JP2002231173A - Image pick-up device using electron beam, and method for manufacturing device using the same image pick-up device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron beam device capable of correctly evaluating in spite of transmission ratio difference between multiple beams by composing an optical system in such a way that the primary beam and the secondary beam can be separately controlled. SOLUTION: This image pick-up device is provided with a primary optical system 10 to converge plural primary electron beams to scan a sample S by the electron beams. Secondary electrons emitted from the sample by scan by the primary electron beams are separated from the primary optical system 10 by an E×B separator 15 after they are sent through an objective lens 16. An image of the secondary electrons is enlarged by a secondary optical system 20 having at least one stage of a lens, the image of the secondary electrons is respectively detected by plural secondary electron detectors 31, and if a pattern forming condition of the sample is acceptable or not is inspected based on them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam apparatus for inspecting a pattern or the like formed on the surface of a sample by using an electron beam, and more particularly to a method for detecting a defect in a wafer in a semiconductor manufacturing process. An electron beam apparatus that irradiates a sample to be inspected with an electron beam, captures secondary electrons that change according to the surface properties of the sample, forms image data, and inspects the quality of the pattern based on the image data. And 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 in, for example, "Japanese Journal of APPLID".
PHYSICS ”, VOL 28, NO. 10, p.
It is already known as shown in “ti-Beam Nanometer Pattern Inspection”. In the above-mentioned known apparatus, a primary electron beam arranged in a straight line is irradiated on a sample, and a secondary electron beam from the sample is imaged on a multi-detector by a two-stage lens common to the primary electron beam. , E × B, the secondary electron beam separated from the primary electron beam is guided to the detector without passing through the lens. Therefore, the two-stage lens needs to satisfy a common focusing condition for the primary electron beam and the secondary electron beam.

[0003]

However, in the conventional apparatus using a multi-beam as described above, since the primary electron and the secondary electron have two common lenses, the common electron beam of the two electrons is used. It is difficult to adjust the focus condition, image magnification, and the like. Even if the design was matched, it was difficult to adjust without a mechanical moving mechanism when the beam was actually emitted and evaluated, and it was slightly out of order. Further, since the beam current difference between the multiple beams and the transmittance difference of the secondary electrons are aligned on a straight line, there is a beam close to the optical axis and a beam far from the optical axis. There is a big problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and one problem to be solved by the present invention is to enable an optical system to control a primary beam and a secondary beam independently of each other. An object of the present invention is to provide an electron beam apparatus which can correctly evaluate even if there is a difference in transmittance between the multi-beams. Another object to be solved by the present invention is to provide an electron beam apparatus that converts a secondary electron beam into a digital signal, creates image data using the digital signal, and automatically compares the contrast in the pattern to be evaluated to inspect the sample. To provide. Still another object to be solved by the present invention is to provide a method for manufacturing a device for evaluating a sample during a process using the electron beam apparatus as described above.

[0005]

The invention of the present application comprises a primary optical system for converging a plurality of primary electron beams and scanning the sample with the electron beams, and 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 gun by an E × B separator, and the secondary electron image is enlarged by a secondary optical system having at least one stage lens. Are detected by a plurality of secondary electron detectors, respectively,
In the electron beam apparatus for inspecting the quality of the pattern formation state of the sample thereby, the detection signal detected by the secondary electron detector is converted into a digital signal by an A / D converter,
The digital signal is used to form image data, and the contrast of the pattern to be evaluated is automatically compared to inspect the quality of the pattern.

In one embodiment of the electron beam apparatus according to the present invention, a contrast difference between the plurality of electron beams may be normalized by a contrast other than a pattern portion to be evaluated. Further, the pattern to be evaluated may be a contact hole or a via. Further, the interval between the plurality of electron beams may be larger than the resolution of the secondary optical system in terms of the sample surface. Another object of the present invention is to provide a device manufacturing method characterized by detecting a defect of a wafer during a process using the above-mentioned electron beam apparatus.

[0007]

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 20, and a detection system 30. 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 an electrostatic device that focuses the primary electron beam emitted from the electron gun 11. A lens or condenser lens 12;
And a multi-aperture plate 13 having a plurality of openings formed therein to form a primary electron beam into a plurality of primary electron beams, that is, a multi-beam; a reducing lens 14 which is an electrostatic lens for reducing the primary electron beam; , A Wien filter or EXB separator 15, and an objective lens 16, which are arranged in order with the electron gun 11 at the top as shown in FIG. Are arranged so that the optical axis of the sample is perpendicular to the surface (sample surface) of the sample S. In order to eliminate the influence of the field curvature aberration of the reduction lens 14 and the objective lens 16, a plurality (9 in this embodiment) of apertures 131 formed in the multi-aperture plate 13.
Are formed on the same circumference as shown in FIG. 2, and are arranged so that the distance Lx in the X direction between the projected images of the openings is the same.

