JP2002373612A - Electron beam device, and manufacturing method of the device using electron beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron beam device, capable of maximally utilizing an advantage of using multi-beams by providing a specific signal processing circuit processing a detection signal, after detecting a secondary electron by a detector. SOLUTION: The electron beam device is provided with a primary optical system 10 scanning a sample by focusing a plurality of primary electron beams, a secondary optical system 30 introducing a plurality of secondary electrons emitted from the sample by the first electron beams to each detector 41, and a detection system 40 performing image processing of a plurality of detection signals outputted from each detector. In the detection system, an analog-to- digital converter 42 which converts detection signal from a detector into a digital signal, an imaging circuit 43 converting the digital signal into a two-dimensional pattern, a circuit 44 detecting an edge of the two-dimensional pattern and converting it into an edge image, and a pattern comparison circuit 48 comparing the detected two-dimensional pattern with a two-dimensional pattern from pattern data are individually provided by each detector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has a minimum line width of 0.1 .mu.m.
Wafer and mask defect detection with the following patterns,
The present invention relates to an electron beam apparatus that performs sample evaluation such as CD measurement and potential contrast measurement with high throughput and high reliability, and further relates to a device manufacturing method using such an electron beam apparatus.

[0002]

2. Description of the Related Art An electron beam apparatus using a plurality of electron beams, that is, a multi-beam, is described, for example, in Japanese
PHYSICS ", VOL 28, NO. 10, October 205
From page 8 to page 2064, “Multi-Beam Concept
s for Nanometer Device ”. In the known device, a plurality of primary electron beams arranged in parallel are focused on a sample by a deceleration immersion lens to scan the sample, and the secondary electrons emitted from the sample are subjected to a Wiener filter (E × B separator). And separates it from the primary electron beam to form a secondary electron image on the multi-detector.

[0003]

However, in the conventional apparatus using a multi-beam as described above, after a secondary electron is detected by a detector, how the detection signal is processed to form an image. However, the specific signal processing method and its circuit are not clear, and it has not always been possible to provide a method and circuit capable of maximizing the advantage of using the multi-beam.

The present invention has been made in view of the above problems, and one problem to be solved by the present invention is to detect a secondary electron with a detector and then process the detected signal. An object of the present invention is to provide a signal processing circuit and an electron beam apparatus capable of maximizing the advantage of using a multi-beam. Another problem to be solved by the present invention is to provide a method for manufacturing a device for evaluating a sample in the course of a process using the above-described electron beam apparatus.

[0005]

According to the present invention, there is provided a primary optical system which focuses a plurality of primary electron beams and scans the sample with the electron beams, and a secondary optical system which is emitted from the sample by the scanning of the primary electron beams. After passing the secondary electrons through the objective lens, the secondary electrons are separated from the primary optical system by an E × B separator, and a plurality of secondary electron images are introduced into each detector. An electron beam apparatus comprising: a detection system that performs image processing on a plurality of detection signals that are output; wherein the detection system includes an A / D converter that converts a detection signal from the detector into a digital signal; An image forming circuit that forms a two-dimensional pattern with reference to a scanning signal from the circuit, a circuit that detects an edge of the two-dimensional pattern and converts the detected two-dimensional pattern into an edge image, and converts the detected two-dimensional pattern into two-dimensional pattern data. Pattern to compare with the pattern And over down comparator circuit, a has independently for each detector.

According to another aspect of the present invention, there is provided a primary optical system for converging a plurality of primary electron beams and scanning the sample with the electron beams, and an object for secondary electrons emitted from the sample by the scanning of the primary electron beams. After passing through the lens, it is separated from the primary optical system by an E × B separator, and a plurality of secondary electron images are introduced into each detector, and a plurality of secondary electrons are output independently from each detector. A detection system for performing image processing on the detection signal, wherein the detection system includes an A / D converter for converting a detection signal from the detector into a digital signal, and a two-dimensional pattern from the digital signal. An image forming circuit for forming a contour line image based on image data from the image forming circuit; and a pattern comparison circuit for comparing the detected two-dimensional pattern with a two-dimensional pattern from pattern data. When provided with independently for each detector.

