JP2003511855A - Array of multi-charged particle beam radiation columns - Google Patents

Abstract

  (57) [Summary] The present invention relates to an electron beam source, and more particularly to generating multiple electron beams. A lithographic apparatus includes an array having a charged particle (electron) beam column, the array including a plurality of charged particle beam columns for selectively exposing a target to a plurality of charged particle beams. Each charged particle beam column has a beam source that selectively generates a plurality of charged particle beams, an anode that is coaxial with the charged particle beam and accelerates the plurality of charged particle beams from the beam source, and a charged particle beam. A coaxial lens is included that reduces the charged particle beam. A beam source is a photocathode array that selectively supplies a number of electron beams when illuminated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

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

[0002]

[Prior art]

High resolution electron beam sources are used in systems such as scanning electron microscopes, defect detection equipment, VLSI inspection equipment and electron beam (e-beam) lithography. In general,
The e-beam system includes an electron beam source and an electro-optical device. The electrons are accelerated from the source and focused to clearly form an image on the target. These systems typically use a bright, physically small electronic source.

Improvements in optical lithography techniques in recent years have enabled a considerable reduction in the linewidth of circuit elements in integrated circuits. However, optical methods will soon reach the limit of resolution. Circuit elements with smaller line width (for example, about 0.1
The production of (less than μm) requires new techniques such as X-ray lithography and e-beam lithography.

In e-beam lithography, a controllable electron source is required. The photocathode used to form the patterned array of e-beams is shown in FIG. Baum et al
US Patent No. 5,684,360, entitled "Electron Sources Utilizing Negat"
ive Electron Affinity Photocathods with Ultra-Small Emission Areas ",
This type of patterned photocathode system has been described.

A photocathode array 100 including a transparent substrate 101 and a photoemissive layer 102 with three photocathodes 110 is shown in FIG. The photocathode is the photoemissive layer 1 in the illuminated area 105.
Back-illuminated by a light beam 103 focused on 02. Photoelectric emission layer 1
Radiation area 1 on the opposite side of each illumination area 105 as a result of the backside illumination on 02.
The electron beam 104 is generated at 08. Other systems have been designed in which the photoemitter is illuminated in the front, that is to say the light beam is incident on the same plane as the photoemitter emitting the electron beam.

The light beam 103 or the electron beam 104 is often masked. In FIG. 1, the light beam 103 is incident on the irradiation spot 108, but the light beam 103 is masked by using a mask 106 that prevents the light from entering the other regions of the photoelectric emission layer 102. FIG. 1 also shows a mask 107 that causes electrons to be emitted from the photoelectric emission layer 102 only in a certain surface spot corresponding to the emission region. 1 light beam on the photocathode
A mask may be provided between the transparent substrate 101 and the photoelectric emission layer 102 so as to block the light beam so that 03 enters only the irradiation spot 105. In general, the photocathode 110 may not include a masking layer or may be provided with one or more masking layers.

Each illuminated area 105 can be a single circular spot that represents a larger pixel in shape, the larger shape being formed by an assembly with multiple photocathodes 110 in the photocathode array 100. In that case, the irradiation area 105 may be as small as the wavelength that can be given to the light beam incident on the photocathode 100. Typically, a group of pixel illuminated areas have dimensions of 100-200 μm. Each pixel can be as small as 0.1 μm (ie diameter). Alternatively, the illumination spot 105 and the emission area 108 can be shaped larger. In either case, the image formed by the emissive region 108 will be e-beam 10 as long as the entire illuminated region 105 is illuminated by the light beam 103.
4 will be transferred.

Photoelectric emitting layer 102 is made of any material that emits electrons when illuminated with light. These materials include metal films (gold, aluminum, etc.) and, in the case of negative affinity (NEA) photocathodes, semiconductor materials (particularly III-V compounds such as gallium arsenide). Photoemissive layers in negative electron affinity (NEA) photocathodes are described in Baum (US Patent No. 5,684,360).

When irradiated with photons having an energy higher than the work function of the material, the photo-emissive layer 10
2 emits an electron. Typically, the photo-emissive layer 102 is grounded so that electrons can be replenished. The photo-emissive layer 102 may be shaped in the emitting region 108 to better control the irradiation of the beam of electrons emitted from the emitting region 108. Further control of the e-beam is done in the vacuum pump column shown in FIG.

The light beam 103 is typically emitted from a laser, but may be emitted from a lamp such as a UV lamp. To illuminate each of the focal points 105, the laser or lamp output is typically split into several beams. A set of parallel light beams 103 can be created using one laser and beam splitter. The collimated light beam may originate from one UV source. Alternatively, the entire photoemissive array 100 may be illuminated if the light source has sufficient intensity in the array.

The photons in the light beam 103 have energy of at least the work function of the photo-emissive layer 102. The intensity of the light beam 103 is related to the number of electrons generated at the focus 105, and thus to the number of electrons emitted from the emitting area 108. Since the photoelectric emission layer 102 is sufficiently thin and the energy of photons in the light beam 103 is sufficiently large, the differential number of electrons generated in the irradiation region 103 moves and is finally emitted from the emission layer 108. .

