JPH07286842A - Method and device for inspecting dimension - Google Patents

Abstract

PURPOSE:To measure the width of a pattern with high precision. CONSTITUTION:When a sample 21 is scanned with an electron beam, the incident angle of the electron beam is set in, at least, two different directions by means of beam incident angle selecting means 16, 18, 40, and 41. After setting the incident angles, the the sample 21 is scanned with the electron bean at the incident angles and each waveform output is obtained as the function of the scanning position by detecting secondary and reflected electrons generated when the scanning is made. A pattern width calculating means 42 finds the width of a pattern by processing the profile of the waveform outputs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection apparatus for semiconductor wafers and masks formed in a semiconductor manufacturing process, and more particularly to a dimension inspection method and apparatus for measuring pattern dimensions with high accuracy.

[0002]

2. Description of the Related Art As a dimension inspection method for inspecting such a pattern width, there are an optical type and an electron beam type. Among them, the laser spot scan method is an optical method. In this method, as shown in FIG. 7, a laser spot is irradiated onto a measured pattern 1 of a semiconductor wafer, which is a sample, in a direction perpendicular to the pattern, and scanning is performed, and scattered light from an edge generated at this time is detected by each detector 2. To detect. Then, the pattern width (line width) is obtained based on the scanning of the laser spot, that is, the output signal (FIG. 8) of each detector 2 corresponding to the moving distance of the stage 3.

With this method, accuracy can be increased by minimizing the size of the laser spot, but the laser spot size is limited to a beam diameter of about 0.8 μm,
There is a case where an error occurs between the measured value and the true value due to the sagging of the edge of the pattern 1. Therefore, it seems that the pattern width is about 0.5 μm as the measurement limit.

On the other hand, as a technique to which the electron beam method is applied, there is a scanning electron microscope (SEM). This SEM
Is to measure the pattern size from an enlarged image of the wafer surface pattern. As shown in FIG. 9, the electron beam is irradiated from the direction perpendicular to the measured pattern 1 and scanning is performed, and the secondary electrons obtained at this time are The backscattered electrons are detected and the intensity change thereof is obtained as a function of the scanning position as shown in FIG. Then, this is output as an image, and the pattern width is obtained from the distance between the pattern edges.

The electron beam is scanned on the sample by scanning the pattern to be measured 1 with deflection control by a scan coil. By such scanning control, the electron beam has a different beam incident angle depending on its scanning position as shown in FIG.

Therefore, the closer to the periphery of the scanning area, the more the electron beam is distorted due to the difference in beam incident angle, the deflection distortion, etc., and the error occurs in the pattern width measurement. Further, since there are shadows on the unevenness of the measured pattern 1, the pattern edge portion may not be accurately output, which makes it difficult to perform highly accurate measurement.

[0007]

As described above, since the beam incident angle differs depending on the scanning position of the electron beam, an error occurs in the pattern width measurement toward the peripheral side of the scanning area.
In addition, since there are shadows on the unevenness of the measured pattern 1, this also makes it difficult to perform highly accurate measurement. Therefore, an object of the present invention is to provide a dimension inspection method and an apparatus therefor capable of highly accurate pattern width measurement.

[0008]

According to a first aspect of the present invention, a sample on which a pattern is formed is scanned with an electron beam, and secondary electrons and backscattered electrons generated at this time are detected as a function of the scanning position. In a dimension inspection method for outputting a waveform to obtain a pattern width, a beam incidence angle of an electron beam with respect to a sample is set in at least two different directions, and profile processing is performed based on each waveform output when the electron beam is scanned at these beam incidence angles. Then, the dimension inspection method aims to achieve the above object by obtaining the pattern width.

According to a second aspect of the present invention, a sample on which a pattern is formed is scanned with an electron beam and generated at this time.
In a dimension inspection apparatus for detecting a secondary electron and a reflected electron and outputting the waveform as a function of a scanning position to obtain a pattern width, a beam incident angle selecting means for selectively setting a beam incident angle of an electron beam with respect to a sample in at least two different directions. A pattern width calculation means for obtaining a pattern width by performing profile processing on the basis of each waveform output when an electron beam is scanned at each beam incident angle.

