JP2002352763A - Electron beam system and device manufacturing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damages in the cathode of an electron gun by positive ions, while keeping high vacuum level for an electron gun chamber, even when the vacuum level of a lens/deflection system is low. SOLUTION: An apparatus relates to an electron beam system having a multi-beam/multi-column structure. A plurality of lens barrels 32, arranged in parallel in this electron beam apparatus, comprise the electron gun chamber 1 for emitting a plurality of electron beams from a plurality of projections of cathodes 3 and electron optical systems Y for forming the images of the plurality of electron beams on the surface of a sample. The electron beam apparatus also comprises a partition plate S, that separates the electron gun chamber 1 from a plurality of electron optical systems Y and has holes 8, through which a plurality of electron beams can pass. The plurality of electron beams are formed on a circumference centered on the optical axis of each corresponding electron optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an image forming apparatus having a minimum line width of 0.1.
The present invention relates to an electron beam apparatus suitable for performing high-throughput, high-reliability evaluation of a sample such as a wafer and a mask having a submicron pattern and a device manufacturing method using the same.

[0002]

2. Description of the Related Art An electron beam apparatus using a multi-beam is already known. For example, one or more electron beams converged to a predetermined diameter are emitted from an electron gun to form an image on the surface of a sample to be inspected, and the surface of the sample to be inspected is moved by the electron beam by moving the sample to be inspected. Scanning, detecting secondary electrons and reflected electrons emitted from the sample to be inspected by multiple detection elements, and processing the outputs of those detection elements simultaneously or in parallel to reduce the evaluation time of fine patterns An electron beam apparatus adapted to do so is known.

Further, in order to eliminate variations in spot shapes of electron beams emitted from a plurality of electron guns and to improve the accuracy of fine pattern evaluation, a sample to be inspected is irradiated with a plurality of primary electron beams. There is also known a fine pattern evaluation device that detects the secondary electrons and reflected electrons for each primary electron beam and adjusts the electrode voltage or the excitation current for each primary electron beam.

In such a multi-beam type electron beam apparatus, the required degree of vacuum differs between the electron gun and the lens / deflection system. For example, in the case of a multi-emitter type or thermal field emission type electron gun, the vicinity of the cathode of the electron gun cannot operate safely unless the degree of vacuum is better than 10 ^-8 torr, while the lens / deflection is not good. Even if the system uses an electrostatic lens or an electrostatic deflector,
It can operate satisfactorily if a degree of vacuum of about 10 ^-6 torr is achieved. Therefore, there is a problem that a predetermined degree of vacuum must be maintained for each component of the electron beam apparatus.

[0005] Further, since an extremely large number of ions are present on the optical axis of the electron beam in the electron optical column, there is also a problem that positive ions collide with the cathode of the electron gun and make holes in the cathode.

Further, in the case of manufacturing a multi-beam and multi-column electron beam apparatus, there is no clear answer to the question of how to fix each column.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve the above-mentioned problems, and maintains a high degree of vacuum of the electron gun even when the degree of vacuum of the lens / deflection system is low. Accordingly, an object of the present invention is to provide an electron beam apparatus that prevents damage to a cathode of an electron gun and is resistant to vibration, and a device manufacturing method using the same.

[0008]

In order to solve the above problems, the present invention provides an electron beam forming means for forming a plurality of electron beams and an electron optical system for forming an image of the plurality of electron beams on a surface of a sample. A plurality of electron beam devices arranged in parallel, each partitioning between the electron beam forming means and the plurality of electron optical systems, and having at least two holes through which the plurality of electron beams can pass. The system further includes a partition plate common to the system, wherein the plurality of electron beams are arranged on a circumference around the optical axis of each corresponding electron optical system.

According to the present invention, a plurality of electron beams are formed from each of a plurality of parallel electron beam forming means.
For example, the electron beam forming means has a plurality of projections on an electron gun cathode, and these projections emit an electron beam.
The plurality of electron beams thus formed pass through the holes of the partition plate, enter each of the plurality of electron optical systems arranged in parallel, and are imaged on the surface of the sample via the electron optical systems. . Since the plurality of electron beams are arranged on a circumference centered on the optical axis of each corresponding electron optical system, a large number of positive ions on the optical axis of the electron optical system are Even when returning to the electron beam forming means from the other side, since there is no individual electron beam source (for example, the above-described cathode projection) on the optical axis, the cathode projection is not damaged by positive ions.

