KR20010089522A - Array of multiple charged particle beamlet emitting columns - Google Patents

Abstract

The present invention relates to a lithographic apparatus using an array of charged particle (electron) columns, each comprising a plurality of charged particle beam columns that selectively expose a target to a plurality of charged particle beams. Each charged particle beam column includes a beam source for selectively generating a plurality of charged particle beams; An anode that accelerates the plurality of charged particle beams from the beam source and is coaxial with the charged particle beams; And a lens coaxial with the charged particle beams and reducing the charged particle beams. The beam source is a photocathode array that selectively supplies multiple electron beams when irradiated.

Description

ARRAY OF MULTIPLE CHARGED PARTICLE BEAMLET EMITTING COLUMNS}

High resolution electron beam sources are used in systems such as scanning electron microscopy, defect detection machines, VLSI test equipment and electron beam lithography. In general, electron beam systems include an electron beam source and electron optics. Electrons are accelerated from the source and concentrated to form an image on the target. Such systems typically use a physically small electron source with high brightness.

Recent developments in optical lithography techniques have allowed for a significant reduction in the linewidths of circuit elements in integrated circuits. However, optical methods will soon reach their resolution limit. The production of smaller linewidth circuit elements (ie smaller than .1 μm) will require new techniques such as X-ray or electron beam lithography.

In electron beam lithography, a source that can control the electrons is needed. A photocathode used to produce an array of patterned electron-beams is shown in FIG. 1. US Patent No. 5,684,360, entitled "Electron Sources Utilizing Negative Electron Affinity Photocathodes with Ultra," which is incorporated by reference in its entirety and incorporated herein by reference in its entirety. -small emission areas "describes this type of patterned photocathode system.

1 shows a photovoltaic cathode array 100 having three photovoltaic cathodes 110 including a transparent substrate 101 and a light emitting layer 102. The photocathode is back-illuminated with light beams 103 that are concentrated on the light emitting layer in an irradiation region 105. As a result of back-irradiation onto the light emitting layer 102, the electron beams 104 are generated in the emitting region 108 opposite each irradiation region 105. Other systems have been designed in which photoemitters are front-illuminated, that is, light is incident on the same side of the photo emitter from which the electron beam is emitted.

Sometimes the light beams 103 or electron beams 104 are masked. In FIG. 1, the light beam 103 irradiates light with a mask 106 that allows light on spots 108 but prevents light from being incident on other areas of the light emitting layer 102. Are masked using. 1 also shows a mask 107 that allows electrons to exit the light emitting layer 102 only at some surface spots corresponding to the emitting regions 105. The photocathode may also have a mask between the transparent substrate 101 and the light emitting layer 102 to block the light beam such that the light beam is incident only on the irradiation spots 105. In general, the photocathode cathode 110 may have no mask layers or may have one or more masking layers.

Each emission region 105 will be a single circular spot representing a larger shaped pixel, which is formed by the collection of a plurality of photocathode cathodes 110 of the photovoltaic cathode array 100. In that case, the irradiation area 105 can be as small as possible given the wavelength of the light beam incident on the photocathode cathode 100. Typically, the set of pixel irradiation areas has sizes of 100-200 μm. Each pixel may have sizes as small as 0.1 μm (ie, diameters). Alternatively, irradiation spot 105 and emitting region 108 may be of a larger shape. In either case, the image formed by the emitting area 108 will be transferred to the electron beam as long as the entirety of the irradiation area 105 is irradiated by the light beam 103.

The light emitting layer 102 is made of any material that emits electrons when light is irradiated. Such materials include metal films (gold, aluminum, etc.) and semiconductor materials (particularly III-V compounds such as gallium arsenide) in the case of negative affinity (NEA) photoelectric cathodes. Light emitting layers of negative electron affinity photocathode are described in Baum (US Pat. No. 5,684,360).

When irradiated with photons with energy greater than the work function of the material, the light emitting layer 102 emits electrons. Typically, the light emitting layer 102 is grounded to replenish electrons. The light emitting layer 102 may be shaped in the emitting region 108 to provide better control of the irradiation of the beam of electrons emitted from the emitting region 108. Further control of the electron beam is provided in the vacuum column shown in FIG.

The light beams 103 typically start with a laser, but may also start with a lamp, such as a UV lamp. The laser or lamp output is typically split into several beams to irradiate the respective focal points 105. A set of parallel light beams 103 can be generated using a single laser and beam splitter. Parallel light beams can also originate from a single UV source. Alternatively, the entire light emitting array 100 can be irradiated if the light source has sufficient intensity.