According to a third aspect of the present invention, the beam incident angle selecting means includes a deflector, a memory that stores a plurality of beam incident angles in advance, and at least two different beam incident angles stored in the memory. An angle control device for selecting a beam incident angle and supplying each exciting current corresponding to the beam incident angle to the deflector.

According to the fourth aspect, the pattern width calculation means adds the respective waveform outputs when the electron beam is scanned at each beam incident angle to obtain an output corresponding to the pattern and subtracts the output in the pattern inclination direction. It has a function of obtaining a corresponding output, obtaining a pattern profile based on these outputs, and obtaining a pattern width.

[0012]

According to the first aspect, when the electron beam is scanned on the sample, the beam incident angles of the electron beam are set in at least two different directions, and the respective scanning is performed. Each waveform output is obtained as a function of scanning position by detecting electrons, and profile processing is performed based on these waveform outputs to obtain the pattern width.

According to the second aspect, when the electron beam is scanned on the sample, the beam incident angle selecting means sets the beam incident angle of the electron beam in at least two different directions. Then, the electron beam is scanned at each of these beam incident angles, secondary electrons and backscattered electrons generated at this time are detected, and each waveform output is obtained as a function of the scanning position. Based on these waveform outputs by the pattern width calculation means. Profile processing is performed to obtain the pattern width.

In this case, according to the third aspect, at least a memory having a plurality of beam incident angles stored in advance is used.
One beam incident angle is selected, and each exciting current corresponding to these beam incident angles is supplied to the deflector to set each beam incident angle of the electron beam.

According to a fourth aspect of the present invention, the waveform outputs obtained by scanning the electron beam at each beam incident angle are added to obtain an output corresponding to the pattern, and an output corresponding to the pattern is subtracted from the waveform output to obtain the pattern inclination direction. Get the output. Then, the pattern profile is obtained based on the outputs of the addition and the subtraction to obtain the pattern width.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a dimension inspection apparatus applied to a scanning electron microscope (SEM). An electron gun 11 is provided above the microscope body 10.

In the microscope body 10, a blanking coil 12, a condenser lens 13, a scan coil 14, an electron beam for turning on and off the electron beam along the traveling direction of the electron beam emitted from the electron gun 11. A reduction lens 15, a deflector 16, and an objective lens 17 for finely focusing the image are arranged.

These coils 12, 14 and each lens 1
The beam control device 18 controls the exciting current of each of Nos. 3, 15 and the like to adjust the beam shape of the electron beam, the irradiation area, and the like.

An XY stage 20 is movably arranged below the microscope body 10, and the XY stage 20 is also provided.
A sample 21 such as a semiconductor wafer is placed on top. The XY stage 20 is moved on the XY plane by a stage control device 22 provided outside the microscope body 10.

The laser position detector 23 has a function of irradiating the mirror with laser light, receiving the reflected laser light, and detecting the position of the sample 21 from the round-trip time. XY
An electronic detector 30 such as a detector is arranged diagonally above the stage 20. The electron detector 30 detects secondary electrons or reflected electrons when the sample 21 is irradiated with an electron beam, and outputs an electric signal according to the intensity of the electrons.

The secondary electron detection processing device 31 has a function of receiving an electric signal from the electron detector 30 and obtaining its waveform output. On the other hand, the main controller 40 is connected to the beam controller 18, the stage controller 22, the secondary electron detection processing device 31, the beam incident angle memory 41, and the length measurement processing device 42.

The beam incident angle memory 41 stores a plurality of beam incident angles of the electron beam with respect to the sample 21 in advance. These beam incident angles are, for example, electron beams a, b, and c as shown in FIG.
Is the beam incident angle θ1 and the electron beam c is the beam incident angle θ2. These beam incident angles θ1 and θ2 are values previously obtained by calibration of deflection angles and irradiation points (not shown), and can be set and changed to arbitrary angles.

