JP3995479B2 - Electron beam apparatus and device manufacturing method using the electron beam apparatus - Google Patents

Description

[0001]
[Industrial application fields]
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, and more specifically, a sample having a device pattern having a minimum line width of 0.1 μm or less. Yield can be improved by evaluating an electron beam apparatus capable of performing evaluation with high throughput and high reliability, a defect inspection apparatus for a device having the electron beam apparatus, and a wafer after the process is completed using the defect inspection apparatus. The present invention relates to a method for manufacturing a device that can be used.
[0002]
[Prior art]
In an electron beam apparatus that evaluates a sample having a device pattern with a minimum line width of 0.1 μm or less, the formed electron beam is narrowed down and irradiated onto the sample, and secondary electrons emitted from the sample are detected. An electron beam apparatus for evaluating a sample has been proposed. In such an apparatus, at least a three-stage lens is used for an optical system for shaping an electron beam. Further, when forming a thin electron beam of 0.1 μm or less, a crossover reduced 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, although a TFE electron gun can obtain a beam current 3 to 10 times that of a thermionic emission electron gun (for example, a LaB6 electron gun), the S / N ratio is not so good due to a large shot noise of the electron beam. It is difficult to evaluate samples with high throughput.
In addition, with a crossover reduced beam using a LaB6 electron gun, the beam current cannot be increased, and it is difficult to evaluate a sample with high throughput.
Furthermore, in the shaped beam system using the LaB6 electron gun, the lens barrel length is long because three or more stages of lenses are used, and an extra deflector for alignment is necessary. In addition, the space charge effect increases as the optical path length increases, and it is difficult to obtain good electron beam intensity and position stability.
[0004]
One problem to be solved by the present invention is to provide an electron beam apparatus that can improve the S / N ratio by reducing shot noise of an electron beam and can evaluate a sample with high throughput. .
Another problem to be solved by the present invention is to provide an electron beam apparatus capable of increasing a beam current and enabling a sample to be evaluated 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 column for controlling with high stability by forming a shaped beam with only two stages of lenses. That is.
Still another problem to be solved by the present invention is to provide a device manufacturing method for evaluating a sample after completion of the process using the electron beam apparatus as described above.
[0005]
[Means for Solving the Problems]
The above problem is solved by the following means. That is, an electron beam apparatus for irradiating a sample with an electron beam emitted from an electron gun and detecting secondary electrons emitted from the sample surface, wherein the electron gun is a thermoelectron emission electron gun, and the thermoelectron emission electron A shaping opening and an NA opening are arranged in front of the gun, and an image of the shaping opening irradiated with the electron beam from the thermoelectron emission electron gun is formed on the sample surface by a two-stage lens. Here, “front” refers to the sample side with respect to the traveling direction of the electron beam.
Further, in another invention of the electron beam apparatus, an electron beam apparatus for irradiating a sample with an electron beam emitted from an electron gun and detecting secondary electrons emitted from a sample surface, wherein the electron gun is a thermal electron emission An electron gun, a shaping aperture and an NA aperture are sequentially arranged in front of the thermionic emission electron gun, a crossover formed by an electron beam from the thermionic emission electron gun is imaged on the NA aperture, and the heat An image of the shaping aperture irradiated with the electron beam from the electron emission electron gun is formed on the sample surface.
[0006]
In another invention of the electron beam apparatus, an electron beam having a primary optical system for irradiating the sample with an electron beam emitted from an electron gun, and detecting a secondary electron emitted from the sample surface with a detection device An apparatus is provided with a molding aperture and a two-stage lens disposed in the primary optical system, and an E × B separator disposed between the two-stage lenses, and an electron beam from the electron gun. The image of the irradiated shaping aperture is reduced and formed on the sample surface by a two-stage lens, and secondary electrons emitted from the sample surface are separated from the primary optical system by the E × B separator. The light is incident on the detection device.
In another invention of the electron beam apparatus, an electron beam having a primary optical system for irradiating the sample with an electron beam emitted from an electron gun, and detecting a secondary electron emitted from the sample surface with a detection device In the first optical system, a molding aperture, an NA aperture, a condenser lens, and an objective lens are sequentially arranged along the optical axis of the primary optical system, and a cross of an electron beam from the electron gun is arranged. The overshoot 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 the sample with an electron beam emitted from an electron gun, and detecting a secondary electron emitted from the sample surface with a detection device In the first 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. It is arranged on the electron gun side of the objective lens, and an electron beam crossover image is formed at the NA aperture.
