JPH11224840A - Method and device for exposure of charged particle beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charged particle beam exposure device wherein the blurs, distortions, and changes in the focal point of an image due to coulomb effect are reduced. SOLUTION: Blurs, distortions, and changes of an image in focal point due to coulomb effect are reduced by allowing a shape of irradiating region 251 of electron beam projecting a reticle 25, in other words the cross-sectional shape of an electron beam to be rectangular, by especially allowing the aspect ratio of the irradiating region 251 to be 20 or larger, the image blur is 55% or smaller than that of conventional cases. Further, by allowing beam cross-sectional shape to be rectangle, the deflection width of charged particle beam is narrower than before, and current and voltage of a power source used for an exposure device are lowered, while the number of bits of a digital-to-analog converter is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a charged particle beam exposure apparatus such as an electron beam exposure apparatus used in semiconductor manufacturing and an exposure method.

[0002]

FIG. 7 is a schematic diagram showing a schematic configuration of an electron beam exposure apparatus. Electron beam B from electron beam source 1
Is shaped into a beam having a predetermined cross-sectional shape (for example, a square) by the aperture 3, is focused by the condenser lens 2, and is then radiated to one of the reticle subfields 51 of the reticle 5 by the illumination system deflector 4. The electron beam B having passed through the reticle subfield 51 is imaged at a predetermined position on the wafer 11 by the projection lens 9. Note that the reticle 5 and the wafer 11 are
The reticle stage 6, which is driven in the x and y directions by the
The position 12 is detected by position detectors 14 and 15 such as a laser interferometer, respectively. The controller 1 controls the entire exposure apparatus.
6, the deflector 4, the stages 6, 12 and the like are controlled based on the detection results of the position detectors 14, 15.

FIG. 8 is a view for explaining exposure transfer of a reticle pattern onto a wafer by an electron beam. The reticle 5 is divided into a plurality of rectangular reticle subfields 51 as shown in FIG. 8, and the electron beam 3 passing through the reticle subfield 51 is converted into a wafer subfield 81 on the wafer 11 by the projection lens 9 (see FIG. 7). It is imaged. Reference numeral 8 denotes a chip area where a pattern of a semiconductor element is formed. As the reticle subfield 51 of the reticle 5, there is a reticle subfield 51 in which a pattern is formed with a heavy metal on a thin film having a thickness of about 0.1 μm, and a reticle subfield 51 in which a patterned hole is formed in a thin film having a thickness of 2 μm. A beam 52 is formed on the reticle 5 in order to maintain the strength of the thin film and prevent a change in temperature. Further, although not shown, peripheral portions of the reticle subfield 51 (between the reticle subfield 51 and the reticle subfield 51 and the reticle subfield 51). Subfield 51 and beam 52
A thin film portion (skirt portion) without a pattern is formed between the two. This skirt portion prevents the exposure amount from becoming non-uniform due to deformation of the irradiation electron beam, or an area for excessive scanning during scanning exposure in which exposure is performed while scanning the electron beam (when scanning with the electron beam). Area corresponding to the run-up section).

On the other hand, the chip area 8 of the wafer 11 is divided into a plurality of wafer subfields 81 corresponding to the reticle subfields 51 of the reticle 5. The reticle subfield 51 is a region that is collectively irradiated with the electron beam B having a slightly larger cross section than the size of the reticle subfield 51, and the pattern of the reticle subfield 51 is collectively exposed to the corresponding wafer subfield 81 of the wafer 11. Typical dimensions of reticle subfield 51 are 1 mm x 1 mm
Since the magnification of the projection lens 9 is generally 1/4, the size of the wafer subfield 81 is 0.25 mm.
× 0.25 mm.

The electron beam B for irradiating the reticle 5 irradiates the reticle subfield 51 selected by the illumination system deflector 4 as described above, and the electron beam B passing through the reticle 5 is used for the projection system deflector (not shown). As a result, the deflection aberration is corrected and projected onto the wafer subfield 81. At this time, the deflection direction of the illumination deflection system 4 is x in FIG.
Exposure for each reticle subfield is sequentially performed in the direction of arrow R1 in the figure. Typical illumination system deflector 4
Has a deflection width of 40 mm and a projection system deflector has a deflection width of 10 mm.
And this range is called a main field. That is, the range of the subfields in a row arranged in the x direction is called a main field, the range of the main field on the reticle 5 is 1 mm × 40 mm, and the range of the main field on the wafer 11 is 0.25 mm × 10 mm.

