JPS603773B2 - Electron beam exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure apparatus that can remove edge roughness and perform highly accurate electron beam exposure.

In recent years, with the development of integrated circuit technology, precise IC mask patterning has become required.

This patterning is generally performed by electron beam exposure using an electron beam exposure device. This electron beam exposure involves vector scanning, in which the irradiation point of the electron beam is moved in any direction on the surface to be exposed, and exposure is performed in one direction while slowly sweeping in a direction perpendicular to the above direction. There is raster scanning that performs exposure. but,
Although the above-mentioned vector scanning can perform highly precise exposure, it has the problem that its scanning control system is very complicated and expensive. On the other hand, raster scanning requires a simple scanning control system and is inexpensive, but there is a problem in that edge roughness occurs at pattern edges perpendicular to the scanning direction.
That is, the scanning pitch of a typical raster scanning type electron beam exposure apparatus is 0.25 to 0.50 mm. Exposure is performed using an electron beam having a diameter substantially the same as the scanning pitch. For this reason, unevenness, that is, edge roughness, occurs on the pattern edge of the exposed surface. Therefore, it was considered to reduce the edge roughness by narrowing the scanning pick interval, but since the electron beam irradiation dose distribution generally has a Gaussian function profile, it was not possible to effectively remove the edge roughness. . The present invention has been made in consideration of these circumstances, and its purpose is to reduce edge roughness in an inexpensive raster scanning electron beam exposure apparatus with a simple scanning control system, and to reduce edge roughness, for example. It is an object of the present invention to provide an electron beam exposure apparatus that can perform good patterning even in cases where an exposure precision of 0.1 French is required.

That is, the present invention focuses on the fact that the electron beam for exposure irradiation has a Gaussian function type profile, and by adjusting the diameter of the electron beam, the electron beam irradiation amount of the raster scanned pattern is made uniform, and the electron beam irradiation amount at the putter edge is made uniform. This is intended to reduce the occurrence of edge roughness.

Due to this reduction in edge roughness, even if the scanning pitch and interval are 0.25 to 0.50A, for example, 0.
It is possible to perform patterning with an accuracy of 10 mounds, and to perform exposure with high precision in line with the development of integrated circuit technology. Hereinafter, details of the present invention will be explained with reference to the drawings.

In a circular cross-section electron beam having a Gaussian function profile, the beam intensity 〆(r) at a position at a distance r from the irradiation center position of the electron beam is expressed by the following equation.

〆(r) = pu云Xp(-孝) However, 0 is the spread constant of the electron beam.The electron beam has an intensity distribution shown by this formula, and the electron beam is irradiated at a scanning pitch of 2d as shown in Figure 1. In this case, the beam intensity n a(r
) is shown by the following formula.

a(r)=Xp(-difference) That is, at the above point a, contributions are received from both the electron beam A and the electron beam B.

Here, if the above-mentioned point a is located at the entrance examination position from each beam center point with respect to the scanning pitch 2d, the electron beam intensity 〆a(r) is expressed by the following equation. Ne (r) = Goun Xp (-
On the other hand, the beam intensity 〆b(r) at point b, which is the center position of the electron beam and is a distance d from the center position on the scanning line.
is expressed by the following equation.

That is, from electron beam A and electron beam C, respectively.

It receives a contribution from the beam intensity of transmission x p(-).

Also, from electron beam B.

The beam intensity contributes to Xp (-step).

Therefore, Nab (r) becomes River (r) = Puyun Xp (-Street) 10 years old Xp (- Vessel).

Here, when the changes in the above 〆a(r) and ``nab(r)'' are shown using d/〇 as a variable, it becomes as shown in Fig. 2. As shown in this FIG. is approximately in the range of 0.8 to 1.1,
It can be seen that the above n a(r) and n b(r) are approximately equal. In other words, 0.8≦d/OSI. When scanning is performed at a scanning pitch of 2d using an electron beam that satisfies the condition 1, the intensity of the electron beam at the edge of the pattern becomes approximately uniform. on the other hand,
The diameter of the electron beam is defined as the intensity n(o) at a distance r from the center point, where the intensity at the center point of the electron beam is p(o).
It is determined by 2-r when r) is halved.

That is, it is defined by the diameter of the distribution figure of the points at distance r that satisfy n(r)=back f(o), that is, 2·r. This diameter 2·r is calculated as 1.1773J- from the previous formula 〆(r)=Pakko×p(-difference).

