JPH05259042A - Electron beam aligner - Google Patents

Abstract

PURPOSE:To stabilize the amount of deflection of an electron beam and to expose accurately a continuous graphic form by a method wherein the electron beam is temporarily made to stop at points, where are located outside the region where a group of figures positioned within an exposure region should be drawn, and are located in the position near the figure group. CONSTITUTION:A pattern to be exposed is assumed a linear grating(LG). That is, an electron beam is scanned from the left to the right with one by one of the respective lines 11 of the LG as a group of figures and is scanned from a starting point 13 of the one line 11 to the end point 14 of the one line 11. When the beam is emitted on a stop point 10 for a prescribed time before the following scanning, an overshoot due to flying of the beam from the end point 14 is restored during this emission and the amount of deflection of the beam is stabilized. Thereby, by the constitution, wherein the normal scanning method is merely modified, of a laser, the effect of the overshoot can be suppressed without controlling a blanking or the like, an exposure is performed after the amount of deflection of the beam is stabilized and the pattern can be precisely exposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam exposure method for exposing a resist coated on a substrate, for example, by irradiating the electron beam while scanning.

[0002]

2. Description of the Related Art An electron beam exposure apparatus comprises an electron beam optical system, an apparatus for controlling them, and an electronic computer. Scan data of a pattern to be formed generated by an electronic computer is converted into an analog scan signal by a digital-analog converter (hereinafter abbreviated as DA converter) and applied to an electron beam deflector of an electron beam optical system. The electron beam deflector deflects the electron beam according to the applied scanning signal, but since it has an inductance, it cannot follow the change when the scanning signal changes abruptly. As a result, the trajectory of the electron beam is not as intended, which is called overshoot.
Electron beam is excessively deflected, insufficiently deflected, or distorted.

In particular, this phenomenon is remarkable in the electromagnetic deflector, and the amount is small in the electrostatic deflector. However, the electrostatic type has a problem that the deflection efficiency cannot be increased. In an actual electron beam exposure apparatus, a system in which a deflector is composed of only an electromagnetic type deflector, or an electrostatic type is used in a small deflection area and an electromagnetic type is used in a large deflection area. It is common to use a method of using both a mold and an electromagnetic type. Therefore, the problem of overshoot is unavoidable.

For exposure of the electronic LSI element pattern, it is general to use a shaped beam type electron beam exposure apparatus which is excellent in throughput. In this type of electron beam exposure method, a pattern designed by CAD is divided into small exposure unit figures, and each unit figure is exposed. The electron beam is deflected to the coordinates of the unit figure to be exposed, and the electron beam is continuously irradiated for a time corresponding to the electron beam dose amount determined by the sensitivity of the electron beam resist. Such an exposure method is called shot exposure, and a series of processes from the deflection of the electron beam to the end of electron beam irradiation is called a shot.
In each shot, the electron beam is blanked until the time when it is estimated that the deflection amount of the electron beam is stable after the electron beam irradiation of the previous shot is completed and the deflection signal is given to the electron beam deflector. .. Blanking is
By applying a voltage to a blanking electrode provided under the electron gun, the electron beam generated by the electron gun is bent so that the path of the electron beam is bent, and the electron beam is blocked by an aperture in the beam path. By this method, the electron beam is irradiated to a desired position after the amount of deflection of the electron beam is stabilized, and the figure can be accurately exposed.

[0005]

The overshoot suppressing method by blanking in the conventional electron beam exposure method is suitable for the shot exposure method using a shaped beam. However, in the electron beam exposure method that uses a convergent beam and irradiates it while scanning it, exposure is not performed in shots, and as a result, the time until the electron beam stabilizes within the shot (settling time)
The method of blanking cannot be adopted.

Therefore, an object of the present invention is to make it possible to accurately expose a figure by suppressing the influence of the overshoot of the electron beam when the exposure is performed by irradiating the converged electron beam while scanning. An exposure method is provided.

[0007]

According to a first aspect of the present invention, there is provided an electron beam exposure method, in which an electron beam is irradiated while being scanned, and then a series of geometrically arranged figures are drawn in the exposure area before the drawing. It is characterized in that the electron beam is temporarily stopped at a point outside the power region and close to the series of figures.

