JP2003203596A - Electron beam device and method of manufacturing device using this electron beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam device capable of reducing shot noise of an electron beam, capable of increasing a beam current, capable of forming a molding beam by only two-stage lenses, and operable with high stability. <P>SOLUTION: This electron beam device detects a secondary electron emitted from a sample surface by irradiating a sample with the electron beam emitted from an electron gun. The electron gun 11 is a thermoelectron emitting electron gun. A molding opening 13 and a NA opening 16 are arranged in front of the thermoelectron emitting electron gun 11. An image of the molding opening 13 by the electron beam C emitted from the thermoelectron emitting electron gun 11 is formed on the sample surface only by the two-stage lenses 17 and 20. <P>COPYRIGHT: (C)2003,JPO

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, a defect inspection apparatus for a device having the electron beam apparatus, and a device manufacturing method using the defect inspection apparatus. More specifically, the minimum line width is 0.1 μm or less. Electron beam apparatus capable of evaluating a sample having a device pattern with high throughput and high reliability, a defect inspection apparatus for a device having the electron beam apparatus, and a wafer after process completion using the defect inspection apparatus Thus, the present invention relates to a device manufacturing method capable of improving yield.

[0002]

2. Description of the Related Art In an electron beam apparatus for evaluating a sample having a device pattern having a minimum line width of 0.1 μm or less, a molded electron beam is narrowed down and irradiated onto the sample, and secondary electrons emitted from the sample are emitted. An electron beam apparatus has been proposed for detecting a sample and evaluating a sample. In such an apparatus, at least three stages of lenses are used in the optical system for shaping the electron beam. Further, when forming a thin electron beam of 0.1 μm or less, a crossover reduction type beam is used. Further, in order to perform evaluation with high reliability, it is necessary to increase the intensity of the electron beam, and a thermal field emission electron gun (TFE electron gun) is used to obtain a large current beam of 0.1 μm or less.

[0003]

[Problems to be Solved by the Invention] However, TFE
In the electron gun, a thermionic emission electron gun (for example, LaB6 electron gun)
Although a beam current that is 3 to 10 times as high as that of the sample can be obtained, the S / N ratio is not so good because the shot noise of the electron beam is large, and it is difficult to evaluate the sample with high throughput. Further, in the crossover reduction type beam using the LaB6 electron gun, the beam current cannot be increased and it is difficult to evaluate the sample with high throughput. Further, in the shaped beam method using the LaB6 electron gun, since the lens having three or more stages is used, the lens barrel length is long and an additional deflector for axis alignment is required. Further, the space charge effect also increases as the optical path length increases, and it is difficult to obtain good electron beam intensity and position stability.

One problem to be solved by the present invention is
The shot noise of the electron beam is reduced to improve the S / N ratio,
An object is to provide an electron beam apparatus capable of evaluating a sample with high throughput. Another problem to be solved by the present invention is to provide an electron beam apparatus capable of increasing the beam current and enabling evaluation of a sample with high throughput. Another problem to be solved by the present invention is to provide an apparatus completed as a defect inspection apparatus by forming an electron optical lens barrel for forming a shaped beam with only two stages of lenses and controlling it with high stability. That is. Still another problem to be solved by the present invention is to provide a method for manufacturing a device for evaluating a sample after the process is finished by using the electron beam apparatus as described above.

[0005]

The above-mentioned problems can be solved by the following means. That is, an electron beam device for irradiating a sample with an electron beam emitted from an electron gun to detect secondary electrons emitted from the sample surface, wherein the electron gun is a thermionic emission electron gun, and the thermionic emission electron is used. Molded opening and NA in front of the gun
An aperture is arranged so that an image of the shaping aperture irradiated with the electron beam from the thermionic emission electron gun is formed on the sample surface by a two-stage lens. The term "front" means the sample side with respect to the direction in which the electron beam travels. Further, in another invention of the electron beam apparatus, there is provided an electron beam apparatus for irradiating a sample with an electron beam emitted from an electron gun to detect secondary electrons emitted from the surface of the sample, wherein the electron gun emits thermoelectrons. An electron gun, a shaping opening and an NA opening are sequentially arranged in front of the thermionic emission electron gun, and a crossover formed by an electron beam from the thermionic emission electron gun is imaged on the NA opening. An image of the molding aperture irradiated with the electron beam from the electron emission electron gun is formed on the sample surface.

