JP2000251815A - Blanking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blanking device, wherein a form opening image does not move on a mask during blanking transition, even when a blanking deflector is composed of a one staged electrostatic deflector. SOLUTION: This blanking device is equipped with a blanking deflector 7 arranged on an electron gun 1 side of a form opening 13, and a blanking opening 21 arranged between the form opening 13 and a mask 31. The form opening 13 receives electron beam irradiation of roughly the same luminous intensity, regardless of whether it is a blanking state, a non-blanking state, or a transient state. Thus, the form opening 13 thermally stabilizes because the form opening 13 is irradiated at blanking the same as during non-blanking at all times and the form opening 13 does not undergo a heat cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a blanking device in an illumination optical system for illuminating a mask in an electron beam reduction transfer device or the like. In particular, the present invention relates to an illumination optical system having features such as being able to uniformly irradiate a forming opening or a mask or requiring a small deflection angle of a blanking deflector.

[0002]

2. Description of the Related Art FIG. 2 shows an electron beam lithography apparatus (variable shaped beam system) disclosed in Japanese Patent Application Laid-Open No. 57-122518.
1 shows a configuration of an optical system. In the figure, the beam forming aperture 10 is shown.
4 and 2 show a blanking deflector 105, a blanking aperture 106, an objective lens 108, and a sample 109. Note that the blanking openings 106 are omitted in the figures in the above publication. In this optical system, the principal ray trajectory at the time of blanking is largely deflected by the first-stage deflector 105a (111 → 112) as shown by alternate long and short dash lines 111, 112, and 113 in FIG. It is turned back (112 → 113) by the deflector 105b. When the beam 113 toward the objective lens 108 is extended upward (broken line 114), the beam 113 passes through the center of the forming opening 104.

That is, the blanking deflector 105 is provided with two stages 105a and 105b below the shaping opening, and is designed so that the deflection fulcrum coincides with the center of the shaping opening. The reason for this is that it is necessary to always irradiate the beam to stabilize the forming opening 104 thermally, and to prevent the image of the forming opening 104 from moving on the sample 109 during the blanking transition. It is.

[0004]

In the above-mentioned prior art, when a beam deflected outside the optical axis in the first stage 105a of the two-stage electrostatic deflector electrode is returned to the second stage 105b, the beam is deflected. It is necessary to adjust the center to the position of the forming opening 104. Therefore, when the distance between the shaping opening 104 and the blanking opening 106 is short, the deflection electric field strength must be increased to obtain a large deflection angle. For this purpose, it is necessary to make the dimension between the left and right deflection electrodes extremely small or to make the blanking voltage extremely high (300 V or more). Otherwise, there arises a problem that the intensity of the mask illumination beam during blanking cannot be sufficiently reduced.

In an electron beam exposure apparatus of the type that selects an exposure area of a mask, an electromagnetic deflector (field-selection deflector, not shown in FIG. 2) for selecting an exposure area (subfield) is provided below a forming opening. (Shown) are arranged to deflect the illumination beam at high speed. Due to the influence of the magnetic field of the deflector, an eddy current may flow through the blanking deflector, and the speed of the deflection may be reduced. In order to prevent this, the blanking deflector needs to have a structure in which an insulator is coated with a metal film on the surface, and the structure becomes complicated.

The present invention has been made in view of such a conventional problem, and has as its object to provide the following blanking device. (1) Even when the blanking deflector is constituted by a one-stage electrostatic deflector, the formed aperture image does not move on the mask during blanking transition. (2) The forming aperture always receives the same amount of beam irradiation. (3) The deflection voltage can be reduced even if the distance between the opposing electrodes of the deflector is made sufficiently large.

[0007]

Means for Solving the Problems and Embodiments of the Invention In order to solve the above problems, a blanking device according to the present invention comprises:
A blanking device in an illumination optical system for irradiating a shaped aperture with an electron beam emitted from an electron gun and forming an image of the shaped aperture on a mask; a blanking device disposed closer to the electron gun than the shaped aperture. A deflector, a blanking opening disposed between the forming opening and the mask, a state in which the electron beam is deflected by the blanking deflector and the electron beam is blocked by an opening plate of the blanking opening (a blanking state), Either a state in which the electron beam passes through the blanking opening without deflecting the electron beam by the blanking deflector (non-blanking state) or a transient state between the blanking state and the non-blanking state (transient state) Irrespective of the above, the above-mentioned forming opening receives the electron beam irradiation of almost the same intensity.

