JP2002279922A - Electron beam device and method of manufacturing device using the electron beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens that can make chromatic aberrations coefficient small by voltage applied to a lens electrode. SOLUTION: In this electron beam device, electron beams emitted from an electron gun 11 are converged by electrostatic lenses 14, 17 and irradiated on a sample S to be scanned; secondary electrons emitted from the irradiated part of the sample are detected by a detector 31 to evaluate the sample; and the space between a plurality of electrodes of the electrostatic lens is made small, and the bore diameter of the electrodes is made large, to reduce the axial chromatic aberration of the electrostatic lenses.

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 and a method for manufacturing a device using the electron beam apparatus.
An electron beam apparatus for evaluating a sample having a device pattern with a minimum line width of 0.1 μm or less with high throughput and high reliability, and improving the yield by evaluating a wafer in the process using the electron beam apparatus. The present invention relates to a method for manufacturing a device capable of performing the following.

[0002]

2. Description of the Related Art An electron beam apparatus for evaluating a sample having a device pattern having a minimum line width of 0.1 μm or less by scanning and irradiating an electron beam formed by narrowly converging an electron beam onto a sample has already been proposed. In such a device, a single-potential lens is conventionally known as an electrostatic lens. It consists of three axially symmetric electrodes, of which a positive or negative voltage is applied to the center electrode, the electrodes on both sides of the center electrode are grounded without applying a voltage, and the voltage applied to the center electrode is changed. This satisfies the focusing condition. As a method of reducing the aberration of such an electrostatic lens, the chromatic aberration coefficient is reduced by reducing the distance between the electrodes and reducing the bore diameter of the electrodes. Further, in a deceleration electric field type objective lens, spherical aberration and chromatic aberration have been reduced by increasing the energy of electrons when entering the lens and decreasing the landing energy.

[0003]

However, in the method of reducing chromatic aberration by the geometrical shape of the electrostatic lens as described above, there is a limit in reducing the bore diameter of the electrode and the interval between the electrodes, and the effect is reduced. It was not possible to reduce chromatic aberration. In the method of increasing the ratio of the energy on the incident side to the landing energy to reduce chromatic aberration, a high voltage is required for all of the electron gun, the condenser lens, and the deflector, which makes the apparatus expensive and increases reliability. May be reduced.

The present invention has been made in view of the above problems, and one object to be solved by the present invention is to provide an objective lens capable of reducing a chromatic aberration coefficient by applying a voltage to a lens electrode. is there. Another object of the present invention is to provide an electron beam apparatus that can perform dynamic focus by controlling electrodes with a voltage close to the ground. 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 above object is achieved by the following means. That is, one of the inventions of the present application is that an electron beam emitted from an electron gun is focused on a sample by an electrostatic lens, scanned and irradiated, and secondary electrons emitted from an irradiated portion of the sample are detected by a detector. In an electron beam apparatus that detects and evaluates a sample by reducing the distance between a plurality of electrodes of the electrostatic lens and increasing the bore diameter of the electrodes, the voltage to be applied to the electrodes serving as focusing conditions is reduced. It is configured to be higher to reduce axial chromatic aberration of the electrostatic lens. With such a configuration, it is possible to reduce chromatic aberration caused by the electrostatic lens, and it is possible to secure high inspection accuracy. Further, another invention of the present application focuses an electron beam emitted from an electron gun on a sample with an electrostatic lens,
In an electron beam apparatus which scans and irradiates a sample and irradiates the sample and evaluates the sample by detecting secondary electrons emitted from an irradiated portion of the sample, the electrostatic lens includes at least three electrodes. A positive high voltage is applied to the center electrode of the electrodes, and a voltage lower than the voltage applied to the center electrode is applied to the electron gun side and the sample side electrodes of the center electrode, respectively. The electrode has a smaller bore diameter than the other electrodes. With this configuration, the chromatic aberration coefficient can be reduced by increasing the voltage applied to the lens electrode.