Further, in another invention of the electron beam apparatus, it has a primary optical system for irradiating the sample with an electron beam emitted from an electron gun, and a secondary electron emitted from the surface of the sample is detected by a detector. In the electron beam apparatus, a molding aperture and a two-stage lens are arranged in the primary optical system, and an E × B separator is arranged between the two-stage lenses. An image of the molding aperture irradiated by the electron beam is reduced and imaged on the sample surface by a two-stage lens, and secondary electrons emitted from the sample surface are emitted from the primary optical system by the E × B separator. They are separated and made incident on the detection device. In another invention of the electron beam apparatus, an electron beam having a primary optical system for irradiating a sample with an electron beam emitted from an electron gun, and detecting a secondary electron emitted from the surface of the sample with a detection device. In the device, a molding aperture, an NA aperture, a condenser lens, and an objective lens are sequentially arranged in the primary optical system along an optical axis of the primary optical system, and a cross of an electron beam from the electron gun is crossed. The over is made to coincide with the NA aperture by controlling the Wehnelt bias of the electron gun. In another invention of the electron beam apparatus, an electron beam having a primary optical system for irradiating a sample with an electron beam emitted from an electron gun, and detecting a secondary electron emitted from the surface of the sample with a detection device. In the apparatus, a molding aperture, a condenser lens, and an objective lens are sequentially arranged in the primary optical system along an optical axis of the primary optical system, and an NA aperture is adjacent to the objective lens. It is arranged on the electron gun side of the objective lens so that a crossover image of an electron beam is formed at the NA aperture.

Still another invention of the present application provides a defect inspection apparatus for a device including an electron beam apparatus according to the one invention or another invention.

According to still another aspect of the present invention, the defect inspection apparatus is used to evaluate the wafer after the process and manufacture the device.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an electron beam apparatus according to the present invention will be described below with reference to the drawings. In FIG. 1, an electron beam device 1 according to a first embodiment of the present invention is schematically shown. The electron beam device 1 includes a primary optical system 10 and
The secondary optical system 30 and the detection device 40 are provided. The primary optical system 10 is an optical system that irradiates the sample S with an electron beam, and includes an electron gun 11 that emits an electron beam, an electrostatic deflector 12 for axial alignment, a molding aperture 13, and an axial alignment. Electrostatic deflectors 14 and 15, NA aperture 16, condenser lens 17 that reduces the electron beam that has passed through shaping aperture 13, electrostatic deflector 18 for scanning, E × B separator 19, and objective lens 20 and an axisymmetric electrode 21, which are shown in FIG.
As shown in FIG. 3, the electron gun 11 is arranged in the uppermost position in order and the optical axis A of the electron beam emitted from the electron gun is perpendicular to the surface S of the sample. The E × B separator 19 includes an electrostatic deflector 191, electromagnetic deflectors 192 and 193, and a permalloy core 194. Furthermore, the electron beam apparatus 1 includes a power source 22 that applies a negative potential to the sample S. In the present embodiment, the electron gun 11 is a thermionic emission type LaB6 electron gun, and the LaB6 cathode 11 is used.
1, a graphite heater 112, a support fitting 113, a Wehnelt electrode 114, and an anode 115.
By making the bias of the Wehnelt electrode 114 of the electron gun 11 deep to some extent, the electron gun 11 can be controlled within the space charge limited region. The shaping opening 13 has a square shape and is arranged on the electron gun side of the NA opening 16. Also, a two-stage lens (that is, a condenser lens 1
7 and the objective lens 20) are both arranged in front of the shaping aperture 13 and the NA aperture 16 (that is, on the sample side with respect to the electron beam advancing direction).