That is, despite the presence of the blanking deflector on the electron beam upstream side of the shaping aperture, the shaping aperture receives an electron beam of almost the same intensity regardless of the blanking state. Therefore, even during blanking, the forming opening is always irradiated in the same manner as during non-blanking, and the forming opening is thermally stabilized without undergoing a thermal cycle. In addition, even if the beam having uniform intensity hits the periphery of the forming opening with a relatively wide margin, and even if the beam slightly shakes, the uniformity of the beam passing through the forming opening can be ensured, If the beam movement on the forming aperture surface is designed to be sufficiently smaller than the beam movement on the blanking opening during blanking, forming on the mask without using the forming opening surface as a deflection fulcrum The movement of the aperture image can be completely stopped.

In the blanking device of the present invention, it is preferable that the blanking deflector comprises a one-stage electrostatic deflector. Unlike the above-described prior art, when only the deflection is performed by a single-stage electrostatic deflector without turning the beam, the length of the deflector can be increased. In addition, since the beam can be efficiently deflected because the beam is not folded, blanking can be performed at about 100 V without making the interval between the deflection electrodes too small. Furthermore, there is no electromagnetic deflector that deflects at high speed near the position of the blanking deflector (on the electron gun side of the forming aperture), so that the deflector electrode can be made of bulk metal.

In the blanking device of the present invention, an opening having a slightly larger opening than the shaping opening and blocking an electron beam distant from the optical axis is arranged on the blanking deflector side of the shaping opening. Is preferred. The slightly wider aperture blocks the beam in the peripheral area away from the optical axis so that it does not hit the forming aperture. Therefore, the amount of heat input to the forming opening can be reduced and uniformized. Note that it is preferable that the slightly wide opening has a structure in which heat is easily released by providing a water-cooled heat sink or by using a thick copper plate.

In the blanking device of the present invention, it is preferable that a magnetic lens (condenser lens) is arranged outside the blanking deflector. The electron beam passing through the orbit away from the optical axis is bent in the optical axis direction by the convergence action of the condenser lens, so that the swing width of the blanking deflector over the blanking opening can be reduced.

In the blanking apparatus of the present invention, it is preferable that the formed aperture image does not move on the mask during the blanking transition. Even during the blanking transition, the beams emitted in all directions from the forming aperture are returned by the lens to the incident point on the mask during non-blanking,
Irradiation unevenness of the mask does not occur at the time of blanking transition.

Hereinafter, description will be made with reference to the drawings. FIG.
FIG. 1 is a diagram for explaining a configuration and an imaging relationship of an electron beam illumination optical system having a blanking device according to one embodiment of the present invention. First, the arrangement and individual operation of each device of the optical system will be described. The cathode of the electron gun is indicated by reference numeral 1 at the top of the figure. The cathode 1 emits an electron beam downward in the figure. In this specification, the upstream side of the electron beam (charged particle beam) is referred to as “up”, and the downstream side is referred to as “down”.

Below the electron gun, a first condenser lens 3 which is an electromagnetic lens is arranged. The first condenser lens 3 converges the electron beam emitted from the cathode 1 and forms a cathode image on the forming aperture 13 in cooperation with a second condenser lens 11 described later. Below the first condenser lens 3, a trim opening 5 is arranged. At the same position as the trim opening 5, a crossover image CO of the electron beam emitted from the cathode 1 and converged by the first condenser lens 3 is formed. In the trim opening 5, the beam intensity has a Gaussian distribution, and the beam intensity does not become zero until the beam is somewhat distant from the optical axis. If the diameter of the trim opening 5 is made substantially equal to the crossover diameter, the beam amount is reduced by 50%, but the amount of beam deflection on the blanking opening 21 during blanking can be reduced to less than half.

A blanking deflector 7 is arranged below the trim opening 5 (at the same position as the second condenser lens 11). The deflector 7 is an electrostatic deflector and has two electrode plates facing each other with the optical axis interposed therebetween. When the electron beam (illumination beam) is not desired to be applied to the mask 31, the deflector 7 largely changes the direction of the electron beam and applies the electron beam (reference numeral 43) to the opening plate of the blanking opening 21.

The second condenser lens 11 is also an electromagnetic lens, and forms a cathode image on the forming aperture 13 in cooperation with the first condenser lens 3 as described above (two-dot chain line 45).
reference). The second condenser lens 11 is arranged outside the blanking deflector 7 at the same position in the optical axis direction as the blanking deflector 7.