The main controller 40 includes a beam incident angle memory 4
It has a function of selecting at least two different beam incident angles among the beam incident angles stored in No. 1 and sending an instruction command of these beam incident angles to the beam control device 18. In this case, the main controller 34 sends a function of selecting two beam incident angles according to an operator's instruction and a command of beam incident angle to the beam controller 18 and a command to continuously move the stage 22. It has the function of sending to.

When the beam control device 18 receives an instruction of two beam incident angles θ1 and θ2, these beam incident angles θ1 and θ2
It has a function of supplying each exciting current corresponding to 1 and θ2 to the deflector 16.

Therefore, the deflector 16, the beam controller 18, the main controller 40 and the beam incident angle memory 41 form a beam incident angle selecting means. The stage controller 22 controls the XY stage 20 when the sample 21 is irradiated with the electron beam at each beam incident angle.
Is continuously moved in a predetermined direction of the XY plane to scan the sample 21 with the electron beam.

The stage control device 22 is used for the sample 21.
Function to send a position command to the XY stage 20 according to the upper pattern inspection area, XY from the laser position detector 23
It has a function of receiving the position of the table 20 and positioning the sample 21 in a desired pattern inspection region.

The length measurement processing unit 42 receives the output waveform obtained by the secondary electron detection processing unit 31 through the main control unit 40 and adds the output waveforms at the time of electron beam scanning at each beam incident angle to add the pattern. It has a function of obtaining and outputting the output according to the pattern inclination direction and obtaining the output according to the pattern inclination direction, and obtaining the pattern profile based on these output waveforms to obtain the pattern width.

A monitor television 43, a CRT display 44 and a floppy disk 45 are connected to the length measurement processing device 42, and the pattern width of the sample 21 is displayed on the monitor television 43 and the CRT display 44 and the floppy disk. 45 has the function of storing.

The main controller 40 includes a beam controller 18, a stage controller 22, and a secondary electron detection processor 3.
1 and a function of controlling each operation of the length measurement processing device 42.

Next, the operation of the apparatus constructed as described above will be described. When an electron beam is emitted from the electron gun 11, the electron beam becomes a uniform electron beam by the condenser lens 13 and is focused so as to cross at the center position of the scan coil 14. Then, the electron beam is focused again by the objective lens 17 and irradiated on the sample 21. At this time, the irradiation position of the electron beam is positioned anywhere on the sample 21 by the control of the deflector 16.

The electron beam thus irradiated on the sample 21 is the electron beam a shown in FIG. 2. If the XY stage 20 is continuously moved in this state, the electron beam as shown in FIG. The beam a is scanned.

By the way, in this apparatus, the sample 21 is scanned with the electron beam as follows. That is, main controller 40 selects at least two different beam incident angles among the plurality of beam incident angles stored in beam incident angle memory 41.
Two beam incident angles, for example, beam incident angles θ1 and θ2 are selected. In this case, if there is an instruction from the operator, main controller 34 selects two beam incident angles according to this instruction.

Next, the main controller 40 first sends an instruction command for the beam incident angle θ1 to the beam controller 18. The beam control device 18 supplies an exciting current according to the beam incident angle θ1 to the deflector 16.

As a result, the electron beam is deflected when passing through the deflector 16 and passes through the path of the electron beam b shown in FIG. 2 and is irradiated onto the sample 21 at the beam incident angle θ1. At the same time, main controller 40 sends a stage movement command to stage controller 22. The stage control device 22 continuously moves the XY stage 20, that is, the sample 21 in a predetermined direction by receiving a stage movement command.

When the sample 21 is irradiated with the electron beam b having the beam incident angle θ1 and the sample 21 is continuously moved, the electron beam b scans the sample 21 as shown in FIG. 3B.

