Patent Application
20190096632
This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2017-185151 filed on Sep. 26, 2017 in Japan, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a charged particle beam irradiation apparatus and a method for reducing electrification of a substrate and relates to, for example, a method for reducing electrification generated on a substrate due to irradiation with an electron beam.
In recent years, with an increase in integration density of an LSI, a circuit line width of semiconductor devices is getting still smaller. As a method for forming an exposure mask (also referred to as a reticle) to form a circuit pattern on these semiconductor devices, an electron beam (EB) lithography technique having excellent resolution is used.
Irradiating a substrate with an electron beam causes a problem that the upper surface of the substrate is charged. Electrification of the substrate surface leads to deterioration in writing accuracy. Thus, in order to eliminate such electrification, passing an ion gas for neutralization onto the substrate is considered. In addition, contaminants such as particles adhering to the substrate and the like cause deterioration in writing accuracy. In order to remove such contaminants, discharging plasma or the like onto the substrate is considered. Such a problem occurs not only in an electron beam lithography apparatus, but also in an apparatus for irradiating a target object with an electron beam such as an electron microscope and an electron beam inspection apparatus. For example, arranging an ion and plasma generating apparatus for supplying an ion gas in a chamber of a scanning electron microscope (SEM) is disclosed (see Japanese Unexamined Patent Application Publication No. 2007-149449, for example). However, if an ion generating apparatus is arranged near or inside an apparatus that emits an electron beam, the scale of the apparatus becomes large. In addition, when such an ion generating apparatus generates a magnetic field, problems such as a magnetic field generated by an electromagnetic lens constituting an original electron beam optical system of the electron beam lithography apparatus being likely to be affected may occur.
According to one aspect of the present invention, a charged particle beam irradiation apparatus includes:
an emission source configured to emit a charged particle beam;
an electromagnetic lens configured to refract the charged particle beam;
a plurality of electrodes arranged in a magnetic field space of the electromagnetic lens and also arranged so as to surround a space on an outer side of a passing region of the charged particle beam; and
a potential control circuit configured to control potentials of the plurality of electrodes so as to generate plasma in the space surrounded by the plurality of electrodes and so as to control movement of positive ions or electrons and negative ions generated by the plasma, wherein
positive ions, electrons and negative ions, or active species are emitted from the space of the plasma.
According to another aspect of the present invention, a method for reducing electrification includes:
controlling potentials of a plurality of electrodes arranged in a magnetic field space of an objective lens that focuses a charged particle beam on a substrate surface and also arranged so as to surround a space on an outer side of a passing region of the charged particle beam to cause the plurality of electrodes to generate plasma in the space surrounded by the plurality of electrodes and also to control movement of positive ions or electrons and negative ions generated by the plasma; and
reducing electrification of the substrate by allowing to emit the positive ions or the electrons and negative ions from the space of the plasma toward the substrate.
In Embodiments described below, an apparatus and a method capable of reducing charging or/and removing contaminants without affecting a magnetic field generated by an electromagnetic lens constituting a charged particle beam optical system inherent to the apparatus that emits a charged particle beam will be described.
In Embodiments described below, the configuration using an electron beam will be described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and a beam such as an ion beam using charged particles may also be used. Also, an electron beam lithography apparatus will be described as an example of a charged particle beam irradiation apparatus. However, the charged particle beam irradiation apparatus is not limited to a lithography apparatus and may be any apparatus that uses an electromagnetic lens in an optical system and emits a charged particle beam such as an electron microscope or an electron beam inspection apparatus. Further, as an example of the electron beam lithography apparatus, a variable-shaped beam type lithography apparatus and a multiple-beam lithography apparatus will be described.
The control system circuit 160 has a control computer 110, a memory 112, a deflection control circuit 120, a lens control circuit 122, a potential control circuit 124, a gas control circuit 126, and storage devices 140, 142 such as a magnetic disk drive. The control computer 110, the memory 112, the deflection control circuit 120, the lens control circuit 122, the potential control circuit 124, the gas control circuit 126, and the storage devices 140, 142 are mutually connected via a bus (not shown). The deflector 208 is connected to the deflection control circuit 120 and controlled. Also, though not shown, the blanking deflector 212 and the deflector 205 are connected to the deflection control circuit 120 and controlled. The objective lens 207 is connected to the lens control circuit 122 and controlled. Also, though not shown, the illumination lens 202 and the projection lens 204 are connected to the lens control circuit 122 and controlled. The electrodes 220, 222, 224, 226 are connected to the potential control circuit 124 and controlled. Also, the potentials of the substrate 101 and the retarding electrode 228 are controlled by a power supply device (not shown) or the like.
Necessary input data or computed results in the control computer 110 are stored in the memory 112 each time.
Pattern writing data (chip data) in which data of a chip pattern is defined is input from outside the lithography apparatus 100 and stored in the storage device 140.
Here, in
When a pattern writing process is performed, the control computer 110 controls the deflection control circuit 120, the lens control circuit 122, the potential control circuit 124, the gas control circuit 126, the pattern writing mechanism 150 and the like to start the pattern writing process. The control computer 110 reads the chip data (pattern writing data) stored in the storage device 140 and divides a plurality of figure patterns in the chip data into a plurality of shot figures of a size that can be shaped by the lithography apparatus 100 for each figure pattern to generate shot data for each shot figure. The shot data defines the figure type, the shot position coordinates of the figure, the shot size, and the like. The generated shot data is stored in the storage device 142. Then, the pattern writing mechanism 150 writes a pattern to each shot position using the electron beam 200 under the control of the deflection control circuit 120 and the lens control circuit 122. A more specific operation is as described below.
