principal component values over the first new axle, a plurality of second principal component values over the second new axle, . . . , and a plurality of Nth principal component values over the Nth new axle; processing the plurality of first principal component values, the plurality of second principal component values, . . . , and the plurality of Nth principal component values in accordance with a confidence index to calculate a plurality of health indices over the plurality of principal component characteristic values; finally generating a plurality of global index data based on the plurality of principal component characteristic values.
10. The method for detecting variation in semiconductor processes according to claim 9 , wherein the confidence index is built based on experience by engineers.
11. The method for detecting variation in semiconductor processes according to claim 9 , wherein the confidence index simplifies the plurality of second raw data through retaining low order principal component values while ignoring high order principal component values.
12. The method for detecting variation in semiconductor processes according to claim 1 , wherein the third statistic analysis method is an Analysis of Covariance (ANCOVA).
13. The method for detecting variation in semiconductor processes according to claim 12 , wherein processing the tool process data, the global index data and the correlation data by mean of ANCOVA operation comprises: building a relationship between the tool process data, global index data and correlation data by means of a design model; performing ANCOVA operation on the built relationship between the tool process data, global index data and correlation data to calculate the interrelationship indices.
14. The method for detecting variation in semiconductor processes according to claim 1 , wherein the interrelationship indices represent the results of influence on the correlation data by the tool process data and the global index data.
15. A method for detecting variation in semiconductor processes, comprising the following steps:
collecting, respectively:
a plurality of tool process data from a plurality of process tools,
a plurality of first raw data associated with a wafer acceptance test (WAT) system, and
a plurality of second raw data associated with a fault detection and classification (FDC) system;
pre-processing said first raw data and said second raw data by an operation management unit;
via a feature extract device, generating a plurality of correlation data by processing the first raw data using a first statistic analysis method;
via a latent variable extract device, identifying a plurality of global index data by processing the second raw data using a second statistic analysis method, the second statistic analysis method being the principle component analysis (PCA), wherein the steps of PCA for processing the second raw data comprise:
classifying the plurality of second raw data, performing a linear conversion of the plurality of second raw data, which linear conversion converts the plurality of second raw data existing in an original coordinate system into a plurality of second raw data existing in a new coordinate system, in which the new coordinate system has a plurality of new axles respectively referred as a first new axle, a second new axle, . . . , and a Nth new axle,
locating a projecting amount of the second raw data projected onto the plurality of new axles, acquiring a plurality of first principal component values over the first new axle, a plurality of second principal component values over the second new axle, . . . , and a plurality of Nth principal component values over the Nth new axle,
processing the plurality of first principal component values, the plurality of second principal component values, . . . , and the plurality of Nth principal component values in accordance with a confidence index to calculate a plurality of health indices over the plurality of principal component characteristic values, and
generating a plurality of global index data based on the plurality of principal component characteristic values;
via a variance detect device, building a plurality of interrelationship indices by processing the tool process data, global index data, and the correlation data using a third statistic analysis method; and
identifying an essential reason causing such a semiconductor process variation based on the plurality of interrelationship indices by the operation management unit.
16. The method for detecting variation in semiconductor processes according to claim 15 , wherein the confidence index is built based on experience by engineers.
17. The method for detecting variation in semiconductor processes according to claim 15 , wherein the confidence index simplifies the plurality of second raw data through retaining low order principal component values while ignoring high order principal component values.
18. The method for detecting variation in semiconductor processes according to claim 15 , wherein the third statistic analysis method is an Analysis of Covariance (ANCOVA).
19. The method for detecting variation in semiconductor processes according to claim 18 , wherein processing the tool process data, the global index data and the correlation data by mean of ANCOVA operation comprises: building a relationship between the tool process data, global index data and correlation data by means of a design model; performing ANCOVA operation on the built relationship between the tool process data, global index data and correlation data to calculate the interrelationship indices.
20. The method for detecting variation in semiconductor processes according to claim 15 , wherein the interrelationship indices represent results of influence on the correlation data by the tool process data and the global index data.