In still another aspect of the present invention, an electron beam emitted from an electron gun is focused, scanned and irradiated on a sample, and secondary electrons emitted from an irradiated portion of the sample are detected by a detector. In an electron beam apparatus for evaluating the sample, so as to focus the electron beam with at least three-pole axially symmetric electrode,
By applying a positive high voltage to the center electrode of the at least three-pole axially symmetric electrodes, applying a positive voltage to each electrode on both sides of the center electrode, and boosting the voltage of the electrodes on both sides, It is configured to increase the voltage that satisfies the focusing condition applied to the center electrode. In still another invention of the present application, an electron beam emitted from an electron gun is focused, scanned and irradiated on a sample, and secondary electrons emitted from an irradiated portion of the sample are detected by a detector to detect the sample. In the electron beam device to be evaluated, the electron beam is focused by at least a quadrupole axially symmetric electrode, and a high voltage is applied to the at least quadrupole axially symmetric electrode that is secondly arranged from the sample side. A positive voltage is also applied to the electrodes arranged on both sides of the second electrode from the sample side, and the voltage applied to the electrodes arranged closer to the electron gun than the three electrodes is changed. It is configured to perform dynamic focus.

[0007] Still another aspect of the present invention provides a device manufacturing method in which a wafer is evaluated during or after a process using the electron beam apparatus.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An 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 apparatus 1 includes a primary optical system 10 and a secondary optical system 20.
And an inspection device 30. Primary optical system 10
Is an optical system for irradiating the surface of the sample S with an electron beam (sample surface).
, A condenser lens 14 for converging an electron beam, an electrostatic deflector 15 for scanning the electron beam, an E × B separator 16 and an objective lens 17. As shown in FIG. 11 are arranged in order with 11 as the top. Electron gun 1
1 is TFE cathode 111, Schottky shield 11
2 and the anode 113. The secondary optical system 20 is disposed near the E × B separator 16 of the primary optical system 10 along an optical axis B inclined with respect to the optical axis A of the primary optical system. . The inspection device 30 includes a detector 31.

In this embodiment, since the condenser lens 14 and the objective lens 17 are electrostatic axis symmetric lenses and have substantially the same configuration, the configuration of the objective lens 17 will be described. The objective lens 14 is provided with a main body 171 formed by cutting an integral ceramic into a shape as shown in FIG. This body 1
Reference numeral 71 denotes a circular hole formed at the center, and three protrusions 172 separated along the optical axis A on the inner peripheral side.
Through 174 are formed. The surface of the main body 171 is selectively coated with a metal coating 175 to 177. The metal coatings 175 to 177 are referred to as an electron gun side electrode 175, an intermediate electrode 176, and a sample side electrode 177, respectively. A positive high voltage is applied to the intermediate electrode 176, and a lower voltage is applied to the electron gun-side electrode 175 and the sample-side electrode 177 to perform the function of a lens. With such a configuration, the outer diameter of the lens can be reduced.

As described above, since the outer diameter of the objective lens and the condenser lens can be reduced, the outer diameter of the lens barrel housing the electron beam device can also be reduced.
Therefore, it is possible to arrange a plurality of lens barrels on one wafer and evaluate points on a plurality of samples at the same time. Thereby, the throughput can be increased by the number of lens barrels. In the present embodiment, for example, as shown in FIG. 2, four lens barrels 2 arranged in the X direction are arranged in two rows in the Y direction, and a total of eight lens barrels 2 are formed into one sample. It is arranged for. Such an arrangement becomes possible by arranging the secondary optical system 20 and the detection device 30 in a direction that does not interfere with the adjacent lens barrel. When the stage (not shown) holding the sample S is continuously moved in the Y direction and is scanned and evaluated by each lens barrel in the X direction, an evaluation using only one electron beam is performed. Double throughput is obtained. Further, there is a possibility that about 16 lens barrels can be arranged on a 12-inch wafer.

In the above-mentioned electron beam apparatus, the electron beam emitted from the TFE cathode 111 of the electron gun 11 is accelerated by the anode 112, and the two-stage alignment deflector 1 is used.
The axes 2 and 13 are aligned with the condenser lens 14. The electron beam is focused by the condenser lens 14,
A crossover is formed on the electron gun side of the objective lens 17,
Further, the sample S is focused on by the objective lens 17. in this case,
The electron beam is deflected by the electrostatic deflector 15 and the electromagnetic deflector 161 of the E × B separator 16 and scans and irradiates the sample S. The sample S is designed so that a negative high voltage is applied and the landing energy is 500 V. Secondary electrons emitted from the sample S by the irradiation with the electron beam are accelerated and focused by the acceleration electric field applied between the objective lens 17 and the sample S, and pass through the objective lens 17. Secondary electrons that have passed through the objective lens are converted into an E × B separator 1
The sample S is deflected in the direction along the optical axis B of the secondary optical system 20 by the detector 6 and is detected by the detector 31 of the detector 30 to evaluate the sample S.