Photons of the light beam 103 have at least energy of the work function of the light emitting layer 102. The intensity of the light beam 103 is related to the number of electrons generated at the focal point 105 and therefore to the number of electrons emitted from the emission region 108. The light emitting layer 102 is thin enough and the energy of photons in the light beam 103 is large enough so that a significant number of electrons generated in the emitting region 103 move and eventually emit from the emitting layer 108.

The transparent substrate 101 is structurally rigid enough to support a photocathode cathode device in an electron beam column, which is transparent to the light beam and can be a conventional column or a microcolumn. The transparent substrate 101 may also be shaped at the surface on which the light beams 103 enter to provide focusing lenses for the light beams 103. Although other substrate materials such as sapphire or fused silica are also used, typically the transparent substrate 101 is made of glass.

If the mask 106 is located on the surface of the transparent substrate 101 or deposited between the transparent substrate 101 and the light emitting layer 102, it is opaque to the light beam 103. If mask 107 is present, it absorbs electrons and thereby prevents emission from emission region 108. Mask 107 may also provide an electrical ground for light emitting layer 102 if mask 107 is conductive.

The photocathode cathode 100 may be included in a conventional electron beam column or micro column. Information on the workings of microcolumns is generally given in articles and patents below: "Experimental Evaluation of 20x20 mm Footprint Microcolumns by E. Kratschmer et al. of a 20x20 mm Footprint Microcolumn, Journal of Vacuum Science Technology Bulletin 14 (6), pp. 3792-96, Nov./Dec. 1996; by THP Chang et al. Electron Beam Technology-SEM to Microcolumn, "Microelectronic Engineering 32, pp. 113-130, 1996; by THP Chang et al (" Electron Beam Microcolumns "). Electron Beam Microcolumn Technology And Applications, ", Electron-Beam Sources and Charged-Particle Optics, SPIE Vol. 2522, pp. 4-12, 1995; Thomson And MCR Thomson and THP Chang "Lens and Deflector Design for Microcolumns," Journal of Vacuum Science Technology Bulletin 13 (6), pp. 2445-49, Nov. / Dec. 1995; "Miniature Schottky Electron Source," by HSKim et al., Journal of Vacuum Science Technology Bulletin 13 (6), pp. 2468-72, Nov./Dec. 1995; "Electron-beam Microcolumns for Lithography and Related Applications" by THP Chang et al., Journal of Vacuum Science Technology Bulletin 14 ( 6), pp. 3774-80, Nov./Dec. 1996; and US Pat. No. 5,155,412 to Chang et al., All of which are incorporated herein by reference in their entirety.

2 shows a typical electron beam column 200 using a photocathode array 100 as the electron source. Column 200 is enclosed in a vacuum column chamber (not shown). The photocathode cathode array 100 may be completely closed in the remnant column chamber or the transparent substrate 101 may form a window into the vacuum chamber where the light beams 103 approach from outside the vacuum chamber. The electron beams 104 are emitted from the emission region 108 into the vacuum column chamber and carry an image of the emission region 108. The electron beam 104 may be further shaped by other components of the column 200.

The electron beams 104 are accelerated by the voltage supplied between the anode 201 and the light emitting layer 102 between the photocathode array 100 and the anode 201. The voltage between photovoltaic cathode array 100 and anode 201 produced by power source 208 (received outside of the vacuum chamber) is typically several kilovolts to several tens of kilovolts. The electron beam then passes through an electron lens 204 which concentrates the electron beam into a limiting aperture 202. The limiting aperture 202 blocks the components of the electron beams having an emission solidarity larger than desired. The electron lens 205 refocuses the electron beam. The electron lenses 204 and 205 focus and reduce the image carried by the electron beam onto the target 207. Deflector 203 moves the electron beam laterally while allowing control of the position of the image carried by the electron beam on target 207. In 0.1 μm lithography systems, the size of the circular pixel incident on the target 207 is an order of 0.05 μm. Therefore, the image of the emitting area 108 needs to be reduced to a factor of approximately 2 to 10 depending on the size of the emitting area 108. The target 207 may be made of a semiconductor wafer or mask blank.

Conventional variable shape electron beam lithography columns form the shape of an electron beam by deflecting the electron beam across one or more shape forming apertures. The resulting image in the shaped electron beam is then delivered to the target 207 with a large overall linear column reduction. The need for large overall linear reduction (supplied by the electron lenses 204 and 205) results in large column lengths while increasing electron-electron interactions that limit the current density of the column. Low electron current densities result in low yields when columns are used in lithography. Another major drawback in using known electron beam systems is the inability to adjust the electron beam without modulating the light source itself, which is typically a laser. The adjustment of the laser requires a large amount of space and typically involves a large amount of control circuitry and can be slowed down. In addition, in a patterned array of photoelectric cathodes, the adjustment of the individual photoelectric cathodes in the array is extremely difficult. Finally, higher resolution is required for lithographic systems to meet future needs of semiconductor material processing.