The current distribution of the electron beam 200 emitted from the electron gun assembly 201 (emission source) is limited to the vicinity of the distribution center by the beam limiting aperture plate substrate 214, and when passing through the blanking deflector 212, for example, a portion of the electron beam 200 is controlled by the blanking deflector 212 to pass through the opening provided in the first shaping aperture plate substrate 203 in the beam ON state, and the electron beam 200 is deflected such that none thereof passes through the opening provided in the first shaping aperture plate substrate 203 and the electron beam is totally blocked by the first shaping aperture plate substrate 203 in the beam OFF state. The duration between the two consecutive changes of state, a change from the beam off state to the beam on state and a change from the beam on state to the beam off state, is the duration of one shot of electron beam. The blanking deflector 212 controls the direction of the passing electron beam 200 to alternately generate the beam ON state and the beam OFF state. For example, no voltage is applied in the beam ON state, and a voltage may be applied to the blanking deflector 212 when the beam is OFF. The dose per shot of the electron beam 200 with which the substrate 101 is irradiated is adjusted in the beam irradiation time of each shot.
In the beam ON state, as described above, the electron beam 200 having passed through the beam limiting aperture plate substrate 214 and the blanking deflector 212 illuminates the entire first shaping aperture plate substrate 203 having a rectangular hole through the illumination lens 202. Here, the electron beam 200 is first shaped into a rectangular shape. Then, the electron beam 200 of a first aperture plate image having passed through the first shaping aperture plate substrate 203 is projected onto the second shaping aperture plate substrate 206 by the projection lens 204. The first aperture plate image on the second shaping aperture plate substrate 206 is controlled to deflect by the deflector 205 so that the beam shape and dimensions can be changed (variably shaped). Such variable shaping is performed for each shot and beam shapes and dimensions are normally different for each shot. Then, the electron beam 200 passing through the second aperture plate is focused on the surface of the substrate 101 by the objective lens 207 so that the cross section of the electron beam 200 passing through the second aperture plate is imaged on the substrate 101. This is called. Then, the electron beam 200 is deflected to irradiate a desired position on the surface of the substrate 101 by the deflector 208. In other words, the electron beam 200 is irradiated on a desired position of the substrate 101 placed on the continuously moving XY stage 105. As described above, a plurality of shots of the electron beam 200 is successively made on the substrate 101. As described above, the electron beam 200 proceeds to the surface of substrate 101 while being refracted by each electromagnetic lens such as the illumination lens 202, the projection lens 204, and the objective lens 207.
Since each electrode is exposured to high-temperature plasma, the heat inflow from the plasma may become large depending on the conditions of plasma. Therefore, a cooling means is provided if necessary. For example, water-cooled piping may be attached to the outside of the electrode so that cooling water is circulated using a constant-temperature water circulation device via a pipe made of an insulator. This also applies to other Embodiments.
The potential control circuit 124 (potential control unit) according to Embodiment 1 controls the potentials of a plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226 so as to generate plasma in the space 14 surrounded by the plurality of electrodes and so as to control the movement of positive ions, or electrons and negative ions generated by the plasma. A more specific operation is as described below. Plasma is generated in the space 14 in a vacuum state surrounded by the plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226 using the plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226 and a magnetic field space of the objective lens 207. The plasma is generated by, for example, the Penning discharge. Here, the Penning discharge is a discharge that, by providing a space including a region of low potential on both ends of a region of high potential along lines of magnetic force, traps electrons in the region of high potential, thereby generating or maintaining a discharge of a gas in the space. A potential Vout is applied to the outer electrode 220 and a potential Vin is applied to the inner electrode 222 from the potential control circuit 124 while allowing a predetermined gas to flow from the gas supply line 132 in a state where a strong longitudinal magnetic field is generated by the objective lens 207 in the space 14 surrounded by the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226.
In this case, the same potential is applied as the potential Vout of the outer electrode 220 and the potential Vin of the inner electrode 222. When the potential Vout of the outer electrode 220 and the potential Vin of the inner electrode 222 become higher than the potentials of the upper electrode 224 and the lower electrode 226 by a predetermined potential difference or more, plasma by the Penning discharge can be generated in the space 14. It is effective to reduce the amount of supply gas necessary to maintain discharge by closing gap portions of the four electrodes 220, 222, 224, 226 with an insulator such as ceramic so as to provide airtightness to suppress the outflow of the supplied gas from the space 14. Also, the load of an exhaust system required for maintaining the vacuum in a region through which the electron beam passes can be reduced. Further, for example, a vacuum evacuation pipe may be connected to a position different in phase from the gas supply line 132 of the upper electrode 224 from outside so that evacuation of the space 14 can be performed.