At the time of exposure, the reticle stage 6 and the wafer stage 12 are moved in opposite directions in the y direction, and are exposed for each subfield. That is, R in FIG.
When the exposure in one direction is completed, the exposure of the main field in the second row is performed as indicated by an arrow R2. Here, a group of a plurality of main fields arranged in the stage movement direction (y direction) is called a stripe. At present, the size of one chip is about 20 mm x 40 mm, so one chip has a width of 10 mm.
Divided into two stripes (the size of one stripe is 10 mm × 40 mm), and in the case of a complementary mask, twice as many as four stripes are required.

In the electron beam exposure apparatus, the number of processed wafers per unit time (so-called throughput) is one of the problems. If the sensitivity of the resist applied on the wafer 11 is the same, the current of the electron beam B is increased. The larger the is, the higher the throughput is. Therefore, an electron beam exposure apparatus capable of flowing a large current beam is desired.

[0008]

However, when the current of the electron beam B is increased, the interaction between electrons (Coulomb effect) increases, and the image becomes blurred, distorted, and the focal position changes. In particular, reticle subfield 5
Since the pattern density within 1 is not uniform, the blur, distortion, and change in the focal position of the image in the wafer subfield 81 due to the Coulomb effect are not uniform but change locally.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charged particle beam exposure apparatus and an exposure method capable of reducing blurring, distortion, and change in focal position of an image due to the Coulomb effect.

[0010]

An embodiment of the present invention will be described with reference to FIGS. 1 and 6. FIG. (1) The invention of claim 1 is applied to a charged particle beam exposure apparatus that irradiates a charged particle beam onto a mask 25 on which a pattern is formed and forms an image of the pattern on a sensitive substrate, and a charged particle beam beam The above object is achieved by making the cross-sectional shape (the shape of the irradiation region shown in FIG. 1) a rectangle. Here, a reticle and a mask used in the charged particle beam exposure apparatus are collectively called a mask. (2) According to a second aspect of the present invention, in the charged particle beam exposure apparatus according to the first aspect, the length of the long side of the beam cross-sectional shape is 20 times or more the length of the short side. (3) Explained in connection with FIG. 6, the invention according to claim 3 is the exposure method of the charged particle beam exposure apparatus according to claim 1 or 2, wherein the charged particle beam is cross-sectioned on the mask 25. The above object is achieved by performing exposure while scanning in a direction orthogonal to the long side of the shape.

In the section of the means for solving the above-mentioned problem which explains the constitution of the present invention, the drawings of the embodiments of the present invention are used in order to make the present invention easy to understand. However, the present invention is not limited to the embodiment.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The configuration of the charged particle beam exposure apparatus will be described using the apparatus shown in FIG. The Coulomb effect in a charged particle beam exposure system is due to the Coulomb force between electrons, and the relationship between the shape of the irradiation area (that is, the cross-sectional shape of the beam) when reticle is irradiated with an electron beam and the image blur due to the Coulomb effect Was analyzed by calculation simulation, and the following relationship was found. Although the shape of the conventional irradiation area is a square having an aspect ratio of 1 as shown in FIG. 1A, the aspect ratio is A while maintaining the area S equal to that of the conventional irradiation area as shown in FIG. In this case, image blurring resulted as shown in FIG.
In FIG. 2, the vertical axis represents the image blur, the horizontal axis represents the aspect ratio A, and the image blur is expressed as a percentage of the image blur when A = 1.

If the image blur at the main points in the graph shown in FIG. 2 is described as (A, image blur%), (10, 63%),
(25, 53%), (100, 40%), (400, 3
0%) and (1600, 23%). As is clear from FIG. 2, the image blur due to the Coulomb effect decreases as the aspect ratio A increases, and the reduction rate particularly around A = 1 to 20 increases. When A ≧ 20, the image blur decreases to 55% or less. It is considered that such a decrease in image blur is due to a decrease in the Coulomb effect because the average distance between electrons increases as the aspect ratio A increases. In addition, the fact that the image blur is reduced means that, when exposure is performed with the same degree of image blur as in the related art, the beam current can be increased compared to the conventional art, and the throughput can be improved. Here, the simulation result regarding the image blur is shown, but since this is a result of the Coulomb effect being reduced, the image distortion and the focal position shift due to the Coulomb effect are similarly reduced.

Based on the above results, in the exposure apparatus of the present embodiment, exposure is performed by changing the shape of the irradiation area from a conventional square to a rectangle. FIG. 3 is a diagram showing an example, and 251 is an irradiation area. The area of the reticle irradiation area 251 has almost the same area as the conventional irradiation area (reticle subfield 51) shown in FIG. 8, and the beam current applied to this area 251 is set to be almost the same. In FIG. 3, the length of the long side (length in the x direction) of the reticle irradiation area 251 is set to の of the length of the main field, and the deflection width of the beam in the x direction is approximately 1 in the conventional art.
/ 2. Reference numeral 281 denotes a wafer exposure region of the electron beam that has passed through the reticle irradiation region 251, and the pattern of the reticle subfield 252 is collectively exposed and transferred to the wafer subfield 282.