The present invention relates to electron beam sources and, more particularly, to the generation of multiple electron beams.

1 shows a patterned photoelectric cathode according to the prior art.

FIG. 2 shows a typical electron beam pillar using the photocathode shown in FIG. 1.

3A and 3B show a photoelectric cathode according to the invention.

4 shows a part of a photovoltaic cathode array having two photovoltaic cathodes according to the invention.

5 shows a photoelectric cathode according to the invention having a gate electrode with multiple segments.

6A shows a photovoltaic cathode according to the invention with multiple independent segments.

6B and 6C show sample patterned electron beams caused by selectively operating the segments shown in the gate electrode of FIG. 6A.

7A-7F illustrate a process of forming a photovoltaic cathode according to an embodiment of the invention shown in FIG. 4.

8 shows a photocathode array according to the invention.

9 shows a micro-column using a photocathode according to the invention.

10 shows a multi-segment gated photovoltaic cathode used in an electron beam column in which a beam shape is formed in the photoelectric cathode.

11 shows a typical variable shape beam electron beam column having multiple shape components.

12A illustrates multiple micro columns arranged in an array according to one embodiment.

12B briefly illustrates a top view of the array of FIG. 12A, according to one embodiment.

In the figures, components having the same or similar functions are given the same reference numerals.

One embodiment of the invention includes an array of charged particle beam columns in which each charged particle beam column selectively exposes a target to multiple charged particle beams. Each charged particle beam column includes a beam source for selectively generating a plurality of charged particle beams; An anode coaxial with the charged particle beams for accelerating a plurality of charged particle beams from the beam source; And a lens coaxial with the charged particle beams for reducing the charged particle beams.

In one embodiment, the beam source is a photocathode array that selectively supplies multiple electron beams when irradiated. In this embodiment, the photocathode array is electrically connected to the gate electrode of the at least one photocathode by at least one photocathode and interconnect line comprising a gate electrode that adjusts the electron beam in response to a voltage applied to the gate electrode. At least one pad connected and allowing external control of the at least one gate electrode.

Thereby, an embodiment of the present invention includes a method of imaging a pattern onto a target, the method comprising: generating a plurality of charged particle beams; Gathering the beams into groups; Selectively controlling each group of charged particle beams; And directing each of the groups onto a target. In this embodiment, each group is included in one charged particle beam column.

The invention and various variations of the invention will be further explained with the following figures and articles.

3A and 3B show an embodiment of a photovoltaic cathode 300 according to the present invention in a side view (typically related housings, electrical leads, etc. are not shown). In FIG. 3A, photoemitter 302 is deposited on a transparent substrate 301. Although other transparent materials with sufficient structural strength may be used for support, the transparent substrate 301 is typically fused silica or sapphire.

A light beam 303 is incident on the transparent substrate 301, passes through the transparent substrate 301, and is absorbed by the photo emitter 302 in the irradiation region 308. Photo emitter 302 emits electrons from emitting region 305 and on the surface of opposing photo emitter 302 of irradiation region 308 when light beam 303 is incident on irradiation region 308. Is located.

The emission region 305 may generally be of any shape and size at which the gate electrode 307 determines the electric field. Some useful shapes include circles, squares, rectangles, hexagons, and octagons. Irradiation area 308 should cover at least one emission area 305.

The gate insulator 306 is deposited on the photo emitter 302 so that the emission region 305 is surrounded, but not covered by the gate insulator 306. Gate insulator 306 may be made of any electrically insulating material, and is preferably made of SiO ₂ . Gate electrode 307 is deposited on the side of gate insulator 306 away from emission region 305. The gate electrode 307 may be made of any conductive material.

Photo emitter 302 may be made of any material that emits electrons when irradiated. The most effective photoelectron emitting materials include semiconductors such as cesium tellurium (Cs ₂ Te) and metals such as gold, aluminum and carbide materials. In addition, many III-V semiconductors such as gallium arsenide (GaAs) are suitable photo emitter materials. Preferably, the photo emitter 302 has a thickness of about 100 GPa.

Photo emitter 302 will have a work function that is determined by the actual photo emitter material. The work function is the minimum energy required to release electrons from the material. In order for the photo emitter 302 to emit electrons, the photons of the light beam 303 must have at least as much work function as energy.

The light beam 303 is absorbed by the photo emitter 302 at or near the surface of the photo emitter 302 corresponding to the irradiation area 308. At that point, the electrons will have the same kinetic energy as the photon energy minus the work function. These electrons move from the irradiation region 308 to the emission region 305 and are released from the material in the emission region 305 if they have not lost too much energy to collisions in the photoemitter material. As such, the thickness of the photo emitter 302 should be sufficient to absorb the light beam 303 but should not be thick enough to reabsorb a significant number of generated free electrons.