According to another aspect of the present invention, there is provided a primary optical system that focuses a plurality of primary electron beams and scans the sample with the electron beam, and uses a secondary electron emitted from the sample by the scanning of the primary electron beam as an object. After passing through the lens, it is separated from the primary optical system by an E × B separator, and a plurality of secondary electron images are introduced into each detector, and a plurality of detection signals output from each detector. And a detection system for image processing the
The detection system includes an A / D converter for converting a detection signal from the detector into a digital signal, an image forming circuit for forming a two-dimensional pattern from the digital signal, and detecting an edge of the two-dimensional pattern. A circuit for converting to an edge image, a signal strength image forming circuit for forming a contour image based on image data from the image forming circuit, and a changeover switch for selectively switching the circuit for converting to the edge image or the signal strength image forming circuit And a pattern comparison circuit for comparing the detected two-dimensional pattern with a two-dimensional pattern from pattern data, independently for each detector.

[0008] Still another invention of the present application is directed to a primary optical system that focuses a plurality of primary electron beams and scans the sample with the electron beam, and converts a secondary electron emitted from the sample by the scanning of the primary electron beam. After passing through the objective lens, it is separated from the primary optical system by an E × B separator, and a plurality of secondary electron images are introduced into each detector, and a plurality of detections output from each detector are provided. And a signal processing circuit that independently processes signals, wherein the plurality of secondary electron images are closer to the detector than the deflection main surface or the deflection main surface of the E × B separator. It is configured to be formed. Still another object of the present invention is to provide a device manufacturing method for evaluating a wafer during a process using an electron beam apparatus.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an electron beam apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an electron beam device 1 according to the present embodiment. The electron beam device 1 includes a primary optical system 10, a secondary optical system 30, and a detection system 40. The primary optical system 10 is an optical system that irradiates the surface of an inspection target (hereinafter, a sample) S with an electron beam, and includes an electron gun 11 that emits an electron beam and a condenser that focuses a primary electron beam C emitted from the electron gun 11. A lens 12, a condenser lens 13 disposed below the condenser lens 12 for focusing the primary electron beam,
A multi-aperture plate 14 arranged below the condenser lens 13 and formed with a plurality of (eight in this embodiment) openings 141 for forming a primary electron beam into a plurality of primary electron beams, that is, a multi-beam; , An electrostatic deflector 16 for deflecting and scanning the primary electron beam, a Wien filter, ie, E × B separators 17 and 18, and objective lenses 19, 20 and 21. As shown in FIG. 1, the electron gun 11 is arranged in order with the electron gun 11 at the top, and furthermore, the optical axis of the primary electron beam emitted from the electron gun is perpendicular to the surface (sample surface) of the sample S. The cathode 111 of the electron gun 11 is formed so as to have eight projections on the same plane on the circumference around the optical axis A of the primary optical system, and the Wehnelt 112 is located at a position corresponding to the projection of the cathode. It is formed to have only holes.

The secondary optical system 30 includes an E × B deflector 17,
It has two stages of magnifying lenses 31 and 32 for passing secondary electrons separated from the primary optical system 10 by 18, and a multi-aperture detection plate 33. The openings 331 formed in the multi-aperture detection plate 33 correspond one-to-one with the openings 141 formed in the multi-aperture plate 14 of the primary optical system.

The detection system 40 includes a plurality (eight in this embodiment) of detectors 41 disposed in close proximity to and corresponding to the respective openings 331 of the multi-aperture detection plate 33 of the secondary optical system 30.
An A / D converter 42 that converts a detection signal from each detector 41 into a digital signal; an image forming circuit 43 that converts a digital signal into a two-dimensional pattern; and an edge image that detects edges of the two-dimensional pattern. , A signal strength image forming circuit 45 for forming a contour image based on the image data from the image forming circuit 43, and a changeover switch for selectively switching the circuit 44 for converting to an edge image or the signal strength image forming circuit 45. 46 and 47 and a pattern comparison circuit 48 for comparing the detected two-dimensional pattern with a two-dimensional pattern from pattern data are provided independently for each detector. The detection system 40 includes a central processing unit 49 for controlling each of the above circuits.

