JP3465469B2 - Electron beam writing method, writing apparatus and semiconductor integrated circuit device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electron beam writing used for manufacturing semiconductor devices and the like, and more particularly to an electron beam writing method and apparatus for collectively writing with electron beams having a shape repeatedly appearing in a writing pattern.

[0002]

2. Description of the Related Art Electron beam drawing is used in the manufacture of photomasks and the research and development of advanced devices in semiconductor manufacturing because of its high resolution and the ability to generate patterns. In recent years, with the miniaturization of semiconductor elements, the processing dimension thereof has become about the same as the wavelength of the light source for optical exposure, and is approaching the resolution limit. Therefore, electron beam drawing is being applied to a production line for mass production on a layer that is difficult to be resolved by light exposure even if a super-resolution technique or the like is used. Even though the batch beam drawing method, which irradiates a group of apertures with a specific function at one time, has been put into practical use and the drawing speed has been greatly improved, a much higher drawing speed is required for electron beam drawing. ing.

A factor for further improving the writing speed of the collective beam system is the expansion of the area of the collective beam. However, since the beam current emitted from a certain electron gun is constant, increasing the area of the collective beam results in a decrease in current density. Further, it is not possible to draw all the patterns of the semiconductor element only with the collective beam, and it is practical to use the variable shaping method together. When the area of the collective beam is expanded and the current density of the electron beam is reduced, on the contrary, the drawing speed of the part where the variable shaped beam is used is decreased. Therefore, the area of the collective beam is usually optimized in consideration of factors such as resist sensitivity and deflection settling waiting time in order to obtain the maximum drawing speed.

Further, since the collective beam method is a method of irradiating a plurality of patterns at a time for writing, the irradiation amount cannot be changed in the range of irradiating at a time. On the other hand, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-137520, a method has been proposed in which the irradiation amount has a distribution by overlapping a mesh-shaped opening different from the collective pattern opening. ing.

[0005]

In the electron beam writing of the collective beam method, it is an effective means to increase the area of the collective beam and reduce the number of shots in order to improve the throughput. However, the amount of current emitted from the electron gun is constant because it is determined by the physical properties. Therefore,
Increasing the area of the collective beam will reduce the current density of the beam. Since the sensitivity of the photosensitizer is determined by the product of current density and irradiation time, if the sensitivity of the photosensitizer is constant, the total irradiation time is constant regardless of the beam area.

Normally, even with the collective beam method, it is not possible to draw a pattern other than repetitive patterns only with the collective beam. Therefore, it is practical to use the variable shaped beam method together. When the area of the collective beam is expanded and the current density is reduced, the current density of the variable shaped beam is also reduced. Therefore, the writing speed of the portion to be drawn with the variable shaped beam is reduced, and the overall throughput is reduced.
That is, only a part of the beam to be irradiated is used, and the beam irradiated to other than the aperture does not contribute to drawing, which is a waste.

This problem can be solved by switching the beam size between when irradiating the aperture of the collective beam portion and when irradiating the aperture of the variable shaped beam portion. But,
To switch the beam size, the focusing condition of the lens must be changed. The time required for this is much longer than that for selecting the aperture, and therefore the overall throughput is not improved.

[0008]

A group of apertures having a specific function using a deflector for aperture selection on a diaphragm that determines the shape of a collective beam, or a deflector dedicated to scanning is arranged. The apparent area of the collective beam is expanded by scanning with a beam that is 1/2 or less of each side of the collective beam shape or 1/4 or less in area. By forming the variable shaped beam with a beam having a small area, patterns other than the collective beam pattern can be drawn with high current density. In addition, the irradiation amount is controlled by changing the scanning speed and the number of scans.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the collective beam electron beam writing, in order to improve the throughput, it is effective to enlarge the area of the collective beam and reduce the number of shots. Increasing the area of the collective beam will reduce the current density of the beam. If the sensitivity of the photosensitizer is constant, the total irradiation time is constant regardless of the beam area. Usually, even with the collective beam method, it is not possible to draw all the patterns with only the collective beam. Therefore,
It is practical to use together with the variable shaped beam system. When the area of the collective beam is expanded and the current density is reduced, the current density of the variable shaped beam is also reduced. As a result, the writing speed of the portion drawn by the variable shaped beam is reduced, and the overall throughput is reduced.

