EP1386342A2

EP1386342A2 - Deflection system for a particle beam device

Info

Publication number: EP1386342A2
Application number: EP02724193A
Authority: EP
Inventors: Matthias Brunner; Ralf Schmid
Original assignee: AKT Electron Beam Tech GmbH
Current assignee: AKT Electron Beam Tech GmbH
Priority date: 2001-05-11
Filing date: 2002-03-04
Publication date: 2004-02-04
Also published as: WO2002093610A2; JP3899317B2; TW565871B; DE10122957B4; US7105833B2; KR20040005943A; KR100881236B1; JP2004527885A; WO2002093610A3; DE10122957A1; US20040188630A1

Abstract

A particle beam device and a device for energy-correcting deflection of a particle beam at a predetermined deflection angle, said particle beam being incident along a beam axis, wherein the particle beam consists of charged particles with energy scattered at a predetermined energy value. The device has a corrector, wherein said corrector performs direction changes of the charged particles depending on their energy by means of a first electrical field and a first superimposed magnetic field and wherein the direction of the charged particles is maintained with the predetermined energy value as they pass through the corrector. The device also has a deflector connected downstream of the corrector, wherein said deflector deflects the charged particles having the predetermined energy value away from the beam axis at a given deflection angle by means of a second electrical field or a second magnetic field, wherein the deflector focuses the charged particles. The device further has a control device for controlling the corrector and the deflector.

Description

Deflection system for a particle beam device

description

The invention relates to a particle beam apparatus and a device for the energy-corrected deflection of a particle beam from charged particles and a method for the energy-corrected deflection of a particle beam.

Devices for deflecting particle beams from charged particles are used for particle beam devices such as e.g. Electron microscopes, devices of electron or ion beam lithography and used for display devices. It is usually a question of deflecting a particle beam of charged particles from an incident direction into variable directions in order to be able to move to different positions on a target surface.

The deflection of particle beams from an direction of incidence to a direction of exit is generally carried out by using electrical or magnetic fields which exert lateral forces on the particle beam. The electric or magnetic fields are generated by deflectors, the electric or magnetic multipoles, e.g. Dipoles or quadrupoles. The deflection angle between the direction of incidence and the direction of exit a ^, which a homogeneous magnetic field of strength B perpendicular to the particle beam causes on the particle beam, is given by

where SQRT (W) is the square root of the kinetic particle energy W of the charged particles and k _{m is} a constant which depends on the particle mass, particle charge, the magnetic field strength and the angle between the magnetic field and the particle beam direction. Eq. (1) applies in particular in the event that the deflection angle is small compared to the angle between the particle beam and the magnetic field.

The angle of deflection between the direction of incidence and the direction of exit α _e , which a homogeneous electric field of strength E with a direction perpendicular to the particle beam generates on the particle beam, is given by

(2) α _e = k _e / W,

where k _{e is} a constant that depends on the particle mass, particle charge, the electric field strength and the angle between the electric field and the particle beam direction. Eq. (2) applies in particular to the case where the deflection angle is small compared to the angle between the particle beam and the electric field.

The dependence of the deflection angle on the particle energy W leads to the fact that only particles with a predefined energy value change direction by the predefined deflection angle. Particles with higher energy than the given energy value are deflected less and particles with lower energy are deflected more. Since the charged particles of a particle beam have a certain scatter in energy in practice, the dependence of the deflection angle on the energy of the charged particles leads to the fact that particle beams from charged particles experience an energy-dependent expansion when deflected. An energy-dependent expansion of a particle beam, which is also called _ _mci _.___. Before aberration or color errors, is often undesirable, since it can limit the spatial resolution of particle beam devices, in particular electron microscopes, devices of electron or ion beam lithography and display devices. A device for how a particle beam of charged particles can be deflected in an energy-corrected manner by a predetermined deflection angle is disclosed in the patent application US 4,362,945. An electric field and a magnetic field are superimposed therein perpendicularly, the forces of the electric field on the charged particles of the particle beam counteracting the forces of the magnetic field on the charged particles. The strength of the magnetic field is also so great that the predetermined magnetic deflection angle α _{m is} twice as large as the predetermined electrical deflection angle α _e , as a result of which the energy-dependent deviations from the predetermined deflection angle compensate one another. In the case of compensating the energy-dependent deviation, the following therefore applies to the deflection angle α:

(3) α = α _m - α _e = ^ α _m

The compensation of the energy-dependent expansion of the particle beam results from Eq. (1) and (2) making up the equations

and

(5) δα _e / δW = - α _e / W

can be derived. Eq. (4) and (5) state that with the same deflection angles α _m ^ the energy-dependent expansion of the particle beam by an electric field is essentially twice as large as by a magnetic field.

Furthermore, the denser the particle beam deflection points of the electric field and, the better the compensation of the energy-dependent deviations of the magnetic field are close together. The particle beam deflection points of a deflector result from the cross point that the beam axis of the incident particle beam forms with the axis of the particle beam emerging from the respective field.

The effort to manufacture particle beam devices with energy-correcting deflectors that superimpose electrical and magnetic fields is considerable, since the fields for such deflectors must be larger than for a deflector without energy correction. The reason for this is that the fields not only have to deflect the particle beam but also have to partially compensate each other. The multipole elements for generating such fields must therefore be larger and more complex; however, the generation of stronger magnetic fields requires e.g. larger coils or higher coil currents in the particle beam range, which may require additional cooling.

In addition, deflectors require a large opening so that deflected particle beams can be passed through the deflector unhindered even with a large deflection angle. For the energy-correcting deflector described, a large opening means large baffle spacings and large coil spacings. In order to be able to provide the necessary electrical and magnetic field strengths in the particle beam range, the electrical potential at the deflection plates and the currents at the coils must be scaled up accordingly. This leads to a further increase in the £ _., _^ . Voltages and / or coil currents of the deflector, which thereby makes it even larger and further limits the possible uses.

The present invention is therefore based on the object of a particle beam apparatus, a device and a method for energy-corrected deflection To provide particle beam, which do not have the disadvantages described above.