It is effective in improving controllability of the pressure in the space 14 to make the evacuation speed of the vacuum evacuation pipe changeable. In order to efficiently start the discharge, a material that emits thermoelectrons by a tungsten filament or the like being heated may be installed near the upper electrode 224 so that the discharge is started by passing a current from an external power source for heating to emit electrons. Even if the filament current is stopped after the discharge starts normally, the discharge continues. As a method for assisting the discharge start, a high-frequency wave generated by a high frequency source placed outside the electron optical column is guided to the boundary of the space 14 by using a coaxial waveguide to be able to generate plasma by discharging the high-frequency wave into the space 14 using an antenna provided at the waveguide outlet, for example, a loop antenna or a horn antenna. The frequency of the microwave is set to, for example, an electron cyclotron frequency corresponding to the magnetic flux density near the center of the space 14 and plasma is generated by accelerating electrons by the electron cyclotron resonance phenomenon to promote the ionization phenomenon. The electron cyclotron frequency corresponding to the magnetic flux density 1T is about 28 GHz. In addition, introducing the high-frequency wave continuously is effective in maintaining the discharge. The electrons (e−) in the space 14 are restricted in movement in the radial direction by a strong longitudinal magnetic field. Further, electrons in the space 14 are also restricted in movement in the vertical direction by applying a potential Vup lower than the potential Vout and the potential Vin to the upper electrode 224 and also applying a potential Vdown lower than the potential Vout and the potential Vin to the lower electrode 226. For example, a magnetic field of 4 to 6 kG is generated by the objective lens 207. In such a magnetic field space, the potential difference between Vin, Vout and Vup, Vdown is set such that Vin, Vout are higher by, for example, about 1 kV. For example, 50 V is applied as the potential Vout. As the potential Vin, for example, 50 V, which is the same potential as the potential Vout, is applied. For example, −850 V is applied as the potential Vup. For example, −950 V is applied as the potential Vdown. The retarding electrode 228 is grounded. Due to this effect, trapped electrons ionize the gas molecules supplied from the gas supply line 132 to generate ions (for example, positive ions X+). At the same time, neutral active species (O*) such as radicals are generated. X+ is decelerated by an electric field between the lower electrode 226 and the retarding electrode 228 to become low-energy ions mainly of about 50 eV or less before reaching the surface of the target object. Ions of higher energy can be emitted on average by increasing the energy level of Vin, Vout, Vup, Vdown as a whole.
Incidentally, a grid structure may be adopted for the upper electrode 224 instead of a plate-like material so that, as shown in a modification of
Further, a filament made of a refractory metal, for example, tungsten may be installed near the opening 227 of the retarding electrode 228 so that electrons can be caused to reach the surface of the target object together with ions by supplying a current from an external power source (not shown) to heat the filament to emit electrons. In this manner, positive ions and electrons of low energy can reach the surface of the substrate 101. When the substrate surface is negatively charged, positive ions are absorbed by the substrate 101 and when positively charged, electrons are absorbed. Accordingly, electrification of the surface of the substrate 101 can be alleviated.
In Embodiment 1, as described above, ions (for example, positive ions X+), electrons (e−), and active species (O*) can be generated in the space 14 surrounded by a plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226 by arranging the plurality of electrodes in the magnetic field space of the objective lens 207 and applying respectively set potentials. The electrification reduction (or removal) of the substrate 101 and/or the cleaning of contaminants (contamination removal) is performed using such ions (for example, positive ions X+), electrons (e−), and active species (O*). A gas that is not particularly ionized is sufficient as the gas supplied from the gas supply line 132. For example, an oxygen gas, a hydrogen gas, or a rare gas such as helium or argon is suitably used. Alternatively, water vapor may also be used.
As the gas supply process (S102), the gas supply device 130 supplies a gas into the electromagnetic lens (for example, the objective lens 207) through the gas supply line 132 under the control of the gas control circuit 126. Incidentally, as will be described below, the gas supply device 130 (supply mechanism) supplies a gas to the plasma space.
As the plasma generation process (S104), the potential control circuit 124 controls the potentials of a plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226 arranged in a magnetic field space of the objective lens 207 that focuses the electron beam 200 on the surface of the substrate 101 and arranged so as to surround the space 14 on the outer side of the passing region 12 of the electron beam 200 to cause the plurality of electrodes to generate plasma in the space 14 surrounded by the plurality of electrodes and also to control the movement of positive ions, or electrons and negative ions generated by the plasma. More specifically, the potential control circuit 124 applies the potential Vout to the outer electrode 220 and the potential Vin, which is the same potential as the potential Vout, to the inner electrode 222. Then, a potential Vup lower than the potential Vout and the potential Vin is applied to the upper electrode 224 and a potential Vdown lower than the potential Vup is applied to the lower electrode 226. By applying such potentials, plasma by the Penning discharge can be generated in the space 14. At the same time, the vertical movement of electrons in the space 14 is also restricted.
However, due to the influence of the electric field and the magnetic field between the electrodes 224, 226 and the electrodes 220, 222, the gyrating center of electrons moves in the circumferential direction while the electrons are gyrating by the magnetic field. This is called an E×B (E cross B) drift. For the E×B drift, there is also an electric field arising from the charge distribution in plasma 14. Also, when the lines of magnetic field has a curvature, the gyrating center moves in the circumferential direction. Since the curvature of a magnetic field line is accompanied with a gradient of the amplitude of the magnetic flux density, and the latter also causes a drift, respective contributions are called a curvature drift and a gradient B drift.
As the emission process (S106), positive ions, electrons and negative ions, or active species are released from the space 14 of plasma. In the example of
Alternatively, positive ions (X+) may be emitted from the space 14 toward the substrate 101 by daring to apply the negative potential Vsb to the substrate 101 from a power source indicated by a dotted line in
When a strong lens magnetic field is applied to the vicinity of the substrate 101 (a space from an opening (229 in this example) for emitting ions or electrons to a desired region of the substrate 101), the trajectory of positive ions is bent. Thus, by making the distance from the ion extraction port (opening) 229 to the desired region on the substrate 101 shorter than the reachable distance of ions, the ions can be made to reach the desired region. In the case of a uniform magnetic field, the distance should be shorter than twice the Larmor radius of the ion. For example, the Larmor radius ((√(2·MV/e))/B) in a uniform magnetic field B=1 kG of a monovalent positive argon ion (mass M=40×1.67e−27 kg) with energy eV=50 eV is about 6.5 cm and so, positive ions of argon can be made to reach the desired region by bringing the ion extraction port 229 closer to the desired region such that the distance therebetween is shorter than twice the Larmor radius. The potential applied to each electrode and the amount of supply gas are adjusted so that emitted ions reach the desired position of the substrate with desired energy as a desired current.
