JP2605633B2 - Aperture for electron beam writing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing method for drawing an electron beam directly on a resist applied to a semiconductor substrate to form a circuit pattern such as a semiconductor integrated circuit on the semiconductor substrate. It relates to an aperture for drawing.

[0002]

2. Description of the Related Art In recent years, the progress of semiconductor integrated circuits has been remarkable, and in particular, in memory devices such as DRAMs, the storage capacity has been increased to four times every three years. This progress is largely due to advances in microfabrication technology, and in particular depends on advances in lithography technology.

In order to form a fine pattern on a semiconductor substrate wafer, a reduction exposure apparatus using ultraviolet light as a light source, a so-called stepper, has been used. However, in order to transfer a finer pattern, the wavelength of the light source is shortened. From the g-line (436 nm) of the mercury lamp to the i-line (365 nm) of the same mercury lamp, and further, KrF using krypton fluoride gas is used. It has changed to excimer laser light (249 nm). However, the improvement of the fine pattern transfer capability, that is, the resolution, by shortening the wavelength of the light source, on the contrary, causes a decrease in the depth of focus.

In the production of semiconductor integrated circuits,
Since the pattern transfer is repeated 10 to 30 times, the patterns are sequentially superimposed on the semiconductor substrate, resulting in a large step. Therefore, a decrease in the depth of focus makes it difficult to transfer a pattern onto a step and makes it difficult to manufacture a semiconductor integrated circuit.
Therefore, an electron beam drawing method, which has a drastically wider depth of focus than light exposure, has attracted attention.

In this electron beam writing method, a pattern of a semiconductor integrated circuit is drawn by sequentially following an electron beam with a small spot, so that finer processing is possible, but the processing capability is lower than that of the light exposure method. there were. However, instead of this one-stroke drawing method, a partial batch electron beam drawing method is used, in which batch transfer is performed using an aperture that newly forms a part of the semiconductor integrated circuit, and these collective patterns are connected to transfer the entire circuit pattern. It has been developed and processing capacity has improved dramatically.

FIG. 7 is a perspective view showing the structure of an electron optical system for explaining an example of an electron beam writing apparatus using an aperture forming a part of a semiconductor integrated circuit. In this partial batch writing method, as shown in FIG. 7, an electron beam 8 from an electron gun 1 is shaped into an appropriate size and shape by a first aperture 2, and then formed on a second aperture 4 by a selective deflector 3. Irradiate. A partial collective pattern group which is a part of the semiconductor integrated circuit pattern is formed in the second aperture 4, and one of these pattern groups is selected by the selection deflector 3. Then, the electron beam that has passed through the pattern group of the selected second aperture 4 is
The image is reduced by a reduction lens 5 serving as an objective lens, and is further collectively drawn at a desired position on a semiconductor substrate 7 by a positioning deflector 6.

FIGS. 8A to 8C are a cross-sectional view of the second aperture, a diagram showing an electron beam distribution intensity of an electron beam transmitted through the second aperture, and a cross-sectional view showing a resist pattern of a semiconductor substrate. However, in this partial batch writing method, there is a problem that the pattern group formed on the second aperture 4 is not drawn faithfully on the resist on the semiconductor substrate 7 due to the proximity effect.

For example, as shown in FIG. 8A, if five drawing opening patterns 11 to 15 are formed as a pattern group in the main body 4 of the second aperture,
The electron beam passing through these pattern groups is applied to the semiconductor substrate 7
Is projected to The electron beam directly incident on the resist on the semiconductor substrate 7 is incident on the resist, is reflected on the semiconductor substrate surface, and returns to the semiconductor substrate again. This repetition of incidence and reflection becomes so-called backscattered electrons, which affects the size or shape of the pattern to be drawn. The extent of the spread of the backscattered electrons varies depending on the acceleration voltage of the incident electron beam, the material of the semiconductor substrate, and the like, but the number of the backscattered electrons decreases as the distance from the electron beam incident position on the semiconductor substrate increases.

Therefore, the influence on the drawing pattern due to the proximity effect generally needs to be considered only for the incident position and the pattern on both sides. That is, in the portion 23 on the semiconductor substrate 7, in addition to the incident electrons and the backscattered electrons from the drawing aperture pattern 13, the drawing aperture patterns 12 and 14
8B is affected by the backscattered electrons by the electron beam applied to the semiconductor substrate 7 and has an electron intensity distribution as shown in FIG. On the other hand, the portion 21 on the semiconductor substrate 7 is affected by incident electrons and backscattered electrons from the opening pattern 11 for drawing and backscattered electrons by the electron beam passing through the opening pattern 12 for drawing. At this time, there is only the drawing opening pattern 12 next to the drawing opening pattern 11, and therefore, the backscattered electrons are small and the influence of the proximity effect is small, so that the electron intensity is as shown in FIG. It is lower than the parts 22 to 24 on the seven plates.

