Non contact measuring method for three dimensional micro pattern in measuring object

• US 6,005,669 A
• Filed: 04/24/1998
• Issued: 12/21/1999
• Est. Priority Date: 10/24/1997
• Status: Expired due to Fees

• Current Assignee: Heui Jae Pahk, Sung Wook Cho
• Original Assignee: Heui Jae Pahk, Sung Wook Cho
• Inventors: Ahn, Woo Jung, Pahk, Heui Jae, Cho, Sung Wook
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US09/065,493
• Time in Patent Office: 606 Days
• Field of Search: 356/376, 356/372, 356/371, 356/359, 356/369, 356/357, 356/124, 356/360
• US Class Current: 356/602
• CPC Class Codes: G01B 11/02 for measuring length, width or thickness G01B11/08 takes precedence
• CPC Class Codes: G01B 11/0608 Height gauges

Abstract

A non-contacting measuring method for three dimensional micro pattern in a measuring object is disclosed. Three dimensional micro pattern of the surface of the measuring object is measured using blur of light. For measurement, a mechanism of an optical window with a slit is inserted between light source and the measuring object. The blurred image is captured by charge coupled device sensor based image frame grabber, and is analyzed in personal computers. All the values of the relative height differences are obtained in overall scanning measurement area of the measuring object. The relative height differences are the distances from the reference position to the other positions. The reference position is selected when its image is sharp in focus on the screen. At this time, images of the other positions except the reference position are blurred out of focus on the screen. Also, from the law of geometric optics and the geometric similarity of triangles, the relation equation between the height difference and the ratio of blurred image size to sharp image size can be constructed. When the size of the image of the reference position and the sizes of the images with the blurred image of the other positions are measured, all the height differences between the reference position and the other position can be calculated if the coefficients of the relation equation are evaluated.

Claims

1. A non-contacting measuring method for three dimensional micro pattern in a measuring object comprising the steps of:

(a) forming light emitted from a source into slit-shaped light by means of an optical window;

(b) applying the slit-shaped light to a first scanning measurement line with a micro width of the measuring object with a plurality of surfaces which have step heights wherein each of the surfaces has three dimensional micro depth profile;

(c) finding a reference surface among the surfaces by passing the light reflected from the surfaces through a lens and capturing images of the surfaces on a screen wherein the reference surface is in focus on the screen;

(d) finding a reference position in the reference surface whose image is sharp in focus on the screen wherein images of the other positions except the reference position are blurred out of focus on the screen;

(e) measuring a size of the sharp image corresponding to the reference position and sizes of the images with blurred image corresponding to the other positions;

(f) calculating ratio values of the sizes of the images with the blurred image to the size of the sharp image corresponding to the reference position;

(g) obtaining relative height differences between the reference position and the other positions;

(h) establishing a relation equation between ratio value and relative height difference by the ratio values of the sizes of the images with the blurred image to the size of the sharp image and the relative height differences between the reference position and the other positions wherein the relation equation between the ratio value and the relative height difference is given as δ

=C₁ -C₂ /k, where C₁ =α

when α

is distance from the lens to the reference position of the reference surface and C₂ =α

·

b₂ /b₁ when b₁ is a distance from the sharp image to the lens and b₂ are distances from the blurred image to the lens;

(i) obtaining all the values of the relative height differences between the reference position and the other positions by the established relation equation between the ratio value and the relative height difference; and

(j) repeating said steps (f) and (i) while moving the measuring object until obtaining all the values of the relative height differences in overall scanning measurement area of the measuring object.

2. A method as recited as claim 1, wherein the reference surface is located at a lowermost height among the surfaces in said step of finding the reference surface among the surfaces, and the reference position is located at a lowermost height in the reference surface in said step of finding the reference position in the reference surface.

3. A method as recited as claim 1, wherein all the values of the relative height differences between the reference position and all the other positions in the scanning measurement area are simultaneously obtained along each scanning measurement line of the measuring object by the established relation equation between the ratio value and the relative height difference and by a line-scanning technique.

4. A non-contacting measuring method for three dimensional micro pattern in a measuring object comprising the steps of:

(a) forming light emitted from a source into slit-shaped light by means of an optical window;

(b) applying the slit-shaped light to a first scanning measurement line with a micro width of the measuring object;

(c) finding a reference position by passing the light reflected from the measuring object through a lens and capturing images on a screen whose image is sharp in focus on the screen wherein images of the other positions except the reference position are blurred out of focus on the screen;

(d) measuring a size of the sharp image corresponding to the reference position and sizes of the images with blurred image corresponding to the other positions;

(e) calculating ratio values of the sizes of the images with the blurred image to the size of the sharp image corresponding to the reference position;

(f) obtaining relative height differences between the reference position and the other positions;

(g) establishing a relation equation between ratio value and relative height difference by the ratio values of the sizes of the images with the blurred image to the size of the sharp image and the relative height differences between the reference position and the other positions wherein the relation equation between the ratio value and the relative height difference is given as δ

=C₁ -C₂ /k, where C₁ =α

when α

is distance from the lens to the reference position of the reference surface and C₂ -α

·

b₂ /b₁ when b₁ is a distance from the sharp image to the lens and b₂ are distances from the blurred image to the lens; and

(h) obtaining all the values of the relative height differences between the reference position and all the other positions in overall scanning measurement area by the established relation equation between the ratio value and the relative height difference.

5. A non-contacting measuring method for three dimensional micro pattern in a measuring object comprising the steps of:

(a) forming light emitted from a source into slit-shaped light by means of an optical window;

(b) applying the slit-shaped light to a master specimen where all the relative height differences are known;

(c) selecting a reference position by passing the light reflected from the master specimen through a lens and capturing images on a screen whose image is sharp in focus on the screen wherein images of the other positions except the reference position are blurred out of focus on the screen;

(d) measuring a size of the sharp image corresponding to the reference position and sizes of the images with blurred image corresponding to the other positions;

(e) calculating ratio values of the sizes of the images with the blurred image to the size of the sharp image corresponding to the reference position;

(f) obtaining relative height differences between the reference position and the other positions which are known;

(g) establishing a relation equation between ratio value and relative height difference by the ratio values of the sizes of the images with the blurred image to the size of the sharp image and the relative height differences between the reference position and the other positions wherein the relation equation between the ratio value and the relative height difference is given us δ

=C₁ C₂ /k, where C₁ =α

when α

is distance from the lens to the reference position of the reference surface and C₂ =α

·

b₂ /b₁ when b₁ is a distance from the sharp image to the lens and b₂ are distances from the blurred image to the lens; and

(h) obtaining all the values of the relative height differences between a reference position whose image is sharp in focus and all the other positions whose images are blurred out of focus in overall scanning measurement area of the measuring object by the established relation equation between the ratio value and the relative height difference and ratio values of sizes of the images with blurred image to a size of the sharp image corresponding to the reference position.