When a strong lens magnetic field is applied to the vicinity of the substrate 101, the mass of an electron is light and thus, it is difficult for electrons to reach a desired region on the surface of the substrate 101 because the trajectory thereof is easily bent by the magnetic field. On the other hand, the mass of a negative ion is large and thus, it is possible for negative ions to reach a desired position. For example, taking the negative ion O2− of a monovalent oxygen molecule (mass M=2×16×1.67e−27 kg) with energy eV=50 eV in a uniform magnetic field of B=1 kG as an example, the Larmor radius (√/(2·MV/e))/B) is about 6 cm and so, negative ions of oxygen can be made to reach the desired region by bringing the ion extraction port 229 closer to the desired region as compared with twice the Larmor radius. The potential applied to each electrode and the amount of supply gas are adjusted so that emitted ions reach the desired position of the substrate with desired energy as a desired current.
In Embodiment 1, as described above, positive ions or electrons (and negative ions) can be emitted in accordance with the sign of electrification even when the surface of the substrate 101 is charged positively or negatively so that the electrification can be reduced or eliminated. Thus, Embodiment 1 can be applied regardless of the charged state. In addition, the electrode 226 may have a grid structure with a high opening ratio so that the electric field between the electrodes 226 and 227 can be made to penetrate the inner side of the electrode 226. The configuration can efficiently extract electrons (e−) and negative ions generated near the electrode 226 and thus is useful in extracting particularly electrons (e−) and negative ions.
In addition, by switching the voltage applied to the electrodes while continuing the plasma generation, it is possible to switch the extraction of positive ions, and electrons and negative ions.
The energy distribution and types (positive ions, negative ions/electrons) of charged particles (ions, electrons) emitted to the surface of the target object can be controlled by exercising control so as to change the potentials while maintaining the potential difference of Vin, Vout, Vup, Vdown. Further, the energy distribution of emitted charged particles can be controlled by further providing one or a plurality of grid structure electrodes between the electrode 226 and the electrode 228 and controlling the potential distribution thereof.
Alternatively, by daring to apply a negative potential to the substrate 101 from a power source indicated by a dotted line in
Also when the electrification reduction of the substrate 101 described above with reference to
In the above examples, the electrification reduction and/or impurity removal of the substrate 101 has been described, but Embodiment 1 is not limited to such examples.
As shown in
In the example of
In the above example, a case where the outer electrode 220 and the inner electrode 222 are used as a configuration in which plasma is to be generated in the magnetic field space on the outer side the passing region 12 of the electron beam 200 by Penning discharge has been described, but Embodiment 1 is not limited to such a case.
In the modification of Embodiment 1, as described above, ions (for example, positive ions X+), electrons (e−), and active species (O*) can be generated in the space 14 surrounded by a plurality of electrodes such as the plurality of ring electrodes 221 arranged in the circumferential direction, the upper electrode 224, and the lower electrode 226 by arranging the plurality of electrodes in a magnetic field space of the objective lens 207 and applying respectively set potentials. The electrification reduction (or removal) of the substrate 101 and/or the cleaning of contaminants (contamination removal) is performed using such ions (for example, positive ions X+), electrons (e−), and active species (O*). The way of reducing (or removing) the electrification of the substrate 101 or/and cleaning of contaminants (contamination removal) is the same as in the example of
According to Embodiment 1, as described above, it is possible to reduce the electrification of the substrate 101 or/and to remove contaminants of the substrate 101 (deflectors 205, 208) and the like without affecting a magnetic field generated by an electromagnetic lens (for example, the projection lens 204 and the objective lens 207) constituting an electron beam optical system inherent to the apparatus that emits the electron beam 200. As a result, high-precision pattern writing can be performed.
In Embodiment 1, a case where plasma is generated by the Penning discharge using the magnetic field of an electromagnetic lens has been described, but the method for generating the plasma is not limited to such a case. In Embodiment 2, a configuration for generating plasma by a different method will be described. The configuration of the lithography apparatus 100 according to Embodiment 2 is similar to that of
The potential control circuit 124 (potential control unit) according to Embodiment 2 controls the potentials of a plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226 so as to generate plasma in the space 14 surrounded by the plurality of electrodes and so as to control the movement of positive ions, or electrons and negative ions generated by the plasma. A more specific operation is as described below. Plasma is generated in the space 14 in a vacuum state of a magnetic field space of the objective lens 207 and surrounded by a plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226. The plasma is generated here by the magnetron discharge. A potential Vout is applied to the outer electrode 220 and a potential Vin is applied to the inner electrode 222 from the potential control circuit 124 while allowing a predetermined gas to flow from the gas supply line 132 in a state where a strong longitudinal magnetic field is generated by the objective lens 207 in the space 14 surrounded by the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226. In such a case, a potential sufficiently lower than the potential Vin is applied as the potential Vout of the outer electrode 220. When the potential difference between the potential Vout of the outer electrode 220 and the potential Vin of the inner electrode 222 becomes larger than a predetermined potential difference, plasma by the magnetron discharge can be generated in the space 14. Further, a potential Vup lower than the potential Vout and the potential Vin is applied to the upper electrode 224 and also, a potential Vdown lower than the potential Vout and the potential Vin is applied to the lower electrode 226. For example, a magnetic field of 4 to 6 kG is generated by the objective lens 207. In such a magnetic field space, for example, 50 V is applied as the potential Vin. For example, −850 V is applied as the potential Vout. As the potential Vup, a potential lower than the potential Vout, for example, −1000 V is applied. As the potential Vdown, a potential lower than the potential Vup, for example, −1050 V is applied. Due to this effect, trapped electrons ionize the gas molecules supplied from the gas supply line 132 to generate ions (for example, positive ions X+). At the same time, neutral active species (O*) such as radicals are generated.