The transparent substrate 101 is transparent to the light beam and is structurally sufficiently rigid to support the photocathode device in an electron beam column, which may be a conventional column or a microcolumn. Since the focus adjusting lens is provided for the light beam, the transparent substrate 101 may be shaped on the surface on which the light beam 103 is incident. The transparent substrate 101 is typically glass, although other substrate materials such as sapphire or fused silica are also used.

The mask 106 exists on the surface of the transparent substrate 101, or the transparent substrate 10
1, the substrate is opaque to the light beam 103. The presence of mask 107, if present, absorbs electrons, thereby preventing emission of electrons from emissive region 108. If the mask 107 is a conductive array, the mask 107 also provides an electrical grounding facility for the photo-emissive layer 102.

The photocathode 100 may be incorporated into a conventional electron beam column or microcolumn. Information relating to the action of microcolumns is generally found in the following paper: Journal of Vacuum Science Technology Bulletin 14 (6), pp.3792-96,
Nov./Dec. 1996, E. Kratschmer et al., "Experimental Evaluation of a 20x
20mm Footprint Microcolumn ", Microelectronic Engineering 32, pp.113-130,
1996, THP Chang et al., "Electron Beam Technology-SEM to Microcolum
n ", Electron Beam Source and Charged-Particle Optics, SPIE Vol. 252, pp.4
-12, 1995, THP Chang et al., "Electron Beam Microcolumn Technology A
nd Applications ", Journal of Vacuum Science Technology Bulletin 13 (6), p
p.2445-49, 1995, MGR Thomson and THP Chang, "Lens and Deflector Des
ign for Microcolumns ", Journal of Vacuum Science Technology Bulletin 13 (
6), pp.2468-72, Nov./Dec. 1995, HSKim et al., "Miniature Schottky Elec
tron Source ", Journal of Vacuum Science Technology Bulletin 14 (6), pp. 3
774-80, Nov./Dec. 1996, THP Chang et al., "Electron-Beam Microcolumns
for Lithography and Related Applications ", THP Chang et al., US Pate
nt No. 5,122,663, THP Chang et al., UP Patent No. 5,155,412.

A typical electron beam column 200 using the photocathode array 100 as an electron source is shown in FIG. The column 200 is sealed in a column chamber that has been degassed under reduced pressure. The photocathode array 100 can be completely closed in a vacuum degassed column chamber, or the transparent substrate 101 forms a window to the vacuum chamber for the light beam 103 to access from outside the vacuum chamber. Good. The electron beam 104 is emitted from the emission region 108 into the inside of the column chamber that has been degassed under reduced pressure, and carries the image of the emission region 108. The electron beam may be shaped by other components of column 200.

The electron beam 104 is accelerated between the photocathode array 100 and the anode 201 by the voltage applied between the anode 201 and the photoelectric emission layer 102. The voltage generated between the photocathode array 100 and the anode 201 by the power supply 208 (stored outside the vacuum chamber) is typically in the range of several kilovolts to tens of kilovolts. The electron beam then passes through an electron lens 204 that focuses the electron beam onto a restricted aperture 202. The limiting aperture 202 blocks those components of the electron beam that have a larger emission solid angle than the target. Electronic lens 2
05 refocuses the electron beam. The electron lenses 204 and 205 adjust the focus of the image carried by the electron beam on the target 207 and reduce the image. Deflector 20
Reference numeral 3 shifts the electron beam in the lateral direction so that the position of the image carried by the electron beam on the target 207 can be controlled.

In a 0.1 μm lithography system, the size of a circular pixel incident on the target 207 is on the order of 0.05 μm. Therefore, the image of the illuminated area 108 needs to be scaled down by a factor, approximately 2-10, depending on the size of the illuminated area 108. The target 207 may be a semiconductor wafer or a mask blank.

[0018]

[Problems to be Solved by the Invention]

A conventional variable shaped electron beam lithography column shapes an electron beam by deflecting the electron beam through one or more shaping apertures. The resulting image in the shaped electron beam is then transferred to the target 207 with a large total linear column reduction. Due to the need for large-scale total linear column reduction (performed by the electronic lenses 204, 205),
The result is a large column length and increased electron-electron interactions that ultimately limit the electron flow density in the column. When the column is used for lithography, a low electron flow density results in a low throughput.

Another known shortcoming in the use of e-beam systems is that the electron beam cannot be modulated without modulating the light source (usually the laser) itself. Modulation of the laser typically involves a large number of control complex circuits, requires a large amount of space and can be slow. Moreover, with patterned arrays of photocathodes, the modulation of individual photocathodes within the array is extremely difficult. To conclude, lithography systems require higher resolution to meet future demands for processing semiconductor materials.

[0020]

[Means for Solving the Problems]

One embodiment of the present invention comprises an array with charged particle beam columns, each charged particle beam column selectively exposing one target to multiple charged particle beams. In each charged particle beam column, a beam source that selectively generates a plurality of charged particle beams, a plurality of charged particle beams from a beam source are accelerated, and an anode coaxial with the charged particle beam and a charged particle beam are reduced. And includes a lens coaxial with the charged particle beam.

