Method for non-destructive, non-contact measurement of dielectric constant of thin films

• US 5,528,153 A
• Filed: 11/07/1994
• Issued: 06/18/1996
• Est. Priority Date: 11/07/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Taylor, Kelly J., Hsu, Wei-Yung
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US08/335,030
• Time in Patent Office: 589 Days
• Field of Search: 324/661, 324/662, 324/663, 324/671
• US Class Current: 324/671
• CPC Class Codes: G01R 27/2623 Measuring-systems or electronic circuits G01R27/2635, G01R27/2682 take precedence
• CPC Class Codes: G01R 31/2831 Testing of materials or semi-finished products, e.g. semiconductor wafers or substrates G01R31/318511 takes precedence; testing during manufacture H01L22/00
• CPC Class Codes: H01L 22/14 for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means

Abstract

A method for measurement of dielectric constant of a thin film is disclosed which is non-destructive and avoids contact with the film and the substrate carrying it. A first characteristic of the substrate is measured using a capacitance measuring device. Then, the thin film is deposited on the substrate. The first characteristic of the substrate is measured a second time after the film has been deposited. Thereafter, the true film thickness is measured. A ratio of the measurements made with the capacitance measuring device is then established with the actual thickness measurement. The dielectric constant can then be derived from a lookup table or graph calibrated for the tools being used for the measurements.

Claims

1. A method for non-contact, non-destructive measuring of the dielectric constant of a thin film on a semiconductor wafer comprising the steps of:

(a) measuring a first characteristic of said wafer using a capacitance measuring tool;

(b) depositing a thin film of a dielectric material on said wafer;

(c) measuring said first characteristic of said wafer with said thin film deposited thereon using a capacitance measuring tool;

(d) measuring the true thickness of said thin film; and

(e) forming a ratio of said measurement in step c minus the measurement in step a divided by the measurement in step d and deriving the dielectric constant for said deposited thin film from a calibrated table as a function of said ratio.

2. A method for non contact, nondestructive measuring of the dielectric constant of a thin film on a semiconductor wafer comprising the steps of:

placing a wafer between the probes of a capacitive measuring tool and measuring the capacitance C_i therebetween;

placing a thin film of a dielectric on said wafer;

placing the film coated wafer between the probes of a capacitive measuring tool and measuring the capacitance C_f therebetween;

measuring the true thickness t_d of the film deposited on the wafer; and

calculating the dielectric constant for said thin film using the formula

space="preserve" listing-type="equation">K=[1-β

(C.sub.f -C.sub.i)/C.sub.f C.sub.i t.sub.d ].sup.-1

where

β

is a constant which has been determined by experiment to validate said formula for the tools utilized to make said measurements.

3. A method for non-contact, nondestructive measuring of the dielectric constant of a thin film on a semiconductor wafer comprising the steps of:

measuring the thickness of said wafer T_prior using a capacitance measuring tool;

depositing a thin film of a dielectric material on said wafer;

measuring the thickness of said wafer with said thin film thereon T_post using a capacitance measuring tool;

measuring the true thickness T_actual of said thin film thereon; and

calculating the dielectric constant for said thin film using the formula

space="preserve" listing-type="equation">K=[1-α

(T.sub.post -T.sub.prior)/T.sub.actual ].sup.-1

where α

is a constant greater than zero and less than or equal to 1 which has been determined by experiment to validate said formula for the tools utilized to make said measurements.

4. The method of claim 3 wherein α

is approximately 0.91.