At this time, when the sample 21 is irradiated with the electron beam b, secondary electrons or reflected electrons are generated from the sample 21. The electron detector 30 detects these secondary electrons or reflected electrons and outputs an electric signal corresponding to the intensity of the electrons. The secondary electron detection processing device 31 receives the electric signal from the electron detector 30 and obtains its waveform output shown in FIG. 4 (b). Main controller 40 stores this waveform output in a storage device (not shown).

Next, main controller 40 determines beam incident angle θ2.
Is sent to the beam controller 18. The beam control device 18 supplies an exciting current according to the beam incident angle θ2 to the deflector 16.

As a result, the electron beam is deflected when passing through the deflector 16 and is irradiated onto the sample 21 through the path of the electron beam c shown in FIG. Along with this, main controller 40 sends a stage movement command to stage controller 22 as described above. Upon receiving the stage movement command, the stage control device 22 continuously moves the XY stage 20 in a predetermined direction to move the sample 21.

As described above, when the sample 21 is irradiated with the electron beam c having the beam incident angle θ2 and the sample 21 is continuously moved, the electron beam c is changed to the sample 21 as shown in FIG. 3 (c).
Scan over.

At this time, when the sample 21 is irradiated with the electron beam c, secondary electrons or reflected electrons are generated from the sample 21. The electron detector 30 detects these secondary electrons or reflected electrons and outputs an electric signal corresponding to the intensity of the electrons. The secondary electron detection processing device 31 receives the electric signal from the electron detector 30 and obtains its waveform output shown in FIG. 4 (c). Main controller 40 stores this waveform output in a storage device (not shown).

The output waveform in FIG. 4A shows the case where the sample 21 is scanned with the electron beam a. Next, the length measurement processing device 42 causes the beam incident angles θ1 at the time of electron beam scanning stored in the storage device through the main control device 40,
Each output waveform corresponding to θ2 is received, and the pattern width is obtained based on these output waveforms.

That is, the length measurement processor 42 adds the output waveforms of the respective beam incident angles θ1 and θ2 to obtain the output according to the pattern shown in FIG. Along with this, the length measurement processing device 4
2 subtracts these output waveforms, that is, the beam incident angle θ1
The output waveform at the beam incident angle θ2 is subtracted from the output waveform at this time to obtain an output according to the pattern inclination direction.

In this way, the length measurement processing device 42 obtains a pattern profile based on the output waveforms obtained by these additions and subtractions, edge processing for this pattern profile, and the pattern width from the movement distance of the XY stage 20.

Then, the length measurement processing device 42 displays this pattern width on the monitor television 43 and the CRT display 44 and stores it together with the floppy disk 45.

As described above, in the above embodiment, the beam incident angle of the electron beam is at least two different directions θ1,
Set to θ2, scan each, detect secondary electrons and backscattered electrons generated at this time, obtain each waveform output as a function of the scanning position, and perform profile processing based on these waveform outputs to obtain the pattern width. As a result, the electron beam can faithfully scan the pattern inclined surface by interpolating the unevenness of the measured pattern with the electron beams having the respective beam incident angles θ1 and θ2, and faithfully and accurately reproduces the profile of the measured pattern. it can.

As a result, an error in the pattern width measurement caused by the difference in the beam incident angle with respect to the sample 21 depending on the scanning position of the electron beam, or a measurement for producing a shadow on the unevenness of the measured pattern 1 The pattern width can be accurately measured without causing an error.

The pattern density of semiconductors will become higher in the future and the pattern width will become thinner, for example, to 0.1 μm or less. As a result, the dimension inspection will have a higher resolution (higher magnification) than the present. ) Is now required.

Under the current circumstances, if an electron beam that can reduce the beam diameter is used and the pattern width is obtained from the output waveform when scanning is performed while changing the beam incident angle, a highly integrated semiconductor wafer can be obtained. Fine patterns can be measured with high resolution and high accuracy.

Further, since a plurality of beam incident angles are stored in advance in the beam incident angle memory 41, the beam incident angle corresponding to the inclination of the pattern is selected from the design data of the pattern to be measured to obtain a highly accurate pattern width. You can measure.

