JP3237013B2 - Electron beam reduction transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam reduction transfer device capable of adjusting a reduction magnification.

[0002]

2. Description of the Related Art In order to transfer a circuit pattern or the like formed on a mask to a semiconductor substrate or the like at a predetermined reduction ratio (reduction ratio), an electron beam reduction transfer device is used. In this type of transfer device, it is required that the distortion at the time of transfer be within an allowable range and that the reduction ratio be as close as possible to a predetermined value. In this regard, since the semiconductor substrate and the like may expand and contract to some extent through various processes, an adjustment mechanism for adjusting the reduction magnification of the transfer device is necessary in accordance with the expansion and contraction. Further, in order to reduce the manufacturing cost, for example, when the manufacturing accuracy of each part and the accuracy of the installation position of each lens are roughly set, when the reduction magnification does not fall within the allowable range with respect to the design value. Also, a mechanism for adjusting the reduction magnification is required.

[0003] In order to adjust such a reduction ratio,
In the conventional electron beam reduction transfer apparatus, as shown in FIG. 4, the coil of the reduction lens 20 on the electron beam transmission mask side is wound separately on the coil 21 on the mask side and the coil 22 on the target side. Then, the reduction ratio is changed by changing the ratio of the current flowing through the coil 21 and the coil 22 to equivalently change the lens position of the reduction lens 20.

[0004]

In such a conventional electron beam reduction transfer apparatus, the reduction magnification can be adjusted by changing the lens position equivalently. However, when the lens position is changed, the distortion increases, so that there is a disadvantage that the adjustment range of the reduction magnification is narrow in order to suppress the distortion within an allowable range. Furthermore, since the lens position is almost always determined by the magnetic pole position, the current ratio must be greatly changed to equivalently change the lens position and obtain the required change in the reduction ratio, which complicates the adjustment circuit and the like. There was an inconvenience to do.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide an electron beam reduction transfer device having a wide range of adjustment of reduction magnification while keeping distortion within an allowable range.

[0006]

[0007]

According to the first aspect of the present invention, there is provided:
For example, as shown in FIG. 1, the electron beam reduction transfer device transfers an electron beam emitted from an electron beam source (1) to an electron beam transmission mask (9) via an illumination lens system (4, 5, 7). The electron beam transmitted through the electron beam transmission mask (9) is irradiated with the first reduction lens system (10) and the second reduction lens system (1).
In the electron beam reduction transfer device for guiding the electron beam onto the target (17) via 4), the first reduction lens system (10) includes a first main coil (11) having a large product of the current and the number of turns, and the current. A second sub-coil (12) having a small product of the number of turns is wound, and a second main coil (15) having a large product of the current and the number of turns is applied to the second reduction lens system (14). The second auxiliary coil (16) having a small product of the number of turns is wound.

Further, in a second electron beam reduction transfer apparatus according to the present invention, for example, as shown in FIG. 1, an electron beam emitted from an electron beam source (1) is transmitted to an illumination lens system (4, 5, 7). The electron beam transmission mask (9) is irradiated through the first reduction lens system (1) with the electron beam transmitted through the electron beam transmission mask (9).
0) and the electron beam reduction transfer device for guiding the electron beam onto the target (17) through the second reduction lens system (14), the first reduction lens system (10) has a large current-turn number product. One main coil (11) and a first sub-coil (12) having a small product of the current and the number of turns are wound, and the second reduction lens system (14) has a large product of the current and the number of turns. And a second sub-coil (16) having a small product of the current and the number of turns, and winding the first main coil (1).
Current is supplied to the 1) and the second main coil (15) in series from the same power supply. Also, the according to the invention
The electron beam reduction transfer device 3 is, for example, as shown in FIG.
An electron beam emitted from the electron beam source (1) is irradiated to an electron beam transmission mask (9) through an illumination lens system (4, 5, 7), and the electron beam transmitted through the electron beam transmission mask (9). Are replaced by a first reduction lens system (10) and a second reduction lens system (1).
In the electron beam reduction transfer device for guiding the electron beam onto the target (17) via 4), the first reduction lens system (10) includes a first main coil (11) having a large product of the current and the number of turns, and the current. A second sub-coil (12) having a small product of the number of turns is wound, and a second main coil (15) having a large product of the current and the number of turns is applied to the second reduction lens system (14). A second main coil (11) and a second main coil (15) are wound around the second sub coil (16) having a small product of the number of turns.
Supplies a current from the same power supply in series, and adjusts a current flowing through the first sub-coil (12) and the second sub-coil (16) to thereby control the first reduction lens system (1).
0) and the reduction magnification by the second reduction lens system (14).

