JP2005233757A - Method and device for inspecting hole pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inspecting apertures in a hole pattern, which is simplified by using a scanning electron microscope (SEM). <P>SOLUTION: A dimension curve of the hole pattern is obtained from contrast information of secondary electrons in the SEM system, and a rate of change (gradient of tangent) in hole pattern dimensions is calculated at a certain threshold, thereby quantitatively evaluating as to whether or not states of the apertures in the hole pattern are good. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hole pattern inspection method and a hole pattern inspection apparatus, and more particularly, to reliably and easily identify the opening state of a fine hole (hole) pattern using secondary electrons or the like when manufacturing a semiconductor device or the like. The present invention relates to a hole pattern inspection method and a hole pattern inspection apparatus.

  A semiconductor device such as a semiconductor integrated circuit device has layered wiring layers that are stacked one on another, and an insulating layer is provided between each wiring layer. In order to establish this semiconductor device as an electric circuit, holes called “contact holes” or “via holes” are formed in desired portions of the insulating layer and filled with a conductive material. It is necessary to electrically connect each wiring layer.

FIG. 6 is a process sectional view showing a contact hole forming process.
An etched film 501 such as SiO ₂ is provided on a base 500 made of a semiconductor substrate or a lower wiring layer. First, a mask 502 is formed on the etching target film 501 by a lithography process. Specifically, a photosensitive polymer film called “photoresist” or the like is formed and subjected to alkali development to form a fine hole pattern (FIG. 6A).
Next, the etching process causes the mask 502 to function as an etching blocking portion, and a hole pattern, which is a transfer image of the mask pattern, is formed on the etching target film 501 (FIG. 6B).
Subsequently, a conductive material 503 is embedded in the hole pattern to form a connection portion (FIG. 6C).

  As can be seen from the above-described steps, the hole pattern formed in the mask 502 or the etching target film 501 needs to be strictly opened. Such an inspection of the hole pattern in the hole pattern can be performed with a scanning electron microscope (SEM). That is, whether or not the hole pattern has a desired opening state is determined based on the fact that the measured value of the dimension by SEM is not specific and the appearance of the bottom of the hole in the secondary electron contrast image is not abnormal. It was. Of these, the determination as to whether the measured value of the dimension is not specific can be uniquely determined by comparison with a reference value, so that automation is easy. However, the determination of whether or not the appearance of the bottom of the hole is abnormal is a manual operation, which has been a major obstacle to the automation of SEM inspection.

  As described above, in the conventional inspection method, it is necessary to perform a manual operation to determine whether or not the hole pattern is open. Furthermore, in recent years, with the miniaturization of the hole pattern, the amount of secondary electron information obtained from the bottom of the hole has been greatly reduced, the SEM image of the bottom of the hole has become unclear, and it has become difficult to make manual judgments. I came.

  The present invention has been made based on the recognition of such a problem, and an object thereof is to provide a simplified hole pattern inspection method using SEM or the like. It is another object of the present invention to provide an automated hole pattern inspection apparatus by using this inspection method.

  FIG. 7 is a schematic diagram showing a method for determining a pattern dimension in the SEM.

  When the SEM is used, the pattern dimension can be determined by using a phenomenon in which the intensity of the secondary electrons varies depending on the shape of the pattern and using the contrast information of the secondary electrons. FIG. 7A shows a cross-sectional shape of the hole pattern 601, and FIG. 7B shows a contrast waveform 602 of secondary electrons of the hole pattern 601.

  The hole pattern dimension is a distance between edges at a specific secondary electron intensity (hereinafter referred to as “threshold”), that is, a line where a contrast waveform 602 and a straight line 603 corresponding to the threshold intersect. Determined by the length of the minute 604. As the threshold value of the secondary electron intensity, a value of about 50% of the maximum value and the minimum value of the secondary electron intensity can be used. This is because the state of the side wall of the hole pattern side wall can be well expressed and stable measurement can be performed.

  In the contrast waveform 602, secondary electrons are likely to be emitted at the corners of the opening end above the hole pattern, and the intensity becomes strong. The hole pattern side wall portion has strength corresponding to the inclination and depth, and the bottom portion has strength corresponding to the material and depth. As described above, the shape of the secondary electron contrast waveform obtained by SEM observation strongly reflects the cross-sectional shape of the hole pattern. Therefore, if the pattern dimensions at every threshold value are examined in detail using this contrast waveform, the pattern shape can be grasped in detail.