[0007]
Still another invention of the present application provides a device defect inspection apparatus including the electron beam apparatus according to the one invention or another invention.
[0008]
According to still another aspect of the present invention, a device is manufactured by evaluating the wafer after completion of the process using the defect inspection apparatus.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an electron beam apparatus according to the present invention will be described below with reference to the drawings.
1, an electron beam device 1 is shown schematically by the implementation of the invention. The electron beam apparatus 1 includes a primary optical system 10, a secondary optical system 30, and a detection device 40.
The primary optical system 10 is an optical system that irradiates the sample S with an electron beam, and an electron gun 11 that emits an electron beam, an electrostatic deflector 12 for axial alignment, a molding opening 13, and an axis for axial alignment. Electrostatic deflectors 14 and 15, NA aperture 16, condenser lens 17 for reducing 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 axially symmetric electrode 21, which are arranged in order with the electron gun 11 at the top as shown in FIG. 1, and the optical axis A of the electron beam emitted from the electron gun is perpendicular to the surface S of the sample. It is arranged to be. The E × B separator 19 includes an electrostatic deflector 191, electromagnetic deflectors 192 and 193, and a permalloy core 194. The electron beam apparatus 1 further 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 includes a LaB6 cathode 111, 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 deeper 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. The two-stage lenses (that is, the condenser lens 17 and the objective lens 20) are both disposed in front of the molding aperture 13 and the NA aperture 16 (that is, the sample side with respect to the direction in which the electron beam travels).
[0010]
The secondary optical system 30 is an optical system that introduces secondary electrons emitted from the sample S into the detection device 40, and is an optical axis B that is inclined with respect to the optical axis A near the E × B separator 19. Are arranged along.
The detection device 40 includes a detector 401.
[0011]
Next, the operation of the electron beam apparatus 1 having the above configuration will be described.
The electron beam C emitted from the electron gun 11 adjusts the Wehnelt voltage of the electron gun 11 to form a crossover C1 at a position coincident with the NA opening 16. At the same time, the electron gun 11 is adjusted to operate in the space charge limited region by adjusting the current flowing through the graphite heater 112. Therefore, the shot noise generated by the electron beam can be greatly reduced. The electron beam that forms the crossover C1 diverges at a spread angle that is not so large, and is converged 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 excitation voltage of the condenser lens 17 is determined so that the electron beam forms a crossover C2 at the position of the main surface of the objective lens 20.
On the other hand, the image of the molding opening 13 formed by the electron beam is reduced to the position of C3 by the condenser lens 17, and further reduced to 0.1 μm or less on the surface of the sample S by the objective lens. Form an image. This adjustment is easily performed by changing the excitation of the condenser lens 17.
When the sample is scanned, the sample is deflected in two stages by the electrostatic deflector 18 and the electrostatic deflector 191 of the E × B separator. In this case, by placing the deflection center at the position C4 immediately above the objective lens 20, the total value of the deflection chromatic aberration, coma aberration and astigmatism is minimized.
[0012]
The sample S is irradiated with the electron beam, and the secondary electrons emitted from the sample are accelerated and converged by the accelerating electric field of the objective lens 20, deflected by the E × B separator 19, and input to the secondary optical system 30. The In this case, since the sample S is usually given a negative voltage by the power source 22, almost all secondary electrons pass through the objective lens 20 and are deflected by the E × B separator 19. Secondary electrons move along the optical axis B and are detected by the detector 401.
[0013]
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 are provided. You may make it give a filter action by giving a low voltage. In that case, the potential contrast of the pattern on the sample surface can be obtained.
Furthermore, it is possible to accurately perform defect inspection by controlling the changeover switch 24 with a computer to obtain a normal scanning electron microscope image or a potential contrast image. Therefore, the electron beam apparatus according to the present invention can be applied to a device defect inspection apparatus.
[0014]
FIG. 2 is a diagram showing another embodiment of the electron beam apparatus of the present invention as a reference. In the figure, the same components as the implementation form shown in FIG. 1 denoted by the same reference numerals. In addition, constituent elements corresponding to the constituent elements of the embodiment of FIG. 1 but having a different configuration are denoted by the symbol “′” on the same reference numerals.
