JP4610029B2 - Electron beam irradiation device electrostatic deflector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic deflector used in an electron beam irradiation apparatus that irradiates an electron beam such as an electron beam exposure apparatus or an electron microscope.
An electron beam can be narrowed down to a few tens of nanometers, and apparatuses for irradiating an electron beam such as an electron microscope and an electron beam exposure apparatus have been put into practical use. In such an electron beam irradiation apparatus, a deflector is used to change the irradiation position of the electron beam focused on the sample. As the deflector, an electromagnetic deflector having a large deflection range but relatively low response speed, an electrostatic deflector having a narrow deflection range but high response speed, or a combination thereof is used. The present invention relates to this electrostatic deflector. In the following description, an electrostatic deflector of an electron beam exposure apparatus will be described as an example, but the present invention is not limited to this, and any electrostatic deflector used in an electron beam irradiation apparatus may be used. It can be applied to anything.
[0002]
[Prior art]
In recent years, miniaturization and higher density of integrated circuits have progressed, and further miniaturization has become difficult with the photolithography technology that has been the mainstream of fine pattern formation for many years. Therefore, in place of the photolithography technique, an exposure method using a charged particle beam such as an electron beam or an ion beam, or a new exposure method using X-rays has been studied and realized. Among these, electron beam exposure for forming a pattern using an electron beam is in the limelight because it can form a fine pattern of 0.1 μm or less. Accordingly, the electron beam exposure apparatus is also required to have stable operation, high throughput, and further fine workability as a semiconductor mass production apparatus.
[0003]
In a typical conventional electron beam exposure apparatus, a deflecting means combining an electromagnetic deflector and an electrostatic deflector is used. The electromagnetic deflector is called a main deflector and the electrostatic deflector is called a sub deflector. Divide the deflection range (main deflection range) of the electromagnetic deflector into several areas (sub-deflection ranges) slightly smaller than the deflection range of the electrostatic deflector, and set the deflection position by the electromagnetic deflector to the center of each sub-deflection range. In general, each sub-deflection range is deflected by an electrostatic deflector after being positioned. The column of the electron beam exposure apparatus incorporates a projection lens for irradiating the wafer with an electron beam having an appropriately shaped cross section. The electromagnetic deflector and the electrostatic deflector described above are connected to the projection lens. Almost integrally, more specifically, the electrostatic deflector is disposed in the electromagnetic deflector.
[0004]
Therefore, if a highly conductive metal is used for the electrostatic deflector (sub-deflector) and its peripheral parts, although it has good workability and accuracy, the electromagnetic deflector (main deflector) is affected by eddy currents. Inconveniences such as a slow response speed occur. This is a serious problem for an electron beam exposure apparatus that requires high throughput.
In order to reduce the eddy current, an electrostatic deflector was formed by plating the inside of a cylindrical nonconductive material (for example, alumina) (for example, NiP for the base and Au for the surface). As a result, there is a problem of plating and plating, so that an AlTiC (compound of alumina and titanium carbide) ceramic with an ideal resistivity value is ground and platinum plated to form an electrostatic deflection electrode. The electrostatic deflector is configured by being fixed to a hollow cylinder of insulating alumina ceramic.
[0005]
1A and 1B are diagrams showing a conventional example of an electrostatic deflector of an electron beam exposure apparatus. FIG. 1A shows an external configuration of the electrostatic deflector, and FIG. 1B shows an AA ′ line in FIG. (C) is a sectional view taken along line BB ′ in (b).
The illustrated electrostatic deflector 10 is disposed inside an electromagnetic deflector and used as a sub-deflector in an electron beam exposure apparatus using an electromagnetic deflector as a main deflector (not shown). As illustrated, the electrostatic deflector 10 includes an electrode group 11 and a hollow cylindrical holding member 12 to which the electrode group 11 is fixed.
[0006]
The electrode group 11 is composed of eight AlTiC ceramic electrode materials E _{1 to} E ₈ , and each electrode material E _i (i = 1 to 8) is arranged and fixed in an axially symmetrical manner inside the outer cylinder 12. (See FIG. 1 (b)). Each electrode material E _i is formed in the same shape by grinding, and a metal film is formed on the surface. This metal film is a platinum group metal such as ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt). It is formed directly on the surface of the ceramic.
[0007]
On the other hand, the holding member 12 needs to insulate the electrode materials _Ei from each other, and is formed of a non-conductive material. The holding member 12 is provided with an opening 31 as shown. These openings are used when the electrode group 11 (eight electrode materials E _{1 to} E ₈ ) is arranged and fixed inside, and two (a total of 16) openings are provided for each electrode material Ei. Provided.
