Eliminating Inline Positional Errors for Four-Point Resistance Measurement

• US 20080294365A1
• Filed: 10/17/2006
• Published: 11/27/2008
• Est. Priority Date: 10/17/2005
• Status: Active Grant

• Current Assignee: CAPRES A/S (KLA Corporation)
• Original Assignee: CAPRES A/S (KLA Corporation)
• Inventors: Hansen, Torben M.
• Granted Patent: US 7,852,093 B2
• Time in Patent Office: Days
• US Class Current: 702/107
• CPC Class Codes: G01R 27/08 Measuring resistance by measuring both voltage and current

Abstract

A method for calculating correction factors for reducing positional errors in resistance measurements using a probe having four probe arms includes: positioning the probe anus to contact a test sample; selecting a first set of first and second probe arms and a second set of third and fourth probe arms; applying a first current from the first to the second probe arms of the first set, through the sample; detecting a first voltage between the third and fourth probe arms of the second set; calculating a first resistance as a ratio of the first voltage and the first current; selecting a third set of first and second probe arms including no more than one of the probe arms of the first set, and a fourth set of third and fourth probe arms including no more than one of the probe arms of the second set; applying a second current from the first to the second probe arms of the third set, through the sample; detecting a second voltage at the third and fourth probe arms of the fourth set; calculating a second resistance as a ratio of the second voltage and the second current; and calculating a correction factor based on the first and second resistances.

Claims

1. A method for calculating a correction factor for reduction of positional errors in resistance measurements using a four-point probe, said four-point probe having a body and four probe anus each including a probe, said probe arms extending parallel from said body, said four-point probe including electrical contact points for establishing electrical contact between said probes of said probe arms and a test apparatus operable for transmitting and receiving electrical signals, said method comprising said steps of:

(a) positioning said probe arms in contact with a surface of a test sample,

(b) selecting a first set comprising a first and a second probe arm and a second set comprising a third and a fourth probe arm,

(c) applying a first current from said test apparatus through said first probe arm of said first set to said second probe arm of said first set said first current propagating through said test sample,

(d) detecting a first induced voltage between said third and fourth probe arms of said second set,

(e) calculating a first four-point resistance, R_first, being a ratio of said first voltage and said first current,

(f) selecting a third set comprising a first and a second probe arm, wherein said third set includes no more than one of said probe arms of said first set, and a fourth set comprising a third and a fourth probe aim wherein said fourth set includes no more than one of said probe arms of said second set,

(g) applying a second current from said test apparatus through said first probe arm of said third set to said second probe arm of said third set, said second current propagating through said test sample,

(h) detecting a second induced voltage at said third and fourth probe arms of said fourth set,

(i) calculating a second four-point resistance, R_second, being a ratio of said second voltage and said second current, and

(j) calculating a correction factor based on said first and second four-point resistances.

2. The method according to claim 1, wherein said method further includes:

(k) performing a measurement for calculating a resistance of said test sample using said correction factor.

3. The method according to claim 1, wherein said four-point probe is moved to a remote position and said steps (a) through (j) are performed for the remote position.

13. A test apparatus, comprising:

a first holder configured holding a test sample;

a second holder configured for holding a test probe;

a memory device operable for storing a computer implementation of the method according to claim 1; and

a microprocessor operable for executing said computer implementation.

4. A method for performing resistance measurements using four-point probes using a correction factor for reduction or elimination of positional errors, said four-point probe having a body and four probe arms each including a probe, said probe arms extending parallel from said body, said four-point probe including electrical contact points for establishing electrical contact between said probes of said probe arms and a test apparatus operable for transmitting and receiving electrical signals, said method comprising said steps of:

(a) positioning said probe arms in contact with a surface of a test sample,

(b) selecting a first set comprising a first and a second probe arm and a second set comprising a third and a fourth probe arm,

(c) applying a first current from said test apparatus through said first probe arm of said first set to said second probe arm of said first set, said first current propagating through said test sample,

(d) detecting a first induced voltage at said third and fourth probe arms of said second set,

(e) calculating a first four-point resistance, R_first, being a ratio of said first voltage and said first current,

(f) selecting a third set comprising a first and a second probe arm, wherein said third set includes no more than one of said probe arms of said first set, and a fourth set comprising a third and a fourth probe arm wherein said fourth set includes no more than one of said probe arms of said second set,

(g) applying a second current from said test apparatus through said first probe arm of said third set to said second probe arm of said third set, said second current propagating through said test sample,

(h) detecting a second induced voltage between said third and fourth probe arms of said fourth set,

(i) calculating a second four-point resistance, R_second, being a ratio of said second voltage and said second current,

(j) calculating a correction factor based on said first and second four-point resistances, and

(k) calculating a resistance of said test sample using said correction factor.

5. The method according to claim 4, wherein said four-point probe is moved to a remote position and said steps (a) through (k) are performed for the remote position.

14. A test apparatus, comprising:

a first holder configured for holding a test sample;

a second holder configured for holding a test probe;

a memory device operable for storing a computer implementation of the method according to claim 4; and

a microprocessor operable for executing said computer implementation.

6. (canceled)

7. A method for obtaining a characteristic electrical property of a test sample by using a probe having a body and at least four probe arms each including a probe tip, said characteristic electrical property including a resistance property, said probe arms extending parallel from said body, said probe including electrical contact points for establishing electrical contact between said probe tips and a test apparatus operable for transmitting and receiving electrical signals to and from said probe tips, said method comprising the following steps:

(a) positioning said probe tips in contact with a surface of a test sample,

(b) selecting a subset of four probe tips for performing a measurement by applying a current between a first set of two probe tips and determining a voltage between a second set of two probe tips not including any of the probe tips of said first set, and performing said measurement for all combinations of sets of probe tips,

(c) establishing a model value of said characteristic electrical property,

(d) calculating model data for said characteristic electrical property based on said model value,

(e) if said measurement and said calculated model data do not converge, establishing an adjusted model value and repeating step (d) using said adjusted model value, and

(f) if said measurement and said calculated model data do converge, extracting said characteristic electrical property from said model data.

8. The method according to claim 7, wherein said step (b) further comprises calculating a corrected value of one of said measurements.

9. The method according to claim 7, wherein said characteristic electrical property is selected from the group consisting of top-layer resistance, bottom-layer resistance, resistance-area product, and any combination thereof.

10. The method according to claim 7, wherein said model data is calculated using the formula

11. The method according to claim 7, wherein said method further includes performing a correction on one of said calculated model data.

15. A test apparatus, comprising:

a first holder configured for holding a test sample;

a second holder configured for holding a test probe;

a memory device operable for storing a computer implementation of the method according to claim 7; and

a microprocessor operable for executing said computer implementation.

12. (canceled)