A deflector for selecting an aperture is used on an aperture for determining the shape of the collective beam, or a deflector dedicated to scanning is arranged, and the area is larger than that of the collective beam shape which is a group of apertures having a specific function. By scanning with a small beam, the apparent collective beam area is enlarged.

When scanning with a beam having an area smaller than the shape of the collective beam, the minimum number of times of scanning the area of the collective beam is two round trips, so it is effective to use a beam having a size of 1/2 or less of the area. Is. When ½ or more of the beam is used, a scan region required for two scans has an extra portion, which does not contribute to drawing. This is because irradiation unevenness occurs when multiple drawing is performed in the first and second times, and it is necessary to perform scanning so as not to overlap. Therefore, a beam which is ½ or less of each side of the scanned region and ¼ or less in area is used. By forming a variable shaped beam with a beam having a small area, drawing can be performed with a high current density. In addition, the irradiation amount is controlled by changing the scanning speed and the number of scans.

(Embodiment 1) FIG. 1 is a view showing a first embodiment of the present invention.

An electron beam 2 emitted from an electron source 1 (showing an image forming relationship) is converged by one or more focusing lenses 3 and shaped by a first aperture 4, and then a first shaped lens 5 and a second shaped lens. It is converged by the lens 7 and imaged on the second aperture 8. The image on the second aperture 8 is projected and deflected by the objective lens 9 and the objective deflector 10, and is irradiated on the sample 11 coated with the photosensitive agent to perform drawing. At this time, the deflector 6 selects a plurality of pattern-shaped openings to be drawn, which are provided in the second aperture 8 in advance.

Since the radiation angle current density of the electron source 1 is determined depending on the physical properties of the material, the current value that can be used for writing with an electron beam having a certain uniform current density and a specific area is constant. In order to increase the area of the collective beam, it is necessary to adjust the focusing lens 3 to widen the aperture angle for irradiation. Therefore, for example, if the area of the collective beam is doubled, the current density becomes 1/2. Usually, the actual pattern of the semiconductor integrated circuit is complicated and it is not possible to perform drawing with only the collective beam. Therefore, the second aperture 8 is also provided with an opening for the variable molding method, and the drawing is switched according to the pattern. Is going. Since the pattern that is drawn by the variable shaping method is usually smaller than the area of the collective beam, using a beam with a low current density for the collective beam increases the number of beams that do not reach the sample and do not contribute to the drawing. become.

In order to solve this problem, the focusing power of the focusing lens 3 is switched between the collective beam and the variable molding,
It is possible if the beam areas are set to the optimum ones. However, since the focusing lens 3 usually uses an electromagnetic lens having a large inductance, switching the focusing force requires a longer time than selecting the aperture on the second aperture 8 by the deflector 6. As a result, the switching of the convergence force does not improve the drawing speed.

Therefore, if the current density required for the variable shaping method is set by the focusing lens 3 and the collective beam portion having a larger area is scanned with the beam, a collective beam having a larger area can be realized. If the beam area is constant, the focusing lens 3 may be unnecessary. The sensitivity of the photosensitizer applied on the sample 11 is equal to the electron beam irradiation amount per unit area, and is determined by the product of the electron beam current density and the residence time. When the sensitivity of the photosensitizer is constant, the dwell time when the current density is low and the area is large is equal to the total dwell time when the beam having a high current density is continuously scanned. Therefore, the time required for scanning the opening on the second aperture 8 with a beam having a smaller area than that of the collective beam and for expanding the area of the collective beam is the same.

FIG. 2 shows a case where scanning is performed with a beam having an area smaller than that of the collective beam. The collective beam aperture 12 which is a group of apertures having a specific function on the second aperture 8 is scanned by the electron beam 2 which is smaller than the area of the aperture. At this time, the opening 13 for the variable shaped beam may be larger than the area of the electron beam 2. On the other hand, the conventional collective beam system is shown in FIG. The collective beam opening 12 on the second aperture 8 was collectively irradiated with the electron beam 2 having a larger area than the area of the opening.

