JPH03106015A - Charged particle beam lithography method - Google Patents

Abstract

PURPOSE:To make it possible to form a necessary pattern in a highly precise manner even when a substrate is deformed and recovered to the original state by a method wherein the amount of deformation of the substrate corresponding to the pattern formed prior to patterning is computed and the irradiation position of a charged particle beam is corrected in accordance with the amount of the above-mentioned deformation. CONSTITUTION:Before performance of patterning, the coefficient of elasticity of material substrate 3 is computed, patterning data is changed in accordance with the above-mentioned elasticity coefficient, a pattern is drawn in accordance with the expansion and contraction of the substrate 3, most of thin film 2 is removed finally from the substrate 3 by etching, and when the deformation of the substrate 3 is returned to the original state, a pattern is formed in the prescribed accuracy. Accordingly, the effect of adhesion of the thin film on the substrate 3 can be eliminated. As a result, a necessary pattern can be formed in a highly precise manner even when the substrate is deformed, or it returns to its original state.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a charged particle beam that is suitable for use when creating masks used in semiconductor manufacturing using electron beam or ion beam lithography. Concerning drawing methods.

(Prior Art) FIG. 2 is a diagram illustrating a method of creating a mask for semiconductor manufacturing by electron beam lithography, and FIG. 2(a) shows a glass substrate 1. As shown in FIG. This glass substrate 1 has
A thin film 2 of a material that blocks light, such as chromium (Cr), is deposited by vacuum evaporation or the like (
Figure 2(b)).

Thereafter, a resist 3 is applied onto the thin film 2, as shown in FIG. 2(c). Note that due to the attachment of the thin film 2 shown in FIG. 2(b), the glass substrate 1 is deformed due to the internal stress and thermal stress of the thin film.

After applying the resist, a desired portion is irradiated with an electron beam EB, as shown in FIG. 2(d). In this example, the electron beam is irradiated in a band shape at intervals of a. If the resist 3 is a positive type resist, as shown in FIG. 2(e), when the resist is developed, only the portion irradiated with the electron beam is removed. When etching is performed after the development of the resist is completed, only the thin film irradiated with the electron beam is removed, as shown in FIG. 2(f). The distance between the strips from which the thin film has been removed is shown in Fig. 2(f).
In this state, the thin film 2 is still attached to most of the substrate 1, and the deformation of the glass substrate 1 is as shown in FIG. 2(b).
The condition is not much different from that of , and the electron beam irradiation interval a
and the interval b between the band-shaped portions are approximately equal.

(Problem to be Solved by the Invention) On the other hand, when a negative resist is used, the steps up to electron beam lithography are the same as those for positive resist lithography shown in FIGS. 2(a) to 2(d). When the resist is developed, as shown in FIG. 3(a), only the resist in the part irradiated with the electron beam remains, and the resist in other parts is removed. When etching is performed after developing the resist as shown in FIG. 3(a), the thin film is removed except for the portion where the resist remains, as shown in FIG. 3(b).

When a negative resist is used in this way, a thin film is left only in the areas irradiated with the electron beam. In such a case, since the thin film is removed from most parts of the substrate 1, the substrate that has been deformed due to the internal stress of the thin film, etc.
As shown in FIG. 3(b), the deformed state returns to the original state. As a result, the distance C between the remaining thin films is
This deviates from the irradiation interval a of the electron beam, and the precision of the pattern formed by drawing deteriorates.

The present invention has been made in view of these points, and its purpose is to provide a charged particle beam drawing method that can form a required pattern with high accuracy even if the substrate is deformed and then returned to its original shape. It is in the realization.

(Means for Solving the Problems) In the charged particle beam writing method based on the present invention, a thin film is deposited on a substrate to be drawn, a resist for the charged particle beam is applied thereon, and the charged particle beam is applied onto the resist. In a charged particle beam writing method that draws a desired pattern, the amount of deformation of the substrate corresponding to the pattern to be formed is determined prior to writing, and the irradiation position of the charged particle beam is corrected according to this amount of deformation. It is characterized by the fact that

(Function) The degree of deformation of the substrate is determined in advance according to the pattern to be drawn, and during actual drawing, the required pattern is drawn at intervals corrected in consideration of the amount of deformation of the substrate.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of an electron beam lithography apparatus for carrying out the lithography method based on the present invention. The electron beam EB generated from the electron gun 1 is focused onto the material 3 to be drawn by the focusing lens 2.
It is placed above. The stage 4 is moved by a drive mechanism 5, which is controlled by a computer 6. The irradiation position of the electron beam on the material 3 is changed by a deflection signal to a deflection coil 7, which is supplied from a deflection circuit 8 controlled by a computer 6.

