JPH05175113A - Electron beam contraction transfer apparatus - Google Patents

Abstract

PURPOSE:To increase a regulating range of a contraction magnification by limiting a distortion to an allowable range. CONSTITUTION:A main coil 11 having a large product of a current and number of turns and a sub coil 12 having a small product of a current and number of turns are wound on a projection lens 10, and a main coil 15 having a large product of a current and number of turns and a sub coil 16 having a small product of a current and number of turns are wound on an objective lens 14. The coils 11, 15 are connected in series, a current is supplied from the same power source thereto, and a contraction magnification is regulated by regulating the currents flowing to the coils 12, 16.

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 An electron beam reduction transfer apparatus is used to transfer a circuit pattern or the like formed on a mask onto a semiconductor substrate or the like at a predetermined reduction ratio (reduction ratio). In this type of transfer device, it is required that the distortion at the time of transfer be kept 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 adjusting mechanism for adjusting the reduction ratio on the transfer device side is required accordingly. 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 ratio does not fall within the allowable range with respect to the design value, Also, a mechanism for adjusting the reduction ratio is required.

In order to adjust such a reduction ratio,
In the conventional electron beam reduction transfer device, as shown in FIG. 4, the coil of the reduction lens 20 on the electron beam transmission mask side is separately wound around the mask side coil 21 and the target side coil 22. Then, the reduction magnification is changed by changing the ratio of the currents flowing through the coils 21 and 22 and equivalently changing the lens position of the reduction lens 20.

[0004]

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

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an electron beam reduction transfer apparatus in which distortion is contained within a permissible range and the reduction magnification adjustment range is wide.

[0006]

A first electron beam reduction transfer apparatus according to the present invention is, for example, as shown in FIG. 1, an electron beam emitted from an electron beam source (1) for illuminating a lens system (4, 5). ，
An electron beam which irradiates the electron beam transmission mask (9) via 7) and guides the electron beam transmitted through this electron beam transmission mask (9) onto a target through two reduction lens systems (10, 14). In the reduction transfer device, the reduction ratio by the two reduction lens systems (10, 14) is adjusted by changing the current ratio of the two reduction lens systems (10, 14).

The second electron beam reduction transfer apparatus according to the present invention uses an illumination lens system (4, 5, 7) for an electron beam emitted from an electron beam source (1) as shown in FIG. 1, for example. The electron beam transmission mask (9) is irradiated with the electron beam through the electron beam transmission mask (9) and the electron beam transmitted through the electron beam transmission mask (9) is passed through the first reduction lens system (1).
0) and the second reduction lens system (14) to guide the electron beam to the target (17), the first reduction lens system (10) has a large product of current and winding number. One main coil (11) and a first sub-coil (12) having a small product of current and the number of turns are wound, and the second reduction lens system (14) also has a large product of the current and the number of turns. The second main coil (15) and the second sub coil (16) having a small product of the current and the number of turns are wound, and the first main coil (1)
1) Supplying a current to the second main coil (15) and the second main coil (15) in series from the same power source, and adjusting the currents flowing through the first sub coil (12) and the second sub coil (16). Thus, the reduction magnification by the first reduction lens system (10) and the second reduction lens system (14) is adjusted.

The third electron beam reduction transfer apparatus according to the present invention uses an illumination lens system (4, 5, 7) for an electron beam emitted from an electron beam source (1) as shown in FIG. 1, for example. The electron beam transmitting mask (9) is irradiated with the electron beam through the electron beam transmitting mask (9), and the electron beam transmitted through the electron beam transmitting mask (9) is reduced by a reduction lens system (10, 1).
4) In the electron beam reduction transfer apparatus for guiding the electron beam through the target (17) via the electron beam transmission mask (9) or the target (17) in the optical axis direction, the reduction lens is moved. The reduction ratio of the system (10, 14) is adjusted. Furthermore, the positions of both the electron beam transmission mask (9) and the target (17) in the optical axis direction may be shifted.

[0009]

According to the first electron beam reduction transfer apparatus of the present invention, the reduction lens system (10) on the electron beam transmission mask (9) side of the two reduction lens systems (10, 14) is used. The focal length is f1, and the reduction lens system (14) on the target (17) side
, The reduction ratio β is approximately f2 / f.
It becomes 1. Then, these two reduction lens systems (10,
When the current ratio of 14) is changed, the focal length ratio f1 / f2 also changes correspondingly, and consequently the reduction ratio β which is the reciprocal of the focal length ratio also changes. In this case, since the lens position does not change and the distortion remains small, it is possible to suppress the distortion to a small degree and relatively change the reduction ratio.