Next, the operation of the electron beam apparatus 1 having the above configuration will be described. The primary electron beam emitted from the electron gun 11 becomes eight electron beams C substantially parallel to the optical axis A, is focused by the condenser lens 12 of the primary optical system 10, and the emission angle of the electron beam is enlarged, and the condenser lens 13 Focused by Next, the primary electron beam C is applied to the multi-aperture plate 14.
Are formed into a plurality of electron beams through the plurality of openings 141. The electron beam passing through the multi-aperture plate forms a crossover at a position P1, and a reduced image of the multi-aperture plate 14 is formed at P2 by a reduction lens 15. This reduced image is focused by the objective lenses 19, 20, and 21 and focused on the surface of the sample S. In the E × B separators 17 and 18, the voltage and the current are set such that the electron beam is very slightly deflected.
This electron beam is deflected by both the E × B separators 17 and 18 and the electrostatic deflector 16 so as to simultaneously scan the surface of the sample S. The sample S is irradiated at a plurality of points by the plurality of focused electron beams, and secondary electrons D are emitted from the plurality of irradiated points. This secondary electron D is applied to the center electrode 20 of the objective lenses 19, 20, and 21.
Are accelerated and focused by the high voltage applied to and pass through the objective lens. Further, the light is deflected by the E × B separators 17 and 18 and is input to the secondary optical system 30 to be incident along the optical axis B of the secondary optical system. At this time, the image due to the secondary electrons is E × B
It is formed on the principal deflection surface of the separators 17 and 18 or P3 slightly on the detector side of the principal deflection surface.

The secondary electron image formed at the position P3 is expanded in the two-stage magnifying lenses 31 and 32 so that the distance between the secondary electrons is enlarged and focused on the corresponding aperture 331 of the multi-aperture detection plate 33. The image is detected by the detector 41 arranged corresponding to each opening 331. The detector 41 converts the detected electron beam into an electric signal representing the intensity. The detectors 41 each have an amplifier and amplify the converted electric signal.
The electric signals amplified in this manner are output from the detectors 41, converted into digital signals by the A / D converters 42, and then input to the image forming circuit 43.
The image forming circuit 43 converts the input digital signal into a two-dimensional pattern. The image forming circuit 43 is supplied with a scanning signal for deflecting the primary electron beam from a deflection scanning power supply 50. After being converted into a two-dimensional pattern, the pattern edge is detected by the edge detection circuit 44 and converted into an accurate two-dimensional pattern, thereby forming an edge image. Next, the signal of the edge image is input to a pattern comparison circuit, and the quality of the detected (evaluated) pattern of the sample S is compared with a standard two-dimensional pattern set in advance or an image of the same location of a previous die. Is detected.

Apart from the above, the changeover switches 46 and 47 are switched to the signal intensity image forming circuit 45 side, and the image data output from the image forming circuit 43 is input to the signal intensity image forming circuit 45, thereby forming the contour line image. It is also possible to form When detecting a contact failure of the via by looking at the potential contrast image, the signal intensity image forming circuit 45
It is advantageous to switch to It is desirable that any circuit can be selected by a command from the central processing unit 49 depending on the pattern to be evaluated. When obtaining a potential contrast image, the objective lens 19.2
A voltage of a potential lower than that of the sample (eg, wafer) may be applied to the lower electrode 21 of 0, 21 so as to drive some of the secondary electrons back to the wafer.

In the edge detection circuit 44, a single threshold value is set, and it is set to 1 for an address of a secondary electron signal larger than the threshold value, and set to 0 for an address of a secondary electron signal smaller than the threshold value. All addresses are converted to binary and converted to a binary pattern image. Also,
In the image of the signal strength, a plurality of threshold values are set by equally dividing the maximum value and the minimum value of the signal strength, and an equal strength curve of each threshold value is drawn. This iso-intensity curve may be modified so as to be a smooth curve because the unevenness in pixels is severe.

