JPH0732111B2 - Charged beam projection exposure apparatus - Google Patents

Description

The present invention relates to an apparatus for transferring a reduced image of a mask pattern onto a sample surface at high speed and with high precision by using an electron beam for manufacturing a semiconductor LSI or the like. It is a thing.

[Conventional technology]

Conventionally, a mask pattern is transferred onto a sample (wafer) by using an electron beam for manufacturing a semiconductor such as an LSI, and is drawn by using photoelectrons generated from the mask (hereinafter referred to as "photoelectron drawing device"). There is a device for irradiating an electron beam on a perforated mask (shadow mask) to form an image of the electron beam on a sample surface for drawing (hereinafter referred to as "aperture mask drawing device"). The optoelectronic drawing device is, for example, JP Scott, 1: 1 electron image projector, solid state technology / May, 1977 (JPScot, Electron image P
rojector, Solid State Technology / May, 1977). This uses a special electron optical system that superimposes a uniform magnetic field and a uniform electrolysis so that all of the photoelectrons generated can be irradiated onto the sample surface. The current density is extremely low and the energy is low. It solves the problem of highly dispersed photoelectron sources.

However, this method has the following drawbacks.

(A) It is not possible to reduce the pattern, which is becoming more necessary as the pattern becomes finer. Even if a reduction optical system is added and it is attempted to do so, only a very small number of photoelectrons can be used in terms of aberration of the electron optical system, resulting in extremely low productivity.

(B) The shape of the projected figure cannot be corrected. Further, since the current density for mark detection is low, highly accurate alignment drawing cannot be performed.

(C) The life of the photoelectron generating part is short.

Perforated mask lithography systems include, for example, Etch Boren et al., High Throughput Submicron Lithography With Electron Beam Proximity Printing, Solid State Technology / 9.
Mon, 1984 (H. Bohlen et al. High Throughput Submicron
Lithography with Electron Beam Proximity Printing,
Solid State Technology / September, 1984). This will be described with reference to FIGS. 6 to 9.

FIG. 6 shows an electron optical system. 1 is an electron gun, 2 is an irradiation lens, 3 is an electron beam, 4 is a large deflector (aligner), 5 is a small deflector (small aligner), and 6 is a pattern mask. , 7 are mask holders. Here, the electron beam 3 irradiating the mask 6 is a parallel bundle as shown in the figure,
The large deflector 4 scans this beam bundle on the mask 6. At the time of scanning, the shape of the projected figure of the mask can be slightly changed by slightly changing the inclination of the beam bundle using the small deflector 5. This is shown in FIG. FIG. 7 (a) is an example of pattern drawing in both the X and Y directions without changing the position. By interlocking this with the scanning in the Y direction and changing the irradiation position only in the X direction, FIG.
It is possible to transform the projected figure from (f) to (f). A more complicated deformation can be realized by superimposing a change in the irradiation position in the Y direction on these. FIG. 8 shows an example in which the mask used in this technique and its pattern are transferred onto the sample surface. In FIG. 8 (a), 10 is a mask pattern, 11 is a mark (perforated mark) in the mask 6, 12 is a registration mark on the surface of the sample 14, and 13 is a sample 14 in FIG. 8 (b). These are 10 projected figures on the surface. At the time of drawing, after the sample 14 is positioned at a predetermined position, the beam bundle is applied to the mark 11 in the mask 6 by the large deflector 4 and then the alignment mark 12 is scanned with a small amplitude by the small deflector 5. The mark is detected once. This operation is repeated 4 times. As a result, the sum of the deformation amount of the sample surface area corresponding to the projected figure 13 and the deformation amount of the shape of the mask pattern 10 itself can be obtained. Using this data, the pattern drawing is performed while correcting the irradiation position described in FIG. 7 so that each pattern on the mask 6 is accurately projected at the desired position on the sample surface. This drawing may be performed by using the large deflector 4 so that the entire surface of the mask pattern 10 is scanned by the beam bundle. After this operation, the sample 14 is moved and the same operation is repeated to complete the pattern drawing on the entire sample surface as shown in FIG.