Like in Embodiment 1, a grid structure may be adopted for the upper electrode 224 instead of a plate-like material so that a structure provided with the external upper electrode 724 to which a potential approximately the same as or higher than Vin, for example, 100 V, is applied further upstream can be created.
In addition, the electrode 226 may have a grid structure with a high opening ratio so that the electric field between the electrodes 226 and 228 can be made to penetrate the inner side of the electrode 226. The configuration can efficiently extract electrons (e−) and negative ions generated near the electrode 226 and thus is useful in extracting particularly electrons (e−) and negative ions.
Here, the energy distribution and types (positive ions, negative ions/electrons) of charged particles (ions, electrons) emitted to the surface of the target object can be controlled by exercising control so as to change the potentials while maintaining the potential difference of Vin, Vout, Vup, Vdown. Further, the energy distribution of emitted charged particles can be controlled by further providing one or a plurality of grid structure electrodes between the electrode 226 and the electrode 228 and controlling the potential distribution thereof.
In Embodiment 2, as described above, ions (for example, positive ions X+), electrons (e−), and active species (O*) can be generated by plasma by the magnetron discharge in the space 14 surrounded by a plurality of electrodes such as the outer electrode 220, the inner electrode 222, the upper electrode 224, and the lower electrode 226 by arranging the plurality of electrodes in the magnetic field space of the objective lens 207 and applying respectively set potentials. The charging reduction (or removal) of the substrate 101 or/and the cleaning of contaminants (contamination removal) is performed using such ions (for example, positive ions X+) and active species (O*). A gas that is not particularly ionized is sufficient as the gas supplied from the gas supply line 132. For example, an oxygen gas, a hydrogen gas, or a rare gas such as helium or argon is suitably used. Alternatively, water vapor may also be used. In Embodiment 2, by using the magnetron discharge, it is possible to reduce or eliminate an uneven distribution of occurrence locations of ions (for example, positive ions X+), electrons (e−), and active species (O*) in the space 14 in a ring shape. Therefore, the uniformity of emission amount when ions (for example, positive ions X+) and active species (O*) are emitted toward the substrate 101 can be enhanced.
Further, a filament made of a refractory metal, for example, tungsten may be installed near the opening 227 of the retarding electrode 228 so that electrons can be caused to reach the surface of the target object together with ions by supplying a current from an external power source (not shown) to heat the filament to emit electrons.
Then, as the emission process (S106), positive ions or active species are emitted from the space 14 of plasma. In the example of
Alternatively, positive ions (X+) may be emitted from the space 14 toward the substrate 101 by daring to apply the negative potential Vsb to the substrate 101 from a power source indicated by a dotted line in
Alternatively, similarly to the example in
Also in this case, the inner electrode 222, the upper electrode 224, and the lower electrode 226 may have a double structure so that unnecessary outflow of charged particles can be suppressed.
In Embodiment 2, as described above, like in Embodiment 1, positive ions or electrons (and negative ions) can be emitted in accordance with the sign of electrification even when the surface of the substrate 101 is charged positively or negatively so that the electrification can be reduced or eliminated. Thus, Embodiment 2 can be applied regardless of the charged state.
Also here, like in the example in Embodiment 1, it is possible to adopt a double structure (222, 722) for the inner electrode and to apply a potential higher than Vin by, for example, 50 V to an electrode 222a so as to suppress the outflow of positive ions X+ flowing out from the opening 223. Further, a potential lower than Vdown may be applied to the electrode 222a to suppress the outflow of negative ions Y− flowing out from the opening 223. For the electrode 222a, a grid structure may be used, or a plate material having an opening may be used. Alternatively, by adopting a triple structure (222, 722a, 722b), it is also possible to have a structure that suppresses the outflow of both positive ions, and electrons or negative ions.
Like in Embodiment 1, it is needless to say that, instead of the opening 227 of the lower electrode 226 and the opening 229 of the retarding electrode 228, only the plurality of openings 223 may be formed in the inner electrode 222 in the radial direction. In such a case, impurities adhering to the deflector 208 due to the emission of active species (O*) to the deflector 208 side can be removed.