In one embodiment, the beam source is a photocathode array that selectively provides multiple electron beams upon irradiation. In this embodiment, the photocathode array includes at least one photocathode that includes a gate electrode that modulates the electron beam in response to a voltage applied to the gate electrode, and at least one pad, where at least one photocathode. The pad is electrically connected to the gate electrode of the at least one photocathode by a connecting line, and the at least one pad enables external control of the gate electrode of the at least one photocathode.

Accordingly, one embodiment of the present invention includes a method of imaging an image of a pattern on a target, the method comprising generating a plurality of charged particle beams, the beams being grouped together. Steps, selectively controlling each of the groups of charged particle beams, and directing each of the groups onto a target. In this example, each of the groups is contained within one charged particle beam column.

The invention and its various embodiments are described in more detail in conjunction with the following figures and accompanying text.

[0024]

DETAILED DESCRIPTION OF THE INVENTION

3A and 3B are side views of an embodiment of the photocathode 300 according to the present invention (the related art housings, electrical leads, etc. are not shown). In FIG. 3A, a photoemitter 302 is deposited on a transparent substrate 301. The transparent substrate 301 may be made of another transparent material having a sufficient structural strength to support it, but is usually glass, fused silica or sapphire.

The light beam 303 is incident on the transparent substrate 301, passes through the transparent substrate 301 and is absorbed by the photoelectric radiator 302 in the illuminated area 308. When the light beam 303 is incident on the irradiation region 308, the photoelectric radiator 302 emits electrons from the irradiation region 305 located on the surface of the photoelectric radiator 302 opposite to the irradiation region 308.

Irradiated region 305 can generally be any shape and any size such that gate electrode 307 determines the electric field. Some useful shapes include circles, squares, rectangles, octagons and hexagons. The illuminated area 308 should cover at least the illuminated area 305.

[0027]   The illuminated area 305 is surrounded by but covered by the gate insulator 306.
Gate insulator 306 is deposited on the photoemitter 302 so that there is no Gate
Insulator 306 may be made of any electrically insulating material, preferably SiO. ₂ Create from. The gate electrode 307 is placed in a direction away from the emitting region 305.
Deposited on the surface of the insulator. The gate electrode 307 can be made of any conductive material.
Wear.

The photo-emitter 302 can be made of any material that emits electrons when illuminated. The most efficient photoelectric emitting materials include semiconductors such as cesium tellurium (Cs ₂ Te) and materials such as gold, aluminum and carbide materials. In addition, many Group III-V semiconductors such as gallium arsenide (GaAs) are suitable photoemitter materials. Preferably, the photoemitter 302 has a thickness of about 100Å.

The photo-emitter 302 will have a work function that depends on the actual photo-emitter material. Work function is the minimum energy required to emit an electron from a material. The photons in the light beam 303 must have at least as much energy as the work function so that the photoemitter 302 emits electrons.

The light beam 303 is absorbed by the photoelectric radiator 302 at or near the surface of the photoelectric radiator 302 corresponding to the illuminated area 308. At that point, the electron will have a kinetic energy equal to the photon energy minus the work function. These electrons move from the irradiation region 308 to the irradiation region 305 and are emitted from the material in the irradiation region 305, provided that the electrons do not lose excessive energy due to the collision inside the photoelectric radiator material. To do. Therefore, the thickness of the photo-emitter 302 must be sufficient to absorb the light beam 303, but not so thick that it again absorbs a significant amount of the created free electrons.

In the embodiment of the present invention, the kinetic energy of the emitted electrons is not excessive,
The emitted electrons are preferably less than 0.5 eV so that they can be reflected by the voltage applied to the gate electrode 307, but can be as large as several eV. If the photoemitter 302 has a work function of 3.5-4.5 eV, the photon wavelength of the light beam is 275 n in order to generate photons with the appropriate photon energy.
m or less.

The transparent substrate 301 must be transparent to the light beam 303 so that the maximum possible amount of light is incident on the illuminated area 308. The transparent substrate 301 can have any thickness, but is preferably several millimeters. Further, the light beam 303
May be focused so as to cover the irradiation spot 308 with an area corresponding to the radiation region 305.

The intensity distribution of the light beam 303 is typically Gaussian-shaped and therefore the light beam 30
In No. 3, the strength is higher in the central portion than in the edge portions. In order for the electron beam 304 to have a substantially uniform intensity, the light beam 303 is preferably focussed in such a way that its intensity is substantially uniform over the illuminated area 308. However, in general, the light beam 303 can be focused as needed.

The gate electrode 307 is fabricated on the insulator 306 and can be made of any conductive material. The thickness of the gate insulator 306 is preferably about 1000-5000Å,
The thickness of the gate electrode 307 is likewise preferably about 1000Å. In one embodiment, photoelectric emitter 302 is held at a ground voltage and gate electrode 307 is at a voltage greater than ground potential, about +10, to accelerate electrons emitted from photoelectric emitter 302.
Bias is applied at V. The gate electrode 307 has a voltage lower than the ground potential, about −
When biased at 10 V, the emitted electrons are reflected back into the photoemitter 30.
Returned to direction 2. Furthermore, by coupling a resistor 311 between the photoelectric radiator 302 and the gate electrode 307 and using radiation intensity feedback (ie, a self-biasing system), stable radiation can be realized. For example, as the emission of electrons becomes stronger, the gate voltage drops correspondingly, and the lowered gate voltage then lowers the emission intensity.