In the present technology, for a donut-shaped mask pattern, a pair of complementary masks 15 and 16 as shown in FIG.
By repeating the above-mentioned pattern drawing twice by using, the complete pattern 17 shown in FIG. 9B is transferred. This method doubles the series of drawing operations, but compared to the conventional method of supporting the inside of the donut with a fine mesh, etc.
Since the mask 6 is easy to manufacture and the beam is not scattered at the mesh portion, the complementary mask is practically superior at this stage.

As described above, this perforated mask drawing device can transfer a pattern with high current density and high productivity as compared with the photoelectron drawing device, and since the current density at the time of mark detection is also high, it is faster and more accurate. It has the advantage that it can detect marks and can accurately correct complicated deformations of the mask and sample.

[Problems to be solved by the invention]

However, this perforated mask drawing apparatus has the following drawbacks.

 The pattern cannot be reduced.

The deflection area of the large deflector 4 needs to be at least as large as the area of the LSI chip, which increases the aberration of each part of the electron optical system due to the deflection, and also in this respect for the transfer of even finer semiconductor patterns. I can not cope.

Since the beam position at the time of detecting the mark is the angle of the chip that is most distant from the beam axis, there is a deterioration in the mark detection accuracy due to loss of the symmetry of the signal of the backscattered electron detector.

[Means for solving problems]

In order to eliminate such defects, the present invention provides a mask stage on which a mask is mounted, a sample stage on which a sample is mounted, and a mask on which a charge beam is scanned while continuously moving the mask stage and the sample stage. And an electron optical system having a means for

[Action]

According to the present invention, the reduced image of the charged beam of the mask pattern is transferred at the same time as the reduced image is transferred while being corrected so that the reduced image has a desired shape during the transfer operation. Further, during the drawing operation, the mask and the sample are drawn while continuously moving.

〔Example〕

FIG. 1 shows a first embodiment of the present invention, in which 20 is an electron gun,
21 is an electron beam, 22 is a first irradiation lens, 23 is a second irradiation lens, 24 is a beam shaping aperture, 25 is a large deflector as a device for scanning the mask with a charge beam, 26 is a mask stage, and 27 is small. A deflector, 28 is a focus correction lens, 29 is a reduction projection lens, 30 is a detector for the height of the sample surface and reflected electrons, 31 is a sample stage, and 32 is an electron optical system. Further, 40 is a control computer, 41 is a lens power supply, 42 is a large deflection control circuit, 43 is a stage control unit, 44 is a sub deflection / correction lens control circuit,
Reference numeral 45 is a signal processing circuit, 46 is a laser length measuring machine for mask stage, 47 is a mask stage driving device, 48 is a laser length measuring device for sample stage, and 49 is a sample stage driving device. First
In the figure, the same or corresponding parts as those in FIGS. 6, 8 and 9 are designated by the same reference numerals.

Prior to the description of the operation of the apparatus thus configured, the operation of the electron optical system 32 will be described with reference to FIG. In Figure 2
50 is a beam shaping lens. The electron beam 21 from the electron gun 20 becomes a parallel beam bundle having a predetermined distribution by the irradiation lenses 22 and 23, and irradiates the beam shaping aperture 24. The beam bundle that has passed through the aperture of the beam shaping aperture 24 irradiates the mask 6 on the mask stage 26. The current density at this time is controlled by changing the diameter of the beam bundle. The mask 6 is a perforated mask (shadow mask). A reduction projection lens 29 projects the electron beam image of the mask 6 onto the sample 14 as a reduction image, and prints (draws) a pattern. In this embodiment, the reduction ratio of the reduction projection lens 29 is 1/2 and 1/4.
It is possible to switch between two stages.

The large deflector 25 scans the mask 6 with a beam. Along with this, the irradiation beam on the surface of the sample 14 also scans the region corresponding to the reduction ratio. In the course of this scanning, the irradiation position is corrected using the small deflector 27. For this, the same correction method as described in FIG. 7 is used. Further, the small deflector 27 is also used for small deflection for mark scanning. The reflected electron signal at that time is obtained by using the detector 30. The beam shaping aperture
Instead of directly irradiating the mask 6 with the electron beam 21 that has passed through 24, the aperture image of the beam shaping aperture 24 may be projected onto the mask 6 using the beam shaping lens 50.

From the above, if the electron optical system 32 in the present embodiment is used,
It was found that a reduced image of the scanning area of the mask 6 can be drawn on the surface of the sample 14. The following operations are required to draw the pattern of the entire area of the mask 6 with high accuracy over the entire area of the sample.