In embodiments of the present invention, it is also preferred that the kinetic energies of the emitted electrons are not too large, preferably less than 0.5 eV, but the emitted electrons can be reflected by the voltage applied to the gate electrode 307. It can be as large as eV. If the photoemitter 302 has a work function of 3.5 to 4.5 eV, a light beam with a photon wavelength of 257 nm or less is needed to produce photons with the appropriate photon energy.

The transparent substrate 301 must be transparent to the light beam 303 such that the maximum amount of light is incident on the irradiation area 308. The transparent substrate 301 may be any thickness, but preferably has a thickness of several millimeters. Additionally, the light beam 303 may be concentrated to cover the irradiation spot 308 in the region corresponding to the emitting region 305.

The intensity distribution of the light beam 303 is generally Gaussian such that the light beam 303 will be stronger at its center than its edge. The light beam 303 is preferably concentrated such that the intensity is almost uniform throughout the irradiation area 308 such that the electron beam 304 has an almost uniform intensity. In general, however, the light beam 303 may be focused as desired.

The gate electrodes 307 may be fabricated on the insulators and made of any conductive material. The thickness of the gate insulator 306 is preferably about 1000 to 5000 kPa. In one embodiment, photoemitter 302 is maintained at ground and gate electrode 307 is biased, about + 10V, to a voltage above ground to accelerate electrons emitted from photoemitter 302. When the gate electrode 307 is biased at voltages lower than ground, about −10 V, the emitted electrons are reflected back toward the photo emitter 302. Moreover, stable emission can be obtained by coupling the resistor 311 between the photo emitter 302 and the gate electrode 307 and using the emission intensity for feedback. For example, as electron emission increases, the gate voltage decreases correspondingly, again lowering the emission intensity.

Positive electrode 310 is maintained at several kilovolts to tens of kilovolts and accelerates electrons out of photoelectric cathode 300 and into a vacuum electron beam column. Alternatively, the photo emitter 302 is maintained at a high negative voltage, the gate electrodes 307 are biased at ± 10 V relative to the photo emitter 302, and both electrodes 310 are grounded.

In Fig. 3A, the gate electrode 307 is maintained at + 10V. This voltage is selected to match the positive field to be established between the positive electrode 310 and the photo emitter 302 in the absence of the insulator 306 and the gate electrode 307. When the voltage of the gate electrode is 10V, the electron beam 304 having the image of the emission region 305 is accelerated out of the emission region 305. The insulators 306 and the gate electrode 307 also serve as masks to better form an image of the emission region 305 included in the electron beam 304.

In Fig. 3B, the gate electrode 307 is maintained at -10V. At this voltage, electrons emitted by the emission region 305 are accelerated back toward the emission region 305 by an electric field generated between the gate electrode 307 and the photoemitter 302. No electron beam 304 is generated because electrons emitted from the emission region 305 are reflected back to the photo emitter 302 rather than accelerated away from the photo emitter 302. Instead of an electron beam, an electron cloud 309 is created where electrons are emitted out of the photo emitter 302 and accelerated directly back to the photo emitter 302.

In some embodiments of the invention, the voltage of the gate electrode 307 is varied to control the intensity of the electron beam. As the voltage difference between the gate electrode 307 and the photo emitter 302 increases, the number of electrons leaving the photocathode cathode 300 increases. The maximum number of possible electrons emitted from the emission region 305 due to the light beam 303 is obtained when the gate electrodes are set to the maximum (about 10V).

Although the examples shown here have a gate bias voltage of + 10V for maximum on operation and -10V for maximum off operation, other parameters for gate voltages are possible. The maximum on bias voltage and the voltage applied to the positive electrode 310 coincide with the electric field present at the maximum on bias voltage in the absence of the gate electrode 307 and the gate insulator 306 at the maximum on bias voltage. Since it should be, the thickness of the insulator 306 is determined. The maximum off bias voltage limits the incident light beam photon energy because electrons emitted from the emitting region 308 must be reflected back to the photoemitter 302 in the maximum off operation. Moreover, the gate electrode 307 should be a dominant element that determines the electric fields near the emission region 308. Therefore, the size of the emission region 308 is limited by the distances and relative sizes between the gate electrodes 306 and the positive electrode 310.

In embodiments where switching time is important, the RC time constant of the gate electrode 307 should be relatively small. The spacing between the gate electrode and the photoemitter and the thickness of the electrodes determine the RC time constant and thus the maximum speed of the switching.