According to another aspect of the present invention, there is provided an electron beam exposure method, wherein deflection data for scanning the electron beam stored in the first memory and the electron beam stored in the second memory corresponding to the deflection data. According to the blanking data,
An electron beam exposure method for exposing a predetermined area by irradiating while scanning the electron beam, wherein a deflection position is provided between deflection data in which an overshoot of the electron beam occurs and deflection data next thereto. The number of dummy deflection data corresponding to the period until stabilization is stored in the first memory in a state where the dummy deflection data is inserted, and the blanking data is stored in the second memory in correspondence with the dummy deflection data. The electron beam is blanked based on the dummy deflection data and blanking data corresponding thereto.

An electron beam exposure method according to a third aspect of the present invention is an electron beam exposure method for exposing a predetermined area by irradiating an electron beam while scanning, which is the final step of a memory for storing deflection data for scanning. Data for causing a jump in the electron beam deflection amount is stored at the address, and the deflection voltage corresponding to the data for causing the jump is held until the deflection data for the next scan is written in the memory and conversion starts. It is characterized by

[0010]

According to the structure of the first aspect, before the drawing of a series of positions arranged in the exposure area is completed, the electron beam is applied to a point outside the area to be drawn and close to the series of figures. Is temporarily stopped, the amount of deflection of the electron beam is stabilized, and then a series of figures are exposed by the electron beam, whereby the figures can be accurately exposed.

According to the structure of claim 2, deflection data for scanning the electron beam stored in the first memory;
In accordance with the deflection data and the blanking data of the electron beam stored in the second memory, the electron beam overshoots when the predetermined area is exposed by irradiating the electron beam while scanning. Between the deflection data and the next deflection data, the dummy deflection data of the number corresponding to the period until the deflection position is stabilized is inserted into the first memory and stored in the second memory. Blanking data is stored corresponding to the dummy deflection data, the beam deflection amount is stabilized by blanking the electron beam based on the dummy deflection data and the blanking data corresponding thereto, and then the exposure is restarted. As a result, the figure can be accurately exposed.

According to the third aspect of the invention, the data for causing the jump in the electron beam deflection amount is stored at the final address of the memory for storing the deflection data for scanning, and corresponds to the data for causing the jump. By holding the deflection voltage for the next scan until the conversion is started by writing the deflection data for the next scan into the memory, the beam deflection amount is stabilized until the next conversion starts, and then the exposure is performed. As a result, the figure can be accurately exposed.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. First, FIG. 5 shows a schematic configuration diagram of an electron beam exposure apparatus used when carrying out the electron beam exposure method of the present invention. In FIG. 5, 51 is an electron beam optical system,
Reference numeral 52 is an electronic computer for generating control and drawing data, and 53.
Is a DA converter and has a built-in memory 54 for temporarily storing data such as deflection data and blanking data sent from the electronic computer 52. The digital drawing data calculated by the electronic calculator 52 is converted into an analog signal by the DA converter 53, and the signal is applied to the deflector of the electron beam optical system 51. This controls the scanning of the electron beam.

Next, referring to FIG. 1, the electron beam scanning method in the first embodiment (corresponding to claim 1) of the electron beam exposure method which is implemented by using the above-mentioned electron beam exposure apparatus is described. While explaining. In this embodiment, an example in which a linear grating (LG) is used as an exposed pattern is shown. LG is one of the most basic diffraction gratings,
It has a pattern as shown in FIG. For example, for electron beam resist, polymethylmethacrylate (PMM
Using A), it is applied on a silicon substrate to a thickness of 0.2 μm.
The exposure conditions include, for example, an electron beam acceleration voltage of 40 kV, a beam current of 0.8 nA, and a beam diameter of 0.
It is 1 μm. The size of LG is, for example, 1 mm x 1
mm, the cycle of the line 11 is 0.8 μm, for example, the line 11
Has a line width of 0.4 μm, for example.

