JP2001236919A - Electron beam equipment and device fabrication method by means of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve S/N ratio, obtain good signals even when high-speed scanning is made, improve throughput and reduce scanning distortion of the electron beam in the electron beam equipment used for inspection of semiconductor devices or the like. SOLUTION: There are an electron gun 100 to emit the electron beam, a condenser lens 103 to give a crossover to the electron beam emitted from the electron gun 100, and an objective lens 7 to focus the electron beam on surface of a specimen, and the latter two are provided between the electron gun and a specimen 10. Each lens consists of an electrostatic lens having the first and second electrodes provided at the sides of electron gun and specimen, respectively. This equipment is also equipped with an electric-potential supplying means 110 that gives positive electric potentials to the first electrode of the condenser lens and the second electrode of the objective lens, and a detecting means 8, 15 that are located at the electron-gun side of the objective lens to detect reflected or secondary electrons from the specimen and generate a detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention generally relates to device defect inspection and critical dimension (CD).
More particularly, the present invention relates to an electron beam apparatus for performing inspection and measurement of a pattern having a minimum line width of 0.1 μm or less in a semiconductor device with high accuracy and high throughput. Further, the present invention relates to a device manufacturing method for checking a device manufacturing process using such an electron beam apparatus.

[0002]

2. Description of the Related Art Conventionally, there has been proposed an electron beam apparatus for performing a defect inspection or the like of a sample using a multi-beam. Such an electron beam apparatus is disclosed in Japanese Patent Application Laid-Open Publication No.
JP-A-361544, JP-A-5-82607, JP-A-5-82607
251315, JP-A-5-251316, JP-A-9
-304305, JP-A-9-311112 and JP-A-10-134575. Also John B
ickley, Atsuyuki Owada, "Microscopic Observation by KLA-2710" (Semiconductor World Monthly, June 1993)
The month issue, pp. 46-52) includes an electromagnetic lens (Snorkel Lens) disposed below the sample and an extraction electrode (Ex).
traction Electrode) and Wien Fil
ter) and an electron beam apparatus for efficiently guiding secondary electrons to a detector.

[0003]

However, according to Japanese Patent Application Laid-Open No. 4-361544 and the like, mainly reflected electrons are detected, so that even if the primary beam is made thin, the primary beam is deep inside the sample. There is a problem that information of a relatively large area is confused because the information enters and spreads, and the resolution of detection cannot be increased much.

According to Japanese Patent Application Laid-Open No. 5-251316, since the detector is provided below the lens, when used under deceleration electric field conditions, secondary electrons generated near the optical axis almost pass through the lens hole. There was a problem that it was not detected.

Further, according to Japanese Patent Application Laid-Open No. 9-311112, a non-axially symmetric electric field is applied between the objective lens and the sample, so that it is necessary to narrow the beam narrowly in this portion, and the scanning distortion is large. There was a problem of becoming.

Further, according to the method using an electromagnetic lens or the like described in the above-mentioned "observation of minute defects by KLA-2710", the external dimensions become large because a magnetic field is used. Therefore, since a large number of electron beams cannot be generated in a certain area such as a semiconductor wafer, there is a problem that inspection or the like cannot be performed at a high throughput.

[0007] In view of the above, a first object of the present invention is to improve the S / S ratio by focusing secondary electrons efficiently.
An object of the present invention is to provide an electron beam apparatus capable of improving an N ratio and obtaining a good signal even when scanning at high speed. Further, a second object of the present invention is to provide an electron beam apparatus which improves the throughput in device inspection and the like and reduces the scanning distortion of an electron beam. Further, a third object of the present invention is to provide a device manufacturing method for checking a device manufacturing process using such an electron beam apparatus.

[0008]

In order to solve the above problems, an electron beam apparatus according to a first aspect of the present invention makes an electron beam incident on a sample and detects reflected electrons or secondary electrons from the incident point. An electron gun for emitting an electron beam, a condenser lens and an objective lens provided between the electron gun and the sample, and a first lens provided on the electron gun side. And a condenser lens for forming a crossover with the electron beam emitted from the electron gun, and the electron beam is focused on the surface of the sample. An objective lens, a potential supply means for applying a positive potential to the first electrode of the condenser lens and the second electrode of the objective lens, and an electron gun provided closer to the electron gun than the objective lens, and configured to reflect reflected electrons from the sample. It is provided with a detecting means for generating a detection signal by detecting the secondary electrons. According to the above configuration, the detection means provided closer to the electron gun than the objective lens detects reflected electrons or secondary electrons from the sample, so that the S / N ratio is improved by efficiently focusing the secondary electrons. it can. Therefore, a good signal can be obtained even when scanning at high speed.

