JP2005181058A - Aperture pattern evaluating method and semiconductor inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine accurately the quality of the hole bottom aperture of an aperture pattern. <P>SOLUTION: A signal waveform 41 is generated, based on a secondary charged particle beam of a length-measuring SEM. If the minimum signal intensity of the generated signal waveform 41 is set to 0% and the maximum signal intensity to 100%, a tangent 43 of the signal waveform 41 having the signal intensity of 5-20% is determined. A tangential angle 44, formed by the determined tangent 43 and the base 47 of the signal waveform 41, is calculated. The calculated tangential angle 44 is compared with a reference value, to thereby determine the aperture quality of the aperture pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor inspection apparatus using a charged particle beam, and more particularly to evaluation of opening quality of a hole bottom portion of an opening pattern.

Conventionally, an opening pattern formed on a substrate has been evaluated using a length measurement SEM (also referred to as “CD-SEM”) (see, for example, Patent Document 1). However, for example, in an opening pattern having a high aspect ratio of 10 or more, secondary electrons generated from the bottom of the hole may be absorbed by the side wall of the hole or may not reach the detection unit disposed above the opening pattern. . For this reason, the secondary electron reception level from the hole bottom is low, and there is a problem that it is difficult to evaluate the opening quality of the hole bottom.
Conventionally, when evaluating an opening pattern with a high aspect ratio, as shown in FIGS. 8 and 9, the half-value widths 51 and 52 of the signal waveforms 41 and 42 of the length measurement SEM are compared with a reference value. That is, when the minimum signal intensity of the signal waveforms 41 and 42 is 0% and the maximum signal intensity is 100%, the hole diameters 51 and 52 at the signal intensity of 50% are used as length measurement values.

JP 2002-289128 A (page 4)

  However, in the above-described conventional method, there is a problem that the hole diameters 51 and 52 that are the length measurement values show values larger than the actual dimension of the bottom of the opening pattern (hereinafter referred to as “hole bottom opening dimension”). there were. For example, in the case of a hole pattern with a 120 nm diameter, even if the pattern is a defective opening, the hole diameter 52 as a length measurement value shows a value near 110 nm, and therefore becomes the same as the hole diameter 51 of a pattern with good opening. . That is, the conventional method in which the hole diameter at a signal intensity of 50% is a length measurement value has a problem that it cannot follow the actual shape of the bottom of the opening pattern. Therefore, with the conventional method, it is difficult to determine whether the hole bottom opening is good or bad.

  The present invention has been made to solve the above-described conventional problems, and it is an object of the present invention to accurately determine the quality of a hole bottom opening of an opening pattern.

The opening pattern evaluation method according to the present invention is a method for evaluating the opening pattern based on the signal waveform of the opening pattern obtained by a length-measuring scanning electron microscope,
Calculating an angle formed by a base of the signal waveform and a tangent of the signal waveform in the vicinity of the base;
Based on the calculated angle, the step of determining the opening quality of the hole bottom portion of the opening pattern;
It is characterized by including.

  In the opening pattern evaluation method according to the present invention, in the step of calculating the angle, the signal strength is 5% to 20% when the minimum signal strength of the signal waveform is 0% and the maximum signal strength is 100%. It is preferable to obtain a tangent of the signal waveform and calculate an angle between the obtained tangent and the base.

  In the opening pattern evaluation method according to the present invention, it is preferable that the determination is performed by comparing the calculated angle with a reference value set between 20 ° and 85 °.

An opening pattern evaluation method according to the present invention includes a step of irradiating a substrate having an opening pattern with a primary charged particle beam,
Detecting a secondary charged particle beam generated from the substrate;
Generating a signal waveform based on the detected secondary charged particle beam;
Obtaining a tangent of the signal waveform having a signal strength of 5% to 20% when the minimum signal strength of the generated signal waveform is 0% and the maximum signal strength is 100%;
Calculating an angle formed by the tangent and the bottom of the signal waveform;
Based on the calculated angle, the step of determining the opening quality of the hole bottom portion of the opening pattern;
It is characterized by including.

  In the opening pattern evaluation method according to the present invention, it is preferable that the determination is performed by comparing the calculated angle with a reference value set between 20 ° and 85 °.