In the evaluation of a sample by the electron beam apparatus as described above, in order to improve the resolution of the optical system, it is necessary to obtain a large beam current by narrowly focusing the electron beam. For that purpose, it is necessary to reduce the axial chromatic aberration coefficient of the objective lens and the condenser lens, and the aberration was calculated by simulation. Since the condenser lens hardly generates aberration, this simulation aberration calculation was performed only for the objective lens. FIG.
Indicates a simulation model of the objective lens.
In this figure, reference numeral 50 denotes an electron gun-side electrode, 51 denotes a center electrode, 52 denotes a sample-side electrode, 53 denotes an optical axis, and 54 to 5.
Reference numeral 6 denotes an inter-electrode insulating spacer. In the case where the number of the electrodes is three, a voltage of KV or more is applied to all of these electrodes, so that it becomes difficult to perform dynamic focus. Therefore, a fourth electrode 57 is provided, and this electrode is set to a voltage close to the ground. Therefore, the power supply for the dynamic focus connected to the power supply may be a ground voltage, so that the voltage can be changed at high speed. In the drawing, r ₁ is the electron gun side electrode 50 and the sample side electrode 52
And it represents the bore radius of the fourth electrode 57, respectively, r ₂ represents the bore radius of the central electrode 51.

FIG. 4 shows the model shown in FIG.
The result of simulation calculation of the relationship between the bore radii r ₁ and r _{2 of the} electrode and the aberration is shown. The vertical axis represents the aberration (nm) on a logarithmic scale, and the horizontal axis represents the bore radius (mm) on a uniform scale. It is. In this simulation calculation, the Z-direction dimension t of the inter-electrode insulating spacers 54 to 56 is set to 4 mm, the energy width is set to 5 eV, and the half-angle of the aperture (that is, the half-angle of convergence on the image plane) is set to 5 mrad to reduce the aberration near the optical axis 53. Calculated. In the figure, reference numeral 61 denotes spherical aberration, 6
2 denotes coma, 63 denotes astigmatism, 64 denotes field curvature, 65 denotes distortion, 66 denotes axial chromatic aberration, and 67 denotes lateral chromatic aberration in nanometers (nm). The axial chromatic aberration 66 is
When the bore radii r ₁ and r ₂ are 1.5 mm, it is 42 nm, but when the bore radii r ₁ and r ₂ are 9 mm, the diameter is reduced to 9.9 nm. This indicates that the voltage applied to the center electrode 51 that satisfies the focusing condition is increased by increasing the bore radii r ₁ and r ₂ , thereby decreasing the chromatic aberration coefficient. In other words, it is shown that the axial chromatic aberration can be reduced by reducing the distance between the electrodes so that no discharge occurs and increasing the bore radius.

FIG. 5 shows the model shown in FIG.
The result of simulation calculation of the relationship between the axial chromatic aberration and the voltage applied to the center electrode, which is the focusing condition, is shown. The vertical axis represents the voltage (KV) applied to the central electrode, and the horizontal axis is the axial chromatic aberration (nm). Is represented. In this simulation calculation, the Z-direction dimension t of the inter-electrode insulating spacers 54 to 56 is all 1 mm, and the distance between the sample-side electrode 52 and the sample S is 2 mm. The axial chromatic aberration was calculated by setting the energy width ΔE to 5 eV and the opening half angle to 5 mrad. In the figure, a curve 81 represents four electrodes (electron gun side electrode 50, center electrode 51, sample side electrode 52 and fourth electrode).
Are the calculation results when the bore radii r ₁ and r ₂ of the electrode 57) are all 2 mm, and the curve 82 shows that the bore radius r ₂ of the center electrode 51 alone is 1 mm and the bore radii r ₁ of the other electrodes are 2
This is a calculation result when mm is set. Points 83 and 90 are when the voltage applied to the electrodes 50 and 52 is -2.5 KV, points 84 and 91 are when the voltage applied to the electrodes 50 and 52 is -1.5 KV, and points 85 and 92 are the electrodes 50,
If the voltage applied to 52 is -0.5 KV, point 86
Indicates that the voltage applied to the electrodes 50 and 52 is +0.5 KV, and the point 87 indicates that the voltage applied to the electrodes 50 and 52 is +1.
When the voltage applied to the electrodes 50 and 52 is set to +2.5 KV, the point 88 is set to the point 88 when the voltage applied to the electrodes 50 and 52 is
This is a calculated value when the voltage applied to No. 2 is +3.5 KV.

