Critical dimension measuring method and equipment thereof

• US 5,555,319 A
• Filed: 05/03/1994
• Issued: 09/10/1996
• Est. Priority Date: 05/06/1993
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Tsubusaki, Koji, Komatsu, Fumio
• Primary Examiner(s): Mancuso, Joseph
• Application Number:
  US08/237,169
• Time in Patent Office: 861 Days
• Field of Search: 382/145, 382/203, 382/168, 382/169, 382/170, 250/311, 250/492.2, 356/379, 364/564
• US Class Current: 382/170
• CPC Class Codes: G06V 10/44 Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components

Abstract

A critical dimension measuring equipment includes a filtering circuit for inputting image data from a SEM and performs spatial filtering processing of the image data, a histogram processing circuit implements histogram processing of the image data, a threshold value detection circuit obtains a threshold value based on a discriminant criteria method, a three-value conversion processing circuits implements three-value conversion of the image data based on the threshold value, a first calculation circuit obtains the area and perimeter of the bottom section of the pattern based on this data, a second calculation circuit obtains the diameters of the patterns based on this data, and a critical shape recognition circuit decide whether the pattern is circular or elliptical based on the critical diameter, calculates the diameter of the circle based on the area if the pattern is circular, and calculating the major axis and the minor axis of the ellipse based on the area and the perimeter if the pattern is elliptical.

Claims

1. Critical dimension measuring equipment comprising:

irradiating means for irradiating an electron beam onto a measured pattern to be measured;

detecting means for detecting a secondary and reflected electron reflected from the measured pattern;

filtering means for receiving image data as the secondary and reflected electron detected by the detecting means and implementing a spatial filtering processing of the image data and storing the result of the spatial filtering processing into a first memory;

histogram processing means for receiving the image data which been obtained after the spatial filtering processing stored in the first memory, implementing histogram processing of the image data, and storing the result of the histogram processing into a second memory;

threshold value detection means for receiving the result of the histogram processing stored in the second memory, generating a threshold value by automatically separating classes in a histogram obtained by the histogram processing based on the discriminant criteria method, and storing the result generated by the threshold value detection means into a third memory;

three-value conversion processing means for receiving the threshold value stored in the third memory, implementing three-value conversion of the image data stored in the first memory obtained after spatial filtering processing based on the threshold value, and storing the result obtained by the three-value conversion means into a fourth memory;

first calculation means for receiving image data stored in the fourth memory obtained after three-value conversion processing, obtaining the area and perimeter of the bottom section of the pattern based on this data, and storing the result obtained by the first calculation means into a fifth memory;

second calculation means for receiving the area and the perimeter of the bottom section of the pattern stored in the fifth memory, obtaining the diameters of the patterns based on this data, and storing the result obtained by the second calculation means into a sixth memory; and

pattern shape recognition means for automatically deciding whether the pattern is circular or elliptical based on the pattern diameter stored in the sixth memory, calculating the diameter of the circle based on the area if the pattern is circular, and calculating a major axis and a minor axis of the ellipse based on the area and the perimeter if the pattern is elliptical.

2. The critical dimension measuring equipment as claimed in claim 1, wherein the pattern shape recognition means decides whether the pattern is a circle shape or an elliptical shape by using a rate (d1/d2) of a pattern radius (d1) obtained from the area of the pattern stored in the fifth memory and a critical radius (d2) obtained from a perimeter of a bottom section of the pattern stored in the fifth memory.

3. A critical dimension measuring method comprising:

a first process for performing a spatial filtering processing of Scanning Electron Microscope (SEM) image data obtained by a scanning electron beam on a pattern to be measured;

a second process for performing a histogram processing of image data obtained after spatial filtering processing;

a third process for obtaining a threshold value by automatically separating classes obtained by the histogram processing based on a discriminant criteria method;

a fourth process for performing a three-value conversion of the image data obtained after spatial filtering processing based on the threshold value;

a fifth process for obtaining the area and perimeter of the bottom section of the pattern based on the image data obtained after the three-value conversion process;

a sixth process for obtaining the diameters of the patterns based on the area and perimeter of the bottom section of the pattern; and

a seventh process for automatically deciding whether the pattern is circular or elliptical based on the pattern diameter, calculating the diameter of the circle based on the area if the pattern is circular, and calculating the major axis and the minor axis of the ellipse based on the area and the perimeter if the pattern is elliptical.