This object is achieved by the particle beam apparatus according to claim 5, by the device for energy-corrected deflection of a particle beam according to claim 6 and by the method according to claim 20.

Further advantageous embodiments, refinements 10 and aspects of the present invention result from the dependent patent claims, the description and the accompanying drawings.

The particle beam apparatus according to the invention, the

.5 device and the inventive method allow an energy-corrected deflection of a particle beam by a predetermined deflection angle without the disadvantages mentioned above. According to the invention, the corrector exerts forces on the incident particle beam which correspond to the directions of the

: 0 change charged particles depending on their energy so that the energy-dependent deflection of the deflector focuses them. The corrector thus preferably compensates for an energy-dependent expansion of the particle beam, which the deflector would add to the particle beam without a corrector.

5

The corrector, which provides the first electrical and the first magnetic field, can have a small opening since the first electrical and the first magnetic field of the corrector are set according to the invention such that

0, the charged particles with de _ _y <_ _b c enes energy value maintain their direction. Only the charged particles with λron of the energy deviating from the given energy value are changed in direction. The size of the opening of the corrector is no longer determined by the maximum deflection angle of the

5 particle beam but determined by the degree of scattering of the particle energies around the specified energy value. In many particle beam apparatuses, this is small enough to to make the opening of the corrector sufficiently small. The opening of the corrector is blenkplattenabstand or generally by the _A given by the coil pitch of the baffle plates and coils of the corrector. 5

The invention makes it possible to distribute the functions of the deflection and the energy correction to two spatially separate units, namely the corrector and the deflector. This allows both components to be independent

10 are dimensioned from each other with regard to optimal functioning, volume and cost. For example, the corrector, which must provide high electrical or magnetic field strengths, can have a small aperture and the deflector, which must provide small electrical or magnetic field strengths

15 must be equipped with a large opening. By avoiding energy-correcting electrical or magnetic fields, the deflector in particular can be manufactured with a small volume. This means that the particle beam apparatus also has a small working distance

20 between the objective lens and the target surface, the possibility of arranging the deflector (viewed in the particle beam direction) behind the objective lens,.

It is a significant advantage to distract the user

_5 particle beam (3) to be arranged behind the objective lens (7), since this enables the particle beam (3) to be adjusted such that it can traverse the objective lens (7) along the optical axis (20). As a result, chromatic and spherical aberration errors of the objective lens (7) are largely

SO eliminated. In addition, the Öf _ _^ .v__. Objective lens (7), which is given, for example, by the bore diameter, can be significantly reduced, which significantly reduces the effort for the lens optics. Preferably, the opening of the objective lens

(7) thus less than 20 mm and preferably less than 10

■ 5 mm. The particle beam (3) is preferably adjusted so that its distance from the optical axis (20) as it passes through the objective lens (7) is less than 2 mm and preferably less than 0.5 mm.

According to the invention, the corrector changes the direction of the charged particles as a function of their energy. These changes in direction are such that the deflector focuses the charged particles with the second electric field or the second magnetic field. In this respect, the corrector corrects the 10 energy-dependent expansion of the particle beam that the deflector would produce without a corrector.

Particle beam devices with a particle beam source, objective lens, corrector and deflector are used as

L5 electron microscopes, devices for electron or ion beam lithography or other devices that shoot with focused particle beams from charged particles at target surfaces. Target surfaces can e.g. be the samples or surfaces of samples that match the

! 0 focused particle beam to be examined; Target surfaces can also be samples that are to be structured with the focused particle beam, e.g. Wafers for micromechanics or microelectronics or biological samples; Finally, target surfaces can

15 can also be surfaces which are excited by the bombardment with the particle beam for any other reactions such as lighting or switching.

Generate the particle beam source in the particle beam apparatus according to the invention. ^" _._ ilchenstrahl. The charged particles are preferably free electrons or ions. The particle beam is preferably limited to a maximum beam diameter by aperture diaphragms, electrical or magnetic lenses or other devices, the 5 particle beam direction and the particle beam cross section characterizing a beam axis. The beam axis is preferred of the particle beam generated at the particle beam source largely identical to the beam axis of the incident particle beam to be deflected or to the optical axis of the objective lens.

5 The charged particles of the particle beam are preferably accelerated to a predetermined energy value, so that the particle beam, when it arrives on the objective lens, on the corrector or on the deflector, consists of charged particles with energies scattered by a predetermined energy value L0.

The objective lens of the particle beam apparatus is preferably a magnetic, electrical or electromagnetic lens, which has a focusing effect on the particle beam

.5 exercises charged particles. The degree of focusing of the particle beam is crucial for a good spatial resolution with which a sample is observed, structured or otherwise treated. In order to avoid optical errors due to spherical or chromatic aberration through the i0 objective lens, the charged particle beam traverses the objective lens along the optical axis. Such a particle beam guidance is possible if the deflector is arranged behind the objective lens in the particle beam. The present invention enables one

5 such an arrangement with a small working distance, by disclosing a deflector that can be arranged in a compact design behind the objective lens without a corrector.

For the greatest possible spatial resolution of a 0 particle beam apparatus, _; _. required that the objective lens is arranged very close, ie a few millimeters above the target surface. In this case one speaks of a short working distance. The short working distance can cause considerable problems if additional optical components such as a deflector have to be attached between the 5 objective lens and the target surface. To avoid placing the deflector in front of the objective lens there is great interest in making the spatial dimensions of the deflector as small as possible.

A small shape of the deflector limits the possibilities for equipping it with energy-correcting components for 5 space reasons. The device according to the invention solves this problem because, in a first preferred embodiment, the corrector in front of the objective lens and the deflector behind the objective lens

10 is arranged. Since the corrector according to the invention leaves the direction of the charged particles with the specified energy value, it can be ensured that the charged particles with the specified energy value cross the objective lens along their optical axis.