[0008]
The portion corresponding to the opening of the electrode material E _i, is joined for the metal pad is formed and injecting bonding metal, such as solder into the opening in a state of positioning the respective electrode material E _i to the holding member 12 Then, each electrode material E _i is fixed to the holding member 12.
An electron beam is a flow of electrons, and if it collides with a nonconductive material, charges are accumulated on the surface of the nonconductive material. The accumulated charge affects the surrounding electric field. The electrostatic deflector applies a voltage to each electrode material Ei to generate an electric field inside the electrode group 11, and deflects an incident electron beam with the force of the electric field. For this reason, if electric charges accumulate on the surface of the surrounding holding member 12 to disturb the electric field, there arises a problem that a desired deflection amount cannot be obtained. Therefore, in the conventional electrostatic deflector shown in FIG. 1, the cross section of each electrode material Ei is crank-shaped so that the inner surface of the holding member 12 cannot be directly seen from the central axis of the cylinder. With such a shape, even if an electron beam passing through the inside of the cylinder is scattered, the scattered electrons do not collide with any electrode material Ei and reach the inner surface of the holding member 12. ing.
[0009]
[Problems to be solved by the invention]
However, when actually used, there is a problem that electric charges are accumulated (charged up) on the surface of the holding member 12 and the electric field is disturbed regardless of the structure shown in FIG. This problem will be described with reference to FIG.
In the electron beam exposure apparatus, the electrostatic deflector 10 is accommodated inside the electromagnetic deflector 9 and is disposed at a portion closest to the sample (wafer) 1. A resist layer 2 is formed on the surface of the sample 1 and is irradiated with an electron beam 3. The electron beam applied to the resist layer 2 is absorbed by the resist layer 2 to expose the resist layer 2, but a part of the electron beam is reflected by the surface of the resist layer 2 and returns to the electrostatic deflector 10. In addition, some of the secondary electrons that are scattered in the resist layer 2 or are once absorbed and then emitted from the resist layer 2 also return to the electrostatic deflector 10. Such reflected electrons and secondary electrons are accumulated in a portion near the end of the holding member 12. Further, the electron beam 3 is deflected while passing through the electrostatic deflector 10 and the electromagnetic deflector 9 and enters the sample 1. If the deflection amount is large, the electron beam 3 is at a position close to a surface obtained by extending the surface of the electrode material Ei. It will enter the sample. Reflected electrons and secondary electrons from such a position are more likely to reach the surface of the holding member 12 even if the electrode material Ei has the crank shape as described above. For the reasons as described above, the holding member 12 has a problem that charges are easily accumulated (charged up) particularly on the side close to the sample 1 and an error occurs in the exposure position of the electron beam.
[0010]
Charge-up also occurs due to other causes. In an electron beam exposure apparatus, the inside of a column and the inside of a chamber for exposure processing coupled to the column are usually in a high vacuum state, but in reality there is evaporation of resist to be exposed, etc. When irradiated with an electron beam, a compound containing carbon or the like as a main component (that is, dirt) is generated. Since this contamination is not a good conductor, a charge-up occurs on the electrode surface, causing a problem that the electric field is disturbed and an error occurs in the exposure position of the electron beam. In particular, this problem appears more conspicuously with respect to an electrostatic deflector (sub-deflector) located in the vicinity of a wafer coated with a resist.
[0011]
In the conventional technology, when the charge-up amount exceeds a certain level, the electrostatic deflector itself is replaced with a new one. To perform this replacement, the high vacuum state inside the column and the chamber is once released. It was necessary to do (that is, let the air leak). For this reason, while the exposure apparatus is started up again after the replacement work (for example, initial setting of deflection data to be applied to each deflector, etc.), the apparatus is stopped and the throughput is reduced. In order to cope with this, a method called an “in-situ” cleaning method is used in which the inside of the column and the chamber is removed without causing air leakage. This is because oxygen plasma is generated by introducing a very small amount of oxygen-based gas into the apparatus and applying high-frequency power to the electrostatic deflection electrode in this dilute gas atmosphere, and by ashing (ashing treatment) It is a method of removing dirt. However, by performing this “in-situ” cleaning method, a conductive material that forms a metal film on the electrode surface or a material that contaminates the surface of the electrode is sputtered, and the surface of the non-conductive holding member 12 As a result, the insulation resistance between the electrodes is lowered and unexpected charge-up is caused, resulting in a decrease in exposure position accuracy.