Deflection deflector distortion correction Measurement and correction of sample surface distortion (deformation) Sample full surface pattern drawing Here, the sample full surface pattern drawing is performed by the control computer 40.
Under the control of the mask stage controller 43 under the control of the mask stage drive device 47 and the sample stage drive device 49, the mask stage 26 and the sample stage 31 are moved while the laser measurement for the mask stage is performed. The information of the machine 46 and the laser measuring machine 48 for the sample stage is used. Hereinafter, each operation will be described in the order of above.

Correction of deflection distortion of deflector: A method of correcting deflection distortion of a large deflector will be described with reference to FIG. In FIG. 3, reference numeral 100 is a standard pattern (opening) provided on the mask 6, and its image 110 is projected on the surface of the sample 14. In FIG. 3, the same or corresponding parts as those in FIG. 1 are designated by the same reference numerals. First, as shown in FIG. 3A, the mask stage controller 43 positions the standard pattern 100 on the beam axis, and the large deflector 25 is used to scan the standard pattern 100 with a small amplitude. Electron beam 21
Since the detector 30 obtains a backscattered electron signal when the beam crosses the standard pattern 100, it uses the traveling signal and the signal obtained by the detector 30 (in the same manner as in normal mark detection) to determine the beam axis and the standard beam. It is possible to know the precise positional relationship with the pattern 100. The control computer 40 stores the measured value M1 and the length measurement information L1 of the mask stage laser length measuring machine 46 at that time. Next, as shown in FIG. 3B, the standard pattern 100
Is moved by a predetermined distance to obtain the length measurement information L2 of the mask stage laser length measuring machine 46 at that time. The large deflector 25 deflects the electron beam 21 by a distance of l = L2−L1 + M1, and the small amplitude scanning described above is performed on the standard pattern 100 to accurately measure the deviation M2 between the beam deflection position and the standard pattern 100. To measure. Here, the deviation M2 is a deflection distortion when deflected by the distance l. Such deflection distortion is measured at a plurality of measurement points, and based on this, the deflection data of the large deflector is corrected to correct the deflection distortion.

The correction of deflection distortion of small deflectors is a well known fact. That is, the standard marks on the surface of the sample 14 are positioned at a plurality of locations, and the standard marks are detected and the deflection distortion is measured using the length measurement information of the laser length measuring machine 48 for the sample stage at each time. To do.

From the above, the large / small deflector 25 based on the laser coordinate system
・ 27 deflection distortions were corrected.

Measurement and correction of strain (deformation) on the sample surface: This will be described with reference to FIG. To detect the upper left chip mark, as shown in FIG.
The mark 11 and the alignment mark 12 therein are positioned on the beam axis of the electron beam 21. Align the reduced image of mark 11 and mark 12
If they have the same shape, they will overlap with each other with a chip distortion. Here, the image of the mark 11 in the mask pattern 10 is scanned with a small amplitude (mark scanning) using the small deflector 27, and the amount of this deviation is measured. At the same time, the height detector in the detector 30 detects the height of the peripheral region of the alignment mark 12.

Next, to detect the chip mark on the upper right, refer to FIG.
As shown in, the upper right mark 11 and the alignment mark 12 in the mask pattern 10 are positioned on the beam axis of the electron beam 21, and the above operation is repeated. The above is repeated with four chip marks to measure the deformation of the chip on the sample surface. Using this measurement data, the small deflector
Performs highly accurate matching drawing operation while correcting the irradiation position with.

Pattern drawing of entire surface of sample: This will be described with reference to FIGS. 4 (c) to 4 (k). Where the fourth
Reference numeral 350 shown in FIGS. 4D and 4K is a unit drawing area in which continuous movement of both the mask stage 26 and the sample stage 31 (hereinafter referred to as “stage”) and steps and repeats are repeated, and FIG. Reference numeral 400 shown in e) indicates a stage step and repeat path for chip mark detection, and reference numeral 410 shown in FIG. 4 (i) indicates a repeat drawn by one continuous movement of the stage. 420 (f) to (i) is an arrow indicating the direction of the region that expands as it is drawn on the sample surface at that time, and 430 and 440 shown in FIG. 4 (f) are the electron beam irradiation region and the electron. This is a beam scanning path. FIG. 4 (c) is a mask pattern used in this example, and in FIG. 4 (c),
6 is a mask, 10 is a mask pattern, and 11 is a mark.