L5 Only the charged particles that deviate from the specified energy value are deflected away from the optical axis of the objective lens and are exposed to spherical or chromatic aberration errors of the objective lens. The influence of spherical or chromatic

-0 Aberration error of the objective lens is, however, only a second-order error, since it only affects those charged particles that deviate from the specified energy value.

If the working distance is large, e.g. larger than about 30 mm,

! 5 so it is advantageous if both corrector and

Deflector seen behind the particle beam direction

Objective lens are arranged. In this case, all charged particles along the optical axis of the

Objective lens traverse this, so that for the

> 0 charged particles that deviate from the given energy value, no spherical or chromatic

Aberration effects occur. The corrector who is responsible for

Compensation for the energy-dependent expansion of the

Particle beam strong electric and magnetic fields

5 can be equipped with a small opening, while the first deflector is used for the deflection large opening required, only comparatively small electrical or magnetic fields must deliver.

The corrector changes the direction of the charged particles depending on their energy, so that the particle beam is expanded. Only the direction of the charged particles with the specified energy value is maintained when crossing the corrector. This is achieved when the ratio of the field strengths from the first magnetic field, B, to the first electric field, E, which is perpendicular thereto, essentially by the relationship:

given is. SQRT (m / 2W) is the square root

(m / 2W), where m is the mass of the charged particles, E is the electric field strength perpendicular to the particle beam and B is the magnetic field strength perpendicular to the particle beam and perpendicular to the electric field. Eq. (6) holds in the first approximation for non-relativistic particle energies and must be expanded in the case of relativistic energies of the charged particles.

By maintaining the direction of the charged particles with a given energy value, the opening of the corrector can be chosen so small that it has to be adapted to the expansion of the particle beam, but not to an additional deflection of the particle beam. The directions of the charged particles with the predetermined energy value are preferred by the correction. _..._, i maintain that the changes in the particle trajectories are less than 3 degrees and preferably less than 1 degree.

The changes in direction carried out on the charged particles are such that the subsequent deflector focuses the changed-direction and the direction-left charged particles. This is achieved that the size and direction of the first electric field E and the first magnetic field B are set such that the energy-dependent deflection of the particle beam by the second electric or the second magnetic field of the deflector, the expansion of the particle beam by the first electric field E and the first counteracts magnetic field B of the corrector.

The fact that the deflector with the charged particles

If the predetermined energy value is deflected away from the beam axis, it is possible that the deflector is connected directly behind the corrector, since the corrector has left the charged particles with a predetermined energy value on the beam axis.

"Connected directly behind the corrector" means that none

.5 Components that generate electrical or magnetic fields

Control of the particle beam between the corrector and deflector are arranged. This can make an energy correcting

Deflection by means of a corrector and deflector with few optical components and with little space requirement

! 0 are executed.

Due to the fact that the deflector deflects the charged particles with a predetermined energy value away from the beam axis, it is also possible for the objective lens to be arranged between the corrector and the deflector, the particle beam passing through the objective lens along the optical axis. In this case, the deflection in the particle beam direction is carried out behind the objective lens.

0 The object preferably points. ^" "^' __ a focal length that focuses the particle beam on the same point as the deflector. This enables a focal point with the smallest possible extent to be created. The smaller the focus point, the greater the resolution with which the

5 Structured or scanned particle beam apparatus. The device for energy-corrected deflection and preferably also the particle beam apparatus have a control system which controls the deflector and the corrector as a function of the predetermined deflection angle. The 5 control causes, on the one hand, that the charged particles with the specified energy value maintain their direction when passing through the corrector regardless of the specified deflection angle and the deflector focuses the charged particles on a target surface LO regardless of the specified deflection angle. The target area can be, for example, the surface of a sample to be observed, a sample to be structured and in particular a sample to be tested.

The spatial resolution when structuring

L5 or when scanning the target surface is largely limited by the focus area of the particle beam. The

The focus area is the area that the cross section of the deflected particle beam forms with the target area.

The focus area is preferably independent of the predefined one

.0 deflection angle less than ten times the

Particle beam cross section of the incident at the corrector

Particle beam. This requirement is achieved if the field strengths and field directions of the corrector and the

Field strength and field direction of the deflector are sufficient

! 5 can be coordinated.

The focus area is preferably independent of the predefined one

Deflection angle also smaller than the simple one

Particle beam cross section of the incident at the corrector

■ 0 particle beam. This experience is made possible in particular by the use of an objective lens.

Devices that superimpose electrical and magnetic fields to generate energy-dependent

5 changes in direction of charged particles

Generating particle beams are also known as Wien filters.

So far, the Vienna filter has mainly been used Energy analysis and for the separation of charged particles of different energy without the additional condition to compensate for the energy-dependent deflection errors of a subsequent deflector. 5

The corrector preferably has a first electrical multipole for generating a first electrical field and a first magnetic multipole for generating a first magnetic field. The first electric LO field and the first magnetic field preferably exert lateral forces on the charged particles, which are opposed to one another. The oppositely directed forces preferably compensate on average, so that the direction of charged particles is left with a predetermined energy.

L5

Because the energy-dependent expansion of the particle beam is twice as large due to a deflection in the electric field compared to a magnetic field with the same deflection angle (see Eq. (4) and (5)), the expansion of the particle beam by the corrector can be changed by changing the B and E field strength can be freely set with constant B / E ratio. The B and E field strengths are set according to the invention at a constant B / E ratio so that the deflector focuses the charged particles of the expanded particle beam. With a constant B / E ratio, the B and E field strengths are preferably further adjusted such that the charged particles are focused on the target surface. The charged particles are preferably further focused on the target surface with a focal area which, independently of the given deflection angle, is smaller than ten times the cross-sectional area of the particle beam incident on the corrector and preferably smaller than the simple cross-sectional area of the particle beam incident on the corrector.

The superposition of the first electric field with the first magnetic field causes the Particle beam deflection points of the first electric field and the first magnetic field are close together. The particle beam deflection point of the first electrical field results from the point of intersection which the beam axis of the incident particle beam forms with the axis of the particle beam emerging from the first electrical field when the first magnetic field is switched off. The particle beam deflection point of the first magnetic field results from the point of intersection formed by the beam axis of the incident particle beam with the beam axis of the particle beam emerging from the first magnetic field when the first electrical field is switched off.

