KR101097830B1 - The apparatus and method of controller circuit analysis and scan generation moulation for enhancing sem image - Google Patents

Abstract

The present invention is to improve the problem that the SEM image output from the scanning electron microscope (SEM: SEM image is displayed in the state of the distortion of the scan signal is severe due to the impedance component of the deflection coil, scanning waveform controller, The scanning waveform control device is composed of a deflection coil, a secondary electronic signal detection unit, an AD converter unit, a DA converter unit, and an SEM image control unit. It can be set by using the B-Spline curve generation method to minimize the distortion at the point where the waveform starts rising after falling, which is the most distortion part of the scan signal. Minimized, less than 10% distortion of the SEM image can be reduced, It is an object of the present invention to provide a scanning waveform control apparatus and method for increasing the SEM resolution capable of reading a good SEM image at high magnification.

Scan waveform control unit, deflection coil, secondary electronic signal detector, DSP, SEM image controller

Description

TECHNICAL APPARATUS AND METHOD OF CONTROLLER CIRCUIT ANALYSIS AND SCAN GENERATION MOULATION FOR ENHANCING SEM IMAGE

The present invention relates to a scanning waveform control apparatus and method for increasing the resolution of a scanning electron microscope (SEM), which is mainly used for observing biological sample tissues such as metals, ceramics, semiconductors, polymer composites, and medicine. will be.

Scanning Electron Microscopes (SEM) are used to analyze the surfaces required for fabricating semiconductor devices, such as the surface of a sample.

For example, in order to measure CD (Critical Dimension) etc. of the pattern formed in the sample surface, the method of obtaining the SEM image of the sample surface and measuring the CD of the pattern shown in such a SEM image is used.

The SEM apparatus is composed of an electron gun that generates electromagnetic waves, and the electromagnetic waves produced by the tank gun form an electron beam, and the electron beam is connected while passing through several lenses to form a very small probe.

In this case, the probe is scanned to a predetermined surface portion of the specimen surface by a deflection coil in the objective lens.

The intrinsic magnetic field of the electron beam and the magnetic field of the deflection coil induce a pushing force and a pulling force in parallel to each other, so that the electron beam is deflected to some extent by the magnetic field of each other to show the scanning area.

Here, the range of the scanning area is determined by the current or the voltage. The larger the intensity of the current voltage is, the wider the range is applied to the magnetic field and the electric field, thereby scanning a wide area.

When the electron beam irradiates the surface of the specimen, the surface of the specimen emits a fine electronic signal with height information. When this signal is detected by the detector, amplified and scanned synchronously on the monitor, an SEM image showing the height of the surface is produced. .

In the prior art, Korean Patent Laid-Open Publication No. 10-2002-0032283 discloses a chamber, an electron beam portion which scans the beam across the surface of a sample which is introduced into the chamber and generates a single-character electron beam mounted in the chamber, wherein A secondary electron detector which detects secondary electrons introduced into the chamber and emitted from the sample and generates a signal representative of the surface of the target from which the secondary electrons are emitted; and a secondary electron detector connected to the secondary electron detector to image the signal. An image capturing unit including a processing unit to change the image; And a scanning electron microscope image and method used to obtain a scanning electron microscope image including a charge generating portion which is connected to the image pickup unit and generates an electrical charge and serves to provide a surface of the sample has been presented,

This is because after scanning the SEM, the SEM image is difficult to read because the SEM image is displayed in a state where the distortion of the scan signal is severe due to the impedance component of the deflection coil.

In order to solve the above problems, in the present invention, the optimum frequency of the scan waveform in consideration of the resolution and the real-time SEM image update time can be set through the SEM image control unit, and the rising edge of the waveform, which is the most distorted portion of the scan signal, is raised. In order to minimize the distortion at this starting point, by using the B-Spline curve generation method, the waveform distortion can be minimized by sufficiently securing the time before the rising point, thereby reducing the distortion of the SEM image by less than 10%. Accordingly, an object of the present invention is to provide a scanning waveform control apparatus and method for increasing the SEM resolution capable of reading a good SEM image at high magnification.

