JPS6182431A - Electron beam transfer method - Google Patents

Abstract

PURPOSE:To reduce the pattern dimensional error caused by a proximity effect by auxiliarily exposing the nonpattern range of a special pattern periphery by the emitting amount less than the emitting amount D1 necessary to form a pattern. CONSTITUTION:A photoelectric mask 101 and a sample 20 are opposed, an electric field is formed by a DC high voltage power source 31 therebetween, a magnetic field is applied by a focusing magnet 32, ultraviolet ray is emitted to achieve an electron beam equimultiple projection exposure, an electron beam 41 is emitted in the beam emitting amount D0 necessary to form a selective pattern to project and expose the pattern region. Then, an electron pattern transfer is performed by a photoelectric mask 102 having a mask pattern 13, the entire surface of the pattern region and the nonpattern region of the sample 20 is projected and exposed by the beam 42 by 20% of the amount D1. The dimensional variation amount of 0.5mum line of the transferred pattern becomes within 0.06mum, and the dimensional variation amount of the fine pattern caused by the proximity effect is remarkably reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in an electron beam transfer method, and particularly to an electron beam transfer method in which the proximity effect is reduced.

[Technical background of the invention and its problems]

In recent years, the trend toward miniaturization of LSI devices has progressed, and devices with dimensions of 0.5 [μm] and even 0.25 [μm] are about to appear in the near future. Such fine devices are difficult to manufacture using conventional methods using optical steppers, and new lithography is desperately needed. Among these, electron beam lithography is widely recognized as the most promising.

However, electron beam lithography technology has problems with 1
There is a problem that a pattern smaller than [μ7FL] cannot be formed accurately. For this reason, efforts have been made to avoid the proximity effect problem by using new techniques such as a multilayer resist method, pattern size correction or irradiation dose correction using a large-scale electronic computer, or increasing the acceleration voltage. However, none of these methods were satisfactory due to problems with dimensional accuracy and complexity of the process. That is, the dimensional tolerance II (±10 of the pattern) required for the formation of fine devices as described above.
%, i.e. 0.5μm±0.05μm or 0.25μm ±0.025μTrL), the dimensional error is ±0.1
It was extremely difficult to even keep it within [μTrL]. Therefore, the key to practical application of submicron-sized electron beam lithography technology is how to reduce pattern size errors due to the proximity effect.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electron beam transfer method that can reduce pattern dimensional errors caused by the proximity effect in a simple manner and can support ultra-miniaturization of LSI devices.

[Summary of the invention]

With the aim of reducing pattern dimensional errors caused by the aforementioned proximity effect, the present inventors have conducted extensive research and various experiments, and have found that It has been found that by supplementary beam irradiation with a smaller irradiation amount than the beam irradiation amount, the pattern dimensional error can be significantly reduced. Here, the above-mentioned auxiliary beam irradiation may be either drawing or projection exposure (transfer), and is not limited to electron beams, but also ultraviolet rays, far ultraviolet rays, or X! It may be a first class electromagnetic wave. Furthermore, it is also possible to use an ion beam instead of an electron beam. Further, the area for auxiliary beam irradiation may be the entire surface of the sample, a non-pattern area, or a specific pattern area.

The present invention focuses on such points, and irradiates light onto a photoelectric mask that emits electron beams in a desired pattern by light irradiation.
An electron beam transfer method in which an electron beam emitted from the mask is focused by a magnetic field and an electric field and irradiated onto a sample, and a selective pattern corresponding to the pattern formed on the mask is projected onto the sample, After or before selective projection exposure of the pattern area with an electron beam using the beam irradiation amount Do required for selective pattern formation, the irradiation amount D! required to form the pattern with a charged beam or electromagnetic wave is applied. This is a method in which at least a non-pattern area around a specific pattern is supplementally exposed with a smaller amount of radiation.

(Effects of the Invention) According to the present invention, it is possible to significantly reduce pattern size errors caused by the proximity effect compared to conventional methods.According to experiments conducted by the present inventors, <0.5 [μrn 'l
The amount of variation in the butterfly and -n dimensions should be ±0.03 [μr] at worst.
It was possible to keep it within rtJ, and in the best case it was also possible to keep it within ±0.015 rμm3.

That is, the most important weakness of the electron beam transfer method can be overcome, making it extremely effective as a next-generation lithography technology.

Further, since the proximity effect can be reduced without complicating the process steps, it can be easily implemented and has great practical advantages.