(Embodiment 2) FIG. 4 shows a scanning path of the electron beam 2. FIG. 4A shows that the electron beam 2 scans the collective beam aperture 12 on the second aperture 8 through the scanning path 14. In this way, the collective beam opening 12
If the entire area is scanned with the electron beam 2, the collective beam aperture 12 may have any pattern.

However, in actual semiconductor manufacturing, there is a layer in which each pattern to be drawn has a small area, such as a hole system. In the example shown in FIG. 4B, the collective beam opening 1 is used.
The area of the opening 15 occupying in 2 is small, and the electron beam 2 with which the portion other than the opening is irradiated does not contribute to drawing. When the openings 15 of the respective patterns are small and the openings 15 are apart from each other, only the opening portions are selectively scanned like the scanning path 16. In this case, the current of the electron beam 2 can be effectively used, and the drawing speed is further improved. In this method, it is necessary to change the scanning position every time the drawing pattern changes. Therefore, the positional information may be recorded when the second aperture 8 is manufactured, and the pattern arrangement information may be read every time the pattern changes.

If only the portion of the opening 15 is selected for scanning, the drawing speed can be increased by the ratio of the area of the electron beam 2 to the collective beam opening 12.

(Embodiment 3) As shown in FIG.
In the so-called collective beam method, it is a usual method to control the irradiation amount by the time from when the electron beam 2 is turned on to when it is turned off.
On the other hand, in the present drawing method shown in FIG. 2, the following two types of methods for controlling the irradiation amount are possible. First
Is a system in which the electron beam 2 scans the collective beam opening 12 only once. This changes the scanning speed according to the staying time of the electron beam 2 which is determined from the required irradiation amount and the current density of the electron beam 2. The second is a method for scanning the collective beam opening 12 a plurality of times. In this, the speed of one-time scanning is fixed, and the scanning is performed for the required number of irradiations.

The case where the irradiation amount is changed by scanning only once will be described in detail. When scanning the entire area of the collective beam opening 12 with the electron beam 2 as shown in FIG.
The scanning speed may be changed in inverse proportion to the required irradiation amount. Further, when the scanning path 16 selectively scans only the opening portion as shown in FIG. 4B, the scanning is stopped while the electron beam 2 stays in the opening 15 and the scanning is started from the opening. The movement to the aperture may be performed by scanning at the maximum speed of the scanning deflector. Further, when the area of the electron beam 2 is larger than that of the opening 15, the stop stability of the scanning deflector can be relaxed by the difference between the lengths of the electron beam 2 and the opening 15 in the scanning direction. .

In the case of scanning a plurality of times, in both cases of FIGS. 4A and 4B, the number of scans may be increased only for the portion having a large irradiation amount.

As a result of using this method, the irradiation amount inside the collective figure can be arbitrarily set, and in particular, the proximity effect correction depending on the irradiation amount can be performed with high accuracy.

(Embodiment 4) FIG. 5 is an enlarged view of the first molded lens 5 and the second molded lens 7, showing an example in which a scanning signal is superimposed on a deflector. By adding the scanning signal from the scanning signal generator 18 to the signal of the selection control device 17 which sends a signal to the deflector 6, the same deflector 6 is selected and scanned.
Done in.

(Embodiment 5) FIG. 6 is an enlarged view of the first molded lens 5 and the second molded lens 7, showing an example in which a deflector for scanning is newly added. The conventional deflector 6 is supplied with a signal from the selection control device 17, and the scanning deflector 19 is supplied with a scanning signal from the scanning signal generator 18, so that selection and scanning are performed independently.

(Embodiment 6) FIG. 7 shows a manufacturing process of a semiconductor integrated circuit using the electron beam drawing method of the present invention.

7A to 7D are sectional views of the element showing the steps. The P well layer 21, the P layer 22, and the field oxide film 2 are formed on the N-minus silicon substrate 20 by a usual method.
3. A polycrystalline silicon / silicon oxide film gate 24, a P high concentration diffusion layer 25, an N high concentration diffusion layer 26, etc. were formed (FIG. 7A). Next, an insulating film 27 made of phosphorus glass (PSG)
And the insulating film 27 was dry-etched to form a contact hole 28 (FIG. 7B).

Next, the W / TiN electrode wiring 3 is formed by a usual method.
Material No. 0 was adhered, a photosensitizer 29 was applied on the No. 0 material, and the photosensitizer 29 was patterned using the electron beam drawing method of the present invention (FIG. 7C). Then, the W / TiN electrode wiring 30 was formed by dry etching or the like.