The secondary optical system 20 includes magnifying lenses 21 and 22 which are two-stage electrostatic lenses for passing secondary electrons separated from the primary optical system by the E × B deflector 14, and a multi-aperture detecting plate 23. It has. The openings 231 formed in the multi-aperture detection plate 23 correspond one-to-one with the openings 131 formed in the multi-aperture plate 13 of the primary optical system.

The detection system 30 includes a plurality (nine in this embodiment) of detectors 31 arranged in close proximity to the respective openings 231 of the multi-aperture detection plate 23 of the secondary optical system 20.
And an image processing unit 33 electrically connected to each detector 31 via an A / D converter 32.

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 is focused by the condenser lens 12 of the primary optical system 10 and forms a crossover at the point P1. On the other hand, the primary electron beam focused by the condenser lens 12 is formed into a plurality of primary electron beams through the plurality of openings 131 of the multi-aperture plate, reduced by the reduction lens 14 and projected to the position P2. After focusing at the position P2, focusing is further performed on the surface of the sample S by the objective lens 16. On the other hand, the primary electron beam is deflected by a deflector 17 disposed between the reduction lens 14 and the objective lens 16 so as to scan the surface of the sample S. The sample S is irradiated at a plurality of points by the focused (in this embodiment, nine) primary electron beams, and secondary electrons are emitted from these irradiated points. This secondary electron is
It is narrowed and focused by the electric field of the objective lens 16 and E × B
The light is deflected by the separator 15 and is input to the secondary optical system 20.
The image due to the secondary electrons is focused at a position P3 closer to the deflector 15 than the position P2. This is because the primary electron beam has energy of 500 eV on the sample surface, while the secondary electron has energy of only several ev.

The image of the secondary electron focused at the position P3 is converted by a two-stage magnifying lens into the corresponding aperture 2 of the multi-aperture detection plate 23.
The image is focused on 31, and the image is detected by the detector 31 arranged corresponding to each opening 231. The detector 31 converts the detected electron beam into an electric signal indicating its intensity. The electric signal thus converted is output from each detector 31 and is converted into a digital signal by the A / D converter 32, and then input to the image processing unit 33. Image processing unit 3
Reference numeral 3 converts the input digital signal into image data.
Since the scanning signal for deflecting the primary electron beam is supplied to the image processing unit 33, the image processing unit displays an image representing the surface of the sample. The quality of the detected (evaluated) pattern of the sample S is detected by comparing this image with a standard pattern preset in a setting device (not shown) and a comparator (not shown). Further, the pattern to be measured of the sample S is moved to a position near the optical axis of the primary optical system by registration, and a line width evaluation signal is taken out by performing a line scan, and the signal is appropriately calibrated to be formed on the surface of the sample. The line width of the patterned pattern can be measured.

When the primary electron beam that has passed through the aperture of the multi-aperture plate 13 of the primary optical system is focused on the surface of the sample S and secondary electrons emitted from the sample are imaged on the detector 31, Special care must be taken to minimize the effects of three aberrations, distortion, magnification chromatic aberration, and visual field astigmatism, which occur in the primary optical system. Regarding the relationship between the intervals between a plurality of primary electron beams and the secondary optical system, if the interval between the primary electron beams is separated by a distance larger than the aberration of the secondary optical system, crosstalk between the multiple beams can be reduced. Can be eliminated.

FIG. 3 is a diagram showing an arrangement of contact holes on a sample detected by three detectors for secondary electrons and a line contrast obtained by the three detectors for the arrangement. That is, in FIG.
Of the multi-aperture plate 13 shown in FIG.
a, A shows the arrangement of contact holes on the sample S inspected by scanning of the primary electron beam passing through 131b and 131c, and [B] shows lines AA ', B in [A].
The detection values obtained by the detector for the arrangement of the contact holes from which the -B 'and C-C' are drawn (the secondary electrons emitted from the sample surface by the irradiation of the primary electron beam passing through the above three openings are reduced by three). The values of the line contrast obtained from two detectors are shown.

The value Vs of the line contrast from the portion other than the contact hole, that is, from the sample surface where the contact hole is not formed should be essentially the same value in any portion. However, the measurement result Vsa (value α) of the contact hole in which the line AA ′ is drawn,
The measurement result Vsb (value β) of the contact hole drawn along the line BB ′ is different from the measurement result Vsc (value γ) of the contact hole drawn along the line CC ′. The possible reason is that the opening 131
a, the beam current of the primary electron beam that passed through a was the largest, or the transmittance of the secondary electrons emitted by the irradiation of the primary electron beam was the largest, and conversely, the primary electron beam that passed through the opening 131b. Is the smallest or the transmittance of the secondary electrons emitted by the irradiation of the primary electron beam is the smallest. In such a case, it is necessary to adjust the values of Vsa, Vsb, and Vsc so that the values Vs of the line contrast in portions other than the contact holes are all the same. As this method, a method of adjusting a beam current of each multi-beam or a method of adjusting the transmittance of secondary electrons can be considered, but it is difficult to implement such a method.