4 illustrates one embodiment of a photovoltaic cathode array 400. In FIG. 4, two emission regions 402 of the photocathode array 400 are shown, both emitting regions being irradiated by a light beam 403 which simultaneously irradiates the entire portion of the photovoltaic cathode array 400 shown. Instead of concentrating each beam on a separate emission area 402, parallel light beams 403 may be used. The photovoltaic cathode array 400 includes a transparent substrate 401, a conductor 408, a gate insulator 406, gate electrodes 407, and photo emitters 402.

Conductor 408, which may be made of any conductive material but is preferably aluminum, is deposited on transparent substrate 401 and has an opening within which photoemitter 402 can be fabricated. As discussed above, the photoemitter 402 can be made of any material that emits electrons when irradiated with photons. Again, the photo emitter 402 has a work function and the photons in the light beam 403 must have at least as much energy as the work function in order for the electrons to be emitted from the emission region 405. The transparent substrate 401 is preferably glass but may be made of any material that is transparent to the light beam 403, such as sapphire or fused silica. Conductor 408 is opaque to light beam 403 and does not emit electrons in front of it when irradiated from the back by light beam 403. Therefore, the conductor 408 acts as a mask and forms the irradiation area 408. The emission region 405 may be located directly opposite the irradiation region 408 on the photo emitter and may have any shape or size in which the gate electrodes 407 determine the electric field.

The gate insulator 406 is fabricated on the conductor 408 and has an opening 410 such that the photoemitters 402 are not covered by the insulators 406. Gate electrodes 407 are deposited on gate insulator 406. In this embodiment, the gate electrodes 407 protrude above the opening 410 in an amount sufficient to ensure that the electric fields generated in the emission region 405 are not substantially distorted by the gate insulator 406. As in FIGS. 3A and 3B, the gate electrode 407 can turn the electron beam 404 on and off with the voltage applied to the gate electrode 407. The on and off voltages correspond approximately to + 10V and -10V, respectively. In addition, the maximum electron beam intensity is adjusted by varying the gate electrode voltage. Self-biasing resistor 411 is also provided between gate electrode 407 and conductor 408 to provide feedback for controlling the strength of electron beam 404 by self-biasing. Can be connected.

In the photoelectric cathodes shown in FIGS. 3A, 3B and 4, the intensity of the electron beams can be controlled by controlling the actual voltage between the gate electrode and the photoemitter. The lower the voltage the electron beams will have lower intensity because fewer electrons will exit the electron cloud having a statistical velocity distribution in the direction in which the electron beam propagates. Also, gate electrodes will be used to adjust the intensity of the electron beam caused. In some embodiments, a resistor is placed between the gate electrode and the photoemitter so that self-biasing feedback occurs, which means that as emission increases, the gate voltage decreases accordingly.

In FIG. 4, the gate electrode 407 appears the same for each emission region 405. In general, however, each emission region 405 has a gate electrode 407 that is electrically isolated from other gate electrodes. In addition, the gate electrode for a particular emission region may include several segments, each of which is electrically isolated from all others.

In some embodiments, the gate electrode surrounding the emission region has multiple segments. The multiple segments make it possible to turn on some parts of the emission area while turning off other parts of the emission area while forming an image carried by the electron beam 404.

FIG. 5 shows the photocathode shown in FIG. 3 with a right gate segment 510 and a left segment 511 instead of a single segment gate electrode 307. The result of this structure is that the electron beam can be switched on selectively. For example, in FIG. 5, the right gate segment 510 is kept at maximum on a bias voltage of 10V and the left segment 511 is at maximum off at a bias voltage of -10V. The resulting electric field reflects electrons emitted by the emission region 305 near the left gate segment 511 while the accelerated electrons are emitted from the emission region near the right gate segment 510 of the photocathode 500. . The resulting electron beam 504 is in this example an image of half of the emission area 305. The resulting electron beam 504 distribution is not uniform and is strongest near the right gate segment 510 and essentially off at the middle point between the two segments 510 and 511.

6A shows a top view of a four segment gate electrode configuration. Gate segments are segments A 601, B 602, C 603 and D 604. In this example the emitting region 305 is square. The emission area 305 may be of any shape but is preferably square. Other useful shapes include circles, squares, octagons, and hexagons.

6B shows when gate segments A 601, C 603, and D 604 are on (i.e., maintained at + 10V) and gate segment B 602 is off (i.e., maintained at -10V). A plan view of the generated electron beam 504 is shown. 6C shows a top view of the electron beam 504 that occurs when gate segments B 602 and C 603 are off and gate segments A 601 and D 604 are on. Other shaped electron beams can also be formed by selectively controlling the voltage of the segments of the gate electrodes. This ability provides great flexibility in making useful photocathode arrays for a variety of different tasks. 10 shows a photocathode having a split gate electrode used in an electron beam pillar for electron beam lithography.

