JP3803271B2 - Electron beam apparatus and device manufacturing method using the apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an electron beam apparatus capable of evaluating a wafer having a pattern with a minimum line width of 0.1 μm or less with high throughput and high reliability, and a device manufacturing method using such an electron beam apparatus.
[0002]
[Prior art]
A device combining a differential exhaust device and an electron beam device is already known. An apparatus that incorporates a differential evacuation device under an objective lens and exposes a wafer in the atmosphere with an electron beam has been published in the past.
[0003]
[Problems to be solved by the invention]
In such a conventional apparatus having a differential exhaust device under the objective lens, the image point distance of the objective lens becomes long, inevitably increases spherical aberration and chromatic aberration of the objective lens, and LaB ₆ is used for the cathode. When used in combination with an electron gun having a large energy width such as an electron gun, there was a problem that the beam could not be narrowed down.
In addition, the electron beam apparatus that applies retarding has a problem in that the optical characteristics are not good because a member installed for differential pumping is inserted between the lens and the wafer.
[0004]
One problem to be solved by the present invention is to provide an electron beam apparatus that can perform differential pumping even with an electrostatic lens having severe vacuum conditions.
Another problem to be solved by the present invention is to provide an electron beam apparatus that enables differential pumping in a system that tends to cause discharge, such as a deceleration electric field objective lens.
Another problem to be solved by the present invention is that it is possible to combine an electron gun using a LaB ₆ cathode and differential exhaust, and the advantage of shot noise reduction by operating the electron gun under space charge limited conditions. It is to provide an electron beam device that makes the best use of it.
Another problem to be solved by the present invention is to provide a device manufacturing method for manufacturing a semiconductor device using the electron beam apparatus as described above.
[0005]
According to the first aspect of the present invention, an electron optical system having an objective lens including an electron gun and an electrostatic lens that irradiates an inspection target with a primary electron beam emitted from the electron gun, and an outer side of the objective lens. The differential exhaust system exhaust head further includes an upper electrode, a center electrode, and a lower electrode, and the exhaust head includes an inner member of the exhaust head. An outer peripheral portion of the inspection object in a stage device that is disposed outside the objective lens and is disposed outside the cylindrical portion of the lower electrode, coaxial with the electrode, and the inspection object A feature is that a differential exhaust member having the same height as the inspection object is provided in a portion on the stage device where the exhaust head is located when the inspection object is moved to the replacement position of the inspection object. A.
The invention according to claim 2 of the present application resides in a device manufacturing method characterized by evaluating a wafer after completion of each wafer process using the electron beam apparatus.
[0008]
Embodiment
Embodiments of an electron beam apparatus according to the present invention will be described below with reference to the drawings, using an example in which a wafer is used as an inspection target. In FIG. 1, the schematic structure of the electron beam apparatus 1 which is one Embodiment of this invention is shown.
In FIG. 1, an electron beam apparatus 1 includes an electron gun 2 having a cathode 21, a flat Wehnelt 22 and an anode 23 made of a single crystal of LaB ₆ , a condenser lens 3 as an electrostatic lens, and a condenser lens 3. 1 includes an aperture plate 4 that is disposed adjacent to the aperture plate 4 and defines an aperture 41, a reduction lens 5, an E × B separator 6, and an objective lens 7 that is an electrostatic lens, which are shown in FIG. It is arranged in such a positional relationship. The above components constitute the primary electron optical system of the electron beam apparatus 1. Between the reduction lens 5 and the objective lens 7, a shield tube 8 is provided coaxially with the optical axis X1. This shield tube 8 is for preventing the electric field leaking from the collector electrode 9 provided coaxially with the optical axis X2 of the secondary electron optical system from affecting the primary electron beam traveling along the optical axis X1. It is.
[0009]
In the primary and secondary electron optical systems, the primary electron beam emitted from the cathode 21 of the electron gun 2 diverges from the crossover C at the position of the opening of the anode 23 and is focused by the condenser lens 3. Irradiate the square opening 41. The beam shaped at the aperture is reduced by the reduction lens 5 and the objective lens 7 and imaged on the surface of the wafer W. Secondary electrons emitted from the surface of the wafer W are accelerated by an accelerating electric field formed by a negative voltage applied to the wafer and a positive high voltage applied to the central electrode of the objective lens 7, and pass through the objective lens 7. After that, it is deflected by the E × B separator 6 and detected by the secondary electron detector 10. The detected secondary electrons are sent to a determination circuit (not shown), and the determination circuit determines the quality of a pattern or the like formed on the surface of the wafer W.