The first electric field and the first magnetic field are preferably superimposed on one another in such a way that the particle beam deflection points of the first electric field and of the first magnetic field are closer together than 10 mm, closer than 5 mm and preferably closer than 1 mm. This ensures that the corrector not only leaves the direction of the charged particles with the specified energy value but also prevents a parallel displacement of these charged particles.

In a first preferred embodiment, the deflector has a second electrical multipole for generating the second electrical field. In this case the deflector is an electrical deflector. In a second preferred

Execution, the deflector has a second magnetic

Multipole for generating the second magnetic field. In this case the deflector is __ _lt -. _a __etic deflector. In a further embodiment, the deflector generates both a second electrical and a second magnetic field. However, the deflector preferably has either a second electrical one

Field or a second magnetic field. The deflector is therefore preferably either an electrical deflector or a magnetic deflector. In a further preferred embodiment, the first and / or second electrical multipole is an electrical dipole which has two opposite deflection plates which generate the first and / or second electrical field. The predetermined deflection of the particle beam can thus take place in the plane given by the particle beam direction and the plane given by the direction of the first electric field. When deflecting the particle beam in this plane, however, the deflected particle beam can only drive the points of a line LO on the target surface. The distance between the deflecting plates preferably determines the size of the opening of the deflector and preferably also that of the corrector.

In a further preferred embodiment, the first is

L5 and / or second electrical multipole an electrical

Quadrupole or an electrical octupole, which have deflection plates, which are preferably arranged symmetrically to the beam axis. In this case, by applying suitable voltages to the opposite one

-0 Deflection plates generate first and / or second electrical fields which can deflect the particle beam in any plane lying on the beam axis. This allows the distracted

Particle beam to control the points of a surface on the target surface. The distance preferably determines the

! 5 opposite baffles to each other the size of the

Opening of the deflector and preferably also that of the corrector.

In a further preferred embodiment, the first and / or second magnetic multipole is a magnetic dipole,

10 which generates a first and / or two fields preferably perpendicular to the beam axis. The field strength of the first and / or second magnetic field is preferably controlled by a coil current at the magnetic dipole. This allows the predetermined deflection of the particle beam in

5 of the plane perpendicular to the first magnetic field, the direction of the magnetic field being given by the orientation of the magnetic dipole. At the Deflecting the particle beam onto a target surface means that the deflected particle beam can only control the points of a line on the target surface.

In a further preferred embodiment, the first and / or the second magnetic multipole is a magnetic quadrupole or a magnetic octupole, which are preferably arranged symmetrically to the beam axis. The field strength of the first and / or second magnetic field is preferably controlled by a plurality of coil currents on the magnetic quadrupole or magnetic octupole. In this case, by applying suitable coil currents, first magnetic fields can be generated, which can deflect the particle beam in every plane lying on the beam axis. As a result, the particle beam can drive the points of a surface on the target surface when the particle beam is deflected.

If the deflector has a second electrical multipole, the first and second electrical multipoles are aligned with one another in such a way that they can generate first and second electrical fields that are parallel or antiparallel to one another on the particle beam. An energy-correcting deflection can thus be carried out in an advantageous manner.

If the deflector has a second magnetic multipole, the first and second magnetic multipoles are aligned with one another in such a way that they generate first and second magnetic fields parallel or antiparallel to one another on the particle beam. The second magnetic field in the particle beam region is preferably perpendicular to the second electrical field.

In order to obtain a first and / or second magnetic field with a sufficient and as homogeneous as possible field strength in the area of the particle beam, the coils of the magnetic multipoles are preferably saddle coils or Toroidal coils. Furthermore, the first and / or second magnetic field are preferably bundled by magnetic pole shoes.

5 Preferably, the controller automatically controls the first deflector and corrector when a predetermined deflection angle is entered, so that for each predetermined deflection angle the first electrical field required for the energy-corrected deflection, the first magnetic LO field and the second electrical or the second magnetic Field are generated automatically. The control is preferably carried out synchronously so that the energy-corrected deflection persists at all times.

-5 The controller preferably has a predetermined algorithm which calculates and executes the parameters required for controlling the corrector and the first deflector for each predetermined deflection angle. With this algorithm, preference is given to every predetermined deflection angle of the

10 particle beam calculates the voltages required for the electrodes of the electrical multipoles and the coil currents for the magnetic multipoles.

The charged particles of the particle beam are preferred

! 5 electrons generated by an electron source.

In particular, the electron source is a thermal one

Electron source by thermal excitation of the

Electrons in a filament emit them. Such

Electron sources can, for example, tungsten filament sources, LaB ₆ -

0 sources or thermisv. rc emission sources.

Thermal electron sources have the advantage that they are easy to manufacture and can be operated even under a comparatively weak vacuum. Their disadvantage is that they have comparatively high particle beams

5 Generate energy distribution so that an energy-correcting distraction is of particular importance in the case of distractions. Various embodiments of the present invention are illustrated below with reference to figures. Show it:

5

Fig. La a first embodiment of the invention

Particle beam apparatus with the objective lens behind the corrector.

LO Fig. Lb a second embodiment of the invention

Particle beam apparatus with the objective lens in front of the corrector.

2a-b show a first embodiment of an L5 device according to the invention for energy-corrected deflection with two different predetermined deflection angles.

3a-b show a second embodiment of a device according to the invention for energy-corrected deflection with two different predetermined deflection angles.

Fig. 4 shows an embodiment of a

.5 corrector.

Fig.la schematically shows a first embodiment of a particle beam apparatus 50 according to the invention. In this embodiment, the deflector 18 is in the particle beam direction

10 seen behind the lens. ,, while the corrector 5 is seen in front of the objective lens 7 in the particle beam direction. This embodiment allows the objective lens 7 to be arranged close to a target surface 22, since the deflector 18 as a simple electrical or magnetic multipole without

15 correction optics can be realized. This allows the deflector 18 to be made spatially small, so that it too can fit in with a small working distance between objective lens 7 and target surface 22.