[0009]

[0010]

SUMMARY OF According to the electron beam reduction transfer apparatus of the present invention,
For example, changing the ratio of the current flowing through the first sub-coil (12) of the first reduction lens system (10) to the current flowing through the second sub-coil (16) of the second reduction lens system (14). Thereby, the ratio of the focal length between the first reduction lens system (10) and the second reduction lens system (14) is finely adjusted. Therefore,
The reduction ratio is also finely adjusted. In this case, a current is supplied from the same power supply to the first main coil (11) of the first reduction lens system (10) and the second main coil (15) of the second reduction lens system (14). Therefore, even if the current value changes due to power supply fluctuations, the upper and lower reduction lens systems (10, 14) fluctuate almost simultaneously at the same time, so that fluctuations such as reduction magnification and rotation are extremely small.

[0011]

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electron beam reduction transfer apparatus according to the present invention will be described below with reference to FIGS. In the present embodiment, the present invention is applied to an electron beam reduction transfer device using a symmetric magnetic doublet as a reduction lens system. FIG.
FIG. 1 shows the configuration of the electron beam reduction transfer apparatus of the present embodiment. In FIG. 1, an electron gun comprises a cathode 1, a Wehnelt (focusing electrode) 2, and an anode 3 to which an accelerating voltage is applied. A first condenser lens 4, a second condenser lens 5, an aperture plate 6, a third condenser lens 7, a shutter 8, and an electron beam transmission mask 9 are disposed in this order from the electron gun. The electron beam transmitting mask 9 has a mask pattern formed of a circuit pattern and the like, and an alignment mark. The shutter 8 has an opening 8a for irradiating only the mask pattern with an electron beam and an alignment mark. And a window portion 8b for irradiating an electron beam only on the surface.

A projection lens 10 and an aperture plate 1 as an aperture stop are arranged in this order from the electron beam transmission mask 9 to the lower side.
3. The objective lens 14 and the target 17 are arranged. From the projection lens 10 and the objective lens 14, a predetermined reduction magnification β
Symmetric magnetic doublets are constructed. In this example, first, for the projection lens 10, the bore diameter on the target 17 side is set smaller than that on the electron beam transmission mask 9 side, and for the objective lens 14, the target 17
The bore diameter on the electron beam transmission mask 9 side is set smaller than the bore diameter on the side. Thereby, interference between the magnetic field of the projection lens 10 and the magnetic field of the objective lens 14 is reduced, and distortion is reduced.

Next, in this embodiment, the coil wound around the projection lens 10 is divided into a main coil 11 having a large ampere-turn AT, which is a product of the current and the number of turns, and a sub-coil 12 having a small ampere-turn AT, and is coaxial. Wrap around. Similarly, the coil wound around the objective lens 14 is divided into a main coil 15 having a large ampere-turn AT and a sub-coil 16 having a small ampere-turn AT, and is wound coaxially.

In this case, the main coil 11 and the main coil 15 are connected in series, and the same current flows from a common power supply circuit. The design of the main coil 11 and the main coil 15 is such that the number of turns of the coil is adjusted so as to satisfy the condition of the symmetric magnetic doublet when the same current flows. However,
The magnetic field generated by the main coil 11 and the magnetic field generated by the main coil 15 have opposite polarities. The sub coil 12
The number of turns of the coils of the main coils 11 and 1 are respectively
5 is set to 1/100 of the number of turns, and the sub-coils 12 and 16
Is set to 1/10 of the current value flowing through the main coils 11 and 15, respectively.

To explain the operation of this embodiment, the electron beam emitted from the cathode 1 of the electron gun is focused on the opening of the aperture plate 6 by the condenser lenses 4 and 5 as shown by a typical trajectory 18. Thereby, the size of the crossover which is the image of the electron beam source is adjusted. The electron beam emitted from the aperture of the aperture plate 6 is converted into a parallel beam by the condenser lens 7 and then irradiates the electron beam transmission mask 9 through the aperture of the shutter 8. Electron beam transmission mask 9
The electron beam formed by the objective lens 1 is focused near the opening of the aperture plate 13 by the projection lens
The light is irradiated onto the target 17 through the target 4. As a result, the pattern of the electron beam transmission mask 9 has a predetermined reduction magnification β.
And the image is formed on the target 17. The reduction lens system composed of the projection lens 10 and the objective lens 14 is bilateral telecentric. If the focal length of the projection lens 10 is f1 and the focal length of the objective lens 14 is f2, the reduction magnification β can be substantially expressed by f2 / f1. it can.