Scanning waveform control apparatus for increasing the SEM resolution according to the present invention to achieve the above object

Removably connected to the scanning electron microscope (SEM), and bi-directional data communication with the SEM image control unit, the first generation of the scanning waveform consisting of the X · Y triangular wave, and then from the SEM image control unit A scan waveform controller for generating a scan waveform secondly according to the resolution of the transmitted SEM image and the frequency of the scan waveform according to the SEM image acquisition time;

A deflection coil which converts the scan waveform corrected by the scan waveform controller into an electron beam and scans the sample surface;

A secondary electron signal detector for detecting a secondary electron signal radiated from the sample surface;

An AD converter which converts a secondary electron analog signal output from the secondary electronic signal detector into a digital signal and transmits the digital signal to the SEM image controller;

A DA converter unit for converting the resolution of the SEM image output from the SEM image controller and the frequency of the scan waveform according to the SEM image acquisition time into an analog signal and transmitting the analog signal to the scan waveform controller;

It is connected to the AD converter unit by USB, PCI, PCI-E, and serial communication with the scan generator, and SEM image of the sample surface of the secondary electron digital signal output from the AD converter. And the SEM image control unit for setting the frequency of the scan waveform according to the resolution of the SEM image and the SEM image acquisition time, and transmitting the same to the scanning waveform control unit.

As described above, in the present invention, the optimum frequency of the scan waveform in consideration of the resolution and the real-time SEM image update time can be set through the SEM image control unit, and the rising of the waveform after falling, which is the most severe distortion part of the scan signal, starts. In order to minimize the distortion at the point where it occurs, the B-Spline curve generation method is used to secure enough time before the rising point to minimize the distortion of the waveform, thereby reducing the distortion of the SEM image by less than 10%. In addition, it is possible to read high quality SEM images at high magnification, and above all, to effectively reduce the stabilization period at the beginning of the SEM operation.

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

1 is a block diagram showing the components of a scanning waveform control apparatus for increasing the SEM resolution according to the present invention, which is a scanning waveform controller 100, a deflection coil 200, a secondary electronic signal detection unit 300 , The AD converter 400, the DA converter 500, and the SEM image controller 600.

The scanning waveform control unit 100 is detachably connected to a scanning electron microscope (SEM), and performs a bidirectional data communication with the SEM image control unit in serial communication. After the generation, the scan waveform is secondarily generated according to the resolution of the SEM image transmitted from the SEM image control unit and the frequency of the scan waveform according to the SEM image acquisition time, which is shown in FIG. 2. 110), a scan waveform generator (Scan Generator) 120, and a scan driver (Scan Driver) (130).

The serial communication unit 110 performs bidirectional data communication with the SEM image control unit through serial communication.

The scan generator 120 generates a scan waveform consisting of X and Y triangle waves and transmits the scan waveform to a scan driver.

The scan driver 130 applies a voltage and a current to the scan waveform generated by the scan generator to scan the waveform according to the resolution and SEM image acquisition time of the SEM image transmitted from the SEM image controller. The bandwidth of the scan waveform is corrected according to the frequency of.

Here, the voltage level of the scan waveform corresponds to a scanning region in a scanning electron microscope (SEM). The bandwidth of the scan driver considering the impedance component of the deflection coil and the frequency of the scan waveform is set to the maximum frequency of the scan waveform.

In the present invention, the maximum frequency of the scan waveform is set to 3.5KHz to 4.5KHz.

The reason is that when the frequency of the scan waveform exceeds 3.5KHz to 4.5KHz, the scan signal is distorted due to the overshoot of the scan signal, and the scanning area is changed, so that it is difficult to read the SEM image. Most preferably, the maximum frequency of the scan waveform is set to 3.5KHz to 4.5KHz.

The deflection coil 200 converts the scan waveform corrected by the scan waveform controller into an electron beam and scans the sample surface.

The secondary electronic signal detection unit 300 serves to detect a secondary electron signal emitted from the surface of the sample.