Further, according to the second electron beam reduction transfer device, the first sub-coil (1) of the first reduction lens system (10) is used.
By changing the ratio of the current flowing in 2) and the current flowing in the second sub-coil (16) of the second reduction lens system (14), the first reduction lens system (10) and the second reduction lens The ratio of the focal length with the system (14) is finely adjusted. Therefore, the reduction ratio is also finely adjusted. In this case, current is supplied from the same power source 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 fluctuations in the power supply or the like, the upper and lower reduction lens systems (10, 14) change at substantially the same time.

Further, according to the third electron beam reduction transfer device, when the position of the electron beam transmission mask (9) is brought closer to the target (17) side, the electron beam transmission mask (9) and the reduction lens system (10). , 14) with respect to the entire main plane, the reduction ratio β increases. On the contrary, if the position of the electron beam transmission mask (9) is kept away from the target (17), the reduction ratio β becomes small. Similarly, the reduction ratio β can be changed by changing the position of the target (17). Although the distortion increases as the reduction magnification β changes, in order to reduce the distortion, the reduction lens system (1
0, 14) to adjust the current.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electron beam reduction transfer apparatus according to the present invention will be described below with reference to FIGS. In this embodiment, the present invention is applied to an electron beam reduction transfer apparatus using a symmetrical magnetic doublet as a reduction lens system. Figure 1
Shows the structure of the electron beam reduction transfer apparatus of this example. In FIG. 1, an electron gun is composed of a cathode 1, a Wehnelt (focusing electrode) 2 and an anode 3 to which an acceleration 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 arranged in this order from the electron gun to the lower side. A mask pattern made of a circuit pattern or the like and an alignment mark are formed on the electron beam transmission mask 9, and the shutter 8 has an opening 8a for irradiating only the mask pattern with an electron beam and an alignment mark. A window portion 8b for irradiating the electron beam is formed only on.

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 downward.
3, the objective lens 14 and the target 17 are arranged. The projection lens 10 and the objective lens 14 provide a predetermined reduction ratio β.
Symmetric magnetic doublets are constructed. In this example, first, for the projection lens 10, the Bohr diameter on the target 17 side is set smaller than the Bohr diameter on the electron beam transmission mask 9 side, and for the objective lens 14, the target 17 is set.
The Bohr diameter on the electron beam transmission mask 9 side is set smaller than the Bohr diameter on the side. As a result, 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 example, the coil wound around the projection lens 10 is divided into a main coil 11 having a large ampere turn AT, which is the product of the current and the number of turns, and a sub coil 12 having a small ampere turn AT, which are 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 wound coaxially.

In this case, the main coil 11 and the main coil 15 are connected in series, and the same current flows from the common power supply circuit. The main coil 11 and the main coil 15 are designed so that the number of turns of the coils is adjusted so that the condition of the symmetrical magnetic doublet is satisfied when the same current is applied. However,
The polarities of the magnetic field generated by the main coil 11 and the magnetic field generated by the main coil 15 are opposite. In addition, the sub coil 12
And the number of turns of the coils of 16 are the main coils 11 and 1 respectively.
Set to 1/100 of the number of turns of 5 and the auxiliary coils 12 and 16
The value of the current flowing in the coil is set to 1/10 of the value of the current flowing in the main coils 11 and 15.

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. Thus, the size of the crossover which is the image of the electron beam source is adjusted. The electron beam emitted from the opening of the aperture plate 6 is converted into a parallel beam by the condenser lens 7, and then the electron beam transmission mask 9 is irradiated through the opening of the shutter 8. Electron beam transparent mask 9
The electron beam formed in 1 is focused by the projection lens 10 near the aperture of the aperture plate 13 and then the objective lens 1
It is irradiated onto the target 17 via the beam line 4. As a result, the pattern of the electron beam transmission mask 9 has a predetermined reduction ratio β.
Is reduced and imaged on the target 17. The reduction lens system including the projection lens 10 and the objective lens 14 is a telecentric on both sides, and when 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 represented by approximately f2 / f1. it can.

In this example, when the current flowing through the sub-coil 12 is changed by α%, the ampere turn AT of the projection lens 11 as a whole is about α / 1000000 (= α /
Change by 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 as a whole by about γ / 100000 times. 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, which in turn results in a focal length. The ratio of is fine-tuned. This means that the reduction ratio β is finely adjusted.

In this case, in this example, 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 from the common power source to the main coils 11 and 15, and The ampere-turn AT of the sub-coils 12 and 16 is the main coil 11 and 15 respectively.
It is set to 1/1000 compared to. Therefore, the characteristics of the projection lens 10 and the characteristics of the objective lens 14 change at the same time and almost in the same manner even if the current value changes due to a power supply change or the like, so that the magnification or rotation does not change.

Also, due to manufacturing errors such as lens dimensions,
If the reduction ratio β is largely deviated 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. By doing so, the reduction ratio β is adjusted to the design value.