Below the second condenser lens 11 and below the blanking deflector 7, a heat sink opening 12 and a forming opening 13 are arranged. The shaping opening 13 is for shaping the outer shape of the electron beam (illumination beam) applied to the mask 31. For example, the outer shape of the illumination beam is formed into a square of a little over 1 mm on the mask 31. As described above, a cathode image is formed at the position of the forming opening 13. The heat sink opening 12 has an opening slightly larger than the shaping opening on the blanking deflector side of the shaping opening, and blocks an electron beam away from the optical axis. The slightly wide aperture 12 blocks the beam in the peripheral portion away from the optical axis so that it does not hit the forming aperture 13. Therefore, the heat input amount of the forming opening 13 can be reduced and uniformized. The heat sink opening 12 has a structure in which heat can easily escape by providing a water-cooled heat sink or by using a thick copper plate.

The field selecting deflector 20 has a two-stage blanking opening 21 between the forming opening 13 and the blanking opening 21.
And the mask 31 are arranged in three stages. These deflectors change the position of the shaped aperture image (illumination beam) on the mask 31 within the deflectable visual field, and selectively select a number of subfields (unit exposure areas, not shown) formed on the mask 31. To illuminate.

Below the forming opening 13, the first illumination lens 1
9 are arranged. The first illumination lens 19 converges a principal ray passing through the center of the shaping aperture 13 into a beam parallel to the optical axis. Then, a shaped aperture image is formed on the mask 31 in cooperation with a second illumination lens 25 described later.

A blanking opening 21 is arranged below the first illumination lens 19. Blanking opening 21
Is for blocking the beam when illumination is unnecessary as described above. A crossover image of the cathode 1 is formed at the center of the blanking opening 21.

A second illumination lens 25 is arranged below the blanking opening 21. This second illumination lens 25
Converges a beam incident parallel to the optical axis on the mask 31. These two-stage illumination lenses 19 and 25 contractively project the image of the shaping aperture 13 onto the mask 31. In this example, the projection ratio is 1/1.

The overall image forming operation of the illumination optical system shown in FIG. 1 will be described. A two-dot chain line 45 indicates a conjugate plane of the forming opening 13. The upper end of the two-dot chain line 45 is the virtual image position 41 (center position) of the cathode 1. The two-dot chain line 45 emerges from the optical axis of the cathode virtual image, bends parallel to the optical axis by the first condenser lens 3, and intersects the optical axis at the position of the forming opening 13.
Thereafter, the illumination lens 25 intersects the optical axis on the curved mask 31 to form an image. As a result, the cathode virtual image surface 41, the forming aperture 13, and the mask surface 31 are conjugate to each other.

The solid line 43 indicates the trajectory of the principal ray during blanking. It can be easily understood that the trajectory at the time of blanking below the forming opening is as shown by the solid line 43. Above the forming opening, it can be understood that this solid line 43 is extended to the upstream side. The orbit 43 is bent in the optical axis direction from the diverging direction by the second condenser lens 12 and passes through the optical axis at the position of the forming opening 13. Then proceed in the direction away from the optical axis,
The light is bent parallel to the optical axis by the illumination lens 19, and is blocked by the blanking opening 21.

Here, the beam 46 that has traveled on the optical axis from the trim opening 5 is not targeted because it is shielded by the heat sink opening 12 as shown. In other words, it is necessary to consider the beam that is most difficult to block. In order to reduce the intensity at the time of blanking to 1/10 ⁴ , it is sufficient if the beam can be deflected about three times the crossover diameter on the blanking opening 21. If the second condenser lens 11 is not provided, the beam that has passed through the center of the trim opening 5 follows the trajectory of the broken line 51 if it is not blanked. However, since the second condenser lens 11 is located at the same position as the deflector 7, the broken line 49 The trajectory is parallel to the optical axis. That is, if the second condenser lens 11 is not provided, it is necessary to deflect by the swing width 57 at the position of the first illumination lens 19 at the time of bunking.

The heating opening 7 is located directly above the molding opening 13.
During blanking deflection, the irradiation area that illuminates the heating opening moves, but the irradiation area is sufficiently larger than the heating opening. Since the irradiation is performed in the same manner as at the time, the molding opening is not subjected to thermal fluctuation. Further, as shown in the drawing, there is a distance between the forming opening 13 and the blanking opening 21 (for example, 150 mm), so that the beam largely moves on the blanking opening 21 at a small blanking angle. The deflection sensitivity can be relatively small.