The AD converter 400 converts a secondary electron analog signal output from the secondary electronic signal detector into a digital signal and transmits the converted digital signal to the SEM image controller. As shown in FIG. After converting the SEM image signal consisting of the X-direction scan waveform and the Y-direction scan waveform of the secondary electrons output from the electronic signal detector into a digital signal through a third DSP (Digital Signal Processor), the SEM image controller Configured to transmit.

The third DSP (Digital Signal Processor) is a control chip made for the purpose of digital signal processing, and is composed of a DSP for signal processing to perform 32-bit data processing.

The DA converter 500 converts the resolution of the SEM image output from the SEM image controller and the frequency of the scan waveform according to the SEM image acquisition time into an analog signal, and transmits the analog signal to the scan waveform controller. Similarly, the first DA converter 510 and the second DA converter 520 are configured.

As illustrated in FIG. 7, the first DA converter 510 generates a scan waveform in the X direction through a first DSP (Digital Signal Processor) when a first trigger signal (Trigger in) is input from the SEM image controller. After converting to analog signal, it converts into analog signal and outputs it to the scanning waveform controller.

As illustrated in FIG. 7, when the second trigger signal (Trigger in) is input from the SEM image controller, the second DA converter 520 generates a scan waveform in the Y direction through a second DSP (Digital Signal Processor). After converting to analog signal, it converts into analog signal and outputs it to the scanning waveform controller.

Here, the first DSP and the second DSP are control chips made for the purpose of digital signal processing, and are composed of DSP for signal processing to perform 32-bit data processing.

The SEM image controller 600 is connected to the AD converter by USB, PCI, PCI-E, and is connected in serial communication with a scan generator, and the secondary electrons output from the AD converter. The digital signal is converted into an SEM image of the sample surface, and the scan waveform frequency is set by transmitting the scan waveform according to the resolution of the SEM image and the SEM image acquisition time. The scan waveform frequency is shown in FIG. 4. The setting unit 610 and the scan waveform curve setting unit 620.

The scan waveform frequency setting unit 610 sets the frequency of the scan waveform through the resolution of the SEM image and the SEM image acquisition time.

That is, the frequency of the X-direction scan waveform is determined in consideration of the resolution of the SEM image and the sampling time for digital conversion of the analog input signal. The scan frequency in the Y direction is set equal to the update time of the SEM image per second.

The frequency Tx of the X-direction scan waveform and the frequency Ty of the Y-direction scan waveform can be expressed by Equations 1 and 2 below.

여기서, Px는 X방향의 스캔파형을 나타내고, I_R은 X방향의 스캔파형시 흐르는 피크전류를 나타낸다.

Here, Px represents a scan waveform in the X direction and I _R represents a peak current flowing in the scan waveform in the X direction.

여기서, P_Y는 Y방향의 스캔파형을 나타낸다.

Here, P _Y represents a scan waveform in the Y direction.

Since the scan frequency in the Y direction is set to be equal to the update time of the SEM image per second, the update frequency Fs of the SEM image per second can be expressed by the following expression (3).

For example, in order to obtain a SEM image having a resolution of 320 × 320 in a scanning electron microscope (SEM), if the sampling time of the analog input signal is up to 1.25MHz, the frequency of the scan waveform in the X direction is 3.906 KHz, and the frequency of the scan waveform in the Y direction is 12.2 KHz.

The number of SEM image information updates per second is 12 frames.

For example, FIG. 5 relates to a graph comparing and analyzing a scan waveform and a SEM image according to a frequency change by changing a frequency set through the scan waveform frequency setting unit according to the present invention, which is a waveform generated from a scan signal generator and a scan driver. It shows the waveform applied to the deflection coil via.

Analyzing the waveform in which the actual scan area is determined, it can be seen that the distortion ratio of the waveform at the pole increases rapidly as the frequency increases.

As the ratio of distortion increases, the linear section of the scan waveform decreases, resulting in a change in the scan area, which may cause distortion of the SEM image.

The scan waveform curve setting unit 620 curves the pole section to minimize the distortion at the point where the waveform starts rising after the most dense portion of the scan signal, which is a B-Spline curve generation algorithm. It is composed.

