JPH10301255A - Electron beam mask plotting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve throughput by imparting information on the presence or absence of proximity effect correction in each of parts where dimensional accuracy is severe and parts where the dimensional accuracy is less severe and continuously plotting the presence and absence of the proximity effect correction with this information at the time of plotting. SOLUTION: An electron beam 2 accelerated by an acceleration voltage control 1 is cast through a blanker 3 for determining an exposure time and an electronic lens 4 onto a mask 5. On the other hand, the patterns 6 to be plotted are sent through a proximity decision section 7 and through a proximity effect correction unit 8 or directly to an exposure setting unit 9. At this time, the patterns 6 on the mask 5 are divided to the parts where the dimensional accuracy is severe and the parts where the dimensional accuracy is less severe. The plotting is continuously executed at one time by imparting the information on the presence of the proximity effect correction to the patterns of the core part where the dimensional accuracy is severe and the information on the absence of the proximity effect correction to other light shielding body parts and the plotting patterns of peripheral circuits, by which the relative position accuracy of the patterns of the core parts and the patterns of the peripheral circuit part is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam mask drawing method.

[0002]

2. Description of the Related Art Conventional electron beam mask writing has an acceleration voltage of 20.
kv or less and without the proximity effect correction. Since the minimum drawing dimension on the mask was at most about 2 μm, it could sufficiently cope with the acceleration voltage of 20 kv. However, as the integration of semiconductor elements progresses, the drawing size becomes smaller and smaller, and the reticle magnification changes from 5 times to 4 times the conventional value, so that today's minimum drawing size is required to be 1 μm. When a 1 μm pattern is drawn on a mask at a conventional acceleration voltage of 20 kv, a 2 μm × 1 μm rectangular beam is usually formed and irradiated on the mask. However, the beam is blurred due to the Coulomb effect and the 1 μm The dimensions could not be obtained. In order to solve this problem, it is possible to reduce the Coulomb effect by reducing the size of the shot of the electron beam to be drawn and to hit many shots, but the drawing speed is extremely lowered.

Accordingly, while maintaining the size of the shot of the electron beam to be drawn, the minimum drawing size of, for example, 1 μm is reduced to 2 μm.
To draw with a shot of μm × 1 μm, it is necessary to increase the acceleration voltage to, for example, about 50 kv.

On the other hand, when the exposure is performed with the acceleration voltage increased, the number of reflected electrons from the mask substrate increases and a proximity effect phenomenon in which the resist is exposed with the reflected electrons appears. It has been found that this proximity effect becomes more remarkable in a portion with a high pattern density, so a portion with a high pattern density is given a low exposure dose, and a portion with a low pattern density is given a high exposure dose, and exposed in accordance with the pattern density. A so-called pattern density proximity correction method in which the amount is changed has been proposed.

First, when a high acceleration voltage, for example, 50 kv, and a proximity effect correction method are combined, a minimum drawing size of about 1 μm required today can be obtained. However, the mask drawing area is usually as large as about 120 mm × 120 mm, and the proximity effect correction is applied to the entire surface. Therefore, the time spent for the proximity effect correction occupies ２〜 to ３ of the entire drawing time.

At present, this is a major alienation factor that increases the throughput.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to perform continuous mask drawing to improve the throughput.

[0008]

In order to achieve the above object, the present invention combines an acceleration voltage of 50 kv and a proximity effect correction method according to a pattern density, and separates a portion having strict dimensional accuracy from a portion having gradual accuracy. Information on the presence / absence of the proximity effect correction is given to each part, and the drawing with / without the proximity effect correction is continuously drawn with the information at the time of drawing.

In recent years, the processing dimensions have been steadily miniaturized in accordance with the high integration of semiconductor elements. For example, 0.25μ
The minimum dimension of the m-element on the mask is 1.25μ in case of 5 times
m, it is 1.0 μm when quadrupled. To obtain a fine pattern with an electron beam, increase the accelerating voltage, reduce the Coulomb effect, reduce the blur, and reduce the forward scatter when irradiating the resist to reduce the pattern of 1 μm or less on the mask. Can be achieved. On the other hand, proximity effect correction is also used in order to reduce the influence of the reflected electrons from the substrate, but the time spent for the proximity effect correction occupies about ２〜 to 描画 of the entire drawing time. Therefore, if the pattern to be drawn is separated according to the dimensional accuracy, a portion with strict dimensional accuracy is extracted, and the proximity effect correction drawing is performed only on the portion, and if the other portion is not subjected to the proximity correction, a single mask is drawn. Time is shorter.

