METHOD OF DETERMINING THE SHEET RESISTANCE AND MEASURING DEVICE THEREFOR

• US 3,735,254 A
• Filed: 06/03/1971
• Issued: 05/22/1973
• Est. Priority Date: 06/06/1970
• Status: Expired due to Term

• Current Assignee: Petrus Johannes Wilhelmus Severin
• Original Assignee: Petrus Johannes Wilhelmus Severin
• Inventors: Severin, Petrus Johannes Wilhelmus
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US05/149,533
• Time in Patent Office: 719 Days
• Field of Search: 324/64,158R,158D,158P
• US Class Current: 324/716
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00
• CPC Class Codes: G01R 31/2637 for testing other individual devices G01R31/2608 - G01R31/2632, G01R31/27 take precedence

Abstract

The invention relates to the determination of the sheet resistance (resistance per square) of a layer which changes into a second layer via a rectifying junction. In this determination, four or more electrodes are arranged on the layer to be measured, for example on a straight line. In a first step, a current is conveyed through two electrodes at a comparatively low voltage and the voltage associated with said current is determined between two other electrodes as is usual in a normal four point measurement. In a second step of the measurement the same measurement is carried out without changing the place of the electrodes but while changing a current supply and a voltage take-off electrode, with the difference that at least electrodes for current supply or voltage measurement have a different distance as compared with that of the first measurement. The sheet resistance or a quantity associated therewith is obtained in an accurate manner from the results.

Claims

1. A method of determining the sheet resistance (resistance per square) or a quantity associated with the sheet resIstance, in particular in the manufacture of a semiconductor device, in which at least four electrodes are placed at a distance form each other on a layer to be measured, said layer changing into a second layer via a rectifying junction, in particular a p-n junction, a current being conveyed between two electrodes, the voltage associated with said current being determined between two other electrodes, the sheet resistance or a quantity associated with the sheet resistance being determined from the results of the measurements, characterized in that, after arranging the electrodes on the layer to be measured, at least two such measurements are carried out with the same arrangement of the electrodes on the layer and that said measurements are carried out with a voltage difference between the two current-conveying electrodes, in which across the rectifying junction and the p-n junction, respectively, a voltage difference is formed in a range of voltages across the rectifying junction the p-n junction, respectively, in which same behaves as a substantially constant resistance, preferably near the zero point of the current-voltage characteristic, and that during the first measurement a current is conveyed through two electrodes, hereinafter termed the first pair of electrodes, while the voltage is determined between two other electrodes, hereinafter termed second pair of electrodes, and that during the second measurement four electrodes are chosen having a different distance between at least two electrodes relative to the first measurement, in which a current is conveyed through two of these electrodes, while the voltage is determined between the two remaining electrodes of said electrodes, the sheet resistance or a quantity associated therewith being determined from the results of said measurements.

2. A method as claimed in claim 1, characterized in that four electrodes are arranged on the layer to be measured and that during the second measurement a current is conveyed through an electrode of the first pair of electrodes and an electrode of the second pair of electrodes, the voltage being determined between the remaining electrodes of the first and the second pair of electrodes, the sheet resistance of a quantity associated therewith being determined from the results of the two measurements.

3. A method as claimed in claim 1, characterized in that the contact resistance between the two layers is determined from the results of the measurements.

4. A method as claimed in claim 2, characterized in that after the second measurement a third such measurement is carried out with the same arrangement of the electrodes, a pair of electrodes being constituted by the electrode through which in the two preceding measurements current was conveyed and the electrode which was used in the two preceding measurements to determine the voltage, the two remaining electrodes constituting the second pair of electrodes, a current being conveyed through the electrodes of one of the two said pairs of electrodes, the voltage associated with said current being determined between the electrodes of the other pair of electrodes, information on the lateral uniformity of the layer and junction being obtained from the results of the three measurements.

5. A method as claimed in claim 2, characterized in that four punctiform electrodes are arranged on a surface of the layer to be measured, the electrodes at the surface being arranged on a straight line and at equal distances between two successive electrodes.

6. A method as claimed in claim 5, characterized in that the first pair of electrodes is constituted by the two outermost electrodes, the second pair of electrodes being constituted by the two innermost electrodes, the sheet resistance or a quantity associated therewith being determined from the results in cooperation with a previously composed table.

7. A method as claimed in claim 1 characterized in that the measurements are carried out at such low voltages between the current conveying electroDes at which the voltage across the junction is lower than KT/q and preferably lower than KT/3q.

8. A method as claimed in claim 1, characterized in that a method is used on a layer of one conductivity type which is provided on a layer of the opposite conductivity type.

9. A method as claimed in claim 8, characterized in that the method is used on a thin and high-ohmic layer, the thickness of which is in particular smaller than 6 micron and the resistivity larger than 5 ohm cm.

10. A method as claimed in claim 8, characterized in that the method is used on a layer of one conductivity type on a substrate of the opposite conductivity type which has been conducted along as a test body during providing a layer of one conductivity type on a substrate of the same conductivity type, in which in the same circumstances a layer of one conductivity type is formed on the test body and on the substrate of one conductivity type, the sheet resistance or a quantity associated therewith of the layer of one conductivity type on the substrate of the same conductivity type being determined from the result of the measurement at the test body.

11. A method as claimed in claim 8, characterized in that the method is applied to a layer of one conductivity type on a substrate of the opposite conductivity type which has been conducted along as a test body during providing a layer of one conductivity type on a substrate of the opposite conductivity type, in which at the interface between the layer and the substrate are present locally buried layers of one conductivity type, the sheet resistance or a quantity associated therewith of the layer of one conductivity type on a substrate of the opposite conductivity type with the buried layers of one conductivity type locally present at the interface between the layer and the substrate being determined from the result of the measurements at the test body.

12. A measuring device for use in the method as claimed in claim 1 comprising at least four electrodes at a distance from each other in which a current can be conveyed through two electrodes and the voltage can be determined between two other electrodes, characterized in that means are present by which a current can be conveyed through two electrodes, while the voltage can be determined between two other electrodes, said four electrodes constituting a first electrode combination, and by which a second combination of four electrodes can then be chosen with a different distance between at least two electrodes relative to the first combination of four electrodes, in which a current can be conveyed through two electrodes of the second combination, while the voltage can be determined between the two remaining electrodes of the second combination.