The anode electrode 310 is held at a voltage in the range of several kilovolts to several tens of kilovolts, accelerates the electrons emitted from the photocathode 300, and directs them into the reduced pressure deaeration electron beam column. Alternatively, the photo-emitter 302 is held at a large negative voltage, the gate electrode 307 is biased at +/- 10V compared to the photo-emitter 302, and the anode electrode 310 is grounded.

In FIG. 3A, the gate electrode 307 is held at + 10V. This voltage is insulator 3
06 and the gate electrode 307 are not present, the anode electrode 310 and the photoelectric radiator 302
It is chosen to match the electric field that is believed to be set up between and. At a gate electrode voltage of 10 V, the electron beam 304 carrying the image of the emission region 305 is accelerated out of the emission region 305. The insulator 306 and the gate electrode 307 also function as a mask because they better shape the image of the emission region 305 included in the electron beam 304.

In FIG. 3B, the gate electrode 307 is held at −10V. With this voltage, the electrons emitted in the emission region 305 are accelerated by the electric field created between the gate electrode 307 and the photoelectric emitter 302, and are returned in the direction of the emission region 305. Radiation area 30
Since the electrons emitted from 5 are reflected back to the inside of the photoelectric radiator 302 rather than being accelerated in the direction away from the photoelectric radiator 302, an electron beam is not created. Instead of an electron beam, an electron cloud 309 is created where electrons are emitted from the photoemitter 302 and are immediately accelerated back into the photoemitter 302.

In some embodiments of the invention, the voltage on gate electrode 307 is varied to control the intensity of the electron beam. The greater the voltage difference between the gate electrode 307 and the photoemitter 302, the greater the number of electrons emitted from the photocathode 300. The maximum number of electrons available, which are emitted from the emission region 305 as a result of the light beam 303, are extracted when the gate electrode is set to the fully on state (about 10 V).

In the example described in this specification, +10 V is applied to the gate for the operation state in which all outputs are turned on.
-10V for a full output off operating condition, with other bias voltages, but other parameters for gate voltage are possible. The bias voltage at the time of full output on and the voltage applied to the anode electrode 310 determine the thickness of the insulator 306, because the electric field created by the bias voltage at the time of full output on by the gate electrode 307 is This is because it must match the electric field that is considered to exist when the gate electrode 307 and the gate insulator 306 are not present. The bias voltage at the time of full power off limits the photon energy of the incident light beam, because the radiation area 3 is at the time of full power off operation.
This is because the electrons emitted from 08 must be reflected and returned to the inside of the photoelectric radiator 302. In addition, the gate electrode 307 should be the main feature that determines the electric field in the vicinity of the emission region 308. Therefore, the size of the emitting region 308 is limited by the relative size and distance between the gate electrode 306 and the anode electrode 310.

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

FIG. 4 shows an embodiment of the photocathode array 400. In FIG. 4, the photocathode array 40 is shown.
Two emission regions 402 of 0 are described, both emission regions 402 being illuminated by a light beam 403 which simultaneously illuminates the entire portion of the photocathode array 400 shown.
Alternatively, collimated light beams can be used, in which case each beam is focused on a separate emission area 402. The photocathode array 400 includes a transparent substrate 401, a conductor 408, a gate insulator 406, a gate electrode 407, and a photoemitter 402.

The conductor 408 can be made of any conductive material, but is preferably aluminum, having an opening deposited on the transparent substrate 401, within which the light emitter 402 is fabricated. The photoemitter 402 can be any material that emits electrons when illuminated with photons, as described above. Again, the photo-emitter 402 has a work function and the photons in the light beam 403 have at least as much energy as the work function so that electrons are emitted from the emission region 405. Transparent substrate 40
1 is preferably glass, but may be made of any material that is transparent to the light beam 403, such as sapphire or fused silica. The conductor 408 is opaque to the light beam 403 and does not emit electrons from its front surface when illuminated by the light beam 403 from the back surface. Thus, the conductor 408 acts as a mask, defining the illuminated area 408. Emissive region 405 is on the opposite side of illuminated region 408 on photoelectric emitter 402 and can be sized in any shape as long as it is arrayed with gate electrode 407 determining the electric field.