The B-Spline curve generation algorithm uses the property of passing through the first control point and the last control point, and (n + k + 1) -t ₀ to t _{n + k} Sets the knot value t _i .

Where ti is the knot value and k represents the B-Spline's order.

In fact, after the origin return of the X waveform, which has the most distortion of the scan waveform, the most distortion occurs at the starting point to the rising curve section of the scan waveform.

At this time, by changing the position of the control point through the B-Spline curve generation algorithm according to the present invention to generate a curve that minimizes the ratio of distortion at the pole by delaying the time of the rising section after falling of the severely distorted waveform .

This ensures linearity in the rising section of the waveform in the rising section as the variation in the induced voltage decreases as the counter electromotive force of the deflection coil decreases.

For example, Figure 6 is a graph comparing the SEM image data while holding the start and end points to the position corresponding to the pole through the B-Spline curve generation algorithm according to the present invention while changing the positions of the remaining three points It is about.

This can be seen that the faster the fall time of the waveform and the more the delay time before the rise time, the smaller the distortion ratio of the SEM image. The reason for this is that a sudden rise in the current of the coil induces a magnetic force in the coil to shift the position of the beam.

Hereinafter, a scanning waveform control method for increasing the SEM resolution according to the present invention will be described in detail.

First, the scanning waveform control unit first generates a scanning waveform consisting of X and Y triangle waves.

Here, the scan waveform controller generates scan waveform pattern data composed of X and Y triangle waves for scanning the deflection coil.

Subsequently, the scanning waveform corrected by the scanning waveform controller is converted into an electron beam through the deflection coil and scanned on the sample surface.

Subsequently, a secondary electron signal emitted from the surface of the sample is detected through the secondary electron signal detector.

Subsequently, a secondary electron analog signal output from the secondary electronic signal detector through the AD converter is converted into a digital signal and transmitted to the SEM image controller.

Subsequently, the SEM image control unit converts the secondary electron digital signal output from the AD converter into the SEM image of the sample surface, and sets the resolution of the SEM image and the frequency of the scan waveform according to the SEM image acquisition time.

Here, converting the secondary electron digital signal into an SEM image of the surface of the sample is made of two-dimensional array data (triangle wave of XY) for outputting the secondary electron digital signal on the screen. In order to convert the two-dimensional array data (triangular wave of XY) into SEM image data, the two-dimensional array data (triangular wave of XY) is mapped and converted to each pixel of the SEM image.

In addition, the Spline curve generation algorithm of the scan waveform curve setting unit increases the SEM resolution by curved the pole section to minimize the distortion at the point where the waveform starts rising after the most severe distortion in the scan signal.

The converted SEM image is output on the PC monitor screen through Ethernet communication.

Setting the frequency of the scan waveform according to the resolution and SEM image acquisition time of the SEM image is to change the set frequency through the scan waveform frequency setting unit to compare and analyze the scanning waveform and the SEM image of the sample surface according to the frequency change, The frequency of the X-direction scan waveform is determined by considering the resolution of the SEM image and the sampling time for the digital conversion of the analog input signal. The scan frequency in the Y direction is set equal to the update time of the SEM image per second.

Subsequently, the resolution of the SEM image output from the SEM image controller and the frequency of the scan waveform according to the SEM image acquisition time are converted into an analog signal and transmitted to the scan waveform controller through the DA converter.

Subsequently, the scan waveform controller generates a scan waveform secondly according to the resolution of the SEM image transmitted from the SEM image controller and the frequency of the scan waveform according to the SEM image acquisition time.

That is, the bandwidth of the scan waveform is corrected according to the resolution of the SEM image transmitted from the SEM image controller through the scan driver of the scan waveform controller and the frequency of the scan waveform according to the SEM image acquisition time.

Subsequently, the secondary scan waveform corrected by the scanning waveform controller is converted into an electron beam through the deflection coil and scanned on the sample surface.

Subsequently, a secondary electron signal emitted from the surface of the sample is detected through the secondary electron signal detector.

Subsequently, a secondary electron analog signal output from the secondary electronic signal detector through the AD converter is converted into a digital signal and transmitted to the SEM image controller.