[Embodiments of the invention]

First, the method of the present invention basically consists of the steps shown in FIGS. 1(a) to (d).
It can be divided into four aspects as shown in the following. The first method, as shown in FIG. 1(a), is the so-called ordinary electron beam transfer (hereinafter EB This is a method of exposing the entire surface of the pattern area and non-pattern area with a radiation dose D2 that is smaller than the radiation dose D1 necessary to form the pattern using an electron beam or electromagnetic waves. The second method is
111. As shown in (b), this is a method of selectively exposing non-pattern areas after EB transfer. The third method is
As shown in FIG. 1(C), after EB transfer, a non-pattern area is selectively exposed, and the entire surface is further exposed. In addition, the fourth method is as shown in FIG. 1(d).
This is a method in which the correction pattern is selectively exposed after transfer.

In addition, in each of the above embodiments, the order of each step may be changed without any problem. Furthermore, exposure for auxiliary exposure includes both a method of drawing by scanning a beam on the sample and a method of projection exposure (transfer) using a mask. It is also possible to use an ion beam for auxiliary exposure.

Examples based on the above aspects will be described below. Note that 50 [KeV] was used as the acceleration voltage of the electron beam.

<Example 1> This example is an example in which the method shown in FIG. 1(a) is applied.

First, as shown in FIG.
10) and the sample 20 to be subjected to electron beam transfer are placed facing each other, an electric field is applied between them from a DC high voltage power source 314%, and a magnetic field is applied from a focusing magnet 32 &-. Irradiate ultraviolet light onto 10,
Regular electron beam transfer and JiiJt! Electron beam full-scale projection exposure was performed. As a result, the sample F120 was irradiated with the electron beam 41 at a beam irradiation amount Do necessary for selective pattern formation, as shown in FIG. 3(a), and the pattern area was exposed by projection (EB transfer).

Here, the photoelectric mask 10 is made of a transparent substrate 11. such as a quartz substrate that transmits ultraviolet light. 2. A transparent conductive layer coated on the bottom surface of this substrate 11. A mask pattern 13 made of 771M (for example, chromium) is attached to the lower surface of the transparent conductor 1i11112 and blocks ultraviolet light, and a charging surface 1 made of Cs1 or the like is coated on the lower surface of these and emits photoelectrons upon receiving ultraviolet light.
It is formed from 4.

Further, the sample 20 is formed by applying a positive resist 22 made of PMMA (polymethyl methacrylate) onto an S1 wafer 21. The high-voltage power supply 31 is connected between the transparent conductive film 12 and the silica 21, and applies an electric field in a direction facing the mask 10 and the sample 2°.

Further, the focusing magnet 32 applies a focusing magnetic field in the same direction as the direction in which the electric field is applied. In addition,
For this pattern transfer, an electron beam transfer device as described later was used.

Next, as shown in FIG. 2(b), electron beam transfer was performed using a photoelectric mask 102 without a mask pattern 13 in place of the photoelectric mask 101.

As a result, as shown in FIG. 3(b), the entire surface of the patterned area and non-patterned area of the sample 20 is covered with the beam irradiation amount D2 which is 20[%] of the irradiation amount D1 (-Do) required for selective pattern formation. Projection exposure (full surface exposure) was performed using beam 42.

The drawing pattern at this time is as shown in Fig. 4 (a>(b)
As shown in the figure, there were two large-area patterns and two 0.5 [μTrL] line patterns penetrating these patterns. The height of the large area pattern is 200 [μ? FL], width is W (variable), 0.5 [μTIL] line length is 40
0 [μm].

The amount of dimensional variation of the pattern thus transferred and formed, especially the amount of dimensional variation of the 0.5 [μrrL] line, was within <0.06 [μTrL] as shown in FIG.

That is, the amount of variation in pattern dimensions could be kept within 0.5 [μm] ±10r% of the pattern JX (±0.03 μm). In FIG. 5, the horizontal axis represents the width W1 of the large-area pattern, and the vertical axis represents the dimensional difference ΔS from the design pattern of the 0.5 cμ'rrL1 line.

On the other hand, in the case of the conventional method, as shown in FIG. 15 (where the pattern is only selectively projected and exposed with the beam irradiation amount Do), the amount of variation in the pattern dimensions is 0.0, as shown in FIG. 16.
25 [μTrL] is also available, and the tolerance for dimensional variation within ±10 [%] of the 0°5 [μTrL] pattern is ±0.05.
It was not possible to satisfy the value within [μm].