[0012]
An object of the present invention is to solve such a problem, and it is an object of the present invention to reduce exposure position accuracy by reducing charge-up of a non-conductor holding member that causes a decrease in exposure position accuracy. And
[0013]
[Means for Solving the Problems]
FIG. 3 is a diagram showing the basic configuration of the electrostatic deflector of the electron beam irradiation apparatus of the present invention, where (a) shows the basic configuration of the first mode and (b) shows the basic configuration of the second mode. (C) shows the basic configuration of the third aspect.
The electrostatic deflector of the electron beam irradiation apparatus of the present invention has a cylindrical holding member 22 made of a non-conductive material and at least a part of the surface fixed separately from each other in the circumferential direction inside the holding member. An electrostatic deflector comprising a plurality of conductive electrodes 11, and in such an electrostatic deflector, in the first aspect of the present invention, as shown in FIG. Has an opening 30 extending in a direction parallel to the axial direction of the cylinder in a portion facing between adjacent electrodes. In the second aspect of the present invention, as shown in FIG. 11 extends from the holding member 22 in the electron beam emission direction. In the third embodiment of the present invention, as shown in FIG. 3C, the holding member includes a plurality of independent holding units 22a and 22b. The total length of the plurality of holding units is sufficiently shorter than the length of the electrode 11 And features.
[0014]
A plurality of electrodes 11 are fixed on the inner side of the holding member, and directly facing the inner side of the cylinder is between adjacent electrodes. Electric charges are accumulated in a portion between the electrodes, and an electric field inside the cylinder is stored. To affect. The insulation resistance between the electrodes is affected by the surface resistance of the portion between the electrodes of the holding member 22. According to the first aspect of the present invention, since the opening 30 extending in the direction parallel to the axial direction of the cylinder is provided in the portion between the electrodes, the portion of the holding member 22 positioned between the electrodes The area is reduced. Accordingly, since the amount of electric charge stored is reduced as compared with the conventional example, the influence on the electric field is reduced. Further, since the area (width) between the electrodes of the holding member 12 is also reduced, the surface resistance is increased. Accordingly, the insulation resistance between the electrodes increases, and even if a conductor substance or a contaminant adheres to the portion, the influence can be reduced.
[0015]
As described above, it is mainly on the side close to the sample that charging up of the holding member and adhesion of a conductive substance or contaminant to the holding member become a problem. According to the second aspect of the present invention, the plurality of electrodes 11 extend from the holding member 22 in the electron beam emission direction, and the holding member is located away from the sample. Is less likely to occur. The holding member is preferably separated from the sample by 1/3 or more of the length of the electrode.
[0016]
The 3rd aspect of this invention reduces the area of the part between the electrodes of the holding member 22 similarly to the 1st aspect. In the first and second aspects, the holding member 22 has a predetermined shape, and the plurality of electrodes 11 are arranged in a predetermined positional relationship by being fixed to the holding member 22. On the other hand, in the third aspect, the holding member is divided into a plurality of independent holding units, and the mutual positional relationship is not determined as it is. Therefore, in the third aspect, the positional relationship between the plurality of electrodes is defined by fixing the plurality of electrodes and the plurality of holding units in a positioned state. That is, a plurality of electrodes also function as a structure that defines the positional relationship.
[0017]
It is also possible to have a structure combining the first to third aspects described above.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 4 is a perspective view showing the configuration of the electrostatic deflector according to the first embodiment of the present invention. Further, FIG. 5 shows a sectional view of the fixed electrode member E _i and the electrode member E _i constituting the electrode group to the holding member. The electrostatic deflector of the first embodiment has a configuration in which the first and second modes are combined. In the electrostatic deflector of the first embodiment, only the holding member 22 is different from the conventional example shown in FIG. 1, and the electrode group 11 composed of eight electrode materials is the same as the electrode group of the conventional example of FIG. is there.
[0019]
The electrode material E _i constituting the electrode group 11 of the electrostatic deflector of the first embodiment is ground with AlTiC ceramic and platinum-plated on the surface in the same manner as in the conventional example. 8 are used. In order to manufacture the electrode material E _i , first, it is processed into the same shape by grinding. Next, on each electrode material E _i , a conductive metal pad 23 mainly composed of titanium (Ti) is formed by a metallization method as a portion to which a voltage is applied from a driver. Further, bonding metal pads 24 and 25 having Ti as a main component are formed by metallization at any two locations of the portion fixed to the holding member 22. Note that the size of each metal pad 23 to 25 is minimized. Next, after cleaning the surface of each electrode material E _i , platinum (Pt) is directly formed on the surface of each electrode material E _i by electrolytic plating. At this time, the plating thickness was 2 μm or less.