In general, any number of gate segments may be used. The more gate segments there are, the more users of the photocathode can have more control over the electron beam generated from a given emission region. This ability can be very important in effectively writing devices onto semiconductor substrates. In addition, resistors may be coupled between the photometer and the individual segments of the gate electrode to provide self biasing control for the electron beam intensity, as described above.

The photovoltaic cathodes described above are conductive for miniaturization and precision integration into multiple photocathode sources. The photocathode array can be fabricated on a single substrate by accurately positioning the photocathode cathodes. In particular, FIGS. 7A-7F illustrate a process of manufacturing the photocathode illustrated in FIG. 4 using conventional semiconductor processing steps. The illustrated process shows only a single photoelectric cathode of the photocathode array. However, one of ordinary skill in the art can produce a photocathode array with accurately positioned photocathode cathodes having various emission region shapes and gate structures from this example. In addition, those skilled in the art can modify this process to produce other photocathode cathodes according to the present invention or alter this process in a way that results in the same photocathode production.

7A is a cross-sectional view illustrating a first step of a process in which an opaque layer of a conductive film is deposited on a transparent substrate 401 such as glass fused silica or sapphire. Preferably, the transparent substrate 401 is a glass substrate. As shown in Figure 7B, the conductive film is masked and a window having a suitable size and shape for forming the emission region 410 is etched through the conductive film. Gate insulator 406 is then deposited on conductive film 408 and also fills the window of emission region 410. Gate insulator 406 may be any electrical insulator but is preferably SiO ₂ . Gate electrode layer 407 is then deposited on top of gate insulator 406 as shown in FIG. 7D.

The gate insulator 406 is then masked and a hole 411 is etched through the gate electrode layer 407 and insulator film 406 as shown in FIG. 7E. The hole 411 is aligned with the emission area 410 and is slightly larger than the emission area 410. In addition, all of the insulator film 406 is removed from the window of the emission region 410 by this etch.

In FIG. 7F, the selective isotropic etch creates recessed holes 412 in the insulator film 406 such that the gate electrode 407 protrudes over the openings formed in the holes 411 and the recessed holes 412. Finally, photocathode cathode 402 is deposited from point source or ionized sputter deposition using a direct deposition technique such as thermal evaporation. This final deposition forms the photovoltaic cathode 400 into a self-aligned gate aperture and the photocathode is electrically connected to the conductive layer 408 but electrically from the gate electrodes 407. It is formed to maintain isolation.

In addition, in the array of photoelectric cathodes fabricated by this process, each gate electrode segment surrounding each photoelectric cathode can be formed by appropriately masking the gate electrode 406 while the gate electrode layer 407 is being deposited. Alternatively, gate electrode layer 407 may be individually etched to form individual gate segments. In addition, interconnect lines connecting the gate electrode segments to the pads may be formed along the gate electrode segments or deposited in a subsequent process step.

In an alternative manufacturing method, the substrate may first be coated with a conductive layer 408, a gate insulator 406, and a gate electrode 407. The window 411 is then etched through all the films to the transparent substrate 401. Using an optional isotropic etch, the opening of the gate electrode 407 can be slightly enlarged relative to the corresponding window 410 of the conductive layer 408. Also alternatively, multiple segments of the gate electrodes are created around each of the holes by isotropically etching the insulating breaks of the gate electrode 407.

In some embodiments, the surface of the substrate 401 may be formed into a shape for concentrating the light beam onto an irradiation area corresponding to the emitting area 410 of the photoemitter 402. In addition, in some embodiments, photoemitter 402 itself may be formed in a shape to better focus the resulting electron beam emitted from the photocathode.

8 shows a top view of a 4 × 4 array of patterned photocathodes. Any shape can be made, including circles, rectangles, hexagons, and octagons, but the emission regions 801 in this example are square. Gate electrode 804 completely surrounds each emission region 801. Although a single segment gate electrode is shown in FIG. 8, the gate electrode 804 is typically fabricated with multiple electrode segments to further control electron emission from the emission region 801. Gate electrode 804 is connected to bonding pad 803 by interconnect line 802. Both the bonding pads 803 and interconnects 802 are preferably made of the same material as the gate electrode 804, but any conductor that makes electrical contact with the gate electrode 804 can be used. In general, in lithographic systems, it is desirable to physically separate between two adjacent emission regions such that the array is square. The minimum separation between the emitting regions is about four times the physical sizes of the emitting regions. In FIG. 8, the size of the square emission region by current microfabrication techniques can be as small as 0.1 μm. Preferably, the side size of the emission area is 0.1 μm. Therefore, the entire 4 × 4 array shown in FIG. 8 can be fabricated in a square with sides 1.6 μm, which is within the limits of conventional microfabrication techniques.