Now, if the electron intensity is _Io , the parts 22 to
24 is a drawing opening pattern 1
If it is formed to have dimensions corresponding to 2 to 14,
In FIGS. 1 and 25, as shown in FIG. 8C, the resist pattern 9 is thinner than the portions 22 to 24, and sometimes the resist pattern 9 has no head and its height is low. As described above, the pattern of the portion that is not easily affected by the proximity effect has a smaller size than the pattern of the portion that is easily affected by the proximity effect. As a countermeasure against this, an electron beam writing method adopting a method of correcting the proximity effect is disclosed in JP-A-4-261012 and JP-A-3-261012.
It is disclosed in 174716.

FIGS. 9 and 10 are a sectional view (a) of a second aperture, an electron intensity distribution chart (b), and a schematic sectional view (c) of a resist pattern for explaining an example of a conventional aperture. Second aperture disclosed in Japanese Patent Laid-Open No. Hei 4-26102, as shown in FIG. 9 (a), near to the square of the drawing aperture pattern 13 of one side is d ₁ to the position of the center of the main body 4A The drawing opening patterns 11 and 15 have one side wider by d ₂ . Therefore, the opening patterns 11 and 15 for drawing on the semiconductor substrate 7 are formed.
In the portions 21 and 25 corresponding to
The number of incident electrons is larger than that of the portions 22 to 24 corresponding to 2 to 14, and the number of incident electrons of the portion 23 corresponding to the drawing opening pattern 13 is the smallest. As a result, as shown in FIG. 9B, the electron intensity distribution of the portions 21 and 25 becomes wider and higher than before the dimension correction, and as shown in FIG. The dimensions of the pattern 9 become equal.

As shown in FIG. 10A, the second aperture disclosed in Japanese Patent Application Laid-Open No. 3-174716 is provided in the drawing opening patterns 12 to 14 provided at the center of the main body 4B. Are provided with mesh-shaped shields 12A to 14A that are smaller than the resolution of the electron beam, and the number of electrons passing through the drawing aperture patterns 12 to 14 is smaller than the number of electrons passing through the drawing aperture patterns 1 and 15. , The proximity effect is corrected. As a result, FIG.
As shown in (2), the electron intensity is low at the portions 22, 23, and 24 on the semiconductor substrate, and the electron intensity is almost the same as the portions 21, 25.
In the pattern to be drawn, the dimensions of all the resist patterns 9 from the portions 21 to 25 are equal as shown in FIG.

[0013]

In the above-mentioned conventional aperture for electron beam drawing, the area of the drawing opening pattern in the peripheral portion is reduced by the opening pattern in the central portion.
Although the proximity effect is corrected by adjusting the electron intensity by making the area larger than the area of 3, the area to be increased becomes smaller as the pattern to be drawn becomes smaller, and the increased area is converted into the increased side. The increase in the side (d ₂ ) is very small. Processing such a small dimensional difference into the aperture drawing pattern itself of the aperture is close to the resolution of the lithographic processing technology, and it is difficult to accurately obtain the increased side (d ₂ ). Further, unless the increase (d ₂ ) of this side is accurately obtained, there is a problem that the dimension of the resist pattern formed by the outermost drawing opening pattern is greatly deviated by only a small dimensional error.

Further, the type of the semiconductor substrate is different,
If the material deposited on the semiconductor substrate, such as silicon oxide or tungsten, is different, the number of generated backscattered electrons is different, resulting in various changes in the electron intensity distribution. Therefore, in order to obtain a certain resist size, an aperture for electron beam writing in which d ₂ is variously changed according to the base material is prepared, and the aperture is changed to an aperture having the optimum d ₂ every time the type of the base of the semiconductor substrate changes. There is a need. This complicates the manufacture of the semiconductor device and causes an increase in operation costs, which leads to a problem of an increase in price.

On the other hand, in the latter electron beam writing aperture, the number of passing electrons is controlled by adding a fine mesh-shaped electron beam shield to the writing aperture pattern. Although it is not critical and has the advantage that the control can be performed slowly and broadly with the size of the mesh, the addition of a mesh-like electron shield to the aperture pattern itself not only complicates the design and manufacture of the aperture but also requires a great deal of Requires man-hours. This leads to a price increase, as in the former case. Furthermore, since the number of electrons radiated by the shield is reduced, not only is the electron beam not effectively used, but also the drawing time is increased by the decrease in the electron beam energy,
There is also a problem that the processing capacity of the device is reduced.