  The present invention provides an inspection method for quantitatively evaluating the cross-sectional shape of a pattern by examining the pattern dimensions at every threshold in detail and knowing the rate of change in the hole pattern dimension at a predetermined threshold. Is.

That is, according to the present invention,
A procedure for obtaining a secondary electron signal by irradiating an electron beam to a hole pattern;
A range in which the intensity of the secondary electron signal becomes a specified intensity is a hole pattern opening size, and the hole pattern in a range from a first specified intensity to a second specified intensity greater than the first specified intensity. A procedure for calculating a dimension curve of the opening dimension of
Calculating a rate of change of the dimension curve of the opening dimension at a third specified intensity between the first value and the second value;
From the rate of change, a procedure for determining the quality of the hole pattern formation state;
A hole pattern inspection method is provided.

  Here, the first designated strength is a minimum value of the secondary electron signal, the second designated strength is a maximum value of the secondary electron signal, and the third designated strength is It may be an approximate average value of the first and second designated intensities.

  In addition, when the rate of change is smaller than a predetermined value, the formation state of the hole pattern can be determined as good.

  Further, from the procedure for calculating the change rate of the dimension curve of the opening dimension in the vicinity of the first specified strength and the change rate in the vicinity of the first specified strength, the formation state of the hole pattern is determined. And a procedure for determining pass / fail.

  Further, in this case, when the rate of change in the vicinity of the first designated intensity is greater than a predetermined value, the hole pattern formation state can be determined to be good.

Or according to the invention,
Means for irradiating a hole pattern with an electron beam to obtain a secondary electron signal;
A range in which the intensity of the secondary electron signal becomes a specified intensity is a hole pattern opening size, and the hole pattern in a range from a first specified intensity to a second specified intensity greater than the first specified intensity. Means for calculating a dimensional curve of the opening size of
Means for calculating a rate of change of the dimension curve of the aperture size at a third specified intensity between the first value and the second value;
Means for determining the quality of the formation state of the hole pattern from the rate of change;
A hole pattern inspection apparatus is provided.

  Here, from the means for calculating the rate of change of the dimension curve of the aperture size in the vicinity of the first specified intensity, and the rate of change in the vicinity of the first specified intensity, the formation state of the hole pattern And a means for judging whether the quality is good or bad.

  According to the present invention, it is possible to quantitatively evaluate the cross-sectional shape of the hole pattern by examining the hole pattern dimensions at every threshold value in detail. At this time, since the quality of the hole pattern shape can be determined using the rate of change of the hole pattern dimension at a certain threshold value, the hole pattern opening state can be automatically identified.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart showing a hole pattern inspection method according to an embodiment of the present invention.
That is, in this embodiment, first, in step S102, the secondary electron signal waveform of the measurement object is acquired. Specifically, for example, a wafer on which a hole pattern is formed is placed in an SEM and irradiated with an electron beam to acquire a secondary electron signal waveform corresponding to the shape of the hole pattern.

  FIG. 2 is a schematic view illustrating the cross-sectional shape of the hole pattern. FIG. 2A shows a pattern 101 with a good pattern at the bottom of the pattern, and FIG. 2B shows a pattern 102 with a poor pattern at the bottom of the pattern. The hole pattern 101 has a straight side wall and a sharp boundary shape between the side wall and the bottom. On the other hand, the hole pattern 102 has a short straight section on the side wall, and the boundary shape between the side wall and the bottom is rounded.

  FIG. 3 is a schematic diagram showing a secondary electron contrast waveform of the hole pattern shown in FIG. 3A shows the contrast waveform 201 of the pattern 101 in FIG. 2A, and FIG. 3B shows the contrast waveform 202 of the pattern 102 in FIG. 2B. Comparing the contrast waveforms 201 and 202, it can be seen that in the contrast waveform 202, the inclination of the side wall portion is gentle, and the radius of curvature of the boundary region between the side wall portion and the bottom portion is also increased.

  Returning to FIG. 1 again, the description will be continued. Next, in step S104, a pattern dimension curve is calculated. That is, the aperture size of the hole pattern at each threshold value is calculated from the secondary electron signal waveform acquired in step S102.

