JP3929873B2 - Electron beam apparatus and device manufacturing method using the apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION
[0001]
The present invention relates to an electron beam apparatus for performing high throughput evaluation of a sample having a pattern with a minimum line width of 0.1 μm or less, and a method for manufacturing a device with a high yield using the electron beam apparatus.
[0002]
[Prior art]
[0003]
Conventionally, an electron gun using a Schottky cathode has been used to inspect a defect having a pattern of 0.1 μm or less. For example, Non-Patent Document 1 discloses an SEM that can perform defect inspection effectively even when an electrical defect such as a short or an open in a via formation process or a wiring process occurs in a lower layer of a wafer using a Schottky electron source. Disclosure.
[0004]
An apparatus and method for inspecting a sample for defect inspection by generating a plurality of electron beams are also known. For example, Patent Document 1 discloses that a sample of a mask, a reticle, and other samples is simultaneously irradiated with a plurality of primary electron beams. Discloses an apparatus for inspecting a sample for defects using a plurality of secondary electrons emitted from the substrate. Further, an apparatus for inspecting a sample for defects by forming a plurality of electron beams with a plurality of electron guns and guiding a plurality of electron beams to the sample with a plurality of optical systems corresponding to the electron beams has already been announced.
[0005]
However, an electron gun using a Schottky cathode has a problem that shot noise is large. In order to solve this problem and obtain a signal with a good S / N ratio, it is necessary to irradiate the sample with a large amount of electron beam, which may cause damage to the sample.
[0006]
In addition, when a plurality of electron guns are provided to simultaneously form a plurality of electron beams in order to shorten the inspection time, if a thermionic emission cathode is used for these electron guns, the amount of heat generated by the electron gun becomes too large. There is a risk. If the temperature of the electron gun rises to such an extent that the stability of the system is impaired, a reduction in the vacuum degree of the lens barrel becomes a problem. Further, when the thermionic emission cathode is heated, there is a problem that the relative position between the thermionic emission cathode and the anode changes.
[Non-Patent Document 1]
Hiroyuki Shinada et al., “High-Speed, High-Current SEM Optical System for Wafer Inspection”, LSI Testing Symposium / 2000 Proceedings (H12.11.9-10), p. 151-156
[Patent Document 1]
US Pat. No. 5,922,224 [Problems to be solved by the invention]
[0007]
The present invention has been proposed in view of the above problems, and the object of the present invention is to adjust the relative position even if the relative position between the cathode and the anode changes due to a temperature rise or the like. Another object of the present invention is to provide an electron beam apparatus capable of suppressing heat generation of vacuum components other than the cathode even when the cathode is heated, and a device manufacturing method using the electron beam apparatus.
[Means for Solving the Problems]
[0008]
In order to achieve the above object, the invention of claim 1
An electron beam apparatus comprising: a plurality of electron guns each having a cathode and an anode capable of providing a wobble; and an electron optical system having an opening provided for each of the electron guns and a mechanism capable of displaying an image of the opening Because
In each of the electron guns, an adjustment mechanism for changing the relative position between the cathode and the anode is provided, and the movement of the image of the opening when wobbling the anode is minimized. An electron beam device characterized by controlling an adjusting mechanism;
I will provide a.
[0009]
The invention according to claim 2 is characterized in that the adjusting mechanism is
An insulator supporting the cathode;
A plurality of piezoelectric elements that support the insulator and expand and contract in response to application of a voltage;
It is characterized by providing.
[0010]
According to a third aspect of the present invention, a metal component for reflecting the radiation emitted from the cathode and its heater to the vicinity of the tip of the cathode is provided in the vicinity of the cathode.
[0011]
The invention according to claim 4 is characterized in that the metal part is also used as a metal fitting for preventing evaporation from a Wehnelt or cathode from the insulator.
[0012]
According to a fifth aspect of the present invention, the electron optical system includes a shaping opening, an axis alignment deflector arranged on the electron gun side of the shaping opening, an NA arranged on the sample side of the shaping opening and capable of measuring an absorption current. The aperture image is displayed, and the current absorbed by the NA aperture after the electron beam that has been two-dimensionally scanned by the alignment deflector passes through the shaping aperture is detected. It is characterized by being performed by giving to a cathode ray tube.
[0013]
A sixth aspect of the invention is characterized in that a semiconductor component is inspected using the electron beam apparatus according to any one of the first to fifth aspects.