9 shows a side view of a photocathode array mounted within a microcolumn 900 in accordance with the present invention. The micro column 900 is included in an evacuated chamber (not shown). The substrate of the photovoltaic cathode array 910 is sufficient or alternatively a vacuum window that allows a laser light source onto the irradiation areas of the photovoltaic cathode array 910, so that the photovoltaic cathode array 910 will be completely enclosed within the chamber. The electron beams 911 are emitted from the emission regions of the photocathode array 910 and are accelerated through the anode 901, depending on the control inputs to the gate electrodes 909 of the photocathode array 910. The anode 901 is maintained at a voltage from one kilovolt to tens of kilos with respect to the voltage of the photo emitters of the photoelectric cathode 910. Limiting aperture 902 blocks a portion of beams 911 that have an emission solid angle greater than desired. The deflector 903 allows an image of the emission regions included in the electron beams 911 to be scanned and moved laterally throughout the substrate. Einzel lenses with electrodes 904, 905, and 906 focus and shrink the image on the target 907. The target 907 is one of a mask blank for semiconductor wafers or electron beam lithography.

The photovoltaic cathode array 910 can include any number of individual photovoltaic cathodes. Each individual photocathode may comprise a single segment gate or multiple segment gates. The image formed in the electron beam 911 depends on the emission regions of each individual photocathode and the states of the gate electrodes of each individual photocathode. For example, a photocathode array 910 having one photocathode with a single segment gate can only produce an image of the emission region of the photocathode. In a photocathode array 910 having multiple photovoltaic cathodes with a single segment gate each individually controlled, individually controlled to form conglomerates of the emission regions of the respective photocathode cathodes that are "on". Various images can be formed by selectively turning on the photocathode cathodes. The photovoltaic cathode array 910, where some photocathodes have multiple divided gate electrodes, is most flexible because images can be formed using portions of the emission regions of the individual photocathodes.

In one embodiment, the limiting aperture 902 is not used so that the full emitted solid angle of the beam 911 is used. Instead, gate electrodes 909 are used to blank the beam 911, that is, to prevent exposure of the target from the beam 911. Thus, the length of the microcolumn 900 is reduced and therefore the electron-electronic interactions are reduced. Such electron-electronic interactions blur the image formed by the beams 911 on the target 907.

10 shows an electron source 1001 with a single photoelectric cathode 1004. The photocathode 1004 has an emission region 1002 and a four segment gate structure 1003. The four segment gate structure can selectively image the emission region 1002. In the example of FIG. 10, four segment gate structures 1003 are used to form the shape of an electron beam image that corresponds to half of the emission region 1002. The electron beam carrying the electron beam image is drawn from the photocathode cathode 1004 by the extraction electrode 1005. The reduction lens 1006 reduces the electron beam image onto the wafer or mask blank 1008 to form a beam image of the final shape. The system shown in FIG. 10 with a minimum number of components allows shaped electron beam columns to be fabricated using a minimum amount of space and in particular lengths, thereby reducing the effect of electron-electronic interactions.

FIG. 11 shows a typical variable shape electron beam column, compared to the electron beam column shown in FIG. 10. The electron beam is formed at the electron source 1101. The electron beam may be a thermal ion cathode _, such as hexaboronide lanthanum, LaB _6, or a single gated photoelectric cathode similar to that shown in FIG. 3. The electron beam is shaped by the square aperture 1102 to form a shaped electron beam. The shape electron beam is concentrated in the area 1110 by the electron lens 1103. The spot shape deflector 1104 deflects the electron beam in the focus region 1110 such that the shape electron beam is moved. The shaped electron beam then penetrates through the square aperture 1105 to form an intermediate shaped electron beam. Square aperture 1105 passes a portion of the electron beam that overlaps the aperture and blocks a portion of the electron beam outside the aperture so that only a portion of the image formed by square aperture 1102 passes through the intermediate shape beam image. The reduction lens 1106 shrinks the image and focuses the image onto the final shape beam image 1108 on the wafer or blank 1109. The yield of lithographic systems is generally limited by the total beam current. When the total beam current is increased, electron-electron interactions in the beam cause blur, which lowers the resolution of the pattern recorded on the target. If the total beam current is distributed evenly among several columns, each column generates a lower beam current. Thus, each column produces images with less blurring and hence higher resolution. In addition, the distribution of beam currents allows for higher electron current densities, which allows higher yields when the columns are used in lithography.