FIG. 2 shows the aberration calculation result of this example. The horizontal axis of FIG. 2 is the current value (standard value) of the sub-coil 16 of the objective lens 14, the left vertical axis is the distortion in the visual field of 27 mm × 27 mm,
The vertical axis on the right side shows the reduction ratio and the astigmatism coefficient. As shown by the curve K1 in FIG. 2, the astigmatism coefficient, which is the main cause 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 distortion value is 0.1 μm or less even when the lens current changes from 0.7934 to 0.7938. Correspondingly, the reduction ratio 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, the reduction ratio β can be finely adjusted 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 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 ratio β accordingly. Can be transcribed.

Next, FIG. 3 shows the position D of the electron beam transmission mask 9.
3 is a result of aberration calculation when 1 is changed. A curve K4 in FIG. 3A is a reduction magnification, and a curve K5 in FIG. 3B is 27 mm ×
The distortion in the field of view of 27 mm is shown. The mask position D1 has a positive (+) direction toward the target 17. 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. As shown in FIG. 3B, the mask position D1 is -6 mm
It can be seen that the strain is 0.1 μm or less even when the width is changed to 9 mm by 21 mm. Corresponding to this, as shown in FIG. 3A, the reduction ratio is from 0.33499 to 0.3327.
It has changed to 3. This means that by changing the mask position D1, the reduction ratio β can be changed relatively large within the range of about 0.678% under the condition that the strain is 0.1 μm or less. Similarly, even if the position D2 of the target 17 is changed, the reduction ratio can be changed relatively greatly.

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 ratio β is relatively large from the design value, for example, 1.
%, The reduction ratio β can be brought close 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. .. As a result, the manufacturing precision of the electro-optical system can be roughened. It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0023]

According to the first electron beam reduction transfer apparatus of the present invention, the reduction magnification is changed by changing the current ratio of the two reduction lens systems. Therefore, since the lens position of the reduction lens system does not change, there is an advantage that the reduction magnification can be finely adjusted in a relatively wide range while suppressing distortion. Further, the reduction ratio can be easily adjusted electrically by computer control or the like.

According to the second electron beam reduction transfer device,
The current ratio between the first reduction lens system and the second reduction lens system is adjusted by adjusting the current flowing through the sub-coil and the second sub-coil, and the reduction magnification is adjusted accordingly.
Furthermore, since the first main coil and the second main coil are connected in series and the same current is supplied, even if the current value changes due to power supply fluctuations, the characteristics of the two lenses are Since it changes almost in the same manner, there is an advantage that the reduction ratio and the rotation do not change. Further, according to the third electron beam reduction transfer apparatus, by shifting the position of the electron beam transmission mask or the target in the optical axis direction of the electron optical lens barrel from the design position, the distortion can be suppressed to be small and the reduction magnification can be further increased. Coarse adjustment is possible in a wide range. Therefore, even if the manufacturing precision of the electron optical system is roughly set, there is an advantage that the reduction ratio can be easily brought close to the target value.

[Brief description of 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 showing a change in image forming characteristic when the lens current is changed in the example.

3A is a characteristic diagram showing a change in reduction ratio 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. Is.

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

[Explanation of symbols]

 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)

[Claims] 1. An electron beam emitted from an electron beam source is applied to an electron beam transmission mask through an illumination lens system, and the electron beam transmitted through the electron beam transmission mask is targeted through two reduction lens systems. In the electron beam reduction transfer apparatus guided to the above, the reduction ratio by the two reduction lens systems is adjusted by changing the current ratio of the two reduction lens systems. .. 2. An electron beam emitted from an electron beam source is applied to an electron beam transmissive mask through an illumination lens system, and the electron beam transmitted through the electron beam transmissive mask is a first reduction lens system and a second reduction lens system. In an electron beam reduction transfer apparatus for guiding onto a target via a reduction lens system, a first main coil having a large product of current and the number of turns and a first main coil having a small product of the current and the number of turns are provided to the first reduction lens system. A sub coil is wound, and a second main coil having a large product of current and the number of windings and a second sub coil having a small product of the current and the number of windings are also wound on 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 source, and the currents flowing through the first sub coil and the second sub coil are adjusted to adjust the first reduction lens. System and the second reduction lens system Things electron ray reduction transfer apparatus according to claim. 3. An electron beam emitted from an electron beam source is applied to an electron beam transmissive mask through an illumination lens system, and the electron beam transmitted through the electron beam transmissive mask is guided onto a target through a reduction lens system. In the electron beam reduction transfer device, the electron beam reduction mask is characterized in that the reduction magnification of the reduction lens system is adjusted by shifting the position of the electron beam transmission mask or the target in the optical axis direction from the design position. Transfer device.