As a method of making the cross-sectional shape of the electron beam B rectangular, the beam shaped into a square by the aperture 3 in FIG. 7 is transformed into a rectangle using a quadrupole, or For example, there is a method of using a rectangular aperture 30 as shown in FIG.

In FIG. 3, the length of the long side of the reticle irradiation area 251 is １ ／ of the length of the main field, but may be the same as the length of the main field as in the reticle irradiation area 261 of FIG. Reference numeral 291 denotes a wafer exposure area corresponding to the reticle irradiation area 261. This has the following advantages. Since the deflection width of the beam becomes almost zero and it is not necessary to deflect in the x direction, the current and voltage of the power supply can be reduced by the amount that the deflection in the x direction is omitted.
Further, the number of bits of a digital-to-analog converter (DAC) can be extremely reduced.

In the case where the reticle irradiation area 261 is scanned in the y direction to expose and transfer the pattern of the area 262 as shown in FIG. 6, excessive scanning is performed to keep the irradiation amount of the electron beam constant. Although it is necessary, since the size of the rectangular reticle irradiation area 261 in the scanning direction (y direction) is smaller than that in the related art, the area of the skirt required for overscanning can be small, and the reticle can be downsized. it can.
For example, if the area of the reticle irradiation area 261 is the same as the irradiation area (1 mm × 1 mm) shown in FIG. 8 and the dimension in the x direction is 40 mm, the dimension in the y direction is 0.025 mm. 8, which is about 1/40.
As described above, when performing scanning exposure, it is possible to avoid using a highly accurate DAC used in an exposure apparatus that performs exposure transfer for each of a plurality of subfields, thereby reducing the cost of the exposure apparatus. be able to.

In the above-described embodiment, an electron beam exposure apparatus has been described as an example. However, the present invention is not limited to this and can be applied to a general charged particle beam exposure apparatus.

[0019]

As described above, according to the present invention,
The Coulomb effect can be reduced, and image blur, image distortion, and focal position change due to the Coulomb effect can be reduced. In particular, by setting the length of the long side of the beam cross-sectional shape of the charged particle beam to be at least 20 times the length of the short side as in claim 2, image blur can be reduced to 55% or less of that of the related art. . Furthermore, by making the beam cross-sectional shape rectangular, the deflection width of the charged particle beam can be made smaller than before, and the current and voltage of the power supply used for the exposure apparatus can be made lower than before, and digital and analog The number of bits of the converter can be reduced. Also,
According to the third aspect of the present invention, it is possible to reduce the overscanning area required when scanning the charged particle beam, and to reduce the size of the mask.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams illustrating an irradiation area, where FIG. 1A shows a conventional irradiation area, and FIG. 1B shows an irradiation area according to the present invention.

FIG. 2 is a graph showing a relationship between an aspect ratio A of an irradiation area and image blur.

FIG. 3 is a diagram showing an example of a reticle irradiation region and a wafer exposure region in the present embodiment.

FIG. 4 is a diagram showing an aperture used in the exposure apparatus of the present embodiment.

FIG. 5 is a diagram showing another example of a reticle irradiation area and a wafer exposure area.

FIG. 6 is a diagram illustrating exposure scanning.

FIG. 7 is a diagram illustrating a conventional charged particle beam exposure apparatus, and is a schematic diagram illustrating a schematic configuration of an electron beam exposure apparatus.

FIG. 8 is a view for explaining exposure transfer by an electron beam.

[Explanation of symbols]

 3,30 aperture 5,25 reticle 8 chip area 11 wafer 251,261 reticle irradiation area 281,291 wafer exposure area

Claims (3)

[Claims] 1. A charged particle beam exposure apparatus for irradiating a charged particle beam onto a mask on which a pattern is formed to form an image of the pattern on a sensitive substrate, wherein the beam cross section of the charged particle beam is rectangular. A charged particle beam exposure apparatus. 2. The charged particle beam exposure apparatus according to claim 1, wherein a length of a long side of the beam cross-sectional shape is 20 times or more of a length of a short side. . 3. The exposure method for a charged particle beam exposure apparatus according to claim 1, wherein the charged particle beam is exposed on the mask while scanning the charged particle beam in a direction orthogonal to a long side of a cross-sectional shape of the charged particle beam. Exposure method.