Attaching the deflector 18 behind the objective lens 7 is therefore of importance, since as a result the particle beam 3 can always pass through the optical axis of the objective lens 7, which is preferably arranged axially symmetrically to the beam axis 20, so that chromatic and spherical errors of the objective lens 7 do not occur or hardly occur. The LO deflection by the deflector 18 only takes place after the objective lens 7 in FIG.

.5 The particle beam apparatus 50 further has a particle beam source 40, which emits charged particles into the vacuum 44. In this preferred embodiment, the particle beam source 40 is a thermal electron source, for example a LaB ₆ source, a tungsten filament source or one

! 0 thermal field emission source that emits the electrons by thermal excitation. Depending on the type of particle beam source, typical temperatures for the emission operation are in the range between 1000 C to approximately 4000 C and preferably between 1600 C and 3000 C. After the emission, the

! 5 released electrons accelerated to the specified energy value by an anode 41, which is at a specified electrical potential.

By the acceleration and preferably by 0 aperture diaphragms, which are shown in FIG. _. As shown through the opening 41a in the anode 41, the accelerated electrons form a pond beam 3 with an incident direction 2, the particle beam 3 consisting of electrons with an energy 5 scattered by the predetermined energy value. The scatter of the energy depends, for example, on the voltage stability of the voltage at the anode 41 and on the type of particle beam source 40. thermal Particle beam sources are known to produce particle beams with greater energy spread compared to cold field emission sources. In this embodiment, the energy spread of the particle beam by a predetermined 5 energy value of 20 keV is less than about 5 eV and preferably less than 2 V. This energy spread can lead to an energy-dependent expansion of the particle beam in the case of a non-energy-corrected deflection, which increases the spatial resolving power of a Particle beam apparatus -0 impaired.

The invention is largely independent of the energy of the charged particles of the particle beam. It is preferably applied to particle beam apparatus with .5 particle beams 3 in the energy range between 500 eV and 15 keV and even more preferably in the two energy ranges between 700 eV and 2000 eV or 6 keV and 10 keV.

The cross section of the incident on the corrector 5

10 particle beam can be very different depending on the application. The cross section of the particle beam 3 incident on the corrector 5 is preferably smaller than the opening of the

Corrector 5, the deflector 18 and the objective lens.

Furthermore, the smaller the cross section in comparison

5 to open the objective lens, the smaller the effects of chromatic and spherical aberration through the

Objective lens 7. The diameters are preferred

Particle beam cross sections when entering the focusing

Objective lens larger than 200 μm and preferably larger than 400

0 μm.

The corrector 5 carries out the changes of direction 15 according to the invention on the charged particles as a function of their energy, the corrector 5 being set so that the charged particles with the predetermined energy keep their direction within a deviation of 3 degrees and preferably within 1 degree , The Particle beam 3 is expanded depending on the energy due to its energy spread. La therefore shows the particle beam 9 with the charged particles with a predetermined energy value, a particle beam 9a with charged particles with an energy less than the predetermined energy and the particle beam 9b with charged particles with an energy greater than the predetermined energy value. The corrector 5 preferably does not change the energy of the charged particles of the particle beam 3 or does so by less than 1%.

LO

The energy-dependent expansion of the particle beam 3 in this embodiment is determined by the electrical field of an electrical multipole, e.g. an electrical dipole, quadrupole or octupole, and by the magnetic field of one

.5 magnetic multipoles, e.g. a magnetic dipole, quadrupole or octupole (both not shown in Fig. la). Both fields overlap, so that they preferentially exert the same opposite forces on the charged particles with predetermined energy at each point

! 0 detailed description of the electrical and magnetic fields in the corrector 5 are set out in the description of FIG. 4.

After leaving the corrector 5, the

! 5 particle beam 3 expanded onto the objective lens 7. The

In this embodiment, objective lens 7 serves to focus the particle beam 3 onto the target surface 22, which e.g. the

Surface of a sample to be observed, structured or tested. The objective lens 7 is ordinary

0 one of the electrical, magnetic, <= __ and electromagnetic

Lenses known to those skilled in the art. In a preferred embodiment, the objective lens 7 is arranged less than 60 cm, in another preferred embodiment less than 10 mm millimeters in front of the target surface 22.

5

The charged particles with predetermined energy 9 preferably pass through the objective lens along the optical axis 7. As a result, the beam of charged particles with a predetermined energy 9 is guided through the objective lens 7 without refraction, as a result of which spherical and chromatic aberration effects of the objective lens 7 are eliminated. Only 5 the rays of charged particles with energies deviating from the specified energy value, 9a and 9b, hit the objective lens outside the optical axis and are exposed to spherical and chromatic aberration effects. If the energy spread of the particle beam 3 is sufficiently small, however, these effects only play a subordinate role for the resolving power of the particle beam on the target surface 22.

After the particle beam 3 with the beams 9, 9a and

L5 9b has passed through the objective lens, it strikes the deflector 18. The deflector 18 deflects the beam of charged particles with a predetermined energy value by the predetermined deflection angle 12. Because of the energy-dependent deflection force inherent in the deflector 18, it focuses

^» 0 simultaneously the beams of the charged particles on the target surface 22, the cross section of the particle beam on the target surface forming the focus surface 24. Preferably, the first electric field and the first magnetic field of the corrector are set so that the deflector 18 at one

! 5 predetermined deflection angle 12 generates a minimum focus area 24. Due to the additional focusing by the objective lens 7, the focus area 24 can be smaller than the cross-section of the particle beam 3 when entering the corrector 5, despite the deflection. The objective lens is preferred

10 7 is set so as d ^"..-. Eil ends particle beam 3 is focused on the target surface 22.