The secondary optical system 30 is an optical system for introducing the secondary electrons emitted from the sample S to the detection device 40, and E × B.
Optical axis B tilted with respect to optical axis A near the separator 19
Are arranged along. The detector 40 is a detector 401.
Is equipped with.

Next, the operation of the electron beam apparatus 1 having the above structure will be described. The electron beam C emitted from the electron gun 11 is
By adjusting the Wehnelt voltage of the electron gun 11, N
A crossover C1 is formed at a position corresponding to the A opening 16. At the same time, the electron gun 11 is connected to the graphite heater 11
The current flowing through 2 is adjusted to operate in the space charge limited region. Therefore, shot noise generated by the electron beam can be significantly reduced. The electron beam forming the crossover C1 diverges at a divergence angle that is not so large and is focused by the condenser lens 17 to form a crossover C2 at the position of the main surface of the objective lens 20.
In this case, the condenser lens 17 is arranged so that the electron beam forms a crossover C2 at the position of the main surface of the objective lens 20.
Excitation voltage is determined. On the other hand, the image of the forming aperture 13 formed by the electron beam is C by the condenser lens 17.
The image is reduced to the position of 3 and imaged, and further reduced to 0.1 μm or less and imaged on the surface of the sample S by the objective lens. This adjustment is easily performed by changing the excitation of the condenser lens 17. When scanning the sample, the electrostatic deflector 18 and the electrostatic deflector 191 of the E × B separator are used.
It is performed by deflecting in two steps with and. in this case,
By placing the deflection center at the position of C4 directly above the objective lens 20, the total value of the deflection chromatic aberration, the coma aberration and the astigmatism is minimized.

The secondary electron emitted from the sample S by irradiating the sample S with the electron beam is accelerated and converged by the accelerating electric field of the objective lens 20, and is deflected by the E × B separator 19 to be secondary optical system 30. Be thrown into. In this case, normally, the sample S
Since a negative voltage is applied by the power source 22, almost all the secondary electrons pass through the objective lens 20 and the E × B separator 1
Biased at 9. The secondary electrons move along the optical axis B and are detected by the detector 401.

An axially symmetric electrode 21 is arranged on the sample side of the objective lens 20, and a power source 23 for applying a positive or negative voltage to the axially symmetric electrode 21 and a changeover switch 24 therefor are provided. A filter action may be provided by applying a voltage lower than that of the sample. In that case, the potential contrast of the pattern on the sample surface can be obtained. Further, the changeover switch 24 is controlled by a computer to obtain a normal scanning electron microscope image,
The defect inspection can be performed with high accuracy by obtaining the potential contrast image. Therefore, the electron beam apparatus according to the present invention can be applied to a device defect inspection apparatus.

Next, an electron beam apparatus 1'according to the second embodiment of the present invention will be described with reference to FIG. In this figure,
The same components as those in the first embodiment shown in FIG. 1 are designated by the same reference numerals. Further, the constituent elements corresponding to the constituent elements of the first embodiment but having a different configuration from the constituent elements are represented by adding the symbol "'" on the same reference numerals.
Unlike the first embodiment, the electron beam apparatus 1 ′ according to the present embodiment includes only the primary optical system 10 ′ and the detection device 40 ′. The primary optical system 10 'includes an electron gun 11 having a structure similar to that of the first embodiment, an electrostatic deflector 12 for axial alignment, a molding aperture 13, and an electrostatic deflector 14 for axial alignment.
A condenser lens 17 for reducing the electron beam that has passed through the shaping aperture 13, and electrostatic deflectors 18 and 25 for scanning.
A NA aperture 16 and an objective lens 20, which are arranged so that the electron gun 11 is at the top and the optical axis A of the electron beam emitted from the electron gun is perpendicular to the surface S of the sample. Has been done. Also in the electron gun 11 of this embodiment, the electron gun can be controlled within the space charge limited region by making the bias of the Wehnelt electrode deep to some extent. As clearly shown in FIG. 2, the NA aperture 16 is arranged adjacent to the objective lens 20 on the electron gun side of the objective lens. Also, unlike the first embodiment, the electrostatic deflector for axial alignment has two stages, and the E × B separator and the axially symmetric electrode are not provided.

