USING ICP MASS SPECTROSCOPY WITH ELECTROTHERMAL ATOMIZATION

A NOVEL APPROACH TO SENSITIVE DIRECT ANALYSIS OF III-V COMPOUNDS AND OTHER SEMICONDUCTOR MATERIALS IS PROPOSED. FEASIBILITY DEPENDS ON THE SUCCESSFUL MODIFICATION OF HARDWARE AND SOFTWARE OF A COMMERCIALLY AVAILABLE INDUCTIVELY COUPLED PLASMA MASS SPECTROMETER (ICP/MS). FOR ROUTINE BULK ANALYSIS OF SEMICONDUCTOR SUBSTRATES, EPITAXIAL FILMS, DOPANTS, OR SOURCE MATERIALS, THE FOLLOWING CONCEPT IS PROPOSED. A SPECIALLY DESIGNED ELECTROTHERMAL ATOMIZER WOULD CONTAIN THE SOLID OR LIQUID SAMPLE AND CUSTOM SOFTWARE WOULD BE WRITTEN TO COLLECT ANALYTICAL DATA AS A FUNCTION OF THE THREE DIMENSIONS OF ION COUNTS, ATOMIC MASS, AND FURNANCE TEMPERATURE. BY THE PROPER CHOICE OF THE CARRIER GAS PASSING OVER THE SAMPLE, SEPARATION OF THE VARIOUS ELEMENTS CONTAINED IN THE SAMPLE SHOULD BE ACHIEVABLE IN THE THIRD DIMENSION OF TEMPERATURE. SPATIAL SEPARATION IN THE TEMPERATURE DIMENSION COULD BE USED TO ELIMINATE MANY MASS INTERFERENCE. DETECTION LIMITS FOR MOST ELEMENTS OF THE PERIODIC CHART ARE EXPECTED TO RANGE BETWEEN 0.01 AND 0.1 PPB. DEPTH PROFILES SHOULD BE ACHIEVABLE BY MASKING OFF THE AREA TO BE PROTECTED AND MOUNTING THE SAMPLE INSIDE THE ATOMIZER TUBE. THE CARRIER GAS WOULD THEN BE PASSED OVER THE SURFACE OF THE MOUNTED SAMPLE AT A TEMPERATURE SUFFICIENT TO ATOMIZE THE ELEMENTS OF INTEREST. THE TIME DIMENSION OF THIS THREE DIMENSIONAL DATA SET OF ION COUNTS, ATOMIC MASS, AND TIME COULD BE CALIBRATED TO DEPTH AND A PROFILE OF EACH ELEMENT AND ITS ISOTOPE RATIOS COULD BE CREATED WITH SUB-PPB SENSITIVITY.