In this embodiment, the deflector 18 has an electrical multipole electrode (not shown in FIG

5 and lb), which a second electric field to deflect the

Particle beam 3 performs. The particle beam deflection point

46 is through the intersection of the lines that the in the Describe deflector 18 incident and emerging from the deflector 18 charged particles with the predetermined energy value given. Alternatively, the deflection by the deflector 18 can also be carried out by the second magnetic field 5.

In order to be able to focus the particle beam 3 on the smallest possible focal area 24, it is advantageous to expand the particle beam 3 as a function of energy

10 to adjust the corrector 5 to the predetermined deflection angle 12. The present embodiment preferably has a controller 30 which, based on the stipulation of a predetermined deflection angle 12 via the control input 26, the electrical and electrical signals required for optimal focusing

L5 magnetic fields from the corrector 5 and the first deflector 18 are calculated and set via a control. In particular, the controller 30 can calculate the electrical and magnetic fields of the corrector 5 and the first deflector 18 such that the focus area 24 on the target area 22 is minimized

Become _0.

The controller 30 preferably also controls the objective lens 7, so that the objective lens 7 also focuses the particle beam 3 onto the target surface 20. In this

.5 case, the focus of the objective lens 7, which reduces the spatial expansion of the particle beam, coincides with the focus of the deflector 18, which returns the energetic expansion of the particle beam 3. In this case, the focus area 24 can also with a large predetermined deflection 12

10 be significantly smaller than de_ _ of the particle beam 3 when entering the corrector. The focus area 24 and thus the spatial resolution of the particle beam apparatus 50 can thus be significantly smaller than in conventional particle beam apparatuses in which the deflector is in front of the

(5 objective lens 7 is attached. Fig. Lb shows an embodiment of a particle beam apparatus 50 according to the invention as in Fig. La with the difference that the objective lens 7 is arranged in front of the corrector 5. This embodiment has the advantage that the particle beam 35 can pass through the objective lens 7 independently of the energy of the charged particles along the optical axis 7 thereof. This further reduces spherical or chromatic aberration effects through the objective lens 7 in comparison to FIG. However, for reasons of LO space it is not always possible to place both corrector 5 and deflector 18 between a target surface and objective lens 7.

The advantage of the energy-correcting distraction

.5 to perform a corrector 5 according to the invention and a deflector 18 according to the invention is furthermore in FIG. 1b that the strong first electrical and first magnetic required for an energy-dependent correction

Field can be generated in a corrector with a small opening

! 0 can, since the particle beam 3 in the corrector 5 is not deflected but only widened. This reduces the outlay in terms of equipment in order to have to generate strong electrical and magnetic fields with a large opening. A large opening is only required for the deflector 18, but only where

: 5 a comparatively weak electrical or magnetic

Field strength is required to deflect the particle beam 3.

2a and 2b show an embodiment of the device 1 according to the invention, e.g. in one

0 particle beam apparatus 50 in _ _.._ or lb can be installed. 2a and 2b show the device 1 with a particle beam 3 incident from the direction of incidence 2, which is deflected in an energy-corrected manner by two predetermined deflection angles 12.

5

The particle beam 3 incident from the direction of incidence 2 first falls on the corrector 5 has a first electrical multipole 71 and a first magnetic multipole 74. The first electrical multipole 71 generates the first electrical field 70, which exerts a lateral force on the incident particle beam 3. 5 The first magnetic multipole 74 generates a first magnetic field 73, which exerts a lateral force on the incident particle beam 3, which counteracts the lateral force of the first electrical field 70.

LO The ratio of the two field strengths is set so that the forces on the charged particles with the specified energy value compensate on average. As a result, the direction of the incident charged particles with the predetermined energy value when crossing the

Leave L5 corrector 5. Furthermore, the orientation of the first electric field 70 and the first magnetic field 73 is set such that charged particles with an energy smaller than the predetermined energy value experience a change in direction that corresponds to the predetermined deflection angle

! 0 12 is opposite. A beam of such charged particles is designated by 9a in FIG. 2a. Through the same fields, a beam of charged particles with an energy higher than the predetermined energy value undergoes a change in direction that is in the same direction as that of the

! 5 has a predetermined deflection angle 12. A beam of such charged particles is designated by 9b in FIG. 2a.

The first electrical multipole 71 and the first magnetic multipole 74 are preferably oriented such that the first

.0 electric field 70 at T < _C n ₀ __. Ahl 3 perpendicular to the particle beam 3 and the first magnetic field 73 on the particle beam 3 perpendicular to the particle beam 3 and perpendicular to the first electric field 70. In a preferred embodiment, the first electrical multipole 71 and the

5 first magnetic multipole 74 dipoles. This is a simple structure, but the particle beam 3 can only be in one given by the orientation of the dipoles given plane.

In a preferred embodiment, the first 5 electrical multipole 71 and the first magnetic multipole 74 are quadrupoles or octupoles. In this embodiment, the plane in which the particle beam 3 is expanded can be freely set by the selection of suitable voltages at the electrodes of the electrical multipole 71 and suitable currents in the coils LO of the magnetic multipole 74. An energy-corrected deflection in any desired plane that leads along the beam axis 20 is thus possible through a suitable control of the field strengths.

L5 The particle beam 3 widened by the corrector 5 then enters the deflector 18. In this preferred embodiment, the deflector 18 has a second electrical multipole 61 which generates a second electrical field 60. The second is analogous to the corrector 5

! 0 electrical multipole 61 preferably a dipole, quadrupole or octupole, depending on whether the first electrical multipole 71 is a dipole, quadrupole or octupole. The second electrical multipole 61 is preferably arranged symmetrically to the beam axis 20. In this way it can be guaranteed

5 that the second electrical field 60 of the deflector 18 is aligned parallel or antiparallel to the first electrical field 70 of the corrector 5. This can ensure that the deflection by the predetermined deflection angle 12 takes place in the same plane as the changes in direction 15

0 of the particle beam 3 through u__riktor 5, which is necessary for the most complete possible energy correction for the given deflection.

