JPH0727854B2 - Electron beam writer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an electron beam drawing apparatus for drawing an ultrafine figure with an electron beam.

[Background of the Invention]

Electron beam drawing for focusing and deflecting an electron beam to irradiate it on a substrate and drawing an arbitrary figure is used for manufacturing a semiconductor integrated circuit device or the like. When using this to draw ultra-fine figures of 0.2 μm or less, the beam to be irradiated is limited to a small beam divergence angle because it is necessary to reduce blur due to aberration, so the current value is small and drawing is long. The drawback is time-consuming.

In the prior art, in order to solve the problem, the beam spot is changed according to the figure to speed up the drawing.
It is disclosed in Japanese Patent No. 89579.

However, although this prior art describes that the deflection direction and the focus position shift are corrected in accordance with the change of the lens magnification, it has a problem that it takes a lot of time and labor.

In the above-mentioned prior art, besides adjusting the bias voltage of the electron gun in order to change the beam diameter, the lens condition is changed and readjustment of the deflection direction is also shown. This work is generally described as requiring a long time and automation is desirable, but no specific disclosure is given.

Lens operations and figures (c) and (d) using FIGS.
The adjustment of the deviation of the deflection direction and the deflection sensitivity when drawing a square will be described.

With the beam diameter in FIG. 10A as the standard, increasing the beam diameter weakens the excitation of the focusing lens so that the object point position A in FIG. At this time, the focal position of the objective lens changes from above the exposed object. Again, the objective lens is strongly excited and adjusted in order to bring the focus position of the objective lens onto the object to be exposed. As a result, both the focusing lens and the objective lens become an expanding system as compared with (a), and the beam diameter increases.

The deflection direction of the deflector and the deflection sensitivity are completely different between FIG. (B) and FIG. (A) according to the excitation change of the objective lens.

Therefore, it becomes necessary to recalibrate the deflection (generally requiring a very long time).

A conceptual description of how the deflection sensitivity and the deflection direction differ is as follows.

That is, for example, it is assumed that the deflector is adjusted so as to draw a square of which one side is L in the state of FIG. (Figure C),
When the same deflection signal as that shown in FIG. 7A is applied in the state of FIG. 9B (the objective lens is strongly excited), when written extremely, the rotation of one side 1 smaller than L as shown by the solid line in FIG. It becomes a square. This does not improve drawing accuracy. In order for the lens to draw a square with one side L as shown in FIG. 7C in the state shown in FIG. 7B, a strong signal different from that shown in FIG. When this is written by the formula, X ′ ＝ (1 + A ₁ ) X ＋ B ₁ Y ＋ C ₁ X ² ＋ D ₁ XY ＋ E ₁ Y ² ＋ O ₁ (3) Y ′ ＝ A ₂ X ＋ (1 + B ₂ ) Y ＋ C ₂ X ² XY ＋ E ₂ Y ² + O ₂ (3) where A to E are coefficients, and O (3) is a correction term of the third or higher order of X and Y.

Now, for the deflection signals X and Y, in the state (a), all the coefficients are A = B = C = D = E = O, O ₁ = 0 ₂ = O, and the square on one side of FIG. However, in the state (b), it is necessary to obtain the non-O coefficient and apply the signals X ', Y'added according to the above equation to the deflector. Generally, it takes a long time to obtain these coefficients. if,
If it is done by hand, it requires an order of time. Moreover, the focus of the beam needs to be calibrated at the same time as the astigmatism adjustment, which is more complicated and time-consuming.

[Object of the Invention]

An object of the present invention is to provide an electron beam drawing apparatus capable of high-accuracy and high-speed electron beam drawing, except for the above-mentioned drawbacks when adjusting the deviation of the radial deflection direction and the deflection sensitivity due to beam change. .

The present invention provides a drawing apparatus that can change the beam diameter at the same object point position because high-speed drawing that cannot be realized by the above-mentioned known example can be achieved.

[Outline of Invention]

In order to achieve the above object, in the present invention, not all graphics to be drawn, such as a semiconductor integrated circuit element, are fine and require high precision, and in many cases loose precision is sufficient. Therefore, the beam diameter (and current) is switched according to the figure. Fine and high-precision ones are designed to draw with a small beam diameter and a small pitch, and other than that, it is configured to draw with a large beam diameter and large pitch. The drawing time can be greatly shortened.