In this embodiment, for example, if the current flowing through the sub-coil 12 is changed by α%, the ampere turn AT of the projection lens 10 as a whole becomes about α / 100000 (= α /
100 × (1/100) × (1/10)) times.
Similarly, when the current flowing through the sub coil 16 is changed by γ%,
The ampere turn AT of the objective lens 14 changes about γ / 100000 times as a whole. Therefore, when the current flowing through the sub-coil 12, the current flowing through the sub-coil 16, or the current flowing through the sub-coils 12 and 16 is changed, the current ratio between the projection lens 10 and the objective lens 14 is finely adjusted as a whole, and as a result, the focal length Is fine-tuned. This means that the reduction magnification β is finely adjusted.

In this case, in this embodiment, the main coil 11 of the projection lens 10 and the main coil 15 of the objective lens 14 are connected in series, and the same current is supplied to the main coils 11 and 15 from a common power source. The ampere turns AT of the sub coils 12 and 16 are equal to the main coils 11 and 15 respectively.
Is set to 1/1000 as compared with. Therefore, even if the current value changes due to power supply fluctuation or the like, the characteristics of the projection lens 10 and the characteristics of the objective lens 14 change at the same time and almost the same, so that the magnification or rotation does not change.

Also, due to manufacturing errors such as lens dimensions, etc.,
In the case where the reduction magnification β greatly deviates from the design value, in this example, the position D1 of the electron beam transmission mask 9 in the optical axis direction of the electron optical column or the position D2 of the target 17 in the optical axis direction is adjusted. Thereby, the reduction magnification β is adjusted to the design value.

FIG. 2 shows the aberration calculation result of the present embodiment. The horizontal axis in FIG. 2 is the current value (standard value) of the sub coil 16 of the objective lens 14, the vertical axis on the left is distortion in a field of view of 27 mm × 27 mm,
The vertical axis on the right side shows the reduction magnification and the astigmatism coefficient. As shown by the curve K1 in FIG. 2, the astigmatism coefficient which is a main factor of the blur of the electron beam hardly changes even when the lens current is changed. On the other hand, the distortion changes in a valley shape as shown by the curve K3, but the value of the distortion is 0.1 μm or less even when the lens current changes from 0.7934 to 0.7938. Correspondingly, the reduction magnification changes from 0.33417 to 0.3334 as shown by the curve K2. This indicates that by adjusting the current value of the objective lens 14, it is possible to finely adjust the reduction magnification β by about 0.22% under the condition that the distortion is 0.1 μm or less. Therefore, even if the semiconductor wafer as the target 17 shown in FIG. 1 expands and contracts by about 0.1% through various processes, the mask pattern can always be formed with high overlay accuracy by finely adjusting the reduction magnification β accordingly. Can be transcribed.

FIG. 3 shows the position D of the electron beam transmitting mask 9.
3 are the aberration calculation results when 1 is changed. The curve K4 in FIG. 3A is the reduction magnification, and the curve K5 in FIG.
The distortion in a visual field of 27 mm is shown. The mask position D1 takes the direction approaching the target 17 as positive (+). However, each time the mask position D1 is changed, the current values of the projection lens 10 and the objective lens 14 are changed so that the distortion is minimized. 3B, the mask position D1 is set to -6 mm or more.
It can be seen that even if the width is changed by 15 mm to 9 mm, the strain is 0.1 μm or less. Correspondingly, as shown in FIG. 3A, the reduction magnification is from 0.33499 to 0.3327.
It has changed to 3. This means that, by changing the mask position D1, the reduction magnification β can be changed relatively largely within the range of about 0.678% under the condition that the distortion is 0.1 μm or less. Similarly, even if the position D2 of the target 17 is changed, the reduction magnification can be changed relatively large.

Therefore, in order to reduce the manufacturing cost, for example, the processing accuracy of the lens component and the accuracy of the lens position are roughly set, and the reduction magnification β is relatively large from the design value, for example, 1
%, The reduction magnification β can be made closer to the design value by adjusting the position D1 of the electron beam transmission mask 9 in the optical axis direction or the position D2 of the target 17 in the optical axis direction. . Thereby, the manufacturing accuracy of the electron optical system can be reduced. Also, in the above embodiment,
For example, as shown in FIG.
The electron beam emitted from the source (1) is transmitted to the illumination lens system (4, 4).
Irradiate the electron beam transmission mask (9) through (5, 7),
The electron beam transmitted through the electron beam transmission mask (9)
Target (17) via small lens system (10, 14)
In the electron beam reduction transfer device leading up, the two reductions
By changing the current ratio of the small lens system (10, 14)
And reduction by the two reduction lens systems (10, 14).
Can be considered as adjusting the small magnification.
You. According to this electron beam reduction transfer device, two reduction lenses
Change the reduction ratio by changing the current ratio of the
I have to. Therefore, the lens position of the reduction lens system changes.
, The distortion is kept small and the reduction ratio is relatively wide.
It has the advantage that it can be fine-tuned within a small range. In addition, the reduction
It can be easily adjusted by computer control or the like. Ma
In addition, the electron beam reduction transfer device of the above-described embodiment is, for example, shown in FIG.
As shown in the figure, the electron beam emitted from the electron beam source (1) is
Electron beam transmission mask via illumination lens system (4,5,7)
(9), and is transmitted through this electron beam transmission mask (9).
Target beam through the reduction lens system (10, 14).
In the electron beam reduction transfer device leading to the
Electron beam transmission mask (9) or its target (1)
7) Adjust the position of the optical axis (or both of them)
Or the electron beam transmission mask (9) or
Optical axis direction of the target (17) (or both)
By shifting the direction from the design position, the reduction
Adjustment of reduction ratio of lens system (10, 14)
Can also be considered as something. This electron beam reduction
According to the imaging apparatus, the electron beam transmission mask or the target
Adjusting the position in the optical axis direction of the child light Science barrel (design position
To reduce distortion while keeping distortion low.
The magnification can be roughly adjusted over a wider range. Therefore, electron optics
Easy reduction ratio even when system manufacturing accuracy is set roughly
Has the advantage that it can approach the target value. It should be noted that the present invention is not limited to the above-described embodiments, but can take various configurations without departing from the gist of the present invention.