Because having an electric field on charged particles

5 small energy performs a greater change of direction than on charged particles with high energy, the beam of charged particles with an energy smaller than that predefined energy 9a deflected more than the beam of charged particles with an energy greater than the predefined energy 9b. As a result, the charged particles are focused in order to form the focus surface 24 on the target plane.

FIG. 2a further shows a controller 30, which preferably matches the field strengths of the electrical and magnetic fields of the corrector 5 and deflector 18 to one another. This is

LO is particularly necessary if the predefined deflection angle 12 is changed continuously, since for each predefined deflection angle 12 changed electrical and magnetic fields must be applied in the corrector 5 and the first deflector 18. In particular, if the focus area 24

.5 should be made small or even minimized at the same time on the target area 22, the field strengths of the corrector 5 and the first deflector 18 must be precisely coordinated. This coordination is preferably based on a calculation using a predetermined algorithm in the controller 30

'0 performed.

Fig. 2b shows the device 1 with the difference to Fig. 2a that the predetermined deflection angle 12 is larger. The larger change in the deflection angle 12 requires a stronger one

5 second electric field 60 for deflecting and at the same time a larger expansion of the particle beam 3 in the corrector 5, so that the particle beam is focused on the target surface with the smallest possible focus surface 24. The larger expansion of the particle beam 3 in the corrector 5 occurs

0 by increasing the field _._ of the first electric field 70 and the first magnetic field 73 while maintaining the ratio of the two field strengths to one another.

3a and 3b show the same device 1 as in FIGS. 2a and 2b with the difference that the deflector 18 has a second magnetic multipole 64 for generating the second magnetic field 63. In this embodiment, the particle beam is deflected by the predetermined deflection angle 12 not by an electric field but by the second magnetic field 63, which is generated by a second magnetic multipole 64. The direction of the second magnetic field 63 is preferably the same as the direction of the first magnetic field 73 in order to achieve an optimal energy correction during deflection. In particular, the second magnetic multipole 64 is preferably a dipole, quadrupole or LO octupole, depending on whether the first magnetic multipole 74 is a dipole, quadrupole or octupole.

In the device 1 in Fig. 3a and 3b, it is necessary that the 12 for each predetermined deflection angle

L5 fields of the corrector 5 must be reset if one wants to achieve a minimum focus area 24 on a predetermined target area 22. Thus, the processing of the particle beam 3 by the corrector 5 in Fig. 3b is significantly larger by the particle beam 3 by the much larger

10 deflect deflection angle 12 and focus on a comparable large focus area 24

4a and 4b show a schematic embodiment of a corrector 5 with a magnetic quadrupole and a: 5 electrical quadrupole. 4a shows a cross section through the corrector 5 in the plane perpendicular to the beam axis 20, FIG. 5b shows the same corrector 5 from the side along the beam axis 20.

0 In a housing 116 si: "" coils 108 with the four

Pole shoes 110 attached, which are each rotated at a 90 degree angle to one another and together form the magnetic quadrupole. The four coils 108 and the four pole shoes 110 are preferably symmetrical to the beam axis

5 20 arranged. By applying suitable currents to the four coils 108, a first magnetic field perpendicular to the __ _

29

Beam axis 20 are generated with any direction of rotation about the beam axis 20.

5 four baffle plates 106 are furthermore attached symmetrically to the four pole shoes 110, which together form the electrical quadrupole. By applying suitable voltages to the four deflection plates 106, a first electric field perpendicular to the beam axis 20 can be generated with any direction of rotation about the beam axis 20. Furthermore, by applying suitable voltages to the deflection plates 106, it is possible for the first electrical field to be oriented perpendicular to the beam direction 20 and perpendicular to the direction of the first magnetic field. As a result, the corrector 5 can expand the particle beam 3 in each plane along 5 the beam direction, so that the particle beam 3 can be deflected in any direction with the aid of the deflector 18 in an energy-corrected manner.

Due to the high geometric symmetry between the four

20 magnetic pole pieces 110 and the four deflection plates 106 with respect to the beam axis 20 ensures that the first magnetic field and the second electrical field can be perpendicular to one another with high precision on the beam axis 20; due to the largely identical arrangement of the

5 electric baffles 106 and magnetic pole pieces 110 with respect to a position of the particle beam path can furthermore be achieved that the particle beam deflection point of the electrical quadrupole from the particle beam deflection point of the magnetic quadrupole by less than 10 mm and i0 preferably less than 5 mm. -...- _^ , he are removed. The smaller this distance, the smaller the parallel offset between the particle beam entering the corrector 5 and the particle beam emerging from the corrector 5. 4b is one for second electrical and second

5 drawn magnetic field common particle beam deflection point 46, the distance between the two particle beam deflection points being less than 10 mm. In this embodiment, the diameter of the opening 114 is given by the distance between the opposite baffle plates 106. Because the corrector 5 does not deflect the particle beam but only widens it, the diameter of the opening 114 can be kept small, which significantly reduces the expenditure for the generation of the necessary first electrical and first magnetic field.

10

The corrector 5 with the electrical or magnetic quadrupole is only one example of how the corrector can be constructed. For many applications, electrical and magnetic dipoles are sufficient instead of quadrupoles. The two

L5 dipoles can be designed similarly as shown in FIGS. 4a and 4b, the difference preferably being that instead of the four pole shoes, coils and deflection plates rotated by 90 degrees to one another, only two pole shoes, coils and deflection plates rotated by 180 degrees to one another are arranged are. 0

Similarly, the corrector 5 can have electrical and magnetic octupoles instead of dipoles or quadrupoles. The electrical and magnetic octupoles have instead of the four pole shoes rotated 90 degrees to each other,

_5 coils and baffles each on eight pole pieces, coils and baffles rotated by 45 degrees to each other. With octupoles, with a rotation of the electrical and magnetic dipole fields around the beam axis 20, an even greater homogeneity of the first electrical and the first

10 magnetic fields on the street ___. _* _: 20 can be achieved. Legend

1 device

2 direction of incidence 3 particle beam

5 corrector

7 objective lens

9 Beam of charged particles with a given energy value

9a Beam of charged particles with an energy less than the specified energy value

9b Beam of charged particles with an energy greater than the specified energy value