Therefore, the following equation holds true between the beam diameter 2·r and the pitch interval 2d. 1.0 SrSI. By scanning with an electron beam having a diameter of four lines, that is, a diameter of 1.06 to 1.4 vowels compared to the scanning pitch 2d, exposure can be performed in which the adverse effects of edge roughness are removed.

Figures 3 and 4 show the experimental data when a pattern of 4.0 mm on a side was formed by exposure at a scanning pitch of 0.5 A kite using an electron beam whose beam diameter was controlled as described above. It is something.

Note that FIG. 3 shows the measured dimensions of edge roughness and the radius of curvature of the corners. In this experimental example, as shown in FIG. 4, when a pattern is formed with a beam diameter of approximately 0.56 to 0.62 degrees, the edge roughness is reduced. Above 0
．． 56 ~ 0.62 The beam diameter of one skin is the scanning pitch of 0.5
It is approximately 1.12 to 1.24 times as large as that of 〃, and fully satisfies the relationship between the scanning pitch and the beam diameter shown above. Incidentally, generally, the pattern width X formed by electron beam scanning n times (n≧4) at a scanning pitch of 2d is X=n·phantom.

Further, such calculation is performed to set the pattern width data X. For this reason, the pattern width X was set stepwise in steps of the scanning pitch D. Therefore, for example, when the scanning pitch is 0.5r, the pattern size can only be adjusted in units of 0.5 degrees. On the other hand, when adjusting pattern dimensions, highly accurate pattern dimensions can be obtained by setting the exposure darkness value at a distribution point where the change in the distribution intensity of the electron beam is the steepest. That is, when r=0, dna(r)/dr becomes maximum. When forming a pattern by setting the exposure darkness value in this manner, electron beam exposure is generally performed at an intensity as shown in FIG. In other words, the electron beam spreads by performing exposure based on the data of the pattern width X. The pattern is formed up to a point Q where is r. Therefore, a difference occurs between the actually formed pattern dimension Y and the pattern width x as shown in the following equation. Y=×+(〇-d)x2 Y word X+d=.

On the other hand, as explained earlier.

Between the electron beam diameter 2r and the electron beam diameter there is a station...77=Kinaru station. Therefore, the above equation is expressed as (day+d)M7=r, that is, (Y-×+2d)1.177=2r, and a certain relationship exists between the electron beam length 2r and the pattern size B.

Therefore, for example, even if data for the pattern width By doing so, it becomes possible to adjust in units of 0.1 French. In this way, the electron beam diameter 2
By adjusting r, the pattern dimensions, which could conventionally be changed only in steps of 0.5 steps, can now be adjusted in steps of, for example, 0.1 steps.

Therefore, when forming a pattern for a very large scale integrated circuit, it is possible to easily improve the processing speed. Further, even when pattern formation with extremely high precision dimensions is required, it can be easily achieved. In this way, in this apparatus, the diameter of the electron beam is adjusted in a predetermined relationship with the scanning pitch interval, and the object to be exposed is scanned and exposed to form a pattern on the object. It is possible to reduce edge roughness, and furthermore, it is possible to have various advantages such as, for example, pattern dimensions can be obtained with high accuracy in units of 0.1 French.

The electron beam exposure apparatus to which the present invention is applied may be one that mechanically moves the object to be exposed, or may be one that scans the electron beam by electrostatically or electromagnetically deflecting it.

The scanning method is not limited to last scan, but may also be vector scan. That is, the present invention can be implemented with various modifications without departing from the gist thereof. As described in detail above, the present invention can provide an electron beam exposure apparatus having various special advantages such as being able to reduce edge roughness at pattern edges and obtain pattern dimensions with high accuracy.

[Brief explanation of drawings]

The figures explain the operation of the device of the present invention. Figure 1 is a diagram showing the relationship between the electron beam and its irradiation position, Figure 2 is a diagram showing the intensity distribution of the electron beam, and Figure 3 is a diagram showing the relationship between the electron beam and its irradiation position. FIG. 4 is a diagram showing the relationship between edge roughness and radius of curvature with respect to changes in electron beam diameter, and FIG. 5 is a diagram showing the relationship between pattern dimensions. A, B, C...Electron beam, 2d...
Scanning pitch, 2r... Electron beam diameter.・・・・・・Spread constant. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. When exposing an object by raster scanning a circular cross-section electron beam having a Gaussian function profile, an electron beam having a diameter approximately 1.06 to 1.46 times the scanning pitch interval of the electron beam is used. An electron beam exposure apparatus characterized by scanning exposure.