As described above, according to the method of this embodiment, the amount of variation in pattern dimensions caused by the proximity effect, especially the amount of dimensional variation in fine patterns, which is the most problematic, can be reduced from the conventional 0.25 [μTIL] to 0.
It can be significantly reduced to within 0.06 [μm] (±0.03μm). Therefore, it can fully cope with the formation of devices with submicron patterns in the future, and its usefulness is enormous.

In this example, electron beam projection exposure was performed as auxiliary exposure (full surface exposure), but an electron beam lithography system was used, and the beam irradiation amount D1 was smaller than that required to form the selective pattern (Ds). ) irradiation within 50% of 10
In step 2, the entire surface of the sample may be subjected to electron beam lithography.

Further, as the auxiliary exposure, it is also possible to use electromagnetic waves such as ultraviolet rays, far ultraviolet rays, or X-rays instead of the electron beam. In this case, the dose (
The entire surface of the sample 10 may be exposed with a dose D2 (within 50% of Dr). Even with full-scale exposure to this electromagnetic wave,
The present inventors have confirmed that effects similar to those described above can be obtained. Furthermore, for auxiliary exposure, it is also possible to use an ion beam instead of an electron beam.

<Example 2> This example is an example in which the method shown in FIG. 1 (1)) is applied.

First, as shown in FIG. 6(a), a desired pattern was exposed by electron beam projection exposure (EB transfer) using an electron beam 41 as shown in FIG. 7(a), as in Example 1 described above. Next, as shown in FIG. 6(1), electron beam projection exposure was performed using a charged mask 103 having a mask pattern 13 opposite to that of the mask 101 instead of the mask 102. As a result, as shown in FIG. 7(b), the irradiation amount Dl (-Do) required for selective pattern formation is
The non-pattern area of the sample 20 was selectively projected exposed (selective pattern exposure) with an electron beam 43 at a beam irradiation dose D3 of 20%. The drawing pattern at this time is
As shown in FIGS. 4(a) and 4(b), the same procedure as in Example 1 was conducted.

The amount of dimensional variation of the pattern thus transferred and formed, especially the dimensional variation of the 0.5Eμ'rrL] line, was <ClO4[μml] as shown in FIG. In other words, the pattern dimension variation is 0.5 [μm”] ±10 [%] of the pattern.
] (±0.02 μm), and the same effect as in Example 1 can be obtained.

In this embodiment as well, it goes without saying that electron beam writing or electromagnetic exposure may be used as auxiliary exposure (non-pattern exposure). Furthermore, the order of the EB paper transfer non-pattern exposure is not limited to Kawatani.

Further, in this embodiment, projection exposure was performed twice, but by selecting the material of the mask pattern 13, projection exposure can be performed only once. That is, a material that is semitransparent to ultraviolet light is used as the material for the mask pattern 13, and the ultraviolet light transmittance of the mask pattern 13 is set to about 20%.

By using such a photoelectric mask 101', it becomes possible to perform E8 transfer and non-pattern exposure simultaneously in the process shown in FIG. 6(a).

<Example 3> This example is an example in which the method shown in FIG. 1(C) is applied.

First, <28 transfer and non-pattern exposure were performed as shown in factors 6 (a) and (b) above, and then the entire surface was exposed as shown in the M2 diagram (1)). That is, as shown in FIG. 9(a), after projection exposure (E8 transfer) of a desired pattern with an electron beam 41 as in the previous embodiment 1, as shown in FIG. The non-pattern area of the sample 10 was selectively projected exposed (non-pattern exposure) with the electron beam 43 at a beam irradiation dose D3 of 20c% of the irradiation dose 0r(-Do).Then, as shown in No. 91i1(c) Sample 2 was irradiated with a beam of 1 kDs at 20% of the above irradiation dose D1.
The entire surface of 0 was projected exposed (full surface exposure) with an electron beam 42. The transfer pattern at this time is shown in FIG. 4(a) above.
As shown in (b), the same procedure as in Example 1 was conducted.

The amount of dimensional variation of the pattern thus drawn and formed, especially the dimensional variation of the 0.5 C .mu.m line, was <0.03 .mu.m, as shown in FIG.

In other words, the pattern size variation could be kept within ±10c%j (±0.015um) of the 0.25 [μm] pattern.

In this embodiment as well, it is possible to perform electron beam lithography or mm exposure as auxiliary exposure, and the order of E8 transfer, non-pattern exposure, and full surface exposure can be changed as appropriate.