Next, an embodiment of a method of manufacturing a semiconductor device according to the present invention will be described with reference to FIGS. FIG.
3 is a flowchart showing one embodiment of a method for manufacturing a semiconductor device according to the present invention. The manufacturing process of this embodiment includes the following main processes. (1) Wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer) (2) Mask manufacturing process for manufacturing a mask used for exposure (or mask preparing process for preparing a mask) (3) Necessary for wafer (4) Chip assembling step of cutting out chips formed on a wafer one by one and making them operable (5) Chip inspection step of inspecting the resulting chips The main process further comprises several sub-processes.

Among these main steps, the wafer processing step (3) has a decisive effect on the performance of the semiconductor device. In this step, designed circuit patterns are sequentially stacked on a wafer, and a number of chips that operate as memories and MPUs are formed. This wafer processing step includes the following steps. (1) A thin film forming step (CVD) for forming a dielectric thin film or wiring portion serving as an insulating layer, or a metal thin film forming an electrode portion.
(2) Oxidation step of oxidizing this thin film layer or wafer substrate (3) Lithography to form a resist pattern using a mask (reticle) to selectively process the thin film layer or wafer substrate Step (4) Etching step of processing a thin film layer or a substrate according to a resist pattern (for example, using a dry etching technique) (5) Ion / impurity implantation / diffusion step (6) Resist stripping step (7) Step of inspecting the processed wafer It should be noted that the wafer processing step is repeated by the required number of layers to manufacture a semiconductor device that operates as designed.

FIG. 3 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. This lithography step includes the following steps. (1) A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the previous step (2) A step of exposing the resist (3) A developing step of developing the exposed resist to obtain a resist pattern ( 4) Annealing Step for Stabilizing the Developed Resist Pattern The above-described semiconductor device manufacturing step, wafer processing step, and lithography step are well known and need no further explanation. When the defect inspection method and the defect inspection apparatus according to the present invention are used in the inspection step (7), even a semiconductor device having a fine pattern can be used.
Since the inspection can be performed with a high throughput, it is possible to perform the 100% inspection, thereby improving the yield of products and preventing the shipment of defective products.

[0019]

According to the present invention, the following effects can be obtained. (A) Since the sample is evaluated using the multi-beam, the throughput of the evaluation can be increased by a multiple corresponding to the number of beams. (B) Since various circuits for image processing of the detection system are provided independently and signals from each beam can be processed independently, it is no longer necessary to consider the problem of a connection region between beams. (C) When detecting a shape defect of a sample, a pattern edge image is used, and when detecting a defect from a potential contrast, a signal intensity image is used, so that an optimal circuit can be selected according to a pattern. . (D) When forming a two-dimensional image, the processing at the boundary between the beams can be omitted.

[Brief description of the drawings]

FIG. 1 is a schematic view of one embodiment of an electron beam device according to the present invention.

FIG. 2 is a flowchart showing one embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIG. 3 is a flowchart showing a lithography step which is a core of the wafer processing step of FIG. 2;

[Explanation of symbols]

1: electron beam device 10: primary optical system 11: electron gun 12, 13: condenser lens 14: multi-aperture plate 15: reduction lens 16: electrostatic deflector 17, 18:
Ex × B deflector 19, 20, 21: Objective lens 30: Secondary optical system 31, 32: Magnifying lens 33: Multi-aperture detection plate 40: Detection system 41: Detector 42: A / D converter 43: Image formation Circuit 44: Circuit for converting to an edge image 45: Signal strength image forming circuit 46, 47:
Changeover switch 48: Pattern comparison circuit 49: Central processing unit 50: Deflection scanning power supply