  FIG. 4 is a graph showing pattern dimensions obtained from the contrast waveform when the threshold value is changed from 0 to 100 percent. That is, the horizontal axis in the figure represents the threshold value, and the vertical axis represents the pattern dimension when the pattern dimension at the threshold of 50% is 1.0. Here, the threshold value of 50% is used as a reference because a stable pattern dimension can be obtained in this vicinity.

  4A shows the dimensional curve 301 obtained from FIG. 3A, and FIG. 4B shows the dimensional curve 302 obtained from FIG. 3B. In the dimension curves 301 and 302, as the threshold value decreases from around 50%, the dimension decreases linearly and tends to decrease sharply at a certain value. It can be seen that the point at which the size is suddenly reduced is in the vicinity of the boundary region between the side wall and the bottom of the hole pattern, and the curve of the dimension curve reflects the pattern shape of the bottom.

  Returning to FIG. 1 again, the description will be continued. Next, in step S106, an inclination at a predetermined threshold value is calculated. That is, in the dimensional curve illustrated in FIG. 4, the slope of the curve at a predetermined threshold value is calculated.

For example, in FIGS. 4 (a) and 4 (b), a certain threshold value in a section in which the dimension decreases linearly, for example, tangent lines at a threshold value of 50% are tangent lines 303 and 304, respectively.

(Slope of tangent 303) <(Slope of tangent 304)

It becomes.

  That is, the inclination when the threshold value is 50% is smaller in the hole pattern 101 than in the hole pattern 102. This is because, as can be seen from FIGS. 2 and 3, when the side wall of the hole pattern is formed steeper, the slope of the straight line portion in the dimension curve becomes smaller.

  Therefore, in this case, when the slope at the threshold value of 50% is equal to or smaller than the predetermined value in step S108 shown in FIG. 1, it can be determined that the hole pattern has a good hole state.

On the other hand, when a threshold having a section in which the dimension decreases rapidly, for example, tangents at a threshold of 5% are tangents 305 and 306, respectively.

(Slope of tangent 305)> (Slope of tangent 306)

It becomes.

  That is, the inclination at the threshold of 5% is larger in the hole pattern 101 than in the hole pattern 102. This is because, as can be seen from FIGS. 2 and 3, when the side wall of the hole pattern is formed more steeply, the slope of the dimensional curve near the bottom of the opening becomes large.

  Therefore, in this case, when the slope at the threshold value of 5% is equal to or larger than the predetermined value in step S108 shown in FIG. 1, it can be determined that the hole pattern has a good hole state.

  That is, as can be seen from FIGS. 2 to 3, it can be determined that the hole pattern 101 has a smaller tangential slope at the threshold of 50% and a larger tangent slope at the threshold of 5% and has a better opening state. . Here, the threshold value of 5% is shown as an example of the boundary region between the side wall and bottom of the hole pattern, but any value close to the minimum value of the threshold may be used.

The inventor examined the tangential slope of the dimensional curve obtained from the contrast waveform in many patterns of open states.

(Slope of tangent 303) <0.2

(Inclination of tangent 305)> 20

The result was obtained.

  In other words, when inspecting the hole pattern, the threshold value is changed from the minimum value to the maximum value to obtain a dimensional curve, and the slope of the tangent line when the threshold value is 50% is calculated, and this value is 0.2 or more In addition, the open state can be determined as “NG”.

  Similarly, the threshold value is changed from the minimum value to the maximum value to obtain a dimensional curve, and the slope of the tangent line at the time of the threshold value of 5% is calculated. NG ".

  Thus, the quality of the hole pattern open state can be determined by the magnitude of the tangent slope of the dimension curve.

FIG. 5 is a block diagram illustrating the main configuration of the hole pattern inspection apparatus according to the embodiment of the invention.
The hole pattern inspection device 40 includes an SEM device 401, a computer 402, and an input unit 403. The SEM apparatus 401 includes an electron optical system 404, a stage 405 on which the measurement target S is placed, an electron optical system processing unit 406, a secondary electron detector 407, and a signal processing unit 408. The electron optical system 404 generates an electron beam and irradiates the measurement object S on which a hole pattern to be inspected is formed with the electron beam. The secondary electron detector 407 detects secondary electrons emitted from the surface of the measurement object S by irradiation with an electron beam. The signal processing unit 408 converts secondary electrons detected by the secondary electron detector 407 and supplies the converted electrons to the computer 402 as secondary electron signals. A computer 402 controls the entire apparatus. The computer 402 processes the secondary electron signal supplied from the SEM device 401, and determines the quality of the shape of the hole pattern according to the procedure described in the hole pattern inspection method. The input unit 403 is connected to the computer 402, and can input threshold data and tangential slope data.

