JPH01276629A - Calibration of astigmatism in rectangular beam lithography apparatus - Google Patents

Abstract

PURPOSE:To enhance the resolution of a drawing pattern by making a rise of a beam profile steep by a method wherein, after a focus of an objective has been adjusted, astigmatism in the x and y directions is corrected by using an astigmatism corrector. CONSTITUTION:A mark having a right-angled part is arranged on a material 13; while the intensity of an objective 11 is changed, this mark is scanned in the x and y directions by means of a rectangular beam; intensity Lx, Ly of the objective when a peak in an obtained edge rise signal has become maximum are stored. Then, the intensity of the objective is set to Lx+Ly/2; after that, while the intensity of the signal to an astigmatism corrector 19 is changed, the mark is scanned by means of the rectangular beam; the astigmatism corrector is set to a value obtained when a peak in an obtained edge rise signal in the x and y directions has become maximum. By this setup, a rise of a beam profile of the rectangular beam is made steep; the resolution of a drawing pattern can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for calibrating astigmatism in a rectangular beam drawing apparatus.

[Prior Art] When drawing a specific pattern on a material using a drawing device such as an electron beam drawing device, there are two types of electron beams used: a spot beam type and a rectangular beam type. The former is used when drawing a fine pattern on a material, and the latter is used when a pattern needs to be exposed at high speed. FIG. 5 is a diagram showing an example of a conventional configuration of a rectangular beam drawing apparatus using a rectangular beam.

An electron beam Bi emitted from an electron gun (not shown) irradiates the first shaping aperture 1 . The first shaping aperture 1 has a rectangular hole, and the electron beam 3i passing through the first shaping aperture becomes rectangular. On the other hand, cpu
s outputs deflection data to the DAC amplifier 9. The DAC
The amplifier 9 drives the first deflector 3, and as a result, the rectangular beam is deflected in a predetermined direction. The deflected rectangular beam 13i illuminates the second shaping aperture 2. The second shaping aperture 2 also has a predetermined rectangular hole, and of the irradiated rectangular beam, only that which passes through this hole passes through the second shaping aperture 172 as a drawing rectangular beam.

FIG. 6 is a dimensional drawing showing how a rectangular beam is created.

When a rectangular electron beam 12 is irradiated into a hole 11 made in the second shaping aperture 2 as shown in the figure, only the portion that overlaps with the hole 11 (the shaded area in the figure) becomes a rectangular beam for drawing. The size of this drawing rectangular beam can be made into any rectangular shape by changing the voltage applied to the eleventh direction device 3. On the other hand, the CPLI 8 reads out the graphic data stored in the memory 7 and uses D as drawing data.
to the AC amplifier 10. The rectangular beam that has passed through the second shaping aperture 2 in this way is sent to the second shaping aperture via the DAC amplifier 10 that receives the drawing data output from the CPU 8.
It is driven by the deflector 4. The second deflector 4 deflects the rectangular beam passing through the second shaping aperture 2 in two-dimensional directions, which is then focused by an objective lens 5 and irradiated onto a material 6.

[Problems to be Solved by the Invention] In this type of rectangular beam drawing apparatus, a rectangular beam Bi as shown in FIG. 7 is formed on the material 6 by the above-described operation. Due to astigmatism caused by the electron optical system, this rectangular beam Bi has a difference in the rise of the edge portion between the X-direction profile and the X-direction profile (
(hereinafter referred to as astigmatism). Here, the height of the beam profile in each of the x and y directions represents the beam intensity.

This rounded rise of the beam profile causes blurring at the periphery of the rectangular beam 3i, deteriorating the resolution of the drawn pattern.

The present invention was made in view of these problems, and its purpose is to provide a method for calibrating astigmatism for a rectangular beam writing system that can sharpen the rise of the beam profile and improve the resolution of the writing pattern. It is about realization.

[Means for Solving the Problems] The present invention, which solves the above-mentioned problems, places a mark having a right angle on a material or arranges an orthogonal member on the same plane as the material near the material, and A rectangular beam is scanned over this mark or orthogonal member in each x and y direction while varying the intensity, and the intensity of the objective lens (Lx . The present invention is characterized in that the astigmatism corrector is set to the value when the peak among the edge rising signals in each of the x and y directions sequentially obtained by scanning is maximized.

[Operation] First, after adjusting the focus of the objective lens, use the astigmatism corrector to
, y-direction astigmatism correction is performed.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the main parts of an apparatus for carrying out the method of the present invention. In the figure, 3i is a rectangular beam, 11 is a rectangular beam B
12 is a deflector that deflects the rectangular beam [3i] focused by the objective lens 11 in two-dimensional directions. 13 is a material, and 14 is an imaging point of a rectangular beam. 15 is a detector that detects a signal (secondary electrons or reflected electrons) from the imaging point 14; 16 is an arithmetic circuit that receives the output of the detector 15 and performs various calculations to be described later; the output is sent to a control circuit 17 is input. , 17 is a control circuit that performs various controls, and for example, a CPU is used.

A DAC amplifier 18 converts the deflection data (drawing data) output from the control circuit 17 into an analog signal, and its output is applied to the deflector 12. One is control circuit 1
A stigma corrector (
Stigmeter). The output of the control circuit 17 is also
The signal is also included in the objective lens 11 as a drive signal. This J
The operation of the device configured as follows is as follows.

First, a method for evaluating rectangular beam profile edges will be explained. Materials Δ and B having different electron beam reflectances are placed on the material 13 so that a straight boundary appears to the right, as shown in FIG. 2(a). Then, the deflector 12 scans the material 13 with a beam in the → direction in the figure, and in synchronization with this, the detector 15 detects reflected electrons from the materials A and B.