<Example 4> This example is an example in which the method shown in FIG. 1(d) is applied.

First, ordinary electron beam transfer was performed using a photoelectric mask 10f as shown in FIG. 11(a), and then electron beam transfer was performed using a mask 104 having a correction pattern as shown in FIG. 11(b). That is, as shown in FIG. 12(a), a desired pattern is projected and exposed using an electron beam 41 as in the first embodiment (after being transferred to EB paper, as shown in FIG. 12(1)), which is necessary for selective pattern formation. irradiation amount D1 (=Da
), the correction pattern area of the sample 2o was selectively projected exposed (correction pattern exposure) with the electron beam 44 at a beam irradiation dose D4 of 20%1. The transfer pattern at this time is the same as in the first embodiment as shown in FIGS. It was defined as an area.

The dimensional difference ΔS from the design value of the pattern drawn and formed in this way is almost the same as the characteristic shown in FIG. As in Example 2, 0.04 [μTr
L]. In other words, the amount of pattern dimension variation is 0.5 [μ
7FL] within ±10[%] of the pattern (±0.02μm
).

In this embodiment as well, it is possible to perform electron beam lithography or electromagnetic exposure as supplementary exposure, and EB
The order of paper transfer correction pattern exposure is not equally specified. Here, when exposing the correction pattern, beam scanning may be performed based on the correction pattern data in the case of electron beam drawing, and a mask corresponding to the correction pattern may be used in the case of electron beam transfer or electromagnetic exposure.

Next, an example of an electron beam transfer apparatus used in each of the above embodiment methods will be described. FIG. 14 is a schematic configuration diagram showing the same device. The inside of the vacuum container (sample chamber) 51 is evacuated to about 104 [tOrrl] by a vacuum pump (not shown). The photoelectric mask 10 described above is placed at a predetermined position within the vacuum container 51. The above-mentioned sample 20 is placed below the photoelectric mask 10 and facing the mask 1o at a distance of, for example, about 10 seconds. Further, there is a light transmitting window in the clay wall of the container 51, and a transparent plate 52 is attached to close this window. Ultraviolet light from a light source 53 is introduced into the container 51 through the transparent plate 52, and the upper surface of the mask 10 is illuminated.

On the other hand, a focusing magnet 32 made of, for example, a Helmholtz coil is provided outside the container 51.
A direct current is supplied to this magnet 32 from a power source 54, and a magnetic field is applied in the vertical direction of the paper, that is, in the direction in which the mask 10 and the sample 20 face each other. In addition, mask 10
A high voltage is applied between the sample 2o and the sample 2o from a DC high voltage power supply 31, thereby applying an electric field in the same direction as the magnetic field application direction. In addition, 55 in the figure is light 8!
Reference numeral 53 indicates a lighting power supply, 56 indicates a shutter, and 57 indicates a shutter drive system.

In the apparatus with the above configuration, the ultraviolet light emitted from the light source 53 is irradiated onto the upper surface of the photoelectric mask 1o through the transparent plate 52,
As a result, an electron beam (photoelectron) is emitted from the photocathode 14 of the mask 10.

This electron beam is focused by the magnetic field and electric field, travels downward, and impinges on the resist 22 on the sample 20.

Thereby, the resist 22 is projected and exposed according to the mask pattern 13, and pattern transfer is performed.

Note that the method of the present invention is not limited to the above-mentioned embodiments. For example, the irradiation amount during the supplementary exposure is the irradiation f! required to form the selective pattern. kD1
The radiation dose is not limited to 20%, and may be set as appropriate within a range less than the irradiation amount D1 (preferably within 50%). Further, - the above-mentioned EB paper transfer is not limited to electron beam equal-magnification exposure, but electron beam reduction projection exposure may also be performed.