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01J 37/28 H01J 37/28 B 37/29 37/29 // G01R 31/02 G01R 31/02 (72 ) Inventor: Mamoru Nakasuji Inside Ebara Meister Co., Ltd., 11-1, Haneda, Asahi-cho, Ota-ku, Tokyo (72) Inventor Takao Kato Inside Ebara Seisakusho, Inc. 11-1, Asahi-cho, Haneda, Ota-ku, Tokyo (72) Inventor Noji Shinji 11-1 Haneda Asahimachi, Ota-ku, Tokyo Ebara Corporation (72) Inventor Toru Satake 11-1 Haneda Asahi-cho, Ota-ku, Tokyo F-term in Ebara Corporation (reference) 2G001 AA03 AA10 BA07 CA03 DA09 EA05 FA01 KA03 LA11 MA05 SA01 2G014 AA01 AA02 AA03 AA08 AB59 AC11 5C033 NN01 UU04 UU05

Claims (5)

[Claims] 1. A primary optical system for converging a plurality of primary electron beams and scanning the sample with the electron beams, and after passing secondary electrons emitted from the sample by the scanning of the primary electron beams through an objective lens. A secondary optical system that separates from the primary optical system with an E × B separator and introduces a plurality of secondary electron images to each detector, and a plurality of detection signals that are output independently from each detector. An electron beam apparatus comprising: a detection system for processing; an A / D converter for converting a detection signal from the detector into a digital signal; and an image forming apparatus for forming a two-dimensional pattern from the digital signal. A circuit for detecting an edge of the two-dimensional pattern and converting the detected two-dimensional pattern into an edge image; and a pattern comparison circuit for comparing the detected two-dimensional pattern with a two-dimensional pattern from pattern data. Independently prepared An electron beam apparatus characterized in that: 2. A primary optical system for converging a plurality of primary electron beams and scanning the sample with the electron beams, and after passing secondary electrons emitted from the sample by the scanning of the primary electron beams through an objective lens. A secondary optical system that separates from the primary optical system with an E × B separator and introduces a plurality of secondary electron images to each detector, and a plurality of detection signals that are output independently from each detector. An electron beam apparatus comprising: a detection system for processing; an A / D converter for converting a detection signal from the detector into a digital signal; and an image forming apparatus for forming a two-dimensional pattern from the digital signal. Circuit, a signal intensity image forming circuit for forming a contour image based on image data from the image forming circuit, and a pattern comparing circuit for comparing the detected two-dimensional pattern with a two-dimensional pattern from pattern data. Every vessel An electron beam apparatus, which is provided independently of the above. 3. A primary optical system for converging a plurality of primary electron beams and scanning the sample with the electron beams, and after passing secondary electrons emitted from the sample by the scanning of the primary electron beams through an objective lens. A secondary optical system that separates from the primary optical system with an E × B separator and introduces a plurality of secondary electron images into each detector, and a detection that performs image processing on a plurality of detection signals output from each detector An electron beam apparatus comprising: an A / D converter that converts a detection signal from the detector into a digital signal; an image forming circuit that forms a two-dimensional pattern from the digital signal; A circuit for detecting an edge of the two-dimensional pattern and converting it to an edge image; a signal intensity image forming circuit for forming a contour image based on image data from the image forming circuit; a circuit for converting the edge image to the edge image or the signal intensity Image shape A changeover switch for selectively switching a circuit, and a pattern comparison circuit for comparing the detected two-dimensional pattern with a two-dimensional pattern from pattern data, independently provided for each detector. Electron beam device. 4. A primary optical system for converging a plurality of primary electron beams and scanning the sample with the electron beam, and after passing secondary electrons emitted from the sample by the scanning of the primary electron beam through an objective lens. A secondary optical system that separates from the primary optical system with an E × B separator and introduces a plurality of secondary electron images into each detector, and a plurality of detection signals output from each detector are independently provided. An electron beam apparatus comprising a signal processing circuit for processing, wherein the plurality of secondary electron images are formed on the detector main surface of the E × B separator or slightly on the detector side of the main deflection surface. Electron beam device. 5. A device manufacturing method for evaluating a wafer during a process using the electron beam apparatus according to claim 1.