The line width is larger than the beam diameter because the electron beam is scattered in the resist. In order to manufacture such an LG having a submicron period, as shown in FIG. 1, each line 11 constituting the LG is line-scanned by a constant distance (moving by a constant distance and a fixed time is passed at each scanning point). It is realized by exposing with an electron beam). The scanning interval of line scanning (distance between one scanning point and the next scanning point) is, for example, 0.04 μm. The beam irradiation time at each scanning point is 20 μsec. It is difficult to manufacture such a grating having a short period (for example, 0.8 μm) by the fill exposure method. Therefore, the electron beam is scanned from left to right in the form of a set of figures for each line 11 of the LG, and the line 11 is scanned from the start point 13 to the end point 14. 2 at stop 12 before scanning the next line 11.
Scan data is created so that the electron beam is emitted for 0 msec. During this stop, the overshoot due to the electron beam flying from the right end (end point 14) of the front line 11 is stopped, and the beam deflection amount becomes stable. After that, scanning of the next line 11 is performed, but the distance between the stationary point 12 and the starting point 13 of the next line 11 is set to about 50 μm at which no overshoot occurs. It is possible to scan up to and accurately draw the line 11. By repeating this and drawing all the lines 11, LG having an accurate shape is exposed. The stationary point 12 is outside the region to be drawn, that is, outside the LG and at a position near a series of figures, that is, one line 11, that is, when the electron beam is scanned from the stationary point 12 to the starting point 13 of the next line 11. Is provided at a position where the overshoot of the electron beam is sufficiently suppressed.

Next, referring to FIG. 2, the electron beam scanning method in the second embodiment (corresponding to claim 1) of the electron beam exposure method which is implemented by using the electron beam exposure apparatus as described above, will be described. While explaining. This embodiment is LG
In the drawing, when the stopping point is close to the starting point of the line but not in the immediate vicinity, when the stopping point is separated from the starting point of the line by about 200 μm or more and the electron beam is scanned from the stopping point to the starting end, This shows a scanning method capable of suppressing this overshoot when a slight overshoot is generated, although the overshoot is not as large as when the electron beam is scanned from the end point 14 of the line 11.

In this embodiment, as shown in FIG. 2, a preliminary scan 24 is carried out between the stationary point 22 and the starting point 23 of one line 21 of the LG corresponding to the stationary point 22. The preparatory scan 24 is performed by making the scanning interval of the electron beam larger than that in a portion where normal exposure is performed, that is, by making the electron beam dose amount smaller so that no line is formed. For example, when the scan interval of the line scan is 0.04 μm, the scan interval of the preliminary scan 24 is 0.4 μm. If the scan interval of the preliminary scan 24 is set to about 10 times the scan interval of the line scan, the preliminary scan portion will not be formed as a line.

Then, similar to the scanning method of FIG. 1, by scanning each line 21, an accurate LG can be manufactured.
The drawing pattern is not limited to LG but can be applied to a curve grating, a chirp grating, or the like. Next, an electron beam scanning method in a third embodiment (corresponding to claim 2) of an electron beam exposure method which is implemented by using the above-mentioned electron beam exposure apparatus will be described with reference to FIG. To do.

This embodiment will be described using a linear grating. As shown in FIG. 3 (a), one line 31 is scanned, and before the next line 32 is scanned,
At the starting point 33 of the next line 32, scanning is performed so that the electron beam stays for a certain period of time. While the electron beam remains at the starting point 33, the electron beam is blanked.

FIG. 3B shows the contents of data for the above scanning. The upper row shows deflection data for scanning, which is stored in the first memory, and the lower row shows blanking data, which controls ON / OFF of blanking, stored in the second memory. To be done. For example, deflection data for scanning the first line 31 (in FIG. 3B, for convenience, the same reference numerals as the lines are used; other deflection data are the same) and deflection for scanning the second line 32. Deflection data indicating the position of the starting point 33 of the second line 32 is repeatedly inserted between the data and the data as dummy deflection data for stopping the electron beam at the starting point 33. This insertion amount is a number corresponding to the dwell time of the electron beam necessary for stabilizing the beam deflection amount. For example, when the length of the line 32 is 1 mm, the dwell time is about 20 mse.
It is about c, and the number of dummy deflection data is determined by the relationship between the memory read clock period and the dwell time. By turning off the blanking data corresponding to the deflection data for scanning the line 32, the electron beam is irradiated and the line 32 is exposed. Blanking data corresponding to dummy deflection data indicating the position of the starting point 33 of the second line 32, which is inserted for stabilizing the deflection amount, is turned on to prevent unnecessary exposure.

