Method and device for measuring the thickness of a slightly doped layer in a semiconductor slice

• Main Author: JEAN-BAPTISTE QUOIRIN
• Format: Patent
• Language: English; French
• Published: 26.07.1984
• Edition: 4
• Subjects: MEASURING; MEASURING ANGLES; MEASURING AREAS; MEASURING ELECTRIC VARIABLES; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS; MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS; MEASURING MAGNETIC VARIABLES; PHYSICS; TESTING

In order to measure the thickness of a slightly doped layer superimposed on a highly doped layer in a semiconductor slice, there is applied, by the intermediary of a drop of mercury with a contact surface which is well known and calibrated by a probe 18, a variable voltage V between the two faces of the slice; a Schottky contact is thus formed; the slope of the current i variation in the probe in forward bias is measured, which gives the electrical resistance offered by the slice in the direction of its thickness; there is also measured the slope of the variation of the inverse square of the capacitance C of the diode formed between the faces of the slice in reverse bias, which gives an indication of the resistivity of the slightly doped layer. The thickness of the slice is derived from this by a computation using the product of these two slopes. POUR MESURER L'EPAISSEUR D'UNE COUCHE PEU DOPEE SUPERPOSEE A UNE COUCHE FORTEMENT DOPEE DANS UNE TRANCHE SEMICONDUCTRICE, ON APPLIQUE, PAR L'INTERMEDIAIRE D'UNE GOUTTE DE MERCURE DE SURFACE DE CONTACT BIEN CONNUE CALIBREE PAR UNE SONDE 18, UNE TENSION VARIABLE V ENTRE LES DEUX FACES DE LA TRANCHE; ON REALISE AINSI UN CONTACT SCHOTTKY; ON MESURE LA PENTE DE VARIATION DU COURANT I DANS LA SONDE EN POLARISATION DIRECTE, QUI DONNE LA RESISTANCE ELECTRIQUE OPPOSEE PAR LA TRANCHE DANS LE SENS DE SON EPAISSEUR; ON MESURE AUSSI LA PENTE DE VARIATION DE L'INVERSE DU CARRE DE LA CAPACITE C DE LA DIODE PRESENTEE ENTRE LES FACES DE LA TRANCHE EN POLARISATION INVERSE, QUI DONNE UNE INDICATION DE LA RESISTIVITE DE LA COUCHE PEU DOPEE. ON EN DEDUIT L'EPAISSEUR DE LA TRANCHE PAR UN CALCUL FAISANT INTERVENIR LE PRODUIT DE CES DEUX PENTES.