Finally, the secondary electron digital signal output from the AD converter through the SEM image controller is converted into a SEM image of the sample surface to complete.

Here, converting the secondary electron digital signal into an SEM image of the surface of the sample is made of two-dimensional array data (triangle wave of XY) for outputting the secondary electron digital signal on the screen. In order to convert the two-dimensional array data (triangular wave of XY) into SEM image data, the two-dimensional array data (triangular wave of XY) is mapped and converted to each pixel of the SEM image.

In addition, the Spline curve generation algorithm of the scan waveform curve setting unit increases the SEM resolution by curved the pole section to minimize the distortion at the point where the waveform starts rising after the most severe distortion in the scan signal.

1 is a block diagram showing the components of a scanning waveform control apparatus for increasing the SEM resolution according to the present invention;

2 is a block diagram showing the components of the scanning waveform control unit 100 according to the present invention;

3 is a block diagram showing the components of the DA converter unit according to the present invention;

4 is a block diagram showing the components of the scanning waveform control unit 600 according to the present invention;

5 is a graph comparing and analyzing a scan waveform and a SEM image according to a frequency change by changing a frequency set through a scan waveform frequency setting unit according to the present invention;

Figure 6 is a graph comparing the SEM image data while changing the position of the remaining three points while holding the start and end points of the control point position corresponding to the pole through the B-Spline curve generation algorithm according to the present invention,

7 is a digital signal of a SEM image signal consisting of X- and Y-direction scan waveforms of secondary electrons output from the secondary electron signal detector according to the present invention through a third DSP (Digital Signal Processor). After converting to, and transmitting to the SEM image control unit; And, if the first trigger signal (Trigger in) is input from the SEM image control unit, after generating a scan waveform in the X direction through a first DSP (Digital Signal Processor) Converting the signal into an analog signal and outputting the converted waveform to the scan waveform controller; When a second trigger signal (Trigger in) is input from the SEM image control unit, a scan waveform in the Y direction is generated through a second DSP (Digital Signal Processor), and then converted into an analog signal and output to the scan waveform controller. In one embodiment,

8 is a flowchart illustrating a scanning waveform control method for increasing SEM resolution according to the present invention.

※ Brief description of reference numerals ※

100: scan waveform control unit 200: deflection coil

300: secondary electronic signal detection unit 400: AD converter unit

500: DA converter unit 600: SEM image control unit

610: scan waveform frequency setting unit 620: scan waveform curve setting unit

Claims (7)