The potential control circuit 124 (potential control unit) generates plasma in the space 14 surrounded by the plurality of electrodes such as the plurality of cylindrical electrodes 225, the inner electrode 222, the upper electrode 224, and the lower electrode 226, and also controls the potentials of the plurality of electrodes so as to control the movement of positive ions, or electrons and negative ions generated by the plasma. A more specific operation is as described below. Plasma is generated by the magnetron discharge in the space 14 in a vacuum state surrounded by the plurality of electrodes such as the plurality of cylindrical electrodes 225, the inner electrode 222, the upper electrode 224, and the lower electrode 226 using the plurality of electrodes such as the plurality of cylindrical electrodes 225, the inner electrode 222, the upper electrode 224, and the lower electrode 226 and a magnetic field space of the objective lens 207. The positive potential Vout is applied to the plurality of cylindrical electrodes 225 from the potential control circuit 124 while allowing a predetermined gas to flow from the gas supply line 132 in a state where a strong longitudinal magnetic field is generated by the objective lens 207. The potentials of the other electrodes are the same as those in
According to Embodiment 2, as described above, plasma by the magnetron discharge can be generated without affecting the magnetic field generated by the electromagnetic lens (for example, the projection lens 204 and the objective lens 207) constituting the electron beam optical system inherent to the apparatus that emits the electron beam 200. Therefore, it is possible to generate ions (for example positive ions X+), electrons (e−) and active species (O*), and also to reduce the electrification of the substrate 101 or/and to remove contaminants of the substrate 101 (deflectors 205, 208) and the like. As a result, high-precision pattern writing can be performed.
In each of the above-described Embodiments, a case where a longitudinal magnetic field is generated by the objective lens 207 and plasma is generated by using such a longitudinal magnetic field has been described. However, the generation direction of the magnetic field is not limited to the above case. The configuration of the lithography apparatus 100 according to Embodiment 3 is the same as that in
In
As shown in
Further, as shown in
The potential control circuit 124 (potential control unit) according to Embodiment 3 controls the potentials of a plurality of electrodes such as the upper electrode 320, the lower electrode 322, the outer electrode 324, and the inner electrode 326 so as to generate plasma in the space 14 surrounded by the plurality of electrodes and also so as to control the movement of positive ions, or electrons and negative ions generated by the plasma. A more specific operation is as described below. Plasma is generated in the space 14 in a vacuum state surrounded by the plurality of electrodes such as the upper electrode 320, the lower electrode 322, the outer electrode 324, and the inner electrode 326 using the plurality of electrodes such as the upper electrode 320, the lower electrode 322, the outer electrode 324, and the inner electrode 326 and a magnetic field space of the objective lens 207.
When the plasma is generated by, for example, the Penning discharge, the potential is applied as follows. A potential Vup′ is applied to the upper electrode 320 and a potential Vdown′ is applied to the lower electrode 322 from the potential control circuit 124 while allowing a predetermined gas to flow from the gas supply line 132 arranged so as to pass through the outer electrode 324 in a state where a strong transverse magnetic field is generated by the objective lens 207 in the space 14. In such a case, an equal positive potential is applied as the potential Vup′ of the upper electrode 320 and the potential Vdown′ of the lower electrode 322. When the potential Vup′ of the upper electrode 320 and the potential Vdown′ of the lower electrode 322 become higher than the potential Vout′ of the outer electrode 324 and the potential Vin′ of the inner electrode 326 by a predetermined potential difference or more, plasma by the Penning discharge can be generated in the space 14. The movement of electrons (e−) in the space 14 is restricted in the vertical direction by the strong transverse magnetic field. By applying a potential Vout′ lower than the potential Vup′ and the potential Vdown′ to the outer electrode 324 and a potential Vin′ lower than the potential Vout′ to the inner electrode 326, the movement of electrons in the space 14 is also restricted in the radial direction. For example, a magnetic field of 4 to 6 kG is generated by the objective lens 207. In such a magnetic field space, for example, 50 V is applied as the potential Vup′. As the potential Vdown′, for example, 50 V, which is the same potential as the potential Vup′, is applied. As the potential Vout′, a potential lower than Vdown′, for example, −850 V is applied. As the potential Vin′, a potential lower than the potential Vin′, for example, −950 V is applied. Due to this effect, trapped electrons ionize the gas molecules supplied from a gas supply line 133 to generate ions (for example, positive ions X+). At the same time, neutral active species (O*) such as radicals are generated. In order to efficiently start the discharge, a material that emits thermoelectrons by a tungsten filament or the like being heated may be installed near the outer electrode 324 so that the discharge is started by passing a current from an external power source for heating the material to emit electrons. Even if the filament current is stopped after the discharge starts normally, the discharge continues. Further, a filament made of a refractory metal, for example, tungsten may be installed near an opening 327 of the inner electrode 326 or an opening of the retarding electrode 328 so that electrons can be caused to reach the surface of the target object together with positive ions X+ by supplying a current from an external power source (not shown) for heating the filament to emit electrons.
When the plasma is generated by, for example, the magnetron discharge, a potential sufficiently higher than the potential Vup′ of the upper electrode 320 is applied as the potential Vdown′ of the lower electrode 322. For example, 50 V is applied as Vdown′ and, for example, −850 V, −1050 V, and −1000 V are applied as Vup′, Vin′, and Vout′ respectively. When the potential difference between the potential Vup′ of the upper electrode 320 and the potential Vdown′ of the lower electrode 322 becomes larger than a predetermined potential difference, plasma by the magnetron discharge can be generated in the space 14. Due to this effect, trapped electrons ionize the gas molecules supplied from a gas supply line 133 to generate ions (for example, positive ions X+). At the same time, neutral active species (O*) such as radicals are generated. In order to efficiently start the discharge, a material that emits thermoelectrons by a tungsten filament or the like being heated may be installed near the outer electrode 324 so that the discharge is started by passing a current from an external power source for heating the material to emit electrons. Even if the filament current is stopped after the discharge starts normally, the discharge continues. Further, a filament made of a refractory metal, for example, tungsten may be installed near the opening 327 of the inner electrode 326 or the opening of the retarding electrode 328 so that electrons can be caused to reach the surface of the target object together with positive ions X+ by supplying a current from an external power source (not shown) for heating the filament to emit electrons.