[0023]

[0024]

According to the electron beam reduction transfer apparatus of the present invention,
For example, by adjusting the current flowing through the first sub-coil and the second sub-coil, the current ratio between the first reduction lens system and the second reduction lens system is adjusted, and thus the reduction magnification is adjusted. . Furthermore, since the first main coil and the second main coil are connected in series and supplied with the same current, even if the current value changes due to power fluctuation or the like, the characteristics of the two lenses are simultaneously and simultaneously. Since the fluctuations are almost the same, there is an advantage that the reduction ratio and the rotation do not fluctuate.

[Brief description of the drawings]

FIG. 1 is an end view of a longitudinal section showing an embodiment of an electron beam reduction transfer apparatus according to the present invention.

FIG. 2 is a characteristic diagram illustrating a change in an imaging characteristic when a lens current is changed in the embodiment.

FIG. 3A is a characteristic diagram showing a change in reduction magnification when the mask position D1 is changed in the embodiment, and FIG. 3B is a characteristic diagram showing a change in distortion when the mask position D1 is changed in the embodiment. It is.

FIG. 4 is an end view of a cross section of a reduction lens on an electron beam transmission mask side of a conventional electron beam reduction transfer device.

[Explanation of symbols]

 Reference Signs List 1 cathode 4 first condenser lens 5 second condenser lens 7 third condenser lens 9 electron beam transmission mask 10 projection lens 11 main coil 12 sub-coil 14 objective lens 15 main coil 16 sub-coil 17 target

Claims (3)

(57) [Claims] An electron beam emitted from an electron beam source is irradiated on an electron beam transmission mask via an illumination lens system, and the electron beam transmitted through the electron beam transmission mask is irradiated with a first reduction lens system and a second reduction lens system. An electron beam reduction transfer device for guiding a target through a reduction lens system, wherein the first reduction lens system has a first main coil having a large product of the current and the number of turns, and a first main coil having a small product of the current and the number of turns. And a second main coil having a large product of the current and the number of turns and a second sub coil having a small product of the current and the number of turns are also wound around the second reduction lens system. Characteristic electron beam reduction transfer device. 2. An electron beam emitted from an electron beam source is irradiated on an electron beam transmission mask via an illumination lens system, and the electron beam transmitted through the electron beam transmission mask is irradiated with a first reduction lens system and a second electron beam. An electron beam reduction transfer device for guiding a target through a reduction lens system, wherein the first reduction lens system has a first main coil having a large product of the current and the number of turns, and a first main coil having a small product of the current and the number of turns. A second main coil having a large product of the current and the number of turns and a second sub coil having a small product of the current and the number of turns in the second reduction lens system; An electron beam reduction transfer apparatus, wherein current is supplied to the first main coil and the second main coil in series from the same power supply. 3. An electron beam emitted from an electron beam source is applied to an electron beam transmission mask via an illumination lens system, and the electron beam transmitted through the electron beam transmission mask is irradiated with a first reduction lens system and a second electron beam. An electron beam reduction transfer device for guiding a target through a reduction lens system, wherein the first reduction lens system has a first main coil having a large product of the current and the number of turns, and a first main coil having a small product of the current and the number of turns. A second main coil having a large product of the current and the number of turns and a second sub coil having a small product of the current and the number of turns in the second reduction lens system; A current is supplied to the first main coil and the second main coil in series from the same power supply, and the current flowing to the first sub coil and the second sub coil is adjusted to thereby reduce the first reduction lens. System and the second reduction lens system to adjust the reduction magnification. Things electron ray reduction transfer apparatus according to claim.