Accordingly, an object of the present invention is to provide an inexpensive aperture for electron beam lithography in which the dimension of a resist pattern can be easily controlled, and which can be easily designed and manufactured.

[0017]

A feature of the present invention is to provide an electron beam writing aperture formed by arranging a plurality of writing opening patterns to be written on a resist applied to a semiconductor substrate on a plate member. The amount of electrons below the resolution limit of the resist, which is disposed adjacent to the drawing opening pattern at a predetermined interval and corrects a proximity effect on the drawing pattern by the outermost drawing opening pattern. Is an aperture for electron beam writing provided with an aperture for controlling the amount of electrons having a width passing through the aperture. It is preferable that the predetermined interval is adjusted to correct the proximity effect on the drawing pattern.

Still another feature of the present invention is the aperture for electron beam lithography, wherein the electron quantity control aperture is provided between the lithography aperture patterns formed side by side.

[0019]

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 (a) and 1 (b) are plan views of an aperture for electron beam lithography and FIG.
It is A sectional drawing. This electron beam writing aperture is
As shown in FIG. 1, rectangular drawing opening patterns 11 to 11 having the same opening shape and opening area and being formed in a horizontal row.
15 and a linear opening which is disposed adjacent to the outer drawing opening patterns 11 and 15 and allows the passage of an electron having a quantity of electrons that is insensitive to the resist, and the drawing opening is formed by the quantity of electrons passing through the opening. The main body 4c is provided with electron quantity control openings 16 and 17 for correcting the proximity effect on the patterns drawn by the patterns 11 and 15.

The drawing opening patterns 11 to 15 are openings having a length l ₁ and a width d ₁ . The electron amount control openings 16 and 17 are the outermost drawing opening pattern 1.
Adjacent at 1,15 and spacing w ₁ are arranged in parallel, an opening having a length l _1, line widths of d _3. Then, the minimum possible pattern size of pattern resolution by an electron beam lithography apparatus using the present aperture is represented by the length component on the present aperture as R
Then, a relationship of d ₃ ≦ R <d ₁ is established. This can be grasped by using a resist with a normal resolution limit, opening an aperture smaller than the resolution limit in the aperture, passing electrons through this opening, and projecting it on the resist. It is a thing.

For example, the resolution limit of the resist is 0.1 μm.
Assuming that m and the reduction ratio of the drawing pattern to the drawing opening pattern are 1/25, the dimensional component of R is 0.5 μm even if it is simply calculated. That is, the line width of the electron amount control openings 16 and 17 may be set to be equal to or less than the resolution limit R, for example, 0.3 μm. This 0.3
A linear opening having a width of μm can be easily obtained by the current lithography technology. In addition, the width of the opening is set in the range of 0.1 to 0.5 μm to correct the proximity effect to the drawing pattern.

FIGS. 2A to 2C are cross-sectional views of the electron beam writing aperture, diagrams showing electron intensity distribution, and drawn resist patterns for explaining the operation of the electron beam writing aperture of FIG. FIG. Now, FIG.
As shown in (a), when the electron beam 8 is irradiated on the main body 4c of the aperture, the opening patterns 12 to 15 for drawing and the openings 16 and 17 for controlling the amount of electrons have the number of electrons corresponding to the respective openings. The electron beam passes. As a result, as shown in FIG.
Corresponding to 5, an electron flow waveform having a peak exceeding the specified electron intensity I ₀ at which the resist can be sensitive is formed at the portions 21 to 25 on the semiconductor substrate 7. On the other hand, the intensity of the electron beam passing through the electron quantity control apertures 16 and 17 having a small aperture equal to or smaller than the resolution limit is equal to the electron flow waveform indicated by S having a low and gentle peak at the intensity equal to or smaller than the resolution limit. Become. And
The electron intensity distribution at the portions 21 and 25 is combined with the electron intensity distribution to increase the electron intensity at the portions 21 and 25.

As a result, the outermost portions 21 and 25 which are not affected by the proximity effect from the adjacent pattern on the semiconductor substrate 7
The proximity effect is corrected by the above-mentioned combined electron intensity, and the resist pattern 9 is obtained in the same size as the resist pattern of the portions 22 to 24. In other words, the electron flow that has passed through the electron amount control openings 16 and 17 enters the resist of the semiconductor substrate 7 and generates backscattered electrons from the base, thereby increasing the electron intensity of the portions 21 and 25 on the semiconductor substrate 7. Part 2
It can be formed in the same pattern as the resist patterns 9 of 2 to 24.