The shaping aperture is illuminated with a sufficient margin (a beam with uniform intensity hits around the opening with a relatively wide margin, and even if the beam slightly shakes, the uniformity of the beam passing through the shaping aperture is uniform. State that can secure the nature),
At the time of blanking, if the movement of the beam on the forming aperture is designed to be sufficiently smaller than the movement of the beam on the blanking aperture, the mask can be moved on the mask without using the forming aperture as a deflection fulcrum. The movement of the shaped aperture image can be stopped.

Next, a specific example of design numerical values will be described. Assuming that the convergent half angle of 8 mrad on the wafer, the reduction ratio is 1/4, and the focal length of the second illumination lens 25 is 110 mm, the crossover diameter D on the blanking opening 21 is as follows. D = 2 ×
2 mrad × 110 mm = 0.44 mm Therefore, the deflection width 55 of the first illumination lens 19 is 3 × 0.44 = 1.
It becomes 32 mm.

Acceleration voltage 100 KV, blanking voltage ± 1
Assuming that 00V, the length of the deflector is 10 cm, and the distance from the center of the deflector to the main surface of the lens 9 is 161 mm, the electrode interval d of the electrostatic deflector is as follows. d = 50mm / 1.32mm x 161mm x 20
0/10 ⁵ = 8.25 mm, and a sufficiently large electrostatic deflector can be used.

The movement amount 53 of the beam at the time of blanking on the forming opening 13 is as follows. 1.32 mm × 51/161 = 0.42 mm A heat sink opening 7 (1.2 mm square) is provided on the electron gun side of the forming opening 13 (1.1 mm square). In that case,
1.2 mm × (2) ^1/2 +0.42 mm = 2.
If the beam intensity is substantially uniform in a region larger than the diameter by 12 mm, the amount of the beam passing through the heat sink opening 12 is substantially constant. Therefore, in this case, the forming opening 1
No. 3 receives a constant irradiation regardless of blanking. The trajectory at the time of the transient is as indicated by a broken line 59, and the formed aperture image does not move on the mask 31.

In the present blanking apparatus, blanking can be performed by the upper one-stage deflector, so that an electrostatic deflector is not required between the forming opening and the mask. Therefore, the electromagnetic deflector and the dynamic focus lens provided at this position can operate at high speed without eddy current problems.

[0031]

As is apparent from the above description, according to the present invention, there is provided a blanking device in an illumination optical system for illuminating a mask in an electron beam reduction transfer device or the like. It is possible to provide an illumination optical system having such a feature that the deflection angle of the blanking deflector can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a configuration and an imaging relationship of an electron beam illumination optical system according to one embodiment of the present invention.

FIG. 2 shows a configuration of a mask illumination optical system disclosed in Japanese Patent Application Laid-Open No. 57-122518.

[Explanation of symbols]

Reference Signs List 1 cathode 3 first condenser lens 5 trim opening 7 blanking deflector 11 second condenser lens 12 heat sink opening 13 forming opening 19 first lighting lens 21 blanking opening 25 second lighting lens 31 mask 41 cathode virtual image 53 forming in forming opening Beam movement amount at ranking 55, 57 Deflection width

Claims (6)

[Claims] 1. A blanking device in an illumination optical system for irradiating a shaped opening with an electron beam emitted from an electron gun and forming an image of the shaped opening on a mask; A blanking deflector arranged, a blanking opening arranged between the forming opening and the mask,
A state in which the electron beam is deflected by a blanking deflector and the electron beam is blocked by a blanking opening plate (a blanking state). Irrespective of the passing state (non-blanking state) or the transient state (transient state) between the blanking state and the non-blanking state, the above-mentioned forming opening receives the electron beam irradiation of almost the same intensity. A blanking device characterized by the above-mentioned. 2. The blanking apparatus according to claim 1, wherein said blanking deflector comprises a one-stage electrostatic deflector. 3. An opening having an opening slightly larger than the shaping opening and blocking an electron beam distant from the optical axis is arranged on the blanking deflector side of the shaping opening. Or the blanking device according to 2. 4. The blanking device according to claim 1, wherein a magnetic lens (condenser lens) is disposed outside the blanking deflector. 5. The blanking apparatus according to claim 1, wherein the formed aperture image hardly moves on the mask at the time of blanking transition. 6. The apparatus according to claim 1, wherein a magnetic lens (condenser lens) is disposed outside the blanking deflector, and the formed aperture image hardly moves on the mask during blanking transition. The blanking device as described.