[0010]
The electron beam apparatus 1 further includes an exhaust head 12 constituting a differential exhaust apparatus so as to surround the objective lens 7 between the E × B separator 6 and the wafer W to be inspected. The wafer is disposed on the mounting surface of the stage apparatus 13 having a known structure and function, and is held open by a known method. The stage device and the exhaust head 12 are separated from the outside air by a housing disposed in a lower part of a lens barrel (not shown) of the electron beam apparatus 1 and are placed in a sample chamber 14 which can be controlled to a desired atmosphere by a known method. Has been placed. Tables 15 and 16 are arranged and fixed around the wafer W on the mounting surface. The heights of the upper surfaces of these tables 15 and 16 are determined so as to be flush with the upper surface of the wafer. This is because a part of the exhaust head 12 is detached from the upper surface of the wafer when the peripheral portion of the wafer W is inspected or when the wafer is moved to the wafer exchange position. This is to ensure the differential exhaust function of the differential exhaust device. Therefore, as shown in FIG. 2, the table 15 is arranged over substantially the entire circumference of the wafer, and its radial width (width seen in the radial direction centered on the center of the wafer W) L1 is the periphery of the wafer. When the part is inspected, the differential exhaust function via the exhaust head 12 is not impaired when the wafer is displaced to the maximum with respect to the optical axis of the primary optical system. On the other hand, the table 16 is arranged only at a part of the outer periphery, that is, only on the right side of the wafer in FIG.
[0011]
In this embodiment, the distance between the outer peripheral edge of the wafer W and the edges of the bases 15 and 16 (the edge adjacent to the outer peripheral edge of the wafer) is 0.3 μm or less. If the pressure is not 101.3 kPa (1 atm) but exhausted to 10 ⁻¹ torr or less, there is no problem even if this interval is about 0.5 mm.
[0012]
In FIG. 3, an enlarged view of the vicinity of the objective lens 7 of FIG. 1 is shown. In the figure, 61 is an electrostatic deflector of the E × B separator 6, and 62 and 63 are an X coil and a Y coil of an electromagnetic deflector for the E × B separator, respectively. Reference numeral 64 denotes a ferrite core for an E × B separator. The upper electrode 71 of the objective lens 7 has a cylindrical shape in order to minimize the lens outer diameter. The axis of the upper electrode 71 is arranged coaxially with the optical axis X1 of the primary optical system, and a disc-shaped portion 71b is integrally joined to one end (the upper end in FIG. 3). The central electrode 72 of the objective lens is disposed adjacent to the tip (lower end in FIG. 3) of the upper electrode 71 and has a disk shape. The central electrode 72 is integrally connected with a cylindrical portion 72a disposed coaxially with the upper electrode 71 on the outer side, and an outer disk-shaped portion 72b is integrally joined to the upper end of the cylindrical portion 72a. Yes. Further, the lower electrode 73 of the objective lens is disposed adjacent to the lower side (in FIG. 3) of the central electrode 72 and has a disk shape. A cylindrical portion 73a that is coaxial with the upper electrode and disposed outside the cylindrical portion 72a of the central electrode is integrally joined to the lower electrode 73, and an outer disk-shaped portion 73b is formed at the upper end of the cylindrical portion 73a. They are joined together. The upper electrode 71 and the center electrode 72 are insulated by an insulating member 75 and are held at a predetermined interval. The center electrode 72 and the lower electrode 73 are insulated by an insulating member 76 and are held at a predetermined interval. A positive high voltage is applied to the center electrode 72. When measuring the potential contrast, the lower electrode 73 is applied with a voltage that is several hundred volts lower than the voltage applied to the wafer, forming a barrier that does not allow the secondary electrons from the wafer to cross, and has a high voltage pattern. The secondary electrons emitted from the sample are returned to the sample side, and the filter serves as a filter for passing the secondary electrons emitted from the low voltage pattern. The working distance of the objective lens, that is, the distance between the upper surface of the wafer W to be inspected and the lower surface of the lower electrode 73 is defined as Dw.
[0013]
In this embodiment, the exhaust head 12 of the working exhaust device has three annular members that are rotationally symmetric with respect to the optical axis X1, that is, arranged in a radial direction with the optical axis X1 as a common axis, that is, An inner member 121, an intermediate member 122, and an outer member 123 are provided. A gap 125 between the outermost cylindrical portion 73a of the objective lens 7 and the inner member 121 is connected to an ion pump via a conduit (not shown), and is exhausted by the ion pump. Yes. In addition, the gap 126 between the inner member 121 and the intermediate member 122 is connected to a turbo molecular pump via a conduit (not shown), and is exhausted by the turbo molecular pump. A gap 127 between the intermediate member 122 and the outer member 123 is connected to a mechanical booster (not shown). The inner member, the intermediate member, and the outer member constitute a differential exhaust system, that is, a member that limits the exhaust conductance of the apparatus.
