Method of measuring a line edge roughness of micro objects in scanning microscopes

• US 20030190069A1
• Filed: 04/03/2002
• Published: 10/09/2003
• Est. Priority Date: 04/03/2002
• Status: Active Grant

• Current Assignee: Arkady Nikitin, Dmitriy Yeremin
• Original Assignee: Arkady Nikitin, Dmitriy Yeremin
• Inventors: Nikitin, Arkady, Yeremin, Dmitriy
• Granted Patent: US 6,909,791 B2
• Time in Patent Office: Days
• US Class Current: 382/145
• CPC Class Codes: G06T 2207/10056 Microscopic image
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: G06T 7/73 using feature-based methods
• CPC Class Codes: H01J 2237/2815 Depth profile

Abstract

A line edge roughness of micro objects is determined in a microscope by corresponding scanning and determination of deviations of points of the edge from a straight line.

Claims

1. A method of determining a line edge roughness of a micro object, comprising the steps of orienting a micro object in a microscope so that an edge of an object to be analyzed is non parallel to a direction of a scan line which is an axis X of an image;

line-by-line scanning of the object to be measured with electron beam and measuring of a dependency of a video signal S from a coordinate x along a scanning line as a function S(x) for each line;

determining a coordinate of an edge X_E on the function S(x) for each line to form a set of values X_E(i) wherein (i) is a number of line;

approximation of said set of values X_E(i) with a linear function and calculation of parameters A and B in an equation;

X(i)=A*i+B,

which approximates the set of values X_E;

calculation for each line an individual deviation Δ

x(i) of a position of an edge from a straight line along a direction of the scan (axis x);

Δ

x(i)=X(i)−

X_E(i);

wherein X(i) is an X coordinate of a line of intersection of an approximating line with a scan line having number (i);

calculating for each scan line an individual deviation Δ

l(i) of a position of the edge from a straight line in a direction of a perpendicular line to the approximating straight line in accordance with the formula;

2. A method as defined in claim 1, and further comprising processing including finding maximum positive and negative deviations among the values Δ

l(i).

3. A method as defined in claim 1;

and further comprising processing including characterizing a line edge roughness by a single numeral selected from the group consisting of an average deviation and an average square deviation.

4. A method as defined in claim 1;

and further comprising processing includes forming graphs of a dependency of Δ

l(i) from a line number (i).

5. A method as defined in claim 1;

and further comprising processing including analyzing a spectral oscillation Δ

l(i) and calculating of characteristic space frequencies of oscillations.

6. A method of determining a line edge roughness of a micro object along a lower line of a trapezoidal section, comprising the steps of orienting a micro object in a microscope so that an edge of an object to be analyzed is non parallel to a direction of a scan line which is an axis X of an image;

line-by-line scanning of the object to be measured with electron beam and measuring a dependency of a video signal S from a coordinate x along a scanning line as a function S(x) for each line;

determining a coordinate of an edge X_E on the function S(x) for each line by finding on a video signal S(x) of two pronounced maximums located on edges of an object, selecting on each maximum working slopes which adjoin a lower line of a trapezoidal cross-section so that for objects with trapezoidal ledges these are exterior slopes and for objects in form of trenches these are interior slopes, on the working slope of each left and right maximum finding reference points as points where an absolute value of a derivative of the video signal has a maximum value and considering abscissas of such reference points as coordinates of an edge of the trapezoidal object along a lower line of its cross-section;

approximating a set of values of X_E(i) with a linear function and calculating parameters A and B with equation;

X(i)=A*i+B

which approximates the set of values X_E calculating individually a deviation Δ

x(i) of a position of the edge from a straight line for each line along the direction of the scan line (axis X)

Δ

x(i)=X(i)−

X_E(i),

wherein X(i) is a coordinate of a point of intersection of the approximating straight line with the scan line having the number (i);

calculating of an individual deviation Δ

l(i) of position of edge from a straight line for each scan line in direction of a perpendicular to the approximating straight line in accordance with the formula

7. A method as defined in claim 6;

and further comprising processing including finding maximum positive and negative deviations among the values Δ

l(i).

8. A method as defined in claim 6;

and further comprising processing including characterizing a non straight nature of an edge by a single numeral selected from the group consisting of a mean deviation and a mean square deviation.

9. A method as defined in claim 6;

and further comprising processing includes forming graphs of a dependency of Δ

l(i) from a line number (i).

10. A method as defined in claim 6;

and further comprising processing including analyzing a spectral oscillation Δ

l(i) and calculating of characteristic space frequencies of oscillations.