  The input unit 403 is configured to set in the hole pattern inspection apparatus that, for example, when the tangent slope of the dimensional curve at the threshold value of 50% is 0.2 or more, the hole state is determined as “NG”. Thus, the subsequent pattern inspection can be automatically performed.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

For example, the present invention is not used only for measuring the opening state of contact holes and via holes. For example, a trench for obtaining a capacitor or a gate structure, a trench for forming an inter-element insulating layer, etc. When applied to the measurement of the open state of various holes, the same effect can be obtained. Further, the measuring apparatus is not limited to the one using the SEM, and may be any apparatus that can detect the secondary electrons by irradiating the measurement object with an electron beam.
The present invention can also be applied to verification of electron beam drawing data for performing electron beam drawing on an object to be processed on which a resist is formed on a semiconductor integrated circuit wafer.

  In addition, all hole pattern inspection methods and hole pattern inspection apparatuses that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

It is a flowchart showing the hole pattern inspection method concerning embodiment of this invention. It is a schematic diagram which shows the cross-sectional shape of a hole pattern. FIG. 3 is a schematic diagram illustrating a contrast waveform of the hole pattern illustrated in FIG. 2. It is the graph which showed the pattern dimension dimension curve calculated | required from the contrast waveform represented to FIG. It is a block diagram of the inspection apparatus using the hole pattern inspection method of the present invention. It is a schematic diagram which shows the process of contact hole formation. It is a schematic diagram showing the determination method of the pattern dimension in SEM.

Explanation of symbols

101, 102, 601 Hole pattern 40 Hole pattern inspection device 401 SEM device 402 Computer 403 Input unit 404 Electro-optical system 405 Stage 406 Electro-optical system processing unit 407 Secondary electron detector 408 Signal processing unit 501 Etched film 502 Photoresist 503 Conductive material

Claims (7)

A procedure for obtaining a secondary electron signal by irradiating an electron beam to a hole pattern;
A range in which the intensity of the secondary electron signal becomes a specified intensity is a hole pattern opening size, and the hole pattern in a range from a first specified intensity to a second specified intensity greater than the first specified intensity. A procedure for calculating a dimension curve of the opening dimension of
Calculating a rate of change of the dimension curve of the opening dimension at a third specified intensity between the first value and the second value;
From the rate of change, a procedure for determining the quality of the hole pattern formation state;
A hole pattern inspection method characterized by comprising: The first designated intensity is a minimum value of the secondary electron signal;
The second designated intensity is a maximum value of the secondary electron signal;
2. The hole pattern inspection method according to claim 1, wherein the third designated intensity is a substantially average value of the first and second designated intensity.   The hole pattern inspection method according to claim 2, wherein the hole pattern formation state is determined to be good when the rate of change is smaller than a predetermined value. Calculating a rate of change of the dimension curve of the aperture size in the vicinity of the first specified strength;
A procedure for determining pass / fail of the formation state of the hole pattern from the rate of change in the vicinity of the first designated intensity;
The hole pattern inspection method according to claim 1, further comprising:   5. The hole pattern inspection method according to claim 4, wherein when the rate of change in the vicinity of the first designated intensity is greater than a predetermined value, the hole pattern formation state is determined to be good. Means for irradiating a hole pattern with an electron beam to obtain a secondary electron signal;
A range in which the intensity of the secondary electron signal becomes a specified intensity is a hole pattern opening size, and the hole pattern in a range from a first specified intensity to a second specified intensity greater than the first specified intensity. Means for calculating a dimensional curve of the opening size of
Means for calculating a rate of change of the dimension curve of the aperture size at a third specified intensity between the first value and the second value;
Means for determining the quality of the formation state of the hole pattern from the rate of change;
A hole pattern inspection apparatus comprising: Means for calculating a rate of change of a dimension curve of the aperture size in the vicinity of the first designated strength;
Means for determining the quality of the formation state of the hole pattern from the rate of change in the vicinity of the first designated intensity;
The hole pattern inspection apparatus according to claim 6, further comprising:

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