Then, as the emission process (S106), positive ions, electrons and negative ions, or active species are emitted from the space 14 of plasma. In the example of
In Embodiment 3, since a strong magnetic field is generally applied to the vicinity of the substrate 101, it is difficult to cause electrons to reach a desired region of the substrate 101. When irradiated with positive ions (X+) and negative ions (Y−), the potential of each electrode is adjusted in consideration of the Larmor radius so that a desired current can reach a desired region of the substrate 101.
According to Embodiment 3, as described above, plasma by the Penning discharge or magnetron discharge can be generated without affecting the magnetic field generated by the electromagnetic lens (for example, the projection lens 204 and the objective lens 207) constituting the electron beam optical system inherent to the apparatus that emits the electron beam 200 even if the magnetic field is a transverse magnetic field in the radial direction. Therefore, it is possible to generate ions (for example positive ions X+), electrons (e−) and active species (O*), and also to reduce the electrification of the substrate 101 or/and to remove contaminants of the substrate 101 (deflectors 205, 208) and the like. As a result, high-precision pattern writing can be performed.
In each of Embodiments described above, the case where the plasma generation mechanism is applied to the lithography apparatus 100 using a single beam has been described. However, the present disclosure is not limited to such a case. In Embodiment 4, a case where a plasma generation mechanism is applied to a lithography apparatus using multiple beams will be described.
Here, in
The shaping aperture plate array substrate 603 has holes (openings) 22 of p rows high (y direction)×q rows wide (x direction) (p, q≥2) formed with predetermined arrangement pitches in a matrix of rows and columns. For example, the holes 22 of 512×512 rows are formed in length and width (x, y directions). Each of the holes 22 is formed in a rectangular shape of the same size and shape. Alternatively, each of the holes 22 may be formed in a circular shape of the same diameter. With the passage of a portion of an electron beam 600 through the plurality of holes 22, multiple beams 20 are formed and also, each beam is formed into a desired shape. Also, the way of arranging the holes 22 is not limited to a case of arranging holes in a grid shape in length and width. For example, the holes in the k-th row and the (k+1)-th row in the length direction (y direction) may be arranged by being shifted by a dimension a in the width direction (x direction). Similarly, the holes in the (k+1)-th row and the (k+2)-th row in the length direction (y direction) may be arranged by being shifted by a dimension b in the width direction (x direction).
The shaping aperture plate array substrate 603 has a passing hole 25 (opening) for passing each beam of multiple beams opened at a position corresponding to each of the holes 22 formed in the shaping aperture plate array substrate 603. In other words, in a membrane region 330 of a substrate 31, a plurality of passing holes 25 through which corresponding beams of multiple beams using electron beams pass is formed in an array shape. Then, a plurality of electrode pairs having two electrodes is arranged at positions facing each other across the corresponding passing hole 25 of the plurality of passing holes 25. More specifically, a pair of a blanking deflecting control electrode and a counter electrode (blanker: blanking deflector) is arranged with the passing hole 25 therebetween.
The electron beam 20 passing through each passing hole is independently deflected by the voltages applied to the control electrode and the counter electrode forming a pair. Blanking control is exercised by such deflection. More specifically, a pair of the control electrode and the counter electrode individually deflects by blanking corresponding beams of the multiple beams by the potentials switched by respective corresponding switching circuits. Thus, a plurality of blankers deflects by blanking, among multiple beams having passed through the plurality of holes 22 (openings) of the shaping aperture plate array substrate 603, respective corresponding beams.
Next, the operation of the pattern writing mechanism 550 in the lithography apparatus 500 will be described. The electron beam 600 emitted from the electron gun assembly 601 (emission source) illuminates the entire shaping aperture plate array substrate 603 almost vertically through the illumination lens 602. A plurality of rectangular holes (openings) are formed in the shaping aperture plate array substrate 603, and the electron beam 600 illuminates a region including all the plurality of holes. A plurality of electron beams (multiple beams) 20a to 20e in, for example, a rectangular shape is formed by each portion of the electron beam 600 with which the positions of the plurality of holes are irradiated being passed through each of the plurality of holes of the shaping aperture plate array substrate 603. The multiple beams 20a to 20e pass through the respective corresponding blankers (first deflector: individual blanking mechanism) of the blanking aperture array mechanism 604. Such blankers individually deflect (deflect by blanking) the passing electron beam 20.
The multiple beams 20a to 20e having passed through the blanking aperture array mechanism 604 are reduced by the reducing lens 605 before traveling toward a hole in the center formed in the limiting aperture plate substrate 606. Here, the electron beam 20a deflected by the blanker of the blanking aperture array mechanism 604 deviates from the position of the hole in the center of the limiting aperture plate substrate 606 and is shielded by the limiting aperture plate substrate 606. Meanwhile, the electron beams 20b to 20e that are not deflected by the blanker of the blanking aperture array mechanism 604 pass, as shown in
As for the objective lens 607, like in each of Embodiments described above, a plasma generation mechanism can be constructed by arranging a plurality of electrodes inside. The objective lens 607 has, like the objective lens 207 in each Embodiment described above, a pole piece (yoke) and a coil. Then, a magnetic field is generated in the traveling direction of the electron beam 200 (downward in
In
Then, a potential control circuit (potential control unit) (not shown) controls the potentials of the plurality of electrodes such as the outer electrode 620, the inner electrode 622, the upper electrode 624, and the lower electrode 626 so as to generate plasma in the space 15 surrounded by the plurality of electrodes and also so as to control the movement of positive ions, or electrons and negative ions generated by the plasma. As mentioned above, plasma can be generated by the Penning discharge or magnetron discharge.