In a preferred aspect of the present invention, each of the plurality of electron optical systems is provided inside a ferromagnetic tubular member. In another preferred aspect of the present invention, a plurality of electron optical systems are arranged in a row of M rows and two columns on one sample, and the electron beam apparatus scans the plurality of electron beams in a row direction. In addition, the evaluation of the sample is performed while continuously moving the sample stage in a column direction perpendicular to the row direction. Thereby, the surface of the sample can be efficiently evaluated.

In still another preferred aspect of the present invention, the plurality of electron optical systems further include: an E × B separation means for deflecting secondary electrons emitted from the sample in a predetermined direction with respect to an optical axis; And a secondary optical system for guiding the secondary electrons to the secondary electron detector by at least one lens, and the two rows of secondary electron optical systems opposing each other extend away from each other. It is characterized by the following.

Thus, a plurality of lens barrels can be efficiently arranged without the secondary electron optical systems protruding from the lens barrel of the electron optical system interfering with each other. That is, as many electron optical systems as possible can be juxtaposed on the surface of the sample, and the sample can be evaluated with high throughput.

The use of the electron beam apparatus according to the present invention makes it possible to evaluate a wafer in the middle of a process or after completion with high throughput and high accuracy while preventing the influence of positive ions and the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an electron beam apparatus according to the present invention will be described below with reference to FIG. In FIG. 1, the electron beam device has a multi-beam multi-column structure, and is separated into an electron gun portion X and an electron optical system Y by a thick partition plate S whose both ends are fixed to a lens barrel 32. , Partitioned. The electron gun section X includes a plurality of electron gun chambers 1 each having a cylindrical shape and connected to each other by a bellows 2.
A thermionic electron gun equipped with a LaB ₆ cathode 3 and a Wehnelt 4 is supported by a high-voltage insulator 5. Each electron gun is supplied with power by a high-voltage cable 6 and has a LaB ₆ cathode 3
Emits a plurality of electron beams.

Each of the electron gun chambers 1 is fixed to a partition plate S by screws 7. For this reason, it is necessary that the partition plate S has a predetermined thickness so as to have a sufficient rigidity. If the rigidity of the partition plate S is not sufficient, a reinforcing rib is provided between the adjacent electron gun chambers 1. It is desirable to arrange. Each of the electron gun chambers 1 is connected to an ion pump (not shown) for exhaust.

The partition plates S are provided with the electron guns of the respective electron gun chambers 1 so that all the electron beams emitted from the plurality of projections of the LaB ₆ cathode 3 of each electron gun can pass through the partition plates S. One hole 8 centering on the optical axis is formed. Each of these holes 8 has a large aspect ratio (ratio of hole diameter to hole length) so as not to deteriorate the degree of vacuum in the electron gun chamber.

On the other hand, the electron optical system Y includes a plurality of electron gun chambers 1.
Has a lens / deflection system 10 installed corresponding to each electron gun chamber 1 in order to shape and reduce the shape of each electron beam so as to irradiate a sample W such as a wafer with a plurality of electron beams emitted from the electron gun chamber 1 . Each lens / deflection system 10 includes an elongated ferromagnetic pipe 1 fixed to a partition plate S by screws 7 so as to surround a hole 8 through which an electron beam from a corresponding electron gun passes.
1, a required lens and a deflector are arranged inside each pipe 11, and the electron beam passing through the hole 8 of the partition plate S is shaped, reduced, and vertically incident on the sample W. Thus, a multi-column electron optical system Y is configured.

For this reason, each lens / deflection system 10
In a pipe 11, a condenser lens 12, a multi-aperture plate 14, a reduction lens 16, a deflector 24 and an objective lens 1
8 are provided in order. Condenser lens 1
2 converges the electron beam that has passed through the hole 8 formed in the partition plate S. The multi-aperture plate 14 includes the condenser lens 12
And the same number of small holes as the number of the cathode projections so that the electron beam converged by the above-mentioned method is passed. The reduction lens 16 reduces the beam size and interval of the electron beam that has passed through the multi-aperture plate 14 and allows the electron beam to pass through the deflector 30. The deflector 30 changes the traveling direction of the electron beam so that the electron beam reduced by the reduction lens 16 scans on the sample. Objective lens 1
Reference numeral 8 focuses the electron beam passing through the deflectors 30 and 31 on the sample W.