The electron beam apparatus further comprises at least one deflector for deflecting the electron beam focused by the condenser lens to scan on the surface of the sample, and passing the electron beam toward the sample along the incident axis. And an electromagnetic filter for guiding reflected electrons or secondary electrons from the sample to the detection means away from the incident axis.

Further, the electron beam apparatus further comprises a sample stage capable of grounding the sample, wherein the potential supply means applies a higher potential to the first electrode than to the second electrode of the condenser lens, A configuration may be such that a higher potential is applied to the second electrode than to the first electrode. According to the above configuration, since the energy of the electron beam can be reduced between the condenser lens and the objective lens, the deflector and the electromagnetic filter provided therebetween can control the electron beam with a low voltage and a small magnetic field. become.

An electron beam apparatus according to a second aspect of the present invention comprises:
An electron beam apparatus for causing a plurality of electron beams to be incident on a sample and detecting reflected electrons or secondary electrons from an incident point, and provided between an electron gun for emitting an electron beam and the electron gun and the sample. A condenser lens and an objective lens, each comprising an electrostatic lens having a first electrode provided on the electron gun side and a second electrode provided on the sample side, and emitted from the electron gun. A condenser lens for forming a crossover in the electron beam, an objective lens for focusing the electron beam on the surface of the sample, and a condenser lens for deflecting the electron beam focused by the condenser lens to scan the surface of the sample. A plurality of blocks of the electron beam apparatus including at least one deflector are arranged at two intervals X1 and Y1 in two orthogonal directions, respectively. , At least one deflector is capable of scanning the electron beam over the surface of the sample in two orthogonal directions at a distance X2 and a distance Y2, respectively. A sample stage movable in the directions of at least the distance (X1-X2) and the distance (Y1-Y2), and potential supply means for applying a positive potential to the first electrode of the condenser lens and the second electrode of the objective lens And detecting means for detecting reflected electrons or secondary electrons from the sample to generate a detection signal. According to the above configuration, device inspection or the like can be performed using a plurality of electron beams at the same time.
Throughput in device inspection and the like can be improved, and scanning distortion of an electron beam can be reduced.

In the above, the electron beam apparatus further includes an axially symmetric electrode provided between the objective lens and the sample stage, and the potential supply means supplies a lower potential than the second electrode of the objective lens. You may comprise so that it may give to an electrode. According to the above configuration, even if the electron beam device has a plurality of blocks, it is possible to prevent reflected electrons from the sample from entering the detectors of the adjacent blocks.

Further, the device manufacturing method according to the present invention comprises:
By using the electron beam apparatus as described above, by detecting reflected electrons or secondary electrons from the device formed in the sample, it is possible to observe and measure the surface of the sample, and in the manufacturing process of the device. It includes a step of checking the situation.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows one block for irradiating one electron beam in an electron beam apparatus according to one embodiment of the present invention and a peripheral portion thereof. The electron beam apparatus according to the present embodiment has a plurality of blocks, and can irradiate a plurality of electron beams at the same time. However, FIG. 1 shows only one block. This portion is surrounded by a lens barrel (not shown) having a shape (for example, a cylindrical shape) symmetrical with respect to the longitudinal axis. Then, a plurality of such lens barrels are assembled and installed in a vacuum chamber.

The thermal field emission electron gun 100 includes a cathode electrode 101 and an anode electrode 102 and emits an electron beam downward. Below the electron gun 100, a condenser lens 103, an electrostatic deflector 1, and a Wien filter 6
, An electrostatic deflector 2 and an objective lens 7 are provided. A crossover of the electron beam is formed by the condenser lens 103, and the electron beam is imaged on the sample 10 by the objective lens 7. The sample 10 is a driving unit 1
20 is placed on a sample stage 130 movable in the X-axis direction and the Y-axis direction. Condenser lens 103
A potential supply means 110 is provided to supply a predetermined potential to and other parts.