In accordance with one embodiment of the present invention, as depicted briefly in FIG. 12A, multiple microcolums 1201-1 through 1201-4 are arranged in array 1200. Any microcolumn using a combination of photoelectric cathode array 910 and gate electrodes 909 (FIG. 9) as a source of charged particle beams is suitable. For example, microcolumn 900 (FIG. 9) is an exemplary embodiment of any of microcolums 1201-1 through 1201-4. In FIG. 12A, beam source 1202-1 indicates a combination of photoelectric cathode array 910 and gate electrodes 909. Beam sources 1202-2 through 1202-4 are similar to 1202-1. The microcolums 1201-1 through 1201-4 of the array 1200 selectively select each of the beams 1204-1 through 1204-4 as a target 1206 which is either a semiconductor wafer or a mask blank for electron beam lithography. To emit.

For both sizes of the array, the pitch (distance from center to center) between adjacent microcolumns in the array 1200 is, for example, 2 cm, which is an individual comprising a housing of each microcolumn. Typical diameter of microcolumns. The "footprint" of a single microcolumn, i.e., 2 cm or less in diameter, therefore, an array in which many microcolumns occupy the footprint (area) of a typical 9 "or 12" diameter semiconductor wafer, for example. Can be arranged to.

Of course, the arrangement of the micro columns of the array 1200 can vary, for example, into any of the two-way arrays of size M X N where M and N represent the number of microcolumns in the X and Y directions, respectively. 12B depicts a top view of an N X M array. This array is not limiting.

By using the photoelectric cathode array 910 to generate multiple beamlets, the beam current of each micro column is divided into multiple beamlets, which reduces bleeding due to electron-electronic interactions and thus each micro Allow higher total beam current in the column. As a result, the yield of the recorded pattern increases.

In one embodiment, the microcolumns of array 1200 use recording methods, such as the well known MEBES raster scan write approach currently used to make masks into a single electron beam column. See, for example, IBM US Pat. Nos. 4,818,885 and Bell Labs US Pat. Nos. 4,668,083 and 3,900,737, which disclose the entirety of this MEBERS recording approach and are incorporated herein by reference. Thus, a system architecture using an array of microcolumns 1200 includes, in one embodiment, many other techniques developed for MEBES, such as the underlying data path and multipath and multipixel technologies. do. See IBM US Pat. Nos. 5,393,987 and 5,103,101, which are incorporated by reference in their entirety. In addition, other well-known electron beam lithography techniques, such as gray scale or shape beams, can be used with the array 1200; See, for example, IBM US Pat. Nos. 5,213,916, 5,334,467, 4,568,861, and 4,423,305, which are incorporated by reference in their entirety.

The examples described above are merely illustrative. Modifications apparent to those skilled in the art are within the scope of the present invention. As such, this application is limited only by the following claims.

Claims (13)

A charged particle beam column device, the device comprising: Support for a target; And Charged particle beam columns arranged to expose the target to charged particle beams, each charged particle beam column comprising: A beam source for selectively generating a plurality of charged particle beams; An anode accelerating the plurality of charged particle beams from the beam source and coaxial with the charged particle beams; And And a lens that reduces the charged particle beams and is coaxial with the charged particle beams. The particle beam column apparatus of claim 1, wherein the array is formed in a square shape. 2. The particle beam column apparatus of claim 1, wherein the array comprises an array of N X M charged particle beam columns in which N is not equal to M. 2. The particle beam column device of claim 1, wherein each charged particle beam column is a microcolumn. The photocathode array of claim 1, wherein the beam source comprises a photocathode array that selectively supplies multiple electron beams when irradiated, wherein the photocathode array includes: At least one photovoltaic cathode having a gate electrode for adjusting an electron beam in response to a voltage applied to the gate electrode; And And at least one pad electrically connected to said gate electrode of said at least one photoelectric cathode, thereby allowing external control of said gate electrode. 6. The particle beam column device of claim 5, wherein the gate electrode of the at least one photovoltaic cathode comprises at least one segment. 6. The particle beam column device of claim 5, wherein the gate electrode of the at least one photoelectric cathode comprises four segments. 6. The particle beam column device of claim 5, wherein the gate electrode of the at least one photoelectric cathode comprises eight segments. A method of imaging a pattern onto a target, the method comprising: Generating a plurality of charged particle beams; Gathering the beams into groups; Selectively controlling each group of charged particle beams; And Directing the respective groups onto the target. 10. The method of claim 9, wherein each group is contained in one charged particle beam column. The method of claim 10, wherein the particle beam columns are arranged in an array. The pattern imaging method of claim 11, wherein the array is formed in a square shape. The pattern imaging method of claim 11, wherein the array is formed in a rectangle.