By this electron beam exposure method, the beam deflection amount can be stabilized without exposing an unnecessary pattern, so that the figure to be drawn can be accurately exposed. The data for stabilizing the electron beam does not necessarily have to be the starting point of the line, and the starting point 3 of the next line 32
Any data may be used as long as the beam deflection amount is stable when exposing No. 3. For example, in the case of data for scanning a straight line connecting the end point of the front line 31 (the end portion on the side opposite to the start point 33) and the start point 33 of the next line 32, there is no problem because the deflection amount jump does not occur.

Next, referring to FIG. 4, the electron beam scanning method in the fourth embodiment (corresponding to claim 3) of the electron beam exposure method which is implemented by using the above-mentioned electron beam exposure apparatus is described. While explaining. In this embodiment, as an example, a plurality of rectangles 41 as shown in FIG.
A beam scanning method by this electron beam exposure method when exposing 42, ... Will be described. Each rectangle 41, 42, ...
The short side is 5 μm, the long side is 20 μm, and the five rectangles 41 to 45 are arranged at different angles as shown in FIG. 4A. Each rectangle 41, 42, ...
Is exposed by the fill method. 5 rectangles 41-
Reference numeral 45 denotes a series of figures, which are sequentially scanned from the left end rectangle 41 to the right end rectangle 45. Rectangle 4 at the right end of the first row
Since the positions of 5 and the leftmost rectangle 41 'of the second stage are distant from each other, overshooting occurs when continuous scanning is performed.

Therefore, the following scanning is performed. After drawing five rectangles 41 to 45, the next five rectangles 4
Before drawing 1'-45 ', the electron beam is stopped at a certain fixed point 46 (referred to as a discarding point), and finally, the leading point 4 for the fill scan of the rectangle 41' to be drawn next.
Scan 7. The deflection data for scanning is shown in FIG.
It is created as shown in (b). That is, this deflection data is composed of the deflection data of five rectangles 41 to 45, the deflection data of the discard point 46, and the deflection data of the leading point 47 for the fill scan of the rectangle 41 'to be drawn next ( In FIG. 4B, for convenience, the rectangles or the same symbols as dots are used. The deflection data of the five rectangles 41 to 45 are sequentially stored from the head address of the memory 54 in the DA converter 52, and the deflection data of the head point 47 is stored in the memory 54.
Is stored in the final address of the memory 54, the deflection data of the discard point 46 is stored so as to fill the unstored area of the memory 54, and the sum of the data amounts thereof matches the capacity of the memory 54.

Device memory 54 using the method of the present invention
Has a capacity capable of storing deflection data of 65536 scanning points. In the example shown above, the memory 5 is composed of 5 rectangles.
Although most of the capacity of 4 is used, it varies depending on the size and arrangement of the figure and the scanning interval for filling. The scan data is created as described above, and the data stored in the memory 54 is sequentially read from the head of the memory at a clock of a constant cycle and DA converted, that is, the electron beam is scanned and exposure is performed. For example, the electron beam draws five rectangles 41 to 45, and then the electron beam moves to the discarding point 46 and stays there for a certain time.

Then, when the final data is converted, the electron beam moves to the leading point 47. At this time, discard point 46
Since it is far away from the leading point 47, overshoot occurs in the DA-converted deflection signal, but when the electron beam is located at the leading point 47, blanking is turned on and the electron beam is blocked. To be done. After that, until new deflection data is written in the memory 54 and the DA conversion is started, the electron beam remains at the leading point 47 and blanking is applied, and the leading point 47 is not exposed. This period is about 200 msec, during which the deflection signal stabilizes at a value corresponding to the next leading point 47.

The blanking on / off is controlled by the electronic computer 52 or the built-in circuit of the DA converter 53, and the time is set by the electronic computer 52. As a result, even if the next conversion is started, the jump of the beam deflection amount does not occur at all. By this method, an accurate figure can be drawn.