Next, an interlayer insulating film 31 was formed and a hole pattern 32 was formed by a usual method. Hole pattern 32
The inside was filled with a W plug and the Al second wiring 33 was connected (FIG. 7D). The subsequent passivation process used the conventional method.

Although only the main manufacturing steps are described in this embodiment, the same steps as the conventional method are used except that the electron beam drawing method of the present invention is used in the lithography step for forming the W / TiN electrode wiring. . Through the above steps, a pattern can be formed without deterioration in quality, and CMOSL
It was possible to manufacture SI with a high yield. As a result of manufacturing a semiconductor integrated circuit using the electron beam drawing method of the present invention, the production rate per unit time increased due to the improvement of the drawing speed.

[0032]

EFFECTS OF THE INVENTION By scanning the collective beam aperture with a beam having a smaller area than the collective beam shape which is a group of apertures having a specific function, the apparent collective beam area is enlarged and high-speed writing is performed. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a case where scanning is performed with a beam having a small area.

FIG. 3 is a diagram showing a conventional collective beam system.

FIG. 4 is a diagram showing a scanning path.

FIG. 5 is a diagram showing an example in which a scanning signal is superimposed on a deflector.

FIG. 6 is a diagram showing an example in which a deflector for scanning is newly added.

FIG. 7 is a diagram showing a manufacturing process of a semiconductor integrated circuit using the electron beam drawing method of the present invention.

[Explanation of symbols]

1: electron source, 2: electron beam, 3: converging lens, 4: first aperture, 5: first shaping lens, 6: deflector, 7:
Second shaped lens, 8: second aperture, 9: objective lens, 10: objective deflector, 11: sample, 12: collective beam aperture, 13: variable shaped beam aperture, 14: scanning path, 15: aperture, 16: scanning path, 17: selection controller, 18: scanning signal generator, 19 scanning deflector, 2
0: N minus silicon substrate, 21: P well layer, 2
2: P layer, 23: field oxide film, 24: polycrystalline silicon / silicon oxide film gate, 25: P high concentration diffusion layer,
26: N high concentration diffusion layer, 27: Insulating film, 28: Contact hole, 29: Photosensitizer, 30: W / Ti electrode wiring, 3
1: interlayer insulating film, 32: hole pattern, 33: aluminum second wiring

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Nakayama 1-280, Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor, Tokuro Saito 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Institute (56) Reference JP-A-4-88626 (JP, A) JP-A-4-124810 (JP, A) JP-A-4-302132 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027

Claims (6)

(57) [Claims] 1. A electron source for emitting an electron beam and the electron beam shape a collection opening group having a function of determining the
A plurality of apertures are arranged and arranged on the aperture
Select one of the
A first deflector for irradiating said electron beam to said aperture group, in the one or more electron beam writing method using an electromagnetic lens for projecting the electron beam, occupied by an opening group of the a collection An electron beam drawing method characterized in that drawing is performed by scanning with the electron beam composed of ½ or less of each side of the area. Wherein in the electronic beam drawing method according to claim 1, to carry out drawing by performing scanning with an electron beam further 1/4 or less of the area of the region occupied by the aperture groups of the one chunk Characteristic electron beam drawing method. 3. The electron beam drawing method according to claim 1, wherein the aperture group is one of the plurality of aperture groups.
An electron beam drawing method characterized by performing drawing by selecting only an opening in a region occupied by the area and performing scanning. 4. In the electron beam writing method of any of claims 1 or claim 2 or claim 3, said one
An electron beam writing method characterized in that writing is performed by changing the electron beam irradiation amount by changing the scanning speed or the number of times of scanning depending on the location of the group of apertures on the aperture . 5. In the electron beam lithography system characterized by using an electron beam writing method of any one of claims 1 to 4 serial <br/> mounting, of the plurality of specific shapes An electron beam drawing apparatus having a function of superimposing a scanning signal on a first deflector for selecting an aperture. 6. There claims 1 to an electron beam lithography system characterized by using an electron beam writing method of the serial <br/> mounting any one of claims 4, to scan on the sample An electron beam drawing apparatus provided with a second deflector.