FIGS. 3A and 3B are graphs showing the relationship between the width of the aperture for controlling the amount of electrons and the distance between the aperture and the drawing pattern, and the size of the resist pattern. next,
The width d _{3 of the} electron quantity control openings 16 and 17, the shortest distance W ₁ between the outermost drawing opening patterns 11 and 16, and the resist pattern dimensions will be described with reference to the drawings. As shown in FIG. 3 (a), the width d of the electronic volume control opening 16, 17 when the d _3, a resist pattern is formed in a desired dimension d _1.
When the dimension allowed for the resist pattern is d ₁ ± Δd ₁ , the dimension allowed for the electron amount control openings 16 and 17 is between d ₃ ′ and d ₃ ″.

[0026] Applying the case of the conventional example described above this, when placed on the opening pattern 11 of FIG. 8 dimensions corrected by d, in order to obtain a resist pattern dimension d ₁ is d
_Two corrections were needed. Therefore, when the permissible dimension of the resist pattern is d ₁ ± Δd ₁ , the permissible dimensional accuracy of the aperture is between d ₂ ′ and d ₂ ″. 17 has a dimension allowable width (d ₃ ′ to d ₃ ″) which is considerably wider than the dimensional allowance (d ₂ ′ to d ₂ ″) of the conventional aperture pattern itself provided with the electron quantity control function. It can be seen that the dimensional accuracy with respect to is easy to make.

Next, the distance between the electron quantity controlling openings 16 and 17 and the drawing open patterns 11 and 15 will be described with reference to FIG.
This will be described with reference to FIG. Now, when the spacing distance W is the desired dimension d ₁ when W ₁ is obtained, as shown in FIG. 3 (b), it becomes greater than W ₁ a resolution limit R,
The resist dimension x hardly changes. This means that W
It can be seen that the effect is greater when R is smaller than R. Further, when the aperture pattern becomes small and a minute amount of electrons needs to be controlled, it is more preferable to make the electron amount controlling openings 16 and 17 of an easy-to-manufacture width, and to correct the proximity effect by the distance W to control. It is easy to do.

FIG. 4 is a plan view of an electron beam writing aperture according to another embodiment of the present invention, and FIG. 5 is a diagram showing the relationship between the allowable value of the width of the electron quantity control opening and the resist pattern size of the writing aperture pattern. It is a graph shown. As shown in FIG. 4, the electron beam writing aperture
Drawing opening patterns 11 and 15 disposed outside D
Is provided with a group of apertures 18 and 19 for controlling the amount of electrons, which are constituted by a plurality of intermittent linear apertures. Here, each of the linear openings constituting the electron amount control opening groups 18 and 19 is a d ₄ × d ₅ rectangular pattern having a width and a length smaller than the resolution limit R.

In this embodiment, the aperture 18 for controlling the amount of electrons
19 is that a plurality of linear openings are arranged to form gaps between the openings, thereby reducing the proximity effect on the opening degree. As a result, dimensional error of the opening width d ₅ of the electronic volume controlling opening 18 and 19 for the tolerance of the resist pattern to be drawn is more relaxed the allowable size of the pattern as compared to the elongated electron amount controlling opening of the aforementioned It was started. In other words, the degree of influence on the pattern size due to the difference in the size of the electron amount control opening is further reduced.
As shown in the figure, the allowable size of the resist pattern is d ₁ ± Δ
Assuming that d ₁ , the width d ₅ ) of the rectangular opening is d ₅ ′ to d ₅ ″.
Is acceptable. This has a wider allowable range than the above-described embodiment, and from this point, it can be seen that aperture creation is easier.

In the above-described embodiment, the linear electron quantity control opening is described as a rectangular opening having a small width. However, in actual manufacturing, the opening may be not necessarily rectangular but may be easily manufactured. For example, as shown in FIG. 4, a triangular or arc opening may be used instead of a square opening. However, in any shape, it is desirable that the side adjacent to the outer side of the drawing opening pattern be parallel. Then, the overhang dimension of the corner or the arc portion opposite to the parallel side is determined by the resolution limit R.
The amount should be as follows.

FIG. 6 is a partial plan view of an aperture for explaining an example in which the present invention is applied to another electron beam writing aperture. In the above-described embodiment, the electron amount control opening is formed adjacent to the outermost drawing opening pattern.
The effect can be obtained even if the aperture for controlling the amount of electrons is provided between the opening patterns for drawing, not necessarily around the opening pattern for drawing.