Each of the pipes 11 is provided with an exhaust hole 17 so that the inside of a lens barrel (not shown) that accommodates the partition plate S, the electron gun section X, and the electron optical system Y is kept at a vacuum. The inside of each pipe 9 is also kept at a vacuum by the pump. The condenser lens 12, the multi-aperture plate 1
3. A required voltage is applied to the reduction lens 14, the deflector 15, and the objective lens 16 via a lead wire (not shown). If necessary, the condenser lens 12, the multi-aperture plate 14, the reduction lens 16, the deflector 30 and the objective lens 18 are attached to the inner wall of the pipe 11 via an insulating spacer 33.

FIG. 2 is a conceptual diagram of the electron beam apparatus of the present invention as viewed from above. The primary optical system indicated by reference numeral 121 is arranged on a single 8-inch or 12-inch wafer W in five rows and two columns, and the first column and the second column are shifted by a half pitch, so as to be arranged in the x direction. The optical axes are arranged at intervals. Around each optical system, four primary electron beams 123 are arranged on a circumference centered on the optical axis. Each beam was simultaneously scanned in the x direction, and the wafer W was evaluated while moving the stage continuously in the y direction in parallel with the scanning.

The secondary electrons generated from the scanning point of each beam are deflected by the E × B separator to the secondary optical systems formed in two rows in opposite directions by the secondary optical system 122.
The images are guided to the detector 124 after the image interval between the images is enlarged by an enlargement optical system (not shown). The secondary electrons are detected by the detector 124.
After that, the detection signal is amplified and AD
After conversion, an image signal is finally formed.

When the beam interval when the multi-beam is projected on the x-coordinate is, for example, 50 μm, the amplitude for scanning each beam is, for example, 49 μm so that the scanning regions do not overlap each other. On the other hand, the distance between the lens barrels is set to 30 mm and shifted by half a cycle.
mm intervals. An evaluation of a width of 199 μm is performed by one stage scan. If a non-evaluation area of 1 μm is provided, the scanning areas do not overlap. After performing the stage scanning 75 times, a connecting region between the lens barrels occurs. Here, since the time has passed, the charge is discharged even if the overlap scanning is performed, so that the device is not destroyed.

The electron beam apparatus shown in FIG. 2 is used as an evaluation apparatus for defect inspection, line width measurement, alignment accuracy measurement, potential contrast measurement, defect review, or strobe SEM to evaluate a wafer in the process. can do. (Second Embodiment: Method for Manufacturing Semiconductor Device) In this embodiment, the electron beam apparatus shown in the above embodiment is applied to evaluation of a wafer in a semiconductor device manufacturing process.

An example of the device manufacturing process will be described with reference to the flowchart of FIG. This example of the manufacturing process includes the following main processes. Wafer manufacturing process for manufacturing wafer W (or preparation process for preparing wafer) (step 100) Mask manufacturing process for manufacturing a mask used for exposure (or mask preparing process for preparing mask) (step 1)
01) Wafer processing step for performing necessary processing on the wafer (Step 102) Chip assembling step for cutting out chips formed on the wafer one by one and making it operable (Step 1)
03) Chip inspection step of inspecting the assembled chip (step 104) Each step is further composed of several sub-steps.

Among these main steps, the main step that has a decisive effect on the performance of the semiconductor device is the wafer processing step. 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. A thin film forming step (using CVD or sputtering, etc.) for forming a dielectric thin film or a wiring portion, or a metal thin film for forming an electrode portion, which serves as an insulating layer; Lithography process to form resist pattern using mask (reticle) to selectively process wafer substrate etc. Etching process to process thin film layer and substrate according to resist pattern (for example, using dry etching technology) Ion / impurity implantation Diffusion process Resist stripping process Inspection process for inspecting the processed wafer The wafer processing process is repeated as many times as necessary to manufacture semiconductor devices that operate as designed.

FIG. 4 is a flow chart showing the lithography step which is the core of the wafer processing step. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the previous step (step 2)
00) Exposure step of exposing the resist (Step 201) Development step of developing the exposed resist to obtain a resist pattern (Step 202) Annealing step for stabilizing the developed pattern (Step 203) Known processes are applied to the device manufacturing process, the wafer processing process, and the lithography process.