At the beginning of drawing in the unit drawing area 350 of FIG.
As shown in FIG. 7E, marks are detected one after another in the order of the path 400, and finally the stage is positioned at the continuous movement drawing start point. In FIG. 4 (e), the alignment correction data of the two chips is obtained at this point. In FIGS. 4D and 4E, 12 is a mark, 13 is a projected figure of a mask pattern, 14
Is a sample. Next, as shown in FIG. 4 (f), the stage is moved while raster scanning the electron beam 21 on the mask 6 by the large deflector 25. At this time, the moving speed of the sample stage 31 is M times that of the mask stage 26 (M is the reduction ratio of the reducing projection lens 29), and the moving directions are different from each other. The stage movement error is measured in real time by the mask stage laser length measuring machine 46 and the sample stage laser length measuring machine 48.
The result is fed back to the beam position in real time via the large deflector 25 and the small deflector 27, and as a result, the irradiation position on the mask 6 and the sample 14 is sufficiently accurate. The scanning direction of the electron beam 21 on the mask 6 is set substantially at right angles to the moving direction of the stage, and the stage speed is set according to the irradiation time of the electron beam 21. Therefore, the correction amount based on the laser values of the large deflector 25 and the small deflector 27 need only be the correction for the speed fluctuation of the stage. Figure 4 (g), (h)
In the figure, the drawing state under this continuous movement is illustrated. That is, the electron beam 21 is scanned on the mask 6 in the θ direction, while the mask 6 and the sample 14 are sent in the direction of the arrow 421. As shown in FIG. 4 (h), the area where the mask 6 is scanned and the area where the sample 14 is drawn are enlarged after a certain time t seconds. The area 421 is drawn by one drawing under this continuous movement.
Draw the area. Next, as shown in FIG. 4 (i),
The direction of movement of the stage is reversed and the drawing operation is performed under the same continuous movement. By repeating the above operation, the unit drawing area 350
Finish drawing. Deformation in the X and Y planes of the sample during this drawing process is corrected by using the small deflector 27 by the method described above.

An example of the correction formula is shown below.

x = Lx + M (A1 + A2 ・ X + A3 ・ Y + A4 ・ XY) y = Ly + M (B1 + B2 ・ X + B3 ・ Y + B4 ・ XY) where X and Y are the coordinates on the mask pattern 10 and x and y are the deflection of the small deflector 27. Amount of correction to be performed (represented by the coordinates of sample 14). Further, Lx and Ly are laser feedback amounts, Ai and Bi are correction coefficients for matching (correction of deformation of the mask 6 and the sample 14), and M is a reduction ratio of the reduction projection lens 29.

In addition, the focus position of the beam is corrected in real time using the focus correction lens 28 shown in FIG. 1 according to the deformation in the height direction (Z direction) of the sample. As a result, a fine pattern can be drawn with high accuracy regardless of the deformation of the sample surface. After the drawing of the unit drawing area 350 is completed, the drawing operation of the next unit drawing area is started. By repeating the above, drawing on the entire surface of the sample is completed.

Next, an example of drawing using a complementary mask will be described.
In this example, (451,452) and (453,4) shown in FIG.
54), using the complementary mask consisting of two sets of mask patterns, first, in the above-described method, the unit drawing area 350 is formed by (451, 452).
Draw according to the area. Next, the stage is moved, and (453,454) is used to perform drawing again in accordance with the same unit drawing area 350, and the complete pattern is transferred.

FIG. 5 shows a second embodiment of the present invention. In the case of this embodiment, three electron optical systems 32 are arranged in parallel, and a mask 6 and a sample 14 are installed in each of them. Where the mask 6
One for each of the sample and 14 stages is required. Also, since the lens and deflector are electrostatic type, only one drive circuit is required. The one provided for each electron optical system includes a second irradiation lens 23, a small deflector 27, a focus correction lens 28,
This is a control or drive circuit for the detector 30.

In pattern writing, from the measurement of the deformation of the sample surface described in the first embodiment, the entire surface of the sample is simultaneously drawn by each electron optical system. As a result, the processing time per sample
It becomes 1/3.

