JPH0547646A - Plotting method for electron beam - Google Patents

Abstract

PURPOSE:To accurately plot by measuring a height of an alignment mark and a chip, and correcting an alignment correction coefficient based on an obtained step difference. CONSTITUTION:A height between A-A' of a sample 101 is measured by using a laser light, maximum and minimum values of data are obtained, and set as a slice level to an average value. Then, average of data of larger values than the slice level is calculated as a height of a chip. Similarly, an average value of data of the level or lower is used as a height of a scribing area 103, and a difference between both is regarded as a step difference (h). Then, alignment marks 104 on the wafer are sequentially detected to obtain an alignment coefficient, and a height of the area 103 is measured. At the time of plotting, sum of the height of the area 103 and the difference (h) is used as a height of a plotting surface, and plotting is performed. Since the position of the mark and the actual position of the plotting surface are corrected, accurate plotting is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing apparatus, and more particularly to a drawing method for realizing highly accurate drawing.

[0002]

2. Description of the Related Art In the manufacture of a semiconductor device, as shown in FIG. 1, a sample 101 has a large number of portions 102 for forming devices called chips. A space called the scribe area 103 is provided between the chip portions. The region is a region for separating the sample 101 into each chip after the semiconductor element is completed. Therefore, since the region is an unnecessary region for the element, a pattern such as the alignment mark 104 that is not directly related to the function of the element is formed.

On the other hand, the position of the sample with respect to the electron beam irradiation axis is important for realizing high-precision drawing by the electron beam drawing method. FIG. 2 shows an electron beam 201 emitted from an electron gun.
This is a case where only the light is deflected and the point P on the sample surface a is irradiated. At this time, if the sample position fluctuates and the sample surface is on the b surface lowered by Δz, the electron beam 301
Will illuminate point Q. As a result, a drawing error of Δx occurs. For example, when the distance from the change point O to the sample surface a is 100 mm and the change amount x is 3.5 mm,
When Δz changes by 3 μm, Δx becomes 0.1 μm.
This value is a large error for drawing a pattern in the submicron region. Therefore, in high-accuracy drawing, the position of the sample is measured, and if the sample surface is at the position of b, the deflection amount is reduced so that the electron beam has a deflection distance x on the b surface as shown in FIG. Position of P '
Drawing was performed with correction so as to irradiate points.

[0004]

However, as miniaturization progresses, the structure of semiconductor devices becomes more complicated,
As a result, the following new problems have arisen. That is,
The AA ′ cross section of the sample shown in FIG. 1 has a structure as shown in FIG. 2. However, in the recent semiconductor element, the step h between the scribe area 103 and the chip portion 102 is several μm.
Is getting bigger. As described above, the alignment mark is usually formed in the scribe area 103, and in direct writing, the alignment mark is detected to obtain the positional consistency between the existing pattern and the new writing pattern. There is. However, if the step h becomes several μm, the position error becomes an unacceptable value as described with reference to FIG.
As a result, even if the alignment mark is detected and the alignment drawing is performed, sufficient drawing accuracy cannot be obtained.

An object of the present invention is to provide a highly accurate drawing method in direct drawing, paying attention to such problems. Hereinafter, the position of the sample surface with respect to the electron beam axis will be referred to as the sample height, and the present invention will be described.

[0006]

In order to solve the above problems, the height of the alignment mark and the heights of two portions of the chip portion where drawing is performed are measured, and the step between them is obtained. Further, drawing is performed by correcting the correction coefficient based on the obtained step difference.

[0007]

The height of the alignment mark and the height of the chip are measured, and the alignment drawing coefficient is corrected according to the result. Therefore, the alignment coefficient at the actual drawing is the alignment coefficient on the drawing surface, that is, the chip surface. Has become. Therefore, it is possible to prevent the drawing error due to the difference in height between the scribe area and the chip portion as described in FIG.

[0008]

EXAMPLES Examples of the present invention will be described below. Figure 4
FIG. 1 is a schematic configuration diagram of an electron beam drawing apparatus used in the present invention. The electron optical system 400 includes an electron gun 401 and an electron lens 4.
02, 403. In the sample chamber 404, there is a sample table 405 for mounting the sample 406,
The sample stage is connected to a drive motor 407 and a drive shaft 408. The movement of the sample table is controlled by the sample table control circuit 41.
4, the deflection of the electron beam is controlled by the data control circuit 412. The sample height was measured as follows. Laser light is obliquely emitted from the laser diode 409, the reflected light from the sample 406 is detected by the position detector 410, and the measurement result is
Processing was performed by the signal processing circuit 413 to obtain the sample height. Further, the control of the electron beam drawing apparatus is controlled by the control computer 4
Performed at 11.

The correction of the sample height based on the present invention was performed as follows. First, the height between AA 'shown in FIG. 1 was measured. FIG. 5 shows the result. The measured value also changes according to the height change of the sample surface. The signal processing circuit 413, which has obtained the measurement result, first
The maximum value and the minimum value of the data were obtained, and the slice level 501 was set to half the value. Next, the data having a value larger than the slice level was averaged and used as the height of the chip portion. Similarly, the average value of the data below the slice level was taken as the height of the scribe area, and the difference between the two was considered as the step h. Next, the alignment coefficient was obtained by sequentially detecting the alignment marks 104 on the wafer, and the height of the scribe area was measured. When drawing,
Drawing was performed with the height of the scribe area plus the step h previously obtained as the height of the drawing surface.

As described above, by obtaining the alignment correction coefficient in consideration of the height at the alignment mark portion and the height at the chip portion, it is possible to perform highly accurate drawing which has never been achieved.

[0011]

According to the present invention, since the position of the alignment mark and the position of the actual drawing surface are corrected, highly accurate drawing is possible.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a planar structure of a sample.

FIG. 2 is a diagram illustrating a drawing error caused by a change in sample position.

FIG. 3 is a diagram illustrating a cross-sectional structure of a sample.

FIG. 4 is a schematic configuration diagram of an electron beam drawing apparatus used in an embodiment of the present invention.

FIG. 5 shows an example of the measurement result of the sample position.

[Explanation of symbols]

101 ... Sample, 102 ... Chip, 103 ... Scribing area, 104 ... Alignment mark, 201 ... Electron beam, 202
... electron beam, 400 ... electron optical lens barrel, 401 ... electron gun, 4
Reference numeral 02 ... Electron lens, 403 ... Electron lens, 404 ... Sample chamber, 405 ... Sample stand, 406 ... Sample, 407 ... Drive motor, 408 ... Drive shaft, 409 ... Laser diode, 41
0 ... Position detector, 411 ... Control computer, 412 ... Data control circuit, 413 ... Signal processing circuit, 414 ... Sample stage control circuit, 501 ... Slice level.

Claims (1)

[Claims] 1. An electron beam drawing apparatus for deflecting an electron beam of a predetermined shape to draw a predetermined pattern on a sample, and measuring the position of an area on the sample where an alignment mark is present with respect to the electron beam irradiation axis. An electron beam drawing method comprising: a means, a means for measuring a position of an area for drawing with respect to an electron beam irradiation axis, a means for obtaining a difference between the positions of the areas, and a means for reflecting the difference between the positions in a correction coefficient.