In the above wafer inspection process, when the electron beam apparatus according to the above embodiment of the present invention is used, even a semiconductor device having a fine pattern can be evaluated with high throughput and high accuracy. Yield can be improved and defective products can be prevented from being shipped.

[0028]

As will be understood from the above description of the embodiments of the electron beam apparatus according to the present invention, the present invention provides: Since the electron gun section (electron beam forming means) and the electron optical system are separated by the partition plate, it is possible to achieve a required degree of vacuum independently for each section. 2. Since the electron gun unit and the electron optical system can be connected by a hole having a small conductance, a large pressure difference between the electron gun unit and the electron optical system can be obtained. Since a plurality of electron beams are arranged on a circle around the optical axis (for example, the cathode has a plurality of projections on a circle around the optical axis to form a plurality of electron beams). Even if positive ions return on the optical axis from the sample or the electron optical system toward the cathode of the electron gun, there are no individual electron beam sources (for example, projections on the cathode) on the optical axis. Thus, the cathode projection is not particularly damaged.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a configuration of an embodiment of an electron beam apparatus according to the present invention.

FIG. 2 is a view for explaining a step of evaluating a wafer in the middle of a process using the electron beam apparatus according to the present invention.

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

FIG. 4 is a flowchart illustrating a lithography process in the semiconductor device manufacturing process of FIG. 3;

[Description of References] X: Electron gun, S: Partition plate, Y: Electron optical system,
1: electron gun chamber, 2: bellows, 3: cathode,
4: Wehnelt, 5: High voltage insulator, 6: High voltage cable, 8: Hole, 9: Beam orbit, 10: Lens / deflection system, 12: Condenser lens, 13: Condenser lens, 14: Multi aperture plate, 15: NA aperture, 16: reduction lens, 17: E × B separator,
18: objective lens, 19: lead wire, 20: electrostatic chuck, 21: stage, 22: sample chamber,
23: O-ring, 24: Axis alignment device, 25:
Rotating lens, 26: astigmatism corrector, 27, 28:
29: Axis alignment, 30: Scanning deflector, 31: Electromagnetic deflector for E × B separation, 32: Lens barrel, 33: Insulating spacer 34: Exhaust hole, 12
1: primary optical system, 122: secondary optical system, 12
3: primary electron beam, 124: detector, 12
5: Scanning direction of primary electron beam

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01J 37/29 H01J 37/29 5F056 H01L 21/027 H01L 21/66 J 21/66 21/30 541B (72 ) Inventor Toru Satake 11-1 Haneda Asahimachi, Ota-ku, Tokyo F-term in Ebara Corporation (reference) BA02 CA39 CA41 DB18 5C030 BC06 5C033 BB02 UU02 UU04 5F056 AA33 AA35 EA12 EA16

Claims (5)

[Claims] 1. An electron beam apparatus comprising: a plurality of electron beam forming means for forming a plurality of electron beams; and a plurality of electron optical systems for imaging the plurality of electron beams on a surface of a sample. A partition plate for separating the electron beam forming means and the plurality of electron optical systems and having a hole through which the plurality of electron beams can pass; a partition plate common to at least two electron optical systems; Are arranged on a circumference centered on the optical axis of each corresponding electron optical system. 2. The electron beam apparatus according to claim 1, wherein each of the plurality of electron optical systems is provided inside a ferromagnetic tubular member. 3. The plurality of electron optical systems are arranged in a row of M rows and two columns on a single sample, and the electron beam apparatus scans the plurality of electron beams in a row direction, and scans the plurality of electron beams. Characterized by performing the evaluation of the sample while continuously moving the sample stage in the column direction perpendicular to the direction,
The electron beam device according to claim 1. 4. The electron optics system further comprises: an E × B separation unit for deflecting the secondary electrons emitted from the sample in a predetermined direction with respect to an optical axis; A secondary optical system for guiding to a secondary electron detector by a single-stage lens, wherein two opposing secondary electron optical systems extend away from each other in opposite directions. 4. The electron beam device according to 3. 5. A device manufacturing method, comprising: evaluating a wafer during or after a process using the electron beam apparatus according to claim 1.