The secondary electrons 11 generated by the incidence of the electron beam on the sample are transmitted to the objective lens 7 and the electrostatic deflector 2.
And is directed by the Wien filter 6 in the direction of the detector 8. The detector 8 includes a secondary electron focusing electrode 12 for focusing secondary electrons, and the secondary electron focusing electrode 1.
2 and a scintillator 13 for converting incident secondary electrons into light. Scintillator 13
Since it is necessary to connect a photo guide 14 (optical fiber or the like), a small-sized one is used. The light output from the detector 8 is guided to the outside of the vacuum chamber through the photoguide 14 and is converted into an electric signal by the photomultiplier 15.

Next, the structure and operation of the electron beam apparatus shown in FIG. 1 will be described in detail. In FIG. 1, a voltage of −500 V is applied to the cathode electrode 101 of the thermal field emission electron gun 100, and a voltage of 20 kV is applied to the anode electrode 102. Thus, electrons are extracted from the cathode electrode 101. A voltage of 20 kV is applied to the upper electrode 104 of the condenser lens 103, and 5 kV is applied to the lower electrode 105.
Is applied. Thereby, a crossover of the electron beam is formed.

Each of the electrostatic deflectors 1 and 2 is composed of eight electrodes, and deflects the electron beam passing through the condenser lens 103 to scan on the sample surface. Note that the electrostatic deflectors can be integrated into one. In this case, the electron beam is vertically incident on the sample surface such that the principal deflection point is located at a position above the objective lens 7 by a focal distance.

The objective lens 7 is a bi-potential type electrostatic lens. A voltage of 5 kV is applied to the upper electrode 4 and a voltage of 20 kV is applied to the lower electrode 5 so that the upper electrode is lower than the lower electrode. Potential. Therefore, when the electron beam has a high energy of about 20 keV when passing through the objective lens 7, diffraction is small. Further, the diameter of the electron beam when passing through the lens is small, that is, the aperture angle is small. On the other hand, after passing through the objective lens 7, when the light enters the sample, the energy is as low as 0.5 to 1 keV, so that the aperture angle when entering the sample surface becomes large.
Therefore, spherical aberration and chromatic aberration are also small. As a result, the primary electron beam can be narrowed down with a large current value.

In addition, as an objective lens,
A unipotential lens may be used. In this case, if the central electrode is set to a low potential and the sample side is set to a high potential, the same effect as the bipotential lens can be obtained.

In FIG. 1, the trajectory of the principal ray of the primary electron beam at the time of scanning is indicated by reference numeral 3. The electron beam is deflected so as to pass through the center of the objective lens 7. Further, since the portion below the objective lens 7 is axially symmetric, deflection distortion and deflection aberration are small, and blurring of the electron beam and scanning distortion during scanning are small. Further, since the Wien filter 6 is provided closer to the electron gun than the deflector 2, the deflector 2 can be placed near the objective lens 7, so that the scanning beam at this position is less deviated from the axis and the deflection aberration can be reduced. .

The orbit of the secondary electrons is indicated by reference numeral 11. Secondary electrons emitted from the sample at a large angle with respect to the optical axis are also collected in the optical axis direction by the potential created by the partition 9 and the objective lens 7. On the other hand, since the electron beam reflected from the sample 10 travels straight without being affected by the electric field, it is mixed into the detector 8 by reducing the hole diameter of the objective lens 7 and the solid angle viewed from the sample. Reflected electrons can be reduced.

The partition 9 is made of a material having a low atomic number, such as aluminum or carbon, so that secondary electrons are less generated even when reflected electrons are incident. By applying a voltage of about −20 V to the partition 9, secondary electrons 11 generated from the sample 10 are directed in the optical axis direction. On the other hand, the reflected electrons are absorbed so as not to go to the detector 8.

The Wien filter 6 generates an electric field E and a magnetic field B which are orthogonal to each other when viewed from above, thereby causing the electron beam 3 traveling from the electron gun 100 to the specimen 10 to go straight, and secondary electrons traveling upward from the specimen 10. The track 11 is bent and directed toward the detector 8. In the present embodiment,
As a means for generating the magnetic field B, a permanent magnet is used to reduce the size of the device.