Example of Invention

An embodiment of the present invention will be described below. FIG. 1 shows an example of switching the beam diameter (and current). Reference numeral 1 denotes an electron source. For the purpose of drawing an ultrafine figure, a field emission cathode having a small source diameter and high brightness is used. It is preferable to use. 2, 3 and 4 are electronic lenses, and 5 is a substrate to be drawn. In the state (a) of the drawing, the beam diameter is small, only the electron lenses 3 and 4 are used, and the source is reduced and projected onto the substrate. In the same figure (b), the beam diameter is made large, and the electron lens 2 and 4 are used as a magnifying system. in this case,
By setting the electron lenses 2 and 3 so that the positions of the object points of the electron lens 4 are the same, the usage conditions of the electron lens 4 can be made the same. That is, the lens 2
The beam diameter can be changed simply by selecting which of 3 and 3 is used. In this case, the change in beam current is the square of the magnification. Therefore, if the magnification ratio is set to 1: 2, the beam diameter (and current) will change at 1: 4.

When the electron beam current is increased, the scanning speed needs to be increased if the deflection scanning pitch for writing is the same, but when a field emission cathode is used as the electron source, the required speed is increased due to the large current density. It becomes very large and causes a problem in the response of the deflection electric circuit. Therefore, it is preferable to make the scanning pitch rough so as to make the scanning speed equal.

A high-precision drawing device is usually subjected to digital deflection. Therefore, if the scanning pitch is selected as an integer multiple ratio of the minimum deflection unit (LSB) and the beam current ratio is the square of the scanning pitch, the scanning speeds can be made equal. Third
The figure shows an example of a figure drawn by the above method. The figure (a) is a figure drawn with a fine scanning pitch with a small beam diameter, and the figure (b) is a rough scanning pitch with a large beam diameter. It is a drawn figure. As can be seen from the figure, when writing with a large beam diameter, the number of beam irradiations is small (the reciprocal of the beam current ratio) and the scanning speed is the same, so the writing time is shortened.

Although the two-stage switching is exemplified above, it is easy to set the number of stages to three or more depending on the required accuracy of the figure.
In the electronic lens switching shown in the figure, it is possible to realize an arbitrary magnification between the magnifications obtained by only the lens 2 and the lens 3 by appropriately exciting 2 and 3.

〔The invention's effect〕

As described above, according to the present invention, a graphic with low accuracy can be drawn at high speed, so that the drawing time as a whole can be greatly shortened. For example, if the drawing area ratio is 20% for high-precision figures, and the drawing is performed in two stages with a beam diameter ratio of 1: 2 (beam current ratio of 1: 4), compared to the conventional method of drawing with a small beam diameter , Can be drawn in 40% of the time.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention, FIG. 2 is a diagram for explaining a lens operation and a deflection direction and a deflection sensitivity when a figure is drawn in a conventionally known example, and FIG. 3 is a drawing according to the present invention. It is a figure explaining an example of a figure. 1 ... Electron source, 2,3,4 ... Electronic lens, 5 ... Substrate, 6,
6 ′ …… Aperture.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tokuro Saito 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Katsuyuki Harada 1839 Ono, Atsugi-shi, Kanagawa Nippon Telegraph and Telephone Public Corporation Atsugi Inside the Telecommunications Research Institute (72) Inventor Myouhei Fujinami 1839 Ono, Atsugi-shi, Kanagawa Nippon Telegraph and Telephone Public Corporation Atsugi Telecommunications Research Institute (72) Inventor Kazumi Iwatate 1839 Ono, Atsugi-shi, Kanagawa Nippon Telegraph and Telephone Public Corporation Atsugi Electric Communication Research Laboratory (56) References JP 54-89579 (JP, A) JP 48-49376 (JP, A)

Claims (1)

[Claims] 1. An electron beam in which a field emission cathode is used as an electron source for emitting an electron beam, and the electron beam emitted from the electron source is projected through a plurality of electron lenses onto a substrate to be drawn. In the drawing apparatus, means for switching the diameter of the electron beam projected on the substrate into a plurality of stages by switching the excitation of the other two electron lenses in a state where the object point position of the final stage electron lens is held, An electron beam drawing apparatus further comprising means for switching the drawing scanning pitch in proportion to the beam diameter ratio in response to the switching of the projected electron beam diameter.