12 specified deflection angles

15 Change of direction

18 deflectors

20 optical axis 1 beam axis

22 target area

24 focus area

26 control input

30 control

0 particle beam source 1 anode 1a opening of the anode 4 vacuum 6 particle beam deflection point 8 opening of the corrector

0 particle beam apparatus

0 second electrical field 1 second electrical multipole 3 second magnetic field 4 second magnetic multipole first electrical field first electrical multipole first magnetic field first magnetic multipole

Claims

claims

1. particle beam apparatus (50) with:

5 a particle beam source (40) for generating a particle beam (3) from charged particles with energies scattered by a predetermined energy value;

LO of an objective lens (7) with an optical axis (20), the charged particles with the predetermined energy value crossing the objective lens (7) along the optical axis (20);

L5 a corrector (5) which, by means of a first electric field (70) and a superimposed first magnetic field (73), changes the direction (15) of the charged particles as a function of their energy, the charged particles having the predetermined energy value at

! 0 Maintain direction by crossing the corrector (5); and

a deflector (18), which is connected downstream of the corrector (5) and the objective lens (7) and which uses a second electrical field (60) or a second magnetic field (63) to charge the charged particles with the predetermined energy value by a predetermined value Deflection angle (12) deflects away from the optical axis (20), the charged particles being focused.

2nd Particle beam apparatus according to claim 1, so that the objective lens (7) is connected downstream of the corrector (5) 5.

3rd Particle beam apparatus according to claim 1, characterized in that the corrector (5) is connected downstream of the objective lens (7).

₅ 4. Particle beam apparatus according to one of the preceding claims, characterized in that a controller (30) controls the corrector (5) and the deflector (18) so that the charged particles with the

10 predetermined energy value when crossing the corrector (5) regardless of the predetermined deflection angle (12) maintain their direction and the deflector (18) focuses the charged particles regardless of the predetermined deflection angle (12) on a target surface (22).

L5

5. Device (1) for energy-corrected deflection of a particle beam (3) incident along a beam axis (21) by a predetermined deflection angle -0 (12), the particle beam (3) consisting of charged particles with energies scattered by a predetermined energy value

a corrector (5) which, by means of a first electric field (70) and a superimposed first magnetic field (73), changes the direction (15) of the charged particles as a function of their energy, the charged particles having the predetermined energy value when crossing maintain the direction of the corrector (5); 0 a deflector (18), which is connected downstream of the corrector (5) and which, by means of a second electrical field (60) or by means of a second magnetic field (63), charges the charged particles with the predetermined energy value by 5 a predetermined deflection angle (12) deflects the beam axis (21) away; and a controller (30) which controls the corrector (5) and deflector (18) so that the charged particles with the predetermined energy value pass through the corrector (5) regardless of the predetermined deflection angle (12) and the deflector (18) the charged particles are focused on a target surface (22) regardless of the predetermined deflection angle (12).

LO

6. Apparatus according to claim 5 or particle beam apparatus according to one of claims 1 to, that the corrector (5) has a first electrical multipole (71) for generating the first electrical field (70) and one

L5 has first magnetic multipole (74) for generating the first magnetic field (73).

7. Device according to one of claims 5 to 6 or particle beam apparatus according to one of claims 1 to 4,

The deflector (18) has a second electrical multipole (61) for generating the second electrical field (60) or a second magnetic multipole (64) for generating the second magnetic field (63).

! 5

8. The device or particle beam apparatus according to claim 6 or 7, characterized in that the second electrical multipole (61) and / or the first 0 electrical multipole (71). ^"" _.___. are the dipoles and / or the second magnetic multipole (64) and / or the first magnetic multipole (74) are magnetic dipoles.

9. Device or particle beam apparatus according to one of 5 claims 6 to 7, characterized in that the second electrical multipole (61), the first electrical multipole (71), the second magnetic multipole (64) and / or the first magnetic multipole (74) are magnetic or electrical octupoles. 5

10.Device or particle beam apparatus according to one of claims 6 to 9 d a d u r c h g e k e n n z e i c h n e t that the first magnetic multipole (74) and / or second LO magnetic multipole (64) has saddle coils or toroidal coils.

11. Device according to one of claims 5 to 10 or

Particle beam apparatus according to one of claims 1 to 4,. 5 d a d u r c h g e k e n n z e i c h n e t that the first magnetic field (73) and / or the second magnetic field (63) is bound by magnetic pole pieces11.

: 0

12.Device according to one of claims 5 to 10 or particle beam apparatus according to claim 4, d a d u r c h g e k e n n z e i c h n e t that the controller (30) the first electrical multipole (71), the first magnetic multipole (74) and the deflector

5 (18) controlled synchronously.

13.Device according to one of claims 5 to 10 or

Particle beam apparatus according to one of claims 1 to 4, characterized in that 0 the charged particles Ele. _* _, lnd, which are generated by an electron source, in particular by a thermal electron source.

14.Method for the energy-corrected deflection of a particle beam (3) incident along a beam axis (21) by a predetermined deflection angle (12), the particle beam (3) consisting of charged particles having a given energy value is scattered energies, with the steps:

make changes of direction (15) to the charged 5 particles of the incident particle beam (3) in

Dependence on their energy; wherein the charged particles maintain their direction with the given energy value;

0 deflect the charged particles with the predetermined energy value by the predetermined deflection angle (12) away from the beam axis (21); focusing the charged particles; and

5 control the direction changes (15) so that the charged particles are focused regardless of the deflection angle (12).

15. The method according to claim 14,

20 d a d u r c h g e k n n z e i c h n e t that the

Particle beam (3) is focused, the focus area (24) regardless of the predetermined deflection angle (12) smaller than ten times the cross-sectional area of the particle beam (3) at the point of direction changes (15)

5 and is preferably smaller than the simple cross-sectional area of the particle beam (3) at the point of the direction changes (15).