[0014]
[Action]
[0015]
Even if the relative position between the cathode and the anode changes due to temperature rise or the like, the relative position can be adjusted by the adjusting mechanism, and even if the cathode is heated, the heat generation of the vacuum parts other than the cathode is suppressed. be able to.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A is a diagram schematically showing a main part of one embodiment of an electron beam apparatus according to the present invention, and FIG. 1B is an enlarged sectional view of one electron gun EG2. As shown in the figure, this electron beam apparatus has a predetermined number of electron guns EG1, EG2, EG3,..., And a corresponding number of optical systems OS1 for irradiating a sample S such as a single wafer or mask. , OS2, OS3,... And the sample S such as a wafer can be evaluated with high throughput. The structures of the electron guns EG1, EG2, EG3,... Are the same, and the optical systems OS1, OS2, OS3,. The configuration of the optical system OS2 will be described as an example. The electron guns EG1, EG2, EG3,... Are arranged in the xy plane, and the optical axes of the optical systems OS1, OS2, OS3,... Are in a direction perpendicular to the xy plane.
[0017]
The cathode 1 of the electron gun EG2 is thermionic emission type cathode made of L _a B _6, the cathode 1 is welded to the tip of the tungsten-hairpin 2 is fixed to the ceramic base 4 by a tungsten hairpin 2 stem 3 . The ceramic base 4 is supported in the center of a through hole formed in the ceramic substrate P so as to be in the xy plane by four piezo elements 5, and electrodes 6 are provided on the opposing end surfaces of the individual piezo elements 5. It is done.
[0018]
A shielding plate 7 is provided between the cathode 1 and the ceramic base 4 to prevent the material of the cathode 1 and the tungsten hairpin 2 from evaporating and being sputtered on the surface of the ceramic base 4 to lower the insulation. Is provided. The shielding plate 7 is formed in a concave shape on the cathode 1 side so that the radiation emitted from the cathode 1 and the tungsten hairpin 2 is reflected in the direction of the cathode 1. Similarly, the side surface 9 facing the cathode 1 of the Wehnelt 8 provided in the electron gun EG2 is also shaped so that the radiation rays emitted from the cathode 1 and the tungsten hairpin 2 are reflected near the tip of the cathode 1, for example, the cathode A recess is formed on one side.
[0019]
The anode of the electron gun EG2 is composed of a first anode 10 and a second anode 11. A voltage is applied to the anodes 10 and 11 so that the electron beam emitted from the cathode 1 forms a crossover in the molding opening 13 by the convex lens action of the anodes 10 and 11.
[0020]
The tip of the cathode 1 is a part of a sphere having a radius of curvature of 30 μm. When the electron gun current is set to a specific value, the luminance of the cathode 1 is Langmuir limit (1.4 × 10 ⁵ A / cm ² sr at 4.5 kV). ) May be one order of magnitude higher than In order to obtain such high luminance, it is necessary that the axes of the cathode 1, the Wehnelt 8, and the anodes 10 and 11 are accurately aligned. In order to realize this, in this embodiment, as shown in FIG. 2, the ceramic base 4 to which the cathode 1 is fixed is supported by the four piezo elements 5 in the front, rear, left and right, and the second anode An axial alignment deflector 12 is disposed between 11 and the molding opening 13.
[0021]
The first anode 10 can be wobbled. Therefore, the portion of the electron beam that has passed through the shaping opening 13 is detected as a current that is absorbed by the NA opening 16, and the electron beam is two-dimensionally scanned by the alignment deflector 12, thereby being placed on a cathode ray tube (not shown). In a state where the image of the molding opening 13 is displayed, wobble is given to the first anode. At this time, a voltage is applied to each piezoelectric element 5 from the electrode 6 so that the image of the shaping opening 13 does not move in the x and y directions. This is because the position of the ceramic base 4 is made minute by applying a voltage in the extending direction to one piezo element 5 and in the contracting direction to the other piezo element 5 in a pair of opposing piezo elements 5. This can be realized by adjusting the voltage so that the movement of the image of the shaping opening 13 becomes zero when the wobble is applied. Furthermore, when the voltage applied to the first anode 10 and the second anode 11 and the electron gun current are appropriately selected, when the optical axes of the elements of the optical system OS2 are accurately matched, the Langmuir Brightness far exceeding the limit can be obtained. These controls can be automatically controlled by using the electrode voltage or the like as computer control and the current absorbed in the MA opening as a sensor.
[0022]
The electron beam formed in the forming opening 13 is reduced by the reduction lens 17 and the objective lens 20 each having three electrodes, and a probe of about 50 nm is formed on the sample S. When the scanning beam deflector 18 and the E × B separator 19 disposed between the reduction lens 17 and the objective lens 20 are used to cause the electron beam to scan two-dimensionally on the sample S, secondary electrons are emitted from the sample S. The The secondary electrons are separated from the primary electron beam by the E × B separator 19 and detected by the secondary electron detector 22 through the trajectory 21. Using this detection result, an SEM image can be created. The secondary electron detector 22 is provided in the short direction of the ceramic substrate P so that the secondary electrons can be detected even when the deflection amount in the E × B separator 19 is minimum.