[0020]
The holding member 22 uses alumina as a non-conductive material and has a cylindrical shape having a length equal to or less than 2/3 of the length of the electrode material E _i. Eight elongated holes 30 extending in parallel are formed. Further, 16 holes 31 are formed at positions where the bonding metal pads 24 and 25 of each electrode material E _i come into contact with each other when the electrode materials E _i are arranged and fixed inside, and an inner wall portion of each hole 31 is formed. The metal pads 26 and 27 for bonding mainly containing Ti or molybdenum-manganese (Mo-Mn) are formed by metallization.
[0021]
Next, each electrode material E _i is inserted into the holding member 22 with the assembly jig positioned with high accuracy, and a small amount of brazing material or solder material 28 is injected into the holes 31 formed in the holding member 22 ( Heat (see FIG. 5B). As a result, the bonding metal pads 24 and 25 formed on each electrode material E _i and the bonding metal pads 26 and 27 formed on the holding member 22 are fixed to each other. That is, each electrode material E _i is firmly fixed to the holding member 22 in a predetermined positional relationship.
[0022]
As described above, the electrostatic deflector of the first embodiment is realized.
FIG. 6 is a perspective view showing the configuration of the electrostatic deflector according to the second embodiment of the present invention. As illustrated, in the electrostatic deflector of the second embodiment, the holding member 22 is divided into two short holding units 22a and 22b. Holding units 22a and 22b, for example length at 1/10 of the cylinder of the length of the electrode member E _i, is provided with eight holes 23. Everything else is the same as in the first embodiment. In other words, in the holding member 22 of the electrostatic deflector of the first embodiment shown in FIG. 4, the portion corresponding to the length of the long hole 30 is eliminated and the holding member is divided into two portions. Therefore, the lower holding unit 22b is disposed at a position separated from the lower end of the electrode group 21 by 1/3 or more of the length of the electrode.
[0023]
The electrostatic deflector according to the second embodiment is not assembled in the same manner as the first embodiment because the holding member is divided into two holding units 22a and 22b. Assembling is performed by injecting and fixing a brazing material or a solder material into the hole 31 in a state where the eight electrode materials E _i and the two holding units 22a and 22b are positioned with high accuracy by an assembly jig.
[0024]
【The invention's effect】
As described above, according to the electrostatic deflector according to the present invention, the charge-up of the holding member that holds the electrode and the adhesion of contaminants are reduced, and the disturbance of the electric field of the electrostatic deflector is reduced. The exposure position accuracy is improved.
[Brief description of the drawings]
FIG. 1 is a view schematically showing an external appearance and an internal configuration of an electrostatic deflector of an electron beam exposure apparatus of a conventional example.
FIG. 2 is a diagram for explaining charge-up and contamination adhesion on the side close to a sample.
FIG. 3 is a diagram showing a basic configuration of an electrostatic deflector according to the present invention.
FIG. 4 is a perspective view showing the configuration of the electrostatic deflector of the first embodiment.
FIG. 5 is a view showing a state when the electrode material of the first embodiment and the electrode material are fixed to a holding member.
FIG. 6 is a perspective view showing a configuration of an electrostatic deflector according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Electrostatic deflector 11 ... Electrode group 22 ... Holding member 23 ... Conductive metal pads 24-27 ... Joining metal pad 28 ... Joining metal (solder etc.)
30 ... opening (long hole)
31 ... Openings E _{1 to} E ₈ ... Electrode material

Claims (3)

An electron beam irradiation apparatus comprising: a cylindrical holding member made of a non-conductive material; and a plurality of electrodes, at least a part of which is electrically conductive and separated from each other in the circumferential direction inside the holding member In the electrostatic deflector of
The electrostatic deflector of an electron beam irradiation apparatus, wherein the holding member has an opening extending in a direction parallel to an axial direction of a cylinder in a portion facing between the adjacent electrodes. An electrostatic deflector of the electron beam irradiation apparatus according to claim 1,
The plurality of electrodes are electrostatic deflectors of an electron beam irradiation apparatus extending in the electron beam emission direction from the holding member. An electrostatic deflector for an electron beam irradiation apparatus according to claim 2,
The length of the plurality of electrodes extending from the holding member in the electron beam emitting direction is 1/3 or more of the length of the electrodes.

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