Unlike the embodiment of FIG. 1, 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 the same structure as that of the embodiment of FIG. 1, an electrostatic deflector 12 for axial alignment, a shaping aperture 13, and an electrostatic deflector 14 for axial alignment. A condenser lens 17 that reduces the electron beam that has passed through the shaping aperture 13, scanning electrostatic deflectors 18 and 25, an NA aperture 16, and an objective lens 20. In addition, the optical axis A of the electron beam emitted from the electron gun is arranged to be perpendicular to the surface S of the sample.
The electron gun 11 of this embodiment can also control the electron gun within the space charge limited region by increasing the Wehnelt electrode bias to some extent.
As clearly shown in FIG. 2, the NA aperture 16 is disposed adjacent to the objective lens 20 on the electron gun side of the objective lens. Further, unlike the embodiment of FIG. 1 , the axis alignment electrostatic deflector has two stages, and the E × B separator and the axially symmetric electrode are not provided.
[0015]
In the present embodiment, the secondary optical system is not particularly provided, and as will be described later, secondary electrons emitted from the sample S are attracted by the electric field of the detector 401 ′ of the detection device 40 ′ and are directly detected by the detector 401. 'Is incident.
The detection device 40 ′ includes a detector 401 ′, an A / D converter, and an image processing circuit 403.
[0016]
The operation of the electron beam apparatus according to the present embodiment will be described. The electron beam C emitted from the electron gun 11 passes through the shaping opening 13, forms a crossover C1 'at a predetermined position between the shaping opening 13 and the condenser lens 17, and is not so large from the crossover C1'. Diverges at the spread angle. The diverged electron beam is focused by the condenser lens 17 to form a crossover C2 ′ in the NA aperture 16. After the formation of the crossover C2 ′, the electron beam travels toward the sample S and travels toward the sample S by the objective lens 21. The image of the molding opening 17 is reduced by the condenser lens 17 and the objective lens 16 and formed on the sample S.
When the sample is scanned, the sample is deflected in two stages by the electrostatic deflector 18 and the electrostatic deflector 25.
[0017]
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 input to the detector 401 ′. The detector 401 ′ converts the detected secondary electrons into an electric signal representing the intensity. The electrical 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 apparatus of this embodiment can also be applied to a device defect inspection apparatus.
[0018]
Next, with reference to FIG. 3 and FIG. 4, the manufacturing method of the semiconductor device which evaluates the sample after completion | finish of a process using the above electron beam apparatuses by this invention is demonstrated.
FIG. 3 is a flowchart showing an embodiment of a semiconductor device manufacturing method according to the present invention. The process of this embodiment includes the following main processes.
(1) Wafer manufacturing process for manufacturing a wafer (or wafer preparation process for preparing a wafer)
(2) Mask manufacturing process for manufacturing a mask for manufacturing a mask used for exposure (or mask preparation process for preparing a mask)
(3) Wafer processing step for performing necessary processing on the wafer (4) Chip assembly step for cutting out the chips formed on the wafer one by one and making them operable (5) Chip inspection step for inspecting the completed chips Each of the above main processes is further composed of several sub-processes.
[0019]
Among these main processes, the wafer processing process (3) has a decisive influence on the performance of the semiconductor device. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps.
(1) A thin film forming process for forming a dielectric thin film to be an insulating layer, a wiring part, or a metal thin film for forming an electrode part (using CVD, sputtering, etc.)
(2) Oxidation step for oxidizing the thin film layer and wafer substrate (3) Lithography step for forming a resist pattern using a mask (reticle) to selectively process the thin film layer and wafer substrate (4) According to the resist pattern Etching process for processing thin film layers and substrates (for example, using dry etching technology)
(5) Ion / impurity implantation / diffusion process (6) Resist stripping process (7) Process for inspecting a processed wafer The wafer processing process is repeated for the required number of layers to manufacture a semiconductor device that operates as designed.
[0020]
FIG. 4 is a flowchart showing a lithography process that forms the core of the wafer processing process of FIG. The lithography process includes the following processes.