[0023]
It should be noted that the axial alignment of the NA aperture 16 and the reduction lens 17 can be performed by interlocking the axial alignment deflectors 14 and 15. The scanning deflector 18 disposed between the reduction lens 17 and the E × B separator 19 may have an axis alignment function. The E × B separator 19 is preferably connected to an astigmatism correction power supply in addition to a DC power supply for its operation. In the embodiment shown in FIG. 1, in order to form the magnetic field of the E × B separator 19, the permanent magnets 23 that do not require wiring are arranged at opposing positions, and a permalloy is provided between the two permanent magnets 26. A magnetic circuit is formed by coupling by a pair of half rings 24 made of metal. It is desirable to apply a negative voltage to the sample S to reduce the spherical and axial chromatic aberration of the objective lens 20.
[0024]
The assembly of the electron guns EG1, EG2, EG3,... And the optical systems OS1, OS2, OS3,.
(1) One ceramic substrate of the required length and thickness, such as ceramic substrate P, one for the cathode, one for the Wehnelt, two for the anode, three for the axial deflector, and for the opening 2 for the lens, 6 for the lens, 2 for the scanning deflector,
(2) A circular hole is formed in each of these ceramic substrates by the number of electron guns,
(3) Each ceramic substrate is arranged at a predetermined position after being subjected to necessary processing so that the optical axes coincide with each other,
(4) A necessary and sufficient metal coating is applied to a required portion of each ceramic substrate,
(5) Finally, it is performed through a procedure for assembling with high precision using a knock pin.
[0025]
In order to prevent the slender ceramic substrate from being bent, if necessary, the side surface in the length direction of the ceramic substrate may be used as a rib structure 25 to increase the thickness.
[0026]
In practice, as shown in FIG. 2A, in each electron gun, a pair of opposing piezo elements are arranged on the x-axis, and the remaining pair of piezo elements are arranged on the y-axis. Are arranged to be inclined 45 degrees with respect to the x-axis and the y-axis. As a result, the optical systems OS1, OS2, OS3,... Are arranged apart from each other by 1 / √2 of the distance between the optical axes of adjacent optical systems in the x-axis direction. Therefore, by adjusting the ceramic substrate P within 45 degrees, the length in the x direction of the distance between the optical axes of the adjacent optical systems can be matched with the chip arranged on the surface of the sample S. For example, if 20 optical systems are arranged on a 15-inch wafer, a throughput of about 15 times can be obtained.
[0027]
Hereinafter, a semiconductor device manufacturing method using the electron beam apparatus according to the present invention will be described. FIG. 3 is a flowchart showing an example of such a manufacturing method. The manufacturing process of this example includes the following main processes. Each main process consists of several sub-processes.
[0028]
(1) Process P11 for manufacturing wafer P12 (or preparing a wafer),
(2) A mask manufacturing process for manufacturing a mask (reticle) P22 used for exposure (or a mask preparing process for preparing a mask) P21,
(3) a wafer processing step P13 for performing necessary processing on the wafer P12;
(4) Chip assembling process P14 that enables the chip P15 formed on the wafer P12 to be cut and operated one by one,
(5) A chip inspection process P16 for inspecting the chip P15 produced in the chip assembly process P14.
[0029]
Among these main processes, the main process that has a decisive influence on the performance of the semiconductor device is the wafer processing process P13. In this process, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. The wafer processing process P13 includes the following processes.
[0030]
(A) A thin film forming process for forming a dielectric thin film as an insulating layer or a metal thin film for forming a wiring part or an electrode part (using CVD, sputtering, etc.)
(B) oxidation process for oxidizing thin film layers and wafer substrates;
(C) a lithography process P23 for forming a resist pattern using a mask (reticle) P22 for selectively processing a thin film layer, a wafer substrate, or the like;
(D) Ion / impurity implantation / diffusion process,
(E) resist stripping step,
(F) An inspection process for inspecting a further processed wafer.
The wafer processing step P13 is repeatedly performed for the required number of layers, and the semiconductor device P17 operating as designed is manufactured.
[0031]
The core of the wafer processing step P13 in FIG. 3 is the lithography step P23, and FIG. 4 shows the steps performed in the lithography step P23. That is, the lithography process P23
(A) a resist coating step P31 for coating a resist on the wafer on which the circuit pattern is formed in the previous step;
(B) an exposure step P32 for exposing the resist;
(C) Development step P33 for developing the exposed resist to obtain a resist pattern;
(D) An annealing step P34 for stabilizing the developed resist pattern;
including.