A gate insulator 406 is fabricated on the conductor 408 and a photoelectric radiator 402 is formed on the insulator 4
The opening portion 410 is provided so as not to be covered with 06. Gate electrode 407 is deposited on gate insulator 406. In this embodiment, the gate electrode 407 is the irradiation region 4
The electric field created at 05 overhangs the opening 410 by a sufficient amount so that it is not substantially distorted by the gate insulator 406. As shown in FIGS. 3A and 3B,
The gate electrode 407 is controlled by the voltage applied to the gate electrode 407 to cause the electron beam 4 to move.
04 has the ability to turn on and off. ON and OFF voltages are + 10V and 1 respectively
Almost corresponds to 0V. Moreover, the ultimate electron beam intensity may be adjusted by changing the gate electrode voltage. Similarly, the self-bias applying resistor 411 may be connected between the gate electrode 407 and the conductor 408 so as to perform feedback for controlling the intensity of the electron beam 404 by applying the self-bias.

In the photocathode shown in FIGS. 3A, 3B and 4, the intensity of the electron beam may be controlled by controlling the actual voltage between the gate electrode and the photoemitter. The lower the voltage, the less intense the electron beam has, because the number of electrons that escape the electron cloud, which has a statistical velocity distribution in the electron beam propagation direction, is smaller. Furthermore, a gate electrode may be used to adjust the intensity of the resulting electron beam. In some embodiments, a resistor is placed between the gate electrode and the photoemitter so that self-biased feedback is provided, that is, the gate voltage drops correspondingly as the emission is enhanced.

In FIG. 4, the gate electrode 407 is shown as being identical for each illuminated area 405. However, in general, each illuminated region 405 will have a gate electrode 407 electrically isolated from the other gate electrode. Moreover, the gate electrode for a particular illuminated area may include several segments, each electrically isolated from all others.

In some embodiments, the gate electrode surrounding the emitting region has multiple segments. By having multiple segments, it is possible to turn on a portion of the emission region while turning off another portion, shaping the image carried by the electron beam 404.

A photocathode as in FIG. 3 is illustrated in FIG. 5, but instead of a single segment gate electrode 307, a right gate segment 510 and a left gate segment 5 are included.
11 is provided. As a result of this structure, the electron beam can be selectively switched on. For example, in FIG. 5, the right gate segment 510 is held at the full output on state with a bias voltage of 10V, and the left gate segment 511 is bias voltage of -10V.
Holds all outputs off. The resulting electric field reflects electrons emitted from the emission region 305 near the left gate segment 511, while accelerated electrons are emitted out of 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 the emission area 305. The resulting distribution of the electron beam 504 is not uniform,
Near the right gate segment 510, the strongest, two segments 510
Essentially off at the midpoint of 511.

FIG. 6A shows a plan view of a four segment gate electrode arrangement. The gate segments are segments A601, B602, C603, D604. The emission area 305 in this example is square. The emission area 305 can be any shape, but is preferably rectangular. Other useful shapes include circles, rectangles, octagons and hexagons.

The gate segments A601, C603, D604 are turned on (that is, held at + 10V), and the gate electrode B602 is turned off (that is, held at -10V).
A plan view of the sometimes resulting electron beam 504 is illustrated in FIG. 6B. Gate segments A601 and D60 while gate segments B602 and C603 are off
A top view of the electron beam 504 resulting when 4 is turned on is shown in FIG. 6C.
Other shapes of electron beam can be formed by selectively controlling the voltage on the gate electrode segments. This ability contributes to a great deal of diversion to the construction of photocathode arrays that can be used for a variety of different tasks. Illustrated in FIG. 10 is a photocathode with segmented gate electrodes for use in an electron beam column for electron beam lithography.

In general, any number of gate segments can be used. The greater the number of gate segments, the more control the photocathode user has with respect to the electron beam created from a given irradiation area. This ability can be said to be extremely important for efficiently drawing features on a semiconductor substrate. Furthermore, as mentioned above, a resistor can be coupled between the individual segments of the gate electrode and the photoemitter for self-biasing control over the intensity of the electron beam.

The photocathode described in the preceding sentence contributes to miniaturization leading to multiple photocathode sources and precise integration. The photocathode array can be built on a single substrate by precisely positioning the photocathodes. In particular, the photocathode fabrication process illustrated in FIG. 4 using conventional semiconductor processing steps is illustrated in FIGS. 7A-7F. Only one photocathode of the photocathode array is shown in the illustrated process. However, those skilled in the art can manufacture photocathode arrays in which irradiation areas having various shapes and photocathodes having various gate structures are precisely arranged from those illustrated. Furthermore, it is possible for a person skilled in the art to modify the process in order to produce other photocathodes according to the invention or to modify it in such a way that the same photocathode structure is formed as a result.

The conductive film of the opaque layer is a transparent substrate 40 such as glass, fused silica or sapphire.
A cross-sectional view of the first step in the process deposited on 1 is illustrated in Figure 7A.
Preferably, the transparent substrate 401 is a glass substrate. As shown in FIG. 7B, the conductive film is masked and a window of appropriate size and shape is etched through the conductive film to form the illuminated area 410. A gate insulator 406 is then deposited on the top surface of the conducting film 408, filling the window of the illuminated area 410 as well. The gate insulator 406 may be any electrical insulator, but is preferably SiO ₂ .
A gate electrode layer 407 is then deposited on top of the gate insulator 406 as shown in Figure 7D.