When the plasma is generated by, for example, the Penning discharge, the potential is applied as follows. The potential Vout is applied to the outer electrode 620 and the potential Vin is applied to the inner electrode 622 from the potential control circuit (not shown) while allowing a predetermined gas to flow from the gas supply line 532 in a state where a strong transverse magnetic field is generated by the objective lens 607 in the space 15. In such a case, the same positive potential is applied as the potential Vout of the outer electrode 620 and the potential Vin of the inner electrode 622. The potential Vup lower than the potential Vout and the potential Vin is applied to the upper electrode 624 and the potential Vdown lower than the potential Vup is applied to the lower electrode 626. When the potential Vout of the outer electrode 620 and the potential Vin of the inner electrode 622 become higher than the potentials of the upper electrode 624 and the lower electrode 626 by a predetermined potential difference or more, plasma by the Penning discharge can be generated in the space 15. The value of each potential may be the same as that in Embodiment 1. When the potential Vout of the outer electrode 620 and the potential Vin of the inner electrode 622 become higher than a predetermined potential, plasma by the Penning discharge can be generated in the space 15. The movement in the horizontal direction of electrons (e−) in the space 15 is restricted by a strong longitudinal magnetic field. In addition, electrons in the space 15 are also restricted in movement in the vertical direction by an electric field associated with the potential distribution in the space 15. Due to this effect, trapped electrons ionize the gas molecules supplied from the gas supply line 532 to generate ions (for example, positive ions X+). At the same time, neutral active species (O*) such as radicals are generated. In order to efficiently start the discharge, a material like a tungsten filament that emits thermoelectrons by being heated may be installed near the upper electrode 624 so that the discharge is started by passing a current from an external power source for heating the material to emit electrons. Even if the filament current is stopped after the discharge starts normally, the discharge continues. Further, a filament made of a refractory metal, for example, tungsten may be installed near the opening of the retarding electrode 628 so that electrons can be caused to reach the surface of the target object together with ions by supplying a current from an external power source (not shown) for heating the filament to emit electrons.
When the plasma is generated by, for example, the magnetron discharge, a potential sufficiently higher than the potential Vout of the outer electrode 620 is applied as the potential Vin of the inner electrode 622. The value of the potential Vin may be the same as that in Embodiment 2. When the difference between the potential Vin of the inner electrode 622 and the potential Vout of the outer electrode 620 becomes larger than a predetermined potential difference, plasma by the magnetron discharge can be generated in the space 15. Due to this effect, trapped electrons ionize the gas molecules supplied from the gas supply line 532 to generate ions (for example, positive ions X+). At the same time, neutral active species (O*) such as radicals are generated. In order to efficiently start the discharge, a material like a tungsten filament that emits thermoelectrons by being heated may be installed near the upper electrode 624 so that the discharge is started by passing a current from an external power source for heating the material to emit electrons. Even if the filament current is stopped after the discharge starts normally, the discharge continues. Further, a filament made of a refractory metal, for example, tungsten may be installed near the opening of the retarding electrode 628 so that electrons can be caused to reach the surface of the target object together with ions by supplying a current from an external power source (not shown) for heating the filament to emit electrons.
When a magnetic field is applied to the vicinity of the substrate 101, the potentials of the respective electrodes are adjusted similarly to the above-described embodiment so that ions (positive ions X+, negative ions Y−) can be caused to reach desired regions of the substrate 101.
Then, as the emission process (S106), positive ions, electrons and negative ions, or active species are emitted from the plasma space 15. In the example of
According to Embodiment 4, as described above, plasma by the Penning discharge or magnetron discharge can be generated without affecting the magnetic field generated by the electromagnetic lens (for example, the objective lens 607) constituting the electron beam optical system inherent to the apparatus that emits the multiple beams 20. Therefore, ions (for example, positive ions X+), electrons (e−), and active species (O*) can be generated and also, the electrification of the substrate 101 can be reduced or/and contaminants of the substrate 101 (the deflector 608) and the like can be removed. As a result, high-precision pattern writing can be performed.
In each of Embodiments described above, the retarding electrode may be configured as follows. Hereinafter, as an example, a description will be provided using a modification of the configuration in
In the foregoing, Embodiments have been described with reference to concrete examples. However, the present disclosure is not limited to these concrete examples. In the examples described above, a case where a one-stage deflector 208 (608) is arranged as an objective deflector has been described, but the present disclosure is not limited to such examples. For example, multi-stage deflectors having different deflection regions may be arranged. In such a case, the present disclosure can also be applied to cleaning of multi-stage deflectors.
Portions of the apparatus configuration, the control method, and the like that are not needed directly for the description of the present disclosure omitted, but a necessary apparatus configuration or a necessary control method may be appropriately selected and used. For example, the description of the controller configuration that controls the lithography apparatus 100 (500) is omitted, but a necessary controller configuration is appropriately selected and used, as a matter of course.
In addition, all charged particle beam irradiation apparatuses and methods for reducing electrification of a substrate including the elements of the present invention and can be attained by appropriately changing in design by a person skilled in the art are included in the spirit and scope of the present invention.
Additional advantages and modification will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-185151 | Sep 2017 | JP | national |
