Patent CA-2305477-A1 (CA)
Inventor: MANDELIS ANDREAS
IPC: G01R31/311
Filed: 2000-04-17
Abstract: There is provided a metrologic methodology, useful for in-situ, non- destructive monitoring, comprising of combination of novel signal generation and analysis techniques , computational software, and laser infrared radiometric instrumental configurations for measuring thermal and electronic properties of industrial semiconductor wafers and engineering materials. The combination of the frequency sweep (Chirp) and conventional frequency scan techniques fo r rapid measurement of electronic and thermal transport properties of semiconductor and engineering materials/devices involves providing a sample such as a semiconductor wafer or other engineeri ng material, irradiating the sample with an excitation source (laser), generating a square-wave chirp  from a dual-channel fast Fourier transform (FFT) analyzer to drive an acousto-optic modulator and produce periodic frequency sweeps (Chirps) of the laser beam in the range including (but not confined to) do to 100 kHz, generating a plank-radiation (infrared radiometric) signal in an instrumentation of transfer function, H(f), by fitting the frequency-scan data from a reference sample t o a theoretical model, storing the data from the arbitrary sample in a personal computer, fitting t he obtained (amplitude and phase) radiometric signal from arbitrary semiconductor samples to the same theoretical model, corrected for the instrumental transfer function to obtain the thermal and/or electronic parameters of the said samples. The common rejection mode (dual pulse) method for detectio n of very weak inhomogeneities among materials involves: providing a sample of the material , irradiating the sample with an optical or otherwise excitation source of thermal waves, generating a real time periodic waveform consisting of two incident pulses, detecting the signal (phototherm al or any signal generation principle) and feeding it to a lock-in amplifier. This methodolog y is not confined to thermal-wave signal generation, but encompasses all manner of modulated signals, such as acoustic, luminescent optical, ultrasonic, X-rays and other signal generation methods.  The multiparameter computational method for determining a unique set of thermal and electronic parameters of industrial semiconductor (i.e. Si) wafers, from frequency domain measurements, involves : providing a semiconductor wafer (or sample), irradiating the sample with a periodic optical (laser) or other free- carrier raising energy source generating a photothermal signal, detecting sa id photothermal (radiometric or otherwise) signal, imputting said signal to a lock-in amplifier, storing the frequency scans in a personal computer, applying the multiparameter fitting procedure (by means of an electronic sheet or any other code program, i.e C, Fortran).The depth profilometry and roughness elimination method for determining thermal diffusivity profiles of rough samples involves: (a) providing a sample of process-related inhomogeneous material or multi-layer structures; (b) irradiating the sample with a periodically excited source (laser); (c) detecting the photothermal frequency sweep signal with a lock-in amplifier and storing the experimental  data in a personal computer; (d) processing the experimental data with a heuristic approach to roughness so as to eliminate the effects of roughness; (e) applying to the processed data the theoretical/computational model to reconstruct the thermal diffusivity profile.