It is also possible to completely perform the proximity effect correction drawing and the drawing without the correction in two separate steps.
Since the drawing speed slows down and the relative position accuracy of the drawing pattern deteriorates due to drawing twice and under different conditions, it is automatically determined whether or not proximity correction is performed, and continuous drawing is performed. It is necessary to.

[0011]

FIG. 1 shows a first embodiment in which a proximity judging section 7 is added to the conventional device.

The electron beam 2 accelerated to about 50 kv by the acceleration voltage control 1 is irradiated on the mask 5 via the blanker 3 for determining the exposure time and the electron lens 4. On the other hand, the pattern 6 to be drawn is sent to the exposure setting unit 9 via the proximity determining unit 7 and the proximity effect correction unit 8 or is sent directly to the exposure setting unit 9. After that, a signal is sent from the exposure setting unit 9 to the blanker 3 to control the electron beam and the plate is drawn.

Here, information as to whether or not to perform proximity effect correction drawing is added to a pattern to be drawn in advance and stored in the buffer memory 6. FIG. 3 shows an example. The pattern 22 performs proximity drawing by adding the proximity correction bit 1. The pattern 23 and the pattern 24 are drawn without proximity correction by adding the proximity correction bit 0. When the information is sent to the proximity determination unit 7 along with the drawing pattern, if the information indicates that the proximity effect correction is performed, the switch 10 is set to the A side, and the drawing pattern is sent to the proximity effect correction unit and the pattern density is sent. Is sent to the exposure setting unit, and the plate is drawn by controlling the electron beam.

On the other hand, when information indicating that there is no proximity effect correction is sent to the proximity determining unit 7 along with the drawing pattern, the switch 10 is set to the B side, and the drawing pattern is directly sent to the exposure setting unit. The plate is exposed without proximity correction.

Next, a drawing method by pattern division according to the strictness of dimensional accuracy will be described with reference to FIG. In general,
The pattern on the mask 21 is divided into a part with strict dimensional accuracy and a gentle part. Shielding part 22 The dimensional accuracy is usually moderate. Further, depending on the drawing pattern, the dimensional accuracy is strict only in the portion 24 corresponding to the core of the semiconductor element, and the dimensional accuracy in the peripheral circuit portion 23 may be loose. In this case, the information of the proximity effect correction is given to the pattern of the core portion 24 with strict dimensional accuracy, and the information of the no proximity effect correction is given to the other light-shielding body portion 22 and the drawing pattern of the peripheral circuit 23 to continuously perform. By drawing at once, the relative positional accuracy of the pattern of the core portion 24 and the pattern of the peripheral circuit portion 23 can be maintained.

FIG. 4 shows a second embodiment. When the information of the proximity correction bit is not given to the pattern information, the pattern 22 having two buffer memories and not performing the proximity correction on the surface A, the pattern 23 for performing the proximity correction on the surface B, and the pattern 24 are stored. Pattern 2 without proximity correction from drawing control CPU 11
In the case of drawing 2, the surface of the buffer memory A is selected and drawing is performed. When drawing the patterns 23 and 24 for proximity correction, the drawing control CPU 11 selects the surface of the buffer memory B and executes drawing.

[0017]

According to the present invention, it is possible to supply a mask which can draw a fine pattern on a mask at high speed and with high accuracy and which can meet the required dimensional accuracy, which is becoming stricter year by year.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a drawing method in which a pattern is divided according to dimensional accuracy.

FIG. 3 is an explanatory diagram of pattern information.

FIG. 4 is an explanatory view of a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Acceleration voltage control, 2 ... Electron beam, 3 ... Blanker, 4 ... Electronic lens, 5 ... Plate, 6 ... Buffer memory, 7 ... Proximity determination unit, 8 ... Proximity correction unit, 9 ... Exposure amount setting unit, 10 ... switch.

Claims (2)

[Claims] In an electron beam mask writing apparatus for manufacturing a mask substrate used for manufacturing a semiconductor element, writing is performed by combining an acceleration voltage of 20 kV or more and a pattern density proximity effect correction method for changing an exposure amount according to an area density of a writing pattern. In the apparatus, the pattern data of one layer to be drawn is divided into a portion having a strict pattern dimensional accuracy and a portion having a gentle pattern dimensional accuracy. An electron beam mask drawing method characterized by drawing without giving. 2. A method according to claim 1, wherein information of a portion having a strict pattern dimensional accuracy and information of a portion having a gradual accuracy are input as drawing pattern information, and a drawing obtained by performing a proximity effect correction based on said information is not provided. An electron beam mask writing method that performs writing continuously.