Drawing pattern data for the drawing material 3 is stored in a pattern data memory 9, and schedule data including information on how many chips to draw on the material is stored in a schedule data memory 10. Furthermore, a memory 11 that stores the amount of deformation of the material substrate 3, which will be described later, is connected to the computer 6. In addition, in this example,
Although each memory is provided independently, a single memory may be used and its areas may be divided to store different data.

With the above-described configuration, prior to actual drawing, the amount of deformation of the material substrate 3 to be drawn, that is, the expansion/contraction coefficient G of each pattern or the interval between patterns due to the final deformation is determined. Now, the ratio of the area of the thin film portion left by drawing to the total area of the chip to be drawn, that is, the area ratio, is A.
1. If the resist type is S (negative resist is S--1, positive resist is S-1) and the expansion/contraction coefficient of the thin film used is K110, then the expansion/contraction coefficient G of the material substrate is as follows. can be expressed.

G-SXAX (K, +K2+...10K, l)
The area ratio A is determined from the pattern data and schedule data stored in the memory 9 and the memory 10.

The computer 6 calculates the expansion/contraction coefficient G and stores it in the memory 11. After that, the computer 6
The stage drive mechanism 5 and deflection circuit 8 are controlled based on the pattern data and schedule data to draw a desired pattern. At this time, for example, the length in the X direction is X1, Y
When supplied with pattern data having a length in the direction Y1, the computer 6 performs the following calculation.

X' -XxG Y -YxG In this way, during actual drawing, the drawing pattern data is converted according to the contraction of the material substrate 3, and the deflection circuit 8 and the stage drive mechanism 5 are controlled by this converted data. be done. As a result, the length of the pattern at the time of drawing is shortened, but after the unnecessary portions of the thin film are finally removed by etching, the shrinkage of the material substrate is halved, so the exact length is shortened. It becomes Satoshi. for example,
In the example shown in FIGS. 2 and 3, when writing with the electron beam shown in FIG. 2(d), the writing interval is a Sometimes the spacing b will be approximately equal to a due to no shrinkage of the substrate.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, although we have explained using a negative resist as an example, even when using a positive resist, if a large part of the substrate is irradiated with the electron beam and only a small portion of the thin film remains, the substrate may be deformed. This can no longer be ignored, and it becomes necessary to apply the present invention. Furthermore, although the explanation has been given using electron beam lithography as an example, the present invention can also be applied to ion beam lithography. Furthermore, the method of determining the shrinkage coefficient of the substrate is not limited to the above method. For example, it can be determined as follows.

Now, the Young's modulus of the substrate is Em, and the thickness of the substrate is d. , the thickness of the thin film is d I , the radius of the substrate is γ, the Poisson's ratio of the substrate is ν, and the stress of the deposited thin film is σ, then the deflection of the substrate δ is:
It can be expressed as follows.

The elongation Δg of the substrate is as follows, assuming that the diameter of the substrate is g (-27).

Therefore, the contraction coefficient G is as follows.

(Effects of the Invention) As explained above, in the present invention, prior to drawing, the expansion/contraction coefficient of the material substrate is determined, the drawing data is converted according to this expansion/contraction coefficient, the drawing is performed according to the expansion/contraction of the substrate, and the final When most of the thin film is removed from the substrate by etching and the substrate deforms back to its original shape, an accurate pattern is formed with a predetermined precision, so the effect of thin film adhesion to the substrate is reduced. It can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an electron beam lithography apparatus for implementing the method based on the present invention, and FIGS. 2 and 3 are diagrams illustrating the steps of creating a mask by electron beam lithography. 1... Electron gun 2... Focusing lens 3...
Drawing material substrate 4...Stage 5...Drive mechanism
6... Computer 7... Deflection coil 8
...Deflection circuit 9, 10.11...Memory

Claims (1)

[Claims] In a charged particle beam drawing method in which a thin film is deposited on a substrate to be drawn, a resist for a charged particle beam is applied thereon, and a desired pattern is drawn on the resist by a charged particle beam, prior to drawing, A charged particle beam drawing method that calculates the amount of deformation of a substrate according to the pattern to be formed, and corrects the irradiation position of the charged particle beam according to this amount of deformation.