Further, the pattern width can be obtained from each output waveform by scanning the electron beam a plurality of times using not only the beam incident angles θ1 and θ2 but also two or more different beam incident angles. By doing so, a more accurate pattern profile and pattern width can be obtained.

Further, the length measurement processing device 42 can obtain the inclination direction of the measured pattern edge by subtracting each waveform output in the process of obtaining the pattern width. The present invention is not limited to the above-mentioned one embodiment and may be modified as follows. For example, the present invention can be applied not only to the pattern inspection of the semiconductor wafer but also to the evaluation of the exposure mask pattern and the like.

[0052]

As described above in detail, according to the present invention, it is possible to provide the dimension inspection method and the apparatus therefor capable of highly accurate pattern width measurement.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment when a dimension inspection apparatus according to the present invention is applied to a scanning electron microscope.

FIG. 2 is a diagram showing a beam incident angle of an electron beam.

FIG. 3 is a diagram showing scanning at each beam incident angle of an electron beam.

FIG. 4 is a diagram showing each output waveform at each beam incident angle of the electron beam.

FIG. 5 is a diagram showing a waveform of addition processing of output waveforms.

FIG. 6 is a diagram showing a waveform of a subtraction process of each output waveform.

FIG. 7 is a diagram for explaining a conventional laser spot method.

FIG. 8 is a diagram showing calculation of a pattern width by a laser spot method.

FIG. 9 is a diagram for explaining a conventional electron beam system.

FIG. 10 is a diagram showing calculation of a pattern width by an electron beam method.

FIG. 11 is a diagram showing distortion generation in the electron beam system.

[Explanation of symbols]

10 ... Microscope main body, 11 ... Electron gun, 13 ... Condenser lens, 14 ... Scan coil, 16 ... Deflector, 17 ... Objective lens, 20 ... XY stage, 21 ... Specimen, 22 ... Stage control device, 23 ... Laser position detection Reference numeral 30 ... Electron detector, 31 ... Secondary electron detection processing device, 40 ... Main control device, 41 ... Beam incident angle memory, 42 ... Length measurement processing device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroaki Honishi 33, Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Inside the Toshiba Industrial Technology Institute, Inc. (72) Yuji Fukudome Shin-isogo-cho, Isogo-ku, Yokohama-shi, Kanagawa No. 33 Incorporated company Toshiba Production Engineering Laboratory

Claims (4)

[Claims] 1. A dimension inspection for scanning a patterned sample with an electron beam, detecting secondary electrons and reflected electrons generated at this time, and outputting the waveform as a function of the scanning position to obtain the pattern width. In the method, the beam incident angle of the electron beam with respect to the sample is set in at least two different directions, and the pattern width is obtained by performing profile processing based on each waveform output when the electron beam is scanned at these beam incident angles. A dimension inspection method characterized by the above. 2. A dimension inspection for scanning a patterned sample with an electron beam, detecting secondary electrons and reflected electrons generated at this time, and outputting the waveform as a function of the scanning position to obtain the pattern width. In the apparatus, beam incident angle selecting means for selectively setting the beam incident angle of the electron beam with respect to the sample in at least two different directions, and profile processing based on each waveform output when the electron beam is scanned at each beam incident angle. And a pattern width calculating means for determining the pattern width. 3. The beam incident angle selection means includes a deflector, a memory storing a plurality of beam incident angles in advance, and at least two different beam incident angles among the beam incident angles stored in the memory. 3. The dimension inspection apparatus according to claim 2, further comprising: an angle control device that selects and supplies each exciting current corresponding to the beam incident angle to the deflector. 4. The pattern width calculation means adds the respective waveform outputs when the electron beam is scanned at each beam incident angle to obtain an output according to the pattern and subtracts the output according to the pattern inclination direction. 3. The dimension inspection apparatus according to claim 2, further comprising a function of obtaining a pattern profile based on these outputs and obtaining the pattern width.