A semiconductor inspection apparatus according to the present invention is a semiconductor inspection apparatus that inspects an opening pattern formed on a substrate,
A stage for holding the substrate;
A charged particle source disposed above the stage and emitting a charged particle beam;
A deflector for scanning a primary charged particle beam emitted from the charged particle source to irradiate the vicinity of the opening pattern;
A detector for detecting a secondary charged particle beam generated from the substrate;
A signal waveform generator for generating a signal waveform based on the secondary charged particle beam detected by the detector;
When the minimum signal intensity of the signal waveform generated by the signal waveform generation unit is 0% and the maximum signal intensity is 100%, a tangent line of the signal waveform having a signal intensity of 5 to 20% is obtained. A tangent angle calculation unit for calculating an angle formed by the tangent and the bottom of the signal waveform;
A hole bottom opening determination unit that compares the angle calculated by the tangent angle calculation unit with a reference value to determine whether the hole bottom of the opening pattern is open or not;
It is characterized by comprising.

  As described above, the present invention compares the tangent angle calculated based on the signal waveform of the secondary charged particle beam with the reference value, and can accurately determine the quality of the hole bottom opening of the opening pattern. .

First, a method for evaluating an opening pattern according to an embodiment of the present invention will be described. The opening pattern is a hole pattern having a high aspect ratio (for example, 10 or more), an isolated space pattern, or the like.
FIG. 1 is a flowchart for explaining an opening pattern evaluation method according to an embodiment of the present invention. FIG. 2 is a diagram showing an opening pattern with a good opening and a signal waveform of a secondary charged particle beam obtained by observing the opening pattern with a length measurement SEM. FIG. 3 is a diagram showing an opening pattern with insufficient opening and a signal waveform of a secondary charged particle beam obtained by observing the opening pattern with a length measurement SEM. FIG. 4 is a diagram for explaining opening quality determination based on the signal waveform shown in FIG. FIG. 5 is a diagram for explaining opening quality determination based on the signal waveform shown in FIG. 3.

First, a substrate having an opening pattern is irradiated with a primary charged particle beam (step S1).
Next, a secondary charged particle beam generated from the substrate is detected (step S2).

Then, a signal waveform (that is, a signal waveform of the length measurement SEM image) is generated based on the detected secondary charged particle beam (step S3).
As shown in FIG. 2, a signal waveform 41 is generated by observing the opening pattern 32 with a good opening on the substrate 31 by a length measurement SEM. When the aperture is good, the slope of the signal waveform 41 at the edge portion of the waveform bottom is large, and the curvature of the corner of the edge portion is small.
On the other hand, as shown in FIG. 3, a signal waveform 42 is generated by observing an opening pattern 33 with insufficient opening on the substrate 31 by length measurement SEM. When the opening is insufficient, the slope of the signal waveform 42 at the edge portion of the waveform bottom is small, and the curvature of the corner of the edge portion is large.

  Next, when the minimum signal strength of the signal waveform generated in step S3 is 0% and the maximum signal strength is 100%, a tangent of the signal waveform having a signal strength of 5% to 20% is obtained, and the obtained tangent An angle formed by the bottom of the signal waveform (hereinafter referred to as “tangent angle”) is calculated (step S4). Here, the lower limit of the signal intensity is set to 5% or more. When the tangential angle in the area of less than 5% where the signal intensity is smaller (that is, the area extremely close to the waveform bottom) is obtained, the secondary charged particles This is because the amount of lines decreases, resulting in an unclear SEM image, and the signal waveform contrast deteriorates. Further, in order to judge whether the hole bottom opening is good or not, 20% closer to the hole bottom is set as the upper limit of the signal intensity. Therefore, 30% can be set as the upper limit of the signal intensity, but it is preferable to set 20% as the upper limit. The range width of 0 to 100% on the vertical axis of the signal waveform may be normalized by counting the number of secondary charged particles and the number of reflected charged particles using a good opening pattern as a reference pattern. The aspect ratio on the display screen when calculating the tangent angle may be such that the range width of 0 to 100% and the display length of the target eye dimension (for example, 120 nm) are the same.