In the conventional single potential lens, a ground voltage is applied to the electrodes 50 and 52 which are grounded. However, according to the result of the present simulation, these electrodes 50 and 5 are used.
It can be seen that the value of longitudinal chromatic aberration can be controlled by applying a voltage to 2. Specifically, when −2.5 KV was applied to the electrodes 50 and 52, the axial chromatic aberration was as large as 16 nm, but when −0.5 KV was applied, the axial chromatic aberration was 1
It has been greatly reduced to 3 nm. This indicates that the axial chromatic aberration coefficient can be controlled by the voltages applied to the electrodes 50 and 52 even when the dimensions of the lens electrodes are fixed. Curve 82
There curve 81 differs is that of reduced bore radius r ₂ of only the central electrode 51 to 1 mm. In the curve 82, the axial chromatic aberration was 20 nm at the point 83 where −2.5 KV was applied to the electrodes 50 and 52, but the axial chromatic aberration was 11 nm at the point 89 where +3.5 KV was applied to the electrodes 50 and 52.
At 3 nm, it can be seen that the axial chromatic aberration is reduced by half. As apparent from the comparison curve 81 and curve 82, whether the voltage of reduced bore radius r ₂ only the center electrode 51 (curve 82) it is applied to the center electrode is reduced, or longitudinal chromatic aberration coefficient decreases Great practical advantages.

When a lens constructed based on the above simulation results is applied to an electron beam apparatus, if the axial chromatic aberration is halved at the same half angle of aperture and the same energy width, the beam current obtained will be It can be increased by a factor of four. Also, as the voltage difference applied to each electrode increases, the risk of discharge increases, so that a high voltage can be applied by coating a metal (for example, platinum) having a large work function on the surface of each electrode. , The axial chromatic aberration coefficient can be further reduced.

Next, a method of manufacturing a semiconductor device according to the present invention will be described with reference to FIGS. FIG. 6 is a flowchart showing one embodiment of a method for manufacturing a semiconductor device according to the present invention. The steps of this embodiment include the following main steps. (1) Wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer) (2) Mask manufacturing process for manufacturing a mask for manufacturing a mask used for exposure (or mask preparing process for preparing a mask) (3) ) Wafer processing step of performing necessary processing on the wafer (4) Chip assembling step of cutting out chips formed on the wafer one by one and making them operable (5) Chip inspection step of inspecting the completed chips Each of the main steps further comprises several sub-steps.

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 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 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) Oxidation step of oxidizing this thin film layer or wafer substrate (3) Lithography step of forming a resist pattern using a mask (reticle) to selectively process the thin film layer or wafer substrate (4) An etching step of processing a thin film layer or a substrate according to a resist pattern (for example, using a dry etching technique) (5) An ion / impurity implantation diffusion step (6) A resist peeling step (7) A step of inspecting a processed wafer The wafer processing step is repeated for the required number of layers to manufacture a semiconductor device that operates as designed.

FIG. 7 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. The 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. The above (7)
When the defect inspection method and the defect inspection apparatus according to the present invention are used in the inspection process, even a semiconductor device having a fine pattern can be inspected with high throughput, so that 100% inspection can be performed, thereby improving the product yield and shipping defective products. Prevention becomes possible.