The lower electrode 105 of the condenser lens 103
Since the potential of the upper electrode 4 of the objective lens 7 is 5 kV, the energy of the secondary electrons at the position where the Wien filter 6 is provided is as low as about 5 keV, and the trajectory of the secondary electrons is reduced by a relatively weak electric field and magnetic field. Can be bent. Since the secondary electrons are in a beam bundle with a large diameter,
The potential of the secondary electron focusing electrode 12 of the detector 8 was set to 20 kV, the same as the lower electrode of the objective lens 7.

FIG. 2 shows an example of the arrangement pitch, scanning dimensions, and the like of the lens barrel of the electron beam apparatus on the wafer to be inspected. Although there are several types of diameters of the wafer 20, here, 200 mm
The case where a wafer of φ is used will be described. If one lens barrel is designed to have an outer dimension of 30 mmφ or less,
By providing 32 blocks, it is possible to simultaneously irradiate 32 electron beams 21 as shown in FIG.

Here, the scanning range of one electron beam is set to 2
Assuming a mm square, the distance X3 in the X direction that the sample stage has to move can be obtained using the beam pitch X1 and the scanning dimension X2. X3 = X1−X2 = 30 mm−2 mm = 28 mm Similarly, the distance Y3 in the Y direction that the sample stage has to move can be obtained using the beam pitch Y1 and the scanning dimension Y2. Y3 = Y1−Y2 = 30 mm−2 mm = 28 mm That is, if there is a movement range of 28 mm square, the entire surface of the 200 mmφ wafer can be inspected. Since the distance of one movement is as small as 2 mm, it is not necessary to move at high speed.
It is sufficient to use a vacuum chamber that is slightly larger than the size capable of accommodating the 200 mmφ wafer, and the floor area required by the electron beam apparatus can be reduced.

FIG. 3 is a flowchart showing an example of a device manufacturing method using the electron beam apparatus according to the present invention. Here, a case where a semiconductor device is manufactured using a silicon wafer will be described. First, in a wafer manufacturing step S31, a silicon wafer serving as a silicon substrate of a semiconductor device is manufactured. Next, a wafer processing step S3
In 2, a device isolation film is formed on a silicon substrate by a LOCOS method or the like. On the other hand, in a mask manufacturing step S33, a mask (reticle) such as an electrode or a wiring formed on the silicon substrate is manufactured.

Next, in step S34, a semiconductor element is formed. Here, a case where a MOSFET is formed as a semiconductor element will be described. First, a silicon substrate is thermally oxidized to form an oxide film in an element formation region of the silicon substrate, and polycrystalline silicon containing impurities is formed by a CVD method. Next, a gate oxide film and a gate electrode are patterned by forming a resist by a lithography technique and etching the oxide film and the polycrystalline silicon in an element formation region where the resist is not formed. Next, impurity ions are implanted into predetermined regions of the silicon substrate to form impurity diffusion regions serving as source / drain in the silicon substrate. afterwards,
An interlayer insulating film is formed, a contact hole is formed in the interlayer insulating film, a conductive film is sputtered, and a wiring is formed by patterning by lithography. If necessary, a multilayer wiring can be obtained by repeating the wiring forming process. Thus, the main part of the semiconductor device is formed. When an electrode, a wiring, or the like is formed in step S34, a line width inspection is performed using the electron beam apparatus according to the present invention in a line width inspection step S35. Steps S34 and S35 are repeated as many times as necessary.

Here, the lithography step included in the step S34 and the line width inspection step S35 will be described in detail with reference to FIG. First, the resist coating step S
At 34a, for one lot of semiconductor devices included in the wafer, a resist is applied on the conductive film or the silicon substrate. Next, in an exposure step S34b, the pattern on the mask (reticle) is sequentially transferred to the applied resist by exposing using a light or charged particle beam exposure apparatus. Next, in a developing step S34c, the exposed pattern on the resist is developed. Next, in the etching step S34d, the wafer including the semiconductor device of one lot is etched using the developed resist pattern as a mask, and a pattern on the mask (reticle) is formed on the wafer. Further, in the line width inspection step S35, the line width of the electrode or wiring formed in this manner is
The inspection is performed using the electron beam apparatus according to the present invention. In forming a gate electrode and a multilayer wiring, the above steps are repeated.

[0031]

As described above, according to the present invention, the S / N ratio can be improved by efficiently converging the secondary electrons, and a good signal can be obtained even when scanning at high speed.
Further, by providing a plurality of blocks for irradiating an electron beam and detecting secondary electrons, the throughput in device inspection and the like is improved, and the scanning distortion of the electron beam is reduced. Thereby, devices can be manufactured with good yield.