In this embodiment, the secondary optical system is not provided in particular, and as described later, the secondary electrons emitted from the sample S are directly attracted to the electric field of the detector 401 'of the detection device 40' and directly. It is incident on the detector 401 ′. Detector 40 '
Is a detector 401 ′, an A / D converter, and an image processing circuit 4
It has 03.

The operation of the above-described configuration of the electron beam apparatus according to this embodiment will be described. The electron beam C emitted from the electron gun 11 passes through the shaping aperture 13 and forms a crossover C1 ′ at a predetermined position between the shaping aperture 13 and the condenser lens 17, and is not so large from the crossover C1 ′. Diversify at divergence angle. The diverging electron beam is focused by the condenser lens 17 to form a crossover C2 ′ at the NA aperture 16. After forming the crossover C2 ′, the electron beam advances toward the sample S and is directed toward the sample S by the objective lens 21. The image of the molding aperture 17 is reduced by the condenser lens 17 and the objective lens 16 and formed on the sample S. The scanning of the sample is performed by deflecting the electrostatic deflector 18 and the electrostatic deflector 25 in two steps.

The sample S is irradiated with the electron beam, and the secondary electrons emitted from the sample S are deflected by the electric field of the detector 401 'and injected into the detector 401'. Detector 40
1'converts the detected secondary electron into an electric signal representing its intensity. The electric signal output from the detector is converted into a digital signal by the A / D converter 402, then received by the image processing circuit 403, and converted into image data. The defect of the sample S can be detected by comparing this image with the standard pattern. Therefore, the electronic device of this embodiment can also be applied to a device defect inspection apparatus.

Next, with reference to FIGS. 3 and 4, a method of manufacturing a semiconductor device according to the present invention for evaluating a sample after the process using the electron beam apparatus as described above will be described. FIG. 3 is a flow chart showing an embodiment of the method for manufacturing a semiconductor device according to the present invention. The steps of this embodiment include the following main steps. (1) Wafer manufacturing step for manufacturing a wafer (or wafer preparing step for preparing a wafer) (2) Mask manufacturing step for manufacturing a mask for manufacturing a mask used for exposure (or mask preparing step for preparing a mask) (3 ) Wafer processing step for performing necessary processing on the wafer (4) Chip assembling step for cutting out the chips formed on the wafer one by one to make them operable (5) Chip inspection step for inspecting the completed chips Each of the main steps of is composed of several sub steps.

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

FIG. 4 is a flow chart showing the lithography process which is the core of the wafer processing process of FIG. The lithography process includes the following steps. (1) A resist coating step of coating a resist on a wafer on which a circuit pattern is formed in the preceding 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 semiconductor device manufacturing step, wafer processing step, and lithography step described above are well known and need no further explanation. Above (7)
If the defect inspection method and the defect inspection apparatus according to the present invention are used in the inspection step, even a semiconductor device having a fine pattern can be inspected with good throughput, so that it is possible to perform 100% inspection, improve product yield, and ship defective products. Prevention is possible.

[0021]

According to the present invention, the following effects can be achieved. (1) Since the number of lens stages can be two compared to the conventional optical system using three-stage lenses, the number of lens axis alignment devices can be reduced by one stage. Therefore, the length of the optical path is shortened and the blur of the electron beam due to the space charge effect is reduced. Further, since the number of parts used in the optical system and the control circuit for one stage of the lens and one stage of the electrostatic deflector are reduced, the reliability of the electron beam apparatus can be improved. (2) A large beam current can be obtained with the same electron beam size as compared with the crossover reduction type beam. (3) Since the electron gun can be operated in the space charge limited region, the shot noise of the electron beam can be significantly reduced, and the noise of secondary electrons can also be reduced. (4) Since the NA aperture is placed in front of the reduction lens,
A secondary electron detector can be provided in front of the objective lens. (5) When the NA aperture is arranged adjacent to the objective lens,
It is not necessary to accurately position the electron beam crossover.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an optical system of an electron beam apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing an optical system of an electron beam apparatus according to a second embodiment of the present invention.