The gate insulator 406 is then masked and the holes 411 are etched through the gate electrode layer 407 and the insulating film 406 as shown in FIG. 7E. The hole 411 is aligned with the irradiation area 410 and is slightly larger than the irradiation area 410. Moreover, the insulating film 406 is completely removed from the window of the irradiation region 410 by this etching.

In FIG. 7F, the recess holes 41 are formed in the insulating film 406 by selective isotropic etching.
2 is formed, the gate electrode 407 is formed in the hole 411 and the recess hole 4 at this stage.
It overhangs above the opening created in 12. Finally, the photocathode material 402 is deposited using thermal evaporation from a point source or directional deposition techniques such as ionized sputter deposition. This final deposition forms the photocathode 400 with self-centering gate apertures, so that the photocathode is electrically connected to the conductive layer 408, but remains electrically isolated from the gate electrode 407.

Further, in an array with photocathodes produced by this process, each gate electrode segment surrounding each photocathode may be formed by appropriately masking the gate insulator 406 during the deposition of the gate electrode layer 407. Good. Alternatively, the gate electrode layer 407 may be individually etched to form individual gate segments. Similarly, the connecting line connecting the gate electrode segment to the pad may be formed with the gate electrode segment or may be deposited in a later process step.

As an alternative manufacturing method, the substrate could first be coated with a conductive layer 408, a gate insulator 406 and a gate electrode 407. Window 411 is then etched down through all the films up to transparent substrate 401. It is possible that a selective isotropic etch could be employed to slightly enlarge the opening in the gate electrode 407 with respect to the corresponding window 410 in the conductive layer 408. Similarly, multiple segments of the gate electrode are created around each hole 411 by isotropic etching of insulation breaks in the gate electrode 407.

In some embodiments, the surface of the substrate 401 may be shaped to focus the light beam onto an illuminated area corresponding to the illuminated area 410 of the photoemitter 402. Similarly, in some embodiments, the photoemitter itself may be shaped to better focus the resulting electron beam emitted from the photocathode.

A plan view of a 4x4 array with patterned photocathodes is shown in FIG. The illuminated area 801 in this example is square, although any shape can be made, including circular, rectangular, hexagonal and octagonal. The gate electrode 804 is formed in each irradiation area 80.
Completely surrounds 1. Although only a single-segment gate electrode is shown in FIG. 8, the gate electrode 80 is used to further control the emission of electrons from the irradiation area 801.
4 may generally be constructed with multiple electrode segments. The gate electrode 804 is connected to the bonding pad 803 by the connection line 802. Bonding pad 80
3 and connecting line 802 are both preferably made of the same material as gate electrode 804, but any conductor that makes electrical contact to gate electrode 804 can be used. In a lithographic system, it is generally desirable that the physical separation between two adjacent emission areas be such that the array is rectangular. The minimum separation between the emission areas is about 4 times the physical dimensions of the emission areas. In FIG. 8, the size of the rectangular radiation region according to the current miniaturization manufacturing technology can be reduced to about 0.1 μm. Preferably, the dimension of one side of the emitting region is 0.1 μm. Therefore, the entire 4 × 4 configuration array shown in FIG. 8 can be constructed within a 1.6 μm square, which is well within conventional miniaturization manufacturing limits.

A side view of a photocathode array 910 according to the present invention mounted inside a microcolumn 900 is shown in FIG. The micro column 900 is housed inside a vacuum degassing chamber (not shown). It can be said that the substrate of the photocathode array 910 is sufficient as a vacuum window, allowing or instead of arranging a laser light source on the illuminated area of the photocathode array 910, the photocathode array 910 has a vacuum chamber. It may be completely enclosed. The electron beam 911 is the photocathode array 9
Emitted from the emission regions of 10 and is accelerated across the interior of the anode 901 by the control input to the gate electrode 909 of the photocathode array 910. The anode 901 is held at a voltage of 1 kilovolt to several tens of kilovolts, which is higher than the voltage of the photoemitter of the photocathode 910. The limiting aperture 902 blocks some beams 911 that have a larger radiation solid angle than the target. The deflector 903 makes it possible to scan the image of the radiation area contained inside the electron beam 911 over the entire substrate and to shift it laterally. An Einzel lens with electrodes 904, 905 and 906 focuses the image on the target 907 and reduces it. The target 907 may be either a semiconductor wafer used for electron beam lithography or a mask blank.

Photocathode array 910 can include any number of individual photocathodes. Each of the individual photocathodes can include a single segment gate or multiple segment gates. The image formed by the electron beam 911 depends on the irradiation area of each individual photocathode and the state of each gate electrode of each individual photocathode. For example, a photocathode array 910 having one photocathode with a single segment gate can be formed for only one image of the illuminated area of the photocathode. Photocathode array 91 with multiple photocathodes each having individually controlled single segment gates
At 0, various images can be formed by selectively turning on individually controlled photocathodes to form an assemblage of images for each illuminated area of the "on" photocathode. Photocathode array 910, in which some of the photocathodes have multi-segmented gate electrodes, has the greatest versatility because it allows the formation of images using portions of the illuminated areas of the individual photocathodes.