Therefore, in the present invention, as shown in FIG. 1, each of the A / D converters 32 is provided with an attached gain adjuster 35 to detect a value different from a reference value (α in this case). The gain adjustment devices 35 of the amplifiers connected to the detected detectors are individually adjusted to obtain the line contrast values Vsa, Vsb, and Vsc of portions other than the contact holes.
Was made to match. Of course, the above adjustment was performed for all the detectors, and the line contrast values of the portions other than the contact holes (the surface of the sample) were made the same. After the adjustment, the line contrast value Vh of each contact hole portion was examined, and an appropriate value was judged as good, and the others were judged as bad. In the case of the above example, the contact holes h1 to h1
Of the five line contrast values Vh1 to Vh15, Vh1, Vh2, and Vh5 are smaller than the other values. For this reason, the contact holes h1, h2, and h5 having obtained the small line contrast values were determined to be defective, and the other contact holes having large values were determined to be good. Such determination is automatically performed by the image processing unit 33 by a known method.

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 a wiring portion serving as an insulating layer, or a metal thin film forming an electrode portion.
(2) An oxidation step of oxidizing the thin film layer or the wafer substrate. (3) Lithography for forming a resist pattern using a mask (reticle) to selectively process the thin film layer or the 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 as many times as necessary to manufacture a semiconductor device that operates as designed.

FIG. 5 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 inspection can be performed with high throughput, 100% inspection can be performed, and the yield of products can be improved, and shipment of defective products can be prevented.

[0019]

According to the present invention, the following effects can be obtained. (A) Correct judgment can be made even if there is a difference in the beam current or the detection efficiency of secondary electrons between the multiple beams. (B) Since the automatic evaluation is performed using a multi-beam, the throughput is high and many contact holes can be efficiently evaluated. (C) The lens through which the primary beam and the secondary beam pass in common is 1
Since there are only steps, and both the primary beam and the secondary beam have other lenses, the focusing condition and the imaging magnification can be adjusted independently.

[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 diagram showing a positional relationship of openings of a multi-aperture plate used in a primary optical system of the electron beam apparatus of FIG.

FIG. 3 is a diagram showing an example of judging pass / fail of a contact hole using the electron beam apparatus of the present invention.

FIG. 4 is a flowchart showing one embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. 4;

[Explanation of symbols]

Reference Signs List 1 electron beam device 10 primary optical system 11 electron gun 12 focusing lens 13 multi-aperture plate 14 reduction lens 15 E × B deflector 20 secondary optical system 21, 22 magnifying lens 23 multi-aperture detection plate 30 detection system 31 detector 32 A / D converter 33 Image processing unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G21K 5/04 G21K 5/04 MW H01J 37/29 H01J 37/29 11-1 Haneda Asahimachi, Ota-ku Ebara Meister Co., Ltd. (72) Inventor Shinji Noji 11-1, Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Works Co., Ltd. (72) Inventor Toru Satake Haneda, Ota-ku, Tokyo 11-1 Asahimachi F-term in EBARA CORPORATION (reference) 2G001 AA03 AA10 BA07 CA03 DA02 DA06 EA05 GA06 JA16 KA03 LA11 MA05 SA01 2G088 EE30 FF10 FF14 JJ05 KK05 KK24 KK32

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 secondary electrons emitted from the sample by the scanning of the primary electron beams are passed through an objective lens. After that, the secondary electron image is separated from the primary optical system gun by an E × B separator, and the secondary electron image is enlarged by a secondary optical system having at least one lens, and the secondary electron image is divided into a plurality of secondary electron images. In an electron beam apparatus, each of which is detected by a detector and thereby inspects the quality of the pattern formation state of the sample, the detection signal detected by the detector of the secondary electrons is A / A
An electron beam apparatus comprising: converting a digital signal into a digital signal by a D converter; forming image data based on the digital signal; 2. The electron beam apparatus according to claim 1, wherein
An electron beam apparatus, wherein a contrast difference between the plurality of electron beams is normalized by a contrast other than a pattern portion to be evaluated. 3. The electron beam device according to claim 1, wherein the pattern to be evaluated is a contact hole or a via. 4. The electron beam apparatus according to claim 1, wherein an interval between said plurality of electron beams is larger than a resolution of a secondary optical system in terms of a sample surface. apparatus. 5. A method of manufacturing a device for detecting a defect of a wafer during a process using the electron beam apparatus according to claim 1.