For example, as shown in FIG. 6, the present invention can be applied to a case where drawing opening patterns 15A having different widths are formed side by side. In this case, the outermost drawing opening pattern 1
An elongated electron amount control opening 16A or a drawing opening pattern 15A is provided adjacent to the outside of the wide portion of 5A.
A desired pattern size can be obtained by providing the electron quantity control opening 18A adjacent to the narrow part of the width. In short, the electron amount control opening may be provided adjacent to the drawing opening pattern which is not affected by the proximity effect by the electron beam passing through the adjacent drawing opening pattern.

[0033]

As described above, according to the present invention, among a plurality of drawing opening pattern groups formed side by side on a plate-shaped body,
By providing an electron amount control opening that controls the amount of electrons passing adjacent to the drawing opening pattern that is less susceptible to the proximity effect and within the resolution limit of the resist and corrects the proximity effect, the drawing opening pattern itself as in the past There is no need to provide an electron quantity control mechanism for correcting the proximity effect, and the opening can be designed and manufactured independently, so that it is possible to design and manufacture in a very short time and obtain an inexpensive effect.

Since the aperture for controlling the amount of electrons is provided at a position distant from the opening pattern for writing, the degree of influence of the proximity effect on the pattern to be drawn with the amount of electrons passing therethrough has an effect on the opening pattern itself for drawing. Compared with the related art having a control mechanism, the size is smaller than in the related art, and the control is not critical as in the related art, and the size of the resist pattern to be drawn can be easily controlled. As a result, a highly accurate and stable drawn pattern can be obtained.

[Brief description of the drawings]

1A and 1B are a plan view and an AA cross-sectional view of an aperture for electron beam lithography showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electron beam writing aperture for explaining the operation of the electron beam writing aperture shown in FIG. 1, a diagram showing an electron intensity distribution, and a diagram showing a drawn resist pattern.

FIG. 3 is a graph showing the relationship between the width of an electron amount control opening and the distance between the opening pattern and a resist pattern dimension.

FIG. 4 is a plan view of an aperture for electron beam writing according to another embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the allowable value of the width of the electron amount control opening and the resist pattern size of the drawing opening pattern.

FIG. 6 is a partial plan view of an aperture for explaining an example in which the present invention is applied to an electron beam writing aperture.

FIG. 7 is a perspective view showing a configuration of an electron optical system for explaining an example of an electron beam drawing apparatus using an aperture in which a part of a semiconductor integrated circuit is formed.

FIG. 8 is a cross-sectional view of a second aperture, a diagram illustrating an electron beam distribution intensity of an electron beam transmitted through the second aperture, and a cross-sectional diagram illustrating a resist pattern of a semiconductor substrate.

FIG. 9 illustrates a second example of a conventional aperture.
It is a sectional view of an aperture (a), an electron intensity distribution diagram (b), and a schematic sectional view of a resist pattern (c).

FIG. 10 is a sectional view of a second aperture for explaining another example of the conventional aperture (a) and an electron intensity distribution diagram (b).
FIG. 4C is a schematic cross-sectional view of the resist pattern.

[Explanation of symbols]

Reference Signs List 1 electron gun 2 first aperture 3 selective deflector 4, 4A, 4B, 4C, 4D body 5 reduction lens 6 positioning deflector 7 semiconductor substrate 8 electron beam 9 resist pattern 11, 12, 13, 14, 15, 15A Opening pattern 12A, 13A, 14A Shielding object 16, 16A, 17, 18A, Electron amount control opening 18, 19 Electron amount control opening group

Claims (5)

(57) [Claims] 1. An electron beam drawing aperture formed by arranging a plurality of drawing opening patterns to be drawn on a resist applied to a semiconductor substrate on a plate member, wherein a predetermined interval is provided between the outermost drawing opening patterns. For controlling the electron amount having a width passing through the electron amount equal to or less than the resolution limit of the resist, which is disposed adjacent to and which corrects a proximity effect to the drawing pattern by the outermost drawing opening pattern. An aperture for electron beam lithography, comprising an opening. 2. The electron beam writing aperture according to claim 1, wherein the predetermined interval is adjusted to correct a proximity effect on the writing pattern. 3. The opening according to claim 1, wherein the electron quantity control opening is a strip-shaped opening having the width and a side having substantially the same length as the drawing opening pattern. Aperture for electron beam writing. 4. The electron quantity controlling opening is arranged in parallel with the drawing opening pattern and is constituted by a plurality of openings having the width and sides having dimensions smaller than the width. 3. The aperture for electron beam lithography according to claim 1, wherein 5. An electron beam writing aperture, wherein the electron quantity control opening according to claim 1 is disposed between said writing opening patterns formed side by side.