[0027]

According to the electron beam exposure method of the first aspect of the present invention, before drawing a series of geometrically arranged figures in the exposure area, the position is outside the area to be drawn and close to the series of figures. With a configuration that only changes the normal scanning method such as temporarily stopping the electron beam at a certain point,
By suppressing the influence of overshoot without controlling the blanking and stabilizing the electron beam deflection amount and then performing the exposure, the figure can be accurately exposed.

According to the electron beam exposure method of the second aspect, a number corresponding to the period until the deflection position becomes stable between the deflection data in which the electron beam overshoot occurs and the next deflection data. The dummy deflection data is stored in the first memory in the inserted state, the blanking data is stored in the second memory in correspondence with the dummy deflection data, and the dummy deflection data and the blanking data corresponding thereto are stored. Based on the above, by blanking the electron beam, the effect of overshoot can be suppressed without exposing unnecessary patterns, and the amount of electron beam deflection can be stabilized before exposure, so that the figure can be accurately exposed. be able to.

According to the electron beam exposure method of the third aspect, data for causing a jump in the electron beam deflection amount is stored in the final address of the memory for storing the deflection data for scanning, and the data for causing the jump is stored. The deflection voltage corresponding to is held until the deflection data for the next scan is written in the memory and the conversion starts, so that blanking is not controlled during a series of scans and unnecessary. It is possible to accurately expose a figure by suppressing the influence of overshoot and stabilizing the electron beam deflection amount without exposing the pattern and then performing the exposure.

By using the method of the invention described in claims 1 to 3 described above, it is possible to reduce the distortion of the graphic forming the optical element and thereby reduce the aberration of the optical element due to the graphic distortion. it can. Here, the aberration will be described. An optical diffraction grating such as a grating mainly has a function of changing (deflecting) the propagation direction of a light beam, and the amount of deflection is determined by the angle between the light beam and the line of the grating and the period of the grating. Therefore, if an error occurs in the angle and period of the grating due to the graphic distortion, the designed deflection amount cannot be obtained and an aberration occurs. For example, the light beam may not pass through the designed position, or the light beam may not converge at the designed position.

[Brief description of drawings]

1 is a first electron beam exposure method according to claim 1;
3 is a schematic view showing a beam scanning method in the embodiment of FIG.

FIG. 2 is a second electron beam exposure method according to claim 1;
3 is a schematic view showing a beam scanning method in the embodiment of FIG.

FIG. 3 is a third electron beam exposure method according to claim 2;
3 is a schematic view showing a beam scanning method in the embodiment of FIG.

FIG. 4 is a fourth electron beam exposure method according to claim 3;
3 is a schematic view showing a beam scanning method in the embodiment of FIG.

FIG. 5 is a schematic view showing the arrangement of an electron beam exposure apparatus used when carrying out the electron beam exposure method of the present invention.

[Explanation of symbols]

 11 lines 12 stop points 13 start points 14 end points 21 lines 22 stop points 23 start points 24 preparatory scans 31, 32 lines 33 stop points 41-45 rectangles 46 discard points 47 start points 48 rectangles

Claims (3)

[Claims] 1. A point outside an area to be drawn and at a position close to the series of figures before drawing a series of figures that are positionally arranged in an exposure area by irradiating while scanning with an electron beam. An electron beam exposure method, characterized in that the electron beam is temporarily stopped. 2. The electron beam according to deflection data for scanning the electron beam stored in the first memory, and blanking data of the electron beam stored in the second memory corresponding to the deflection data. Is an electron beam exposure method for exposing a predetermined area by irradiating while scanning, and between the deflection data where the electron beam overshoot occurs and the next deflection data until the deflection position becomes stable. The dummy deflection data of a number corresponding to the period is stored in the first memory, and the blanking data is stored in the second memory in correspondence with the dummy deflection data. An electron beam exposure method, wherein the electron beam is blanked based on deflection data and blanking data corresponding thereto. 3. An electron beam exposure method for exposing a predetermined area by irradiating while scanning an electron beam, wherein the electron beam deflection amount is jumped to the final address of a memory storing deflection data for scanning. An electron beam characterized by storing data to be generated and holding a deflection voltage corresponding to the data to generate the jump until the deflection data for the next scanning is written in the memory and conversion is started. Exposure method.