In one embodiment, the limiting aperture 902 is not used, so the full radiation solid angle of the beam 911 is used. Instead, the gate electrode 909 is used to mask the beam 911, ie to prevent the exposure of the target 907 to the beam 911. Therefore, the length of the microcolumn 900 is reduced, which reduces the interaction between the electrons. Such electron-electron interaction causes "blur" that occurs in the image formed on the target 907 by the beam 911.

An electron source 1001 with one photocathode 1004 is shown in FIG. The photocathode 1004 has an illuminated area 1002 and a 4-segment gate structure 1003. The 4-segment gate structure can selectively image the illuminated area 1002. In the example of FIG. 10, the 4-segment gate structure 1003 is used for forming an electron beam image corresponding to 1/2 of the irradiation region 1002. The electron beam carrying the electron beam image is extracted from the photocathode 1004 by the extraction electrode 1005. The reduction lens 1006 reduces the electron beam image on the wafer or mask blank 1008 to form the final shaped image. Although the system illustrated in FIG. 10 has a minimal number of components, it allows the shaped electron beam column to be constructed with a particularly minimal amount of space and length, and therefore the interaction between electrons. The effect of is reduced.

Illustrated in FIG. 11 is a conventional variable shaped electron beam column presented in contrast to the electron beam column shown in FIG. The electron beam is formed by the electron source 1101. The electron source 1101 may be a thermionic cathode such as lanthanum hexaboride LaB ₆ or a single gated photocathode similar to that shown in FIG. The electron beam is shaped by the rectangular aperture 1102 to form a shaped electron beam. The shaped electron beam is projected onto the area 1110 by the electron lens 1103.
Focused within. The spot shaping deflector 1104 deflects the electron beam in the focal region 1110 so that the shaped electron beam is shifted. The shaped electron beam then passes through the rectangular aperture 1105 to form an intermediate shaped electron beam. Since the rectangular aperture 1105 allows the electron beam in the portion overlapping the aperture to pass therethrough and blocks the electron beam in the portion outside the aperture, only the image portion formed by the rectangular aperture 1102 passes through to form an intermediate shaped beam image. . The reduction lens 1106 reduces the image and focuses it on the wafer or mask blank 1109 into the final shaped beam image 1108.

The throughput of a lithographic system is usually limited by the total beam current. As the total beam current increases, "blur" occurs due to the interaction between electrons in the beam, and the "blur" causes a reduction in the resolution of the pattern written on the target. When the total beam current is evenly distributed among a few columns, each column produces a smaller beam current. As a result, each column produces an image with less "blur" and therefore higher resolution. Furthermore, the distribution of beam currents allows for higher electron current densities, which in turn allows for greater throughput when using the column for lithography.

According to one embodiment of the invention, a number of microcolumns 1201-1 to 1201-4 are arranged in an array 1200, as schematically depicted in FIG. 12A. Any microcolumn that uses the composite of photocathode array 910 and gate electrode 909 (FIG. 9) as the source of the charged particle beam is also suitable for use. For example, microcolumn 900 (FIG. 9) is an illustrative example of any of microcolumns 1201-1 through 1201-4. In FIG. 12A, beam source 1201-1 refers to the composite of photocathode 910 and gate electrode 909. Beam source 1202-1
202-4 is similar to 1202-1. Micro-column 120 of array 1200
Reference numerals 1-1 to 1201-4 denote respective beams 1204 on a target 1206 which is either a semiconductor wafer or a mask blank used for electron beam lithography.
-1 to 1204-4 are selectively emitted.

The pitch between adjacent microcolumns (center-to-center pitch) in both dimensions of array 1200 in that array is, for example, 2 cm, which is representative of the individual microcolumns, including the housing of each microcolumn. Diameter. "
Footprint ", that is, the diameter of a single microcolumn is, for example, 2 cm or less, and thus many microcolumns are arranged in an array that occupies the footprint of a conventional 9 or 12 inch diameter semiconductor wafer, for example. can do.

Of course, the array of microcolumns in the array 1200 is, for example, MxN in size.
Can be changed to an array of two sides, where M and N represent the numbers of microcolumns in the X and Y directions, respectively. In FIG. 12B, an outline of a plan view of the NxM array is described. This array is not restrictive.

By using the photocathode array 910 to generate a large number of beamlets, the beam current in each microcolumn is split into a number of beamlets that further reduce "blur" due to electron-electron interactions. Therefore, a larger total beam current is expected for each microcolumn. As a result, the throughput of the drawn pattern is increased.

In one embodiment, the microcolumns of array 1200 employ a writing scheme such as the well-known MEBES raster scan writing approach currently employed to fabricate masks in a single electron beam column. There is. This MEBES drawing approach has been disclosed and is incorporated herein by reference in its entirety, such as IBM's U.S. Pat. No. 4,818,885, Bell Labs U.S. Pat. Nos. 4,668,083, 3,900. , 737. Thus, array 1 with microcolumns
The system architecture that employs 200 includes the basic datapath in one embodiment and many other advanced techniques such as multi-pass and multi-pixel techniques developed for MEBES. The entire text is incorporated herein by reference.
BM US Pat. No. 5,621,216, and Etec System Inc. US Pat.
See 393, 987 and 5, 103, 101. Similarly, other well-known electron beam lithography techniques, such as gray scale techniques or shaped beam techniques, can also be applied with the array 1200, but are incorporated by reference herein in their entirety, eg, IBM US Pat. 213, 916, No. 5, 334, 46.
7, No. 4,568,861 and No. 4,423,305.