[0032]
The semiconductor device manufacturing process, the wafer processing process P13, and the lithography process P23 described above are well known, and descriptions thereof are omitted.
[0033]
When defect inspection is performed using the electron beam apparatus according to the present invention for the chip inspection process P16 of (5) above, even a semiconductor device having a fine pattern can be inspected with high throughput, and 100% inspection is possible. In addition, the yield of products can be improved, and the shipment of defective products can be prevented.
[0034]
Although one embodiment of the electron beam apparatus according to the present invention has been described above, the present invention is not limited to this embodiment.
【The invention's effect】
[0035]
As will be understood from the description of one embodiment of the present invention,
(1) Since the axis alignment of the cathode and the anode can be performed with high accuracy by the adjustment mechanism, when a large number of optical systems are used, adjustment can be made even if the production accuracy of a small number of electron guns is poor.
(2) When a metal part for reflecting the radiation emitted from the cathode to the vicinity of the tip of the cathode is provided in the vicinity of the cathode, most of the radiation emitted from the cathode and the filament for heating the cathode, Since it can be confined in the space surrounded by Wehnelt and metal parts, not only the components, insulators, and vacuum walls of the optical system are hard to be heated by such radiation, but also the required cathode temperature can be obtained with low power.
(3) Since a high vacuum can be easily obtained, even if a plurality of optical systems are densely arranged, the heating power can be made relatively small.
(4) Shot noise can be reduced by using the cathode under space charge limiting conditions.
(5) High-speed scanning of 100 MHz or more can be realized even with a small beam current.
(6) The wafer can be evaluated during the process with a high yield.
There is a special effect.
[Brief description of the drawings]
[0036]
FIG. 1A is a view schematically showing one embodiment of an electron beam apparatus according to the present invention, and FIG. 1B is an enlarged cross-sectional view of one electron gun in the electron beam apparatus. .
2A is a plan view for explaining the configuration and arrangement of an electron gun in the electron beam apparatus of FIG. 1, and FIG. 2B is an E × B separator of the electron beam apparatus of FIG. It is a top view which shows a structure.
FIG. 3 is a flowchart for explaining a semiconductor device manufacturing method using an electron beam apparatus according to the present invention. FIG. 4 is a flowchart for explaining a process performed in a lithography process in FIG. Explanation of]
[0037]
EG1, EG2, EG3, ...: Electron gun, P: Ceramic substrate, 1: Cathode, 2: Tungsten hairpin, 3: Stem, 4: Ceramic base, 5: Piezo element, 6: Electrode for piezo element, 7 : Curved shielding plate, 8: Wehnelt, 9: side surface of Wehnelt, 10: first anode, 11: second anode, OS1, OS2, OS3, ...: optical system, 12, 14, 15: shaft Alignment deflector 13: Molding aperture 16: NA aperture 17: Reduction lens 18: Scanning deflector 19: E × B separator 20: Objective lens 21: Secondary electron trajectory 22: Secondary Electron detector, S: Sample, 23: Permanent magnet, 24: Half ring, 25: Rib structure

Claims (6)

An electron beam apparatus comprising: a plurality of electron guns each having a cathode and an anode capable of providing a wobble; and an electron optical system having an opening provided for each of the electron guns and a mechanism capable of displaying an image of the opening Because
In each of the electron guns, an adjustment mechanism for changing the relative position between the cathode and the anode is provided, and the movement of the image of the opening when wobbling the anode is minimized. An electron beam apparatus characterized by controlling an adjusting mechanism . The adjustment mechanism is
An insulator supporting the cathode;
A plurality of piezoelectric elements that support the insulator and expand and contract in response to application of a voltage;
The electron beam apparatus according to claim 1, further comprising:   2. The electron beam apparatus according to claim 1, wherein a metal part for reflecting the radiation emitted from the cathode to the vicinity of the tip of the cathode is provided in the vicinity of the cathode.   4. The electron beam apparatus according to claim 3, wherein the metal part also serves as a metal fitting for preventing evaporation from a Wehnelt or cathode from adhering to the insulator. The electron optical system includes a shaping opening, an axis alignment deflector arranged on the electron gun side of the shaping opening, and an NA opening arranged on the sample side of the shaping opening and capable of measuring an absorption current,
The aperture image is displayed by detecting the current absorbed in the NA aperture after the electron beam that has been two-dimensionally scanned by the alignment deflector passes through the shaping aperture, and applying the detected current to the cathode ray tube. The electron beam apparatus according to claim 1 , wherein:   A device manufacturing method, comprising: inspecting a semiconductor component using the electron beam apparatus according to claim 1.

Images