While the embodiments of FIGS. 1 and 2 have been described above, the results of these embodiments are as follows.

Since the reduced projection of LSI patterns is possible, future L
It can correspond to the miniaturization of SI patterns.

Since it is not necessary to increase the beam deflection amount at the time of drawing, the aberration of the electron optical system can be reduced, a large beam current value can be obtained, and a fine pattern can be processed at high speed.

Since a plurality of electron optical systems can be provided by adding a small number of constituent parts, it is possible to shorten the drawing time and the time required for measuring the sample surface deformation and the like.

In the above description, the electron beam is used, but an ion beam may be used instead of the electron beam. That is, various charged beams can be used in this embodiment.

〔The invention's effect〕

As described above, according to the present invention, the mask stage on which the mask is mounted, the sample stage on which the sample is mounted on the sample, and the mask stage and the sample stage are continuously moved by scanning the mask with the charged beam. By providing the electron optical system having the means, the following effects are produced.

Since the reduced projection of the pattern is possible, fine pattern drawing is possible.

Since each mask and sample has a stage,
Even if the deflection amount for pattern drawing is small, productivity is not impaired, and as a result, the charged beam current is increased,
In addition, since a charged beam projection image with less blur can be obtained, a fine pattern can be drawn with high productivity.

High-accuracy pattern writing is possible by measuring the moving amount of both the mask and sample stages with a laser length measuring machine and feeding back the results to the charged beam irradiation position of the mask and sample. Since the moving direction and the mask scanning direction are substantially perpendicular to each other, the correction amount of the charged beam irradiation position with respect to the movement of the stage can be small.

If the chip mark is detected right under the beam axis, the mark can be detected with high accuracy, and as a result, the pattern can be drawn with high accuracy.

Since a plurality of electron optical systems are provided, it is possible to reduce dead time such as mark detection time as well as pattern drawing time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a first view of a charged particle beam projection exposure apparatus according to the present invention.
FIG. 2 is a block diagram showing an electron optical system thereof, FIG. 3 is an explanatory diagram for explaining a deflection distortion correcting method, and FIG. 4 is a distortion (deformation) of a sample surface. FIG. 5 is an explanatory view for explaining a method of measurement and correction and a method of drawing a pattern on the entire surface of the sample, FIG. 5 is a configuration diagram showing a second embodiment of a charged beam projection exposure apparatus according to the present invention, and FIG. FIG. 7 is a block diagram showing a conventional electron optical system, FIG. 7 is a pattern diagram showing an example of pattern drawing in the conventional electron optical system, and FIG. 8 is an example of transferring a mask and its pattern onto a sample surface in a conventional apparatus. FIG. 9 is a pattern diagram showing an example of transfer using a pair of complementary masks in a conventional apparatus. 6 ... Mask, 14 ... Sample, 20 ... Electron gun, 21 ... Electron beam, 22,23 ... Irradiation lens, 24 ... Beam shaping aperture, 25 ... Large deflector, 26 ... Mask stage, 27 ...
… Small deflector, 28 …… Focus correction lens, 29 …… Reduction projection lens, 30 …… Detector, 31 …… Sample stage, 32 …… Electronic optical system, 40 …… Control computer, 41 …… Lens power supply , 42 ...
… Large deflection control circuit, 43 …… Mask stage controller, 44
...... Control circuit for sub-deflection / correction lens, 45 …… Signal processing circuit, 46 …… Laser length measuring machine for mask stage, 47 …… Mask stage driving device, 48 …… Laser measuring machine for sample stage, 49… … Sample stage drive, 50… Beam shaping lens.

Claims (3)

[Claims] 1. A charged beam projection exposure apparatus for projecting an image of a pattern by using a charged beam, wherein a mask stage on which a mask is mounted, a sample stage on which a sample is mounted, the mask stage and the sample stage are continuously arranged. A charged beam projection exposure apparatus, comprising: an electron optical system having a means for scanning the mask with the charged beam while moving the mask. 2. A charged beam projection exposure apparatus according to claim 1, wherein a plurality of said electron optical systems are provided. 3. The charged beam projection exposure apparatus according to claim 2, wherein the plurality of electron optical systems commonly use one mask stage and one sample stage.