[Brief description of the drawings]

FIG. 1 is a diagram showing one block and its peripheral portion in an electron beam device according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a beam arrangement pitch, a scanning dimension, and the like of an electron beam apparatus on a wafer to be inspected.

FIG. 3 is a flowchart illustrating an example of a device manufacturing method using the electron beam apparatus according to the present invention.

FIG. 4 is a flowchart for explaining in detail a lithography process and a line width inspection process shown in FIG. 3;

[Explanation of symbols]

 1, 2 Electrostatic deflector 3 Primary electron beam 6 Wien filter 7 Objective lens 8 Detector 9 Partition 10 Sample 11 Secondary electron 12 Secondary electron focusing electrode 13 Scintillator 14 Photoguide 15 Photomar 100 Electron gun 103 Condenser lens 110 Potential supply Means 120 Driving means 130 Sample stage

Claims (6)

[Claims] An electron beam apparatus for causing an electron beam to enter a sample and detecting reflected electrons or secondary electrons from an incident point, comprising: an electron gun for emitting an electron beam; the electron gun and the sample A condenser lens and an objective lens provided between the first and second electrodes, each comprising an electrostatic lens having a first electrode provided on the electron gun side and a second electrode provided on the sample side. And the condenser lens for forming a crossover in the electron beam emitted from the electron gun, the objective lens for focusing the electron beam on the surface of the sample, a first electrode of the condenser lens, A potential supply means for applying a positive potential to the second electrode of the objective lens; a potential supply means provided closer to the electron gun than the objective lens, for detecting reflected electrons or secondary electrons from the sample to detect Electron beam apparatus characterized by comprising detection means for generating a signal. 2. An at least one deflector for deflecting the electron beam focused by the condenser lens to scan on the surface of the sample, and passing the electron beam toward the sample along an incident axis; An electromagnetic filter that guides reflected electrons or secondary electrons from the sample away from the incident axis to the detection unit, wherein the electromagnetic filter is provided closer to the electron gun than the deflector. The electron beam apparatus according to claim 1, wherein 3. The apparatus according to claim 2, further comprising a sample stage capable of grounding the sample, wherein the potential supply means applies a higher potential to a first electrode than to a second electrode of the condenser lens, and 2. The electron beam apparatus according to claim 1, wherein a higher potential is applied to the second electrode than to the first electrode. 4. An electron beam apparatus for causing a plurality of electron beams to be incident on a sample and detecting reflected electrons or secondary electrons from an incident point, comprising: an electron gun for emitting an electron beam; An electrostatic lens having a first electrode provided on the electron gun side and a second electrode provided on the sample side, each of which is a condenser lens and an objective lens provided between the sample and the sample. The condenser lens for forming a crossover to the electron beam emitted from the electron gun, the objective lens for focusing the electron beam on the surface of the sample, and the electron focused by the condenser lens. At least one for deflecting the beam to scan over the surface of the sample;
A plurality of blocks of the electron beam apparatus including two deflectors are arranged in two orthogonal directions at intervals X1 and Y1, respectively. In each block of the electron beam apparatus, the at least one deflector includes two orthogonal cross sections. An electron beam can be scanned over the surface of the sample in a range of a distance X2 and a distance Y2 in two directions, respectively. In order to inspect the sample, at least a distance (X1-X2) in two orthogonal directions is used. ) And distance (Y1-Y
A sample stage that can move in the range of 2); a potential supply unit that applies a positive potential to the first electrode of the condenser lens and the second electrode of the objective lens; and a reflected electron or a secondary electron from the sample. An electron beam apparatus, further comprising: detecting means for detecting and generating a detection signal. 5. The apparatus according to claim 1, further comprising an axis-symmetric electrode provided between said objective lens and said sample stage, wherein said potential supply means applies a potential lower than a second electrode of said objective lens to said electrode. The electron beam apparatus according to claim 1 or 4, wherein the electron beam is supplied to the electron beam apparatus. 6. A method for manufacturing a device by detecting reflected electrons or secondary electrons from a device formed in the sample using the electron beam apparatus according to claim 1. A device manufacturing method, comprising a step of inspecting a situation in a process.