Patent Number: 
Section: claims

1. A method of investigating a sample using Scanning Electron Microscopy, comprising the following steps:irradiating a surface (S) of the sample using a probing electron beam in a plurality (N) of measurement sessions, each measurement session having an associated beam parameter (P) value that is chosen from a range of such values and that differs between measurement sessions;detecting stimulated radiation emitted by the sample during each measurement session, associating a measurand (M) therewith and noting a value of the measurand for each measurement session, thus allowing compilation of a data set (D) of data pairs (Pi, Mi), where 1≦i≦N;employing a statistical Blind Source Separation technique to automatically process the data set (D) and spatially resolve the data set into a result set (R) of imaging pairs (Qk, Lk), in which an imaging quantity (Q) having a value Qk is associated with a discrete depth level Lk referenced to the surface S. 2. The method according to claim 1, wherein:successive values of the beam parameter (P) associated with successive measurement sessions differ from one another by a substantially constant increment (ΔP); andsuccessive discrete depth levels in the obtained result set (R) are separated from one another by a substantially constant distance increment (ΔL). 3. The method as claimed in claim 1, wherein:the beam parameter (P) is selected from the group comprising beam energy, beam convergence angle and beam focal depth;the stimulated radiation is selected from the group comprising secondary electrons, backscattered electrons and X-ray radiation; andthe measurand (M) is selected from the group comprising intensity and current. 4. The method as claimed in claim 1, wherein the imaging quantity (Q) is selected from the group comprising intensity, current, angular distribution and energy spread. 5. The method according to claim 1, wherein the statistical Blind Source Separation technique is selected from the group comprising Principal Component Analysis (PCA) and Independent Component Analysis (ICA). 6. The method according to claim 5, wherein:the statistical Blind Source Separation technique is PCA;the beam parameter (P) comprises beam energy, whereby successive measurement sessions have a larger associated value of this parameter;the stimulated radiation comprises secondary electrons and the measurand (M) comprises current;the imaging quantity (Q) comprises intensity;an alignment transform is performed on the elements of the data set D so as to laterally align and/or scale them;an iterative series of data processing steps is performed in which, for each integral value of k in the range [2, . . . , N]:PCA decomposition is applied to the subset of data pairs (Pi, Mi), i=1, . . . , k;an independent component of this decomposition having least correlation to said subset is identified, and the independent component is associated with level Lk beneath the surface S,whereby the result set R=((Q1, L1), . . . , (QN, LN)) is generated for a spectrum of discrete levels Lk progressing from the surface (S) into the sample. 7. The method according to claim 6, wherein:components of the PCA decomposition are relatively weighted using a weight factor that, for a given component, is equal or proportional to the reciprocal of the Eigenvalue for that component; andthe result set (R) is augmented by adding to the elements of the result set (R) a factor corresponding to a matrix response of the sample. 8. The method according to claim 6, wherein said PCA decomposition is a Karhunen-Loeve transform operation. 9. The method according to claim 1, wherein the obtained result set (R) is post-processed using statistical noise reduction and restoration techniques. 10. The method according to claim 1, wherein the result set (R) yields information regarding both a geometry and a material composition of the sample. 11. The method according to claim 1, wherein:said steps of irradiating the surface (S) of the sample, detecting stimulated radiation emitted by the sample to obtain the data set (D), and applying a statistical Blind Source Separation technique to process the data set (D), are comprised in a computational slicing step; andsaid computational slicing step is combined with a physical slicing step, whereby a physical material removal method is used to physically remove a layer of material from the original surface (S), thereby revealing a newly exposed surface (S′). 12. The method as claimed in claim 11, wherein said physical material removal method is selected from the group comprising mechanical milling with a blade device, ion milling with an ion beam, and ablation with a beam of electromagnetic energy. 13. The method as claimed in claim 11, wherein said computational slicing step and said physical slicing step are alternately repeated in multiple iterations. 14. An apparatus constructed and arranged to carry out the method of claim 1. 15. An apparatus for investigating a sample using Scanning Electron Microscopy, the apparatus comprising:means for irradiating a surface (S) of the sample using a probing electron beam in a plurality (N) of measurement sessions, each measurement session having an associated beam parameter (P) value that is chosen from a range of such values and that differs between measurement sessions;means for detecting stimulated radiation emitted by the sample during each measurement session, associating a measurand (M) therewith and noting a value of the measurand for each measurement session, thus allowing compilation of, a data set (D) of data pairs (Pi, Mi), where 1≦i≦N;means for employing a statistical Blind Source Separation technique to automatically process the data set (D) and spatially resolve the data set into a result set (R) of imaging pairs (Qk, Lk), in which an imaging quantity (Q) having a value Qk is associated with a discrete depth level Lk referenced to the surface S. 16. The apparatus of claim 15, wherein:successive values of the beam parameter (P) associated with successive measurement sessions differ from one another by a substantially constant increment (ΔP); andsuccessive discrete depth levels in the obtained result set (R) are separated from one another by a substantially constant distance increment (ΔL). 17. The apparatus of claim 15, wherein:the beam parameter (P) is selected from the group comprising beam energy, beam convergence angle and beam focal depth;the stimulated radiation is selected from the group comprising secondary electrons, backscattered electrons and X-ray radiation;the measurand (M) is selected from the group comprising intensity and current;the imaging quantity (Q) is selected from the group comprising intensity, current, angular distribution and energy spread; andthe statistical Blind Source Separation technique is selected from the group comprising Principal Component Analysis (PCA) and Independent Component Analysis (ICA). 18. The apparatus of claim 17, wherein:the beam parameter (P) comprises beam energy, whereby successive measurement sessions have a larger associated value of this parameter;the stimulated radiation comprises secondary electrons;the measurand (M) comprises current;the imaging quantity (Q) comprises intensity;the statistical Blind Source Separation technique is PCA;the apparatus further comprising:means for performing an alignment transform on the elements of the data set D so as to laterally align and/or scale them;means for performing an iterative series of data processing steps comprising, for each integral value of k in the range [2, . . . , N]:applying PCA decomposition to the subset of data pairs (Pi, Mi), where i=1, . . . , k;identifying an independent component of the PCA decomposition having least correlation to said subset, andassociating the independent component with level Lk beneath the surface S,means for generating the result set R=((Q1, L1), . . . , (QN, Ln)) for a spectrum of discrete levels Lk progressing from the surface (S) into the sample. 19. The apparatus of claim 1, further comprising means for physically removing a layer of material from the original surface (S), thereby revealing a newly exposed surface (S′). 20. The apparatus of claim 19, wherein said means for physically removing a layer of material is selected from the group comprising:means for mechanical milling with a blade device,means for ion milling with an ion beam, andmeans for ablation with a beam of electromagnetic energy.