FIG. 3 is a flowchart showing a device manufacturing process.

FIG. 4 is a flowchart showing a lithography process.

[Explanation of symbols]

1, 1 ': Electron beam device 10, 10': Primary optical system 11: Electron gun 12: Electrostatic deflector (for axis alignment) 13: Molding opening 14, 15: Electrostatic deflector (for axis alignment) 16: NA aperture 17: Condenser lens 18: Electrostatic deflector 19: E × B separator 20: Objective lens 21: Axisymmetric electrodes 22, 23: Power supply 24: Changeover switch 25: Electrostatic deflector 30: Secondary Optical system 40, 40 ': Detection device 401, 40
1 ': Detector 402: A / D converter 403: Image processing circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/66 H01L 21/30 502V (72) Inventor Toru Satake 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo EBARA CORPORATION (72) Inventor Kenji Watanabe 11-11 Haneda-Asahicho, Ota-ku, Tokyo Inside EBARA CORPORATION (72) Inventor Takeshi Murakami 11-11 Haneda-Asahi-cho, Ota-ku, Tokyo EBARA CORPORATION Inner F term (reference) 4M106 AA01 BA02 CA39 CA41 DB05 DB18 DB30 5C030 BB04 BC03 BC06 5C033 BB01 BB02 DE02 DE06 UU02

Claims (7)

[Claims] 1. An electron beam apparatus for irradiating a sample with an electron beam emitted from an electron gun to detect secondary electrons emitted from the surface of the sample, wherein the electron gun is a thermoelectron emission electron gun. A shaping aperture and an NA aperture are arranged in front of the electron emission electron gun, and an image of the shaping aperture irradiated with the electron beam from the thermionic emission electron gun is formed on the sample surface by a two-stage lens. , Electron beam equipment. 2. An electron beam apparatus for irradiating a sample with an electron beam emitted from an electron gun and detecting secondary electrons emitted from the surface of the sample, wherein the electron gun is a thermoelectron emission electron gun. A shaping aperture and an NA aperture are sequentially arranged in front of the electron emission electron gun, and a crossover formed by an electron beam from the thermionic emission electron gun is imaged on the NA aperture. An electron beam apparatus, which is configured to form an image of a molding aperture irradiated with an electron beam on a sample surface. 3. An electron beam apparatus having a primary optical system for irradiating a sample with an electron beam emitted from an electron gun, wherein a secondary electron emitted from the surface of the sample is detected by a detector. A molding aperture and a two-stage lens are arranged in the primary optical system,
Further, an E × B separator is arranged between the two-stage lenses, and an image of the molding aperture irradiated by the electron beam from the electron gun is reduced and formed on the sample surface by the two-stage lenses. An electron beam device in which secondary electrons emitted from the sample surface are separated from the primary optical system by the E × B separator and made incident on a detection device. 4. An electron beam apparatus having a primary optical system for irradiating a sample with an electron beam emitted from an electron gun, wherein secondary electrons emitted from the surface of the sample are detected by a detector. A molding aperture, an NA aperture, a condenser lens, and an objective lens are arranged in order in the primary optical system along the optical axis of the primary optical system, and a crossover of an electron beam from the electron gun is set in the electron gun. An electron beam device in which the Wehnelt bias is controlled to match the NA aperture. 5. An electron beam apparatus having a primary optical system for irradiating a sample with an electron beam emitted from an electron gun, and detecting a secondary electron emitted from the surface of the sample with a detector. In the primary optical system, a molding aperture, a condenser lens, and an objective lens are sequentially arranged along the optical axis of the primary optical system, and an NA aperture is adjacent to the objective lens and the electron gun side of the objective lens. And place the electron beam crossover image on the N
An electron beam device formed in the A opening. 6. A device defect inspection apparatus comprising the electron beam apparatus according to any one of claims 1 to 5. 7. A method of manufacturing a device, wherein the defect inspection apparatus according to claim 6 is used to evaluate a wafer after the process is completed.