In the apparatus for controlling the scanning waveform to increase the resolution of the scanning electron microscope (SEM), The scanning waveform control device is detachably connected to a scanning electron microscope (SEM), and performs a two-way data communication through a serial communication with a SEM image controller, thereby generating a scanning waveform consisting of X and Y triangle waves as a primary. Then, the scanning waveform control unit 100 for generating the scan waveform secondary to the resolution of the SEM image transmitted from the SEM image control unit and the frequency of the scan waveform according to the SEM image acquisition time, A deflection coil 200 which converts the scan waveform generated by the scan waveform controller into an electron beam and scans the sample surface; A secondary electron signal detector 300 for detecting a secondary electron signal radiated from the sample surface, An AD converter 400 for converting a secondary electron analog signal output from the secondary electronic signal detector into a digital signal and transmitting the digital signal to the SEM image controller; A DA converter unit 500 for converting the resolution of the SEM image output from the SEM image controller and the frequency of the scan waveform according to the SEM image acquisition time into an analog signal and transmitting the analog signal to the scan waveform controller; It is connected to the AD converter unit by USB, PCI, PCI-E, and serial communication with the scan generator. The SEM image of the sample surface shows the secondary electron digital signal output from the AD converter unit. Scan image for increasing the SEM resolution, characterized in that consisting of the SEM image control unit 600 is converted to the image, and set the frequency of the scan waveform according to the SEM image resolution and SEM image acquisition time to transmit to the scanning waveform control unit 100 Mold control device. The method of claim 1, wherein the scanning waveform control unit 100 A serial communication unit (Serial Communication) (110) for bidirectional data communication with the SEM image control unit and serial communication, A scan generator 120 for generating a scan waveform consisting of X and Y triangle waves and transmitting the scan waveform to a scan driver; Bandwidth of the scan waveform according to the resolution of the SEM image transmitted from the SEM image controller and the frequency of the scan waveform according to the SEM image acquisition time by applying voltage and current to the scan waveform generated by the scan generator. Scan waveform control apparatus for increasing the SEM resolution, characterized in that consisting of a scan driver (Scan Driver) (130) for correcting. The analog converter 500 of claim 1, wherein the DA converter 500 generates a scan waveform in the X direction through a first digital signal processor (DSP) when a first trigger signal (Trigger in) is input from the SEM image controller, A first DA converter 510 which converts the signal into a signal and outputs the result to the scanning waveform controller; When the second trigger signal (Trigger in) is input from the SEM image control unit, the second DA generates a scan waveform in the Y direction through a second DSP (Digital Signal Processor), converts it into an analog signal, and outputs it to the scan waveform controller. Scan waveform control apparatus for increasing the SEM resolution, characterized in that consisting of a converter (520). The digital converter of claim 1, wherein the AD converter 400 outputs an image signal including an X-direction scan waveform and a Y-direction scan waveform relating to secondary electrons output from the secondary electronic signal detector. After converting into a digital signal through a processor, and transmits to the SEM image control unit, the scanning waveform control device for increasing the SEM resolution, characterized in that configured. The method of claim 1, wherein the SEM image control unit 600 is a scan waveform frequency setting unit 610 for setting the frequency of the scan waveform through the resolution and SEM image acquisition time of the SEM image, To increase the SEM resolution of the scan signal, the scan waveform curve setting unit 620 curves the pole section to minimize the distortion at the point where the waveform starts rising after the most severe distortion of the scan signal. Scanning waveform control device. Generating, by the scanning waveform control unit, a scanning waveform consisting of triangular waves of X Y in a first order (S100); Converting the scanning waveform generated by the scanning waveform controller through the deflection coil into an electron beam and scanning the sample surface (S110); Detecting a secondary electron signal emitted from the surface of the sample through the secondary electron signal detection unit (S120); Converting a secondary electron analog signal output from the secondary electronic signal detection unit through the AD converter into a digital signal and transmitting the digital signal to the SEM image control unit (S130); Converting the secondary electron digital signal output from the AD converter to the SEM image of the sample surface through the SEM image control unit, and setting the frequency of the scan waveform according to the resolution of the SEM image and the SEM image acquisition time (S140) )Wow,  Converting the resolution of the SEM image output from the SEM image control unit and the frequency of the scan waveform according to the SEM image acquisition time through the DA converter unit into an analog signal and transmitting the analog signal to the scanning waveform control unit (S150); In step S160, the scan waveform controller generates a scan waveform in accordance with the resolution of the SEM image transmitted from the SEM image controller and the frequency of the scan waveform according to the SEM image acquisition time (S160). Converting the second scan waveform corrected by the scan waveform controller into an electron beam through the deflection coil and scanning the sample on the surface of the sample (S180); Detecting a secondary electron signal emitted from the surface of the sample through the secondary electron signal detection unit (S190); Converting a secondary electron analog signal output from the secondary electronic signal detector through the AD converter into a digital signal and transmitting the digital signal to the SEM image controller (S200); And converting the secondary electron digital signal output from the AD converter through the SEM image control unit into a SEM image of the surface of the sample, thereby completing the scanning waveform control method for increasing the SEM resolution. 7. The method of claim 6, wherein converting the secondary electron digital signal into an SEM image of a sample surface SEM image to make 2D array data (triangle wave of XY) to output secondary electron digital signal to the screen, and to convert 2D array data (triangle wave of XY) into SEM image data Mapping and converting two-dimensional array data (triangle wave of X and Y) to each pixel of, and using the Spline curve generation algorithm of the scan waveform curve setting section, the waveform rises after falling, which is the most distorted part of the scan signal. Scanning waveform control method for increasing the SEM resolution, characterized in that to increase the SEM resolution by curving the pole section to minimize the distortion at the point.

Images