As a result, an original signal as shown in FIG. 2(b) is obtained from the detector 15. This original signal is sent to the subsequent arithmetic circuit 16
is first differentiated to the first order. As a result, a first-order differential signal (beam profile signal 0) as shown in FIG. Next, when the obtained first-order differential signal is further differentiated, a second-order differential signal (edge rising signal) as shown in (d) is obtained by 1!7.

By performing the above operations in each of the x and y directions, x
, the edge rising signal for each direction can be reduced by one.

Next, the astigmatism detection method will be explained using FIG. A on the material 13 parallel to the rectangular beam Bi as shown in the figure.
An L-shaped mark 20 with material B placed thereon is placed. Here, the material BeL-shaped mark is used. In this state, the rectangular beam Bi@deflector 12 scans in each of the x and y directions. Detector 15 detects backscattered electrons as a result of scanning.
and edge rising signals in each of the x and y directions are obtained using the method described with reference to FIG.

First, while varying the intensity of the objective lens 11 in the X direction, the mark 20 is scanned in the X direction with the rectangular beam 13i each time, and sequentially 1! ′? The intensity (Lx) of the objective lens when the peak value of the edge rising signal reached the maximum is memorized, and then the rectangular beam 3i is changed each time while changing the objective lens in the same way from the peak value in the Y direction. mark 20
Scan the top in the Y direction, and similarly record the intensity (Ly) of the objective lens when the peak value reaches the maximum g5. The edge rising signal is input from the arithmetic circuit 16 to the control circuit 17, and the control circuit 17 can detect the maximum value of the peak value of the edge, and also detect and store the lens strength at that time. I can do it. Figure 4 shows objective lens 1.
1 is a diagram showing an astigmatic state corresponding to Lx and Ly of 1. FIG. Here, a reference plane l is assumed to be exactly midway between lx and Ly. Then, the lens strength of the objective lens 11 is set to (Lx+LV)/2.

In this state, the astigmatism corrector 19 is adjusted so that the edge rising confidence in each of the x and y directions is maximized.

Specifically, while changing the signal applied from the control circuit 17 to the astigmatism corrector 19 little by little, the astigmatism corrector detects the peak value of the second-order differential signal as before, and the peak value becomes the maximum. We will find the value of .

Normally, the astigmatism corrector is 4I4J and consists of a set of 8-pole coils or electrodes, and each corrector is set to a value that maximizes the peak value. Thereby, the beam profile of the rectangular beam [3i (see FIG. 7) can be adjusted to have a steep rise. As a result, the resolution of the drawn pattern can be improved.

In the above description, a method of detecting and differentiating backscattered electrons was used as a method of obtaining a beam profile. As another method, a member 2 that shields the beam such as a knife
A Faraday cup may be provided under the edge of the shielding member to scan the edge of the shielding member, and the signal may be detected by the Faraday cup. Further, in the above description, an electron beam lithography device was used as the rectangular beam lithography device, but the present invention is not limited to this, and can be applied to a charged particle beam lithography device such as a focused ion beam device. Furthermore, the astigmatism method described above can be easily automated.

[Effects of the Invention] As explained above in detail, the present invention places a mark having a right angle on a material or arranges a perpendicular member on the same plane as the material near the material to increase the strength of the objective lens. Scan the mark or orthogonal member in each x and y direction with a rectangular beam while varying the intensity, and calculate the intensity of the objective lens when the peak among the edge rising signals obtained is the maximum (Lx, L"/) and then set the intensity of the objective lens to (L The astigmatism corrector is set to the value when the peak of the edge rise signals in each of the x and y directions obtained by scanning the orthogonal member is the maximum, so the rise of the beam profile of the rectangular beam is It is possible to improve the sharpness of the pattern drawn by the rectangular beam drawing device.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the main parts of equipment 2 for carrying out the method of the present invention;
The figure is an explanatory diagram of the evaluation method for rectangular beam profile edges.
Figure 3 is an explanatory diagram of the astigmatism detection method, and Figure 4 is the objective lens 11.
Figure 1 shows the astigmatic state corresponding to the arrows x and Ly, Figure 5 shows an example of the conventional configuration of a rectangular beam drawing device using a rectangular beam, and Figure 6 shows how the rectangular beam is created. , 7th
The figure shows a beam profile of a rectangular beam. 11... Objective lens 12... Deflector 13...
・Material 14... Image forming point 15... Detector 16... Sieve circuit 17... Control circuit
18... DAC amplifier 19... Astigmatism corrector patent applicant population Thu Denshi Co., Ltd.
Ceremony for the meeting Patent attorney
Fuji Ijima 1 person Figure 1 Figure 6 Figure 750

Claims (1)

[Claims] A mark with a right angle is placed on the material, or a perpendicular member is placed on the same plane as the material near the material, and a rectangular beam is directed over the mark or the orthogonal member by x while varying the intensity of the objective lens each time. , y, and memorize the intensity (Lx, Ly) of the objective lens when the peak among the sequentially obtained edge rising signals becomes maximum.
Next, after setting the intensity of the objective lens to (Lx+Ly)/2, the rectangular beam scans the mark or orthogonal member each time while varying the signal intensity to the astigmatism corrector, and the results are sequentially obtained. A method for calibrating astigmatism for a rectangular beam drawing device, characterized in that an astigmatism corrector is set to a value when the peak of edge rising signals in each of the x and y directions is maximum.