The specific examples discussed in the preamble are for illustration purposes only. Modifications obvious to those skilled in the art are within the scope of the invention. Accordingly, the limitations of the invention are limited to the claims that follow.

[Brief description of drawings]

[Figure 1]   FIG. 1 is a diagram of a photocathode patterned according to the prior art.

[Fig. 2]   FIG. 4 is a view of a conventional electron beam column using the photocathode shown in FIG. 1.

[Figure 3]   3A and 3B are diagrams of a photocathode according to the present invention.

[Figure 4]   FIG. 3 shows a part of a photocathode array with two photocathodes according to the invention.

FIG. 5 is a diagram of a photocathode according to the invention having a gate electrode with multiple segments.

FIG. 6A is a diagram of a photocathode according to the present invention having a number of independent segments in the gate electrode, and B, C selectively turning on the segment shown in the gate electrode described in A. FIG. FIG. 6 is a diagram of a patterned e-beam of a sample formed in FIG.

7A-7F are process diagrams for forming a photocathode according to the embodiment of the invention presented in FIG.

[Figure 8]   FIG. 3 is a diagram of a photocathode array according to the present invention.

[Figure 9]   FIG. 3 is a diagram of a micro-column using a photocathode according to the present invention.

FIG. 10 is a diagram of a multi-segment gated photocathode used in an electron beam column in which the beam shaping is performed by the photocathode.

FIG. 11 is a diagram of a conventional variable shaped beam electron beam column having multiple shaping components.

12A is a diagram of a number of microcolumns arranged in an array according to one embodiment, and FIG. 12B illustrates a schematic top view of the array described in FIG. 12A according to one embodiment. In the drawings, constituent elements having the same or similar functions are designated by the same reference numerals.

[Explanation of symbols]

100 ... Photocathode array, 101 ... Substrate (transparent), 102 ... Photoemission layer, 10
3 ... Optical beam, 104 ... E-beam, 105 ... Irradiation area, 106 ... Mask, 10
7 ... Mask, 108 ... Emission area, 110 ... Photocathode.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01J 37/305 H01L 21/30 541W (81) Designated country EP (AT, BE, CH, CY, DE, DK) , ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR , NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, BZ, CA, CH, CN, CR CU, CZ, DE, DK, DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR , KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, UZ, VN, YU, ZA, ZW (72) Inventor Chang, Tai Hong, P.i. 1105 (72) Nimitz Lane, Foster City, California, USA Inventor Lee, Kim, Wy. Fremont, California, United States, Benchmark 2672 (72) Inventor Burglund, See. , Nail USA, Oregon, Oregon City, S. Clackamas River Drive 15361 F Term (Reference) 2H097 CA16 LA10 5C030 CC10 5C033 FF10 JJ07 MM07 UU02 5C034 BB01 BB02 5F056 AA33 EA05 EA08 EA10

Claims (13)

[Claims] 1. A charged particle beam column device comprising: a target support; and an array of charged particle beam columns arranged to expose the target to a charged particle beam, each of the charged particle beam columns comprising: A beam source that selectively generates a plurality of charged particle beams; an anode that is coaxial with the charged particle beam and that accelerates the plurality of charged particle beams from the beam source; and a coaxial with the charged particle beam A charged particle beam column device comprising a lens for reducing the charged particle beam. 2. The device of claim 1, wherein the array is square shaped. 3. The apparatus of claim 1, wherein the array comprises an array comprising M × N charged particle beam columns, N not equal to M. 4. The charged particle beam column is a microcolumn.
The device according to. 5. The beam source comprises a photocathode array for selectively supplying a large number of electron beams during irradiation, and the photocathode array modulates the electron beams according to a voltage applied to a gate electrode. 2. At least one photocathode provided with the gate electrode, and at least one pad electrically connected to the gate electrode of the at least one photocathode so that the gate electrode can be controlled from the outside. The device according to. 6. The device of claim 5, wherein the gate electrode of the at least one photocathode comprises at least one segment. 7. The device of claim 5, wherein the gate electrode of the at least one photocathode comprises four segments. 8. The device of claim 5, wherein the gate electrode of the at least one photocathode comprises 8 segments. 9. A method of imaging a pattern on a target comprising:   Generating a plurality of charged particle beams,   Assembling the beams into groups,   Selectively controlling each of the groups comprising a charged particle beam;   Orienting each of the groups on the target; A method comprising. 10. The method of claim 9, wherein each of said groups is contained within one charged particle beam column. 11. The charged particle beam column is arranged in an array.
The method described in 0. 12. The method of claim 11, wherein the array is square shaped. 13. The method of claim 11, wherein the array is shaped into a rectangle.