[0014]
In this embodiment, the distances d1, d2, and d3 between the wafer-side surfaces of the members 121, 122, and 123 of the exhaust head 12 and the upper surface of the wafer W are all set to be equal to the working distance Dw of the objective lens. It has been. As described above, since the distances d1, d2, and d3 between the respective members of the exhaust head 12 and the wafer are all equal to the working distance Dw of the objective lens, the axial chromatic aberration coefficient of the objective lens 7 can be reduced. Even when an electron gun having a relatively large energy width such as an electron gun using thermoelectrons such as a cathode made of LaB ₆ is used, a relatively large beam current can be obtained. Furthermore, since the shot noise can be reduced to about 13% by using the electron gun under the space charge limited condition, even if scanning is performed at a much higher speed than when the thermal field effect electron gun is used, the same S / N ratio is obtained. A ratio signal can be obtained. In the above embodiment, the working distance Dw of the objective lens is all equal to the intervals d1, d2, and d3, but may be smaller than that.
[0015]
Next, an embodiment of a semiconductor device manufacturing method according to the present invention will be described with reference to FIGS.
FIG. 4 is a flowchart showing an embodiment of a semiconductor device manufacturing method according to the present invention. The manufacturing 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 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 chips formed on the wafer one by one and making them operable (5) Chip inspection step for inspecting the completed chips Each of the main processes described above further includes several sub-processes.
[0016]
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.
(A) A thin film forming process for forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film for forming an electrode portion (using CVD, sputtering, etc.)
(B) Oxidation process for oxidizing the thin film layer and wafer substrate (C) Lithography process for forming a resist pattern using a mask (reticle) to selectively process the thin film layer and wafer substrate, etc. (D) Resist pattern Etching process (eg using dry etching technology) to process thin film layers and substrates according to
(E) Ion / impurity implantation diffusion process (F) Resist stripping process (G) In addition, a process for inspecting the processed wafer In addition, the wafer processing process is repeated as many times as necessary to manufacture a semiconductor device that operates as designed. To do.
[0017]
FIG. 5 is a flowchart showing a lithography process that forms the core of the wafer processing process of FIG. This lithography process includes the following steps.
(A) A resist coating step for coating a resist on the wafer on which a circuit pattern is formed in the previous step (b) an exposure step for exposing the resist (c) a development step for developing the exposed resist to obtain a resist pattern (D) Annealing process for stabilizing the developed resist pattern The semiconductor device manufacturing process, wafer processing process, and lithography process are well known and need no further explanation.
When the defect inspection apparatus, the defect inspection method, the exposure apparatus, and the exposure method according to the present invention are used in the inspection process (G) or the exposure process (c), a fine pattern can be inspected stably with high accuracy or Since exposure is possible, it is possible to improve product yield and prevent shipment of defective products.
[0018]
【The invention's effect】
According to the present invention, the following effects can be obtained.
(A) It is possible to provide an electron beam apparatus that can perform differential pumping even with an electrostatic lens that has a stricter vacuum condition than a magnetic lens.
(B) It is possible to provide an electron beam apparatus that enables differential pumping in a system that easily causes discharge such as a decelerating electric field objective lens.
(C) Since the exhaust head for the differential exhaust device is arranged outside the objective lens, the working distance of the objective lens can be shortened, the axial chromatic aberration coefficient can be reduced, and even when LaB6 is used for the cathode of the electron gun A large beam current can be obtained, and a signal with a high S / N ratio can be obtained by using the effect of shot noise with a low space charge limiting condition.
(D) Since the chamber in which the sample is placed is set to a pressure lower than the atmospheric pressure, the differential exhaust is not loaded.
(E) The yield of devices can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an embodiment of an electron beam apparatus of the present invention.
2 is a top plan view of a wafer mounting surface of the electron beam apparatus of FIG. 1; FIG.
3 is an enlarged sectional view of a part of the periphery of an objective lens of the electron beam apparatus of FIG.
FIG. 4 is a flowchart showing a device manufacturing process.
FIG. 5 is a flowchart showing a lithography process.
[Explanation of symbols]
1 Electron Beam Device 2 Electron Gun 3 Condenser Lens 4 Aperture Plate 5 Reduction Lens 6 E × B Separator 7 Objective Lens 10 Secondary Electron Detector 12 Exhaust Head 14 Sample Chamber

Claims (2)

  An electron optical system having an objective lens including an electron gun and an electrostatic lens that irradiates an inspection target with a primary electron beam emitted from the electron gun; and an exhaust head of a differential exhaust system disposed outside the objective lens; The objective lens includes an upper electrode, a center electrode, and a lower electrode, and the exhaust head has an inner member of the exhaust head that is coaxial with the upper electrode. An outer peripheral portion of the inspection object in the stage device that is arranged outside the objective lens so as to be arranged outside the cylindrical portion and supports the inspection object, and the inspection object is an exchange position of the inspection object An electron beam apparatus characterized in that a differential exhaust member having the same height as the object to be inspected is provided in a portion on the stage apparatus where the exhaust head is located when the exhaust head is moved.   A device manufacturing method, comprising: evaluating a wafer after completion of each wafer process using the electron beam apparatus according to claim 1.

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