(1) Resist coating step for coating a resist on the wafer on which a circuit pattern has been formed in the previous step (2) Step for exposing the resist (3) Development step for developing the exposed resist to obtain a resist pattern ( 4) Annealing process for stabilizing the developed resist pattern The semiconductor device manufacturing process, the wafer processing process, and the lithography process 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 process of (7) above, even a semiconductor device having a fine pattern can be inspected with high throughput, so that 100% inspection can be performed and the yield of products can be improved. It is possible to prevent shipment of defective products.
[0021]
【The invention's effect】
According to the present invention, the following effects can be obtained.
(1) Since the number of lens stages can be two as compared with a conventional optical system using a three-stage lens, the number of lens alignment devices can be reduced by one stage. Accordingly, 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 reduced beam.
(3) Since the electron gun can be operated in the space charge limited region, the shot noise of the electron beam can be greatly reduced, and the secondary electron noise can also be reduced.
(4) Since the NA aperture is arranged in front of the reduction lens, the secondary electron detector can be provided in front of the objective lens.
(5) When the NA aperture is disposed adjacent to the objective lens, it is not necessary to accurately position the crossover position of the electron beam.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing an optical system of the electron beam apparatus according to implementation embodiments of the present invention.
FIG. 2 is a diagram showing another embodiment of the electron beam apparatus of the present invention as a reference.
FIG. 3 is a flowchart showing a device manufacturing process.
FIG. 4 is a flowchart showing a lithography process.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 1 ': Electron beam apparatus 10, 10': Primary optical system 11: Electron gun 12: Electrostatic deflector (for axis alignment)
13: Molding opening 14, 15: Electrostatic deflector (for axial alignment)
16: NA aperture 17: Condenser lens 18: Electrostatic deflector 19: E × B separator 20: Objective lens 21: Axisymmetric electrode 22, 23: Power supply 24: Changeover switch 25: Electrostatic deflector 30: Secondary Optical system 40, 40 ': Detection device 401, 401': Detector 402: A / D converter 403: Image processing circuit

Claims (6)

A primary optical system, a secondary optical system, and a detection device are provided. The sample is irradiated with an electron beam emitted from an electron gun disposed in the primary optical system and emitted from the sample surface. An electron beam device for detecting secondary electrons,
The electron gun is a thermionic emission electron gun, the electron gun has a Wehnelt electrode,
A molding opening disposed in front of the thermionic emission electron gun;
NA opening arranged in front of the molding opening,
Further, the primary optical system has , as a lens structure, only a two-stage lens of a condenser lens arranged in front of the NA aperture and an objective lens arranged in front of the condenser lens,
Adjusting the voltage of the Wehnelt electrode so as to form a crossover at a position coincident with the NA opening;
The excitation voltage of the condenser lens is adjusted so as to form a crossover at the position of the main surface of the objective lens, and an image of the molding aperture irradiated with the electron beam from the thermionic emission electron gun is used as a two-stage lens An electron beam device that forms an image on the sample surface.   A device defect inspection apparatus comprising the electron beam apparatus according to claim 1.   A device manufacturing method, comprising: evaluating a wafer after completion of a process using the defect inspection apparatus according to claim 2. An electron beam emitted from a thermionic emission electron gun having a Wehnelt electrode arranged in the primary optical system of an electron beam apparatus comprising a primary optical system, a secondary optical system, and a detection device Is an electron beam detection method for detecting secondary electrons emitted from the sample surface,
A molding opening is arranged in front of the thermionic emission electron gun,
An NA opening is arranged in front of the molding opening,
Further, in the primary optical system, as a lens structure, only a two-stage lens is arranged, which is a condenser lens arranged in front of the NA aperture and an objective lens arranged in front of the condenser lens,
Adjusting the voltage of the Wehnelt electrode so as to form a crossover at a position coincident with the NA opening;
The excitation voltage of the condenser lens is adjusted so as to form a crossover at the position of the main surface of the objective lens, and an image of the molding aperture irradiated with the electron beam from the thermionic emission electron gun is used as a two-stage lens An electron beam detection method that forms an image on the sample surface with In the electron beam detection method of Claim 4,
An electrostatic deflector for scanning is arranged in front of the condenser lens,
An E × B separator is disposed in front of the electrostatic deflector,
An electron beam detection method comprising deflecting an electron beam by deflecting the electrostatic deflector and the E × B separator. In the electron beam detection method of Claim 5,
The electron beam detecting method, wherein the electrostatic deflector and the E × B separator are adjusted so that a deflection center is placed immediately above the objective lens.

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