As shown in FIG. 4, with respect to the favorable opening pattern 32, when the minimum signal intensity of the signal waveform 41 shown in FIG. 2 is 0% and the maximum signal intensity is 100%, the signal intensity is 5% to 20%. The tangent line 43 of the signal waveform is obtained. Then, a tangent angle 44 formed by the tangent line 43 and the base 47 of the signal waveform 41 is calculated. The base 47 is a reference line indicating the minimum signal strength, that is, the signal strength is 0%.
On the other hand, as shown in FIG. 5, similarly for the opening pattern 33 with insufficient opening, when the minimum signal strength of the signal waveform 42 shown in FIG. 3 is 0% and the maximum signal strength is 100%, The tangent line 45 of the signal waveform with 5% to 20% is obtained. Then, a tangent angle 46 formed by the tangent line 45 and the base 48 of the signal waveform 42 is calculated.

And it is discriminate | determined whether the tangent angles 44 and 46 calculated by step S4 are more than a reference value (step S5). Here, the reference value is a value set between 20 ° and 85 ° according to the request for the performance of the device.
If it is determined in step S5 that the tangent angle is greater than or equal to the reference value, a good determination is made regarding the opening at the bottom of the opening pattern (step S6). On the other hand, when it is determined that the tangent angle is smaller than the reference value, a defect determination is made regarding the opening at the bottom of the opening pattern (step S7).

Next, a semiconductor inspection apparatus for executing the above-described evaluation of the opening pattern will be described.
FIG. 6 is a conceptual diagram for explaining the semiconductor inspection apparatus according to the present embodiment.
As shown in FIG. 6, the substrate 3 is held on a stage 4 that can move in the XY directions. An opening pattern is formed on the substrate 3. That is, a resist film or an insulating film having an opening pattern is formed.

Above the stage 4, a charged particle source 1 that emits a (primary) charged particle beam 10 with respect to the substrate 3 is arranged. For example, an electron gun that emits an electron beam 10 can be used as the charged particle source 1.
Between the charged particle source 1 and the stage 4, a deflector 2 is disposed as a scanning mechanism that scans the primary charged particle beam 10 emitted from the charged particle source 1 and irradiates the substrate 3. The deflector 2 irradiates the primary charged particle beam 10 near the opening pattern on the substrate 3. Secondary charged particle beams 11 such as secondary electrons generated from the substrate 3 are detected by a detector 5 disposed above the stage 4.

The arithmetic processing unit 20 is for performing processing evaluation of the opening pattern based on the secondary charged particle beam 11 detected by the detector 5.
The signal waveform generation unit 21 of the arithmetic processing unit 20 generates a signal waveform as shown in FIGS. 2 and 3 based on the secondary charged particle beam 11 detected by the detector 5. The tangent angle calculation unit 22 calculates the tangent of the signal waveform when the signal strength is 5 to 20% when the minimum signal strength of the signal waveform generated by the signal waveform generation unit 21 is 0% and the maximum signal strength is 100%. Then, the tangent angle formed by the obtained tangent and the bottom of the signal waveform is calculated.
The hole bottom opening quality determination unit 23 determines the quality of the opening at the hole bottom of the opening pattern by comparing the angle calculated by the tangent angle calculation unit 22 with a preset reference value, and outputs the result. The reference value is a value set in advance in response to a request for the performance of the device, and is preferably in the range of 20 ° to 85 °.

As described above, in this embodiment, a tangent at the bottom edge portion of the signal waveform obtained by the length measurement SEM observation is obtained, and a tangent angle formed by the tangent and the signal waveform bottom is calculated. Then, the quality of the hole bottom opening is judged by comparing the calculated tangential angle with a reference value. Since the method according to the present embodiment is based on the tangential angle in the vicinity of the hole bottom of the opening pattern, it can follow the hole bottom shape of the opening pattern. As shown in FIG. 7, for example, in the evaluation of an opening pattern with a hole diameter of 120 nm, if the method of the present invention is applied to a region with a tangent angle of less than 80 °, which was determined to be good in the conventional method, it is considered that the opening is defective. Can be determined. Therefore, it is possible to accurately determine whether the opening pattern is open or not.
In addition, as described above, the quality of the opening pattern can be determined with high accuracy, so that the exposure conditions such as exposure energy and the focus margin can be evaluated with high accuracy.