[0020]

According to the present invention, the following effects can be obtained. (1) Since the axial chromatic aberration coefficient of the condenser lens and the objective lens (hereinafter, referred to as an electrostatic lens in this section) can be reduced, the beam current of the same beam size of the electron beam is significantly increased. It is possible to greatly improve the S / N ratio of an image while keeping the resolution of the optical system constant. (2) Since the beam current of the same beam size of the electron beam can be dramatically increased, the throughput of the evaluation device is improved. (3) In order to form an electrostatic lens with an integral ceramic,
The outer dimensions of the lens barrel housing the electron beam device can be reduced, a large number of lens barrels can be arranged in one wafer, and the throughput can be improved. (4) By reducing the bore diameter of only the center electrode of the electrostatic lens, it is possible to reduce the voltage applied to the center electrode and reduce the axial chromatic aberration. (5) The fourth electrode is provided on the electrostatic lens, and the voltage applied to this electrode is set to a voltage close to the ground, and the power supply for controlling the dynamic focus is set to about the ground voltage, so that high-speed response is possible. (6) The axial chromatic aberration can be electrically controlled by changing the voltage applied to each electrode of the electrostatic lens. (7) The yield of the semiconductor manufacturing process can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing an optical system of an electron beam device according to the present invention.

FIG. 2 is a view showing a state where optical systems of an electron beam apparatus according to the present invention are arranged in parallel on a wafer in two rows and plural columns.

FIG. 3 is a diagram showing a simulation model of an objective lens.

FIG. 4 is a diagram showing a result of a simulation calculation of a relationship between a bore radius of an electrode and aberration in the model shown in FIG. 3;

FIG. 5 is a diagram showing a result of a simulation calculation of a relationship between axial chromatic aberration and a voltage applied to a center electrode, which is a focusing condition, in the model shown in FIG. 3;

FIG. 6 is a flowchart showing a device manufacturing process.

FIG. 7 is a flowchart showing a lithography process.

[Explanation of symbols]

1: electron beam device 10: primary optical system 11: electron gun 12, 1
3: Axis deflector 14: Condenser lens 15: Electrostatic deflector 16: E × B separator 17: Objective lens 20: Secondary optical system 30: Inspection device 31: Detector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tohru Satake 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation (72) Inventor Takeshi Murakami 11-1 Asahi-cho Haneda, Ota-ku, Tokyo EBARA F-term (reference) 4M106 AA01 BA02 CA38 DB05 DH24 DH33 5C033 CC01 MM03 MM07

Claims (5)

[Claims] An electron beam emitted from an electron gun is focused on a sample by an electrostatic lens, scanned and irradiated, and secondary electrons emitted from an irradiated portion of the sample are detected by a detector. In the electron beam apparatus for evaluating the above, by reducing the spacing between the plurality of electrodes of the electrostatic lens and increasing the bore diameter of the electrodes, the voltage applied to the electrodes that are in focus conditions is increased, An electron beam apparatus wherein axial chromatic aberration of an electrostatic lens is reduced. 2. An electron beam emitted from an electron gun is focused on a sample by an electrostatic lens, scanned and irradiated, and secondary electrons emitted from an irradiated portion of the sample are detected by a detector. In the electron beam apparatus, the electrostatic lens is constituted by at least three electrodes, a positive high voltage is applied to a center electrode among the electrodes, and an electrode on the electron gun side and the sample side of the center electrode. In the electron beam apparatus, a voltage lower than a voltage applied to the central electrode is applied, and a bore diameter of the central electrode is smaller than bore diameters of other electrodes. 3. Focusing an electron beam emitted from an electron gun,
In an electron beam apparatus that scans and irradiates a sample and evaluates the sample by detecting secondary electrons emitted from an irradiated portion of the sample with a detector, the electron beam is irradiated by at least three axially symmetric electrodes. Focusing, applying a positive high voltage to the center electrode of the at least three-pole axisymmetric electrodes, applying a positive voltage to both electrodes on both sides of the center electrode, and boosting the voltage of the electrodes on both sides An electron beam apparatus, wherein a voltage satisfying a focusing condition applied to the center electrode is increased. 4. Focusing an electron beam emitted from an electron gun,
An electron beam apparatus that scans and irradiates a sample, irradiates the sample, and detects a secondary electron emitted from an irradiated portion of the sample by a detector to evaluate the sample. To apply a high voltage to the second electrode from the sample side of the at least quadrupole axially symmetric electrodes, and also to the electrodes arranged on both sides of the second electrode from the sample side An electron beam apparatus wherein dynamic focusing is performed by applying a positive voltage to each of the electrodes and changing a voltage applied to an electrode disposed closer to the electron gun than the three electrodes. 5. A method for manufacturing a device, comprising: evaluating a wafer during or after a process using the electron beam apparatus according to claim 1.