Furthermore, the order of the EB paper transfer auxiliary exposure can be changed as described above. It goes without saying that the present invention can also be applied to PMMA resist. Furthermore, the apparatus for implementing the method of the present invention is not limited to that shown in FIG. 14 above. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the basic steps of the method of the present invention divided into four categories, and FIGS. 2 to 5 are for explaining the method of the first embodiment of the present invention, respectively. FIG. 3 is a cross-sectional view showing the pattern forming process, FIG. 4 is a diagram showing the pattern shape, FIG. 5 is a characteristic diagram showing the change in dimensional difference ΔS from the designed pattern with respect to the width W of the large area pattern, and FIG. 6 FIGS. 6 to 8 are for explaining the method of the second embodiment, and FIGS. 6 and 7 are cross-sectional views showing the pattern forming process, and FIG. 8 is a characteristic showing changes in the dimensional difference ΔS with respect to the width W. 9 and 10 are for explaining the method of the third embodiment, respectively. FIG. 9 is a cross-sectional view showing the pattern forming process, and FIG. 10 shows the change in the dimensional difference ΔS with respect to the width W. The characteristic diagrams and FIGS. 11 to 13 are for explaining the method of the fourth embodiment, respectively. FIGS. 11 and 12 are cross-sectional views showing the pattern forming process, and FIG. 13 is a diagram showing the pattern shape. , FIG. 14 is a schematic configuration diagram showing the electron beam transfer apparatus used in the above embodiment method, and FIGS. 15 and 16 are
Each figure is for explaining the problems of the conventional method.
FIG. 5 is a sectional view showing a conventional pattern forming process, and FIG. 16 is a characteristic diagram showing changes in dimensional difference ΔS with respect to width W in the conventional method. 10.101, 102.103.104... Photoelectric mask, 11... Transparent substrate, 12... Transparent conductive film, 13
...Mask pattern, 14... Photoelectric film, 20...
Sample, 21... 3i substrate, 22... PMMA resist, 31... High voltage power supply, 32... Focusing magnet,
41... Electron beam for EB transfer, 42... Electron beam for whole surface exposure, 43... Electron beam for non-pattern exposure, 44... Electron beam for correction pattern exposure, 51...
- Vacuum container, 53... light source. Applicant's agent Patent attorney Takehiko Suzue Figure 1 (a) (1)
) (c) (d) Figure 2 Figure 3 @ Figure 4 (a) (b) Figure 5 Figure 6 Figure 7t'A Kiilftz? ? -y -frh (pm) 1st
1 Prisoner No. 12 rA Fig. 13 (a) (b) Fig. 14 Fig. 15 Fig. 16

Claims (11)

[Claims] (1) A photoelectric mask that emits an electron beam in a desired pattern by light irradiation is irradiated with light, and the electron beam emitted from the mask is focused and irradiated onto a sample, so that the mask is formed on the sample. In an electron beam transfer method for projecting and exposing a selective pattern according to the pattern, there is a step of selectively projecting and exposing a pattern area with an electron beam at a beam irradiation amount D_0 necessary for selective pattern formation, and a step before or after the step. An electron beam characterized by comprising the step of auxiliary beam irradiation of at least a non-pattern area around a specific pattern with a dose smaller than the dose D_1 required to later form the pattern with a charged beam or electromagnetic waves. Transfer method. (2) The electron beam transfer method according to claim 1, wherein the step of selectively projecting and exposing the pattern area is performing electron beam equal-magnification projection exposure. (3) The electron beam transfer method according to claim 1, wherein the step of selectively projecting and exposing the pattern area is performing electron beam reduction projection exposure. (4) In the step of auxiliary beam irradiation, the entire surface of the pattern area and the non-pattern area is irradiated with the beam at a dose D_2 smaller than the dose D_1. Transfer method. (5) In the step of auxiliary beam irradiation, the non-pattern area is selectively irradiated with a beam at a dose D_3 smaller than the dose D_1. Transfer method. (6) As the step of auxiliary beam irradiation, the entire surface of the pattern area and non-pattern area is irradiated with a beam at a dose D_2 smaller than the dose D_1, and before or after that, a dose smaller than the dose D_1 is applied. D_3
2. The electron beam transfer method according to claim 1, wherein the non-pattern area is selectively irradiated with the beam. (7) The irradiation amount D_2 is set to 50 [ of the irradiation amount D_1].
%] or less. %] or less. (8) The irradiation amount D_3 is set to 50 [ of the irradiation amount D_1].
%] or less, the electron beam transfer method according to claim 5 or 6, wherein (9) As the light shielding member constituting a part of the photoelectric mask, a film having a predetermined semi-transmittance to ultraviolet light is used. Electron beam transfer method. (10) In the step of auxiliary beam irradiation, a desired correction pattern including a specific pattern is selectively irradiated with a beam at a dose D_4 smaller than the dose D_1. Electron beam transfer method as described. (11) The irradiation amount D_4 is set to 50 of the irradiation amount D_1.
11. The electron beam transfer method according to claim 10, wherein the electron beam transfer method is set to [%] or less.