It is a flowchart for demonstrating the opening pattern evaluation method by embodiment of this invention. It is a figure which shows an opening pattern with favorable opening, and the signal waveform of the secondary charged particle beam obtained by length measurement SEM observation of this opening pattern. It is a figure which shows the signal pattern of the secondary charged particle beam obtained by an opening pattern with insufficient opening, and the opening pattern obtained by length measurement SEM observation. It is a figure for demonstrating opening quality determination based on the signal waveform shown in FIG. It is a figure for demonstrating the quality determination of opening based on the signal waveform shown in FIG. It is a conceptual diagram for demonstrating the semiconductor inspection apparatus by embodiment of this invention. It is the figure which compared the area | region determined with favorable opening by embodiment of this invention and the area | region determined with the conventional method as an opening area | region. It is a figure for demonstrating the conventional opening quality determination. It is a figure for demonstrating the conventional opening quality determination.

Explanation of symbols

1 Charged particle source (electron gun)
2 Deflector 3 Substrate 4 Stage 5 Detector 10 Primary charged particle beam 11 Secondary charged particle beam (secondary electron)
DESCRIPTION OF SYMBOLS 20 Arithmetic processing part 21 Signal waveform generation part 22 Tangent angle calculation part 23 Hole bottom opening quality determination part 31 Substrate 32 Opening pattern 33 Opening pattern 41 Signal waveform 42 Signal waveform 43 Tangent 44 Tangent angle 45 Tangent 46 Tangent angle 47 Base 48 Bottom

Claims (6)

A method of evaluating the opening pattern based on the signal waveform of the opening pattern obtained by a length-measuring scanning electron microscope,
Calculating an angle formed by a base of the signal waveform and a tangent of the signal waveform in the vicinity of the base;
Based on the calculated angle, the step of determining the opening quality of the hole bottom portion of the opening pattern;
The opening pattern evaluation method characterized by including. In the opening pattern evaluation method according to claim 1,
In the step of calculating the angle, when the minimum signal strength of the signal waveform is 0% and the maximum signal strength is 100%, a tangent line of the signal waveform having a signal strength of 5% to 20% is obtained and obtained. An opening pattern evaluation method, wherein an angle between a tangent and the base is calculated. In the opening pattern evaluation method according to claim 1 or 2,
The opening pattern evaluation method, wherein the determination is performed by comparing the calculated angle with a reference value set between 20 ° and 85 °. Irradiating a substrate having an opening pattern with a primary charged particle beam;
Detecting a secondary charged particle beam generated from the substrate;
Generating a signal waveform based on the detected secondary charged particle beam;
Obtaining a tangent of the signal waveform having a signal strength of 5% to 20% when the minimum signal strength of the generated signal waveform is 0% and the maximum signal strength is 100%;
Calculating an angle formed by the tangent and the bottom of the signal waveform;
Based on the calculated angle, the step of determining the opening quality of the hole bottom portion of the opening pattern;
The opening pattern evaluation method characterized by including. In the opening pattern evaluation method according to claim 4,
The opening pattern evaluation method, wherein the determination is performed by comparing the calculated angle with a reference value set between 20 ° and 85 °. A semiconductor inspection apparatus for inspecting an opening pattern formed on a substrate,
A stage for holding the substrate;
A charged particle source disposed above the stage and emitting a charged particle beam;
A deflector for scanning a primary charged particle beam emitted from the charged particle source to irradiate the vicinity of the opening pattern;
A detector for detecting a secondary charged particle beam generated from the substrate;
A signal waveform generator for generating a signal waveform based on the secondary charged particle beam detected by the detector;
When the minimum signal intensity of the signal waveform generated by the signal waveform generation unit is 0% and the maximum signal intensity is 100%, a tangent line of the signal waveform having a signal intensity of 5 to 20% is obtained. A tangent angle calculation unit for calculating an angle formed by the tangent and the bottom of the signal waveform;
A hole bottom opening determination unit that compares the angle calculated by the tangent angle calculation unit with a reference value to determine whether the hole bottom of the opening pattern is open or not;
A semiconductor inspection apparatus comprising:

Images